Molluscan Record From a 

Mid-Cretaceous Borehole in 

Weston County, Wyoming

By WILLIAM A. COBBAN

GEOLOGICAL SURVEY PROFESSIONAL PAPER 1271

Brief descriptions, illustrations, and 

stratigraphic ranges of the 

more common fossils

UNITED STATES GOVERNMENT PRINTING OFFICE WASHINGTON : 1984
UNITED STATES DEPARTMENT OF THE INTERIOR 

WILLIAM P. CLARK, Secretary

GEOLOGICAL SURVEY 

Dallas L. Peck, Director

Library of Congress Cataloging in Publication Data 

Cobban, William Aubrey, 1916-

Molluscan record from a mid-Cretaceous borehole in Weston County, Wyoming.

(Geological Survey Professional Paper; 1271)

Bibliography: 21 p.

1. Mollusks, Fossil. 2. Paleontology Cretaceous. 3. Paleontology Wyoming Weston County. 4.

Borings Wyoming Weston County.

I. Title. II. Series.

QE801.C55 1983 564'.11'0978714 82-600120

For sale by the Branch of Distribution

U.S. Geological Survey

604 South Pickett Street

Alexandria, VA 22304
CONTENTS

Page

Abstract ............................................ 1

Introduction .......................................... 1

Acknowledgments ....................................... 1

Stratigraphy summary .................................... 1

Preservation of fossils ..................................... 2

Stratigraphic distribution and age .............................. 2

Molluscan zones ........................................ 2

Megafossil content ....................................... 4

Characteristic fossils ...................................... 8

References cited ........................................ 19

ILLUSTRATIONS

[Plates follow index]

Page

PLATES 1-5. Molluscan fossils 

FIGURE 1. Ranges of bivalves and ammonites ...................... 3

HI

MOLLUSCAN RECORD FROM A MID-CRETACEOUS BOREHOLE 

IN WESTON COUNTY, WYOMING

By WILLIAM A. COBBAN

ABSTRACT

A core borehole in the Osage oilfield on the west flank of the Black 

Hills uplift in eastern Wyoming penetrated, in decending order, most 

of the Carlile Shale, all of the Greenhorn Formation, and the upper 

part of the underlying Belle Fourche Shale. Molluscan fossils are 

abundant in parts of the core and indicate an age span of early Coniacian to the middle Cenomanian. Most of the fossils are bivalves and 

ammonites; gastropods are scarce. 

Fossils in the cores indicate the following zones 

Lower Coniacian

Crem.noceramusl waltersdorfensis 

Upper Turonian

Scaphites corvensis 

S. nigricollensis 

S. whitfieldi 

S. warreni 

Middle Turonian

Collignoniceras woollgari 

Lower Turonian

Mytiloides mytiloides 

Mytiloides aff. M. duplicostatus 

Upper Cenomanian

Sciponoceras gracile 

Dunveganoceras albertense 

D. pondi 

Middle Cenomanian

Acanthoceras amphibolmn

INTRODUCTION

A cored borehole was drilled by the U.S. Geological 

Survey in 1976 in the Osage oilfield on the west flank 

of the Black Hills uplift in eastern Wyoming 

(Merewether, 1980). This borehole, in the SW1/4NW1/4 

sec. 30, T. 46 N., R. 63 W., Weston County, was drilled 

to a total depth of 270.8 meters. The purpose was to 

obtain fresh samples for sedimentologic and paleontologic analyses as well as to obtain geophysical logs 

for references to subsurface studies of mid-Cretaceous 

rocks in the Powder River Basin. The site of the 

borehole was selected because of its proximity to measured outcrop sections of mid-Cretaceous rocks. Cores 

from the borehole were split along bedding planes for 

molluscan fossils, and samples of the cores were taken

at intervals for investigations of the foraminifera, dinoflagellates, and palynomorphs. Unfortunately, the diameter of the cores is small (47 mm), but, nevertheless, 

an impressive fossil record was obtained.

ACKNOWLEDGMENTS

E. A. Merewether of the U.S. Geological Survey proposed this project, selected the borehole site, and 

supervised the coring. He also split most of the cores 

and collected most of the megafossils as well as the 

samples for micropaleontological studies. R. E. Burkholder, also of the Geological Survey, photographed the 

megafossils and prepared some of the specimens.

All illustrated specimens are stored in the National 

Museum of Natural History in Washington, D. C., and 

have USNM catalog numbers.

STRATIGRAPHIC SUMMARY

A graphic log of the borehole showing formational 

assignments and lithologic contacts was presented by 

Merewether (1980, fig. 4). The top of the borehole is 

probably a little below the top of the Carlile Shale. 

Here the Carlile consists of three members. The upper 

member, Sage Breaks, consists of calcareous and noncalcareous shale with scattered limestone concretions. 

About 85 m were penetrated in the borehole. 

Merewether (1980, p. 13) noted thicknesses of 91-94 

m in wells in the Osage oilfield. The Turner Sandy 

Member, the middle part of the Carlile, extends from 

depths of 85-140 m and consists of interbedded fineto very fine grained sandstone, siltstone, and noncalcareous shale with sandy or silty limestone concretions. 

The underlying Pool Creek Member extends from 140- 

163 m and consists of calcareous shale. Calcareous shale 

and thin beds of limestone make up the Greenhorn Formation, which extends from 163 to 240 m. Noncalcareous shale with several beds of bentonite comprise the 

underlying Belle Fourche Shale of which the upper 31 

m were penetrated in the borehole.
MOLLUSCAN RECORD FROM MID-CRETACEOUS BOREHOLE, WYOMING

PRESERVATION OF FOSSILS

With few exceptions, the mollusks in the cores occur 

crushed in dark-gray shale. Some specimens are completely flattened. Other specimens, especially those in 

more silty matrices, are not as crushed. A few specimens in gray siltstone beds in the Turner Sandy Member of the Carlile Shale are almost undeformed. Some 

shell material is usually preserved on most specimens. 

Pyritic fossils are common in the lower part of the 

Greenhorn Formation at depths of 216-230 m and 244- 

247.5m.

STRATIGRAPHIC DISTRIBUTION 

AND AGE

The ranges of most of the mollusks from the borehole 

are shown in figure 1. Gastropods are extremely scarce, 

and none is shown.

The mollusks reveal an age span of the cores of middle Cenomanian into early Coniacian. The middle 

Cenomanian age of the lowest cores is based mainly 

on the occurrence of the ammonite Acanthoceras at 

depths of 243.8-257.3 m. With the exception of A. hippocastanum (J. de C. Sowerby), most occurrences of 

the genus are in rocks regarded as middle Cenomanian 

age (for example Kennedy and Hancock, 1976, p. 5.15; 

1977, p. 130-135). Cores from depths of 237.7-246 m 

contain Inoceramus crippsi Mantell, a species found 

mostly in lower and middle Cenomanian rocks of 

Europe. Cores from depths of 220.7-240 m contain Inoceramus prefragilis Stephenson, a species restricted 

to the ammonite zones of Plesiacanthoceras 

wyomingense (Reagan) and Dunveganoceras pondi 

Haas in the Western Interior. These ammonites, which 

developed out of Acanthoceras, seem best assigned a 

late Cenomanian age. The boundary between the middle and upper Cenomanian is probably near a depth 

of 240 m in the borehole.

The boundary between the Cenomanian and Turonian 

seems best placed at a depth of about 180 m, which 

lies about at the top of the range of Inoceramus pictus 

J. de C. Sowerby and base of the range of Mytiloides. 

Ammonites associated with I. pictus in cores from 

depths of 181.1-184.7 m include Scaphites (Pteroscaphites) minutus Moreman, Worthoceras vermiculum 

(Shumard), and Allocrioceras annulatum (Shumard), 

which are restricted to the zone of Sciponoceras gracile 

(Shumard). This zone is usually regarded as the top 

of the Cenomanian (for example Kennedy and Hancock, 

1976, p. 5.16; 1977, p. 134-136).

The boundary between the lower and middle Turonian lies near the top of the Greenhorn Formation. Collignoniceras woollgari regulare (Haas), which occurs in 

the cores of the basal part of the Carlile Shale at depths 

of 155-160.9 m, is a middle Turonian ammonite (Cobban 

and Hook, 1979, p. 12). Mytiloides mytiloides (Mantell), 

found in cores from the upper part of the Greenhorn 

Formation at depths of 164-171.4 m, is usually regarded 

as a guide fossil to the lower Turonian although the 

species overlaps the lower range of C. woollgari. 

Mytiloides subhercynicus (Seitz) occurs in cores from 

depths of 167.1-168.4 m. Inasmuch as this fossil is found 

with both the early (woollgari woollgari) and late 

(woollgari regulare) forms of C. woollgari, the boundary between the lower and middle Turonian is probably 

best placed at a depth of about 168 m.

The boundary between the middle and upper Turonian lies somewhere between depths of 136-155 m. 

Megafossils were not found in the cores from those 

depths. A core from a depth of 155 m has Collignoniceras woollgari regulare (Haas) of middle Turonian 

age, and a core from a depth of 136 m has Scaphites 

warreni Meek and Hay den of early late Turonian age.

The boundary between the Turonian and Coniacian 

is placed at the lowest occurrence of Cremnoceramusl 

waltersdorfensis (Andert) and C? rotundatus (Fiege) 

following the proposals by Kauffman, Cobban, and 

Eicher (1976 p. 23.16). This is at a depth of about 70 

m. The next lower control point is a core from a depth 

of 76 m that contains Mytiloides fiegei fiegei (Troger) 

of late Turonian age.

MOLLUSCAN ZONES

Fossils from the lowest part of the core include Acanthoceras amphibolum Morrow and Inoceramus rutherfordi Warren, both restricted to the middle Cenomanian 

zone of A. amphibolum. That ammonite has long been 

accepted as a guide fossil to one of the Western Interior 

Cenomanian zones (Cobban, 1951a, p. 2197; Cobban and 

Reeside, 1952a, p. 1017). The top of the zone is placed 

at a depth of 248 m in the borehole.

Plesiacanthoceras wyomingense (Reagan) marks the 

next Cenomanian zone above that of A. amphibolum 

in the Western Interior. The zone of P. wyomingense 

was originally recorded as the zone of Acanthoceras^ 

n. sp. (Cobban, 1951a, p. 2197), next as the zone of 

Acanthoceras'! sp. A (Cobban and Reeside, 1952a, p. 

1017), later as the zone of Acanthocerast wyomingense 

(Cobban, 1958, p. 117-119), and finally as the zone of 

Plesiacanthoceras wyomingense (Merewether and Cobban, 1972, p. D59). On outcrops in the vicinity of the 

borehole, a disconformity separates the Belle Fourche
METERS 

0

i MOLLUSCAN FOSSILS 

BIVALVES AMMONITES

FIGURE 1. Ranges of most of the bivalves and ammonites in the cores from the borehole in 

sec. 30, T. 46 N., R. 63 W., Weston County, Wyo.
MOLLUSCAN RECORD FROM MID-CRETACEOUS BOREHOLE, WYOMING

Shale from the overlying Greenhorn Formation, and P. 

wyomingense, which normally should be in the uppermost Belle Fourche Shale, is missing.

In the Western Interior, the ammonite Dunveganoceras pondi Haas marks the next Cenomanian 

zone above that of P. wyomingense. The zone of D. 

pondi (Cobban, 1951a, p. 2197) is best documented in 

the lower part of the Greenhorn Formation in the central Great Plains and in the equivalent part of the Fron 

tier Formation of Wyoming, where the upper part of 

the range of Inoceramus prefragilis Stephenson overlaps the range of D. pondi. Dunveganoceras pondi was 

not found in the cores from the borehole, but /. prefragilis occurs in the cores from the lower part of the 

Greenhorn Formation at depths of 221-240 m, and this 

interval is assumed to represent the zone of D. pondi.

The zone of Dunveganoceras albertense (Warren) 

(Cobban, 1951a, p. 2197) is the next Cenomanian zone 

above that of D. pondi in the Western Interior. Guide 

fossils to the zone of D. albertense include Inoceramus 

ginterensis Pergament and Metoicoceras mosbyense 

Cobban, which occur in the cores from depths of 192.5- 

199 m and 216 m, respectively. Inoceramus pictus pictus, which may be restricted to the overlying zone of 

Sciponoceras gracile (Shumard), occurs in a core at a 

depth of 189 m, and, accordingly, the zone of D. albertense probably extends from about 190-221 m.

The latest Cenomanian zone of Sciponoceras gracile 

(Shumard) (Cobban, 195la, p. 2197) occupies the interval 181-190 m in the borehole. Characteristic ammonites of this zone in the cores include Allocrioceras annulatum (Shumard), Worthoceras vermiculum 

(Shumard), and Scaphites (Pteroscaphites) minutus 

Moreman found at depths of 181.1-184.7 m. The zone 

is extended to a depth of 189 m because of the presence 

of Inoceramus pictus pictus in cores from depths of 

185-189 m.

Owing to the lack of ammonites and the fragmentary 

state of the inoceramids in the cores from the upper 

part of the Greenhorn Formation at depths of 164-180 

m, well-defined early Turonian zones, like those at 

Pueblo, Colo. (Cobban and Scott, 1972, p. 31, 32), cannot be satisfactorily determined for the borehole. The 

inoceramids, however, reveal at least two early Turonian zones, a lower one of Mytiloides aff. M. duplicostatus (Anderson) and an upper one of M. mytiloides 

(Mantell). The first clearly defined zone 

above the Greenhorn Formation is that of Collignoniceras woollgari regulare (Haas) in the cores from 

depths of 155-160.9 m.

Lack of mollusks in the 19 m of Carlile Shale overlying the highest occurrence of C. woollgari regulare in 

the borehole prevents the recognition of other middle 

Turonian zones, such as that of Scaphites carlilensis

Morrow-Prionocyclus hyatti (Stanton) (Cobban, 1951a, 

p. 2197). A single specimen of Scaphites warreni Meek 

and Hayden at a depth of 136 m reveals the presence 

of this late Turonian zone, but the thickness of the zone 

cannot be determined. Likewise, the occurrence of 

Prionocyclus novimexicanus (Marcou) in a core at a 

depth of 106.1 m indicates the zone of Scaphites whitfieldi Cobban (1951a, p. 2197), but the thickness is unknown. The next younger Turonian scaphite zone, that 

of Scaphites nigricollensis Cobban (1951a, p. 2197), is 

well represented in the cores from the depths of 96-104 

m, and the youngest Turonian scaphite zone of S. corvensis Cobban is indicated by the presence of specimens 

in the cores of the lower part of the Sage Breaks Member of the Carlile Shale at depths of 76-81 m. The zone 

of S. corvensis should extend lower inasmuch as the 

scaphite also occurs in the upper part of the Turner 

Sandy Member at outcrops in the Black Hills area. 

Above this scaphite zonation, the only molluscan zone 

that can be recognized in the cores is the early Coniacian zone of Cremnoceramusl waltersdorfensis (Andert) at depths of 32-70 m.

MEGAFOSSIL CONTENT

Megafossils, chiefly mollusks, were collected from 

cores at the following depths. The first number is the 

USGS Mesozoic locality number, and the second is the 

depth.

CARLILE SHALE 

SAGE BREAKS MEMBER

D9982. 32-33 m. Calcareous shale.

Phelopteria sp.

Cremnoceramusl waltersdorfensis (Andert)

Lucina sp. 

D9983. 33.5-35 m. Calcareous shale.

Nucula (Pectinucula) sp.

Nuculana sp.

