If yon no longer need this publication write to the Geological Survey in Washington for nn 

official mailing label to use in returning it

UNITED STATES DEPARTMENT OP THE INTERIOR

PALEOCENE FRESH-WATER MOLLUSKS 

FROM SOUTHERN MONTANA

GEOLOGICAL SURVEY PROFESSIONAL PAPER 214-C

UNITED STATES DEPARTMENT OF THE INTERIOR 

J. A. Krug, Secretary

GEOLOGICAL SURVEY 

W. E. Wrather, Director

Professional Paper 214-C

PALEOCENE FRESH-WATER MOLLUSKS 

FROM SOUTHERN MONTANA

BY

TENG-CHIEN. YEN

Shorter Contributions to General Geology, 1947

(Pages 35-50)

UNITED STATES

GOVERNMENT PRINTING OFFICE 

WASHINGTON : 1948

For sale by the Superintendent of Documents, U. S. Government Printing Office, Washington 25, D. C.

Price 15 cents
CONTENTS

Page

Abstract..________________________________________ .___________-___-___---_-_--__.__--__---_--_ _______ __._.__ 35

Introduction______________________________ ___________________________________________________ ____________ ._.. 35

Previous work _________________________________________________________________________________________________ 35

Composition and ecologic significance of the fauna.________________________ ___________________________ ____________ 36

Stratigraphic distribution and age of the fauna_ _____-_________________----_---_---_-_-_---_---_---_---_--__---____ 36

Geographic distribution of the collections_-___.___-_____________-______--__---_-------_--__--__----_-_---__---_.__ 37

Systematic descriptions._-______-___--__-__-____________________-___---___-___--_____--__---_--___-__--_________ 40

Bibliography._____--__________.___-_____-_-___._______________-___-_____-__-___--__--___.-_-__--_--_-_,--___._ 44

Index _.______-____-__________-_-_-_______-___-_______________-_._---___--____-____-____-___-_____._-______.__ 49

ILLUSTRATION

Page 

PLATE 10. Paleocene fresh-water mollusks from southern Montana-_________-_.____.__.. .--___-_--__-__.__-___-__.-. 46

ii
PALEOCENE FRESH-WATER MOLLTJSKS FROM SOUTHERN MONTANA

By TENG-CHIEN YEN

ABSTRACT

Twenty-two species of fresh-water mollusks (two new) are 

described and illustrated from 45 localities in southern Montana. 

The genera Viviparus, Campeloma, Lioplacodes, Fluminicola, 

Pleurocera, Goniobasis, Ferrissia, Palaeancylus (new), Pleurolimnaea, Physa, Aplexa, Gyraulus, Carinorbis, Sphaerium, and 

Elliptio are represented. The fauna conies mainly from the 

Tongue River member of the Fort Union formation and is 

assigned to the Paleocene, though it seems divisible into an older 

and a younger group of species and extends into beds that on 

other grounds are considered to belong to the Wasatch formation 

and to be of early Eocene age.

INTRODUCTION

During 1940 and 1941 R. P. Bryson, of the U. S. 

Geological Survey, assisted by W. H. Haas and F. S. 

MacNeil, obtained an interesting collection of fossil 

fresh-water mollusks from 45 localities in southern 

Montana. I have had the privilege of studying this 

large collection of generally well preserved specimens. 

The material was collected mainly at places in Powder 

River and Big Horn Counties, but a few lots were obtained in Rosebud County and a few at places in Wyoming a short distance south of the Wyoming-Montana 

boundary.

In completing this work, I wish to express my thanks 

to the administrative officers of the Geological Society 

of America for their continuous support in making a 

further grant from the Penrose Bequest to carry on 

the project. Thanks are also due Dr. John B. Reeside, 

Jr., of the U. S. Geological Survey, for his valuable 

suggestions and also for his untiring encouragement. 

To Dr. H. A. Pilsbry, of the Academy of Natural 

Sciences of Philadelphia, I am much indebted for his 

expert advice on my work, and I appreciate his personal 

interest.

PREVIOUS WORK

The earliest records of molluscan species from the 

Fort Union formation were made by Meek and Hay den 

from 1856 to 1861. The following 25 species were reported from what they called then "the Lignite group" 

of the upper Missouri River. These species were redescribed and figured, with the exception of one or 

two forms, by Meek in 1876. The following list is in 

systematic order, though the original generic assignment 

is retained:

Valvata subumbilicata Meek and Hayden 1856 

Valvata parvula Meek and Hayden 1856 

792023—48

Valvata montanaensis Meek 1876 

Paludina retusa Meek and Hayden 1856 

Paludina leai Meek and Hayden 1856 

Paludina peculiaris Meek and Hayden 1856 

Paludina trochiformis Meek and Hayden 1856 

Paludina leidyi Meek and Hayden 1856 

Viviparus leidyi var. formosus Meek 1876 

Vivipara raynoldsana Meek and Hayden 1861 

Bulirnus nebrascensis Meek and Hayden 1856 

Melania multistriata Meek and Hayden 1856 

Melania nebrascensis Meek and Hayden 1856 

Bulimus limnaeiformis Meek and Hayden 1856 

Melania anthonyi Meek and Hayden 1856 

Melania ivarrenana Meek and Hayden 1857 

Hydrobiaf eulimoides Meek 1876 

Melania minutula Meek and Hayden 1856 

Melania tenuicarinata Meek and Hayden 1857 

Velletia (Ancylus) minuta Meek and Hayden 1856 

Li'mnaea tenuicosta Meek and Hayden 1856 

Physa longiuscula Meek and Hayden 1856 

Physa rhomboidea Meek and Hayden 1856 

Cydas formosa Meek and Hayden 1856 

Cyclas subellipticus Meek and Hayden 1856

Except for a few additional forms recorded in recent 

years, this earliest list of fresh-water mollusks from the 

Fort Union formation contains almost all the characteristic species of the formation. These species v^ere 

originally described from several casual collections 

of material, and the exact stratigraphic position of their 

occurrence within the formation is unknown. However, by checking with the records made in later years, 

it would seem that they were obtained from several 

horizons in North Dakota and Montana.

In 1886 C. A. White recorded most of the abovementioned species in the vicinity of Wales, Utah, although he assigned the fossiliferous beds to the " Wasatch group," which was then extended, probably unintentionally, to include at that place deposits of Fort 

Union age and even Cretaceous beds (Spieker, 194f, p. 

134). Ten years later a number of these characteristic 

species were identified by T. W. Staiiton among specimens collected from the eastern slope of the Crazy 

Mountains on Lebo Creek, Mont. (Weed, 1896, p. 216), 

where they are found in limestone, shale, and sandstone 

of the Fort Union formation of that area. In 1931 

L. S. Russell recorded six of these species from Fort 

Union strata exposed in Park County, northwestern 

Wyoming. In 1946 I gave a record of nine species 

of fresh-water mollusks from a horizon just above the 

commonly accepted base of the Wasatch formation

35
36 SHORTER CONTRIBUTIONS TO GENERAL GEOLOGY, 1947

(Roland coal bed) in Sheridan County, Wyo., the majority of which are species of the Fort Union formation.

COMPOSITION AND ECOLOGIC SIGNIFICANCE OF THE

FAUNA

The generic assignment of some of the species described in the literature needs revision, and a few 

changes are proposed in this paper. Paleontologic data 

indicate that many genera of fresh-water mollusks have 

a long range in geologic history, and some of the common genera of the living fauna may be traced back to 

much earlier ages. However, it is difficult to make a 

precise decision as to proper allocation of species when 

some of the "catch-all" genera are involved. A thorough study of these groups of fresh-water mollusks will 

provide opportunity for an important contribution by 

anyone interested in this vast field of knowledge.

A summary list of the species here identified is as 

follows:

Viviparus raynoldsanus (Meek and Hayden) 

Viviparus trochiformis (Meek and Hayden) 

Viviparus retusus (Meek and Hayden) 

Campeloma nebrascensis (Meek and Hayden) 

Lioplacodes mariana Yen 

Lioplacodes tenuicarinata (Meek and Hayden)

Lioplac,ode,s limnaeiformis (Meek and Hayden) 

Amnicolidae.___ Fluminicola protea Yen, n. sp.

(Pleurocera ivarrenanum (Meek and Hayden) 

Pleuroceratidae___'f(romob<ms nebrascensis (Meek and Hayden)

(Goniobasis nebrascensis producta (White) 

. r , I Ferrissia minuta (Meek and Hayden)

y --------^ palaeancylus radiatus Yen, n. gen. and sp.

Lymiiaeidae____ Pleurolimnaea tenuicosta (Meek and Hayden)

Viviparidae.

Planorbidae 

Sphaeriidae_

Union idae

\ Physa cf. P. bridqerensis Meek 

~[ Aplexa cf . A. longiuscula ( Meek and Hayden)

(Gyraulus militaris (White) 

.\ Gyraulus parvulus (Meek and Hayder)

(Carinorbis planospiralis Yen 

. Sphaerium cf. S. formosum (Meek and Hayden)

[ Elliptio cf . E. priscus (Meek and Hayden) 

_•{ Elliptio cf. E. silberlingi Russell

["Unio" sp. undet.

