Upper Cretaceous Gastropods 

From the Pierre Shale at 

Red Bird, Wyoming

GEOLOGICAL SURVEY PROFESSIONAL PAPER 393-B
Upper Cretaceous Gastropods 

From the Pierre Shale at 

Red Bird,Wyomin

By NORMAN F. SOHL

STRATIGRAPHY, PALEONTOLOGY, AND SEDIMENTATION OF 

A CLASSIC REFERENCE LOCALITY OF THE PIERRE SHALE

GEOLOGICAL SURVEY PROFESSIONAL PAPER 393-B

A discussion of the Pierre Shale gastropod fauna, 

including a description of 23 named species, 

occurring in the Red Bird section

UNITED STATES GOVERNMENT PRINTING OFFICE, WASHINGTON : 1967
UNITED STATES DEPARTMENT OF THE INTERIOR 

STEWART L. UDALL, Secretary

GEOLOGICAL SURVEY 

William T. Pecora, Director

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

Washington, D.C. 20402 - Price 65 cents (paper cover)
CONTENTS

Page

Abstract. _ _ _ _ __ __________________________________ Bl

Introduction _______________________________________ 1

Acknowledgments ___________________________________ 2

General remarks on Cretaceous gastropods of the western

interior._________________________________________ 2

Pierre Shale gastropods______________________________ 3

Red Bird section_ ________ _______________________ 3

Diversity,_________________________________ 3

Abundance and occurrence___________________ 3

Preservation. ______________________________ 3

Notes on ecology.__________________________ 3

Other areas ____________________________________ 5

Colorado._________________________________ 5

South Dakota and Montana.________________ 7

Bearpaw Shale of Montana and Canada_______ 8

Summary _ _____________________________________ 8

Proposed new species ________________________________ 9

Changes in generic or specific assignment ______________ 9

Measurements of specimens __________________________ 9

Systematic descriptions._______

Order Archaeogastropoda__ 

Family Trochidae_--__

Order Mesogastropoda_

Family Aporrhaidae___ 

Family Vanikoridae___ 

Family Trichotropidae. 

Family Naticidae_____ 

Family Cymatiidae___.

Order Neogastropoda______

Family Fasciolariidae_.

Order Cephalaspidea ______

Family Acteonidae____

Family Ringiculidae__. 

Family Scaphandridae. 

Family Bullidae______

Order Bassomatophora____

Family Siphonariidae_. 

References ___________________

Index.______________________

Page

BIO

10

10

11

11

22

23

24

28

29

29

33

33

34

35

35

36

36

40

43

ILLUSTRATIONS

[Plates follow index]

PLATE 1. Atiral, Euspira, Euspiraf, and Lunatia.

2. Aporrhais.

3. Drepanochilus.

4. Astandes and Drepanochilus.

5. Vanikoropsis and Vanikoro.

6. Vanikoropsis, Fasciolaria, Trachytriton, and Serrifusus.

7. Bullopsis, Ellipsoschapha, Cryptorhytis, Anomalofusust', and Graphidula.

8. Nonacteonina, Oligoptycha, and Anisomyon. 

9-11. Anisomyon.

Page

FIGURE 1. Chart showing geographic and stratigraphic distribution of the gastropod species of

the Pierre Shale of the Red Bird section_ _______________..-.---------------------- B6

2. Graph showing comparison of the suture to upper whorl carination and the intercarination distances in the Pierre Shale species of Drepanochilus--.-,-------.------------- 13

3-7. Diagrams showing relation between whorl number and height and between whorl 

number and width:

3. Drepanochilus evansi Cossmaim------------------------------------------ 14

4. Drepanochilus pusillus (Stanton)____________-________--_----_------------ 15

5. Drepanochilus scotti Sohl, n. sp__________-___________------------.-------- 16

6. Drepanochilus nebrascensis (Evans and Shumard)._ _____________-_-------_ 18

7. Aporrhais biangulata Meek and Hayden_________________--_---_---_----- 21

8. Comparative plot between Euspira obliquata (Hall and Meek) (dots) and Natica subcrassa Meek and Hayden (crosses) of pleural angle versus height of shell____ __________ 26

9. Graph showing comparison of height-width variation between Euspira rectilabrum

(Conrad) and Euspira obliquata (Hall and Meek)________________---_--_---------- 26

10. Drawing of muscle-scar pattern of some species of Anisomyon Meek and Hayden ________ 37

11. Diagram of sculpture pattern of Anisomyon centrale.--------------------------- 38
IV CONTENTS

TABLES

Page 

TABLE 1. Distribution of the gastropod species in the members of the Pierre Shale of the Red Bird

section. ____________________________________________________________________ B4

2. Distribution and abundance of aporrhaid genera in the Cretaceous rocks of North

America_________________________________________________________________ 12
STRATIGRAPHY, PALEONTOLOGY, AND SEDIMENTATION OF A CLASSIC REFERENCE LOCALITY

OF THE PIERRE SHALE

UPPER CRETACEOUS GASTROPODS FROM THE PIERRE SHALE 

AT RED BIRD, WYOMING

By NORMAN F. SOHL

ABSTRACT

The Pierre Shale gastropod faunas show a great similarity 

at almost all stratigrapliic levels over the whole of the western 

interior, from Colorado and Wyoming eastward to the Dakotas 

and eastern Montana. The equivalent Bearpaw Shale of Canada 

and Montana contains the same fauna. Aside from taxonomic 

uniformity, one consistent feature of the fauna is that the upper 

stratigraphic levels contain a greater abundance and diversity 

of gastropods than the lower stratigraphic levels. Compared 

to the overlying Fox Hills Sandstone there is a significant 

change, very few species being common to the .two formations, and many genera that are common in one formation are 

absent in the other.

Contrary to published consensus the Pierre .Shale gastropod 

fauna 'Shows considerable similarity to the contemporaneous 

faunas of the gulf coast. This similarity increases to the south 

in Colorado, especially in the sandier units, such as the I/arimer 

Sandstone Member of the Pierre Shale of the Front Range of 

Colorado. As an example, of the 53 gastropod genera represented in the Pierre Shale only 8 are not common to the gulf 

coast. Some genera, such as Bullopsis, Oliffoptycha, Belliscala, 

Lomirosa, Remera, Scobinodolus, and Napultts, are known only 

from these two areas. In spite of these similarities, genera 

such as Turriteila, and Pugnellus, $<o common in the Coastal 

Plain Cretaceous sediments, are absent in the Pierre Shale, 

although in some nearshore sandier facies, such as the Lewis 

Shale, they may be abundant.

The gastropod fauna is consistent with a marine shallowwater environment and includes both epifaunal and infaunal 

elements. Feeding habits range from plant browsers to detritus 

feeders and carnivores. The absence of filter feeding snails may 

be a reflection of particle size of the sediment or excessive 

turbidity.

Gastropods occur through 1,700 feet of the 3,137-foot sequence 

of Pierre Shale in the Red Bird section. They first appear in 

the uppermost bed of the Mitten Black Shale Member and range 

upward to the lower part of the Baculites grandis zone beds. 

They are most abundant and diverse in the upper part of the 

section, especially in beds of the Baculitcs baculus zone.

In the Red Bird section, 23 distinct gastropod species occur. 

Several others are assignable only to genera because of poor 

preservation. Two-thirds of the gastropods belong to the subclass Streptoneura and one-third to the Euthyneura. Although 

four 'species are cited as new, only two, DrepanocMlus scotti 

and D. obesus, are represented by sufficient material to name

formally. These two species represent part of an evolving lineage characterized by a change from older to younger species in 

1. The upper whorl carination becoming proportionally closer 

to the suture,

2. Proportional narrowing of the intercarination area,

3. Progressive development of nodes on the upper body whorl 

carination, and

4. Loss on inner surface of expanded outer lip wing of a welt 

that parallels wing edge.

Of special note is the discovery of specimens retaining the 

muscle-scar pattern in species of the unusual siphonariid 

pulmonate gastropod Anisomyon. Although all retain the basic 

muscle-scar pattern with an interruption of the band in the 

right posterior quadrant, the amount of variation in positioning 

of other parts of the 'band is high.

Many of the species are figured for the first time since Meek's 

classic studies (1876) ; therefore the opportunity has 'been taken 

to illustrate photographically most of the type specimens.

INTRODUCTION

The primary purpose of this paper is to redefine, 

describe, and figure the gastropod species occurring in 

a complete section of the Pierre Shale in the vicinity of 

Eed Bird, Niobrara County, Wyo. (sees. 13, 14, 23, T. 

38 N., R. 62 W.). This work is a part of a larger investigation of the fauna and microflora recovered from 

the more than 3,000 feet of Pierre Shale at this locality. 

The detailed stratigraphy and associated problems have 

been outlined by Gill and Cobban (1966). The stratigraphic nomenclature and faunal zonation used in this 

paper are defined by the aforementioned authors.

To adequately discuss and define the gastropod species 

of the Red Bird section it has been necessary to include 

figures of the type material, most of which has not been 

figured since the time of Meek (1876). Collections 

from other areas of outcrop in the Fox Hills Sandstone 

and Pierre Shale have been studied, and some specimens 

from these formations have been included herein. The 

most valuable of these consist of the gastropod portions 

of more than 1,000 collections, made by W. A. Cdbban 

and associates, from the Pierre Shale of the Front

Bl
B2 DESCRIPTIVE STUDY OF A CLASSIC REFERENCE LOCALITY OF THE PIER RE SHALE

Range in Colorado. All collections are precisely located stratigraphically and have formed the major basis 

for defining the total stratigraphic range of the species. 

Without them the present work could have been little 

more than an outline taxonomic contribution based on 

a few specimens.

ACKNOWLEDGMENTS

Grateful acknowledgment is made Dr. Harald 

Render, Division of Mollusks of the U.S. National 

Museum, who furnished specimens of Vanikoro for 

study and figuring. Dr. N. D. Newell, of the American 

Museum of Natural History, kindly arranged for the 

loan of some of the Hall and Meek types. The photographs were made by R. H. McKinney. Type specimens are deposited in the U.S. National Museum.

GENERAL REMARKS ON CRETACEOUS GASTROPODS 

OF THE WESTERN INTERIOR

Of the larger marine invertebrates in the western interior Cretaceous sequence, more concentrated work has 

been done on the ammonites than on any other group. 

To a large degree this has been because of their recognized stratigraphic utility. For the same reason Inoceramus among the clams has received considerable 

attention. Most of the gastropods described from these 

beds were first described by such men as Meek, Hayden, 

Evans, Shumard, C. A. White, Whitfield, and Stanton. 

A few additional gastropods have been described in recent years, but mainly as adjuncts to papers dealing 

primarily with ammonites. Thus, names proposed by 

Meek and other early authors have been handed down 

with relatively few nomenclatural changes, and most 

have been used in the broadest sense in faunal lists. 

Such usage without reappraisal of the species concept 

has engendered common misuse. This is especially 

unfortunate because many of these species are the types, 

for genera to which species from Cretaceous sequences 

in areas as distant from the western interior as Africa 

have been assigned.

It is clear that some foreign authors have used these 

genera, not in the sense of the original author but in that 

of some subsequent author who may have misidentified 

his material. Commonly, such misuse can be ascribed 

to hazy definition of genera that results from inadequate 

original material. An indication of the extent to which 

reexamination and new material can change the assignment of some species is the example of Fasciolaria buccinoides Meek and Hayden from the Fox Hills Sandstone of South Dakota. Specimens collected recently 

by me (pi. 6, figs. 5, 9) show a denticulate inner surface 

of the outer lip and a highly denticulate parietal surface 

of the inner lip. These features, as noted in the discussion of Trachytriton below, ally F. buccinoides with

the Tonnacea rather than the Fasciolariidae of the Buccinacea. The change in assignment is not only at the 

superfamily level, but shifts the species from the Order 

Neogastropoda to the Order Mesogastropoda.

Obvious reason for the lack of interest in the Cretaceous gastropods of the western interior are their generally poor state of preservation in many stratigraphic 

units, restricted local abundances, and difficulty of recovery when found. Most commonly gastropods 'are 

found in concretions which generally yield complete 

ammonites but only exfoliated snails. Even when exfoliated the ammonites may be indentified, but for confident placement of the gastropods it is usually necessary to have a knowledge of their apertural features in 

addition to their sculpture. Therefore, it usually takes 

great care and meticulous preparation to clean and recover the gastropods. Another, but less important, 

factor is that many snails are very small and thus 

easily overlooked.

Some workers may have been discouraged from giving the gastropods sufficient study by statements in the 

literature. For example, in summarizing the paleogeography of the Cretaceous of the western interior, 

Reeside (1957, p. 539) states that the CampanianMaestrichtian faunas have a provincial aspect and that 

"among the gastropods the number of species common 

to the two regions [western interior and gulf coast] is 

almost infinitesimal in comparison to the total fauna." 

In fact, in comparing the faunas from these two areas 

Stephenson and Reeside (1958) list only two species of 

gastropods, Capulus spcongleri and Anisomyon borealis, 

that are presently accepted as of common occurrence. 

The few others they list have been kept separate by 

later workers. At our present state of knowledge, one 

must admit that few species occur in common in the 

two regions. On the other hand, almost all genera 

occur in common and many species are closely related. 

For example, of the 16 genera in the Pierre Shale 

gastropod fauna at Red Bird, only Atira, Trcwhytriton, 

and Serrifusus are not also present on the Gulf and 

Atlantic Coastal Plains. Although Trackytriton and 

Serrifusus have been reported from the Cretaceous of 

New Jersey (Whitfield, 1892; Weller, 1907; Richards 

and Ramsdell, 1962), the reports are based on internal 

molds of dubious affinities. The same character is seen 

when the total Pierre Shale gastropod fauna is compared to the larger Campanian faunas of the Gulf and 

Atlantic Coastal Plains. I have tentatively identified 

55 gastropod genera as present in the Pierre and Bearpaw Shales. Of these, 49 genera occur in both, and 18 

are restricted solely to the two regions. Distinct differences are noted when faunal comparisons are made 

to other areas in North America. For example, only
UPPE'R CRETACEOUS GASTROPODS, RED BIRD, WYOMING B3

5 gastropod genera of the 72 present in the CampanianMaestrichtian rocks of Puerto Rico are to be found in 

the Pierre Shale. Similarly, the Pacific Coast fauna 

yields few close ties. With continued collecting, additional genera are found that occur both in the western 

interior and on the coastal plains. It is clear, therefore, 

that the endemic aspect of the marine Upper Cretaceous 

gastropod fauna of the western interior has been 

overemphasized.

PIERRE SHALE GASTROPODS

RED BIRD SECTION

DIVERSITY

The gastropod fauna of the Pierre Shale of the Red 

Bird section comprises 23 distinct species plus several 

specimens that are either placeable only to genus or 

are indeterminate. Four species appear to be new, but 

only two are judged to be represented by adequate 

material to merit formal description. Slightly more 

than two-thirds of the recognizable species belong to 

the Streptoneura (Prosobranchia) and one-third to the 

Euthyneura. Of the prosobranchs only one species, 

Atira\ nebrascensis, belongs to the Archaeogastropoda. 

Most of the species belong in the Mesogastropoda, and 

only Serrifmus, Anomalofusus, Graphidula, and 

OryptorJiytis represent the Neogastropoda. It is unusual that almost one-third of the taxa represent 

euthyneurous snails. Sohl (1964, p. 158, and fig. 13) 

has noted that representation of this group in any 

assemblage in the geologic column rarely exceeds 6 or 

8 percent. When one considers the size of the total 

fauna and the overall sparse record of gastropods, 

however, such figures are not likely to be very significant. If one considers not the total fauna but only the 

fauna of a given bed, no more than two euthyneuran 

species occur in any single collection.

Gastropods are not abundant at any individual 

stratigraphic level, but the greater diversity as well as 

the greater number appears to be in the two unnamed 

shale members. Collections from the Baculites baculus 

and B. grandis zones, in the upper part of the section, 

contain the most abundant and diverse gastropod assemblage. Although bed 93 has yielded only 7 species, 

it has the most diverse of all the gastropod assemblages.

ABUNDANCE AND OCCURRENCE

The earliest gastropods are found in bed 33 at the top 

of the Mitten Black Shale Member in the medial part 

of the Baculites giTberti zone. They have not been 

noted in the lower 1,071 feet of the Red Bird section 

which includes the Gammon Ferrugenous Member, the 

Sharon Springs Member, and all but the uppermost 

unit of the Mitten Black Shale Member (see table 1,

and Gill and Cobban, 1966). Beginning with bed 33, 

gastropods occur sporadically through the Red Bird 

Silty Member, the lower unnamed shale member, the 

Kara Bentonite Member, and the lower half of the 

upper unnamed shale member. They last occur in 

bed 95 in the lower part of the Baculites grandis zone 

about 374 feet below the Pierre Shale-Fox Hills Sandstone contract. Thus, gastropods occur through 1,692 

feet of the 3,137 feet, or somewhat more than half of 

the Red Bird Pierre Shale section.

PRESERVATION

Most of the gastropods are basically well preserved, 

with species such as Atira'l nebrascensis retaining their 

lustrous nacreous layer. However, the difficulties inherent in extraction of complete specimens from the 

matrix are great. Most specimens exfoliated when the 

concretions were split. Even these, however, were useful when the surrounding matrix was retained because 

the external molds could be cleaned of shell and external 

impressions that retained the details of sculpture could 

be made (see pi. 7, fig. 20). In addition, internal molds 

were sectioned to determine the features of the 

columella.

NOTES ON ECOLOGY

Paleoecologic interpretations based upon so few specimens are naturally subject to limitations. Considered 

ecologically, one of the more interesting features of the 

fauna is the presence of Anisomyon, a member of the 

Siphonariidae. The siphonariids are at present patelliform pulmonates that cling to rocks or other hard objects in the intertidal zone. Anisomyon differs from the 

typical Siphonariidae in having the muscle scar interrupted at the posterior-lateral rather than anteriorlateral position (fig. 10). This interruption marks the 

position of the lung aperture. The presence of such a 

structure is suggestive that Anisomyon lived, as does 

Siphonaria,, in the intertidal zone. The mere possession 

of such a "lung," however, does not restrict such forms 

to the intertidal zone. The majority of the Bassomatophora are amphibious, and Sipkonaria itself is interpreted as a pulmonate thoroughly readapted to 

submerged life in which the "lung" is filled with water. 

Anisomyon occurs in the Red Bird Silty Member and in 

the upper unnamed shale member. Zapp and Cobban 

(1962, fig. 134.1) have shown that during the time of 

deposition of the Red Bird Silty Member (Parkman regression), the shoreline lay some 60 miles to the west of 

Red Bird. If this be so, then Anisomyon was most 

likely not an intertidal dweller. The associated mollusks are not diverse, but the presence of Ostrea and 

Pteria suggests shallowT -water conditions.
B4 DESCRIPTIVE STUDY OF A CLASSIC REFERENCE LOCALITY OiF THE PIEKRE SHALE

TABLE 1. Disposition of the gastropod species in the members of the Pierre Shale of the Red Bird section. Sees. 13, 14,

T. 38 N., R. 62 W., Niobrara County, Wyo.

Species

Bed. 

D. nebrascensis (Evans and Shumard)

D. sp

Aporrhais biangulata Meek and Hay den _

Anomalofususl sp _

G. cf. G. alleni (White)_-_--------__. __________

A. sp

Black Shale Mitten 

1 Baculites gilberti 33 zone

£

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1 0

X

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3 "§

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1 Oi

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1

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Baculites scottizone

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Didymoceras stevensoni zone

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Bentonite Kara 

Baculites eliasizone

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In total, the gastropods are those expectable in shallow marine waters, but the sparsity of the archaeogastropods is worthy of special comment. Only one species, 

Atira1 nebrascensis (Meek and Hay den), represents 

this order in the fauna. Snails such as these are usually 

browsers on vegetation and are quite common, if not 

abundant, in most marine shallow-water fossil faunas. 

Although scarcity of archaeograstropods is negative evidence, it raises the question as to whether vegetation was 

abundant in these shallow waters. If vegetation was 

abundant, why are the plant browsers so scarce ?

The feeding habits of the more common snails may be 

inferred from the habits of related living genera. For 

example, Drepanochilus (Yonge, 1937) probably plowed

through the bottom at or just below the surface, feeding 

primarily on plant debris. The naticid Euspira, perhaps the most abundant species in the gastropod fauna, 

probably crawled shallowly below the sediment-water 

interface in search of bivalves into which it bored. The 

carnivorous Fasciolariidae, such as Graphidula, generally prey on live mollusks. The opisthobranchs, including Nonacteonma and Oligoptycha, range from 

deposit feeders to those that ingest whole organisms 

including bivalves, univalves, and f orams.

In spite of the abundance of these potential predators, 

few of the Red Bird shells show bore holes. Similarly, 

I have seen no shells infected by the boring sponge 

Clione that so commonly excavates marine shells in the
UPPER CRETACEOUS GASTROPODS, RED BIRD, WYOMING B5

coastal plain faunas. One thick-shelled specimen of 

Serrifusus did display several boring clams in its shell 

walls.

In summary, all the gastropods are forms consistent 

with a marine shallow-water environment and representative of both epifaunal and infaunal elements. 

Feeding habits range from plant browsers and detritus 

feeders to various kinds of carnivores. Finally, it may 

be significant that no filter feeder gastropods are 

present.

OTHER AREAS

Except for Anomalofusus ? sp., Aporrhais n. sp., and 

Bullopsis n. sp., all the gastropod species of the Pierre 

Shale Red Bird sequence are known from other areas of 

the Pierre Shale, Bearpaw Shale, or Fox Hills Sandstone outcrop. Figure 1 indicates their total stratigraphic range and general geographic distribution.

COLORADO

A comparison of the Pierre Shale gastropod fauna 

from the Red Bird section with that from the Front 

Range of Colorado shows a close similarity at almost all 

stratigraphic levels.

Pierre Shale gastropods -from the Front Range of Colorado

[Asterisk indicates species that occur in common between the Front 

Range and the Red Bird section of Wyoming. The numbers following 

the species name in the list below indicate the ammonite zones in which 

they occur in the Front Range Pierre Shale sections. These zones are 

1. Baculites o~btusus. 2. B. mclearni. 3. B. asperiformis. 4. B. perplexus. 5. B. gregoryensis. 6. B. n. sp. 7. B. scotti. 8. Dldymoceras 

nebrascense. 9. D. stevensoni. 10. Exiteloceras jenneyi. 11. Didymoceras cheyennense. 12. Baculites compressus. 13. B. cuneatus. 14. 

B. reesidei. 15. B. jenseni. 16. B. eliasi. 17. B. ~baculus, 18. B. 

19. B. cllnolo'batusl

Acmaea occidentalis (Meek and Hayden) 9,10,12,13,14 

A. papillata (Meek and Hayden) 15

*Atira'i nebrascensis (Meek and Hayden) 10, 14, 15, 19

Margarites sp. 4, 9

Anchura haydeni White 13,14,15

"Aporrhais" meeki Whitfield 3,4, 7

*Drepanochilus evansi Cossmann (transitional form) 17, 

18, 19

*D. scotti Sohl 14,15,16,17

*D. nebrascensis (Evans and Shumard) 10, 11, 12, 13

*D. obesus Sohl 7, 8

D. sp. 4

cf. Confusiscala n. sp. 14

*Astandes densatus Wade 15 

Capuliis spcmgleri Henderson 14, 15 

Xenophora cf. X. leprosa Morton 10,11

*Vanikoropsis haydeni Cossmann 10,14, 15 

Cypraea sp. A, 11 

C. sp. B, 14

*Euspira obliquata (Hall and Meek) 4, 5, 6, 7, 8, 9, 10, 14,

15,16,17,18,19 

E. sip. 4

Gyrodes sp. 13,14 

Pseudamaura lirata (Wade) ? 12

P. palitdinaeformis (Meek and Hayden) 10

*Trachytriton vinculum (Hall and Meek) 14?, 15, 5

* Serrifusus sp. 14, 10? 

Deussenia! sp. 14

*Graphidula culbcrtsoni (Meek and Hayden) 19

Bellifusus 11, 15, 18, 9, 7, 19

B. sp. 6

Cryptorhytis cheyennensis (Meek and Hayden) 13, cf. 7,

12, 10, 14?, 11

C. flexicosta (Meek and Hayden) 19 

Graphidula n. sp. 7, 8 

Hydrotribulusl sp. 7,12,11,13,9 

Drillutal sp. 8 

Napulus sp. 14

"Volutoderma" clativorthyi (Henderson) 14 

Amuletum sp. 10, 15 

Lutema minor ( Meek and Hayden ) 15

*Anisomyon borealis Mo'rton 4?, 10

* A. centrale (Meek and Hayden) 7

A. subovatus (Meek and Hayden) 10, 11?, 14, 15

*Anisomyon n. sp. 1

A. sp. 12, 4, 10, 9

Anisomyon alveolus Meek and Hayden 11 ( ?) , 14, 16

A. cf. A. alveolus Meek and Hayden 1, 2

*0liffoptycha concinna (Hall and Meek) 10, 14, 15

Acteon sp. 14, 10

Eoacteon 14

Cylindrotrnncus'i glansorysa (Whitfield) 11, 12, 15

*EllipsoscapJia! s ubcylindrica (Meek and Hayden) 10, 14,

*E. oocidcntalis (Meek and Hayden) 10, 11, 14

Cylichna sp. 10, 11, 14, 15, 19

Tornatellaea'i sp. 14, 15

Scobinodolus cf. S. guttatus Sohl 15

Ringicula (Ringicula) cf. R. (R.) pulchella Shumard 14

In addition to the above, there are a number of specimens of fusiform snails that I am unable to place until 

better preserved material is available. The list can only 

be viewed as provisional, and no doubt more thorough 

study will reveal new species and others will be 

reassigned.

The upper part of the section (Exiteloceras jenneyi 

through Baculites clinolobatus zones) contain both 

the greatest diversity and the greatest number of gastropods. The Rocky Ridge, Larimer, and Richard Sandstone Members (Baculites reesidei and B, jenseni zones) 

contain the greatest variety of all the units. These 

sandstones, as well as some lower units such as the Terry 

Sandstone Member, have yielded species belonging to 

Cypraea, Xenophora, Anchura, Gyrodes, Napulus and 

Eulima. These genera are either exceptionally rare or 

unknown elsewhere in the outcrop of the Pierre Shale 

and equivalent units.

The Pierre Shale gastropod fauna of the Front Range 

contains more species that are common to the gulf 

coast than do the Pierre Shale faunas to the north.

223-112 O 6 
B6 DESCRIPTIVE STUDY OF A CLASSIC REFERENCE LOCALITY OF THE PIERRE SHALE

EXPLAT

Occurrence of species

NlATION

in the Red Brrd section

-» * t fTi

Occurrence of species in the Pierre Shale of 

the Front Range of Colorado

Iliidili 

Occurrence of species in the Pierre Shale of 

South Dakota and Montana

Total

Afira? nebrascens/s (Meek 

Drepanochi/us evansi Coss 

Drepanochi/us scoff/' Sohl, 

Drepanochilus nebrascensis 

Drepanochi/us obesus Sohl 

Aporrhais biangu/afa Meel 

Vanikoropsis nebraskensis ( 

Asfandes densafus Wade

||

range

mann

(Evans and Shumard)

(, and Hayden

Meek and Hayden)

Euspiro ob/iquofo (Hall and Meek)

Trochyfrifon vincufum (Hall 

Serrifusus dokofensis (Meek 

Grophidu/o cufberfsoni (Me 

Groph/dufo cf. G. o//en/' (\A 

Crypforhyfis cheyennens/s ( 

Nonocfoeonino offenuofo (r 

Ofigopfycho concinno (Hal 

Ellipsoscapha occidenfo/is (

Anisomyon boreo/is, (Mortor

Anisomyon pofel/iformis Me

and Meek)

and Hayden)

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*/leek and Hayden)

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Meek and Hayden)

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ek and Hayden

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FIGURE 1. Geographic and stratigraphic distribution of the gastropod species of the Pierre Shale of the Red Bird section.
UPPER CRETACEOUS GASTROPODS, RED BIRD, WYOMING B7

This fact appears to indicate an influx of species from 

the gulf northward, especially during the time of deposition of the Rocky Ridge and Larimer Sandstone Members (B. reesidei zone). These affinities decrease in the 

stratigraphieally higher Richard Sandstone Member. 

In spite of the many forms introduced in these sandstones, the fauna maintains its western-interior character. In terms of gastropods the medial part of the 

Pierre Shale of the Front Range represents a time of 

mixed faunas during which a normal Pierre Shale 

fauna was supplemented periodically by migrants from 

the gulf coast.

These middle sandstones are especially noteworthy 

biologically because of the diversity and abundance of 

opisthobranch gastropods.

The similarity between the Pierre Shale gastropod 

fauna of the Red Bird section of Wyoming and the 

Front Range of Colorado lies not only in the common 

occurrence of many species but also in the absence or 

rarity of gastropods in the lower part of the formation 

in both areas. In addition, in the faunas of both areas 

the most abundant gastropods are Euspira, Drepanochilus, and, perhaps, Anisomyon.

SOUTH DAKOTA AND MONTANA

The Gammon Ferruginous Member of the Pierre 

Shale north of the Black Hills at USGS 23478 has 

yielded the following gastropod fauna:

Cerithiopsis (CeritMellal) n. sp.

Potamides n. sp. A.

Potamides n. sp. B.

Promathilda (Clathrobaculus) n. sp.

Drepanochilus sp. (evansi lineage)

Aporrhais 1! sp.

Acirsa (Hemiacirsa) n. sp.

Euspira cf. E. obliquata (Hall and Meek)

Lomirosa n. sp.

Rhombopsist sp.

Bellifusus n. sp.

Remera cf. R. stephensoni Harbison

Graphidula cf. G. obscura (Wade)

Graphidula n. sp. ( cuIbertsoni lineage)

This locality represents a level near the base of the 

Pierre Shale (zone of ScapTiites hippocrepis, late or 

fine-ribbed form) at a position not well represented in 

terms of gastropods anywhere else in the western interior. The fauna contains some elements, such as 

Promathilda, that are virtually unknown elsewhere. 

Although all the genera represented are to be found in 

the Gulf Coastal Plain Upper Cretaceous, the closest 

specific ties remain with the higher beds of the Pierre 

Shale. For example, the Drepanochilus is of the western interior, not the gulf coast, type. One Graphidula 

and the Bellifusus represent new species that are obvious 

forerunners of species to be found at higher Pierre Shale

levels. Except for the total absence of Euthyneura, in 

terms of general groups the fauna again is a typical 

Pierre Shale gastropod assemblage. No species 

definitely occur in common with the Red Bird fauna, 

but many are closely related.

Whitfield (1880) made a study of the fossil faunas 

from the Black Hills region that included 19 species of 

gastropods from the Pierre Shale. Some of the species 

(Drepanochilus obesus, Graphidula culbertsoni, Anisomyon borealis) occur in the Red Bird section but all 

are known from other areas of the Pierre Shale outcrop. 

The work describes relatively few gastropods that come 

from many zones and no large assemblage is given that 

would serve for comparison.

The following list is of gastropods in two collections 

from the Baculites compressus zone in the Wasta-Sage 

Creek area of South Dakota that represent the Pierre 

assemblage from the upper part of the middle Pierre 

Shale (USGS 23070, 23072). Species described by 

Evans and Shumard and Hall and Meek from "Sage 

Creek" are marked by an asterisk (*).

*Acmaea occidentalis (Hall and Meek)

*Margaritella flexistriata (Evans and Shumard) 

Atiral nebrascensis (Meek and Hayden) 

Belliscalal n. sp.

*Closteriscus tenuilineatus (Hall and Meek)

*Drepanochilus nebrascensis (Evans and Shumard)

*Euspira obliquata (Hall and Meek)

*Pseudamaura paludinaeformis (Hall and Meek)

Xenophora sp.

Trachytriton vinculum (Hall and Meek)

Cryptorhytis cheyennensis (Hall and Meek)

Mesorhytist sp.

Oligoptycha ooncinna (Hall and Meek)

Except for Euspira obliqua.ta, all the above species are 

restricted to the Pierre Shale and equivalents, and few 

are found at stratigraphic levels below the B. compressus zone. Of the 13 species listed, only 6 (Atiral nebrascensi-s, Drepanochilus nebrascensis, Euspira obliquata, 

Trachytriton vinculum, Oligoptycha concinna, and 

Cryptorhytis cheyennensis) are found also in the Red 

Bird section. In part this is explainable by the fact 

that three zones (D. cheyennense, B. compressus, and B. 

cuneatus zones) spanning the Sage Creek beds are 

missing in the Red Bird section. In other respects the 

fauna shows a dominance of Mesogastropoda and 

Neogastropoda characteristic of the other Pierre gastropod assemblages.