Striarca sp.

Cremnoceramusl waltersdorfensis (Andert).

Scaphites sp. 

D9984. 35.5-36.5 m. Slightly calcareous to noncalcareous shale.

calcareous worm tubes

Nucula (Pectinucula) sp.

Striarca sp.

Cremnoceramusl waltersdorfensis (Andert).

Baculites sp. 

D9985. 38.9-39.6 m. Slightly calcareous shale.

Cremnoceramusl rotundatus (Fiege). 

D9986. 40.2-42.1 m. Slightly calcareous to noncalcareous shale.

Cremnoceramusl waltersdorfensis (Andert)

Pholadomya sp. 

D9987. 45-^5.2 m. Slightly calcareous shale.

Cremnoceramusl walterdorfensis (Andert)

Veniella goniophora Meek

Baculites yokoyamai Tokunaga and Shimizu
MEGAFOSSIL CONTENT

D9988. 47.9 m. Very slightly calcareous shale.

Pseudoperna sp.

Baculites yokoyamai Tokunaga and Shimizu 

D9989. 52.7 m. Noncalcareous shale.

Compressed, indeterminate mesogastropod 

D9990. 57.2 m. Noncalcareous shale.

Nuculana sp.

Baculites sp. 

D9991. 69.9 m. Noncalcareous shale.

Cremnoceramusl waltersdorfensis (Andert)

C.I rotundatus (Fiege) 

D9992. 76-76.7m. Noncalcareous shale.

Mytiloidesfiegeifiegei (Troger)

Scaphites corvensis Cobban 

D9993. 78.7-79.8 m. Noncalcareous shale.

Calcareous worm tube

Nucula (Pectinucula) sp.

Striarca sp.

Veniella goniophora Meek

Corbulid

Scaphites corvensis Cobban 

D9994. 80.6-81.2 m. Slightly calcareous to noncalcareous shale.

Mytiloidesfiegeifiegei (Troger)

Compressed incomplete aporrhaid gastropod

Scaphites corvensis Cobban 

D9995. 81.7-82 m. Slightly calcareous to noncalcareous shale.

Phelopteria sp.

Cremnoceramusl cf. C.I rotundatus (Fiege)

Baculites sp.

Prionocyclus sp. 

D9996. 84.8-84.9 m. Noncalcareous shale.

Mytiloides cf. M. dresdensis labiatoidiformis (Troger)

Scaphites sp.

TURNER SANDY MEMBER

D9997. 85.5-86.6 m. Bioturbated argillaceous siltstone.

Mytiloides fiegei mytiloidiformis (Troger)

Amauropsisl sp.

Baculites yokoyamai Tokunaga and Shimizu

D9998. 87-88.9 m. Bioturbated argillaceous siltstone and very fine 

grained sandstone.

Mytiloidesfiegeifiegei (Troger)

M. fiegei mytiloidiformis (Troger)

Veniella goniophora Meek

Barnacle plate

D9999. 90.1-91 m. Bioturbated siltstone and very fine grained sandstone.

Mytiloidesfiegeifiegei (Troger)

Baculites yokoyamai Tokunaga and Shimizu 

D10000. 92.2-93.6 m. Bioturbated argillaceous siltstone.

Striarcat sp.

Mytiloidesfiegeifiegei (Troger)

Baculites yokoyamai Tokunaga and Shimizu 

D10001. 95.8-97.4 m. Bioturbated siltstone.

Nuculana sp.

Amauropsis bulbiformis Stanton, non Sowerby

Baculites yokoyamai Tokunaga and Shimizu

Scaphites nigricollensis Cobban

Prionocyclus sp. 

D10002. 97.8-100 m. Bioturbated siltstone.

Nuculana sp.

Mytiloidesfiegeifiegei (Troger)

Bellifususl sp.

Baculites yokoyamai Tokunaga and Shimizu

Prionocyclus sp.

D10003. 100.9-102.4 m. Bioturbated siltstone.

Mytiloidesfiegeifiegei (Troger)

Bellifususl sp.

Baculites yokoyamai Tokunaga and Shimizu

Scaphites sp. 

D10004. 103.1-104 m. Bioturbated siltstone.

Mytiloides fiegei mytiloidiformis (Troger)

Scaphites nigricollensis Cobban 

D10005. 104.2-105.3 m. Silty shale.

Inoceramus perplexus Whitfield

Amauropsis bulbiformis Stanton, non Sowerby

Gyrodes sp.

Baculites yokoyamai Tokunaga and Shimizu

Hoploparia sp. 

D10006. 106.1-106.4 m. Bioturbated very fine grained sandstone.

Nuculana sp.

Inoceramus perplexus Whitfield

Indeterminate neogastropod

Baculites yokoyamai Tokunaga and Shimizu

Prionocyclus novimexicanus (Marcou) 

D10007. 106.7-107.9 m. Bioturbated very fine grained sandstone.

Inoceramus perplexus Whitfield

Baculites yokoyamai Tokunaga and Shimizu 

D10008. 109-111.4 m. Bioturbated shaly siltstone.

Inoceramus perplexus Whitfield

Plicatula sp. 

D10009. 111.6-112.8 m. Noncalcareous shale.

Nuculana sp.

Inoceramus perplexus Whitfield

Entolium sp.

Prionocyclus sp. 

D10010. 114.6 m. Bioturbated sandy siltstone.

Inoceramus perplexus Whitfield 

D10011. 123.9-124.2 m. Noncalcareous shale.

Inoceramus perplexus Whitfield

Scaphites sp. 

D10012. 127.4 m. Very fine grained sandstone.

Prionocyclus sp. 

D10013. 136 m. Noncalcareous shale.

Scaphites warreni Meek and Hayden

POOL CREEK MEMBER

D10014. 155 m. Calcareous shale.

Pseudoperna bentonensis (Logan)

Collignoniceras woollgari regulare (Haas) 

D10015. 155.7-155.8 m. Noncalcareous to slightly calcareous shale.

Collignoniceras woollgari regulare (Haas) 

D10016. 157-157.9 m. Noncalcareous shale.

Collignoniceras woollgari regulare (Haas) 

D10017. 160.9 Calcareous shale.

Collignoniceras woollgari regulare (Haas)

GREENHORN FORMATION

D10018. 164-164.2 m. Calcareous shale and calcarenite.

Mytiloides mytiloides (Mantell) 

D10019. 164.9 m. Calcareous shale and calcarenite.

Mytiloides mytiloides (Mantell) 

D10020. 167.1-167.6 m. Argillaceous limestone.

Mytiloides mytiloides (Mantell)

M. subhercynicus (Seitz)

M. opalensis (Bose) 

D10021. 168-168.4 m. Argillaceous limestone.

Mytiloides mytiloides (Mantell)

M. subhercynicus (Seitz)
MOLLUSCAN RECORD FROM MID-CRETACEOUS BOREHOLE, WYOMING

D10022. 168.7-168.9 m. Argillaceous limestone.

Mytiloides mytiloides (Mantell) 

D10023. 169.2 m. Argillaceous limestone.

Mytiloides mytiloides (Mantell) 

D10024. 169.5-169.8 m. Argillaceous limestone.

Mytiloides mytiloides (Mantell) 

D10025. 170.5-171.4 m. Calcareous shale and calcarenite.

Mytiloides mytiloides (Mantell)

M. opalensis (Bose). 

D10026. 171.7-172 m. Calcareous shale.

Mytiloides aff. M. duplicostatus (Anderson) 

D10027. 172.6-173.4 m. Calcareous shale.

Mytiloides aff. M. duplicostatus (Anderson)

M. sp. (fine growth lines) 

D10028. 176.3 m. Speckled limestone.

Mytiloides aff. M. duplicostatus (Anderson) 

D10029. 178.7-178.9 m. Calcareous shale.

Mytiloides sp. (fine growth lines)

M. opalensis (Bose) 

D10030. 179.3-179.4 m. Calcareous shale.

Mytiloides sp. (fine growth lines)

Inoceramus cf. /. pictus J. de C. Sowerby 

D10031. 181.1-181.7 m. Calcareous shale.

Solitary coral

Phelopteria sp.

Inoceramus pictus neocaledonicus Jeannet

Baculitesl sp.

Scaphites (Pteroscaphites) minutus Moreman

Worthoceras sp. 

D10032. 182.7-182.9 m. Calcareous shale.

Inoceramus pictus neocaledonicus Jeannet

Baculitesl sp.

Worthoceras sp. 

D10033. 183.2-184.7 m. Calcareous shale.

Inoceramus pictus neocaledonicus Jeannet

Sciponocerasl sp.

Allocrioceras annulatum (Shumard)

Worthoceras vermiculum (Shumard)

Metoicoceras sp. 

D10034. 185.1 m. Noncalcareous shale.

Inoceramus pictus pictus J. de C. Sowerby 

D10035. 185.9-186.2 m. Noncalcareous shale.

Phelopteria minuta Kauffman and Powell

Inoceramus pictus neocaledonicus Jeannet

D10036. 186.6-186.8 m. Noncalcareous shale.

Phelopteria minuta Kauffman and Powell

Inoceramus pictus pictus J. de C. Sowerby 

D10037. 187.1-188.1 m. Noncalcareous shale.

Phelopteria minuta Kauffman and Powell

Inoceramus pictus pictus J. de C. Sowerby 

D10038. 188.6-188.9m. Noncalcareous shale.

Inoceramus pictus pictus J. de C. Sowerby 

D10039. 189.6-189.7m. Noncalcareous shale.

Inoceramus pictus pictus J. de C. Sowerby 

D10040. 190.4-190.6 m. Calcareous to noncalcareous shale.

Inoceramus pictus neocaledonicus Jeannet 

D10041. 192.5 m. Calcareous to noncalcareous shale.

Inoceramus ginterensis Pergament 

D10042. 194.2 m. Calcareous to noncalcareous shale.

Inoceramus ginterensis Pergament

D10043. 194.6 m. Noncalcareous shale. 

Phelopterial sp. 

Inoceramus sp. 

Juvenile ammonites

D10044. 195.6-195.9 m. Noncalcareous shale.

Inoceramus flavus pictoides Sornay

Metaptychoceras reesidei (Cobban and Scott) 

D10045. 197-197.1 m. Calcareous to noncalcareous shale.

Inoceramus ginterensis Pergament

7. cf. /. pictus bohemicus Leonhard 

D10046. 197.7-198.1 m. Noncalcareous shale.

Inoceramus ginterensis Pergament

Hamites (Stomohamites) simplex d'Orbigny 

D10047. 198.1-198.9 m. Slightly calcareous shale.

Inoceramus ginterensis Pergament.

Entolium sp.

Astarte sp.

Neocardioceras sp. 

D10048. 199.1-199.3 m. Calcareous to noncalcareous shale.

Inoceramus sp.

Neocardioceras sp.

Metoicoceras sp.

D10049. 199.8-200 m. Calcareous to noncalcareous shale.

Inoceramus sp.

Entolium sp.

Metaptychoceras reesidei (Cobban and Scott)

Neocardioceras sp. 

D10050. 200.6-201.5 m. Calcareous to noncalcareous shale.

Inoceramus ginterensis Pergament

Entolium sp.

Minute bivalve

Metaptychoceras sp.

Neocardioceras sp. 

D10051. 201.5-202.7 m. Calcareous to noncalcareous shale.

Inoceramus ginterensis Pergament

Immature archeogastropod, possibly Calliomphalus

Euspiral sp.

Metaptychoceras reesidei (Cobban and Scott)

Hamites (Stomohamites) simplex d'Orbigny

Neocardioceras sp. 

D10052. 203.1-204.1 m. Noncalcareous shale.

Inoceramus ginterensis Pergament

/. sp. 

D10053. 204.5-204.9 m. Calcareous to noncalcareous shale.

Inoceramus ginterensis Pergament

Entolium sp.

Metaptychoceras reesidei (Cobban and Scott)

Neocardioceras sp.

D10054. 207.9 m. Slightly calcareous shale.

Inoceramus ginterensis Pergament 

D10055. 209.9-210.2 m. Slightly calcareous to noncalcareous shale.

Inoceramus sp.

Metoicoceras sp. 

D10056. 210.3-210.9 m. Slightly calcareous to noncalcareous shale.

Inoceramus sp.

Moremanoceras sp. 

D10057. 211.2-211.5 m. Slightly calcareous to noncalcareous shale.

Inoceramus sp.

Entolium sp.

D10058. 211.8-211.9 m. Calcareous to noncalcareous shale.

Inoceramus sp.

Entolium sp.

Neocardioceras sp.

Moremanoceras sp. 

D10059. 212.1-212.8 m. Slightly calcareous shale.

Entolium sp.

Hamites (Stomohamites) simplex d'Orbigny

Metoicoceras sp.
MEGAFOSSIL CONTENT

Neocardioceras sp.

Ammonite undet. 

D10060. 214.1 m. Calcareous shale.

Entolium sp. 

D10061. 215.9-216.8 m. Slightly calcareous to noncalcareous shale.

Inoceramus cf. 7. flavus Sornay

Entolium sp.

Astarte sp.

Hamites (Stomohamites) simplex d'Orbigny

Metoicoceras cf. M. mosbyense Cobban

Neocardioceras sp. 

D10062. 218.2-218.3 m. Noncalcareous shale.

Nuculana sp.

Astarte sp.

Hamites (Stomohamites) sp.

Metoicoceras sp. 

D10063. 218.5-219 m. Noncalcareous shale; pyritic fossils.

Astarte sp.

Hamites (Stomohamites) simplex d'Orbigny

Neocardioceras sp.

D10064. 219.5-219.9 m. Noncalcareous to slightly calcareous shale; 

pyritic fossils.

Nuculana sp.

Astarte! sp.

Crenellal sp.

Hamites (Stomohamites) sp.

Dunveganocerast sp.

Neocardioceras sp. 

D10065. 220.1-220.5 m. Noncalcareous shale; pyritic fossils.

Astarte sp.

Hamites (Stomohamites) simplex d'Orbigny

Neocardiocras sp. 

D10066. 220.7-221.8 m. Noncalcareous shale; pyritic fossils.

Inoceramus prefragilis Stephenson

Hamites (Stomohamites) simplex d'Orbigny

Metoicoceras sp.

D10067. 222.7-222.8 m. Noncalcareous shale; pyritic fossils.

Inoceramus prefragilis Stephenson

Hamites (Stomohamites) simplex d'Orbigny

Moremanoceras sp. 

D10068. 223.1-223.3 m. Noncalcareous shale; pyritic fossils.

Hamites (Stomohamites) simplex d'Orbigny

Ammonite (new genus?)

D10069. 223.5-224 m. Noncalcareous shale; pyritic fossils.

Inoceramus prefragilis Stephenson

Hamites (Stomohamites) simplex d'Orbigny

Moremanoceras n. sp.

Borissiakoceras sp. 

D10070. 224.2-224.6 m. Noncalcareous shale; pyritic fossils.

Hamites (Stomohamites) simplex d'Orbigny

Moremanoceras sp.

Neocardioceras sp. 

D10071. 224.9-225.5 m. Slightly calcareous shale.

Entolium sp.

Hamites (Stomohamites) simplex d'Orbigny

Moremanoceras sp.

Neocardioceras sp. 

D10072. 225.8-226.5 m. Noncalcareous shale; pyritic fossils.

Inoceramus cf. /. prefragilis Stephenson

Astartel sp.

Hamites (Stomohamites) sp.

Neocardioceras sp.

Borissiakoceras sp.