The abundant occurrence of viviparids and unios implies that the enclosing rocks were fluviatile deposits. 

These forms in the living fauna exist more commonly 

in rivers and streams of various sizes. The presence of 

abundant shells of fresh-water pulmonates in a number 

of the lots, such as that from locality 17, implies perhaps a shore facies of the river deposits, where the 

water was shallow and rich aquatic vegetation gra<w.

STRATIGRAPHIC DISTRIBUTION AND AGE OF THE

FAUNA

The accompanying table shows the distribution of the 

molluscan species in the intervals between the successive 

coal beds of the region. The generalized section is 

taken from the report of A. A. Baker (1929, pp. 33-38) 

on the northward extension of the Sheridan coal field 

into Big Horn and Rosebud Counties, southern 

Montana.

It is to be noted that the level commonly accepted as 

the boundary between the Tongue River member of the 

Fort Union formation, assigned to the Paleocene, and 

the Wasatch formation, assigned to the lower Eocene, 

is the top of the Roland coal bed, though there is every

Distribution of species by number of localities in each interval between coal beds

Generalized sequence of the coal beds and barren 

intervals, after A. A. Baker (1929, pp. 33-38)

Part of Wasatch formation: 

Badger coal bed.. _ __ . _ __ _ ....-.--. ...

Local coal bed ___ .. _ . _ __ __ ... __ . __

Tongue River member of Fort Union formation: 

Roland coal bed.. __ .. .. ______ ... ____ .

Smith coal bed ___ -.... ______ . .. _ . ..

Interval—... __ __ _ ___ . — __ _ . 

Powers coal bed __ - __ _ . __ __ ..-.-

Internal ....... __ ....... _ __ .. __ ... 

Anderson coal bed... __ _______ .. _ . ...

Dietz No. 1 coal bed. ___ .. . __ ... ... . __ ...

Canyon coal bed __ __ . ___________ _._

Wall coal bed. ___ . ._... __ ... ___ ... .

Interval _ . __ . _ .. __ __ . . _ _ _ 

Brewster-Arnold coal bed... __ . _ ..--.--.--.„

Knoblock coal bed...-. _ ... .. _ . ____ ..

Thickness 

(feet)

0-7

180 0-5

180 

0-13

1 UO

0-20

70 

0-10

60 

10-27

65 0-16

6-24

6-32

10-17

170 

20

396

Viviparus raynoldsanus

1-

\ ,

I 3

j ,

{ ,

( 9

{ ,

j

}--

i.§,

5

7

1

1 

s

1

1

nebrascensis Campeloma 

Lioplacodes mariana

9

7

7

1

1

1

1

Lioplacodes tenuicarinata

1

7

9

1

1

'i

.-1

8

S

1

S

63 

I"

H

5

3

fi

1

1

1

Fhiminicola protea

1

Pleurocera wanenanum

7

1

•2 

1

63 

8

'S

<§

1

o

e,

1 .0

8

•2

s

o

Gs

1

1

minuta Ferrissia 

1

Palaeancylus radiatus

1

tenuicosta Pleurolimnaea 

1

bridgerensis Physa P. cf.

1

,63 

'S1

8

•2

"3

|

1

militaris Oyraulus 

~s

I

s 

1

3

-2 

S

1S

•2

o

5

R

1

S

1 

S

•S.

5Q

*& 

S

63 

1

1

1

E. priscus Elliptio cf. 

4

1

f,

1

'S 

1

•S1

1

1

1

1a 

-S

T
PALEOCENE FRESH-WATER MOLLUSKS FROM SOUTHERN MONTANA 37

appearance in southern Montana of continuity of deposition across this level. The reason for using the top 

of the Roland coal bed is that it is a readily traceable 

plane and that it is believed to lie near the stratigraphic position of the base of the Kingsbury conglomerate member of the Wasatch formation of the western margin of the Powder River Basin of Wyoming 

(Thorn and Dobbin, 1924). The Kingsbury conglomerate has yielded mammals of the genera Hyracotherium and Coryphodon (Wegemann, 1918; Brown, 

1948), which are accepted as establishing jts Eocene age. 

The extensive flora and vertebrate fauna of the Fort 

Union formation establish it as of Paleocene age.

Most of the fresh-water mollusks contained in the 

present collection are species originally described from 

the Fort Union formation. Characteristic and common 

Upper Cretaceous species, such as Tulotoma ikompsoni 

White, "Melania" insculpta Meek, and "Melania" 

wyomingensis Meek, are conspicuously absent. On the 

other hand, several forms of so-called Goniobasis, 

widely reported from deposits of Wasatch age, are 

also lacking. The present fauna therefore seems 

clearly to represent a distinct unit different from that 

of the Lance formation or that of the Wasatch formation of other areas. Furthermore, both the Lance and 

the Wasatch formations are probably of fluviatile 

origin and the differences between the faunas of these 

two formations and that of the Fort Union would seem 

to be due to difference in age rather than to some difference in conditions of deposition.

Within the present fauna it is possible to distinguish 

between the assemblage above the Wall coal bed and 

that below it. The difference is not striking, however, 

and it is undetermined whether it is persistent into other 

regions and will be useful in determining relative stratigraphic position.

The lots recorded from the beds above the Wall coal 

bed seem to contain a more or less similar group of 

species. Each lot contains a few of the following 

characteristic forms:

Viviparus raynoldsanus (Meek and Haydeii) 

Viviparus trochiforrnis (Meek and Hay den) 

Lioplacodes mariana Yen

Lioplacodes limnaeijdrmis (Meek and Hayden) 

Lioplacodes tenuicarinata (Meek and Hayden) 

Pleurocera warrenanum (Meek and Hayden) 

Goniobasis nebrascensis (Meek and Hayden) 

Ferrissia minuta (Meek and Hayden) 

Pleurolimnaea tenuicosta (Meek and Hayden) 

Carinorbis pianospiralis Yen

On the other hand, collections made below the Wall 

coal bed differ by the presence of Campeloma nebrascensis 

(Meek and Hayden) and Goniobasis nebrascensis (Meek 

and Hayden) and its variety or subspecies producta 

(White), which have not been found in the beds above 

the Wall coal. In previous records these three forms 

were described or reported from deposits variously

assigned to the Laramie (in the strict sense), Lance, and 

Fort Union formations without mention of exact 

stratigraphic position within the several formations, and 

little help can be obtained from these records for the 

purpose of correlating the present collections. However, it seems to be a fact that these forms are found only 

in strata occupying positions lower than the upper part 

of the Fort Union formation. Whether these forms 

will justify a separation of the containing rocks a* an 

age unit distinct from the main body of the Fort Union 

formation will have to depend on further collections of 

material to demonstrate how persistent then1 occurrence 

is in these lower beds.

GEOGRAPHIC DISTRIBUTION OF THE COLLECTIONS

The collections represent 45 localities, mainb- in 

Tps. 7, 8, and 9 S., Rs. 44 to 49 E., but with a few farther 

south and east. The horizons represented extend 

through a thickness of about 1,000 feet. A description 

of each locality and a list of the species at each follow:

Locality I—The NE# sec. 2, T. 7 S., R. 44 E., Eosebud County; at the base of a steep butte, more than 

200 feet above the Anderson clinker.

Viviparus cf. V. raynoldsanus (Meek and Hayden) 

Lioplacodes mariana Yen

Lioplacodes limnaeiformis (Meek and Hayden) 

"Unio" sp.

Locality 2.—Southwest of center sec. 7, T. 9 S., R. 

44 E., Big Horn County; exposure just above Ro] and 

coal bed.

Viviparus sp. undet. 

Lioplacodes cf. L. mariana Yen 

Lioplacodes limnaeiformis (Meek and Hayden) 

Pleurocera warrenanum (Meek and Hayden) 

Elliptio cf. E. priscus (Meek and Hayden) 

"Unio" sp.

Locality 3.—Southeast of center sec. 7, T. 9 S., R. 

44 E., Big Horn County; sandstone ledge below RoJand 

coal bed.

Lioplacodes mariana Yen

Elliptio cf. E. priscus (Meek and Hayden)

"Unio" sp.

Locality 4.—The SEtf sec. 8, T. 9 S., R. 44 E., Big 

Horn County; about 130 feet above the Smith coal bed.

Viviparus trochiformis (Meek and Hayden) 

Lioplacodes mariana Yen 

Elliptio cf. E. silberlingi Russell

Locality 5— The SEtf sec. 30, T. 9 S., R. 44 E., Big 

Horn County; about 50 feet above the Roland coal bed.

Viviparus trochiformis (Meek and Hayden) 

Lioplacodes mariana Yen 

Lioplacodes tenuicarinata (Meek and Hayden) 

Lioplacodes limnaeiformis (Meek and Hayden) 

Pleurocera warrenanum (Meek and Hayden) 

Elliptio cf. E. priscus (Meek and Hayden)
38 SHORTER CONTRIBUTIONS TO GENERAL GEOLOGY, 1947

Locality 6.—West of center sec. 35, T. 9 S., R. 44 E., 

Big Horn County; in and below the fossiliferous sandstone ledge above the Roland coal horizon.