The high Pierre Shale gastropod assemblages are best 

typified by those of the Baculites l)aculus zone of the 

Cedar Creek anticline near Glendive, Mont. These 

beds yielded many fossils described by Meek and others 

from the general region 150 miles above the mouth of 

the Yellowstone. Meek and others have noted that 

there is an intermixture of fossils of Fox Hills type and
B8 DESCRIPTIVE STUDY OF A CLASSIC REFERENCE LOCALITY OF THE P1ERRE SHALE

of the Pierre Shale type in these beds. It is true that, 

in many ways, the gastropods of these upper Pierre beds 

are more advanced than typical Pierre species, but the 

gastropod assemblages of both formations are 

distinctive.

The following list was compiled from Meek, 1876, and 

is supplemented by identifications from USGS collections from the Baculites baculus of the Glendive area, 

Montana. An asterisk (*) preceding the species names 

indicates that the species range upward into the Fox 

Hills Sandstone.

Atiral nebrascensis (Meek and Hayden)

*Euspira obliquata (Hall and Meek) 

Aporrhais biangulata Meek and Hayden

*Drepanochilus evansi (Evans and Shumard) (includes

Anchura sublevis and A. ? parva) 

Astandes densatus (Wade) ? 

Vanikoropsis haydeni Oossmann

*Rhombopsis newberryi (Meek and Hayden)

*R. subturritus (Meek and Hayden)

*R. 1 intertextus (Meek and Hayden)

*Pseudobuccinum nebrascense (Meek and Hayden)

*Graphidula culbertsoni (Meek and Hayden)

Mesorhytis gracilenta Meek

Cryptorhytis flewicostata (Meek and Hayden)

*Amuletum minor (Evans and Shumard) 

Eoacteon n. sp.

Nonaotaeonina attenuate, (Meek and Hayden) 

Ellipsoscapha occidentalis (Meek and Hayden) 

E. n. sp.

*0liffoptycha concinna (Hall and Meek)

SooMn&dolus sp.

Anisomyon patelliformis Meek and Hayden

A. subovcvtus Meek and Hayden

A. alveolus Meek and Hayden

A. sewsulcatus Meek and Hayden

Of the 24 species listed above only 9 are to be found in 

the overlying Fox Hills Sandstone of the type area. 

This is not what should be expected in beds said to contain a mixed Fox Hills and Pierre fauna. Obviously, 

the snail assemblages are considerably different in the 

two formations. Similarly, of the 27 species described 

from the Fox Hills Sandstone by Meek (1876), only 9 

are common to the 2 formations. However, the vast 

majority of genera occur in common. One obvious difference is the total absence in the Fox Hills of any 

species of Anisomyon, a genus so common in the Pierre 

Shale.

Compared with the gulf coast Campanian-Maestrichtian gastropod faunas, all genera except Atiral, Vanikoropsis, and Pseudobuccinum occur in common. 

Atira, Aporrhais, Astandes, Mesorhytis, Nonactaeonina, Scobinodolus, and Anisomyon do not occur in the 

Fox Hills Sandstone. Consequently, at the generic 

level, both the Fox Hills fauna and the gulf coast fauna 

show great similarities to the Pierre Shale assemblages.

BBARPAW SHALE OF MONTANA AND CANADA

Although the gastropod fauna of the Bearpaw Shale 

of Montana and Alberta, Canada, is closely related to 

that of the Pierre Shale, it is somewhat less diverse. 

The following tentative listing of gastropod species is 

compiled from Dowling (1917), Williams and Dyer 

(1930), and Landes (1940) for Canada and from a 

cursory examination of the Montana Bearpaw Shale collections of the U.S. Geological Survey at the U. S. National Museum. An intensive investigation would 

undoubtedly add a few more species to the list.

Atria"! nebrascensis (Meek and Hayden)

Cerithioderma n. sp.

Drepanochilus evansi Cossmann

D. nebrascensis (Evans and Shumard)

Euspira obliquata (Hall and Meek)

Vanikoropsis tuomeyana (Meek and Hay den)

V. nebrascensis (Meek and Hayden)

Trachytr-iton vinculum (Hall and Meek)

Anomalofusus! sp.

OrapMdula culbertsoni (Meek and Hayden)

Pseudobuccinum nebrascense (Meek and Hayden)

Paladmete n. sp.

Nonactaeonina attenuata (Meek and Hayden)

Ellipsoscapha occidentalis (Meek and Hayden)

Ellipsoscaphal subcylindrica (Meek and Hayden)

Oligoptycha concinna (Hall and Meek)

Anisomyon patelliformis Meek and Hayden

A. alveolus Meek and Hayden

A. centrale Meek

SUMMARY

The Pierre Shale gastropod fauna in the western interior maintains a significant uniformity both geographically and stratigraphically. Certain genera are 

common to all areas and stratigraphic levels of the formation. From a negative standpoint, but perhaps just 

as significantly, certain other types of snails are usually 

lacking. In general, the Archaeogastropoda are very 

poorly represented either in terms of diversity or in 

terms of individual specimens. Only 5 species of the 

order Archaeogastropoda are included among the 70 

gastropod species of the Pierre fauna. In terms of 

number of species or in individual abundance the order 

Mesogastropoda is the best represented, Euspira and 

Drepanochilus being the two most abundant snails in the 

fauna. Neogastropods are moderately diverse but are 

not individually abundant. This is expectable for any 

group of carnivores. For the Subclass Euthyneura, the 

pulmonate group Anisomyon (Siphonariidae) is common to all levels in the Pierre Shale, but does not occur 

in the Fox Hills Sandstone. In addition to these patelliform snails, the bulloid euthyneurans (Ellipsoscapha 

and others) are to be found at most levels.

All the Pierre Shale gastropods are shallow-water 

types, but they represent a wide variety of feeding 

habits ranging from plant browsers to carnivores and,
UPPE.R CRETACEOUS GASTROPODS, RED BIRD, WYOMING B9

perhaps, parasites (Eulima). In spite of the strong 

evidence of very shallow water furnished by Anisomyon, 

other groups that one would associate with such condition are remarkably scarce or absent. For example, 

other patellif orm snails are absent, except for rare specimens of Acmaea. There are no species of either the Littorinacea or Neritacea, both very common shallow water 

forms. Perhaps the lack of a rocky coast would account 

for the absence of many of the above forms, but why, 

then, are the ceritheaceans so uncommon? Although 

most Upper Cretaceous faunas contain turritellids, 

often in great abundance, none are known from the 

Pierre Shale. In addition, there are no Vermetidae and 

only a very few Cerithiidae and Cerithiopsidae. This 

sparsity is true not only of the shale but also of the 

sandier sequences of Colorado where one would expect 

representatives of such groups. However, Turritella is 

abundant in the near-shore sandy facies of the Baculites 

Ixwulus zone (the Lewis Shale of south-central Wyoming, USGS D-^755). The general lack of turritellids 

and vermetids in the shale facies may reflect turbid 

water or suspended material not conducive to the 

support of such ciliary and mucous string feeders.

Much more study of this peculiar assemblage is needed 

before any answers can be found. Certainly, on the 

basis of groups represented, the Pierre Shale gastropod 

fauna bears little resemblance to the more normal shallow-water Cretaceous shelf faunas of the Gulf Coastal 

Plain. There, such groups as Anisomyon and Drepanochilus are uncommon, but archaeogastropods are 

abundant, if not diverse, and ceritheaceans are both 

abundant and diverse.

In spite of the many dissimilarities, however, it is 

clear that the Pierre Shale gastropod fauna is most 

similar taxonomically to the Upper Cretaceous faunas 

of the gulf coast. A few genera occur in common 

with the Pacific Coast Campanian-Maestrichtian faunas 

(Anderson, 1958). However, most, like Euspira and 

Drepanochilus) have little significance because such 

genera are found in most Upper Cretaceous gastropod faunas. Only Atira and Serrifusus indicate any 

significant relationship. In contrast, almost all genera 

in the Pierre Shale occur also in the CampanianMaestrichtian beds of the Gulf Coastal Plain. Some 

genera, such as Oligoptycha, Bullopsis, Margaritella, 

Belliscal^ Lomirosa, Remera, Scobinodolus, Cylindrotrwncus, and Napuim, are unknown outside the two 

areas. The many common genera indicate a similar 

source for much of the fauna.

Certainly, the Pierre Shale fauna was occasionally 

replenished by invasions from the gulf coast, as is shown 

by the increased similarity of the two faunas toward 

the south, especially in the Rocky Ridge Sandstone and 

Larimer Sandstone Members of Colorado.

The fauna shows a dominance of species lineages 

that are restricted to the western interior, but are generically related to gulf coast lineages, suggesting a common source in earlier Cretaceous times. On this basic 

plan are superimposed a few exotic, perhaps boreal, 

migrants.

PROPOSED NEW SPECIES

Two new species are proposed Drepanochibus scotti 

and DrepanocMlMS obesus.

CHANGES IN GENERIC OR SPECIFIC ASSIGNMENT

The following are changes in generic or specific assignment of previously described species (see also list 

on p. B19 for Aporrhais} :

Old assignment

Trochidae:

Margarita nebrascensis Meek

and Hayden. 

Aporrhaidae:

Aporrhais sublevis Meek

Hayden. 

Anchura ( Drepanochilus)

evansi pusilla Stanton. 

Anchura (Drepanochilus) nebrascensis Whitfield [non

Evana and Shumard]. 

Vanikoridae:

Fossart nebrascensis Meek and

Hayden. 

Natica f ambigua Meek and

Hayden. 

Natica haydeni Cossmann______

Natica praenominata Coasmann_ 

Naticidae:

NaticaMeekiCossmann (=Natica paludinaeformis Hall and

Meek). 

Cymatiidae:

"Fasciolaria" buccinoides Meek

and Hayden from the Fasciolariidae to the Cymatiidae. 

Fasciolariidae:

Serrifusus ? crosswickensis

Whitfield. 

Fasciolaria (Piestochilus) alleni White. 

Actaeon (Solidula) attenuatus

Meek and Hayden.

New assignment

Atira"! nebrascensis (Meek 

and Hayden)

and Drepanochilus evansi

Drepanochilus pusillus

(Stanton) 

Drepanochilus obesus

Sohl

Vanikoropsis 

Vanikoropsis

Vanikoropsis 

Vanikoropsis

Pseudamaura

Pterocerella 

Graphidula 

Nonacteonina

MEASUREMENTS OF SPECIMENS

Measurements of individual specimens of many 

species are given under a sidehead following the specific 

descriptions. Larger specimens were measured with 

vernier calipers, and the smaller forms were measured 

with the aid of a microscope equipped with a calibrated 

eyepiece. All measurements are in millimeters.

223-112 O--66 3
BIO DESCRIPTIVE STUDY OF A CLASSIC REFEiREOSTCE LOCALITY OF THE PIEIRRE SHALE

The conchologic features measured vary with the 

individual groups. For example, the Aporrhaidae 

develop an expanded outer lip, and the set of measurements used to indicate the relation of the lip to the shell 

must be different from that used to measure a less 

complex group.

Listed below are the abbreviations used as headings 

of the column of measurements and their definitions.

DPW Diameter of penultimate whorl, measured normal to 

teleoconch axis of coiling.

MD Maximum diameter, measured normal to teleoconch 

axis of coiling.

MDW Maximum diameter, including the length of an expanded outer lip or wing.

H* Total height of shell, measured parallel to axis of coiling.

HA Height of aperture, measured parallel to axis of coiling.

HB Height of body whorl, measured parallel to axis of 

coiling.

ML Median line length, in Anisomyon measured parallel to 

an imaginary plane bisecting the anterior and posterior margins of the shell.

W Width, in Anisomyon measured normal to ML half the 

distance between the anterior and posterior margins.

LC Length of carination, in Anisomyon measured from 

apex to intersection of carination with posterior 

margin.

AM Width of anterior margin, in Anisomyon measured 

normal to ML at anterior one-quarter of shell length.

PM Width of posterior margin, in Anisomyon measured 

normal to ML at posterior one-quarter of shell length.

PA Pleural angle, measured in degrees.

SYSTEMATIC DESCRIPTIONS

The arrangements of families and the grouping of 

genera follows the classification of Taylor and Sohl 

(1962). Morphologic terminology conforms to that 

used in the "Treatise on Invertebrate Paleontology" 

(Moore, 1960).

Abbreviations are as follows:

USNM U.S. National Museum

ANSP Academy of Natural Sciences of Philadelphia

AMNH American Museum of Natural History

USGS U.S. Geological Survey Mesozoic locality

Order ARCHAEOGASTROPODA 

Superfamily TROCHACEA

Family TROGHIDAE 

Subfamily MARGARITINAE 

Genus ATIRA Stewart, 1927

Type by original designation: Angaria ornati-ssima 

Gabb, 1864

Diagnosis. Small turbiniform phaneromphalous 

shells, aperture rounded. Umbilical margin angulate. 

Sculpture usually faint but present on umbilical walls.

Discussion. Stewart (1927, p. 315) proposed Atira

as a subgenus of Margarites "Leach" Gray. He included the type species Angaria ornatissima Gabb, and 

Architectonic a inornata Gabb, both of the Upper Cretaceous of California. Whiteaves (1879) and White 

(1889) also cite the occurrence of the type species in the 

Upper Cretaceous of Sucia and Sheep Jack Islands, 

Vancouver, British Columbia.

Stewart (1927, p. 315) notes: "This genus differs from 

Margarites in having an angulated umbilicus. The 

angle is not ridged as in Solariella. The umbilicus 

is much narrower and the walls are more sloping than in 

Gaza Watson, which the fine sculpturing particularly 

that of M. inornatus somewhat resembles."

Atira? nebrascensis (Meek and Hayden)

Plate 1, figures 1-11 

1856. Turbo nebrascensis Meek and Hayden, Acad. Nat. Sci.

Philadelphia Proc., v. 8, p. 64. 

1860. Margarita nebrascensis Meek and Hayden, Acad. Nat. Sci.

Philadelphia Proc., v. 12, p. 185. 

1876. Margarita nebrascensis Meek and Hayden, Meek, U.S.

Geol. Survey Terr. (Hayden) Kept., v. 9, p. 298, pi. 19,

figs. 8a, b, 9a (not9b). 

1880. Margarita nebrascensis Meek and Hayden, Whitfield, U.S.

Geog. and Geol. Survey Rocky Mtn. Region (Powell),

p. 432, pi. 12, fig. 15. 

1918. Eumargarita (Solariella) nebrascensis Cossmann, Essais

de paleoconchologie comparee, no. 11, p. 260. 

1951. Bolariella nebrascensis (Meek and Hayden). Collignon,

Madagascar Service mines, Annales, Geol., pt. 19, p. 101.

Type locality. "Yellowstone River, 150 miles from 

its mouth" (Meek, 1876, p. 299). This locality corresponds to the upper part of the Pierre Shale BaauLites 

bacuki£ zone in the vicinity of Glendive, Mont.

Diagnosis. Atira-like, with marginal umbilical 

crenulations developing from accentuated transverse 

riblets.

Description. Moderately small turbiniform phaneromphalous shells with round-sided to gently angulate 

whorls. Shell about as wide as high, spire about onehalf total shell height, pleural angle 80°-85°. Protoconch paucispiral, low, smooth surfaced, and round 

sided. Suture abuting. First one-half teleoconch 

whorl round sided, but gradually developing a flattened 

subsutural area that on second teleoconch whorl becomes 

a shelf 0.1 mm wide bounded by a strong spiral cord. 

This shelf rounds off on later whorls. Mature whorls 

rather well rounded, but some develop a slight flattening 

over periphery that is delimited above and below by a 

very weak angulation. Umbilicus broad and open, 

bounded by a rounded angulation; umbilical walls 

steeply sloping gently convex. Sculpture of first teleoconch whorl begins with a few weak spiral lines that 

strengthen to threads; thread at subsutural shoulder 

strongest. Faint but continuous transverse ribs begin 

on second teleoconch whorl. On third whorl, spiral
UPPER CRETACEOUS GASTROPODS, RE'D BIRD, WYOMING Bll

cords remain stronger, but ribs strengthened to form low 

nodes at intersection with spiral threads over shelf and 

shoulder cord. Sculpture usually weak on penultimate 

and body whorl, especially over periphery and laterally 

on base. On body whorl, spiral sculpture consists of 

closely spaced round-topped spiral threads that are 

wider than their interspaces over most of surface; 

threads are about of equal strength over upper whorl 

surface and periphery, but broaden to cords or ribbons 

on umbilical wall. Transverse sculpture on body consists of low broad collabral ribs that are strongest near 

suture, die out on periphery, but again strengthen over 

base, becoming accentuated to narrower but sharper ribs 

over umbilical rim and wall. Growth lines steeply 

prosocline between suture and basal margin. Aperture 

incompletely known, subcircular in outline with outer 

lip more fully rounded than inner lip. Inner lip 

curved and presumably nonreflected.

Measurements. Explanation of measurements and 

symbols used in the following table appears in the section "Measurement of specimens" (p. B9).

Specimen and locality

Holotype: USNM 249a (B. baculus zone) __

Paratype: USNM 132951 (B. baculus zone) __ 

Glendive, Mont. (B. baculus zone) _

Do_______. _______ ______________________

Do_______. _____________________________

Red Bird (Didymoceras stevensoni zone) _

Do___ __________________________________

H

6.3 +

6. 4+

5.8+

6. 0

8.3

7.0+

6.2

MD

6. 4

7.3 

5. 3

6. 0

7.8

7. 7

7.2

Discussion. Atiral nebrascensis is of questionable 

placement. It certainly does not belong in Margarita, 

where it was assigned by Meek, as it retains a crenulate 

umbilical margin. /SolarieUa Woods, where it was 

placed by Cossmann (1915) and Collignon (1951), does 

possess such a character, but the crenulations of the 

umbilical margin of /Solarietta develop from a strong 

spiral rib that borders the umbilical margin, a feature 

somewhat analogous to that in Architectonica. In 

Atiral nebrascensis the umbilical crenulations develop 

from the strengthening of the transverse elements. 

The crenulations are variable (compare pi. 1, figs. 8,11) 

and do not appear to be delimited by a single strong 

spiral rib. The umbilical wall sculpture and subangulate umbilical margin are like those in Atira Stewart.

Meek's (1876, p. 299) type specimens came from the 

Pierre Shale (Cretaceous No. 4 of Meek), "on the Yellowstone Kiver 150 miles from its mouth" ( = Glendive, 

Mont.). In addition, he figured an additional specimen 

(Meek, 1876, pi. 19, fig. 9b) from the Fox Hills Sandstone at Long Lake, S. Dak. This latter specimen 

represents a large undescribed species that lacks the 

umbilical nodings and subsutural sculpture of Atiral 

nebrascensis.

The illustrations of the type specimens given by Meek 

(1876, pi. 9, figs. 8a, b, 9a) are exaggerated. These 

specimens, one of which is here refigured (pi. 1, figs. 

2-4), are little more than internal molds retaining 

only patches of shell material adhering to the surface. 

The description given above is based on the type specimens supplemented by additional specimens from the 

type area near Glendive, Mont., and from the Red Bird 

section of Wyoming.

The specimens from the Ked Bird Pierre Shale section of Niobrara County, Wyo., compare closely with 

those of the type locality. They are found in both the 

lower and upper unnamed shale members (beds 58-87) 

from the Didymoceras stevensoni to the Baculites 

baculus zones. In the Pierre Shale of the Front Range 

of Colorado the species is found from the Exiteloceras 

jenneyi through the Baculites clinolobatus zones and 

is especially abundant in the B. reesidei and B. jenseni 

zones.

Types: Holotype USNM 249; para type, USNM 132951; 

hypotypes USNM 249, 132668, 132669, 132670, 132983, 132950.

Occurrences: Wyoming: Pierre Shale (Red Bird section), 

Didymoceras stevensoni zone, USGS D-1939, D-1940; Eaciteloceras jenneyi zone, D-1637, D-1942; Baculites baculus zone, 

D-1973. Colorado: Pierre Shale, Exiteloceras jenneyir-B. clinolobatus zones.

Order MESOGASTROPODA

Superfamily STROMBACEA

Family APORRHAIDAE

Representatives of this family are among the more 

common gastropods in the Cretaceous rocks of the 

western interior. Although the genera Perissoptera, 

Cyphosolenus, Ancliura, Aporrhais, Lispodesthes and 

ArrTioges are all present, Drepanochilus is perhaps the 

most common aporrhaid. This is in direct contrast to 

the Upper Cretaceous sequence in the Gulf and Atlantic 

Coastal Plains where Drepanochilus is rare and the 

genera AncTiura and (rracilmla are common (table 2). 

In the western interior, Graciliala is absent and 

Anchura is found no farther north than the Front 

Range of Colorado in the Pierre Shale, although it is 

present in Minnesota in the Colorado Group.

Genus DREPANOCHILUS Meek, 1964

Type by original designation: Rostellaria americana 

Evans and S h u m a r d 1857 (non d'Orbigny, 

1842) = Drepanochilus evansi Cossmann, 1904.

Diagnosis. Medium-sized high-spired shells with 

round-sided whorls. Initial sculpture of fine spiral 

threads. Sculpture of spire commonly dominated by 

transverse ribs that virtually disappear on body whorl; 

body whorl sculpture dominated by two or three spiral 

cords or carinations with upper carination continuous
B12 DESCRIPTIVE STUDY OF A CLASSIC REFERENCE LOCALITY OF THE PIEKRE SHALE 

TABLE 2. Distribution and abundance of aporrhaid genera in the Cretaceous rocks of North America

Genus

Arrhoges _ __ _____ _

Monocyphus--- _____ __

Lispodesthes _ ________ _

Cyphosolenus . _ _____

Tessarolax. __________

Tundora. _ __ _ __

Pterocerella.. ___ __ ____ _

Atlantic Coastal Plain

Common, Cenomanian-Maestrichtian.

Common, Santonian-Maestrichtian. 

Rare__ __ _ __

Rare, SantonianMaestrichtian.

Common, Campanian-Maestrichtian.

Gulf Coastal Plain

Common, Cenomanian- Maestrichtian.

Rare, Maestrichtian. 

Rare, CampanianMaestrichtian.

Common, Santonian-Maestrichtian. 

Rare___ ____

Common, Lower 

CretaceousUpper Cretaceous.

Rare, Albian.

(Texas). 

Rare, Cenomanian 

(Texas). 

Rare, Albian

(Texas).

Common, Campanian-Maestrichtian.

Western interior

Northern part (Minnesota to Wyoming)

Rare, Cenomanian 

(Minnesota) .

Common, Campanian-Maestrichtian.

Southern part (Colorado 

to New Mexico)

Rare, ConiacianCampanian.

Common, Campanian.

Rare, Cenomanian (Kansas).

Rare__ _____ _

Rare, Turonian. _ _

Rare, Turonian

(Utah).

Rare, Turonian

(Utah).

West coast

Rare, Upper Cretaceous (California-British 

Columbia).

Rare, Upper Cretaceous (California) .

Rare, Cenomanian-Turonian 

(California).

Rare, Cenomanian (California). 

Rare, Upper Cretaceous (California) .

Common, Turonian (Lower 

California to 

British Columbia).

over single narrow upturned spur of the expanded outer 

lip. Anterior canal short to moderate length.

Discussion. Drepanochilus is one of the more widespread Cretaceous and lower Tertiary aporrhaid genera. 

The typical subgenus has been reported in North America, Europe, and Africa with the subgenus Tulochihis 

Finlay and Marwick occurring in Paleocene rocks in 

North Dakota, Tunisia, New Zealand, and possibly California. Species of Drepanochilus are among the more 

widely distributed and most abundant gastropods found 

in the upper part of the Upper Cretaceous of the western interior. Concretions 'bearing little else than hundreds of specimens of Drepanochilus have been encountered in both the Fox Hills Sandstone and Pierre Shale 

from Colorado to Montana. Their abundance in this

area stands in distinct contrast, however, to their rarity 

in the equivalent Campanian and Maestrichtian rocks of 

the Gulf and Atlantic Coastal Plains (Sohl, 1960, p. 99- 

101). Not only is there a disparity in abundance 

between the two areas, but no single species occurs 

in common. Drepanochilus is represented in these 

areas by two separate evolving lineages.

Evolution of western interior Drepanochilus. The 

gulf coast species as shown by Sohl (1960, fig. 10) show 

a trend with time in which Drepanochilus texanus 

Stephenson, from the Kemp clay of Texas, develops 

from the older D. quadriliratus (Wade), from the Exogyra cancellata zone of Tennessee, by progressive suppression of the spiral cords of the body whorl. Progressive changes are also present in the western interior
UPPER CRETACEOUS GASTROPODS, RE'D BIRD, WYOMING B13

Drepanochilus lineage. Figure 2 graphically presents 

the changes in the proportional distance of the upper 

body whorl carination from the suture and in the distance separating the two carinations. Except for the 

reversal in D. nebrascensis, the overall trend is for the 

upper whorl carination to move closer to the suture and 

the distance between the carinations to lessen with 

higher stratigraphic position. Other changes occur in 

that the older species have non-noded spiral carinations, 

a welt paralleling the lateral outer lip margin below the 

extended spike, and more obese whorls; whereas the 

younger species, such as D. pusillus and D, evansi, possess nodings on the spiral carinations, have a more 

angulate body, and lack a pronounced welt parallel to 

the margin of the lower part of the expanded outer 

lip.

D. pusillus 

evansi 

scofti

nebroscensis 

obesus

2345 

MILLIMETERS

FIGURE 2. Comparison of the suture to upper whorl carination and 

the intercarination distances in the Pierre Shale species of 

Drepanochilus. The left-hand margin of the graph represents the 

position of the suture; the shaded area, the average distance between the suture and the upper whorl carination; and the unlined 

portion is the average distance between the carinations. The species 

are arranged with the oldest at the bottom. All specimens measured 

were adult individuals.

Drepanochilus evansi Cossmann 

Plate 3, figures 10-21

1857. Rostellaria Americana Evans and Shumard, Acad. Sci. St. 

Louis Trans., v 1, p. 42 [non R. americana d'Orbigny].

1860. Aporrhais Americana (Evans and Shumard). Meek and 

Hayden, Acad. Nat. Sci. Philadelphia Proc., v. 12, p. 423.

1860. Aporrhais suUevis Meek and Hayden, Acad Nat. Sci. 

Philadelphia Proc., v. 12, p. 178 (misprint Aporrahais 

sublevata appears on p. 428).

1864. Anchura (Drepanochilus) americana (Evans and Shumard). Meek, Smithsonian Misc. Colln. v. 7, p. 19.

1864. Anchura? sublevis Meek and Hayden. Meek, Smithsonian 

Misc. Colln. v. 7, p. 19.

1876. Anchura (Drepanochilus) americana (Evans and Shumard). Meek, U.S. Geol Survey Terr., (Hayden) Kept., 

v. 9, p. 324, pi. 32, figs. 8a, b.

1876. Anchura? sublevis (Meek and Hayden). Meek, U.S. Geol. 

Survey Terr., (Hayden) Kept., v. 9, p. 327, pi. 19, figs. 

3a, b.

1879. Anchura americana (Evans and Shumard). White, U.S. 

Geol. Survey Terr., (Hayden), llth Ann. Kept., 1877, 

p. 185.

1885. Anchura americana (Evans and Shumard). Whiteaves,

Canada Geol. Survey, Contr. Canadian Paleontology,

v. 1, pt. 1, p. 48-49. 

1904. Drepanochilus evansi Crossmann, Essais de paleoconchologie comparee, v. 6, p. 75. 

1917. Anchura americana (Evans and Shumard). Dowling,

Canada Geol. Survey Mem. 93, p. 31, pi. 29, figs. 5, 5a. 

1921. Anchura (Drepanochilus) americana (Evans and Shumard). Stanton, U.S. Geol. Survey Prof. Paper 128-A,

p. 37, pi. 6, fig. 13. 

1934. Alaria (Anchura) nebrascensis Coryell and Salmon (non

Evans and Shumard), Am. Mus. Novitates 746, p. 10. 

1940. Drepanochilus (Drepanochilus) americanum (Evans and

Shumard). Wenz, Gastropoda, in Schindewolf, O. H.

Handbueh der Palaozoologie, v. 6, pt. 4, p. 912, fig. 2683. 

1944. Drepanochilus americanum (Evans and Shumard). Shimer and Shrock, Index Fossils of North America, p. 497,

pi. 203, fig. 24. 

1960. Drepanochilus evansi Cossmann. Sohl, U.S. Geol. Survey

Prof. Paper 331-A, p. 100, pi. 11, figs. 23,26

Type locality. "Moreau and Grand Rivers" (Evans 

and Shumard, 1857). The type specimens cannot be 

located, but they obviously came from the Fox Hills 

Sandstone of South Dakota.

Diagnosis. Shell above average size for genus, body 

whorl strongly bicarinate, upper carination noded by 

collabral transverse swellings.

Description. Medium-size turriculate shell, spire a 

little more than half total shell height. Pleural angle 

25°-30°. Protoconch consists of 2%-21/^ smooth naticoid whorls; the last whorl increases rapidly in size to 

almost the diameter of the first teleoconch whorl and is 

well rounded and smooth. Immediate preteleoconch 

whorl globose with well-rounded and smooth sides. 

Suture flush and straight, teleoconch whorls six to eight 

in number, whorl sides well rounded on spire. Body 

whorl bicarinate, whorl steeply sloping and flat above 

upper carination, flat to gently concave between carinations and broadly convex below, tapering to a narrow 

prolonged anterior pillar. Sculpture begins on first 

teleoconch whorl with about seven spiral threads with 

an eighth one ^interjected just below the suture after 

about seven and one-quarter turns; weak irregularly 

spaced arcuately opisthocyrt, opisthocline transverse 

ribs appear at this time. On second teleoconch whorl, 

transverse ribs become stronger and evenly spaced, 

forming an almost cancellate pattern with about 20 ribs 

on the whorl. Ribs continue to increase in strength 

until they become stronger, higher, and broader than the 

overriding spiral cords. Spiral threads increase in 

strength to narrow ribbons that are narrower than their 

interspaces, but do not increase in number until the teleoconch whorl, where secondary cords appear between the 

primaries. The secondary spiral cords increase in 

strength until they approximate the strength of the primaries ; on the penultimate whorl there are generally
B14 DESCRIPTIVE STUDY OF A CLASSIC REFERENCE LOCALITY OF THE PIEKRE SHALE

24-26 cords, but as many as 33 may be present. The 

transverse ribs also increase in number to a maximum of 

28 on the penultimate whorl, but begin to weaken generally in late penultimate whorl stage as the ribs begin 

to die out below.

On the body whorl, spiral sculpture remains strong 

with a spiral carination developing and increasing in 

strength toward the outer lip about 3 mm below the suture. This carination carries several spiral ribbons or 

cords on its surface. A second carination develops 

lower on the whorl on the basal slope. This carination 

is continuous with the spiral cord that is situated at the 

suture of the preceding whorls. Fine spiral cords cover 

the base of the body. The upper carination carries out 

to the end of the extended outer lip spike and is the surface reflection of the incised groove of the inner surface 

of the outer lip. The lower carination is but an accentuated spiral cord that dies out at the outer lip margin.

The transverse ribs of the body are weak wide-spaced 

swellings, but they are accentuated to form nodes as they 

intersect the upper spiral carination, then carry weakly 

to the lower carination. Growth line is opisthoclinely 

opisthocyrt. Aperture lanceolate in outline narrowed 

anteriorly, slightly angulated posteriorly. Outer lip 

expanded to a broad wing that tapers to, and terminates 

in, a sharp pointed upward curving spine; lip thickened 

along edges with a narrow groove paralleling upper 

edge of wing; groove is continuous with carination of 

outer whorl surface. Upper edge of outer lip curving 

up to embrace lower one-third of penultimate whorl; 

lower edge of outer lip sinuous below lower carination,

with a double concave sinus when viewed from outer surface. Inner lip with moderately thick, sharply marginal callus; parietal callus evanesces a short distance 

over body and has an arcuate margin that thins to a 

sharp edge over the short anterior siphonal area.

Measurements. Explanation of measurements and 

symbols used in the following table appears in the section "Measurements of specimens" (p. B9). (See 

also fig. 3.)

Specimen and locality

Hypotype: 

USNM 274 Fox Hills SandDo. ___________________

USNM 274 (Figured by 

Stanton, 1921)_. _--.---_-.

