Middle and Upper Ordovician 

Symmetrical Univalved Mollusks 

(Monoplaeophora and Bellerophontina) 

of the Cincinnati Arch Region

U.S. GEOLOGICAL SURVEY PROFESSIONAL PAPER 1066-O

Prepared in cooperation with the 

Commonwealth of Kentucky, University of 

Kentucky, and Kentucky Geological Survey
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Middle and Upper Ordovician 

Symmetrical Univalved Mollusks 

(Monoplacophora and Bellerophontina) 

of the Cincinnati Arch Region

By G.P. WAHLMAN

CONTRIBUTIONS TO THE ORDOVICIAN PALEONTOLOGY OF KENTUCKY 

AND NEARBY STATES

Edited by JOHN POJETA, JR.

U.S. GEOLOGICAL SURVEY PROFESSIONAL PAPER 1066-O

Prepared in cooperation with the 

Commonwealth of Kentucky, University of 

Kentucky, and Kentucky Geological Survey

Stratigraphic distribution, ecology, functional 

morphology, phylogeny, and systematic 

paleontology of 86 species of Ordovician 

symmetrical univalved mollusks from the 

midcontinent

UNITED STATES GOVERNMENT PRINTING OFFICE, WASHINGTON: 1992
U.S. DEPARTMENT OF THE INTERJK INTERIOR 

MANUEL LUJAN, Jr., Secretary

U.S. GEOLOGICAL SURVEY 

Dallas L. Peck, Director

Any use of trade, product, or firm names in this publication is for

descriptive purposes only and does not imply endorsement by the

U.S. Government

Library of Congress Cataloging in Publication Data

Wahlman, G.P.

Middle and Upper Ordovician symmetrical univalved mollusks (Monoplacophora and Bellerophontina) of the Cincinnati arch 

region / G.P. Wahlman.

p. cm. (Contributions to the Ordovician paleontology of Kentucky and nearby States) (Geological Survey professional

paper ; 1066-0)

Includes bibliographical references. 

Supt. of Docs, no.: I 19.16:1066-0 

1. Monoplacophora, Fossil Middle West. 2. Archaeogastropoda, Fossil Middle West. 3. Paleontology Ordovician.

4. Paleontology Middle West. I. Title. II. Series. III. Series: Geological Survey professional paper ; 1066-0. 

QE805.W35 1992

564-dc20 89-600358

CIP

For sale by the Books and Open-File Reports Section, U.S. Geological Survey, 

Federal Center, Box 25425, Denver, CO 80225
CONTENTS

Abstract..........................................................................

Introduction.....................................................................

Acknowledgments.............................................................

Stratigraphy and Geologic Setting.......................................

Biostratigraphic Classification.......................................

Structural-Paleogeographic History...............................

Ordovician Lithostratigraphy of Central Tennessee ..........

Stones River Group ..............................................

Nashville Group ....................................................

"Eden Group"......................................................

"Maysville Group".................................................

"Richmond Group"................................................

Middle Ordovician Lithostratigraphy of Kentucky............

High Bridge Group...............................................

Lexington Limestone .............................................

Upper Ordovician Lithostratigraphy of Kentucky,

Southwestern Ohio, and Southeastern Indiana........

Upper Ordovician Lithostratigraphy of South-Central 

Kentucky ...................................................

Clays Ferry Formation....................................

Garrard Siltstone............................................

Galloway Creek Limestone...............................

Ashlock Formation..........................................

Drakes Formation...........................................

Upper Ordovician Lithostratigraphy of North-Central 

Kentucky and Southwestern Ohio...................

Kope Formation.............................................

Fairview Formation........................................

Bellevue Limestone.........................................

Miamitown Shale............................................

Grant Lake Limestone.....................................

Bull Fork Formation.......................................

Drakes Formation...........................................

Upper Ordovician Lithostratigraphy of Southeastern 

Indiana......................................................

Kope Formation (Indiana)................................

Dillsboro Formation........................................

Saluda Formation...........................................

Whitewater Formation....................................

Material and Preservation..................................................

Measurements..................................................................

Stratigraphic Distribution of Ordovician Monoplacophora and 

Bellerophontacean Gastropoda in the Cincinnati Arch 

Region...................................................................

Paleoecology of Symmetrical Univalved Mollusks...................

Introduction...............................................................

Autecology of Monoplacophorans...................................

Page

01

2

3

3

3

4

6

6

8

12

12

12

13

13

14

17

19

19

20

20

20

21

22

22

22

23

23

23

23

24

24

24

24

25

25

25

26

27

27

27

27

Paleoecology of Symmetrical Univalved Mollusks Continued

Autecology of Bellerophontaceans.................................. 030

Previous Ordovician Paleoecological Studies..................... 32

Ordovician Clastic Environments.............................. 32

Ordovician Carbonate Environments......................... 34

Post-Ordovician Paleoecological Studies of Note................ 34

Paleoecology of Symmetrical Univalved Mollusks of the 

Tyrone Limestone and the Lexington Limestone of 

Central Kentucky............................................... 34

Tyrone Limestone................................................. 36

Lexington Limestone ............................................ 37

Comments on the Paleoecology of the Stones River Group

of Central Tennessee.......................................... 39

Comments on the Paleoecology of the Nashville Group of

Central Tennessee............................................. 39

Hermitage Formation............................................ 39

Bigby-Cannon Limestone....................................... 39

Comments on the Paleoecology of Upper Ordovician

Faunas............................................................. 40

Shell Sculpturing and Encrustation as Defenses Against

Predation......................................................... 41

Functional Morphology...................................................... 42

Introduction............................................................... 42

Monoplacophora.......................................................... 42

Tryblidiida........................................................... 42

Cyrtonellida......................................................... 43

Bellerophontacea........................................................ 44

Shell Coiling........................................................ 44

Functional Aspects of Selected Bellerophontacean

Shell Forms................................................ 47

Explanate Shells............................................. 47

Trilobed Shells............................................... 48

Pallial System and Labral Emargination......................... 49

Parietal Deposits........................................................ 50

Muscle Scars and their Functional Significance ................ 51

Phylogeny and Classification............................................... 53

The Bellerophont Conundrum....................................... 53

Classification and Phylogeny of the Monoplacophora......... 58

Suprageneric Classification and Phylogeny of the

Bellerophontacean Gastropoda............................. 61

Systematic Paleontology.................................................... 64

References Cited.............................

Appendix: Locality Register..............

U.S. Geological Survey Localities.

Non-USGS Collections................

Index.............................................

186

196

196

203

205

in
IV CONTENTS

ILLUSTRATIONS

[Plates follow index]

PLATE 1. Micropileus and Vallatotheca.

2. Helcionopsis and Archinacella.

3. Archinacellat and Archinacella.

4. Archinacella, Cyrtolites (Cyrtolites), and Carinaropsis.

5. Cyrtolites (Cyrtolites) and Archinacella.

6. Cyrtolites (Cyrtolites).

1, 8. Cyrtolites (Cyrtolites) and C. (Paracyrtolites).

9-11. Sinuites.

12-17. Bucania.

18. Bucania and Bellerophon.

19. Bucania.

20. Bucania, Kokenospira, and Tetranota.

21, 22. Tetranota.

23. Undulabucania.

24, 25. Salpingostoma.

26. Salpingostoma and Pterotheca.

27. Bucanopsis and Bucania.

28. Bellerophon (Bellerophon) and Sphenosphaera.

29-32. Sphenosphaera.

33. Sphenosphaera and Bellerophon (Bellerophon).

34-36. Sphenosphaera.

37. Carinaropsis.

38. Carinaropsis and Tetranota.

39. Pterotheca.

40. Pterotheca and Carinaropsis.

41. Sphenosphaera and Tropidodiscus.

42. Tropidodiscus, Temnodiscus, and Phragmolites.

43, 44. Phragmolites.

45. Sinuites and Phragmolites.

FIGURE 1.

2. 

3, 4.

5-8.

10. 

11, 12.

13, 14.

15.

16.

Map showing outcrop areas of Ordovician sedimentary deposits in Eastern North America and area of present study .. 

Chart showing late Middle and Upper Ordovician Series and Stages in Eastern North America. ...............................

Maps showing:

3. Major structural features of the Cincinnati arch and location of the Appalachian basin and the associated

erogenic belt during Ordovician continental convergence...................................................................

4. General paleogeographic settings in the Eastern United States during Middle and Late Ordovician time ........

Charts showing:

5. Lithofacies relationships of Middle and Upper Ordovician stratigraphic units in the Cincinnati arch

region of southeastern Indiana, southwestern Ohio, central Kentucky, and central Tennessee.................

Champlainian and Edenian lithostratigraphic units in central Tennessee....................................................

Facies relationships of the members of the Hermitage Formation in central Tennessee ................................

Page

02

4

6.

7.

8. Facies relationships of the members of the Bigby-Cannon Limestone across the central Tennessee high ......... 10

Diagram showing idealized paleogeographic setting in central Tennessee during deposition of the Bigby-Cannon

Limestone............................................................................................................................................. 10

Map showing depositional facies of the Bigby-Cannon Limestone in central Tennessee ............................................ 11

Charts showing:

11. Facies relationships between the major members of the Lexington Limestone and the Clays Ferry

Formation in central Kentucky..................................................................................................... 14

12. Cincinnatian lithostratigraphic units in Ohio, Indiana, Kentucky, and central Tennessee ............................. 18

Drawings showing:

13. Common measurements made on fossil specimens................................................................................. 27

14. Paths of water currents through the shells and mantle cavities of monoplacophorans .................................. 43

Chart showing morphological and corresponding ecological trends in Middle Ordovician bellerophontaceans ............... 46

Drawings showing paths of water currents through the shells and mantle cavities of some Ordovician

bellerophontacean gastropods.................................................................................................................. 50
CONTENTS V

Page

17. Chart showing four primary models suggesting possible phylogenetic relationships between monoplacophorans,

bellerophontaceans, and pleurotomariaceans.............................................................................................. 057

18. Drawing showing four general morphotypes of monoplacophorans representing four superfamilies ........................... 60

19. Diagram showing phylogenetic relationships of bellerophontacean slit-bearing subfamilies present in Eastern North

America during the Late Cambrian-Middle Ordovician................................................................................ 64

20. Graph illustrating apparent growth rate of the holotype of Helcionopsis striata .................................................... 67

21-23. Bivariate plots of measurements made on specimens of:

21. Vallatotheca unguifortnis. ................................................................................................................ 71

22. Archinacella simulatrix................................................................................................................... 77

23. Archinacella indianensis.................................................................................................................. 85

24. Chart showing stratigraphic ranges of species of Cyrtolites (Cyrtolites) and C. (Paracyrtolites) in the Middle and

Upper Ordovician of the Cincinnati arch region.......................................................................................... 89

25-33. Bivariate plots of measurements made on specimens of:

25. Cyrtolites (Cyrtolites) ornatus........................................................................................................... 93

26. Cyrtolites (Cyrtolites) retrorsus from the Logana Member of the Lexington Limestone in central Kentucky... 97

27. Cyrtolites (Cyrtolites) retrorsus from the Grier Limestone Member of the Lexington Limestone in central

Kentucky................................................................................................................................. 98

28. Cyrtolites (Cyrtolites) claysferryensis new species from the Clays Ferry Formation in north-central

Kentucky................................................................................................................................. 101

29. Cyrtolites (Cyrtolites) minor............................................................................................................. 103

30. Cyrtolites (Cyrtolites) hornyi............................................................................................................ 105

31. Salpingostoma kentuckyense and S. buelli.......................................................................................... 153

32. Salpingostoma richmondensis and Bucania simulatrix ......................................................................... 156

33. Bucanopsis carinifera and B. diabloensis new species........................................................................... 163

TABLES

TABLE 1. Distribution of bellerophontaceans in the Stones River Group of central Tennessee................................................ 027

2. Distribution of monoplacophorans and bellerophontaceans in the Nashville Group of central Tennessee..................... 27

3. Distribution of species of monoplacophorans and bellerophontacean gastropods in the Tyrone Limestone of the High

Bridge Group, the members of the Lexington Limestone, and the Clays Ferry Formation of central Kentucky.... 28

4. Distribution of species of monoplacophorans and bellerophontacean gastropods in the Upper Ordovician stratigraphic

units of the Cincinnati arch region ........................................................................................................... 29

5-14. Relative abundance of species in USGS silicified samples from the:

5. Tyrone Limestone ........................................................................................................................... 36

6. Curdsville Limestone Member of the Lexington Limestone.................................................................... 37

7. Logana Member of the Lexington Limestone ....................................................................................... 37

8. Grier Limestone Member of the Lexington Limestone........................................................................... 37

9. Perryville Limestone Member of the Lexington Limestone .................................................................... 37

10. Devils Hollow Member of the Lexington Limestone.............................................................................. 38

11. Millersburg Member of the Lexington Limestone ................................................................................. 38

12. Tanglewood Limestone Member of the Lexington Limestone.................................................................. 38

13. Clays Ferry Formation .................................................................................................................... 38

14. Dillsboro Formation in Indiana.......................................................................................................... 40

15. Examples of post-Cambrian bellerophontiform molluscan univalves for which muscle scars have been described......... 52

16. Classification of the class Monoplacophora to family level................................................................................... 61

17. Suprageneric classification of the Bellerophontacea, with diagnoses of family-level taxa.......................................... 63

18. Helcionopsis striata .................................................................................................................................... 66

19. Distances between growth lines of the holotype of Helcionopsis striata (USNM 45827).......................................... 66

20. Vallatotheca unguiformis............................................................................................................................. 70

21. Micropileus variabilis.................................................................................................................................. 73

22. Archinacella simulatrix............................................................................................................................... 77

23. Archinacella cingulata ................................................................................................................................ 79

24. Archinacella indianensis ............................................................................................................................. 83

25. Cyrtolites (Cyrtolites) ornatus....................................................................................................................... 92

26. Cyrtolites (Cyrtolites) retrorsus..................................................................................................................... 95

27. Cyrtolites (Cyrtolites) claysferryensis............................................................................................................. 100

28. Cyrtolites (Cyrtolites) minor......................................................................................................................... 103

29. Cyrtolites (Cyrtolites) hornyi........................................................................................................................ 104
VI CONTENTS

	Page

TABLES 18-88. Measurements of:

30. Cyrtolites (Cyrtolites) disjunctus ....................................................................................................... 0106

31. Cyrtolites (Paracyrtolites) subplanus ................................................................................................. 107

32. Cyrtolites (Paracyrtolites) carinatus .................................................................................................. 108

33. Sinuites cancellatus......................................................................................................................... Ill

34. Sinuites obesus............................................................................................................................... 113

35. Sinuites granistriatus ...................................................................................................................... 114

36. Sinuites globularis .......................................................................................................................... 115

37. Tropidodiscus subacutus .................................................................................................................. 119

38. Tropidodiscus cristatus .................................................................................................................... 119

39. Tropidodiscus magnus ..................................................................................................................... 120

40. Phragmolites compressus ................................................................................................................. 121

41. Phragmolites grandis.... ................................................................................................................... 122

42. Phragmolites cellulosus ................................................................................................................... 122

43. Phragmolites bellulus ...................................................................................................................... 123

44. Phragmolites elegans....................................................................................................................... 123

45. Phragmolites dyeri.......................................................................................................................... 124

46. Temnodiscus nitidula ...................................................................................................................... 126

47. Bucania emmonsi (lectotype)............................................................................................................ 129

48. Bucania halli ................................................................................................................................. 129

49. Bucania subangulata....... ................................................................................................................ 130

50. Bucania lindsleyi.. .......................................................................................................................... 131

51. Bucania nashvillensis... ................................................................................................................... 132

52. Bucaniafrankfortensis (holotype)...................................................................................................... 134

53. Bucania peracuta (holotype)............................................................................................................. 134

54. Bucania sublata (lectotype).............................................................................................................. 135

55. Bucania micronema (holotype).......................................................................................................... 136

56. Bucania rugatina....... ..................................................................................................................... 137

57. Bucania singularis (lectotype) .......................................................................................................... 137

58. Bucaniapojetai .............................................................................................................................. 138

59. Bucania simulatrix (lectotype).......................................................................................................... 139

60. Bucania crassa............................................................................................................................... 140

61. Kokenospira costalis.. ...................................................................................................................... 141

62. Undulabucania gorbyi (holotype)....................................................................................................... 142

63. Undulabucania punctifrons .............................................................................................................. 143

64. Tetranota bidorsata..... .................................................................................................................... 145

65. Tetranota obsoleta........................................................................................................................... 147

66. Tetranota sexcarinata...................................................................................................................... 147

67. Tetranota msconsinensis.................................................................................................................. 148

68. Salpingostoma buelli....................................................................................................................... 151

69. Salpingostoma kentuckyense.......... ................................................................................................... 152

70. Salpingostoma richmondensis ........................................................................................................... 155

71. Bellerophon (Bellerophon) subglobulus ............................................................................................... 159

72. Bellerophon (Bellerophon) bilineatus.................................................................................................. 160

73. Bellerophon (Bellerophon) nana ........................................................................................................ 160

74. Bellerophon (Bellerophon) subpatula...................... ............................................................................ 161

75. Bucanopsis carinifera...................................................................................................................... 164

76. Bucanopsis diabloensis .................................................................................................................... 165

77. Sphenosphaera clausus .................................................................................................................... 168

78. Sphenosphaera troosti...................................................................................................................... 170

79. Sphenosphaera burginensis............................................................................................................... 170

80. Sphenosphaera recurvus................................................................................................................... 171

81. Sphenosphaera subangularis............................................................................................................. 172

82. Sp/iewosp/iaeracapax....................................................................................................................... 172

83. Sphenosphaera mohri ...................................................................................................................... 173

84. Carinaropsis acuta...... .................................................................................................................... 177

85. Carinaropsis cunulae ...................................................................................................................... 178

86. Carinaropsis cymbula...................................................................................................................... 179

87. Pterotheca saffordi .......................................................................................................................... 183

88. Pterotheca expansa........... ............................................................................................................... 184
CONTRIBUTIONS TO THE ORDOVICIAN PALEONTOLOGY OF KENTUCKY AND NEARBY STATES

MIDDLE AND UPPER ORDOVICIAN SYMMETRICAL UNIVALVED 

MOLLUSKS (MONOPLACOPHORA AND BELLEROPHONTINA) OF THE

CINCINNATI ARCH REGION

By G.P. WAHLMAN 1

ABSTRACT

The taxonomy, phylogenetic relationships, biostratigraphy, functional morphology, and paleoecology of Middle and Upper Ordovician 

(Blackriveran-Richmondian) symmetrical univalved mollusks of the 

Cincinnati arch region are discussed. Six genera and 30 species of 

tryblidiids and cyrtonellids, and 13 genera and 56 species of bellerophontaceans, are evaluated. The study centered on extensive collections of silicified fossils made by the U.S. Geological Survey during a 

geologic mapping program of the State of Kentucky. Museum collections, including the type specimens for most species discussed, were 

also examined.

Recent sedimentological and structural studies suggest that a protoCincinnati arch existed during Middle and Late Ordovician time as a 

discontinuous positive platform running northwest-southeast, paralleling the continental margin. This proto-Cincinnati arch may have 

resulted from the continental convergence of North America with 

Europe and possibly Africa, and it reflects upward movement along a 

hinge line between the miogeocline to the east and the craton to the 

west. During Middle Ordovician time, carbonate deposition was more 

dominant on this platform than in the adjacent lower lying areas, which 

were dominated by shale deposition. Shale deposition increased on the 

platform during Late Ordovician time as a result of erosion of tectonic 

lands to the east.

Ordovician symmetrical univalved mollusks are found throughout a 

spectrum of shallow marine shelf paleoenvironments. Bellerophontacean faunas of low diversity often dominated very shallow, restricted 

marine paleoenvironments. In normal marine shelf paleoenvironments, 

fewer individuals are found, but a greater diversity of taxa is seen. 

Ordovician symmetrical univalved mollusks probably led a variety of 

modes of life, and could inhabit both firm- and soft-bottom environments. Different taxa were probably algal mat grazers, algal foliage 

dwellers and feeders, deposit feeders, scavengers, and possibly even 

predators feeding on such sedentary benthos as sponges and bryozoans. Paleoecological analyses of the faunas of the individual members of 

the Lexington Limestone in central Kentucky do not show any clear 

trends in the distribution of most taxa. Future synecological analyses 

may reveal trends.

In the Cincinnati arch, symmetrical molluscan univalved fauna, all 

limpet-form taxa, and all sinuate planispiral taxa are assigned to the

Manuscript approved for publication October 18, 1989. 

1Amoco Production Company, Houston, Tex.

Monoplacophora. Assignment of some planispiral taxa to the Monoplacophora is based on known muscle scar patterns (multiple discrete 

pairs) and on the possible functional significance of diamond-shaped 

apertures and umbilical reentrants, both of which may have channeled 

water currents to a posterior mantle cavity. Assignment of the 

planispiral Bellerophontacea to the Gastropoda is based on known 

muscle scar patterns (single circumumbilical pair), the presence of a 

median labral slit (especially a deep slit), a trilobate aperture, massive 

parietal deposits, or an inner apertural parietal platform. It is concluded that in some cases the functional analysis of shell morphology is 

more reliable than muscle scar patterns in distinguishing planispiral 

monoplacophorans from planispiral bellerophontacean gastropods.

Four models for the phylogenetic relationships of monoplacophorans, 

bellerophontaceans, and pleurotomariacean archaeogastropods are considered. One model considers bellerophontaceans to be monoplacophorans and not ancestral to the pleurotomariaceans. The other three 

consider bellerophontaceans to be gastropods, and to be either an 

independent group, or ancestral to or descended from the pleurotomariaceans. However, before any of these models is accepted, a great deal 

more morphological and phylogenetic analysis is needed. Primarily 

because many of the taxa have a median labral slit, I believe that the 

bellerophontaceans and pleurotomariaceans are closely related phylogenetically.

Within the Bellerophontacea, there was a trend during the Late 

Cambrian and Ordovician toward tighter coiling of the shell and an 

increased rate of whorl expansion, both of which acted to make the shell 

more compact and more mobile. The increased mobility allowed bellerophontaceans to occupy higher energy environments and a greater 

variety of niches. This greater adaptability, along with the environmental heterogeneity resulting from tectonism during the Ordovician, 

the radiation of marine algal groups, and the general diversification of 

the marine biota, was responsible for the radiation of the Bellerophontacea during the Middle and Late Ordovician.

Proposed classifications for the Monoplacophora and Bellerophontacea are morphologically and phylogenetically based. Within the Monoplacophora, two orders are recognized Tryblidiida and Cyrtonellida. 

The more primitive order, Tryblidiida, includes three superfamilies 

the Kirengellacea, Tryblidiacea, and Archinacellacea. The Cyrtonellida 

includes the superfamily Cyrtolitacea. The slit-bearing families of the 

superfamily Bellerophontacea are, in order of increasing phylogenetic 

advancement, the Tropidodiscidae, Bucaniidae, Bellerophontidae, and 

Carinaropsidae. Tentatively recognized within the Bellerophontacea,

01
02 CONTRIBUTIONS TO THE ORDOVICIAN PALEONTOLOGY OF KENTUCKY AND NEARBY STATES

although none were present in the fauna under consideration, are the 

sinuate planispiral families Bucanellidae, Grandostomatidae, Tremanotidae, and Euphemitidae.

New taxa of Monoplacophora named herein are Micropileus variabilis, Archinacella alta, Archinacellal davisi, Archinacella area, Cyrtolites (Cyrtolites) claysferryensis, Cyrtolites (Cyrtolites) hornyi, and 

the subgenus Cyrtolites (Paracyrtolites). New taxa of Bellerophontacea named herein are subfamily Undulabucaniinae, genus Undulabucania, subfamily Bucanopsinae, Bucanopsis diabloensis, Bucania 

pojetai, and subfamily Pedasiolinae.

INTRODUCTION

The purpose of this paper is to discuss the taxonomy, 

functional morphology, paleoecology, biostratigraphy, 

and phylogenetic relationships of the Middle and Upper 

Ordovician Monoplacophora and bellerophontacean Gastropoda of the Cincinnati arch region in central Kentucky, Tennessee, southwestern Ohio, and southeastern 

Indiana (fig. 1). The most recent comprehensive treatment of these faunas was a monograph by Ulrich and 

Scofield in 1897. Although fossil monoplacophorans and 

gastropods can be locally common elements of North

FIGURE 1. Outcrop areas of Ordovician sedimentary deposits 

(shaded) in Eastern North America. Area of present study (enclosed 

by solid lines) includes outcrop areas around the Cincinnati arch in 

southeastern Indiana, southwestern Ohio, central Kentucky and 

central Tennessee.

American Ordovician faunas, they have received almost 

no modern study. The lack of attention to these faunas is 

due primarily to the scarcity of well-preserved specimens. The original aragonitic skeletons of these mollusks 

generally were dissolved in early diagenesis, and therefore most known specimens are preserved as internal 

molds. Fortunately, silicification of fossils is widespread 

in the Middle Ordovician limestones of central Kentucky 

and Tennessee. Many of the specimens described by 

Ulrich and Scofield (1897) were silicified specimens that 

had weathered out of these limestones. Silicified fossils 

are much less common in the Upper Ordovician strata of 

the Cincinnati arch region, so most mollusk taxa from 

these rocks are known mainly from internal molds and 

from scarce calcitic replicas.

The present work centered on abundant new silicified 

fossil collections made by the U.S. Geological Survey 

(USGS) during the geologic mapping program of the 

State of Kentucky conducted in cooperation with the 

Kentucky Geological Survey (Pojeta, 1979). Field samples were taken as bulk limestone blocks, which were 

later etched in acid baths in the laboratories of the USGS 

in Washington, D.C., to release a residue of abundant 

silicified fossils. These new collections provide numerous 

specimens of many heretofore poorly known species. 

Moreover, the field samples were precisely located both 

stratigraphically and geographically, unlike many earlier 

collections for which locality and formation data are 

vague and outdated. Thus, these collections provide a 

superior new data base for taxonomic, paleoecologic, and 

biostratigraphic studies. Because of the abundance of 

new material and the great diversity of the Cincinnati 

arch fauna, only the symmetrical molluscan univalves are 

covered herein. Previous reports on other invertebrate 

fossil groups from the new collections have dealt with 

trilobites (Ross, 1967, 1979), brachiopods (Neuman, 

1967; Alberstadt, 1979; Howe, 1979; Pope, 1982; Walker, 

1982), echinoderms (Bell, 1979; Branstrator, 1979; 

Parsley, 1981), corals (Elias, 1983), ostracodes 

(Warshauer and Berdan, 1982; Berdan, 1984), and bryozoans (Karklins, 1984).

The Cincinnati arch fauna includes 19 genera and 86 

species of monoplacophorans and bellerophontacean gastropods from 89 localities. In addition to the new silicified 

collections, many museum collections were also examined, including the type specimens for most of the species 

discussed; altogether, about 3,000 specimens were examined. Photographs of many of the type specimens are 

presented here for the first time.

Middle and Upper Ordovician symmetrical molluscan 

univalves have important bearing on a current controversy in molluscan phylogenetic studies concerning the 

class-level assignment of the Bellerophontida and their 

evolutionary role, if any, in the origin of the class
MIDDLE AND UPPER ORDOVICIAN SYMMETRICAL UNIVALVED MOLLUSKS, CINCINNATI ARCH REGION 03

Gastropoda. One group of paleontologists believes the 

Bellerophontida were evolutionary intermediates 

between the monoplacophorans and the archaeogastropods, while another group believes the Bellerophontida 

were monoplacophorans and were not ancestral to the 

archaeogastropods. Early and Middle Cambrian symmetrical molluscan univalved faunas, all of which are 

minute in size, have been found to be diverse and 

widespread, but their relation to later Paleozoic faunas is 

still a matter of active debate (Berg-Madsen and Peel, 

1978; Yochelson, 1978, 1979; Runnegar, 1983). During 

the Late Cambrian and Early Ordovician, there 

appeared relatively larger molluscan univalves that are 

related to later Paleozoic taxa, but these faunas are 

uncommon and apparently of low diversity. Therefore, 

the diverse Middle and Late Ordovician symmetrical 

molluscan univalved faunas are particularly significant, 

because they represent the first radiation of bellerophontiform taxa that persisted throughout the Paleozoic. 

These Ordovician faunas provide the first adequate sample of typical Paleozoic morphotypes on which to base a 

range of functional morphological interpretations and 

taxonomic conclusions.

From analyses of functional morphology, I conclude 

that the bellerophontaceans are archaeogastropods, but 

that some sinuate planispiral taxa can be interpreted to 

be monoplacophorans.

ACKNOWLEDGMENTS

I would like to express my sincere gratitude to Kenneth E. Caster, Wayne A. Pryor, and David L. Meyer, 

all of the Department of Geology, University of Cincinnati, and to John Pojeta, Jr., of the U.S. Geological 

Survey, Reston, Va., who offered their advice and 

encouragement throughout the course of this work. 

Special thanks are due Caster and Pojeta, whose detailed 

reviews of the manuscript at various stages contributed 

greatly to the final form. E.R. Cressman (U.S. Geological Survey, Denver, Colo.) and R.M. Linsley (Colgate 

University, Hamilton, N.Y.) provided timely and 

thoughtful reviews of the manuscript; to both I give 

extended thanks and appreciation. I would also like to 

thank Ellis Yochelson, U.S. Geological Survey, Washington, D.C., for advice during the early part of the 

study.

For the generous loan of museum specimens, I thank 

the curatorial staffs of the Museum of Natural History, 

Smithsonian Institution, Washington, D.C.; the American Museum of Natural History, New York, N.Y.; the 

Field Museum of Natural History, Chicago, 111.; the 

Geology Museum at the University of Cincinnati, Cincinnati, Ohio; and the Geology Museum at the University of

Miami, Oxford, Ohio. Thanks also to Steve Felton of 

Cincinnati, Ohio, for the loan of specimens from his 

personal collections and for many enjoyable and informative discussions.

I appreciate the many courtesies of the U.S. Geological 

Survey geologists mapping the State of Kentucky, particularly Earle R. Cressman and Gordon W. Weir. Many 

thanks are also due George Sanderson of the Amoco 

Research Center, Tulsa, Okla., who provided facilities 

for the typing of the manuscript.

STRATIGRAPHY AND GEOLOGIC SETTING

BIOSTRATIGRAPHIC CLASSIFICATION

The Middle and Upper Ordovician time-stratigraphic 

units adopted herein were defined by Sweet and Bergstrom (1971, p. 624, fig. 10; 1976, figs. 2, 3) and Sweet 

(1979, fig. 3) on the basis of conodont zonation. They 

recognized the traditional separation of Middle and 

Upper Ordovician rocks into the Champlainian and Cincinnatian Series, respectively, but proposed a partly new 

stadial classification, which has been accepted by the 

U.S. Geological Survey (Pojeta, 1979, p. A14, A15).

Sweet and Bergstrom (1971, p. 624) accepted the 

long-standing tripartite subdivision of the Cincinnatian 

Series into the (ascending) Edenian, Maysvillian, and 

Richmondian Stages. These three divisions had historically been used dually as lithostratigraphic (Groups) and 

time-stratigraphic (Stages) units (Orton, 1873; Foerste, 

1903; Cumings, 1908). Their restriction to stadial usage 

was facilitated by a complete revision of the lithostratigraphic nomenclature of the Cincinnatian strata of the 

type area, which is discussed in a later section.

The standard upper Champlainian section for North 

America is in the Black River and Mohawk Valleys of 

New York. Traditionally, these rocks have been divided 

into the Black River Group below and the Trenton Group 

above. Kay (1948, p. 1401) proposed the term "Trentonian" as a series name, and since then it has sometimes 

been used as a stadial term. Twenty years later, Kay 

(1968) reverted back to using the Trenton Group purely 

as a lithic term, and proposed an entirely new lithic 

subdivision to replace the traditional formations, which 

he had concluded were actually faunal-based units. Kay 

(1968) then proposed that the older geographically 

named, faunal-based subdivisions be converted to timestratigraphic units. These were, in ascending order, the 

Rocklandian, Kirkfieldian, Shermanian, and Cobourgian 

Stages. Sweet and Bergstrom (1971, p. 624) accepted 

Kay's (1968) stadial classification for the most part. 

However, they concluded from conodont studies that the 

top of the Shermanian Stage in New York was at the
04 CONTRIBUTIONS TO THE ORDOVICIAN PALEONTOLOGY OF KENTUCKY AND NEARBY STATES

same stratigraphic level as the base of the Edenian Stage 

in the Cincinnati area. Because the name "Edenian" had 

priority over "Cobourgian," the latter term was rejected. 

Sweet and Bergstrom (1976, fig. 3) maintained the term 

"Blackriveran" for the stage below the Rocklandian.

The resulting classification for upper Middle (upper 

Champlainian) and Upper (Cincinnatian) Ordovician 

rocks of North America, which has been accepted by the 

USGS (Pojeta, 1979, p. A13-A15), is, in ascending order, 

the Blackriveran, Rocklandian, Kirkfieldian, Shermanian, Edenian, Maysvillian, and Richmondian Stages 

(fig. 2).

STRUCTURAL-PALEOGEOGRAPHIC HISTORY

The Middle and Late Ordovician was a period of 

continental convergence. The laepetus (proto-Atlantic) 

Ocean was being closed by convergence of the North 

American Plate with the plates of Eurasia and Africa. As 

these three plates approached one another during the 

Middle Ordovician, a subduction zone and island-arc 

system formed along the orogenic belt running approximately parallel to the present eastern coast of North 

America (fig. 3) (Bird and Dewey, 1970; Hatcher, 1972).

Landward of this orogenic belt, the Appalachian geosyncline became a composite foreland basin during the

SERIES

c

CD

4-1

CD

C

c

o

c

CJ

Champlainian

STAGES

Richmondian

Maysvillian

Edenian

Shermanian

Kirkfieldian

Rocklandian

Blackriveran

FIGURE 2. Late Middle and Upper Ordovician Series 

and Stages in Eastern North America.

Continental 

< Plate 

Convergence

Cumberland 

Sag

Nashville^ 

Dome

100 MILES

FIGURE 3. Major structural features of the Cincinnati arch and 

location of the Appalachian basin and the associated orogenic belt 

during Ordovician continental convergence.

Middle Ordovician, with a miogeocline plunging seaward 

toward the subduction zone (fig. 4A) (Dickenson, 1981). 

During this time, deposition on the craton and upper 

miogeoclinal shelf was primarily carbonate, while deep 

marine shales were being deposited in the eugeosyncline, 

or foredeep basin, directly adjacent to the arc (Kay, 

1951, p. 15; Reed, 1980; Shanmugam and Walker, 1980; 

Shanmugam and Lash, 1982).

As convergence continued, the orogenic belt apparently built into a continuous linear tectonic landmass. 

This tectonic landmass shed great amounts of sediment 

into the foreland basin, eventually nearly filling it. By 

Late Ordovician time, great deltas, most notably the 

Queenston delta, built out across the basin landward 

(fig. 4B).

This sequence of events is reflected in the Middle and 

Upper Ordovician sediments of the Cincinnati arch 

region. There is a marked increase in the clastic portion 

of the section in latest Middle Ordovician time. The 

Upper Ordovician strata of the area are characterized by 

interbedding, in varying proportions, of limestone and 

shale.

The Cincinnati arch runs roughly parallel to the Appalachian Basin, basically forming a geanticline (Kay, 1951, 

p. 17) between it and the cratonic interior (fig. 3). A 

matter of great controversy since the original description 

of the Cincinnati "geanticline" (Locke, 1838) has been the 

timing of the first expression of an arch. Schuchert (1943, 

p. 539-545) summarized the history of that controversy 

to the time of his writing. Borella and Osborne (1978) 

more recently addressed the problem, bringing to bear 

new stratigraphic evidence resulting from Wilson's
MIDDLE AND UPPER ORDOVICIAN SYMMETRICAL UNIVALVED MOLLUSKS, CINCINNATI ARCH REGION 05

0 100 KILOMETERS

B

ix / VIM / vii / vi ;^ v /

/ > ' > ^ i

/ i ' 1^1 / • / / ~.t

' > ' /? / ' ' ' <. i ' ' / / ' * ''/'(/

0 100 MILES 

0 100 KILOMETERS

FIGURE 4. General paleogeographic settings in the Eastern United 

States during Middle and Late Ordovician time. A, Early Middle to 

middle Middle Ordovician time: I, Tectonic land; II, Foreland basin 

(eugeosyncline); III, Shelf (miogeocline); and IV, Cratonic interior. 

B, Latest Middle and Late Ordovician time: V, Tectonic land 

(eroding and shedding sediment westward); VI, Fluvia-deltaic systems (transporting sediment westward); VII, Shallow to deep 

marine shelf (site of deposition of shales of Martinsburg formation); 

VIII, Carbonate platform (proto-Cincinnati arch); and IX, Cratonic 

interior basin (site of deposition of Maquoketa Group).

(1949, 1962) work around the Nashville dome of Tennessee and from work done by numerous geologists during 

the USGS mapping project around the Jessamine dome 

of Kentucky.

The Cincinnati arch is composed of five primary structural elements (fig. 3). These are, from north to south, 

the Kankakee arch of Indiana and the Findlay arch of 

Ohio, which merge near Cincinnati; the Jessamine dome

of central Kentucky; the Cumberland sag (or saddle) at 

the Kentucky-Tennessee border; and the Nashville dome 

of central Tennessee. Of primary concern herein are the 

Jessamine and Nashville domes, as they are primarily 

responsible for the fine exposures of Ordovician strata in 

the study area.

Wilson (1962, p. 494, fig. 16) suggested that the 

Nashville dome was initiated as a small bulging in 

Kirkfieldian time during deposition of the Hermitage 

Formation. He referred to this proto-Nashville dome as 

the central Tennessee bank or high. He further suggested that the same period of crustal movement produced the much more prominent Ozark dome to the west 

and the tectonic lands (Appalachia) to the east, both of 

which were high enough to be eroded and provide fine 

clastic sediments to the intervening low area. Ervin and 

McGinnis (1975, p. 1290) also considered the Ozark dome 

to have been initiated during the Ordovician, and they 

agreed that the origin of the Nashville dome was related.

Borella and Osborne (1978) summarized the continuing controversy over the origin of the Jessamine 

dome. Using facies distribution maps for the 

Kirkfieldian-Shermanian-age Lexington Limestone and 

sedimentologic-stratigraphic data from other authors, 

they concluded that the Jessamine and Nashville domes, 

or precursors of these domes, were present during late 

Middle and early Late Ordovician time. However, they 

claimed that there was no continuous Cincinnati arch at 

that time, it being created by renewed activation in the 

Late Devonian during the final closing of the protoAtlantic Ocean. E.R. Cressman (written commun., Dec. 

1988) disagreed with Borella and Osborne's (1978) interpretations, and cited erosional unconformities in the 

Ordovician section west of the Cincinnati arch as evidence that there was no structural arch during Ordovician time.

Elias (1982, text-fig. 4) and Meyer and others (1981, 

fig. 3) showed that during the Late Ordovician, carbonate sedimentation was concentrated along the 

Algonquin-Cincinnati line (Kay, 1951, p. 21), with fine 

elastics of the Maquoketa Group to the west and the 

Martinsburg Formation to the east. They referred to this 

area of carbonate deposition as a"carbonate platform," 

and did not really address the structural controversy. 

However, the insinuation is that it was paleotopographically high.

It is concluded here that the Cincinnati arch formed a 

hinge line between the Appalachian foreland basin and 

the cratonic interior. As such, its origin, degree of 

expression, areal extent, and orientation were directly 

related to continental margin tectonic activity. Stratigraphic evidence presented by some workers supports 

the contention that although the arch as now known did 

not exist until the middle Paleozoic, it was initiated
06 CONTRIBUTIONS TO THE ORDOVICIAN PALEONTOLOGY OF KENTUCKY AND NEARBY STATES

FIGURE 5. Lithofacies relationships of Middle and Upper Ordovician stratigraphic units in the Cincinnati arch region of southeastern Indiana, 

southwestern Ohio, central Kentucky, and central Tennessee. (Modified from Sweet, 1979).

during the Middle Ordovician and must have been a low, 

broad, discontinuous, linear, paleotopographic high 

extending from southern Ontario (Algonquin arch) to 

central Tennessee (Nashville dome).

ORDOVICIAN LITHOSTRATIGRAPHY OF 

CENTRAL TENNESSEE

The following discussion concerns only the Middle and 

Upper Ordovician stratigraphy of the Central Basin of 

Tennessee; it does not cover the strata of eastern Tennessee. Nearly all of the information related here was 

drawn directly from the works of Charles W. Wilson, Jr. 

(1949, 1962). Stratigraphic correlations are based largely 

on Sweet (1979) and Pojeta and Repetski (1982). The 

Central Basin Ordovician section consists of, in ascending order, the Stones River, Nashville, 

"Maysville," and "Richmond" Groups.

STONES RIVER GROUP

"Eden,"

The Stones River Group is Blackriveran-Kirkfieldian 

in age and correlates with the High Bridge Group and 

lowest Lexington Limestone of central Kentucky (figs. 

5, 6). The group consists of, in ascending order, the 

Murfreesboro Limestone, Pierce Limestone, Ridley 

Limestone, Lebanon Limestone, and Carters Limestone 

(fig. 6).

Murfreesboro Limestone.—The Murfreesboro is the 

oldest Ordovician formation exposed in the Central Basin 

of Tennessee. The base of the formation is not exposed, 

but the maximum known surface thickness is 70 ft (feet). 

It is overlain conformably by the Pierce Limestone.
MIDDLE AND UPPER ORDOVICIAN SYMMETRICAL UNIVALVED MOLLUSKS, CINCINNATI ARCH REGION 07

CENTRAL TENNESSEE

Q.

15

0

i_

CD

.C

CD

z

Q.

15

0

0

CD

E

CO

CD

C

0 l-l

C/)

Catheys Formation

Bigby-Cannon

Limestone

Hermitage Formation

Carters Limestone

Lebanon Limestone

Ridley Limestone

Pierce Limestone

Murfreesboro Limestone

FIGURE 6. Champlainian and Edenian lithostratigraphic units in central Tennessee.

The Murfreesboro Limestone is mainly dark gray, 

very fine grained, and massively bedded. Locally, it has 

laminations, mud cracks, intraformational conglomerate, 

and selectively dolomitized burrows. Chert is common. 

The fauna is dominantly mollusks, particularly gastropods.

Evidence indicates that the Murfreesboro was deposited in a shallow, probably restricted marine environment, most likely inner shelf lagoons and associated tidal 

flats.

Pierce Limestone.—The Pierce is 23-28 ft of dense, 

very fine grained, gray, blue-gray, or dove-colored limestone. It is essentially a thin-bedded unit separating the 

more massively bedded overlying Ridley and underlying 

Murfreesboro Limestones. The thin beds (average 2 

inches thick) are separated by partings of gray calcareous shale. The fauna is abundant and is concentrated on 

the bedding surfaces; it consists mainly of a diverse 

brachiopod and bryozoan assemblage. This unit represents fairly quiet subtidal, normal marine environments.

Ridley Limestone. The Ridley consists of about 90 to 

115 ft of massive-bedded (up to 4 ft thick), gray to 

bluish-gray to tan limestone. It is chiefly fine grained, 

but medium to coarse textures are common. Selectively 

dolomitized burrows and chert are common. A widespread thin-bedded, clay-rich member is present 25-30 ft

above the base of the formation. The Ridley fauna is 

dominated by a diverse assemblage of brachiopods and 

bryozoans.

This formation was deposited in a normal marine 

subtidal environment. The thin-bedded member seems 

to reflect a temporary return to conditions similar to 

those under which the Pierce Limestone was deposited.

Lebanon Limestone.—The Lebanon is 74-118 ft of 

gray, bluish-gray, or tan, dense, fine-grained limestone, 

with interbeds of coarser grained limestones. The 1- to 

6-in-thick limestone beds are separated by thin calcareous shale partings. Very characteristic of this unit are 

dolomitic and clayey burrows that weather differentially, 

giving the limestone a "worm-eaten" appearance.

The Lebanon Limestone is conformable with the 

underlying Ridley, but it is overlain unconformably by 

the Carters Limestone. Similar to the Pierce Limestone, 

the Lebanon also has a thin-bedded unit separating two 

more massively bedded units. The Lebanon fauna is 

diverse and is concentrated on the platy bedding surfaces. It is dominated by a bryozoan-brachiopod assemblage. The environment of deposition was quiet subtidal 

and normal marine.

Carters Limestone.—The Carters is divided into two 

informal members the lower and upper members.

Lower member. This member ranges from 27 to 65 ft 

thick. Beds are 1 to 4 ft thick, though some beds are 

thinner. Limestone lithologies vary from fine grained 

and dense, through medium to coarse grained and even 

coquinoid.

Alberstadt, Walker, and Zurawski (1974) described 

patch reefs in southern Tennessee from the lower Carters Limestone built primarily by stromatoporoids, corals, and algae. Wilson (1949, p. 56) cited colonial corals 

such as Columnaria and Tetradium as the most characteristic fossils in the lower member.

Upper member. This member reaches 28 ft in thickness and consists mainly of dense, fine-grained, laminated, argillaceous, gray to tan limestone. The most 

characteristic fossils are ribbonlike bryozoans and the 

colonial coral Tetradium cellulosum, but there is also a 

moderately diverse assemblage of gastropods, ostracodes, and brachiopods.

The Carters represents shallow marine shelf facies, 

mainly of normal salinity but of variable energy conditions. The lower member appears to represent generally 

higher energy carbonate bank conditions. The lower and 

upper members are conformable, but the upper member 

is overlain unconformably by the Hermitage Formation 

of the Nashville Group.

Summary of Stones River Group facies. As is apparent from the preceding descriptions, two basic facies 

make up the Stones River Group. The first facies, 

Wilson's (1949, p. 67) Facies A, consists of pure, massive-
08 CONTRIBUTIONS TO THE ORDOVICIAN PALEONTOLOGY OF KENTUCKY AND NEARBY STATES

NORTHWEST

F=-<-^— 1QQ'

SOUTHEAST

Davidson 

County

Rutherford 

County

Cannon 

County

' '-Silty nodular limestone member

=r=—i===-i—=Laminated araillaceous member — ,-—-, —r _-r-_Tr""

FIGURE 7. Fades relationships of the members of the Hermitage Formation in central Tennessee (from

Wilson, 1949).

bedded limestone that commonly contains dolomitized 

burrows, chert, and a fauna of corals, stromatoporoids, 

brachiopods, bryozoans, mollusks, and others. The second facies, Wilson's (1949) Facies B, consists of thin 

limestone beds separated by shale partings and containing a fauna characterized by fragile ramose and ribbonlike bryozoans, brachiopods, and some mollusks and 

ostracodes. The alternation of these two facies defines 

the succession of formations in the Stones River Group.

Wilson (1949) believed that silt and clay their presence or absence were the primary controls over facies 

and faunal distributions within the Stones River Group. 

He suggested that the alternation of the two facies in the 

group was the result of periodic uplifting and erosion of 

surrounding positive areas.

It should be noted that sedimentary features characteristic of tidal flat conditions (for example, lamination 

and fenestral fabric) are present locally throughout the 

Stones River Group but characterize only the basal 

formation, the Murfreesboro Limestone. The only widespread unconformities recognized in this group of rocks 

are at the base and the top of the Carters Limestone.

NASHVILLE GROUP

The Nashville Group is Kirkfieldian, Shermanian, and 

Edenian in age (figs. 5, 6). It correlates with the Lexington Limestone, Clays Ferry Formation, and Kope 

Formation of Kentucky. The included formations are, in

ascending order, the Hermitage Formation, BigbyCannon Limestone (as used by Wilson, 1949), and 

Catheys Formation (figs. 5, 6)

Hermitage Formation.—The Hermitage Formation 

thickens westward across the Central Basin from 70 to 

180 ft maximum. Wilson (1949, p. 82, 83) subdivided the 

formation into numerous members, including the basal 

Curdsville Limestone Member, which onlaps the Carters 

Limestone on the flanks of the Nashville dome island; 

two tongues, the laminated argillaceous member, which 

thickens westward, and the silty nodular limestone member, which thickens eastward in complement; and four 

lentils, the Dalmanella coquina member, the granular 

phosphatic member, the "Ctenodonta member," and the 

blue clay-shale member (fig. 7). These lentils rise diagonally northwestward through the formation between the 

two tongues (Wilson, 1949, fig. 15).

Curdsville Limestone Member. This thin- to 

medium-bedded, coarsely crystalline limestone onlapped 

the Nashville dome island, lying unconformably on the 

Carters Limestone. The member is only 7 ft thick on the 

western flank, but is 10 to 15 ft thick on the eastern 

flank. It is absent over the top of the island.

The limestone is blue to gray in color and is coarsely 

crystalline. Beds are 1 to 10 in thick, averaging 2 to 3 in, 

and are separated by thin gray shale partings. Fossils 

are abundant. Brachiopods and bryozoans predominate, 

but mollusks, trilobites, corals, crinoids, and ostracodes
MIDDLE AND UPPER ORDOVICIAN SYMMETRICAL UNIVALVED MOLLUSKS, CINCINNATI ARCH REGION 09

also are present. The Curdsville is interpreted as a 

shallow subtidal, normal marine, transgressive unit.

Laminated argillaceous member. This tongue thickens westward across the Central Basin from 20 to 70 ft, 

but it has been reported to be as thick as 180 ft in the 

subsurface. It is conformable with the underlying Curdsville and with the various overlying lentils of the Hermitage Formation.

The limestone is bluish gray and argillaceous, and 

commonly is evenly laminated. Fossils are sparse, but 

those species found are typical of the entire formation. 

Beds are 2 to 10 in thick and are separated by shale 

partings or thin shale beds. Penecontemporaneous bedding deformation is common, with contorted and rolledup beds being interbedded with beds consisting of 

rounded cobbles and boulders of the same lithology. The 

even lamination and the sparse fauna suggest a relatively 

deep, stagnant depositional environment.

Dalmanella coquina member. This lentil is present 

in a north-south belt that attains a thickness of 30 ft. It 

is a massive-bedded, grayish-blue, silty limestone containing a great profusion of dalmanellid shells, which 

contribute to a coquinoid character. The lentil grades 

westward into the laminated argillaceous member and 

eastward into the silty nodular limestone member. The 

Bigby-Cannon Limestone overlies the lentil across a local 

minor unconformity (fig. 7).

The abundant dalmanellid shells are generally unbroken, but they are shingled. Wilson (1962, p. 485, 486) 

suggested that the environment of deposition was relatively deep and quiet, with the currents strong enough to 

stack the rather thin delicate shells but not strong 

enough to break them.

Granular phosphatic member. This member is probably a series of several lentils rather than one continuous 

lentil. It ranges from 5 to 30 ft thick in any single 

exposure. The limestone is coarse grained and crossbedded, and it contains varying amounts of phosphate. 

Bedding is massive to irregular. The lentils are surrounded by, and grade into, the laminated argillaceous 

member and the silty nodular limestone member.

The fauna is mostly worn and broken, and generally 

the only well-preserved fossils are sturdy equidimensional brachiopods and massive bryozoans. This member 

represents shoaling areas that were acted upon by 

intense waves and currents. Wilson (1962, p. 486) suggested that the lentils formed in a north-south shoal belt.

Ctenodonta member. This lentil is nearly circular in 

outcrop outline and reaches a maximum thickness of 

about 20 ft. The limestone is thin bedded, laminated, 

argillaceous, and fine to medium grained. Beds are 

separated by shale partings. The blue-gray limestone 

weathers to yellowish brown as a result of oxidation of 

disseminated iron. The fauna is dominated by the pelecypod "Ctenodonta" hermitagensis and other mollusks, 

which in many places cover the surfaces of slabs. The 

lentil grades westward into the laminated argillaceous 

member and eastward into the silty nodular limestone 

member.

Blue clay-shale member. This lentil consists of calcareous blue clay-shale. It grades into the laminated 

argillaceous member to the west and reaches a thickness 

of 30 ft to the southeast. Fossils are sparse.

Silty nodular limestone member. This tongue thickens eastward across the Central Basin to a thickness of 

about 30 ft, and grades westward into the Dalmanella 

coquina, granular phosphatic, Ctenodonta, and blue clayshale members. It consists of nodular beds of limestone 3 

to 8 in thick separated by irregular clay-shale partings. 

The fauna is moderately diverse and common, the most 

characteristic elements being bryozoans and corals, but 

also with other normal marine fossils. This unit contains 

less clastic silt than any other member of the Hermitage. 

Wilson (1949) suggested that this reflects a western to 

southwestern source for the elastics in the formation.

Bigby-Cannon Limestone.—The Bigby-Cannon Limestone is Kirkfieldian-Shermanian in age, and correlates 

with much of the Lexington Limestone of central Kentucky (fig. 5). The formation ranges from about 60 to 100 

ft thick and consists of three major lithofacies, which are 

distributed in north-south-trending belts through the 

Central Basin. From west to east, these lithofacies are 

the Bigby fades, the dove-colored fades, and the Cannon 

fades (figs. 8-10).

The contact between the Bigby-Cannon Limestone 

and the underlying Hermitage Formation is locally 

unconformable. In apparent paleotopographic high 

areas, the Hermitage shows thinning resulting from 

erosion. However, in other areas, lithologies of the two 

formations clearly intertongue, demonstrating continuous deposition. Other than the papers of Wilson (1949, 

1962) and Alberstadt (1973), very little has been written 

in the modern literature about this interesting and 

important unit.

Bigby fades. This facies makes up the westernmost 

facies belt in the formation. It rarely exceeds 60 ft in 

composite thickness, and its facies belt has a maximum 

width of 40 miles.

The Bigby Limestone is coarse grained and crossbedded, and the constituent grains are mainly thoroughly 

broken and abraded skeletal fragments. The fauna was 

so damaged by the intense wave action under which it 

was deposited that it is generally poorly preserved. 

Fossils are better preserved eastward, and a diverse 

fauna is known, the most prominent being brachiopods, 

bryozoans, gastropods, pelecypods, and corals. Locally 

within the Bigby, there are lentils of massive, coarsegrained, gray limestone that have long been referred to
010 CONTRIBUTIONS TO THE ORDOVICIAN PALEONTOLOGY OF KENTUCKY AND NEARBY STATES

FIGURE 8. Fades relationships of the members of the Bigby-Cannon Limestone across the 

central Tennessee high (from Wilson, 1949).

as the "Cyrtodonta" beds or member. The fauna in this 

latter unit consists almost entirely of the pelecypods 

Cyrtodonta and Vanuxemia and the gastropods Lophospira, Bucania, and Bellerophon,

The Bigby facies represents the limits of Wilson's 

(1949) central Tennessee bank, which he interpreted as a 

topographically high, broad shoaling area where the 

water never exceeded 30 ft in depth (fig. 9). Westward 

off this bank, the water deepened rapidly and a laminated argillaceous limestone facies was deposited; this 

facies is now exposed only in the Western Highland Rim 

of the Central Basin. Eastward off the bank, the Bigby 

grades into the dove-colored facies, which represents 

shallow lagoonal and tidal flat conditions (fig. 8).

Dove-colored facies. This facies consists of lentils 

present in a north-south belt between the Bigby and 

Cannon facies belts (fig. 8). Its maximum composite

thickness is 60 to 70 ft. The bases of these lentils in many 

places show evidence of scouring prior to deposition.

The facies is so named because of its light-gray color on 

fresh surfaces; however, it becomes chalky upon weathering. The limestone is very fine grained, dense, and 

brittle. Beds vary in thickness from 2 in to 3 ft and 

average about 1 ft. The beds are characteristically laminated, and fenestral fabric and mud cracks are common. 

Fossils are rare and are generally restricted to ostracodes and high-spired gastropods, with occasional small 

vertical burrows. Beds of corals, brachiopods, and other 

normal marine fauna are present in some places, but 

Wilson (1949, 1962) interpreted these as detritus washed 

off the Bigby bank during storms.

Cannon facies. This easternmost facies of the BigbyCannon Limestone thickens eastward from its intertonguing with the dove-colored facies to a maximum

Laminated argillaceous 

limestone

APPALACHIAN 

GEOSYNCLINE

— Shallow water

— Relatively shallow water 

Relatively deep water

CINCINNATI ARCH

FIGURE 9. Idealized paleogeographic setting in central Tennessee during deposition of the Bigby-Cannon Limestone

(from Wilson, 1949).
MIDDLE AND UPPER ORDOVICIAN SYMMETRICAL UNIVALVED MOLLUSKS, CINCINNATI ARCH REGION Oil

EXPLANATION 

Y /\ Laminated mud and sand [V

[ ':'.'':-;.| Back-reef detritus |

| | Silty calcareous ooze o 

(Cannon facies) \-

Granular phosphatic beds 

(Bigby facies) 

Dove-colored facies

25 50 MILES

0 25 50 KILOMETERS

FIGURE 10. Depositional facies of the Bigby-Cannon Limestone in 

central Tennessee (from Wilson, 1949).

thickness of 100 ft in the eastern Central Basin and the 

Sequatchie Valley of southeastern Tennessee (figs. 

8-10).

The Cannon Limestone is dark gray, fine to medium 

grained, moderately fossiliferous, and evenly bedded. 

Beds average about 1 ft thick and in many places have 

silty partings, though silt is nearly absent in the limestone itself.

Fossils are moderately abundant and well preserved in 

the Cannon; they consist mainly of brachiopods, gastropods, corals, and other normal marine fauna (Wilson, 

1949). Alberstadt (1973, p. 630) cited work demonstrating that most Cannon communities were dominated by 

bellerophontid and lophospired gastropods and leperditid 

ostracodes, which might indicate somewhat restricted 

conditions. Alberstadt further reported encrusting and 

boring blue-green algae, green algae, and the red alga 

Solenopora in the Cannon facies.

Because of the algal-gastropod-ostracode assemblage 

and the predominance of a carbonate mud matrix, Alberstadt (1973) concluded that the Cannon was deposited 

under relatively quiet lagoonal conditions. The salinity of 

the environment was probably normal marine to slightly 

restricted. Because stenohaline taxa are common, the 

predominantly "restricted fauna" may reflect quiet, 

nearly stagnant conditions more than hypersalinity.

Bassler (1932) had made a comprehensive study of the 

"Cannon" fauna, but Wilson (1949) stated that his reinterpetation of the formational contact between the Cannon and the overlying Catheys Formation was so different as to put the current stratigraphic placement of many 

species in some doubt. Most type specimens described 

herein from this section were collected during the late 

19th century, before Bassler's or Wilson's work, so 

stratigraphic placement of many type specimens is 

difficult.

Catheys Formation.—The Catheys Formation is 

Shermanian-Edenian in age, correlating with the Clays 

Ferry Formation and Kope Formation in Kentucky (fig. 

5). Wilson (1949, 1962) claimed that the Catheys was 

unconformable with the underlying Bigby-Cannon Limestone over the central Tennessee high, but that the 

hiatus was of short duration and the two formations are 

conformable to the east and west.

The Catheys thickens eastward across central Tennessee from about 25 ft in the eastern Central Basin to 

nearly 250 ft in the Sequatchie Valley of southeastern 

Tennessee. The formation consists of six interbedded 

and intertonguing facies, which are described below 

(fig. 8).

Granular phosphatic facies. This facies is essentially 

identical to the like units in the Hermitage and BigbyCannon Formations. The massive-bedded, coarsegrained, blue-gray limestone is present in 5- to 10- 

ft-thick lentils. These lentils are most common in the 

lower half of the formation, and are most prominent in 

the westernmost Central Basin. Fossils are mainly very 

worn and fragmented.

Dove-colored facies. This facies is present as lentils 

less than 5 ft thick in the basal 25 ft of the formation. The 

limestone is light gray, fine grained, dense, and brittle. 

It differs from the like-named facies of the Bigby-Cannon 

Limestone mainly in its appreciably higher clay and 

glauconite content. Ostracodes are the most common 

element of a very sparse fauna.

Pale-colored facies. Nearly half the Catheys Formation is made up of this blue limestone, which weathers to 

characteristically pale hues. The facies thickens eastward, along with the total formation, from 10 to 125 ft in 

composite thickness.

The limestone is dark blue on fresh surfaces, fine 

grained, and dense. Beds range from 3 to 24 in thick, 

have wavy surfaces, and are separated by blue-gray 

shale partings that sometimes thicken to several inches. 

The fauna is moderately diverse and is dominated by 

brachiopods and bryozoans.

Shaly facies. This blue-gray shale facies is very 

irregular in its occurrence within the formation and in its 

thickness. It commonly is present in shale beds about 5 ft 

thick, but it can reach 20 ft in thickness. It varies from 

soft, crumbly, clay-shale to fissile, compact, calcareous 

shale that breaks into flakes.

The most typical fossils in these shales are slender 

branching bryozoans, particularly Constellaria, which in
012 CONTRIBUTIONS TO THE ORDOVICIAN PALEONTOLOGY OF KENTUCKY AND NEARBY STATES

many places is crowded into beds. Other fossils include 

brachiopods and lophospirid and bellerophontid gastropods, as well as the gastropod Cyclonema.

Nodular fades. This facies makes up about one-third 

of the formation. It is distributed throughout the unit 

and throughout the Central Basin, and it interbeds with 

all the other facies. It thickens from west to east, 

attaining a maximum composite thickness of 75 ft.

This blue-gray limestone contains the most well preserved fossils of any facies of the formation. The fauna is 

composed mainly of a brachiopod-bryozoan assemblage. 

The beds are 3 to 8 in thick, have irregular knobby 

surfaces, and are separated by thin shale partings.

Laminated siltstone facies. This facies consists of 

thin laminae of fine-grained, blue-gray limestone uniformly interlaminated with laminae of silt and clay. It is 

present as a 5- to 10-ft-thick unit near the base of the 

formation, and grades laterally and vertically into the 

shaly facies. It is nearly barren of fossils.

"EDEN GROUP"

Inman Formation. The Inman Formation varies 

from 40 to 70 ft in thickness and has a rather limited area 

of exposure. The formation consists of greenish-gray, 

calcareous shale, and zones of red shale interbedded with 

uniformly bedded, greenish-gray to light-gray, finegrained, dense limestone having fenestral fabric. The 

fauna is neither abundant nor diverse, and consists 

mainly of brachiopods and bryozoans. It seems to represent a quiet, shallow, subtidal to intertidal environment 

of deposition. The red shales might represent the first 

incursion of the Queenston delta red bed facies into the 

area. The entire Inman Formation probably is Edenian 

in age, but the upper part may be early Maysvillian in 

age (fig. 5).

"MAYSVILLE GROUP"

Leipers Formation.—The Leipers Formation is generally less than 75 ft thick, but it reaches 175 ft thick in 

northernmost central Tennessee. The Leipers is late 

Edenian-Maysvillian in age (fig. 5), although these rocks 

have traditionally been called the Maysville Group in 

Tennessee. Wilson (1949, p. 182-190) described three 

facies.

Argillaceous facies. This variable facies consists of 

(1) thin-bedded nodular limestone with shale partings, (2) 

slabby-bedded argillaceous to rather pure blue-gray 

limestone, (3) massive-bedded argillaceous to silty limestone, (4) blue-gray calcareous shale, and (5) light-gray 

to bluish-gray mudstone and siltstone. All subfacies 

except the last contain an abundant brachiopod-bryozoan 

assemblage.

Granular facies. This massive-bedded, coarse 

grained, dark-blue limestone is in most places crossbedded or irregularly bedded, but locally it contains lenses of 

gray calcareous shale. Fossils are generally very broken 

and abraded. The facies thickens westward, just as do 

the similar facies of the Bigby-Cannon Limestone and 

Catheys Formation, to a maximum composite thickness 

of 75 ft.

Pale-colored facies. This fine-grained, dense limestone is dark blue when fresh, but it weathers to pale 

blue. The beds are 2 to 24 in thick and are separated by 

shale partings. The unit may be 25 to 50 ft in composite 

thickness.

Fossils are not as abundant in this facies as in the 

previous two, but they are common. The most representative members of the fauna are the brachiopod Platystrophia ponderosa and several species of gastropods.

Summary of Leipers Formation. The granular facies 

dominates the formation in the western outcrop area, the 

argillaceous facies dominates the lower formation to the 

east, and the pale-colored facies dominates the upper 

formation in the east. The pattern is interpreted as a 

western shoaling area or bank, with a broad lagoon to the 

east which probably shallowed upward over time.

"RICHMOND GROUP"

The group is bounded by unconformities and contains 

two main formations, the Arnheim Formation and the 

Fernvale Limestone, with tongues of the Sequatchie 

Formation entering the section from the east. These 

rocks have traditionally been called the Richmond Group 

in Tennessee. The Nashville dome was a positive feature 

during Richmondian time, and the Arnheim and Fernvale apparently were deposited only around the western 

and northern flanks of the dome.

Arnheim Formation.—This unit probably does not 

correlate with the type Arnheim Formation of the Cincinnati area. Faunal evidence indicates a somewhat 

different age for the Tennessee unit (Bassler, 1932, p. 

122,124; McFarlan, 1943, p. 29; Sweet, 1979; Elias, 1982, 

p. 27, 28). The unit probably is late Maysvillian and early 

Richmondian in age (fig. 5).

The Tennessee Arnheim varies from 10 to 20 ft thick 

around the northern and western flanks of the Nashville 

dome. It consists of four facies, which intergrade laterally and vertically: (1) massive-bedded, argillaceous, 

rubbly limestone, (2) thin-bedded, nodular, blue-gray 

limestone, (3) cherty, argillaceous, blue-gray limestone, 

and (4) gray shale. The unit is very fossiliferous, the 

fauna being dominated by brachiopods.

In most places the lowermost Arnheim is a basal 

conglomerate that lies on a red, iron-stained contact with 

the underlying Leipers Formation. In some areas the
MIDDLE AND UPPER ORDOVICIAN SYMMETRICAL UNIVALVED MOLLUSKS, CINCINNATI ARCH REGION 013

Arnheim is overlain by a massive-bedded, calcareous 

mudstone tongue of the Sequatchie Formation, rather 

than by the Fernvale Limestone.

Fernvale Limestone. The Fernvale Limestone typically consists of massive- or irregularly bedded, very 

coarsely crystalline, gray limestone containing varicolored grains. In some places, thin, wavy, lenticular beds 

can be discerned within the massive beds. In some areas, 

the unit becomes ferruginous or phosphatic.

The Fernvale generally overlies either the Arnheim or 

Leipers unconformably, but it overlies a tongue of the 

Sequatchie Formation where the latter is present. The 

formation grades eastward into the Sequatchie Formation. Brachiopods, particularly Rhynchotrema capax, 

dominate the moderately common fossil assemblage. The 

Fernvale is early Richmondian in age (fig. 5).

MIDDLE ORDOVICIAN LITHOSTRATIGRAPHY 

OF KENTUCKY

The Middle Ordovician strata of Kentucky are exposed 

around the flanks of the Jessamine dome. The section 

includes the High Bridge Group (BlackriveranKirkfieldian) and the Lexington Limestone (KirkfieldianShermanian). In different areas, the Clays Ferry Formation, Kope Formation, and Lexington Limestone 

straddle the Middle-Upper Ordovician boundary (Pojeta, 

1979, p. A14) (fig. 5). Cressman (1973) and Cressman and 

Noger (1976) provided comprehensive reviews of the 

Middle Ordovician lithostratigraphy of Kentucky.

HIGH BRIDGE GROUP

The carbonate rocks of the High Bridge Group range 

from 550 to 700 ft thick. The High Bridge Group is 

divided into three formations, which are, in ascending 

order, the Camp Nelson Limestone, Oregon Formation, 

and Tyrone Limestone. These are the oldest strata 

exposed in Kentucky. They crop out in the gorge carved 

by the Kentucky River across the Jessamine dome. The 

thickest exposed section of the High Bridge Group is in 

this gorge, and measures 440 ft in thickness. The lower 

part of the Camp Nelson Limestone is known only from 

drill cores.

Cressman and Noger (1976) and Kuhnhenn, 

Grabowski, and Dever (1981) have described the carbonate rocks of the High Bridge Group. They interpreted 

the depositional environments of the group as being 

analogous to the shallow subtidal, intertidal, and supratidal facies of the modern Bahama Islands. Peritidal 

carbonates dominate in a series of shallowing upward 

cycles resulting from constantly migrating environments 

on a stable cratonic platform. Cressman and Noger 

(1976, p. 9-13) compared the High Bridge Group with

other correlative carbonate sequences in Alabama, 

Arkansas, New York, and Ontario. They concluded that 

the High Bridge Group was part of a vast complex of 

tidal flats and associated environments that extended 

over much of the craton of Eastern North America 

during Blackriveran-Rocklandian time. The High Bridge 

Group of central Kentucky is directly correlative with 

the Stones River Group of central Tennessee (Sweet and 

Bergstrom, 1976, text-fig. 3; Pojeta and Repetski, 1982, 

col. 58) (figs. 5, 6).

Camp Nelson Limestone.—The Camp Nelson Limestone is the lowermost formation in the High Bridge 

Group. It unconformably overlies the Whiterockian-age 

Wells Creek Dolomite in the subsurface (Sweet and 

Bergstrom, 1976, text-fig. 3) and is conformable with the 

overlying Oregon Formation. The Camp Nelson is composed of micrite, pelmicrite, and biopelmicrite (Cressman and Noger, 1976, p. 1). Burrows are common 

throughout most of the unit, and many are dolomitized 

selectively.

Most of the Camp Nelson represents shallow subtidal 

environments, with subordinate peritidal deposits. Some 

biomicrites have a diverse fauna of ostracodes, trilobites, 

brachiopods, corals (Tetradium), bryozoans, pelecypods, 

and nautiloids. The peritidal carbonates display algal 

laminae, fenestral fabric, intraformational conglomerates, and mud cracks. The two types of carbonates are 

arranged in shallowing-upward cycles. These cycles are 

thicker than those in the two overlying formations.

Oregon Formation.—The Oregon Formation ranges 

from 6 to 65 ft thick. It is composed mainly of a finely 

crystalline dolomite that is interbedded with micritic 

limestone. The contacts with the adjacent limestone 

formations are placed at the base of the lowest dolomite 

bed and the top of the highest dolomite bed.

Peritidal depositional environments in repeated 

shallowing-upward cycles characterize the formation. 

Biopelsparites contain fragments of crinoids, bryozoans, 

brachiopods, ostracodes, and tabulate corals. Biomicrites 

have a more restricted fauna of ostracodes, gastropods, 

and some trilobites and tabulate corals. Peritidal carbonates, which predominate, have cryptalgalaminated and 

thin-bedded dolostones with desiccation features and 

some intraclastic layers (Kuhnhenn and others, 1981).

Dolomite is much more abundant in the Oregon Formation than in the Camp Nelson or Tyrone Limestone. 

Kuhnhenn, Grabowski, and Dever (1981, p. 9) suggested 

that the Oregon sediments were more exposed as parts 

of low, broad islands. They believed the dolomite is 

diagenetic in origin, because lithologies in the Oregon do 

not differ significantly from those of the Tyrone Limestone.

Tyrone Limestone.—The Tyrone Limestone is 55 to 

155 ft thick, the thickness varying in complement with
014 CONTRIBUTIONS TO THE ORDOVICIAN PALEONTOLOGY OF KENTUCKY AND NEARBY STATES

SOUTH CENTRAL KENTUCKY NORTH

^— —^ g-— - ^

c- —— — ______ ^^

Clays herry hormation ^__^ ____—--- — S

\ ^> \ — — — —^ i — —— -* \

f . . > P> Devils Hollow Member^

Sulphur Well Member <- ——————————————— -^

<; Tanglewood

Brannon Member <^ ————————————— x Limestone ^? Brannon Member c— —— ;

^ Member ^ ———— ^^

Perryville Limestone C^ \

Member <s, \

, ————— ^ \

\

•s

s

s

^ \

s

Curdsville Limestone Member

Millersburg Member

^_____--- — •"""' <~~~^^

Tanglewood 

Limestone Member />

Logana Member

i

FIGURE 11. Fades relationships between the major members of the Lexington Limestone and the Clays Ferry Formation in central Kentucky

(modified from Cressman, 1973, and his unpublished figure).

the thinning of the Oregon Formation, with which it 

intertongues in its lower part. The Tyrone is conformable 

with the underlying Oregon but is disconformable with 

the overlying Lexington Limestone (Cressman, 1973, p. 

12, 13). The limestones of the Tyrone are biopelsparites, 

biomicrites, and peritidal micrites, similar to the rocks of 

the underlying Oregon Formation but with less dolomite. 

Just as in the lower High Bridge strata, the Tyrone 

carbonates are arranged in shallowing-upward cycles. 

These cycles become shorter and simpler in the upper 

part of the Tyrone (Kuhnhenn and others, 1981, p. 5). 

Greene (1966) listed a mainly molluscan fauna dominated 

by gastropod species. In addition, the Tyrone contains 

Tetradium thickets and pelecypod, nautiloid, and polyplacophoran mollusks.

LEXINGTON LIMESTONE

The Lexington Limestone is a complex facies mosaic of 

mostly bioclastic and fossiliferous limestones cropping 

out around the Jessamine dome in central Kentucky (fig. 

11). Sweet and Bergstrom (1976, text-fig. 3) and Sweet 

(1979, p. G13) assigned a Kirkfieldian-Edenian age to the 

unit (fig. 5).

Black, Cressman, and MacQuown (1965) redefined the 

formation to include all strata formerly assigned to the 

Lexington Limestone and the Cynthiana Formation

(McFarlan, 1943; McFarlan and White, 1948; Nosow and 

McFarlan, 1960), with the exception of the Cynthiana 

beds placed in the Clays Ferry Formation by Weir, 

Greene, and Simmons (1965). The mainly bioclastic and 

fossiliferous limestones of the Lexington contrast greatly 

with the mainly micritic Tyrone limestones below and the 

interbedded shales and limestones of the Clays Ferry 

Formation above.

The Lexington Limestone unconformably overlies the 

Tyrone Limestone. Cressman (1973, p. 12, 13) demonstrated at least 10 ft of erosional relief on the Tyrone 

Limestone, over which the Curdsville Limestone Member of the Lexington Limestone transgressed, but he felt 

that the time gap represented was small.

The contact between the Lexington Limestone and the 

overlying Clays Ferry Formation is conformable and 

diachronous because of intertonguing (figs. 5, 11). The 

Lexington is up to 320 ft thick in its central outcrop area, 

but it thins to less than 200 ft to the north and south 

because of intertonguing of the upper members of the 

Lexington Limestone with the shale and limestone of the 

Clays Ferry Formation. Silicified fossil horizons are 

common in the Lexington Limestone, and the majority of 

silicified fossils studied here were collected from this unit 

by the USGS. Cressman (1973) presented an excellent 

detailed lithostratigraphic study of the Lexington Limestone. The following descriptions of the members of the
MIDDLE AND UPPER ORDOVICIAN SYMMETRICAL UNIVALVED MOLLUSKS, CINCINNATI ARCH REGION 015

Lexington Limestone are taken primarily from that 

report.

Curdsville Limestone Member.—The Curdsville 

Limestone Member is the basal unit in the Lexington 

Limestone (fig. 11). The contact with the underlying 

Tyrone Limestone is an erosional unconformity. The 

member ranges from about 20 to 40 ft thick, thinning 

westward owing to facies gradation into the Logana 

Member. The Curdsville is overlain by the Logana 

Member in the central and northern outcrop areas, and 

by the Grier Limestone Member to the south.

MacQuown (1967) divided the Curdsville into three 

informal units, which are gradational at their contacts. 

The lower 10-ft-thick unit is light-colored bioclastic limestone that consists of calcirudites, and crossbedded and 

ripple-marked calcarenites. The lower unit is composed 

of well-sorted, abraded skeletal debris having about 5 to 

10 percent quartz sand. The middle unit is present from 

10 to 20 ft above the base of the member and consists of 

bioclastic calcarenite and calcirudite interbedded with 

calcisiltite and shale. The upper unit consists of mediumgray, irregularly bedded, fossiliferous limestone and 

bioclastic calcarenite. Cressman (1973, p. 14) interpreted 

this sequence as recording a marine transgression, with 

higher energy, shallow-water deposits grading upward 

into lower energy deposits. The close interbedding 

between calcirudite, calcarenite, calcisiltite, and minor 

shales probably represents small migrating bars separated by intervening low areas.

Logana Member.—The Logana Member reaches 50 ft 

thick in the northern outcrop area and thins southward, 

where it intertongues with the underlying Curdsville and 

overlying Grier Limestone Members (fig. 11). The member consists of interbedded dark calcisiltite and shale in 

nearly equal proportions. The calcisiltite is generally 

argillaceous, is in broad lensing beds about 0.2 to 0.3 ft 

thick, and in many places has a petroliferous odor. The 

interbedded shales are brownish gray, fissile, calcareous, and partly dolomitic.

Most beds are unfossiliferous, but silicified mollusks 

and brachiopods are common in some places. Dalmanellid 

brachiopods can occur as coquinas, or can coat upper and 

lower bed surfaces, with pelecyods closely packed in the 

bed interior. Cressman (1973, p. 17) believed that the 

Logana was deposited at the height of the initial Lexington transgression, and that its facies relationship with 

the Curdsville and Grier Limestone Members reflects a 

deepening of water to the north. The dark color, even 

tabular bedding, and general sparsity of fossils or burrows in the Logana suggest deeper water, quiet conditions, and poor oxygenation.

Grier Limestone Member.—The Grier Limestone 

Member consists predominantly of thin- and irregularly 

bedded to nodular-bedded, poorly sorted, fossiliferous

limestone. It ranges in thickness from 100 to 180 ft, the 

variation resulting mainly from intertonguing of the 

lower part with the Logana Member and the upper part 

with the Tangle wood Limestone Member (fig. 11).

Through the northern outcrop area, the Grier conformably overlies the Logana Member, and in the southern area it has a gradational contact through 10 to 15 ft 

with the Curdsville Limestone Member. Through most of 

central Kentucky, the Grier is overlain by the calcarenites of the Tanglewood Limestone Member, the two 

members complexly intertonguing, but in the southcentral outcrop area it is overlain by the calcisiltite and 

shale of the generally unfossiliferous Brannon Member

(fig. IDThe most common bedding assemblage in the Grier 

Limestone Member consists of sets, about 0.5 ft thick, of 

nodular-bedded, fossiliferous calcisiltite to very poorly 

sorted, fossiliferous calcarenite with minor shale partings, alternating with slightly irregular, 0.4-ft-thick beds 

of poorly sorted, fossiliferous calcarenite. Brachiopods 

and bryozoans are the most conspicuous fossils, but 

gastropods are common in some calcisiltites, and ostracodes, crinoids, pelecypods, and trilobites are also 

present. This member apparently was deposited in shallow, well-aerated, moderately agitated water of normal 

salinity. The nodular bedding is probably due to the 

activity of burrowing organisms. Cressman (1973, p. 19) 

estimated that the member was deposited in water 50 ft 

or less deep.

Perryville Limestone Member.—Cressman (1973, p. 

23) defined the Perryville Limestone Member as the beds 

lying between the calcarenite of the Tanglewood Limestone Member below and the interbedded calcisiltite and 

shale of the Brannon Member above, in the southwestern 

part of the Lexington Limestone outcrop area (fig. 11).

The Perryville has been divided into three units. The 

basal unit, called the Faulconer Bed, consists of 40 ft of 

brownish-gray, fossiliferous, micritic limestone. Beds 

are about 0.5 ft thick, have rough surfaces, and show 

nodular internal structure upon weathering. The fauna of 

the Faulconer Bed consists of ostracodes, pelecypods, 

gastropods, brachiopods, bryozoans, crinoids, colonial 

corals, and stromatoporoids. The fossils show little 

breakage or abrasion, and no obvious sorting or orientation, and many are coated by encrusting algae (probably 

Girvanelld).

The middle unit of the Perryville, called the Sal visa 

Bed, consists of 10 to 15 ft of interbedded light-gray to 

light-olive-gray micritic limestone and brownish-gray 

micritic limestone. Fossils are sparse in most places but 

may be abundant locally (for example, USGS 5015-CO, 

appendix); ostracodes are most common, and gastropods 

and pelecypods are scattered. The matrix is largely 

pelletal and is burrowed in many places.
016 CONTRIBUTIONS TO THE ORDOVICIAN PALEONTOLOGY OF KENTUCKY AND NEARBY STATES

The upper unit, the Cornishville Bed, is 2 to 10 ft thick 

and consists of mostly nodular bedded calcisiltite and 

fine-grained calcarenite containing abundant brachiopods and some bryozoans. The unit resembles the Grier 

Limestone Member and may be a tongue of that unit 

(Cressman, 1973, p. 28).

The Faulconer Bed was deposited in shallow, quiet 

water of normal marine salinity. The Salvisa Bed was 

deposited under quiet, perhaps more hypersaline conditions, as indicated by its more restricted fauna. The 

Cornishville Bed was deposited in an environment similar to that of the Grier Limestone Member (Cressman, 

1973).

Tanglewood Limestone Member.—The Tanglewood 

Limestone Member is an extensive irregular body of 

bioclastic calcarenite that completely intertongues with 

other members of the upper Lexington Limestone and 

the Clays Ferry Formation (fig. 11). It is typically a 

crossbedded, phosphatic, pinkish-gray, medium-grained, 

well-sorted, bioclastic calcarenite in which whole fossils 

or large fossil fragments are rather uncommon. The unit 

ranges in thickness from 60 to 100 ft, the variation due to 

intertonguing with other members. The calcarenite consists largely of bryozoan, brachiopod, and crinoid fragments that are thought to have been transported from 

adjacent sites of accumulation of the Grier Limestone 

and Millersburg Members.

Crossbedding is common in the Tanglewood calcarenites. Harbar, Cressman, and Potter (1971) found these 

crossbeds to be bimodal, and interpreted them to be the 

result of tidal currents. Cressman (1973, p. 31, 32) 

interpreted the Tanglewood calcarenite body as a bank 

that stood above surrounding areas of the sea floor, with 

tidal currents producing migrating sandbars.

Brannon Member.—The Brannon Member consists of 

about 30 ft of interbedded calcisiltite and shale. Throughout most of its area of exposure, it is both overlain and 

underlain by the Tanglewood Limestone Member. In 

other areas, the Brannon lies on the Grier or Perryville 

Limestone Member, and is overlain by the Sulphur Well 

Member (fig. 11).

The interbedded calcisiltite and shale of the Brannon 

are present in nearly equal proportions, so that the 

member closely resembles the Logana Member. The 

calcisiltite is medium to light gray and generally occurs in 

smooth-surfaced tabular beds about 0.2 to 0.3 ft thick. 

The shale is calcareous and medium to dark gray. Fossils 

are sparse in the unit and less abundant than in the 

Logana Member; however, thin-shelled brachiopods are 

present on some bedding surfaces.

The Brannon weathers to a clayey soil containing 

abundant chert. Campbell (1898) placed the Brannon 

beds in what he called the Flanagan Chert because of the 

cherty float in residuum derived from this unit. McFarlan and White (1948, p. 1636) stated that the Flanagan 

Chert was mainly included in the Brannon Member. 

Recognizing what was meant by the term "Flanagan 

Chert" in the modern stratigraphic scheme is important 

because numerous type specimens of bellerophontids 

described by Ulrich and Scofield (1897) were cited as 

coming from that unit. Apparently, silicified beds at 

many different stratigraphic levels were erroneously 

called the Flanagan Chert. No monoplacophorans or 

bellerophontaceans were present in USGS silicified samples from the Brannon Member.

The Brannon apparently was deposited in an environment similar to that of the Logana Member, that is, in 

quiet water below wave base, where bottom conditions 

were generally inhospitable for life (Cressman, 1973, 

p. 37).

Sulphur Well Member.—The Sulphur Well Member 

consists of about 35 ft of mostly poorly sorted bryozoan 

calcirudite having a clay and silt-rich, calcitic to dolomitic 

matrix. Beds are lenticular and irregular, a few inches 

thick generally, and are separated by thin shale partings. 

Bryozoans are found throughout the unit, but are most 

abundant on bedding surfaces. Brachiopods are fairly 

common in some places.

The Sulphur Well Member in all places has a sharp 

planar contact with the underlying unit, which may be 

the Brannon, Tanglewood Limestone, or Grier Limestone Member (fig. 11). It is overlain by the Clays Ferry 

Formation, this contact being either sharp or gradational. Cressman (1973, p. 37) stated that the Sulphur 

Well and Grier Limestone Members were deposited 

under similar environmental conditions, that is, in moderately agitated, normal marine waters slightly below 

wave base.

Stamping Ground Member.—This member consists of 

about 15 ft of fossiliferous nodular limestone that apparently is entirely surrounded by the Tanglewood Limestone Member. The brachiopod Rhynchotrema, which is 

commonly silicified, is the most conspicuous fossil in the 

unit. At many localities, stromatoporoids are present 

directly above the Stamping Ground Member in the basal 

Tanglewood Limestone Member. Cressman (1973, p. 39) 

suggested that the environment of deposition was similar 

to that of the Millersburg Member, that is, shallow, 

moderately turbulent, normal marine water.

Greendale Lentil.—This unit is a 10- to-15-ft thick 

lentil surrounded entirely by the Tanglewood Limestone 

Member. It consists of 75 percent limestone and 25 

percent shale. Bedding sets 0.2 to 1.5 ft thick consist of 

olive-gray to light-gray, fossiliferous, argillaceous calcisiltite in nodular beds separated by irregular shale 

partings and thin shale beds that alternate with 0.2- to 

0.5-ft thick irregular beds of light-gray, coarse-grained, 

fossiliferous calcarenite. This lentil is restricted to parts
MIDDLE AND UPPER ORDOVICIAN SYMMETRICAL UNIVALVED MOLLUSKS, CINCINNATI ARCH REGION 017

of the Georgetown and Lexington West quadrangles, in 

the area immediately northwest of Lexington, Ky.

Devils Hollow Member.—The Devils Hollow Member 

was described (McFarlan and White, 1948, p. 1640) at its 

type locality as consisting of 15 ft of coarse-grained, 

gastropod coquina overlain by 10 ft of micritic limestone 

containing ostracodes (resembling the Tyrone Limestone). These two rock types intertongue, and at some 

localities only one of the two types is present. The 

member is underlain conformably by the Tanglewood 

Limestone Member, and is overlain conformably by the 

Tanglewood calcarenites or by the nodular, fossiliferous, 

shaly limestone of the Millersburg Member (fig. 11).

The gastropod coquina is a coarse biosparite crowded 

with specimens of such species as Sphenosphaera troosti, 

Tropidodiscus subacutus, and Lophospira medialis 

(McFarlan and White, 1948, p. 1637). Locally, the 

coquina may be composed of brachiopods rather than 

gastropods; in either instance, the fossils may be silicified. The micritic limestone contains only ostracodes 

and sparse gastropods and pelecypods, which may be 

silicified.

The Devils Hollow Member seems to represent very 

shallow subtidal to intertidal environments of deposition, 

because sedimentary structures characteristic of tidal 

flats (that is, mud cracks, intraformational breccia) are 

not present in the micritic limestones. Cressman (1973, 

p. 41) suggested that these beds were deposited in 

shallow restricted lagoons of higher than normal salinity. 

The gastropod coquinas were bar and (or) beach deposits 

directly associated with these lagoons.

Millersburg Member. The Millersburg Member is a 

0- to 90-ft-thick body of nodular- and irregularly bedded, 

fossiliferous limestone and shale that completely intertongues with the Tanglewood Limestone Member and 

the overlying Clays Ferry Formation (fig. 11). The 

Millersburg limestone is gray to brownish gray and 

nodular bedded. It consists of whole and broken fossils in 

a silt- to clay-sized carbonate matrix. Shale makes up 

about one-third of the member. Characteristically, the 

Millersburg appears as limestone nodules several inches 

in diameter aligned along bedding and set in a matrix of 

calcareous shale. The nodular beds alternate with irregular beds of poorly sorted calcarenite. Both fragments 

and whole fossils of bryozoans, brachiopods, mollusks, 

and trilobites are abundant, and scattered stromatoporoids and colonial corals are present in several horizons.

The Millersburg is similar in lithology, bedding, and 

gross fossil content to the Grier Limestone Member, but 

it contains a greater proportion of shale. Both were 

deposited in shallow, well-aerated, moderately agitated, 

normal marine waters probably less than 15 m (meters) 

deep (Cressman, 1973, p. 43). The nodular bedding is 

probably due to active burrowing. The high shale content

of the Millersburg is the result of the increased supply of 

terriginous sediment to the area during latest Middle 

Ordovician time, which is also reflected in the composition of the intertonguing Clays Ferry Formation.

UPPER ORDOVICIAN LITHOSTRATIGRAPHY OF

KENTUCKY, SOUTHWESTERN OHIO,

AND SOUTHEASTERN INDIANA

The tristate area surrounding Cincinnati, Ohio (OhioIndiana-Kentucky), exposes the type section for the 

Upper Ordovician (Cincinnatian Series) of North America. Traditionally, the Cincinnatian Series has been 

divided into three groups, which are now considered 

stages (fig. 12). These are, in ascending order, the 

Edenian, Maysvillian, and Richmondian Stages. The 

history of lithostratigraphic nomenclature for this region 

is extremely complex. Excellent summaries of this history have been given by Gutstadt (1958), Weiss and 

Norman (1960), and Weir and others (1984).

Throughout much of this century the basic stratigraphic scheme outlined by Patton, Perry, and Wayne 

(1953) and Caster, Dalve, and Pope (1955) has been used 

throughout the tristate region (fig. 12). However, more 

recent work has demonstrated that many of these traditional units were based more on paleontologic parameters than on lithologic parameters. Therefore, numerous 

new lithostratigraphic names have been proposed. These 

new classifications apply more or less to the three 

adjacent geographic areas: central Kentucky, southeastern Indiana, and southwestern Ohio-northern Kentucky 

(fig. 12). The change in nomenclature from central Kentucky to northern Kentucky and southwestern Ohio 

seems well warranted because of facies changes. The 

change in nomenclature in southeastern Indiana is due 

more to the crossing of State borders than to any change 

in the character of the strata. The application of some 

names coined for strata in northern Kentucky to strata in 

southwestern Ohio has not been satisfactorily confirmed 

by mapping in Ohio, but the general scheme seems to 

work (Gordon Weir, written commun., 1977). As is 

discussed below, some workers do not agree with this 

extention of the Kentucky nomenclature.

In central Kentucky, Upper Ordovician strata crop out 

around the perimeter of the Jessamine dome, outlining 

the Middle Ordovician strata previously discussed. 

Nearly all of the Ordovician strata to the north in the 

tristate area are Late Ordovician in age; exceptions are 

some exposures of the Point Pleasant Tongue of the 

Clays Ferry Formation along the Ohio River Valley.

The revision of stratigraphic nomenclature in these 

areas began in the early 1960's. Weiss and Sweet (1964) 

renamed the Eden Shale of northern Kentucky and
018 CONTRIBUTIONS TO THE ORDOVICIAN PALEONTOLOGY OF KENTUCKY AND NEARBY STATES

CINCINNATIAN LITHOSTRATIGRAPHIC UNITS

SERIES

CINCINNATIAN

STAGES

Richmondian

Maysvillian

Edenian

OHIO-INDIANA-KENTUCKY 

(Caster, Dalve, and Pope, 1955)

Formations

Elkhorn

U. Whitewater

Saluda

L. Whitewater

Liberty

Waynesville

Arnheim

McMillan 

Formation

Fairview 

Formation

Latonia 

Formation

Members

Blanchester

Clarkesville

Ft. Ancient

Oregonia

Sunset

Mt. Auburn

Corryville

Bellevue

Fairmount

Mt. Hope

McMicken

Southgate

Economy

SOUTHEAST 

INDIANA

(Brown and 

Lineback, 1966)

Whitewater 

Formation

Saluda Formation

Dillsboro 

Formation

Kope 

Formation

SOUTHWEST 

OHIO

(Weiss and Sweet, 

1964; Ford, 1967)

Unnamed 

Units

Bellevue 

Limestone

Miamitown Shale

Fairview 

Formation

Kope 

Formation

NORTHERN 

KENTUCKY

(Peck, 1966)

Drakes 

Formation

Bull 

Fork 

Formation

Grant 

Lake 

Limestone

Fairview 

Formation

Kope 

Formation

SOUTHCENTRAL 

KENTUCKY

(Weir and 

others, 1965)

Formation Drakes 

Ashlock Formation

Preachersville 

Member

Rowland 

Member

Reba Member

Terrill Member

Gilbert 

Member

Stingy Creek 

Member

Tate 

Member

Galloway 

Creek 

Limestone

Garrard 

Siltstone

Clays 

Ferry 

Formation

CENTRAL 

TENNESSEE

(Wilson, 1949)

Fernvale 

Formation _ /-

"Arnheim" 

Formation

Leipers 

Formation

Inman 

Formation

Catheys 

Formation

FIGURE 12. Cincinnatian lithostratigraphic units in Ohio, Indiana, Kentucky, and central Tennessee.

southwestern Ohio, calling it the Kope Formation (fig. 

12). They argued that the term Eden has a stadial 

connotation.

In south-central Kentucky, Weir and Greene (1965) 

named the Clays Ferry Formation to replace the Edenian faunally based units such as the Cynthiana Formation 

and Million Shale, and retained usage of the late Edenian 

Garrard Siltstone. In the same area, Weir, Greene, and 

Simmons (1965) named the Galloway Creek Limestone, 

Ashlock Formation, and Drakes Formation for traditional Maysvillian and Richmondian units previously 

extended from the Cincinnati area on faunal bases 

(fig. 12).

Peck (1966) studied the Upper Ordovician strata in 

northern Kentucky along the eastern flank of the Cincinnati arch. He found it difficult to trace rock units above 

the Fairview Formation (early Maysvillian) from the 

type sections in the Cincinnati area to the Maysville, 

Ky., area. He concluded that these post-Fairview units 

had been previously identified in the Maysville area on 

faunal bases, and rejected the traditional units. He 

assigned strata previously called the Bellevue, Corryville, and Mt. Auburn Members of the McMillan Formation to the Grant Lake Limestone. Also, he assigned 

strata previously called the Arnheim, Waynesville, Liberty, and Whitewater Formations in that area to the Bull 

Fork Formation. Finally, Peck extended the Preachersville Member of the Drakes Formation (Weir and others, 

1965) from south-central Kentucky to the Maysville area 

for the uppermost Ordovician strata, which had previously been assigned to the Whitewater and Elkhorn 

Formations.

Ford (1967) mapped Ordovician strata in the southwestern corner of Ohio, on the western side of Cincinnati. He recognized the Kope Formation, Fairview Formation, Miamitown Shale, and Bellevue Limestone as 

mappable units in the area (fig. 12). He did not address 

stratigraphy above the Bellevue Limestone. Pojeta 

(1979, fig. 2) extended the use of the Bull Fork Formation for post-Bellevue units in southwestern Ohio.

Brown and Lineback (1966) revised the Upper Ordovician lithostratigraphy of southeastern Indiana (fig. 12). 

They recognized the Kope Formation and proposed the 

name Dillsboro Formation for "the sequence of highly
MIDDLE AND UPPER ORDOVICIAN SYMMETRICAL UNIVALVED MOLLUSKS, CINCINNATI ARCH REGION 019

fossiliferous argillaceous limestones and calcareous 

shales that lie between the shale of the Kope Formation 

and the dolomitic limestone of the Saluda Formation" (p. 

1020). They continued recognition of the Saluda Formation and the Whitewater Formation for the latest 

Richmondian-age strata of the area. Shaver and others 

(1970) supported this classification, as did Gray (1972), 

who placed all the Cincinnatian units in Indiana in the 

Maquoketa Group.

Hay, Pope, and Frey (1981) and Tobin (1982, 1986) 

have proposed Upper Ordovician lithostratigraphic classifications that apply to southwestern Ohio, southeastern 

Indiana, and adjacent northernmost Kentucky. Both 

classifications accept the Kope and Fairview Formations, and the Bellevue Limestone and Miamitown Shale 

as used by Ford (1967). However, the later Maysvillianand Richmondian-age strata are classified quite 

differently.

Hay, Pope, and Frey (1981) introduced the Brookville 

Formation for limestone and shale wedges between the 

Bellevue Limestone and Whitewater Formation. They 

recognized four new members, as well as the Waynesville Shale and Liberty Limestone of the traditional 

classification. However, this classification has been outlined only in a guidebook, and is not valid according to 

the rules of the Code of Stratigraphic Nomenclature.

Tobin (1982,1986) disagreed with the approach of most 

recent workers, who have chosen to combine the traditional stratigraphic units, which they believed to be 

faunally based, into larger units (for example, Brown and 

Lineback, 1966; Peck, 1966; Hay and others, 1981). 

Through references to original descriptions of the traditional stratigraphic units and extensive fieldwork, Tobin 

concluded that many of the traditional units were indeed 

valid. Tobin (1982, 1986) recognized three shallowingupward carbonate sequences in the Cincinnatian Series. 

These sequences are described below in ascending order.

Kope to Bellevue sequence. In this sequence, the 

Kope represents an offshore facies, the Fairview a 

transitional facies, and the Bellevue a shoreface facies.

Corryville to Oregonia sequence. In this sequence, 

the Corryville is an offshore facies, the Sunset is a 

transitional facies which contains the Mt. Auburn offshore bar facies, and the Oregonia is a shoreface facies.

Waynesville to Saluda sequence. In this sequence, 

the Waynesville Shale represents an offshore facies, the 

Liberty Limestone is a transitional facies, the Whitewater Formation is a shoreface facies, and the Saluda 

Formation dolomite represents restricted lagoonal, 

intertidal and supratidal facies.

Tobin (1982) recognized all of these facies as formations. He stated that these facies built eastward down 

the paleoslope toward the Appalachian Basin. The diachronous nature of the Cincinnatian units had been demonstrated previously by conodont studies (Sweet, 1979, 

fig. 3). Viewing the Cincinnatian Series in this way is a 

significant step toward understanding this important 

type section.

The most modern recognized stratigraphic classifications are used herein (fig. 12). The lithostratigraphy of 

Weir and Greene (1965) and Weir, Greene, and Simmons 

(1965) are used for south-central Kentucky. The units of 

Peck (1966) are used for north-central Kentucky. The 

units of Ford (1967) and Peck (1966) are used for southwestern Ohio and adjacent northernmost Kentucky. 

Weir and others (1984) documented and summarized the 

Upper Ordovician stratigraphy of Kentucky. The classification of Brown and Lineback (1966) is used for southeastern Indiana. The distribution of these stratigraphic 

units in the tristate area is shown in figure 5.

The revision of the traditional Cincinnatian lithostratigraphic classification seems to have been warranted in 

most cases. However, the complete abandonment of the 

traditional units seems unwise. The paleontological and 

paleoecological knowledge accumulated through years of 

work in this type section is based on the traditional 

classification. If this wealth of data is to be retained and 

used effectively in both understanding the type section 

and extrapolating to other areas, the traditional units 

must be retained in some form. Therefore, these traditional units are used herein as informal biofacies units. 

For example, in this paper, Cyrtolites (Cyrtolites) hornyi n. sp. is said to come from the Liberty biofacies of the 

Dillsboro Formation in southeastern Indiana.

The lithostratigraphy of the tristate region is 

described in three sections: south-central Kentucky, 

north-central Kentucky and southwestern Ohio, and 

southeastern Indiana. Formations are considered in 

ascending order for each area within the region.

UPPER ORDOVICIAN LITHOSTRATIGRAPHY OF 

SOUTH-CENTRAL KENTUCKY

As a result of the joint U.S. Geological SurveyKentucky Geological Survey mapping program of the 

State of Kentucky, Weir and Greene (1965) and Weir, 

Greene, and Simmons (1965) completely revised the 

Upper Ordovician lithostratigraphic classification for 

south-central Kentucky (fig. 12). Weir and others (1984) 

documented and summarized previous work. Except 

where noted, the descriptions given below are drawn 

from those works.

CLAYS FERRY FORMATION

The Clays Ferry Formation was named by Weir and 

Greene (1965) to encompass strata previously included in 

the Cynthiana Formation, Fulton Shale, and Million 

Shale as used by Foerste (1906) and Palmquist and Hall
020 CONTRIBUTIONS TO THE ORDOVICIAN PALEONTOLOGY OF KENTUCKY AND NEARBY STATES

(1961). This 120 to 220 ft of interbedded limestone and 

shale straddles the Middle-Upper Ordovician boundary 

(fig. 5). To the south it intertongues with the upper 

members of the Lexington Limestone, but to the north it 

becomes younger and intertongues with the shales of the 

Kope Formation in north-central Kentucky (figs. 5, 11).

Limestone makes up 30 to 60 percent of the Clays 

Ferry Formation. Beds are even and 1 to 6 in thick. The 

limestone varies from medium- to dark-gray, argillaceous calcisiltite to medium-gray brachiopodal limestone 

to medium-gray crinoidal calcarenite. The calcisiltite is 

sparsely fossiliferous and contains mainly crinoidal fragments and some gastropods. The brachiopodal limestone 

is characterized by abundant Rafinesquina, some of 

which are shingled, as well as by Sowerbyella and 

Dalmanella, all packed in a mud matrix. Bryozoans are 

also common.

Shale makes up 30 to 60 percent of the formation. It is 

generally greenish to olive gray, and is present in 

distinctly laminated sets 1 to 12 in thick. Fossils generally are sparse in these shales, though bryozoans are 

common at some locations.

Siltstone makes up 5 to 10 percent of the unit, occurring mainly in the upper part. It is present mostly in 1- 

to 3-in even beds in which fossils are sparse. This 

lithology resembles the Garrard Siltstone, which overlies 

the Clays Ferry in south-central Kentucky.

Point Pleasant Tongue.—Along the Ohio River Valley, the Lexington Limestone and Kope Formation are 

separated by 100 ft of limestone and shale interbedded in 

nearly equal proportions (fig. 5). This unit's even bedding 

and regular interbedding of limestone and shale are 

reminiscent of the Clays Ferry Formation, but in the 

upper part are beds as thick as 10 ft that consist of 

crossbedded calcarenite.

This unit has a complex nomenclatural history. Until 

recently it had been assigned to the Cynthiana Formation, but the USGS mapped it as the Point Pleasant 

Formation (Weiss and others, 1965; Cressman, 1973). 

Now the unit is considered the Point Pleasant Tongue of 

the Clays Ferry Formation (Swadley, 1975), and is 

correlated with the upper Lexington Limestone and 

lower Clays Ferry (Cressman, 1973; Sweet, 1979, fig. 3). 

It is overlain by the Kope Formation.

Cressman (1973, p. 45) suggested that the finer 

grained, less fossiliferous parts of the Clays Ferry Formation were deposited in quiet water at least 80 ft deep, 

similar to the depositional environments of the Logana 

and Brannon Members of the Lexington Limestone. The 

more fossiliferous parts of the formation probably were 

deposited at shallower depths, but currents were never 

strong enough to remove fine elastics or to break up the 

skeletal material effectively. The Point Pleasant Tongue 

was, at least in its upper portion, a much shallower

facies, with thick crossbeds indicating rather high energy 

conditions. It is noteworthy that these upper Point 

Pleasant beds are directly overlain by Kope shales 

characterized by a trilobite-crinoid fauna. This situation 

apparently reflects a rapid transgression at the end of 

Point Pleasant deposition.

GARRARD SILTSTONE

The Garrard Siltstone is a 10- to 100-ft-thick unit of 

chiefly limy siltstone with minor thin lenses of mudstone 

and limestone. Most beds are 6 to 24 in thick, and many 

are laminated. Ball-and-pillow structures are common. 

Fossils, except for brachiopods, are scarce in the thin 

limestone lenses. Bryozoans are also known in the unit.

The Garrard is late Edenian in age, correlating with 

the upper Kope Formation to the north (figs. 5, 12). It is 

conformable with the underlying Clays Ferry Formation 

and overlying Galloway Creek Limestone. Ford (1968, p. 

1784) suggested that the northward decrease in grain 

size from the Garrard to the Kope implied tectonic 

control of sedimentation from a southerly source.

GALLOWAY CREEK LIMESTONE

This early Maysvillian-age unit ranges from 80 to 130 ft 

thick in south-central Kentucky. It consists of 70 to 

80 percent fine- to medium-grained, thin-bedded, gray 

limestone, 15 to 25 percent greenish-gray calcareous 

shale, and about 5 percent calcareous siltstone. Fossils 

are abundant, with brachiopods and bryozoans most 

conspicuous.

The Galloway Creek Limestone is transitional with 

both the underlying Garrard Siltstone and the overlying 

Ashlock Formation (figs. 5, 12). It grades northward into 

the Fairview Formation, which is similar in lithologic and 

faunal character but is much thicker bedded.

ASHLOCK FORMATION

The Ashlock Formation is a 125- to 145-ft-thick unit of 

late Maysvillian and early Richmondian age in southcentral Kentucky (figs. 5, 12). Weir, Greene, and Simmons (1965) divided the formation into five members, 

which are described in ascending order below.

Tate Member.—The Tate was originally described by 

Foerste (1912) as a member of the McMillan Formation. 

This 30- to 80-ft-thick unit consists of greenish-gray, 

laminated to thin-bedded, sparsely glauconitic, calcareous to dolomitic mudstone that commonly grades into an 

argillaceous limestone at the top. Fossils are uncommon, 

except for a silicified brachiopod-bryozoan assemblage in 

the Back Bed, a coarse-grained, silty limestone present 5 

to 15 ft above the base of the member. This member 

belongs to Weir and Peck's (1968, p. 168) dolomitic
MIDDLE AND UPPER ORDOVICIAN SYMMETRICAL UNIVALVED MOLLUSKS, CINCINNATI ARCH REGION 021

mudstone lithofacies, which was thought to have been 

deposited in very shallow, quiet, subtidal to tidal flat 

environments.

Stingy Creek Member.—This term replaced the name 

"Mt. Auburn Member of the McMillan Formation" in 

south-central Kentucky. The Stingy Creek is a 5- to 

15-ft-thick unit of gray limy siltstone and silty limestone 

that is obscurely thin bedded and contains an abundance 

of brachiopods and bryozoans. This member belongs to 

Weir and Peck's (1968) nodular-bedded, fossiliferous 

limestone and mudstone lithofacies, which was deposited 

under somewhat higher energy conditions than was the 

Gilbert Member, possibly in wave-agitated shoals on a 

sloping shelf.

Gilbert Member.—The Gilbert was also recognized by 

Foerste (1912) as a member of the McMillan Formation. 

It consists of bluish- to olive-gray, fine- to mediumgrained limestone occurring in thin, wavy beds. A 

brachiopod-bryozoan fauna is common and well preserved. The unit is 10 to 20 ft thick. The limestone beds, 

each a few inches thick, are generally separated by gray 

limy siltstone partings less than 1 in thick. This member 

belongs to Weir and Peck's (1968) micrograined limestone lithofacies, which was deposited in shallow, quiet 

lagoons.

Terrill Member.—This term replaced the name "Sunset Member of the Arnheim Formation." The unit consists mainly of greenish-gray, laminated, limy or dolomitic mudstone. Bedding surfaces characteristically 

display ripple marks and mud cracks, and fossils are 

rare. However, the basal few feet of the 5- to 15-ft-thick 

member commonly contains a rich brachiopod-bryozoan 

fauna. The Terrill belongs to Weir and Peck's (1968) 

dolomitic mudstone lithofacies, which was probably 

deposited mainly on broad tidal flats.

Reba Member.—This unit was previously known as 

the Oregonia Member of the Arnheim Formation in 

south-central Kentucky. The 10- to 25-ft-thick member is 

made up of a basal micrograined limestone overlain by 

medium-grained limestones that become more silty and 

argillaceous near the top. The basal unit is essentially 

barren of fossils, except for some ostracodes and trace 

fossils. The overlying thin-bedded limestones contain a 

fairly abundant brachiopod-bryozoan fauna. This member belongs to the same lithofacies as the Stingy Creek 

Member.

DRAKES FORMATION

Weir, Greene, and Simmons (1965, p. 16) named the 

Drakes Formation for Richmondian-age strata in southcentral Kentucky formerly called the Waynesville, Liberty, and Whitewater beds (fig. 12). The formation 

consists of 120 to 150 ft of grayish-green, dolomitic or 

calcareous, silty mudstone to argillaceous, finely crystalline dolomite or dolomitic limestone.

On the southern and eastern sides of the Lexington 

dome in central Kentucky, the formation is divisible into 

the Rowland and overlying Preachersville Members. On 

the western side of the dome, the formation is divisible 

into (ascending) the Rowland, Bardstown, and Saluda 

Dolomite Members.

Rowland Member.—This member mainly encompasses strata assigned earlier to the Waynesville Limestone. The 40- to 60-ft-thick member consists chiefly of 

grayish-green, sparsely glauconitic, dolomitic or calcareous, silty mudstone. The mudstone is obscurely bedded, 

and many of the bedding surfaces are covered by ripple 

marks and mud cracks. Fossils are rare to absent. The 

Rowland belongs to Weir and Peck's (1968) dolomitic 

mudstone facies, and is thought to have been deposited 

on extensive tidal flats.

Preachersville Member. —Strata included in this member previously were assigned to the Liberty and Whitewater Formations. The 55- to 95-ft-thick unit is similar to 

the underlying Rowland Member, but it contains 10 to 20 

percent argillaceous, finely crystalline dolomite or dolomitic limestone. Locally, the basal 6-8 ft is a limestone 

rich in colonial corals and stromatoporoids known as the 

Otter Creek Coral Bed (Simmons and Oliver, 1967). 

Peterson (1970) correlated these beds with coral-rich 

layers in the Bardstown Member on the western side of 

the Cincinnati arch.

Bardstown Member.—This 12- to 40-ft-thick member 

overlies the Rowland Member and underlies the Saluda 

Dolomite Member on the western side of the Cincinnati 

arch in Kentucky. It consists of about 90 percent gray to 

greenish-gray, fine- to medium-grained limestone containing abundant whole or fragmented fossils. These 

beds are 1 to 8 in thick. About 10 percent of the member 

is bioclastic to coquinoid limestone. Peterson (1970) 

described two to four layers in the middle two-thirds 

of the member that contain concentrations of colonial 

corals.

Saluda Dolomite Member.—This member reaches a 

maximum thickness of 75 ft in Kentucky on the western 

side of the Cincinnati arch. Northward in Indiana, it is as 

much as 60 ft thick and is recognized as a formation. The 

Saluda is a dolomite or calcareous dolomite, and is 

distinguished from the underlying Bardstown Member 

by the abrupt change from the fossiliferous limestone of 

the latter to a mainly unfossiliferous dolomite. Hatfield 

(1968) described the Saluda in Indiana in detail. His work 

is discussed later, in the section on Indiana Upper 

Ordovician lithostratigraphy.
022 CONTRIBUTIONS TO THE ORDOVICIAN PALEONTOLOGY OF KENTUCKY AND NEARBY STATES

UPPER ORDOVICIAN LITHOSTRATIGRAPHY OF

NORTH-CENTRAL KENTUCKY AND

SOUTHWESTERN OHIO

It was in this area, particularly in the vicinity of 

Cincinnati, Ohio, that the stratigraphic units of the 

traditional classification mainly were originally described 

(Caster and others, 1955) (fig. 12). The stratigraphic 

revisions of Peck (1966), Ford (1967), and Pojeta (1979) 

are used here (fig. 12).

KOPE FORMATION

The Kope Formation is Edenian and locally early 

Maysvillian in age (fig. 5). It grades southward into the 

Clays Ferry Formation (fig. 5). It lies conformably on the 

Point Pleasant Member of the Clays Ferry Formation 

east and west of Cincinnati, but this contact becomes 

unconformable northwestward (Rooney, 1966; Gray, 

1972). The Kope is overlain conformably by the Fairview 

Formation in Ohio and Kentucky, and the two intertongue in some areas (Sweet, 1979, fig. 3). The Kope 

ranges in thickness from 150 to 280 ft over the IndianaOhio-Kentucky tristate outcrop area.

The Kope Formation is 70 to 80 percent shale, with 

some shales being more than 3 ft thick. The shales are 

interbedded with limestones and minor siltstone beds. 

Kope limestones are thin to medium bedded and generally contain whole or broken fossils in varying numbers. 

The shales also are fossiliferous in many places. The 

fauna is dominated by brachiopods and bryozoans, but 

crinoids, trilobites, and mollusks are characteristic of 

some parts of the section (Weiss and others, 1965).

The name Kope Formation was proposed by Weiss and 

Sweet (1964) to replace the term "Eden shales," as 

"Eden" has stadial connotations. The traditional fourpart subdivision of the Eden shales (Nickles, 1902) was 

rejected by Weiss and others (1965) because the four 

"members" were based largely on biofacies exposed in 

the immediate vicinity of Cincinnati and could not be 

traced consistently into surrounding areas. In this fourpart scheme, the basal Fulton beds consist of 5 ft of dark 

shales characterized by the presence of the trilobite 

Triarthus eatoni. The overlying Economy Shale was 

characterized by the trilobite Cryptolithus and by crinoids and delicate brachiopods. The upper Southgate and 

McMicken "members" contained more and thicker bedded limestones, some characterized by ripple marks and 

by robust brachiopods and bryozoans. This sequence 

reflects shallowing upward toward higher energy Fairview conditions.

Weiss and others (1965, p. 49, 50) concluded that the 

Kope and Clays Ferry shales and siltstones were derived 

from the southeast and east, based on percentage of 

elastics, grain-size increase, and paleogeography. Ford 

(1968) suggested a southerly source area.

Weiss and others (1965) postulated that clastic mud 

accumulated in depressed areas on a sea floor of low, 

broad relief, while limestones were deposited on the tops 

and flanks of topographically higher areas, with skeletal 

debris occasionally being swept into adjacent lows. They 

estimated an average depth of accumulation of 25 m.

Anstey and Fowler (1969) also studied Kope depositional environments. They estimated, on the basis of 

bryozoan growth forms, that water depth averaged more 

than 20 m. They claimed that the Kope limestones 

formed by the growth of benthonic communities dominated by bryozoans, on slightly elevated areas of the sea 

floor. They also outlined an upward shallowing of water 

depth, on the basis of an upward increase in limestone 

content and fauna abundance, an upward decrease in the 

wave length of megaripples, and the presence of oncolites and mud cracks in the overlying Dillsboro Formation in Indiana.

FAIRVIEW FORMATION

The Maysvillian-age Fairview Formation ranges from 

70 to 110 ft in thickness over southwestern Ohio and 

northern Kentucky (fig. 12). The formation consists of 

interbedded limestone, shale, and minor siltstone. Limestone makes up 50 to 60 percent of the unit; it consists of 

medium- to coarse-grained skeletal limestone in the 

lower part and fine-grained, silty, sparsely fossiliferous 

limestone in the upper part. Shale makes up 35 to 40 

percent of the formation, occurring as thin beds or 

partings between the limestones. Siltstone makes up 5 to 

15 percent of the unit, occurring as thin to medium beds 

that become more abundant upward (Peck, 1966).

The Fairview was originally referred to as the "Hill 

quarry beds" (Pojeta, 1984) in the vicinity of Cincinnati, 

where it was extensively quarried. Nickles (1902) named 

the Fairmont (Dekayia aspera) beds and the underlying 

Mount Hope (Amplexopora septosa) beds, which were 

later combined as members of the Fairview Formation 

by Bassler (1906). Peck (1966, p. B5) felt that these two 

members were based more on faunal than lithologic 

characters, and did not favor their use outside the 

immediate type area.

Ford (1967, p. 935) postulated that the coarse, fragmental limestones of the Fairview were formed around 

submarine topographic highs. He envisioned a situation 

in which waves and currents broke and sorted skeletal 

material on the highs, and deposited progressively finer 

skeletal debris in progressively deeper surrounding 

areas, where fine elastics were also settling. The positions of these highs and intervening depressions 

migrated laterally through time.

The Fairview Formation lies conformably on and 

intertongues with the Kope Formation (fig. 5), and
MIDDLE AND UPPER ORDOVICIAN SYMMETRICAL UNIVALVED MOLLUSKS, CINCINNATI ARCH REGION 023

locally is as old as Edenian in age. In the Cincinnati area, 

it is conformably overlain by two local units, the Miamitown Shale and Bellevue Limestone. Elsewhere, it is 

conformably overlain by the Grant Lake Limestone. The 

Fairview grades westward into the Kope and Dillsboro 

Formations of Indiana, and southward into the Ashlock 

Formation of Kentucky (fig. 12).

BELLEVUE LIMESTONE

Ford (1967, p. 932-934) redefined the Bellevue Limestone as a sequence of medium- to thin-bedded, coquinoid 

limestones, with minor interbedded shales present in the 

vicinity of Cincinnati (fig. 12). Its maximum known 

thickness is 25 ft at the type locality.

Ford (1967) noted that the formation had a limited 

areal extent, and that it thickened south and southeast of 

Cincinnati. He suggested that the Bellevue might be a 

northwestward tongue of the Grant Lake Limestone, 

and Luft (1971) mapped it as such (fig. 5). Tobin (1982) 

considered the Bellevue to be the top unit of a 

shallowing-upward carbonate sequence which began 

with Kope deposition.

MIAMITOWN SHALE

Ford (1967) proposed the Miamitown Shale for 5 to 35 

ft of shale and mudstone with widely spaced limestone 

interbeds that conformably overlies the Fairview Formation in the vicinity of Cincinnati (fig. 12). The limestones in this unit are commonly nodular bedded and 

contain a characteristic gastropod-pelecypod assemblage 

that includes Lophospira, Cyclonema, and Ambonychia.

Ford (1967) suggested that the Miamitown Shale 

reflects a return to conditions of Kope deposition. Considering the Miamitown's relatively small areal extent, 

its position between the rather high energy Fairview and 

Bellevue limestones, and the presence of a predominantly molluscan fauna, it seems improbable that the 

Miamitown was deposited in water as deep as Kope 

sediments. The Miamitown may reflect a period of 

increased fine clastic influx into a protected lagoonal 

setting.

GRANT LAKE LIMESTONE

The Grant Lake Limestone is MaysvillianRichmondian in age and is distributed through northern 

Kentucky and parts of adjacent southwestern Ohio (fig. 

12). The Bellevue Limestone of the Cincinnati area is 

thought to be a northern tongue of the Grant Lake (fig. 

5) (Ford, 1967; Luft, 1971). The formation is conformable 

with the underlying Fairview Formation and overlying 

Bull Fork Formation. It grades westward into the Dillsboro Formation of Indiana, and southward into the 

Galloway Creek Limestone and Ashlock Formation 

(fig. 5).

Peck (1966) named the Grant Lake Limestone for 

strata in the Maysville, Ky., area that had previously 

been assigned to the Bellevue, Corryville, and Mt. 

Auburn Members of the McMillan Formation. He 

described the Grant Lake as chiefly irregularly bedded 

argillaceous limestone and minor interbedded calcareous 

shale. Limestone makes up 70 to 90 percent of the unit, 

and is mainly gray with olive-gray mottling, micrograined to medium grained, argillaceous, and very fossiliferous. Some well-sorted, fine- to coarse-grained, 

bioclastic limestones are present locally. The fauna is 

dominated by brachiopods and bryozoans, but gastropods, cephalopods, pelecypods, crinoids, trilobites, and 

ostracodes are common locally.

The formation belongs to Weir and Peck's (1968) 

nodular-bedded, fossiliferous limestone and mudstone 

lithofacies, which they regarded as representing a relatively high energy shelf environment, such as waveagitated shoals (Pojeta, 1979).

BULL FORK FORMATION

Peck (1966) named the Bull Fork Formation for strata 

previously called Arnheim, Waynesville, Liberty, and 

Whitewater Formations in the Maysville, Ky., area. The 

unit was mapped in north-central Kentucky on the 

eastern side of the Cincinnati arch (fig. 12). Pojeta (1979, 

fig. 2) extended its use into southwestern Ohio to include 

strata above the Bellevue Limestone that Ford (1967) 

had left unnamed.

The Bull Fork Formation is 200 ft thick in its type 

area. It consists of interbedded limestone and shale. The 

shale content gradually increases from 20 percent near 

the base to about 80 percent in the upper part, and is 

mainly calcareous, medium gray to greenish gray, and 

fissile to poorly fissile. The formation contains three main 

types of limestone. The most common type, which 

accounts for 50 to 70 percent of the total limestone, is 

gray, with some olive-gray mottling, and has fine- to 

medium-grained matrix encasing medium- to very coarse 

grained fossil fragments. This type of limestone is evenly 

to irregularly bedded, with beds 1 to 8 in thick, and in 

some locations has large ripple marks on upper bed 

surfaces. The second limestone type, which makes up 5 

to 40 percent of the limestone, consists of 1- to 8- 

inch-thick, even beds composed of olive-gray, microgranular limestone containing sparse fossil fragments. The 

third limestone type, which makes up 5 to 30 percent of 

the limestone, is medium- to bluish-gray, fine- to coarsegrained, well-sorted, bioclastic limestone. This limestone 

type is present in 2- to 18-in-thick, even beds that display
024 CONTRIBUTIONS TO THE ORDOVICIAN PALEONTOLOGY OF KENTUCKY AND NEARBY STATES

crossbedding in many places. Brachiopods and bryozoans 

are the dominant faunal elements, but solitary and 

colonial corals, gastropods, cephalopods, pelecypods, crinoids, trilobites, and ostracodes are common locally.

The Bull Fork belongs to Weir and Peck's (1968) 

planar-bedded, fossiliferous limestone and mudstone 

lithofacies. This lithofacies is believed to represent a 

deeper, more protected environment than the nodularbedded limestone and mudstone lithofacies (Pojeta, 1979, 

p. A6).

DRAKES FORMATION

The only part of the Drakes Formation present in this 

area is 25 to 30 ft of the Preachersville Member (fig. 12). 

The unit thickens southward toward its type area in 

south-central Kentucky (Weir and others, 1965).

The Preachersville Member in northern Kentucky 

consists of calcareous to dolomitic mudstone and minor 

interbedded dolomitic limestone and dolomite. The mudstone makes up 90 percent of the unit. It is mainly 

grayish green, but it becomes reddish purple locally near 

the top. It is thin bedded, fissile to blocky, and locally 

silty. The dolomitic limestone and dolomite are gray to 

brown, fine to medium grained, and argillaceous to silty, 

and occur as thin lenses and irregular beds. Megafossils 

are sparse and poorly preserved (Peck, 1966, p. B22).

The Preachersville is generally overlain unconformably by the Lower Silurian Brassfield Formation, or by 

even younger units, in different areas.

UPPER ORDOVICIAN LITHOSTRATIGRAPHY OF 

SOUTHEASTERN INDIANA

The Point Pleasant Tongue of the Clays Ferry Formation is exposed at a few localities along the Ohio River in 

southeastern Indiana (Brown and Anstey, 1968) and 

across the river in Kentucky (Swadley, 1969), where it is 

directly overlain by the Kope Formation. The contact is 

well defined by the change from the mud-free bioclastic 

limestone of the Point Pleasant to the argillaceous limestones and shales of the Kope.

Rooney (1966) described an erosional unconformity at 

the top of the "Trenton" in all but extreme southwestern 

Indiana. He delineated a northeast-southwest hinge line 

that ran from the Findlay arch in Ohio to the Ozark dome 

in Missouri. Uplift of the area northwest of this hinge line 

at the end of "Trenton" deposition culminated in the 

emergence of a broad plateau, while deposition remained 

continuous southeast of the hinge line (Rooney, 1966, 

figs. 1-9). The plateau was transgressed in Edenian time 

by Kope muds. The unconformable contact is marked by 

truncation of "Trenton" beds, karst solution features, 

and concentrations of pyrite, angular chert, phosphatic 

grains, and carbonate breccia.

The Kope Formation was discussed previously, so a 

detailed description is not necessary here. However, 

some local features are noted below. Discussed in more 

detail are the younger Ordovician units recognized 

in Indiana: the Dillsboro, Saluda, and White water 

Formations.

KOPE FORMATION (INDIANA)

Brown and Lineback (1966, p. 1020) extended the use 

of this formational name into Indiana from the type 

section in the Maysville area of Kentucky and Ohio, 

which was described by Weiss and Sweet (1964) (fig. 12).

The Kope thickens northward in southeastern Indiana 

from 220 ft in outcrop to 550 ft in the subsurface in 

Wayne County. It overlies the Point Pleasant Tongue 

conformably in extreme southeastern Indiana (Swadley, 

1969), where the pre-Kope thins northward in concert 

with the Kope thickening (fig. 5). Brown and Lineback 

(1966) suggested that this might reflect a facies relationship.

In Indiana, the Kope Formation consists mainly of 

bluish- to brownish-gray clay-shale, with only 5 percent 

limestone, most of which is present in the upper onethird of the unit. The limestone generally is fossiliferous 

and occurs as rather discontinuous beds. The Kope is 

overlain conformably by the Dillsboro Formation in 

Indiana. The contact is marked by a much lower percentage of limestone in the Kope.

DILLSBORO FORMATION

Brown and Lineback (1966, p. 1020) named the Dillsboro Formation for "the sequence of highly fossiliferous 

argillaceous limestones and calcareous shales that lie 

between the shales of the Kope Formation and the 

dolomitic limestone of the Saluda Formation" in southeastern Indiana (fig. 12). The formation is Maysvillian 

and early Richmondian in age. It was proposed to take 

the place of the biofacies units of traditional usage 

(Patton and others, 1953). The replaced units were, in 

ascending order, the Mount Hope, Fairmount, Bellevue, 

Corryville, Mount Auburn, Arnheim, Waynesville, and 

Liberty Formations. It is recommended here that these 

units continue to be cited as informal biofacies units 

within the Dillsboro, in order to retain paleontological 

information for paleoecological and biostratigraphic 

purposes.

The Dillsboro contains about 30 percent limestone and 

70 percent shale. Shale becomes more predominant 

southward in the lower part of the formation. Limestones are variable, but are mainly argillaceous and 

contain an abundant fossil fauna. Brachiopods and bryozoans are most conspicuous, but various mollusks, 

arthropods, and echinoderms are common locally.
MIDDLE AND UPPER ORDOVICIAN SYMMETRICAL UNIVALVED MOLLUSKS, CINCINNATI ARCH REGION 025

Pojeta (1979, p. A7) noted that much of the Dillsboro is 

lithologically and faunally similar to the Bull Fork Formation. The Bull Fork is a direct lateral equivalent of the 

upper Dillsboro (Sweet, 1979, fig. 3), but the name 

changes going across State borders from Ohio-Kentucky 

to Indiana (fig. 5).

SALUDA FORMATION

The Richmondian-age Saluda Formation is a broad, 

lens-shaped unit distributed through southeastern Indiana and extending into adjacent southwestern Ohio and 

northern Kentucky (figs. 5, 12). In Indiana it lies conformably between the Dillsboro and Whitewater Formations, although where the Whitewater has been removed 

by erosion the Lower Silurian Brassfield Formation lies 

on the Saluda unconformably. In Ohio the Saluda has 

generally been considered a thin (6-ft-thick) member of 

the Whitewater Formation, separating the upper and 

lower members of that formation (Caster and others, 

1955). In Kentucky, Weir, Greene, and Simmons (1965) 

made the Saluda a member of the Drakes Formation 

along the western flank of the Cincinnati arch (see 

discussion of lithostratigraphy of central Kentucky). The 

Saluda Formation of Indiana has been described in detail 

by Hatfield (1968). The formation is composed mainly of 

dolomitic mudstone, but it also contains a coral-rich zone 

at the base and a coral-stromatoporoid-rich zone just 

above the top of the formation.

The basal coral zone is composed of large heads of the 

colonial corals Tetradium and Favistella in a matrix of 

dolomitic limestone, skeletal-micritic limestone, or calcareous shale. The zone ranges from 2 to 12 ft thick and 

may be present within either the Saluda or Dillsboro 

formation or may overlap the boundary between them. 

An upper TWradmm-stromatoporoid zone lies just above 

the Saluda in the lowermost Whitewater Formation.

The Saluda itself is mainly calcitic dolomite that in 

many places exhibits laminations, mud cracks, and small 

ripple marks. Ostracodes are the only common fossils. 

Beds of more bioclastic limestone or shales are present 

locally.

Hatfield (1968) concluded that the Saluda was deposited in a broad, shallow lagoon enclosed by broad, low 

banks of corals. Dolomite content increases toward the 

interior of this lagoon. Hatfield interpreted bioclastic 

limestones and shales as storm deposits washed into the 

lagoon. Evidence suggests that water depth in the lagoon 

was usually a few inches to a few feet, and that salinities 

were above normal.

WHITEWATER FORMATION

The Whitewater Formation was originally named by 

Nickles (1903). As currently recognized, the formation

includes the Elkhorn Formation of other classifications 

(Utgaard and Perry, 1964; Brown and Lineback, 1966; 

Shaver and others, 1970).

The Whitewater is the youngest Richmondian-age 

formation in the Cincinnatian type section (fig. 12). It 

conformably overlies the Saluda Formation, and is 

unconformably overlain by either the Lower Silurian 

Brassfield Formation or the Middle Silurian Osgood 

Formation. In general, the Whitewater contains a higher 

percentage of limestone than do the strata beneath the 

Saluda.

The Whitewater consists of various types of limestone 

interbedded with calcareous shales. The limestones 

include thin-bedded, argillaceous, fossiliferous limestone, thin-bedded ostracodal limestone, mediumbedded, relatively unfossiliferous limestone, mediumbedded limestone containing burrows, and rubblyweathering, argillaceous limestone (Brown and 

Lineback, 1966, p. 1022). Because the Whitewater thickens in concert with Saluda thinning, the two are thought 

to be facies of one another. The Whitewater is generally 

believed to reflect the shallowing upward associated with 

the Ordovician-Silurian unconformity. The fauna of the 

Whitewater is dominated by a brachiopod-bryozoan 

assemblage, and locally is also rich in mollusks.

MATERIAL AND PRESERVATION

The silicified collections that constitute the core of this 

study were made mostly between 1961 and 1972 as part 

of the joint geologic mapping project of the State of 

Kentucky undertaken by the U.S. Geological Survey and 

the Kentucky Geological Survey. Nearly 1,100 fossil 

collections were made during the mapping project, of 

which more than 200 contained silicified fossils. Altogether, almost 36,000 pounds of limestone containing 

silicified fossils were collected. The Lexington Limestone was found to have the most widespread silicification, both stratigraphically and geographically, and this 

unit accounts for 116 of the silicified fossil collections. 

Twenty-five silicified collections were made from the 

High Bridge Group, and 64 silicified collections were 

made from rock units above the Lexington Limestone. 

Pojeta (1979, p. A15-A19) described these collections 

and the methods by which the silicified fossils were 

etched from the bulk limestone samples.

Other specimens described herein came primarily from 

museum collections. Examined were collections from the 

U.S. National Museum of Natural History (USNM), 

Smithsonian Institution, Washington, D.C.; the American Museum of Natural History (AMNH), New York, 

N.Y.; the University of Chicago (UC) Walker Museum 

(collections now at the Field Museum of Natural History,
026 CONTRIBUTIONS TO THE ORDOVICIAN PALEONTOLOGY OF KENTUCKY AND NEARBY STATES

Chicago, 111.); and the geology museums of the University of Cincinnati (UCGM), Cincinnati, Ohio, and Miami 

University (MU), Oxford, Ohio. The type materials for 

most of the species described herein were examined, and 

many were photographed for the first time. A small 

proportion of specimens studied were new collections 

made by the author.

The symmetrical univalved mollusks described herein 

occur in five different modes of preservation: (1) internal 

molds (pi. 3, figs. 4-6), (2) external molds (pi. 2, figs. 4, 

5), (3) composite molds (pi. 24, figs. 1-5) (McAlester, 

1962), (4) calcitic casts or replicas (pi. 7, figs. 11-16), 

some apparently coated by micrite envelopes (Bathurst, 

1966), and (5) silicified casts or replicas (pi. 25, figs. 

1-14). The first four of these modes of preservation are 

prevalent in the interbedded shales and limestones of the 

Cincinnatian Series. However, the vast majority of specimens known from the limestones of the Lexington 

Limestone and High Bridge Group in central Kentucky 

and the Stones River and Nashville Groups of central 

Tennessee are silicified replicas.

Generally, the aragonitic shells of mollusks are dissolved soon after burial, leaving only internal and (or) 

external molds. Therefore, calcitic replicas were the 

least common preservational mode encountered. However, these aragonitic shells occasionally were replaced 

by calcite. Probably more common are calcitic specimens 

preserved by micrite envelopes (Bathurst, 1966) produced by algal borings into the mollusk shells after the 

death of the individuals. After the algal filaments died 

and decayed, micritic aragonite filled the borings, forming a micrite envelope that preserved the outer form of 

the original shell.

Many internal molds of mollusk fossils also retain the 

markings of the shell exterior. McAlester (1962) proposed that such composite molds resulted from the early 

dissolution of the aragonitic mollusk shells while the 

enclosing matrix was still in a plastic state. After dissolution, compaction of the sediment imprinted the external mold on the surface of the internal mold. The 

interpretation of internal and composite molds must be 

done with care. Many molds are distorted by compaction, 

and their size is generally much smaller than the original 

shell, with shrinkage of up to 40 percent of original size 

known (McAlester, 1962; Basan and Frey, 1982).

As noted above, nearly all fossil mollusks from the 

Middle Ordovician strata of the Cincinnati arch province 

described herein are silicified. The source of silica for 

these silicified fossil horizons may have been volcanic ash 

falls or siliceous skeletal material in the sediment. 

Laufeld and Jeppson (1976) made conclusions of broad 

application in their study of bentonites and silicified fossil 

horizons in the Silurian strata of Gotland. They reported 

that the Gotland silicified fossil horizons were generally

restricted to fairly thin stratiform levels. They found 

that in most silicified horizons only the skeletal material 

was silicified, not the matrix. They noted that many of 

these silicified fossil horizons almost certainly were 

caused by bentonite layers that were deposited in adjacent quieter water environments. Finally, they agreed 

generally with other studies of silicified faunas about the 

sequence of silicification by taxonomic groups and shell 

mineralogy (Hintze, 1983; Newell and others, 1953; Dapples, 1967; Cooper and Grant, 1972). The low-Mg calcite 

skeletons of bryozoans, brachiopods, and corals are most 

susceptible to replacement by silica, followed by high-Mg 

calcite groups, such as crinoids and ostracodes, and 

aragonite groups, such as gastropods and pelecypods.

The distribution, taphonomy, and diagenesis of the 

Cincinnati arch Middle Ordovician silicified fossil horizons have not yet been analyzed in detail, but some 

generalizations from observations are possible. As noted 

for many other such occurrences (Laufeld and Jeppson, 

1976), the Kentucky silicified fossil horizons appear to be 

restricted to fairly thin stratiform levels. However, most 

silicified fossil horizons are not known to be associated 

with bentonite seams. There are various grades of silicification among the Kentucky specimens. Some, particularly those that weathered out of the limestones naturally, are hard and durable; others are brittle and fragile, 

and still others are coarsely crystalline and friable. 

Among symmetrical univalved mollusks, correlation 

between taxa and grade of preservation was observed, 

and it is concluded that the preservational differences are 

strictly diagenetic. Some specimens seem to have layers 

of silicification that peel away like an onion skin. This 

might reflect differential silicification of shell layers. 

Detailed analyses of these different patterns of silicification are needed, such as those of Permian silicified fossil 

assemblages from Wyoming by Boyd and Newell (1972) 

and Schmitt and Boyd (1981).

MEASUREMENTS

When sufficient material was available, series of measurements were made. These measurements are listed 

with the descriptions of the individual species in the 

section on "Systematic Paleontology." The orientations 

of the most common measurements are shown in figure 

13. These measurements were shell length, aperture 

length, aperture width, and umbilical diameter. Other 

common measurements were ventral width, posterior 

width, and dorsal width. These latter measurements 

recorded the width of the body whorl at points evenly 

spaced around the coiled shell in order to assess rate of 

whorl expansion.

There is bound to be some error in many of the 

measurements because of the nature of the fossil mate-
MIDDLE AND UPPER ORDOVICIAN SYMMETRICAL UNIVALVED MOLLUSKS, CINCINNATI ARCH REGION 027

EXPLANATION 

a — Shell length 

b — Aperture length 

c — Aperture width 

d — Umbilical diameter

FIGURE 13. Common measurements made on fossil 

specimens.

rial. Many of the specimens measured were fragmentary 

or were embedded in rock, and thus were difficult to 

measure; nevertheless, the measurements listed will 

give the reader an appreciation for the sizes and relative 

dimensions of the individual species. When measurements were sufficiently accurate to have important bearing on the differentiation of species, bivariate plots were 

drawn and regression analyses carried out.

