Otter Creek Coral Bed and 

Its Fauna, East-Central 

Kentucky

By GEORGE C. SIMMONS and WILLIAM A. OLIVER, JR.

CONTRIBUTIONS TO STRATIGRAPHY

GEOLOGICAL SURVEY BULLETIN 1244-F

Prepared in cooperation with the 

Kentucky Geological Survey
UNITED STATES DEPARTMENT OF THE INTERIOR 

STEWART L. UDALL, Secretary

GEOLOGICAL SURVEY 

William T. Pecora, Director

U.S. GOVERNMENT PRINTING OFFICE, WASHINGTON : 1967

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

Washington, D.C. 20402 - Price 15 cents
CONTENTS

Page

Abstract__ ____----______--______..____-__-________.______________ Fl

Introduction. ______________________________________________________ 1

Stratigraphic relations and lithology__________________________________ 2

Fauna__ _________________________________________________________ 6

Systematic annotations______-___-..__-__-_________--_______-__--__ 9

Stromatoporoids_ _ ____________________________________________ 9

Solitary (horn) corals-______-__.._--_-_-_________-___-____----__ 9

Colonial corals_________________________________________________ 10

Fossil localities.____________________________________________________ 12

References cited.___________________________________________________ 12

ILLUSTRATIONS

Page 

FIGURE 1. Index map showing location of sites from which fossils were

collected.____________________________________________ F2

2. Nomenclature chart.____________________________________ 3

3. Outcrop of the Otter Creek coral bed______________________ 4

4. Band of colonial corals in residuum_________-___-____---___ 4

TABLES

Page 

TABLE 1. Number of specimens of each species of coral and stromatoporoid identified in the Otter Creek coral bed.____________ F6

2. Fossils other than corals and stromatoporoids identified in the

Otter Creek coral bed_______________-_____-_-__--___--- 8

in

CONTRIBUTIONS TO STRATIGRAPHY

OTTER CREEK CORAL BED AND ITS FAUNA, 

EAST-CENTRAL KENTUCKY

By GEORGE C. SIMMONS and WILLIAM A. OLIVER, JR.

ABSTRACT

The Otter Creek coral bed is a gray medium-grained limestone of Late 

Ordovician (Richmond) age on the east flank of the Cincinnati arch in Kentucky. The coral bed is lithologicaily transitional with the grayish-green finegrained muddy dolomite of the underlying Rowland Member of the Drakes 

Formation, and is intercalated with and conformably overlain by dark-yellowishorange fine- to coarse-grained dolomite of the Preachersville Member of the 

same formation. Where present, the Otter Creek is considered the basal unit 

of the Preachersville.

The most abundant fossils in the Otter Creek coral bed are the corals 

Calapoecia hnronensis, Foerstepliyttum vacuum, Grcwingkia rustica, and Tetradium approximatitm. The stromatoporoid Aulacera cylindrica and brachiopods 

of the genera Hcbertella and Platystropliia also are common. The'se fossils and 

others are widespread in these beds on the east side of the Cincinnati arch 

and were identified in seven collections from the Richmond North, Union City, 

Palmer, and Lancaster quadrangles, Kentucky. Upper Ordovician coral beds 

containing similar faunas occur on the west side of the Cincinnati arch, but 

their relation to the Otter Creek coral bed is uncertain. Systematic annotations 

of the corals and stromatoporoids in the Otter Creek coral bed are included.

INTRODUCTION

The Otter Creek coral bed is a useful stratigraphic marker at the 

base of the Preachersville Member of the Drakes Formation (Upper 

Ordovician); it separates the Preachersville from the underlying 

Rowland Member of the Drakes Formation in parts of southeast - 

central Kentucky (Weir and others, 1965, p. 18). The Otter Creek 

is stratigraphically important because it contains the only wellpreserved fauna that has been recognized in the Drakes Formation 

on the east side of the Cincinnati arch, and because it is one of 

several similar beds in Upper Ordovician rocks of the KentuckyOhio-Indiana region. The Otter Creek coral bed has been mapped 

in the Richmond North, Union City, and Palmer quadrangles (unpub. 

data) as part of the U.S. Geological Survey mapping program in

Fl
F2 CONTRIBUTIONS TO STRATIGRAPHY

cooperation with the Kentucky Geological Survey. Seven fossil collections (fig. 1), six from these three quadrangles and one from the 

nearby Lancaster quadrangle, provide a basis for comparing the 

Otter Creek with other coral beds of similar age.

