Pelecypoda and Rostroconchia of the 

Anisden Formation (Mississippian 

and Pennsylvanian) of Wyoming

GEOLOGICAL SURVEY PROFESSIONAL PAPER 848-E
Pelecypoda and Rostroconchia of the 

Amsden Formation (Mississippian 

and Pennsylvanian) of Wyoming

By MACKENZIE GORDON, JR., and JOHN POJETA, JR.

THE AMSDEN FORMATION (MISSISSIPPIAN AND PENNSYLVANIAN) 

OF WYOMING

GEOLOGICAL SURVEY PROFESSIONAL PAPER 848-E

Descriptions and illustrations of 

41 taxa of pelecypods and 1 

rostroconchian, with comments on 

their distribution

UNITED STATES GOVERNMENT PRINTING OFFICE, WASHINGTON : 1975
UNITED STATES DEPARTMENT OF THE INTERIOR 

ROGERS C. B. MORTON, Secretary

GEOLOGICAL SURVEY 

V. E. McKelvey, Director

Library of Congress Cataloging in Publication Data

Gordon, Mackenzie, 1913-

Pelecypoda and Rostroconchia of the Amsden Formation (Mississippian and Pennsylvanian) of Wyoming.

(The Amsden Formation (Mississippian and Pennsylvanian) of Wyoming) (Professional paper Geological Survey ; 848-E)

Bibliography: p.

Includes index.

Supt. of Docs, no.: I 19.16:848-E.

1. Lamellibranchiata, Fossil. 2. Rostroconchia. 3. Paleontology Carboniferous. 4. Paleontology Wyoming. I. Pojeta, John, joint author. II. Title. III. Series. IV. Series: United States. Geological Survey. Professional 

paper ; 848-E.

QE811.G67 564'11'09787 74-32078

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

Washington, D.C. 20402 

Stock Number 024-001-02638-4
CONTENTS

Abstract _ . 

Introduction. _________ __________.

Previous work ____ _ __________.

Present investigation ________________

Acknowledgments _______________.

Composition of the fauna ___________.

Faunal diversity _________________.

Relation to the Mississippian-Pennsylvanian 

boundary ___________________

Page

El

1

1

2

2

2

3

Composition of the fauna Continued

Stratigraphic considerations _,________

Geographic and stratigraphic occurrence of the

pelecypods ________________________

Mississippian fauna __________ _ __

Pennsylvanian fauna __________________

Rostroconchians _________________________

Systematic paleontology _________________

References cited ____________________________

Index ______________________________________

Page

E4

4

5

7

20

23

ILLUSTRATIONS

[Plates follow index]

PLATE 1. Palaeotaxodonta.

2. Isofilibranchia? and Pteriomorpha.

3. Pteriomorpha and Heteroconchia.

4. Heteroconchia, Anomalodesmata, and Rostroconchia.

Page

FIGURE 1. Diagrammatic sketch of muscle scar pattern of Paleyoldia amsdenensis (Branson and Greger) __________ _ _ _ ElO

TABLES

TABLE 1. Taxonomic relationships and relative abundance of pelecypods in 

the Amsden Formation _________________________________

2. Major life-habit groups of Amsden pelecypods ____ 

3. Pelecypod and rostroconchian fauna of the Amsden Formation of 

Wyoming ______________________________________

4. Checklist of pelecypod and rostroconchian collections ___________

Page

E3 

3

5

6

in

THE AMSDEN FORMATION (MISSISSIPPIAN AND PENNSYLVANIAN) OF WYOMING

PELECYPODA AND ROSTROCONCHIA OF 

THE AMSDEN FORMATION (MISSISSIPPIAN AND PENNSYLVANIAN) OF WYOMING

By MACKENZIE GORDON, JR., and JOHN POJETA, JR.

ABSTRACT

The study of the pelecypods of the Amsden Formation 

of Wyoming is based on 285 specimens from the collections 

of the U.S. Geological Survey, the U.S. National Museum, 

the University of Missouri, and the University of Wyoming. 

Of these, 275 are recognizable at least to genus and are assigned to 16 families, 22 genera, and 41 species. Although 

this material is not particularly well preserved, it is sufficient to show pelecypod diversity at the species level on 

both sides of the Mississippian-Pennsylvanian boundary. Thus 

it helps to fill a gap in existing knowledge. In the late 

Paleozoic, most pelecypod genera are long ranging and are 

of little use as biostratigraphic tools; at the species level 

the pelecypods can be useful in this respect. Although all 

of the Amsden specimens are assigned to Mississippian or 

Pennsylvanian parts of the formation, this has been accomplished almost solely by reliance on the foraminifers 

and brachiopods.

All the principal subclasses of late Paleozoic pelecypods 

are present in the Amsden, as are a quarter of all Paleozoic families; the latter include all the common marine 

late Paleozoic families with the exception of the Parallelodoritidae.

Because of the poor preservation of the material, the 

nomenclature is of necessity limited. Only five taxa have 

been identified to species; one of these, Aviculopecten 

gravidus, is new. A lectotype is designated for Paleyoldia 

amsdenensis (Branson and Greger). The rostroconchians are 

limited to a single fragmentary specimen.

INTRODUCTION

All too often the less well preserved elements of a 

fossil biota are omitted in otherwise comprehensive 

systematic studies, yet these organisms may have 

formed an important part of the biota. Even though 

such fossils do not lend themselves to formal descriptive paleontology, they may fill important gaps 

in paleontologic knowledge. We include, therefore, 

a special chapter on the Amsden pelecypod fauna 

which, although restricted in its distribution and 

generally not well preserved, contains representatives of 25 percent of all Paleozoic pelecypod families. Our study of this fauna has provided information as to what happened to this important molluscan class as it crossed the Mississippian-Pennsylvanian boundary and has added to our knowledge of 

the mode of life and diversification of pelecypods in 

the late Paleozoic.

The pelecypod fauna of the Amsden Formation is 

highly varied. Compared to the brachiopods, the 

pelscypods are much fewer in number, but there is 

greater diversity in proportion to their number. Our 

study of these pelecypods was based upon 285 specimens from the collections of several institutions. Of 

these specimens, 8 are unidentifiable below clr.ss 

level, 2 are identifiable only to subclass, and the remaining 275 are considered to belong in 41 species, 

22 genera, and 16 families.

PREVIOUS WORK

Relatively little work has been done previously on 

the Amsden pelecypods. They have figured only incidentally in three brief descriptive papers. Branson 

and Greger (1918, p. 321-323, pi. 19, figs. 11, 23-26; 

text fig. 1) described and figured three species of 

pelecypods in their paper on the Amsden fauna. 

These are listed below, together with our present 

assignments.

Branson and Greger (1918) This paper

Microdon cf. M. oblongus (Hall) ..Nuculo>psis*sp. A

Cypricardella sp. 

Myalina sancti-ludovici

(Worthen) __ _ ____ Septimyalina sp.

Paleoneilo amsdenensis n. sp __ -Paleyoldia amsdenensis

(Branson and Greger')

C. C. Branson (1937, p. 657, 658, pi. 89, fig. 

added three more species to the list, one a rostroconchian; these are cited below in the same manner 

as above.

El
E2 THE AMSDEN FORMATION (MISSISSIPPIAN AND PENNSYLVANIAN) OF WYOMING

C. C. Branson (1937) This paper

Nucula sp _______________Nuculopsis sp. A. 

Schizodus sp ___________ Schizodus cf. S. depressus

(Worthen). 

Conocardium orientale n. sp _ Conocardium orientale C.

C. Branson.

Burk (1954, p. 14, 15, pi. 1, figs. 38-40) added 

Allorisma terminate (Hall) to the list. His material 

is included in the present paper as Sanguinolites sp., 

Wilkingia terminalis (Hall), and W. sp.

All previously described material has come from 

the Mississippian part of the Amsden in the Wind 

River Range. The fauna from the Pennsylvanian 

part of the formation has been cited only in faunal 

lists. The original description of the Amsden Formation (Barton, 1906, p. 34) listed one collection of 

Pennsylvanian age among which several species of 

pelecypods had been identified by Girty and assigned 

to Edmondia, Pleurophorus [ = Permophorus~], and 

Entolium [=Pernopecten~\. These are included in 

the present study (colln. 52).

Blackwelder (1913, p. 176) also published Girty's 

identifications of several pelecypods from the Mississippian part of the Amsden and a rostroconchian 

from the Pennsylvanian part, both in the section at 

Darwin Peak. We have also restudied and briefly described this material (collns. 137, 139).

Shaw (1955, p. 63) listed some pelecypods from 

the vicinity of Rawlins, Wyo., and mentioned a pelecypod fauna not yet studied. We have not seen 

Shaw's Rawlins material but some of the species are 

probably the same as those in our collections from 

the Rawlins hills (collns. 1, 2, 3, 5).

PRESENT INVESTIGATION

Our study of the Amsden pelecypods includes a 

restudy of material in the collections of the University of Missouri and the University of Wyoming 

that has been described and figured or mentioned by 

previous authors and also includes description of 

new material from the collections of the U.S. National Museum and the U.S. Geological Survey.

Because of the generally poor preservation of the 

Amsden pelecypods, only five species, one of them 

new, are cited by name in this report. Formal descriptions are given only for the better preserved 

material. Nearly all of the specimens are identified 

as to genus, some in terms of a closely allied or 

possibly identical species. Lectotypes have been 

chosen where necessary and synonymies are given 

where appropriate. The synonymies have been compiled from the literature and, for the most part, do 

not imply actual examination of the specimens. Type

material belongs to the U.S. National Museum 

(USNM), the University of Missouri (UM), and 

the University of Wyoming (UW).

ACKNOWLEDGMENTS

We are grateful to our colleagues from other institutions who have loaned us Amsden pelecypods 

for this study. We thank G. A. Cooper and E. G. 

Kauffman of the U.S. National Museum, A. G. 

Unklesbay, J. A. Wolleben, R. L. Ethington, R. E. 

Peck, and J. H. Witt of the University of Missouri, 

and D. W. Boyd of the University of Wyoming for 

this kindness. Photographs were prepared by Robert 

McKinney and Haruo Mochizuki, U.S. Geological 

survey. The manuscript was reviewed by E. G. 

Kauffman and E. L. Yochelson.

COMPOSITION OF THE FAUFA

All of the major subclasses recognized by Pojeta 

(1971) are present in the Amsden, although the 

occurrence of the Isofilibranchia is based on questionable material. Considering the number of specimens at the subclass level one finds the following 

representation: Palaeotaxodonta (30.? percent), 

Isofilibranchia (0.7 percent), Pteriomorpha (32.9 

percent), Heteroconchia (20.9 percent), and Anomalodesmata (15.2 percent). The class Rostroconchia is represented by a single fragmentary specimen.

In table 1 the families and genera of pelecypods 

recorded in the Amsden Formation are listed, the 

number of specimens of Mississippian age and of 

Pennsylvanian age and the total for each genus are 

given, as are the percentages of the total number of 

pelecypods that these figures represent. The isofilibranchians (two specimens) have been omitted 

from this table because they are not identifiable as 

to family and genus.

Amsden pelecypods can be divided into three major life-habit groups: infaunal labial palp deposit 

feeders, burrowing infaunal suspension feeders, and 

attached suspension feeders. The distribution of the 

Amsden genera in these groups is shown in table 2. 

In our selection of these groups no attempt has been 

made to separate attached epifaunal suspension 

feeders (epibyssate and cemented species) from 

attached semi-infaunal suspension feeders (endobyssate species). Stanley (1972) proposed that the 

great bulk of equivalved byssate pelecypods with 

anterior lobes were semi-infaunal (endobyssate). 

