Fresh-Water Mollusks 

of Cretaceous Age From 

Montana and Wyoming

GEOLOGICAL SURVEY PROFESSIONAL PAPER 233-A
Fresh-Water Mollusks 

of Cretaceous Age From 

Montana and Wyomin

By TENG-CHIEN YEN

SHORTER CONTRIBUTIONS TO GENERAL GEOLOGY, 1950, PAGES 1-20

GEOLOGICAL SURVEY PROFESSIONAL PAPER 233-A

Part I: A fluviatile fauna from the Kootenai

formation near Harlowton, Montana 

Part 2: An Upper Cretaceous fauna from the

Leeds Creek • area, Lincoln County',

Wyoming

UNITED STATES GOVERNMENT PRINTING OFFICE, WASHINGTON : 1951
UNITED STATES DEPARTMENT OF THE INTERIOR

Oscar L. Chapman, Secretary

GEOLOGICAL SURVEY

W. E. Wrather, Director

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

Washington 25, D. C. - Price 45 cents (paper cover)
CONTENTS

Page

Part 1. A fluviatile fauna from the Kootenai formation near Harlowton, Montana. _ 1

Abstract- ______________________________________________________________ 1

Introduction ___________________________________________________________ 1

Composition of the fauna, and its origin.._________________________________ 1

Stratigraphic position and correlations_______________________________---___ 2

Systematic descriptions.__________________________________________________ 4

Bibliography. __________________________________________________________ 9

Part 2. An Upper Cretaceous fauna from the Leeds Creek area, Lincoln County,

Wyoming_________________________________________________________ 11

Abstract.__________________-_________________________-____:__-_-_---___ 11

Introduction ___________________________________________________________ 11

Review of previous records___.._______-___-__-____________-_--______---___ 11

Composition of the faunas.______________________________________________ 11

Stratigraphic positions_________________________________________________ 13

Systematic descriptions of the molluscan species.______ _ _________________ 14

Bibliography._ _________________________________________________________ 17

Index..._________________________________________________________________ 19

ILLUSTRATIONS

Plate 1. Fossil and recent fresh-water mollusks._______________________ Following index

2. Upper Cretaceous nonmarine mollusks_-___-_--_____________ Following index

ni

FRESH-WATER MOLLUSKS OF CRETACEOUS AGE FROM 

MONTANA AND WYOMING l

By TENG-CHIEN YEN

PART 1. A FLUVIATILE FAUNA FROM THE KOOTENAI FORMATION NEAR

HARLOWTON, MONTANA

ABSTRACT

The paper presents a fresh-water molluscan assemblage found 

in the Kootenai formation southeast of Harlowton, Montana, 

which indicates that the enclosing bed is of fluviatile origin. 

Molluscan faunas from contemporary beds, such as the Cloverly 

formation of central Wyoming and the Peterson limestone in the 

Gannett group of western Wyoming, are compared with it. An 

account of 29 species of pelecypods and gastropods is given, of 

which 4 genera and 8 species of gastropods are herein described 

as new.

INTRODUCTION

It is nearly half a century since the invertebrate 

fauna of the Kootenai formation near Harlowton, 

Montana, was first described by T. W. Stanton. Dr. 

Stanton's paper (1903) was based on a collection made 

by members of the Geology Department of Princeton 

University, and in it he described the following species 

of fresh-water mollusks:

Unio ja/rri Stanton

Unio douglassi Stanton

Campeloma harlowtonensis Stanton

Viviparus montanensis Stanton

Goniobasis? ortmani Stanton

Goniobasis? silberlingi Stanton

On the evidence of these few species, Dr. Stanton concluded at this initial stage of geological exploration of 

the area, that the fossil-bearing bed is "certainly not 

older than Lower Cretaceous." The conclusion was 

significant as the recognition of a new assemblage, still 

acceptable as the standard Lower Cretaceous fresh 

water molluscan fauna in North America.

The fossiliferous bed is exposed in the SW% sec. 27, 

T. 7N.,K. 16E., about 12 miles southeast of Harlowton, about 6 miles southwest of Winnicook, and about 

\% miles northwest of the old Widdecomb Kanch. The 

bed is well exposed over a few hundred square feet at 

the top of a low foothill of the West Dome of the

i A contribution from a research project (NR-081-097) supported by the Geophysics 

Branch, Office of Naval Research, Department of Navy. It is carried on under 

ONE Contract N9-onr-92601 with the Smithsonian Institution, Washington, D. C., 

and is published by permission of the Secretary of the Smithsonian Institution.

Shawmut anticline, on the west side of a trail leading 

to the abandoned ranch.

After publication of Dr. Stanton's report, several 

additional collections were made at this locality. They, 

plus certain species from the Cloverly formation and 

the Peterson limestone of Wyoming, are the basis of the 

present paper.

COMPOSITION OF THE FAUNA, AND ITS ORIGIN

The fossiliferous bed, which consists of coarse-grained, 

shaly sandstone and nodular limestone of rusty color, 

yielded the following species of mollusks in addition to 

some ostracodes and teeth of fish and reptiles:

Pelecypoda

Family Unionidae

Protelliptio douglassi Stanton

Unio farri Stanton

U. natosini McLearn 

Family Sphaeridae

Eupera onestae (McLearn)' 

Gastropoda

Family Neritidae

Mesoneritina nebrascensis (Meek and Hayden) 

Family Amnicolidae

Reesidella montanaensis (Stanton), n. gen.

Stantonogyra silberlingi (Stanton)

Mesochilina cretacea, n. gen and sp. 

Family Viviparidae

Campeloma harlowtonensis Stanton 

Family Pleuroceratidae

Circamelania ortmanni (Stanton), n. gen. 

Family Physidae

Physa montanensis, n. sp.

P. sp. undet. A 

Family Planorbidae

Gyraulus cf. G. veternus (Meek and Hayden)

Carinulorbis sp. undet.

The molluscan fauna is rich in variety as well as in 

individuals. The prosobranchian gastropods include 

six species represented by many specimens, but the 

pulmonates yield only four species, each represented by 

only a few individuals.

The fauna seems to indicate that the enclosing bed 

was of fluviatile origin and that molluscan species

1
FRESH-WATER MOLLUSKS FROM MONTANA AND WYOMING

from the upper course of a river were drifted by floods 

and gathered in a "pocket," where they were preserved. 

A strikingly similar Recent molluscan assemblage was 

collected from silt at a high-flood level at the Great 

Falls of the Potomac River, near Washington, D. C. 

The similarity is emphasized when the faunas are listed 

in parallel columns:

Kootenai bed near Harlowton

Protelliptio douglassi (common)

Unio farri (rare) 

Unio natosini (rare) 

Eupera onestae (common)

Mesoneritina nebrascensis

(rare) 

Reesidella montanaensis

(abundant) 

Stantonogyra silberlingi

(rare)

Mesochilina cretacea (rare) 

Campeloma harlowtonensis

(rare)

Circamelania 

(abundant)

ortmanni

Great Falls of the Potomac 

River 2

Elliptic complanatus (common)

Sphaerium stamineum 

(abundant)

Amnicola limosa (common)

Amnicola decisa (rare) 

Gillia altilis (common)

Campeloma decisum (rare)

Lioplax subcarinatus (common)

Goniobasis virginica (abundant)

Anculosa carinata (common)

Physa heterostropha (rare)

Physa montanensis (rare) 

Physa sp. undet. A (rare) 

Gyraulus cf. G. veternus

(rare) 

Carinulorbis sp. undet. ___________________________

(rare)

However remote it may be, the possibility that the 

Kootenai formation is lacustrine should be considered. 

A few molluscan species similar to those in the assemblage found at the Great Falls are also obtainable in 

lakes, especially in large ones connected with streams. 

In such lakes the assemblage of species is generally 

different, however, for there are generally more species 

of pulmonates and more shallow-water forms, and the 

fluviatile species, if any, may be represented by few 

individuals. A convincing example is an assemblage 

drifted to the shore of Bear Lake, Idaho and Utah, 

which includes the following molluscan species:

Sphaeriidae

Sphaerium pilsbryanum Sterki (common) 

Pisidium compressum Prime (abundant)

Valvatidae

Valvata utahensis Call (common)

Valvata humeralis californica Pilsbry (common)

2 The collection was made by Dr. John B. Reeside, Jr., of United States Geological 

Survey in October 1946 from pockets of sand on bare metamorphic rocks near Great 

Falls of Potomac River. The dead shells were probably brought in from the -upper 

course of the River at high flood and preserved with silt and sand in crevices and 

pockets. In addition to the fresh-water mollusks, the collection contains eight species 

of terrestrial snails.

Amnicolidae

Amnicola longinqua Gould (abundant) 

Fluminicola fusca (Haldeman) (common)

Physidae

Physa ampullacea Gould (rare) 

Physa sp. undet. (common)

Lymnaeidae

Lymnaea utahensis Call (abundant) 

Lymnaea palustris buttoni Baker (common)

Planorbidae

Gyraulus vermicularis (Gould) (rare) 

Helisoma subcrenatum (Cooper) (rare) 

Carinifex newberryi (Lea) (abundant)

The similarity in composition of the Kootenai fauna 

to that of the deposit near the Great Falls of the 

Potomac River, in addition to suggesting a fluviatile 

origin for the Kootenai formation, may possibly also 

imply a general similarity of the water body, in which 

the Kootenai formation was deposited, in movements, 

depth, and volume of the water, permanency and size 

of the river, and constituents of soil and climate of the 

area. However, the abundance of rissoid snails, 

together with planorbid species, in the Kootenai formation may indicate that a more luxuriant aquatic vegetation along the extinct river favored such gastropods.

The faunal lists indicate only relative abundance and 

the species listed are not to be taken as completely 

representative of the existing fauna. Likewise, it is 

known that, although planorbid species have been found 

in some parts of the Potomac River they are not represented in the collection made at the Great Falls. This 

incompleteness suggests that the assemblage has come 

together from parts of the river where planorbids are 

rare or wanting and the other species are abundant.

STRATIGRAPHIC POSITION AND CORRELATIONS

It is generally accepted now that the Kootenai formation in Montana is of Early Cretaceous age. On the 

evidence of the molluscan species, part of these beds 

may be correlated with the Cleverly formation in 

Wyoming and part with the Peterson limestone of the 

Gannett group in Wyoming and Idaho. The precise 

position of these beds in the Lower Cretaceous is not 

definitely known, for it is generally recognized merely 

that they occur below the Upper Cretaceous and above 

the Upper Jurassic. Therefore, a detailed comparison 

of their molluscan faunas is of interest. (See table, p. 3.)

As differing contemporary faunal facies are generally 

incompletely represented by fossil assemblages at most 

times in geologic history, it is difficult to correlate contemporary beds with maximum accuracy on the basis of 

the fossil assemblages that may have been derived from 

several facies. It has been mentioned that the Kootenai
FLUVIATILE FAUNA FROM KOOTENAI FORMATION IN MONTANA

formation near Harlowton contains a drifted assemblage 

of fluviatile origin. The molluscan species of the 

Cleverly formation near Sage Dome, Wyoming (Yen, 

1946) may also imply a fluviatile origin for the enclosing 

rocks. Those of the Cleverly formation near Bacon 

Ridge in the Jackson -Hole area, Wyoming, seem, 

however, to belong to a lenitic assemblage, in water 

4 to 5 feet or less in depth. Such an assemblage is 

commonly found on the shore of a lake or in a partly 

enclosed bay where the water is relatively quiet and 

aquatic vegetation is abundant. The Peterson limestone considered here is probably of lacustrine origin, 

possibly representing a quiet littoral zone some distance 

from the shore, where the water is deeper and there is 

less vegetation.