The field observations and collections were made by Simmons, except for collection USGS 4662-CO, which was made by G. W. Weir. 

The identification and study of corals and stromatoporoids were made 

by Oliver.

STRATIGRAPHIC RELATIONS AND LITHOLOGY

The Drakes Formation comprises the uppermost Ordovician strata 

in the area studied. It is conformably overlain by the Brassfield

QUADRANGLES 

A, Richmond North 

B, Union City 

C, Palmer 

D, Lancaster

38°00'00'

84°45'00"

37< 

52'30"

FOSSIL COLLECTIONS 

a, USGS D1370-CO 

4468-CO 

4545-CO 

4662-CO 

4760-CO 

5308-CO

b, USGS 

c, USGS 

d, USGS 

e, USGS 

f, USGS 

g, USGS 5309-CO

FIGURE 1. Location of sites from which fossils were collected from the Otter

Creek coral bed.
OTTER CREEK CORAL BED, KENTUCKY F3

Dolomite (Lower Silurian) and conformably overlies and is transitional with the Keba Member of the Ashlock Formation (Upper 

Ordovician). The Drakes ranges in thickness from 130 to 160 feet 

and is divided into two members: the Preachersville (upper) and the 

Rowland (lower). The Preachersville ranges from 75 to 100 feet 

in thickness, and the Rowland, from 45 to 60 feet. The nomenclature 

used here is that of Weir, Greene, and Simmons (1965); it is compared with previous nomenclature in figure 2.

The Rowland Member constitutes grayish-green fine-grained muddy 

dolomite that grades into and is interbedded with dolomitic mudstone. 

It is 45-75 percent dolomite and 25-55 percent clay and silt. The 

rocks commonly are laminated to thin bedded; weathered outcrops 

yield fragments ranging from thin plates 0.04 inch thick to blocky 

pieces an inch or two thick.

The Preachersville Member is chiefly composed of grayish-green 

fine-grained muddy dolomite and dolomitic mudstone similar to those 

rocks in the Rowland Member. However, the Preachersville contains 

about 20 percent (field estimate) fine- to coarse-grained calcitic doloPREVIOUS 

NOMENCLATURE

Hall Palmquist (1960) and 

?£TO 2

c ^

McFark Goodwir

Brassfield 

Formation

Whitewater 

and

Formations 

undifferentiated

Waynesville

Formation

Oregonia

Arnheim

Formation Sunset

LITHOLOGY

jf/lf ^ ^X ^s-

^- -S" s/"'- ^x

X^ >X /^ ^^ /

x^ x^ J/f ^

X^ X''' ^X" ^X"

 ^X* . - . /^ ^X" ... ^X" 

'>' ^~^:-^^'~^:

 ^^ ^ ^ii:^

 <f~ ' '^~~^' '^ ^x' '

 -,/' /' -^ ^- /

. . .^ -/. . .^/ ^S. .

i ^S. . .^x' JSf~ jS' 

. .^x^ ^x"- - .^< ^x. . .

./^ ^x** *x^ >^- -^x1

 ^X'- x"' x^- - - x^ X

x^ x"' -X -X

o ^^ry^ijcr^i

r^llL^TTT^ll^TTTx-

 ^x- -x' x'- X' > J ' '^~T^' i '^~^'"

 ^. . .^/ ^^. . .^^ ^-^.

rj^T^i^^li^:

- -,X^ >*^ - v^- ^^ fs^-

 ^' ^/ ^< . .^ -^

 /; . .^^ -s*. - s' >^- 'S*-

1 1 1 1 1 ]

1 1 1 1 1 1

1 1 1 1 1

' s ^> f^s ' s '-^

^^PE^.-iv-ZrrvP-i:

, z * ~ 1-

O (/) LlJ 

5 LJ lJ-

"~ Z

10-25

75-100

45-60

4-15

10-15

PRESENT 

NOMENCLATURE 

(Weir and others, 1965)

Brassfield 

Dolomite

Preachersville 

Member

Otter Creek coral bed \

Rowland 

Member

Reba Member

Terrill Member

c 

o

Drakes Format

c 3 .°

o to

< 0

LL

FIGUBE 2. Comparison of previous and present stratigraphic nomenclature in 

southeast-central Kentucky.
F4 CONTRIBUTIONS TO STRATIGRAPHY

mite. This calcitic dolomite is gray in fresh exposures and weathers 

dark yellowish orange. Most beds of calcitic dolomite are 0.1-0.5 

foot thick, but some are as much as 2 feet thick. These beds are 

everywhere abundant in the lower part of the Preachersville, and they 

occur so closely spaced near the base of the member that they form 

a ledge at most places. The contact between the Rowland and the 

Preachersville is mapped at the base of this ledge where the Otter 

Creek coral bed is absent.

The Otter Creek coral bed is a medium-light-gray limestone which 

weathers light olive gray to medium gray. Most of the limestone is 

medium grained, although fine- and coarse-grained varieties are 

common. Colonial corals, other fossils, and fossile fragments are 

abundant. Inclusions of yellowish-green clay, some as much as 0.1 

inch long, are also abundant; specks of pyrite are less common. 

Bedding varies from thin laminations to layers more than 1 foot 

thick. The coral bed has a sporadic distribution and ranges in thickness from 0 to 8 feet. In many places where it is more than 3 feet

FIGURE 3. Outcrop of the Otter Creek coral bed along a small tributary to 

East Fork Otter Creek in the Union City quadrangle, Kentucky. A large 

colonial coral Is weathering out of the limestone bed adjacent to the pick. 

Two smaller corals that weathered free are by the pencil in the foreground.
OTTER CREEK CORAL BED, KENTUCKY F5

thick, the coral bed crops out as a small ledge (fig. 3), but more 

commonly it is thinner (2-3 ft thick) and is marked by a band of 

colonial corals in the residuum and by corals and limestone colluvium 

downslope from the bed (fig. 4).

Where present, the Otter Creek coral bed is the basal unit of the 

Preachersville Member. At many places the contact of the coral bed 

with overlying dolomite is abrupt, but at others, limestone of the 

coral bed is intercalated in 1-inch-thick beds with dark-yellowishorange dolomite through a vertical interval of as much as 6 inches. 

The coral bed is transitional with the Kowland Member through a 

thickness of a few inches to as much as 3 feet. Where the transition 

zone is thin it is marked by an abrupt compositional change from 

dolomite below to limestone above. Where the zone is thick the 

transition is one of alternating 1-inch-thick beds of shaly grayishgreen dolomite-rich beds and pale-grayish-green lime-rich beds. The 

contact is placed so that the transitonal beds are included in the Otter 

Creek coral bed; thus, all fossiliferous layers are in the Otter Creek. 

Transitional lithologies are also common near the margins of the 

Otter Creek coral bed where it wedges out.

FIGURE 4. Band of colonial corals weathered out of the Otter Creek coral bed 

near East Fork Otter Creek in the Union City quadrangle, Kentucky. Limestone fragments and corals are in the colluvium downslope. 

233-812 O 67 2
F6 CONTRIBUTIONS TO STRATIGRAPHY

FAUNA

The most abundant fossils in the Otter Creek coral bed are the 

corals Calapoecia huronensis, Foerstepkyllwm, vacuum, Grewingikia 

rustica, and Tetradium approximation. These corals are present at 

most places where the Otter Creek crops out. The cylindrical stromatoporoid Aulacera cylindrica and brachiopods belonging to the genera 

HeberteUa and Platystrophia are also common.

The collections listed in table 1 were made with the intention of 

obtaining a large overall sample, particularly of corals and stromatoporoids. The number of specimens of each species collected for 

study from each locality is indicated, but it is an index of abundance 

in only a general way. The table clearly indicates that some species 

are more common than others, but relative and actual numbers of 

specimens collected at each locality are a function of overall collection 

size and collecting bias. Collection D1370-CO is more objective than 

the others as it preceded any paleontologic identifications and is larger. 