Viviparus trochiformis (Meek and Hayden) 

Lioplacodes mariana Yen 

Elliptic cf. E. priscus (Meek and Hayden) 

"Unio" sp. undet.

Locality 7.—Montana-Wyoming boundary line; about 

% mile southeast from southeast corner of sec. 35, T. 9 

S., R. 44 E., Big Horn County; just above a fossiliferous 

sandstone ledge in soft -buff sand.

Viviparus sp. undet.

Lioplacodes mariana Yen

Lioplacodes tenuicarinata. (Meek and Hayden)

Pleurocera warrenanum (Meek and Hayden)

Gyraulhs militatis (White)

Gyravins parvulus (Meek and Hayden)

Carinotbi* planospiralis Yen

"Unio" sp.

Locality 8.—In Sheridan County, Wyo., just across 

State boundary from SW}£ sec. 23, T. 9 S., R. 45 E., 

Montana; on hillside 100 feet above the Wall coal bed 

of Warren.

Viviparus sp. 

Lioplacodes sp. 

"Unio" sp.

Locality 9.—The NWtf sec. 25, T. 7 S., R. 45 E., 

Powder River County; 108 feet above the Wall coal 

bed.

Lioplacode^ mariana Yen

Lioplacodes limnaeiformis (Meek and Hayden)

"Unio" ap.

Locality 10—The SWtfSEtfSWtf sec. 9, T. 8 S., R. 

45 E., Powder River County; just south of east-west 

fault and below a stump bed; 25 to 50 feet below the 

Smith coal bed.

Viviparus trochiformis (Meek and Hayden) 

Lioplacodes mariana Yen 

"Unio" sp.

Locality 11.—The NWJ4 sec. 12, T. 9 S., R. 45 E., 

Powder River County; sandstone ledge below Roland 

coal bed.

Lioplacodes cf. L. mariana Yen

Lioplacodes limnaeiformis (Meek and Hayden)

"Unio" sp. undet.

Locality 12.—The SEtf sec. 13, T. 9 S., R. 45 E., 

Powder River County; roof of Roland coal bed.

Viviparus sp.

Lioplacodes mariana Yen

Pleurocera warrenanum (Meek and Hayden)*

Carinorbis planospiralis Yen

Locality 13.—The SE$3E#SWtf sec. 17, T. 9 S., R. 

45 E., Powder River County; about 35 feet above the 

Roland coal bed.

Viviparus cf. V. trochiformis (Meek and Hayden) 

Lioplacodes mariana Yen

Lioplacodes tenuicarinata (Meek and Hayden) 

Lioplacodes limnaeiformis (Meek and Hayden) 

Pleurocera warrenanum (Meek and Hayden) 

Carinorbis planospiralis Yen

Locality 14.—The, NWK sec. 3, T. 7 S., R. 46 E., 

Powder River County; about 75 feet below the Wall 

coal bed.

Viviparus sp. undet. 

"Unio" sp.

Locality 15.~South edge of SEtf sec. 21, T. S., R. 

46 E., Powder River County; 20 to 50 feet below the 

Canyon coal bed.

Viviparus raynoldsanus (Meek and Hayden) 

Lioplacodes cf. L. mariana Yen 

Elliptic cf. E. priscus (Meek and Hayden) 

Elliptic cf. E. silberlingi Russell

Locality 16.—The NE#SE# sec. 32, T. 8 S., R. 46 E., 

Powder River County; 6 to 12 feet above the Anderson 

coal bed.

Vieiparus trochiformis (Meek and Hayden)

Lioplacodes mariana Yen

Lioplacodes limnaeformis (Meek and Hayden)

Carinorbis sp. undet.

"Unio" sp.

Locality 17.—300 feet east from the southeast corner 

sec. 32, T. 8 S., R. 46 E., Powder River County; 100 

feet above base of Anderson clinker.

Viviparus sp. undet.

Fluminicola protm n. sp.

Lioplacodes tenuicarinata (Meek and Hayden)

Lioplacodes limnaeiformis (Meek and Hayden)

Lioplacodes sp. undet.

Ferrissia minuta (Meek and Hayden)

Palaeancylus radiatus n. sp.

Pleurolimnaea tenuicosta (Meek and Hayden)

Physa cf. P. bridgerensis Meek

Aplexa cf. A. longiuscula (Meek an<? Hayden)

Carinorbis sp. undet.

Sphaerium sp. undet.

Locality 18.—The SE^SE^NWtf sec, 18, T. 9 S., R. 

46 E., Powder River County; about 25 feet above the 

base of Roland clinker.

Viviparus trochiformis (Meek and Hayc'en) 

Lioplacodes mariana Yen

Lioplacodes limnaeiformis (Meek and Hayden) 

Pleurocera warrenanum (Meek and Hayden) 

Carinorbis planospiralis Yen 

Gyraulus parvulus (Meek and Hayden) 

Unio" sp.

Locality 19—The NW#NW# sec. 28, T. 9 S., R. 46 

E., Powder River County; 50 to 75 feet below the 

Roland coal bed.

Viviparus cf. V. trochiformis (Meek and Hayden) 

Lioplacodes mariana Yen 

Pleurocera warrenanum (Meek and Hayden) 

Gyraulus militaris (White) 

Gyraulus parvulus (Meek and Hayden) 

Unio" sp.
PALEOCENE FRESH-WATER MOLLUSKS FROM SOUTHERN MONTANA 39

Locality 20— The SWtfNWJi sec. 31, T. 9 S., R. 46 

E., Powder River County; gray shale, 1 foot above the 

Roland coal bed.

Viviparus cf. V. trochifonnis (Meek and Hayden)

Lioplacodes mariana Yen

Lioplacodes limnaeiformis (Meek and Hayden)

Pleurocera warrenanum (Meek and Hayden)

Carinorbis pianos piralis- Yen

Elliptio cf. E. prisons (Meek and Hayden)

Locality 21.—About 1,100 feet west of southeast 

corner sec. 30, T. 9 S., R. 46 E., Powder River County; 

about 10 feet above the Dietz coal bed.

Lioplacodes tenuicarinata (Meek and Hayden) 

Lioplacodes limnaeiformis (Meek and Hayden)

Locality 22.—Near Montana-Wyoming boundary, 

about 300 feet northeast of southeast corner sec. 32, 

T. 9 S., R. 46 E., Powder River County; 50 to 75 feet 

below Roland coal bed.

Viviparus sp. undet.

Lioplacodes cf. L. mariana Yen

Lioplacodes tenuicarinata (Meek and Hayden)

Lioplacodes limnaeiformis (Meek and Hayden)

"Unio" sp.

Locality 23.—Montana-Wyoming boundary, near 

southeast corner sec. 36, T. 9 S., R. 45 E.; about 150 

feet south of the boundary line and 60 feet below base 

of Roland coal bed.

Viviparus trochiformis (Meek and Hayden) 

Lioplacodes cf. L. mariana Yen 

Lioplacodes tenuicarinata (Meek and Hayden) 

Gyraulus parvulus (Meek and Hayden) 

Elliptio cf. E. priscus (Meek and Hayden)

Locality &£.—The NE }{ SE % sec. 1, T. 7 S., R. 47 

E., Powder River County; about 2 miles northeast of 

Diamond Butte triangulation station; between Dietz 

and Andersoii coal beds.

Viviparus raynoldsanus (Meek and Hayden) 

Lioplacodes mariana Yen

Lioplacodes tenuicarinata (Meek and Hayden) 

Lioplacodes limnaeiformis (Meek and Hayden) 

"Unio" sp.

Locality 25— East of center sec. 4, T. 7 S., R. 47 E., 

Powder River County; 25 to 30 feet below the Dietz 

coal bed.

Vivipajus raynoldsanus (Meek and Hayden) 

Lioplacodes mariana Yen 

: 'Unio" sp.

Locality 26.—The NWtf sec, 11, T. 7 S., R. 47 E., 

Powder River County; about 130 feet above -the Anderson coal bed.

"Unio" sp.

Locality 27.—-Center sec. 36, T. 7 S., R. 47 E., 

Powder River County; 40 to 50 feet below the Diamond 

bed.

Viviparus raynoldsanus (Meek and Hayden) 

Lioplacodes mariana Yeii

Lioplacodes tenuicarinata (Meek and Hayden) 

Lioplacodes limnaeiformis (Meek and Hayden) 

Elliptio cf. E. priscus (Meek and Hayden

Locality 28.—About 1,100 feet east of southwest 

corner sec. 19, T. 8 S., R. 47E., Powder River County; 

about 25 feet above the Smith coal bed. 

"Unio" sp.

Locality 29.—The NWtfSW# sec. 28, T. 8 S., R. 47 

E., Powder River County; about 165 feet above the 

Smith coal bed.