The differences in the molluscan assemblages of the 

four localities shown in the table below are obviously 

due to the differences in habitat conditions represented. 

In most cases a drifted assemblage contains a greater 

number of varieties, because it is gathered from various 

parts of a water body. Accordingly, 6 out of 14 species, 

or nearly 43 percent from the Kootenai formation

mentioned above, were not found in the other three 

localities. On the other hand the differences in the list 

of forms contained in the Cleverly formation at the two 

localities seems to be partly due to difference in the 

habitat conditions represented. The congeneric forms 

of the two are closely related and difficulty in establishing specific identification is in part due to imperfect 

preservation. Allowance must be made for that factor. 

However, it seems significant that the Peterson limestone contains 3 out of 11 species, or about 27 percent, 

which have not been found in the other three beds. 

Reesidellaf lanistoides has been found only in the 

Peterson limestone, and Mesocochliopa cretacea and 

Zaptychius cf. Z. cylindricus are closely related to species 

of the Morrison formation (Late Jurassic). Such differences may well indicate a difference in age.

The faunal similarities revealed by the table below 

suggest that part of the Peterson limestone may be 

older and part contemporaneous with the Cleverly 

formation, and that part of the Cleverly formation 

may be contemporaneous and part slightly older than 

the Kootenai formation in Montana.

Mollusca in Lower Cretaceous deposits at four localities 

[x indicates identical forms; r indicates related forms]

Protelliptio douglassi.. .... . ____ •. ________ _ _ __ ___ _ ___ _____

natosini. . . ______________ _______ _ ___ ____ ___________

Eupera onestae.. . . . .. __ ____ ____ _____ ___ __ _, ________

Rubeyella carinata... . __ ____________ __ _ ______ __ ____ _ __

cylindricus.... ... .. ____ ___ _______ _ ___________________

Mesochilina cretacea ... ____ __ _________ __ ___ ___ _______ _______

montanensis ..... _______ _________ _ _ ________ __ ____ __

sp. undet. A. ..._____ _ _ _ ___ ___ ____ _ __ _ ______________

Aplexa sp. undet _ ____ _ _ _ _ _ _________ __ _ ___ ____ ____

Gyraulus cf. G. veternus. . . .... . . ________ ___ _ _ _ ______ __

cretacea.... _ _ _ __ ____ ___ _____ ____________ __ _ ________

Kootenai 

formation 

near 

Harlowton

X

X

X

X

X

X

X

Cleverly 

formation 

in Sage 

Dome

X

X

X

X

X

X

X

X

r

X

r

X

Cleverly 

formation 

near 

Jackson 

Hole

r

r

r

X

X

X

X

X

Peterson 

limestone 

near 

Cokeville

r

r

r

X

X

r

X

r
FRESH-WATER MOLLTJSKS FROM MONTANA AND WYOMING 

SYSTEMATIC DESCRIPTIONS Family SPHAERIIDAE

Class PEIECYPODA 

Family UNIONIDAE 

Protelliptio douglassi (Stanton)

Plate 1, figure 1

/

Unio douglassi Stanton Am. Philos. Soe., Proe., vol. 42, p. 195, 

pi. 4, fig. 3, 4, 1903.

This species and its varieties are commonly found in 

the Lower Cretaceous of Montana, Wyoming, and 

Nevada. Commonly it is found in association with 

Unio farri Stanton, Eupera onestae (McLearn) and a 

number of gastropods, as shown on the accompanying 

table.

It is characterized by its ovately oblong outline of 

shell, moderate convexity of both valves, and markedly 

distinct concentric ribs on the umbonal region. The 

number and degree of development of these concentric 

ribs seem to be varied, but the biological or stratigraphic 

significance of such variation is unknown.

Figured specimen: U. S. Nat. Mus. 106606.

Sulcatapex cretaceus Yen

Sulcatapex cretaceus Yen, Aead. Nat. Sei. Philadelphia Notulae 

naturae, no. 166, p. 6, figs. 2, 2a-c, 1946.

This species is known only from the Cloverly formation at the south end of the Sage Creek dome, Fremont 

County, Wyoming. Specimens representing another 

species of the genus have been found in Lower 

Cretaceous beds exposed north of Pryor, Montana.

Unio farri Stanton

Unio farri Stanton, Am. Philos. Soe. Proe., vol. 42, p. 194, pi. 4, 

fig. 1, 2, 1903.

This species has generally been found with Protelliptio douglassi (Stanton), but it is easily distinguished 

by its subovate outline, smaller size, and lack of concentric ribs on its umbonal area.

Unio natosini Mclearn 

Plate 1, figure 2

Unio natosini MeLearn, Nat. Mus. Canada Bull. 58, p. 73, pi. 13, 

fig. 7-9, 1929.

The illustrated specimen was found in the Kootenai 

formation, about 12 miles southeast of Harlowton. 

The species has also been found north of Pryor, Montana, but it seems to be less abundant than P. douglassi.

The species was described on immature and imperfectly preserved specimens. The illustrated specimen 

is about 71 mm. long and 40 mm. high. One of the 

examples in the type lot was given by McLearn as 

"length 50 mm., height 35 mm."

Figured specimen: U.S.N.M. 106772.

Eupera onestae (Mclearn)

Corbula? onestae MeLearn, Nat. Mus. Canada Bull. 58, p. 75,

pi. 14, fig. 1-4, 1929.

Eupera onestae, Yen, Aead. Nat. Sei. Philadelphia Notulae 

Naturae, no. 166, p. 7, fig. 4a-f, 1946.

This species is abundant in most of the Lower Cretaceous beds in Montana and Wyoming. It is generally 

found in association with Protelliptio douglassi, Unio 

farri, and Campeloma harlowtonensis, possibly preferring to live on muddy bottom.

Class GASTROPODA

Family NERITIDAE

Mesoneritina nebrascensis (Meek and Hayden)

Plate 1, figure 3

Mesoneritina nebrascensis Yen, Aead. Nat. Sei. Philadelphia 

Notulae Naturae, no. 166, p. 9, fig. 5, 1946.

The specimen figured here is somewhat compressed 

by distortion and it appears to be more elongated in 

outline than is normal but it agrees well with the 

species, originally described from the "head of Wind 

River," Wyo.

The species has been recorded from Lower Cretaceous 

beds at several localities. Several almost perfectly preserved specimens were collected southeast of Dillon, 

Montana.

Figured specimen: U.S.N.M. 106607.

Family VIVIPARIDAE

Campeloma harlowtonensis Stanton

Plate 1, figure 4

Campeloma harlowtonensis Stanton, Am. Philos. Soe. Proe. 42, 

p. 196, pi. 4, fig. 11, 12, 1903.

This is a well-characterized species of Campeloma. 

The specimen figured here is in a collection made by 

Dr. Stanton from the type locality. The apex and 

outer lip are restored in the illustration.

This species, or a closely related form, has been 

recorded at various horizons of the Lower Cretaceous. 

It differs from Campeloma macrospira Meek, from the 

Bear River formation of Upper Cretaceous age, by its 

larger size in about same number of whorls, broader 

outline of shell, and less convex whorls.

Figured specimen: U.S.N.M. 30158.

Lioplacodes cretaceus (Stanton)

Lioplacodes cretaceus (Stanton). Yen, Aead. Nat. Sei. Philadelphia 

Notulae Naturae, no. 166, p. 11, fig. 10, 1946.

This species is more abundant in the "Gastropod 

limestone" of southwestern Montana, occupying a 

higher stratigraphic position than in the Kootenai 

formation exposed near Harlowton.
FLUVIATILE FAUNA FROM KOOTENAI FORMATION EST MONTANA

Lioplacodes convexiculus Ten

Lioplacodes convexiculus Yen, Acad. Nat. Sci. Philadelphia 

Notulae Naturae, no. 166, p. 11, fig. 9, 9b, 1946.

This species occurs more commonly in the "Gastropod 

limestone." It was also found at a locality southeast 

of Dillon, Montana that has yielded a molluscan fauna 

very similar to that of the Kootenai formation near 

Harlowton.

Rubeyella Ten, n. gen.

SheU imperforate or narrowly perforate, melanoid in 

outline, having a turritid spire and somewhat dilated 

body whorl. Whorls rapidly increasing in size, strongly 

convex and carinated along the periphery. Aperture 

angulately ovate in outline, peristomal margin thin, 

more or less continuous, and parietal wall well defined.

Genotype: Rubeyella carinata Yen

The genus superficially resembles Cassiopella White, 

but it differs distinctly by the absence of a well exposed 

and deep umbilicus and by its less turritid outline. It 

resembles Lioplacodes Meek and Hayden more closely, 

but is readily distinguished from that genus in its 

strong primary and secondary carinae and its adnate 

aperture.

Rubeyella carinata Ten, n. sp.

Plate 1, figure 5

Shell imperforate, broadly melanoid in outline, having 

a highly turritid spire and obliquely dilated body 

whorl. Whorls increasing in size, coiling below the 

periphery and strongly convex; surface with a strong 

peripheral carina traceable to early whorls and occasionally with secondary carinae on the later and body 

whorls. Aperture adnate, angulately subovate in outline; peristomal margin thin and continuous, angulated 

on outer lip; parietal wall thin and well defined; columellar margin short and more or less appressed on 

basal part of body whorl.

Measurements of holotype: 20.0 mm. in altitude of 

sheh1 , 10.0 mm. in width; 9.0 in height of aperture, 6.4 

in width; Q% whorls.

The holotype and a number of free specimens were 

obtained at a locality about 13 miles south of Dillon, in 

the west branch of Small Horn Canyon, Montana, 

together with a number of other species that are in 

common with the Kootenai formation near Harlowton, 

Montana. The species also occurs in the Peterson limestone, in which, however, the shells are preserved as 

replacements of crystaUine calcite in a hard, impure 

limestone matrix and are not extractable.

Holotype: U.S.N.M. 106608; paratypes: U.S.N.M. 

106609.

Family AMNICOIIDAE 

Protamnicola naticoides Ten

Protamnicola naticoides Yen, Acad. Nat. Sci. Philadelphia 

Notulae Naturae, no. 166, p. 9, fig. 6, 1946.

This species is characterized by its almost globose 

outline, well-thickened inner lip, and gibbous body 

whorl. The height of spire is somewhat varied, but 

the spire is never much elevated.

Charydrobia cretacea Ten

Charydrobia cretacea Yen, Acad. Nat. Sci. Philadelphia Notulae 

Naturae, no. 166, p. 10, fig. 8, 1946.

This species is characterized by its ovately oblong 

outline of shell, tapering toward the apex, gently or 

scarcely convex whorls, and obtusely angulated periphery of the body whorl.

Wenz considered Charydrobia Stache a synonym of 

Pseudamnicola Paulucci but it sems desirable to retain 

this genus to include the more or less elongated species 

of rissoid gastropods that existed during Cretaceous 

time.

Mesocochliopa cretacea Ten, n. sp. 

Plate 1, figures 6a-c

Shell subglobose in outline, having an elevated spire 

and dilated body whorl. Whorls about 5, increasing 

moderately rapidly in size; surface shouldered and very 

convex. Suture well impressed. Aperture descending, 

ovate in outline; outer lip and parietal margin thin; 

columellar lip bearing a distinct plica, the plica lying 

horizontally near the upper extremity of the columella. 

Umbilicus well exposed, deep, about % of the diameter 

of the shell.

Measurements of holotype: 2.3 mm. in altitude of 

shell; 2.1 mm. in width; 1.2 mm. in height of aperture, 

0.9 mm. in width; diameter of umbilicus 0.76; about 

5 whorls.