USGS 23513 Fox Hills SandUS GS 23342 Fox Hills SandDo. _______ ________________

Do_____. -_.-- _.. _-

H

30.7

27. 1 +

24. 0

21. 1 +

22.2 +

23. 6

22.2

MDW

21. 6+

20. 0

16. 3

14. 6 +

17. 4 +

?

14. 8 +

HB

15.0 +

15. 0

10. 2 +

Discussion. Drepanochilus evansi is one of the 

larger species of the genus and is easily distinguished 

from the other western-interior species from lower 

stratigraphic positions by having a noded upper whorl 

carination. DrepanocTiilus pusillus (Stanton) (1921, 

p. 38) from the Paleocene Cannonball Member of the 

Fort Union Formation of South Dakota is consistently 

smaller in size (fig. 4), has coarser nodings of the upper 

carination (pi. 4, fig. 6), has more spiral cords at an 

earlier stage of growth, has a less sinuous trace of the

3r

20

1234 

HEIGHT, IN MILLIMETERS

345 

WIDTH, IN MILLIMETERS

FIGURE 3. Ontogeny of Drepanochilus evansi Cossmann. Measurements made using an arbitrary whorl height of 1.5 mm as the

zero whorl.
UPPER CRETACEOUS GASTROPODS, RED BIRD, WYOMING B15

lower part of the outer lip, and has a higher pleural 

angle. The ontogeny differs in that transverse ribs 

appear to be the first element of sculpture developed on 

D. pusillus (pi. 4, fig. 6), whereas spiral threads appear 

first on D. evansi (pi. 3, fig. 11). D. nebrascensis 

(Evans and Shumard) from the Pierre Shale at its type 

locality is a smaller species lacking nodes on the spiral 

carinae of the body (pi. 3, fig. 1). In addition, the 

spiral elements of the spire are finer, and the transverse 

ribs are more highly inclined.

Drepanochilus sublevis (Meek and Hayden) (pi. 3, 

fig. 16) represents a form transitional between D, evansi 

and D. scotti. Meek and Hay den's type of sublevis 

came from 150 miles above the mouth of the Yellowstone in beds near the top of the Pierre Shale (Baculites 

baculus zone). Other specimens in the collections of 

the Geological Survey from this same zone near Glendive (pi. 3, figs. 13,14) show similar suppression of the 

transverse elements, although not quite so extreme. 

Anchural sublevis Whitfield (non Meek and Hayden) 

possesses the 'cancellate early sculpture and general spire 

sculpture of D. evansi, but is an immature specimen 

that cannot presently be properly placed.

The occurrences of individuals assignable to this 

species in the Ked Bird section are restricted to a few 

generally small specimens from the Baculites baculus 

and B. grandis zones. All probably belong to the transitional types similar to those from the Pierre Shale 

of the Glendive region (pi. 3, figs. 13, 14) of eastern 

Montana (B. baculus zone). The specimen from locality D-1985, B. grandis zone, pi. 3, figure 20, in the upper

unnamed tongue of the Ked Bird section conforms to 

this type especially well in its weak spiral carinae and 

nodes.

Types. Holotype, lost; hypotypes, USNM 274, 132683, 132680, 

132685,132688, 132690, 132692, 132952.

Occurrences. Wyoming: Pierre Shale, Bed Bird section 

(Baculites grandis zone), USG>S D-1985; (B. baculus) USG^S 

D-1983. Montana: Glendive area, upper part of the Pierre 

Shale (B. baculus zone). South Dakota: Fox Hills Sandstone 

and uppermost part of Pierre Shale. North Dakota: Fox Hills 

Sandstone, Colorado: Front Range, Pierre Shale (B. baouliw 

zone), USGS D-1542 (B. clinolo'batus zone), USGS D-3720, D1294 and D-1545? Canada: Questionably present in the Bearpaw Shale of Alberta.

Drepanochilus scotti Sohl, n. sp. 

Plate 4, figures 13,14,17-24

Type locality. Pierre Shale (Baculites jenseni zone) 

2.4 miles west-northwest of Niwot, on southeast side of 

Haystack Mountain in NE^SW^SE^NW^ sec. 27, 

T. 2 N., K. TO W., Boulder County, Colo. (USGS 

D-335).

Diagnosis. Shell large for genus, body whorl weakly 

bicarinate, transverse sculpture subdued, growth line 

sinuous.

Description. Medium-sized turriculate shell, spire a 

little more than one-third total shell height. Pleural 

angle 22°-32°. Protoconch consisting of about 2i£ 

smooth round-sided whorls with first whorl somewhat 

depressed. Teleoconch whorls about seven in number, 

have well-rounded sides. Body whorl bicarinate; upper spiral carination low, developing one-third to onehalf whorl behind aperture. A second variable, weaker

3r

2 0

O

i 1

3 -

1234 

HEIGHT, IN MILLIMETERS

3

go -

O

i 1

2345 

WIDTH, IN MILLIMETERS

F'IGUEE 4. Ontogeny of Drepanochilus pusillus (Stanton). Measurements made using the arbitrary whorl height of 1.5 mm as the 

zero Whorl.
B16 DESCRIPTIVE STUDY OF A CLASSIC REFERENCE LOCALITY OF THE PIEIRRE SHALE

spiral carination develops low on whorl. Whorl profile 

flattens above and between carinations; body concavely 

tapers below to the pillar. Sculpture begins on first 

teleoconch whorl with three very faint threads over the 

rounded upper whorl surface; spiral threads strengthen 

and are added to until at the end of the whorl, eight 

spiral threads cover the surface. Low arcuately 

opisthocyrt opisthocline transverse ribs appear with the 

beginning of the second teleoconch whorl.

On later whorls, spiral elements increase in strength 

to rounded cords or flat-topped ribbons that override 

transverse ribs and are narrower than interspaces; ribbons may number 13-16 on the penultimate whorl. 

Secondary spirals may occur on body. Transverse ribs 

may number 26-29 per whorl; ribs decrease in strength 

until only an occasional faint transverse swelling may 

be present on the body whorl and last half of the 

penultimate whorl. The upper carination of the body 

whorl carries out to the spire that terminates the outer 

lip. Growth lines opisthoclinely opisthocyrt on spire. 

Aperture incompletely known but with outer lip expanded to a wing that embraces the lower part of the 

penultimate whorl above, is extended into an elongate 

taperin'g spike reinforced by the main spiral carination 

of the body with a corresponding incised groove 

interiorly.

Measurements. No specimens are perfectly preserved. The maximum recorded height attained is estimated at 35 mm: maximum diameter about 16 mm,

including the extended outer lip; and a body whorl 

about 12 mm in height. (See fig. 5.)

Discussion. This species is easily distinguished from 

the DrepanocMlus of higher stratigraphic positions in 

its lack of transverse ribs on the body whorl, non-noded 

spiral carination, less arcuate growth line, weaker spiral 

carination, more numerous transverse ribs on the spire, 

and in other details of sculpture. Drepa/nocMlus scotti 

is a larger species than D. nebrascensis which occurs at 

lower stratigraphic level and has coarser sculpture with 

less highly opisthocline transverse ribs.

DrepcmochHus scotti ranges through the BacuUtes 

jenseni and B. eliasi zones and occurs rarely in the 

upper part of the B. reesidei zone in Colorado. Only 

one questionably assigned specimen, an internal mold 

from the upper part of the B. reesidei zone, occurs in the 

Red Bird sequence, but it does conform in size and in 

f aintness of the carinations to this species.

D. scotti appears to be ancestral to the typical D. 

evansi of the Fox Hills through transitional forms, such 

as those from the B. baculus and B. clinolobatus zones 

of the upper part of the Pierre Shale at such localities as 

Glendive, Mont., the Red Bird sequence of Wyoming, 

and the Front Range of Colorado. These transitional 

forms show an intermixture of characters of both 

species, being like D. scotti in their suppressed transverse sculpture but similar in body whorl features to D. 

evansi. The species is named for Glenn Scott of the 

U.S. Geological Survey, who collected the type material.

1234 

HEIGHT, IN MILLIMETERS

3456 

WIDTH, IN MILLIMETERS

10

FIGURE 5. Ontogeny of Drepanochilus scotti Sohl, n. Measurements made using the arbitrary whorl height 1.5 mm as the 

zero whorl.
UPPER CRETACEOUS GASTROPODS, RED BIRD, WYOMING B17

Types: Holotype, USNM 132958; paratypes, USNM 132682, 

132686, 132689, 132694, 132954, 132957, 132959, 132960, 132962.

Occurrences: Colorado: Pierre Shale (B. eliasi zone), USGS 

16093, D-476, D-1078, D-335; (B. jenseni zone), D-16093, 

D-374 ; (B. reesidei zone?) USGS D-1567, D-2820, D-728, D-631. 

Wyoming: Pierre Shale (B. reesidei zone, upper part), USGS 

D-1952.

DrepanocMlus nebrascensis (Evans and Shumard) 

Plate 3, figures 1-9

1854. Rostellaria nebrascensis Evans and Shumard, Acad. Nat.

Sci. Philadelphia Proc., v. 7, p. 164. 

1860. Aporrhais nebrascensis (Evans and Shumard). Meek

and Hayden, Acad. Nat. Sci. Philadelphia Proc., v. 12,

p. 423. 

1864. Anchura (Drepanochilus) nebrascensis (Evans and

Shumard). Meek and Hayden, Smithsonian Misc.

Colln., v. 7, p. 19. 

1876. Anchura (Drepanovnilus) nebrascensis (Evans and

Shumard). Meek (part), U.S. Geol. Surv. Terr. (Hayden) Kept., v. 9, p. 326, pi. 13, figs. 5a, b, c (figures

questionably assigned to species). 

1900. Anohura nebrascensis (Evans and Shumard). Knight,

Wyoming Univ. Bull. 45, p. 154, pi. 9, fig. 7 (copy of

Meek's 1876 figures). 

1904. Arrhoffes (Drepanochilus) nebrascensis (Evans and

Shumard). Cossmann, Essais de paleoconchologie

compared, v. 6, p. 77.

Type locality. "Sage Creek, Nebraska" (Evans and 

Shumard, 1854, p. 164). According to W. A. Cobban 

(written commun., 1964), the material from Sage Creek 

(now in the State of South Dakota) is from the Baculites compressus zone occurring in dark gray fossiliferous concretions.

Diagnosis. Shells medium to small for genus, body 

with two strong carinations that lack nodes. E-idge on 

inner surface of outer lip near and parallel to edge.

Description. Medium-sized turriculate spire slightly 

more than one-half total shell height. Pleural angle 

20°-23°. Protoconch naticiform consisting of two 

smooth well-rounded whorls. Teleoconch of 4-6 convex sided whorls. Body whorl strongly bicarinate, 

whorl almost flat between suture and upper caririation, 

concave between carinations and broadly concave below 

sloping to the anterior pillar. Sculpture of first teleoconch whorl begins with about six low spiral threads. 

After one-quarter of a turn, weak arcuate transverse 

ribs appear that strengthen until, at beginning of second 

teleoconch, whorl, sculpture pattern is cancellate. Bibs 

continue to strengthen and on second and third whorls 

they are higher, broader, and stronger than the overriding spiral ribbons. By the penultimate whorl the 

ribs broaden, become lower and weaker. Spiral elements remain strong, but the ribbons become rounder 

topped and become wider spaced with occasional secondary spiral threads interpolated between the primaries.

Spiral elements may increase from the 6 primaries to as 

many as 14 cords and threads on the penultimate whorl.

Bibs number on penultimate whorl from 16 to 24. 

Upper spiral carination of body whorl stronger than 

lower and carries out onto expanded outer lip continuing onto extremity, forming a slightly upcurved spike. 

Growth line opisthoclinely opisthocyrt. Aperture 

lanceolate in outline, narrowest anteriorly, angulated 

posteriorly, outer lip expanded to form a moderately 

broad wing, tapering to a sharp pointed, slightly upcurving spike, interiorly outer lip grooved in position 

of the upper whorl carination and with a ridge of callus 

extending posteriorly parallel to but about iy2 mm behind edge of outer lip. Bidge terminates at groove. 

Callus ridge commonly reflected as an irregular swelling on outer surface of wing.

Measurements. The maximum size recorded for 

specimens from the type locality at the mouth of Sage 

Creek, South Dakota (USGS 23072) is 16 mm in height 

and 10.5 mm in diameter including the expanded outer 

lip (see also fig. 6).

Discussion. The species occurs abundantly at the 

type area in concretions containing hundreds of 

individuals. Within such concretions considerable 

variation in both size and sculpture can be detected. 

Variation in size is shown in the measurements given 

above and on figure 6 (locality USGS 23072). Variation in sculpture primarily affects the strength of the 

spiral carinae and the transverse ribbing, On small 

specimens the spiral carinations of the body whorl may 

start at the beginning of the whorl or may be present 

over only the later half of the whorl. Transverse ribs 

are usually present on the penultimate whorl, but there 

is every gradation from strong to weak, and total absence of such ribs. The number of transverse ribs 

appears to vary more with stratigraphic position than 

within individual populations. The specimens from 

higher stratigraphic levels commonly have a greater 

number of ribs than those of the B. compressus zone.

The specimens figured by Meek (1876, pi. 19, figs. 

5a-c) come from "Crow Creek, near Black Hills, from 

the upper beds of the Fort Pierre Group" (p. 327). 

According to W. A. Cobban (written commun., June 

1964), there is a Crow Creek in the vicinity of Belle 

Fourche at the north end of the Black Hills. The 

creek, however, drains only areas of Greenhorn and 

Belle Fourche rocks of Turonian-Cenomanian age. 

Meek's "Crow Creek" specimens (pi. 3, fig. 7) compare 

favorably with specimens from the type area on Sage 

Creek (B. compressus zone) in size; but they have weak 

carinations and very fine highly inclined transverse 

sculpture, and in some ways more closely approximate 

specimens from the lower range of D. americanus
B18 DESCRIPTIVE STUDY 'OF A CLASSIC REFERENCE LOCALITY OF THE PIERRE SHALE

(B. bacuhts-B. clinolobatus zones). The matrix in 

which Meek's specimens occur is dark-gray concretionary sandstone similar to the Pierre concretions from 

other localities, but the concretion appears to have been 

much smoothed, perhaps by running water. Only 

small fragments of a few other mollusks save Drepanochilus are present and thus afford no aid in fixing the 

stratigraphic position. In view of their somewhat 

distinctive morphology and the. inability to place accurately their occurrence either geographically or 

stratigraphically, assignment to a species is deferred 

until sufficient information is available.

The specimens assigned to this species by Whitfield 

(1880, p. 429) are herein redescribed as Drepanochilus 

obesus. Coryell and Salmon (1934, p. 10) assigned 

specimens from the Cedar Creek anticline near Glendive, Mont., to this species. They describe an indeterminate internal mold from the upper part of the Pierre 

Shale that, judging by the stratigraphic position, probably belongs in D. evansi.

Compared to Drepanochilus obesus, which occurs at 

a stratigraphically lower position, D. nebrascensis is 

smaller and more slender; the proportionally lower position of the peripheral carination (fig. 2) and smaller 

size and lack of peripheral nodings separate D. nebrascensis from D. evansi; and it is more slender, smaller, 

and has stronger peripheral carinations than D. scotti.

Drepanochilus nebrascensis ranges from the Didymoceras stevensoni zone up into the B. reesidei zones of 

Colorado, Wyoming, and South Dakota. The specimens from the Red Bird section from the Didymoceras 

stevensoni zone are immature and can only questionably 

be assigned to this species.

Types: Holotype, lost; hypotypes, USNM 132678, 132679, 

132681,132693,132697,132695,132705,132963.

Occurrences: Wyoming: Pierre Shale (Red Bird section), a 

questionable occurrence at USGS D-1939 (Didymoceras stevensoni zone). South Dakota: Pierre Shale (Baculites oompressus 

zone). Colorado: Front Range (Exiteloceras jenneyi through 

B. cuneatus zones; especially common in B. cuneatus zone).

Drepanochilus obesus Sohl, n. sp 

Plate 4, figures 15, 25-31

1880. Anchura (Drepanochilus) nebrascensis (Evans and Shumard). Whitfield, U.S. Geog. and Geol. Survey Rocky 

Mtn. Region (Powell), p. 429, pi. 12, figs. 2, 3.

Type locality. Pierre Shale, Red Bird Silty Member, Baculites gregoryensis zone at sec. 13, 19, 23, T. 38 

N., R. 62 W., Niobrara County, Wyo. Holotype, 

USNM 132642 (USGS Mesozoic loc. D-1917).

Diagnosis. Shell large and obese for genus with a 

high pleural angle. Body whorl strongly bicarinate 

with upper carination proportionately low on whorl, 

and distance between carinations proportionately great 

(fig. 2). Transverse ribs highly inclined for genus, 

spiral sculpture of numerous fine spiral threads.

Description. Shell of medium size, turriculate, with 

spire and body whorl height almost equal. Pleural 

angle 32°-33°. Protoconch unknown. Early sculpture of fine spiral ribbons that override very arcuate 

transverse ribs; at about 1.5 mm whorl height, ribs number 24-28 per whorl and spiral cords average 20 per 

whorl. Ribs become wider spaced on later whorls and 

may disappear on about the last one-quarter of the 

penultimate whorl. Spiral sculpture increases mainly 

by the addition of fine spiral threads between the cords. 

The penultimate whorl usually bears 22-26 cords and

3r1234 

HEIGHT, IN MILLIMETERS

3456 

WIDTH. IN MILLIMETERS

FIGURE 6. Ontogeny of Drepanochilus nebrascensis (Evans and gbumard). Measurements made using the arbitrary whorl height

of 1.5 mm as the zero whorl.
UPPER CRETACEOUS GASTROPODS, RED BIRD, WYOMING B19

threads. Transverse sculpture absent on body whorl. 

Spiral sculpture of body whorl dominated by two prominent carinations; the posterior carination is strongest 

and continues to the spikelike termination of the outer 

lip; 20-24 spiral cords and threads occur on the rounded 

surface above the posterior carination, 6-8 threads are 

present on the broadly concave area between the carinations ; the steep anterior slope is covered with spiral 

threads. Growth line strongly opisthocyrt, opisthocline 

in total. Aperture incompletely known, outer lip expanded to a broad wing that tapers to a slightly curving 

spike; interior of lip grooved along trend of spiral carination to spikelike termination and ridged along lower 

two-thirds of extent parallel to edge.

Measurements. Explanation of measurements and 

symbols used in the following table appears in the section "Measurements of specimens" (p. B9).

Specimen and locality

USNM 12309 (Whitfleld, 1880) 

Do. _ ______

USGS D-1271 Colorado____ _____________

USGS D-1917 Wyoming. _ ______________

HB

91

66

74

107 +

MDW

112

96

104

175

Discussion. This species attains the largest size 

known for any member of the genus and has a higher 

pleural angle. Compared to D. nebrascensis^ this is a 

much larger and more obese species. In convexity of 

whorl it is 'approached only by D. scotti from the B. 

reesidei through B. eliasi zones, but that species has 

more subdued spiral carinations and more direct transverse ribs. D. evansi has noded carinations, lacks a 

ridge near the lower margin of the outer lip, and the 

whorl between suture 'and carination is concave rather 

than convex in profile.

The ridge on the inner lip parallel to the outer extremity allies this species to Drepanochilus nebrascensis.

The figured specimens assigned by Whitfield and here 

refigured (pi. 4, figs. 30, 31) came from "East Fork of 

Beaver Creek, 3 miles west of Camp Jenny, Black 

Hills." W. A. Cobban (written commun., June 15,1964) 

states that Whitfield's collections from Beaver Creek include species from the Exiteloceras jennyi and 

Didymoceras stevensoni zones and probably species as 

old as the Baculites gregoryensis zone. Although it is 

not possible to place Whitfield's specimens accurately, 

they obviously came from beds within the range of D. 

obesus and morphologically conform well to the species.

Types: Holotype, USNM 132642; hypotypes, 132675, 132700- 

132703.

Occurrences: Wyoming: Pierre Shale, Red. Bird section, Red 

Bird Silty Member (B. gregoryensis zone), USGS D-1917. 

Colorado: Pierre Shale, Front Range (Baculites scotti and

Didymoceras nebrascense zones). South Dakota: Pierre Shale 

(Whitfleld 1880, p. 429, position uncertain).

Genus APORRHAIS Da Costa 1778

Type by monotypy, S trombus pespelicani Limie, 1758.

Diagnosis. Medium-sized aporrhaids with surface 

covered by fine spiral cords. Transverse sculpture of 

poorly developed ribs normally absent on earliest 

whorls. Eibs accentuated to nodes where they cross 

spiral carination. Body whorl bicarinate to tricarinate 

Aperture expanded to a broad wing with three digitations, one extending posteriorly and adnate to spire, the 

other two extending laterally as continuations of spiral 

carinae of body. Anterior canal moderately short.

Discussion. Numerous Cretaceous species in both 

hemispheres have been assigned to Aporrhais. Most, 

however, appear to belong in other genera. The species 

here described from the Pierre Shale of the western 

interior and one undescribed form from the Blufftown 

Formation (lower Campanian) of Alabama appear to 

be the only true members of the genus in the Cretaceous 

of North America. The following list is an attempt to 

assign the North American Cretaceous species commonly ascribed to Aporrhais.

To Anchura Conrad, 1860

Aporrhais angulata Gabb, 1864 by Stewart, 1926 (California )

Aporrhais falciformis, Gabb, 1864 by Gabb, 1868 (California ) 

To Arrhoges Gabb, 1868

Aporrhais oalifornioa Gabb, 1864 by 'Stewart, 1926 (California )

Aporrhais travisensis Stanton, 1947 (Comanche Peak lamestone, Texas)

Aporrhais tarrantensis 'Stanton, 1947, assignment questionable (Comanche Peak Limestone, Texas) 

To Cyphosolenus P. Fischer, 1884

Aporrhais nencensis Stanton, 1947 (Comanche Peak Limestone, Texas) 

To Drepanochilus Meek, 1864

Aporrhais sublevis Meek and Hayden (Pierre Shale,

Montana) 

To Graciliala Sohl, 1960

Aporrhais decemlirata Conrad, 1858 

To Monocyphus Piette, 1876

Aporrhais ~brittsi Staruton, 1947' (Edwards Limestone,

Texas)

Aporrhais singleyi Stanton, 1947 (Edwards Limestone, 

Texas)

Such species as Aporrhais (Perissoptera] proldbiata 

(White) of Stanton, 1894, A. (Pterocerella] tippana 

(Conrad) of Wenz, 1940, and A. (Lispodesthes] nuptialls (White) of Bergquist, 1944, are automatically 

assigned when the subgenera are raised to generic rank 

as is now generally accepted.
B20 DESCRIPTIVE STUDY OF A CLASSIC REFERENCE LOCALITY OF THE PIEIRRE SHALE

Generically indeterminate:

Aporrhais <sp. Ravn, 1911 (Neocomian, Greenland)

A. spp. Ravn, 1918 (Senonian, Greenland)

A. ? elpasensis 'Stanton, 1947

A.l Jcentensis Stanton, 1947 (may belong in the Colombellinidae) 

A. ? subfusiformis (Shumard) Stanton, 1947

Aporrhais biangulata Meek and Hayden

Plate 2, figure 8-18

1856. Rostellaria bianffulata Meek and Hayden, Acad. Nat. Sci.

Philadelphia Proc., y. 8, p. 65. 

1860. Aporrhais biangulata Meek and Hayden, Aoad. Nat. Sci.

Philadelphia, Proc. v. 12, p. 186. 

1876. Aporrhais biangulata Meek and Hayden. Meek, U.S. Geol.

Survey Terr. (Hayden), Kept. v. 9, p. 322, pi. 19, fig's.

6a, b, c, fig. 37. 

1904. Chenopus (Chenopus) biangulata (Meek and Hayden).

Cossmann, Essais de pal£oconchologie compared, v. 6, p.

55. 

1917. Aporrhais biangulata (Meek and Hayden). Bowling,

Canada Geol. Survey Mem. 93, p. 46, pi. 29, figs. 6, 6a.

Type locality. "Yellowstone River, 150 miles from 

its mouth" (Meek, 1876, p. 323). This locality is the 

upper part of the Pierre Shale (Baculites baculus zone) 

in the vicinity of Olendive, Mont.

Diagnosis. Medium-sized Aporrhais with sculpture 

dominated by fine spiral sculpture giving rise to a bicarinate body whorl; transverse sculpture restricted to 

normally low collabral incomplete ribs accentuated over 

carination of spire but absent on body.

Description. Medium-sized turriculate shells, spire 

slightly more than one-half total height. Pleural angle 

28°-31°. Protoconch unknown, teleoconch whorls 

about seven in number, broadly rounded on sides with 

greatest curvature at about two-thirds to three-fourths 

below suture; a peripheral carination develops at this 

position, usually on the penultimate whorl. Body 

whorl bicarinate with upper carination strongest, whorl 

profile convex suture to carination, concave between 

carinations, steeply sloping and broadly concave below. 

Sculpture dominantly spiral consisting of numerous 

crowded spiral threads of variable strength that cover 

the whorl surface. Transverse sculpture of generally 

weak highly arcuate collabral ribs. Eibs restricted 

normally to medial half of whorl accentuated at periphery to subnodings. Aperture lanceolate, anteriorly 

extended to an elongate shallow canallike groove of the 

curved pillar, inner lip with moderately thick callus that 

is posteriorly, laterally, and anteriorly continuous with 

the expanded outer lip. Outer lip expanded to a broad 

flaring wing that extends upward adnate to the spire for 

nearly its full length. This flange is not grooved interiorly, lies at an angle to the lateral extensions, and is 

partly separated by a sulcus; lateral wing extension 

grooved interiorly in harmony with the lateral extenSpecimen and locality

Holotype: USNM 275 Pierre Shale

Paratype: 

USNM 132964 Pierre Shale 

(B. baculus zone), Montana _ 

USNM 276 Pierre Shale (B.

Do______-__--__________.

USNM 132965 Pierre Shale 

(B. baculus zone), Montana. _

Hypotype: 

USNM 132704 Pierre Shale,

USNM 132696 Pierre Shale,

USNM 132699 Pierre Shale, 

Montana. ________

USNM 132698 Pierre Shale,

H

12.7+

147

18. 3

12.4

19. 1 +

14 4+

13. 5

MDW

9.8

12.9 + 

9. 5

15.4

13.4+

11.3

15. 4 

13.7+

9. 0+

HB

6.4

9.3 

7.3

7.4

9. 9

7.4

9.0

sion of the carinations of the body whorl, which terminate in blunted spikes separated by a broad shallow 

sulcus; posterior slope of wing broadly concave curving 

to the elongate curved anterior spike. Growth line 

strongly arcuate, opisthoclinely opisthocyrt.

Measurements. Explanation of measurements and 

symbols used in the following table appears in the section "Measurements of specimens" (p. B9). (See also 

fig. 7.)

Discussion. This, distinctive small species shows 

variation primarily in the strength of the transverse 

ribs which are barely developed on some specimens (pi. 

2, fig. 15) but on others may be accentuated to rather 

strong nodes on the periphery (pi. 2, figs. 12, 18). 

Normally, ribs are restricted to the penultimate whorl; 

in a few specimens, ribs may be seen on the antipenultimate whorl.

No available specimen preserves a full wing or nuclear whorls. This is not surprising as the shell material is paper thin and exfoliates easily during preparation of the specimens or because of breakage before 

burial.

Compared with the type species, Aporrhais pespelicani (pi. 2, figs. 1-5) from the North Atlantic, it can 

readily be seen that A. biangulata conforms closely in 

shape of the wing. The main differences rest in the 

recent species having stronger tranverse sculpture, 

larger size, and a less arcuate and opisthocline growth 

line. Ontogeny of sculpture with early whorls lacking 

transverse ribs is, however, quite similar (compare pi. 

2, fig. 1, and pi. 2, fig. 15).

Aporrhais biangulata in the Red Bird section is 

known from only one incomplete specimen from the 

upper unnamed member of the Pierre Shale in the 

Baculites baculus zone. The type specimens come from 

the same zone near Glendive, Mont., at Meek's locality 

"150 miles above the mouth of the Yellowstone." Fig-
UPPER CRETACEOUS GASTROPODS, RED BIRD, WYOMING B21

ures 11 and 15-17 on plate 2 all come from his type lot 

of specimens. The specimens figured on plate 2, figures 

10,12,14,18, also come from Montana, presumably from 

about the same level, but adequate locality data are 

lacking.

Holatype USNM 275; paratype, USNM 132964; 

132965, 132967; hypotypes, USNM 132696, 132698, 132699, 

132704, 132684.

Occurrences: Wyoming: Pierre Shale, Red Bird section (Baculites bacillus zone), USGS D-1981. Montana: Pierre Shale 

(Baculites baculus zone), near Glendive.

Aporrhais n. sp. 

Plate 2, figures 6, 7

Discussion. One incomplete specimen from the uppermost beds of the Mitten Black Shale Member of the 

Red Bird section (D-1877) Baculites gilberti zone) 

possesses such distinctive characters that it is obviously 

a new species. However, it lacks an outer lip, and the 

formal naming of the taxon should await better preserved material. This is especially true inasmuch as 

the most distinctive character, the nodes upon the transverse ribs, are a feature to be found on Aporrhais 

bicmgulata (Meek and Hay den). This species, however, differs in its suppression of the transverse ribs 

with nodes commonly restricted to the penultimate 

whorl and in having a much more sinuous growth line.

The specimen here discussed consists of about seven 

whorls, but is missing the apical tip, the expanded 

outer lip, and fragments of the surface. The shell is 

17 mm high, with the body whorl 8 mm high and 7^ 

mm in diameter. The pleural angle is 22°. Sculpture 

of the early whorls is poorly preserved, but is dominated

by strong transverse ribs that are overridden by low 

spiral cords. The ribs are accentuated to nodes at about 

the anterior three-quarters length of the whorl where 

they intersect a spiral subcarination. Below the nodings the ribs diminish to mere transverse swellings. On 

later whorls the ribs diminish in vigor, and on the latter 

half of the penultimate whorl they are irregularly 

spaced swellings. The spiral carination of the spire 

continues onto the body whorl, forming the upper whorl 

carination. The body whorl is bicarinate and covered 

by lesser spiral cords. The whorl profile is straight 

and steeply sloping between the suture and upper whorl 

carinations with an openly concave slope anteriorly. 

The specimen is broken at the lip, but the beginnings of 

the lip expansion can be seen as the upper suture of the 

body begins to rise adnate onto the penultimate whorl. 

The growth line is arcuately opisthocline above the 

nodes and steeply opisthocline below the nodes on the 

spire.

The generic placement of this species is in doubt. In 

general form, one is tempted to place it in Drepanochilus, especially because of the presence of ribs at an early 

stage of growth. However, the presence of the spiral 

carination at an early stage of growth and the nodings 

of the ribs are not unlike characters displayed by Aporrhais pespelicani, the type of species of Aporrhais. In 

addition, the slender spire argues for placement in 

Aporrhais, as the DrepanodiUus from this part of the 

section have rather obese whorls.

Type: Figured specimen, USNM 132672. 

Occurrence: Wyoming: Mitten Black Shale Member, Pierre 

Shale, Red Bird section (Baculites qilbertl zone), USGS D-1877.

3r

2345 

HEIGHT, IN MILLIMETERS

3r

12345 

WIDTH, IN MILLIMETERS

FIGUEE 7. Ontogeny of Aporrhais biangulata Meek and Hayden. Measurements made using the arbitrary whorl height of 1.5 mm as the Zero whorl. 

223-112 O 66 4
B22 DESCRIPTIVE STUDY OF A CLASSIC REFERENCE LOCALITY O'F THE PIE:RRE SHALE

Superfamily HIPPONICACEA

Family VANIKOBJDAE 

Genus VA1TCKOROPSIS Meek, 1876

Type by original designation: Natica toumeyana 

Meek and Hayden, 1856.

Diagnosis. Medium-sized thick naticiform shells. 

Sculpture dominated by strong broad spiral ribbons 

with transverse sculpture absent or as low and broad 

collabral rugosities. Umbilicus narrow.

Discussion. Meek (1876) proposed this genus for 

thick unumbilicate shells, with strong growth rugae. 

He provisionally placed the genus in the Vanikoridae. 

Cossmann (1925) followed by Wenz (1941) assigned it 

to the Naticidae in part. They proposed such an assignment because of the supposed lack of an umbilicus.

Meek founded the genus on the holotype of Vanikoropsis tuomeyana from "the mouth of the Judith 

Eiver * * * from the top of the Fox Hills Group." 

It is an incomplete specimen with a worn spire and with 

the body whorl broken back for about one-half whorl 

but, as figures (pi. 5, figs. 15, 16) of the holotype show, 

it possesses a narrow umbilical chink.