Kauffman (1969) felt that many mytilids with an 

anterior lobe were epifaunal and related current
PELECYPODA AND ROSTROCONCHIA OF THE AMSDEN FORMATION OF WYOMING E3

TABLE 1. Taxonomic relationships and relative abundance of pelecypods in the Amsden Formation

Mississippian Pennsylyanian 

specimens specimens Totals

Family Genus Number Percent Number Percent Number Percent

Paleyoldia __ _ ___ _

Posidoniidae Posidonici

4 1.46 7 2.54 11 4.00 

_ __ 2 .73 2 .73

69 25.09 2 .73 71 25.82 

_ _ 13 4.73 13 4.73

9 3.27 2 .73 11 4.00 

1 .36 _ _ __ 1 .36

1 .36 15 5.45 16 5.81 

4 1.46 4 1.46

Entoliidae _______ - Pernopecten __ ___ _____ _ _ 3 1.09 3 1.09

Aviculopectinidae _ _ Streblopteria _ ____ 1 -36 1 .36

Aviculopecten ______ _ _

Edmondiidae _ _______ Edmondia _ __ ________

14 5.09 26 9.45 40 14.54 

8 2.91 10 3.64 18 6.55 

4 1.46 23 8.36 27 9.82 

2 .73 _ _ ____ 2 .73

1 .36 10 3.64 11 4.00 

9 3.27 9 3.27

Grammysiidae _ _ _ _ _ ___ Sphenotus _ _ __ _____ 2 .73 _ .. 2 .73

Sanguinolites ___________ 1 .36 _ ____ 1 .36

Sedgwickia _____ - 1 .36 1 .36

Pholadomyidae _ __ _ Wilkingia _______________

Total _______ __ _____ _ __ _ _ ]

flow patterns to the shell morphology of such exposed forms. The empirical base from which Stanley 

drew his conclusions is rather small; most of his 

hypothesis is based upon the study of eight species 

of mytilids from the North Atlantic. Stanley's hypothesis nevertheless has great potential as a unifying concept in the study of attached pelecypods. It 

needs a broader data base, however, particularly 

one derived from the study of fossil forms that have 

been preserved in place.

TABLE 2. Major life-habit groups of Amsden pelecypods

Infaunal labial palp Infaunal burrowing Attached suspension 

deposit feeders suspension feeders feeders

Nuculopsis Schizodus Myalina 

Phestia Permophorus Septimyalina 

Paleyoldia Astartella Pseudomon&tis 

Cypricardella Posidonia 

Edmondia Pernopecten 

Sphenotus Streblopteria 

Sanguinolites Aviculopecten 

Sedgtvickia Aviculopinna 

Wilkingia Leptodesma 

Caneyella 

Isofilibranchian?

FAUNAL DIVERSITY

The diversity of the Amsden pelecypod fauna is 

noteworthy. Representatives of all the common marine late Paleozoic families, except the Parallelodontidae, have been found in the formation. At the 

generic level the Amsden fauna supports the concept of a period of late Paleozoic stability in the 

increase in diversity of the Pelecypoda (Stanley,

8 2.91 21 7.64 29 10.55

L29 46.91 146 53.08 275 99.99

1968). Although some of the genera found in the 

Amsden are limited to either its Mississippian or 

Pennsylvanian parts, elsewhere all of them except 

Paleyoldia and Caneyella range from Mississippian 

into Permian rocks. Some of the genera range downward into the middle Paleozoic and some upwrrd 

into the Mesozoic. In contrast to generic stability, 

however, numerous demonstrable differences exist 

between Mississippian and Pennsylvanian specimens 

of these genera that occur in both parts of the formation. For the most part, we have treated these 

morphological differences as indicating different 

species. Thus we see no period of late Paleozoic stability at the species level. 

In North America, except for a relatively few 

taxa, it is difficult to recognize the upper Paleozoic 

systems and series on the basis of pelecypod genera 

alone. One must turn instead to pelecypod species. 

Unfortunately, except for the aviculopectinids and 

myalinids (Newell 1937, 1942), the species-level 

taxonomy of North American late Paleozoic pelecypods is poorly understood and badly in need of 

monographic systematic treatment.

RELATION TO THE 

MISSISSIPPIAN-PENNSYLVANIAN BOUNDARY

Our study of 41 species shows that 21 are preso.nt 

in the Mississippian part of the formation and 22 

occur in the Pennsylvanian part; 2 species, Permophorus sp. A and Wilkingia terminalis (Hall), 

occur in both parts. Although some Amsden genera
E4 THE AMSDEN FORMATION (MISSISSIPPIAN AND PENNSYLVANIAN) OF WYOMING

seem to be restricted to either the Miasissippian or 

the Pennsylvanian, all of the genera present in the 

Amsden are known to cross the MississippianPennsylvanian boundary elsewhere in North America and to range widely through upper Paleozoic 

rocks. The pelecypods, therefore, because of their 

sporadic occurrence in the Amsden, their generally 

poor preservation, and the long ranges of the genera, have limited use as biostratigraphic tools. 

Nevertheless, because of their diversity at the species level they can be used in some sections in the 

absence of foraminifers and brachiopods.

STRATIGRAPHIC CONSIDERATIONS

The lithology and biostratigraphy of the Amsden 

is discussed by Sando, Gordon, and Dutro (1974). 

In considering the distribution of the fossil faunas 

within this formation, its transgressive nature must 

be borne in mind. The same member may contain 

Mississippian or Pennsylvanian fossils at different 

localities or in different strata at the same locality.

Four members are recognized within the Amsden 

Formation, three of them throughout its outcrop 

area in Wyoming. These three, in descending order, 

are: the Ranchester Limestone Member, the Horseshoe Shale Member, and the Darwin Sandstone 

Member. In western Wyoming the fourth member, 

the Moffat Trail Limestone Member, tongues into 

the upper two-thirds of the Horseshoe Shale Member, thus separating a thin Horseshoe Shale Member from the overlying Ranchester.

No fossils have been found in the Darwin Sandstone Member, but fossils in the underlying and 

overlying rocks and the derived depositional history 

of the basin indicate that it is Late Mississippian in 

age throughout its area of outcrop. The Moffat Trail 

Limestone Member, as shown by its contained fossils, is Late Mississippian (Chesterian) in age.

The Horseshoe Shale Member is Late Mississippian (Chesterian) in age in western and westcentral Wyoming, but in east-central Wyoming it is 

Mississippian (late Chesterian) and Pennsylvanian 

(Morrowan).

The lower part of the Ranchester Limestone 

Member in western Wyoming is Mississippian (late 

Chesterian) in age and its upper part is Pennsylvanian (Morrowan and early Atokan). In westcentral and east-central Wyoming this member is 

Pennsylvanian (Morrowan and early Atokan) 

throughout.

For these reasons one must designate the Mississippian and Pennsylvanian parts of the formation 

as well as identify its members.

The pelecypod distribution is, for the most part, 

the same as the coral and brachiopo<? zones that 

have been recognized during this study. These are, 

in descending order :

Pennsylvanian :

Mesolobus Zone __ _ East-central

Wyoming.

Neokoninckophyllum hamatilis Zone _ Do. 

Antiquatonia blackwelderi Zone __ _ Western

YTyoming. 

Mississippian:

Anthracospirifer welleri-shawi Zone Western and

r^est-central

Composita poposiensis Subzone ____ West-central

Wyoming.

Carlinia amsdeniana Subzone __ ____ Do.

Caninia Zone _____ __ _ ___ ___Western

Wyoming.

Pelecypods have been found in all but the Mesolobus Zone, but are particularly common in the Carlinia amsdeniana Subzone and the Neokoninckophyllum hamatilis Zone. At several Pennsylvanian localities in west-central and east-central Wyoming, 

mollusks predominate and cannot be definitely assigned to coral or brachiopod zones.

GEOGRAPHIC AND STRATIGRAPHIC 

OCCURRENCE OF THE PELECYPODS

Pelecypods are present in 31 collections from this 

formation, but in 16 of them only one species is 

present. Only three collections can be sr.id to be predominantly molluscan (collns. 40, 50, 52), and all of 

these are in the Pennsylvanian part of the formation. The remaining collections are mixed brachiopod-mollusk assemblages with the br^.ciopods predominant. Of these, eight occur in JTississippian 

rocks (collns. 20, 22, 28, 29, 36c, 36d, 46, 137) and 

four in Pennsylvanian rocks (collns. 1, 3, 5, 53). 

In the discussion that follows, the collections of 

Mississippian and Pennsylvanian age are discussed 

separately.

The Mississippian pelecypod localities in Wyoming are restricted to the western and central 

regions of Amsden outcrop which include Teton, 

Lincoln, and Fremont Counties. Pennsylvanian pelecypod localities are limited to one in each of these 

two regions. The western locality is represented by 

two collections having the same species from the 

same locality and bed. Most of the Pennsylvanian 

localities occur in the eastern region of Amsden outcrop, which includes Sheridan, Johnson, Washakie, 

and Carbon Counties.
PELECYPODA AND ROSTROCONCHIA OF THE AMSDEN FORMATION OF WYOMING E5

In table 3 the distribution of the pelecypods and 

rostroconchians by collection and by stratigraphic 

member is shown. The Amsden collections have been 

given numbers from 1 to 160 for the purpose of 

simplification; full descriptions are given in Sando, 

Gordon, and Dutro (1974). A checklist of the pelecypod and rostroconchian collections is given in 

table 4.

MISSISSIPPIAN FAUNA

Pelecypods are sporadically distributed in the 

Mississippian part of the Amsden in the western 

and central regions of its outcrop. Most of our specimens have come from the drainage basin of the 

Little Popo Agie River in the Wind River Range,

20 to 25 miles south of Lander; this area has also 

been the most thoroughly collected.

Lincoln County. The earliest pelecypods in the 

Amsden are two incomplete valves referred to Aviculopecten sp., which were collected in the Moffat 

Trail and Covey Cutoff sections (collns. 79, 92), 

associated with corals of the Caninia Zone and 

foraminifers of Mamet's Zone 17 of middle Chest erian age (see Mamet, 1974). These were the only 

pelecypods found in the Moffat Trail Limestone 

Member.

Teton County. At Hoback Canyon, in the mountain range of the same name, Aviculopecten sp. A. is 

present in the Horseshoe Shale Member (colln. 118) 

a few feet below the base of the Moffat Trail LimeTABLE 3. Pelecypod and rostroconchian fauna of the Amsden Formation of Wyoming

Horseshoe Shale Member

Moffat 

Trail 

Limestone 

Member

Ranches ter

Limestone

Member

1 2 3 5 20 22 27 28 29 30 31 36a 36b 36c 36d 36e 41 43 46 53 118 137 159 79 92 40 50 52 67 130 131 139

Pelecypoda:

Nuculopsis sp. A . __ __ __ _ __ __ __ __ __ __ __ _ __ X X _ __ _ _ __ __ _ _ _ _ _ __ _ _ _ _

sp. B __ -_ __ _- __ _- __ __ __ __ -_ __ __ __ X __ __ __ __ __ __ X __ __ __ __ __

Phestia sp _ _ _ __ __ _ __ -- __ __ __ _ _ _ __ __ _ __ _ _ _ __ _ _ _ _ X _ _ __ __ _

PaleyoLdia amsdenensis

(Branson and Greger) __ __ __ __ __ __ X __ X __ __ __ X __ X __ __ __ __ __ __ __ __ __ __ __ __ __ __ __ _ __

sp _______ ... __ __ __ __ X __ __ __ __ __ __ X __ __ __ __

Isofilibranchian? gen. and

sp. indet _ _ - -- __ __ __ X X __ _ __ _ __ __ __ __ __ __ __ __

Myalina (Myalina) sp X __ __ __ _ _ _ _ __ _ _ __ _ __. __

Septimyalina sp. A __ __ __ __ __ X X _ _ _ __ ? __ __ _ __

Septimyalinal sp. indet . __ _ __ __ __ __ _ _ __ __ _ _ _ __ __ _ _ __ _ __ _ __ __ __ __ X X

Caneyella sp _ . __ __ __ __ -_ -_ __ _ _ __ __ __ _ X __ __ __ __ __

Leptodesma spp _ _ . -- -- X __ __ _ _ _ _ __ __ _ _ X __ __

Posidonia sp. indet . -- _ __ X __ __ __ __

Aviculopinna sp _ _ .-- _- -- __ __ __ _- __ __ _ __ __ __ __ __ __ __ __ __ __ X __ __ __

Pernopecten sp. indet .-- __ __ __ __ __ __ __ __ __ __ __ __ __ __ __ __ __ __ X __ __ __

Pseudomonotis sp _ .-- -- -- _- __ __ __ _- __ __ __ __ __ __ __ X __ __ __

Streblopteria sp. indet ____ -- _- __ __ __ __ _ _ __ __ X __ __ _ __ __ __ _

Aviculopecten gravidus n.

sp __-___-_ . - - X __ __ __ __ __ __ __ __ __ __ __ __ __ __ __ __ __ __ __ __ __ __ __ __ __ __ __ __ __

sp. A ____________. __ __ __ ._ __ __ __ __ __ __ __ __ __ X __ __ __ __ __ __ __ __ __ __ __

sp. B ___________. __ X __ __ __ __ __ __ X __ __ __ __ __

spp. indet _______. X __ __ __ __ __ __ __ X X __ __ __ __ __ __ __ __ __ X ______ X X __ __ __ __ __ __ __