In making the later, smaller collections (higher numbers), the intention was to obtain variety rather than proportional numbers.

Coral beds of Kichmond age on the west side of the Cincinnati arch 

have been extensively described, most recently by Browne (1964, 

1965), who also reviewed previous work. Browne concluded that four 

coral zones occur in formations of Richmond age: one in the WaynesTABLE 1. Number of specimens of each species of coral and stromatoporoid identified 

in the Otter Creek coral bed

(Identifications by W. A. Oliver, Jr.]

Stromatoporoids

Solitary corals

'S." sp. C_ _ - ______________ .......

'S." sp. D_ ____.___.______ _________.__

Colonial corals

USOS collection

4662-CO

4

1 

1

1

1

2 

2

3 

2

2

19

D1370-CO

22

15

3

3

5

3

11

10

72

5309-CO

3

2

6

2

13

6308-CO

6 

3

1

7

11

4

32

4468-CO

7

1

4

1

5

1

7

4

4

34

4545-CO

1

?

1

2 

3

1

9

17

4760-CO

4

2 

1

2

1

2

8

20

Total

47 

4

22 

2 

3 

4 

12 

10 

1

24 

2 

35 

2 

39

207
OTTER CREEK CORAL BED, KENTUCKY F7

ville, two in the Liberty, and one in the Whitewater Formation 

(Browne, 1964, p. 385; 1965, p. 1180-1181). Browne (1965) summarized the distribution of corals and described the colonial corals 

except for Tetradium. This recent work, based on Kentucky sections 

west of the Cincinnati arch, provides a standard with which the Otter 

Creek coral bed on the southeast side of the arch can be compared.

Foerste (1912, p. 19-22) was the first to recognize (near Eichmond, 

Ky.) what is here called the Otter Creek coral bed. Foerste considered 

the corals equivalent to his Bardstown coral reef at the base of the 

"Liberty bed" near Bardstown, Ky., on the west side of the Cincinnati 

arch.

The coral bed has been traced by geologic mapping across the adjacent Richmond North, Union City, and Palmer quadrangles, so collections from these areas are considered a single fauna. The Otter 

Creek coral bed is the source of all collections listed in table 1 except 

4662, which is from the Lancaster quadrangle, 20 miles southwest of 

the other quadrangles. The bed has not been traced from the other 

quadrangles into the Lancaster quadrangle, and collection 4662 may 

represent another coral bed at a different horizon within the Preachersville Member of the Drakes Formation.

So restricted, the coral fauna can be compared with Browne's beds 

3 and 4, upper Liberty bed, and Whitewater bed, respectively. Of 

the Otter Creek species, F oerstepliyttum vacuum ("subsp." vacuum 

and magnum) and Calapoecia Jmronensis characterize Browne's beds 

3 and 4. Bed 4, however, also includes Favistina steUata and SaffordopJiyUum floweri, so that if collection 4662 is included, the Otter 

Creek fauna most closely resembles that of Browne's Whitewater 

coral bed.

The ranges given by Browne (1964), p. 387; 1965, p. 1179) indicate 

that the species content of the beds cannot be used for detailed correlation, as many species range through coral beds in which they 

do not occur. It is likely that if coral-bed environments existed 

somewhat earlier or later than known coral beds, their species composition would have been similar to that of the known beds. Therefore, the general similarity in species content of the Otter Creek coral 

bed and of Browne's beds 3 and 4 suggests that these beds are of 

the same general age but not necessarily contemporaneous. Richmond 

coral biostratigraphy will have to be known in much greater detail 

before detailed correlations will be practical.

Table 2 lists fossils other than corals and stromatoporoids that 

have been identified from the Otter Creek coral bed. No attempt 

was made to obtain a comprehensive collection at any of the localities, 

and the identifications cannot be used as a basis for comparing one 

collection with another.
F8 CONTRIBUTIONS TO STRATIGRAPHY

TABLE 2. Fossils other than corals and stromatoporoids identified in the Otter

Creek coral bed

[Identifications: bryozoans by O. L. Karklins; brachiopods in collection D1370-CO by E. J. Eoss, Jr; 

other brachiopods by R. B. Neuman; gastropods by E. L. Yochelson; pelecypods by John Pojeta, Jr.]