D10073. 226.6-227.1 m. Noncalcareous to calcareous shale; pyritic fossils.

Hamites (Stomohamites) sp.

Neocardioceras sp.

Borissiakoceras cf. B. orbiculatum Stephenson 

D10074. 227.7-228.2 m. Noncalcareous to slightly calcareous shale; 

pyritic fossils.

Inoceramus cf. /. prefragilis Stephenson

Hamites (Stomohamites) simplex d'Orbigny

Neocardioceras sp.

Borissiakoceras cf. B. orbiculatum Stephenson 

D10075. 228.4-229.1 m. Slightly calcareous shale; pyritic fossils.

Inoceramus sp.

Entolium sp.

Hamites (Stomohamites) simplex d'Orbigny

Neocardioceras sp.

Borissiakoceras cf. B. orbiculatum Stephenson 

D10076. 229.2-229.5 m. Calcareous shale; pyritic fossils.

Inoceramus sp.

Entolium sp.

Hamites (Stomohamites) simplex d'Orbigny

Neocardioceras sp.

Borissiakoceras cf. B. orbiculatum Stephenson 

D10077. 229.8-230.4 m. Calcareous shale.

Inoceramus sp.

Entolium sp.

Hamites (Stomohamites) simplex d'Orbigny

Neocardioceras sp.

Borissiakoceras cf.B. orbiculatum Stephenson 

D10078. 231-231.4 m. Calcareous to noncalcareous shale.

Lingula sp.

Minute bivalve

Arrhoges"! sp.

Hamites (Stomohamites) simplex d'Orbigny

Neocardioceras sp.

Metoicoceras sp.

Borissiakoceras sp. 

D10079. 231.6-232.4 m. Calcareous shale.

Inoceramus prefragilis Stephenson

Hamites (Stomohamites) simplex d'Orbigny

Neostlingoceras kottlowskii Cobban and Hook

Neocardioceras sp.

Borissiakoceras sp.

Metoicoceras sp. 

D10080. 239.9-233.4 m. Calcareous shale.

Inoceramus prefragilis Stephenson

Hamites (Stomohamites) simplex d'Orbigny

Borissiakoceras sp. 

D10081. 234.2-234.7 m. Calcareous shale.

Hamites (Stomohamities) simplex d'Orbigny

Neocardioceras sp.

Borissiakoceras sp. 

D10082. 235.3-237.2 m. Calcareous shale.

Inoceramus sp.

Minute bivalve

Hamites (Stomohamites) simplex d'Orbigny

Moremanoceras sp.

Neocardioceras sp.

Borissiakoceras sp. 

D10083. 237.7-239.1 m. Noncalcareous to calcareous shale.

Inoceramus crippsi Mantell

Minute bivalve

Hamites (Stomohamites) simplex d'Orbigny

Neocardioceras sp.

Borissiakoceras sp.
MOLLUSCAN RECORD FROM MID-CRETACEOUS BOREHOLE, WYOMING

D10084. 239.3-240 m. Calcareous shale.

Inoceramus prefragilis Stephenson

Minute bivalve

Moremanoceras sp.

Borissiakoceras sp.

Shark tooth 

D10085. 240.3-240.7m. Noncalcareous shale.

Solemya sp.

Pleuriocardia sp. 

D10086. 241.1-241.7m. Noncalcareous shale.

Pleuriocardia sp.

Indeterminate neogastropod

Hamites sp. 

D10087. 242.3-243.8 m. Noncalcareous shale.

Lingula sp.

Solemya sp.

Inoceramus sp.

Pleuriocardia sp.

Compressed indeterminate neogastropod

Hamites sp. 

D10088. 243.8-246 m. Noncalcareous shale; pyritic fossils.

Solemya sp.

Inoceramus crippsi Mantell

Minute bivalve

Immediate post-larval stages of a probable aporrhaid 

gastropod

Hamites sp.

Borissiakoceras reesidei Morrow

Acanthoceras sp. 

D10089. 246-247.5 m. Noncalcareous shale, pyritic fossils.

Lingula sp.

Solemya sp.

Minute bivalve

Immediate post-larval stages of probable aporrhaid

gastropod 

D10090. 247.5-248.2 m. Slightly calcareous shale.

Minute bivalve

Juvenile aporrhaid gastropod

Hamites (Stomohamites) simplex d'Orbigny

Acanthoceras amphibolum Morrow

Borissiakoceras reesidei Morrow 

D10091. 248.6-249.1 m. Noncalcareous to slightly calcareous shale.

Lingula sp.

Inoceramus sp.

Hamites sp.

Acanthoceras amphibolum Morrow

Borissiakoceras sp.

BELLE FOURCHE SHALE

D10092. 252.8-253.3 m. Noncalcareous shale.

Inoceramus rutherfordi Warren 

D10093. 254.5-254.8 m. Noncalcareous shale.

Inoceramus sp.

Acanthoceras amphibolum Morrow 

D10094. 255.9 m. Noncalcareous shale.

Ostrea beloiti Logan 

D10095. 256.4-257.3 m. Noncalcareous shale.

Inoceramus sp.

Ostrea beloiti Logan

Acanthoceras sp. 

D10096. 257.6-257.7 m. Noncalcareous shale.

Inoceramus sp.

Ostrea beloiti Logan

D10098. 258.3-258.6 m. Noncalcareous shale.

Inoceramus sp.

Small thin-shelled bivalve 

D10099. 261.8 m. Noncalcareous shale.

Parmicorbula sp. 

D10100. 262.1 m. Noncalcareous shale.

Inoceramus sp. 

D10101. 265 m. Noncalcareous shale.

Inoceramus rutherfordi Warren

CHARACTERISTIC FOSSILS

Common or important molluscan fossils are briefly 

described and illustrated. The paper is not intended as 

a detailed systematic work but rather as a general overview of the subsurface mid-Cretaceous fossil record at 

one locality in the Powder River Basin. New species 

are not described or formally named, and synonomies 

are limited to the original papers and one or two later 

papers that have good illustrations or important 

changes in names of taxa.

Inoceramids and ammonites are the most biostratigraphically important mollusks in the cores. Owing to 

the large size of the adults of these fossils and the small 

diameter of the cores, only parts of the specimens are 

available for study, and many of them can only be assigned to genera.

Cremnoceramus? waltersdorfensis (Andert)

Plate 1, figure 1

Inoceramus walterdorfensis Andert, 1911, p. 53, pi. 5, figs. 2-5. 

Inoceramus walterdorfensis Andert. Troger, 1967, p. 114, pi. 12, figs.

1-4; pi. 13, figs. 1-9; text figs. 30, 31. 

Cremnoceratnusl waltersdorfensis (Andert). Kauffman, 1979, p. 59.

The juveniles of this subquadrate medium-sized 

species have closely spaced, subequal, strongly raised 

growth lines that curve sharply along the umbo-ventral 

axis of the shell. At a later growth stage, a few irregular rugae may occur with the raised growth lines. The 

posterior part of the shell is flattened, and the ornamentation tends to trend in a straight line across it.

Troger (1967, p. 114-120) recognized two forms of 

this species, waltersdorfensis waltersdorfensis Andert 

and waltersdorfensis hannovrensis Heinz. The latter 

was differentiated in having a higher and more erect 

form with a flatter cross section and more numerous 

rugae.

Several small inoceramids in the cores at depths of 

32-70 m have closely spaced, subequal, raised juvenile 

growth lines that usually bend conspicuously along the 

umbo-ventral axis. These specimens seem to be C? waltersdorfensis although they are too few and fragmentary for positive assignment to either of Troger's subspecies.
CHARACTERISTIC FOSSILS 9

Cremnoceramusl waltersdorfensis is widely distributed in rocks near the Turonian-Coniacian boundary in 

Europe, Asia, and North America. Until the last few 

years, the species has been regarded of late Turonian 

age (for example Andert, 1934, p. 114; Troger, 1967, 

p. 117), but with the recent move to consider the Turonian-Coniacian boundary at a lower level (summarized 

by Seibertz, 1979), C.I walterdorfensis falls in the basal 

Coniacian (Kauffinan and others, 1976, p. 23.16). The 

species has been used as a guide fossil for the basal 

Coniacian faunal zone in the Western Interior 

(Merewether and others, 1976, p. 38; Merewether and 

others, 1979, p. 70).

Type. Hypotype USNM 308017.

Cremnoceramus? rotundatus (Fiege)

Plate 1, figures 2, 3,

Inoceramus inconstans rotundatus Fiege, 1930, p. 42, pi. 7, fig. 32;

pi. 8, fig. 31; text fig. 3. 

Inoceramus rotundatus Fiege. Troger, 1967, p. 110, pi. 12, figs. 5,

6; pi. 13, figs. 10-13; text fig. 29. 

Cremnoceramus'! rotundatus (Fiege). Kaufftnan, 1979, p. 68, pi. 9,

figs. A, C.

Cremnoceramusl rotundatus is closely related to C.? 

walterdorfensis and, like that species, it has closely and 

regularly spaced raised growth lines on the umbo. 

Cremnoceramus'! rotundatus differs, however, in having a more convex shell ornamented by closely spaced 

conspicuous rugae. The posterior side is flattened, and 

the rugae trend fairly straight across it.

Specimens that seem referable to C.I rotundatus 

occur in the cores at depths between 35.4 and 70 m. 

A fragment of a large specimen on which calcareous 

worm tubes are attached (pi. 1, fig. 2), closely resembles 

one of the types (Fiege, 1930, pi. 7, fig. 32).

Cremnoceramusl rotundatus was originally described from Germany. The species is known from many 

localities in Europe and North America. Although the 

species was considered of late Turonian age at first, 

it is now assigned to the base of the Coniacian 

(Kauffman and others, 1976, p. 23.16; Seibertz, 1979, 

p. 116).

Types. Hypotypes USNM 308018, 308019.

Mytiloides fiegei fiegei (Troger)

Plate 1, fig. 10

Inoceramus inconstans inconstans Woods. Fiege, 1930, p. 38, pi.

5, figs. 16, 17; pi. 6, figs. 18, 19. 

Inoceramus fiegei fiegei Troger, 1967, p. 105, pi. 13, figs. 14, 15,

17, 20; pi. 11, fig. 3. 

Mytiloides fiegei fiegei (Troger). Kauffman, 1977, p. 180.

This flattened inoceramid has a rounded outline and 

a distinctive ornamentation that consists of equally

spaced concentric rugae separated by several equally 

spaced raised growth lines. The species is closely allied 

to, if not conspecific with, Inoceramus incertus Jimbo 

(1894, p. 43, pi. 8, fig. 7) as amended and illustrated 

by Nagao and Matsumoto (1940, p. 10, pi. 3, figs. 1-5; 

pi. 10, fig. 2). Jimbo's illustration (drawing) of the type 

specimen shows an elongate form, whereas Nagao and 

Matsumoto's illustrations are of rounded and prosocline 

forms. Although specimens from the Western Interior 

have been compared to /. incertus (Merewether and 

Cobban, 1972, p. D59; Merewether and others, 1975, 

p. 75; Merewether and others, 1976, p. 38), or reported 

as /. incertus (Merewether, 1980, p. 12), they are probably better assigned to the more clearly defined European species M. fiegei fiegei. Specimens referable to 

M. fiegei fiegei occur in cores of Carlile Shale from the 

borehole at depths of 76-102 m.

Mytiloides fiegei was described from the upper Turonian of Germany. The species occur at the top of the 

Turonian in the Western Interior (Kauffman and 

others, 1976, p. 23.16).

Types. Rypotypes USNM 308024, 308025.

Mytiloides fiegei mytiloidiformis (Troger)

Plate 1, figs. 8, 9, 11, 12; plate 2, fig. 12

Inoceramus inconstans inconstans Woods. Fiege, 1930, p. 38. pi.

6, fig. 19. 

Inoceramus fiegei mytiloidiformis Troger, 1967, p. 108, pi. 11, fig.

4; pi. 13, figs. 16, 18.

This subspecies differs from the typical form of the 

species in having a more elongate form. Specimens referable to it occur in the cores of the Turner Sandy 

Member of the Carlile Shale at depths from 85.5 to 

104m.

The holotype of M. fiegei mytiloidiformis is from the 

upper Turonian of Germany. An example from the uppermost part of the Carlile Shale of south-central Colorado was illustrated by Kauffman (in Kauffman and 

others, 1976, pi. 14, fig. 4).

Types. Hypotypes USNM 308024, 308026-508028, 

308044.

Mytiloides mytiloides (Mantell)

Plate 2, figures 14, 15

Inoceramus mytiloides Mantell, 1822, p. 215, pi. 28, fig. 2. 

Mytiloides mytiloides (Mantell). Kauffman and Powell, 1977, p. 74, 

pi. 6, figs. 11-16.

An elongate form, low convexity, presence of a posterior auricle, and distinctive ornamentation or more 

or less evenly spaced rugae separated by numerous 

raised growth lines characterize this lower Turonian
10 MOLLUSCAN RECORD FROM MID-CRETACEOUS BOREHOLE, WYOMING

species. The axis of the shell forms an angle of about 

40°-50° to the straight hinge line.

The species is abundant in the upper part of the 

Greenhorn Formation in the Great Plains region and 

in equivalent nearshore sandstone beds farther west. 

Near the site of the borehole, M. mytiloides was collected llm below the top of the Greenhorn Formation 

(Merewether, 1980, p. 7). Specimens are abundant in 

cores from the borehole in thin beds of limestone in 

the Greenhorn Formation at depths of 164-171 m.

Mytiloides mytiloides was originally described from 

the Middle Chalk of England. The species is most abundant in the upper part of the lower Turonian, but it 

ranges up into the lower part of the middle Turonian. 

In the literature, most records of Inoceramus labiatus 

(Schlotheim) are probably M. mytiloides. Specimens 

identified as I. labiatus have been recorded from Turonian rocks over most of the world. In the Western Interior, M. mytiloides has been recorded from northern 

Montana (Cobban and others, 1976, p. 41-44) south into 

New Mexico (Hook and Cobban, 1980, p. 43).

Types. Hypotypes USNM 308046, 308047.

Mytiloides opalensis (Bose)

Plate 2, figures 10, 11

Inoceramus opalensis Bose, 1923, p. 184, pi. 13, figs. 1-3. 

Mytiloides opalensis (Bose). Kauffman and Powell, 1977, p. 79, pi. 

6, figs. 3, 6.

Bose illustrated two moderately prosocline specimens 

that have very low convexity, an inflated ovate outline, 

and broadly rounded concentric ornament. One specimen has prominent equally spaced growth lines on the 

earlier part of the shell and low rugae on the later part, 

whereas the other specimen has nearly equally spaced 

rugae over the entire shell and equally spaced growth 

lines on much of the shell. Rose's specimens came from 

Turonian rocks at Opal, Zacatecas, Mexico.

Specimens that resemble one or the other of Rose's 

types occur in the cores of the Greenhorn Formation 

from the borehole at depths of 167-179 m.

Types. Hypotypes USNM 308042, 308043.

Mytiloides aff. M. duplicostatus (Anderson)

Plate 2, figure 13

Mytiloides sp. aff. M. duplicostatus (Anderson). Kauffman and Powell, 1977, p. 81, p. 6, fig. 5; pi. 7, figs. 2, 6.

This prosocline ovate species has a low covexity, long 

hingeline, convex anterior side, and narrowly rounded 

beaks projecting above the hingelines at its anterior 

end. Ornament consists of fairly regularly spaced rugae 

that usually have two prominent growth lines on their 

crests and as many as three raised growth lines in the 

rugae interspaces. The ornament resembles that of 

Mytiloides duplicostatus (Anderson, 1958, p. 100, pi.