Schizodus cf. S. depressus

Worthen ___________ __ X __ __ X ? __ __ __ __ __ X __ __ __ __ __ __ __

aff. S. affinis Herrick . _ __ -_ _ __ _ __ _ __ _ __ __ _ _ _- -_ __ __ _ _ X X __ _ __ __ __

alpinns (Hall)? ___. __ __ __ __ __ __ __ __ __ __ __ __ __ __ __ __ __ X __ __ __ __ __ __ __ __ __ __ __ __

sp. A _ . -- -_ __ __ __ _ __ X _ _ __ _ -- -- -- -- -- _- __

sp. B __________. -- -_ X __ __ __ __ __ __ __ __ __ __ __ __ __ __ __ -_ __ __ __ __ __ __ __ __ __ __ __ __ __

Permophorus sp. A ____. __ ? __ _ __ __ _ _ _ __ __ __ __ __ __ __ __ __ X __ __ X __ __ __ X X __ __ __ __

Cypricardella sp ______. -- __ __ __ __ _ _ __ __ __ __ __ _ X __ _ -- -- -- __ __ __ __ __ __ __ __ __ _ __

Cypricardellal sp. indet __.-_ __ __ __ X __ __ __ __ _ __ _ __ _ __ _ __ __ __ __ __ __ __ __ __ __ __

Astartella concentrica

(Conrad) _________- __ ? __ ._ __ __ __ __ __ __ __ __ __ __ __ -_ X __ __ ______ XXX __ __ __ 

sp _____________.-- __ __ __ __ __ __ __ __ _ _ __ __ __ __ _ X __ __ __ __ __ _ __ __ __ __ __ _ _ __

Edmondia spp _______.-_ __ __ __ __ __ _ _ _ _ __ __ __ __ _ _ __ __ __ __ __ __ __ _ __ X XX __ _ __ __

Spfienotus sp ______. -- __ __ __ __ __ __ __ __ __ __ __ __ _ ? _ __ __ __ __ _ X _ __ __ _ __ _ _ __ __ __

Sangninolites sp ______. _ __ __ __ X _ _ _ __ __ _ __ __ __ _ __ __ __ _ __ __ _ __ _ __ _ __ __ __ __ __

Sedgwickial sp. indet ___. -- __ __ X __ __ __ _ _ _ __ __ __ __ __ _ __ __ __ __ _ __ __ __ __ __ __ __ __ __ __ __

Wilkingia terminate (Hall) X X X X ________ __ __ __ __ __ __ __ X X __ __ __ __ __ __ __ __ X __ __ __ __ __

sp ___ __ _ . _- __ X __ __ __ __ __ _ __ __ __ ._ __ __ __ __ __ _ __ __ __ __ __ __ __ __

Rostroconchia:

"Conocardium" sp. indet __. -- -- __ __ _ __ __ __ __ __ __ _ __ _ __ _ __ __ __ _ __ __ __ __ __ _ _ __ __ _ __ X
EG THE AMSDEN FORMATION (MISSISSIPPIAN AND PENNSYLVANIAN) OF WYOMING

TABLE 4. Checklist of pelecypod and rostroconchian collections from the Amsden Formation

Collection 

No. 

in

report

Permanent 

institutional 

locality No.

Name of locality Mountain range County Location Member

1 .

2 .

3 .

5 . 

20 . 

22 .

27 .

28 .

29 .

30 .

31 . 

36a 

36b

36c 

36d

36e

40 .

41 . 

43 . 

46 . 

50 .

52 .

53 . 

67 . 

79 .

92 . 

118 .

130 .

131 .

137 .

139 .

159 .

USGS 5441-PC __ Cherokee Spring _ Rawlins hills __ Carbon ___ Probably in SW% sec. 11,

T. 21 N., R. 88 W. 

USGS 8071-PC __ ___do _______ ___do _____ ___do __ Probably in SW 1^ sec. 11,

T. 21 N., R. 88 W. 

USGS 3139-PC __ ___do ______ ___do ____ ___do __ NW%SW% sec. 11, T. 21

N., R. 88 W. 

USGS 3085-PC __ Cherokee Peak __ ___do ____ ___do __ SE%NE% sec. 10, T. 21

N., R. 88 W. 

USGS 19285-PC _ Tweed Creek ___ Wind River Fremont ___ Probably in SE^ sec. 22,

Range. T. 30 N., R. 99 W. 

UW 3099/9A __ South Pass ____ ___do ____ ___do __ Center sec. 9, T. 30 N.,

R. 99 W. 

USGS 19283-PC _ Cherry Creek __ ___dx> _____ ___do __ Probably in sec. 30. T. 31

N., R. 99 W. 

UW 3199/19B2 __ ___do ______ ___do ____ ___do _.__ SE^NW^ sec. 19, T. 31

N., R. 99 W.

UW 3199/19B3 __ ___do _______ ___do ____ ___do __ ___do ___________- 

UW 3199/19B4 __ __.do _______ ___do ____ ___do __ ___do ___________. 

UW 3199/19B5 __ ___do _______ ___do _____ ___do ____ ___do ___________. 

UM specimens _ ___do _______ ___do ____ ___do __ Sec. 19, T. 31 N., R. 99 W. 

___do _______ Cherry Creek(?) _ ____do _____ ____do ____ Same, but labeled "sec. 31,

T. 19 N., R. 99 W." 

___do ______ Near Lander ____ _____do _______ _____do ____ Exactly locality not known.

____do _______ Little Popo Agie ___do _____ ___do ____ ___do __ __ ____ _.

River.

USNM 487A __ Cherry Creek __ ___do ____ ___do __ Sec. 19, T. 31 N., R. 99 W. 

USGS 21676-PC _ Bull Lake Creek _ ___do ____ ___do __ SW% sec. 2, T. 2 N.,

R. 4 W. 

USGS 19156-PC _ Soda Creek ____ Washakie Teton ____ Trail in sec. 5, T. 45 N..

Range. R. 110 W. 

UW 43106/19B _ Horse Creek ___ ___do _______ Fremont __ SW 1^ sec. 19, T. 43 N.,

R. 106 W. 

USGS 16197-PC _ Wiggins Fork __ ___do ____ ___do __ SW% sec. 7, T. 42 N.,

R. 105 W. 

USGS 19187-PC _ Trout Creek ___ Big-horn Washakie __ Sec. 19, T. 41 N., R. 88 W.

Mountains.

USGS 2461-PC, North Fork, Crazy ___do ____ Johnson __ SE% sec. 28 or NE 1^ sei. 

2461A-PC. Woman Creek. 33, T. 49 N., R. 83 W. 

USGS 19241-PC _ South Fork, Rock ___do ____ ___do __ SW% sec. 25, T. 52 N.,

Creek. R. 84 W. 

USGS 16215-PC _ Amsden Creek __ ___do ____ Sheridan __ SW 1^ sec. 34, T. 57 N.,

R. 87 W.

USGS 22981-PC _ Moffat Trail ___ Salt River Lincoln __ NW%NE% sec. 3, T. 3f

Range. N., R. 117 W.

USGS 6965-PC __ Covey Cutoff ___ ___do ____ ___do __ NWHNE^, sec. 27, T. 34

N., R. 117 W. 

USGS 16207-PC _ Hoback Canyon __ Hoback range _ Teton ____ Sec. 2, T. 38 N., R. 115 W.

USGS 18786-PC _ ___do _______ ___do ____ ___do __ Sec. 2, T. 38 N., R. 115 Vr.

USGS 16210-PC _ ___do _______ ___do ____ ___do __ ___do __________-

USGS 6191-PC __ Darwin Peak ___ Gros Ventre ___do __ S% sec. 28, T. 40 N.,

Range. R. 112 W. 

USGS 6191A-PC _ ___do _______ ___do ____ ___do __ S% sec. 28, T. 40 N.,

R. 112 W. 

USGS 24050-PC _ Elk Ridge ____ Teton Range __ ___do __ SW^ sec. 26, T. 47 N.,

R. 116 W.

Horseshoe 

Shale. 

Do.

Do. 

Do. 

Do. 

Do. 

Do. 

Do.

Do. 

Do. 

Do. 

Do. 

Do.

Do. 

Do.

Do.

Ranchester 

Limestone. 

Horseshoe 

Shale. 

Do.

Do.

Ranchester 

Limestone. 

Do.

Horseshoe

Shale. 

Ranchester

Limestone. 

Moffat

Trail

Limestone. 

Do.

Horseshoe

Shale. 

Ranchester

Limestone.

Do. 

Horseshoe

Shale. 

Ranchester

Limestone. 

Horseshoe

Shale.

stone Member. The base of the Moffat Trail Limestone Member is shown by Mamet's foraminiferal 

studies to be somewhat younger here than in Lincoln County due to transgressive stratigraphic relationships, so this Aviculopecten may not be quite as 

early as the previously cited species.

At Soda Creek in the Washakie Range, a heteroconch pelecypod identified as Astartella sp. was 

found in the basal 10 feet of the Horseshoe Shale 

Member (colln. 41). It was associated with a braciopod fauna that includes Diaphragmvs nivosus n. 

sp., a productoid characteristic of the Heath Shale 

of Montana of Late Mississippian (Che^terian) age. 

The Darwin Peak section in the Gros Ventre
PELECYPODA AND ROSTROCONCHIA OF THE AMSDEN FORMATION OF WYOMING E7

Range includes a limestone bed near the middle of 

the Horseshoe Shale Member (colln. 137), in which 

the pelecypods Septimyalina sp. A? and Sphenotus 

sp. were found associated with brachiopods characteristic of the Carlinia amsdenia-na Subzone.

At Berry Creek in the Teton Range, the highest 

Mississippian beds in the upper part of the Horseshoe Shale Member (colln. 159) contained Permophorus sp. A and some pelecypods that are unidentifiable because they are poorly preserved. The 

Berry Creek beds are in B. L. Mamet's foraminiferal Zone 19. (See Mamet, 1974.)

Fremont County. In the drainage basin of the 

Little Popo Agie River, which includes Cherry 

Creek, considerable collecting over a period of years 

has turned up the following pelecypods, most, if not 

all of which are probably from the Carlinia amsdeniana Subzone (collns. 20, 27-31, 36a-e) :

Nuculopsis sp. A

Paleyoldia amsdenensis (Branson and Greger)

Isofilibranchian?, gen. and sp. indet.

Septimyalina sp. A

Leptodesma sp.

Aviculopecten sp. indet.

Schizodus cf. S. depressus Worthen

sp. A

Cypricardella sp. 

Cypricardellal sp. indet. 

Sphenotus sp.? 

Sanguinolites sp. 

Wilkingia terminalis (Hall)

sp.

Fossils from the Horseshoe Shale Member at 

South Pass in the same mountain range (colln. 20) 

include Sanguinolites sp. and Wilkingia sp.

In the Washakie Range, pelecypods occur at two 

localities in Fremont County. The first is at Horse 

Creek, where C. A. Biggs collected Wilkingia terminalis (Hall), which was figured by Burk (1954, pi. 

1, figs. 39, 40). The second is at Livingston Ranch 

where W. J. Sando found pelecypods in a shale bed 

with Lingula, 8 feet below a limestone containing 

brachiopods of the Carlinia amsdeniana Subzone 

(colln. 46). These pelecypods are Caneyella sp., 

Posidonia sp., and Streblopteria sp.

PENNSYLVANIAN FAUNA

Despite the fact that our Pennsylvanian collections contain only one more pelecypod species and a 

few more individuals than the Mississippian collections available to us, it is evident that pelecypods 

are much more common in the Pennsylvanian part 

of the formation, particularly in the eastern region 

of Amsden outcrop. Had the eastern region been 

worked as exhaustively as the central one, certainly 

many more pelecypods and perhaps more pelecypod 

species would be available.

Teton County. In the section at Hoback Canyon, 

a myalinid species identified as Septwiyalinat sp. is 

present in the Antiquatonia blaekwelderi Zone in 

the Ranchester Limestone Member (collns. 130, 

131). This is the only pelecypod species found in the 

Pennsylvanian part of the Amsden in its western 

region.

Fremont County. At Bull Lake Creek in the 

Wind River Range a bed of fine-grained, very light 

gray dolomite at the base of the Ranchester Limestone Member (colln. 40) contains a molluscan mold 

fauna which includes the following pelecypods: 

Schizodus aff. S. affinis Herrick, Astartella concentrica (Conrad), Edmondia sp., and some indeterminate pelecypods. This mold assemblage is the only 

one of Pennsylvanian age found in the central region, and here the mollusks served to date the rocks.

Washakie County. At Trout Creek, on the western slope of the Bighorn Mountains (colln. 50), a 

tan marlstone has provided a fairly large molluscan 

fauna, among which are the following pelecypods:

Nticulopsis sp. B.

Phestia sp.

Paleyoldia sp.

Leptodesma sp.