Fossarl. nebrascensis Meek and Hayden (1860) (includes Natica ambigua Meek and Hayden (1856), N. 

haydeni Cossmann (1899) and N. praenominata Cossmann (1920)) is here included in Vanikoropsis because 

of similarities in shape, sculpture pattern, thickness of 

shell, and presence of an umbilical chink. The type 

species V. toumeyana differs from V. nebrascensis in its 

coarse growth rugae and its proportionally broader and 

more depressed spire. The low spire and breadth (pi. 

5, fig. 15) of the holotype, however, are accentuated by 

wear of the spire and breakage of the body whorl.

Assignment of Vanikoropsis to the Naticidae is questionable, and I prefer to place it in the Vanikoridae. 

Cossmann (1925, p. 165) actually placed one of the hereincluded species (Natica ambigua) in Vanikoro. Compared with Vanikoro as exemplified by the type species 

V. cancellata (Chemnitz) (pi. 5, figs. 2-4), Vanikoropsis 

differs in having a thicker shell, a lower spire, and a 

more rounded aperture, especially the inner lip. As can 

be seen on some specimens of the Recent species Vanikoro lygata Recluz (pi. 5, figs. 11,13), sculpture pattern 

can be similar in the two genera. Cossmann (1925, p. 

41) lists a number of fossil species ranging from Jurassic (Portlandian) through the Upper Cretaceous as belonging in this genus, but they all appear to be globose 

nonumbilicate naticids with spiral sculpture that are 

not closely related to V. toumeyana.

Other Cretaceous species from the Western Hemisphere have been assigned to Vanikoropsis and Vanikoro, 

but most do not belong.

Vanikoro propingua Cragin (1894) (from the Comanche series 

(Kiowa Shale) of Kansas (see Stanton, 1947, p. 104), has never

been figured, but the description appears to foe of an unrelated 

siphonostomous shell.

Vanikoro n. sp.? Spa'th (1936, 1946), from the Jurassic and 

Cretaceous of Greenland, is represented by incomplete internal 

molds which are impossible to place with confidence.

Vanikoropsis suciensis White (1889), from the Cretaceous of 

Sucia Islands, is an internal mold of uncertain affinities.

Vanikoro kiHani Wilckens (1910), from the Antarctic Upper 

Cretaceous, according to Wilckens figures, has a sinuate inner 

lip not typical of Vanikoro.

Vanikoro pulchella Whiteaves (1884), from the Queen Charlotte Islands of British Columbia, probably is a neritacean related to Lyosoma White.

Vanikoropsis nebrascensis (Meek and Hayden) 

Plate 5, figures 1, 5-10, 12, 14, 17; plate 6, figures 1-4, 11

1856. Natical ambigua Meek and Hayden, Acad. Nat. Sci. Philadelphia Proc., v. 8, p. 64 (non Morris and Lyeett, 1854). 

1860. Fossarl nebrascensis Meek and Hayden, Acad. Nat. Sci.

Philadelphia Proc., v. 12, p. 423. 

1864. Vanikoro ambigua (Meek and Hayden). Meek, Smithsonian Misc. Coll., v. 15, p. 18. 

1876. Vanikoro ambigua (Meek and Hayden). Meek, U.S. Geol.

Survey Terr. (Hayden) Kept., v. 9, p. 330, pi. 19, figs.

12a-d. 

1880. Vanikoro ambigua (Meek and Hayden). Whitfield, U.S.

Geog. and Geol. Survey Rocky Mtn. Region (Powell),

p. 430, pi. 12, fig. 14. 

1899. Natica haydeni Cossman, Rev. critique paleozoologie, v. 3,

no. 3, p. 136. 

1920. Natica praenominata Cossman, Rev. geologic, v. 1, no. 1,

p. 69. 

1925. Vanikoro ambigua (Meek and Hayden). Cossman, Essais

de paleoconchologie comparee, v. 13, p. 165.

Type locality. "Yellowstone River 150 miles above 

its mouth." The locality is near Glendive, Mont., in the 

upper part of the Pierre Shale (Baculites ~baculus zone).

Diagnosis. Spire high and pleural angle low for 

genus. Transverse rugae uncommon.

Description. Shells medium sized, naticiform, moderately thick; spire about one-third total shell height. 

Pleural angle /75°-80°. Protoconch is dome shaped and 

paucispiral with smooth-surfaced whorls. 'Suture impressed ; whorls round sided. Sculpture dominated by 

spiral ribbons that cover the whorl; ribbons are broader 

than interspaces over whorl sides, but are narrower on 

base with interspaces equal to or wider than ribbons. 

Transverse sculpture restricted growth lines or broad 

usually discontinuous swellings. Growth lines prosocline, inclined about 15° to the axis of coiling. Aperture subovate, well rounded anteriorly, subangulate 

posteriorly. Inner lip broadly arched over parietal 

area, strongly curved anteriorly; parietal callus thin at 

edge. Umbilicus narrow, open, and free of callus.

Measurements. Explanation of measurements and 

symbols used in the following table appears in the section "Measurements of specimens" (p. B9).
UPPER CRETACEOUS GASTROPODS, RED BIRD, WYOMING B23

Specimen and locality

Holotype: USNM 267 Pierre Shale (B. baculus zone), 

Montana ___________ ______ __ __ ___ _

Paratype : 

USNM 132967 Pierre Shale (B. baculus zone), Montana. _ 

USNM 267 Pierre Shale (B. baculus zone), Montana __

Hypotype: USNM 132663 Pierre Shale (B. baculus zone), 

Red Bird, Wyoming ____ _ ____ ___ __

USGS 1896 Pierre Shale (B. baculus zone) Montana ________

Do__ _ _____________________________________________

USNM 21893 Fox Hills Sandstone, Montana. ______________

Do___________________________ _______________________

Hypotype: USNM 132664 Fox Hills Sandstone. ____________

Vanikoro cancellata (pi. 5, fig. 2)__ _ ____

H

15. 6

13.2 + 

14. 0 +

19. 3 +

14.4

17.5

16.5 +

22.4

13. 5

1Q 0

MD

11.0

10. 8 

13. 5

18.6

13.4

10. 7

17. 1

14. 1

20. 5

14 1

20.7

H/MD

1.3

1. 2

1. 2

1.3

1.2

1.2

1. 3

1.2

. 9

.9

DPW

8.6

9. 1 

11.8

15.9

10.0

9. 1

14.4

11.0

17. 2

HB

10.5

11.4 

13. 3

16.6

13. 0

10. 1

15.7

14. 1

21. 0

HA

8.3

8.6 

10.8

12. 9

10.8

8.5

11.9

11. 1

16.0

HB/MD

1. 1

1. 3 

1.2

1. 3

1.2

1.2

1.3

1. 3

1.3

Discussion. The assignment of Vanikoropsis nebrascensis to Vanikoro is untenable. In that genus the spire 

and protoconch 'are much depressed. The type species, 

Vanikoro ccmcellata (pi. 5, fig. 2), differs in its strong 

sculpture. V. lygata (pi. 5, fig. 11) is similar in adult 

sculpture, but both species differ greatly in body proportions, spire height (H/MD ratio of 0.9:1 vs. 1.2-1.3:1 

for V. nebrascensis} , and in having a much rounder 

aperture and thinner shell.

The synonymy of Vanikoropsis nebrascensis is complex. The combination Natica ambigua, of Meek and 

Hayden (1856) is a homonym preoccupied by Morris 

and Lycett (1851) for a Jurassic species. In 1860, 

Meek and Hayden reassigned their species to Fossar, 

but as they pointed out, Fossar ambigua was preoccupied and they substituted the name nebrascensis. 

However, Meek in 1864 and later in 1876 reassigned the 

species to Vanikoro and resurrected the original name 

ambigua. This designation held until 1899 when Cossmann pointed out the homonymy of the original combination Natical ambigua, and substituted the name 

Natica haydeni.

In 1920, Cossmann again pointed out that Natical 

ambigua Meek and Hayden was a homonym of Morris 

and Lycett's species. Cossmann evidently forgot his 

previous substitution of Natica haydeni and proposed 

the new name Natica pradnominata. Later in 1925, 

Cossmann in his "Essais" again reassigned the species 

placing it in Vanikoroa (pro Vanikoro} and accepted 

the original name ambigua. In my opinion the first 

substituted name nebrascensis must stand for the species, 

and Cossmann's subsequent substitutions are invalid.

Specimens of Vanikoropsis nebrascensis are rare at 

individual collecting localities, but are widely distributed. As the measurements indicate, the available 

specimens vary greatly in size, but in body proportions 

they are very close. The largest specimens come from 

the Fox Hills Sandstone of North and South Dakota 

(pi. 5, figs. 7,17), and the Pierre Shale of the Red Bird 

section. Thus, size appears to 'be no criteria of stratigraphic position. The specimens of the type lot are 

among the smaller specimens. Variation in sculpture 

primarily affects the strength and spacing of the spiral 

elements. Such variation is more noticeable on small 

specimens or at earlier stages of growth. In general, 

the spiral ribbons are stronger and more stable on the 

later whorls (pi. 5, fig. 17). The transverse rugae, 

when present, are strongest near the suture and are well 

displayed on one paratype (pi. 5, figs. 9,10), on a specimen from an unknown locality in the Montana Group 

(pi. 5, fig. 8), and on a small specimen from the Pierre 

Shale at Glendive, Mont. The thickness of the shell 

behind the aperture is well shown by several specimens 

(pi. 5, figs. 1,14).

The specimen from the Red Bird section when compared to the holotype is much larger and has stronger 

sculpture. When compared with specimens from other 

localities, especially those from the Fox Hills Sandstone, however, it fits well within the species.

As viewed here, Vanikoropsis nebrascensis (Meek and 

Hayden) ranges from the upper part of the Pierre 

Shale into the Fox Hills Sandstone and also occurs in 

equivalent formations in Wyoming, Colorado, Montana, 

and South Dakota.

Types: Holotype, USNM 267; paratype, USNM 132667, 

132967; hypotypes, USNM 132663-132666, 132668.

Occurrences: Wyoming: Pierre Shale, Red Bird section 

(BacuUtes 'baculus zone), D-1983; Lewis (?) Shale USGS 

28588. Montana: Bearpaw Shale, USGS 233361, 2891, 1212; 

Pierre Shale, USGS 1896 (B. baculus zone). South Dakota: 

Fox Hills Sandstone, USGS, 27487, 5925. Colorado: Pierre 

Shale (Front Range), BacuUtes reesidei and B. jenseni zones.

Superfamily CALYPTKAEACEA

Family TRICHOTEOPIDAE 

Genus ASTANDES Wade, 1917

Type by original designation: Astandes densatus 

Wade.

Discussion. Wade (1926, p. 157) characterized 

Astandes as having a direct prosocline growth line, a 

D-shaped aperture, and an outer lip that is denticulate
B24 DESCRIPTIVE STUDY OF A CLASSIC REFERENCE LOCALITY OF THE PIEIRRE SHALE

on its inner surface. Knowledge of the type species, 

Astandes densatus, is based solely upon the holotype 

(USNM 32944) (Sohl, 1960, p. 92). This specimen, 

from the Bipley Formation on Coon Creek, Tenn., as 

can be seen from Wade's (1917, p. 17, figs. 7, 8) original 

figures, possesses an incomplete aperture with the outer 

lip broken. I have been unable to verify the presence 

of denticles on the outer lip inner surface. Such 

denticles are certainly absent on Tritonium cretaceum 

Miiller from the Upper Cretaceous, Aachen, Germany 

assigned to Astandes by Wade. In other genera, such 

as Paladmete, denticles are a variable feature even 

within individual species and therefore it should not be 

viewed as a generically significant feature of Astandes. 

The specimens described below from the Pierre Shale 

agree with the concept of the genus except for the denticulate outer lip.

Astandes densatus Wade 

Plate 4, figure 1-5, 10, 12

1917. Astandes densatus Wade. Acad. Nat. Sci. Philadelphia 

Proc., v. 69, p. 299, pi. 17, figs. 7, 8.

1925. Astandes densatus Wade. Cossmann, Essais pa!6oconchologie comparee, v. 13, p. 273, pi. 8, figs. 18-19.

1926. Astandes densatus Wade. Wade, U. S. Geol. Survey Prof.

Paper 137, p. 158, pi. 54, figs. 19, 20. 

1926. Astandes densatus Wade. Wenz Gastropoda, in Schindewolf, Handbuch der Palaozoologie, v. 6, pt. 4, p. 892, fig.

2622. 

1940. Astandes densatus Wade. Sohl, U.S. Geol. Survey Prof.

Paper 331-B, p. 92.

Diagnosis. High turbiniform shell, round-sided 

whorls, strong prosocline transverse ribs crossed by 

strong spiral ribbons and minor cords. Aperture 

D-shaped, anterior canal short.

Type locality. Ripley Formation, Coon Creek, McNairy County, Tenn. (Wade, 1926, p. 158). This level 

may be equivalent to the Baculites compressus zone.

Description. Medium-sized high turbiniform shell, 

spire two-fifths total shell height. Pleural angle 45°- 

48°. Protoconch unknown. Suture impressed. Whorls 

round sided, base broadly rounded but constricting 

rapidly. Sculpture consists of 18-20 strong roundtopped collabral transverse ribs that are continuous 

from suture to well down on base. Spiral sculpture of 

strong raised spiral elements that are narrower than the 

spiral elements, but are broadly round topped to flat on 

their upper surfaces. These spirals are strongest over 

the periphrey where a few secondary threads may appear in the interspaces; on base, spacing of cords increases. Growth lines prosocline, becoming arcuate below periphery on basal slope. Aperture, broadly 

D-shaped, anterior canal very short, slightly twisted; 

inner lip smooth, callus thin at edge and on parietal surSpecimen and locality

Holotype: 

USNM 32944 Ripley 

Formation, Mississippi. _ 

USNM 132929 Pierre 

Shale (B. baculus zone),

USNM 132969 Pierre 

Shale (B. baculus zone),

USNM 22850 Pierre 

Shale (B. baculus zone),

Hypotype: USNM 22970 

Pierre Shale (B. baculus

Hi

11 + 

16. 5

14+

12 +

15 +

HB

7 

9

9

7

10

MD

8 

10

11

8

11

HB/MD

0.9:1 

.9:1

.8:1

.9:1

. 9:1

face, thickening within and over columellar lip. Outer 

lip incompletely known.

Measurements. Explanation of measurements and 

symbols used in the following table appears in the 

section "Measurements of specimens" (p. B9).

i Estimated.

All the specimens of Astandes densatus measured are 

incomplete, lacking either a part of the spire or outer 

lip. All the western-interior specimens are larger than 

the holotype from Tennessee, and they may represent 

a somewhat more mature stage of growth. With increased size the base of the whorls seems to become 

more rounded.

All the western-interior specimens occur at a higher 

stratigraphic position (Baculites jenseni-B. baculus 

zones) than the type specimen from the Eipley Formation on Coon Creek, Tenn. (= Baculites compressus 

zone?). Despite such differences, all specimens fall 

within a close proportional size range, and have a similar 

pattern of sculpture. There is insufficient material from 

the type locality to indicate range of variation of 

Astandes densatus, and it is the conservative course to 

consider all these specimens the same species.

Types: Holotype, USNM 32944 (Tennessee) ; hypotypes, 

USNM 22970, 132969 (Montana), USNM 132928, 132929 

(Wyoming).

Occurrences: Wyoming: Pierre Shale, Red Bird section, 

USGS D-1981, D-1984 (Baculites baculus zone). Montana: 

Pierre Shale, Glendive area, B. baculus zone. Colorado: Pierre 

Shale, Front Range (B. jenseni zone). Tennessee: Ripley 

Formation (Upper Exogyra cancellata zone).

Superfamily NATICACEA

Family NATICIDAE 

Genus EUSPIRA Agassiz (in Sower by), 1838

Type by subsequent designation Dall, 1915: Natica 

glaucinaides Sowerby, 1812.

Discussion. Species of Euspira are the most common 

and widespread of the naticids in Upper Cretaceous
UPPER CRETACEOUS GASTROPOD'S, RE'D BIRD, WYOMING B25

rocks of North America. Sohl (1960, p. 122) has discussed the confusion of Euspira and Lunatia Gray, 184Y, 

and accepted the latter as a synonym. It is under the 

name Lunatia that the western-interior species 

discussed below have usually been accepted.

These globose naticids are common through a long 

stratigraphic range. Their generalized smooth globose 

shells make for difficulty in separation to species. Probably some names have been applied solely on the basis of 

stratigraphic or geographic separation leading to a 

multiplicity of names for the same taxonomic unit. The 

following list is an attempt to assign western-interior 

Cretaceous species described as Natica or Lunatia.

Lunatia adnae Sidwell, 1982, Frontier Formation, Wyoming. 

This species is based on inadequate material, but the open 

and broad umbilicus suggest affinities with Gyrodes Conrad.

Natica"! ambiffua Meek and Hayden, 1856, is assigned to Vanikoropsis nebrascensis (Meek and Hayden) herein.

Amauropsis bulbiformis Sowerby of Stanton, 1893, has been 

renamed Ampullospira stantonl Cossmann and reassigned to 

the genus Pseudamaura by Sohl, 1960.

Euspira coalvillensis White. Stanton, 1893, asisigns this species 

to Lunatia utahensis White.

Lunatia concinna Stanton (1893), non Hall and Meek, is from 

the Colorado Group of Utah. All specimens seen possess fine 

spiral striations, and except for being consistently of smaller 

size and more slender, they are similar to Lunatia dakotensis 

Henderson. They deserve to be redescribed as a new species 

of Euspirat.

Natica daJcotensis Henderson, 1920. (=Natica (Lunatia) 

ooddentalis Meek and Hayden, non Hall, 1845) is known only 

from the holotype (U'SNM 290) from the Fox Hills Sandstone 

of South Dakota. Cossmann's (1925, p. 54) assignment of this 

'species to Ampullospira Harris, a synonym of Pseudamaura 

Fischer, is untenable, as the shells lack the channeled suture, 

shoulders, and umbilical characters of that genus. It appears 

to be closest to Euspira in most characters', but lacks inner 

lip callus.

Natica haydeni Cossmann, 1899, see Vanikoropsis nebrascensis 

(Meek and Hayden) in text.

Naticat occidentalis Hall, 1845 (non Meek and Hayden, 1856). 

Henderson (1985, p. 165) suggests this fossil is a Tertiary 

fresh-water species, perhaps assignable to Viviparus. D. W. 

Taylor, oral common., May 1964, states the type locality is 

in the Pliocene of southwest Idaho.)

Natica paludinaeformis Hall and Meek, 1856 (non N. paludinaeformis d'Orbigny) from the Pierre Shale (Baculites oompressus zone) of South Dakota was removed to Amauropsis 

by Meek in 1876. Cossmann, 1899, pointed out the homonym 

status of Meek's name and substituted Natica meeJci. The 

species more properly belongs in Pseudamaura.

Natica praenominata Cossmann, 1929 (=N. haydeni Cossmann, 

1899 (see Vanikoropsis nebrascensis in text)).

Natica subcrassa (Meek and Hayden), 1856. (Claggett Formation.) Subsequent authors have consistently assigned this 

species to Lunatia. The best preserved specimens of this 

species show a conspicuous shouldering of the whorl, a subshoulder constriction of the whorls, and a sharp-edged inner 

lip callus that evanesces anteriorly. These features are not 

typical of either Euspira or Natica.

Lunatia utahensis White, 1877. (Includes Euspira coalvillensis White, 1879; see Stanton, 1893.) This is an unumbilicate 

species from the Colorado Group that in apertural features 

seems close to Eocernina but has a much higher spire than 

typical for that genus. It does, however, belong in the 

Glofoulariinae.

Euspira obliquata (Hall and Meek) 

Plate 1, figures 12-19

1856. Natica obliquata Hall and Meek [non Deshayes, 1866],

Am. Acad. Arts and Sci. Mem., v. 5, p. 389, pi. 3, figs.

la, b. 

1856. Natica ooncinna Hall and Meek, Am. Acad. Arts and Sci.

Mem., v. 5, p. 389, pi. 3, fig's. 2a-d. 

1856. Natica moreauensis Meek and Hayden, Acad. Nat. Sci.

Philadelphia Proc., v. 8, p. 64.

1860. Natica (Lunaftia) moreauensis Meek and Hayden, Acad. 

Nat. Sci. Philadelphia Proc., v. 12, p. 422.

1861. Lunatia moreauensis Gabb, Am Philos, Soc. Proc. v. 8,

p. 58. 

1876. Lunatia concinna (Hall and Meek). Meek, U.S. Geol.

Survey Terr. (Hayden) Bept, v. 9, p. 314, 315, pi. 32,

figs, lla-c. 

1880. Lunatia ooncinna (Halland Meek). Whitfield, U.S. Geog.

and Geol. Survey Rocky Mtn. Region (Powell), p.

430, pi. 12, fig. 13. 

1885. Lunatia concinna (Hall and Meek) Whiteaves, Canada

Geol. Survey, Contr. Canadian Paleontology, v. 1, pt. 1,

p. 48. 

1917. Lunatia concinna (Hall and Meek). Bowling, Canada

Geol. Survey Mem. 93, p. 30, 46, pi. 29, figs. 4-4B. 

1921. Lunatia obliquata (Hall and Meek). Stanton, U.S. Geol.

Survey Prof. Paper 128-A, p. 35, pi. 6, figs. lOa, b. 

1925. Crommium (Amauropsella) concinna (Hall and Meek).

Cossmann, Essais de paleoconchologie comparee, v. 13,

p. 45. (Assignment for Meek, 1876.) 

1925. Natica (Lunatia) concinna (Hall and Me^k). Cossmann,

Essais de paleoconchologie comparee, v. 13, p. 134. 

1960. Euspira concinna (Hall and Meek). Sohl, U.S..Geol. Survey Prof. Paper 331-A, p. 123. 

Not: 

1893. Lunatia concinna (Hall and Meek). Stanton, U.S. Geol.

Survey Bull. 106, p. 134, pi. 29, figs. 9,10. 

1900. Lunatia concinna (Hall and Meek)?. Knight, Wyoming

Univ. Bull. 45, pi. 8, fig. 5. (Illustration appears to have

been taken from Stanton, 1893.) 

Questionable assignment: 

1918. Natica (Lunatia) concinna (Hall and Meek). Ravn,

Medd. om Gr0nland, v. 56, p. 357, pi. 8, fig. 9. 

1944. Polinices concinna (Hall and Meek). Bergquist, Jour.

Paleontology, v. 18, no. 1, p. 26.

Type locality. "Great Bend of the Missouri. From 

clay beds of division No. 4 of section" (Hall and Meek, 

1856, p. 388). "The original typical specimen of L. 

concinna was found on Sage Creek, Dakota" (Meek, 

18Y6,p.315).

Diagnosis. Euspiras with a moderately broad umbilicus, inner lip callus not invading umbilicus, parietal 

callus thin.

Description. Medium-sized globose shells, spire onethird to one-quarter total shell height. Pleural angle
B26 DESCRIPTIVE STUDY OF A CLASSIC REFEiREiNCE LOCALITY OF THE PIElRRE' SHALE

73°-108°. Sutures abutting to slightly impressed. 

Whorls well rounded. Surface smooth, sometimes 

with a few faint microscopic spiral threads. Growth 

lines prosocline. Aperture sublunulate, broader and 

more well rounded anteriorly; outer lip well rounded, 

inclined about 20°-22° to the axis of coiling. Inner lip 

almost straight over parietal and upper columellar 

area, lower columellar lip well rounded and slightly

evanescing. Parietal callus rather thin extending only 

a slight distance out of the aperture. Umbilicus open, 

lacking callus infringement.

Measurements. Explanation of measurements and 

symbols used in the following table appears in the section "Measurements of specimens" (p. B9). The 

measurements form the basis for the plots of specimens 

of Euspira obliquata given in figures 8 and 9.

Specimen and locality

Holotype: 

AMNH 9465/1 (Natica obliquata) __ _______ ___________ ________

AMNH 9364/1 (Natica concinna) _____ ___ ___ _____ _

USNM 264 (Natica moreauensis)... ____ ___ ____ ____ _ ___

USNM 264 Fox Hills Sandstone, South Dakota. _ _ _ _ ___ _ _ _ _ _____

Do_________________. -------_--_-__--.-_____-________________

Do____-__-_-__-________---_--______-----____________________

Do___----__-___-_--_______-_-__--_-__-_-____________________

Do___----____-______-_--_-_---_-__----_____.________________

US GS 27487 Fox Hills Sandstone, South Dakota. ___. ________ _______

Do____ _____________ _ _ ________________________________

Do___-__________.___-_-_--__-_______________________________

Do___---_-__-_________-_-_________--________________________

Do____---___________--__--______-__-__-.____________________

Do__----_-_-___-____-_-_--_---_____--____________ ___________

USGS 27485 Fox Hills Sandstone, South Dakota __ ____ __ __ ___

Do-___--____________________________________________________

Do__________________________________________________________

Do___-_-_____-____________________________________________ _

US GS 27490 Fox Hills Sandstone, South Dakota _ _ _ _ ___ _______

Do_-___-__-__________.______________________________________

Do_____________________.__________________

PA

96

98

91

73

76

82

85

96

82

95

90

92

91

108

102

101

91

101

96

H

Q 8

6 9

21. 5

1Q

19

17

14. 5

12

20. 5

24

20

12

14. 5

20

20

16

15. 5

26

14. 5

20

MD

8.0

6. 0

19.5

ICC

16

15

13

11. 5

19

21

18

10

14

19

18

17

19

15

22

14

20

HB

7 9

4.3

14. 5

13.0

13. 5

12

10

Q

16

15. 5

15.0

8.5

12. 0

15

14

13

14

13

18

11

1Q

H/MD

1.22

1 HQ

1. 10

1 93

1. 18

1 13

1. 11

1 O3

1 08

1. 14

1. 11

1.2

1.36

1.05

1. 11

.94

1. 03

1.18

1.03

1. 0

H/HB

1.36

1.44

1.41

1 1Q

1. 11

1.25

1.30

1.28

1. 19

1.35

1. 2

1. 18

1. 17

1.26

1.29

1.30

1.36

1. 15

1. 22

1.27

1. 05

co 28

cc

I 26

Ij

124

z

_T22

LJ

E °20

16

14

12

65 70 75 80 85 90 95 100 105 110 115 

PLEURAL ANGLE, IN DEGREES

FIGURE 8. Comparative plot between Euspira obliquata (Hall and 

Meek) (dots) and Natica subcrassa Meek and Hayden (crosses) of 

pleural angle versus height of shell. Euspira obliquata decreases 

in pleural angle with increase in size, whereas N. subcrassa remains 

virtually the same. The gap between the outlined areas of E. 

obliquata is interpreted as sexual dimorphism.

36

34

32

30

UJ

I 26

d 24 

\22

^"20

UJ

co 18

u_ O 16

H

UJ

I 12 

10

6 8 10 12 14 16 18 20 22 24 26 28 30 32 34 

MAXIMUM DIAMETER, IN MILLIMETERS

FIGURE 9. Comparison of height-width variation between Euspira 

obliquata (Hall and Meek) and Euspira rectilabrum (Conrad). 

Crosses are plots of selected specimens of E. obliquata from the 

Pox Hills Sandstone of South Dakota. Dots are plots of a suite 

of specimens collected in the Ripley Formation on Coon Creek, 

McNairy County, Tenn. (Exogyra cancellata zone, USGS Mesozoic 

loc. 25406).
UPPER CRETACEOUS GASTROPOD'S, RED BIRD, WYOMING B27

The following table summarizes the data given above 

on Euspira obliquata and compares them to data assembled for other associated or related naticid species.

Euspira obliquata ...

Natica subcrassa ....

PA

Range

73-108 

73-99

65

102-112

Avg

91 

81

65

108

H

Range

6. 2-26. 0 

6. 7-31. 5

23

13-31

MD

Range

6.0-22 

5.8-21

19

12-3. 25

HB

Range

4.3-19 

5.8-21

15

10. 6-20. 8

H/MD

Range

0. 94-1. 36 

1. 13-1. 58

1.21

. 96-1. 19

MD/HB

Range

1. 11-1. 44 

. 75-1. 33

1.26

1. 09-1. 20

Discussion. Considered ontogenically, this species 

usually increases proportionally more in height than 

width with increased size. This change is accompanied 

by a decrease in pleural angle through growth (figs. 8, 

9). There are so many exceptions to this generality, 

however, that some explanation is necessary. Such 

differences may be due to sexual dimorphism, as many 

recent relatives of Euspira show morphologic distinctions; the female has more inflated whorls and thus 

yields a lower spire and higher pleural angle.

Sculpture is normally lacking, but an occasional specimen may show fine spiral threads. Another peculiarity 

is the rare specimen showing somewhat irregular low 

ribs that run across the whorl oblique to the axis, but 

for the most part at right angles to the growth lines (pi. 

1, fig. 16). Such ribs usually do not carry on for more 

than one-half whorl. A similar feature has been noted 

on the holotype of Euspiral dakotensis (Henderson) 

(pi. 1, fig. 21).

Euspira obliquata is one of the most common gastropods in the marine Campanian to Paleocene rocks of the 

western interior and has had a most troubled taxonomic 

history. As interpreted here, three separately described 

species are involved: Natica obliquata Hall and Meek, 

N. concinna Hall and Meek, and N. moreauensis Meek 

and Hayden. Most references in faunal lists and taxonomic treatments refer to this species as Lunatia concinna. In 1876, Meek redescribed Natica concinna, 

assigning it to Lunatia,, but noted that Euspira might 

eventually replace Lunatia. The specimens he figured 

and described at this time, those that almost all subsequent authors have relied upon as typical of L. concinna, 

are those upon which N. moreauensis Meek and Hayden 

(1856) was based. Meek (1876, p. 314) 2 however, 

stated:

This shell varies somewhat in form ; some individuals being proportionally a little shorter, and having the body-volution more 

ventricose than others. For a long time, it was believed to be 

distinct from N. concinna and consequently the name N. 

moreauensis was proposed for it. Since seeing a good series of 

specimens, however, * * * I am led to believe that it is not 

specifically distinct from the type of N. concinna which is now 

believed to be a young individual.

Meek (1876, p. 315) after synonymizing N. moreauensis with N. concinna, then discusses N. obliquata.

Lunatia obliquata ( Natica obliquata, Hall and Meek) is also 

a very closely allied type, so much so, indeed, that I have sometimes suspected that both the original E. concinna and the shell 

here ranged under that name, should be regarded as belonging 

to that species. In one character, however, E. obliquata seems 

to present a rather marked and important difference: that is, 

in having a well-defined opercular groove along the columella, 

not seen in the original E. concinna.

The holotypes of both N. concinna and N. obliquata 

are preserved in the collections of the American Museum 

of Natural History. Both specimens represent immature forms (see measurements and pi. 1, figs. 12, 13, 

18,19).

All subsequent authors except Stanton in 1921 accepted Meek's figures of 1876 as typical of L. concinna. 

Stanton (1921) was evidently the first to reexamine all 

the primary type material. He concluded that the two 

species concinna and obliquata were synonymous and by 

virtue of page preference accepted obliquata. Concerning the confused status of the involved species he stated 

(Stanton, 1921, p. 35) : "Meek's final opinion was that 

L. moreauensis is a synonym of L. concinna, though he 

also called attention to the close relationship with L. 

obliquata, which seemed to differ chiefly in the presence 

of 'an opercular groove along the columella.' " Stanton 

then states that he has compared the type specimens. 

On page 36, he concludes, "My opinion is that the Fox 

Hills specimens which have been called L. moreauensis 

and L. concinna * * * should be referred to L. 

obliquata"

Stanton observed that in specimens he examined, most 

lacked an opercular groove but one had it. He could 

not separate them on other grounds. In addition, he 

thought, as did Whitfield and Hovey (1898, p. 429), 

that the specimen preserved as the type species of L. 

concinna was perhaps a recent shell because of the exceptional state of preservation. I cannot agree with the 

latter conclusion. The shell is well preserved and of a 

milky-gray porcelaneous look, but I have seen exactly 

this same type of shell preservation at many outcrops 

of the Fox Hills Sandstone in the Dakotas. I do, however, accept Stanton as the first revisor and accept his 

designation of obliquata as the preserved name, although the more common use of concinna offers room 

for argument.

Euspira dakotensis (Henderson) (= Natica occidentalis Meek, non Hall) has a lower pleural angle (see section on measurements), a proportionally higher spire 

and possesses spiral sculpture.

