The Paleontology of Rostroconch Mollusks 

and the Early History of the 

Phylum Mollusca

GEOLOGICAL SURVEY PROFESSIONAL PAPER 968
The Paleontology of Rostroconch Mollusks 

and the Early History of the 

Phylum Mollusca

By JOHN POJETA, JR., and BRUCE RUNNEGAR

GEOLOGICAL SURVEY PROFESSIONAL PAPER 968

An analysis of the functional morphology, taphonomy, 

stratigraphic ranges, phylogenetic relationships, and 

taxonomic variability of rostroconch mollusks, and the 

evolutionary history of other early mollusks

UNITED STATES GOVERNMENT PRINTING OFFICE, WASHINGTON : 1976
UNITED STATES DEPARTMENT OF THE INTERIOR 

THOMAS S. KLEPPE, Secretary

GEOLOGICAL SURVEY 

V. E. McKelvey, Director

Library of Congress Cataloging in Publication Data

Pojeta, John

The paleontology of rostroconch mollusks and the early history of the phylum Mollusca. 

(Geological Survey professional paper ; 968) 

Bibliography: p. 

Includes index.

1. Rostroconchia. 2. Mollusks Evolution. 3. Paleontology Paloezoic. I. Runnegar, Bruce, joint author. II. Title. 

III. Series: United States. Geological Survey. Professional paper ; 968.

QE814.P64 564 76-18911

For sale by the Superintendent of Documents, U.S. Government Printing Office

Washington, D.C. 20402 

Stock Number 024-001-02822-1
CONTENTS

Abstract ________________.

Introduction _______________.

Acknowledgments __________.

Functional morphology _______. 

Orientation ________________.

Larval shell __________

Metamorphosis ___________.

Subsequent shell growth _____.

Summary of shell growth ___ 

Opening of the valves ____. 

Musculature ________________.

Pedal musculature ______.

Pallial musculature ________

Alimentary canal _______.

Feeding structures _____________

Cleaning the mantle cavity _____

Water currents and gills _____ 

Function of the hood __________

Taphonomy ________________

Phylogeny _________________. 

Origin of the Mollusca _______

The ancestral mollusk ________.

The oldest known fossil mollusks _ 

Early Cambrian univalves ______

Radiation of the Monoplacophora 

Origin of the Gastropoda _______

Origin of the Cephalopoda ____ 

Origin of the Rostroconchia ___

Radiation of the Rostroconchia

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Phylogeny Continued

Origin of the Rostroconchia Continued

Origin of the Pelecypoda _ ______ ______ _.

Bivalved condition in the Mollusca ______-_-

Limits of convergence in shell form _______

Rostroconchs as ancestors of the Pelecypoda. 

Accompanying modification of body form____

Radiation of the Pelecypoda __-_ __ _-- 

Origin of the Scaphopoda ________ __________

Mattheva and Stenothecoida (Probivalvia) _____

Molluscan subphyla _________ __ _______ _.

Glossary of morphological terms -___ __ __-- 

Systematic paleontology _____________________ ___-

Synoptic classification of known rostroconch 

mollusks ____ _ _ ____ _____________

Ribeirioida - 

Ribeiriidae __________----__- ______ ___-

Technophoridae _____________-__-----_-__-

Ischyrinioida ____________-_--- ______ ____.

Ischyriniidae -___ _ - ___--_ _- 

Conocardioida ____________________--_---__-.

Eopteriidae _____________ __________ __-

Conocardiidae _________ _ __ -_ ____-

Bransoniidae _________________ _________

Hippocardiidae _______________----_---_--

Incertae sedis _________________________ __ 

References cited _________________ ______________

Index ____________________________________ ___.

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ILLUSTRATIONS

	[Plates follow inidex]

PLATE 1. Yochelcionella.

2. Heraultipegma.

3. Watsonella, Wanwania, and Ribeirina.

4-8. Ribeiria.

9. Ribeiria and Pinnocaris.

10. Pinnocaris, "Technophorus," Myocaris, Oepikila, and Technophorus.

11-13. Technophorus.

14. Technophorus and Tolmachovia.

15. IMacroscenella.

16. Tolmachovia.

17. Tolmachovia and Anabarella.

18. Anisotechnophorus and Ischyrinia.

19. Ischyrinia.

20. Pseudotechnophorus.

21. Pseudoeuchasma, Wanwanoidea, and Wanwanella.

22-26. Eopteria.

27-29. Euchasma. in
IV CONTENTS

PLATES 30,31. Ribeiria.

32. Pseudoconocardium, Hippocardia, and Bransonia.

33. Hippocardia.

34. Mulceodens.

35. Mulceodens and Bigalea.

36. Blgalea.

37. Bigalea and Conocardium.

38,39. Conocardium.

40. Conocardium and Psewdocowocard.MW.

41. Pseudoconocardium.

4{2l Pseudoconocardium and Arceodomws.

43. Arceodomws.

44. Arceodoraws and Hippocardia.

45-49. Hippocardia.

50. Hippocardia and Bransonia.

51. Bransonia and Cowocardmm.

52-54. Bransonia.

FIGURE 1. Paper cutout models to illustrate the growth of the ribeirioid shell _ _ _ __.

2. Schematic diagrams illustrating the posterior growth of conocardiid and pelecypod shells

3. Musculature of various genera of Ischyrinioida and Ribeirioida _-___ __ ___________

4. Composite diagram of musculature of Eopteria ventricosa _____ __ ______ __ ___.

5. Musculature of various genera of the Conocardiacea ____ ______________ __ _____

6. Origin of the ribeiriid rostroconchs __________ __________________________ _____

7. Variation in shell form of Cambrian univalves _ __ _ __ ___ - _____

8. Shell muscle insertions of cyclomyan monoplacophorans________________ __ __ _ 

9. Reconstructions of Helcionella and Yochelcionella ________ __ __ ______ __ __ .

10. Reconstruction of Scenella __________________ ______________ __ __ __ __ .

11. Diversity of form in the Rostroconchia _________ - _- _-__ - -

12. Reconstructions of Fordilla _______________________ __ __ ___ _________ _

13. Schematic view of the origin of molluscan classes _____-___--_ __________ __ __ _

14. Historical record of the initial radiation of the Mollusca _____________ __ __ _____

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TABLES

Page

TABLE 1. Range chart showing the known stratigraphic distribution of all species of Ribeiriidae recognized

herein ___________________________ _ - - - 49

2. Range chart showing the known stratigraphic distribution of all species of Technophoridae recognized herein ___________________ ____ __ ______ _ __ __ __ __ - - 57

3. Range chart showing the stratigraphic distribution of all species of Ischyriniidae and Eopteriidae recognized herein ___ _ _ ______ 63
THE PALEONTOLOGY OF ROSTROCONCH MOLLUSKS AND THE 

EARLY HISTORY OF THE PHYLUM MOLLUSCA

By JOHN POJETA, JRV and BRUCE RUNNEGAR x

ABSTRACT

The class Rostroconchia is known in the fossil record from 

the Early Cambrian to the Late Permian; the taxa herein 

included within it have not previously been recognized as a 

biological entity and are grouped together for the first time. 

We functionally analyze the morphology of rostroconchs as to 

orientation, modes of growth, method of opening the valves, 

musculature, feeding structures, and so forth, and conclude 

that the group has a common biological pattern which indicates a commonality of descent. Thus, the Rostroconchia are 

treated here as a separate and extinct class of the phylum 

Mollusca.

Phylogenetically, it is possible to show that mollusks began 

to diversify and radiate in the Early Cambrian and that at 

this time the Monoplacophora gave rise to the Gastropoda and 

the Rostroconchia. We present evidence that the helcionellacians, formerly regarded as gastropods, are monoplacophorans 

and that they gave rise to the Rostroconchia. The Rostroconchia in turn gave rise to the Pelecypoda in the late Early 

Cambrian and possibly to the Scaphopoda in the Ordovician. 

The rostroconchs underwent a major radiation in the Early 

Ordovician, at which time thsy were as diverse as the Pelecypoda. Only one order of rostroconchs survived the Ordovician, a fact that we attribute to the competition between rostroconchs and pelecypods for living space and food.

All the known Cambrian and Ordovioian species of rostroconchs are described, discussed, and documented stratigraphically. We did not have adequate collections of post-Ordovician 

material to analyze all species, and we limit our systematic 

and stratigraphic considerations to those forms that show the 

generic diversity of the Conocardioida, the single known postOrdovician order. For the practicing stratigrapher, we present 

a new tool, a group of organisms heretofore neglected stratigraphically because they were not recognized as a biological 

entity.

The following new taxa are proposed: families Bransoniidae and Hippocardiidae; genera Anisotechnophorus, 

Arceodomus, Bigalea, Bransonia, Heraultipegma, and Mulceodens; species Ribeiria australiensis, R. taylori, Pinnocaris 

americana, Technophorus marija, T. milleri, Tolmachovia! 

jelli, Eopteria conocardiformis, Euchasma jonesi, E. mytiliforme, Conocardium pseudobellum, Bransonia wilsoni, B. alabamensis, B. cressmani, Mulceodens jaanussoni, Hippocardia 

cooperi, Bigalea yangi, B. ohioensis, and B. visbyensis.

1 University of New England, Armidale, New South Wales, Australia.

INTRODUCTION

Rostroconchs are a small but widespread and persistent Paleozoic faunal element. To date, they have 

been little studied because of the lack of adequate 

material and because they were not recognized as a 

separate molluscan lineage. It has been general practice to treat the older members of the class as arthropods and the younger members as unusual 

pelecypods.

The oldest known rostroconchs are assigned to the 

genus Heraultipegma (=HeraultiaCobbold) and are 

from Lower Cambrian rocks in France (Cobbold, 

1935). According to Waterhouse (1967), the rostroconch "Conocardium" occurs in the Makarewan 

Stage of New Zealand, which is placed at the top of 

the Permian System. Thus, rostroconchs range 

throughout the Paleozoic. We agree with Morris 

(1967) that the Triassic species placed in Conocardium by Healy (1908) probably belong to the pelecypod groups Poromyacea or Burmesiidae.

Herein, we review the paleontology of the rostroconchs throughout their stratigraphic range and indicate the importance of early rostroconchs in the 

phylogeny of the Mollusca. In order to study any 

group throughout its stratigraphic range, it is necessary to have sizable collections. It was obviously not 

possible to collect the entire Paleozoic throughout 

the world, so we turned to the museums of four continents and borrowed specimens from more than 30 

institutions. We examined more than 3,600 specimens ranging in age from Early Cambrian to Late 

Permian.

The study of what are now called rostroconchs began when Martin (1809) described one species and 

Sowerby (1815) described two species. Martin's 

work was subsequently declared invalid for nomenclatural purposes (Hemming, 1954, ICZN Opinion 

231). Bronn (1835) named the genus Conocardium, 

citing a single species name, Cardium elongatum
PALEONTOLOGY OF ROSTROCONCH MOLLUSKS

Sowerby, which is the type species of the genus by 

monotypy. The name Conocardium was subsequently 

used for almost all Silurian-Permian species and 

some Ordovician species. At least 275 species were 

assigned to the genus. Herein we subdivide the genus 

Conocardium into seven generic-level taxa.

To date, the study of rostroconchs has largely consisted of the description of species, little attempt 

having been made at interpretation above this level. 

Major monographs, summaries of species, or bibliographies of rostroconchs include: Babin (1966), 

Barrande (1881), Beushausen (1895), Branson 

(1942a, b; 1948; 1966), Fletcher (1943), Hall 

(1885), Hind (1900), Kobayashi (1933), LaRocque 

(1950), Paul (1941), Pohl (1929), Schubert and 

Waagen (1904), Ulrich (1894), Weller (1898), and 

Whidborne (1892).

It was not recognized until recently that conocardiaceans are allied to eopteriids (Pojeta, 1971) and 

ribeirioids (Morris, 1967; Pojeta and others, 1972) 

and that all three groups are neither pelecypods nor 

arthropods. Previously, the conocardiaceans had 

consistently been treated as pelecypods and usually 

allied to the cardiids. In the Treatise on Invertebrate 

Paleontology, Branson, LaRocque, and Newell 

(1969) regarded them as pelecypods, but placed 

them in their own order and regarded the subclass 

assignment as uncertain. Pojeta (1971) placed Conocardium, Eopteria, and Euchasma in a separate subclass of pelecypods and noted that the rostroconchs 

formed an enigmatic group whose pelecypod affinities were not well established. In 1972, Pojeta, Runnegar, Morris, and Newell made the rostroconchs a 

separate class of mollusks, which then included four 

genera; they also noted that rostroconchs were allied 

to the ribeirioids.

Although most ribeirioids and their allies have at 

one time or another been regarded as mollusks, 

usually pelecypods, in the 20th century they have 

been consistently placed with the arthropods. Schubert and Waagen (1904) argued against a pelecypod placement of Ribeiria and came to the conclusion 

that it was an apodid arthropod that has been much 

compressed laterally. Kobayashi (1933) accepted 

the arthropod placement of Ribeiria and its allies 

and treated them as notostracans. The molluscan 

nature of ribeirioids is indicated by the presence of 

a protoconch (pi. 41; pi. 47, figs. 13-15), by the calcareous shells which have growth lines (pi. 5, figs. 

13, 14), and by the prominent muscle scars which 

also show the growth increments (pi. 6, figs. 1, 4, 

14).

Because of the need to accumulate large numbers 

of specimens from many museums, the names of the 

museums are subsequently abbreviated as follows: 

AMS, Australian Museum, Sydney; AM, American 

Museum of Natural History, New York; BM, British 

Museum (Natural History), London; BMR, Australian Bureau of Mineral Resources, Canberra; FM, 

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

Institute of Geological Sciences, London, England; 

GSC, Geological Survey of Canada, Ottawa, Ont.; 

MCZ, Museum of Comparative Zoology, Harvard 

University, Cambridge, Mass.; MU, Miami University, Oxford, Ohio; NYSM, New York State Museum, Albany; PRI, Paleontological Research Institution, Ithaca, N.Y.; ROM, Royal Ontario Museum, 

Toronto; SM, Sedgwick Museum, University of 

Cambridge, England; SMNH, Swedish Museum of 

Natural History, Stockholm; UCB, University of 

California, Berkeley; UCM, University of Cincinnati Museum, Cincinnati, Ohio; UI, University of 

Illinois, Urbana; UM, University of Michigan, Ann 

Arbor; UMN, University of Minnesota, Minneapolis, 

Minn.; UNE, University of New England, Armidale, 

New South Wales, Australia; UO, University of 

Oslo, Norway; UOK, University of Oklahoma, Norman ; UQ, University of Queensland, Brisbane, Australia; USNM, United States National Museum, 

Washington, D.C.; YU, Yale University, New 

Haven, Conn.

ACKNOWLEDGMENTS

We are deeply indebted to museum curators and 

collection managers on four continents. Without 

their active help and cooperation we would not have 

been able to pursue this study. Large numbers of 

specimens were lent to us from many institutions, 

each of which we gratefully acknowledge.

We would like to thank the following persons for 

placing specimens and type material at our disposal: A. Ritchie, Australian Museum, Sydney; N. 

D. Newell, American Museum of Natural History, 

New York; A. A. Opik and J. H. Shergold, Australian Bureau of Mineral Resources, Canberra; L. F. 

Hintze, Brigham Young University, Provo, Utah; 

R. J. Cleevely and N. J. Morris, British Museum 

(Natural History), London; J. Wyatt Durham and 

J. H. Peck, University of California, Berkeley; C. L. 

Forbes, C. P. Hughes, R. B. Rickards, and H. B. 

Whittington, University of Cambridge, England; T. 

E. Bolton, M. J. Copeland, and W. T. Dean, Geological Survey of Canada, Ottawa; K. E. Caster and R. 

A. Davis, University of Cincinnati, Cincinnati, Ohio;
ACKNOWLEDGMENTS

S. J. Gould, Bernhard Kummel, and R. D. K. Thomas, 

Museum of Comparative Zoology, Harvard University, Cambridge, Mass.; Jif i Kf iz, Central Geological 

Survey, Prague, Czechoslovakia; K. Krueger and 

M. H. Nitecki, Field Museum of Natural History, 

Chicago, 111.; Jochen Helms, Humboldt University, 

Berlin, Deutsche Demokratische Republik; A. W. A. 

Rushton, Institute of Geological Sciences, London, 

England; D. B. Blake, University of Illinois, Urbana; A. S. Horowitz, Indiana University, Bloomington; E. C. Wilson, Los Angeles County Museum, 

Los Angeles, Calif.; T. E. Yancey, University of 

Malaya, Kuala Lumpur; J. H. Marak and J. K. Pope, 

Miami University, Oxford, Ohio; D. B. Macurda, Jr., 

University of Michigan, Ann Arbor, Mich.; P. K. 

Sims, Minnesota Geological Survey, St. Paul; R. E. 

Sloan, F. M. Swain, and D. Wallace, University of 

Minnesota, Minneapolis; R. H. Flower, New Mexico 

Institute of Mining and Technology, Socorro; B. M. 

Bell, Robert Conrad, and D. W. Fisher, New York 

State Geological Survey, Albany; S. M. Bergstrom 

and W. C. Sweet, Ohio State University, Columbus; 

T. W. Amsden, Oklahoma Geological Survey, Norman ; R. M. Bonem and C. C. Branson, University of 

Oklahoma, Norman; D. H. Collins, M. A. Fritz, and 

John Monteith, Royal Ontario Museum, Toronto; D. 

L. Bruton and G. Henningsmoen, University of Oslo, 

Norway; K. V. W. Palmer, Paleontological Research 

Institution, Ithaca, N.Y.; Robert Hansman, Princeton University, Princeton, N.J.; D. Hill and J. S. 

Jell, University of Queensland, Brisbane, Australia; 

J. F. Bokkelie and Valdar Jaanusson, Swedish Museum of Natural History, Stockholm; T. Kobayashi 

and T. Hanai, University of Tokyo, Japan; R. J. 

Ross, U.S. Geological Survey, Denver, Colo.; Leonard Alberstadt, Vanderbilt University, Nashville, 

Tenn.; and A. L. McAlester, Yale University, New 

Haven, Conn.

For helpful conversations, correspondence, or for 

reading the manuscript we would like to thank; J. H. 

Shergold and J. Gilbert-Tomlinson, Australian Bureau of Mineral Resources, Canberra; John Taylor, 

British Museum (Natural History), London; J. W. 

Wells, Cornell University, Ithaca, N.Y.; David 

Nicol, University of Florida, Gainesville; C. M. 

Yonge, University of Glasgow, Scotland; L. S. Kent, 

Illinois Geological Survey, Urbana; E. R. Trueman, 

University of Manchester, England; A. Graham and 

V. Fretter, University of Reading, England; A. R. 

Palmer, State University of New York, Stony Brook; 

A. J. Boucot, Oregon State University, Corvallis; 

J. C. Brower, Syracuse University, Syracuse, N.Y.; 

D. Herm, University of Tubingen, Federal Republic

of Germany; M. E. Taylor and E. L. Yochelson, U.S. 

Geological Survey, Washington, D.C.; E. G. Kauffman, U.S. National Museum, Washington, D.C.; 

Anders Martinsson, University of Uppsala, Sweden; 

D. L. Clark and Klaus Westphal, University of Wisconsin, Madison.

For the photograph of Anabarella plana we are 

indebted to Robin Godwin and S. C. Matthews, University of Bristol, England. S. C. Mathews provided 

specimens of Heraultipegma for this study and 

Douglas Lorenz, University of California, Los Angeles, supplied two specimens of Technophorus from 

Edenian rocks of Kentucky. Scanning electron 

microscope photographs of Heraultipegma were supplied by the University of Cambridge, England.

FUNCTIONAL MORPHOLOGY

ORIENTATION

In any group of extinct metazoans, the problem of 

morphological orientation exists. Because rostroconchs are extinct mollusks, the correct orientation 

of their skeleton is not immediately obvious. Their 

orientation can be established by comparing rostroconchs with other groups of mollusks and by considering their probable phylogenetic relationships. Previous discussions of this topic have assumed that 

rostroconchs were either pelecypod mollusks or 

arthropods, whereas we treat rostroconchs as a separate class of mollusks. Various recent workers 

(Branson, 1965, 1966; LaRocque, 1950; Nicol, 1970; 

Wilson, 1970) have oriented the Conocardiacea as 

we do.

Rostroconchs are bilaterally symmetrical about 

the commissural plane which separates the valves 

into mirror images (pi. 40, figs. 4-7). By analogy 

with other bivalved mollusks, we regard the hinged 

part of the shell as dorsal (pi. 40, fig. 5). Our phylogenetic conclusions, which indicate an evolutionary 

relationship of the rostroconchs to the Monoplacophora on the one hand and the Pelecypoda on the 

other, reinforce this interpretation.

Many older workers (for example, Dall, 1913) 

regarded the rostrate end of the conocardiacean shell 

as anterior. This was by analogy with pelecypods, at 

least in part. In most pelecypods, the direction of 

coiling of the umbos is toward the anterior, and in 

conocardiaceans, the umbos coil toward the rostrate 

end. However, most recent workers regard the rostrate end of rostroconchs as posterior and the gaping 

end as anterior (LaRocque, 1950; Wilson, 1970).

Conocardiaceans have a relatively large gape at 

one end of the shell (pi. 40, figs. 6,11), and a narrow
4 PALEONTOLOGY OF ROSTROCONCH MOLLUSKS

tubular rostrum at the other (pi. 43, figs. 5, 6). The 

most logical explanation of the large gape is that it 

allowed for the protrusion of the foot from the shell. 

The large gape is therefore anatomically anteroventral and functionally anterior. This interpretation is 

supported by the existence of analogs among the 

pelecypods, many of which have large anterior pedal 

gapes. In addition, most primitive rostroconchs possess a large anterior plate or pegma that connects 

the valves dorsally (pi. 4, figs. 20-22).

By analogy with scaphopods, pelecypods, and some 

gastropods, the rostrum of rostroconchs allowed water and excretory products to enter and leave the 

mantle cavity; it was most likely posterior. The 

morphology of advanced conocardiaceans, when 

traced back through morphologically gradational 

rostroconchs to the most primitive members of the 

class, reinforces the interpretation of the orientation 

of the anterior-posterior axis on the basis of the 

postulated phylogenetic connection of the Rostroconchia with the Monoplacophora and the 

Pelecypoda.

As in pelecypods (Cox and others, 1969), ventral 

is more difficult to define. If it be taken to coincide 

with the sole of the protracted foot, then the large 

(anterior) shell or pedal gape of many rostroconchs 

should be anatomically ventral. We adopt a more 

geometric view and term the margin of the shell opposite the hinge as ventral. We thus treat the four 

coordinates, anterior, posterior, dorsal, and ventral, 

as mutually orthogonal directions in the commissural 

plane. All are related to the hinge, which is fixed as 

dorsal.)

Like pelecypods, rostroconchs may have umbos 

that coil anteriorly (prosogyral, pi. 28, fig. 13) or 

posteriorly (opisthogyral, pi. 40, fig. 5). The direction of coiling is related to the geometry of shell 

growth (as in the Pelecypoda) and has nothing to 

do with the orientation of the shell.

As a general rule, conocardiaceans are anteriorly 

expanded, have an anterior gape, and a posterior 

rostrum (pi. 40, figs. 5-14) ; most other rostroconchs 

are posteriorly expanded and have an anterior pegma (pi. 11, fig. 22).

LARVAL SHELL

The valves of rostroconchs have only a single beak 

because growth originates from a single cap-shaped 

larval shell situated between the umbos of the juvenile shell (pi. 41; pi. 47, figs. 13-15). This structure, 

termed the protoconch (Pojeta and others, 1972), is 

normally destroyed in conocardiaceans by crushing 

caused by inrolling of the umbos. In ribeirioids, it is

usually visible at the apex of well-preserved specimens (pi. 10, fig. 16; pi. 12, fig. 17). The boundaries 

of the protoconch are not easily identified, but in 

most forms the protoconch appears to have been 

about 300-600 microns in diameter. Its size compares favorably with the larval shell of other mollusks; the prodissoconch II (veliconch) of pelecypods is 200-600 microns in diameter (Cox and others, 1969, p. N95), and the protoconch of bivalved 

gastropods is about 250 microns in diameter (Kawaguti, 1959).

In the conocardiaceans, the protoconch is a limpetshaped structure, which is separated from the adjacent valves by shallow concave areas formed as a 

necessary consequence of the change from a univalved to a bivalved shell (pi. 41, figs. 1-5). Radial 

ribs first appear after this change has taken place 

(pi. 41, fig. 5), and the protoconch seems to have 

been relatively smooth. In the Ribeiriidae and Technophoridae, the valves are less inflated than in conocardiaceans, so that the distinction between the protoconch and the juvenile shell is less clear (pi. 4, figs. 

20, 21, 23). Well-preserved internal molds of all 

genera often have a small cone-shaped elevation in 

the center of the hinge area; we interpret this to be 

a natural cast of the interior of the protoconch and 

early juvenile shell (pi. 22, fig. 11; pi. 23, fig. 1).

The protoconch or its natural mold has been observed in the following genera: Anisotechnophorus 

(pi. 18, figs. 7-9) ; Bransonia (pi. 52, figs. 3-5) ; 

Eopteria (pi. 22, fig. 11) ; Pseudoconocardium (pi. 

41, figs. 1-5) ; Pseudotechnophorus (pi. 20, figs. 13- 

15) ; Ribeiria (pi. 4, figs. 20, 21, 23) ; Technophorus 

(pi. 12, fig. 17) ; and Hippocardial (pi. 47, figs. 13- 

15).

METAMORPHOSIS

We suggest that the bivalved postlarval shell be 

known as the dissoconch to conform with the terminology applied to pelecypods. There is no clearly defined junction between the protoconch and the dissoconch except posteriorly in some conocardiaceans, 

where an obvious transverse cleft separates the protoconch from the rostral area of the shell (pi. 40, 

fig. 5).

Metamorphosis apparently occurs by accelerated 

growth of the left and right flanks of the protoconch, 

producing the two valves of the dissoconch. Because 

rostroconchs characteristically have no adductor 

muscles, the two newly formed valves must grow 

rapidly to encompass the body. One specimen of the 

conocardiacean Bransonia wilsoni shows steplike 

growth increments on the posterior and lateral flanks
FUNCTIONAL MORPHOLOGY

of the immediately postlarval shell (pi. 52, fig. 4), 

indicating that the juvenile shell remained pyramidal in shape to a size of at least 1.5 mm. Other 

specimens show that the anterior edge of the postlarval shell developed a shallow sulcus generated by 

a sinus in the anterior commissure (pi. 47, figs. 14, 

15). As growth continued, the lobes on either side of 

the sulcus enlarged to form the snout region of the 

valves.

Lateral growth occurred at the same time to produce the flanks of the valves, but because the juvenile flanks are rotated dorsally by subsequent growth 

at the ventral commissure, even small shells (pi. 47, 

fig. 15) are deformed where the larval shell becomes 

obviously bivalved. In the Conocardiacea, this deformation is extreme, and it frequently obliterates 

the protoconch.

The protoconch survives in forms like Bransonia 

wilsoni because the outermost longitudinal clefts 

separate the protoconch from the carinal areas of the 

shell (pi. 51, fig. 17). In contrast to conocardiaceans, 

the valves of technophorids, ribeiriids, and Eopteria 

are less inflated, so the protoconch is more easily 

preserved (pi. 22, fig. 11).

The larval and juvenile growth of advanced rostroconchs like Bransonia and Pseudoconocardium reflects the broad outlines of the phylogeny of the class. 

The protoconch resembles the monoplacophoran 

shell; it is succeeded by a simple bilobed shell like 

that of some ribeirioids, which in turn grows into the 

inflated radially ribbed shell characteristic of 

conocardiaceans.

SUBSEQUENT SHELL GROWTH

Adult rostroconchs range in size from 2 mm to 

150 mm in length. The postlarval growth of many 

rostroconch shells produces complex skeletal structures which have no counterparts in other previously described mollusks. Because some of these structures are restricted to one or two genera and because 

homologies between structures are uncertain, it is 

convenient to describe the growth of several different forms separately. In this section, we describe the 

growth of the skeletal elements of Ribeiria, Euchasma, Pseudoconocardium, Hippocardia, and Arceodomus.

1. Growth of the ribeiriid shell (fig. 1). Our knowledge of the growth of the ribeiriid shell is 

based mainly on thin-section studies of the 

shell of Ribeiria apusoides Schubert and Waagen from the Ordovician of Bohemia and on 

silicified exteriors of Ribeiria calcifera Billings 

from the Ordovician of Ontario.

The ribeiriid shell grew from a protoconch 

situated nearer the anterior end of the dorsal 

margin (pi. 6, figs. 7, 11, 13). Growth lines on 

the shell of Ribeiria apusoides show that the 

valves separated a little during growth and 

that the longer posterior dorsal margin functioned as a hinge. A strong plate, termed the 

pegma, extends posteroventrally from the apex 

of the shell (pi. 5, fig. 4). The pegma is attached to both valves (pi. 4, figs. 22, 23; pi. 5, 

figs. 2-4) ; it divides the apical area of the 

shell into anterior and posterior cavities.

In front of the beak, the dorsal margin of 

the shell drops abruptly, and a second short 

hinge region occurs between the beak and the 

dorsal edge of the anterior gape (pi. 5, figs. 9, 

12). This is best seen in the silicified replicas of 

Ribeiria calcifera. Because the two hinge axes 

of Ribeiria are approximately parallel, but not 

colinear, a curved tensional fracture developed 

below the beak (pi. 4, fig. 9). The ventral edges 

of each fracture enlarged as growth continued 

so that the two hinge axes remained the same 

proportional distance apart, irrespective of the 

size of the shell. We use the term "anterior 

clefts" for the right and left ends of this tensional fracture.

In some individuals of Ribeiria calcifera, the 

anterior gape extends posteriorly along the 

anterior dorsal margin for some distance (pi. 

4, fig. 8). If this embayment continued as far 

as the beak, the need for the anterior clefts 

would disappear as it does in pelecypods and 

the bivalved gastropods. In these shells, the 

valves rotate about the ligament and separate 

at other parts of the dorsal margin.

Serial thin sections cut perpendicular to the 

anterior-posterior axis of Ribeiria apusoides 

show that the shell consists of three main layers a thin outer layer of relatively uniform 

thickness (pi. 30, fig. 5) formed at the commissure by the outer surface of the outer 

mantle fold, and thicker middle and inner shell 

layers separated by a discontinuity formed by 

the myostracum of the linear lateral muscle 

bands. The middle and inner shell layers were 

secreted by the outer surface of the mantle, 

and they lapped against the inner surface of 

the outer shell layer (pi. 30, fig. 5). All layers 

are continuous across the hinge of the shell.

When first formed, the outer shell layer and 

the immediately underlying middle shell layer 

were bent in acute angle at the anterior and
PALEONTOLOGY OF ROSTROCONCH MOLLUSKS

Anterior cleft

Protoconch

 Growth line

FIGURE 1. Paper cutout models to illustrate the growth of the ribeirioid shell. Drawings are based on 

Ribeiria lucan (Walcott). Black areas represent muscle insertions; stippled areas show thickness of 

shell along dorsal margin of completed models. Compare models to see how anterior clefts enlarge 

mechanically during growth because the shell at the ventral edges of these clefts cannot be resorbed. 

Growth line on lower model is same size as entire upper model.

Instructions: 1, photocopy page; 2, cut each model from photocopy, cut along all dashed lines; 3, 

use transparent adhesive tape to fix edges marked "B" together; 4, staple points marked "A" together; flatten area below protoconch by gently pushing taped area inwards.

posterior ends of the dorsal margin (pi. 31, 

figs. 2, 5). Subsequent deposition of thick inner 

and middle shell layers cemented the hinge 

into an inverted U-shape (pi. 30, fig. 4), and

the early formed layers were forced apart. 

This allowed for growth of the shell.

The growing edge of the pegma is concave 

posteriorly so it appears as two lobes project-
FUNCTIONAL MORPHOLOGY

2.

ing from the inner surfaces of the valves in 

more posterior sections (pi. 31, fig. 3). These 

lobes coalesce in more anterior sections (pi. 

31, fig. 1). Because the posterior face of the 

pegma is the site of a large muscle insertion 

(pi. 5, fig. 4; pi. 6, fig. 8), it is marked with 

growth lines showing successive positions of 

the ventral edge of the muscle. These growth 

lines mark the boundaries between successive 

increments of the middle shell layers forming 

the pegma. Consequently, sections through the 

pegma show that the growth increments of the 

middle shell layers intersect its upper face (pi. 

31, fig. 3).

The inner shell layer was deposited behind 

the linear lateral muscle bands as they migrated ventrally during growth. This layer 

buried the old muscle insertion areas above the 

dorsal edges of the muscles. It appears in 

transverse section as a series of overlapping 

layers which extend laterally from the dorsal 

margin (pi. 31, fig. 3). Near the apex of the 

posterior cavity, the whole posterior face of 

the pegma is covered with inner shell layer 

(pi. 30, fig. 2).

Obviously, if the early formed parts of the 

valves were separated during growth, the pegma would be subjected to tensional stress. Tensional fractures parallel to the commissural 

(symmetry) plane are visible in thin sections 

of the early formed parts of the pegma in the 

two specimens of Ribeiria apusoides that were 

fully examined (pi. 30, figs. 2, 3; pi. 31, fig. 1). 

Because these fractures do not penetrate subsequently formed shell layers, it is clear that 

they were not produced after the death of the 

organism.

Growth of Euchasma. This interpretation of the 

growth of Euchasma is based mainly on information obtained from silicified replicas of the 

shells of E. jonesi n. sp. and E. mytiliforme 

n. sp. from the Ordovician of Malaysia.

Unlike Ribeiria, Euchasma has a strongly 

inflated shell, which is more or less flattened 

anteroventrally (pi. 29, figs. 6-13). Because of 

the inflation, the valves must separate more 

during growth, and prominent umbos appear 

on either side of the protoconch region. As in 

Ribeiria, the valves are connected by an anterior plat© (pi. 29, figs. 3, 11, 14, 15), which 

also effectively blocks a reduced, almost circular anterodorsal aperture (pi. 28, figs. 15, 16). 

Also as in Ribeiria, there are two hinge axes,

so anterior clefts are well developed (pi. 27, fig. 

13; pi. 28, fig. 17). The posterior dorsal margin 

is the main hinge axis. Posterior clefts may 

also form (pi. 29, fig. 10) ; see discussion under 

3 for an explanation of posterior clefts.

Because both small and large specimens of 

Euchasma are similar in form and because all 

have apertural plates (modified pegmas), it is 

difficult to understand how they grew when the 

valves were held rigidly together by the apertural plate. Unlike the pegma of Ribeiria, the 

apertural plate of Euchasma is attached to the 

valves at only four points, two dorsal and two 

lateral (pi. 29, figs. 3, 15). The dorsal attachments could remain more or less static during 

life without affecting shell growth, but the 

right and left lateral attachments appear to 

have moved ventrally as the shell grew. Apparently shell was added to the ventral edge of 

each lateral attachment and at the same time 

resorbed from its dorsal edge. In this way, the 

valves could separate relatively widely during 

growth, while remaining rigidly joined by the 

modified pegma or apertural plate. 

3. Growth of Pseudoconocardium (fig. 2). Pseudoconocardium lanterna (Branson) has an inflated shell with a huge anterior gape (pi. 40, 

figs. 6, 11) but no complex internal skeletal 

elements. It is known from more than 100 undistorted specimens from the Pennsylvanian of 

north-central Texas.

Growth started from a well-defined protoconch (pi. 41, figs. 1-5), which merged into the 

juvenile shell. Growth lines on the shell show 

that subsequent growth moved the juvenile 

shells farther and farther apart, as in other 

invertebrates having paired calcareous valves. 

By the time the shell was sufficiently large, 

umbos formed on either side of the protoconch 

(pi. 41, fig. 2).

The shape of the growth lines on Pseudoconocardium lanterna (pi. 40, fig. 3) shows 

that the valves rotated about the anterior dorsal margin as the shell became larger. We term 

this the hinge axis. Because the valves are 

joined along this axis, the hinge must either 

bend or break as the valves grow. An anterior 

view of the shell (pi. 40, fig. 6) shows that the 

dorsal margin forms a smooth U-shaped curve 

at the commissure. Equivalent earlier formed 

parts of the shell were progressively deformed 

as growth preceded, and were cemented into 

their deformed shape by subsequently depos-
PALEONTOLOGY OF ROSTROCONCH MOLLUSKS

Rostral 

orifice

Ligament

Ventral orifice

Protoconch

Rostral 

structure

Rostral 

orifice

Ventral orifice

FIGURE 2. Schematic diagrams illustrating the posterior 

growth of conocardiid rostroconch and pelecypod shells. A. 

Hippocardia hibernica (Sowerby). Rostral orifice is almost 

colinear with the hinge axis of the shell, and growth lines 

(a-/) rotate about rostral orifice as shell grows. Only minor 

deformation of the upper surface of the rostrum occurs during growth. Note how the dorsal edges of the hood overlap 

to hide the hinge axis and protoconch. B. Hippocardia cunea 

(Conrad). Rostral orifice is below hinge axis, and orifice 

generates hoodlike rostral structure through growth. Growth 

lines (a-d) continue radially to protoconch. C, Pseudoconocardium lanterna (Branson) or Bransonia wilsoni n. sp., 

rostral orifice is below hinge axis, but no rostral structure

Rostral cleft 

(size exaggerated)

Ventral orifice

is produced. Instead, tension fractures (rostral clefts, exaggerated in this diagram for comparison with B) form between the loci of the ventral edge of the rostral orifice and 

the sides of the tubular rostrum. These clefts do not penetrate through the shell because new shell layers are continually added internally. Growth lines on such shells are 

interrupted where they cross the rostral clefts. D, The pelecypod Hecuba scortum (Linnaeus) (modified from Carter, 

1967, pi. 7, fig. 17), which has spinose carinae. The spines 

are formed at the posteroventral part of the commissure 

and are moved outwards during growth in the same way 

that the rostroconch hood is formed.
FUNCTIONAL MORPHOLOGY

ited prograding layers of inner shell material. 

These layers in turn were deformed by additional growth at the anterior end of the shell, 

and this growth also redeformed the previously 

formed layers. Each inner shell layer was thus 

slightly less strained than the next older one.

The effects of this deformation can be seen 

in thin sections of the hinge of Pseudoconocardium lanterna (pi. 32, fig. 2). In the specimen figured, tensional stresses caused by the 

bending of the shell have fractured the earlier 

formed shell layers, and the damage has been 

repaired by the youngest layers. Occasionally 

the whole anterior hinge may rupture during 

life (Pojeta and others, 1972, fig. 1).

In Pseudoconocardium lanterna and other 

conocardiaceans that we have sectioned, the 

outer shell layer is not continuous across the 

hinge (pi. 32, figs. 1, 2), and thus was not 

normally deformed during growth. However, 

because the outer shell layer is relatively thin, 

the hinge of P. lanterna is almost as thick as 

the flanks of the valves (pi. 32, fig. 2).

Because the anterior dorsal margin of conocardiaceans is the hinge axis, the posterior dorsal margin must have compensated for valve 

rotation in some other way. All well-preserved 

specimens of P. lanterna have a series of symmetrical fissures, termed clefts, behind the umbos (pi. 40, figs. 5, 7), which result from the 

periodic failure of the shell across and on each 

side of the tubular rostrum. In the past, these 

clefts were thought to be ligament grooves 

(Hind, 1900), but they do not penetrate the 

shell, were not connected to the secretory mantle, and thus could not have contained ligamental material. In transverse section, they 

appear as V-shaped fissures which penetrate at 

right angles to the growth lamellae. On some 

well-preserved exteriors of P. lanterna, the 

outer clefts cut previously formed growth 

lines. Because the clefts do not extend as far 

on small shells that are similar in size to the 

growth lines cut by the clefts on larger shells, 

we conclude that the clefts are fractures which 

enlarged as the shell grew. They are comparable to the anterior clefts of Ribeiria and 

Euchasma, and formed for much the same 

reason.

The clefts are best developed in inflated 

shells such as P. lanterna where the rostrum 

occurs below and at an angle to the hinge axis 

(pi. 40, fig. 8). In these shells, the posterior

commissure is again defined by the growing 

edge of the inner shell layers. It extends dorsally from the ventral orifice and continues 

around the tip of the rostrum. It does not extend along the dorsal surface of the rostrum 

(pi. 40, fig. 5) as it does in Hippocardia cunea 

(Conrad) (Case 4). This difference between 

these shells accounts for the presence of the 

rostral clefts in Pseudoconocardium lanterna 

but not in Hippocardia cunea. The need for the 

clefts is easier to understand if Bransonia wilsoni n. sp. (pi. 52, figs. 1-5) is considered as 

an intermediate form.

In lateral view, the ventral surfaces of the 

rostra of Hippocardia cunea (pi. 48, fig. 8) and 

Bransonia wilsoni (pi. 51, fig. 1) are similar in 

general form. However, their upper surfaces 

are quite different because B. wilsoni has a 

pair of deep clefts on either side of the rostrum 

(pi. 51, fig. 17) and in addition has smaller 

clefts near the protoconch. Between the large 

clefts, the rostrum is relatively uniform in 

width when viewed dorsally (pi. 51, fig. 17).

The outer edges of the large rostral clefts of 

Bransonia wilsoni are topologically equivalent 

to the angular edges of the rostral structure of 

Hippocardia cunea (pi. 48, figs. 10, 11), and 

growth lines on each type of shell intersect 

these edges in an acute angle which opens anteriorly. In Hippocardia cunea, the growth 

lines are immediately reflected toward the protoconch, and the upper surface of the rostral 

structure is covered with growth lines that 

radiate from the beak. Thus, the dorsal rostral 

surface of Hippocardia cunea grows like the 

lunule of a venerid pelecypod.

In contrast, the dorsal surface of the rostrum 

of shells with a rostrum like Bransonia wilsoni 

and Pseudoconocardium lanterna is marked 

with growth lines that cross the dorsal margin 

at right angles to the commissural plane. In 

these shells, the rostrum can only grow distally, ventrally, and internally. In shells where the 

upper surface of the rostrum is in line 

with the hinge axis, there is no problem, 

and the rostrum grows like the posterior 

wing of various pteriacean pelecypods (pi. 

43, figs. 1, 5). But in those forms where 

the rostrum is below and at an angle to 

the hinge axis, the rostrum would split dorsally 

as the valves grew. This is avoided in forms 

like Pseudoconocardium lanterna and Bransonia wilsoni by the formation of tensional
10 PALEONTOLOGY OF ROSTROCONCH MOLLUSKS

fractures, clefts, on either side of the rostrum. 

These occupy the space filled by additional shell 

secreted along the dorsal margin of the rostrum in Hippocardia cunea.

There are two kinds of rostral clefts in 

Pseudoconocardium lanterna and most other 

conocardiids: symmetrical longitudinal clefts 

resulting from tensional stresses more or less 

parallel to the rostrum, and one or more transverse clefts which apparently compensate for 

the required rotation of the rostrum within the 

commissural plane (pi. 40, figs. 5, 7). If allometric changes in the angle the rostrum 

makes with the shell are to be avoided, the 

rostrum must be gradually raised during 

growth. Apparently the transverse clefts 

closed slowly during growth and allowed for 

this rotation. The first-formed transverse cleft 

separates the protoconch from the rostral area 

of the dissoconch in this and many other conocardiids (pi. 40, fig. 5).

In thin section, the shells of Pseudoconocardium lanterna and Bransonia wilsoni are 

formed of two obviously different layers. The 

outer shell layer is relatively transparent and 

coarsely prismatic (pi. 32, fig. 4). The inner 

shell layers are darker and well laminated, 

though they show no obvious microstructure 

(pi. 32, fig. 1, 2, 4). They may have been 

nacreous, cross-lamellar, or homogeneous.

Because the exterior of the shell is covered 

with narrow closely spaced radial and comarginal walls (pi. 40, fig. 12), thin sections 

sometimes give the impression that the outer 

shell layer contains a series of roofed pits or 

vacuoles. Similar structures have been reported from other conocardiids (Panella and 

MacClintock, 1968, pi. 8, fig. 5). These views 

can result from oblique sections through intersecting radial and comarginal walls, and there 

is no evidence that the intervening pits were 

roofed over in P. lanterna. In at least some 

specimens of P. lanterna, small secondary ribs 

run between the vertical lamellae of the Comarginal markings in the interspaces between 

primary ribs (pi. 42, fig. 6). The intersection 

of the vertical lamellae and the secondary ribs 

produces a grid pattern that significantly reduces the space open to the exterior between 

adjacent lamellae.

The inside of the anterior aperture of Pseudoconocardium lanterna and many other rostroconchs is lined with a series of blunt pro4.

jections (pi. 40, figs. 6, 11) that we have 

termed commissural (or marginal) denticles. 

These are formed of the prismatic outer shell 

layer secreted at the edge of the mantle. Similar smaller denticles line the inside of the rest 

of the commissure as far as the base of the 

rostrum. As the shell grew, these commissural 

denticles were buried by prograding inner shell 

layers secreted by the external surface of the 

mantle. As growth continued, the commissural 

denticles generated internal ribs which were 

totally submerged by the inner shell layers. 

Sometimes solution of the inner shell layers 

before lithification may expose the ribbed internal surface of the outer shell layer, thus 

giving the impression that the interior of the 

shell was ornamented with radial ribs (pi. 45, 

fig. 4). The inner shell layers that bury the submerged ribs are relatively uniform in thickness, and so they form concentric folds over the 

ribs of the outer shell layer. When the inner 

shell layers became thick enough, they became 

relatively flat (pi. 42, figs. 13, 14).

The growth of the anterior dorsal margin of 

P. lanterna also illustrates features found in 

many conocardiids. Well-preserved specimens 

normally have two subcircular depressions, one 

on either side of the middorsal line, just inside 

the anterior commissure (pi. 40, fig. 11; pi. 42, 

fig. 5). These depressions are separated by a 

wall of shell, best shown by views of the 

growth layers in transverse section (pi. 32, fig. 

1). The function of the depressions is uncertain, but they may have been muscle insertions 

because they are filled by subsequent deposits 

of inner shell material. The abrupt contact between these latter deposits and the base of the 

depression may represent the myostracal layer 

of the muscle insertion.

Growth of Hippocardia (fig. 2). Hippocardia 

cunea (Conrad), the most common rostroconch 

in the northeastern United States Devonian, 

has a spectacular hood attached to the carinal 

area of the shell (pi. 48, fig. 2). The species is 

well known from external molds in New York 

State, silicified replicas of the outer shell layer 

from the Falls of the Ohio River along the 

Kentucky-Indiana border, and original shells 

from Ohio (pis. 48, 49).

The hood of Hippocardia was secreted by a 

tubular extension of the mantle at the ventral 

orifice, which is located midventrally on the 

posterior face of the shell (pi. 49, figs. 5, 6).
FUNCTIONAL MORPHOLOGY 11

The ventral surface of the hood forms a continuous curved surface with the posterior 

flanks of the valves, but it lacks radial ribs (pi. 

49, figs. 4, 10). Both upper and lower surfaces 

of the hood are ornamented with fine closely 

spaced growth lines that are continuous with 

growth lines on the rest of the shell. The 

growth lines indicate that new shell material 

was periodically added to the hood along the 

entire length of the tubular extension of the 

ventral orifice as the valves gradually separated. Thus, the hood represents a surface 

generated by a tube at the posterior ventral 

commissure and was inevitably produced if the 

tube was maintained throughout the life of the 

animal. It follows that the hood may have had 

no function; it may only represent the loci of 

the edges of the tube. Alternatively, the only 

function of the tubular extension of the third 

aperture may have been to generate the hood, 

and the hood may be the functionally important structure.

There is no evidence for allometric changes 

in the size of the hood during growth. Consequently, in shells that have inflated valves, the 

edges of the hood on left and right valves may 

have interfered with one another as the umbos 

enrolled. This problem appears to have been 

solved, as it is in living heart cockles, by having the hood of one valve slightly ahead of that 

of the other.

Serial transverse sections of the hood of 

Hippocardia cunea show that it is formed of 

concave lamellae which are separated by open 

spaces in the distal part of the body (pi. 32, 

figs. 5, 6). Proximally, these spaces are filled 

with prismatic outer shell material (pi. 32, fig. 

5). Thus, the whole of the hood is constructed 

of the outer shell layer. Because the outer shell 

layer of mollusks is normally only secreted at 

the mantle edge by the outer surface of the 

outer fold of the mantle, we believe that a hypertrophied part of the outer mantle fold 

formed the hood of Hippocardia.

The rostral structure of Hippocardia cunea 

simulates a second hood (pi. 48, figs. 10, 11). 

Like the hood, it is a curved surface generated 

through growth by a tube at the commissure. 

There are, however, two important differences. 

First, it is clear by comparison with other 

conocardiaceans that it is the tube, not the 

structure generated by the tube, that is functionally important. And second, again by comparison with other conocardiaceans, it is certain that the tube (rostrum) is formed of all 

shell layers (see 3).

5. Growth of Arceodomus. Arceodomus is best 

known from recrystallized original shells of A. 

glabrata (Easton) from the Mississippian and 

Pennsylvanian of Montana, Nevada, and Texas 

(pi. 42, figs. 8-10; pi. 43, figs. 1-4; 7-12) and 

from silicified replicas of A. langenheimi (Wilson) from the Permian of California (pi. 43, 

figs. 13-15). Arceodomus resembles Conocardium (pi. 38) but lacks radial ornament on the 

body of the shell. Externally, the growth of 

Arceodomus is similar to that of Pseudoconocardium, and small rostral clefts are visible in 

A. glabrata (pi. 43, fig. 10). We use these two 

species to illustrate the formation and growth 

of the anterior longitudinal shelves (pi. 43, figs. 

12, 13).

Anterior longitudinal shelves are curved 

plates composed of the outer (prismatic) shell 

layer (pi. 43, fig. 13) that project more or less 

horizontally across the snout region of Arceodomus and Conocardium. As growth continued, 

the older parts of the shelves were buried in 

thick deposits of inner shell layer (Wilson, 

1970, figs. 10-18). Wilson (1970) recognized 

the microstructural difference between the 

shelves and the inner shell layers, but tentatively interpreted the shelves as myostracal 

layers.

The shelves are unusually enlarged commissural denticles, and clear transitions can be 

seen in several morphological series, for example, Pseudoconocardium lanterna (pi. 40, 

figs. 6, 11), Mulceodens jaanussoni n. sp. (pi. 

34, figs. 3-5), Hippocardia zeileri (Beushausen) (pi. 47, figs. 8, 9), and Arceodomus glabrata (pi. 43, fig. 12). Significance of the 

shelves lies in the fact that they were formed 

of the outer shell layer, implying that they 

were formed by the mantle edge. We conclude 

that the anterior part of the mantle of Arceodomus (and Conocardium) was enlarged, that 

it was complexly folded when withdrawn into 

the shell, and that the edges of the mantle must 

have been located at the growing edges of the 

anterior shelves when the mantle was at rest 

in the shell.

SUMMARY OF SHELL GROWTH 

All rostroconchs grew a bilobed shell (dissoconch) 

from a univalved protoconch or juvenile shell. Primitive rostroconchs (Ribeirioida) have all shell layers
12 PALEONTOLOGY OF ROSTROCONCH MOLLUSKS

continuous across the dorsal margin, but in advanced 

rostroconchs (Conocardiacea), the outer shell layer 

is dorsally discontinuous, except in the region of the 

protoconch. Primitive rostroconchs have the valves 

connected by a stout anterior pegma (Ribeirioida, 

some Eopteriidae) or anterior and posterior pegmas

(Ischyrinioida) which is deformed (Ribeiria) or 

partially resorbed (Euchasma) to allow for valve 

separation during growth.

Parts of the dorsal shell margin of all rostroconchs 

function as a poorly elastic hinge during growth, but 

during day-to-day living, the valves were held rigidly together. If the shells are anteriorly elongated

(Pseudotechnophorus, Conocardiacea), the anterior 

dorsal margin functions as the hinge. In posteriorly 

elongated shells (Ribeiriidae, Technophoridae), the 

reverse is true. Because the dorsal shell margin is 

rarely straight, transverse and longitudinal tensional fractures called clefts form between the main 

hinge and the less elevated parts of the dorsal margin. In subequidimensional shells (Eopteria, Euchasma), clefts are present on both sides of the protoconch ; anteriorly or posteriorly elongated shells normally have clefts only at the shorter end of the shell. 

The distribution of the clefts can be explained by the 

geometry of shell growth.

All rostroconchs that have visible shell structure 

have an outer (often prismatic) shell layer formed 

by the outer edge of the mantle. One or more inner 

shell layers are lapped against the internal surface 

of the outer shell layer by the outer surface of the 

mantle. The hood of Hippocardia is formed of outer 

shell material only; the commissural denticles and 

anterior shelves of conocardiaceans are also part of 

the outer shell layer, implying that the edge of the 

mantle could be withdrawn into the anterior part of 

the shell in some forms.

OPENING OF THE VALVES

The valves of pelecypods and bivalved gastropods 

are joined dorsally by an elastic structure called a 

ligament. Owen, Trueman, and Yonge (1953) 

showed that the simplest pelecypod ligament consists of three layers (periostracum, lamellar, and 

fibrous layers), which are continuous with comparable shell layers in the right and left valves. The 

probable structure of the ligament of the Early Cambrian pelecypod Fordilla (Pojeta and others, 1973) 

and the nature of the ligament of the bivalved gastropod Berthelinia (Kawaguti and Yamasu, 1961) 

support this observation. Thus, the valves and ligament are part of a single structure (the shell) and 

differ only in the degree of calcification of the protein matrix. This explanation is supported by the 

ontogeny of living pelecypods, whereby a single larval shell gland secretes "a saddle-shaped cuticular 

pellicle, which becomes calcified at two symmetrical 

points, right and left of the middle line" (Pelseneer, 

1906, p. 245).

In engineering terms, the ligament can be described as a spring, because it stores energy supplied 

by contractions of the adductor muscles attached to 

each valve. This energy is released when the adductors relax, and experimental studies show that 

the elastic efficiency of the ligament can be estimated 

from the size of the hysteresis loop obtained by loading and unloading a freshly killed individual (Trueman, 1953; Hunter and Grant, 1962). Pelecypods 

having a mechanically inefficient ligament use muscular energy transmitted hydrostatically through the 

foot or mantle cavity to open the valves (Hunter 

and Grant, 1962).

The pelecypod ligament is strained when the 

valves are closed. Above the hinge axis, the strain is 

tensile; below it, the strain is compressional. Normally the ligament is constructed so that the junction between the functional parts of the lamellar and 

fibrous layers more or less coincides with the hinge 

axis, because each layer is resistant to only one kind 

of stress.

Only some of the energy stored in the pelecypod 

ligament comes from the adductor muscles. Galtsoff 

(1964) noted that if the adductor muscle of an 

oyster is cut, the valves open farther than they do 

when the oyster is narcotized and the adductor fully 

relaxed. The origin of this extra energy remains 

unclear.

Trueman (1949) found that the functional part 

of the ligament of Tellina tennis is not, as would be 

expected, the most recently formed part; he suggested that additional secretion of fibrous layer in the 

middle part of the ligament stretches the lamellar 

layer so that early formed parts of the ligament 

remain functional for long periods of time. If this 

did not happen, only the last formed part of the ligament could function, because the strain on the older 

parts would be gradually released as the valves 

opened slowly during growth. In fact, in many 

pelecypods, the anterior part of the ligament is torn 

apart as each valve grows in a separate helical spiral 

(Perkins, 1969, p. N756). Thus, Trueman (1950) 

found that in Mytilus edulis, the whole of the original 

ligament of a shell 16 mm long is destroyed when the 

mussel has grown to a length of 70 mm. Thus, only 

the posterior part of the ligament of M. edulis functions at any one time. Trueman concluded that the
FUNCTIONAL MORPHOLOGY 13

ligament of M. edulis becomes functional when the 

lamellar layer is subjected to tensile strain by the 

growth of the fibrous layer beneath it. This strain is 

increased when the valves are closed, but a significant part of the opening force is generated biochemically by the mantle during the formation of 

the ligament. This extra energy may assist in opening the valves for locomotion, burrowing, and feeding, but equally importantly, it enables the valves to 

open slowly during growth.

Bevelander and Nakahara (1969) reported that 

the fibrous layer of the ligament of M. edulis is 

formed of long euhedral pseudohexagonal needles of 

aragonite dispersed in a homogeneous organic matrix. The diameter of each needle increases away 

from the calcification front, and it may be this expansion in volume that stretches the outer layer and 

activates the ligament. Alternatively, quinone tanning of the protein forming the lamellar layer may 

cause it to shrink and thus compress the underlying 

fibrous layer.

A closer analog to the rostroconchs is found in the 

extraordinary living pelecypod Pinna. In Pinna, the 

valves are joined rigidly by a long simple ligament, 

which has both lamellar and fibrous layers impregnated with calcium carbonate. Yonge (1953b) reported that the ligament of Pinna is not elastic and 

has no opening thrust on the valves. When the adductor muscles contract, the valves are flexible 

enough to be pulled together, but the ligament does 

not bend appreciably (Yonge, 1953b, p. 338).

Growth lines on the shell of Pinna show that earlier growth increments gape more widely than later 

formed ones, so that the valves must have opened 

slowly during the growth of the shell. The force 

that causes the valves to gape during growth has not 

been documented, but the ligament may generate 

this opening moment. If Pinna has a self-opening 

shell, rostroconchs may have functioned in a similar 

manner.

In contrast to most pelecypods and the bivalved 

gastropods, all rostroconchs had valves that were 

rigidly joined dorsally. In some genera like Conocardium (pi. 38, figs. 1, 3, 6, 11, 14) and Arceodomus (pi. 43, figs. 9, 11, 14), the ventral and posterior shell margins are tightly apposed, but in 

others like Ribeiria (pi. 6, figs. 3, 5, 6) Eopteria 

(pi. 24, figs. 14, 15, 20) and Pseudoconocardium (pi. 

40, figs. 4, 6, 11), there are prominent shell gapes. 

Growth lines on both kinds of shells show that the 

valves opened slowly during life, so that the ventral 

edges of early increments may eventually gape at 

angles of 180° or more.

Because the valves of rostroconchs are joined dorsally, energy was needed to separate the valves so 

that new increments could be added at the commissure. This energy could have been supplied in several, not necessarily mutually exclusive, ways. Although applied in small amounts for long periods of 

time, the energy was sufficient to rupture parts of 

the dorsal shell margin in almost all rostroconchs.

The most obvious primary source of mechanical 

energy in any animal is its musculature. Energy 

generated by the contraction of muscles could be 

transmitted hydrostatically to the shell either 

through fluids in the body cavity, particularly blood 

in the pedal haemocoele, or by the fluid (sea water) 

in the mantle cavity. If the volume of blood in the 

foot of a rostroconch could be kept constant by 

means of a Keber's valve or some comparable structure, the foot could be protracted between the ventral valve edges by contraction of its intrinsic transverse muscles and then inflated by means of the 

pedal retractors inserted on the shell. This would 

force the valves apart. Alternatively, the foot and 

(or) hypertrophied mantle tissue could be withdrawn into the shell by appropriate muscles, and if 

no sea water were allowed to escape, hydrostatic 

pressure would tend to open the valves.

We prefer the former explanation for forms like 

Ribeiria, Eopteria, and possibly Bransonia and 

Pseudoconocardium, as it is difficult to see how they 

could have effectively sealed all shell gapes to conserve water in the mantle cavity. However, it is 

equally difficult to envisage that Arceodomus and 

Conocardium had a foot large enough to open the 

valves, as the anterior gape is almost completely 

blocked by the anterior longitudinal shelves (pi. 43, 

fig. 13). In these latter forms, it seems more likely 

that the withdrawal of mantle tissue increased the 

hydrostatic pressure in the mantle cavity if muscular energy were used to open the valves.

Muscular energy may not have been the prime or 

only force that opened the valves of rostroconchs. 

Other possibilities include growth pressure resulting 

from the addition of new cells to the body mass, 

osmotic pressure in the body mass, or the unexplained opening moment of the pelecypod ligament 

which may be generated by crystallization pressure 

in the fibrous layer of the ligament.

MUSCULATURE

The principal muscles of shelled mollusks serve 

the foot and the mantle edges; other smaller muscles 

may be used to move the head, jaw apparatus, gills, 

and visceral mass. Most of the muscles are attached
14 PALEONTOLOGY OF ROSTROCONCH MOLLUSKS

to the shell at surfaces known as insertion areas 

(muscle scars) where minute microvilli reinforced 

by cytoplasmic fibrils fill tiny pits in the surface of 

the shell (Hubendick, 1957). Each muscle insertion 

moves toward the commissure and increases in size 

during growth; it also generates a thin shell layer 

with characteristic ultrastructure and mineralogy 

known as the myostracum (Oberling, 1964; Taylor 

and others, 1969; Batten, 1972). If the muscle insertion is linear, the corresponding myostracal layer 

will be planar, but if the insertion area is circular or 

oval, it generates a linear piece of myostracum 

(Waller, 1972).

Growth lines reflecting the shape of the commissural side of the muscle are normally produced on 

the surface of the insertion area by fluctuations in 

the rate of deposition of the underlying shell layers 

or the myostracum. As the trailing edge of the 

muscle moves toward the commissure during growth, 

new shell layers wholly or partly obliterate the areas 

where the muscle was previously inserted. If these 

shell layers are thinner across the old muscle-insertion areas than they are in other parts of the shell, 

a smooth concave muscle track is visible on the inside of the shell.

Sometimes a muscle inserted on the shell may run 

parallel to it for some distance, for example, the 

siphonal retractor muscles of siphonate pelecypods. 

In such a case, some individuals in a population may 

mold shell around the muscle bundles so that a series 

of linear concave depressions is formed on the inside 

of the shell (Runnegar, 1972). We refer to these 

structures as muscle impressions; they give evidence 

for the direction of action of the muscle.