Viviparus trochiformis (Meek and Hayden)

Lioplacodes mariana Yen

Lioplacodes limnaeiformis (Meek and Hayden)

Gyraulus militaris White

Gyraulus parvulus (Meek and Hayden) :: • Carinorbis planospiralis Yen

Elliptio cf. E. priscus (Meek and Haydeu)

Elliptio cf. E. filberlingi Russell

Locality 30.—The SWtfSEtf sec. 34, T. 8 S., R. 47 E., 

Powder River County; about 70 feet below E : etz 

clinker.

"Unio" spp.

Locality 31.—About 700 feet from southeast comer 

sec. 13, T. 8 S., R. 46 E., Powder River County; 

25 to 50 feet below the Smith bed.

Viviparus sp. undet. 

Lioplacodes mariana Yen 

"Unio" sp.

Locality 32.—The NWtfNEtf sec. 5, T. 9 S., R. 47 

E., Powder River County; 150 to 200 feet above the 

Anderson coal bed.

Viviparus trochiformis (Meek and Hayden) 

Lioplacodes mariana Yen

Lioplacodes tenuicarinata (Meek and Hayden) 

"Unio" sp.

Locality 33.—About 300 feet northeast from southwest corner sec. 17, T. 9 S., R. 47 E., Powder River 

County; about 150 feet above the Anderson coal 1 °d.

Viviparus trochiformis (Meek and Hayden) 

Lioplacodes mariana Yen

Lioplacodes limnaeiformis (Meek and Hayden) 

"Unio" sp.

Locality 34.—Center NE# sec. 23, T. 9 S., R. 47 E., 

Powder River County; about 50 feet below the Canyon 

coal bed.

Viviparus cf. V. raynoldsanus (Meek and Hayden) 

Lioplacodes tenuicarinata (Meek and Hayden) 

Elliptio cf. E. priscus (Meek and Hayden)

Locality 35— The NE#SE# sec. 31, T. 9 S., R. 47 E., 

Powder River County; about 150 feet above the 

Anderson coal bed.

Viviparus trochiformis (Meek and Hayden) 

Lioplacodes mariana Yen 

"Unio" sp.
40 SHORTER CONTRIBUTIONS TO GENERAL GEOLOGY, 1947

Locality 86— SE^SEtf sec. 32, T. 9 S., R. 47 E., 

Powder River County; about 135 feet above the 

Anderson coal bed.

Viviparus trochiformis (Meek and Hayden) 

Lioplacodes tenuicarinata (Meek and Hayden)

Locality 37— The NEJSNWtf sec. 32, T. 8 S., R. 48 

E., Powder River County; about 100 feet above the 

base of Canyon coal.

Viviparus cf. V. raynoldsanus (Meek and Hayden) 

Lioplacodes mariana Yen

Lioplacodes cf. L. tenuicarinata (Meek and Hayden) 

Elliptio cf. E. prisons (Meek and Hayden)

Locality 38.—The SW#SW# sec. 6, T. 9 S., R. 48 

E., Powder River County; about 100 feet above the 

base of Canyon coal bed.

Elliptio cf. E. priscus (Meek and Hayden)

Locality 39.—T. 2 S., R. 49 E., Powder River County; 

about 180 feet above the Brewster-Arnold bed. 

Viviparus retusus (Meek and Hayden) 

Lioplacodes limnaeiformis (Meek and Hayden) 

Campeloma nebrascensis (Meek and Hayden) 

Goniobasis nebrascensis producta (White) 

"Unto" sp.

Locality 40.—The NWtf sec. 31, T. 9 S., R. 49 E., 

Powder River County; about 125 feet above the 

Anderson coal bed.

Viviparus raynoldsanus (Meek and Hayden) 

Lioplacodes mariana Yen 

Lioplacodes tenuicarinata (Meek and Hayden) 

Lioplacodes limnaeiformis (Meek and Hayden) 

Gyraulus militaris (White) 

Gyraulus parvulus (Meek and Hayden) 

Sphaerium sp. undet. 

"Unio" spp.

Locality 41.—The SE# sec. 31, T. 9 S., R. 49 E., 

Powder River County; about 100 feet above the 

Anderson coal bed.

Viviparus raynoldsanus (Meek and Hayden) 

Lioplacodes mariana Yen

Lioplacodes tenuicarinata (Meek and Hayden) 

Lioplacodes limnaeiformis (Meek and Hayden) 

Gyraulus parvulus (Meek and Hayden) 

"Unio" sp.

Locality 42— The SWtfgEtf sec. 4, T. 7 S., R. 50 E., 

Powder River County; about 12 feet above a local bed 

below the Cache coal bed. 

Campeloma nebrascensis (Meek and Hayden) 

Lioplacodes limnaeiformis (Meek and Hayden) 

Goniobasis nebrascensis (Meek and Hayden) 

Goniobasis nebrascensis producta (White) 

Sphaerium sp. undet. 

"Unio" sp.

Locality 43— West edge sec. 32, T. 1 S., R. 51 E., 

Powder River County; reworked specimens in a terrace 

deposit capping a high ridge of uppermost somber beds.

Viviparus retusus (Meek and Hayden) 

Campeloma nebrascensis (Meek and Hayden) 

Goniobasis nebrascensis producta (White) 

"Unio" sp.

Locality 44.—Center S}£ sec. 30, T. 9 S., R. 51 E., 

Powder River County; about 75 feet above tho Cache 

coal bed.

Campeloma nebrascensis (Meek and Hayden) 

Lioplacodes limnaeformis (Meek and Hayden) 

"Unio" sp.

Locality 45.—Sec. 24, T. 58 N., R. 77 W., Wyoming; 

about 50 to 75 feet below the Roland coal bed. 

Viviparus trochiformis (Meek and Hayden) 

Lioplacodes mariana Yen 

"Unio" sp.

SYSTEMATIC DESCRIPTIONS

Family VIVIPABIDAE 

Viviparus raynoldsanus (Meek and Hayden)

Plate 10, figure 1

Vivipara raynoldsana Meek and Hayden, Acad. Nat. S"i. Philadelphia Proc., vol. 13, p. 446, 1861.

This species is recorded here by rather perfectly 

preserved specimens from five localities. The whorls 

are greatly convex and bear growth and spiral lines. 

The development of spiral striae varies from obscure to 

faintly traceable, and they are never prominent. It is 

easily distinguished from the next species by tho outline 

of shell and sculpture. The illustrated specimen measures 45 mm. in altitude and 30 mm. in width of the shell, 

22 mm. in height and 16.2 mm. in width of aperture, 

and has 6K whorls.

Plesiotype, U. S. Nat. Mus. 560162.

Viviparus trochiformis (Meek and Hayden)

Plate 10, figures 2, 2a

Paludina trochiformis Meek and Hayden, Acad. Nat. £'ci. Philadelphia Proc., vol. 8, p. 122, 1856.

This species was described on the basis of an immature specimen. Specimens corresponding to s, similar 

stage of development are found in the present collection, 

together with a large series of adult specimers. The 

sculpture is prominent and consists of 4 to 5 primary 

spiral lines with secondary ones in the interspaces. 

The shell also bears very distinct lines of growth. The 

differences of sculpture on the shells of viviparids generally indicate the different development of the marginal 

processes of the mantle on the embryos of different 

species, and they are generally considered to be good 

specific characters, particularly in Viviparus, the 

species of which vary, often considerably, in general 

outline, size, and shape of aperture. The figured 

specimen measures 40.5 mm. in altitude and 2^.5 mm. 

in width of shell, 16.7 mm. in height and 15 mm. in 

width of aperture, and has 7 whorls.

Plesiotypes, U. S. Nat. Mus. 560163.

Viviparus retusus (Meek and Hayden)

Plate 10, figure 3

Paludina retusa Meek and Hayden, Acad. Nat. Sci. Philadelphia 

Proc., vol. 8, p. 122, 1856.
PALEOCENE FRESH-WATER MOLLUSKS FROM SOUTHERN MONTANA 41

A few specimens from localities 39 and 43 are identical 

with this species. It is characterized by its scarcely 

convex whorls, angulated periphery, and closed umbilicus.

Plesiotype, U. S. Nat. Mus. 560164.

Campeloma nebrascensis (Meek and Hayden)

Plate 10, figures 4, 4a, 5, 5a, b

Bulimus nebrascensis Meek and Hayden, Acad. Nat. Sci. Philadelphia Proc., vol. 8, p. 118, 1856.

This species is recorded here from two localities in the 

lower part of the formation. It is characterized by 

its shell substance, inflated body whorl, and thickened 

inner lip margin. Some shells, probably males, have 

a less inflated body whorl, which gives a narrower outline to the shell. The spiral lines are faintly traceable 

in a few specimens in this collection. The measurements in millimeters of two specimens are as follows:

Altitude of shell-------------- ___ -

Width of shell--_--_--_--------- __ _

21. 7+

11.0

9.0

6.0

5/2 +

15. 6

7.8

6.5

4.2

7

Altitude of shell _ _________

Width of shell. _________

Height of aperture

Width of aperture

Number of whorls

33. 0 +

18.2

14. 0

10. 5

K_l_

28. 5

16. 5

13. 8

Q n

5

Plesiotypes, U. S. Nat, Mus. 560165, 560166.