STRATIGRAPHIC DISTRIBUTION OF

ORDOVICIAN MONOPLACOPHORA AND

BELLEROPHONTACEAN GASTROPODA IN THE

CINCINNATI ARCH REGION

In the accompanying tables (tables 1-4) are listed the 

stratigraphic distributions of monoplacophorans and bellerophontaceans in the Middle and Upper Ordovician 

lithostratigraphic units of the Cincinnati arch region.

PALEOECOLOGY OF SYMMETRICAL 

UNIVALVED MOLLUSKS

INTRODUCTION

Paleontologists have generally regarded bellerophontaceans, and those Paleozoic taxa now recognized as 

monoplacophorans, as algal grazers that mainly inhabited nearshore shallow subtidal and intertidal marine 

environments. This general conclusion has been based on 

common paleoenvironmental occurrences and faunal 

associations in the fossil record, as well as on comparison 

with some modern archaeogastropods (mainly limpets). 

However, data on fossil archaeogastropods and monoplacophorans show this conclusion to be an oversimplification.

TABLE I.—Distribution of bellerophontaceans in the Stones River 

Group of central Tennessee

[Data are based on museum collections and species listed in Wilson (1949). 

MP = Murfreesboro Limestone; PL = Pierce Limestone; RL = Ridley Limestone; LL = Lebanon Limestone; CL = Carters Limestone. X = present]

Species

Bucania emmonsi

Phragmolites grandis

Pterotheca expansa

P. saffordi

P. undulata

Tetranota bidorsata

T. sexcarinata

MF PL

X

X

X X

RL LL

X

X

X X

X

CL

X

AUTECOLOGY OF MONOPLACOPHORANS

All modern monoplacophorans, such as Neopilina, live 

at water depths of 200 m or more, are limpet shaped, and 

are thought to be deposit feeders (Cesari and Guidastri, 

1976). In contrast, Paleozoic taxa here interpreted to be 

monoplacophorans inhabited a relatively shallow subtidal 

shelf and had limpet shaped (pis. 1-4), convolute (pi. 9, 

figs. 1-4), involute (pi. 5, figs. 5-7), and evolute (pi. 6, 

figs. 19-22) isostrophically coiled shells. Detailed paleoecological data on these Paleozoic monoplacophorans are 

scarce, and at present their life habits can only be 

speculated on. Lemche and Wingstrand (1959, p. 63) 

stated that the modern monoplacophoran Neopilina was 

taken from abyssal, dark, muddy, clay sediment where 

there were no suitable objects for the animal to creep on.

TABLE 2. Distribution of monoplacophorans and bellerophontaceans in the Nashville Group of central Tennessee

[Data are based on museum collections and species listed in Wilson (1949).

X = present]

Bigby-Cannon Limestone

Species Hermitage 

Formation Bigby 

fades

Cannon

facies

Dovecolored 

facies

Catheys 

Formation

Archinacella depressa 

A. patelliformis 

A. valida

Bucania frankfortensis 

B. lindsleyi 

B. nashvillensis 

B. peracuta 

B. singularis 

Bucania sp. 

Bucanopsis carinifera 

Carinaropsis cunulae 

Cyrtolites (Cyrtolites)

retrorsus

Phragmolites cellulosus 

Sphenosphaera clausus 

S. troosti

Sphenosphaera sp. 

Tropidodiscus cristatus 

T. subacutus 

Undulabucania

punctifrons

X

X

X

X

X

X
028 CONTRIBUTIONS TO THE ORDOVICIAN PALEONTOLOGY OF KENTUCKY AND NEARBY STATES

TABLE 3. Distribution of species of monoplacophorans and bellerophontacean gastropods in the Tyrone Limestone of the High Bridge 

Group, the members of the Lexington Limestone, and the Clays Ferry 

Formation of central Kentucky

[Data are based on the U.S. Geological Survey silicified collections and on 

museum collections. Note that Middle Ordovician stratigraphic units in the 

central Kentucky area from which no taxa are known are not included in the 

table. TY = Tyrone Limestone; CF = Clays Ferry Formation; members of the 

Lexington Limestone are designated: CL = Curdsville Limestone; 

LO = Logana; GL = Grier Limestone; PL = Perryville Limestone; DH = Devils 

Hollow; TL = Tanglewood Limestone; and ML = Millersburg. X = present; 

interrogation points indicate uncertainty of occurrence]

Species

Micropileus variabilis 

Vallatotheca unguiformis 

Archinacella simulatrix

A. cingulata 

A. alta

Cyrotlites (Cyrtolites) retrorsus 

C. (Cyrtolites) claysferryensis 

C. (Paracyrtolites) subplanus 

C. (Paracyrtolites) parvus 

Sinuites pervoluta

S. obesus

S. cancellatus

Tropidodiscus subacutus 

Phragmolites compressus 

Temnodisus nitidula

Bucania halli

B. subangulata 

B. nashvillensis

B. frankfortensis 

B. sublata

B. micronema

B. rugatina 

Tetranota obsoleta

Salpingostoma kentuckyense 

Bucanopsis carinifera

B. diabloensis

Sphenosphaera ausus 

Sphenosphaera sp. indet. 

S. troosti

S. subglobulus

S. bilineatus

Carinaropsis acuta 

C. cymbula 

C. explanata 

Pterotheca saffordi

P. expansa 

P. angusta

TY CL LO GL PL

X 

X X 

X X X X

X

X X X X 

X ? 

X X

X X

X ?

X ? ? X 

?

X X

X X 

X X

X X

?

X

X X 

X X

XXX 

X 

X X

?

X X 

XXX

X

X X 

X

DH TL ML CF

X 

X

X ? 

X

X

X

X 

X

X 

X

X

X

X

X X X X

X

X 

X

However, Lowenstam (1978) reported that specimens of 

Vema, another modern monoplacophoran, were found 

clinging to phosphate pebbles in dredge samples from 

bathyl depths. He observed these living monoplacophorans in a tank for nearly a month, and noted a maximum 

linear movement of only 10 cm (centimeters). Similarly, 

many Paleozoic limpet-shaped monoplacophorans were 

probably also clingers.

The cap-shaped to conical tryblidiid monoplacophorans 

in the Ordovician strata of the Cincinnati arch are 

distributed throughout a spectrum of depositional environments (tables l-fy. In the USGS silicified collections, 

Archinacella simulatrix (pi. 2, figs. 7-12) occurs in such 

varied facies as the Tyrone Limestone, and the lowermost Curdsville Limestone and Grier Limestone Members of the Lexington Limestone. One common factor in 

these occurrences is that all of these facies probably were 

deposited in less than 15 m of water (Cressman, 1973).

Other species of Archinacella cited herein are found in 

various Middle and Upper Ordovician formations, many 

of which contain multiple facies of different depositional 

origins. Most of these occurrences are known from 

museum specimens, and the sedimentological and faunal 

associations generally are unknown. Therefore, correlation between taxa or morphotypes and depositional environments is not possible at present.

There are some consistent environmental distributions 

for other tryblidiid genera in the USGS silicified collections. Vallatotheca unguiformis (pi. 1, figs. 12-31) and 

Micropileus variabilis (pi. 1, figs. 1-7) are known only 

from very shallow water facies. V. unguiformis is known 

only from the Salvisa Bed of the Perryville Limestone 

Member and the basal meter of the Curdsville Limestone 

Member of the Lexington Limestone. The fine-grained 

limestones of the Salvisa Bed were deposited in water 2 

m or less deep and are characterized by an ostracode 

fauna and some mollusk shell beds (Cressman, 1973, p. 

30). The lower part of the Curdsville Limestone Member 

consists of crossbedded bioclastic limestone deposited 

above wave base in a transgressive sea (Cressman, 1973, 

p. 14). V. unguiformis most likely was an algal grazer. 

M. variabilis was found only in the basal 2 ft of the 

Curdsville Limestone Member of the Lexington Limestone. Its unsculptured low, conical shell, and its apparent possession of a continuous muscle ring, suggest that 

it led a limpetlike existence, clinging to and rasping algae 

from exposed lithified surfaces of the Tyrone Limestone 

along the shoreline of the transgressing Curdsville sea.

The common bryozoan encrustation of tryblidiid shells 

in the fauna under study suggests that these mollusks 

lived exposed lives in firm-bottom depositional environments. Such encrustations are known on the shells of 

Archinacella simulatrix (pi. 2, figs. 7, 8), A. indianensis 

(pi. 3, figs. 16-18), Helcionopsis striata (pi. 2, figs. 1-5), 

Vallatotheca unguiformis (pi. 1, figs. 30, 31), and V. 

manitoulini (pi. 1, figs. 8-11). The highly sculptured 

dorsal shells of genera such as Vallatotheca and Helcionopsis also argue against the deposit-feeding habit, in 

which the shell is often at least partly submerged in soft 

sediment. All of these taxa were probably algal grazers 

in shallow-water habitats.

Some smooth-shelled tryblidiids occur in more shalerich facies, for example, Archinacella area (pi. 3, figs. 

7-10) from the Bull Fork Formation and A. alta (pi. 3, 

figs. 4-6) from the Clays Ferry Formation. Hurst (1979)
MIDDLE AND UPPER ORDOVICIAN SYMMETRICAL UNIVALVED MOLLUSKS, CINCINNATI ARCH REGION 029

TABLE 4. Distribution of species of monoplacophorans and bellerophontacean gastropods in the Upper Ordovician Stratigraphic units of the

Cincinnati arch region

[Stratigraphic units in southeastern Indiana are designated: KO = Kope Formation, DO = Dillsboro Formation, SA = Saluda Formation, and WW=Whitewater 

Formation. Units in southwestern Ohio and north-central Kentucky are designated: KO = Kope Formation, FV = Fairview Formation, BL = Bellevue Limestone, 

GL = Grant Lake Limestone, BF = Bull Fork Formation, and DR = Drakes Formation. Unit in south-central Kentucky is designated: AS = Ashlock Formation. Units 

in central Tennessee are designated: LP = Liepers Formation, and AR = Arnheim Formation (as used by Wilson, 1949). X = present; interrogation points indicate 

uncertainty of occurrence]

Species

SE. Indiana SW. Ohio-N. Kentucky

KO DO SA WW KO FV BL GL BF DR

S. Ky.

AS

Term.

LP AR

Vallatotheca manitoulini 

Helcionopsis striata 

Archinacella davisi 

Archinacella cf. patelliformis 

A. rugatina

A. area

A. indianensis

Cyrtolites (Cyrtolites) ornatus

C. (Cyrtolites) cf. C. (C.) retrorsus

C. (Cyrtolites) claysferryensis

C. (Cyrtolites) minor

C. (Cyrtolites) hornyi

C. (Paracyrtolites) carinatus

Sinuites cancellatus

S. planodorsatus

S. granistriatus 

S. globularis 

S. subcompressus 

Tropidodiscus magnus 

Phragmolites bellulus

P. elegans 

P. dyeri

Undulabucania gorbyi 

Bucania pojetai 

B. simulatrix

B. crassa

Kokenospira costalis 

Tetranota bidorsata 

Salpingostomarichmondensis 

Sphenosphaera recurvus

S. subangularis 

S. capax 

S. mohri 

Pterotheca harviei

X

X

X X X

X

X

X

X

X

X

X X

X X

X X

X X

X

X

cited Archinacella sp. and indeterminate monoplacophorans from offshore shale facies in the British Caradocian 

Series. These monoplacophorans may have been deposit 

feeders. However, it must be noted that archinacellids 

have a continuous muscle ring, which is generally 

thought to be characteristic of clinging molluscan 

univalves.

Species of the cyrtonellid monoplacophoran genera 

Cyrtolites (pi. 6) and Sinuites (pi. 9) were highly successful during the Middle and Late Ordovician and are found 

in most Ordovician formations in the Cincinnati arch 

region (tables 2-4). Species of both genera were probably 

sluggish vagrant benthos. In many cases they occur 

together, but one genus is usually clearly dominant over 

the other in any single collection. They are often found in 

shaly and silty rocks. In fact, they are the dominant 

symmetrical univalved mollusks in both the Logana

Member (Kirkfieldian) of the Lexington Limestone and 

the Kope Formation (Edenian), which are the deepest 

water units in the Kentucky-Indiana-Ohio Ordovician 

section. However, Cyrtolites retrorsus (pi. 5, figs. 1-26) 

is also common throughout shallow-water facies of the 

Lexington Limestone, and C. ornatus (pi. 6, figs. 1-18) is 

common throughout most of the Cincinnatian section. C. 

ornatus is commonly encrusted by bryozoans (pi. 6, figs. 

12-14), and the encrustation can be shown to have 

occurred both during the life of the animal and after 

death (see later section on encrustation). Such encrustation suggests that the animal lived exposed on firm 

substrates under normal marine conditions. In contrast, 

few specimens of Sinuites are encrusted. The absence of 

encrustation may be attributable to their smoother shell 

surfaces, their occupation of more turbid environments, 

some aspect of their mode of life, or a combination of
030 CONTRIBUTIONS TO THE ORDOVICIAN PALEONTOLOGY OF KENTUCKY AND NEARBY STATES

these factors. Sinuites seems to be more dominant than 

Cyrtolites in deeper water fades. The highly irregular 

apertural margin in Sinuites also seems better adapted 

to the efficient channeling of water through the shell than 

to clamping onto a firm surface (see section on "Functional Morphology"). It appears that Sinuites may have 

been a deposit feeder on soft bottoms, whereas Cyrtolites was more likely an algal feeder in predominantly 

firm bottom areas.

AUTECOLOGY OF BELLEROPHONTACEANS

Bellerophontaceans are often allied closely with pleurotomariaceans because of their common possession of a 

median labral emargination along the apertural margin 

(Knight, 1952) and their common association in Paleozoic 

fossil assemblages. Unfortunately, ecological comparison 

of bellerophontaceans with modern pleurotomariaceans 

is nearly fruitless, because today the latter group is 

represented by only a small number of relict species 

living in deeper water environments (Vermeij, 1978, p. 

221). A more fruitful ecological comparison can be made 

between bellerophontaceans and those modern archaeogastropods that occupy the same shallow subtidal environmental regime. These modern groups are mainly 

algal grazers. They either rasp algae (mainly blue-green 

algae) from hard surfaces, like many patellaceans, or 

feed on the thalli of erect green algae, like other patellaceans and most trochaceans (Morton, 1967, p. 96-98).

Steneck and Watling (1982) and Steneck (1983) have 

discussed morphological limitations on the feeding capabilities of herbivorous mollusks. They concluded that 

bellerophontaceans and Paleozoic monoplacophorans 

were probably restricted to feeding on delicate filamentous and microscopic algae (browsing habit), as are most 

recent nonlimpet archaeogastropods. These modern 

archaeogastropods, and modern monoplacophorans, 

have radulae with organic teeth that are too soft to 

excavate calcareous substrata. This morphological feature is thought to have restricted their feeding on 

calcareous algae. However, patellacean archaeogastropods have strong buccal muscles and uniquely designed 

radular teeth that are strengthened by silicate and iron 

mineral coatings, which allow them to excavate calcareous substrates effectively and even to feed on crustose 

red algae (Steneck and Watling, 1982; Steneck, 1983). 

Hickman (1984b) and Harasewych and others (1988) 

demonstrated that the rhipidoglossate radula can be used 

to feed on sponges, in addition to browsing on algae.

As pointed out by Peel (1977b, p. 41^13), there are 

some notable exceptions to the algal feeding habit in 

modern archaeogastropods. Some fissurellids feed on 

sponges (Morton, 1967), and the deep-water pleurotomariacean Mikadotrochus includes sponges in its

microphagous scavenging habit (Fretter, 1964). Fretter 

(1964) also found foraminifers, diatoms, algal fragments, 

and organic detritus in the stomach of Mikadotrochus. 

Woodward (1901), Matsumato and others (1972), Yonge 

(1973), and Hickman (1976, 1984a) have inferred or 

observed carnivory (particularly on sponges) by modern 

pleurotomariaceans. Harasewych and others (1988) presented evidence from in situ observations and analyses of 

gut contents showing that the modern pleurotomariids 

Petrotrochus midas and P. amabilis feed predominantly 

and selectively on sponges. Fretter (1975) has even 

observed ciliary suspension feeding in the modern trochid Umbonium. Morton (1967) has discussed the minor 

anatomical modifications needed for the adaptation of 

archaeogastropods to these alternative feeding habits. 

Because the necessary anatomical evolution allowing the 

carnivorous, the microphagous deposit-feeding (scavenging), and the ciliary suspension-feeding habits is present 

in modern archaeogastropods, there is no reason to 

assume such adaptations did not also take place in 

Paleozoic forms.

Some exceptions to the algal browsing habit in Paleozoic archaeogastropods have been demonstrated. For 

example, Bowsher (1955) showed that many platycerids 

were coprophagous on crinoids. The common Upper 

Ordovician platycerid genus Cyclonema is commonly 

associated with camerate crinoids (Thompson, 1970, p. 

222-224). McKerrow (1978, p. 80-82) claimed that Ordovician bellerophontaceans, which he considered to be 

monoplacophorans, were bottom-dwelling detritus feeders and scavengers, but he offered no evidence to support this conclusion. Yochelson (1971) and Peel (1975b) 

interpreted open-coiled Paleozoic gastropods as sedentary ciliary suspension feeders on the basis of comparison 

with modern forms. Runnegar (1983, p. 128) has also 

suggested that macluritid and euomphalid archaeogastropods were suspension feeders, from analysis of the 

"living fossil" Neomphalus (McLean, 1981), a modern 

filter-feeding limpet interpreted to be a euomphalid. Peel 

(1977b, p. 47) suggested that explanate bellerophontaceans were epifaunal deposit feeders on soft substrates, 

micromorphic bellerophontaceans were grazers among 

algal foliage, and other shell forms led one or the other of 

these life styles. However, Peel emphasized that 

although other life habits have been demonstrated for 

modern archaeogastropods (as cited above), sufficient 

evidence of such alternative habits is usually lacking in 

the fossil record.

Batten (1958) noted the common association of pleurotomariaceans and sponges in shallow, muddy-bottom 

paleoenvironments in the Permian strata of the Southwestern United States. Batten (1958) and Finks (1960) 

cited four instances when one or more specimens of the 

pleurotomariacean G. (Glyptotomaria) marginata were
MIDDLE AND UPPER ORDOVICIAN SYMMETRICAL UNIVALVED MOLLUSKS, CINCINNATI ARCH REGION 031

found within the cloacas of the demosponge Heliospongia 

vokesi. Batten (1958) suggested that the gastropods may 

have fed on algal material collected on the cloacal walls. 

However, because some modern fissurellids (Morton, 

1967), and possibly some pleurotomariaceans (Fretter, 

1964), feed on sponges, it is possible that some Paleozoic 

archaeogastropods also did so.

Yonge (1947) claimed that archaeogastropods were 

restricted to firm substrates in relatively clean water 

environments because their bipectinate aspidobranch 

gills are prone to clogging by fine sediment particles. 

However, evidence from the fossil record amply demonstrates the common occurrence of archaeogastropods, 

and bellerophontaceans, in muddy sediments. Peel 

(1977b, p. 41^46) has discussed this problem at some 

length; he emphasized two important points. First, the 

general absence of modern archaeogastropods adapted to 

life on a soft bottom may be a result of post-Paleozoic 

competition with the more advanced caenogastropods, 

whose monopectinate ctenidia and anterior siphon 

enabled them to cope more easily with soft-bottom 

conditions. Second, some Paleozoic forms now included 

in the Archaeogastropoda may actually be caenogastropods, or may even be of a now-extinct organizational 

grade. More recently, Gilinsky (1984) compared rates of 

oxygen consumption by Holocene archaeogastropods and 

caenogastropods living in turbid water. He found no 

significant differences in oxygen consumption between 

the two groups. He concluded that his data cast doubt on 

Yonge's (1947) hypothesis, and suggested that other 

physical and biotic factors might play roles in controlling 

gastropod distribution and should be investigated.

Assuming Yonge's (1947) assessment of the bipectinate gill has merit, there are at least three ways to 

explain the presence of archaeogastropods in muddy 

sediment deposits. First, the gastropods might have 

been supported on algal films that bind and cover the 

muddy sediment surface. Gebelein (1969) cited gelatinous films of algal mucilage from modern carbonate 

environments in Bermuda, where they stabilized substrates and passively trapped carbonate muds. Peel 

(1977b, p. 45) cited examples of modern caenogastropods 

living on such films and pointed out that these films 

would also furnish an abundant food source. Ferguson 

(1962) described an assemblage of small bellerophontaceans (generally less than 10 mm (millimeters) in diameter) from British Mississippian-age shales of intertidal 

to shallow subtidal environments in a transgressive 

sequence. He postulated that the small snails could 

survive on the muddy bottom because the rate of sedimentation was very slow and the sediment surface may 

have been loosely bound by organic slime.

The second possibility is that the snails lived on 

drifting masses of algae comparable to the modern

Sargassum (Peel, 1977b, p. 44). Ruedemann (1934) 

explained the presence of benthic faunas in Paleozoic 

black shales in this way. However, it is unlikely this is an 

important mechanism explaining the widespread occurrence of archaeogastropods in normal marine shales 

deposited in shallow aerobic settings.

The third and most common explanation is that the 

snails were algal foliage dwellers, living above the turbid 

mud bottoms in stands of erect algae (Chronic, 1952; 

Johnson, 1962, 1964; Gromaczakiewicz-Lomnicka, 1972; 

Bowen and others, 1974; Peel, 1977b; Goldring and 

Langenstrassen, 1979). Johnson (1961, p. 5, 6) claimed 

that Ordovician seas supported a rich algal flora of 

noncalcareous and slightly calcified marine algae. The 

mild climates and widespread areas of shallow marine 

carbonate deposition of the Ordovician were an ideal 

setting for the development of calcareous marine algae. 

Johnson believed that the floors of Ordovician shallow 

shelf areas were covered by an algal flora as populous 

and diverse as those of modern seas, and he envisioned 

these algae as the basic food supply for the teeming 

marine invertebrate communities of the period.

The late Middle Ordovician radiation of archaeogastropods could be linked to the early Middle Ordovician 

radiation of marine algae. Blue-green algae, in the form 

of stromatolites and oncolitic encrustations, dominated 

pre-Middle Ordovician marine algal floras, but during the 

Middle Ordovician, a radiation of green (Codiaceae and 

Dasycladaceae) and red (Solenoparaceae) algae occurred 

(Johnson, 1961; Wray, 1977, fig. 161). Moore (1977, p. 18) 

reported an abundant and diverse marine algal flora 

composed of both calcareous and noncalcareous components from the early Middle Ordovician (Chazyan) limestones of eastern Tennessee, and described an algal 

ecologic zonation comparable to that of recent shallow 

marine environments. Moore found green and red algae 

to be most abundant in the broad shelf-lagoon environment and its contained patch reefs, but absent in shelf 

margin shoal and reef environments. Tidal flats and 

associated environments showed the influences of stromatolite growth.

There are also some fairly well preserved erect noncalcareous algae known from Ordovician strata. Arbey 

and Koeniguer (1979) reported casts of small seaweeds 

from the Ordovician of the Sahara Desert which are 

similar to the well-known Devonian-age Protaxites 

(Koeniguer, 1974; Jonker, 1979). Also, Fry (1969, 1983) 

described collections of noncalcareous marine algae made 

by G. Winston Sinclair from the dolomites of the Late 

Ordovician (Richmondian) Red River Formation of Manitoba. He recognized numerous erect morphotypes that 

most closely resemble modern red, green, and brown 

algae.
032 CONTRIBUTIONS TO THE ORDOVICIAN PALEONTOLOGY OF KENTUCKY AND NEARBY STATES

Numerous authors discussing Paleozoic marine benthic communities have cited bellerophontaceans as common inhabitants of nearshore delta front shales and 

siltstones (Johnson, 1962; Sturgeon, 1964; Bretsky, 1969; 

Sutton and others, 1970; West, 1972; Bowen and others, 

1974; Thayer, 1974; Goldring and Langenstrassen, 1979; 

Linsley, 1979; Rollins and others, 1979; MacLeod, 1982). 

Bowen and others (1974) suggested that their Bellerophon Community from the Devonian of New York was 

located near delta channel mouths during periods of 

active progradation, when outflowing nutrients would 

provide for the most prolific growth of marine plants. 

Johnson (1962) likewise associated Pennsylvanian gastropod assemblages in the Illinois Basin with areas of 

prolific plant growth in delta front areas. Likewise, 

MacLeod (1982, p. 172) cited a bellerophontid community 

in delta front and interdistributary bay environments in 

the Upper Pennsylvanian of north-central Texas and 

suggested that they fed on benthic algae. It should be 

noted that these delta front areas must have also been 

sites of active fine clastic sedimentation and accordingly 

would have been turbid.

Peel (1977b, p. 43^46) has pointed out some possible 

shortcomings of the algal-foliage-dweller hypothesis. In 

modern seas, the dominant types of vegetation on soft 

sediment in shallow water are sea grasses, whereas algal 

stands are more characteristic of modern rocky shoreline 

areas. However, sea grasses did not appear in the fossil 

record until the Tertiary (Brazier, 1975), and therefore it 

is necessary to suggest that during the Paleozoic 

algae dominated marine areas in which they are now 

subordinate.

Peel (1977b, p. 44) further pointed out that the supporting ability of algal foliage restricts the size of gastropods that can live on it. Most modern algal-foliagedwelling gastropods are quite small. Warmke and 

Almodovar (1963) found that 99 percent of the mollusks 

associated with algae in Puerto Rico were gastropods, 

but they were mainly less than 2 mm in diameter. 

Brazier (1975) cited the presence of small gastropod 

faunas as a possible way to recognize former grass beds 

in the Tertiary fossil record. Johnson (1964, p. 123) 

claimed that a modern gastropod assemblage dominated 

by a few species in fine-grained sediments generally 

indicates the presence of plants. Diverse diminutive 

molluscan faunas have also been interpreted as algalfoliage-dwelling faunas in the Upper Ordovician 

Maquoketa Formation (Bretsky and Bermingham, 1970) 

and the Lower Silurian Brassfield Formation (Harrison 

and Harrison, 1975). Peel (1978, p. 302) suggested, in his 

study of the gastropod faunas of the Silurian Arisaig 

Group in Nova Scotia, that many of the smaller forms of 

5 mm or less in diameter were probably algal foliage 

dwellers, and that those in the 10- 15-mm size range may

also have been. However, he doubted that the high 

proportion of Arisaig gastropods attaining 20 mm or 

more in size could have lived in algal foliage. However, 

large and small species of archaeogastropods are commonly found together in Paleozoic fine-grained deposits. 

Sturgeon (1964, p. 193) stressed the cooccurrence of 

gastropods ranging in size from 5.5 to 35 mm in the 

Pennsylvanian shales of Ohio. Chronic (1952, p. 109-111) 

claimed that small, finely ornamented delicate snails of 

the fine-grained Permian Kaibab Limestone of Arizona 

lived in "seaweed forests" above calcareous mud substrates, while contemporary thick- and smooth-shelled 

large forms lived on the sea floor beneath. Heuer (1973, 

p. 527, 528) suggested that bellerophontaceans lived on 

soft, muddy bottoms in Late Pennsylvanian delta front 

settings in Texas, while most associated pleurotomariaceans lived above the sea floor on erect algae, crinoids, 

bryozoans, and sponges. Peel (1977b, p. 43) cited examples of modern stratified gastropod faunas in algal foliage 

habitats, and noted that their death would result in 

ecologically mixed assemblages made up of forms from 

different foliage levels, as well as forms that had lived 

among the holdfasts and at the sediment surface.

It therefore appears that the algal-foliage-dwelling 

habit may partly explain small Paleozoic archaeogastropods in muddy sediments, but they are generally associated with other species thought to be too large to have 

been supported by algal foliage. Apparently, at least 

some Paleozoic archaeogastropods had adaptations that 

allowed them to cope with soft substrates, and it is likely 

that feeding habits were much more varied than is 

generally supposed.

PREVIOUS ORDOVICIAN PALEOECOLOGICAL STUDIES

There are very few published studies focusing on 

Ordovician bellerophontacean-monoplacophoran paleoecology. However, a small number of genera are commonly cited in more general Ordovician community studies. These studies can be conveniently divided into those 

concerned with clastic depositional environments and 

those dealing with carbonate depositional environments. 

A brief review of these studies documents that monoplacophorans and bellerophontaceans occupied a wide variety of Paleozoic habitats.

ORDOVICIAN CLASTIC ENVIRONMENTS

Bretsky (1969, 1970b) studied marine benthic communities in Upper Ordovician clastic depositional environments along the Queenston delta front in the Central 

Appalachians. He reported Plectonotus sp. and Bucania 

sp. from shallow subtidal and intertidal silt and fine-sand 

bottom environments. They are present in Bretsky's
MIDDLE AND UPPER ORDOVICIAN SYMMETRICAL UNIVALVED MOLLUSKS, CINCINNATI ARCH REGION 033

Orthorhynchula-Ambonychia assemblage, and are associated with rhynchonellid and linguloid brachiopods and 

with modiomorphid, ambonychiid, and nuculoid bivalves. 

Although the bellerophontaceans are found in sediments 

of the same texture as pleurotomariaceans, the two 

groups do not commonly co-occur, the bellerophontaceans occupying more nearshore areas adjacent to crossbedded sand and organic-rich mud depositional environments. Plectonotus sp. was by far the more abundant of 

the two bellerophontaceans, and was commonly found in 

clumps of numerous specimens in sediment stained with 

more organic matter than were surrounding sediments. 

These specimens likely were concentrated on a common 

food source, probably algal.

Brenchley and Cocks (1982) recognized ten faunal 

associations in the latest Ordovician regressive sequence 

in Norway. Unidentified bellerophontaceans were 

present in three of these associations. All three occurrences were in mudstones, but the three were in deepshelf, midshelf, and inner-shelf environments, respectively. None were reported from nearshore or onshore 

facies.

Pickerill and Brenchley (1979) described benthic 

marine communities in the clastic rocks of the Caradocian 

Series in North Wales. They recognized four communities, all of which were believed to have been deposited in 

offshore shelf areas 30 m or less deep. Cyrtolites sp., 

Sinuites sp., Bucania sp., Bucanopsis sp., and indeterminate bellerophontaceans were found in fine-sand, silt, 

and mud bottom environments 25 m or less deep. Cyrtolites sp. was also found in coarse sands deposited in less 

than 10 m, and Sinuites was also found in brachiopodbryozoan-trilobite assemblages originating in water 

deeper than 25 m.

Hurst (1979) described the succession of benthic 

marine faunas of the type Upper Caradocian Series of 

England, a transgressive clastic sequence ranging from 

coarse onshore sands to deep-water, organic-rich, laminated shales. Bellerophontaceans were rare in nearshore 

sand and silt facies, but they composed up to 8.1 percent 

of the total fauna in stable offshore silt facies, and were 

locally common in deeper mud environments. In a gradient of 14 depositional facies (1=onshore sands, 

14=deep offshore bioturbated and laminated muds) and 

faunal assemblages, bellerophontaceans and monoplacophorans were common faunal elements (2 to 8 percent 

of total fauna) in only facies 10 through 13 (offshore silts 

to muds). Taxa cited were indeterminate bellerophontaceans (facies 6-13), Sinuites sp. (facies 8-13), Cyrtolites 

sp. (facies 11), Temnodiscus sp. (facies 10-12), Cymbularia sp. (facies 11-13), Archinacella sp. (facies 12, 13), 

and indeterminate monoplacophorans (facies 12, 13). It is 

noteworthy that Archinacella sp. and indeterminate 

monoplacophorans were found in only the deepest water

assemblages. Sinuites was the most wide ranging taxon 

in the sequence, while Cyrtolites and recognizable bellerophontaceans were concentrated in facies 10 through 12 

that occurred in offshore silt bottom environments. 

Hurst (1979, p. 239) noted that, as in the successional 

faunal stages from the Upper Ordovician of Quebec 

described by Bretsky and Bretsky (1975), Temnodiscus 

sp. and Sinuites sp. are characteristic of early diversification faunas succeeding a Nuculites-trilobite fauna that 

colonized barren fine-mud bottoms. It seems likely that 

these mollusks were dependent on the establishment of 

some member or members of a pioneer community that 

may have served as a food source and (or) a supporting 

structure above the mud bottom.

Horny (1963a) described Middle and Upper Ordovician 

bellerophontaceans from Bohemia and briefly discussed 

their paleoecology. The Bohemian Ordovician section 

consists predominantly of shales, siltstones, and sandstones, with scattered limestones. His data showed that 

bellerophontacean genera are generally distributed 

through two or more facies, but that individual species 

are restricted to a single facies. He observed that while 

few clay-shales contained bellerophontaceans, many calcareous shales contained abundant specimens. He further observed that while some explanate bellerophontacean species (Grandostoma grande, Pterotheca 

consobrind) were found only in shaly sediments, other 

explanate morphotypes (Grandostoma bohemicum, 

Bucanopsis calypso) were found in both shales and 

sandstones, and still others (Cyclotheca bohemica, 

Tremanotus tuboides) were found only in coarse-grained 

bioclastic-tuffaceous limestones around volcanic islands. 

His data suggest that the explanate shell form was not 

adapted to any special substrate conditions.

McKerrow (1978, p. 78, 83, 89) cited undetermined 

bellerophontaceans from three Ordovician communities: 

the Dinorthis Community of shallow shelf, coarse clastic 

bottoms; the Diverse Brachiopod Community of the 

middle to deep shelf environment; and the ChristianiaSampo Community of the deep shelf.

In summary, Ordovician bellerophontaceans living on 

clastic sediment substrates seem to be most common in 

siltstones and somewhat less common in calcareous 

shales, and are found only occasionally in sandstones. 

However, the environmental settings of these substrate 

types can be quite variable. Bretsky (1969, 1970b) cited 

bellerophontaceans as nearshore silt-bottom inhabitants 

in a progradational delta front setting, similar to the 

occurrences in Devonian and Pennsylvanian strata cited 

above. Conversely, Pickerill and Brenchley (1979) and 

Hurst (1979) cited their silt-bottom-dwelling bellerophontaceans and monoplacophorans from relatively deep 

offshore environments in a transgressive setting. This 

apparent discrepancy is clarified when the character and
034 CONTRIBUTIONS TO THE ORDOVICIAN PALEONTOLOGY OF KENTUCKY AND NEARBY STATES

composition of the faunas from the two settings are 

considered. Bretsky's delta front fauna contained only 

two species, with Plectonotus sp. being clearly dominant. That species may have been an opportunist, capable of surviving the relatively unstable delta front conditions with eurytopism and a high rate of fecundity (see 

Levinton, 1970). Moreover, trilobation of the shell, as in 

Plectonotus sp., has been convincingly interpreted as a 

modification of the entrance to the mantle cavity to 

increase the efficiency of water circulation (Peel, 1974, p. 

249), and thereby to assist in keeping the gills unfouled in 

turbid delta front conditions. On the other hand, the 

monoplacophoran-bellerophontacean assemblages cited 

from the British Caradocian Series are much more 

diverse (at least 10 genera), as is expected in more stable 

offshore environmental settings (see Sanders, 1968). 

Moreover, a diversity of general shell forms is present in 

the Caradocian, including cap-shaped, involute, convolute, and explanate morphotypes, probably representing 

the occupation of a variety of niches.

ORDOVICIAN CARBONATE ENVIRONMENTS

Berry (1974, p. 159) cited nautiloid cephalopods and 

bellerophontaceans and macluritacean archaeogastropods as the dominant fauna of the extensive tidal 

flat environments of the Late Cambrian-Early Ordovician carbonate platforms in North America. He interpreted all three groups as algal grazers. He (1974, 

p. 161) claimed that this nautiloid-bellerophontaceanmacluritacean fauna continued to dominate intertidal and 

adjacent shallow subtidal carbonate environments 

through the end of the Ordovician, while orthidstrophomenid brachiopod faunas came to dominate 

essentially all other subtidal carbonate environments.

Walker (1972), who studied the community ecology of 

the Black River Group (Blackriveran) of New York 

State, cited only one bellerophont, Plectonotus sp., that 

being from his wave-baffle margin community. This 

community occupied the front and back flanks of Tetradium coral banks and was dominated (80 percent of total 

biovolume) by the byssate pelecypod Cyrtodonta and the 

high-spired gastropod Loxoplocus.

There was a distinct increase in abundance and diversity of molluscan univalves in post-Blackriveran strata in 

Eastern North America. In their work on communities of 

the lower Trenton Group (Rocklandian-Shermanian) of 

New York State, Titus and Cameron (1976) cited 

Phragmolites compressus, Sinuites bilobatus corrugatus, Sinuites cancellatus, and Sinuites cancellatus acutus as common elements in the Triplesia community of 

the lagoonal facies and in the Liospira community of the 

nearshore shoal facies. Phragmolites compressus was 

also a member of the Encrinurus community of the

foreshoal shallow shelf facies. Titus (1982) continued this 

work on the communities of the middle Trenton Group 

(Shermanian) of New York State. He reported Sinuites 

cancellatus liratus from the Liospira community in the 

nearshore shoal facies, Sinuites cancellatus from the 

Encrinurus community in the foreshoal shallow shelf 

facies, and Sinuites bilobatus corrugatus from the Trematis community in the offshore open shelf facies.

Byers and Galvin (1979) studied two contemporaneous 

communities from normal marine shallow subtidal deposits of the Platteville Formation (Rocklandian) in Wisconsin. Sinuites sp. and Phragmolites sp. were found to 

make up 11 and 2 percent of the first community, 

respectively. The second community, which contained 

the same common taxa but in different percentages, had 

Sinuites sp. and Phragmolites sp. making up 26 and 1 

percent of the community, respectively, with Sinuites 

sp. being the most abundant fossil in the total assemblage. Sinuites sp., which was considered to be an 

algal-browsing archaeogastropod, was in many places 

found alone covering bedding planes, and the authors 

suggested that it might have been an opportunistic 

species.

The scant data on molluscan univalves from studies of 

communities on carbonate strata of the Champlainian 

Series give a deceptive impression of low diversities. The 

monoplacophoran-bellerophontacean faunas of the Lexington Limestone covered herein show that these mollusks could be abundant and diverse, The apparent 

abundance of species of Sinuites and Phragmolites in 

Middle Ordovician studies from New York and Wisconsin 

cannot be readily explained, as these genera are not 

dominant in the Middle Ordovician strata of the intervening Cincinnati arch region but are more common in 

the more shale rich Late Ordovician strata of that area.

In summary, it appears from examination of Middle 

and Upper Ordovician benthic marine community studies 

that only a small number of bellerophontacean and 

monoplacophoran taxa were associated with onshore 

environments; rather, most were distributed throughout nearshore and offshore normal marine shelf 

environments.

POST-ORDOVICIAN PALEOECOLOGICAL STUDIES 

OF NOTE

In a general study of Silurian-Devonian communities, 

Boucot (1975, p. 13-18) charted six benthic assemblages. 

His only mention of bellerophontaceans was his 

Homolonotid-Plectonotus community, which characterized the most nearshore assemblage zone (Benthic 

Assemblage 1). Berry (1975, p. 49, fig. 15) interpreted 

this community as occupying a quiet-water, high intertidal environment.
MIDDLE AND UPPER ORDOVICIAN SYMMETRICAL UNIVALVED MOLLUSKS, CINCINNATI ARCH REGION 035

Peel (1975a, c, 1977b, 1978) contributed greatly to the 

understanding of the paleoecology of Paleozoic gastropods through his studies of the faunas of the Silurian 

Arisaig Group of Nova Scotia. The morphotypic composition of these Silurian monoplacophoranbellerophontacean faunas is similar to the compositions of 

Middle and Late Ordovician faunas, so Peel's observations apply to the present investigation. The Arisaig 

Group is a 1,300-m-thick siltstone-dominated sequence 

that provides a nearly continuous faunal record of shallow marine communities throughout the Silurian and 

Early Devonian Periods. Watkins and Boucot (1975) and 

Bambach (1969) have studied the brachiopods and pelecypods of the Arisaig Group, respectively. Watkins and 

Boucot (1975) concluded that most of the Arisaig could be 

referred to nearshore Benthic Assemblage 2 of Boucot 

(1975), with offshore Benthic Assemblages 3 and 4 in 

some parts of the group. Peel's (1977b, 1978) observations on bellerophontacean paleoenvironmental distributions are summarized below.

1. The hard-bottom shallow marine platform fauna was 

characterized by trochiform pleurotomariaceans, 

with the small, globose bellerophontacean Bucanopsis sp. making up 12 percent of the gastropod fauna.

2. The soft-bottom shallow marine platform fauna was 

dominated by high-spired murchisoniids and loxonomataceans, with the trilobed Tritonophon trilobata and the explanate Phragmosphaera globata 

making up 14-25 and 12 percent of the gastropod 

fauna, respectively.

3. The soft-bottom open lagoon fauna typically was 

heavily dominated by trochiform holopeids. With a 

decrease in water depth, the holopeids were 

replaced by a fauna of small bellerophontaceans, 

including trilobed plectonotinids, and by lenticular 

pleurotomariaceans and some high-spired gastropods.

Peel (1975a, c, 1978) suggested that explanate bellerophontaceans in the Arisaig, such as Phragmosphaera 

globata, were adapted to life on soft substrata, the 

broadly expanded apertures serving to support the shell 

on top of the sediment. He further reasoned (1978, p. 

302, 303) that gastropods ranging up to 10-15 mm in 

diameter, including species of Tritonophon, Tropidodiscus, Pharetrolites, and Cymbularia, could have been 

algal foliage dwellers.

Heuer (1973, p. 510-541) discussed the paleoecology of 

Upper Pennsylvanian gastropods from the Wolf Mountain Shale (Canyon Group, Missourian Series) of northcentral Texas. The Wolf Mountain Shale was deposited in 

a prodeltaic shallow shelf setting. The formation contains 

a diverse gastropod fauna, including 13 genera and 24 

species of pleurotomariaceans, and 3 genera and 4 species of bellerophontaceans, as well as less common

euomphalaceans, murchisoniaceans, and subulitaceans. 

Heuer (1973, p. 527-530) concluded that the bellerophontaceans were deposit feeders that lived on the sea floor, 

while the pleurotomariaceans mostly dwelled above the 

sea floor on erect organisms such as algae, crinoids, 

bryozoans, and sponges. He proposed that the pleurotomariaceans either fed directly on their supporting hosts 

or fed on epizoans and organic detritus on the surfaces of 

the hosts. Heuer claimed that the morphology of the 

bellerophontaceans was better adapted to life on soft 

substrates, as indicated by (1) generally shorter labral 

slits than in the cooccurring pleurotomariaceans, reflecting shallower mantle cavities that could be more easily 

flushed of fouling detritus by rapid contractions of the 

shell muscles, (2) a symmetrical shell with a low center of 

mass due to the weighting of thick parietal deposits, 

which would give greater stability during movement 

through soft sediments, and (3) the presence of broad to 

explanate apertural margins in three of four bellerophontacean species (B. (Bellerophori) sp., B. (Pharkidonotus) 

percarinatus, and Knightites (Cymatospird) montfortianus) in the fauna, reflecting a broad foot that would 

prevent sinking into soft sediment.

A survey of a complete spectrum of Paleozoic community studies gives the impression that bellerophontaceans were most abundant during the Devonian and 

Pennsylvanian Periods, and most commonly occurred in 

communities associated with delta front environments 

(as previously discussed). It should be noted that in such 

occurrences a single species is usually dominant and 

probably represents opportunistic situations. More significantly, most bellerophontacean genera have been 

cited from Paleozoic communities throughout the marine 

environmental spectrum. Linsley (1968, p. 360) found 

bellerophonts in environments associated with Devonian 

coral-stromatoporoid biostromes. Moore (1964, p. 

339-341) cited bellerophontaceans as being scattered 

throughout most marine facies in Kansas PennsylvanianLower Permian cyclothems, but they were most abundant in nearshore limestones containing algal (Osagia)- 

molluscan assemblages. Stevens (1965,1966) and Yancey 

and Stevens (1981) cited bellerophontaceans (Euphemitid community) as characterizing Middle Pennsylvanian to Lower Permian communities inhabiting the subtidal to lower intertidal zone of large bays or sounds, 

where sedimentation was rapid and salinity was variable, 

though generally normal. Yochelson (1969) and Imbrie 

and others (1964) cited bellerophontaceans from firmsubstrate "shelly facies" from Mississippian and Pennsylvanian carbonates, respectively. Ausich and others 

(1979, p. 1191-1193), who studied Mississippian Borden 

delta communities in Indiana and Kentucky, noted bellerophontaceans in prodelta slope and basin siltstones 

and shales deposited in up to 500 ft of water. They
036 CONTRIBUTIONS TO THE ORDOVICIAN PALEONTOLOGY OF KENTUCKY AND NEARBY STATES

speculated that these patchy basinal communities, which 

were dominated by gastropods, survived at these depths 

by feeding on plant debris channeled down submarine 

canyons. Interestingly, some modern pleurotomariaceans lead a similar mode of life in deep western 

Atlantic waters (Abbott, 1968, p. 52).

Monoplacophorans are generally so rare in Paleozoic 

communities that they are not even cited in paleoecological studies. Notable exceptions are species of the isostrophically coiled Ordovician genera Sinuites and Cyrtolites, both of which are locally abundant in Ordovician 

mollusk-dominated assemblages discussed in the following sections.

In summary, from this review it appears that Paleozoic 

monoplacophorans and bellerophontaceans were not uniformly nearshore algal grazers as generally assumed, but 

occupied a wide range of depositional environments and 

probably led a number of different modes of life. Most 

probably fed on marine algae and therefore occupied 

those shallow-water depositional environments where 

plant growth was most prolific. Some must have grazed 

on algal mats and rasped algal coatings from hard 

surfaces. Others, particularly those taxa characterized 

by small, lightweight shells, dwelled within and fed upon 

the foliage of erect benthic algae. Those taxa occurring in 

deeper soft-bottom facies, as well as many of those that 

were so abundant in turbid delta front areas, were most 

likely detritus feeders and scavengers. Some taxa having 

disjunct coils, or other features that seem to indicate an 

essentially immobile existence, may have been suspension feeders. The common occurrence of bellerophontaceans in fine-grained soft-bottom facies does not lend 

support to Yonge's (1947) conclusion that the presumed 

aspidobranch gill of primitive mollusks is intolerant of 

turbid conditions. Bellerophontaceans thought to be too 

large and too heavy to have been supported in algal 

foliage are commonly found in "muddy" rocks, and probably dwelled on the soft bottoms. Many bellerophontaceans were euryhaline and were able to build large 

populations in such unstable environments as delta 

fronts, bays, and restricted lagoons. In fact, lowdiversity bellerophontacean assemblages dominate the 

faunas of many such depositional environments, particuTABLE 5. Relative abundance of species in USGS silicified samples

from the Tyrone Limestone 

[Total number of samples = 3; total number of specimens = 40]

Species Percentage 

of fauna

No. of 

samples

Salpingostoma kentuckyense

Pterotheca expansa

Tropidodiscus cf. T. subacutus

Archinacella cf. A. simulatrix

68

28

2

2

1

1

1

1

larly in Devonian though Permian strata. However, at 

least in Ordovician strata, higher diversity assemblages 

of bellerophontaceans and monoplacophorans occur in 

more normal marine settings but are much less abundant 

in number of specimens.

PALEOECOLOGY OF SYMMETRICAL UNIVALVED 

MOLLUSKS OF THE TYRONE LIMESTONE AND THE 

LEXINGTON LIMESTONE OF CENTRAL KENTUCKY

The USGS silicified fossil collections from the Middle 

Ordovician limestones of Kentucky were taken as bulk 

samples that were precisely located both stratigraphically and geographically. Such collections afford a potential for paleoecological analyses never before available. 

Most previously existing collections of fossils from these 

strata were gathered around the turn of the century and 

generally are accompanied by vague locality data which 

are difficult to use because of changes in stratigraphic 

nomenclature and geographic markers.

Of the 200 silicified collections from the Ordovician 

strata of Kentucky and adjacent States (Pojeta, 1979), 87 

contained approximately 2,700 specimens of monoplacophorans and bellerophontacean gastropods classifiable 

to species. In attempting to analyze the paleoenvironmental distribution of these data, it was found that data 

regarding mere presence or absence in the various 

stratigraphic units reveal little of paleoecological significance (table 3). Many taxa were distributed through 

numerous stratigraphic units, and therefore through 

many depositional environments. However, upon 

constructing histograms of relative abundance of 

taxa by percentage of the total monoplacophoranbellerophontacean fauna in a stratigraphic unit, the 

dominance of certain species in different paleoenvironmental settings became obvious. Tables 5-13 display the 

distribution and relative abundance of individual species 

in the USGS silicified collections from the Tyrone Limestone, various members of the Lexington Limestone and 

the Clays Ferry Formation.

TYRONE LIMESTONE

Three silicified samples from the Tyrone Limestone 

contained 40 specimens of monoplacophorans and bellerophontaceans. Two of these samples each contained 

only a single specimen of one of two species, Tropidodiscus cf. T. subacutus and Archinacella cf. A. simulatrix 

(table 5). The third sample (6034-CO) contributed 96 

percent of the Tyrone specimens two explanate species, Salpingostoma kentuckyense (pi. 25, figs. 1-14) and 

Pterotheca expansa (pi. 40. figs. 5-7). The low diversity 

of the Tyrone fauna may be partly the result of the small 

number of samples. The apparent abundance of the two 

explanate species might demonstrate support for Peel's
MIDDLE AND UPPER ORDOVICIAN SYMMETRICAL UNIVALVED MOLLUSKS, CINCINNATI ARCH REGION 037

TABLE 6. Relative abundance of species in USGS silicified samples 

from the Curdsville Limestone Member of the Lexington 

Limestone

[Total number of samples = 13; total number of specimens = 263]

Species

Sinuites obesus

Cyrtolites cf. C. (Cyrtolites) retrorsus

Salpingostoma kentuckyense

Carinaropsis acuta

Salpingostoma sp. indet.

Pterotheca expansa

Micropileus variabilis

Sphenosphaera sp. indet.

Bucania cf. B. halli

Tropidodiscus sp. indet.

Archinacella cf. A. simulatrix

Bucania sp. indet.

Cyrtolitesh sp. indet.

Tetranota cf. T. obsoleta

Vallatotheca cf. V. unguiformis

Pterotheca angusta

Bucania subangulata

Percentage 

of fauna

41

24

9

6

4

4

3

2

1.5

1.5

1

1

1

1

1

1

1

No. of 

samples

9

3

2

5

2

2

2

2

2

2

1

4

2

1

1

1

1

Species

Carinaropsis cymbula

Sphenosphaera clausus

Bucanopsis carinifera

Cyrtolites (Cyrtolites) retrorsus

Sphenosphaera cf. S. burginensis

Sphenosphaera cf. S. troosti

Cyrtolites (Paracyrtolites) subplanus

Archinacella simulatrix

Bucania cf. B. nashvillensis

Bucania sp. indet.

Bucania subangulata

Cyrtolites sp. indet.

Sphenosphaera cf. S. clausus

Sphenosphaera sp. indet.

Carinaropsis sp. indet.

Bucania cf. B. sublata

Tropidodiscus sp. indet.

Sinuites sp. indet.

Percentage 

of fauna

25

19

13

9

8

7

4

3

3

2

1

1

1

1

1

1

1

1

No. of 

samples

11

6

6

6

3

3

1

4

2

4

2

3

2

2

2

1

1

1

(1978) hypothesis that explanate shell forms were an 

adaptation for soft substrates, as the Tyrone is characterized by very fine-grained limestone lithologies representing mainly lime mud deposited in shallow lagoon and 

tidal flat environments. However, collection 6034-CO is 

from a shell bed within a calcarenite surrounded by fine 

grained limestone lithologies.

LEXINGTON LIMESTONE

The distribution of monoplacophoran-bellerophontacean assemblages in the members of the Lexington 

Limestone seems to reflect three stages of faunal dominance. Different taxa groups dominate (1) the Curdsville 

Limestone and Logana Members (tables 6, 7), (2) the 

Grier Limestone Member (table 8), and (3) the upper 

Lexington limestone members and the intertonguing 

Clays Ferry Formation (tables 9-13). It should be noted 

that these three stages are stratigraphically distributed 

through the lower, middle, and upper parts of the 

Lexington Limestone.

TABLE 8.—Relative abundance of species in the USGS silicified 

samples from the Grier Limestone Member of the Lexington Limestone

[Total number of samples = 18; total number of specimens = 541]

The lowest members of the Lexington, the Curdsville 

Limestone and Logana Members, were dominated by 

two species, these being, in order of decreasing abundance, Sinuites obesus (pi. 9, figs. 1-12) and Cyrtolites 

(C.) retrorsus (pi. 5, figs. 1-4, 13), with Salpingostoma 

kentuckyense (pi. 24. figs. 10-12) continuing to be a 

common element from the Tyrone Limestone into the 

transgressive deposits of the lower portion of the Curdsville Limestone Member (tables 6, 7). The Curdsville has 

a high species diversity (17 species), probably reflecting 

the variety of depositional environments represented in 

the unit, from shallow transgressive bar and interbar 

deposits in the lower part of the unit to deeper subtidal 

environments in the upper part where it intertongues 

with the Logana Member. The three species cited above 

constitute 74 percent of the Curdsville fauna. The

TABLE 9.—Relative abundance of species in USGS silicified samples

from the Perryville Limestone Member of the Lexington Limestone

[Total number of samples = 5; total number of specimens = 217]

TABLE 7.— Relative abundance of species in USGS silicified samples 

from the Logana Member of the Lexington Limestone 

[Total number of samples = 8; total number of specimens = 534]

Soecies Percentage No. of 

v of fauna samples

Sinuites obesus 77 6 

Cyrtolites (Cyrtolites) retrorsus 11 4 

Cyrtolites cf. C. (C.) retrorsus 11 5 

Carinaropsis cymbula 1 1 

Cyrtolites (Paracyrtolites) subplanus 1 1 

Carinaropsis cf. C. acuta 1 1

Species

Sphenosphaera clausus 

Bucanopsis carinifera 

Bucania cf. B. sublata 

Vallatotheca unguiformis 

Carinaropsis cymbula

Bucania cf. B. nashvillensis 

Sphenosphaera cf. S. burginensis 

Sphenosphaera sp. indet. 

Tropidodiscus subacutus 

Cyrtolites (Cyrtolites) retrorsus

Sphenosphaera cf. -S. bilineatus

Percentage 

of fauna

47 

12 

7 

6 

6

5 

4 

4 

3 

2

1

No. of 

samples

4 

4 

2 

3 

1

3 

1 

2 

3

1

1
038 CONTRIBUTIONS TO THE ORDOVICIAN PALEONTOLOGY OF KENTUCKY AND NEARBY STATES

TABLE 10. Relative abundance of species in USGS silicified samples

from the Devils Hollow Member of the Lexington Limestone

[Total number of samples =4; total number of specimens = 187]

Species

Tropidodiscus subacutus

Bucania cf. B. frankfortensis

Bucanopsis diabloensis

Sphenosphaera sp. indet.

Tropidodiscus sp. indet.

Sphenosphaera cf. S. clausus

Bucofnia cf. B. sublata

Sphenosphaera clausus

Percentage 

of fauna

70

11

7

5

4

2

1

1

No. of 

samples

2

1

2

1

2

1

2

1

Logana Member represents the height of the initial 

Lexington transgression, and may represent the deepest 

water environments in the formation. Although the 

Logana is a much more homogeneous lithologic unit of 

deeper water origin compared with the Curdsville Limestone, it is dominated by two of the same species. S. 

obesus makes up 77 percent of the low-diversity Logana 

fauna and is present in six of eight silicified samples. 

The C. retrorsus group makes up 22 percent of the 

Logana fauna (table 7). It is noteworthy that the 

monoplacophoran-bellerophontacean fauna of the Edenian Kope Formation, which consists of relatively deep 

water shales at the base of the Cincinnatian Series, is 

also dominated by species of Sinuites and Cyrtolites. The 

Logana fauna is low in diversity, having only five species 

in three genera, and three of those species accounting for 

only about 1 percent of the symmetrical univalved fauna. 

The Grier Limestone Member represents the 

most enduring, widespread, and uniform environmental conditions during Lexington deposition. Its 

monoplacophoran-bellerophontacean fauna is somewhat 

transitional in composition, and its high diversity (18 

species) and even distribution of species relative abundance (table 8) apparently reflect the stability of the 

Grier environment. The nodular wackestones of the 

Grier indicate a soft-bottom environment with shell beds, 

and the abundance and variety of a normal marine fauna 

indicate a very favorable habitat. The three dominant 

symmetrical univalved molluscan species in the Grier 

are, in order of descending abundance, Carinaropsis

TABLE 11. —Relative abundance of species in USGS silicified samples

from the Millersburg Member of the Lexington Limestone

[Total number of samples = 5; total number of specimens = 80]

Species

Sphenosphaera clausus 

Cyrtolites (Cyrtolites) retrorsus 

Archinacella sp. indet. 

Cyrtolites sp. indet. 

Sphenosphaera sp. indet.

Percentage 

of fauna

68 

19 

9 

4 

1

No. of 

samples

5 

2 

1 

2 

1

TABLE 12. Relative abundance of species in USGS silicified samples 

from the Tanglewood Limestone Member of the Lexington 

Limestone

[Total number of samples = 5; total number of specimens = 89]

Species

Sphenosphaera cf. S. clausus

Sphenosphaera clausus

Bucanopsis carinifera

Sphenosphaera sp. indet.

Carinaropsis cymbula

Carinaropsis sp. indet.

Percentage 

of fauna

65

15

13

5

1

1

No. of 

samples

3

1

1

1

1

1

cymbula (25 percent) (pi. 38, figs. 1-12), Sphenosphaera 

clausus (19 percent) (pi. 31, figs. 7-10), and Bucanopsis 

carinifera (13 percent) (pi. 27, figs. 8-12). All have 

rapidly expanding shell forms, but only the first can be 

considered truly explanate. The abundance of morphotypes having broadly expanded apertures is comparable 

to Peel's (1977b, 1978) soft-bottom shallow-marine platform fauna from the Silurian Arisaig Group discussed 

earlier. It should be noted that the intrageneric species 

diversities are higher than in any other member of the 

Lexington Limestone. Cyrtolites, Bucania, and Spheno 

sphaera all have more than one species in the Grier, 

probably attesting to environmental stability and 

greater partitioning of niches.

The upper Lexington Limestone is a complex facies 

mosaic of interfingering carbonate depositional environments which intertongues upward with the more shaly 

deposits of the Clays Ferry Formation. Except for the 

Devils Hollow Member, all members of the upper Lexington Limestone, as well as the intertonguing Clays 

Ferry Formation, are dominated by Sphenosphaera 

clausus, with species of Bucanopsis, Cyrtolites, and 

Carinaropsis distributed throughout (tables 9-13). 

Whereas the S. clausus group makes up nearly 70 

percent of the upper Lexington monoplacophoranbellerophontacean fauna, it is nearly absent from the 

Devils Hollow Member, which is dominated by 70 percent Tropidodiscus subacutus, a species that is rare in 

other members. This discrepancy might be explained by 

the small number of samples from the Devils Hollow

TABLE 13. Relative abundance of species in USGS silicified samples

from the Clays Ferry Formation 

[Total number of samples = 12; total number of specimens = 419]

Species

Sphenosphaera clausus 

Cyrtolites (Cyrtolites) claysferryensis 

Sphenosphaera cf. S. clausus 

Sphenosphaera sp. indet. 

Bucania rugatina 

Bucania sp. indet.

Percentage 

of fauna

73 

16 

8 

2 

1 

1

No. of 

samples

7 

10 

3 

3 

2 

2
MIDDLE AND UPPER ORDOVICIAN SYMMETRICAL UNIVALVED MOLLUSKS, CINCINNATI ARCH REGION 039

Member. Only one sample accounts for the apparent 

dominance by T. subacutus in the unit; however, if this 

sample is ignored, Sphenosphaera spp. is still subordinate to other species in the Devils Hollow. Cressman 

(1973, p. 41) suggested that the Devils Hollow represents 

very shallow restricted lagoon and bar deposits. Most 

other upper Lexington members represent more normal 

shallow marine conditions, possibly accounting for the 

faunal differences.

The marked dominance of S. clausus through such 

varied depositional environments as the Perryville Limestone, Millersburg, and Tanglewood Limestone Members of the upper Lexington Limestone, as well as the 

relatively shale rich Clays Ferry Formation, is difficult 

to explain. It can only be assumed that there was some 

unifying environmental factor, such as a food source, in 

these varied environments that allowed the species to 

flourish during this period. In any case, S. clausus must 

have been an ecological generalist. When the paleosynecology of the entire Lexington fauna is analyzed, explanations for the distribution of individual taxa may 

become more clear. It is interesting that while most of 

the members of the upper Lexington Limestone are 

moderately shallow water facies and would seem to be 

adequate habitats for symmetrical molluscan univalves, 

diversities generally are relatively low. The Perryville 

Limestone Member is most diverse with 11 species; next 

is the Devils Hollow Member with 8 species. The Millersburg and Tanglewood Limestone Members, as well as 

the Clays Ferry Formation, contain only 5-6 species 

each. The Millersburg, which is similar to the Grier 

Limestone Member in lithology, bedding style, and overall fauna (Cressman, 1973, p. 43), would especially be 

expected to contain a more diverse fauna. This apparent 

anomaly can probably be explained by there being only 5 

samples from the Millersburg, compared with 18 samples 

from the Grier Limestone Member.

COMMENTS ON THE PALEOECOLOGY OF THE 

STONES RIVER GROUP OF CENTRAL TENNESSEE

The bellerophontaceans from the BlackriveranKirkfieldian-age Stones River Group of central Tennessee are listed in table 1. Data are derived from Wilson 

(1949) and museum specimens examined in the present 

study. No relative-abundance data or any other significant paleoecological data on the fauna are available, and 

except for a few observations made below, the available 

data do not permit detailed analyses. No monoplacophorans are listed in Wilson (1949).

The apparent low diversity of the Stones River fauna 

may be the result of a scarcity of collections. Only four 

genera and seven species are known (table 1). However, 

both the Stones River and High Bridge Groups represent

shallow subtidal-intertidal environments that are generally thought to be ideal habitats for the animals under 

discussion, and the low-diversity assemblages may truly 

reflect a paucity of species during that time.

Tetranota bidorsata is distributed throughout the 

Stones River Group (table 1). Both Pterotheca expansa 

and P. saffordi (pi. 39, figs. 1, 2) occur in thin-bedded 

limestones in association with abundant leperditicopid 

ostracodes, suggesting that these species were adapted 

to tidal flat and restricted lagoonal environments (pi. 39, 

figs. 5, 12 13; pi. 40, figs. 8, 9). Such occurrences are also 

known from the correlative High Bridge Group of 

Kentucky.

COMMENTS ON THE PALEOECOLOGY OF THE 

NASHVILLE GROUP OF CENTRAL TENNESSEE

The occurrences of monoplacophoran and bellerophontacean taxa in the Nashville Group are listed in table 2. 

Data are from museum specimens examined in this study 

and from faunal lists by Wilson (1949). No relativeabundance data are available.

HERMITAGE FORMATION

The monoplacophoran-bellerophontacean fauna of the 

Hermitage Formation is apparently of low diversity and 

abundance. Wilson (1949) reported species from only two 

members, Phragmolites cellulosus (pi. 43, figs. 4-12) 

from the Curdsville Limestone Member and P. cellulosus with Cyrtolites retrorsus from the "Ctenodonta 

member." Other species identified from museum collections in this study were Archinacella valida (pi. 2, figs. 

15, 16) and Undulabucania punctifrons (pi. 23, figs. 

1-9). Museum labels on these specimens do not allow 

more precise placement within the members of the 

formation. One noteworthy point is that both of the 

species listed by Wilson (1949) were reported from 

the two shallowest subtidal facies of the Hermitage 

Formation.

BIGBY-CANNON LIMESTONE

It is unfortunate that currently only presence-absence 

data are available for species from the Bigby-Cannon 

Limestone. That formation seems to be an ideal unit for 

paleoecological analysis, as it consists of a high-energy 

subtidal shoaling facies (Bigby facies), a low-energy shelf 

lagoon facies (Cannon facies), and a restricted lagoontidal flat facies (dove-colored facies). Nevertheless, some 

trends are discernible. Table 2 shows the distribution of 

monoplacophoran-bellerophontacean taxa in these three 

facies, as well as in the overlying Catheys Formation. 

Data are derived from both Wilson's (1949) species lists
040 CONTRIBUTIONS TO THE ORDOVICIAN PALEONTOLOGY OF KENTUCKY AND NEARBY STATES

and specimens in museum collections examined during 

the present study.

The Cannon facies contains nine species of monoplacophorans and bellerophontaceans, approximately twice 

the number reported from either of the other facies of the 

Bigby-Cannon Limestone. Alberstadt (1973, p. 630) cited 

preliminary work showing that most Cannon communities were dominated by bellerophontid and lophospirid 

gastropods and leperditicopid ostracodes. He suggested 

that the dark, organic-rich, muddy wackestonepackstone of the Cannon indicates quiet, nearly stagnant 

lagoonal conditions. Alberstadt (1973, p. 626) attributed 

much of the organic material in the Cannon to marine 

algae. Blue-green algal encrustations are common, but 

the rock also contains an appreciable amount of crushed, 

dark-orange and brown fragments of unidentifiable 

organic fossils, which probably are of algal origin. One 

such fragment illustrated by Alberstadt (1973, fig. 5D) 

resembles a small plumose growth of blue-green algae. It 

seems likely that the abundant gastropods and other 

fauna lived above the fetid mud bottom on such algal 

masses. Considering the moderately large shells of some 

of the Cannon bellerophontaceans (for example, Bucania 

sp. and Sphenosphaera spp.), if the animals were indeed 

algal foliage dwellers, the algae may have formed low, 

thick bushes or mats capable of supporting their weight. 

It seems the algae not only would have been a food 

source for the gastropods, but also might have baffled 

and stabilized the muddy sediment, effectively reducing 

turbidity. If the Cannon bellerophontaceans were not 

algal foliage dwellers, they must have been able to cope 

with muddy substrate conditions much better than predicted by Yonge (1947). In fact, the abundance of bellerophontaceans in such organic-rich fine sediments might 

lend support to the interpretation that they were 

bottom-dwelling detritus feeders and scavengers.

Each facies of the Bigby-Cannon Limestone contains a 

variety of general bellerophontacean morphotypes, and 

without relative-abundance data, no patterns are obvious. The high-energy shoals of the Bigby facies and the 

lagoonal-tidal flat muds of the dove-colored facies each 

supported approximately the same number of 

monoplacophoran-bellerophontacean species, three of 

which are common to both facies. Four of the species in 

the dove-colored facies are also found in the Cannon 

facies, but only two of the five Bigby species also are 

found in the Cannon.

COMMENTS ON THE PALEOECOLOGY OF 

UPPER ORDOVICIAN FAUNAS

Data on the paleoecology of the molluscan univalve 

taxa in the Upper Ordovician of the tristate area are 

scant. Previous paleoecological studies have focused on

TABLE 14.—Relative abundance of species in USGS silicified samples

from the Dillsboro Formation in Indiana 

[Total number of samples = 2; total number of specimens = 337]

Species

Sphenosphaera mohri 

Cyrtolites (Cyrtolites) hornyi 

Archinacella indianensis 

Bellerophontacean sp. indet.

Percentage 

of fauna

74 

13 

12 

1

No. of 

samples

2 

1 

1 

1

the prolific brachiopod and bryozoan faunas of these 

strata, and gastropods generally are mentioned only as a 

general grouping (Fox, 1962, 1968; Hatfield, 1968; Richards, 1972; Richards and Bambach, 1975; Harris and 

Martin, 1979). Mollusks usually are abundant only in 

sparse, mollusk-rich beds scattered through the section. 

Pojeta (1971) has discussed the autecology of Upper 

Ordovician pelecypods, but the synecology and environmental distribution of entire molluscan communities 

remain unstudied.

Silicified beds and fossils are uncommon in the Upper 

Ordovician of the tristate area, and only a few collections 

were made by the USGS. Most specimens examined here 

were from existing museum collections. The current data 

base does not allow detailed paleoecological analysis. The 

USGS silicified samples from the Liberty biofacies of the 

Dillsboro Formation (Richmondian) of southeastern Indiana (6139-CO, 6140-CO) were the only Upper Ordovician 

USGS collections containing abundant well-preserved 

and silicified specimens (table 14). These samples contained specimens of Cyrtolites hornyi (pi. 8, figs. 1-12), 

Sphenosphaera mohri (pi. 36, figs. 1-12), and Archinacella indianensis (pi. 3, figs. 19, 20). The only other 

common genera in Upper Ordovician rocks of the area 

are species of Sinuites (pi. 10, figs. 1-13) and Salpingostoma (pi. 26, figs. 1-8).

By far the most abundant taxa in the Cincinnatian 

section are species of Sinuites and Cyrtolites. Specimens 

of these two genera are locally abundant in molluskdominated beds, in many places occurring together, 

generally with one or the other clearly dominant. Such 

mollusk beds generally are thin limestone beds or lenses 

in interbedded limestone and shale sections. Adjacent 

strata are commonly dominated by brachiopod-bryozoan 

assemblages. The mollusk beds are generally considered 

to represent special environmental conditions, such as 

nearshore areas having abnormal marine salinities, but 

at present there are few sedimentological data to support 

such interpretations. Before interpretations can be made 

with confidence, detailed sedimentological and paleoecological analyses of thick stratigraphic sections are 

needed. One such section is locality KY-1 (see appendix), 

near Carrollton, Ky., where the well-exposed Kope 

Formation contains a number of such isolated mollusk 

beds. The small slab shown on plate 8, figure 21, is from
MIDDLE AND UPPER ORDOVICIAN SYMMETRICAL UNIVALVED MOLLUSKS, CINCINNATI ARCH REGION 041

this locality and demonstrates the diversity of mollusks 

that can be present in such beds.

At locality OH-1 (Bear Creek Quarry), an argillaceous, 

mollusk-rich limestone lens surrounded by gray shale 

was found in the lower Kope Formation, about 10 ft 

above the Point Pleasant Tongue of the Clays Ferry 

Formation. This small lens was only a few feet across and 

a maximum of about 3 in thick. The surrounding shale 

and overlying and underlying limestone beds were dominated by trilobite-crinoid-brachiopod assemblages. 

Excavation of about 4 ft2 (square feet) of the lens 

produced more than 100 well-preserved specimens of 

Sinuites planodorsatus, 5 specimens of Tetranota bidorsata (pi. 21, figs. 1-8), 1 specimen of Cyrtolites claysferryensis, and sparse othoconic nautiloids, lingulid brachiopods, small loxonometacean gastropods, crinoid 

ossicles and Cryptolithus trilobite fragments (pi. 4, fig. 

17; pi. 21, fig. 1). This great concentration of symmetrical 

molluscan univalves is puzzling, as the surrounding 

strata apparently are barren of the taxa; perhaps it can 

be attributed to a localized food source. Petrographic 

analysis has not yielded any significant clues as to the 

nature of this possible food source. Another possible 

interpretation is that the mollusks were not the feeders, 

but rather the meal. Could such a concentration of shells 

be the ''nest" of predatory nautiloids? It should be noted 

that the monoplacophoran and bellerophontacean shells 

are exceedingly well preserved and show no breakage. 

But then, there is no evidence for the presence of an 

operculum in these early forms that would have required 

forced entry by predators. Other such occurrences 

should be watched for, in the hope that clues to their 

origin can be found.

A third field occurrence, from the Clays Ferry Formation of north-central Kentucky, was a mollusk bed dominated by Cyrtolites claysferryensis and also containing 

lophospirid gastropods and sparse pelecypods (pi. 4, figs. 

15, 16). Of particular interest is a specimen of C. (Cyrtolites) claysferryensis with an apparent borehole 

through its dorsum (pi. 4, fig. 15). Fenton and Fenton 

(1931), Carriker and Yochelson (1968), and Sohl (1969) 

have reviewed the occurrence of Paleozoic borings, 

which are common in brachiopods in the Upper Ordovician. Although Fenton and Fenton (1931) and most other 

early authors assumed that these borings were made by 

predatory gastropods, reviews of more recent authors 

have concluded that there is little evidence to support 

this interpretation. Sohl (1969) believed that the predatory boring habit common to many Holocene snails did 

not arise until Late Cretaceous time. He further agreed 

with Carriker and Yochelson (1968) that Paleozoic borers 

probably were mainly unknown soft-bodied organisms 

that employed a purely chemical means of boring. The 

boring shown here is believed to be the first reported in

a monoplacophoran shell. It is interesting that this 

boring is in the approximate position of the shell muscles.

The possible sources of nutrition and modes of feeding 

for primitive gastropods and monoplacophorans were 

discussed earlier, and it was stressed that evidence in the 

fossil record is scarce indeed. One approach to solving 

this puzzle is to draw conclusions from repeated associations. For example, the repeated occurrence of species 

of Pterotheca with leperditiid ostracodes in restricted 

lagoonal to intertidal environments in the Stones River 

and High Bridge Groups could be viewed as evidence 

of an algal grazing habit (pi. 39, figs. 3-5, 12, 13; pi. 40, 

figs. 8, 9).

Another association that has been observed repeatedly 

in Upper Ordovician strata is the occurrence of species of 

Phragmolites with small sticklike bryozoans. Phragmolites was never observed in mollusk-dominated beds, but 

was seen only in predominantly bryozoan-brachiopod 

assemblages. P. dyeri is shown on plate 45, figure 11, 

with abundant sticklike bryozoans. Specimens in the 

original type suite of P. elegans (pi. 45, fig. 10) are 

preserved with the aperture attached to sticklike bryozoans. The evidence is far from conclusive, but it is 

suggested that Phragmolites may have grazed on these 

bryozoans. The shells of most species of Phragmolites 

are small and thin enough to have been supported in 

bryozoan thickets. Note also the specimen of the related 

species Undulabucania punctifrons preserved with its 

aperture clamped over a massive bryozoan colony (pi. 23, 

figs. 2, 3).

Sphenosphaera mohri (pi. 35, figs. 1-14) and Salpingostoma richmondensis (pi. 26, figs. 1-8) have been 

observed in the rubbly, higher energy deposits in the 

Richmondian-age Whitewater Formation of southeastern Indiana. These relatively large, massive-shelled species are commonly associated with massive bryozoans 

and brachiopods in transported shell-debris deposits, 

where much of the skeletal material is broken and worn. 

S. mohri is commonly found encrusted by massive bryozoans. Apparently these taxa inhabited higher energy 

environments either on or surrounding shoaling areas.

SHELL SCULPTURING AND ENCRUSTATION AS 

DEFENSES AGAINST PREDATION

As noted in the "Systematic Paleontology" section 

under the appropriate species, shell sculpturing might be 

an adaptation for camouflage against predators. Most 

notable examples are the reticulate patterns on the shells 

of species of C. (Cyrtolites) (pis. 4-7) and the fine wavy 

patterns on the shells of species of Undulabucania 

(pi. 23, figs. 1-15).

Of even greater advantage for camouflage is encrustation by epizoans. Carrier shells (gastropods that cement
042 CONTRIBUTIONS TO THE ORDOVICIAN PALEONTOLOGY OF KENTUCKY AND NEARBY STATES

skeletal debris to their surface for camouflage) are 

known from the Devonian (Linsley and Yochelson, 1973) 

to the Holocene. McNamara (1978) has discussed the 

encrustation of Late Ordovician gastropods by bryozoans, and suggested a symbiotic relationship. The gastropod was afforded protection from predators, while the 

bryozoan benefited by having a perch from which to 

suspension feed. Benefit to the bryozoan was enhanced 

by currents created by the movement of the gastropod, 

as well as by the movement of currents through the shell 

of the gastropod.

Bryozoan-encrusted shell debris of all kinds abounds in 

many Upper Ordovician beds of the tristate area, and is 

usually easily attributable to postmortem encrustation. 

Many of the shells illustrated on the plates herein have 

bryozoan encrustations. Judging from the positions of 

many of the encrustations, or their extremely massive 

character, most of these encrustations took place after 

the animal died (pi. 1, figs. 9-11; pi. 30, fig. 19; pi. 32, 

figs. 6-9; pi. 34, figs. 4, 6; pi. 37, figs. 18, 19; pi. 41, figs. 

4, 5). However, other encrustations thinly cover both 

sides of a coiled shell, but not the outer apertural lip. 

Such cases are particularly common in species of Cyrtolites (pi. 6, figs. 1, 12-16; pi. 7, figs. 5-7). Morris and 

Rollins (1971, figs. 4, 5) illustrated another such specimen of Cyrtolites cf. C. ornatus that is completely 

encrusted by bryozoans but also has further encrustation 

by Cornulites worm tubes. Of particular significance is 

the symmetrical attachment of these Cornulites on the 

upper umbilical regions of both sides of the shell, and the 

mutual adapertural orientation of the worm tubes. This 

occurrence is strong evidence for encrustation of the 

Cyrtolites shell while still occupied by a living animal. 

These encrustations not only would serve to camouflage 

the shell, but also would strengthen it against crushing, 

by predators such as nautiloids, and thicken it so as to 

make entry by drilling more difficult. The borehole in a 

shell of C. (Cyrtolites) claysferryensis (pi. 4, fig. 15) 

demonstrates the presence of drilling predators.

Signer and Brett (1984) proposed that bellerophontaceans and other invertebrate groups showed an increase 

in the frequency of predation-resistant morphologic features during the mid-Paleozoic in response to the rapid 

radiation of durophagous (shell-crushing) predators (primarily crustaceans and fishes). They pointed out that 

among mid-Paleozoic bellerophontaceans, there is a 

decrease in the frequency of phaneromphalous genera 

and an increase in the frequency of genera having 

sculptured shells. Vermeij (1975, 1978) has demonstrated that modern gastropods having phaneromphalous shells or unsculptured shells are more susceptible to durophagous predation. It should be noted that a 

trend toward reduction of the umbilicus in Ordovician 

bellerophontaceans is thought here to have facilitated the

transport of the bellerophontiform shell, but apparently 

this more mobile shell form was also preadapted to deal 

with durophagous predators (see "Functional Morphology" section).

FUNCTIONAL MORPHOLOGY

INTRODUCTION

The primary functions of the shell in molluscan univalves are to house and protect the animal from the 

dangers of its external environment and to provide sites 

for muscle attachment. The ancestral monoplacophoran 

univalve is generally assumed to have had a simple low 

conical shell reflecting the form of the animal's visceral 

hump (Stasek, 1972). As evolution progressed and the 

visceral mass and its containing shell became larger and 

more elongate, the shell coiled in order to maintain 

balance. The factors that seem to have had the greatest 

control over coiled shell morphology are the balancing of 

the shell itself and the efficient channeling of water 

currents through the shell for respiration and, sometimes, feeding.

In a symmetrically coiled monoplacophoran, which has 

not undergone the larval process of torsion, the head of 

the animal is under the coil (exogastric). In a symmetrically coiled bellerophontacean gastropod, which has 

undergone torsion, the head is toward the outer apertural margin and the shell coils posteriorly away from the 

head (endogastric). These opposite orientations should 

be reflected in the functional aspects of shell morphology 

(Peel, 1987, p. 326). Herein, morphological evidence for 

each orientation in bellerophontiform shells is discussed.

Raup (1966) presented four parameters that can be 

used in the description and functional analysis of coiled 

shells: the shape of the generating curve (whorl shape), 

the rate of whorl expansion (W), the distance of the 

generating curve from the axis (D), and the movement of 

the generating curve along the axis (whorl 

translation=T). In planispiral shells, T always equals 

zero. Raup (1967, text-fig. 3) illustrated cephalopod shell 

forms under a continuum of varying W and D values. 

This approach is also useful in picturing the effects of 

these parameters on bellerophontacean-monoplacophoran shell forms. These W and D values are referred to 

repeatedly in the following functional analyses (Peel, 

1987, p. 322).

MONOPLACOPHORA

TRYBLIDIIDA

The shells of monoplacophorans of the order Tryblidiida grade from cap shaped to conical in form, and are
MIDDLE AND UPPER ORDOVICIAN SYMMETRICAL UNIVALVED MOLLUSKS, CINCINNATI ARCH REGION 043

generally considered more primitive morphotypes than 

the coiled shells of the Cytronellida. However, Pojeta 

and Runnegar (1976, p. 29) pointed out that relatively 

tall shells are the first to appear in the Tommotian fossil 

record, and that limpet-shaped shells seem to have 

developed from them. They suggested that the limpetform shells may not represent the ancestral stock, but 

rather were secondarily adapted for benthic grazing. 

Indeed, the morphological similarities of the typical 

cap-shaped tryblidiid shell and the shell of the patelliform 

gastropods, which are probably secondarily adapted for 

clinging and grazing, suggest a common mode of life for 

the two groups. In fact, Lowenstam (1978, p. 231) has 

reported the modern monoplacophoran Vema clinging to 

phosphorite nodules in dredge samples and noted that 

the animals were nearly stationary during a month of 

laboratory observation. On the other hand, Lemche and 

Wingstrand (1959, p. 63) cited Neopilina, whose shell is 

essentially identical to that of Vema, as a deposit feeder 

from abyssal, dark, muddy sediment where, they 

claimed, there was an absence of suitable hard substrata 

for clinging. It remains uncertain whether the monoplacophoran cap-shaped shell is adapted secondarily to a 

clinging mode of life, like that of the patellacean gastropods, or simply reflects the primitive condition.

The encrustation of many Ordovician tryblidiid shells 

by bryozoans suggests that the animals led an exposed 

life, such as that of an algal grazer, rather than the often 

partially covered life of a bottom-dwelling deposit feeder. 

Furthermore, the highly sculptured shells of some genera, such as Helcionopsis (pi. 2, figs. 1-3) and Vallatotheca (pi. 1, figs. 8-31), argue against a deposit-feeding 

habit. Vermeij (1978, p. 33) pointed out that gastropods 

living under wave-energy stress generally have lower 

shells, many with smoother surfaces, and a relatively 

larger aperture and foot than animals living in more 

sheltered surroundings. These observations probably 

also hold true for Paleozoic monoplacophorans living in 

shallow-water habitats. However, at present, detailed 

paleoecological data on the distribution of tryblidiid taxa 

are insufficient to test this model.

Through studies of the anatomy of Neopilina 

galatheae by Lemche and Wingstrand (1959), tryblidiid 

monoplacophorans are known to have a poorly developed 

head, and to have numerous pedal muscles and five or six 

pairs of gills distributed around the lateral and posterolateral shell margins. Pojeta and Runnegar (1976, fig. 10) 

confidently adapted this morphology to the Cambrian 

genus Scenella. They traced the probable path of water 

flow through the shell as entering anterolaterally, running along the lateral mantle cavity, and exiting posterolaterally (figs. 14A, 5). In side view, the lateral margins 

of Ordovician tryblidiid shells can be straight (pi. 2, figs. 

3, 8, 20), convex (pi. 1, figs. 27, 28), or concave (pi. 3,

B

FIGURE 14. Paths of water currents through the shells and mantle 

cavities of monoplacophorans. Fusiform-shaped structures represent 

the gills. A, B, Right-lateral and dorsal views of a tryblidiid, which 

had multiple pairs of gills in a lateral to posterolateral mantle cavity. 

C, D, Right-lateral and dorsal views of Cyrtolites, which had a single 

pair of gills in a posterior mantle cavity. Water currents enter around 

the lateral angulations of the diamond-shaped aperture and exit 

through the dorsal angulation, which is sinuate in some species. E, F, 

Right-lateral and dorsal views of Sinuites, which had a single pair of 

gills in a posterior mantle cavity. Water currents enter through 

apertural reentrants in the lobate aperture and exit through a deep 

dorsal sinus.

figs. 9, 22). It seems likely that these different lateral 

apertural margin profiles were designed to channel currents more efficiently through the mantle cavity. However, it is at this time impossible to say what significance 

these different lateral apertural profiles had to possibly 

varied modes of life.

CYRTONELLIDA

The Cyrtonellida is generally believed to be the more 

advanced of the two monoplacophoran orders. Because of 

the mechanical requirements of a coiled shell, the isostrophic cyrtonellids had fewer pedal retractor muscle 

scars than the tryblidiids. These scars typically form 

anterior, posterior, and lateral pairs arranged in a ring 

well within the aperture (Rollins, 1969). Stasek (1972, p. 

21) proposed that this migration of the muscle insertions 

deeper into the shell suggests the concomitant development of a larger posterior mantle cavity and the ability of 

the animal to draw into it. Peel (1980) also suggested that 

circumumbilical muscle attachment in sinuitids represents the ability to retract into the shell and reflects a 

monoplacophoran morphological grade that may have 

first undergone torsion. Stasek (1972) further claimed 

that the enlarged mantle cavity was accompanied by a 

reduction in the number of the gills, but an increase in 

their size. Finally, Stasek claimed that the steep anterior 

slope of the coiled shell might indicate the development 

of a distinct head in the organisms.

Such anatomical modification could explain the success 

of the cyrtonellid genera Cyrtolites and Sinuites during
044 CONTRIBUTIONS TO THE ORDOVICIAN PALEONTOLOGY OF KENTUCKY AND NEARBY STATES

the Middle and Late Ordovician. Features of the shell 

morphology of these two successful Ordovician genera 

demonstrate adaptations in the exogastric shell for more 

efficient water flow through the mantle cavity. Linsley 

(1978a, b) pointed out that the obstruction of anterior 

inhalant passages into the shell by the coil and the fleshy 

stalk leading from the foot to the visceral mass made it 

necessary for the inhalant ducts to the posterior mantle 

cavity to be concentrated laterally. Typically, species of 

Cyrtolites have diamond-shaped apertures (pi. 5, figs. 

11, 14; pi. 8, figs. 1, 5, 8; figs. 14C, D). Starobogatov 

(1970) and Linsley (1978b, p. 437) have interpreted the 

lateral angulations of these apertures as inhalant canals, 

and the dorsal angulation, which is sinuate in Middle 

Ordovician species of Cyrtolites, as the exhalant canal. It 

should be noted that not all species of Cyrtolites have 

such angulated apertures. C. (Cyrtolites) retrorsus 

shows a complete gradational series in apertural outlines, from diamond shaped to nearly circular (pi. 5, figs. 

3, 5, 8, 11, 14, 18, 22). However, the marked lateral 

angulations of the apertures in C. (C.) claysferryensis 

(pi. 8, figs. 11, 15) and C. (Paracyrtolites) carinatus (pi. 

7, figs. 18-25), which occupied the clay-rich environments of the Clays Ferry and Kope Formations, might 

indicate a need for more efficient channeling of currents, 

and thereby support Linsley's conclusions.

Starobogatov (1970) noted grooves along the sides of 

the final whorl in the Devonian cyrtonellid Sinuitopsis 

that he interpreted as inhalant channels, with the posterior sinus acting as an exhalant canal. He claimed that 

the narrow streams of water that would be channeled 

through these lateral grooves into the posterior mantle 

cavity could probably bathe only one pair of posterolateral gills efficiently. This sinuitid hydrodynamic design is 

also demonstrated well by Ordovician species of Sinuites 

illustrated herein (figs. I4E, F). Water would be drawn 

into the shell anterolaterally through umbilical reentrants along the inner apertural margin (pi. 9, figs. 3, 4, 

12; pi. 11, figs. 3, 7, 9). After passing over the gills, the 

deoxygenated water and waste products would be 

expelled through the posterior apertural sinus (pi. 11, 

figs. 1, 2, 6, 10, 11). The lateral apertural lobes of 

Sinuites, which project downward to varying degrees in 

different species, probably protected the single pair of 

large gills. These lobes also could have acted as struts, 

supporting the shell while the animal was inactive yet stll 

allowing movement of water through the shell. Such 

supportive struts are known in the shells of living and 

fossil gastropods (Linsley and others, 1978).

Although the apertural margins of Sinuites and Crytolites have been modified for the same purpose, the 

general shell morphologies of the two genera are quite 

different. Species of Cyrtolites are loosely coiled and 

widely umbilicate (pi. 5, figs. 6, 9, 12; pi. 6, figs. 1, 6, 18)

(high D value of Raup, 1966), and even become disjuctly 

coiled in C. (C.) disjunctus (pi. 6, figs. 19-22). The plane 

of the aperture in Cyrtolites is tangential to the coil, 

enabling the animal to clamp down onto hard substrata. 

Middle Ordovician species, such as C. (C.) retrorsus, had 

a shallow apertural sinus (pi. 5, figs. 7, 13) that would 

have prevented a complete seal around the clampeddown aperture, but would have enabled more efficient 

expulsion of water from the mantle cavity. This apertural 

sinus is not present in Late Ordovician species, such as 

C. (C.) ornatus (pi. 6, figs. 7, 10), so that the entire 

apertural margin was in the same plane and the clampeddown shell would be more completely sealed off. Perhaps 

such protection was of more benefit to the survival of 

species of Cyrtolites than was the sinus and its exhalant 

function.

In contrast, species of Sinuites have more tightly 

coiled shells (pi. 9, figs. 4, 8; pi. 11, figs. 3, 8) (low D 

value), which are nonumbilicate or nearly so, have 

rounded whorls, and have very irregular apertural margins. As discussed above, the inhalant umbilical reentrants, the jutting posterolateral lobes, and the pronounced posteromedian sinus (pi. 11, figs. 6-11) are all 

clear adaptations for efficient channeling of water 

through the shell, but such irregularities of the apertural 

margin would surely preclude efficient clamping down on 

firm substrates. In the faunas studied here, species of 

Sinuites are most common and diverse from the deeper 

water, muddy environments of the Logana Member of 

the Lexington Limestone and the Kope Formation. 

Living in these soft-substrate environments must have 

made efficient channeling of water through the shell (in 

order to prevent fouling of the bipectinate gills by fine 

sediment) more important to survival than the ability to 

clamp down. Also, the tightly coiled shell of Sinuites 

most likely indicates a more vagrant mode of life than 

that of Cyrtolites. Of possible significance to this point is 

the fact that specimens of Cyrtolites commonly are 

encrusted by epizoans, whereas specimens of Sinuites 

are rarely encrusted.

BELLEROPHONTACEA

SHELL COILING

Linsley (1977, 1978a, b) discussed the benefits and 

problems resulting from the coiling of the shell in the 

Gastropoda. Shell coiling lowers the center of gravity 

and the pressure point, reduces the total surface area of 

the shell subject to fluid drag, reduces the shearing 

effect, and thus reduces the energy necessary to move 

the shell forward. In other words, shell coiling enables 

the animal to be more mobile, an obvious advantage for 

feeding and self protection.
MIDDLE AND UPPER ORDOVICIAN SYMMETRICAL UNIVALVED MOLLUSKS, CINCINNATI ARCH REGION 045

An anisostrophically coiled shell, such as that of the 

vast majority of gastropods, is naturally unbalanced. 

Shell balance must be restored by positioning the center 

of gravity over the midline of the foot (Linsley, 1977). 

This is done through the tipping up of the shell (inclination) and the twisting of the coil toward the rear so that 

torsion is effectively reduced (regulatory detorsion). On 

the other hand, the isostrophically coiled gastropod shell, 

such as that of a bellerophontacean, is naturally balanced. Its axis of coiling is parallel to the substrate, and 

its center of gravity is automatically positioned over the 

midline of the foot. Nevertheless, a loosely coiled isostrophic shell can also be difficult to balance, as it affords 

broad areas of resistance from all sides. Just as in an 

anisostrophically coiled form, a loose coil hinders movement, makes the animal more prone to predation, and 

probably restricts it to either algal grazing or sedentary 

suspension feeding in a quiet-water environment. Bellerophontaceans adopted three adaptive strategies to 

reduce resistance of their planispiral shells to movement 

and (or) currents: (1) lateral compression of the whorl 

shape, (2) tightening of the coiling radius (decrease in D), 

which increased whorl overlap and reduced the size of 

the umbilicus, and (3) increase in the rate of whorl 

expansion (W) (Linsley, 1977).

In the early evolution of the Bellerophontacea, there is 

a clear trend from primitive loose shell coiling toward 

tighter shell coiling (decrease in D value) or reduction of 

the coil altogether (fig. 15). All of the earliest bellerophontaceans are loosely coiled (high D value). The Upper 

Cambrian Chalarostrepsis is actually disjunctly coiled in 

adulthood (Knight and others, 1960, fig. 94). Yochelson 

(1971) and Peel (1975b) have interpreted disjunct coiling 

in gastropods as representing a sedentary suspensionfeeding mode of life. The descendants of Chalarostrepsis, the Ordovician genera Tropidodiscus (pi. 41, figs. 

6-13) and Phragmolites (pi. 44, figs. 1, 5, 8), have loose 

but contiguous coils, leaving a wide-open umbilicus. 

Their laterally compressed shells are generally thin and 

light, probably to make balancing easier. These forms 

must have inhabited only quiet-water areas (Linsley, 

1978b) and were probably algal grazers or algal foliage 

dwellers.

The progressive trend toward tighter coiling is exemplified within the genus Bucania (fig. 15). The earliest 

appearing and more morphologically primitive members 

of the genus, those species in Ulrich and Scofield's (1897) 

B. sulcatina group (pi. 12, figs. 1-9), have wide umbilici 

(high D values) and deep, narrow slits like the tropidodiscids, but have broad, depressed whorls (with low W 

values). Members of the new genus Undulabucania (pi. 

23, figs. 1-15) are of the same morphological grade. From 

this level, there is a complete morphological gradation 

within the genus Bucania to the more advanced B.

nashvillensis group (pi. 14, figs. 1-14), which is characterized by tighter coiling (lower D values), smaller 

umbilici, longer apertures (higher W values), more 

rounded whorls, and, in many cases, thicker shells. 

These features lowered the shell's center of gravity, 

reduced its surface area, and streamlined its form, thus 

making it easier to balance and transport. The thickening 

of the shell suggests migration of some specimens into 

new, higher energy environments. The lengthening of 

the aperture, and presumably the foot, indicates a trend 

toward faster movement. The rounding of the whorls 

served to streamline the shell, reducing resistance 

against movement. These modifications indicate an 

increase in the mobility of species of Bucania during the 

Middle Ordovician. The broad, bulky shells of the B. 

sulcatina group probably represent sluggish grazers. 

The more compact and streamlined shells of the B. 

nashvillensis group must have allowed a greater variety 

of life habits. Most species of both groups have moderately large to large shells, and must represent bottomdwelling animals. Bucania micronema (pi. 19, figs. 1-6) 

may have been small and lightweight enough to have 

been an algal foliage-dweller.

This progression went still further in more advanced 

Middle Ordovician bellerophontaceans. The bucanopsids 

and bellerophontids have still more tightly coiled shells 

(low D values), and most species have completely or 

nearly closed umbilici. The rate of whorl expansion (W) 

in the shells also increases, resulting in a more compact 

coil. The compact, rounded shells at this level of development are thought to represent the most mobile of the 

Ordovician bellerophontaceans. This interpretation could 

partly account for the wide distribution and large numbers of species, such as Sphenosphaera clausus (pi. 30, 

figs. 1-23; pi. 31, figs. 1-13) and Bucanopsis carinifera 

(pi. 27, figs. 1-16), in the Middle Ordovician deposits of 

Kentucky and Tennessee (see section on paleoecology). 

These species apparently occupied a variety of depositional environments and may have had a wide range of 

life habits.

The next step in this morphological sequence was 

toward specialization through reduction of the coil and 

development of a broadly expanded aperture (very high 

W values), as seen in the carinaropsids and pterothecids. 

Sphenosphaera showed the incipient stages of apertural 

platform evolution in the lineage (pi. 30, figs. 2, 9, 17). In 

Carinaropsis, the apertural platform evolved to cover 

approximately one-third of the aperture opening (pi. 37, 

figs. 3, 4, 18,19). The platform's function must have been 

to support the animal's visceral mass, a function the 

reduced coil could no longer serve in the adult animal. 

This specialized shell form probably represents a mobile, 

but sluggish creature. The extreme of this trend is seen 

in Pterotheca and its relatives. They exhibit a reduced
046 CONTRIBUTIONS TO THE ORDOVICIAN PALEONTOLOGY OF KENTUCKY AND NEARBY STATES

MORPHOLOGICAL AND ECOLOGICAL TRENDS IN ORDOVICIAN BELLEROPHONTACEANS

ECOLOGICAL 

TREND

Increase in mobility

Probable decrease in mobility

Increase in rate of whorl expansion (W)

g

2 I

O LU

X CC.

0- hcc 

O

Reduction of coil

Tightening of coiling (decrease in D)

Decrease in size of umbilicus

Development of inner aperture platform

Slit generally 

deep and narrow Slit generally short and wide Slit as open keel

TYPICAL

SHELL

FORMS

Bucania sulcatina Bucania nashvillensis Sphenosphaera 

clausus

Carinaropsis 

cymbu/a

FIGURE 15. Morphological and corresponding ecological trends in 

Middle Ordovician bellerophontaceans. Five general levels of development are recognized. Dashed line indicates early beginning of 

inner apertural platform. Level 1 (a, b) Left-lateral and ventral 

views of Bucania sulcatina. Typical of this level of development are 

a wide, open umbilicus and a deep labral slit up to a half-whorl deep. 

Species of Bucania and Undulabucania in this group have broad, 

depressed whorl forms; however, the tropidodiscids, most of which 

have high, narrow, laterally compressed whorl forms, also belong in 

this group. Level 1 taxa probably were sluggish vagrant benthos. 

Level 2 (c, d) Left-lateral and ventral views of Bucania nashvillensis. Note the increase in the rate of whorl expansion, the decrease 

in the coiling radius, the lengthening of the whorl form, and the 

shortening of the labral slit. Similar shell forms such as those of 

Tetranota bidorsata also belong to this group. Level 2 taxa probably 

were moderately mobile vagrant benthos. Level 3 (e, f, g): Leftlateral, anterodorsal, and ventral views of Sphenosphaera clausus. 

Note the closing of the umbilicus through continued increase in the

rate of whorl expansion and decrease in theradius of coiling. Note also 

the increase in the flaring of the aperture lips and the incipient 

outbuilding of an inner apertural platform. Species of Bellerophon and 

Bucanopsis also belong to this group, which is thought to be the most 

mobile of the Ordovician bellerophontaceans. Level 4 (h, i, j) Leftlateral, anterodorsal (with dorsum partly cut out to show apertural 

platform), and ventral views of Carinaropsis cymbula. At this level, 

the rate of whorl expansion has increased to the point where the coil 

is nearly completely reduced in the adult animal. The coil can no longer 

support the visceral mass in the adult animal, and an inner apertural 

platform evolved and served the same support function. Level 4 taxa 

probably were sluggish vagrant benthos. Level 5 (k, 1, m) Left-lateral 

cross-sectional transverse cross-sectional, and ventral views of 

Pterotheca saffordi. At this specialized level of development, the coil 

is completely reduced, and the apertural platform evolved so as to 

cover approxiately two-thirds of the aperture. Level 5 taxa probably 

were very sluggish, nearly sedentary animals. W, rate of whorl 

expansion; D, distance of generating curve (whorl) from axis.

vestigial coil and an interior apertural platform that 

covered more than one-half of the aperture opening (pi. 

40, figs. 4, 6). This more highly specialized animal was 

probably nearly sedentary, living in shallow nearshore 

areas and possibly suspension feeding, like morphologically similar Crepidula of modern seas, or sluggishly 

grazing on algal mats.

In summary, there was a trend toward tighter coiling 

of the shell and the decreasing size of the umbilicus 

(decreasing D values) in Ordovician bellerophontaceans. 

This trend was in many cases accompanied by an increase 

in the rate of whorl expansion (W). These trends allowed 

easier balance and transport of the shell, and thereby 

permitted greater mobility. This greater mobility
MIDDLE AND UPPER ORDOVICIAN SYMMETRICAL UNIVALVED MOLLUSKS, CINCINNATI ARCH REGION 047

enabled the bellerophontaceans to live in higher energy 

habitats and to adopt new modes of life. The greater 

mobility is regarded as an important factor in the Middle 

Ordovician radiation of the bellerophontaceans. The very 

high W values seen in carinaropsids resulted in nearly 

immobile animals.

These conclusions differ slightly from those of Rollins 

(1967, p. 54-64), who postulated three forms of bellerophontaceans: clingers, creepers, and ploughers. Clinging 

forms were thought to be sluggish in their habits and to 

have clamped their shells vertically down over the foot 

against firm substrates in limpetlike fashion for protection. Typically, Rollins' clingers had rapidly expanding, 

even explanate, apertures with flat margins. Ordovician 

genera in this group are Carinaropsis, Pterotheca, and 

possibly Salpingostoma (pi. 25, figs. 1-14). However, 

only the last of these genera was found associated with 

firm substrates in the present study. Salpingostoma 

kentuckyense is present in bioclastic beds of the Tyrone 

Limestone and the lower Curdsville Limestone Member 

of the Lexington Limestone, and S. richmondensis is 

present in Upper Ordovician bioclastic beds. Carinaropsis and Pterotheca are more common in fine-grained 

limestones in the Middle Ordovician rocks of Kentucky 

and Tennessee. Peel (1977b, p. 47) has proposed that 

low, explanate shell forms were adapted to life on soft 

substrates, where their broad shells would act like 

snowshoes to prevent the animal from sinking into the 

soft sediment. "Clinger" is probably a poor term for this 

group, as they were more likely sluggish vagrant, benthonic animals. Horny (1963a) reported explanate shells 

of similar morphology from both soft, muddy paleoenvironments and firm bioclastic paleoenvironments. It may 

be that the explanate shell form was not adapted to any 

specific substrate conditions.

Rollins' (1967) second group, the creepers, was 

thought to include more mobile types and to be capable of 

total retraction of the head-foot mass into the shell like 

most conispiral gastropods. He included in this group 

such Ordovician genera as Bellerophon (pi. 18, figs. 

10-17), Kokenospira (pi. 20, figs. 9-12), Tetranota (pis. 

21, 22), Tropidodiscus (pi. 41, figs. 6-13), Phragmolites 

(pis. 43, 44), and Temnodiscus (pi. 42, figs. 3-6). I would 

add to the group the genera Sphenosphaera (pis. 29-36), 

Bucanopsis (pi. 27, figs. 1-20), and Bucania (pis. 12-20), 

which Rollins considered clingers. The relative mobility 

of individual species in this group was probably quite 

variable. Mobility should have increased with an increase 

in the whorl overlap (decrease in D), a decrease in the 

size of the umbilicus, and an increase in the rate of whorl 

expansion (W) to a point where the coil was small and 

lightweight but stll large enough to support of the 

visceral mass. Other important considerations in estimating relative mobility are shell thickness and whorl 

cross-sectional area and shape.

Rollins' (1967) third group, the ploughers, included 

only such late Paleozoic forms as Euphemites, which has 

extensive inductural deposits over much of the body 

whorl. They were believed to have ploughed through soft 

sediment in search of food much like the modern gastropod Polinices. Such forms must have been either deposit 

feeders or predators, like Polinices.

Linsley (1978a) attempted to estimate bellerophontacean locomotion rates from shell forms and used generic 

morphotypes for examples. He concluded that low 

explanate shells belonged to sluggish grazers or deposit 

feeders. He thought the form of Tropidodiscus, with its 

laterally compressed whorls, indicated considerable 

mobility, but that its high center of gravity must have 

restricted it to quiet-water environments. He considered 

the tightly coiled Bellerophon and Euphemites morphotypes to be the most mobile of the bellerophonts. Finally, 

he considered Knightites, which is a moderate-sized shell 

having a small umbilicus and a slightly flaring aperture, 

a sluggish grazing animal because of its high development of ornamentation. I generally agree with Linsley's 

conclusions, but I tend to disagree with the last. I doubt 

that the shell ornamentation of Knightites would have 

hindered its mobility. In fact, I believe the general shell 

form to have the potential of a least moderate locomotion. The same general morphotype also characterizes 

many other taxa, the most notable here being the 

Bucania nashvillensis group and species of Tetranota, 

such as T. bidorsata and T. wisconsinensis.

FUNCTIONAL ASPECTS OF SELECTED 

BELLEROPHONTACEAN SHELL FORMS

EXPLANATE SHELLS

An explanate shell is one in which the rate of whorl 

expansion increases markedly during maturation, so that 

in maturity the aperture is broadly expanded and oriented tangential to the coil and the substratum. Many 

unrelated bellerophontacean genera are characterized by 

this adult expansion of the shell. Notable examples 

among the fauna included in this study are Salpingostoma (pis. 24, 25) and Carinaroposis (pis. 37, 38).

Before expansion, the shell of Salpingostoma (pi. 24, 

figs. 8, 14) closely resembles shells of members of the 

Bucania sulcatina group, except that it apparently has a 

nearly radial aperture. Linsley (1977, p. 197) defined a 

radial aperture as one whose apertural plane passes 

through the axis of coiling, rather than being tangential 

to the body whorl. Linsley claimed that modern gastropods having radial apertures typically are nearly sedentary and live with the apertural plane perpendicular to 

the substrate, rather than parallel to the substrate as in
048 CONTRIBUTIONS TO THE ORDOVICIAN PALEONTOLOGY OF KENTUCKY AND NEARBY STATES

tangential forms. The adult expanded aperture of Salpingostoma is tangential to the coil. Using this criterion, 

it seems that juvenile Salpingostoma may have led an 

essentially sedentary existence, like most gastropods 

having radial apertures (Linsley, 1977, p. 198), but 

became more capable of mobility with the development of 

the tangential aperture in maturity. Furthermore, the 

expanded bell-shaped aperture of the adult is in many 

cases quite thickened and, of course, has the long, open 

slit characteristic of the genus. The apparently sedentary 

juvenile may have lived through suspension feeding in 

more sheltered microhabitats. The adult, with its tangential and thickened aperture, could sluggishly move its 

broadly umbilicate shell into more current swept areas, 

where its expanded foot would cling to firm substrates. 

The long adult slit probably served an enlarged single 

pair of gills and furnished a large exhalant area, making 

it possible to move a larger amount of water through the 

mantle cavity. This would have been of particular advantage if the animal were a suspension filter feeder. The 

modern suspension-feeding caenogastropod Siliquaria 

has a long, open slit that serves a single large foodcollecting gill.

In Carinaropsis the coil is nearly lost, and in Pterotheca it is completely lost. In both genera, the shell is 

thin and lightweight. In these forms, the visceral mass is 

supported within a broadly expanded body whorl by an 

internal platform similar to that of the modern slipper 

limpet Crepidula fornicata, which is a nearly sedentary 

suspension feeder.

Explanate shells have often been interpreted as being 

adapted to a clinging mode of life. Concomitant with the 

development of an expanded explanate aperture is the 

expansion of the foot. Vermeij (1978, p. 33) has reported 

that modern marine gastropods living in higher energy 

settings generally have lower shells and a relatively 

larger aperture and foot than gastropods living in adjacent more sheltered settings. Of course, the expanded 

foot would give a broader, more powerful base for 

clinging. On the other hand, Peel (1975a, c, 1977b, 1978) 

has suggested that the expanded aperture and foot of 

explanate bellerophontaceans was an adaptation for life 

on soft substrates, acting like snowshoes to prevent 

submergence of the animal into the sediment, as in the 

modern deposit-feeding gastropod Aporrhais. He supported this conclusion by citing occurrences of the 

explanate bellerophontacean genera Anapetopsis and 

Phragmosphaera in soft-bottom environments in the 

Silurian Arisaig Group of Nova Scotia. A comparable 

association was reported by Gromaczakiewicz-Lomnicka 

(1972) from a Carboniferous black shale in Poland, where 

the explanate bellerophontacean Patellilabia is the only 

large gastropod in a fauna of otherwise diminutive algalfoliage-dwelling gastropods. However, Horny (1963a, p.

66, 67) cited bellerophontaceans having explanate apertures and similar shell morphologies from soft-bottom, 

muddy facies and from firm-bottom facies of tuffaceous 

and skeletal debris rocks in the Ordovician-Silurian of 

Bohemia.

Perhaps the broadly explanate aperture of bellerophontaceans was an adaptation that could serve different 

functions. Other morphological characteristics of the 

shells, such as shell size and thickness, must also be 

taken into account in functional analyses. For example, 

Carinaropsis generally has a very thin, lightweight 

shell, and among the faunas described herein was most 

common in the Grier Limestone Member of the Lexington Limestone, an apparently soft bottom facies. Conversely, those explanate shells adapted for powerful 

clinging in higher energy conditions would be expected to 

be thicker and heavier. One such example might be 

Salpingostoma richmondensis, which is common in 

deposits of broken and worn skeletal debris in the 

Richmondian Whitewater Formation of Indiana and 

Ohio.

TRILOBED SHELLS

Peel (1974) reported at least five genera of bellerophontaceans having trilobate shells in Lower Ordovician 

through Devonian strata. The appearance of the trilobed 

whorl form in unrelated stocks can be explained through 

its functional attributes. Peel (1974, p. 248, 249) interpreted the trilobate dorsum as a modification of the 

shape of the mantle cavity and its openings to separate 

inhalant streams of clean water from the exhalant current of fouled and deoxygenated water. Such a modified 

design would increase the efficiency of water flow 

through the mantle cavity and would therefore be a likely 

functional adaptation in unrelated stocks.

Peel (1977b, 1978) has noted the common occurrence of 

trilobate bellerophonts in nearshore fine-grained sediments in Ordovician and Silurian-Devonian deposits. He 

cited Tritonophon as common in soft-bottom, shallow 

marine platform facies in the Arisaig Group of Nova 

Scotia, but absent from contemporary firm-bottom faunas. He considered the genus to be a probable algal 

foliage dweller. Likewise, Bretsky (1970b) cited the 

trilobate Plectonotus sp. from delta front silts and shales 

of the Upper Ordovician Queenston delta of the Central 

Appalachian region. He also speculated that this form 

was an algal foliage dweller.

Of the fauna studied here, Tetranota (pi. 21) is the only 

trilobed bellerophontacean. In the Middle Ordovician 

Stones River Group of Tennessee, the genus occurs in 

fine-grained limestones. It also is present in the offshore 

shales of the Upper Ordovician Kope Formation in 

Kentucky and Ohio. Both occurrences reflect soft-bottom
MIDDLE AND UPPER ORDOVICIAN SYMMETRICAL UNIVALVED MOLLUSKS, CINCINNATI ARCH REGION 049

environments. It may be that the increased efficiency of 

water flow through, the mantle cavity of the trilobate 

shell allowed these animals to inhabit fine-sediment, 

soft-bottom facies.

PALLIAL SYSTEM AND LABRAL EMARGINATION

The mantle cavity is one of the most characteristic 

features of the Mollusca. In gastropods, it is primarily a 

respiratory chamber housing the ctenidia (gills) and the 

associated osphradia and hypobranchial glands, which 

together form a functional unit (Yonge, 1947). The 

osphradia, which are situated near the entrance to the 

cavity, "estimate" the sediment influx. The hypobranchial glands secrete mucus to consolidate the invading 

sediment particles, so that they do not foul the ctenidia 

and are easier to expel. The ctenidia are cilia-covered 

featherlike structures that exchange gases and sometimes collect food from water passing through the mantle 

cavity. Also, in gastropods, the alimentary, renal, and 

reproductive systems open into the upper exhalant portion of the mantle cavity, so that their discharged 

materials can be carried outward by the exhalant pallial 

currents.

Yonge (1947) thoroughly described and analyzed the 

structure and function of the organs housed in the mantle 

cavity in aspidobranch Gastropoda. The term "aspidobranch" refers to the presence of bipectinate ctenidia, 

which characterize the Archaeogastropoda and are considered the most primitive of known gastropod gill types. 

Yonge (1947) recognized four aspidobranch arrangements in modern archaeogastropods: (1) asymmetrical 

shell with two asymmetrical ctenidia (all Zeugobranchia 

except the Fissurellacea), (2) secondarily symmetrical 

shell with two symmetrical ctenidia (Fissurellacea), (3) 

asymmetrical shell with loss of one ctenidium (Neritacea, 

Valvatacea, Trochacea), and (4) secondarily symmetrical 

shell with loss of one or both ctenidia (Patellacea, Cocculinacea, some Neritacea).

In the zeugobranchiate mollusks (arrangements 1 and 

2), Yonge (1947) reported, inhalant currents created by 

ctenidial cilia are drawn into the mantle cavity on both 

sides and above the animal's head. After passing over the 

ctenidia, the deoxygenated currents pass upward and out 

of the cavity through a dorsal labral slit or emargination 

(as in the Pleurotomariidae, Scissurellidae, and some 

Fissurellidae, for example, Emarginula), through a single apical trema (as in some Fissurellidae, for example, 

Diodora (Fissurella)), or through a series of tremata (as 

in the Haliotidae, for example, Haliotis). Such shell 

emarginations and perforations are morphological adaptations to prevent the mixing of fresh incoming currents 

and deoxygenated and fouled exiting currents in zeugobranchiate forms. Cox (1960, p. 1130) defined emarginate 

gastropods as those "with margin of outer lip notched or 

variously excavated."

In gastropods having only one ctenidium, such as the 

more advanced archaeogastropods and the caenogastropods, inhalant currents enter the mantle cavity on one 

side of the head and exhalant currents are expelled on 

the other side of the head. Therefore, there is no need for 

a slit type of labral emargination. A few highly specialized caenogastropods do bear labral slits, such as the 

Siliquariidae, which are sessile suspension feeders having a single enlarged food-gathering ctenidium. In 1843, 

de Konnick noted the similarity between the labral slit 

emargination of Bellerophon and that of the modern 

fissurellid Emarginula. Meek (1866) supported this comparison and further noted the similarity of the tremata of 

the Silurian bellerophont Tremanotus. These comparisons convinced these early authors, and most subsequent 

authors, of the close phylogenetic relationship between 

the pleurotomariacean archaeogastropods and bellerophontaceans. Knight (1952) used Yonge's (1947) analysis 

of the zeugobranchiate pallial system to reconstruct the 

soft anatomy of bellerophonts. He diagramed bellerophonts as having a zeugobranchiate pallial system, with 

a pair of bipectinate ctenidia receiving anterolateral 

inhalant currents from either side of the head, these 

currents moving upward and inward through the mantle 

cavity, converging near the top, and being expelled 

through a dorsal slit. Such a reconstruction is also 

supported here.

It should be noted that some genera formerly considered bellerophontaceans, but currently interpreted as 

monoplacophorans because of their muscle scar patterns 

(for example, Sinuites, Sinuitopsis, and Cyrtolites), may 

also have a distinct labral sinus. This is not surprising, as 

these forms are also believed to have one or more pairs of 

bipectinate gills arranged on either side of the body. 

Even though the path of currents through the posterior 

mantle cavities of these forms would be quite different 

from that of a gastropod, with inhalant currents entering 

at the opposite end, the zeugobranchiate condition would 

still be served by an exhalant sinus. Thus far no species 

having a well-defined slit-selenizone complex has been 

accepted as a monoplacophoran, but such homeomorphy 

would not be impossible.

In the Pleurotomariacea and the Bellerophontacea, the 

characteristic labral emargination can be in the form of a 

sinus or a slit. A sinus is a simple U-shaped to V-shaped 

reentrant of the apertural margin. A slit is a parallelsided reentrant varying from a short notch (pi. 14, fig. 

14) to a deep fissure as much as a half-whorl in extent (pi. 

23, figs. 10-13; pi. 44, figs. 3, 6). A slit is generally 

located at the apex of a shallow sinus, and generates a 

slitband or selenizone. A selenizone (pi. 16, fig. 15; pi. 18,
050 CONTRIBUTIONS TO THE ORDOVICIAN PALEONTOLOGY OF KENTUCKY AND NEARBY STATES

FIGURE 16. Paths of water currents through the shells and mantle 

cavities of some Ordovician bellerophontacean gastropods. Fusiformshaped structures represent the gills. A, Tropidodiscus, left-lateral 

view; water currents entered shell anteriorly and exited through the 

deep slit posterodorsally, which is similar to such living pleurotomariaceans as Entemnotrochus. B, Salpingostoma, left-lateral view; 

water currents entered the broad aperture anterolaterally, passed 

over an enlarged pair of gills, and exited posterodorsally through the 

deep slit. C, Sphenosphaera, left-lateral view; water currents 

entered shell anterolaterally and curved around to exit dorsally 

through a short slit, which is similar to such living pleurotomariaceans as Perotrochus.

fig. 5; pi. 28, fig. 5; pi. 30, fig. 6; pi. 31, fig. 6) is a spiral 

band tracing the path of the slit around the shell, and is 

best expressed when marked by a series of concentric 

growth lines (lunulae) bordered by a pair of spiral 

threads. If the selenizone is not well defined by lunulae 

and bordering threads, it may be expressed as a simple, 

generally slightly elevated band often referred to as a 

"pseudoselenizone." Horny (1963a, p. 68) has pointed out 

that there seems to be a complete morphological gradation from the U-shaped sinus to the narrow, channellike 

slit. Regardless of its form, a median labral emargination, with few exceptions, indicates the presence of a 

dibranchiate pallial system.

The labral emargination can occur in Paleozoic symmetrical molluscan univalves in five general forms: (1) a 

V-shaped to U-shaped sinus, as in Sinuites (pi. 11, figs. 

1, 6, 11), (2) a short, relatively broad notch or slit, as in 

advanced bucaniids and bellerophontids (pi. 38, fig. 16), 

(3) a deep, narrow slit that may extend up to one-half 

whorl back from the apertural margin, as in tropidodiscids and primitive bucaniids (pi. 23, fig. 10; pi. 44, figs. 3, 

6, 12), (4) a long, open slit closed off at the anterior 

margin, such as in Salpingostoma (pi. 24, figs. 1-3), and 

(5) one or a series of discrete openings, such as the 

tremata of Tremanotus, which according to Peel (1972) 

are repeated closings of a deep labral sinus.

Linsley (1978b, p. 438, 439) concluded that broad, 

shallow slits were generally associated with broad shell 

forms, such as Bellerophon, illustrated here by Sphenosphaera (fig. 16C). The breadth of the outer lip of the 

shell allowed inhalant currents to be spread to the 

anterolateral extremities. In these forms, he envisioned 

a shallow mantle cavity in which anterolateral inhalant 

currents were effectively separated, by virtue of the 

shell's width, from the exhalant currents exiting through

the dorsomedian slit. In contrast, in narrow shell forms, 

such as Tropidodiscus (fig. 16A), Linsley (1978b) pointed 

out, the separation of inhalant and exhalant currents 

would be difficult. The solution was a greatly deepened 

slit and mantle cavity. In such a form, currents could 

enter anteriorly into the mantle cavity, bathe the 

ctenidia, and continue on in nearly the same line to exit 

posteriorly at the back of the deep slit. This arrangement 

in effect created a posteriorly placed anus.

There are some exceptions to Linsley's astute observations concerning the association of a deep slit with only 

narrow shell forms. Some bellerophonts having broad, 

depressed whorls, such as species of the Bucania sulcatina group (pi. 12, figs. 1-3) and Undulabucania spp. (pi. 

23, figs. 5, 11), also apparently had deep slits. As 

discussed elsewhere, all of these broadly umbilicate 

forms with deep slits, regardless of the whorl shape, are 

considered morphologically primitive. None of the more 

advanced genera have deep slits, and therefore the 

structure's functional advantages for respiration must 

have been overshadowed by some disadvantages, such as 

weakening of the shell and increased exposure of the 

animal to predation.

The homeomorphic explanate genera Salpingostoma 

(pi. 24, figs. 1-3; pi. 25, fig. 1; fig. 165) and Tremanotus 

(Peel, 1972) also bear deeply inset shell openings in the 

form of a deep slit that is closed off anteriorly and a line 

of open tremata, respectively. It is suggested here, in 

the discussion of explanate shell forms, that these genera 

may have been suspension feeders. The deep emarginations would be useful in allowing more water to move 

through an enlarged set of ctenidia. As noted, this 

situation is known in the modern caenogastropod family 

Siliquariidae.

PARIETAL DEPOSITS

Knight (1952) and Rollins and Batten (1968) argued 

that parietal deposits and long trails near the apertural 

side of a curved or coiled shell would impede the maneuverability of a protracted head in a monoplacophoran, 

and therefore one would not expect to find these features 

in that class of mollusks. Parietal deposits are secondary 

shell layers laid down on the inner lip of the aperture. 

Trails are shelly extensions of the outer lip of the 

aperture away from the coil, as in Salpingostoma (pi. 

25). Pojeta and Runnegar (1976, p. 32) disagreed with 

these authors, pointing out that cowries and other gastropods secrete secondary shell layers over the entire 

shell, and that there was no valid reason why parietal 

deposits could not be secreted by epithelium near the 

head. This point is well taken; however, I agree with 

Harper and Rollins (1982, p. 228) that the crux of the 

problem is not the capability of secreting secondary
MIDDLE AND UPPER ORDOVICIAN SYMMETRICAL UNIVALVED MOLLUSKS, CINCINNATI ARCH REGION 051

deposits in any certain region of the shell, but rather the 

functional utility of secreting massive secondary deposits 

in the parietal region.

Sinuites granistriatus and related species are generally accepted as monoplacophorans, and are known to 

have a thin swash of secondary deposits in the parietal 

region and over the ventral coil (pi. 45, figs. 1, 2). 

However, these deposits are so thin that they do not 

mask the original morphology of the covered areas.

In contrast, many bellerophontaceans have strongly 

thickened inner apertural margins and parietal areas. 

Rollins (1966) has described thick, padlike parietal deposits in Ptomatis, an explanate Devonian genus. Salpingostoma kentuckyense (pi. 25, figs. 2, 8, 10), Bucania 

nashvillensis (pi. 13, fig. 19; pi. 14, figs. 1-5), Bucania 

peracuta (pi. 16, figs. 5-8), Bucania crassa (pi. 19, figs. 

7-10), and other species in the present study clearly 

demonstrate the common thickening of the parietal lip in 

bellerophontaceans. Specimens of Sphenosphaera 

clausus show the marked thickening of the entire parietal region by secretion of rather massive secondary shell 

layers over the medial region (pi. 30, figs. 2-5, 8, 9; 

pi. 31, figs. 2, 3, 8).

Thickened parietal regions in bellerophontacean gastropods seem to serve two functions. First, such deposits 

add considerable weight to the part of the shell that lies 

on the central portion of the foot, thereby creating a 

fulcrum for balancing the shell. The added weight would 

also serve to stabilize the shell under higher energy 

conditions. Considering the difficulty of balancing large 

umbilicate shells such as some of those cited above, the 

added weight in a low central position would be of 

obvious advantage. Second, thickened parietal deposits 

may modify the design of the parietal region. This is 

particularly noticeable in S. clausus. Such modification 

of the parietal region in S. clausus would provide a 

broader, more stable area for the shell to rest on when 

the foot was extended.

The outbuilding of the parietal region, evident in the 

figures of S. clausus cited above, was taken to its 

maximum development in species of Carinaropsis (pi. 

37, figs. 3, 4, 18, 19). In Carinaropsis, the coil has been 

reduced to the point of no longer being able to support 

the visceral mass of the mature animal. The extensive 

outbuilding of the parietal region in this specialized case 

was for the support of the visceral mass. The apertural 

platform of the modern gastropod Crepidula is clearly 

analogous in its morphology and function to that of 

Carinaropsis.

In summary, it is concluded that thickened parietal 

regions furnish greater weight over the central area of 

the gastropod, for better balance and stabilization of the 

shell. It is further concluded that such deposits may 

assist in supporting the shell on the extended foot, and

may even provide a better surface over which to move 

the foot in and out of the shell. Such thickened deposits 

would overlie the head region in an untorted monoplacophoran, and would not seem to serve any reasonable 

function. In fact, massive deposits in such a position 

would seem to be impractical and would probably hinder 

the balancing of the shell in a monoplacophoran. Therefore, it is here considered highly doubtful that monoplacophorans would secrete thickened secondary parietal 

deposits. Harper and Rollins (1982) went so far as to 

claim that the development of a thickened parietal inductura is the single most reliable criterion for distinguishing fossil gastropods from monoplacophorans among 

Paleozoic isostrophic shells.

MUSCLE SCARS AND THEIR 

FUNCTIONAL SIGNIFICANCE

Muscle patterns in fossil univalved mollusks are central to the continuing debate over the class-level affinities of Paleozoic bilaterally symmetrical isostrophic 

shells. These muscle patterns occasionally are discovered 

through fortuitous preservation of muscle scars. Calcification of the shell material is inhibited over the sites of 

muscle attachment on the shell interior, and as a result 

there develops a slight depression the muscle scar 

(Fretter and Graham, 1962, p. 142). In some fossil 

specimens, these muscle scars are preserved as raised 

fillings of the original scar depression on internal molds 

of the shell.

The modern monoplacophoran Neopilina has six pairs 

of discrete muscle scars arranged around the interior 

periphery of the shell (Lemche and Wingstrand, 1959). A 

number of Early to Middle Paleozoic limpetlike shells, 

the Tryblidiida, have five to eight pairs of discrete scars 

in a form and arrangement similar to that of Neopilina, 

and therefore have been interpreted as monoplacophorans (Wenz, 1940; Knight, 1952). Pojeta and Runnegar 

(1976, p. 29) have convincingly reconstructed the musculature of the Middle Cambrian genus Scenella using 

Neopilina as a model.

Pairs of discrete dorsal muscle scars have also been 

found in some isostrophically coiled early Paleozoic genera. Wenz (1940) first described such a muscle scar 

pattern in Cyrtonella from the Devonian of Michigan. On 

the basis of that single occurrence, he proposed that all 

bilaterally symmetrical isostrophic Paleozoic molluscan 

univalves were untorted, and were not gastropods as 

generally believed. A number years later, Horny (1963c) 

described symmetrical pairs of muscle scars in the Late 

Ordovician Cyrtolites ornatus. Rollins and Batten (1968) 

then found monoplacophoranlike muscle scars in the 

Middle Devonian Sinuitopsis acutilira, and more 

recently Runnegar (1981) and Peel (1980) recognized
052 CONTRIBUTIONS TO THE ORDOVICIAN PALEONTOLOGY OF KENTUCKY AND NEARBY STATES

TABLE 15. Examples of post-Cambrian bellerophontiform molluscan univalves for which muscle scars have been described

Species Age Area Author(s)

Monoplacophoran-type muscle scars Multiple discrete pairs

Cyrtonella mitella 

Cyrtolites ornatus 

Sinuitopsis acutilira 

Sinmtes cancellatus 

Sylvestrosphaera lemchei 

christianae

Devonian

Ordovician

Devonian

Ordovician

Silurian

Ordovician

Michigan 

New York 

New York 

New York 

Britain 

Norway

Wenz (1940)

Horny (1965a)

Rollins and Batten (1968)

Runnegar (1981)

Peel (1980)

Runnegar (1981)

Gastropod-type muscle scars Single symmetrical pair, columellar, circumumbilical

Bellerophon gibsoni

Bellerophon sp.

Bellerophon cf. B. gibsoni

Bellerophon sp.

Pharkidonotus labioreflexus

Sinuitina brevilineata

Tremanotus alphaeus

Salpingostoma buelli

Bellerophon sp.

Megalomphala taenia

Bellerophon recticostatus

Mississippian

Pennsylvanian

Mississippian

Pennsylvanian

Pennsylvanian

Devonian

Silurian

Ordovician

Pennsylvanian

Carboniferous

Silurian

Carboniferous

Indiana

Indiana

Indiana

Missouri

Ohio

New York

Illinois

Wisconsin

U.S.A.

Ireland

Gotland

Ireland

Knight (1947a)

Knight (1947a)

Rollins (1967)

Rollins (1967)

Rollins (1967)

Rollins (1967); Rollins

and others (1971)

Peel (1972)

Peel (1972)

Peel (1972)

Peel (1972)

Peel (1976)

Peel (1982)

similar scars in two other sinuitid species, the Late 

Ordovician Sinuites cancellatus and the Late Silurian 

Sylvestrosphaera lemchei, respectively.

The muscle scars in limpet-form monoplacophorans, 

and in some isostrophically coiled taxa, are located in a 

ring just inside the apertural margin. Such an arrangement indicates that the animal could not retract into the 

shell, but rather must have clamped the shell down over 

the body for protection. In contrast, muscle scars in the 

sinuitids are inset more deeply into the shell opening and 

in some cases are even located at the umbilical shoulder 

a half-whorl back, suggesting that these forms were 

probably capable of retracting into the shell (Peel, 1980, 

p. 95, 96). Considering the widespread use and success of 

retractability in the gastropods, it is not surprising that 

the Monoplacophora also evolved this ability as a protective strategy.

The shell, or columellar, muscles in coiled gastropods 

attach to the inner surface of the shell at the columella. 

Most prosobranch gastropods have only a single columellar muscle as the result of larval reduction of the second 

retractor muscle. However, numerous archaeogastropods, including the Haliotidae, Scissurellidae, and some 

Neritacea, as well as some mesogastropods, have a pair 

of columellar muscles (Knight, 1952, p. 12; Fretter and 

Graham, 1962, p. 140). All of these taxa have asymmetrically coiled shells, and the posttorsional right muscle is 

always larger than the left muscle. Symmetrical paired 

columellar muscle scars on the internal molds of a 

number of bellerophontaceans have been described 

(table 15).

In the bilaterally symmetrical patellacean gastropods 

(limpets), the shell muscles form a horseshoe-shaped ring 

around the inner shell margin, the open anterior end 

marking the position of the mantle cavity. The continuous horseshoe-shaped muscle is the product of a pair of 

lateral muscles, one on either side of the torted visceral 

mass, that increase in size and gradually extend their 

insertions in a backward direction during ontogeny until 

they coalesce (Fretter and Graham, 1962, p. 140; Bandel, 

1982, p. 32, 33). All of these patelliform gastropods are 

thought to be descended from asymmetrically coiled 

ancestors which are presumed to have had two asymmetrical shell muscles. Therefore, the bilateral symmetry of 

the shell muscles in patelliform gastropods is an adaptation to the secondary symmetry "of their shells.

Just as in the Monoplacophora, the arrangement of 

muscle scars around the inner periphery of the shell 

opening in patelliform gastropods indicates a clamping 

mechanism for protection, while a circumumbilical muscle position demonstrates the ability to retract the body 

into the shell. Linsley (1978a, b) and Peel (1980) have 

suggested that the location of muscle scars half a whorl 

back from the aperture in sinuitid monoplacophorans, as 

well as their fusion into fewer attachment sites, were 

adaptations favorable to development of torsion. Peel 

(1980) proposed that these sinuitid muscles may represent a morphological grade similar to possible gastropod 

ancestors in terms of retraction.

Peel (1980) and Harper and Rollins (1982) stressed how 

muscle arrangements in bellerophontiform mollusks are 

controlled by the mechanical requirements of shell form
MIDDLE AND UPPER ORDOVICIAN SYMMETRICAL UNIVALVED MOLLUSKS, CINCINNATI ARCH REGION 053

and by the functional requirements of the animal's mode 

of life. Both monoplacophorans and gastropods can have 

muscles arranged in a ring around the aperture. Further, 

the discreteness of these muscle scars is not significant, 

as the supposedly continuous horseshoe-shaped muscle 

scar of diotocardian limpets actually represents a series 

of discrete bundles of muscle fibers, which may leave 

discrete scars in some cases (Fretter and Graham, 1962; 

Harper and Rollins, 1982). Moreover, muscle scars positioned in the circumumbilical region in retractile monoplacophorans can appear quite similar to the columellar 

scars of gastropods (Peel, 1980).

I agree with Peel (1980) and Harper and Rollins (1982) 

in their conclusion that muscle scars are not a reliable 

criterion for assessing class-level affinities of molluscan 

univalves. The genera Cyrtolites and Sinuites are 

assigned to the Monoplacophora in this study because of 

their multiple sets of discrete muscle scars, and because 

their apertural forms can be rationalized as serving an 

exogastric animal. However, much more work on modern gastropod muscle patterns is needed before transfers 

of taxa from the Gastropoda to the Monoplacophora can 

be made confidently. Studies such as that of Gundrum 

(1981) are heading in the right direction, but tangible 

data remain rather scarce. Another factor that should be 

recognized is that muscle scars on internal molds are 

quite difficult to see. For instance, Runnegar (1981, p. 

315), Knight (1952), and Peel (1980) have all observed 

different numbers and forms of muscle scars on a single 

specimen of Sinuites cancellatus.

Runnegar (1981, p. 315) described a single pair of 

muscle scars that cross the edges of the umbilici in a 

specimen of IBucania christianae (Koken). It should be 

noted that this species was described by Koken (1925) as 

a species of Bucaniella, a sinuate genus. Even Runnegar 

stated that the specimen was sinuate and did not possess 

a slit-selenizone complex, and thus it is unclear why he 

referred the specimen to the slit-bearing genus IBucania. Runnegar (1981, p. 315) agreed with Peel (1980) and 

Harper and Rollins (1982) that positions of muscle scars 

can be directly correlated with shell form, and he illustrated an evolutionary sequence for these two characteristics in monoplacophorans that matches another 

sequence of opposite polarity in living trochacean gastropods (Runnegar, 1981, fig. 4). On the basis of these two 

sequences, he concluded that all bellerophonts were 

probably monoplacophorans. I disagree with Runnegar's 

conclusion. If anything, Runnegar's figure seems to show 

what Peel (1980) and Harper and Rollins (1982) claimed; 

that is, muscle patterns in gastropods and monoplacophorans can be essentially identical, and therefore cannot 

be used exclusively as a reliable criterion in determining 

the class-level assignment of bilaterally symmetrical 

molluscan univalves. Muscle patterns are controlled by

the mechanical requirements of shell form and by functional aspects related to the animal's mode of life.

PHYLOGENY AND CLASSIFICATION

THE BELLEROPHONT CONUNDRUM

The class-level assignment of Paleozoic bellerophontiform mollusks has been debated since the early 19th 

century (Yochelson, 1967). The current controversy over 

the classification of the Bellerophontacea centers on 

whether or not these mollusks had undergone torsion, 

the larval process that defines the class Gastropoda. 

Torsion is the process by which the larval shell and 

visceral mass of the veliger are rotated 180 degrees with 

respect to the head-foot mass. According to Crofts (1937, 

1955), torsion results from the differential development 

and growth of the larval left and right retractor muscles. 

However, Bandel (1982, p. 27, 28) recently observed that 

torsion is caused by the differential growth of epithelial 

cells and is not related to muscle activities. As a result of 

torsion, the originally posterior mantle cavity, and its 

respiratory, sensory, reproductive, and renal organs, 

are brought into an anterior position above the head and 

the shell coils backward away from the head (endogastrically). Monoplacophorans, which are believed to be the 

group ancestral to the gastropods, do not undergo torsion, and therefore their mantle cavity remains posteriorly positioned and the shell coils forward over the head 

(exogastrically). The debate over classification of the 

bellerophontaceans was rekindled in recent years by the 

discovery of multiple symmetrical pairs of discrete muscle scars in some bellerophontiform taxa, and by the 

description of diverse Lower and Middle Cambrian mollusk faunas. One group of paleontologists claims that this 

new evidence from the fossil record indicates that the 

Paleozoic bellerophontiform univalves were untorted, 

exogastrically oriented mollusks assignable to the class 

Monoplacophora (Wenz, 1940; Moore and others, 1952; 

Runnegar and Pojeta, 1974; Pojeta and Runnegar, 1976; 

Salvini-Plawen, 1980; Runnegar, 1981, 1983). However, 

most Paleozoic gastropod specialists consider such fossils 

to represent torted, endogastrically oriented archaeogastropods (Knight, 1947a, b, 1952; Knight and others, 

1960; Yochelson, 1967, 1978; Berg-Madsen and Peel, 

1978; Linsley, 1978a, b; Peel, 1980, 1987; Harper and 

Rollins, 1982). The latter viewpoint is accepted herein. 

Below, evidence is reviewed that suggests that the 

slit-bearing bellerophontaceans, and many of the morphologically similar sinuate taxa, are gastropods and are 

closely related to the pleurotomariaceans.