Muscle insertions in fossil mollusks are best observed on natural or artificial internal molds of the 

shell. Growth lines on the insertion areas or welldefined muscle tracks unequivocally identify muscleinsertion areas; the shape of the leading and trailing 

edge of the insertion is also important. Characteristically, the leading edge will be a smooth, poorly 

defined curve; the trailing edge is usually well defined and is often scalloped. If the insertion is too 

poorly preserved to show any of these features, a 

thin section of a shelled specimen may reveal a 

myostracal layer or a discontinuity representing a 

thin myostracum.

It must be pointed out that only some of the 

original muscle insertions may be preserved. Many 

specimens of Paleozoic pelecypods have well-preserved adductor and pedal muscle-insertion areas 

but show no trace of a pallial line. Only one specimen 

in many may show this structure, and one should be

extremely cautious in using such negative evidence. 

Thus, although many ribeirioids have well-preserved 

pedal muscle insertions, only a few specimens show 

traces of the pallial line. We feel that these differences are due to preservation and that a pallial line 

was probably present in many rostroconchs.

Because there are no living rostroconchs, no modern analogs can be used to predict what rostroconch 

musculature looked like. Muscle-insertion areas must 

be recognized in one or more of the ways indicated 

above, and it is necessary to be most rigorous in 

assessing the significance of depressions on the interiors of shells.

Yonge (1953a) observed that pelecypods probably 

differ from primitive ancestral mollusks in having 

the peripheral part of the mantle attached to the 

shell by a series of radial muscles, the insertions of 

which coalesce to form the pallial line. He suggested 

that pallial attachment probably became necessary 

as lateral compression enlarged the mantle and shell 

relative to the foot and visceral mass. When the 

bivalved condition finally developed, the adductor 

muscles were formed by cross-fusion of the distal 

ends of the anterior and posterior radial muscles of 

the mantle. Yonge therefore made an important distinction between an inner series of shell or pedal 

muscles that control the foot and support the visceral mass, and an outer set of pallial muscles that 

control the edges of the mantle and serve to close 

the valves.

It is the enlarged mantle cavity of rostroconchs 

and pelecypods that creates the need for strong pallial retractor muscles and hence a well-defined pallial 

line. Small scattered pallial retractor muscles are 

present in Neopilina, and it also has a broad roughly 

circular zone where cells in the mantle epithelium 

are attached to the shell (Lemche and Wingstrand, 

1959). Batten (1972) described myostracal shell 

layers in several Pennsylvanian gastropods which 

he attributes to muscles attaching the mantle to the 

shell. Thus, although Neopilina and the fossil gastropods lack what is conventionally called a pallial line, 

they have small muscles or appropriate mantle 

epithelial cells in comparable positions. Presumably 

these could be hypertrophied to form a well-defined 

pallial line if the proper conditions arose.

Yonge's twofold classification of the shell-attached 

muscles of the pelecypods can be conveniently applied to the Rostroconchia. We distinguish pedal and 

pallial muscles in many forms. Normally, the pedal 

muscles are more deeply inserted into the shell and 

are therefore more commonly preserved than the 

pallial muscles.
FUNCTIONAL MORPHOLOGY 15

PEDAL MUSCULATURE

The oldest known rostroconchs that have wellpreserved muscle-insertion areas are Early Ordovician ribeirioids (fig. 3) and eopteriids (fig. 4). A 

simple muscle array is shown by Tolmachovial jelli 

n. sp. (fig. 3C, D ; pi. 14, figs. 9-19). This species has 

subequal oval insertion areas on the anterior and 

posterior sides of the umbonal cavity (pi. 14, figs. 

9-16,18,19) which are connected ventrally by linear 

insertion areas on the left and right umbonal flanks 

(pi. 14, figs. 11, 12). Because this ribeirioid is approximately equilateral, we feel that the foot projected ventrally and was formed mainly of subequal 

anterior and posterior retractor muscles inserted on 

the shell at the two oval depressions. The foot probably also contained circular and transverse intrinsic 

muscle fibers that were not attached to the shell. 

These muscles could oppose the longitudinal retractor muscles through the hydrostatic skeleton of 

the pedal haemocoele to lengthen or broaden the foot 

for probing and pedal anchorage. The linear insertion areas connecting the two pedal retractor insertions may have contained the ends of longitudinal 

muscles forming the sides of the foot, or they may 

have been the areas of attachment of muscles supporting the gills.

The anterior and posterior pedal retractor insertions lie across the midline of the shell. We term 

these the anterior and posterior median insertions of 

the anterior and posterior median pedal retractor 

muscles, and distinguish them from right and left 

pedal retractor muscle insertions arranged symmetrically in both valves in advanced rostroconchs 

(pi. 22, figs. 5, 6) and most pelecypods. As we are 

uncertain of the function of the linear muscles connecting the median muscles, we name them descriptively as the right and left linear insertion areas of 

the corresponding side muscles.

Anterior and posterior median and left and right 

linear muscle insertions are present in several 

ribeirioid genera (fig. 3). In those forms having a 

well-developed pegma, the anterior median retractor 

is inserted on the posterior face of the pegma (pi. 5, 

fig. 4), and all muscle insertions are confined to the 

posterior umbonal cavity. In Ribeiria lucan (Walcott), a series of discrete circular- to kidney-shaped 

insertions replace the linear insertions of the left 

and right side muscles (fig. 3£"; pi. 8, fig. 14).

Complex right and left linear muscle insertions 

also are present in the ischyrinioid Ischyrinia norvegica Soot-Ryen (fig. 3A; pi. 19, figs. 10-14). It is 

not known whether Ischyrinia has large anterior and 

posterior median insertions, but because of the presence of side muscles, we assume that the anterior 

and posterior retractors of the foot originated on the 

inner sides of the two pegmas found in Ischyrinia 

(pi. 18, figs. 22, 25).

The protoconch of another ischyrinioid, Pseudotechnophorus typicalis Kobayashi, has a tiny anterior median muscle insertion and an equally small 

linear insertion area preserved only on the left side 

of the specimen (fig. 3F; pi. 20, figs. 13-15). We 

view these structures as the insertions of muscles 

that were larger in the ancestors of Pseudotechnophorus but that became limited to the shell apex 

when new right and left lateral pedal muscles 

evolved; the relict structures also indicate a phylogenetic relationship of Pseudotechnophorus to the 

ribeirioids. The lateral pedal muscles of Pseudotechnophorus were attached at one large insertion and 

several smaller insertions on the right and left flanks 

of the valves (fig. 3G; pi. 20, fig. 8). We term the 

large lateral pedal muscle, the primary pedal retractor, and the small lateral pedal muscles the 

"secondary retractors," to differentiate them from 

the median retractors of ribeirioids and the anterior, 

umbonal, and posterior pedal retractors of 

pelecypods.

Eopteria, like Pseudotechnophorus, has a large 

lateral pedal muscle insertion (pi. 22, figs. 5, 6) and 

three smaller secondary insertions on each valve (pi. 

22, figs. 5, 6). A reconstruction of the musculature 

of Eopteria is shown in figure 4. The entire musculature of this genus is not known from any one specimen, and the reconstruction is based on several specimens from the same locality, each of which shows 

some of the muscle insertions. The interpretation of 

the musculature of Eopteria given here differs from 

that of Pojeta, Runnegar, Morris, and Newell 

(1972), in that three small dorsally located insertions shown on the earlier diagram are now thought 

to be discontinuous muscle insertions forming the 

dorsal part of the anterior end of the pallial sinus 

(pi. 22, figs. 3, 4, 7, 8). Figures 3 and 4 on plate 22, 

show that in this specimen the pallial sinus is discontinuous dorsally but not ventrally, and figures 7 

and 8, on plate 22, show three discontinuous small 

dorsal muscles in the same approximate position as 

the dorsal part of the pallial line of the other specimen. The similarity of the adult musculature of 

Eopteria and Pseudotechnophorus suggests a phylogenetic link between the ischyrinioids and the 

conocardioids.

Some of the few known specimens of conocardiaceans that have muscle-insertion areas preserved 

(fig. 5) have a large primary pedal-retractor inser-
16 PALEONTOLOGY OF ROSTROCONCH MOLLUSKS

omm

omm

pmm

pmm

pmm

FIGURE 3. (See explanation on facing page.)
FUNCTIONAL MORPHOLOGY 17

am?

FIGURE 4. Composite diagram of the muscle insertions of the left valve of Eopteria ventricosa 

(Whitfield); am, adductor muscle insertion(?); 

mi, muscle impression; mt, muscle track; ppr, 

primary pedal-retractor muscle insertion; ps, 

pallial sinus; pi, pallial line; spr, secondary 

pedal-retractor muscle insertions.

tion in the umbonal cavity of each valve (pi. 38, figs. 

21, 22, 24). Smaller insertions in this area are regarded as secondary pedal retractors (pi. 53, figs. 

21-23). Some conocardiaceans show no obvious 

pedal-retractor-insertion areas (pi. 53, figs. 1-4).

Some pelecypods have muscles inserted on the 

shell that serve to protract the foot. In some forms, 

the distal ends of these muscles run transversely 

around the foot, forming a sphincter which is used 

to confine blood to the pedal haemocoele. Contraction 

of the intrinsic transverse muscles of the foot then 

protracts the foot if the shell-inserted pedal retractors are simultaneously relaxed. The living solenid 

Ensis operates its foot in this way (Trueman, 1967).

Other pelecypods (unionids, arcaceans, trigoniids) 

have a pedal muscle inserted on the shell below the 

insertion of the anterior adductor. In these animals, 

the muscles act in directions that enable them to 

move the foot anteriorly and ventrally. Such muscles 

are termed "pedal-protractor muscles."

FIGURE 3. Musculature of various genera of the Ischyrinioida 

and Ribeirioida; amm, anterior median muscle insertion; mt, 

muscle track; pmm, posterior median muscle insertion; ppr, 

primary pedal-retractor muscle insertion; prm, pallial retractor muscle insertion; sm, side muscle insertion; spr, secondary pedal-retractor muscle insertions. A, Composite 

diagram of left valve of Ischyrinia winchelli Billings and 7. 

norvegica Soot-Ryen. B, Left valve of Tolmachovia concentrica Howell and Kobayashi. C, D, Dorsal and left-valve 

views of Tolmachovial jelli n. sp. E, Left valve of Ribeiria 

lucan (Walcott). F, G, Enlargement of larval musculature 

and a diagram of adult musculature of Pseudotechnophoms 

typicalis Kobayashi. H, Composite diagram of left valve of 

Technophorus sp. 7, J, dorsal- and left-valve views of 

Ribeiria pholadiformis Sharpe.

None of the primary and secondary pedal-muscle 

insertions of rostroconchs are low enough on the 

shell to have functioned as direct pedal protractors, 

and we cannot determine whether any of them 

served as sphincters. Thus, in rostroconchs, pedal 

protraction seems to have been accomplished only by 

hydrostatic means.

PALLIAL MUSCULATURE

The Ordovician ribeirioid Wanwania shows traces 

of a pallial line (pi. 3, fig. 7). We believe that most 

ribeirioids, with the possible exceptions of Heraultipegma and Watsonella, had pallial lines where the 

peripheral parts of the mantle were attached to the 

shell by radial mantle muscles. As noted, many specimens of many species of Paleozoic pelecypods preserve impressions of the adductor and pedal muscles, 

but only a very few specimens preserve the pallial 

line. The internal molds of ribeirioids that we have 

studied are generally not well enough preserved to 

show the shallow insertions of the small radial muscles of the mantle.

Several specimens of Eopteria preserve parts of 

the pallial line (fig. 4; pi. 22, figs. 1, 2, 3, 4; pi. 23, 

figs. 2, 3). There is an obvious anterior pallial sinus, 

and one specimen shows shallow impressions of the 

radial muscles of the mantle within the pallial sinus 

(pi. 22, figs. 5, 6). The absence of visible impressions 

on other parts of the shell indicates that the radial 

mantle muscles were both larger and longer in the 

area of the sinus. If so, the anterior part of the 

mantle was also enlarged in this area, and, by analogy with pelecypods, could be extended beyond the 

limits of the shell. We term these enlarged radial 

muscles of the mantle pallial retractor muscles.

The pallial line and associated radial muscle tracks 

are best preserved in one specimen of Euchasma 

from the Lower Ordovician of Newfoundland (pi. 27, 

fig. 9). The bending of the pallial line laterally in the 

anterodorsal region of the shell shows that an anterior pallial sinus was also present in Euchasma, but 

this part of the specimen is not well preserved, and 

no radial mantle muscle impressions are visible.

Pseudotechnophoms has a large muscle insertion 

in the isolated cavity of the shell above the anterior 

pegma (fig. 3G; pi. 20, figs. 10, 11). A muscle 

originating in this position is unlikely to have been 

connected to the foot, because the pegma effectively 

separates this cavity from the main mantle cavity. 

We assume that Pseudotechnophorus had radial 

mantle muscles, even though a pallial line is not preserved on any of the specimens seen by us; and we 

interpret the muscle in the anterior umbonal cavity
18 PALEONTOLOGY OF ROSTROCONCH MOLLUSKS

spr

pi

G

H
FUNCTIONAL MORPHOLOGY 19

as an enlarged radial mantle muscle which functioned as a pallial retractor.

We do not have many conocardiaceans that have 

preserved pallial muscle insertions. In the few specimens we do have, the pallial line is smooth (fig. 5; 

pi. 53, figs. 1-4, 21-23). In Bransonial sp. (fig. 5E, 

F; pi. 53, figs. 1-4), and B. robustum (Fletcher) 

(fig. 5Z>, G ; pi. 53, figs. 21-23), the anterodorsal part 

of the pallial line is Y-shaped and has anterior, posterior, and ventral branches; in these two species, 

the junction of these three branches (the pallial 

junction) is the site of a larger muscle insertion (pi. 

53, figs. 1, 21, 23). In B. cressmani n. sp. (pi. 54) 

and Conocardium elongatum (Sowerby) (pi. 38, fig. 

22), the anterior part of the pallial line is not Yshaped. In Conocardium aliformel (Sowerby) the 

posterior branch is not connected with the anterior 

and ventral branches (fig. 5#; pi. 51, fig. 11). This 

species has well-defined radial mantle impressions 

emanating from the anterior and possibly the posterior branch of the pallial line (fig. 5#; pi. 51, fig. 

11), indicating that as in Eopteria, these parts of 

the pallial line had pallial retractor muscles which 

could withdraw mantle tissue extended from the 

aperture of the shell. The larger muscle insertion at 

the junction of the branches of the pallial line in 

Bransoniaf sp. and B. robustum probably housed a 

muscle that performed the same function.

Several conocardiacean species have circular to 

elongate depressions on both sides of the hinge just 

inside the anterior aperture of the shell (fig. 5B, C ; 

pi. 40, fig. 11; pi. 47, fig. 12). These depressions were 

filled by subsequently deposited inner shell layers as 

the shell grew. We interpret them to be muscle insertions and suggest that they housed muscles used 

to protract mantle tissue from the anterior aperture 

of the shell (pallial protractor muscles). This interpretation helps to explain their unusual position on 

the shell and suggests the method used by conocardiaceans to protract the mantle. No similar insertions are known in either Eopteria, or Pseudotechnophorus, and we assume that mantle protracFIGURE 5. Musculature of various genera of the Conocardiacea; ab, anterior branch of the pallial line; mi, muscle 

impression; pb, posterior branch of the pallial line; pj, 

pallial junction; pi, pallial line; ppm, pallial-protractor 

muscle insertion (?) ; pprf primary pedal-retractor muscle 

insertion; prm, pallial retractor muscle insertion; spr, secondary pedal retractor muscle insertion. A, Reconstruction 

of Conocardium elongatum (Sowerby). B, C, Dorsal and 

left-lateral views of Hippocardia zeileri (Beuhausen). D, 

G, Left and dorsal views of Bransonia robustum (Fletcher). 

E, F, Dorsal and left-lateral views of Bransonial sp. H, 

Left-lateral view of Conocardium aliformel (Sowerby).

tion in these forms was accomplished entirely by 

hydrostatic means.

Pojeta, Runnegar, Morris, and Newell (1972) 

argued that no rostroconchs had cross-fused radial 

mantle muscles and therefore no adductor muscles. 

This statement was based on the premise that crossfusion could not have occurred because the mantle 

lobes were not embayed dorsally. We now feel that 

the large insertion at the posterior terminus of the 

pallial line in Eopteria (fig. 4; pi. 22, figs. 1, 2) may 

have housed an adductor muscle that served to flex 

the shell and to create water currents in the mantle 

cavity. No other rostroconch is known to have had 

a. comparable structure.

ALIMENTARY CANAL

Rostroconchs are regarded as having an anterior 

mouth and a posterior anus. This conclusion is supported by the lack of any evidence of torsion in rostroconchs and by the likelihood that they are descended from monoplacophorans and were ancestral 

to pelecypods. In primitive rostroconchs like Heraultipegma and Ribeiria, the mouth was probably 

close to the anterior gape, but in such highly specialized genera as Conocardium and Arceodomus, the 

mouth was probably situated at the anterior end of 

the mantle cavity, near the junction of the body and 

snout. We assume that the mouth moved posteriorly 

(in a relative sense) as the feeding structures of the 

snout became increasingly more complex.

Before the development of a prominent posterior 

rostrum, the anus probably was near the dorsal side 

of the posterior shell gape. Because of the small diameter of the rostrum in many forms, the anus was 

probably not at its distal end. We conclude that in 

rostrate forms, the anus was near the proximal end 

of the rostrum and that water currents generated by 

cilia removed feces from the mantle cavity.

FEEDING STRUCTURES

Various rostroconchs have features indicating that 

structures could be protruded from the anterior shell 

gape. These features are: (1) the anterior pallial 

sinuses of Eopteria (pi. 22, figs. 1-4; pi. 23, figs. 2- 

3), Euchasma (pi. 27, fig. 9), and perhaps Wanivania (pi. 3, fig. 7) ; (2) the impressions of enlarged radial muscles of the mantle at the anterior 

end of the pallial line of Eopteria (pi. 22, figs. 5, 6) 

and Conocardium (pi. 51, fig. 11) ; (3) the apertural 

denticles of all conocardioids, probably formed by 

folds in the enlarged mantle as it was withdrawn 

into the shell (pi. 34; figs. 9-10); and (4) the muscle 

insertions interpreted as pallial protractor muscles
20 PALEONTOLOGY OF ROSTROCONCH MOLLUSKS

that occur inside the edge of the anterior aperture in 

conocardiaceans (pi. 47, fig. 12). We believe that 

rostroconchs used this enlarged and extendible mantle tissue for deposit feeding.

Scaphopods and palaeotaxodont pelecypods use 

cephalic tentacles (captaculae and palp proboscides) 

in deposit feeding to collect food particles; similar 

structures are used for the same purpose by various 

prosobranch gastropods. It seems likely that many 

primitive rostroconchs used cephalic outgrowths to 

gather food. However, in the Conocardiidae, at least, 

these structures seem to have been superseded by 

outgrowths of pallial (mantle) tissue. In Conocardium and Arceodomus, the snout was effectively 

blocked by several pairs of enlarged marginal denticles, called longitudinal shelves (pi. 43, figs. 12, 13; 

pi. 44, figs. 2, 4). These shelves contained complex 

folds of the mantle, because the growing edges of 

the shelves, which oppose one another at the midline, 

are formed of outer shell layer. This composition implies that the mantle edge rested along the edges of 

the longitudinal shelves when the mantle was withdrawn. Because the mantle epithelium of mollusks is 

characteristically ciliated, we feel that the mantle 

resting on these anterior longitudinal shelves formed 

a complex sorting structure which collected and 

sorted food for eventual transmission to the mouth. 

The mouth was at the end of an elongate passage 

that penetrated between the various pairs of shelves 

(pi. 43, fig. 13). Because another characteristic of 

the molluscan mantle is the widespread occurrence 

of tentacles fringing the mantle edge, it is reasonable to believe that similar pallial tentacles may have 

assisted in the food-gathering process of rostroconchs. We thus view the feeding structure of conocardiids as a set of forward-opening ciliated cones 

that acquired food by means of an inhalent water 

current and the manipulative abilities of fringing 

pallial tentacles. The food particles were moved posteriorly by cilia lining the cones, sorted, and transferred to the mouth through a small aperture on the 

posteroventral side of the cones. Inhaled sediment 

was transferred anteriorly and exited along a rejection tract at the ventral edge of the feeding 

aperture.

The shape of conocardiids suggests that they both 

lived and fed infaunally. The scaphopods are good 

functional analogs for such genera as Conocardium 

(pi. 38, figs. 2, 8) and Arceodomus (pi. 43, figs. 5, 

15), except that they use cephalic captaculae rather 

than mantle tissue to collect food.

Conocardium and Arceodomus are highly specialized rostroconchs. More primitive rostroconchs have

less complex anterior skeletal structures, and we 

speculate that they had a primitive version of the 

conocardiid feeding apparatus. Probably they used 

enlarged flaps of the mantle to collect and funnel 

food to the mouth. Some forms may have had a 

structure analogous to a pelecypod siphon which 

projected from the anterior gape. We envisage such 

a structure as being present in the ischyriniid 

Pseudotechnophorus because the anterodorsal gape 

is oval or kidney shaped, and because an insertion of 

a large muscle, which probably retracted the mantle 

(fig. 3G), is dorsal to the anterior pegma. Living 

tellinacean pelecypods use their posterior siphons 

for deposit feeding in this way (Pohlo, 1969).

Most technophorid rostroconchs as well as the 

genus Ischyrinia have no anterior gape. These forms 

are laterally compressed, have a posterior rostrum, 

and probably lived infaunally. It seems likely that 

they were filter feeders which used cilia on the gills 

or mantle to pump water and suspended food in the 

posterior shell apertures.

The mode of life of the eopteriid Euchasma is 

more difficult to interpret. All species of this genus 

have the anterior end of the shell reduced. The shells 

of E. blumenbachii (pi. 27, figs. 1-16) and E. mytiliforme (pi. 29, figs. 6-8) resemble those of living 

epifaunal mytilid and dreissenid pelecypods. E. jonesei has a small anterior lobe, and the shell is more or 

less similar to that of living modioliform pelecypods (pi. 28, figs. 12-15).

By analogy with living pelecypods (Stanley, 

1972), the mytiliform Euchasmas probably lived epifaunally, and the modioliform Euchasmas may have 

lived semi-infaunally. The narrowness of the anteroventral shell gape (pi. 29, figs. 8, 9, 12) of Euchasma 

and the shell shape suggest that this genus was 

sessile. This conclusion is supported by the narrowness of the ventral shell gape, which would make it 

difficult for a foot to project ventrally. If, however, 

Euchasma is compared with the epifaunal cowrie 

gastropods, which it also approximates in form, a 

different interpretation results. This comparison 

shows that a large and effective foot can project 

through a narrow shell aperture, so Euchasma may 

have been a motile epifaunal or semi-infaunal animal. The presence of marginal denticles lining the 

ventral gape indicates that mantle tissue at least 

was probably extended through this aperture.

Euchasma has a sizable circular shell aperture 

above the anteroventral gape. This circular hole is 

formed by the edges of both valves (pi. 28, figs. 15, 

16). It is effectively blocked by the pegma (pi. 29, 

figs. 3, 11, 14, 15), although there are small holes
FUNCTIONAL MORPHOLOGY 21

on either side between the pegma and the valves (pi. 

29, fig. 15). Euchasma has an anterior pallial sinus 

(pi. 27, fig. 9), so mantle tissue could probably have 

been extended from and withdrawn into this area of 

the shell. This mantle tissue may have been used for 

deposit feeding, as it was in other rostroconchs, and 

the pegma may have blocked sediment from entering 

the shell. The circular aperture is anatomically anterior but functionally ventral, as during life, it 

would have been apposed to the substrate. Thus, 

Euchasma may have been an epifaunal to semi-infaunal deposit feeder which "vacuumed" organic 

matter from the sediment-water interface. This unusual mode of life may explain why it could not compete successfully with epifaunal suspension-feeding 

pelecypods, which first became abundant in the Middle Ordovician.

An alternative explanation of the mode of life of 

Euchasma is that the circular anterior aperture contained a structure for attaching the animal to the 

substrate. The attachment structures may have been 

similar to the byssus of pelecypods or the pedicle of 

brachiopods, and the animal may have suspensionfed from the posterior shell gape. Because rostroconchs probably had hypertrophied anterior pallial 

structures, Euchasma may have been attached by 

one or more hypertrophied pallial tentacles. These 

tentacles could have been manipulated by contained 

fluid and pallial retractor muscles attached at the 

anterior pallial sinus. On the whole, we prefer the 

explanation that Euchasma was a mobile epifaunal 

or near epifaunal deposit feeder.

CLEANING THE MANTLE CAVITY

Suspension-feeding organisms that have an enclosed mantle cavity have the problem of eliminating unwanted particulate matter (pseudofeces) 

swept into the mantle cavity along with the food. 

Pseudofeces continually accumulate in enclosed 

shells and must be continually removed. In most 

pelecypods, pseudofeces fall from the gills and mantle to the floor of the mantle cavity and are then 

ejected by sudden contractions of the adductor muscles (Cox and others, 1969, p. N19). In brachiopods, 

reversal of the frontal cilia of the lophophore transports the pseudofeces to the mantle, and then mantle 

cilia move them to the mantle edge. They are expelled when the valves are adducted (Rudwick, 1970, 

p. 121).

Some pelecypods have the ventral edges of the 

mantle extensively fused together, leaving only the 

two posterior siphonal orifices and a relatively small 

aperture for the foot. Many such animals also have

a small fourth aperture between the pedal and siphonal orifices (Yonge, 1948; Runnegar, 1972). In 

active burrowers like Ensis, this aperture acts as a 

safety valve to lower the fluid pressure in the mantle 

cavity which peaks with adduction in the digging 

cycle (Trueman, 1968). In more passive burrowers, 

the fourth aperture functions as an outlet for 

pseudofeces carried to it by ciliated tracts on the 

mantle and visceral mass (Yonge, 1948).

Nearly all rostroconchs that have reduced posterior and ventral shell apertures retain a small circular ventral orifice between the posterior end of 

the anterior gape and the rostrum (pi. 40, fig. 7). 

This orifice probably functioned in the same way as 

the fourth aperture of less actively burrowing pelecypods as an outlet for pseudofeces. Such a ventral 

orifice does not occur in the Conocardiidae, but, as 

mentioned previously, these rostroconchs may have 

had effective sediment screens in their anterior 

gapes and thus may not have been troubled by the 

accumulation of pseudofeces in the mantle cavity.

WATER CURRENTS AND GILLS

The helcionellacean univalves, like Neopilina 

(Lemche and Wingstrand, 1959), probably drew water in under the anterolateral eaves of the shell and 

passed it out posterolaterally (figs. 6, 9). We assume 

that the gills were laterally disposed in these animals and that cilia on the gills and epithelium of the 

mantle cavity generated the water currents. In the 

univalve genera Yochelcionella (pi. 1, figs. 1-7) and 

Anabarella (pi. 17, fig. 8), the water current probably entered anteriorly (figs. 6, 9). When the shell 

became modified into the ribeiriid shape, water was 

drawn in through the anterior gape and left the 

shell posteriorly (fig. 6). This water current was 

used for feeding as well as respiration. Ribeiria may 

have had a single pair of gills, the blood vessel being 

connected with the heart through the discontinuity 

in the side muscles seen in some species (fig. 3/).

A similar water flow may have taken place in the 

eopteriids and conocardiceans. However, it is equally 

likely that the Conocardiacea drew water for respiration in through the posterior rostrum. Scaphopods 

use the posterior shell aperture to obtain water for 

respiration, although they deposit feed anteriorly. 

In the conocardiaceans, the exhalent current may 

also have flowed out the rostral orifice, or it may have 

left through the ventral orifice. Perhaps both apertures were used for this purpose. We suggest that all 

rostroconchs had gills because they all have an expanded mantle cavity.

The technophoridg and Ischyrinia have no anteri-
22 PALEONTOLOGY OF ROSTROCONCH MOLLUSKS

or shell apertures. We conclude that water entered 

and left the mantle cavity via the two posterior shell 

apertures.

FUNCTION OF THE HOOD

Some Ordovician through Mississippian conocardiaceans have a hood attached to the carinal areas of 

the valves (pi. 45, figs. 10-13; pi. 48, fig. 2). There 

are two obvious possible explanations for the existence of the hood, and either or both may have functional significance. First, the significant structure 

may be the hood, which could have been used to support the shell in a soft substrate, or it could have deflected water currents to or away from the rostral 

orifice. Some hooded rostroconchs resemble some living tropical cardiid pelecypods that are flattened in 

an anterior-posterior direction because the body tissue contains symbiotic algae which receive sunlight 

through the thin shell (Kawaguti, 1950). These 

clams lie exposed and are metabolically connected 

with the algae in their tissue. However, the resemblance of these cardiids to hooded rostroconchs is 

only superficial. The hood is a totally external structure, composed of the outer shell layer, which contained living tissue only along its central axis, the 

elongated ventral orifice. Thus, the hood probably 

had some other function.

The second possibility is that the final structure, 

the hood, is not of primary functional significance; 

rather the structure that forms it, the elongated ventral orifice, is the functionally significant structure. 

If rostroconchs evolved a long thin tube at the posteroventral commissure, they could maintain such a 

structure during growth only by generating a planar 

structure on each valve. We speculate that the prolongation of the ventral orifice, for whatever functional reason, may have had more functional significance than the finished hood. Once the hood 

formed, it may have provided support, enabling the 

animal to live in soft substrates, but the hood may 

have just been the necessary consequence of the elongation of the ventral orifice.

TAPHONOMY

Post-Ordovician rostroconchs (Conocardioida) 

are most common in marine shales and silts and reef 

limestones. Older rostroconchs are presently known 

most commonly from the carbonate sequences of 

epicontinental seas. Jameison (1971, p. 1334) noted 

that "Conocardium" has only been found in marginal 

reef deposits in the Devonian of western Canada, 

"and is therefore considered indicative of shallow, 

turbulent, open marine conditions." Similarly, conocardiids are common in Visean (Mississippian)

shoreline cliff talus of the Wagon Creek Breccia 

(Veevers and Roberts, 1966) in northwestern Australia (John Roberts, oral commun., May 1972).

In contrast, Pseudoconocardium and Arceodomus 

are most common in low-energy marine shales of the 

Pennsylvanian of north-central Texas. Bransonia 

occurs in a similar environment in coastal outcrops 

of the middle Permian Wandrawandian Siltstone in 

New South Wales, Australia. At one important locality, a recent shore platform at the town of Ulladulla, many specimens of Bransonia robustum 

(Fletcher) occur in silty beds. They are associated 

with many other fossils, most specimens of which 

have been preserved in situ. These include life-oriented productoid and spiriferoid brachiopods; shallow-burrowing, free-swimming, and endobyssate 

pelecypods; collapsed but articulated crinoids; large 

unbroken colonies of lacy fenestrate bryozoans; and 

discoidal poriferans.

The section of the Wandrawandian Siltstone exposed at Ulladulla contains several thin sands that 

vary in thickness from a few centimetres to tens of 

centimetres. These sands are also fossiliferous, but 

most of the fossils they contain are transported. The 

sands appear to have formed during rare highenergy events and therefore contain disoriented 

skeletons of organisms that (1) inhabited the surface of the silt and were light enough or were sufficiently loosely attached to be transported with the 

sand; and (2) that were unable to disinter themselves after burial in the sand. The sand beds also 

contain life-oriented burrowing pelecypods that 

rapidly recolonized the substrate after each highenergy event.

Extensive collecting has shown that there are few 

if any specimens of Bransonia in the sand beds. Nor 

are there any byssate pelecypods or attached echinoderms. At least three alternative explanations are 

possible: (1) Bransonia burrowed so deeply that it 

was never disinterred by the high-energy currents 

that deposited the sands; this is unlikely, as there is 

no evidence of an elongate rostrum or large posterior siphons in Bransonia. (2) Bransonia was attached 

to the substrate by some structure comparable with 

the pelecypod byssus; this too is unlikely, as Bransonia shows no anterior reduction, a feature seen in 

the epifaunal species of Euchasma. (3) Bransonia 

was sufficiently mobile to tunnel out of the sand after 

transportation and burial; this seems to be the most 

reasonable alternative and is the one we prefer.

We have searched for specimens of rostroconchs 

encrusted with other organisms that might provide 

some clue to the life habits of the rostroconchs. Such
PHYLOGENY 23

specimens are difficult to find in museum collections, 

and it is always difficult to prove conclusively that 

the encrusting organisms lived during the life of 

the rostroconch rather than encrusting it after 

death. The most useful specimen we have found is 

an individual of Hippocardia encrusted by an auloporid tabulate coral (pi. 33, figs. 1-2). The coral 

colony on this specimen seems to have been broken 

at least three times by the growth of the hood of the 

Hippocardia, suggesting that both organisms were 

growing simultaneously. The coral growth in this 

specimen also suggests that in life this species of 

Hippocardia had the whole of the dorsal surface of 

the hood exposed and was at most semi-infaunal.

A more equivocal example is a bryozoan holdfast 

attached to the rostral area of the right valve of a 

specimen of Bransonia wilsoni (pi. 52, fig. 9). On 

this specimen, a matching mark on the corresponding part of the left valve suggests, but does not 

prove, that the holdfast was attached to the rostroconch while the rostroconch was alive. Similar holdfasts on the interiors of productid brachiopod valves 

at the same locality show that bryozoans were growing on some of the dead organisms.

In summary, we have very limited paleoecological 

evidence. Most of the specimens for this study were 

gathered from museums, and paleoecological information must usually be gathered in the field. What 

information we do have tends to confirm the conclusions reached on comparative and functional morphology, that is, that most rostroconchs were mobile 

members of the shelf benthos and lived wholly or 

partially buried in the sediment. We have been unable to devote much time for research in this area 

and suggest it as a profitable and challenging direction for further enquiry.

PHYLOGENY

Living and fossil mollusks constitute the second 

largest and most variable invertebrate phylum (Barrington, 1967; Stasek, 1972). Most mollusks can be 

described as free-living metazoans that utilize a 

dorsal calcareous exoskeleton to provide structural 

support for a muscular foot (or its specialized derivative) and to provide an enclosed space outside 

the body (mantle cavity) that is used for feeding, 

respiration, and sometimes, locomotion. Because 

mollusks are so variable, no single unique character 

is present in all members of the phylum; they are 

unified by morphological gradations between different forms, by embryonic similarities, and by fossil 

evidence of their evolutionary history.

We recognize eight classes of mollusks and refer 

these to four subphyla:

Phylum MOLLUSCA Cuvier, 1797

Subphylum ACULIFERA Hatscheck, 1891 

Class APLACOPHORA von Ihering,

1876

Subphylum PLACOPHORA von Ihering, 

1876

Class POLYPLACOPHORA de Blainville, 1816

Subphylum CYRTOSOMA Runnegar and 

Pojeta, 1974

Class MONOPLACOPHORA Wenz,

1040

Class GASTROPODA Cuvier, 1797 

Class CEPHALOPODA Cuvier, 1797 

Subphylum DIASOMA Runnegar and 

Pojeta, 1974

Class ROSTROCONCHIA Pojeta,

Runnegar, Morris, and Newell, 1972 

Class PELECYPODA Goldfuss, 1820 

Class SCAPHOPODA Bronn, 1862

We do not doubt that the forms Yochelson (1966, 

1969) placed in the classes Mattheva and Stenothecoida (= Probivalvia Aksarina, 1968) are mollusks, 

but we prefer to assign them to other molluscan 

classes. They are discussed in subsequent parts of 

this section. Tentaculites, lapworthellids, cornulitids, 

hyoliths, and hyolithellids probably belong to other 

phyla (Fisher, 1962; Matthews, 1973; Runnegar 

and others, 1975).

ORIGIN OF THE MOLLUSCA

Stasek (1972) produced a thoughtful review of 

the data pertinent to this problem. We agree with 

his conclusion that the mollusks evolved from a preannelid stock of small ciliated acoelomate, vermiform 

organisms that had a diverticulated gut, longitudinal nerve cords, and a series of dorsoventral body 

muscles. None of the known Ediacaran fossils of 

soft-bodied organisms of late Precambrian age 

(Glaessner, 1971) resemble this hypothetical ancestor, but it is obviously similar to known living 

turbellarian flatworms.

THE ANCESTRAL MOLLUSK

Nineteenth century biologists visualized the common ancestor of mollusks as a bilaterally symmetrical untorted snail-like animal that had a limpetshaped shell and a posterior anus opening into a 

small mantle cavity containing a pair of simple 

ctenidia (Pelseneer, 1906). This concept of an archetypical mollusk was derived mainly from studies of
24 PALEONTOLOGY OF ROSTROCONCH MOLLUSKS

the comparative anatomy of living forms, but it was 

also widely accepted by paleontologists.

When the living monoplacophoran Neopilina Lemche was discovered (Lemche, 1957), it was hailed as 

a living archetype. The only significant difference between Neopilina and the theoretical ancestral mollusk lies in the structure of the gills, which are arranged in a series lateral to the foot in Neopilina.

Because of the close similarity of Neopilina and 

early Paleozoic Monoplacophora, Neopilina is often 

considered to resemble the ancestor of all other 

molluscan classes. This archetypical concept has 

been criticized by Yochelson (1963), Horny (1965), 

Harry (1969), and Stasek (1972). An alternative 

view advocated by some authors is to derive the 

Monoplacophora and the other molluscan classes 

from nonshelled organisms that may have existed 

before and with early monoplacophorans. In this 

scheme, the differences between the various classes 

are produced in the nonshelled organisms, and calcification occurs after the characters of each class 

have been attained.

Stasek (1972) argued that the Aplacophora, Polyplacophora, and Monoplacophora were derived sequentially from an evolving ancestral stock. At 

present little evidence from fossils supports, or contradicts this suggestion. However, the Polyplacophora may have been derived from monoplacophorans that evolved multiple centers of calcification 

(Runnegar and Pojeta, 1974). Our study is largely 

concerned with the Monoplacophora and the five 

molluscan classes that we suggest were derived from 

it. This radiation began in the earliest Cambrian and 

is adequately shown in the fossil record (Runnegar 

and Pojeta, 1974).

THE OLDEST KNOWN FOSSIL MOLLUSKS

Russian stratigraphers divide the Early Cambrian 

of the Siberian Platform into four stages: from 

oldest to youngest Tommotian, Atdabanian, Botomian, and Lenian (Zhuravleva, 1970). The Tommotian 

deposits predate the first trilobites in the Siberian 

succession, and they contain a characteristic biota 

of archaeocyaths, mollusks, hyoliths, algae, and 

Problematica (Rozanov and others, 1969). In the 

fossil record, the base of the Tommotian appears to 

reflect-the first appearance, ki abundance, of animals 

that had calcareous skeletons, which is one definition 

of the beginning of the Cambrian (Zhuravleva, 

1970; Webby, 1973).

Tommotian mollusks are small or minute limpetshaped planispiral or helically coiled univalves 

(Rozanov and others, 1969). They include forms resembling the widely known Cambrian genera Scenella Billings, Helcionella Grabau and Shinier, and 

Pelagiella Matthews, which are variously regarded 

as monoplacophorans, gastropods, or representatives 

of other primitive classes of mollusks (Knight, 1952; 

Rasetti, 1957; Horny, 1965; Yochelson, 1963, 1967). 

Rozanov and others (1969) referred all these univalves to the superfamilies Helcionellacea Wenz, 

1938, and Pelagiellacea Knight, 1956, and considered 

them to be gastropods.

One of the Tommotian mollusks, the genus Anabarella Vostokova, is a laterally compressed planispiral univalve having a ventral margin that is obviously curved when the shell is viewed laterally (figs. 

6, 7; pi. 17, fig. 8). Anabarella is intermediate in 

shell form between more typical Cambrian univalves 

like Helcionella, Latouchella Cobbold, and Igorella 

Missarzhevsky, and the first ribeiriid rostroconch, 

Heraultipegma n. gen. (=Heraultia Cobbold), from 

the Lower Cambrian of France (fig. 6; pi. 2). If 

Heraultipegma is derived from Anabarella, it is unlikely that Anabarella was a gastropod, as the Late 

Cambrian and Ordovician descendents of Heraultipegma show no evidence of torsion. It is therefore 

pertinent to examine the biological placement of 

Anabarella and other Early Cambrian univalves.

EARLY CAMBRIAN UNIVALVES

The class Gastropoda comprises animals that have 

a distinct head, a solelike foot adapted for creeping, 

a radula, and a visceral mass that is apparently rotated 180° about a vertical axis so that the anus and 

organs of the mantle cavity are above the head. This 

twisting of the visceral mass is known as torsion; in 

living gastropods, it occurs in early ontogeny by 

rapid contraction of the asymmetrical right larval 

retractor muscle and by differential growth (Fretter, 

1969). The torsion seen in all primitive and most 

advanced gastropods isolates them from their presumed ancestors, the Monoplacophora (Knight and 

others, 1960).

Most gastropods have the body contained in a 

calcareous univalved shell which coils posteriorly 

away from the head and is therefore termed "endogastric." With the exception of the specialized limpets and a few aberrant forms, living gastropods 

have the shell coiled in a helical spiral. Normally 

this coiling is orthostrophic and dextral, but rare 

individuals or species have hyperstrophic (ultradextral) or sinistral shells.

Planispiral (isostrophic) shells resembling gastropods in external ornament and other features occur as fossils from the earliest Cambrian to the
PHYLOGENY 25

Early Triassic (Knight and others, 1960). These are 

now normally referred to the gastropod suborder 

Bellerophontida, though there has been a long debate as to whether they were torted (gastropods) or 

untorted (monoplacophorans) (Yochelson, 1967). 

Recent studies have suggested that externally similar planispiral shells housed both monoplacophorans 

and gastropods (Rollins and Batten, 1968). If the 

shells have several bilaterally symmetrical muscle 

insertions, they are believed to be untorted and hence 

monoplacophorans; all others have been considered 

to be gastropods until proved otherwise. This argument is supported by the obvious asymmetry of the 

shell musculature in the otherwise symmetrical bivalved snails (Kawaguti and Yamasu, 1960), and 

by the presence of only one pair of pedal muscles in 

some bellerophontids (Knight, 1947; Peel, 1972).

If no muscle insertions are preserved, other criteria have been used. Knight (1952) and others suggested that the presence of (1) an anal slit or sinus, 

(2) secondary inner shell layers (parietal deposits) 

covering the exterior of earlier formed parts of the 

coil, and (3) an elongate trail, could be used to distinguish torted bellerophontids from untorted monoplacophorans (Rollins and Batten, 1968). The most 

compelling argument related to the anal slit or sinus, 

as it was believed that these structures only became 

necessary when torsion juxtaposed the anus and 

gills. Subsequently, Rojlins and Batten (1968) 

showed that the Devonian planispiral univalve 

Sinuitopsis Perner has a series of bilaterally symmetrical muscle insertions (fig. 8) as well as a deep 

sinus, and they concluded that it was a sinus-bearing 

monoplacophoran. They speculated that a posterior 

anal sinus was probably advantageous in achieving 

maximum separation of respiratory currents and 

excretory products. They discouraged the use of a 

sinus as a tool for recognizing gastropods and emphasized the criteria of parietal deposits and posterior trails.

No Early Cambrian univalves have parietal deposits, but some have the concave side of the shell

E

FIGURE 6. Speculative view of the origin of the ribeiriid 

rostroconchs (A-B) from Early Cambrian helcionellacean 

monoplacophorans. Arrows indicate probable path of water 

currents through the mantle cavity. The extent of the shell 

aperture is shown by the thick black line. Dotted shading 

in A represents the radial mantle muscles attached to the 

shell at the pallial line. Pedal muscle insertions in D are 

modeled from the Devonian cyclomyan monoplacophoran 

shown in E. A, Ribeiria, Late Cambrian-Ordovician; B, 

Heraultipegma, Early Cambrian; C, Anabarella, Early Cambrian; D, Latouchella, Early-Late Cambrian; E, Cyrtonella, 

Middle Devonian;-
26 PALEONTOLOGY OF ROSTROCONCH MOLLUSKS

E

D

G

FIGURE 7. (See explanation on facing page.)
PHYLOGENY 27

FIGURE 8. Shell muscle insertions of cyclomyan monoplacophorans. A, Sinuitopsis, data from Rollins and Batten 

(1968); B and C, Cyrtolites, modified from Horny (1965).

expanded to form a trail (fig. 9). Knight (1952) 

argued that a trail would impede the maneuverability of the protracted head of the animal and concluded that such shells must have been coiled endogastrically away from the head (fig. 9A, modified 

from Knight (1952)). For this reason, Knight referred Helcionella and related Early Cambrian univalves to the Gastropoda. No muscle insertions have 

been seen in these forms.

In 1954, Rasetti illustrated internal molds of a 

small limpet-shaped shell from the Middle Cambrian 

Mt. Whyte Formation of British Columbia. These 

specimens have a number of small muscle insertions 

that are effectively bilaterally symmetrical. Rasetti 

referred the specimens to Scenella and concluded 

that they were monoplacophorans. A reconstruction 

of the body, modeled from Neopilina (fig. 10), vindicates this decision.

Knight and others (1960) referred Scenella and 

the enigmatic genus Palaeacmaea Hall and Whitfield 

to a separate family of the Monoplacophora. Rozanov and others (1969), however, referred the externally similar genus Tannuella Missarzhevsky to 

the Helcionellacea, and there is a gradation in external shell form from Helcionella through Bemella 

Missarzhevsky, Ginella Missarzhevsky, and Tannuella to Scenella (Rozanov and others, 1969). We 

therefore believe that the Helcionellacea are monoplacophorans, not gastropods.

Additional support for the monoplacophoran 

placement of the Helcionellacea comes from the Australian Cambrian helcionellid, Yochelcionella Runnegar and Pojeta, 1974 (pi. 1), which differs from 

other helcionellids by having a tube attached to the 

concave side of the shell. Figure 9 shows normal and 

tube-bearing heliconellids reconstructed as gastropods and monoplacophorans. The first reconstruction (fig. 9A) is modified from Knight (1952), who 

described it as a "harmonious and plausible picture." 

We agree. However, if the tube-bearing helcionellid 

is reconstructed in the same way (fig. 9C), the tube 

has no apparent function. By analogy with other 

mollusks, the tube probably carried water in or out 

of the mantle cavity. It could do this if the animal 

were an exogastric monoplacophoran (fig. 9J9), an 

endogastric monoplacophoran (fig. 9F), or an exogastric gastropod (fig. 9£").

Because of torsion, and hence by definition, all 

gastropods are endogastric (Knight and others, 

1960). The gradations in shell form between Helcionella and Scenella, and Helcionella and Heraultipegma indicate that the helcionellids were exogastric (shell coiled forward over the head). We conclude that the Helcionellacea were exogastric monoplacophorans, not endogastric gastropods.

RADIATION OF THE MONOPLACOPHORA

Horny (1965) divided the Monoplacophora into 

two groups designated by the terms Tergomya and 

Cyclomya. As the names imply, tergomyan monoplacophorans normally have a series of discrete muscle 

insertions on each side of the shell (as in Scenella 

and Neopilina), whereas the cyclomyans have the 

muscle insertions more or less fused into a ring. The

FIGURE 7. Variation in shell form of Cambrian univalves. 

The shells are shown in left-lateral profile. Heavy lines 

show approximate shape of generating curves (apertural 

shape). A, Anabarella plana Vostokova, from pi. 17, fig. 8. 

B, Igorella ungulata Missarzhevsky, modified from Rozanov 

and others, 1969, pi. 4, fig. 21. C, Latouchella instdcata 

(Rasetti), modified from Rasetti, 1957, pi. 122, fig. 11. D,

Helcionella carinata Rasetti, modified from Rasetti, 1957, 

pi. 122, fig. 5. E, Hypseloconus bessemerense (Ulrich, 

Foerste, and Miller), modified from Stinchombe and Echols, 

1966, pi. 79, fig. 13. F, Helcionellal rugosa var. comleyensis 

Cobbold modified from Cobbold, 1921. G, Scenella sp., showing muscle-insertion areas, modified from Rasetti, 1954, pi. 

12, figs. 5-8.
28 PALEONTOLOGY OF ROSTROCONCH MOLLUSKS

FIGURE 9. (See explanation on facing page).
PHYLOGENY 29

Anus

FIGURE 10. Rasetti's Middle Cambrian specimens of Scenella 

reconstructed as a monoplacophoran, using Neopilina for a 

model. Stippled ring represents incipient pallial line indicated by change in slope of shell. Radial fluting of shell 

outside pallial line probably reflects weak radial mantle 

muscles shown here on left side only by short stippled 

lines. Other features shown are radial and circular muscles 

of the foot and muscles controlling head (anterior pair hypothetical). Arrows indicate probable direction of water 

flow through the right mantle cavity. Data from Rasetti 

(1954); from Runnegar and Pojeta (1974, fig. 2). Copyright 1974 by the American Association for the Advancement of Science, published with permission.

tergomyans are normally limpet shaped, and the cyclomyans are taller coiled shells.

Little distinguishes Ordovician, Silurian, and 

Devonian cyclomyan monoplacophorans like Cyrtolites Conrad (Horny, 1965), Yochelsonellis Horny 

(Horny, 1965), and Cyrtonella Hall (Rollins, 1969) 

from helcionellids like Latouchella (Cobbold, 1921) 

and Igorella (Rozanov and others, 1969), except for 

the anterior trail in some forms. The external ornaFIGURE 9. Helcionella and related tube-bearing helcionellid 

Yochelcionella Runnegar and Pojeta reconstructed as an 

endogastric gastropod (A, C), an exogastric monoplacophoran (B, D), an exogastric gastropod (E), and an endogastric monoplacophoran (F). B and D are considered 

correct. See text for further explanation. A, Modified from 

Knight (1952).

ment of Scenella and of some species of Helcionella, 

Anabarella, and Cyrtonella is quite similar (Knight, 

1941; Rozanov and others, 1969), consisting of fine 

radial threads between comarginal ribs, rugae, or 

other elements. We suggest that the post-Cambrian 

cyclomyan monoplacophorans are derived directly 

from the Helcionellacea.

Most students of molluscan phylogeny derive the 

cyclomyan monoplacophorans from apparently more 

primitive limpet-shaped shells. The Tommotian fossil record suggests that the reverse may have been 

true. The oldest zone of the Tommotian Stage yields 

the relatively tall shells Bemella, Igorella, Anabarella, and Latouchella (Rozanov and others, 1969, table 

9). The intermediate form Ginella appears in the 

two succeeding zones, and the limpet^shaped shells 

Tannuella and Helcionella [sic] are absent until the 

base of the overlying Atdabanian stage. As the taller, coiled helcionellaceans are closer to the earliest 

gastropods, rostroconchs, and cephalopods than the 

limpet-shaped shells are, we- suggest that the tergomyan monoplacophorans are not the ancestral 

stock but were secondarily adapted for benthic 

grazing.

ORIGIN OF THE GASTROPODA

Most malacologists consider the Bellerophontacea 

to be intermediate between the planispiral monoplacophorans and helically coiled primitive gastropods 

(Knight, 1952; Knight and others, 1960; Morton and 

Yonge, 1964; Batten and others, 1967; Stasek, 1972). 

In this scheme, planispiral coiling precedes torsion 

and helical coiling follows it. The model implies that 

the shell and visceral mass rotate 180° with respect 

to the head and foot so that the gut becomes twisted, 

the left and right gills come to lie on right and left 

sides of the body, and the nervous system forms a 

figure of eight. It has always been difficult to imagine 

how this process could occur phylogenetically and to 

explain its adaptive significance (Knight and others, 

1960; Ghiselin, 1966; Stasek, 1972). Stasek (1972) 

summarized two long-held theories: (1) that torsion 

had adaptive significance for the swimming veliger 

larva by bringing the mantle cavity into a position 

where the tender vellum could be more easily retracted into the shell; and (2) that torsion would be 

beneficial to the adult, as it would move the sensory 

osphradia and gills away from water dirtied by the 

locomotion of the animal. Stasek rejected both explanations and suggested that torsion resulted from 

the temporary need of juvenile and adult monoplacophorans to be able to twist the body to provide 

space for a protractible head. This, he suggested,
30 PALEONTOLOGY OF ROSTROCONCH MOLLUSKS

resulted in muscular asymmetry that was transferred to the larval stage in gastropods.

Ghiselin (1966) had a different explanation of the 

adaptive significance of torsion, which is more consistent with the early Tommotian fossil record. He 

argued that planktonic larvae with a helically coiled 

exogastric shell would have problems settling because the spire would interfere with their locomotion. Unfortunately, Ghiselin relied mainly on deductions from the morphology of the protoconch and 

shell of Neopilina galatheae for his functional interpretation. This species was reported to have a 

helically coiled protoconch by Lemche (1957) and 

Lemche and Wingstrand (1959). Other species of 

Neopilina taken subsequently have a bilaterally symmetrical bulbous protoconch (N. W. Riser, written 

commun., 1974), similar to that found on comparably shaped early Paleozoic forms (pi. 15). Consequently, we believe that all known living and extinct 

monoplacophorans are bilaterally symmetrical at all 

stages of growth. In a rejoinder to Ghiselin's paper, 

Batten, Rollins, and Gould (1967) attempted to relate Ghiselin's model to the fossil record. They suggested that Ordovician-Devonian planispiral cyclomyans were the ancestors of the gastropods.

Pelagiella Matthew is a small helically coiled shell 

that is widely distributed in Lower Cambrian rocks 

(Knight and others, 1960). Although it resembles 

younger gastropods in shape, most authors have preferred to regard it as an end-product of early molluscan experimentation rather than a primitive 

member of the class Gastropoda (Wenz, 1938; 

Knight, 1952; Knight and others, 1960; Yochelson, 

1963).

The oldest zone of the Tommotian Stage yields 

ribbed and smooth helically coiled pelagiellids referred to species of Aldanella Vostokova (Runnegar 

and Pojeta, 1974; Rozanov and others, 1969). 

Coarsely plicated helcionellids called Latouchella 

memorabilis and Latouchella korobkovi occur in the 

same beds. Both genera are preserved as minute 

phosphatic internal molds; we conclude that they 

were closely related. Specimens of Pelagiella from 

the English Lower Cambrian (Runnegar and Pojeta, 

1974) are intermediate in form between Aldanella 

and Latouchella.

If Latouchella were a monoplacophoran, it had an 

anterior mouth, posterior anus, and probably one or 

more pairs of gills attached to the lateral or posterolateral flanks of the body (fig. 6D). All body structures were bilaterally symmetrical; Latouchella was 

untorted.

Latouchella has a bilaterally symmetrical shell; in 

life, its plane of symmetry was probably vertical 

(fig. 6D). Aldanella has an asymmetric shell coiled 

in a low dextral spiral (Runnegar and Pojeta, 1974; 

fig. 13). Although the shells of Aldanella are very 

small (maximum diameter about 2 mm), they are 

significantly larger than the larval shells of living 

prosobranch gastropods that remain for an unusually long time in the plankton (Fretter and Graham, 

1962, p. 462-463). Unless Aldanella was adapted 

for postlarval planktonic life, therefore, it would 

probably have settled out of the plankton when the 

shell reached a size of 300-400 microns (J. Taylor, 

oral commun., 1973) and had one or two whorls of 

coiling. Some species of Pelagiella are much larger 

(Knight, 1941), suggesting that the whole group 

lived benthonically as adults.

During its planktonic larval life, the shell of Aldanella could have been coiled exogastrically over the 

head. During settling, this orientation would be awkward, because in living prosobranchs the foot is 

poorly formed at this stage (Fretter and Graham, 

1962; Ghiselin, 1966), and the larva would have 

difficulty balancing the shell vertically. Furthermore, 

to creep along the substrate, it would have to carry 

the spire and visceral mass instead of dragging them 

behind (Ghiselin, 1966). Between periods of activity, the shell probably rested on one side; the newly 

settled larva of the living archaeogastropod Haliotis 

rests on its posttorsional left side during this period 

of its development (Fretter and Graham, 1962, p. 

435). The dextrally coiled shells of Aldanella would 

probably have fallen onto their umbilical side. Other 

dextrally coiled species referred to Pelagiella are 

significantly flattened on the side away from the umbilicus (Robison, 1964, pi. 92, figs. 7-10; Hill and 

others, 1971, pi. 2, figs. 25-28), suggesting that the 

opposite side of the coil may have been the resting 

surface. Knight and others (1960, p. 323) reported 

that some species of Pelagiella contain both dextral 

and sinistral individuals, indicating that the side on 

which the larval shell rested may not have been 

rigidly fixed.

Aldanella is consistently dextrally coiled and probably rested with its umbilicus downward during and 

after settlement. If the body of Aldanella was organized in the same way as the body of Latouchella, 

the head and foot of Aldanella would need to rotate 

about 90° in the shell aperture to compensate for the 

change in orientation with respect to the substrate. 

This would allow the animal to protract its foot over 

the functionally ventral edge of the shell aperture 

and to move the coil from an anterior to a posterior
PHYLOGENY 31

position (fig. 13). The unlikely alternative is that 

the animal protracted its foot by contracting the 

intrinsic circular muscles, anchored the end of the 

foot in the substrate, and then contracted the shellinserted pedal retractor muscles to lift the shell into 

a vertical position above the head. We prefer the 

former explanation because: (1) it would have adaptive significance for the settling larva and juvenile 

animal; (2) it shows how torsion could have originated as a result of a small change in life orientation; (3) it implies that pelagiellids are primitive 

gastropods, as their shape suggests; and (4) it allows us to derive the Gastropoda directly from the 

Helcionellacea in the Early Cambrian.

Because of the asymmetry of the spire of Aldanella, the side of the aperture that is homologous with 

the left side of the shell of Latouchella is relatively 

enlarged, and the aperture is now asymmetric. This 

differential growth may have shifted the anus in the 

opposite direction to the mouth in the shell aperture. 

Aldanella crassa (Rozanov and others, 1969, pi. 3, 

fig. 16) has a small apertural sinus above the peripheral part of the whorl, suggesting that the anus had 

moved in this way. We conclude that various parts of 

the body of Aldanella were probably rotated between 

30° and 90° in two directions with respect to their 

positions in Latouchella. We note that the peripheral 

part of the shell of Aldanella is homologous with the 

convex edge of the shell of Latouchella; in a geometric sense, both shells are exogastric.1

If Aldanella is oriented like a primitive gastropod 

(fig. 13), however, the shell would be described as 

endogastric (coiling away from the head), and the 

body is partly or completely torted. The anus lies 

above and slightly left of the head, the left gill on its 

right side. The nervous system forms a figure of 

eight, and the gut is bent into a simple U. We conclude that Aldanella and Pelagiella were primitive 

gastropods. Only a small readjustment is needed to 

produce the organization found in living pleurotomariid gastropods (Knight, 1952; Knight and others, 1960).

We conclude that earliest Cambrian planispiral 

exogastric monoplacophorans evolved directly into 

helically coiled, torted, primitive gastropods (Pelagiellids) when the orientation of the shell with respect to the substrate changed. During the initial 

period of experimentation, both sinistral and dextral 

forms developed, depending on whether the left or

1 The distinction between endogastric and exogastric gastropods is not 

the same as the distinction between endogastric and exogastric cephalopods. In gastropods, both shells coil the same way, but the orientation on 

the head-foot differs; in cephalopods, the two types of shells are believed 

to have coiled in opposite directions.

right side of the ancestral monoplacophoran came to 

lie on the substrate. When this occurred, torsion became necessary because the head-foot had to operate 

in a direction away from the coil instead of beneath 

it. This relatively small change converted the animals from untorted exogastric monoplacophorans to 

torted endogastric gastropods.

In living primitive gastropods, torsion is caused 

by a separation in the time of development of left 

and right larval retractor muscles (Fretter and 

Graham, 1962; Fretter, 1969). The pretorsional veliger develops only the right retractor muscle; when 

torsion begins, this muscle contracts rapidly (within 

3-6 hours) and rotates the dorsal side of the velum 

to the pretorsional right side of the shell (Fretter 

and Graham, 1962, fig. 227). This muscle becomes 

the posttorsional left pedal retractor when the velum 

is lost. The right pedal retractor muscle develops 

later, during the period when differential growth 

completes the torsional process.

It is not only the delayed development of the posttorsional right pedal retractor muscle which allows 

the initial 90° rotation of the velum to occur; most 

of the torque exerted by the pretorsional right larval 

retractor results from the way the distal ends of the 

fibers of this muscle run around the velum and are 

inserted on its pretorsional left side (Fretter and 

Graham, 1962, fig. 227; Morton and Yonge, 1964, fig. 

3). If this did not happen, it would be difficult or 

impossible for a shell-inserted retractor muscle to 

rotate the velum in the plane of the shell aperture.

Ordovician, Silurian, and Devonian planispiral 

monoplacophorans have simpler shell musculature 

than Neopilina, Scenella, and most other limpetshaped tergomyans (Horny, 1965; Rollins and Batten, 1968; Lemche and Wingstrand, 1959). Presumably this difference is related to shell form; as the 

shells became taller, the insertions of the longitudinal (retractor) muscles of the foot would coalesce or 

be reduced in number, and the circular muscles of 

the foot that are inserted on the shell in Neopilina, 

Tryblidium Lindstrom, and Scenella (Lemche and 

Wingstrand, 1959) would no longer be attached to 

the shell. It would be difficult for any of these muscles to rotate the head-foot in the shell aperture. 

Stasek (1972) has suggested that the delayed development of the left muscles of one or more pairs of 

pedal retractors would have allowed the cyclomyan 

monoplacophorans to twist the shell and visceral 

mass on the head-foot and so become preadapted for 

torsion. We disagree; even if these muscles were 

asymmetrically developed (spatially or temporally), 

they could only retract the head-foot into the shell.
32 PALEONTOLOGY OF ROSTROCONCH MOLLUSKS

In the tall, helically coiled shells, where the muscle 

insertions are about 90° of coiling from the shell 

aperture, it would be impossible for differential contraction of the longitudinal muscles of the foot to 

rotate the head-foot in the shell aperture.