This species has been found both in the Cleverly 

formation and in the Peterson limestone. The type 

lot was collected from NW^SW^ sec. 13, T. 40 N., 

R. Ill W., Teton County, Wyoming.

The species is weh1 differentiated from Mesocochliopa, 

assiminoides Yen and Reeside (1946) by the more 

globose outline of the shell, shouldered whorls, and 

wider umbilicus.

The genus Mesocochliopa was described on the basis 

of three specimens collected from the Morrison formation exposed near Lower Green River Lake, Wyoming. 

The aperture of the genotype is not well preserved and 

the internal tooth is hardly traceable. As the Lower 

Cretaceous species is characterized by a distinct tooth
FRESH-WATER MOLLUSKS FROM MONTANA AND WYOMING

at the columellar margin, the generic description should 

be revised to include the internal plicae or lamellae as 

a morphological character of the genus.

Holotype: U.S.N.M. 106610; paratypes: U.S.N.M. 

106611.

Stantonogyra silberlingi (Stanton)

Stantonogyra silberlingi Yen, Acad. Nat. Sci. Philadelphia 

Notulae Naturae, no. 166, p. 10, fig. 7, 1946.

This species is rare in the Kootenai formation near 

Harlowton, Montana (type locality), but it is rather 

common in the Cleverly formation near Sage Creek 

dome, Wyoming. This is the only 1 of the 6 species 

described by Dr. Stanton from the type locality that 

are not represented in more recent collections from the 

same bed.

Reesidella Ten, new genus

Shell imperforate, subovate to globose in outline, 

rather stout, large among commonly known rissoid 

snails. It has a more or less elevated spire and ventricose body whorl. Whorls rapidly increasing in size, 

distinctly shouldered, and very convex on surface. 

Aperture pyriform in outline, peristome continuous and 

well thickened, outer lip expanding and slightly reflected, parietal wall appressed to the preceding whorl. 

Columellar margin short and slightly oblique. Operculum pyriform in outline, thick and of calcareous 

substance; whorls concentric on the external side, and 

spiral in the young stages and concentric in the more 

mature stages on the inner side; nucleus subcentral and 

close to the inner margin.

The new genus has an operculum similar to that of 

Bulimus Scopoli (=Bithynia Leach), but it differs by 

its pyriform outline and fewer concentric whorls on the 

external side. The shell differs by its larger size, distinct shoulder of the whorls, and expanding outer lip 

margin. Superficially it resembles the rissoid genera 

Somatopyrus Gill and Fluminicola Stimpson, but differs 

from both in opercular and in shell features. The shell 

outline closely resembles that of Parabithynia Pilsbry 

(for example P. humerosa v. Martens), operculum 

differs markedly.

This genus resembles in some degree Turbinicola 

Ammandale and Prashad, of the Ampullariidae, but it 

differs by its smaller imperforate shell, and by the 

broader outline of the operculum with fewer concentric 

whorls on the external side.

The known morphological features of shell and 

operculum, the new genus seems to be more closely 

related to genera of the Amnicolidae rather than for the 

Viviparidae and Ampullariidae.

Amnicola gilloides Yen and Reeside, Ampullaria? 

powelli Walcott, and similar species should be included 

in this genus, as they bear precisely the same type of

operculum and in some shell features resemble R. montanaensis.

Reesidella montanaensis (Stanton)

Plate 1, figures 7a-f

Viviparus montanaensis Stanton, Am. Philos. Soc. Proc., vol. 42, 

p. 195, pi. 4, fig. 5, 1903.

This species is abundant in the Kootenai formation 

12 miles southeast of Harlowton, and occurs in the 

Cloverly formation and the Peterson limestone in 

Montana and Wyoming.

Some of the well-preserved specimens distinctly show 

two colored bands on the body whorl, and a few specimens have their opercula preserved in natural position.

Figured specimens: U.S.N.M. 106612, 106613.

Reesidella? lanistoides Yen, n. sp. 

Plate 1, figure 8

Shell sinistral, median in size, with elevated spire and 

laterally dilated body whorl. Whorls 4 to 5, moderately 

rapidly increasing in size, having the surface roundly 

convex and slightly shouldered. Aperture descending, 

ovate in outline; peristome more or less continuous.

Measurements of the holotype: 12.0 mm. in altitude 

of shell, 9.0 mm. in height; 7.0 mm. in height of aperture, 5.0 mm. in width.

The type lot contains 6 specimens, collected in the 

Peterson limestone at the center of NE# sec. 8, T. 29 

N., R. 118 W., Lincoln County, Wyoming. The species 

has also been found in the lower part of the Peterson 

limestone on both sides of Lander-Cutoff road in SWK 

sec. 15, T. 29 N., R. 118 W., Lincoln County, Wyoming.

The poorly preserved specimens in the type lot reveal 

only a general outline of the shell and the shape of 

aperture in cross-section. However, these features 

seem to be characteristic enough to indicate a distinct 

species. It is provisionally assigned to Reesidella 

because the outline of the shell is similar in reverse to 

that of R. montanaensis. The calcite replacement of 

the shell in hard limestone matrix makes it impossible 

to separate them. No free specimen has been obtained, 

and definite settlement of the generic status must be 

deferred until better preserved specimens are available.

Holotype: U.S.N.M. 106614; paratypes: U.S.N.M. 

106615.

Family PLEUROCERATIDAE 

Circamelania Yen, new genus

Shell narrowly perforate or imperforate, moderate in 

size; a few gently or strongly convex whorls, with sculptured or smooth surface and well-impressed suture. 

Aperture subovate in outline; peristome continuous, 

more or less thickened, and slightly notched on basal 

margin.

Genotype: Goniobasis? ortmanni Stanton.
FLUVIATILE FAUNA FROM KOOTENAI FORMATION IN MONTANA

Circamelania differs from Goniobasis by its more 

roundly convex whorls, deeply impressed suture, and 

especially by the well-thickened peristomal margin. 

The apertural features and smaller number of whorls 

also differentiate this Lower Cretaceous genus from 

other Pleurocera-like genera, to which Circamelania 

may be an ancestral group.

Circamelania ortmanni (Stanton) 

Plate 1, figures 9a-c

Goniobasis? ortmanni Stanton, Am. Phil. Soc. Proc., vol. 42, 

p. 197, pi. 4, fig. 7-10, 1903.

This species is so far known only from the Kootenai 

formation near Harlowton, Mont., but it is very 

abundant there and numerous free specimens may be 

obtained. As Dr. Stanton has already remarked, the 

species includes both smooth and sculptured forms, as 

does the living species, Goniobasis virginica Gmelin.

Figured specimens: U.S.N.M. 106616.

Family EIIOBHDAE

Zaptychius tetonensis Yen, n. sp.

Plate 1, figures lOa, b

Shell imperforate, narrowly oblong in outline, having 

a high spire and a rather compressed body whorl. 

Whorls scarcely convex and slightly shouldered below 

the upper suture, increasing rapidly in size. The surface bears sharp-margined, lamella-like ribs with fine 

but distinct rib lines on their interspaces. Aperture 

narrowly elongate in outline, descending, slightly produced at the base, peristome continuous, outer lip 

margin thin and reflected, inner lip thin and bearing 

two well-developed, oblique plicae near the upper 

extremity of the columellar margin.

A score of specimens contained in the type lot was 

collected from a bed in the Cleverly formation exposed 

in the NW^SWX sec. 13, T. 40 N., R. Ill W., 

Teton County, Wyo. Most specimens are broken 

but each has the last 3 to 4 whorls preserved and 

they have sufficient characteristic features to distinguish the species. It resembles closely Zaptychius 

carbonaria Walcott, from the Lower Cretaceous near 

Eureka, Nev., but it differs by having conspicuous 

lamella-like ribs on the less convex whorls, and it is 

much smaller. It differs from Tortacella haldemani 

White, from the early Upper Cretaceous near Cokeville, 

Wyo., by its larger size, expanding peristomal margin 

and the presence of well developed lamella-like ribs on 

the whorls.

After examining the available specimens, it seems 

certain that Tortacella White, 1895, is a synonym of 

Zaptychius Walcott, 1883. The genus may be closely 

related to Pleurolimnaea Meek, 1866, which was 

described from early Tertiary beds in Montana.

Holotype: U.S.N.M. 106617; paratypes: U.S.N.M. 

106618.

Zaptychius cylindricus Yen, n. sp. 

Plate 1, figure 11

Shell slender and cylindrical, having a high spire and 

a compressed body whorl. Whorls are slightly convex 

and increasing rapidly in size; the surface bears fine 

but distinct rib lines extending from suture to suture. 

Aperture narrowly oblong, wider towards the base; 

peristome continuous, simple, and thin, slightly produced at the basal margin, and more or less twisted 

at the columella.

The holotype measures 4.0 mm. in altitude of shell, 

1.0 mm. in width; 1.5 mm. in height of aperture, 0.8 

mm. in width; 5 whorls.

Numerous specimens in the type lot were found in 

the same bed as Zaptychius tetonensis n. sp., but Z. 

cylindricus n. sp. is much smaller, and lacks the lamellalike ribs and columellar plicae.

Holotype: U.S.N.M. 106619; paratypes: U.S.N.M. 

106620.

Mesochilina Yen, new genus

Shell small, imperforate, more or less ovate in outline, 

having a moderately-elevated spire and somewhat 

dilated body whorl. Whorls increase in size, are 

slightly convex, and bear costulate lines of growth and 

incised spiral sculpture. Aperture ovately oblong; 

peristome more or less continuous, slightly produced 

at the base; parietal wall well defined, eolumella short 

and bears an oblique plica-like fold.

Genotype: Mesochilina cretacea, n. sp.

The new genus resembles Chilina Gray, of which 

about 30 species have been described from the Recent 

fauna in Argentina, Chile, and Brazil. It differs from 

this living genus by its much smaller size, its axial fold 

or plica, and its distinct sculpture of axial ribs and 

spiral lines.

Mesochilina cretacea Yen, n. sp. 

Plate 1, figure 12

Shell subovate in outline, having a conically elevated 

spire and narrowly dilated body whorl, the former about 

same in height as the latter. Whorls increasing moderately rapidly in size, gently convex and bearing close, 

costulate lines of growth, and sparse but incised lines of 

spiral. Aperture narrowly ovate in outline, peristome 

continuous and bearing an oblique columellar fold or 

plica.

Holotype measures 3.0 mm. in altitude of shell, 1.6 

mm. in width; 1.4 mm. in height of aperture, 1.1 mm. 

in width; about 4 whorls.

The type lot was collected in the Kootenai formation 

12 miles southeast of Harlowton, Mont.

Holotype: U.S.N.M. 106621; paratype: U.S.N.M. 

106622.
8 FRESH-WATER MOLLUSKS FROM MONTANA AND WYOMING

Family PHYSIDAE

Physa cf. P. walcotti Yen and Reeside 

Physa prisca Walcott, Science, vol. 2, p. 808, 1883 (non Noulet

1854).

Physa walcotti Yen and Reeside, Jour. Paleontology, vol. 20, p. 

57, fig. 10, 1946; Yen, Acad. Nat. Sci. Philadelphia Notulae 

Naturae, no. 166, p. 13, fig. 13, 1946.

Several imperfectly preserved specimens from the 

Cleverly formation in NWtfSWK sec. 13, T. 40 N., E. 

Ill W., Teton County, Wyo., resemble closely the 

form recorded from the Cloverly at the Sage Creek 

dome, Wyoming. Specimens from both localities resemble P. walcotti from the Lower Cretaceous of the 

Eureka, Nev., area, but are smaller and have a 

lower spire. They may represent a young stage of the 

species.

Physa montanensis Yen, n. sp. 

Plate 1, figure 13

Shell large, ovately globose in outline, with an elevated spire and inflated body whorl; the spire is slightly 

smaller than the body whorl. Whorls roundly convex, 

slightly shouldered, and rapidly increasing in size. 