Bryozoans 

Heterotrypa subramosa (Ulrich) _ _ __ ____

H. sp. form e_ ______ __ ___

Stigmatellaf sp _ ____ __ _ _______

Constellaria sp___ _______ _ ______

Amplexoporasp.---- . _____ ____ _____ _

Hallopora sp. form c-3__-__ _ ____ ___ __

Homotrypa ramulosa Bassler_ _ ___ ___ ____

H. sp____ _ ____________________________

GortaniporaCt) sp. form c. _ _ _ ___ ___ _

Homotrypid new genus 3_ _ _ ______

Brachiopods 

Hebertella occidentalis (Hall) _ ___________

H. sp. cf. H. sinuata (Hall)_ ____ _ _ _

H. sp_----__ _-_____-_____-__-____-_.___

Lepidocyclus capax (Conrad) ____ __ ___

Plaesiomys subquadrata (Hall)_ ___ _ ___ _

P. sp. cf. P. clarksvillensis Foerste. _ ___ _

P. Sp ___ ---_------_______-________-__-_

Zygospira kentuckiensis James. __ __ __

Z. sp. (small) _ _ _ _

Gastropods

Loxoplocus (Lophospira) bowdeni (Saff ord) _ _

l\Sfiiv*/*n fi*infn ?*/*? QTI inHp'f"

High-spired gastropod indet. cf. Murchisonia. 

Pelecypods

USGS collection

4662-CO

X

X

D1370-CO

v

X

X

v

v

X

X 

X 

X 

X

v

v

X

X

5309-CO

X

X

X

X

5308-CO

X

X

X

X

4468-CO

v

X

X

v

X 

X

X

X

X

X 

X

X

X

X

X

4545-CO

X

X

X 

X

4760-CO

X

X

X

----

X

X
OTTER CREEK CORAL BED, KENTUCKY F9

SYSTEMATIC ANNOTATIONS

Although much systematic work has been done on the Richmond 

corals, a number of uncertainties remain, and several taxa have not 

yet been described or analyzed by modern methods. The Otter Creek 

collections are not large enough for redescription or revision, but 

their study has produced some data and conclusions that may be of 

value to other workers. The basis for the identifications in table 1, 

references to illustrations, and annotations are included in the following paragraphs for those who wish to use this as a field guide.

STROMATOPOROIDS

1. Aulacera cylindrica (Foerste). Specimens apparently referable 

to the nominal species A. cylindrica and A, plutnmeri as well as to 

one or two nodulose "species" are present in the collection. Variation in internal and external morphology is extreme, and intermediates between all forms are included. At present it is impractical to 

recognize more than one species in the Otter Creek collections, and 

the senior name among those available has been chosen for the present 

purpose.

Study of larger collections and comparison with material from 

other Cincinnati arch areas is desirable. The present identification 

is based on descriptions and illustrations in Galloway and St. Jean 

(1961, p. 21-39 and pis. 3-5, 12).

Aulacera cylindrica fragments are easily recognized by their cylindrical form and coarsely cystose axial zone with surrounding concentric structure. Diameters in the 47 specimens studied range from 

1 to 5 cm; lengths are as much as 8 cm.

2. Labecliia huronensis (Billings), as described by Galloway and 

St. Jean (1961, p. 50-53 and pi. 7), is the only massive stromatoporoid 

in the Otter Creek collections. The largest of four specimens has 

a maximum dimension of 15 cm.

SOLITARY (HORN) CORALS

3. Grewingkia rustica (Billings). This is the common large horn 

coral of Richmond age in the Cincinnati arch area. Coral bed specimens are as large as 40 mm in diameter and 8 cm in length. Twentytwo specimens were examined and compared with specimens from 

other Kentucky, Indiana, and Ohio collections.