An alternative explanation is that the pelagiellids 

were virtually untorted when the foot was withdrawn. It was only when the foot was protracted 

by contraction of its circular muscles that the shell 

assumed a posterior position. Individuals that could 

twist the head-foot efficiently would be selected for, 

particularly if the torsion was visible before the 

larva settled. Thus, torsion may have had adaptive 

significance for both the larva (as suggested by 

Garstang, 1928) and the adult. The limited information does not allow us to suggest whether the 

pelagiellids were functionally (temporarily) or morphogenetically (permanently) torted; they may have 

been both.

A corollary of this explanation for the origin of 

torsion and the Gastropoda is that the planispiral 

Bellerophontacea are no longer required as intermediates and may not have been torted (Runnegar 

and Pojeta, 1974). Our explanation only allows them 

to be torted if they are secondarily symmetrical, 

having descended from primitive helically coiled 

forms.

As mentioned previously, Rollins and Batten 

(1968) used three criteria to identify bellerophontaceans as gastropods: (1) a long trail on the concave 

side of the shell, said to impede the maneuverability 

of a protracted head (Knight, 1952); (2) secondary 

inner shell layers (parietal deposits) covering the 

exterior of earlier formed parts of the coil; and (3) 

paired muscle insertions limited to the left and right 

sides of the columella (Knight, 1947).

By treating the Helcionellacea as monoplacophorans, we dispute criterion 1; possibly the trail provided structural support for a sessile head and radular apparatus as in Neopilina (Lemche and Wingstrand, 1959). Cowries and other gastropods secrete 

secondary shell layers on all parts of the shell; the 

argument that the parietal deposits of bellerophontaceans could not be secreted by epithelium near the 

head is questionable (N. J. Morris, oral commun., 

May 1973). The difference in shell musculature in 

externally similar planispiral univalves is more 

problematical. Starobogatov (1970) suggested that 

the main muscles of a planispiral gastropod would 

be inserted on the columella of the spire to counterbalance its weight over the posterior part of the foot. 

Planispiral monoplacophorans would need their 

main muscles on the opposite side of the shell because the spire was suspended over the head. We 

agree that it is unlikely that planispiral gastropods 

could have muscles on the outer side of the shell, but 

there is no reason why similarly shaped monoplacophorans could not have had their main pedal muscles 

attached to the columella. Morris (oral commun. 

May, 1973) has suggested that planispiral monoplacophorans that had lateral gills could have had their 

main pedal muscles attached posteriorly; those that 

had more posterior gills may have emphasized the 

anterior musculature.

We conclude that the small dextrally coiled Early 

Cambrian shells Aldanella and Pelagiella are the 

first gastropods; they gave rise to the sinuopeids, 

raphistomenids, and eotomariids of the Late Cambrian (Knight and others, 1960).

ORIGIN OF THE CEPHALOPODA

Cephalopods have the mouth and anus juxtaposed, 

but the body is not torted; it is still bilaterally symmetrical. Most living cephalopods lack a calcareous 

exoskeleton and are thought to be derived from more 

primitive shelled forms (Teichert, 1967). Apart 

from the enigmatic fossil Vologdinella Balashov 

(Ruzhentsev and others, 1962), no septate shells 

that could be cephalopods have been found in rocks 

older than the Late Cambrian (Teichert, 1967; 

Yochelson and others, 1973). These primitive cephalopods, referred to the family Plectronoceratidae 

Kobayashi, have elongate, straight, or endogastrically curved shells, many closely spaced septa, and large 

ventral siphuncles (Flower, 1964; Teichert and others, 1964). The apparently oldest and most primitive 

genus is Plectronoceras Ulrich and Foerste, in which 

the shell expands rapidly towards the aperture.

As noted previously, most monoplacophorans have 

exogastrically coiled shells. However the Late Cambrian and Early Ordovician genera Hypseloconus 

Berkey and Yochelsoniella Flower, are tall, laterally 

compressed shells, which appear to have been endogastrically coiled (Knight and others, 1960; 

Stinchcombe and Echols, 1966; Yochelson and others, 1973). Such shells first appear in the early Late 

Cambrian (Lochman and Duncan, 1944, pi. 12, figs 

37-38). Some forms have apical septa, and Yochelson, Flower, and Webers (1973), suggested that 

they became primitive cephalopods when they developed a siphuncle. We believe that the hypseloconids were derived from Early Cambrian orthocones 

like Tannuella (Rozanov and others, 1969) ; as Yochelson, Flower, and Webers (1973) suggested, the 

class Cephalopoda probably did not appear before 

the Late Cambrian.
PHYLOGENY 33

Flower (1964, 1968), Teichert (1967), and Teichert and others (1964) have discussed the subsequent 

radiation of the Cephalopoda.

ORIGIN OF THE ROSTROCONCHIA

The Early Cambrian genus Heraultipegma n. gen. 

(=Heraultia Cobbold) is a simple laterally compressed shell that has gaping anterior, ventral, and 

posterior margins (pi. 2, figs. 1-13). It is the oldest 

known rostroconch. We envisage a laterally compressed monoplacophoran such as Anabarella (fig. 

6; pi. 17, fig. 8) giving rise to Heraultipegma by the 

middle Early Cambrian. Internally, Heraultipegma 

is poorly known, but it clearly has a small pegma (pi. 

2, figs. 7, 8) produced by a fold in the shell between 

the dorsal edge of the anterior gape and the anterior 

slope. We assume that Heraultipegma gave rise to a 

Ribeiria-like animal when the fold of shell beneath 

the beak thickened internally to form a transverse 

plate or pegma.

Heraultipegma is known only from ferruginous 

internal molds which abound at the type locality 

(Thoral, 1935, pi. 1, fig. 3). It had only one center of 

calcification because the growth rugae cross the 

dorsal margin at right angles to the midsagittal 

plane (pi. 2, fig. 12). Watsonella Grabau is another 

laterally compressed shell from the Lower Cambrian 

of Massachusetts, which is probably allied to 

Heraultipegma; however, it is known only from the 

type specimens which are not well preserved (pi. 3, 

figs. 1-4) and yield little additional information 

about this type of animal.

The change in shell form from a univalved monoplacophoran to a pseudobivalved ribeiriid like Heraultipegma was probably accompanied by a change 

in life habits. Both Harry (1969) and Stasek (1972) 

described hypothetical animals which they felt must 

have existed as intermediates between monoplacophorans and pelecypods; both authors accurately describe the morphology of Anabarella, Heraultipegma, and other ribeiriid rostroconchs.

Stasek's fuller explanation (1972, p. 31-32 is particularly pertinent:

By and large, the monoplacophorans and primitive gastropods 

(Helcionellacea) of the early Cambrian seem to have been 

sluggish grazers of surface films or larger benthic algae. It 

was earlier inferred that within the herbivorous adaptive zone, 

and while the phylogenetically fertile Monoplacophora were 

still less than 1 cm long, some side groups were experiencing 

anatomical trends toward increased efficiency of individual 

pairs of their pseudometamerous organ systems. In relation 

to the heightened form of the body and mantle cavity, some 

of these monoplacophorans had already successfully reduced 

the number of ctenidia to one pair. Ciliation upon the surfaces

of the gill filaments continued to function in creating a respiratory water current and in removing participate matter 

from it and the gills. This unwanted material undoubtedly included detritus and living plankton; that is, it comprised a 

quantity of material drawn from the same bank of organic 

energy that, from their earliest history, entire other phyla, 

especially the sponges and brachiopods, had tapped as a source 

of food. It is not surprising that one or more of the archaic 

monoplacophoran populations should have gradually come to 

exploit the same bank for its food supply, since a collecting mechanism already existed in the ciliary cleaning device of its 

gills. The source, but not the kind of food would have changed, 

for the original filter-feeding types probably retained the 

essentially herbivorous habits of their ancestors.

Some gastropods, such as Crepidula, utilize similar mechanisms for collecting food, but having arisen late, found their 

potential for radiation somewhat stifled by preexisting and 

highly diversified filter-feeding mollusks. The Cambrian filterfeeding types, on the other hand, had entered an adaptive 

zone that had been untried by previous members of the 

phylum.

The filter-feeding Monoplacophora [?Anabarella, Heraultipegma, Ribeiria] are envisaged to have undergone trends 

toward increasing the length of the gill axes and of the filaments upon them in correlation with ventral expansion of the 

eaves of the mantle and shell, which housed the body cavity. 

Passage of mucus-bound material anteriorly may originally 

have been by way of ciliary tracts on the surface of the body, 

but channeling devices and flaps of the body wall soon funneled potential food into the mouth. These flaps, the labial 

palps, later expanded and acquired a sorting mechanism based 

on the relative sizes of the particles gathered by the ctenidia.

Retrospectively, the Bivalvia (Pelecypoda) are descendents 

of these hypothetical monoplacophorans.

Eventually the ribeiriids became adapted for infaunal life, becoming deposit feeders or filter feeders 

rather than browsers or grazers. This allowed them 

to diversify and to exploit the soft-sediment environment. We speculate that decephalization may have 

accompanied this change.

RADIATION OF THE ROSTROGONGHIA

In so far as possible, we rely on the stratigraphic 

succession in placing the gradations in morphology 

between various rostroconch taxa in their proper 

phylogenetic sequence. Thus, primitive characters 

are those known to have arisen first and are found 

in the oldest members of the class; advanced characters occur in younger forms thought to have evolved 

from primitive members. Admittedly, this approach 

presents some difficulties. New discoveries may 

change present thoughts on correlations, they may 

extend the ranges of critical taxa, or they may provide specimens that show morphological features not 

previously known. Sometimes a late-surviving primitive form may provide more insight into phylogenetic relationships than stratigraphically older 

forms. Nevertheless, the stratigraphic succession of 

organisms is basic to our notions of primitive and
34 PALEONTOLOGY OF ROSTROCONCH MOLLUSKS

advanced features and ancestors and descendents; 

each instance where it is not used is individually 

justified.

Rostroconchs are not common fossils. Yet, in spite 

of this, we can demonstrate close morphological 

gradations between all major taxa, and in most cases, 

we can relate these changes to the stratigraphic succession. It is the kind of paleontological situation 

which is theoretically called for, but which all too 

often cannot be observed in the fossil record. This 

situation makes systematic subdivision of the class 

difficult, because the taxa (both major and minor) 

that we recognize are parts of a continuum and are 

therefore difficult to define in the Linnean hierarchical system.

The only Early Cambrian rostroconchs known are 

Heraultipegma varensalense (Cobbold) from southern France (pi. 2, figs. 1-13), and Watsonella crosbyi Grabau from Massachusetts (pi. 3, figs. 1-4). 

Both occur with trilobites and are therefore Atdabanian or younger in age. They are small laterally 

compressed pseudobivalves, which gape anteriorly, 

ventrally, and posteriorly.

In the Late Cambrian, Ribeiria taylori n. sp. is 

known from Trempealeauan rocks of New York 

State (pi. 8, figs 12, 13); R. australiensis (pi. 4, figs 

26-29) is present in the Mindyallan rocks of Queensland, Australia; Wanwania cambrica Kobayashi (pi. 

3, figs 5, 11-14) occurs in the Cambrian Tsinania 

Zone of Manchuria; and Oepikila cambrica, (pi. 10, 

figs 14, 15) is found in the Idamean rocks of Queensland. These Late Cambrian ribeiriids retain the 

prominent comarginal ornament of Heraultipegma 

and Watsonella, the gaping margins, and the dominant posterior growth component. They are larger 

than Heraultipegma and Watsonella and have a 

larger and more prominent pegma.

What we know of Cambrian rostroconchs shows 

that a minimum radiation of the group took place at 

that time: two families, five genera, and six species. 

In the Early Ordovician, rostroconchs underwent 

their greatest radiation, diversifying into four 

known families, 14 genera, and about 43 species. In 

comparison, only one family, genus, and species of 

Cambrian pelecypods are known. By the Early Ordovician there are six families, 16 genera, and about 

45 species of pelecypods. All mollusks, and indeed 

many invertebrates, radiated rapidly in the Early 

Ordovician (Tremadocian-Arenigian; Canadian), 

although they are known from few forms in the 

Cambrian,

In the Middle and Late Ordovician, rostroconchs 

remained at about the same level of diversity as in

the Early Ordovician: five families, 10 genera, and 

about 40 species. In contrast, pelecypods continued 

to radiate explosively and are represented by about 

16 families, 140 genera, and 1,400 species in the same 

period of time.

In the remainder of the Paleozoic, rostroconchs 

are represented by two families, seven genera, and 

about 275 known species. Pelecypods of the same 

age are referred to approximately 75 families, many 

hundreds of genera, and thousands of species. Thus 

rostroconchs form one of the smaller classes of mollusks, comparable in the number of named taxa to 

the Aplacophora, Monoplacophora, and Scaphopoda.

The dominant rostroconchs of the Ordovician 

were ribeiriids, technophorids, and eopteriids; ischyriniids and bransoniids were present in smaller numbers. Technophorids, eopteriids, and ischyriniids 

show a melange of primitive and advanced features, 

indicating that the Ordovician was a time of adaptive radiation for the class; various marine habitats 

were invaded, and several modes of life were evolved. 

Of the various combinations of morphology known in 

Ordovician rostroconchs, only the combination seen 

in the bransoniids (Conocardiacea) survives the end 

of the period. Perhaps only the conocardiaceans 

evolved a morphology that enabled them to exist with 

the far more efficient pelecypods during the latter 

part of the Paleozoic. The last rostroconchs occur in 

some of the youngest Permian deposits known 

(Newell, 1940; Waterhouse, 1967, p. 178); their 

fossil record terminates at the close of the Paleozoic.

We now review the history of the class in greater 

detail. The most primitive family is the Ribeiriidae; 

it is the first to appear, its oldest members grade 

morphologically into primitive monoplacophorans, 

and all species referred to it have a simply constructed shell, little different from the earliest member of the family. Most ribeiriids are posteriorly 

elongated (fig. 11), have a well-developed pegma, 

and have a shell that gapes anteriorly, ventrally, and 

posteriorly (primitive forms: Heraultipegma, Ribeiria, Ribeirina), or only anteriorly and posteriorly 

(advanced forms: Ribeiria, Wanwania, Pinnocaris). Assuming that all ribeiriids had similar shell 

musculature, the foot was attached to the shell by 

anterior and posterior median pedal retractors and 

possibly by left and right side muscles; the mantle 

was attached to the shell along a pallial line that had 

a shallow sinus near its anterior end. Ribeiriids 

probably had one pair of laterally disposed gills 

which created anterior to posterior water currents 

in the mantle cavity. The animals were motile, lived 

infaunally, and obtained food by a combination of
PHYLOGENY 35

deposit and filter-feeding methods. Although the pegma may have provided needed structural support for 

the anterior retractor muscle of the foot, its presence created problems during growth, and as a result 

the shell and mantle cavity remained narrow. Primitive ribeiriids are therefore laterally compressed; 

only in the advanced species Wanwania cambrica 

Kobayashi (fig. IIj) does the shell become inflated, 

thus showing a trend toward the eopteriid 

Euchasma.

Like ribeiriids, technophorids also have a large 

and prominent anterior pegma (pi. 11, figs 21, 22), 

anterior and posterior median muscle insertions, and 

left and right linear muscle insertions (fig. 3H, 

lift). The occurrence of these primitive features and 

the general similarity in shell form indicates a 

close phylogenetic relationship between technophorids and ribeiriids; this relationship is reflected 

in the systematics of the class by placing both families in the same order (Ribeirioida).

Technophorids have advanced beyond the ribeiriid stage in that, except for Myocaris Salter, they 

no longer have an anterior or ventral shell gape (pi. 

11, figs 10, 11). In most forms, the posterior gape of 

the ribeiriids has been reduced to two small orifices 

formed by opposing folds (plicae) of the posterior 

part of the shell. Some technophorids (Technophorus) developed a primitive rostrum, formed by an 

extension of the posterior dorsal margin of the shell 

(pi. 14, figs 6, 7); this rostrum terminated in a relatively larger dorsal posterior orifice (pi. 11, fig. 9). 

We homologize the smaller lower orifice, with the 

more distinct ventral orifice of younger conocardiaceans; this structure appears for the first time in the 

Technophoridae.

The organization of the body of ribeiriids and 

technophorids appears to have been similar, but the 

shell of the technophorids is effectively closed anteriorly and ventrally, except perhaps when the foot 

forced the valves apart. We conclude that technophorids could not have moved around easily and that 

water entered and left the mantle cavity through the 

two posterior orifices. By analogy with younger 

conocardiaceans, the dorsal rostral orifice was the 

inhalant (and possibly exhalant aperture) ; the ventral orifice may have served as an exit for pseudofeces. We regard technophorids as infaunal suspension feeders, functionally analogous to coeval and 

younger pelecypods. As in the Ribeiriidae, the pegma inhibited the inflation of the mantle cavity. This 

and the other restrictions of an inflexible hinge 

reduced their chances of competing successfully with 

the Pelecypoda.

Two technophorids, Tolmachovial jelli n. sp. and 

Tolmachovia concentrica Howell and Kobayashi, are 

almost equally expanded anteriorly and posteriorly

(figs. 3B-D, life). In Tolmachovia, the cavity of the 

shell that contained the visceral mass is bounded 

anteriorly and posteriorly by transverse shelly partitions anterior and posterior pegmas. These subequilateral species connect the technophorids to the 

genus Ischyrinia Billings of the late Middle and Late 

Ordovician (fig. 3A). Significantly, there is a close 

resemblance between the Middle Ordovician Tolmachovia concentrica and the oldest species of Ischyrinia, I. norvegica Soot-Ryen, from the upper Middle 

Ordovician of Norway.

The ischyriniids are the first rostroconchs to have 

a dominant anterior growth component, so that the 

umbos came to lie at the center of the hinge, or posterior to the center (fig. llo-<?). They retained the 

anterior pegma, and in Pseudotechnophorus Kobayashi this pegma has evolved into a greatly elongated 

structure (pi. 20, figs. 10, 11). In addition to the 

anterior pegma, all ischyriniids have a posterior pegma. Like technophorids, Ischyrinia lacks anterior 

and ventral shell gapes, and the posterior gape is 

restricted to two discrete orifices. Pseudotechnophorus has an oval or kidney-shaped anterior dorsal 

aperture and a small posterior rostrum.

In Ischyrinia, the more dorsal of the two posterior 

orifices forms the aperture of the projecting rostrum, 

well differentiated in Ischyrinia winchelli Billings 

(pi. 18, figs. 22-25). In two species of Ischyrinia, 

the ventral orifice coincides with a posterior carina 

and is a widely flaring transverse aperture that appears to form late in ontogeny (fig. 3 A; pi. 18, fig. 

23).

The musculature of Ischyrinia is apparently ribeiriidlike. It consists of a linear muscle insertion connecting the ends of the two pegmas (fig. 3A), and 

presumably of anterior and posterior median pedal 

retractor insertions. Pseudotechnophorus has more 

advanced lateral pedal insertions, like those of the 

conocardiacean Eopteria, and another large muscle 

insertion which forms a ring or a horseshoe in the 

cavity in front of the anterior pegma. For reasons 

explained elsewhere, we interpret this latter insertion as the attachment point of hypertrophied radial 

muscles of the mantle, termed pallial retractor muscles. Significantly, the protoconch of Pseudotechnophorus has a tiny anterior median muscle insertion 

and an equally small linear insertion that passes 

from the anterior median muscle posteriorly behind 

the beak. We view these structures as the insertions 

of atrophied ribeiriid pedal muscles and conclude
36 PALEONTOLOGY OF ROSTROCONCH MOLLUSKS

Hr^rrrrr^ EOPTERIIDAE sf\^z==

FIGURE 11. (See explanation on facing page.)
PHYLOGENY 37

that the functional pedal muscles of Pseudotechnophorus were a new development.

Ischyrinia and Pseudotechnophorus are referred 

to the same family (Ischyriniidae) and order (Ischyrinioida) because of their similarities in shell 

form. However, Pseudotechnophorus is more advanced than Ischyrinia, in its shell musculature. It 

cannot have been derived from Ischyrinia if Ischyrinia, is descended from Tolmachovia,, because Pseudotechnophorus is Early Ordovician in age. Pseudotechnophorus may have evolved from Eopteria, 

which is also found in the Early Ordovician and 

which resembles Pseudotechnophorus in shell musculature and to some extent in shell form (fig. 11). 

We realize the Ischyriniidae may be a nonphylogenetic grouping, but find it convenient at this stage 

of knowledge. It is difficult to place too much emphasis on stratigraphic occurrences at this time because the ischyriniids are known from only a handful of specimens from a few localities.

Both Ischyrinia and Pseudotechnophorus have 

relatively few primitive characteristics and have 

departed farther from the ribeiriid stem stock than 

have the technophorids. Primitive features are the 

presence of an anterior pegma and the ribeiriidlike 

musculature of Ischyrinia and the protoconch of 

Pseudotechnophorus; advanced features include the 

closing of the anterior and ventral parts of the shell, 

the development of a rostrum and specialized ventral 

orifice, the addition of a second pegma, and the dominant anterior growth component. Despite these relatively complex features, which to some extent mimic 

features found in younger conocardiaceans, we believe that the ischyrinioids, like the technophorids, 

are a side branch of the rostroconch evolutionary 

tree. Throughout their history, conocardiaceans retained an anterior gape and lacked a pegma. We 

regard the less elaborate Eopteriidae as the ancestors of the Conocardiacea. In the Early Ordovician radiation of rostroconchs, several lineages 

developed comparable structures by parallel evolution; such parallel features include the closing of 

the ventral shell gape, the development of a rostrum,

FIGURE 11. Diversity of form in the Class Rostroconchia. 

Arrows indicate probable paths of evolution. Genera belonging to the same family are shaded in the same way. a, 

Latouchella; b, Anabarella; c, Heraultipegma; d-f, Ribeiria; g-h, Pinnocaris; i-j, Wanwania; k-l, Tolmachovia; m, 

Myocaris; n, Technophorus; o-p, Ischyrinia; q, Pseudotechnophorus; r-s, Eopteria; t, Wanwanella; u-w, Euchasma; x-z, Bransonia: aa, Hippocardia; bb, Conocardium.

and restriction of the posterior shell gape to one or 

two apertures.

The inhomogeneity of the Ischyrinioida is also reflected in our interpretation of the life habits and 

soft-part morphology of Ischyrinia and Technophorus. Ischyrinia probably developed the suspension 

feeding habit of its technophorid ancestors. It was 

probably buried to the depth of the carina, remained 

stationary, and fed and obtained oxygen through its 

posterior orifices.

In contrast, we believe that Pseudotechnophorus 

was motile, had an anterior to posterior water current, and used protractible mantle tissue to deposit 

feed from the sediment-water interface. This presumed life habit also places Pseudotechnophorus 

closer to Eopteria than to Ischyrinia, but the similarities may be due to convergence.

All other rostroconchs are referred to the order 

Conocardioida. The Early and Middle Ordovician 

Eopteriidae are the oldest members of this order, 

and they are connected through Wanwanella Kobayashi (Eopteriidae) and Wanwania (Ribeiriidae) 

to the Ribeiriidae (fig. 11).

The Eopteriidae includes the genera Eopteria 

Billings (pis. 22-26) and Euchasma Billings (pis. 27- 

29), which are the first known rostroconchs to have 

marginal denticles (pi. 23, figs. 4, 5; pi. 24, fig. 14; 

pi. 29, fig. 4) and external radial ribs (pi. 24, figs. 12, 

18; pi. 28, figs. 12-15), features seen on all subsequent conocardiaceans. The ribeiriid affinities of the 

Eopteriidae are shown by the presence of an anterior pegma in Euchasma (pi. 29, figs. 3, 11, 15) and 

Wanwanella (pi. 21, figs. 18-20), and by the fact 

that the eopteriids still have gaping anterior, ventral, and posterior valve margins (pi. 24, figs. 14, 15, 

20).

The shell musculature of Eopteria is well known 

from E. ventricosa (Whitfield) (fig. 4; pi. 22, figs. 1- 

6; pi. 23, figs. 2, 3). Like Pseudotechnophorus, Eopteria has the pedal muscles inserted laterally on each 

valve, but there is no trace of the relict ribeiriid musculature seen in Pseudotechnophorus. The pallial line 

is well preserved; there is an anterior sinus which 

housed pallial retractor muscles, and there is possibly a posterior adductor muscle. This latter muscle 

may have been used to flex the valves and so create 

water currents in and out of the mantle cavity.

Some Middle Ordovician species of Eopteria show 

a dominant anterior growth component (pi. 26, figs. 

12-18) at about the time that conocardiaceans first 

appear in the fossil record. Both Euchasma and Eopteria developed an incipient rostrum at the posteri-
38 PALEONTOLOGY OF ROSTROCONCH MOLLUSKS

or end of the shell (pi. 24, figs. 11, 12; pi. 28, figs. 12, 

13), and all eopteriids had a more inflated shell and 

mantle cavity than the ribeiriids and technophorids. 

Thus, the presence in the eopteriids of a combination 

of ribeiriid and conocardiacean features suggests 

that they are descended from the former and are 

ancestral to the latter.

The loss of the pegma in Eopteria and the modification of its edges in Euchasma allowed the valves to 

grow in tighter spiral, thus enlarging the mantle 

cavity. This lateral expansion of the shell produced 

umbones on either side of the beak of Euchasma, as 

it did in all members of the Conocardiacea. At this 

evolutionary level, the shells of rostroconchs, although still starting growth from a univalved protoconch, became clearly bivalved and thus superficially resemble the shells of pelecypods.

The inflation of the mantle cavity also affected the 

topography of the hinge. It became increasingly difficult for rostroconchs to maintain an approximately 

rectilinear hinge; tensional fractures called clefts 

developed between topographically high and low 

parts of the hinge. These are visible in front of the 

beak of some ribeiriids (pi. 4, fig. 9), but they are 

much more obviously developed in the eopteriids (pi. 

27, fig. 13) and conocardiaceans (pi. 40, figs. 5, 7). 

In general, those forms having a dominant posterior 

growth component like Euchasma, have well-developed anterior clefts (pi. 27, fig. 13); those having a 

dominant anterior growth component (Conocardiacea) have posterior clefts (pi. 34, figs. 6-8) ; and 

those having subequilateral shells (Eopteria) may 

have clefts on both sides of the beak. The need for 

the clefts is explained by figure 1.

As well as being strongly inflated, most species of 

Euchasma are flattened anteroventrally, and one 

species, Euchasma mytiliforme n. sp. has the external shell forms of epibyssate mytilid and dreissenid 

pelecypods (pi. 29, figs. 6-15). This suggests that 

Euchasma lived epifaunally. Although the shell of 

Euchasma has a narrow ventral to posterior gape 

(pi. 29, figs. 8, 9), the only sizable shell aperture is 

a circular hole formed by the edges of both valves at 

the dorsal anterior margin, just in front of the pegma (pi. 28, figs. 15, 16). If Euchasma were orientated as an epifaunal animal, this hole would face 

the substrate. We speculate that it contained a structure formed by hypertrophy of one or more pallial 

tentacles and that was manipulated by pallial retractor muscles attached in an anterior sinus in the 

pallial line (pi. 27, fig. 9). Euchasma may have lived 

attached to the substrate by this structure and may 

have suspension fed from water entering and leaving

the mantle cavity through the posterior gape. 

Euchasma may have been a sessile epifaunal suspension feeder.

By contrast, Eopteria seems to have been a motile 

semi-infaunal deposit feeder which collected food 

from the sediment-water interface, using hypertrophied mantle tissue and possibly pallial tentacles 

for the collecting structure. This tissue was extruded 

from the anterior gape and withdrawn by pallial 

retractor muscles located in the anterior pallial sinus. 

A narrow pelecypodlike foot was used for locomotion, and a posterior adductor muscle may have been 

used to clean the mantle cavity.

Eopteria is a suitable ancestor for the Conocardiacea, and in fact, only the presence of a well-developed 

posterior rostrum distinguishes the Ordovician conocardiacean Bransonia cressmani n. sp. (pi. 52, figs. 

10-14; pi. 53, figs. 6-21) from Eopteria (pi. 26, figs. 

12-18). Eopteria is similar to the conocardiaceans in 

retaining an anterior gape, in lacking a pegma, in 

its musculature, and in having well-developed external ribs and commissural denticles. It differs from 

conocardiaceans in having a continuous posteroventral gape instead of a rostrum and a discrete ventral orifice. Eopteria is also more variable in shape. 

Only some species are anteriorly expanded (pi. 26, 

figs. 12-18) like the Conocardiacea; others are subequilateral (pi. 26, figs. 1, 2) or posteriorly expanded 

(pi. 25, fig. 15).

The technophorids and Ischyrmia differ from 

eopteriids, ribeiriids, and conocardiaceans in that 

they have a closed anterior end; they disappear by 

the end of the Ordovician. Only the anteriorly gaping Conocardiacea are found in the post-Ordovician 

Paleozoic.

There is evidence that most of the advanced rostroconch genera having anteriorly gaping shells had 

hypertrophied mantle tissue which could be protracted through the anterior gape. The three important indications of the existence of this tissue 

are: (1) commissural denticles, formed by folds in 

the enlarged mantle as it was withdrawn into the 

shell (functionally analogous to the denticles lining 

the apertures of living cowrie shells) ; (2) the anterior pallial sinuses of Wanwania, Eopteria, and 

Euchasma; and (3) the impressions of the radial 

muscles of the mantle seen in species of Eopteria and 

Bransonia n. gen. In more primitive rostroconchs 

like Eopteria and Pseudotechnophorus, the mantle 

tissue seems to have been protracted hydrostatically. 

In the Conocardiacea, pallial protractor muscles inserted just inside the anterior end of the hinge 

probably pulled the mantle tissue out of the shell.
PHYLOGENY 39

In the highly complex rostroconchs Conocardium 

Bronn and Arceodomus n. gen., the anterior gape is 

largely obstructed by internal calcareous shelves 

(pi. 43, fig. 13). These are formed of outer shell 

layer, implying that the outer edge of the mantle 

formed them. We conclude that the mantle was complexly folded in these areas in these forms. We 

homologize the shelves with the marginal denticles 

found in all other conocardiaceans, because these are 

also formed initially of the outer shell layer.

In all conocardiaceans, the posterior shell gape is 

reduced to the small aperture at the end of the rostrum, and in most an even smaller ventral orifice. 

The Conocardiidae have only the rostral orifice. We 

therefore doubt that any of these animals could have 

been posterior suspension feeders and conclude that 

they were all anterior deposit feeders using hypertrophied mantle tissue and perhaps pallial tentacles 

to accumulate food. The more primitive forms probably operated like Eopteria; the most advanced 

forms (Conocardiidae) may have had complex sorting structures formed by ciliated mantle surfaces 

resting on the anterior shelves.

The inflated mantle cavity of all conocardiacean 

rostroconchs suggests that all genera had gills. This 

may account for the most striking difference in form 

between species like Conocardium elongatum and its 

functional analog, the tusk-shaped scaphopods. We 

assume that these gills pumped water in and out of 

the rostrum to supply oxygen to the organism and 

to remove body wastes. The ventral orifice may have 

been used to remove pseudofeces from the mantle 

cavity; its absence in the Conocardiidae may reflect 

the sophisticated sorting devices at the anterior end 

of the shell which prevented anything but food from 

entering the mantle cavity. We conclude that all 

conocardiaceans were deposit feeders. The filterfeeding rostroconchs (technophorids, Ischyrinia, and 

Euchasma) became extinct by the end of the Ordovician. The Ordovician was a time of major expansions in the suspension-feeding pelecypods and 

brachiopods, and competition for this mode of life 

may have led to the extinction of suspension-feeding 

rostroconchs,

As mentioned above, the unspecialized eopteriid 

Eopteria gave rise to the most primitive conocardiaceans, the Bransoniidae, in the Middle Ordovician. 

The bransoniids rapidly diverged into two longranging types, the hooded and nonhooded forms. 

Bransonia n. gen. (pi. 51, figs. 1-10, 12-16) is a 

simple conocardiacean having a large anterior gape, 

small commissural denticles, a small rostrum sharply delimited by posterior clefts, coarse full body ribbing, and a well-defined ventral orifice. Hippocardia 

Brown has all of the conocardiacean features of 

Bransonia, but has in addition a hood (pi. 48, fig. 2) 

attached to the umbonal areas of the valves, an extended ventral orifice where the left and right sides 

of the hood meet, and enlarged anterior marginal 

denticles or small anterior shelves.

The hooded lineage begins with Hippocardia, 

which gives rise to the Silurian-Devonian genus 

Bigalea n. gen. This form possesses two small hoods, 

one anterior to the other (pi. 37, fig. 4). Each hood 

has an aperture along the ventral margin, so that 

Bigalea has four commissural orifices, rather than 

the three usually found in conocardiaceans. In Bigalea, the hoods are always small and never reach the 

enormous size of some species of Hippocardia (pi. 

48, fig. 2).

The most complex rostroconchs belong to the family Conocardiidae. These have elaborate longitudinal 

shelves in the anterior aperture and an elongate 

shell clearly separable into three regions rostrum, 

body, and snout (pi. 43, figs. 7, 5, 13, 15). Two genera are placed in this family, Conocardium Bronn 

(pi. 38) and Arceodomus n. gen. (pi. 43). They 

differ principally in the ornament on the body of the 

shell and are clearly closely related; Conocardium is 

the older of the two and presumably ancestral to 

Arceodomus.

As noted above, the longitudinal shelves are probably enlarged commissural denticles. In the bransoniid genus Mulceodens n. gen., the denticles in the 

ventral part of the aperture are enlarged so that 

those from opposite sides are in contact (pi. 34, figs. 

9-14). The denticles project into the aperture and 

are elongated anteroposteriorly (pi. 34, figs. 3-5). 

Further enlargement of such denticles could easily 

lead to longitudinal shelves, and the bransoniids 

probably gave rise to the conocardiids.

Pseudoconocardium Zawodovsky is a bransoniid 

having an anterior gape that occupies almost the 

entire anterior face. The gape is not restricted to an 

anterodorsal position as it is in other conocardiaceans. It seems likely that Pseudoconocardium was derived from Bransonia by an enlargement of the anterior aperture in a ventral direction.

In summary, ribeiriids are looked upon as the rostroconch stem stock, which in the Ordovician gave 

rise to the technophorids, ischyriniids, and eopteriids. The ribeiriids continued until the end of the 

Ordovician. In the Middle Ordovician, Eopteria 

produced the first conocardiacean, which rapidly diversified into the hooded and nonhooded lineages of 

the Hippocardiidae and Bransoniidae. The most spe-
40 PALEONTOLOGY OF ROSTROCONCH MOLLUSKS

cialized rostroconchs, the Conocardiidae, were derived from the bransoniids in the middle Paleozoic. 

The class became extinct at the end of the Permian. 

The Ordovician was the period of greatest radiation 

and diversification of the Rostroconchia; during this 

time, rostroconchs became adapted for infaunal and 

epifaunal suspension feeding as well as infaunal deposit feeding. Only the deposit feeders survived the 

end of the Ordovician.

ORIGIN OF THE PELECYPODA

BIVALVED CONDITION IN THE MOLLUSGA

Several kinds of mollusks have a bivalved shell, 

and the bivalved condition is the distinctive feature 

of the classes Rostroconchia, Pelecypoda, and the 

enigmatic group Stenothecoida. A few gastropods 

have a bivalved shell, and at least one species of 

octopus habitually inhabits discarded pelecypod 

shells.

Other mollusks have shells composed of two or 

more parts (chitons, gastropods having opercula, 

pholad pelecypods having accessory plates, cephalopods having aptychi), which are normally separate, 

but which in rare 'cases may be joined by a flexible 

structure resembling the pelecypod ligament. Such 

structures occur in some of the plates of the living 

chiton Schizoplax Dall (Dall, 1878; Knight and others, 1960; Harry, 1969) and in the junction between 

the operculum and shell of the Virgin Islands land 

snail Thyrophorella (Girard, 1895; Boettger, 1962; 

Harry, 1969). None of these shells are bivalved, but 

they demonstrate that two or more centers of calcification have arisen independently in many different 

kinds of mollusks.

Some mollusks may be secondarily univalved, having descended from bivalved ancestors. Some clavagellid pelecypods clearly fit this category, and there 

is some embryological evidence that the ancestors of 

the Scaphopoda had a bivalved shell (LacazeDuthiers, 1856-57; Yonge, 1957). By contrast, the 

oldest rostroconchs are morphologically intermediate 

between univalved monoplacophorans and younger 

bivalved forms. In this case, there is no clear distinction between bivalved and univalved shells.

The phylogenetic and behavioral changes accompanying the attainment of a bivalved shell may or 

may not be reflected by major changes in the organization of the body. Thus, the body and habits of the 

living bivalved opisthobranch snails (Juliidae) 

differ very little from those of related univalved 

opisthobranchs (Kay, 1968) ; the oldest pelecypod, 

Fordilla Barrande (Pojeta and others, 1973), however, had its body organized quite differently from

its univalved monoplacophoran ancestor. Despite 

these differences, the shells of the simplest juliid 

Berthelinia Beets and Fordilla are remarkably similar in external form.

The orientation of the valves on the body also 

varies. Rostroconchs, pelecypods, and bivalved opisthobranch gastropods have the valves disposed on 

right and left sides of the body, the junction between 

the valves being in the anatomically dorsal position. 

The gastropods and rostroconchs retain this primitive orientation of the organism with respect to the 

substrate, but many pelecypods lie on left or right 

valves or even on the hinge (Cox and others, 1969). 

Oysters, for example, developed valves that are functionally dorsal and ventral as in some productid 

brachiopods (Grant, 1966). Tridacnid clams have 

the plane of symmetry vertical but lie on the hinge 

(Yonge, 1953a).

The stenothecoids (Yochelson, 1969) and the bivalved limpets Hipponix antiqucdus (Linnaeus) 

(Yonge, 1953b) and Cheilea equestris (Linnaeus) 

have two subequal valves, but these are anatomically 

and functionally dorsal and ventral. The soft-part 

morphology of Stenothecoides Resser and related 

genera is not easily reconstructed, but the ventral 

valve of Hipponix is formed by the sole of the foot, 

and thus is in no way analogous to the right and left 

valves of other mollusks.

LIMITS OF CONVERGENCE IN SHELL FORM

All pelecypods have a shell that is bivalved from 

the time that calcification begins (Raven, 1958). 

Before this stage, there is a single dorsal uncalcified 

cuticle (shell gland) on the larva. When calcification 

begins, it starts at two points on left and right sides 

of the saddle-shaped cuticle; these points eventually 

become the beaks of the valves. The intervening uncalified zone becomes the ligament, or the ligament 

may suddenly appear in this region in later ontogeny 

(Chanley and Chanley, 1970, pi. 3).

Initially the hinge is long and straight so that the 

early larval shells of most pelecypods are characteristically D-shaped. As inflation of the valves proceeds, umbos form on either side of the hinge, and 

the ligament becomes proportionally shorter. In 

most adult pelecypods, the ligament is relatively 

short, so that the valves are circular or oval. The 

growth lines reflecting the edge of the mantle curve 

towards the beaks and cross the hinge at the posterior and functionally anterior ends of the ligament.

In the Rostroconchia, the larval shell is univalved, 

there is only one center of calcification, and the bivalved condition arises through postlarval accentu-
PHYLOGENY 41

ated growth of the lateral lobes of the shell. Because 

the valves are always effectively closed, there is no 

need for deep anterior and posterior embayments, so 

the growth lines are not recurved towards the beak.

In the bivalved opisthobranch gastropods, the 

larva has a helically coiled shell and an operculum 

that is eventually shed. When the bivalved shell begins to form, it is not symmetrical because the ligament forms on the right side of the helical protoconch (Kawaguti, 1959). This is a third situation in 

which there is originally a single center of calcification (the protoconch) and a second center of calcification (the right valve), develops subsequently. 

The adult shell is superficially bilaterally symmetrical but has the asymmetrically placed protoconch 

and a different arrangement of muscles attached to 

each valve (Kawaguti and Yamasu, 1960).

For the pelecypod or gastropod ligament to function efficiently, it must be relatively straight. Because the generating curve of primitive pelecypod 

and bivalved snail shells is approximately circular 

or elliptical, it would be mechanically inefficient to 

have the hinge on both sides of the beaks. In primitive pelecypods, the ligament is always behind the 

beaks (opisthodetic) and grows from its posterior 

end; in the bivalved opisthobranch snails, the reverse is true, and the ligament is entirely prosodetic. 

The resulting shells are quite similar in external 

form except that the left valve of a primitive pelecypod like Fordilla resembles the right valve of the 

bivalved gastropod Ber>thelinia.

The origin of the bivalved condition in the Stenothecoida is not well understood, but the growth lines 

on each valve run completely round the beak, producing a good deal of interumbonal growth (Yochelson, 

1969, fig. 3). Analogous growth increments are 

found in many brachiopods, where the valves are 

totally separate structures! growing at all edges; 

growth lines also occur in the shells of the bivalved 

limpets. This growth pattern reinforces the view 

that stenothecoids are only remotely related to rostroconchs and pelecypods.

ROSTROGONCHS AS ANCESTORS OF THE 

PELECYPODA

Fordilla troyensis Barrande from the Early Cambrian is the oldest known pelecypod (Pojeta and 

others, 1973; Pojeta and Runnegar, 1974; Pojeta, 

1975). It has a laterally compressed shell, and prominent, but not rugose, comarginal ornament. Fordilla 

is about the same size and age as the ribeiriid Herautipegma (pi. 2, figs. 1-13), and the two genera 

have similar lateral profiles. Fordilla has a bivalved

larval shell, a simple ligament-insertion area, adductor muscles, pelecypodlike pedal muscles, and a 

well-developed pallial musculature. There are no 

shell gapes; when the adductors contracted, the 

valve margins were tightly closed. In contrast, 

Heraultipegma has a univalved larval shell, a pseudobivalved adult shell, and an anterior through posterior shell gape; by analogy with younger ribeiriids, 

Heraultipegma probably lacked adductor muscles.

Several Cambrian-Ordovician ribeiriids resemble 

coeval pelecypods in external form, and decalcification of the posterior dorsal margin in successive 

generations could have produced the primitive opisthodetic parivincular ligament found in early pelecypods. Such a ligament could only function if the 

anterior embayment of the shell extended as far as 

the beak, and both evolutionary changes may have 

progressed simultaneously. Increasing flexibility of 

the posterior hinge would have enabled the valves to 

open wider anteriorly, and less shell may have been 

secreted along the anterior dorsal margin. Obviously 

the pegma would have inhibited valve movement, so 

forms like Heraultipegma that have a small pegma 

are more likely to have developed a flexible hinge.

The main difference, however, between pelecypods 

and rostroconchs is that in pelecypods, the shell is 

bivalved from the very beginning of its growth. Rostroconchs have a univalved larval shell and only one 

primary center of calcification. This is a fundamental difference; there can be no intermediates. 

Once a flexible ligament was established in the larval 

shell, the adult would inevitably resemble a pelecypod. The hinge would remain relatively short to retain flexibility, and each center of calcification would 

have a generating curve that terminated at the ends 

of the hinge. By contrast, the ribeiriids could never 

produce a pelecypodlike shell because the univalved 

protoconch remains attached to both valves.

The conchological differences between rostroconchs and early pelecypods like Fordilla, Redonia 

Rouault, Babinka Barrande, and Lyrodesma Conrad are considerable (Pojeta, 1971), but most of the 

differences relate to the geometric effects of growth 

from two centers of calcification. The shape of the 

valves and the presence of the ligament on the longer 

side of the sheill are a direct consequence of two 

growth centers, as precisely the same structures are 

found in primitive pelecypods and bivalved opisthobranch gastropods. We believe that a single mutation producing a flexible hinge in the larval shell 

would be sufficient to convert a ribeiriid into a pelecypod, if the difference were judged on shell form
42 PALEONTOLOGY OF ROSTROCONCH MOLLUSKS

C

D

FIGURE 12. Four possible explanations of the shell muscle 

insertions of the Early Cambrian pelecypod Fordilla. Adductor muscles are cross hatched; radial pallial muscles are 

stippled; muscles extending from the shell to the inner 

surface of the mantle are diagonally shaded; pedal muscle

alone. This change probably occurred in the Atdabanian Stage of the Early Cambrian, when Fordilla 

evolved from Heraultipegma or some closely related 

form.

ACCOMPANYING MODIFICATION OF BODY FORM

Judging from Neopilina and the muscle insertions 

visible on fossil monoplacophoran shells, CambrianOrdovician monoplacophorans were untorted snaillike animals with a head, a visceral mass, laterally 

disposed gills, and a ventrally flattened creeping foot 

attached to the shell by muscles inserted in a continuous or discontinuous ring. Tiny muscles controlling 

the edges of the mantle occur in Neopilina, but none 

of the ancient or modern shells shows a well-differentiated' pallial line.

In marked contrast, ancient pelecypods resemble 

their modern counterparts in having a reduced head 

and a laterally flattened probing foot attached to the 

shell mainly above the anterior and posterior adductor muscles. The radial muscles in the mantle are 

greatly enlarged to form a continuous pallial line, 

and the adductor muscles which close the valves are 

believed to be hypertrophied radial muscles which 

have been cross-fused in the anterior and posterior 

embayments (Yonge, 1953a). The pedal musculature 

of Fordilla is particularly significant, as the main 

pedal retractors are inserted anteriorly and posteriorly, implying that the extrinsic muscle fibers of the 

foot were arranged in a geodetic net as in modern 

pelecypods (Trueman, 1967). Thus, the foot of 

Fordilla must have been used for burrowing rather 

than creeping.

Fordilla also has an unusually large set of muscle 

insertions forming the posterior part of the pallial 

line (fig. 12). None of the explanations of the function of these muscles offered by Pojeta, Runnegar, 

and Kfiz (1973) (siphonal retractors, accessory adductors, muscles retracting the inner surface of the 

mantle) would be logical if Fordilla were a monoplacophoran having a bivalved shell. We conclude 

that Fordilla and similar Ordovician genera were already well adapted for life as bivalved organisms. 

They were pelecypods and not bivalved monoplacophorans^

We have already noted that the ribeiriids are transitional between the Monoplacophora and Pelecypoda in shell form. The ribeiriid shape would allow 

the animal to become adapted for life in a bivalved

insertions are black. Arrows indicate possible water flow in 

and out of the mantle cavity. Note that if B were correct, 

the whole of the posterior end of the shell would be effectively sealed. A and B are less likely, C and D more likely.
PHYLOGENY 43

shell before the truly bivalved condition developed. 

Presumably, Heraultipegma and Watsonella were 

infaunal animals capable of deposit or filter feeding. They may have lacked a well-formed head, and 

their foot was probably already adapted for probing 

rather than creeping. Thus, they may have had the 

soft-part morphology of early pelecypods in an effectively univalved shell. A single mutation producing two centers of calcification in the larval shell 

would then produce a pelecypod, preadapted for exploiting the new shell form.

We have no information on the musculature of 

Heraultipegma or Watsonella, and ribeiriids in 

which the muscle insertions are known postdate 

Fordilla by some 50-70 million years. Ribeiriids are 

almost as rare as pelecypods throughout the Cambrian, so our interpretation of the evolution of the 

pelecypods from the monoplacophorans via the 

ribeiriids is based as much on comparative morphology as on stratigraphic sequence. However, we believe that the Ordovician representatives of all three 

groups retain the fundamental features of their 

Cambrian ancestors, just as living fish, reptiles, and 

mammals reflect their Mesozoic and early Cenozoic 

counterparts.

If this be so, some Cambrian ribeiriids, like their 

Ordovician descendents, had probably developed a 

pallial line. The pedal musculature still formed a ring 

on the shell, as in the Cambrian-Ordovician monoplacophorans. Eventually the muscles on the midline 

were enlarged to operate a pelecypodlike foot. When 

the truly bivalved condition was attained, the anterior and posterior radial muscles of the mantle 

cross-fused to form adductors, and the anterior and 

posterior median muscles split to form the paired 

pedal retractors attached above the adductor insertions on each valve. The remaining parts of the pedal 

musculature, already fragmented in some ribeiriids, 

formed the small visceral/pedal muscles found in 

Fordilla and many Ordovician pelecypods.

It is the adductor muscles and well-developed hinge 

teeth of Cambrian-Ordovician pelecypods that so 

clearly separate them from coeval rostroconchs, but 

both of these structures would normally be unnecessary until a flexible ligament evolved. Both are present in bivalved snails, suggesting they can form 

rapidly when the need arises. As some univalved 

snails have an adductor muscle that is used to pump 

water in and out of the mantle cavity (Marcus and 

Marcus, 1956), some rostroconchs may have developed adductors for the same purpose. Eopteria, for 

example, seems to have a posterior adductor muscle. 

If some primitive ribeiriids had adductor muscles,

they would obviously have been more successful 

when the ligament evolved.

RADIATION OF THE PELEGYPODA

Apart from the curiously enlarged pallial muscles, 

Fordilla troyensis is a suitable ancestor for all the 

known subclasses of the Pelecypoda (Pojeta and 

others, 1973; Pojeta and Runnegar, 1974). Recent 

discoveries summarized by Pojeta (1975) show that 

the pelecypod subclasses visible in the Ordovician 

(Pojeta, 1971) could easily have stemmed from a 

single Cambrian stock. We conclude that the class 

appeared from the ribeiriid rostroconchs in the Atdabanian Stage of the Early Cambrian, remained an 

almost insignificant component of the biosphere until the Tremadocian, and then radiated rapidly into 

all the existing subclasses by the late Middle Ordovician (Pojeta, 1971).

ORIGIN OF THE SGAPHOPODA

Scaphopods have a tubular shell which is often 

gently curved and is invariably open at both ends. 

Growth proceeds by the deposition of new shell at 

the larger end of the tube and simultaneous resorbtion at the opposite end.

Coarsely silicified replicas of tusk-shaped shells 

resembling later undoubted scaphopods are known 

from the Ordovician of the United States. We believe the class was probably well differentiated by 

this time. However, Yochelson (oral commun., 1973) 

maintains a more conservative view of the range of 

the class, preferring to accept only Devonian and 

younger tusk-shaped shells as scaphopod mollusks. 

The presence of a slit in the smaller shell aperture is 

probably the best evidence for distinguishing scaphopods from similarly shaped worm tubes or other organisms. Unfortunately, the Ordovician specimens 

are too poorly preserved to show this feature.

The ontogeny of the living scaphopod Dentalium 

shows that the larval mantle and shell first appear 

dorsally and then grow left and right lobes which 

eventually coalesce ventrally to produce the tubular 

juvenile and adult shell (Lacaze-Duthiers, 1856-57). 

This embryological observation has led to the belief 

that scaphopods are more closely related to the Pelecypoda than they are to any other group of extant 

mollusks.

We also rely on the embryological evidence to postulate that the Scaphopoda may have evolved from 

the ribeiriid rostroconchs. If the inner edges of the 

mantle lobes of a ribeiriid fused ventrally, the shell 

could still grow normally, as it does in pelecypods 

that have ventrally fused mantle margins. Subse-
44 PALEONTOLOGY OF ROSTROCONCH MOLLUSKS

quent fusion of the outer edges of the mantle could 

have produced a ventrally fused shell. As soon as 

this happened, the postlarval shell would become 

tubular, and all subsequent growth would proceed 

as in living scaphopods. The result would be the immediate production of a scaphopodlike shell; there 

could be no morphological intermediates between the 

two growth forms. If our reasoning be correct, we 

are unlikely to discover fossils that prove the phylogenetic connection between the two classes.

Intermediate forms could occur if ventral fusion 

of the shell first occurred in late ontogeny and was 

subsequently transferred to the larval shell. For example, the juvenile bivalved shell is preserved on the 

dorsal side of the tubular "adventitious" shell of the 

clavagellid pelecypod Brechites (Purchon, 1960). So 

far, no fossil ribeiriids showing similar features have 

been discovered.

If we can demonstrate a connection between the 

monoplacophorans and ribeiriids, it would allow us 

to argue that the ancestral group would have shared 

primitive anatomical features found in living scaphopods. In particular, living scaphopods have a radula. 

If the scaphopods developed from the ribeiriids, we 

can conclude that some or all ribeiriids also had a 

radula. The ribeiriid Pinnocaris (pi. 9, figs. 11-24) 

has a shell form approaching that of scaphopods but 

still has a prominent pegma.

MATTHEVA AND STENOTHECOIDA (PROBIVALVIA)

Yochelson (1966, 1968, 1969) and Aksarina 

(1968) placed two small groups of enigmatic Early 

Cambrian fossils in separate molluscan classes 

called Mattheva Yochelson 1966 and Stenothecoida 

Yochelson 1968 or Probivalvia Aksarina 1968. The 

names Stenothecoida and Probivalvia Aksarina are 

objective synonyms; Yochelson's name was published 

in an abstract in August 1968, and Aksarina's at an 

unspecified time in 1968. As Harry (1969) also used 

Probivalvia in a different sense, and the name has 

some phylogenetic connotations, we suggest that 

Yochelson's name be used for this group of 

organisms.

The class Mattheva is based on a single genus, 

Matthevia. It is known from two, co-occurring, subequal, massive conical plates that are flattened on 

one side and that have two tapering cavities on the 

side that was attached to the animal. The plates show 

growth lines and probably formed part or all of the 

exoskeleton of a primitive mollusk (Yochelson, 

1966). Runnegar and Pojeta (1974) suggested that 

Matthevia is a primitive chiton.

The class Stenothecoida is more diverse; it probably includes the following genera: Stenothecoides 

Resser, Bagenovia Radugin, Cambridium Horny, 

Bagenoviella Aksarina, Sulcocarina Aksarina, 

Kaschkadakia Aksarina, and Makarakia Aksarina 

(Aksarina, 1968; Yochelson, 1969). Stenothecoids 

are demonstrably or inferentially bivalved shells 

that are normally found disarticulated. The valves 

resemble coeval limpet-shaped tergomyan monoplacophorans in shape, except that they are slightly 

asymmetrical, and valves that look like the right and 

left valves of some pelecypods can usually be distinguished (Poulsen, 1932; Yochelson, 1969). The 

few articulated specimens known (Aksarina, 1968; 

Yochelson, 1969) are slightly inequivalved.

The shell morphology is best known from Stenothecoides (Rasetti, 1954; Horny, 1957; Robison, 

1964; Yochelson, 1969). The valves are unornamented except for obvious comarginal growth lines 

and a subangular carina that runs from the beak to 

near the midpoint of the opposite part of the commissure. Apparently well preserved internal molds 

have a relatively smooth median zone that appears to 

coincide with this external carina, and a series of 

branching elevations that reflect grooves in the shell 

that run away from the central zone on both sides of 

the valve. These grooves may reflect bilaterally arranged canals or tubes in the mantle; if so, these 

grooves branch towards the margin of the shell, and 

they all appear to join the central zone.

Externally, stenothecoids vary from relatively 

smooth shells to elongate oysterlike forms ornamented by divergent angular folds in the shell (Aksarina, 1968). These folds interlock at the valve 

margins and may be homologous with radial markings on the interiors of the smoother shells. Yochelson interpreted Stenothecoides as a brachiopodlike 

mollusk. Runnegar and Pojeta (1974) offered the 

alternative suggestion that it may have been a bivalved monoplacophoran, the lower (smaller?) 

valve being formed by the sole of the foot. A few 

living limpets form a second valve in this way, although in the limpets, the lower valve is cemented to 

rocks.

MOLLUSCAN SUBPHYLA

Stasek (1972) theorized that the extant mollusks 

are the progeny of three lineages that separated before the phylum was well established. He noted that 

no known intermediate forms, fossil or living, bridge 

the "enormous gaps between any two of the three 

lineages." He therefore treated each as a separate 

subphylum. They are: (1) the subphylum Aculifera,
PHYLOGENY 45

containing only the class Aplacophora, derived from 

the most primitive of the ancestors of the Mollusca; 

(2) the subphylum Placophora, containing only the 

class Polyplacophora and emphasizing the pseudometamerism of its more advanced premollusk ancestor; and (3) the subphylum Conchifera, containing the class Monoplacophora and the other classes 

derived from it.

We have no expert knowledge of the aplacophoran 

and polyplacophoran mollusks, but we agree with 

Stasek that major differences exist between these 

organisms and other mollusks. We adopt his basic 

subdivisions of the phylum but suggest that the 

Conchifera can itself be separated into two major 

lineages worthy of the rank of subphylum (fig. 13). 

The fossil record indicates that the Monoplacophora 

gave rise to the Gastropoda, Cephalopoda, and Rostroconchia, and that the Pelecypoda and Scaphopoda 

are derived from the Rostroconchia. These last three 

classes thus form a lineage that diverged from the 

Monoplacophora in the Early Cambrian. They emphasized a shell that in all groups is primitively 

open at both ends, allowing the gut to remain relatively straight, and having an anterior mouth and 

posterior anus. We coined the term Diasoma 

(through-body) for the subphylum containing the 

three classes Rostroconchia, Pelecypoda, and Scaphopoda (Runnegar and Pojeta, 1974). The remaining 

three classes (Monoplacophora, Gastropoda, and 

Cephalopoda) emphasize a conical univalved shell,

usually twisted into a spiral. The relatively small 

single shell aperture forces the anus to lie close to 

the mouth, and the gut is bent into a U. We use the 

name Cyrtosoma (hunchback-body) for the subphylum containing these three classes (Runnegar and 

Pojeta, 1974). Strictly speaking, the cyrtosomes are 

the ancestors of the diasomes, but in fact both subphyla appeared and began to diversify within a few 

millions of years in the Early Cambrian. The Cambrian-Ordovician record of molluscan higher taxa is 

shown in figure 14.

GLOSSARY OF MORPHOLOGICAL TERMS

acline. Perpendicular to hinge or almost so.

adductor muscle. Muscle used to draw the two halves of a 

bivalved shell together; believed to have developed by 

cross-fusion of distal ends of opposing pallial retractor 

muscles (pi. 22, figs. 1, 2).

anterior. Edge of shell having gape and commissural denticles (Eopteriidae, Conocardiidae) (pi. 24, fig. 14; pi. 40, 

fig. 6); or end of shell having pegma (Ribeiriidae, Technophoridae) (pi. 6, fig. 7; pi. 11. fig. 22).

anterior branch. Part of pallial line extending dorsally from 

the pallial junction toward the midline (pi. 53, fig. 1).

anterior clefts. Tension fractures formed during growth on 

either side of shell in front of beak (pi. 4. fig. 9; pi. 28, 

fig. 17).

anterior gape. Opening at anterior end of shell (pi. 2, fig. 

12; pi. 6, fig. 5; pi. 24, fig. 14; pi. 28, fig. 15; pi. 40, fig. 

6; pi. 43, fig. 13).

anterior umbonal cavity. Part of umbonal cavity of ribeirioids in front of pegma (pi. 5, fig. 9).

Aldanella. SUBPHYLUM

Latonchella

I PRIMITIVE 

MONOPLACOPHORA MOLLUSK

Ribeiria

Knightoconus 

^ Plectronoceras

DIASOMA

Pinnocaris

SUBPHYLUM

Anabarella

CYRTOSOMA

'\

Eopteria 

Cycloconcha

FIGURE 13. Schematic view of the origin of the univalved and bivalved molluscan classes. Most drawings are based on 

internal molds of the shells. Thick lines show extent of shell apertures; stippled areas represent muscle insertions; 

shaded areas show probable position of gut, and mouth is indicated by asterisk. From Runnegar and Pojeta, 1974, figure 4; Copyright 1974 by the American Association for the Advancement of Science, published with permission.
46 PALEONTOLOGY OF ROSTROCONCH MOLLUSKS

apertural plate. Internal subcircular disk attached to both 

valves behind the anterior gape of some eopteriids; a modified pegma (pi. 29, figs. 14,15 ).

apertural (longitudinal) shelves. Curved plates of outer 

shell layer projecting horizontally across the snout region 

of some eonocardioids (pi. 43, figs. 12, 13).

beak. Projecting juvenile part of shell (pi. 6, fig. 7).

bivalved shell. Shell having two obviously expanded lateral 

lobes (valves), not necessarily distinguished in early ontogeny.

body of shell. Inflated part of shell between snout and

rostrum (pi. 43, fig. 5).

carina. Angulation of umbo (pi. 29, figs. 6, 7; pi. 50, fig. 38). 

comarginal. Feature on exterior surface of shell parallel to

growing margin.

commissure. Growing edge of shell. 

commissural (marginal) denticle. Visible part of submerged

rib immediately inside commissure (pi. 34, figs. 9, 13). 

dissoconch. Postlarval shell.

PRECAMBRIAN 

VENDIAN-EDIACARAN

FIGURE 14. Historical record of the initial radiation of the Mollusca, scaled against time divisions based primarily on the 

succession of fossil archaeocyaths and trilobites. The two largest molluscan subphyla (Cyrtosoma, fine-shaded columns, 

and Diasoma, coarse-shaded columns) separated in the Early Cambrian. Modified from Runnegar and Pojeta, 1974, figure 1.
GLOSSAEY OF MORPHOLOGICAL TERMS 47

divaricate. Exterior ornament which is neither simply radial

nor simply comarginal (pi. 11, fig. 16; pi. 14, fig. 2). 

dorsal. Fused junction of midsagittal plane passing between

valves. 

height. Distance between two planes parallel to hinge axis

and perpendicular to plane of symmetry, which just touch

most dorsal and ventral parts of shell.

hinge. Dorsal margin of shell which rotates during growth. 

hinge axis. Imaginary line about which the valves rotate

during growth. 

hood. Curved lamellose plates connected to carinae in Conocardiidae; growing edges form tubular extension of ventral orifice (=00liar, schleppe, eventail, fringe, Kragen)

(pi. 45, fig. 14; pi. 47, fig. 1; pi. 48, fig. 2). 

inflation. Distance between two planes parallel to midsagittal plane, which just touch the lateral edges of the

shell. 

insertion, insertion area. Place where a muscle is attached

to the shell (=muscle scar). 

length. Distance between two planes perpendicular to hinge

axis and just touching anterior and posterior extremities

of shell. 

longitudinal clefts. Rostral clefts that are subparallel to the

rostrum (pi. 40, fig. 5; pi. 43, fig. 10).

median muscles. Single anterior and posterior pedal retractor muscles inserted across the dorsal midline of the

shells of ribeirioids (pi. 6, figs. 4, 14). 

muscle impression. Mold of muscle bundle on interior of

shell. 

muscle track. Depression of inner surface of shell caused

by thinning of shell layers over underlying myostracum;

shows direction of movement of muscle insertion during

growth.

myostracum. Shell layer formed at muscle-insertion area, 

opisthodetic. Wholly behind the protoconch. 

pallial junction. Junction of anterior and posterior branches

of pallial line (pi. 53, fig. 1). 

pallial line. Linear, continuous or discontinuous insertion

area of radial muscles of mantle (pi. 22, figs. 1, 2, 3, 4, 13). 

pallial muscles. Radial muscles of the mantle attached to

the shell. 

pallial protractor muscles. Radial muscles of the mantle

that serve to protract the mantle edge (pi. 47, fig. 12). 

pallial retractor muscles. Radial muscles of the mantle that

serve to retract the mantle edge (pi. 20, figs. 10, 11). 

pallial sinus. Embayment of pallial line due to retreat of

pallial muscle insertions away from commissure (pi. 22,

figs. 1,2,3,4, 13). 

pedal muscles. Muscles of the foot (pi. 5, fig. 4; pi. 6, fig.