Aperture subovate in outline and slightly twisted at 

columella.

The holotype measures 22.5 mm. in altitude of shell, 

14.0 mm. in width; 15.2 in height of aperture, 7.2 in 

width. Last 4 whorls preserved by apical part broken.

This species is characterized by its ovately globose 

outline, rather prominent spire, large size of shell, and 

rather narrow aperture. It resembles some Tertiary 

species of the genus, such as Physa bridgerensis Meek, 

but it is smaller, narrower in lateral outline, has a prominent spire and a less inflated body whorl.

The holotype and paratype were collected in the 

Kootenai formation from the same bed near Harlowton, 

Mont., but they were obtained in different collections.

Holotype: U.S.N.M. 106773; paratype: U.S.N.M. 

106623.

Physa sp. undet. A 

Plate 1, figure 14

Two imperfectly preserved examples were collected 

from the Kootenai formation near Harlowton, Mont., 

that appear to be of small" size with an exerted spire. 

They are decidedly different from Physa montanensis 

in their much smaller size and higher spire. The 

figured specimen measures 6. 8 mm. in altitude of shell, 

4.0 mm. in width, and has about 4% whorls.

Figured specimen: U.S.N.M. 106624.

Physa sp. undet. B

A single specimen was found in the Peterson limestone 

at the center of NEJi sec. 8, T. 29 N., E. 118 W., Lincoln 

County, Wyo. It differs from the preceding form by 

having a much lower spire and a rather dilated body 

whorl. The specimen is too poor to describe.

Aplexa sp. undet.

Several specimens were collected from the Cloverly 

formation in the NW%SW% sec. 13, T. 40 N., E. Ill 

W., Teton County, Wyo., but none of them is well 

preserved. In slender outline of shell, high spire, and 

nearly flat surface of the whorls, this species seems to 

belong to the genus Aplexa, but the specimens are too 

poor to permit a full description or specific identification.

Family PLANORBIDAE

Gyraulus cf. G. veternus (Meek and Hayden)

Plate 1, figure 15a-c

A score of poorly preserved undeterminable specimens 

were collected from the Kootenai formation 12 miles 

southeast of Harlowton, Mont. Eelated forms have 

been found in the Cloverly formation in Wyoming and 

the Peterson limestone near Cokeville, Wyo. It differs 

from Gyraulus veternus (which was described from the 

Morrison formation) by its smaller size of shell.

Figured specimen: U.S.N.M. 106625.

Carinulorbis sp. undet. 

Plate 1, figure 16a-c

One specimen belonging to this genus found in the 

Kootenai formation 12 miles southeast of Harlowton, 

Mont. It resembles in outline of shell Carinulorbis 

planospiralis (Yen), from the Fort Union beds (Paleocene) in Montana and Wyoming, but it differs by its 

much smaller size and slightly sunken spire. Better 

specimens are needed to establish its specific status.

Figured specimen: U.S.N.M. 106626.

Family LYMNAEIDAE 

Lymnaea sagensis Yen

Lymnaea sagensis Yen, Acad. Nat. Sci. Philadelphia Notulae 

Naturae, no. 166, p. 12, fig. 12, 1946.

This species has been so far recorded only from the 

type locality, namely in the Cloverly formation near 

the Sage Creek dome, Wyoming.

Lymnaea cretacea Yen, n. sp. 

Plate 1, figure 17

Shell, small, narrowly umbilicated, ovately oblong in 

outline, having an elevated spire and descending body 

whorl. The height of spire is about same as the height 

of the last whorl. Whorls gently convex, rapidly 

increasing in size and obtusely shouldered. The surface 

bears distinct but fine, close growth lines. Aperture 

ovate in outline, slightly oblique and reflected.

The holotype measures 3.3 mm. in altitude of shell, 

1.6 mm. in width; 1.7 mm." in height of aperture, 1.0 in 

width; about 4% whorls.

The species is characterized by its ovately oblong 

outline of shell, narrowly inflated and descending body 

whorl, and sculpture of growth lines. The type lot was
FLTJVIATILE FAUNA FROM KOOTENAI FORMATION IN MONTANA 9

collected from the Cleverly formation in the

sec. 13, T. 40 N., R. Ill W., Teton County, Wyo.

Holotype: U.S.N.M. 106627; paratypes: U.S.N.M. 

106628.

BIBLIOGRAPHY 

MACNEIL, F. STEARNS, 1939, Freshwater invertebrates and land

plants of Cretaceous age from Eureka, Nev.: Jour.

Paleontology, vol. 13, pp. 355-360, 1 pi. 

MANSFIELD, G. R., 1927, Geography, geology, and mineral

resources of part of southeastern Idaho: U. S. Geol. Survey

Prof. Paper 152. 

McLEAKN, F. H., 1929, Cretaceous invertebrates, in Mesozoic

paleontology of Blairmore region, Alberta: Nat. Mus.

Canada Bull. 58, pp. 73-79, 7 pis. 

PILSBKY, H. A., 1928, Parabithynia for Paranerita Ammandale

1920: Nautilus, vol. 41, p. 108.

STANTON, T. W., 1899, Mesozoic fossils of the Yellowstone 

- National Park: U. S. Geol. Survey Mon. 32, pt. 2, pp.

600-650. 

————, 1903, A new freshwater molluscan faunule from the

Cretaceous of Montana: Am. Philos. Soc. Proc., vol. 42,

pp. 188-199, 1 pi.

THIELE, Johannes, 1929-31, Handbuch der systematischen 

Weichtierkunde, Teil I-II.

WALCOTT, C. D., 1884, Paleontology of the Eureka district: 

U. S. Geol. Survey Mon. 8.

WHITE, C. A., 1877, Paleontological Papers, No. 2, Descriptions 

of new species of Unios and a new genus of freshwater 

gastropoda from the Tertiary strata of Wyoming and Utah: 

U. S. Geol. Geog. Survey Terr. Bull. 3, pp. 603-606.

————, 1895, The Bear River formation and its characteristic

fauna: U. S. Geol. Survey Bull. 128. 

YEN, T. C., 1946, On Lower Cretaceous freshwater mollusks of

Sage Creek, Wyo.: Acad. Nat. Sci. Philadelphia Notulae

Naturae no. 166.

————, 1948, Paleocene freshwater mollusks from southern 

Montana: U. S. Geol. Survey Prof. Paper 214-C.

————, 1949, Review of the Lower Cretaceous freshwater 

molluscan faunas of North America: Jour. Paleontology, 

vol. 23, pp. 465-470. 

-, 1949, A new name for Carinorbis Yen: Jour. Paleontology,

vol. 23, p. 573.

YEN, T. C., and REESIDE, J. B., Jr., 1946, Freshwater mollusks 

from the Morrison formation (Jurassic): Jour. Paleontology, 

vol. 20, pp. 52-58, 1 pi.

PART 2. AN UPPER CRETACEOUS NONMARINE MOLLUSCAN FAUNA FROM 

THE LEEDS CREEK AREA, LINCOLN COUNTY, WYOMING

ABSTRACT

This paper describes a nonmarine fauna from the lower part 

of a 6,000-foot unit formerly considered part of the Bear River 

formation. Sixteen species of gastropods are recognized. The 

new genus Melampoides and new species in Parateinostoma, 

Parhydrobia, Goniobasis, and Anisopsis are proposed. The 

fauna is interpreted to be a shallow- and still-water assemblage 

that characterizes the fresh-water extreme of a series of sediments deposited in waters ranging from fresh through brackish 

to marine.

INTRODUCTION

A nonmarine molluscan fauna was collected from a 

limestone bed exposed about two miles south of Antelope Creek, three miles south of Leeds Creek, and threefourths of a mile east of U. S. Highway SON, in sec. 17, 

T. 22 N., R. 119 W., Lincoln County, Wyoming. The 

fossil-bearing stratum is in the lower part of a 6,000-foot 

unit at present unnamed, but formerly considered part 

of the Bear River formation.

In studying the habitat conditions and age of the 

fossil zone, the closely related beds in the general area 

were examined in addition to those in the immediate 

vicinity of the present site. Eight exposures of fossilbearing beds are discussed: six (in the area 2 miles 

south of Antelope Creek), I designate Ll, L2, L3, L4, 

L5, and L6; one in the SE#SE% sec. 5, T. 22 N., R. 119 

W., near the Antelope Creek Coal mine, L7; one in the 

SE#SW# sec. 25, T. 28 N., R. 119 W., L8 (probably 

the one referred to by White (1895) as "20 miles north 

of Cokeville"). The present paper is based primarily 

on specimens from L5. With the exception of those 

from bed L8, fossils included in the present paper are 

recorded for the first time.

The present paper results from one of the collections 

made on a field trip in 1949. My heartfelt thanks are 

extended to Mr. W. W. Rubey of U. S. Geological 

Survey for his personal guidance in the field. His unreserved cooperation and his many years of field experience made this season indeed a success. I am 

equally grateful to Mr. John B. Reeside, Jr., also of 

U. S. Geological Survey, for the benefit of his personal 

discussion from time to time, his helpful advice, and 

keen interest in the work. I also appreciate highly 

their kindness in reading the manuscript of this paper, 

making constructive criticisms and providing much 

useful information.

REVIEW OF PREVIOUS RECORDS

The best Upper Cretaceous nonmarine faunas hi 

North America are those of the Bear River formation 

near the base of the series, those of the Fruitland, 

Judith River, and Belly River formations above the 

middle, and those of the Laramie and Lance formations 

at the top: Each is correlated with a marine sequence 

and each is characterized by a distinctive assemblage 

of molluscan species. Nonmarine forms have been 

reported from other horizons but are not well known. 

The Bear River species were described and recorded by 

Meek (1860; 1877) and White (1895); the Judith River 

species by Stanton and Hatcher (1905) and those of 

the Belly River chiefly by Whiteaves (1885); the Fruitland species by Stanton (1916); and the Lance species 

(= the Laramie, in the strict sense) chiefly by White 

(1877) and Whitfield (1903, 1907).

Comparable European nonmarine molluscan faunas 

from Upper Cretaceous strata were described for the 

Lignite beds hi southern France by Matheroh (1842), 

from the coal-bearing beds near Ajka in western 

Hungary by von Tausch (1886) and Oppenheim (1892), 

and from the St. Briz beds hi southern Steiermark by 

von Tausch (1888) and Hoernes (1888).

There are few nonmarine molluscan species from 

North American beds contemporary with the deposit 

here described which is evidently younger than the 

Bear River and very much older than the Fruitland 

and the Judith River.

COMPOSITION OF THE FAUNAS

Bed L5.—This bed is 1 to 2 feet in thickness and 

consists of a limestone containing much silt. Most of 

the fossils are silicified but a few have been replaced by 

calcite. The gastropods occupy a dominant position 

in the fauna and the following species were found:

Family Valvatidae

Valvata praecursoris (White) 

Family Neritidae

Mesoneritina naticiformis (White)

Mesoneritina stantoni (White) * 

Family Viviparidae

Lioplacodes stachei (White)

11
12 FRESH-WATER MOLLUSKS FROM MONTANA AND WYOMING

Family Amnicolidae

Parateinostoma altispirale, n. sp.

Parateinostoma convexum, n. sp.

Parateinostoma contractum, n. sp.

Parhydrobia cylindrica, n. sp. 

Family Pleuroceritidae

Goniobasis leedsensis, n. sp. 

Family Ellobiidae

Zaptychius cf. Z. haldemani (White)

Rhytophorus cf. R. meeki (White)

Melampoides clarki (White), n. gen. 

Family Planorbidae

Anisopsis minuta, n. sp. 

Family Physidae

Physa usitata (White)

Physa sp. undet.

Physa, sp. undet.