Euspira, rectilabrum (Conrad) from the Gulf Coastal 

Plain region is closely allied in form and occurs in
B28 DESCRIPTIVE STUDY 'OF A CLASSIC REFEiRENCE LOCALITY OF THE PIElRRE SHALE

correlative units. That species differs primarily from 

N. obliquata in its narrower umbilicus, thick callus on 

the parietal area, and in having a proportionately 

higher spire (fig. 9).

Natica subcrassa Meek and Hayden is a naticid commonly occurring with Euspira obliquata. However, 

it is easily distinguished by its lower spire, larger size, 

thicker shell, heavier parietal callus, slight constriction 

of the upper whorl, higher pleural angle, and more 

highly inclined outer lip. (fig. 8).

Euspira obliquata is one of the most common and 

widespread gastropods in the Upper Cretaceous of the 

western interior. It occurs at least as low as the 

Baculites perplexus zone in the Pierre Shale of Colorado and as high as the Fox Hills of the Dakotas. 

Stanton has reported it from the Paleocene Cannonball 

Member of the Fort Union Formation in North Dakota. 

Reference to the presence of this species in Turonian of 

Utah (Stanton, 1893) and the Coleraine Formation of 

Stauffer (in Stauffer and Thiel, 1933) (Cenomanian) 

in the Mesabi Range of Minnesota (Bergquist, 1944) 

is erroneous. The species is known to occur in equivalent units of the Pierre and Fox Hills from Colorado 

in the south to Canada in the north (Whiteaves, 1885, 

Dowling, 1917, and others). The specimen from 

Greenland assigned to this species by Ravn (1918) 

lacks the aperture and cannot be placed generically with 

confidence.

Euspira obliquata is well represented in the Red Bird 

section, but all specimens are small.

Types: Holotype, AMNH 9465; holotype of Natica concinna 

Hall and Meek, AMNH 9364; holotype Natica moreauensis 

Meek and Hayden, USNM 264; hypotypes, USNM 12250 (Whitfield, 1880, pi. 12, fig. 13), USNM 132708, 132709.

Occurrences: Wyoming: Pierre Shale, Red Bird section, 

USGS D-1917 (B. gregoryensis zone) ; USGS D-1939, D-1940 

(Didymoceras stevensoni zone) ; USGS D-1967 (Baculites 

eliasi zone) ; USGS D-1970, D-1978, D-1983 (Baculites baculus 

zone); USGS D-1985 (Baculites granais zone). Colorado: 

Pierre Shale (Baculites perplexus zone through B. clinolobatus 

zones), Milliken Sandstone Member of the Fox Hills Sandstone, 

Mesaverde (upper). Montana : Pierre Shale (Baculites baculus 

zone), Bearpaw Shale, Claggett Shale. North Dakota: Fox 

Hills Sandstone and Cannonball Member of Fort Union Formation (Paleocene). South Dakota: Pierre Shale (upper part) 

and Fox Hills Sandstone. Canada: Bearpaw Shale.

Superfamily TONNACEA

Family CYMATIIDAE 

Genus TRACHYTRITON Meek 1864

Type by original designation: Buccinum 1* mnculum 

Hall and Meek, 1856.

Diagnosis. Fusiform shells sculptured by strong ribbons and round-topped transverse ribs. Outer lip denticulate within; inner lip with well-margined evanescing columella and smooth parietal surface.

Discussion. The shape of the shell, the denticulations of the inner surface of the outer lip, and the broad 

well-defined inner lip callus are all features allying 

TracJiytriton mnculum (Hall and Meek) with the Cymatiidae. However, other typical features, such as 

parietal teeth or nodes, are lacking.

Other North American species assigned to this genus 

must all be questioned. Trachytriton^. holmdelense 

Whitfield, T. ? multivaricosum Whitfield, T. atlanticum 

Whitfield, all from the Upper Cretaceous of New 

Jersey, are based on internal molds of fusiform outline 

that not only lack the characters of Trachytriton but 

are unassignable to family.

Trachytriton^. sp. Stephenson (1952, p. 181) from the 

Woodbine Formation of Texas is based on an incomplete specimen with strong transverse sculpture, weak 

spiral threads, and thin inner lip callus. It may belong 

in the Fusidae.

Tritonium (Trachytriton} tejonensis Gabb (1869), 

from the Eocene, Tejon Formation of California, has 

been placed as a synonym under Olequahia hornii 

(Gabb) by Stewart (1927, p. 382).

We are thus left with only the type species as a North 

American representative.

Trachytriton vinculum (Hall and Meek) 

Plate 6, figures 10, 14-17

1856. Buccinuml vinculum Hall and Meek, Am. Acad. Arts Sci.

Mem., v. 5, p. 390, pi. 3, figs. 5a, b. 

1860. Fusus vinculum (Hall and Meek). Meek and Hayden,

Acad. Nat. Sci. Philadelphia, Proc., v. 12, p. 1-85. 

1864. Trachytriton mnculum (Hall and Meek). Meek, Smithsonian Misc. Oolln., v. 7, p. 22 and 37. 

1876. Trachytriton mnculum (Hall and Meek). Meek, U.S.

Geol. and Geog. Surv. Terr. (Hayden) Kept., v. 9, p. 304,

pi. 19, figs. 7a-d. 

1903. Pirene (Trachytriton) vinculum (Hall and Meek).

Cossmann, Essais de paleoconchologie compared, v. 5, p.

110, pi. 4, fig. 18. 

1941. Argobuccinum (Trachytriton) vinculum (Hall and Meek).

Wenz, Gastropoda, in Schindewolf, O. H., Handbuch

der Palaozoologie, v. 6, pt. 5, p. 1057, fig. 3021.

Type locality. Pierre Shale, "Great Bend of the 

Missouri River." (Baculites gregoryensis or B. scotti 

zones)

Diagnosis. Same as for genus.

Description. Medium-sized fusiform shells with 

spire a little less than one-half total shell height. Protoconch unknown. Pleural angle 35°-40°. Whorls 

rounded, suture impressed. Body with a well-rounded 

periphery tapering below to a rather broad pillar. 

Sculpture of collabral, rounded and broad transverse 

ribs that are strongest on the earlier whorls. Spiral 

sculpture dominated by spiral ribbons that are narrower 

than interspaces, but which override the transverse ribs; 

ribbons number 6-7 on penultimate whorl. On body,
UPPER CRETACEOUS GASTROPODS, RED BIRD, WYOMING B29

transverse sculpture weak; spiral ribbons narrower or 

cordlike on base with occasional fine threads in interspaces. Growth lines broadly opisthocyrt on whorls of 

spire; on body, growth lines strongly prosocline for first 

few millimeters below suture, arcuately and gently opisthocline over periphery and upper part of basal slope, 

and for the most part prosocline on pillar. Aperture 

lanceolate; outer lip denticulate within, thin at edge 

serrated by the termination of spiral ribbons; inner lip 

with a broad sharply margined callus. Parietal callus 

smooth surfaced and broad. Columellar lip smooth.

Measurements. Explanation of measurements and 

symbols used in the following table appears in the section "Measurements of specimens" (p. B9).

Specimen and locality

Hypotype: 

USNM 261 Pierre Shale, South Dakota. __ 

USNM 132985 Pierre Shale, South DakotaUSNM 132644 Pierre Shale, Red Bird,

USNM 132645 Pierre Shale, Red Bird,

H

35 

43 +

MD

15. 5 

24. 9

16.7

16.3

Discussion. Trachytriton mnculum is a rare species, 

and as known, is restricted to the Pierre Shale.

The specimens from the Red Bird Silty Member compare well with Meek's hypotypes figured on plate 6, figures 16 and 17, from the Pierre Shale of the Great Bend 

of the Missouri River. The specimen from USGS 

D-1926 (pi. 6, fig. 14) shows the impression of the teeth 

on the interior of the outer lip typical of TracJiytriton. 

The other specimen from USGS D-1904 (pi. 6, fig. 15) 

has somewhat stronger transverse ribs at a later stage 

of development, and the whorls appear to be slightly 

more rounded than on Meek's material.

One additional internal mold from locality USGS 

D-1900 (USNM 132646) probably belongs to this species. It shows strong denticulate varices occurring at 

about one-half whorl intervals on the last three whorls.

The only other superficially similar species in the 

Cretaceous faunas of the western interior is Fasciolaria 

buccinoides Meek and Hay den (pi. 6, figs. 5-9). It, 

however, possesses weaker transverse sculpture and 

thinner lip callus than Trachytriton vinculmn and also 

has two plications on the inner lip. Cossmann (1901, 

p. 51) assigned that species (F. buccinoides) to Mazsalina of the Fasciolariidae. It approaches that genus 

in several characters, but it has two columellar plications that are constant in strength and placement. More 

significantly, there are nodes and teeth on the parietal 

wall and denticulations on the inner surface of the outer 

lip (pi. 6, figs. 5,9) that were not noted by Meek. These 

features suggest placement of "Fasciolaria" buccinoides

in the Cymatiidae of the Tonnaca rather than in the 

Fasciolariidae.

Types: Holotype, unknown; hypotypes, USNM 261, 132644, 

132645, 132984, 132985, mentioned specimen 132646.

Occurrence: Wyoming: Pierre Shale, Bed Bird section, USGS 

D-1900, D-1904 (Baculltes gregoryensls zone), USGS D-1926 

(Baculites scotti zone), USGS D-1938 (Didymoceras nebrascensis zone). Colorado: Pierre Shale, Front Range (Baculites 

gregoryensis zone). South Dakota: Pierre Shale.

Order NEOGASTROPODA

Suborder STENOGLOSSA

Superfamily BTTCCINACEA

Family FASCIOLARIIDAE

Subfamily FTTSIMlffAE 

Genus SERRIFTTSTTS Meek, 1876

Type by original designation: Fusus dakotensis Meek 

and Hayden, 1856.

Diagnosis. "Shell short-fusiform; body volution 

large, and bi- or tricarinate, with carinae more or less 

nodose; spire and canal moderate, the latter bent and 

more or less twisted; outer lip broadly but slightly sinuous in outline, between the upper carina and the suture" 

(Meek, 1876, p. 373).

Discussion. Meek proposed Serrifusus as a monotypic subgenus of Fusus. Most subsequent authors have 

considered it close to Fusus, but Cossmann (1901, p. 8) 

thought it most closely approached Buccinofusus 

Conrad.

Five North American Cretaceous species have been 

assigned to this genus, but most probably belong in other 

genera. These species are:

Serrifusus dakotensis var. vancouverensis Whiteaves 

1879, from the Upper Cretaceous Middle Shale, Division 

D, on Hormby Island (Maestrichtian?) of Vancouver 

Island area, Canada. This species is close to the type 

species.

/Serrifusus \ crosswickensis Whitfield, 1892, from the 

Navesink Formation of New Jersey, an indeterminate 

internal mold possibly belonging to Pterocerella.

Serrifusus (Lirofusus) nodocarinatus Whitfield, 1892, 

from the Navesink Formation of New Jersey. This 

species is based on a poorly preserved indeterminate 

specimen.

Serrifusus tennesseensis Wade, 1926, from the Ripley 

Formation of Tennessee, has been placed in Hercorhyncus by Sohl (1964, p. 222).

Serrifusus joaquinensis Anderson, 1958, from the 

Campanian, Panoche Formation of California, appears 

to be correctly assigned.

I know of no correctly assigned species outside North 

America. The genus has a western distribution, and 

as presently known, is restricted to the Campanian and 

Maestrichtian stages of the Upper Cretaceous.
B30 DESCRIPTIVE STUDY OF A CLASSIC REFERENCE LOCALITY OF THE PIERRE SHALE

Serrifusus dakotensis (Meek and Hayden) ?

Plate 6, figure 12, 13, 18-21

1856. Fusus Dakotensis Meek and Hayden, Acad. Nat. Sci. Philadelphia Proc., v. 8, p. 65. 

1860. Fusus (Neptunea) Dakotensis Meek and Hayden, Acad.

Nat. Sci. Philadelphia Proc., v. 12, p. 421. 

1964. Tudicla? Dakotensis (Meek and Hayden). Meek, Smithsonian Misc. C'olln., v. 7, p. 23. 

1876. Fusus? (Serrifusus) Dakotensis Meek and Hayden, Meek,

U.S. Geol. and Geog. Survey Terr. (Hayden) Kept., v. 9,

p. 374, pi. 31, fig. 11; pi. 32, figs. 6a, c. 

1876. Fusus? (Serrifusus) goniophorus Meek, U.S. Geol. and

Geog. Survey Terr. (Hayden) Rept, v. 9, p. 375, pi. 32,

fig. 7a (7b?) cited under Fusus (Serrifusus) Dakotensis

var. 

1901. Serrifusus dakotensis (Meek and Hayden). Cossmann,

Essais de paleoeonchologie comparee, v. 4, p. 8, pi. 7, fig.

7. 

1941. Fusinus (Serrifusus) dakotensis (Meek and Hayden).

Wenz, Gastropoda, in Schindewolf, O. H., Handbuch der

Palaozoologie, v. 6, pt. 5, p. 1262, fig. 3594. 

1945. Fusus dakotensis Meek and Hayden. Morgan and Petsch,

South Dakota Geol. Survey Rept. Inv. 49, pi. 5, fig. 4;

pi. 6, fig. 4.

Type locality. "Moreau River, Dakota" (Meek, 1876, 

p. 377). The holotype is from the Fox Hills Sandstone 

of South Dakota.

Diagnosis. Strongly bicarinate whorls covered by 

finer spiral lirations.

Measurements. Explanation of measurements and 

symbols used in the following table appears in the section "Measurements of specimens" (p. B9).

Specimen and locality

Holotype: USNM 256 Fox Hills .Sandstone, South Dakota

Paratype: USNM 132971 Fox Hills SandHypotype: USNM 132643 Pierre Shale (B.

H

71. 5 +

35. 3

59. 3 +

MD

47. 0

22. 0+

44. 0

Discussions. The specimen from the Red Bird section (pi. 6, fig. 20) is much worn. The external surface 

has evidently been worn or dissolved to such an extent 

that there is no evidence of spiral sculp'ture except for 

the carinations. On the other hand, the specimen does 

compare closely with Meek's holotype (pi. 6, fig. 18) 

in size, outline, and possession of a bicarinate body 

having strong nodes on the upper carina.

My main reservation in assigning the specimen from 

locality USGS D-1982 to Meek's species Serrifusus 

dakotensis is that there appears to be an undescribed 

species of Serrifusus in the "Fox Hills Formation" of 

Wyoming. This specimen (pi. 6, fig. 13) can presently 

only be located geographically as coming from Niobrara County, Wyo., and in terms of stratigraphic

position is probably closer to that of the Red Bird section than is that of Meek's type material which comes 

from the Moreau River in the type Fox Hills area. The 

Wyoming specimen (USNM 32150) is incomplete, but 

has a bicarinate whorl that is noded at the shoulder and 

thus seems to be a true /Serrifusus. Compared with the 

type species, however, it has decidedly suppressed spiral 

sculpture. This raises the question, then, that perhaps 

the Red Bird specimen is not so worn but that, in spite 

of its closeness in shape to the type specimens, it belongs 

to another undescribed species with subdued spiral 

sculpture.

Types: Holotype, USNM 256; Paratype, USNM 132971; 

figured specimen, USNM 132643.

Occurrences: Wyoming: Pierre Shale, Red Bird section, USGS 

D-1982 (Baculites baculus zone), USGS D-1985 (Baculites 

grandis zone), and questionably from the Fox Hills Sandstone. 

South Dakota: Fox Hills Sandstone. North Dakota : Fox Hills 

Sandstone. Colorado : Fox Hills Sandstone.

Genus ANOMALOFUSUS Wade, 1916

Type by original designation: Anomalofusus substriatus Wade.

Diagnosis. High spired fusiform shells, protoconch 

naticoid proportionally large. Whorls rounded to 

slightly shouldered above. Sculpture cancellate developing to dominantly spiral ribbons with secondary 

threads between, Columella slightly twisted lacking 

plications; outer lip dentate within. Varices common.

Discussion. Anomalofusus is a moderately common 

genus in the Campanian-Maestrichtian rocks of the 

Gulf Coastal Plain. It has never previously been noted 

in the Cretaceous of the western interior, and the assignment of the specimen described below is very tenuous.

Anomalofusus? sp. 

Plate 7, figure 20

Discussion. One incomplete specimen consisting of 

an internal and external mold is present in the collections from USGS D-1948 (Exiteloceras jenneyi zone) 

that may belong in Anomalofusus. The specimen is 21 

mm high and has a maximum diameter of about 8.5 

mm. It has four well-rounded whorls with a slight, 

tendency for constriction on the last whorl. Sculptureconsists of about eight raised strong spiral ribbons that 

override round-topped opisthcyrt transverse ribs on the 

whorls of the spire. The ribs are more widely spaced 

than the ribbons. On the body whorl, spiral cords are 

wider spaced and stronger above, becoming narrower, 

closer spaced, and weaker on the medial and anterior 

parts of the whorl. Transverse ribs die out just below 

the periphery of the whorl.

In many respects, such as lack of columellar plications, shape, and size, this specimen approaches
UPPER CRETACEOUS GASTROPODS, RED BIRD, WYOMING B31

Anomalofusus, but lacking material that preserves a 

protoconch, its assignment is very tenuous. It differs 

from typical Anomalofusus in that it has a lesser tendency for development of a whorl shoulder, the transverse ribs remain strong to a later growth stage, and the 

spiral ribbon interspaces lack secondary threads. One 

might suggest that the specimen represents the early developmental stages of a Graphidula. However, the 

whorls of the Red Bird specimen are more rounded, and 

as can be observed on the internal mold, there are no 

columellar plications.

Better preserved material must be found before this 

species can be described and placed with confidence.

Types: Figured specimen, USNM 132927. 

Occurrence: Wyoming: Pierre Shale, Red Bird section, USGS 

D-1948 (Eseiteloceras jenneyi zone).

Subfamily FASCIOLARIESTAE 

Genus GRAPHIDULA Stephenson, 1941

Type by original designation: Graphidula terebreformis Stephenson.

Diagnosis. Medium-sized slender elongate fusiform 

shells. Spire usually longer than aperture. Sculpture 

ornate with transverse elements commonly becoming 

subdued on later whorls. Aperture lanceolate, posteriorly angulate, siphonal canal elongate and straight. 

Columella straight, at maturity bearing one plait, but 

plait not visible at aperture.

Discussion. Piestochilus Meek and Graphidula Stephenson appear to be closely related genera. Sohl 

(1964, p. 211) has discussed their relationships and reassigned the Cretaceous species from North America. 

In general, Piestochilus, as exemplified by the type species P. scarboroughi (Meek and Hayden), is lower 

spired than Graphidula, having an apical angle that approaches 45° as against 20°-25° in Graphidula. In 

spite of the differences in outline the two genera are 

closely similar in apertural features.

Graphidula is a common element in the CampanianMaestrichtian faunas of the Gulf and Atlantic Coastal 

Plains from New Jersey to Texas. The range of the 

genus seems to be similar in the western interior. The 

earliest Graphidula I know comes from the Gammon 

Ferruginous Member near the base of the Pierre Shale 

in the Black Hills area and ranges through the Fox 

Hills Sandstone. Graphidula culbertsoni discussed below is one of the more widespread and abundant of the 

gastropods, especially in the northern part of the western interior.

Graphidula culbertsoni (Meek and Hayden) 

Plate 7, figures 21-24, 29-31

1856. Fusus culbertsoni Meek and Hayden, Acad. Nat. Sci. Philadelphia Proc., v. 8, p. 66.

1857. Fusus haydeni Evans and Shumard, St. Louis Acad. Sci. 

Trans., v. 1, p. 41.

1876. Fasciolaria (Piestochilus) culbertsoni (Meek and Hayden). Meek, U.S. Geol. and Geog. Survey Terr. 

(Hayden) Kept., v. 9, p. 360, pi. 32, figs, la-f, text fig. 44.

1879. Fasciolaria (Piestochilus) culbertsoni (Meek and Hayden). White, U.S. Geol. and Geog. Survey Terr. 

(Hayden), llth Ann. Kept., p. 185.

1880. Fasciolaria (Piestochilus) culbertsoni (Meek and Hayden). Whitfield, U.S. Geol. and Geog. Survey, Rocky 

Mtn. Region (Powell), p. 423, pi. 12, fig. 11.

1901. Cryptorhytis (Piestochilus) culbertsoni (Meek and Hayden). Cossmann, Essais de paleoconchologie compared, 

v. 4, p. 59, text fig. 18.

1962. Fasciolaria (Piestochilus) culbertsoni (Meek and Hayden. Kellum, Michigan Acad. Sci., v. 47, p. 66, pi. 2, 

figs. 2, 3.

1964. Graphidula culbertsoni (Meek and Hayden). Sohl, U.S. 

Geol. Survey Prof. Paper 331-B, p. 211.

Type locality. "Moreau Eiver; from the Fox Hills 

Group" (Meek, 1876, p. 362).

Diagnosis. Shell large for genus, whorls round sided, 

transverse ribs restricted to earlier growth stages.

Measurements. No specimens are complete, but the 

largest specimen noted must have attained a length of 

at least 90 mm, a maximum width of 23 mm, and a body 

whorl about 50 mm in height.

Discussion. One specimen, missing both extremities 

but preserving other features diagnostic of Graphidula 

culbertsoni, has been recovered from the Red Bird section (USGSD-1985).

This species is one of the more abundant highly variable species in the Upper Cretaceous of the western interior. The most consistent feature is the spiral ornament consisting on the early whorls of thin spiral ribbons that are somewhat wider than their interspaces; on 

later whorls these ribbons become wider spaced and may 

also become more subdued. The holotype (pi. 7, fig. 

22) from the Fox Hills Sandstone is decidedly atypical. 

It possesses strong transverse ribs at a much later stage 

than most specimens. More typically, transverse ribs 

are restricted to only the first few whorls or may not be 

present at all. The holotype also is atypical in its 

small size, but its relationship to large individuals, such 

as that figure on plate 7, figure 30, is obvious when compared with Meek's (1876, pi. 32, fig. le) paratype, herein 

(pi. 7, fig. 24), which combines the coarse transverse 

ribs of the early whorls with a body whorl that retains 

only spiral sculpture.

The plaits of the columellar surface also vary. Near 

the aperture all specimens have only one weak plication ; however, a range from none to three or four plaits 

may occur on the very earliest whorls. These variations all occur within suites of specimens from the same 

locality.
B32 DESCRIPTIVE STUDY OF A CLASSIC REFERENCE LOCALITY OF THE PIERRE SHALE

Although all specimens show a similar ontogeny with 

the height of the whorl increasing proportionally more 

rapidly in later growth stages, the range of variation in 

whorl height is moderately high.

This is one of the more abundant and widely distributed species of gastropods in the northern part of the 

western interior, ranging from the Baculites baculus 

zone of the Pierre Shale through the Fox Hills Sandstone in South Dakota, North Dakota, Wyoming, Montana, and Colorado.

Fasciolaria (Piestochilus} alleni White (1880) from 

the Yellowstone Eiver of Montana (pi. 7, figs. 33, 34) 

is more slender with a lower pleural angle and lacks 

transverse sculpture, but is similar in other respects and 

probably belongs to the same lineage. Fasciolaria 

(Piestochilus} galpiniana (Meek and Hay den) from 

the Fox Hills Sandstone of South Dakota possesses 

sculpture similar to Graphidula, but the anterior canal 

is short and curved and probably the species belongs in 

an entirely different genus. The gulf coast Cretaceous 

species of Graphidula (Sohl, 1964) all possess stronger 

transverse sculpture at a later stage than G. culbertsoni, 

Graphidula pergracilis (Wade) being the most closely 

similar species. Graphidula pergacilis, however, not 

only retains transverse sculpture to a later stage, but 

has wider spaced spiral sculpture and whorls that are 

less constricted posteriorly. Several undescribed species of Graphidula are present in beds of equivalent age 

in Montana and South Dakota. In the Pierre Shale at 

Glendive, Mont. (USGS 12 and USGS 3896), a related 

form occurs that differs in its straighter growth line and 

in having secondary spiral cords on the whorl sides. 

In the Fox Hills Sandstone of South Dakota (USGS 

27491, 27485, 27484), another undescribed species occurs 

that is characterized by its lack of transverse sculpture, 

its thin spiral thread sculpture, and by its well-rounded 

whorls that are strongly constricted subsuturally.

Types: Holotype, USNM 258; paratype, USNM 132973; hypotypes, USNM 132647-132651.

Occurrences: Wyoming: Pierre Shale, Red Bird section, USGS 

D-1985 (Baculites grandis zone), Fox Hills Sandstone. North 

Dakota: Fox Hills Sandstone. Montana: Pierre Shales (B. 

booulus zone). Colorado: Pierre Shale, Front Range (Baculites 

clinolo'batus zone), Fox Hills Sandstone.

Graphidula cf. Galleni (White) 

Plate 7, figures 25-28, 32

1880. Fasciolaria (Piestochilus) alleni White, U.S. Geol. and 

Geog. Survey Terr. (Hayden), 12th Ann. Rept., 1878, 

pt. 1, p. 34, 35, pi. 12, fig. la.

Type locality. "Cretaceous strata, valley of Yellowstone Eiver, Montana" (White, 1880, p. 35). Probably 

Campanian in age, but exact stratigraphic level 

uncertain.

Discussion. In 1880, White described and figured a 

fusiform snail from an undefined stratigraphic position 

in Montana. The holotype (USNM 8046) is accompanied in the type collections of the U.S. National 

Museum by a second specimen. The holotype consists 

of six whorls with corroded shell material irregularly 

adhering. Surface sculpture can be seen only over a 

part of the body whorl (pi. 7, fig. 34). White's original illustration is a reconstruction. The second specimen is a smaller shell that again retains only patches of 

shell and is partially embedded in a fossiliferous concretionary matrix that contains Euspira obliquata 

(Hall and Meek), Gylichna sp., and indeterminable 

fragments and molds of other mollusks. The assemblage has the aspect of a Pierre Shale fauna.

Compared to Graphidula culbertsoni which they approach in form, the shells are more slender with a 

pleural angle of 18°-19° as compared to 22°-27° for G. 

culbertsoni. In addition, the whorls of G. alleni appear 

to be proportionally more elongate at the same stage of 

growth and flatter sided. Neither specimen bears any 

trace of transverse sculpture, except for the strong 

sinuous growth lines typical of the genus.

Several poorly preserved specimens (pi. 7, figs. 26- 

28) from the Didymoceras stevensoni zone of the lower 

unnamed shale member of the Pierre Shale in the Red 

Bird section of Wyoming closely approach Graphidula 

alleni. All lack transverse sculpture even on the earlier 

whorls, have flat-sided proportionally elongate whorls 

and irregular spiral cords, and possess the single strong 

columellar plication of Graphidula. A similar form 

occurs in the Didymoceras nebrascense zone of the 

Tepee-Butte limestone (of local usage) of the Pierre 

Shale of the Front Eange of Colorado (pi. 7, fig. 32). 

Poorly preserved specimens probably belonging to this 

same group range from the Baculites scotti zone 

through the Ewiteloceras jenneyi zone in the Front 

Range, but their condition is such that identification is 

tenuous at best.

Types: Figured specimens, USNM 132673, 132674, 132707, 

132974.

Occurrences: Wyoming: Pierre Shale, Red Bird section, D1939; D-1940 (Didymoceras stevensoni zone). Colorado: Pierre 

Shale, Front Range (Didymoceras stevensoni zone and possibly 

Baculites scotti through Exiteloceras jenneyi zones. Montana : 

Position uncertain.

Genus CRYPTORHYTIS, 1876

Type by original designation: Rostellaria fusiformis 

Hall and Meek, 1854 (non R. fusiformis Pictet and 

Roux, or R. fusiformis Whitfield, 1892). = Gladius1 

cheyennensis Meek and Hayden, 1860.

Discussion. Confusion as to the relationship of this 

genus has arisen primarily because of the poor state of 

preservation of the type material. The holotype of the
UPPER CRETACEOUS GASTROPODS, RED BIRD, WYOMING B33

type species is an internal mold retaining only parts of 

the shell. Sohl (1964, p. 231) has discussed the history 

of assignment of Cryptorhytis to the Fasciolariidae and 

Vasidae by various authors. He accepted Meek's statement that the columellar plait lies high on the columella 

and suggested that the genus lies close to Ornopsis. Reexamination of the type material, however, shows that 

the plication lies somewhat below the middle of the 

apertural length in a position similar to that in Bellifusus. In possession of a columellar constriction and 

sinuate ribs the two are further similar. This suggests 

the possibility of synonymizing Bellifusus with Cryptorhytis, but until better preserved specimens of C. 

cheyennensis (Meek and Hay den) are available, the two 

genera should be kept separate.

Cryptorhytis cheyennensis (Meek and Hayden) 

Plate 7, figures 15-19

1854. Rostellaria fusiformis Hall and Meek, Am. Acad. Arts and

Sci. Mem. 5, p. 393, pi. 3, fig. 10 [non Pictet and Roux,

1842]. 

1860. Gladius"! Cheyennensis Meek and Hayden, Aead. Nat. Sci.

Philadelphia Proc., v. 12, p. 422. 

1864. Gladius Cheyennensis Meek and Hayden, Meek, Smithsonian Misc. Coll n., v. 7, p. 20. 

1876. Fasciolariat (Cryptorhytis) Cheyennensis (Meek and

Hayden). Meek, U.S. Geol. and Geog. Survey Terr.

(Hayden) Kept., v. 9, p. 365, pi. 19, fig. 13. 

1880. Fasciolaria (Cryptorhytis) fusiformis (Hall and Meek).

Whitfield, U.S. Geog. & Geol. Survey Rocky Mtn. Region

(Powell), p. 421, pi. 12, fig. 12. 

1901. Cryptorhytis cheyennensis ( Meek and Hayden). Cossmann Essais de paleoconchologie compared, v. 4, p. 56, 57.

(Also spelled cheyemensis.)

1944. Piestochilus (Cryptorhytis) fusiformis (Meek and Hayden), (error for Hall and Meek). Wenz, Gastropoda, in

Schindewolf, O. H., Handbuch der Palaozoologie, v. 6, pi.

6, p. 1308, fig. 3728.

Type locality. "Sage Creek. Upper clay or upper 

part of division No. 4 of section". (Hall and Meek, 

1854, p. 393.) The original specimen was from the 

Baculites compressus zone.

Dissension. Three poorly preserved specimens from 

the Pierre Shale of the Red Bird section, Wyoming, are 

here assigned to Cryptorhytis cheyennensis. They display the typical whorl shape, posterior whorl constriction, and strong transverse ribs of that species. The 

type material is from the Baculites compressus zone of 

Sage Creek. Meek's figured specimen of 1876 (pi. 19, 

figs. 3a,'b) from the Pierre Shale of the South Fork of 

the Cheyenne River, however, cannot be as precisely 

located, except that it probably came from some level between the Didymoceras stevensoni and Baculites compressus zones. The Red Bird specimens come from the 

Exiteloceras jenneyi and Baculites reesidei zones, 

respectively.

Type: Holotype, AMNH 5370; figured specimens, USNM 289, 

USNM 132921, 132922.

Occurrences: Wyoming: Pierre Shale, Red Bird section, 

USGS D-1945, (Exiteloceras jennyi zone) and USGS D-1952 

(Baculites reesidei zone). South Dakota: Pierre Shale (Baculites compressus zone). Colorado : Pierre Shale (Front Range) 

(Exiteloceras jennyi, Baculites compressus, Baculites reesidei, 

and Baculites jenseni zones).

Indeterminate fusiform gastropods

Two internal molds from the Pierre Shale at USGS 

D-1925 and USGS D-1924 represent, respectively, an 

unknown high slender fusiform snail and a lower spired 

neogastropod, possibly akin to Cryptorhytis. Both are 

too poorly preserved to warrant figuring.

Subclass ETTTHYNETTKA

Order CEPHALASPIDEA

Superfamily ACTEONACEA

Family ACTEONIDAE 

Genus NONACTEONINA Stephenson, 1941 

Type by original designation: Nonacteonina graphoides Stephenson, 1941.

Discussion. Stephenson erected this genus for many 

of the Cretaceous species previously assigned to 

Acteonma, d'Orbigny. It differs most strikingly from 

Acteon Montfort in having a smooth columella.

Acteon (Solidulal) attenuatus Meek and Hayden 

(pi. 8, fig. 2) is from the upper part of the Pierre Shale 

(Baculites ~baculus zone) on the "Yellowstone River, 

one hundred and fifty miles from its mouth" near Glendive, Mont. It appears to lack any trace of columellar 

plications, and has the slender elongates whorls and 

punctate spiral sculpture similar to Nonacteonina.

Nonacteonina attenuata (Meek and Hayden) ? 