14; pi. 22, figs. 5, 6). 

pegma. Plate connecting right and left valves in umbonal

part of shell (pi. 4, figs. 21, 22; pi. 5, figs. 2, 4); supports

large muscle in ribeirioids. 

posterior. End of shell opposite that having anterior gape

and (or) pegma. 

posterior branch. Posterior part of pallial line extending

dorsally from the pallial junction along the anterior slope

(pi. 53, fig. 1). 

posterior clefts. Tension fractures formed during growth on

either side of the shell behind the beak (pi. 40, fig. 5). 

posterior gape. Relatively large opening at posterior end of

shell (pi. 6, fig. 6).

posterior umbonal cavity. Part of umbonal cavity of ribeirioids behind pegma (pi. 6, fig. 15).

primary pedal retractor muscles. Relatively large bilaterally paired pedal muscles inserted on the body of the shell 

of advanced rostroconchs (pi. 22, figs. 1, 2, 5, 6).

prosocline. Shells having demarcation line inclined posteriorly.

prosodetic. Anterior to protoconch.

protoconch. Larval shell (pi. 41; pi. 47, figs. 13-15).

rostral area. Area surrounding rostrum, bordered by hood, 

carina, or prominent rib.

rostral clefts. Elongate tension factures bordering or crossing the dorsal part of the rostrum (pi. 40, fig. 5).

rostral orifice. Hole in commissure at end of rostrum (pi. 

43, fig. 11).

rostral structure. Curved, hoodlike structure generated at 

rostral orifice of some conocardioids (see hood).

rostrum. Tubular extension of posterodorsal part of shell 

(pi. 39, fig. 3; pi. 43, fig. 5).

secondary pedal retractor muscles. Relatively small bilaterally paired pedal muscles inserted on the body of the 

shell of advanced rostroconchs (pi. 22, figs. 5, 6).

shell muscles. Muscles inserted on the shell that are used 

to control the foot and support the visceral mass.

side muscles. Lateral pedal and (or) visceral muscles of 

ribeirioids; insertions form left and right linear connections between anterior and posterior median muscle insertions (pi. 6, fig. 8; pi. 7, fig. 1; pi. 8, fig. 14; pi. 12, 

figs. 13, 17).

snout. Enlarged anterior part of shell, separated from body 

by sulcus and differences in sculpture (pi. 38, fig. 2; pi. 

43, fig. 7).

submerged ribs. Ribs generated by commissural denticles 

and covered by growth of inner shell layers: (pi. 43, fig. 1; 

pi. 45, fig. 4; pi. 50, fig. 2).

transverse clefts. Clefts that cross the rostrum (pi. 40, fig. 

5).

umbo. Dorsal projection of valve above protoconch (pi. 42,

fig. 1).

ventral. Part of shell opposite fused dorsal margin. 

ventral orifice(s). Small aperture(s) in commissure between

rostrum and anterior gape (pi. 24, fig. 15).

SYSTEMATIC PALEONTOLOGY

SYNOPTIC CLASSIFICATION OF KNOWN 

ROSTROCONCH MOLLUSKS

Phylum MOLLUSCA

Subphylum DIASOMA

Class ROSTROCONCHIA 

Order RIBEIRIOIDA

Family RIBEIRIIDAE 

Ribeiria 

HerauUipegma 

Pinnocaris 

Ribeirina, 

Wanwania 

Watsonella,

Family TECHNOPHORIDAE 

Technophorus 

Anisotechnophoms 

Myocaris 

Oepikila 

Tolmachovia
48 PALEONTOLOGY OF ROSTROCONCH MOLLUSKS

Order ISCHYRINIOIDA

Family ISCHYRINIIDAE 

Ischyrinia 

Eoischyrina 

Pseudotechnophorus 

Order CONOCARDIOIDA

Superfamily EOPTERIACEA 

Family EOPTERIIDAE 

Eopteria 

JBuchasma 

Wanwanella 

Wanwanoidea

Superfamily CONOCARDIACEA 

Family CONOCARDIIDAE 

Conocardium 

Arceodomus

Family BRANSONIIDAE 

Bransonia 

Mulceodens 

Pseudoconocardium 

Family HIPPOCARDIIDAE 

Hippocardia 

Bigalea

Rostroconchia incertae sedis 

Euchasmella 

Myona 

Pseudoeuchasma

Phylum MOLLUSCA Cuvier, 1797 

Subphylum DIASOMA Runnegar and Pojeta, 1974

Class ROSTROCONCHIA Pojeta, Runnegar, Morris, and Newell, 1972

Diagnosis. Mollusks with an uncoiled and untorted univalved larval shell which straddles the 

dorsal midline, and a bivalved adult shell with one 

or more shell layers continuous across the dorsal 

margin so that a dorsal commissure is lacking.

Stratigraphic distribution. Lower Cambrian 

(Georgien)-Upper Permian (Makarewan). We 

agree with Morris (1967) that the Triassic species 

placed in Conocardium by Healy (1908) are pelecypods probably belonging to the Poromyacea or the 

Burmesiidae.

Order R1BE1RIOIDA Kobayashi, 1933

Diagnosis. Rostroconchs with all shell layers 

continuous across the dorsal margin, an anterior 

pegma, and a dominant posterior growth component; 

musculature consists of anterior and posterior median pedal retractor muscles connected by right and 

left side muscles.

Stratigraphic distribution. Lower Cambrian 

(Georgien)-Upper Ordovician (Ashgillian).

Discussion. This order contains two families and 

11 genera and includes the stratigraphically oldest,

morphologically simplest, and phylogenetically most 

primitive rostroconchs. All the forms included here 

have previously been classified as bivalved (conchostracan) arthropods (Ulrich and Bassler, 1931; Kobayashi, 1933; Salter, 1864; Etheridge, 1878). Molluscan nature of these forms is indicated by the 

presence of a protoconch, comarginal growth increments growth increments on the muscle scars, and 

a pallial line in some forms.

Family RIBEIRIIDAE Kobayashi, 1933

Diagnosis. Ribeirioids with anterior and posterior shell gapes and lacking radial ornament.

Stratigraphic distribution. Lower Cambrian 

(Georgien)-Upper Ordovician (Ashgillian). The 

Stratigraphic range of each species is shown in table 

1.

Discussion. Our concept of this family differs 

significantly from that of Kobayashi (1933) in that 

he included all nonconocardiacean rostroconchs in 

the Ribeiriidae. In 1936, he maintained the same concept of the family but used the name Eopteriidae 

Miller (1889). As used herein, this family contains 

six known genera and approximately 23 known species. It is presently known from all continents except 

Antarctica, and is known from a greater number of 

geographic localities in North America than on the 

other continents.

Genus RIBEIRIA Sharpe, 1853

Plates 4-9, 30, 31

1853. Ribeiria Sharpe, in Ribeiro, Geol. Soc. London Quart.

Jour., v. 9, p. 157. 

1865. Ribeiria Sharpe [partim], Billings, Palaeozoic Fossils,

v. 1, p. 339. 

1877. Ribeiria Sharpe, Tromelin, Soc. Linnean Normandie

Bull, ser. 3, v. 1, p. 35. 

1886. Ribeiria Sharpe [partim], Whitfield, Am. Mus. Nat.

History Bull., v. 1, p. 343.

1889. Ribeiria Sharpe [partim], Miller, North American 

Geology and Paleontology, p. 566.

1890. Ribeiria Sharpe [partim], Etheridge, Woodward, and 

Jones. British Assoc. Adv. Sci., Kept. 59th Mtg. 

1889, p. 66.

1900. Ribeiria Sharpe [partim], Cleland, Bulls. Am. Paleontology, v. 3, no. 13, p. 20.

1904. Ribeiria Sharpe [partim], Schubert and Waagen, K. 

K. Geol. Reichsanstalt Jahrb., v. 53, p. 41.

1904. [Non] Ribeiria Clarke, New York State Mus. Mem. 6, 

pt. 2, p. 406.

1924. Ozomia Walcott, Smithsonian Misc. Colln., v. 67, no. 9, 

p. 531.

1933. Ribeiria Sharpe [partim], Kobayashi, Tokyo Imp. 

Univ., Fac. Sci. Jour., sec. 2, v. 3, pt. 7 p. 289.

1935. Ribeiria Sharpe, Thoral, Contr. etude paleont. Ordovician inferieur *** Montagne Noire, p. 200.

1957. Ribeiria Sharpe, Yang, Acad. Sinica, Inst. Paleontology, 

p. 320.
SYSTEMATIC PALEONTOLOGY 49

SPECIES

TIME SCALE

05 05 05

Cincinnatian 

(Caradocian-Ashgillian)

Wildernessian-Shermanian 

(Caradocian)

Marmprian-Porterfieldian 

(Llanvirnian-Caradocian) V7/

Canadian-Whiterockian 

(Tremadocian-Arenigian)

Mindyallan-Trempealeauan

MIDDLE CAMBRIAN

EARLY CAMBRIAN

TABLE 1. Range chart showing the known stratigraphic distribution of all species of Ribeiriidae recognized herein

[Species roughly arranged according to stratigraphic order, from oldest to youngest, for each genus]
50 PALEONTOLOGY OF ROSTROCONCH MOLLUSKS

1965. [?] Technophorus Branisa, Bolivia Serv. Geol. Bol. 6, 

p. 76.

Type species. Ribeiria pholadiformis Sharpe, 

1853 (p. 158) by monotypy.

Diagnosis. Posteriorly elongated ribeiriids in 

which the dorsal and ventral margins are not subparallel and which lack rugose comarginal ornament.

Stratigraphic distribution. Upper Cambrian 

(Mindyallan)-Upper Ordovician (Ashgillian).

Discussion. It is not our intention to describe 

each of the species that we regard as belonging to 

Ribeiria. We have not been able to obtain specimens 

of certain species, and for knowledge of these spe^ 

cies we are totally dependent upon an aging literature. The known material of some species is not well 

preserved, and detailed description would provide 

little more information than the figures provided on 

our plates. In the following section, we list all the 

species known to us, figure and diagnose those for 

which we have been able to obtain adequate material, 

make various comments, and provide descriptions 

only for those species that are newly named herein.

Ribeiria pholadiformis Sharpe, 1853

Plate 7, figures 3-16

Diagnosis. Ribeiria with shell thickening above 

posterior median pedal retractor muscle, producing 

a prominent notch in the posterior dorsal margin of 

internal molds. Also in internal molds, apical part of 

shell usually projecting well above rest of dorsum.

Types and materials. This is the type species of 

the genus. It is based upon a syntypic suite of which 

we choose as the lectotype the specimen figured by 

Sharpe, 1853, on his plate 9, figures 17 b-c (GB 

7798), which is figured herein on plate 7, figures 3-7. 

The paralectotypes are figured herein on plate 7, 

figures 8-10 (BM PL 4176a, b; BM PL 4177). We 

had three other specimens of this species (pi. 7, figs. 

11-16) in addition to the type material.

Stratigraphic distribution. On the basis of the 

geographic information given by Sharpe (1853, p. 

158) and the associated mollusks, many of which 

were redescribed by Babin (1966), the type material 

of R. pholadiformis is probably Llandeilian (Middle 

Ordovician) in age from Portugal. Two specimens 

of the species from Normandy, France (pi. 7, figs. 

11, 12), are at the Sedgwick Museum, University of 

Cambridge, England, and are listed as middle Arenigian (Early Ordovician) in age.

Ribeiria apusoides Schubert and Waagen in Perner, 1903

Plate 5, figures 1-14; plate 6, figures 1-12, 14,15; 

plate 7, figures 1, 2; plate 30, figures 1-5; plate 31, figures 1-5

Diagnosis. Large Ribeiria with gently concave 

dorsal margin lacking a prominent posterior dorsal 

notch.

Types and materials. R. apusoides is based upon 

a syntypic suite, of which we choose as the lectotype 

the specimen figured by Schubert and Waagen, in 

Perner, 1903, plate 49, figures 18-20 (Schubert and 

Waagen, 1904, pi. 1, fig. 9). A plastotype (USNM 

209402) of this specimen is shown herein on plate 6, 

figures 1-4. Plastotypes of paralectotypes of the species are shown herein on plate 5, figures 9-11, 13, 14. 

In addition to the plastotypes, we had 16 other specimens of R. apusoides to examine.

Stratigraphic distribution. According to Kfiz 

(oral commun., July 1973), the type material of this 

species is from the Caradocian (Middle-Late Ordovician) of Bohemia, Czechoslovakia. Also according 

to Kfiz, the specimen shown herein on plate 6, figure 

5, may be Llanvirnian (Middle Ordovician) in age; 

however, this is uncertain. So far as known, the 

species is limited to the Middle and Upper Ordovician rocks of Bohemia. The specimen assigned to 

R. apusoides by Termier and Termier (1950, pi. 184, 

fig. 45) from the Llanvirnian of Morocco does not 

belong to this species as it has a gently convex dorsal margin.

Ribeiria australiensis n. sp. 

Plate 4, figures 26-29

Description. Small Ribeiria with straight to 

gently concave dorsal margin, posteriorly attenuated; shell gaping posteriorly, ventrally, and anteriorly, with anterior gape extending dorsally to 

protoconch; protoconch terminal. The only internal 

feature presently known is a small pegma.

Types. The holotype (BMR CPC 14670) is shown 

on plate 4, figures 27, 29; it is 9.4 mm long and 5.9 

mm high. One paratype (BMR CPC 14671) is 

shown on plate 4, figures 26, 28; it is 9.6 mm long 

and 5.7 mm high.

Type locality. All specimens of this species are 

presently known only from one locality, Australian 

Bureau of Mineral Resources locality G 128 (Opik, 

1967); western Queensland, Australia, lat. 22°, 17' 

S., long 139°, 01' E., Glenormiston 1:250,000 Geological Series Sheet SF 54-9 (Casey and others, 

1965). The locality is indicated on the Glenormiston 

sheet. The specimens are from the Mungerebar 

Limestone.
SYSTEMATIC PALEONTOLOGY 51

Stratigraphic distribution. According to Opik 

(1967) the age of G-128 is Mindyallan (early Late 

Cambrian). R. australiensis n. sp. is only one of six 

known species of Cambrian rostroconchs and is the 

oldest known species of the genus Ribeiria.

Etymology. The species name is derived from 

Australia.

Ribeiria bassleri Kobayasbi, 1933

Discussion. This species is known from only one 

specimen which was figured by Kobayashi (1933, pi. 

4, figs. 4a, b). Although we have seen a replica of 

this specimen, it is not well executed, and we can do 

little more than to list the species here.

Stratigraphic distribution. Kobayashi (1933, p. 

292) listed the species as coming from the "Wanwankou dolomite; Wan-wan-kou in the Niuhsintai 

Basin, South Manchuria." On p. 259, he indicated 

that the Wanwankou Dolomite is assigned to the 

Wanwanian Stage (Early Ordovician).

Ribeiria bussacensis Tromelin, 1877

Discussion. This species name is listed by Tromelin (1877, p. 35) and Etheridge, Woodward, and 

Jones (1890, p. 67) as a synonym of R. pholadiformis Sharpe and is,credited to Sharpe. The Sharpe 

reference given by both papers that cite R. bussacensis is exactly the same as that for R. pholadiformis down to plate and figure number. Apparently R. 

bussacensis was intended as a substitute name for 

R. pholadiformis. To our knowledge, Sharpe never 

used R. bussacensis in print, and the reason for the 

possible substitute name is not given by either Tromelin or Etheridge, Woodward, and Jones.

Ribeiria calcifera Billings, 1865 

Plate 4, figures 1-24

Diagnosis. Ribeiria with convex dorsal margin 

and anterior clefts.

Types and materials. This species is also based 

on a syntypic series, of which we choose the specimen shown here on plate 4, figures 4-6 as the lectotype (GSC 469). Paralectotypes are shown on plate 

4, figures 1-3, 7-12 (GSC 469a, b, d). In addition to 

the type suite, we figure four other specimens of the 

species (pi. 4, figs. 13-24).

Stratigraphic distribution. R. calcifera is known 

from several localities in the Beekmantown Group 

(Lower Ordovician) of Ontario, Canada. Recent 

work by Yochelson and Copeland (1974) indicates 

that the beds containing this species are latest Canadian (late Early Ordovician) in age in Ontario. 

Two specimens from the Tanyard Formation of 

Texas (lower Lower Ordovician) are herein also

assigned to R. calcifera (USNM 127908, 127909); 

these specimens were previously figured by Cloud 

and Barnes (1948). The Texas specimens show that 

the pegma of R. calcifera is almost horizontal.

Ribeiria complanata Salter, 1866 

Plate 9, figure 10

Discussion. This species is known only from the 

holotype (GB 12434), which is not markedly attenuated posteriorly and which has a nearly straight 

dorsal margin. This specimen is from the lower 

Llandeilian (Middle Ordovician) of North Wales.

Ribeiria compressa Whitfield, 1886

Plate 8, figures 1-5

Diagnosis. Narrowly convex Ribeiria with markedly straight dorsal margin.

Types and materials. The type material of R. 

compressa consists only of the holotype (pi. 8, figures 

1, 2; AM 491). We place in synonymy with R. compressa, the name R. nuculitiformis equilatera Cleland. We choose as the lectotype of R. nuculitiformis 

equilatera the specimen figured by Cleland (1900, 

pi. 16, fig. 15), which is figured herein on plate 8, 

figures 3-5 (PRI5081).

Stratigraphic distribution. The museum label 

lists the holotype of R. compressa as coming from 

the "Ft. Cassin bed, Fort Cassin, Vermont" (upper 

Canadian, upper Lower Ordovician). Cleland (1900, 

p. 22) listed R. nuculitiformis equilatera as coming 

from the "Calciferous [Beekmantown] at Fort Hunter, N.Y." (Lower Ordovician). We have found R. 

compressa to be abundant in the "Fonda Limestone 

Member" of the Tribes Hill Formation (lower Canadian; lower Lower Ordovician) of New York 

State.

Ribeiria conform!* Tromelin, 1877

Discussion. This name was first proposed as a 

nomen nudum by Salter, in Bigsby (1868, p. 141). 

The species has never been figured, and Tromelin 

(1877, p. 35) is the only author to have commented 

upon the form. He felt that it was probably synonymous with R. pholadiformis Sharpe (R. bussacensis). R. conformis is from the Budleigh-Salterton 

Pebble Bed, a Triassic unit which contains Caradocian (Middle-Upper Ordovician) fossils in the 

pebbles.

Ribeiria crassa (Thoral), 1935

Discussion. We have seen no specimens of this 

species, and to our knowledge it is known only from 

the material figured by Thoral (1935, pi. 10, figs. 

9a, b). Thoral placed the species in the genus Ribeir-
52 PALEONTOLOGY OF ROSTROCONCH MOLLUSKS

ella Schubert and Waagen, which we regard as 

synonymous with Technophorus Miller. We do not 

regard Ribeiria crassa as belonging to Technophorus 

because it lacks radial ornament. On his plate 10, 

Thoral listed the species as occurring in the "Tremadoc superieur-Arenig inferieur" (Lower Ordovician), St. Chinian, France. On his p. 209, figure 14, 

he gave the stratigraphic occurrence as "Tremadoc 

superieur (?)"; also on p. 209, under Horizon and 

Locality he listed R. crassa as occurring in the 

"Arenig inferieur."

Ribeiria inflate Schubert and Waagen, 1904

Discussion. This species is much like R. apusoides; we have seen no specimens of R. inflata. Schubert and Waagen (1904) felt that there might be 

intermediates between the two forms. It is probably 

best to consider R. inflata as a synonym of R. apusoides; both forms are known only from the Caradocian (Middle-Upper Ordovician) of Bohemia, 

Czechoslovakia.

Ribeiria lucan (Walcott), 1924

Plate 8, figures 14-24

Diagnosis. Ribeiria with pegma at high angle to 

dorsal margin and with side muscles bundled into 

discontinuous attachment areas.

Types and materials. This species is known only 

from the type suite, of which we choose the specimen 

herein figured on plate 8, figure 14, as the lectotype 

(USNM 209397). Paralectotypes are shown on plate 

8, figures 15-24.

Stratigraphic distribution. R. lucan is known 

only from the Mons Formation (Lower Ordovician) 

of Alberta, Canada.

Discussion. Walcott (1924) made this form the 

type species of his genus Ozomia, a name which may 

prove useful in the future. At present, however, 

Ribeiria lucan is well within the range of variation 

shown by species that we place in the genus Ribeiria.

Ribeiria magnifica Tromelin, 1877

Discussion. This name was first proposed as a 

nomen nudum by Salter, in Bigsby (1868, p. 141). 

The species has never been figured, and Tromelin 

(1877, p. 36) is the only author to have commented 

on the form. R. magnifica is from the BudleighSalterton Pebble Bed, a Triassic unit which contains 

Caradocian (Middle-Upper Ordovician) fossils in 

the pebbles.

Ribeiria manchnrica Kobayashi, 1933

Plate 8, figures 6-11

Diagnosis. Tumid Ribeiria with small rounded 

pegma.

Types and materials. This species is known only 

from the material described by Kobayashi (1933, p. 

291). We were able to obtain replicas of the holotype 

(pi. 8, figs. 6, 7; USNM 209394) and of a previously 

unfigured paratype (pi. 8, figs. 8-11; USNM 

209395). In addition, we saw two poorly preserved 

specimens of the species which are not figured 

herein.

Stratigraphic distribution. Kobayashi (1933, p.

291) listed the species as coming from the "Wanwankou dolomite; Wan-wan-kou in the Niuhsintai 

Basin, South Manchuria." He (1933, p. 259) indicated that the Wanwankou Dolomite is assigned to 

the Wanwanian Stage (Lower Ordovician).

Ribeiria manchurica pennata Kobayashi, 1933

Discussion. We have seen no specimens of this 

form, and the only known figures are those of Kobayashi (1933, pi. 9, figs. 4a, b). Kobayashi (1933, p.

292) noted that: "If complete specimens [of R. 

manchurica pennata] be procured, it may not be 

possible to separate this specifically from the typical 

form [R. manchurica]." Probably this form should 

be regarded as a synonym of R. manchurica. The 

Stratigraphic occurrence and locality are the same as 

for R. manchurica.

Ribeiria parva Collie, 1903

Plate 9, figures 7-9

Diagnosis. Ribeiria with subcircular lateral outline.

Types and materials. R. parva is known only 

from the holotype (YU 7933), which is figured herein on plate 9, figures 7-9.

Stratigraphic distribution. This species is known 

only from the Beekmantown Formation (Lower Ordovician), Beliefonte, Pennsylvania.

Ribeiria personata Thoral, 1935

Discussion. We have seen no specimens of this 

species. Thoral (1935, p. 201) gave the name of the 

species as R. personata; on the explanation for his 

plate 10, figures 6a, b, he gave the name as "R. personata forme typica." Thoral (p. 202) gave the occurrence of the form as "Tremadoc superieur ou de 

la base de 1'Arenig des environs de Saint Chinian," 

France.

Ribeiria personata lata Thoral, 1935

Discussion. We have seen no specimens of this 

form. Thoral (1935, pi. 10, fig. 7) gave the occurrence as: "Arenig inferieur, St. Chinian" (Lower 

Ordovician), France.
SYSTEMATIC PALEONTOLOGY 53

Ribeiria personata obsolete Thoral, 1935

Discussion. We have seen no specimens of this 

form. Thoral (1935, p. 205, fig. 12) gave the stratigraphic occurrence as: "Tremadoc superieur-Arenig 

inferieur" (Lower Ordovician), France.

Ribeiria soleaeformis Thoral, 1935

Discussion. We have seen no specimens of this 

form. Thoral (1935, pi. 10, fig 8) gave the occurrence as: "Tremadoc superieur-Arenig inferieur, St. 

Chinian" (Lower Ordovician), France.

Comments about the species of Ribeiria proposed 

by Thoral (1935). R. soleaeformis is much like R. 

pholadiformis Sharpe (1953) in shell shape, in having a projecting apical area in internal molds, and 

in having a prominent notch in the posterior dorsal 

margin of internal molds. R. soleaeformis is probably a synonym of R. pholadiformis. The other species proposed by Thoral appear to be based on incomplete specimens which preserve only the anterior 

two-thirds of the valves. They are much like R. pholadiformis in shape and have a projecting apical 

area; it seems likely that they are synonyms of R. 

pholadiformis. Because we have not seen Thoral's 

original material, it is difficult to synonymize his 

names with R. pholadiformis, however, on the basis 

of his figures, this synonymization seems likely. 

Forms similar to those figured by Thoral and to R. 

pholadiformis were figured by Gigout (1951, pi. 2, 

figs. 15-16) and Termier and Termier (1950, pi. 184, 

figs. 32-35) from the Llanvirnian and Llandeilian 

(Middle Ordovician) of Morocco.

Ribeiria taylori n. sp.

Plate 8, figures 12, 13

Description. Small Ribeiria with colinear parts 

of the hinge anterior and posterior to the beak. Beak 

projecting but little above the dorsal margin, not 

recumbent.

Typ.e. The holotype (USNM 209396) is shown 

on plate 8, figures 12, 13. It is an incomplete specimen with the posterior end missing. We have polished the posterior face in an effort to examine shell 

microstructure. The microstructure was not visible 

although shell layers were recognizable.

Type locality. The holotype is from USGS loc. 

470B (old series), Hall Farm, 1 mile northeast of 

Whitehall, N.Y. (Taylor and Halley, 1974, p. 32).

Stratigraphic distribution. The species is from 

the Whitehall Formation, Saukia Zone, probably Saukiella serotina (Trempaleauan, Upper Cambrian), 

of New York. According to Taylor and Halley 

(1974), the Cambrian-Ordovician boundary occurs 

in the Whitehall Formation.

Etymology. The species name is proposed for 

M. E. Taylor, U.S. Geological Survey, who brought 

the holotype to our attention.

Ribeiria turgida Cleland, 1903 

Plate 9, figure 1

Discussion. This form is known only from a 

specimen in the collections of the U.S. National Museum (USNM 84630; pi. 9, fig. 1), which is labeled 

holotype. The specimen does not resemble either of 

the figures given by Cleland (1903, pi. 3 figs. 6, 7). 

We assume that the specimen is correctly labeled; 

however, it is incomplete, and it is thus difficult to 

determine the concept indicated by this name. The 

museum label gives the occurrence of the holotype 

as: "Tribes Hill Is., Canajoharie?, New York" (Lower Ordovician).

Ribeiria spp.

Plate 4, figure 25; plate 6, figure 13; 

plate 7, figures 17,18; plate 9, figures 2-6

Discussion. The forms figured and discussed under this heading are based upon incomplete or poorly 

preserved specimens of Ribeiria. They do add data 

to the stratigraphic and geographic distribution of 

the genus. The specimen shown on plate 4, figure 25, 

is from the Lower Ordovician part (Warendian) of 

the Ninmaroo Formation at northern peak of Digby 

Peaks, 60 miles north of Boulia, Queensland, Australia. The specimen shown on plate 6, figure 13, is a 

paralectotype of R. apusoides Schubert and Waagen 

from the Ashgillian (Upper Ordovician) rocks of 

Bohemia, Czechoslovakia; it differs from other specimens assigned to R. apusoides in its straight dorsal 

margin and in its length-height ratio. It is also the 

youngest known specimen of the genus Ribeiria.

The specimens shown on plate 7, figures 17, 18, are 

from the Lower Ordovician of Utah; they are both 

incomplete posteriorly. The specimens shown on 

plate 9, figures 2-6, are from the Stonehenge Formation (Lower Ordovician) of Maryland.

Genns HERAULTIPEGMA new genus

Plate 2

1920. [Noi\]Heraultia Villeneuve, Soc. Entomol. Belgique,

Annales v. 60, p. 119. 

1935. Heraultia Cobbold, Annales and Mag. Nat. History,

ser. 10, v. 16, p. 37. 

1974. Heraultia Cobbold, Runnegar and Pojeta, Science, v.

186, p. 315.

1974. Heraultia Cobbold, Pojeta and Runnegar, Am. Scientist, 

v. 62, p. 711.

1975. Heraultia Cobbold, Pojeta, Bulls. Am. Paleontology, v. 

67, p. 375.
54 PALEONTOLOGY OF ROSTROCONCH MOLLUSKS

Type species. Heraultia varensalensis Cobbold, 

1935 (p. 38), is designated the type species of the 

genus Heraultipegma,

Diagnosis. Posteriorly elongate ribeiriids with a 

small pegma, wide anterior, posterior, and ventral 

shell gapes, and prominent rugose comarginal ornament.

Stratigraphic distribution. Upper Lower Cambrian (Georgien).

Geographic distribution. The genus is unequivocally known only from the St. Genies de Varensal 

area in the Herault district of France. One specimen, which was placed in Fordilla troyensis by 

Shaler and Foerste (1888), from the Lower Cambrian of Massachusetts has the shape of Heraultipegma; it may belong to that genus or to Watsonella, 

but nothing is known of its ornament or shell gapes.

Discussion. The new generic name Heraultipegma is proposed for those rostroconchs placed in 

Heraultia by Cobbold (1935). The name Heraultia 

Cobbold is a junior homonym of Heraultia Villeneuve (1920) which was used for a dipteran insect.

Etymology. Herault, a region of France; pegma, 

Greek, meaning fastened or fixed; also a structure in 

rostroconchs. Gender neuter.

Heraultipegma varensalense (Cobbold), 1935

Plate 2, figures 1-13

Diagnosis. Small Heraultipegma with about 

equally developed anterior, ventral, and posterior 

shell gapes.

Types and materials. We have not seen Cobbold's 

(1935) types of this species. However, S. C. Matthews of the University of Bristol, England, has generously given us topotypes of the species; these topotypes are figured herein (USNM 209414-209417).

Stratigraphic distribution. All specimens of H. 

varensalense are presently known only from the 

Georgien (Lower Cambrian) rocks near St. Genies 

de Varensal, France.

Genus PINNOCARIS Etheridge, 1878 

Plates 9, 10

1878. Pinnocaris Etheridge, Royal Soc. Edinburgh Proc., v.

4, p. 167. 

1880. Pinnocaris Etheridge, Nicholson and Etheridge, Mon.

Silurian Fossils Girvan District in Ayrshire, v. 1, p.

207. 

1892. Pinnocaris Etheridge, Jones, and Woodward, Mon.

British Paleozoic Phyllopoda, pt. 2, p. 117. 

1895. Pinnocaris Etheridge, Jones, and Woodward, Geol.

Mag., Decade 4, v. 2, p. 542. 

1907. Pinnocaris Etheridge, Reed, Geol. Mag., Decade 5, v.

4. p. 110.

Type species. Pinnocaris lapworthi Etheridge, 

1878 (p. 169), by monotypy.

Diagnosis. Posteriorly elongated compressed 

ribeiriids with anterior clefts and with posterior end 

drawn out into a rostrum.

Stratigraphic distribution. Lower Caradocian 

(Middle Ordovician)-Ashgillian (Upper Ordovician).

Pinnocaris lapworthi Etheridge, 1878 

Plate 9, figures 13-23

Diagnosis. Pinnocaris with a nearly straight 

dorsal margin, a long straight rostrum, and rugose 

comarginal ornament.

Types and materials. This is the type species of 

the genus. It is based upon a syntypic series, of 

which we choose as the lectotype the specimen figured by Etheridge, 1878, on his plate 2, figure 5 

(BM In 20367) ; this specimen is figured herein on 

plate 9, figure 21. The paralectotypes are figured 

herein on plate 9, figures 20, 22 (BM In 20366, In 

20368). In addition, we figure four other specimens 

of the species.

Stratigraphic distribution. This species is presently known only from Scotland. It is from the Balclatchie Group which Whittington (1972) placed in 

the lower Caradocian (Middle Ordovician).

Pinnocaris americana n. sp. 

Plate 9, figures 11, 12

Description. Pinnocaris lacking rugose ornament, with a gently concave dorsal margin and a 

short posterior rostrum. The only known internal 

feature is the pegma.

Types. P. americana is presently known only 

from two specimens. The holotype is shown on plate 

9, figure 12 (USNM 209393) ; it is about 20 mm 

long and 7.5 mm high. The paralectotype (USNM 

209392) is shown on plate 9, figure 11; it is about 

20 mm long and 8 mm high. Both specimens show 

the anterior clefts.

Type locality. The museum label gives the locality as: "Elkader, Iowa."

Stratigraphic distribution. The museum label 

gives the horizon as: "Prosser limestone',(Middle 

Ordovician).

Etymology. The species name is derived from 

America.

Pinnocaris curvata Reed, 1907

Plate 9, figures 24, 25; plate 10, figures 1-10 

Diagnosis. Pinnocaris with a markedly concave 

dorsal margin.
SYSTEMATIC PALEONTOLOGY 55

Materials. We have not seen Reed's type material ; we figure seven other specimens of the species.

Stratigraphic distribution. P. curvata is presently known only from the Drummuck Group (Upper 

Ordovician) of Scotland.

Genus RIBEIRINA Billings, 1865

Plate 3 

1865. Ribeirina Billings [partim], Palaeozoic fossils, v. 1,

Geol. Survey Canada, p. 340.

1934. [Non] Ribeirina Parker, Monog. frogs Microhylidae, p. 

115.

Type species. Ribeirial longiuscula Billings, 

1865 (p. 341), designated herein.

Diagnosis. Posteriorly elongated ribeiriids with 

nearly parallel dorsal and ventral margins.

Stratigraphic distribution. Upper Canadian (upper Lower Ordovician).

Ribeirina longiuscula (Billings), 1865 

Plate 3, figures 15-23

Diagnosis. Ribeirina with small beak and with 

flaring shell margins to either side of the anterior 

gape.

Types and materials. The holotype of the species 

(GSC 470) is shown on plate 3, figures 21-23; it is 

about 32 mm long and 15 mm high. The species is 

known from only two specimens besides the holetype; these are shown on plate 3, figures 15-20.

Stratigraphic distribution. Two of the known 

specimens (GSC 470; ROM 26 cal.) of the species 

are labeled "Beekmantown" (Lower Ordovician), 

Ontario, Canada. The third specimen (USNM 

209413) is from the Oxford Formation (GSC loc. 

89453), Ontario, Canada; recent work by Yochelson 

and Copeland (1974) suggests that this specimen is 

latest Canadian (late Early Ordovician) in age.

Genus WANWANIA Kobayashi, 1933 

Plate 3

1933. Wanwania Kobayashi Tokyo, Imp. Univ. Fac. Sci.

Jour., v. 3, pt. 7, p. 282. 

1957. Wanwania Kobayashi, Yang, Chung-kuo piao chun hua

shih, p. 320.

Type species. Wanwania cambrica Kobayashi, 

1933 (p. 292), by original designation.

Diagnosis. Dorsoventrally elongated ribeiriids in 

which the shell is higher than long or is subquadrate.

Stratigraphic distribution. Upper Cambrian 

(Tsinania Zone, Yingtzu Series)-Lower Ordovician 

(Wanwanian) of Manchuria.

Wanwania cambrica Kobayashi, 1933

Plate 3, figures 5, 11-14

Diagnosis. Subquadrate Wanwania in which the 

length and height are subequal.

Materials. We had three plastotypes of this 

species to examine. The plastoholotype is figured on 

plate 3, figures 11-14 (USNM 209412), and a plastoparatype is shown on plate 3, figure 5 (USNM 

209409).

Stratigraphic distribution. According to Kobayashi (1933, p. 283), this species is known only from 

the: "Upper Cambrian, Tsinania zone, Paichia-shan, 

in the northern part of the Wuhutsui Basin and at 

Hsishan in the southern part of the same basin, at 

the neck of the Liaotung Peninsula, Manchuria." On 

p. 259, he showed the Tsinania zone as occurring in 

the lower Yingtzu Series. Jones, Shergold, and Druce 

(1971) show the Yingtzu Series as being late Late 

Cambrian in age.

Wanwania compressa Kobayashi, 1933

Plate 3, figures 6-9

Diagnosis. Small Wanwania in which the height 

is greater than the length, and with an anteriorly 

sinuate pallial line.

Materials. This species is known only from the 

holotype, of which we had a replica (USNM 

209410). The holotype is incomplete posteriorly, and 

the plastoholotype clearly shows the anterior gape 

(pi. 3, fig. 9), the pegma (pi. 3, fig. 7), and the pallial 

line (pi. 3, fig. 7).

Stratigraphic distribution. Wanwanian (Lower 

Ordovician). According to Kobayashi (1933, p. 284), 

W. compressa is from the Wanwankou Dolomite, 

Wan-wan-kou in the Niuhsintai Basin, south 

Manchuria.

Discussion. W. compressa is much like W. ambonychiformis and may be a synonym of that species. 

Kobayashi (1933) separated them on slight differences in shape. As we had only one plaster replica of 

each species to examine, we cannot be positive about 

the synonymy; however, it seems likely that the two 

names belong to the same form.

Wanwania ambonychifonnis Kobayashi, 1933

Plate 3, figure 10

Diagnosis. Large Wanwania in which the height 

is greater than the length.

Material Although Kobayashi (1933, p. 284) 

noted that this was a common form, we had only a 

replica of the holotype to examine (USNM 209411).

Stratigraphic distribution. Wanwanian (Lower 

Ordovician). Wanwankou Dolomite, Wan-wan-kou 

in the Niuhsintai Basin, south Manchuria.

Discussion. As noted above under W. compressa, 

this species is probably synonymous with that 

species.
56 PALEONTOLOGY OF ROSTROCONCH MOLLUSKS

Genus WATSONELLA Grabau, 1900 

Plate 3

1900. Watsonella Grabau, Boston Soc. Nat. History Occas. 

Papers, v. 4, pt. 2, p. 631.

1912. [Non] Watsonella Thiele, Deutsch. Sudpolar Exped. 

1901-03, v. 13, Zool. 5, p. 237.

1935. Watsonella Grabau, Cobbold, Ann. and Mag. Nat. History, ser. 10, v. 16, p. 38.

1938. Stenotheca Salter [partim], Resser, Smithsonian Misc. 

Colln., v. 97, no. 10, p. 24.

Type species. Watsonella crosbyi Grabau, 1900 

(p. 631), by original designation and monotypy.

Diagnosis. Small concentrically marked forms, 

probably with small anterior and posterior shell 

gapes.

Stratigraphic distribution. Lower Cambrian of 

eastern Massachusetts.

Discussion. Cobbold (1935) noted the similarity 

of Watsonella to Heraultipegma. His analysis was 

based on Grabau's (1900) figures of Watsonella, 

which are stylized; the known specimens of Watsonella are not as well preserved as indicated by 

Grabau's figures. It may be that Watsonella and 

Heraultipegma are synonymous, but the known material of Watsonella suggests that it had small anterior and posterior gapes, unlike the large gapes of 

Heraultipegma. On the basis of the known material 

of Watsonella, the genus is similar to such helcionellacean monoplacophorans as Anabarella.

Watsonella crosbyi Grabau, 1900 

Plate 3, figures 1-4

Discussion. The known material of this species 

is not well preserved. It does show that W. crosbyi 

is a laterally compressed form with comarginal ornament. We choose as the lectotype the specimen 

figured by Grabau (1900) on his plate 31, figure 9b. 

This specimen is herein figured on plate 3, figure 1.

Stratigraphic distribution. Grabau's specimens 

of W. crosbyi are all from Lower Cambrian boulders 

at Sandy Cove and Pleasant Beach, Cohasset, Mass.

Family TECHNOPHORIDAE Miller, 1889

Diagnosis. Ribeirioids with radial ornament, 

some with both divaricate and radial ornament.

Stratigraphic distribution. Upper Cambrian (Idamean)-Upper Ordovician (Richmondian). The 

Stratigraphic range of each species is shown in table 

2.

Discussion. This family contains five known genera and approximately 21 known species. It is known 

from all continents except Africa and Antarctica; 

more than half the known species occur in North 

America.

Genus TECHNOPHORUS Miller, 1889 

Plates 10-14

1889. Technophorus Miller, North American Geology and 

Palaeontology, p. 514.

1894. Technophorus Miller, Ulrich, Lower Silurian Lamellibranchiata of Minnesota, from Minnesota Geol. and 

Nat. History Survey Final Rept. v. 3, p. 612 [Published under separate cover prior to entire v. 3.]

1897. Technophorus Miller, Ulrich, Minnesota Geol. and Nat, 

History Survey Final Rept, v. 3, pt. 2, p. 612 [Reprinting of 1894 paper.]

1904. Ribeirella Schubert and Waagen, K.K. Geol. Reichsanst 

Jahrb., v. 53, p. 45.

1933. Ribeirella Schubert and Waagen, Kobayashi, Tokyo 

Imp. Univ. Fac. Sci. Jour., Sec. 2, 3, pt. 7, p. 292, 

316.

1933. Technophorus Miller, Kobayashi, Tokyo Imp. Univ. 

Fac. Sci., Sec. 2, v. 7, pt. 2, p. 299, 316.

1935. [Non] Ribeirella Thoral, Contr. etude Paleont. Ordovicien inferieur *** Montagne Noire, p. 208.

1936. Technophorus Miller, Kobayashi, Geol. Soc. Japan,

Jour. v. 43, p. 350, [?] 352. 

1936. Ribeirella Schubert and Waagen, Kobayashi, Geol. Soc.

Japan, Jour. v. 43, p. 350. 

1960. Technophorus Miller, Soot-Ryen, Norsk Geol. Tidsskr.,

v. 40, p. 125. 

1965. [Non?] Technophorus Branisa, Bolivia Serv. Geol. Bol.

6, p. 76.

Type species. Technophorus faberi Miller, 1889 

(p. 514), by original designation and monotypy.

Diagnosis. Small, equivalved, posteriorly elongate technophorids, with a single pegma which is at 

or nearly at a right angle to the dorsal margin, and 

with well-developed posterior radial ribs.

Stratigraphic distribution. Lower Ordovician 

(Wolungian)-Upper Ordovician (Richmondian).

Discussion. As with Ribeiria, and for the same 

reasons, it is not our intention to describe each of the 

species we regard as belonging to Technophorus. In 

the following section, we list all the species known 

to us, figure and diagnose those for which we have 

been able to obtain material, make various comments, and provide descriptions only for those species that are newly named herein. We have not been 

able to locate the holotypes of T. divaricatus Ulrich 

and T. extenuatus Ulrich and regard them as lost, 

nor have we been able to locate the type material of 

T. otoviensis Kobayashi. Of T. coreanica, (Kobayashi), we have seen only a replica of the holotype. 

We have significant new material of Technophorus 

from Australia, Bohemia, Indiana, Kentucky, Minnesota, Ohio, and Siberia.

Technophorus faberi Miller, 1889

Plate 10, figures 16-21; 

plate 11, figures 1-6

Diagnosis. Technophorus with two posterior
SYSTEMATIC PALEONTOLOGY 57

SPECIES

TIME SCALE

Cincinnatian 

(Caradocian-Ashgillian)

Wildernessian-Shermanian 

(Caradocian)

Marmorian-Porterfieldian 

(Llanvirnian-Caradocian)

Canadian-Whiterockian 

(Tremadocian-Arenigian)

Mindyallan-Trempealeauan

TABLE 2. Range chart showing the known stratigraphic distribution of all species of Technophoridae recognized herein

[Species roughly arranged according to stratigraphic order, from oldest to youngest, for each genus]
58 PALEONTOLOGY OF ROSTROCONCH MOLLUSKS

radial ribs and markedly concave dorsal margin in 

adults.

Types and materials. The species is based upon 

two syntypes, of which we choose the specimen herein figured on plate 11, figures 5, 6, as the lectotype 

(FM 8831). The paralectotype is shown on plate 10, 

figures 16, 17 (FM 8831). In addition to the type 

suite, we had about 30 other specimens of this species to examine; most of these were poorly preserved. 

We figure the four best preserved specimens on plate 

10, figures 18-21 and plate 11, figures 1-4.

Stratigraphic distribution. All the known material of the species is from Edenian and Maysvillian 

(Upper Ordovician) rocks in Ohio and Kentucky.

Technophorus bellistriatus Branson, 1909

Plate 11, figures 7-13

Diagnosis. Technophorus with reticulate ornament over the body of the shell and with divaricate 

ornament between the posterior ribs; the more anterior of the two posterior ribs weakly expressed.

Types and materials. The species is known from 

only two specimens; the holotype (FM 11551) is 

shown on plate 11, figures 10-13. The other specimen is shown on plate 11, figures 7-9 (FM 23942).

Stratigraphic distribution. T. bellistriatus is 

known from the "Auburn Chert" and Decorah Shale 

(Middle Ordovician) of Missouri.

Technophorus cancellatus Ruedemann, 1901 

Plate 11, figures 15-20, 23

Diagnosis. Technophorus with reticulate ornament over the body of the shell and with divaricate 

ornament between the posterior ribs; the more anterior of the two posterior ribs well developed.

Types and materials. The type suite of T. cancellatus contains six syntypes, of which the specimen 

shown herein on plate 11, figure 16, is chosen as the 

lectotype (NYSM 3190). In addition to these specimens, Ruedemann (1912) figured two hypotypes 

(NYSM 9890, 9891), which are shown herein on 

plate 11, figures 15, 19. We place in synonymy with 

T. cancellatus, T. punctostriatus quincuncialis Foerste, 1914; we choose as the lectotype (GSC 8415) of 

the latter species the specimen figured herein on 

plate 11, figure 23.

Stratigraphic distribution. Ruedemann's specimens of T. cancellatus are from the Snake Hill Formation (Middle Ordovician) of New York. The type 

material of T. punctostriatus quincuncialis is labeled 

as coming from the Upper Ordovician, Chambly, 

Quebec, Canada.

Technophorus cincinnatiensis Miller and Faber, 1894

Plate 12, figures 4-11

Diagnosis. Technophorus with two posterior 

radial ribs which do not reach the protoconch and 

with a prominent rostrum.

Types and materials. The holotype of the species 

is shown herein on plate 12, figures 4-6 (UCM 3886). 

We had four other specimens of this species, two of 

which form the type suite of Technophorus punctostriatus Ulrich, 1895 (USNM 46313, 209383), which 

species we regard as synonymous with T. cincinnatiensis. We choose as the lectotype of T. punctostriatus 

the specimen figured herein on plate 12, figure 7 

(USNM 46313).

Stratigraphic distribution. T. cincinnatiensis is 

known from Edenian and Maysvillian (Upper Ordovician) rocks of Ohio and Kentucky.

Technophorus coreanica (Kobayashi), 1934

Plate 11, figure 14

Discussion. This species is known only from the 

holotype, of which we had a replica (USNM 209389) 

to examine. It is a small internal mold which shows 

a nearly vertical pegma and either the side muscle or 

the ridge that parallels this muscle. Kobayashi 

(1934) questionably placed the form in Ribeiria; 

however, its shape and erect pegma indicate it should 

be placed in Technophorus.

Stratigraphic distribution. T. coreanica is from 

the Clarkella Zone (Lower Ordovician; Wolungian, 

Tateiwa, 1958, p. 16) of Saisho-ri, South Korea.

Technophorns divaricatns Ulrich, 1892a 

Plate 14, figures 2-5

Discussion. The holotype of this species could 

not be located, and we assume it to be lost. As figured 

by Ulrich (1892a, pi. 7, figs. 15, 16), it has one posterior rib and divaricate ornament impinging on 

this rib. According to Bassler (1915, p. 1258), T. 

divaricatus is from the Decorah Shale (Middle Ordovician) of Minnesota.

We have a specimen of Technophorus from the 

Decorah Shale of Minnesota (pi. 14, fig. 2) which 

shows divaricate ornament. It has two posterior 

radial ribs; however, the more anterior of these ribs 

is weakly expressed. This specimen is herein tentatively placed in T. divaricatus. In addition, we have 

two specimens from the Elkhorn Formation (Upper 

Ordovician) of Indiana, which have divaricate ornament (pi. 14, figs. 3-5). They have comarginal ornament similar to the specimen from Minnesota in that 

it is not simple growth lines; rather, the comarginal
SYSTEMATIC PALEONTOLOGY 59

markings bifurcate (pi. 14, fig. 3). These two specimens are also tentatively placed in T. divaricatus.

Technophorus extenuatus Ulrich, 1892b

Discussion. The holotype and only known specimen of this species could not be located, and we assume it to be lost. As figured by Ulrich (1892b, fig. 

8), it has only one posterior rib and a concave dorsal 

margin. Bassler (1915, p. 1258) noted that the species is from the Decorah Shale (Middle Ordovician) 

of Minnesota.

Technophorus filistriatus Ulrich, 1892a

Plate 13, figures 15, 16; 

plate 14, figure 1

Diagnosis. Technophorus with a single posterior 

rib, not markedly attenuated posteriorly, and with 

termination of rib at or below midpoint of posterior 

margin.

Types and materials. The holotype of the species 

is shown on plate 13, figure 16 (USNM 46312). In 

addition, we had two other specimens of the species 

(USNM 47204; UMN 12236).

Stratigraphic distribution. The holotype of the 

species is from Blackriveran rocks (Middle Ordovician) of Minnesota. Of the other two specimens, 

one is listed as coming from the Trentonian (Middle 

Ordovician?) of Minnesota, and the other is listed as 

coming from the Decorah Shale (Middle Ordovician) 

of Minnesota.

Technophorus marija n. sp. 

Plate 12, figures 12-15

Description. Robust and tumid Technophorus 

with two subdued posterior radial ribs, convexity of 

both valves about equal to height of shell. Internally 

there is a prominent thick pegma, well-developed 

side muscles, and a relatively small posterior median 

muscle,

Types. At present this species is known only 

from the holotype (Geological Museum, Academy of 

Sciences, U.S.S.R., 1849/2027) which measures 

about 14 mm long, 8 mm high, and 7 mm in convexity 

(both valves).

Type locality. The museum label reads: "Boulder on right bank of Moyero River, 6 miles above 

mouth of Ukdama River, Khatango-Anabar Region, 

northern Siberia.;"

Stratigraphic distribution. The museum label 

gives the Stratigraphic occurrence as Middle 

Ordovician.

Etymology. The species is named for Marija 

Balanc, U.S. Geological Survey, in appreciation of

her helpfulness in translating literature from several languages.

Technophorus milleri n. sp. 

Plate 14, figures 6, 7

Description. Markedly elongate Technophorus 

with two prominent posterior radial ribs, divaricate 

ornament between the radial ribs, and with the dorsoposterior margin strongly drawn out into a prominent tubular posterior rostrum. The only internal 

feature presently known is the pegma.

Types. At present, the species is known only 

from the holotype (MU 6848), which consists of 

part and counterpart and measures about 14 mm 

long and 5.5 mm high.

Type locality. The holotype is from Dodge's 

Creek, 0.5 miles north of Oxford, Ohio.

Stratigraphic distribution. The holotype is from 

the lower Whitewater Formation (Richmondian, upper Upper Ordovician).

Etymology. The species is named for S. A. Miller 

who named the genus Technophorus and pioneered 

in the study of these animals.

Technophorus? otaviensis Kobayashi, 1936

Discussion. As figured by Kobayashi (1936, figures 5-7), this form does not show posterior ribs or 

a pegma. We have seen no specimens or replicas. 

According to Kobayashi (1936, p. 352), the form is 

from "a late Middle (?) Ordovician sandstone of 

Otavi, Bolivia * * *." Branisa (1965) tentatively 

assigned a specimen from the Llanvirnian (Middle 

Ordovician) of Bolivia to this species, his specimen 

appears to belong to Ribeiria.

Technophorus plicatus (Billings), 1866 

Plate 12, figures 1-3

Discussion. The holotype of this species (GSC 

2291) is a weathered specimen from which most of 

the shell has been removed (pi. 12, figs. 1, 2). It has 

two posterior ribs, relict divaricate ornament, and 

recticulate ornament on the still adhering parts of 

the shell. Another specimen from the same locality 

as the holotype also shows relict divaricate ornament between the posterior ribs (pi. 12, fig. 3; YU 

3063/40); this specimen is tentatively assigned to 

T. plicatus. Billings placed this species in the genus 

Ischyrinia; however, as noted by Ulrich (1894,1897) 

and Twenhofel (1928), the species should be placed 

in Technophorus because it has only a single pegma.

Stratigraphic distribution. The holotype is from 

the Ellis Bay Formation (Upper Ordovician), Junction Cliff, Anticosti Island, Quebec, Canada.
60 PALEONTOLOGY OF ROSTROCONCH MOLLUSKS

Technophorns sharpei (Barrande) in Perner, 1903

Plate 12, figures 18, 19; plate 13, figures 1-14

Diagnosis. Markedly posteriorly attenuated 

Technophorus with a single posterior rib and a bilobed posterior gape.

Types and materials. T. sharpei is based upon a 

syntypic series of which we had replicas to examine 

(USNM 209381, 209382, 209387, 209388). We do not 

choose a lectotype of this species because all the syntypes figured in Perner (1903) are right valves, 

whereas all the replicas we have are left valves; 

possibly the original figures were reversed, but this 

is still uncertain. In addition, we figure six other 

specimens of the species.

Stratigraphic distribution. The species ranges in 

age from Llanvirnian (Middle Ordovician) to Ashgillian (Late Ordovician) of Bohemia, Czechoslovakia.

Technophorus stoermeri Soot-Ryen, 1960

Plate 14, figure 8

Discussion. This species is known only from the 

holotype (UO 5849), which is a small specimen with 

a single posterior rib. Soot-Ryen (1960) noted that 

T. stoermeri is similar to T. sharpei, and the two 

names may be synonymous.

Stratigraphic distribution. This species is known 

from the middle Caradocian (4b/?, Middle Ordovician) , Ostoya, Baerum, Norway.

Technophorus subacntus Ulrich, 1892a 

Plate 11, figure 22

Discussion. This species is known only from the 

holotype (UMN 8338), which is a small specimen 

with two posterior ribs and a prominent posterodorsal notch.

Stratigraphic distribution. Ulrich (1892a, p. 

101) gave the horizon and locality of T. subacutus as 

"Upper part of the limestone of the Trenton Formation at Minneapolis, Minnesota." Bassler (1915, p. 

1259) gave the horizon as "Black River (Platteville)." Presumably the species is from the Middle 

Ordovician.

"Technophorus" yoldiaformis (Ulrich), 1879 

Plate 10, figures 11, 12

Discussion. This species was originally placed 

in the pelecypod genus Nuculites Conrad by Ulrich 

(1879). In 1892, Ulrich (1892b) placed it in the 

genus Technophorus. As noted by Kobayashi (1936), 

"T." yoldiaformis is a pelecypod; this placement is 

indicated by the anterior and posterior adductor

muscle scars and the dorsal commissure. The species 

is under study by Pojeta.

Technophorus spp. 

Plate 11, figure 21; plate 12, figures 16, 17

Discussion. The specimens discussed under this 

heading are not well enough preserved to be placed 

in one of the named species; they are included here 

because they provide new Stratigraphic, geographic, 

or morphological information about the genus.

The form shown on plate 11, figure 21, is known 

from only one small silicified internal mold. It is the 

first known representative of the genus Technophorus from Australia occurring in the upper Ninmaroo 

Formation (Lower Ordovician; Warendian) at 

northern peak of Digby Peaks, 60 miles north of 

Boulia, Queensland.

The specimens shown on plate 12, figures 16, 17, 

are from the Edenian (Upper Ordovician) of Kentucky. They show the side muscles and an unusual 

almost square protoconch.

Genns ANISOTECHNOPHORUS new genus 

Plate 18

1900. Ribeiria Sharpe [partim], Cleland, Bulls. Am. Paleotology, v. 3, no. 13, p. 20.

Type species. Ribeiria"! nuculitiformis Cleland, 

1900 (p. 21), is herein designated the type species of 

the new genus Anisotechnophorus.

Description. Small, inequivalved, posteriorly 

elongate technophorids with a single pegma which is 

oblique to the dorsal margin, and with well-developed 

posterior radial ribs. The posterior terminations of 

the ribs alternate with one another on the two 

halves of the shell, producing a zigzag posterior 

commissure.

Stratigraphic distribution. Canadian (Lower 

Ordovician) of New York State.

Etymology. Anisos, Greek, meaning unequal; 

Technophorus, a genus of ribeirioids. Gender 

masculine.

Anisotechnophorus nuculitiformis (Cleland), 1900 

Plate 18, figures 1-21

Diagnosis. Anisotechnophorus in which the 

length of the shell is about twice the height of the 

shell.

Types and materials. The species is based upon 

a syntypic series, of which we choose the specimen 

shown on plate 18, figures 1-6, as the lectotype (PRI 

5080). The paralectotypes are shown on plate 18, 

figures 13, 15, 16, and 19 (PRI 5079). We had literally thousands of specimens of this species to exam-
SYSTEMATIC PALEONTOLOGY 61

ine, as it is extremely abundant at some localities in 

the "Fonda Limestone Member" of the Tribes Hill 

Limestone of New York State. None of the many 

known specimens of this species are preserved well 

enough to show internal details other than the 

pegma.

Stratigraphic distribution. The type suite is simply labeled "Calciferous [Beekmantown, Lower Ordovician], Fort Hunter Section, New York." As 

noted above, we have found the species to be extremely abundant at some outcrops of the "Fonda 

Limestone Member" of the Tribes Hill Limestone 

(lower Lower Ordovician) of central New York 

State. M. E. Taylor gave us one specimen (pi. 18, 

fig. 18) from the Missisquoia Zone (basal Lower Ordovician) of the upper Whitehall Formation of 

eastern New York State. In addition, we have two 

specimens (pi. 18, figs. 7-10, 20), the museum labels 

of which suggest that the species may occur in the 

latest Cambrian of New York State. One label reads: 

"Ozarkic (Little Falls), Fort Hunter, New York," 

and the other label reads: "Little Falls, Fort Hunter, 

N.Y." If the "Little Falls" in the two labels refers to 

the Little Falls Dolomite, this unit is regarded as 

Late Cambrian in age. Thus, A. nuculitiformis may 

occur in the uppermost Cambrian; it is well documented to occur in the lower Lower Ordovician.

Genus MYOCARIS Sailer, 1864

Plate 10 

1864. Myocaris Salter, Geol. Mag., v. 1, p. 11.

Type species. Myocaris lutraria Salter, 1864 (p. 

11) by monotypy.

Diagnosis. Large technophorids with radial ribs 

projecting posteriorly beyond body of shell.

Stratigraphic distribution. Middle Ordovician 

(from the Budleigh-Salterton Pebble Bed), Devon, 

England.,

Myocaris lutraria Salter, 1864 

Plate 10, figure 13

Discussion. This species is known from one complete specimen, the holotype (pi. 10, fig. 13; BM 

I 7204), and several fragmentary specimens. It is 

unusual because of its large size (about 60 mm 

long); in fact, it is the largest known Ordovician 

rostroconch. The concave anterior margin is also 

unusual, for it suggests the presence of an anterior 

gape, a feature unknown in other technophorids. 

Only the finding of additional material will determine whether or not an anterior gape is present.

Stratigraphic distribution. The museum label accompanying the holotype reads: "Ordovician, Llandeilo, from Trias Pebble Bed, Budleigh-Salterton, 

Devon," England.

Genus OEP1KILA Runnegar and Pojeta, 1974 

Plate 10

1940. [Non] Opikella Thorsland, Sveriges Geol. Undersokning ser. c, no. 436, p. 181.

1974. Opikella Runnegar and Pojeta, Science, v. 186, p. 315. 

1974. Oepikila Runnegar and Pojeta, Science, v. 186, p. 316.

Type species. Opikella cambrica Runnegar and 

Pojeta, 1974 (p. 317) by original designation and 

monotypy.

Diagnosis. Small technophorids with protoconch 

projecting prominently above the dorsal margin, and 

with radial ornament consisting of a single umbonal 

carina.

Stratigraphic distribution. Idamean (Upper 

Cambrian), Queensland, Australia.

Etymology. The genus was named for A. A. 

O'pik, Australian Bureau of Mineral Resources, who 

collected the known material.

Oepikila cambrica (Runnegar and Pojeta), 1974 

Plate 10, figures 14, 15

Diagnosis. Subquadrate Oepikila in which the 

uinbonal carina divides the shell into nearly equal 

anterior and posterior halves.

Types. The species is presently known only from 

the holotype (BMR CPC 13953; pi. 10, figs. 14, 15), 

which preserves both the part and counterpart.

Stratigraphic distribution. Presently known only 

from BMR locality W9, western Queensland, Australia, north-central part of Mount Whelan 

1:250,000 Geological Series Sheet SF 54-13 (1966, 

Reynolds). The locality is indicated on the Mount 

Whelan Sheet, and the specimen is from the Georgina Limestone. According to Opik (oral commun., 

1973) the fossils from locality W9 are Idamean 

(early Late Cambrian) in age.

Genus TOLMACHOVIA Howell and Kobayashi, 1936 

Plates 14, 16, 17

1936. Tolmachovia Howell and Kobayashi, Carnegie Mus. 

Annals, v. 25, p. 60.