Lioplacodes mariana Yen

Plate 10, figures 6, 6a, b, c

Lioplacodes mariana Yen, Am. Jour. Sci., vol. 224, No. 1, p. 44, 

pi. 1, figs. 5a-c, 1946.

This species has been recorded, I believe, in the early 

literature under Lioplax nebrascensis or Goniobasis 

nebrascensis. However, it is readily distinguished from 

that species, as I have already pointed out elsewhere. 

It seems to be a common species of the Fort Union formation, and in several localities it is found in association 

with the next species.

There are specimens in the collection having a narrower outline of the shell, though the other features are 

essentially identical with those of the broader form.

The measurements in millimeters for four specimens

Altitude of shell _ _ _ _

Width of shell.. ________

Height of aperture

Width of aperture _ _ _

Number of whorls ___

20. 0

9. 5

8.0

5.5

7

19. 5

8. 5

7.0

5.0

7

17. 6

7.8

7.0

4. 5

7

Q n

5. 0

4. 5

2.8

5>2

Plesiotypes, U. S. Nat. Mus. 560168, 560169, 560170.

Lioplacodes tenuicarinata (Meek and Hayden)

Plate 10, figures 7, 7a-d

Melania tenuicarinata Meek and Hayden, Acad. Nat. Sci. Philadelphia Proc., vol. 9, p. 137, 1857.

This species was described on the basis of a young 

shell, which one of the specimens figured here resembles 

very closely. The adult specimens reach a much larger

792023—48———2

size and bear a narrowly open umbilicus. It differs 

from the preceding species by having distinct spiral 

sculpture in young specimens as well as in the adult 

ones.

The measurements hi millimeters for two examples 

are as follows:

Plesiotypes, U. S. Nat. Mus. 560171, 560172.

Lioplacodes limnaeiformis (Meek and Hayden)

Plate 10, figure 11

Bulimus limnaeiformis Meek and Hayden, Acad. Nat. Sci. 

Philadelphia Proc., vol. 8, p. 118, 1856.

This is one of the more characteristic forms in the 

Fort Union formation. It is easily recognized by its 

narrowly oblong outline, tapering gradually toward the 

apex, its scarcely convex whorls, and its narrowly perforated umbilicus. One of the well-preserved specimens is 20 mm. in altitude and 8 mm. in width of the 

shell, 8 mm. in height and 4.1 mm. in its width of aperture, and has 7 whorls.

Plesiotype, U. S. Nat. Mus. 560173.

Family AMNICOLIDAE

Fluminicola protea Yen, n. sp.

Plate 10, figure 12

Shell broadly ovate in outline, of thin substance, 

having an elevated spire and moderately dilated body 

whorl. Whorls increasing rapidly in size, convex, 

and bearing fine but distinct lines of growth and spiral 

striae. Aperture subovate in outline, apparently 

having a thin peristomal margin.

The measurements in millimeters of the holotype 

and para type are as follows:

Width of shell.---.----------- ------

8.5

6.3

43/

7.0

5.7

4

This form has all the features of Fluminicola, species 

of which are recorded so far from Pliocene to Recent 

time in North America. I find no valid reason v^hy 

Fluminicola could not have preceded the Pliocene, even 

though the relationship of the present species to others 

of the genus is not clear at present.

One of the specimens here has its operculum partly 

preserved in its natural position, and this seems to be 

much like the type of operculum in Viviparus.

Holotype, U. S. Nat. Mus. 560174; paratypes, U. 

S. Nat. Mus. 560175.
42 SHORTER CONTRIBUTIONS TO GENERAL GEOLOGY, 1947

Family PLEUROCERATIDAE 

Pleurocera warrenanum (Meek and Hayden)

Plate 10, figure 8

Melania warrenana Meek and Hayden, Acad. Nat. Sci. Philadelphia Proc., vol. 9, p. 137, 1857.

The type of this species has the last 6 whorls preserved, and possibly would have 7, if perfect. Some of 

the larger specimens in the present collection have 8 to 

8K whorls, but they are identical with the type in other 

features. The species is characterized by the scarcely 

convex or nearly flat surface of the early whorls, which 

are acutely angulated. The aiigulatioii is obtuse only 

along the periphery.

Meek was not certain of the generic position of the 

species. It was originally described as Melania and 

subsequently changed to Hydrobia. By its narrowly 

oblong outline, acute spire, nearly flattened whorls, and 

imperforate shell, it seems more closely related to 

Pleurocera. One of the well-preserved specimens measures 11.3 mm. in altitude and 4.5 mm. in width of the 

shell, 3.3 mm. in height and 2.8 mm. in width of aperture, and has the last 7 whorls preserved.

Plesiotype, U. S. Nat. Mus. 560176.

Goniobasis nebrascensis (Meek and Hayden)

Plate 10, figure 9

Melania nebrascensis Meek and Hayden, Acad. Nat. Sci. Philadelphia Proc., vol. 8, p. 124, 1856.

This species was found only at one locality of the 

present collection, but it is represented by more than 80 

specimens. It is characterized by its acute spire, dilated 

body whorl, scarcely convex whorls, and by having its 

basal lip margin somewhat produced. Judged by the 

features visible in this series of specimens, this form resembles more closely species of Goniobasis than those of 

Campeloma and Lioplax, although it may not be a 

Goniobasis in the restricted sense. One of the adult 

specimens measures 26.5 mm. in altitude and 13 mm. in 

width of the shell, 11.1 mm. in height and 7.8 mm. in 

width of aperture, and has the last 5 whorls preserved.

Plesiotype, U. S. Nat. Mus. 560177.

Goniobasis nebrascensis producta (White) 

Plate 10, figure 10

Campeloma producta White, U. S. Nat. Mus. Proc., vol. 5, p. 97, 

pi. 3, figs. 7-9, 1883.

A few specimens seem to agree well with this form, 

which differs from the typical form of the species by its 

more elongate outline. However, it agrees well with 

the typical form in other features. One of the adult 

specimens measures 31 mm. in altitude and 13.4 mm. in 

width of the shell, 10.7 mm. in height and 7.1 mm. in 

width of aperture, and has the last 6 whorls preserved.

Plesiotype, U. S. Nat. Mus. 560178.

Family ANCYLIDAE 

Ferrissia minuta (Meek and Hayden)

Plate 10, figure 14

Valletta (Ancylus) minuta Meek and Hayden, Acad. Nat. Sci. 

Philadelphia Proc., vol. 8, p. 120, 1856.

A few fairly well preserved specimens are identical 

with this species. It is characterized by its small size, 

ovate-oblong outline, anterior apex, which points toward the anterior margin, and fine but distinct concentric lines of growth with occasional undulations over 

the surface. The anterior right margin seems- to be 

slightly contracted. The average-sized specimer measures 4 mm. in length and 3 mm. in width.

Plesiotypes, U. S. Nat. Mus. 560179.

Palaeancylus, n. gen.

Shell limpetlike, ovate in outline, of thin substance, 

and of moderate size in Ancylidae. Apex apparently 

sinistral, slightly coiled, subcentrally posterior in 

position, and having a distinct dimplelike depression 

on the apical surface. The dimple is well-defined by an 

encircling margin. The sculpture consists of distinct 

but fine concentric lines of growth and radiating lines 

all over the surface.

Genotype: Palaeancylus radiatus, 11. sp.

The new genus now under consideration is differentiated from most of the fresh-water limpets by a small 

dimplelike depression on its apical surface, which 

feature has been found oil all the well-preserved specimens in the present collection.

The morphological significance of this apical depression is unknown, but it seems to be quite a distinct 

feature that has been ignored or taken as an individual 

abnormality by early investigators. In the living 

fauna, I have noted several species, such as Ancylus 

jluviatilis Mueller, Ancylus abissinicus Jickeli, Ancylus 

caliculatus Bourgguignat, and "Ferrissia" platyrhynchus 

Walker, described from southern Europe and northern 

Africa, which also bear this distinct feature, though 

differing in degree in its development. These species 

seem to belong to Pseudoancylus Walker 1921, with 

Ancylus jluviatilis as its genotype, from which Palaeancylus, n. gen., of the Fort Union formation, differs by 

having an apparently sinistral apex, posteriorly contracted margin on the left side, and more distinct 

sculpture.

Palaeancylus radiatus, n. sp.

Plate 10, figure 13

Shell essentially the same as described for the genus. 

The radiating sculpture is stronger than the concentric 

lines; the apex is apparently sinistral, subcentrally 

posterior in position, somewhat nearer the left side of 

the peristomal margin, where the marginal line i^ somewhat contracted. The right side of the margin is 

entire.
PALEOCENE FRESH-WATER MOLLTJSKS FROM SOUTHERN MONTANA 43

The measurements in millimeters of the holotype and 

the paratype are as follows:

Length of shell

Width of shell _

4. 5 

3. 5

10.3 

8.0

Holotype, U. S. Nat. Mus. 560180; paratypes, U. S. 

Nat. Mus. 560181.