A few ostracodes and an abundance of stems and 

oogonia of Chara-like algae are associated with the 

gastropods.

The gastropod fauna is a rich and homogeneous one. 

Species of Valvata, Lioplacodes, Parateinostoma, Goniobasis, and Physa yield a large number of individuals, 

including many young, but specimens of Anisopsis are 

rare. The assemblage clearly indicates that the fossilbearing bed represents the original habitat in which the 

fauna lived.

Species of Valvata are known to live generally at the 

bottom of rivers or lakes, especially where submerged 

plants grow and reed swamp borders the banks. They 

inhabit both muddy and stony bottoms, but they 

usually are most prolific when the bottom is covered 

with stones and gravel, coated with algae. Lioplacodes, presumably a viviparous genus, may have lived 

like Viviparus, and if so, may have lived on both stony 

and muddy bottoms. Parateinostoma, also an extinct 

genus, may have lived much as the Amnicola-]ike snails 

live, in sheltered places in aquatic vegetation. The 

Physa-like species of today prefer to live in dense 

growths of submerged plants along the shore. None 

of the members of the present assemblage appear to 

be rheophilous, although some of them may be able to 

endure exposure to some current. The assemblage is a 

lenitic, or still-water, society.

Chara-like algae generally grow today in protected 

shoals, ponds, and in the borders of lakes at depths 

below the heavy reach of strong wave action. They 

prefer waters that flow from calcareous soils and often 

attach to a stony bottom. An abundance of such algae 

offers a favorable environment to such gastropods as 

Valvata, Parateinostoma, Zaptychius, and Physa.

The present assemblage of organic remains indicates 

that the fossil-bearing bed L5 represents a shore deposit 

where the water was relatively shallow and still, with 

abundant aquatic vegetation, of high concentration in

lime, in part muddy and in part somewhat sandy at the 

bottom.

Bed L4-—This bed lies approximately 100 feet above 

bed L5. The fossil content of bed L4 is exceedingly 

rich, almost rock-forming, but the fossils are very much 

distorted. Despite the poor state of preservation, the 

molluscan forms contained seem to indicate clearly that 

the bed was deposited in brackish water, perhaps approaching marine water in composition, and thus reveal 

a considerable change in habitat.

Bed Z$.—A bed about 60 feet stratigraphically above 

bed L4 is of fresh-water origin and consists of impure 

limestone that contains silt and chert. It has a rich 

content of fossils, but they are only superficially silicified, and imbedded in the cherty matrix. The follow 

ing gastropods were seen on the weathered surface:

Valvata cf. V. praecursoris (White)

Lioplacodes cf. L. stachei (White)

Parateinostoma sp. undet.

Hydrobia sp. undet.

Zaptychius sp. undet.

Anisopsis sp. undet.

Physa sp. undet.

Several species of Sphaerium- and Pisidium-like pelecypods, ostracodes, and oogonia of Chara-like algae are 

also found with the gastropods. Although fewer 

species are found in bed L3, the fauna is essentially like 

that of bed L5.

Bed L2.—This bed lies about 60 feel; above bed L3, 

consists of silty limestone of fine texture. Poorly preserved calcified specimens on the weathered surface 

indicate a fauna essentially like that of bed L3:

Lioplacodes sp. undet.

Hydrobia sp. undet.

Zaptychius sp. undet.

Anisopsis sp. undet.

Physa sp. undet.

Bed LI.—A bed of silty limestone that lies about 

10 feet above bed L2 is the uppermost unit considered 

here. It contains the following assemblage of molluscan genera in addition to minute, generically undeterminable gastropods, some ostracodes, and a few oogonia 

of Chara-like algae:

Unio sp. undet.

Unio sp. undet.

Lioplacodes sp. undet.

Micropyrgus! sp. undet.

Goniobasis! sp. undet.

Despite the poor preservation of the mollusks and 

their mode of occurrence the collection indicates clearly 

that the fauna is different from that of the beds below 

bed LI.
UPPER CRETACEOUS FAUNA, LEEDS CREEK AREA, WYOMING 13

Bed L6.—Bed L6 is about 280 feet below bed L5 stratigraphically. It consists of dark argillaceous and calcareous shales, and contains a rich molluscan fauna that 

indicates a brackish-water origin for the deposit, perhaps tending toward fresh water. Several of the 

species in bed L6 are found also in bed L8.

In summary, the faunas of beds L6 to Ll indicate 

fluctuating habitat conditions at the times of deposition. Bed L6, at the botton, is of brackish-water 

origin, tending toward fresh water, and the large 

variety of forms indicates a large water body. Bed Lo 

is of fresh water origin—possibly the sea retreated from 

the area and the water was freshened by discharge 

from inland; the area was large and the average depth 

perhaps not much more than 10 feet.

The fossil content of bed L4 indicates a considerable 

change, from fresh-water to brackish-water habitat. 

Perhaps the advancing sea covered a large deltalike 

area, where such molluscan species as Ostrea, Corbula, 

Glycymeris, Clarocerithium, and Cerithium-like genera 

were accumulated, possibly by tidal action. The invasion was apparently short-lived, as there was relatively prompt return to fresh-water deposition in later 

beds.

When the sea retreated, the water was again freshened, and beds L2 and L3 contain faunas that resemble 

but are less varied than that of bed L5.

Bed Ll yields a somewhat different fauna, but still 

one of fresh-water origin. The differences may indicate that the deposit represents a sublittoral zone 

possibly over 20 feet in depth, where vegetation was 

scanty except for some algae. Today, species of Unio 

are generally important members of the fauna in such 

an environment as they prefer a muddy —and vegetation-free bottom.

Bed L7.—This bed of fine-grained, silty limestone lies 

approximately 2 miles north and 160 feet higher stratigraphically than bed L5. The molluscan fauna includes the following species:

Unio sp. undet.

Unio sp. undet.

Valvata cf. V. praecursoris (White)

Lioplacodes cf. L. stachei (White)

Lioplacodes sp. undet.

Parateinostoma sp. undet.

Hydrobia sp. undet.

"Pachymelania" cf. "P." macilenta (White)

Zaptychius cf. Z. haldemani (White)

Physa sp. undet.

This deposit seems to be well correlated with bed Ll 

or L2, and both beds seem to be close in time. The 

slight difference in assemblage of molluscan species may 

indicate a difference in habitat conditions. The occurrence of two species of Unio, which is absent in bed L5, 

may imply a comparative dearth of vegetation, as the 

unionids generally prefer muddy bottoms more or less 

free of vegetation. The reduction in species of pulmonates may also indicate lesser growth of emergent 

plants. On the other hand, an increase of prosobranchian elements in proportion generally implies 

deeper water more favorable to these gastropods.

Bed L8.—This bed is exposed 35 miles north of bed 

L5 and, from uncertain correlations, about 1,000 feet 

lower stratigraphically. It is very richly fossiliferous, 

and consists of dark argillaceous and calcareous shales. 

The fauna includes the following molluscan species, 

mostly as silicified fossils:

Unio sp. undet.

Valvata praecursoris (White)

Mesoneritina naticiformis (White)

Viviparus sp. undet.

Campeloma sp. undet.

Lioplacodes cf. L, stachei (White)

Lioplacodes sp. undet.

Helicina sp. undet.

Parateinostoma latente (White)

"Pachymelania"'! macilenta (White)

Mesocochliopa sp. undet.

"Tornatellina'"! cf. "T." isoclina (White)

Pyrgulifera sp. undet. (young forms)

Zaptychius haldemani (White)

Anisopsis sp. undet.

Physa usitata (White)

Physa sp. undet.

Physa sp. undet. (low spired)

This fauna is essentially similar in ecological assemblage to that of bed L5, and this similarity implies 

that the living faunas were similar. Valvata, Lioplacodes, Zaptychins, and Physa are the dominant genera 

in the assemblage and yield many specimens including 

young shells. In addition to the molluscan species, 

some ostracodes and oogonia of Chara-like algae are 

also not uncommon in the bed.

Despite the similarity in ecological assemblage, the 

fauna of bed L8 differs considerably in composition of 

species from that of bed L5. Only six out of a total of 

26 species are found in both beds, perhaps because of 

a difference in age that is dealt with below.

STRATIGRAPHIC POSITION AND AGE OF THE FOSSILIFEROUS BEDS

Bed L5 is in the lower part of a 6,000-foot sequence 

of Cretaceous rocks, the exact age of which is unknown. 

It is about 2,000 feet above the top of a zone containing 

a Bear River fauna and typified by the beds exposed 20 

miles north of Cokeville, which includes bed L8. In

928014—51-
14 FRESH-WATER MOLLUSKS FROM MONTANA AND WYOMING

the strata above bed L5 lie four fossiliferous beds of 

brackish or fresh-water origin and below it lie several 

similar beds, which with the intervening deposits constitute a thickness of several hundred feet.

The nonmarine molluscan faunas contained in this 

series of limestones indicate that bed L5 is younger than 

bed L8 which in turn seems to be younger than the 

typical Bear River bed.

First, only six (less than one-fourth) of the molluscan 

species are present in both beds. If the two faunas 

lived in very similar environments, in areas only 35 

miles apart, and at about the same time, they certainly 

should have more species of mollusks in common.

Second, species of Pyrgulifera are absent from the 

series of limestones in the Leeds Creek area, but they 

are found in the beds north of Cokeville and in the beds 

exposed in the NEK Sec. 9, T. 22 N., R. 119 W., about 

1.6 miles north-northeast of L5 and 2,400 feet below it. 

Species of Pyrgulifera have been recorded in Europe 

from beds considered to be younger than the Cenomanian age commonly assigned to the Bear River and 

Aspen formations, but they have not been found in 

beds younger than the Aspen in North America.

Third, species of Parateinostoma, which have not 

been reported in earlier beds in North America but 

constitute one of the dominant groups in bed L5, have 

been described from coal-bearing beds near Ajka in 

western Hungary that are considered to be much 

younger than Cenomanian.

SYSTEMATIC DESCRIPTIONS

Family VALVATIDAE

Valvata praecursoris (White)

Plate 2, figures la-g

Planorbis praecursoris White, U. S. Geol. Survey Bull. 128, 

p. 46, pi. 6, figs. 4, 5, 6, 7, 1895.

This form was described as a species of Planorbis and 

in the subgenus Gyraulus. Indeed its planorboid outline resembles that of a Planorbis. However, the tubular form of the whorls, impressed suture, circular 

aperture with continuous peristome, and wide and deep 

umbilicus well characterize it as a species of Valvata.

It is abundant in the present collection, and specimens in the collection form a developmental series. 

Younger ones appear to be more flattened on the apical 

side and the increasing convexity of the later whorls 

produces a "very slightly concave" appearance of the 

apical whorls.

The specimens contained in the type lot were obtained 

from a locality "20 miles north of Cokeville." Three 

of them seem to be young specimens, and the fourth 

is a species of Planorbis. White's original description 

was apparently based on the specimens illustrated

as his figures 4, 5, and 7, by which the present specimens 

are identified.

Figured specimen: U.S.N.M. 106774; additional specmens: U.S.N.M. 106775.

Family NERITIDAE

Mesoneritina naticiformis (White)

Plate 2, figure 2

Neritina naticiformis White, U. S. Geol. and Geog. Survey Terr. 

Bull., vol. 4, p. 7, 5, 1878; U. S. Geol. Survey Bull. 128, p. 49, 

pi. 6, figs. 10, 11, 12, 1895.

Only immature specimens represent this species in 

the present collection, but they are typical in their 

naticoid outline, strongly thickened but somewhat 

excavated columellar margin and roundly convex 

whorls.

Figured specimen: U.S.N.M. 106776;additional specimens: U.S.N.M. 106777.