17, figs. 3, 4) from Turonian rocks of California, but 

Anderson's species is more elongate.

Specimens that show affinities to M. duplicostatus 

occur in the cores of the Greenhorn Formation from 

the borehole at depths of 172-176 m.

Mytiloides aff. M. duplicostatus is abundant near the 

middle of the Rridge Creek Limestone Member of the 

Greenhorn Formation in the central Great Plains. The 

species is especially abundant and well preserved near 

Pueblo, Colo., in bed 97 of the published measured section, where the species is listed as Inoceramus labiatus 

(Cobban and Scott, 1972, p. 23). Ammonites from bed 

97 include Watinoceras coloradoense (Henderson) and 

Vascoceras (Greenhomoceras) birchbyi Cobban and 

Scott of early Turonian age. Mytiloides aff. M. duplicostatus is present in Survey collections from as far 

southwest as the Silver City area in southwestern New 

Mexico and as far south as Trans-Pecos, Texas.

Type. Figured specimen USNM 308045.

Mytiloides subhercynicus (Seitz)

Plate 2, figure 8

Inoceramus labiatiis var. subhercynica Seitz, 1934, p. 465, pi. 40, 

figs. 1-5; text fig. 18.

This broadly ovate, nearly equivalve, prosocline 

species has a moderately low convexity, fairly long 

hinge line, and very convex anterior margin. Reaks are 

low, rounded, and barely extend over the hinge line. 

The valves have a subcircular outline at first, and later 

become elongated. Ornament on the early part consists 

of nearly equally spaced raised growth lines. Later, 

closely spaced rugae form, which may have raised 

growth lines on them and (or) in the interspaces.

In the Western Interior, Mytiloides subhercynicus 

occurs in the uppermost part of the Greenhorn Formation and in the basal part of the Carlile Shale in the 

central Great Plains and in the equivalent rocks farther 

west. In the borehole, specimens that may be M. subhercynicus occur in the cores from the Greenhorn Formation at depths of 167-168.4 m.

Mytiloides subhercynicus was first decribed from 

Turonian rocks of Germany. The species also occurs in 

other countries in Europe and North America. In the 

Western Interior, M. subhercynicus occurs in the late 

early Turonian zone of Mammites nodosoides and in 

the overlying early middle Turonian zone of Collignoniceras woollgari (Mantell).

Type. Hypotype USNM 308040.

Mytiloides sp.

Plate 3, figure 1

A species of Mytiloides that has numerous closely 

spaced growth lines of irregular height on the early
CHARACTERISTIC FOSSILS 11

part of the valves occurs in the Greenhorn Formation 

in the cores from the borehole at depths of 172.6-179.4 

m. At later growth stages, ornamentation consists of 

irregular rugae with or without well-defined growth 

lines. The species is characteristic of bed 86 of the 

Bridge Creek Limestone Member at Pueblo, Colo. 

(Cobban and Scott, 1972, p. 23), where it was listed 

as Inoceramus labiatus (Schlotheim). Bed 86 lies only 

2.4 m above the top of the latest Cenomanian zone of 

Sciponoceras gracile (Shumard).

Type. Figured specimen USNM 308049.

Inoceramus pictus neocaledonicus Jeannet

Plate 3, figures 3, 4, 14

Inoceramus pictus J. de C. Sowerby. Woods, 1911, p. 279 (part), 

pi. 49, figs. 5, 6, not text fig. 36.

Inoceramus neocaledonicus Jeannet, 1922, p. 251, text fig. 5. 

Inoceramus pictus neocaledonicus Jeannet. Troger, 1967, p. 50, pi. 

4, fig. 4a, text fig. 13.

This subspecies is characterized by coarser and more 

widely spaced growth lines than those on Inoceramus 

pictus pictus, rugae are less conspicuous, and the early 

part of the shell has more evenly spaced growth lines. 

Specimens that seem referable to /. pictus 

neocaledonicus occur in the cores in the Greenhorn Formation at depths of 181-190 m.

Types. Hypotypes USNM 308051-308053.

Inoceramus pictus pictus J. de C. Sowerby

Plate 3, figures 5-7

Inoceramus pictus J. de C. Sowerby, 1829, p. 215, pi. 604, fig. 1. 

Inoceramus pictus J. de C. Sowerby. Woods, 1911, p. 279, text fig.

36 only. 

Inoceramus pictus pictus J. de C. Sowerby. Troger, 1967, p. 36.,

pi. 3, figs. 1-6; text figs. 6, 7.

This rather erect inequivalve species is moderately 

convex; it is higher than it is long, and the outline is 

subtriangular with a concave anterior side. Beaks are 

narrow, incurved, and project over the fairly short 

hinge line. Ornament consists of closely spaced raised 

growth lines and irregularly spaced rugae. The 

holotype, from the Chalk Marl of England, retains some 

of its original radial color bands; hence, the origin of 

its specific name.

Inoceramus pictus is widely distributed in the uppermost Cenomanian rocks of Europe, Africa, Australia, 

and North America. Several varietal and subspecific 

names have been proposed for this variable species. The 

neotype proposed by Moreman (1942, p. 197, pi. 32, 

figs. 1, 3) for Inoceramus capulus Shumard (1860, p. 

606) may be a subspecies of /. pictus. Moreman's specimen came from the late Cenomanian zone of Sciponoceras gracile in the Eagle Ford Formation of 

Texas.

In the Western Interior, Inoceramus pictus may be 

restricted to the zone of Sciponoceras gracile, which 

has been considered the top of the Cenomanian. The 

basal part of the Bridge Creek Limestone Member of 

the Greenhorn Formation in the central Great Plains 

lies in this zone. Cores from the borehole at depths 

of 185-189 m in the Greenhorn Formation contain inoceramids that seem referable to I. pictus pictus as 

restricted by Troger (1967).

Types. Hypotypes USNM 308054-508056.

Inoceramus cf. I. pictus bohemicus Leonhard

Plate 3, Figure 8

Inoceramus bohemicus Leonhard, 1897, p. 26, pi. 5, figs, la - c. 

Inoceramus pictus bohemicus Leonhard. Troger, 1967, p. 52, pi. 3, 

figs. 9-11; text fig. 14.

Leonhard illustrated two small specimens from the 

Cenomanian of Czechoslovakia. Both are ornamentated 

by closely spaced growth lines. One of them, illustrated 

by two views (Leonhard, 1897, pi. 5, figs. Ib, c), shows 

a low convexity profile and growth lines numbering 

about 27 in a distance of about 21.5 mm from the beak. 

A small flattened inoceramid (pi. 3, fig. 8) from the 

Greenhorn Formation at a depth of 197 m in the 

borehole resembles Leonhard's specimen in having 

numerous growth lines 29 in a distance of 17 mm from 

the beak.

Type. Figured specimen USMN 308057.

Inoceramus cf. I. pictus J. de C. Sowerby

Plate 2, figure 16

A flattened, suberect inoceramid that has conspicuous 

evenly and closely spaced raised growth lines on the 

early part of the valve and closely spaced rugae on the 

later part is represented by a single specimen from the 

Greenhorn Formation at a depth of 179.5 m. The 

growth lines and rugae curve more sharply than on figured specimens of /. pictus. The specimen may be 

transitional to Mytiloides.

Type. Figured specimen USNM 308048.

Inoceramus perplexus Whitfield

Plate 2, figures 1-3

Inoceramus perplexus Whitfield, 1877, p. 31.

Inoceramus perplexus Whitfield. Whitfield, 1880, p. 392, pi. 8, fig. 

3; pi. 10, figs. 4, 5.

This erect, nearly equivalve species is higher than 

long and has a subrectangular outline. The projecting 

beak is at the dorsoanterior corner. The anterior margin is steep and slightly concave. The hinge line is 

straight and fairly long. Ornament typically consists of 

rugae of irregular strength and spacing.

Inoceramus perplexus was originally described from
12 MOLLUSCAN RECORD FROM MID-CRETACEOlJS BOREHOLE, WYOMING

the Carlile Shale on the west flank of the Black Hills 

at a locality about 58 km northwest of the borehole. 

The species is abundant in limestone and sandstone concretions in the Turner Sandy Member of the Carlile 

Shale along the flanks of the Black Hills (Cobban, 

1951a, p. 2188; Mapel and Pillmore, 1964, p. J26). Near 

the site of the borehole, /. perplexus was collected from 

sandstone concretions 24 m below the top of the Turner 

Sandy Member (Merewether, 1980, p. 12). The bivalve 

occurs in cores of sandstone, siltstone, and silty shale, 

in the middle of the Turner Member at depths of 104- 

124 m in the borehole.

Inoceramus perplexus is present in many U.S. 

Geological Survey collections from rocks equivalent to 

the Turner Member from south-central Montana south 

to south-central New Mexico. The species is restricted 

to the upper Turonian.

Types. Hypotypes USNM 308033-^308035.

Inoceramus ginterensis Pergament

Plate 3, figures 10-12; plate 4, figure 1

Inoceramus ginterensis Pergament, 1966, p. 50, pi. 25, fig. 5; pi. 

26, figs. 1, 2; pi. 27, figs. 1, 2; pi. 28, figs. 1, 2; pi. 29, fig. 

1.

Inoceramus ginterensis is a suberect, inequivalve, 

slightly convex species that is higher than it is long. 

The outline is subrectangular to ovate with nearly 

straight to slightly concave anterior side. The beaks 

are at the anterior end and slightly project above the 

moderately long hinge line. A posterior auricle is present, although not well set off from the rest of the shell. 

Rugae of irregular height and spacing characterize the 

ornament. Fairly weak and irregular growth lines may 

be present, especially on the umbonal part.

Inoceramus ginterensis was originally described from 

Cenomanian rocks on the Pacific side of the USSR: Pergament (1966) presented many good illustrations. The 

species is widely distributed in the Western Interior 

in the late Cenomanian zone of Dunveganoceras albertense (Warren). Specimens have been illustrated from 

the Hartland Shale Member of the Greenhorn Formation of western Oklahoma (Kauffman and Powell, 1977, 

pi. 1, fig. 2; pi. 3, fig. 1-4, 6; pi. 4, figs. 1,3-6; pi. 

5, figs. 2, 3, 5) and from the Twowells Tongue of the 

Dakota Sandstone of central western New Mexico (Cob 

ban, 1977, pi. 19, fig. 3).

Many inoceramids in the cores from the borehole at 

depths of 192.5-199 m are referred to /. ginterensis, 

although most of the specimens tend to have ornaments 

not quite as broadly curved as that on the majority 

of specimens illustrated by Pergament (1966). The 

specimens from the borehole are from the middle part 

of the Greenhorn Formation.

. Hypotypes USNM 308058-308060, 308068.

Inoceramus sp.

Plate 3, figures 15, 16

Inoceramids that have a quadrate outline and ornament of very fine radial striae in addition to rugae and 

growth lines of irregular height, occur in cores from 

the borehole at depths of 203-211 m below the middle 

of the Greenhorn Formation. Beaks are located at the 

anterior end of a moderately long straight hinge line.

Types. Figured specimens USNM 308061, 308062.

Inoceramus prefragilis Stephenson

Plate 4, figures 10, 11; plate 5, figure 6.

Inoceramus prefragilis Stephenson, 1952, [1953], p. 64, pi. 12, figs. 

10-12; pi. 13, figs. 1, 2.

Inoceramus prefragilis is a fairly large suberect 

species that has an ovate to subrectangular outline and 

moderate convexity. The anterior side is steep and 

slightly concave. The hinge line is moderately long, and 

the narrow, sharp, incurved beaks project slightly 

above it at the anterior end. Large specimens may have 

a weak, shallow sulcus posterior to and paralleling the 

umbonal axis. Ornament consists of strong, flat raised 

growth lines that tend to be of even size and a few 

weak to moderately strong rugae.

Stephenson's types are from the Woodbine Formation 

of north Texas. The species is common in the lower 

part of the Greenhorn Formation in the Western Interior. Specimens occur in cores from the borehole at 

depths of 221-240m.

Types. Hypotypes USNM 308076-308078, 308084.

Inoceramus crippsi Mantell

Plate 5, figures 1-3

Inoceramus crippsi Mantell, 1822, p. 133, pi. 27, fig. 11. 

Inoceramus crippsi Mantell. Woods, 1911, p. 273, pi. 48, figs. 2,3; 

text figs., 33-35.

This erect inoceramid has a subrectangular outline 

that is higher than it is long. The hinge line is moderately long and is at a very high angle to the axis of 

the shell. The anterior border is slightly convex. Ornament consists of prominent closely spaced rugae which, 

on some specimens, are of nearly equal size.

Mantell's type came from the Chalk Marl of England. 

Specimens that seem referable to the species occur in 

a core in the basal part of the Greenhorn Formation 

at depths of 238 and 244 m. One specimen has fine 

growth lines -on and between the rugae on the umbo, 

and in this manner, it resembles the ornament on a 

specimen of /. crippsi var. reachensis Etheridge from 

England illustrated by Woods (1911, pi. 49, fig. 1).

Types. Hypotypes USNM 308085-308087.
CHARACTERISTIC FOSSILS 13

Inoceramus rutherfordi Warren

Plate 5, figure 12 

Inoceramus rutherfordi Warren, 1930, p. 59, pi. 7, figs. 1-3.

A squarish outline and posteroventral-trending folds 

and sulci feature this moderately inequivalve species. 

The shell is prosocline, and the beaks project over the 

fairly long hinge line. Ornament consists of irregular 

rugae.

Inoceramus rutherfordi was originally described from 

the Dunvegan Formation in the Peace River area of 

Alberta. The species has been found at many localities 

in the middle Cenomanian zone of Acanthoceras amphibolum Morrow in the Western Interior of the United 

States from Montana south to Trans-Pecos, Texas. In 

the borehole, fragments of inoceramids in the cores at 

depths of 253-265 m seem to represent this species. 

At nearby outcrops, I. rutherfordi occurs in dusky-red 

ferruginous concretions 7-13 m below the top of the 

Belle Fourche Shale (Merewether, 1980, p. 5).

Type. Hypotype USNM 308092.

VenieLLa goniophora Meek

Plate 1, figure 4

Veniella goniophora Meek, 1876, p. 152, pi. 4, fig. 4, text fig. 12.

This very convex equivalve bivalve has a subquadrate 

outline, prominent umbo, sharp posterior ridge, and 

ornament of a few strong concentric lamellae. The 

species is small for the genus. Meek's type came from 

the Marias River Shale at Fort Benton, Mont.

Veniella goniophora is fairly common in the upper 

part of the Carlile Shale of the Black Hills, in the Kevin 

Member of the Marias River Shale of north-central 

Montana, and in the equivalent part of the Cody Shale 

of Wyoming. The age range is late Turonian-Santonian. 

Most records from the Black Hills are from the Sage 

Breaks Member of the Carlile Shale (Robinson and 

others, 1964, p. 69), but a specimen recorded as Veniella cf. V. goniophora was collected about 36 m above 

the base of the Turner Sandy Member 15 km northwest 

of the borehole site (Mapel and Pillmore, 1964, p. J26). 

In cores from the borehole, small specimens of V. 

goniophora occur in slightly calcareous to noncalcareous 

shale in the Sage Breaks Member at depths of 4&-80 

m (pi. 1, fig. 4) and in clayey siltstone in the upper 

part of the Turner Sandy Member at a depth of about 

88m.