In the early 19th century, Bellerophon and its allies 

were generally considered nautiloid cephalopods (Yoch-
054 CONTRIBUTIONS TO THE ORDOVICIAN PALEONTOLOGY OF KENTUCKY AND NEARBY STATES

elson, 1967). This opinion persisted even after Defrance 

(1824) demonstrated that bellerophonts lacked both a 

siphuncle and septa. Some other authors of that period 

considered bellerophonts to be heteropods, prosobranch 

gastropods adapted to a pelagic mode of life (Yochelson, 

1967). De Konnick (1843) and Meek (1866) first linked 

bellerophonts to the archaeogastropods by comparing 

their labral emarginations to those of Emarginula, the 

modern keyhole limpet. Meek (1866) also argued that the 

shells of most bellerophonts seemed much too thick and 

heavy for the animals to have led a pelagic mode of life.

Since Meek's (1866) paper, the association of the 

bellerophonts with the archaeogastropods has been 

widely accepted, with some notable exceptions. Simroth 

(1906) proposed a separate class of mollusks for the 

bellerophonts, which he termed Amphigastropoda. This 

class was later also used by Thiele (1935) in his mollusk 

classification. Also, Naef (1911) taxonomically isolated 

the bellerophonts by placing them in a division that he 

called the Planospiralia. All of these authors considered 

the bellerophonts to be pelagic swimming animals, a 

belief that Yochelson (1967, p. 149) claimed must have 

influenced their views on classification. Moore and others 

(1952, p. 289), who also used Amphigastropoda and allied 

the group with the tryblidiids, did not consider them to 

be pelagic.

The current period of controversy was initiated by 

Wenz's (1938) observation that the symmetrical, paired 

muscle scars of the Silurian patelliform genus Tryblidium seemed to indicate that the animal's soft parts were 

symmetrical and untorted. He proposed that Tryblidium 

and its allies be transferred from the Patellacea to a new 

superfamily, the Tryblidiacea. Wenz (1940) then also 

found multiple pairs of muscle scars on an internal mold 

of the Devonian species Cyrtonella mitella (Hall), an 

incompletely coiled isostrophic form. On the basis of this 

evidence, Wenz (1940) concluded that all Paleozoic bellerophontiform taxa represent primitive untorted mollusks. He placed all such taxa in the subclass Amphigastropoda, and all anisostrophic gastropods in the subclass 

Prosobranchia.

Knight (1947a, 1952) strongly contested Wenz's (1940) 

conclusion that the bellerophonts had not undergone 

torsion. In rebuttal, Knight (1947a) described single 

pairs of gastropodlike columellar muscle scars in two 

species of Bellerophon and in Sinuites cancellatus. However, additional muscle scar pairs have recently been 

recognized in Knight's specimen of S. cancellatus, thus 

apparently demonstrating its monoplacophoran affinities 

(Peel, 1980; Runnegar, 1981). Knight (1952, fig. 10) also 

reconstructed the soft anatomy of a bellerophontacean on 

the basis of the pleurotomariacean gastropod design. He 

claimed that the median labral slit in these two groups 

was a homologous structure and therefore indicated that

bellerophontaceans had undergone torsion. He envisioned the bellerophontacean animal to have an anterior 

dibranchiate mantle cavity. As known from pleurotomariaceans having this arrangement, oxygenated water 

enters the mantle cavity anteriorly and passes over the 

gills, and then the deoxygenated water and waste products are expelled through the dorsal labral emargination 

(Yonge, 1947). This reconstruction is accepted herein. 

Knight (1952, p. 52) argued that three common morphological characteristics demonstrated a close relationship 

between the bellerophontaceans and the pleurotomariaceans: (1) a deep, hollow, usually closely coiled shell, (2) 

a sinus or a slit (and selenizone), and (3) a single pair of 

columellar retractor muscles. As is discussed below, it 

now seems likely that monoplacophorans could also have 

a coiled shell and a labral sinus.

Horny (1963c) reported multiple pairs of discrete muscle scars in the Upper Ordovician isostrophic species 

Cyrtolites ornatus, and Rollins and Batten (1968) also 

described such scars in the Middle Devonian sinuitid 

Sinuitopsis acutilira (table 15). S. acutilira bears a deep 

labral sinus, and some Middle Ordovician species of 

Cyrtolites bear a shallow labral sinus. Recently, monoplacophoranlike muscle scars have also been reported in 

the sinuitids Sinuites and Sylvestrosphaera (Peel, 1980; 

Runnegar, 1981). So far, all isostrophic species reported 

to have multiple pairs of monoplacophoranlike muscle 

scars have been cyrtolitids and sinuitids, except for a 

single specimen of questionable taxonomic affinity cited 

by Runnegar (1981) as IBucania christianae (table 15). 

Bellerophont genera reported to have a single pair of 

gastropodlike columellar muscle scars include Bellerophon, Pharkidonotus, Tremanotus, Salpingostoma, 

Sinuitina, and Megalomphala (table 15).

The reliability of muscle scars as a primary taxobase 

on which to base class-level assignments of bellerophontiform fossils may be questionable. First, the muscle scar 

patterns of most extinct or extant gastropods have not 

been assessed, and therefore the range of variability of 

this feature is unknown. Second, muscle scars are rarely 

preserved, and when they are, their recognition and 

interpretation is open to differences of opinion. A case in 

point is the specimen of Sinuites cancellatus on which 

Knight (1947a) saw a single pair of columellar scars, but 

on which Runnegar (1981) recognized a second pair, and 

Peel (1980) recognized yet a third pair (see Runnegar, 

1981, p. 315). In another case, Runnegar and Jell (1976, 

p. 127) recognized monoplacophoranlike muscle insertions on illustrations of species of Sinuitina and Tremanotus by Horny (1963a, pi. 8, fig. 9, and pi. 19, figs. 3-5, 

respectively), but Berg-Madsen and Peel (1978, p. 123) 

criticized these observations. The latter authors claimed 

that in the specimen of Sinuitina, the proposed scar 

might be no more than a spurious mark. Regarding the
MIDDLE AND UPPER ORDOVICIAN SYMMETRICAL UNIVALVED MOLLUSKS, CINCINNATI ARCH REGION 055

specimen of Tremanotus, Berg-Madsen and Peel (1978, 

p. 123) claimed that Runnegar and Jell's (1976) supposed 

muscle scars were actually umbilical nodes, which are 

common in tremanotids. Moreover, gastropodlike columellar scars have also been reported in other species of 

Sinuitina and Tremanotus by Rollins and others (1971) 

and Peel (1972), respectively.

Recently, evidence from comparative and functional 

morphological observations has been cited to suggest 

further hazards in total reliance on muscle scars as class 

discriminators in bellerophontiform fossils (Linsley, 

1978b, p. 437, 438; Peel, 1980, p. 95, 96; Harper and 

Rollins, 1982, p. 228-230). Many authors have concluded 

that the number and position of muscle scars are related 

primarily to shell form and mode of life,, and that 

therefore the muscle scars in some monoplacophorans 

and gastropods could appear identical. For example, 

tryblidiid and some cyrtonellid monoplacophorans have 

numerous pairs of muscle scars or a muscle band 

arranged around the aperture opening. Similarly, patellacean gastropods have a horseshoe-shaped muscle scar 

around their aperture openings. It should be noted that 

although the muscle band of most patellacean gastropods 

is continuous, it actually consists of separate bundles of 

muscle fibers, a condition that is in some cases reflected 

in the muscle scars (Fretter and Graham, 1962; Harper 

and Rollins, 1982). All of these arrangements suggest a 

clinging animal that could not retract into its shell for 

protection, but rather clamped the shell opening down 

onto firm substrates. Starobogatov (1970) has argued 

that the Archinacellacea, which herein are assigned to 

the Monoplacophora, were actually limpet-form gastropods, because their continuous muscle band would leave 

no room for a head if exogastrically oriented. It appears, 

therefore, that a ring of muscles, whether a continuous 

band or consisting of multiple discrete pairs, may be 

either functional or phylogenetic in origin. Detailed 

analyses of muscle scars are needed, but even then, as in 

Archinacellacea, interpretations are open to question.

Isostrophic taxa that are capable of retracting into the 

shell for protection typically have muscle insertions set 

deep into the shell. Bellerophontaceans and some coiled 

monoplacophorans, such as Sinuites and Sylvestrosphaera, have deeply inset circumumbilical muscle scars 

(Peel, 1980,. p. 95, 96). Although Sinuites also has one or 

more dorsal pairs of muscle scars, Sylvestrosphaera 

apparently has no dorsal scars (Peel, 1980). The fusion of 

muscle scars into more localized lateral positions 

improved the ability to retract into the shell, and it is 

probable that some coiled monoplacophorans having only 

a single pair of circumumbilical muscles are present in 

the fossil record. In such a case, it would be virtually 

impossible to distinguish isostrophic gastropods from

monoplacophorans on the basis of muscle scars only 

(Peel, 1980, p. 96).

Linsley (1978a, b), Peel (1980), and Harper and Rollins 

(1982) have suggested that morphological features other 

than muscle scars, such as the form of the aperture 

opening, may be more reliable taxobases for class-level 

assignments of bellerophontiform taxa. As discussed in 

the section "Functional Morphology," an endogastric 

versus exogastric orientation for bellerophontiform 

shells should be discernible from the functional analysis 

of shell morphologies. For example, Peel (1974) has 

demonstrated that the trilobate isostrophic shell is an 

adaptive strategy by which an endogastric gastropod 

separates incoming and outgoing mantle cavity currents. 

Linsley (1978b, p. 440) has shown that the deep slit of the 

narrow tropidodiscid shell (pi. 44, figs. 3, 6) effectively 

provides a posterior exhalant area in a gastropod presumed to be endogastric. The same effect would be had in 

broader shell forms having deep slits, such as Undulabucania (pi. 23, figs. 5, 10) and the Bucania sulcatina 

group (pi. 12, figs. 1-9) (see "Functional Morphology"). 

Harper and Rollins (1982, p. 228) concluded that massive 

secondary parietal deposits may be the most reliable 

criterion for recognizing gastropods among Paleozoic 

isostrophic shells. I agree with the importance of this 

characteristic (see "Functional Morphology"). The massive parietal deposits on bellerophontaceans such as 

Sphenosphaera clausus would clearly serve as a stabilizing structure in an endogastric gastropod, but they 

would seem to be a hindrance to an exogastric monoplacophoran. The large parietal platforms of the specialized 

Ordovician bellerophontaceans Carinaropsis and 

Pterotheca are analogous in position, and presumably in 

function, to the parietal platform of the modern gastropod Crepidula. The presence of a slit that generates a 

selenizone is strong evidence of a close affinity between the bellerophontaceans and pleurotomariacean 

gastropods.

Functional morphological interpretations have also 

been used to support an exogastric orientation for some 

bellerophontiform taxa (see "Functional Morphology"). 

For example, Starobogatov (1970) interpreted the lateral 

angles of the typically diamond shaped aperture of 

Cyrtolites as inhalant ducts to a posterior mantle cavity. 

Subsequently, Linsley (1978b, p. 437) suggested that 

such diamond-shaped apertures could serve to distiguish 

untorted monoplacophorans in bellerophontiform genera 

where muscle scars were unknown. Starobogatov (1970, 

p. 295) also noted narrow umbilical grooves on Sinuitopsis which he interpreted as inhalant channels to a posterior mantle cavity. Peel (1975c) has since noted similar 

umbilical grooves in two species of Pharetrolites, and 

Berg-Madsen and Peel (1978, p. 120, 121) have ob-
056 CONTRIBUTIONS TO THE ORDOVICIAN PALEONTOLOGY OF KENTUCKY AND NEARBY STATES

served such channels in the minute Middle Cambrian 

Protowenella.

The other body of evidence used to suggest that all 

Paleozoic bellerophontiform taxa were monoplacophorans are the recently described diverse Early and Middle 

Cambrian mollusk faunas, such as those from the Early 

Cambrian Tommotian Stage of the Siberian Platform 

(Rozanov and others, 1969; Runnegar and Pojeta, 1974; 

Matthews and Missarzhevsky, 1975; Pojeta and Runnegar, 1976; Runnegar and Jell, 1976; Runnegar, 1981, 

1983). All of these Early and Middle Cambrian mollusks 

are minute in size, and many are preserved as phosphatized internal molds (Runnegar, 1983). The univalved 

mollusks occur as both isostrophic and anisostrophic 

forms. The higher taxonomic assignment of many of 

these minute fossils, such as the low-spired pellagiellaceans, is a matter of some debate (Knight, 1952; 

Yochelson, 1967, 1975, 1978; Berg-Madsen and Peel, 

1978; Runnegar, 1983). Rozanov and others (1969) 

regarded all the Tommotian molluscan univalves as gastropods, but Runnegar and Pojeta (1974) have interpreted them all as monoplacophorans and have used 

them as groundwork for a new viewpoint on molluscan 

phylogeny. Runnegar and Pojeta (1974, p. 313, 314) have 

proposed that the pellagiellaceans were anisostrophic 

monoplacophorans ancestral to the pleurotomariacean 

gastropods through an intermediate primitive gastropod 

form such as the Cambrian genus Aldanella. They 

preferred Ghiselin's (1966) theory concerning the origin 

or torsion, which states that torsion is a necessary 

consequence of helical coiling. They suggested that the 

larval shell of the anisostrophic pellagiellacean was awkward to balance upon settling from the plankton, so the 

animal adopted a functional torsion in order to move the 

shell into a more manageable position. Subsequently, 

torsion was selected for because of its advantages to the 

larval animal. Runnegar (1983) has elaborated on pellagiellaceans and the adult animals' ability to cope with 

some degree of functional torsion.

Knight (1952) had previously proposed that torsion in 

isostrophic monoplacophorans gave rise to the bellerophontacean gastropods, which in turn gave rise to the 

anisostrophic pleurotomariacean gastropods. In support 

of this model, Morton (1958) suggested that torsion was 

of obvious benefit to the adult animal, as well as to the 

larva, by moving the mantle cavity into an anterior 

position, where the gills and pallial sense organs were 

put in a more advantageous place from which to sample 

the environment into which the animal was moving. In 

further support of this model, Batten, Rollins, and Gould 

(1967) concluded that an exogastric isostrophic shell 

would be as difficult to balance as an exogastric anisostrophic shell for both the larval and adult monoplacophoran, and therefore it would be beneficial to both morphotypes to move the coil around 180 degrees to rest on 

the foot. Linsley (1978a, b) and Peel (1980) have 

attempted to demonstrate that there was a trend in 

isostrophically coiled monoplacophorans to fuse and 

localize muscle insertions into lateral areas deep in the 

shell, which resulted in a morphological grade favorable 

to the development of torsion. They claimed that the 

development of an isostrophically coiled monoplacophoran shell was accompanied by the development of a 

narrow neck between the visceral and head-foot masses, 

which would have faciliated the torsional rotation of the 

visceral mass and shell.

In Knight's (1952) model, it is assumed that there are 

both monoplacophorans and gastropods among the Paleozoic bellerophontiform taxa. However, in Runnegar and 

Pojeta's (1974) model, no torted isostrophic intermediate 

form is required in the evolution of the Pleurotomariacea 

from the Monoplacophora. Because of this viewpoint, 

and the fact that some bellerophontiform taxa have been 

found to have multiple pairs of discrete muscle scars, 

Runnegar and Pojeta (1974) have concluded that all 

bellerophontiform taxa were untorted monoplacophorans. Peel (1987) has pointed out that there is no evidence that torsion was a unique event, as both the above 

models assume. Rather, the Gastropoda may represent a 

grade of evolution, and torsion may have occurred in 

both ways, and even several times in different lineages. 

Rollins and Batten (1968, p. 134) have suggested that the 

bellerophontaceans themselves may be polyphyletic, 

evolving from monoplacophoran ancestors as many 

as three different times during the early to middle 

Paleozoic.

Regardless of how torsion originated, for reasons of 

comparative and functional morphology the Bellerophontacea are herein considered to be archaeogastropods 

related to the pleurotomariaceans. If this viewpoint is 

accepted, then there are three main phylogenetic models 

to consider (fig. 17). First, (fig. 175), as Knight (1952) 

proposed, the Bellerophontacea may be evolutionary 

intermediates between the isostrophic monoplacophorans and the pleurotomariacean gastropods. Second, (fig. 

17C), the bellerophontaceans may represent one or more 

independent lineages of gastropods that evolved from 

isostrophic monoplacophorans but did not give rise to any 

descendant groups. Such a scenario could accept multiple 

origins of torsion. It would also deny the homology 

between the slit-selenizone complexes of the bellerophontaceans and pleurotomariaceans, unless a common 

ancestral slit-bearing monoplacophoran group existed. A 

third possible phylogenetic model has not been adequately considered, in my opinion (fig. 17Z)). The bellerophontaceans may be secondarily symmetrical and 

descended from the pleurotomariaceans. Yochelson 

(1967, p. 154; 1978, p. 177; 1984, p. 262) has repeatedly
MIDDLE AND UPPER ORDOVICIAN SYMMETRICAL UNIVALVED MOLLUSKS, CINCINNATI ARCH REGION 057

MONOPLACOPHORAN 

MODEL

(Runnegar and Pojeta, 1974)

GASTROPOD MODELS

Intermediate

Model 

(Knight, 1952)

Independent

Lineage

Model

Secondary

Symmetry

Model

Pleurotomariacean 

Gastropods

Pleurotomariacean 

Gastropods

Bellerophontacean 

Gastropods

Earliest 

Gastropods 

(Aldanella)

Anisostrophic

Isostrophic Monoplacophorans 

Monoplacophorans (Pelagiella)

including 

Bellerophonts

Pleurotomariacean 

Gastropods

Bellerophontacean 

Gastropods

Bellerophontacean 

Gastropods

Pleurotomariacean 

Gastropods

Isostrophic 

Monoplacophorans

Isostrophic Anisostrophic 

Monoplacophorans Monoplacophorans

Isostrophic Anisostrophic 

Monoplacophorans Monoplacophorans

Tryblidiid 

Monoplacophorans A

Tryblidiid 

Monoplacophorans B

Tryblidiid 

Monoplacophorans C

Tryblidiid 

Monoplacophorans D

FIGURE 17. Four primary models suggesting possible phylogenetic 

relationships between monoplacophorans, bellerophontaceans, and 

pleurotomariaceans. A, Considers bellerophontaceans to be isostrophic monoplacophorans and suggests that pleurotornariacean gastropods descended from anisostrophic monoplacophorans. B-D, Consider bellerophontaceans to be gastropods. The intermediate model 

(B) suggests that bellerophontaceans are phylogenetically intermediate between isostrophic monoplacophorans and pleurotomariacean 

gastropods. The independent lineage model (C) suggests that bellerophontaceans and pleurotomariaceans developed independently from 

different monoplacophoran ancestors. The secondary symmetry model 

(D) suggests that pleurotomariaceans developed from anisostrophic 

monoplacophorans, and that bellerophontaceans are secondary symmetrical pleurotomariaceans.

expressed this opinion but has never documented it. 

Such a model has ample precedent. Secondary symmetry 

is known in at least nine stocks of Tertiary and modern 

archaeogastopods (Bales, 1950, p. 191; Vermeij, 1975, 

p. 419).

The derivation of the bellerophontaceans from the 

pleurotomariaceans can be supported both by comparative morphology and by the biostratigraphic development of the two groups. Well-documented pleurotomariaceans are known from rocks as old as Late Cambrian 

and rapidly diversified into three families: the Sinuopeidae, Eotomariidae, and Raphistomatidae (Knight and 

others, 1960). Slit-bearing bellerophontaceans also first 

appeared during the Late Cambrian, but are currently 

known from only the single tropidodiscid genus Chalarostrepsis Knight. A number of sinuate bellerophontiform genera also appeared during the Late Cambrian, 

but many of these taxa are still poorly understood, and
058 CONTRIBUTIONS TO THE ORDOVICIAN PALEONTOLOGY OF KENTUCKY AND NEARBY STATES

the group probably contains both monoplacophorans and 

gastropods. Bellerophontacean diversity appears to have 

remained low through the Early Ordovician, with only 

Eobucania Kobayashi known from that time. It was not 

until the late Middle Ordovician (BlackriveranShermanian) that the bellerophontaceans radiated into a 

diversity of forms.

Many of the early pleurotomariaceans (Late 

Cambrian-Early Ordovician) had very low spired shells 

and wide-open umbilici. Of particular interest is the 

raphistomatid subfamily Ophiletinae (see Knight and 

others, 1960, p. 1200, fig. 113), which contains such 

genera as Dirachopea Ulrich and Bridge and Calaurops 

Whitfield. These genera are characterized by very low 

spires (low rate of whorl translation), large, open umbilici, lanceolate whorl shapes, slits with selenizones, and 

disjunct coiling in adulthood. Such forms could have been 

ancestral to the Late Cambrian tropidodiscid bellerophontacean Chalarostrepsis, which differs from this 

description only in its planispiral coil. The Late Cambrian sinuate genus Strepsodiscus Knight, which was 

placed in the Cyrtolitidae by Knight and others (1960, p. 

1174), also matches this description fairly well, and it is 

even slightly anisostrophically coiled. Schizopea Butts 

represents a Ophiletinae morphotype that has a broader 

whorl shape and a greater rate of whorl expansion, and it 

could similarly represent an ancestor of a bellerophontacean such as Eobucania. The low-spired, widely umbilicate shells of the Ophiletinae probably were awkward to 

carry. Secondary symmetry would have allowed the shell 

to be more easily carried in a vertical position on the foot.

Salvini-Plawen (1980, p. 254) pointed out that the 

apparent absence of a helically coiled protoconch in 

bellerophontaceans speaks against a secondary symmetrical origin for the group. Salvini-Plawen may be correct 

in this observation, but it should be noted that bellerophontacean protoconchs have never really been investigated. Moreover, Bandel (1982, p. 32, 33) has asserted 

that some patellaceans and other related archaeogastropod limpets do not have a trochospiral shell stage in early 

ontogeny. He has observed that the bilateral symmetry 

of the adult secondary shell may be carried into the early 

development of the embryonic (primary) shell, so that 

the trochospiral twist of the larval shell may disappear 

completely. Also, it is of interest to note that Lemche 

(1957, p. 414) reported a dextrally coiled helical protoconch on the modern monoplacophoran Neopilina 

galatheae, although other modern monoplacophorans 

have been reported to have only bulbous protoconchs 

(Pojeta and Runnegar, 1976, p. 30)

The secondary symmetry model for the origin of 

bellerophontacean gastropods deserves further investigation. More detailed comparison of early pleurotomariacean and bellerophontacean morphologies is needed

before the model can become a viable alternative. One 

possibly attractive aspect of the model is that it allows 

acceptance of Runnegar and Pojeta's (1974) theory of the 

evolution of the Gastropoda, but also accepts Knight's 

(1952) premise that the bellerophontaceans were archaeogastropods. The apparent absence of an anisostrophic 

protoconch in bellerophontaceans (Salvini-Plawen, 1980) 

does not necessarily exclude the hypothesis from further 

consideration.

In summary, there is good evidence from functional 

morphological analyses and muscle scar patterns to indicate that there are both monoplacophorans and gastropods among the Paleozoic bellerophontiform taxa. So far, 

only sinuate bellerophontiform taxa have been proven to 

be monoplacophorans. The slit-bearing bellerophontaceans, and many similar sinuate forms, are thought to be 

archaeogastropods and closely related to the pleurotomariaceans. The diverse minute molluscan faunas of the 

Early and Middle Cambrian are not typical bellerophontaceans, and conclusions derived from such forms cannot 

be automatically applied to all planispiral molluscan 

univalves. Many conclusions drawn from those minute 

faunas are based on an unproven theory on the origin of 

torsion and on highly interpretive functional morphology. On the other hand, the comparative and functional 

morphologic evidence supporting the assignment of most 

bellerophontaceans to the Gastropoda is much more 

tangible and relies on direct comparison with living 

animals. Clearly, a great deal more detailed morphological analysis is needed to clarify the phylogenetic role of 

bellerophontaceans. At least four possible phylogenetic 

models bear close scrunity (fig. 17). Continued concentrated and cooperative research should eventually result 

in the resolution of the problem, or at least a consensus.

CLASSIFICATION AND PHYLOGENY OF 

THE MONOPLACOPHORA

Knight (1952) proposed the Monoplacophora as an 

order of the gastropod subclass Isopleura. However, he 

credited the concept of the taxon to Wenz (1938, 1940). 

Wenz recognized that the presence of multiple pairs of 

discrete muscle scars in Paleozoic symmetrical molluscan 

univalves, such as Tryblidium and Cyrtonella, suggested that they had not undergone the larval process of 

torsion. Wenz (1940) concluded that all symmetrical 

molluscan univalves were untorted, and he assigned 

them to Simroth's (1906) subclass Amphigastropoda. 

Knight (1952, p. 5) disagreed with this conclusion and 

restricted the Monoplacophora to three families the 

Tryblidiidae, Hypseloconidae, and Archinacellidae. A 

few years later, Lemche (1957) described the living 

monoplacophoran Neopilina galatheae and elevated the 

Monoplacophora to class level. Knight and Yochelson
MIDDLE AND UPPER ORDOVICIAN SYMMETRICAL UNIVALVED MOLLUSKS, CINCINNATI ARCH REGION 059

(1958, p. 37-39) recognized this new class and modified 

Knight's (1952) classification accordingly. Also at that 

time, Knight and Yochelson (1958, p. 38) developed the 

modern concept of the class Gastropoda as mollusks that 

undergo larval torsion, the process by which the visceral 

mass and shell are rotated counterclockwise 180 degrees 

with respect to the head-foot mass. Knight and Yochelson (1958, p. 38-40) included three orders within the 

Monoplacophora the Tryblidioidea, Archinacelloidea, 

and ?Cambridioidea. The Tryblidioidea was considered 

the "heart of the class" and included those symmetrical 

forms having discrete paired muscle scars assigned to the 

superfamilies Tryblidiacea and Cyrtonellacea. The 

Archinacelloidea was considered an artificial grouping of 

forms that did not fit conveniently in the Tryblidioidea, 

but some of which were known to have completely or 

nearly completely fused muscle scar bands., The single 

superfamily Archinacellacea included the families Archinacellidae and Hypseloconidae. The order Cambridioidea 

accounted for questionable monoplacophorans and 

included elongate, slightly asymmetrical shells in which 

the muscle scars were unknown. Knight and Yochelson 

(1960, p. 177-183) continued to follow this classification in 

their "Treatise on Invertebrate Paleontology."

Horny (1965b, p. 10) outlined a revised higher classification of the Monoplacophora in which he presented two 

new subclasses the Tergomya and Cyclomya. The Tergomya included limpetlike genera having several pairs of 

discrete muscle scars arranged in a ring, with the 

anterior apex of the shell located outside that ring. The 

Cyclomya included limpetlike, cone-shaped, and planispiral genera having discrete paired or fused muscle scars 

arranged in a ring, with the apex of the shell located 

inside that ring. The Tergomya included the order Tryblidiida, and the Cyclomya included the orders Archinacellida and Cyrtonellida. Horny (1963c) had erected the 

order Cyrtonellida for incompletely or completely coiled 

forms whose muscle scars are reduced in number and, in 

many cases, specialized. In the Cyrtonellida, Horny 

(1965b, p. 10) included the family Cyrtolitidae with 

the subfamilies Cyrtolitinae, Cyrtonellinae, and 

Cyrtonellopsinae.

Starobogatov (1970) proposed another revision of the 

classification of the Monoplacophora based on his functional analyses of shell features and muscle scars. First, 

he excluded the family Palaeacmeidae (including 

Scenelld) and the Cambridioidea from the class because, 

he claimed, the scars reported from genera of both 

groups were not really muscle scars. However, subsequent to Starobogatov, Runnegar and Pojeta (1974, 

fig. 2) convincingly reconstructed the musculature of 

Scenella using the modern monoplacophoran Neopilina 

as a model. Starobogatov (1970) also removed the Archinacellida from the Monoplacophora and suggested that

they were a specialized order of the Gastropoda. He 

argued that the circular muscle of Archinacella 

approached so near the apical end of the shell that there 

was no room left for the animal's head, and he reinterpreted the pair of discrete muscle scars at the contraapical end of the muscle ring in Archinacelliopsis as 

radular muscle scars. Starobogatov (1970) recognized 

three monoplacophoran orders the Tryblidiida, Cyrtonellida, and the new order Sinuitopsida. He redefined 

the Cyrtonellida as those planispiral shells having few 

whorls and two or three pairs of shell muscles inserted on 

the periphery of the final whorl, and he concluded that 

such forms retained multiple pairs of gills. Only the 

family Cyrtonellidae was included in this order. He 

proposed the order Sinuitopsida for planispiral forms 

having several whorls and only one pair of shell muscles. 

He concluded that other muscle scars described in Cyrtolites by Horny (1963c) and in Sinuitopsis by Rollins and 

Batten (1968) were muscle scars of the radula and 

genitalia. He interpreted apertural features of these 

genera as indicating narrow inhalant channels to a posterior mantle cavity, and concluded that these forms 

must have had only a single pair of enlarged posterior 

gills. In the Sinuitopsida, he placed the families Cyrtolitidae, Bucanellidae, and Cyclocyrtonellidae. In the order 

Tryblidiida, he included the superfamilies Tryblidioidea, 

Neopilinoidea, and Kirengelloidea.

Bjaly (1973, p. 326) added the order Multifariida to the 

class Monoplacophora, and based the order on the single 

species Multifariites lenaensis Bjaly from the Lower 

Ordovician of the Siberian Platform. The Multifariida 

was said to be similar to the Sinuitopsida in its number of 

whorls, but was distinguishable by its four pairs of 

identical muscle scars. The new order was considered 

unique in its duplication of the muscles during the growth 

of the shell.

Rosov (1975) elevated the superfamily Kirengelloidea 

to the order Kirengellida and included three families 

the Kirengellidae (including Scenella and Moyerokania), 

the Romaniellidae (including Romaniella and Hypseloconus), and the Archaeophialidae (including Archaeophiala). He defined the order as having conical shells, with 

the apex generally anterocentrally located but varying 

from anterior to central to postcentral, and sometimes 

having a tendency to coil, but for no more than one-third 

of a whorl (fig. ISA). Muscle scars in the order vary from 

six to eight pairs arranged around the apex. Rosov (1975) 

suggested that the Kirengellida were the most primitive 

monoplacophoran group known and that they gave rise to 

the Archinacellida (fig. 185) and Tryblidiida (fig. 18C) 

through forward displacement of the apex and simultaneous flattening of the shell, and to the Cyrtonellida by 

further coiling of the shell (fig. 18Z)). He claimed that
060 CONTRIBUTIONS TO THE ORDOVICIAN PALEONTOLOGY OF KENTUCKY AND NEARBY STATES

C D

FIGURE 18. Four general morphotypes of monoplacophorans representing four superfamilies. A, Kirengellacean: Simple conical shell 

with discrete to fused muscle scars. B, Tryblidiacean: Low limpetform shell with discrete muscle scars. C, Archinacellacean: Low to 

high limpet-form shell with fused muscle scars. D, Crytonellacean: 

Coiled shell with multiple discrete muscle scars. According to Rosov 

(1975), the kirengellaceans gave rise to the tryblidiaceans and 

archinacellaceans through forward displacement of the shell apex and 

simultaneous flattening of the shell, and to the crytonellaceans 

through progressive coiling of the conical shell.

evolution toward fusion of the muscle scars occurred in 

all four orders.

Runnegar and Jell (1976) proposed a new classification 

of the Monoplacophora based on a theory of molluscan 

evolution proposed by Runnegar and Pojeta (1974) and 

Pojeta and Runnegar (1976). Their concept of the Monoplacophora closely approximated that of Wenz (1940), in 

which all Paleozoic symmetrical univalves were considered to be untorted. Unlike other modern classifiers of 

the Monoplacophora, Runnegar and Jell (1976) emphasized shell morphology in their ordinal diagnoses and did 

not mention muscle scar patterns. They recognized three 

orders the Tryblidiida, Cyrtonellida, and Bellerophontida. They defined the Tryblidiida as limpet-shaped 

forms having an anteriorly placed protoconch; the Cyrtonellida as orthoconic, cyrtoconic, laterally compressed, 

and evolute planispiral forms lacking a well-formed apertural sinus or slit; and the Bellerophontida as involute to 

evolute planispiral forms having an apertural sinus or 

slit. They included in the order Bellerophontida the 

families Bellerophontidae, Sinuitidae (=Sinuitopsida 

Starobogatov, 1970), and Multifariidae (=Multifariida 

Bjaly, 1973).

The classification of Runnegar and Jell (1976) cannot 

be accepted here, primarily because I consider the taxa 

in their family Bellerophontidae to be archaeogastropods 

rather than monoplacophorans. Also, Runnegar and 

Jell's (1976) concept of the Cyrtonellida does not seem 

acceptable. Their diagnosis of that order departs greatly 

from the original meaning of the taxon given by Horny 

(1963c, 1965a, b). Moreover, Runnegar and Jell (1976, p. 

116) stated that Horny's (1965a) subclass Cyclomya is an 

alternative taxon to Cyrtonellida, but was not appropriately named. However, Horny (1965a, b) cited the Cyrtonellida as one of two orders in the subclass Cyclomya, 

and therefore the two taxa should not be considered 

alternative to one another. Finally, Runnegar and Jell's 

(1976) use of the presence or absence of a labral emargination as an ordinal taxobasis is placed in doubt here by 

the demonstration that Middle Ordovician species of 

Cyrtolites bear a labral sinus (pi. 5, figs. 7, 10, 13), 

whereas similar Upper Ordovician species of Cyrtolites 

lack a labral sinus (pi. 6, figs. 7, 10, 17).

As previously discussed, Berg-Madsen and Peel 

(1978), Linsley (1977, 1978b), and Peel (1980) have 

argued against the claim that all bellerophontiform mollusks are monoplacophorans. On the basis of analyses of 

functional morphology, those authors concluded that 

both gastropods and monoplacophorans are present in 

that group. That opinion is shared here. On the other 

hand, Harper and Rollins (1982) concluded that muscle 

scar patterns reflect life habits and shell form rather than 

phylogenetic origins, and proposed that all cyrtonellid 

monoplacophorans and bellerophontaceans were gastropods. They accepted only the Tryblidiida as true monoplacophorans.

The higher classification of the class Monoplacophora 

adopted here is shown in table 16. This classification is 

considered conservative and tentative, but workable. 

The classification is based on my experience with mainly 

Ordovician taxa and on a survey of the literature. At 

present I consider the Monoplacophora to consist of two 

orders the Tryblidiida and the Cyrtonellida.

The order Tryblidiida sensu Starobogatov (1970) is 

accepted here with some important modifications. The 

Archinacellacea is retained within the Monoplacophora 

as a superfamily of the Tryblidiida. Certainly Starobogatov's (1970) argument for returning the Archinacellacea to the Gastropoda warrants further investigation, but at present, the bulk of the evidence more 

strongly suggests that the group evolved from the 

Kirengellacea, as proposed by Rosov (1975), and should 

remain within the Monoplacophora. Also, the superfamily Kirengellacea Starobogatov, 1970, is recognized here 

in the sense of Rosov's (1975) order Kirengellida, consisting of the three families, the Kirengellidae, 

Romaniellidae, and Archaeophialidae. Rosov's (1975) 

order Kirengellida is quite similar in concept and composition to the family Scenellidae Wenz, 1938, sensu Runnegar and Jell (1976, p. 117). Noting the similarities in 

muscle scar patterns in the Cambrian Scenella, the 

Silurian Tryblidium and Pilina, and the modern Neopilina, Runnegar and Jell (1976, p. 119) suggested that 

these taxa represent a conservative lineage of monoplacophorans that survived from the Cambrian to the 

present. I agree with Runnegar and Jell (1976), and with 

the views of Rosov (1975), and support the proposal that
MIDDLE AND UPPER ORDOVICIAN SYMMETRICAL UNIVALVED MOLLUSKS, CINCINNATI ARCH REGION 061

TABLE 16. Classification of the class Monoplacophora to family

level

Class Monoplacophora Wenz in Knight, 1952 

Order Tryblidiida Lemche, 1957 

Superfamily Tryblidiacea Pilsbry in Eastman, 1899

Family Tryblidiidae Pilsbry in Eastman, 1899

Family Proplinidae Knight and Yochelson, 1958

Family Bipulvinidae Starobogatov, 1970

Family Drahomiridae Knight and Yochelson, 1958

Family Neopilinidae Knight and Yochelson, 1958 

Superfamily Kirengellacea Starobogatov, 1970

Family Kirengellidae Starobogatov, 1970

Family Romaniellidae Rosov, 1975

Family Archaeophialidae Knight and Yochelson, 1958

Family Hypseloconidae Knight, 1956 

Superfamily Archinacellacea Knight, 1956

Family Archinacellidae Knight, 1956 

Order Cyrtonellida Horny, 1963c 

Superfamily Cyrtonellacea Knight and Yochelson, 1958

Family Cyrtolitidae Miller, 1889

Family Cyrtonellidae Knight and Yochelson, 1958

Family Cyclocyrtonellidae Horny, 1962

Family Sinuitidae Dall in Eastman, 1913

Family Multifariidae Bjaly, 1973 

Order Uncertain 

Superfamily Helcionellacea Wenz, 1930

Family Helcionellidae Wenz, 1930 (sensu Runnegar and Jell, 

1976)

Family Yochelcioniellidae Runnegar and Jell, 1976 

Superfamily Uncertain

Family Palaeacmaeidae Grabau and Shinier, 1909

the simple conical kirengellaceans seem to be the most 

morphologically primitive group of monoplacophorans. I 

also agree that they probably gave rise to the tryblidiaceans and archinacellaceans through forward displacement of the apex and simultaneous flattening of the shell, 

and to the cyrtonellaceans through progressive coiling of 

the lengthening conical tube.

The order Cyrtonellida here includes both the orders 

Cyrtonellida and Sinuitopsida sensu Starobogatov 

(1970). As pointed out by Peel (1980, p. 92), the order 

Sinuitopsida was inappropriately defined in terms of 

interpreted muscle functions and numbers of supposed 

gills. Furthermore, Rollins (1969) has shown that the 

muscle scar patterns of Cyrtonella and Sinuitopsis are 

more alike than previously thought, and Peel (1980) has 

demonstrated that the musculature of sinuitids can vary 

considerably.

Herein, the Superfamily Helcionellacea and some other 

problematical taxa are assigned to the Monoplacophora, 

but their affinities within that group remain unclear.

SUPRAGENERIC CLASSIFICATION AND PHYLOGENY OF 

THE BELLEROPHONTACEAN GASTROPODA

In the discussion of the conundrum of the class-level 

assignment of the Bellerophontacea, I concluded that the

group belongs to the class Gastropoda and is closely 

related to the pleurotomariacean Archaeogastropoda. In 

this section, the suprageneric classification of the Bellerophontacea is reviewed, and a classification is proposed 

that satisfies both morphological similarities and inferred 

phylogenetic relationships. The families and subfamilies 

of the Bellerophontacea are discussed individually and in 

more detail in the "Systematic Paleontology" section.

The monograph by Ulrich and Scofield (1897) on the 

Ordovician gastropods from the Cincinnati arch and 

upper Mississippi Valley regions of North America laid 

the groundwork for subsequent classifications of the 

Bellerophontacea. They recognized five bellerophontacean families the Cyrtolitidae, Protowarthiidae 

(=Sinuitidae), Bucaniidae, Bellerophontidae, and Carinaropsidae. Both the Cyrtolitidae Miller, 1889, and the 

Sinuitidae Dall, 1913, now are considered families of the 

class Monoplacophora. The Bucaniidae Ulrich and 

Scofield (1897) was established to account for planispiral 

genera that are involute and relatively loosely coiled, 

with a wide-open umbilicus, a slit and selenizone, collabral and revolving ornament that always cross at or 

nearly at right angles, and, commonly, expanded apertures. Ulrich and Scofield (1897, p. 849-852) included in 

the Bucaniidae the genera Bucania, Tetranota, Kokenia 

(=Kokenospird), Megalomphala, Salpingostoma, Tremanotus, Conradella (=Phragmolites), and Oxydiscus 

(=Tropidodiscus\ Ulrich and Scofield (1897, p. 852-857) 

considered the family Bellerophontidae to contain planispiral shells that are involute, rapidly expanding, and 

relatively tightly coiled, with a small or closed umbilicus, 

a slit and selenizone, and, generally, only collabral ornament. When revolving ornament was present in a bellerophontid, it was said to always parallel the longitudinal 

axis of the shell whorl, and not to curve to maintain right 

angles with curving collabral ornament, as it does in the 

Bucaniidae. Within the Bellerophontidae, Ulrich and 

Scofield placed the genera Bellerophon, Bucanopsis, 

Patellostium, Euphemites, Warthia, Mogulia, and 

Stachella. Although the concept of this family has 

remained essentially unchanged to the present, the 

generic composition has changed greatly. Euphemites, 

Warthia, and Stachella have been found to lack a true slit 

and selenizone and were transferred to sinuate families, 

Mogulia has been placed in synonomy with B. (Bellerophon) by Knight and others, (1960, p. 1182), and Patellostium is considered problematical and may be a heterogeneous taxon. More recently, a number of new genera 

have been added to the Bellerophontidae (see Knight and 

others, 1960, and Horny, 1963a). The family Carinaropsidae Ulrich and Scofield, 1897, was established for 

planispiral shells having greatly expanded apertures and 

a small or completely reduced coil, with a slit and a 

well-developed inner apertural platform. Ulrich and
062 CONTRIBUTIONS TO THE ORDOVICIAN PALEONTOLOGY OF KENTUCKY AND NEARBY STATES

Scofield (1897, p. 857, 858) included the genera Carinaropsis and Pterotheca in this family.

Koken (1925) recognized the single family Bellerophontidae, but he divided it into four subfamilies the 

Bellerophontinae, Cyrtolitinae, Bucaniinae, and the new 

Salpingostomatinae, which housed the single genus 

Salpingostoma.

Wenz (1938, p. 93-112) recognized the same five 

families as Ulrich and Scofield (1897), but added the 

families Pterothecidae and ?Procarinariidae. Procarinaria is now considered a pelecypod (Horny, 1963a, p. 

69). Wenz (1938) retained Salpingostoma in the family 

Bucaniidae.

In "Treatise on Invertebrate Paleontology," Knight 

and others (1960, p. 1171-1184) constructed a familial 

classification for the Bellerophontacea based primarily 

on the character of the labral emargination. This classification was the first to arrange bellerophontacean suprageneric taxa in such way as to suggest phylogenetic 

relationships within the group. The Cyrtolitidae were 

defined by a shallow, commonly angular, labral sinus, 

with no slit. The Sinuitidae were defined by an open, 

U-shaped labral sinus, with no slit. Three subfamilies 

were recognized within the Sinuitidae the Sinuitinae, 

Bucanellinae, and Euphemitinae. It was said that in 

some advanced Euphemitinae, the sinus could become a 

broad slit. All of the slit-bearing bellerophontaceans 

were placed in the family Bellerophontidae and were 

divided among the subfamilies Tropidodiscinae, Bucaniinae (tribes Bucaniides and Salpingostomatides), Carinaropsinae, Pterothecinae, Bellerophontinae, and Knightitinae. The Tropidodiscinae Knight, 1956, were 

separated from the Bucaniinae because of the former's 

narrow coil, broad umbilicus, deep slit, and posterior 

labral train (Knight and others, 1960, p. 1179). The 

Knightitinae Knight, 1956, was distinguished from the 

Bellerophontinae by the former's strong spiral ornament. It should be noted that Knight and others (1960, p. 

1172) included the superfamily Helcionellacea Wenz, 

1938, in the suborder Bellerophontina. The class-level 

assignment of the Helcionellacea has also been a matter 

of debate in recent years (Knight, 1952; Knight and 

others, 1960; Yochelson, 1967; Pojeta and Runnegar, 

1976; Runnegar and Jell, 1976). The Helcionellacea is 

assigned to the Monoplacophora herein, but its relationships within that class are considered unresolved.

Horny (1963a, p. 69) proposed a number of amendments to the classification of Knight and others (1960). 

First, because of the discovery of multiple pairs of 

discrete muscle scars in Cyrtolites ornatus, he transferred the family Cyrtolitidae to the class Monoplacophora. He (1963a, p. 69) elevated the Euphemitinae to the 

family Euphemitidae because of the unique development 

of the apertural region and anal emargination, and the

peculiar development of inductural deposits over much of 

the shell. He also reestablished the family Pterothecidae 

because the existence of a true selenizone in the group 

has not been confirmed, and because of the lack of shell 

coiling and the presence of a large parietal platform. He 

reestablished the family Salpingostomatidae, including 

Salpingostoma, Tremanotus, and Boiotremus, all of 

which have either a deep slit or a series of open tremata 

across the dorsum of an expanded aperture. He (1963a, 

p. 69) erected the new subfamily Grandostomatinae of 

the family Sinuitidae for sinuate taxa having greatly 

laterally expanded apertures. He also erected the new 

subfamily Temnodiscinae of the family Sinuitidae for 

taxa in which the sinus became a parallel-sided notch 

similar to a true slit. Finally, he (1963a, p. 69) erected the 

new subfamily Cymbulariinae of the family Bellerophontidae for taxa having the slit diverging into a V-shaped 

sinus rather than meeting the anterior margin of the 

shell aperture at nearly right angles.

Boucot and Yochelson (1966, p. A7) cited evidence 

confirming the presence of a true slit in the trilobate 

genus Plectonotus, which previously had been assigned 

to the sinuate subfamily Bucanellinae of the Sinuitidae by 

Knight and others (1960). Because of this new evidence, 

they transferred Plectonotus to the family Bellerophontidae and proposed the subfamily Plectonotinae for bellerophontids having a trilobate cross section.

Peel (1972, p. 419) demonstrated that Tremanotus was 

sinuate and that its series of open tremata was the result 

of successive closings of a deep sinus. Therefore, he 

separated the genera Tremanotus and Boiotremus into 

the new subfamily Tremanotinae of the family Sinuitidae, and returned Salpingostoma to the subfamily Bucaniinae of the Bellerophontidae, thereby eliminating the 

family Salpingostomatidae.

Golikov and Starobogatov (1975) preferred to recognize most suprageneric taxa within the Bellerophontacea 

as distinct families. They listed the Sinuitidae, Grandostomatidae, Temnodiscidae, Tropidodiscidae, Bucaniidae, 

Salpingostomatidae, Carinaropsidae, Pterothecidae, 

Bellerophontidae, Cymbulariidae, Knightitidae, and 

Euphemitidae.

Because of the discovery of monoplacophoranlike muscle scars in Sinuites and the morphologically similar 

Sinuitopsis and Sylvestrosphaera, the family Sinuitidae 

has recently been transferred to the Monoplacophora. 

Strangulites Horny, 1962, almost certainly belongs in 

this family also. Other genera included in the Sinuitidae 

by Knight and others (1960) have little in common with 

the true sinuitids except for a rounded sinuate aperture 

and have been variously assigned to the Monoplacophora 

or Gastropoda.

As previously discussed, Runnegar and Jell (1976, p. 

121) assigned the superfamily Bellerophontacea to the
MIDDLE AND UPPER ORDOVICIAN SYMMETRICAL UNIVALVED MOLLUSKS, CINCINNATI ARCH REGION 063

TABLE l7. — Suprageneric classification of the Bellerophontacea with diagnoses of family-level taxa

Class Gastropoda 

Subclass Prosobranchia 

Order Archaeogastropoda 

Suborder Bellerophontina 

Superfamily Bellerophontacea

Family Bucanellidae Shell sinuate, phaneromphalous, broad dorsally; transverse and radial ornament. 

Family Grandostomatidae Shell explanate, phaneromphalous, sinuate; transverse and radial ornament.

Family Tremanotidae Shell gradually expanding, phaneromphalous, having bell-shaped aperture, sinuate, having tremata developed.

Family Euphemitidae Shell somewhat inflated, anomphalous; inductural deposits over most or all of shell; sinus narrow to slitlike.

Family Tropidodiscidae Shell laterally compressed, phaneromphalous; slit deep. 

Family Bucaniidae Shell gradually expanded, widely phaneromphalous; whorls depressed to evenly rounded; apertural margins

tending to flare; usually collabral and radial lines; slit short to deep. 

Subfamily Bucaniinae Slit short to deep, open at apertural margin; dorsum rounded. 

Subfamily Salpingostomatinae Slit deep, closed at apertural margin in adult. 

Subfamily Plectonotinae Whorls trilobate in cross section; slit short.

Subfamily Undulabucaniinae Slit deep; ornament of closely spaced, regularly wavy, fine collabral threads only. 

Family Bellerophontidae Shell rounded, with narrow to closed umbilicus; apertural margins tend to flare; parietal lip generally

reflexed; slit short. 

Subfamily Bellerophontinae Shell convolute or nearly so; whorls rounded to globose; no median ridge on whorl floor; growth

lines only. 

Subfamily Bucanopsinae Shell anomphalous or nearly so; median ridge on whorl floor; selenizone slightly elevated in many

cases.

Family Carinaropsidae Shell greatly expanded; aperture explanate, having coil nearly or completely reduced; posteromedian platform developed within aperture.

Subfamily Carinaropsinae Shell with small coil, then rapidly and broadly expanded; slit or short notch generating a selenizone. 

Subfamily Pterothecinae Coil completely reduced; apex marginal and low. 

Subfamily Pedasiolinae Coil completely reduced; apex submarginal and elevated.

Monoplacophora. They placed all sinuate bellerophontiform taxa in the Sinuitidae and all slit-bearing taxa in the 

Bellerophontidae. They did not give any subfamily 

groupings. As previously stated, I disagree with their 

classification.

The suprageneric classification of the Bellerophontacea adopted herein is shown in table 17. It is based 

mainly on my experience with Ordovician taxa, and 

conclusions regarding the placement of post-Ordovician 

taxa are based primarily on the current literature. The 

classification attempts to show phylogenetic relation 

within the Bellerophontacea by the grouping of related 

subfamilies within more broadly based and traditional 

families.

The sinuate families Bucanellidae Koken, 1925, Grandostomatidae Horny, 1963a, and Tremanotidae Peel, 

1972, are tentatively recognized here. However, the 

relations among these sinuate families, and between 

them and the slit-bearing families, are unresolved. 

Herein, taxa from these sinuate families are present in 

the fauna under consideration. The class-level assignment of many sinuate bellerophontiform genera is not yet 

resolved. Some genera are still too poorly known to 

classify with confidence; however, others have morphological features indicative of gastropod affinities (Peel, 

1974, p. 232-234). Sinuitina (of the Bucanellidae herein) 

has been shown to have gastropodlike columellar muscle

scars (Rollins and others, 1971). Ptomatis and related 

genera of the Grandostomatinae are quite different morphologically from the sinuitids, and Ptomatis has been 

functionally interpreted to be a gastropod (Rollins, 1966). 

The euphemitids are considered herein to be gastropods, 

primarily because of their extensive inductural deposits. 

Herein, the tremanotids, which Peel (1972) showed to be 

sinuate, are considered to be gastropods because their 

series of open tremata appear to be homeomorphic with 

the long, open slit of the salpingostomatids. Much work 

needs to be done on these groups in order to determine 

whether sinuate forms and morphologically similar slitbearing forms are phylogenetically related or are homeomorphic. It should be noted that Bandel (1982, p. 37) 

concluded from his studies of the development of modern 

fissurellids and scissurellids that the presence or absence 

of a slit is of questionable value in assessing systematic 

assignments.

All of the slit-bearing families, and many of their 

subfamilies are represented in the fauna under consideration. Four slit-bearing families (nine subfamilies) are 

recognized herein the Tropidodiscidae, Bucaniidae, 

Bellerophontidae, and Carinaropsidae (fig. 19). Each of 

these families represents a morphological grade of development. The Tropidodiscidae is the most primitive slitbearing family, and its genera are characterized by 

narrow, loosely coiled, widely phaneromphalous shells
064 CONTRIBUTIONS TO THE ORDOVICIAN PALEONTOLOGY OF KENTUCKY AND NEARBY STATES

Pterothecinae

Carinaropsinae

Bellerophontinae

Bucanopsinae

Plectonotinae Salpingostomatinae

Bucaniinae 

Undulabucaniinae

Tropidodiscinae

FIGURE 19. Phylogenetic relationships of bellerophontacean slitbearing subfamilies present in Eastern North America during the 

Late Cambrian-Middle Ordovician.

having slits as deep as one-half whorl back from the 

apertural margin. The Bucaniidae developed from tropidodiscid ancestors. Primitive members of the subfamilies 

Bucaniinae (such as the Bucania sulcatina group of 

Ulrich and Scofield, 1897) and Undulabucaniinae are also 

widely phaneromphalous and have deep slits like the 

tropidodiscids, but their whorls are wider and more 

depressed. The Salpingostomatinae, with their deep, 

closed-off slit, probably developed from primitive Bucaniinae. Juvenile specimens of Salpingostoma, prior to 

the adult expansion of the aperture, closely resemble 

members of the Bucania sulcatina group.

In more advanced Bucaniinae (such as species of the 

Bucania lindsleyi group of Ulrich and Scofield, 1897), 

the shell becomes more tightly coiled, reducing the size 

of the umbilicus, the whorls become more rapidly 

expanding and more rounded, and the slit becomes 

shorter. A similar trend can be seen in the genus 

Tetranota of the Plectonotinae.

In the family Bellerophontidae, the shells have become 

still more tightly coiled, so that the umbilicus is closed, or 

nearly so, and the whorls are generally quite rapidly 

expanded and rounded, resulting in a more compact 

shell. The subfamily Bucanopsinae is probably the most 

primitive in the family. Within that subfamily is seen the 

incipient building of a parietal platform in the genus 

Sphenosphaera, which is thought to be ancestral to the 

Carinaropsidae. In the Carinaropsidae, the rate of whorl 

expansion has increased to the point where the coil is 

nearly or completely reduced in the adult, and a large

parietal platform has developed to support the visceral 

mass within the shell. This development reached its peak 

in the genus Pterotheca.

The morphological trends summarized in the above 

paragraphs are treated in more detail in the section on 

"Functional Morphology." This morphological progression can also be traced upward stratigraphically from the 

Upper Cambrian through the Middle Ordovician. The 

tropidodiscid Chalarostrepsis appeared during the Late 

Cambrian, followed by the somewhat transitional genus 

Eobucania during the Early Ordovician. The primitive 

bucaniids of the Bucania sulcatina group appeared 

during the early Middle Ordovician (ChazyanBlackriveran). The more advanced Bucaniinae, the Salpingostomatinae, and the Plectonotinae appeared near 

the beginning of the late Middle Ordovician 

(Blackriveran-Rocklandian). The Bucanopsinae, as well 

as the Carinaropsidae, appeared during the latest Middle 

Ordovician (Rocklandian-Shermanian).

The broad epicontinental seas of the Middle Ordovician 

transgression apparently provided an ideal environment 

for the radiation of the bellerophontaceans, as well as 

many other invertebrate groups. The Middle Ordovician 

radiation of the bellerophontaceans probably had internal and external driving forces. The beginning of continental convergence during that time may have played a 

part by creating depositional topography over the eratonic sea floor (such as the proto-Lexington and protoNashville domes see section on stratigraphy), which 

provided heterogeneous, and even somewhat isolated, 

environmental settings. As mentioned in the section on 

paleoecology, there was also a radiation of calcareous 

algal groups during the early Middle Ordovician, which 

would have offered a greater variety of food sources, and 

thus niches, to the predominantly algal feeding archaeogastropods. The contemporaneous diversification of 

other invertebrate groups during the Middle Ordovician 

also would have encouraged bellerophontacean radiation 

as entire new communities evolved. Finally, the trend 

toward more rapid whorl expansion and tighter coiling in 

the bellerophontaceans produced more mobile shell 

forms, which must have enabled the group to occupy 

new, particularly higher energy, environments and additional niches.

SYSTEMATIC PALEONTOLOGY

In the following taxonomic descriptions of species, the 

type species of a genus is described first, where possible, 

and all other species descriptions are arranged in ascending stratigraphic order.

The following abbreviations for museum depositories 

are used:
MIDDLE AND UPPER ORDOVICIAN SYMMETRICAL UNIVALVED MOLLUSKS, CINCINNATI ARCH REGION 065

AMNH American Museum of Natural History, New 

York, N.Y.

CMNH Cincinnati Museum of Natural History, Cincinnati, Ohio

GSC Geological Survey of Canada, Ottawa, Ontario, 

Canada

MU Miami University Geology Museum, Oxford, 

Ohio

UC Field Museum of Natural History, Chicago, 111.

UCGM University of Cincinnati Geology Museum, Cincinnati, Ohio

USNM U.S. National Museum of Natural History, 

Smithsonian Institution, Washington, D.C. 

The U.S. Geological Survey collections cited in the

text have a four-digit number and the -CO (CambrianOrdovician) suffix (for example, 6134-CO). The collecting

localities for these and other collections are listed in the

"Locality Register" (appendix).

Phylum MOLLUSCA Cuvier, 1797

Subphylum CYRTOSOMA Runnegar and Pojeta, 1974

Class MONOPLACOPHORA Wenz in Knight, 1952

Diagnosis. Mollusks having a single, bilaterally symmetrical, cap-shaped, orthoconic, cyrtoconic, or planispiral shell, the apex generally being anteriorly situated, 

with symmetrical muscle scars arranged in discrete pairs 

or in partly to completely fused ring around aperture.

Stratigraphic range. — Lowest Cambrian (Tommotian)- 

Holocene.

Discussion. — The diagnosis given above is conchological. The Monoplacophora can be further defined in 

zoological terms, on the basis of limited information 

provided by the few known living species, as untorted 

mollusks having an anterior mouth, a posteromedian 

anus, a lateral to posterior mantle cavity, pseudometamerically arranged organ systems, a radula, and a 

gastropodlike foot.

Order TRYBLIDIIDA Lemche, 1957

Diagnosis.—Shells cap shaped to cone shaped; apex 

may be central, but generally is anteriorly situated, 

being subcentral, submarginal, marginal, or supramarginal, and in many cases incurved to varying degrees; 

muscle scars arranged nearly or completely around inner 

margin of shell, either in discrete pairs or in partly to 

completely fused ring.

Stratigraphic range.—Lower Cambrian-Holocene.

Discussion.— This order was defined by Lemche 

(1957), who described it primarily in zoological terms on 

the basis of the then newly discovered Holocene monoplacophoran Neopilina. His definition is difficult to apply 

to a study of fossils, and in reality is probably too limited 

even for the group of genera Lemche recognized as 

members. The diagnosis given above is paleontological in

its applications, and is most similar to that of Starobogatov (1970), but with significant differences in the 

composition of the order. Herein, the superfamily Archinacellacea is included in this order; the order Archinacellida is rejected. The superfamily Kirengellacea also is 

included in the Tryblidiida, but it has the same composition as Rosov's (1975) order Kirengellida. The superfamily Tryblidiacea is included nearly as conceived by Starobogatov (1970), except for the transfer of the family 

Archaeophialidae to the superfamily Kirengellacea. For 

further discussion of these actions, see the section on 

"Phylogeny and Classification" and table 16.

Superfamily TRYBLIDIACEA Pilsbry, 1899

Diagnosis. Shell cap shaped, apex marginal or supramarginal; muscle scars in discrete pairs. 

Stratigraphic range.—Lower Cambrian-Holocene.

Family TRYBLIDIIDAE Pilsbry, 1899

Diagnosis.— Shell more or less cap shaped, being 

broadly rounded posteriorly, narrowing rapidly near 

anterior end; convexity low; apex marginal or slightly 

supramarginal; comarginal growth lines distinct, in some 

cases lamellose, in many cases accompanied by radial 

lines; muscle scars in five to eight discrete pairs, commonly more complex anteriorly.

Stratigraphic range.—The family contains species 

from the Upper Cambrian (Propilina Kobayashi, 1933) 

to the Holocene (Neopilina Lemche, 1957), but members 

are most common in Middle Ordovician to Middle Silurian 

strata.

Discussion.— The original concept of the family Tryblidiidae by Pilsbry (1899) was as follows: "Limpets with 

muscle scars broken into numerous separate impressions." This definition would now more closely fit the 

order Tryblidiida. As muscle scars were found in more 

genera, a considerable diversity was discovered and the 

concept of the family was restricted to fit the OrdovicianSilurian genus Tryblidium and closely related forms.

Subfamily TRYBLIDIINAE Pilsbry, 1899

Diagnosis.— Same as for family.

Genus HELCIONOPSIS Ulrich and Scofield, 1897

Diagnosis.— Shell having slightly supramarginal apex 

and distinct, widely spaced growth lines crossed by 

prominent radiating threads.

Description. — Shell cap shaped, moderate in size, convexity low; apertural outline subovate; posterior broadly 

rounded, narrowing anteriorly to small beak area; apex 

protruding slightly beyond anterior apertural margin; 

comarginal growth lines distinct, widely and irregularly 

spaced; radial threads prominent, bifurcating posteriorly; muscle scars unknown.
066 CONTRIBUTIONS TO THE ORDOVICIAN PALEONTOLOGY OF KENTUCKY AND NEARBY STATES

Type species.—Helcionopsis fissicostata Ulrich and 

Scofield, 1897, by original designation; lapsus calami for 

Helcionopsis striata Ulrich and Scofield, 1897 (Knight, 

1941, p. 142).

Distribution.— Middle Cambrian (Ordian stage of 

Australia)-Middle Silurian (Wenlockian) of Gotland 

(Sweden). In North America the genus is known only 

from the Ordovician (Shermanian?-Richmondian).

Discussion.—Runnegar and Jell (1976) reported Helcionopsis sp. from the Middle Cambrian of Australia on 

the basis of small internal molds having the shell form 

and radial markings characteristic of the genus. Their 

identification appears to be correct. Easton (1943) 

described Helcionopsisl reticulatus from the Upper Mississippian Pitkin Formation of Arkansas, but this occurrence requires reexamination.

When Ulrich and Scofield (1897, p. 826, 827) named the 

genus Helcionopsis, they included three species: H. 

striata Ulrich and Scofield, H. subcarinata Ulrich and 

Scofield, and H. radiata (Lindstrom). H. striata, from 

the Maysvillian and Richmondian strata of the Cincinnati 

province, is a well-known, distinctive species. H. subcarinata is known from only a few internal molds from the 

Prosser Formation (Ulrich, 1911) (Shermanian-Edenian) 

of Minnesota. Its placement in this genus is questionable. 

From Ulrich and Scofield's (1897, pi. 61, fig. 28) figure of 

this species, it appears to have the shell outline of an 

archinacellid, and its radial ornament is very poorly 

defined. The third species, H. radiata, was described by 

Lindstrom (1884, p. 58) as ITryblidium radiatum from 

the Silurian "crystalline limestone of Wialmsudd near 

Farosund," and it appears to be a valid member of the 

genus.

The muscle scars of this genus are unknown, and its 

higher systematic position is difficult to determine. 

Knight and Yochelson (1960) placed a question mark 

before the genus name and associated it with Pilina 

because of similarities in shell forms and the common 

possession of radial ornament. These two genera are 

closely related, but Helcionopsis is distinct in its possession of heavy radiating threads, rather than the faint 

radiating grooves exhibited by Pilina.

Helcionopsis striata Ulrich and Scofield, 1897 

Plate 2, figures 1-6

Helcionopsis striata Ulrich and Scofield, 1897, p. 827, pi. 61, figs. 29, 

30; Knight, 1941, p. 142, 143, pi. 3. fig. 5; Knight and Yochelson, 

1960, p. 179, figs. 46.7.

Tryblidium striatum (Ulrich and Scofield), Shinier and Shrock, 1944, 

p. 437, pi. 174, fig. 3.

Diagnosis.— Shell elongate, subovate, broadly 

rounded posteriorly, with narrow anterior beak area; 

apex slightly supramarginal, pointing horizontally to 

slightly downcurved in later growth.

TABLE 18. Measurements (in millimeters) of Helcionopsis striata

USNM 

No.

45827

263785

47494

Shell 

length

23.25

14.20

14.00

Shell 

width

17.40

11.85

11.15

Shell 

height

6.1

5.2

4.3

Aperture 

length

22.90

13.70

13.55

Apex 

height

1.5

3.5

2.0

Description.— Shell elongate, subovate in outline, 

broadly rounded posteriorly, narrowing rapidly to small 

beak area at anterior end; lateral apertural margin 

horizontal; dorsally low and broadly convex, becoming 

more gently convex on posterior slope; anterior slope 

tightly concave; apex extending slightly beyond anterior 

apertural margin, pointing essentially horizontally in 

immature specimens, becoming increasingly downcurved 

in mature growth stages; protoconch small smooth cone; 

shell thin, with surface marked by widely, mostly irregularly spaced comarginal growth lines of varying prominence; radial threads slightly rounded, bifurcate posteriorly, with secondary ribs intercalated in maturity; 

radiating costellae varying in spacing over length of shell 

(four per millimeter near beak, three per millimeter 5 or 

6 mm from apex, and two per millimeter 20 mm from 

apex).

Measurements.— Measurements of H. striata are 

listed in table 18. Table 19 lists measurements of the 

distances between growth lines of the holotype (USNM 

45827), and figure 20 graphically displays the apparent 

growth rate of the specimen.

Material.—No new specimens were found in the 

USGS silicified collections from the Cincinnati arch 

region. Only three specimens were located in the U.S. 

National Museum of Natural History and examined. The 

holotype, USNM 45827, is an external mold in the base of 

a bryozoan colony (pi. 2, figs. 1-3 are latex molds made 

from the holotype), as is specimen USNM 47494 (pi. 2, 

figs. 4, 5; fig. 5 is a latex mold). The third specimen, 

USNM 263785, retains the shell and protoconch (pi. 2, 

fig. 6).

Distribution.-The holotype, USNM 45827, is from 

Richmondian-age strata in Marion County, Ky.; no further stratigraphic or locality data are given with the

TABLE 19.—Measurements (in millimeters) of distances between 

growth lines of the holotype of Helcionopsis striata (USNM 

45827)

[Row A gives the numbers assigned to each growth line, moving from anterior to 

posterior. Row B designates the relative strength of each growth line 

(s = strong, m = medium, and w = weak). Row C gives the measurements from 

one growth line to the next, the first measurement being taken from the apex 

to the first distinct growth line]

A123456789101112 

B swmwws s smwsm 

C 3.4 1.7 2.8 0.5 1.0 1.0 1.9 6.0 1.0 1.4 1.3 1.0
MIDDLE AND UPPER ORDOVICIAN SYMMETRICAL UNIVALVED MOLLUSKS, CINCINNATI ARCH REGION 067

3r10 15

SHELL LENGTH, IN MILLIMETERS

20 25

FIGURE 20.-Apparent growth rate of the holotype (USNM 45827) of 

Helcionopsis striata. The strongest growth lines were measured 

from the apex to the posterior shell margin on the assumption that 

these lines marked annual growth increments. Three periods of 

growth are recognized, and an apparent decrease in growth rate with 

age is evident.

specimen. Specimen USNM 263785, Maysvillian or Richmondian in age, is from the Arnheim Formation at 

Clifton, Tenn. Specimen USNM 47494 is from the 

Maysvillian-age Bellevue Tongue of the Grant Lake 

Limestone at Cincinnati, Ohio. Therefore, the species is 

known only from the middle and upper Upper Ordovician 

(Maysvillian-Richmondian) of the Cincinnati arch province (table 4).

Comparison,—H. striata is the only species of monoplacophoran in the Cincinnati arch province to have 

prominent radial ribs that cross growth increments (pi. 

2, figs. 1-6). Vallatotheca unguiformis (Ulrich, 1897) 

(Kirkfieldian-Shermanian) (pi. 1, figs. 12-31) and V. 

manitoulini Foerste, 1914a (Richmondian) (pi. 1, figs. 

8-11), have regular, closely spaced, sublamellose growth 

lines and fine radiating threads that are restricted to 

individual growth increments.

Discussion.— The two specimens preserved as external molds in the bases of calcitic bryozoan colonies (pi. 2, 

figs. 1-3, 4, 5) strongly suggest that the shell of H. striata 

was aragonitic in composition, having been preferentially 

dissolved away. The specimen from Tennessee (pi. 2, fig. 

6) is the only known specimen of the species preserving 

the shell. The shell is somewhat worn, but it is clear that 

it was very thin and probably quite delicate. This in part 

accounts for the rareness of H. striata.

The protoconch preserved in the Tennessee specimen 

(pi. 2, fig. 6) is very small, apparently smooth, and 

symmetrically cone shaped. It is nothing like the supposed protoconch of Neopilina galatheae described by 

Lemche and Wingstrand (1959), which was said to be 

coiled. All other monoplacophorans have had noncoiled, 

bulbous protoconchs. In any case, the pointed, coneshaped protoconch of H. striata is neither coiled nor 

bulbous.

The bifurcation and intercalation of the radial ribbing 

in this species is strikingly reminiscent of brachiopod 

costallae patterns (pi. 2, fig. 1). If other species of 

Helcionopsis are found, these patterns might prove 

useful for specific differentiation.

The unusual cone-shaped protoconch, the bifurcation 

and intercalation of radial ribs, and the absence of data 

on musculature cause me some uncertainty in the higher 

systematic assignment of this taxon.

Of considerable interest is the periodicity of the comarginal growth lines in the holotype of H. striata (pi. 2, 

figs. 1-3). Table 19 lists the distances between these lines 

and the relative strength of the lines. The pattern shown 

by the growth lines in figure 20 could be interpreted as 

representing seasonal or annual growth increments. The 

first possible growth period (lines 1-7) shows a general 

decrease in the width of the growth increments. It should 

be noted that there were two very faint lines between 

lines 2 and 3 which were about 1.0 mm from each other 

and from stronger adjacent lines. The second period 

(lines 7-8) shows more continuous growth over a relatively large distance and only very faint cessation of 

growth. The third period is again more punctuated (lines 

9-12), similar to the first. These period boundaries were 

identified subjectively, but they appear to form a pattern. When the length of each growth period is plotted, 

the general decrease in growth rate is obvious (fig. 20).

The holotype and its encrusting bryozoan occur in a 

matrix of fairly coarse biosparite containing fragments of 

brachiopods, bryozoans, and trilobites. Because this 

specimen's shell markings are well preserved, and considering the rather high energy conditions indicated by 

the matrix, it seems the animal might have been 

encrusted while it was alive. The encrusting bryozoan is 

not very thick, so the animal probably could have supported it easily. As is the case with Cyrtolites (Cyrtolites) ornatus, such encrustation may have furnished 

camouflage and protection from predation. In contrast, 

the second encrusted specimen (pi. 2, figs. 4, 5) probably 

was encrusted after the animal died. The bryozoan is well 

preserved, but the external mold of the shell in its base 

is somewhat worn. Furthermore, the bryozoan colony is 

quite large relative to the monoplacophoran shell, and 

most likely would have been too massive for the animal to 

have supported it in life.

The Tennessee specimen (pi. 2, fig. 6) also occurs in a 

rather coarse, fragmental biosparite matrix, but it must 

have been buried quickly in order for the thin shell to 

have been preserved. It is difficult to determine whether 

the slight breakage and wear of the shell occurred before 

burial or by weathering on the outcrop. The latter seems 

more likely, because the shell retains the protoconch, 

which would have been readily broken off during 

transport.
068 CONTRIBUTIONS TO THE ORDOVICIAN PALEONTOLOGY OF KENTUCKY AND NEARBY STATES

Evidence suggests that H. striata lived in normal 

marine waters of moderate to high energy, but well 

offshore in a bryozoan-brachiopod community.

Family PROPLINIDAE Knight and Yochelson, 1958

Diagnosis.— Shell elongate, more or less cap shaped, 

wider posteriorly, quite narrow anteriorly, moderately 

to strongly convex; apex distinctly extending past anterior shell margin; six pairs of elongate muscle scars 

situated normal to margin of aperture, posterior pair 

particularly elongate and continuing well into interior of 

shell.

Stratigraphic range.—Upper Cambrian-Upper Ordovician.

Discussion.—Knight and Yochelson (1958, 1960) recognized this grouping as a subfamily of the family 

Tryblidiidae, including in it Proplina Kobayashi, 1933, 

and IVallatotheca Foerste, 1914a.

Starobogatov (1970) used the grouping at the family 

level and added three genera: Kotysium Horny, 1961; 

Litavina Horny, 1963a; and 1 Pilinopsis Horny, 1961. 

Horny (1961) had originally placed both Kotysium and 

Pilinopsis in the subfamily Trybliniinae. Kotysium 

resembles Proplina in its shell form, but Horny claimed 

that its five known pairs of muscle scars are quite 

different from the muscle scars of Proplina. Pilinopsis 

resembles Pilina in its shell form, but its muscle scars 

are unknown. The genus Pilinopsis is based on Helcionopsis eminens Perner, and bears closely spaced comarginal growth lines, with short radiating lines restricted 

to the spaces between these growth lines (Perner, 1903, 

fig. lOc), resulting in an ornament pattern very similar to 

that of the genus Vallatotheca. The shell form of Pilinopsis (according to Perner, 1903, figs. lOa, b) is very 

similar to that of Helcionopsis, or even to that of some 

archinacellids. Clearly, the assignment of these genera to 

higher taxonomic groupings is difficult because of the 

differing levels of knowledge of their rather simple 

morphologies.

Vallatotheca, the only genus of the family studied 

here, is a distinctive taxon that is included in the 

Proplinidae because of its general shell form and its 

distinctly supramarginal apex, both of which resemble 

Proplina. Unfortunately, nothing is known about the 

muscle scars of Vallatotheca.

Genus VALLATOTHECA Foerste, 1914a

Diagnosis.— Shell distinctly convex; apex curved 

downward; growth lines closely and regularly spaced, 

sublamellose, with fine radial threads restricted to 

growth increments between sublamellose growth lines.

Description.— Shell distinctly convex dorsally, 

broadly rounded in posterior two-thirds, anterior third 

narrowing rapidly to blunt beak area; apex blunt, downcurved, becoming more so with growth, and extending 

far beyond apertural margin; apertural outline elongateoval; lateral apertural margin horizontal; growth lines 

closely and regularly spaced, sublamellose; radial 

threads fine, closely spaced, restricted to growth increments between sublamellose growth lines; shell moderately thick.

Type species. —V. manitoulini Foerste, 1914a, by 

original designation, reported from the "Cape Smyth or 

Waynesville Member of the Richmond, at Clay Cliffs on 

the eastern side of Cape Smyth, three miles north of 

Wekmemikongsing, on the eastern shore of Manitoulin 

Island" (Ontario, Canada) (Foerste, 1914a, p. 482).

Distribution.—The genus is known with certainty 

from the Lexington Limestone (upper Middle Ordovician) of central Kentucky, and from the Richmondian 

(upper Upper Ordovician) strata of southwestern Ohio 

and of Manitoulin Island, Ontario, Canada. Runnegar 

and Jell (1976) assigned some Middle Cambrian specimens from Australia to the genus, but for reasons given 

below, this assignment is not accepted. Talent (1959) has 

described specimens from the Lower Devonian of Australia that appear to represent a valid species of Vallatotheca. Therefore, the genus is currently known from 

the late Middle Ordovician to the Early Devonian.

Comparison.— The shell form of Vallatotheca is similar to that of Proplina Kobayashi, 1933, but its sublamellose growth lines with their enclosed fine radial threads 

distinguish it from Proplina.

Vallatotheca is similar to Helcionopsis, as both have 

radial ornament. However, the close, regular spacing of 

the growth lines, the fine character of the radial threads, 

and particularly their restriction to individual growth 

increments, and the general shell form of Vallatotheca 

easily distinguish it from Helcionopsis.

Discussion.—Foerste (1914a) originally placed two 

species in the genus V. manitoulini Foerste, 1914a, 

and V. unguiformis (Ulrich, 1897). The latter species 

was described from the Middle Ordovician Lexington 

Limestone of central Kentucky as Stenotheca unguiformis. The former species was described as the type 

species of the genus (Foerste, 1914a, p. 482, pi. 4, figs. 

4a, b): "Genotype differing from the congeneric Stenotheca unguiformis Ulrich, in its much larger size, and the 

greater curvature of the beak. The concentric markings 

are not due to transverse folds, but are successive 

lamellose outgrowths of the shell, striated only on their 

apical sides."

Miller (1897) believed S. unguiformis should be 

included in the genus Tryblidium Lindstrom. Shimer 

and Shrock (1944, p. 437) placed the species in the genus 

Proplina, and assigned V. manitoulini to the genus 

Tryblidium. The present investigation revealed no justification for separating the two species originally placed
MIDDLE AND UPPER ORDOVICIAN SYMMETRICAL UNIVALVED MOLLUSKS, CINCINNATI ARCH REGION 069

in Vallatotheca by Foerste (1914a). On the contrary, the 

new silicified material from the Ordovician of Kentucky 

shows that the two species are morphologically closer 

than originally believed. Knight and Yochelson (1958, 

1960) were influenced by the lack of confidence shown by 

these previous authors in the validity of the genus 

Vallatotheca when they placed a question mark before 

the genus name.

Runnegar and Jell (1976, p. 131, 132, figs. 9A. 1-5) 

referred four small specimens from the Middle Cambrian 

of Australia to Vallatotheca sp., but this assignment 

seems unwarranted because the Australian Cambrian 

specimens have very coarse comarginal and radial shell 

markings. Runnegar and Jell referred to the coarse 

comarginal rings as "plicae," and it is clear from their fine 

photographs that this is the appropriate terminology. 

Furthermore, their figure 9A, 2, clearly shows that the 

radial ribs cross over and between the plicae. In contrast, the American Ordovician species have fine radial 

threads that are restricted to individual concentric lamellae. Therefore, it appears that the Australian Cambrian 

specimens are only superficially similar to Vallatotheca, 

differing significantly in the basic mode of growth of the 

shell. Runnegar and Jell's specimens bear much closer 

resemblance to some species of the comarginally plicate 

genera Latouchella and Helcionella, which are also 

illustrated in their figure 9. However, the occurrence of 

radial ribbing on their specimens may give a clue to the 

ancestry of Ordovician genera that also exhibit radial 

ornament, including Vallatotheca, Helcionopsis, Cyrtolites, and others. Radial ornament seems to be more 

common in the Monoplacophora and Bellerophontida 

than is generally recognized. Most of these genera show 

a basic difference in their types of radial ornament. The 

types of comarginal and radial ornament in Vallatotheca 

and Cyrtolites (Cyrtolites) may indicate a common origin 

for the genera.

Vallatotheca manitoulini Foerste, 1914a

Plate 1, figures 8-11

Vallatotheca manitoulini Foerste, 1914a, p. 482, pi. 4, figs. 4a, b. 

Tryblidium manitoulini (Foerste), Shimer and Shrock, 1944, p. 437, 

pi. 174, fig. 2.

Diagnosis.— Shell relatively broad (shell length/width 

ratio 1.30), somewhat inflated.

Description.— Shell broadly teardrop shaped in outline, quite broad posteriorly, narrowing in anterior third 

to blunt beak; shell length/width ratio 1.30; dorsally and 

posteriorly broad and somewhat inflated; apex bluntly 

pointed, markedly downcurved to near level of aperture, 

extending well beyond anterior apertural margin; 

growth lines closely and regularly spaced, sublamellose; 

radial threads fine, closely spaced, restricted to individual growth increments.

Measurements.—The specimens examined were not 

sufficiently exposed to allow reliable measurements. 

Foerste's (1914a, pi. 4, figs. 4a, b) figure of the holotype 

was measured, and the shell length/width ratio was 1.30.

Material.—Only two specimens of this species were 

available for examination, MU 244T (pi. 1, figs. 8, 9) and 

MU 245T (pi. 1, figs. 10, 11), both calcitic replacements. 

The holotype, No. 8448 in the collections of the Geological Survey of Canada, Ottawa, was not examined, but 

both Foerste (1914a, pi. 4, figs. 4a, b) and Knight (1941, 

pi. 3, figs. 4a, b) adequately illustrated this specimen.

Distribution.—Foerste (1914a, p. 482) described the 

species from "the Cape Smyth or Waynesville Member of 

the Richmond, at Clay Cliffs on the eastern side of Cape 

Smyth, three miles north of Wekmemikongsing, on the 

eastern shore of Manitoulin Island," Ontario, Canada. 

The two specimens examined here came from correlative 

strata in southwestern Ohio. Specimen MU 244T came 

from the Elkhorn biofacies of the Drakes Formation 

(Richmondian), just south of Morning Sun, Ohio. MU 

245T came from the Whitewater Formation (Richmondian) near Camden, Ohio.

Comparison. — Foerste (1914a, p. 482) stated that V. 

manitoulini differs from V. unguiformis "...in its much 

larger size and the greater curvature of the beak." The 

new silicified material from Kentucky shows that V. 

unguiformis attains a larger size than previously known 

(up to 22 mm in shell length), and that the beak increases 

in its downward curvature in later adult growth so that 

it nearly reaches the apertural plane (pi. 1, figs. 27, 28). 

Nevertheless, the two species can be separated on the 

basis of their convexity, V. manitoulini being more 

inflated, and their relative shell length/width ratios. V. 

manitoulini has a ratio of 1.30, and V. unguiformis has 

a ratio of 1.40, showing that the former species is 

somewhat wider.

Discussion.— The new specimens of V. manitoulini 

described herein are the first reported since the original 

description of the species from Manitoulin Island (Foerste, 1914a). It is likely that the species is more widespread than currently recognized, and its rarity may in 

part be due to poor preservation of small aragonitic 

shells. Also, as is later speculated about Cyrtolites 

(Cyrtolites) ornatus, bryozoan encrustation may have 

played a part in camouflaging the shells from detection 

by Ordovician predators, as well as Holocene collectors. 

V. manitoulini and C. (C.) ornatus have very similar 

shell sculpturing, which in both cases may have been 

preferred by settling bryozoan larvae (see discussion of 

C. (C.) ornatus). Lending some support to this speculation is specimen MU 245T of V. manitoulini (pi. 1, figs. 

10, 11), which was revealed only after an encrusting 

bryozoan was partly removed.
070 CONTRIBUTIONS TO THE ORDOVICIAN PALEONTOLOGY OF KENTUCKY AND NEARBY STATES

TABLE 20. Measurements (in milllimeters) of Vallatotheca unguiformis

USNM No.

45990

265930

265931

265932

265933

387030

387030

265934

265935

265936

387031

387031

387032

Shell length

12.65

13.45

7.50

7.10

9.55

6.60

5.80

9.80

10.30

21.60

9.20

_

22.50

Shell width

9.05

9.40

6.30

6.15

6.85

5.05

4.55

7.55

7.30

13.50

6.60

9.20

15.00

Shell height

4.85

5.50

3.50

3.20

3.35

3.10

2.20

3.80

3.50

7.85

4.30

5.45

10.00

Aperture length Beak height

10.9 0.5

11.1 0.9

6.9

-

-

_ -

_

9.2

_ -

18.4

_ _

_ -

-

No. of growth 

lines in 1 mm

3

-

5

-

-

-

-

2

-

2

2

_

-

Vallatotheca unguiformis (Ulrich, 1897) 

Plate 1, figures 12-31

Stenotheca unguiformis Ulrich in Ulrich and Scofield, 1897, p. 843, pi.

61, figs. 42^4.

Tryblidium unguiforme (Ulrich), Miller, 1897, p. 771. 

Vallatotheca unguiformis (Ulrich), Foerste, 1914a, p. 482. 

Proplina unguiformis (Ulrich), Shinier and Shrock, 1944, p. 397, pi.

174, figs. 7, 8.

Diagnosis. — Shell narrowly teardrop shaped in dorsal 

outline (shell length/width ratio 1.40), moderately 

convex.

Description.—Shell narrowly teardrop shaped in dorsal outline, broadly rounded posteriorly, tapering rapidly 

in anterior third to blunt beak; shell length/width ratio 

1.40; apex bluntly pointed, extending well beyond anterior apertural margin, curving downward, the curvature 

increasing in later growth so that apex may reach to 

plane of apertural margin; dorsal shell surface broadly 

and gently convex, increasing in convexity over beak 

area; growth lines closely and regularly spaced, sublamellose; radiating threads fine, closely spaced, 

restricted to individual growth increments.

Measurements.— Measurements of V. unguiformis 

are listed in table 20 and shown graphically in figure 21.

Material.— The type suite consists of three silicified 

syntypes cataloged under the number USNM 45990. The 

specimen shown herein on plate 1, figures 12-15, is 

designated the lectotype and retains the original USNM 

number. The other two syntypes, shown on plate 1, 

figures 21, 22 and 23, 24, are designated paralectotypes 

and assigned the numbers USNM 265930 and 265931, 

respectively.

Fifteen specimens of this species were found in the 

new silicified collections from samples 5015-CO, 6915- 

CO, 6916-CO, and 7784-CO. Specimens USNM 265932 

(pi. 1, figs. 18-20), USNM 265933 (pi. 1, figs. 30, 31), and 

USNM 387030 are from sample 5015-CO. Specimens 

USNM 265934-265936 (pi. 1, figs. 16, 17, 29, and 25-28,

respectively) and USNM 387031 are from sample 6915- 

CO. Collections 5015-CO, 6915-CO, and 6916-CO are 

from the Salvisa Bed, Perryville Limestone Member, 

Lexington Limestone, Perryville quadrangle, Kentucky. 

Collection 7784-CO is from the Curdsville Limestone 

Member, Lexington Limestone, Little Hickman quadrangle, Kentucky.

Distribution.—The museum label with the type suite 

(USNM 45990, 265930, 265931) reads "Upper Trenton" 

at "Harrodsburg Junction, Cincinnati and Southern Railroad, Kentucky." Ulrich (in Ulrich and Scofield, 1897) 

listed the locality for the types as "Upper beds of the 

Trenton Group, between Burgin and Danville, Kentucky." The geologic map of the Danville quadrangle, 

Boyle and Mercer Counties, Ky. (USGS GQ-985; Cressman, 1972), shows that the tracks of the Southern 

Railroad between Burgin and Danville pass mainly 

through exposures of the Curdsville Limestone and 

Grier Limestone Members of the Lexington Limestone, 

but they also cut across exposures of the Perryville 

Limestone Member of the same formation just south of 

Burgin and just north of Danville.

In the USGS silicified collections, one questionable 

specimen of the species was found in sample 7784-CO 

from the Curdsville Limestone Member (Kirkfieldian), 

Lexington Limestone. All other specimens were found in 

samples 5015-CO, 6915-CO, and 6916-CO, all from the 

Salvisa Bed of the Perryville Limestone Member (Shermanian) of the Lexington Limestone near Perryville, 

Ky.

Comparison. —V. manitoulini is distinguished by its 

wider, more convex shell form.

Discussion. — V. unguiformis is known with certainty 

only from the Salvisa Bed of the Perryville Limestone 

Member of the Lexington Limestone in central Kentucky. The Salvisa Bed is a calcilutite containing ostracodes, gastropods, and other shelly megafossils, and has 

been interpreted to represent shallow, quiet marine
MIDDLE AND UPPER ORDOVICIAN SYMMETRICAL UNIVALVED MOLLUSKS, CINCINNATI ARCH REGION 071

20

10

20

10

0 10 20 

APERTURE LENGTH, IN MILLIMETERS

10 20 

SHELL WIDTH, IN MILLIMETERS

20

10

O,

20

S 10

10 

SHELL HEIGHT, IN MILLIMETERS

20 10 

SHELL HEIGHT, IN MILLIMETERS

20

FIGURE 21. Bivariate plots of measurements made on specimens of Vallatotheca unguiformis. The solid dots in the 

graphs of shell length to shell height and shell width represent Vallatotheca manitoulini, which is slightly wider 

than V. unguiformis.

conditions of greater than normal salinity, such as tidal 

lagoons (Cressman, 1973). It therefore appears that V. 

unguiformis occupied nearshore to onshore depositional 

environments. It is inferred that the species was an algal 

grazer.

Superfamily KIRENGELLACEA Starobogatov, 1970

Diagnosis. — Shell conical, some with tendency to coil 

for one-fourth to one-third whorl; apex high, in most 

cases located in a slightly anterocentral to marginal 

position, but may be central or even posterocentral in 

position; muscle scars in six to eight discrete pairs 

located about halfway between shell margin and apex.

Stratigraphic range.—Lower Cambrian-Lower 

Devonian.

Discussion.— Starobogatov (1970) proposed this 

superfamily for the single genus Kirengella Rosov, 1968. 

Rosov (1975) erected the order Kirengellida, including 

three families Kirengellidae Starobogatov, 1970 (genera Scenella Billings, 1872; Kirengella Rosov, 1968; 

Moyerokania Rosov, 1970), Romaniellidae Rosov 

(Romaniella Doguzhaeva, 1972; Hypseloconus Berkey, 

1898; Nyuella Rosov, 1975), and Archaeophialidae 

Knight and Yochelson, 1958 (Archaeophiala Koken in 

Perner, 1903). Concerning this new order Rosov (1975) 

stated,
072 CONTRIBUTIONS TO THE ORDOVICIAN PALEONTOLOGY OF KENTUCKY AND NEARBY STATES

We have combined the oldest monoplacophorans into a new order with 

a stratigraphic range extending from the Lower Cambrian to the 

Middle Ordovician inclusive. They are apparently the most primitive 

members of the class, ones that gave rise to other branches: to the 

orders Tryblidiida Lemche, 1957, Archinacellida Knight and Yochelson, 1958, and Cyrtonellida Horny, 1963c. Evolution proceeded in the 

direction of further curling of the shell (order Cyrtonellida) or farther 

forward displacement of the apex with simultaneous flattening of the 

shell (orders Tryblidiida and Archinacellida); the muscle scars evolved 

toward fusion of adjacent pairs of scars, which is to be seen to some 

degree in members of all four orders. [See fig. 18 herein.]

Rosov's (1975) concept of the Kirengellida is considered 

useful, but is used herein as a superfamily, the Kirengellacea, of the order Tryblidiida.

Family ARCHAEOPHIALIDAE Knight and Yochelson, 1958

Diagnosis.— Shell broadly conical, with subcircular to 

oval aperture outline; apex high, slightly anterocentral to 

nearly marginal; muscle scars in six to eight discrete 

pairs, the anterior pairs being more complex.

Stratigraphic range.— Middle Ordovician-Lower 

Devonian.

Discussion.— Knight and Yochelson (1958, 1960) 

included three genera in this group Archaeophiala 

Perner, 1903, IMicropileus Wilson, 1951, and ICalloconus Perner, 1903 but used the taxon as a subfamily 

(Archaeophialinae) of the family Tryblidiidae. Starobogatov (1970) elevated the taxon to the family level in 

the superfamily Tryblidiacea. Then Rosov (1975) transferred the family to his new order Kirengellida. The 

muscle scars of Micropileus and Calloconus are 

unknown, but because of similarities in shell form the 

genera are generally classified with Archaeophiala, 

whose muscle scars are well known. Starobogatov (1970) 

included a fourth genus, Platypilina Horny, 1961, whose 

type species is Scenella! tardissima Perner, 1903. This 

species, as figured by Perner (1903, figs. 23a-c, and 1907, 

pi. 117, figs. 1-3) has radial ornament crossed by growth 

lines on a shell having a slightly curled anterocentral 

apex. Platypilina tardissima seems to be close to Macroscenella Wilson, 1951, which was proposed to include 

many of the Ordovician species assigned to Scenella by 

Ulrich and Scofield, 1897. The subcentral apex and 

closely similar shell sculpturing suggest a close relationship between Platypilina and Macroscenella. They seem 

better accommodated in the superfamily Kirengellacea, 

and provisionally in the family Archaeophialidae or, 

because of their Scenella-\ike markings, possibly in the 

family Kirengellidae.

Rosov (1975) included the genera Romaniella 

Doguzhaeva, 1972, Nyuella Rosov, 1975, and Hypseloconus Berkey, 1898, in the then newly proposed family 

Romaniellidae. Rosov pointed out that the similar shell 

forms and ranges of Romaniella and Hypseloconus 

indicate that they are synonyms. This group of genera is 

characterized in part by the fusion of some pairs of

muscle scars. Hypseloconus was once placed in the 

Archinacellacea by Knight and Yochelson (1958, 1960) 

because it was thought to have fused scars. Stinchcomb 

(1980, p. 45^7) described discrete, paired muscle scars 

in specimens of Hypseloconus, as well as one or more 

continuous rings that have previously been interpreted 

as muscle bands. The classification of Hypseloconus in 

the superfamily Kirengellacea seems valid; however, its 

familial affinities remain uncertain. The species Nyuella 

bjalyi Rosov, 1975, has a shell form that is quite comparable to that of some archinacellids. For example, compare the species (Rosov, 1975, figs. 2a-d) with Archinacella area n. sp. (herein, pi. 3, figs. 7-10); dorsally there 

is a resemblance, but N. bjaly has a convex lateral 

apertural margin, whereas A. area has a distinctly 

concave apertural margin. It seems that the Romaniellidae may be the ancestors of the archinacellids, through 

flattening of the shell and fusion of the shell muscles, as 

suggested by Rosov (1975).

Genus MICROPILEUS Wilson, 1951

Diagnosis.— Shell having blunt, elevated, submarginal apex; shell slopes smooth to slightly wrinkled, with 

no distinct ornament; apertural outline subcircular to 

subovate.

Description.— Shell high, cap shaped; apertural outline subcircular to subovate; apex blunt, elevated, 

located slightly within, or nearly over, anterior shell 

margin; anterior shell slope slightly concave (particularly 

in immature shells), flat, or slightly convex; posterior 

slope broadly convex; comarginal striae and (or) weak 

undulations; muscle scars unknown.

Type species.—M. obesus Wilson, 1951, by original 

designation; reported from the Lowville-Leray beds 

(Blackriveran) of eastern Canada.

Distribution.— Wilson (1951) described two species 

from the Lowville-Leray beds (Blackriveran) of the 

Ottawa-St. Lawrence Lowland, Canada. The new species described below was found in the Curdsville Limestone Member of the Lexington Limestone (Kirkfieldian). On the basis of the figures and description given by 

Hussey (1926, p. 171, pi. 6, fig. 1), Archinacella simmonsi Hussey from the Stonington beds (Richmondian) 

of Michigan is herein transferred to Micropileus. Therefore, the genus is known from the upper Middle 

Ordovician (Blackriveran) to the upper Upper 

Ordovician (Richmondian).

Discussion. Wilson (1951) proposed two new genera, 

Micropileus and Macroscenella, for Ordovician capshaped shells originally assigned to the genus Scenella, 

which is currently considered to be restricted to the 

Cambrian Period. Macroscenella differs from Micropileus in its more subcentral apex, the presence of a 

supposed labral emargination, and a reticulate type of
MIDDLE AND UPPER ORDOVICIAN SYMMETRICAL UNIVALVED MOLLUSKS, CINCINNATI ARCH REGION 073

TABLE 21. Measurements (in millimeters) of Micropileus 

variabilis

USNM No.

265926

265927

265928

265929

Shell 

length

12.70

13.50

12.45

Shell 

width

11.4

12.4

11.6

10.6

Shell 

height

7.25

10.65

7.60

8.25

shell ornament formed by comarginal growth lines and 

radial striae (rather than only comarginal growth lines 

and (or) undulations as in Micropileus). Wilson assigned 

a number of Middle Ordovician species placed in Scenella 

by Ulrich and Scofield (1897) and others to Macroscenella, but did not assign any previously described 

species to Micropileus, although she believed many 

Ordovician species that had been assigned to Scenella 

would eventually be transferred to Micropileus when 

better known. Herein, the following North American 

species are placed in Micropileus: M. obesus Wilson, M. 

ottawaensis Wilson, M. simmonsi (Hussey), and M. 

variabilis n. sp.

Although Wilson (1951) was uncertain where to place 

Micropileus in the hierarchy, it now seems best to 

recognize it as a genus closely related to the European 

Ordovician genus Archaeophiala based on the similar 

shell form. Macroscenella seems more closely related to 

Scenella than to Micropileus, as indicated by its more 

central apex and reticulate ornament.

Micropileus variabilis new species

Plate 1, figures 1-7

Diagnosis.— Shell having submarginal apex and 

slightly concave to nearly flat anterior slope; apertural 

outline subcircular; shell exterior in some specimens 

having irregular comarginal undulations.

Description.—Shell medium sized (up to 13.5 mm 

long), high cap shaped; apertural outline subcircular to 

broadly subovate, length about 1.15 times width, and 

about 1.60 times shell height; apex position somewhat 

variable, but in all specimens submarginal and generally 

located about halfway between center of shell and anterior shell margin; apex bluntly pointed, elevated; anterior slope steep, slightly concave to flat; posterior slope 

more gently sloped and broadly convex; shell essentially 

smooth, but commonly with one or more comarginal 

undulations; fine radial striae faintly visible near aperture of some specimens; shell fairly thin.

Measurements.— Measurements of M. variabilis n. 

sp. are listed in table 21.

Material. — This species is known from about 15 silicified specimens from USGS sample 7784-CO and from 1 

silicified specimen from USGS sample 7817-CO. The

latter specimen (pi. 1, figs. 1^1) is herein designated the 

holotype (USNM 265926). Three paratypes from USGS 

7784-CO are figured: USNM 265927 (pi. 1, fig. 7), USNM 

265928 (pi. 1, fig. 5), and USNM 265929 (pi. 1, fig. 6). The 

other paratypes, most of them fragments, are combined 

under the number USNM 265956.

Distribution.—M. variabilis is known only from the 

lower 6 ft of the Curdsville Limestone Member of the 

Lexington Limestone (Kirkfieldian). It was found at 

USGS localities 7784-CO and 7817-CO in the Little 

Hickman quadrangle, Jessamine County, Ky. The holotype (USNM 265926) is from 6 in above the CurdsvilleTyrone contact at a roadcut along Kentucky Route 39, 

0.3 mi (miles) southeast of Black Bridge, which crosses 

Hickman Creek (USGS 7817-CO). The paratypes are 

from the basal 2 ft of the Curdsville Limestone Member, 

at an exposure 0.3 mi southeast of a bridge crossing the 

Kentucky River on U.S. Route 27 (7784-CO).

Comparison.—M. variabilis n. sp. differs from the 

type species M. obesus Wilson in its slightly smaller size 

and centrally located apex.

Discussion.—Two specimens of M. variabilis, USNM 

265926 (pi. 1, figs. 1-4) and USNM 265927 (pi. 1, fig. 7), 

show a comarginal undulation in the shell about halfway 

between the apertural margin and the apex. These 

bandlike comarginal undulations are suggestive of a 

muscle scar in their appearance and location. It is 

possible that at maturity, the muscles caused an undulation in these thin-shelled animals. Considering that the 

basal Lexington Limestone is transgressive in nature, 

the animal may have occupied a higher energy environment in which strength of attachment to the substrate 

was of paramount importance. M. variabilis may have 

led a limpetlike existence, clinging to protruding irregularities of the lithified surface of the Tyrone Limestone, 

which was being transgressed during Curdsville deposition. The nature of this disconformable contact was 

described by Cressman (1973, p. 12, 13).

Superfamily ARCHINACELLACEA Knight, 1956

Diagnosis.— Shell cap shaped, height variable, generally widest anteriorly; apex located distinctly anteriorly, 

submarginal, marginal, or supramarginal; muscle scars 

fused completely into ringlike band, or incompletely into 

horseshoe-shaped scar that is open posteriorly; accessory 

scars in some cases located along band itself or in opening 

of horseshoe-shaped scar.

Stratigraphic range.— Chazyan (middle Middle 

Ordovician)-Richmondian (upper Upper Ordovician). It 

should be noted that Knight and Yochelson (1960) listed 

the range for the superfamily as Upper Cambrian to 

Lower Silurian, but with the transfer of Hypseloconus to 

the Kirengellacea (Rosov, 1975), all Upper Cambrian and 

Lower Ordovician taxa were removed from the super-
074 CONTRIBUTIONS TO THE ORDOVICIAN PALEONTOLOGY OF KENTUCKY AND NEARBY STATES

family. I know of no Silurian archinacellaceans. Horny 

(1965a, p. 63) listed the superfamily as Upper Cambrian 

to ?Lower Silurian, but noted that the group is probably 

not known above the uppermost Ordovician. He did, 

however, suggest that the Silurian genus Archaeopmga 

may be a descendant of this line.

Discussion. Knight and Yochelson (1958) defined the 

superfamily Archinacellacea as containing the families 

Archinacellidae Knight, 1956, and ?Hypseloconidae 

Knight, 1956, and placed it in the monotypic order 

Archinacelloidea. This classification was continued in 

"Treatise on Invertebrate Paleontology" (Knight and 

Yochelson, 1960). In 1958, these authors noted that this 

order was an unsatisfactory and artificial grouping of 

forms. They defined the Archinacelloidea as follows 

(1958, p. 39): "Shell shape variable, but always bilaterally 

symmetrical and with distinct apex, presumed to be 

anterior; muscle scars, where known, forming an incomplete to complete ring."

Horny (1965a) corrected the ordinal name to Archinacellida and defined it as follows: "Shell never coiled, scars 

often fused to form a complete ring; apex anterior 

or central." He did not elaborate on subordinal 

classification.

Knight (1952, p. 52) included molluscan univalves 

having a continuous muscle scar, such as Archinacella 

Ulrich and Scofield, 1897, with those having discrete 

paired scars in the Monoplacophora. He pointed out that 

in both types the scars have elements that close or nearly 

close the circlet anteriorly. He proposed that these 

forms, like the Polyplacophora, did not have an anterior 

pallial cavity and had not undergone torsion. He suggested that the scars narrowed anteriorly because the 

muscles attached in that area were extensions from the 

pedal muscles at each side arching over the head.

However, Starobogatov (1970) has argued in favor of 

the return of the Archinacellida to the class Gastropoda, 

based on interpretation of the muscle scar patterns in 

Archinacella, Archinacelliopsis, Archinacellina, and 

Archaeopraga. It should be noted that Archinacellina 

and Archinacelliopsis are not present as such in "Treatise on Invertebrate Paleontology" (Knight and Yochelson, 1960). Archinacellina was erected by Horny (1961) 

for those species originally assigned to Archinacella that 

have two pairs of nearly isolated, triangular scars posterolaterally on the inner side of the ring-shaped principal 

scar. Archinacelliopsis was erected by Horny (1963c) for 

those archinacellids having an open contra-apical end on 

the main muscle band, with a pair of discrete scars 

located in the gap; this genus is represented in Knight 

and Yochelson (1960, fig. 50.4) by Archinacella patelliformis. Starobogatov (1970) argued that the circular 

muscle of Archinacella approaches slightly too close to 

the shell margin at the apical end, leaving no room for the

head. Conversely, at the contra-apical end the circular 

muscle is sufficiently removed, and is even open in 

Archinacelliopsis. Starobogatov interpreted the pair of 

discrete scars in the gap at the contra-apical end of 

Archinacelliopsis as radular muscle scars similar to 

those of the cap-shaped Monoplacophora and Docoglossa. 

He believed that the looplike thickenings of the circular 

muscle located along the sides of the apex of both genera 

indicate the original point of insertion of the shell muscles. He compared the position of the pair of muscle scars 

on the Silurian patellid gastropod Archaeopraga (Horny, 

1963b), which converge at the apical end and separate at 

the contra-apical end, with the position of the circular 

muscle in Archinacella, Archinacelliopsis, and Archinacellina. On the basis of this comparison, Starobogatov 

concluded that the contra-apical end, rather than the 

apical end, was anterior in the archinacellids and therefore that the Archinacellida should be an order within the 

Gastropoda.

Starobogatov's arguments (1970) are impressive, but 

his conclusions require more documentation. Other 

authors (Horny, 1965a, b; Rosov, 1975) have shown how 

archinacellid scars fit well into the monoplacophoran 

picture, and their conclusions are generally accepted. 

Starobogatov's interpretation concerning the placement 

of the discrete scars in the open contra-apical end of the 

muscle scar of Archinacelliopsis is particularly interesting. It is not understood why this monoplacophoran 

would preferentially segregate muscles posteriorly. But 

then, the problem can be looked at in an opposite 

manner: Maybe these discrete scars indicate a more 

primitive condition than seen in Archinacella, one in 

which the muscle band has not yet completely fused. 

Rosov (1975) suggested that the evolution toward fusion 

of adjacent pairs of muscle scars can be seen to some 

degree in members of all the orders of the Monoplacophora, the trend reaching completion in the Archinacellida. 

Also, Starobogatov's (1970) argument that there is not 

sufficient space for the head of the animal beneath the 

beak of Archinacella does not seem conclusive. The head 

region of Neopilina seems quite small. For the present, 

the Archinacellida should continue to be classified as 

monoplacophorans.

Rosov (1975) recognized the order Archinacellida but 

rejected placement of the family Hypseloconidae in that 

order, and instead included the genus Hypseloconus 

Berkey, 1898, in the Romaniellidae of the order 

Kirengellida.

Runnegar and Jell (1976) placed the family Hypseloconidae in their order Cyrtonellida and superfamily 

Helcionellacea, noting the group's possible ancestry to 

the Cephalopoda, as proposed by Yochelson, Flower, 

and Webers (1973). Furthermore, Runnegar and Jell 

rejected the order Archinacellida; they did not consider
MIDDLE AND UPPER ORDOVICIAN SYMMETRICAL UNIVALVED MOLLUSKS, CINCINNATI ARCH REGION 075

the fusion of muscle scars a significant higher level 

taxobase, and placed the archinacellids in the family 

Tryblidiidae. While I agree with these authors that the 

archinacellids should not be considered a separate order 

of monoplacophorans, I do not agree that they should be 

included with the Tryblidiidae. Rather, I support placement of the superfamily Archinacellacea in the order 

Tryblidiida. The Tryblidiacea should be reserved for 

cap-shaped shells having an anteriorly placed apex and 

discrete muscle scars. As demonstrated by the emplacement of a pair of discrete muscle scars in the posterior 

gap of a fused, horseshoe-shaped muscle scar in Archinacelliopsis, it appears that the Archinacellacea developed from ancestors having discrete paired scars by 

progressive fusion of such scars. Ancestors of the Archinacellacea might be found within the family Romaniellidae of the superfamily Kirengellacea. Nyuella bjalyi 

Rosov (1975) of that family exhibits fusion of the anterior 

scars of its muscle ring. Fusion of muscle scars probably 

progressed posteriorly, resulting in such forms as Archinacelliopsis and finally in the completely fused ring seen 

in Archinacella.

Family ARCHINACELLIDAE Knight, 1956

Diagnosis and stratigraphic range. —Same as for 

superfamily.

Discussion.—Knight and Yochelson (1958) recognized 

two genera in this family: Archinacella and tPtychopeltis. The latter genus is a poorly understood form from the 

Middle Ordovician of eastern Europe (Perner, 1903) that 

was placed in the Archinacellidae because its shell shape 

has some resemblance to Archinacella. The muscle scars 

of Ptychopeltis are unknown, and its placement in this 

family is doubted.

Three genera are currently placed in the family Archinacellidae: Archinacella Ulrich and Scofield, Archinacellina Horny, and Archinacelliopsis Horny. Until fairly 

recently, Archinacella included all Ordovician capshaped species exhibiting horseshoe-shaped or circular 

muscle bands, as well as species sharing the general shell 

characteristics of forms in which the muscle scars are 

known. Horny (1963c) created the genus Archinacelliopsis for species such as A. patelliformis (Hall) that exhibit 

an incomplete muscle ring with a pair of discrete scars 

situated in the open posterior end of the ring. In 1961, 

Horny (1961) also proposed the genus Archinacellina for 

species such as A. modesta (Perner, 1903) that have two 

pairs of nearly isolated, triangular muscle scars located 

on the inner posterolateral margins of a complete muscle 

ring. The validity of these two genera is questionable, 

because the muscle scars of very few species of archinacellids have been described, and therefore the variation 

in the scar patterns within the group is virtually 

unknown.

Genus ARCHINACELLA Ulrich and Scofield, 1897

Diagnosis.— Shell patelliform, ovate to subcircular, 

generally widest anteriorly; position of apex variable; 

lateral apertural margin horizontal and straight to 

arched; only comarginal shell ornament; muscle scar a 

continuous band around the interior periphery of shell.

Description.— Shell low to fairly high, cap shaped, 

ovate to subcircular in dorsal profile, in most cases 

widest anteriorly; apex distinct, may be situated up to 

one-third the shell length from anterior shell margin, 

directly over that margin, or slightly overhanging it, but 

shows little or no incurving; lateral apertural profile 

horizontal and straight to markedly arched; shell ornament generally weak, consisting only of regular to irregular, comarginal growth lines; muscle scars form continuous band just inside periphery of shell.

Type species.—A. powersi Ulrich and Scofield, 1897, 

by original designation.

Distribution.—Chazyan (middle Middle Ordovician)- 

Richmondian (upper Upper Ordovician). Knight and 

Yochelson (1960) reported the genus as extending into 

the Lower Silurian but did not document any Silurian 

species.

Comparison.—Archinacella includes a rather heterogeneous assemblage of shell forms. The apex may be 

situated from well posterior to the anterior shell margin 

(pi. 3, figs. 11-24) to slightly past the anterior margin (pi. 

3, fig. 9). The lateral apertural margin is horizontal and 

straight (pi. 4, fig. 7) to distinctly arched (pi. 3, fig. 9). 

The shell ranges from low and streamlined (pi. 2, figs. 8, 

10, 11) to high and somewhat inflated (pi. 3, figs. 5, 9). 

The genus is in most cases identified by its ovate dorsal 

shell profile, its elevated, anteriorly located, nonincurved to slightly incurved apex, and the presence of 

only comarginal growth lines. The genus is easily distinguished from the cap-shaped genera in the present study 

by its lack of radial ornament, its straight or nearly 

straight apex, and in most cases by general shell form. 

Archinacella is separated from its relatives Archinacellina and Archinacelliopsis by the form of the muscle 

band; the latter two genera have discrete accessory 

muscles posteriorly.

Discussion.— Ulrich and Scofield (1897) proposed the 

genus Archinacella for species previously assigned in 

part to Metoptoma Phillips by Billings (1865), and in part 

to Tryblidium Lindstrom by Whiteaves (1884) and Whitfield (1886). In addition, Ulrich and Scofield (1897) 

described a number of new species. Their original 

generic description was as follows (1897, p. 821): "Shell 

patelliform, ovate to subcircular, usually widest anteriorly, forming a low cone with the apex in front of the 

center and often submarginal. Muscle scars forming a 

continuous band. Surface markings concentric only." 

When preserved muscle scars were lacking in specimens,
076 CONTRIBUTIONS TO THE ORDOVICIAN PALEONTOLOGY OF KENTUCKY AND NEARBY STATES

they distinguished Archinacella from Tryblidium by the 

characteristic wider and more rounded anterior end of 

Archinacella.

Ulrich and Scofield (1897) considered the continuous 

muscle band of Archinacella to show close affinity to the 

patellacean gastropods, which have a continuous 

horseshoe-shaped scar that opens anteriorly. In A. powersi, they described a discrete pair of rostral scars on the 

band beneath the apex, a narrow pair of scars just within 

the band on either side of the beak, an anterolateral pair 

of scars outside the band, a pair of loops extending 

outward from the band at about midlength, and numerous looplike irregularities along the outer band around 

the posterior end (Ulrich and Scofield, 1897, p. 829, pi. 

61, fig. 5). However, Knight (1941, p. 44, 45, pi. 1, figs, 

a-g) disagreed with their interpretation of the form of the 

muscle ring in A. powersi. He stated:

These authors interpret what I regard as the sharply impressed inner 

margin of the principal horseshoe-shaped scar as the principal scar 

itself, wholly ignoring the outer margin of the scar. The evidence for 

what they regard as rostral scars is almost nonexistent. What they 

interpret as a narrow pair of scars lying close to the principal scar just 

within its forward ends I interpret simply as local thickening of the 

secondary deposits within the circle of the principal scar. It must be 

remembered that molluscan muscle scars are commonly produced by 

resorption of shell material, not by piling up of secondary deposits. 

Their "faint impressions of a larger anterior pair without the band" are 

simply slight spots of seemingly fortuitous ferruginous stain within the 

area of what I regard as the principal muscle scar.

Knight and Yochelson (1958, p. 43, 44) reaffirmed 

Knight's (1941) interpretation of an "unbroken ringshaped muscle scar" in A. powersi, and noted the discovery of a specimen of A. patelliformis (Hall) from the 

Blackriveran strata of New York State that shows, 

instead of a continuous ring, an incomplete ring with a 

pair of scars at the posterior of the exposed continuous 

ring (Knight and Yochelson, 1958, pi. 5, fig. 4). They 

(1960, fig. 50, Ib and 4) later illustrated both types 

of archinacellid muscle scars. As previously pointed 

out, Horny (1963a) erected Archinacelliopsis for A. 

patelliformis.

Thirty-two species of Archinacella from North America have been proposed; all are from Ordovician strata in 

the eastern half of the continent. This large number of 

species in a genus having such a simple shell form and 

ornament seems unlikely. The conceptualization of the 

species is complicated by the high degree of intraspecific 

variability in the shell form of many monoplacophorans. 

Unfortunately, many species of Archinacella are known 

from only a few specimens, many of which are poorly 

preserved. Given the present state of knowledge of the 

species of Archinacella, there is no alternative to proposing new species names for distinctive morphologies. 

Even the new silicified collections described herein do 

not contain adequate numbers of specimens of Archinacella for variability analyses, and in general the quality

of preservation is not good. The archinacellids generally 

were too badly fragmented to allow reliable measurements. However, these samples are sufficient to give a 

better impression of intraspecific variability on a qualitative level than any other collections known, largely 

because it is known whether or not all of the specimens 

came from a single bed.

Many species of Archinacella are known only from 

internal molds, and thus are unsatisfactory for diagnosis 

and comparison. The preservation of A. indianensis 

(Miller) as external molds in the bases of calcitic bryozoan colonies (pi. 3, fig. 16; pi. 4, figs. 8, 9) suggests that 

the shell of Archinacella was aragonitic, and thus easily 

dissolved. Also, where known, the shells of Archinacella 

seem to be fairly thin (pi. 2, figs. 13, 14, pi. 3, figs. 19, 

20). These facts suggest why well-preserved specimens 

are rare. Collections of any one species generally consist 

of only a few specimens; this may simply be a result of 

poor preservation, or it may be partly related to the 

population dynamics of the species. It is possible that 

these animals maintained small populations, or had 

widely spaced population distributions. Still another 

factor may be the apparent ecology of these animals. 

Their continuous muscle bands suggest that the archinacellids led a limpetlike existence, clinging to solid objects 

in environments or even microenvironments where rapid 

burial was unlikely.

Specific differences are based on five main criteria: (1) 

position of the apex relative to the anterior apertural 

margin, (2) relative convexity and height of the shell, (3) 

the horizontal or arched character of the lateral apertural 

margins, (4) the shape of the shell aperture, and (5) shell 

length/width ratio. In most specimens examined, the 

shell margins are fragmented and incomplete, so criteria 

3 and 4 were often difficult to evaluate. The species of 

Archinacella recognized herein are based on small samples, and some may by synonymized when better material becomes available.

Archinacella simulatrix Ulrich and Scofield, 1897

Plate 2, figures 7-12

Archinacella simulatrix Ulrich and Scofield, 1897, p. 833, pi. 61, figs. 

10, 11; Grabau and Shimer, 1909, p. 606, figs. 805f, i.

Diagnosis.— Shell small (up to 15 mm long), subovate, 

wider anteriorly, with narrowly rounded dorsomedian 

crest; aperture horizontal; apex sharp, scarcely 

incurved, extends to nearly over anterior shell margin.

Description.—Shell small for genus (up to 15 mm 

long), subovate, slightly wider anteriorly; convexity low; 

narrowly rounded dorsomedian crest runs most of length 

of shell, crest sharpest toward apex; lateral slopes splay 

outward slightly in larger specimens; apex sharply 

pointed in dorsal view, scarcely incurved with gently
MIDDLE AND UPPER ORDOVICIAN SYMMETRICAL UNIVALVED MOLLUSKS, CINCINNATI ARCH REGION 077

TABLE 22. Measurements (in millimeters) of Archinacella

simulatrix

USNM No.

45695

47471

265944

265945

387033

387033

387033

387034

387035

387035

387036

Shell 

length

10.50

14.88

11.55

12.60

9.90

8.40

6.10

10.15

10.20

11.20

7.70

Shell 

width

8.3

13.0

10.0

9.6

7.3

6.8

4.2

8.5

8.0

8.3

6.6

Shell 

height

3.30

5.50

4.60

4.60

4.50

3.40

2.15

-

4.50

5.00

2.85

Apex 

height

2.1

2.8

-

-

-

-

-

-

-

-

-

concave anterior shell slope, extends to just over to 

scarcely beyond anterior shell margin; comarginal 

growth lines faint.

Measurements.—Measurements of A. simulatrix are 

listed in table 22 and shown graphically in figure 22. Note 

that many measurements were made on incomplete 

specimens and therefore are open to some amount of 

error.

Material.—The holotype of A. simulatrix (USNM 

45695) is an external mold in the base of a bryozoan 

colony from the Decorah Formation (RocklandianKirkfieldian), St. Paul, Minn. A latex replica is shown on 

plate 2, figures 7, 8. The best preserved specimen

co 20 - 20

10

0 10 20 

SHELL WIDTH, IN MILLIMETERS

0 10 20 

SHELL HEIGHT, IN MILLIMETERS

20

S 10

o

O,

0 10 20 

SHELL HEIGHT, IN MILLIMETERS

FIGURE 22. Bivariate plots of measurements made on specimens of Archinacella simulatrix.
078 CONTRIBUTIONS TO THE ORDOVICIAN PALEONTOLOGY OF KENTUCKY AND NEARBY STATES

examined was USNM 47471 (pi. 2, fig. 12), which the 

museum label says is from the "Modiolodon beds of the 

Hermitage member" of the Lexington Limestone. These 

beds are now included in the upper Logana Member of 

the Lexington Limestone.

The new silicified collections contain mostly fragmented specimens of A. simulatrix. Poorly preserved 

specimens, here termed A. cf. A. simulatrix, were 

recognized from the Tyrone Limestone (one specimen 

from 6035-CO; USNM 387034), and from the Curdsville 

Limestone (7784-CO; USNM 387035) and Grier Limestone (4874-CO and 4959-CO; USNM 387036) Members 

of the Lexington Limestone. A number of fairly well 

preserved specimens of A. simulatrix were found in 

sample 4073-CO (USNM 387033) from the Grier Limestone Member; two of these, USNM 265944 (pi. 2, fig. 11) 

and USNM 265945 (pi. 2, fig. 10), are figured here.

Distribution. — Ulrich and Scofield (1897, p. 833) listed 

A. simulatrix from the "Black River Group, Phylloporina bed, St. Paul, Minnesota; Trenton Group, Modiolodon bed, Frankfort, Kentucky." According to Weiss 

(1957), the Phylloporina-Fucoid bed in Minnesota would 

now be considered the upper Decorah Formation, which 

is Kirkfieldian rather than Blackriveran in age. The 

Modiolodon bed of Kentucky would now be placed in the 

Logana Member of the Lexington Limestone, which is 

also Kirkfieldian in age.

The new silicified collections contain probable specimens of this species from the Tyrone Limestone (Rocklandian) and the Curdsville Limestone and Grier Limestone Members of the Lexington Limestone 

(Kirkfieldian-Shermanian). Specimen USNM 47471 confirms the occurrence of the species in the Logana Member of the Lexington Limestone. A. simulatrix may 

occur in the Rocklandian strata of Kentucky; it does 

occur in the Kirkfieldian-age rocks of Kentucky and 

Minnesota, and in the Shermanian rocks of Kentucky.

Comparison.—A. simulatrix is generally easily recognized by its small size, wide anterior end, and relatively sharp dorsomedian crest leading to its marginal 

apex.

Ulrich and Scofield (1897) stated: "This species is 

distinguished from A. deleta, A. valida, A. patelliformis 

in having a less regularly elliptical outline, the anterior 

half being wider. In this particular it is like the much 

larger A. cingulata."

Discussion.—This is the most common species of 

Archinacella in the upper Middle Ordovician of Kentucky. The fact that it is known in Kirkfieldian strata of 

Kentucky and Minnesota suggests that it is useful for 

midcontinent correlation.

The preservation of the holotype as an external mold in 

the base of a calcitic bryozoan colony suggests that the 

shell was aragonitic. The specimen apparently was

encrusted after the animal died. The shell was somewhat 

worn before encrustation, as the surface of the latex 

replica (pi. 2, figs. 7, 8) is somewhat irregular.

The specimens from sample 4073-CO (pi. 2, figs. 10,11) 

from the Grier Limestone Member occur with the pelecypod Cyrtodonta sp. Specimens from the Logana Member of the Lexington Limestone (pi. 2, fig. 12) occur with 

the pelecypod Modiolodon sp. It is therefore inferred 

that A. simulatrix was commonly a member of molluscan 

communities.

Archinacella valida (Sardeson, 1892) 

Plate 2, figures 15, 16

Tryblidium validum Sardeson, 1892, p. 337, pi. 6, figs. 1, 2. 

Archinacella valida (Sardeson), Ulrich and Scofield, 1897, p. 832, pi. 

61, figs. 14, 15.

Diagnosis.— Moderate-sized shell (16-18 mm long) 

with ovate outline; apertural margin horizontal; apex 

small, submarginal, slightly incurved.

Description.—Shell moderate in size, regularly ovate 

in outline, length/width ratio about 1.2; apertural margin 

horizontal; apex laterally compressed, dorsally narrowly 

rounded, broadening posteriorly, located just within 

shell margin, slightly incurved so that anterior shell 

slope is distinctly concave; growth lines faint but distinct, 

closely and fairly regularly spaced.

Measurements.— Measurements of USNM 47467 are 

as follows: length from apex to posterior margin 17.2 

mm; aperture length 18.2 mm; aperture width 15.4 mm; 

shell height 6.0 mm; height of apex over anterior shell 

margin 3.3 mm. Ulrich and Scofield (1897) gave measurements of a small specimen as "length 16.5 mm; width 

15.4 mm; height nearly 7 mm."

Material.— Only one specimen was examined (USNM 

47467); it is labeled "Archinacella patelliformis, from the 

Trenton (Ctenodonta horizon), Mt. Parnassus, Columbia, Tennessee." This specimen is not A. patelliformis 

Hall, because it is larger and relatively broader, its 

dorsum is not as carinate, and its apex is submarginal. 

The specimen is a calcitic cast embedded in a buff 

biosparite matrix; most associated skeletal debris is 

brachiopod fragments, but there is also a small bellerophontid, possibly Bucanopsis.

Distribution.—Ulrich and Scofield (1897, p. 833) listed 

A. valida as from the "Trenton Group, Clitambonites 

bed, near Canyon Falls and Kenyon, Minnesota." 

According to Weiss (1957, fig. 1), the Clitambonites bed, 

which was then regarded as basal "Trenton," is now 

considered the Cummingsville Member of the Galena 

Formation (Kirkfieldian-Shermanian). Specimen USNM 

47467 came from the Ctenodonta member of the Hermitage Formation of Tennessee (Kirkfieldian). A. valida is 

therefore known from Kirkfieldian- and Shermanian-age 

strata in Minnesota and Tennessee.
MIDDLE AND UPPER ORDOVICIAN SYMMETRICAL UNIVALVED MOLLUSKS, CINCINNATI ARCH REGION 079

Comparison. -Ulrich and Scofield (1897, p. 832) 

stated: "Specifically A. valida is nearer A. (Carinaropsis) patelliformis Hall from the Trenton of New York, 

than any other form known to us. The lateral profile 

especially is nearly or quite the same in the two species. 

The New York species, however, is smaller, has more 

distinct surface markings, and is obtusely carinated on 

the back. It should be noted further that the apex of A. 

patelliformis is more incurved and extends past the 

anterior shell margin slightly." This differs from the 

specimen of A. valida figured here, in which the apex is 

submarginal.

In dorsal view A. valida is similar to A. powersi Ulrich 

and Scofield (Ulrich and Scofield, 1897, pi. 61, figs. 4,14), 

but the two species can be easily distinguished in lateral 

view, the former being higher and having a horizontal 

lateral apertural margin, the latter being lower and 

having an arched apertural margin.

Discussion. — The single well-preserved specimen 

(USNM 47467) studied here agrees with every essential 

aspect of A. valida described by Ulrich and Scofield 

(1897). The only notable difference is that the specimen 

from Tennessee is not as inflated as the specimens they 

described from Minnesota.

Archinacella cingulata Ulrich, 1897

Plate 2, figures 22-26

Archinacella cingulata Ulrich in Ulrich and Scofield, 1897, p. 829, 830, 

pi. 61, figs. 1, 2.

Diagnosis. — Shell large (up to 44 mm long), with 

broadly convex lateral profiles; apex blunt, slightly 

downcurved, projecting slightly beyond apertural margin; growth lines distinct, sublamellose, with close, regular spacing.

Description. — Shell relatively large for genus, outline 

subovate, wider anteriorly, gradually narrowing posteriorly; lateral profile broadly convex, with greatest shell 

height about one-third shell length back from anterior 

shell margin; lateral apertural margin nearly horizontal, 

scarcely arched; apex blunt, curved downward slightly to 

about one-half shell height, and projecting just beyond 

anterior apertural margin; growth lines distinct, sublamellose fine ridges, with close regular spacing; nearly 

consistent 1 mm spacing of growth lines over most of 

shell.

Measurements.— Measurements of A. cingulata are 

listed in table 23.

Material.-The holotype of the species (USNM 45686) 

(pi. 2, figs. 22-24) is a worn silicified replica from the 

"Amygdalocystites bed" of the Curdville Limestone 

Member of the Lexington Limestone. The only other 

known specimen is in the Miami University collections 

(MU 249T) (pi. 2, figs. 25, 26); that specimen is a large

TABLE 23. Measurements (in millimeters) of Archinacella 

cingulata

Museum No.

USNM 45686 

MU 249T

Length Apex 

to posterior 

margin

30.4 

44.1

Shell 

height

11.5 

12.1

Aperture 

length

29.0 

43.6

Aperture 

width

23.85 

34.5

Apex 

height

4.5 

6.8

internal mold from the Clays Ferry Formation, collected 

near Owenton, Ky., about 2 mi east of the intersection of 

U.S. Route 127 and Kentucky Route 35.

Distribution.—Kirkfieldian (upper Middle Ordovician) 

to Edenian (lower Upper Ordovician) of Kentucky.

Comparison. — Ulrich and Scofield (1897) noted that 

A. powersi differs from A. cingulata in its strongly 

arched aperture. A. simulatrix resembles A. cingulata 

somewhat in general shell form, but the latter species 

is much larger and has much more distinct growth 

markings.

Discussion.— Ulrich and Scofield (1897) described the 

aperture of A. cingulata as horizontal, but in both 

specimens examined here, the lateral apertural profile is 

slightly arched. There also seem to be faint traces of 

radiating lines between the growth lines in this species, 

but this observation cannot be confirmed without more 

specimens. If so, the species should be removed from the 

Archinacella and possibly be placed in Helcionopsis or 

Vallatotheca because of the similarity in their regular 

sublamellose growth lines.

Archinacella cf. A. depressa Ulrich and Scofield, 1897

Plate 2, figures 13, 14

Archinacella depressa Ulrich and Scofield, 1897, p. 830, pi. 61, 

figs. 8, 9.

Description. Shell medium sized for genus (16-17 mm 

long), outline broadly oval, convexity low; anterior slope 

gently concave, posterior slope gently convex; apex 

located distinctly within anterior shell margin; lateral 

apertural margin slightly arched; growth lines faint and 

closely spaced through most of shell, becoming strong 

and lamellose near outer shell margin.

Measurements.— Measurements of the single specimen examined are as follows: length from beak to 

posterior margin 15.0 mm; aperture length 16.8 mm; 

aperture width 15.2 mm; shell height 5.2 mm; height of 

apex 3.6 mm.

Material.—The single specimen identified as A. cf. A. 

depressa (USNM 59295) is a siliceous cast embedded in a 

wackestone matrix containing fragments of bryozoans 

and brachiopods.

Distribution. — Ulrich and Scofield (1897) reported A. 

depressa from the "Stones River Group, Vaunexemia 

bed, Minneapolis, Minnesota." According to Weiss (1957, 

fig. 1), this would be in the middle part of the Platteville
080 CONTRIBUTIONS TO THE ORDOVICIAN PALEONTOLOGY OF KENTUCKY AND NEARBY STATES

Formation (Rocklandian) (regarded as Blackriveran by 

Ross and others, 1982). The specimen described herein 

(USNM 59295) is from the Cannon facies of the BigbyCannon Limestone (Kirkfieldian-Shermanian) at Hartsville, Trousdale County, Tenn.

Comparison.— Ulrich and Scofield (1897) emphasized 

the similarity between A. depressa and A. perovalis 

(Whitfield) from the Platteville Formation of the 

Minnesota-Wisconsin area, saying that the only difference of any consequence between the two species is the 

greater width of A. depressa.

A. subrotunda Ulrich and Scofield from the Decorah 

Formation (Rocklandian-Kirkfieldian) of Minnesota is 

also somewhat similar to A. depressa, but the former is 

higher and more convex, based on Ulrich and Scofield's 

(1897, pi. 61, figs. 26, 27) illustration. Wilson (1951, p. 18, 

pi. 1, figs. 9, 10) described A. subrotunda from the 

Cobourg beds (Edenian) of Ontario, Canada, but her 

figures look more like A. depressa, having a shell of low 

convexity.

Discussion.— The specimen from the Cannon facies of 

Tennessee compares favorably with the description of A. 

depressa given by Ulrich and Scofield (1897). Points on 

which it agrees are its broad ovate outline, its low 

convexity, its submarginal apex, and its slightly arched 

lateral apertural margin. Measurements for the species 

reported by Ulrich and Scofield (1897, p. 830) give a 

length/width ratio of 1.13. The Tennessee specimen has a 

length/width ratio of 1.10, showing close agreement. The 

species is known from Blackriveran-age strata in Minnesota and Kirkfieldian-Shermanian-age strata in the Cincinnati arch province, and perhaps from the Edenian of 

Ontario.

Archinacella alta new species

Plate 3, figures 4-6

Diagnosis.—Shell medium sized, high, inflated; outline ovate; lateral apertural margin horizontal; apex 

blunt, slightly downcurved, situated above shell margin.

Description. — Shell medium sized for genus (about 15 

mm long), high, somewhat inflated, with highly convex 

dorsal and posterior slopes; highest point on shell about 

one-third shell length back from anterior margin; anterior slope distinctly concave; shell outline regularly oval; 

beak area narrowly rounded medially in dorsal view, 

becoming gradually broader toward posterior; apex 

blunt, slightly downcurved about three-eights the shell 

height, situated above anterior shell margin; lateral 

apertural margin horizontal to very slightly arched; 

growth lines barely discernible.

Measurements.—Measurements of the holotype are as 

follows: shell length at aperture or apex 14.75 mm; 

aperture width 13.2 mm; shell height 8.1 mm; height of

apex 4.9 mm (length/width ratio 1.12; length/height ratio 

1.82; width/height 1.63).

Material The holotype (MU 248T) is the only known 

specimen. It appears to be a highly recrystallized calcitic 

cast, and was collected from the Clays Ferry Formation 

in northern Kentucky. The locality given for the specimen, No. OC3, could not be traced. The Miami University museum label states that the late Prof. Shideler 

suggested the specific name of "alta" for the new species, 

referring to its high shell, and that name is used here. 

The specimen is partly embedded in a limestone matrix.

Distribution.—The new species is known only from 

the Edenian part of the Clays Ferry Formation of 

Kentucky.

Comparison. —A. alta bears some resemblance to A. 

laevis Foerste (1924, p. 202, pi. 30, figs. 3a-d) from the 

Richmondian of Snake Island, Ontario, but the former 

has a much higher shell. It also resembles A. subrotunda 

Ulrich and Scofield (1897, p. 834, pi. 61, figs. 6, 7) in 

having a marginal apex and a horizontal apertural margin. However, when the proportionate measurements 

are compared, the difference is striking. For example, 

the shell length/shell height ratios for A. alta, A. subrotunda, and A. laevis are 1.8, 2.5, and 3.1, respectively 

(measurements for latter two species taken from illustrations of the holotypes).

Archinacella? davisi new species

Plate 3, figures 1-3

Diagnosis. — Shell very large, with broad subovate 

outline; beak long and fairly narrow, with apex slightly 

downcurved and apparently extending well beyond anterior shell margin; lateral apertural margin straight.

Description. — Shell very large for genus (70 mm long), 

outline broadly subovate; dorsolateral profile broadly 

convex; lateral apertural profile apparently horizontal; 

beak area long and narrow, ending in pointed apex which 

is slightly downcurved and apparently extends well past 

anterior apertural margin; anterior slope distinctly concave; shell thickness and markings unknown.

Measurements.—The holotype and only known specimen measures as follows: length from apex to posterior 

margin 70 mm; aperture length 63 mm; aperture width 54 

mm; shell height 23 mm. The specimen is poorly preserved (pi. 3, figs. 1-3), and these measurements are 

only approximations.

Material.-The holotype (CMNH P2) is the only 

known specimen of the new species. The specimen is a 

large internal mold in rather fissile gray shale, and the 

specimen boundaries are difficult to pinpoint. The lines 

that appear to be possible comarginal growth lines are 

actually shale laminae (pi. 3, figs. 1-3).

Distribution.—The holotype was found in the Cincinnati Museum of Natural History Collections with only
MIDDLE AND UPPER ORDOVICIAN SYMMETRICAL UNIVALVED MOLLUSKS, CINCINNATI ARCH REGION 081

locality data. It came from the Gallatin, Ky., area. The 

character of the matrix and the stratigraphy of the type 

area strongly suggest that the specimen came from the 

Kope Formation (Edenian).

Derivation of species name. The species is named for 

Richard Davis of the Cincinnati Museum of Natural 

History, through whose courtesy the specimen was made 

available for study.

Comparison. Because of the poor preservation of the 

holotype, its generic placement is open to question. The 

only other possible generic assignment is Carinaropsis, 

which also has a long, extended beak area (the coil could 

be missing from the internal mold). However, the dorsal 

beak of A. ? davisi shows no evidence of a carina, it is 

quite rounded, and there is no evidence of an anteromedian slit or a trailing slitband; also, the apertural outline 

appears too regularly ovate for Carinaropsis. If the 

generic assignment is correct, this is the largest known 

species of Archinacella.

Archinacella cf. A. pulaskiensis Foerste, 1914b

Plate 2, figures 17, 18

Carinaropsis patelliformis Hall (in part), 1847, p. 306, pi. 83, figs.

7a, b. 

Carinaropsis patelliformis Hall, Miller, 1874, p. 314; (in part) 1889, p.

400. 

Archinacella pulaskiensis Foerste, 1914b, p. 309, pi. 3, figs. 3a-d;

1924, p. 203, pi. 31, figs. 3a, b; pi. 29, fig. 1.

Description. Shell fairly small for genus (about 8 mm 

long), subovate, broader anteriorly than posteriorly; 

convexity low; lateral apertural margin horizontal; beak 

area sharply angular dorsomedially, rapidly becoming 

broadly convex posteromedially; apex sharply pointed, 

slightly incurved, situated over anterior apertural margin; comarginal growth lines fairly distinct.

Measurements.—The measurements of the single 

specimen available are as follows: shell length 8.4 mm; 

shell width 6.4 mm; shell height 2.2 mm; widest point on 

shell (from apex) 3.5 mm.

Material.—The only specimen available was UCGM 

19640 from Maysvillian strata. This specimen is small and 

has poorly preserved margins. The type specimens were 

not examined directly. However, I did examine previous 

authors' illustrations of the species, including Foerste's 

(1914b) figures of the types.

Distribution.—The single specimen UCGM 19640 is 

labeled as coming from the "Maysville," but no further 

stratigraphic or locality data are given. The specimen 

most likely is from the Cincinnati, Ohio, area. Miller 

(1874, p. 314) reported finding Carinaropsis patelliformis (Hall) (the Cincinnatian specimens placed in this 

species by Hall, 1847, are now considered to be A. 

pulaskiensis) from "the quarries back of Cincinnati." 

These hill quarries were in the Fairview Formation 

(Maysvillian) (Pojeta, 1984, p. E79).

Comparison.— This species is similar to A. simulatrix, but it lacks the angularity of the beak posteriorly. 