This species is commonly referred to as G. rustica or Streptelasma 

r-usticum in the literature concerning the Cincinnati area. However, 

the original material on which the name was based is from Snake 

Island, Lake St. John, Quebec, and may not be of the same age
F10 CONTRIBUTIONS TO STRATIGRAPHY

(Flower, 1961, p. 18, 86). The types should be restudied to determine 

if the name is applicable to the Kentucky-Ohio-Indiana species. 

Topotype specimens illustrated by Stumm (1963, pi. 2, figs. 8-10) 

are similar to the Kentucky forms.

4. "Streptelasma" spp. Thirty-two small horn corals are in the 

Otter Creek collections. If the Kichmond horn coral classification 

were to be thoroughly revised, some of these would certainly be referable to named species, but others may be early stages of G. rustica. 

At present, the designations Streptelasma sp. A to E refer to morphologic types, the systematic importance of which is unknown. Comparison of these types with specimens in other collections shows that 

some of the forms are present in the Liberty and Whitewater Formations near Kichmond and Liberty, Ind., in the Whitewater Formation 

near Oxford, Ohio, and at several localities on both sides of the 

Cincinnati arch in Kentucky.

5. "Streptelasma" angulatum (Billings). The identification of a 

single specimen is based on external form only. Study of abundant 

material might show this to be an early stage of another species.

COLONIAL CORALS

6. Calapoecia huronensis Billings. Twenty-four specimens of 

Calapoecia from the Otter Creek collections are variable, but all are 

assignable to this one species. This is a senior synonym of C. 

cribriformis as used by Foerste and others in the pre-1950 literature.

Colonies are massive and as large as 21 cm in maximum diameter; 

corallite diameters average 3-4 mm. Weathered surfaces show the 

porous wall, so that specimens can commonly be generically identified 

in the field.

The species was recently redescribed and illustrated by Browne 

(1965, p. 1184-1185 and pis. 147, 152).

7. Favistina stellata (Hall). Two fragments of Favistina from 

locality 4662 are the only specimens of this species in the collections. 

They were identified by their large corallites (5-6 mm) and long 

septa. The presence of long septa distinguishes these forms from 

Foerstephyllum vacuum, which is otherwise similar in appearance.

Flower (1961, p. 76-81) and Browne (1965, p. 1186) discussed the 

involved nomenclatorial problems of this genus and species. Browne 

considered the genus Favistina Flower (=Favistella of authors) to 

be a junior synonym of Cyathophylloides. Our knowledge of this 

genus and its type species is so limited, however, that it seems best 

to utilize Favistina Flower, which has a known, well-described type 

species, until adequate data on other possible genera are available.

The Otter Creek specimens have been compared with the lectotype
OTTER CREEK CORAL BED, KENTUCKY Fll

of the species (selected by Browne, 1965, p. 1186) and with many 

specimens from other localities. Richmond Favistina have recently 

been illustrated by Flower (1961, pis. 38-40) and by Browne (196,5, 

pis. 147-149, 151, 152).

8. F oerstephyllum vacuum (Foerste). This species is referred to 

as Columnaria vacua in the pre-1950 literature. Colonies are massive; 

35 Otter Creek specimens range from 1 to 19 cm in maximum diameter. 

Average corallite size in colonies ranges from 3 to 5 mm or more. This 

species differs from Favistina stellata by having no septa, or very 

short ones; locally these may be amplexoid, extending nearly to the 

axis on the upper surfaces of tabulae.

Browne (1965, p. 1182-1183, pis. 146, 152) recognized F. vacuum 

and F. vacuum magnum from the coral beds west of the Cincinnati 

arch, the two taxa being associated in most of her collections. 

Browne's specimens were compared with those from the Otter Creek, 

and the typical "subspecies" and "subspecies" magnum occur in at 

least two of the collections. Browne's subspecies are here interpreted 

as extremes in a morphologically variable species.

9. Saffordophyllum floweri Browne. Two specimens from locality 

4662 have been compared with Browne's types (Browne, 1965, p. 1183- 

1184 and pis. 146, 151) and are certainly conspecific. The species is 

massive and compact and has corallites approximately 2 mm in 

diameter. The larger colony from locality 4662 has long and short 

diameters of 16 and 8 cm, respectively, and a height of 5.5 cm. In 

hand specimen, $. floweri can be confused with Calapoecia huronensis, 

but the latter has a porous wall.