Plate 8, figures 1, 2

1858. Actaeon (Solidula"!) attenuatus Meek and Hayden, Acad.

Nat. Sci. Philadelphia Proc., v. 10, p. 54. 

1860. Solidula attenuata Meek and Hayden, Acad. Nat. Sci.

Philadelphia Proc., v. 12, p. 185. 

1876. Actaeon attenuatus Meek and Hayden. Meek, Rept. U.S.

Geol. Survey Terr. (Hayden) Rept., v. 9, p. 281, pi. 19,

fig. 17a, b. 

1917. Actaeon attenuatus Meek and Hayden. Dowling, Canada

Geol. Survey Mem. 93, p. 30, pi. 28, fig. 9 (figure copied

from Meek, 1876). 

1934. Aoteonina attenuatus (Meek and Hayden). Warren,

Royal Soc. Canada, Trans., 3d ser., v. 28, p. 93 (occurrence questionable).

Type locality. From beds of the upper part of the 

Pierre Shale (Baculites baculus zone) on the "Yellowstone River, one hundred and fifty miles from its 

mouth."

Discussion. The shell here discussed is closely allied 

to Nonacteonina attenuata Meek and Hayden, but is too

223-112 O 66
B34 DESCRIPTIVE STUDY 'OF A CLASSIC REFERENCE LOCALITY OF THE PIEIRRE SHAiLE

poorly preserved for confident placement. The shell of 

the Red Bird specimen is longer than the holotype from 

the Pierre Shale of Montana, but the proportions are 

similar. Although the body whorl of the Wyoming 

specimen (pi. 8, fig. 1) is preserved only as an internal 

mold, the shell material adhering to the spire shows the 

punctate spiral sculpture typical of the species.

Warren (1934, p. 93) stated that he had seen specimens from the Bearpaw Shale of Canada that reached 

3 cm in length. Neither of Pierre specimens figured 

here approaches such a size, but there are specimens of 

a Nonacteonina in the collections of the U.S. Geological 

Survey from the Bearpaw Shale of Montana that attain such a size. These specimens, however, appear to 

belong to an undescribed species characterized by a 

higher pleural angle and by spiral grooves that are 

crossed by very low transverse lines. The specimens 

from the Bearpaw Shale of Canada mentioned by Warren may belong to this same species.

Types: Holotype, USNM 285; figured specimen, USNM 132676.

Occurrences: Wyoming: Pierre Shale, Red Bird section, 

D-1940 (Didymoceras stevensoni zone). Montana: Pierre Shale 

(Baculites baculus zone).

Family Ringieulidae 

Genus Oligoptycha Meek, 1876

Type by original designation: Actaeon concmnus 

Hall and Meek, 1854.

Diagnosis. Globose shell, spire depressed. Sculpture of incised spirals consisting of a series of chainlike 

links. Outer lip thickened to a rounded rim at mature 

stage, interiorly smooth to denticulate. Columella has 

a strong anterior fold and bears from zero to two weaker 

parietal folds.

Discussion. The distribution, relationships, and developmental history of the genus has been discussed by 

Sohl (1964, p. 295). Oligoptycha is restricted to the 

Upper Cretaceous of North America.

Oligoptycha concinna (Hall and Meek) 

Plate 8, figures 3-6

1854. Acteon concinnus Hall and Meek, Am. Acad. Arts and Sci.

Mem., v. 5, p. 390, pi. 3, fig. 4. 

1856. Avellana subglobosa (Meek and Hall). Meek and Hayden,

Acad. Nat. Sci. Philadelphia Proc., v. 8, p. 64. 

1860. Cinulia concinna (Hall and Meek). Meek and Hayden,

Acad. Nat. Sci. Philadelphia Proc., v. 12, p. 424. 

1876. Cinulia (Oligoptycha) concinna (Hall and Meek). Meek,

U.S. Geol. Survey Terr., (Hayden) Rept., v. 9, p. 284,

pi. 31, figs. 6a, b, c. 

1895. Cinulia (Oligoptycha) concinnus (Hall and Meek). Cossmann, Essais de paleoconchologie comparee, v. 1, p. 121,

pi. 7, fig. 15.

1941. Oligoptycha concinna (Hall and Meek). Stephenson, 

Texas Univ. Bull. 4101, p. 390.

1957. Oligoptycha concinna (Hall and Meek). Popenoe, California Univ. Pubs. Geol. Sci., v. 30, no. 6, p. 431, pi. 50, 

figs. 3, 4.

1959. Cinulia (Oligoptycha) concinna (Hall and Meek). Zilch, 

Gastropoda, in Schindewolf, O. H, Handbuch der 

Palaozoologie, v. 6, pt. 2, fig. 61.

1964. Oligoptycha concinna (Hall and Meek). Sohl, U.S. Geol. 

Survey Prof. Paper 331-B, p. 295.

Type locality. The type specimens came from the 

upper part of the Pierre Shale on "Sage Creek" South 

Dakota (Baculites compressus zone).

Diagnosis. Oligoptycha having a single strong 

inclined fold low on the inner lip and a nondenticulate 

inner surface of the outer lip.

Description. Small globular shells with a low spire. 

Suture incised. Protoconch unknown. Sculpture dominated by spiral incised ribbons that are constricted to 

series of chainlike links where crossed by growth lines. 

Spiral grooves closest spaced over medial part of whorl. 

Aperture narrows posteriorly, broadens anteriorly. 

Outer lip well rounded, thickened by a rounded callus 

ridge, inner surface nondenticulate. Inner lip having 

a thick well-margined callus that extends over parietal 

surface and onto body a short distance above, but covers 

whorl base below and is continuous with callus ridge of 

outer lip. Columellar lip bears one strong thick plait 

that is inclined anteriorly into aperture.

Discussion. The small internal mold figured (pi. 8, 

fig. 6) from the Red Bird section appears to conform 

closely to the characters of Oligoptycha concinna (Hall 

and Meek). This species was originally described from 

specimens from the Pierre Shale on Sage Creek in South 

Dakota. Meek (1876, p. 284) based his expanded descriptions and discussion primarily on specimens from 

the Fox Hills Sandstone of the type area. The specimen (USNM 129866) from the Fox Hills Sandstone 

near Wakpala, S. Dak., figured on plate 8, figure 4, is 

larger in size than the holotype (pi. 8, fig. 3) or the 

specimens illustrated by Meek in 1876, but displays the 

character of the species well.

The holotype (pi. 8, figs. 3, 4) is a shell representing 

an early mature growth stage with inner lip callus just 

beginning to develop and the outer lip has not yet 

thickened.

Types: Holotype, AMNH 9491; hypotypes, USNM 291, 129866, 

132662.

Occurrences: Wyoming : Pierre Shale, Red Bird section, USGS 

D-1978, D-1983 (Baculites baculus zone). South Dakota: 

Pierre Shale and Fox Hills Sandstone. Montana: Bearpaw 

Shale. Colorado: Pierre Shale (Baculites reesidei and B. 

jenseni zones). Canada: Bearpaw Shale.
UPPER CRETACEOUS GASTROPODS, RED BIRD, WYOMING B35

Superfamily PHILINACEA

Family SCAPHANDRIDAE

Genus ELLIPSOSCAPHA Stephenson, 1941

Type by original designation: Cylichna, striatella 

Shumard, 1861.

Diagnosis. Subelliptical, involute, tightly coiled 

shells with a moderately small apical pit. Sculpture of 

punctate spiral grooves. Aperture narrow and curving 

over upper surface and broadening below to a rounded 

anterior margin. Inner lip callused over columellar 

area and bears a low weak fold.

Discussion. Stephenson (1941, p. 391) proposed this 

genus to include a group of species from the Coastal 

Plains and the western interior. Among these was Ellipsoscapha occidentalis (Meek and Hayden) from the 

Pierre Shale that is described below.

Scaphander Montf ort is similar to Ellipsoscapha, but 

has an imperforate apex and is umbilicate. Bulla Linnaeus is grossly like Ellipsoscapha, but lacks spiral 

sculpture on the middle of the whorl and has callus 

distributed over the parietal as well as the columellar 

surfaces. Haminea is more ovate in outline and has a 

broader apical perforation.

Ellipsoscapha occidentalis (Meek and Hayden) 

Plate 7, figures 7, 9-14

1856. Bulla occidentalis Meek and Hayden, Acad. Nat. Sci. Philadelphia Proc., v. 8, p. 69.

1861. Bulla nelrascensis Meek and Hayden, Acad. Nat. Sci. 

Philadelphia Proc., v. 13, p. 427.

1876. Haminea occidentalis (Meek and Hayden). Meek, U.S. 

Geol. Survey Terr. (Hayden) Kept, v. 9, p. 271, pi. 18, 

figs, lla, b, 12a, b.

1885. Haminea occidentalis (Meek and Hayden). Whiteaves, 

Canada Geol. Survey, Oontr. Canadian Paleontology, v. 

1, pt. 1, p. 45.

1895. Romania occidentalis (Meek and Hayden). Cossmann, 

Essais de Paleoconchologie comparee, v. 1, p. 99.

1917. Haminea occidentalis (Meek and Hayden). Dowling, 

Canada Geol. Survey Mem. 93, p. 30, pi. 28, figs. 7, 7a, 7b.

1941. Ellipsoscapha occidentalis (Meek and Hayden). Stephenson, Texas Univ. Bull. 4101, p.392.

Type locality. The type specimen came from the 

upper beds of the Pierre Shale on the "Yellowstone 

River, 150 miles above its mouth" near Glendive, Mont. 

(Baculites baculus zone).

Description. Medium-sized elliptical involute shells. 

Protoconch submerged, not visible. Whorls have wellrounded sides, shell broadest medially and posteriorly 

rounding down into a narrow moderately deep apical 

pit. Sculpture of narrow, variably spaced, incised 

grooves; grooves closer spaced on upper rounded surface 

of whorl, but wide spaced on wall of umbilical pit. 

Growth lines very gently prosocline over whorl sides. 

Aperture narrow, curving posteriorly, terminating in

rounded margin at apical pit; aperture broadens rapidly 

below midwhorl and well rounded anteriorly; columellar 

lip callused and relatively straight.

Measurements. Explanation of measurements and 

symbols used in the following table appears in the section "Measurements of specimens" (p. B9). All specimens are from the type locality.

Specimen

Syntype: USNM 278_. __________

Do.__-_____. _______________

Lectotype: USNM 132652________

Syntype: USNM 132975_ ________

H

12

12.2

11.6

11.4

MD

7.8

8.7

7.9

8.0

Discussion. Sever, specimens are in the type lot 

USNM 278) used by Meek in defining this species. I am 

unable to identify confidently the three specimens he 

figured (Meek, 1876, pi. 18). Schuchert and others 

(1905, p. 108) in their catalogue of type specimens in 

the U.S. National Museum cite a holotype and paratypes, but no specimen was segregated as holotype or 

marked in any special manner. One of the seven specimens retains most of its shell material (pi. 7, figs. 7,11), 

and I hereby designate it as lectotype (USNM 132652).

The specimens from the Red Bird section (pi. 7, figs. 

10, 12-14) here included in Ellipsoscapha occidentalis 

are internal molds, and most are smaller in size than the 

specimens from the type lot. However, they agree in 

body proportions and in the reflection of the ornament 

on the internal molds.

Compared to the other species of Ellipsoscapha from 

the Upper Cretaceous of the western interior E. occidentalis is smaller in size, less slender or cylindrical, 

apically blunter, and has a proportionally shorter columella than E. subcylindrica (Meek and Hayden) from 

the Pierre Shale at the mouth of the Milk River, Montana. Ellipsoscapha ? minor (Meek and Hayden), from 

the Fox Hills Formation, is more globular in outline, 

posteriorly more attenuated, and has a more highly 

inclined columellar lip.

Types: Leototype, USNM 132652, syntypes, USNM 278,132975; 

hypotypes, USNM 132653,132654,132671.

Occurrences: Wyoming: Pierre Shale, Red Bird section D1983 (Baculites ^aculus zone), D-1985 (Baculites grandis zone). 

Montana: Pierce Shale (Baculites baculus zone), Bearpaw 

Shale. Canada : Bearpaw Shale.

Superfamily BTTLLACEA

Family BTTLLIDAE 

Genus BTTLLOPSIS Conrad, 1858

Type by monotypy, Bullopsis cretacea Conrad.

Diagnosis. Apically truncate bulloid shells with an 

open apical depression. Sculpture of incised spiral 

grooves. Columella with two strong oblique plications.
B36 DESCRIPTIVE STUDY OF A CLASSIC REFERENCE LOCALITY OF THE PIEIRRE SHAiLE

Discussion. The familial affinities of Bullopsis have 

been discussed by Sohl (1964, p. 306).

This is the first report of this genus outside the Upper 

Cretaceous of the Mississippi embayment region of the 

Gulf Coastal Plain. The type species B. cretacea is 

from the Owl Creek Formation of Mississippi. Only 

one additional species, B. demersus Sohl, from the Kipley Formation of the same area, is known.

The species described below appears to represent a 

separate species, but the material is insufficient to assign 

a new name.

Bullopsis n. sp. 

Plate 7, figures 4^-6

Diagnosis. A Bullopsis with incised spiral lines covering shell surface.

Description. Medium-sized apically truncate subglobose shells. Spire depressed, apical depression 

broad with heterostrophic protoconch visible at center. 

Suture in an impressed groove. Teleoconch of about 

four whorls. Body whorl with upper surface rounded 

and decreasing with increased curvature into the apical 

depression; whorl sides well rounded. Sculpture consists of shallowly impressed spiral grooves that cover the 

surface; spiral grooves are weak over the curved upper 

whorl surface, but are wider spaced and stronger over 

the basal slope. Growth lines rather straight and gently 

prosocline. Aperture expands rapidly anteriorly, narrowly rounded posteriorly; columella with two low 

parallel oblique plications.

Measurements. Explanation of measurements and 

symbols used in the following table appears in the section "Measurements of specimens" (p. B9).

Specimen and locality

Bullopsis n. sp. (USNM 132661), Pierce 

Shale, Red Bird, Wyoming _ _

Bullopsis cretacea (topotype), Owl Creek 

Formation, Mississippi _ _ _

Do_ ____________________________

Do _ __ .

H

12.6

13.4

13. 0

17.8

MD

9.9

10. 0

10. 1

13. 5

H/MD

1.3

1.3

1.3

1.3

Discussion. Compared with topotypes of the .type 

species Bullopsis cretacea Conrad, from the Owl Creek 

Formation of Mississippi, this species compares favorably in size and proportions (see measurements) and in 

apical features (compare pi. 7, fig. 3, and pi. 7, fig. 4). 

Bullopsis n. sp. from the Pierre Shale of the Eed Bird 

section, however, has stronger spiral sculpture that covers the shell surface and has weaker lower columellar

plications than B. cretacea. Bullopsis demersus Sohl 

from the Kipley Formation of Tennessee, is smaller, 

lacks spiral sculpture on the medial part of the whorl, 

has a narrower apical pit, and has stronger columellar 

plications.

The description and discussion given above are based 

upon the sole specimen from the upper unnamed member of the Pierre Shale of the Red Bird section. The 

specimen is an internal mold that preserves the reflection 

of the surface sculpture and has parts of the shell still 

attached. The inner lip has been excavated from the 

rock matrix sufficiently to show the columellar folds, 

but their low character may in part be due to mechanical 

breakage during excavation. Specific variation cannot 

be ascertained with the available material and therefore 

assignment of a new name is withheld until more material is available.

Types: Figured specimen, USNM 132661. 

Occurrence: Wyoming: Pierre Shale, Bed Bird section, D-1985 

(Baculites grandis zone).

Order BASSOMATOPHORA 

Superfamily SIPHONARIACEA

Family SIPHONARIIDAE 

Genus ANTSOMYON Meek and Hayden, 1860

Type by original designation: Helcion patelliformis 

Meek and Hayden, 1856.

Diagnosis. Medium-sized patelliform shells having 

a medial or midanterior apex that is reflexed posteriorly 

at tip. Muscle scar horseshoe shaped having enlarged 

anterior ends joined by line and broken and offset on 

right posterior side.

Discussion. Anisomyon is restricted to the Cretaceous and is one of the more widely distributed gastropod genera in the western interior. In addition, it has 

been reported from the west coast and the Gulf and 

Atlantic Coastal Plains. Some of the species are of 

questionable placement because the internal muscle pattern is unknown.

The following is an annotated list of species described 

as Anisomyon from the Cretaceous rocks of North 

America.

Anisomyon alveolus Meek and Hayden: Pierre Shale, Bearpaw 

Shale, western interior, and Canada.

A. apicalis Sidwell: Carlile Shale, western interior.

A. borealis (Morton) : Pierre Shale, western interior and questionably Gulf Coastal Plain.

A. centrale Meek: Coloradoan( ?), Bearpaw, Pierre Shale, 

western interior, and Canada.

A1 cragini Twenhofel: Comanchean, Kansas.

A. frontierensis Sidwell: Frontier Formation, Wyoming.
UPPER CRETACEOUS GASTROPODS, RED BIRD, WYOMING B37

A. haydeni Sfoumard: Nacatoch Sand, Texas, and questionably 

in Mount Laurel Sand of Delaware.

A. jessupi Richards and Shapiro: Mount Laurel Sand, Delaware.

A. meelcii Gabb: Lower Cretaceous, California and Canada.

A. patelliformis Meek and Hayden: Pierre Shale, western interior. Smoky River Formation, Canada.

A. shumardi Meek and Hayden: Pierre Shale, western interior.

A. seuesuloatus Meek and Hayden : Pierre Shale, western interior.

A. subovatus Meek and Hayden: Pierre Shale, western interior.

A. wieseri Wade: Ripley Formation, Gulf Coastal Plain.

A. sp. Stephenson: Snow Hill Marl Member, Black Creek Formation. Atlantic Coastal Plain outside North America.

Of the species listed above, Anisomyon wieseri Wade 

belongs in Siphonaria (see Sohl, 1960, p. 47, 52). Of 

the other species, several have the general features of 

apex and shell form of Anisomyon; but until their 

muscle-scar patterns are known, acceptance in Anisomyon must be questioned.

Anisomyon borealis (Morton) 

Plate 8, figures 7-16; plate 9, figures 3-11

1842. Hipponyx borealis Morton, Acad. Nat. Sci. Philadelphia

Jour., v. 8, p. 210, pi. 11, fig. 6. 

1856. Helcion carinatus Meek and Hayden, Acad. Nat. Sci.

Philadelphia Proc., v. 6, p. .68. 

1860. Anisomyon borealis (Morton). Meek and Hayden, Am.

Jour. Sci. and Arts, v. 28, 2d ser., p. 35.

1876. Anisomyon borealis (Morton). Meek, U.S. Geol. Survey 

Terr. (Hayden) Rept., v. 9, p. 288, pi. 18, fig. 9a-e.

1877. Anisomyon borealis (Morton), White, U.S. Geog. Surveys

West 100th Meridian (Wheeler), v. 4, Paleontology, pt.

1, p. 193, pi. 18, figs. 9a, b. (Assignment very

questionable.) 

1880. Anisomyon borealis (Morton). Whitfield, U.S. Geog. and

Geol. Survey Rock Mtn. Region (Powell), p. 436, pi.

12, figs. 21-23.

1941. Anisomyon borealis (Morton) ? Stephenson, Texas Univ. 

Pub. 4101, p. 397, pi. 74, figs. 16,17.

Type locality. "Great Bend of the Missouri below 

Fort Pierre; from the base of the Fort Pierre Group" 

(Meek, 1876, p. 289).

Diagnosis. Base circular in outline, apex well forward with a posterior medial carination (fig. 10).

Description. Meek's (1876, p. 288) description is as 

follows:

Shell thin, bonnet shaped, the summit being prominent, with 

a general forward obliquity, and located in advance of middle; 

immediate apex very small, abruptly pointed, and having the 

characteristic abrupt backward curve well-marked; base nearly 

circular, anterior and anterior-lateral slopes abrupt and distinctly concave; posterior and posterior-lateral slopes convex, 

the former being carinated along the middle, and the latter usually supporting a few very obscure radiating ridges; surface, 

when slightly worn, appearing smooth, but in well-preserved 

examples marked by fine, inconspicuous lines of growth, which 

are crossed by similar closely arranged, radiating striae, scarcely 

visible without the aid of magnifier; radiating from the apex 

may also be seen six equidistant deeply-impressed hair-lines, 

four of which pass down the posterior and lateral slopes, and 

two down the anterior-lateral.

To the above must be added: shell margin subround 

in outline rising anteriorly, so that apex to anteriormargin distance is less than anterior-lateral margin to 

apex; impressed lines uncommon on shell interior, but 

carination strongly impressed. Muscle scars consisting 

of a strong upper left scar that tapers posteriorly, ending in enlarged scars just left of posterior carination; 

scars interrupted and offset over carination; scar thin 

and curved at lower right, enlarging over medial right

FIGURE 10. The muscle-scar pattern of some species of Anisomyon Meek and Hayden. Figure on left is A. centrale Meek, center 

A. borealis (Morton), right A. patelliformis Meek and Hayden. The X on the central anterior of the figures indicates the position 

of the apex. The curved posteriorly directed lines indicate the position of the carination, which is lacking in A. patelliformis. 

Slightly reduced from natural size.
B38 DESCRIPTIVE STUDY 'OF A CLASSIC REFE'REOSTCE LOCALITY OF THE PIEIRRE SHALE

side and anteriorly rounded; enlarged right- and leftanterior scars joined by a thin scar running across just 

anterior and below apex.

Measurements. Explanation of measurements and 

symbols used in the following tables appears in the section "Measurements of specimens" (p. B9).

Specimen and locality

Hypotype: 

USNM 132706 Pierre

USNM 132658 Pierre 

Shale (E. jenneyi zone), 

Red Bird, Wyoming____

USNM 132656 Pierre 

Shale (E. jenneyi zone), 

Red Bird, Wyoming___

USNM 132977 Pierre 

Shale, South Dakota _____

USNM 248 -------------

ML

51

60

48

44

w

50. 5

57

46

H

26

27 +

22. 5

19. 0

LC

43

33

45

43

Discussion. The additional information as to musculature was taken from the specimen illustrated on 

plate 8, figure 12, which comes from shale exposures 2 

miles northeast of Harper station, Wyoming. The 

characteristic uncoiled but reflexed protoconch typical 

of Anisomyon is best exhibited by the specimen figured 

on plate 8, figure 8, from the Pierre Shale at the Great 

Bend of the Missouri River. This specimen plus that 

figured from the same locality on plate 9, figures 3, 4, 8, 

exhibit sculpture to the best advantage.

Except for the medioposterior carination, sculpture 

appears to be very variable. Although the lack of impressed lines may, as Meek noted, be due to wear of the 

surface, the lack of secondary radiating ridges on the 

specimen (syntype of H. carinatus} USNM 132976 (pi. 

9, figs. 7, 9) cannot be explained, due to wear. This 

specimen possesses the carination and the impressed 

lines, but lacks the radiating ridges present on so many 

other specimens. On all specimens where present, the 

impressed lines are strongest near the apex and decrease 

in strength marginward. The radiating ridges in contrast are generally strongest away from the apex.

In shape, this species is rounder in outline than most 

other species of Anisomyon. Although usually rather 

high in outline, some specimens are proportionally low 

(compare plate 8, figures 8, 9).

Compared to other species, Anisomyon ~borealis is proportionally lower than A. centrale or A. shumardi, has 

a less central apex, and lacks the strong impressed line 

on the posterior slope of these species. Anisomyon subovat/us, A. patelliformis, A. haydeni, and A. alveolus are 

all lower and more lenticular in outline and have a much 

more subdued and noncarinate sculpture.

This is one of the more widely distributed gastropod 

species occurring in the lower part of the Pierre Shale

and equivalents in Colorado, South Dakota, and Wyoming. It occurs in the Red Bird Silty Member (Baculites gregoryensis zone), D-1910, and the overlying unnamed member, D-1947, 1948 (Exiteloceras jenneyi 

zone) of the Red Bird section.

Types: Holotype, lost; hypotypes, USNM 248 (2), USNM 

28586,132655-132658,132706,132976-132978.

Occurrences: Wyoming: Pierre Shale, Red Bird section, 

USGS D-1910 (Baculites gregoryensis zone), USGS D-1947, 

D-1948 (Exiteloceras jenneyi zone). Colorado: Pierre Shale, 

Front Range (Baculites perplexus and Baculites gregoryensis 

zones). South Dakota : Pierre Shale, near base.

Anisomyon centrale Meek 

Plate 9, figures 1, 2; pi. 10, figs. 1-15; pi. 11, figs. 1-7, 9

1871. Anisomyon centrale Meek, U.S. Geol. and Geog. Survey 

Terr., 4th Ann. Rept, p. 312.

1877. Anisomoyon centrale Meek. White, U.S. Geog. Surveys 

West 100th Meridian (Wheeler), v. 4, Paleontology pt. 1, 

p. 194, pi. 18, figs. 8a, t>. (Assignment questionable)

1879. Anisomyon centrale Meek. White, U.S. Geol. and Geog. 

Survey Terr. (Hayden), llth Ann. Rept., 1877, p. 206, 

225, 303, pi. 9, fig. la-d.

1885. Anisomyon centrale Meek. Whiteaves, Canada Geol. Survey, Contr. Canadian Paleontology, v. 1, pt. 1, p. 47, pi. 

7, figs. 1, la, 2, 2a.

1917. Anisomyon centrale (Meek). Dowling, Canada Geol. Survey Mem. 93, p. 30, pi. 28, figs. 12-12b.

Type locality. "Box Elder and Colorado City, Colorado" (Meek, 1871, p. 312).

Diagnosis. Subconical shell about as wide as high, 

.apex central, with strong grooves on anterior slope (figs. 

10, 11).

FIGURE 11. Diagram of sculpture pattern of Anisomyon centrale 

Meek and Hayden. Length of horizontal lines equivalent to circumference of aperture of individual specimen. Vertical line 

connects position of anterior radial groove. Shaded areas below horizontal lines, mark width and position of lateral radial 

grooves. Shaded areas above horizontal line mark position and 

width of right posterior platform. Specimen numbers : 1. USGS, 

D-1382 (Baculites jenseni zone) Wyoming. 2. USGS, D-16217 

(B. reesidei zone) Colorado. 3. Same locality, aberrant form. 

4. Lectotype, USNM 12430a, Pierre Shale, Colorado. 5. USGS, 

D-2,819 (B. reesidei zone) Colorado. 6. Cotype USNM 12430b, 

Pierre Shale, Colorado. 7. USGS, D-2701 (B. reesidei zone) 

Colorado. 8. USGS, D-372 (B. reesidei zone) Colorado.
UPPER CRETACEOUS GASTROPODS, RED BIRD, WYOMING B39

Description. Medium-sized subconical shells about 

as wide as high with a straight anterior slope and 

broadly convex posterior lateral slopes; left-lateral 

slope less steep than right. Apex approximately central in position; nucleus unknown, but apex asymmetrically reflexed posteriorly. Sculpture dominated by 

radial grooves; main groove deep and strong with a 

broadly concave base and is situated at about midanterior slope; minor incised grooves variable in 

number and strength, covering about one-half of leftanterior quadrant and all right-anterior quadrant. 

Usually, a carination is present on right-posterior slope 

forming posterior limit of a broad raised platformlike 

area covering medial one-half of right-posterior quadrant. Concentric sculpture usually limited to growth 

lines and low welts that are strongest over raised radial 

welt of right-posterior quadrant.

Growth lines faint to moderately prominent; lines 

nearly straight between radiating grooves, but flexed 

over grooves and very sharply flexed toward apex over 

posterior carination. Aperture subcircular in outline; 

in profile, anterior margin higher than posterior. 

Muscle scars consist of two prominent strong muscle 

scars on the anterior-lateral flanks joined by moderately 

wide scar band on the anterior slope. On left-lateral 

flank behind the broad anterior scar a moderately 

broad scar band continues posteriorly, being first directed down and posteriorly at an angle of about 30° 

from the horizontal, then becoming virtually horizontal 

and continuing almost to the posterior carination, 

where it is interrupted. On the right-posterior flank, 

muscle scars again begin just beyond the umbonal ridge 

but higher on the shell than those of the left-posterior 

flank, then curve downward, then swing up to the main 

right interior scar.

Measurements. Explanation of measurements and 

symbols used in the following table appears in the section "Measurements of specimens" (p. B9). (See also 

fig. 11.)

Discussion. Anisomyon centrale, as is typical of 

other species of the genus, shows considerable variability in most aspects of sculpture. In form it is consistently subcircular. Most available specimens are 

internal molds, but a few possess at least a part of the 

shell (pi. 11, figs. 1^1); in general, the radiating 

grooves are less pronounced on the shells than on the 

internal molds. The shell itself is rather thin, and the 

muscle scars are not deeply impressed. When observable, the muscle scars are preserved as shell material 

adhering to the internal molds.

Small specimens closely approach a circular outline, 

but in larger individuals there is an increasing tendency 

toward asymmetry. At all stages of growth the rightposterior area is largest and deviates most from the 

overall circularity of the aperture, making the posterior 

half of the shell broader than the anterior. Proportions of height to length vary greatly, but, in general, 

the smaller specimens are proportionately higher, usually with height nearly equal to width (pi. 10, fig. 5), 

whereas some larger specimens (pi. 9, fig. 2) have a 

length iy2 to almost twice the height (see measurements). The specimen from the Pierre Shale of the 

Front Range figured on plate 11, figure 3 (USGS 16217, 

USNM 132713) is the most atypical not only in its low 

spire but in its subdued sculpture and long anterior 

slope.

The apex is broken on almost all available specimens, 

but the specimen from USGS locality D-372, figured 

on plate 10, figure 9, shows it to be well reflexed toward 

the posterior and skewed to the left of the median 

plane. It is suggestive that the larval shell was a 

simple cup shape similar to that in some of the nudibranchs. This has, however, never been seen on actual 

specimens.

The most constant feature of the radiating sculpture 

is the strong deep anterior groove commonly flanked 

by broader grooves on either side and the swollen 

raised platform of the right-posterior quadrant. Figure 11 shows these features to be present on all specimens, but that they vary in strength and width generally with size of the specimen. The lateral grooves of 

the internal molds on specimens retaining the shell, 

however, are not simple troughs but are divided by a 

central rib (fig. 11, specimen 3). This feature is well

Specimen and locality

Lectotype: USNM 12430 Pierre Shale, Colorado

Syntype: USNM 132979 Pierre Shale, Colorado

Hypotype: USNM 132660 Pierre Shale, Red Bird, Wyoming. ______

USGS D-1382 Pierre Shale (B. jenseni zone), Colorado___ __ _ __

Do________ _ _______ ______ _

Do__________________

Do_________. ______

USGS 16217 Pierre Shale (B. reesidei zone), Colorado. _ ____________

Do__ ____________

USGS D-372 Pierre Shale (B. reesidei zone), Colorado

H

24. 6

19. 0

31. 0 +

29

31. 2

21

22

24

18

16

AM

24. 5

23

30

27

27

25

21. 1

24

22

PM

27

23

32 +

37

36

29. 5

26

27. 5

26

ML

29. 4

23. 9

36. 1 +

36

38. 9

37. 0

32. 5

33

35. 5

21

w

29. 8

22.2

37. 5

32

39. 2

33

31

31

33. 5

20. 5

ML/W

0. 98

1. 07

. 99

1. 12

. 99

1. 12

1. 05

1. 06

1.06

1. 02
B40 DESCRIPTIVE STUDY OF A CLASSIC REFERENCE LOCALITY OF THE PIERRE SHALE

displayed by the specimens figured on plate 11, figures 

1-4. Growth lines commonly are strongly flexed up 

over this ridge. The significance of the anterior 

groove is questionable. The raised platform of the 

right posterior margin, however, is associated with the 

interruption of the muscle-scar band (see figs. 10, 11) 

and has functional significance. This band is delimited 

on its anterior side by a radiating groove, but on its 

posterior side it is bounded by a low to well-marked 

carination not unlike that seen on Anisomyon boreali-s. 

The interruption of the muscle-scar band coincides with 

the lung aperture of these pulmonates.

In outline, Anisomyon shumardi Meek and Hayden 

from the Pierre Shale of the Great Bend of the Missouri is perhaps the species most similar to A. centrale. 

Anisomyon shumardi, however, has a much less central 

apex and lacks the strong radiating grooves. Anisomyon sexsulcatus Meek and Hayden from the Pierre 

Shale near Glendive, Mont., is lower in outline with a 

less central apex and has scattered radiating grooves.

White (1877, pi. 18, figs. 8a, b) assigned internal 

molds from Gallinas Creek, N. Mex., to A. centrale. 