Amculopecten sp. B

Schizodus aff. <S. affinis Herrick

Permophorus sp. A

Astartella concentrica (Conrad)

Edmondia sp.

Wilkingia terminalis (Hall)

These fossils are associated with foraminifers determined by Mamet as belonging in Zone 20 and conodonts determined by J. W. Huddle as Morrowan in 

age.

Sheridan County. In the valley of Amsden 

Creek, on the east slope of the Bighorn Mountains, 

a small collection from the Ranchester Limestone 

Member (colln. 67), mostly of brachiopods, contains 

Airicidopinna sp. Also present are Morrowan foraminifers and conodonts.

Johnson County. At South Fork, Rock Cre^k, 

also on the east slope of the Bighorns, pelecypods 

occur with a predominantly brachiopod fauna at the 

base of the Horseshoe Shale Member (colln. 53) £.nd 

include the following:

Nuculopsis sp. B 

Paleyoldia sp. 

Aviculopecten sp. B

sp. indet.

Schisodus alpinus (Hall) ? 

Permophorus sp. A 

Astartella concentrica (Conrad)

Most of the pelecypod species at this locality are 

present also in the collection from Trout Creek 

cited above.
E8 THE AMSDEN FORMATION (MISSISSIPPIAN AND PENNSYLVANIAN) OF WYOMING

At North Fork, Crazy Woman Creek a bed of tan 

granular chert near the top of the Ranchester Limestone Member (colln. 52) has also yielded a predominantly molluscan fauna among which are the 

following pelecypods:

Pernopecten sp. indet. 

Pseudomotiotis sp. 

Permophorus sp. A 

Astartella concentrica (Conrad) 

Edmondia 3 spp.

The stratigraphic position of this collection suggests 

that it is post-early Morrowan, but whether it is 

late Morrowan or early Atokan in age is not yet 

known.

Carbon County. In the region of the Rawlins 

hills, collections made in the vicinity of Cherokee 

Spring and at Cherokee Peak (collns. 1, 2, 3, 5) 

from the Neokoninckophyllum hamatilis Zone in the 

Horseshoe Shale Member contain the following pelecypods :

Myalina (Myalina) sp. 

Aviwilopecten gravidus n. sp.

sp. indet. 

Schizodus sp. B 

Permophorus sp. A? 

Astartella concentrica (Conrad) ? 

Sedgwickial sp. indet. 

Wilkingia terminalis (Hall)

These collections are regarded as late Morrowan in 

age; they are associated with foraminifers identified by Mamet as belonging in Zone 20. Wilkingia 

is common to all four collections.

ROSTROCONCHIANS

This group has recently been made a separate 

class of mollusks (Pojeta and others, 1972) ; it is 

exceedingly rare in the Amsden Formation. A small 

rostroconch fragment, from the Ranchester Member 

at Darwin Peak (colln. 139) in the Pennsylvanian 

part of the Amsden, was listed by Blackwelder 

(1913, p. 176) on Girty's determination. This specimen is figured in the present report (pi. 4, fig. 22).

Another specimen, presumably from the Horseshoe Shale Member in the drainage basin of the 

Little Popo Agie River and therefore probably Mississippian in age, was described and figured by C. C, 

Branson (1937, p. 657, pi. 89, fig. 23) as Conocardium orientate n. sp. Unfortunately, the specimen 

was not available to us for study and seems to be 

lost.

SYSTEMATIC PALEONTOLOGY

Phylum MOLLUSCA

Class PELECYPODA 

Subclass PALAEOTAXODONTA

Order NUCULOIDA 

Superfamily NUCULACEA Gray

Family NUCULIDAE Gray 

Genus NUCULOPSIS Girty, 1911

Nuculopsis sp. A

Plate 1, figures 1-5

Microdon cf. M. oblongus (Hall). Branson and Greger, 1918

[part], p. 321, 322, pi. 19, fig. 11 [not fig. 25]. 

Nucula sp. C. Branson, 1937, p. 658.

Four limonitic internal molds of Niiculopsis, from 

the Mississippian part of the formation in the Wind 

River Range, are present in the University of Missouri collections (UM 2657, 6630, 12791). The molds 

are elongate, suboval to subtriangular in outline, 

have prominent umbos, and are boat-shaped in dorsal view, being narrow posteriorly, truncated and 

beveled anteriorly. They range from about 8 to 16 

mm in length, 6 to 11 mm in height, and 4.5 to 8.5 

mm in width. The umbos are opisthogyral and located one-fourth to one-third of the length from the 

posterior end; in the broad area between them, 

along the plane of commisure, is the small raised 

mold of the resilifer and a zigzag line marking the 

underside of the taxodont dentition (pi. 1, figs. 2, 

4). The zigzag line is not well enough preserved on 

any of the specimens to permit a determination of 

the number of teeth.

Oval anterior and posterior adductor muscle scars 

are preserved on both valves (pi. 1, fig. 1). The anterior adductor scars are slightly larger than the 

posterior ones and occupy the beveled end of the 

valves. Small paired oval anterior and posterior 

pedal scars are present, one of each in each valve. 

They are located on the dorsum a short distance 

behind and in front of the anterior and posterior 

adductor muscle scars (pi. 1, figs. 2, 4).

The specimen figured here on plate 1, figures 3-5 

(UM 2657) was illustrated by Bransor and Gregor 

(1918) as Microdon [Cypricardella]. Two of the 

other three specimens, one of which is figured here 

on plate 1, figures 1, 2, are from a lot (UM 6630) 

identified by C. C. Branson (1937) as Uucula sp.

Nuculopsis sp. A occurs in the s?.me beds as 

Paleyoldia amsdenensis (Branson and Greger) but 

is not nearly as abundant.

Figured specimens. UM 2657, 6630.

Occurrence and number of specimens. Horseshoe 

Shale Member: collections 36c (1), 3H (3), Fremont County, Wyo.
PELECYPODA AND ROSTROCONCHIA OF THE AMSDEN FORMATION OF WYOMING E9

Nuculopsis sp. B

Plate I, figures 6-9

Specimens from two localities in the Pennsylvanian part of the Amsden are placed in this taxon. 

This species is suboval to subtriangular in outline 

and smaller than Nuculopsis sp. A. The largest 

specimen (USNM 174018) is a single valve measuring 8.3 mm long, 6.6 mm high, and having a maximum convexity of 2 mm. The umbos are opisthogyral and located about one-third of the length from 

the posterior end. The surface ornament consists of 

closely spaced fine concentric growth lines. The zigzag trace of the ventral part of the taxodont dentition and suboval anterior adductor muscle scars are 

visible on one internal mold (USNM 174020; pi. 1, 

figs. 8, 9).

The known material of this species consists of two 

single valves and three articulated internal molds 

which are suboval in outline and two internal molds 

of single valves which are subtriangular in outline; 

the latter are slightly less convex than the suboval 

specimens. The subtriangular specimens have almost straight anterodorsal margins (pi. 1, fig. 7), 

whereas the suboval forms have gently convex anterodorsal margins interrupted by a slight medial 

angulation (pi. 1, fig. 6). It may be that two species 

are herein included in Nuculopsis sp. B, but, as both 

shapes occur at both localities, we attribute the differences to individual variation and differences in 

configuration between internal and external molds 

and place them in a single taxon.

Figured specimens. USNM 174018-174020.

Occurrence and number of specimens. Horseshoe 

Shale Member: collection 53 (2), Johnson County, 

Wyo. Ranchester Limestone Member: collection 50 

(5), Washakie County, Wyo.

Superfamily NUCULANACEA Adams and Adams

Family NUCULANIDAE Adams and Adams

Genus PHESTIA Chernyshev, 1951

Phestia sp.

Plate 1, figures 10, 11

Two specimens assignable to this genus have been 

collected from a tan marlstone of Pennsylvania!! age 

on the west slope of the Bighorn Mountains. One is 

an internal mold (pi. 1, fig. 11) in which the rostrum is poorly preserved and which is approximately 

11 mm long and 5.5 mm high; the second is an external mold which shows the pointed posterior end 

and the concentric ornament (pi. 1, fig. 10) and is 

5.8 mm long and 3.1 mm high. No internal structures are visible on either specimen.

The external mold closely resembles Phestia inflata (Girty) from the Pennsylvanian (Morrowan) 

Brentwood Limestone Member of the Bloyd Shale in

northwest Arkansas; this species was illustrated by 

Morningstar (1922, pi. 10, figs. 22-24). However, 

the Amsden material is not well enough preserved to 

make a specific identification.

Figured specimens. USNM 174022, 174023.

Occurrence and number of specimens. Ranchester Limestone Member: collection 50 (2), Washakie 

County, Wyo.

Genus PALEYOLDIA Lintz, 1958 

Paleyoldia amsdenensis (Branson and Greger)

Plate I, figures 14-31; figure 1

Paleoneilo amsdensensis Branson and Greger, 1918, p. 323, 

pi. 19, figs. 23, 24, text fig. 1.

Description. Shell yoldiaform in shape, strongly 

rostrate; surface marked with concentric growth 

lines and vague radial markings (pi. 1, fig. 2^); 

beaks opisthogyral, peaks of umbos near midlength, 

essentially central in younger specimens but offset 

slightly anteriorly in older individuals.

Pallial line having shallow posterior ,sinus (pi, 1, 

fig. 26). Anterior adductor muscle scars large, 

elongate, and quadrate; posterior adductor muscle 

scars smaller and more oval (pi. 1, figs. 26, 30, SI). 

Accessory muscle scars prominent, consisting of 

paired anterior and posterior pedal scars (pi. 1, fig. 

31) and two (pi. 1, fig. 30) or three (pi. 1, fig. 26) 

pairs of medial muscle scars in the region of the 

umbos. Dentition consisting of anterior and posterior tooth rows interrupted by a resilifer placed between beaks (pi. 1, figs. 24, 25) ; anterior tooth row 

longer than posterior row.

Discussion. The description is based on th^ 2 

primary types (UM 2665) and 63 additional specimens from another University of Missouri collection 

(UM 6639). Nine of these specimens are figured in 

this paper. Branson and Greger (1918, p. 323) mentioned 25 specimens in their collection, but whether 

their unfigured material has been lost or whether it 

was incorporated with Branson's later collection 

(UM 6639) is not known.

The lectotype is herein designated as the specimen figured by Branson and Greger (1918) on plate 

19, figures 23, 24; it is figured in this paper on 

plate 1, figures 14-16. The dimensions of the le~totype are: length 14 mm, height 8 mm, and maximum 

convexity 4.7 mm (both valves slightly gaping) ; it 

probably lacks 1 to 1.5 mm of its former length. The 

paralectotype is missing the posterior end, but it 

shows more of the surface sculpture than the lectotype, it was figured by Branson and Greger (1918) 

as text figure 1 and is here figured on plate 1, figures 17-19. The measurements of the paralectotype 

are: length (incomplete) 12 mm, height 8.7 mm,
E10 THE AMSDEN FORMATION (MISSISSIPPIAN AND PENNSYLVANIAN) OF WYOMING

and maximum convexity 5 mm (both valves) ; it 

probably lacks 3 to 4 mm of its former length.

The limonitic molds of Paleyoldia amsdenensis 

are the best preserved specimens of any of the Amsden pelecypods we have seen and preserve impressions of virtually all of the shell morphology of the 

species. P. amsdenensis is the first Paleyoldia in 

which the musculature is completely known (fig. 1). 

Although P. amsdenensis is yoldiaform in shape, its 

musculature differs significantly from that of living

aa

appr

mm

ppr

ppr

0.5 cm

FIGURE 1. Diagrammatic sketch of muscle scar pattern of 

Paleyoldia amsdenensis (Branson and Greger). A, Dorsal 

view; B, lateral view, aa, anterior adductor; appr, anterior pedal protractor and retractor; mm, medial muscles; 

ppr, posterior pedal retractor; pa, posterior adductor;, 

pi, pallial line; ps, pallial sinus.

Yoldia (Heath, 1937, pi. 10; Driscoll, 19«4, fig. 2) ; 

it is most similar to that of the Paleozoic nuculanid 

Phestia (Driscoll, 1966, figs. 1-5).

Living species of Yoldia are rapid burrowers 

(Stanley, 1970) and have large well-developed pedal 

muscles (Heath, 1937, pi. 10). .By comparison the 

pedal muscles of Paleyoldia amsdenensis are small 

(fig. 1) and indicate that the animal probably did 

not burrow with the same speed and efficiency as 

modern Yoldia. No separation of the anterior pedal 

protractor and retractor muscle scars occurs in 

Paleyoldia, the posterior pedal retractor scars are 

much smaller than those of Yoldia, and the pallial 

sinus is only slightly developed.