Without more and better material, no further comparisons are possible, but the possibility of synonymy 

between the two species names should be kept in mind.

Hall (1847, p. 183) remarked as follows about C. 

patelliformis: "There are one or two other species in the 

Hudson River Group [as the Upper Ordovician was then 

called], and a single more elevated one in the Trenton 

limestone, which has not been satisfactorily determined." Miller (1874, p. 314; 1889, p. 400) identified the 

same species in Maysvillian-age strata at Cincinnati, 

Ohio. In their discussion of Archinacella deleta, Ulrich 

and Scofield (1897, p. 831) stated:

This is the first of a group of species that seems to be related to A. 

(Carinaropsis) patelliformis Hall. One or the other of these forms 

occurs in, or in the equivalent of, every one of the principal beds 

between the base of the Black River Group and the top of the 

Cincinnati formation. None of the western or northwestern species 

however seem to be strictly identical with the New York types of 

patelliformis, all of them having a nearly smooth surface, while Hall's 

species according to his figures and description has the surface marked 

by regular concentric, sublamelliform striae.

They then compared A. patelliformis to A. deleta Sardeson, A. valida, A. semicarinata Ulrich and Scofield, and 

A. simulatrix.

Foerste (1914b, p. 309) described A. pulaskiensis from 

the late Maysvillian-age Pulaski Formation of New York 

and Quebec, starting his description as follows: "The 

form figured by Hall from the Lorraine at Pulaski, New 

York, as Archinacella patelliformis, differs in outline 

from his Trenton types....This shell [A. pulaskiensis] is 

broader and more convex along the middle and the 

outline, therefore, rather broadly ovate than ovate 

oblong. Otherwise the shells are closely similar." Foerste 

(1924, p. 203) also cited this species from the Cryptolithus zone of New York and Quebec, which he correlated with the "Southgate member of the Eden" in the 

Cincinnati area.

The species in the Maysvillian strata of the Cincinnati 

area reported by Miller (1874, 1889) is here placed in A. 

pulaskiensis Foerste because the two agree in their 

small size, low convexity, and sharply pointed marginal 

apex. The exact apertural outline of the shell of the 

specimen studied herein is not shown, and this characteristic is stressed by Foerste in comparing it with A. 

patelliformis. A review of all species that are directly 

comparable to A. patelliformis is needed; however, 

sufficient collections to carry out such a study are not 

available.

Archinacella rugatina Ulrich, 1897

Plate 2, figures 19-21

Archinacella rugatina Ulrich in Ulrich and Scofield, 1897, p. 835, pi. 

82, figs. 5, 6.
082 CONTRIBUTIONS TO THE ORDOVICIAN PALEONTOLOGY OF KENTUCKY AND NEARBY STATES

Diagnosis.— Shell medium sized, nearly circular in 

outline, moderately high and convex in lateral profile; 

apex inset from shell margin; apertural margin nearly 

horizontal; strong sublamellose growth lines in later 

adult growth.

Description.— Shell medium sized for genus (about 20 

mm long), outline nearly circular, lateral profile moderately high and convex; highest point on shell near apex; 

apex distinct, fairly blunt, slightly curved anteriorly, 

situated distinctly just within anterior shell margin; 

anterior slope convex near shell margin, becoming concave beneath apex; lateral apertural margin nearly horizontal, but arches slightly dorsally; growth lines strong 

and apparently sublamellose in later growth stages.

Measurements.— Measurements of the holotype are as 

follows: length from apex to posterior margin 19.5 mm; 

aperture length 20.85 mm; aperture width 20.4 mm; shell 

height 7.0 mm; height of apex 5.7 mm; width between 

later growth lines 1.5-2.0 mm.

Material.— The holotype of the species was examined 

(USNM 45693). It is an internal mold with some highly 

recrystallized and weathered shell material around the 

posterior margin. One other specimen of the species was 

located. It is an unnumbered specimen on display in the 

Miami University Geology Museum, Oxford, Ohio.

Distribution.-The holotype (USNM 45693) is from 

what was formerly called the "Arnheim Formation" and 

now is placed in the Bull Fork Formation (early 

Richmondian-upper Upper Ordovician) at Middletown, 

Ohio. Nickles (1902) listed the species as part of the 

"Lower Richmond Fauna."

Comparison.—Ulrich (Ulrich and Scofield, 1897) compared A. rugatina as follows: "This species agrees closely 

with A. richmondensis [A. indianensis] Ulrich, but may 

be distinguished by its more distinct and slightly 

incurved apex, somewhat arched aperture, and stronger 

surface markings. The latter are coarsely lamelliform in 

the outer third." Herein, A. richmondensis is placed in 

subjective synonymy with A. indianensis Miller. 

Ulrich's comparison can be expanded. First, A. indianensis can have a horizontal or slightly arched aperture 

(pi. 3, figs. 21, 22; pi. 4, fig. 7), so this morphological 

feature is not a reliable basis for comparison. Better 

distinctions are provided by the character of the apex, it 

being more curved in A. rugatina (pi. 2, figs. 20, 21), the 

general form of the shell, which in A. rugatina is much 

broader in outline and more convex in lateral profile (pi. 

2, figs. 19-21), and the sublamellose growth lines of A. 

rugatina.

Discussion.—A. rugatina is known only from the 

lower Richmondian strata of Ohio, whereas A. indianensis occurs in the middle and upper Richmondian strata 

of a much greater area. The two species are quite similar 

morphologically, and it is likely that A. indianensis was

descended from A. rugatina', alternatively, the two 

species may have had a common ancestor.

On the left posterolateral slope of the holotype of A. 

rugatina (pi. 2, figs. 19-21) there is a prominent comarginal protuberance. I have concluded that this feature is 

probably a product of weathering, but it may represent 

the position of a muscle scar.

Archinacella area new species

Plate 3, figures 7-10

Diagnosis.— Shell medium sized, highly convex, 

nearly circular in outline; apex bluntly pointed, situated 

high over, and slightly past, anterior apertural margin; 

lateral apertural margin strongly arched.

Description.— Shell medium sized for genus (about 19 

mm long), nearly circular in outline, quite high and 

strongly convex dorsally and posteriorly; lateral slopes 

nearly flat, anterior slope broadly concave; apex distinct, 

bluntly pointed, slightly curved anteriorly, situated high 

over, and slightly past, anterior apertural margin, which 

is slightly convex; posterior apertural margin broadly 

convex; lateral apertural margin strongly arched, 

increasingly so posteriorly; growth lines fairly widely 

spaced in immature shell, in mature shell become more 

closely spaced and slightly irregular, even showing mild 

wrinkling near base of anterior slope.

Measurements.—The measurements of the holotype 

are as follows: length from apex to posterior margin 19.5 

mm; aperture length 17.85 mm; shell width 20.5 mm; 

shell height 9.3 mm; height of apex 7.7 mm; distance 

between growth lines 1.0 to 1.5 mm.

Material.-Only the holotype (USNM 40615) of the 

species is known; it apparently is a partial composite 

mold. No shell material seems to be present, but rather 

the surface of the specimen is coated by a hard, dense, 

dark outer layer, as is often the case with composite 

molds. The specimen is embedded in a matrix of gray 

micrite, the only other skeletal material visible being a 

brachiopod fragment.

Distribution.—The single known specimen is labeled 

as coming from the "Waynesville Formation (Richmond)" at Waynesville, Ohio. This unit is now part of 

the Bull Fork Formation (Richmondian-upper Upper 

Ordovician).

Comparison.— There can be no doubt about the distinctiveness of this species. The only similar species is A. 

powersi Ulrich and Scofield, the type species of Archinacella. It too has a strongly arcuate lateral apertural 

margin and a broad shell, and its apex is similarly 

positioned and formed (Ulrich and Scofield, 1897, p. 829, 

pi. 61, figs. 3-5). But A. area is higher and more convex, 

and is proportionately wider, even being slightly wider 

than long. A. area cannot be confused with other Rich-
MIDDLE AND UPPER ORDOVICIAN SYMMETRICAL UNIVALVED MOLLUSKS, CINCINNATI ARCH REGION 083

mondian species of the study area, all of which have 

submarginal apices, straighter lateral apertural margins, 

and less convex shells.

Discussion.— The only species comparable to A. area 

is A. powersi, which is listed by Ulrich and Scofield as 

coming from the "Stones River Group" at Beloit, Wis. In 

modern terms, this probably means the Platteville Formation, which is Rocklandian (late Middle Ordovician) in 

age (Weiss, 1957; Sweet and Bergstrom, 1976). Both 

these species have a strongly arcuate lateral aperture, 

which results in a broad posterior apron (pi. 3, figs. 8, 9). 

The arched lateral margins probably allowed better flow 

of oxygenated water to the pairs of lateral gills. The 

broad posterior apron does not seem to have provided an 

efficient exit for water circulating through the mantle 

cavity, but it must have provided protection for a broad 

foot.

As seen particularly well on plate 3, figures 7, 8, there 

seems to be a wide, smooth band over the posterodorsal 

slope of A. area which angles slightly downward and 

narrows anteriorly and runs beneath the apex (pi. 3, figs. 

9, 10). This band does not seem to be a positive relief 

feature, but it may represent a broad muscle band 

insertion. It appears to be identical in position to the 

muscle band of A. powersi (Ulrich and Scofield, 1897, pi. 

61, fig. 5; Knight and Yochelson, 1960, fig. 50, Ib), 

although in A. area the band is extraordinarily wide. On 

the other hand, it is possible that the borders of this band 

are simply growth lines. If it does represent a remnant of 

a muscle band like that in A. powersi, then these species 

might be interpreted as strong clingers, where the apron 

protected the large muscular foot posteriorly, and the 

fused muscle band furnished strong, even pulling force 

for adherence. Morphology suggests that A. area is a 

descendant of A. powersi.

Archinacella indianensis (Miller, 1892) 

Plate 3, figures 13-24; Plate 4, figures 1-14; Plate 5, figures 27, 28

Tryblidium indianense Miller, 1892, p. 695, pi. 14, fig. 14; Cumings,

1908, p. 977, pi. 39, fig. 11. 

Archinacella richmondensis Ulrich in Ulrich and Scofield, 1897, p.

834, pi. 61, figs. 6, 7; Foerste, 1924, p. 201, 202, pi. 34, figs, la, b. 

Archinacella kagawongensis Foerste, 1924, p. 202, pi. 35, figs. 2a-d;

Hussey, 1926, p. 171, pi. 6, figs. 2, 3, 4, 9, 10.

Diagnosis. — Shell medium sized, with subovate outline and fairly low convexity; apex distinct, elevated, not 

incurved, located distinctly within shell margin; lateral 

apertural margin horizontal to slightly arched.

Description.— Shell medium sized for genus (up to 

about 20 mm long), subovate in outline, fairly low 

convexity; anterior slope gently concave and sloped 

anteriorly, posterior slope broadly convex to nearly flat, 

particularly in later growth; lateral slopes flat to slightly 

concave near margins; apex distinct, elevated, not

TABLE 24. Measurements (in millimeters) of Archinacella 

indianensis

Museum 

No.

Length 

Apex to 

posterior

Shell 

width

Shell 

height

Aperture 

length

Beak

height

USNM 

45691 

47468 

70467 

265946

265950

265951

265954

265954

265954

265954

265954

265954

265954

265954

265954

265854

UCGM 

10048 

10048 

19642 

19642

MU 

247T

15541

15542 

246T 

15540

15540 

250T 

15545

20.50

13.40

20.30

12.75

12.85

13.50

9.50

11.15

10.70

7.80

19.00

18.46

10.95

16.0

19.6 

6.6

17.0

17.1

15.5

14.3

11.1

24.0

18.2

20.20

14.10

16.50

12.20

10.20

12.55

4.40

5.30

3.70

4.30

3.70

3.00

6.80

4.25

15.4

10.7

20.3

7.0

15.70

14.20

11.80

14.20

15.50

11.15

21.50

17.60

6.00

4.40

6.00

6.15

5.65

6.10

4.6

6.1 

5.0

6.55

6.20

5.90

5.30

5.00

6.90

6.20

24.40

16.30

21.20

16.20

13.50

16.70

9.45

10.20

8.10

8.30

7.70

5.80

16.40

10.25

8.90

20.0

13.9

22.6

8.2

20.00

18.15

16.50

17.00

18.40

12.50

26.55

20.45

5.5 

3.6 

4.2

incurved, located well within the shell margin at about 

one-sixth shell length from anterior end; lateral apertural 

margin generally horizontal, but slightly arched in some 

specimens; comarginal growth lines distinct in outer half 

of shell, somewhat irregular in some specimens.

Measurements.— Measurements of A. indianensis are 

listed in table 24. Specimens that were measured but not 

figured are treated as a suite and given one museum 

number.

Material.—The holotype of A. richmondensis (USNM 

45691) (pi. 3, figs. 16-18) is an external mold in the base 

of a bryozoan colony, as is specimen USNM 47468 (pi. 4, 

figs. 8-12); the two specimens are from the White water 

Formation at Richmond, Ind., and the Bull Fork Formation (Waynesville biofacies) at Oregonia, Ohio, respectively. Specimen USNM 70467 from Richmondian strata 

at Oakland, Ohio, preserves the shell and the irregular 

nature of the growth lines seen in some specimens (pi. 4, 

figs. 1, 2).

The holotype of A. indianensis (UC 6065) (pi. 3, figs. 

13-15) is an internal mold, but it preserves the outline
084 CONTRIBUTIONS TO THE ORDOVICIAN PALEONTOLOGY OF KENTUCKY AND NEARBY STATES

and form of the shell quite well. Specimens MU 246T 

(pi. 3, fig. 21), MU 247T (pi. 3, figs. 23, 24), MU 250T 

(pi. 3, fig. 22), MU 15540-15545, and UCGM 10048, all 

from the Drakes Formation (Elkhorn biofacies) just 

south of Morning Sun, Ohio, and UCGM 19642, from the 

Drakes at Whitewater, Ind. (total of 15 specimens), were 

also examined.

New material from the USGS silicified collections 

consists of about 45 specimens and fragments from the 

Dillsboro Formation (Liberty biofacies) from the New 

Point quadrangle of southeastern Indiana (locality 6139- 

CO). Specimens USNM 265946 (pi. 3, figs. 19, 20), 

USNM 265949 (pi. 4, figs. 13, 14), USNM 265950 (pi. 5, 

figs. 27, 28), and USNM 265951 (pi. 4, figs. 3-7) of this 

collection are figured; all measured but unfigured specimens are placed under the number USNM 265954.

Distribution.—A. indianensis is known from 

Richmondian-age strata in southeastern Indiana and 

southwestern Ohio. It probably is present in correlative 

strata in central Kentucky. The subjective synonym A. 

kagawongensis extends the species' geographic range to 

the Upper Peninsula of Michigan and Manitoulin Island, 

Ontario, where it also is present in Richmondian-age 

rocks.

Comparison.—A. indianensis Miller has been considered as possibly conspecific with A. richmondensis ever 

since the original description of the latter species. Ulrich 

and Scofield (1897, p. 834) closed their discussion of A. 

richmondensis by stating, "We could come to no positive 

conclusion respecting Miller's Tryblidium indianese, but 

if his description is reliable it is certainly distinct." 

Bassler (1915) advised comparison of the two. Foerste 

(1924) noted only that Miller's figure of the species 

showed it to be shorter, relatively narrower anteriorly, 

and broader posteriorly than A. richmondensis. The 

holotypes of A. indianensis and A. richmondensis are 

very close in their shell form, having submarginal apices, 

gently curved posterior slopes, rather steeply concave 

anterior slopes, and broad, ovate apertural outlines. I 

regard them as conspecific, and Miller's (1892) species 

name has priority.

Foerste (1924) described A. kagawongensis with the 

beginning line, "Specimens similar to Archinacella richmondensis', one specimen being 20 mm long, 16 mm wide, 

and 7 mm high...." When these measurements are plotted on the graphs for A. indianensis in figure 23, they 

agree quite well with measurements of specimens of that 

species. Foerste (1924) went on to say that his new 

species from the Richmondian strata of Manitoulin 

Island, Ontario, differed from A. richmondensis by 

having the apex curved downward farther, by being 

somewhat smaller, and by having less distinct growth 

lines. Hussey (1926, p. 171) began his description of A. 

kagawongensis from the Richmondian strata of the

Upper Peninsula of Michigan by stating, "This is a 

variable species." He figured two specimens, the first 

(Hussey, 1926, pi. 1, figs. 3-9) appearing to be quite 

similar to Foerste's (1924) figured specimens; however, 

the second (Hussey, 1926, pi. 6, figs. 4-10) looks like a 

specimen of a typical A. indianensis from the Cincinnati 

arch area, and Hussey pointed out that this latter 

specimen was "more like the typical form."

My examination of a large number of specimens of A. 

indianensis shows clearly that their shape varies widely. 

Foerste's (1924) and Hussey's (1926) descriptions and 

figures of A. kagawongensis show that it clearly falls 

within the range of variability for A. indianensis. Specimens from the study area in the Miami University 

collections labeled A. kagawongensis and A. richmondensis are indistinguishable, and many are from the 

same locality at Morning Sun, Ohio. This morphological 

variation, as well as the exact stratigraphic correlation of 

the two species, argues for suppression of the name A. 

kagawongensis.

Ulrich and Scofield (1897, p. 834) compared A. richmondensis to the geologically older species A. depressa 

Ulrich and Scofield (see pi. 2, figs. 13, 14 herein), but 

stated that the latter species' "arched aperture, lesser 

convexity and somewhat different outline" distinguish it 

from the former. They further stated a belief that "A. 

richmondensis is probably more nearly related to A. 

subrotunda," but did not elaborate. A. indianensis 

shows a close morphological similarity to A. depressa, 

both having rather low shells with distinctly submarginal 

apices.

Specimen USNM 265955 should be noted here (pi. 3, 

figs. 11, 12). This single specimen from the Grier Limestone Member of the Lexington Limestone appears to be 

an Archinacella, but it is too poorly preserved to allow 

specific determination. It is a rather high shell with 

slightly convex slopes and a distinctly submarginal apex. 

It bears some resemblance to A. indianensis in its 

general form and the positioning of its apex, and could be 

related to this species.

Discussion.— The fact that both the holotype of A. 

richmondensis (USNM 45691) and specimen USNM 

47468 are preserved as external molds in the bases of 

calcitic bryozoan colonies, but come from different stratigraphic levels and localities, strongly suggests that 

Archinacella had an aragonitic shell. However, a fair 

number of specimens of Archinacella (pi. 4, figs. 1, 2) are 

also known to have a recrystallized calcitic shell. Considerable insight into shell compositions would be gained if 

in future collecting, the nature of the preservation of 

associated mollusks were noted.

The graphs in figure 23 show high correlation values 

for plots dealing with shell length and width, but much 

lower correlation values for plots dealing with shell
MIDDLE AND UPPER ORDOVICIAN SYMMETRICAL UNIVALVED MOLLUSKS, CINCINNATI ARCH REGION 085

30

20

:r

CD

10

30

O/

o

20

10

O

30

20

10

10 20 

SHELL WIDTH, IN MILLIMETERS

O

10 20 

APEX-POSTERIOR MARGIN LENGTH

30

10

10 20 

SHELL HEIGHT, IN MILLIMETERS

10 20 

SHELL HEIGHT, IN MILLIMETERS

FIGURE 23. Bivariate plots of measurements made on specimens of Archinacella indianensis.

height. The shell height was the most difficult measurement to make, because many specimens have fragmented margins or broken apices and many have shell 

margins embedded in matrix.

Ulrich and Scofield (1897) believed that the lateral 

apertural margin of this species is "nearly or quite 

horizontal." However, examination of type and new 

material reveals considerable variation in this characteristic. Although most specimens have essentially horizontal apertural margins (pi. 3, figs. 18, 21, 24; pi. 4, fig. 7), 

a few have obviously arched lateral margins (pi. 3, fig. 

22). If these forms are accepted as conspecific, as confluent variation suggests, then the use of shape of the 

lateral apertural margin (as often employed by Ulrich 

and Scofield) as a specific taxobasis is questionable. If the 

members of Archinacella were clinging animals, as their 

limpetlike form and fused ringlike muscle scar suggest, 

then the shape of their lateral apertural margins may
086 CONTRIBUTIONS TO THE ORDOVICIAN PALEONTOLOGY OF KENTUCKY AND NEARBY STATES

reflect ontogenetic deformation by the shape of the 

substrate.

Order CYRTONELLIDA Horny, 1963c

Diagnosis.— Shells planispirally coiled, with symmetrical paired muscle scars that are generally discrete but 

show a tendency toward fusion. Aperture nonsinuate or 

sinus bearing, but no slits known.

Stratigraphic range.—Upper Cambrian-Middle Devonian; some Lower and Middle Cambrian taxa may also be 

cyrtonellids.

Discussion.— The diagnosis for the Cyrtonellida given 

above follows the concept of Horny (1963c) rather than 

that of Runnegar and Jell (1976). The latter authors 

defined the order as essentially including all monoplacophorans that lack a labral emargination. They included 

many genera, such as the helcionellids, hypseloconids, 

and yochelcionellids, whose taxonomic placement is 

debated, and others, such as scenellids, that I assign to 

the Tryblidiida. It should also be noted that they 

included Cyrtolites in their concept of the Cyrtonellida; 

however, herein I show that several species of Cyrtolites 

bear a labral sinus. Runnegar and Jell's ordinal concept 

needs to be restructured, as its composition, and therefore its definition, are questionable.

Superfamily CYRTOLITACEA Miller, 1889

Diagnosis.—Same as for order.

Family CYRTOLITIDAE Miller, 1889

Diagnosis. Shell evolute to involute, with open umbilicus; whorls in many cases angular or narrowly rounded 

dorsally and laterally; may or may not have an apertural 

sinus.

Stratigraphic range.— Lower Ordovician-Middle 

Devonian.

Genus CYRTOLITES Conrad, 1838

Diagnosis.— Shell rather loosely coiled, umbilicus 

widely open, aperture generally quadrangular, but may 

be rounded; aperture sinuate in many cases; growth lines 

raised, in many cases with intervening fine revolving 

threads; collabral rugae present in many cases.

Description.— Shell planispiral, consisting of about 

three whorls as adult, with wide-open umbilicus; coils 

contiguous, but barely touching, and disjunct in one 

known species. Aperture generally quadrangular to 

rhomboidal; may be rounded to sharply angular laterally; 

dorsal crest angular in most cases, but may be carinate. 

Whorls generally expand gradually and show only slight 

tendency toward flaring in gerontic stages. Aperture 

with dorsomedian sinus in some species, but in all cases 

lacks slit and selenizone. External markings always 

consist of distinctly raised thin growth lines, these

passing straight over the dorsal crest or swinging abaperturally to varying degrees to form a sinus; growth lines 

in many cases connected by short revolving threads that 

form a reticulate pattern; some species have collabral 

rugae developed at fairly regular intervals along dorsal 

and dorsolateral flanks of whorls. Shell thin.

Muscle scars in five discrete symmetrical pairs 

arranged in main and secondary rings. Main ring consists 

of three pairs, the first near dorsal crest, the second on 

lower dorsal slope, and the third on ventral slope. 

Secondary ring consists of two pairs of small scars on 

upper and lower slopes, respectively, that lie just anterior (abaperturally) to main ring.

Type species. —C. ornatus Conrad, 1838, by 

monotypy.

Distribution.— Middle Ordovician (Blackriveran)- 

Lower Silurian (Llandoverian) of North America and 

Europe; occurs throughout Eastern North America.

Comparison. —Cyrtolites is generally easily distinguished from similarly shaped genera, such as Cloudia 

Knight (1947b), by its quadrangular whorl shape and 

distinctly raised growth lines, as well as by the fine 

revolving threads (forming a reticulate pattern) and 

rugae marking many species.

Discussion.— The genus Cyrtolites was described by 

Conrad (1838, p. 118) in the following brief statement: 

"Shell with general form of Cyrtoceras, but destitute of 

septa." Conrad's (1838) original illustration of C. ornatus 

is a disjunct internal mold. For many years afterward, a 

variety of fossil shells were assigned to this genus 

(Bassler, 1915, p. 365-368). Ulrich and Scofield (1897, p. 

858) recognized this vague usage of the genus for symmetrically evolute shells having a carinate or angular 

dorsum and a broad umbilicus. They noted: "These 

characters pertain to several widely distinct genera, and 

to use them as characteristic of a single genus is to 

bring together a most heterogeneous assemblage of 

forms....We must return to the original type C. ornatus, 

and restrict the genus to species possessing essentially 

the same generic peculiarities."

Reed (1921, p. 23) criticized Ulrich and Scofield's 

generic definition, saying that it was too broad and 

included species probably referable to Temnodiscus 

Koken. However, comparison of Reed's definition with 

that of Ulrich and Scofield shows no greater morphological restriction of the genus. It should be noted that 

Ulrich and Scofield stressed removal of shells having slits 

from the genus Cyrtolites. They assigned shells having 

deep slits to a new genus, Cyrtolitina, which Knight 

(1941) cited as an objective synonym of Temnodiscus 

Koken, 1896, as Cyrtolites lamellifer Lindstrom, 1884, 

was designated the type species for both genera.

Prior to 1965, Cyrtolites had generally been considered a bellerophontid gastropod. However, Horny
MIDDLE AND UPPER ORDOVICIAN SYMMETRICAL UNIVALVED MOLLUSKS, CINCINNATI ARCH REGION 087

(1965a) described several specimens of C. ornatus Conrad from the Upper Ordovician of Canada (specimens 

now in the British Museum of Natural History) that show 

five pairs of discrete symmetrical muscle scars arranged 

in main and secondary rings. He placed Cyrtolites in the 

class Monoplacophora.

Horny (1965a, p. 62) argued that Cyrtolites differs 

from the Bellerophontacea in the following features: (1) 

absence of a sinus, (2) absence of parietal inductura, and 

(3) presence of symmetrical multiple pairs of discrete 

muscle scars. The latter two differences are still valid. 

However, my work shows the presence of a shallow 

posterior apertural sinus in several species of Cyrtolites 

from the Middle and early Late Ordovician (pi. 5, figs. 7, 

9, 10, 13; pi. 7, figs. 11, 14, 23, 34, 35; pi. 8, figs. 13, 17), 

because the growth lines turn conspicuously abaperturally over the dorsal crests of the shells. In his 

discussion, Horny conceded that there appeared to be 

some evidence of sinus development in American Cyrtolites, but he suggested that if any emargination were 

present, these species could be regarded as true bellerophontaceans (which he considered to be gastropods). I 

regard such a separation of forms to be contrary to the 

generic unity of Cyrtolites expressed by other morphological features. It should be noted that Horny's study 

was prior to Rollins and Batten's (1968) description of 

symmetrical pairs of discrete muscle scars in the sinuate 

monoplacophoran Sinuitopsis acutilira (Hall).

Horny (1965a) recognized the need for a revision of the 

North American species of Cyrtolites, and predicted that 

they would prove rather variable with regard to coiling 

and external ornamentation. He also expected there 

would emerge a continuous gradational series between 

C. disjunctus Ulrich and Scofield, 1897, and C. ornatus 

Conrad, 1838. He was correct about the variation in 

external ornamentation in the American species of Cyrtolites, which is expressed mainly in the strength of the 

rugae, growth lines, and revolving threads at the 

intraspecific level. The most striking intraspecific variation is in the cross-sectional shape of the whorls themselves. C. retrorsus Ulrich and Scofield can have a 

variety of apertural outlines in any one population, from 

quadrangular (pi. 5, fig. 14) to dorsally arched (pi. 5, fig. 

18) to nearly circular (pi. 5, fig. 22). C. ornatus is also 

quite variable in cross-sectional shape, but not to the 

extent of C. retrorsus. There is no gradational series 

showing any progressive uncoiling in C. ornatus. Many 

internal molds of this species have been examined for this 

study, and when the inner coils are sufficiently visible, all 

specimens appear disjunct (pi. 6, fig. 18; pi. 7, fig. 1); 

shelled specimens are not disjunct, however. When C. 

ornatus is compared with C. disjunctus Ulrich and 

Scofield (pi. 6, figs. 19-22), the difference in the rate of

whorl expansion and increase in coiling radius are clearly 

very different in the two species. Shelled specimens of C. 

disjunctus are disjunct.

Discussion of subgenera. The two subgenera of the 

genus Cyrtolites recognized in the Cincinnati arch province, C. (Cyrtolites) Conrad and C. (Paracyrtolites) n. 

subgen., are separated on the basis of differences in shell 

sculpture. C. (Cyrtolites) exhibits a distinct reticulate 

ornament pattern formed by short revolving threads 

between coarser raised growth lines (pi. 5, fig. 26; pi. 8, 

fig. 18), as well as regularly spaced collabral swellings 

along the slopes of the whorls, herein termed "rugae" (pi. 

5, figs. 7, 12, 26; pi. 6, figs. 6, 19; pi. 8, figs. 2, 14). This 

subgenus contains those species most closely fitting the 

traditional concept of the genus, and includes the type 

species of the genus C. ornatus Conrad. C. (Paracyrtolites), on the other hand, is composed of those species 

that lack rugae and have only faint revolving threads (pi. 

7, figs. 23, 27, 30, 32, 34, 35), in contrast to the distinct 

threads that give the strong reticulate ornament pattern 

in C. (Cyrtolites).

The oldest species in each of these two subgenera, C. 

(C.) retrorsus Ulrich and C. (P.) subplanus Ulrich in 

Ulrich and Scofield, 1897, both have V-shaped growth 

lines deflected abaperturally on the dorsal slopes, showing that each had a sinuate aperture (pi. 5, fig. 7; pi. 7, 

figs. 34, 35). Both of these species are found in the 

Kirkfieldian-Shermanian strata of Kentucky and Tennessee. The probable descendants of C. (P.) subplanus in 

the study area are C. (P.) carinatus Miller (pi. 7, figs. 

18-25) and C. (P.) parvus Ulrich (pi. 7, fig. 17). Both of 

these species retain a sinuate aperture and are known 

from only the Edenian (lower Upper Ordovician) portion 

of the Kope Formation of northern Kentucky and southwestern Ohio. The longer lived, more diverse lineage 

stemming from C. (C.) retrorsus loses the labral sinus 

after Edenian time. Both C. (C.) claysferryensis (latest 

Shermanian and Edenian; pi. 8, figs. 11-20) and C. (C.) 

retrorsus (Edenian; pi. 5, figs. 6, 7, 9, 10, 13, 19, 23, 26) 

retain the shallow sinus. C. (C.) minor Ulrich 

(Kirkfieldian-early Maysvillian) has growth lines that 

pass essentially at right angles over the dorsal crest with 

little or no deflection (pi. 7, figs. 2, 5, 8). All subsequent 

species of the lineage in the Cincinnatian have nondeflected growth lines passing straight over the dorsal 

crest, and thus had a nonsinuate aperture.

The reasons for the loss of the sinus in C. (Cyrtolites) 

in the Late Ordovician are unclear, but may be related to 

the changing depositional systems from the Champlainian to the Cincinnatian Series in the study area. The 

Champlainian was much more free of clastic sedimentation than the Cincinnatian Sea. Toward the end of Middle 

Ordovician time, fine clastic sediments began to be fed 

into the system in large quantities, so that the Cincin-
088 CONTRIBUTIONS TO THE ORDOVICIAN PALEONTOLOGY OF KENTUCKY AND NEARBY STATES

natian Series is characterized by alternating shale and 

limestone deposition. The loss of the sinus, therefore, 

may have been an adaptation to protect the mantle cavity 

from fouling by clay-sized sediment. Other general morphologic trends in the subgenus C. (Cyrtolites) are (1) in 

some species a slight increase in the width of the 

aperture relative to the height, (2) a slightly looser 

coiling and a more open umbilicus, and (3) in the postEdenian rocks, a general increase in size.

The distinct external sculpturing of Cyrtolites is of 

some interest. Hall (1847), Meek (1873), and Ulrich and 

Scofield (1897) all included magnified illustrations of the 

reticulate sculpturing pattern seen in C. (Cyrtolites). On 

C. (C.) retrorsus (pi. 5, fig. 26), each raised growth line 

is the termination of a sublamellate increment of growth, 

and each growth increment between the growth lines 

bears a series of slightly finer revolving threads which 

are raised to, or nearly to, the same height as the lines 

they intersect. These short revolving threads generally 

alternate from one increment to the next, so that they 

appear as bricks in a wall (pi. 5, figs. 15, 26). The 

strength of the connecting threads varies among species 

of Cyrtolites, but preservation usually affects their 

expression.

The revolving threads between the growth lines are 

indistinct and faint in C. (Paracyrtolites), and, therefore, 

so is the recticulate ornamentation. C. (P.) subplanus 

Ulrich in Ulrich and Scofield has finer growth lines than 

any species of C. (Cyrtolites) (pi. 7, figs. 27, 30, 34, 35), 

and its weak connecting threads are revealed only by 

very close examination. The descendants of C. (P.) 

subplanus retain this faint type of ornamentation (pi. 7, 

figs. 18, 23, 24). Miller (1874) did not recognize a reticulate pattern in the original description of C. (P.) carinatus Miller, but Ulrich and Scofield (1897, p. 863) 

observed that only the best preserved material retained 

the delicate revolving threads, and that just short exposure to weathering could remove them entirely. The 

same authors claimed that C. (P.) parvus Ulrich in 

Ulrich and Scofield has a strong ornament, but the 

holotype (pi. 7, fig. 17) does not support this contention.

It is important to note that the ornament of C. (P.) 

carinatus appears to decrease in strength during 

growth, in contrast to the strengthening of ornament 

during the growth of C. (C.) retrorsus. The presence of 

distinct reticulate ornament in juveniles of C. (P.) carinatus suggests that C. (Paracyrtolites) had a common 

origin with, or possibly was descended from, C. (Cyrtolites). While the weakly reticulate subgenus C. (Paracyrtolites) is not known from rocks younger than Edenian (lower Upper Ordovician), the strongly reticulate C. 

(Cyrtolites) persisted throughout the remainder of Cincinnatian time.

C. (C.) ornatus Conrad is commonly found encrusted 

by bryozoans in the Maysvillian and Richmondian strata 

of the study area (pi. 6, figs. 12-16), and one specimen of 

C. (C.) minor Ulrich from the Edenian Kope Formation 

is known to be similarly encrusted (pi. 7, figs. 5-7). No 

other species of the genus are known to be encrusted. 

The encrusting bryozoans may have preferred the distinctly reticulate surface of these species as a base for 

larval settlement and colony growth. Many of these 

specimens appear to have been encrusted while alive. 

The apertural rim is generally not encrusted in otherwise 

completely encrusted shells, and in few cases do the 

bryozoans attain a thickness such that their weight might 

interfere with the mollusks' locomotion (pi. 6, figs. 12,13, 

15, 16). Morris and Rollins (1971, p. 162, figs. 4, 5) also 

assumed a symbiotic bryozoan encrustation of a specimen of C. (C.) ornatus from the study area, because of 

additional encrustation by oriented cornulitid tubes. 

Such a relationship would have been mutually beneficial; 

the monoplacophoran would acquire greater shell 

strength and a camouflage to assist in protection against 

predation, while the bryozoan would be assured an 

elevated attachment site. The suspension-feeding bryozoans might have further benefited from the molluscan 

feeding scraps and fecal products, or the microorganisms 

attracted thereto. McNamara (1978) reached similar 

conclusions from a study of gastropods encrusted by 

trepostome bryozoans from the Upper Ordovician of 

England. He pointed out that the bryozoans might have 

benefited from increased water flow over the colony 

caused by the gastropod's movement. Vermeij (1978, p. 

64) suggested that "complex shell topography" might 

promote encrustation of modern gastropods by calcareous algae and other epizoans, and this might increase 

predator resistance.

Evolution and speciation.— Horny (1965a, p. 63, 64) 

proposed that the Cyrtolitidae were descended from the 

Archinacellacea (Upper Cambrian-Richmondian). He 

claimed that the muscle scars of Cyrtolites resemble the 

complete muscle ring of the archinacellids, and that the 

"decomposition of the continuous archinacellan band-like 

scar" and the addition of the anterior scars are caused by 

the coiling of the shell of Cyrtolites and its relatives. He 

also proposed that Cyrtolites was the ancestor of the 

Silurian genera Yochelsonia and Cyclocyrtonella and the 

Devonian genera Cyrtonella and Neocyrtolites. Horny 

believed that Cyrtolites and its allies were not an important stem stock for any subsequent major taxa, and 

hence did not give rise to any groups of Gastropoda. 

Rather, he believed that they represented a "highly 

specialized group of mollusks," though he did not say 

exactly how, or for what, they were specialized.

C. (Cyrtolites) and C. (Paracyrtolites) are closely 

related to one another because (1) they have a common
MIDDLE AND UPPER ORDOVICIAN SYMMETRICAL UNIVALVED MOLLUSKS, CINCINNATI ARCH REGION 089

general shell form, (2) the oldest species of both groups 

have shallow sinuate apertures, and (3) both exhibit 

reticulate surface sculpturing, although this is only 

weakly developed in C. (Paracyrtolites). C. (C.) retrorsus fillmorensis from the Blackriveran strata of Minnesota was named by Ulrich and Scofield (1897, p. 862) and 

regarded as the oldest member of that species and the 

genus (this name is herein placed in synonymy with C. 

(C.) retrorsus Ulrich because knowledge of the taxon 

sufficient to distinguish it from C. (C.) retrorsus retrorsus is lacking). The oldest known species of C. (Paracyrtolites) is C. (P.) subplanus Ulrich from the KirkfieldianShermanian Lexington and Bigby-Cannon Limestones of 

Kentucky and Tennessee, respectively. C. (C.) retrorsus 

occurs in the same strata. It is likely that C. (P.) 

subplanus had a common ancestor with C. (C.) retrorsus. 

Stratigraphic ranges of species of Cyrtolites in the Cincinnati arch region are given in figure 24.

C. (Paracyrtolites) was a relatively short lived taxon 

and is rare relative to members of the subgenus C. 

(Cyrtolites). C. (P.) subplanus (pi. 7, figs. 26-35) apparently gave rise to C. (P.) carinatus (pi. 7, figs. 18-25) and 

C. (P.) parvus (pi. 7, fig. 17) near the beginning of 

Edenian deposition. C. (Cyrtolites) was a relatively long 

lived taxon, and some species were highly successful; for 

example, C. (C.) retrorsus (pi. 7, figs. 11-16) and C. (C.) 

ornatus (pi. 6, figs. 1-18) are abundant throughout much 

of their stratigraphic range in the Cincinnati arch region. 

C. (C.) ornatus is particularly abundant and widespread, 

being known essentially everywhere in Eastern North 

America where Upper Ordovician carbonates are 

exposed. Like C. (P.) subplanus, C. (C.) retrorsus gave 

rise to two descendants near the ChamplainianCincinnatian boundary in the study area. C. (C.) claysferryensis n. sp. (pi. 8, figs. 11-20) appears in the late 

Shermanian- to Edenian-age Clays Ferry and Kope 

Formations of Kentucky and Ohio. C. (C.) minor (pi. 7, 

figs. 2-10) Ulrich and Scofield first appears in the Edenian portion of the Kope Formation of the study area, 

although it has been reported from the uppermost Champlainian of Minnesota (Ulrich and Scofield, 1897) and 

possibly from New Jersey (Weller, 1903).

Four new species of Cyrtolites appeared near the 

Champlainian-Cincinnatian (Middle Ordovician-Upper 

Ordovician) boundary. This correlates with a marked 

change in sedimentological conditions throughout the 

region, with predominantly carbonate deposition giving 

way to intermittent shale and carbonate deposition. C. 

(C.) claysferryensis is similar to the more angular forms 

of C. (C.) retrorsus, the former inhabiting a somewhat 

more muddy environment. The other three new species C. (C.) minor, C. (P.) carinatus, and C. (P.) parvus—are found in the dominantly shaly Kope environments, which are thought to reflect somewhat deeper

(/)

LU

OC

LU

(/)

C

CD

4->

CD

C 

C

'o

c

CJ

c

CD

C

CD "a.

E

CD

.C

O

STAGE

Richmondian

Maysvillian

Edenian

Shermanian

Kirkfieldian

Rocklandian

Blackriveran

RANGE




£ c. ° -S,

y. -2 ~

o E —

^. ^->

u

0

-i2 0 C/5 <n c _3

^4 11

1 oj U a n

1 *^ ^ —— ' ^ £}

tn3' 

S2

S

1

U

u

- ly — u ———— 55- — s; - - zti- -

5 ! 1 U|U

u 5atn

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C)

FIGURE 24. Stratigraphic ranges of species of Cyrtolites (Cyrtolites) and C. (Paracyrtolites) in the 

Middle and Upper Ordovician of the Cincinnati arch 

region. C. (C.) retrorsus is known from the Blackriveran only in the Upper Mississippi Valley (Ulrich 

and Scofield, 1897). Dashed line indicates uncertainty of occurrence.

water. These three small species (shell lengths generally 

less than 15 mm) probably led rather similar modes of 

life. Their small sizes may have kept them from sinking 

into the soft bottoms of Kope environments. Peel (1978, 

p. 301-304) has suggested that small gastropod species 

from the Lower Silurian Arisaig Group were algal foliage 

dwellers. Such minute gastropod faunas are well known 

in the modern seas living on sea grasses and various 

algae (Warmke and Almodovar, 1963; Brasier, 1975). As 

in modern sea grass communities, the Ordovician algae 

would have provided a protective habitat, with abundant 

food above a possibly turbid sediment-water interface. 

Johnson (1961) has demonstrated a prolific calcareous 

algal flora in the Ordovician and Silurian; this suggests 

that noncalcified algae could also have been abundant 

(see section on paleoecology). Although the mode of
090 CONTRIBUTIONS TO THE ORDOVICIAN PALEONTOLOGY OF KENTUCKY AND NEARBY STATES

feeding of Paleozoic monoplacophorans is not known, 

most previous workers have assumed an algal-feeding 

habit similar to that of many gastropods. The common 

association of gastropods and monoplacophorans in fossil 

assemblages provides some support for this concept.

C. (C.) minor was the only one of these small cyrtolitids to survive into Maysvillian time (Fairview Formation 

of southwestern Ohio). This species most likely was 

ancestral to C. (C.) ornatus, as indicated by their very 

similar morphologic characteristics, except for size. C. 

(C.) minor was originally described by Ulrich and 

Scofield (1897) as a subspecies of C. (C.) ornatus, the 

main difference being the small size of C. (C.) minor. The 

smaller species is not known from strata younger than 

the Fairview Formation, and it is in that unit that C. (C.) 

ornatus first appears in the study area. The Fairview 

Formation is distinguished from the underlying Kope 

Formation by a marked increase in carbonate deposition 

relative to shale deposition, and it may be that this 

species turnover correlates with changing environmental 

conditions.

C. (C.) ornatus is believed to have given rise to C. (C.) 

disjunctus in Richmondian time, as the two are quite 

similar, but the coiling of the latter species is disjunct. C. 

(C.) disjunctus is known only from the Richmondian 

strata of Minnesota, but it is treated in this study 

because of the possibility of confusing it with internal 

molds of C. (C.) ornatus. It may be that this rare disjunct 

form is not a valid species, but rather a morphological 

variant of C. (C.) ornatus.

C. (C.) hornyi n. sp. (pi. 8, figs. 1-10) is known only 

from USGS silicified sample 6139-CO from a single 

locality in southeastern Indiana. It is from the upper 

Dillsboro Formation, from strata formerly designated 

the Liberty Formation or Strophomena planumbona 

Bed (see Shaver and others, 1970, p. 45-58); these strata 

consist of interbedded shales and limestones. This species morphologically resembles C. (C.) claysferryensis n. 

sp. from the Clays Ferry Formation of Kentucky, which 

also consists of interbedded shale and limestone characterized at many horizons by the strophomenacean brachiopod Rafinesquina (see Weir and Greene, 1965, p. Bll). 

The presence of large, flat strophomenid brachiopods 

such as Strophomena and Rafinesquina is generally 

considered to indicate level, soft-bottom conditions (Fox, 

1968; Richards, 1972; Walker and Parker, 1976).

C. (C.) retrorsus and C. (C.) ornatus have much in 

common. They are the longest lived and most abundant 

of the species of Cyrtolites considered herein; both show 

a high degree of intraspecific variability, and both inhabited depositional systems that were complex facies mosaics. In both species, different morphotypes cooccur, 

suggesting a genetic rather than ecophenotypic origin for 

their variable morphologies. These species were probably ecological generalists that maintained genetic flexibility in their populations. This flexibility permitted 

them to adapt readily to constantly shifting 

sedimentologic-environmental conditions. In contrast to 

these two species, the other species of Cyrtolites in the 

study area, particularly the three small species from the 

Kope Formation, may have been ecologic specialists. 

Their relatively short stratigraphic ranges and small 

populations suggest that they were more finely tuned to 

certain environmental conditions and less able to adapt to 

environmental fluctuations.

The modes of speciation occurring in Cyrtolites are 

difficult to discern because of the nature of cratonic 

stratigraphic sequences, which are characterized by 

shifting environments and diastemic breaks in sedimentation. Speciation events seem to happen rather quickly 

across boundaries of marked environmental change, such 

as the Champlainian-Cincinnatian boundary. However, 

abundant species such as C. (C.) retrorsus, which show a 

high degree of intraspecific variability and cross many 

environmental boundaries, give an impression of phyletic 

gradualism. It can be discerned that C. (C.) retrorsus 

was able to maintain large populations in a variety of 

dominantly carbonate environments from Rocklandian to 

Shermanian time, apparently without any species turnover. This success may be partly the result of a regional 

consistency in carbonate deposition. C. (C.) ornatus 

behaved similarly during the extended period of alternating carbonate and shale deposition during Maysvillian 

and Richmondian times, again a period of overall regional 

consistency in deposition, even though of a fluctuating 

character. The greatest apparent proliferation of species 

took place when there was a rather drastic change in 

regional depositional conditions, that is, during the flood 

of clay-sized sediments in latest Shermanian and Edenian 

times. Therefore, speciation in the genus Cyrtolites 

seems to be linked to regional environmental conditions, 

and species distribution shows a correlation with the 

percentage of clay-shale deposition.

Notes on British species of Cyrtolites.—Reed (1921) 

described five species of Cyrtolites from the Ordovician 

and Lower Silurian of the British Isles. These species are 

listed below with comments.

1. C. budleighensis Reed This species is known only 

from internal molds occurring in Ordovician pebbles 

found in Triassic conglomerates. Reed cited resemblance of this species to C. subplanus and C. 

retrorsus. Based on his figures of the species, it 

most resembles C. ornatus in both general shape 

and the development of strong rugae.

2. C. craigensis Reed This species from the Stinchar 

Limestone (Caradocian), known only from poor 

internal molds, has a morphology comparable to 

that of C. subplanus.
MIDDLE AND UPPER ORDOVICIAN SYMMETRICAL UNIVALVED MOLLUSKS, CINCINNATI ARCH REGION 091

3. C. nodosus nodosus (Salter) This subspecies comes 

from the Bala Series (Caradocian-Ashgillian) of 

Wales. It is characterized by growth lines that are 

deflected abaperturally over the dorsal crest of the 

shell, a distinct reticulate ornament, and rugae that 

are distinct and slightly rounded and extend about 

three-fourths of the way up the width of the dorsal 

whorl slope. C. nodosus seems to be nearly identical to the North American species C. retrorsus and 

is probably a synonym of that species.

4. C. nodosus llandoveria Reed-This supposed "variety" of C. nodosus was found in Lower Llandoverian rocks. It differs from the type subspecies in 

having sharper rugae that extend all the way up the 

dorsal whorl slope to the dorsal carina, and in 

having straight growth lines that are not deflected 

abaperturally. Reed believed that both the longer 

rugae and the nondeflected growth lines suggest a 

relationship to C. ornatus.

5. C. thraivensis Reed This species, collected from the 

Drummuck Group (Ashgillian), Scotland, is very 

similar in general form and style of ornamentation 

to C. ornatus, which Reed called an allied species.

Although it is beyond the scope of this study to 

evaluate the British species of Cyrtolites, some insight 

into their taxonomy may be gained from comparison with 

American species. Only three of the British species 

names can be used confidently (species 3-5 above); these 

three are adequately preserved and their stratigraphic 

location is given. The oldest of the three is C. nodosus 

nodosus (Caradocian-Ashgillian), which is very similar to 

the North American species C. retrorsus (KirkfieldianShermanian) in the development of its rugae and the 

abapertural curvature of its growth lines. The other two 

species, C. nodosus llandoveria (Lower Llandoverian) 

and C. thraivensis (Ashgillian), compare quite favorably 

with the American species C, ornatus in the lengthening 

of their rugae and the straightening of their growth lines 

dorsally. Although stratigraphic correlation between the 

two faunas is rather broad, the same morphologic trends 

toward the accentuation of rugae and the loss of an 

apertural sinus are seen during late Middle and Late 

Ordovician times in North America and Great Britain. In 

fact, the British and American species names are probably synonyms. The two associations seem to have been 

given different specific names because of their presentday wide geographic separation. In any case, there can 

be little doubt about their derivation from a common 

ancestral stock, and their similar paths of evolution 

strongly suggest some genetic exchange between the 

two faunas.

Submenus CYRTOLITES (CYRTOLITES) Conrad, 1838

Diagnosis.— Shell having rugae developed on dorsal 

slopes of whorls and distinct, short revolving threads 

between raised growth lines to form strong reticulate 

external shell sculpture. Apertural sinus and abaperturally deflected growth lines present in stratigraphically older species; younger species nonsinuate, with 

growth lines passing straight over dorsal crest of shell.

Type species. —C. (C.) ornatus Conrad, 1838, by 

monotypy.

Distribution.—Blackriveran (Middle Ordovician)- 

Richmondian (Latest Ordovician) of Eastern North 

American; Caradocian (Middle Ordovician)-Lower Llandoverian (Lower Silurian) of Great Britain.

North American species. —C. (C.) retrorsus Ulrich 

and Scofield, C. (C.) claysferryensis n. sp., C. (C.) minor 

Ulrich, C. (C.) ornatus Conrad, C. (C.) hornyi n. sp., C. 

(C.) disjunctus Ulrich and Scofield.

British species. —C. (C.) nodosus nodosus (Salter), C. 

(C.) nodosus llandoveria Reed, C. (C.) thraivensis 

Reed. The other two British species assigned to Cyrtolites by Reed (1921) are known only from internal molds 

and cannot be assigned to a subgenus.

Cyrtolites (Cyrtolites) ornatus Conrad, 1838 

Plate 6, figures 1-18; Plate 7, figure 1

Cyrtolites ornatus Conrad, 1838, p. 118; Conrad, 1839, p. 63; Conrad, 

1841, p. 37; Hall, 1847, p. 308, pi. 84, figs, la-g; Rogers, 1858, p. 

820, fig. 619; Billings, 1863, p. 217, fig. 226; Meek, 1873, p. 148, pi. 

13, figs. 3a-b; Miller, 1874, p. 308; Lesley, 1889, p. 182, figs. ; 

Miller, 1889, p. 402, fig. 669; Ulrich and Scofield, 1897, p. 860, pi. 

62, figs. 27-29; Cumings, 1908, p. 962, pi. 40, figs. 8-8a; Grabau 

and Shinier, 1909, p. 609, figs. 815a-b; Foerste, 1924, p. 203-204, 

pi. 34, fig. 3; Knight, 1941, p. 94, pi. 5, figs. 5a-d; Shinier and 

Shrock, 1944, p. 439, pi. 175, figs. 24, 25; Knight and others, 1960, 

p. 1175, fig. 90, 4; Caster, Dalve, and Pope, 1955 (1961), p. 41, pi. 

5, fig. 11.

Porcelia ornata Sharpe, Emmons, 1860, p. 102, fig. 7. (Also see 

possible synonyms in discussion of British species.)

Diagnosis.— Shell large, with subquadrangular aperture, angular dorsally and narrowly rounded at umbilical 

shoulders; rugae well developed, generally rounded; 

growth lines not deflected abaperturally, pass straight 

over dorsal crest.

Description.— Shell relatively large (up to 33 mm 

long); umbilici large and open; whorls loosely coiled. 

Aperture subquadrangular, dorsum sharply angular to 

distinctly carinate, dorsal slopes convex, umbilical shoulders narrowly rounded to angular, ventral slopes flat to 

slightly concave. Rugae well developed, broadly rounded 

in many specimens but narrow ridges in others; rugae 

extend from umbilical shoulders to dorsal crest; rugae 

weakly developed on upper ventral slopes of some larger 

specimens. Growth lines not deflected abaperturally,
092 CONTRIBUTIONS TO THE ORDOVICIAN PALEONTOLOGY OF KENTUCKY AND NEARBY STATES

TABLE 25. Measurements (in millimeters) o/Cyrtolites (Cyrtolites) ornatus

Museum 

No.

USNM

45786

265906

265907

265908

UCGM

3097

19671

SF

2008

Shell length

27.6

30.4

26.9

32.9

21.8

24.1

29.0

Aperture length

14.5

18.5

15.4

19.0

13.9

13.9

15.8

Aperture width

16.7

16.8

17.1

_

15.8

15.8

15.8

Maximum 

umbilical 

diameter

15.3

16.2

12.9

15.7

-

-

-

Width at 

base of 

aperture

4.9

6.2

5.7

-

-

-

-

Wave length 

of rugae

2-3

3^

2-3

2.7-4.5

-

-

-

pass straight over dorsal crest of shell; reticulate ornament formed by somewhat weaker revolving threads.

Measurements. Reliable measurements could be 

made on only a few specimens; these are listed in table 25 

and shown graphically in figure 25. The poor quality of 

the measurements is reflected in the value of the plot. 

Measurements for USNM 45786, 265906, and 265907 are 

fairly reliable, but USNM 265908 is a large internal mold. 

UCGM 3097 and 19671 and SF 2008 are totally encrusted 

by bryozoans, so only partial measurement was possible.

Material. —No new specimens of this species were 

found in the USGS silicified collections. Collections at the 

U.S. National Museum, the University of Cincinnati, 

Miami University, and the Cincinnati Museum of Natural 

History were examined. All these collections were dominated by specimens from the Cincinnati arch region, and 

all were predominantly internal molds, composite molds, 

and bryozoan-encrusted specimens. SF 2008 is from the 

private collection of Steve Felton of Cincinnati, Ohio, and 

is not figured herein.

Knight (1941, p. 94) designated the specimen illustrated by Hall (1862, pi. 11, fig. 19) the lectotype of the 

species, but its whereabouts is unknown. Knight suggested that a collection of specimens in the Academy of 

Natural Sciences of Philadelphia (No. 13307) might be 

Conrad's original syntypes. The only previously figured 

specimen examined by me is a hypotype (USNM 45786) 

that was figured by Ulrich and Scofield (1897, pi. 62, fig. 

27). A photograph of that specimen appears here for the 

first time (pi. 6, figs. 1-3). A collection of specimens 

bearing the same USNM number as this hypotype, but 

found in a separate box and drawer, was also examined, 

and three specimens from that collection are also figured 

here (pi. 6, figs. 6-8, 9-11; pi. 7, fig. 1; these hypotypes 

are here assigned numbers USNM 265906, 265907, and 

265908, respectively). All of these specimens (originally 

with suite number USNM 45786) are labeled as coming 

from the "Corryville member of the McMillan Formation 

(Maysvillian) at Cincinnati, Ohio" (equivalent to Grant 

Lake Limestone or a tongue of the Bull Fork Formation).

Distribution.— Maysvillian (middle Upper Ordovician) 

and Richmondian (upper Upper Ordovician) of Eastern 

North America. The species is present in all formations 

of the middle to upper Upper Ordovician in the Cincinnati arch area, and according to the comments of other 

authors, it is common in many places throughout its 

geographic range.

Comparison. — The Maysvillian-age C. (C.) minor is 

similar in shell form and ornament (pi. 7, figs. 2-10) to C. 

(C.) ornatus, but is much smaller. The only other 

Richmondian-age species currently recognized in North 

America are C. (C.) hornyi n. sp. and C. (C.) disjunctus. 

C. (C.) hornyi (pi. 8, figs. 1-10) is more angular in its 

form and has flatter whorl slopes than C. (C.) ornatus. C. 

(C.) disjunctus (pi. 6, figs. 19-22) is disjunctly coiled, 

being distinguished from disjunct internal molds of C. 

(C.) ornatus by the rate of whorl expansion and the rate 

of increase in the radius of coiling.

Discussion. —C. (C.) ornatus Conrad, 1838, is the 

type species of the genus Cyrtolites, and the species in 

which Horny (1963c) discovered symmetrical discrete 

pairs of muscle scars, which led to the transfer of the 

genus to the class Monoplacophora. The species is distinguished from other species by its relatively large size (pi. 

6, figs. 6-8), its usually broadly rounded rugae that 

extend from the umbilical shoulders to the dorsal crest of 

the shell (pi. 6, figs. 1, 6, 17), and its straight growth 

lines (pi. 6, figs. 7, 10), which cross the dorsum at right 

angles to the dorsal crest.

Horny (1965a) believed study eventually would reveal 

a continuous morphological gradational series of forms 

between C. (C.) ornatus and C. (C.) disjunctus. This 

idea is not supported by this study, although rarely a 

gerontic specimen of C. (C.) ornatus is found that 

appears to have a slight tendency to uncoil near the end 

of the body whorl.

C. (C.) ornatus exhibits a large amount of intraspecific 

variability in the shape of its whorls and the expression 

of its rugae. Figured here is a representative collection of 

forms; the specimens shown on plate 6, figures 1-3, 6-8,
MIDDLE AND UPPER ORDOVICIAN SYMMETRICAL UNIVALVED MOLLUSKS, CINCINNATI ARCH REGION 093

30

20

00 10

O

30

20

10

O

O

O

30

20

10

10 20 

APERTURE LENGTH, IN MILLIMETERS

O

10 20 

APERTURE WIDTH, IN MILLIMETERS

30

^ 20

10

O

Or

10 20 

UMBILICAL DIAMETER, IN MILLIMETERS

10 20 

APERTURE WIDTH, IN MILLIMETERS

FIGURE 25. Bivariate plots of measurements made on specimens of Cyrtolites (Cyrtolites) ornatus.

and 9-11, as well as the disjunct internal mold shown on 

plate 7, figure 1, are from one collection from Maysvillian 

strata at Cincinnati, Ohio. Contributing significantly to 

the difficulty of clearly defining the species is the variety

of preservational states in which it is commonly found. 

Most common are internal molds (pi. 7, fig. 1), which can 

be quite variable in appearance. Composite molds, in 

which the external mold is impressed upon the internal
094 CONTRIBUTIONS TO THE ORDOVICIAN PALEONTOLOGY OF KENTUCKY AND NEARBY STATES

mold as a result of early dissolution of the shell material 

while the enclosing sediment was still in a plastic state 

(pi. 6, figs. 6-8, 9-11), are not uncommon. Many of these 

composite molds, and even some internal molds, have a 

thin, hard, resistant coating over their surfaces. This 

coating may be the remains of the organic content of the 

shell, or could be the remnants of a micritized layer, as 

discussed by Bathurst (1966). Molds are commonly compressed and distorted, so their preserved morphology 

can vary greatly. Some calcitic casts are known (pi. 6, 

fig. 17); most specimens whose shells are preserved 

intact are encrusted by bryozoans (pi. 6, figs. 12-14, 15, 

16, showing Maysvillian and Richmondian specimens, 

respectively).

The New York specimens of the species that I examined (Conrad originally based the species on New York 

material) (pi. 6, figs. 4, 5) generally are somewhat 

smaller, narrower, and more carinate dorsally than specimens of C. (C.) ornatus from the Cincinnati arch region. 

Comprehensive examination of material from the different areas of Eastern North America where the species 

has been recognized could result in the subdivision of this 

well-known species into subspecies, or even into discrete 

species. However, there is a great deal of variation in the 

Cincinnati arch material, and it is best interpreted as 

intraspecific variation.

Cyrtolites (Cyrtolites) retrorsus Ulrich, 1897

Plate 5, figures 1-26; Plate 7, figures 11-16

Cyrtolites retrorsus Ulrich in Ulrich and Scofield, 1897, p. 861, pi. 62, 

figs. 32-37; Bassler, 1932, pi. 20, figs. 6, 7; Shimer and Shrock, 

1944, p. 439, pi. 175, figs. 24, 25.

Cyrtolites retrorsus fillmorensis Ulrich and Scofield, 1897, p. 862, pi. 

62, figs. 38, 39.

Diagnosis. Shell moderate in size (up to 23 mm long), 

relatively tightly coiled; aperture varying from quadrangular to rounded; rugae as narrow, sharply rounded 

ridges extending from umbilical shoulders to near dorsal 

crest; curved growth lines and revolving threads of near 

equal strength form distinct reticulate ornament pattern; 

median labral sinus broad and shallow.

Description. — Shell moderate in size for genus, broad 

in dorsal view, relatively tightly coiled, with fairly wide 

umbilicus. Aperture generally quadrangular to subquadrangular, but can be quite rounded; average length- 

/width ratio 0.85-0.90; dorsum carinate in juveniles, 

becoming angular to sharply rounded in adults; dorsal 

whorl slopes broadly convex, except near dorsal carina, 

where they may become concave briefly; umbilical shoulders angular to sharply rounded in juveniles, becoming 

sharply to broadly rounded in adults; ventral slopes 

generally flat to slightly concave, but can be slightly 

convex in inflated forms. Rugae well developed as low, 

narrow, rather sharply rounded, regularly spaced ridges

which extend from umbilical shoulders to near dorsal 

crest, generally weakening dorsally, and in some cases 

extending slightly onto the uppermost ventral slope; 

rugae generally lacking in juveniles. Distinct reticulate 

shell sculpture formed by coarse transverse raised 

growth lines that swing gently abaperturally across 

dorsal crest, and short revolving connecting threads of 

nearly equal strength that alternate from one growth 

increment to next. Labral sinus broad and shallow. Shell 

fairly thin; rugae can be very weakly expressed on shell 

interior.

Measurements.— Measurements, first of the type 

samples and then arranged by stratigraphic unit, are 

given in table 26. Figures 26 and 27 show graphs and 

measurements for specimens from the Logana and Grier 

Limestone Members of the Lexington Limestone, 

respectively.

Material.—The Logana Member (fig. 26) yielded the 

most and best preserved specimens of C. (C.) retrorsus 

in the USGS silicified collections. A total of 87 Logana 

specimens from four samples were measured for at least 

one parameter, depending on the quality and completeness of the preservation (USGS collections 5092-CO, 

6419-CO, 7791-CO, and D-1196). Other Logana samples 

containing this species were USGS collections 4865-CO, 

5073-CO, 5086-CO, and 5091-CO.

Nine samples from the Grier Limestone Member (fig. 

27) contained this species: USGS collections 4073-CO, 

4852-CO, 4876-CO, 4879-CO, 4883-CO, and 5067-CO, 

which contained measurable specimens, and 4874-CO, 

4880-CO, and 4929-CO, which contained only poor material.

It should be noted that correlation coefficients for sets 

of measurements graphed in figures 26 and 27 are high 

(greater than 0.90) and that the ratios and slopes of 

graphs for the two different stratigraphic collections are 

in close agreement with one another.

Types from Tennessee samples.—The only Tennessee 

specimens of this species examined were four of Ulrich 

and Scofield's (1897) syntypes (USNM 45789), which are 

large silicified casts ranging from well preserved to 

rather worn and are labeled "Trenton, near Nashville, 

Tennessee." One of these specimens is here designated 

the lectotype of the species and retains the museum 

number USNM 45789 (pi. 5, figs. 5-7). The other three 

specimens from the Tennessee syntype suite are designated paralectotypes and have been assigned museum 

numbers USNM 265901 (pi. 5, figs. 8-10), USNM 265902 

(pi. 5, figs. 11, 12), and USNM 265937 (not figured).

Types from Kentucky samples.— Ulrich and Scofield's 

(1897) syntypic suite included seven silicified casts and 

one internal mold labeled "Trenton (Flanagan), about 1 

mile south of Burgin, Kentucky." The stratigraphic unit 

"Flanagan" is no longer used, as it was found to include
MIDDLE AND UPPER ORDOVICIAN SYMMETRICAL UNIVALVED MOLLUSKS, CINCINNATI ARCH REGION 095

TABLE 26. Measurements (in millimeters) o/Cyrtolites (Cyrtolites) retrorsus

USNM No.

Type samples

45789

265902

265901

265899

265900

265938

45790

Lexington Limestone

Curdsville Limestone

387024

387024

265939

265939

265940

Logana Member

265942

265942

265942

265942

265942

265942

265942

265942

265942

265942

265942

265942

265942

265942

265942

265943

265943

265943

265943

265943

265943

265943

265943

265943

265943

265943

265943

265943

265942

265943

265943

265943

265943

265943

265943

265943

265943

265943

265943

265943

265943

265943

265943

265943

265943

265943

Shell 

length

23.20

20.50

22.45

16.05

21.00

12.95

12.20

Member

13.1

14.2

14.7

-

17.7

17.1

-

-

-

-

9.2

11.0

-

-

11.9

8.8

-

11.0

-

12.4

15.4

14.6

-

13.9

11.6

9.0

-

-

11.1

7.9

20.1

17.2

18.4

20.6

-

_

-

18.4

16.8

-

_

18.4

18.0

16.7

-

15.7

17.9

16.8

-

-

19.5

Aperture 

length

13.1

14.7

14.3

10.5

11.8

8.4

6.8

-

-

9.70

_

11.95

14.4

7.1

12.7

-

-

6.0

-

8.9

12.0

8.3

5.5

-

6.5

5.2

7.5

11.0

10.9

-

9.4

9.0

6.0

-

-

-

5.0

12.8

10.4

12.4

13.1

11.3

14.5

11.5

12.5

11.4

14.1

12.9

-

12.4

12.1

12.1

10.2

11.9

11.9

-

10.7

12.7

Aperture 

width

18.40

17.00

19.60

10.70

14.25

8.05

7.85

_

_

11.3

_

15.7

14.90

7.00

14.35

-

-

6.90

-

10.10

12.90

-

7.00

-

8.80

6.20

7.00

11.30

11.95

13.10

-

10.50

8.55

-

-

-

5.00

12.80

12.50

13.70

14.60

12.60

16.35

15.20

14.00

12.75

16.90

15.70

_

14.20

13.10

12.70

11.90

14.20

11.95

11.70

12.50

13.60

Umbilical 

diameter

10.15

9.80

9.20

7.30

11.30

6.80

6.20

8.8

_

8.4

_

-

10.00

-

-

-

-

5.00

6.05

-

-

5.50

5.00

-

4.50

-

6.50

8.10

8.05

8.10

7.90

8.30

5.55

10.00

7.60

6.60

4.70

9.35

_

9.10

10.50

-

_

-

9.40

8.95

-

_

10.10

9.40

9.20

-

9.00

8.80

-

7.70

-

9.30

Ventral 

width

4.4

4.3

3.7

3.1

3.3

2.3

2.0

2.7

2.2

2.7

-

3.5

5.2

-

-

-

-

1.0

-

-

-

-

_

-

-

-

2.0

3.1

3.1

3.0

2.8

2.5

_

-

-

-

-

3.7

-

3.6

3.8

-

-

-

-

3.4

-

-

-

-

2.5

-

2.7

-

-

3.2

-

3.9

Wave length 

of rugae

3.0

2.5

2.0

-

-

2.0

-

2.0

-

-

2.0

-

1.50

1.50

2.00

2.00

1.75

_

-

-

-

-

1.50

2.00

2.00

-

-

1-1.50

1-2.0

1-1.5

-

-

_

2.0

-

-

-

1.5-2.3

2.0

-

2.0

-

1.5-2.0

2.0

2.0

-

-

1-2

1.5-2.0

2.0

2.0

-

1.5-2.0

-

-

-

-

-

No. of 

growth lines 

per mm

6

_

5

5-6

5

_

-

7

-

-

4

5

4

3^

2-3

3

3^

4

-

3

4

5

_

4

^4

4

5

4

4-5

5

4-5

4-5

4

4-5

4

^4

4

5

5

5

5-6

4

4

^4

5

-

5

5-6

-

5

4-5

-

4-5

-

4-5

-

-

5
096 CONTRIBUTIONS TO THE ORDOVICIAN PALEONTOLOGY OF KENTUCKY AND NEARBY STATES

TABLE 26. Measurements (in millimeters) o/Cyrtolites (Cyrtolites) retrorsus Continued

USNM No.

265943

265943

265943

265943

265943

265943

265943

265943

265943

265943

265943

265943

265943

265943

265943

265943

265943

265943

265943

265943

265943

265943

265943

265943

265943

387025

387025

387025

387025

387025

387025

387025

265953

265953

265953

265953

Shell 

length

18.0

16.9

16.0

12.1

13.6

_

17.7

13.1

10.4

-

_

16.1

-

-

-

15.0

18.3

15.6

14.8

18.5

17.5

19.6

15.3

-

7.9

17.6

-

18.2

13.4

-

17.7

15.0

12.7

14.8

8.3

9.3

Aperture 

length

11.6

11.6

11.0

8.2

8.4

_

11.2

8.1

6.5

10.2

_

10.5

-

-

8.0

10.7

13.5

10.7

10.4

13.2

11.2

13.4

9.6

10.4

5.2

10.4

4.7

11.2

8.3

10.4

11.1

9.5

8.5

9.5

5.2

5.4

Aperture 

width

12.40

13.50

12.20

8.40

9.65

12.90

11.75

8.90

7.40

12.10

11.30

12.30

10.40

7.40

9.25

12.45

13.55

11.40

11.40

14.00

12.90

13.50

10.95

11.40

6.15

12.9

5.0

12.8

8.4

11.2

14.1

12.4

9.2

9.8

5.8

6.9

Umbilical 

diameter

9.00

9.40

7.70

7.30

6.60

8.90

8.80

6.50

6.20

8.20

7.90

-

8.80

5.50

-

_

9.40

_

8.10

8.80

9.00

_

7.40

-

3.80

9.0

4.8

9.2

6.4

-

10.2

7.9

5.8

8.0

3.9

4.0

Ventral 

width

3.4

2.5

2.9

1.8

2.4

3.0

3.8

2.4

_

-

2.5

-

2.7

2.0

-

_

3.5

3.2

3.4

4.5

3.4

-

3.1

-

-

_

_

3.5

3.0

-

_

3.0

2.8

-

1.4

2.6

Wave length 

of rugae

_

-

-

-

2.0

_

-

1.5

_

-

_

-

-

-

-

_

-

-

1.5-2.0

2.0

1.5-2.0

-

-

-

-

2.0

-

2.0

_

-

_

1.5-2.0

1-1.5

1.5-2.0

-

-

No. of 

growth lines 

per mm

5

3

4-5

5

4-5

-

5

5

5

4

-

4

-

3-4

4-5

5

4

6

4

4

5

4

5

-

4

4

-

3

4

3^

_

4

-

4-5

-

-

Grier Limestone Member

387026

387026

387027

387027

265958

265958

265958

265958

265958

265958

265958

265958

387028

387028

387029

387029

265973

265973

265973

265973

265973

265973

Millersburg Member

265968

265968

12.2

7.3

7.0

11.2

9.3

14.6

13.1

11.8

_

-

9.7

11.7

4.0

-

7.0

_

15.8

17.0

16.2

13.3

6.0

11.0

18.8

9.9

7.0

5.0

4.3

5.5

4.9

_

8.5

7.4

4.7

4.5

6.1

6.7

2.3

3.7

4.4

5.5

10.6

10.3

11.4

9.0

3.5

7.3

11.5

5.9

8.8

7.0

4.4

8.6

7.1

12.4

11.2

9.4

8.0

6.5

8.2

8.7

2.9

3.7

5.1

7.6

11.9

12.6

12.0

10.4

3.6

9.0

14.7

7.9

7.0

4.5

4.2

5.5

5.3

7.6

6.1

_

-

-

5.1

5.8

2.0

-

3.7

_

8.5

8.1

8.4

7.1

3.8

5.6

11.1

5.9

3.0

_

_

_

2.2

_

2.6

_

_

-

_

-

1.0

-

-

_

3.1

3.9

3.8

2.4

_

2.2

3.8

2.0

_

_

_

1.5

-

_

_

-

-

-

-

2.0

-

-

-

_

1.5-2.0

-

1.5-2.0

1.5-2.0

-

1.5-2.0

2.0

-

_

_

5

_

-

_

-

-

-

-

4

3^

-

-

-

_

4-5

5

4-5

5-6

5

5

4-5

4
MIDDLE AND UPPER ORDOVICIAN SYMMETRICAL UNIVALVED MOLLUSKS, CINCINNATI ARCH REGION 097 

TABLE 26. Measurements (in millimeters) o/Cyrtolites (Cyrtolites) retrorsus Continued

USNM No.

Millersburg Member Continued 

265968 

265968

Perryville Limestone Member 

265959 

265959

Shell 

length

-

6.2

17.8

Aperture 

length

-

4.0 

12.8

Aperture 

width

14.0

7.8

4.0 

15.0

Umbilical 

diameter

11.0 

5.3

3.7

8.0

Ventral 

width

-

1.6

3.8

Wave length 

of rugae

-

-

No. of 

growth lines 

per mm

-

4

different units in different areas, but the USGS map of 

the Danville quadrangle (Cressman, 1972) shows the 

designated area as exposing the Curdsville, Grier, and

Perryville Limestone Members of the Lexington Limestone. All of these specimens are here designated paralectotypes. The five paralectotypes not figured in this

20

10

20

10

o o

0 10 20 

APERTURE LENGTH, IN MILLIMETERS

10 20 

UMBILICAL DIAMETER, IN MILLIMETERS

20

10

20

10

O,b

o

10 20 

APERTURE WIDTH, IN MILLIMETERS

10 20 

APERTURE WIDTH, IN MILLIMETERS

FIGURE 26. Bivariate plots of measurements made on specimens of Cyrtolites (Cyrtolites) retrorsus from the Logana

Member of the Lexington Limestone in central Kentucky.
098

30 i20

10

CONTRIBUTIONS TO THE ORDOVICIAN PALEONTOLOGY OF KENTUCKY AND NEARBY STATES

30 i20

O

10

O

10 20 

APERTURE LENGTH, IN MILLIMETERS

30 10 20 

APERTURE WIDTH, IN MILLIMETERS

30

30-

20

10

30

20

10

O

10 20 

UMBILICAL DIAMETER, IN MILLIMETERS

30 10 20 

APERTURE WIDTH, IN MILLIMETERS

30

FIGURE 27. Bivariate plots of measurements made on specimens of Cyrtolites (Cyrtolites) retrorsus from the Grier Limestone Member of the

Lexington Limestone in central Kentucky.

study remain under the original museum number USNM 

45790; the other three are figured here and are given the 

new numbers USNM 265938 (pi. 5, figs. 1, 2), USNM 

265899 (pi. 5, figs. 3, 4), and USNM 265900 (pi. 5, fig. 13). 

Distribution.—In the USGS silicified collections, C. 

(C.) retrorsus was recognized in the Curdsville Limestone (5022-CO, 5023-CO, 5080-CO, 5100-CO), Logana 

(D-1196-CO, 4865-CO, 5073-CO, 5086-CO, 5091-CO,

5092-CO, 6419-CO, 7791-CO), Grier Limestone (4073- 

CO, 4852-CO, 4876-CO, 4879-CO, 4880-CO, 4883-CO, 

5067-CO), Millersburg (7344-CO, 7353-CO, 7455-CO), 

and Perryville Limestone (5015-CO) Members of the 

Lexington Limestone (Kirkfieldian-Shermanian). The 

most and best preserved specimens came from the 

Logana Member; fairly good specimens came from 

the Grier Limestone Member; and the other members of
MIDDLE AND UPPER ORDOVICIAN SYMMETRICAL UNIVALVED MOLLUSKS, CINCINNATI ARCH REGION 099

the Lexington Limestone contained few specimens, and 

those are fair to poor in preservation.

Two calcitic specimens of C. (C.) retrorsus (USNM 

265909 and 265910; pi. 7, figs. 11-13, 14-16), which are 

well preserved but have variable form, came from the 

Edenian portion of the Kope Formation at Covington,

Ky.

Thus, C. (C.) retrorsus is known in Kentucky from the 

Lexington Limestone (Kirkfieldian-Shermanian) to the 

Kope Formation (Edenian). A supposed subspecies (C. 

retrorsus fillmorensis) was described by Ulrich and 

Scofield (1897) from Blackriveran strata of Minnesota. 

Because this supposed "subspecies" is very poorly known 

and does not seem clearly distinct from the stock as 

known in the type area, and because C. (C.) retrorsus is 

shown here to have a variable shell morphology, the 

Minnesota "subspecies" is synonymized with C. (C.) 

retrorsus,

In Tennessee, Bassler (1932) and Wilson (1949) 

reported the species from (1) the Ctenodonta member of 

the Hermitage Formation, (2) the Bigby, Cannon, and 

dove-colored facies of the Bigby-Cannon Limestone, and 

(3) the upper Catheys Formation. The first two occurrences are Kirkfieldian-Shermanian in age, and the third 

is either Shermanian or Edenian in age, probably the 

latter (Sweet and Bergstrom, 1976, text-fig. 3).

Comparison. —C. (C.) retrorsus is quite variable in 

shape, but, as shown in figures 26 and 27, its whorl 

dimensions are notably consistent. The only other 

Kirkfieldian-Shermanian species currently recognized in 

North America is C. (P.) subplanus (pi. 7, figs. 26-35); it 

can be readily distinguished by its noncarinate dorsal 

crest, its lack of rugae, and its much weaker growth 

lines, with revolving threads absent or only barely 

discernible, so that no reticulate sculpturing is obvious.

The latest Shermanian-Edenian species, C. (C.) claysferryensis n. sp. (pi. 8, figs. 11-20), is very similar to C. 

(C.) retrorsus, but the former species has a slightly wider 

aperture and sharply angular umbilical shoulders. In the 

Edenian, juveniles of C. (C.) retrorsus might easily be 

confused with C. (P.) carinatus (pi. 7, figs. 18-25), which 

is a small species; these two should be distinguishable by 

the difference in the number of whorls present in the 

juveniles of the former versus the adults of C. (P.) 

carinatus.

Specimens of C. (C.) retrorsus (pi. 7, figs. 11-16) from 

the Edenian portion of the Kope Formation vary in shell 

form, but the character of their surface markings suggests that they are conspecific with the specimens from 

Kirkfieldian-Shermanian-age strata.

Discussion. —In their discussion of the species C. 

retrorsus, Ulrich and Scofield (1897, p. 861, 862) were 

confident of its specific distinctiveness, but they 

expressed concern about the inclusion of some specimens, particularly those from the basal beds of what they 

called the Trenton Group in Kentucky and Tennessee. 

They stated: "So far as the form of the shell and the 

volutions are concerned, the specimens in question certainly agree very closely with C. retrorsus, and if appearances are not deceptive, they are like it also in the 

backward swing of the surface markings. The evidence at 

hand, therefore, seems to indicate that all of the Tennessee and Kentucky specimens hitherto referred to C. 

ornatus really belong to C. retrorsus."

It is not surprising that Ulrich and Scofield were 

apprehensive about this species, because it exhibits a 

high degree of intraspecific variation in shape. It is 

recognized mainly on the basis of its distinct reticulate 

ornament pattern (in adult shells), the gentle curving of 

its growth lines over the dorsal crest of the shell, and its 

aperture height/width ratio regardless of the apertural 

outline. As shown on plate 5, figures 14, 18, and 22, the 

aperture shape of C. (C.) retrorsus can vary from quadrangular to nearly circular in a single population. All 

three of these figured specimens are from a single sample 

from the Logana Member of the Lexington Limestone 

(USGS sample 6419-CO) in central Kentucky. This sample is considered to represent a single population because 

of (1) its occurrence in a single sampled bed, (2) the 

presence of a gradational growth series, and (3) the 

quality of preservation, which suggests very little transport. It appears that this intraspecific variability in 

whorl shape is largely genetic, rather than ecophenotypic, in origin. However, there also appears to be 

ecophenotypic variation between populations from different stratigraphic units. For example, when some of 

the more rounded, inflated forms from the Logana 

Member of the Lexington Limestone (pi. 5, figs. 18-25) 

are compared directly with more angular forms, such as 

Ulrich and Scofield's (1897) type specimens from Tennessee (pi. 5, figs. 5-12), there appear to be two possible 

species. However, Ulrich and Scofield's type specimensfrom Kentucky (pi. 5, figs. 1^4, 13) are intermediate in 

form, as are many other specimens, including some of the 

Logana specimens (pi. 5, figs. 14-17). Such marked 

variation makes the formulation of a concise description 

of the species difficult. Equally frustrating are ontogenetic changes in shell form. Most juvenile specimens are 

quite angular, some even being carinate dorsally and 

laterally, and the dorsal slopes can be slightly concave. These small, smooth, angular specimens resemble 

C. (P.) carinatus, but can be distinguished by their 

narrower form and fewer whorls. This situation is not 

uncommon when dealing with isotrophic molluscan univalves. Ulrich and Scofield (1897) claimed that immature 

specimens of Cyrtolites and Carinaropsis are virtually 

indistinguishable. Thein and Nitecki (1974, p. 55) encountered a similar problem with Chesterian bellerophontids,
0100 CONTRIBUTIONS TO THE ORDOVICIAN PALEONTOLOGY OF KENTUCKY AND NEARBY STATES

TABLE 27. Measurements (in millimeters) o/Cyrtolites (Cyrtolites) claysferryensis

USNM No.

265923

265924

265925

265973

265973

265973

265973

265973

265970

265970

265970

265970

265972

265976

Shell 

length

16.9

15.0

19.0

16.1

-

_

14.1

16.9

17.3

16.7

15.8

15.1

13.5

15.2

Aperture 

length

9.7

9.0

12.8

10.4

10.4

12.2

10.7

11.5

13.1

10.9

10.7

-

7.6

-

Aperture 

width

13.0

12.7

16.2

14.4

14.6

13.8

12.5

16.4

17.1

15.8

13.0

13.2

10.5

-

Umbilical 

diameter

9.1

8.6

9.5

8.1

-

11.2

_

8.0

10.1

8.0

8.9

9.1

7.7

6.9

Ventral 

width

3.4

3.0

4.5

3.6

-

_

_

3.5

4.7

3.7

2.8

3.0

3.0

3.6

Wave length 

of rugae

1.5-2.0

1.5

2.0-3.0

1.5-2.0

2.0

_

_

-

-

2.0

2.0

2.0

1.5

1.5-2.0

No. of 

growth lines 

per mm

4

5^6

4

-

5

_

_

-

5^6

-

4

4-5

4

5^6

finding that the differentiation of three subgenera 

of Knightites by looking at immature specimens was 

impossible.

During adult and gerontic growth, shell form may 

change continuously. Some shells retain some of the 

angularity of youth (pi. 5, fig. 11), but the aperture 

broadens and the dorsal whorl slopes become convex. 

Other shells lose their angularity completely in the final 

volution, with the dorsal crest becoming almost rounded, 

so that a more inflated shell results (pi. 5, figs. 22-25).

Also, the coarseness of the rugae can be quite variable, 

and does not vary in concert with the degree of angularity or roundness of the shell. For example, the lectotype 

(pi. 5, figs. 5-7) and a paralectotype (pi. 5, figs. 8-10) 

from the same collection from Tennessee are very similar 

in general form, but the former specimen has more 

distinct ridgelike rugae, similar to some of the inflated 

Logana forms (pi. 5, figs. 22-25). Regardless of shell 

form, all adult specimens of the species have distinct 

reticulate shell sculpturing, with abaperturally curved 

growth lines reflecting a broad, shallow, dorsal labral 

sinus.

C. (C.) retrorsus apparently gave rise to a fairly 

diverse group of Late Ordovician descendants. The two 

specimens of C. (C.) retrorsus from the Edenian Kope 

Formation (pi. 7, figs. 11-13,14-16) previously discussed 

may represent the last surviving populations of C. (C.) 

retrorsus in the study area, possibly struggling for 

existence under the more turbid conditions of the early 

Cincinnatian seas.

Cyrtolites (Cyrtolites) claysferryensis new species

Plate 4, figures 15-17; Plate 8, figures 11-20

Diagnosis. Shell moderate in size (up to 19 mm long), 

angular; aperture wide and subquadrangular, dorsal 

crest and umbilical shoulders sharply angular, dorsal

slopes convex, ventral slopes concave; reticulate ornament distinct; sinus shallow.

Description. — Shell moderate in size for genus, broad 

angular; coiling moderately loose; umbilicus wide and 

rather deep. Aperture subquadrangular and broad, aperture height/width ratio 0.76; dorsum carinate in juveniles, becoming sharply angular in adults; dorsal slopes 

broadly convex, draping slightly at umbilical shoulders in 

some large specimens; umbilical shoulders sharply angular; ventral slopes distinctly concave. Rugae distinct, 

thin, regularly spaced, forming small nodes at umbilical 

shoulder and extending dorsally for about three-fourths 

the width of dorsal slope; rugae do not influence ventral 

slopes. Growth lines swing quite gently abaperturally 

over dorsal crest of shell, reflecting a broad, shallow, 

dorsomedian labral sinus; short, alternating, revolving 

threads of near equal prominence, resulting in distinct 

reticulate surface sculpturing.

Measurements.— Measurements of C. (C.) claysferryensis are listed in table 27 and shown graphically in 

figure 28. For all parameters plotted, growth appears to 

be highly coordinated; correlation coefficients are 

0.97-0.98. All regression lines approach the graph origins quite closely.

Types.— The new species was found in the following 

USGS silicified samples from the Clays Ferry Formation: 6143-CO, 6990-CO, 7343-CO, 7348-CO, 7349-CO, 

7350-CO, 7458-CO, 7461-CO, and 7812-CO. The specimen here designated the holotype for C. (C). claysferryensis is USNM 265924 (pi. 8, figs. 14-18) (shell length 

15.0 mm; aperture length 9.0 mm; aperture width 12.7 

mm) from USGS 6143-CO, from the upper tongue of the 

Clays Ferry Formation in a road exposure on the eastern 

side of Kentucky Route 982, 0.4 mi south of the junction 

of Kentucky Routes 32, 36, and 982 in Cynthiana, Ky. 

Two silicified paratypes are also figured, USNM 265923 

(pi. 8, figs. 19, 20), from the same collection as the
MIDDLE AND UPPER ORDOVICIAN SYMMETRICAL UNIVALVED MOLLUSKS, CINCINNATI ARCH REGION 0101

20

10

0

Oi o

20

10

o

o

0 10 20 

APERTURE LENGTH, IN MILLIMETERS

10 20 

APERTURE WIDTH, IN MILLIMETERS

20

10

20

10

O

10 20 

UMBILICAL DIAMETER, IN MILLIMETERS

10 20 

APERTURE WIDTH, IN MILLIMETERS

FIGURE 28. Bivariate plots of measurements made on specimens of Cyrtolites (Cyrtolites) claysferryensis new species 

from the Clays Ferry Formation in north-central Kentucky.

holotype, and USNM 265925 (pi. 8, figs. 11-13), from 

USGS sample 6990-CO. About 60-70 specimens and 

fragments are present in the silicified collections, but 

only 14 were sufficiently preserved to be measured.

Two calcitic specimens collected by me are also designated paratypes. Paratype USNM 265959 (pi. 4, figs. 15, 

16) was found in a mollusk bed composed predominantly 

of small pelecypods and gastropods, in the Kope Formation at the Carrollton, Ky., exit from Interstate 1-71 

(locality KY-1). Paratype USNM 315609 (pi. 4, fig. 17) 

was found in a mollusk bed dominated by Sinuites 

granistriatus in the lower Kope Formation, about 10 ft 

above the contact with the Point Pleasant Tongue of the 

Clays Ferry Formation, just north of Ohio Route 52

along the north shore of the Ohio River, at Bear Creek 

Quarry, between Neville and Chilo, Ohio (locality OH-1).

Distribution.—The new species is known from the 

lower Kope Formation (Edenian) in Kentucky and southwestern Ohio.

Comparison. — C. (C.) claysferryensis is very similar 

to some of the more angular forms of C. (C.) retrorsus, 

but it differs in several ways: its aperture height/width 

ratio is smaller, reflecting its relatively broader aperture; its umbilical shoulders are consistently more 

sharply angular, this impression being accentuated by 

the concave slopes of the broad umbilicus; its growth 

lines generally do not swing abaperturally as deeply 

(reflecting a shallower sinus) (pi. 8, fig. 18); and its rugae
0102 CONTRIBUTIONS TO THE ORDOVICIAN PALEONTOLOGY OF KENTUCKY AND NEARBY STATES

are generally thinner and sharper (pi. 8, fig. 14), and 

never extend onto the upper ventral slopes. C. (C.) 

claysferryensis is also quite similar in some respects to 

C. (C.) hornyi n. sp. from the Richmondian Dillsboro 

Formation of southeastern Indiana, but the latter species 

has flatter whorl slopes (pi. 8, fig. 1) and straight growth 

lines (pi. 8, fig. 2), and it attains a somewhat larger size 

(pi. 8, figs. 1-4).

Discussion. — It is clear that C. (C.) claysferryensis 

evolved directly from C. (C.) retrorsus, which not only 

closely resembles the former species in many morphological features, but also immediately precedes and partially 

overlaps it stratigraphically. C. (C.) retrorsus thrived in 

the dominantly carbonate environments of the upper 

Middle Ordovician Lexington Limestone, and apparently 

only barely survived into the overlying Edenian Kope 

Formation. C. (C.) claysferryensis first appears in the 

Clays Ferry Formation, which straddles the MiddleUpper Ordovician boundary and is adjacent to both the 

upper Lexington Limestone and the lower Kope Formation, having more shale than the former and less than the 

latter. The new species is also recognized in the Kope 

Formation. Apparently, the evolution of a wider, more 

angular aperture, with a shallower dorsomedian sinus, 

helped C. (C.) claysferryensis survive the more turbid 

conditions of the early Cincinnatian seas. This apertural 

modification may have enabled better channeling of 

currents through the mantle cavity and thus prevented 

clogging of the ctenidia by fine sediments, or may have 

assisted in supporting the shell on softer substrates.

It should be noted that whereas the dorsal slope of C. 

(C.) retrorsus is relatively well developed, that of C. (C.) 

claysferryensis is somewhat shallower, and later species 

lack the sinus altogether. It is difficult to understand 

why this lineage would show this trend toward reduction 

of a labral sinus, because an emargination is known to be 

highly efficient as an exhalant canal in pleurotomariacean 

gastropods, and it would seem to be likewise useful in 

monoplacophorans. Perhaps its absence allowed a tighter 

seal when the animal clamped down onto the substrate 

for protection.

As noted above, C. (C.) claysferryensis is similar to C. 

(C.) hornyi from the Richmondian part of the Dillsboro 

Formation of Indiana. The species inhabited similar 

depositional environments of alternating carbonate and 

shale sedimentation, and C. (C.) hornyi is likely the end 

product of slow intrafacies evolution, but at present 

intermediate forms are not known.

Cyrtolites (Cyrtolites) minor Ulrich, 1897

Plate 7, figures 2-10

Cyrtolites ornatus minor Ulrich in Ulrich and Scofield, 1897, p. 860, pi. 

62, figs. 30, 31; Weller, 1903, p. 174, 175, pi. 12, figs. 6, 7.

Diagnosis. Shell small (up to 13.5 mm long), narrow; 

dorsal carina high and sharp, umbilical shoulders 

rounded to narrowly rounded; rugae distinct; growth 

lines pass over dorsal carina with little or no deflection; 

reticulate ornament distinct.

Description. — Shell small and narrow in form, umbilicus fairly wide. Aperture subquadrangular; dorsal carina 

well developed, high, and sharp; dorsal slopes concave 

for short distance near dorsal carina, becoming convex 

through most of their extent; umbilical shoulders 

rounded to narrowly rounded; ventral slopes flat to 

slightly concave. Rugae well developed, particularly at 

umbilical shoulder, over which they extend onto upper 

ventral slope; rugae thick and rounded at umbilical 

shoulder, becoming weaker dorsally to near dorsal carina. Growth lines generally at right angle to dorsal 

carina, but may be slightly deflected abaperturally; 

revolving threads of near equal strength to growth lines, 

together forming a distinct reticulate shell sculpture.

Measurements.— Measurements of three specimens, 

including the holotype, of C. (C.) minor are listed in table 

28 and shown graphically in figure 29. The fourth set of 

measurements listed in table 28 were taken from 

Welter's (1903, pi. 12, figs. 6, 7) figure of the species from 

New Jersey. Although only a few specimens were available for measurement, growth appears highly coordinated, with high correlation values, but the regression 

lines do not approach the graph origins very closely. It is 

likely that this picture would change greatly with the 

measurement of more specimens.

Material.—Only three specimens of C. (C.) minor are 

known from the study area, the holotype (USNM 45787), 

a specimen from the Kope Formation (UC 19668), and a 

specimen from the Fairview Formation collected by 

Steve Felton of Cincinnati (UC 44275). All three specimens are calcitic casts, and the Kope specimen in 

encrusted by bryozoans.

Distribution.-The holotype (USNM 45787) is from 

the Clitambonites bed of the Prosser Formation at 

Cannon Falls, Minn., which Ulrich and Scofield (1897) 

considered the base of the "Trenton Series" and which 

Templeton and William (1963, figs. 19A-B) considered 

the basal beds and formation of the Galena Group. Weiss 

(1957) split off the lower Prosser into a new unit, the 

Cummingsville Formation, which Sweet and Bergstrom 

(1976, text-fig. 3) considered Kirkfieldian-Shermanian in 

age. Ross and others (1982) listed the Cummingsville and 

Prosser Members of the Galena Formation as Kirkfieldian to Shermanian in age. Weller (1903) reported the 

species from the "Trenton Series" of New Jersey. In 

Kentucky and Ohio, C. (C.) minor is known from the 

Kope Formation (Edenian) and the Fairview Formation 

(Maysvillian) in the vicinity of Cincinnati, Ohio.
MIDDLE AND UPPER ORDOVICIAN SYMMETRICAL UNIVALVED MOLLUSKS, CINCINNATI ARCH REGION 0103 

TABLE 28. Measurements (in millimeters) o/Cyrtolites (Cyrtolites) minor

Museum No.

USNM 45787 

UC 19668 

UC 44275 

Weller (1903)

Shell 

length

9.8 

13.5 

12.0 

11.5

Aperture 

length

6.4 

8.0 

7.0

Aperture 

width

6.2 

7.0 

6.5

8.5

Umbilical 

diameter

4.7 

6.2 

6.5

Ventral 

width

1.4 

2.0 

2.0

Wave length 

of rugae

1.0 

2.0 

2.0

Comparison. — C. (C.) minor is quite similar in form to 

C. (C.) ornatus, of which it was originally considered a 

"variety" by Ulrich and Scofield (1897). However, C. (C.) 

minor is much smaller than C. (C.) ornatus, and there 

can be no doubt that the specimens assigned to C. (C.) 

minor are adults and not juveniles of the C. (C.) ornatus, 

as they possess at least two whorls and have welldeveloped rugae and reticulate shell sculpturing. Two 

observations have prompted me to regard C. (C.) minor 

as a distinct species. First, it is consistent in its forms 

over a wide geographic area (Minnesota to Kentucky to 

New Jersey) and through a distinct stratigraphic range

(Kirkfieldian-lower Maysvillian). Second, besides its 

smaller size, it differs from C. (C.) ornatus in its slightly 

narrower shell form, and by having the growth lines 

slightly deflected abaperturally over the dorsal crest (at 

least in the geologically older forms of the species), 

showing a possible transitional relationship with C. (C.) 

retrorsus.

It is easy to confuse C. (C.) minor with C. (P.) 

carinatus (pi. 7, figs. 18-25), as the general shell form of 

the two species can be quite similar. Both are small 

species having distinct dorsal carinae, and the two occur 

in the same stratigraphic interval (Edenian) in the study

20-

^ 10

20

0 10 20 

APERTURE LENGTH, IN MILLIMETERS

20-

^ 10

0 10 20 

UMBILICAL DIAMETER, IN MILLIMETERS

0 10 20 

APERTURE WIDTH, IN MILLIMETERS

20-

10

0 10 20 

APERTURE WIDTH, IN MILLIMETERS

FIGURE 29. Bivariate plots of measurements made on specimens of Cyrtolites (Cyrtolites) minor.
0104 CONTRIBUTIONS TO THE ORDOVICIAN PALEONTOLOGY OF KENTUCKY AND NEARBY STATES

TABLE 29. Measurements (in millimeters) o/Cyrtolites (Cyrtolites) hornyi

USNM No.

265920

265921

265922

265978

Shell 

length

26.9

22.7

22.9

12.8

Aperture 

length

17.9

14.5

15.0

8.65

Aperture 

width

21.9

17.2

18.1

10.4

Umbilical 

diameter

14.6

11.35

13.0

7.0

Ventral 

width

2.4

2.7

-

-

Wave length 

of rugae

3.0

3.0

2-3

-

No. of growth 

lines per mm

4

4-5

4

-

area. C. (P.) carinatus differs in lacking rugae and a 

distinct reticulate ornament, as well as in having sharply 

angular to carinate umbilical shoulders.

Discussion.—C. (C.) minor may be an intermediate 

species between C. (C.) retrorsus and C. (C.) ornatus. 

Not only does the stratigraphic range of C. (C.) minor 

overlap with the upper part of the stratigraphic range of 

C. (C.) retrorsus and the lowest part of the range of C. 

(C.) ornatus, but the curvature of the growth lines of C. 

(C.) minor is also intermediate between these two other 

species. The holotype (pi. 7, figs. 2-4) of C. (C.) minor 

from the uppermost Champlainian strata (Prosser Formation) of Minnesota has surface markings that are 

essentially identical with those of C. (C.) ornatus, 

"except the transverse striae in crossing the dorsal 

carina are sometimes bent slightly backward" (Ulrich 

and Scofield, 1897, p. 861). Weller (1903, p. 174), in the 

description of his specimens from the "Trenton" of New 

Jersey, noted that the growth lines ran "almost straight 

across the volutions." The Cincinnatian (Edenian and 

lower Maysvillian) specimens from the present study 

area appear to show no abapertural deflection of the 

growth lines dorsally (pi. 7, figs. 5-7, 8-10). Therefore, 

there appears to be a gradual evolutionary trend within 

the species C. (C.) minor toward the final and complete 

reduction of an apertural sinus in the C. (Cyrtolites) 

lineage.

Cyrtolites (Cyrtolites) hornyi new species

Plate 8, figures 1-10

Diagnosis.— Shell large (up to 27 mm long), with 

broad, angular shell form and relatively rapid rate of 

whorl expansion; aperture diamond shaped, dorsally and 

laterally sharply angular, dorsal and ventral slopes 

nearly flat; rugae thin, growth lines not deflected anteriorly over dorsum, revolving lines weak.

Description.— Shell relatively large for genus, having 

broad, angular form; relatively rapid rate of whorl 

expansion, whorls barely contiguous, even showing 

slight tendency toward uncoiling in largest specimens; 

adult shell with two or three whorls. Aperture quadrangular and diamond shaped; dorsal and ventral slopes 

slightly concave in juveniles, becoming nearly flat in 

adults; dorsum and umbilical shoulders slightly carinate 

in juveniles, becoming sharply angular in adults. Rugae

thin, distinct, with regularly spaced ridges, in many 

specimens forming nodes along umbilical shoulders and 

extending to near dorsal crest. Growth lines directed 

straight over dorsal crest of shell without any abapertural deflection, stronger than revolving connecting 

threads, so that reticulate surface sculpturing is not 

conspicuous.

Measurements.—Measurements of C. (C.) hornyi are 

listed in table 29 and shown graphically in figure 30. All 

parameters plotted for this species have very high correlation coefficients (nearly perfect), and the regression 

lines approach the graph origins closely. Although only 

four specimens were measurable, the species appears to 

have nearly isometric growth, as the ratios between the 

plotted parameters stay constant throughout growth.

Type material. —C. (C.) hornyi n. sp. is known from 

about 16 specimens, most of which are fragmentary, 

from USGS silicified collection 6139-CO, which is from 

the upper Dillsboro Formation along the southern bank 

of Salt Creek, 900 ft upstream from the covered bridge 

on Enochsburg-Oldenburg Road, in the New Point quadrangle, Indiana. The holotype (USNM 265920) (shell 

length 26.9 mm; aperture length 17.9 mm; aperture 

width 21.9 mm) is here designated the specimen shown 

on plate 8, figures 1-4. Two paratypes are also figured 

(USNM 265921 and 265922 on pi. 8, figs. 5-10). All other 

paratypes are placed together under the number USNM 

265978.

Distribution.—The new species is known only from 

the single locality given above in the Richmondian part 

(upper Upper Ordovician) of the Dillsboro Formation of 

southeastern Indiana. The single sample came from the 

part of the Dillsboro Formation previously termed the 

"Liberty Formation" (and even earlier termed "the Strophomena beds"). This portion of the formation is 

referred to herein as the "Liberty biofacies."

Comparison. —C. (C.) hornyi is clearly distinguishable from all other Richmondian species of Cyrtolites. C. 

(C.) ornatus has a somewhat narrower, more rounded 

shell form, and its rugae are much more strongly 

expressed (pi. 6, figs. 1-18). C. (C.) disjunctus is even 

more distinct, being disjunctly coiled and even more 

rounded than C. (C.) ornatus (pi. 6, figs. 19-22). C. (C.) 

hornyi (pi. 8, figs. 1-10) most closely resembles C. (C.) 

claysferryensis (pi. 8, figs. 11-20). However, the whorl 

slopes of C. (C.) hornyi are much flatter, giving a
MIDDLE AND UPPER ORDOVICIAN SYMMETRICAL UNIVALVED MOLLUSKS, CINCINNATI ARCH REGION 0105

30 r

20

10

30 i20

10

10 20 

APERTURE LENGTH, IN MILLIMETERS

10 20 

APERTURE WIDTH, IN MILLIMETERS

30 r

20

10

30 i20

10

10 20 

UMBILICAL DIAMETER, IN MILLIMETERS

10 20 

APERTURE WIDTH, IN MILLIMETERS

FIGURE 30. Bivariate plots of measurements made on specimens of Cyrtolites (Cyrtolites) hornyi new species.

distinctly diamond shaped aperture, and its growth lines 

are straight rather than deflected abaperturally over the 

dorsal crest, demonstrating the lack of an apertural sinus 

as is clearly present in C. (C.) claysferryensis. Figures 

28 and 30 show that the modes of growth in the two 

species are also very similar, the most striking difference 

being in the larger size attained by the Richmondian 

species.

Discussion. —C. (C.) hornyi almost certainly is 

descended from C. (C.) claysferryensis. Not only are the 

two species quite similar morphologically, but they 

apparently inhabited similar depositional environments 

(see "Discussion of subgenera"), which were characterized by intermittent carbonate and shale deposition. 

Both stratigraphic units in which the respective species 

are found are characterized in part by the presence of
0106 CONTRIBUTIONS TO THE ORDOVICIAN PALEONTOLOGY OF KENTUCKY AND NEARBY STATES 

TABLE 30. Measurements (in millimeters) o/Cyrtolites (Cyrtolites) disjunctus

USNM No.

45785

Shell 

length

23.0

Aperture 

length

12.1

Aperture 

width

11.0

Umbilical 

diameter

11.2

Ventral 

width

-

Wave length 

of rugae

2-3

No. of 

growth lines 

per mm

4-5

large, flat strophomenid brachiopods. Although it is not 

known whether either species inhabited these brachiopod communities, the widespread presence of these 

environments indicates a similar depositional system 

operating during deposition of the formations. I collected 

C. (C.) claysferryensis from two localities, one in the 

Clays Ferry Formation and one in the lower Kope 

Formation, and in both places the species was restricted 

to thin horizons characterized by almost entirely molluscan assemblages. Given our current knowledge, and 

considering the apparent rarity of C. (C.) hornyi and 

the lack of known intermediate Maysvillian forms, 

it is inferred that this species was more specialized 

in its habits than the more abundant MaysvillianRichmondian-agespecies C. (C.) ornatus,

Cyrtolites (Cyrtolites) disjunctus Ulrich and Scofield, 1897 

Plate 6, figures 19-22

Cyrtolites disjunctus Ulrich and Scofield, 1897, p. 864, pi. 62, figs. 48,

49. 

[?] Cyrtolites cf. C. disjunctus Ulrich and Scofield, Wilson, 1951, p. 23,

pi. 2, figs. 3, 4.

Diagnosis.— Shell with disjunct coiling; aperture 

ovoid; rugae well developed as rounded ridges; growth 

lines not deflected over dorsal crest, revolving threads of 

near equal strength with growth lines, and the two 

forming distinct reticulate surface sculpture.

Description.— Shell moderate in size for genus (up to 

23 mm long), disjunctly coiled, whorls rapidly expanding 

in size; narrow in dorsal view. Aperture broadly ovoid, 

narrowing dorsally to a low dorsal carina; dorsal slopes 

convex; umbilical shoulders broadly rounded; ventral 

slopes convex and shorter than dorsal slopes. Ventral 

side of whorl bears revolving, elevated, tapering band, 

with squared-off raised margins bordering depressed 

central furrow. Rugae strongly developed as broadly 

rounded ridges, which extend from lower ventral slopes 

to near dorsal carina. Distinct reticulate shell ornament 

formed by straight growth lines, which are not deflected 

abaperturally over dorsal crest, and revolving connecting threads of equal strength. Shell thin.

Measurements.— Measurements of the holotype of C. 

(C.) disjunctus are listed in table 30.

Material.— The only known specimen of this species is 

the holotype (USNM 45785), but that single specimen 

preserves the shell and its markings excellently.

Distribution. The holotype is from Upper Ordovician 

strata near Spring Valley, Minn. Wilson (1951) reported 

Cyrtolites cf. C. disjunctus from the Rockland beds 

(Rocklandian-upper Middle Ordovician) of the OttawaSt. Lawrence Lowland, Canada, but emphasized: "The 

specimens at hand are too poorly preserved for certain 

identification, but they show the free final whorl." She 

figured only a copy of the drawing of the holotype given 

by Ulrich and Scofield (1897, pi. 62, figs. 48, 49), and did 

not show any of her material. I doubt very strongly that 

Wilson's specimens belong to C. (C.) disjunctus, mainly 

because of their much lower stratigraphic position. I 

suspect that she might have been looking at internal 

molds of another species of Cyrtolites, many of which, 

because of the loose coiling of the genus, are disjunct (see 

pi. 7, fig. 1, for an example of a disjunct internal mold of 

C. (C.) ornatus).

Comparison.—Even though C. (C.) disjunctus is not 

known from the Cincinnati arch region, it is treated 

herein so that it could be compared with the disjunct 

internal molds of C. (C.) ornatus, which are quite 

common in the Upper Ordovician of the study area (pi. 6, 

fig. 18; pi. 7, fig. 1). The whorls of C. (C.) disjunctus 

expand at a different and somewhat more rapid rate, and 

the volutions increase their distance from the axis of 

coiling at a much higher rate. This mode of coiling results 

in a shell having a relatively small initial whorl and a 

relatively large adult whorl that is exposed on all sides, 

including the venter. Moreover, the ovoid whorl shape of 

C. (C.) disjunctus is much more rounded.

Discussion.—It is important to note that C. (C.) 

disjunctus retains the ventral "saddle" on the venter of 

the whorl which would fit over the dorsal crest of the 

preceding whorl in conjunctly coiled species (pi. 6, figs. 

20, 22). This would seem to indicate that this species 

developed directly from a conjunct species. C. (C.) 

ornatus most likely is the ancestor. The two species have 

similar whorl shapes, although C. (C.) disjunctus has 

more rounded umbilical shoulders. Their external sculpturing is especially similar. Both have well-developed, 

thick, ridgelike rugae and a distinct reticulate sculpture 

pattern, with nearly equally strong, straight growth 

lines and revolving threads. Furthermore, some gerontic 

specimens of C. (C.) ornatus show a tendency to uncoil in 

the last quarter-whorl or so. Disjunct coiling is generally 

considered an adaptation to a more sessile mode of life
MIDDLE AND UPPER ORDOVICIAN SYMMETRICAL UNIVALVED MOLLUSKS, CINCINNATI ARCH REGION 0107

in the Gastropoda, and this may also apply to the 

Monoplacophora.

Subgenus CYRTOLITES (PARACYRTOLITES) new subgenus

Description.— Shell having no rugae developed on 

whorl slopes, and having no, or only weakly developed, 

reticulate ornament. Aperture sinuate, with V-shaped 

growth lines deflected abaperturally over dorsal crest of 

shell.

Distribution.—Kirkfieldian (upper Middle 

Ordovician)-Edenian (lower Upper Ordovician) of Eastern North America.

Type species. —C. (P.) subplanus Ulrich in Ulrich and 

Scofield, 1897.

Other species. —C. (P.) subplanus Ulrich in Ulrich and 

Scofield, C. (P.) carinatus Miller, and C. (P.) parvus 

Ulrich in Ulrich and Scofield.

Cyrtolites (Paracyrtolites) subplanus Ulrich, 1897

Plate 7, figures 26-35; Plate 8, figures 22-27

Cyrtolites subplanus Ulrich in Ulrich and Scofield, 1897, pi. 62, figs. 

40-44; Bassler, 1932, pi. 20, figs. 8, 9; not Foerste, 1924, p. 204, pi. 

34, fig. 5; not Wilson, 1951, p. 23, pi. 2, figs. 5, 6.

Diagnosis.— Shell medium in size (up to 12.4 mm 

long), narrow, rounded; umbilicus small and nearly circular; aperture subquadrangular, dorsum sharply 

rounded, dorsal slopes and umbilical shoulders rounded, 

ventral slopes flat to slightly concave; no distinct rugae 

developed; growth lines fine, deflected strongly abaperturally over dorsum, revolving threads weak or lacking.

Description.— Shell medium in size for genus, narrow 

in dorsal view, rather tightly coiled; umbilicus relatively 

small, nearly circular. Aperture rounded, subquadrangular, height and width nearly equal; dorsum sharply 

rounded with no carina developed, dorsal slopes gently 

convex, umbilical shoulders rounded, ventral slopes flat 

to slightly concave. Dorsal slopes smooth, lacking distinct rugae, but may have some gentle wrinkling, particularly near aperture of larger specimens. Growth lines 

fine but distinct, becoming slightly stronger with 

growth; lines turn sharply abaperturally over dorsum, 

increasing in angle near crest, reflecting relatively deep 

labral sinus. Very faint revolving connecting threads, 

barely visible on adult specimens, not distinct enough to 

create reticulate pattern, but can give a faint impression 

of pitting. Shell thin.

Measurements. Measurements of the types of C. (P.) 

subplanus are listed in table 31. Because the species is 

relatively thin shelled and therefore is not generally 

completely preserved, the measurements are open to 

greater error than those of thicker shelled species. 

Although it is difficult to determine actual proportions of 

the species and their variation, the measurements should

TABLE 31. Measurements (in millimeters) of Cyrtolites (Paracyrtolites) subplanus

USNM No.

45792 

265914

Shell 

length

12.4

Aperture 

length

13.3

Aperture 

width

12.1

7.5

Umbilical 

diameter

6.3

be accurate enough to give a general impression of size 

and trends.

Material.—\J\rich and Scofield's (1897) types include 

two silicified specimens (USNM 45792) collected from 

the Bigby-Cannon Formation at Snow's Hill, 4 mi east of 

Liberty, Tenn. A note in the box containing the two 

types indicates that the specimens came from the 

Lophospira sumnerensis zone of the "Upper Trenton." 

Wilson (1949, p. 129) listed L. sumnerensis as a typical 

fossil of the Cannon facies of the Bigby-Cannon Formation. The larger of these two types is here designated the 

lectotype (USNM 45792) (pi. 7, figs. 26, 27); the other is 

designated the paralectotype (USNM 265914) (pi. 7, figs. 

28, 29). It is noted that Ulrich and Scofield (1897, pi. 62, 

figs. 40-43) showed a partial reconstruction of the 

lectotype.

The species was recognized for the first time in Kentucky from USGS silicified collections D-1196-CO from 

the Logana Member and 4852-CO from the Grier Limestone Member of the Lexington Limestone. The best of 

these specimens is from the Logana collection (pi. 7, figs. 

30-32, 34) (USNM 265915); it preserves the aperture 

shape and surface ornament very well. Specimen USNM 

265917 (pi. 8, fig. 27) also comes from this collection. The 

collection from the Grier Limestone Member includes 

forms that compare favorably with C. (P.) subplanus. 

Specimens USNM 265918 (pi. 7, fig. 33) and USNM 

265916 (pi. 8, figs. 22-24) are fragmentary, and their 

shells seem a bit too broad for the species. Specimen 

USNM 265919 (pi. 8, figs. 25, 26) has the same features, 

but is also worn nearly smooth and is bored.

Distribution.—The species is known from strata of 

Kirkfieldian-Shermanian ages (late Middle Ordovician) in 

Tennessee and Kentucky. In Tennessee the species is 

known from the Cannon facies of the Bigby-Cannon 

Formation, according to the label with the types and to 

Wilson (1949). Bassler (1915) listed the species from the 

Catheys Formation (Shermanian-Edenian). Foerste 

(1924, p. 204) confirmed the occurrence of the species in 

the Catheys, and he further cited a possible specimen 

from Edenian strata of Manitoulin Island, Canada. He 

did not figure the latter specimen, but from his description it is more like C. (P.) carinatus, having angular 

umbilical shoulders. In Kentucky C. (P.) subplanus is 

known for certain from the Logana Member (Kirkfieldian) of the Lexington Limestone, and probably also from
0108 CONTRIBUTIONS TO THE ORDOVICIAN PALEONTOLOGY OF KENTUCKY AND NEARBY STATES

the Grier Limestone Member (early Shermanian) of the 

same formation.

Comparison.— This distinctive species is separable 

from the cooccurring C. (C.) retrorsus (pi. 5, figs. 1-26) 

in several ways: it is narrower in dorsal view (pi. 7, figs. 

27, 29, 30); it has a nearly smooth, rounded, but not 

inflated form, lacking rugae (pi. 7, figs. 26, 28, 32); the 

dorsal crest of the shell (pi. 7, figs. 34, 35) has a more 

deeply cut V-shaped sinus; and the short, revolving 

connecting threads between the growth lines are so weak 

that there is no apparent reticulate sculpture.

Discussion.— Bassler (1915, p. 386) listed a page number in Ulrich and Scofield's (1897) on which the original 

description of the species is supposed to be found, and 

the latter authors gave the same page reference in their 

plate description for the species. However, there is no 

description of Cyrtolites subplanus on that or any other 

page in Ulrich and Scofield (1897), so the new species was 

only figured by them. Therefore, the description given 

herein is the first published for the species. This is the 

oldest species known for C. (Paracyrtolites) and is the 

type species for the subgenus. It is believed to be 

ancestral to the Edenian species C. (P.) carinatus and C. 

(P.) parvus.

The ecological requirements of the C. (P.) subplanus 

species appear to have been the same as for C. (C.) 

retrorsus, with which it cooccurs in USGS silicified 

samples D-1196-CO from the Logana Member and 4852- 

CO from the Grier Limestone Member of the Lexington 

Limestone.

Cyrtolites (Paracyrtolites) carinatus Miller, 1874

Plate 7, figures 18-25; Plate 8, figure 21

Cyrtolites carinat^^s Miller, 1874, p. 311, fig. 32; Miller, 1889, p. 401, 

text-fig. 67; Ulrich and Scofield, 1897, p. 862, pi. 62, figs. 50-51; 

Grabau and Shinier, 1909, p. 610, figs. 815e-g; Foerste, 1924, p. 

205, pi. 34, figs. 2a-c, pi. 35, figs. 5a, b

Diagnosis. Shell moderate in size (up to 22 mm long), 

angular, narrow; aperture quadrangular and nearly equidimensional; dorsal carina high and sharp, lateral carinae 

not as prominent, dorsal and ventral whorl slopes essentially flat; distinct rugae lacking; growth lines very fine, 

swing abaperturally over dorsum; revolving threads 

very faint.

Description.— Shell moderate in size; form angular 

and narrow, tightly coiled; umbilici large, open, and 

nearly circular. Aperture quadrangular; dorsum with 

high, sharp carina; lateral angles with low, sharp carinae; 

dorsal whorl slopes nearly flat, but can be slightly convex 

or concave; ventral whorl slopes flat to slightly concave. 

Distinct rugae lacking, but weak wrinkling of shell 

visible on dorsal slopes of some specimens, particularly in 

gerontic specimens. Growth lines very fine and closely 

spaced, swinging gently abaperturally over dorsum;

TABLE 32. Measurements (in millimeters) of Cyrtolites (Paracyrtolites) carinatus

Museum 

No.

Shell 

length

Aperture 

length

Aperture 

width

Umbilical 

diameter

Ventral 

width

USNM 

49993 

265913 

265912 

265911 

47499

45783

45783

45783

UCGM

44277

44278

44279

22.00

17.95

13.05

8.20

12.90

13.80

11.25

11.10

12.5

12.8

13.1

14.30

10.25

7.00

5.60

9.25

7.3

7.4

11.6

12.2

7.6

6.0

7.2

8.7

7.0 

7.4

11.0 

8.7 

7.5 

5.0 

7.3

6.9

6.7

6.9 

6.2

7.2

3.0 

3.5 

2.1 

1.1

2.5

2.1 

2.5

revolving threads lacking or very faintly developed, 

particularly in immature specimens.

Measurements.— Measurements of C. (P.) carinatus 

are listed in table 32.

Material. —-No specimens of this species were recognized in the new USGS silicified collections. The holotype 

(pi. 7, figs. 18, 19) is specimen UC 8895. Twelve specimens listed under three museum numbers (USNM 

45783, 47499, 49993) and labeled as Ulrich and Scofield's 

(1897) "plesiotypes" were also examined. Four specimens from suite 47499 are figured herein: USNM 265913 

(pi. 7, figs. 24, 25), which is a fairly large specimen with 

part of the shell preserved; USNM 265912 (pi. 7, fig. 21); 

USNM 265911 (pi. 7, fig. 23); and USNM 47499 (pi. 7, fig. 

22). The largest specimen, USNM 49993, is not figured; 

nor are specimens of the suite USNM 45783. This 

collection of specimens was labeled as being from the 

Kope Formation (Edenian) at Newport, Ky.

A few specimens of the species were found in the 

University of Cincinnati Geological Museum under 

UCGM 19658. Steve Felton of Cincinnati made a number 

of specimens from the Kope Formation near Carrolton, 

Ky., available. These latter specimens were collected 

from a thin bed made up almost entirely of a molluscan 

assemblage (pi. 8, fig. 21). These calcitic specimens are 

UCGM 44277 (pi. 7, fig. 20), UCGM 44278, and UCGM 

44279 (pi. 8, fig. 21). These specimens are better preserved than any others examined.

Distribution.— Ulrich and Scofield (1897) stated that 

the species was to be found in the lower shales of the 

Cincinnatian in the Cincinnati, Ohio, area, as well as 

probably in Wisconsin, Iowa, and Minnesota. More 

recent collections confirm that the species appears 

restricted to the Kope Formation (Edenian) of the study 

area. Foerste (1924) reported the species from the Edenian Sheguiandah Formation on Manitoulin Island, 

Ontario, Canada.
MIDDLE AND UPPER ORDOVICIAN SYMMETRICAL UNIVALVED MOLLUSKS, CINCINNATI ARCH REGION 0109

Comparison.— This species can be distinguished from 

all other species of C. (Paracyrtolites) by its possession 

of both dorsal and lateral carinae. It does resemble C. 

(C.) claysferryensis, but it (1) does not attain as large a 

size, (2) lacks distinct rugae on the whorl slopes, (3) has 

finer growth lines, and (4) has such fine revolving lines 

that they are generally not even discernible.

Discussion. Miller (1874) did not mention any revolving connecting threads in his original description of the 

species, but Ulrich and Scofield (1897, p. 863) observed a 

faint but distinct reticulate pattern on the inner volutions 

of some well-preserved specimens. They claimed that the 

connecting threads are present in young growth stages, 

but become weaker through growth and are removed by 

even minimal abrasion.

To my knowledge, C. (P.) carinatus always occurs in a 

molluscan assemblage in thin limestone beds of the Kope 

Formation (pi. 8, fig. 21). The molluscan association 

recalls the usual occurrence of C. (C.) claysferryensis 

and C. (C.) ornatus.

Cyrtolites (Paracyrtolites) parvus Ulrich, 1897

Plate 7, figure 17

Cyrtolites parvus Ulrich in Ulrich and Scofield, 1897, p. 846, pi. 62, 

figs. 45-47; Foerste, 1924, p. 204-205, pi. 34, figs. 4a, b.

Description. — Shell small (up to 8.5 mm long), tightly 

coiled; umbilicus relatively small. Aperture subquadrangular; dorsum with low carina; dorsal slopes gently 

convex; umbilical shoulders rounded; ventral slopes 

nearly flat. Rugae absent. Growth lines fine but distinct, 

swinging abaperturally over dorsum; no revolving 

threads known.

Measurements.—The only measurements possible on 

the single specimen examined were shell height (8.55 

mm) and maximum umbilical diameter (3.75 mm).

Material.—The only specimen available is the holotype, USNM 45788, which is a small, rather poorly 

preserved calcitic cast (pi. 7, fig. 17).

Distribution.—The holotype, USNM 45788, is from 

"near the top of the Trenton group at Covington, Kentucky," according to a museum label. The specimen most 

likely was collected before the submergence of sub-Kope 

(Edenian) outcrops along the Ohio River Valley near 

Cincinnati by the damming of the Ohio River. In presentday stratigraphic nomenclature, these beds probably 

would be assigned to the Point Pleasant Tongue of the 

Clays Ferry Formation of latest Shermanian age. Foerste (1924, p. 204) cited the species as from the "Cynthiana Formation," now included in the Clays Ferry 

Formation, at Covington, Ky. He also noted specimens 

"resembling this species" in the Maysvillian strata of 

Manitoulin Island, Ontario, Canada.

Comparison.—Ulrich and Scofield (1897) claimed that 

this species is characterized by stronger surface markings than any other member of the genus. The holotype 

does not support this contention (pi. 7, fig. 17). The 

holotype bears some resemblance to small specimens of 

C. (C.) retrorsus (pi. 5, figs. 1, 2), but is less carinate 

dorsally and laterally than juveniles of that species, and 

also than juveniles of C. (P.) carinatus.

Discussion.—The holotype of this species does not 

support the contention in the original description that the 

species bears stronger surface markings than any other 

species of the genus. Because the holotype does not 

support the original description, the validity of the 

species may be suspect. Nevertheless, the single, rather 

poorly preserved specimen does not fit readily into any 

other known species, so the name C. (P.) parvus is 

retained herein. On the basis of the faint ornament 

of the holotype, the species is placed in the subgenus C. 

(Paracyrtolites).

Family SINUITIDAE Dall in Eastman, 1913

Diagnosis.— Shell tightly involute to convolute; umbilicus moderately small to lacking; whorls rounded to 

globose; sinus relatively wide, U-shaped to rounded 

V-shaped; lateral apertural margins rounded to distinctly lobate; surface markings generally very fine collabral lines; thin inductural deposits in some cases 

extending slightly beyond parietal area.

Stratigraphic range.—As defined, in the Ordovician 

the family is known with certainty from BlackriveranRichmondian-age strata in Eastern North America. 

However, it may extend into the Lower Ordovician 

(Bassler, 1915, p. 1160, 1161). Rollins and Batten (1968) 

reported the genus Sinuitopsis from Devonian rocks.

Genera included.—Sinuites Koken, 1896; Sinuitopsis 

Perner, 1903; Strangulites Horny, 1962; Sylvestrosphaera Peel, 1980.

Discussion.—As defined herein, the family Sinuitidae 

is more restricted than ever before and consists of four 

closely related genera. Previously, authors such as 

Knight and others (1960) included many genera that had 

little more in common with Sinuites and its phylogenetic 

allies than a similarly shaped sinus. With the discovery of 

discrete paired muscle scars in Sinuitopsis, Sinuites, 

and Sylvestrosphaera by Rollins and Batten (1968), Peel 

(1980), and Runnegar (1982), these genera were transferred to the Monoplacophora. Muscle scars are not yet 

known in Strangulites. The other genera previously 

placed in the Sinuitidae by Knight and others (1960) and 

Horny (1963a) are tentatively assigned to the Bucanellidae of the superfamily Bellerophontacea. Runnegar and 

Jell (1976, p. 121) included such genera as Cloudia and 

Strepsodiscus in the Sinuitidae, but I do not think these
0110 CONTRIBUTIONS TO THE ORDOVICIAN PALEONTOLOGY OF KENTUCKY AND NEARBY STATES

genera are evolutionarily closely related to the sinuitid 

genera cited herein.

Genus SINUITES Koken, 1896

Diagnosis.— Shell tightly coiled, convolute, umbilicus 

closed or very small; dorsum generally rounded, flattened somewhat in some cases, with dorsomedian ridge 

in very few; aperture large, generally longer than wide, 

with deep, rounded, median sinus and lateral margins 

projecting downward as rounded or subangular lobes; 

parietal deposits thin, ornamented in many cases; growth 

lines fine, closely spaced, in many cases intersected by 

faint revolving lines.

Type species.—Bellerophon bilobatus Sowerby, 1839, 

by subsequent designation of Bassler (1915, p. 1159).

Distribution. Middle and Upper Ordovician of North 

America, Europe, and North Africa.

Comparison.—Most species placed in the genus Sinuites are quite distinctive, and confusion with other genera is likely only when poorly preserved internal molds 

are encountered. In that case, there may be confusion 

with species of Sphenosphaera Knight or Bellerophon 

Montfort.

Knight and others (1960, p. 1177) treated Sinuitopsis 

Perner as a subgenus of Sinuites, but Horny (1963a, p. 

76, 77) strongly contested this assignment. He claimed 

that their hand-drawn figures 93/7a, b (Knight and 

others, 1960, p. 1176) misinterpreted the lateral lobes of 

Sinuitopsis, and show a circumumbilical structure not 

present in the type species or related species. Important 

features distinguishing Sinuitopsis are its higher, 

rounder shell shape on lateral view, its distinctly open 

umbilicus, its rounded, but not lobate, lateral apertural 

margins, and its narrower apertural sinus.

Horny (1962, p. 473; 1963a, p. 75) proposed the genus 

Strangulites, stating that it differs from Sinuites by 

having more rounded, closely involuted whorls with 

characteristic deep constrictions of the adult body whorl. 

He noted (1963a) that a number of the British Upper 

Ordovician species of Sinuites described by Reed (1921) 

also bear body whorl constrictions, but that these species 

are laterally compressed and have lobate lateral apertural margins. The type species, Strangulites strangulatus (Perner), is certainly globose, but no more so than 

the Kentucky species Sinuites obesus (Ulrich) (compare 

Horny, 1963a, pi. 6, figs. 1-3, with pi. 9, figs. 1-12, 

herein). Furthermore, Horny's (1963a, pi. 6, fig. 2, and 

pi. 5, fig. 4) figures seem to show that the lateral lips of 

S. strangulatus actually are mildly lobate (note growth 

lines). Horny admitted that Strangulites might be considered a subgenus of Sinuites. It is concluded here that 

the two are synonymous.

Discussion.— Species of Sinuites described prior to 

1896-97 were generally assigned to Bellerophon. Koken

(1896, p. 392) erected the new genus Sinuites to contain 

European Ordovician species. Unaware of this new 

genus, Ulrich and Scofield (1897, p. 848) proposed the 

genus Protowarthia for American species. Bassler (1915, 

p. 1159) recognized the synonymy and the priority of 

Sinuites Koken, and formally designated Bellerophon 

bilobatus Sowerby the type species of Sinuites. Reed 

(1921, p. 5) pointed out that "unfortunately, the species 

B. bilobatus has been made to comprise a somewhat 

miscellaneous assortment of forms, and the customary 

usage of the specific name has become loose and unsatisfactory." Therefore, he subdivided B. bilobatus into 

three new species and restricted the definition of the 

original taxon.

The American species Sinuites cancellatus (Hall) may 

be plagued by the same problem pointed out by Reed for 

S. bilobatus. Specimens of Sinuites are fairly common in 

the Upper Ordovician of the Cincinnati arch region, but 

just as in other areas of occurrence, these specimens are 

nearly always internal molds. S. cancellatus has become 

the usual receptacle for these specimens. At least three 

subspecies have been named (Bassler, 1915, p. 1159), but 

their validity is questionable (see discussions of species 

below).

The genus Sinuites is greatly in need of a comprehensive specific review. It is an important taxon not only 

because of its broad geographic and stratigraphic distribution and its relative abundance in some strata, but also 

because of its phylogenetic significance (see sections on 

"Functional Morphology" and "Phylogeny and Classification").

Sinuites pervoluta (Ulrich and Scofield, 1897)

Protowarthia pervoluta Ulrich and Scofield, 1897, p. 871, pi. 63, figs.

21-27; Grabau and Shimer, 1909, p. 611, figs. 817d-f. 

Sinuites pervolutus (Ulrich and Scofield), Bassler, 1915, p. 1160.

Diagnosis. Shell small (less than 15 mm long), tightly 

enrolled, rather globose; dorsum uniformly rounded, 

without ridge or flattening; aperture wider than long; 

parietal deposits granistriate; growth and revolving lines 

exceedingly fine.

Material.-The type material (USNM 45968-45970) 

was adequately illustrated by Ulrich and Scofield (1897, 

pi. 63, figs. 21-27) and is not figured herein. No new 

material is known.

Distribution.—Ulrich and Scofield (1897, p. 871) listed 

the species from the "Black River group and in the 

lowest bed (Orthis or Modiolodon bed) of the Trenton 

group" in Kentucky and equivalent strata in Minnesota 

(Decorah Formation). In modern terms, the Kentucky 

occurrences are in the Tyrone Limestone (Rocklandian) 

and the Logana Member of the Lexington Limestone 

(Kirkfieldian).
MIDDLE AND UPPER ORDOVICIAN SYMMETRICAL UNIVALVED MOLLUSKS, CINCINNATI ARCH REGION 0111 

TABLE 33. Measurements (in millimeters) o/Sinuites cancellatus

UCGM

No.

44304

44307

Shell 

length

24.4

24.6

Shell 

height

16.3

16.5

Aperture 

length

16.3

17.4

Aperture 

width

21.9

21.0

Dorsal 

width

14.4

16.0

Posterior 

width

11.8

13.7

Ventral 

width

9.7

-

Sinus 

depth

10.8

9.8

Sinus 

width

14.2

9.9

Comparison.— Ulrich and Scofield (1897, p. 871) noted 

that S. pervoluta might be a "variety" of S. granistriatus 

(Ulrich). However, S. pervoluta is smaller (the shell 

being less than 15 mm long), more tightly coiled, and 

more globose, and has a wider aperture than S. granistriata. S. pervoluta also lacks a dorsal ridge or a flattening of the dorsum.

In their discussion of S. obesus (Ulrich), Ulrich and 

Scofield (1897, p. 875) stated: "Very young specimens 

may look much like the largest of P. pervoluta, but the 

adult form, which is all we have seen, is certainly quite 

distinct." A number of small specimens of a globose 

species of Sinuites were found in USGS silicified samples 

5023-CO, 5084-CO, and 5100-CO from the Curdsville 

Limestone Member of the Lexington Limestone. These 

small, poorly preserved silicified specimens are probably 

not S. pervoluta, because some show a small umbilicus, 

as cited for S. obesus; as a result, they were placed in the 

latter species. Unless well-preserved material is available, juveniles of S. obesus and adults of S. pervoluta are 

extremely difficult to distinguish.

Sinuites cancellatus (Hall), 1847 

Plate 11, figures 6-12

Bellerophon bilobatus Emmons (not Sowerby), 1842, p. 392, fig. 6;

Hall, 1847, p. 184, pi. 40, figs. 3a-d; Miller, 1874, p. 306; Lesley,

1889, p. 81, figs.; Miller, 1889, p. 396, fig. 652. 

Cyrtolites bilobatus Emmons, 1855, p. 166, figs. 2, 3, 22, 24; pi. 17, fig.

lOc.

Bellerophon cancellatus Hall, 1847, p. 307, pi. 83, figs. lOa-c. 

Protowarthia cancellata (Hall), Ulrich and Scofield, 1897, p. 872, pi.

63, figs. 1-14; Weller, 1903, p. 175, pi. 12, figs. 3-5; Cumings, 1908,

p. 971, pi. 39, figs. 6a, b; Grabau and Shinier, 1909, p. 611, figs.

817g-i; Knight, 1941, p. 279, pi. 6, figs. 3a, b. 

Sinuites cancellatus (Hall), Bassler, 1915, p. 1159; Bassler, 1919, p.

313, pi. 50, figs. 37-39; pi. 55, figs. 12-21; Foerste, 1924, p. 205, pi.

34, fig. 6; Ruedemann, 1926, p. 62, pi. 8, fig. 6; Bassler, 1932, pi.

21, figs. 16-18; Shinier and Shrock, 1944, p. 441, pi. 176, figs. 24,

25; Wilson, 1951, p. 25, pi. 2, figs. 11, 12; Caster, Dalve, and Pope,

1955, pi. 1, figs. 16, 17; Pope and Martin, 1977, pi. 1, figs. 16, 17.

Diagnosis.— Shell medium in size, smoothly rounded 

dorsally and laterally, subglobose, involute, umbilicus 

closed; sinus moderately shallow, lateral aperture lobes 

well rounded; growth lines fine, revolving lines even 

finer.

Description. Shell medium in size (adult about 25 mm 

long), involute, with closed umbilicus, generally subglobose, smoothly rounded dorsally and laterally, degree of 

convexity variable. Sinus moderately shallow, V-shaped,

having well-rounded apex; lateral apertural margins 

merge into well-rounded lobes. Aperture distinctly 

wider than long. Parietal inductura thin, folding over 

venter of coil onto umbilical region, marked by fine, 

wavy revolving lines. Shell ornament of fine, closely 

spaced growth lines crossed by even finer revolving 

lines, giving a faint cancellate appearance.

Measurements.—Measurements of S. cancellatus are 

listed in table 33.

Material.— The holotype was adequately figured by 

Knight (1941, p. 6, fig. 3a). Specimens preserving the 

shell examined here are UCGM 44304 and UCGM 44307. 

Numerous internal molds of the species, most of which 

are unnumbered, were examined in the collections of the 

geology museums of the University of Cincinnati and 

Miami University.

Distribution.—The species has been reported from 

"Trenton through Richmond groups" (KirkfieldianShermanian to Richmondian) throughout the eastern half 

of the United States and Canada (Ulrich and Scofield, 

1897; Bassler, 1915; Shinier and Shrock, 1944). Herein, 

the species is recognized from Shermanian- through 

Richmondian-age strata in the Cincinnati arch region.

Comparison.—S. cancellatus is distinguished from S. 

planodorsatus (Ulrich) and S. granistriatus (Ulrich) by 

its smoothly rounded dorsum, being neither flattened nor 

bearing a ridge. It is further distinguished from these 

species, as well as from S. rectangularis (Ulrich and 

Scofield), by its more broadly rounded lateral aperture 

lobes and its shallower apertural sinus.

Discussion.—S. cancellatus is long ranging stratigraphically and widely distributed geographically for 

species of Sinuites. It is difficult to evaluate the species 

properly without examining specimens from its entire 

distribution. All specimens examined for this study were 

from the Shermanian- through Richmondian-age strata 

of the Cincinnatian arch province. Nearly all were internal molds, and none of the few specimens retaining the 

shell preserved the shell ornament satisfactorily. Furthermore, many of the internal molds were badly compressed, apparently owing to the animal's thin, probably 

aragonitic shell, which must have dissolved prior to 

compaction of the generally fine grained encasing sediment. Such specimens are commonly weathered out of 

Cincinnatian shales.

Even dealing only with Cincinnati arch material, and 

mainly with internal molds, the morphological variation
0112 CONTRIBUTIONS TO THE ORDOVICIAN PALEONTOLOGY OF KENTUCKY AND NEARBY STATES

of specimens included in this species was quite apparent. 