Mesoneritina stantoni (White) 

Plate 2, figure 3

Neritina stantoni White, U. S. Geol. Survey Bull. 128, p. 49, 

pi. 6, figs. 16, 17, 18, 1895.

Several young specimens represent the species in the 

present collection. It is well characterized by its single, 

conspicuous carina on the shoulder of the early whorls 

and on the body whorl.

Figured specimen: U.S.N.M. 106778; additional specimens U.S.N.M. 106779.

Family VIYIPARIDAE

Lioplacod.es stachei (White)

Plate 2, figure 4a-g

Charydrobia stachei White, U. S. Geol. Survey Bull. 128, p. 58, 

pi. 10, fig. 7, 8, 9, 1895.

This species is abundant in the present collection. 

The width of the shell varies somewhat and specimens 

having a narrower outline may represent males. They 

closely resemble the typical specimens obtained at the 

locality about 20 miles north of Cokeville.

The younger specimens appear broader and somewhat 

globose. The early whorls increase gradually in size 

and the later ones increase more rapidly in height than 

in width, so that a more mature shell has a subfusiform 

outline.

Figured specimens: U.S.N.M. 106780; additional 

specimens: U.S.N.M. 106781.

Family AMNICOUDAE

Parateinostoma altispirale Yen, n. sp.

Plate 2, figures 5a-d

Shell, minute, narrowly oblong in outline, imperforate 

or narrowly perforate, with a high spire tapering gradually towards the apex and an inflated body whorl, final
UPPER CRETACEOUS FAUNA, LEEDS CREEK AREA, WYOMING 15

half of which bears a well-developed shoulder. Whorls 

gently convex, gradually increasing in size. Suture well 

impressed. Aperture subovate in outline; peristomal 

margin continuous, slightly thickened within; outer lip 

angulated, somewhat retreating above, expanding in 

lower part, basal margin produced and bearing a slightly 

developed notch; inner lip well defined, nearly straight 

at columella.

Measurements (in millimeters):

Altitude of shell._____________________ 4.0

Width of shell____-_________________ 1. 6

Height of aperture-___________________ 1. 2

Width of aperture.___________________ .6

Number of whorls ____________________ 6%

The species differs from Parateinostoma manum 

(Tausch 1886, p. 11, pi. 1, figs. 44a-d), which was 

described from an Upper Cretaceous horizon (Danian, 

according to Wenz) near Ajka in western Hungary, by 

its broader outline of shell, more convex whorls, and 

inflated body whorl.

It resembles closely Hydrobia occulta White (1895, 

p. 57, pi. 10, fig. 12, 13), but differs by its longer shell, 

less convex whorls, and more expanded outer lip and 

basal margins.

It is highly probable that Hydrobia occulta White 

may prove to be a species of Parateinostoma.

Holotype: U.S.N.M. 106782; paratypes: U.S.N.M. 

106783.

Parateinostoma convexum Yen, n. sp. 

Plate 2, figure 6a-c

Shell, minute, ovately oblong in outline, narrowly 

perforate, with a high spire and a moderately inflated 

body whorl. The whorls are roundly convex, gradually 

increasing in size. Suture well impressed. Aperture 

subovate in outline; periostomal margin continuous and 

slightly thickened; outer lip more or less retreating at 

upper part and expanding below; inner lip well defined 

and slightly oblique.

Measurements (in millimeters):

Altitude of shell__________-___________ 3. 0

Width of shell____--_-__-___________-_ 1. 5

Height of aperture-_-__--__-_______-__ 1. 0

Width of aperture.___________________ .5

Number of whorls ____________________ 5/>_

This species differs from the preceding one by its 

smaller size and broader outline, more convex whorls, 

and wider aperture. It is readily differentiated from 

younger shells of the preceding species by its expanding 

outer lip and thickened peristomal margin.

Holotype: U.S.N.M. 106784; paratypes: U.S.N.M. 

106785.

Farateinostoma contractum Yen, n. sp. 

Plate 2, figures 7a-c

Shell minute, subovate in outline, narrowly perforate, 

with a high spire and laterally dilated body whorl. 

Whorls roundly convex and gradually increasing in 

size. Suture well impressed. Aperture laterally descending, barely adnate, and subovate in outline. 

Peristomal margin continuous; outer-lip expanding, 

inner lip well defined and slightly oblique.

Measurements (in millimeters):

Altitude of shell_-v _-__---_____----__-- 2. 5

Width of shell— — —_ — — - — — __- 1. 5 

Width of shell— ———— ————— ——— 1. 5

Height of aperture-___________________ 1.0

Width of aperture.___________________ .5

Number of whorls ____________________ 5

The species differs from P. convexum by its pupoid 

outline and smaller shell, more inflated body whorl and 

laterally descending aperture. It resembles Bythinella 

latentis White (1895, p. 58, pi. 10, fig. 10, 11), better 

referred to Parateinostoma, but differs by its expanding 

outer lip and more inflated body whorl.

This species is represented by more individuals in 

the present collection than either one of the preceding 

two congeneric species. These species seem to form a 

decidedly dominant group in this fossil assemblage and 

its stratigraphic value should be carefully considered.

Holotype: U.S.N.M. 106786; paratypes: U.S.N.M. 

106787.

Pachydrobia cylindrica Yen, n. sp. 

Plate 2, figures 8a-b

Shell minute, cylindrical, with a highly turrited spire 

and moderately dilated body whorl. Whorls increasing 

gradually in size, closely coiled, convex. Suture well 

impressed by convexity of the whorls. Aperture 

descending, subcircular in outline; peristomal margin 

thickened, inner lip well defined, columella margin 

short and free.

Measurements (in millimeters):

Altitude of shell. _______-______---__ 3. 5+

Width of shell—— — — — — — — — — 1. 1

Height of aperture._________________ .5

Width of aperture____-----_ —------ . 5

Number of whorls__________________ 8+

The species is characterized by its minute, cylindrical shell, close coiling, and convex body whorl.

The generic assignment is provisional. Pachydrobia 

Cossmann was described from the Bartonian beds of 

France. It is a very interesting species, and no closely 

similar species been reported from an earlier bed on
16 FRESH-WATER MOLLTJSKS FROM MONTANA AND WYOMING

either side of the Atlantic. Only two imperfectly 

preserved specimens have been found.

Holotype: U.S.N.M. 106788; paratypes: U.S.N.M. 

106789.

Family Pleuroceratidae

Goniohasis leedsensis Yen, n. sp. 

Plate 2, figures 9a-e

Shell narrowly oblong in outline, imperforate, with a 

highly turrited spire and dilated body whorl. Whorls 

gently convex, increasingly gradually in size and slightly 

constricted near the suture. Apex rising, the first four 

whorls apparently smooth and subsequent ones with 

axial ribs. These ribs are rather faint on the early 

stages but become stronger on the later whorls. A set 

of four to six strongly developed spirals appears on the 

base of the body whorl. Aperture pyriform in outline, 

descending in front; outerlip slightly retreating above 

and produced below; inner lip well defined and thickened 

«o as to covering the umbilical area.

Measurements of two specimens (in millimeters) : 

Altitude of shelL._________ 10.0+ 12.0+

Width of shell_____ _ ____ 4.0 4.5

Height of aperture. _______ 3.0 4.0

Width of aperture.. _ ____ 2. 2 2. 5

Number of whorls _ ______ 5+

This species is assigned for the present to this 

broadly conceived North American genus. It also resembles some forms of other Melania-]ike genera, such 

as Melanoides Olivier and Hemisinus Swainson, but 

does not agree well with any of them.

It is characterized by its narrowly oblong outline, 

gently convex whorls gradually increasing in size, welldeveloped riblets and well-thickened inner lip margin. 

It is distinctly different from any fossil species of 

Goniobasis recorded from the Cretaceous and Tertiary 

beds in the Western Interior of North America.

Holotype: U.S.N.M. 106790; paratypes: U.S.N.M. 

106791.

Family EIIOBIIDAE

Zaptychius haldemani (White) 

Plate 2, figures lOa-b

Acella haldemani White, U. S. Geol. and Geog. Survey Terr.

Bull., vol. 4, p. 714, 1878. 

Tortacella haldemani White, U. S. Geol. Survey Bull. 128, p. 44,

pi. 5, figs. 8-12, 1895.

This species seems to be a common form in the collection, and the specimens agree well with the typical 

form, originally described from the Bear River formation. The genus lived from Upper Jurassic to Upper 

Cretaceous times. Species have been recorded from the 

Morrison formation, the Cloverly formation and the 

Peterson limestone, and from the present deposit.

Figured specimen: U.S.N.M. 106792; additional 

specimens: U.S.N.M. 106793.

Rhytophorus cf. R. meeki White 

Plate 2, figure 11

Rhytophorus meekii White, in Powell, Rept. Geol. Uinta Mountains, p. 118, 1876; U. S. Geol. Survey Bull. 128, p. 43, pi. 5, 

fig. 6, 7, 1895.

Only one very imperfect specimen was found in the 

course of the present investigation. Its visible shell 

features agree with those of Rhytophorus but it may 

be specifically different from R. meeki, as the two folds 

in the columellar margin are distinctly stronger and 

the inner lip is much more thickened.

Figured specimen: U.S.N.M. 106794.

Melampoides Yen, n. gen.

Shell small and of thin substance, imperforate, subovate in outline. Apex prominent, erect; spire small 

in contrast with a large body whorl. Whorls few, 

early ones more or less closely coiled and gradually 

increasing in size, last one rapidly dilated and constituting over two-thirds of the entire shell. Aperture 

narrowly oblong, slightly notched at anterior end; 

outer lip simple and nearly straight, and inner lip more 

or less thickened and bearing columellar folds.

Genotype: Melampus clarki White.

The genus differs from Melampus Montfort by its 

much smaller size, thin shell substance, simple inside 

of the outer lip and the slight notch on the basal margin.

Melampoides clarki (White) 

Plate 2, figure 12

Melampus clarki White, U. S. Geol. Survey Bull. 128, p. 42, fig. 

2, 3, 1899.

Most of the specimens in the present collection are 

of immature shells, but they agree well with the described characteristics of this species. It is characterized by its small size, prominent apex, short spire of 

conical form, narrowly oblong aperture and plica-like 

folds on the columellar margin, two on the young and 

three on the adult shell.

Figured specimen: U.S.N.M. 106795; additional 

specimens: U.S.N.M. 106796.

Family PIANORBIDAE * 

Anisopsis minuta Yen, n. sp. 

Plate 2, figure 13a-c

. Shell, minute, planorbid in outline, somewhat concave on the apical view and nearly flat on the base. 

Whorls rapidly increasing in size, obtusely carinated on 

the shoulder and more distinctly angulated along the 

periphery of the body whorls. The rapid increase in
UPPER CRETACEOUS FAUNA, LEEDS CREEK AREA, WYOMING 17

size and convexity of the body whorl produces a sunken 

aspect of the apical whorls. Aperture semilunate in 

outline, outer lip thin and biangulated.

Measurements (in millimeters):

Altitude of shell______________________ 1. 5

Width of shelL-__-._____________. . 5

Height of aperture.-...-..-..___________

Width of aperture.___________________

Number of whorls.___________________ 3}{

The species resembles Anisopsis calcula (Sandberger) 

and A. loryi (Coquand) in outline of shell, but differs 

from both by having much smaller size and being 

nearly flat on the basal side of the shell.

Only three specimens were found, but the species is 

quite distinct in its minute size, lower apical whorls 

and bicarinated body whorl.

Holotype: U.S.N.M. 106797; paratypes: U.S.N.M. 

106798.

Family PHYSIDAE

Physa usitata White 

Plate 2, figure 14

Physa usitata White, U. S. Geol. Survey Bull. 128, p. 47, pi. 6, 

figs. 8, 9, 1895.