Family LYMNAEIDAE 

Pleurolimnaea tenuicosta (Meek and Hayden)

Plate 10, figure 15

Limnaea tenuicosta Meek and Hayden, Acad. Nat. Sei. Philadelphia Proc., vol. 8, p. 119, 1856.

This species is so far known only from the Fort 

Union formation. A few well-preserved specimens 

were found at one locality of the present collection.

Both on morphological and on stratigraphical 

grounds, Pleurolimnaea Meek may well be considered 

as a distinct genus, but its family assignment may need 

further consideration. The genus may belong to 

Ellobiidae and is possibly related to Tortacella.

An adult specimen measures 13.1 mm. in altitude 

and 4.5 mm. in width of the shell, 6 mm. in height and 

2.2 mm. in width of aperture, and has 5 whorls.

Plesiotype, U. S. Nat. Mus. 560182.

Family PHYSIDAE 

Physa cf. P. bridgerensis Meek

Plate 10, figure 16

Physa bridgerensis Meek, Hayden Survey, 6th Ann. Kept., p. 

516, 1872.

A few specimens seem to resemble closely Physa 

bridgerensis but differ by having smaller size, lower 

spire, and more whorls.

The largest specimen measures 27.5 mm. in altitude 

and 17.1 mm. in width of shell, 18 mm. in height and 

9 mm. in width of aperture, and has about 6 whorls.

Figured specimen, U. S. Nat. Mus. 560183.

Aplexa cf. A. longiuscula (Meek and Hayden)

Plate 10, figure 17

Physa longiuscula Meek and Hayden, Acad. Nat. Sei. Philadelphia Proc., vol. 8, p. 119, 1856.

A few examples in the collection, which represent 

different stages of development, resemble closely this 

species, but they differ by having a more acute and 

higher spire, and they are of much smaller size, with a 

similar number of whorls. It may be a new species, 

but none of the available specimens show the aperture 

well enough for a satisfactory description. One of the 

adult specimens measures 11.5 mm. in altitude and 6.1 

mm. in width and has 6 to 7 whorls.

Figured specimen. U. S. Nat Mus. 560184.

Family PLANORBIDAE 

Gyraulus militaris (White)

Plate 10, figure 18

Planorbis militaris White, U. S. Nat. Mus. Proc., vol. 3, p. 159, 

1880.

Only one lot in the present collection contains 

abundant specimens of this species, and in others it is 

represented by a few individuals. This species is often 

found in association with the next species, but it is 

easily distinguished by the absence of a carina on the 

basal surface and by a slightly larger size. One of the 

adult specimens measures 1.4 mm. in altitude and 3 

mm. in width and has 3K whorls.

Plesiotypes, U. S. Nat. Mus. 560185.

Gyraulus parvulus (Meek and Hayden)

Plate 10, figures 20, 20a

Valvata parvula Meek and Hayden, Acad. Nat. Sci. Philadelphia 

Proc., vol. 8, p. 123, 1856.

This species is recorded from four localities in the 

present collection. It is one of the very few spe°ies 

described by Meek and Hayden without a figure of the 

type. However, it was originally described as "having 

near the middle of the upper and lower sides a distinct 

linear carina," a feature which is well shown in the 

specimens in the present collection. One of the adult 

specimens measures 1 mm. in altitude and 3 mm. in 

width and has about 3 whorls.

In 1935 Henderson (Geol. Soc. America Spec. PsDer 

3, p. 191) followed Cossman (Essais de paleoconchologie 

compare1 e, livr. 12, p. 170, 1921) in changing the np.me 

of this species to Valvata subparvula, because V. parvula 

had been used by Deshayes for a Thanetian species 

from France. By examining the original citatior, of 

both species, I am obliged to point out that Cossmann's 

change cannot be sustained. Meek and Hayden proposed the name in May 1856 and published it some 

time between June 1856 and April 1857; whereas Deshayes' name appeared on page 526, volume 2, of his 

"Descriptions des animaux sans vertebres du Bassin de 

Paris," which was not published until May 1862. The 

name proposed by Meek and Hayden has ample priority over that of Deshayes, and the French specie? is 

here renamed Valvata deshayesi, new name.

Plesiotypes, U. S. Nat. Mus. 560186.

Carinorbis planospiralis Yen

Plate 10, figure 19

Carinorbis planospiralis Yen, Am. Jour. Sci., vol. 224, No. 1, 

p. 46, pi. 1, figs. 6a-c, 1946.

This species is one of the characteristic forms of the 

Fort Union formation, although it is recorded from only 

six localities in the present collection. It is easily 

recognized by its carinated outline and nearly flattened 

spire. One of the adult specimens measures 2.1 mm.
44 SHORTER CONTRIBUTIONS TO GENERAL GEOLOGY, 1947

in altitude and 4.4 mm. in width of the shell, 2 mm. in 

height and 1.2 mm. in width of aperture, and has 4 

whorls.

Plesiotype, U. S. Nat. Mus. 560187.

Family SPHAERIIDAE 

Sphaerium cf. S. formosum (Meek and Hayden)

Plate 10, figure 21

Cyclas formosa Meek and Hayden, Acad. Nat. Sci. Philadelphia 

Proc., vol. S, p. 115, 1856.

A few specimens from one lot of the present collection resemble this species in general outline, though the 

hinge structure is not observable. In another lot are 

three left valves that show the hinge line slightly curved, 

with two short, parallel cardinals and single anterior 

and posterior laterals. The posterior lateral is long 

and slightly truncated in the middle and moderately 

raised at its end; the anterior lateral is short and is 

terminated by a prominent tooth of triangular shape.

Figured specimen, U. S. Nat. Mus. 560188.

Family UNIONIDAE 

Elliptic cf. E. priscus (Meek and Hayden)

Plate 10, figures 22, 22a

Unio priscus Meek and Hayden, Acad. Nat. Sei. Philadelphia 

Proc., vol. 8, p. 117, 1856.

Specimens from several localities in the present collection externally resemble this species closely.

The structure of the hinge was not described in the 

original description. One lot in the present collection 

contains a large series of single valves that show the 

hinge plate to be narrow, with two pseudocardinals 

and two laterals in the left valve; one prominent 

pseudocardinal and one lateral in the right valve. The 

anterior muscular impression is of subtriangular shape 

and large size.

Figured specimens, U. S. Nat. Mus. 560189.

Elliptic cf. E. silberlingi Russell

Plate 10, figures 23a, b

Ell'iptio silberlingi Russell, Washington Acad. Sci. Jour., vol. 24, 

p. 128, figs. 1, 2, 1934.

This form differs from the preceding species by its 

more elongate outline, less prominent pseudocardinals, 

and shorter laterals on both valves, but their number 

and arrangement are essentially similar.

The specimens in the present collection are much 

smaller in size than the type, which was described from

the Eagle coal mine, Bear Creek, Carbon County, 

Alont.

Figured specimens, U. S. Nat. Mus. 560190.

"Unio" sp. undet.

Plate 10, figure 24

Several specimens were obtained from locality 6 that 

are decidedly different from other Unios in the collection but are not sufficiently well preserved to permit 

generic or specific identification. They are characterized by an almost lanceolate outline and are rather 

pointed toward the posterior end. The valves are 

closed.

Figured specimen, U. S. Nat. Mus. 560191.

BIBLIOGRAPHY

BAKER, A. A., The northward extension of the Sherdan coal

field, Big Horn and Rosebud Counties, Mont.; U. S. Geol.

Suvey Bull. 806-B, 1929. 

BROWN, R. W., The age of the Kingsbury conglomerate is

Eocene: Geol. Soc. America Bull, (in press). 

COSSMAN, MAURICE, Essais de paleoconchyliologie comparee,

vol. 12, 1921. 

HENDERSON, JUNIUS, Fossil nonmarine Mollusca of North

America: Geol. Soc. America Spec. Paper 3, 1935. 

MEEK, F. B., A report on invertebrate Cretaceous and Tertiary

fossils of the upper Missouri country: U. S. Geol. and Geog.

Survey Terr. Repts., vol. 9, 1876. 

MEEK, F. B., and HAYDEN, F. V., Descriptions of new species of

Acephala and Gastropoda, from the Tertiary formations of

Nebraska Territory: Acad. Nat. Sci. Philadelphia Proc., vol. 8,

pp. 111-126, 1856.

—— Descriptions of new species and genera of fossils, collected 

by Dr. F. V. Hayden in Nebraska Territory: Acad. Nat. Sci. 

Philadelphia Proc., vol. 9, pp. 117-148, 1857.

RUSSELL, L. S., Early Tertiary Mollusca from Wyoming: Am. 

Paleontology Bull., vol. 18, No. 64, 1931.

SPIEKER, E. M., Late Mesozoic and Early Cenozoic Hstory of 

central Utah: U. S. Geol. Survey Prof. Paper 205-D, 1946.

THOM, W. T., JR., and DOBBIN, C. E., Stratigraphy of the Cretaceous-Eocene transition beds in eastern Montana and the 

Dakotas: Geol. Soc. America Bull., vol. 35, pp. 495-496, 1924.

WEED, W. H., The Fort Union formation: Am. Geologist, vol. 

18, No. 4, pp. 201-211, 1896.