However, no consistent pattern could be discerned which 

could provide a basis for subdividing S. cancellatus with 

confidence. A number of subspecies have been named by 

previous authors. Bassler (1915, p. 1159) recognized S. 

cancellatus acutus (Hall, 1847) and S. cancellatus corrugatus (Hall, 1847). These were originally named subspecies of S. bilobatus Emmons, which was placed in 

synonymy with S. cancellatus by Bassler. Ulrich and 

Scofield (1897, p. 872) named S. cancellatus trentonensis 

for specimens from the "Trenton group" which "are 

almost constantly a trifle more narrowly rounded dorsally than is the geologically higher typical form of the 

species." It should be noted that the species was originally described from the Trenton Group of New York, so 

the Trenton material is actually "typical." Wilson (1951) 

persisted in using S. bilobatus corrugatus (Hall), and 

named two new subspecies, S. cancellatus angularis and 

S. cancellatus liratus (the latter being equivalent to S. 

cancellatus acutus). I do not believe any specimens 

bearing a dorsal ridge should be included in S. cancellatus, and therefore I regard S. liratus Wilson as a distinct 

species. However, based on her illustration, the specimen's placement in Sinuites is uncertain.

In the Cincinnati arch material, three general variants 

of S. cancellatus are recognized as end members in a 

maze of morphological gradations. The first end member 

would be placed in S. cancellatus corrugatus (Hall) of 

some authors. However, the distal corrugations of this 

variant are variable in strength and number (1-3) and 

were seen only in internal molds. Furthermore, corrugated specimens occur in collections in which most of the 

internal molds lack corrugations, and I strongly suspect 

that the corrugations are the result of compaction. The 

other two variants have more narrowly rounded (S. 

cancellatus acutus) or more broadly rounded (S. cancellatus cancellatus) dorsal shell forms (pi. 11, figs. 10-12 

and 6-9, respectively). Even though these two general 

forms were seen in specimens preserving the shell as 

well as in internal molds, there was much gradation 

between the two end members, and such a feature can be 

influenced by compaction. Therefore, at present it is not 

possible to subdivide S. cancellatus from the Cincinnati 

arch region into subspecies, and S. cancellatus acutus, 

S. cancellatus corrugatus, S. cancellatus trentonensis, 

and S. cancellatus angularis are treated as synonyms of 

S. cancellatus cancellatus.

The specimens shown herein (pi. 11, figs. 6-12) are 

slightly worn and preserve only a trace of the growth 

lines. Knight (1941, pi. 6, fig. 3a) illustrated the holotype, 

which although unfortunately distorted by crushing, 

preserves the cancellate shell ornament very well. 

Knight's (1941, pi. 6, fig. 3b) hypotype has the more 

typical preservation.

Sinuites obesus (Ulrich), 1897

Plate 9, figures 1-12

Protowarthia obesus Ulrich in Ulrich and Scofield, 1897, p. 874, 875, pi. 

63, figs. 45-47. Sinuites obesus (Ulrich), Bassler, 1915, p. 1160.

Diagnosis.—Shell large (up to 36 mm long), obese; 

umbilicus closed; sinus broad and shallow, lateral lobes 

rounded.

Description.— Shell large, involute, with umbilicus 

closed; whorl form obese, broadly and uniformly 

rounded; dorsum smooth. Aperture distinctly wider than 

long, fairly semicircular in outline around outer margins, 

inner margins angling inward. Aperture lip thickened 

near contact with coil, thinning outward around periphery. Parietal deposits quite thin, ornamentation 

unknown. Sinus broad, moderately shallow; lateral lobes 

broadly rounded. Growth lines very fine.

Measurements.—As seen on plate 9, figures 1-12, 

specimens of this species are generally too badly fragmented for many reliable measurements. Measurements 

listed in table 34 are meant to give only general relative 

dimensions.

Material.- Ulrich and Scofield's (1897, p. 874, 875, pi. 

63, figs. 45^7) type specimens (USNM 45961, 45962) are 

internal molds from the Curdsville Limestone Member of 

the Lexington Limestone.

New USGS silicified material from Kentucky comes 

from the Curdsville Limestone Member (4940-CO, 5022- 

CO, 5023-CO, 5072-CO, 5084-CO, 5100-CO, and 7785- 

CO) and the Logana Member (4865-CO, 5073-CO, 5086- 

CO, 5092-CO, 6419-CO, and 7791-CO) of the Lexington 

Limestone. Essentially all silicified specimens are incomplete, so that accurate counts and measurements were 

not possible. The most prolific samples (5092-CO, 6419- 

CO, and 7791-CO) contained more than 100 specimens 

and fragments. Specimens cataloged under USNM 

315634, 315635, 315636, and 315637 were selected for 

illustration herein (pi. 9, figs. 1-12).

Distribution.—The species occurs in the Curdsville 

Limestone and Logana Members of the Lexington Limestone (Kirkfieldian), and is currently known only from 

central Kentucky.

Comparison. —In the smooth roundness of the whorls, 

S. obesus matches S. cancellatus, but S. obesus is much 

larger and more obese. As discussed under S. pervoluta, 

adults of that species might be confused with juveniles of 

S. obesus.

Discussion.—Ulrich and Scofield (1897, p. 875) cited a 

shallow sinus as characteristic of this species, but that 

conclusion is the result of looking at poor material. 

USNM 315636 (pi. 9, fig. 5) clearly shows by its growth 

lines that the sinus is at least moderately deep. This 

growth-line evidence further points out that even new 

silicified material that appears to have a nearly complete
MIDDLE AND UPPER ORDOVICIAN SYMMETRICAL UNIVALVED MOLLUSKS, CINCINNATI ARCH REGION 0113 

TABLE 34. Measurements (in millimeters) o/Sinuites obesus

USNM No.

315658

315634

315659

315659

315659

315659

315660

315661

315635

315635

315667

315663

315663

315663

315663

315664

315664

315664

315664

Shell 

length

23.4

31.2

28.5

-

16.1

_

10.4

9.9

11.6

36.1

29.0

_

26.0

16.9

15.9

12.9

-

17.0

13.4

Shell 

height

17.0

21.5

20.3

8.7

-

_

_

8.0

9.0

-

_

_

18.2

11.6

-

13.4

-

_

10.1

Aperture 

length

10.5

17.7

17.1

5.8

9.4

12.7

6.2

5.0

7.1

22.1

17.5

_

16.0

9.2

9.5

10.5

_

9.4

8.1

Aperture 

width

_

30.7

26.0

12.1

20.6

22.2

10.6

10.8

10.9

36.3

27.7

19.4

25.4

16.8

16.4

18.4

29.1

16.0

12.9

Dorsal 

width

_

20.5

_

8.4

-

_

_

_

7.5

23.0

_

13.7

18.8

11.2

11.9

12.3

18.9

11.6

-

Posterior 

width

_

17.3

-

6.9

-

_

-

-

6.3

17.4

_

10.9

15.4

9.5

-

10.1

16.3

9.8

-

Ventral 

width

_

14.0

11.1

5.2

7.4

10.0

-

_

4.6

14.4

_

-

11.6

8.1

-

8.1

11.9

8.2

6.3

apertural margin (pi. 9, figs. 1-4, 6-12) actually has had 

the thin outer apertural margin completely broken away.

Another distinctive feature of S. obesus is the transverse furrows on the outer whorls of internal molds. 

These are much like the furrows of so-called S. cancellatus corrugatus (Hall). No such furrows were seen on 

the silicified material, either externally or internally. As 

in S. cancellatus corrugatus, such wrinkles in S. obesus 

internal molds may be a response in local populations to 

some environmental stress, may be a gerontic feature, 

may reflect actual internal soft parts such as bandlike 

muscles, or may be due to deformation from compaction 

of the encasing sediments. In any case, the use of 

transverse wrinkles on internal molds as a diagnostic 

species level taxobasis is not advocated here.

Ulrich and Scofield (1897) also noted a faint dorsomedian ridge on internal molds. Like the wrinkles on 

internal molds, this is not seen on silicified replicas of the 

shells.

Sinuites planodorsatus (Ulrich)

Protowarthia planodorsata Ulrich in Ulrich and Scofield, 1897, p. 

871, pi. 63, figs. 31-35.

Sinuites planodorsatus (Ulrich), Bassler, 1915, p. 1160; Ruedemann, 

1926, p. 61, pi. 8, fig. 5.

Diagnosis.— Shell medium in size; dorsum narrowly 

and smoothly rounded in submaturity, becoming broad 

and flattened in maturity.

Material.— Ulrich and Scofield's (1897) type suite 

(USNM 45960) consisted of six specimens, three of which 

they illustrated (their pi. 63, figs. 31-35). Their illustrations are adequate, and the species is not illustrated 

here. No definite new material was found, though some

unnumbered internal molds in the University of Cincinnati Geology Museum collections from the Kope Formation may be assignable to this species.

Distribution.—The type material comes from the 

Southgate biofacies of the Kope Formation (middle 

Edenian) at Covington, Ky. (Ulrich and Scofield, 1897; 

Bassler, 1915). Ruedemann (1926, p. 61) reported the 

species from Edenian-age strata in New York.

Comparison.— Ulrich and Scofield (1897, p. 871) 

stated that this species might be a "variety" of S. 

granistriatus (Ulrich), the two species being similar in 

general shell form and ornamentation. However, S. 

planodorsatus differs in having a much more emphasized 

dorsal flattening and lacking a dorsal ridge.

Discussion. — This species seems to be valid and is 

distinct from S. granistriatus, though the two certainly 

are closely related. Ruedemann (1926, p. 61) noted that 

S. planodorsatus "fills a thin band" at one stratigraphic 

section he studied. Such an occurrence is typical of other 

species of Sinuites this author has collected from Edenian strata (S. cancellatus and S. granistriatus).

Sinuites granistriatus (Ulrich), 1897

Plate 11, figures 1-5; Plate 21, figure 1; Plate 45, figures 1-9

Protowarthia granistriata Ulrich and Scofield, 1897, p. 870, pi. 63, figs.

28-30. 

Sinuites granistriatus (Ulrich), Bassler, 1915, p. 1160; 1919, p. 314, pi.

50, figs. 40^1; pi. 55, figs. 9-11; Ruedemann, 1926, p. 63, pi. 8,

figs. 7, 8.

Diagnosis.— Shell medium in size (up to 30 mm long), 

involute; dorsomedian ridge distinct through submaturity, weakening or disappearing in maturity.

Description.— Shell medium in size, rather tightly 

involute; umbilicus closed. Whorls relatively narrow in
0114 CONTRIBUTIONS TO THE ORDOVICIAN PALEONTOLOGY OF KENTUCKY AND NEARBY STATES

TABLE 35. Measurements (in millimeters) o/Sinuites granistriatus

USNM No.

44295

44296

44297

Shell 

length

30.0

29.5

27.0

Shell 

height

20.2

-

19.0

Aperture 

length

22.0

21.3

-

Aperture 

width

22.0

21.7

-

Dorsal 

width

16.7

15.3

-

Posterior 

width

13.0

12.2

11.3

Ventral 

width

10.3

10.2

9.5

early growth, broadening dorsally and inflating somewhat laterally toward maturity. Dorsomedian ridge distinct, rounded, marked by faint revolving striae in 

submaturity; in maturity, dorsum flattens, dorsomedian 

ridge becomes lower and broader, eventually disappearing completely in some specimens. Dorsomedian ridge 

bordered by shallow furrows in some compressed specimens. Aperture width and length (from inner lateral lip 

contact with whorl) nearly equal, or width slightly 

greater. Labral sinus moderately deep; lateral aperture 

lobes distinctly projecting, lobe margins apparently 

rounded but bending rather sharply inward in adults at 

contact with flattened dorsum. Shell thin except at inner 

apertural margins; parietal deposits fairly thin, with fine 

pitting. Shell surface marked by fine growth lines and 

very delicate revolving lines.

Measurements.—The measurements in table 35 are of 

three of the largest and best preserved specimens from 

locality OH-1 (Bear Creek Quarry); however, because of 

the consistently fragmented aperture lip, the four measurements of the shell and aperture are only approximations. Ulrich and Scofield (1897, p. 870) presented a 

series of average measurements apparently from smaller 

specimens (average shell 19 mm long). Their aperture 

length was taken from a median point, whereas measurements reported herein were taken at the lateral 

extremity, where the lip reaches the coil.

Material.—Ulrich and Scofield's (1897) type suite is 

USNM 45959. These specimens are from the Kope 

Formation (Edenian) at Cincinnati, Ohio. The new specimens described here are UCGM 44295, 44296, 44297, 

44298 (pis. 11, 21, 45), and a number of unfigured 

specimens cataloged under UCGM 44299. Almost all 

these specimens retain at least part of the shell, but none 

is complete. All these new specimens were collected from 

a single limestone lens in the Kope Formation (Edenian) 

at Bear Creek Quarry (locality OH-1), Ohio. UCGM 

44306 (pi. 45, figs. 5-7), another specimen retaining the 

shell, was collected from the Kope Formation (Edenian) 

at locality KY-1, Carroll County, Ky.

Distribution.—The species is known only from the 

Edenian portion of the Kope Formation in southwestern 

Ohio and northern Kentucky.

Comparisons.— S. granistriatus resembles S. planodorsatus in shell size and form, particularly in the 

flattening of the dorsum in maturity, but the former can

be easily distinguished from that species, as well as from 

S. cancellatus, by its submature dorsomedian ridge. 

Sinuites globularis (Miller and Faber) is smaller and 

broader, and has a flattened dorsum with a median ridge 

and two diverging lateral ridges throughout growth.

Discussion.—Ulrich and Scofield (1897, p. 870) 

described the dorsomedian ridge of S. granistriatus as 

continuing to the apertural margin and as being bounded 

by wide furrows. Their specimens averaged only 19 mm 

in shell length. Larger adult specimens described herein 

show that the dorsomedian ridge becomes lower and 

broader, and even disappears completely in many 

mature specimens (pi. 11, figs. 1-5; pi. 45, figs. 3-9). The 

adult specimens described herein also show that the 

dorsomedian ridge is not bounded by true furrows; 

rather, furrows commonly result from vertical compression owing to the thinner shell material on either side of 

the thickened ridge.

A collection of more than 100 specimens of this species 

was found in a lenticular argillaceous limestone bed 

enclosed by shale in the lower Kope Formation at 

Locality OH-1. Tetranota bidorsata is associated with S. 

granistriatus but occurs in small numbers. Other associated skeletal fragments include sparse trilobite (Cryptolithus) and crinoid debris (pi. 21, fig. 1). The shale 

encasement may have been responsible for preservation 

of the thin, delicate shells, but even such an ideal 

circumstance did not allow preservation of any complete 

specimens. This case demonstrates why well-preserved 

specimens of this species, and of other species of Sinuites, are so rare.

Sinuites globularis (Miller and Faber), 1894

Plate 10, figures 1-13

Bellerophon globularis Miller and Faber, 1894, p. 28, pi. 1, figs. 21, 22. 

Sinuites globularis (Miller and Faber), Bassler, 1915, p. 1160.

Diagnosis.— Shell moderately small, umbilicus closed; 

dorsum broad; rounded dorsomedian ridge and two lateral, low, diverging ridges present throughout growth.

Description.— Shell moderately small (up to 20 mm 

long), tightly coiled; umbilicus closed. Whorls broad, 

inflated; dorsum with distinct, round dorsomedian ridge, 

bounded by shallow widening furrows, which in turn are 

bordered by low, rounded, diverging ridges. Aperture 

broad, semicircular in general outline; parietal deposits
MIDDLE AND UPPER ORDOVICIAN SYMMETRICAL UNIVALVED MOLLUSKS, CINCINNATI ARCH REGION 0115 

TABLE 36. Measurements (in millimeters) o/Sinuites globularis

Museum No.

UC 881 la 

UC 8811b 

UCGM 44305

Shell length

19.6 

20.0 

16.5

Shell height

12.0 

14.0 

11.1

Aperture length

12.8 

9.8

Aperture width

17.6 

18.4 

14.3

Dorsal width

11.2 

12.0 

9.9

Posterior width

8.4 

8.8

8.7

Ventral width

6.4

unknown; sinus deep, lateral aperture lobes well 

rounded. Growth lines fine, closely spaced; revolving 

lines not known.

Measurements.— Measurements of S. globularis are 

listed in table 36.

Material.— The lectotype (UC 8811a) and paralectotype (UC 8811b) (pi. 10, figs. 1-7 and 11-13, respectively) are calcareous replicas. One other similar specimen, UCGM 44305 (pi. 10, figs. 8-10), was collected 

during the course of this study from locality KY-1.

Distribution. The type specimens are from the Kope 

Formation (Edenian) at Cincinnati, Ohio. The new specimen cited above is from the same Kope Formation at 

locality KY-1, near Carrollton, Ky.

Comparison. — The dorsomedian ridge of this species 

is broader than that of S. granistriatus. The latter 

species also appears in some specimens to have lateral 

furrows, but this seems to be simply a result of vertical 

compaction of the thin shell adjacent to the thickened 

median ridge. Further, S. globularis is broader and more 

globular than S. granistriatus, and has true dorsolateral 

ridges.

Sinuites subcompressus (Ulrich, 1897)

Protowarthia subcompressa Ulrich in Ulrich and Scofield, 1897, p. 873,

pi. 63, figs. 40-44; Cumings, 1908, p. 972, pi. 39, figs. 5-56. 

Sinuites subcompressus (Ulrich), Bassler, 1915, p. 1161.

Diagnosis.—Shell large, well-rounded dorsally, somewhat compressed laterally, umbilicus closed; aperture 

semiovate, sinus width and depth nearly equal, lateral 

lobes gently rounded; growth lines fine, revolving lines 

not known.

Material. Ulrich's types are USNM 45973 and 45974. 

No additional material is known. The original illustrations are adequate, and the species is not figured here.

Distribution.—The species is known only from the 

Waynesville biofacies of the Dillsboro Formation (Richmondian) in Butler County, Ohio, and near Versailles, 

Ind. (Bassler, 1915).

Comparison.—S. subcompressus differs from S. cancellatus (Hall) in its greater size, narrower and flatter 

sides, and apparent lack of revolving shell ornament.

Class GASTROPODA Cuvier, 1797

Diagnosis. Mollusks having a distinct head, a radula, 

a solelike foot adapted for creeping, and a visceral mass 

that has been rotated up to 180 degrees with respect to

the head-foot, so that the gut becomes twisted, the left 

and right gills come to lie, respectively, on the right and 

left sides of the body, and the nervous system forms a 

"figure eight" (Runnegar and Pojeta, 1974).

Subclass PROSOBRANCHIA Milne-Edwards, 1848

Diagnosis.— Gastropods displaying the full effects of 

torsion as defined by Knight and others (1960, p. 1171).

Order ARCHAEOGASTROPODA Thiele, 1925

Diagnosis. — Prosobranchia having aspidobranch 

ctenidia (that is, bipectinate, with filaments alternating 

on two sides of axis) that are free at one end; organs of 

pallial complex, including ctenidia, paired primitively, 

the right set generally partly or completely reduced; no 

siphon or proboscis, and thus no siphonal canal at shell 

margin.

Discussion.—Knight and others (1960, p. 1155, 1156) 

preferred the term "Archaeogastropoda" over earlier 

used names (that is, Scutibranchia, Aspidobranchia, 

Streptoneura, and Diotocardia) because of inconsistency 

in the use of those names and because the present term 

embraces the desired groups of fossil snails without the 

restriction of implying the existence of certain anatomical conditions. The Archaeogastropoda is a fairly diverse 

assemblage of taxa that exhibit the primitive features 

attributed, in varying degrees, to the hypothetical newly 

torted ancestral form (Knight and others, 1960).

The morphological characteristics used to define 

archaeogastropods are largely anatomical, but have 

direct bearing on the form of the shell containing them. 

Yonge (1947) described the features of the aspidobranch 

condition in detail. He noted that the possession of paired 

gills by the pleurotomariaceans is reflected by a labral 

emargination. This labral emargination, in the form of a 

sinus or slit, acts as an exhalant passage midway 

between the pair of gills, affecting the more efficient 

expulsion of deoxygenated water (which has passed over 

the gills), fecal wastes, and sediment contaminants. 

Knight (1952) strongly supported homology between the 

pleurotomariaceans and the bellerophontaceans in this 

regard. Yonge (1947) cited four aspidobranch conditions 

in living prosobranches: (1) asymmetrical shell with two 

asymmetrical ctenidia (Zeugobranchia), (2) secondarily 

symmetrical shell with two symmetrical ctenidia (Fissurellidae), (3) asymmetrical shell with loss of one or both 

ctenidia (Neritacea, Valvatacea, Trochacea), and (4) sec-
0116 CONTRIBUTIONS TO THE ORDOVICIAN PALEONTOLOGY OF KENTUCKY AND NEARBY STATES

ondarily symmetrical shell with loss of one or both 

ctenidia (Patellacea, Cocculinacea, some Neritacea).

Knight (1952) envisioned the Bellerophontacea as evolutionary intermediates between untorted mollusks and 

the asymmetrically coiled Pleurotomariacea. Recent 

observations of Early and Middle Cambrian molluscan 

univalves place some doubt on this interpretation and 

suggest that torsion was a slow adaptive process resulting from the asymmetrical coiling of primitive untorted 

mollusks (Runnegar and Pojeta, 1974; Pojeta and Runnegar, 1976; Runnegar, 1983). However, even if this 

view is excepted, it does not mean that the Bellerophontacea were untorted, as secondary symmetry is common 

in the Archaeogastropoda. Pojeta and Runnegar (1976, 

p. 32) noted that the earliest pleurotomariaceans, such as 

the sinuopeids, raphistomenids, and eotomariids of the 

Late Cambrian, were low spired shell forms. The nearly 

synchronous appearance of the bellerophontaceans and 

these low spired pleurotomariaceans in the Late Cambrian might also be significant in this matter. In any 

case, the homology of the labral emargination and other 

features of the shell are considered herein to support a 

close relationship between the pleurotomariaceans and 

bellerophontaceans. Therefore, the Bellerophontacea is 

assigned to the Archaeogastropoda, not to the Monoplacophora. (See section on "Phylogeny and Classification" 

for complete discussion.)

Suborder BELLEROPHONTINA Ulrich and Scofield, 1897

Diagnosis.—Shell isostrophic, bilaterally symmetrical; coiling generally contiguous, involute to convolute, 

but disjunct coiling is known; apertural margin with 

median sinus or slit, the latter generating a selenizone, 

the former resulting in the development of tremata in 

some cases; no opercula known; presence of paired 

aspidobranch ctenidia implied by presence of labral 

emargination; circumumbilical muscle scars infer single 

pair of retractor muscles.

Stratigraphic range.—Upper Cambrian-Lower Triassic.

Superfamily BELLEROPHONTACEA McCoy, 1851

Diagnosis.—Same as for order.

Stratigraphic range.—Same as for order.

Discussion. Table 17 gives a summary of the higher 

taxonomic classification of the Bellerophontacea used 

herein. The first four families listed (Bucanellidae 

through Euphemitidae) have a labral emargination in the 

form of a sinus. The next four families (Tropidodiscidae 

through Carinaropsidae) have a true slit. In all other 

ways, the shell morphologies of the eight families are 

quite similar. Knight and others (1960) placed considerable taxonomic emphasis on the presence or absence of a 

slit in bellerophontaceans. However, Horny (1963a)

noted the likelihood of a gradation between a sinus and a 

slit, and their application as features of great taxonomic 

significance has been questioned.

The families Cyrtolitidae and Sinuitidae are here 

assigned to the Monoplacophora; both families are sinusbearing and were assigned to the Bellerophontacea by 

Knight and others (1960). This change in class-level 

assignment resulted from the discovery of dorsally discrete multiple paired muscle scars in species of Cyrtolites 

and Sinuitopsis (Horny, 1963c; Rollins and Batten, 

1968). Runnegar (1982) reported monoplacophoranlike 

muscle scars in Sinuites, in contrast to Knight's (1947a) 

claim of columellar muscle scars in that genus. Runnegar's discovery is not surprising, because Sinuites and 

Sinuitopsis are close morphologically; Knight and others 

(1960) treated these two taxa as subgenera. Rollins and 

others (1971) reported gastropodlike columellar scars in 

a species of the sinus-bearing genus Sinuitina. Because 

of the general overall conchological similarities of many 

sinus-bearing and slit-bearing symmetrical univalved 

mollusks, and because some have muscle scars here 

interpreted as monoplacophoranlike whereas others 

have gastropodlike columellar muscle scars, I believe it is 

premature to transfer all sinus-bearing species to the 

Monoplacophora.

Thus, until new information indicates otherwise, I will 

treat the sinus-bearing families Bucanellidae, Grandostomatidae, Tremanotidae, and Euphemitidae as bellerophontacean gastropods. No members of these families 

are present in the faunas described herein; however, a 

brief discussion of each family follows.

The family Bucanellidae (Koken, 1925) occurs in rocks 

ranging in age from Late Cambrian to Middle Permian. 

It is characterized by a relatively broad phaneromphalous shell having a sinus-bearing apertural margin, fairly fine collabral threads, and, in some cases, 

spiral threads. The genera here included in the Bucanellidae were placed by Knight and others (1960) in three 

family-level taxa Cyrtolitidae, Bucanellinae, and Sinuitinae. As mentioned previously, Cyrtolites and Sinuites, 

and close allies, are now classified as monoplacophorans, 

not as gastropods. Sinuitina closely resembles Cyrtolites in its conchology, but because of its gastropodlike 

columellar muscle scars, it is here placed in the family 

Bucanellidae. The trilobate shell of Bucanella also suggests gastropod affinities, based on the convincing functional analyses of such shells done by Peel (1974). Other 

genera placed in the Bucanellidae are Owenella and, with 

question, Trigyra, Anconochilus, and Crenistriella.

The family Grandostomatidae is characterized by an 

explanate adult shell that is phaneromphalous and sinuate and has transverse and spiral ornament. The family 

ranges from the Middle Ordovician to the Devonian, and 

is made up of the genera Grandostoma, Ptomatis, and
MIDDLE AND UPPER ORDOVICIAN SYMMETRICAL UNIVALVED MOLLUSKS, CINCINNATI ARCH REGION 0117

1 Patellostium. Horny (1962) proposed this grouping as a 

subfamily of the Sinuitidae in order to distinguish sinuate 

forms having a greatly expanded body whorl. This shell 

form seems convergent with some slit-bearing bellerophontaceans, such as members of the Carinaropsidae. 

Peel (1977b) has interpreted such expanded shell forms 

as adaptations to life on soft substrates, the broad 

surface area inhibiting sinking into the mud.

The Tremanotidae includes sinuate shells having dorsal tremata developed in association with an expanded 

aperture. The family is represented by the Middle Silurian and Lower Devonian genera Tremanotus and 

Boiotremus, respectively. Peel (1972, p. 419) erected the 

subfamily Tremanotinae of the family Sinuitidae, demonstrating that the previous close association of these 

genera to Salpingostoma was due to homeomorphy. He 

showed that the tremata of Tremanotus and Boiotremus 

were formed by the periodic expansion of the aperture 

and closing off of a deep sinus, and that no slit was 

present. Peel pointed out that the periodic expansions of 

the shell aperture in Tremanotus commenced only in 

later ontogenetic stages, whereas in Boiotremus they 

occurred throughout ontogeny. He assumed that the 

successive flared apertures were resorbed with continuation of growth.

The family Euphemitidae is characterized by a shell 

entirely covered by inductural layers, with a narrow 

sinus that nearly becomes a slit in some species. The 

family is known from the Mississippian to the Permian, 

with questionable members in the Devonian. The family 

includes the genera Euphemites, Paleuphemites, 

Euphemitopsis, Warthia, and IStachella. The exact 

position of this family in the phylogeny of the bellerophontaceans is uncertain, and its relationships to other 

sinuate and slit-bearing families needs to be evaluated 

carefully. Rollins (1967) interpreted this group as being 

"ploughers" that ploughed through the surface sediments in search of food, similarly to the modern moon 

snail Polinices.

The sinuate forms appeared during the Late Cambrian 

along with the slit-bearing bellerophontaceans, but in 

greater diversity and abundance. Both groups maintained low diversities through the Early Ordovician. The 

Middle Ordovician was a time of great radiation for the 

slit-bearing group. The only sinus-bearing group to 

become truly abundant and diverse seems to be the late 

Paleozoic euphemitids; their success may be related to 

their specialized morphology. All slit-bearing families, 

and most of the subfamilies, are present in the faunas 

considered herein.

Family TROPIDODISCIDAE Knight, 1956

Diagnosis.— Shell small to moderate in size, whorls 

laterally compressed and narrow, though somewhat

expanded in some cases; umbilicus wide; slit deep, 

extending as much as one-half whorl from the apertural 

margin; parietal inductura not developed; posterior train 

present in few cases.

Stratigraphic range.—Upper Cambrian-Lower Devonian.

Discussion. Most American species of Tropidodiscus 

Meek and Worthen, 1866, and Phragmolites Conrad, 

1838, were described under the synonymous names 

Oxydiscus deKonnick, 1882, and Conradella Ulrich and 

Scofield (1897), respectively. Ulrich and Scofield (1897, 

p. 851, 852) assigned these two genera (under the names 

Oxydiscus and Conradella) to the family Bucaniidae, 

believing they were allied to Bucania through the common possession of a deep slit, a wide umbilicus, and the 

lack of a parietal callosity. Dall, in Eastman (1927), and 

Wenz (1938) continued this practice.

Knight (1956, p. 42) erected the new subfamily Tropidodiscinae, and Knight and others (1960) placed it in the 

family Bellerophontidae (adjacent to the Bucaniinae). 

They included the genera Tropidodiscus, Phragmolites, 

Temnodiscus Koken, 1896, and Chalarostrepsis Knight, 

1948, in the Tropidodiscinae. All but the last of these 

genera occurs in the Ordovician faunas of the Cincinnati 

arch region. Horny (1963a, p. 70) supported the classification of Knight and others (I960), but Golikov and 

Starobogatov (1975, p. 207) elevated the Tropidodiscinae 

to the family level, a change that is supported here.

The familial assignment of the genus Temnodiscus is a 

matter of some controversy. Koken had associated the 

genus with sinuate forms, as did Horny (1962), who 

claimed the genus did not bear a true slit. However, I 

agree with the classification of Knight and others (1960), 

as Knight's (1941, pi. 10, figs. 3a-d) figures clearly show 

a true slit and selenizone in the type species of the genus, 

which is Temnodiscus lamellifer (Lindstrom, 1884).

The tropidodiscids seem to have played a significant 

role in the ancestry of other early Paleozoic bellerophontaceans. Chalarostrepsis praecursor Knight, 1947b, 

from the Upper Cambrian of Quebec, and ? Tropidodiscus sp., from the Middle or Upper Cambrian of Bolivia, 

are the earliest known bellerophontaceans (Curry and 

Morris, 1967, p. 426). Chalarostrepsis is exemplary of 

the primitive morphological traits of the Bellerophontacea: a loose style of coiling, a wide-open umbilicus, and a 

deep anteromedian apertural slit (see "Functional Morphology" section). Chalarostrepsis is apparently ancestral to the other genera of the family, which show a trend 

toward tighter involute coiling.

The Lower Ordovician Eobucania Kobayashi, 1955, 

seems to have descended from the tropidodiscids, or at 

least from the same stock, both having deep slits and 

well-defined selenizones. Also, like Chalarostrepsis and 

Tropidodiscus, Eobucania has only collabral shell orna-
0118 CONTRIBUTIONS TO THE ORDOVICIAN PALEONTOLOGY OF KENTUCKY AND NEARBY STATES

ment, except for threads bordering the selenizone. The 

more primitive members of the genus Bucania (the B. 

sulcatina group of Ulrich and Scofield, 1897) also are 

characterized by a wide-open umbilicus and a deep slit, 

as are species of the new genus Undulabucania, these 

forms differing from the tropidodiscids mainly in their 

more broadly rounded, depressed whorl forms. It seems 

likely that the tropidodiscids are ancestors of the 

bucaniids.

Such traits as the narrow whorl form and the presence 

of a posterior train in some tropidodiscids could suggest 

a link to the Early and Middle Cambrian helcionellaceans, but such a connection is not actively supported 

here. At present, relations between Upper Cambrian 

molluscan univalves and those earlier forms remain a 

matter of some controversy and require a great deal 

more study.

Genus TROPIDODISCUS Meek and Worthen, 1866

Diagnosis.—Shell laterally compressed, whorls gradually expanding, barely contiguous; umbilicus large; slit 

deep, selenizone as thin keel, with or without lunulae; 

growth lines only ornament.

Description. Shell small to moderate in size, strongly 

compressed laterally; whorls gradually expanding 

throughout growth, barely contiguous, resulting in 

large, open umbilicus exposing all previous volutions. 

Apertural outline subtriangular to lanceolate; sinus 

broadly curved, rather deep; slit deep, narrow; selenizone on high, thin keel, which may be sharp or slightly 

truncated and with lunulae. Growth lines as fine threads 

or fine imbricating lamellae. No revolving ornament.

Type species.—Bellerophon curvilineatus (Conrad, 

1842), by original designation (Knight, 1941, p. 360, 361).

Distribution.—The genus is known from the Early 

Ordovician (Canadian) to the Late Devonian. Species are 

present in upper Middle Ordovician (KirkfieldianShermanian) and Late Ordovician (Richmondian) strata 

in the Cincinnati arch region.

Comparison. — Tropidodiscus could be confused only 

with species of Phragmolites, the latter differing mainly 

in its consistent strong, wavy lamellae, which do not 

curve over the surface of the shell, thus reflecting the 

absence of an apertural sinus.

Discussion.—Knight (1941, p. 360, 361) wrote a 

detailed review and opinion on the complex nomenclatural history of this genus. The genus originally was 

named Tropidiscus Meek (1866), but this was an invalid 

homonym. Meek and Worthen (1866, p. 160) emended 

the name to Tropidodiscus (whether purposely or not is 

a matter of question). DeKoninck (1882, p. 81) erected 

the genus Tropidocyclus as an objective synonym of 

Tropidiscus, designating Bellerophon curvilineatus 

Conrad, 1842, the type species. Koken (1889, p. 390)

erected the genus Oxydiscus to replace the homonym 

Tropidiscus and its emendation, and Tropidocyclus, 

which he rejected because it encompassed unrelated 

species. Knight (1941, p. 361) strongly disagreed with 

Koken's action. He favored the adoption of Tropidocyclus as the valid genus name, but reluctantly accepted 

the principles of the International Commission of Zoological Nomenclature, which dictated retention of the 

emended name Tropidodiscus Meek and Worthen (1866). 

Tropidodiscus shows relationship to the Bucaniidae in 

its large umbilicus, lack of a parietal callosity, and deep 

slit, but this evidence is offset by its lack of any spiral 

ornament. Nevertheless, the genus probably is a representative of a primitive stock of bellerophontaceans that 

gave rise to the Bellerophontidae and Bucaniidae. The 

earliest known bucaniid genus, Eobucania Kobayashi 

(1955), agrees with Tropidodiscus in its open umbilicus 

and deep apertural slit, and, significantly, its spiral 

ornament consisting of only two threads bordering the 

selenizone.

Tropidodiscus subacutus (Ulrich), 1897

Plate 41, figures 9-13

Oxydiscus subacutus Ulrich in Ulrich and Scofield, 1897, p. 913, pi. 62, 

figs. 62-65; pi. 82, figs. 23-25; Weller, 1903, p. 179, pi. 12, figs. 8, 

9; Grabau and Shimer, 1909, p. 616, 826; Bassler, 1932, p. 222, pi. 

20, figs. 11, 12.

Cyrtolites subacutus Miller, 1897, p. 767.

Tropidodiscus subacutus (Ulrich), Shimer and Shrock, 1944, p. 443, pi. 

178, figs. 8, 9.

Diagnosis.— Shell moderately small (up to 13 mm 

long), lenticular, with 3.5-4.5 volutions, each embracing 

one-third to one-half the preceding one; whorl floor keel 

distinct, narrow, sharply rounded.

Description.— Shell moderately small, lenticular, the 

greatest width about one-half the shell height; 3.5-4.5 

volutions in adult, each volution embracing one-third to 

one-half the preceding one. Shell width and thickness 

greatest at narrowly rounded umbilical shoulder; dorsal 

slopes slightly concave to flat; dorsum acutely carinate, 

but with narrow truncation at crest for selenizone. 

Umbilici wide, all earlier volutions visible; umbilical 

slopes cut inward essentially horizontally. Whorl floor 

keel distinct, narrow, sharply rounded. Slit deep, narrow; sinus narrow, V-shaped, relatively deep. Growth 

lines fine, closely and fairly regularly spaced.

Measurements.—Measurements of T. subacutus are 

listed in table 37.

Material.— The lectotype is from the original type 

suite (USNM 45952) and is herein designated USNM 

387021 (pi. 41, figs. 11-13). It and 20 paralectotypes 

(USNM 45952), as well as all of the new USGS collections 

cited above, are silicified. No complete specimens are 

known, all having at least the anteromedian, slit-bearing,
MIDDLE AND UPPER ORDOVICIAN SYMMETRICAL UNIVALVED MOLLUSKS, CINCINNATI ARCH REGION 0119

TABLE SI.—Measurements (in millimeters) of Tropidodiscus 

subacutus

USNM No. Shell 

length

Shell 

height

Aperture 

length

Aperture 

width

Umbilical 

diameter

387021 12.95 9.9 6.4 5.2

area broken away. As in Salpingostoma, the shell adjacent to the deep slit must have been thinnest and 

weakest, and thereby most easily broken.

Distribution.—Ulrich and Scofield (1897) reported this 

species from the upper beds of the "Trenton Group" near 

Danville, Ky., and their 21 type specimens are labeled as 

coming from the "Flanagan" beds of that vicinity, which 

are now considered to be in the upper Lexington Limestone (Shermanian). The name "Flanagan chert beds" 

was abandoned after it was found that the name had been 

used for different silicified limestone horizons at various 

stratigraphic levels within the Lexington Limestone. 

Ulrich and Scofield also claimed possible recognition of 

the species "in Tennessee and in the Fusispira beds in 

Minnesota." Weller (1903, p. 46) reported the species 

from talus blocks from "the upper Black River and the 

lower Trenton beds" of New Jersey.

In the USGS silicified collections, T. subacutus was 

identified from the Salvisa Bed of the Perryville Limestone Member (6915-CO, 6916-CO) and the upper Devils 

Hollow Member (5087-CO, 5095-CO) of the Lexington 

Limestone. Fragmentary specimens assigned to T. cf. T. 

subacutus were found in the Tyrone Limestone (5075- 

CO) and the Faulconer Bed of the Perryville Limestone 

Member (6136-CO) of the Lexington Limestone. Additional fragmentary specimens classifiable only to T. sp. 

indet., but probably belonging to this species, were 

found in the Curdsville Limestone Member (6134-CO, 

7784-CO), the Grier Limestone Member (4880-CO), and 

the Devils Hollow Member (5036-CO, 7789-CO) of the 

Lexington Limestone.

Therefore, T. subacutus is certainly recognized from 

the upper Lexington Limestone (Shermanian), but probably occurs also in the Tyrone Limestone (Rocklandian) 

and in the lower Lexington Limestone (Kirkfieldian).

Comparison.—The only other species in the fauna 

warranting comparison is T. cristatus (Safford), which 

differs in its somewhat larger size, its more rapid expansion and fewer number of volutions at maturity, its looser 

coiling (volutions embrace only about one-sixth the 

height of the preceding whorl), resulting in a larger 

umbilicus, and its more rounded whorl floor keel (Ulrich 

and Scofield, 1897, p. 914).

Discussion. —T. subacutus appears to have been a 

geographically widespread, and possibly stratigraphically long ranging, species. Its rather thin, delicate, 

small shell makes its preservation and recognition diffiTABLE 38. Measurements (in millimeters) of Tropidodiscus

cristatus

USNM No.

45950 

45950

Shell 

length

21.9

22.8

Shell 

height

17.0 

20.2

Aperture 

length

8.7 

8.8

Aperture 

width

8.0 

9.1

Umbilical 

diameter

6.5

8.4

cult. It appears to have inhabited a wide range of normal 

marine shallow-water carbonate environments.

Tropidodiscus cristatus (Safford), 1869

Plate 41, figures 6-8

Cyrtolites cristatus Safford, 1869, p. 289.

Oxydiscus cristatus Ulrich and Scofield, 1897, p. 914, pi. 82, figs. 

26-28.

Diagnosis.— Shell moderately large (up to 23 mm 

long), with 3.0-3.5 volutions in adult, each embracing 

about one-sixth the previous one; whorl floor keel relatively low and rounded.

Measurements.—Measurements of T. cristatus are 

listed in table 38.

Material.—Only the two type specimens (USNM 

45950) are known. Both of these are silicified and have 

the last one-third whorl broken away. The specimen 

figured on plate 41, figures 6-8, is here designated the 

lectotype.

Distribution.—The type specimens are from the Cannon facies of the Bigby-Cannon Limestone (KirkfieldianShermanian) of Jackson County, Tenn.

Comparison.— The most similar species is T. subacutus', for comparisons between the two, see "Comparison" 

under that species. (Also see Ulrich and Scofield, 1897, p. 

814.)

Tropidodiscus magnus (Miller), 1878 

Plate 42, figures 1, 2

Cyrtolites magnus Miller, 1878, p. 103, pi. 3, fig. 10. 

Oxydiscus magnus Ulrich and Scofield, 1897, p. 859; Cumings, 1908, p. 

970, pi. 41, fig. 5.

Diagnosis.— Shell large (up to 27 mm long), narrow, 

lenticular, dorsal slopes gently convex, dorsum rounded; 

three or more volutions, each embracing about one-third 

of previous one; sinus narrow and deep.

Measurements.— Measurements of the holotype of T. 

magnus are listed in table 39.

Material.-The holotype (UC 10838; pi. 42, figs. 1, 2) 

is a very weathered calcitic specimen. A few other poorly 

preserved unnumbered specimens are in the University 

of Cincinnati Geology Museum collections.

Distribution.—The holotype is from Richmondian-age 

strata near Richmond, Ind. (Miller, 1878). Unnumbered 

specimens in the University of Cincinnati collections are
0120 CONTRIBUTIONS TO THE ORDOVICIAN PALEONTOLOGY OF KENTUCKY AND NEARBY STATES

TABLE 39. Measurements (in millimeters) of Tropidodiscus

magnus

UCNo. Shell Shell

length height length

Aperture Aperture Umbilical

width diameter

10838 27.0 24.0 18.5 10.0

labeled as coming from the Saluda Formation at 

Madison, Ind.

Comparison.—The convex dorsal slopes and rounded 

dorsum of T. magnus distinguish it from any other 

known species of the genus.

Discussion. Although T. magnus is known from only 

a small number of specimens, no other species has such a 

rounded (rather than carinate) dorsum (pi. 42, figs. 1, 2). 

T. magnus is the only species of Tropidodiscus recognized from the Upper Ordovician of the Cincinnati arch 

region. However, I note that 16 poorly preserved silicified fragments assignable only to T. sp. indet. were 

recognized in four USGS samples (6411-CO, 6412-CO, 

6414-CO, 7843-CO) from the Gilbert Member of the 

Ashlock Formation (Maysvillian) of Kentucky.

Genus PHRAGMOLITES Conrad, 1838

Diagnosis.— Shell generally rather small (in most 

cases less than 10 mm long); sinus lacking, slit half a 

volution deep; growth increments lamellose, corrugated, 

scalloped; fine revolving threads present.

Description.— Shell rather small, generally narrow 

and gradually expanding, but in a few cases broad and 

rapidly expanding; whorl slopes gently convex; umbilicus 

wide; apertural outline elliptical, subcordate to subtriangular; parietal deposits lacking. Sinus lacking; slit half a 

volution deep; selenizone narrow, lunulate, bordered by 

revolving threads, in many cases elevated on a carina. 

Growth lines fine, straight; periodic growth increments 

lamellose, corrugated, scalloped, evenly spaced; fine 

revolving threads generally present.

Type species.—Phragmolites compressus Conrad, 

1838, by monotypy.

Distribution.— Middle and Upper Ordovician 

(Blackriveran-Richmondian) in North America and 

Europe.

Comparison.— The lamellose, corrugated, scalloped, 

and uncurved (nonsinuate) growth increments readily 

distinguish Phragmolites from Tropidodiscus, which has 

a similar shell form and a deep slit. Temnodiscus can 

have many lamellose growth increments similar to those 

of Phragmolites, but it differs by having a sinus and a 

relatively shallow slit.

Discussion.—Conrad (1838) thought P. compressus to 

be a chambered shell, hence the genus name, translating 

"partitioned stone." Hall (1847) asserted that the species 

was not chambered and placed it in the genus Cyrtolites.

Ulrich and Scofield (1897, p. 905) recognized the species' 

generic distinctiveness, but chose not to revive the name 

Phragmolites as it gave "an incorrect idea of the fossil." 

They concluded, "Had the name [Phragmolites] ever 

attained currency, we would feel ourselves bound to 

revive it, on the score of priority, despite its inappropriateness, but as no one, so far as we can learn, ever 

adopted it, we thought it best to view the name as one 

that has failed of being established because of incorrect 

and insufficient definition." Hence, they renamed the 

genus Conradella, but curiously made C. obliqua Ulrich 

and Scofield the type species, even though Conrad's 

original type species was recognized as a member of the 

new genus. Bassler (1915) used the name Phragmolites 

rather than Conradella, but numerous other authors, 

including Koken (1898, 1925) and Reed (1921), used 

Conradella. Wenz (1938, p. 102) placed Conradella in 

synonymy with Phragmolites. Knight (1941) described 

the type species of both genera, and Knight and others 

(1960, p. 1179) followed Wenz (1938). All modern authors 

agree with the priority of Phragmolites.

Ulrich and Scofield (1897, p. 905), citing a long apertural slit, large umbilicus, generally gradually expanding 

whorls, and surface sculpture as phylogenetic morphological characteristics, proposed that Phragmolites and 

Bucania Hall were derived from the same stock. This 

viewpoint is heartily supported here. Among the Tropidodiscidae, Phragmolites shows the closest morphological connection to the Bucaniidae. Especially comparable 

to Phragmolites is Undulabucania n. gen., which 

includes species whose general form resembles that of 

the Bucania sulcatina group, but which have very deep 

slits and distinctly wavy, intersecting or nearly intersecting, growth lines. In the latter two characteristics, 

Undulabucania shows common morphologic traits with 

Phragmolites.

Phragmolites compressus Conrad, 1838

Plate 42, figure 14; Plate 44, figures 1-A

Phragmolites compressus Conrad, 1838, p. 119; Weller, 1903, p. 178,

pi. 12, figs. 16, 17; Knight, 1941, p. 242, pi. 9, fig. 2; Shinier and

Shrock, 1944, p. 443, pi. 178, fig. 5; Wilson, 1951, p. 29, pi. 2, figs.

17, 18. 

Cyrtolites compressus (Conrad), Hall, 1847, p. 188, pi. 40A, figs. 2a-f;

1862, p. 40, fig. 4; Chamberlin, 1883, p. 158, fig.; Lesley, 1889, p.

182, fig. 

Conradella compressa (Conrad), Ulrich and Scofield, 1897, p. 906, not

described or figured. 

Conradella similis Ulrich in Ulrich and Scofield, 1897, p. 906, not

figured.

Diagnosis.— Shell narrow, very gradually expanding; 

whorls barely contiguous, lanceolate-shaped, longer than 

wide; corrugated growth lamellae widely spaced, with 

five or six reentrants per side.
MIDDLE AND UPPER ORDOVICIAN SYMMETRICAL UNIVALVED MOLLUSKS, CINCINNATI ARCH REGION 0121

TABLE 40. Measurements (in millimeters) of Phragmolites 

compressus

USNM No.

387019 

387020

Shell 

length

12.7 

9.0

Shell 

height

7.3

Aperture 

length

5.5

4.8

Aperture 

width

4.7

Lamellae 

spacing

1.0 

0.7-1.0

Description. Shell small (up to 13 mm long), narrow, 

very gradually expanding; whorls barely contiguous, 

embracing only the dorsal carina of the preceding whorl. 

Dorsal carina prominent, slightly rounded, with faint 

lunulae; dorsal slopes briefly concave near carina, then 

becoming evenly convex; umbilical shoulders sharply 

rounded; ventral slopes slightly convex to nearly flat. 

Apertural outline lanceolate, higher than wide. Umbilici 

wide. Slit deep, apparently about one-half a volution. 

Growth lines fine, closely spaced; very fine revolving 

lines visible in some specimens. Periodic corrugated 

growth lamellae rather widely spaced, with five or six 

square reentrants from shoulder to carina.

Measurements.— Measurements of P. compressus, 

listed in table 40, are estimates based on fragmentary 

material (pi. 44, figs. 1^4).

Material.— Three specimens from Kentucky were 

examined. The holotype of P. similis (USNM 47568; pi. 

42, fig. 14) is a fragmentary silicified specimen. USNM 

387020 (pi. 44, figs. 2-4) is a broken silicified shell having 

a well-preserved exterior. USNM 387019 (pi. 44, fig. 1) is 

a calcitic specimen embedded in a limestone with brachiopod and bryozoan fragments.

The whereabouts of Conrad's (1838) type is unknown, 

but Knight (1941, p. 242, pi. 9, fig. 2) described and 

figured Hall's (1847, p. 188, pi. 40A, figs. 2a, b) hypotype. Knight assumed that because Conrad was a colleague of Hall, Hall was familiar with the species, and his 

description might well be based on the type material. 

Knight believed that Hall's figured specimen may have 

been part of Conrad's type suite.

Distribution.— This species has been reported from 

the "Trenton Group" of New York, New Jersey, Pennsylvania, and Ontario. The label included with the Kentucky hypotype (pi. 44, figs. 1^4) described here reads: 

"Lower part of Trenton and perhaps Black River, 2-4 

miles north of Burgin, Mercer Co., Kentucky." These 

specimens are Kirkfieldian-Shermanian, and probably 

Rocklandian, in age. The holotype of P. similis is probably Blackriveran in age. Thus, the total stratigraphic 

range is Blackriveran-Shermanian.

Comparison.—P. compressus has a lanceolate apertural outline that is longer than wide, whereas P. obliqua 

has a nearly circular aperture, and P. grandis and P. 

triangularis have apertures that are wider than long.

Discussion. — Conradella similis Ulrich is put in synonymy with this species. The holotype (USNM 47568) of 

C. similis is a poorly preserved fragment (pi. 42, fig. 14) 

that is closest to P. compressus, and no other specimens 

were located. A label in the museum tray containing the 

holotype of C. similis, initialed by Ulrich, reads: "Two 

other specimens formerly in this box are of C. compressa 

and have been removed." The single remaining specimen 

resembles P. compressa in its size and general shell 

form, and in the obliquity of its corrugated growth 

lamellae and the number of reentrants on those lamellae. 

This specimen is from the High Bridge Group (Blackriveran) of Kentucky.

Phragmolites grandis (Ulrich), 1897

Plate 42, figures 7-13; Plate 43, figures 1-3

Conradella grandis Ulrich in Ulrich and Scofield, 1897, p. 908, pi. 62,

fig. 67; pi. 67, figs. 16-18. 

Phragmolites grandis (Ulrich), Bassler, 1932, p. 194, pi. 6, figs. 11, 12.

Diagnosis. — Shell relatively large (up to 30.5 mm 

long) and rapidly expanding; aperture subtriangular, 

wider than long; corrugated lamellae with five or six 

reentrants per side.

Description. — Shell large and rapidly expanding for 

genus, lateral flaring of aperture increases in adulthood. 

Dorsal slopes gently convex, umbilical shoulders sharply 

rounded, umbilical slopes nearly flat and horizontal; 

umbilicus moderate in size, deep. Apertural outline 

subtriangular, width becoming increasingly greater than 

length through growth. Slit about one-half volution deep, 

rather wide; selenizone on truncated dorsum, bordered 

by revolving threads. Growth lines fine, closely spaced, 

crossed by fine, widely spaced revolving lines; periodic 

corrugated growth lamellae distinct, with five or six 

reentrants from whorl crest to shoulder.

Measurements.—Measurements of the lectotype and a 

paralectotype of P. grandis are listed in table 41.

Material. — Five calcitic specimens are in the original 

type suite (USNM 45756). The specimen shown on plate 

42, figures 10-13, is here designated the lectotype, 

because it was Ulrich and Scofield's (1897, pi. 67, figs. 

16-18) figured specimen; it is given the number USNM 

315667. The paralectotypes figured here (pi. 42, figs. 7-9; 

pi. 43, figs. 1-3) are numbered USNM 315668 and 

387018, respectively. The remaining two unfigured paralectotypes retain the number USNM 45756.

Distribution.—The species is known only from the 

Lebanon Limestone (Blackriveran) in the vicinity of 

Lebanon, Tenn.

Comparison.—P. grandis is similar to P. triangularis 

Ulrich and Scofield from Blackriveran strata of the 

Upper Mississippi Valley, but it is larger and more 

rapidly expanding, and has more convex dorsal slopes, a
0122 CONTRIBUTIONS TO THE ORDOVICIAN PALEONTOLOGY OF KENTUCKY AND NEARBY STATES

TABLE 41. Measurements (in millimeters) of Phragmolites grandis

USNM No.

315667 

315668

Shell 

length

30.5 

20.0

Shell 

height

23.0 

13.7

Aperture 

length

16.0 

11.4

Aperture 

width

19.0

Umbilical 

diameter

9.8 

5.4

Ventral 

width

8.8 

7.2

Wave length 

of lamellae

1.5-2.0 

1.5

relatively wider aperture, fewer corrugated lamellae 

folds, and more distinct revolving lines (Ulrich and 

Scofield, 1897, p. 908-909).

Discussion. The smaller, submature specimens of 

this species, as shown by the paralectotype USNM 

387018 (pi. 43, figs. 1-3), are proportionately narrower. 

The increase in whorl expansion rate apparently was an 

adult occurrence. The two adult specimens figured here 

(pi. 42, figs. 7-9 and 10-13) at first glance appear 

different; however, this difference seems to be a result of 

preservation. The paralectotype (pi. 42, figs. 7-9) has the 

expanded aperture broken away, its right side is an 

internal mold, and the preserved shell material on the 

left side is worn. The lectotype, USNM 315667 (pi. 42, 

figs. 10-13), preserves the aperture and shell sculpturing 

much better. The broad expanded aperture of this 

species is uncharacteristic of the genus and 

suggests a phylogenetic relationship to Bucania and 

Undulabucania.

Phragmolites cellulosus (Ulrich and Scofield), 1897

Plate 43, figures 4-12

Conradella dyeri var. cellulosa Ulrich and Scofield, 1897, p. 910, pi. 67,

figs. 27-29; Cumings, 1908, pi. 39, fig. 9. 

Phragmolites dyeri cellullosus (Ulrich and Scofield), Bassler, 1915, p.

972.

Diagnosis.— Shell small, gradually expanding, whorls 

somewhat inflated in adults; aperture subcordate; corrugated lamellae closely spaced, spiral threads weak.

Description. — Shell small (up to 11.5 mm long), gradually expanding, narrow; whorls becoming somewhat 

inflated in adulthood. Dorsal slopes moderately convex; 

umbilical shoulders rather narrowly rounded; ventral 

slopes slightly convex, angled downward. Apertural 

outline subcordate. Slit deep; selenizone on prominent, 

elevated, rounded dorsomedian keel, lunulae faint. Corrugated growth lamellae very closely spaced (four per 

millimeter), scalloping generally not distinctly squared; 

revolving threads moderately distinct on well-preserved 

surface, generally three per millimeter.

Measurements.— Measurements of P. cellulosus are 

listed in table 42.

Material.— Three specimens were examined. USNM 

47562 is a complete shell whose surface is worn (pi. 43, 

figs. 7-9). USNM 61029 is a specimen whose surface is 

well preserved (pi. 43, figs. 4-6). USNM 79250 is a

specimen whose ventral whorl is broken away (pi. 43, 

figs. 10-12). The holotype (USNM 45753) is not figured.

Distribution.—-The specimens examined here are all 

from the Hermitage Formation (Kirkfieldian) of central 

Tennessee. Ulrich and Scofield (1897, p. 910) reported 

this species from the "Clitambonites bed" at St. Paul and 

Cannon Falls, Minn., which was their basal "Trenton" 

unit. Bassler (1915, p. 972) stated that the species 

occurred in the Prosser Formation at the same localities, 

which, according to Sweet and Bergstrom (1976, textfig. 3), is Shermanian-Edenian in age. Ross and others 

(1982) showed the unit as Shermanian in age.

Comparison.—Ulrich and Scofield (1897, p. 910) distinguished P. dyeri var. cellulosus from P. dyeri dyeri 

by the former's much smaller dorsal keel and by differences in their surface markings. I recognize P. cellullosus as a distinct species on the basis of these characteristics. The Tennessee specimens assigned to P. 

cellulosus have a very prominent dorsal keel, but their 

surface markings are subtly different from P. dyeri. The 

lamellae of P. cellullosus are more distinctly scalloped 

and are not quite as closely spaced as in P. dyeri. The 

Tennessee specimens also attain a slightly larger size, 

and their whorls become more inflated, compared with 

typical Richmondian P. dyeri.

Discussion.—As implied above, the differences 

between P. cellulosus and P. dyeri are subtle, but they 

are recognizable. Confusion between the two species 

should not be a problem, and their stratigraphic ranges 

are not known to overlap.

P. cellulosus occurs in Safford's (1869) "Orthis bed" 

(Hermitage Formation) in Tennessee and in Ulrich and 

Scofield's (1897) "Clitambonites bed" (Prosser Formation) in Minnesota, each considered the base of the 

"Trenton" by those authors. Both formations are interbedded shales and argillaceous limestones containing 

abundant brachiopod faunas.

TABLE 42.—Measurements (in millimeters) of Phragmolites 

cellulosus

USNM No.

47562

79250

61029

Shell 

length

8.5

10.0

11.5

Shell 

height

7.30

-

9.25

Aperture 

length

3.6

4.1

6.5

Aperture 

width

4.3

5.5

6.0

Umbilical 

diameter

3.5

-

4.6

Ventral 

width

1.9

1.9

3.0
MIDDLE AND UPPER ORDOVICIAN SYMMETRICAL UNIVALVED MOLLUSKS, CINCINNATI ARCH REGION 0123

TABLE 43. Measurements (in millimeters) of the holotype of 

Phragmolites bellulus

USNM No.

45751

Shell 

length

10.75

Shell 

height

9.1

Aperture 

length

4.5

Aperture 

width

4.0

Ventral 

width

1.9

Phragmolites bellulus (Ulrich), 1897

Plate 44, figures 5-7

Conradella bellulus Ulrich in Ulrich and Scofield, 1897, p. 910, pi. 67,

figs. 23-26. 

Phragmolites bellulus (Ulrich), Bassler, 1915, p. 971.

Diagnosis. — Shell small (up to 11 mm long), narrow; 

slit only one-quarter whorl deep; selenizone with distinct 

lunulae; corrugated growth lamellae moderately closely 

spaced, with eight or nine reentrants per side.

Description.— Shell small, very gradually expanding, 

narrow throughout. Dorsal slopes broadly convex, 

umbilical shoulders rather well rounded, umbilical slopes 

gently convex; apertural outline subovate to subcordate. 

Dorsal carina elevated, truncate, with distinct lunulae. 

Slit apparently open only one-quarter whorl. Corrugated 

growth lamellae moderately closely spaced (three per 

millimeter), with eight or nine reentrants from shoulder 

to crest, but losing corrugations within the umbilicus. 

Revolving lines fairly distinct, about six from shoulder to 

crest (two lines per millimeter).

Measurements.— Measurements of the holotype of P. 

bellulus are listed in table 43.

Material.-The holotype (USNM 45751) (pi. 44, figs. 

5-7), and only known specimen, of P. bellulus is a 

well-preserved calcitic specimen.

Distribution. The holotype came from the Fairmount 

biofacies of the Fairview Formation at Covington, Ky. 

(Maysvillian).

Comparison. Ulrich and Scofield (1897) placed P. 

bellulus in an intermediate position between P. elegans 

Miller and P. dyeri Hall. P. bellulus differs from P. 

elegans in its "more slender whorls and less coarsely 

marked surface," and from P. dyeri in its narrower shell 

and less crowded corrugated lamellae, and in having 

distinct lunulae on the slitband.

Phragmolites elegans (Miller), 1874 

Plate 44, figures 11-15; Plate 45, figure 10

Cyrtolites dyeri Hall (part), Meek, 1873, p. 149, pi. 13, figs. 2d, e. 

Cyrtolites elegans Miller, 1874, p. 310, fig. 31; 1889, p. 402, fig. 668. 

Conradella elegans (Miller), Ulrich and Scofield, 1897, p. 911, pi. 67,

figs. 12-15. 

Phragmolites elegans (Miller), Bassler, 1915, p. 972.

Diagnosis.— Shell small (up to 11.4 mm long); apertural outline lanceolate with angular shoulders; seleniTABLE 44. Measurements (in millimeters) of Phragmolites

elegans

USNM 

No.

Shell Shell Aperture Aperture Umbilical Ventral 

length height length width diameter width

315669

315671

315670

315672

8.0

11.4

6.0

4.4

6.6

8.2

5.3

3.8

4.5

5.6

-

2.5

4.0

25.6

3.3

2.2

3.3

4.5

2.7

1.8

1.7

2.0

-

0.8

zone with distinct lunulae; corrugated growth lamellae 

moderately spaced, with five or six shallow reentrants 

per side.

Description.— Shell small, gradually expanding, relatively tightly enrolled, with each volution embracing 

one-third to one-half the previous one, and consisting of 

about three whorls. Dorsal slopes very gently convex 

and quite acute to one another; umbilical shoulders 

subangular; ventral slopes nearly flat and sloping inward; 

apertural outline lanceolate. Slit one-half whorl deep; 

selenizone on moderately elevated dorsomedian keel, flat 

topped, with bordering threads and distinct, closely 

spaced lunulae. Corrugated growth lamellae moderately 

spaced, with five or six shallow reentrants per side. 

Growth lines very fine; revolving threads apparently 

lacking.

Measurements.—Four of Ulrich and Scofield's (1897) 

hypotypes were measured (table 44).

Material.—Four of twelve calcitic specimens in Ulrich 

and Scofield's (1897) hypotype suite (USNM 45754) are 

figured here: USNM 315669 (pi. 44, figs. 11-13), USNM 

315670 (pi. 44, fig. 14), USNM 315671 (pi. 44, fig. 15), and 

USNM 315672 (pi. 45, fig. 10). Other calcitic specimens 

examined were UCGM 19819 and 19820.

Distribution.—Tine species is known only from the 

Corryville biofacies of the Grant Lake or Bull Fork 

Formation (late Maysvillian) in the vicinity of Cincinnati, 

Ohio.

Comparison.—P. grandis (Ulrich) and P. triangularis 

Ulrich and Scofield have shell forms similar to P. elegans, but both of these Blackriveran species attain much 

greater size and have coarser ornament. The early 

Maysvillian species P. bellulus Ulrich differs in its more 

rounded whorl form and its generally more closely 

spaced and more scalloped lamellae. The Richmondian 

species P. dyeri (Hall) differs similarly, but also lacks 

distinct lunulae and bears distinct revolving threads.

Discussion.—P. elegans is a distinctive species 

related to both P. bellulus and P. dyeri. P. bellulus 

apparently is ancestral to P. dyeri. P. elegans seems to 

have evolved separately, as shown by the different 

character of its shell lamellae. P. elegans may be 

descended from P. grandis, which, while larger, had a 

similar whorl form and corrugated lamellae.
0124 CONTRIBUTIONS TO THE ORDOVICIAN PALEONTOLOGY OF KENTUCKY AND NEARBY STATES

Meek (1873) thought this species bore revolving 

threads, but Miller (1874, p. 310, 311) claimed that what 

Meek described "were merely the rows formed by the 

flexures of the transverse lamellae." Miller's point is 

demonstrated in specimen USNM 315669 (pi. 44, fig. 11) 

in the last few visible corrugated lamellae near the 

apertural margin.

It is to be noted that like other Cincinnatian species of 

the genus, P. elegans is associated with ramose bryozoa. 

Plate 45, figure 10, is only one of three of Ulrich and 

Scofield's specimens found "attached" at the aperture to 

a ramose bryozoan fragment. Two possibilities other 

than chance could explain this repeated association and 

position. The bellerophont could have used the elevated 

position for a site from which to suspension feed, or it 

may have been actually feeding at the surface of contact, 

either preying on the bryozoan itself or possibly grazing 

on algae growing on a dead colony. In any case, such 

occurrences probably reflect essentially instantaneous 

burial, in which the bellerophont clamped down, clinging 

to the bryozoan branch, and was entombed.

Phragmolites dyeri (Hall), 1872 

Plate 44, figures 8-10; Plate 45, figure 11

Cyrtolites dyeri Hall, 1872, p. 230, pi. 8, figs. 7, 8; Meek, 1873, p. 149, 

pi. 13, figs. 2a-c, not figs. 2d, e; Miller, 1874, p. 309.

Conradella dyeri (Hall), Ulrich and Scofield, 1897, p. 909, pi. 67, figs. 

30-33; Cumings, 1908, p. 957, pi. 39, figs. 8a-c.

Phragmolithes dyeri (Hall), Grabau and Shinier, 1909, p. 618, figs. 

823e, f.

Phragmolites dyeri (Hall), Bassler, 1915, p. 972.

Diagnosis. Shell small (up to 9.0 mm long); apertural 

outline cordate; dorsal carina elevated, rounded, lacking 

distinct lunulae; corrugated growth lamellae very closely 

spaced, with about 10 reentrants per side; revolving 

threads prominent.

Description.— Shell small, rarely greater than 10 mm 

in diameter, gradually expanding, each whorl embracing 

about one-third of previous one. Apertural outline cordate; dorsal slopes broadly rounded, becoming more 

tightly enrolled at umbilical shoulders, ventral slopes 

convex, angled downward. Slit depth uncertain, but 

apparently less than one-half whorl; selenizone on elevated dorsomedian carina, crest rounded, lunulae lacking. Corrugated growth lamellae very closely spaced 

(four or five per millimeter), notched at contact with 

prominent spiral threads (about three per millimeter), 

straight to round or square between threads, about 10 

notches from whorl shoulder to crest.

Measurements.— Measurements of P. dyeri are listed 

in table 45.

Material.— Ulrich and Scofield's (1897) hypotype 

material (USNM 45752) consists of four calcitic specimens and a small slab containing two additional speciTABLE 45.—Measurements (in millimeters) of Phragmolites dyeri

USNM Shell Shell Aperture Aperture Umbilical Ventral 

No. length height length width diameter width

315673

45752

45752

8.0

9.0

5.7

6.5

7.6

-

4.0

4.3

2.5

4.5

4.4

2.8

3.0

3.0

2.0

1.6

1.8

-

mens. USNM 315673 (pi. 44, figs. 8-10) and USNM 

315674 (pi. 45, fig. 11) were selected from the USNM 

45752 suite for illustration of the species herein. Numerous unnumbered specimens in the collections of the 

University of Cincinnati and Miami University Geology 

Museums were examined.

Distribution.-Ulrich and Scofield (1897, p. 910) 

reported this species from the "Richmond Group" of 

southeastern Indiana, southwestern Ohio, north-central 

Kentucky, and near Spring Valley, Minn. Specimens 

examined here came from the Arnheim, Waynesville, 

and Liberty biofacies of the Bull Fork Formation (Richmondian) of the Indiana-Ohio-Kentucky area.

Comparison.—P. dyeri is readily distinguished from 

P. bellulus and P. elegans by its more cordate shaped 

aperture, its more closely spaced lamellae, its prominent spiral threads, and the absence of lunulae on its 

selenizone.

Discussion. — This species is rather uncommon, probably largely as a result of being overlooked because of its 

small size; when found, it is never abundant. Many 

specimens are quite well preserved, and they are generally found in association with a brachiopod-ramose 

bryozoan-trilobite assemblage. The small slab (USNM 

315674) shown on plate 45, figure 11, is typical. The 

implications of the association between Cincinnatian species of Phragmolites and ramose bryozoans are presented in the discussion of P. elegans.

Ulrich and Scofield (1897, p. 910) claimed that the 

revolving threads of P. dyeri were "as a rule not ridges 

at all, but only an appearance due to the elevation and 

longitudinal arrangement of the closely following loops of 

the transverse lamellae." Contrary to this claim, and in 

agreement with other descriptions, specimens examined 

here, including those of the Ulrich and Scofield collection 

(pi. 44, figs. 8-10), appear to have distinct revolving 

ridges independent of the scalloping of the lamellae.

Although lunulae generally appear to be lacking on the 

selenizone of this species, there is a suggestion of lunulae 

on the specimen shown on plate 44 (fig. 9).

From material examined, it appears that P. dyeri's slit 

is much shorter than the general depth of one-half whorl, 

but at present an exact slit depth for the species cannot 

be given. It should be noted that the most closely related 

species, P. bellulus (Maysvillian), has a slit only one-
MIDDLE AND UPPER ORDOVICIAN SYMMETRICAL UNIVALVED MOLLUSKS, CINCINNATI ARCH REGION 0125

quarter whorl deep. It seems a reduction of slit depth 

may be characteristic of this latest Ordovician lineage of 

Phragmolites.

Genus TEMNODISCUS Koken, 1896

Diagnosis.— Shell small, disjunct to loosely coiled, 

relatively rapidly expanding; whorl slopes convex; aperture sinuate, with shallow slit; selenizone generally on 

truncated dorsum, narrow to broad, with lunulae, without distinct borders, can be ridgelike in submaturity; 

growth lines sublamellose to distinctly lamellose, finely 

crenulated in some cases, with fine revolving threads 

between growth lines.

Type species. —Cyrtolites lamellifer Lindstrom, 1884, 

by subsequent designation of Reed (1921, p. 47).

Distribution. — Temnodiscus is known from the Silurian of Sweden (Lindstrom, 1884) and Great Britain 

(Reed, 1921), and possibly from the Late Ordovician and 

Silurian of Bohemia (Horny, 1963a). The single known 

North American species is from late Middle Ordovician 

(Shermanian) strata near Cincinnati, Ohio.

Comparison. —Temnodiscus is distinguished from 

Tropidodiscus by its lamellose growth increments and 

revolving threads, from Phragmolites by its curved 

(sinuate), more finely crenulated lamellae, and from both 

by its generally more rapid rate of whorl expansion, its 

occasionally disjunct coiling, and its relatively shallow 

slit.

Discussion.— Koken (1896, p. 100) erected the genus 

Temnodiscus for five species placed in Cyrtolites that 

were described by Lindstrom (1884) from the Silurian of 

Sweden. Unaware of Koken's genus name, Ulrich (1897) 

proposed the genus Cyrtolitina for a single American 

species, C. nitidula, and the five species assigned by 

Koken to Temnodiscus; he also designated Cyrtolites 

lamellifer Lindstrom the type species. Reed (1921, p. 47) 

correctly recognized the validity of Temnodiscus indicating C. lamellifer as the type species (Knight, 1941, 

p. 345).

The familial placement of Temnodiscus is a subject of 

some uncertainty. Lindstrom (1884) and Ulrich and 

Scofield (1897) clearly described and figured slitbands in 

the species they described. Koken (1896) agreed with 

these descriptions, but then in 1897 gave a new description of the genus, in which he stated that no slitband was 

present (Reed, 1921, p. 47). Horny (1963a, p. 90), after 

describing three new species of Temnodiscus from the 

Ordovician-Silurian of Bohemia and examining Knight's 

(1941, pi. 10, figs. 3a-d) photographs of the type species, 

concluded that there was no real selenizone in T. lamellifer and congeneric species. He stated (p. 90), "The 

apparent selenizone originates from the very narrow and 

deep true sinus with nearly parallel sides." I also examined Knight's (1941) figures, and believe that the species

does have a true selenizone with distinct lunulae. However, the species described by Horny do not appear to 

have true selenizones; rather, they have sharp dorsal 

carinae. The species described by Reed (1921) are said to 

have narrow slitbands (with lunulae) mounted on flattopped carinae; in one case (T. monilifer), the slitband is 

flattened in maturity, but becomes "narrower and completely (?) closed to form an acute keel in proximal part of 

shell" (p. 48).

The presence of a slit in T. nitidula (Ulrich) is also 

problematical. Its truncate dorsum seems to have distinct "lunulae," but some of these "lunulae" appear 

continuous with growth lines, whereas others do not (pi. 

42, figs. 4, 6). There are no distinct bordering threads 

separating the selenizone from the dorsal slopes of the 

shell, and the emargination present is not nearly as deep 

as in species of Tropidodiscus and Phragmolites. This 

"pseudoselenizone" is similar to those of some other 

bellerophontacean species, such as Tetranota bidorsata 

(Hall) and T. sexcarinata Ulrich and Scofield (pis. 21, 

22). Furthermore, the "pseudoselenizone" is relatively 

well defined compared with species such as Sphenospliaera troosti (d'Orbigny) (pi. 29) that have only a 

dorsomedian ridge but are clearly closely related to S. 

clausus (Ulrich) (pi. 30), which has an excellently defined 

slitband with lunulae.

In light of these observations, Temnodiscus is retained 

in the Tropidodiscidae. Direct comparison of specimens 

of species from the various areas is needed to determine 

the uniformity and validity of composition of the genus 

Temnodiscus.

Temnodiscus nitidula (Ulrich) 1897

Plate 42, figures 3-6

Cyrtolites nitidula Ulrich, 1879, p. 12, pi. 7, figs. 7, 7a.

Cyrtolitina nitidula Ulrich in Ulrich and Scofield, 1897, p. 866, pi. 62,

figs. 53-55. 

Temnodiscus nitidula Knight, 1941, p. 345.

Diagnosis.— Shell small (up to 9 mm long), rapidly 

expanding, relatively tightly coiled; dorsum broadly 

truncated, selenizone broad, with distinct lunulae; 

growth lines sublamellose; revolving threads fine.

Description. Shell small, expanding rather rapidly to 

about two volutions; relatively tightly coiled for genus, 

the outer volution embracing about half of the inner one; 

umbilicus moderate in size, with rounded shoulders. 

Dorsal slopes entirely gently convex; dorsum broadly 

truncated; parietal deposits not seen; apertural outline 

subcordate. Selenizone broad, borderless, with distinct 

lunulae. Sinus deep, slit relatively shallow. Growth lines 

strong, apparently sublamellose, closely and evenly 

spaced, strongly curved. Fine revolving threads.

Measurements.— Measurements of T. nitidula are 

listed in table 46.
0126 CONTRIBUTIONS TO THE ORDOVICIAN PALEONTOLOGY OF KENTUCKY AND NEARBY STATES

TABLE 46. Measurements (in millimeters) of Temnodiscus

nitidula

USNM Shell Aperture Aperture Umbilical Ventral Selenizone 

No. length length width diameter width width

315542 

315543

9.0

7.8

5.5 

5.1

5.4 

4.9

5.0 

4.0

2.0 

1.5

1.1 

1.1

Material.— The four specimens located were Ulrich's 

types, all cataloged under USNM 45793. Shell material is 

lacking in all, but external ornament is well preserved, 

and thus the specimens probably are composite molds. 

From this suite, USNM 315542 (pi. 42, figs. 3, 4) is 

designated the lectotype, and USNM 315543 (pi. 42, figs. 

5, 6) and the other two specimens (left under the original 

number) are paralectotypes.

Distribution.— Ulrich and Scofield (1897, p. 867) cited 

the species as occurring in the "upper part of the Trenton 

Group, in the river quarries just west of Covington, 

Kentucky." These beds are now assigned to the 

Point Pleasant Tongue of the Clays Ferry Formation 

(Shermanian).

Comparison.— Probably the species most easily confused with T. nitidula, would be the monoplacophorans 

Cyrtolites (Paracyrtolites) carinatus and C. (P.) parvus. 

Both can be readily distinguished from T. nitidula by 

their carinate, rather than distinctly truncate, dorsal 

sides.

Discussion.— This species is rare, possibly because of 

its small size and the apparent lack of preservation of its 

shell. It cannot be confirmed, but the uniform preservation of the type suite suggests collection from a single 

bed.

Family BUCANIIDAE Ulrich and Scofield, 1897

Diagnosis.— Shell having numerous volutions that are 

barely contiguous to slightly overlapping, with early 

volutions visible in moderately narrow to wide umbilicus; 

generally having shallow labral slit that generates a 

selenizone; shell surface having collabral growth lines or 

lamellae, which generally are crossed by revolving lines 

varying from angular ridges to threads.

Stratigraphic range. —Lower Ordovician-Devonian.

Discussion.— Ulrich and Scofield (1897) erected this 

family and included some genera that have since been 

removed. Knight (1956) recognized the distinctiveness of 

some of the genera and moved them to the Tropidodiscidae. Peel (1972), demonstrating that the genus was 

sinuate and did not possess a true slit, placed Tremanotus in the Tremanotidae.

There has never been significant disagreement about 

the distinctiveness of this family, only about how the 

distinctiveness should be expressed in the classification 

scheme within the Bellerophontacea. Koken (1925),

Knight and others (1960), and Horny (1963a) considered 

the grouping to be a subfamily of the Bellerophontidae. 

Ulrich and Scofield (1897), Dall in Eastman (1913), Wenz 

(1938), and Golikov and Starobogatov (1975) have considered the grouping to be an independent family, as is 

done herein. The separation of the Bucaniidae from the 

Bellerophontidae expresses more clearly that the former 

group is a distinct and more primitive phylogenetic 

entity.

The Bucaniidae encompasses four recognized subfamilies Bucaniinae (Ulrich and Scofield, 1897), Salpingostomatinae (Koken, 1925), Plectonotinae (Boucot and 

Yochelson, 1966), and Undulabucaniinae new subfamily.

As is obvious from its name, the Lower Ordovician 

genus Eobucania Kobayashi, 1955, was from its inception considered to be closely related to Bucania. Knight 

and others (1960) placed Eobucania in the Bucaniinae, 

thus supporting such a relationship. However, Eobucania bears as much, or more, resemblance to the Tropidodiscidae as to the Bucaniidae. Like Tropidodiscus, 

Eobucania has a deep slit and only fine, closely spaced 

collabral shell markings. The aperture in Eobucania 

does flare and expand like that of a bucaniid, but its 

whorl form is quite distinct. Eobucania is intermediate 

in morphology and phylogeny between Tropidodiscus 

and Bucania, and probably represents a group of early 

bellerophontaceans some species of which gave rise to 

Bucania and its relatives. Thus, it is understandable that 

Eobucania would be difficult to classify at the family 

level; however, as noted below, it is here placed in the 

Bucaniinae.

Subfamily BUCANIINAE Ulrich and Scofield, 1897

Diagnosis.— Shell with apertural margins tending to 

flare, mainly laterally; slit relatively short, open at 

apertural margin; collabral growth lines in many cases 

crossed by revolving threads.

Stratigraphic range.—Lower Ordovician-Devonian.

Genera included.—Bucania Hall, 1847, Kokenospira 

Bassler, 1915, ?Megalomphala Ulrich and Scofield, 1897, 

and Eobucania Kobayashi, 1955 are members of this 

subfamily. Horny (1963a) removed Coelocyclus Perner, 

1903, from the Bucaniinae, where it had been placed by 

Knight and others (1960), and assigned it to the subfamily Cymbulariinae Horny of the Bellerophontidae. However, Coelocyclus's open umbilicus and depressed whorls 

suggest that it should remain with the bucaniids.

Genera considered here.—Bucania, Kokenospira,.

Discussion.— Bucaniinae is the core grouping of the 

family Bucaniidae; it encompasses nearly the same 

grouping of genera considered the tribe Bucaniides by 

Knight and others (1960). The group apparently 

descended from the tropidodiscids through an intermediate stock such as that represented by the Lower
MIDDLE AND UPPER ORDOVICIAN SYMMETRICAL UNIVALVED MOLLUSKS, CINCINNATI ARCH REGION 0127

Ordovician genus Eobucania. It would seem that the 

other subfamilies of the Bucaniidae, as well as possibly 

the subfamily Bucanopsinae of the Bellerophontidae, 

evolved from the Bucaniinae during the Early to Middle 

Ordovician radiation of the bellerophontaceans.

Genus BUCANIA Hall, 1847

Diagnosis. — Shell having medium to large umbilicus; 

revolving ornamentation running normal to, and generally interrupted by, growth lines or lamellae.

Description. — Shell size from small to large, the 

whorls rounded or depressed and generally gradually 

expanding; umbilicus medium to large. Outer aperture 

lip thin, with broad, V-shaped sinus and central slit; slit 

shallow to quite deep; selenizone generally narrow, being 

slightly elevated, flat, or channellike; inner aperture of 

lip thickened in many cases. Shell surface marked by 

transverse growth lines or lamellae and revolving 

threads; revolving threads run normal to, and are generally interrupted by, growth lines; growth lines in many 

specimens become lamellose in maturity, accompanied 

by a general thickening of the whorl laterally and posterolaterally.

Type species.—Bellerophon sulcatinus Emmons, 

1842, by subsequent designation of Waagen (1880, 

p. 130).

Distribution. —Lower Middle Ordovician (Chazyan) to 

Middle Silurian (Niagaran) in Eastern North America 

(Bassler, 1915), and Middle Ordovician to Silurian in 

Europe and northeast Asia (Knight and others, 1960).

Comparison.—Salpingostoma Roemer, 1876, differs 

from Bucania in having abrupt expansion of the adult 

whorls and a long, distally closed off slit. Tetranota 

Ulrich and Scofield, 1897, differs in having the selenizone 

mounted on a broad, elevated dorsomedian band, in 

many cases with one or two lateral ridges. Members of 

the new genus Undulabucania resemble species of the 

Bucania sulcatina group (see discussion below) in shell 

form, but differ in lacking revolving threads and having 

the more Phragmolites-like features of a deep slit and 

regularly wavy growth lines.

Discussion.—Hall (1847, p. 32) erected the genus 

Bucania for those species previously assigned to Bellerophon Montfort (1808) that have an umbilicus of sufficient size to reveal the earlier volutions. In the following 

years, most authors found it impossible to mark a proper 

boundary between Bucania and Bellerophon based 

solely on umbilical size, and therefore generally considered the two names synonyms. Nevertheless, Hall (1861, 

p. 93) reaffirmed his contention that Bucania was a 

useful genus; unfortunately, he offered no further supportive evidence.

Waagen (1880, p. 150) asserted that the primary 

taxobasis of the genus Bucania was its spiral ornamentation. He noted that the umbilicus was generally larger 

in species of Bucania than in species of Bellerophon, but 

he believed that the overlap between the two genera 

excluded that characteristic as the primary taxobasis. 

Waagen also emphasized the presence of distinct transverse growth lines crossing the revolving threads, and 

the general thinness of the shell, except for the massive 

thickening of the inner lip in many species.

Ulrich and Scofield (1897, p. 883, 884) commended 

Waagen's definition of the genus, but showed that it was 

too broad, encompassing a variety of distinct forms that 

also bear revolving ornament (such as Salpingostoma, 

Kokenospira, and Bucanopsis). Until now, Ulrich and 

Scofield's review and redefinition of the genus was the 

most definitive statement on Bucania. They believed 

that Bucania should be restricted to species that have 

fairly large umbilici, a broad, V-shaped sinus with a 

central slit, and the characteristic shell markings. They 

emphasized that these shell markings differed from other 

genera having revolving lines, in that both the revolving 

and transverse markings in Bucania were oblique to the 

direction of coiling. All other comparable genera are 

characterized by revolving lines parallel to the direction 

of coiling.

Ulrich and Scofield (1897, p. 851) recognized two 

informal "groups" of species. The first, their "typical 

section" (the B. sulcatina group herein), was characterized by a thin shell, a broad umbilicus, broad whorls with 

a slow expansion rate, no massive parietal thickening, 

and a long slit. The second group, referred to as both the 

"5. nashvillensis section" (p. 851) and the ((B. lindsleyi 

section" (p. 884), was described as having a thicker shell, 

a smaller umbilicus, more rapidly expanding whorls with 

a relatively longer aperture, in many cases with massive 

parietal thickening, and a shorter slit. These two groups 

are left informal here because, although the two end 

members, B. sulcatina and B. lindsleyi, are distinct, 

some species are gradational between them and exhibit 

characteristics of both groups. For example, B. rugatina 

resembles B. lindsleyi in its small umbilicus and its 

surface markings, but was placed in the B. sulcatina 

group by Ulrich and Scofield (1897) because of its gradual 

whorl expansion and thin shell.

The B. sulcatina group is more primitive than, and 

ancestral to, the B. lindsleyi group. The former group is 

mainly Chazyan and Blackriveran in age, with only two 

known Kirkfieldian-Shermanian species. The B. lindsleyi group first appeared during Kirkfieldian time and 

continued into the Silurian Period.

At one time, Knight (1942, p. 487) advocated placement of the B. lindsleyi group in the genus Loxobucania 

Knight, which he claimed was essentially the genus 

Bucania as conceived by Ulrich and Scofield (1897, p. 

850). They had characterized Bucania largely by the
0128 CONTRIBUTIONS TO THE ORDOVICIAN PALEONTOLOGY OF KENTUCKY AND NEARBY STATES

possession of revolving ornament that runs normal to the 

apertural margin (and thus the growth lines), converges 

inward upon the slit and selenizone, and is generally 

interrupted by the growth lines or lamellae (pi. 14, fig. 

14; pi. 17, fig. 2; pi. 18, fig. 7). Knight (1942) pointed out 

that B. sulcatina, the type species of Bucania, differs 

from that definition by the possession of revolving ornament that meets the apertural margin at a slight angle, 

runs parallel to the selenizone, and continues uninterrupted by the growth lines (pi. 12, figs. 1-5). Examination of Knight's (1941, pi. 11, figs, la, b) figures of the 

holotype of B. sulcatina confirms these observations. 

However, Knight and others (1960, p. 1180) placed 

Loxobucania in synonymy with Bucania. I have found 

no explanation for this reversal in judgment; it might be 

explained in the following manner. The members of the 

B. sulcatina group do not have a deep, V-shaped sinus 

with broadly rounded anterolateral apertural margins, 

as do members of the B. lindsleyi group. Rather, members of the B. sulcatina group have nearly straight 

anterior apertural margins (as reflected by their straight 

dorsal growth lines) that angle back slightly to form a 

very broadly obtuse, shallow, anteromedian sinus (pi. 12, 

fig. 5). The revolving ornament seems to be nearly 

normal to this straight apertural margin. It appears that 

in the more advanced group the revolving threads came 

to converge on the selenizone at a higher angle by the 

curving of the anterior apertural margin and development of a deep, V-shaped sinus (pi. 18, fig. 7). B. 

sulcatina and its allies probably did not need a deep sinus 

to assist in efficient circulation of water through the 

mantle cavity because they had a deep slit.

As pointed out elsewhere in this paper, the broken 

dorsal shells of numerous specimens of other deepslit-bearing genera, such as Salpingostoma and Tropidodiscus, suggest a structural weakness of the shell in that 

area. The shortening of the slit and development of a 

deeper V-shaped sinus may have been apertural modifications in more advanced species of the genus Bucania, 

modifications that allowed maintenance of efficient water 

circulation through the mantle cavity as well as strengthening of the shell dorsum. Because of the gradational 

morphologic progression between the end-member species of these two groups, the genus Loxobucania is not 

used herein.

The B. sulcatina group is thought here to have 

descended from the Phragmolites stock of the tropidodiscids. Both groups have wide umbilici, long slits, and 

revolving ornament. The new genus Undulabucania also 

appears to have developed from that common stock. U. 

punctifrons was included in the "5. sulcatina group" by 

Ulrich and Scofield, but it differs significantly from the 

other species in that group in its lack of spiral ornament

and its wavy growth lines reminiscent of the corrugated 

shell markings of Phragmolites.

The genus Salpingostoma undoubtedly is closely 

related to, and probably evolved from, a species of 

Bucania. Juveniles of species of Salpingostoma are very 

similar to the "5. sulcatina group" in their large umbilici, depressed whorls, thin shell, and deep slit. Upon 

adult expansion, these species take on a shell form 

similar to members of the "5. lindsleyi group," with a 

longer aperture and thickened parietal lip. Also, the two 

genera have very similar shell markings.

Bucania emmonsi Ulrich and Scofield, 1897

Plate 12, figures 1^ 

Bucania emmonsi Ulrich and Scofield, 1897, p. 887, pi. 66, figs. 1-3.

Diagnosis.— Shell widely umbilicate, umbilical slopes 

gently convex, sutures deep with wavy indentations; 

shell width increases by 2.8 times in one volution; 

revolving threads strongly angled mediad over dorsum.

Description. — Shell relatively small (up to 18 mm 

long), thin, consisting of three or four volutions; rate of 

whorl expansion fairly rapid, the shell width increasing 

by about 2.8 times in one volution. Umbilici widely open, 

so that all earlier whorls are clearly visible; umbilical 

slopes gently convex, causing whorl sutures to be quite 

deep. Ventral whorl surface, as visible along suture 

lines, has numerous gentle, wavy indentations. Shell 

dorsum gently and evenly convex, and umbilical shoulders sharply to narrowly rounded, giving aperture a 

rounded, subtrapezoidal outline. Slit unknown, but selenizone narrow and channellike.

Shell ornament dominated by revolving threads, which 

are equal in strength but widen slightly in their spacing 

outward from the dorsomedian line and number about 12 

on either side; revolving threads pass over shell dorsum 

with obvious obliqueness to direction of coiling, angling 

mediad at about 10 degrees toward selenizone, and 

angling laterad on ventral shell slopes, thus always 

remaining perpendicular to curved growth lines and 

growing shell margin; growth lines only faintly visible, 

reflecting a rather straight sided, slightly convex, Vshaped apertural sinus.

Measurements.— Measurements of B. emmonsi are 

listed in table 47.

Material.—The lectotype of B. emmonsi, numbered 

USNM 46049, is a silicified replica that was figured by 

Ulrich and Scofield (1897, pi. 66, figs. 1-3). The other 

syntype, USNM 46050, is now the paralectotype.

Distribution.—The lectotype, USNM 46049, was collected from the Murfreesboro Limestone (Blackriveran) 

at Murfreesboro, Tenn. Ulrich and Scofield (1897, p. 888) 

also cited the species from the Vanuxemia and Ctenodonta beds of Minnesota, which Weiss (1957, fig. 1)
MIDDLE AND UPPER ORDOVICIAN SYMMETRICAL UNIVALVED MOLLUSKS, CINCINNATI ARCH REGION 0129 

TABLE 47. Measurements (in millimeters) of lectotype o/Bucania emmonsi

USNM No.

46049

Shell 

length

18.4

Shell 

height

14.25

Aperture 

length

10.0

Aperture 

width

17.0

Umbilical 

diameter

12.15

Dorsal 

width

11.45

Posterior 

width

7.85

Ventral 

width

6.1

Selenizone 

width

0.5

considered parts of the Platteville (Rockfieldian) and 

Decorah (Kirkfieldian) Formations, respectively.

Comparison.— This species is distinguished from B. 

halli by its smaller size, its more rapid whorl expansion, 

and its larger number of revolving threads, which are 

more obtuse to the midline. B. emmonsi also resembles 

B. intexta Hall (Middle Ordovician, New York), but 

differs from that species, and all others, by the wavy 

indentations on its deep suture lines.

Bucania halli Ulrich and Scofield, 1897

Plate 12, figures 5-18

Bucania halli Ulrich and Scofield, 1897, p. 886, pi. 66, figs. 4-8; Grabau 

and Shinier, 1909, p. 614, fig. 822; Wilson, 1951, p. 27, pi. 2, figs. 

15, 16.

Diagnosis.— Shell widely umbilicate, umbilical shoulders subangular, umbilical slopes nearly flat; shell width 

increases by about 2.25 times in one volution; revolving 

ribs equal in strength and spacing, angled very slightly 

toward selenizone.

Description.— Shell moderate in size (20-30 mm long); 

three or four volutions; depressed whorls increase in size 

gradually, the shell width increasing by about 2.25 times 

in one volution; umbilicus widely open, umbilical shoulders subangular to sharply rounded, and umbilical slopes 

nearly flat. Shell dorsum broadly and evenly convex, 

ventral whorl gently concave, reflecting opposing shape 

of previous whorl; aperture shape subtrapezoidal, 

length/width ratio 6.2.

Revolving threads dominate shell ornament, consisting of about 12 dorsal threads on either side of selenizone 

that angle very slightly toward midline; weaker growth 

lines interrupt revolving threads only slightly, and are 

only slightly curved across dorsal slopes, reflecting a 

broad, shallow, V-shaped sinus. Slit unknown; selenizone 

slightly elevated, but concave.

Measurements.—Measurements of B. halli are listed 

in table 48.

Material.— The lectotype designated herein is specimen USNM 45717 (pi. 12, figs. 5-9), which is apparently

a composite mold dorsally and an internal mold in the 

umbilical areas. This specimen from Minnesota was 

illustrated previously by Ulrich and Scofield (1897, 

pi. 66, figs. 4, 5).

The remainder of the syntypic suite consists of seven 

specimens from the Curdsville Limestone Member of the 

Lexington Limestone of Mercer County, Ky. Six of these 

are poorly preserved internal molds, and are here designated paralectotypes under the original number, 

USNM 45718. The seventh, also a paralectotype (USNM 

315582), is a very weathered silicified specimen retaining 

some aspect of the shell on the posterior coil and around 

the aperture (pi. 12, figs. 10-14); it may be the specimen 

figured in outline by Ulrich and Scofield (1897, pi. 66, 

fig. 8).

Two specimens of B. halli were found in the USGS 

silicified collections from Kentucky. The first, USNM 

315544 (pi. 12, figs. 15, 16), is from the Grier Limestone 

Member (4073-CO), and the second, USNM 315545 (pi. 

12, figs. 17, 18), is from the lower Curdsville Limestone 

Member (5100-CO), both from the Lexington Limestone. 

The first is referred to B. halli with confidence. However, the second is referred to B. cf. B. halli; it is an 

internal mold, apparently with a very thick shell remnant. This latter specimen's shell form (depressed 

whorls, wide umbilicus) agree well with B. halli, and the 

apparently thick shell may reflect expansion during 

silicification.

Distribution,—The lectotype (USNM 45717) is from 

the Decorah Formation (Rocklandian) (Black River 

Group of Ulrich and Winchell, 1897) at Cannon Falls, 

Minn. The paralectotypes, USNM 45718 and 315582, are 

from the Curdsville Limestone Member (Kirkfieldian) of 

the Lexington Limestone of Mercer County, Kentucky. 

USNM 315544 is from USGS sample 4073-CO, Grier 

Limestone Member (Shermanian) of the Lexington 

Limestone, and USNM 315545 is from USGS sample 

5100-CO, Curdsville Limestone Member of the same 

formation (Kirkfieldian). Wilson (1951, p. 27) reported B.

TABLE 48. Measurements (in millimeters) of Bucania halli

USNM No.

45717

315582

Shell 

length

21.3

37.0

Shell 

height

15.0

23.1

Aperture 

length

10.5

23.7

Aperture 

width

16.9

30.0

Umbilical 

diameter

13.8

14.9

Dorsal 

width

13.20

16.75

Posterior 

width

10.0

14.8

Ventral 

width

7.5

12.3

Selenizone 

width

0.8
0130 CONTRIBUTIONS TO THE ORDOVICIAN PALEONTOLOGY OF KENTUCKY AND NEARBY STATES

TABLE 49.—Measurements (in millimeters) o/Bucania subangulata

USNM No.

315559

315560

315575

315578

265989

315576

315577

315596

Shell 

length

22.55

22.30

13.35

-

9.60

14.30

_

-

Shell 

height

19.0

14.5

9.2

-

6.3

8.9

_

-

Aperture 

length

19.5

14.5

6.4

-

6.4

9.0

_

-

Aperture 

width

30.0

_

10.2

21.7

7.8

10.9

16.8

13.2

Umbilical 

diameter

11.5

10.5

6.1

-

4.5

6.5

-

-

Dorsal 

width

11.5

10.5

7.0

12.8

5.5

6.8

10.7

7.9

Posterior 

width

7.1

7.5

5.4

-

4.0

4.7

-

5.9

Ventral 

width

6.3

-

3.3

6.8

_

2.8

-

3.8

Selenizone 

width

_

1.4

-

-

0.6

0.9

-

-

halli from the Lowville and Leray beds (Blackriveran) of 

eastern Canada.

Comparison.— B, fialli resembles B. emmonsi, both 

having the broad umbilici and depressed whorls of the B. 

sulcatina group. However, the whorls of B. halli expand 

more slowly (the width increasing by about 2.25 times in 

one volution, compared with 2.8 times in B. emmonsi). 

The umbilical shoulders of B. halli are more angular, its 

umbilical slopes are flatter, and its revolving threads 

approach the dorsomedian selenizone at a smaller angle.

Discussion.—Specimen USNM 315544 (pi. 12, figs. 15, 

16) confirms the occurrence of B. halli in the Ordovician 

of Kentucky. The internal molds of the type suite 

(USNM 45718) are questionable in their species assignment. The figured paralectotype (pi. 12, figs. 10-14), 

USNM 315582, shows differences from the lectotype cf. 

B. halli. It may be the specimen shown in Ulrich and 

Scofield's plate 66, figure 8, which they said was only 

doubtfully referred to the species, "the back being 

unusually convex and the sides too blunt." When one 

examines the photographs of this specimen, it appears 

that the whorls are depressed and less convex in the 

early portion of the last whorl, but about one-third 

through that volution the whorl begins to expand toward 

the anterior, making the whorl much more convex dorsally. The umbilical form of USNM 315582 (pi. 12, figs. 

12, 13) is comparable to that of the lectotype (pi. 12, fig. 

9), both having subangular shoulders and flat slopes, but 

the umbilical form of USNM 315582 appears slightly 

deeper. It should be noted that in the last one-third 

volution of the lectotype, the shell shows a tendency 

toward increased anterior expansion of the whorl. 

Finally, specimen USNM 315582 shows strong lamellose 

growth lines on the expanded aperture (pi. 12, figs. 13, 

14), whereas the lectotype (which is a composite mold) 

shows only weak evidence of growth lines. However, it is 

common in bucaniids for growth lines to become stronger, and even lamellose, in maturity. Therefore, the 

specimen is assigned to B. halli. In doing so, it is shown 

that the B. sulcatina group may have undergone an 

expansion and thickening of the shell similar to that of 

the B. lindsleyi group in maturity. It might also be noted

that the mature B. halli, as shown by specimen USNM 

315582, somewhat resembles the Richmondian species B. 

crassa (pi. 19, figs. 7-10) in its highly convex dorsum and 

angular, deep umbilicus. However, B. crassa is more 

globose.

Bucania subangulata Ulrich, 1897

Plate 14, figures 15-19; Plate 15, figures 8-24; 

Plate 38, figures 11, 12

Bucania subangulata Ulrich in Ulrich and Scofield, 1897, p. 891, pi. 66, 

figs. 20-23.

Diagnosis.— Shell small, rapidly expanding; umbilicus 

moderately wide; whorl shape cordate to subtriangular; 

aperture slightly flared in maturity; selenizone elevated, 

flat; growth lines sublamellose, scalloped.

Description.— Shell small (up to 22.5 mm long) but 

rapidly expanding, consisting of about 3.5 volutions at 

maturity; umbilicus moderately wide, clearly exposing 

earlier whorls; dorsum rounded in juveniles, but becoming increasingly angular with a greater rate of aperture 

length growth, resulting in a prominent dorsomedian 

angle with steep, gently convex dorsolateral slopes; 

umbilical shoulders narrowly rounded to angular, umbilical slopes cut inward sharply and nearly flat. Adult 

apertural outline cordate to subtriangular. Selenizone 

moderately wide and nearly flat topped, showing distinct 

lunulae in some specimens. Growth lines broadly sweeping, becoming sublamellose with scalloped margins in 

maturity; revolving threads fine and closely spaced.

Measurements.— Measurements of B. subangulata 

are listed in table 49.

Material.—The type suite, USNM 45731, consists of 

eight silicified syntypes. Six of these are small and too 

poorly preserved to yield significant data; they are 

designated paralectotypes, are not figured, and are 

cataloged under the type suite number. A seventh syntype, here designated a paralectotype, is figured under 

the number USNM 315560 (pi. 14, fig. 19). The eighth 

syntype is here designated the lectotype, USNM 315559 

(pi. 14, figs. 15-18). I note that the anteromedian portion 

of the lectotype was reconstructed with plaster by the
MIDDLE AND UPPER ORDOVICIAN SYMMETRICAL UNIVALVED MOLLUSKS, CINCINNATI ARCH REGION 0131

TABLE 50. Measurements (in millimeters) o/Bucania lindsleyi

USNM No.

315550 

315551

Shell 

length

-36.0

19.8

Shell 

height

22.2

14.3

Aperture 

length

21.8 

10.6

Aperture 

width

30.5 

18.0

Umbilical 

diameter

13.0

7.6

Dorsal 

width

21.0 

13.2

Posterior 

width

17.0 

11.0

Ventral 

width

14.7 

8.0

Selenizone 

width

2.0

1.5

original author, but the reconstruction appears correct to 

me.

A number of specimens belonging to this species were 

found in the USGS silicified collections. USGS sample 

7785-CO yielded four specimens that appear to be silicified internal molds; one is figured as USNM 315575 (pi. 

15, figs. 8-12). USGS sample 5094-CO contained six 

specimens, including USNM 265989 (pi. 38, figs. 11, 12), 

315576 (pi. 15, figs. 13-15), 315577 (pi. 15, figs. 16-20), 

and 315596. USGS sample 5096-CO contained two fragments, including USNM 315578 (pi. 15, figs. 21-24).

Distribution.—The type material was collected from 

the "Flanagan beds," an outdated unit in the upper 

Lexington Limestone (Shermanian) subsequently found 

to represent several silicified horizons, 1.5 mi south of 

Burgin, Ky. The type suite may be from the Grier or 

Perryville Limestone Members of the Lexington Limestone.

The species is recognized here from the Curdsville 

Limestone Member (7785-CO) and Grier Limestone 

Member (5094-CO, 5096-CO) of the lower part of the 

Lexington Limestone.

Comparison. — Ulrich and Scofield (1897, p. 891) 

stated that B. subangulata could be distinguished from 

the associated B. rugatina by its subtriangular apertural 

outline. The more similar species B. frankfortensis and 

B. nashvillensis, which also have an angular dorsum 

(though to somewhat different degrees), can be readily 

distinguished from B. subangulata by their larger shells 

and smaller umbilici.

Another feature that helps in recognizing this species 

is the sublamellose, scalloped growth lines on the adult 

dorsolateral slopes. The scalloping may be accentuated 

by weathering of the fine revolving threads along the 

margins of the sublamellose growth lines. The feature is 

present in both the lectotype (pi. 14, figs. 15-18) and the 

USGS material (pi. 15, figs. 14, 15, 21, 24), and is not as 

well developed in any other species.

Discussion. — The rapidly expanding shell and dorsomedian angulation of B. subangulata indicate a relation 

to B. frankfortensis and B. nashvillensis. The larger 

umbilicus of B. subangulata may indicate that it is more 

primitive than these other species, because large umbilici 

are characteristic of the B. sulcatina group.

The lectotype, USNM 315559 (pi. 14, figs. 15-18), 

shows the overall morphology of the species better than 

any other known specimen. The paralectotype, USNM

315560 (pi. 14, fig. 19), shows two critical morphological 

features not clearly visible on the lectotype, the truncated slitband with lunulae and the fine revolving lines 

(on the right dorsolateral slope). A number of the USGS 

specimens exhibit the scalloping of the growth lines (pi. 

15, figs. 14, 15) also seen in the lectotype (pi. 14, fig. 17). 

Specimen USGS 315577 (pi. 15, figs. 16-20) preserves 

the slitband; such preservation is unusual for such a small 

specimen.

Ulrich and Scofield (1897, p. 891) stated that this 

species was associated with B. rugatina in the upper 

Lexington Limestone. Specimen USNM 265989 (pi. 38, 

figs. 11, 12) shows that the species also occurs in association with Carinaropsis cymbula.

Bucania lindsleyi (Safford), 1869

Plate 18, figures 1-9

Bellerophon lindsleyi Safford, 1869, pi. 3(G), figs. 3a, b, d, e. 

Bucania lindsleyi Safford, Ulrich and Scofield, 1897, p. 889, pi. 66, 

figs. 24, 25; Bassler, 1932, pi. 20, fig. 28.

Diagnosis.— Shell rapidly expanding, broadly and 

evenly convex dorsally; selenizone concave, lunulae 

strong; revolving threads and growth lines strong, latter 

becoming lamellose in adulthood.

Description.— Shell moderately large (up to 36 mm 

long), consisting of three to four fairly rapidly expanding 

whorls which are rather closely coiled; umbilicus of 

moderate size and deep, with rather narrowly rounded 

shoulders and steeply cut, slightly convex umbilical 

slopes; dorsum of shell broadly convex, becoming 

broader and more evenly convex through growth, 

becoming nearly semicircular; whorl outline distinctly 

wider than long, and rather flat ventrally. Aperture lips 

remain thin, even on inner side, and even in adulthood. 

Selenizone distinct, bordered by thin ridges, wide, 

broadly concave, and marked by strong lunulae; slit 

unknown. Revolving threads strongly developed over 

entire shell, including umbilical slopes; growth lines also 

distinct, being broadly curved, reflecting a rather deep 

apertural sinus, becoming very lamellose in adulthood, 

and being very regularly spaced throughout growth.

Measurements. Measurements of the lectotype and a 

paralectotype of B. lindsleyi are listed in table 50.

Material.— The three syntypes of the species examined were cataloged as USNM 45719. No other specimens were found. Two of the syntypes are figured here. 

One is now numbered USNM 315550, and is designated
0132 CONTRIBUTIONS TO THE ORDOVICIAN PALEONTOLOGY OF KENTUCKY AND NEARBY STATES

TABLE 51.—Measurements (in millimeters) o/Bucania nashvillensis

USNM No.

315557

315558

45724

315566

315567

315569

Shell 

length

25.8

-

-36.0

-

-

-

Shell 

height

15.3

21.1

21.7

-11.1

-15.9

16.2

Aperture 

length

18.1

26.1

-27.0

-

-

-

Aperture 

width

26.0

27.8

-33.0

-16.2

-19.8

-20.0

Umbilical 

diameter

9.2

-

-12.9

-6.1

-9.5

8.1

Dorsal 

width

14.4

-

19.3

10.0

-11.3

-

Posterior 

width

11.4

-

14.4

7.3

-8.3

-

Ventral 

width

-7.8

-

10.1

-

-6.3

-

Selenizone 

width

1.4

1.8

1.5

-

-0.7

1.3

Slit 

length

-5.3

-6.6

-

-

-

-

the lectotype (pi. 18, figs. 1-6). The other is now USNM 

315551, and is designated a paralectotype (pi. 18, figs. 

7-9). The third syntype, an unfigured paralectotype, 

remains cataloged under the original museum number. 

All three are brown, weathered, silicified replicas. The 

lectotype is quite well preserved, probably because it 

was largely encrusted by bryozoans, most of which have 

been broken away to reveal the shell.

Distribution.—Ulrich and Scofield (1897, p. 890) and 

Bassler (1915, p. 136) cited B. lindsleyi as coming from 

the Catheys Formation of Dekalb County, Tenn., and 

possibly from the Prosser Formation near Cannon Falls, 

Minn. Both occurrences are in Shermanian-Edenian-age 

strata.

Bassler (1932) listed the species from the Stromatacerium pustulosum bed of the Catheys Formation, and the 

Cannon Limestone (Kirkfieldian-Shermanian) of central 

Tennessee.

Comparison.—B. lindsleyi differs from the closely 

related B. nashvillensis in being somewhat less tightly 

coiled, resulting in a larger umbilicus, in having a broadly 

rounded rather than angled whorl dorsum, in having a 

depressed, channellike rather than elevated selenizone, a 

thinner shell, and stronger shell markings. B. micronema is similar to B. lindsleyi, but the former is much 

smaller, and its revolving threads are finer and slightly 

wavy. B. lindsleyi differs from B. rugatina in being 

larger, less tightly coiled, and less expanded and having 

a concave selenizone.

Discussion.—B. lindsleyi and B. nashvillensis are 

closely related. They are representative of the more 

advanced group of bucaniids, which was designated 

informally by Ulrich and Scofield (1897, p. 851, 844, 886). 

They are the earliest known members of this informal 

group of species and gave rise to a number of late Middle 

and Upper Ordovician species. B. lindsleyi apparently 

evolved from the B. sulcatina group by the lengthening 

of the whorl outline and the development of a tighter coil, 

which was probably an adaptation facilitating the carrying and balancing of the shell.

Bucania nashvillensis Ulrich, 1897

Plate 13, figures 15-21; Plate 14, figures 1-14; 

Plate 15, figures 1-7; Plate 27, figures 21, 22

Bucania nashvillensis Ulrich in Ulrich and Scofield, 1897, p. 890, 891, 

pi. 66, figs. 36-40; Bassler, 1932, pi. 20, figs. 19, 20.

Diagnosis.— Shell having somewhat flattened dorsolateral slopes and subangular dorsum; umbilici relatively 

small; transverse and radial ornament distinct.

Description.— Shell moderately large (up to 36 mm 

long), consisting of about three rapidly expanding volutions; coiling rather tight, umbilicus relatively small and 

deep. Dorsolateral whorl slopes slightly flattened, making the dorsal crest subangular; umbilical shoulders 

tightly rounded; ventral whorl only slightly concave, 

with low, broad hump on parietal floor, reflecting adjacent subangular dorsum. Aperture broad and roughly 

subtriangular. Shell becomes quite thick in mature 

growth, particularly along posterolateral (inner) whorl 

slopes. Slit fairly deep, about one-fourth the aperture 

length, and situated in broad, rounded sinus; selenizone 

moderately wide, forming a flattened to slightly elevated 

crest to subangular dorsum. Growth lines evenly and 

closely spaced, becoming coarsely lamellose in later 

growth; revolving threads closely spaced, and, although 

distinct, weaker than growth lines and much stronger 

dorsally than within umbilicus.

Measurements.— Measurements of B. nashvillensis 

are listed in table 51.

Material.—Ulrich's (1897) type suite consists of six 

silicified syntypes; five are numbered USNM 45725, and 

one is numbered USNM 45724. Three of these syntypes 

are figured here: USNM 315557 (from suite 45725) (pi. 

14, figs. 10-14) is here designated the lectotype; USNM 

315558 (from suite 45725) (pi. 14, figs. 6-9), USNM 45724 

(pi. 14, figs. 1-5), and the three unfigured specimens left 

under number USNM 45725 are designated paralectotypes.

Numerous specimens in the USGS silicified collections 

from the Lexington Limestone of Kentucky are assigned 

to this species. Those figured here are designated USNM
MIDDLE AND UPPER ORDOVICIAN SYMMETRICAL UNIVALVED MOLLUSKS, CINCINNATI ARCH REGION 0133

315566 (pi. 13, figs. 15, 16), 315567 (pi. 13, figs. 17, 18), 

315568 (pi. 13, fig. 19), 315569 (pi. 13, figs. 20, 21), 315572 

(pi. 15, figs. 1, 2), 315573 (pi. 15, figs. 3-5), and 315574 

(pi. 15, figs. 6, 7). Another new silicified specimen from 

Tennessee, UCGM 44284, is shown on plate 27, figures 

21 and 22. In all, about 32 new specimens were identified 

as B. nashvillensis.

Distribution. — Ulrich and Scofield's (1897) type specimens are labeled as coming from the Cannon facies of 

the Bigby-Cannon Limestone (Kirkfieldian-Shermanian) 

at Nashville and in Dekalb County, Tenn. Specimen 

UCGM 44284 is from the same unit at a "hill north of Well 

No. 1, Smith Co., Tennessee."

Specimens of B. nashvillensis in the USGS silicified 

collections from Kentucky came from the Grier Limestone Member (4073-CO, 4959-CO) and the Salvisa (5015- 

CO, 6915-CO, 6916-CO) and Faulconer (6136-CO) Beds of 

the Perryville Limestone Member (Shermanian) of the 

Lexington Limestone.

Comparison.— The six type specimens for which this 

species was named were originally assigned to Bucania 

lindsleyi (Safford) by Safford (1869), but Ulrich and 

Scofield (1897, p. 890) concluded that they constituted a 

distinct species. B. nashvillensis has a slightly more 

rapid rate of whorl expansion and is more tightly coiled, 

resulting in a slightly smaller and deeper umbilicus (pi. 

14, figs. 3, 12; pi. 27, fig. 22) compared with B. lindsleyi 

(pi. 18, fig. 3). The dorsum of B. nashvillensis is slightly 

angled medially and has somewhat flattened dorsolateral 

slopes (pi. 14, figs. 1-5, 6, 9, 11, 13), whereas that of B. 

lindsleyi is broadly rounded (pi. 18, figs. 1, 7). The 

slitband of B. nashvillensis is slightly elevated (pi. 14, 

figs. 2, 6, 13) instead of channellike (pi. 18, figs. 1, 5, 7), 

and the lunulae are not as strongly developed as in B. 

lindsleyi (pi. 18, figs. 5, 7). Differences in shell sculpture 

between the two species cited by Ulrich and Scofield 

(1897, p. 890) are difficult to evaluate because of generally poor preservation, but one point is certain: the 

revolving threads of B. nashvillensis (pi. 14, figs. 3, 7, 

13, 14) are much weaker than those of B. lindsleyi (pi.

18. figs. 3, 4, 6, 7). Finally, the shell is thicker in B. 

nashvillensis.

Discussion. Prior to this study, B. nashvillensis had 

been reported only from the Bigby-Cannon Formation of 

Tennessee. Ulrich and Scofield (1897, p. 891) cited the 

species from the "Trenton group, Dekalb County, and 

Nasvhille, Tennessee." Bassler (1932, p. 106, pi. 20, figs.

19. 20) reported the species from the "Cannon limestone," which is in agreement with the labeling of the 

type suite. Wilson (1949, p. 118, 125), on the other hand, 

reported the species from only the Bigby and dovecolored facies of the Bigby-Cannon Limestone. Specimen 

UCGM 44284 (pi. 27, figs. 21, 22) was in a collection of

gastropods from the Cannon facies in Smith County, 

Tenn.

Numerous fragmentary specimens from the USGS 

silicified material from Kentucky are smaller than the 

large specimens of the type suite (pi. 14, figs. 1-14); 

however, they resemble these type specimens in their 

angular whorl forms. The characteristic revolving 

threads of Bucania are not clearly preserved on any of 

these specimens from the Lexington Limestone of Kentucky, but neither are they preserved in paralectotype 

USNM 45724 (pi. 14, figs. 1-5). It should be noted that 

many other bellerophontaceans from some of the silicified collections from Kentucky described herein that are 

known to have shell markings also lack preserved ornament markings (see, for example, Bucanopsis carinifera, pi. 27, figs. 5, 16).

The small specimens from the Grier Limestone Member (pi. 15, figs. 1-7) appear to have the typical umbilical 

size and whorl form, and show a tendency toward slight 

dorsal angulation. It must be noted that, as seen in the 

earlier volutions of the type specimens of B. nashvillensis (pi. 14, figs. 5, 6), the dorsomedian angulation was an 

adult feature; submature specimens have a more evenly 

rounded dorsum (as in the small Grier specimens). Similarly, the specimens from the Perryville Limestone 

Member that are assigned to B. nashvillensis, such as 

specimen USNM 315569 (pi. 13, figs. 20, 21), are somewhat larger than the Grier specimens and show greater 

dorsomedian angulation, as do the lower dorsal fragments of USNM 315566 (pi. 13, figs. 15, 16) and USNM 

315568 (pi. 13, fig. 19), which also shows a thickened 

parietal lip as seen in the type specimens (pi. 14, figs. 3, 

5, 7). Although different collections of Kentucky specimens differ in small ways from the type suite, I believe 

they are all so similar in overall morphology that they are 

best assigned to B. nashvillensis.

Bucania frankfortensis Ulrich, 1897

Plate 13, figures 22-24; Plate 16, figures 1-4

Bucania frankfortensis Ulrich in Ulrich and Scofield, 1897, p. 891, pi. 

66, figs. 30-33; Bassler, 1932, pi. 21, figs. 11, 12.

Diagnosis.— Shell aperture having distinctly triangular outline; whorls high, relatively narrow, with subangular dorsal crest.

Description.—Shell moderately large (up to 40.5 mm 

long), consisting of about three or four volutions; umbilicus moderately wide and deep; juvenile whorls somewhat depressed, subreniform in shape, and only slightly, 

if at all, angled dorsally; whorls expand more rapidly 

anteriorly in later growth so that dorsum becomes 

increasingly angular; adult dorsal slopes gently convex 

and steeply inclined, umbilical shoulders rather tightly 

rounded, and umbilical slopes steep, broadly convex,
0134 CONTRIBUTIONS TO THE ORDOVICIAN PALEONTOLOGY OF KENTUCKY AND NEARBY STATES 

TABLE 52. Measurements (in millimeters) of holotype o/Bucania frankfortensis

USNM No. Shell 

length

Shell 

height

Aperture 

length

Aperture 

width

Umbilical 

diameter

Dorsal 

width

Posterior 

width

Ventral 

width

45716 40.5 25.5 14.0 16.9 14.0 11.5

resulting in gently rounded but distinctly triangular 

apertural outline. Inner aperture lip thickened and 

folded back to form a posterior shelf to aperture; apertural margins thin around lateral rims to broad, fairly 

deep anterior sinus; slit unknown; selenizone slightly 

elevated and rounded. Shell markings known only on 

adult thickened aperture flanks, consisting of rather 

regularly spaced, wrinkled, lamellose growth lines; 

revolving threads very weak.

Measurements.— Measurements of the holotype of B. 

frankfortensis are listed in table 52.

Material.-The holotype, USNM 45716 (pi. 16, figs. 

1-4), is a silicified replica in which the anteromedian 

portion of the shell has been rebuilt with plaster. The 

reconstruction appears to be quite faithful to the form of 

the actual shell. The species was identified here from 

silicified fragments, mainly of the thickened posterior 

aperture, from USGS sample 5036-CO.

Distribution.—The museum label states that the holotype, USNM 45716, is from the "Trenton (Cynthiana) at 

Frankfort, Kentucky." Writing on the specimen itself 

states, "Top of Trenton, Gastropoda beds, Frankfort, 

Kentucky." The highest gastropodal beds in the interval 

previously referred to as the Cynthiana Formation in the 

vicinity of Frankfort, Ky., are those of the Devils Hollow 

Member of the Lexington Limestone (Shermanian) 

(Pomeroy, 1968), which in part is characterized by a 

profusion of gastropods, most conspicuously species of 

the genus Lophospira, this facies being interpreted as 

very shallow bank deposits (Cressman, 1973, p. 40, 41). 

B. frankfortensis occurs in USGS silicified sample 5036- 

CO from the Devils Hollow Member of the Lexington 

Limestone (Shermanian) in the Coletown quadrangle, 

Ky. Bassler (1932, p. 113, 114, pi. 21, figs. 11, 12) cited 

this species as being characteristic of the Catheys Formation (Shermanian-Edenian) of the Central Basin of 

Tennessee.

Comparison.—This species most resembles B. nashvillensis, which also has an angular dorsum, but the 

dorsum of B. frankfortensis is higher, its dorsal whorl 

slopes are steeper, and its aperture is much more triangular. The coarse, wrinklelike growth lamellae on the 

thickened posterior portion of the adult whorl of B. 

frankfortensis, as well as the weakness of the revolving 

threads, also distinguish the species.

Discussion.—By virtue of their similar shell forms, 

particularly the angular dorsal whorl, B. frankfortensis 

and B. nashvillensis are closely related, but distinct, 

species.

Bucania peracuta Ulrich, 1897

Plate 16, figures 5-8

Bucania peracuta Ulrich in Ulrich and Scofield, 1897, p. 896, pi. 66, 

figs. 34, 35; Bassler, 1932, pi. 20, fig. 29.

Diagnosis.— Shell medium in size, thick; aperture 

broadly subtriangular, angular dorsally and laterally; 

umbilici wide; dorsolateral slopes with rugae.

Description. Shell medium in size (up to 29 mm long) 

and thick, the adult parietal lip being particularly massive. Aperture broadly subtriangular, the width being 

more than twice the length; whorl dorsum angular, 

dorsolateral slopes broadly spread and gently convex; 

umbilical shoulders angular; umbilical slopes deeply cut 

and slightly concave to nearly flat; base of whorl nearly 

flat, except for low ridge over previous dorsal angle. Slit 

unknown, but selenizone rather narrow for such a large 

shell, being slightly elevated and truncated. Dorsolateral 

slopes marked by low, but rather sharp and distinct, 

rugae that angle straight back from umbilical shoulder to 

selenizone, reflecting a very straight sided, V-shaped 

apertural sinus; rugae form nodes at umbilical shoulder, 

but do not pass over it. Growth lines indistinct, and 

revolving threads unknown.

Measurements.— Measurements of the holotype of B. 

peracuta (USNM 45726) are listed in table 53. Figures 

5-8 on plate 21 show the difficulties in making these 

measurements.

Material.—Only one specimen of B. peracuta is 

known, the holotype (USNM 45726). This specimen is a 

large, thick, brown, weathered, silicified fragment.

TABLE 53. Measurements (in millimeters) of holotype of Bucania peracuta

USNM No. Shell 

length

Shell 

height

Aperture 

length

Aperture 

width

Umbilical 

diameter

Dorsal

width

Posterior 

width

Ventral 

width

45726 29.1 20.0 16.3 15.5 21.0 15.3
MIDDLE AND UPPER ORDOVICIAN SYMMETRICAL UNIVALVED MOLLUSKS, CINCINNATI ARCH REGION 0135 

TABLE 54. Measurements (in millimeters) of lectotype o/Bucania sublata

USNM No. Shell 

length

Shell 

height

Aperture 

length

Aperture 

width

Umbilical 

diameter

Dorsal

width

Posterior 

width

Ventral 

width

315561 9.5 7.1 11.5 6.7 9.4 6.4 5.0

Distribution.—The museum label states that the holotype is from the "Trenton (Cannon), Dekalb Co., Tennessee." Bassler (1915, p. 137) cited the species from the 

Catheys Formation, but this is probably incorrect, 

because Bassler (1932, p. 106) later confirmed the occurrence as in the Cannon facies of the Bigby-Cannon 

Limestone (Kirkfieldian-Shermanian) of central 

Tennessee.

Comparison.— The rugae on the dorsolateral slopes of 

this species are reminiscent of Cyrtolites, but B. peracuta's extremely thick shell and slitband show that this 

resemblance is only superficial. Its rapid rate of expansion and angular dorsum led Ulrich and Scofield (1897, p. 

897) to suggest a possible relation to B. nashvillensis.

The common possession of rugae and a rather narrow, 

slightly elevated selenizone show a close relationship 

between B. peracuta and B. singularis (pi. 19, fig. 15-18) 

of the Catheys Formation (Shermanian-Edenian) of 

Tennessee.

Discussion. —B. peracuta is similar to members of the 

B. lindsleyi group of species; however, the thick, angular 

shell of B. peracuta sets it apart from the more rounded 

species. It may represent a branch of the B. lindsleyi 

group, or, as indicated by its wide, angular umbilicus, it 

may be an independent evolution from the ancestral B. 

sulcatina group.

Although I place B. peracuta in the genus Bucania, I 

point out that revolving lines are not confirmed on the 

holotype. However, the specimen is worn. Likewise, the 

specimens of the possible descendant species, B. singularis, are too poorly preserved to retain any ornament 

other than the rugae (pi. 19, figs. 15-18). Based on my 

examination of the known specimens of both species, I 

believe both species have very fine shell markings that 

are extremely difficult to discern and photograph.

Bucania sublata Ulrich and Scofield, 1897

Plate 13, figures 1-14

Bucania sublata Ulrich and Scofield, 1897, p. 888, 889, pi. 66, figs. 

16-19.

Diagnosis. — Shell small (up to about 12 mm long), 

umbilicus moderately wide, whorls very broad, globose; 

selenizone wide, flush with dorsum, bordered by distinct 

thin ridges; slit short, sinus shallow or absent.

Description. — Shell small, rate of whorl expansion 

gradual; umbilicus moderately wide, exposing earlier 

volutions; umbilical shoulders sharply rounded in early

growth, becoming more rounded in adult growth; umbilical slopes nearly flat. Dorsum very broad and somewhat 

globose; apertural outline acutely subelliptical, becoming 

less angular with growth; whorl floor has low, broad, 

median ridge. Selenizone wide, flush with adjacent whorl 

slopes, and bordered by distinct thin ridges; slit short, 

and, as shown by growth lines, which run nearly straight 

over dorsal slopes, sinus either very shallow or possibly 

lacking. Growth lines weak, evenly spaced, essentially 

straight; revolving threads even weaker, fine, closely 

spaced.

Measurements.— Measurements of the lectotype of B. 

sublata are listed in table 54.

Material.—The type suite consists of three silicified 

syntypes listed under the museum number USNM 

45733. Of these, the specimen on plate 13, figures 1-4, is 

designated the lectotype for B. sublata and assigned the 

new number USNM 315561. Specimen USNM 315562 

(pi. 13, figs. 5-8) and the unfigured third syntype 

(retained under USNM 45733) are paralectotypes. Specimens from the USGS collections identified as B. cf. B. 

sublata are USNM 315563 (pi. 13, figs. 9, 10), 315564 (pi. 

13, fig. 11), and 315565 (pi. 13, figs. 12-14).

Distribution.—The type suite was collected from the 

so-called "Flanagan beds," a name that erroneously was 

applied to silicified beds at different horizons in the upper 

Lexington Limestone (Shermanian) and treated as correlatives of a silicified bed, near Burgin, Ky.

Specimens of B. cf. B. sublata from the Lexington 

Limestone were found as fragments in USGS silicified 

samples from the Grier Limestone Member (4879-CO) 

(pi. 13, figs. 9, 10), the Faulconer Bed of the Perryville 

Limestone Member (6136-CO) (pi. 13, fig. 11), and the 

Devils Hollow Member (5095-CO) (pi. 13, figs. 12-14) 

(Shermanian).

Comparison.—B. sublata can be distinguished from 

related species such as B. halli and B. emmonsi by its 

broader, more globose whorls, its slightly smaller umbilicus, its essentially straight growth lines, its very weak 

revolving lines, and its wide, flush selenizone bordered 

by distinct, thin ridges.

Discussion.—B. sublata is a member of the B. sulcatina group, as indicated by its large, open umbilici and 

depressed whorls, and is related to B. halli and B. 

emmonsi, which are present in the Cincinnati arch area 

in slightly older strata. B. sublata shows a more 

advanced condition, because of its more globose dorsal
0136 CONTRIBUTIONS TO THE ORDOVICIAN PALEONTOLOGY OF KENTUCKY AND NEARBY STATES

TABLE 55. Measurements (in millimeters) of holotype o/Bucania micronema

USNM No.

45720

Shell 

length

9.8

Shell 

height

7.2

Aperture 

length

6.0

Aperture 

width

10.2

Umbilical 

diameter

4.7

Dorsal 

width

6.5

Posterior 

width

4.0

Ventral 

width

3.0

Selenizone 

width

0.7

whorls and its small umbilici, both traits seen in the more 

advanced B. lindsleyi group.

All the specimens identified here as B. cf. B. sublata 

are fragments in which silicification has destroyed all 

traces of shell ornament. USNM 315563 (pi. 13, figs. 9, 

10) compares well in its small shell size, umbilical size, 

and aperture lip shape to a paralectotype of B. subalata, 

USNM 315562 (pi. 13, figs. 5-8). The other fragments 

from the USGS collections are somewhat larger, but 

their whorl breadth and umbilical size suggest that they 

probably belong to this species.

Bucania micronema Ulrich, 1897

Plate 19, figures 1-6

Bucania micronema Ulrich in Ulrich and Scofield, 1897, p. 892, pi. 66, 

figs. 26-29.

Diagnosis.— Shell small (up to about 10 mm long), 

rapidly expanding, umbilicus of moderate size, with 

narrowly rounded shoulders; aperture broadly rounded, 

subtriangular; revolving lines fine (five per millimeter), 

continuous, slightly wavy; selenizone slightly elevated, 

flat topped, having distinct lunulae, and bordered by 

very fine ridges.

Measurements.—Measurements of the holotype 

(USNM 45720) of B. micronema are listed in table 55.

Material.—The holotype (USNM 45720) is a small 

silicified replica and is the only known specimen of the 

species.

Distribution.—The holotype is labeled as coming from 

the so-called "Flanagan Chert," a name that erroneously 

recognized silicified beds at different horizons in the 

upper Lexington Limestone (Shermanian) of central 

Kentucky as the same bed. The specimen was collected 

at Danville, Ky.

Comparison.—The species is quite similar to B. lindsleyi (pi. 18, figs. 1-9), but is much smaller, and its 

revolving threads are finer, more continuous across 

growth lines, and slightly wavy (pi. 19, fig. 6).

Discussion.—B. micronema is known only from the 

holotype, but it appears to be a valid taxon, as that 

specimen preserves sufficient detail to demonstrate its 

distinctiveness. Its relation to B. lindsleyi is obvious, 

and it likely is descended from that species. Its small size 

may have enabled it to dwell among erect marine algal 

foliage.

Bucania rugatina Ulrich, 1897

Plate 16, figures 9-15; Plate 17, figures 1-12

Bucania rugatina Ulrich in Ulrich and Scofield, 1897, p. 890, pi. 66, 

figs. 13-15.

Diagnosis. Shell moderate in size (up to 26 mm long), 

whorls rapidly expanding and tightly enrolled; umbilicus 

small; selenizone flush with dorsum; growth lines evenly 

and closely spaced, gently wrinkled to sublamellose; 

revolving threads distinct, but subordinate to growth 

lines.

Description.— Shell moderate in size, reaching a maximum length of about 26 mm; whorls rapidly expanding 

and relatively tightly enrolled, resulting in rather small, 

deep umbilici. Dorsum broad and very convex, umbilical 

shoulders well rounded. Adult aperture nearly semicircular and somewhat explanate laterally, never much 

thickened; thin inner parietal lip blankets previous dorsal 

whorl, resulting in broad ridge at base of aperture; outer 

parietal lip folds back over coil slightly beyond plane of 

aperture. Selenizone of moderate width, bordered by 

fine ridges, flush with dorsolateral slopes. Growth lines 

evenly and closely spaced, may be developed as weak 

wrinkles or weak lamellae, the latter becoming stronger 

in maturity; lines strongly developed onto umbilical 

slopes. Revolving threads slightly subordinate to growth 

lines, but still quite distinct as fairly coarse ridges that 

appear increasingly restricted to single growth increments as growth lines become more lamellose.

Measurements.— Measurements of B. rugatina are 

listed in table 56.

MafenaZ.-Ulrich's (1897) type suite (USNM 45728) 

consists of five silicified syntypes. From this suite, 

USNM 315555 (pi. 16, figs. 9-12) is here made the 

lectotype; USNM 315556 (pi. 16, figs. 13-15), a paralectotype, is figured, and the other three paralectotypes 

retain the original museum number, USNM 45728.

From the USGS silicified collections, four specimens 

have been identified as B. rugatina: USNM 315579 (pi. 

17, figs. 1-6), 315580 (pi. 17, figs. 7-11), 315581 (pi. 17, 

fig. 12), and 315597 (not figured).

Distribution.—Ulrich's (1897) type specimens are 

labeled as coming from the "Trenton (Flanagan), 1-1/2 

miles south of Burgin, Kentucky." According to McFarlan (1943, p. 14), the Flanagan is an obsolete unit in the 

upper Lexington Limestone (Shermanian). It included
MIDDLE AND UPPER ORDOVICIAN SYMMETRICAL UNIVALVED MOLLUSKS, CINCINNATI ARCH REGION 0137 

TABLE 56. Measurements (in millimeters) o/Bucania rugatina

USNM No.

315555

315556

315580

315579

315597

Shell 

length

_

-

-26.3

-21.3

-

Shell 

height

-12.6

10.9

18.0

11.9

-7.6

Aperture 

length

-10.6

-6.0

-16.0

-13.2

-

Aperture 

width

14.6

10.8

21.6

23.2

-10.7

Umbilical 

diameter

7.1

6.5

8.2

-7.1

5.0

Dorsal 

width

11.6

9.0

15.8

12.5

-5.9

Posterior 

width

8.5

7.0

_

-8.3

-4.5

Ventral 

width

6.6

-

-9.4

6.7

-3.3

Selenizone 

width

_

1.4

0.9

-

-

different silicified beds now in the Grier and (or) Perryville Limestone Members of the Lexington Limestone. 

The species is known from two USGS silicified samples 

from Kentucky, 6143-CO and 7348-CO, both from the 

upper tongue of the Clays Ferry Formation (Shermanian), which is overlain by the Tanglewood Limestone 

Member and underlain by the Millersburg Member of the 

Lexington Limestone.

Comparison.— B. rugatina is generally similar to B. 

lindsleyi, but differs in its smaller size, its more 

explanate aperture, its flush (rather than concave) selenizone, and its more closely spaced, wrinkled growth 

lines. Ulrich and Scofield (1897, p. 890) claimed that the 

umbilicus of B. rugatina was smaller than that of B. 

lindsleyi. Measurements show that the shell length/umbilical diameter ratio is about 3.1 in B. rugatina and 2.7 

in B. lindsleyi, supporting their claim. A difference is 

also reflected in the dorsal width/ventral width ratio, 

which is 1.77 in B. rugatina and 1.46 in B. lindsleyi. 

Combined, these two ratios show that B. rugatina 

expands its shell width at a greater rate while coiling 

more tightly, which supports Ulrich and Scofield's (1897) 

qualitative observations. B. rugatina also might be confused with B. nashvillensis, but the former's more 

globose dorsum, flush selenizone, and distinctive sculpturing should distinguish it.

Discussion. — This species obviously is closely related 

to B. lindsleyi and B. nashvillensis, and may have 

evolved from B. lindsleyi.

Bucania singularis Ulrich, 1897

Plate 19, figures 15-18

Bucania singularis Ulrich in Ulrich and Scofield, 1897, p. 894, pi. 66, 

fig. 47.

Diagnosis. Shell moderate in size (up to 27 mm long), 

whorls depressed, broadly convex dorsally, with narrowly rounded umbilical shoulders; dorsolateral slopes 

with prominent rugae, forming nodes at shoulders; selenizone elevated, flat topped, notably wider over last 

half-whorl; adult aperture laterally expanded and more 

or less square in outline.

Measurements.—Measurements of the poorly preserved lectotype of B. singularis are listed in table 57.

Material.— The specimen shown on plate 19, figures 

15-18, is here made the lectotype and given the number 

USNM 315549. The other syntype, which is now a 

paralectotype, retains the original suite number, USNM 

45730 (unfigured). The lectotype retains very little shell 

material; its umbilici and ventral aperture are covered by 

matrix, its dorsum is largely covered by an encrusting 

bryozoan, and the entire specimen is weathered.

Distribution.—The museum label with the type specimens states that they came from the Catheys Formation 

(Shermanian-Edenian) at Nashville, Tenn. No other 

occurrences are known.

Comparison.— Ulrich and Scofield (1897, p. 894) were 

in doubt about the evolutionary relations of this species, 

but believed it to be nearest B. crassa and B. lindsleyi. 

They did not state their reasons for this conclusion, and 

I can see no reason for these comparisons.

The broad, depressed whorls of B. singularis are 

reminiscent of the B. sulcatina group, as is the squaredoff adult aperture. The only other species of Bucania 

that displays the dorsal rugae of the shell is B. peracuta, 

but that species is larger and has a highly angular 

dorsum, resulting in a more triangular apertural outline.

Discussion.— After first examining the poorly preserved type specimens of B. singularis, I was uncertain 

about the validity of the species. However, further 

examination and comparison with Ulrich and Scofield's 

(1897, pi. 66, fig. 47) interpretive, but accurate, reconstruction led me to conclude that the specimens do 

represent a distinct species of Bucania. Its more or less 

square apertural outline, prominent rugae, and distinctly 

elevated selenizone distinguish it from all other species.