This species is represented only by immature shells 

in the present collection. These specimens are much 

smaller in size than the adult and have only about three 

whorls, which evidently represent the initial whorls of a 

mature shell.

The type specimen of Physa usitata measures 16.0 

mm. in altitude of shell and 8.5 mm. in width and has 

about 7 whorls. The body whorl constitutes about 

two-thirds of the entire shell and has about six gradually 

increasing and closely coiling whorls on the spire (which 

is a little over 5 mm. in altitude).

Measurements:

Altitude of shell._________________ _. 5. 5

Width of shell-_____--______--_-___ 4. 0

Height of aperture____________________ 5. 0

Width of aperture-_______________ 2. 2

Number of whorls____________________ 3

Figured specimen: U.S.N.M. 106799; additional specimens: U.S.N.M. 106800.

Physa sp. indet. 

Plate 2, figure 15

One well-preserved specimen in the collection is 

minute ovate outline, and has about 3 whorls. It is

probably an immature shell of an undescribed species, 

but the single specimen does not warrant description 

of a new species. 

Figured specimen: U.S.N.M. 106801.

Physa, sp. undet. 

Plate 2, figure 16

Three imperfectly preserved specimens in the collection are characterized by subglobose shell, very small 

.spire and narrowly oblong aperture. The state of 

preservation does not permit a full description of a 

species, especially as none of the shells have the basal 

part of the aperture well preserved.

Figured specimen: U.S.N.M. 106802; additional 

specimens: U.S.N.M. 106803.

BIBLIOGRAPHY

HOERNES, R., 1888, Ein Beitrag zur Kenntnis der suedsteirischen

Kohlen-Bildungen: Naturwiss. Ver. Steiermark Mitt., Jahrg.

1887; pp. 35-46. 

MATHERON, PHILIPPE, 1842, Catalogue me'thodique et descriptif

des corps organises fossiles du department des Bouches-duRhone et lieux circonvoisins, Marseille. 

MEEK, F. B., 1860, Descriptions of new fossil remains collected

in Nebraska and Utah: Acad. Nat. Sci. Philadelphia Proc.,

vol. 12, pp. 308-315.

————, 1877, Paleontology: U, S. Geol. Explor. 40th Parallel, 

voL 4, pt. 1, pp. 1-197. 17 pis.

OPPENHEIM, PAUL, 1892, Ueber einige Brackwasser- und BinnenMollusken aus der Kreide und dem Eocan Ungarns: Deutsche geol. Gesell. Zeitschr., vol. 44, pp. 697-818, pis. 31-36.

PRTJVOST, PIERRE, 1942, Un bassin houiller paralique d'age 

cenomanien: Les lignites de Pont-Saint-Esprit: Soc. g6ol. 

France Bull., ser. 5, vol. 12, pp. 165-180, figs.

SANDBERGER, FRIDOLIN VON, 1870-1875, Die Land- und Suesswasser-Conchylien der Vorwelt, Wiesbaden.

STACHE, GUIDO, 1889, Die liburnische Stufe und deren GrenzHorizonte: K. k. geol. Reichsanstalt Abh. vol. 13, pt. 1.

STANTON, T. W., 1892, The stratigraphic position of the Bear 

River formation: Am. Jour. Sci., 3d ser., vol. 43, pp. 98-115.

————t 1916, Non-marine Cretaceous invertebrates of the San 

Juan Basin: U. S. Geol. Survey Prof. Paper 98-R, pp. 

309-326. 

-, and HATCHER, J. B., 1905, Geology and paleontology of

the Judith River beds: U. S. Geol. Survey Bull. 257.

TAUSCH, LEOPOLD VON, 1886, Ueber die Fauna nicht-marinen

Ablagerungen der oberen Kreide des Csingerthales bei Ajka

im Bakony: K. k. geol. Reischsanstalt Abh., vol. 12, pt. 1.

————, 1888, Ueber die Fossilien von St. Briz in Suedsteiermark: 

K. k. geol. Reichsanstalt Verh., Jahrg. 1888, pp. 192-195.

VEATCH, A. C., 1907, Geography and geology of a portion of 

southwestern Wyoming: U. S. Geol. Survey Prof. Paper 56.

WENZ, W., 1938-1944, Gastropoda: Handbuch der Palaeozoologie, vol. 6, pts. 1-7, Berlin.

————, 1941, Angulorbis: Arch. Molluskenkunde, vol. 73, p. 221.
18 FRESH-WATER MOLLUSKS FROM MONTANA AND WYOMING

WHITE, C. A., 1878, Descriptions of new species of invertebrate 

fossils from the Laramie group: U. S. Geol. and Geog. 

Survey Terr. Bull., vol. 4, Art. 28, pp. 707-719.

—————, 1880, On the antiquity of certain subordinate types of 

freshwater and land mollusca: Am. Jour. Sci., 3d ser., vol. 

20, pp. 44-49.

————} 1883, A review of non-marine fossil mollusca of North 

America: U. S. Geol. Survey Third Ann. Rept., pp. 403-550.

————, 1892, On the Bear River formation, a series of strata 

hitherto known as the Bear River Laramie: Am. Jour. Sci., 

3d ser., vol. 43, pp. 91-97.

————, 1895, The Bear River formation and its characteristic.

WHITEAVES, J. F., 1885, Report on the invertebrata of the 

Laramie and Cretaceous rocks of the vicinity of the Bow 

and Belly Rivers and adjacent localities in the North-West 

Territory: Canada Geol. and Nat. Hist. Survey, Contrib. 

Can. Palaeontology, vol. 1, no. 1.

WHITFIELD, R. P., 1903, Notice of six new species of Unios from 

the Laramie group: Am. Mus. Nat. History Bull., vol. 19, 

no. 15, pp. 483-487.

————, 1907, Remarks on and descriptions of new fossil Unionidae from the Laramie clays of Montana: Am. Mus. Nat. 

History Bull., vol. 28, no. 26, pp. 623-628.

fauna: U. S. Geol. Survey Bull. 128.
INDEX

Abstract__-__—- 

Acetta haldemani... 

Age of the deposits. 

Algae__--„--__.

attilis, Gillia..................................................................

aUispirale, Parateinostoma..................................._.. 12, 14; pi. 2,

Amnicola decisa _____________________.._........_____.......

limosa..........

longinqua...... -

Amnicolidae_-.--. 

Ampullaria powelli. 

Ampullariidae.- 

Anculosa carinata... 

Anisopsis calcula...

loryi..-.........

minuta....................................................... 12, 16; pi. 2,

SP-_-_.__.______ - ——— —— ——— ——— ——— —— —— __ —————— ——— ——— .——— ——— —— -

Aplexasp.__.___.______.___.__.._____.______.________

assiminoides, Mesocochliopa....................................................

B

Bithynia-----....... _______

Bulimus.-----------.-.--..

buttoni, Lymnaea palustris.

Page

1,11

16

2,13

12

2

fig. 4 

2 

6 

2 

2

12,14 

6 

6 

2 

17 

17

fig. 13

12,13

3,8

5

6

6

2

calcula, Anisopsis............................................................. 17

californica, Valvata humeralis.................................................. 2

Campeloma decisum.......................................................... 2

harlowtonensis...._..____.._._....__...._.... 1, 2, 3, 4; pi. 1, fig. 4

macrospira................................................................ 4

sp.——————————— — ——.. ——— — ————____——_ 13

carbonaria, Zaptychius......................................................... 7

carinata, Anculosa............................................................ 2

Rubeyella.............................J....................... 3, B; pi. 1, fig. 5

Carinifex newberryi—.......................................................... 2

Carinulorbisplanospiralis.---................................................. 8

sp.- — -..- —............................................. 1,2,3,8;pi. 1, fig. 16

Cassiopella...... _._.,__.—_____ — __ — — __........._._......_.. 5

Cerithium..................................................................... 13

Cftara-like algae.___.___.._______..._.________.___.. 12 

Charydrobia cretacea............................__............................. 3,5

stachei.................................................................... 14

C.rcan._.<m.a_---_----_ _______________________________________________________ 6, 7

ortmanni............................................_..... 1, 2, 3, 7; pi. 1, fig. 9

elarki, Melampoides..............................."............... 12, 16; pi. 2, fig. 12

Clarocerithium.... _______________.___--..-....._.__..._..__--____ 13

complanatus, Elliptic......................................................... 2

compressum, Pisidium........................................................ 2

contractum, Parateinostoma....................................... 12, 15; pi. 2, fig. 7

convexiculus, Lioplacodes...................................................... 3,5

convexum, Parateinostoma-...................................... 12, 15; pi. 2, fig. 6

Corbula....................................................................... 13

Correlations. — ._______ — __—___________._._._..__-...-- 2,13

cretacea, Charydrobia.......................................................... 3,i

Lymnaea—..................................................... 3 8; pi. 1, fig. 17

MesQphilina............................................... 1, 2, 3, 7; pi. 1, fig. 12

Mesocochliopa................................................... 3, ff;pl. 1, fig. 6

cretaceus, Lioplacodes......................................................... 3,4

Sulcatapex................................................................ 3,4

cylindrica, Parahydrobia.............................. ___.__'____.________ 12

Parateinostoma................................................... -5; pi. 2, fig. 8

cylindricus, Zaptychius............................................. 3, 7; pi. 1, fig. 11

D 

decisa, Amnicola.............................................................. 2

decisum, Campeloma.......................................................... 2

if, Protettiptio........................................... l,-2, 3, 4; pi. 1, fig. 1

Vhio..................................................................... 1

Elliptio complanatus. 2 

1, 2, 3, 4

/am, Unio— —........................................................... 1, 2, 3, 4

Faunas, composition and origin___._. —_—...____ — — — - — —... 1,11

Fluminicola..-------.......................----.................-..--........ 6

fusca...................................................................... 2

fusca, Fluminicola............................................................ 2

a

GilliaaltiUs—-.———....-.. — -.——-.-——..-.——.— ——— 2

gilloides, Amnicola—---------....____ — —————_. ——...- —. —.. 6

Glycymeris-....................................---........................... 13

Goniobasisleedsensis.............................................. 12, 16;p\. 2, fig. 9

ortmanni......................................---------- — — _ — _.... _- 1

silberlingi----------------------------------------------------------------- 1

virginica....................................................... 2, 7; pi. 1, fig. 18

sp__—_._._ —— ____......_. —__.___—____—_____.-.———-— — _- 12

Gyraulusvermicularis...-..................................................... 2

1,2,3,8; pi. 1, fig. 15

H

haldemani, Acella......................-..--.......-..........---............. 16

Tortacella........................................................ —...... 7,16

Zaptychius........--... —...................— .......... 12, 13, _<J;pl. 2, fig. 10

harlowtonensis, Campeloma.................................... 1, 2, 3, 4; Pi- 1, fig. 4

Helicinasv-.................................................................. 13

Helisoma subcrenatum..... ____________._ —.. —— -.— — __ — — — ——— 2

Hemisinus...................................................................- 16

heterostropha, Physa.........................................— — — _.——— 2

humeralis californica, Valvata......................----...-.-----.---------..— 2

humerosa, Parabtihynia....................................—— -... — -...— 6

Hydrobia occulta.--------...-..._._____ — — ———— — —. — — — —— 15

sp........................................................................ 12

I 

Introduction..____._._____________———___——————————— 1,11

lanistoides, Reesidetta................................................ 3, 6; pi. 1,:

leedsensis, Goniobasis—..——..._ —— — ------ — — —— — — — 12, 16; pi. 2,

limosa, Ammcola.............................................................