WEGEMANN, C. H., Wasatch fossils in so-called Fort Union beds 

of the Powder River Basin, Wyo., and their bearing on the 

stratigraphy of the region: U. S. Geol. Survey Prof. Piper 108, 

pp. 57-60, 1918.

WHITE, C. A., On the relation of the Laramie molluscan fauna 

to that of the succeeding fresh-water Eocene and other 

groups: U. S. Geol. Survey Bull. 34, 1S86.

YEN, TENC-CHIEN, Paleocene fresh-water mollusks from Sheridan 

County, Wyo.: Am. Jour. Sci., vol. 224, pp. 41-48, 1946.

—— Eocene nonmarine gastropods from Hot Springs County, 

Wyo.: Jour. Paleontology, vol. 20, No. 5, pp. 495-500, 1946.
PLATE 10

45
PLATE 10

[Figures natural size unless otherwise designated]

Page

FIGURE 1. Viviparus raynoldsanus (Meek and Hayden). Locality 24__ ____---_--_-_______-_--___„_____--__---._-_____--- 40

2. Viviparus trochiformis (Meek and Hayden). Locality 25__-__---_----__--------------__--__---_----.-_-_----_ 40

. 3. Viviparus retusus (Meek and Hayden). Locality 39__-_...--__-.__--___-__-.----______--_---__-_-_---_-_--- 40

4, 5. Campeloma nebrascensis (Meek and Hayden). 4, 4a, Locality 42. 5, 5a, 5b, Locality 43__-._-— _______________ 41

6. Lioplacodes mariana Yen, X 2. 6, Locality 7. 6a, Locality 35. 6b, Locality 40-i.---____--___--__---__-__--___ 41

7. Lioplacodes tenuicarinata (Meek and Hayden), X 2. 7, 7a, Locality 24. 7b, 7c, 7d, Locality 40____...__________ 41

8. Pleurocera warrenanum (Meek and Hayden), X 2. Locality 13____--.__-__-_____.______________--__-_-__--_- 42

9. Go niobasis nebrascensis (Meek and Hayden), X 2. Locality 42____,._. _________ .___________-___.---___ ________ 42

10. Goniobasis nebrascensis producta (White), X 2. Locality 42_____.____ .____.______________._.--______---_____- 42

11. Lioplacodes limnaeiformis (Meek anc1 Hayden), X 2. Locality—____________--_--_-____-____-______---_____- 41

12. Fluminicola protea Yen, n. sp. holotype, X 2. Locality 17__----------_----__--__----_-------------_---_----- 41

13. Palaeancylus radiaiu*. Yen, n. gen. and sp., holotype, X 10. Locality 17-___-.________________________________ 42

14. Ferrissia minuta (Meek and Hayden), X 10. Locality 17------- __-____-_-_---__--_---_---_---_--__---_---_- 42

15. Pleurolimnaea tenuicosta (Meek and Hayden), X 2. Locality 17__ ___________________________________________ 43

16. Physa cf. P. bridgerensis Meek. Locality 17----_------------_-_-----_------------------------------------- 43

17. Aplexa cf. A. longiuscula (Meek and Hayc"en), X 2. Locality 17.____________________________________________ 43

18. Gyraulus militaris (White), X 4. Locality 29_..--__--_-__--------_-_----_---_---_------------------------- 43

19. Carinorbis planospiralis Yen, X 4. Locality 12--.____ _____________________________________________________ 43

20. Gyraulus parvulus (Meek and Hayden), X 4. Locality 29_-.----------__---_---_---_---------------_--__----- 43

21. Sphaerium cf. S. formosum (Meek and Hayden), X 4. Locality 42 _____..-___-_______-__-__-____--__-_-__-_-_ 44

22. Elliptio cf. E. prisons (Meek and Hayden). Locality 29_ ______-.__._-___ .________-_____-___-_-_--_________-_ 44

23. Elliptio cf. E. silberlingi Russell. Locality 29_.___.__--.-___-__.---.___-._---_---__------_-..---__---_----_ 44

24. Unio sp. undetermined. Locality 6-____._--______________________________________________________________ 44

46
GEOLOGICAL SURVEY PROFESSIONAL PAPER 214 PLATE 10

PALEOCENE MOLLUSKS

INDEX

Page 

abissinicus, Ancylus————.-------.-___.__________.— — _ —__...__.. 42

Acknowledgments for aid.....- —._.--..-.__—___.__ — ____ — ___.___.. 35

Ancylus abissinicus——--____—————______........___.._— _..._ 42

caliculatus__._.--.-.-----___...._..___....__...._________ 42

fluviatilis.-____---------_____..__...........____..._.. 42

anthonyi, Melania____...._-------__....__.....___....__. 35

Aplexa.--------------- — ------- — __-------___-.._____....__-. 35

longiuscula- — --————— — ———— —— ———_... 36,38, 43, pi. 10

Bibliography _._.______________._._._.-_-_-_-_.........___-____ 44

Big Horn County, fossils from______................._......_.____.. 37-38

bridgerensis, Physa. - — _-_-____.____..____..._____ 36, 38, 43, pi. 10

Bulimuslimnaeiformis--------_....___..............__.___.___.. 35,41

nebrascensis._.- —. — -.-.---_-_-_.__...._____.________ 35,41

caliculatus, Ancylus..._---------____-.....__-_-.._-__...._____..._. 42

Campeloma.--._——....—-__.__...___________.......__ 35,42

nebrascensis-----__-----....._._..._____.__.____ 36, 37, 40, 41, pi. 10

producta---.--—_——— —— —____.... ___.___.-.___..._.. 42

Carinorbis.__._ — ——-...___.____._.____.______.___. 35,38 

planospiralis--.---___...._____________... 36, 37, 38, 39, 43-44, pi. 10

Coryphodon_...... — ----------- —— _-__...__......_____.....-__.__ 37

Crazy Mountains, mollusks from-_-_----__-------_-______..__._.._ 35

Cyclas formosa.-----------------____.-.-___-____-------__...__ 35,44

subellipticus_____-_..._._.......____......_____....__. 35

deshayesi, Valvata. 43

Elliptic....____.______.________._______..______._.., 35 

priscus---_ —- — ----„-—------„ — ----_—- 36, 37, 38, 39, 40, 44, pi. 10

silberlingi-.————— — — ———— „. ———......... 36, 37, 38, 39, 44, pi. 10

eulimoides, Hydrobia. — ___- — __-__ ..... — -.____._____...___........ 35

Ferrissia..._-__-- ——— - —— -————— — __-— _____-______.. 35 

minuta-—— —————————————————.———— 36, 37, 38, 42, pi. 10

platyrhynchus ...___------_---____________._-.--.-.... 42

Flnminicola.-----------------__..._--.-._--.-----......_.________ 35, 41

protea, ............-—...--.-.-..--. — -.-----.............. 36, 38, 41, pi. 10

fluviatilis, Ancylus------——————-— —.____.-_._________.____ 42

formosa, Cyclas_.- — — ---- —— ---.--_______.. —-__—_—____——____ 35,44

formosum, Sphaeriutn..__________....._____._.________ 36, 44, pi. 10

formosus, Viviparus leidyi-——— -------—__________...._.....____ 35

Fort Union formation, ageof-..__._____...__._____-_____ 37 

mollusks from.----._...__.-..____------_....________. 35

Fossil collections, geographic distribution of_-----_-_-_-______.___.... 37-40

source of.---------_---__------__-_-__--________._._...____._. 35

Goniobasis___.__.._____________.__________-_______._ 35, 37, 42 

nebrascensis-._._.....__.________.__._-36, 37, 40, 41, 42, pi. 10 

nebrascensis producta.-..______________..___ 36, 37, 40, 42, pi. 10

Gyraulus..---__..._ ——————.————__--------_-__...____.. 35

militaris....--.--._.-..--.-.--.-..-—-------.-.----..--.. 36, 38, 39, 40, 43, pi. 10

parvulus---------_______...._______._____ 36, 38, 39,40, 43, pi. 10

Hydrobia—....

eulimoides _-

Hyracotheriuminsculpta, Melania.