TABLE 57.—Measurements (in millimeters) of Bucania singularis

USNM No. Shell 

length

Shell 

height

Aperture 

ler

Aperture 

width

Dorsal 

width

Posterior 

width

Ventral 

width

315549 27.0 20.2 18.3 20.2 17.0 14.2 11.1
0138 CONTRIBUTIONS TO THE ORDOVICIAN PALEONTOLOGY OF KENTUCKY AND NEARBY STATES

TABLE 58. Measurements (in millimeters) o/Bucania pojetai

UCGM No.

44285

44286

44287

44288

44288

44289

Shell 

length

40.4

42.9

32.5

28.3

24.5

28.6

Shell 

height

26.5

26.5

21.9

_

19.4

19.8

Aperture 

length

22.0

27.5

17.0

11.6

11.9

14.9

Aperture 

width

31.7

29.1

25.5

22.0

17.5

19.6

Umbilical 

diameter

17.2

17.0

14.2

_

11.7

-

Dorsal width

19.4

18.4

17.4

17.6

15.2

-

Posterior 

width

16.5

15.2

12.6

14.0

13.5

-

Ventral 

width

12.8

14.0

10.6

-

-

-

Selenizone 

width

_

-

-

2.1

1.6

2.3

The common possession of distinct rugae on the dorsolateral slopes of this species and B. peracuta may 

indicate a genetic relationship. As stated in the discussion of B. peracuta, that species may be part of a 

separate phylogenetic branch of the genus Bucania 

distinct from the B. lindsleyi group. If so, B. singularis 

also appears to be part of the branch, and might indicate 

by its depressed whorl form the connection to ancestors 

in the more ancient B. sulcatina group.

Bucania pojetai new species

Plate 20, figures 1-8

Diagnosis.— Shell moderately large (up to 43 mm 

long), gradually expanding; umbilici large; whorl shape 

reniform in submaturity, cordate in maturity; growth 

lines wrinkled in maturity.

Description. — Shell moderately large, rate of whorl 

expansion gradual. Umbilicus large and circular in 

appearance, showing relatively loose style of coiling. 

Submature whorls depressed and reniform in outline, 

broadly and evenly rounded dorsally, with well-rounded 

umbilical shoulders and gently concave ventral side 

covering only the dorsum of the previous whorl; with 

growth toward maturity, length of aperture increases at 

greater rate than width, so that dorsum becomes jutting 

and angular, and apertural outline becomes subtriangular to cordate. Thickness of shell unknown, but parietal 

lip became moderately thick in adulthood. Slit unknown; 

selenizone a low rounded ridge showing only faint lunulae. Growth lines preserved as low wrinkles (almost 

rugose) fairly closely spaced; lines swing back over 

dorsum very gently, reflecting only a shallow anteromedian apertural sinus; wrinkled growth lines become 

stronger with growth. No revolving ornament known.

Measurements.—Measurements of B. pojetai are 

listed in table 58.

Material.— Twelve specimens of this new species are 

known. Figured specimens are the holotype, UCGM 

44285 (pi. 20, figs. 3, 4), and paratypes UCGM 44286 (pi. 

20, figs. 1, 2) and 44287 (pi. 20, figs. 5-8). Eight 

paratypes are placed under one number, UCGM 44288, 

and the eleventh paratype is cataloged under UCGM 

44289. Most of the specimens have some calcitic shell 

material preserved (see "Discussion").

Distribution. All known specimens are from a collection made by R. Flower and W. Shideler from the 

Liepers Formation (Maysvillian) at Rowena Ferry, Russell County, Ky. Note that this locality is in southern 

Kentucky near the Tennessee border where the Central 

Basin facies persist and their stratigraphic names are 

used.

Comparison.—B. pojetai is quite similar to B. simulatrix (pi. 19, figs. 11-14) and Salpingostoma richmondensis (pi. 26, figs. 1-8). Problems with separation of the 

latter two species are covered in discussions in their 

respective sections. The three species have very similar 

shell forms, but S. richmondensis shows evidence of a 

long, open slit that was closed off anteriorly, as is 

characteristic of Salpingostoma. As in B. simulatrix (pi. 

19, figs. 11-14), the slit in B. pojetai (pi. 20, figs. 1, 3, 6) 

appears to have been covered by a selenizone to near the 

apertural margin. B. pojetai differs from B. simulatrix 

in having a broader whorl form, a less elevated selenizone, and wrinklelike growth lines.

Discussion. — The marked similarity between the 

Maysvillian B. pojetai and the Richmondian B. simulatrix indicates a close evolutionary relationship. B. pojetai 

almost certainly is an ancestor of B. simulatrix.

The mode of preservation of B. pojetai is quite similar 

to that of B. simulatrix and S. richmondensis. Although 

specimens of B. pojetai have remnants of replaced original shell, the only ornament preserved is the wrinklelike 

(almost rugose) growth lines in one specimen (pi. 20, figs. 

5-8). Where the shell is broken away, the deep-brown 

calcitic shell material can be seen to be quite thin dorsally 

(pi. 20, figs. 1, 6); however, the parietal lip clearly was 

progressively thickened in mature growth, as seen by 

coarse crystalline calcite remnants in the umbilici of adult 

specimens (pi. 20, figs. 2, 4). B. simulatrix has a similar 

thin, dorsal, poorly preserved, calcitic shell remnant, and 

its holotype shows a parietal gap (which may have been 

widened through vertical compaction); the latter probably reflects a similar thickened adult parietal region (pi. 

19, fig. 13). It is difficult to determine whether these 

similar conditions of preservation are due to similar 

original shell structure and mineralogy or similar diagenetic histories, or both. The shells of known specimens of 

B. pojetai apparently have been so totally recrystallized,
MIDDLE AND UPPER ORDOVICIAN SYMMETRICAL UNIVALVED MOLLUSKS, CINCINNATI ARCH REGION 0139 

TABLE 59. Measurements (in millimeters) of lectotype o/Bucania simulatrix

USNM 

No.

Shell 

length

Shell 

height

Aperture 

length

Aperture 

width

Umbilical 

diameter

Dorsal

width

Posterior 

width

Ventral 

width

315548 45.6 26.8 24.7 31.7 -23.0 17.6 12.9 9.6

or acted upon by surface dissolution, that details of 

ornamentation are masked. What remains may be a 

single more stable shell layer.

Bucania simulatrix Ulrich, 1897

Plate 19, figures 11-14

Bucania simulatrix Ulrich in Ulrich and Scofield, 1897, p. 892, pi. 63, 

figs. 48, 49; pi. 67, fig. 45; Cumings, 1908, p. 955, pi. 42, figs. 9, 9a.

Diagnosis.— Shell large (up to 45.6 mm long), loosely 

coiled, with large, open umbilicus; submature whorls 

subreniform, adult aperture greatly expanded anteriorly 

with elongate subtriangular outline.

Description.— Shell large, consisting of about three 

volutions, loosely coiled so as to create a wide, open 

umbilicus. Submature whorls rather narrow and 

depressed, subreniform in outline; dorsum gently convex, convexity gradually increases at greater rate than 

width, but in adulthood aperture expands anteriorly at 

even a greater rate, resulting in an elongate subtriangular outline. Posterolateral lip of adult aperture slightly 

reflexed; anterior lip curved upward into fairly deep 

V-shaped sinus; parietal lip apparently thickened centrally. Dorsomedian ridge over expanded portion of 

whorl on internal molds reflects an elevated, hollow 

slitband. No surface markings known.

Measurements.— Measurements of the lectotype of B. 

simulatrix are given in table 59. Weathering of the 

specimen and the mode of preservation affected the 

measurements.

Material-Specimen USNM 315548 (pi. 19, figs. 

11-14) is here designated the lectotype. The paralectotype retains the suite number USNM 45729, which was 

originally used for both syntypes. Numerous other 

unnumbered specimens in the U.S. National Museum of 

Natural History and Miami University collections were 

also examined. Two types of preservation were 

observed. One group of specimens are generally micritic, 

compressed and distorted internal molds. The second 

group, nearly as large and very similar, are internal 

molds coated by a hard, glossy, resistant layer, most 

likely representing some portion of the original shell. The 

type specimens are preserved in this second manner (pi. 

19, figs. 11-14). The lectotype shows a gap between the 

coil and parietal lip of the expanded aperture, representing a thickened area of the shell now dissolved (pi. 19, fig. 

13). Some layer of the shell may have been of a different

mineralogy and retained preferentially, thus accounting 

for the glossy, thin, calcitic coating on such specimens.

Distribution.—The species is known only from the 

Whitewater Formation (Richmondian) in the vicinity of 

Richmond, Ind.

Comparison.—A detailed comparison of this species 

and Salpingostoma richmondensis is presented in the 

section on the latter species. The primary reason for 

distinguishing B. simulatrix from that species is the 

apparent continuation of the dorsomedian ridge, which 

represents the path of the slit, to the outer margin of the 

aperture lip in B. simulatrix (pi. 19, figs. 11-13). B. 

simulatrix differs from B. pojetai in having a more 

narrow whorl form and a more elevated selenizone, and 

in lacking the wrinklelike growth lines of B. pojetai.

Discussion.—Present evidence supports Ulrich's 

claim for distinction of this species from S. richmondensis, as the dorsomedian ridge of B. simulatrix (pi. 19, 

figs. 11-14) apparently represents the path of a raised, 

hollow selenizone. However, better preserved material 

will be required to confirm differentiation of these 

species.

Bucania crassa Ulrich, 1897

Plate 19, figures 7-10

Bucania crassa Ulrich in Ulrich and Scofield, 1897, p. 893, pi. 67, figs. 

46-48; Cumings, 1908, p. 955, pi. 39, figs. 4^6.

Diagnosis.— Shell moderately large (up to 36 mm 

long), dorsal whorl inflated, nearly semicircular, uniformly convex; umbilicus moderately small, with sharply 

rounded shoulders; shell very thick and massive.

Description.— Shell moderately large, thick, massive, 

rather tightly coiled. Umbilicus deep, moderately small, 

circular in appearance, with sharply rounded umbilical 

shoulders and nearly horizontal umbilical slopes. Dorsal 

whorl inflated, nearly semicircular and evenly convex. 

Outer aperture lip has broad, V-shaped sinus and 

becomes slightly upturned in maturity; inner and posterolateral aperture lips massively thickened. Selenizone 

slightly elevated and moderately wide. Growth lines 

broadly curved and rather evenly spaced. Revolving 

threads finer, closely spaced, always intersecting growth 

lines at right angles.

Measurements.— Measurements of the lectotype of B. 

crassa (USNM 315547) are listed in table 60.

Material.—Only Ulrich's two syntypes are known; 

both are calcitic replicas and were cataloged under
0140 CONTRIBUTIONS TO THE ORDOVICIAN PALEONTOLOGY OF KENTUCKY AND NEARBY STATES

TABLE 60. Measurements (in millimeters) o/Bucania crassa

USNM 

No.

Shell 

length

Shell 

height

Aperture 

length

Aperture 

width

Umbilical 

diameter

Dorsal 

width

Posterior 

width

Ventral 

width

315547 23.9 19.7 29.2 11.65 18.0 15.2 12.9

USNM 45714. The specimen figured (pi. 19, figs. 7-10) is 

the same one illustrated by Ulrich (1897, pi. 67, figs. 

46-48), and is here designated the lectotype, USNM 

315547. The second specimen, designated the paralectotype, retains the number USNM 45714.

Distribution.—The species is known only from 

Elkhorn Falls, near Richmond, Ind., from the Elkhorn 

biofacies of the Whitewater Formation (Richmondian), 

at the top of the Cincinnatian Series.

Comparison.— There can be no doubt about the distinctiveness of this species. Ulrich (1897) pointed out that 

its evenly convex, inflated dorsum and its smaller, more 

abrupt umbilicus readily distinguish it from species such 

as B. frankfortensis and B. nashvillensis, which have a 

more subangular dorsum. He also noted a resemblance 

between B. crassa (pi. 19, fig. 9) and B. lindsleyi (pi. 18, 

figs. 1-9). B. crassa is closely related to B. lindsleyi, 

which has both comparable shell markings and a similarly 

evenly rounded dorsum (pi. 18, figs. 1-9), but B. crassa 

has deeper umbilici and a much thicker, more massive 

shell.

Discussion.—Uppermost Cincinnatian rocks represent the last deposition of a regressing Ordovician sea on 

the Cincinnati arch Region, and are characterized by 

coarse grainstones made up of broken and worn skeletal 

fragments. The strata are further characterized in many 

places by thick-shelled invertebrates and massive bryozoan colonies, all indicating rather high energy environmental conditions. The massive shell of B. crassa seems 

to fit well into this picture.

Genus KOKENOSPIRA Bassler, 1915

[pro] Kokenia Ulrich and Scofield, 1897, p. 849. 

[not] Kokenia Holzapfel, 1895.

Diagnosis.— Shell phaneromphalous, gradually 

expanding; selenizone elevated, flat topped; shell surface 

with numerous uninterrupted revolving threads.

Description. — Shell gradually and evenly expanding; 

umbilicus moderately wide. Selenizone elevated, flat 

topped; adjacent dorsolateral slopes on either side concave; outer dorsolateral slopes and umbilical shoulders 

convex; umbilical slopes convex to flat. Shell surface 

marked by numerous uninterrupted threads; growth 

lines very weak, in many cases not visible.

Type species. —Bucaniella esthona Koken (1889, p. 

389), by original designation.

Distribution.—The type species of the genus is known 

only from Ordovician float in Pleistocene glacial drift at

Berlin, Germany. The only other known species, K. 

costalis, was described by Ulrich and Scofield (1897, p. 

883) from the Prosser Formation (Shermanian-Edenian) 

near Cannon Falls, Minn., and was reported from the 

Ordovician of Frobisher Bay, Baffin Land, Canada, by 

Schuchert (1900). K. costalis is reported here for the first 

time from the Kope Formation (Edenian) at Cincinnati, 

Ohio.

Comparison.—As pointed out by Ulrich and Scofield 

(1897, p. 882), Kokenospira differs from Tetranota in two 

significant ways: first, the aperture is much less 

expanded laterally than it is in Tetranota; and second, 

the revolving surface lines continue to the aperture, are 

more numerous, and are more threadlike and less angular than in Tetranota.

The type species, K. esthona (Koken, 1889), was 

originally placed in Bucanella, but was distinguished 

from that sinus-bearing genus by its possession of a slit 

by Ulrich and Scofield (1897).

Discussion.—By its shell form, elevated slitband, and 

dominant revolving threads, Kokenospira shows a close 

relationship to Tetranota, the two most likely having 

evolved from a common ancestral stock. Bucania also 

had a common ancestry with these two genera. All three 

genera evolved in the Middle Ordovician.

Kokenospira costalis (Ulrich and Scofield), 1897

Plate 20, figures 9-12 

Kokenia costalis Ulrich and Scofield, 1897, p. 882, pi. 64, figs. 46-49.

Diagnosis.—Shell moderately small (up to 13.5 mm 

long); slitband elevated, flat topped; six or seven revolving threads on each dorsolateral slope.

Description. — Shell moderately small and apparently 

rather thin, gradually expanding. Umbilicus rather large 

and open. Selenizone distinctly elevated and flat topped, 

with fine, sharp bordering threads. Dorsolateral slopes 

concave immediately adjacent to slitband, but rapidly 

become convex, continuing to be rounded over umbilical 

shoulders. Whorls reniform in section, aperture length/ 

width ratio about 0.60-0.65. Growth lines indistinct; each 

dorsolateral slope with six or seven thin, uninterrupted 

revolving threads which continue to apertural margin; 

first revolving thread adjacent to slitband weaker than 

others on dorsal whorl slope, as are other threads within 

umbilicus.

Measurements.— Measurements of K. costalis are 

listed in table 61.
MIDDLE AND UPPER ORDOVICIAN SYMMETRICAL UNIVALVED MOLLUSKS, CINCINNATI ARCH REGION 0141

TABLE 61.—Measurements (in millimeters) o/Kokenospira costalis

UCGM

No.

Shell 

length

Shell 

height

Aperture 

length

Aperture 

width

Umbilical 

diameter

26519 13.5 12.0 8.0 12.4 12.5

Material.— Only one specimen of this species was 

examined, UCGM 26519, a worn and fragmentary calcitic replica (pi. 20, figs. 9-12) collected by Leigh Van 

Valen. The holotype is cataloged under USNM 45868.

Distribution.-Ulrich and Scofield (1897, p. 883) 

described the species on the basis of a single specimen 

from the Clitambonites bed, Prosser Formation 

(Shermanian-Edenian), near Cannon Falls, Minn. 

Schuchert (1900, p. 164) reported the species from the 

"Trenton" of Frobisher Bay, Baffin Land, Canada.

The specimen described here comes from the Southgate biofacies of the Kope Formation (Edenian), from a 

pit on Beekman Street, Cincinnati, Ohio.

Comparison.— K. costalis differs from K. esthona 

(Koken) in having a less prominent slitband and a more 

rounded shell form. K. costalis can be distinguished from 

similar species of the genus Tetranota by its more 

numerous revolving threads which remain distinct to the 

apertural margin.

Discussion. — This rare species appears to be quite 

widespread geographically. The specimen described here 

(UCGM 26519) (pi. 20, figs. 9-12) compares well with 

Ulrich and Scofield's (1897) single specimen, which was 

reported to be about 10 mm long. Measurements of the 

aperture on the figures of their specimen (their pi. 64, 

fig. 48) give an aperture length/width ratio of 0.61, 

closely comparable to the ratio of 0.64 for the Cincinnati 

specimen. UCGM 26519 clearly shows the centralmost 

revolving thread to be weaker than the others, but it is 

difficult to say with certainty whether six or seven 

threads are present on each side.

Subfamily UNDULABUCANIINAE new subfamily

Diagnosis. Whorls subtrapezoidal to rounded in 

cross section; slit long, narrow, generates selenizone; 

shell surface marked only by closely spaced, regularly 

wavy, fine collabral threads, which may or may not 

intersect.

Stratigraphic range.— Middle Ordovician (Kirkfieldian)-Upper Ordovician (Maysvillian).

Type genus. — Undulabucania n. gen. is the type and 

only known genus of the subfamily.

Discussion. — The subfamily Undulabucaniinae is 

unique in its possession of a deep slit, a characteristic 

ornament of closely spaced, wavy threads, and a shell 

form similar to that of the primitive Bucania sulcatina 

group, with broad-topped, depressed whorls and wide

umbilici. The long slit and wavy shell markings suggest 

descent from the Tropidodiscidae, and most likely from 

Phragmolites.

Genus UNDULABUCANIA new genus

Diagnosis. —Shell gradually expanding, with wide, 

open umbilici; slit very deep; shell ornament of fine, 

closely spaced, undulating collabral threads, which may 

or may not intersect.

Description.—Shell small to moderate in size (about 

15-20 mm long), gradually and evenly expanding; umbilici wide, open. Whorl shape generally subtrapezoidal, 

but may be much more uniformly rounded. Slit very 

deep, usually generating channellike selenizone. Surface 

sculpturing of fine, closely spaced, undulating collabral 

threads, which when intersecting form a netlike meshwork. No revolving ornament known, except for threads 

bordering selenizone.

Type species.—Bellerophon gorbyi Miller, 1892 (p. 

694), is here designated the type species of the new 

genus Undulabucania.

Other species placed in Undulabucania.—In addition 

to the type species, Bellerophon punctifrons Emmons 

(1842) and Bucania punctifrons primaeva Bradley (1930) 

are here assigned to Undulabucania n. gen.

Distribution. — Species of the new genus are known 

from strata ranging in age from the Kirkfieldian (upper 

Middle Ordovician) to Maysvillian (middle Upper Ordovician) Stages in Eastern North America.

Discussion.— Of the three species included in Undulabucania, U. punctifrons (Emmons, 1842) and U. gorbyi (Miller, 1892) were originally described as members 

of the genus Bellerophon, although Hall (1847) transferred U. punctifrons to Bucania. The third species, U. 

primaeva, was described from the Kimmswick Limestone (Kirkfieldian-Edenian) near Dutchtown, 111., as 

Bucania punctifrons primaeva by Bradley (1930, p. 236, 

pi. 25, figs. 23-24). This taxon is here regarded as a 

distinct species bacause of its more narrow, somewhat 

circular whorl form. All three of the species, but particularly U. punctifrons and U. gorbyi, have a shell form 

closely resembling that of species belonging to the Bucania sulcatina group. They have thin shells, broad umbilici, gradually enlarging depressed whorls, a wide, yet 

not expanded, aperture with thin lips, and a long slit. 

Although the species of Undulabucania exhibit all of 

these traits, they differ in one very significant aspect. By 

definition, species of the genus Bucania have revolving 

threads that intersect the growth lines at right angles. 

The species here included in Undulabucania lack revolving ornament, except threads bordering the selenizone; 

they do have the common presence of fine, undulating 

growth lines that intersect, or nearly do so.
0142 CONTRIBUTIONS TO THE ORDOVICIAN PALEONTOLOGY OF KENTUCKY AND NEARBY STATES 

TABLE 62. Measurements (in millimeters) ofholotype of Undulabucania gorbyi

uc

No.

Shell 

length

Shell 

height

Aperture 

length

Aperture 

width

Umbilical 

diameter

Dorsal 

width

Posterior 

width

Ventral 

width

Selenizone 

width

Slit 

length

6138 20.5 14.3 12.4 13.5 10.0 11.7 9.5 15.0

The similarity in all characteristics but shell sculpturing suggests that Undulabucania had a common ancestry with the Bucania sulcatina group. As discussed 

previously, it is likely that Undulabucania and Bucania 

had a common ancestral connection with the tropidodiscids. That family contains the oldest known slit-bearing 

bellerophont, Chalarostrepsis Knight, 1948, from the 

Upper Cambrian of Canada. It is assumed that this 

genus was of the stock that gave rise to Phragmolites 

Conrad (1838) and Tropidodiscus Meek and Worthen 

(1866) in the Ordovician. Undulabucania and Phragmolites have a great deal in common, such as their wide 

umbilici, their long slits, and, particularly, their wavy 

growth lines. However, Undulabucania differs from 

Phragmolites in its lack of spiral ornament and its shell 

form, which closely resembles that of the Bucania sulcatina group. Given our present knowledge, it seems 

possible that Undulabucania evolved from a 

Phragmolites-like tropidodiscid.

Undulabucania gorbyi (Miller), 1892 

Plate 23, figures 10-15

Bellerophon gorbyi Miller, 1892, p. 694, pi. 14, figs. 7-9; Cumings, 

1908, p. 953, pi. 39, figs. 1-16.

Diagnosis.— Shell having broad, dorsally rounded, 

subtrapezoidal whorl outline; slit deep and narrow; 

growth lines fine, wavy, closely spaced but not 

intersecting.

Description. Shell small to moderate in size (about 20 

mm long), increasing in size gradually and evenly. Umbilici fairly wide; dorsum of shell evenly and highly convex; 

umbilical shoulders narrow but well rounded; umbilical 

slopes flat to slightly convex, angling rather gently from 

shoulders to lower dorsolateral slope of previous whorl; 

ventral whorl deeply concave as it closely covers dorsum 

of previous whorl. Slit long and narrow, bordered by fine 

ridge on either side; selenizone slightly depressed, with 

fine lunulae. Shell ornament of very fine, closely spaced, 

nearly equidistant, wavy growth lines which never intersect; growth lines bend back over dorsum, reflecting a 

broad, moderately deep apertural sinus. Only revolving 

ornament known is ridges bordering selenizone. Aperture lips tend to flare laterally slightly in maturity.

Measurements.— Measurements of the holotype of U. 

gorbyi are listed in table 62.

Material.—Only one specimen of this species was 

located, UC 6138, which is the holotype. This wellpreserved calcitic replica was collected by S. S. Gorby, 

after whom it was named, and is deposited in the Gurley 

Collection at the Field Museum of Natural History, 

Chicago, 111.

Distribution. The holotype was collected from Maysvillian (middle Upper Ordovician) strata in Dearborn 

County, Ind. No more specific horizon or locality was 

given by the original author on the museum label. 

Maysvillian-age strata in southeastern Indiana are now 

included in the Dillsboro Formation.

Comparison.— This species obviously is closely 

related to U. punctifrons, but its whorls are much 

broader (pi. 23, figs. 11, 12) and its wavy growth lines 

never intersect, but remain nearly equidistant (pi. 23, 

fig. 10).

Discussion.— Superficially, the shell ornament of U. 

gorbyi appears much like that of U. punctifrons. On 

closer examination, however, the wavy growth lines can 

be seen to remain separate, although they do come close 

to touching one another. Nevertheless, the camouflage 

effect of the ornament would be the same as for U. 

punctifrons, which was probably directly ancestral to 

this species.

The slit of U. gorbyi is very long (15 mm) (pi. 23, figs. 

10, 11, 13, 14). As the shell of the holotype is so well 

preserved, it is doubtful that this impression is false. 

Lunulae are visible dorsally where the slit was covered 

by the selenizone, and there the dorsomedian line is 

barely depressed, whereas anteriorly it is excavated as a 

deep channel. It should also be noted that the small bump 

situated about one-third of a whorl back on the right side 

of the slit (pi. 23, fig. 10) is a small bryozoan colony. This 

colony may have been situated on the living gastropod so 

as to take advantage of exhalant currents being emitted 

from the deep slit.

Undulabucania punctifrons (Emmons), 1842 

Plate 23, figures 1-9

Bellerophon punctifrons Emmons, 1842, p. 392, fig. 5; Lesley, 1889, p.

87, figs. 

Bucania punctifrons (Emmons) Hall, 1847, p. 187, pi. 40A, figs, la-e;

Ulrich and Scofield, 1897, p. 894, pi. 67, figs. 41-44; Raymond,

1902, pi. 19, figs. 9, 10; Weller, 1903, p. 177, pi. 12, figs. 10-12;

Grabau and Shimer, 1909, p. 614; Bassler, 1932, pi. 13, figs. 16, 17;

Wilson, 1951, p. 27, pi. 2, figs. 21-23.

Diagnosis. — Shell having relatively large umbilici; 

aperture rounded subtrapezoidal; undulating growth 

lines intersecting to form netlike meshwork.
MIDDLE AND UPPER ORDOVICIAN SYMMETRICAL UNIVALVED MOLLUSKS, CINCINNATI ARCH REGION 0143 

TABLE 63. Measurements (in millimeters) of Undulabucania punctifrons

USNM 

No.

45727 

315546

Shell 

length

19.75 

17.4

Shell 

height

14.35 

12.5

Aperture 

length

10.35 

9.0

Aperture 

width

13.25 

12.25

Umbilical 

diameter

10.8 

10.3

Dorsal 

width

10.4 

10.0

Posterior 

width

8.65 

8.15

Ventral 

width

6.7 

6.6

Selenizone 

width

0.7 

0.6

Description. Shell small to moderate in size (up to 20 

mm long), consisting of about three volutions; gradually 

and evenly expanding throughout growth. Umbilici relatively wide for genus; whorls rounded subtrapezoidal in 

outline, with evenly and rather deeply convex dorsum 

and sharply rounded umbilical shoulders, flat and broad 

umbilical slopes that angle gently inward to shoulder of 

previous whorl, and concave ventrum covering surface of 

previous whorl. Aperture shows only very slight flaring 

as an adult, and has wide, fairly deep anterior sinus; slit 

quite deep, generating channellike selenizone bordered 

by thin, sharp ridge on either side. Shell surface covered 

by evenly undulating, wavy growth lines which intersect 

to form fine, slightly raised, netlike meshwork; this 

sculpturing present on juvenile whorls visible in umbilicus. Growth becomes coarsely lamellose in later growth.

Measurements.— Measurements of U. punctifrons are 

listed in table 63.

Material.-Only Ulrich and Scofield's (1897, pi. 67, 

figs. 41^14) two hypotypes from the Hermitage Formation at Nashville, Tenn., were examined. One retains the 

original museum number, USNM 45727 (pi. 23, figs. 

1^1). This well-preserved calcitic specimen has a massive 

bryozoan colony plugging the aperture (probably a post 

mortem association) and is missing some of the dorsal 

shell. The other specimen, here numbered USNM 315546 

(pi. 23, figs. 5-9), is very similarly preserved and is also 

missing a small portion of the dorsal shell. Emmon's 

(1842) original type material could not be located and is 

assumed to be lost.

Distribution.—This species is known from Rocklandian to Edenian rocks throughout Eastern North America. Emmons (1842), Hall (1847), Lesley (1889), and 

Ulrich and Scofield (1897) reported the species from the 

Trenton Group in New York, Canada, Pennsylvania, and 

Tennessee. Wilson (1951, p. 27) reported it from the 

Rockland, Sherman Falls, and Cobourg beds 

(Rocklandian-Edenian) of the Ottawa Formation in the 

Ottawa-St. Lawrence Lowland, Ontario, Canada. Weller 

(1903) cited the species from the Trenton Group in New 

Jersey. Bassler (1932, pi. 13, figs. 16, 17) reported the 

species from the Hermitage Formation (Kirkfieldian) of 

central Tennessee, which are the horizon and area where 

the specimens figured here (pi. 23, figs. 1-9) were 

collected.

Comparison.— The shell form of U. punctifrons is 

similar to that of members of the B. sulcatina group,

particularly B. halli, but its meshlike shell sculpturing 

easily distinguish it. U. punctifrons can be distinguished 

from U. gorbyi by the intersection of its wavy collabral 

threads, which in U. gorbyi remain separated.

Discussion.—Hall (1847, pi. 40A, fig. le) and Ulrich 

and Scofield (1897, pi. 67, fig. 44), among other authors, 

have illustrated the shell markings of U. punctifrons as 

being a regular pitting of the shell surface. As shown 

here on plate 23, figure 4, this sculpturing is in reality a 

rather regular netlike meshwork of raised, wavy, intersecting collabral threads. This shell pattern may have 

served as camouflage for the animal, mingling with the 

intersecting patterns of light in a shallow subaqueous 

environment much like a fishnet. Such an adaptation 

would be an important protective cover from predators.

Subfamily PLECTONOTINAE Boucot and Yochelson, 1966

Diagnosis.— Shell having raised dorsomedian lobe, 

giving the whorls a trilobed cross section.

Stratigraphic range.— Middle Ordovician-Devonian.

Genera included. —Tetranota Ulrich and Scofield, 

1897; Plectonotus Clarke, 1899; Tritonophon Opik, 1953.

Genera considered here. — Tetranota.

Discussion.—Plectonotus was described by Clarke 

(1899) as having a slit that generates a selenizone. Knight 

(1941) redescribed the type material and noted only a 

V-shaped sinus in the apertural margin. Therefore, 

Knight and others (1960) placed Plectonotus in the 

Sinuitidae as a subgenus of Bucanella Meek (1871). 

Boucot and Saul (in Boucot, Saul, and Finks, 1963) 

discovered new material from the Devonian of Ghana 

that confirmed Clarke's original observation of a slit in 

the genus. In light of this discovery, Horny (1963a) 

placed Plectonotus near Tetranota in the subfamily 

Bucaniinae of the Bellerophontidae. Boucot and Yochelson (1966) proposed the subfamily Plectonotinae of the 

Bellerophontidae, including only the genus Plectonotus. 

Peel (1974) summarized the information about trilobed 

bellerophontaceans and analyzed their functional morphology. He accepted the subfamily Plectonotinae and 

added the genus Tritonophon, placing Nylanderina 

Boucot (1967) in synonymy with it. Herein, Tetranota is 

also placed in the Plectonotinae.

The Plectonotinae is transferred to the family Bucaniidae because of their somewhat depressed whorl forms, 

open umbilici, flaring lateral apertural margins, and 

spiral ornamentation.
0144 CONTRIBUTIONS TO THE ORDOVICIAN PALEONTOLOGY OF KENTUCKY AND NEARBY STATES

Tetranota is the earliest known member of the subfamily and is regarded as ancestral to the later genera. 

Bretsky (1970a) reported Plectonotusl from the Upper 

Ordovician of the Central Appalachians, but these internal molds may actually belong to the widespread Ordovician genus Tetranota. Peel (1974) suggested that 

Bucanella might also have a slit, rather than merely a 

sinus, but currently known material is too poorly preserved to resolve the matter. If it is found that 

Bucanella is slit bearing, then that genus should also be 

placed in the Plectonotinae. It would thereby be the 

oldest member of the subfamily, being Early Ordovician 

in age.

Genus TETRANOTA Ulrich and Scofield, 1897

Diagnosis.— Shell with selenizone lying on broad, elevated dorsomedian band, in many cases bordered by pair 

of revolving threads, with one or two pairs of dorsolateral revolving angular ridges; aperture lip chiefly 

expanded laterally.

Description.—Shell variable in size, thin. Umbilici 

moderate to large in size, deep. Whorls broad and 

depressed, aperture wider than long throughout growth. 

In maturity, aperture lips tend to flare, chiefly in lateral 

directions. Parietal lip without thickened callosity. Selenizone on broad, elevated, gently convex to nearly flat 

topped dorsomedian band, which generally has revolving 

threads along its edges; lunulae faint in most cases. 

Outward from dorsal band, shell briefly concave to 

dorsolateral pair of angular revolving ridges; in some 

cases a second outer pair of dorsolateral ridges also 

present; pairs of dorsolateral ridges best developed in 

youth, gradually becoming indistinguishable in many 

mature shells. Apertural sinus broad and moderately 

deep, terminating in wide, short slit. Growth lines fine, 

closely spaced.

Type species.—Bucania bidorsata Hall, 1847, by original designation.

Other North American Ordovician species. —T. sexcarinata Ulrich and Scofield, 1897; T. macra Ulrich and 

Scofield, 1897; T. obseleta Ulrich and Scofield, 1897, T. 

wisconsinensis (Whitfield, 1878), T. charon (Billings, 

1860); T. rugosa (Emmons).

Distribution.—In Eastern North America, the genus 

is widely known from strata of latest Chazyan or early 

Blackriveran to Maysvillian age. Walcott (1884) also 

reported the type species from the upper Pogonip Group 

(Whiterockian?) of Nevada.

In Europe, the genus is known only from the British 

Isles. Reed (1921, p. 41) described a possible species 

from the Lower-Middle Ordovician Arenigian Series of 

England, and three "varieties" of a species from the 

Stinchar Limestone (Llanvirnian-Llandeilian), the Balclatchie Group (Caradocian), and the Drummock Group

(Ashgillian) of Girvan. These occurrences are discussed 

further below.

Discussion.— Of the species now included in the genus 

Tetranota, T. bidorsata (Hall, 1847) was originally 

assigned to Bucania, and T. charon (Billings, 1860), T. 

rugosa (Emmons), and T. wisconsinensis (Whitfield, 

1878) were first placed in Bellerophon. Koken (1889, p. 

389) incorrectly placed T. bidorsata with unrelated 

Silurian-Devonian European species in the sinuate genus 

Bucanella (for discussion, see Ulrich and Scofield, 1897, 

p. 876).

Ulrich and Scofield (1897, p. 875) proposed the genus 

Tetranota for those Ordovician species that are phaneromphalous and slit-bearing and have four revolving 

ridges on the shell, two bordering an elevated slit and 

two dorsolaterally. The lines bordering the slitband are 

often not well preserved; when they are (pi. 21, figs. 2-9, 

14), they appear to be quite threadlike. The dorsolateral 

lines are not threadlike, but rather are like angled ridges 

or carinas. In this respect, these dorsolateral revolving 

ridges are more similar to the revolving ornament of 

Kokenospira than to the ornament of genera such as 

Bucania or Bucanopsis. In its gradually expanding, 

depressed whorls, and in its possession of revolving 

ornament, Tetranota shows relationship to Bucania and 

Kokenospira. Besides the difference in the character of 

the revolving ornament, Tetranota also differs from 

Bucania in expanding at maturity chiefly only in the 

lateral directions, rather than anteriorly. In addition to 

the similarity in the character of the revolving lines, 

Kokenospira costalis (pi. 20, figs. 9-12) also bears an 

elevated, nearly flat topped, dorsomedian band similar to 

that of Tetranota. Therefore, Kokenospira and Tetranota may be closely related bucaniid genera, even though 

they are placed in separate subfamilies.

The earliest occurrences of Tetranota in North America are those of T. bidorsata reported by Walcott (1884) 

from the Upper? Pogonip Group (Whiterockian?) of 

Nevada, and by Raymond (1908) from Chazyan strata in 

New York; Butts (1926) reported T. cf. T. obseleta from 

the Little Oak Limestone north of Pelham, Ala. (see 

herein, pi. 22, figs. 16-18). Ross and others (1982) dated 

the Little Oak as upper Whiterockian in age. Reed (1921, 

p. 43) reported T. hippapus (Salter) from the Lowerlower Middle Ordovician Arenigian Series of England, 

but noted (p. 44) that the two known specimens are 

poorly preserved. Reed also described three "varieties" 

of T. carrickensis Reed, the earliest being from the 

Stinchar Limestone, which Bergstrom (1971, p. 114) 

correlated with the upper Lenoir Limestone of eastern 

Tennessee. As shown by Ross and others (1982), in some 

places the upper Lenoir and Little Oak Limestones are 

time equivalent, suggesting age correlation between the 

confirmed occurrences of Tetranota in Great Britain and
MIDDLE AND UPPER ORDOVICIAN SYMMETRICAL UNIVALVED MOLLUSKS, CINCINNATI ARCH REGION 0145

TABLE 64. Measurements (in millimeters) o/Tetranota bidorsata

Museum 

No.

AMNH Fl

29592

787

29594

29593

USNM

17301

47545

UCGM

44291a

44291b

44292

44293

44294

Shell 

length

-20.0

-

18.0

-21.0

20.5

22.0

-

-

-16.1

-

-

Shell 

height

-16.5

-

-14.0

-

14.9

-

-

-

-13.0

-

-

Aperture 

length

-

-

14.5

-13.1

9.3

12.2

-

-

-8.5

-

-

Aperture 

width

-

-

16.7

24.1

23.6

34.9

-

-

-18.0

-

-12.1

Umbilical 

diameter

-

-

11.6

12.0

6.4

9.8

-

-

8.5

-

-

Dorsal 

width

-

-

-14.0

15.2

-13.0

16.3

-

-

-

-

-

Posterior 

width

-

-

-9.3

13.3

-

14.5

-

-

11.4

-

-

Ventral Selenizone 

width width

-

2.2

-8.5 -2.8

-4.0

8.2 3.0

3.0

1.8

2.1

2.0

1.9

1.4

Width of 

lateral ridges

-

-7.2

-8.9

-

-

-

8.1

8.4

9.0

-10.0

6.5

North America. Comparisons between the specimens I 

examined and Reed's illustrations are difficult, but British species of Tetranota do not appear significantly 

different from the American species. Examination of 

Reed's specimens probably will show the species names 

he proposed to be synonymous with American species 

names.

As pointed out by Ulrich and Scofield (1897, p. 877), 

some species of Tetranota are quite long ranging relative 

to most other bellerophontaceans. For example, T. 

bidorsata occurs in rocks ranging in age from Whiterockian through Edenian. As far as preservation and present 

collections allow, specimens of T. bidorsata from widely 

different stratigraphic levels and geographic localities 

appear essentially morphologically identical (compare pi. 

22, figs. 1 and 5). Scheltema (1977, p. 105) pointed out 

that there may be a relationship between larvae dispersal potential, geographic range, and longevity of 

species. Geographically widespread and stratigraphically 

wide ranging species are generally eurytopic and have a 

greater genetic diversity. Following this line of reasoning, most bellerophontacean species, which are usually 

quite short ranging and local, may have been stenotopic, 

being too narrowly specialized to survive long periods in 

a constantly fluctuating epicontinental environment. T. 

bidorsata is a likely exception to this scenario, because of 

its broad geographic and stratigraphic distribution.

Tetranota bidorsata (Hall), 1847

Plate 21, figures 1-14; Plate 22, figures 1-10

Bucania bidorsata Hall, 1847, p. 186, pi. 40, figs. 8a-g; 1862, p. 39, fig.

6; Chamberlin, 1883, p. 158, fig.; Walcott, 1884, pi. 1, figs. 13a-c;

Lesley, 1889, p. 96, figs. 

Tetranota bidorsata (Hall), Ulrich and Scofield, 1897, p. 877, pi. 65,

figs. 10-18; Weller, 1903, p. 176, pi. 12, figs. 18, 19; Raymond,

1908, p. 197, pi. 50, fig. 5; Grabau and Shimer, 1909, p. 612, figs.

819a-d; Knight, 1941, p. 347, pi. 8, fig. 4; Shimer and Shrock, 1944,

p. 441, pi. 177, fig. 119; Steele and Sinclair, 1971, p. 19, pi. 10, figs. 

4, 15; ?Wilson, 1951, p. 30, pi. 4, figs. 1, 2.

Diagnosis. Shell having prominently elevated, broad 

dorsomedian band with distinct bordering threads and 

carrying slightly concave selenizone; dorsolateral slopes 

with centrolateral grooves between median band and 

single pair of distinct lateral revolving ridges.

Description. — Shell small to moderate in size, maximum known shell length about 22 mm. Whorls 

depressed, subreniform in outline, more than twice as 

wide as long, this ratio increasing in maturity, when 

aperture flares laterally somewhat. Umbilici wide and 

deep; shoulders squared off and angular in specimens 

that retain shell, tightly rounded in internal molds. 

Dorsum with prominently elevated, broad median band 

that carries slightly concave selenizone having fine but 

distinct lunulae, bordered by two angular revolving 

threads; median line visible down axis of selenizone of 

some specimens. Median band appears as broad, flat 

topped to rounded ridge in molds. Outward from the 

dorsomedian band is pair of centrolateral concave 

grooves, followed by pair of angular, slightly elevated 

ridges; lateral ridges distinct in small- to moderate-sized 

shells, but as known from molds only, tend to disappear 

in maturity, the dorsal slopes flattening and flaring 

laterally; outer dorsal slope nearly flat to the angular 

umbilical shoulder. Growth lines very fine, closely 

spaced, and quite distinct, being nearly straight, though 

angled slightly toward posterior on outer slopes, then 

increasing in curvature from dorsolateral ridges to 

median band; fine collabral threads pass over dorsolateral ridges uninterrupted.

Measurements.— Measurements of T. bidorsata are 

listed in table 64.

Material.— Hall's (1847) type suite was examined. 

Specimen AMNH Fl 29592 (pi. 21, figs. 12, 13) (Hall, 

1847, pi. 40, figs. 8c, d) was designated the lectotype by
0146 CONTRIBUTIONS TO THE ORDOVICIAN PALEONTOLOGY OF KENTUCKY AND NEARBY STATES

Knight (1941, p. 347, pi. 8, fig. 4). That specimen retains 

part of the shell, but all the paralectotypes, AMNH Fl 

29593 (pi. 22, fig. 1), AMNH Fl 29594 (pi. 22, figs. 2-4), 

AMNH Fl 29595, and AMNH Fl 787 (pi. 21, fig. 14), are 

black, micritic internal molds. Walcott's (1884, pi. 1, fig. 

13) specimen from Nevada (USNM 17301) is also largely 

an internal mold, but it retains some shell on the left 

anterodorsal slope (pi. 22, figs. 5-10).

Ulrich and Scofield (1897, pi. 65, fig. 24) illustrated a 

specimen they identified as T. sp. indet. from Edenian 

strata at Cincinnati. They favored an identification as T. 

obsoleta rather than T. bidorsata because of the "obsolescence of the laterodorsal ridges." This specimen, 

USNM 47545 (pi. 21, figs. 9-11), is here identified as T. 

bidorsata, and is discussed further below. Some small, 

partially crushed specimens of the species, UCGM 44308 

and 8695, were found in other collections from Edenian 

strata in the Cincinnati area.

Five well-preserved specimens retaining the shell, 

UCGM 44291a, 44291b, 44292, 44293, and 44294 (pi. 21, 

figs. 1-8), were collected by John Pojeta, Jr., William 

Harrison, and me from a mollusk bed in Edenian strata 

east of Cincinnati (locality OH-1, Bear Creek Quarry). To 

my knowledge, these are the best preserved specimens 

of T. bidorsata available, and they clarify features poorly 

shown in the lectotype.

Distribution.-Ulrich and Scofield (1897, p. 878) listed 

T. bidorsata from Blackriveran to Edenian strata 

throughout Eastern North America, including New 

York and adjacent Canada, West Virginia, Kentucky, 

Tennessee, Ohio, and Minnesota. Weller (1903) reported 

the species from numerous horizons in the "Trenton 

limestone" of New Jersey. Raymond (1908, p. 197) 

tentatively identified specimens from Chazyan (Whiterockian) strata on Valcour Island, N.Y., as T. bidorsata. Walcott (1884) reported the species from the upper 

Pogonip Group (Whiterockian?) in the White Pine District of Nevada. Wilson (1951) and Steele and Sinclair 

(1971) reported the species from Blackriveran strata in 

eastern Canada.

The new specimens shown here are five wellpreserved calcitic replicas from the Kope Formation 

(Edenian) at Bear Creek Quarry (locality OH-1), located 

in the bluffs on the northern side of the Ohio River, on 

the northeastern corner of the junction of U.S. Route 52 

and Bear Creek Road, between Neville and Chilo, Ohio. 

The specimens came from a lenticular mollusk bed about 

10 ft above the Point Pleasant Tongue of the Clays Ferry 

Formation (Shermanian), and were associated with 

abundant specimens of Sinuites granistriatus, as well as 

sparse specimens of C. (Cyrtolites) claysferryensis, 

small lophospirids, and orthoconic nautiloids.

Comparison. — T. bidorsata can be distinguished from 

T. wisconsinensis (pi. 38, figs. 13-16) by its prominent

dorsolateral revolving ridges (pi. 21, figs. 1-14; pi. 22, 

figs. 1-10). Otherwise, the two species are quite similar. 

T. sexcarinata is somewhat more globose than T. bidorsata and has a second pair of lateral ridges.

Discussion. —T. bidorsata is unusually long ranging 

stratigraphically and widespread geographically for a 

bellerophontacean. This may be a result of the similar 

appearance of internal molds of a group of closely related 

species. Most known specimens are internal molds. Comparison of steinkerns from New York (pi. 22, figs. 1-4), 

Ohio (pi. 21, figs. 9-11), and Nevada (pi. 22, figs. 5-10) 

shows that all have the same depressed, laterally spreading whorls, the same broad, elevated dorsomedian band, 

and the same low, rounded lateral ridges. The last two of 

these specimens retain some remnant of the shell, and 

both show fine, closely spaced growth lines. Besides the 

lectotype of the species (pi. 21, figs. 12, 13), the only 

specimens preserving a significant portion of the shell 

are five new specimens collected from the Edenian 

portion of the Kope Formation in southern Ohio (pi. 21, 

figs. 1-8). These specimens are mostly deeply embedded 

in fairly compact mudstone, but they nevertheless show, 

for the first time, the true form of the shell and nature of 

the ornament. They show that the lateral revolving lines 

are not cords, but angular ridges over which the growth 

lines pass essentially uninterrupted. They also confirm 

the presence of a dark median line along the selenizone 

(pi. 21, figs. 2, 3), which is also visible in the lectotype 

(pi. 21, fig. 13). The origin of this median line is unknown.

Specimen USNM 47545 (pi. 21, figs. 9-11), an 

Edenian-age internal mold, was identified as T. obseletal 

by Ulrich and Scofield (1897, pi. 65, fig. 24) because of 

the "obsolescence of the laterodorsal ridges"; however, 

as shown here (pi. 21, figs. 9-11), there are faint low 

ridges over the dorsal slopes of the specimen, and the 

form of the shell, the flaring of the adult aperture, and 

the large umbilicus clearly indicate that the specimen 

belongs to T. bidorsata.

Tetranota obsoleta Ulrich and Scofield, 1897 

Plate 20, figures 13-15; Plate 22, figures 16-21

Tetranota obsoleta Ulrich and Scofield, 1897, p. 880, pi. 65, figs. 19-23; 

Grabau amd Shimer, 1909, p. 613, figs. 819i-k; Bassler, 1919, p. 

310, pi. 55, figs. 22-24; Butts, 1926, pi. 26, figs. 12,13, Shimer and 

Shrock, 1944, p. 441, pi. 177, figs. 20, 21.

Diagnosis.— Shell relatively tightly coiled, umbilici 

relatively small; dorsum evenly rounded, nearly semicircular, with low, broad median band and single pair of 

weak dorsolateral ridges which disappear by adulthood.

Description.— Shell small (up to about 14 mm long), 

thin, rather tightly coiled; umbilici small and deep for 

genus. Aperture subelliptical to nearly semicircular; 

umbilical slopes flat, slightly sloped to nearly horizontal; 

umbilical shoulders tightly rounded; dorsum evenly
MIDDLE AND UPPER ORDOVICIAN SYMMETRICAL UNIVALVED MOLLUSKS, CINCINNATI ARCH REGION 0147 

TABLE 65. Measurements (in millimeters) o/Tetranota obsoleta

USNM 

No.

46014

71496

315541

Shell 

length

13.8

11.7

9.5

Shell 

height

11.0

10.2

-

Aperture 

length

7.8

5.3

4.2

Aperture 

width

16.2

11.3

9.9

Umbilical 

diameter

4.4

4.3

4.0

Posterior 

width

7.2

-

-

Selenizone 

width

2.4

1.5

1.2

rounded. No distinct parietal lip over previous whorl 

surface at base of aperture. Dorsomedian band slightly 

elevated, slightly concave, bordered by distinct revolving threads; band gradually widens with growth. Low, 

angular dorsolateral ridges present on juvenile whorls, 

but disappear toward maturity. No lunulae or growth 

lines well preserved.

Measurements.— Measurements of T. obsoleta are 

listed in table 65.

Material.— Three specimens were examined; all are 

silicified. Specimen USNM 46014 (pi. 22, figs. 19-21) is 

here designated the lectotype. Specimen USNM 71496 

was previously figured by Butts (1926; herein pi. 22, figs. 

16-18) as T. cf. T. obsoleta, and is here accepted as a 

valid member of the species. Specimen USNM 315541 

(pi. 20, figs. 13-15) is a fragment of a little more than a 

half-whorl here referred to T. cf. T. obsoleta.

Distribution. -Ulrich and Scofield (1897, p. 880) cited 

T. obsoleta from Blackriveran- and Shermanian-age 

strata in Minnesota and Wisconsin, from Blackriveranage strata in Mercer County, Ky., and from Edenian-age 

strata in the vicinity of Cincinnati, Ohio. Bassler (1919, 

p. 310, 311) reported it from the Edenian-age portion of 

the Martinsburg Shale in Maryland. Butts (1926, pi. 26, 

figs. 12, 13) found the species in the Little Oak Limestone north of Pelham, Ala., which Ross and others 

(1982) dated as late Whiterockian in age.

One specimen of T. cf. T. obsoleta, USNM 315541, was 

found in USGS silicified collection 6131-CO from the 

upper Curdsville Member of the Lexington Limestone 

(Kirkfieldian) of central Kentucky.

Comparison.—Specimens of this species examined 

here are smaller than average specimens of T. bidorsata, 

T. sexcarinata, and T. wisconsinensis, but Ulrich and 

Scofield (1897, p. 880) cited specimens up to 30 mm long. 

T. obsoleta differs from T. bidorsata and T. sexcarinata 

in lacking lateral revolving ridges in adulthood, and 

having only a weak pair as a juvenile. T. wisconsinensis, 

which is known only from dolomitic steinkerns, also

seems to lack dorsolateral revolving ridges in adulthood, 

but the species is easily distinguished by its smaller 

umbilicus and by the form of its adult whorl, which is 

more similar to that of T. bidorsata in its lateral flaring 

and its flattened anterior slope.

Discussion. — T. obsoleta is regarded as a species the 

genus Tetronata because of the presence of a pair of 

dorsolateral ridges on the juvenile whorls of the lectotype (pi. 22, figs. 19-21), and on the small specimen, 

USNM 315541 (pi. 20, figs. 13,14). Like T. bidorsata and 

T. sexcarinata, T. obsoleta is widely distributed geographically and stratigraphically.

Tetranota sexcarinata Ulrich and Scofield, 1897 

Plate 22, figures 11-15

Tetranota sexcarinata Ulrich and Scofield, 1897, p. 878, 879, pi. 65, 

figs. 3-9; Grabau and Shimer, 1909, p. 613, figs. 819e-h, 1; Shimer 

and Shrock, 1944, p. 441, pi. 177, figs. 9-11; Wilson, 1951, p. 31, pi. 

4, figs. 10, 11.

Diagnosis.— Shell relatively large (up to 23.6 mm 

long), dorsum broad; two pairs of dorsolateral ridges on 

either side of elevated dorsomedian selenizone.

Description.— Shell relatively large and inflated for 

genus, broader over dorsum than other species; umbilici 

wide, open. Dorsomedian band wide, distinctly elevated, 

only slightly concave; bordering ridges somewhat indistinct. Two pairs of angular dorsolateral ridges present, 

with broad grooves between each; area between outer 

dorsolateral ridge and angular umbilical shoulder narrower and only slightly concave to flat. Lunulae of 

selenizone poorly known, but appear to have been 

straight. Growth lines are raised threads, rather widely 

spaced for genus, and distinct on umbilical slopes as well 

as dorsally, where they increase in their backward 

deflection across each dorsolateral ridge; these lines 

reflect broad sinus, narrowing to rather deeply set, 

squared-off slit.

Measurements.—Measurements of T. sexcarinata are 

listed in table 66.

TABLE 66.—Measurements (in millimeters) o/Tetranota sexcarinata

USNM 

No.

46018 

47712

Shell 

length

23.6

18.8

Shell 

height

22.6 

15.0

Aperture 

length

13.3

7.7

Aperture 

width

25.3 

7.9

Umbilical 

diameter

12.7 

8.9

Ventral 

width

16.9

8.5

Selenizone 

width

3.9 

2.6

1st ridge 

width

11.7

7.2

2d ridge 

width

18.7 

11.3
0148 CONTRIBUTIONS TO THE ORDOVICIAN PALEONTOLOGY OF KENTUCKY AND NEARBY STATES

TABLE 67. Measurements (in millimeters) o/Tetranota wisconsinensis

USNM 

No.

158279

Shell 

length

21.4

Shell 

height

14.75

Aperture 

length

12.4

Aperture 

width

23.95

Umbilical 

diameter

7.4

Ventral 

width

8.15

Selenizone 

width

3.5

Material.—No new specimens of T. sexcarinata are 

described here. All of Ulrich and Scofield's (1897) type 

specimens (USNM 46016-46018) are from the MinnesotaIllinois area. USNM 46018 is here designated the lectotype (pi. 22, figs. 14, 15). This specimen probably is a 

recrystallized calcitic replica. The only other specimen 

figured here (USNM 47712) (pi. 22, figs. 11-13) is an 

internal mold from Tennessee, which clearly shows the 

outer pair of lateral ridges.

Distribution.—The lectotype, USNM 46018, is from 

the Fusispira bed of the Prosser Formation (Shermanian) at Wykoff, Minn. The paralectotypes are from the 

Platteville Formation (Blackriveran): USNM 46017 is 

from the Vanuxemia bed at Minneapolis, Minn., and 

USNM 46016 is from Dixon, 111. USNM 47712 is from the 

Lebanon Formation (Blackriveran) at Lavergne, Tenn. 

Wilson (1951, p. 31) reported the species from numerous 

localities in the Ottawa-St. Lawrence Lowland of eastern 

Canada, in beds ranging from Blackriveran to at least 

Edenian in age. In summary, T. sexcarinata has been 

reported from Blackriveran- to Edenian-age strata 

throughout Eastern North America.

Comparison. —T. sexcarinata is similar to T. bidorsata (Hall), but differs in being larger and broader, in 

having six rather than four revolving lines of ornament, 

and in having slightly coarser and more widely spaced 

growth lines.

Discussion. — With the discovery of the new specimens of T. bidorsata from the Kope Formation of Ohio 

(pi. 21, figs. 1-8), it is possible for the first time to make 

clear side-by-side comparisons of this species and T. 

sexcarinata (pi. 22, figs. 14, 15). Although the differences stated above are clear, there can be little doubt 

that the two species are closely related. It is interesting 

that they share a very similar stratigraphic distribution, 

being known over most of Eastern North America from 

Blackriveran to Edenian strata. The main differences in 

their distribution is that T. bidorsata apparently is more 

common and also has been reported from Western North 

America.

Tetranota wisconsinensis (Whitfield, 1878) 

Plate 38, figures 13-16

Bellerophon wisconsinensis Whitfield, 1878, p. 78; 1882, p. 223, pi. 26,

figs. 15, 16. 

Tetranota wisconsinensis (Whitfield), Ulrich and Scofield, 1897, p. 881,

pi. 65, figs. 26-29; Shrock and Raasch, 1937, p. 558, 559, pi. 8, figs.

1-9.

Diagnosis.— Shell rather large (up to 21.4 mm long), 

whorls broad and depressed; adult aperture lip 

expanded, mainly laterally; dorsolateral ridges present 

in juveniles, lacking in adults.

Description. — Shell large, tightly coiled, consisting of 

2.5 to 3 whorls in adults. Whorls broad and depressed. 

Dorsomedian band wide and distinctly elevated; selenizone is groove between two prominent, rather thick 

cords. Dorsal slopes broad, showing low dorsolateral 

ridges in juvenile whorls, these gradually disappearing 

during ontogeny; umbilical shoulders tightly rounded; 

umbilical slopes cut steeply inward; umbilical slopes cut 

steeply inward; umbilici moderately small and deep. At 

maturity, aperture expands laterally and anterior slope 

flattens somewhat; expanded aperture has broad sinus 

which ends in wide slit having nearly parallel sides, and 

an arch-shaped termination. Ornamentation unknown.

Measurements.— Measurements of T. wisconsinensis 

are listed in table 67.

Material.—The holotype could not be located, but 

Shrock and Raasch's (1937, pi. 8, fig. 1) hypotype 

(USNM 158279) was examined and is shown here on 

plate 38, figures 13-15.

Small collections of unnumbered specimens of the 

species were also examined at the University of Cincinnati and Miami University Geology Museums. One specimen, MU 25IT, is shown here because of its excellent 

preservation of the slit (pi. 38, fig. 16). All known 

specimens of the species are dolomitized steinkerns.

Distribution.- Ulrich and Scofield (1897, p. 881, 882) 

reported the species from the Blackriveran strata of 

Minnesota and Wisconsin; Bassler (1915, p. 1271) specified these occurrences as being from the Platteville 

Formation. Shrock and Raasch (1937, p. 558, 559) also 

cited the species as occurring in the Platteville Formation, at McCray quarry, Kentland, Ind. Although the 

Platteville traditionally has been considered Blackriveran in age, Sweet and Bergstrom (1976, text-fig. 3) 

indicated that it is Rocklandian in age. Ross and others 

(1982) showed the Platteville as late Blackriveran in age.

Comparison. —T. wisconsinensis is distinguished 

from T. obseleta by its laterally expanded adult aperture 

and its more prominent dorsal band, but shares with that 

species the loss of the dorsolateral ridges in maturity.

The depressed whorls, prominent dorsal band, and 

laterally expanded adult aperture ally T. wisconsinensis 

with T. bidorsata, but T. wisconsinensis lacks the adult 

dorsolateral ridges generally so prominent in (even in
MIDDLE AND UPPER ORDOVICIAN SYMMETRICAL UNIVALVED MOLLUSKS, CINCINNATI ARCH REGION 0149

steinkerns of) T. bidorsata. For example, compare plate 

38, figures 13-15, and plate 22, figures 5-10. T. wisconsinensis could eventually be placed in synonymy with T. 

bidorsata, if specimens retaining the shell are found to 

retain dorsolateral ridges in adulthood.

Discussion.— Although T. wisconsinensis is from just 

outside the present area of study, and is actually from an 

adjacent faunal province, the species is considered here 

because of its morphological similarity to T. bidorsata. 

These two species are without doubt closely related, and 

both might have evolved from an earlier, simpler stock 

represented by T. obseleta. If new material confirms a 

pattern of continuing accentuation of the dorsal ridges in 

Tetranota, then T. sexcarinata could be considered a 

more advanced species and Tetranota could be considered to have developed from an early bucaniid such as 

Eobucania Kobayashi, which had revolving lines only 

along the borders of the selenizone. However, the tendency toward reduction of the dorsolateral ridges during 

ontogeny in T. obsoleta and T. wisconsinensis, and to 

some extent in gerontic specimens of T. bidorsata, 

suggests an opposite evolutionary trend. This problem 

can be resolved only when more specimens of all North 

American species of Tetranota are available.

Subfamily SALPINGOSTOMATINAE Koken, 1925

Diagnosis. — Shell having wide umbilici; submature 

whorls depressed and gradually expanding, aperture 

greatly expanded at maturity; slit long and open on adult 

whorl, being closed off anteriorly; selenizone generated 

over submature whorls.

Stratigraphic range.— Middle Ordovician-Middle 

Silurian.

Genera included.—The only genus included in this 

subfamily at present is Salpingostoma Roemer, 1876, 

which is considered below.

Discussion.— Koken (1925) erected the subfamily Salpingostomatinae, which then included only the type 

genus and was placed in the family Bellerophontidae 

McCoy. Knight and others (1960, p. 1180) made this 

taxon into the tribe Salpingostomatides of the subfamily 

Bucaniinae, family Bellerophontidae; they included the 

genera Salpingostoma and Tremanotus, and defined the 

group on the basis of the presence of an exhalant orifice 

consisting of one or more tremata. Horny (1962), on the 

other hand, elevated the subfamily to family rank and 

included in it the genera Salpingostoma, Tremanotus, 

and Boiotremus Horny from the Upper Silurian and 

Lower Devonian of Bohemia. Boiotremus included species previously assigned to Tremanotus, but only those 

that developed tremata throughout ontogeny rather than 

merely during adulthood. Boiotremus probably evolved 

directly from the Lower Silurian genus Tremanotus. The 

evolution may have been paedomorphic in nature, that is,

involving maturation at the juvenile stage of development. Sprinkle and Bell (1978, p. 82) have pointed out 

that "organisms entering new niches or colonizing new 

environments different from or marginal to their ancestral range often show large and rapid evolutionary 

changes in their morphology, life history, and mode of 

reproduction." Horny (1963a, p. 65, fig. 6) showed that 

Tremanotus occurs in a largely clastic sequence of strata 

and occupied (p. 67) "a hard bottom of tuffaceous and 

organic debris" in shallow seas near volcanic islands; 

Boiotremus, in contrast, occurs in an immediately overlying carbonate sequence of bituminous limestones in the 

Upper Silurian and biohermal facies in the Lower Devonian. This regional change in sedimentologic conditions 

may have encouraged the proliferation of taxa that 

develop tremata at early growth stages.

Peel (1972) believed that Salpingostoma was only 

homeomorphic with Tremanotus and Boiotremus. He 

pointed out that while Salpingostoma had a slit throughout its ontogeny, the other two genera were merely 

sinuate, and that their tremata were formed by repeated 

expansion of the aperture and concomitant closing off of 

all but the deepest portion of the sinus. He therefore 

rejected Horny's (1962) familial grouping, transferring 

Salpingostoma back to the subfamily Bucaniinae (as in 

Knight and others, 1960), and erected the new subfamily 

Tremanotinae of the family Sinuitidae for the other two 

closely related genera.

Peel's (1972) emendation seems valid, because the 

basic difference in the development of the shells of 

Salpingostoma and Tremanotus-Boiotremus would 

seem to indicate quite different origins. The separation of 

the Salpingostomatinae into a separate subfamily of the 

Bucaniidae expresses the close resemblance of Salpingostoma to some species of Bucania in most characteristics save the morphology of the elongated closed-off 

slit.

Genus SALPINGOSTOMA Roemer, 1876

Diagnosis. Adult shell having expanded, trumpetlike aperture and long, open slit extending from dorsum 

to slightly inside outer lip, where it is closed off.

Description.— Shell generally large, involute, with 

wide, open umbilici revealing numerous earlier volutions; submature whorls in many cases vertically 

depressed, subreniform, and submature aperture at 

plane level with ventral umbilical shoulder; at maturity, 

aperture expanding abruptly to trumpetlike form, 

becoming tangentially oriented toward coil; submature 

whorls with selenizone; mature expanded whorl with 

long, open slit extending from dorsum to near outer 

sinuate apertural margin, where it is closed off; shell 

surface in many cases marked by transverse and radial 

ornament.
0150 CONTRIBUTIONS TO THE ORDOVICIAN PALEONTOLOGY OF KENTUCKY AND NEARBY STATES

Type species.—Bellerophon megalostoma Eichwald, 

1840, by monotypy.

Other North American species. Ordovician species of 

Salpingostoma in North America are S. billingsi Wilson; 

S. buelli (Whitfield); S. kentuckyense Ulrich and 

Scofield; S. canadense (Billings); S. expansa (Hall); S. 

fratemus (Billings); S. imbricata Ulrich and Scofield; 

S.(?) lata Foerste; S. richmondensis Ulrich and Scofield; 

and S. sculptilis Ulrich and Scofield. Silurian species in 

North America (Canada) listed by Peel (1972, p. 420) are 

S. boreale Whiteaves; S. dilatus (Sowerby); S. inornatum Northrop; and S. orientalis Twenhofel.

Distribution.— Middle Ordovician (Blackriveran)- 

Middle Silurian (Niagaran) of North America. In 

Europe, the genus supposedly appears lower in the 

Middle Ordovician (Koken, 1925) and continues at least 

to the end of the Ordovician.

Discussion. The genus Salpingostoma was proposed 

by Roemer (1876) for Bellerophon megalostoma Eichwald, 1840, from the Ordovician of Estonia. Koken (1925) 

later listed 15 species from the Ordovician of the Baltic 

area. However, Koken's generic assignments and species 

should be reevaluated, as he recognized cephalopodlike 

chambers in one supposed species, S. locator (Eichwald) 

(Koken, 1925, p. 26).

Adult specimens of Salpingostoma are easily recognized by their expanded trumpetlike aperture and long, 

open slit. The slit is recognizable on internal molds as a 

long dorsal ridge that ends rather abruptly just inside 

the aperture lip (pi. 24, figs. 1-3; pi. 26, figs. 1-3, 6). 

However, in immaturity, before the above-mentioned 

morphological features are developed, the genus is not 

nearly so distinctive. Ulrich and Scofield (1897, p. 897) 

believed that juvenile specimens "correspond in nearly 

every respect with the whole adult shell of the most 

typical species of Bucania." They proposed that there 

was a progressive morphological development from one 

genus to another in a series Bucania to Salpingostoma 

to Tremanotus. They stated (p. 900): "In the first the 

aperture is never greatly expanded, in the second it 

flares abruptly at maturity, while in the third the 

expanded mouth is developed at more or less frequent 

intervals." They further suggested that the resemblance 

of the external sculpturing of these three genera demonstrates their close evolutionary relationship. I believe 

that the depressed whorl forms, broad umbilici, and long 

slits that characterize submature specimens of species of 

Salpingostoma (pi. 24, figs. 6-8, 13-16) and adults of the 

Bucania sulcatina group (pi. 12, figs. 1-9) show that the 

former is directly descended from the latter.

Koken (1925) disagreed with Ulrich and Scofield's 

(1897) interpretations concerning not only their progressive evolutionary sequence, but even their generic identification of the American species. Koken apparently

believed that the American species assigned to the genus 

Salpingostoma by Ulrich and Scofield should instead be 

placed in his Bucania cornu group, which he asserted to 

have had a derivation different from that of the true 

Salpingostoma group. Koken claimed that the style of 

ornament of S. buelli (Whitfield) from the Middle Ordovician of Minnesota was more like that of a Bucania and 

that its slit was situated too far anterior. He further 

pointed to S. sculptilis Ulrich and Scofield as clearly 

being derived from a Bucania, as shown by its ornament, 

slit, and selenizone. Koken noted Ulrich and Scofield's 

(1897) claims that Salpingostoma should include shells 

whose inner volutions resemble the adult shell of Bucania sulcatina (Emmons), and that it is only in the fully 

mature specimens that the peculiarities of the genus are 

apparent. Koken stated that these claims demonstrated 

that the American species differed from the type species 

of the genus. Koken did not believe that juvenile specimens of the type species resembled Bucania, or that the 

type species was distinct throughout growth. In Koken's 

generic description he claimed that in many specimens, 

particularly juveniles, the shell is characteristically wrinkled, the wrinkling being independent of the threadlike 

growth lines, and also distinct from the wrinkled spiral 

lines of Bucania. Some of his figures of species of 

Salpingostoma (Koken, 1925, pis. 19-21) show this 

transverse wrinkling, but others do not. It should be 

noted that some of Reed's (1921, pi. 12, figs. 1, 2) species 

from the Ordovician of Great Britain also show rather 

strong transverse wrinkling. However, the American 

species illustrated by Ulrich and Scofield (1897, pis. 67, 

82) do not. Koken (1925, p. 27, 28) concluded that 

Salpingostoma and Bucania are completely unrelated, 

but that several species of Bucania in the submature 

state are misleadingly similar to Salpingostoma. He 

further concluded that Tremanotus and Salpingostoma 

are not directly related because of the differences in the 

production of the expanded aperture in the two genera, 

being abrupt and occurring only once (at maturity) 

in Salpingostoma, but occurring periodically in 

Tremanotus.

Although American species of Salpingostoma lack the 

marked transverse wrinkling of the shell present in many 

of the European species, this does not seem to be 

adequate justification for generic differentiation. The 

common features shown by both the American and 

European species expanded aperture, long, closed-off 

slit, shell markings are numerous and indicate a close 

evolutionary relationship.

Salpingostoma buelli (Whitfield, 1878) 

Plate 24, figures 1-9

Bucania buelli Whitfield, 1878, p. 76; Chamberlin, 1883, p. 158, fig. 

33f.
MIDDLE AND UPPER ORDOVICIAN SYMMETRICAL UNIVALVED MOLLUSKS, CINCINNATI ARCH REGION 0151 

TABLE 68. Measurements (in millimeters) of Salpingostoma buelli

USNM 

No.

265957

45980

47590

Shell 

length

20.5

46.3

48.5

Shell 

height

22.0

22.0

-

Aperture 

length

7.4

35.4

38.4

Aperture 

width

13.9

34.3

36.0

Umbilical 

diameter

8.0

21.3

-

Dorsal 

width

11.85

15.50

-

Posterior 

width

8.85

13.20

-

Ventral 

width

5.85

-

11.09

Bucania (Tremanotusl) buelli Whitfield, 1882, p. 224, pi. 6, figs.

12-14. 

Salpingostoma buelli (Whitfield), Whiteaves, 1897, p. 189; Ulrich and

Scofield, 1897, p. 900, pi. 67, figs. 34-37; Grabau and Shinier, 1909,

p. 614, figs. 823a-c; Shinier and Shrock, 1944, p. 443, pi. 177, figs.

14-16; Knight and others, 1960, figs. 96-£a, b.

Diagnosis.— Moderately large Salpingostoma (up to 

48.5 mm long), having expanded adult aperture extended 

anteriorly into a long, slightly recurved apron; shell 

surface entirely sculptured by curving, transverse 

growth lines and thin, nodular revolving threads, the 

latter increasing in strength on expanded aperture, with 

a smaller set being intercalated between, giving an 

alternating pattern; adult shell length/umbilical diameter 

ratio 2.17.

Measurements.—Measurements of S. buelli are listed 

in table 68.

Material.— Two dolomitized specimens from a set of 

five of Ulrich and Scofield's (1897) hypotypes, suite 

number USNM 45980, are illustrated here. USNM 

265957 (pi. 24, figs. 6-8) is a submature internal mold; 

USNM 265960 (pi. 24, figs. 1-5) is an adult specimen that 

preserves part of the shell around the expanded apertural margin, the remainder of the specimen being a 

composite mold retaining an impression of the shell 

ornament pattern. These specimens are from the Platteville Formation (Blackriveran) at Beloit, Wis. USNM 

45790 (pi. 24, fig. 9) is a dark-gray calcitic (partly 

carbonaceous?) replica that is embedded in gray, finely 

crystalline biosparite from the Platteville Formation of 

Minnesota.

Distribution. -Ulrich and Scofield (1897, p. 901) 

reported S. buelli from the "Stones River Group" of 

Minnesota and the "Black River Group" of Wisconsin, 

which strata are now recognized as the Platteville and 

Decorah Formations (Blackriveran-Rocklandian) (Weiss, 

1957; Sweet and Bergstrom, 1976; Ross and others, 

1982). Weiss (1957, fig. 1) reported Salpingostoma sp. 

(probably S. buelli from the Cummingsville Member of 

the Galena Formation (Kirkfieldian-Shermanian) of Minnesota. Bassler (1915) cited the species from Wisconsin, 

Minnesota, Illinois, and Manitoba.

Comparison. — See this heading under S. kentuckyense Ulrich and Scofield.

Discussion. — This species is not represented in the 

fauna of the Cincinnati arch region, but is considered

here for comparison with S. kentuckyense Ulrich and 

Scofield, which was originally designated a subspecies of 

S. buelli.

Specimen USNM 265957 (pi. 24, figs. 6-8) apparently 

is a specimen on the verge of maturity, just before the 

aperture began its abrupt expansion, because the shell 

height of this specimen is equal to that of an expanded 

adult specimen (USNM 265960, pi. 24, figs. 1-5). Note 

that this submature specimen of S. buelli is nearly 

identical to a submature specimen of the stratigraphically younger S. richmondensis Ulrich and Scofield (pi. 

24, figs. 13-16), although the relative proportions are 

slightly different. In all submature specimens of the 

genus examined for this study, the plane of the aperture 

is at a level with the ventral umbilical shoulder. This 

nearly radial orientation of the apertural plane of juveniles may indicate a much less mobile life style than that 

led by the adults, which had a tangential aperture. This 

interpretation is supported by Linsley's (1978a) observations of modern conispiral gastropods, which have shells 

with radial apertures and are generally very sluggish or 

even sedentary. Also note the depressed form of the 

juvenile whorls of S. buelli (pi. 24, fig. 8), which would 

seem to make the shell rather awkward to balance in a 

highly active organism. As pointed out in the discussion 

of S. kentuckyense, the whorls of the submature coil are 

quite thin shelled, and this may have alleviated this 

awkwardness to some degree.

Specimen USNM 265960 (pi. 24, figs. 1-5) is an adult of 

S. buelli. The shell around the apertural margin shows 

how the lip was expanded far to the anterior as an apron. 

On the portion of the specimen where the shell is lacking, 

there is a prominent dorsomedian ridge over the anterior 

slope. This ridge is the reflection of the long, open slit of 

the shell. Lateral to this ridge, the mold becomes composite and the external sculpturing is preserved (pi. 24, 

figs. 1-3). The sculpture consists of growth lines that 

curved back toward the slit, and thin, parallel revolving 

threads. Specimen USNM 47590 (pi. 24, fig. 9) was 

photographed without whitening for better definition. 

This specimen shows the shape of the aperture, with its 

anterior sinus and wide anterior marginal apron.

Salpingostoma kentuckyense Ulrich and Scofield, 1897

Plate 24, figures 10-12; Plate 25, figures 1-14; Plate 26, 

figures 11, 12
0152 CONTRIBUTIONS TO THE ORDOVICIAN PALEONTOLOGY OF KENTUCKY AND NEARBY STATES

TABLE 69. —Measurements (in millimeters) of Salpingostoma kentuckyense

USNM 

No.

265961

265964

265965

265966

265979

265980

265980

265980

265980

265980

265980

265980

265980

265980

265980

265980

265980

265980

265981

265981

Shell 

length

43.5

42.4

41.2

-

-

45.2

-

45.3

-

-

-

-

-

-

-

-

-

-

-

-

Shell Aperture 

height length

28.7 32.40

23.3 30.70

22.5 29.75

30.10

32.80

35.05

49.75

22.5 36.60

32.85

31.60

40.30

26.20

28.00

25.55

34.30

32.30

29.80

39.40

33.90

41.30

Aperture 

width

31.0

30.2

31.5

31.3

32.8

35.0

45.0

33.0

33.7

33.4

40.5

27.7

27.8

27.4

38.2

31.6

32.4

36.0

32.5

39.3

Umbilical 

length

_

19.1

15.0

-

-

16.5

-

17.3

-

-

-

-

-

-

-

-

-

-

-

-

Umbilical 

height

_

13.9

13.6

-

-

14.5

-

15.0

-

-

-

-

-

-

-

-

-

-

-

-

Dorsal Ventral 

width width

_ _

18.80 11.65

18.25 10.90

-

11.45

17.25 13.05

-

19.80 12.50

-

12.80

14.85

10.70

-

-

-

-

12.20

13.85

_

-

Salpingostoma buelli var. kentuckyense Ulrich and Scofield, 1897, p. 

901.

Diagnosis. — Shell moderately large (up to 45.5 mm 

long), expanded apertural rim thickened and massive, 

not strongly flexed anteriorly; shell markings restricted 

to external rim of expanded aperture, consisting of 

coarse spiral ribs and growth lines; adult shell length/ 

umbilical diameter ratio 2.70.

Description.— Shell moderately large, relatively thin 

on submature portion, becoming thick and massive on 

mature expanded aperture; volutions numerous, visible 

in wide, open umbilici; sutures deeply impressed; submature whorls depressed, subreniform, with dorsum 

broadly convex, umbilical shoulders narrowly rounded, 

venter slightly concave; whorl size increases quite gradually until maturity, when aperture abruptly expands 

and thickens; shell length/umbilical diameter ratio in 

adults averages 2.70; expanded aperture may slope anteriorly to margin, or may reflex slightly to form short 

apron; anteromedian sinus quite shallow; dorsomedian 

slit extends from dorsum down the anterior slope, where 

it is closed far posterior to the anterior apertural margin; 

selenizone distinct, narrow, appears as rounded cord; 

posterior expanded aperture with broad reentrant 

around previous whorl; outer parietal rim of expanded 

aperture, where coil rests, in many specimens bears 

coarse, chevronlike wrinkles angling outward and downward; submature shell surface smooth; mature expanded 

shell surface marked by coarse radiating ribs and fine to 

lamellose growth lines.

Measurements.— Measurements of S. kentuckyense 

are listed in table 69 and shown graphically in figure 31.

Material. Ulrich and Scofield (1897) designated eight 

"cotypes" now listed under the number USNM 45981. All 

eight are fragmentary, highly weathered silicified casts 

from the Curdsville Limestone Member of the Lexington 

Limestone. Two specimens from this set of syntypes are 

figured here; USNM 265961 (pi. 24, figs. 11, 12), here 

designated the lectotype for the species, and USNM 

265962, a paralectotype (pi. 24, fig. 10). The other six 

specimens retain the number USNM 45981 and are 

designated paralectotypes.

The USGS silicified collections from Kentucky yielded 

numerous new specimens that are far better preserved 

than the type suite. Sample 6034-CO, from the Tyrone 

Limestone, includes USNM 265964 (pi. 25, figs. 1-8), 

USNM 265965 (pi. 25, figs. 9-13), USNM 265966 (pi. 26, 

figs. 11, 12), USNM 265979 (pi. 25, fig. 14), and USNM 

265980; the last is used for a set of about 40 specimens 

and fragments. All of the specimens from sample 6034- 

CO are firmly silicified. All other new specimens are 

from USGS samples 6131-CO, 7784-CO, and 7785-CO, all 

are coarsely silicified fragments of columellas and aperture rims, and all are from the Curdsville Limestone 

Member of the Lexington Limestone.
MIDDLE AND UPPER ORDOVICIAN SYMMETRICAL UNIVALVED MOLLUSKS, CINCINNATI ARCH REGION 0153

60 r

50

40

^ 30

20

10

60 r

50

40

A

^ 30

nf

CD 

Z 

LJJ

^ 20

LJJ

^

co 

10

10 20 30 40 

APERTURE LENGTH, IN MILLIMETERS

50 10 20 30 40 

APERTURE WIDTH, IN MILLIMETERS

50

60 r

50

40

30

20

10

60 r

50

fc

=1 40

30

20

10

A

10 20 30 40 

APERTURE WIDTH, IN MILLIMETERS

50 10 20 30 40 

APERTURE WIDTH, IN MILLIMETERS

50

EXPLANATION

O Salpingostoma kentuckyense 

A Salpingostoma buelli

FIGURE 31. Bivariate plots of measurements made on specimens of Salpingostoma kentuckyense and S. buelli.

Distribution.—S. kentuckyense is known from the 

Tyrone Limestone of the High Bridge Group (Rocklandian) and the Curdsville Limestone Member of the 

Lexington Limestone (Kirkfieldian). The species was 

found in the Tyrone Limestone (6034-CO) in the Little 

Hickman quadrangle, Jessamine County, Ky., at 1-2 ft 

(7784-CO) and 11-12 ft (7785-CO) above the base of the

Curdsville Limestone Member in the same quadrangle 

and county, and also at 23 ft above the base of that unit 

(6131-CO) in the Danville quadrangle, Boyle County, Ky. 

Comparison.—Ulrich and Scofield (1897, p. 902) 

briefly described S. buelli var. kentuckyense from silicified fragments from the "Black River Limestone of 

Kentucky" and stated that it differed from S. buelli "in
0154 CONTRIBUTIONS TO THE ORDOVICIAN PALEONTOLOGY OF KENTUCKY AND NEARBY STATES

having a thicker shell, coarser surface markings, and 

smaller inner volutions when compared with the 

expanded aperture which is fully as large as S. buelli." 

Like S. expansa, the apertural rim of S. kentuckyense is 

not so abruptly turned outward as in S. buelli', S. 

kentuckyense is smaller than S. expansa, and it is 

rounded over the dorsum rather than subangular. Two of 

Ulrich and Scofield's (1897) type specimens are shown 

herein (pi. 24, figs. 10-12); Ulrich and Scofield (1897) did 

not illustrate the species. The new and much better 

preserved USGS silicified material confirms many of 

Ulrich and Scofield's (1897) interpretations and 

has revealed more detail, enabling recognition of the 

Kentucky specimens as a distinct species.

The mature expanded aperture of the Kentucky specimens is greatly thickened and much more massive than 

that of S. buelli (pi. 25, figs. 10-12). In the Kentucky 

specimens, this expanded aperture is sculptured with 

rather thick radiating ribs and often lamellose growth 

lines (pi. 24, figs. 1-8, 9-11); the submature portion of the 

shell seems to lack ornament. On the other hand, S. 

buelli has relatively fine transverse and spiral threads 

which seem to cover the entire shell (pi. 24, figs. 1-3).

Ulrich and Scofield (1897) stated that the Kentucky 

specimens had a smaller coil in proportion to the size of 

the expanded aperture. The umbilical diameter/shell 

length ratio in S. buelli (USNM 265960) is 2.17, compared with an average ratio for three specimens of S. 

kentuckyense of 2.70, thus demonstrating that the latter 

species has a relatively smaller coil. Although the average aperture length/aperture width ratios of the two 

species do not differ significantly, the form of the 

extended anterior margin does differ. S. buelli has a 

steeper anterior slope, the anterior lip then flattening 

outward into a relatively broad apron. Many specimens 

of S. kentuckyense show no tendency to form an anterior 

apron (pi. 25, figs. 4, 5), but a few specimens do reflex 

the apertural margin to form a relatively small apron (pi. 

25, fig. 11). S. buelli and S. kentuckyense were contemporaries during the Rocklandian and Kirkfieldian Stages. 

There can be little doubt that the two are closely related, 

but subtle differences in morphology, as well as different 

paleogeographic distributions, suggest that they are 

geographic variants and distinct species.

Another species that should be considered closely 

related to S. buelli and S. kentuckyense is S. billingsi 

Wilson (1951, p. 28) from the Blackriveran and Rocklandian strata of the Ottawa-St. Lawrence Lowland, Canada. According to Wilson, "the species differs from both 

S. buelli (Whitfield) and S. expansum (Hall) in its 

smaller size, more rapidly increasing and more tightly 

coiled whorls, and in its less abrupt aperture." S. billingsi is very similar in size to S. kentuckyense, and it also 

has a thickened expanded aperture with lamellose

growth increments (Wilson, 1951, pi. 3, figs. 1-3). The 

only obvious differences between the two species are 

that S. billingsi bears S. buelli-like sculpturing on the 

entire shell and apparently has a more highly raised 

anteromedian sinus. S. buelli, S. kentuckyense, and S. 

billingsi seem to form a closely related group. S. billingsi appeared first, in the Blackriveran, and may have 

given rise to the other two.

Discussion.— The expanded aperture of S. kentuckyense is much thicker than the submature portion of the 

shell. As a result, the great majority of the specimens in 

Ulrich and Scofield's (1897) type suite and in the USGS 

silicified collections are only the apertural rims of the 

shells (pi. 24, fig. 10; pi. 25, fig. 14; pi. 26, fig. 11). All the 

more complete specimens of the species (pi. 25, figs. 

11-13) are missing the anterior slope of the expanded 

aperture, presumably because of the structural weakness resulting from the long, open slit. Ulrich and 

Scofield (1897, p. 898) pointed out that the anterior 

closing of the slit may have been a "necessity of overcoming the liability of fracture to which the aperture 

would have been subject had the slit been allowed to 

continue to the outer margin."

The only known specimen that preserves any portion 

of the slit, USNM 265964 (pi. 25, figs. 1-8), shows only 

the uppermost part. In that specimen, the slit was closed 

well back from the apertural edge. Specimen USNM 

265965 (pi. 25, figs. 9, 10) shows the slit in the process of 

being closed anteriorly, with only a crack remaining 

dorsally and being entirely closed ventrally. As known 

from the apertural rims only, adults of all sizes had the 

slit closed anteriorly. When most of these specimens are 

held up to light, the median closed-off slit area is slightly 

translucent, showing that it is distinctly thinner than the 

lateral portions of the rim. The shell along this anteromedian line originally was secreted thinner than the 

adjacent shell rim. It seems that as the expanding 

aperture grew anteriorly along its outer edge, the slit 

must have been lengthened anteriorly by resorption of 

the thin shell along the median line. When the animal 

reached a certain age in later ontogeny, it essentially 

halted further outward growth and thickened only the 

aperture rim, apparently also filling in the already closed 

off anterior part of the slit with interior shell layers 

(pi. 25, figs. 9, 10).

Salpingostoma richmondensis Ulrich, 1897

Plate 24, figures 13-16; Plate 26, figures 1-8

Salpingostoma richmondensis Ulrich in Ulrich and Scofield, 1897, p. 

903, pi. 67, figs. 39, 40; Cumings, 1908, p. 974, pi. 39, figs. 7, 7a; 

Grabau and Shimer, 1909, p. 614, figs. 823d-3; Shimer and Shrock, 

1944, p. 443, pi. 177, figs. 17, 18; Foerste, 1924, p. 206, pi. 34, 

fig. 8.
MIDDLE AND UPPER ORDOVICIAN SYMMETRICAL UNIVALVED MOLLUSKS, CINCINNATI ARCH REGION 0155

TABLE 7'0. Measurements (in millimeters) of Salpingostoma richmondensis

Museum 

No.

USNM

45983

UCGM

28660

44281

44280

38549

38549

Shell 

length

43.3

27.3

47.6

24.6

26.9

49.6

Shell 

height

25.0

20.3

28.6

19.2

19.9

25.3

Aperture 

length

37.0

13.50

32.50

10.10

10.85

34.75

Aperture 

width

33.6

22.2

32.2

19.2

20.7

28.8

Umbilical 

diameter

13.4

13.7

19.9

13.6

14.2

23.6

Dorsal 

width

16.8

17.50

18.15

16.50

17.00

19.85

Posterior 

width

-

14.1

15.0

13.2

14.0

16.7

Ventral 

width

11.9

10.5

12.0

10.5

10.5

13.6

Diagnosis.— Shell moderately large (up to 50 mm 

long); submature whorls depressed, reniform, width 

about twice length; coiling loose; at maturity, aperture 

expands abruptly, extending anteriorly at much greater 

rate than laterally, so that aperture becomes longer than 

wide, anterior slope steep, lateral margins slightly 

explanate.

Description.— Shell moderately large for genus, with 

about three loosely coiled volutions and wide-open umbilici; submature whorls depressed, reniform, width about 

twice length (length/width ratio 0.55), broadly convex 

dorsally, umbilical shoulders narrowly rounded, venter 

concave where contiguous with preceding whorl; at about 

15-20 mm shell length, aperture expands abruptly, 

mainly anteriorly, so that in fully mature specimens 

aperture length slightly exceeds width (length/width 

ratio 1.11); expanded aperture widest posteriorly, reaching back to about even with posterior umbilical shoulder, 

lateral and posterolateral apertural margins flare 

slightly but do not recurve upward; anterior slope of 

expanded aperture steeply convex to or nearly to margin, generally flaring very little, anterior margin raised 

above level of lateral margins in broad, shallow sinus; slit 

open from dorsum to just inside anterior apertural 

margin, the anteromedian closure being marked by shallow linear indentation; selenizone apparently developed 

on submature whorls; no shell markings known.

Measurements.—Measurements of S. richmondensis 

are listed in table 70.

Material.-The holotype (USNM 45983), which preserves some shell around the margin of the expanded 

aperture (pi. 26, figs. 1-5), and hypotypes UCGM 44281 

(pi. 26, figs. 6-8), UCGM 44280 (pi. 24, figs. 13-16), and 

UCGM 28660 and UCGM 38549 (the latter two measured 

but not figured) are all internal molds. Numerous other 

internal molds in the collections of the U.S. National 

Museum of Natural History and the geology museums of 

the University of Cincinnati and Miami University were 

examined.

Distribution.—The species is known only from the 

Richmondian (upper Upper Ordovician) of southeastern

Indiana and southwestern Ohio. Most collections examined are from the Whitewater Formation (Richmondian), 

near Richmond, Ind., orCamden, Ohio. Other collections 

are labeled only "Richmond." All of Cumings' (1908, p. 

975) specimens are from the Whitewater Formation near 

Richmond, Ind., being most abundant near the top of the 

unit. Cumings (1908, p. 662, 663) noted the species as 

common in "lumpy limestones" associated with abundant 

Rhynchotrema dentatum, several species of gastropods, 

and Strophomena sulcata. He cited S. richmondensis as 

occurring in a typical Whitewater biofacies of brachiopods and bryozoans.

Comparison.—As noted by Ulrich and Scofield (1897, 

p. 904), many specimens of this species in old collections 

are labeled Bucania expansa Hall, a species from the 

Middle Ordovician of New York that is now placed in 

Salpingostoma. The two species are easily distinguished 

morphologically. -S. richmondensis has one less volution 

than S. expansa for the same size of shell. In addition, S. 

expansa has a subtriangular whorl shape, which is in 

sharp contrast to the broader reniform whorl shape of S. 

richmondensis.

It is much more difficult to distinguish between S. 

richmondensis and Bucania simulatrix Ulrich. The two 

species are homeomorphic, and thus have very similar 

shell forms. Both species are known mainly or completely 

from internal molds, and both are found in the Richmondian Whitewater Formation in the vicinity of Richmond, 

Ind. Preliminary examination gave me the impression 

that the two species are synonymous, but on close 

scrutiny I became certain they are distinct. Many 

museum collections that are labeled as containing one 

species or the other commonly include both species. 

In well-preserved specimens, the slit of B. simulatrix 

can be observed to extend to the anterior apertural 

margin, readily distinguishing that species from S. 

richmondensis.

Comparison of the lectotype of B. simulatrix (USNM 

315548 pi. 19, figs. 11-14) with the holotype of S. 

richmondensis (USNM 45983, pi. 26, figs. 1-5) shows the 

distinctiveness of the two species. Figure 32 shows the
0156 CONTRIBUTIONS TO THE ORDOVICIAN PALEONTOLOGY OF KENTUCKY AND NEARBY STATES

60 r

50

fc 40

1

_i 

^

^

^ 30 x"

CD

z

LU

d 20

oo

10

A

O

60 r

50

40

^ 30 x"

CD

LU

20

10

O

10 20 30 40 

APERTURE LENGTH, IN MILLIMETERS

50 10 20 30 40 

APERTURE WIDTH, IN MILLIMETERS

50

60 r

50

40

x 30

CD

20

10

60

50

H 40

30

20

10

O

A

10 20 30 40 

APERTURE WIDTH, IN MILLIMETERS

50 10 20 30 40 

APERTURE WIDTH, IN MILLIMETERS

50

EXPLANATION

O Salpingostoma richmondensis 

A Bucania simulatrix

FIGURE 32. Bivariate plots of measurements made on specimens of Salpingostoma richmondensis and Bucania

simulatrix.

lateral expansion rates of six (three immature and three 

mature) specimens of S. richmondensis and the lectotype of B. simulatrix, using width measurements taken 

at every quarter volution on the last whorl. These 

measurements reveal that the last whorl of B. simulatrix

is a good deal narrower than that of S. richmondensis. 

Moreover, in B. simulatrix the anterior width gradually 

and constantly increases throughout ontogeny. Conversely, S. richmondensis grows gradually until maturity, then expands abruptly, reaching the same width as
MIDDLE AND UPPER ORDOVICIAN SYMMETRICAL UNIVALVED MOLLUSKS, CINCINNATI ARCH REGION 0157

B. simulatrix, but over a shorter length and after a much 

briefer period of increased expansion.

Figure 32 shows scattergrams for the six specimens of 

S. richmondensis listed in table 70, as well as for the 

lectotype of B. simulatrix. The regression line was 

calculated only for the measurements of S. richmondensis. B. simulatrix stands slightly away from the other 

points in three of the four graphs, agreeing best on the 

plot of shell length versus aperture width.

Although there are no known complete specimens of S. 

richmondensis retaining the shell, there can be little 

doubt about its generic placement. In the anteromedian 

area of the holotype, where some shell is preserved, 

there is a shallow linear indentation (pi. 26, fig. 1), just as 

in S. kentuckyense (pi. 25, fig. 9), which reflect the 

thinness of the shell there. This thin strip of shell 

apparently was easily resorbed in the lengthening of the 

slit as the anterior margin of the aperture was extended. 

Posterior to this indentation is a low, weathered median 

ridge (pi. 26, figs. 1-3) reflecting the long, open slit on 

the internal mold. This ridge is better preserved on 

another internal mold, UCGM 44281 (pi. 26, figs. 6, 7). 

Furthermore, the anteromedian apertural margin is 

raised above the level of the lateral margins (pi. 26, 

fig. 8), but only slightly, and there apparently is only a 

broad, shallow sinus.

Although the general shell form of B. simulatrix (pi. 

19, figs. 11-14) is very similar to that of S. richmondensis (pi. 26, figs. 1-5), the anteromedian expanded aperture of B. simulatrix shows a deeply cut, V-shaped sinus 

in the anteromedian lip which reaches to about the level 

of the dorsal umbilical shoulder on the coil (pi. 19, figs. 

11,14). Posterior to this deep sinus is a long median ridge 

in the internal mold (pi. 19, figs. 11, 12) as was seen in S. 

richmondensis; however, in B. simulatrix the ridge 

reaches all the way to the tip of the sinus. It is doubtful 

that this ridge reflects a long, open slit; it more likely 

represents a selenizone on an elevated dorsal carina 

which formed an internal channel along the interior 

median crest of the shell.

Discussion.— Ulrich and Scofield (1897) observed 

revolving ribs and transverse growth lines preserved on 

the dorsum of a single specimen of S. richmondensis, but 

no ornament was seen on any specimens examined 

during this study. Therefore, these features have not 

been included in the description given here. I could not 

locate any such specimen among Ulrich's collections at 

the U.S. National Museum of Natural History.

The species most similar to S. richmondensis is the 

Middle Ordovician S. expansa from New York, and that 

species might be ancestral to S. richmondensis. However, this similarity may be superficial, and the result of 

similar preservation of both species as internal molds. 

Such preservation suggests that these species were

fairly thin shelled compared with S. buelli, S. kentuckyense, and S. billingsi, which have thickened apertures. 

In further support of this contention is the fact that 

molds of S. richmondensis commonly are strongly compressed. A similar situation exists with some species of 

Sinuites (for example, S. cancellatus) in the Cincinnatian rocks of the study area, and it is known that these 

species were quite thin shelled.

As previously noted, Cumings (1908, p. 662, 663) cited 

S. richmondensis as characteristic of the Rhynchotrema 

dentatum beds near the top of the Whitewater Formation, where it occurred in "lumpy limestone" beds with 

several species of gastropods, and R. dentatum and 

Strophomena sulcata. Although most internal molds of 

S. richmondensis are composed of fine carbonate mudstone or wackestone, the matrix in which most specimens 

occur is packstone to grainstone. Putting this information together, it seems that S. richmondensis probably 

inhabited a quiet environment in a typical molluscanbrachiopod community. Shells commonly were transported into adjacent higher energy environments (probably during storms) and deposited in adjacent banks of 

shell debris, being associated there with a more typical 

bryozoan-brachiopod assemblage. This reasoning is in 

keeping with the regressive nature of the Whitewater 

Formation, which records the last stage of Ordovician 

deposition in the northwestern part of the area. Scattered low, shelly banks and intervening quieter lagoons 

would fit this picture. Moreover, this interpretation 

agrees with Peel's (1977b) conclusion that explanate 

bellerophontaceans are adapted for life on fine 

substrates.

I collected very fragmentary specimens of S. richmondensis at Thistlewaite Falls along the Whitewater River 

at Richmond, Ind. The specimens occurred in nodular 

limestone beds composed of the fragmented skeletal 

debris of brachiopods, bryozoans, and mollusks. The 

fragmented, worn skeletal debris was neither sorted nor 

oriented, but gave the impression of debris transported 

and deposited by storms.

Family BELLEROPHONTIDAE McCoy, 1851

Diagnosis.— Shell rounded, in many cases inflated; 

apertural margins in many cases flaring or even somewhat explanate, parietal lip generally reflexed; anteromedian slit generating distinct selenizone; umbilicus narrow or closed.

Stratigraphic range.— Middle Ordovician-Lower Triassic.

Discussion.— This family encompasses most late Paleozoic bellerophonts. Golikov and Starobogatov (1975) 

preferred to recognize as families the taxa herein treated 

as subfamilies. The problem is how to best represent the 

phylogenetic relationships between these taxa in the
0158 CONTRIBUTIONS TO THE ORDOVICIAN PALEONTOLOGY OF KENTUCKY AND NEARBY STATES

systematic hierarchy. It is believed here that the common morphological features of the taxa represent a 

phylogenetic grade of shell development that is best 

treated under one family name. Four subfamilies are 

recognized within the family Bellerophontidae Bellerophontinae McCoy, 1851; Bucanopsinae new subfamily; 

Knightitinae Knight, 1956; and Cymbularinae Horny, 

1962.

As discussed later, in the section on the family Carinaropsidae, Bucanopsis and Sphenosphaera are quite 

distinct from Carinaropsis and are not included in that 

family; herein, they are placed in the new subfamily 

Bucanopsinae of the Bellerophontidae. The strong 

revolving ornament of Bucanopsis indicates a common 

ancestry with the subfamily Bucaniinae of the family 

Bucaniidae. Sphenosphaera has a shell form very similar 

to that of Bucanopsis, and both bear a keel along the 

median whorl floor. Sphenosphaera also bears a striking 

resemblance to Bellerophon in general shell form. Sphenosphaera was separated from Bellerophon because of 

subtle differences in the form of the parietal lip and the 

presence of a median whorl floor keel (Knight, 1945a, p. 

334). It is likely that the Bellerophontinae evolved from 

the Bucanopsinae, through Sphenosphaera. It may be 

that the Knightitinae also evolved from the Bucanopsinae through Bucanopsis or closely related forms. This 

view is supported by the common possession of strong 

radial ornament by Bucanopsis and genera of the 

Knightitinae, and by the presence of a whorl floor keel in 

at least one species of Knightites, as reported by Rollins 

(1967), who also regarded Bucanopsis as the ancestor of 

the Knightitinae.

The Cymbularinae was proposed by Horny (1962) for 

globose shells having a distinct V-shaped sinus preceding 

the slit. Its ancestry is unclear, and its placement within 

the Bellerophontidae is debatable. If the genus Coelocyclus is a valid member of the Cymbularinae, as Horny 

thought, then the Cymbularinae may have evolved from 

the Bucaniinae of the Bucaniidae. Bucaniinae is the 

subfamily to which Coelocyclus was assigned by Knight 

and others (1960).

Subfamily BELLEROPHONTINAE McCoy, 1851

Diagnosis.—Shell convolute or nearly so, umbilici 

small or absent; whorls in most cases broadly rounded, 

somewhat globose; slit fairly short, generating selenizone; shell surface having only growth lines.

Stratigraphic range.— Middle Ordovician-Lower 

Triassic.

Genera included.—B. (Bellerophon) Montfort, 1808; 

B. (Aglaoglyptd) Knight, 1942; B. (Pharkidonotus) 

Girty, 1912; Liljevallospira Knight, 1945a; IPtychobellerophon Delpey, 1941',! Bubovicus Horny, 1962. Horny 

(1962) assigned two rather unusual genera to the Bellerophontinae, Bubovicus Horny and Kodymites Horny. 

Both genera could be placed in the Bellerophontidae, but 

they do not conform to the morphobases used for defining 

the subfamily Bellerophontinae. Kodymites has umbilici 

filled with the inductural deposits, and may represent a 

new subfamily, as suggested by Horny (1962). Bubovicus 

is here left in the Bellerophontinae for the time being, 

but its high, narrow whorls and moderately small, open 

umbilicus are somewhat atypical of the subfamily. 

Because of some spiral ornamentation, Horny (1963a, p. 

121) suggested a possible relationship to Kokenospira, 

but concluded that the development of the selenizone and 

the general shape of the growth lines are typical of the 

Bellerophontinae. Thus far, only one species of Bubovicus has been described, and more data are needed before its higher level placement can be decided with 

confidence.

Discussion. — With Horny's (1962) removal of the 

Cymbulariinae from the subfamily (three or four genera), 

the Bellerophontinae is now a very homogeneous grouping of genera. Because of the close morphologic similarity 

between these genera and Sphenosphaera, there is little 

doubt that the Bellerophontinae evolved from the Bucanopsinae through Sphenosphaera, or a genus much like it.

Genus BELLEROPHON Montfort, 1808

Diagnosis.— Shells having broadly rounded whorls, 

but some having subdued dorsal crest; umbilici small or 

closed; median whorl floor ridge absent.

Type species.—Bellerophon vasulites Montfort, 1808, 

by original designation.

Distribution.— Middle Ordovician-Lower Triassic. 

Cosmopolitan.

Discussion.— Throughout most of the 19th century, 

the genus Bellerophon encompassed nearly all described 

bellerophontaceans. Late in that century, subtle differences in different groups of species within the genus 

were recognized and new genera were described and 

proposed.

Knight (1945a, p. 334) proposed the genus Sphenosphaera to include American Ordovician species assigned 

to Bellerophon by Ulrich and Scofield (1897), and related 

species. The primary taxobasis distinguishing Sphenosphaera was the presence of a median whorl floor ridge. 

Rollins (1967) has contested the collective assignment of 

American Ordovician species to Sphenosphaera, pointing 

out that some of these species lack a whorl floor ridge, 

and in many others the whorl floor is not known. He 

believed that all such species should be returned to B. 

(Bellerophon). It should be noted that the whorl floor 

ridge dies out at the parietal callosity in Sphenosphaera, 

and does not extend outside the aperture, so any filling of 

the aperture prevents being able to see this structure.
MIDDLE AND UPPER ORDOVICIAN SYMMETRICAL UNIVALVED MOLLUSKS, CINCINNATI ARCH REGION 0159 

TABLE 71. Measurements (in millimeters) of Bellerophon (Bellerophon) subglobulus

USNM 

No.

45709

387022

Shell 

length

19.4

11.8

Shell 

height

13.8

8.6

Aperture 

length

14.6

8.4

Aperture 

width

16.0

10.5

Dorsal 

width

11.8

7.5

Posterior 

width

_

5.3

Ventral 

width

_

3.6

Selenizone 

width

0.85

0.60

In the fauna discussed here, three species are confirmed as members of B. (Bellerophon) (lacking a whorl 

floor ridge), five species are confirmed as members of 

Sphenosphaera (possessing a whorl floor ridge), and 

three species are of uncertain generic assignment (specimens not exposing the whorl floor). The generic placement of the group of uncertain species was based on 

other comparative morphological features. Two of these 

species, S. recurvus (Ulrich) (pi. 33, figs. 1-4) and S. 

subangularis (Ulrich) (pi. 33, figs. 10-15), have comparatively angled, nonglobose shells and nearly closed umbilici, and seem to be related to S. clausus Ulrich. The 

third species of uncertain affinity, Bellerophon subglobulus Ulrich (pi. 33, figs. 7-9), is poorly preserved and its 

proper generic assignment is difficult to determine, 

particularly because it is the earliest known species of 

the two genera in the Cincinnati arch faunas 

(Blackriveran-Rocklandian in age). It is similar to S. 

troosti in the size of its umbilici and its thin, ridgelike 

selenizone, but because of the globosity of its shell and 

the lack of evidence of a whorl floor keel, the species is 

tentatively assigned to B. (Bellerophon).

With confirmation of the assignment of B. (B.) bilineatus, B. (B.) nana, and B. (B.) subpatula to the 

subgenus Bellerophon (Bellerophon), the range of the 

genus is once again extended back to the Middle Ordovician. This is at variance with Knight and others (1960), 

who claimed a Silurian origin for B. (Bellerophon).

Subgenus BELLEROPHON (BELLEROPHON) Montfort, 1808

Diagnosis. Shell rounded or commonly globose; selenizone distinct, in some cases on dorsal crest; aperture 

lips flaring slightly near small umbilici; inductura thin to 

slightly thickened but in all cases smooth, and extending 

only short distance out of plane of aperture; ornament 

predominantly collabral.

Type species.—Same as for genus.

Distribution.—Same as for genus.

Discussion.— Three subgenera are currently recognized within the genus Bellerophon. B. (Aglaoglypto) is 

like B. (Bellerophon) but is ornamented with quincuncially arranged pustules (Knight and others, 1960). B. 

(Pharkidonotus) differs from the other two subgenera in 

having strongly thickened inductural deposits that in 

many cases are padlike in shape, an ornament of collabral 

undulations, a crested selenizone, and no umbilicus

(Knight and others, 1960). The subgenera B. (Aglaoglypta) and B. (Pharkidonotus) are Middle and Late 

Paleozoic in age. B. (Bellerophon) is the oldest of the 

three subgenera (appearing in the Middle Ordovician), 

and most likely was ancestral to the other two more 

specialized subgenera.

Bellerophon (Bellerophon) subglobulus Ulrich, 1897 

Plate 33, figures 7-9

Bellerophon subglobulus Ulrich in Ulrich and Scofield, 1897, p. 917, pi. 

64, figs. 17, 18.

Diagnosis.— Shell moderately small (up to 19.4 mm 

long), subglobose; umbilici small, circular; selenizone 

thin, elevated, ridgelike, with lunulae.

Description.— Shell moderately small, subglobose in 

form; dorsal slopes uniformly well rounded; umbilici 

small, circular, with slightly reflexed parietal lip passing 

just beneath them. Aperture rounded; whorl floor not 

visible because of filling by matrix. Growth lines broadly 

rounded over dorsum, sharp, evenly and closely spaced. 

Selenizone thin, elevated, ridgelike, with lunulae.

Measurements.—The measurements of B. (B.) subglobulus given in table 71 are only approximations, because of the poor preservation of the known 

specimens.

Material.— Only two specimens were located, both 

cataloged under USNM 45709. The lectotype designated 

herein (pi. 33, figs. 7-9) retains that number, and the 

unfigured paralectotype is assigned the number USNM 

387022.

Distribution.—Ulrich and Scofield (1897) stated only 

that the specimens came from the "Black River limestone, Mercer County, Kentucky." The species probably 

occurs in the High Bridge Group (BlackriveranRocklandian) of central Kentucky.

Comparison.— Although poorly preserved, the type 

specimens of B. (Bellerophon) subglobulus can be distinguished from Sphenosphaera troosti by their lack of 

distinct continuous whorl floor ridges and by their more 

globose form, their more broadly curved and threadlike 

growth lines, their narrower, ridgelike selenizone, and, 

probably, their smaller parietal callosity. S. clausus 

shows the same differences and also has a channellike 

selenizone and lacks umbilici. B. (Bellerophon) bilineatus has larger umbilici and a channellike selenizone.
0160 CONTRIBUTIONS TO THE ORDOVICIAN PALEONTOLOGY OF KENTUCKY AND NEARBY STATES 

TABLE 72. Measurements (in millimeters) of Bellerophon (Bellerophon) bilineatus

USNM 

No.

45697

45697

315612

Shell 

length

12.9

-

-

Shell 

height

10.9

8.7

14.6

Aperture 

length

5.0

-

-

Aperture 

width

14.0

13.6

20.2

Dorsal 

width

8.6

7.3

-

Posterior 

width

6.5

5.9

-

Ventral 

width

5.4

4.9

-

Selenizone 

width

0.9

0.9

-

Bellerophon (Bellerophon) bilineatus Ulrich, 1897

Plate 28, figures 1-9

Bellerophon bilineatus Ulrich in Ulrich and Scofield, 1897, p. 917, pi. 

64, figs. 19-21.

Diagnosis.— Shell moderately small (up to 13 mm 

long); umbilici relatively large; whorl floor keel very low 

or absent; selenizone concave, bordered, and lunulate.

Description.— Shell moderately small, expanding 

rather slowly. Whorl slopes cutting downward sharply, 

forming rounded dorsolateral shoulder and giving shell a 

squarer appearance than in other species. Umbilici relatively large for genus. Parietal lip not much thickened 

centrally; posterolateral lips folded back just beneath 

umbilici. Low, rounded whorl floor keel present in some 

specimens. Selenizone nearly flush with dorsal whorl 

slopes, slightly concave, bordered by distinct revolving 

thread on either side, lunulae well developed. Growth 

lines fine, threadlike, very closely and evenly spaced, 

gently curved.

Measurements.— Measurements on B. (B.) bilineatus 

are listed in table 72.

Material.-Both the holotype (USNM 45697) (pi. 28, 

figs. 1-5) and the unfigured paratype (USNM 387023) are 

silicified and fragmentary. One possible new specimen of 

B. (B.) cf. bilineatus was identified from USGS silicified 

sample 6136-CO (USNM 315612) (pi. 28, figs. 6-9).

Distribution.—The type specimens are listed as coming from the "upper portion of the Trenton Group, near 

Danville, Kentucky" (Ulrich and Scofield, 1897), this 

corresponding to the upper Lexington Limestone (Shermanian) of modern usage. The possible new specimen is 

from the Faulconer Bed of the Perryville Limestone 

Member of the Lexington Limestone (Shermanian) in 

central Kentucky.

Comparison.— This species is most similar to Sphenosphaera troosti and S. burginensis, but is distinguished 

by its larger umbilicus, its squarer whorl form, its lack of

a distinct whorl floor keel, and its concave, lunulate 

selenizone bordered by revolving threads.

Discussion.— As pointed out by Rollins (1967, p. 118), 

the holotype of this species apparently lacks a true whorl 

floor ridge, and therefore does not fit the definition of the 

genus Sphenosphaera. In every other characteristic, the 

holotype seems closely related to contemporaneous species of that genus, but by definition it must be assigned 

to Bellerophon (Bellerophon). The relatively large umbilicus of the species is a primitive morphological feature.

Bellerophon (Bellerophon) nana (Ulrich), 1897

Plate 18, figures 13-17

Bucania nana Ulrich in Ulrich and Scofield, 1897, p. 895, pi. 66, figs.

41-44. 

Sphenosphaera nana (Ulrich), Rollins, 1967, p. 119, pi. 4, figs. 2, 3.

Diagnosis.— Shell small (up to 9.5 mm long), whorls 

rounded but relatively narrow; selenizone channellike 

and bordered by thin ridges; growth lines broadly 

curved.

Description.— Shell small; whorls rounded dorsally 

and laterally, but relatively narrow rather than globose; 

umbilici of moderate size for genus; apertural outline 

subreniform, lips not known to flare laterally. Sinus 

moderately shallow; selenizone concave, channellike, 

with distinct lunulae and bordering threads. Growth 

lines broadly curved over dorsum, threadlike, closely and 

quite evenly spaced.

Measurements. Measurements of the lectotype and a 

paralectotype of B. (Bellerophon) nana are listed in table 

73.

Material.-The lectotype, USNM 315553 (pi. 18, figs. 

13, 14), and a paralectotype, USNM 315554 (pi. 18, figs. 

15-17), are figured from Ulrich's (Ulrich and Scofield, 

1897) syntypic suite of 11 small silicified specimens. The 

remaining nine paralectotypes remain cataloged under 

USNM 45722. No new material is known.

TABLE 73. Measurements (in millimeters) of Bellerophon (Bellerophon) nana

USNM 

No.

315553 

315554

Shell 

length

6.4 

9.5

Shell 

height

4.8 

7.0

Aperture 

length

4.0 

5.0

Aperture 

width

5.5

8.0

Dorsal 

width

4.5 

5.0

Posterior 

width

3.5

3.8

Ventral 

width

3.0 

3.2
MIDDLE AND UPPER ORDOVICIAN SYMMETRICAL UNIVALVED MOLLUSKS, CINCINNATI ARCH REGION 0161 

TABLE 74. Measurements (in millimeters) of Bellerophon (Bellerophon) subpatula

USNM 

No.

315552

Shell 

length

7.1

Shell 

height

4.5

Aperture 

length

4.0

Aperture 

width

7.0

Dorsal 

width

4.7

Posterior 

width

3.3

Ventral 

width

2.8

Distribution.—The museum label with the type material says the collection is from the "Flanagan beds of the 

Trenton, one and a half miles south of Burgin, Kentucky." The Flanagan is an outdated stratigraphic name 

for silicified beds in the upper Lexington Limestone that 

are at different levels; however, the geographic locality 

makes it probable that the specimens are from the 

Perryville Limestone Member of the Lexington Limestone (Shermanian).

Comparison. — This species can be differentiated from 

B. (B.) bilineatus by its smaller umbilici and narrower 

whorl form.

Discussion. —\J\rich and Scofield (1897, p. 896) 

assigned this species and its supposed subspecies B. 

nana subpatula to the genus Bucania because they 

believed Bellerophon nana to have faint revolving 

threads. However, they qualified the assignment to 

Bucania by noting that they were not satisfied that 

either was a "true Bucania," as their umbilici were too 

small and their sculpturing was "not what it should be."

Rollins (1967, p. 119) suggested that both subspecies 

might be juveniles of Sphenosphaera troosti or S. 

clausus, because of similarities in the character of the 

collabral ornament and the presence of strong threads 

bordering the selenizone; he decided to call the species 

Sphenosphaera nana.

It appears that this species is distinct, particularly by 

virtue of its rounded but narrow whorls. It shows 

no evidence of a whorl floor ridge (pi. 18, figs. 14, 17), 

and therefore it is recognized here as a species of B. 

(Bellerophon).

Bellerophon (Bellerophon) subpatula (Ulrich), 1897 

Plate 18, figures 10-12

Bucania nana var. subpatula Ulrich in Ulrich and Scofield, 1897, p. 

896, pi. 66, figs. 45, 46.

Diagnosis.— Shell small (up to 7.1 mm long); whorls 

broadly rounded over dorsum; umbilici moderately small; 

selenizone narrow, slightly concave, with fine bordering 

threads; growth lines fine, threadlike, only slightly 

curved over dorsum, reflecting a very shallow apertural 

sinus.

Measurements.— Measurements of the lectotype of B. 

(Bellerophon) subpatula are listed in table 74.

Material—The lectotype, USNM 315552 (pi. 18, figs. 

10-12), is here designated from the syntypic suite,

USNM 45723, which consists of three small silicified 

specimens. No new material is known.

Distribution. The museum label with the type suite 

reads "Trenton, 1.5 miles south of Burgin, Kentucky." 

The specimens most likely are from the upper Lexington 

Limestone (Shermanian).

Comparison. — This species can be distinguished from 

B. (B.) nana by its wider aperture and whorl form, its 

slightly smaller umbilici, its narrower and less concave 

selenizone, and its nearly straight growth lines.

Discussion.—See the discussion under B. (B.) nana 

for the history of B. (B.) subpatula. The species is 

included in B. (Bellerophon) because the lectotype shows 

no evidence of bearing a whorl floor ridge (pi. 18, fig. 11).

Subfamily BUCANOPSINAE new subfamily

Diagnosis.— Shell anomphalous or very nearly so; 

median keel or ridge on whorl floor; selenizone generally 

slightly elevated.

Stratigraphic range.— Middle Ordovician-Silurian.

Genera included.—Bucanopsis Ulrich in Ulrich and 

Scofield, 1897, the type genus, and Sphenosphaera 

Knight, 1945a.

Discussion. — The revolving ornament of Bucanopsis 

suggests that the genus may be ancestral to the Knightitinae. Rollin's (1967) observation of the presence of a 

median whorl floor ridge in a species of Knightites 

further supports this idea.

The Bucanopsinae is thought to be ancestral to the 

Bellerophontinae. Knight (1945a) proposed the genus 

Sphenosphaera for Ordovician species previously 

assigned to Bellerophon. The two genera are almost 

indistinguishable except for the presence of a prominent 

whorl floor keel in Sphenosphaera. The median whorl 

floor keel in the tropidodiscids, the earliest appearing 

family of the slit-bearing Bellerophontacea, is simply the 

result of the wrapping of a subsequent whorl coiling over 

the carinate dorsum of the previous whorl. However, in 

the Bucanopsinae, this whorl floor keel persists even in 

forms lacking a dorsomedian prominence. The whorl 

floor keel may have served an unknown function. A 

function would explain the continued presence of a whorl 

floor keel when no dorsomedian prominence is present. 

On the other hand, the whorl floor keel of the bucanopsids may be a vestigial structure.

Knight and others (1960, p. 1180) placed Bucanopsis 

and Sphenosphaera in the Carinaropsinae because of 

their rapidly expanding shells and their possession of
0162 CONTRIBUTIONS TO THE ORDOVICIAN PALEONTOLOGY OF KENTUCKY AND NEARBY STATES

whorl floor keels. However, these two genera do not 

have the parietal lip developed into a platform that 

extends well into the apertural opening; nor do they 

show true reduction of the coil. It is believed here that 

Carinaropsis and its relatives, which do show these 

features, are a distinct, specialized group, and that group 

is placed in a separate family within the bellerophontacean taxonomic scheme. However, it is quite likely that 

the Carinaropsidae and Bucanopsinae had a common 

ancestry, or that the Carinaropsidae evolved from a 

bucanopsid such as Sphenosphaera.

Genus BUCANOPSIS Ulrich and Scofield, 1897

Diagnosis.— Shell rapidly expanding, selenizone elevated; parietal lip broad, shelflike, with sharp median 

keel developed over ventral whorl floor; ornament of 

fine, straight, parallel revolving threads and fine growth 

lines.

Description.— Shell small to moderate in size, rapidly 

expanding; umbilici of moderate size. Selenizone generally elevated on dorsomedian ridge. Aperture broadly 

expanded; parietal lip reflexed over coil and spread 

laterally to form ventral shelf posterior to aperture 

opening; whorl floor and parietal shelf with median keel 

caused by covering of dorsomedian elevation by thin 

parietal lip. Shell surface marked by fine, unwrinkled, 

uninterrupted revolving threads which run parallel to 

direction of coiling. In some cases, faint growth lines are 

of sufficient strength to give weak reticulate pattern to 

shell.

Type species.—Bucanopsis carinifera Ulrich and 

Scofield, 1897, by original designation.

Distribution.—In the Ordovician of North America, 

Bucanopsis is known from the species B. carinifera and 

B. diabloensis n. sp., which are found in the Lexington 

Limestone of Kentucky and the Bigby-Cannon Limestone of Tennessee, both formations being KirkfieldianShermanian in age.

Reed (1921, p. 58-62) reported four species of Bucanopsis from Caradocian, Ashgillian, and Wenlockian age 

(Middle Ordovician-Upper Silurian) strata of Great Britain. Horny (1963a, p. 113-116) described four species of 

Bucanopsis from Llandeilian, Caradocian, and Ashgillian strata of Bohemia. Three species of Bellerophon 

named by Lindstrom (1884) from the Middle Silurian 

of Scotland have been referred to Bucanopsis by Rollins 

(1967, p. 116,117). Therefore, Bucanopsis is known from 

the Middle Ordovician to Upper Silurian in North 

America and Europe.

Discussion.— Ulrich and Scofield (1897, p. 922-924) 

proposed the genus Bucanopsis for species resembling 

Bellerophon but having straight, nonwrinkled revolving 

lines which run parallel with the direction of coiling. 

They discussed the history of these species in some

detail, and only a brief synopsis is presented here. 

Paleontologists prior to 1880 classified species placed by 

Ulrich and Scofield (1897) in Bucanopsis in the genus 

Bellerophon. Waagen (1880) separated such species from 

Bellerophon on the basis of their spiral sculpture, and 

placed them in Bucania Hall. Koken (1889, p. 379) 

adopted this approach. Ulrich and Scofield (1897) 

believed the shell form of species they placed in Bucanopsis was more similar to that of Bellerophon than 

Bucania, and emphasized differences between Bucania 

and Bucanopsis in the character of the revolving ornament. Species of Bucania are characterized by oblique 

revolving lines that are wrinkled and generally interrupted regularly by growth lines; in contrast, the revolving threads of species of Bucanopsis are straight and 

parallel to the direction of coiling, and are never wrinkled 

or broken by stronger growth lines. Knight (1945a, p. 

335) proposed the genus Retispira and placed therein all 

Devonian- through Permian-age species previously 

placed in Bucanopsis; he stated that Retispira differs 

from Bucanopsis "by its simple, inductural inner lip and 

its lack of the sharp ridge on the floor of the interior of 

the whorl." Knight and others (1960) treated Retispira as 

a subgenus of Knightites in the Bellerophontidae, and 

placed Bucanopsis in the Carinaropsinae, stating that 

the presence of a whorl floor keel and expanded aperture 

allied Bucanopsis with Sphenosphaera and Carinaropsis 

(also see Knight, 1945a, p. 334, 335).

As noted by Rollins (1968, p. 112), it is here recognized 

that the whorl floor keel of Bucanopsis is quite different 

from those of Sphenosphaera and Carinaropsis. Bucanopsis is partly characterized by a selenizone carried on a 

highly prominent dorsal carina, as exemplified by the 

type species Bucanopsis carinifera (pi. 27, figs. 1, 16). 

The whorl floor keel in that species is the result of the 

covering of this dorsal carina by the parietal lip of the 

subsequent whorl. This is also shown by the presence of 

the keel ventrally over the entire parietal lip (pi. 27, figs. 

4, 11, 14, 20). Species of Sphenosphaera and Carinaropsis, on the other hand, do not generally have a prominent 

dorsal carina (although there are exceptions), but they 

still develop a whorl floor keel. Furthermore, the whorl 

floor keel in these genera does not continue ventrally 

over the extended parietal lip (pis. 28-38).

Bucanopsis may represent a more primitive condition. 

Sphenosphaera and Carinaropsis may represent intermediate and advanced forms, respectively, that evolved 

from Bucanopsis. Sphenosphaera and Carinaropsis 

apparently have lost distinct revolving ornament, except 

for the threads commonly bordering their selenizones. 

However, faint revolving threads have been found here 

in a single silicified specimen of Carinaropsis cymbula 

(Hall) (pi. 38, fig. 8). The selenizones of Sphenosphaera 

and Carinaropsis are generally either flat or on low
MIDDLE AND UPPER ORDOVICIAN SYMMETRICAL UNIVALVED MOLLUSKS, CINCINNATI ARCH REGION 0163

ridges, but both genera retain a sharp whorl floor keel. 

This may be because it has assumed some functional 

significance, such as a muscle attachment site.

Rollins (1967, p. 131, 132) suggested that Bucanopsis 

was ancestral to the subfamily Knightitinae because of 

similarities in their ornament patterns, their parietal 

lips, and the presence of a low parietal keel in at least one 

species of Knightites.

Bucanopsis carinifera Ulrich, 1897

Plate 27, figures 1-16

Bucanopsis carinifera Ulrich in Ulrich and Scofield, 1897, p. 925, pi. 

62, figs. 56-61; Grabau and Shinier, 1909, p. 622, fig. 836; Shinier 

and Shrock, 1944, p. 443, pi. 178, figs. 24, 25.

Diagnosis.— Shell small (up to nearly 11 mm long), 

with moderate-sized umbilici; aperture cordate in outline, width nearly twice length; sides of whorls somewhat 

square; high dorsomedian carina becoming increasingly 

flat topped in maturity.

Description. — Shell small, compact, rapidly expanding, and tightly coiled, so that parietal lip is reflexed and 

coils about umbilical shoulder. Whorls broad and somewhat square at shoulders in dorsal view. Selenizone 

clearly visible only in adulthood when prominent dorsal 

carina gradually becomes less angular and more flat 

topped. Dorsal slopes briefly concave adjacent to carina, 

then becoming gently convex; umbilical shoulders narrowly rounded, the change of slope being abrupt and 

giving an angular impression; umbilici moderate in size 

and deep. Aperture broadly cordate, width nearly twice 

length; parietal lip folds back over coil to form rather 

broad ventral shelf posterior to aperture opening; parietal lip thickens laterally from median whorl floor carina 

that results from covering of dorsal carina by thin 

parietal lip; whorl floor carina extends length of reflexed 

parietal lip. Shell sculpturing of numerous thin revolving 

threads which run parallel to direction of coiling and 

seem restricted to dorsal slopes of whorls. In some 

specimens, transverse growth lines, which reflect 

broadly curved apertural sinus, become strong enough in 

maturity to create reticulate pattern on shell.

Measurements.— Measurements of B. carinifera are 

listed in table 75 and shown graphically in figure 33.

Material.—All specimens known are silicified replicas. 

The lectotype was designated by Knight (1943, p. 60, pi. 

14, figs. 3a, b), and was cataloged under the same 

number as the other original syntypes. It is here numbered USNM 315583 (pi. 27, figs. 1, 2). The paralectotypes remain cataloged under USNM 45734, except for 

two figured here, USNM 315584 (pi. 27, fig. 3) and 

USNM 315585 (pi. 27, fig. 4). New Kentucky specimens 

in the USGS silicified collections are from USGS samples 

4073-CO (USNM 315592), 4883-CO, 4928-CO (including 

USNM 315586), 4959-CO (including USNM 315593),

Bucanopsis diabloensis

Bucanopsis carinifera

EXPLANATION

Devils Hollow Member

Tanglewood Limestone Member 

D Perryville Limestone Member (Salvisa Bed) 

Grier Limestone Member

* 10 -

DORSAL WHORL WIDTH, IN MILLIMETERS

FIGURE 33. Bivariate plots of measurements made on specimens of 

Bucanopsis carinifera and B. diabloensis new species.

5015-CO (including USNM 315587, 315588, 315594), 

5096-CO, 5099-CO, 6136-CO (including USNM 315589), 

6915-CO (including USNM 315598), 6916-CO, and 7796- 

CO (including USNM 315595). One specimen from 

Tennessee is numbered UCGM 44283.

Distribution.—The type specimens are labeled as having been collected from the "Trenton (Flanagan), near 

Danville, Kentucky." The Flanagan chert is an outdated 

term formerly used for different silicified horizons in the 

upper Lexington Limestone (Shermanian). Ulrich and 

Scofield (1897, p. 925) also reported the species from 

Maysvillian strata in the Cincinnati, Ohio, area, but no 

specimens from Cincinnatian beds were located during 

this study, and such an occurrence cannot be confirmed.

The species was found in the USGS silicified collections 

from Kentucky in the Grier Limestone Member (4073-
0164 CONTRIBUTIONS TO THE ORDOVICIAN PALEONTOLOGY OF KENTUCKY AND NEARBY STATES

TABLE 75. Measurements (in millimeters) o/Bucanopsis carinifera

USNM 

No.

315583

45734

45734

45734

45734

45734

45734

45734

315592

315592

315592

315592

315592

315592

315592

315592

315592

315592

315592

315592

315592

315592

315592

315592

315592

315592

315586

315593

315589

315594

315594

315594

315594

315594

315594

315594

315594

315594

315595

315595

315595

Shell 

length

_

-8.7

9.0

9.4

5.7

5.9

7.0

_

8.8

7.0

7.7

8.0

4.3

6.4

3.7

7.3

8.2

5.7

5.5

8.2

8.3

_

7.9

7.2

7.8

5.3

-

-

10.8

-

_

-

-

-

-

_

-

-

-

-

-

Shell 

height

9.2

-6.0

7.0

7.1

4.5

5.0

5.7

3.9

6.0

5.2

5.3

5.6

3.5

4.8

3.0

4.5

6.0

4.0

4.2

6.0

6.0

_

6.0

5.9

5.3

4.2

-

-

8.0

-

_

_

-

-

-

_

-

-

-

-

-

Aperture 

length

_

-6.0

6.9

7.0

4.5

4.5

_

_

7.5

6.5

6.6

6.5

3.0

5.5

2.9

5.8

7.5

4.3

4.5

6.3

_

_

6.2

5.4

5.2

4.3

-

_

8.3

-

_

_

_

_

-

_

-

-

-

-

-

Aperture 

width

13.5

8.1

9.6

8.7

6.2

5.8

7.9

5.2

8.3

7.4

7.3

7.2

4.2

7.0

3.8

7.8

9.5

6.1

5.5

8.3

8.3

6.8

7.8

7.1

7.2

5.6

14.0

10.0

10.0

13.6

17.0

14.4

10.0

9.5

7.8

10.4

17.9

12.2

10.7

6.6

7.2

Umbilical 

diameter

4.5

3.2

3.4

3.5

2.3

2.2

3.0

2.1

-

-

_

-

-

-

-

_

-

-

-

-

_

-

-

-

-

_

-

-

-

-

_

-

-

-

-

_

-

-

-

-

-

Dorsal 

width

7.6

-

-

-

-

_

-

-

5.1

-

4.4

4.4

-

-

-

4.0

5.3

3.2

-

4.7

4.9

4.4

4.7

4.3

4.3

3.4

7.3

5.2

6.1

8.0

8.0

7.9

4.9

4.9

5.0

6.3

9.8

6.4

5.2

3.2

3.6

Posterior Selenizone 

width width

5.4 0.9

0.9

-

-

-

_ _

-

-

-

-

- -

-

-

-

-

- -

-

-

-

-

_ _

- -

- -

- -

-

_ -

-

-

5.5

-

_ _

- -

-

- -

-

_ _

-

-

-

-

-

CO, 4883-CO, 4928-CO, 4959-CO, 5096-CO, 5099-CO), 

the Salvisa (5015-CO, 6915-CO, 6916-CO) and Faulconer 

(6136-CO) Beds of the Perryville Limestone Member, 

and the lower tongue of the Tanglewood Member (7796- 

CO) of the Lexington Limestone (Shermanian). Specimens are most abundant in the Grier Limestone Member, particularly in sample 4073-CO, which contains 

about 50 specimens.

One specimen (UCGM 44283) (pi. 27, figs. 5-7) was 

found in a collection from the Cannon facies of the 

Bigby-Cannon Limestone (Kirkfieldian-Shermanian) in 

Smith County, Tenn., which is the first report of the 

species in that State.

Comparison.— Bucanopsis carinifera could be confused with species of Sphenosphaera, if the revolving 

threads are not preserved. However, even when these

are not present, the whorl outline of B. carinifera is not 

as evenly rounded as that of most species of Sphenosphaera, the former having a more abrupt change in angle 

at the umbilical shoulder. Also, the dorsomedian carina 

of B. carinifera is more prominent, and its whorl floorkeel runs ventrally over the entire length of the parietal 

lip, which forms a broader shelf posterior to the aperture 

opening.

Discussion. The specimens of B. carinifera show 

well the problems encountered when working with silicified material. Because all specimens examined here 

were silicified, it is difficult to completely assess the 

impact of silicification on the shell. The lectotype, USNM 

315583 (pi. 27, figs. 1, 2), preserves the revolving threads 

better than any other specimen seen here, and also 

shows how the carina widens into a flat-topped, elevated
MIDDLE AND UPPER ORDOVICIAN SYMMETRICAL UNIVALVED MOLLUSKS, CINCINNATI ARCH REGION 0165

selenizone in adulthood. Note the fineness of these 

revolving threads and how they are not visible when the 

lighting is parallel to them (pi. 27, fig. 2). Most specimens 

do not preserve these threads at all (pi. 27, figs. 3-10). 

Some specimens show them very weakly (pi. 27, figs. 13, 

15, 16). Some specimens show up to three different shell 

layers which peel away like layers of an onion (pi. 27, fig. 

13). Such circumstances of preservation make it impossible to rely on the presence of the revolving threads to 

distinguish the species, or even the genus, although this 

characteristic is a primary generic taxobasis. B. carinifera is found in a variety of facies in the Lexington 

Limestone and apparently was a broadly adapted 

species.

Bucanopsis diabloensis new species

Plate 27, figures 17-20

Diagnosis. — Shell small (up to 15.8 mm long), rapidly 

expanding; aperture broad, nearly semicircular posteriorly; coil relatively small, rounded, narrow.

Description.— Shell small, compactly coiled, and rapidly expanding, so that coil is relatively small in comparison to broad aperture; dorsum has distinct median 

carina and well-rounded slopes; umbilical shoulders well 

rounded, and umbilici of moderate size and depth. Aperture broad, apparently subelliptical in outline, and 

broadly rounded, nearly semicircular in its posterior 

portion; parietal lip somewhat reflexed, folding back over 

ventral coil to form wide shelf posterior and posterolateral to aperture opening; whorl floor has distinct, sharp 

median carina which continues over parietal shelf. Shell 

ornament unknown.

Measurements.—Because available specimens are not 

well preserved (generally only the coil and posterior 

aperture are preserved), only two measurements are 

consistently reliable. These are listed in table 76.

Material.—All known specimens are from the USGS 

silicified collections from Kentucky. Selected from USGS 

sample 5095-CO, USNM 315590 (pi. 27, figs. 17-20) is 

designated the holotype. Eleven specimens cataloged 

under 315591 are also from USGS 5095-CO and are 

designated paralectotypes, as are two specimens cataloged under USNM 315599 from USGS sample 5087-CO.

Distribution.—B. diabloensis is known only from the 

Devils Hollow Member of the Lexington Limestone 

(Shermanian) of central Kentucky (USGS samples 5087- 

CO and 5095-CO).

Comparison.—B. diabloensis is distinguished from B. 

carinifera, which is also found in the upper Lexington 

Limestone, by its more rapidly expanding shell, its 

relatively smaller, more rounded, narrower coil, and its 

more broadly rounded parietal shelf (pi. 27, figs. 17-20).

TABLE 76.—Measurements (in millimeters) of Bucanopsis diabloensis

USNM 

No.

Aperture 

width

Dorsal

width

315590

315591

315591

315591

315591

315591

315591

315599

15.8

13.2

12.2

10.5

13.0

11.3

12.1

11.5

7.15

6.2

5.45

5.0

6.2

5.15

6.0

5.65

Discussion.—None of the available specimens of B. 

diabloensis preserve any surface ornament; however, as 

stated previously, very few specimens of B. carinifera, 

which is also known only from silicified material, have 

the revolving threads preserved. Although, B. diabloensis could be placed in the genus Sphenosphaera, I have 

placed the species in the genus Bucanopsis because of its 

similarity to B. carinifera, specifically, the tight coiling, 

the size of the umbilici, the dorsomedian carina, and the 

especially broad parietal shelf over which the whorl floor 

carina continues.

The difference between B. carinifera and B. diabolensis in the rate of whorl expansion is displayed in a 

crossplot of aperture width versus dorsal whorl width 

(fig. 33). In successive samples from the Grier Limestone, Perryville Limestone, and Tanglewood Limestone 

Members, the aperture width/dorsal whorl width ratios 

for B. carinifera are 1.75, 1.82, and 2.04, respectively; 

the equivalent ratio for B. diabloensis from the Devils 

Hollow Member is 2.14. B. diabloensis was apparently 

an offshoot (or a culmination) of a phyletic trend in B. 

carinifera of increasing rate of whorl expansion.

Genus SPHENOSPHAERA Knight, 1945a

Diagnosis.— Shell moderately rapidly expanding, 

aperture flaring posteriorly and laterally; whorl floor 

with distinct median ridge, ridge not present on parietal 

shelf; ornament collabral.