The similarity of the muscle scar patterns of 

Paleyoldia and Phestia suggest a phylogenetic relationship between these Paleozoic nuculanid genera. 

Because Phestia is the older genus, it is the presumed ancestor of Paleyoldia. The muscle similarity 

also suggests that Phestia had about the same burrowing ability as Paleyoldia and that increase in 

speed and efficiency of nuculanid burrowing was 

largely a post-Paleozoic development. All occurrences of P. amsdenensis are from the Mississippian 

(late Chesterian) part of the formation. According 

to Puri (1969), Paleyoldia has not previously been 

reported from rocks older than Pennsylvr.nian.

Figured specimens. UM 2665, 6639.

Occurrence and number of specimens. Horseshoe 

Shale Member: collections 27 (3), 29 (1), 36b (2), 

36d (63), Fremont County, Wyo.

Paleyoldia sp.

Plate 1, figures 12, 13

Two specimens of Paleyoldia, both of which are 

figured, from the Pennsylvanian part of the Amsden 

Formation probably represent a second species of 

the genus. They are from localities on either side of 

the Bighorn Mountains. The two valves measure 22 

and 12 mm in length, 11.7 and 6.8 mm in height, and 

4 and 2 mm in greatest convexity, respectively. Although the posterior end is not clearly outlined in 

either specimen, in both the strongly o^isthogyral 

beaks are slightly more than halfway back from the 

anterior end, which contrasts with P. amsdenensis 

in which the length of the shell posterior to the 

beaks is equal to or greater than the length anterior 

to the beaks.

The smaller of the. .two specimens (pi. 1, fig. 13) 

preserves some of the surface sculpture which consists of fine concentric growth lines separated by 

wider interspaces. Internal features ar^ not preserved on either specimen.
PELECYPODA AND ROSTROCONCHIA OF THE AMSDEN FORMATION OF WYOMING Ell

Figured specimens. USNM 174024, 174025.

Occurrence and number of specimens. Horseshoe 

Shale Member: collection 53 (1), Johnson County, 

Wyo. Ranchester Limestone Member: collection 50 

(1), Washakie County, Wyo.

Subclass ISOFILIBRANCHIA

Isofilibranchian ? gen. and sp. indet.

Plate 2, figures 1, 2

Two poorly preserved modioliform internal molds 

from the Mississippian part of the Amsden Formation are here tentatively placed in the Isofilibranchia. As defined by Pojeta (1971), this subclass 

includes only the mytilaceans. The Amsden specimens have some resemblance to the mytilacean 

genus Promytilus but may belong to the Myalinidae, 

some of which are homeomorphic in shape to the 

Mytilacea. These specimens are the only possible 

representatives of the Isofilibranchia so far found 

in the Amsden Formation.

The specimen shown on plate 2, figure 1, is 15 mm 

long, 6.5 mm high, and has a maximum convexity 

of 2.3 mm. The specimen shown on plate 2, figure 2, 

is 13 mm long, 7.5 mm high, and has a maximum 

convexity of 2 mm.

Figured specimens. UW A201, A1275.

Occurrence and number of specimens. Horseshoe 

Shale Member: collections 28 (1), 31 (1), Fremont 

County, Wyo.

Snbclass PTERIOMORPHIA

Order PTERIOIDA 

Superfamily AMBONYCHIACEA Miller

Family MYALINIDAE Frech 

Genus MYALINA de Koninck, 1842

Myalina (Myalina) sp.

Plate 2, figures 6, 7

One poorly preserved lot of specimens consisting 

of 10 left and 3 right valves, from the Neokoninckophyllum hamatilis Zone in the Rawlins hills, is 

referred to this taxon. The figured right valve (pi. 

2, fig. 6) is approximately 19 mm high, 15 mm long, 

and has a maximum convexity of 5 mm. The angle 

between the dorsal margin and the umbonal ridge 

cannot be accurately measured because of the poor 

preservation of the dorsal margin, but it is about 

60°. The shell is moderately thick and is ornamented 

with concentric growth lines that are particularly 

prominent near the shell margins. The presence of 

a small anterior lobe and the shape of the shell suggests that this Pennsylvanian form belongs to Myalina (Myalina).

Figured specimens. USNM 174026, 174027.

Occurrence and number of specimens. Horseshoe 

Shale Member: collection 3 (13), Carbon County, 

Wyo.

Genus SEPTIMYALINA Newell, 1942

 Septimyalina sp. A 

Plate 2, figures 8-15

Myalina sancti-ludovici Worthen. Branson and Greger, 1918,

p. 322, pi. 19, fig. 26. 

Septimyalina n. sp. Easton, 1962 [part?], p. 92, pi. 12, fig. 24

[probably not figs. 23, 25].

Description. Shell small, prosocline, inequivalve, 

right valve being slightly less convex than left (pi. 

2, figs. 9, 13, 15). Largest and best preserved specimen (pi. 2, figs. 12-15) was previously figured by 

maximum convexity of 9.2 mm (both valves). Angle 

between dorsal margin and umbonal ridge (argle 

alpha) approximates 50° and that between dorsal 

and posterior margins (angle beta) approximates 

120°. Beaks are strongly prosogyral and shell is 

moderately thick and strongly lamellose; in some 

specimens a weak umbonal septum is present.

Discussion. This species is known from specimens in the University of Missouri collections that 

came from limonitic shales in the Wind River B?,sin 

probably belonging in the Carlinia amsdeniana Subzone of Late Mississippian age. The largest specimen (pi. 2, figs. 12-15) was previously figured by 

Branson and Greger (1918, pi. 19, fig. 26) as Myalina sancti-ludovici and by Easton (1962, pi. 12, fig. 

24) as Septimyalina n. sp. The specimens from the 

Cameron Creek Formation of Montana referred by 

Easton (1962) to Septimyalina n. sp. may belong 

to a different species than those from the Amslen 

of Wyoming; in the Montana specimens the angle 

between the dorsal margin and the umbonal ridge 

(angle alpha) is greater than the same angle in the 

Wyoming specimens.

The juvenile specimen shown on plate 2, figures 

8, 9, is more strongly prosocline than those shown 

on plate 2, figures 10, 11, 12-15, angle alpha being 

about 36°. As demonstrated by Newell (1942, p. 47, 

48), this angle tends to be more acute in the yoking 

stages of some myalinid species; thus increase, in 

the size of this angle is an ontogenetic trend.

Figured specimens. UM 2658, 6638.

Occurrence and number of specimens. Horseshoe 

Shale Member: collections 36c (1), 36d (6), Fremont County. ?137 (2), Teton County, Wyo.

Septimyalina? sp. indet. 

Plate 2, figure 5

Another myalinid, from the Pennsylvanian part 

of the Amsden at Hoback Canyon, is represented1 by 

two left valves, the more complete one of which is 

figured. The umbonal area and the dorsal margin 

of this specimen are not well preserved; the angle 

between the umbonal ridge and dorsal margin ap-
E12 THE AMSDEN FORMATION (MISSISSIPPIAN AND PENNSYLVANIAN) OF WYOMING

proximates 60°. Both specimens have the prominent 

concentric lamellae of Septimyalina but are so poorly 

preserved that one cannot determine whether or not 

an umbonal shelf or an anterior lobe was present. 

They differ from the Mississippian Amsden shells 

referred to this genus in their larger size and 

greater umbonal angle.

Figured specimen. USNM 174028.

Occurrence and number of specimens. Ranchester Limestone Member: collections 130 (1), 131 (1), 

Teton County, Wyo.

Superfamily PTERIACEA Gray, 1847

Family PTERINEIDAE Miller 

Genus CANEYELLA Girty, 1909

Caneyella sp.

Plate 2, figure 4

A unique specimen from a shale in the Washakie 

Range that occurs 8 feet below a limestone containing brachiopods of the Car lima amsdeniana Subzone 

(Mississippian) is referred to the genus Caneyella. 

This right valve is gently convex in the umbonal 

area but is otherwise nearly flat. A short remnant 

of what is probably the dorsal margin is preserved, 

and the height of the specimen measured down from 

this point is 17.5 mm. The surface sculpture consists of relatively narrow concentric undulations 

crossed by low radial costae. The costae are only 

well preserved near the middle of the valve.

This specimen bears a resemblance to Caneyella 

percostata Girty from the Caney Shale of Oklahoma, but because C. percostata disappears in the 

Oklahoma-Arkansas section at a lower level in the 

Chesterian series than is represented by the Amsden 

beds and because the one specimen we have is poorly 

preserved, we are not extending the range of Girty's 

species into Wyoming.

Figured specimen. USNM 174029.

Occurrence and number of specimens. Horseshoe 

Shale Member: collection 46 (1), Fremont County, 

Wyo.

Genus LEPTODESMA, Hall, 1883 

Leptodesma spp.

Plate 2, figure 19

A small species of Leptodesma occurs in the Pennsylvanian part of the Amsden Formation. The specimens are all molds which are not well preserved. 

One left valve is figured; it shows the shell shape, 

the presence of a posterior auricle and an anterior 

lobe, and the highly prosocline nature of the species; 

the angle between the dorsal margin and the umbonal ridge (angle alpha) is about 30°. The dimensions of this specimen are: length 10 mm, height 6

mm, diagonal dimension 10 mm, and maximum convexity 2.3 mm.

Also referred to this genus is a small left valve 

from Cherry Creek, preserved in sandstone, in the 

collection of the University of Wyoming (A11123). 

This specimen has ornamentation of narrow concentric growth lines.

Figured specimen. USNM 174030.

Occurrence and number of specimens. Horseshoe 

Shale Member: collection 28 (1), Fremont County, 

Wyo. Ranchester Limestone Member: collection 50 

(15), Washakie County, Wyo.

Family POSIDONIIDAE Frech

Following the suggestion of Stanley (1972) we 

are herein including this family in the Pteriacea 

rather than the Pectinacea where it has traditionally been placed.

Genus POSIDONIA Bronn, 1828

Posidonia sp. indet.

Plate 2, figure 3

A small species referred tentatively to Posidonia 

occurs with Lingula and Streblopteria in a shale of 

Mississippian age in the Washakie Range. In this 

form the umbo is located near but not at the anterior end of the hinge, and the surface of the shell is 

ornamented with several shallow concentric undulations. The dimensions of a moderately large specimen are: length 5.0 mm and height 6.5 mm; the 

maximum convexity could not be measured because 

of diagenetic compression of the shell.

This form is somewhat similar to Posidonia wapanuckensis (Girty) from the Caney Shale of southeastern Oklahoma, but the Wyoming material is not 

adequate for detailed comparison with otHr species.

Figured specimen. USNM 174032.

Occurrence and number of specimens. Horseshoe 

Shale Member: collection 46 (4), Fremont County, 

Wyo.

Superfamily PINNACEA Leach

Family PINNIDAE Leach 

Genus AVICULOPINNA Meek, 1864

Aviculopinna sp.

Plate 2, figures 20-22

An elongate, cuneiform, incomplete, articulated 

specimen from the Pennsylvanian part of the Amsden Formation at Amsden Creek is placed in this 

genus. Although the specimen is only a fragment, it 

has the characteristic shape and concentric markings of Aviculopinna. It is most similar to A. peracuta (Shumard) which has been reported from 

many localities in the Pennsylvanian of the American midcontinent.

Figured specimen. USNM 174033.
F13

Occurrence and number of specimens. Ranchester Limestone Member: collection 67 (1), Sheridan 

County, Wyo.

Superfamily PECTINACEA Rafinesque

Family ENTOLIIDAE Korobkov 

Genus PERNOPECTEN Winchell, 1865

Pernopecten sp. indet.

Plate 2, figure 23

Three specimens from a granular chert bed of 

Pennsylvanian age near the top of the Amsden on 

the east slope of the Bighorn Mountains belong to 

the genus Pernopecten. The specimen shown on 

plate 2, figure 23, is the most complete of the three; 

it is probably a left valve and its dimensions are: 

length 14.5 mm, height 17.3 mm, and maximum convexity 1.2 mm. This shell is gently convex and has 

two shallow sulci which diverge at an angle of about 

60° from the dorsal margin.

These specimens were identified as Entolium aviculatum by Girty in a faunal list published by Darton (1906, p. 34) in his original description of the 

Amsden Formation. In our opinion the material is 

neither complete enough nor well enough preserved 

to assign it to a species.

Figured specimen. USNM 174034.

Occurrence and number of specimens. Ranchester Limestone Member: collection 52 (3), Johnson 

County, Wyo.

Family PSEUDOMONOTIDAE Newell 

Genus PSEUDOMONOTIS von Beyrich, 1862

Pseudomonotis sp.