Type. Hypotype USNM 308020

Phelopteria minuta Kauffman and Powell

Plate 3, figure 2

Phelopteria minuta Kauffman and Powell, 1977, p. 50, pi. 8, figs. 

4,6.

Kauffman and Powell noted that this nearly smooth 

bivalve was small for the genus, and that the largest 

adult at hand attained a height of 21 mm. They noted 

that the species is moderately prosocline with an average angle of inclination of 42°, and that the outline is 

subrounded in juveniles and subrhombic in adults. The 

hinge line is long and straight, and triangular anterior 

and posterior auricles are present. The small beak projects slightly above the hinge line. Ornament consists 

of very fine raised growth lines. The holotype is from 

the middle part of the Hartland Shale Member of the 

Greenhorn Formation of the Oklahoma Panhandle.

Specimens that seem assignable to P. minuta occur 

in cores of noncalcareous shale of the Greenhorn Formation from depths of 186-188 m in the borehole.

Type. Hypotype USNM 308050.

Entolium sp.

Plate 4, figure 7

Many of the cores of calcareous to noncalcareous 

shale from the lower half of the Greenhorn Formation 

from the borehole have very thin-shelled, small, fragile 

bivalves referable to Entolium. The specimens are 

crushed flat, have a subrounded outline, and do not exceed 12 mm in height. Beaks are small and subcentral, 

and anterior and posterior auricles are triangular and 

nearly equisized. Both valves have very fine irregular 

concentric growth lines. Left valves have, in addition, 

very fine radial riblets. Many of the specimens closely 

resemble Entolium gregarium Kauffman and Powell 

(1977, p. 87, pi. 4, fig. 2; pi. 5, fig. 4; pi. 6, figs. 8, 

9; pi. 8, figs. 1, 2), and some may be that species. Radial 

ornamentation, however, is said to be absent on E. gregarium.

Type. Figured specimen USNM 308074.

Ostrea beloiti Logan

Plate 5, figure 11

Ostrea beloiti Logan, 1899, p. 214, pi. 25, figs. 7, 8.

This small oyster usually has an elongated gently 

curved outline. The left valve is convex, and the right 

one is almost flat. Small ridglets and pits (chomata) are 

conspicuous on the periphery of the inner surfaces. The 

valves are fairly smooth except for a few weak radial 

ribs on the ventroanterior part of some left valves. 

Shells were loosely cemented together to form thin 

biostromes, or they were attached to other mollusks.

Ostrea beloiti was originally described from the basal 

part of the Greenhorn Formation of north-central Kansas. The species has a range of middle and late Cenomanian; it is most abundant in the middle Cenomanian 

zones of Acanthoceras alvaradoense Moreman and A.
14 MOLLUSCAN RECORD FROM MID-CRETACEOUS BOREHOLE, WYOMING

amphibolum Morrow. The geographic range is great 

and extends from Manitoba to the Mexican border. A 

map showing the distribution of the species in the Western Interior was presented by Cobban and Hook (1980, 

fig. 3).

Ostrea beloiti was collected from a ferruginous concretion 27 m below the top of the Belle Fourche Shale 

near the borehole site (Merewether, 1980, p. 5). Cores 

of noncalcareous shale from the upper part of the Belle 

Fourche Shale from the borehole at depths of 256-258 

m contain 0. beloiti.

Type. Rypotype USNM 308091.

Baculites yokoyamai Tokunaga and Shimizu

Plate 1, figures 5, 6

Baculites yokoyamai Tokunaga and Shimizu, 1926, p. 195, pi. 22,

fig. 5a, b; pi. 26, fig. 11.

Baculites besairiei Collignon, 1931, p. 37, pi. 5, figs. 6-9. 

Baculites cf. B. yokoyamai Tokunaga and Shimizu. Cobban and Scott,

1972 [1973], p. 48, pi. 20, figs. 15-21.

This small, straight ammonite has a nearly elliptical 

section, small degree of taper, finely ribbed venter, 

smooth to very weakly ribbed flanks, and suture simple 

for the genus. The holotype is from rocks of Coniacian 

Age of Japan.

Specimens identical to those from Japan are abundant 

and widely distributed in Turonian rocks in the Western 

Interior. The Western Interior specimens were at first 

reported as Baculites cf. B. besairiei Collignon (Cobban, 1951a, p. 2188, 2190-92; Cobban and Reeside, 

1952a, p. 1018 and chart). Matsumoto and Obata (1963, 

p. 34) have shown that B. besairiei Collignon from 

Madagascar is quite likely a synonym of B. yokoyamai.

Near the site of the borehole, B. yokoyamai was collected from sandstone concretions about 17 m below 

that top of the Turner Sandy Member of Carlile Shale 

(Merewether, 1980, p. 12). Crushed fragments of 

smooth baculites are common in the borehole cores of 

the Sage Breaks Member (pi. 1, fig. 5) and Turner 

Sandy Member (pi. 1, fig. 6) at depths of 45-108 m.

Types. Hypotypes USNM 308021, 308022.

Scaphites corvensis Cobban

Plate 1, figure 7

Scaphites corvensis Cobban, 1951b [1952], p. 26, pi. 7, figs. 6-17.

This is a moderately large species that has ribs 

equally spaced on the venter of the adult body chamber. 

The species occurs in two forms a large stout one 

(holotype) herein interpreted as a female, and a small 

slender one believed to be a male. The latter was given 

the varietal name bighomensis (Cobban, 1951b, p. 26). 

The holotype, 63.5 mm long, has 15 primary ribs and 

52 secondary ribs on the body chamber.

Scaphites corvensis is a guide fossil to one of the late 

Turonian ammonite zones in the Western Interior. The 

species is especially common in the upper part of the 

Carlile Shale of the Black Hills area (Mapel and 

Pillmore, 1963a, p. M36; 1963b, p. N48; Robinson and 

others, 1964, p. 68, 69) and in the upper part of the 

Frontier Formation farther west in Wyoming 

(Merewether and others, 1979, pi. 2, figs. 15, 16). In 

the vicinity of the borehole, S. corvensis was collected 

about 5 m below the top of the Turner Sandy Member 

of the Carlile Shale (Merewether, 1980, p. 12). The 

species also occurs in the lower part of the overlying 

Sage Breaks Member (Cobban, 1951b, p. 26; Robinson 

and others, 1964, p. 69).

In the borehole, crushed specimens of S. corvensis 

are present in the cores of the lower part of the Sage 

Breaks Member from depths of 76-81 m.

Type. Hypotype USNM 308023.

Prionocyclus novimexicanus (Marcou)

Plate 1, figures 15, 16.

Ammonites novi-mexicani Marcou, 1858, p. 35, pi. 1, figs. 2, 2a. 

Prionocyclus novimexicanus (Marcou). Hook and Cobban, 1979, p. 

35, fig. 3E-L.

Characteristic features of this moderately large evolute ammonite are its closely spaced flexuous ribs on 

juveniles, its umbilical bullae or bullate umbilical tubercles, its single row of small ventrolateral tubercles, and 

its finely serrate keel.

The species is widely distributed in upper Turonian 

rocks in the Western Interior. The type specimen came 

from the Mancos Shale west of Albuquerque, N. Mex. 

Specimens are common in the Juana Lopez Member of 

the Mancos Shale of New Mexico, Utah and Colorado, 

in the basal part of the Niobrara Formation in southern 

Colorado, in the Turner Sandy Member of the Carlile 

Shale of the Black Hills area, in the Wall Creek Member of the Frontier Formation of central Wyoming, and 

in the Carlile Member of the Cody Shale of south-central Montana. In the Black Hills area, P. 

novimexicanus seems to be restricted to the lower part 

of the upper half of the Turner Sandy Member, where 

the species has usually been referred to as P. 

wyomingensis var. elegans Haas (Cobban, 1951a, p. 

2188). Specimens were noted at a depth of 106 m in 

the cores of the Turner Sandy Member from the 

borehole.

Types. Kypotypes USNM 308031, 308032.

Collignoniceras woollgari regulare (Haas)

Plate 2, figures 6, 7

Prionotropis woollgari var. regularis Haas, 1946, p. 154, pi. 16, figs. 

1-17; text figs. 10-12, 59-74, 78, 80, 81, 83.
CHARACTERISTIC FOSSILS 15

Prionotropis woollgari (Mantell) forma typica and varieties. Haas,

1946. 

Collignoniceras woollgari (Mantell) (late form). Merewether, Cobban

and Cavanaugh, 1979, pi. 3, figs. 4, 5. 

Collignoniceras woollgari regulare (Haas). Cobban and Hook, 1979

[1980], p. 22, pi. 3; pi. 12, fig. 3.

This moderately evolute, ornate subspecies has been 

well illustrated by Meek (1876), Haas (1946), Matsumoto (1965), and Cobban and Hook (1979). The subspecies has conspicuous prorsiradiate ribs, umbilical and 

double ventrolateral tubercles, and a strongly serrate 

keel in which the siphonal clavi match the ventrolateral 

tubercles and ribs in number. Juveniles have numerous 

and closely spaced ribs that may be somewhat flexuous, 

whereas adults have widely spaced straight ribs of 

about equal size. Ventrolateral tubercles of adults 

merge into prominent horns.

Collignoniceras woollgari regulare is widely distributed, generally in calcareous beds, in the Western Interior. The subspecies is found in the F airport Chalky 

Member and Pool Creek Member of the Carlile Shale 

in the central Great Plains, where it has been designated a guide fossil to one of the Turonian zones (Cobban and Reeside, 1952a, p. 1018). Farther northwest 

on the Sweetgrass arch of north-central Montana, the 

subspecies has been found at the top of the Cone Member of the Marias River Shale (Cobban and others, 1956; 

Cobban and others, 1976, p. 42). In southwestern 

Wyoming, C. woollgari regulare occurs in the Oyster 

Ridge Sandstone Member of the Frontier Formation 

(Cobban and Reeside, 1952b, p. 1925), and in the shale 

just below the Oyster Ridge Sandstone Member farther 

southwest in northeastern Utah (Trexler, 1966, p. 23). 

In east-central Utah, the subspecies has been recorded 

from the lower part of the Mancos Shale on the east 

flank of the San Rafael Swell (Fisher and others, 1960, 

p. 27) as well as on the west flank (Katich, 1954, p. 

46). In southern Utah, the subspecies occurs in the 

upper part of the Tropic Shale (Peterson and Waldrop, 

1965, p. 61, 62), and in northeastern Arizona, the subspecies occurs in the Mancos Shale (Repenning and 

Page, 1956, p. 263, 265, 268). Cobban and Hook (1979, 

fig. 2) noted several occurrences of C. woollgari regulare in the Mancos Shale in northwestern New Mexico.

Limestone concretions about 14 m below the top of 

the Pool Creek Member of the Carlile Shale near the 

borehole contain well-preserved specimens of C. 

woollgari regulare (Merewether, 1980, p. 10). In the 

borehole, flattened specimens are abundant in cores of 

calcareous and noncalcareous shale at depths of 155-161 

m. These specimens are important in that they date 

this part of the borehole as of about the middle part 

of the middle Turonian (Cobban and Hook, 1979, fig. 

1).

Types. Hypotypes USNM 308038, 308039.

Scaphites nigricollensis Cobban

Plate 1, figure 13

Scaphites nigricollensis Cobban, 1951b [1952], p. 25, pi. 5, figs. 9-26; 

pi. 6, fig. 1-17; pi. 7, figs. 1-5.

This species is similar to S. corvensis in size and general form, but differs in that it has more numerous ribs, 

as well as a tendency to lose ribbing on the older half 

of the body chamber of internal molds. The species is 

restricted to the upper part of the Turner Sandy Member of Carlile Shale of the Black Hills area (Cobban 

1951a, p. 2188) and the equivalent part of the Carlile 

Shale of south-central Montana (Richards, 1955, p. 54) 

and Ferdig Member of the Marias River Shale of northcentral Montana (Cobban and others, 1976, p. 47-49).

Scaphites nigricollensis occurs in two forms a 

large stout one (holotype) assumed to be a female and 

a small slender one assumed to be a male. The male 

was given the varietal name meeki (Cobban, 1951b, p. 

26).

The species was collected from the upper part of the 

Turner Sandy Member on outcrops near the borehole 

(Robinson and others, 1964, p. 72). Small slender specimens (males) occur in cores of the Turner Sandy Member from the borehole at depths of 96-104 m.

Type. Hypotype USNM 308029.

Scaphites warreni Meek and Hayden

Plate 1, figure 14

Scaphites warreni Meek and Hayden, 1860, p. 177. 

Scaphites warreni Meek and Hayden. Meek, 1876, p. 420, pi. 6, fig. 

5.

Scaphites warreni is a small and more sparsely ribbed 

species than S. nigricollensis, but like it, S. warreni 

occurs in a large, stout form (female) and a small, slender form (male). The holotype is a female, and the male 

form was given the varietal name ubiquitosus (Cobban, 

1951b, p. 23). Both forms have the ribbing on the venter more widely spaced on the older part of the adult 

body chamber than on the young part.

Scaphites warreni is abundant in the lower part of 

the Turner Sandy Member of the Carlile Shale of the 

Black Hills area (Cobban, 1951a, p. 2189; Mapel and 

Pillmore, 1963b, p. N48; Robinson and others, 1964, 

p. 67-69); in the upper part of the Frontier Formation 

farther west in Wyoming (Merewether and others, 

1979, p. 85, pi. 2, figs. 6-9); and in the Juana Lopez 

Member of the Mancos Shale farther south in Colorado, 

Utah, and New Mexico (Cobban, 1951b, p. 22, 23, table 

opposite p. 12).

Near the borehole, S. warreni was found in sandstone 

concretions about 40 m below the top of the Turner 

Sandy Member of the Carlile Shale and in sandstone 

1 m above the base of the member (Merewether, 1980,
16 MOLLUSCAN RECORD FROM MID-CRETACEOUS BOREHOLE, WYOMING

p. 12). In the borehole, a fairly slender sparsely ribbed 

phragmocone with part of the body chamber attached 

is referred to this species. The specimen is from the 

lower part of the Turner Sandy Member of the Carlile 

Shale at a depth of 136 m. 

Type. Hypotype USNM 308030.

Scaphites (Pteroscaphites) minutus Moreman

Plate 2, figure 9

Scaphites minutus Moreman, 1942, p. 216, pi. 34, figs. 9, 10; text

fig. 2s.

Otoscaphites minutus (Moreman). Wright, 1953, p. 475. 

Scaphites (Pteroscaphites) minutus (Moreman). Wiedmann, 1965, p.

435, pi. 58, figs. 5a-c; text fig. 6b.

This very small species has a moderately evolute septal coil and a large, very uncoiled U-shaped body 

chamber that is well separated from the coil. The aperture is collared, and lateral lappets are present. Ornament consists of closely spaced primary and secondary 

ribs.

This species is known only from the late Cenomanian 

zone of Sciponoceras gracile (Shumard). The holotype, 

an adult 11.5 mm long, is from the Eagle Ford Formation of north-central Texas. The species is scarce in the 

Western Interior, but a few examples may be present 

in the USGS collections from the Greenhorn Formation 

(Cobban, 1951a, p. 2185).

A flattened specimen of S. (P.) minutus is present 

in a core of calcareous shale from the borehole at a 

depth of 181.5 m. The specimen is from the top of the 

zone of Sciponoceras gracile.

Type. Hypotype USNM 308041.

Worthoceras vermiculus (Shumard)

Plate 2, figure 5

Scaphites vermiculus Shumard, 1860, Academy of Science of St.