Kingsbury conglomerate, age of_.

leai, Paludina...---.———.—..- ————.__-----_.__..___..___ 35 

leidyi, Paludina.-._——__........._.................................... 35

Lignite group, mollusks from____.________. ________ _____ 35 

Limnaea tenuicosta—_._.___-___-___-._.——........._-.---..-______.. 35, 43

limnaeiformis, Bulimus.—........_______--____...___.__ 35, 41

Lioplacodes........—————................... 36, 37, 38, 39, 40, 41, pi. 10

Lioplacodes._.___.______.________.._____________ 35,38 

limnaeiformis....-..--- ——- — -.----„-... 36, 37,48, 39, 40, 41, pi. 10

mariana——-------------—--------.--------_. 36, 37, 38, 39, 40, 41, pi. 10

tenuicarinata———— — —— —— —— ———— ——— 36, 37, 38, 39, 40, 41, pi. 10

Pagi 

Lioplax--.__________________----- —— —— ——.——..... 47

nebrascensis-___.__-----_________-.... ————— —..——. 41

longinscula, Aplexa..-._.................................._._.. 36, 38, 43, pi. 11

Physa—...——. ————_———.——-_.——.————.———————— 35,43

mariana, Lioplacodes--—..........................—..„ 36, 37, 38, 39, 40, 41, pi. n

Melania..........—............-.—......-.....-....—.._—„.„.....— 49

anthonyi..------__...._________.--. —.-.-————..---- — -— 35

insculpta.-----------_----------_.-.____—__ ———.—__..._.. 37

minutula._---_.._..___ — ______----------____------------ 35

multistriata _--._-.--_____-----___...---.--.--___------------ 35

nebrascensis-----_.___----------__------__-____--.___ 35, 42

tenuicarinata_..___________._...-------___..._____ 35, 41

warrenana—..._.___.....___....._... ——.._ —— ————.. — — — 35, 42

•wyomingensis..--.—__._.____-------—----- ——— —— — — — 37

militaris, Gyraulus.-..............................—...... 36, 38, 39, 40, 43, pi. 10

Planorbis——— -- —— -—-----.—--———---- — ---——-—~— 43

minuta, Ferrissia,-. —. — .... — ......—........-„ — -„--.. 36,37,38, 42, pi. 10

Valletta (Ancylus)-.................................................__. 35,42

minutula, Melania.....______-----_-----—----- ——...—......_ 35

Mollusks, age of.. ——_—.—.——————— ——-——————--_...... 36-37

earliest records of__—____..---________-__.______...___ 35

ecologic significance of..___.________.———————— ———.... 36

species of, summary of.. ———_._-_ ————————— — ——....... —— — 36

stratigraphic distribution of—....._..-..——— —..... —————— ———— 36-37

montanaensis, Valvata_—_.___-.-..-.—„..- ——... ——— —— ———. 35

multistriata, Melania______.-.-.-__——. ——.-——————————. 35

nebrascpnsis, Bulimus.-_________.._---------- ———_____.. 35,41

Campeloma—————————— —— ———————— —_ 36, 37, 40, 41, pi. IT

Goniobasis----------..-----------------------_------- 36, 37, 40, 41, 42, pi. 10

Lioplax. -_-_-------------_-----_------- — ------------ —— - ————— —— 41

Melania......__.________________---____...______ 35, 49

North Dakota, mollusks from......____..——.——————————————— 3"

Palaeancylus__--________.._.........___-- —..——————...__ 35,42

radiatns— —— — —— ———— ————— —.—— —————— 36, 38, 42-43, pi. 1'j

Paludina leai____ — — -----------——-___—___-_---_— — — ——— ————— 35

leidyi...———— — —--.--..-. —— — —— .--- — ---——-.-.-— 35

peculiaris__._____---..-. — — — — ———— —— — ----- —— ------ 35

retusa_ — _ ———. -___ — ____-_— —— —.--.. —— ———........—— —... 35,4')

trochiformis.-..______..______ — ________-__________ 35,40 

parvula, Valvata_ — ____..___-..._-...._—— —. — .———_—..... 35,43

parvulus, Gyraulus._......._-__.________-—36, 38, 39, 40, 43, pi. IT

peciliaris, Paludina_ —— —__.. — ___-__------—......___------__. 3"

Physa---—-- — ..-——.. — --- — --—---——--——- — — ---- 35,43,pi. 10

bridgorensis_._____..._______._______._____ 36,38, 43, pi. 10 

longiuscula- — ____......._____ —.___.- ———— - — - ———— -—— 35,43

rhomboidea-- ...._. —...................... — ——— —— —————. —— 35

Planorbis militaris__.__ — -.-.-. —.........—— ..-- ————— ----- —. 43

planospiralis, Oarinorbls—.-—---.. — -———-—- 36, 37, 38, 39, 43-44, pi. 10 

platyrhynchus, Ferrissia_ ___.__._.....__._--.- — ————— — __.— 42

Pleurocera.__.________.__.__...________________-__ 35,42 

warrenanum———-.— —— — ———--- ———- 36,37,38,39,42, pi. 10

Pleurolimnaea— — ___-------_...._...--_------ —— ——— - —.. —.. 35,43

tenuicosta.-—-----------------------------------------_ 36, 37, 38, 43, pi. 10

Powder River County, fossils from.. — _______.. —— -- ———-——_——— 38-40

priscus, Elliptic—-—— — — -————-———— 36, 37, 38, 39, 40, 44, pi. 10

Unio-..—————.——— —— — —————————.——- 41

producta, Goniobasis nebrascensis-----_.__....__..._- 36, 37, 40, 42, pi. 10

protea, Fluminicola.________._______.__________ 36, 38, 41, pi. 10

Pseudoancylus--._____... ___...---__------ —— ————————— 42

radiatus, Palaeancylus.—-._ — --—————————--.—-— 36,38,42-43,pi. 10

raynoldsana, Vivipara.-_..-..--...._ — — ._—__———— ——————.—— 35,40

raynoldsanus, Viviparus..-.----------------_..——..... 36,37,38,39,40,pi. 10

retusa, Paludina__._______.._______ —...—————„____._- 35,40 

retusus, Viviparus— .....————. ————— ——————....—— 36,40-41, pi. 10

rhomboidea, Physa......—————— — —— — — —————— ————————.. 35

Roland coal bed, mollusks from__.......____ ——.———————————— 35-3i3

Rosebud County, fossils from____________....——————..... ——.. 3?

49
50 INDEX

Page 

silberlingi, Elliptic.--.----_-_--_-_---_-_-..-.-.-----......-.. 36, 37, 38, 39, 44, pi. 10

Sphaerium.______.___._...._-...._-_--_-______________-_.___. 35, 38, 40,

formosum.- ._— — - — — — — — — ...---.._-.....--.....____.__._ 36, 44, pi. 10

sp— — — ———— ——— ——— ————— — — — — — -----.----..-------.._. 40

subellipticus, Cyclas_ 

subparvula, Valvata__ 

subumbilicata, Valvata.

tenuiearinata, Lioplaeodes_____.________..._.__ 36, 37, 38, 39, 40, 41, pi. 10

Melania..__......_..-. — .__.... — .-.... —.......__.__...... 35,41

tenuicosta, Limnaea.....-....-....„._..............._.._________._ ... 35,43

Pleurolimnaea------_____ —..._____._-____-.__._ 36, 37, 38, 43, pi. 10

thompsoni, Tulotoma.............___ _______.__. ..................._... 37

Tongue River member and Wasateh formation, boundary between........... 36-37

Tortacella.—„. —————.......„..........._.......—————. —... — .. 43

trochiformis, Paludina----.-.--.-_-...__- — .......-...„._.............. 35,40

Viviparus. —.- —— . — - — ----..--... .—...„.. —— „..„. 36, 37, 38, 40, pi. 10

Tulotoma thompsoni..____._____._._ .—...........„..... — .................. 37

Um'o priseus... ------------__........ — ._____........_ — _—— — _—. 44

spp—— — --. — - — - — ——— --_- — . — -. — .— 30, 37, 38, 39, 40, 44, pi. 10

Utah, mollusks from.......____-.-——_-__. — ___ —____—__ —_—_..—_ _ _______ 35

Page 

Valvata deshayesL....._.__ — — - — -———- — ——- — -- — - ——- — . 43

montanaensis-..--------------.---------_--------------------------------. 35

parvula ..__.._...--...-- — .._..._..—...—.__._.__-_._-..... 35, 43

subparvula----------.----—-____------ — --_----.——.---._ — .— ._- — 43

subumbilicata.-.. _.-_-— — — ----- — — — ._--- — -——— — — - — — --- 35

Velletia. (Ancylus) minuta.. .—.---- — ------. ——.-.---.--. ------------------ 35,42

Vivipara raynoldsana. _— ____—_-— — ._ — — — - — —— — -___—. — _ — _ 35,40

Viviparus......__-_.-.-...._-__._-. --.--. — — ..- — ---.--.— 35, 38, 39, 40, 41

Viviparus leidyi formosus_-.-------------..-------- ..-.-..----.---- — ..--. 35

raynoldsanus__....__......._.--...___—.- — -..-. 36, 37, 38, 39, 40, pi. 10

retusus........_ — .-..—-__.__.____._..._..._ 36, 40-41, pi. 10

trochiformis.------.--..---.--.-.---- —----------- 36, 37,38, 39, 40, pi. 10

sp.__...__... — ___ — _--_-_--..-.-.__....____._._.__... 37,39

warrenana, Melania — — .. — _._-- — - — - — ——------------- —._.----. —.. 35,42

.warrenanum, Pleuroeera._.__.___ — _...___.... _..._ 36, 37, "8, 39, 42, pi. 10

Wasatch formation and Tongue River member, boundary between._...._ 36-37

Wasatch group, fossiliferous beds of..._— —— — ..--____-___..___ ——_-—.. — ..35

Wyoming, mollusks from -- — - — — — -„----„.---------— 35-36, 38, 39, 40

Wyomingensis, Melania.. —...--------- —— ------------ — — — .„ —., —.. 37

o