Plate 2, figure 25

A unique specimen from the same granular chert 

bed as the previous species is assigned to Pseudomonotis. It is a left valve measuring 23.5 mm long, 

27.5 mm high, 13.5 mm along the dorsal margin, 

and having a maximum convexity of 4.5 mm.

The specimen is slightly prosocline and is of moderate convexity. The anterior auricle is weakly set 

off from the body of the shell by a rounded diagonal 

concave area, whereas the posterior auricle merges 

into the body of the shell without a break.

Surface sculpture consists principally of radial 

costae which increase in number by intercalation 

and are of somewhat variable strength in an alternating pattern; the costae are not absolutely 

straight and about 85 occur on this specimen. They 

are crossed by fine concentric markings that become 

stronger and somewhat lamellose near the posterior 

margin; some beading is present where the concentric lirae cross the costae.

Figured specimen. USNM 174035.

Occurrence and number of specimens. Ranchester Limestone Member: collection 52 (1), Johnson 

County, Wyo.

Family AVICULOPECTINIDAE Meek and Hayden

Subfamily STREBLOCHRONDRIINAE Newell

Genus STREBLOPTERIA McCoy, 1851

Streblopteria sp. iudet.

Plate 2, figure 24

The Amsden record of this genus consists of one 

left valve preserved in a grayish-tan shale of Late 

Mississippian age in the Washakie Range. The bed 

is 8 feet below a limestone containing brachiopods 

of the Carlinia amsdeniana Subzone.

This specimen is subcircular, opisthocline, and 

measures 14.8 mm long and 13.8 mm high; it is 

gently convex but is probably diagenetically compressed. The shell surface is smooth and the auricles 

are incompletely preserved.

Figured specimen. USNM 174036.

Occurrence and number of specimens. Horseshoe 

Shale Member: collection 46 (1), Fremont Courty, 

Wyo.

Subfamily AVICULOPECTININAE Meek and Hayden 

Genus AVICULOPECTEN McCoy, 1851

Aviculopecten gravidus n. sp.

Plate 3, figures 5-7

Description. -Shell markedly inequivalve, having 

strongly convex left valve and nearly flat right 

valve, acline to slightly prosocline. Left valve ovr.te, 

rounding into auricles; height greater than length; 

in longitudinal profile, curvature is greatest near 

umbo, decreasing slightly toward ventral margin; 

greatest convexity a little above middle. Anterior 

auricle set off from main part of valve by weak 

diagonal sulcus; posterior auricle not sharply separated from main part of valve but delimited by shallow posterior embayment.

Right valve gently convex in umbonal region, 

gradually becoming almost flat near margin. Anterior auricle long and separated from body of valve by 

deep byssal notch; posterior auricle not so well defined, or preserved, but seemingly with very shallow 

concave area of intersection with disk.

Surface sculpture of both valves consisting of f ne 

rounded radial costellae separated by subequal interspaces. Costellae increase by intercalation on Mt 

valve; method of increase not possible to determine 

on the only right valve because of inadequate preservation. Roughly 125-135 costellae present on left 

valve covering both disk of valve and auricles; number uncertain on right valve; anterior auricle of 

right valve ornamented only by growth lines. Radial 

sculpture crossed by concentric growth lines, some 

of which are quite prominent and indicate periods
E14 THE AMSDEN FORMATION (MISSISSIPPIAN AND PENNSYLVANIA!*) OP WYOMING

of slow growth. Toward margins of left valve, 

growth lines become stronger and lamellose. Occasionally, intersecting costellae and growth lines 

combine to give reticulate appearance to surface. 

Dimensions (in mm). 

USNM 174041 

LV (holotype)

44

37

14

USNM174042 

RV (paratype)

39

34

4

24

Height _____________

Length _______

Convexity _____

Dorsal margin ____

1 Approximate because incompletely preserved. LV, left valve: RV right 

valve.

Discussion. This species is based on specimens 

from a single locality in the Neokoninckophyllum 

hamatilis Zone of Pennsylvanian age in the Rawlins 

hills. The type lot consists of 12 specimens, all but 

one of which are left valves. Although none of the 

valves is complete, the aggregate lot gives most of 

the essential characters, the most distinctive of 

which are the unusual disparity in convexity between the two valves and the distinctive fine sculpture which has a reticulate appearance in places. 

The left valve bears some resemblance to that of 

members of the genus Pseudomonotis, but the right 

valve is that of a typical Aviculopecten.

Types. Holotype USNM 174041, paratypes 

USNM 174042-174044.

Occurrence and number of specimens. Horseshoe 

Shale Member: collection 3 (12), Carbon County, 

Wyo.

Aviculopecten sp. A

Plate 3, figure 1

This small species has an acline suboval shell with 

the length of the dorsal margin approximately equal 

to two-thirds of the length of the shell. The most 

complete specimen (the larger of the two left valves 

illustrated) measures 9.9 mm high, 8.9 mm long, 

and has a maximum convexity of 1.3 mm; the dorsal 

margin is 6 mm long. The auricles are indistinctly 

set off from the main part of the shell; the anterior 

auricle has a straight to rounded anterior margin, 

whereas the posterior auricle has a concave posterior 

margin and is slightly alate at its dorsal terminus.

Surface sculpture consists of about 100 radial 

costellae distributed over the body and auricles 

which are separated by wider to subequal flatbottomed interspaces. The costae increase in number 

by intercalation, but the new elements quickly reach 

the strength of the earlier ones so that the shell 

appears evenly costellate. The costellae are crossed 

by fine concentric growth lines.

Most of our specimens are fragmentary; all of 

them are probably left valves. They came from a bed 

of Mississippian age just beneath the Moffat Trail

Limestone Member at a locality in the Hoback 

Range.

Figured specimens. USNM. 174037A, B.

Occurrence and number of specimens. Horseshoe 

Shale Member: collection 118 (1), Teton County, 

Wyo.

Aviculopecten sp. B

Plate 2, figures 16-18; plate 3, figure 2

This small species has a slightly prosocline shell. 

The specimen shown on plate 3, figure 2, is 10.4 mm 

high, 10 mm long, and has a maximum convexity of 

2.5 mm; the dorsal margin is 7.8 mm long. The shell 

is unusually convex for its small size. The anterior 

auricle is relatively short and is sharply set off from 

the body of the shell; the posterior auricle is longer 

than the anterior and is not as abruptly set off from 

the body of the shell.

Shell sculpture is well preserved en only one 

specimen (USNM 174038). It has 10 narrow primary costae having wide, flat to gently concave 

interspaces; the primary costae are more closely 

spaced posteriorly than anteriorly. At 3 to 4 mm 

from the beak, intercalary costae begin to appear 

and they increase rapidly in strength. No costae 

have been seen on the auricles. Concentric growth 

lines are faintly preserved. Two left valves (USNM 

174039, 174040) preserve some details of the dorsal 

margin (pi. 2, figs. 16-18) which, considering the 

size of the species, has a wide subtriangular shelf 

extending from the beak to the commissure. This 

shelf is marked by horizontal growth lines.

Aviculopecten sp. B is found at two Pennsylvanian localities at either side of the Bighorn Mountains. Of 12 specimens referred to this taxon, 7 are 

left valves and the others are also probably left 

valves although they are not complete. The relatively sparse radial sculpture and the wide dorsal 

shelf readily differentiate this form from other 

Amsden Aviculopectens.

Figured specimens. USNM. 174038-174040.

Occurrence and number of specimens. Horseshoe 

Shale Member: collection 53 (3), Johrson County, 

Wyo. Ranchester Limestone Member: collection 50 

(9), Washakie County, Wyo.

Aviculopecten spp. indet.

Plate 3, figures 3, 4

Besides the three distinctive species already described, which are represented by reasonably well 

preserved material, several fragmental and poorly 

preserved valves are scattered througl the collections, probably representing at least thr^e additional
PELECYPODA AND 410STROCONCHIA OF THE AMSDEN FORMATION OF WYOMING E15

species of Aviculopecten. We will consider these in 

order of age from older to younger.

Two fragments (USNM 174046, 174047), possibly belonging to the same species, were found in the 

Caninia Zone (Moffat Trail Limestone Member) in 

the Salt River Range at localities about l 1/^ miles 

apart. This species is a medium^sized Aviculopecten 

having the left valve ornamented by rather narrow 

costae of alternating strength, separated by wider 

interspaces. The flat right valve has costae that increase by bifurcation, as is typical in this genus.

A lot of three weathered specimens (UW A11102) 

from the Carlinia amsdeniana Subzone (Horseshoe 

Member) at Cherry Creek belongs in a different 

species. The shell is convex and ornamented by more 

than 15 rather strong costae separated by 1 to 3 

noticeably weaker ones. Only one of the three shells 

is well enough preserved to show the finer sculpture. 

Another poorly preserved specimen (UW All 137) 

from the underlying bed probably represents the 

same species.

Lastly, two specimens of Aviculopecten occur in 

beds of Pennsylvanian age in the Horseshoe Shale 

Member. The more complete of these (USNM 

174045, pi. 3, figs. 3, 4) is from the base of this 

member on the east flank of the Bighorn Mountains. 

The other one (USNM 174021), a fragment of the 

umbonal area, probably of a left valve, is from the 

Neokoninckophylhim hamatilis Zone in the Rawlins 

hills.

Figured specimen. USNM 174045.

Occurrence and number of specimens. Horseshoe 

Shale Member: collections 1 (1), Carbon County; 

29 (1), 30 (3), Fremont County; 53 (1) Johnson 

County, Wyo. Moffat Trail Limestone Member: collections 79 (1), 92 (1) Lincoln County, Wyo.

Subclass HETEROCONCHIA

Order TRIGONIOIDA 

Superfamily TRIGONIACEA Lamarck

Family MYOPHORIIDAE Bronn 

Genus SCHIZODUS deVerneuil and Murchison, 1844

Schizodus cf. S. depressus W or then

Plate 3, figures 10-13

Schizodus depressus Worthen, 1884, p. 11; 1890, p. 100, pi. 

18, figs. 8, 8a; Girty, 1915a, p. 98, pi. 9, figs. 13, 

13a; Weller, 1916, p. 250, pi. 16, figs. 25-27.

Schizodus sp. Branson, 1937, p. 658.

Description. Shell moderately small, subtriangular, having convex curved margins, length slightly 

exceeding height; anterior margin rather evenly 

rounded, posterior margin having two subangulations interrupting its curved outline; valves moderately shallow. Umbonal ridge rounded but fairly 

well marked; postumbonal slope gently concave, inclined at angle of roughly 50° to plane of commissure.

Dimensions (in mm). 

uw

LV

Height ___-________ 14.5 

Length _____________ 16.7 

Convexity __ 2.9 

Thickness (both valves) 

UW

A1288 

RV

13.4

16.2

3.0

UM66so

*BV RV

8.2

9.0 8.4 

(2.2) 2.2 

4.4

1 Ventral part broken off. BV indicates both valves.

Discussion. The first two specimens in the to.ble 

above are from a calcareous sandstone collected in 

place in the Carlinia am.sdeniana Subzone, 45 feet 

above the base of the Amsden Formation at Cherry 

Creek. These shells approximate in their dimens'ons 

and configuration typical specimens of <S. depre?sus 

from the Ste. Genevieve Limestone of Late Mirsissippian (Meramecian) age in Monroe County, 111. 

The two specimens from the limonitic shale b^ds 

of the Amsden are smaller and in the more complete 

valve the length is subequal to the height. One well 

preserved but incomplete internal mold (pi. 3, figs. 

10, 11) preserves the imprint of the lower side of 

the cardinal tooth, which is small and delicate.

The references given in the synonymy as <S. depressus are limited to those of the Illinois form. 

Girty (1915a, p. 98) identified two specimens of the 

Illinois form with question from the Batesville 

Sandstone of northern Arkansas. This identification 

implies that the Arkansas specimens might actually 

represent one of the end points in the range of variation of the subspecies S. depressus abruptus Girty, 

which differs in the decidedly steeper inclination of 

the posterodorsal slope. The Wyoming shells do not 

exhibit this steeper inclination. Because our specimens are few in number and not very well preserved, we are merely comparing the Wyoming form 

with the Illinois species.

Figured and measured specimens. UM 6630, UW 

A1288, A11121, USNM 174048; A1288 not figur-d.

Occurrence and number of specimens. Horseshoe 

Shale Member: collections 20 (1), 28 (4), ?29 (1), 

36d (1), Fremont County, Wyo.

Schizodus aff. S. affinis Herrick, 1887

Plate 3, figures 15, 16 

Schizodus affinis Herrick, 1887, p. 41, pi. 4, figs. 22, 22a.