Description.— Shell small to moderate in size, rather 

rapidly expanding, rounded but generally not globose in 

form; umbilici small or closed. Aperture broader than 

long; margins flared laterally and posteriorly, producing 

flat to slightly excavated posterolateral shelves; parietal 

lip reflexed over venter of previous whorl; whorl floor 

with narrowly rounded to well-rounded median ridge, 

ridge not extending over onto ventral parietal lip. Slit 

shallow to moderately deep, housed in broad sinus; 

selenizone distinct, either a rounded to flat-topped ridge 

or a concave channel, in many cases with distinct lunulae 

and a thin revolving thread bordering on each side. Shell 

surface marked only by fine, generally closely spaced 

growth lines.
0166 CONTRIBUTIONS TO THE ORDOVICIAN PALEONTOLOGY OF KENTUCKY AND NEARBY STATES

Type species.—Bellerophon clausus Ulrich, 1897, by 

original designation (Knight, 1945a).

Distribution.— Sphenosphaera is known from Middle 

Ordovician (Blackriveran?-Rocklandian) to Upper Ordovician (Richmondian) strata in Eastern and Central 

North America (Rollins, 1967).

Comparisons.—Sphenosphaera differs from Bellerophon Montfort in its generally less globose whorl form, 

its more flared apertural margins, which form prominent 

posterolateral shelves (pi. 30, figs. 9, 10), and, particularly, its distinct, rounded median ridge on the whorl 

floor (pi. 30, figs. 2, 9, 17).

Carinaropsis Hall has a median whorl floor ridge, but 

it is sharp rather than rounded (pi. 38, figs. 9, 11). It also 

differs from Sphenosphaera in having a reduced coil, a 

much greater rate of whorl expansion, and a parietal 

platform extending well into the apertural cavity (pi. 38, 

figs. 3-5).

Bucanopsis Ulrich also has a sharp median whorl floor 

ridge as in Carinaropsis, but its ridge continues over the 

ventral parietal shelf. Bucanopsis is further distinguished by revolving shell markings. Rollins (1967) noted 

that some species of Knightites bear a low, rounded 

whorl floor ridge, but that genus is also characterized by 

revolving shell ornament. In the fauna under consideration, species of Bucania having small umbilici can 

closely resemble Sphenosphaera in their general shell 

form. Bucaniids can be readily distinguished, however, 

by their revolving ornament and their lack of median 

whorl floor keel.

Discussion. Knight (1945a, p. 334) defined the genus 

Sphenosphaera for the Ordovician species assigned to 

Bellerophon by Ulrich and Scofield (1897) and other 

related species. He believed that the median whorl floor 

ridge and the posterolaterally flaring apertural margins 

allied these species more closely to the Ordovician genera 

Carinaropsis and Bucanopsis. Knight and others (1960, 

p. 1180) placed these three genera together in the 

subfamily Carinaropsinae Ulrich and Scofield, 1897.

Rollins (1967, p. 117-121) recognized only three species of Sphenosphaera: S. clausus, S. troosti, and, tentatively, S. mohri. He claimed that the median floor 

ridge which largely defines the genus is not present, or at 

least is not known to be present (owing to lack of 

preservation), in other Ordovician species, which he 

returned to B. (Bellerophon). In this study, the presence 

of a median whorl floor ridge is illustrated in S. clausus 

(pi. 30, figs. 2, 9, 17; pi. 31, fig. 3; pi. 32, fig. 4) and S. 

troosti (pi. 29, figs. 4, 9, 13, 15), and is confirmed in S. 

mohri (pi. 41, figs. 1, 3).

The presence of a whorl floor ridge is also shown here 

in two additional species. The type specimens of Bellerophon troosti burginensis Ulrich (=Sphenosphaera 

burginensis, herein) do not expose the whorl floor, but

fragmentary silicified specimens of the species from 

USGS sample 4883-CO show a distinct, narrowly 

rounded whorl floor ridge. The situation is the same with 

Sphenosphaera capax (Ulrich), as new silicified material 

from USGS sample 6412-CO (pi. 34, figs. 10-13) of that 

species reveals a distinct, rounded whorl floor ridge. 

Therefore, both species are assigned to the genus 

Sphenosphaera.

Three Ordovician species named by Ulrich (see Ulrich 

and Scofield, 1897) are assigned to B. (Bellerophon) here, 

as was done by Rollins (1967), because of the apparent 

absence of a median whorl floor keel. These are B. (B.) 

bilineatus Ulrich, B. (B.) nana (Ulrich), and B. (B.) 

subpatula (Ulrich.) B. (B.) subglobulus Ulrich is also 

placed in Bellerophon for reasons noted in the section on 

that genus.

Two other species in the fauna under discussion 

unquestionably belong to either B. (Bellerophon) or 

Sphenosphaera and herein are tentatively assigned to 

the Sphenosphaera. The known specimens of S. recurvus 

(Ulrich) (pi. 33, figs. 1-6) and S. subangularis Ulrich (pi. 

33, figs. 10-15) do not expose the whorl floor; however, 

because of greater similarity of shell morphology with 

species of Sphenosphaera, they were believed better 

placed in that genus (see discussion in section on B. 

(Bellerophon)).

The whorl floor keel ends within the aperture at the 

parietal callosity in Sphenosphaera, as it also does in 

Carinaropsis; however, the keel extends onto the parietal lip in Bucanopsis, Phragmolites, and Tropidodiscus, where it is the result of the blanketing of a dorsal 

carina by the parietal lip. The whorl floor keel in Sphenosphaera and Carinaropsis may be a vestigial structure, and might have been retained in the more advanced 

genera as a muscle attachment site.

Contrary to Knight and others (1960), who placed 

Sphenosphaera in the Carinaropsinae, the genus is here 

allied with Bellerophon in the Bellerophontinae. There is 

almost certainly a relationship between Sphenosphaera 

and Carinaropsis, the two either arising from the same 

stock, or more likely the latter being a specialized 

evolution from the former. The reduction of the coil and 

the marked growth of a platform into the apertural 

cavity distinguish the Carinaropsinae. Sphenosphaera 

could easily be considered a subgenus of Bellerophon, the 

only major distinguishing feature being the whorl floor 

ridge. This whorl floor ridge is rounded, rather than 

sharp as in Carinaropsis, and Rollins (1967) noted low, 

rounded whorl floor ridges in some members of the 

Knightitinae, so that the significance of that characteristic as a supragenetic taxobasis is rather dubious.

Here, two previously named species are placed in 

synonomy: Bellerophon rogersensis Foerste (1914c) with
MIDDLE AND UPPER ORDOVICIAN SYMMETRICAL UNIVALVED MOLLUSKS, CINCINNATI ARCH REGION 0167

S. clausus (Ulrich, 1897), and Bellerophon cincinnatiensis Miller and Faber (1894) with S, mohri (Miller), 1874.

Sphenosphaera clausus (Ulrich), 1897

Plate 30, figures 1-23; Plate 31, figures 1-13; 

Plate 32, figures 1-15

Bellerophon clausus Ulrich in Ulrich and Scofield, 1897, p. 916, pi. 64, 

figs. 7-10; Bassler, 1932, pi. 20, figs. 17, 18; Knight and others, 

1960, figs. 98, 2a-c.

Bellerophon rogersensis Foerste, 1914c, p. 141, pi. 2, figs. 4a-c.

Diagnosis.—Shell moderate in size (up to 26.5 mm 

long), umbilici closed; parietal lip thickened in central 

area, reflexed posterolaterally forming excavated 

shelves; selenizone elevated, with distinct bordering 

threads and lunulae.

Description.— Shell moderate in size and in rate of 

expansion; umbilici completely closed by reflexed parietal lip; dorsal whorl slopes broadly convex, angle of slope 

becoming more obtuse with growth. Selenizone on elevated, flat-topped median carina, bordered by fine 

revolving threads on either side, lunulae distinct. Apertural outline subtriangular, flared posteriorly to form 

concave posterolateral shelves; median parietal area 

thickened; median whorl floor ridge well rounded, not 

extending onto parietal callosity. Growth lines as thin 

threads, closely spaced and regular, becoming less so in 

maturity, broadly curved over dorsal slopes, reflecting 

broad, shallow sinus; slit shallow.

Measurements.— Measurements of S. clausus are 

listed in table 77.

Material-The holotype, USNM 45701 (pi. 30, figs. 

1-6), is a brown, silicified specimen from the BigbyCannon Limestone of Tennessee. An Ulrich and Scofield 

(1897, pi. 64, fig. 9) paratype from Kentucky (USNM 

45700, pi. 30, figs. 7, 8) was the only calcitic specimen 

examined here.

The species is common in the new silicified samples 

from Kentucky. It was recognized in the Grier Limestone Member of the Lexington Limestone (4879-CO, 

4880-CO, 4928-CO, 5067-CO, 5094-CO, 5096-CO, 5107- 

CO), the Salvisa Bed of the Perryville Limestone Member of the Lexington Limestone (5015-CO, 6915-CO, 

6916-CO), the Tanglewood Limestone (7783-CO, 7787- 

CO, 7796-CO), Devils Hollow (5087-CO, 5095-CO), and 

Millersburg (7344-CO, 7353-CO) Members of the Lexington Limestone, and the Clays Ferry Formation (6128- 

CO, 6142-CO, 6143-CO, 7343-CO, 7345-CO, 7348-CO, 

7349-CO, 7350-CO, 7450-CO, 7458-CO, 7812-CO).

Two weathered slabs (UCGM 44301 and 44302) from 

the Cannon Facies of the Bigby-Cannon Limestone of 

Smith County, Tenn., show well-preserved silicified 

specimens associated with other mollusk debris and 

tabulate corals (pi. 31, figs. 11-13).

Distribution.—The species is known from both the 

Cannon and Bigby facies of the Bigby-Cannon Limestone 

in central Tennessee (Bassler, 1932; Wilson, 1949). In 

Kentucky, it is known throughout the Lexington Limestone above the Logana Member (see "Material" above) 

and from the Clays Ferry Formation, mainly where this 

unit intertongues with the Lexington Limestone. S. 

clausus apparently is restricted to strata of KirkfieldianShermanian age.

S. clausus was the most abundant species in the USGS 

silicified collections from the middle and upper Lexington 

Limestone of central Kentucky (see section on paleoecology).

Comparison. —S. clausus is very similar in form to S. 

troosti (d'Orbigny), but the former's umbilici are entirely 

closed, its selenizone is more clearly defined by bordering threads and distinct lunulae, and its parietal lip has a 

more thickened central callosity which is bordered by 

shallow concavities on the posteriorly flared aperture 

shelves. The closed umbilicus and the much thickened 

parietal area also distinguish S. clausus from other 

congeneric species in the Cincinnati arch fauna.

Discussion.—S. clausus is by far the most common 

species of the genus Sphenosphaera in the Cincinnati 

arch fauna. It undoubtedly is closely related to S. troosti, 

and working with poorly preserved material it is difficult 

if not impossible to distinguish the two species. It is 

believed here that the closure of the umbilicus is an 

advanced characteristic, and therefore that S. clausus is 

derived from S. troosti or some earlier umbilicate species. Late Ordovician species having closed umbilici, such 

as S. recurvus, S. subangularis, and S. mohri, most 

likely were descended from S. clausus. The extremely 

well marked selenizone of S. clausus is also thought to be 

an advanced feature.

S. clausus, more than any other species of Sphenosphaera, shows similarity to Carinaropsis cymbula (pis. 

37, figs. 1-11), and it is likely that the Carinaropsis 

evolved from Sphenosphaera. Like C. cymbula, S. 

clausus has a well-defined selenizone; more importantly, 

the two species have similar inner apertural regions. 

Both species have a median whorl floor ridge, an 

enlarged parietal area, and posterolateral excavations on 

the parietal shelf. However, the whorl floor ridge is 

broadly rounded in S. clausus (pi. 30, figs. 2, 9, 14, 17), 

rather than narrow and sharp as in Carinaropsis (pi. 38, 

figs. 9, 11). The parietal area of S. clausus is thickened 

and slightly extended (pi. 30, figs. 9, 10), but it does not 

protrude well into the apertural cavity as it does in 

Carinaropsis (pi. 38, figs. 1, 2, 4, 5). The posterolateral 

excavation of the parietal shelf in both species is the 

result of the median parietal thickening and the flaring 

and draping of the apertural margins. These excavations 

probably served similar functions in the two species, but
0168 CONTRIBUTIONS TO THE ORDOVICIAN PALEONTOLOGY OF KENTUCKY AND NEARBY STATES

TABLE 77. Measurements (in millimeters) of Sphenosphaera clausus

USNM 

No.

45701

45700

315618

315640

315640

315640

315640

315645

315645

315645

315645

315645

315645

315645

315645

315645

315645

315647

315647

315647

315647

315647

315647

315647

315647

315647

315647

315647

315649

315648

315648

315648

315622

315623

Shell 

length

-22.0

-18.0

-16.0

-

-

_

_

12.6

_

12.3

_

_

_

_

-

_

-

-

-

-

_

_

_

_

-

_

_

12.8

_

-

_

-

10.6

-

Shell 

height

15.3

12.1

13.0

7.8

-

11.6

10.1

9.3

7.2

8.6

_

_

_

_

-

_

-

7.2

-

11.8

9.4

_

_

12.8

-

_

_

9.3

14.6

-

_

11.0

8.1

-

Aperture 

length

16.5

-11.6

7.5

-

-

_

_

9.0

_

9.7

_

_

_

_

-

_

-

-

_

-

_

_

_

_

-

_

_

9.4

_

-

_

_

7.3

-

Aperture 

width

-21.9

-17.6

18.95

11.7

12.5

19.0

18.0

13.7

10.6

11.7

11.4

13.8

_

10.9

9.1

8.5

9.9

10.7

9.7

19.0

14.6

18.8

16.4

19.6

16.2

19.5

23.5

13.7

20.2

17.0

17.0

15.7

12.4

20.9

Dorsal 

width

12.75

-10.0

9.8

6.7

-

_

9.5

7.0

6.1

-

_

-

7.2

5.9

5.3

4.9

6.4

5.7

-

11.1

9.1

-

-

-

7.1

_

_

7.9

_

-

11.2

10.1

7.7

-

Posterior 

width

10.3

9.6

9.1

5.0

6.1

10.0

7.1

-

4.5

-

5.2

-

-

-

-

_

-

5.0

-

8.0

6.9

-

-

9.6

6.6

9.2

-

7.0

-

-

_

9.2

6.4

-

Ventral 

width

8.2

7.0

6.7

3.4

4.8

7.7

6.3

-

3.1

4.2

4.3

4.6

4.4

3.6

-

_

-

3.7

-

6.7

5.5

6.4

5.8

7.7

5.0

7.3

10.7

4.9

-

-

-

6.7

5.1

7.8

Selenizone 

width

1.0

1.1

0.6

0.6

-

-

-

0.6

0.7

-

-

-

0.7

-

-

0.5

0.7

0.6

0.6

1.3

0.8

-

-

-

-

-

-

-

-

-

-

1.1

0.5

1.0

they do not seem to have been effective channels for 

currents, as they are not linear; nor do they open to the 

shell interior. The concavities probably housed the posterior foot when the animal clamped down against the 

substrate.

Bellerophon rogersensis Foerste (1914c) was 

described from compressed internal molds and a single 

shell fragment collected from the Clays Ferry Formation 

just above the Millersburg Member of Lexington Limestone in central Kentucky. It was reported from a 

"gastropod horizon" that also contained specimens of 

Tetranota, Liospira, and Lophospira and was bounded 

above and below by strata containing brachiopodbryozoan-trilobite assemblages. Foerste (1914c, p. 141) 

compared the species to Sphenosphaera recurvus, both 

having a relatively elongate aperture. I believe that 

compressed internal molds give this mistaken impression 

(pi. 32, figs. 13-15), and that the specimens described by 

Foerste belong to S. clausus, which is also reported from 

the Clays Ferry Formation here (pi. 30, figs. 17-21). The 

general shell form and the wavy parietal lip that curls 

back and closes (or nearly closes) the umbilicus support

this conclusion. Further support is given by Foerste's 

single shell fragment, which shows a slightly elevated 

selenizone that is concave and bordered by thin threads, 

as in S. clausus. Thus, Bellerophon rogersensis Foerste 

(1914c) is placed in synonymy with Sphenosphaera 

clausus (Ulrich), 1897. The specimen figured by Foerste 

(1914c, pi. 2, figs. 4a-c) and figured herein on plate 32, 

figures 13-15 (USNM 315601) is designated the lectotype 

of Bellerophon rogersensis Foerste.

Sphenosphaera troosti (d'Orbigny), 1840

Plate 29, figures 1-22

Bellerophon troosti d'Orbigny, 1840, p. 206; Safford, 1869, p. 289, pi. 

3G, figs. 4a-d; Ulrich and Scofield, 1897, p. 915, pi. 64, figs. 1-5; 

Grabau and Shimer, 1909, p. 618, figs. 829a-c; Bassler, 1909, p. 

183, figs. 20, 9, 10; Bassler, 1932, pi. 20, figs. 14-16; McFarlan, 

1931, pi. 4, fig. 8; Shimer and Shrock, 1944, p. 443, pi. 178, figs. 

12-14; Wilson, 1948, pi. 10, figs. 7-9; Wilson, 1949, pi. 10, figs. 7-9.

Diagnosis.— Shell moderately small (up to 19.5 mm 

long); whorls broad, somewhat inflated; umbilici narrowly open, small; selenizone a rounded dorsomedian 

ridge, lunulae faint.
MIDDLE AND UPPER ORDOVICIAN SYMMETRICAL UNIVALVED MOLLUSKS, CINCINNATI ARCH REGION 0169

TABLE 77. Measurements (in millimeters) of Sphenosphaera clausus Continued

USNM 

No.

315651

315624

315652

315652

315652

315652

315652

315653

315626

315627

315628

315654

315654

315654

315654

315654

315654

315654

315654

315654

315654

315654

315654

315654

315654

315654

315654

315654

315654

315654

315654

315654

315654

315654

Shell 

length

18.0

18.55

26.5

23.5

21.0

_

-

-

23.0

-

_

18.5

20.2

22.5

-

_

_

13.8

13.6

16.5

_

-

-

-

-

_

-

-

-

-

_

-

12.1

-

Shell 

height

_

13.5

-

-

14.8

_

_

10.4

17.7

12.0

14.0

14.8

14.1

14.7

-

_

_

9.4

9.4

11.1

13.6

12.5

12.1

12.8

12.5

_

12.3

_

12.7

10.4

10.5

_

9.4

8.9

Aperture 

length

_

14.75

19.1

18.4

16.7

_

_

_

10.7

-

_

15.8

16.0

17.8

-

_

_

8.2

9.8

12.9

_

_

_

_

-

_

_

_

_

-

_

_

9.0

-

Aperture 

width

20.8

21.05

26.0

28.0

26.0

20.8

20.2

19.0

22.7

21.0

24.5

22.5

23.0

24.0

23.1

24.5

24.6

16.1

15.5

17.1

22.9

19.0

17.3

18.5

20.2

22.2

22.8

17.0

19.0

16.9

15.8

17.0

13.6

13.3

Dorsal 

width

_

12.75

_

14.8

12.2

11.0

9.1

9.4

_

10.7

13.0

10.7

12.1

-

13.7

_

_

8.9

-

9.3

11.0

9.7

9.4

9.9

9.6

_

_

10.2

_

9.6

_

_

7.6

7.7

Posterior 

width

_

8.2

-

11.7

9.7

_

7.3

8.2

_

8.8

10.0

9.4

10.6

-

9.5

_

-

6.5

7.0

7.7

9.1

8.2

8.0

7.5

-

_

_

8.1

_

7.3

_

_

_

6.5

Ventral 

width

_

7.1

-

-

7.0

6.2

6.2

6.0

_

6.5

7.8

7.8

7.7

-

8.0

_

-

5.5

5.6

6.8

8.4

7.5

6.4

6.5

7.2

8.1

-

6.4

_

6.5

_

_

_

5.3

Selenizone 

width

_

1.3

1.2

-

-

1.2

1.0

-

-

1.5

_

1.4

1.1

-

-

_

-

-

0.9

1.2

1.5

1.3

1.25

1.1

1.2

_

-

1.3

-

1.1

1.2

1.4

0.8

0.9

Description. — Shell moderately small; whorls somewhat inflated, dorsal slopes broadly convex, width greatest at base, outline subtriangular. Umbilici open, small, 

in some specimens partly covered by reflexed parietal 

lip. Apertural margin flared posteriorly and laterally, 

forming shelves with slight excavations; parietal thickening moderate; whorl floor ridge low, well rounded. 

Selenizone a prominent, rounded, dorsomedian ridge, 

with lunulae faint or lacking. Growth lines fine, closely 

spaced, becoming coarser and even slightly wrinkled on 

lateral whorl slopes in maturity; growth lines curve 

gently, showing broad, shallow sinus.

Measurements.—Measurements of S. troosti are listed 

in table 78.

Material.—Two collections of previously figured 

material were examined. USNM 45710 consists of 6 

silicified specimens from the Cannon facies of the BigbyCannon Limestone at Nashville, Tenn., and USNM 

45711 consists of 17 silicified specimens labeled "Flanagan Chert" from near Danville, Ky. Ulrich and Scofield 

(1897, p. 916) stated that these collections were made by 

J.M. Safford and by E.G. Ulrich, respectively. The

Tennessee specimens are probably the hypotypes on 

which Safford based his figures of the species; from this 

collection, USNM 315602 (pi. 29, figs. 1-4) is here 

designated the neotype of the species and USNM 315665 

(pi. 29, figs. 5-9) and the four specimens retaining the 

number USNM 45710 are designated paraneotypes. The 

hypotypes USNM 315603 (pi. 29, figs. 10-13) and USNM 

315604 (pi. 29, figs. 14-16) were selected from Ulrich's 

Kentucky collection (USNM 45711) for illustration. New 

specimens from the USGS silicified collections were 

recognized in samples from the Grier Limestone Member 

(4073-CO, 4959-CO, 5067-CO) of the Lexington Limestone.

Distribution. —In Tennessee, S. troosti is known from 

the Cannon and dove-colored facies of the Bigby-Cannon 

Limestone (Bassler, 1932; Wilson, 1949). In Kentucky, 

the species occurs in the Grier Limestone Member of the 

Lexington Limestone; McFarlan (1931, pi. 20) reported 

the species from the Faulconer Bed of the Perryville 

Limestone Member of the Lexington Limestone. The 

hypotype collection made by E.O. Ulrich is from the 

"Flanagan Chert" of the upper Lexington Limestone, an
0170 CONTRIBUTIONS TO THE ORDOVICIAN PALEONTOLOGY OF KENTUCKY AND NEARBY STATES

TABLE 78. Measurements (in millimeters) of Sphenosphaera troosti

USNM 

No.

315602

315665

315603

315604

45711

45711

45711

45711

45711

45711

315613

Shell 

length

19.5

17.8

-

9.5

-

14.0

14.1

_

_

7.2

-

Shell 

height

14.75

13.9

12.8

7.65

-

11.0

10.8

9.0

7.5

5.3

9.5

Aperture 

length

8.0

7.5

_

4.1

_

6.0

6.1

_

_

3.1

-

Aperture 

width

22.5

20.8

19.6

9.8

18.2

16.5

15.9

14.4

9.8

7.3

17.0

Dorsal 

width

11.7

10.7

10.4

5.85

10.15

8.75

8.50

7.20

5.85

4.35

8.6

Posterior 

width

9.3

7.8

7.8

4.6

7.8

6.2

7.8

5.3

4.6

3.7

7.1

Ventral 

width

7.5

6.9

6.9

3.9

6.6

5.7

6.1

4.7

3.9

2.7

5.4

Selenizone 

width

1.1

1.0

1.25

0.5

1.1

0.8

0.8

0.7

0.5

0.5

-

outdated term known to represent various silicified 

horizons.

Some poor fragments of small specimens of Sphenosphaera sp. indet. were found in USGS silicified samples 

5022-CO and 6131-CO from the Curdsville Limestone 

Member of the Lexington Limestone. These specimens 

have an angular dorsum and small, open umbilici; therefore, they may be related to S. troosti.

Comparison.—The most distinctive features of S. 

troosti, which serve to distinguish it from contemporaneous species, are its small but distinctly open umbilicus 

and its prominent, rounded, ridgelike selenizone.

Discussion. Although similar to S. clausus, S. 

troosti is easily recognized when sufficiently well preserved material is available. S. troosti is regarded as 

closely related to S. clausus.

It is interesting that Wilson (1949) listed S. clausus 

from the Bigby-Cannon Limestone. The two species 

overlapped in the normal marine shelf environment 

(Cannon), but S. troosti also inhabited quiet nearshore 

lagoons and mudflats (dove-colored facies), whereas S. 

clausus also dwelt in a high-energy shoaling environment (Bigby facies). The more tightly coiled, nonumbilicate shell of S. clausus may have been streamlined for 

life in higher energy environments. The two species were 

not found to co-occur in the USGS Kentucky samples.

Sphenosphaera burginensis (Ulrich), 1897

Plate 28, figures 10-23

Bellerophon troosti burginensis Ulrich in Ulrich and Scofield, 1897, p. 

916, pi. 64, fig. 6.

Diagnosis.— Shell moderate in size (up to 21.5 mm 

long); whorls relatively narrow; umbilici narrowly open; 

posterolateral apertural margins horizontal; selenizone 

thin, elevated, concave, with bordering threads and 

lunulae.

Description.— Shell moderate in size; expanding 

rather slowly so that whorls are relatively narrow; whorl 

slopes evenly convex. Umbilici moderate in size. Posterolateral apertural margins reflexed horizontally, not 

curling over umbilicus, passing straight beneath it. 

Whorl floor ridge narrow, sharply rounded. Selenizone 

elevated on thin dorsomedian carina, concave, bordered 

by thin revolving threads; lunulae present. Growth lines 

thin, threadlike, evenly and closely spaced, curving back 

rather strongly toward selenizone, reflecting moderately 

deep sinus.

Measurements.— Measurements of S. burginensis are 

listed in table 79.

Material.-The holotype, USNM 45712 (pi. 28, figs. 

10-12), is a brown, worn, silicified specimen. The single 

paratype, USNM 47595 (pi. 28, figs. 13-15), also is 

silicified. S. burginensis was found in the new USGS 

silicified collections (pi. 28, figs. 16-23) from the Grier 

Limestone (4883-CO, 5094-CO, 5096-CO) and Perryville 

Limestone Members (S. cf. burginensis) (6915-CO) of the 

Lexington Limestone.

Distribution.—The type specimens cited above are 

labeled as coming from the "Flanagan Chert" near Burgin, Ky.; this is an archaic name used for silicified beds at 

different horizons in the upper Lexington Limestone.

TABLE */'9.— Measurements (in millimeters) of Sphenosphaera burginensis

USNM 

No.

45712

47595

315615

315641

315616

Shell 

length

21.5

19.15

14.3

_

17.4

Shell 

height

15.3

13.8

11.0

_

9.8

Aperture 

length

16.45

14.5

10.2

-

11.8

Aperture 

width

22.4

21.0

15.0

13.2

15.5

Dorsal 

width

11.5

9.9

8.7

-

8.25

Posterior 

width

9.8

7.6

6.2

5.0

6.0

Ventral 

width

_

-

4.4

3.5

5.3

Selenizone 

width

1.1

1.2

-

-

0.75
MIDDLE AND UPPER ORDOVICIAN SYMMETRICAL UNIVALVED MOLLUSKS, CINCINNATI ARCH REGION 0171 

TABLE SO.—Measurements (in millimeters) of Sphenosphaera recurvus

USNM 

No.

45705

Shell 

length

16.8

Shell 

height

11.6

Aperture 

length

12.7

Aperture 

width

-

Dorsal 

width

9.4

Posterior 

width

7.8

Ventral 

width

5.6

Selenizone 

width

1.2

New material comes from the Grier Limestone and 

Perryville Limestone Members of the Lexington Limestone (Shermanian).

Comparison.—This species can be separated from all 

others by its narrow whorl form, resulting from a slower 

whorl expansion rate and less flaring of the apertural 

margins. Like S. troosti, it has a small, open umbilicus.

Discussion. — S. burginensis was originally described 

as a "variety" of S. troosti by Ulrich (Ulrich and Scofield, 

1897) with some reservations. Considering the subtle 

differences used to define species of Sphenosphaera, S. 

burginensis, with its distinctly narrower whorl profile, 

is distinct enough to warrant an independent specific 

designation.

Sphenosphaera recurvus (Ulrich), 1897 

Plate 33, figures 1-6

Bellerophon recurvus Ulrich in Ulrich and Scofield, 1897, p. 920, pi. 64, 

figs. 11-13.

Diagnosis. — Shell moderately small (16.8 mm long), 

rather narrow; umbilici closed; selenizone elevated, 

rounded; growth lines strongly curved back.

Description. — Shell moderately small in size, rather 

narrow in dorsal view, gradually expanding. Umbilici 

completely closed by thin parietal lip curled back over 

ventral coil. Aperture seemingly elongate, probably subtriangular, not expanded laterally. Selenizone elevated, 

truncated but rounded, with no lunulae visible. Growth 

lines wrinkled-sublamellose, broadly curved, becoming 

strongly curved backward dorsally to reflect relatively 

deep sinus, not evenly spaced.

Measurements.— Measurements of S. recurvus are 

listed in table 80.

Material. — Ulrich (Ulrich and Scofield, 1897) reported 

that a few specimens of this species were known. Only 

one was located for this study, the holotype (USNM 

45705), a calcitic specimen having a broken aperture and 

a well-preserved shell surface (pi. 33, figs. 1-4).

Distribution. The holotype is labeled as coming from 

the Corryville biofacies, which is now the Grant Lake 

Limestone or Bull Fork Formation (Maysvillian), in the 

Mt. Auburn area of Cincinnati, Ohio.

A few highly recrystallized, fragmentary specimens 

from the Maysvillian Leipers Limestone, Rowena Ferry, 

Russell County, Ky., are here identified as S. aff. S. 

recurvus. The specimens have closed umbilici and rather 

narrow coils, and seem to have wrinkled growth lines.

The specimen figured here (pi. 33, figs. 5, 6; UCGM 

44282) shows moderate lateral expansion of the aperture, 

a feature that is not preserved in the holotype of the 

species.

Comparison.—S. recurvus resembles S. clausus, but 

is narrower in form, with a more elongate aperture. 

Also, S. recurvus has a rounded selenizone with no 

bordering threads or lunulae, sublamellose rather than 

threadlike growth lines, a deeper apertural sinus, and a 

lesser parietal callosity. S. subangularis is even higher 

and narrower than S. recurvus, and has thin threadlike, 

closely and evenly spaced growth lines.

Discussion.— This species was placed in B. (Bellerophon) Montfort by Rollins (1967), because no specimen 

was sufficiently well preserved to prove the presence of 

a median whorl floor ridge. The species is here tentatively placed in Sphenosphaera Knight, as Knight 

(1945a) intended, and is regarded as descended from S. 

clausus. The wrinkled sublamellose growth lines of this 

species are unique among related species in the fauna 

under consideration.

Sphenosphaera subangularis (Ulrich), 1897 

Plate 33, figures 10-15

Bellerophon subangularis Ulrich in Ulrich and Scofield, 1897, p. 920, 

pi. 64, figs. 14-16.

Diagnosis. Shell moderate in size (up to 21 mm long), 

with high, angular dorsum; umbilici closed; aperture 

longer than wide.

Description. Shell moderate in size; whorl expansion 

rather rapid; umbilici closed by thin reflexed parietal lip. 

Median parietal callosity poorly developed. Whorls very 

high, increasingly so in maturity, the dorsal slopes being 

gently convex and forming an acute angle with one 

another. Apertural outline subtriangular, lateral expansion apparently slight so that aperture is longer than 

wide. Selenizone low and rounded in early growth, 

becoming more prominent in maturity; no lunulae or 

bordering threads known. Growth lines fine, threadlike, 

evenly and closely spaced, broadly curved.

Measurements.—Measurements of S. subangularis 

are listed in table 81.

Material.—Two worn calcitic specimens were cataloged as "holotype(s)" under USNM 45708. The specimen 

here left cataloged under that number (pi. 33, figs. 11-15) 

is designated the lectotype. The second specimen (pi. 33,
0172 CONTRIBUTIONS TO THE ORDOVICIAN PALEONTOLOGY OF KENTUCKY AND NEARBY STATES

TABLE 81. Measurements (in millimeters) of Sphenosphaera subangularis

USNM 

No.

45708 

315666

Shell 

length

-21.0 

-13.0

Shell 

height

15.4

9.8

Aperture 

length

-16.5

Aperture 

width

-16.2

Dorsal 

width

10.1

Posterior 

width

8.6

Ventral 

width

6.8

Selenizone 

width

0.9 

0.7

fig. 10) is designated the paralectotype, and is here 

cataloged under USNM 315666.

Distribution.—The type specimens are labeled as 

coming from the "Richmond Group [Richmondian], Richmond, Indiana."

Comparison.—The extremely high dorsum of this 

species separates it from S. clausus and S. recurvus, 

which are otherwise closest to it morphologically.

Discussion.—No known specimen reveals the whorl 

floor, so it is not known if a whorl floor ridge is present 

or absent. However, because the species appears to be 

descended from S. clausus, it is placed in Sphenosphaera. S. recurvus is morphologically, and thus probably phylogenetically, intermediate between S. clausus 

and S. subangularis.

Sphenosphaera capax (Ulrich), 1897

Plate 34, figures 1-13

Bellerophon capax Ulrich in Ulrich and Scofield, 1897, p. 921, pi. 63, 

figs. 50, 51; pi. 64, figs. 40-43.

Diagnosis.— Shell large, whorls rapidly expanding; 

whorls somewhat inflated; whorl floor keel large, broadly 

rounded.

Description.— Shell large, whorls rather rapidly 

expanding throughout growth, abruptly expanded laterally in maturity. Apertural outline nearly semicircular, 

broadening to more semielliptical in maturity. In relation 

to this, whorls somewhat inflated, becoming less so in 

maturity. Umbilici moderate in size, in many specimens 

partly covered by reflexed parietal lip. Selenizone a low, 

rounded ridge, no lunulae known. Whorl floor keel large, 

broadly rounded; little or no parietal callosity; parietal lip 

thin, folded back and over coil and reflexed posterolaterally. Shell moderately thin, expanded adult aperture 

somewhat thicker. Growth lines poorly known, apparently fine, gently curved, becoming more sharply curved 

dorsally, reflecting rather deep, narrow sinus.

Measurements.—The measurements of S. capax, 

listed in table 82, were made on poorly preserved 

specimens.

Material.—Eight poorly preserved calcitic specimens 

are cataloged as "cotypes" under USNM 45698, and a 

ninth "cotype" is cataloged under USNM 45699. The 

lectotype was chosen from this group and numbered 

USNM 315606, (pi. 34, figs. 1-3). All others from this 

group are paralectotypes; three are figured here (pi. 34, 

figs. 4-9)-USNM 315607 and 315608, both formerly in 

the USNM 45698 suite, and USNM 45699. A small 

number of fragmentary specimens in USGS silicified 

collections 6411-CO, 6412-CO, and 6414-CO, including 

USNM 387016 (pi. 34, fig. 10) and USNM 387017 (pi. 34, 

figs. 11-13), are here placed in S. capax.

Distribution.-Ulrich and Scofield (1897, p. 922) cited 

the species as occurring in the "lower part of the Loraine 

group and upper part of the Utica group...in the vicinity 

of Cincinnati, Ohio," the old stratigraphic names being 

equivalent to strata of late Edenian and early Maysvillian 

age. The type suite is from the Maysvillian-age Fairmount biofacies of the Fairview Formation at Covington, 

Ky. The new silicified material is from the Gilbert 

Member of the Ashlock Formation (late Maysvillian) in 

central Kentucky.

Comparison.—S. capax is quite similar in general 

shell form to S. mohri (Miller), but can be distinguished 

by its open umbilicus, its much less prominent selenizone, and its more prominent whorl floor ridge. S. capax 

is also easily distinguished from S. recurvus by its open 

umbilicus, as well as by its more inflated and more 

greatly expanded and inflated whorl form. Additional 

comments about S. capax are included in the discussion 

of S. mohri.

TABLE 82. Measurements (in millimeters) of Sphenosphaera capax

USNM 

No.

Shell 

length

Shell 

height

Aperture 

length

Aperture 

width

Dorsal 

width

Posterior 

width

Ventral 

width

Selenizone 

width

315606

315607

315608

45699

33.0

38.2

37.3

18.0

26.3

26.4

28.0

24.8

27.5

33.2

35.6

38.3

45.7

15.95

21.3

13.5

17.4

11.0

14.0 1.3
MIDDLE AND UPPER ORDOVICIAN SYMMETRICAL UNIVALVED MOLLUSKS, CINCINNATI ARCH REGION 0173 

TABLE 83. Measurements (in millimeters) of Sphenosphaera mohri

Museum 

No.

uc

8796

8793a

USNM

315629

315630

315631

315632

315633

315656

315656

315656

315656

315656

315656

315656

315656

315656

315656

315656

315656

315656

315656

315656

315656

315656

315656

315656

315656

315656

315656

Shell Shell . , , ,, 

length height Aperture length

36.4 16.8 30.4

_ _

30.0 18.9 22.4

_ _ _

19.0

7.5

12.0

18.6

_ _ _

15.8

_ _ _

15.5

19.1

17.5

_ _ _

_

_

14.0

13.9

_ _ _

_ _ _

_

13.2

_ _ _

_ _ _

_ _ _

9.5

6.1

- -

Aperture 

width

_

-32.1

37.25

41.1

37.0

11.6

21.0

39.3

46.3

33.4

30.8

29.0

32.3

-

30.2

22.4

30.0

26.7

25.3

34.0

27.5

27.7

20.7

20.0

23.4

17.9

15.3

10.4

9.75

Dorsal 

width

13.2

16.0

16.4

18.4

17.5

5.7

9.4

15.4

18.7

14.2

13.9

13.1

15.2

14.0

_

13.5

14.5

12.0

11.5

15.1

13.3

-

10.7

9.2

10.4

9.75

8.6

5.1

5.2

Posterior 

width

11.3

10.3

13.0

14.4

14.3

4.5

7.85

13.3

14.3

-

11.1

8.0

12.2

11.7

12.4

-

9.3

10.2

8.0

13.7

11.0

12.5

9.25

7.2

8.1

7.55

7.0

4.4

4.15

Ventral 

width

8.0

-

9.8

12.8

11.7

-

6.0

10.7

12.2

-

-

6.8

11.0

9.3

-

-

7.4

7.2

6.4

11.0

8.2

9.5

6.7

5.2

6.3

5.5

5.0

3.4

-

Selenizone 

width 

UC

1.65

1.9

1.5

-

1.6

0.5

1.0

_

-

1.4

-

-

-

-

-

-

-

-

-

-

-

-

_

-

-

-

0.6

_

-

Sphenosphaera mohri (Miller), 1874

Plate 35, figures 1-16; Plate 36, figures 1-15; 

Plate 41, figures 1-5

Bellerophon mohri Miller, 1874, p. 306, fig. 30; 1889, p. 397, fig. 653; 

Ulrich and Scofield, 1897, p. 920, pi. 64, figs. 44, 45; Cumings, 

1908, p. 954, pi. 39, figs. 2, 2a; Foerste, 1924, p. 208, pi. 34, fig. 9.

Bellerophon cincinnatiensis Miller and Faber, 1894, p. 29, pi. 1, figs. 

23, 24.

Bellerophon parksi Foerste, 1924, p. 208, pi. 35, figs. 4a-d.

Diagnosis. — Shell large (up to 36.4 mm long), umbilici 

closed; whorls rapidly expanding, somewhat inflated; 

aperture broad, nearly semicircular; selenizone a prominent ridge.

Description.— Shell large; whorls somewhat inflated, 

expanding rapidly throughout growth, abruptly expanding laterally in adulthood; umbilici closed. Aperture 

broad, anterior and lateral margins thin and nearly 

semicircular in outline; posterolateral margins form 

rounded corners; inner lip nearly straight and parallel to 

axis of coiling, thickening inward toward well-developed 

median parietal callosity, and reflexed over coil to close 

umbilicus. Whorl floor ridge prominent, narrowly 

rounded to rounded. Selenizone elevated, nearly flat

topped, becoming more prominent through growth; lunulae faint. Sinus moderately narrow and deep; slit apparently rather wide and deep. Growth lines distinct fine 

threads, very closely spaced throughout growth, broadly 

curved over whorl slopes, turning abruptly backward 

only in immediate proximity of selenizone.

Measurements.— Measurements of S. mohri are listed 

in table 83.

Material.—The syntypes of S. mohri, three calcitic 

specimens, are in the Faber Collection at the Field 

Museum of Natural History, Chicago, 111. UC 8793a is 

designated the lectotype (pi. 35, figs. 1-4), and UC 8793b 

and UC 8793c, both crushed and distorted by compression, are paralectotypes (pi. 35, figs. 5-8).

The holotype (UC 8796), and only known specimen, of 

Bellerophon cincinnatiensis Miller and Faber (1894) is 

illustrated here (pi. 35, figs. 15, 16), and that species is 

placed in synonymy with S. mohri. Bellerophon parksi 

Foerste (1924) is also placed in synonymy with S. mohri.

Ulrich's (Ulrich and Scofield, 1897) hypotypes (USNM 

45702) are nine calcitic casts and internal molds, some of 

which probably do not belong in this species or genus. 

Two of the better preserved specimens belong to S.
0174 CONTRIBUTIONS TO THE ORDOVICIAN PALEONTOLOGY OF KENTUCKY AND NEARBY STATES

mohri, have been removed from this collection, and are 

now cataloged under USNM 315610 (pi. 35, figs. 12-14) 

and USNM 315611 (pi. 35, figs. 9-11).

Numerous specimens were found in the collections of 

the University of Cincinnati and Miami University. 

Specimens used here are UCGM 44303 (pi. 36, figs. 14, 

15), an internal mold; MU 14539 (pi. 36, fig. 13), apparently an external mold but seeming to retain some part of 

the shell; and MU 252T (pi. 41, figs. 3-5), a calcitic cast.

New silicified material is from USGS samples 6139- 

CO, which yielded more than 200 specimens and fragments, and 6140-CO, which contains about 30 poor 

fragments. From the 6139-CO collection, 5 specimens 

were selected for illustration (USNM 315629-315633) 

(pis. 36, 41), and 22 other specimens were measured 

(USNM 315656).

Distribution.—S. mohri is distributed throughout 

Richmondian-age strata in the Indiana-Ohio-Kentucky 

tristate area, and also occurs in lower Maysvillian rocks. 

It is best known from the Whitewater Formation in the 

vicinity of Richmond, Ind., but has also been recognized 

in the Saluda Formation, and the Liberty and Waynesville biofacies of the Dillsboro Formation.

The holotype of Bellerophon cincinnatiensis (=S. 

mohri) is from the Maysvillian Fairview Formation 

at Cincinnati, Ohio. Bellerophon parksi Foerste, 1924 

(=S. mohri) is from Richmondian-age strata of Ontario, 

Canada.

Comparison.—S. mohri differs from S. capax in having closed umbilici, a more rapidly expanded shell, a 

more prominent selenizone, and a smaller, narrower 

whorl floor ridge. S. recurvus, which also has a closed 

umbilicus, is less inflated and expanded than S. mohri, 

and does not have as prominent a selenizone.

Discussion.— Miller (1874) referred to S. mohri as 

involute, implying the presence of umbilici, but his type 

specimens, particularly UC 8793c (pi. 35, figs. 6-8), 

clearly show that the umbilici are closed by the parietal 

lip. Likewise, Ulrich and Scofield (1897, p. 920) mentioned small umbilici, but the two specimens from their 

collections shown here (pi. 35, figs. 9-11, 12-14) also 

show the umbilici closed. Foerste (1924, p. 208) named 

Bellerophon parksi from Richmondian-age strata in 

Ontario, saying that it differed from S. mohri in its 

closed umbilici. As it is clear that the umbilici of S. mohri 

are closed, Foerste's specimens are essentially identical 

to S. mohri.

Miller and Faber (1894) named Bellerophon cincinnatiensis for rare specimens from the Maysvillian Fairview 

Formation at Cincinnati, Ohio. The holotype, and only 

specimen of B. cincinnatiensis, is a vertically compressed specimen comparing favorably with S. mohri in 

its closed umbilicus, high selenizone, and distinct, closely 

spaced growth lines, as well as in its general shell form.

Miller and Faber (1894) described the aperture as 

expanded and probably wider than long, but their specimen is not well enough preserved that the shape or size 

of the aperture could be determined accurately. Because 

B. cincinnatiensis has no distinctive morphological traits 

to distinguish it from S. mohri, the two species names 

are considered to be synonyms. This extends the range of 

S. mohri from late Richmondian to early Maysvillian.

S. mohri is the most common member of the genus 

Sphenosphaera in the Cincinnatian Series, being abundant in the late Richmondian Whitewater Formation in 

southeastern Indiana. Specimens from Indiana can be 

common locally, but they are generally poorly preserved. 

Many are internal molds (pi. 36, figs. 14, 15), encrusted 

by bryozoan colonies. In the upper Dillsboro Formation 

(USGS 6139-CO; Richmondian), some specimens are 

silicified. They can be recrystallized (pi. 35, figs. 9-11), 

and many are crushed and distorted by compression (pi. 

35, figs. 5, 6-8). Similar preservation is characteristic of 

other bellerophontaceans and gastropods in Indiana 

Ordovician faunas (see Salpingostoma richmondensis, 

Bucania simulatrix, Cyrtolites ornatus). On the other 

hand, many groups, such as the articulate brachiopods 

and horn corals, are well preserved in these beds. These 

circumstances support the conclusion that these bellerophontaceans and gastropods had predominantly aragonitic shells. This aspect of preservation compounds the 

problem of dealing with rather simple, subtly different 

morphologies. Consider the subtle differences in the 

whorl forms of USNM 315631 and 315629 (pi. 36, figs. 1-3 

and 4-7, respectively); the specimens are from the same 

collection, but USNM 315631 is more inflated and robust 

than USNM 315629. The bryozoan-encrusted paralectotypes of S. capax (pi. 34, figs. 4-7) are quite difficult to 

distinguish from S. mohri. The two species are closely 

related. Both are larger than their Middle Ordovician 

ancestors, both have rapidly expanding shells with 

marked lateral expansion in adulthood, and both occur in 

rubbly, bioclastic limestone sequences associated with a 

diverse fauna. Many are completely encrusted by bryozoans. The expanded, thickened adult apertures of these 

species suggest that they were sluggish vagrant benthos 

living in moderately high energy environments, probably 

grazing on benthic algae.

Family CARINAROPSIDAE Ulrich and Scofield, 1897

Diagnosis.— Shell greatly expanded, coil nearly or 

completely reduced; interior posteromedian septum 

developed within aperture; slit as short notch with 

selenizone, or as raised hollow keel.

Stratigraphic range.— Middle Ordovician-Middle 

Devonian.

Genera included. —Carinaropsis Hall, 1847; 

Gyrospira Boucot, 1956; Pterotheca Salter, 1853;
MIDDLE AND UPPER ORDOVICIAN SYMMETRICAL UNIVALVED MOLLUSKS, CINCINNATI ARCH REGION 0175

Cyclotheca Teichert, 1935; Aspidotheca Teichert, 1935; 

and Pedasiola Spriesterbach, 1919.

Discussion.— Ulrich and Scofield (1897) placed Carinaropsis and Pterotheca in the Carinaropsidae. Teichert 

(1928, 1930, 1935) also concluded that, after a series of 

studies of Pterotheca, the two genera were closely 

related. Wenz (1938) and Golikov and Starobogatov 

(1975) recognized two families, the Carinaropsidae and 

Pterothecidae, but treated the two as closely related.

Knight and others (1960) included the Carinaropsinae 

and Pterothecinae as subfamilies of the Bellerophontidae. In the Carinaropsinae, they included a number of 

genera showing a tendency toward rapid expansion of 

whorls and reduction of coiling, and generally having 

development of the parietal lip into a platelike extension, 

with a whorl floor keel, and a selenizone on a moderately 

developed dorsal crest. As noted later in the discussion of 

Carinaropsis cymbula (Hall), the internal septum of 

Carinaropsis is not simply a reflexed parietal lip, as in 

Bucanopsis and Sphenosphaera, but is a greatly 

extended outgrowth of the parietal region that protrudes 

into the apertural opening as a separate structural 

element. Rollins (1967) came to a similar conclusion 

regarding the Carinaropsinae (sensu Knight and others, 

1960). He stated (p. 149): "The Carinaropsinae reflect an 

unnatural grouping of genera. Gyrospira and Carinaropsis are quite distinct, by virtue of an incipient aperture 

plate, from Bucanopsis and Sphenosphaera. The former 

genera reflect a trend that culminated in the Pterothecidae, with the development of a Crepidula-like platform." However, Rollins (1967) did not formally propose 

redefinition of the Carinaropsinae (sensu Knight and 

others, 1960). That step is taken here, with Bucanopsis 

and Sphenosphaera transferred to the new subfamily 

Bucanopsinae of the Bellerophontidae, and Carinaropsis 

and Gyrospira left in the Carinaropsinae.

The Carinaropsidae is here treated as a family, and is 

considered to contain three distinct but closely related 

subfamilies: Carinaropsinae, Pterothecinae, and Pedasiolinae. It is believed that the Carinaropsinae was 

ancestral to the other two subfamilies, which include the 

genera assigned to the Pterothecinae by Knight and 

others (1960). The Carinaropsinae are characterized by 

the possession of a small coil and the development of an 

apertural platform. The Pterothecinae is restricted to 

genera having a completely reduced coil and a marginal 

apex, and includes the genera Pterotheca Salter, 1853, 

and Cyclotheca, Teichert, 1935. The Pedasiolinae is 

proposed here as a new subfamily of the Carinaropsidae.

Subfamily PEDASIOLINAE new subfamily

Diagnosis.— Carinaropsidae having completely 

reduced coil, submarginal elevated apex, and slit developed as raised median keel.

Stratigraphic range.— Lower-Middle Devonian.

Type genus.—Pedasiola Spriesterbach (1919).

Genera included.—Pedasiola Spriesterbach (1919), 

Middle Devonian; and Aspidotheca Teichert (1935), 

Lower Devonian.

Discussion. The stratigraphic position of these genera suggests that they developed from the Pterothecinae. However, their elevated submarginal apex would 

seem to be a less advanced condition, being morphologically intermediate between the shell forms of the Carinaropsinae and Pterothecinae. The Pedasiolinae probably evolved from the Carinaropsinae separately from the 

Pterothecinae, which also evolved from the Carinaropsinae. No genera of this subfamily occur in the Ordovician 

rocks in the area included in this study.

Subfamily CARINAROPSINAE Ulrich and Scofield, 1897

Diagnosis.— Shell having small but distinct phaneromphalous coil, then broadly expanding rapidly; posteromedian septum well developed within aperture, but 

relatively small; slit as short notch, generating distinct 

selenizone.

Stratigraphic range.— Middle Ordovician-?Devonian.

Genera included. —Carinaropsis Hall, 1847, which 

occurs in the Middle and Upper Ordovician of North 

America and Europe; and Gyrospira Boucot, 1956, 

whose occurrence in South America is probably in Devonian rocks (Knight and others, 1960).

Discussion. The retention of a small coil and a distinct selenizone, and the relatively small apertural septum, show the Carinaropsinae to be the most morphologically primitive taxon within the family; thus, 

phylogenetic roots for the family depend on comparisons 

with Carinaropsis. A genus that may fit the role of 

ancestor to Carinaropsis is the Lower Ordovician Eobucania Kobayashi (1955), which has a small, involute coil, 

a moderately expanded adult aperture, and a distinct 

selenizone with bordering threads; partial reduction of 

the coil and greater expansion of the aperture of a species 

of Eobucania would result in a Carinaropsis-like shell. 

This appears to be the direction of the general morphologic trend within the Carinaropsidae. The Bucanopsinae 

appear to have a common ancestry with the Carinaropsinae; however, in the Carinaropsinae, coil reduction and 

rapid shell expansion developed much further than in 

bucanopsins. Sphenosphaera shows incipient outbuilding 

of the parietal area, as well as a tendency toward an 

increasing rate of whorl expansion, and a species of that 

genus is considered to be the most likely ancestor to 

Carinaropsis.

Genus CARINAROPSIS Hall, 1847

Diagnosis.— Shell having small carinate coil, followed 

by greatly expanded adult whorl; slit short; selenizone
0176 CONTRIBUTIONS TO THE ORDOVICIAN PALEONTOLOGY OF KENTUCKY AND NEARBY STATES

moderately wide, bordered by small ridges; posteromedian platform in apertural cavity bearing dorsomedian 

keel.

Description.— Shell having small juvenile coil with 

carinate dorsum, convex lateral slopes, and open umbilicus, followed at maturity by rapid, broad expansion of 

whorl, producing a patelliform appearance, having 

broadly convex dorsum; expanded aperture widest posteriorly; slit a short notch; selenizone moderately wide, 

with lunulae; posteromedian platform protruding into 

apertural cavity, the anterior margin being straight to 

concave-upward, having sharp keel dorsomedially; parietal lip excavated to varying degrees; shell thin; growth 

lines broadly sweeping.

Type species. —C. carinata Hall, 1847, by subsequent 

designation of Fischer (1885).

Other North American species. —C. acuta Ulrich and 

Scofield, 1897; C. carinata (Hall), 1847; C. cunulae 

(Hall), 1861; C. cymbula Hall, 1861; C. explanata Ulrich, 

1897; C. minima Ulrich and Scofield, 1897; C. phalera 

(Sardeson, 1892).

European species. —C. gracilis Reed, 1921; C. 

maccoyi Reed, 1921.

Distribution.—Rocklandian-Edenian of Eastern 

North America (New York, Kentucky, Tennessee, Minnesota) and Great Britain.

Discussion.—Hall (1847, p. 183) described the genus 

Carinaropsis as "symmetrical, subconical, patelliform, 

subangulated or carinated on the dorsal line; apex 

incurved or convolute; aperture oval, narrowed posteriorly." In modern terms, the coil would be considered 

involute. Also, it is now known that the aperture is 

broader posteriorly. Hall (1847) named two species, C. 

carinata and C. patelliformis, the latter of which is now 

the type species for the Ordovician monoplacophoran 

genus Archinacelliopsis Horny, 1963a.

Hall (1861, p. 93-95) named two additional species 

from the Ordovician of Kentucky and Tennessee that he 

said resembled Carinaropsis externally, but also showed 

"a kind of septum as in Crepidula, extending from the 

posterior side one-third the distance across the cavity." 

Concerning this feature, Hall commented: "Should these 

prove to be identical with those which I have designated 

as Carinaropsis, that generic term will have precedence; 

but should this important character not be found in those 

forms, I propose for those now under consideration the 

generic name of Phragmostoma, from the septum within 

the aperture." These two species are now regarded as 

Carinaropsis cunulae and C. cymbula.

Ulrich and Scofield (1897, p. 926, 927) briefly discussed 

the possible relation of Carinaropsis to Bellerophon (by 

which they meant the Ordovician species now assigned to 

Sphenosphaera). They pointed out that both genera have 

an expanded aperture with a parietal plate, a carinate

dorsum, and a selenizone. However, they concluded that 

these features had an outward resemblance, but differed 

greatly in their development. Therefore, they believed 

Carinaropsis to represent a distinct family. They also 

proposed that Pterotheca, a genus that most authors of 

that time believed to be a pteropod, belonged to the same 

family as Carinaropsis; they based their opinion on their 

observation that both genera have a greatly expanded 

adult shell, a well-developed parietal platform, a reduced 

coil, and a carinate dorsum

Teichert (1935), after studying Pterotheca in detail, 

also concluded that Carinaropsis and Pterotheca were 

closely related phylogenetically. Wenz (1938) supported 

this conclusion and placed the families Carinaropsidae 

and Pterothecidae in close association. Wenz placed 

Pedasiola with Carinaropsis in the Carinaropsidae. 

Pedasiola was placed with Pterotheca in the Pterothecinae by Knight and others (1960). Herein, Pedasiola is 

placed with Aspidotheca Teichert (1935), in the new 

subfamily Pedasiolinae of the Carinaropsidae.

Knight and others (1960) allied Carinaropsis with 

Bucanopsis, Sphenosphaera, Gyrospira, and Phragmosphaera in the subfamily Carinaropsinae. This interpretation stressed the reflected parietal lips and whorl floor 

keel common to these genera. Their figure 98, 3a, is 

misleading, as it makes the parietal lip of Carinaropsis 

appear as a simple reflected apertural margin, as in 

Bucanopsis and Sphenosphaera, when the parietal platform of Carinaropsis actually is developed quite differently. This parietal platform, or septum as it is commonly 

called, does not simply reflex around the ventral coil, but 

grows anteriorly into the apertural cavity during ontogeny. As seen in C. cymbula (Hall) (pi. 38, figs. 1, 2), the 

septum is developed from the parietal lip, but apparently 

as a separate structural element. The dorsolateral septal 

surface attaches to the interior shell roof, sloping downward convexly; it then folds back tightly upon itself, 

sloping posteriorly as a concave surface to meet the shell 

wall, and linking that wall to the parietal shell margin. 

As shown on plate 38, figures 1, 2, there appears to be a 

cavity within the septum. Whether this cavity was open 

is uncertain, because it may be a product of silicification; 

this cavity was seen on other silicified specimens also. 

Sections through well-preserved calcitic material, which 

was not available for this study, are needed to confirm 

the presence of this cavity. It is likely that the septum of 

Carinaropsis is quite different from the reflexed parietal 

lips of Bucanopsis and Sphenosphaera, and is similar to 

the interior platform of Pterotheca, as noted here and as 

illustrated by Teichert (1935). It is conceivable that 

Carinaropsis is intermediate in form between such genera as Sphenosphaera and Pterotheca. Supporting this 

notion is the presence of a keel on the dorsal septal floor 

of Carinaropsis.
MIDDLE AND UPPER ORDOVICIAN SYMMETRICAL UNIVALVED MOLLUSKS, CINCINNATI ARCH REGION 0177

Comparison between the septa of Crepidula and those 

of Carinaropsis and Pterotheca has been made ever since 

Hall's (1861) descriptions of Carinaropsis cymbula and 

C. cunulae. Hoagland (1977, p. 358), in her review of the 

Calyptraeidae, stated: "The septum of Crepidula is 

homologous to the columella. Migration of the point of 

muscle insertion to the junction of the septum and the 

shell proper, or onto the shell, is a specialization for 

sedentary limpet like existence, as is the derivation of 

new muscles for shell attachment. The presence of an 

insertion on either side of the septum as shown by the 

presence of two muscle scars is a third solution to the 

problem of attachment of body to shell and substrate." 

She further explained: "The septum supports the viscera 

and provides for muscle attachment. It divides the body 

into three parts; the foot, the viscera, and the head and 

brood chamber regions....The disc like foot covers the 

area of the septum and no more; thus the larger the 

septum proportional to the size of the shell, the greater 

will be the area of the foot. Also, the deeper the septum 

is inserted into the shell, the thicker may be the foot." 

Hoagland was able to use the morphology of the septum 

(median ridge, notches and curves in the margin, positions of muscle attachment) for the differentiation of 

species. However, she noted that the depth of insertions 

and the depth of the notches show some intraspecific 

variation, and that changes in septal area to apertural 

area in ontogeny must be carefully distinguished from 

interspecific differences. Many of her observations probably have application to the Carinaropsidae. It seems 

likely that the carinaropsids were adapted to a largely 

sedentary existence, and the morphology of the carinaropsid septum can be used in specific differentiation. 

Moreover, the increase in the size of the septum from 

Carinaropsis to Pterotheca probably indicates a concomitant increase in the size of the foot, and may denote 

increased specialization for a purely limpetlike existence 

with stronger clamping power. However, it should be 

recognized that although the septa of Crepidula and 

Carinaropsis seem to have analogous functional significance, the septum of Carinaropsis is not columellar (as 

suggested for Crepidula), and the two structures have 

quite different origins.

Carinaropsis acuta Ulrich and Scofield, 1897

Plate 4, figures 18-25 

Carinaropsis acuta Ulrich and Scofield, 1897, p. 928, pi. 62, figs. 6-9.

Diagnosis.—Shell small (up to 13 mm long), submature coil greatly compressed laterally and having sharply 

angular dorsum; adult shell rapidly expanded; apertural 

outline becoming subcircular; septum short.

Description.—Shell small for genus, thin, smooth; 

submature whorls greatly compressed laterally, producTABLE 84. Measurements (in millimeters) of Carinaropsis acuta

USNM Shell Shell Shell Coil Septum Septum 

No. length width height width length width

265992

265993

265994

13.05

-

-

15.15

17.15

10.10

8.35

8.00

-

_

3.6

3.5

6.0

-

-

6.3

-

-

ing relatively high, narrow coil with sharply angular 

dorsal crest; umbilici subcircular and deep; with rapid 

expansion of adult whorl, apertural outline changes from 

triangular to subcircular, dorsal angle becomes less acute 

quickly and broadens to accommodate moderately wide 

selenizone; anterior slope of shell rather steep; posterior 

lip not reflected strongly, but rather explanate; septum 

short.

Measurements.— Measurements of C. acuta are listed 

in table 84. Because the specimens are fragmentary, the 

measurements are approximations.

Material. —C. acuta was recognized in USGS silicified 

samples 5023-CO, 5100-CO, 5101-CO, 7784-CO, and possibly (C. cf. C. acuta) in 6134-CO and 6419-CO; the total 

number of fragmentary specimens was 15. Figured specimens are USNM 265992, 265993, 265994, and 265995 

(pi. 4, figs. 18-25).

Distribution.— Ulrich and Scofield (1897) described C. 

acuta from the Decorah Formation (RocklandianKirkfieldian) of Minnesota. In Kentucky the species was 

recognized in five samples from the Curdsville Limestone Member (5023-CO, 5100-CO, 5101-CO, 6134-CO, 

7784-CO), and another possible specimen was found in 

a sample from the Logana Member (6419-CO) of the 

Lexington Limestone (Kirkfieldian).

Comparison.— The consistently small size of all the 

specimens of Carinaropsis in the Curdsville Limestone 

Member samples suggests that they differ from the 

larger species C. cymbula in the Grier Limestone Member. Close examination of the Curdsville specimens 

shows that, commpared with C. cymbula, they have a 

more laterally compressed submature coil and a more 

prominent dorsal carina (pi. 4, figs. 20, 24), and that their 

expanded whorl is relatively higher and has a subcircular 

outline (pi. 4, figs. 18, 19).

Ulrich and Scofield (1897) differentiated C. acuta from 

C. phalera (Sardeson) by the former's narrower coil and 

shorter septum. The septum of all the Kentucky specimens of C. acuta is poorly preserved, but where visible, 

it is quite short.

Discussion. This is the first identification of C. acuta 

outside Minnesota. The species is distinguished from 

juveniles of C. cymbula and C. cunulae mainly by its 

narrow, sharply crested submature coil. For its small 

size, C. acuta had a rather wide selenizone (pi. 4, figs. 18, 

24), which broadened rapidly as the mature whorl
0178 CONTRIBUTIONS TO THE ORDOVICIAN PALEONTOLOGY OF KENTUCKY AND NEARBY STATES

TABLE 85. Measurements (in millimeters) of Carinaropsis cunulae

USNM 

No.

45738

45738

45738

45738

Shell 

length

20.5

18.9

16.2

15.2

Shell 

width

22.4

22.5

17.75

18.8

Shell 

height

9.2

8.9

8.1

-

Coil 

width

5.1

4.95

5.2

4.5

Septum 

length

9.85

10.0

7.9

9.05

Septum 

width

13.5

-

10.5

11.3

Selenizone 

width

2.0

2.0

2.0

-

expanded rapidly into its steep, subcircular form (pi. 4, 

figs. 18, 19).

Carinaropsis cunulae (Hall, 1861) 

Plate 37, figures 12-14

Phragmostoma cunulae Hall, 1861, p. 95; Miller, 1889, p. 415. 

Carinaropsis cunulae (Hall) Ulrich and Scofield, 1897, p. 927, pi. 62, 

figs. 10-13; Grabau and Shimer, 1909, p. 626, pi. 845a-c.

Diagnosis.— Shell having relatively large initial coil; 

septum relatively small and flat, with shallow excavation 

posteroventrally; posterior apertural margin broad and 

straight.

Description.— Shell moderate in size (up to 20 mm 

long); submature coil relatively large, with sharp dorsal 

crest and rounded lateral whorl slopes, umbilici small but 

deep; coil projects distinctly beyond broad, straight 

posterior apertural margin; dorsum of rapidly expanded 

adult whorl broadly convex; median selenizone distinct 

and moderately wide; septum relatively short, dorsally 

nearly flat with slightly concave upward anterior margin 

and sharp median keel, ventrally with shallow posteroventral excavation; ornament unknown.

Measurements.— Measurements of C. cunulae are 

listed in table 85. Note that all shell length measurements are minimum values, as the anterior shell margin 

was not preserved in any available specimen.

Material.—Hall's types are not at the American 

Museum of Natural History, and could not be located at 

any other museum. Ulrich and Scofield's (1897) hypotypes, USNM 45738, were the only specimens of the 

species located and examined. Their four silicified specimens are all incomplete. Three specimens (USNM 

45738) preserve the expanded dorsum and the septum. 

The fourth specimen, which is missing the dorsum, 

reveals the dorsal side of the septum, and is the only one 

to preserve the submature coil (pi. 37, figs. 12-14); this 

specimen is separated from the hypotypic suite and is 

cataloged under the new number USNM 265998.

Distribution. — Ulrich and Scofield's (1897) hypotypes 

(USNM 45738 and 265998) are listed on the museum label 

as from the Cannon facies of the Bigby-Cannon Limestone (Kirkfieldian-Shermanian) at Nashville, Tenn. The 

authors cited the species as from the "Upper Trenton

group, Nashville, Tennessee, and Boyle County, 

Kentucky."

Comparison. —C. cunulae differs from C. cymbula 

(Hall) in having a more inflated submature coil, a shorter 

and flatter septum, and a shallower posteroventral excavation. The last difference is the most distinctive distinguishing morphological feature (compare pi. 37, figs. 

9-11 and 12-14). Ulrich and Scofield (1897, p. 928) 

compared C. cunulae to C. phalera (Sardeson) from the 

Decorah Formation of Minnesota. They stated that C. 

phalera has a less reflected apertural margin which is 

scarcely truncated posteriorly, a more circular outline, 

and a greater depth to the concavity of the septum.

Discussion. — C. cunulae appears to be less advanced 

than C. cymbula when the major morphological trends of 

the family Carinaropsidae are considered. These trends 

are mainly the reduction of the coil and the increased 

development of the septum. C. cunulae has a more 

inflated coil and a smaller septum.

Carinaropsis cymbula (Hall, 1861) 

Plate 37, figures 1-11, 15-23; Plate 38, figures 1-12

Phragmostoma cymbula Hall, 1861, p. 94.

Phragmostoma natator Hall (in error for cymbula), 1862, pi. 6, figs.

12-14.

Phragmostoma cymbula Hall, Miller, 1889, p. 415, fig. 693. 

Carinaropsis cymbula (Hall), Ulrich and Scofield, 1897, p. 927, pi. 62,

figs. 1-4; Grabau and Shimer, 1909, p. 626, figs. 845d-g; Bassler,

1932, p. 222, pi. 20, figs. 21, 22.

Diagnosis. Shell having relatively narrow initial coil; 

septum relatively large, angled downward toward anterior, anterior margin slightly concave upward; shell 

deeply excavated posteroventrally to rear of septum.

Description.— Shell moderately large (up to about 30 

mm long); submature coil relatively small and narrow, 

with sharp dorsum, convex (but not inflated) lateral 

whorl slopes, umbilici small and deep; coil protruding 

slightly beyond posterior shell margin; dorsum of rapidly 

expanded adult whorl broadly convex, having median 

crest upon which slightly raised selenizone rests, the 

crest becoming increasing rounded during growth; selenizone moderately wide, bordered by low, sharp ridges, 

with median groove, lunulae in some specimens distinct; 

septum relatively large, angled strongly downward
MIDDLE AND UPPER ORDOVICIAN SYMMETRICAL UNIVALVED MOLLUSKS, CINCINNATI ARCH REGION 0179

TABLE 86. Measurements (in millimeters) of Carinaropsis

cymbula

USNM Shell 

No. length

45739 27.8

45739

45739

265997

265996

265984

265986

265987

265990

265988

265985

265987a

265987b

265987b

265987c

Shell 

width

21.3

-

-

13.4

-

42.6

47.0

39.3

-

31.0

31.9

27.7

38.2

36.2

30.7

Shell Coil 

height width

10.8

4.4

8.8 4.6

4.55

3.55

3.9

4.0

4.2

-

4.35

3.6

-

-

-

-

Septum 

width

_

9.5

9.5

9.4

6.8

22.3

21.5

19.3

-

14.4

15.1

14.8

17.9

16.4

17.6

toward anterior, dorsally convex in side view, anterior 

margin nearly straight to strongly concave upward, 

having dorsornedian keel; posteroventral excavation 

deep; growth lines broadly sweeping, showing greatest 

width of shell to be posterolateral, and curving strongly 

backward near selenizone, reflecting rather broad, shallow sinus housing short slit; growth lines in some specimens as low, broad wrinkles; radiating threads visible in 

some specimens; posterior shell margin slightly arched in 

a few specimens; shell thin.

Measurements.— Measurements of C. cymbula are 

listed in table 86. Although a number of specimens were 

available, most were not measured because of the fragmentary condition of the shell margins.

Material.—Type specimens examined were Hall's 

(1861) holotype (pi. 37, figs. 1-4; AMNH 37723a) and 

paratypes (AMNH 37724, 37725a-c) and Ulrich and 

Scofield's (1897) hypotypes (USNM 45739). Two specimens from the latter suite figured here are given the new 

catalog numbers USNM 265996 (pi. 37, figs. 7, 8) and 

USNM 265997 (pi. 37, figs. 9-11). All of these types are 

silicified specimens. USNM 87778 is also figured (pi. 37, 

fig. 23).

A number of excellent specimens were found in the 

following USGS silicified collections from Kentucky: D1196-CO, 5096-CO (USNM 265984, 265986, 265991), 

4879-CO (USNM 265987, 265985, 265988, 265990), 4880- 

CO, 4852-CO, 4876-CO, 4883-CO, 5107-CO, 4073-CO, 

5094-CO, 5074-CO, 5099-CO, 5067-CO, 4959-CO, 5015- 

CO, 7783-CO, 77809-CO (pis. 37, 38).

Distribution.— Hall's (1861) types are labeled as coming from the "Trenton Limestone at Alien's Bluff, Tennessee." Ulrich and Scofield's (1897) hypotypes are 

labeled "Trenton Group, near Danville, Kentucky." It 

should be noted that Hall (1861) had originally mistakenly recorded the species as from the "Hudson River 

Group," which at that time was the equivalent to 

the Cincinnatian. The so-called "Trenton Group" in 

Tennessee would be the Nashville Group of modern 

usage, and in Kentucky would be the Lexington 

Limestone.

In the USGS silicified collections from Kentucky, C. 

cymbula was recognized from the Logana Member (D1196-CO), the Grier Limestone Member (4073-CO, 4852- 

CO, 4876-CO, 4879-CO (USNM 265987), 4880-CO, 4883- 

CO, 4959-CO (USNM 265987a), 5067-CO, 5074-CO, 5094- 

CO, 5096-CO, 5099-CO, 5107-CO), the Salvisa Bed of the 

Perryville Limestone Member (5015-CO (USNM 

265987b)), and the Tangle wood Limestone Member 

(7783-CO (USNM 265987c) and possibly 7809-CO) of the 

Lexington Limestone. All occurrences of the species are 

Kirkfieldian-Shermanian in age.

Comparison. The only species in the study area that 

bears any close resemblance to C. cymbula is C. cunulae. The primary basis for distinguishing these two 

species is the deep excavation of the posteroventral 

septum (pi. 37, figs. 3, 4, 11, 18, 19; pi. 38, figs. 4, 5) of 

C. cymbula, compared with the shallow indentation of 

the posteromedian septum of C. cunulae (pi. 37, fig. 14). 

The septum of C. cymbula is larger, protrudes farther 

into the apertural cavity, and is more convex, sloping 

strongly anteriorly. The submature coil of C. cymbula is 

slightly smaller and distinctly narrower than that of C. 

cunulae.

C. phalera (Sardeson) was originally described as 

having indistinct radial folds on the dorsal surface of the 

shell, but Ulrich and Scofield (1897) did not find any such 

markings on their specimens. However, a single specimen of C. cymbula from USGS sample 5096-CO (Grier 

Limestone Member) does show radial markings, these 

being in the form of faint, widely spaced threads (pi. 38, 

fig. 8). Ulrich and Scofield (1897, p. 928) stated that C. 

phalera is very similar to C. cunulae, which in turn is 

very similar to C. cymbula. These species apparently 

form a closely related group. If new material of C. 

phalera becomes available, it should be compared closely 

with the Cincinnati arch species, as it could be a synonym 

of one of them.

Discussion. —C. cymbula seems to be more advanced 

than C. cunulae, as shown by the former's smaller coil 

and larger septum. Hoagland (1977) correlated the size of 

the septum of modern Crepidula with the size of the foot. 

This relationship may hold true for the analogous carinaropsid septum. The deep posteroventral excavation of 

the septum of C. cymbula may have helped to house an 

enlarged foot when the animal clamped its shell to the 

substrate.

Although a few specimens of C. cymbula were found in 

samples from the Logana, Perryville Limestone, and
0180 CONTRIBUTIONS TO THE ORDOVICIAN PALEONTOLOGY OF KENTUCKY AND NEARBY STATES

Tanglewood Limestone Members of the Lexington Limestone, the species is most abundant, and is often fairly 

well preserved, in samples from the Grier Limestone 

Member. This suggests that the species inhabited a wide 

range of environments but thrived in shallow, only 

moderately agitated, normal marine environments, such 

as those represented by the Grier Limestone Member.

All specimens examined were readily placed in C. 

cymbula if the ventral septum having the deep excavation was visible. As pointed out by Ulrich and Scofield 

(1897), this excavation is the main distinguishing feature 

of the species. The dorsal shell of the species is thin and 

easily fragmented. No specimen having a complete shell 

is known. The most commonly preserved portion of the 

shell is the septum, which is thickened by the recumbent 

folding of the shell layers that construct it. Through most 

of the breadth of the septum, two shell layers are 

sandwiched together; as the species grew larger, the 

lateral areas of the septum apparently opened into a 

small cavity (pi. 38, figs. 1, 2). The double-walled septum 

and parietal lip of the shell is all that is preserved intact 

in most specimens. Therefore, the dimensions of the 

shells and the actual characteristics of the shell margins 

are poorly known, and variability within the species is 

difficult to assess.

The septum of C. cymbula does not show much 

variation in size and form, even within a single population. If these animals led a clinging mode of life, as 

proposed by Rollins (1967), the host object or the energy 

of the environment may have at least partly governed 

the morphology of the septum. This would have been 

particularly true if the septum were the attachment base 

for the shell muscles. For example, compare specimens 

USNM 265984 (pi. 37, figs. 15-21) and USNM 265988 (pi. 

38, figs. 3-6), both from the Grier Limestone Member of 

the Lexington Limestone but from different samples. 

The general form of the septa of the two specimens is 

quite similar, but that of the former is noticeably larger. 

The anteromedian part of the septum generally is protuberant, as in these two specimens, but this "nose" is 

missing from some specimens, particularly of juveniles 

(pi. 37, figs. 3, 9, 11; pi. 38, figs. 11, 12). Also, the 

anterior margin of the septum apparently increases in 

concavity (from an anterior view) during growth.

The submature coil does not appear to have a selenizone, but because of its size it is difficult to tell. The 

selenizone develops quickly with the rapid expansion of 

the shell to a certain width, and then remains essentially 

the same width through the remainder of growth (pi. 37, 

fig. 1). There is a median groove on the selenizone, the 

origin of which is unknown (pi. 37, fig. 1; pi. 38, fig. 10).

The growth lines in the species vary somewhat. In 

most specimens they are only fine lines, giving the 

surface of the shell a rather smooth appearance (pi. 37,

figs. 15,16, 20; pi. 38, figs. 3,10). However, in some they 

are developed as low wrinkles (pi. 37 figs. 1, 2; pi. 38, 

figs. 7, 8).

Except for the sharp, low ridges bordering the selenizone (pi. 37, fig. 1), few specimens of Carinaropsis 

preserve the radial ornament. Contrary to the opinion of 

Ulrich and Scofield (1897), and confirming that of Sardeson that there are indistinct radial wrinkles in C. phalera 

(Sardeson), one USGS silicified specimen of C. cymbula 

from the Grier Limestone Member (USNM 265991) 

shows faint but distinct, widely spaced, radial threads 

(pi. 38, figs. 7, 8). This confirmation of radial ornament in 

the genus supports the opinion that the Carinaropsinae 

had a common origin with, or evolved from, the 

Bucanopsinae.

Carinaropsis explanata Ulrich, 1897

Plate 40, figures 10-14

Carinaropsis explanata Ulrich in Ulrich and Scofield, 1897, p. 939, pi. 

62, fig. 5.

Diagnosis. — Shell having large, prominent, triangular 

beak area with sharp dorsal crest and steep slopes; 

lateral shell slopes gently convex and outward sloping.

Description.— Shell moderately large for genus (minimum of 32 mm long); beak area large, prominently 

elevated, triangular in dorsal view, with sharp dorsal 

crest and steep lateral slopes (although crest broadens 

with growth, median axis of shell remains elevated above 

lateral slopes of shell); broadly but strongly convex in 

side view; contact between beak area and lateral shell 

slopes marked by sharp break in slope, lateral shell 

slopes very gently convex and sloping at much gentler 

angle outward; characteristics of shell and septum 

unknown.

Measurements.—The lectotype (USNM 45740) is a 

minimum of 32 mm long, 41.2 mm wide, and 14.4 mm 

high. The lectotype is a fragmentary internal mold.

Material.—Only two specimens of this species are 

known, both originally cataloged under the number 

USNM 45740. The specimen shown on plate 40, figures 

10-14, is here designated the lectotype (USNM 45740); 

the other specimen is a paralectotype (USNM 315531). 

Both specimens are internal molds.

Distribution.-Ulrich and Scofield (1897, p. 929) cited 

the species as occurring in the "upper part of the Trenton 

Group, Covington, Kentucky." These beds are now covered by the Ohio River and its tributaries, because of the 

damming of the Ohio River; in the present stratigraphic 

framework they would be placed in the Point Pleasant 

Tongue of the Clays Ferry Formation, which is latest 

Shermanian in age.

Comparison.— The large triangular beak area distinguishes the species from all others known.
MIDDLE AND UPPER ORDOVICIAN SYMMETRICAL UNIVALVED MOLLUSKS, CINCINNATI ARCH REGION 0181

Discussion. As far as can be told from examination of 

the type material, Ulrich's (Ulrich and Scofield, 1897, pi. 

62, fig. 5) description of the species is highly interpretive, as is his illustration. The types are fragmentary and 

do not retain the growth lines, so the outline of the shell 

of the species is unknown. Likewise, the nature of the 

septum is unknown. Nevertheless, the form of the specimens strongly supports their assignment to Carinaropsis. The species coil must have been very small (pi. 40, 

figs. 13, 14).

Subfamily PTEROTHECINAE Wenz, 1938

Diagnosis.— Shell with coil completely reduced, apex 

marginal and curved downward; slit developed as raised, 

hollow keel.

Stratigraphic range.— Middle Ordovician-Upper 

Silurian.

Genera included.—Pterotheca Salter, 1853; Cyclotheca Teichert, 1935.

Discussion. — This is the most advanced subfamily in 

the Carinaropsidae, having a completely reduced coil. 

The broad explanate shells and large parietal platforms 

of genera in the Pterothecinae are analogous to the 

morphology of the modern slipper limpet Crepidula, 

which leads a nearly sedentary life. This analogy suggests that species in the Pterothecinae were also sedentary, or nearly so. Species of Pterotheca are commonly 

associated with abundant leperditiid ostracodes (discussed further below), and they probably inhabited shallow lagoons and tidal flats. Based upon their paleoenvironmental occurrence and their shell form, it is generally 

believed that these animals were algal grazers, but 

deposit feeding cannot be ruled out.

Genus PTEROTHECA Salter, 1853

Diagnosis.— Shell broadly expanded, outline ovate to 

subtriangular to subquadrangular; coil completely 

reduced, apex marginal and incurved to varying degrees; 

slit in elevated dorsomedian keel; septum triangular, 

with two short, diverging prongs on upper surface at 

apex.

Description.— Many shell large (up to 50 mm long and 

wide), broadly expanded, generally wider than long, 

outline varying from ovate to subtriangular to subquadrangular; coil absent; apex marginal, incurved to varying degrees, in many cases hooklike; slit more or less 

vertical to apertural plane, generating a prominent elevated dorsomedian keel from apex to anteromedian 

apertural margin, which is generally sinuate; lateral shell 

surfaces convex, with comarginal growth lines, lamellae, 

or undulations, and in some cases with radial markings 

on either side diverging from apex along lines of attachment between ventral septum and ventral shell surface, 

thus defining a slightly elevated triangular area of dorsal

shell overlying septum; radial threads or cords unknown; 

septum triangular, proportionate size and angles variable, flat to convex-upward, with two short, diverging 

prongs at apical end in narrow space between septum 

and shell surface; space between shell dorsum and septum very narrow.

Type species. —Atrypa transversa Portlock, 1843, by 

subsequent designation of Miller (1889, p. 392).

Distribution.—Middle Ordovician (Chazyan) to Upper 

Ordovician (Richmondian) of Eastern North America 

and Europe (Great Britain, Czechoslovakia, Germany, 

Estonia).

Comparison.—Pterotheca is easily distinguished from 

similar genera by its prominent dorsomedian keel, its 

lack of a coil, its marginal incurved apex, and its large 

triangular septum with its short apical supports.

Discussion.—Species of Pterotheca have been erroneously described as brachiopods (Atrypa transversa Portlock, 1843), and the genus itself has often been classified 

with the pteropod or heteropod gastropods.

Hall (1861, p. 96-98), not knowing of the genus 

Pterotheca, Salter (1853), described a number of North 

American species under the generic name Clioderma. 

Hall (1861) did note that the species he described under 

that name were related to Carinaropsis, and that they 

were more distantly related to Bellerophon (Sphenosphaera of modern usage); thus, he recognized the ancestry and relations of the genus. Ulrich and Scofield (1897) 

also regarded Pterotheca as related to the bellerophontids, placing it with Carinaropsis in the family Carinaropsidae. Notwithstanding these views, the genus was 

still often regarded as a pteropod or heteropod by their 

contemporaries. For example, such influential workers 

as Miller (1889) and Ball (in Eastman, 1913) assigned the 

genus to the Pteropoda.

Teichert (1928), in his initial study of the genus, 

considered Pterotheca a heteropod. However, upon 

examination of better material (Teichert, 1935), he concluded that the genus was actually closely related to 

Carinaropsis, as proposed by Ulrich and Scofield (1897), 

and was therefore a bellerophontacean gastropod. 

Teichert (1935) suggested that Pterotheca had descended 

from Carinaropsis and had given rise to the genera 

Cyclotheca Teichert (1935) and Aspidotheca Teichert 

(1935) (Silurian and Devonian, respectively). I agree 

with Teichert's opinion on the ancestry of Pterotheca, 

and that Cyclotheca evolved from a species of Pterotheca; 

however, the genera Aspidotheca and Pedasiola Spriesterbach (1919) seem to have developed along a line of 

evolution separate from the Carinaropsinae. Pterotheca 

and Cyclotheca are characterized by shells having a 

marginal incurved apex, whereas Aspidotheca and Pedasiola are characterized by a distinctly submarginal elevated apex.
0182 CONTRIBUTIONS TO THE ORDOVICIAN PALEONTOLOGY OF KENTUCKY AND NEARBY STATES

Teichert (1935, fig. Ib) showed a transverse cross 

section of a Pterotheca shell with the following caption 

(translated from German): "The cross-section goes 

through the shell and septum, and shows how the shell 

rests in a cavity of the septum." If I understand 

Teichert's diagram and caption correctly, I must disagree with his interpretation. The line that Teichert 

apparently regarded as separating the shell from the 

septum is simply the line along which the septum 

attached to the ventral surface of the shell. Hall (1861, p. 

98) described this structure correctly when he stated, 

"The divergent grooves are apparently caused by the 

thickening at the junction of the ventral partition with 

the outer shell." In internal molds, these lines of attachment are represented by narrow grooves that look like 

sutures. As shown on plate 26, figures 9, 10, these 

suturelike grooves do not reach to the shell margin, but 

only the length of the septum.

Pterotheca is a genus in great need of complete restudy. Most species were named in the mid- to late 19th 

century (many by Hall, 1861), and their sketchy descriptions and poor illustrations make identifications and 

comparisons very difficult. Wilson (1951) also noted this 

difficulty, as well as the problem of poor preservation.

Foerste (1924, p. 218-220) made some instructive 

observations and comparisons concerning American and 

European species of Pterotheca. He informally divided 

the genus into two groups. The first consisted of ovate to 

subtriangular species, including P. attenuata (Hall), P. 

saffordi (Hall) (pi. 39, figs. 1-5, 13), and P. harviei 

Foerste (pi. 26, figs. 9, 10). The second group consisted 

of more subquadrate forms, whose lateral angles were 

sharper and lateral margins were more or less parallel. 

In this latter group he included P. clochensis Foerste, P. 

canaliculata (Hall), P. expansa (Emmons) (pi. 39, figs. 

10, 11), P. anatiformis (Hall), P. undulata (Hall), P. 

angusta Raymond (pi. 39, figs. 8, 9), and P. transversa 

Salter (as identified by Billings, 1866, from the Richmondian strata of Anticosti Island, Canada). Some species in 

the second group (such as P. expansa) are more ovate 

and would be better placed in the first group.

Foerste (1924) employed a taxobasis that is very useful 

for specific differentiation within Pterotheca; the angle at 

which the lateral septal margins diverge from the apex. 

He also used the angle made by the posterior shell 

margins, but this angle is less commonly preserved, as 

the shell margins of most specimens are incomplete. 

However, if growth lines are preserved, they can be 

used. The septal angle seems to be the most useful way 

to differentiate species, because it can be measured (1) 

when only the dorsal shell is preserved or exposed by 

using the radial markings along the line of septal attachment, (2) when only the septum is preserved or exposed, 

and (3) even when only internal molds are available,

because of the suturelike grooves left along lines of septal 

attachment. Where possible, the septal angle is used 

with other morphological features to distinguish species. 

Herein, comparisons were made partly from septal angle 

measurements taken from drawings in older works; such 

drawings may be highly subjective. A restudy of the 

types of all species is necessary so that both interspecific 

and intraspecific variability can be assessed.

Four species are distinguished herein. P. saffordi 

(Hall) (Blackriveran-Rocklandian) is distinguished from 

P. expansa (Emmons) (Blackriveran-Kirkfieldian) 

mainly on the basis of the angularity and abruptness of 

the dorsal keel of the former and on differences in 

ornament features; both species have a septal angle of 

about 80 degrees. P. angusta Raymond (which occurs 

with P. expansa in the USGS silicified collections from 

Kentucky) was distinguished from other species in the 

study area by its low septal angle of about 60 degrees. P. 

harviei Foerste bears a low angular keel, broad shell 

form, and septal angle of about 85 degrees. It occurs in 

the Edenian beds of Kentucky.

By analogy with Crepidula, it is likely that Pterotheca 

led a largely sedentary life. Hoagland (1977) noted that 

juvenile Crepidula are somewhat mobile, but adults are 

sedentary clingers that filter feed. The high keel of 

Pterotheca, with its more or less vertical slit, may have 

been an adaptation to a filter-feeding mode of life. 

However, it seems more likely that Pterotheca was an 

algal grazer. Pterotheca is consistently associated with 

the ostracodes Leperditia and Leperditella (identified by 

Jean Berdan, USGS) (pi. 39, figs, 5, 12,13; pi. 40, figs. 8, 

9) in the Middle Ordovician of Tennessee and Kentucky. 

This common association suggests that Pterotheca inhabited intertidal to shallow nearshore subtidal environments, possibly in waters of increased salinities (Berdan, 

1984). Gastropods living in such restricted environments 

are mostly algal grazers.

Pterotheca saffordi (Hall, 1861) 

Plate 39, figures 1-5, 13; Plate 40, figures 8, 9

Clioderma saffordi Hall, 1861, p. 96, pi. 6, figs. 15-17. 

Pterotheca (Clioderma) saffordi (Hall), Lesley, 1889, p. 821, figs. 

Pterotheca saffordi (Hall), Shimer and Shrock, 1944, p. 445, pi. 180, 

figs. 17, 18.

Diagnosis.— Shell ovate-triangular in outline; dorsomedian keel high, rising abruptly from lateral shell 

slopes, subangular crest becoming rounded through 

ontogeny; septum large, extending two-thirds the shell 

length; growth lines lamellose.

Description.— Shell moderately large (up to 49.5 mm 

long), outline ovate-triangular, length and width more or 

less equal; posterior shell margins slightly concave, 

extending into slightly protuberant beak area, diverging 

from apex at about 114 degrees; shell margins broadly
MIDDLE AND UPPER ORDOVICIAN SYMMETRICAL UNIVALVED MOLLUSKS, CINCINNATI ARCH REGION 0183

TABLE 87. Measurements (in millimeters) o/Pterotheca saffordi

Museum

No.

Hall (1861)

USNM

79262

79268

50093

Plate

6

39

39

39

Figure

15

1,2

5

13

Shell 

length

35.0

37.5

49.5

14.0

Shell 

width

44.7

34.7

50.4

14.5

Septal angle

85

77-80

85

78

Keel 

width

6.4

7.2

6.6

-

Keel 

height

6.5

11.9

9.8

-

rounded anterolaterally, having anteromedian sinus; 

dorsolateral slopes moderately arched; dorsomedian keel 

high, rising abruptly from lateral slopes, subangular 

crest becoming rounded through ontogeny; septum large 

and triangular, convex-upward, extending from apex to 

two-thirds the shell length, the lateral margins diverging 

from apex at angle of 80-85 degrees; shell surface having 

strongly lamellose comarginal growth lines.

Measurements.—Hall (1861, p. 96) stated that the 

species had a shell length of about 1.5 in (3.8 cm), with 

the width being nearly the same.

Most measurements of Pterotheca saffordi are approximate, because many of the thin shell margins are 

broken. The most reliable measurement probably is the 

septal angle, this being easily taken from photographs. 

The measurements of P. saffordi are listed in table 87. 

The row labeled "Hall (1861)" includes measurements 

taken from his plate 6, figure 15. It is obvious from these 

measurements that Hall's (1861) original figures do not 

agree well with the specimens figured here in their 

length-width proportions; however, I note that USNM 

79262 (pi. 39, figs. 1, 2) is a plaster cast of the holotype of 

P. saffordi, and it agrees favorably with other specimens 

measured. Thus, care must be taken when making 

measurements from older hand-drawn interpretive 

illustrations.

Material. The holotype was not examined. However, 

Shimer and Shrock (1944, pi. 180, figs. 17, 18) show good 

photographs of the specimen. A plaster cast of the 

holotype (USNM 79262, pi. 39, figs. 1, 2) is figured here.

A fine calcitic specimen (USNM 79268; pi. 39, figs. 3, 4) 

from the Tyrone Limestone at High Bridge, Ky., was 

found in the U.S. National Museum collections. It is 

embedded in the upper few millimeters of a small slab in 

a matrix of gray micrite, while a few millimeters beneath 

the specimen (on the other side of the slab) is an 

ostracodal biomicrite (packstone) (pi. 39, fig. 5). According to the museum label, specimen USNM 50093 (pi. 39, 

fig. 13) is from the "top of [the] Tyrone just beneath [the] 

lower bentonite beds" at High Bridge, Ky. This small 

slab is mainly micrite, but the surface is covered by a 

densely packed layer of leperditicopid ostracodes, a few 

brachiopod fragments, and a fragment of a small P. 

saffordi, all silicified. Specimen USNM 50099 (pi. 40, 

figs. 8, 9) is also from the Tyrone Limestone at High

Bridge, and occurs in association with ostracodes. Some 

of the specimens identified here as P. cf. P. expansa 

(Emmons) may actually be assignable to P. saffordi. For 

further comments about these specimens, see the discussion of P. cf. P. expansa.

Distribution.—P. saffordi was originally described 

from the Lebanon Limestone (BlackriveranRocklandian) at Lebanon, Tenn. The species is recognized here from the Tyrone Limestone (Rocklandian) of 

central Kentucky.

Comparison.—P. saffordi is distinguished mainly on 

the basis of its high, rounded dorsomedian keel, its ovate 

shell outline, and its lamellose growth lines. Wilson 

(1951, p. 33) stressed the narrow keel of P. expansa in 

distinguishing it from P. saffordi.

Foerste (1924) grouped P saffordi with P. attenuata 

(Hall) and P. harviei Foerste on the basis of their 

relatively ovate shells in comparison with other American species, which he claimed were subquadrangular in 

outline. From Chamberlin's (1883, fig. 33g) figure of P. 

attenuata, it appears that that species is in reality more 

triangular, and relatively longer than P. saffordi, and 

has a smaller septum. Foerste (1924) also stated, "P. 

harviei resembles P. saffordi most nearly in outline, but 

it is a much larger species, of less convexity, and the 

median carina is relatively narrower and less strongly 

elevated."

Discussion.-The specimen USNM 79268 (pi. 39, figs. 

3, 4) confirms the presence of P. saffordi in Kentucky. 

Specimen USNM 50093 (pi. 39, fig. 13) was just one of 

five such small slabs in a collection from the same 

locality. All of these specimens are associated with 

ostracodes, strongly suggesting a very shallow, onshore 

to nearshore habitat for the species.

Pterotheca expansa (Emmons, 1842) 

Plate 39, figures 6, 7, 10-12; Plate 40, figures 1-7

Delthyris expansus Emmons, 1842, p. 397, fig. 109, 2; Owen, 1844, p. 

368, fig. 2; 1844b, p. 84, pi. 17, fig. 14.

Clioderma expansa (Emmons), Hall, 1861, p. 98.

Pterotheca expansa (Emmons), Lesley, 1889, p. 821, fig.; Raymond, 

1902, p. 19, fig. 12; Weller, 1903, p. 179, pi. 12, fig. 35; Branson, 

1909, p. 45, pi. 7, fig. 14; Shrock and Raasch, 1937, p. 570, 571, pi. 

5, figs. 8, 9, 13; Shimer and Shrock, 1944, p. 445, pi. 180, figs. 15, 

16; Wilson, 1951, p. 33, pi. 2, figs. 19, 20; Steele and Sinclair, 1971, 

p. 20, pi. 10, figs. 5-8.
0184 CONTRIBUTIONS TO THE ORDOVICIAN PALEONTOLOGY OF KENTUCKY AND NEARBY STATES

TABLE 88. Measurements (in millimeters) o/Pterotheca expansa

Museum 

No.

USNM

79283

315534

315536

315537

Steele and Sinclair (1971)

GSC 22372

GSC 22375

Plate

39

40

40

40

10

10

Figure

6-7

6-7

1-3

4

5

8

Shell 

length

23-27

_

50-51

40-44

-

-

Shell 

width

31-32

-

58-59

51-52

-

-

Septal angle

-

82

80

80

83

80

Keel 

width

4.7

-

11.0

-

-

-

Keel 

height

7.0

-

13.0

-

-

-

Diagnosis.— Shell moderately large (up to 50 mm 

long), with broad, subovate outline; dorsomedian carina 

high, subangular at crest, basal slopes of keel gently 

concave; septum large, convex upward, septal angle 

about 80 degrees.

Description. — Shell relatively large, subovate in outline, anterior broadly rounded, posterior margins somewhat straighter; dorsum broadly convex; dorsomedian 

keel highly elevated, having gently concave basal slopes, 

crest subangular; septum large, extending from apex at 

about 80 degrees, dorsally convex; growth lines fine, 

very closely spaced.

Measurements.— Because of the fragmentary condition of available specimens of P. expansa, measurements 

are approximate. Examination of figures on plates 39 and 

40 of measured specimens will aid in understanding the 

reliability of measurements listed in table 88.

Material.—Most of Emmons' type invertebrate fossils 

have been lost (Pojeta, written commun., Dec. 1983), and 

P. expansa has no known types. The best preserved 

specimen known, which shows the greatest number of 

morphological taxobases, was illustrated by Steele and 

Sinclair (1971, PL 10, figs. 5-7) and is cataloged by the 

Geological Survey of Canada under GSC 22372. That 

specimen is herein designated the neotype.

All material studied here is from the USNM collections 

and the new USGS silicified collections. Specimens 

assigned to P. expansa include those in USGS sample 

6034-CO, such as USNM 315532 (pi. 40, fig. 5), USNM 

315533 (pi. 39, fig. 11), and USNM 315534 (pi. 40, figs. 6, 

7), and a fragment from 6134-CO (USNM 315535, pi. 39, 

fig. 10). Specimens designated P. cf. P. expansa were 

found in USGS sample 7784-CO, and include USNM 

315536 (pi. 40, figs. 1-3) and 315537 (pi. 40, fig. 4). Other 

specimens designated P. cf. P. expansa include USNM 

50100 (pi. 39, fig. 12) and 79283 (pi. 39, figs. 6, 7).

Distribution.—P. expansa has been reported from 

Blackriveran- to Kirkfieldian-age strata in New York, 

Ontario, Wisconsin, Illinois, Missouri, New Jersey, and 

herein from Kentucky. The Kentucky material is from 

the Tyrone Limestone (6034-CO) (Rocklandian), and 

from the lowest 3 ft of the Curdsville Limestone Member 

of the Lexington Limestone (7784-CO and 6134-CO)

(early Kirkfieldian). Specimen USNM 50100 (pi. 39, fig. 

12) is from the Murfreesboro Limestone (Blackriveran) 

at Murfreesboro, Tenn. Specimen USNM 79283 (pi. 39, 

figs. 6, 7) is from the Curdsville Member of the Lexington Limestone at Curdsville, Ky.

Comparison.—P. expansa was the first described 

species of the genus Pterotheca in North America. 

Emmons (1842, p. 397, fig. 109, 2) figured a drawing of an 

internal mold without a description, placing the new 

species in the brachiopod genus Delthyris. Hall (1861) 

placed the species in the Clioderma Hall, as a gastropod, 

but did not include a figure and stated only that the 

species had "great lateral expansion and a very strong 

dorsal carina" with a shell "length of more than an inch 

and three-fourths on the carina." Lesley (1889, p. 821) 

was the first to publish the species under the generic 

name Pterotheca, but did not include a description and 

used only Emmons' original figure. It should be noted 

that this original illustration shows a broad specimen 

having a septal angle of about 85-90 degrees. Raymond 

(1902) presented a new figure of the species which 

showed a septal angle of about 81 degrees and stated 

only: "This obscure fossil is figured here in hope that the 

attention of other workers will be called to it. Its 

affinities seem to be rather doubtfully understood." 

Weller (1903) figured a single fragment having a sharp 

carina and a septal angle of about 83 degrees.

The first detailed description of P. expansa was by 

Shrock and Raasch (1937, p. 571). The type specimens 

were not examined and are probably lost; instead, 

Shrock and Raasch used new material from Wisconsin 

and the quarries at Kentland, Ind. They said their 

specimens had an average width of 42 mm, an average 

length of 32 mm, and a septal angle of 78-82 degrees. 

They described the two short, diverging, ridgelike supports between the apices of the shell and the septum in 

P. expansa, which had previously been described in P. 

attenuata (Hall, 1861). These authors also used the 

distance between the lateral edge of the septum and the 

posterolateral shell margin as a taxobasis. The distance 

was said to be 7-9 mm in P. expansa, only 5 mm in P. 

attenuata, and 10 mm or more in P. intermedia Shrock. 

These authors concluded: "The angle made by the lateral
MIDDLE AND UPPER ORDOVICIAN SYMMETRICAL UNIVALVED MOLLUSKS, CINCINNATI ARCH REGION 0185

edges of the septum, the distance from the anterior and 

lateral margins of the shell to the anterior and lateral 

edges of the septum, the distance the septum reaches 

into the cavity, the general outline of the shell, and the 

convexity of the carinate exterior surface are the features which are of most value in the identification of this 

form."

Wilson (1951, p. 33) remarked that all known species of 

Pterotheca have been inadequately described and figured 

owing to poor preservation. She stated: "Pterotheca 

expansa, however, is more explanate than other forms. 

The sides of the platform make a greater angle than that 

of Pterotheca transversa. The sharp surface ridge seems 

narrower than that of Pterotheca saffordi, and the sides 

of the interior platform do not seem to be so close to the 

shell margin." Shrock and Raasch (1937) worked with 

internal and external molds, but Wilson (1951) had 

silicified shell material similar to that studied here.

Steele and Sinclair (1971, pi. 10, figs. 5-8) also 

described P. expansa from Wilson's (1951) study area in 

Ontario, and recognized the species sensu Wilson (1951). 

Their material is silicified and appears to conform exactly 

to specimens figured here as P. expansa. The form of the 

dorsal keels, the septa, and the septal angles, the presence of the apical supports, and shell markings are 

essentially identical in the Ontario and Kentucky specimens. There can be no doubt that the Kentucky specimens are P. expansa sensu Wilson, but it is uncertain if 

they are P. expansa sensu Emmons. Most of Emmons' 

types of invertebrate fossils are lost (Pojeta, written 

commun., Dec. 1983). Thus, the designation of a neotype 

for P. expansa made above solves a zoological problem 

by tying the name to a specimen and developing a 

concept for the species. For most of the time since P. 

expansa was proposed, it has been a popular name to 

affix to incomplete specimens. Now that its concept has 

been tied down (Wilson, 1951; Steele and Sinclair, 1971; 

and herein), its purported wide geographic and stratigraphic ranges can be tested.

P. expansa differs from P. attenuata (Hall), P. transversa Salter, and P. angusta Raymond by having a 

septal angle of about 80 degrees, this being 13-20 

degrees greater than in the other species. P. canaliculata (Hall) and P. undulata apparently have never been 

figured, so no comparison can be made. From Hall's 

(1847, pi. 34, fig. 7) illustration of P. anatiformis (Hall), 

that species appears to be quite broad and may be closely 

related to, or a synonym of, P. expansa (Emmons). P. 

clochensis Foerste is quite distinct in its small size and 

different outline. P. harviei has a much lower and more 

angular keel.

P. saffordi (Hall) appears to be more equidimensional 

than P. expansa, but both have a septal angle of about 

80-85 degrees, and both have high, subangular to

rounded keels. It appears that the keel of P. saffordi 

arises more abruptly from the lateral slopes (pi. 39, figs. 

3, 4), whereas the basal keel slopes of P. expansa are 

more gently concave (pi. 39, figs. 10, 11). P. saffordi 

seems to have a rather more broadly rounded abrupt keel 

throughout growth, whereas the keel of P. expansa is 

subangular through most of its ontogeny. However, as 

seen in specimen USNM 315535 (pi. 40, figs. 1-3), in 

large mature specimens of P. expansa the keel appears 

to become much broader, and is similar to that of P. 

saffordi, but such specimens of P. expansa still retain 

the gently concave basal slopes. The surface markings of 

P. saffordi were described by Hall (1861) as "lamellosestriate" (pi. 39, figs. 1^4, herein), and differ from the 

shell markings of P. expansa, which are fine, closely 

spaced growth lines (pi. 40, fig. 5; Steel and Sinclair, 

1971, pi. 10, figs. 5, 8). Although P. expansa and P. 

saffordi are similar morphologically, there are recognizable differences, which I use as species differentia.

Discussion.—If all the specimens identified as P. 

expansa or P. cf. P. expansa represent a single species, 

then this species was quite successful, ranging throughout Eastern North America from the Blackriveran to the 

Kirkfieldian Stages. Throughout this stratigraphic range 

in the present study area, P. expansa is repeatedly 

associated with leperditiid ostracod assemblages, as is P. 

saffordi. If such an association can be demonstrated to be 

characteristic of other species of Pterotheca, it would 

have an important bearing on the paleoautecologic interpretations of the taxon.

Pterotheca angusta Raymond, 1921

Plate 39, figures 8, 9 

Pterotheca angusta Raymond, 1921, p. 29, pi. 8, fig. 8.

Diagnosis. Shell relatively small (up to 24 mm long), 

with sharply angular, moderately high dorsal keel; septal 

angle about 60 degrees.

Description. — Shell relatively small for genus, ovatesubquadrangular in outline, anterolateral margins 

imperfectly known but appear to be quite obtuse; anteromedian sinus shallow; dorsomedian keel moderately 

high, with sharply angular crest and steep, flat to 

concave slopes, having an inverted V-shape; septum long 

but narrow, the sides diverging from the apex at about 

60 degrees; dorsolateral shell surface generally of low 

convexity, the greatest arching over ventral septum, so 

that margins of septum are deflected dorsally by distinct 

radial undulation on either side of shell; shell surface with 

rather widely spaced, weakly undulating, comarginal 

growth lines.

Measurements.— Raymond (1921) gave the length of 

the holotype (GSC 3266) as 16 mm, with a nearly equal 

width, and the septal angle as about 60 degrees. The
0186 CONTRIBUTIONS TO THE ORDOVICIAN PALEONTOLOGY OF KENTUCKY AND NEARBY STATES

single specimen identified here as P. angusta, USNM 

315538, measures as follows: shell length 24 mm, shell 

width 24.9 mm, maximum keel height above lateral shell 

slopes 4.5 mm, and septal angle 60 degrees.

Material.— Only one specimen was examined, USNM 

315538 (pi. 39, figs. 8, 9) from USGS silicified sample 

7784-CO from Kentucky.

Distribution.—Raymond (1921) reported the holotype 

from "the highest layers of the Cobourg at Collingwood," 

Ontario. Sweet and Bergstrom (1971) correlated the 

Coburgian strata of New York with the Edenian and 

earliest Maysvillian strata of the type Cincinnatian section of the present study area. The single specimen found 

in the USGS silicified samples from Kentucky is from the 

basal 2 ft of the Curdsville Limestone Member of the 

Lexington Limestone (early Kirkfieldian) (7784-CO).

Comparison. — This species is immediately separable 

fromother species of the study area by its narrow septal 

angle of about 60 degrees and its very narrow, sharply 

angular dorsomedian keel (pi. 39, figs. 8, 9).

The only other species of Pterotheca that has a comparatively low septal angle is P. attenuata, that also 

being about 60 degrees. Hall (1861), in discussing P. 

attenuata (Hall), stated, "This species closely resembles 

P. canaliculata in form, but has no depressions of the 

shell parallel to the sides, and the surface is apparently 

less distinctly striated." There are no known illustrations 

of P. canaliculata (Hall) for comparison with P. attenuata, but the differences stated by Hall are probably due 

to preservation, and the two species names may be 

synonyms. In any case, P. attenuata is probably closely 

related to P. angusta, as shown by their common possession of extremely acute septal angles.

Discussion. This report of P. angusta from the Kirkfieldian strata of Kentucky is only the second known 

occurrence of the species. The two occurrences are 

widely separated geographically and stratigraphically, 

the first being in the latest Edenian or earliest Maysvillian of Ontario, but the diagnostic morphologic features 

of the two specimens are in close agreement.

Pterotheca harviei Foerste, 1924

Plate 26, figures 9, 10 

Pterotheca harviei Foerste, 1924, p. 219, pi. 26, fig. 6.

Diagnosis.— Shell large (up to 60 mm long), broadly 

ovate in outline; dorsomedian keel of moderate height, 

with sharply angular crest and flat slopes; septal angle 

about 85 degrees; shell surface marked by broadly 

rounded, gently undulating rugose growth increments.

Description.— Shell relatively large, broadly ovatesubtriangular in outline, with moderately low convexity; 

anterolateral margins broadly rounded, posterolateral 

margins nearly straight but slightly convex; beak area

not particularly protuberant but moderately incurved; 

median sinus fairly deep; dorsomedian keel of moderate 

height, but rather low compared with width of shell, with 

sharply angular crest and flat slopes having inverted 

V-shape; septum large, lateral margins diverging from 

apex at about 85 degrees and curving outward slightly; 

shell surface marked by low but distinct, broad, comarginal rugae.

Measurements.—Foerste (1924) gave the following 

approximate measurements for the species: shell length 

60 mm, shell width 75 mm, length of lateral margins of 

septum 40 mm, and septal angle 98 degrees. This measurement of the septal angle appears to be in error, as the 

septal angle of the holotype on his plate 26, figure 6, 

measures about 85 degrees.

The single specimen examined here also yields only 

approximate measurements: shell length 31 mm, shell 

width 50 mm, length of lateral septum margins 28 mm, 

and septal angle 85 degrees.

Material. The specimen identified here as P. harviei, 

USNM 50092 (pi. 26, figs. 9, 10), is a composite mold, 

possibly retaining some shell and coated by a thin, 

resistant, glossy layer that probably consists mainly of 

residual organic matter. As Wilson (1951) pointed out, 

the line of attachment of the septum with the shell is a 

thickening of the shell, which leaves a narrow groove on 

internal molds, such as seen in this specimen. The 

specimen is embedded in gray micrite.

Distribution.—Foerste (1924) originally described P. 

harviei from "two miles northwest of St. Hughes on 

Yamaska, in the Cryptolithus zone of the Lorraine 

Formation," in Ontario, Canada. The specimen figured 

here is from the Kope Formation at Covington, Ky. 

Both occurrences are Edenian in age (lower Upper 

Ordovician).

Comparison.— The Kentucky specimen agrees well 

with the holotype of P. harviei (as figured by Foerste, 

1924, p. 219, pi. 26, fig. 6), the two having shell length- 

/width ratios of 1.29 and 1.25, respectively, septal angles 

of about 85 degrees, and similar shell outlines and keel 

forms. Foerste (1924) stated, "P. harviei resembles P. 

saffordi most nearly in outline, but is a much larger 

species, of less convexity, and the median carina is 

relatively narrower and less strongly elevated."

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Systematic Association Special Volume 12 (Academic Press, London and New York), p. 323-358. 

-1984, Historic and current considerations for revision of Paleozoic gastropod classification: Journal of Paleontology, v. 58, no. 1, 

p. 259-269.

Yochelson, E.L., Flower, R.H., and Webers, G.L., 1973, The bearing 

of the new Late Cambrian monoplacophoran genus Knightoconus 

upon the origin of the Cephalopoda: Lethaia, v. 6, no. 3, p. 

275-309.

Yonge, C.M., 1947, The pallial organs in aspidobranch Gastropoda and 

their evolution throughout the Mollusca: Philosophical Transactions of Royal Society of London, Series B233, p. 433-518.

————1973, Observation of the pleurotomarid Entemnotrochus adansoniana in its natural habitat: Nature, v. 241, no. 5384, p. 66-68.
0196 CONTRIBUTIONS TO THE ORDOVICIAN PALEONTOLOGY OF KENTUCKY AND NEARBY STATES

APPENDIX: LOCALITY REGISTER

During the geologic mapping of the State of Kentucky 

by the Kentucky and U.S. Geological Surveys, Ordovician fossils were collected from nearly 1,100 localities. 

Pojeta (1979, p. A19-A46) listed 317 of these localities 

from which Ordovician fossils were collected and studied. 

Coordinates for the localities use the system of Pojeta 

(1979, p. A19). Below is a list of the USGS localities from 

which the fossils studied for this report were collected. 

The localities are arranged sequentially by collection 

number assigned to each in the USGS register of Cambrian and Ordovician localities (-CO). The following 

abbreviations are used in this locality listing for convenience: C.n., Collection number; G.I., Geographic location; C., Coordinates; F., Formation; S.p., Stratigraphic 

position; Q.n., 7.5 min quadrangle name; S.n., Section 

name; S.no., Section number. Not all localities have 

information in all categories. Do., ditto.

U.S. GEOLOGICAL SURVEY LOCALITIES

C.n. - 4073-CO.

G.I. — Proceed east from Milner, Ky., 0.75 mi and turn 

right (southwest) on Shryock Ferry Road. Continue down Shryock Ferry Road about 1 mi to top 

of section.

C. — 153 mm east, 99 mm north (base of section at 134 

mm east, 87 mm north).

F. — Grier Limestone Member, Lexington Limestone.

S.p. — 148 ft above base of Curdsville Limestone Member, 

Lexington Limestone.

Q.n. — Tyrone, Ky.

S.n. — Tyrone A.

S.no. - 89.

C.n. - 4852-CO.

G.I. — Section along Interstate 75, 1.4 mi south of George­ 

	town, Ky., exit.

C. — 364 mm east, 321 mm north.

F. — Grier Limestone Member, Lexington Limestone.

S.p. — 25 ft below top of Grier Limestone Member.

Q.n. — Georgetown, Ky.

S.n — Georgetown A.

S.no. - 151.

C.n. - 4865-CO.

G.I. — U.S. Route 62 at crossing of Kentucky River; from 

east side of Blackburn Memorial Bridge, take side 

road north 0.1 mi to railroad roadcut exposure.

C. — Base of section at 108 mm east, 197 mm north.

F. — Logana Member, Lexington Limestone.

S.p. — Lower 12 ft of Logana Member.

Q.n. — Tyrone, Ky.

S.n. - Tyrone C, or Ky. Utilities Plant.

S.no. - 174.

C.n. - 4874-CO.

G.I. — Road exposures between Trinity Church and Antioch Church, southwest quadrant, Valley View 

quadrangle, Kentucky, 1 mi southwest of north­

	ern termination of Kentucky Route 595 at Ken­ 

	tucky River.

C. — Base of section at 19 mm east, 176 mm north.

F. — Grier Limestone Member, Lexington Limestone.

S.p — 30 ft above base of section.

Q.n. — Valley View, Ky.

S.n. — Valley View C (Antioch Church Road).

S.no. - 180.

C.n. - 4876-CO.

G.l. - Name as for 4874-CO.

C. - Do.

F. — Grier Limestone Member, Lexington Limestone.

S.p. — 35 ft above base of section.

Q.n. — Valley View, Ky.

S.n. - Valley View C (Antioch Church Road).

S.no. - 180.

C.n. - 4879-CO.

G.I. - Same as for 4874-CO.

C. - Do.

F. — Grier Limestone Member, Lexington Limestone.

S.p. — 43-45 ft above base of section.

Q.n. — Valley View, Ky.

S.n. - Valley View C (Antioch Church Road).

S.no. - 180.

C.n. - 4880-CO.

G.L - Same as for 4874-CO.

C. - Do.

F. — Grier Limestone Member, Lexington Limestone.

S.p. — 47 ft above base of section.

Q.n. — Valley View, Ky.

S.n. - Valley View C (Antioch Church Road).

S.no. - 180.

C.n. - 4883-CO.

G.L - Same as for 4874-CO.

p. - Do.

F. — Grier Limestone Member, Lexington Limestone.

S.p. — 60.5 ft above base of section.

Q.n. — Valley View, Ky.

S.n. - Valley View C (Antioch Church Road).

S.no. - 180.

C.n. - 4928-CO.

G.I. — Road exposure 0.5 mi east and 1.6 mi south of 

	northwestern corner of Sal visa quadrangle, Ken­ 

	tucky.

C. — 32 mm east, 467 mm north.

F. — Grier Limestone Member, Lexington Limestone.

S.p. — 22 ft below base of Brannon Member, Lexington 

	Limestone.

Q.n. — Salvisa, Ky.

S.n. — Salvisa A.

S.no. - 175.

C.n. - 4929-CO.

G.I. - Same as for 4928-CO.

C. - Do.

F. — Grier Limestone Member, Lexington Limestone.

S.p. — 8 ft below base of Brannon Member, Lexington

	Limestone.

Q.n. — Salvisa, Ky.

S.n. — Salvisa A.
MIDDLE AND UPPER ORDOVICIAN SYMMETRICAL UNIVALVED MOLLUSKS, CINCINNATI ARCH REGION 0197

S.no. - 175.

C.n. - 4940-CO.

G.I. — Road exposure on western side of Kentucky River 

at bridge crossing of Central Kentucky Parkway 

on northern side of parkway.

C. — Base of section at 186 mm east, 508 mm north.

F. — Curdsville Limestone Member, Lexington Limestone.

S.p. — 7 ft above top of Tyrone Limestone.

Q.n. - Salvisa, Ky.

S.n. — Salvisa B.

S.no. - 176.

C.n. - 4959-CO.

G.I. - Same as for 4940-CO.

C. - Do.

F. — Grier Limestone Member, Lexington Limestone.

S.p. — 149-152 ft above top of Tyrone Limestone.

Q.n. — Salvisa, Ky.

S.n. — Salvisa B.

S.no. - 176.

C.n. - 5015-CO.

G.I. — Quarry exposure 0.4 mi south of Perry ville, Ky., on 

eastern side of Mitchellsburg Road, eastern side 

of Chaplin River.

C. — 191 mm east, 92 mm north.

F. — Salvisa Bed, Perryville Limestone Member, Lexington Limestone.

S.p. — 5 ft above base of Salvisa Bed.

Q.n. — Perryville, Ky.

S.n. — Perryville B (Perryville South)

S.no. - 30 B.

C.n. - 5016-CO.

G.I. - Same as for 5015-CO.

C. - Do.

F. — Cormshville Bed, Perryville Limestone Member, 

Lexington Limestone.

S.p. — 14 ft above base of Salvisa Bed, Perryville Limestone Member, Lexington Limestone.

Q.n. — Perryville, Ky.

S.n. — Perryville B (Perryville South).

S.no. - SOB.

C.n. - 5022-CO.

G.I. — Section in quarry and road exposures near Clear 

Creek, 0.2 mi east and 2.5 mi south of northwestern corner of Keene quadrangle, Kentucky.

C. — Base of section at 21 mm east, 326 mm north.

F. — Curds ville Limestone Member, Lexington Limestone.

S.p. — Float from lower 22 ft of Curdsville Limestone 

Member.

Q.n. — Keene, Ky.

S.n. — Keene A.

S.no. - 150.

C.n. - 5023-CO. 

G.I. - Same as for 5022-CO. 

C. - Do.

F. — Curdsville Limestone Member, Lexington Limestone.

S.p. — 30 ft above base of Curdsville Limestone Member.

Q.n. - Keene, Ky.

S.n. — Keene A.

S.no. - 150.

C.n. - 5024-CO.

G.I. - Same as for 5022-CO.

C. - Do.

F. — Logana Member, Lexington Limestone.

S.p. — Float from lower Logana Member.

Q.n. - Keene, Ky.

S.n. — Keene A.

S.no. - 150.

C.n. - 5036-CO.

G.I. — Small stream exposure on Squires Road, 1.8 mi

southwest of intersection with U.S. Route 421

(upstream 0.1 mi).

C. — 151 mm east, 494 mm north. 

F. — Devils Hollow Member, Lexington Limestone. 

S.p. — 60 ft above base of Brannon Member, Lexington

Limestone. 

Q.n. — Coletown, Ky.

C.n. - 5067-CO.

G.I. — Hillside pasture exposure on western side of U.S. 

Route 227, 0.4 mi south of intersection of FordHampton Road and U.S. 227, north of Ford, Ky.

C. — 423 mm east, 187 mm north.

F. — Grier Limestone Member, Lexington Limestone.

S.p. — 140 ft above top of Tyrone Limestone.

Q.n. - Ford, Ky.

C.n. - 5072-CO.

G.I. — Immediately behind Old Crow Distillery, northern 

bluff of Glenns Creek Road, 0.7 mi west of 

intersection with Hanley Lane.

C. — 107 mm east, 102 mm north.

F. — Lower Lexington Limestone; mostly basal Curdsville Limestone Member, but with some float 

blocks of Logana Member included in sample.

Q.n. - Frankfort East, Ky.

S.n. - Frankfort East B.

S.no. - 87.

C.n. - 5073-CO.

G.I. — Northwest of Old Crow Distillery on first sharp

north bend of Glenns Creek Road, 0.9 mi west of

intersection with Hanley Lane. 

C. — 82 mm east, 111 mm north. 

F. — Upper Logana Member, Lexington Limestone. 

S.p. — Just below 4-ft-thick dalmanellid coquina. 

Q.n. - Frankfort East, Ky. 

S.n. - Frankfort East B. 

S.no. - 87.

C.n. - 5074-CO.

G.I. — Small quarry on western side of Tates Creek Pike,

north of Gainesway, Ky., and 2 mi south of

intersection with Cooper Road. 

C. — 15.5 mm east, 545 mm north. 

F. — Grier Limestone Member, Lexington Limestone. 

S.n. — Tates Creek Rd. quarry.
0198 CONTRIBUTIONS TO THE ORDOVICIAN PALEONTOLOGY OF KENTUCKY AND NEARBY STATES

C.n. 

G.I.

C.

F.

S.p.

Q.n.

C.n. 

G.I.

C.

F.

Q.n. -

C.n. - 

G.I. -

C.

F. -

S.p. -

Q.n. -

S.n. -

S.no. -

C.n. - 

G.I. - 

C. 

F.

S.p. -

Q.n. -

S.n. -

S.no. -

C.n. -

G.I. - 

C.

F. -

S.p. -

Q.n. -

S.n. -

S.no. -

C.n. - 

G.I. -

C.

F. -

Q.n. -

C.n. - 

G.I. -

C.

F. - 

S.p. - 

Q.n. -

5075-CO.

2d Quarry, Jessamine Creek, southeast of Wilmore,

Ky.

372 mm east, 425.5 mm north. 

Tyrone Limestone. 

Tyrone Limestone. 

Wilmore, Ky.

5080-CO.

First crossing of Southern Railroad tracks by 

unnamed road running due south from two rightangle turns in Kentucky Route 342, 1.2 mi west of 

Herrington Lake spillway.

88 mm east, 158 mm north.

Upper part of Curdsville Limestone Member, Lexington Limestone.

Wilmore, Ky.

5084-CO.

From eastern side of Blackburn Memorial Bridge 

crossing Kentucky River, take first road north 

toward Kentucky Utilities Plant; section in railroad and road exposures.

108 mm east, 214 mm north (railroad exposures).

Curdsville Limestone Member, Lexington Limestone.

5 ft above base of Curdsville Limestone Member.

Tyrone, Ky.

Tyrone C, or Ky. Utilities Plant.

174.

5085-CO

Same as for 5084-CO. 

Do.

Curdsville Limestone Member, Lexington Limestone.

16 ft above Tyrone-Lexington contact. 

Tyrone, Ky.

Tyrone C, or Ky. Utilities Plant. 

174.

5086-CO.

Same as for 5084-CO.

Do.

Logana Member, Lexington Limestone.

18-20 ft above base of Logana Member.

Tyrone, Ky.

Tyrone C.

174.

5087-CO.

Small road exposure on U.S. Route 421, 0.5 mi east

of U.S. Routes 60 and 421 junction. 

242 mm east, 287 mm north. 

Upper part of Devils Hollow Member, Lexington

Limestone. 

Frankfort East, Ky.

5091-CO.

Behind Old Stagg Distillery, north of lock 4

Kentucky River. 

3.5 mm east, 434 mm north. 

Logana Member, Lexington Limestone. 

20 ft above base of Logana Member. 

Frankfort East, Ky.

on

S.n. — Stagg Distillery.

C.n. - 5092-CO.

G.I. - Same as for 5084-CO.

C. — 108 mm east, 197 mm north.

F. — Logana Member, Lexington Limestone.

S.p. — 10-12 ft above base of Logana Member.

Q.n. — Tyrone, Ky.

S.n. - Tyrone C, or Ky. Utilities Plant.

S.no. - 174.

C.n. - 5094-CO.

G.I. — Roadcuts along Devils Hollow Road, 0.7 mi south of

	Buttimer Hill.

C. — 411 mm east, 318 mm north.

F. — Grier Limestone Member, Lexington Limestone.

S.p. — Float 45 ft above Macedonia Bed.

Q.n. - Frankfort West, Ky.

S.n. — Devils Hollow Road.

C.n. - 5095-CO.

G.I. — Road exposure on northern side of westbound lanes

of Interstate 64, 0.5 mi east of bridge over

Kentucky River.

C. — 123 mm east, 195 mm north. 

F. — Devils Hollow Member, Lexington Limestone. 

S.p. — 6-8 ft above base of Devils Hollow Member. 

Q.n. - Frankfort East, Ky. 

S.n. - Frankfort East A. 

S.no. - 86.

C.n. - 5096-CO.

G.I. — Just before ferry crossing of Tates Creek Road and 

Kentucky River, take road west toward Daniel 

Boone YMCA Camp; collection from near top of 

northern bluff of Kentucky River, 0.4 mi southeast of YMCA Camp, in abandoned railroad bed.

C. — 151 mm east, 432 mm north.

F. — Grier Limestone Member, Lexington Limestone.

Q.n. — Valley View, Ky.

C.n. - 5099-CO.

G.I. — Roadcuts along Hunters Ferry Road, 0.85 mi north­ 

	east of Trinity Church. 

C. — 54 mm east, 262 mm north. 

F. — Grier Limestone Member, Lexington Limestone. 

S.p. — 78-80 ft above base of section. 

Q.n. — Valley View, Ky. 

S.n. — Hunters Ferry Road (Valley View B). 

S.no. - 34.

C.n. - 5100-CO.

G.I. — Crisman Mill Road, 0.2 mi west of Hickman Creek 

crossing.

C. — 411 mm east, 451 mm north.

F. — Lower part of Curdsville Limestone Member, Lexington Limestone.

Q.n. — Little Hickman, Ky.

S.n. — Little Hickman B.

C.n. - 5101-CO.

G.I. — Kentucky Route 169 just west of Hickman Creek

crossing. 

C. — 398 mm east, 81 mm north.
MIDDLE AND UPPER ORDOVICIAN SYMMETRICAL UNIVALVED MOLLUSKS, CINCINNATI ARCH REGION 0199

F. 

Q.n.

C.n. 

G.I.

C. 

F. 

Q.n.

C.n. 

G.I.

C.

F. 

S.p. 

Q.n. 

S.n.

C.n. 

G.I. 

C.

F. 

S.p. 

Q.n. 

S.n.

C.n. 

G.I.

C. 

F. 

Q.n.

C.n. 

G.I.

C.

F.

S.p. -

Q.n. -

C.n. -

G.I. -

C.

F.

S.p. 

Q.n. 

C.n.

Lower part of Curdsville Limestone Member, Lexington Limestone. 

Nicholasville, Ky.

5107-CO.

Hillside exposure in farm road leading south from 

U.S. Route 60, just west of Keeneland Racetrack; 

collected at 900-ft contour.

43 mm east, 194 mm north.

Grier Limestone Member, Lexington Limestone.

Lexington West, Ky.

6034-CO.

Section on New Watts Mill Road, 0.1 mi southwest

of intersection with Kentucky Route 39. 

Base of section at 260 mm east, 346 mm north. 

Tyrone Limestone. 

112 ft above base of section. 

Little Hickman, Ky. 

Little Hickman A.

6035-CO.

Same as for 6034-CO.

Do.

Tyrone Limestone.

89-94 ft above base of section.

Little Hickman, Ky.

Little Hickman A.

6127-CO.

Southernmost tributary of Landing Run, 2,000 ft 

east of intersection of U.S. Route 31E and Kentucky Route 46, between Balltown and Culvertown, Ky.

381 mm east, 436 mm north.

Rowland Member, Drakes Formation.

New Haven, Ky.

6128-CO.

Outcrop at farm pond 2,000 ft west of intersection of 

Mt, Horeb and Carrick Roads, 1,000 ft north of 

Carrick Road.

183 mm east, 387 mm north.

Tongue of Clays Ferry Formation between underlying Millersburg Member, Lexington Limestone, and overlying Tanglewood Limestone 

Member, Lexington Limestone.

5-10 ft above base of Clays Ferry Formation 

tongue, 15-20 ft above Allonychia flanaganesis 

zone in Millersburg Member.

Centerville, Ky.

6131-CO.

Section on Kentucky Route 33 just north of bridge 

crossing of Mocks Branch, 2.5 mi north of Danville, Ky.

405 mm east, 307 mm north.

Upper part of Curdsville Member, Lexington Limestone.

23 ft above Tyrone Limestone-Lexington Limestone contact.

Danville, Ky.

- 6134-CO.

G.I. — Road exposures 0.2 mi west of Dix River crossing of 

Kentucky Route 52.

C. — 315 mm east, 78 mm north.

F. — Curdsville Limestone Member, Lexington Limestone.

S.p. — Lower 3 ft of Curdsville Limestone Member.

Q.n. — Bryantsville, Ky.

S.n. — Bryantsville D.

C.n. - 6136-CO.

G.I. — Roadcut on Kentucky Route 52, 1.45 mi east of 

junction with U.S. Route 150; 0.15 mi east of 

crossing of Kentucky Route 52 and Balls Branch 

Run.

C. — 74 mm east, 35 mm north.

F. — Faulconer Bed, Perryville Limestone Member, 

Lexington Limestone.

S.p. — Basal 3-4 ft of Perryville Limestone Member, 

immediately above Tanglewood Limestone Member, Lexington Limestone.

Q.n. — Bryantsville, Ky.

S.n. — Bryantsville B.

C.n. - 6138-CO.

G.I. - Same as for 6136-CO.

C. - Do.

F. — Cornishville Bed, Perryville Limestone Member,

Lexington Limestone. 

S.p. — 16 ft above Perryville Limestone MemberTanglewood Limestone Member contact. 

Q.n. — Bryantsville, Ky. 

S.n. — Bryantsville B.

C.n. - 6139-CO.

G.I. — Southern bank of Salt Creek, 900 ft upstream from

covered bridge on Enochsburg-Oldenburg (Ind.)

Road.

C. — 328 mm east, 378 mm north. 

F. — Upper part of Dillsboro Formation. 

Q.n. — New Point, Ind.

C.n. - 6140-CO.

G.I. — Northern bank of Salt Creek, 0.4 mi upstream from

covered bridge on Enochsburg-Oldenburg (Ind.)

Road.

C. — 315 mm east, 380 mm north. 

F. — Upper part of Dillsboro Formation. 

Q.n. — New Point, Ind.

C.n. - 6142-CO.

G.I. — Road exposure on eastern side of Kentucky Route 

982, 0.4 mi south of junction of Kentucky Routes 

32, 36, and 982 in Cynthiana, Ky. (across from 

River View Mission and Liggett and Meyers 

tobacco warehouse).

C. — 290 mm east, 39 mm north.

F. — Lower tongue of Clays Ferry Formation.

S.p. — 18-20 ft above base of section.

Q.n. — Cynthiana, Ky.

C.n. - 6143-CO.

G.I. - Same as for 6142-CO.

C. - Do.

F. — Upper tongue of Clays Ferry Formation.

S.p. — 30-35 ft above base of section.
0200 CONTRIBUTIONS TO THE ORDOVICIAN PALEONTOLOGY OF KENTUCKY AND NEARBY STATES

Q.n. — Cynthiana, Ky.

C.n. - 6144-CO.

G.I. - Same as for 6142-CO.

C. - Do.

F. — Base of upper tongue of Millersburg Member, Lex-

	ington Limestone.

S.p. — 24 ft above base of section.

Q.n. — Cynthiana, Ky.

C.n. - 6145-CO.

G.I. — Kentucky Route 8, 1 mi south of Carntown, Ky.

C. — 28 mm east, 326 mm north.

F. — Point Pleasant Tongue, Clays Ferry Formation.

S.p. — About 50 ft below base of Kope Formation.

Q.n. — Moscow, Ohio-Kentucky.

C.n. - 6411-CO.

G.I. — U.S. Route 27, 0.1 mi northeast of crossing of Dix

	River.

C. — 42.5 mm east, 342 mm north.

F. — Gilbert Member, Ashlock Formation.

S.p. — 5 ft above base of Gilbert Member.

Q.n. — Lancaster, Ky.

S.n. — Ashlock Cemetery.

S.no. - 21 B.

C.n. - 6412-CO.

G.I. - Same as for 6411-CO.

C. - Do.

F. — Gilbert Member, Ashlock Formation.

S.p. — 11.5 ft above base of Gilbert Member.

Q.n. — Lancaster, Ky.

S.n. — Ashlock Cemetery.

S.no. - 21 B.

C.n. - 6414-CO.

G.I. — Exposures of Kentucky Route 21, 0.9 mi south of

junction of Walnut Meadow Branch and Paint

Lick Creek.

C. — 18 mm east, 372 mm north. 

F. — Gilbert Member, Ashlock Formation. 

S.p. — 1-2-ft silicified zone at top of Gilbert Member. 

Q.n. — Berea, Ky.

C.n. - 6419-CO.

G.I. — 1.4 mi east of Wilmore, Ky., 500 ft north of main 

road.

C. — 420 mm east, 534 mm north.

F. — Lower part of Logana Member, Lexington Limestone.

Q.n. — Wilmore, Ky.

C.n. - 6915-CO.

G.I. — Boyle County quarry, western side of U.S. Route 

68, 1.3 mi northeast of Perryville, Ky.

C. — p!7 mm east, 176 mm north.

F. — Salvisa Bed, Perryville Limestone Member, Lexington Limestone.

S.p. — Basal 2 ft of Salvisa Bed; northwestern wall of 

quarry.

Q.n. — Perryville, Ky.

S.n. — Perryville A (Perryville North).

S.no. - 30 A.

C.n. - 6916-CO.

G.I. - Same as for 6915-CO.

C. - Do.

F. — Salvisa Bed, Perryville Limestone Member, Lexington Limestone.

S.p. — Same as for 6915-CO, but from eastern wall of 

quarry.

Q.n. — Perryville, Ky.

S.n. — Perryville A (Perryville North).

S.no. - 30 A.

C.n. - 6990-CO.

G.I. - Western side of U.S. Route 27, 1,700 ft from 

highway, 0.9 mi south of Lair, Ky.

C. — 245 mm east, 369 mm north.

F. — Top of tongue of Clays Ferry Formation, which lies 

between a lower tongue of Millersburg Member, 

Lexington Limestone, and an upper tongue of 

Tanglewood Limestone Member, Lexington 

Limestone.

S.p. — 60 ft above top of Grier Limestone Member, Lexington Limestone.

Q.n. — Shawhan, Ky.

S.n. — Section at White Farm.

C.n. - 7044-CO.

G.I. — 0.7 mi southwest of junction of Kentucky Route 974 

and Dry Fork Road on Dry Fork Road. Section 

begins in valley of East Fork of Fourmile Creek 

in Tanglewood Limestone Member, Lexington 

Limestone, just below Allonychia flanaganesis 

zone of Millersburg Member, Lexington Limestone. Main part of section is north of East Fork, 

along Dry Fork Road above 823-ft elevation 

mark.

C. — Base of section at 394 mm east, 268 mm north.

F. — Tongue of Clays Ferry Formation.

S.p. — 25 ft above Allonychia flanaganesis horizon.

Q.n. — Winchester, Ky.

S.n. — Winchester A (Dry Fork Road).

S.no. - 1004.

C.n. - 7343-CO.

G.I. - Same as for 6990-CO.

C. - Do.

F. — Top of tongue of Clays Ferry Formation, which lies 

between a lower tongue of Millersburg Member, 

Lexington Limestone, and an upper tongue of 

Tanglewood Limestone Member, Lexington 

Limestone:

S.p. — 60 ft above top of Grier Limestone Member, Lexington Limestone.

Q.n. — Shawhan, Ky.

S.n. — Section at White Farm.

C.n. - 7344-CO.

G.I. - Eastern side of U.S. Route 27, 900 ft from highway,

0.4 mi north of Lair, Ky. 

C. — 246 mm east, 439 mm north. 

F. — Near top of lower tongue of Millersburg Member,

Lexington Limestone. 

Q.n. — Shawhan, Ky.
MIDDLE AND UPPER ORDOVICIAN SYMMETRICAL UNIVALVED MOLLUSKS, CINCINNATI ARCH REGION 0201

C.n. - 7345-CO.

G.I. - Same as for 6142-CO.

C. - Do.

F. — Lower tongue of Clays Ferry Formation.

S.p. — 20-22 ft above base of section.

Q.n. — Cynthiana, Ky.

C.n. - 7348-CO.

G.I. - 4,300 ft east and 6,300 ft south of northwestern 

	corner of Shawhan quadrangle.