Type species. Tolmachovia concentrica Howell 

and Kobayashi, 1936 (p. 60), by original designation and monotypy.

Diagnosis. Equivalved technophorids with anterior and posterior pegmas and weakly developed 

posterior ribs.

Stratigraphic distribution. Warendian (Lower 

Ordovician)-Middle Ordovician of Australia and 

Siberia; Ordovician,of Portugal.
62 PALEONTOLOGY OF ROSTROCONCH MOLLUSKS

Tolmachovia concentrica Howell and Kobayashi, 1936 

Plate 16, figures 1-10; plate 17, figures 1-7, 9-11

Diagnosis. Tolmachovia with narrow pegmas 

and rugose concentric ornament over the anterior 

half of the shell.

Types. This species is known only from its type 

series; these specimens are presently at Princeton 

University, but they bear the numbers of the Geological Museum of the Academy of Science, U.S.S.R., 

and are herein listed under those numbers. The holotype (Academy of Science, U.S.S.R. 1849/2027a) is 

figured on plate 16, figures 8-10. Nine paratypes are 

figured.

Stratigraphic distribution. The museum label 

reads: "Middle Ordovician, boulder on right bank 

of Moyero River, 6 miles above mouth of Ukdama 

River, Khatanga-Anabar region, northern Siberia."

Tolmachovia? jelli n. sp. 

Plate 14, figures 9-19

1969. Hibernal, Hill, Playford, and Woods, Ordovician and 

Silurian Fossils Queensland, p. O 10.

Description. Tolmachovia with wide pegmas; as 

in T. concentrica, the anterior pegma is bounded by 

a dorsal projection of the shell in front of the pegmp, posteriorly no dorsal projection bounds the pegma ; lacking anterior concentric rugose ornament.

Types. The holotype of the species is shown on 

plate 14, figures 9-12 (UQ F 60117); it is about 13.8 

mm long and 10 mm high. The holotype shows the 

anterior and posterior median muscles and the side 

muscles. In addition, we figure three paratypes (pi. 

14, figs. 13-19).

Type locality. Northern peak of Digby Peaks, 

about 60 miles north of Boulia, Queensland, 

Australia.

Stratigraphic distribution. In the top beds of 

the Ninmaroo Formation, just below the Swift Formation contact (Warendian, Lower Ordovician) ; 

presently only known from the type locality.

Etymology. The species is named for John S. 

Jell, University of Queensland, who collected the 

known material.

Discussion. The species is tentatively assigned 

to the genus Tolmachovia, as at present it is only 

known from internal molds.

Tolmachovia sp.

Plate 16, figures 11-14

Discussion. This subcircular form is known from 

only one specimen (BM PL 4434) which is labeled as 

coming from the "Ordovician of Portugal."

Order ISCHYRINIOIDA new order

Diagnosis. Donaciform rostroconchs with a 

dominant anterior growth component so that the 

protoconch is at or posterior to the center of the 

shell, and with two pegmas and overall radial 

ornament.

Stratigraphic distribution.-^Lovfer Ordovician 

(Wanwanian)-Upper Ordovician (Richmondian). 

The Stratigraphic range of each species is shown in 

table 3.

Family ISCHYRINIIDAE Kobayashi, 1933 

(nom. transl. Ischyriniinae Kobayashi, 1954)

Discussion. This is the only family placed in the 

order at present; it has the same definition and 

Stratigraphic range as the order. The family contains 

three known genera and six named species. It is 

known only from North America and Eurasia, where 

it has a northern-latitude distribution.

Genns ISCHYRINIA Billings, 1866 

Plates 18, 19

1866. Ischyrinia Billings [partim], Catalogues Silurian Fossils, Island of Anticosti, p. 16.

1889. Ischyrinia Billings [partim], Miller, North American 

geol. and paleontology, p. 483.

1894. Ischyrinia Billings, Ulrich, Lower Silurian Lamellibranchiata Minnesota, Minnesota Geol. and Nat. History Survey Final Kept. v. 3, p. 612. [Published under separate cover prior to entire v. 3.]

1897. Ischyrinia Billings, Ulrich Minnesota Geol. and Nat. 

History Survey Final Kept, v. 3, pt. 2, p. 613. [Reprinting of 1894 paper.]

1930. Ischyrinia Billings, Teichert, Palaeont. Zeitschr. v. 12, 

p. 130.

1933. Ischyrinia Billings, Kobayashi, Tokyo Imp. Univ. Fac. 

Sci. Jour., sec. 2, v. 3, pt. 7, p. 299, 316.

1943. Ischyrinia Billings, Miildner, Z. Geschiebeforschung, v. 

18, p. 93.

1960. Ischyrinia Billings, Soot-Ryen, Norsk Geol. Tidsskr., 

v. 40, p. 127.

Type species. Ischyrinia winchelli Billings, subsequent designation of Miller, 1889 (p. 483).

Diagnosis. Ischyriniids with anterior and posterior pegmas of about equal length, and with adult 

musculature consisting of side muscles and probably 

anterior and posterior median muscles.

Stratigraphic distribution. Middle Ordovician 

(Cyclocrinus Shale, 4b, Middle Caradocian)-Upper 

Ordovician (Richmondian).

bdyiinia wfackeffi Bffifap, 1866

Plate 18, figures 22-25; plate 19, figures 1-8

Diagnosis. Subquadrate Ischyrinia with fine 

radial ribs, carinate posterior umbonal slope, and 

flaring posteroventral gape.
SYSTEMATIC PALEONTOLOGY 63

SPECIES

TIME SCALE

Kj fci

7>

Cincinnatian 

(Caradocian-Ashgillian)

Wildernessian-Shermanian 

(Caradocian)

Marmorian-Porterfieldian 

(Llanvirnian-Caradocian)

Canadian-Whiterockian 

(Tremadocian-Arenigian) i %

2 0 21 z

TABLE 3. Range chart showing the known stratigraphic distribution of all species of Ischyriniidae and Eopteriidae recognized herein

[Species roughly arranged according to stratigraphic order from oldest to youngest, for each genus]
64 PALEONTOLOGY OF ROSTROCONCH MOLLUSKS

Types and materials. The type suite consists of 

two remaining specimens, of which we choose as the 

lectotype the specimen herein figured on plate 18, 

figures 23-24 (GSC 2114a). The paralectotype (GSC 

2114) is shown on plate 18, figure 25. A second paralectotype is presumed to be lost, as Billings (1866, 

p. 16) figured three specimens; we could not locate 

the specimen shown in his figure 4c. In addition to 

the type suite, we had 25 other specimens of the species to examine from the collection of the Peabody 

Museum, Yale University; of these we figure the 

four best preserved specimens.

Stratigraphic distribution. The species is known 

only from the Upper Ordovician, English Head and 

Ellis Bay Formations (Richmondian) of Anticosti 

Island, Quebec, Canada.

Ischyrinia elongata Miildner, 1943

Discussion. We have seen no specimens of this 

species. As indicated by its name, it is an elongate 

form, and it has a prominent rostrum.

Stratigraphic distribution. According to Neben 

and Krueger (1973), I. elongata is from the Backsteinkalk near Oderberg, Germany; they place the 

Backsteinkalk in the lower Caradocian (Middle 

Ordovician).

Ischyrinia norvegica Soot-Ryen, 1960 

Plate 19, figures 10-14

Diagnosis. Elongate Ischyrinia lacking a posterior carina.

Types. This species is only known from the type 

suite. The holotype (UO 38267) is shown on plate 

19, figures 10-11; three previously unfigured paratypes (UO 38267, 37861) are shown on plate 19, 

figures 12-14.

Stratigraphic distribution. I. norvegica is known 

from the Middle Ordovician Cyclocrinus Shale, 4b 

(middle Caradocian) of Norway.

Ischyrinia schmidti Teichert, 1930

Diagnosis. Coarsely ribbed elongate Ischyrinia 

with a weakly developed posterior carina.

Types. We have not seen the types or any other 

specimens of this species, and our analysis of the 

form is based upon Teichert (1930).

Stratigraphic distribution. I. schmidti is known 

only from the Upper Ordovician (Ashgillian) Lyckholm-Stufe of Estonia.

Ischyrinia spp. 

Plate 19, figures 9, 15-17

Discussion. The specimens listed under this 

heading provide additional Stratigraphic and geographic information about the genus.

The form shown on plate 9, figure 9, is from the 

Whitehead Formation (Upper Ordovician), Mt. St. 

Anne, Perce, Quebec, Canada. The specimens illustrated on plate 19, figures 15, 16, are from the Ordovician, Haverfordwest, Wales. The poorly preserved 

specimen shown on plate 19, figure 17, is from the 

Middle Ordovician of Siberia, and is herein tentatively assigned to Ischyrinia.

Genus E01SCHYRINA Kobayashi, 1933

1933. Eoischyrina Kobayashi, Tokyo Imp. Univ. Fac. Sci. 

Jour., v. 3, pt. 7, p. 298, 316.

Type species. Eoischyrina billingsi Kobayashi, 

1933 (p. 298), by original designation and monotypy.

Diagnosis. Slightly anteriorly elongate nearly 

subquadrate forms with radial ornament.

Stratigraphic distribution. Lower Ordovician 

(Wanwanian) of Manchuria.

Discussion. On the basis of the known figures 

and the material available to us, this genus is tentatively placed in the Ischyriniidae.

Eoischyrina billingsi Kobayashi, 1933

Discussion. This species is known from two 

specimens, of which we had a replica of the holotype 

to study. The replica was not well executed and is 

not figured herein. On the basis of the overall shell 

ribbing, the development of a posterior rostrum, and 

the lack of anterior and ventral gapes, it seems likely that the species is an ischyriniid.

Stratigraphic distribution. According to Kobayashi (1933, p. 298) both known specimens of the 

species are from the "Wanwankou Dolomite [Wanwanian, Lower Ordovician]; Wan-wan-kou in the 

Niuhsintai Basin, South Manchuria."

Genus PSEUDOTECHNOPHORUS Kobayashi, 1933 

Plate 20

1933. Pseudotechnophorus Kobayashi, Tokyo Imp. Univ., Fac. 

Sci. Jour., v. 3, pt. 7, p. 300, 317.

Type species. Pseudotechnophorus typicalis Kobayashi, 1933 (p. 300), by original designation and 

monotypy.

Diagnosis. Ischyriniids in which the anterior 

pegma is several times the length of the posterior 

pegma and in which the median muscles and side 

muscles are confined to the larval shell; the adult 

musculature consists of a large primary pedal retractor muscle and several smaller secondary pedal 

retractor muscles in each valve.

Stratigraphic distribution. Lower Ordovician 

(Wanwanian) of Manchuria.
SYSTEMATIC PALEONTOLOGY 65

Pseudotechnophorus typicalis Kobayashi, 1933 

Plate 20, figures 1-15

Diagnosis. Pseudotechnophorus in which the 

length is about twice the height.

Types and materials. We had a replica (USNM 

209371; pi. 20, figs. 1, 2) of the specimen figured by 

Kobayashi (1933, pi. 9, fig. 8) to examine. In addition, we had four specimens to examine (pi. 20, figs. 

3-15).

Stratigraphic distribution. The species is known 

only from the Wanwankou Dolomite (Wanwanian, 

Lower Ordovician), Wan-wan-kou in the Niuhsintai 

Basin, south Manchuria.

Order CONOCARDIOIDA Neumayr, 1891

Diagnosis. Rostroconchs with external and internal ribs, the latter expressed as marginal denticles 

on the inside edge of the commissure, and with an 

anterior gape and dorsal clefts.

Stratigraphic distribution. Lower Ordovician 

(Canadian)-Upper Permian (Makarewan).

Snperfamily EOPTERIACEA Miller, 1889 

(nom. transl. herein)

Diagnosis. Conocardioids with anterior or both 

anterior and posterior dorsal clefts; anterior, ventral, and posterior shell gapes (which are continuous with one another), rostrum rudimentary or lacking, shell posteriorly elongate in most forms.

Stratigraphic distribution. Lower Ordovician 

(Canadian)-Middle Ordovician (Wildernessian). 

The Stratigraphic range of each species is shown on 

table 3.

Family EOPTERIIDAE Miller, 1889

Discussion. This is the only family presently 

assigned to the Eopteriacea, and it has the same 

definition and Stratigraphic range as that superfamily,

As herein used, the Eopteriidae contains four 

known genera and about 19 species; it is presently 

known only from North America and Eurasia.

Genus EOPTERIA Billings, 1865

Plates 22-26

1865. Eopteria Billings Palaeozoic fossils, v. 1, Canada Geol.

Survey, p. 221, 306. 

1889. Eopteria Billings, Miller, North American Geology and

Paleontology, p. 480. 

1933. Eopteria Billings [partim], Kobayashi, Tokyo Imp.

Univ., Fac. Sci. Jour., v. 3, pt. 7, p. 295. 

1935. Pterinea Thoral, Contr. etude paleont. Ordovicien inferieur *** Montagne Noire, p. 175. 

1944. Eopteria Billings, Shinier and Shrock, Index fossils of

North America, p. 659.

1957. Eopteria Billings, Yang, Chung-kuo piao chun hua shih, 

p. 320.

1971. Eopteria Billings, Pojeta, U.S. Geol. Survey, Prof. 

Paper 695, p. 22.

1972. Eopteria Billings, Pojeta, Runnegar, Morris, and 

Newell, Science, v. 177, p. 264.

Type species. Eopteria typica Billings, 1865 (p. 

221) by indication.

Diagnosis. Eopteriids with a prominent anterior 

snout and lacking a pegma.

Stratigraphic range. Lower Ordovician (Canadian)-Middle Ordovician (Wildernessian).

Discussion. Two species, E. alta Kobayashi and 

E. asiatica Kobayashi are placed by us in the genus 

Wanwanella Kobayashi.

Eopteria typica Billings, 1865

Discussion. Unfortunately, the type material of 

the type species of the genus cannot be located; we 

assume it to be lost. Also unfortunately, Billings 

(1865, p. 221) did not figure the species. Cloud and 

Barnes (1948) figured a form which they assigned 

to E. typica; we figure this specimen on plate 25, 

figures 2-4, and place it in E. richardsoni Billings. 

According to Bassler (1915, p. 491), Billings' material of E. typica was from the Canadian (QuebecG., Lower Ordovician) of Port aux Choix, 

Newfoundland.

Eopteria conocardiformis n. sp.

Plate 26, figures 12-18

Description. Eopteria with markedly elongated 

anterior snout so that the beak is posterior to the 

center of the length of the shell.

Types. The holotype (USNM 209322) is shown 

on plate 26, figures 12-15; it is about 11 mm long 

and 8 mm high. Two paratypes are shown on plate 

26, figures 16-18 (USNM 209333; 209334).

Type localities. The holotype is from a quarry 

about 2 miles north of Pelham, Ala. One paratype 

is from Highbridge, Ky., and the other is from the 

intersection of Bailey Gap Road with main road, 

1.75 miles northeast of New Hope Church, Ala.

Stratigraphic distribution. The holotype and the 

paratype from Alabama are both from the Little 

Oak Limestone (Porterfieldian; Middle Ordovician). 

The paratype from Kentucky is from the High 

Bridge Group (Wildernessian; Middle Ordovician).

Etymology. The species name is derived from the 

genus Conocardium whose shape Eopteria conocardiformis mimics.

Discussion. E. conocardiformis shows anterior 

elongation of the snout to a much more marked degree than does any other species of the genus Eop-
66 PALEONTOLOGY OF ROSTROCONCH MOLLUSKS

teria; it is becoming conocardiacean in shape, although the ventral gape still persists.

Eopteria crassa (Thoral), 1935

Discussion. This species was questionably assigned to the pelecypod genus Pterinea Goldfuss by 

Thoral (1935, p. 175). It is a robust small form 

whose shape and marginal denticles indicate that it 

should be placed in Eopteria. We have not seen Thoral's material, and our analysis is based upon his 

description and figures.

Stratigraphic range. Lower Arenigian (Lower 

Ordovician) of southern France.

Eopteria flora Kobayashi, 1933 

Plate 24, figures 1, 2

Discussion. We had only a replica of the holotype 

of this species to examine (USNM 94042); it clearly shows the shape and elongated anterior snout of 

Eopteria. E. flora is from the Wanwankou Dolomite (Wanwanian; Lower Ordovician) of south 

Manchuria.

Eopteria obsolata Kobayashi, 1933

Plate 24, figures 3, 4

Discussion. We had only a replica of the holotype of this form to examine (USNM 94041); it 

shows the elongated anterior snout of Eopteria. 

Horizon and locality the same as for E. flora above.

Eopteria? ornata Billings, 1865

Discussion. This species was questionably placed 

in Eopteria by Billings (1865, p. 307). Billings' material can no longer be located and we presume it to 

be lost. He listed the species as coming from "Point 

Levis [Quebec] in the upper part of limestone No. 2, 

Quebec Group." Bassler (1915, p. 491) noted that 

E. ornata came from a Levis erratic and gave the age 

as "Ozarkian?."

Eopteria richardsoni Billings, 1865

Plate 24, figures 5-20; plate 25, figures 2-19; plate 26, 

figures 1-11

Diagnosis. Eopteria with radial ornament of fine 

ribs.

Types and materials. This is the only species of 

Eopteria described by Billings (1865), of which the 

type material is still extant. The holotype (GSC 

756) is figured herein on plate 24, figures 5, 6. The 

species occurs widely in North America, and we 

figure specimens from Arkansas, Missouri, Nevada, 

Quebec, and Texas.

Stratigraphic distribution. E. richardsoni is limited to rocks of Early Ordovician age (CanadianWhiterockian). In Quebec, it occurs in the Beekmantown Group (Canadian); in Nevada, it occurs in the 

Antelope Valley Limestone (Whiterockian); in Arkansas, it occurs in the Smithville Formation 

(Canadian); in Missouri, it occurs in the Cotter 

Dolomite and Jefferson City Dolomite (Canadian); 

and in Texas, it occurs in Honeycut Formation and 

Scenic Drive Formation of Flower (1964) 

(Canadian).

Eopteria ventricosa (Whitfield), 1886 

Plate 22, figures 1-15; plate 23, figures 1-10

Diagnosis. Eopteria with dominantly comarginal 

ornament.

Types and materials. The type suite of E. ventricosa consists of two specimens, of which the one 

figured herein on plate 22, figure 11, is chosen as the 

lectotype (AM 492); the paralectotype (AM 492) 

is shown on plate 22, figure 14. In addition to the 

types, we figure 17 other specimens of the species.

Stratigraphic distribution. E. ventricosa is 

known only from the "Fort Cassin Limestone" (Canadian, Lower Ordovician), at Fort Cassin, Vt.

Discussion. This is the morphologically best 

known species of Eopteria, in that some specimens 

show some of the muscle scars. None of the known 

material shows all of the muscle scars, and our diagram (fig. 4) of the musculature of this species is a 

composite.

Eopteria sp. 

Plate 25, figure 1

Discussion. This form is known from three specimens, of which one is figured (USNM 209335). It is 

by far the largest known Eopteria, as much as 50 

mm long, and is probably a distinct species. However, the known material is poorly preserved.

Stratigraphic distribution. Cotter Dolomite 

(Lower Ordovician) of Arkansas.

Genus EUCHASMA Billings, 1865 

Plates 27-29

1865. Euchasma Billings, Paleozoic fossils, v. 1, Canada Geol.

Survey, p. 220, 360. 

1889. Euchasma Billings, Miller, North American geology

and paleontology, p. 480. 

1933. [Non] Euchasma Billings, Kobayashi, Tokyo, Imp.

Univ. Fac. Sci. Jour., v. 3, pt. 7, p. 292. 

1955. Euchasma Billings, Nicol, Jour. Paleontology, v. 29,

p. 552.

1971. Euchasma Billings, Pojeta, U.S. Geol. Survey, Prof. 

Paper 695, p. 22.

1972. Euchasma Billings, Pojeta, Runnegar, Morris, and 

Newell, Science, v. 177, p. 264.
SYSTEMATIC PALEONTOLOGY 67

Type species. Conocardium blumenbachii Billings, 1859 (p. 350), by monotypy.

Diagnosis. Tumid oblique eopteriids with rudimentary rostrum, anterior pegma, a broad anterior 

face, and snout reduced to an anterior lobe; anterior 

gape keyhole shaped.

Stratigraphic range. Lower Ordovician (Canadian-Whiterockian).

Euchasma blumenbachii (Billings), 1859 

Plate 27, figures 1-16

Diagnosis. Large coarsely ribbed Euchasma 

with prominent anterior lobe, dorsal part of keyhole 

gape elliptical.

Types and materials. The type suite consists of 

two syntypes, of which the specimen shown on plate 

27, figures 1-4, is herein chosen as the lectotype 

(GSC 455); the specimen shown on plate 27, figures 

7, 8, is the paralectotype (GSC 455a). In addition, 

we had 19 other specimens of the species to examine, 

six of which are figured here. All known North 

American specimens of Euchasma are herein placed 

in E. blumenbachii,' the species is not presently 

known to occur outside North America. It occurs 

widely in North America, and we figure specimens 

from Newfoundland, Quebec, Texas, and Virginia.

Stratigraphic distribution. E. blumenbachii is 

limited to rocks of Early Ordovician (Canadian) 

age. In Newfoundland, it occurs in the St. George 

Group; in Quebec, it occurs in the Romaine Formation and the Luke Hill Limestone; in Texas, it occurs in the Scenic Drive Formation of Flower 

(1964); and in Virginia, it occurs in the Beekmantown Group..

"Euchasma" eopteriforme Kobayashi, 1933

Discussion. We had only one poorly preserved 

specimen of this species to examine, and it is not figured herein. Kobayashi's (1933) figures of the species show a coarsely ribbed form which does not 

have the shape of other species placed in Euchasma. 

We do not regard the species as belonging to Euchasma, but at present we cannot assign it to any of the 

other known ribbed rostroconch genera. The form 

is from the Wanwankou Dolomite (Wanwanian, 

Lower Ordovician) of Manchuria.

Euchasma jonesi n. sp.

Plate 28, figures 12-18; plate 29, figures 1-5

Description. Small finely ribbed Euchasma with 

dorsal part of keyhole gape subcircular and having 

a dorsal scooplike projection; rostrum rudimentary, 

but marked off from rest of shell by depressed areas.

Types. This species is known from about 150 

silicified specimens, most of which are fragmentary. 

The holotype is shown on plate 28, figures 12-15 

(USNM 162790); it is about 17.5 mm long and 11 

mm high. Seven paratypes are figured.

Type locality. The known material is from off 

south point of Pulau Langgun, Langkawi Islands, 

Malaysia.

Stratigraphic distribution. At present, the species is known only from the lower shelly facies of the 

Setul Formation of Malaysia. Yochelson and Jones 

(1968) dated this part of the Setul Formation as 

late Canadian (Early Ordovician) in age.

Etymology. As pointed out by Yochelson and 

Jones (1968, p. Bl), Clive Jones and Richard Jones 

were instrumental in collecting the material of this 

species. The species name is derived from their common last name.

Euchasma mytilifonne n. sp. 

Plate 29, figures 6-15

Description. Euchasma with highly reduced anterior lobe which does not project forward of the 

umbonal peaks; anterior face strongly flattened and 

broad; ribs weak; poorly developed rostrum.

Types. This species is known from about 50 

specimens, most of which are fragmentary. The holotype (USNM 209312) is shown on plate 29, figures 

6-10; it is about 45 mm long and 41 mm high; in 

addition to the holotype, we figure three paratypes.

Type locality. The known material of E. mytiliforme is from the east side of Pulau Langgun, Langkawi Islands, Malaysia.

Stratigraphic distribution. At present, the species is known only from the lower shelly facies of 

the Setul Formation of Malaysia (upper Canadian; 

Lower Ordovician).

Etymology. The species name is derived from 

the pelecypod genus Mytilus whose shape Euchasma 

mytiliforme mimics.

Euchasma shorinense (Kobayashi), 1933 

Plate 28, figures 8-11

Discussion. This species is known only from the 

holotype, of which we had a replica (USNM 209317) 

to examine. The specimen has the general shape of 

species of Euchasma, including a small anterior lobe. 

The specimen is not well preserved and cannot be 

compared in detail with other species assigned to the 

genus. Kobayashi (1933, p. 286) placed the species 

in the genus Wanwanella, an assignment with which 

we do not agree.
68 PALEONTOLOGY OF ROSTROCONCH MOLLUSKS

Stratigraphic distribution. According to Kobayashi (1933, p. 287), the species is known from the 

"Shorin Bed of Shorinri, near Kenjiho Koshu-gun, 

Kokai-do in northern Korea" (Lower Ordovician, 

Tateiwa, 1958).

Euchasma wanwanense (Kobayashi), 1933 

Plate 38, figures 4-7

Discussion. This species is known from the holotype and a paratype; we had a replica (USNM 

209316) of the former to examine. The specimen has 

the general shape of Euchasma, including a small 

anterior lobe. The known material is not well preserved and cannot be compared in detail with other 

species of the genus. Kobayashi (1933, p. 286) assigned the species to Wanwanella, an assignment 

with which we do not agree.

Stratigraphic distribution. The species is known 

only from the Wanwankou Dolomite (Wanwanian, 

Lower Ordovician) of Manchuria.

Euchasma? sp. 

Plate 28, figures 1-3

Discussion. This form has a shape similar to 

Euchasma, but it is not well enough known for us to 

exclude the possibility that it is a pelecypod. It is 

from the Holonda Limestone (Whiterockian, Lower 

Ordovician) of Norway.

Genus WANWANELLA Kobayashi, 1933 

Plate 21

1933. Wanwanella Kobayashi, Tokyo Imp. Univ. Fac. Sci., 

Jour., v. 3, pt. 7, p. 284.

Type species. Wanwanella striata Kobayashi, 

1933 (p. 285) by original designation.

Diagnosis. Erect eopteriids with a pegma.

Stratigraphic range. Wanwanian (Lower Ordovician) of Manchuria.

Discussion. We had very little material assignable to this genus to examine; most of what we did 

have were replicas of Kobayashi's (1933) types. 

Thus, we do not attempt to diagnose each species; 

rather we discuss and make comments about each. 

Two species, W. shorinensis and W. wanwanensis, 

have been placed by us in the genus Euchasma.

Wanwanella striata Kobayashi, 1933 

Plate 21, figures 9-16

Discussion. We had a replica (USNM 209369) of 

a Kobayashi syntype (1933, pi. 7, fig. 7) and two 

specimens (MCZ 4425, YU 28149) of this species to 

examine. The form is radially ribbed with a prominent pegma; all specimens that we saw were missing 

the posterodorsal part. The species is prominently

rounded anteriorly, giving it an erect appearance 

not seen in Eopteria or Euchasma.

Stratigraphic distribution. Wanwankou Dolomite (Wanwanian, Lower Ordovician), at Wan-wankou in the Niuhsintai Basin, southern Manchuria.

Wanwanella? alta (Kobayashi), 1933 

Plate 21, figure 21

Discussion. We had an old poorly executed replica of the holotype (USNM 94045) and a poorly preserved specimen of this form to examine. Both show 

overall body ribbing, a pegma, and a rounded anterior end. Kobayashi (1933) placed this form in 

Eopteria; because of the presence of the pegma and 

the rounded anterior end, we do not accept this assignment. We regard the form as being closest to 

species placed in Wanwanella.

Stratigraphic distribution. Wanwankou Dolomite (Wanwanian, Lower Ordovician), Wan-wankou in the Niuhsintai Basin, south Manchuria.

Wanwanella? asiatica (Kobayashi), 1933

Discussion. We had only a poorly executed replica of the holotype of this species to examine, which 

we do not figure. The form has overall body ribbing, 

a pegma, and a rounded anterior end. Kobayashi 

(1933) placed the species in Eopteria; because of 

the pegma and the rounded anterior end, we do not 

accept this assignment. We regard the form as being 

closest to species placed in Wanwanella.

Stratigraphic distribution. Wanwankou Dolomite (Wanwanian, Lower Ordovician), Wan-wankou in the Niuhsintai Basin, southern Manchuria.

Wanwanella striata auriculata Kobayashi, 1933 

Plate 21, figures 17-20

Discussion. We had a replica of the holotype of 

this form to examine (USNM 209370). It has a 

prominent posterodorsal auriculate rostrum. The 

known specimens of W. striata are missing this part 

of the shell, and it seems likely that W. striata auriculata is a junior synonym of W. striata. According 

to Kobayashi (1933, p. 286), W. striata auriculata is 

known from "One specimen obtained in the same 

locality with Wanwanella striata s. sir."

Wanwanella tumida Kobayashi, 1933 

Plate 21, figures 7, 8

Discussion. We had a replica of the holotype of 

this form to examine (USNM 209368). The specimen 

is much like W.I alta in shape, and the two names 

may be synonymous, W. tumida having page precedence. The two forms are from the same horizon and 

locality.
SYSTEMATIC PALEONTOLOGY 69

Genus WANWANOIDEA Kobayashi, 1933

Plate 21

1933. Wanwanoidea Kobayashi, Tokyo, Imp. Univ. Fac. Sci., 

Jour., v. 3, pt 7, p. 287.

Type species. Wanwanoidea trigonalis Kobayashi, 1933 (p. 287), by original designation.

Discussion. The only specimens assignable to 

this genus that we have seen are replicas of the holotype of one subspecies and the figured syntype of the 

other species. When the replicas are compared with 

Kobayashi's figures (1933, pi. 8, fig. 6; pi. 9, fig. 3), 

it is obvious that neither specimen is complete. They 

do show full body ribbing and a pegma, and in this 

regard are like Wanwanella. Kobayashi (1933, p. 

315) distinguished them primarily on shape. On the 

basis of the material of Wanwanoidea that we have 

seen, we are not in a position to diagnose the genus. 

In addition to the material that he figured, Kobayashi (1933, p. 288) noted that he had three unfigured syntypes of the type species.

Stratigraphic distribution. Wanwanian (Lower 

Ordovician) of Manchuria.

Wanwanoidea trigonalis Kobayashi, 1933

Plate 21, figures 4-6

Discussion. We had only a replica of a syntype 

of this species to examine (USNM 209367) ; as noted 

above, the original is an incomplete specimen. The 

species is from the Wanwankou Dolomite (Wanwanian, Lower Ordovician) of southern Manchuria.

Wanwanoidea trigonalis delicata Kobayashi, 1933

Plate 21, figure 3

Discussion. We had only a replica of the holotype of the subspecies to examine (USNM 209366) ; 

as noted above, the original is an incomplete specimen. This form is from the Wanwankou Dolomite 

(Wanwanian, Lower Ordovician) of southern 

Manchuria.

Superfamily CONOCARDIACEA Miller, 1889 

(nom. transl. Conocardiidae Miller, Newell, 1965)

Diagnosis. Anteriorly elongate conocardioids 

with well-developed rostrum arid posterior dorsal 

clefts when the hinge and rostrum are not colinear; 

prominent anterior gape, posterior gape reduced to 

aperture of rostrum and ventral orifice (when present) , ventral gape absent. Inner shell layer continuous across the dorsal margin.

Stratigraphic distribution. Middle Ordovician 

(Marmorian)-Upper Permian (Makarewan; Waterhouse, 1967),

Discussion. We cannot review all species of conocardiaceans herein; at least 275 species have been

placed in this superfamily, and we have not been 

able to obtain specimens of all of these. We discuss 

all Ordovician species and those post-Ordovician 

forms for which we could obtain specimens that illustrate the morphological diversity and stratigraphic and geographic occurrence of the group.

Family CONOCARDIIDAE Miller, 1889

Diagnosis. Markedly anteriorly elongate conocardiaceans with shell clearly regioned into a posterior rostrum, median body, and anterior snout; 

internally, snout has elongate apertural (longitudinal) shelves; hood absent.

Stratigraphic distribution. Lower Devonian 

(Schoharie Formation)-Lower Permian (McCloud 

Limestone).

Genus CONOCARDIUM Bronn, 1835

Plates 37-40

Type species. Cardium elongatum Sowerby, 1815 

(p. 188) by monotypy. Arcites rostratus Martin, 

1809, is often cited as the type species of Conocardium (Hind 1900) because the specimens figured by 

Martin (1809) and Sowerby (1815) are regarded as 

conspecific; in fact, Hind (1900) felt that the figures 

of both authors might be based on the same specimen. Whether or not this is the case was made moot 

by the International Commission on Zoological Nomenclature, which has declared Martin's Petrifacta 

derbiensia invalid for nomenclatural purposes 

(Hemming, 1954, ICZN Opinion 231). Bronn 

(1835), when he proposed Conocardium, mentioned 

only Cardium elongatum Sowerby, which becomes 

the type species by monotypy. Sowerby (1815, p. 

188), following the name Cardium elongatum, indicated that the species was illustrated on his plate 82, 

figure 3; his description clearly indicates that C. 

elongatum is illustrated on his plate 82, figure 2.

Diagnosis. Conocardiids in which the body of 

the shell is externally fully radially ribbed.

Stratigraphic distribution. Lower Devonian 

(Schoharie Formation)-Pennsylvania!!. The youngest specimen .(USNM 100704) we have seen of 

Conocardium is labeled "Pennsylvanian, St. Joseph, 

Missouri."

Conocardium elongatum (Sowerby), 1815 

Plate 37, figures 16,17; plate 38, figures 1-24 

Types and materials. The holotype (BM PL 794) 

of C. elongatum is figured herein on plate 38, figures 

9-14; the photographs of this specimen are courtesy 

of the Department of Palaeontology, British Museum (Natural History). The specimen was also figured by Hind (1900, pi. 51, figures 6, 6a, 6). The
70 PALEONTOLOGY OF ROSTROCONCH MOLLUSKS

holotype is a radially ornamented subcylindrical shell 

broken at both ends. In addition to the holotype, we 

had four specimens of this species from England 

(pi. 38, figs 8, 15-24). One of these, a topotype (BM 

L 13496), shows the presence of longitudinal shelves 

in the species. Another (SM E.549, pi. 38, fig. 8) 

shows that there is little radial ribbing on the snout. 

The remaining two (BM PL 4431, 4432) show the 

muscle-insertion areas. Because the hinge and dorsal margin of the rostrum are approximately colinear, the valves were able to rotate during growth, 

and there are no well-defined rostral clefts; ventral 

aperture lacking.

In addition to the English material, we have two 

specimens from North America (pi. 37, figs. 16, 17; 

pi. 38, figs. 1-7) which are similar to the English 

material in shape and general body form but differ 

in having a radially ribbed snout. Just what weight 

should be given to this characteristic is as yet uncertain, because it has not been possible to gather 

together the material of the known species of Conocardium. Probably the American specimens represent a different species, and they are herein treated 

as Conocardium aff. C. elongatum.

Stratigraphic distribution. The English specimens of this species are all from Carboniferous 

(Mississippian) limestone. The American specimens 

are from the Carterville Formation (Upper Mississippian) of Missouri (pi. 38, figs. 4-7), and the 

Pennsylvanian of Missouri (pi. 37, figs. 16, 17; pi.

38. figs. 1-3).

Conocardium aliforme (Sowerby), 1815 

Plate 39, figures 8-10; plate 51, figure 11

Material. We figure two specimens of this species, one of which is a Hind (1900, pi. 54, fig. 8; SM 

E.561) hypotype. The body of the shell of this species is more erect and less rounded than in C. 

elongatum.

Stratigraphic distribution. Carboniferous (Mississippian) limestone of England.

Conocardium attenuatum (Conrad), 1842 

Plate 39, figures 11-13; plate 40, figures 1, 2

Material. We figure three specimens of this form, 

none of which are complete and two of which are 

Hall (1885) hypo types. They clearly show the presence of longitudinal shelves (pi. 39, fig. 11; pi. 40, 

fig. 1) and radial ribs on the body of the shell (pi.

39. figs. 12,13; pi. 40, fig. 2).

Stratigraphic distribution. The species is known 

only from the Schoharie Formation (Lower Devonian) of New York State.

Conocardium normale Hall, 1883 

Plate 39, figures 4-7

Type. We figure the lectotype (AM 5349/1) of 

the species (herein chosen) which shows the ribbing 

on the body of the shell and unusually thick longitudinal shelves. The body of the shell is more oblique 

than in C. aliforme but not rounded as in C. 

elongatum.

Stratigraphic distribution. The species is known 

from the Hamilton Group (Middle Devonian) of 

Maryland.

Conocardium pseudobellum n. sp. 

Plate 38, figures 25, 26; plate 39, figures 1-3

Description. Posterior carina at junction of rostral area with body of shell, small ventral aperture 

at posterior commissural junction of the carinae; 

rostrum long; body of shell oblique as in C. attenuatum, but apertural shelves not as robust as in that 

species.

Types. The holotype (USNM 209299) is shown 

on plate 38, figure 25 and plate 39, figures 1, 2. It is 

about 28 mm long and 16 mm high. The rostrum of 

the specimen was reconstructed in plaster by Yang 

(1939). In addition to the holotype, we figure two 

paratypes of the species (USNM 209300; UM 

47287), which show the longitudinal shelves and the 

elongate rostrum. Yang (1939) made serial and 

oblique sections of this species, showing a pair of 

longitudinal shelves which terminate posteriorly as 

enclosed tubes in the umbonal region of the shell.

Type locality. The types are from Four Mile dam, 

Thunder Bay River, 2 miles upstream from Alpena, 

Mich.

Stratigraphic distribution. The species is presently known from the upper Alpena Limestone and 

Four Mile Dam Formation (Middle Devonian) of 

Michigan.

Discussion. C. pseudobellum resembles Hippocardia bella (Cooper and Cloud) (pi. 44, figs. 5-14) 

in general external form and was identified with 

that species by Yang (1939). However, H. bella 

differs in having a small but obvious hood (pi. 44, 

figs. 5, 6, 11) and in lacking longitudinal shelves.

Etymology. Pseudo, Greek, meaning false, lie; 

Bella, a species of Hippocardia externally similar to 

Conocardium pseudobellum.

Genus ARCEODOMUS new genus 

Plates 42-44

Type species. Conocardium glabratum Easton, 

1962 (p. 95) is herein designated the type species of 

the new genus Arceodomus.
SYSTEMATIC PALEONTOLOGY 71

Description. Conocardiidae with one or more 

pairs of longitudinal shelves within the anterior 

gape; shell strongly regioned into posterior rostrum, 

medial body, and anterior snout. Junction of body 

and snout marked by pronounced change in shell ornament; body of shell ornamented only with comarginal markings, snout strongly radially ribbed.

Stratigraphic distribution. Upper Mississippian 

(Heath Formation, Diamond Peak Formation) - 

Lower Permian (McCloud Limestone).

Geographic distribution. In the United States, 

the genus is presently known from California, Montana, Nevada, and Texas. Outside, the United States 

it occurs in the U.S.S.E.

Etymology. Arcea, Latin, meaning to shut up or 

enclose; Domus, Latin meaning home. Gender 

feminine.

Discussion. Two named species are assigned to 

this genus, A. glabrata (Easton), 1962, and A. 

langenheimi (Wilson), 1970. Other forms that belong to the genus are herein listed as showing affinities to one of the named species, or as Arceodomus 

sp.

Arceodomus glabrata (Easton), 1962

Plate 42, figures 8-11; plate 43; figures 1-3, 7-12; 

plate 44, figures 1-4

Types and materials. The holotype (USNM 

118858) is shown on plate 43, figures 1-3; it clearly 

shows the comarginal ornament on the body of the 

shell and the impressions of the longitudinal shelves. 

Dorsally, the specimen has been weathered, and the 

internal ribs show where the comarginal ornament 

has been removed. Anteriorly, the specimen is incomplete, and most of the snout is not present.

In addition to the holotype, we assign two other 

Mississippian specimens to this species (pi. 42, figs. 

8-10; pi. 43, figs. 7-12); these specimens clearly 

show the radial ribs of the snout. The two specimens 

were brought to our attention by Mackenzie Gordon, 

Jr. A form similar to A. glabrata occurs in the Pennsylvanian of Texas and is figured on plate 42, figure 

11, and plate 44, figures 1-4.

Stratigraphic distribution. The holotype and the 

two specimens assigned unequivocally to this species 

are from the Upper Mississippian of Montana 

(Heath Formation) and Nevada (Diamond Peak 

Formation). The specimens from Texas, which are 

regarded as showing affinities to A. glabrata, are 

from rocks of Late Pennsylvanian age ("Dickerson 

Shale").

Arceodomus langenheimi (Wilson), 1970 

Plate 43, figures 13-15

Types. This species is known only from the type 

suite which was figured by Wilson (1970). Herein 

we figure the holotype (UCB 10589), which is a 

large, exceptionally well-preserved silicified specimen. It shows that the anterior gape is largely occluded by the longitudinal shelves.

Stratigraphic distribution. At present, this species is known only from the McCloud Limestone 

(Lower Permian), Bollibokka Mountain, Shasta 

County, Calif.

Arceodomus sp. 

Plate 43, figures 4-6

Discussion. This form clearly belongs to the genus Arceodomus; it is presently known from only one 

specimen at the British Museum (BM L 15570) 

which is labeled as coming from the "Carboniferous" 

of the U.S.S.R. R. J. Cleevely, of the British Museum 

(written commun., 1975) noted that Norman Newell 

had annotated the specimen label: "Probably from 

Schwagerina lutugini Beds, one of the "Shikhan 

reefs, Bashkiria (Sakmorian)," after sectioning the 

limestone to which it was attached."

Family BRANSONI1DAE new family

Description. Conocardiaceans lacking anterior 

longitudinal shelves in snout of shell; snout and 

body of shell ribbed, not always clearly separated 

from one another; hood absent.

Stratigraphic distribution. Middle Ordovician 

(Marmorian)-Upper Permian (Capitam'an).

Genus BRANSONIA new genus 

Plates 32, 50-54

Type species. Bransonia wilsoni n. sp. is herein 

designated the type species of the new genus 

Bransonia.

Description. Bransoniids with a reduced anterior 

gape which is largely limited to the dorsal part of 

the anterior face, although it may extend ventrally 

as a narrow slit.

Stratigraphic distribution. Middle Ordovician 

(Marmorian)-Middle Permian (Tiverton Formation).

Etymology. The genus is named for C. C. Branson, University of Oklahoma, who has long worked 

with conocardiaceans. Gender feminine.

Discussion. This long-ranging genus is proposed 

for conocardiaceans of generalized body form; probably when the group becomes better known it will be 

divided into several generic-level taxa.
72 PALEONTOLOGY OF ROSTROCONCH MOLLUSKS

Bransonia wilsoni n. sp.

Plate 32, figure 4; plate 51. figures 1-10, 17; plate 52, 

figures 1-5, 9

Description. Large Bransonia with prominent 

snout and rostrum, rostrum shorter than snout, body 

of shell carinate posteriorly, rostrum and hinge not 

colinear and rostral clefts prominent, ventral aperture present.

Types. The holotype (UNE F14789) is shown on 

plate 51, figures 1-6; it is about 28 mm long and 22 

mm high. In addition to the holotype, we figure five 

paratypes.

Type locality. The types are from the ridge 

southeast of Homevale Homestead, Nebo District, 

Queensland, Australia.

Stratigraphic distribution. Middle part of 

"Homevale Beds," lower Tiverton Formation (Middle Permian).

Etymology. The species is named for E. C. Wilson, Los Angeles County Museum, in recognition of 

the work he has done with Permian conocardiaceans.

Bransonia alabamensis n. sp.

Plate 50, figures 28-37

Description. Small Bransonia with body of shell 

carinate posteriorly, rostrum prominent and about 

equal in length to snout.

Types. The holotype (USNM 209271) is shown 

on plate 50, figures 32-34; it is about 4.5 mm long 

and 3.6 mm high. We had 12 other specimens besides the holotype, of which three paratypes are 

figured.

Type locality. The types are from the Crossroads, 1.75 miles northeast of New Hope Church, 

Alabama.

Stratigraphic distribution. The species is known 

only from the Little Oak Limestone (Porterfieldian, 

Middle Ordovician) of Alabama.

Etymology. The species name is derived from 

the state of Alabama.

Bransonia beecheri (Raymond), 1905

Plate 50, figures 20-24

Diagnosis. Small elongate Bransonia with body 

of shell rounded posteriorly rather than carinate, 

shape eopteriiform.

Types and materials. B. beecheri is based upon a 

syntypic series of which we choose the specimen 

figured herein on plate 50, figure 20, as the lectotype 

(YU 15322C). In addition to the type suite, we had 

three other specimens of this species, which are 

figured on plate 50, figures 22-24.

Stratigraphic distribution. The type suite is from 

rocks of Chazyan (Marmorian, Middle Ordovician)

Age, on Sloop Island, near Valcour Island, Lake 

Champlain, N.Y. We have been to this locality to try 

and collect topotype material but found no additional 

specimens. The species also occurs in Chazyan (Marmorian) Age rocks, Isle LaMotte, Vt. (pi. 50, fig. 

24), the Mosheim Member of Lenoir Limestone 

(Marmorian) of Tennessee (pi. 50, fig. 23), and the 

Row Park Limestone (Marmorian-Ashbyian) of 

Pennsylvania (pi. 50, fig. 22).

Discussion. This species has a subcentral beak 

and a general eopteriiform shape. The presence of a 

well-developed rostrum, a high anterior gape, and 

the lack of a ventral gape indicate that the species is 

not Eopteria. There is a good morphological progression from an eopteriid like Eopteria conocardiformis 

to a bransoniid like Bransonia beecheri. Stratigraphically, the two species are not in sequence, as B. 

beecheri is older. We interpret Eopteria conocardiformis to be a late-surviving primitive type, which 

provides insight into the origin of conocardiaceans.

Bransonia cressmani n. sp.

Plate 52, figures 6, 7,10-14; plate 53, figures 6-20; plate 54

Description. Small subquadrate Bransonia with 

body of shell rounded, not carinate posteriorly; rostrum small but rostral clefts well developed, rostral 

area oblique to dorsal margin in lateral view; snout 

considerably longer than rostrum; musculature consisting of pallial line and primary pedal retractor 

muscle.

Types. The holotype is shown on plate 52, figures 

10-14 (USNM 209266). It is about 3.6 mm long and 

3.2 mm high. We had more than 150 specimens of 

this species, of which most are silicified replicas; 

some are phosphatic internal molds which show the 

musculature. In addition to the holotype, we figure 

seven paratypes.

Type locality. The holotype is from USGS loc. 

5015-CO, a small quarry on east side of Mitchellsburg Road, 0.4 miles south of Perryville, Ky. Some 

of the paratypes are from the same locality as the 

holotype; others are from two additional localities: 

USGS loc. 6916-CO, large quarry on west side of 

U.S. Route 68, 1 mile north of junction with U.S. 

Route 150 in Perryville, Kentucky; and USGS loc. 

D-1200-CO, Frankfort East Section on eastbound 

lanes of Interstate Highway 64, east side of Kentucky River, Franklin County, Ky.

Stratigraphic distribution. The specimens from 

USGS loc. 5015-CO and 6916-CO are from the Perryville Limestone Member of the Lexington Limestone (Middle Ordovician). The specimens from 

locality D-1200-CO are from the Tanglewood Lime-
SYSTEMATIC PALEONTOLOGY 73

stone Member of the Lexington Limestone (Middle 

and Upper Ordovician).

Etymology. The species is named for Earle 

Cressman, U.S. Geological Survey, who has been a 

long-continuing help in collecting the fauna of the 

Lexington Limestone.

Bransonia? immatura (Billings), 1863

Discussion. The lectotype (GSC 1180a, Wilson, 

1956) of this species is an incomplete silica replica 

with an unusually elongate rostrum. It is not figured 

herein, and because of the state of its preservation, 

we are unsure of its generic assignment.

Stratigraphic distribution. The lectotype is from 

Leray-Rockland Beds of Wildernessian Age (Middle 

Ordovician), Paquette Rapids, Ottawa, Ontario, 

Canada.

Bransonia isbergi (Branson), 1942b

Discussion. This species is known only from one 

specimen which was not seen by us. As figured by 

Isberg (1934, pi. 29, fig. 7), it is a small form with 

the rostrum about equal in length to the snout and 

body of the shell. It is from the Upper Ordovician 

(Upper Leptaena Limestone) of Sweden.

Bransonia lindstromi (Isberg), 1934

Discussion. We have not seen any specimens of 

this species. The specimen figured by Isberg (1934, 

pi. 29, fig. 6) is articulated but incomplete at each 

end; it has a highly prominent ridge on the body of 

the shell. The species is known from the Upper Ordovician (Upper Leptaena Limestone) of Sweden.

Bransonia paquettensis (Wilson), 1956 

Plate 50, figures 25-27, 38

Discussion. The holotype (GSC 11585; pi. 50, 

fig. 38) of this species is the largest known Ordovician conocardiacean. The body of the shell has a 

prominent posterior carina. The holotype is from 

rocks of Wildernessian Age (Leray-Rockland Beds) 

(Middle Ordovician), Paquette Rapids, Ottawa 

River, Ottawa, Ontario, Canada.

A much smaller specimen, more or less similar in 

shape to the holotype of B. paquettensis, occurs in 

the Holston Formation (Middle Ordovician), Porterfield quarry, 5 miles east of Saltville, Va. (pi. 50, 

figs. 25-27; USNM 144969) and is herein classified 

as Bransonia aff. B. paquettensis.

Genus MULCEODENS new genus 

Plates 34, 35

Type species. Mulceodens jaanussoni n. sp. is 

herein designated the type species of the new genus 

Mulceodens.

Description. Bransoniids with short rostrum, 

dorsal part of snout rounded in frontal view and 

separated by a constriction from ventral part of 

snout; anterior marginal denticles strongly developed and enlarged so that they extend to the midline 

and touch or almost touch those on the opposite side 

of the shell.

Stratigraphic distribution. Silurian (Wenlockian)-Middle Devonian (Hamiltonian).

Geographic distribution. The genus is presently 

known from the Silurian of Sweden and the Devonian of Michigan and New York.

Etymology. Mulceo, Latin, meaning touch lightly ; Dens, Latin, meaning tooth. Gender masculine.

Mulceodens jaanussoni n. sp.

Plate 34, figures 1-16; plate 35, figures 1-3, 11,12 

Description. Small Mulceodens with prominent 

rostral clefts, marginal denticles of two valves alternate with one another, and with strong constriction 

below dorsal part of snout.

Types. The holotype (SMNH Mo. 151245) is 

shown on plate 35, figures 1-3, 11,12; it is about 6.7 

mm long and 4.7 mm high. In addition to the holotype, we figure 13 paratypes.

Type locality. All known specimens are from the 

Island of Gotland, Sweden.

Stratigraphic distribution. At present, the species is known only from the Silurian (WenlockianLudlovian) rocks of Gotland.

Etymology. The species is named for Valdar 

Jaanusson, Swedish National Museum, for his kindness in sending us a great many conocardiaceans 

from Sweden.

Mulceodens bifarius (Winchell), 1866 

Plate 35, figures 8-10

Discussion. We figure one specimen of this species (USNM 209306) from the upper Alpena Limestone (Middle Devonian) of Michigan, which shows 

the enlarged anterior denticles which almost touch. 

The holotype was figured by Branson (1942a).

Mulceodens denticulatus (Hall), 1883

Discussion. According to Branson (1942a), the 

original material of this species cannot be located. 

Hall's (1883, pi. 68, figs. 24, 25) figures show enlarged marginal denticles which alternate with one 

another, each set extending well beyond the midline 

of the shell. The species is from the Middle Devonian 

(Hamiltonian) of New York.
74 PALEONTOLOGY OF ROSTROCONCH MOLLUSKS

Mulceodens eboraceus (Hall), 1860

Plate 35, figures 4-7

Discussion. The species is known from two syntypes, of which the lectotype (AM 5347/1, herein 

chosen) is figured on plate 35, figures 4-7. Neither 

of the original specimens is complete; however, the 

lectotype shows the enlarged touching marginal denticles (pi. 35, fig. 7). The types are from the Middle 

Devonian (Hamiltonian) rocks of New York State.

Genus PSEUDOCONOCARDIUM Zavodowsky, 1960 

Plates 32, 40-42

Type species. Pseudoconocardium licharewi Zavodowsky, 1960 (p. 31), by monotypy and original 

designation.

Diagnosis. Bransoniids with snout and body of 

shell not obviously demarked from one another; has 

large anterior gape which extends the full height of 

the anterior margin, lacks longitudinal shelves, and 

has the marginal denticles limited to the edges of 

the gape.

Stratigraphic distribution. Upper Pennsylvanian-Upper Permian.

Pseudoconocardinm licharewi Zavodowsky, 1960

Discussion. We have seen no specimens of this 

species. Zavodowsky's (1960, pi. 6, figs. 1, 2) figures 

show that it is elongate, strongly ribbed, and has a 

posterior carina.

Stratigraphic distribution. Limestones of the 

Khivachsk Beds (Upper Permian) of the Gizhigi 

and Omolona River areas of the U.S.S.R.

Pseudoconocardium lanterna (Branson), 1965

Plate 32, figures 1, 2; plate 40, figures 3-14; plate 41;

plate 42, figures 1-7, 12-14

Discussion. This is the only species of the genus 

presently known from North America. It is more 

quadrate than the type species. In cross section, the 

inner shell layer of P. lanterna is continuous across 

the dorsal margin (pi. 32, figs. 1, 2) ; the outer shell 

layer is not continuous. Zavodowsky (1960, p. 32, 

fig. 2) showed a drawing of a cross section of P. 

licharewi; in this cross section, neither shell layer is 

continuous across the dorsal margin and there is 

thus a dorsal commissure. On the basis of what we 

have seen of rostroconchs we consider this to be 

unlikely. In none of the forms examined by us was 

the shell bivalved in the sense of a pelecypod. All 

rostroconchs have at least one shell layer continuous 

across the dorsal margin and, thus, there is no dorsal 

commissure.

Stratigraphic distribution. P. lanterna occurs 

abundantly in rocks of Late Pennsylvanian age

(Cisco Group, Gaptank Formation (in part), Graford Formation and its Brownwood Shale Member, 

Graham Formation, "Hog Creek Shale Member" of 

Caddo Creek Formation, and Palo Pinto Limestone 

of Texas; and Union Valley Formation of 

Oklahoma).

Family HIPPOCARDIIDAE new family

Description. Conocardiaceans with one or more 

hoods around the rostral area of the shell, each hood 

consisting of right and left halves; longitudinal 

shelves present or absent in anterior gape.

Stratigraphic distribution. Middle Ordovician 

(Llandeilian)-Mississippi^ (Tournaisian).

Discussion. This is a large family which at present we have divided into two genera: Hippocardia 

and Bigalea are distinguished by the number of posterior hoods present in each genus. In the future, 

additional generic subdivision of the family may be 

based upon such criteria as the presence or absence 

of longitudinal shelves in the anterior gape, type of 

ornamentation, etc., but at present we do not have 

sufficient material of hippocardiids to attempt such 

subdivision.

Genus HIPPOCARDIA Brown, 1843

Plates 32, 44-50

Type species. Cardium hibernicum Sowerby, 

1815 (p. 187) by original designation and monotypy. 

Sowerby (1815, p. 187), following the name of Cardium hibernicum, indicated that the species was 

illustrated on his plate 82, figures 1, 2; his description clearly indicates that C. hibernicum is illustrated on his plate 82, figures 1, 3. Pleurorhynchus 

Phillips (1836, p. 210), is an invalid senior objective 

synonym of Hippocardia, as both are based upon the 

same type species. The name Pleurorhynchus was 

previously used by Rudolphi (1801) as an invalid 

emendation of Pleurorinchus Nau (1787).

Diagnosis. Hippocardiids with one hood around 

the rostral area of the shell.

Stratigraphic distribution. Middle Ordovician 

(Llandeilian)-Mississippian (Tournaisian).

Discussion. This long-ranging genus contains all 

conocardiaceans with a single hood; it seems likely 

that when the group becomes better known it will be 

divided into several generic-level taxa.

Hippocardia hibernica (Sowerby), 1815 

Plate 46, figures 1-12

Diagnosis. Large Hippocardia with large arcuate 

hood, markedly constricted snout, and longitudinal 

shelves in the anterior gape.
SYSTEMATIC PALEONTOLOGY 75

Types and materials. The lectotype of this species was chosen by Hind (1900, explanation for his 

figure 11, plate 53). We figure five specimens of the 

species.

Stratigraphic distribution. The species is known 

from Lower Carboniferous (Mississippian) rocks of 

England, Ireland, and Belgium.

Hippocardia antiqua (Owen), 1852

Plate 50, figure 14

Discussion. The holotype (USNM 17897) of the 

species is figured herein; it has a carina at the junction of the body of the shell with the rostral area, 

but nothing of the hood is preserved. Branson 

(1942b, pi. 59, fig. 8) figured a specimen of this species showing the hood. The species is from Ordovician rocks, Lower Fort Garry, Red River of the 

North, Manitoba, Canada.

Hippocardia bella (Cooper and Cloud), 1938

Plate 44, figures 5-14

Discussion. This species is from the Devonian 

rocks of Illinois. It has a small but obvious hood. The 

snout is larger, in proportion to the whole shell, than 

that of H. hibernica. The anterior gape is largely 

restricted to the dorsal part of the snout. We figure 

the holotype of the species (USNM 95192a) and 

three paratypes.

Hippocardia bohemica (Barrande), 1881

Plate 32, figure 3; plate 47, figures 1-7 

Discussion. H. bohemica is known from the Devonian of Konieprus, Bohemia, Czechoslovakia. It 

has a prominent hood and a rostrum with an unusually tall base. We figure two specimens.

Hippocardia calcis (Baily), 1860

Discussion. We have seen no specimens of this 

species, but Baily's figures (1860, p. 11) clearly 

show the presence of a hood. Baily gave the stratigraphic occurrence as "Llandeilo?" (Middle Ordovician); it is from the townland of Reafadda, County Tipperary, Northern Ireland.

Hippocardia cooperi n. sp. 

Plate 45, figures 10-14

Description. Small Hippocardia with hood forming prominent flanges on either side of the shell, 

sculpture of snout reticulate, ventral part of anterior 

gape slitlike.

Types. The holotype (USNM 162786) is figured 

on plate 45, figures 10-14; it is about 5.5 mm long 

and 6 mm high. In addition to the holotype, we had 

11 fragmentary specimens, none of which are figured. All specimens are silicified replicas, and only

the outer shell layer is preserved. Pojeta (1971) 

figured this species as Conocardium sp.

Type locality. All known material of H. cooperi 

is from USNM loc. 600 near Strasburg, Va.

Stratigraphic distribution. Lower Chambersburg Limestone (Middle Ordovician).

Etymology. The species is named for G. A. Cooper, U.S. National Museum, who collected the specimens and gave them to us to examine.

Hippocardia cunea (Conrad), 1840

Plate 32, figures 5, 6; plate 33, figures 1, 2; plate 48, 

figures 1-15; plate 49, figures 1-15; plate 50, figures 1, 2

Discussion. Hippocardea cunea is a widely distributed species in the Devonian rocks of the northeastern United States. It is a large species with a 

hood that can exceed the length of the rest of the 

shell. The rostrum is a scooplike structure different 

from other conocardiaceans and is described in the 

section on growth (p. 10-11). According to Branson 

(1942a), Conrad's types are mixed with Hall's 

(1885) hypotypes and can no longer be identified. 

Three of Hall's hypotypes are herein figured on 

plate 48, figures 1, 5, 8-11 (NYSM 2313, AM 

2853a/3, FM 12500).

Stratigraphic distribution. Lower-Middle Devonian of the northeastern United States.

Hippocardia? diptera (Salter), 1851

Discussion. We have not seen the specimens of 

this species figured by Salter (1851) or Hind (1910). 

One of the specimens figured by Hind (1910, pi. 5, 

fig. 30) appears to have a remnant of the hood, and 

on this basis, we tentatively place the species in 

Hippocardia. The species is from the Llandeilian 

(Middle Ordovician) of Scotland.

Hippocardia fusiformis (McCojr), 1844

Plate 45, figures 5-9

Discussion. This is the largest known conocardiacean, reaching a maximum length of at least 100 

mm and having longitudinal shelves. We figure two 

specimens of the species from the Mississippian 

(Tournaisian) of Belgium. Hind (1900) figured 

McCoy's holotype and noted that the species occurs 

in the Mississippian of Ireland.

Hippocardia limatula (Bradley), 1930 

Plate 50, figures 15-19

Discussion. This small species has a prominent 

hood and occurs in the Kimmswick Limestone (Middle Ordovician) of Illinois and Missouri.
76 PALEONTOLOGY OF ROSTROCONCH MOLLUSKS

Hippocardia monroica (Grabau), 1910

Plate 44, figures 15,16; plate 45, figures 1-4

Discussion. The specimens of this species figured 

by us do not show the hood; however, this structure 

is well figured by Branson (1942a) and LaRocque 

(1950). The species occurs in the Middle Devonian 

(Amherstburg Formation, Lucas Formation) of 

Michigan and Ontario.

Hippocardia praepristis (Reed), 1952

Discussion. We have seen no specimens of this 

species. Reed's (1952) figures show the presence of 

a hood. H. praepristis is from the Ordovician of 

County Tyrone, Northern Ireland.

Hippocardia pygmaea (Hisinger), 1837 

Plate 50, figure 3

Discussion. We figure Branson's (1942b) hypotype (USNM 98871) of this species which clearly 

shows the hood. The museum label lists the specimen 

as coming from the "Borkholm Beds, Silurian, Borkholm, Estonia." Valdar Jaanusson (written commun., 1975) noted that the specimen i.s probably 

from Upper Ordovician rocks, Porkuni Stage, Porkuni ("Borkholm"), Estonia.

Hippocardia richmondensis (Foerste), 1910 

Plate 50, figures 6-10

Discussion. We figure the holotype (USNM 

87041) and a second specimen of this species (MU 

209T); both clearly show the presence of a small 

hood. The species is known from Upper Ordovician 

(Richmondian) rocks of Indiana and Ohio.

Hippocardia? zeileri (Beushausen), 1895 

Plate 47, figures 8-12

Discussion. This species has the general form 

and appearance of species placed in Hippocardia, although none of the material seen by us shows a hood. 