This species occurs in a tan marlstone on the west 

side of the Bighorn Mountains and in a chert bed 

in the Wind River Range; both occurrences are 

Pennsylvanian in age. The specimens are mcstly 

small internal molds, longer than high, with the 

umbo occurring about one-third to two-fifths of the 

length posterior to the anterior edge. The most complete specimen (pi. 3, fig. 16) is a right valve which
E16 THE AMSDEN FORMATION (MISSISSIPPIAN AND PENNSYLVANIAN) OF WYOMING

measures 12.4 mm long, 10.4 mm high, and has a 

maximum convexity of 3.5 mm. In this specimen the 

peak of the umbo is 4.5 mm behind the anterior edge. 

The umbonal ridge is narrowly rounded, slopes 

steeply posteriorly, and in some specimens is subcarinate on the posterior slope. The shell outline is 

typical of the genus, rounded anteriorly and 

obliquely but weakly truncated posteriorly. Fragments of shell adhering to the internal molds show 

that the species is thin shelled a nd has a smooth 

shell surface. Internal features are not preserved.

The Amsden specimens are similar to S. affinis 

Herrick, a common form in the Pottsville (Pennsylvanian) of Ohio. However, they differ in being 

smaller and slightly more tumid than S. affinis and 

having the angle formed by the dorsal and posterior 

margins larger than in the Pottsville form.

Figured specimens. USNM 174049, 174050.

Occurrence and number of specimens. Ranchester Limestone Member: collections 40 (1), Fremont 

County; 50 (7), Washakie County, Wyo.

Schizodus alpinus (Hall)?

Plate 3, figure 17

Dolabral alpina Hall, 1858b, p. 716, pi. 29, fig. 2.

Schizodus alpina (Hall), Meek and Hayden, 1865, p. 58;

Keyes, 1891, p. 249; Plummer and Moore, 1921, pi. 21,

fig. 28. 

Schizodus alpinus (Hall), Girty, 1915b, p. 130, pi. 17, fig. 3;

Morgan, 1924, pi. 48, figs. 7, 7a; Morse, 1931, p. 317,

pi. 52, fig. 1.

A right valve from a bed of Pennsylvanian age 

on the east flank of the Bighorn Mountains is referred with question to this species. It measures 21.8 

mm in length, 19.1 mm in height, and has a maximum convexity of 6.6 mm. The somewhat inflated 

umbo is subcentral, located 10 mm posterior to the 

anterior edge. The umbonal ridge extends to the 

posteroventral margin, it is subangular to about 

mid-height and then becomes rounded. The postumbonal slope is gently concave and very steep.

The Amsden specimen is quite close to Hall's 

(1858b) drawing and description of the type specimen of S. alpinus from the "Lower Coal Measures" 

of Iowa.

Figured specimen. USNM 174051.

Occurrence. Horseshoe Shale Member: collection 

53, Johnson County, Wyo.

Schizodus sp. A

Plate 3, figures 8, 9

Among the specimens from Cherry Creek in the 

University of Missouri collections is a larger, more 

tumid species of Schizodus than the one compared 

to S. depressus Worthen. The figured internal mold

is 18.0 mm long, 15.4 mm high, and 10.8 mm wide. 

Impressions of the underside of the interlocking cardinal teeth show that each valve had a rather large 

cardinal tooth. Vestiges of the anterior rnd posterior adductor muscle scars are also preserved. The 

anterior scar (very slightly elevated on the internal 

mold) was situated close to the anterior riargin and 

was almost twice as long as the posterior one.

A second specimen, roughly one-third larger, is 

present in the same lot but is so poorly preserved 

that one cannot be sure it represents the same species.

Figured specimen. UM 6637.

Occurrence and number of specimens. Horseshoe 

Shale Member: collection 36a, Fremort County, 

Wyo.

Schizodus sp B

Plate 3, figure 14

An internal mold of a right valve from a limestone bed of Pennsylvanian age in the Rr.wlins hills 

has the shell shape of Schizodus, but is proportionally longer than other Amsden representatives of 

the genus and probably belongs to a separate species. It measures 30.4 mm in length, about 19.5 mm 

in height, and has a maximum convexity of 8 mm. 

These measurements are proportionally quite close 

to those of S. morrowensis Mather from the Hale 

Formation of Arkansas, but the outline cf that species differs significantly from the Amsden form in 

its more triangular shape. Two other fragments, 

probably of right valves, occur at the same locality 

and may represent the same species.

Easton (1962, p. 96, pi. 12, fig. 26) described another elongate shell, from beds of similar age in the 

Big Snowy Mountains, Montana, as Scluzodusl sp. 

A reexamination of Easton's specimen, however, 

shows that it is an Edmondia.

Figured specimen. USNM 174052.

Occurrence and number of specimens. Horseshoe 

Shale Member: collection 3 (3), Carbon County, 

Wyo.

Order VENEROIDA

Superfamily CARDITACEA Fleming

Family PERMOPHORIDAE van de Poel

Genus PERMOPHORUS Chavan, 1954

Permophorus sp. A

Plate 3, figures 18-23 

IPleurophoriis sp. Easton, 1962 [part], p. 96, p1 . 12, fig. 33.

Description. Shell moderately small, elongate, 

having subparallel dorsal and ventral margins and 

well rounded anterior and posterior margins, and 

strongly convex in cross section. Valve length about 

twice height and five times valve convexity. Dorsal 

margin nearly straight, umboes protruding only
PELECYPODA AND EOSTROCONCHIA OF THE AMSDEN FORMATION OF WYOMING E17

slightly above it; ventral margin nearly straight to 

gently concave in outline; dorsal and ventral margins diverging slightly posteriorly; anterior and 

posterior margins protrude so that the greatest 

length is below midheight. Umbonal ridge extends 

toward posteroventral margin, usually poorly defined and rounded but may be angular. Broad shallow sulcus present on some specimens anterior to 

umbonal ridge.

Lunule narrow, heart shaped, bounded by angular 

margin; escutcheon linear, bounded by nearly 

straight rib, both characters shown on one left valve 

(USNM 174053). Radial ornamentation not normally preserved on our material but the same specimen shows two faint ribs lateral to escutcheon. Surface of shell covered by fine closely spaced growth 

lines.

Internal features not well preserved, but all internal molds show straight myophoric buttress on 

posterior side of oval anterior adductor muscle scar. 

One left valve (USNM 174055) shows cardinal 

socket and the lower of the two lateral teeth that 

are typical of this genus.

Dimensions (in mm). 

Length _____ 18.8

Height _____ 8.5

Convexity __ 3.5

USNM USNM

174055 174054

LV RV

18.2 

9.5 

3.5

USNM USNM USNM USNM

174053 174057 174058 174056

LV LV RV RV

7.7 

3.2

^2.8 

6.9 

3.2

12.6

7.3

3

11.2

6

2.2

1 Posterior edge missing. The first two specimens are from collection 52, 

the next one from collection 53, and the last three from collection 50.

Discussion. The description is based upon specimens from Amsden beds of both Mississippian 

(colln. 159) and Pennsylvanian (collns. 50, 52, 53) 

ages. Specimens from collection 50 on the west side 

of the Bighorns are somewhat smaller than those 

from collections 52 and 53 on the east side of the 

Bighorns but otherwise do not differ significantly. 

Specimens from collection 159 (pi. 3, fig. 20), from 

Berry Creek in the Teton Range, are latest Mississippian in age. They differ from the Pennsylvanian 

forms in having a more angular umbonal ridge and 

in being nearly smooth. They may represent another 

species of Pennophorus, but for the present are 

placed in Permophoms sp. A.

Permophoms sp. A is recognized by its evenly 

convex valves and the paucity of radial ornament 

which is limited to a rib or two near the hinge. 

These characteristics distinguish it from other Late 

Mississippian and Early and early Middle Pennsylvanian species of the genus. However, because of 

the limited present state of knowledge of species of 

the genus Permophoms we are not proposing a new 

name for the Amsden forms.

A form similar to Permophorus sp. A from the 

Alaska Bench Limestone of central Montana, was 

figured by Easton (1962, p. 96, pi. 12, fig. 3?) as 

Pleuroplwrus sp. Easton's unique internal mold 

measures: length 19 mm, height 10.7 mm, and maximum convexity (both valves) 8 mm. The left valve 

is distorted near the posterior end, probably due to 

shell damage during the life of the animal, and the 

shell is not preserved. Hence it is difficult to compare the Alaska Bench form to the Amsden species. 

Nonetheless, they are similar in outline, high convexity, and shell proportions and the Montana and 

Wyoming forms are probably conspecific. Furthermore, the range zone of the Wyoming form includes 

Amsden beds now regarded to be biostratigraphically equivalent to the Alaska Bench Limestone.

Easton (1962, p. 96) also referred to Permophorusl fas Pleiirophorusl^ a specimen from the Otter 

Shale (USGS locality 13374-PC) and another from 

the Heath Formation (USGS locality 13366-PC). 

On reexamination we transfer these specimens to 

the genus Caneyella.

Figured and measured specimens. USNM 

174053-174059; USNM 174058 not figured.

Occurrence and number of specimens. Horseshoe 

Shale Member: collections ?3 (2), Carbon County; 

53 (3), Johnson County; 159 (4) Teton County, 

Wyo. Ranchester Limestone Member: collections 50 

(14), Washakie County; 52 (4), Johnson County, 

Wyo.

Superfamily CRASSATELLACEA Ferussac 

Family CRASSATELLIDAE Ferussac 

Genus CYPRICARDELLA Hall, 1858a

Cypricardella sp.

Plate 4, figure 11

Microdon cf. M. oblongus (Hall), Branson and Greger, 1918 

[part], p. 321, pi. 19, fig. 25 [not fig. 11].

One left valve of this species, from the Mississippian part of the Amsden, is present in the University of Missouri collections. It is subcircular in outline and has pronounced, closely spaced concentric 

rugae and a prominent posterior umbonal carina; 

nothing is known of the internal features. The specimen measures 14 mm long, 12.4 mm high, and has a 

maximum convexity of 4 mm.

This species was compared to Cypricardella oblonga Hall by Branson and Greger; however, the 

latter species is quadrate rather than subcircular, so 

the Amsden form probably belongs to a different 

species.

Figured specimen. UM 2657.

Occurrence. Horseshoe Shale Member: collection 

36c, Fremont County, Wyo.
E18 THE AMSDEN FORMATION (MISSISSIPPIAN AND PENNSYLVANIAN) OF WYOMING

Cypricardella? sp. indet.

Plate 4, figures 8-10

A small articulated and slightly distorted mold 

from the Mississippian part of the formation has 

prominent, closely spaced concentric rugae and is 

more or less like Cypricardella in shape. It measures 

6 mm high, and has a maximum convexity of 2.8 

mm (both valves flattened).

Because of the small size and poor preservation, 

positive generic assignment of this specimen is not 

possible. It is probably a Cypricardella but it could 

be a young stage of some other concentrically rugose 

genus.

Figured specimen. USNM 174060.

Occurence. Horseshoe Shale Member: collection 

20, Fremont County, Wyo.

Family ASTARTIDAE D'Orbigny 

Genus ASTARTELLA Hall, 1858b

Astartella concentrica (Conrad), 1842

Plate 4, figures 4-7

Nuculites concentrica Conrad, 1842, p. 248, pi. 15, fig. 19. 

Posidonia moorei Gabb, 1859 [1860], p. 297; 1860 [1861], p.

55, pi. 1, fig. 2. 

Edmondia concentrica McChesney, 1859 [1860], p. 55; 1865,

pi. 2, figs. 21a, b. 

Astartella concentrica (McChesney). McChesney, 1867

[1868], p. 43, pi. 2, figs. 21a, b; Keyes, 1894, p. 126;

Plummer and Moore, 1921, pi. 13, figs. 38, 38a, 40, pi.

31, figs. 15, 16; Morgan, 1924, pi. 46, fig. 5. 

Astartella concentrica (Conrad). Meek, 1875, p. 341; Girty,

1915b, p. 142, pi. 18, figs. 2-9; Price, 1916, p. 725;

Morningstar, 1922, p. 241, pi. 13, figs. 11-13; Girty,

1927, p. 418, text figs. 1-11; Morse, 1931, p. 319, pi.

52, fig. 3; Plummer, 1950, pi. 21, figs. 3a, b; Chow,

1951, p. 33, pi. 4, fig. 3; Nicol, 1955, p. 157, text figs.

2, 3.

Specimens of this widespread and distinctive species are known from several Amsden localities of 

Pennsylvania!! age. Astartella has a recognizable 

shape and A. concentrica is ornamented with prominent concentric rugae that in typical mature specimens are spaced so that about seven occur in a 

space of 5.0 mm. The specimen shown on plate 4, 

figures 4, 5, measures 12 mm in length, 9.4 mm in 

height, and has a maximum convexity of 3.2 mm. 