C. — 54 mm east, 493 mm north.

F. — Tongue of Clays Ferry Formation underlain by 

	tongue of Millersburg Member, Lexington Lime­ 

	stone, and overlain by tongue of Tangle wood 

	Limestone Member, Lexington Limestone.

S.p. - Float, 4 ft above 810-foot contour.

Q.n. — Shawhan, Ky.

C.n. - 7349-CO.

G.I. - Same as for 7348-CO.

C. - Do.

F. - Do.

S.p. — Float, 5 ft above 810-ft contour.

Q.n. — Shawhan, Ky.

C.n. - 7350-CO.

G.I. - Same as for 7348-CO.

C. - Do.

F. - Do.

S.p. — Float, 6 ft above 810-foot contour.

Q.n. — Shawhan, Ky.

C.n. - 7353-CO.

G.I. — 1 mi northeast of junction of Cook Road and Lair

	Road in stock pond.

C. — 428 mm east, 471 mm north.

F. — Lower tongue of Millersburg Member, Lexington

	Limestone. 

Q.n. — Shawhan, Ky.

C.n. - 7450-CO.

G.I. — Section along road to U.S. Route 25, 0.4 mi west of

	Sadieville, Ky.

C. — Base of section at 295 mm east, 63 mm north.

F. — Tongue of Clays Ferry Formation.

S.p. — 5 ft above base of section.

Q.n. - Sadie ville, Ky.

S.n. - Sadie ville C.

S.no. - 192.

C.n. - 7452-CO.

G.I. - Same as for 7450-CO.

C. - Do.

F. — Tongue of Clays Ferry Formation.

S.p. — 10 ft above base of section.

Q.n. - Sadie ville, Ky.

S.n. - Sadieville C.

S.no. - 192.

C.n. - 7454-CO.

G.I. - Same as for 7450-CO.

C. - Do.

F. — Millersburg Member, Lexington Limestone.

S.p. — 20 ft above base of section.

Q.n. - Sadieville, Ky.

S.n. - Sadieville C.

S.no. — 192.

C.n. - 7455-CO.

p.L - Same as for 7450-CO.

C. - Do.

F. — Millersburg Member, Lexington Limestone.

S.p. — 22 ft above base of section.

Q.n. - Sadieville, Ky.

S.n. - Sadieville C.

S.no. - 192.

C.n. - 7457-CO.

G.I. - Same as for 7450-CO.

C. - Do.

F. — Millersburg Member, Lexington Limestone.

S.p. — 32 ft above base of section.

Q.n. - Sadieville, Ky.

S.n. - Sadieville C.

S.no. - 192.

C.n. - 7458-CO.

G.I. - Same as for 7450-CO.

C. - Do.

F. — Tongue of Clays Ferry Formation.

S.p. — 35 ft above base of section.

Q.n. — Sadieville, Ky.

S.n. - Sadieville C.

S.no. - 192.

C.n. - 7461-CO.

G.I. - Same as for 7450-CO.

C. - Do.

F. — Tongue of Clays Ferry Formation.

S.p. — 50-55 ft above base of section.

Q.n. - Sadieville, Ky.

S.n. - Sadieville C.

S.no. - 192.

C.n. - 7782-CO.

G.I. - Same as for 5084-CO.

C. - Do.

F. — Curdsville Limestone Member, Lexington Lime­ 

	stone.

S.p. — Lower 5 ft of Curdsville Limestone Member.

Q.n. — Tyrone, Ky.

S.n. — Tyrone C, or Ky. Utilities Plant.

S.no. - 174.

C.n. - 7783-CO.

G.I. — Southern side of westbound lanes of Interstate 64,

	0.5 mi south of bridge across Kentucky River. 

C. — 123 mm east, 195 mm north. 

F. — Top bed, upper tongue of Tanglewood Limestone

	Member, Lexington Limestone. 

S.p. — Tanglewood Limestone Member, just below Devils

	Hollow Member, Lexington Limestone. 

Q.n. - Frankfort East, Ky. 

S.n. - Frankfort East A. 

S.no. - 86.
0202 CONTRIBUTIONS TO THE ORDOVICIAN PALEONTOLOGY OF KENTUCKY AND NEARBY STATES

C.n. - 7784-CO.

G.I. — U.S. Route 27, 0.3 mi southeast of crossing of 

Kentucky River bridge on southern side of road.

C. — 41 mm east, 75 mm north.

F. — Curdsville Limestone Member, Lexington Limestone.

S.p. — Basal 2 ft of Curdsville Limestone Member.

Q.n. — Little Hickman, Ky.

C.n. - 7785-CO.

G.I. - Same as for 7784-CO.

C. - Do.

F. — Curdsville Limestone Member, Lexington Limestone.

S.p. — 11-12 ft above base of Curdsville Limestone Member.

Q.n. — Little Hickman, Ky.

C.n. - 7787-CO.

G.I. — Southern side of westbound lanes of Interstate 64,

about 0.8 mi east of bridge over Kentucky River. 

C. — 123 mm east, 195 mm north. 

F. — Top bed of upper tongue of Tanglewood Limestone

Member, Lexington Limestone. 

Q.n. - Frankfort East, Ky. 

S.n. - Frankfort East A. 

S.no. - 86.

C.n. - 7789-CO.

G.I. — Northern and southern sides of eastbound lanes of

Interstate 64, 0.8 mi east of Kentucky River. 

C. — 123 mm east, 195 mm north. 

F. — Upper part of Devils Hollow Member, Lexington

Limestone.

Q.n. - Frankfort East, Ky. 

S.n. - Frankfort East A. 

S.no. - 86.

C.n. - 7791-CO.

G.I. - Same as for 4940-CO.

C. - Do.

F. — Lower part of Logana Member, Lexington Limestone.

S.p. — 35 ft above Tyrone Limestone-Lexington Limestone contact.

Q.n. — Salvisa, Ky.

S.n. - Salvisa B.

S.no. - 176.

C.n. - 7796-CO.

G.I. — Exposures on Interstate 75, 1.3 mi south of exit to 

Kentucky Route 418.

C. — 434 mm east, 313 mm north.

F. — Lowermost tongue of Tanglewood Limestone Member, Lexington Limestone, below Brannon Member, Lexington Limestone.

S.p. — 3-9 ft above base of Cane Run Bed, Grier Limestone Member, Lexington Limestone.

Q.n. — Coletown, Ky.

C.n. - 7809-CO.

G.I. — 75 ft south of junction of Kentucky Route 388 and

U.S. Route 227. 

C. — 384 mm east, 113 mm north.

F. — Tanglewood Limestone Member, Lexington Limestone.

S.p. — First bed above Brannon Member-Tanglewood 

Limestone Member contact.

Q.n. - Ford, Ky.

S.n. — Boonesboro Beach.

C.n. - 7812-CO.

G.I. - Farm pond 250 ft west of U.S. Route 27, 500 ft

south of junction of U.S. Routes 27 and 62. 

C. — 220 mm east, 548 mm north. 

F. — Clays Ferry Formation. 

Q.n. — Shawhan, Ky.

C.n. - 7817-CO.

G.I. — Section on Kentucky Route 39, 0.3 mi southeast of 

Black Bridge crossing over Hickman Creek.

C. — Base of section at 260 mm east, 346 mm north.

F. — Curdsville Limestone Member, Lexington Limestone.

S.p. — 6 in above contact of Tyrone Limestone and Curdsville Member, Lexington Limestone.

Q.n. — Little Hickman, Ky.

S.n. — Little Hickman A.

C.n. - 7843-CO.

G.I. — Exposures on Kentucky Route 35 (U.S. Route 127),

north of Moreland about 2.5 mi. 

C. — 260 mm east, 173.5 mm north. 

F. — Gilbert Member, Ashlock Formation. 

Q.n. — Junction City, Ky.

C.n. - D-1172-CO.

G.I. — Old road to lower Clays Ferry, Ky. Bridge section 

beginning about 1,750 ft west of high bridge piers 

for Interstate 75 bridge crossing of Kentucky 

River.

C. — Base of section at 132 mm east, 31 mm north.

F. — Clays Ferry Formation.

S.p. — 24 ft above top of Tanglewood Limestone Member, 

Lexington Limestone.

Q.n. - Ford, Ky.

S.n. — Clays Ferry (lower part); Ford A.

S.no. - 22 B.

C.n. - D-1196-CO.

G.I. — Eastbound lanes of Interstate 64 from Kentucky

	River bridge crossing to end of exposure. 

C. — Base of section at 88 mm east, 164 mm north. 

F. — Top of Logana Member, Lexington Limestone. 

S.p. — 50 ft above top of Tyrone Limestone. 

Q.n. - Frankfort East, Ky. 

S.n. - Frankfort East A. 

S.no. - 86.

C.n. - D-1206-CO.

G.I. — Southern side of westbound lanes of Interstate 64, 

0.5 mi south of bridge across Kentucky River.

C. — 123 mm east, 195 mm north.

F. — Top of upper tongue of Tanglewood Limestone 

Member, Lexington Limestone.

S.p. - Just below 7783-CO.

Q.n. — Frankfort East, Ky.

S.n. — Frankfort East A.

S.no. - 86.
MIDDLE AND UPPER ORDOVICIAN SYMMETRICAL UNIVALVED MOLLUSKS, CINCINNATI ARCH REGION 0203

NON-USGS COLLECTIONS

C.n. - OH-1 (= 6211-CO, Pojeta, 1979).

G.I. — Bear Creek Quarry, an abandoned quarry along 

bluffs on northern side of Ohio River, at intersection of Bear Creek Road and U.S. Route 52, 3 mi 

east of Neville and 1.1 mi west of Chilo, Washington Co., Ohio.

F. — Kope Formation.

S.p. — 10-15 ft above contact of Kope Formation and Point

Pleasant Tongue, Clays Ferry Formation. 

Q.n. — Moscow, Ohio-Ky. 

S.n. — Bear Creek.

C.n. - KY-1.

G.I. — Roadcut on western side of Interstate 71, at Carrollton, Ky., exit. 

F. — Kope Formation.

S.p. — Mollusk-rich lens along bench in roadcut. 

Q.n. — Carrollton, Ky.

INDEX

[Italic page numbers indicate major references]

Page

Abstract....................................... 1

Abundance of species ............... 36, 37, 38

acuta, Carinaropsis ....28, 36, 37, 177; pl.4

acutilira, Sinuitopsis .......... 51, 52, 54, 87

acutus, Sinuites cancellatus..........34, 112

(Aglaoglypta), Bellerophon ............. 159

Aldanella...................................... 56

Algae..........................................31, 35

archaeogastropod browsing ...... 34

drifting masses........................ 31

feeding habit..........................30, 41

films...................................... 31

flora...................................... 31

foliage dwellers ............ 31, 32, 40, 45

48, 89 

grazers ....................... 26, 30, 34, 45

alphaeus, Tremanotus.... ................ 52

alia, Archinacella.................. 28, 80; pl.3

amabilis, Petrotrochus ................... 30

Amphigastropoda.......................... 54, 58

Amplexopora septosa ..................... 22

Amygdalocystites bed..................... 79

Anapetopsis.................................. 48

anatiformis, Pterotheca......... .....182, 185

Anconochilus................................ 116

angularis, Sinuites cancellatus........ 112

angiista, Pterotheca ........28, 36, 182, 185;

pi. 39 

Anisostrophic coiling ..................... 45, 56

Anterior siphon, caenogastropods..... 31

Apertures, explanate.....................47, 48

margins............................ 43, 44, 85

platform..........................46, 51, 175

radial...................................47, 151

sinus...................................... 44

tangential .............................. 48

Aporrhais..................................... 48

Appalachian geosyncline ................. 4

area, Archinacella............ 28, 29, 82; pl.3

Archaeogastropoda ............30, 31, 63, 115

Archaeophiala........................ .59, 71, 72

Archaeophialidae ......59, 60, 61, 65, 71, 72

Archaeopraga ............................... 74

Archinacella...... 28, 59, 74, 75, 76, 78, 80;

pls.2, 3, 4, 5 

alia............................... 28, 80; pl.3

area ......................... 28, 29, 82; pl.3

cingulata...................28, 78, 79; pl.2

davisi............................ 29, 80; pl.3

deleta .............................. 77, 80, 81

depressa... ................. 27, 80, 84; pl.2

indianensis........28, 29, 40, 76, 82, 83

84, 85; pls.3, 4, 5

Page

Archinacella—Continued

kagawongensis ........................ 84

laevis..................................... 80

patelliformis........... 21, 29, 74, 76, 78

79, 81 

perovalis ................................ 80

powersi..... .................. 75, 76, 79, 82

pulaskiensis ........................... pl.2

richmondensis................... 82, 83, 84

rugatina......................... 29, 81; pl.2

semicarinata........................... 81

simmonsi ............................... 72

simulatrix........ 28, 36, 37, 76, 77, 80;

pl.2 

subrotunda.. .......................... 80, 84

valida... ............... 27, 39, 78, 81; pl.2

sp. ..................................29, 33, 38

(Carinaropsis) patelliformis...... 79

Archinacellacea ............. 55, 59, 60, 61, 65

73, 74, 75 

Archinacellida.............................. 59, 74

Archinacellidae................... 58, 59, 61, 75

Archinacellina ............................. 74, 75

modesta.................................. 75

Archinacelliopsis................. 59, 74, 75, 76

patelliformis............................ 75

Archinacelloidea........................... 59, 74

Archinella pulaskiensis................... 81

simulatrix.............................. 81

Argillaceous facies, Leipers

Formation.............................. 12

Argillaceous member, laminated,

Hermitage Formation............... 9

Arnheim Formation, Richmond

Group....................12, 18, 21, 23, 24

Ashlock Formation................... 18, 20, 23

Ashlock Formation

(See also particular member) 

Aspidobranch ctenidia .................... 115

Aspidobranch gastropoda................ 49

Aspidobranchia.......................... 115, 116

Aspidotheca....................... .175, 176, 181

attenuata, Pterotheca....182, 183, 184, 186

ausus, Sphenosphaera........ ............ 28

Autoecology, bellerophontaceans...... 30

Autoecology, monoplacophorans......26, 27

B

Bardstown Member, Drakes

Formation.............................. 21

Basin siltstones ............................. 35

Bellerophon........ 46, 47, 49, 50, 53, 54, 61

127, 141, 158, 159, 166; pi. 18 

bilineatus............................... 160

Bellerophon—Continued

bilobatus ................................ Ill

cancellatus ............................. Ill

capax .................................... 172

carinifera............................... 164

cincinnatiensis..... 167, 173, 174; pl.35

clausus .............................. 166, 167

diabloensis ............................. 165

gibsoni................................... 52

globularis............................... 114

gorbyi .................................... 141

megalostoma........................... 150

mohri.................................... 173

parksi. ............................... 173, 174

punctifrons ......................... 141, 142

primaeva.......................... 141

recticostatus ........................... 52

recurvus................................. 171

rogersensis .......... 166, 167, 168; pl.32

subangularis........................... 171

subglobulus ............................ 159

sulcatinus .............................. 127

troosti.................................... 168

burginensis....................... 170

vasulites ................................ 158

sp. ........................................ 52

(Aglaoglypta).......................... 159

(Bellerophon)... .......61, 158, 159, 166;

pis. 28, 33 

bilineatus ............. 159, 160; pi. 28

nana ........................... 159, 160

subglobulus ................ 159; pl.33

subpatula..................... 159, 161

sp. .................................. 35

(Pharkidonotus).................. 158, 159

percarinatus..................... 35

Bellerophon............ 61, 158, 159, 166;

pls.28, 33 

Bellerophon sp........................ 35

bilineatus, Bellerophon........ 159, 160;

pl.28 

wcma, Bellerophon ............... 159, 160

5ttcama........................... pi. 18

subglobulus, Bellerophon.... 159; pl.33

subpatula, Bellerophon......... 159, 161

Bucania........................... pi. 18

Bellerophont conundrum................. 55

Bellerophontacea................35, 40, 44, 46

61, 62, 63, 115, 116 

functional morphology .............. 4-4

shell coiling............................. 4-4

Bellerophontidae.......45, 50, 60, 61, 62, 63

64, 156, 158, 175 

Bellerophontina...........................63, 116

Bellerophontinae.....................62, 63, 155

0205
0206 INDEX

Page

Bellevue Limestone Member,

McMillan Formation......... 18, 22, 23, 24

bellulus, Conradella ......................... 123

Phragmolites ............29, 123, 124; pl.44

bidorsata, Bucania ........................... 145

Tetranata.............27, 29, 39, 41, 46, 47

114, 125, 245, 146, 147, 148, 149; 

pls.21, 22 

Bigby facies, Bigby-Cannon

Limestone, Nashville Group ......... 9

Bigby-Cannon Limestone,

Nashville Group ..........................9, 39

(See also particular member) 

bilineatus, Bellerophon. ..................... 160

(Bellerophon)...........159, 160; pi.28

Sphenosphaera. .........................28, 37

billingsi, Salpingostoma ..........150, 154, 156

bilobatus, Bellerophon....................... Ill

corrugatus, Sinuites.................... 34

Cyrtolites .................................. Ill

Sinuites .................................... 110

Biostratigraphic classification.............. 3

Biotremus ....................................... 117

Bipectinate ctenidia........................... 49

Bipectinate gill................................. 31

Bipulvinidae..................................... 61

bjalyi, Nyuella. ................................ 75

Blackriveran Stage, upper Middle

and Upper Ordovician rocks ......... 4

Blue clay-shale member, Hermitage

F ormation, Nashville Group ......... 9

bohemica, Cyclotheca........................ 33

bohemicum, Grandostoma..... ............. 33

Boiotremus.. ...........................62, 117, 149

boreale, Salpingostoma. ..................... 150

Brannon Member, Lexington

Limestone................................. 16

brevilineata, Sinuitina...................... 52

Brookville Formation ........................ 19

Brown, quoted................................. 18

Bryozoan-encrusted shell ................... 42

Bryozoans ....................................... 41

Bubovicus ....................................... 158

Eucanella........................... ...116, 140, 143

Bucanellidae ...................... 59, 63, 109, 116

Bucanellinae .................................... 62

Bucania................ ....38, 45, 46, 47, 61, 118

120, 122, 126, 127, 128, 133, 140

141, 144, 149, 150, 166; pis. 12

13, 14, 15, 16, 17, 18, 19, 20, 27

bidorsata................................... 145

buelli........................................ 150

christianae ............................... 52, 53

cornu group............................... 150

crassa............... .29, 130, 137, 139, 140;

pi. 19 

emmonsi. ..........27, 128, 130, 135; pi. 12

frankfortensis ............... .......27, 28, 38

131, 133, 134, 140; pis. 13, 16 

halli...... 28, 36, 129, 130, 135, 143; pi. 12

intexta.. .................................... 129

lindsleyi.................. ...27, 131, 132, 133

136, 137, 140; pi. 18

Page

Bucania— Continued 

lindsleyi—Continued

group............64, 127, 128, 135, 138

micronema..........28, 45, 132, 136; pi. 19

nana .................................... 160, 161

nashvillensis........27, 28, 37, 46, 51, 131

132, 137, 140; pis. 13, 14, 15, 27 

group...........................45, 47, 127

peracuta........27, 51, 134, 135, 137, 138;

pi. 16 

pojetai. ....................29, 138, 139; pi.20

punctifrons................................... 142

rugatina.............. ..28, 38, 127, 131, 132

136, 137; pis. 16, 17 

simulatrix..................29, 138, 139, 156

157, 174; pi. 19 

singularis................ .27, 135, 137; pi. 19

subangulata...........28, 36, 37, 230, 131;

pis. 14, 15 

sublata ................ 28, 37, 38, 135; pi. 13

subpatula... ............................... 161

sulcatina................................. 46, 150

group............45, 47, 50, 55, 64, 118

120, 127, 128, 130, 132

135, 137, 141, 143, 150

sp. .................27, 32, 33, 36, 37, 38, 40

(Bellerophon) nana......................pl.18

subpatula........................... ..pi. 18

Bucaniella....................................... 53

esthona..................................... 140

Bucaniidae.....45, 50, 61, 62, 63, 64, 126, 143

Bucaniinae....................62, 63, 64, 126, 149

Bucanopsinae...............63, 64, 127, 158, 161

162, 175 

Bucanopsis........38, 46, 47, 61, 127, 144, 158

161, 162, 166, 175, 176; pl.27 

calypso..................................... 33

carinifera............. ....27, 28, 37, 38, 133

162, 163, 164, 165; pl.27 

diabloensis ..........28, 38, 162, 165; pl.27

sp. ..........................................33, 35

budleighensis, Cyrtolites.................... 90

buelli, Bucania................................ 150

Salpingostoma ............52, 150, 151, 153

154, 156; pl.24 

Bull Fork Formation........................ 18, 23

burginensis, Bellerophon troosti.......... 170

Sphenosphaera.......... 37, 166, 170; pl.28

Caenogastropods, anterior siphon........ 31

monopectinate ctenidia ................ 31

calami, Lapsus ................................ 66

Calaurops....................................... 58

Calcareous marine algae .................... 31

Calcitic casts.................................... 26

Calloconus ...................................... 72

Galloway Creek Limestone................ 18, 20

calypso, Bucanopsis.......................... 33

Cambridioidea.................................. 59

Camouflage...................................... 142

Camp Nelson Limestone,

High Bridge Group ..................... 13

Page

canadense, Salpingostoma................. 150

canaliculata, Pterotheca.............. ..182, 185

cancellata, Protowarthia.................... Ill

cancellatus acutus, Sinuites............ .34, 112

angularis Sinuites...................... 112

Bellerophon............................... Ill

cancellatus, Sinuites ................... 112

corrugatus, Sinuites.................... 112

liratus, Sinuites .......................B4, 112

Sinuites .........28, 29, 34, 52, 53, 54, 110

111, 112, 115; pi. 11 

cancellatus.......................... 112

trentonensis, Sinuites.................. 112

Cannon facies, Bigby-Cannon

Limestone, Nashville Group ........ 10, 39

capax, Bellerophon........................... 172

Sphenosphaera...........29, 166, 172, 174;

pl.34

Carbonate environments.................... 34

Carinaropsidae................61, 62, 63, 64, 116

158, 162, 174, 176, 181

Carinaropsinae................... 62, 63, 175, 176

Carinaropsis................. ...38, 47, 48, 51, 55

62, 80, 158, 162, 166, 167, 174

175, 176, 177, 181; pls.4, 37, 38, 40

acuta................ .....28, 36, 37, 177; pl.4

cunulae............. .27, 176, 177, 178, 179;

pl.37 

cymbula............28, 37, 38, 46, 131, 162

167, 176, 177, 178, 179; pls.37, 38 

explatiata..............................2S; pl.40

explanatus ................................ 180

phalera... .............................. 177, 179

sp. ..........................................37, 38

(Carinaropsis) patelliformis,

Archinacella.............................. 79

carinatus, Cyrtolites

(Paracyrtolites).. .............29, 44, 87, 89

99, 103, 108, 109, 126; pis. 7, 8

carinifera, Bellerophon...................... 164

Bucanopsis...............21, 28, 37, 38, 133

162, 163, 164, 165; pl.27

carrickensis, Tetranota. ..................... 144

Carters Limestone, Stones River

Group....................................... 7

Catheys Formation,

Nashville Group ........................ 11, 39

(See also particular facies)

cellulosa, Conradella dyeri................ 122

cellulosum, Tetradium, in Carters

Limestone lower member............. 7

cellulosus, Phragmolites............27, 39, 122;

pl.43 

dyeri .................................. 122

Central Tennessee bank..................... 5

Central Tennessee high ..................... 5

Central Tennessee, Ordovician

lithostratigraphy......................... 6

paleoecology.............................. 39

Chalarostrepsis........45, 57, 58, 64, 117, 142

praecursor. ................................ 117

Champlainian Series.......................... 4

christianae, Bucania........................ 52, 53
INDEX 0207

Page

Ciliary suspension feeders.................. 30

Cincinnati arch................................. 4

Cincinnatian Ordovician rocks, classification

(see Upper Ordovician) 

Cincinnatian Series........................... 4

cincinnatiensis, Bellerophon .......... 167, 173

174; pl.35 

cingulata, Archinacella ........ 28, 78, 79; pl.2

Circumumbilical muscles .............. 43, 52, 55

Classification................................... 52, 53

Bellerophontacea........................ 61

monoplacophora.......................... 58

suprageneric, bellerophontacean

gastropoda........................... 61

Clastic environments, Ordovician ........ 32

clausus, Bellerophon..... ................166, 167

Sphenosphaera...........27, 37, 38, 39, 46

51, 55, 125, 159, 166, 167 

168, 170, 171; pls.30, 31, 32 

Clays Ferry Formation, Lexington

Limestone ............ 18, 19, 20, 37, 38, 41

claysferryensis, Cyrtolites.................. 41

(Cyrtolites)............... 28, 29, 38, 42

44, 87, 89, 90, 99, 100

101, 104, 109, 146; pls.4, 8

Clioderma.... ...............................181, 184

expansa .................................... 183

saffordi. .................................... 182

(Clioderma) saffordi, Pterotheca ......... 182

clochensis, Pterotheca ................... 182, 185

Cloudia.... .....................................86, 109

Cocculinacea ..................................49, 116

Codiaceae........................................ 31

Coelocyclus ................................. 126, 158

Coiling, anisostrophic .......................45, 56

Bellerophontacea........................ 44

disjunct.........................44, 45, 58, 106

isostrophic...................... 45, 51, 52, 56

Columellar muscles and scars............. 52, 53

54, 64 

Columnaria, in Carters Limestone

lower member............................ 7

Composite molds ................ 82, 93, 126, 130

compressa, Conradella...................... 120

Compression, lateral................ 45, 117, 118

compressus, Cyrtolites ..................... 120

Phragmolites ............. 28, 34, 120, 121;

pls.42, 44 

Conodont zonatiori............................ 3

Conradella.... ......................... 61, 117, 120

bellulus... .................................. 123

compressa ................................. 120

dyeri ........................................ 124

cellulosa ............................. 122

elegans ..................................... 123

grandis ..................................... 121

similis. ................................. 120, 121

consobrina, Pterotheca ...................... 33

cornu, Bucania, group ...................... 150

Cornulites ....................................... 41

corrugatus, Sinuites bilobatus ............ 34

cancellatus.......................... 112

Corryville Formation......................... 24

Page

Corryville Member, McMillan

Formation................................ 18, 23

Corryville to Oregonia sequence.......... 19

costalis, Kokenospira ........29, 140, 141, 144;

pl.20 

craigensis, Cyrtolites ........................ 90

crassa, Bucania ........ 29, 130, 137, 139, 140;

pi. 19 

Crenistriella.................................... 116

Crepidula........46, 51, 55, 176, 177, 181, 182

Crepidula fornicata .......................... 48

cristatus, Cyrtolites .......................... 119

Oxydiscus ................................. 119

Tropidodiscus ................. 27, 119; pl.41

Cryptolithus .................................... 22

sp. ............................................pl.21

Ctenidia.......................................... 115

Ctenodonta hermitagensis .................. 9

Ctenodonta member, Hermitage

Formation, Nashville Group ......... 9

cunulae, Carinaropsis.............. 27, 176, 177

178, 179; pi. 37 

Phragmostoma ........................... 178

Curdsville Limestone Member,

Hermitage Formation, Nashville 

Group....................................... 8

Lexington Limestone ................. 15, 37

abundance of species ............. 36

Cyclocyrtonellidae............................ 59, 61

Cyclomya....................................... 59, 60

Cyclonema ...................................... 30

Cyclotheca. .................................. 175, 181

bohemica................................... 33

(Cymatospira) montfortianus,

Knightites ................................. 35

cymbula, Carinaropsis ................28, 37, 38

46, 131, 162, 167, 176

177, 178, 179; pls.37, 38

Phragmostoma........................... 178

Cymbularia. .................................... 35

sp. ........................................... 33

Cymbulariidae.................................. 62

Cymbulariinae.........................62, 126, 158

Cynthiana Formation ....................... 18, 19

Cyrtolitacea..................................... 86

Cyrtolites.. ............29, 36, 38, 42, 43, 44, 49

53, 55, 59, 60, 69, 86, 116, 135 

bilobatus ................................... Ill

budleighensis ............................. 90

claysferryensis........................... 41

compressus ................................ 120

craigensis.................................. 90

cristatus.................................... 119

disjunctus ................................. 87

dyeri .................................... 123, 124

elegans ..................................... 123

hornyi...................................... 40

lamellifer .................................. 125

magnus..................................... 119

nitidula .................................... 125

nodosus llandoveria.................... 91

nodosus .............................. 91

Page

Cyrtolites— Continued

ornatus................... ....29, 42, 51, 52, 5

62, 86, 87, 90, 174 

retrorsus................... 29, 38, 39, 87, 90

subacutus.................................. 118

subplanus ................................. 90

thraivensis ................................ 91

sp. ................................33, 36, 37, 38

(Cyrtolites)............... 41, 87, 88, 89, 91;

pls.4, 5, 6, 7, 8 

claysferryensis..... 28, 29, 38, 42, 44

87, 89, 90, 99, 100, 101

104, 109, 146; pls.4, 8

disjunctus ..................... 44, 90, 92

104, 106; pi.6 

hornyi ...............29, 40, 90, 92, 102

104, 105; pl.8 

minor.................29, 87, 88, 89, 90

92, 102, 103; pi. 7 

ornatus.. ..................29, 44, 67, 69

88, 89, 90, 91, 92, 93

94, 103, 104, 106; pis.6, 7

retrorsus.............27, 28, 36, 37, 38

44, 87, 89, 90, 94

96, 98, 99, 100, 101

104, 108, 109; pls.5, 7

fillmorensis ..................89, 99

subplanus ............................... 99

(Paracyrtolites)...... .......87, 88, 89, 107;

pis. 7, 8 

carinatus ............29, 44, 87, 89, 99

103, 108, 109, 126; pls.7, 8 

parvus.......... .28, 87, 108, 109, 126;

pi. 7 

subplanus ................28, 37, 87, 89

107, 108; pls.7, 8 

(Cyrtolites) claysferryensis,

Cyrtolites..................28, 29, 38, 42, 44

87, 89, 90, 99, 100, 101

104, 109, 146; pls.4, 8

Cyrtolites ................. 41, 87, 88, 89, 91;

pls.4, 5, 6, 7, 8 

disjunctus, Cyrtolites............ 44, 90, 92

104, 106; pl.6 

hornyi, Cyrtolites....... .....29, 40, 90, 92

102, 104, 105; pl.8 

minor, Cyrtolites........ .....29, 87, 88, 89

90, 92, 102, 103; pi. 7 

ornatus, Cyrtolites........... 29, 44, 67, 69

88, 89, 90, 91, 92, 93, 94

103, 104, 106; pls.6, 7

retrorsus, Cyrtolites.... .....27, 28, 36, 37

38, 44, 87, 89, 90, 94, 96, 98, 99

100, 101, 104, 108, 109; pls.5, 7

fillmorensis, Cyrtolites......... 89, 99

subplanus, Cyrtolites.................. 99

Cyrtolitidae ....................59, 61, 62, 86, 116

Cyrtolitina ....................................86, 125

nitidula .................................... 125

Cyrtonella............................... ..51, 58, 61

mitella..................................... 52, 54
0208 INDEX

Cyrtonellacea.................................. 59, 61

Cyrtonellida................43, 55, 59, 60, 61, 86

functional morphology ................. 43

Cyrtonellidae................................... 61

D

Dalmanella coquina member,

Hermitage Formation,

Nashville Group ......................... 9

Dasycladaceae.................................. 31

daviei, Archinacella.................. 29, 80; pi.3

Dekayia aspera ................................ 22

deleta, Archinacella.................... 77, 80, 81

Delta fronts, environment............ 32, 35, 36

fauna........................................ 34

Delthyris expansus ........................... 183

dentatum, Rhynchotrema, beds,

Whitewater Formation ................ 156

Deposit feeders ..................... 27, 30, 35, 47

depressa, Archinacella ......... 27, 80, 84; pl.2

Detorsion, regulatory........................ 45

Detritus feeders ......................... 30, 36, 40

Devils Hollow Member,

Lexington Limestone .................. 17

abundance of species ................... 38

diabloensis, Bellerophon... ................. 165

Bucanopsis..........28, 38, 162, 165; pl.27

dilatus, Salpingostoma... ................... 150

Dillsboro Formation ............... 18, 23, 24, 40

Diodora (Fissurella) ......................... 49

Diotocardia...................................... 115

Dirachopea.... .................................. 58

Disjunct coiling ....................44, 45, 58, 106

disjunctus, Cyrtolites........................ 87

(Cyrtolites)... ...........44, 90, 92, 104

106; pi. 6 

Dove-colored facies ........................... 39

Bigby-Cannon Limestone,

Nashville Group ......................... 10

Catheys Formation,

Nashville Group ......................... 11

Drahomiridae................................... 61

Drakes Formation.................. 18, 21, 24, 25

dyeri cellulosa, Conradella ................ 122

cellulosus, Phragmolites.............. 122

Conradella ................................ 124

Cyrtolites .............................. 123, 124

dyeri, Phragmolites .................... 122

Phragmolites ........29, 41, 122, 123, 124;

pls.44, 45 

dyeri .................................. 122

Phragmolithes... ......................... 124

E

eatoni, Triarthus.... .......................... 22

Economy Shale, Kope Formation ........ 22

Eden Group, Inman Formation........... 12

Eden Shales.................................... 17, 22

Edenian Stage, upper Middle and

Upper Ordovician rocks ............... 4

elegans, Conradella.......................... 123

Cyrtolites .................................. 123

elegans— Continued

Phragmolites...... 29, 123, 124; pls.44, 45

Elkhorn Formation .......................... 18, 25

Emargination, labral ......49, 54, 60, 115, 116

Emarginula..... ...............................49, 54

eminens, Helcionopsis ....................... 68

emmonsi, Bucania........ ....27, 128, 130, 135;

pi. 12 

Encrinurus ..................................... 34

Encrustation...............28, 29, 41, 42, 67, 69

88, 137 

Endogastric orientation ....................42, 55

Entemnotrochus............................... 50

Environments, carbonate,

Ordovician ................................ 34

clastic, Ordovician....................... 32

Eobucania...................58, 64, 117, 118, 126

149, 175 

Eotomariidae................................... 57

esthona, Bucaniella.......................... 140

Euomphalaceans............................... 35

Euomphalid archaeogastropods ........... 30

Euphemites ............................ ..47, 61, 117

Euphemitidae.....................62, 63, 116, 117

Euphemitinae................................... 62

Euphemitopsis ................................. 117

Exogastric orientation ......................42, 55

expansa, Clioderma.......................... 183

Pterotheca........ .27, 28, 36, 39, 182, 183

184, 185; pis.39, 40

Salpingostoma .......... 150, 154, 155, 156

expansus, Delthyris.......................... 183

explanata, Carinaropsis ................ 28; pl.40

Explanate apertures......................... 47, 48

Explanate bellerophontaceans....... 30, 33, 35

Explanate shells .........33, 38, 47, 48, 50, 116

explanatus, Carinaropsis................... 180

External molds................. 66, 76, 77, 78, 83

Facies, Bigby-Cannon Limestone ........ 9

Catheys Formation..................... 11

Leipers Formation...................... 12

Fairmont beds, Fairview

Formation................................. 22

Fairmount Formation........................ 24

Fairview Formation......................... 18, 22

Faulconer Bed, Perryville 

Limestone Member, 

Lexington Limestone ................. 15, 16

Faunas, upper Ordovician,

paleoecology ..................................^0

Feeders, algal.................. 26, 30, 34, 41, 45

ciliary suspension........................ 30

deposit...........................27, 30, 35, 47

detritus............................... 30, 36, 40

grazing ..................................... 47

suspension................................. 48

Fernvale Limestone,

Richmond Group......................... 13

fillmorensis, Cyrtolites (Cyrtolites)

retrorsus .................................. 89, 99

fissicostata, Helcionopsis ................... 66

(Fissurella), Diodora........................ 49

Fissurellacea.................................... 49

Fissurellidae........................30, 31, 49, 115

Flanagan Chert, Lexington

Limestone ........... 16, 119, 131, 135, 136

fornicata, Crepidula ......................... 48

frankfortensis, Bucania. ........27, 28, 38, 131

133, 134, 140; pis. 13, 16

fraternus, Salpingostoma ................... 150

Fulton beds, Kope Formation ............. 22

Fulton Shale.................................... 19

Functional morphology...................... 42

G

galatheae, Neopilina........................ 43, 58

Garrard Siltstone............................. 18, 20

Gastropods...................................... 63

predation................................... 41

size restrictions.......................... 32

Geologic setting................................ 3

gibsoni, Bellerophon ......................... 52

Gilbert Member, Ashlock

Formation................................. 21

Girvanella.. ..................................... 15

globata, Phragmosphaera .................. 35

globularis, Bellerophon ..................... 114

Sinuites ............... ....29, 114, 115; pi. 10

Glyptotomaria (Glyptotomaria)

marginata................................. 30

(Glyptotomaria) marginata,

Glyptotomaria............................ 30

gorbyi, Bellerophon........................... 141

Undulabucania..........2'd, 141, 142, 143;

pl.23 

grande, Grandostoma. ....................... 33

grandis, Conradella .......................... 121

Phragmolites........ .....27, 121, 122, 123;

pls.42, 43 

Grandostoma................................... 116

bohemicum ................................ 33

grande ...................................... 33

Grandostomatidae......................62, 63, 116

Grandostomatinae............................. 62

granistriatus, Sinuites ........29, 51, 111, 113

114, 115, 146; pis. 11, 21, 45 

Grant Lake Limestone...................... 18, 23

(See also McMillan Formation) 

Granular facies, Catheys Formation,

Nashville Group ......................... 11

Hermitage Formation,

Nashville Group ................... 9

Leipers Formation...................... 12

Grazers........................................... 47

Greendale Lentil, Lexington

Limestone................................. 16

Grier Limestone Member,

Lexington Limestone ............ 15, 37, 38

Gyrospira.. ............................ 174, 175, 176

H

Haliotidae........................................ 52

Haliotis .......................................... 49
INDEX 0209

halli, Bucania..............28, 36, 129, 130, 135

143; pi. 12 

harviei, Pterotheca.... .........29, 182, 183, 185

186; pl.26 

Helcionella...................................... 69

Helcionellacea................................. 61, 62

Helcionellaceans............................... 118

Helcionellidae................................... 61

Helcionopsis........2S, 43, 65, 66, 68, 69; pl.2

fissicostata ................................ 66

eminens .................................... 68

radiata ..................................... 66

reticulatus................................. 66

striata .................... 28, 29, 66, 67; pl.2

subcarinata ............................... 66

sp. ........................................... 66

Heliospongia vokesi .......................... 31

Hermitage Formation,

Nashville Group ..........................8, 39

(See also particular member) 

hermitagensis, Ctenodonta.. ............... 9

Heteropod....................................... 181

High Bridge Group ........................... 13

(See also particular member) 

Hill quarry beds (Fairview

Formation)................................ 22

hippapus, Tetranota... ....................... 144

Holopeids........................................ 35

Homolonotid-Plectonotus

community................................. 34

hornyi, Cyrtolites ............................. 40

(Cyrtolites).. .............29, 40, 90, 92

102, 104, 105; pl.8 

Hypseloconiae.................................. 61

Hypseloconidae .......................... 58, 59, 74

Hypseloconus................... 59, 71, 72, 73, 74

I

lapetus (proto-Atlantic) Ocean ............ 4

imbricata, Salpingostoma .................. 150

Indiana, southeastern, upper

Ordovician lithostratigraphy ........ 17, 24

indianensis, Archinacella....... 28, 29, 40, 76

82, 83, 84, 85; pls.3, 4, 5 

Inductural deposits .........................47, 117

Inman Formation, Eden Group ........... 12

inornatum, Salpingostoma................. 150

intermedia, Pterotheca...................... 184

Internal molds..............84, 93, 110, 111, 112

146, 150, 155, 156 

intexta, Bucania .............................. 129

Introduction..................................... 2

Isopleura......................................... 58

Isostrophic shell coiling........... 45, 51, 52, 56

Jessamine dome, Cincinnati arch......... 5

K

kagawongensis, Archinacella.............. 84

Page

Kentucky, middle Ordovician

lithostratigraphy......................... 6

north-central, upper Ordovician

lithostratigraphy................... 22

south-central, upper Ordovician

lithostratigraphy................... 19

upper Ordovician

lithostratigraphy................... 17

kentuckyense, Salpingostoma ............ 28, 36

37, 47, 51, 150, 151, 152

153, 154, 156; pls.24, 25, 26

Kirengella. ...................................... 71

Kirengellacea..............60, 61, 65, 71, 72, 75

Kirengellida.......................... 59, 60, 71, 72

Kirengellidae ........................ 59, 60, 61, 71

Kirengelloidea.................................. 59

Knight, quoted................................. 76

Knightites ................. 47, 158, 161, 162, 166

(Cymatospira) montfortianus....... 35

Knightitidae..................................... 62

Knightitinae............................62, 158, 161

Kodymites....................................... 158

Kokenia........................................ 61, 140

Kokenospira........47, 61, 126, UO, 144, 158;

pl.20 

costalis ................... ..29, 140, 141, 144;

pl.20 

Kope to Bellevue sequence................. 19

Kope Formation .......... 18, 20, 22, 23, 24, 41

Kope Formation (Indiana).................. 24

Kotysium........................................ 68

labioreflexus, Pharkidonotus.............. 52

Labral emargination.......^9, 54, 60, 115, 116

Labral sinus.................................... 49, 62

Labral slit....................................... 54

laevis, Archinacella.......................... 80

lamellifer, Cyrtolites......................... 125

TemnodisciAS.............................. 117

Laminated argillaceous member,

Hermitage Formation,

Nashville Group ......................... 9

Laminated siltstone facies, Catheys

Formation................................. 12

Lapsus calami ................................. 66

lata, Salpingostoma.......................... 150

Laterally compressed shells....... 45, 117, 118

Lebanon Limestone, Stones River

Group....................................... 7

Leipers Formation, Maysville

Group....................................... 12

lemchei, Sylvestrosphaera.................. 52

lenaensis, Multifariites ..................... 59

Leperditella..................................... 182

Leperditia ....................................... 182

Lexington Limestone .................. 14, 20, 37

paleoecology.............................. 36

(See also particular member) 

Liberty bed, Drakes Formation .......... 21

Liberty Formation...................... 18, 23, 24

Drakes Formation....................... 21

Liljevallospira ................................. 158

lindsleyi, Bucania ...................27, 131, 132

133, 136, 137, 140; pi. 18

group..................64, 127, 128, 135, 138

Lineback, quoted.............................. 18

Liospira ........................................ 34, 168

liratus, Sinuites............................... 112

cancellatus ........................34, 112

Litavina.......................................... 68

llandoveria, Cyrtolites nodosus. .......... 91

locator, Salpingostoma...................... 150

Logana Member, Lexington

Limestone................................. 15

abundance of species ................... 37

Lophosphirid gastropods.................... 41

Lophospira...................................... 168

medialis.................................... 17

Low-spired shells.............................. 58

Loxobucania................................ 127, 128

Loxonomataceans............................. 35

Lunulae .......................................... 50

M

Macluritid archaeogastropods.............. 30

Macroscenella.................................. 72

magnus, Cyrtolites ........................... 119

Oxydiscus ................................. 119

Tropidodiscus ...........29, 119, 120; pl.42

manitoulini, Vallatotheca....... 28, 29, 67, 68

69, 70, 71; pl.l 

Mantle cavity................................... 49

marginata, Glyptotomaria

(Glyptotomaria)......................... 30

Material used in study....................... 25

Maysville Group, Leipers

Formation................................. 12

McMicken Member, Kope

Formation................................. 22

McMillan Formation......................... 18, 20

(See also particular member) 

Measurements.................................. 26

medialis, Lophospira ........................ 17

Megalomphala ................................ 54, 61

taenia....................................... 52

megalostoma, Bellerophon ................. 150

Metoptoma ...................................... 75

Miamitown Shale ........................ 18, 23, 23

Micrite envelopes.............................. 26

Micromorphic bellerophontaceans ........ 30

micronema, Bucania..........28, 45, 132, 136;

pi. 19 

Microphagous scavenging,

Mikadotrochus............................ 30

Micropileus .................................. 72; pl.l

obesits....................................... 73

variabilis ..................... 28, 36, 73; pl.l

midas, Petrotrochus. ......................... 30

Middle Ordovician lithostratigraphy,

Kentucky .................................. 6

Mikadotrochus ................................. 30

microphagous scavenging............. 30
0210 INDEX

Page

Millersburg Member, Lexington

Limestone................................. 17

Million Shale................................... 18, 19

minor, Cyrtolites (Cyrtolites) ............ 29, 87

88, 89, 90, 92, 102, 103; pi.7 

mitella, Cyrtonella .......................... 52, 54

Mode of life, and shell form .......... 44, 45, 47

modesta, Archinacellina.................... 75

Mogulia.......................................... 61

mohri, Bellerophon........................... 173

Sphenosphaera. ..............29, 40, 41, 166

167, 172, J73, 174; pls.35, 36, 41 

Molds ............................................. 26

Monopectinate ctenidia,

caenogastropods......................... 31

Monoplacophora..............................61, 116

autoecology................................ 26

classification and phylogeny.......... 58

functional morphology ................. 4%

Tryblidiid.................................. 28

montfortianus, Knightites

(Cymatospira) ........................... 35

Morphology, functional...................... 41

Mount Auburn Formation .................. 24

Mount Auburn Member, McMillan

Formation ........................... 18, 21, 23

Mount Hope beds, Fairview

Formation................................. 22

Mount Hope Formation ..................... 24

Moyerokania .................................. 59, 71

Multifariidae..............................59, 60, 61

Multifariites lenaensis ...................... 59

Murchisoniaceans.............................. 35

Murchisoniids................................... 35

Murfreesboro Limestone, Stones

River Group .............................. 6

Muscles, bands................................. 55

retractor................................... 53

scars.........................43, 51, 52, 53, 54

55, 58, 65, 75, 87 

N

nana, Bellerophon

(Bellerophon)......................... 159, 160

Bucania................................ 160, 161

Bucania (Bellerophon) .................pl.18

Sphenosphaera........................... 160

Nashville dome, Cincinnati arch .......... 5

Nashville Group ............................... 8

paleoecology.............................. 39

nashvillensis, Bucania.. ....27, 28, 37, 46, 51

131, 132, 137, 140; pis. 13, 14, 15, 27 

group.................................45, 47, 127

natator, Phragmostoma. .................... 178

Neomphalus .................................... 30

Neopilina......................................... 27

Neopilina............. .43, 51, 58, 59, 60, 65, 74

galatheae. ................................. 43, 58

Neopilinidae..................................... 61

Neopilinoidea................................... 59

Neritacea ..........................49, 52, 115, 116

nitidula, Cyrtolites........................... 125

Cyrtolitina ................................ 125

Page

nitidula—Continued

Temnodiscus..................125, 126; pl.42

Temnodisus............................... 28

nodosus, Cyrtolites nodosus ............... 91

llandoveria, Cyrtolites................. 91

nodosus, Cyrtolites..................... 91

Nodular facies, Catheys Formation,

Nashville Group ......................... 12

Noncalcareous marine algae................ 31

Nylanderina.................................... 143

Nyuella ......................................... 71, 72

Nyuella bjalyi.................................. 75

0

obesus, Micropileus .......................... 73

Protowarthia ............................. 112

Sinuites ........................28, 36, 37, 111

112, 113; pl.9

obliqua, Phragmolites ....................... 121

obseleta, Tetranota ..........................28, 37

obsoleta, Tetranotal46, 147, 148, 149; pls.20,

22

Ohio, southwestern, upper

Ordovician lithostratigraphy........ 17, 22

Ophiletinae...................................... 58

Ordovician carbonate environments ..... 34

Ordovician clastic environments .......... 32

Ordovician lithostratigraphy,

central Tennessee....................... 6

Ordovician-Silurian unconformity......... 25

Oregon Formation, High Bridge

Group....................................... 13

Oregonia Member, Arnheim

Formation................................. 21

orientalis, Salpingostoma.................. 150

ornatus, Cyrtolites............ 29, 42, 51, 52, 54

62, 86, 87, 90, 174 

(Cyrtolites)............... 29, 44, 67, 69

88, 89, 90, 91, 92, 93, 94 

103, 104, 106; pls.6, 7

Ostracodes....................................... 182

Otter Creek Coral Bed, Drakes

Formation................................. 21

Owenella............. ............................ 116

Oxydiscus .............................. 61, 117, 118

cristatus.................................... 119

magnus..................................... 119

subacutus.................................. 118

Ozark dome ..................................... 5

Palaeacmeidae.................................. 59

Pale-colored facies, Catheys

Formation, Nashville Group ......... 11

Leipers Formation...................... 12

Paleoecological studies...................... 32, 34

Paleoecology, central Tennessee.......... 39

Lexington Limestone .................. 36

post-Ordovician studies................ 34

previous Ordovician studies.......... 32

of symmetrical univalved 

mollusks.................................... 27

Paleoecology, central Tennessee—

Continued

Tyrone Limestone....................... 36

upper Ordovician faunas .............. 40

Paleozoic borings.............................. 41

Paleuphemites ................................. 117

Pallial system................................... 49

(Paracyrtolites) carinatus,

Cyrtolites................ ..29, 44, 87, 89, 99

103, 108, 109, 126; pls.7, 8

Cyrtolites ..........87, 88, 89, 107; pls.7, 8

parvus, Cyrtolites......................28, 87

108, 109, 126; pl.7

subplanus, Cyrtolites .................28, 37

87, 89, 107, 108; pls.7, 8 

Parietal deposits.............................. 50, 55

Parietal inductura............................. 51

Parietal platform .......................... 176, 181

(See also Septum) 

parksi, Bellerophon ...................... 173, 174

parvus, Cyrtolites

(Paracyrtolites)...................28, 87, 108

109, 126; pl.7 

Patellacea......................................49, 116

Patellacean archaeogastropods............ 30

Patellacean gastropods ................43, 52, 55

Patellaceans..................................... 30

patelliformis, Archinacella ...............27, 29

74, 76, 78, 79, 81 

(Carinaropsis) ..................... 79

Archinacelliopsis........................ 75

Patellilabia ..................................... 48

Patellostium..................................61, 117

Pedasiola... ........................... 175, 176, 181

Pedasiolinae............................ 63, 175, 176

Pellagiellaceans................................ 56

peracuta, Bucania .....................27, 51, 134

135, 137, 138; pi. 16 

percarinatus, Bellerophon

(Pharkidonotus) ......................... 35

Perotrochus ..................................... 50

amabilis.... ................................ 30

midas ....................................... 30

perovalis, Archinacella...................... 80

Perryville Limestone Member,

Lexington Limestone .................. 15

abundance of species ................... 37

pervoluta, Protowarthia..................... 110

Sinuites ...........................28, 110, 111

pervolutus, Sinuites.......................... 110

Phagmosphaera................................ 176

phalera, Carinaropsis ................... 177, 179

Pharetrolites................................... 35, 55

Pharkidonotus ................................. 54

labioreflexus.............. ................ 52

(Pharkidonotus), Bellerophon......... 158, 159

percarinatus, Bellerophon............ 35

Phragmolites ........... 41, 45, 47, 61, 117, 118

120, 125, 128, 141, 142; pls.42, 43, 44, 45

bellulus................ ....29, 123, 124; pl.44

cellulosus..................21, 39, 122; pl.43
INDEX 0211

Page

Phragmolites—Continued

compressus.................28, 34, 120, 121;

pls.42, 44 

dyeri ...................29, 41, 122, 123, 124;

pis.44, 45 

cellulosus............................ 122

oVerz .................................. 122

elegans ............. 29, 123, 124; pls.44, 45

grandis.......27, 121, 122, 123; pls.42, 43

obliqua ..................................... 121

similis...................................... 121

triangularis........................... 121, 123

sp. ........................................... 34

Phragmolithes dyeri.......................... 124

Phragmosphaera.............................. 48

grfo&ate...................................... 35

Phragmostoma................................. 176

cunutee..................................... 178

q/m&uta.................................... 178

natator ..................................... 178

Phylogenetic models.......................... 56

Phylogeny....................................... 55

bellerophontacean gastropoda....... 61

monoplacophora.......................... 58

Pierce Limestone, Stones River

Group....................................... 7

Pilina... .........................................60, 66

Pilinopsis........................................ 68

Planispiral shells............................... 45

planodorsatus, Sinuites............ 41, 111, 113

114 

Planospiralia.................................... 54

Platypilina.... .................................. 72

tardissima................................. 72

Plectonotinae .....................63, 64, 126, 143

Plectonotus....................... ...34, 48, 62, 143

sp. ..........................................32, 34

Pleurotomariaceans................30, 32, 33, 35

49, 115, 116 

Pleurotomariidae.............................. 49

Point Pleasant Tongue, Clays Ferry

Formation................................ 20, 24

pojetai, Bucania............ ..29, 138, 139; pl.20

Polinices......................................... 47

powersi, Archinacella............. 75, 76, 79, 82

praecursor, Chalarostrepsis ............... 117

Preachersville Member, Drakes

Formation ........................... 18, 21, 24

Predation....................................... 41, 42

Preservation of study material............ 25

primaeva, Bellerophon punctifrons...... 141

Procarinaria.................................... 62

Procarinariidae................................. 62

Prodelta slopes................................. 35

Proplina ......................................... 68

unguiformis............................... 70

Proplinidae.....................................61, 68

Prosobranch gastropods..................... 54

Prosobranchia ................................63, 115

Protaxites ....................................... 31

Protoconch ..................................... 58, 67

Protowarthia ................................... 110

cancellata.................................. Ill

Page

Protowarthia—Continued

obesus....................................... 112

pervoluta................................... 110

subcompressa.. ........................... 115

Protowarthiidae................................ 61

Protowenella. ................................... 56

Pseudoselenizone ............................50, 125

Pteropod......................................... 181

Pterotheca...........A\, 47, 48, 55, 62, 64, 174

176, 181, 182, 184; pis.26, 39, 40 

anatiformis ........................... 182, 185

angusta............... 28, 36, 182, 185; pl.39

attenuate .................182, 183, 184, 186

canaliculata .......................... 182, 185

clochensis.............................. 182, 185

consobrina................................. 33

expansa.................. .27, 28, 36, 39, 182

183, 184, 185; pis.39, 40 

harviei........29, 182, 183, 185, 186; pl.26

intermedia.. ............................... 184

saffordi............. .......27, 28, 39, 46, 182

183, 185, 186; pis.39, 40 

transversa..... ........................ 182, 185

undulata..................... .....27, 182, 185

(Clioderma) saffordi................... 182

Pterothecidae..........................62, 175, 176

Pterothecinae..................... 62, 63, 175, 181

Ptomatis... ...............................51, 64, 116

Ptychobellerophon............................ 158

Ptychopeltis..................................... 75

pulaskiensis, Archinacella................. pl.2

Archinella................................. 81

punctifrons, Bellerophon ............... 141, 142

Bucarem.................................... 142

primaeva, Bellerophon................ 141

Undulabucania .......... ....27, 39, 41, 128

141, 142, 143; pl.23 

pustulosum, Stromatacerium............. 132

R

Radial apertures.............................47, 151

radiata, Helcionopsis ........................ 66

radiatum, Tryblidium. ...................... 66

Radulae .......................................... 30

Ramose bryozoans ............................ 124

Raphistomatidae............................... 57

Reba Member, Ashlock Formation ...... 21

rectangularis, Sinuites...................... Ill

recticostatus, Bellerophon .................. 52

recurvus, Bellerophon....................... 171

Sphenosphaera............29, 159, 166, 167

171, 172, 174; pi. 33 

References ...................................... 156

Regulatory detorsion......................... 45

reticulatus, Helcionopsis ................... 66

Retispira ......................................... 162

Retractor muscles............................. 53

scars......................................... 43

retrorsus, Cyrtolites.......... 29, 38, 39, 87, 90

(Cyrtolites).......... 21, 28, 36, 37, 38

44, 87, 89, 90, 94, 96, 98, 99 

100, 101, 104, 108, 109; pls.5, 7

Page

retrorsus—Continued

fillmorensis, Cyrtolites

(Cyrtolites).. .............................89, 99

Rhynchotrema dentatum beds,

Whitewater Formation................ 156

Richmond Group............................... 12

richmondensis, Archinacella........ 82, 83, 84

Salpingostoma ................29, 41, 47, 48

138, 139, 150, 151, 155 

156, 157, 174; pls.24, 26 

Richmondian Stage, upper Middle

and Upper Ordovician rocks ......... 4

Ridley Limestone, Stones River

Group....................................... 7

Rocklandian Stage, upper Middle

and Upper Ordovician rocks ......... 4

rogersensis, Bellerophon......... 166, 167, 168;

pi. 32 

Romaniella ............................... 59, 71, 72

Romaniellidae .................. 59, 60, 61, 71, 74

Rosov, quoted.................................. 71

Rowland Member, Drakes

Formation................................. 21

Rugae......................................... 134, 138

rugatina, Archinacella .............. 29, 81; pl.2

Bucania............ ....28, 38, 127, 131, 132

136, 137; pis. 16, 17

S

saffordi, Clioderma........................... 182

Pterotheca....... ..27, 28, 39, 46, 182, 183

185, 186; pls.39, 40 

(Clioderma).. ....................... 182

Salpingostoma ................. 40, 47, 48, 50, 54

61, 62, 64, 117, 119, 127

128, 149, 150; pls.24, 25, 26

billingsi ..........................150, 154, 156

boreale...................................... 150

buelli.. ................ 52, 150, 151, 153, 154

156; pl.24 

canadense ................................. 150

dilate...................................... 150

expansa ................... 150, 154, 155, 156

fraternus................................... 150

imbricata .................................. 150

inornatum................................. 150

kentuckyense .......28, 36, 37, 47, 51, 150

151, 152, 153, 154, 156; pls.24, 25, 26 

lata... ....................................... 150

locator...................................... 150

orientalis .................................. 150

richmondensis................. 29, 41, 47, 48

138, 139, 150, 151, 155

156, 157, 174; pls.24, 26

sculptilis................................... 150

sp. ........................................... 36

Salpingostomatidae .........................62, 149

Salpingostomatinae ............. 63, 64, 126, 149

Saluda Dolomite Member, Drakes

Formation................................. 21

Saluda Formation ....................... 19, 24, 25

Sal visa Bed, Perry ville Limestone Member, Lexington Limestone........... 15, 16
PLATE 1

[All dorsal and ventral views have anterior end down]

FIGURES 1-7. Micropileus variabilis new species (p. 073).

1-4. Dorsal, ventral, and left- and right-lateral views of holotype (x 3). Curdsville Limestone Member, 

Lexington Limestone (Kirkfieldian), USGS 7817- CO. USNM 265926.

5. Left-lateral view of a paratype (x 3). Curdsville Limestone Member, Lexington Limestone 

(Kirkfieldian), USGS 7784-CO. USNM 265928.

6. Left-lateral view of a paratype (x 3). Same collection as figure 5 above. USNM 265929.

7. Left-lateral view of a paratype (x 3). Same sample as figure 5 above. USNM 265927. 

8-11. Vallatotheca manitoulini Foerste, 1914a (p. 069).

8, 9. Oblique left-lateral and dorsal views of calcitic cast (x 3). Elkhorn biofacies, Preachersville Member,

Drakes Formation, from creek just south of Morning Sun, Ohio. MU 244T. 

10, 11. Right-dorsolateral and dorsal views of calcitic cast (x 3). Upper Whitewater Formation, from

tributary of Paint Creek near Camden, Ohio. MU 245T. 

12-31. Vallatotheca unguiformis (Ulrich, 1897) (p. 070).

12-15. Dorsal, ventral, and left- and right-lateral views of lectotype (x 3). Museum label gives horizon and

locality as "Upper Trenton, Harrodsburg Junction, C.S. Railroad, Kentucky." USNM 45990. 

16, 17. Right-lateral and dorsal views of silicifiled specimen (x 4). Salvisa Bed, Perryville Limestone

Member, Lexington Limestone, USGS 6915-CO. USNM 265934. 

18-20. Dorsal and right- and left-lateral views of silicified specimen (x 3). Salvisa Bed, Perryville Limestone

Member, Lexington Limestone, USGS 5015-CO. USNM 265932. 

21, 22. Right-lateral and dorsal views of a paralectotype (x 3). Same collection as figures 12-15 above.

USNM 265930. 

23, 24. Dorsal and right-lateral views of a paralectotype (x 3). Same collection as figures 12-15 above.

USNM 265931. 

25-28. Dorsal, ventral, and left- and right-lateral views of large silicified specimen (x 3). Note that apex is

nearly level with apertural plane. Same collection as figures 16, 17 above. USNM 265936. 

29. Dorsal view of silicified specimen; slightly curved beak probably caused by diagenetic distortion

(x 3). Same collection as figures 16, 17 above. USNM 265935.

30, 31. Dorsal and ventral views of bryozoan-encrusted silicified specimen (x 3). Same collection as figures 

18-20 above. USNM 265933.
U.S. GEOLOGICAL SURVEY PROFESSIONAL PAPER 1066-O PLATE 1

MICROPILEUS AND VALLATOTHECA
PLATE 2

[All dorsal and ventral views, except fig. 17, have anterior end down]

FIGURES 1-6. Helcionopsis striata Ulrich and Scofield, 1897 (p. 066).

1-3. Dorsal, oblique left-lateral, and left-lateral views of latex mold of holotype, which is an external mold 

in the base of a bryozoan colony (x 2). Museum label gives horizon and locality as "Richmond 

Group, Marion County, Kentucky." USNM 45827.

4, 5. Ventrolateral view of external mold in the base of a bryozoan colony (x 2), and dorsal view of latex 

mold of same (x 3.25). Bellevue biofacies, Grant Lake Limestone (Maysvillian), Cincinnati, Ohio. 

USNM 47494. 

6. Dorsal view of calcitic cast showing thin shell of species as well as small cone-shaped protoconch

(x 2). Arnheim Formation (Maysvillian-Richmondian), Clifton, Tenn. USNM 263785. 

7-12. Archinacella simulatrix Ulrich and Scofield, 1897 (p. 076).

7, 8. Dorsal and left-lateral views of latex mold of holotype, which is an external mold in the base of a 

bryozoan colony (x 3). Decorah Formation (Rocklandian-Kirkfieldian), St. Paul, Minn. USNM 

45695.

9. Dorsal view of silicified specimen embedded in matrix (x 3). Grier Limestone Member (Shermanian), 

Lexington Limestone, USGS 5094-CO. USNM 265941.

10. Right-lateral view of silicified specimen (x 2.5). Grier Limestone Member (Shermanian), Lexington 

Limestone, USGS 4073-CO. USNM 265945.

11. Right-lateral view of silicified specimen (x 2.5). Same collection as figure 10 above. USNM 265944.

12. Dorsal view of silicified specimen embedded in matrix (x 2.5). Museum label gives horizon and

locality as "Trenton (Hermitage), Frankfort, Kentucky" (Kirkfieldian). USNM 47471.

13, 14. Archinacella cf. A. depressa Ulrich and Scofield, 1897 (p. 079). Slightly oblique left-lateral and dorsal views of 

silicified specimen (x 2.5). Museum label gives horizon and locality as "Mohawkian (Cannon), Hartsville, 

Tennessee" (Kirkfieldian-Shermanian). USNM 59295.

15, 16. Archinacella valida (Sardeson, 1892) (p. 078). Dorsal and dorsolateral views of calcitic specimen (x 2). Museum 

label gives horizon and locality as "Trenton (Ctenodonta horizon), Mt. Parnassus, Columbia, Tennessee" 

(Kirkfieldian). USNM 47467.

17, 18. Archinacella cf. A. pulaskiensis Foerste, 1914b (p. 081) Dorsal and right- lateral views of fragmentary calcitic 

cast (x 3). Museum label gives only the horizon, as "Maysville," but specimen most likely is from 

Cincinnati, Ohio, area. UCGM 19640. 

19-21. Archinacella rugatina Ulrich, 1897 (p. 081). Dorsal, left-lateral, and dorsolateral views of holotype (x 2).

Arnheim biofacies, Bull Fork Formation (Richmondian), Middleton, Ohio. USNM 45963. 

22-26. Archinacella cingulata Ulrich, 1897 (p. 079).

22-24. Dorsal and right- and left-lateral views of holotype, a weathered silicified specimen (x 2). Curdsville

Limestone Member (Kirkfieldian), Lexington Limestone, Mercer Co., Ky. USNM 45686. 

25, 26. Dorsal and left-lateral views of internal mold (x 1.5). Clays Ferry Formation (Edenian), Owenton, 

Ky. MU 249T.
U.S. GEOLOGICAL SURVEY PROFESSIONAL PAPER 1066-O PLATE 2

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PLATE 3

[All dorsal and ventral views have anterior end down]

FIGURES 1-3. Archinacellat davisi new species (p. 080). Dorsal and right- and left-lateral views of holotype, an internal mold

(x 1.0). Kope Formation(?) (Edenian?), near Glencoe, Ky. CMNH P2. 

4-6. Archinacella alta new species (p. 080). Dorsal, left-lateral, and oblique right-lateral views of holotype (x 2).

Clays Ferry Formation (Edenian), northern Kentucky. MU 248T. 

7-10. Archinacella area new species (p. 082). Dorsal, posterior, right-lateral, and anterior views of holotype (x 2).

Waynesville biofacies, Bull Fork Formation (Richmondian), Waynesville, Ohio. USNM 40615. 

11, 12. Archinacella sp. (p. 075). Right-lateral and dorsal views of coarsely silicified specimen (x 2). Grier Limestone

Member (Shermanian), Lexington Limestone, USGS 4073-CO. USNM 265955. 

13-24. Archinacella indianensis (Miller, 1892) (p. 083).

13-15. Dorsal and left- and right-lateral views of holotype, a highly weathered internal mold (x 1.5).

Museum label gives horizon and locality as "Richmond, Fayette County, Indiana." UC 6065. 

16-18. Ventral view of external mold in the base of a bryozoan colony, and dorsal and right-lateral views of 

latex mold (x 2). Holotype of Archinacella richmondensis Ulrich (1897). Whitewater Formation 

(Richmondian), Richmond, Ind. USNM 45691.

19, 20. Dorsal and oblique dorsal views of silicified specimen (x 2). Liberty biofacies, Dillsboro Formation 

(Richmondian), Ind. USGS 6139-CO. USNM 265946.

21. Left-lateral view of calcitic cast (x 2). Elkhorn biofacies, Drakes Formation, from creek just south of 

Morning Sun, Ohio. MU 246T.

22. Left-lateral view of calcitic cast (x 1.5). Note arched lateral apertural margin. Same horizon and

locality as figure 21 above. MU 250T.

23, 24. Dorsal and left-lateral views of calcitic cast (x 2). No data with specimen; probably from 

Richmondian strata of southwestern Ohio or southeastern Indiana. MU 247T.
U.S. GEOLOGICAL SURVEY PROFESSIONAL PAPER 1066^0 PLATE 3
PLATE 4

FIGURES 1-14. Archinacella indianensis (Miller, 1892) (p. O83). (Dorsal and ventral views have anterior end down.)

1, 2. Dorsal and left-dorsolateral views of calcitic cast showing rather irregular growth lines (x 2).

White water biofacies, Drakes Formation (Richmondian), Oakland, Ohio. USNM 70467. 

3-7. Dorsal, anterodorsal, oblique right-lateral, and left- and right-lateral views of silicified specimen 

(x 2). Liberty biofacies, Dillsboro Formation, (Richmondian), Ind. USGS 6139-CO. USNM 

265951. 

8-12. Ventrolateral and ventral views of external mold in the base of a bryozoan colony, and dorsal,

left-dorsolateral, and right-lateral views of latex mold made from specimen (x 2). Waynesville 

biofacies, Bull Fork Formation (Richmondian), Oregonia, Ohio. USNM 47468. 

13, 14. Left-lateral and dorsal views of anterior portion of fragmentary silicified specimen (x 2). Same

collection as figures 3-7 above. USNM 265949. 

15-17. Cyrtolites (Cyrtolites) claysferryensis new species (p. 0100).

15, 16. Both sides of small slab from a mollusk bed (x 2) containing a paratype of C. (C.) claysferryensis, 

gastropods, pelecypods, some cephalopods, small unidentifiable bellerophontaceans, the trilobite 

Cryptolithus, and brachiopod fragments. Note circular hole in dorsal slope of paratype (lower 

right) in figure 15, which may be a boring. Kope Formation (Edenian), from northern end of 

bench in roadcut on northwestern side of Carrollton, Ky., exit from Interstate I- 71 (locality 

KY-1). USNM 265959.

17. Lower side of slab from lenticular mollusk bed containing Sinuites, Spkenosphaera, Tetranota, a 

paratype of Cyrtolites (C.) claysferryensis (middle left), small conispiral gastropods, and 

cephalopods, in that order of abundance (x 1.5). Lower Kope Formation (Edenian), about 10 ft 

above contact with Point Pleasant Tongue, Clays Ferry Formation, Bear Creek Quarry, just 

north of Ohio River between Neville and Chilo, Ohio (locality OH-1). USNM 315609. 

18-25. Carinaropsis acuta Ulrich and Scofield, 1897 (p. O177).

18, 19. Dorsal and left-lateral views of silicified specimen (x 2). Note subcircular outline and rather wide 

selenizone in figure 18. Basal 2 ft of Curdsville Limestone Member (Kirkfieldian), Lexington 

Limestone, USGS 7784- CO. USNM 265992. 

20, 21. Dorsal and left-lateral views of silicified specimen (x 2). Curdsville Limestone Member

(Kirkfieldian), Lexington Limestone, USGS 7784-CO. USNM 265993. 

22, 23. Dorsal and left-lateral views of silicified specimen (x 3). Curdsville Limestone Member

(Kirkfieldian), Lexington Limestone, USGS 5100-CO. USNM 265994.

24, 25. Dorsal and right-lateral views of silicified specimen (x 3). Curdsville Limestone Member 

(Kirkfieldian), Lexington Limestone, USGS 5023-CO. USNM 265995.
U.S. GEOLOGICAL SURVEY PROFESSIONAL PAPER 1066-O PLATE 4

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ARCHINACELLA, CYRTOLITES, AND CARINAROPSIS
PLATE 5

FIGURES 1-26. Cyrtolites (Cyrtolites) retrorsus Ulrich, 1897 (p. 094).

1, 2. Apertural and left-lateral views of a paralectotype (x 2). Lexington Limestone, about 1 mi south of

Burgin, Ky. USNM 265938. 

3, 4. Apertural and right-lateral views of a paralectotype (x 2). Lexington Limestone, about 1 mi south of

Burgin, Ky. USNM 265899. 

5-7. Apertural, right-lateral, and dorsal views of lectotype (x 2). Museum label reads "Trenton

[Kirkfieldian-Shermanian] near Nashville, Tennessee." USNM 45789. 

8-10. Apertural, left-lateral, and dorsal views of a paralectotype (x 2). Museum label reads "Trenton

[Kirkfieldian-Shermanian], near Nashville, Tennessee." USNM 265901. 

11, 12. Apertural and left-lateral views of a paralectotype (x 2). Museum label reads "Trenton

[Kirkfieldian-Shermanian], near Nashville, Tennessee." USNM 265902. 

13. Dorsal view of a paralectotype (x 2). Lexington Limestone, about 1 mi south of Burgin, Ky. USNM

265900. 

14-17. Apertural, dorsal, and left- and right-lateral views (x 2). Lower Logana Member (Kirkfieldian),

Lexington Limestone, USGS 6419- CO. USNM 265903. 

18-21. Apertural, dorsal, and left- and right-lateral views (x 2). Same collection as figures 14-17 above.

USNM 265904. 

22-25. Apertural, dorsal, and left- and right-lateral views (x 2). Same collection as figures 14-17 above.

USNM 265905. 

26. Dorsal view illustrating shell sculpturing; enlargement of specimen shown in figures 14-17 above

(x5).

27, 28. Archinacella indianensis (Miller, 1892) (p. 083). Dorsal and right-lateral views (x 3). Liberty biofacies, 

Dillsboro Formation (Richmondian), USGS 6139- CO. USNM 265950.
U.S. GEOLOGICAL SURVEY PROFESSIONAL PAPER 1066-OPLATE5

CYRTOLITES AND ARCHINACELLA
PLATE 6

FIGURES 1-18. Cyrtolites (Cyrtolites) ornatus Conrad, 1838 (p. 091).

1-3. Left-lateral (x 2), apertural (x 1.5), and dorsal (x 1.5) views of an Ulrich and Scofield (1897) hypotype. Corryville biofacies, Grant Lake Limestone or Bull Fork Formation (Maysvillian), 

Cincinnati, Ohio. USNM 45786. 

4, 5. Dorsal and left-lateral views of internal mold (x 2). Museum label gives locality and horizon as

"Hudson River Group [Upper Ordovician], northern New York." UCGM 44270. 

6-8. Left-lateral, dorsal, and apertural views of composite mold (x 2). Same locality and horizon as

figures 1-3 above. USNM 265906. 

9-11. Left-lateral, dorsal, and apertural views of composite mold (x 2). Same locality and horizon as

figures 1-3 above. USNM 265907.

12-14. Right-lateral (x 2), dorsal (x 2) and apertural (x 1.5) views of bryozoan- encrusted specimen. 

Museum label gives horizon as "Maysville"; locality not given, but the vicinity of Cincinnati, 

Ohio, seems likely. UCGM 44273.

15, 16. Dorsal and apertural views of bryozoan- encrusted specimen (x 1.5). Museum label gives horizon as 

"Richmond"; locality not given, but southwestern Ohio is likely. UCGM 44272.

17. Dorsal view of vertically compressed specimen preserving calcitic shell (x 1.5). Same sample as 

figures 15, 16 above. UCGM 44271.

18. Right-lateral view of disjunct internal mold (x 2). Waynesville biofacies, Rowland Member, Drakes

Formation (Richmondian), southwestern Ohio. UCGM 44274.

19-22. Cyrtolites (Cyrtolites) disjunctus Ulrich and Scofield, 1897 (p. 0106). Dorsal, apertural, left-lateral, and oblique 

left-lateral views of holotype, which is a calcitic specimen (x 2). Museum label gives horizon and locality as 

"Richmond Group, near Spring Valley, Minnesota." USNM 45785.
U.S. GEOLOGICAL SURVEY PROFESSIONAL PAPER 1066-O PLATE 6

15
PLATE 7

FIGURES 1. Cyrtolites (Cyrtolites) ornatus Conrad, 1838 (p. 091). Right-lateral view of disjunct internal mold (x 2). Same

sample and locality as on plate 6, figures 1-3. USNM 265908. 

2-10. Cyrtolites (Cyrtolites) minor Ulrich, 1897 (p. 0102).

2-4. Dorsal, apertural, and right-lateral views of holotype (x 3). Museum label gives horizon and

locality as "Clitambonites bed, Trenton (Prosser), Cannon Falls, Minnesota." USNM 45787. 

5-7. Dorsal, apertural, and right-lateral views of bryozoan-encrusted specimen (x 2.5). McMicken 

biofacies, Kope Formation (Edenian); no locality given, but probably from the Cincinnati, 

Ohio, area. UCGM 19668. 

8-10. Dorsal, apertural, and right-lateral views of calcitic cast (x 2). Contact of Fairview Formation

and Miamitown Shale (Maysvillian). Hamilton-Butler Co. line, Ohio. USNM 44275. 

11-16. Cyrtolites (Cyrtolites) retrorsus Ulrich, 1897 (p. 094).

11-13. Dorsal, apertural, and right-lateral views of calcitic cast (x 3). Kope Formation (Edenian),

Covington, Ky. USNM 265909. 

14-16. Dorsal, apertural, and left-lateral views of calcitic cast (x 3). Same collection and locality as

figures 11-13 above. USNM 265910. 

17. Cyrtolites (Paracyrtolites) parvus Ulrich, 1897 (p. 0109). Right-lateral view of holotype (x 4). A museum label

gives horizon and locality as "Upper Trenton [Shermanian], Covington, Kentucky." USNM 45788. 

18-25. Cyrtolites (Paracyrtolites) carinatus Miller, 1874 (p. 0108).

18, 19. Left-lateral and dorsal views of holotype (x 3). Kope Formation (Edenian); locality given on

museum label as "within two hundred feet of low water-mark, at Bold Face Creek, opposite 

Fifth Street, and at the excavation for Columbia Avenue." Note that Columbia Avenue is 

now named Columbia Parkway in Cincinnati, Ohio. UC 8895.

20. Apertural view of calcitic cast (x 3). Kope Formation (Edenian), from mollusk bed in lower part 

of large exposure just southeast of Carrollton, Ky. Collected by Steven Felton. UCGM 

44277.

21. Left-lateral view of composite mold, which is an Ulrich and Scofield (1897) hypotype (x 2). 

Southgate biofacies, Kope Formation (Edenian), Newport, Ky. USNM 265912.

22. Left-lateral view of another Ulrich and Scofield (1897) hypotype (x 2). Same collection as figure 

21 above. USNM 47499.

23. Dorsal view of another Ulrich and Scofield (1897) hypotype, which retains the shell and its fine

growth lines (x 3). Same collection as figure 21 above. USNM 265911. 

24, 25. Left-lateral and apertural views of another Ulrich and Scofield (1897) hypotype showing fine

growth lines (x 3). Same collection as figure 21 above. USNM 265913. 

26-32, 34, 35. Cyrtolites (Paracyrtolites) subplanus Ulrich, 1897 (p. 0107).

26, 27, 35. Right-lateral (x 1.5), dorsal (x 1.5), and dorsal closeup (about x 4.5) views of lectotype, a 

slightly weathered silicified cast. Note strong deflection of growth lines, reflecting a 

relatively deep sinus, and the faint trace of revolving threads along some growth lines. 

Cannon facies, Bigby- Cannon Limestone (Kirkfieldian-Shermanian), Snow's Hill, 4 mi east 

of Liberty, Tenn. USNM 45792. 

28, 29. Left-lateral and dorsal views of a paralectotype (x 2). Same collection as figures 26, 27 above.

USNM 265914.

30-32, 34. Dorsal, apertural, and left-lateral views (all x 2) and dorsal closeup view showing detail of shell 

sculpturing (about x 5). Note weak revolving threads, which give surface a faintly pitted 

appearance. Logana Member, Lexington Limestone (Kirkfieldian), USGS D-1196-CO. 

USNM 265915.

33. Cyrtolites (Paracyrtolites) cf. C. (P.) subplanus Ulrich, 1897 (p. 0107). Right-lateral view of silicified specimen 

(x 2). Grier Limestone Member, Lexington Limestone (Shermanian), USGS 4852-CO. USNM 265918.
U.S. GEOLOGICAL SURVEY PROFESSIONAL PAPER 1066-O PLATE 7
PLATE 8

FIGURES 1-10. Cyrtolites (Cyrtolites') hornyi new species (p. O104).

1-4. Apertural, dorsal, and left- and right-lateral views of holotype (x 2). Liberty biofacies, Dillsboro

Formation (Kichmondian), USGS 6139-CO. USNM 265920. 

5-7. Apertural, dorsal, and right-lateral views of a paratype (xl). Same collection as figures 1-4 above.

USNM 265921. 

8-10. Apertural, dorsal, and left-lateral views of another paratype (xl). Same collection as figures 1- 4

above. USNM 265922. 

11-20. Cyrtolites (Cyrtolites) claysferryensis new species (p. O100).

11-13. Apertural, dorsal, and left-lateral views of a paratype (x 2). Clays Ferry Formation (Edenian),

USGS 6990-CO. USNM 265925.

14-18. Dorsal, apertural, and left- and right-lateral views of holotype (all x 2) and dorsal closeup view of 

shell sculpturing (about x 6). Upper tongue of Clays Ferry Formation, USGS 6143-CO. USNM 

265924. 

19, 20. Left-lateral and dorsal views of a paratype (x 2). Same collection as figures 14-18 above. USNM

265923.

21. Cyrtolites (Paracyrtolites) carinatus Miller, 1874 (p. O108). Small slab from mollusk bed. Same horizon and 

locality as plate 7, figure 20, Kope Formation (Edenian), near Carrollton, Ky (x 2). Also shows the 

univalves Lophospira, Liospira, and Sinuites, the pelecypod Ambonychia, and cephalopod fragments. 

Collected by Steven Felton. UCGM 44279. 

22-26. Cyrtolites (Paracyrtolites) cf. C. (P.) subplanus Ulrich, 1897 (p. O107).

22-24. Left-lateral, dorsal, and apertural views of silicified specimen (x 2). Grier Limestone Member,

Lexington Limestone, USGS 4852-CO. USNM 265916. 

25, 26. Left-lateral and dorsal views of worn silicified specimen, which has been bored (x 2). Same collection

as figures 22-24 above. USNM 265919.

27. Cyrtolites (Paracyrtolites) subplanus Ulrich, 1897 (p. O107). Eight-lateral view of small silicified specimen 

(x 2). Logana Member, Lexington Limestone. USGS D-1196-CO. USNM 265917.
U.S. GEOLOGICAL SURVEY PROFESSIONAL PAPER 1066-O PLATE 8

21

CYRTOLITES
PLATE 9

FIGURES 1-12. Sinuites obesus (Ulrich), 1897 (p. 0112).

1^4. Dorsal, ventral, anterior, and left-lateral views of silicified specimen (x 1.5). Curdsville Limestone

Member (Kirkfieldian), Lexington Limestone, USGS 5022-CO. USNM 315634. 

5. Dorsal view of silicified specimen preserving trace of growth lines (x 1.5). Logana Member

(Kirkfieldian), Lexington Limestone, USGS 5092- CO. USNM 315636. 

6-9. Dorsal, ventral, right-lateral, and anterior views of fragmentary silicified specimen (x 1.5). Same

collection as figure 5 above. USNM 315635.

10-12. Dorsal, ventral, and posterior views of fragmentary silicified specimen (x 2). Same collection as 

figure 5 above. USNM 315637.
U.S. GEOLOGICAL SURVEY PROFESSIONAL PAPER 1066-O PLATE 9

11

SINUITES
PLATE 10

FIGURES 1-13. Sinuites globularis (Miller and Faber), 1894 (p. 0114).

1-7. Dorsal, ventral, left-lateral, anterior, right- anterolateral, and right-dorsolateral views (x 2.5) and 

closeup dorsal view (x 6.75) of calcitic lectotype. Kope Formation (Edenian), Cincinnati, Ohio. 

UC 8811a. 

8-10. Dorsal, anterior, and left-lateral views of another calcitic specimen (x 3). Kope Formation (Edenian),

Carrollton, Ky. UCGM 44305.

11-13. Dorsal, left-dorsolateral, and left-lateral views of calcitic paralectotype (x 2.5). Same locality as 

figures 1-7 above. UC 8811b.
U.S. GEOLOGICAL SURVEY PROFESSIONAL PAPER 1066^0 PLATE 10
PLATE 11

FIGURES 1-5. Sinuites granistriatus (Ulrich), 1897 (p. 0113). Dorsal, right-dorsolateral, right-lateral, and ventral views (x 2) 

and closeup dorsal view (x 4.5) of calcitic specimen preserving the growth lines. Kope Formation, Chilo, 

Ohio (locality OH-1). UCGM 44295. 

6-12. Sinuites cancellatus (Hall), 1847 (p. 0111).

6-9. Dorsal, anterior, right-lateral, and left- anterolateral views of calcitic specimen with shell weathered

away dorsally (x 2). Museum label reads only "Cincinnatian, Cincinnati, Ohio." UCGM 44304. 

10-12. Dorsal, posterior, and left-lateral views of calcitic specimen (x 2). Kope Formation (Edenian), 

Cincinnati, Ohio. UCGM 44307.
U.S. GEOLOGICAL SURVEY PROFESSIONAL PAPER 1066-O PLATE 11

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SINUITES
PLATE 12

FIGURES 1-4. Bucania emmonsi Ulrich and Scofield, 1897 (p. 0128). Dorsal, left-posterolateral, posterior, and left-lateral

views of silicified lectotype (x 3). Murfreesboro Limestone (Blackriveran), Tenn. USNM 46049. 

5-16. Bucania halli Ulrich and Scofield, 1897 (p. 0129).

5-9. Dorsal (x 3) and right-anterodorsal, ventral, posterior, and right-lateral (x 2) views of lectotype. 

Museum label reads "Black River Group Decorah Formation [Rocklandian], Cannon Falls, 

Minnesota." USNM 45717.

10-14. Dorsal, ventral, left-lateral, and right- lateral views of a paralectotype (x 1.5) and right-lateral 

closeup view (x 6) showing shell markings. Curdsville Limestone Member (Kirkfieldian), 

Lexington Limestone, Mercer Co., Ky. USNM 315582. 

15, 16. Anterior and right-lateral views of fragmentary silicified specimen (x 3). Grier Limestone Member

(Shermanian), Lexington Limestone, USGS 4073-CO. USNM 315544.

17, 18. Bucania cf. B. halli Ulrich and Scofield. Right-lateral and dorsal views of silicified specimen (x 2). Lower 

Curdsville Limestone Member (Kirkfieldian), Lexington Limestone, USGS 5100-CO. USNM 315545.
U.S. GEOLOGICAL SURVEY

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PLATE 13

FIGURES 1-8. Bucania sublata Ulrich and Scofield, 1897 (p. 0135).

1—4. Dorsal (x 5) and posterior, left- dorsolateral, and left-lateral (x 3) views of silicified lectotype.

Lexington Limestone, near Burgin, Ky. USNM 315561. 

5-8. Right-posterolateral, right-lateral, dorsal, and posterior views of silicified fragment showing large

umbilicus, reflexed parietal lip, and broad median parietal ridge (x 2). Same collection as figures 

1-4 above. Paralectotype, USNM 315562. 

9-14. Bucania cf. B. sublata Ulrich and Scofield, 1897 (p. 0135).

9, 10. Right-lateral and dorsal views of silicified fragment (x 3). Grier Limestone Member, Lexington

Limestone, USGS 4879-CO. USNM 315563. 

11. Left-lateral view of silicified fragment (x 2). Faulconer Bed, Perryville Limestone Member,

Lexington Limestone, USGS 6136-CO. USNM 315564. 

12-14. Right-lateral, posterior, and dorsal views of large silicified fragment (x 1.5). Devils Hollow Member,

Lexington Limestone, USGS 5095- CO. USNM 315565. 

15-21. Bucania nashvillensis Ulrich, 1897 (p. 0132).

15, 16. Two views of two silicified specimens cemented together with other skeletal debris showing

characteristic small umbilicus and narrowly rounded dorsum (x 2). Salvisa Bed, Perryville 

Limestone Member, Lexington Limestone, USGS 5015-CO. USNM 315566. 

17, 18. Posterior (x 3) and right-lateral (x 2) views of incomplete specimen. Same collection as figures 15,

16 above. USNM 315567. 

19. Right-posterolateral view of silicified fragment showing small umbilicus, angular dorsum, and

thickened parietal lip (x 2). Same collection as figures 15, 16 above. USNM 315568. 

20, 21. Left-lateral and dorsal views of silicified specimen (x 2). Salvisa Bed, Perryville Limestone Member,

Lexington Limestone, USGS 6916-CO. USNM 315569. 

22-24. Bucania frankfortensis Ulrich, 1897 (p. 0133).

22. Right-lateral view of silicified fragment showing characteristic wrinkled lateral apertural slope (x 2).

Devils Hollow Member, Lexington Limestone, USGS 5036-CO. USNM 315571.

23, 24. Ventral and right-lateral views of silicified fragment showing subtriangular apertural outline and 

wrinkled lateral apertural slope (x 2). Same collection as figure 22 above. USNM 315570.
L.S. GEOLOGICAL SURVEY PROFESSIONAL PAPER 1066-O PLATE 13

BUCANIA
PLATE 14

FIGURES 1-14. Bucania nashvillensis Ulrich, 1897 (p. 0132).

1-5. Anterior, posterior, left-lateral, dorsal, and ventral views of a silicified paralectotype (x 1.5). Cannon

fades, Bigby-Cannon Limestone, Nashville, Tenn. USNM 45724.

6-9. Posterodorsal, left-lateral, ventral, and anterior views of a bryozoan-encrusted, silicified paralectotype showing deep slit and mature lamellose growth lines (x 1.5). Cannon facies, Bigby-Cannon 

Limestone, Dekalb Co., Tenn. USNM 315558. 

10-14. Oblique anterolateral, dorsal, right-lateral, and anterodorsal views of lectotype (x 2) and closeup

view of slit and shell ornament (x 5). Same collection as figures 6-9 above. USNM 315557. 

15-19. Bucania subangulata Ulrich, 1897 (p. 0130).

15-18. Right-lateral, posterior, antero-right- lateral, and posterodorsal views of silicified lectotype, in which 

anterodorsal shell area has been reconstructed with plaster (lighter colored area) (x 1.5). 

Lexington Limestone, 1.5 mi south of Burgin, Ky. USNM 315559.

19. Dorsal view of a silicified paralectotype showing lunulae of selenizone and shell markings (x 2). Same 

collection as figures 15-18 above. USNM 315560.
U.S. GEOLOGICAL SURVEY 

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PROFESSIONAL PAPER 1066-O PLATE 14

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BUCANIA
PLATE 15

FIGURES 1-7. Bucania nashvillensis Ulrich, 1897 (p. 0132).

1, 2. Right-lateral and anterior views of fragmentary silicified specimen (x 2). Grier Limestone Member,

Lexington Limestone, USGS 4959-CO. USNM 315572. 

3-5. Dorsal, ventral, and left-lateral views of fragmentary specimen (x 3). Same collection as figures 1, 2

above. USNM 315573. 

6, 7. Left-lateral and dorsal views of silicified specimen (x 2.5). Grier Limestone Member, Lexington

Limestone, USGS 4073-CO. USNM 315574. 

8-24. Bucania subangulata Ulrich, 1897 (p. 0130).

8-12. Posterior, dorsal, left-posterior, ventral, and left-lateral views of silicified internal mold (x 3).

Curdsville Limestone Member, Lexington Limestone, USGS 7785-CO. USNM 315575. (For a 

similar specimen from the Grier Limestone Member, USGS 5094-CO, see pi. 38, figs. 11, 12.) 

13-15. Dorsal, right-posterior, and right-lateral views of relatively large fragment of silicified specimen

(x 2.5). Grier Limestone Member, Lexington Limestone, USGS 5094-CO. USNM 315576. 

16-20. Dorsal, ventral, right-lateral, left-lateral, and anterior views of small silicified specimen preserving

selenizone (x 4). Same collection as figures 13-15 above. USNM 315577.

21-24. Posterior, dorsal, ventral, and left-lateral views of fragment of silicified specimen (x 2). Grier 

Limestone Member, Lexington Limestone, USGS 5096-CO. USNM 315578.
U.S. GEOLOGICAL SURVEY

PROFESSIONAL PAPER 1066-O PLATE 15

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PLATE 16

FIGURES 1^4. Bucania frankfortensis Ulrich, 1897 (p. 0133). Dorsal, ventral, left-dorsolateral, and left-lateral views of

silicified holotype (x 1.5), in which much of the dorsum and essentially all of the anteromedian shell have 

been reconstructed with plaster (the smoother, less granular surfaces). Probably Devils Hollow Member, 

Lexington Limestone, Frankfort, Ky. USNM 45716.

5-8. Bucania peracuta Ulrich, 1897 (p. 0134). Posterior, left-lateral, dorsal, and cross-sectional views of silicified 

holotype (x 1.5), in which the anterior portion of the shell has been broken away. Cannon facies, 

Bigby-Cannon Limestone, Dekalb Co., Tenn. USNM 45726. 

9-15. Bucania rugatina Ulrich, 1897 (p. 0136).

9-12. Left-posterolateral view (x 3), closeup view of shell markings (x 6), and left-lateral and dorsal 

views (x 3) of lectotype. Lexington Limestone, 1.5 mi south of Burgin, Ky. USNM 315555. 

13-15. Left-lateral and dorsal views (x 3) of a silicified paralectotype and closeup view of selenizone and 

growth lines (approximately x 6). Same collection as figures 9-12 above. USNM 315556.
U.S. GEOLOGICAL SURVEY PROFESSIONAL PAPER 1066-O PLATE 16

Bt/CAMA
PLATE 17

FIGURES 1-12. Bucania rugatina Ulrich, 1897 (p. 0136).

1-6. Left-posterolateral view (x 2), enlarged left-posterolateral view (x 6), and dorsal, ventral, leftlateral, and posterior views (x 2) of silicified specimen preserving shell markings. Upper tongue, 

Clays Ferry Formation, USGS 6143-CO. USNM 315579.

7-11. Dorsal, ventral, right-lateral, left-lateral, and left-anterodorsal views of silicified specimen encrusted 

by a bryozoan colony (x 2.5). The chimneylike growths of the bryozoan colony in two directions 

may have resulted from partial burial of the shell, exhumation, and reburial in a different 

orientation. Tongue of Clays Ferry Formation between tongues of the underlying Millersburg 

Member and overlying Tanglewood Member of the Lexington Limestone, USGS 7348-CO. 

USNM 315580.

12. Left-lateral view of worn fragment showing characteristic shell markings of species (x 3). Same 

collection as figures 7-11 above. USNM 315581.
U.S. GEOLOGICAL SURVEY PROFESSIONAL PAPER 1066-O PLATE 17

12

BUCANIA
PLATE 18

FIGURES 1-9. Bucania lindsleyi (Safford), 1869 (p. 0131).

1-6. Dorsal, ventral, left-lateral, and left- dorsolateral views of silicified lectotype (x 1.5) and closeup

views of selenizone and of shell markings on left-anterior aperture (x 5). Cannon fades, BigbyCannon Limestone. Dekalb Co., Tenn. USNM 315550.

7-9. Dorsal view (x 3.5) and left-lateral and ventral views (x 2) of a silicified paralectotype. Note that 

this specimen is smaller than that in figures 1-6 above, and has not yet developed the lamellose 

growth lines. Same collection as figures 1-6 above. USNM 315551. 

10-12. Bellerophon (B.) subpatula (Ulrich), 1897 (p. 0161). Dorsal, ventral, and right-lateral views of silicified

lectotype (x 4). Lexington Limestone, 1.5 mi south of Burgin, Ky. USNM 315552. 

13-17. Bellerophon (B.) nana (Ulrich), 1897 (p. 0160).

13, 14. Dorsal and ventral views of silicified lectotype (x 4). Upper Lexington Limestone, 1.5 mi south of

Burgin, Ky. USNM 315553.

15-17. Left-lateral, dorsal, and ventral views of a silicified paralectotype (x 4). Same collection as figures 

13, 14 above. USNM 315554.
U.S. GEOLOGICAL SURVEY

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PROFESSIONAL PAPER 1066 O PLATE 18

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BUCANIA AND BELLEROPHON
PLATE 19

FIGURES 1-6. Bucania micronema Ulrich, 1897 (p. 0136). Dorsal, ventral, left-lateral, posterior, and left- anterodorsal views

of silicified holotype (x 3), and closeup view of the last showing shell markings (x 6). Note that in figure 2

there is an extraneous shell fragment blocking the apertural opening. Upper Lexington Limestone,

Danville, Ky. USNM 45720. 

7-10. Bucania crassa Ulrich, 1897 (p. 0139). Dorsal, ventral, right-anterolateral, and right-lateral views of calcitic

lectotype (x 1.5). Museum label reads "Richmond (Elkhorn Formation), near Richmond, Indiana." USNM

315547. 

11-14. Bucania simulatrix Ulrich, 1897 (p. 0139). Anterodorsal, dorsal, right-lateral, and right- anterolateral views of

calcitic lectotype (x 1.5). Whitewater Formation, Richmond, Ind. USNM 315548. 

15-18. Bucania singularis Ulrich, 1897 (p. 0137). Dorsal, posterior, left-lateral, and ventral views of lectotype (x 1.5).

Catheys Formation, Nashville, Tenn. USNM 315549.
U.S. GEOLOGICAL SURVEY PROFESSIONAL PAPER 1066-O PLATE 19

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BUCANIA
PLATE 20

FIGURES 1-8. Bucania pojetai new species (p. 0138).

1, 2. Dorsal and right-lateral views of calcitic specimen (x 1.5) preserving some remnants of the shell, 

and showing the internal mold of the dorsum as lacking the ridgelike slit filling that would be 

expected in species of Salpingostoma, which has a similar shell form. Leipers Limestone, 

Rowena Ferry, Russell Co., Ky. Paratype, UCGM 44286.

3, 4. Dorsal and left-lateral views of calcitic specimen having apparently highly recrystallized shell, showing the selenizone as a low, rounded ridge (x 1.5). Same collection as figures 1, 2 above. 

Holotype. UCGM 44285. 

5-8. Posterior, dorsal, left-lateral, and oblique dorsal views of a calcitic paratype showing wrinklelike

growth lines (x 1.5). Same collection as figures 1, 2 above. UCGM 44287.

9-12. Kokenospira costalis (Ulrich and Scofield), 1897 (p. 0140). Left-lateral, left-posterolateral, and dorsal views 

(x 2.5) and dorsolateral closeup view of calcitic specimen (x 6). Southgate biofacies, Kope Formation, 

Cincinnati, Ohio. UCGM 26519.

13-15. Tetranota cf. T. obsoleta Ulrich and Scofield, 1897 (p. 0146). Right-posterodorsal, dorsal, and ventral views of 

small silicified specimen (x 4). Upper Curdsville Member, Lexington Limestone, USGS 6131-CO. USNM 

315541.
U.S. GEOLOGICAL SURVEY PROFESSIONAL PAPER 1066-O PLATE 20

BUCANIA, KOKENOSPIRA, AND TETRANOTA
PLATE 21

FIGURES 1-14. Tetranota bidorsata (Hall), 1847 (p. O145).

1-4. Tetranota bidorsata and Sinuites granistriatus (Ulrich) in small slab of limestone (x 1.5), two 

closeup views (x 3 and x 6) emphasizing lateral ridges and selenizone of specimen in upper 

center, and closeup view (x 3) of specimen in lower left showing growth lines. From lenslike 

mollusk bed in Economy biofacies, lower Kope Formation, Chilo, Ohio (locality OH-1). UCGM 

44291. 

5-7. Posterior, anterior, and right-dorsolateral views of calcitic specimen (x 2). Same collection as

figures 1-4 above. UCGM 44292. 

8. Dorsal view of specimen in association with fragments of a crinoid column and the trilobite

Cryptolithus sp., a typical assemblage of the Kope Formation (x 2). Note that the gastropod is 

somewhat crushed. Same collection as figures 1-4 above. UCGM 44293.

9-11. Anterodorsal, right-lateral, and right- anterodorsal views of calcitic specimen preserving the lateral 

apertural expansion of maturity (x 2). Economy biofacies, Kope Formation, Bloody Run, 

Cincinnati, Ohio. USNM 47545. 

12, 13. Left-lateral and ventral views of lectotype (x 2). Trenton Group, Watertown, N.Y. AMNH Fl 29592

(James Hall collection).

14. Dorsal view of a paralectotype (x 2). Trenton Group, Middleville, N.Y. AMNH Fl 787 (James Hall 

collection).
U.S. GEOLOGICAL SURVEY PROFESSIONAL PAPER 1066-O PLATE 21 / •;

TETRANOTA
PLATE 22

FIGURES 1-10. Tetranota bidorsata (Hall), 1847 (p. 0145).

1. Dorsal view of large internal mold (x 2). Trenton Group, Watertown, Jefferson Co., N.Y.

Paralectotype. AMNH Fl 29593. 

2-4. Dorsal, ventral, and right-lateral views of internal mold (x 2). Trenton Group, Watertown, N.Y.

Paralectotype. AMNH Fl 29594. 

5-10. Dorsal, posterior, ventral, left-anterodorsal, left-lateral and right-lateral views of internal mold with

some shell preserved dorsally (x 2). Pogonip Group, White Pine District, Nev. USNM 17301. 

11-15. Tetranota sexcarinata Ulrich and Scofield, 1897 (p. 0147).

11-13. Dorsal and left- and right-dorsolateral views of internal mold (x 2). Lebanon Formation, Lavergne,

Tenn. USNM 47712. 

14, 15. Right dorsolateral (x 2) and dorsal closeup (x 6) views of selenizone, growth lines, and first lateral

ridges. Fusispira bed, Prosser Formation, Wykoff, Minn. Lectotype. USNM 46018. 

16-21. Tetranota obsoleta Ulrich and Scofield, 1897 (p. 0146).

16-18. Dorsal, ventral, and left-lateral views of small silicified specimen (x 2). Hypotype of Butts (1926).

Little Oak Formation, north of Pelham, Ala. USNM 71496.

19-21. Dorsal, ventral, and left-lateral views of silicified lectotype (x 2). Ctenodonta bed, Decorah 

Formation, Chatfield, Minn. USNM 46014.
U.S. GEOLOGICAL SURVEY PROFESSIONAL PAPER 1066-O PLATE 22

TETRANOTA
PLATE 23

FIGURES 1-9. Undulabucania punctifrons (Emmons), 1842 (p. 0142).

1-4. Dorsal, right-lateral, and right-anterodorsal views of calcitic specimen (x 3) and closeup view of the 

last showing shell sculpturing (x 6). Base of Hermitage Formation, Nashville, Tenn. USNM 

45727. 

5-9. Dorsal, ventral, anterior, left-lateral, and left-anterodorsal views of another calcitic specimen (x 3).

Same collection as figures 1-4 above. USNM 315546.

10-15. Undulabucania gorbyi (Miller), 1892 (p. 0142). Anterodorsal (x 4), dorsal, ventral, anterior, right-anterodorsal 

(x 2), and left-anterodorsal (x 1.5) views of calcitic holotype. Maysvillian-age strata, Dearborn Co., Ind. 

UC 6138.
U.S. GEOLOGICAL SURVEY PROFESSIONAL PAPER 1066-O PLATE 23

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UNDULABUCANIA
PLATE 24

FIGURES 1-9. Salpingostoma buelli (Whitfield, 1878) (p. 0150).

1-5. Left- and right-anterolateral, dorsal, and left- and right-lateral views of an Ulrich and Scofield (1897) 

hypotype (x 1.5), which is a composite mold dorsally but retains some dolomitized shell material 

around expanded aperture. Platteville Formation (Blackriveran), Beloit, Wis. USNM 265960. 

6-8. Dorsal, apertural, and right-lateral views of dolomitized internal mold of submature specimen (x 2). 

Same horizon and locality as figures 1-5 above. USNM 265957.

9. Apertural view of dark-gray calcitic cast showing outline of aperture and its anterior sinus (x 1.5). 

Specimen not whitened for photograph. Platteville Formation (Blackriveran), Old Concord, 

Minn. USNM 47590. 

10-12. Salpingostoma kentuckyense Ulrich and Scofield, 1897 (p. 0151).

10. Dorsolateral view of weathered silicified fragment of expanded, thickened aperture rim showing

trace of coarse radiating ribs (x 1.5). Paralectotype. Curdsville Member, Lexington Limestone 

(Kirkfieldian), Mercer Co., Ky. USNM 265962.

11, 12. Left-lateral and ventral views of weathered silicified lectotype (x 1.5). USNM 265961. 

13-16. Salpingostoma richmondensis Ulrich, 1897 (p. 0154). Right-dorsolateral, left-lateral, dorsal, and apertural 

views of internal mold of immature specimen (x 1.5). Museum label gives horizon and locality as 

"Richmond Group, Richmond, Indiana." UCGM 44280.
U.S. GEOLOGICAL SURVEY PROFESSIONAL PAPER 1066-O PLATE 24
PLATE 25

FIGURES 1-14. Salpingostoma kentuckyense Ulrich and Scofield, 1897 (p. 0151).

1-8. Dorsal, apertural, posterior, right-lateral, left-lateral, right oblique and left oblique dorsolateral, and 

left-ventrolateral views of silicified specimen (x 1.5). Tyrone Limestone (Rocklandian), USGS 

6034-CO. USNM 265964. 

9-13. Dorsal, ventral, left-lateral, posterior, and left oblique dorsolateral views of silicified specimen

(x 1.5). Same collection as figures 1-8 above. USNM 265965.

14. Dorsal view of silicified specimen showing chevron wrinkling beneath coil (x 1.5). Same collection as 

figures 1-8 above. USNM 265979.
U.S. GEOLOGICAL SURVEY PROFESSIONAL PAPER 1066^0 PLATE 25
PLATE 26

FIGURES 1-8. Salpingostoma richmondensis Ulrich, 1897 (p. 0154).

1-5. Anterodorsal, right oblique, left oblique, and left- and right-lateral views of internal mold preserving 

some shell around expanded apertural rim (x 1.5). Holotype. Whitewater Formation 

(Richmondian), Richmond, Ind. USNM 45983. 

6-8. Oblique anterodorsal, anterior, and left-lateral views of internal mold (x 1.5). Museum label gives

horizon and locality as "Whitewater Formation, Camden, Ohio." UCGM 44281. 

9, 10. Pterotheca karviei Foerste, 1924 (p. 0186). Dorsal and left-dorsolateral views of composite mold (x 1.5).

Southgate biofacies, Kope Formation (Edenian), Covington, Ky. USNM 50092.

11, 12. Salpingostoma kentuckyense Ulrich and Scofield, 1897 (p. 0151). Dorsal (x 1.5) and closeup (x 3) views of 

posterior area of silicified apertural rim showing chevron wrinkling beneath coil. Same collection as plate 

25, figures 1-8. USNM 265966.
U.S. GEOLOGICAL SURVEY PROFESSIONAL PAPER 1066-O PLATE 26

1--,t;^ V" 12 •

SALPINGOSTOMA AND PTEROTHECA
PLATE 27

FIGURES 1-16. Bucanopsis carinifera Ulrich, 1897 (p. 0163).

1, 2. Dorsal and left-lateral views of silicified lectotype showing revolving threads (x 6). Museum label 

reads "Trenton (Flanagan), near Danville, Kentucky." USNM 315583.

3. Left-lateral view of a silicified paralectotype (x 6). Same collection as figures 1, 2 above. USNM 

315584.

4. Ventral view of another silicified paralectotype showing sharp whorl floor keel (x 6). Same collection

as figures 1, 2 above. USNM 315585. 

5-7. Dorsal, right-lateral, and posterior views of silicified specimen (x 3). Cannon facies, Bigby-Cannon

Limestone, "Hill north of Well No. 1, Smith County, Tennessee." UCGM 44283. 

8-12. Dorsal, left-lateral, posterior, ventral, and anterior views of silicified specimen (x 2.5). Grier 

Limestone Member, Lexington Limestone, USGS 4928-CO. USNM 315586.

13. Dorsal view of small silicified specimen showing outer shell layers peeling away (x 3). Faulconer 

Bed, Perryville Limestone Member, Lexington Limestone, USGS 6136-CO. USNM 315589.

14. Two silicified specimens cemented together showing aperture form and whorl floor keel (x 3). 

Salvisa Bed, Perryville Limestone Member, Lexington Limestone, USGS 5015-CO. USNM 

315587.

15, 16. Dorsal (x 3) and left anterodorsal closeup (x 9) views showing faint revolving threads on weathered 

silicified specimen. Salvisa Bed, Perryville Limestone Member, Lexington Limestone, USGS 

5015-CO. USNM 315588.

17-20. B^anopsis diabloensis new species (p. 0165). Dorsal, left-lateral, posterior, and ventral views of silicified 

holotype (x 2.5). Note narrower coil and relatively wider and more rounded aperture compared with 

Bticanopsis carinifera. Devils Hollow Member, Lexington Limestone, USGS 5095-CO. USNM 315590. 

21, 22. Bucania nashvillensis Ulrich, 1897 (p. 0132). Dorsal and left-lateral views of fragmentary silicified specimen

(x 2.5). Cannon facies, Bigby-Cannon Limestone, "Hill north of Well No. 1, Smith Co., Tennessee." UCGM 

44284.
U.S. GEOLOGICAL SURVEY PROFESSIONAL PAPER 1066-O PLATE 27

BUCANOPSIS AND BUCANIA
PLATE 28

FIGURES 1-5. Bellerophon (Bellerophon) bilineatus Ulrich, 1897 (p. 0160). Dorsal, posterior, left-lateral, and ventral views of 

silicified holotype (x 3) and dorsal closeup view (x 6.5) of selenizone and growth lines. Labeled as coming 

from "Upper portion of the Trenton Group, near Danville, Kentucky." USNM 45697. 

6-9. Bellerophon (Bellerophon) cf. B. (B.) bilineatus Ulrich, 1897 (p. 0160). Posterior, ventral, dorsal, and

right-lateral views of silicified specimen (x 2.5). Faulconer Bed, Perryville Limestone Member, Lexington 

Limestone, USGS 6136-CO. USNM 315612. 

10-23. Sphenosphaera burginensis (Ulrich), 1897 (p. 0170).

10-12. Right-lateral, posterior, and dorsal views of silicified holotype (x 2). Upper Lexington Limestone, 3

mi north of Burgin, Ky. USNM 45712.

13-15. Dorsal (x 2.5) and right-anterodorsal (x 2) views of a silicified paratype and anterodorsal closeup 

view of selenizone (x 6). Upper Lexington Limestone, 1.5 mi south of Burgin, Ky. USNM 

47595. 

16-18. Dorsal and left-lateral (x 2) views of silicified specimen and dorsal closeup view of selenizone (x 10).

Grier Limestone Member, Lexington Limestone, USGS 5096-CO. USNM 315167. 

19, 20. Posterior and dorsal views of silicified specimen (x 2). Grier Limestone Member, Lexington

Limestone, USGS 4883-CO. USNM 315615.

21-23. Posterior, right-lateral, and dorsal views of silicified specimen (x 2). Same collection as figures 16-18 

above. USNM 315616.
U.S. GEOLOGICAL SURVEY PROFESSIONAL PAPER 1066-O PLATE 28

BELLEROPHON AND SPHENOSPHAERA
PLATE 29

FIGURES 1-22. Sphenosphaera troosti (d'Orbigny), 1840 (p. 0168).

1^4. Dorsal closeup view (x 5) and right-lateral, ventral, and anteroventral views (x 2) of silicified

neotype. Cannon fades, Bigby-Cannon Limestone, Nashville, Tenn. USNM 315602. 

5-9. Left-lateral, right-lateral, dorsal, ventral, and anterior views of silicified paraneotype figured by

Ulrich and Scofield (1897) (x 2). Same horizon and locality as figures 1^4 above. USNM 315665. 

10-13. Posterior view (x 2) and dorsal, right- lateral, and anterior views (x 2.5) of silicified hypotype from 

Ulrich and Scofield (1897) collection. Labeled as coming from "Flanagan chert" (Lexington 

Limestone), near Danville, Ky. USNM 315603. 

14-16. Dorsal, anterior, and right-lateral views of another Ulrich and Scofield (1897) silicified hypotype

(x 3). Same collection as figures 10-13 above. USNM 315604. 

17-19. Apertural, dorsal, and right-lateral views of coarsely silicified specimen (x 3). Grier Limestone

Member, Lexington Limestone, USGS 4073-CO. USNM 315614.

20-22. Anterior, dorsal, and left-lateral views of silicified specimen (x 3). Grier Limestone Member, 

Lexington Limestone, USGS 4959-CO. USNM 315613.
U.S. GEOLOGICAL SURVEY PROFESSIONAL PAPER 1066-O PLATE 29

13

SPHENOSPHAERA
PLATE 30

FIGURES 1-23. Sphenosphaera clausus (Ulrich), 1897 (p. 0167).

1-6. Dorsal, anterior, ventral, right-lateral, and left-posterolateral views of silicified holotype (x 2) and 

posterodorsal closeup (x 6) view. Cannon fades, Bigby-Cannon Limestone, central Tennessee. 

USNM 45701. 

7, 8. Dorsal and left-lateral views of a slightly compressed calcitic paratype (x 2). Lexington Limestone,

Frankfort, Ky. USNM 45700. 

9, 10. Anteroventral and ventral views of silicified specimen (x 3). Salvisa Bed, Perryville Limestone

Member, Lexington Limestone, USGS 5015-CO. USNM 315621. 

11-14. Dorsal, right-lateral, ventral, and anteroventral views of silicified specimen (x 2). Same collection as

figures 9, 10 above. USNM 315620.

15, 16. Posterodorsal and right-lateral views of silicified specimen showing an outer shell layer peeling away 

(x 2). Salvisa Bed, Perryville Limestone Member, Lexington Limestone, USGS 6916-CO. 

USNM 315619. 

17, 18. Anterior and left-lateral views of silicified specimen (x 2). Clays Ferry Formation, USGS 7812-CO.

USNM 315628. 

19. Right-lateral view of silicified specimen encrusted by a digitate bryozoan colony (x 2). Same

collection as figures 17, 18 above. USNM 315626. 

20, 21. Dorsal and left-lateral views of silicified specimen (x 2). Same collection as figures 17, 18 above.

USNM 315627.

22, 23. Dorsal and left-lateral views of silicified specimen (x 3). Devils Hollow Member, Lexington 

Limestone, USGS 5087-CO. USNM 315622.
U.S. GEOLOGICAL SURVEY PROFESSIONAL PAPER 1066-O PLATE 30
PLATE 31

FIGURES 1-13. Sphenosphaera clausus (Ulrich), 1897 (p. 0167).

1-6. Dorsal, ventral, anteroventral, posterior, and left-lateral views of silicified specimen (x 2) and dorsal 

closeup view of selenizone (x 8). Millersburg Member, Lexington Limestone, USGS 7353-CO. 

USNM 315624. 

7-10. Dorsal, ventral, left-lateral, and posterior views of silicified specimen (x 2). Grier Limestone

Member, Lexington Limestone, USGS 4879-CO. USNM 315618.

11. Small slab showing ventral view of specimen associated with other silicified skeletal debris in gray, 

dense wackestone-packstone (x 1). Cannon facies, Bigby-Cannon Limestone, "Hill north of Well 

No. 1, Smith Co., Tennessee." UCGM 44301.

12, 13. Small slab showing right-posterolateral view of silicified specimen (x 1.5) and dorsal view of same 

specimen (x 2). Other silicified skeletal material includes lophospirid gastropod and nautiloid 

cephalopod fragments, and a portion of a tabulate coral colony. Same collection as figure 11 

above. UCGM 44302.
U.S. GEOLOGICAL SURVEY PROFESSIONAL PAPER 1066-O PLATE 31

SPHENOSPHAERA
PLATE 32

FIGURES 1-15. Sphenosphaera clausus (Ulrich), 1897 (p. 0167).

1-3. Dorsal and ventral views (x 2) and closeup view of selenizone (x 6) of silicified specimen encrusted 

by a bryozoan colony. Millersburg Limestone Member, Lexington Limestone, USGS 7353-CO. 

USNM 315665. 

4, 5. Anterodorsal and anterior views of fragmentary silicified specimen showing the whorl floor ridge

clearly (x 2). Same collection as figures 1-3 above. USNM 315625.

6-10. Dorsal, right-anterodorsal, ventral, and right- lateral views (x 2) and dorsal closeup view (x 10) of 

silicified specimen encrusted on one side by a digitate bryozoan colony. Millersburg Limestone 

Member, Lexington Limestone, USGS 7344-CO. USNM 315623.

11, 12. Left-lateral and posterior views of calcareous specimen (x 2.5). Museum label states that specimen 

came from "top of the Bromley Shale" (now included in Clays Ferry Formation), 1.5 mi east of 

Sadieville, Ky. MU 235T. 

13-15. Dorsal, right-lateral, and left-lateral views of internal mold (x 2). Specimen is lectotype of

Bellerophon rogersensis Foerste, which is here placed in synonymy with S. clausus. Note that 

the specimen is slightly compressed. Clays Ferry Formation, Rogers Gap, Ky. USNM 315601.
U.S. GEOEOGICAE SURVEY PROFESSIONAE PAPER 1066-O PEATE 32
PLATE 33

FIGURES 1^4. Sphenosphaera recurvus (Ulrich), 1897 (p. 0171). Dorsal (x 2), dorsal closeup (x 8), and right- lateral and right 

posterolateral (x 3) views of calcareous holotype. Corryville biofacies, Grant Lake Limestone, Cincinnati, 

Ohio. USNM 45705. 

5, 6. Sphenosphaera aff. S. recurvus (Ulrich), 1897 (p. 0171). Eight-dorsolateral and anterior views of highly

recrystallized calcareous specimen partly embedded in limestone (x 2). Leipers Limestone, Eowena Ferry, 

Eussell Co., Ky. UCGM 44282. 

7-9. Bellerophon (Bellerophon) subglobulus Ulrich, 1897 (p. 0159). Dorsal, right-lateral, and left-lateral views of

silicified lectotype (x 2). Museum label reads "Black Eiver Group, Mercer Co., Kentucky." USNM 45709. 

10-15. Sphenosphaera subangularis (Ulrich), 1897 (p. 0171).

10. Dorsal view of a paralectotype (x 3). Museum label reads "Eichmond Group, Eichmond, Indiana."

USNM 315666.

11-15. Dorsal, posterior, ventral, left-lateral, and right-lateral views of calcareous lectotype (x 3). Same 

collection as figure 10 above. USNM 45708.
U.S. GEOLOGICAL SURVEY PROFESSIONAL PAPER 1066-O PLATE 33

SPHENOSPHAERA AND BELLEROPHON
PLATE 34

FIGURES 1-13. Sphenospkaera capax (Ulrich), 1897 (p. 0172).

1-3. Dorsal, left-lateral, and ventral views of calcareous lectotype (x 1.5). Fairmount biofacies, Fairview

Formation, Covington, Ky. USNM 315606. 

4, 5. Dorsal and ventral views of a bryozoan- encrusted, calcareous paralectotype (x 2). Note that

specimen is vertically compressed. Same collection as figures 1-3 above. USNM 45699. 

6, 7. Dorsal and ventral views of another bryozoan- encrusted, calcareous paralectotype (x 1.5). This 

specimen is also vertically compressed. Same collection as figures 1-3 above. USNM 315608. 

8, 9. Dorsal and left-lateral views of a calcareous paralectotype (x 1.5). Same collection as figures 1-3

above. USNM 315607. 

10. Posterior view of silicified specimen with shell broken away to expose whorl interior and whorl floor

ridge (x 1.5). Gilbert Member, Ashlock Formation, USGS 6412-CO. USNM 387016.

11-13. Dorsal, posterior, and right-lateral views of silicified specimen with dorsal shell broken away showing 

whorl floor ridge (x 1.5). Same collection as figure 10 above. USNM 387017.
U.S. GEOLOGICAL SURVEY PROFESSIONAL PAPER 1066-O PLATE 34

SPHENOSPHAERA
PLATE 35

FIGURES 1-16. Sphenosphaem mohri (Miller), 1874 (p. 0173).

1^4. Dorsal, posterior, and right-lateral views (x 1.5) and right-dorsolateral closeup view (x 4) of

calcareous lectotype. Whitewater Formation, Richmond, Ind. UC 8793a. 

5. Dorsal view of a large, broken, and vertically compressed, calcareous paralectotype (x 1.5). Same

collection as figures 1^ above. UC 8793b. 

6-8. Ventral, right-dorsolateral, and right-lateral views of broken calcareous paralectotype that has been

distorted by compression (x 1.5). Same collection as figures 1^4 above. UC 8793c. 

9-11. Dorsal, right-lateral, and posterior views of calcareous specimen figured by Ulrich and Scofield (1897)

(x 2). Whitewater Formation, Richmond, Ind. USNM 315611. 

12-14. Dorsal, ventral, and left-lateral views of another calcareous specimen figured by Ulrich and Scofield

(1897) (x 2). Same collection as figures 9-11 above. USNM 315610.

15, 16. Dorsal and left-lateral views of calcareous holotype of Bellerophon cincinnatiensis Miller and Faber, 

1894, which is placed in synonymy with S. mohri (x 1.5). Museum label reads "Maysville, at 

quarries in Cincinnati, Ohio." UC 8796.
U.S. GEOLOGICAL SURVEY 

V.

PROFESSIONAL PAPER 1066-O PLATE 35

12

SPHENOSPHAERA
PLATE 36

FIGURES 1-15. Sphenosphaera mohri (Miller), 1874. (p. 0173).

1-3. Dorsal, posterior, and right-lateral views of silicified specimen (x 1.5). Liberty biofacies, upper

Dillsboro Formation (Richmondian), USGS 6139-CO. USNM 315631. 

4-7. Dorsal, posterior, left-lateral, and ventral views of silicified specimen (x 1.5). Same collection as

figures 1-3 above. USNM 315629. 

8, 9. Dorsal and ventral views of silicified specimen (x 3). Same collection as figures 1-3 above. USNM

315633. 

10-12. Right-lateral, ventral, and dorsal views of juvenile silicified specimen (x 3). Same collection as

figures 1-3 above. USNM 315632.

13. View of concave external impression of shell of fragmentary dorsum showing dorsal slit and growth 

lines (x 1.5). Whitewater Formation; locality unknown, but probably from southwestern Ohio or 

southeastern Indiana. MU 14539. 

14, 15. Anterodorsal view (x 2) showing slit, and ventral view (x 1.5), of internal mold encrusted by

bryozoans. Labeled as from Waynesville Formation; locality not given, but probably from same 

area cited for figure 13 above. UCGM 44303.
U.S. GEOLOGICAL SURVEY PROFESSIONAL PAPER 1066-O PLATE 36

* '-XT- v 

13 '^ \

SPHENOSPHAERA
PLATE 37

FIGURES 1-11, 15-23. Carinaropsis cymbula (Hall, 1861) (p. 0178).

1-4. Dorsal, left-anterodorsal, ventral, and anteroventral views of holotype (x 2). Note median 

groove in selenizone. Museum label gives horizon and locality as "Trenton Limestone, 

Alien's Bluff, Tennessee." AMNH 37725a. 

5, 6. Dorsal and right-lateral views of a paratype (x 2). Same collection as figures 1^1 above.

AMNH 37725b.

7, 8. Dorsal and right-lateral views of specimen from Ulrich and Scofield's (1897) hypotypic suite, 

USNM 45739 (x 3). Museum label gives horizon and locality as "Trenton Group, near 

Danville, Kentucky." USNM 265996. 

9-11. Dorsal, left-lateral, and ventral views of another Ulrich and Scofield (1897) hypotype, USNM

suite 45739 (x 1.5). Same collection as figures 7, 8 above. USNM 265997. 

15-21. Dorsal and left-lateral views (x 1.5), left-lateral closeup view of coil (x 4), and ventral,

anteroventral, left-dorsolateral, and posterior views (x 1.5) of silicified specimen. Grier 

Limestone Member, Lexington Limestone, USGS 5096-CO. USNM 265984.

22. Dorsal view of specimen showing dorsal septum (x 1.5). Grier Limestone Member, 

Lexington Limestone, USGS 4879-CO. USNM 265985.

23. Dorsal view of specimen showing dorsal septum (x 2). Museum label reads "Siliceous layer

below Perryville bed, 2 miles north of Danville, Kentucky." USNM 87778. 

12-14. Carinaropsis cunulae (Hall, 1861) (p. 0178). Dorsal, left-lateral, and ventral views of an Ulrich and

Scofield (1897) hypotype from USNM suite 45738 (x 1.5). Museum label gives horizon and locality 

as "Trenton (Cannon Limestone), Nashville, Tennessee." USNM 265998.
U.S. GEOLOGICAL SURVEY PROFESSIONAL PAPER 1066-O PLATE 37

CARINAROPSIS
PLATE 38

FIGURES 1-12. Carinaropsis cymbula (Hall, 1861) (p. 0178).

1, 2. Anterolateral view (x 1.5) and closeup view of same (about x 6) of broken silicified specimen

showing structure of septum and parietal lip. Grier Limestone Member, Lexington Limestone,

USGS 5096-CO. USNM 265986. 

3-6. Dorsolateral, ventral, anteroventral, and right- lateral views of silicified specimen (x 2). Grier

Limestone Member, Lexington Limestone, USGS 4879-CO. USNM 265988. 

7, 8. Posterior and left-posterolateral views of silicified specimen, the latter view showing fine radial

threads (x 1.5). Same collection as figures 1, 2 above. USNM 265991.

9. Dorsal view of silicified specimen showing coil and septum (x 1.5). Same collection as figures 3-6 

above. USNM 265987.

10. Dorsal view of silicified specimen showing selenizone with median groove (x 2). Same collection as

figures 3-6 above. USNM 265990.

11, 12. Dorsal and anteroventral views of silicified specimen with Bucania subangulata (x 2). Note that 

anterior margin of septum is nearly straight. Grier Limestone Member, Lexington Limestone, 

USGS 5094-CO. USNM 265989. 

13-16. Tetranota wiscansinensis (Whitfield, 1878) (p. 0148).

13-15. Dorsal, right oblique anterodorsal, and posterior views of hypotype of Shrock and Raasch (1937) 

(x 2). Museum label gives horizon and locality as "Platteville Formation, Dir. 4- 6, McCray 

Quarry, 3 miles east of Kentland, Indiana." USNM 158279.

16. Anterior view of another dolomitized internal mold showing high median slit (x 2). No locality or 

horizon data with specimen, but based on mode of preservation, probably from Middle 

Ordovician rocks in the upper Midwest of the United States. MU 251T.
U.S. GEOLOGICAL SURVEY PROFESSIONAL PAPER 1066-O PLATE 38

.- r«**T"*JL> - « t ^>#- » ^

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CARINAROPSIS AND TETRANOTA
PLATE 39

FIGURES 1-5, 13. Pterotheca saffordi (Hall, 1861) (p. 0182).

1,2. Dorsal and left-dorsolateral views of plastotype of holotype (x 1.5). Museum label gives horizon and

locality as "Stones River (Lebanon Limestone), Lebanon, Tennessee." USNM 79262. 

3-5. Dorsal and left-anterolateral views of calcitic specimen (x 1), and view of underside of small slab

showing association with ostracodes (x 1.5). Tyrone Limestone (Rocklandian), High Bridge, Ky. 

USNM 79268. 

13. Dorsal view of small specimen on lower part of slab with abundant leperditiid ostracodes (x 1).

Museum label gives horizon and locality as "Top of Tyrone Limestone just beneath lower bentonite beds, High Bridge, Kentucky." USNM 50093. 

6, 7, 12. Pterotheca cf. P. expansa (Emmons, 1842) (p. 0184).

6, 7. Dorsal and anterodorsal views of weathered silicified specimen (x 1.5). Curdsville Limestone Member, Lexington Limestone, Curdsville, Ky. USNM 79283. 

12. Dorsal view of fragment in center of small slab with abundant leperditiid ostracodes (x 1). Murfreesboro Limestone (Blackriveran), Murfreesboro, Term. USNM 50100.

8, 9. Pterotheca angusta Raymond, 1921 (p. 0185). Dorsal and right-anterolateral oblique views of silicified specimen 

(x 1.5). Note narrow septal angle. Basal 2 ft of Curdsville Limestone Member, Lexington Limestone 

(Kirkfieldian), USGS 7784-CO. USNM 315538. 

10, 11. Pterotheca expansa (Emmons, 1842) (p. 0183).

10. Right-anterolateral oblique view of dorsal fragment showing high, narrowing keel (x 2). Lower part 

of CurdsvDle Limestone Member, Lexington Limestone, USGS 6134-CO. USNM 315535.

11. Dorsal view of fragment of dorsal keel (x 1.5). Tyrone Limestone (Rocklandian), USGS 6034- CO. 

USNM 315533.
PROFESSIONAL PAPER 1066-O PLATE 39

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PTEROTHECA
PLATE 40

FIGURES 1^4. Pterotheca cf. P. expansa (Emmons, 1842) (p. 0184).

1-3. Dorsal, right-anterolateral, and left-lateral views of silicified specimen (x 1). Basal 2 ft of Curdsville 

Limestone Member, Lexington Limestone (Kirkfieldian), USGS 7784-CO. USNM 315536.

4. Dorsal view of silicified specimen showing septum (x 1.5). Note that there is no trace of divergent

apical ridges in specimen. Same collection as figures 1-3 above. USNM 315537. 

5-7. Pterotheca expansa (Emmons, 1842) (p. 0183).

5. Dorsolateral view of fragmentary silicified specimen showing fine, closely spaced growth lines

(x 1.5). Tyrone Limestone (Rocklandian), USGS 6034-CO. USNM 315532. 

6, 7. Dorsal view of fragmentary specimen (x 2), and closeup view of apical area (x 5), showing convex

septum and divergent apical ridges. Same collection as figure 5 above. USNM 315534. 

8, 9. Pterotheca saffordi (Hall, 1861) (p. 0182). Both sides of small slab showing P. saffordi in center in association

with ostracodes (x 1.5). Tyrone Limestone (Rocklandian), High Bridge, Ky. USNM 50099.

10-14. Carinaropsis explanata Ulrich, 1897 (p. 0180). Dorsal, left- and right-anterolateral oblique, posterior, and leftlateral views of lectotype (x 1.5). Museum label gives horizon and locality as "Upper Trenton, Covington, 

Kentucky." USNM 45740.
U.S. GEOLOGICAL SURVEY PROFESSIONAL PAPER 1066-O PLATE 40 

•^>

PTEROTHECA AND CARINAROPSIS
PLATE 41

FIGURES 1-5. Sphenosphaem mohri (Miller), 1874 (p. 0173).

1, 2. Anterodorsal and ventral views of silicified specimen with dorsum broken away to show whorl floor

ridge (x 1.5). Liberty biofacies, Dillsboro Formation, USGS 6139-CO. USNM 315630. 

3-5. Dorsal and ventral views (x 1.5) and closeup view of parietal lip showing bryozoan encrustation 

(about x 5). Saluda Formation, "roadside exposure above upper part of Crooked Creek, 

Madison, Indiana." MU 252T.

6-8. Tropidodiscus cristatus (Safford), 1869 (p. 0119). Left-lateral, anterior, and dorsal views of silicified lectotype 

with anterodorsal portion of shell broken away (x 3). Cannon facies, Bigby-Cannon Limestone, Jackson 

Co., Tenn. USNM 45950. 

9-13. Tropidodiscus subacutus (Ulrich), 1897 (p. 0118).

9, 10. Anterior and right-lateral views of silicified specimen with anterodorsal shell broken away (x 3). 

Salvisa Bed, Perryville Limestone Member, Lexington Limestone, USGS 6915-CO. USNM 

315638.

11-13. Dorsal, anterior, and right-lateral views of silicified lectotype with anterodorsal shell broken away 

(x 3). Upper Lexington Limestone, Danville, Ky. USNM 387021.
U.S. GEOLOGICAL SURVEY PROFESSIONAL PAPER 1066-O PLATE 41

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SPHENOSPHAERA AND TROPIDODISCUS
PLATE 42

FIGURES 1, 2. Tropidodiscus magnus (Miller), 1878 (p. 0119). Left-lateral and ventral views of calcitic holotype (x 2).

"Richmond Group" (Richmondian), Richmond, Ind. UC 10838. 

3-6. Temnodiscus nitidula (Ulrich), 1897 (p. 0125).

3, 4. Left-lateral and dorsal views of lectotype (x 5). "Upper Trenton" (Shermanian), Covington, Ky.

USNM 315542. 

5, 6. Right-lateral and dorsal views of a paralectotype (x 5). Same collection as figures 3, 4 above. USNM

315543. 

7-13. Phragmolites grandis (Ulrich), 1897 (p. 0121).

7-9. Left-lateral, dorsal, and ventral views of a silicified paralectotype (x 2). Lebanon Formation,

Lebanon, Tenn. USNM 315668.

10-13. Dorsal, left-anterolateral, left-lateral, and ventral views of silicified lectotype embedded in finegrained limestone (x 2). Same collection as figures 7-9 above. USNM 315667.

14. Phragmolites compressus Conrad, 1838 (p. 0120). Left-lateral view of silicified holotype of P. similis (Ulrich), 

which herein is placed in synonymy with P. compressus (x 2). Museum label reads "Lowville beds, Black 

River Group, near High Bridge, Mercer Co., Kentucky." USNM 47568.
U.S. GEOLOGICAL SURVEY PROFESSIONAL PAPER 1066-O PLATE 42

13

TROPIDODISCUS, TEMNODISCUS, AND PHRAGMOLITES
PLATE 43

FIGURES 1-3. Phragmolites grandis (Ulrich), 1897 (p. 0121). Left-lateral, dorsal, and ventral views of a silicified

paralectotype, a juvenile (x 6). Lebanon Formation, Lebanon, Tenn. USNM 387018. 

4-12. Phragmolites cellulosus (Ulrich and Scofield), 1897 (p. 0122).

4-6. Left-lateral, dorsal, and ventral views of shelled specimen (x 6). Museum label reads "Orthis bed of

Trenton Group (Hermitage Formation), central Tennessee." USNM 61029. 

7-9. Dorsal, ventral, and right-lateral views of shelled specimen (x 6). Museum label reads "Bed 1,

Trenton Group (Hermitage Formation), 2 miles south of Belfast, Tennessee." USNM 47562. 

10-12. Dorsal, ventral, and right-lateral views of shelled specimen (x 6). Museum label reads "Pelecypod 

beds, Hermitage Formation, 1.5 miles south of Woodbury, Tennessee." USNM 79250.
U.S. GEOLOGICAL SURVEY PROFESSIONAL PAPER 1066-O PLATE 43

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PHRAGMOLITES
PLATE 44

FIGURES 1^4. Phragmolites compressus Conrad, 1838 (p. 0120).

1. Left-lateral view of calcitic specimen embedded in limestone (x 5.75). Museum label reads "Lower 

part of Trenton and perhaps Black River, 2-4 miles north of Burgin, Mercer Co., Kentucky." 

USNM 387019.

2-k. Left-lateral, dorsal, and ventral views of silicified specimen with ventral half of shell broken away 

(x 5.75). Same collection as figure 1 above (probably from a different sample). USNM 387020. 

5-7. Phragmolites bellulus (Ulrich), 1897 (p. 0123). Left-lateral, dorsal, and ventral views of calcitic holotype (x 6).

Fairmount biofacies, Fairview Formation, Covington, Ky. USNM 45751.

8-10. Phragmolites dyeri (Hall), 1872 (p. 0124). Right-lateral, dorsal, and ventral views of an Ulrich and Scofield 

(1897) calcitic hypotype (x 6). Waynesville biofacies, Bull Fork Formation, Butler Co., Ohio. USNM 

315673. 

11-15. Phragmolites elegans (Miller), 1874 (p. 0123).

11-13. Right-lateral, dorsal, and ventral views of an Ulrich and Scofield (1897) calcitic hypotype (x 6). 

Corryville biofacies, Grant Lake or Bull Fork Formation, Cincinnati, Ohio. USNM 315669.

14. Right-lateral view of calcitic specimen (about x 8). Same collection as figures 11-13 above. USNM

315670.

15. Left-lateral view of large calcitic specimen (x 6.5). Same collection as figures 11-13 above. USNM

315671.
U.S. GEOLOGICAL SURVEY PROFESSIONAL PAPER 1066-O PLATE 44

PHRAGMOLITES
PLATE 45

FIGURES 1-9. Sinuites granistriatus (Ulrich), 1897 (p. 0113).

1, 2. Ventral views of calcitic specimen showing pitting on ventral coil and apertural rim (x 2) and (x 7).

Kope Formation, Chilo, Ohio (locality OH-1). UCGM 44298. 

3, 4. Dorsal and ventral views of calcitic specimen (x 2). Same collection as figures 1, 2 above. UCGM

44296. 

5-7. Dorsal, anteroventral, and left-lateral views of calcitic specimen (x 2). Kope Formation. Carroll Co.

Ky. (locality KY-1). UCGM 44306. 

8, 9. Dorsal and anterior views of calcitic specimen (x 2). Same collection as figures 1, 2 above. UCGM

44297.

10. Phragmolites elegans (Miller), 1874 (p. 0123). Left-lateral view of small calcitic specimen showing common 

association of species with ramose bryozoans (about (x 8). Corryville biofacies, Grant Lake or Bull Fork 

Formation, Cincinnati, Ohio. USNM 315672.

11. Phragmolites dyeri (Hall), 1872 (p. 0124). Small slab showing species in center associated with diverse

assemblage of ramose bryozoans, brachiopods, and trilobites (x 1.5). Waynesville biofacies, Bull Fork 

Formation, Butler Co., Ohio. USNM 315674.
U.S. GEOLOGICAL SURVEY PROFESSIONAL PAPER 1066-O PLATE 45

SINUITES AND PHRAGMOLITES

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