Lioplacodes convexiculus........ — — ______-__—------- — — ------ ——

cretaceus..................................................................

stachei..-............................................... 11,12,13, 14; pi. 2,

Lioplax subcarinatus.---------------------------------------------------------

longinqua, Amnicola..........................................................

loryi, Anisopsis....-..-------......-..........................................

Lymnaea cretacea.................................................. 3, 8; pi. 1, fi

palustris buttoni....------___-_-_-—— ——_. ——————— —— —— _

utahensis. 

Lymnaeidae2

3,5

M

fig.4

2

1,8 

17

g. 17 

2

3,8

2

2, 8

M

madlenta, Pachymelania. 

macrospira, Campeloma.. 

manum, Parateinostoma. 

meeki, Melampus.

............................................— 13

__————_—— —— _———————————— 4

——— — —— —— — —— ———————— 15

————— ———— ———— —— —— —————— 16

Rhytophorus.................................................. 12, 16; pi. 2, fig. 11

meekii, Rhytophorus.............................. ... __——————------- —— — 16

Melampoidesclarki————————— —.—————- 12, 16; pi. 2, fig. 12

--._ — ———— —— ——— —— — — —— —— - — ——— - — —— — - —— - —— — 16

Melampus meeki____-—__-__—— — — — ———. —.. — — —— -- 16

Melania.... ____.___-_____._.-._-— —— ------- —— - — ————— 16

Melanoides—...—------------------------------------------------------------- 16

Mesochilina cretaces.... —................................... 1, 2, 3, 7; pi. 1, fig. 12

19
20 INDEX

Page 

Mesocochliopa assiminoides................................................... 5

cretacea......................................................... 3, 5; pi. 1, fig. 6

Mesoneritina naticiformis.......................................... 11, 14; pi. 2, fig. 2

nebrascensis................................................. 1,2, 3, 4; pi. 1, fig. 3

stantoni....................................................... 11, 14; pi. 2, fig. 3

Mieropyrgussp................................................................ 12

minuta, Anisopsis............................................... 12, 16; pi. 2, fig. 13

montanaensis, Reesidella........................................ 1,2,3,5; pi. 1, fig. 7

montanensis, Physa........................................... 1, 2, 3, S; pi. 1, fig. 13

Viviparus................................................................. 1

N 

naticiformis, Mesoneritina........................................ 11, 14; pi. 2, fig. 2

Neritina.................................................................. 14

naticoides, Protamnicola....................................................... 3,5

nebrascensis, Mesoneritina........................................... 1, 2, 3, 4; fig. 3

^natosini, Unio.................................................. 1, 2, 3, 4; pi. 1, fig. 2

Neritidae——-..........^................................................ 1,11,14

Neritina naticiformis. 

stantoni..........

newberryi, Carinifex..

O

occulta, Hydrobia.. ............................................................ 15

onestae, Eupera .... . ..... ...... .... ....... ...... .... ... ................ ..... 1,2,3,4

ortmanni, Circamelania ............... .... ................... .. 1, 2, 3, 7; pi. 1, fig. 9

Qoniobasis.. .......................... .. .................................. 1

Ostrea ........................................................................ 12

Pachymelania macilenta....................................................... 13

palustris buttoni, Lymnaea.................................................... 2

Parabithynia humerosa........................................................ 6

Parahydrobia cylindrica........................................................ 12

Parateinostoma altispirale........................................ 12, 14; pi. 2, fig. 4

contractuum:................................................. 12, 15; pi. 2, fig. 7

convexum.............................—————————_.__ 12, IB; pi. 2, fig. 6

cylindrica...................................___._______ IB; pi. 2, fig. 8

manum......................................................_______ 15

sp. —————————————————————————_ 12,14

Physa bridgerensis............................................................. 8

heterostropha.............................................................. 2

montanensis............................................... 1, 2,3, 8; pi. 1, fig. 13

usitata.................................................... 12,13, 17; pi. 2, fig. 14

walcotti................................................................... 8

sp. A.....—————————————.————————— 1, 2,3, 8; pi. 1, fig. 14

sp.,B..........——.————.———————————————————— 2,3,8

sp.................................................... 12,13, 17; pi. 2, figs. 15,16

Physidae _.-_-____...___......_._..———......_..__......_ 1,16

pilsbryanum, Sphaerium...................................................... 2

Pisidium compressum......................................................... 2

Planorbidae.-__..._-..—...___-___._.__...._________ 1,8,16

planospiralis, Carinulorbis.................................................... 8

Pleuroceratidae............................................................... 1,6,16

Pleurolimnaea................................................................ 7

powetti, AmpuUaria.......................................................... 6

praecursoris, Valvata........................_——_____ 11,12,13, 14; pi. 2, fig. 1

Protamnicola naticoides....................................................... 3,5

Protelliptio douglassi............................................ 1, 2,3, 4; pi. 1, fig. 1

Pseudamnicola................................................................ 5

PyrgvMfera.......———_________————————————-....____ 14

E Page 

Reesidella lanistoides................................................ 3, 6; pi. 1, fig. 8

montanaensis.............................................. 1, 2, 3, 6; pi. 1, fig. 7

—-—--—-———-——————————-———---.——- 6

Rhytophorus meeki.............................................. 12, 16; pi. 2, fig. 11

meekii.................................................................... 16

RubeyeUa carinata.................................................. 3, 5,- pi. 1, fig. 5

sagensis, Lymnaea..........................———.—.—.———.—_—— 3,8

silberlingi, Ooniobasis—....................................................... 1

Stantonogyra............................................................ 1,2,3,5 . Somatopyrus......................... ._..—....-——————————_...——— 6

Sphaeridae....—.————...--.-..---———.—————————————— —— 1

Sphaerium pilsbryanum.........................r ............................. 2

stamineum................................................................ 2

stachei, Charyjlrobia........................................................... 14

Lioplacodes.—.-..-..-...———-.——.———— 11,13, 14; pi. 2, fig. 4

stamineum, Sphaerium....-.................................................. 2

stantoni, Mesoneritina............................................. 11, 14; pi. 2, fig. 3

Neritina.................................................................. 14

Stantonogyra silberlingi...................................................... 1,2,3,5

Stratigraphic position________________._._......—.—————— 2,13

subcarinatus, Lioplax.......................................................... 2

subcrenatum, Helisoma.............-__________________—— 2

Sulcatapex cretaceus...................................................—-—— 3,4

tetonensis, Zaptychivs.............................................. 3, 7; pi. 1, fig. 10

Tortacetta haldemani.......................................................... 7,16

Turbinicola................................................................... 6

U

Unio douglassi.

farri..—-.--—.-—-———-————-——..-—---.--..- 1,2,3,4

natosini.......................................'............. 1, 2, 3, 4; pi. 1, fig. 2

sp..-.—-—.--—.————....................................... 12,13

Unionidae-_______________.—.._..___.—.—.————.—— 1 

usitata, Physa................................................ 12,13, 17; pi. 2, fig. 14

utahensis, Lymnaea........................................................... 2

Valvata................................................................... 2

Valvata humeralis californica...............................................—. 2

praecursoris............................................ 11 12,13, 14; pi. 2, fig. 1

utahensis.................................................................. 2

Valvatidae.................................................................... 11,14

vermicularis, Oyraulus........................................................ 2

veternus, Gyratdus............................................................ 1,2,3

virginica, Qoniobasis........................................................... 2,7

Viviparidae.—————.———————— ———————— 1,4,11,14

Viviparus montanensis.................. — .............'...................... 1

_—...————————— ————— — ————————— 12,13

W

walcotti, Physa.

Zaptychius carbonaria...............-......................................... 7

cylindricus-.-................................................ 3, 7; pi. 1, fig. 11

haldemani................................................ 12,13, 16; pi. 2, fig. 10

tetonensis...————————— ————— ———————— 3, 7; pi. I. fig. 10

sp———— ——— —— —— — —————— — —— ——— ——— ———— 12

O
PLATES 1-2
PLATE 1

FIGURE 1. Protelliptio douglassi (Stanton), X 1. Kootenai formation, Harlowton, Mont. (p. 4).

2. Unio natosini McLearn, X 1. Kootenai formation near Harlowton, Mont. (p. 4).

3. Mesoneritina nebrascensis (Meek and Hayden), X 2. Kootenai formation near Harlowton, Mont. (p. 4).

4. Campeloma harlowtonensis (Stanton), X 1. Kootenai formation near Harlowton, Mont. (p. 4).

5. Rubeyella carinata Yen, X 2. Kootenai formation about 14 miles south of Dillon, Mont. (p. 5). 

6a-c. Mesocochliopa cretacea Yen, X 6. Cloverly formation, Teton County, Wyo. (p. 5). 

7a-f. Reesidella montanaensis (Stanton), X 2. Figure b from Cloverly formation, Teton County, Wyo., others from Kootenai

formation near Harlowton, Mont. (p. 6).

8. Residellat lanistoides Yen, X 1. Peterson limestone, Lincoln County, Wyo. (p. 6). 

9a-c. Circamelania ortmanni (Stanton), X 2. Kootenai formation, near Harlotvton, Mont. (p. 7). 

lOa, b. Zaptychius tetonensis Yen, X 4. Cloverly formation, Teton County, Wyo. (p. 7).

11. Zaptychius cylindricus Yen, X 4. Cloverly formation, Teton County, Wyo. (p. 7).

12. Mesochilina cretacea Yen, X 4. Kootenai formation near Harlowton, Mont. (p. 7).

13. Physa montanensis Yen, X 1. Kootenai formation near Harlowton, Mont. (p. 8).

14. Physa sp. undet. A, X 2. Kootenai formation near Harlowton, Mont. (p. 8).

15a-c. Gyraulus cf. G. veternus (Meek and Hayden), X 6. Kootenai formation near Harlowton, Mont. (p. 8) 

16a-c. Carinulorbis sp. undet., X 6. .Kootenai formation near Harlowton, Mont. (p. 8).

17. Lymnaea cretacea Yen, X 4. Cloverly formation, Teton County, Wyo. (p. 8).

18. Goniobasis virginica (Gmelin), X 2. A Recent species, Great Falls of Potomac River, Maryland, (p. 2).
GEOLOGICAL SURVEY PROFESSIONAL PAPER 233 PLATE 1

17 12 10b 10a

FOSSIL AND RECENT FRESH-WATER MOLLUSKS.
PLATE 2

FIGURES la-g. Valvata praecursoris (White). Figures Ic to Ig represent a series of development stages (p. 14).

2. Mesoneritina natidformis (White), X 4 (p. 14).

3. Mesoneritina stantoni (White), X 8 (p. 14).

4a-g. Lioplacodes stachei (White). Figures 4a-d, X 2; figures 4e-4g, younger stages, X 4 (p. 14). 

5a-d. Parateinostoma altispirale Yen, n. sp., X 8 (p. 14). 

6a-c. Parateinostoma convexum Yen, n. sp., X 8 (p. 15). 

7a—c. Parateinostoma contractum Yen, n. sp., X 8 (p. 15). 

8a—b. Parhydrobia cylindrica Yen, n. sp., X 16 (p. 15).

9a—e. Goniobasis leedsensis Yen, n. sp. Figures X 4 except figure 9e, X 16 (p. 16). 

lOa-b. Zaptychius haldemani (White), X 8 (p. 16).

11. Rhytophorus cf. R. meeki White, X 2 (p. 16).

12. Melampoides darki (White), X 8 (p. 16). 

13a-c. Anisopsis minuta Yen, n. sp., X 16 (p. 16).

14. Physa usitata White, X 4 (p. 17).

15. Physa sp. undetermined, X 8 (p. 17).

16. Physa sp. undetermined, X 8 (p. 17).
GEOLOGICAL SURVEY PROFESSIONAL PAPER 233 PLATE 2

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UPPER CRETACEOUS NONMARINE MOLLUSKS.