10. Tetradium approximatum Bassler. This species is commonly 

ascribed to Ulrich, although the name had no status until Bassler 

(1915, p. 1264-1265) listed descriptions and illustrations of specimens 

that he considered to belong to this species. Ulrich gave no information on the species except its general stratigraphic position, so the 

1915 species concept is that of Bassler, not Ulrich. James (1940, 

p. 645) apparently designated as lectotype the specimen illustrated 

by Foerste (1909, pi. 10, fig. la-lb) as Tetradium minus. As the 

lectotype has not been reexamined, the propriety of the present name 

assignment is uncertain. Foerste (1916), followed by Bassler (1950), 

considered Tetradium Ontario Hall (1884) to be a senior synonym 

of T. approximatum, but as T. Ontario is from New York and the 

types are not available for study, this does not help to stabilize 

matters. However, a distinct Tetradium is present in beds of Richmond age in the Cincinnati arch area, and it would best be termed T. 

approximatum, its most familiar name, until such time as adequate 

search can be made for the necessary specimens.
F12 CONTRIBUTIONS TO STRATIGRAPHY

T. approximatum is massive. Thirty-nine Otter Creek colonies vary 

in size; the largest has a maximum diameter of 20 by 16 cm and a 

maximum height of 9 cm. Individual corallites are less than 1 mm 

in diameter; the typical four septa are short and weakly developed 

in most sections. The most recent description and illustration of 

T. approximatum were given by Bassler (1950, p. 290 and pi. 3, figs. 

8-13, as T. Ontario).

FOSSIL LOCALITIES

Fossil collection localities are listed below according to U.S. Geological Survey fossil-collection numbers and are located by quadrangle, coordinates, and altitude. All fossils are in the collections 

of the U.S. Geological Survey. The coordinates given for each collection are measured from the 10,000-foot grids based on the Kentucky 

coordinate system, indicated on the sides of the topographic maps. 

Three of the quadrangles lie within two overlapping coordinate 

zones, and locations are given according to both zones, in figures that 

are rounded off to the nearest 50 feet. Altitudes given are accurate 

to within 10 feet.

USGS D1370-CO; Richmond North quadrangle; 1 985 050, 108 350 (North) ;

2 418 800, 536 550 (South) ; altitude, 845 feet. 

USGS 4468-CO; Palmer quadrangle; 2 049 600, 91 600 (North) ; 2 483 300,

520 350 (South) ; altitude, 630 feet. 

USGS 4545-CO; Palmer quadrangle; 2 045 550, 113 400 (North) ; 2 479 250,

542 200 (South) ; altitude, 665 feet.

USGS 4662-CO; Lancaster quadrangle; 2 358 400, 427 300; altitude, 900 feet. 

USGS 4760-CO; Palmer quadrangle; 2 057 900, 130 450 (North) ; 2 490 850,

559 800 (South) ; altitude, 625 feet. 

USGS 5308-CO; Union City quadrangle; 2 032 150,125 650 (North) ; 2 459 200,

554 400 (South) ; altitude, 740 feet. 

USGS 5309-CO; Union City quadrangle; 2 007 600, 111 050 (North) ; 2 441 250,

539 250 (South) ; altitude, 850 feet.

REFERENCES CITED

Bassler, R. S., 1915, Bibliographic index of American Ordovician and Silurian 

fossils: U.S. Natl. Mus. Bull. 92, 1521 p.

 1950, Descriptions of Ordovician tetracorals: Geol. Soc. America Mem.

44, p. 253-294, pi. 1-20. 

Browne, R. G., 1964, The coral horizons and stratigraphy of the upper Richmond

Group in Kentucky west of the Cincinnati arch: Jour. Paleontology, v. 38,

p. 385-392.

 1965, Some upper Cincinnatian (Ordovician) colonial corals of northcentral Kentucky: Jour. Paleontology, v. 39, p. 1177-1191, pi. 146-152.

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