Louis Transactions, v. 1, p. 594.

Macroscaphites vermiculus (Shumard). Meek, 1876, p. 419. 

Scaphites vermiculus Shumard. White, 1883, p. 39, pi. 18, fig. 8a. 

Worthoceras vermiculum (Shumard). Adkins, 1928, p. 220. 

Worthoceras vermiculum (Shumard). Moreman, 1942, p. 214, pi. 34

figs. 12, 13; text fig. 2 p.

This small smooth ammonite has a large evolute septate coil and a long, straight shaft and hook. The lower 

part of the shaft is septate, and the mouth border is 

lappeted. The suture is very simple and has a broad 

little-divided lateral saddle and a narrow bifid lateral 

lobe (Moreman, 1942, fig. 2p; Wiedmann, 1965, fig. 10 

e-g). Moreman (1942, p. 214) noted that the type was 

lost, and figured a neotype from the Eagle Ford Formation of north-central Texas.

Worthoceras vermiculus has been found in the late 

Cenomanian zone of Sciponoceras gracile in the 

Greenhorn Formation at many localities in the central

Great Plains (Cobban, 1951a, p. 2185; Cobban and 

Scott, 1972, p. 22; Hattin, 1975, p. 33, pi. 5, figs. A, 

F, K). It is also present in USGS collections from the 

Frontier Formation in Johnson County in north-central 

Wyoming (Merewether, 1980, p. 17), as well as in collections from the Mancos Shale in Socorro County in 

south-central New Mexico. In southwestern New 

Mexico, W. vermiculus occurs not only in the zone of 

Sciponoceras gracile but also ranges up into the overlying zone of Neocardioceras juddii (Barrois and de 

Guerne).

A crushed hook and shaft of a small scaphite in a 

core of calcareous shale in the Greenhorn Formation 

at a depth of 184 m from the borehole seems assignable 

to W. vermiculus. Crushed evolute coils in cores at 

depths of 181-183 m are probably this species.

Type. Kypotype USNM 308037.

Allocrioceras annulatum (Shumard)

Plate 2, figure 4

Ancyloceras annulatus Shumard, 1860, p. 595. 

Helicoceras pariense White, 1877, p. 203, pi. 19, figs. 2a-d. 

Exiteloceras pariense (White). Hyatt, 1894, p. 577. 

Allocrioceras pariense (White). Adkins, 1932, p. 434, 437. 

Allocrioceras annulatum (Shumard). Moreman, 1942, p. 208. 

For full synonomy, see Cobban and Scott, 1972 [1973], p. 51.

*-

This loosely coiled ammonite has some whorls helical 

and others coiled in one plane. Ornament consists of 

conspicuous annular ribs and small, pointed ventrolateral tubercles. Ribs, which number three for the shell, 

diameter, are narrowly rounded except on the venter, 

where they are flattened a little.

Allocrioceras annulatum was originally described 

from the Eagle Ford Formation of north-central Texas. 

The species is common in the late Cenomanian zone 

of Sciponoceras gracile at many localities in the Western Interior. (See Cobban and Scott, 1972, p. 52 for 

general localities and references.)

Crushed fragments of A. annulatum occur in a core 

of calcareous shale in the Greenhorn Formation from 

the borehole at a depth of about 184 m.

Type. Rypotype USNM 308036.

Hamites (Stomohamites) simplex d'Orbigny

Plate 3, figures 9, 13; plate 4, figures 8, 13; plate 5, figures 4, 5.

Hamites simplex d'Orbigny, 1842, p. 550, pi. 134, figs. 12-15.

Wright (1963, p. 597, pi. 81, fig. la-c) summarized 

this species as consisting of an initial open spire, followed by two fairly straight shafts, with the final aperture having three prominent oblique ribs. Whorl sections are oval to nearly circular. Ribs are annular, high 

and narrow, and, on internal molds, about as wide as 

the interspaces. The ribs number about 4V£ in a distance
CHARACTERISTIC FOSSILS 17

equal to the whorl height. Kennedy (1971, p. 6, pi. 1, 

figs. 1-8) figured many specimens from southern England that have 5-10 ribs in a distance equal to the whorl 

height.

Hamites simplex was originally described from 

France, but the species is now known from many 

localities in Europe, Africa, Australia, and North 

America. In England, where mid-Cretaceous ammonite 

faunas have been extensively investigated, H. simplex 

seems to be restricted to the middle Cenomanian (Kennedy and Hancock, 1976, p. 5.15, 5.16).

Fragments of both the straight and curved whorls 

of hamitids that seem assignable to H. simplex are 

present in the USGS collections from many localities 

in the Western Interior. Most specimens are small and 

occur as flattened impressions in dark-gray shale. A 

large specimen that has the collared adult aperture has 

not been found. In faunal lists, the species has been 

reported as Helicoceras n. sp. (Mapel and Pillmore, 

1964, p. J21; Robinson and others, 1964, p. 59), 

Stomohamites aff. S. corrugatus (Stanton) (Robinson 

and others, 1964, p. 63), and Stomohamites cf. S. 

simplex (d'Orbigny) (Cobban and Scott, 1972, p. 44, pi. 

13, figs. 5-10; pi. 17, figs. 3, 4).

In the cores from the borehole, flattened fragments 

of small hamitids are abundant in dark-green calcareous 

to noncalcareous shale in the lower one-half of the 

Greenhorn Formation. These specimens closely match 

those illustrated from England by Kennedy (1971, pi. 

6, figs. 1-8) and are assigned to H. simplex. Most specimens have more than 4Vfe ribs per whorl height mentioned by Wright (1963). Some of the cores reveal the 

very early growth stages of the species. A very small 

initial coil is followed by a smooth shaft 10-11 mm long, 

which is either straight or slightly curved.

Types. Hypotypes USNM 308063-308067, 308073.

Metoicoceras cf. M. mosbyense Cobban

Plate 4, figures 14, 15

Metoicoceras mosbyense Cobban (1953, p. 48, pi. 6, 

figs. 1-14; pi. 7, figures 1-3) is a moderately large compressed involute ammonite that has early whorls with 

umbilical and double ventrolateral tubercles only, and 

adult body chamber without tubercles. Ribs consist of 

conspicuous, prorsiradiate, fairly straight primaries and 

secondaries, which become broad and flat on the venter 

of the adult body chamber. Near the aperture, ribs become narrow and closely spaced.

Metoicoceras mosbyense is confined to the late 

Cenomanian zone of Dunveganoceras albertense (Warren). Specimens are especially abundant in the upper 

part of the Frontier Formation of central Wyoming 

(Merewether and others, 1979, pi. 2, figs. 17, 20-22), 

where the species has been identified as M. defordi

Young (1957, p. 1169, pi. 149, figs. 1-8; text fig. la, 

e, g, i). Near the borehole, M. mosbyense was collected 

27-34 m below the top of the Greenhorn Formation 

(Merewether, 1980, p. 7, listed as M. defordi). Part 

of a juvenile, as well as part of the ventrolateral surface 

of an adult body chamber, is in the core of the 

Greenhorn Formation at a depth of 216 m in the 

borehole (pi. 4, figs. 14, 15). 

Types Rypotypes USNM 308082, 308083.

Neostlingoceras kottlowskii Cobban and Hook

Plate 4, figure 9

Neostlingoceras kottlowskii Cobban and Hook, 1981, p. 26, pi. 4, figs. 

1-28.

Neostlingoceras kottlowskii is a small helically coiled 

(sinistral) ammonite that has an acute apical angle and 

three rows of tubercles of which two are visible in side 

views. Tubercles in the upper row are large and less 

numerous than those in the lower rows.

This ammonite may be confined to the late Cenomanian zone of Dunveganoceras pondi. The species is 

abundant only in the Mancos Shale and Colorado Formation of southwestern New Mexico. A few specimens 

have been found in the Mancos Shale of west-central 

New Mexico and the Benton Shale of north-central Colorado.

On the west flank of the Black Hills, a fragment of 

N. kottlowskii was found in a limestone concretion assigned to the Belle Fourche Shale (Robinson and 

others, 1964, p. 59, identified as Turrilites n. sp.; also 

Mapel and Pillmore, 1964, p. J21). In the borehole, N. 

kottlowskii occurs in a core of calcareous shale from 

the Greenhorn Formation at a depth of 232 m.

Type. Hypotype USNM 308075.

Borissiakoceras reesidei Morrow

Plate 5, figure 8

Borissiakoceras reesidei Morrow, 1935, p. 463, pi. 49, fig. 7a, b; pi. 

50, fig. 5; text fig. 8.

Diagnostic features of this small, compressed, involute ammonite are its nearly flat flanks, rounded venter, and either no ornament or the presence of 5 or 

6 ventrolateral tubercles per half whorl. The types are 

from near the top of the Graneros Shale of central Kansas, where they were associated with Acanthoceras amphibolum Morrow of middle Cenomanian age.

Borissiakoceras reesidei is abundant in limestone concretions in the upper part of the Frontier Formation 

along the east side of the Bighorn Mountains in central 

northern Wyoming (Hose, 1955, p. 100) and in limestone concretions in the Soap Creek Bentonite Bed at 

the top of the Frontier Formation farther north at the
18 MOLLUSCAN RECORD FROM MID-CRETACEOUS BOREHOLE, WYOMING

Wyoming-Montana State line (Cobban, 1961, p. 750, pi. 

88, figs. 4-14).

In the cores from the borehole, B. reesidei occurs 

as flattened specimens in noncalcareous shale from 

depths of 244-248 m.

Type. Hypotype USNM 308088.

Borissiakoceras cf. B. orbiculatum Stephenson

Plate 4, figure 4

Small, smooth specimens that are crushed flat but 

that appear to have a slight angularity of the ventrolateral shoulder occur in cores of calcareous to noncalcareous shale of the lower part of the Greenhorn Formation 

from the borehole at depths of 227-230 m. Borissiakoceras orbiculatum Stephenson (1955, p. 64, pi. 6, 

figs. 1-4) is a small compressed ammonite that has flattened flanks and a subangular ventrolateral shoulder 

with or without low clavate tubercles. Stephenson's 

specimens came from the basal part of the Eagle Ford 

Formation of north-central Texas, where they were associated with Acanthoceras alvaradoense Moreman of 

middle Cenomanian age. The specimens from the 

borehole occur in slightly younger rocks (early late 

Cenomanian) and may be the same as the form referred 

to as Borissiakoceras cf. B. orbiculatum from the later 

Cenomanian zone of Sciponoceras gracile (Shumard) 

(Cobban 1961, p. 753, pi. 89, figs. 10-14; text fig. 5g, 

i).

Type. Figured specimen USNM 308084.

Acanthoceras amphibolum Morrow

Plate 5, figures 9, 10

Acanthoceras! amphibolum Morrow, 1935, p. 470, pi. 49, figs. 1-4, 

6; pi. 51, figs. 3, 4; text fig. 4.

This moderate size involute ammonite has subrectangular to quadrate whorls on which the ornament differs 

greatly from juveniles to adults. Juveniles have umbilical, double ventrolateral, and clavate siphonal tubercles, whereas adults have a low siphonal ridge and ventrolateral horns. The species was designated a zonal 

index in the early 1950's (Cobban 1951a, p. 2197; Cobban and Reeside, 1952a, p. 1017).

Morrow's types are from near the top of the Graneros 

Shale of central Kansas. The species is widely distributed in the Western Interior from south-central Montana (Knechtel and Patterson, 1956, p. 20) to west-central New Mexico (Cobban, 1977, p. 23, pi. 8, figs. 8, 

9; pi. 12, figs. 10-12, 15-23; text fig. 5).

Near the borehole site, A. amphibolum was collected 

from dusky-red ferruginous concretions 7-13 m below 

the top of the Belle Fourche Shale, where they were 

associated with Inoceramus rutherfordi Warren

(Merewether, 1980, p. 5). Cores of noncalcareous to 

slightly calcareous shale from the upper part of the 

Belle Fourche Shale at depths of 248-255 m in the 

borehole contain crushed fragments of ammonites referred to A. amphibolum. 

Type. Rypotypes USNM 308089, 308090.

Metaptychoceras reesidei (Cobban and Scott)

Plate 4, figure 7

Hemiptychoceras reesidei Cobban and Scott, 1972 [1973], p. 45, pi. 

17, figs. 7, 8.

This aberrant ammonite, originally assigned to Hemiptychoceras Spath, seems better assigned to Metaptychoceras Spath (1926, p. 81) because of similarities in 

size and simple suture and in lack of constrictions. 

Wright (1979, p. 284) has recently summarized the 

characteristics of Hemiptychoceras and Metaptychoceras and noted that the differences are small but 

real. The holotype of M. reesidei is from the late 

Cenomanian zone of Sciponoceras gracile (Shumard) in 

the basal part of the Bridge Creek Limestone Member 

of the Greenhorn Formation at Pueblo, Colo.

Cores of calcareous and noncalcareous shale from the 

Greenhorn Formation from the borehole contain 

crushed specimens referred to M. reesidei at depths 

of 195.6-204.5 m.

Type. Hypotype USNM 308074.

Moremanoceras sp.

Plate 4, figures 12, 16; plate 5, figure 7

Moremanoceras is a very involute ammonite that has 

flat sides, broadly rounded venter with a low rounded 

keel, sinous growth lines or very fine ribs, and occasional thicker raised ribs that border the adapical side 

of constrictions. The genus closely resembles Damesites 

Matsumoto in its general appearance, but Damesites 

has a more complex suture with more lobes. According 

to Matsumoto and Obata (1955, p. 126), Damesites has 

a long range of late Cenomanian into Maestrichtian, 

whereas Moremanoceras is restricted to the Cenomanian.

Moremanoceras has been found in Montana, Wyoming, Colorado, Kansas, Oklahoma, New Mexico, and 

Arizona. Specimens from Montana and Wyoming were 

recorded as Puzosia (Latidorsella) n. sp. (Robinson and 

others, 1964, p. 56, 57, 63) or "Puzosia" n. sp. 

(Robinson and others, 1964, p. 59; Mapel and Pillmore, 

1964, p. J21). Kansas and Oklahoma specimens were 

illustrated and recorded as Desmoceras sp. (Hattin, 

1975, p. 24, pi. 2, figs. P, V; Kauffman and Powell, 

1977, p. 101, pi. 9, figs. 2, 6).

In the cores from the borehole, fragments of
REFERENCES CITED 19

Moremanoceras occur in the lower half of the 

Greenhorn Formation at depths of 210-240 m. 

Types. Figured specimens USNM 308079-308081.

Neocardioceras spp.

Plate 4, figures 1-3, 5, 6

Many small ammonites that are crushed flat in cores 

from the borehole are probably undescribed species of 

Neocardioceras Spath (1926 p. 81). All specimens are 

moderately evolute and are ornamented by narrow, 

prorsiradiate ribs and umbilical bullae, small inner and 

outer venrolateral tubercles, and clavate siphonal 

tubercles. At the position of the inner ventrolateral 

tubercles, the ribs bend forward and cross the venter 

as chevrons. None of the specimens exceeds 17 mm in 

diameter. The specimens occur in the lower half of the 

Greenhorn Formation at depths of 198-239 m.

Neocardioceras occurs at many places in the Western 

Interior in rocks of late Cenomanian age. Specimens 

from the west flank of the Black Hills in eastern Wyoming have been reported as "Ammonite n. gen. spp. A 

and B" and Mammites n. sp. (Robinson and others, 

1964, p. 59, 63; Mapel and Pillmore, 1964, p. J21). 