The hood is readily detached from the umbos and 

does not leave a recognizable scar. We tentatively 

place this species in Hippocardia. H. ? zeileri is from 

the Devonian of Germany.

Hippocardia spp. 

Plate 50, figures 4, 5, 11-13

Discussion. The forms discussed under this heading add data about the stratigraphic and geographic 

distribution of Hippocardia but cannot now be placed 

in a species. The specimen shown on plate 50, figures 

4, 5 is from the Silurian (Wenlockian) rocks of the 

Island of Gotland, Sweden. It shows a well-developed 

hood and in general body form is similar to H. 

cooperi n. sp.

The specimen shown on plate 50, figure 11 is incomplete, but shows the occurrence of the genus in 

the Middle Ordovician (Platteville Limestone) of 

Illinois. The form shown on plate 50, figure 12, shows 

the occurrence of Hippocardia in the Ordovician of 

England. The specimen shown on plate 50, figure 13, 

is crushed and incomplete, but it shows the occurrence of the genus in the Middle Ordovician (Porterfieldian) of Virginia.

Genus BIGALEA new genus

Plates 35-37

Type species. Bigalea yangi n. sp. is herein designated the type species of the new genus Bigalea.

Description. Hippocardiids with two small posterior rostral hoods, each with a separate ventral 

aperture; ventral part of anterior gape slitlike.

Stratigraphic distribution. Silurian (Wenlockian)-Middle Devonian ("Petoskey Limestone" in 

Traverse Group).

Geographic distribution. The genus is presently 

known from the Silurian of Sweden and the Devonian of the Falls of the Ohio River, Michigan, and 

Germany.

Etymology. Bi, Latin, meaning two; Galea, Latin, meaning helmet. Gender feminine.

Bigalea yangi n. sp.

Plate 36, figures 13-16; plate 37, figures 1-4

Description. Bigalea with posterior hoods close 

together and near posterior end of umbo; rostral 

area flat not produced ventrally, rostrum short; marginal denticles of two valves touching medially in 

ventral part of anterior gape; length about equal to 

height.

Types. The holotype (USNM 209301) is shown 

on plate 37, figures 1-3; it is about 18.6 mm long and 

13 mm high. In addition, we figure two paratypes 

(FM 18331,18332).

Type locality. The holotype is from a quarry at 

Mud Lake, about 1.5 miles northeast of Bay View, 

Emmet County, Michigan. The paratypes are from 

Kegomic, Little Traverse Bay, Mich.

Stratigraphic distribution. The species is presently known only from the "Petoskey Limestone" in 

the Traverse Group (Middle Devonian) of Michigan.

Etymology. The species is named for S. Y. Yang 

who studied the Devonian mollusks of Michigan at 

Yale University in the late 1930's.

Bigalea clathra (d'Orbigny), 1850

Plate 37, figures 5-15

Diagnosis. Bigalea with hoods at anterior and 

posterior ends of umbo, hoods of about equal length;
SYSTEMATIC PALEONTOLOGY 77

marginal denticles of two valves not touching in 

ventral part of anterior gape.

Materials. We have not seen the type material of 

this species. We figure four specimens from the collections of the Museum of Comparative Zoology, 

Harvard University, and the University of Michigan.

Stratigraphic distribution. B. dathra is presently known only from the Devonian of Germany.

Bigalea ohioensis n. sp. 

Plate 36, figures 5-12

Description. Bigalea with hoods close together, 

but both not at posterior end of umbo; the anterior 

of the two hoods extends down the umbo with a significant gap between it and the posterior hood; anterior hood longer than posterior; rostral area produced ventrally; significantly longer than high.

Types. The holotype (USNM 209302) is shown 

on plate 36, figures 5-7; it is about 8.7 mm long and 

5.5 mm high. In addition, we figure three paratypes 

(USNM 209303-209305).

Type locality. The locality of the known material 

of this species is uncertain; it probably came from 

the Falls of the Ohio River.

Stratigraphic distribution. The stratigraphic occurrence of the species is uncertain; it is probably 

from Devonian rocks at the Falls of the Ohio River.

Etymology. The species name is derived from 

the Ohio River.

Bigalea visbyensis n. sp.

Plate 35, figures 13-17; plate 36, figures 1-4

Description. Bigalea with significant space between two hoods as in B. ohioensis; posterior hood 

longer than anterior and extended ventrally beyond 

the shell proper; rostrum long and colinear with 

hinge; marginal denticles of two valves touching at 

midline in ventral part of anterior gape.

Types. The holotype (SMNH Mo. 18552) is 

shown on plate 35, figures 16, 17, plate 36, figures 1, 

2; it is about 9.3 mm long and 6.7 mm high. In addition, we figure two paratypes (SMNH Mo. 18553, 

18554).

Type locality. Visby on the Island of Gotland, 

Sweden.

Stratigraphic distribution. The species is presently known only from the Silurian (Wenlockian) 

rocks of the Island of Gotland.

Etymology. The species name is derived from 

Visby, Sweden.

ROSTROCONCHIA INCERTAE SEDIS

Discussion. Three monotypic genera of rostroconchs, or probable rostroconchs, remain, which at

present cannot be placed in a family or order. Some 

of the uncertainty about these forms is due to the 

fact that we have not seen specimens or adequate 

replicas of the species concerned. We briefly discuss 

these forms under this heading.

Euchasmella multistriata Kobayashi, 1933

Discussion. This species is known from two 

specimens, of which one was figured by Kobayashi 

(1933). We had a plaster replica of the holotype to 

examine; this plastotype was much deteriorated with 

age and is not figured herein. As figured by Kobayashi (1933, pi. 8, fig. 5), the species is a large finely 

ribbed form with a pegma. It may be allied to the 

Eopteriidae.

According to Kobayashi (1933, p. 295), E. multistriata is from the "Wanwankou dolomite [Lower 

Ordovician]; Wan-wan-kou in the Niuhsintai Basin, 

South Manchuria."

Myona flabelliformis Kobayashi, 1935

Discussion. This species is known only from the 

material described by Kobayashi (1935). It resembles some rostroconchs in shell shape and what appears to be the presence of side muscles. M. flabelliformis is presently known only from internal molds 

preserved on bedding planes. No articulated specimens are known. Extending distally from the supposed side muscle scars and from the posterior dorsal margin are a series of ridges which Kobayashi 

(1935, p. 325) compared with the vascular sinuses 

of brachiopods.

We have seen no specimens, or replicas of specimens, of this species; we suggest that it is a rostroconch on the basis of its shape and the presence of 

apparent side muscle scars. At present, M. flabelliformis is known only from the "Drepanura zone, 

Seison Slate, upper Middle Cambrian, of Saisho-ri, 

South Korea" (Kobayashi, 1935, p. 58, 326).

Pseudoeuchasma typica Kobayashi, 1933 

Plate 21, figures 1, 2

Discussion. This species is known from two 

specimens, of which one was figured by Kobayashi 

(1933). We had a plaster replica of the holotype 

(USNM 94011) to examine. It shows a markedly 

flattened surface of the shell at one end and a carinate umbo; the species bears resemblances to the 

Hippocardiidae. According to Kobayashi (1933, p. 

302), P. typica is from the "Wanwankou dolomite 

[Lower Ordovician]; Wan-wan-kou in the Niuhsintai Basin, Manchuria."
78 PALEONTOLOGY OF ROSTROCONCH MOLLUSKS

REFERENCES CITED

Aksarina, N. A., 1968, [New data on the geology and guide 

fossils of western Siberia, v. 3]: Tomsk, Univ. Tomsk, 

p. 77-86,1 pi. (In Russian.)

Babin, Claude, 1966, Mollusques bivalves et cephalopodes du 

Paleozoique Armoricain: Brest, Imprimerie Commerciale 

et Administrative, 471 p., 18 pis.

Baily, W. H., I860, in Explanations to accompany sheet 145 

of the maps of the Geological Survey of Ireland, illustrating part of the County of Tipperary: Dublin, Alexander 

Thorn & Sons, 35 p.

Barrande, Joachim, 1881, Systeme Silurien du centre de la 

Boheme, v. 6, Acephales: Paris and Prague, 342 p., 361 

pis. (Bound in 4 v.)

Barrington, E. J. W., 1967, Invertebrate structure and function : London, Nelson, 549 p.

Bassler, R. S., 1915, Bibliographic index of American Ordovician and Silurian fossils: U.S. Natl. Mus. Bull. 92, 

1521 p., 4 pis. (Bound in 2 v.)

Batten, R. L., 1972, The ultrastructure of five common Pennsylvanian pleurotomarian gastropod species of United 

States: Am. Mus. Nat. History, Am. Mus. Novitates, no. 

2501, 34 p.

Batten, R. L., Rollins, H. B., and Gould, S. J., 1967, Comments on "The adaptive significance of gastropod torsion": Evolution, v. 21, no. 2, p. 405-406.

Beushausen, H. E. L., 1895, Die Lamellibranchiaten des 

rheinischen Devon mit Ausschluss der Aviculiden: K. 

Preuss. Geol. Landesanst. Abh., new ser., v. 17, 514 p., 

and atlas of plates.

Bevelander, Gerrit, and Nakahara, Hiroshi, 1969, An electron 

microscope study of the formation of the ligament of 

Mytilus edulis and Pinctada radiata: Calcified Tissue Research, v. 4, p. 101-112.

Billings, Elkanah, 1859, Fossils of the calciferous sandrock 

including those of a deposit of white limestone at Mingan, 

supposed to belong to the formation: Canadian Naturalist, v. 4, p. 345-367.

 1863, [Conocardium immaturum'], in Canada Geol. 

Survey, Report of progress from its commencement to 

1863: Montreal, Dawson Brothers, p. 143.

 1865, Palaeozoic fossils, Vol. 1: Canada Geol. Survey, 

426 p.

1866, Catalogues of the Silurian fossils of the Island

of Anticosti: Canada Geol. Survey, 99 p. 

Blainville, H. M. D. de, 1816, Prodrome d'une nouvelle distribution systematique du regne animal: Soc. Philomatique, Paris, Nouveau Bull., p. 51-53, 93-97. 

Boettger, C. R., 1962, Gastropoden mit zwei Schalenklappen:

Deutsch. Zool. Gesell. Wien., Vehr., v. 11 no. 15, p. 403-

439. 

Bradley, J. H., 1930, The fauna of the Kimmswick limestone

of Missouri and Illinois: Chicago Univ., Walker Mus.

Contr., v. 2, no. 6, p. 219-290, 8 pis. 

Branisa, Leonardo, 1965, Los fosiles guias de Bolivia; I.

Paleozoico: Bolivia Serv, Geol. Bol. 6, 282 p., 80 pis. 

Branson, C. C., 1942a, Type invertebrate fossils of North

America (Devonian): Conocardiidae: Philadelphia,

Wagner Free Inst. Sci., 30 cards. 

 1942b, Correction of homonyms in the lamellibranch

genus Conocardium: Jour. Paleontology, v. 16, no. 3, p.

387-392, pi. 59.

 1948, Bibliographic index of Permian invertebrates: 

Geol. Soc. America Mem. 26, 1049 p.

 1965, New species of Conocardium : Oklahoma Geology 

Notes, v. 25, no. 9, p. 247-251.

1966, Conocardium in the Bromide Formation (Ordovician) of Oklahoma: Oklahoma Geology Notes, v. 26, no.

3, p. 78-79. 

Branson, C. C., LaRocque, Aurele, and Newell, N. D., 1969,

in Moore, R. C., ed., Treatise on invertebrate paleontology,

pt. N. Mollusca 6, v. 2: New York and Lawrence, Kans.

Geol. Soc. America and Univ. Kansas Press, p. N859-

N860. 

Branson, E. B., 1909, The fauna of the residuary Auburn

Chert of Lincoln County, Missouri: Acad Sci. St. Louis

Trans., v. 18, no. 4, p. 39-52, pi. 7. 

Bronn, H. G., 1835, Lethaea Geognostica *** Bd. 1: Stuttgart,

E. Schweizerbart, 672 p.

1862, Klassen und Ordnungen des Thier-Reichs wissenschaftlich dargestellt in Wort und Bild. Bd. 1. Malacozoa. Abt. 1, Malacozoa acephala: Leipzig, C. F. Winter. 

518 p., 44 pis.

Brown, Thomas, 1843, The elements of fossil conchology ***: 

London, Houlston & Stoneman, 133 p., 12 pis.

Butts, Charles, 1941, Geology of the Appalachian Valley in 

Virginia. Pt. 2, Fossil plates and descriptions: Virginia 

Geol. Survey Bull. 52, pt. 2, 271 p., pis. 64-135 [1942].

Carter, R. M., 1967, The shell ornament of Hysteroconcha 

and Hecuba (Bivalvia): a test case for inferential functional morphology: Veliger, v. 10, no. 1, p. 59-71, pis. 

5-7.

Casey, J. N., Reynolds, M. A., Pritchard, P. W., Lucas, K. 

G., and Paten, F. J., 1965, Glenormiston, Queensland: 

Australia Bur. Mineral Resources, Geology, and Geophysics, 1:250,000 Geol. Ser. SF54-9 (explanatory notes, 

by M. A. Reynolds).

Chanley, Paul, and Chanley, Matoira, 1970, Larval development of the commensul clam, Montacula percompressa 

Dall: Malacolog. Soc. London Proc., v. 39, p. 59-67, pis. 

1-3.

Clarke, J. M., 3904, Naples fauna in western New York, pt. 

2: New York State Mus. Mem. 6, p. 199-454, pis. 1-20.

Cleland, H. F., 1900, The Calciferous of the Mohawk Valley: 

Bulls. Am. Paleontology, v. 3, no. 13, 26 p., pis. 15-17.

 1903, Further notes on the Calciferous (Beekmantown) Formation of the Mohawk Valley, with descriptions of new species: Bulls. Am. Paleontology, v. 4, no. 

18, 24 p., pis. 3, 4.

Cloud, P. E., and Barnes, V. E., 1948, The Ellenburger Group 

of central Texas: Texas Univ. Pub. 4621, 473 p., 44 pis.

Cobbold, E. S., 1921, The Cambrian horizons of Comley 

(Shropshire), their Brachiopoda, Pteropoda, Gasteropoda, 

etc: Geol. Soc., London, Quart. Jour. v. 76, p. 325-386, 

pis. 21-24.

 1935, Lower Cambrian faunas from Herault, France: 

Annals and Mag. Nat. History, ser. 10, v. 16 no. 91, p. 

25-48, pis. 2-4.

Collie, G. L, 1903, Ordovician section near Bellefonte, Pennsylvania; Geol. Soc. America Bull., v. 14, p. 407-420.

Conrad, T. A., 1840, Third annual report on the palaeontological department of the Survey [of New York]: New York 

Geol. Survey Ann. Rept. 4, p. 199-207.
REFERENCES CITED 79

 1842, Observations on the Silurian and Devonian systems of the United States, with descriptions of new organic remains: Acad. Nat. Sci. Philadelphia Jour., v. 8, 

pt. 2, p. 228-280, pis. 12-17.

Cooper, G A., and Cloud, P. E., 1938, New Devonian fossils 

from Calhoun County, Illinois: Jour. Paleontology, v. 12, 

no. 5, p. 444-460, 2 pis.

Cox, L. R., and others, 1969, in Moore, R. C., ed., Treatise on 

invertebrate paleontology, pt. N, Mollusca 6, v. 1, 2: New 

York and Lawrence, Kansas, Geol. Soc. America and 

Univ. Kansas Press, 2 v.: 952 p.

Cuvier, Georges, 1797, Tableau elementaire de 1'histoire naturelle des animaux: Paris, 710 p., 14 pis.

Dall, W. H., 1878, Descriptions of new forms of mollusks 

from Alaska contained in the collections of the National 

Museum: U.S. Natl. Mus. Proc., v. 1, p. 1-3.

 1913, Pelecypoda, in Zittel, K. A. von, Textbook of 

paleontology, ed. by C. R. Eastman, (2d ed.) : London, 

Macmillan and Co., v. 1, p. 422-507.

Easton, W. H., 1962, Carboniferous formations and faunas 

of central Montana: U.S. Geol. Survey Prof. Paper 348, 

126 p, 14 pis.

Etheridge, Robert, 1878, Notes on a few Silurian fossils from 

the neighborhood of Girvan, Ayrshire: Royal Phys. Soc. 

Edinburgh Proc., v. 4, p. 167-177, pi. 4.

Etheridge, Robert, Woodward, Henry, and Jones, R. T., 1890, 

Seventh report of the committee on the fossil Phyllopoda 

of the Paleozoic rocks: British Assoc. Adv. Sci., Rept. 

59th Meeting (Newcastle-upon-Tyne), p. 63-68.

Fisher, D. W., 1962, in Moore, R. C., ed., Treatise on invertebrate paleontology, pt. W, Miscellanea. New York and 

Lawrence, Kansas, Geol. Soc. America and Univ. Kansas 

Press, p. W98-W143.

Fletcher, H. 0., 1943, The genus Conocardium from Australian Paleozoic rocks: Australian Mus., Sydney, Rec., v. 21, 

no. 4, p. 231-243, pis. 13-14.

Flower, R. H., 1964, The nautiloid order Ellesmeroceratida 

(Cephalopoda): New Mexico Bur. Mines and Mineral Resources Mem. 12, 234 p.

 1968, The first great expansion of the actinoceroids: 

New Mexico Bur. Mines and Min. Resources Mem. 19, 

pt. 1, p. 1-16, 57-86, 118-120.

Foerste, A. F., 1910, Preliminary notes on Cincinnatdan and 

Lexington fossils of Ohio, Indiana, Kentucky, and Tennessee: Denison Univ. Sci. Labs. Bull., v. 16, p. 17-100, 

pis. 1-6.

 1914, Notes on the Lorraine faunas of New York and

Province of Quebec: Denison Univ. Sci. Labs. Bull., v.

17, p. 247-339, pis. 1-5. 

Fretter, V., 1969, Aspects of metamorphosis in prosobranch

gastropods: Malacolog. Soc. London Proc., v. 38, p. 375-

386.

Fretter, V., and Graham, A., 1962, British prosobranch gastropods : London, Ray Soc., 755 p. 

Galtsoff, P. S., 1964, The American oyster Crassostrea virginica Gmelin: U.S. Fish and Wildlife Service Fishery

Bull., v. 64, 480 p., 400 figs. 

Garstang, W., 1928, The origin and evolution of larval forms:

Adv. Sci., 1928, sec. D, p. 1-23; British Assoc. Glasgow

Rept., 1928, sec. D, p. 77-98. 

Ghiselin, M. T., 1966, The adaptive significance of gastropod

torsion: Evolution, v. 20, no. 3, p. 337-348.

Gigout, Marcel, 1951, fitudes geologiques sur la Meseta Marocaine occidentale (arriere-pays de Casablanca, Mazagan 

et Safi): Morocco Serv. Geol., Notes et Mem., no. 86, 

507 p., 18 pis. (Text and plates bound separately.)

Girard, A. A., 1897, Sur le "Thyrophorella thomensis" Greeff, 

gasteropode terrestre muni d'un faux opercule a charniere: Jornal Sciencias Mathematicas, Physicas, Naturaes 

(Lisboa), ser. 2, v. 4, no. 13, p. 28-32 [1895].

Glaessner, M. F., 1971, Geographic distribution and time 

range of the Ediacara Precambrian fauna: Geol. Soc. 

America Bull., v. 82, no. 2, p. 509-513.

Goldfuss, G. A., 1820, Handbuch der zoologie: Niirnberg, 

J. L. Schrag, 2 v.

Grabau, A. W., 1900, Paleontology of the Cambrian terranes 

of the Boston Basin: Boston Soc. Nat. History Occas. 

Papers, v. 4, pt. 3, p. 601-694, 8 pis.

Grabau, A. W., and Sherzer, W. H., 1910, The Monroe Formation of southern Michigan and adjoining regions: Michigan Geol. and Biol. Survey, Geol. Ser., v. 1, pub. 2, 248 p.

Grant, R. E., 1966, A Permian productoid brachiopod: life 

history: Science, v. 152, no. 3722, p. 660-662.

Hall, James, 1860, Descriptions of new species of fossils 

from the Hamilton group of western New York, with 

notices of others from the same horizon in Iowa and 

Indiana: New York State Cabinet Nat. History Ann. Rept. 

13, p. 76-94.

 1883, Lamellibranchiata [plates and explanations]: 

New York Geol. Survey, Paleontolgy, v. 5, pt. 1, 20 p., 

pis. 1-34, 36-41, 43-80.

1885, Lamellibranchiata, II. Descriptions and figures

of the Dimyaria of the Upper Helderberg, Hamilton, 

Portage, and Chemung groups: New York Geol. Survey, 

Paleontology, v. 5, pt. 1, II, p. 269-561, pis. 34-80, 93-96.

Harry, H. W., 1969, An alternative view on the phylogeny of 

the Mollusca, in Symposium on Mollusca, Proc., pt. 1: 

Mandapam Camp, India, Marine Biol. Assoc. India, p. 

170-187.

Hatscheck, Berthold, 1891, in Blumrich, Joseph, Das Integument der Chitonen: Zeitschr. fur Wiss. Zoologie, v. 52, p. 

404-406.

Healey, Maud, 1908, The fauna of the Napeng Beds or 

Rhaetic Beds of upper Burma: India Geol. Survey Mem., 

Palaeontographica Indica, new ser., v. 2, no. 4, 88 p., 9 

pis.

Hemming, F., 1954, Opinion 231: Opinions and declarations 

rendered by the International Commission on Zoological 

Nomenclature, v. 4, pt. 21, p. 239-248.

Hill, Dorothy, Playford, G., and Woods, J. T., editors, 1969, 

Ordovician and Silurian fossils of Queensland: Brisbane, 

Queensland Palaeontographical Soc., 15 p., 7 pis. (Ordovician), 18 p., 8 pis. (Silurian).

 1971, Cambrian fossils of Queensland: Brisbane, 

Queensland Palaeontographical Soc., 32 p.

Hind, Wheelton, 1900, A monograph of the British Carboniferous Lamellibranchiata, Vol. I, Part V, Coelonotidae, 

Solenomyidae, Conocardiidae, Cardiidae: Palaeontographical Soc. (London) Mon., v. 54, p. 361-476, pis. 40-54.

 1910, The lamellibranchs of the Silurian rocks of 

Girvan: Royal Soc. Edinburgh Trans., v. 47, pt. 3, p. 479- 

548, pis. 1-5.
80 PALEONTOLOGY OF ROSTROCONCH MOLLUSKS

Hintze, L. F., 1951, Lower Ordovician detailed stratigraphic 

sections for western Utah: Utah Geol. Mineralog. Survey Bull. 39, 100 p.

Hisinger, Wilhelm, 1837, Lethaea Svecica; seu, Petrifacta 

Sveciae, iconibus et characteribus illustrata: Holmiae, 

Typ. P. A. Norstedt et Filii, 124 p., 39 pis.

Horny, R. J., 1957, Problematicheskie mollyuski (?Amphineura) iz nizhnego kembriya yuzsnoi i vostochnoi Sibiri 

(SSSR) : Czechoslovakia, TJstfed. TJstav. Geol. Sbornik, 

sv. 23 (1956), Paleontologie, p. 397-431, pis. 1-4 (Czech 

and English summaries).

 1965, Cyrtolites Conrad, 1838 and its position among 

The Monoplacophora (Mollusca) : Prague, Narodni Mus., 

Sbornik, Rada B (Pfirodni vedy) v. 21, p. 57-70.

Howell, B. F., and Kobayashi, Teiichi, 1936, A new notastracan genus from the Ordovician of Siberia: Carnegie Mus., 

Annals v. 25, p. 59-61.

Hubendick, Bengt, 1957, On the molluscan adhesive epithelium: Arkiv zoologi, Ser. 2, v. 11, no. 3, p. 31-36, 3 pis.

Hunter, W. R., and Grant, D. C., 1962, Mechanics of the 

ligament in the bivalve Spisula solidissima in relation to 

mode of life: Biol. Bull., v. 122, no. 3, p. 369-379.

Ihering, Hermann von, 1876, Versuch eines natiirlichen Systemes der Mollusken: Deutsch. Malakozool. Gesell., Jahrb. 

3 (1876), p.97-148.

Isberg, Orvar, 1934, Studien iiber lamellibranchiaten des 

Leptaenakalkes in Dalarna: Lund, Hakan Ohlssons Buchdruckerei, 493 p., 32 pis.

Jamieson, E. R., 1971, Paleoecology of Devonian reefs in western Canada, m Reef organisms through time: North 

American Paleont. Convention Proc., Pt. J (1969), p. 

1300-1340.

Jones, P. J., Shergold, J. H., and Druce, E. C., 1971, Late 

Cambrian and Early Ordovician stages in western Queensland: Geol. Soc. Australia Jour., v. 18, pt. 1, p. 1-32.

Jones, T. R., and Woodward, Henry, 1888-1899, A monograph 

of the British Palaeozoic Phyllopoda: London, Palaeontographical Soc., 211 p., 31 pis., (Also issued in the 

Palaeontographical Society [Monographs], v. 41, 46, 52- 

53 for 1887, 1892, 1898-99.)

 1895, On some Palaeozoic Phyllopoda: Geol. Mag., 

new ser., Decade 4, v. 2. no. 12, p. 539-545, pi. 15.

Kawaguti, S., 1950, Observations on the heart shell, Corculum 

cardissa (L.) and its associated Zooxanthellae: Pacific 

Sci., v. 4, p. 43-49.

 1959, Formation of the bivalve shell in the gastropod 

Tamanovalva Umax: Japan Acad. Proc., v. 35, p. 607- 

611.

Kawaguti, S., and Baba, K., 1959, A preliminary note on a 

two-valved sacoglossan gastropod Tamanovalva Umax n. 

gen., n. sp., from Tamano, Japan: Okayama Univ. Biol. 

Jour., v. 5, p. 177-184.

Kawaguti, S., and Yamasu, T., 1960, Formation of the adductor muscle in a bivalved gastropod, Tamanavalva 

Umax: Okayama Univ. Biol. Jour., v. 6, p. 150-159.

 1961, The shell structures of the bivalved gastropod, 

Tamanovalva Umax: Okayama Univ. Biol. Jour., v. 7, 

p. 1-16.

Kay, E. A., 1968, A review of bivalved gastropods and a discussion of evolution within the Sacoglossa, in Fretter, 

Vera, ed., Studies in the structure, physiology, and ecology of Mollusca: New York, Academic Press, p. 109- 

134.

Knight, J. B., 1941, Paleozoic gastropod genotypes: Geol. Soc. 

America Spec. Paper 32, 510 p., 96 pis.

 1947, Bellerophont muscle scars: Jour. Paleontology, 

v. 21, no. 3, p. 264-267, pi. 42.

 1952, Primitive fossil gastropods and their bearing on 

gastropod classification: Smithsonian Misc. Colln., v. 117, 

no. 13, 56 p., 2 pis.

1956, New families of Gastropoda: Washington Acad.

Sci. Jour., v. 46, no. 2, p. 41-42. 

Knight, J. B., and others, 1960, Part I, Mollusca 1, of Moore,

R. C., ed., Treatise on invertebrate paleontology: New

York and Lawrence, Kansas, Geol. Soc. America and

Univ. Kansas Press, 351 p. 

Kobayashi, Teiichi, 1933, Faunal study of the Wanwanian

(basal Ordovician) series with special notes on the

Ribeiridae and the ellesmereoceroids: Tokyo Imp. Univ.

Fac. Sci. Jour. sec. 2, v. 3, pt. 7, p. 249-328, pis. 1-10.

 1934, The Cambro-Ordovician formations and faunas 

of south Chosen, pt. 2, Lower Ordovician faunas: Tokyo 

Imp. Univ. Fac. Sci. Jour., sec. 2, v. 3, pt. 9, p. 521-585, 

pis. 1-8.

 1935, The Cambro-Ordovician formations and faunas 

of south Chosen; Paleontology, Part III, Cambrian faunas 

of south Chosen with a special study on the Cambrian 

trilobite genera and families: Tokyo Imp. Univ. Fac. Sci. 

Jour., sec. 2, v. 4. pt. 2, p. 344, 24 pis.

 1936, The world-wide distribution of the ribeirioid in 

the Ordovician Period: Geol. Soc. Japan Jour., v. 43, no. 

512, p. 349-358, 8 figs.

1954, Fossil estherians and allied fossils: Tokyo Univ.

Fac. Sci. Jour., sec. 2, v. 9, pt. 1, p. 1-192.

Lacaze-Duthiers, Henri, 1856-1857, Histoire de 1'organization 

et du development du Dentale: Sci. Nat. France Ann., 

ser. 4, Zoologie, v. 6, p. 225-281; v. 7, p. 5-51, 171-228; 

v. 8, p. 18-44.

La Rocque, J. A. A., 1950, Pre-Traverse Devonian pelecypods 

of Michigan: Michigan Univ. Mus. Paleontology Contr., 

v. 7, no. 10, p. 271-366, pis., 1-9.

Lemche, Henning, 1957, A new living deep-sea mollusc of the 

Cambro-Devonian Class Monoplacophora: Nature, v. 179, 

p. 413-416.

Lemche, Henning, and Wingstrand, K. G., 1959, The anatomy 

of Neopilina galatheae Lemche, 1957: Galathea Kept., 

v. 3, p. 9-71, pis. 1-56.

Lochman, Christina, and Duncan, Donald, 1944, Early Upper 

Cambrian faunas of central Montana: Geol. Soc. America, 

Spec. Paper 54, 181 p., 19 pis.

McCoy, Frederick, 1844, A synopsis of the characters of the 

Carboniferous limestone fossils of Ireland: Dublin, Univ. 

Press, 207 p., 29 pis.

Marcus, E., and Marcus, E., 1956, On the tectibranch gastropod Cylindrobulla: Acad. Brasil Cienc. Anals v. 28, 

no. 1, p. 119-128, pi. 2.

Martin, William, 1809, Petrifacta derbiensia; or Figures and 

and descriptions of petrifactions collected in Derbyshire: 

Wigan, D. Lyon, 28 p., 52 pis.

Matthews, S. C., 1973, Lapworthellids from the lower Cambrian Strenuella Limestone at Comley, Shropshire: 

Palaeontology, v. 16, pt. 1, p. 139-148, pis. 8-9.

Miller, S. A., 1889, North American geology and palaeontology: Cincinnati, Ohio, Western Methodist Book Concern, 664 p. (First appendix, 1892, p. 665-718; Second 

appendix, 1897, p. 719-793.)
REFERENCES CITED 81

Miller, S. A., and Faber, C. L., 1894, New species of fossils

from the Hudson River Group and remarks upon others:

Cincinnati Soc. Nat. History Jour., v. 17, p. 22-33, pi. 1. 

Morris, N. J., 1967, Mollusca: Scaphopoda and Bivalvia, in

Harland, W. B., and others, The fossil record: London,

Geol. Soc. London, p. 469-477. 

Morton, J. E., and Yonge, C. M., 1964, in Wilbur, K M., and

Yonge, C. M., eds., Physiology of the Mollusca, v. 1: New

York, Academic Press, p. 1-58. 

Miildner, Alfred, 1943, Die ersten Vertreter der Gattung

Ischyrinia in norddeutschen: Zeitschr. Geschiebeforschung

und Flachlandsgeologie, v. 18, p. 93-96, 8 figs. 

Nau, B. S. von, 1787, Beschreibung eines neuen Geschlechtes

der Eingeweiderwurmer: Gesell. Naturf. Freunde, Berlin,

Schrift, v. 7, p. 471-474. 

Neben, W., and Krueger, H. H., 1973, Fossilien ordovicischer

und silurischer Geschiebe: Staringia, no. 2, [10 p.] pis.

51-109. 

Nettleroth, H., 1889, Kentucky fossil shells; a monograph of

the fossil shells of the Silurian and Devonian rocks of

Kentucky: Kentucky Geol. Survey, 245 p. 

Neuman, R. B., and Bruton, D. L., 1974, Early Middle Ordovician fossils from the H01onda area, Trondheim region,

Norway: Norsk Geol. Tiddsskr., v. 54, no. 1, p. 69-115. 

Neumayr, Melchior, 1891, Beitrage zu einer morphologischen

Eintheilung der Bivalven: K. Akad. Wiss. Wien Denkschr., v. 58, p. 701-801. (Foreword by E. Suess, p. 701-

705). 

Newell, N. D., 1940, Invertebrate fauna of the late Permian

Whitehorse Sandstone: Geol. Soc. America Bull., v. 51,

no. 2, p. 261-335.

 1965, Classification of the Bivalvia: Am. Mus. Novitates, no. 2206, 2,5 p.

Nicholson, H. A., and Etheridge, Robert, Jr., 1880, A monograph of the Silurian fossils of the Girvan District in 

Ayrshire: Edinburgh, William Blackwood and Sons, v. 1, 

341 p., 24 pis.

Nicol, David, 1955, Nomenclatural review of the Paleozoic 

pelecypod family Conocardiidae: Jour. Paleontology, v. 

29, nos. 3, p. 552-553.

 1970, Mode of life of Conocardium, a Paleozoic pelecypod: Nautilus, v. 83, p. 77-80.

Oberling, J. J., 1964, Observations on some structural features 

of the pelecypod shell: Naturf. Gesell. Bern Mitt., Neue 

Folge, v. 20, 60 p., 6 pis.

Opik, A. A., 1967, The Mindyallan fauna of north-western 

Queensland: Australia Bur. Mineral Resources, Geology, 

and Geophysics Bull. 74, v. 1. 404 p., v. 2, 67 pis.

Orbigny, Alcide D. d', 1850, Prodrome de paleontologie * * * 

v. 1: Paris, Victor Masson, 394 p.

Owen, D. D., 1852, Report of a geological survey of Wisconsin, 

Iowa, and Minnesota and incidentally of a portion of 

Nebraska Territory: Philadelphia, 638 p.

Owen, Gareth, Trueman, E. R., and Yonge, C. M., 1953, The 

ligament in the Lamellibranchia: Nature, v. 171, p. 73-75.

Pannella, Giorgio, and MacClintock, Copeland, 1968, Biological and environmental rhythms reflected in molluscan 

shell growth, in Paleobiological aspects of growth and 

development, a symposium: Paleont. Soc. Mem. 2 (Jour. 

Paleontology, v. 42, no. 5, supp.), p. 64-80.

Parker, H. W., 1934, A monograph of the frogs of the 

family Microhylidae: London, British Mus. (Nat. History), 207 p., 67 figs.

Paul, Henry, 1941, Lamellibranchiata infracarbonica: Fossilium Catalogus; 1, Animalia (W. Quens-tedt), pars 91, 

348 p.

Peel, J. S., 1972, Observations on some lower Palaeozoic 

tremanotiform Bellerophontacea (Gastropoda) from 

North America: Paleontology, v. 15, pt. 3, p. 412-422, 

pi. 79.

Pelseneer, Paul, 1906, Mollusca, Pt. 5 of Lankester, E. R., 

ed., A treatise on zoology: London, 355 p.

Perkins, B. F., 1969, Rudist morphology, in Moore, R. C., ed., 

Treatise on invertebrate paleontology, Part N, Mollusca 

6, v. 2: New York and Lawrence, Kansas, Geol. Soc. 

America and Univ. Kansas Press, p. N751-N764.

Perner, Jaroslav, 1903, in Barraude, Joachim, Systeme silurien 

du centre de la Boheme, v. 4, Gasteropodes, tome 1: 

Prague, p. 1-64, pis. 1-89. (See pi. 49 and explanation.)

Phillips, John, 1836, Illustrations of the geology of Yorkshire * * * Pt. 2, The Mountain Limestone district: London, John Murray, 253 p., 24 pis.

Pohl, E. R., 1929, The Devonian of Wisconsin; Pt. 1, Lamellibranchiata: Milwaukee Public Mus. Bull., v. 11, no. 1, p. 

1-100, pis. 1-14.

Pohlo, Ross, 1969, Confusion concerning deposit feeding in 

the Tallinacea: Malocolog. Soc. London Proc., v. 38, p. 

361-364.

Pojeta, John, Jr., 1966, North American Ambonychiidae 

(Pelecypoda): Paleontographioa Americana, v. 5, no. 36, 

p. 129-241, pis. 19-47.

 1971, Review of Ordovician pelecypods: U.S. Geol. 

Survey Prof. Paper 695, 46 p., 20 pis.

1975, Fordilla troyensis Barrande and early pelecypod

phylogeny: Bulls. American Paleontology, v. 67, p. 363- 

384, 5 pis.

Pojeta, John, Jr., and Runnegar, Bruce, 1974, Fordilla Troyensis and the early history of pelecypod mollusks: Am. 

Scientist, v. 62, p. 706-711, 8 figs.

Pojeta, John, Jr., Runnegar, Bruce, and Kfiz, Jifi, 1973, 

Fordilla troyensis Barrande: the oldest known pelecypod: 

Science, v. 180, no. 4088, p. 866-868, 2 figs.

Pojeta, John, Jr., Runnegar, Bruce, Morris, N. J^and Newell, 

N. D., 1972, Ro'Stroconchia: a new class of bivalved mollusks: Science, v. 177, no. 4045, p. 264-267, figs.

Poulsen, Chr., 1932, The Lower Cambrian faunas of East 

Greenland: Medd, Gr0nland, v. 87, no. 6, 66 p., 14 pis.

Purchon, R. D., I960, A further note on the biology of 

Brechites penis (L.) (Lamellibranchia) : Malacolog. Soc. 

London, Proc., v. 34, pt. 1, p. 19-23.

Rasetti, F. R., 1954, Internal shell structures in the Middle 

Cambrian gastropod Scenella and the problematic genus 

Stenothecoides: Jour. Paleontology, v. 28, no. 1, p. 59-66, 

pis. 11-12.

 1957, Additional fossils from the Middle Cambrian 

Mt. Whyte Formation of the Canadian Rocky Mountains: 

Jour. Paleontology, v. 31, no. 5, p. 955-972, pis. 118-122.

Raven, C. P., 1958, Morphogenesis: the analysis of molluscan 

development: London, Pergamon Press, 311 p.

Raymond, P. E., 1905, The fauna of the Chazy Limestone: 

Am. Jour. Sci., 4th ser., v. 20, p. 353-382.

Reed, F. R. C., 1907, Crustacea, etc., from Girvan: Geol. Mag., 

Decade 5, v. 4, p. 108-115, pi. 4.

 1952, Revision of certain Ordovician fossils from 

County Tyrone: Royal Irish Acad. Proc., v. 55, sec. B, 

no. 3, p. 29-136, pis. 1-5.
82 PALEONTOLOGY OF ROSTROCONCH MOLLUSKS

Resser, C. E., 1938, Fourth contribution to nomenclature of 

Cambrian fossils: Smithsonian Misc. Colln., v. 97, no. 

10, 43 p.

Reynolds, M. A., 1966, Mount Whelan, Queensland: Australia 

Bur. Mineral Resources, Geology, and Geophysics, 

1:250,000 Geol., Ser., Sheet SF 54-13 (explanatory notes, 

1968).

Robison, R. A., 1964, Late Middle Cambrian faunas from 

western Utah: Jour. Paleontology, v. 38, no. 3, p. 510- 

566, pis. 79-92.

Rollins, H. B., 1969, The taxonomic position of Cyrtonella 

mitetta (Hall) (Mollusca, Monoplacophora) : Jour. Paleontology, v. 43, no. 1, p. 136-140.

Rollins, H. B., and Batten, R. L., 1968, A sinus-bearing 

monoplacophoran and its role in the classification of 

primitive molluscs: Paleontology, v. 11, no. 1, p. 132-140, 

pi. 28.

Rozanov, A. Yu., and others, 1969, Tommotian stage and 

the Cambrian lower boundary problem: Akad. Nauk 

SSSR Doklady, v. 206, 380 p., 55 pis.

Rudolphi, C. A., 1801, Archiv Zoologie und Zootomie (Wiedemann), v. 2, pt. 1, p. 58.

Rudwick, M. J. S., 1970, Living and fossil brachiopods: London, Hutchinson and Co., 199 p.

Ruedemann, Rudolf, 1901, Trenton conglomerate of Rysedorph Hill, Rensselaer Co., N.Y., and its fauna: New 

York State Mus. Bull. 49, p. 3-114.

 1912, The Lower Siluric shales of the Mohawk Valley: 

New York State Mus. Bull. 162, 151 p., 10 pis.

Runnegar, Bruce, 1972, Anatomy of Pholadomya Candida 

(Bivalvia) and the origin of the Pholadomyidae: Malacolog. Soc. London Proc., v. 40, p. 45-58, 2 pis.

Runnegar, Bruce, and Pojeta, John, Jr., 1974, Molluscan 

phylogeny: the paleontological viewpoint: Science, v. 

186, p. 311-317.

Runnegar, Bruce, Pojeta, John, Jr., Morris, N. J., Taylor, J. 

D., Taylor, M. E,, and McClung, Graham, 1975, Biology 

of the Hyolitha: Lethaia, v. 8, p. 181-191, 7 figs.

Ruzhentsev, V. E., and others, 1962, Osnovy paleontologii, 

spravochnik dlya paleontologov i geologov SSSR; [v. 5] 

Mollyuoski; golovonogie, 1, Nautiloidei, endotseratoidei, 

aktinotseratoidei, baktritoidei, ammonoidei (agoniatity, 

goniatity, klimenii): Moscow, Akad. Nauk SSSR, 438 p., 

32 pis.

Salter, J. W., 1851, List and description of the Silurian fossils of Ayrshire, in Murchison, R. I., On the Silurian rocks 

of the south of Scotland: Geol. Soc. London Quart. Jour., 

v. 7, p. 170-178, pis. 8-10.

 1864, On some points in ancient physical geography, 

illustrated by fossils from a pebble-bed at Budleigh 

Salterton, Devonshire: Geol. Mag., v. 1, p. 5-12, 4 figs.

 1866, On the fossils of North Wales, in Ramsay, A. 

C., The geology of North Wales: Great Britain Geol. 

Survey Mem., v. 3, Appendix, p. 240-381, pis. 1-26. (2d 

ed., 1881, p. 311-611.)

1868, [Ribeiria], in Bigsby, Thesaurus Siluricus:

London, John van Voorst, p. 141.

Sando, W. J., 1957, Beekmantown Group (Lower Ordovician) 

of Maryland: Geol. Soc. America Mem. 68, 161 p., 15 pis.

Schubert, R. J., and Waagen, Luka, 1903 in Barrande Joachim, Systeme Silurien du centre de la Boheme v. 4, 

Gasteropodes, tome 1: Prague, pi. 49 and explanation.

 1904, Der untersilurischen Phyllopodengattengen 

Ribeiria Sharpe und Ribeirella gen. nov.: K.-K. Geol. 

Reichsanst. Jahrb., v. 53, p. 33-50, 1 pi.

Shaler, N. S., and Foerste, A. F., 1888, Preliminary description of North Attleboro fossils: Harvard Coll. Mus. 

Comp. Zoology Bull., v. 16, p. 27-41, 2 pis.

Sharpe, Daniel, 1853, Description of the new species of 

Zoophyta and Mollusca (appendix B to Ribeiro, Carlos, 

Carboniferous and Silurian formations of the neighborhood of Bussaco in Portugal): Geol. Soc. London Quart. 

Jour., v. 9, p. 146-158, pis. 7-9.

Shimer, H. W., and Shrock, R. R., 1944, Index fossils of 

North America: New York, John Wiley and Sons, 837 

p., 303 pis.

Soot-Ryen, Helen, 1960, The Middle Ordovician of the Oslo 

region, Norway: 12, Notostraca and Conchostraca: Norsk 

Geol. Tidsskr., v. 40, pt. 2, p. 123-131, pi. 1.

Sowerby, James, 1812-1815, The mineral conchology of Great 

Britain; or coloured figures and descriptions of those 

remains of testaceous animals or shells which have been 

preserved at various times and depths in the Earth, v. 

1, pts. 1-19: London, 234 p., 102 pis. (See p. 187-188, 

pi. 82, 1815.)

Stanley, S. M., 1972, Functional morphology and evolution 

of byssally attached bivalved mollusks: Jour. Paleontology, v. 46, no. 2, p. 165-212.

Starobogatov, Ya. I., 1970, K sistematike rannepaleozoyskikh 

Monoplacophora [Systematics of early Palaeozoic Monoplacophora] : Paleont. Zhur. 1970, no. 3, p. 6-17. (English 

translation in Paleont. Jour., 1970, no. 3, p. 293-302.)

Stasek, C. R., 1972, The molluscan framework, in v. 7, Mollusea, of Florkin, Marcel, and Scheer, B. T., eds., Chemical zoology: New York, Academic Press, p. 1-43.

Stinchcomb, B. L., and Echols, D. J., 1966, Missouri Upper 

Cambrian Monoplacophora previously considered cephalopoda: Jour. Paleontology v. 40, no. 3, p. 647-650.

Tateiwa, Iwao, 1958, Lexique stratigraphique international, 

Asie, Fasc. 2a Korea: Paris, 83 p.

Taylor, J. D., Kennedy, W. J., and Hall, A., 1969, The shell 

structure and mineralogy of Vivalvia * * *: British Mus. 

(Nat. History) Zoology, Suppl. 3, 128 p., 29 pis.

Taylor, M. E., and Halley, R. B., 1974, Systematics, environment, and biogeography of some Late Cambrian and 

Early Ordovician trilobites from eastern New York 

State: U.S. Geol. Survey Prof. Paper 834, 38 p., 4 pis.

Teichert, Curt, 1930, Der erst europaische Vertreter der 

Gattung Ischyrinia Billings (Eucrust. Notostr.) in der 

Lyckholm-Stufe von Estland: Palaeont. Zeitschr., v. 12, 

p. 130-134,1 fig.

 1967, Major features of cephalopod evolution, in 

Essays in paleontology and stratigraphy R. C. Moore 

Commemorative Volume: Kansas Univ., Dept. Geology 

Spec. Pub. 2, p. 162-210.

Teichert, Curt, and others, 1964, in Moore, R. C., ed., Treatise 

on invertebrate paleontology, pt. K, Mollusca 3: New 

York and Lawrence, Kans., Geol. Soc. America and 

Univ. Kansas Press, 519 p.

Templeton, J. S., Jr., and Willman, H. B., 1952, Guidebook 

for the 16th annual field conference, central northern 

Illinois, October 11-12, 1952: Illinois State Geol. Survey 

Guidebook ser. 2, 47 p.
REFERENCES CITED 83

Termier, Genevieve, and Termier, Henri, 1950, Paleontologie 

Marocaine; II, Invertebres de 1'ere primaire; pt. 4, 

Annelides, arthropodes, echinodermes, conularides, et 

graptolithes: Morocco Service Geol. Notes et Mem. no. 

79, 278 p., 57 pis.

Thiele, J., 1912, Die Antarktischen schnecken und muscbeln: 

Deutsche Sudpolar-Expedition 1901-1903, v. 13, Zool. 5, 

p. 185-285.

Thoral, Marcel, 1935, Contribution a 1'etude paleontologique 

de I'Ordovicien Inferieur de la Montagne Noire et revision sommaire de la faune Cambrienne de la Montagne 

Noire: Montpellier, 326 p., 35 pis.

Thorslund, Per, 1940, On the Chasmops Series of Jemtland 

and Sodermanland (Tvaren): Sveriges Geol. Undersokming, ser. C, no. 436 (Arsbok 34, no. 6), 189 p., 15 pis.

Tromelin, M. G. de, 1877, Etude de la Faune du Gres silurien: 

Soc. Linneenne Normandie Bull., ser. 3, v. 1, p. 5-83.

Trueman, E. R., 1949, The ligament of Tellina tennis: Zool. 

Soc. London, Proc., v. 119, p. 717-742.

 1950, Observations on the ligament of Mytilus edulis: 

Quart. Jour. Micros. Sci., v. 91, pt. 3, p. 225-235.

 1953, Observations on certain mechanical properties 

of the ligament of Pecten: Jour. Experimental Biology, 

v. 30, no. 4, p. 453-467.

 1967, The dynamics of burrowing in Ensis (Bivalvia): 

Royal Soc. London Proc., ser. B, v. 166, p. 459-476. 

1968, The burrowing activities of bivalves: Zool. Soc.

London Symposia 22, p. 167-186. 

Twenhofel, W. H., 1928, Geology of Anticosti Island: Canada,

Geol. Survey Mem. 154, 481 p., 60 pis. 

Ulrich, E. O., 1879, Descriptions of new genera and species

of fossils from the Lower Silurian about Cincinnati:

Cincinnati Soc. Nat. Hist. Jour., v. 2, p. 1-22.

 1892a, New Lamellibranchiata, No. 4, Descriptions 

of one new genus and eight new species: Am. Geologist, 

v. 10, no. 2, p. 96-104, pi. 7.

 1892b, New Lower Silurian Lamellibranchiata, chiefly 

from Minnesota rocks: Minnesota Geol. and Nat. History 

Survey, Ann. Rept. 19 (for 1890), p. 211-248.

 1893, New and little known Lamellibranchiata from 

the Lower Silurian rocks of Ohio and adjacent states: 

Ohio Geol. Survey Rept., v. 7, pt. 2, p. 627-693, pis. 45- 

56 [1895].

 1894, The Lower Silurian Lamellibranchiata of Minnesota: Minnesota Geol. and Nat. History Survey Final 

Rept., v. 3, p. 475-628, pis. 35-42. (Published under 

separate cover prior to the entire v. 3.)

 1897, The Lower Silurian Lamellibranchiata of Minnesota: Minnesota Geol. and Nat. History Survey, Final 

Rept., v. 3, pt. 2, Paleontology, p. 475-628, pis. 35-42. 

(A reprinting of the 1894 paper above.)

Ulrich, E. O., and Bassler, R. S., 1931, Cambrian bivalved 

Crustacea of the order Conchostraca: U.S. Natl. Mus. 

Proc., v. 78, art. 4,130 p., 10 pis.

Veevers, J. J., and Roberts, John, 1966, Littoral talus breccia 

and probable beach rock from the Visean of the Bonaparte Gulf basin: Geol. Soc. Australia Jour. v. 13, pt 2, 

p. 387-403, pis. 4-5.

Villeneuve, J., 1920, Dipteres palearctiques nouveaux ou peu 

connus: Soc. Entomologique Belgique Annales, v. 60, p. 

114-120.

Walcott, C. D., 1924, Cambrian geology and paleontology, 

IV; No 9, Cambrian and Ozarkian Brachiopoda, Ozarkian 

Cephalopoda and Notostraea: Smithsonian Misc. Colln., 

v. 67, no. 9, p. 477-554, 21 pis.

Waller, T. R., 1972, The functional significance of some shell 

microstructures in the Pectinacea (Mollusca: Bivalvia): 

Internat. Geol. Gong., 24th, Montreal, Canada, Proc. Sec. 

7, p. 48-56.

Waterhouse, J. B., 1967, Proposal of series and stages for 

the Permian in New Zealand: Royal Soc. New Zealand 

Trans., Geology, v. 5, no. 6, p. 161-180.

Webby, B. D., 1973, Trace fossils from the Lintiss Vale 

Formation of New South Wales: A late Precambrian 

fauna: Search, v. 4, p. 494-496.

Weller, Stuart, 1898, A bibliographic index of North American Carboniferous invertebrates: U.S. Geol. Survey Bull. 

153, 653 p.

Wenz, Wilhelm, 1938-1944, Gastropoda, Teil 1, Prosobranchia, 

v. 6, of Schindewolf, O. H., Handbuch der Palaozoologie: 

Berlin, Gebruder Borntrager, 1639 p., 4211 figs. (Pts. 1, 

2, 1938; pt. 3, 1939; pt. 4, 1940; pt. 5, 1941; pt. 6, 1943; 

pt. 7,1944.) (See pt. 1, p. 240.)

 1940, Ursprung und friihe stanimesgeschichte der 

Gastropoden: Archiv. Mollusken-Kunde, Frankfort, v. 72, 

p. 1-10.

Whidborne, G. F., 1889-1907, A monograph of the Devonian 

fauna of the south of England: London, Palaeontographical Soc., 3 v. (See v. 2, pt. 1, The fauna of the limestones of Lummaton, Wolborough, Chircombe Bridge, and 

Chadleigh (Continued), 1892, 56 p, 5 pis.)

Whitfield, R. P., 1886, Notice of geological investigations 

along the eastern shores of Lake Champlain * * * with 

descriptions of the new fossils discovered: Am. Mus. 

Nat. History Bull., v. 1, p. 293-345.

Whittington, H. B., 1972, Scotland, in Williams, Alwyn, and 

others, A correlation of Ordovician rocks in the British 

Isles: Geol. Soc. London Spec. Rept. 3, p. 49-53.

Wilson, A. E., 1956, Pelecypoda of the Ottawa Formation of 

the Ottawa-St. Lawrence lowland: Canada Geol. Survey 

Bull. 28, 102 p., 9 pis.

Wilson, E. C., 1970, Conocardium langenheimi sp. n. (Mollusca: 

Bivalvia) in the Lower Permian Series of the McCloud 

Limestone, northern California: Los Angeles County 

Mus. Contr. Sci., no. 184, 14 p.

Winchell, Alexander, 1866, The Grand Traverse region: A 

report on the geolo'gical and industrial resources of the 

counties of Antrim, Grand Traverse, Benzie, and Leelanaw in the Lower Peninsula of Michigan: Ann Arbor, 

Mich., 97 p.

Yang. C.-C., 1957, Chung-kuo piao chun hau shih * * * v. 2 

[Basic invertebrate fossils of China * * * v. 2] : Peking, 

Acad. Sinica, Inst. Paleontology (paging for volume not 

available) (see p. 320).

Yang, S. Y., 1939, [Conocardiidae], in Michigan Traverse 

mollusks [Devonian]: New Haven, Conn., Yale Univ., 

Ph.D. dissert., p. 40-55.

Yochelson, E. L., 1963, Problems of the early history of 

Mollusca: Internat. Congress of Zoology, 16th, Washington, Proc., p. 187.

 1966, Mattheva, a proposed new class of mollusks: U.S. 

Geol. Survey Prof. Paper 523-B, 11 p., 1 pi.
84 PALEONTOLOGY OF ROSTROCONCH MOLLUSKS

 1967, Quo vadis, Bellerophonl, in Essays in paleontology and stratigraphy R. C. Moore Commemorative Volume: Kansas Univ., Dept. Geology Spec. Pub. 2, p. 141- 

161.

 1968, Stenothecoida, a proposed new cla&s of Cambrian Mollusca [abs.]: Internat. Paleont. Union, Prague, 

Czechoslovakia, Abstracts, p. 34.

1969, Stenothecoida, a proposed new class of Cambrian Mollusca: Lethaia, v. 2, no. 1, p. 49-62. 

Yochelson, E. L., and Copeland, M. J., 1974, Taphonomy and

taxonomy of the Early Ordovician gastropod Ceratopea

canadensis (Billings), 1865: Canadian Jour. Earth Sci.,

v. 11, p. 189-207, 2 pis. 

Yochelson, E. L., Flower, R. H., and Webers G. F., 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. 

Yochelson, E. L., and Jones, C. R., 1968, Teiichispira, a new

Early Ordovician gastropod genus: U.S. Geol. Survey

Prof. Paper 613-B, 15 p., 2 pis.

Yonge, C. M., 1948, Cleansing mechanism and the function 

of the fourth pallial aperture in Spisula subtruncata (da 

Costa) and Lutraria lutraria (L.) : Marine Biol. Assoc. 

United Kingdom Jour., v. 27, p. 585-596.

 1953a, The monomyarian condition in the Lamellibranchia: Royal Soc. Edinburgh Trans., v. 62, p. 443-478.

 1953b, Form and habit in Pinna carnea: Royal Soc. 

London Philos. Trans., ser. B, v. 237, p. 335-374.

 1957, Mantle fusion in the Lamellibranchia: Stazione 

Zool. Napoli Pub., v. 29, p. 151-171.

Zavodovsky (Zovodovskii), V. M., 1960, [New Permian representatives of Conocardiidae from northeastern SSSR]. 

in Markovsky, B. P., ed., [New species of fossil plants 

and invertebrates of the USSR], v. 2: Moscow, Vsesoyuz. 

Nauch.-Issled. Geol. Inst., p. 31-33, pi. 6. (In Russian.)

Zhuravleva, I. T., 1970, Marine faunas and Lower Cambrian 

stratigraphy: Am. Jour. Sci., v. 269, no. 5, p. 417-445.
INDEX

[Italic page numbers indicate descriptions and major references]

Page

Acoelomate ___-_--__--_______________ 23

Aculifera ___________________ 23 

alabamensis, Bransonia _________ 1, 72; pi. 50

Aldanella ____________________ 30, 31, 32

crassa ____________________ 31

Algae ___________________ 24 

aliforme, Conocardium ____ 19, 70; pis. 39, 51

Alpena Limestone _________________ 70, 73

alto,, Eopteria __________________ 65

Wanwanella ________________ 68; pi. 21

ambonychiformis, Wanwania ________ 55; pi. 3

americana, Pinnocaris __________ 1, 54; pi. 9

Amherstburg Formation __________ 76

Anabarella ____ 21, 24, 25, 29, 33, 37, 56; pi. 17

plana ______ _____ ___ __ 27; pi. 17

Anisotechnophorus _________._ 1, 4, 60; pi. 18

nuculitiformis ____________ SO; pi. 18

Antelope Valley Limestone ___________ 66

antiqua, Hippocardia __________.__ 75; pi. 50

antiquatus, Hipponix ______________ 40

Aplacophora __________ 23,24,34,35 

Apodid arthropod _____-__.__ 2

apusoides, Ribeiria ___________ 5, 7, 50, 52, 53;

pis. 5-7, 30, 31 

Arcaceans ______ ______________ 17

Arceodomus _______1, 5, 11, 19, 20, 22, 39, 48,

70; pis. 42-44

glabrata _ ____ _ _ 11, 71; pis. 42-44

langenheimi ____ ________ 11, 71; pi. 43

«p _.______________-. 71; pi. 43 

Archaeocyaths _.-----_______________ 24, 46

Archaeogastropod _-_----_-_--_--__-___ 30

Arcites rostratus _____ _____ _____ 69

Arthropods _________________ 2,3,48 

asiatica. Eopteria _________________ 65

Wanwanella . __________________ 68

attenuatum, Conocardium _____. 70; pis. 39, 40

Auburn Chert _______ __ ___ 58

auriculata, Wanwanella striata ____ 68; pi. 21

australiens-is, Ribeiria ________ 1, 34, 50; pi. 4

B

Babinka _____________---____-_--______ 41

Bagenovia _____________________ 44

Bagenoviella _________ ___ __ ___ 44

Balclatchie Group _____-____-_.______- 54

bassleri, Ribeiria ____ __ ___ 51

beecheri, Bransonia ______________ 72; pi. 50

Beekmantown Formation ______________ 52

Beekmantown Group _______________ 66, 67

bella, Hippocardia ______________ 70, 75; pi. 44

Bellerophontida ___ __ _----___- 25

Bellerophontids ______________________ 25

bellistriatus, Technophorus _________ 58; pi. 11

Bemella ____________________ 27,29

Berthelinia ________________ 12,40,41

bifarius, Mulceodens _______________ 73; pi. 35

Bigalea ___ ____ _ 1, 39, 74, 76; pis. 35-37 

clathra ..._______________ 76; pi. 37 

ohioensis _________ ___ 1, 77; pi. 36

visbyensis ___________ 1. 77; pis. 35, 36

yangi ____________ 1, 76; pis. 36, 37

Page

billingsi, Eoischyrina ___________ 64

Bivalvia _____________________ 33 

blumenbachii, Conocardium _________ 67

Euchasma _____________ 20, 67, pi. 27

bohemica, Hippocardia ________ 75; pis. 32, 47

Brachiopods ____________ 21,33,41,77 

Brachiopods, productid _____________ 40

Bransonia ________ 1, 4, 5, 13, 19, 22, 37, 38, 39,

71, 72; pis. 32, 50-54 

alabamensis _________________ 1, 72; pi. 50

beecheri ______.____________ 72; pi. 50

cressmani _____ 1, 19, 38, 72; pis. 52-54 

immatura ___________________ 73

isbergi ____________________ 73

lindstromi ____________________ 73

paquettensis _____ -____-_--_ 73; pi. 50

robustum ____________ 19, 22; pis. 51, 53

wilsoni --_-__--__ 1, 4, 5, 8, 9, 10, 23, 72;

pis. 32, 51, 52

sp __ _____ ______ ____ __ 19, pi. 52

Bransoniidae _______._-_______ 1, 39

Bransoniids ___________ 34,39,40,73,74

Brechites ____________________ 44

Brownwood Shale Member ____ __ 74

Budleigh-Salterton Pebble Bed____ 51, 52, 61 

Burmesiidae _________________. 1, 48

bussacensis, Ribeiria _______________ 51

Byssate pelecypods _-__----___________ 22

Caddo Creek Formation _________ 74

calcifera, Ribeiria _______________ 5, 51; pi. 4

calcis, Hippocardia __________________ 75

cambrica, OepikUa __________ 34, 61; pi. 10

Wanwania _________ 34. 35, 55; pi. 3

Cambridium _________________ 44

cancettatus, Technophorus __________ 58; pi. 11

Carboniferous limestone ____________ 70

Cardiid pelecypods ___________ 22

Cardiids _____________________ 2 

Cardium elongatum _____ 1, 69; pis. 37, 38

hibernicum _____ __ __ ____ 74

carinata, Helcionella _________________ 27

Carterville Formation _________ 70

Cephalopoda _____________ 23,32,33,45 

Cephalopods ______________ 29,31,32

Cheilea equestris __________________ 40

cincinnatiensis, Technophorus _____ 58; pi. 12

Clams, Tridacnid ______________ 40 

Clarkella Zone _______________ 58

clathra, Bigalea __________________ 76; pi. 37

Columella __________________ 32 

complanata, Ribeiria ____________ 51; pi. 9

compressa, Ribeiria _____________ 51; pi. 8

Wanwania _________________ 55; pi. 3

concentrica, Tolmachovia __ 17, 35, 61, 62; pis.