He noted that the molds were in clay and compressed 

and thus did not show their true outline. These specimens must be assigned with question, for the apex appears to be subcentral and no trace of musculature 

remains. Whiteaves (1885, pi. 7, figs. 1, 2) figured 

specimens from the Bearpaw Shale of Canada that 

conform well to the species.

Types: Meek's 1871 description was based on two specimens 

(USNM 12430) from the Pierre Shale of "Box Elder and 

Colorado City, Colorado." White (1879, pi. 9, figs, ia-d) produced illustrations of the type specimens prepared by Meek 

just before his death. I hereby designate the specimen illustrated by White (1879) on plate 9, figs, la, and Ib, as lectotype, 

USNM 12430. Syntype, USNM 132979. Hypotypes: USNM 

132659, 132710, 132713, 132716, 132925, 132926 (Pierre Shale, 

Colorado) ; USNM 8659 (New Mexico, White, 1875) ; USNM 

132660,132715 (Pierre Shale, Wyoming).

Occurrences: Wyoming: Pierre Shale, Red Bird section, USGS 

D-1952 (Baculites reesidei zone). Colorado: Pierre Shale, 

Front Range (Baculites reesidei and B. jenseni zones). New 

Mexico: Gallinas Creek (questionable occurrence). Canada: 

Bearpaw Shale (Whiteaves, 1885; Dowling, 1917).

Anisomyon patelliformis Meek and Hayden 

Plate 11, figures 8, 10-17

1856. Helcion patelliformis Meek and Hayden, Acad. Nat. Sci.

Philadelphia Proc., v. 8, p. 68. 

1860. Anisomyon patelliformis Meek and Hayden, Am. Jour. Sci.,

v. 29, p. 35, pi. 1, figs. 1-3. 

1876. Anisomyon patelliformis Meek and Hayden. Meek, U.S.

Geol. Survey Terr. (Hayden) Rept, v. 9, p. 290, pi. 18,

figs. 5a-c, e. 

1880. Anisomyon patelliformis Meek and Hayden. Whitfield,

Geol. and Geol. Survey Rocky Mtn. Region (Powell),

p. 435, pi. 12, figs. 17, 18.

1895. Anisomyon patelliformis Meek and Hayden. Cossmann, 

Essais de paleoconchologie compared, pt. 1, p. 138, pi. 

7, fig. 18.

1917. Anisomyon patelliformis Meek and Hayden. Dowling, 

Canada Geol. Survey Mem. 93, p. 30, 46, pi. 29, figs. 1-lc.

1959. Anisomyon patelliformis Meek and Hayden. Zilch, Gastropoda, in Schindewolf, O. H, Handbueh der Palaozoologie, v. 6, pt. 2, p. 82, fig. 266.

Type locality. "Yellowstone Kiver, 150 miles above 

its mouth" (Meek, 1876, p. 290). This locality is in the 

upper part of Pierre Shale (Baculites baculus zone) in 

the vicinity of Glendive, Mont.

Diagnosis. Apex at about anterior one-third shell; 

profile moderately low, posterior slope well rounded. 

Surface smooth, devoid of all sculpture except for few 

faint radiating lines. Aperture outline widest posteriorly (see fig. 10).

Discussion. One internal mold from the Ked Bird 

section at USGS D-2116 may belong to Anisomyon 

patelliformis. It is larger and laterally less expanding 

than is typical for the species, but is close in position of 

apex and lack of sculpture. Whitfield's (1880) specimen of A. patelliformis comes from the Old Woman 

Creek of Wyoming near Ked Bird and gives ample 

proof of the presence of the species in this area (pi. 

11, fig. 8).

Lack of a strong posterior carination and incised 

grooves separates the species readily from A. centrale 

and A. borealis. Its muscle-scar pattern (fig. 10, and 

pi. 11, figs. 8, 16) is especially distinctive in that the 

connection between the anterior enlarged scars rides 

high on the shell even to the point of being behind the 

apex (pi. 11, fig. 8). On other specimens, however, the 

scar crosses at the apex (pi. 11, figs. 13, 16).

Types: Holotype, USNM 246; paratype, USNM 132980, 132981; 

hypotype, USNM 12268, 132982.

Occurrence®: Wyoming: Pierre Shale, Red Bird section, USGS 

D-2116, (Baculites baculus zone). South Dakota: Fox Hills 

Sandstone. Montana: Pierre Shale (Baculites baculus zone).

Anisomyon sp.

Discussion. Incomplete internal molds probably representing species of Anisomyon occur in the Pierre 

Shale of the Eed Bird section in collections USGS D1887 (Baculites gilberti zone), USGS D-1900 (Baculites gregoryensis zone), and D-1952 (Baculites reesidei 

zone).

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B42 DESCRIPTIVE STTIDY OF A CLASSIC REFERENCE LOCALITY OF THE PIEIRRE SHALE

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INDEX

[Italic page numbers indicate major references or fossil descriptions]

A Page 

Acirsa (Hemiacirsa) .......__.__.__.. B7

Acknowledgments----_.__._._____ 2

Acmaea................_____._____ 9

occidentalis ._____________ 5,7

papillata......... ....___._______. 5

Acteon.... ...-_____________-_. 5,33

concinnus........... ________.__. 34

(Solidula) attenuatus-.......-___.__. 9,33

Acteonacea____.___-_.____...... 33

Acteonidae.--.-..................____._.- 33

Acteonina..... .....____._..______ 33

adnae, Lunatia.....-------........____. 25

Africa... . ... ---.. _...... 2,12

Alabama, Blufitown Formation (lower Campanian)-_________._- 19 

alkni, Fasciolaria (Piestochilus)..... . . ___ 9

Graphidula............................. 32; pi. 7

Amauropsis-..-.............................. 25

bulbiformis. ____-______.__. 25 

ambigua, Fossar..................... ....._ 23

Natica. ........................ 9,22,23,25

Vanikoro................................. 23

.americanus,Drepanochttus .................. 17

Ampullospira................................. 25

stantoni-......,.......................... 25

Amuletum minor............................. %

sp. - .__.____ 5 

Anchura.........................___.__ 11,12

evansipusilla............................. 9

haydeni................................... 5

subkvis..___________.-_.___ 15 

(Depranochilus) nebrascensis.............. 9

Angaria ornatissima........................... 10

angulata, Aporrhais........................... 19

Anisomyon.............................. 3,7,8,9,36

alveolus............................... 5,8,36,38

apicalis.. -------____-----___... 36

borealis ................... 2,4,5,7,36, 37; pi. 8

centrale................ 4,5,8,36,38; pis. 9,10,11

cragini..... .................__.___ 36

frontierensis ______.________ 36

haydeni___.______________ 36,38

jessupi.................................... 36

meekii.................................... 37

patelliformis ------. . 4,8,37,38, 40; pi. 11

sexsulcatus.............................. 8,38,40

shumardi-...-......................... 37,38,40

subovatus............................. 5,8,37,38

wieseri.............................._..... 37

Sp-- - ---- 4,5,37,40

Anomalofusus............................... 3,8,30

substriatus. ............................ 30

apicalis, Anisomyon........................... 36

Aporrhaidae___ .___-__ ...__ 9,10,11 

Aporrhais..-....................... .... 11,12,19,20

angulata----...______..____ 19

biangulata...................... 4,7,20,21;pi.2

brittsi----.. , ..... ............ 19

calif arnica................................ 19

decemlirata................................ 19

elpatemis___.____________.. 20 

falciformis.--.--................____.. 19

kentensis.................................. 20

meeki -_-___-__ - ._ 5 

neucensis........_________. 19

pespekcani. ......................... 20; pi. 2

Page 

Aporrhais Continued

singleyi.- B19

subfusiformis. ................- 20

subkvis ....----------- 9,19

tarrantensis__________..___.. 19 

travisensis................................ 19

(Lispodesthes) nuptiallis............ ..... 19

(Perissoptera) prolabiata.................. 19

(Pterocerella) tippana..................... 19

n. sp. ...______.-__.._ pi. 2 

sp-..--. 7,8,20,^

spp - - 20

Archaeogastropoda.------__....... 10

Architectonica................................. 11

inornata.................................. 10

Arrhoget 11,12,19

Astandes................................... 8,23,24

dewsotos.---.----------------- 5,8,23,24; pi. 4

Atira-.- ............................... 2,8,9,10

nebrascensis. ------.-- 3,4,5,7,8,9, 10, 11; pi. 1

Atlantic Coastal Plain, Campanian and

Maestrichtian rocks.-_____ 12 

atlanticum, Trachytriton....................... 28

attenuata, Nonactaeonina_____. . 4,8,33; pi. 8 

attenuatus, Actaeon (Solidula)................. 9,33

B 

Baculites.. ... ..-. . ...... 9

baculus..- -...................... 3,11,15,16

zone, Pierre Shale, Cedar Creek anticline, Glendive, Mont__ 7 

Pierre Shale, Front Eange of Colorado- ------------------- 15,16

Glendive, Mont 10,

11,15,16,20,22, 23,24,28,32,33,35,40

Eed Bird section, Wyoming. 15,

16,23,24,28,30,34,35

baculus, Baculites........-.-------...-.. 3,11,15,16

Bassomatophora_. _.... 36

Bearpaw Shale, Canada--.- 8, 15,23,28,34,35,36,40 

Montana. 8,23,28,34,35

Bellifusus.---. -- .... .... 5,7,33

sp. . 5,33

Belliscala. - - - --------- 7,9

biangulata, Aporrhais...______. 4,7,20,21; pi. 2 

Black Hills region, S. Dak., fossil faunas 7 

Blufitown Formation (lower Campanian) of

Alabama...-- ----- ----- 19

borealis, Hipponyx... . ... 37 

Anisomyon... 2, 4,5,7,36,37; pi. 8 

British Columbia, Upper Cretaceous, Sucia 

and Sheep Jack Islands, Vancouver....____... . 10

brittsi, Aporrhais........---------------------- 19

Buccinacea...___ _ _ _ ---------- 29

Buccinofusus..... .......... 29

buccinoides, Fasciolaria.-............... 2,9,29; pi. 6

Buccinum vinculum........... .... 28

bulbiformis, Amauropsis.................. .. 25

Butta 35

Bullacea .... - - - -- 35

Bullidae- 35

Buttopsis -- 9,35,36

cretacea... 35,36; pi. 7

demersus....---------- ___ 36

n. sp._----_- - --- pi. 7

sp.. 4,30

Page 

California, Panoche Formation....... ____ B29

Tejon Formation. ..._..._... 28

Upper Cretaceous..____________ 10

californica, Aporrhais... . __.._ 19

Calyptraeacea................................. 23

Canada, Bearpaw Shale..... 8, 15,23,28,34,35,36,40

Hormby Island, Vancouver Island area_ 29 

Cancellata, Vanikoro.................... 22,23; pi. 5

zone, Exogyra............................. 12,24

Cannonball Member of Fort Union Formation, North Dakota__.____ 28 

South Dakota. __ __ ______ 14 

Capulus spangleri........ . 2,5

carinatus, Helcion............................. 37,38

Cedar Creek anticline, Glendive, Mont., 

Pierre Shale, Baculites baculus 

zone.__ 7 

centrale, Anisomyon........ 4,5,8,36,38; pis. 9,10,11

Cephalaspidea ------ - - 33

Cerithioderma................................. 8

Cerithiopsis.. 7

Changes in generic or specific assignment ----- 9

cheyennense zone, Drepanochilus...... ...... 7

cheyennensis, Cryptorhytis..-......... 4,5,7, S3; pi. 7

Gladiut 32

Claggett Shale, Montana - 28 

clatworthyi, Volutoderma... ................ 5

clinolobatus zone, Baculites...-- ...- 5,11,16,28 

Closteriscus tenuilineatus...................... 7

coalvillensis, Euspira.......................... 25

Cobban, W. A., quoted..------ - -- 17

Coleraine Formation of Staufier, Mesabi

Eange, Minnesota..___ 28

Colorado, Fox Hills Sandstone_____ 30,32

Front Eange, Pierre Shale ----------- 11,23

Pierre Shale, gastropods. 1,5 

Eichard Sandstone Member of Pierre

Shale 5,7

Eocky Eidge Sandstone Member of

Pierre Shale-.. ---------- 5,7,9

Terry Sandstone Member of Pierre Shale. 5 

Colorado Group, Minnesota.. .... - 11

concinna, Lunatia................ - 25,27

Natica ................................. 26,27

Oligoptycha..........-- -- 4,5,7,8, S4; pi. 8

concinnus, Actaeon...............-. ----- 34

Confusiscalasp........ -- 5

cragini, Anisomyon... ... ... 36

cretacea, BuUopsis.........- ........... 35,36; pi. 7

cretaceum, Tritonium............. -- 24

crosswickensis, Serrifusus.............-.... . 9,29

Cryptorhytis.... - 3,32,33

cheyennensis----.---.-. ---- 4,5,7,SS;pl. 7

flexicostata.. - - 5,8 

culbertsoni, Graphidula- . 4,5, 7,8,32; pi. 7 

Cylichnasp.- .... --- - 5,32

Cylindrotruncus........ - 9

glansoryza....... .. ..-. ..- - 5

Cymatiidae..- - - 9.28

Cyphosolenus..... ... - - - 11,19

Cypraeasp. A.. .. - - - 5 

sp. B. ------ 5

D 

dakotensis, Euspira .... - 27; pi. 1

Fusus......--- -- -- 29

B43
B44 INDEX

Page 

dakotensis, Euspira Continued

Lunatia..........................____ B25

Nation~---------------_.______ 25

Serrifusus......................... 4,29,30; pi. 6

vancouverensis, Serrifusus........ _____. 29

decemlirata, Aporrhais...... __..._._.... 19

demersus, Buttopsis.-_____.._____ 36 

densatus,Astendes__________ 5,8,23,24; pi. 4

12

Deussmia

Dicroloma.---- ________..______

Distribution and abundance of aporrhaid 

genera in Cretaceous rocks of 

North America._..___________

Distribution of gastropod species In members 

of Pierre Shale, Red Bird section, 

Wyoming..____________ 3,4 

Drepanochilus................. 7, 8,9, 11, 12,16,19,21

americanus... ___ ______._ 17

evolution of western interior_ -____ 12 

evansL.......... 4,5,8,9,11, IS, 15,16,18,19; pi. 3

nebrascensis.............. 4,5,7,8,15,.77,19; pi. 3

obesus............................ 5,7,9, 18; pi. 4

pusillus.............................. 9,14; pi. 4

scottL............................ 15,18,19; pi. 4

sublevis.... ............................. 15

texanus............... __________ 12

sp.

(Drepanochilus) nebrascensis, Anchura. 

Drttlutasp____--.-_-._..__...

E 

Ecology, notes on___._______-.-__-___ 3

Ettipsoscapha------.......................... 8,35

minor...........................'...__ 35

occidentalis....................... 4,5,8,35,-pi. 7

subcylindrica............................. 5,8,35

elpasensis, Aporrhais.......................... 20

Eoacteon...................................... 5,8

Europe_______...__.._____..___ 12 

Euspira----............................... 7,8,9,#4

coalvillensis............................... 25

dakotensis...... ._._...____... 27;pi. 1

obliquata ................. 4,5,7,8, t6, 32; pi. 1

rectilabrum.---........................... 27

sp.

Euthyneura._____________...._ 33

evansi, Drepanochilus...-....________ 4,

5,8,9,11,73,15,16,18,19; pi. 3

Evolution of western interior Drepanochilus-- IS

Exogyra cancellata zone, Tennessee.-..-._.. 12

cancellata zone, Upper Ripley Formation,

Tennessee...._________... 24

fakiformis, Aporrhais.-. ................... 19

Fasciolaria buccinoides................ 2,9,29; pi. 6

(Piestochttus) alleni....................... 9

Fasciolariidae.--._____ _______ 9,29,33

Fasciolariinae...... ___....._...._.__. 31

flexicostata, Cryptorhytis _____-_____ 5,8 

flexistriata, Margaritella----......-............ 7

Fort Union Formation, Cannonball Member,

North Dakota.. ___. _____ 28

Cannonball Member, South Dakota_.. 14

Fossar ambigua............................... 23

nebrascensis............................. 9,22,23

Fossil faunas, Black Hills region, S. Dak___ 7 

Fox Hills Group-. __ _ 22,31

Fox Hills Sandstone, Colorado-...__-___ 30,32

Long Lake, S. Dak_. ___.___...__ 11

Milliken Sandstone Member. ______ 28

Montana.._____.__________ 23,28

South Dakota._____.________ 2, 5, 8,

13, 14, 15, 23, 26, 28, 30, 32, 34, 40

Fox Hills Sandstone, Niobrara County, Wyo.. 30

North Dakota----..-.--......__ 15,23,28,30,32

Fusininae..__.______________ 29 

Fusus................_.._.................... 29

dakotensis....................... ________ 29

O

Page

Galllnas Creek, N. Mex._ .__..._.. B40 

Gammon Ferruginous Member of the Pierre

Shale ... _ _____ 7,31

Gastropod fauna, Pierre Shale, Red Bird section. 1, S 

Gastropod species, distribution in members of 

Pierre Shale, Red Bird section, 

Wyoming...... ............. 3,4

Gaza......................................... 10

 ...... 32

glansoryza, Cylindrotruncus................... 5

glaucinoides, Natica........................... 24

gracilenta, Mesorhytis......................... 8

Graciliala.................................. 11,12,19

Graphidula.. ...................... 3,5,7,9, 31,32

alleni.................................. S#; pi. 7

culbertsoni..................... 4, 5, 7,8,32; pi. 7

obscura............ ....... 7

pergracUis............ ... .____-..- 32

terebreformis. ................- __ 31

graphioides, Nonacteonina. - 33 

Greenland___________________ 28 

guttatus, Scobinodolus ....................... 5

Gyrodes.................. .-_ - 25

sp.._ .. ... 5

H

Haminea.___________________ 35 

haydeni, Anchura................ ........... 5

Natica. ... .......... ... - 9,22,23,25

Vanikoroposis..... ..................... 5,8,23

Helcion carinatus............................. 37,38

pateUiformis...............,_______ 36

Helicaulax.................................... 12

(Hemiacirca), Acirsa.......................... 7

hippocrepis, Scaphites......................... 7

Hipponicacea... _. . .._ 22 

Hipponyx borealis... . . 37 

holmdelense, Trachytriton...................... 28

Hydrotribulus sp_. 5

Indeterminate fusiform gastropods. 

Inoceramus........................

inornata,Architectonica............

inornatus, Margarites..............

intertextus, Rhombopsis.... -........

Introduction..... . ...

jessupi, Anisomyon............... -... 36

joaquinensis, Serrifusus--- 29

Kara Bentonite Member of Pierre Shale, Red 

Bird section, Niobrara County, 

Wyo-.-- - 3,4

Kemp Clay of Texas.....________ 12

kentensis, Aporrhais....... - 20

kiliani, Vanikoro.............................. 22

Larimer Sandstone Member of Pierre Shale,

Colorado- ____________ 5,7,9 

leprosa, Xenophora....................... ..... 5

(Lirofusus) nodocarinatus, Serrifusus......... 29

Lispodesthes.... ____... . 11,12

(Lispodesthes) nuptiallis, Aporrhais........... 19

Lomirosa...-................... 7,9

Lunatia-.-............................... 25,27

adnae... .. .... 25

concinna.......... ----- 25,27

dakotensis --.. -.. 25 

moreauensis........ ._ . 27

obliquata - 27 

subcrassa... ...................... pi. 1

utahensis................................. 25

(Lunatia) occidentalis, Natica................. 25

Page

Lutema minor................................ B5

lygata, Vanikaro.. -.-- --. 22, 23; pi. 5

M

Margarita.......

nebrascensis. 

Margaritella.....

flexistriata.. 

Margarites. .-..

inornatus...

sp.. _ - 

Margaritinae... . . 

Mazzalina- - -- 

Measurements of specimens....__. 

Meek, F.B., quoted...,- . 17,22,27, 

meeki, Aporrhais..-.-... 

Natica --. --- -- - -- - - 

meekii, Anisomyon...... --

Mesabi Range, Minn., Coleraine Formation

of Stauffer_. 

Mesogastropoda - 

Mesorhytis -....-------... --

gracilenta- ... - --

sp.. 

Milliken Sandstone Member of Fox Hills

Sandstone_. ... -

Minnesota, Colorado Group.. 

Mesabi Range, Coleraine Formation of

Stauffer..__ . 

minor, Amuletum...... ._ -_ ...

Ellipsoscapha..........-. -. ...........

Lutema --------------------------------

Mississippi, Owl Creek Formation... _ _

Ripley Formation_ 

Monocyphus..................................

Montana.. -_ . 

Bearpaw Shale.-.--_~. ----- S,23,28,

Claggett Shale_____-_..............

Fox Hills Sandstone... _._ _ 

Glendive, Cedar Creek anticline, Pierre

Shale, Baculites baculus zone ..

Montana Group.. . --

moreauensis, Lunatia... -

Natica..--. --- - 

multivaricosum, Trachytriton..................

7

10

10

5

10

29

9

29,37

5

9,25

37

28

7,11

28

11

28

8

35

5

36

36

12,19

7

34,35

28

23,28

7

23

27

26,27

N

Napulus.

sp.

Natica ambigua..- ................... 9,22,23,25

concinna - -- 26,27 

dakotensis-------------------------.-. 25

glaucinoides.-. ......... 24

haydeni.-. - 9,22,23,25

meeki-. .-- 9,25

moreauensis..... - ---- 26,27

obliquata ............................ 26,27,28

occidentalis....... .........-.............. 27

paludinaeformis... ... - 9,25 

praenominata-.- -------- -------- 9,22,23,25

subcrassa---....- - 25,28

toumeyana.. -. ---- 22

(Lunatia) occidentalis... 25 

Naticacea.................-...... -- 24

Naticidae ------ 9,22,24

Navesink Formation, New Jersey.. 29 

nebrescense, Pseudobuccinum........ ... . 8

nebrascensis, Anchura (Drepanochilus)---..--- 9 

Atira. ................ 3,4,5,7,8,9, 10, 11;pi. 1

Drepanochilus-........... 4,5,7,8,15, 17, 19;pi.3

Fotsar.. 9,22,23

Margarita.............-... 9

Vanikoroptis 8,28,23,25; pis. 5, 6

Neogastropoda. - - - 7,29 

neucensis, Aporrhais.. ....... ....... . 19

New Jersey, Navesink Formation.. 29 

New Mexico, Gallinas Creek... .._-...---- 40

New Zealand_______ 12 

newberryi, Rhombopsis................ .. - 8

nodocarinatus Serrifusus (Lirofusus) ... --- 29
ESTDEX B45

Page 

Nonadaeonina.-.--... -________________ _ B8,9,SS

attenuate------.... _.--_____ 4,8,S3,'pi. 8

graphioides.... . ...... ............ 33

North America, distribution and abundance of 

aporrhaid genera in Cretaceous 

rocks of North America__.--- 12 

North Dakota......................._._.. 12

Cannonball Member of Fort Union Formation...__---._---.___ 28 

Fox HUls Sandstone ----------15,23,28,30,32

nuptiallis, Aporrhais (Lispodesthes) --..._-. _ 19

O

obesus, Drepanochilus.----..... .... 5,7,9, .S;pl.4

obliquata, Euspira.... ___ __ 4,5,7,8, 26, 32; pi. 1

Lunatia-- -. - _-...-_...__...__ 27

Natica-...._............._........ 26,27,28

obscura, Graphidula...... ....________. 7

occidentalis,Acmaea---- ____..____ 5,7

Ellipsoscapha. -................. 4,5,8, 35; pi. 7

Natica_______________.___ 27 

(Lunatia) --.... ..._..___.__ 25

Olequahia hornii...... ___....______ 28

Oligoptycha.... __.___.__________ 9,84

concinna..... __ ___....._... 4,5,7,8, 34; pi.8

Ornopsis________________..____. 33

Ostrea. ________...___._______ 3 

Owl Creek Formation, Mississippi...____ 36

Paladmete.-..--_______....._._._ 8,24

paludinaeformis, Natica..... _. ___... 9,25

Panoche Formation of California....___... 29

papillata, Acmaea...... ____._____.._ 5

patelliformis, Anisomyon.. ...... 4,8,37,38, 40; pi. 11

Helcion.... .______..._._...__ 36

pergracilis, Graphidula-............ .......__ 32

Perissoptera.... ___....___._____. 11,12

(Perissoptera) prolabiata, Aporrhais. ..__-__-__ 19 

pespelicani, Aporrhais..... ...___-._--._ 20

Strombus...-. ...-.---..._____________ 19

Philinacea.. ________________ 35

Pierre Shale, Box Elder Creek, Colo.____ 38

Front Kange of Colorado, gastropods. _ _ _ _ 1,5

Gammon Ferruginous Member_ _ _ 7,31 

gastropod fauna... __ _____ ____ _ %

Great Bend of Missouri Kiver, S. Dak.... 38

Kara Bentonite Member, Bed Bird section, Niobrara County, Wyo.. _ 3, 4 

Larimer Sandstone Member, Colorado... 5,9 

Red Bird section, gastropod fauna____ 1, 8 

Niobrara County, Wyo. _____ 4, 11 

Red Bird Silty Member, Niobrara

County, Wyo.-- - 3,4,29

Richard Sandstone Member, Colorado_ 5,7 

Rocky Ridge Sandstone Member, Colorado.. . ._ _ 5,7,9 

South Dakota.__________ 15,19,29,34,38 

Terry Sandstone Member, Colorado..-.. 5 

Piestochilus ... __..._______. 31 

scarboroughi..... - -____________ 31

(Piestochilus) alleni, Fasciolaria- ...______ 9 

Potamides sp. A._.._____.______ 7

sp. B _ ...... ___,___ ___________ 7

praenominata, Natica-. ___ ___. _. 9,22,23,25 

prolabiata, Aporrhais (Perissoptera)--.-....... 19

Promathttda.-..-__. .._____.__ 7

(Clathrobaculus). - ___..._______... 7

propingua, Vanikoro- ____________. 22

Proposed new species_....___ ____ __ 9

Pseudamaura.--- ________.._______ 9,25

lirata.-. ___________....._______ 5

paludinaeformis---... .._________._ 5,7

Pseudobuccinum......... _________._ 8

nebrascense-.-. ______,_____....__, 8

Pteria......................................_. 3

Pterocerella. ________________... 9,12

(Pterocerella) tippana, Aporrhais_.___-.._. 19

Page

pulchella, Ringicula (Ringicula)..... B5

Vanikoro--... _....._---... 22

pusillus, Drepanochilus -........... . 9,14; pi. 4

guadriliratus, Drepanochilus.

rectilabrum, Euspira--....__. .

Red Bird Silty Member of Pierre Shale, 

Niobrara County, Wyo_ _ 3,

Reeside, J. B., Jr., quoted_______--...

Remera 

stephensoni..-. ... ..__...- .._

Rhombopsis intertextus.............___-...

newberryi.... ------- -

subturritus 

12

27

4,29

2

7,9

7

spRichard Sandstone Member of Pierre Shale of

Colorado...-______.- _ 5,7 

Ringicula (Ringicula) pulchella....... - 5

(Ringicula) pulchella, Ringicula.. 5 

Ripley Formation, Coon Creek, McNairy

County, Term_.__._____ 24 

Mississippi.---- _____ . 36

Tennessee..-----_ ... ._. .. ... 29,36

Upper Exogyra cancellata zone, Tennessee. 24 

Rocky Ridge Sandstone Member of Pierre

Shale, Colorado-------.-------.-- 5,7,9

Rostellaria americana. -..... ..___ _ 11

fusiformis ------------------------- 32

Scaphander.-._______ ______--_ 35 

Scaphandridae--______________ 35 

Scaphites hippocrepis .-_____-____-. __. 7

Scobinodolus__________-________ 8,9 

guttatus - -- ..-.....__ 5

scotti, Drepanochilus.----...--____ 15,18,19; pi. 4

Serrifusus............................... 2,3,5,9,29

crosswickensis ..........________. 9,29

dakotensis . 4,29, SO; pi. 6

vancouverensis--- ____.. ..-- 29 

joaguinensis.-. ......_.-.___ -__ 29

tennesseensis ......_.__________ 29

(Lirofusus) nodocarinatus- _._-------__ 29

sexsulcatus,Anisomyon- _--.____------_ 8,38,40

shumardi, Anisomyon .____._...___ 37,38,40 

singleyit'Aporrhais... ____-__- -_- 19 

Siphonaria ___---_______.--__ 3,37

Siphonariacea....---_____________ 36

Siphonariidae----------------------------_ 36

Solarietta-..................................... 10,11

(Solidula) attenuatus, Acteon. __ _ __ ___ 9,33

South Dakota.._-_----__....__.......... 7

Black Hills region, fossil faunas__.__ 7 

Cannonball Member of Fort Union Formation. .__.__________ 14 

Fox Hills Sandstone...__.............. 2,5,

8,13,14,15,23,26,28,30,32,34,40

at Long Lake...______.____ 11

Pierre Shale- ................. 15,19,29,34,38

spangleri, Capulus ____-..-._-_..__ 2,5 

Stanton, T. W., quoted. ..................... 27

stantoni, Ampullospira________ _____- 25

Stenoglossa_______.___.._____ 29 

stephensoni, Remera.---------___.___- 7

Stewart, R. B., quoted-...__________ 10 

Strombacea...________________ 11

Strombus pespelicani---.........______ 19

subcrassa, Lunatia............................ pi. 1

Natica..--................................ 25,28

subcylindrica, Ellipsoscapha_________ 5,8,35 

sub fusiformis, Aporrhais..............___.. 20

sublevis, Aporrhais 9,19

Drepanochilus............_______ 15

subovatus, Anisomyon-..._____.__ 5,8,37,38 

substriatus, Anomalofusus-_____._--._. 30

Page

subturritus, Rhombopsis. B8 

sudensis, Vanikoropsis. . 22

Summary of Pierre Shale gastropod fauna in

the western interior. . 8 

Systematic descriptions . 10

T

tarrantensis, Aporrhais 19

Tejon Formation of California..---- --- - 28

tejonensis, Tritonium (Trachytriton)...-. ... 28 

Tennessee, Coon Creek, McNairy County,

Ripley Formation_____ 24

Exogyra cancellata zone... 12

Ripley Formation. - 29,36

Upper Exogyra cancellata zone.------- 24

tennesseensis, Serrifusus 29

tenuttineatus, Closteriscus.. ................. 7

terebreformis, Graphidula. .. .- - 31 

Terry Sandstone Member of Pierre Shale of

Colorado.._ -- 5

Tessarolax.................................. 12

texanus, Drepanochilus 12

Texas, Kemp Clay. 12

Woodbine Formation. ... ...... 28

tippana, Aporrhais (Pterocerella)-......... 19

Tonnacea..... 28

Tornatellaea sp... 5

toumeyana, Natica.................... 22

Trachytriton.................................. 2,28

attanticum........................--..--.- 28

holmdelense.......................... .. 28

multivaricosum................-. -- 28

vinculum............. -. 4, 5,7,8, 28; pi. 6

(Trachytriton) tejonensis, Tritonium- 28

travisensis, Aporrhais...... 19

Trichotropidae ._ 23

Tritonium cretaceum 24

(Trachytriton) tejonensis............. 28

Trochacea . 10

Trochidae..------ ------------------------ 9,10

TulochUus . -- 12

Tundora.. 12

Tunisia..... . - 12

tuomeyana, Vanikoropsis......... 8,22; pi. 5

Turritella. .......... 9

U 

utahensis, Lunatia.................... - 25

vancouverensis, Serrifusus dakotensis..... 29

Vanikoridae 9,22

Vanikoro--.-- -- 22 

ambigtia............. 23

cancellata ........................ 22,23; pi. 5

kttiani.............. 22

lygata 22,23; pl.5

propingua.-..------- - 22

pulchella..- 22

sp.. 22

Vanikoropsis-.-.. 8,9,22

havdeni 5,8,23

nebrascensis. . 8,22,23,25; pis. 5,6

sudensis... --- 22

tuomeyana.-..-- . 8,22; pi. 5 

Vasidae ---- ---- - - 33

vinculum, Buccinum - 28

Trachytriton 4,5,7,8,2S; pi. 6

Viviparus -- - - 25 

Volutoderma clatworthyi... - 5

W

Wasta-Sage Creek__ - - 7 

Western interior, Cretaceous gastropods-. 2 

wieseri, Anisomyon.. 37 

Woodbine Formation of Texas 28
B46 INDEX

Page

Wyoming, distribution of gastropod species in 

members of Pierre Shale, Red 

Bird section..____________________ B3,4

Niobrara County, Fox Hills Sandstone.-. 30 

Kara Bentonite Member of Pierre

Shale, Red Bird section. _______ 3,4

Pierre Shale, Red Bird section...,__ 4, 11 

Red Bird Silty Member.--.-.---- 3,4,29

X

Xenophora leprosa.. 

sp.. 