Specimens from the Lincoln Limestone Member of the 

Greenhorn Formation of Kansas have been reported as 

Eucalyoceras sp. B (Hattin, 1975, p. 24, 62, 64, pi. 

2, figs. K-M, Q), and those from the Hartland Shale 

Member of the Greenhorn in the Oklahoma Panhandle 

were recorded as "Acanthoceras group A and group B" 

(Kauffman and Powell, 1977, p. 103, pi. 10, figs. 2, 3, 

6, 7). Impressions of small Neocardioceras near the top 

of the Hartland Shale Member near Pueblo, Colo. were 

recorded as Tarrantocerast sp. (Cobban and Scott, 

1972, p. 17). Small crushed specimens of Neocardioceras are present in the U.S. Geological Survey collections from the Hartland Member along the Front 

Range in Colorado and from farther west in north-central Colorado in the equivalent part of the Benton 

Shale. A younger species of Neocardioceras, N. juddii 

(Barrois and de Guerne), has been found in beds just 

above the late Cenomanian zone of Sciponceras gracile 

(Shumard) in south-central Montana, northeastern 

Arizona, southwestern New Mexico, and Trans-Pecos, 

Texas.

Types. Figured specimens USNM 308068-308072.

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on Stratigraphy, v. 8, no. 2, p. 111-123.

Seitz, Otto, 1934, Die Variabilitat des Inoceramus labiatus v. 

Schloth.: Geologisches Jahrbuch, v. 55, p. 429-474, pis. 36-40.

Shumard, B. J., 1860, Descriptions of new Cretaceous fossils from 

Texas: Academy of Science of St. Louis Transactions, v. 1, p. 

590-610.

Sowerby, J. de C., 1829, The mineral conchology of Great Britain, 

v. 6: London, B. Meredith, p. 201-230, pis. 598-609.

Spath, L. F., 1925, On Upper Albian Ammonoidea from Portuguese 

East Africa, with an appendix on Upper Cretaceous ammonites 

from Maputoland: Annals of the Transvaal Museum, v. 11, p. 

179-200, pis. 28-37.

 1926, On new ammonites from the English Chalk: Geological 

Magazine, v. 63, no. 740, p. 77-83.

Stephenson, L. W., 1952 [1953], Larger invertebrate fossils of the 

Woodbine formation (Cenomanian) of Texas: U.S. Geological Survey Professional Paper 242, 211 p., 58 pis.

 1955, Basal Eagle Ford fauna (Cenomanian) in Johnson and 

Tarrant Counties, Texas: U.S. Geological Survey Professional 

Paper 274-C, p. 53-67, pis. 4-7.

Tokunaga, Shigeyasu, and Shimizu, Saburo, 1926, The Cretaceous 

formation of Futaba in Iwaki and its fossils: Tokyo Imperial University Faculty of Science Journal, sec. 2, v. 1, pt. 6, 181-212, 

pis. 21-27.

Trexler, D. W., 1966, The stratigraphy and structure of the Coalville 

area, northeastern Utah: Colorado School of Mines Professional 

Contributions 2, 69 p.

Troger, Karl-Armin, 1967, Zur Palaontologie, Biostratigraphie und 

fraziellen Ausbildung der unteren Oberkreide (Cenoman bus 

Turon); Teil 1, Palaontologie und Biostratigraphie der Inoceramen des Cenomans bis Turons Mitteleuropas: Dresden Staatlichen Museums fur Mineralogie und Geologie Abhandlungen, v. 

12, p. 13-207, illus.

Warren, P. S., 1930, New species of fossils from Smoky River and 

Dunvegan formations, Alberta: Alberta Research Council of 

Geological Survey Report 21, p. 57-68, pis. 3-7.

White, C. A., 1877, Report upon the invertebrate fossils collected 

in portions of Nevada, Utah, Colorado, New Mexico, and 

Arizona, by parties of the expeditions, of 1871, 1872, 1873, and 

1874: U.S. Geographical and Geological Explorations and Surveys 

West of the 100th Meridian Report (Wheeler), v. 4, pt. 1, 219 

p., 21 pis.

 1883, Contributions to invertebrate paleontology, No. 2; Cretaceous fossils of the Western States and Territories: U.S. Geological and Geographical Survey of the Territories, 12th Annual Report (Hayden), pt. 1, p. 5-39, pis. 11-18.

Whitfield, R. P., 1877, Preliminary report on the paleontology of the 

Black Hills, containing descriptions of new species of fossils from 

the Potsdam, Jurassic, and Cretaceous formations of the Black 

Hills of Dakota: U.S. Geographical and Geological Survey Rocky 

Mountain Region Report (Powell), 49 p.

 1880, Paleontology of the Black Hills of Dakota, in Newton, 

Henry, and Jenney, W.P., Report on the geology and resources 

of the Black Hills of Dakota: U.S. Geographical and Geological 

Survey Rocky Mountain Region (Powell), p. 325-468, 16 pis.

Wiedmann, Jost, 1965, Origin, limits, and systematic position of 

Scaphites: Palaeontology, v. 8, pt. 3, p. 397-453, pis. 53-60.

Woods, Henry, 1911, A monograph of the Cretaceous Lamellibranchia 

of England, v. 2, pt. 7: Palaeontographical Society Monograph, 

v. 64, p. 261-284, pis. 45-50.

Wright, C. W., 1953, Notes on Cretaceous ammonites. 1. Scaphitidae: 

Annals and Magazine of Natural History, ser. 12, v. 6, p. 473- 

476.

 1963, Cretaceous ammonites from Bathurst Island, Northern 

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Series, v. 31, no. 4, p. 281-332, 7 pis.

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County, Arizona: Journal of Paleontology, v. 31, no. 6, p. 1167- 

1174, pis. 149, 150.

INDEX

[Italic numbers indicate major references]