16, 17 

Conchifera _______________ 45

conformis, Ribeiria _______________ 51

Conocardiacea _ 3, 5, 12, 19, 21, 34, 37, 38, 48, 69

Conocardiaceans _ 2, 3, 4, 9, 19, 20, 21, 22, 34, 35,

37, 38, 39, 69, 71, 72, 73, 74, 75

Page

conocardiformis, Eopteria ___ 1, 65, 72; pi. 26 

Conocardiidae ___ 20, 21, 39, 40, 45, 48, 69, 71 

Conocardiids ________._ 8, 10, 20, 22, 39, 69 

Conocardioida _ ____ 1, 10, 12, 22, 37, 48, 65 

Conocardioids ___-_________ 19,65,69

Conocardium . ___ 1, 2, 11, 13, 19, 20, 22, 37, 39, 

48, 65, 69, 70, 75

aliforme ___________ 19, 70; pis. 39, 51 

attenuatum __. -----___ 70; pis. 39, 40

blumenbachii _ ________.__ 67; pi. 27

elongatum _______ 19, 39, 69; pis. 37, 38

glabratum ___ _- _ 70 

normale ___.____________._ 70; pi. 39

pseudobellum ___________ 1, 70; pis. 38, 39

cooperi, Hippocardia -__._____ 7, 75, 76; pi. 45

coreanica, Technophorus __________ 58; pi. 11

Cornulitids ____---___--_----_ 

Cotter Dolomite ___.-___--___

Cowries -____- ______

crassa, Aldanella ____________

Eopteria _________________

Ribeiria _ _

Crepidula _____ ________ _

cressmani. Bransonia __ 1, 19,1

_____ 23

---_-. 66

-_-_.__ 32

_____ 31

66

________ 51

- 33 

3, 72; pis. 52-54

crosbyi, Watsonella ____________ 34, 56; pi. 3

cunea, Hippocardia ______ 8, 9, 10, 11, 75; pis.

32, 33, 48, 49, 50 

curvata, Pinnocaris -_______ 54; pis. 9, 10

Cyclorinus Shale _______________ 62, 64

cyrano, Yochelcionetta _______________ pi. 1

Cyrtobites - _________________ 27,29 

Cyrtonetta ______________._ __ 25,29 

Cyrtosoma _______________ 23,45,46

D

Decorah Shale ____________.___ 58,59 

delicata, Wanwanoidea trigonalis __ 69; pi. 21 

Dentalium _________._____ ._____ 43

denticulatus, Mulceodens ____________ 73

derbiensia, Petrifacta ___ ______ __ 69

Diamond Peak Formation ___________ 71

Diasoma ____________ 23,45,46,47,48 

Diasomes ______ __ _ __ __ 45

Dickerson Shale __.______ ___ 71

diptera, Hippocardia _____________ 75

divaricatus, Technophorus __________ 58; pi. 14

Drummuck Group _________________ 55

E

eboraceus, Mulceodens _____________ 74; pi. 35

Edenian rocks _________________ 58

edulis, Mytilus ________________ 12, 13 

Elkhorn Formation _____ ____ 58

Ellis Bay Formation _________._ 59,64 

elongata, Ischyrinia __________________ 64

elongatum, Cardium ___________________ 1,69

Conocardium ___ 19, 39, 69, 70; pis. 37, 38 

English Head Formation ______________ 64

Ensis ________________________________ 21

Eoischyrina ____________________ 64

billingsi _______________ 64

Eopteria __ 2, 4, 5, 12, 13. 15, 17, 19, 35, 37, 38, 

39, 43, 65, 66, 68; pis. 22-26

85
86 INDEX

Page 

Eopteria Continued

alto, ..........................__.. 65

asiatica .....__________________ 65

eonocardiformis .......... 1, 65, 72; pi. 26

crassa ............................ 66

flora ................._________ 66; pi. 24

obsolata .... ___________________ 66; pi. 24

omata ..._,______________ gg

richardsoni ________________ 65; pis. 24-26

typica .....________________ 65

ventricosa ._______ 17, 37, 66; pis. 22, 23

sp ________ 66; pi. 25

Eopteriacea ___________________ 48,65

eopteriforme, Euchasma ____.____ 67

Eopteriidae __________ 12,37,48,63,65

Eopteriids __ 2, 15, 20, 34, 38, 39, 65 

Eotomariids __________________ 32 

eguestris, Cheilea _______________ 40

equilatera, Ribeiria nueulitiformis ... __ 51

Euchasma ... 2, 5, 7, 9,12, 17, 19, 20, 21, 22, 35,

37, 38, 39, 66, 67, 68; pis. 27-29

blumenbachii __________________ 20, pi. 27

eopteriforme _-----_---.___________ 67

jonesi .............. 1, 7, 20, 67; pis. 28, 29

mytUiforme ....... __ 1, 7, 20, 38, 67; pi. 29

shorinense ................... __ 67; pi. 28

wanwanense .........________ 65; pi. 28

sp _____ 6S;pl. 28 

Euchasmas ___________________ 20

Euchasmella multistriata ...___________ 77

extenuatus, Technophorus _____________ 56,59

faberi, Technophorus . ... ... ... 56; pis. 10, 11

filis triatus, Technophorus ___ __ 59; pis. 13, 14

flabelliformis, Myona ____ ________ __ __ 77

flora, Eopteria ... ... _____ ___ _ ___ 66; pi. 24

Fonda Limestone Member _________ 61 

FordUla ........ ____________ 12,40,41,42,43

troyensis . _____________________ 41,43,54

Fort Cassin Limestone _ ___ __ ______ 66

Four Mile Dam Formation ________ 70 

fusiformis, Hippocardia ..... ..... .. 75; pi. 45

6

galatheae, Neopilina _ _ _ _________ 30

Gaptank Formation ______ __ ___ _ __ 74

Gastropoda _ _____________ 23, 24, 29, 45

Gastropods . ___ 4, 5, 12, 13, 14, 24, 25, 27, 29

30, 31, 32, 33, 40, 41

opisthobranch _-_---_--___ _ _ __ 40,41

Georgina Limestone _------_----_- _ __ 61

Ginetta ............. _____________ ___ 27,29

glabrata, Arceodomus .. _ 11, 71; pis. 42, 43, 44 

glabratum, Conocardium ______________ 70

Graham Formation _-_----___-________ 74

H

Haliotis _______

Hamilton Group 

Heath Formation 

Hecuba scortum _

_ __ __ 30 

___ _ ___ _____ 70

___ _ _________ 71

_________ _ __ 8

Heleionella ... ___ _ _ ________ 24, 27, 29

carinata ... ... __ _ _ ___ __ 27

rugosa .... _______ __ ___ __ _ 27

Helcionellacea _________ 24,27,29,31,32 

Helcionellacians _ _______ 1,21,25,27,29 

Helcionellid ______ _________ 27,29,30 

Heraultia ..................... ... ..... 53

varensalensis ... .... .. .... __ __ 54

Heraultipegma ..... 1, 17, 19, 24, 25, 27, 33, 34,

37, 41, 42, 43, 53, 54; pi. 2 

varensalense ... ..... ... ...... 34, 54; pi. 2

hibemica, Hippoeardia ______ _ 8, 74, 75; pi. 46

hibernicum, Cardium ... _________ 74

High Bridge Group ___ _ ____ 65

Page 

Hippocardia ..... 4, 5,10,12, 23, 37, 39, 70, 74,

75, 76, pis. 32, 44-50 

antiqua _________________ ......75; pi. 50

betta ....................... 70, 75; pi. 44

bohemica .................. 75; pis. 32, 47

colds __ _______ ___ _ 75

cooperi .................. 1, 75, 76; pi. 45

cunea .... 8, 9, 10,11, 75; pis. 32, 33, 48-50

diptera ........................... 75

fusiformis ..................... 75; pi. 45

hibernica ................ 8, 74, 75; pi. 46

limatula. ....................... 75; pi. 50

monroica ___________ 76; pis. 44, 45

praepristis ...... _ _ 76

pygmaea ...................... 76; pi. 50

richmondensis ................. 76; pi. 50

zeUeri ...................... 19, 76; pi. 47

sp ____ ________________ 76; pi. 50 

Hippocardiidae _________----- 1,39,74

Hippocardiids _________.---_---._ 74

Hipponix .....________________ 40

antiguatus ......______-------___ 40

Hog Creek Shale Member _______ 74 

Holonda Limestone ____ -- ---- 68

Holston Formation ______ ._ 73

Honeycut Formation ___. 66 

Hyoliths _____________________ 24 

Hypseloconids _________ __-_ 32 

Hypseloeonus ......____________ 32

bessemerense ______ __ __ 27

Igoretta .............................. 24,29

ungulata ..___________.___ 27

immatura, Bransonia ..............___ 73

inflata, Ribeiria ......________ 52

insulcata, Latouchella ......__________ 27

isbergi, Bransonia ...........________ 73

Ischyrinia ........ 15, 20, 21, 35, 37, 38, 39, 59,

62, 64; pis. 18, 19 

elongata .....______________ 64

norvegica ........... 15, 17, 35, 64; pi. 19

sehmidti ...... .___._.____ 64

winchelli ............ 17, 35, 62; pis. 18, 19

sp __________________ 64; Pi. 19 

Ischyriniid _________ 20,34,35,39,62,64 

Ischyriniidae _____________ 37, 62, 63, 64 

Ischyrinioida ______________ 12,17,37 

Ischyrinioids ____--____ ___ - - 37

jaanussoni, Mulceodene ... 1, 11, 73; pis. 34, 35 

Jefferson City Dolomite _____ ----- 66

jelli, Tolmochovia ...... 1, 15, 17, 35, 62; pi. 14

jonesi, Euchasma ______ 1, 7, 20, 67; pis. 28, 29

K

Kaschkadakia . _____. 

Khivachsk Beds _ - 

Kimmswick Limestone 

korobkovi, Latouchella

44

74

75

30

langenheimi, Arceodomus ....... 11, 71; pi. 43

lanterna, Pseudoconocardium ... 7,8,9,10,11,

74; pis. 32, 40-42

Lapworthellids ____ -- 23

lapworthi, Pinnociris .......... _____ 54', pi. 9

lata, Ribeiria personata .............. 52

Latouchella .............. 24, 25, 29, 30, 31, 37

insulcata .................. ... 27

korobkovi ......___ __ __ - 30

memorabilis __________ _ ___ 30

Leray-Rockland Beds __ 73

Page

Lexington Limestone 72,73 

lieharewi, Pseudoconocardium ... ..... . 74

limatula, Hippocardia .............. 75; pi. 50

lindstromi, Bransonia .. ___ - 73 

Linnean hierarchical system 34 

Little Oak Limestone - 65,72 

longiuscula, Ribeirina ...... -------- 55; pi. 3

Lower Chambersburg Limestone 75 

lucan, Ribeiria ........ ... ..... 6, 17, 52; pi. 8

Lucas Formation ___. - -_ 76

Luke Hill Limestone 67 

lutraria, Myocaris .... ..... ... . .... 61; pi. 10

Lyrodesma ... ... _____ _____ 41

M

McCloud Limestone - 71 

Maeroseenetta montrealensis ..... ... 30; pi. 15

magnified, Ribeiria ... .... ... ..... .... 52

Makarakia _________ 44

manchurica, Ribeiria ... ... ... ... ... . 52; pi. 8

pennata, Ribeiria ... ... ... ....... 52

marija, Technophorus ... _____ - 1, 59; pi. 12

Mattheva __ 23,44 

Matthevia .. .. ___ ____ _ _- 44

Maysvillian rocks 58 

memorabilis, Latouchella .............. 30

Metazoans _ 3,23 

milleri, Technophorus ............ 1, 59; pi. 14

Missisguoia Zone 61

Mollusca _________________ 1,23,48

Monoplacophora _____ 1,3,4,5,23,24,45

tergomyan ... 27,29

Monoplacophoran __ 24,25,27,29,30,31,32,

33, 34, 40, 42, 43, 44

cyclomyan ___________ 25,27,29,30 

monroica, Hippocardia . ... . ... 76; pis. 44, 45

Mons Formation ___ 52 

montrealensis, Maeroseenetta .... ... 30; pi. 15

Morphological terms, glossary 45 

Mount Whelan Sheet 61 

Mt. Whyte Formation _ __-. 27 

Mulceodens .............. 1, 39, 73; pis. 34, 35

bifarius ....... ---------- ..... -- 73; pi. 35

denticulatus ... _ __ -- 7S 

eboraceus ... ... ... ....... ... ... 74', pi. 35

jaanussoni .......... . 1, 11, 73; pis. 34, 35

multistriata, Euchasmella ............. 77

Mungerebar Limestone -- 50 

Myocaris ... . .-..... . 35, 37, 61; pi. 10

lutraria ...... ... ....... 61; pi. 10

Myona flabelliformis ........ .- 77

mytUiforme, Euchasma .. 1, 7, 20, 38, 67; pi. 29 

Mytttus ............. 67

edulis ......... .... . _ - 12,13

N

Neopilina ...... 14, 21, 24, 27, 29, 30, 31, 32, 42

galatheae .. ... ____ __ __- 30

Ninmaroo Formation ___ ___- 53,60,62 

normale, Conocardium ... .. .___ _____ 70; pi. 39

norvegica, Ischyrinia _____ 15, 17, 35, 64; pi. 19

Nuculites ... ... ____--_-_-----__------- 60

nueulitiformis, Anisotechnophorus .. 60; pi. 18 

Ribeiria ...... 60

eguilatera, Ribeiria ... ___ - - 51

O

obsolata, Eopteria ............... .- 66; pi. 24

Ribeiria personata ... .... ... ... ... 5S

Oepikila .... . ... .... .- . -- 61; pi. 10

cambrica ......... . ------- 34, 61; pi. 10

ohioensis, Bigalea ____ _-__-_ 1, 77; pi. 36

Opiketta ..... 61

ornata, Eopteria _ _ __ 66 

otaviensis, Technophorus ______________ 56, 59

Oxford Formation _ -__-____ _ __ 55

Ozomia ... .... ... ........... - 48,52
INDEX 87

Page

Palaeacmaea .._____.__________ 27

Palo Pinto Limestone .____------__-. 74

paguettensis, Branaonia __________ 73; pi. 50

parva, Ribeiria ...._...............5^; pi. 9

Pelagiella ...................... 24, 30, 31, 32

Pelagiellacea ________________ 24

Pelagiellids ___________________ 30, 32

Pelecypoda __ 1, 2, 3, 4, 5, 8, 12, 13, 14, 17, 19,

20, 23, 33, 35, 40, 45

 radiation ____ ___ ___ _____ 43

Pelecypods __ 20, 21, 34, 38, 39, 40, 41, 42, 43,

44, 4S, 60, 74 

pennata, Ribeiria manchurica ......... 52

Permian System __________________ 1

Perryyille Limestone Member -_-_--___ 72 

peraonata, Ribeiria ................... 52

lota, Ribeiria .............______ 52

obsoleta, Ribeiria ................. 53

Petoskey Limestone ______.____ 76

Petrifacta derbienaia .................. 69

pholadiformia, Ribeiria ....... 50, 51, 53; pi. 7

Pinna ______________________ 13 

Pinnocaris ............ 34, 37, 44, 54; pis. 9, 10

americana .................... 1, 54; pi. 9

curvata .................... 54; pis. 9, 10

lapworthi ...... ________________ 54; pi. 9

Placophora _..-_----------------------_ 23,45

plana, Anabaretta ................. 27; pi. 17

Plectronoceraa ........................ 32

Plectronoceratidae __--__-_--_-.______ 32

Pleurorinchua ...................____ 74

Pleurorhynchua ....................... 74

plicatua, Technophorua ............ 59: pi. 12

Polyplacophora _____________ 23,24,45 

Poromvacea _______________________ 1, 48

praepriatia, Hippocirdia ... ___________ 76

Pro^ivalvia ........................... 44

Problematica ________________ 24 

Productid brachiopod __________ 22,23 

Prosser limestone ______-_--__________ 54

paeudobettum, Conocardium ... 1, 70; pis. "8, 39 

Paeitdoconoeardium ........ 4, 5, 11, 13, 22, 39,

74; pis. 40-42

lanterna .. 7, 8, 9, 10, 11, 74; pis. 32, 40-42 

licharewi ......._______________ 74

Paeudoeuchaama typica ......... ___ 77: pi. 21

Paeudotechnophorua .. 4, 12,15, 17, 19, 20, 35,

37, 64, 65; pi. 20

typicalia ............. 15, 17, 64, 65; pi. 20

Pterinea .............................. 65,66

punctoatriatua, Technophorus . _______ 58

quincuncialia, Technophorua ._ _ 58; pi. 11 

pygmacea, Hippocardia ............ 76; pi. 50

Q

quincuncialia, Technophorua

punctoatriatua ______ 8, pi. 11

Raphistomenids ________________ 32

Redonia .........__ ___ ________ 41

Ribeirella ............................. 51, 56

Ribeiria .... 4, 5, 9, 12, 13, 19, 21, 25, 33, 34, 37,

48, 50, 51, 52, 53, 59, 60, 62; pis. 4-9, 30. 31 

apuaoidea ... 5, 7, 50, 52, 53; pis. 5-7, 30, 31 

auatralienaia ............ __ 1, 34, 50; pi. 4

bassleri ......___ _ _ __ 51

buaancenais .........________ 51

calcifera ..................... 5, 51; pi. 4

complanata ..................... 51; pi. 9

eompreasa ........_________ 51; pi. 8

conformia ......................... 51

craaaa ........................... 51

inflata ............................ 52

lucan .................... 6, 17, 52; pi. 8

Page 

Rib eiria Continued

magnifica ......................... 52

manchurica ..................... 52; pi. 8

pennata ........................ 52

nuculitiformia .................... 60

equilatera ........................ 51

parva . ____________________ 52; pi. 9

peraonata ....................... 52

lata ............................ 52

obsoleta ......................... S3

pholadiformia ............ 50, 51, 53; pi. 7

aoleaeformia ...................... S3

taylori .................... 1, 34, 53; pi. 8

turgida ........................ 53; pi. 9

sp _______________ 53; pis. 4, 6, 7, 9 

Ribeiriidae ______ 4,12, 17, 34, 35, 37, 48, 49 

Ribeiriids ___ 25, 33, 34, 35, 37, 38, 39, 41, 42,

43, 44, 54 

Ribeirina ............... ....... 37, 55; pi. 3

longiuscula ..................... 55; pi. 3

Ribeirioida ______________ 11,12,35,45 

Ribeirioids _________ 2, 4, 5, 14,15, 17, 56 

richardsoni, Eopteria ___________ 65; pis. 24-26

richmondenaia, Hippocardia ________ 76; pi. 50

robuatum, Branaonia ........ 19, 22; pis. 51, 53

roatratus, Arcitea _______.

Rostroconch mollusks, synoptic

classification ...

Rostroconchia, incertae sedis .

radiation ______________.

rugoaa, Helcionetta ...........

St. George Group ____________

Snukiella aerotina ....................

Scaphopoda ________ 1,4,23,34,40, 

Scaphopods ___________ 20, 21, 39, 

Scenella ....................... 24,27,

Scenic Drive Formation _____________

Schizoplax ............................

achmidti, lachyrinia ______________ __

Schoharie Formation -----_---.-_ __

Schwogerina lutugini ... _____________

acortum, Hecuba ......................

Seison Slate ______________________

aerotina, SaukieUa ....................

Setul Formation ________--------_--__

aharpei, Technophorua __-.-__ CO; pis. 

ahorinenae, Evchoama . ____________ 67;

ahorinenaia, Wanwanella _____________

Siberian Platform ____________________

Sinuitopaia .._______ ____ _______

Sinuoneids ________________

Smithville Formation --_--___-__-___ 

Snails, opisthobranch .___-.-_______

aoleaeformia, Ribeiria .................

Spiriferoid brachiopods ______________

Snonges ____________ _ _

Stenotheca ......________________

Stenothecoida _________----- 23, 40,

Stenothecoides ........................

Stenothecoids -_____----------__---_

atoermpri, T^chnophorua ........... 60;

Stonehenpre Formation ________________

atriata, Wanwanella ......... ______ 68:

auriculata, Wanwnnella ........ 68:

aubacutua, Technophorua ........... 60;

Sulcocarina .........___________

Swift Formation _ _ ______

69

47 

77 

S3 

27

67

53

43, 45

43,44

29. 31

66

40

64

69,70

71

8

77

53

67

12,13 

pi. 28

68 

24

25,27 

32 

66

40,41 

S3 

22 

33 

56

41,44 

40,44 

40,44 

pi. 14 

53

pi. 21

pi. 21

pi. 11

44

62

Tangl^wood Limestone Member _______ 72

Tannuella ......................... 27,29,32

taylori, Rffieiria ............... 1, 34, 53; pi. 8

Technonhoridae _________ 4,12,47,56.57 

Technophorids _______ 34,35,37,38,39,61

Page

Technophorus ........ 4, 17, 35, 37, 50, 52, 56.

58, 59, 60; pis. 10-14 

bellistriatua ................... 58; pi. 11

cancellatus .................... 58; pi. 11

cincinnatienaia . .............. 58; pi. 12

coreanica ...................... 58; pi. 11

divarieatua .................... 58; pi. 14

extenuatus ....................... 56,59

faberi ..................... 56; pis. 10, 11

filiatriatua ................. 59; pis. 13,14

marija ...................... 1, 59; pi. 12

mitteri ._______________ 1, 59; pi. 14

otovienaia ........................ 56, 59

plicatua ....................... 59; pi. 12

punctoatriatua .................... 58

quincuncialia ................ 58; pi. 11

aharpei ................... 60; pis. 12,13

atoermeri ...................... 60; pi. 14

aubacutua ..................... 60; pi. 11

yoldiaformia ................... 60; pi. 10

sp _______________ 17, 60; pis. 11, 12 

Tettina tennis ........................ 12

Tentaculites _ __ ___ 23 

tennis, Tettina ........................ 12

Thyrophoretta ........................ 40

Tiyerton Formation ___________ 72 

Tolmachovia ....... 35, 37, 61, 62; pis. 14, 16,17

concentrica ...... 17, 35, 61, 62; pis. 16, 17

jelli ............... 1, 15, 17, 35, 62; pi. 14

sp ._ --. 62; pi. 16 

Traverse Group _ . 76 

Trenton Formation _..____________ 60

Tribes Hill Formation _________ 51 

trigonalia, Wanwanoidea ........... 69; pi. 21

delicata, Wanwanoidea ........ 69; pi. 21

Trigoniids _______ _________ 17 

Trilobites ___________________ 34,46

troyenais, FordMa ................. 41, 43, 54

Tryblidium ........................... 31

Tainania Zone of Manchuria _.--__ 34 

tumida, Wanwanella ............... 68; pi. 21

turgida, Ribeiria ................... 53; pi. 9

typica, Eopteria ...................... 65

Peeudoeuchaama ............... 77; pi. 21

U

unculata, Igorella .........

Union Valley Formation __ 

Unionids _ _ 

Upper Leptaena Limestone

27

74

17

73

varenaalenae. Heraultipegma ....34, 54; pi. 2

varenaalensis, Heraultia ............... 54

ventricoaa, Eopteria ..... 17, 37, 66; pis. 22, 23

Vermiform ____________________ 23

viabyenaia, Bigolea ........... 1, 77; pis. 35, 36

Vologdinella .......................... 32

W

Wandrawandian Siltstone _________ 22 

Wanwanella .......... 37, 65, 67, 68, 69; pi. 21

alia ........................... 68; pi. 21

asiatica ........................... 65

ahorinenaia .............. ... ... 68

atriata ....................... 68; pi. 21

auriculata ................... 68; pi. 21

tumida ........................ 68; pi. 21

wanwanenae, Euchaama ............ 68; pi. 28

Wanwania ......... 17, 19, 34, 37, 38, 55; pi. 3

ambonychiformia ............... 55; pi. 3

cambrica ................ 34, 35, 55; pi. 3

compreaaa ...................... 55; pi. 3

Wanwankou Dolomite ____ 52, 55, 64, 65, 66,

67, 68, 69,77
88 INDEX

Page 

Wanwanoidea .._____.__________ 69; pi. 21

trigonalis ......-----__-------- 69; pi. 21

delicata ..................... 69; pi. 21

Watsonella ............... 17, 33, 34, 43, 54, 56

crosbyi _ -________----_ 34, 56; pi. 3

Whitehall Formation __________.. 53,61 

Whitehead Formation _________ .__ 64

Page

Whitewater Formation ______________ 59

wilsoni, Bransonia ..... 1,4,5,8,9,10,23,72;

pis. 32, 51, 52 

winchelli, Ischyrinia ..... 17, 35, 62; pis. 18, 19

Y, Z

yangi, Bigalea .............. 1, 76; pis. 36, 37

Page 

Yochelcionetta ................... 21, 27; pi. 1

cyrano ............................ pi. 1

Yochelaonellis ......................... 29

Yochelsoniella ........_______________ 32

yoldiaformis, Technophorus ......... 60; pi. 10

zeileri, Hippocardia ......... 11, 19, 76; pi. 47
PLATES 1-54

Contact photographs of the plates in this report are available, at

cost, from U.S. Geological Survey Library, Federal Center,

Denver, Colorado 80225
PLATE 1

FIGURES 1-7. Yocheldonella cyrano Runnegar and Pojeta, 1974 (p. 27).

Holotype, USNM 204698; USGS 5959-CO. Collected by Brian Daily from the "first discovery limestone", Redlichia chinensis Zone, Ordian Stage, lower Middle Cambrian, Mootwingee Range area, 

New South Wales, Australia. 1-6 (X 22); 7 (X 60). 1, Oblique left anterior view; 2, Posterior 

view; 3, Anterior view; 4, Dorsal view; 5, Right-lateral view; 6, Left-lateral view; 7, Enlargement 

of apex (protoconch?) of shell showing ornament.
PROFESSIONAL PAPER 968 PLATE 1

YOCHELCIONELLA
PLATE 2

FIGURES 1-13. Heraultipegma varensalense (Cobbold), 1935 (p. 54).

Topotypes. 1-3, Right, anterior, and posterior views of USNM 209414, 1 (X 15), 2, 3 (X 45). 4, 

Right-lateral view of USNM 209415 (X 33). 5, Dorsal view of USNM 209416 (X 43). 6-8, Ventral, left-lateral, and enlargement of anterodorsal area with remnant of the pegma (USNM 

227467); 6, 7 (X 20); 8 (X 65). 9-13, Left-lateral, anterior, oblique left posterior, oblique right 

anterior, and posterior views of USNM 209417 (X 47).
GEOLOGICAL SURVEY PROFESSIONAL PAPER 968 PLATE 2

HERA ULTIPEGMA
PLATE 3

FIGURES 1-4. Watsonella crosbyi Grabau, 1900 (p. 56).

The type suite, of which the specimen shown in figure 1 is herein chosen as the lectotype (Grabau, 

1900, pi. 31, fig. 9b). From Lower Cambrian boulders, Sandy Cove and Pleasant Beach, Gohasset, 

Mass. All left-lateral views (X 4). Specimens at the MCZ where they are cataloged under the 

Boston Society of Natural History Nos. 11951-11954. 

5,11-14. Wanwania cambrica Kobayashi, 1933 (p. 55).

5. Plastoparatype (Kobayashi, 1933, pi. 9, fig. 7), left valve (X 5). Upper Cambrian (Tsinanw 

Zone), Paichia-shan, Wuhutsui Basin, Manchuria. USNM 209409.

11-14. Plastoholotype (Kobayashi, 1933, pi. 7, fig. 1), dorsal (X 4), right-lateral (X 2), leftlateral (X 2), and anterior (x 4) views. Formation and locality the same as in figure 5 above. 

USNM 209412. 

6-9. Wanwania compressa Kobayashi, 1933 (p. 55).

Plastoholotype (Kobayashi, 1933, pi. 7, fig. 5), right-lateral, left-lateral, dorsal, and anterior views 

(X 3). Wanwankou Dolomite (Lower Ordovician),, Wan-wan-kou in the Niuhsintai Basin, south 

Manchuria. USNM 209410. 

10. Wanwania ambonychiformis Kobayashi, 1933 (p. 55).

Plastoholotype (Kobayashi, 1933, pi. 7, fig. 4), right-lateral view (X 2). Formation and locality the

same as in figures 6-9 above. USNM 209411. 

15-23. Ribeirina longiuscula (Billings), 1865 (p. 55).

15-18. Ventral, anterior, dorsal, and left-lateral views (x 2). Oxford Formation (Lower Ordovician), Ottawa-Carleton Highway 3, 2.4 miles northwest of intersection with County Highway 4 

(GSC loc. 89453), Ontario, Canada. USNM 209413.

19,20. Left- and right-lateral views (X 2). Beekmantown Group (Lower Ordovician), Marlborough 

Township, Ontario, Canada. ROM 26 cal.

21-23. Dorsal, anterior, and right-lateral views of holotype (X 2). Beekmantown Group (Lower 

Ordovician), Oxford Township, Ontario, Canada. GSC 470.
GEOLOGICAL SURVEY PROFESSIONAL PAPER 968 PLATE 3

WATSONELLA, WANWANIA, AND RIBEIRINA
PLATE 4

FIGURES 1-24. Ribeiria calcifera Billings, 1865 (p. 51).

1-3. Right-lateral, left-lateral, and dorsal views of paralectotype (X 2). Beekmantown Group 

(Lower Ordovician), Oxford Township, Ontario, Canada. GSC 469a.

4-6. Left-lateral, anterior, and dorsal views of lectotype (X 2). Formation and locality the same as 

in figures 1-3 above. GSC 469.

7-10. Left-lateral (X 2), dorsal (X 2), anterior (X 4), and posterior (X 2) views of paralectotype. 

Formation and locality the same as in figures 1-3 above. GSC 469b.

11,12. Posterior and right-lateral views of paralectotype (X 2). Formation and locality the same 

as in figures 1-3 above. GSC 469d.

13. Anterior view (X 2). Beekmantown Group (Lower Ordovician), Marlborough Township, Ontario, Canada. ROM 13 cal.

14-17. Left-lateral, posterior, ventral, and dorsal views (X 2). Formation and locality the same as 

on plate 3, figures 15-18. USNM 209408.

18,19. Posterior (X 4) and right-lateral (X 2) views. Staendebach Member, Tanyard Formation 

(Lower Ordovician), 3.25 miles airline east-southeast of Round Mountain, Blanco County, Tex. 

This hypotype was previously figured by Cloud and Barnes (1948). USNM 127909.

20-24. Left-lateral (X 2), right-lateral (X 2), latex mold of anterior face showing pegma (X 2), 

anterior (X 3), and posterior (X 4) views. Staendebach Member, Tanyard Formation (Lower 

Ordovician), 1.5 miles west from the ranch headquarters of Mack Yates, Sr., southeastern San 

Saba County, Tex. This hypotype was previously figured by Cloud and Barnes (1948). USNM 

127908. 

25. Ribeiria sp. (p. 53).

Left-lateral view of fragmentary specimen (X 3). Lower Ordovician (Warendian) part of the Ninmaroo Formation, at northern peak of Digby Peaks, 60 miles north of Boulia, Queensland, Australia. UQ F 67149. 

26-29. Ribeiria australiensis n. sp. (p. 50).

26,28. Posterior (X 4) and right-lateral (X 4) views of paratype, Mungerebar Formation (Upper 

Cambrian), Glenormiston, Queensland, Australia. BMR CPC 14671.

27,29. Dorsal and anterior views of holotype (X5). Formation and locality the same as in figures, 

26. 28 above. BMR CPC 14670.
GEOLOGICAL SURVEY PROFESSIONAL PAPER 968 PLATE 4

RIBEIRIA
PLATE 5

FIGURES 1-14. Ribeiria apusoides Schubert and Waagen, 1903 (p. 50).

1-4. Dorsal (X 3), left-lateral (X 2), right-lateral (x 2), and latex replica of posterodorsal face

of pegma, showing muscle insertion area (X 2). Ordovician (D), Bohemia, Czechoslovakia. MCZ

18008. 

5, 6. Right- and left-lateral views (X 2). Horizon and locality the same as in figures 1-4 above.

MCZ 18009. 

7,8. Dorsal (X 3) and left-lateral (X 2) views. Horizon and locality the same as in figures 1-4

above. MCZ 18010. 

9. Latex replica of paralectotype (Schubert and Waagen, in Perner, 1903, pi. 49, fig. 21), left valve

(X 2). Zahorany Formation (Caradocian, Ordovician), Lodenice, Bohemia, Czechoslovakia. USNM

209404.

10,11. Left-lateral and dorsal views (X 2) of replica of paralectotype (Schubert and Waagen, in 

Perner, 1903, pi. 49, figs. 5, 6). Horizon and locality the same as in figure 9 above. USNM

209405.

12. Anterior view showing gape (X 4). Horizon and locality the same as in figures 1-4 above. 

MCZ 18011.

13. Right valve exterior (X 2) of latex replica of paralectotype (Schubert and Waagen, in Perner, 

1903, pi. 49, figs. 22-2S). Caradocian (Ordovician), Liben, Bohemia, Czechoslovakia. USNM 

209406.

14. Left valve exterior (x 2) of latex replica of paralectotype (Schubert and Waagen in Perner, 

1903, pi. 49, figs. 24, 25; Schubert and Waagen, 1904, pi. 1, fig. 8). Horizon and locality the same 

as in figure 9 above. USNM 209407.
PROFESSIONAL PAPER 968 PLATE 5

RIBEIRIA
PLATE 6

FIGURES 1-12, 14,15. Ribeiria apusoides Schubert and Waagen, 1903 (p. 50).

1-4. Left-lateral (X 2), right-lateral (X 2), anterior (X 3), and dorsal (X 3) views of latex 

replica of lectotype (Schubert and Waagen in Perner, 1903, pi. 49, figs. 18-20; Schubert and 

Waagen, 1904, pi. 1, fig. 9). Caradocian (Ordovician), Lodenice, Bohemia, Czechoslovakia. USNM 

209402.

5. Anterior view showing gape (X 4). Llanvirnian(?) (Middle Ordovician), Rokycany, Bohemia, 

Czechoslovakia. MCZ 18012.

6. Posterior view showing gape (X 4). Caradocian (?) (Ordovician), Lodenice, Bohemia, Czechoslovakia. MCZ 18013.

7. Right-lateral view (X 3). Horizon and locality the same as in figure 5 above. MCZ 18014.

8. Right-lateral view showing side muscle (X 3). Horizon and locality the same as in figure 5 

above. MCZ 18015.

9. Right-lateral view (x 3). Horizon and locality the same as in figure 5 above. MCZ 18016.

10. Left-lateral view (x 2). Horizon and locality the same as in figure 5 above. MCZ 18017.

11. Left-lateral view (X 2). Horizon and locality the same as in figure 5 above. MCZ 18018.

12. Right-lateral view (X 3). Horizon and locality the same as in figure 5 above. MCZ 18019.

14. Right-lateral view showing elongate posterior median muscle scar (X 2). Ordovician (D), Bohemia, Czechoslovakia. MCZ 18020.

15. Left-lateral view (X 2). Ordovician (D), Bohemia, Czechoslovakia. MCZ 18021. 

13. Ribeiria sp. (p. 53).

Right-lateral view of replica of paralectotype of R. apusoides (X 2) (Schubert and Waagen in

Perner, 1903, pi. 49, figs. 15-17). This is the youngest known Ribeiria and is probably not R.

apusoides. Ashgillian (Upper Ordovician), Lejskov, Bohemia, Czechoslovakia. USNM 209403.
GEOLOGICAL SURVEY PROFESSIONAL PAPER 968 PLATE 6

RIBEIRIA
PLATE 7

FIGURES 1,2. Ribeiria apusoides Schubert and Waagen, 1903 (p. 50).

1. Left-lateral view showing side muscle scar and posterior median muscle scar (X 3). Ordovician (D), Bohemia, Czechoslovakia. MCZ 18022.

2. Dorsal view showing posterior median muscle scar (X 2). Ordovician (D), Bohemia, Czechoslovakia. MCZ 18023. 

3-12. Ribeiria pholadiformis Sharpe, 1853 (p. 50).

3-7. Dorsal, ventral, right-lateral, left-lateral, and anterior views (X 2) of lectotype (Sharpe, 1853, 

pi. 9, figs. 17b, c). Llandeilian(?) (Middle Ordovician) of Portugal. GB 7798.

8. Right valve external mold, paralectotype (X 2). Horizon and locality the same as in figures 3- 

7 above. BM PL 4176a.

9. Left valve external mold, paralectotype (X 2). Horizon and locality the same as in figures 3-7 

above. BM PL 4176b.

10. Left valve external mold, paralectotype (X 2). Horizon and locality the same as in figures 3- 

7 above. BM PL 4177.

11. Left-lateral view (X 2). Middle Arenigian (Lower Ordovician), from small abandoned quarry 

in hillside, about 200 feet above and 0.25 miles east of road from Carteret to Hattainville, Manche, 

Normandy, France. SM A.60181.

12. Right-lateral view (X 2). Horizon and locality the same as in figure 11 above. SM A.60182. 

13-16. Ribeiria cf. R. pholadiformis Sharpe, 1853 (p. 50).

Left-lateral, right-lateral, latex replica of exterior, and dorsal views (X 2). SM A 46270d, e. 

17,18. Ribeiria sp. (p. 53).

Two specimens showing right- and left-lateral views (X2). From the H Zone of Hintze (1951) at 

the Ibex section, Ibex, Utah (Lower Ordovician), Sec. 6, T. 23 N., R. 14 E. USNM 209400, 

209401.
GEOLOGICAL SURVEY PROFESSIONAL PAPER 968 PLATE 

7
PLATE 8

FIGURES 1-5. Ribeiria compressa Whitfield, 1886 (p. 51).

1,2. Right-lateral and dorsal views of holotype (X 2) . The museum label gives the horizon and

locality as: "Ft. Cassin bed, Fort Cassin, Vermont" (Lower Ordovician). AM 491. 

3-5. Dorsal, left-lateral, and right-lateral views (X 3) of lectotype of Ribeiria equilatera Cleland 

(1900, pi. 16, fig. 15). Cleland (1900, p. 22) gave the horizon and locality as "Calciferous at Fort 

Hunter, New York" (Lower Ordovician). PRI 5081. 

6-11. Ribeiria manchurica Kobayashi, 1933 (p. 52).

6,7. Right-lateral and left-lateral views of a replica of the holotype (x 2). Wanwankou Dolomite 

(Lower Ordovician), Wan-wan-kou in the Niuhsintai Basin, southern Manchuria. USNM 209394. 

8-11. Dorsal (X 2), left-lateral (x 2), right-lateral (X 2), and anterior (X 3) views of a replica 

of a previously unfigured paratype. Horizon and locality the same as in figures 6, 7. USNM 

209395. 

12,13. Ribeiria taylori n. sp. (p. 53).

Dorsal and left-lateral views of holotype (X 4). Whitehall Formation, Saukia Zone, probably Saukiella serotina (Upper Cambrian). USGS loc. 470B (old series), Hall Farm, 1 mile northeast of 

Whitehall, N.Y. (Taylor and Halley, 1974, p. 32). USNM 209396. 

14-24. Ribeiria lucan (Walcott), 1924 (p. 52).

14. Right-lateral view (X 4) of lectotype of Ozomia lucan Walcott, (1924, p. 531), showing multiple insertions of side muscle. Mons Formation (Lower Ordovician), thin-bedded gray limestone 

255 feet from summit of Mons, 8.7 miles northeast in airline of Lake Louise Station on the Canadian Pacific Railway at the east foot of Fossil Mountain, Alberta, Canada. USNM 209397.

15. Right-lateral view (X 4), paralectotype. Horizon and locality the same as in figure 14 above. 

USNM 209398.

16-18. Right-lateral, anterior, and dorsal views (X 4) of paralectotype. Horizon and locality the 

same as in figure 14 above. USNM 209399.

19-24. Posterior, right-lateral, left-lateral, dorsal, ventral, and anterior views (X 4) of paralectotype. Horizon and locality the same as in figure 14 above. USNM 69801.
GEOLOGICAL SURVEY PROFESSIONAL PAPER 968 PLATE

RIBEIRIA
PLATE 9

FIGURES 1. Ribeiria turgida Cleland, 1903 (p. 53).

Right-lateral view of holotype (X 3). The museum label gives the horizon and locality as: "Tribes

Hill Is., Canajoharie?, New York" (Lower Ordovician). USNM 84630. 

2-6. Ribeiria sp. (p. 53).

2. Right-lateral view (X 3) of a specimen figured by Sando (1957, pi. 10, fig. 3). Stonehenge Formation (Lower Ordovician), pasture northeast of Barn on Forsythe Farm, 1.0 miles S. 5° E. of 

St. Pauls Church, Washington County, Md. USNM 123847.

3,4. Right-lateral and dorsal views (X 3). Stonehenge Formation (Lower Ordovician), 1.35 miles 

S. 20° W. of Charlton in pasture 300 feet southeast of barn, Washington County, Md. USNM 

146208. 

5,6. Dorsal and right-lateral views (X 3). Horizon and locality the same as in figures; 3, 4 above.

USNM 209391. 

7-9. Ribeiria parva Collie, 1903 (p. 52).

Right-lateral, dorsal, and left-lateral views of holotype (X 4). Collie (1903, p. 419) gave the horizon and locality as: "Beliefonte, Pennsylvania, in the middle Beekmantown horizon" (Lower Ordovician). YU 7933. 

10. Ribeiria complanata Salter, 1866 (p. 51).

Left-lateral view of holotype (X 3). Lower Llandeiilian (Middle Ordovician), Lord's Hill, Shelve,

North Wales. GB 12434. 

11,12. Pinnocaris americana n. sp. (p. 54).

11. Right-lateral view of paratype (X 2). The museum label gives the horizon and locality as: 

"Prosser limestone, Elkader, Iowa" (Middle Ordovician). USNM 209392.

12. Right-lateral view of holotype (X 2). Horizon and locality the same as in figure 11. USNM

209393. 

13-23. Pinnocaris lapworthi Etheridge, 1878 (p. 54).

13,14. Left valve mold of exterior and latex replica of mold (X 2). Hypotype figured by Jones and

Woodward (1895, pi. 15, figs. 8, 9). The museum label gives the horizon and locality as: "Upper

Ordovician, Lower Ardmillan series, Balclatchie Group; Balclatchie, Girvan, Ayrshire," Scotland.

BM In 20372. 

15-17. Anterior view showing gape (X 4), left-lateral (X 2) right-lateral (X 2) views. The

museum label reads: "Balclatchie." SM A 33722b. 

18,19. Part and counterpart of right valve (X 2). Horizon and locality the same as in figures 13,

14 above. BM In 20422.

20. Broken and distorted left valve (X 2), paralectotype (Etheridge, 1878, pi. 2, fig. 3). Etheridge 

(1878, p. 169) gave the horizon and locality as: "Balcletchie [sic], south-east of Girvan, in rocks of 

Silurian [Ordovician] age; exact horizon not yet determined." BM In 20366.

21. Crushed right valve (X 2), lectotype (Etheridge, 1878, pi. 2, fig. 5). Horizon and locality the 

same as in figure 20 above. BM In 20367.

22. Left valve (X 2), paralectotype (Etheridge, 1878, pi. 2, fig. 4). Horizon and locality the same as 

in figure 20 above. BM In 20368.

23. Left-lateral view (X 2). Horizon and locality the same as in figures 15-17 above. SM A 33722b. 

24,25. Pinnocaris curvata Reed, 1907 (p. 54).

Latex replica and original of a mold of a right valve (X 2). The museum label gives the horizon

and locality as: "Upper Ordovician, Ardmillan series, Drummuck Group, Starfish Bed; Thraive

Glen, Girvan, Ayrshire," Scotland. BM In 20290.
GEOLOGICAL SURVEY PROFESSIONAL PAPER 968 PLATE 9

RIBEIRIA AND PINNOCARIS
PLATE 10

FIGURES 1-10. Pinnocaris curvata Reed, 1907 (p. 54).

1. Internal mold left valve (X 2). Horizon and locality the same as in figures 24, 25, plate 9. BM 

In 20283.

2. Right-lateral view (X 2). The museum label gives the horizon and locality as: "Starfish Bed, 

Upper Drummuck Group: Thraive Glen, Girvan, Ayrshire," Scotland (Upper Ordovician). SM 

A 525594.

3. Left-lateral view (X 2). Horizon and locality the same as in figures 24, 25, plate 9. BM In 20309. 

4,5. Original and latex replica of an external mold of left valve (X 2). This is the other valve of

the specimen shown on plate 9, figures 24, 25. Horizon, locality, and museum number the same as

on plate 9, figures 24, 25. 

6,7. Original and latex replica of external mold of left valve (X 2). Horizon and locality the same

as on plate 9, figures 24, 25. BM In 20337. 

8-10. Left-lateral, right-lateral, and dorsal views (X 2). Horizon and locality the same as on plate

9, figures 24, 25. BM 20337. 

11,12. "Technophorus" yoldiaformis (Ulrich), 1879 (p. 60).

Left-lateral views of two syntypes showing pelecypod adductor muscle impressions (X 5). Cincinnatian (Upper Ordovician), Covington, Ky. USNM 209390, 46315. 

13. Myocaris lutraria Salter, 1864 (p. 61).

Left-lateral view (X 1) of holotype (Salter, 1864, fig. 4). The museum label gives the horizon and

locality as: "Ordovician, Llandeilo, from Trias Pebble Bed, Budleigh-Salterton, Devon," England.

BM I 7204. 

14,15. Oepikila cambrica (Runnegar and Pojeta), 1974 (p. 61).

Part and counterpart of right valve (X 15), holotype. Georgina Limestone, Erixanium sentum Zone,

Idamean Stage (Upper Cambrian), western Queensland, Australia. BMR CPC 13953. 

16-21. Technophorus faberi Miller, 1889 (p. 56).

16,17. Left-lateral and dorsal views (X 2) of paralectotype (Miller, 1889, p. 513, left-hand figure

in fig. 930). The museum label gives the horizon and locality as: "Cincinnatian, near Sharonville,

Ohio" (Upper Ordovician). FM 8831 (Walker Mus. coll).

18-21. Anterior (X 4), dorsal (X 2), right-lateral (X 2), and left-lateral (X 2) views. The museum label gives the horizon and locality as: "Utica, Cincinnati, Ohio" (Upper Ordovician).

USNM 40611.
GEOLOGICAL SURVEY

PROFESSIONAL PAPER 968 PLATE 10

PINNOCARIS, ^'TECHNOPHORUS," MYOCARIS, OEPIKILA, AND TECHNOPHORUS
PLATE 11

FIGURES 1-6. Technophorus faberi Miller, 1889 (p. 56).

1,2. Dorsal and left-lateral views (X 2) of a hypotype (Miller and Faber, 1894, pi. 1, fig. 20). 

Maysvillian (Upper Ordovician), Sharonville, Ohio. FM 8832 (Walker Mus. coll).

3. Left-lateral view (X 3). The museum label gives the horizon and locality as: "Eden Shale, Covington, Kentucky" (Upper Ordovician). USNM 72019.

4. Right-lateral view (X 3). The museum label gives the horizon and locality as: "Maysville Grp. 

(Fairmount beds), Cincinnati, Ohio" (Upper Ordovician). USNM 40612.

5. 6. Right-lateral and left-lateral views of lectotype (X 3). Horizon, locality, and museum number

the same as on plate 10, figures 16,17. 

7 13. Technophorus bellistriatus Branson, 1909 (p. 58).

7-9. Left-lateral, dorsal, and posterior views (X 4); the last shows the gape of the posterior rostrum. Decorah Shale (Middle Ordovician), 2.5 miles west of St. Genevieve, Mo. FM 23942 

(Walker Mus. coll.).

10-13. Anterior, ventral, right-lateral, and left-lateral views of holotype (X 4). The museum label 

gives the horizon and locality as: "Stones River, Auburn, Lincoln Co., Mo." (Middle Ordovician). 

FM 11551 (Walker Mus. coll.). 

14. Technophorus coreanica (Kobayashi), 1934 (p. 58).

Right-lateral view (X 7) of replica of holotype (Kobayashi, 1934, pi. 4, fig. 18). Kobayashi (1934, 

p. 576) gave the horizon and locality as: "Clarkella zone of Saisho-ri;" South Korea (Lower Ordovician). USNM 209389. 

15-20. Technophorus cancellatus Ruedemann, 1901 (p. 58).

15. Right-lateral view (X 6) of hypotype (Ruedemann, 1912, pi. 9, fig. 17). The museum label 

gives the horizon and locality as: "Snake Hill beds, Snake Hill, Saratoga Co., N.Y." (Middle 

Ordovician). NYSM 9890.

16. Right-lateral view (X 4) of lectotype (Ruedemann, 1901, pi. 1, figs. 19, 20). The museum label 

gives the horizon and locality as: "Snake Hill shale, Green Island, Albany Co., N.Y." (Middle 

Ordovician). NYSM 3190.

17. Right-lateral view (X 4) of paralectotype (Ruedemann, 1901, pi. 1, fig. 21). Horizon and locality the same as in figure 16 above. NYSM 3191.

18. Left-lateral view (X 4) of paralectotype (Ruedemann, 1901, pi. 1, fig. 22). Horizon and locality 

the same as in figure 16 above. NYSM 3192.

19. Right-lateral view (X 3) of hypotype (Ruedemann, 1912, pi. 9, fig. 18). Horizon and locality 

the same as in figure 15 above. NYSM 9891.

20. Left-lateral view (X 4) of paralectotype (Ruedemann, 1901, pi. 1, fig. 23). Horizon and locality 

the same as in figure 16 above. NYSM 3193.

21. Technophorus sp. (p. 60).

Right-lateral view (X 4). Lower Ordovician (Warendian) part of the Ninmaroo Formation, at northern peak of Digby Peaks, 60 miles north of Boulia, Queensland, Australia. UQ F67150.

22. Technophorus subacutus Ulrich, 1892a (p. 60).

Left-lateral view of holotype (X 3). Ulrich (1892a, p. 101) gave the horizon and locality as: "Upper 

part of the limestone of the Trenton formation at Minneapolis, Minnesota." Bassler (1915, p. 1259) 

gave the horizon as: "Black River (Platteville)" (Middle Ordovician). UMN 8338.

23. Technophorus cf. T. cancellatus Ruedemann, 1901 (p. 58).

Right-lateral view (X 4) of lectotype of T. punctostriatus quincuncialis Foerste (1914, pi. 2, fig. 

13b). The museum label gives the horizon and locality as: "Upper Ordovician, Chambly, Quebec," 

Canada. GSC 8415.
GEOLOGICAL SURVEY PROFESSIONAL PAPER 968 PLATE 11

TECHNOPHORUS
PLATE 12

FIGURES 1,2. Technophorus plicatus (Billings), 1866 (p. 59).

Right-lateral and left-lateral views of holotype (X 3). The museum label gives the horizon and locality as: "Ellis Bay, Upper Ordovician, Junction Cliff, Anticosti Island," Quebec, Canada. GSC 

2291. 

3. Technophorus cf. T. plicatus (Billings), 1866 (p. 59).

Right-lateral view (X 3). Ordovician of Anticosti Island, Quebec, Canada. YU 3063/40. 

4-11. Technophorus cincinnatiensis Miller and Faber, 1894 (p. 58).

4-6. Right-lateral, dorsal, and left-lateral views of holotype (X 5). The museum label gives the horizon and locality as: "Eden-Economy, Cincinnati (?), O." (Upper Ordovician). UCM 3886.

7. Left-lateral view (X 5) of lectotype of T. punctostriatus Ulrich ([1895], pi. 47, fig. 11). The 

museum label gives the horizon and locality as: "Lorraine, Covington, Kentucky" (Upper Ordovician) . USNM 46313.

8. Right-lateral view (X 5) of paralectotype of T. punctostriatus Ulrich ([1895], pi. 47, figs. 10, 

12). Horizon and locality the same as in figure 7 above. USNM 209383.

9. Right-lateral view (X 5). The museum label gives the horizon and locality as: "Eden Shale, Covington, Kentucky" (Upper Ordovician). USNM 72018.

10.11. Left-lateral and dorsal views (X 5). The museum label read: "Lexington Pike, near Covington, Kentucky" (Upper Ordovician). USNM 209384. 

12-15. Technophorus marija n. sp. (p. 59).

Left-lateral, right-lateral, posterior, and dorsal views of holotype (X 4). The museum label reads: 

"Middle Ord., Boulder on right bank of Moyero River, 6 miles above mouth of Ukdama River, 

Khatango-Anabar Region, northern Siberia." Geological Museum, Academy of Science, U.S.S.R., 

1849/2027. 

16,17. Technophorus sp. (p. 60).

Two specimens, left and right valves, respectively, showing the side muscles (X 5). Kope Formation (Upper Ordovician), 68.3 m above base of section at 497,600 ft N.; 930,000 ft E., Demossville 7.5-minute quadrangle, Kenton County, Ky. Collected by D. M. Lorenz. USNM 209385, 209386. 

18,19. Technophorus sharpei (Barrande) in Perner, 1903 (p. 60).

18. Left-lateral view of latex replica of syntype (X 4). The museum label accompanying this specimen cites it as a replica of Barrande in Perner (1903, pi. 49, fig. 9), which is shown as a right 

valve. Caradocian (Ordovician), Vinice, Bohemia, Czechoslovakia. USNM 209387.

19. Left-lateral view of latex replica of syntype (X 4). The museum label accompanying this specimen cites it as a replica of Barrande in Perner (1903, pi. 49, fig. 7), which is shown as a right 

valve. Caradocian (Ordovician), Liben, Bohemia, Czechoslovakia. USNM 209388.
GEOLOGICAL SURVEY PROFESSIONAL PAPER 968 PLATE 12

TECHNOPHORUS
PLATE 13

FIGURES 1-14. Technophorus sharpei (Barrande) in Perner, 1903 (p. 60).

1. Left-lateral view of latex replica of syntype (X 4). The museum label accompanying this specimen cites it as a replica of Barrande in Perner (1903, pi. 49, fig. 8), which is shown as a right 

valve. Caradocian or Ashgillian (Ordovician), Bohemia, Czechoslovakia. USNM 209381.

2. Left-lateral view of latex replica of syntype (x 4). The museum label accompanying this specimen cites it as a replica of Barrande in Perner (1903, pi. 49, figs. 10, 11), which is shown as 

a right valve. Bohdalec Formation (Caradocian, Ordovician), Velka Chuchle, Bohemia, Czechoslovakia. USNM 209382.

3. Left-lateral view of internal mold (X 5). Ordovician (Caradocian?), Velka Chuchle, Bohemia, 

Czechoslovakia. MCZ 18024.

4. Right-lateral view of composite mold (X 5). Horizon and locality the same as in figure 3 above. 

MCZ 18025.

5. Left-lateral view of internal mold (x 5). Horizon and locality the same as in figure 3 above.

MCZ 18026. 

6-8,13. Right-lateral, left-lateral, dorsal, and anterior views (X 5). Horizon and locality the same

as in figure 3 above. MCZ 6908/3. 

9-12. Right-lateral (X 5), left-lateral (X 5), anterior (X 8), and dorsal (X 5) views. Ordovician

of Bohemia, Czechoslovakia. MCZ 18027.

14. Posterior view showing the bilobed posterior shell gape (X 8). Horizon and locality the same as

in figures 9-12 above. MCZ 18028. 

15,16. Technophorus filistriatus Ulrich, 1892'a (p. 59).

15. Right-lateral view of internal mold (X 5). The museum label gives the horizon and locality as: 

"Trenton, Kenyon, Minnesota" (Middle Ordovician). USNM 47204.

16. Left-lateral view of holotype (X 3). The museum label gives the horizon and locality as: "Black 

River, 6 miles south of Cannon Falls, Minnesota" (Middle Ordovician). USNM 46312.
GEOLOGICAL SURVEY PROFESSIONAL PAPER 968 PLATE 13

TECHNOPHORUS
PLATE 14

FIGURES 1. Technophorus filistriatus Ulrich, 1892a (p. 59).

Left-lateral view of exterior (X 3). The museum label gives the horizon and locality as: "Decorah

sh., b. 5, Cannon Falls," Minnesota (Middle Ordovician). UMN 12236. 

2-5. Technophorus cf. T. divaricatus Ulrich, 1892a (p. 58).

2. Latex replica of the exterior of a right valve (X 5). The museum label gives the horizon and locality as: "Decorah sh., b. 4, St. Paul," Minnesota (Middle Ordovician). UMN 12237. Replica 

USNM 209379.

3. Latex replica of exterior of a right valve (X 4). Elkhorn Formation (Upper Ordovician), along 

road west of Hamburg, Ind. MU 6849. Replica USNM 209380.

4,5. Latex replica and specimen of ventral part of left valve (X 4). Horizon, locality, and museum

number the same as in figure 3 above. 

6,7. Technophorus milleri n. sp. (p. 59).

Part and counterpart of holotype showing ornament and elongated posterior rostrum (X 5). Lower 

Whitewateir Formation (Upper Ordovician), Dodge's Creek, 0.5 miles north of Oxford, Ohio. MU 

6848. 

8. Technophorus stoermeri Soot-Ryen, 1960 (p. 60).

Left-lateral view of holotype (X 4). Middle Caradocian (Middle Ordovician), Ost0ya, Baerum, Norway. UO 5849. 

9-19. Tolmachovia"! jelli n. sp. (p. 62).

9-12. Anterior, dorsal, right-lateral, and left-lateral views of holotype (X 4). Lower O'rdovician 

part (Warendian) of the Ninmaroo Formation, northern peak of Digby Peaks, about 60 miles north 

of Boulia, Queensland, Australia. UQ F 60117.

13,14. Dorsal and anterior views of paratype (X 4). Horizon and locality the same as in figures 

9-12 above. UQ F 60119.

15,16. Anterior and right-lateral views of paratype (X 4). Horizon and locality the same as in figures 9-12 above. UQ F 60118.

17-19. Right-lateral, anterior, and dorsal views of paratype (X 4). Horizon and locality the same 

as in figures 9-12 above. UQ F 67152.
GEOLOGICAL SURVEY

PROFESSIONAL PAPER 9t* PLATE 14

TECHNOPHORUS AND TOLMACHOVIA
PLATE 15

FIGURES 1-4. IMacroscenella cf. M. montrealensis (Billings), 1865 (p. 30).

Left, dorsal, oblique right (X 27) views, and enlargement of protoconch (X 68) of a monoplacophoran showing a planispirally coiled protoconch. Lower Chambersburg Limestone (Middle Ordovician), near Strasburg, Va., USNM locality 600. Specimen identified by E. L. Yochelson, USNM 

209378.
GEOLOGICAL SURVEY PROFESSIONAL PAPER 968 PLATE 15

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PLATE 16

FIGURES 1-10. Tolmachovia concentrica Howell and Kobayashi, 1936 (p. 62).

1-4. Right-lateral, anterior, posterior, and left-lateral views of a previously unfigured paratype (X 

5). The museum label gives the horizon and locality as: "Middle Ordovician, boulder on right bank 

of Moyero River, 6 miles above mouth of Ukdama River, Khatanga-Anabar region, northern Siberia." Geological Museum of the Academy of Science, U.S.S.R. 1849/2027.

5,6. Right-lateral and left-lateral views of paratype (X 5). Horizon and locality the same as in figures 1-4 above. Geological Museum of the Academy of Science, U.S.S.R. 1849/2027c.

7. Right-lateral view of a previously unfigured paratype (X 5). Horizon and locality the same as in 

figures 1-4 above. Geological Museum of the Academy of Science, U.S.S.R., 1849/2027d.

8-10. Left-lateral, right-lateral, and dorsal views of holotype (X 5). Horizon and locality the same

as in figures 1-4 above. Geological Museum of the Academy of Science, U.S.S.R., 1849/2027a. 

11-14. Tolmachovia sp. (p. 62).

Ventral, anterior, posterior, and left-lateral views (X 3). Ordovician of Portugal. BM PL 4434.
GEOLOGICAL SURVEY PROFESSIONAL PAPER 968 PLATE 16

TOLMACHOVIA
PLATE 17

FIGURES 1-7,9-11. Tolmachovia concentrica Howell and Kobayashi, 1936 (p. 62).

1,2,11. Right-lateral, dorsal, and left-lateral views of paratype (X 5). Horizon and locality the

same as in plate 16, figures 1-4. Geological Museum of the Academy of Science, U.S.S.R., 1849/

2027b. 

3,4. Right-lateral and anterior views of a previously unfigured paratype (X 5). Horizon, locality,

and museum number the same as in plate 16, figures 1-4. 

5,6. Right-lateral and anterior views of a previously unfigured paratype (X 5). Horizon, locality,

and museum number the same as in plate 16, figures 1-4. 

7. Posterior view of a previously unfigured paratype (X 5). Horizon, locality, and museum number

the same as in plate 16, figures 1-4.

9. Anterior view of previously unfigured paratype (X 5). Horizon, locality, and museum number 

the same as in plate 16, figures 1-4.

10. Posterior view of a previously unfigured paratype (X 5). Horizon, locality and museum number the same as plate 16, in figures 1-4. 

8. Anabarella plana Vostokova (p. 33).

Left-lateral view of a specimen from the Tommotian (Lower Cambrian) rocks of Siberia (X 12). 

Photograph kindly provided by S. C. Matthews and Robin Goodwin, University of Bristol, Bristol, 

England.
GEOLOGICAL SURVEY PROFESSIONAL PAPER 968 PLATE 17

TOLMACHOVIA AND ANABARELLA
PLATE 18

FIGURES 1 21. Anisotechnophorus nuculitiformis (Cleland), 1900 (p. 60).

1-6. Left-lateral (X 3), right-lateral (X 3), posterior, anterior, ventral, and dorsal (x 5) views 

of lectotype. Cleland (1900, p. 21) gave the horizon and locality as: "Calciferous, Fort Hunter 

Section, New York" (Lower Ordovician). PRI 5080.

7-10. Left-lateral, right-lateral, dorsal, and posterior views (X 5). The museum label gives the 

horizon and locality as: "Ozarkic (Little Falls), Fort Hunter, New York" (Upper Cambrian?). 

YU 2580.

11,12. Dorsal and anterior views (x 5). Horizon, locality, and museum number the same as in figures 7-10 above.