Zone:

Baculites baculus.-___.. -_--__ B4,

7,9,11,15,16,22,23,24,28,30,34,35

clinolobatus---.......-.---...-. 5,11,16,28

compressus.....______ 7,10,11,15,16,17,

18,20, 22,23,24,25,28,32,33,34,35,40 

cuneatus-.....-____.__-_-_- - 7,18

eliasi ................ .. . 4,16,24

gilberti ......................... 3,4,21,40

grandis... . . 4,15,28,30,35,36

Zone Continued Page 

Baculites baculus Continued

-___.-...-- B4,18,19,29,38,40

 - 5,11,15,23,24,33,34,39,40 

perplexus.-----....................... 28,38

reesidei.......... 4,5, 7,11,16,18,33,34,39,40

scotti ............................. 4,29,32

Didymocras nebrascense..-.............. 4,29,32

stevensoni.....---------- 4,11,18,19,28,32,34

Drepanochilus cheyennense................ 7

Exiteloceras jennyi.. ..__.. 4,5,11,18,19,30,32,33

Exogyr a cancellata..................... ... 12,24
PLATES 1-11
PLATE 1

FIGUBES 1-11. Atira! nebrascensis (Meek and Hayden) (p. BIO).

1. Oblique apical view of a specimen (X 10) that shows the flattened subsutural shelf of the early whorls. Pierre

Shale, Didymoceras stevensoni zone, Red Bird section, Wyoming. USGS D-1939, USNM 132983. 

2-4. Back, top, and basal views of a para type (X 5) from the Pierre Shale near Glendive, Mont. Baculites baculus 

zone, USNM 132951.

5. Back view of a specimen (X 5) showing an early stage of sculpture development. Pierre Shale, Didymoceras 

stevensoni zone, Red Bird section, Wyoming. USGS D-1940, USNM 132668.

6. Apical view of a specimen CX 5) from the same locality. USGS D-1940, USNM 132669. 

7-10. Back, base, apertural, and top views of a specimen (X 5) from the same locality. USGS D-1940, USNM 

132670.

11. Basal view of a specimen (X 5) from the Pierre Shale, Baculites baculus zone? near Glendive, Mont. USNM

132950. 

12-19. Euspira obliquata (Hall and Meek) (p. B25).

12. 13. Back and front views of the holotype (X 4) of Natica concinna Hall and Meek (1854, pi. 3, fig. 2) from the 

Pierre Shale, Baculites gregoryensis or B. scotti zones at the Great Bend of the Missouri River, South Dakota. 

AMNH 9364/1.

14, 15. Apertural and profile views of a syntype (X 2) of Natica moreauensis Meek and Hayden (1856, p. 64), 

from the Fox Hills Sandstone on the Moreau River, South Dakota. USNM 132970.

16. Back view of a specimen (X 2) from the Pierre Shale, (Baculites baculus zone), Red Bird section, Wyoming. 

USGS D-1985, USNM 132708.

17. Back view of a specimen (X 2) from the Pierre Shale (Baculites grandis zone), Red Bird section, Wyoming. 

USGS D-1967, USNM 132709.

18. 19. Apertural and back views of the holotype (X 2) from the Pierre Shale (Baculites gregoryensis or B. scotti

zones) at the Great Bend of the Missouri River, South Dakota. AMNH 9465/1. 

20-21. Euspiraf dakotensis Henderson (p. B27). Back and front views of the holotype (X 2) figured by Meek (1876,

pi. 32, figs. 12a-c) as Lunatia occidentalis. Fox Hills Sandstone, Moreau River, South Dakota. USNM 290. 

22-26. Lunatia subcrassa (Meek and Hayden).

22. Apertural view of a specimen (X 2) inserted for comparison from the Timber Lake Member of the Fox Hills 

Sandstone, SEMSEM sec 14, T. 21 N., R. 24 E., Corson County, S. Dak. USGS 27490, USNM 132712.

23. 26. Apertural and back views (X 2) of a specimen from same locality. USGS 27490, USNM 132711.

24. 25. Back and apertural views of a specimen (X 2) from the same locality. USGS 27490, USNM 132714.
GEOLOGICAL SURVEY

X10

PROFESSIONAL PAPER 393-B PLATE 1

ATIRAS!, EUSPIRA, EUSPIRA1, AND LUNATIA
PLATE 2

FIGURES 1-5. Aporrhais pespelecani (Linne) (p. B20).

1. Apertural view of an immature specimen (X 4) enlarged to show development of sculpture. USNM Div. 

Mollusks 187819.

2. 3. Apertural and back views of a specimen (XI) from the same locality. 

4, 5. Apertural and back views of a specimen (XI) from the same locality. 

6, 7. Aporrhais n. sp. (p. B21). Back and front views (X 2) of a specimen from the Pierre Shale (Baculites gilberti

zone), Red Bird section, Wyoming. USGS 1877, USNM 132672. 

8-18. Aporrhais biangulata Meek and Hayden (p. B20).

8, 9. Apertural and back views of the holotype (X 4) of Anchural parva (Meek and Hayden) figured by Meek, 

(1876, pi. 19, figs. 4a, b). Pierre Shale (Baculites baculus zone) near Glendive, Mont. USNM 284.

10. Back view of a specimen (X 3) from the Pierre Shale (Baculites baculus zone) of the Cedar Creek anticline, 

Montana. USNM 132698.

11. Back view of aparatype (X 3) from the Pierre Shale (Baculites baculus zone) near Glendive, Mont. USNM 

132965.

12. Back view of a specimen (X 3) from the Pierre Shale (Baculites baculus zone) of the Cedar Creek anticline, 

Montana. USNM 132699.

13. Back view of a specimen (X 3) from near top of Pierre Shale, Little Beaver Creek about 5 miles southwest of 

Marmarth, N. Dak. USGS 5976, USNM 132684.

14. Back view of a specimen (X 3) from the Pierre Shale (Baculites baculus zone) of the Cedar Creek anticline, 

Montana. USNM 132704.

15. Back view of the holotype (X 3) from the Pierre Shale (Baculites baculus zone?) near Glendive, Mont. USNM 

275.

16. Apertural view of a paratype (X 3) from the Pierre Shale (Baculites baculus zone) near Glendive, Mont. 

USNM 132967.

17. Apertural view of a paratype (X 3) from the same locality. USNM 132964.

18. Back view of a specimen (X 3) from the Pierre Shale (Baculites baculus zone) of the Cedar Creek anticline, 

Montana. USNM 132696.
GEOLOGICAL SURVEY PROFESSIONAL PAPER 393-B PLATE 2

17

APORRHAIS
PLATE 3

FIGURES 1-9. Drepanochilus nebrascensis (Evans and Shumard) (p. B17).

1. Back view of a specimen (X 2) from the Pierre Shale (Baculites compressus zone) Cheyenne River, 1-1.5 miles 

north of mouth of Sage Creek, Pennington County, S. Dak. USGS 23072, USNM 132963.

2. Back view of a specimen (X 2) from the same locality. USGS 23072, USNM 132679.

3. Apertural view of a specimen (X 2) from the same locality, showing initiation of the two spiral carinae of the 

body whorl. USGS 23072, USNM 132695.

4. View of an incomplete specimen (X 2) from the same locality, showing the groove on the interior of the outer 

lip spike and the smooth nature of the anterior-lateral lip ridge. USGS 23072, USNM 132693.

5. Back view of a specimen (X 2) from the same locality, showing relation of the grooves of the interior of the 

outer lip to the external body whorl carinations. USGS 23072, USNM 132697.

6. Back view of a specimen (X 2) from the same locality. USGS 23072, USNM 132681.

7. Back view of the specimen (X 2) figured by Meek (1876, pi. 19, fig. 5) from "Crow Creek near Black Hills 

from the upper beds of the Fort Pierre Group" (p. 327). Reference of this specimen to D. nebrascensis is 

dubious. USNM 288.

8. View of a surface (X 4) showing both the early whorl sculpture and concentration of specimens in concretions 

from the same locality as fig. 1. USGS 23072, USNM 132678.

9. Back view of a specimen (X 2) from the Pierre Shale (Exiteloceras jenneyi zone), Red Bird section, Wyoming.

USGS D-1947, USNM 132705. 

10-21. Drepanochilus evansi Cossmann (p. B13).

10. Apertural view of an immature specimen (X 8) from the Fox Hills Sandstone at Eagle Butte, Dewey County, 

S. Dak., USGS 29199, USNM 132690.

11. Apertural view of an immature specimen (X 4) from the same locality. USGS 29199, USNM 132688.

12. Back view of an immature specimen (X 4) showing the cancellate sculpture of the second teleoconch whorl, 

Fox Hills Sandstone, Trail City Member, 6 miles south-southeast of Bullhead, Corson County, S. Dak. USGS 

23513, USNM 132683.

13. 14. Back view of two specimens (X 2) from the Pierre Shale (Baculites baculus zone) of the Glendive area 

that show suppression of the body whorl carinations. USGS 3496, USNM 156341, 156342.

15. Back view of an incomplete specimen (X 2) from the Pierre Shale (Baculites grandis zone), Red Bird section, 

Wyoming. USGS D-1985, USNM 132680.

16. Back view of the holotype (X 2) of Aporrhais sublevis Meek and Hayden from the Pierre Shale (Baculites 

baculus zone) near Glendive, Mont. USNM 276.

17. Back view of a specimen (X 2) from the Trail City Member, Fox Hills Sandstone, 6 miles south-southeast 

of Bullhead, SE%, sec. 15, T. 20 N., R. 25 E. Corson County, S. Dak. USGS 23513, USNM 132952.

18. 19. Front and back views of the two specimens (X 2) figured by Meek (1876, pi. 32, figs. 8a, 8b), Fox Hills 

Sandstone of South Dakota. USNM 274.

20. Back view of an incomplete specimen (X 2) from the Pierre Shale (Baculites grandis zone), Red Bird section, 

Wyoming, that shows suppressed body carinations. USGS D-1985, USNM 132692.

21. Back view of a specimen (X 2) from the Trail City Member of the Fox Hills Sandstone, Whitehorse Ridge, 

sec. 20, T. 16 N., R. 26 E., Dewey County, S. Dak. USGS 27491, USNM 132685.
GEOLOGICAL SURVEY PROFESSIONAL PAPER 393-B PLATE 3

-N

X2

DREPANOCHIL US
PLATE 4

FIGURES 1-5, 10, 12. Astandes densatus Wade (p. B24).

I, 2. Back and front views of a specimen (X 3) from the Pierre Shale (Baculites baculus zone), Cedar

Creek anticline, Montana. TJSNM 132969. 

3, 4. Back and front views of a specimen (X 3) from the .Pierre Shale (Baculites baculus zone), Red Bird

section, Wyoming. USGS D-1984, USNM 132929. 

5. Back view of a specimen (X 3) from the Pierre Shale (Baculites baculus zone), 20 miles southwest of

Mingusville, Mont. USNM 22970. 

10. Front view of a specimen (X 3) from the Pierre Shale (Baculites baculus zone) of the Red Bird section,

Wyoming. USGS D-1981, USNM 132928. 

12. Back view of the holotype (X 3) from the Ripley Formation on Coon Creek, McNairy County, Tenn.

USNM 32944. 

6-9, 11, 16. Drepanochilus pusillus (Stanton) (p. B14).

6. Back view of a paratype (X 3) from the Cannonball Member of the Fort Union Formation, figured by 

Stanton (1921, pi. 6, fig. 15) as Anchura (Drepanochilus) americana var. pusilla. USNM 32427.

7. Back view of the holotype (X 2) from the same locality. USGS 8477, USNM 32427.

8. 9. Back views of a specimen (X 2) from the Cannonball Member of the Fort Union Formation, east 

bank of Missouri River, 1 mile above Harmony, N. Dak. Views show early sculpture and noding of 

the carination. USGS 16011, USNM 132953.

II. Back view of a specimen (X 2) from the same locality. USGS 16011, USNM 132687.

16. Back view of an immature specimen (X 8) showing the character of the nuclear whorls and the initiation

of teleoconch sculpture. Specimen from same locality. USGS 16011, USNM 132691. 

13, 14, 17-24. Drepanochilus scotti Sohl, n.sp. (p. B15).

13. Back view of a paratype (X 2) from the Pierre Shale (Baculites eliasi zone), Boulder County, Colo. 

USGS D-335, USNM 132957.

14. Back view of a specimen (X 4) from the Pierre Shale (Baculites eliasi zone), south bank of reservoir 

No. 3, sec. 19, T. 9 N., R. 68 W., Larimer County, Colo. USGS 16093, USNM 132694.

17. Back view of an immature specimen (X 4) from the same locality. USGS 16093, USNM 132954.

18. Back view of a paratype (X 2) from the Pierre Shale (Baculites eliasi zone), Boulder County, Colo. 

USGS D-335, USNM 132960.

19. Back view of a paratype (X 2) from the same locality. USGS D-335, USNM 132682.

20. Apertural view of a paratype (X 2) from the same locality. USGS D-335, USNM 132962.

21. Back view of the holotype (X 2) from the same locality. USGS D-335, USNM 132958.

22. Apertural view of a paratype (X 2) from the Pierre Shale (Baculites eliasi zone), Larimer County, 

Colo. USGS 16093, USNM 132686.

23. Apertural view of a paratype (X 2) from the Pierre Shale (Baculites eliasi zone), Boulder County, Colo. 

USGS D-335, USNM 132959.

24. Back view of an internal mold (X 2) from the Pierre Shale (Baculites reesidei zone, upper part), Red

Bird section, Wyoming. USGS D-1952, USNM 132689. 

15, 25-31. Drepanochilus obesus Sohl, n. sp. (p. B18).

15. Back view of a specimen (X 4) from the Pierre Shale (Didymoceras nebrascense zone), NWMNWJ^, 

sec. 10, T. 20 S., R. 64 W., Pueblo County, Colo. USGS D-3935, USNM 132702.

25. Back view of a specimen (X 2) from the Pierre Shale (Baculites scotti zone), NW^NW^t, sec. 19, T. 

7 S., R. 68 W., Douglas County, Colo. USGS D-392, USNM 132703.

26. Back view of a specimen (X 2) from the Pierre Shale (Baculites scotti zone), east side of Baculite Mesa 

Road, NE%SE& sec. 16, T. 20 S., R. 64 W., Pueblo County, Colo. USGS D-1517, USNM 132700.

27. Back view of an immature specimen (X 3) from the Pierre Shale (Baculites scotti zone), NE%NE%, 

sec. 19, T. 7 N., R. 68 W., Kassler quadrangle, Colorado. USGS 22840, USNM 132701.

28. Back view of the holotype (X 2) from the Pierre Shale (Baculites gregoryensis zone), Red Bird section, 

Wyoming. USGS D-1917, USNM 132642.

29. Back view of a specimen (X 3) from the Pierre Shale (Baculites scotti zone), 1.5 miles north of Kassler, 

Jefferson County, Colo. USGS D-148, USNM 132675.

30. Back view of a specimen (X 2) figured by Whitfield (1880, pi. 12, fig. 2), from the Pierre Shale East 

Fork of Beaver Creek, 3 miles west of Camp Jenny, Black Hills, S. Dak. USNM 12309.

31. Back view of a specimen (X 2) figured by Whitfield (1880, pi. 12, fig. 3) from the same locality. USNM 

12309.
GEOLOGICAL SURVEY PROFESSIONAL PAPER 393-B PLATE 4

X2

27 X3 28 X2 

ASTANDES AND DREPANOCHILUS
PLATE 5

FIGURES 1, 5-10, 12, 14, 17. Vanikoropsis nebrascensis (Meek and Hayden) (p. B22).

1, 8. Front and back views of a specimen (X 3) from the Pierre Shale (probably the Baculites baculus

zone), Glendive area, Montana. USNM 19068. 

5, 6. Back and front views of the holotype (X 3) of Natica? ambigua Meek and Hayden (1856)

(=Fossar nebrascensis Meek and Hayden, 1860). From the Pierre Shale (Baculites baculus zone)

near Glendive, Mont. USNM 267. 

7. Apertural view of a specimen (X 3) from the Fox Hills Sandstone, Trail City Member, breaks of a

small tributary of the Grand River, SWM, sec. 14, T. 20 N., R. 25 E., Corson County, S. Dak.

USGS 27487, USNM 132664. 

9, 10. Front and back views of a paratype (X 3) from the Pierre Shale (Baculites baculus zone) near

Glendive, Mont. USNM 132967. 

12. Oblique apical view of a rubber mold (X 3) from the Pierre Shale (Baculites baculus zone), Iron

Bluff on Yellowstone River, 8 or 9 miles above Glendive, Mont. USGS 3896, USNM 132666. 

14,17. Apertural and back view of a specimen (X 3) showing the thickness of the shell. Fox Hills

Sandstone, SEM, sec. 31, T. 20 N., R. 25 E., Standing Rock Reservation, S. Dak. USGS 35925,

USNM 132665.

2-4. Vanikoro cancettata Lamarck (p. B23). Apertural, back, and apical views of a specimen (X 3), a recent 

shell from Vanikoro Island, Santa Cruz Islands, Southwest Pacific Ocean. USNM Div. Mollusks 

217209. 

11,13. Vanikoro lygata Recluz (p. B23). Back and apertural views of a specimen (X 3) from Osima, Osumi,

Japan. USNM Div. Mollusks 343593.

15, 16. Vanikoropsis tuomeyana (Meek and Hayden) (p. B22). Apertural and apical views of the incomplete 

holotype (X 3) from "mouth of the Judith River * * * at the horizon of the top of the Fox Hills group," 

Montana (Meek, 1876, p. 332).
GEOLOGICAL SURVEY PROFESSIONAL PAPER 393-B PLATE 6

X3

17

15

VANIKOROPSIS AND VANIKORO
PLATE 6

FIGURES 1-4, 11. Vanikoropsis nebrascensis (Meek and Hayden) (p. B22).

1. Back view of a specimen (X 3) from the Pierre Shale (Baculites baculus zone), Iron Bluff, Yellowstone 

River, 8 or 9 miles above Glendive, Mont. USGS 3895, USNM 132667.

2. 3. Back and front views of a specimen (X 3) from the Pierre Shale (Baculites baculus zone), Red Bird 

section, Wyoming. USGS D-1983, USNM 132963.

4. 11. Front and back views of a paratype (X 3) from the Pierre Shale (Baculites baculus zone) near Glendive, Mont. USNM 132967. 

5-9. Fasciolaria buccinoides Meek and Hayden (p. B29).

5. 9. Apertural view of an internal mold and rubber impression of the external mold of a specimen (X 3) 

from the Fox Hills Sandstone, Trail City Member, 1.5 miles north-northwest of White Horse Lake, 

Dewey County, S. Dak. Note pustules on parietal lip. USGS 27485, USNM 132677.

6. Front view of an incomplete paratype (X 2) that shows the placement of the columellar plications. 

Fox Hills Sandstone, Moreau River, South Dakota. USNM 132972.

7. 8. Front and back views of the holotype (X 2) from the Fox Hills Sandstone, Moreau River, South

Dakota, USNM 272. 

10, 14-17. Trachytriton vinculum (Hall and Meek) (p. B28).

10. Front view of an internal mold (XI) from the Pierre Shale (Baculites gregoryensis or B. scotti zone)

of the Great Bend of the Missouri River, South Dakota. USNM 132984.

14. Back view of a specimen (XI) from the Pierre Shale (Baculites scotti zone), Red Bird section, Wyoming. 

USGS D-1926, USNM 132645.

15. Back view of a specimen (XI) from the Pierre Shale (Baculites gregoryensis zone), Red Bird section, 

Wyoming. USGS D-1904, USNM 132644.

16. Front view of the specimen (XI) figured by Meek (1876, pi. 19, fig. 7b.) Pierre Shale (Baculites 

gregoryensis or B. scotti zone), Great Bend of the Missouri River, South Dakota. USNM 132985.

17. Back view of a specimen (X 1) figured by Meek (1876, pi. 19, fig. 7a), from the same locality. USNM

261. 

12, 13, 18-21. Serrifusus dakotensis (Meek and Hayden)? (p. B30).

12. Front view of a paratype (XI) from the Fox Hills Sandstone, Moreau River, South Dakota. USNM 

132971.

13. Back view of a specimen (X 1) from the Fox Hills Sandstone, Niobrara County, Wyo. USNM 32150. 

18, 19. Back and front views of the holotype (X 1) from the Fox Hills Sandstone, Moreau River, South

Dakota. USNM 256. 

20, 21. Back and front views of a specimen (X 1) from the Pierre Shale (Baculites baculus zone), Red Bird

section, Wyoming. USGS D-1982, USNM 132643.
GEOLOGICAL SURVEY PROFESSIONAL PAPER 393-B PLATE 6

VANIKOROPSIS, FASCIOLARIA, TRACHYTRITON, AND SERRIFUSUS
PLATE 7

FIGURES 1-3, 8. Bullopsis cretacea Conrad (p. B35, B36).

1. Back view of a topotype (X 2) from the Owl Creek Formation, Tippah County, Miss. USGS 594, 

USNM 20438.

2. 3. Apertural and apical views of a specimen (X 4) from the Owl Creek Formation of Tippah County,

Miss. USGS 25422, USNM 130624.

8. Back view of a topotype (X 2) from the same locality as fig. 1. USGS 707, USNM 130622. 

4-6. Bullopsis n. sp. (p. B36). Apical, apertural, and back views of a specimen (X 3) from the Pierre Shale

(Baculites grandis zone), Red Bird section, Wyoming. USGS D-1985, USNM 132661. 

7, 9-14. Ellipsoscapha occidentalis (Meek and Hayden) (p. B35).

7, 11. Front and apical views of the lectotype (X 4) figured by Meek (1876, pi. 18, fig. 12a, b?). Pierre 

Shale (Baculites baculus zone) near Glendive, Mont. USNM 132652.

9. Back view of a syntype (X 4) from the same locality. USNM 132975.

10. Front view of a specimen (X 4) from the Pierre Shale (Baculites .baculus zone), Red Bird section, 

Wyoming. USGS D-1983, USNM 132653.

12. Back view of a specimen (X 4) from the same locality. USGS D-1983, USNM 132654.

13. 14. Front and back views of a specimen (X 3) from the Pierre Shale (Baculites grandis zone), Red

Bird section, Wyoming. USGS D-1985, USNM 132671. 

15-19. Cryptorhytis cheyennensis (Meek and Hayden) (p. B33).

15. Back view of an internal mold (XI) from the Pierre Shale (Baculites reesidei zone), Red Bird section, 

Wyoming. USGS D-1952, USNM 132921.

16. 17. Front and back views of a specimen (XI) from the Pierre Shale (Exiteloceras jenneyi zone), Red

Bird section, Wyoming. USGS D-1945, USNM 132922. 

18, 19. Back and front views of a specimen (X 1) figured by Meek (1876, pi. 19, fig. 13) from the Pierre

Shale (Baculites compressus zone), Sage Creek, South Dakota. USNM 289. 

20. Anomalofusust sp. (p. B30). Back view of a rubber mold (X 3) from the Pierre Shale (Exiteloceras jenneyi

zone), Red Bird section, Niobrara County, Wyo. USGS D-1948, USNM 132927. 

21-24, 29-31. Graphidula culbertsoni (Meek and Hayden) (p. B31).

21. Back view of a specimen (X 1) from the Fox Hills Sandstone, Trail City Member, 1.5 miles northnorthwest of White Horse Lake, Dewey County, S.Dak. USGS 27485, USNM 132650.

22. Back view of the holotype (X IK) from the Fox Hills Sandstone, Moreau River, South Dakota. 

USNM 258.

23. Back view of a specimen (X 1) from the Pierre Shale (Baculites baculus zone), Red Bird section, 

Wyoming. USGS D-1985, USNM 132647.

24. Front view of a paratype (XI) from the Fox Hills Sandstone figured by Meek (1876, pi. 32, fig. le). 

USNM 132973.

29. Front view of a specimen (XI) from the Fox Hills Sandstone, Trail City Member, Grand River, 

0.4 mile west of Bullhead, Corson County, S.Dak. USGS 27484, USNM 132648.

30. Back view of a specimen (X 1> from the Fox Hills Sandstone, Trail City Member, White Horse Ridge, 

NWK sec. 20, T. 16 N., R. 26 E., Dewey County, S.Dak. USGS 27491, USNM 132649.

31. Back view of a specimen (X 1) from the same locality. USGS 27491, USNM 132651. 

25-28, 32. Graphidula cf. G. atteni (White) (p. B32).

25. View of a rubber mold of a specimen (X 2) from the Pierre Shale (Didymoceras stevensoni zone), Red 

Bird section, Wyoming. USGS D-1939, USNM 132707.

26. View of an incomplete specimen (X 2) from the same locality. USGS D-1940, USNM 132674.

27. Apertural view of a specimen (X 2) from the same locality. (Internal mold belonging to specimen 

from which mold in fig. 25 was made.) USGS D-1940, USNM 132707.

28. View of a fragmentary specimen (X 2) from the same locality. USGS D-1940, USNM 132673.

32. Apertural view of an incomplete specimen (X \Vz) from the Pierre Shale (Didymoceras nebrascense

zone), 2 miles north of Kassler, Jefferson County, Colo. USGS D-284, USNM 132974.

33, 34. Graphidula atteni (White) (p. B32). Back and front views of the holotype (X 1) from "Cretaceous strata, 

valley of the Yellowstone River, Montana" (White, 1880, p. 35). USNM 8046.
GEOLOGICAL SURVEY PROFESSIONAL PAPER 393-B PLATE 7

29

BULLOPSIS, ELLIPSOSCAPHA, CRYPTORHYTIS, ANOMALOFUSUS1, AND GRAPHIDULA
PLATE 8

FIGURES 1, 2. Nonacteonina attenuate, (Meek and Hayden)? (p. B33).

1. Back view of an incomplete internal mold (X 3) from the Pierre Shale (Didymoceras stevensoni zone), the Red 

Bird section, Wyoming. USGS D-1940, USNM 132676.

2. Back view of the incomplete holotype (X 3) from the Pierre Shale (Baculites baculus zone) near Glendive,

Mont. USNM 285. 

3-6. Oligoptycha concinna (Hall and Meek) (p. B34) .

3. Apertural view of the holotype (X 6) from the Pierre Shale (Baculites compressus zone?) on Sage Creek, South 

Dakota. AMNH 7471/1.

4. 5. Apertural and back views of a specimen (X 6) figured by Popenoe (1957, pi. 50, fig. 3) from the Fox Hills 

Sandstone near Wakpala, South Dakota. USGS 5954, USNM 129866.

6. Back view of a specimen (X 6) from the Pierre Shale (Baculites baculus zone), Red Bird section, Wyoming

USGS D-1978, USNM 132662. 

7-16. Anisomyon borealis (Morton) (p. B37).

7. 8. Apical and left views of a specimen (X IK) from the Pierre Shale at the Great Bend of the Missouri River,

South Dakota. A syntype of Helcion carinatus Meek and Hayden. USNM 132977. 

9, 10, 12, 13, 15. Left side, right side, apical, and front views of a specimen (X IK) from the Pierre Shale about

2 miles northeast of Harper Station, Wyo. Note muscle-scar pattern. USGS 1723, USNM 28586. 

11, 14. Right side and apical views of a specimen (X IK) from the Pierre Shale on divide between Skull and

Beaver Creeks, 8 miles northwest of Newcastle, Wyo. USGS 11191, USNM 132706. 

16. Apical view of a specimen (X IK) from the Pierre Shale (Baculites gregoryensis zone), Red Bird section,

Wyoming. USGS D-1910, USNM 132655.
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NONACTEONINA, OLIGOPTYCHA, AND ANISOMYON
PLATE 9

FIQUEES 1, 2. Anisomyon centrale Meek (p. B38). Apical and right-side views of the specimen (X l>i>) mentioned by White

(1879, p. 303), as from the Pierre Shale on "Box Elder Creek, Colorado." USNM 132659. 

3-11. Anisomyon borealis (Morton) (p. B37).

3, 4, 8. Left side, right side, and apical views of a syntype (X 1J4) of Helcion carinatus, figured by Meek (1876, 

pi. 18, figs. 9a-c), Pierre Shale (Baculites gregoryensis zone?), Great Bend of the Missouri River, South Dakota. 

USNM 132976.

5. Apical view of a specimen (X l>i>) from the Pierre Shale, 1 mile northwest of Spencer Siding on divide between 

headwaters of Blacktail Creek and Stockade Beaver Creek, Wyoming. USGS 13876, USNM 132657.

6. Apical view of a specimen (X !/ £) from the Pierre Shale (Exiteloceras jenneyi zone), Red Bird section, Wyoming. 

USGS D-1948, USNM 132656.

7. 9. Apical and left side views of a syntype (X !}£) of Helcion carinatus from the Pierre Shale (Baculites gregoryensis or B. scotti zones), Great Bend of the Missouri, South Dakota. USNM 132978. 

10, 11. Apical and left side views (X 1%) from the Pierre Shale (Exiteloceras jenneyi zone), Red Bird section, 

Wyoming. USGS D-1947, USNM 132658.
GEOLOGICAL SURVEY PROFESSIONAL PAPER 393-B PLATE 9
PLATE 10

FIGURES 1-15. Anisomyon centrale Meek (p. B38).

1-3. Apical, anterior, and left side views of the lectotype (X l/^) figured by White (1879, pi. 9, figs, la, b) from the

Pierre Shale, Box Elder Creek, Colorado. USNM 12430. 

4, 5, 6. Apical and anterior views of a syntype (X 1J4) figured by White (1879, pi. 9, figs, c, d) from the Pierre Shale,

Box Elder Creek, Colorado. USNM 132979. 

7, 8,10-12. Right side, apical, left side, back, and front views of a specimen (X 1H) from the Pierre Shale (Baculites

jenseni zone), one-half mile east of Horse Creek, Laramie County, Wyo. USGS D-1382, USNM 132715. 

9. Left side view of a specimen (X !/ £) from the Pierre Shale (Baculites reesidei zone), 0.8-0.2 mile south of Round

Butte, Larimer County, Colo. USGS D-372, USNM 132926.

13. Right side view of a specimen (X l/>0 from the Pierre Shale (Baculites reesidei zone), Round Butte, Larimer 

County, Colo. USGS 16217, USNM 132716.

14. 15. Left side and apical views of a specimen (X l/-^) from the Pierre Shale (Baculites reesidei zone), Red Bird 

section, Wyoming. USGS D-1952, USNM 132660.
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ANISOMYON

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PLATE 11

FIGURES 1-7, 9. Anisomyon centrale Meek (p. B38) .

1, 2. Apical and right side views of a specimen (X lM) from the Pierre Shale (Baculites reesidei zone), 0.2-0.8

mile south of Round Butte, Larimer County, Colo. USGS D-372, USNM 132925. 

3, 4. Right side and apical views of a specimen (X l/^) from the Pierre Shale (Baculites reesidei zone), Round

Butte, Larimer County, Colo. USGS 16217, USNM 132713. 

5, 6, 7. Apical, left, and right side views of a specimen (X 1H) from the Larimer Sandstone Member of the

Pierre Shale (Baculites reesidei zone), NE%NW}4 , sec. 1, T. 8 N., R. 69 W., Larimer County, Colo. USGS

D-2819, USNM 132710. 

8, 10-17. Anisomyon patelliformis Meek and Hayden (p. B40).

8. Apical view of a specimen (X lYz) figured by Whitfield (1880, pi. 12, figs. 17, 18) from the Pierre Shale

(probably the Baculites baculus zone) on Old Woman Fork, Wyoming. Note muscle-scar crossing behind

apex. USNM 12268. 

10, 11. Right-side and apical views of a paratype (X 1J4) from the Pierre Shale (Baculites baculus zone) near

Glendive, Mont. USNM 132981. 

12, 13, 16. Left side, right side, and apical views of a paratype (X 1H) showing well-developed muscle scars.

Locality same as above. USNM 132980.

14. 17. Left side and apical views of a specimen (X 1J4) from the Pierre Shale (Baculites baculus zone), Red 

Bird section, Wyoming. USGS D-2116, USNM 132982.

15. Apical view of the holotype (X 1M) from the Pierre Shale (Baculites baculus zone) near Glendive, Mont. 

USNM 246.

U.S. GOVERNMENT PRINTING OFFICE: 1966 O 223-1 1 2
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ANISOMYON