D Page I Page

Acanthoeeras alvamdoense ............................. 13, 18

amphibolum ............... 1, 2, 8, 13, 17, 18; pi. 5

hippocastanum ............................................... 2

uryomingense ................................................. 2

sp. A ........................................................... 2

sp. ............................................................ 2, 8

albertense, Dunveganoceras ................... 1, 4, 12, 17

Allocrioceras annulatum ................ 2, 4, 6, ^6; pi. 2

pariense ...................................................... 16

atoaradoewse, Aeawt/wceras ............................ 13, 18

Amauropsis bulbiformis ........................................ 5

sp. ................................................................ 5

Ammonites novi-mexicani ................................... 14

amphibolum, Acanthoeeras . 1, 2, 8, 13, 17, 18; pi. 5 

Ancycloceras annulatus ...................................... 16

annulatum, Allocrioceras ............... 2, 4, 6, iS; pi. 2

annulatus, Ancycloceras ..................................... 16

Arrkoges sp. ........................................................ 7

Astarte sp. .......................................................... 7

B

Baculites besairei ............................................... 14

yokoyamai .................................. 4, 5, J-t; pi. 1

sp. ........................................................ 4, 5, 6

Belle Fourche Shale .............. 1, 2, 8, 13, 14, 17, 18

Bellifusus sp. ...................................................... 5

beloiti, Ostrea ....................................... 8, i#; pi. 5

Benton Shale ................................................ 17, 19

bentonensis, Pseudoperna ..................................... 5

besairiei, Baculites ............................................. 14

Bighorn Mountains ............................................. 17

bighornensis, Scaphites corvensis ......................... 14

birchbyi, Vascoceras (Greenhornoceras) ................ 10

Black Hills uplift ................................................. 1

bohemicus, Inoeeramus ....................................... 11

pictus ...................................... 6, 11; pi. 3

Borissiakoceras orbiculatum ................... 7, 18; pi. 4

reesidei .......................................... 8, i7; pi. 5

sp. ............................................................ 7, 8

Bridge Creek Limestone Member of Greenhorn

Formation .._.............. .. ... 10, 11, 18

bulbiformis, Amauropsis ....................................... 5

Calliomphalus ..................................................... 6

capulus, Inoeeramus .......................................... 11

Carlile Shale ................................... 1, 4, 9, 14, 15

carlilensis, Scaphites ............................................ 4

Chalk Marl of England ................................. 11, 12

Cody Shale .................................................. 13, 14

Collignoniceras woollgari ...................... 1, 2, 10, 15

regulare ........................... 2, 4, 5, U; pi. 2

woollgari ................................................. 2

Colorado Formation ............................................ 17

coloradoense, Watinoceras ................................... 10

Cone Member of Marias River Shale .................. 15

corrugatus, Stomohamites ................................... 17

corvensis, Scaphites ................. 1, 4, 5, 14, 15; pi. 1

bighornensis, Scaphites ................................. 14

Cremnoceramus rotundatus ............. 2, 4, 5, 9; pi. 1

waltersdorfensis ............... 1, 2, 4, 5, #, 9; pi. 1

hannovrensis ........................................... 8

waltersdorfensis ....................................... 8

Crenella sp. ........................................................ 7

crippsi, Inoeeramus ...................... 2, 7, 8, i2; pi. 5

reachensis, Inoeeramus .................................... 12

Dakota Sandstone .............................................. 12

Damesites .......................................................... 18

defordi, Metoieoeeras .......................................... 17

Desmoceras sp. .................................................. 18

dresdensis labiatoidiformis, Mytiloides ................... 5

Dunvegan Formation .......................................... 13

Dunveganoceras albertense .................... 1, 4, 12, 17

pondi .............................................. 1, 2, 4, 17

sp. ................................................................ 7

duplicostatus, Mytiloides ............... 1, 4, 6, JO; pi. 2

E

Eagle Ford Formation ............................ 11, 16, 18

elegant, Prinocyclus vryomingensis ...................... 14

Entolium gregarium ........................................... 13

sp. ......................................... 5, 6, 7, 13; pi. 4

Eucalyoceras ep. B ............................................ 19

Euspira sp. ......................................................... 6

Exiteloceras pariense .......................................... 16

Fairport Chalky Member of Carlile Shale ............ 15

Ferdig Member of Marias River Shale ................ 15

fiegei, Inoeeramus fiegei ....................................... 9

Mytiloides ..................................................... 9

fiegei .................................... 2, 5, 9; pi. 1

fiegei, Inoeeramus .......................................... 9

Mytiloides ............................. 2, 5, 9; pi. 1

mytiloidiformis, Inoeeramus ........................... 9

Mytiloides ............................ 5, 9; pis. 1, 2

flavus, Inoeeramus .............................................. 7

pictoides, Inoeeramus ..................................... 6

Frontier Formation ................................... 4, 14, 15

G

ginterensis, Inoeeramus ............... 4, 6, 11; pis. 3, 4

goniophora, Veniella ......................... 4, 5, ./#; pi. 1

gracile, Sciponoceras ............. 1, 2, 4, 11, 16, 18, 19

Graneros Shale ............................................. 17, 18

Greenhorn Formation .. 1, 2, 4, 5, 10, 16, 17, 18, 19 

(Greenhornoceras) birchbyi, Vascoceras ................ 10

gregarium, Entolium ......................................... 13

Gyrodes sp. ......................................................... 5

H

Hamites simplex ................................................ 16

(Stomohamites) simplex . 6, 7, 8, 16; pis. 3, 4, 5 

sp. .......................................................... 7

sp. ................................................................ 8

hannovrensis, Cremnoceramus waltersdorfensis ....... 8

Hartland Shale Member of Greenhorn Formation . 12,

13,19 

Heliocoeeras pariense ......................................... 16

sp. .............................................................. 17

Hemiptychoceras reesidei .................................... 18

sp. .............................................................. 18

hippocastanum, Acanthoeeras ................................ 2

Hoploparia sp. .................................................... 5

hyatti, Prionoeyelus ............................................. 4

incertus, Inoeeramus ............................................ 9

inconstans, Inoeeramus inconstans ........................ 9

inconstans, Inoeeramus .................................. 9

rotundatus, Inoeeramus .................................. 9

Inoeeramus bohemicus ........................................ 11

capulus ....................................................... 11

crippsi ................................... 2, 7, 8, IS; pi. 5

reachensis ............................................. 12

fiegei fiegei .................................................... 9

mytiloidiformis ........................................ 9

flavus ........................................................... 7

pictoides .................................................. 6

ginterensis ............................ 4, 6, J2; pis. 3, 4

incertus ......................................................... 9

inconstans inconstans ..................................... 9

rotundatus ............................................... 8

labiatus .................................................. 10, 11

subhercynica .......................................... 10

mytiloides ..................................................... 9

neocalendonicus ........................................... 11

opalensis ..................................................... 10

perplexus ....................................... 5, i./; pi. 2

picta ........................................ 2, 6, JJ; pi. 2

bohemicus ................................ 6, U; pi. 3

neocalendonicus ........................ 6, 11; pi. 3

jtnrfws .................................. 4, 6, JJ; pi. 3

prefmgilis .................... 2, 4, 7, 8, J2; pis. 4, 5

rotundatus ..................................................... 9

rutherfordi ............................ 2, 8, J#, 18; pi. 5

walterdorfensis ............................................... 8

sp. ......................................... 6, 7, 8, 1%; pi. 3

J, K

Juana Lopez Member of Manocs Shale ........... 14, 15

juddii, Neocardioceras ................................... 16, 19

Kevin Member of Marias River Shale ................. 13

kottlowskii, Neostlingoceras ..................... 7 17; pi. 4

labiatoidiformia, Mytiloides dresdensis ................... 5

labiatus, Inoeeramus ..................................... 10, 11

subhercynica, Inoeeramus ............................. 10

(Latidorsella) sp., Puzosia .................................. 18

Lincoln Limestone Member of Greenhorn Formation . 19 

Lingula sp. ..................................................... 7, 8

Lucina sp. .......................................................... 4

M

Macroscaphites vermiculus .................................. 16

Mammites nodosoides ......................................... 10

sp. .............................................................. 19

Mancos Shale .................................... 14, 15, 16, 17

Marias River Shale ....................................... 13, 15

meeki, Scaphites nigricollensis ............................ 15

Metaptychoceras reesidei ........................ 6, 18; pi. 4

sp. .............................................................. 18

Metoieoeeras defordi ........................................... 17

mosbyense .................................. 4, 7, 17; pi. 4

sp. ............................................................ 6, 7

Middle Chalk of England .................................... 10

minuta, Phelopteria .............................. 6, 13; pi. 3

minutus, Otoscaphites ........................................ 16

Scaphites ..................................................... 16

(Pteroscaphites) ................. 2, 4, 6, J6; pi. 2

23
24 INDEX

Page 

Molluscan zones ................................................... 2

Moremanoceras sp. ................. 6, 7, 8, 18; pis. 4, 5

mosbyense, Metoicoceras .................... 4, 7, 17; pi. 4

Mytiloides dresdensis labiatoidiformis .................... 5

duplicostatus .......................... 1, 4, 6, J0; pi. 2

........................... 2, 5, 9; pi. 1

mytiloidiformis ..................... 5, 9; pis. 1, 2

mytiloides ....................... 1, 2, 4, 5, 6, 9, pi. 2

sis .................................... 5, 6, 10; pi. 2

.......................... 2, 5, .Z0; pi. 2

Mytiloides sp. ............................ 2, 6, JO, 11; pi. 3

mytiloides, Inoceramus ......................................... 9

Mytiloides ....................... 1, 2, 4, 5, 6, 9; pi. 2

mytiloidiformis, Inoceramus fiegei ......................... 9

Mytiloides fiegei ......................... 5, 9; pis. 1, 2

N

neocalendonicus, Inoceramus .............................. 11

pichts ...................................... 6, 11; pi. 3

Neocardioceras juddii .................................... 16, 19

sp. ............................................. 6, 7, .Z0; pi. 4

Neostlingoceras kottlowskii ..................... 7, -/?; pi. 4

nigricollensis, Scaphites ................. 1, 4, 5, J5; pi. 1

meeki, Scaphites .......................................... 15

Niobrara Formation ............................................ 14

nodosoides, Mammites ........................................ 10

novi-mexicani, Ammonites .................................. 14

novimexicanus, Prionocyclus .............. 4, 5, ./4; pi. 1

Nucula (Pectinucula) sp. ................................ 4, 5

Nuculana sp. .............................................. 4, 5, 7

0

opalensis, Inocramus ......................................... 10

Mytiloides .................................. 5, 6, iO; pi. 2

orbiculatum, Borissiakoceras .................. 7, iS; pi. 4

Osage oilfield ....................................................... 1

Ostrea beloiti ........................................ 8, 13; pi. 5

Otoscaphites minutus ......................................... 16

Oyster Ridge Sandstone Member of Frontier

Formation ...................................... 15

pariense, Allocrioceras ....................................... 16

Exiteloceras ................................................. 16

Helicoceras .................................................. 16

Parmicorbula sp. ................................................. 8

Peace River, Alberta ......................................... 13

(Pectinucula) sp., Nucula ................................. 4, 5

perplexus, Inoceramus ........................... 5, 11; pi. 2

Phelopteria minuta ............................... 6, i5; pi. 3

sp. ........................................................ 4, 5, 6

Pkoladomya sp. ................................................... 4

pictoides, Inoceramus flavus ................................. 6

pictus, Inoceramus ............................ 2, 6, ././; pi. 2

ptcfots .................................. 4, 6, 11; pi. 3

bohemicus, Inoceramus .................... 6, ././; pi. 3

neocalendonicus, Inoceramus ........... 6, i.Z; pi. 3

pictus, Inoceramus ...................... 4, 6, i.Z; pi. 3

Page 

Plesiacanthoceras wyomingense ............................. 2

Pleuriocardia sp. ................................................. 8

Plicatula sp. ....................................................... 5

pondi, Dunveganoceras ........................... 1, 2, 4, 17

Pool Creek Member of Carlile Shale ........... 1, 5, 15

Powder River Basin ......................................... 1, 8

prefragilis, Inoceramus ........ 2, 4, 7, 8, 12; pis. 4, 5

Preservation, fossil ............................................... 2

Prionocyclus hyatti .............................................. 4

novimexicanus ............................ 4, 5, 14; pi. 1

wyomingensis elegans ................................... 14

sp. ................................................................ 5

Prionotropis woollgari ........................................ 15

regularis ............................................... 14

Pseudoperna bentonensis ...................................... 5

sp. ................................................................ 5

(Pteroscaphites) minutus, Scaphites . 2, 4, 6, 16; pi. 2 

Puzosia (Latidorsella) sp. ................................... 18

sp. .............................................................. 18

R

reachensis, Inoceramus crippsi ............................ 12

reesidei, Borissiakoceras ........................ 8, J7; pi. 5

Hemiptychoceras .......................................... 18

Metaptychoceras .............................. 6, JS; pi. 4

regulare, Collignoniceras woollgari . 2, 4, 5, .U; pi- 2 

regularis, Prionotropis woollgari ......................... 14

rotundatus, Cremnoceramus ............ 2, 4, 5, 9; pi. 1

Inoceramus ................................................... 9

inconstans ............................................... 9

rutherfordi, Inoceramus ............... 2, 8, 75, 18; pi. 5

Sage Breaks Member of Carlile Shale ... 1, 4, 13, 14 

San Rafael Swell ............................................... 15

Scaphites carlilensis ............................................. 4

corvensis .......................... 1, 4, 5, U, 15; pi. 1

bighornensis .......................................... 14

minutus ...................................................... 16

nigricollensis .......................... 1, 4, 5, i5; pi. 1

raeefci.................................................... 15

vermiculus .................................................. 16

warreni ............................. 1, 2, 4, 5, J5; pi. 1

ubiquitosus ............................................ 15

whitfieldi ................................................... 1, 4

(Pteroscaphites) minutus .......... 2, 4, 6, -Z6; pi. 2

sp. ............................................................ 4, 5

Sciponoceras gracile .............. 1, 2, 4, 11, 16, 18, 19

sp. .............................................................. 6

simplex, Hamites ............................................... 16

(Stomohamites) ....... 6, 7, 8, 16; pis. 3, 4, 5

Stomohamites .............................................. 17

Soap Creek Bentonite Bed ................................. 17

Solemya sp. ........................................... 8

Stomohamites corrugatus .................................... 17

simplex ....................................................... 17

Page

(Stomohamites) simplex, Hamites ................. 6, 7, 8,

16; pis. 3, 4, 5 

sp., Hamites ................................................. 7

Stratigraphic distribution ...................................... 2

Stratigraphic summary .......................................... 1

Striarea sp. ..................................................... 4, 5

subhereynica, Inoceramus labiatus ...................... 10

subhereynicus, Mytiloides .................. 2, 5, 10; pi. 2

Tarrantoceras sp. ............................................... 19

Tropic Shale ...................................................... 15

Turner Sandy Member of Carlile Shale ....... 1, 2, ^,

5, 9, 12, 13, 14, 15 16 

Turrilites sp. ..................................................... 17

Two wells Tongue of Dakota Sandstone ................ 12

U, V 

ubiquitosus, Scaphites warreni 15

Vascoceras (Greenhornoceras) birchbyi ................. 10

Veniella goniophora .......................... 4, 5, 13; pi. 1

vermiculum, Worthoceras ........................ 2, 4, 6, 16

vermiculus, Macroscaphites ................................. 16

Scaphites ..................................................... 16

Worthoceras ........................................ IS; pi. 2

W, Y

Wall Creek Member of Frontier Formation ......... 14

walterdorfensis, Inoceramus .................................. 8

waltersdorfensis, Cremnoceramus . 1, 2, 4, 5, 8, 9; pi. 1 

waltersdorfensis ....................................... 8

hannovrensis, Cremnoceramus ........................ 8

waltersdorfensis, Cremnoceramus .................... 8

warreni, Scaphites ................... 1, 2, 4, 5, 15; pi. 1

ubiquitosus, Scaphites .................................. 15

Watinoceras coloradoense .................................... 10

whitfieldi, Scaphites ......................................... 1, 4

Woodbine Formation .......................................... 12

woollgari, Collignoniceras ..................... 1, 2, 10, 15

woollgari ................................................. 2

Prionotropis ................................................ 15

regulare, Collignoniceras ......... 2, 4, 5, J.4; pi. 2

regularis, Prionotropis ................................. 14

woollgari, Collignoniceras ............................... 2

Worthoceras vermiculum ......................... 2, 4, 6, 16

vermiculus ......................................... iff; pi. 2

sp. ................................................................ 6

wyomingense, Acanthoceras .................................. 2

Plesiacanthoceras ........................................... 2

elegans, Prionocyclus ................................... 14

yokoyamai, Baculites ........................ 4, 5, 14; pi. 1

U.S. GOVERNMENT PRINTING OFFICE: 1984 776-O41/4O32
PLATES 1-5
PLATE 1

[All figures natural size]

FIGURE 1. Cremnoceramusl waltersdorfensis (Andert) (p. 8).

Hypotype USNM 308017 from depth of 34 m. 

2, 3. Cremnoceramusl rotundatus (Fiege) (p. 9).

Hypotypes USNM 308018 and 308019 from depths of 36 and 39 m. 

4. Veniella goniopkora Meek (p. 13).

Hypotype USNM 308020 from depth of 79 m. 

5, 6. Baculites yokoyamai Tokunaga and Shimizu (p. 14).

Hypotypes USNM 308021 and 308022 from depths of 45 and 107 m. 

7. Scaphites corvensis Cobban (p. 14).

Hypotype USNM 308023 from depth of 81 m. 

8, 9, 11, 12. Mytiloides fiegei mytiloidiformis (Troger) (p. 9).

Hypotypes USNM 308024, 308026-308028 from depths of 86 and 103.1-104 

m. 

10. Mytiloides fiegei fiegei (Troger) (p. 9).

Hypotype USNM 308025 from depth of 76 m.

13. Scaphites nigricollensis Cobban (p. 15).

Hypotype USNM 308029 from depth of 96 m.

14. Scaphites warreni Meek and Hayden (p. 15).

Hypotype USNM 308030 from depth of 136 m. 

15, 16. Prionocyclus novimexicanus (Marcou) (p. 14).

Hypotype USNM 308031 and 308032 from depth of 106.2 m.
GEOLOGICAL SURVEY PROFESSIONAL PAPER 1271 PLATE 1

 &* 

12

13 14

CREMNOCERAMUS1, VENIELLA, BACULITES, SCAPHITES, 

MYTILOIDES, AND PRIONOCYCLUS
PLATE 2

[All figures natural size]

FIGURES 1-3. Inoceramus perplexus Whitfield (p. 11).

Hypotypes USNM 308033-308035 from depths of 106.7-111.4 m.

4. Allocrioceras annulatum (Shumard) (p. 16).

Hypotype USNM 308036 from depth of 184 m.

5. Worthoceras vermiculum (Shumard) (p. 16).

Hypotype USNM 308037 from depth of 184 m. 

6, 7. Collignoniceras woollgari regulare (Haas) (p. 14).

Hypotypes USNM 308038 and 308039 from depths of 155.7-157.9 m.

8. Mytiloides subhercynicus (Seitz) (p. 10).

Hypotype USNM 308040 from depth of 167.1 m.

9. Scaphites (Pteroscaphites) minutus Moreman (p. 16). 

Hypotype USNM 308041 from depth of 181.5 m.

11. Mytiloides opalensis (Bose) (p. 10).

Two different forms like those illustrated by (Bose 1923). Hypotype USNM 

308042 and 308043 from depths of 167.5 and 178.7 m.

12. Mytiloides fiegei mytiloidiformis (Troger) (p. 9). 

Hypotype USNM 308044 from depth of 88 m.

13. Mytiloides aff. M. duplicostatus (Anderson) (p. 10).

Figured specimen USNM 308045 from depth of 173 m. 

14, 15. Mytiloides mytiloides (Mantell) (p. 9).

Hypotypes USNM 308046 and 308047 from depths of 169.2 and 171 m. 

16. Inoceramus cf. /. pieties J. de C. Sowerby (p. 11).

Figured specimen USNM 308048 from depth of 179.5 m.
GEOLOGICAL SURVEY PROFESSIONAL PAPER 1271 PLATE 2

m -

' V

11 12

13 15 16

INOCERAMUS, ALLOCRIOCERAS, WORTHOCERAS, COLLIGNONICERAS, 

MYTILOIDES, AND SCAPHITES
PLATE 3

[All figures natural size]

FIGURE 1. Mytiloides sp. (p. 10).

Figured specimen USNM 308049 from depth of 178.8 m. 

2. Phelopterla minuta Kauffman and Powell (p. 13).

Hypotype USNM 308050 from depth of 186.7 m. 

3, 4, 14. Inoceramus pictus neocaledonicus Jeannet (p. 11).

Hypotypes USNM 308051-308053 from depths of 181.5,186, and 190.5 m. 

5-7. Inoceramus pictus pictus 3. de C. Sowerby (p. 11).

Hypotypes USNM 308054-308056 from depths of 185.1-186.8 m. 

8. Inoceramsu cf. /. pictus bohemicus Leonhard (p. 11).

Figured specimen USNM 308057 from depth of 197 m. 

9, 13. Hamites (Stomohamites) simplex d'Orbigny (p. 16).

Hypotypes USNM 308063 and 308064 from depth of 202 m. 

10-12. Inoceramus ginterensis Pergament (p. 12).

Hypotypes USNM 308058-308060 from depths of 197-201 m. 

15, 16. Inoceramus sp. (p. 12).

Figured specimens USNM 308061 and 308062 from depths of 203.1 and 210.3
GEOLOGICAL SURVEY PROFESSIONAL PAPER 1271 PLATE 3

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MYTILOIDES, PHELOPTERIA, INOCERAMUS, AND HAMITES
PLATE 4

[All figures natural size]

FIGURES 1-3, 5, 6. Neocardioceras spp. (p. 19).

Figured specimens USNM 308068-308072 from depths of 198.4, 198.5, 

211.8, 212.1, and 231.6 m. Figure 1 also has a juvenile Inoceramus 

ginteresis Pergament, and figure 6 also has Hamites (Stomohamites) simplex d'Orbigny. 

4. Borissiakoceras cf. B. arbiculatum Stephenson (p. 18).

Figured specimen USNM 308084 from depth of 228 m. 

7. Metaptychoceras reesidei (Cobban and Scott) (p. 18) and Entolium

sp. (p. 13).

Hypotype USNM 308074 from depth of 200 m. 

8, 13. Hamites (Stomohamites) simplex d'Orbigny (p. 16).

Hypotypes 308073 and 308065 from depths of 225 and 220.5 m. Figure

8 also has a juvenile Neocardioceras sp. 

9. Neostlingoceras kottlowskii Cobban and Hook (p. 17).

Hypotype USNM 308075 from depth of 232 m. 

10, 11. Inoceramus prefragilis Stephenson (p. 12).

Hypotypes USNM 308076 and 308077 from depth of 222.7 m. Figure

11 also has a small Hamites (Stomohamites) simplex d'Orbigny. 

12, 16. Moremanoceras sp. (p. 18).

Figured specimens USNM 308079 and 308080 from depths of 210.5 

and 224 m. Figure 16 also has a specimen of Hamites (Stomohamites) simplex d'Orbigny. 

14, 15. Metoicoceras cf. M. mosbyense Cobban (p. 17).

Hypotypes USNM 308082 and 308083 from depth of 216 m.
GEOLOGICAL SURVEY

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PROFESSIONAL PAPER 1271 PLATE 4

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NEOCARDIOCERAS, BORISSIAKOCERAS, METAPTYCHOCERAS, HAMITES, 

NEOSTLINGOCERAS, AND INOCERAMUS
PLATE 5

[All figures natural size]

FIGURES 1-3. Inoceramus crippsi Mantell (p. 12).

Hypotypes USNM 308085 and 308086 from depth of 238 m and hypotype

USNM 308087 from depth of 244 m. 

4, 5. Handles (Stomohamites) simplex d'Orbigny (p. 16).

Hypotypes USNM 308066 and 308067 from depths of 236 and 233 m.

6. Inoceramus prefragilis Stephenson (p. 12).

Hypotype USNM 308078 associated with a shark tooth from depth of 240 

m.

7. Moremanoceras sp. (p. 18).

Figured specimen USNM 308081 from depth of 222.7 m.

8. Borissiakoceras reesidei Morrow (p. 17).

Hypotype USNM 308088 from depth of 248 m. 

9, 10. Acanthoceras amphibolum Morrow (p. 18).

Hypotype USNM 308089 and 308090 from depths of 254.5 and 249 m.

11. Ostrea beloiti Logan (p. 13).

Hypotype USNM 308091 from depth of 257.7 m.

12. Inoceramus rutherfordi Warren (p. 13).

Hypotype USNM 308092 from depth of 265 m.
GEOLOGICAL SURVEY PROFESSIONAL PAPER 1271 PLATE 5

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INOCERAMUS, HAMITES, MOREMANOCERAS, BORISSIAKOCERAS, 

ACANTHOCERAS, AND OSTREA