13. Right-lateral view of paralectotype (X 5). Horizon and locality the same as in figures 1 6 above. 

PRI 5079.

14. Posterior view (X 5). Horizon, locality, and museum number the same as in figures 7-10 above.

15. Left-lateral view of paralectotype (X 5). Horizon, locality, and museum number the same as in 

figure 13 above.

16. Dorsal view of paralectotype (x 5). Horizon, locality, and museum number the same as in figure 13 above.

17. Dorsal view (X 5). Horizon, locality, and museum number the same as in figures 7-10 above.

18. Right-lateral view (X 5). USGS loc. 7098-CO. Missisquoia Zone (Lower Ordovician) upper 

Whitehall Formation, Skene Mountain, N.Y. (Taylor and Halley, 1974, p. 33). USNM 209375.

19. Dorsal view of paralectotype (X 5). Horizon, locality, and museum number the same as in figure 

13 above.

20. Dorsal view (X 5). The museum label gives the horizon and locality as: "Little Falls, Fort 

Hunter, N.Y." (Upper Cambrian?). USNM 209376.

21. Posterior view (X 5). Horizon and locality the same as in figure 20 above. USNM 209377. 

22-25. Ischyrinia winchelli Billings, 1866 (p. 62).

22. Right-lateral view (X 2). English Head Formation (Upper Ordovician), 1 mile west of White

Cliff, Anticosti Island, Quebec, Canada. YU 3063/13. 

23,24. Right-lateral and posterior views of lectotype (X 2). The museum label reads: "'English

Head'=Vaureal, Upper Ordovician, Macasty Bay, Anticosti Island," Quebec, Canada. GSC 2114a. 

25. Right-lateral view of paralectotype (X 2). Horizon and locality the same as in figures 23, 24

above. GSC 2114.
GEOLOGICAL SURVEY PROFESSIONAL PAPER 968 PLATE 18

ANISOTECHNOPHOEUS AND ISCHYRINIA
PLATE 19

FIGURES 1-8. Ischyrinia winchelli Billings, 1866 (p. 62).

1-4. Right-lateral, posterior, dorsal, and left-lateral views (X 2). English Head Formation (Upper

Ordovician), east side Little Macasty Bay, Anticosti Island, Quebec, Canada. YU 3063/10. 

5. Right-lateral view (X 2). English Head Formation (Upper Ordovician), cliff 1 mile west of

White Cliff, north shore, Anticosti Island, Quebec, Canada. YU 748.

6-8. Left-lateral, dorsal, and posterior views (X 2). The museum label lists no formation; presumably the specimen is Late Ordovician in age. North side Anticosti Island, Quebec, Canada. YU

3063/30. 

9, 15, 16. Ischyrinia sp. (p. 64) .

9. Left-lateral view (X 3). Whitehead Formation (Upper Ordovician), road at Amphitheater, west

side Mt. St. Anne, Perce, Quebec, Canada. USNM 209372. 

15,16. Two specimens, both right valves ( X 2). The museum label reads: "Quarry at Evan's Saw

Mills, North Gate, Haverfordwest" Wales (Oriovician). SM A. 30893-30894. 

10-14. Ischyrinia norvegica Soot-Ryen, 1960 (p. 64).

10,11. Right-lateral view of holotype and latex replica of same (X 3). Middle Caradocian (Middle

Ordovician), Furuberget, Hamar, Norway, UO 38267. Replica, USNM 209373.

12. Left-lateral view of previously unfigured paratype (X 3), on same slab as holotype. Horizon, locality, and museum number the same as in figures 10, 11 above,

13. Latex replica of left valve of paratype (X 3). Horizon and locality the same as in figures 10, 

11 above. UO 37861. Replica USNM 209374.

14. Right-lateral view of previously unfigured paratype (X 3). Horizon, locality, and museum number the same as in figure 13 above. 

17. Ischyrinial (p. 64).

Left-lateral view (X 5). The museum label gives the horizon and locality as: "Middle Ordovician, 

boulder on right bank of Moyero River, 6 miles above mouth of Ukdama River, Khatanga-Anabar 

region, northern Siberia." Geological Museum Academy of Science, U.S.S.R. 1849/2027.
GEOLOGICAL SURVEY PROFESSIONAL PAPER 968 PLATE 19

ISCHYRINIA
PLATE 20

FIGURES 1-15. Pseudotechnophorus typicalis Kobayashi, 1933 (p. 65).

1,2. Left-lateral and dorsal views (X 3) of a replica of the specimen figured by Kobayashi

(1933, pi. 9, fig. 8). Wanwankou Dolomite (Lower Ordovician), Wan-wan-kou in the Niuhsintai

Basin, south Manchuria. USNM 209371. 

3-6. Left-lateral, ventral, posterior, and dorsal views (X 3). Horizon and locality the same as in

figure 1, 2 above. YU 28148. 

7-9. Dorsal, right-lateral, and posterior views (X 3). Horizon and locality the same as in figures 1,

2 above. USNM 94039. 

10,11. Left-lateral view (X 4) and latex replica of same (X 3). Horizon and locality the same as

in figures 1, 2 above. MCZ 4426. 

12-15. Right-lateral view (X 3), dorsal view showing protoconoch (X 3), enlargement of anterior

face of protoconch showing larval musculature (x 60), further enlargement of larval musculature 

(X 100). Horizon and locality the same as in figure 1, 2 above. MCZ 6907.
GEOLOGICAL SURVEY PROFESSIONAL PAPER 968 PLATE 20

PSEUDOTECHNOPHOR US
PLATE 21

FIGURES 1,2. Pseudoeuchasma typica Kobayashi, 1933 (p. 77).

Posterior and right-lateral views (X 4) of replicas of holotype (Kobayashi, 1933, pi. 9, figs. lOa, 

b). Wanwankou Dolomite, Wan-wan-kou in the Niuhsintai Basin, south Manchuria (Lower Ordovician). USNM 94011. 

3. Wanwanoidea trigonalis delicata Kobayashi, 1933 (p. 69).

Right-lateral view (X 4) of replica of holotype (Kobayashi, 1933, pi. 8, fig. 6). Horizon and locality

the same as in figures 1, 2 above. USNM 209366. 

4-6. Wanwanoidea trigonalis Kobayashi, 1933 (p. 69).

Right-lateral, dorsal, and left-lateral views (X 4) of replica of syntype (Kobayashi, 1933, pi. 9, fig.

3). Horizon and locality the same as in figure \, 2 above. USNM 209367. 

7,8. Wanwanella tumida Kobayashi, 1933 (p. 68).

Right-lateral and left-lateral views (X 8) of replica of holotype (Kobayashi, 1933, pi. 7, fig. 10).

Horizon and locality the same as in figures 1, 2 above. USNM 209368. 

9-16. Wanwanella striata Kobayashi, 1933 (p. 68).

9. Replica of syntype (Kobayashi, 1933, pi. 7, fig. 7) (X 5). Horizon and locality the same as in

figures 1, 2 above. USNM 209369. 

10-12. Left-lateral, right-lateral, and dorsal view (X 5). Horizon and locality the same as in figures

1, 2 above. MCZ 4425. 

13-16. Left-lateral, right-lateral, anterior, and dorsal views (X 5). Horizon and locality the same as

in figures 1, 2 above. YU 28149. 

17-20. Wanwanella striata auriculata Kobayashi, 1933 (p. 68).

Dorsal, left-lateral, right-lateral, and anterior views (X 5) of replica of holotype (Kobayashi, 1933,

pi. 7, fig. 6) Horiozn. and locality the same as in figures 1, 2 above. USNM 209370. 

21. Wanwanellal alia (Kobayashi), 1933 (p. 68).

Replica of holotype (X 4). Horizon and locality the same as in figures 1, 2 above. USNM 94045.
GEOLOGICAL SURVEY PROFESSIONAL PAPER 968 PLATE 21

PSEUHOEUCHASMA, WANWANOIDEA, AND WANWANELLA
PLATE 22

FIGURES 1-15. Eopteria ventricosa (Whitfield), 1886 (p. 66).

1. Right-lateral view of internal mold showing muscle impressions (X 3). 2, Same specimen, same 

view and magnification, muscle scars outlined in ink. Fort Cassin Limestone (Lower Ordovician), 

Fort Cassin, Vt. USNM 209357.

3. Right-lateral view of internal mold showing muscle scars (X 3). 4, Same specimen^ same view and 

magnification, muscle scars outlined in ink. Horizon and locality the same as in figures 1, 2 above. 

USNM 209358.

5. Right-lateral view of internal mold showing muscle scars (X 3). 6, Same specimen, same view 

and magnification, muscle scars outlined in ink. Horizon and locality the same as in figures 1, 2 

above. USNM 209359.

7. Left-lateral view of internal mold showing three small muscle markings (X 3). These may be 

separate muscles or simply the muscle tracts left by the dorsal part of the pallial sinus, as suggested by the specimen shown in figures 3, 4 above. 8, Same specimen, same view and magnification, the muscle markings outlined in ink. Horizon and locality the same as in figures 1, 2 above. 

USNM 209360.

9. Left-lateral view of a shelled specimen (X 3). Horizon and locality the same as in figures 1, 2 

above. USNM 209361.

10. Left-lateral view showing marginal denticles (X 5). Horizon and locality the same as in figures 

1, 2 above. USNM 209362.

11. Dorsal view of lectotype showing internal mold of protoconch (x 3). Horizon and locality the 

same as in figures 1, 2 above. AM 492.

12. Left-lateral view (X 3). Horizon and locality the same as in figures 1, 2 above. USNM 209363.

13. Left-lateral view showing anterior pallial sinus (x 3). Horizon and locality the same as in figures 1, 2 above. USNM 209364.

14. Left-lateral view of paralectotype (x 3). Horizon and locality the same as in figures 1, 2 above. 

AM 492.

15. Left valve showing marginal denticles (X 3). Horizon and locality the same as in figures 1, 2 

above. USNM 209365.
GEOLOGICAL SURVEY PROFESSIONAL PAPER 968 PLATE 22

EOPTERIA
PLATE 23

FIGURES 1-10. Eopteria ventricosa (Whitfield) , 1886 (p. 66).

1. Dorsal view showing internal mold of protoconch (X 3). 2, Right-lateral view of internal mold, 

with muscle scars outlined in ink (X 3). 3, Same specimen, same view showing muscle scars (X 

5). Horizon and locality the same as on plate 22, figures 1, 2. USNM 209349.

4. Left valve showing1 anterior marginal denticles (X 3). Horizon and locality the same as on plate 

22, figures 1, 2. USNM 209350.

5. Right valve internal mold showing marginal denticles and protoconch (X 3). Horizon and locality the same as on plate 22, figures 1, 2. USNM 209351.

6. Dorsal view showing internal mold of protoconch (X 3). Horizon and locality the same as on 

plate 22, figures 1, 2. USNM 209352.

7. Right-lateral view (X 3). Horizon and locality the same as on plate 22, figures 1, 2. USNM 

209353.

8. Right-lateral view (X 3). Horizon and locality the same as on plate 22, figures 1, 2. USNM 

2K)9354.

9. Right lateral view (X 3). Horizon and locality the same as on plate 22, figures 1, 2. USNM

209355.

10. Right-lateral view (X 3). Horizon and locality the same as on plate 22, figures 1, 2. USNM

209356.
GEOLOGICAL SURVEY PROFESSIONAL PAPER 968 PLATE 23

EOPTERIA
PLATE 24

FIGURES 1,2. Eopteria flora Kobayashi, 1933 (p. 66).

Dorsal and right-lateral views (X 3) of replicas of the holotype. Wanwankou Dolomite (Lower

Ordovician), Wan-wan-kou in the Niuhsintai Basin, south Manchuria, USNM 94042. 

3,4. Eopteria obsolata Kobayashi, 1933 (p. 66).

Dorsal and right (?)-lateral views of replicas of the holotype (X 3). Horizon and locality the same

as in figures 1, 2 above. USNM 94041. 

5,6,11-20. Eopteria richardsoni Billings, 1865 (p. 66).

5,6. Dorsal and left-lateral views of holotype (x 3). The museum label lists the horizon and locality as: "Beekmantown, St. Antoine de Tilly, Quebec," Canada (Lower Ordovician). GSC 756. 

11-15. Left-lateral, right-lateral, dorsal, anterior, and ventral views (X 5). Smithville Formation

(Lower Ordovician), 1.5 miles north of Smithville, Ark. USNM 162781. 

16-20. Ventral, dorsal, right-lateral, left-lateral, and anterior views (X 5). Horizon and locality the

same as in figures 11-15 above. USNM 162782. 

7-10. Eopteria cf. E. richardsoni Billings, 1865 (p. 66).

7. Left-lateral view (X 3). USGS loc. D-1973-CO, Antelope Valley Limestone, from bioherm 60- 

65 feet above base of bioherm, Meiklejohn Peak section, Nevada (Whiterockian, Lower Ordovician?). R. J. Ross collector. USNM 209347.

8. Left-lateral view (X 3). U.S.G.S. loc. D-1990-CO, Antelope Valley Limestone, from about 45 feet 

above base of bioherm, Meiklejohn Peak section, Nevada (Whiterockian, Lower Ordovician?). R. J. 

Ross collector. USNM 167236.

9. Left-lateral view (X 3). Horizon and locality the same as in figure 7 above. USNM 209348.

10. Left-lateral view (X 3). USGS loc. D-1966-CO, Antelope Valley Limestone, 50 feet above base 

of bioherm, Meiklejohn Peak section, Nevada (Whiterockian, Lower Ordovician?). R. J. Ross collector. USNM 162780.
PROFESSIONAL PAPER 968 PLATE 24

EOPTERIA
PLATE 25

FIGURES 1. Eopteria sp. (p. 66).

Right-lateral view (X 1). Cotter Dolomite or Powell Formation (Lower Ordovician), Graceland

mines, 3-5 miles northwest of Smithville, Ark. USNM 209335. 

2-19. Eopteria richardsoni Billings, 1865 (p. 66).

2-4. Right-lateral, dorsal, and left-lateral views (X 3). Honeycut Formation (Lower Ordovician), 

Ceratopea capuliformis Zone, about 2.5 miles airline, N. 1° W. from headquarters J. F. Barnes 

ranch, northwest of Ellenburger Hills, southeastern San Saba County, Tex. USNM 127900.

5. Left-lateral view (x 5). Horizon and locality the same as on plate 24, figures 11-15. USNM 

209336.

6. Right-lateral view showing anterior marginal denticles (X 3). The museum label gives the horizon and locality as: "Jefferson City chert (residual), Lower Ordovic, 50 yds. N of U.S. Highway 

No. 60, 114 mi. east of Birch Tree, Mo." AM 29322.

7. Anterior view showing gape and marginal denticles (X 4). Canadian (Lower Ordovician), 3 

miles south of Bolivar, Mo. (Jefferson City Dolomite?). USNM 209337.

8-10. Anterior, right-lateral ,and posterior views of an internal mold (X 4). Horizon and locality the 

same as in figure 7 above. USNM 209338.

11. Dorsal view showing protoconch (x 3). Smithville Formation (Lower Ordovician), 1.5 miles 

northeast of Smithville, Ark., on road to Imboden. USNM 209339.

12. Right-lateral view (X 3). Canadian (Lower Ordovician), at old sinkhole in railroad cut, Lutesville, Mo. USNM 209340.

13. Left-lateral view (X 4). Scenic Drive Formation of Flower (1964), Franklin Mts., Scenic 

Drive, El Paso, Tex. R. H. Flower collector. USNM 209341.

14. Anterior view showing gape (x 3). Horizon and locality the same as in figure 11 above. USNM 

209342.

15. Latex replica of external mold (X 4). Cotter Dolomite (Lower Ordovician), on road between 

Swan and Elkhorn Creeks, short distance above confluence, near Chadwick, Mo., USNM 209343.

16,17. Right-lateral and dorsal views (X 4). Canadian (Lower Ordovician), hill just west of Turkey Creek on road from Humansville to Sacrille, Mo., 19 miles west of Humansville. USNM

209344.

18. Right-lateral view (x 4). Horizon, locality, and collector the same as in figure 13 above. USNM

209345.

19. Anterior view (x 4). Horizon and locality the same as in figures 16, 17 above. USNM 209346.
GEOLOGICAL SURVEY PROFESSIONAL PAPER 968 PLATE 25

EOPTERIA
PLATE 26

FIGURES 1-11. Eopteria richardsoni Billings, 1865 (p. 66).

1-4. Right-lateral, left-lateral, ventral, and anterior views (x 3). Canadian (Lower Ordovician), 

west side of Honey Creek, Llano County, Tex. USNM 209325.

5. Dorsal view (X 3). Canadian (Lower Ordovician), 1.5 miles east Buffalo, Mo. USNM 209326.

6. Anterior view (X 3). Horizon and locality the same as on plate 25, figure 15. USNM 209327.

7. Dorsal view (X 3). Horizon and locality the same as on plate 25, figure 15. USNM 209328.

8. Anterior view (X 3). Horizon and locality the same as on plate 25, figure 15. USNM 209329.

9. Left-lateral view (X 4). Horizon, locality, and collector the same as in plate 25, figure 13. USNM 

209330.

10,11. Internal and external views showing denticles and ornament (X 4). Smithville Formation

(Lower Ordovician), Iowa mine, 2 miles north of Smithville, Ark. USNM 209331. 

12-18. Eopteria conocardiformis n. sp. (p. 66).

12-15. Anterior, dorsal, right-lateral and left-lateral views of holotype (X 5). Little Oak Limestone 

(Middle Ordovician), quarry about 2 miles north of Pelham, Ala. USNM 209332.

16. Right-lateral view of paratype (X 3). High Bridge Group (Middle Ordovician), High Bridge, 

Ky. USNM 209333.

17,18. Posterior and right-lateral views (x 6). Little Oak Limestone (Middle Ordovician), intersection of Bailey Gap Road with main road, 1.75 miles northeast of New Hope Church, Ala. USNM 

209334.
GEOLOGICAL SURVEY PROFESSIONAL PAPER 968 PLATE 26

EOPTERIA
PLATE 27

FIGURES 1-16. Euchasma blumenbachii (Billings), 1859 (p. 67).

1-4. Right-lateral, left-lateral, dorsal, and posterior views (X 2) of lectotype. The museum label 

gives the horizon and locality as: "Beekmantown (Romaine), Mingan Islands, Quebec," Canada 

(Lower Ordovician). GSC 455.

5,6. Right-lateral and anterior views of Butts' hypotype (1941). The museum label lists the horizon and locality as: "Beekmantown, Brushy Hills, west of Lexington, Virginia" (Lower Ordovician). USNM 97333.

7,8. Left-lateral and anterior views of paralectotype (X 2). Horizon and locality the same as in 

figures 1-4 above. GSC 455a.

9. Anterior view showing the pallial line with an anterior pallial sinus (X 1.5). Graveyard, hillside immediately northeast of lower cove, south side St. George Peninsula, Newfoundland. St. 

George Group (Lower Ordovician). R. H. Flowsr collector. GSC 41173.

10-13. Right-lateral, left-lateral, anterior, and dorsal views (X 2). Middle of Scenic Drive Formation of Flower (1964), nameless canyon west of Ranger Peak, Franklin Mts., northwest edge of 

El Paso, Tex. (Lower Ordovician). Collected by R. H. Flower. USNM 209321.

14. Anterior view (X 2). Upper Canadian (Lower Ordovician), Brushy Hills Chert, near Lexington, Va. USNM 209322.

15. Left-lateral view (X 2). Horizon and locality the same as in figure 14 above. USNM 209323.

16. Anterior view (X 3). Luke Hill Limestone (Lower Ordovician), ridge east of Phillipsburg, 

Quebec, Canada. USNM 209324.
GEOLOGICAL SUR PROFESSIONAL PAPER 968 PLATE 27

EUCHASMA
PLATE 28

FIGURES 1-3. Euchasma'! sp. (p. 68).

Right-lateral, dorsal, and anterior views of latex replica (X 2). H01onda Limestone (Whiterockian, Lower Ordovician), Trotland Farm, Trondheim, Norway (Neuman and Bruton, 1974). UO 

89105. Replica USNM 209418. 

4-7. Euchasma wanwanense (Kobayashi), 1933 (p. 68).

Right-lateral, left-lateral, anterior, and dorsal views of replica of holotype (X 3). Wanwankou Dolomite, Wan-wan-kou in the Niuhsintai Basin, South Manchuria (Lower Ordovician). USNM 209316. 

8-11. Euchasma shorinense (Kobayashi), 1933 (p. 67).

Dorsal, right-lateral, left-lateral, and anterior views of replica of holotype (X 3). Shorin Bed of 

Shorinri, near Kenjiho Koshu-gun, Kokai-do in northern Korea (Lower Ordovician). USNM 

209317. 

12!-18. Euchasma jonesi n. sp (p. 67).

12-15. Posterior, dorsal, right-lateral, and anterior views of holotype (x 2). Lower shelly fades 

of the Setul Formation, off south point of Pulau Langgun, Langkawi Islands, Malaysia (Lower 

Ordovician). USNM 162790.

16. Anterodorsal part of a broken shell showing the circular part of the anterior gape (paratype, 

X 2.5). Horizon and locality the same as in figures 12-15 above. USNM 209318.

17. Anterior part of the dorsal side showing clefts on either side of the projecting circular part of 

the anterior gape (paratype, X 2.5). Horizon and locality the same as in figures 12-15 above. 

USNM 209319.

18. Interior view of left valve showing marginal denticles (paratype, X 3). Horizon and locality the 

same as in figures 12-15 above. USNM 209320.
GEOLOGICAL SURVEY PROFESSIONAL PAPER 968 PLATE

EUCHASMA
PLATE 29

FIGURES 1-5. Euchasma jonesi n. sp. (p. 67).

I,2. Right-lateral and dorsal views (paratype, X 3). Lower part of the Setul Formation (Lower 

Ordovician), from a small inlet, Pulau Anak Tikas, on the south tip of Pulau Langgun, in the 

Langkawi Islands, western Malaysia. Collected by T. E. Yancey. USNM 209309.

3. View looking from posterior to anterior (posterior part of shell broken off) showing the umbonal cavities on either side of the pegma (paratype, X 3). Horizon and locality the same as on 

plate 28, figures 12-15. USNM 209310.

4. Enlargement of plate 28, figure 18 (X 5).

5. Posteroventral part of shell showing a color line which probably represents the insertion of the 

pallial line (paratype, X 3). Horizon and locality the same as on plate 28, figures 12-15. USNM 

209311. 

6-15. Euchasma mytiliforme n. sp. (p. 67).

6-10. Right-lateral, left-lateral, anterior, ventral, and dorsal views of holotype (X 2). East side 

Pulau Langgun, Langkawi Islands, Malaysia (Lower Ordovician). USNM 209312.

II,12. Paratype. 11, View looking posterior to anterior inside of shell (posterior part of shell broken 

off) showing the anterior gape and the pegma (X 2.5). 12, Same specimen anterior view showing the gape (X 2.5). Horizon and locality the same as in figures 6-10 above. USNM 209313.

13. Interior view of right valve of paratype showing marginal denticles (X 2). Lower part of Setul 

Formation (Lower Ordovician), north shore of main island, Palau Langkawi, Langkawi Islands, 

western Malaysia. Collected by T. E. Yancey. USNM 209314.

14,15. Paratype. 14, Oblique anterior view of broken specimen showing the pegma (X 2.5). 15, 

Same specimen looking posterior to anterior (posterior part of shell broken off), showing the pegma 

and its points of attachment to the shell. Horizon and locality the same as in figures 6-10 

above. USNM 209315.
GEOLOGICAL SURVEY PROFESSIONAL PAPER 968 PLATE 29

EUCHASMA
PLATE 30

FIGURES 1. Schematic diagram of Ribeiria apusoides Schubert and Waagen, (p. 50), to show position of the sections illustrated in this plate, figures 2-5, and plate 31, figures 1-5. Solid black shows thickness of 

shell in midsaggital plane; stippled areas are muscle insertions of the left valve. 

|2,3. Section A in figure 1 (USNM 209308). 2, X 10; 3, X 30. Sections of anterior part of pegma showing

fractured layers underlain by younger unfractured inner shell layers.

4. Section B of figure 1 (USNM 209308). X 10. Showing growth layers continuous across anterior dorsal margin of shell.

5'. Section C of figure 1 (USNM 209308). X 30. Growing edge of shell (inner /surface to left) ; growth 

lamellae reflected outwards to produce fine comarginal growth lines.
GEOLOGICAL SURVEY PROFESSIONAL PAPER 968 PLATE 30

RIBEIR1A
PLATE 31

FIGURES 1. Section D of plate 30, figure 1. (MCZ 7005/4). X 30. Section of pegma showing upper fractured 

layer underlain by younger unfractured layers.

2. Section E of plate 30, figure 1 (MCZ 18029). X 10. Section of posterior dorsal margin of shell.

3. Section F of plate 30, figure 1 (TJSNM 209308). X 10. Section across curved growing edge of pegma 

showing growth lines intersecting upper face of pegma and discontinuity on each side denning position of myostracal layer.

4. Section G of plate 30, figure 1 (MCZ 18030). X 30. Section of shell across linear muscle insertion 

on left valve (muscles are attached above the bulge).

5. Section H of plate 30, figure 1 (MCZ 18031). X 30. Cross section of hinge just behind the beak.
GEOLOGICAL SURVEY PROFESSIONAL PAPER 968 PLATE 31

RIBEIRIA
PLATE 32

FIGURES 1,2. Pseudoconocardiwn lanterna (Branson), 1965 (p. 74).

1, Transverse section of anterior part of hinge showing inverted foldlike structure formed of inner 

shell layers (X 30). 2, Tranverse section of anterior part of hinge showing progressive deformation of inner shell layers from youngest to oldest (X 10). USNM 176950.

3. Hippocardia bohemica (Barrande), 1881 (p. 75).

Vesicular shell structure near anterior gape (X 10). Oklahoma Geol. Survey A-17.

4. Bransonia wilsoni n. sp. (p. 72).

Section of edge of shell showing outer prismatic layer above and recrystallized, probably originally

nacreous, inner layer below. Growth lines extend across both layers (X 30). UNE F12636. 

5,6. Hippocardia cunea (Conrad), 1840 (p. 75).

5, Section of hood showing cross section of tubular extension of ventral aperture and prismatic 

structure of the hood in this area (X 10). 6, Section of one side of the hood cut perpendicular to 

the plane of symmetry of the shell; prismatic structure is confined to the inner part (up) of the 

hood. Outer part (down) consists of curved lamellae originally separated by open spaces (X 30). 

USNM 86915.
GEOLOGICAL SURVEY PROFESSIONAL PAPER 968 PLATE 32

PSEUDOCONOCARDIUM, HIPPOCARDIA, AND BRANSONIA
PLATE 33

FIGURES 1,2. Hippocardia cunea (Conrad), 1840 (p. 75).

Latex replica of original. Arrows point to places where the encrusting auloporoid coral colony 

has broken by subsequent growth of the rostroconch hood; 1 (X 2), 2 (X 6). FM 12502 (Walker 

Mus. coll.). Replica USNM 209307.
GEOLOGICAL SURVEY PROFESSIONAL PAPER 968 PLATE 33

 ^'^:,^-^m^ms^^*^ . » -A .i. ; -- w >: '.-^i*»-/f-i^v^^^ " i-v: 

ife^i *ftrk»3

5» L iiW^^ficI-V'* *;'" Y'"*$ **?"«'» ;'*<<!y 

'"" '. J^^^fe^^^

HIPPOCARDIA
PLATE 34

FIGURES 1-16. Mulceodens jaanussoni n. sp. (p. 73).

1,2. Anterior (X 7) and right-lateral (X 9) views of paratype. Silurian (Ludlovian, Eke, Marl), 

Gotland, Ronehamn, Sweden. SMNH Mo. 18563.

3. Interior of left valve of paratype showing marginal denticles (X 5). Silurian (Wenlockian, 

Mulde Marl), Gotland, Parish of Eksta, Djupvik, Sweden. SMNH Mo. 18302.

4. Interior of left valve of paratype showing marginal denticles (X 5). Horizon and locality the 

same as in figure 3 above. SMNH Mo. 18303.

5. Interior of right valve of paratype showing marginal denticles (X 5). Horizon and locality the 

same as in figure 3 above. SMNH Mo. 18304.

6. Dorsal view of paratype showing protoconch and rostral clefts (X 7). Silurian (Wenlockian, 

Slite Beds), Gotland, Parish of Othem, Samsugn, Sweden. SMNH Mo. 18336.

7. Dorsal view of paratype showing protoconch and rostral clefts (X 8). Horizon and locality the 

same as in figure 6 above. SMNH Mo. 18337.

8. Dorsal view of paratype showing protoconch and marginal denticles (X 8). Horizon and locality 

the same as in figure 6 above. SMNH Mo. 18338.

9. Anterior view of paratype showing marginal denticles (X 7). Silurian, Gotland, Sweden, SMNH 

Mo. 18464.

10. Anterior view of paratype showing marginal denticles (X 7). Horizon and locality the same as 

in figure 3 above. SMNH Mo. 18560.

11. Anterior view of paratype showing marginal denticles (X 7). Silurian (Ludlovian, Hamra 

Beds), Gotland, Parish of Oja, Storviks Kanal, Sweden. SMNH Mo. 18322.

12,13. Left>lateral and anterior views (X 7). Silurian (Ludlovian, Hamra Beds), Gotland, Parish 

of Grotiingbo Uddvide, Sweden. SMNH Mo. 18546.

14. Anterior view of paratype (X 7). Horizon and locality the same as in figures 12-13 above. 

SMNH Mo. 18547.

15,16. Dorsal and right-lateral views of paratype (X 7). Horizon and locality the same as in figure 3 above. SMNH Mo. 151244.
GEOLOGICAL SURVEY PROFESSIONAL PAPER 968 PLATE 34

MULCEODENS
PLATE 35

FIGURES 1-3,11,12. Mulceodens jaanussoni n. sp. (p. 73).

Left-lateral, dorsal, right-lateral, anteroventral, and posterior views of holotype (X 7). Horizon

and locality the same as on plate 34, figure 3. SMNH Mo. 151245. 

4-7. Mulceodens eboraceus (Hall), 1860 (p. 74).

Right-lateral, left-lateral, dorsal, and anterior views of lectotype (X 3). Hamilton Group (Middle

Devonian), York, Livingston County, N.Y. AM5347/1. 

8-10. Mulceodens bifarius (Winchell), 1866 (p. 73).

Dorsal, anterior, and right-lateral views (X 3). Traverse Group, upper Alpena Limestone, 4 Mile

dam, Alpena County, Midi. (Middle Devonian). USNM 209306. 

13-17. Bigalea visbyensis n. sp. (p. 77).

13-15. Left-lateral, ventral, and right lateral views of paratype (X 6). Silurian (Wenlockian,

formation unknown), Visby, Gotland, Sweden. SMNH Mo. 18554.

16, 17. Right-lateral and ventral views of holotype (X 7). Horizon and locality the same as in figure 13-15 above. SMNH Mo. 18552.
GEOLOGICAL SURVEY PROFESSIONAL PAPER 968 PLATE 35

MULCEODENS AND BIGALEA
PLATE 36

FIGURES 1-4. Bigalea visbyensis n. sp. (p. 77).

1,2. Left-lateral and dorsal views of holotype (X 7). Horizon and locality the same as on plate

35, figures 13-15. SMNH Mo. 18552. 

3, 4. Left-lateral and dorsal views of paratype (X 7). Horizon and locality the same as on plate

35, figures 13-15. SMNH Mo. 18553. 

5-12. Bigalea ohioensis n. sp. (p. 77).

5-7. Oblique posterior (x 4), right-lateral, and ventroposterior views (X 6) of holotype. Horizon

and locality uncertain, probably from Devonian rocks exposed at the Falls of the Ohio River.

USNM 209302. 

8, 9. Left-lateral and dorsal views of paratype ( X 6) . Horizon and locality the same as in figures 5-

7 above. USNM 209303. 

10,11. Right-lateral and posterior views of paratype (x 6). Horizon and locality the same as in

figures 5-7 above. USNM 209304.

12. Highly oblique posteroventral view of paratype (X 6). Horizon and locality the same as in figures 5-7 above. USNM 209305. 

13-16. Bigalea yangi n. sp. (p. 76).

Oblique posterior view from left side, ventral, left-lateral, and anterior views of paratype (X 3.5).

Traverse Group (Middle Devonian), Kegomic, Little Traverse Bay, Mich. FM 18331.
GEOLOGICAL SURVEY PROFESSIONAL PAPER 968 PLATE 36

BIGALEA
PLATE 37

FIGURES 1-4. Bigalea yangi n. sp. (p. 76).

1-3. Dorsal, posterior, and left-lateral views of holotype (X 3.5). "Petoskey Limestone" in the 

Traverse Group (Middle Devonian) quarry at Mud Lake, about 1.5 miles northeast of Bay View, 

Emmet County, Mich. USNM 209301.

4. Posterior view of paratype (X 6). Traverse Group (Middle Devonian), Kegomic, Little Traverse Bay, Mich. FM 18332. 

5-15. Bigalea clathra (d'Orbigny), 1850 (p. 76).

5-9. Left-lateral (X 3.5), dorsal (X 3), ventral (X 3), posterior (X 3.5), and anterior (X 3.5) 

views. Devonian, Pelm, Germany?. MCZ 15395.

10-12. Left-lateral, dorsal, and right-lateral views. (X 3.5). Devonian, Prum, Germany?. MCZ 

15608.

13,14. Ventral and right-lateral views (X 3). Devonian?, Eifel, Germany. UM 1788.

15. Right-lateral view (X 3.5). Horizon, locality, and museum number the same as in figures 10-12

above. 

16,17. Conocardium aff. C. elongatum (Sowerby), 1815 (p. 69).

Left-lateral and dorsal views (X 2.5). Pennsylvanian, St. Joseph, Mo. USNM 100704.
PROFESSIONAL PAPER 968 PLATE 37

BIGALEA AND CONOCARDIUM
PLATE 38

FIGURES 1-7. Conocardium aff. C. elongatum (Sowerby), 1815 (p. 69).

1-3. Ventral, right-lateral, and posterior views (X 2.5). Horizon, locality, and museum number 

the same as on plate 37, figures 16, 17.

4-7. Anterior, dorsal, ventral, and left-lateral views (X 2.5). Carterville Formation (Upper Mississippian), mine dump near Duenweg, Mo. USNM 209298. 

8 24. Conocardium elongatum (Sowerby), 1815 (p. 69).

8. Left-lateral view of Hind (1900, pi. 51, fig. 8) hypotype (X 2). Carboniferous (Mississdppian) 

Limestone of Settle, England. SM E.549.

9-14. Right-lateral, left-lateral, ventral, dorsal, anterior, and posterioir views of holotype (x 2). 

Carboniferous (Mississippian), Derbyshire, England. Photographs courtesy British Museum (Natural History). BM PL 794.

15-20. Topotype. 15-18, Ventral, dorsal, left-lateral, and posterior views (X 2). 19, 20, Same figure of polished anterior end showing a longitudinal shelf on the right side (arrow fig. 20) (x 5). 

Carboniferous Limestone (Mississippian), Derbyshire, England. BM L 13496.

21. Right-lateral view internal mold showing some muscle scars (X 3). Four Laws Limestone (Visean, Mississippian), Redesdale, Northumberland, England. BM PL 4431.

22-24. Right-lateral, dorsal, and oblique left-lateral views -showing some muscle scars (X 4). Horizon and locality the same as on figure 21 above. BM PL 4432. 

25,26. Conocardium pseudobellum n. sp. (p. 70).

25. Posterior view of holotype (X 2.5). Traverse Group, upper Alpena Limestone (Middle Devonian), Four Mile dam, Alpena County, Mich. USNM 209299.

26. Polished section of dorsal surface of paratype showing longitudinal shelf on right side (X 3). 

Horizon and locality the same as in figure 25 above. USNM 209300.
GEOLOGICAL SURVEY PROFESSIONAL PAPER 968 PLATE 38

CONOCARDIUM
PLATE 39

FIGURES 1-3. Conocardium pseudobellum n. sp. (p. 70).

1,2. Dorsal and left-lateral views of holotype (X 2.5). Rostrum rebuilt in plaster. Horizon, locality, and museum number the same as on plate 38, figure 25.

3. Left-lateral view of paratype showing elongate rostrum (X 2.5). Four Mile Dam Formation 

(Middle Devonian), Four Mile Dam on Thunder Bay River, 2 miles upstream from Alpena, Mich. 

UM 47287. 

4-7. Conocardium normale Hall, 1883 (p. 70).

Lectotype. Right-lateral, left-lateral, and dorsal views and latex replica of posterior end showing unusually thick longitudinal shelves (X 1.5). Hamilton Group (Middle Devonian), Cumberland, 

Md. AM 5349/1. 

8-10. Conocardium aliforme (Sowerby), 1815 (p. 70).

Posterior, left-lateral, and dorsal views (X 2) of Hind (1900, pi. 54, fig. 8) hypotype. Carboniferous Limestone (Mississippian) of Settle, England. SM E 561. 

11-13. Conocardium attenuatum (Conrad), 1842 (p. 70).

Dorsal, right-lateral, and ventral views (X 2) of a Hall hypotype. Schoharie Formation (Lower 

Devonian), Schoharie, N.Y. NYSM 2321.
GEOLOGICAL SURVEY PROFESSIONAL PAPER 968 PLATE 39

CONOCARDIUM
PLATE 40

FIGURES 1,2. Conocardium attenuatum (Conrad), 1842 (p. 70).

1. Polished section of anterior end showing longitudinal shelves (arrow) (X 2.5). Schoharie Formation (Lower Devonian), 1.75 miles north-northwest of Clarksville, N.Y. USNM 100705.

2. Right-lateral view (X 2) of Hall hypotype (1885, pi. 67, fig. 9). Schoharie Formation, Schoharie,

N.Y. (Lower Devonian). AM 2850/3. 

3-14. Pseudoconocardium lanterna (Branson), 1965 (p. 74).

3-8. Right-lateral, ventral, dorsal, anterior, posterior, and left-lateral views (X 2). Cisco Group 

(Pennsylvanian), Graham, Young County, Tex. USNM 209293.

9. Right-lateral view (X 2). Brad Formation, "Hog Creek Shale Member" of Caddo Creek Formation (Pennsylvanian), 6 miles west of Chico, 1.5 miles north of highway, Wire County, Tex. USNM 

209294.

10. Right-lateral view (X 4). Horizon and locality unknown. UOK 800.

11,12. Anterior and right-lateral views (X 2). Pennsylvanian, Martin's Lake, 3 miles southwest 

of Bridgeport, Tex. USNM 209295.

13. Dorsal view (X 2.5). Horizon and locality unknown. USNM 209296.

14. Right-lateral view (X 2). Brownwood Shale Member of the Graford Formation (Pennsylvanian), 

Signal Peak, Tex. USNM 209297.
GEOLOGICAL SURVEY PROFESSIONAL PAPER 968 PLATE 40

CONOCARDIUM AND PSEUDOCONOCARDIUM
PLATE 41

FIGURES 1-5. Pseudoconocardium lanterna (Branson), 1965 (p. 74).

SEM photographs of protoconch. 1, Posteroright-lateral view (X 26) ; protoconch is the bump at the 

junction of the linear ridges and the umbonal ridges. 2, Posterodorsal view (X 26); protoconch 

is the raised area between the umbonal ridges. 3, Left-lateral view of specimen (x 4). 4, Oblique 

posterior view (X 60); protoconch is the raised area dorsal to the projecting rostrum. 5, Dorsal 

view (X 28); protoconch is the dark area in the posterocentral part of the shell. Gaptank Formation (Pennsylvanian), 2 miles S. 17° E. of Gaptank, 23.5 miles northeast of Marathon, Tex. 

USNM 209292.
GEOLOGICAL SURVEY PROFESSIONAL PAPER 968 PLATE 41

PSEUDOCONOCARDIUM
PLATE 42

FIGURES 1-7,12-14. Pseudoconocardium lanterna (Branson), 1965 (p. 74).

1,2. Posterior and ventral views (X 2). Graford Formation (Pennsylvanian), Martin's Lake, 1.35

miles south of Bridgeport, Wise County, Tex. USNM 209287.

3,4. Right-lateral and dorsal views of an internal mold (X 2). Graham Formation (Pennsylvanian), 0.5 miles west of S. Bend, Young County, Tex. AM 28992.

5. Posteiroventral view (X 2). Palo Pinto Limestone (Pennsylvanian), west side Martin's Lake, 2 

miles south of Bridgeport, Wise County, Tex. UOK 798.

6. Right-lateral view (X 4). Graford Formation (Pennsylvanian), west side of Martin's Lake, 2 

miles south of Bridgeport, Wise County, Tex. USNM 209288.

7. Right-lateral view (X 7). Horizon and locality the same as on plate 41, figures 1-5. USNM 

209289.

12-14. Right-lateral, dorsal, and left-lateral views (X 2) of an internal mold that preserves remnants of muscle scars. Union Valley Formation (Pennsylvanian), 3 miles southeast of Ahloso, Okla. 

NE%, sec. 29, T. 3 N., R. 7 E. UOK 794. 

8-10. Arceodomus glabrata (Easton), 1962 (p. 71).

Left-lateral, right-lateral, and dorsal views (X 2.5). Diamond Peak Formation (Mississippian), 

SW%, SE%, NE%, Sec. 28, T. 19 N., R. 58 E. (USGS loc. 23837-PC), White Pine County, Nev. 

USNM 209290. 

11. Arceodomus aff. A. glabrata (Easton), 1962 (p. 71).

Ventral view (x 2). Pennsylvanian. Little Kickapoo Creek, 0.7 miles southeast of Kickapoo Falls^ 

Hood County, Tex. USNM 209291.
GEOLOGICAL SURVEY PROFESSIONAL PAPER 968 PLATE 42

PSEUDOCONOCARDIUM AND ARCEODOMUS
PLATE 43

FIGURES 1-3,7-12. Arceodomus glabrata (Easton), 1962 (p. 71).

1-3. Right-lateral, dorsal, and anterior views of holotype (X 3). The anterior view shows the longitudinal shelves,. Heath Formation (Mississippian), Stonehouse Canyon, Golden Valley County, 

Mont. USNM 118858. 

7-12. Right-lateral, left-lateral, ventral, dorsal, posterior, and anterior views (X 2.5). Horizon and

locality the same as on plate 42, figures 8-10. USNM 209286. 

4-6. Arceodomm sp. (p. 71).

Posterior, right-lateral, and dorsal views (X 2). Permian (Sakmarian) of the U.S.S.R. BM L

15570. 

13 15. Arceodomus langenheimi (Wilson), 1970 (p. 71).

Anterior (X 3), ventral, and left-lateral views ( X 1.5) of holotype. Figure 13 courtesy of E. C. Wilson. McCloud Limestone (Permian), Bollibokka Mountain, Shasta County, Calif. UCB 10589.
GEOLOGICAL SURVEY PROFESSIONAL PAPER 968 PLATE 43

ARCEODOMUS
PLATE 44

FIGURES 1-4. Arceodomus aff. A. glabrata (Easton), 1962 (p. 71).

1,2. External and internal views of right valve showing ornament and longitudinal shelves (X 

2). "Dickerson Shale" (Pennsylvanian), just under Kickapoo Falls Limestone, 45 miles east northeast of Lipan, Hood County, Tex. USNM 209284.

3,4. Right-lateral and anterior views (X 2.5). "Dickerson Shale" (Pennsylvanian), southeast of

Kickapoo Falls in creek, Hood County, Tex. USNM 209285. 

5-14. Hippocardia bella (Cooper and Cloud), 1938 (p. 75).

5. Right-lateral view of paratype (X 2). Devonian, first hollow south of Kritsville, Calhoun County, 

111. USNM 95192b.

6,7. Right-lateral and posterior views of paratype (X 4). Horizon and locality the same as in figure 5 above. USNM 95192d.

8-10. Right-lateral, posterior, and dorsal views of paratype (X 2.5). Horizon and locality the same 

as in figure 5 above. USNM 95192c.

11-14. Right-lateral, posterior, ventral, and dorsal views of holotype (X 2.5). Horizon and locality

the same as in figure 5 above. USNM 95192a. 

15,16. Hippocardia monroica (Grabau), 1910 (p. 76).

15. Left-lateral view of La Rocque (1950) hypotype (X 2). Detroit River Group, Amherstburg 

Formation (Middle Devonian), Cummins' quairry about 6 miles south and 1.75 miles east of Petersburg, Monroe County, Mich. UM 24524.

16. Dorsal view (X 2). Amherstburg Formation (Middle Devonian), Amherstburg, Ontario, Canada. USNM 60022.
GEOLOGICAL SURVEY PROFESSIONAL PAPER 968 PLATE 44

ARCEODOMUS AND HIPPOCARD1A
PLATE 45

FIGURES 1-4. Hippocardia monroica (Grabau), 1910 (p. 76).

1,2. Right-lateral and anterior views of paratype (X 2) . Horizon, locality, and museum number 

the same as on plate 44, figure 16.

3. Oblique dorsal view of latex replica of La Rocque (1950) hypotype (X 2). Amherstburg Formation (Middle Devonian). LivingstoneChannel, Detroit River, Wayne County, Mich. UM 24529. Replica USNM 209283.

4. Left-lateral view (X 2). Lucas Formation (Middle Devonian), Patrick quarry, Grosse Isle, Mich.

UM 24534. 

5-9. Hippocardia cf. H. fusiformis (McCoy), 1844 (p. 75).

5. 6. Interior and exterior views of left valve (X 1). Tournaisian (Mississippian), Tournai, Belgium.

YU 28150. 

7-9. Ventral, posterior, and right-lateral views (X 0.75). Carboniferous (Mississippian?), Tournai,

Belgium. USNM 63372. 

10-14. Hippocardia cooperi n. sp (p. 75).

Dorsal (X 3), ventral (X 3), right-lateral (X 10), anterior (X 3), and left-lateral (X 10) views

of holotype. Lower Chambersburg Limestone (Middle Ordovician), near Strasburg, Va., USNM

loc. 600. USNM 162786.
GEOLOGICAL SURVEY PROFESSIONAL PAPER 968 PLATE 45

HIPPOCARDIA
PLATE 46

FIGURES 1-12. Hippocardia hibernica (Sowerby), 1815 (p. 74).

1-3. Posterior, dorsal, and anterior views of polished surface showing longitudinal shelves (arrow) 

(X 1). Carboniferous (Mississippian), Tournai, Belgium. MCZ 433.

4. Posterior view (X 1). Carboniferous (Mississippian), Castle Cormell, County Limerick, Ireland. 

USNM 100712.

5-7. Posterior, right-lateral, and dorsal views (X 1). Carboniferous (Mississippian), St. Doulagh's, 

County Dublin, Ireland. SM E1169.

8,9. Left-lateral and posterior views (XI). Carboniferous (Mississippian), Ireland. SM E1176.

10-12. Ventral, right-lateral, and posterior views showing hood and elongate rostrum (X 1). Carboniferous (Mississippian), St. Doulagh's, County Dublin, Ireland. SM E1185.
GEOLOGICAL SURVEY PROFESSIONAL PAPER 968 PLATE 46

HIPPOCARDIA
PLATE 47

FIGURES 1-7. Hippocardia bohemica (Barrande), 1881 (p. 75).

1,2. Posterior view showing hood on left side (X 2) and right-lateral view (X 1). Devonian,

Konieprus, Bohemia, Czechoslovakia. USNM 100623.

3-7. Right-lateral, left-lateral, ventral, posterior, and dorsal views (X 2). Lower Devonian, Konieprus, Bohemia, Czechoslovakia. USNM 209282. 

8-12. Hippocardia 1} zeileri (Beushausen), 1895 (p. 76).

Left-lateral, right-lateral, posterior, anterior (X 3), and dorsal (X 3.5) views showing some muscle

scars. Devonian, Germany. MCZ 18032. 

13-15. Hippocardial (p. 4 ).

Oblique left-lateral, posterior, and dorsal views (X 44) of a specimen showing a .recumbent, snoutshaped protoconch. Shale below Lester Shale (Pennsylvanian), SW SW SW SW sec. 10, T. 6 S., 

R. 2 E., Love County, Okla. UOK 6083.
GEOLOGICAL SURVEY PROFESSIONAL PAPER 968 PLATE 47

HIPPOCARDIA
PLATE 48

FIGURES 1-15. Hippocardia cunea (Conrad), 1840 (p. 75).

1. Ventral view of Hall (1855, pi. 67, fig. 29) hypotype (X 1). Schoharie Grit (Lower Devonian), Schoharie, N.Y. NYSM 2313.

2. Ventral view of a specimen showing the entire hood (X 1). Schoharie Grit (Lower Devonian), 

Saugerties, N.Y. NYSM 6667.

3,4. Left-lateral and dorsal views of an internal mold showing the longitudinal shelves (X 2). Devonian, Columbus, Ohio. FM 59845 (Walker Mus. Coll.).

5. Dorsal view of Hall (1885, pi. 68, fig. 13) hypotype (X 2). Upper Helderberg Limestone (Lower 

Devonian), Columbus, Ohio. AM 2853a/3.

6. 7. Posterodorsal and ventral views showing the filling of the elongate ventral aperture developed 

in forms with a hood (X 1). Devonian (Middle Devonian?, Silver Creek Limestone?), near Louisville, Ky. USNM 33581.

8-11. Right-lateral (X 2), posterior (X 1), oblique posterior (x 1), and dorsal (X 2) views of 

Hall (1885, pi. 68, figs. 10, 11) hypotype. Onondaga Limestone (Jeffersonville?, Middle Devonian?), near Louisville, Ky. FM 12500 Walker Mus. Colln.).

12-14. Fragment of shell showing outer shell layer with ornament on one side and marginal denticles forming internal ribs on the other side. 12, Outside of shell showing ribs (X 2). 13, Inside of shell showing marginal denticles which form internal ribs as they grow (x 2). 14, Ventral 

edge of shell showing that marginal denticles and ornament are continuous at the shell margin 

(X 2). Horizon and locality uncertain, possible Middle Devonian (Beechwood Limestone?), at the 

Falls of the Ohio River. USNM 209280.

15. Oblique view looking into shell at ventral commissure; inner shell layer dissolved away and 

dorsal part of shell broken off. Hole at bottom leads into elongate ventral aperture running the 

length of the hood (x 2). Horizon and locality the same as in figures 12-14 above. USNM 

209281.
HIPPOCARDIA
PLATE 49

FIGURES 1-15. Hippocardia cunea (Conrad), 1840 (p. 75).

1-5. Right-lateral (X 2), oblique dorsal (X 1,5), anterior (X 1.5), ventral (X 1.5), and posterior (x 2) views. The last view shows the lamellae that make up the hood in cross section. 

Horizon and locality the same as on plate 48, figures 12-14. USNM 209276.

6. Posterior view of edge of hood showing lamellae in cross section (X 3.5). Devonian (Jeffersonville Limestone), Falls of the Ohio River. USNM 51373.

7. Oblique view of broken right edge of hood showing length of lamellae which make up that hood

(X 3). Devonian, 2 miles southwest of Sylvania, Lucas County, Ohio. MU 323. 

8-10. Right-lateral, oblique dorsal, and ventral views (X 1.5). Horizon and locality the same as on

plate 48, figures 12-14. USNM 209277. 

11,12. Interior and exterior views of outer shell layer of posteroventral part of right valve with

attached part of hood. Hood begins where radial ribbing stops (X !) Horizons and locality the

same as on plate 48, figures 12-14. USNM 209278. 

13-15. Oblique dorsal, ventral, and right-lateral views (X 3) of Nettleroth hypotype (1889, pi. 5,

figs. 16-18). Horizon and locality as in figure 6 above. USNM 209279.
GEOLOGICAL SURVEY PROFESSIONAL PAPER 968 PLATE 49

HIPPOCARDIA
PLATE 50

FIGURES 1,2. Hippocardia cunea (Conrad), 1840 (p. 75).

1. Right-lateral view (X 2). Horizon and locality the same as on plate 48, figures 12-14. USNM 

209267.

2. Inner surface of outer shell layer of right valve showing the internal ribs built by the marginal 

denticles and the tubular extension of the ventral aperture into the hood. Horizon and locality the 

same as on plate 48, figures 12-14. USNM 209268. 

3. Hippocardia pygmaea (Hisinger), 1837 (p. 76).

Posterior view showing hood (X 3) of Branson hypotype (1942b, pi. 59, fig. 17). According to Valdar 

Jaanusson (written commun., 1975), the specimen is from Upper Ordovician rocks, Porkuni Stage, 

Porkuni "Borkholm"), Estonia, USNM 98871. 

4,5,11-13. Hippocardia sp. (p. 76).

4,5. Left-lateral and dorsal views (X 3). Silurian (Wenlockian, Slite Beds), Gotland, ditch between Angelbos and Norvarg, Parish of Larbro, Sweden. SMNH Mo. 18326.

11. Ventral view showing hood (X 3). Platteville Limestone and Briton Member of Mifflin Formation of Templeton and Willman 1952) (Middle Ordovician), Medusa Portland Cement Co., Lee 

County, near Dixon, 111. UI 5261.

12. Right-lateral view (X 2). Ordovician, quarry north of Church Stake Hall, Criburg district, west 

Shropshire, England. USNM 100707.

13. Ventral view showing hood (X 2.5). Middle Ordovician, Rich Valley, Porterfield quarry, 5 miles

east of Saltsville, Va. USNM 206509. 

6-10. Hippocardia richmondensis (Foreste), 1910 (p. 76).

6-8. Right-lateral, dorsal, and left-lateral views of holotype (X 4). Elkhorn Formation (Upper

Ordovician), 3 miles south of Richmond, Ind. USNM 87041.

9,10. Right-lateral and left-lateral views (X 4). Richmondian (Upper Ordovician), Ohio. MU 209T. 

14. Hippocardia antiqua (Owen), 1852 (p. 75).

Left-lateral view of holotype (X 3). OTdovician; the museum label reads: "Lower Fort Carry, Red

River of the North, Manitoba," Canada. USNM 17897. 

15-19. Hippocardia limatula (Bradley), 1930 (p. 75).

15. Left-lateral view of paralectotype (X 3). Kimmswick Limestone (Middle Ordovician), 1 mile 

north of Batchtown, 111. FM 29052 (Walker Mus. Colln.).

16. Right-lateral view of lectotype (X 3). Hor/zon, locality, and museum number the same as in 

figure 15 above.

17. Posterior view showing hood of paralectotype (X 3). Horizon, locality, and museum number the 

same as in figure 15 above.

18. Posterior view of paralectotype showing remnant of hood (X 3). Horizon, locality, and museum 

number the same as in figure 15 above.

19. Left-lateral view (X 3). Kimmswick Limestone (Middle Ordovician), New Hope, Mo. USNM

209273. 

20-24. Bransonia beecheri (Raymond), 1905 (p. 72).

20. Left-lateral view of lectotype (X 5). Chazyan (Middle Ordovician), Sloop Island, near Valcour Island, N.Y. YU 15322C.

21. Left-lateral view of paralectotype (X 5). Horizon and locality the same as in figure 20 above. 

YU 15322B.

22. Left-lateral view (X 3). Row Park Limestone (Middle Ordovician), 200 feet above base section, 

1.3 miles west of Marion, Pa. USNM 209274.

23. Left-lateral view (X 4). Mosheim Member of Lenoir Limestone (Middle Oirdovician), Climer 

P.O., 7 miles east of Cleveland, Tenn. USNM 209275.

24. Left-lateral view (X 3). Chazyan (Middle Ordovician), Isle LaMotte, Vt. USNM 100709. 

25-27. Bransonia aff. B. paquettensis (Wilson), 1956 (p. 73).

Left-lateral, right-lateral, and posterior views (X 3). Holston Formation (Middle Ordovician), For

terfield quarry, 5 miles east of Saltville, Va. USNM 144969. 

28-37. Bransonia alabamensis n. sp. (p. 72).

28. Right-lateral view of paratype (X 5). Little Oak Limestone (Middle Oirdovician), crossroads

1.75 miles northeast of New Hope Church, Ala. USNM 209269. 

29-31. Left-lateral, right-lateral, and dorsal views of paratype (X 5). Horizon and locality the same

as in figure 28 above. USNM 209270. 

32-34. Left-lateral, dorsal, and right-lateral views of holotype (X 5). Horizon and locality the same

as in figure 28 above. USNM 209271. 

35-37. Right-lateral, dorsal, and left-lateral views of paratype (X 5). Horizon and locality the

same as in figure 28 above. USNM 209272. 

38. Bransonia paquettensis (Wilson), 1956 (p. 73).

Right-lateral view of holotype (X 2). Leray-Rockland Beds (Middle Ordovician), Paquette Rapids,

Ottawa River, Ottawa, Ontario, Canada. GSC 11585.
PROFESSIONAL PAPER 968 PLATE 50

HIPPOCARDIA AND BRANSONIA
PLATE 51

FIGURES 1-10,17. Bransonia wilsoni n. sp. (p. 72).

1-6. Left-lateral, right-lateral, dorsal, ventral, anterior, and posterior views of holotype (x 1.5). 

Middle part of "Homevale beds," lower Tiverton Formation (Permian), ridge southeast of Homevale Homestead, Nebo District, Queensland, Australia. UNE F14789. 

7-10. Posterior, anterior, .right-lateral, and dorsal views of paratype (X 1.5). Horizon and locality

the same as in figures 1-6 above. UNE F14790. 

17. Oblique dorsal view of latex replica of paratype (x 1.5). Horizon and locality the same as in

figures 1-6 above. UNE F14790. 

11. Conocardium aliformet (Sowerby), 1815 (p. 70).

Left-lateral view showing muscle impressions (x 3). Carboniferous limestone (Mississippian),

Lowick, Northumberland, England. SM E1151. 

12-16. Bransonia robiistum (Fletcher), 1943 (p. 19).

Dorsal, ventral, right-lateral, posterior, and anterior views (X 1.5). Permian (Wandrawandian 

Siltstone), Wyro, near Ulladulla, New South Wales, Australia. AMS F21930.
GEOLOGICAL SURVEY PROFESSIONAL PAPER 968 PLATE 51

BRANSONIA AND CONOCARDIUM
PLATE 52

FIGURES 1-5,9. Bransonia wilsoni n. sp. (p. 72).

1. Dorsal view of paratype showing internal mold of protoconch (X 1.5). Horizon and locality the 

same as on plate 51, figures 1-6. UNE F14791.

2-5. Paratype. 2, Latex replica showing ornament and fenestellate bryozoan attached to left posterior face (x 1.5). 3-5, SEM photographs showing protoconch (X 25). Horizon and locality 

the same as on plate 51, figures 1-6. UNE F14792.

9. Posterior view of latex replica of paratype showing attached bryozoan (X 1.5). Horizon and locality the same as on plate 51, figures 1-6. UNE F14793. 

6,7,10-14. Bransonia cressmani n. sp. (p. 72).

6,7. Left-lateral and dorsal views of paratype (X 5). Salvisa Bed, Perryville Limestone Member of the Lexington Limestone (Middle Ordovician), quarry on Mitchellsburg Road, 0.4 miles 

south of Perryville, Ky. (USGS loc. 5015-CO). USNM 209265.

10-14. Ventral, dorsal, posterior, right-lateral, and left-lateral views of holotype (X 5). Horizon and

locality the same as in figures 6, 7 above. USNM 209266. 

8. Bransoniat sp. (p. 19).

Dorsal view of internal mold showing muscle scars (X 3). Windom Formation (Vitulina Zone, 

Hamiltonian, Middle Devonian), Tinkers Falls, Truxton, Cortland County, N.Y. USNM 100703.
GEOLOGICAL SURVEY PROFESSIONAL PAPER 968 PLATE 52

BRANSONIA
PLATE 53

FIGURES 1-5. Bransoniat sp. (p. 19).

Right-lateral, anterior, oblique anterior, left-lateral, and posterior views of an internal mold showing muscle scars (X 3). Horizon, locality, and museum number the same as on plate 52, figure 8. 

6-20. Bransonia cressmani n. sp. (p. 72).

6,7. Dorsal and right-lateral views of paratype (x 5). Perryville Limestone Member of the Lexington Limestone (Middle Ordovician), quarry on west side of U.S. Route 68, 1 mile north of 

junction with U.S. Route 150 in Perryville, Ky. (USGS loc. 6916-CO). USNM 209260.

8-10. Left-lateral, right-lateral, and dorsal views of paratype (X 5). Horizon and locality the same 

as in figures 6, 7 above. USNM 209261.

11-16. Right-lateral, ventral, dorsal, posterior, left-lateral, and anterior views of paratype (X 5). 

Horizon and locality the same as in figures 6, 7 above. USNM 209262.

17-19. Right-lateral, left-lateral, and dorsal views of paratype (X 5). Horizon and locality the same 

as on plate 52, figures 6, 7. USNM 209263.

20. Dorsal view of paratype (X 5). Horizon and locality the same as in figures 6, 7 above. USNM

209264. 

21-23. Bransonia robustum (Fletcher), 1943 (p. 19).

Oblique right-lateral, dorsal, and right-lateral views of pairatype showing muscle scars (X 3). Horizon and locality the same as in figures 11-16, plate 51. AMS F. 21928.
GEOLOGICAL SURVEY PROFESSIONAL PAPER 968 PLATE 53

BRANSONIA
PLATE 54

Bransonia cressmani n. sp. (p. 72).

Stero triplet of internal mold showing a large muscle scar in the top center of the right side; anteriorly from this muscle scar passes a part of the pallial line (X 52). Tanglewood Limestone 

Member of the Lexington Limestone (Middle and Upper Ordovician), 81 feet above the Macedonia 

Bed of Grier Limestone Member of Lexington Limestone (Middle Ordovician) in the Frankfort 

East section on eastbound lanes of Interstate Highway 64, east side of Kentucky River crossing, 

Franklin County, Ky. USGS loc. D-1200-CO. USNM 209259.
GEOLOGICAL SURVEY PROFESSIONAL PAPER 968 PLATE 54

BRANSONIA