Most of our specimens of this species are fragmentary and not well preserved, but they are readily 

identifiable because of their distinctive ornamentation (pi. 4, figs. 6, 7).

Figured specimens. USNM 174061, 174062.

Occurrence and number of specimens. Horseshoe 

Shale Member: collections ?3 (1), Carbon County; 

53 (2), Johnson County, Wyo. Ranchester Limestone Member: collections 40 (2), Fremont County;

50 (4), Washakie County; 52 (1), Johnson County, 

Wyo.

Astartella sp.

Plate 4, figures 1-3

A second species of Astartella is present in the 

Mississippian part of the Amsden. This species is 

less erect than A. concentrica and it lacl's the concentric rugae, being ornamented instead by closely 

spaced, fairly even, relatively fine growth lines. It is 

known from only one left valve which measures 17 

mm long, 11.3 mm high, and has a maximum convexity of 7 mm. Nothing is known of the internal 

features.

Astartella sp. has a shape much like Nuculopsis, 

however the presence of an escutcheon readily separates Astartella from the latter genus.

Figured specimen. USNM 174063.

Occurrence. Horseshoe Shale Member; collection 

41, Teton County, Wyo.

Subclass ANOMALODESMATA

Order PHOLADOMY01DA 

Superfamily EDMONDIACEA King

Family EDMONDIIDAE King 

Genus EDMONDIA deKoninck, 1841

Edmondia spp.

Plate 4, figures 12-16

At least three forms of this genus herein treated 

as species are present in the Pennsylvnian part 

of the Amsden Formation. None of them is well 

preserved, and all are represented by very few 

specimens. They are distinguished by minor differences in shape. All three of them are present in one 

collection, from a granular chert bed r.igh in the 

Amsden Formation on the east slope of the Bighorn 

Mountains (colln. 52) ; this casts some doubt as to 

whether they actually belong in thre^ different 

species.

The most widespread of the three forms, represented by seven specimens from three localities, is 

a small elongate Edmondia (pi. 4, figs. 14, 15), oval 

in shape and similar to E. nebrascensis (Geinitz). 

The better preserved of the two figured specimens 

measures: length 7.9 mm, height 5.7 mm, and maximum convexity 1.9 mm.

A subcircular form (pi. 4, figs. 12, 13) is known 

from a single specimen (colln. 52). It preserves 

remnants of the adductor muscle scars and is erect, 

having the umbo projecting well above the dorsal 

margin. Measurements of this specimen are: length 

about 15 mm, height 13.8 mm, and maximum convexity 6 mm.

The third form (pi. 4, fig. 16), also known from 

one specimen, from the same locality as the last, is
PELECYPODA AND ROSTROCONCHIA OF THE AMSDEN FORMATION OF WYOMING E19

elongate quadrate and preserves some of the concentric surface ornamentation. It measures 21.5 mm 

in length, about 17 mm in height, and has a maximum convexity of 6.3 mm.

Figured specimens. USNM 174064-174067.

Occurrence and number of specimens. Ranchester Limestone Member: collections 40 (1), Fremont 

County; 50 (2), Washakie County; 52 (6), Johnson 

County, Wyo.

Superfamily PHOLADOMYACEA Gray 

Family GRAMMYSIIDAE Miller 

Genus SPHENOTUS Hall, 1885

Sphenotus sp.

Plate 4, figures 17, 18

The figured specimen' has the shape, posterior 

auricle, and umbonal carina typical of Sphenotus; 

it comes from the Carlinia amsdeniana Subzone at 

Darwin Peak. It is a small internal mold which 

measures 14.6 mm long, 7.1 mm high, and 3.5 mm in 

maximum convexity. Another example, a poorly 

preserved articulated internal mold from the same 

part of the formation in Wind River Range (UM 

12791), is referred tentatively to this taxon.

Difference of opinion has existed for some time 

(Hind, 1900; Driscoll, 1965; Pojeta, 1969; Newell 

and LaRocque, 1969) as to whether the genus 

Sphenotus Hall is separable from Sanguinolites 

McCoy. We have followed Driscoll (1965) in this 

regard and have treated the two as separate genera. 

In general, forms assigned to Sphenotus have a less 

prominent concentric sculpture than those placed in 

Sanguinolites.

Figured specimen. USNM 174068.

Occurrence and number of specimens. Horseshoe 

Shale Member: collections ?36d (1), Fremont 

County; 137 (1), Teton County, Wyo.

Genus SANGUINOLITES McCoy, 1844 

Sanguinolites sp.

Plate 4, figures 19-21

Allorisma terminate (Hall). Burk, 1954 [part], p. 14, 15, pi. 

1, fig. 38 [not figs. 39, 40].

A single dorsoventrally crushed articulated limonitic mold from the Mississippian part of the Amsden is here placed in the genus Sanguinolites. It has 

prominent concentric ornament from the umbonal 

ridge across the anterior part of the shell; the 

strength of the ornament is reduced posterodorsal 

to the umbonal carina. In this way it is similar to 

species placed in Sanguinolites by Hind (1900) and 

Pojeta (1969). Measurements of the specimen were 

not made because of its distorted condition.

Figured specimen. UW IT-237.

Occurrence. Horseshoe Shale Member; collection 

22, Fremont County, Wyo.

Genus SEDGWICKIA McCoy, 1844

Sedgwickia? sp. indet. 

Plate 4, figures 23, 24

One highly weathered and incomplete articulated 

internal mold, from the Pennsylvanian part of the 

Amsden, has the general outline of some species 

placed in Sedgwickia by Meek and Hayden (1865) 

and Hind (1899) and is here tentatively referred 

to that genus. It measures about 55 mm in length, 

32.4 mm in height, and has a maximum convexity 

of 19.5 mm (both valves).

Figured specimen. USNM 174069.

Occurrence. Horseshoe Shale Member: ccSection 5, Carbon County, Wyo.

Family PHOLADOMYIDAE Gray 

Genus WILKINGIA Wilson, 1959

Wilkingia terminalis (Hall)

Plate 4, figures 26-30

Allorisma terminalis Hall, 1852, p. 413, pi. 2, figs. 4a, b. 

Allorisma terminate (Hall). Girty, 1903, p. 437, 438, pi. 9,

figs. 4-6 (for synonymy prior to 1903); 1909, p. 90;

Price, 1914, p. 527; 1921, p. 784; Morningstar, 1922,

p. 234, pi. 13, fig. 15; Morse, 1931, p. 318, pi. 51, figs. 2. 

Allorisma subcuneatum (Meek and Hayden). Barbour, 1903,

pi. 2, fig. 18; Raymond, 1910, p. 158, pi. 27, figs. 5, 6;

1911, p. 98, pi. 6, fig. 5; Plummer and Moore, 1921,

pi. 24, fig. 18. 

Allorisma terminate (Hall). Mark, 1911, pi. 10, fig. 10;

Morgan, 1924, pi. 46, figs. 3, 3a; Butts, 1926, p. 200,

pi. 66, fig. 16; French, 1940, p. 328, pi. 3, fig. 23;

Shinier and Shrock, 1944, p. 414, pi. 165, figs. 10, 11;

Branson, 1948, p. 563; Chronic, 1952, p. 146, 147, pi.

9, figs. 4a-c; Chow, 1951, p. 31, pi. 3, figs. 17a-c;

Burk, 1954 [part], p. 14, 15, pi. 1, figs. 39, 40 [not

fig. 38]; Mudge and Yochelson, 1962, p. 90, pi. 16, figs.

5, 6.

A number of specimens from several localities, 

both in the Mississippian and Pennsylvanian parts 

of the Amsden Formation, are referred to this 

ubiquitous and long-ranging species. None is well 

preserved but several show the characteristic pholadomyiform shape with subparallel dorsal and ventral margins and the ornament of prominent concentric rugae. The specimen shown on plate 4, figure 

26, has the following measurements: length 39 mm, 

height 20.1 mm, and maximum convexity 7.8 mm. 

The specimens figured in this paper are from the 

Pennsylvanian part of the formation. Burk (1954, 

pi. 1, figs. 39, 40) has previously figured specimens 

from near the top of the Mississippian part.

Figured specimens. USNM 174070, 174071.

Occurrence and number of specimens. Horseshoe 

Shale Member: collections 1 (2), 2 (1), 3 (8), 5 

(3), Carbon County; 36e (1), 43 (4), Frenont
E20 THE AMSDEN FORMATION (MISSISSIPPIAN AND PENNSYLVANIAN) OF WYOMING

County, Wyo. Ranchester Limestone Member: collection 50 (7), Washakie County, Wyo.

Wilkingia sp.

Plate 4, figure 25

Allorisma terminate (Hall). Burk, 1954 [part], p. 14, 15 

[not pi. 1, figs. 38-40].

A second species of Wilkingia is represented by 

one reasonably complete and two fragmentary 

limonitic molds from the Mississippian part of the 

Amsden Formation at South Pass in the Wind 

River Range. In general outline this species is similar to W. terminal-is but differs in that secondary 

concentric rugae are intercalated between the primary ones about one-fourth of the way back from 

the anterior edge. These secondary rugae do not 

cross the entire shell surface but die out anteriorly. 

The figured specimen measures 18.2 mm long, about 

8 mm high, and has a maximum convexity of 2 mm.

Figured specimen. UW IT-240.

Occurrence and number of specimens. Horseshoe 

Shale Member: collection 22 (3), Fremont County, 

Wyo.

Class ROSTROCONCH1A

Family CONOCARDIIDAE Miller

Genus CONOCARDIUM Bronn, 1835

"Conocardium" sp. indet.

Plate 4, figure 22

In the Amsden collections available to us, rostroconchians are represented by a single incomplete 

specimen from the Mississippian part of the formation which has the general aspect of forms presently assigned to the genus Conocardium. The class 

Rostroconchia is currently under revision by Pojeta 

and Runnegar.

Figured specimen. USNM 182074.

Occurrence and number of specimens. Ranchester Shale Member: collection 139 (1), Teton 

County, Wyo.

REFERENCES CITED

Barbour, E. H., 1903, Report of the State geologist: Nebraska Geol. Survey v. 1, p. 1-258, illus.

Beyrich, H. E., 1862, Protokoll der November-Sitzung: 

Deutsch. Geol. Gesell. Zeitschr., v. 14, no. 1, p. 9-10.

Blackwelder, Eliot, 1913, New or little known Paleozoic 

faunas from Wyoming and Idaho: Am. Jour. Sci., ser. 

4, v. 36 (186), art. 21, p. 174-179.

Branson, C. C., 1937, Stratigraphy and fauna of the Sacajawea formation, Mississippian, of Wyoming: Jour. 

Paleontology, v. 11, no. 8, p. 650-660, pi. 89.

 1948, Bibliographic index of Permian invertebrates: 

Geol. Soc. America Mem. 26, 1049 p.

Branson, E. B., and Greger, D. K., 1918, Amsden formation of the east slope of the Wind River Mountains of

Wyoming and its fauna: Geol. Soc. America Bull., v. 

29, no. 6, p. 309-327, pis. 18, 19.

Bronn, H. G., 1828, Posidonia becheri eine neue fossile Muschel der Uebergangs-Periode: Leonhard Taschenbuch 

fur die gesammte Mineralogie, Zeitschrift fur Mineralogie, neue folge, v. 1, no. 4, p. 262-269, pi. 2.

 1835-37, Lethaea Geognostica oder Abbildungen und 

Beschreibungen der fur die Gebirgs-Formation bezeichnendsten Versteinerungen, v. 1, 544 p., 47 p1 ?. (text and 

plates bound separately) : Stuttgart, E. Schweizerbart.

Burk, C. A., 1954, Faunas and age of the Amsden formation 

in Wyoming: Jour. Paleontology, v. 28, no. 1, p. 1-15., 

pi. 1.

Butts, Charles, 1926, Geology of Alabama the Paleozoic 

rocks: Alabama Geol. Survey Spec. Rept. 14, p. 41-230, 

74 pis., 4 text figs.

Ohavan, Andre, 1954, Les Pleurophorus et genres voisins: 

Cahiers Geol. Thoiry, no. 22, p. 200.

Chernyshev, B. I., 1951, Semeystvo Ledidae iz Kamennougol'nykh otlozheniy SSSR: Trud., Akad. Nauk Ukrain, 

SSR, Kiev, Ser. Strat. i Paleont., v. 2, 40 p., 2 pis.

Chow, M. M., 1951, The Pennsylvanian Mill Creek limestone 

in Pennsylvania: Pennsylvania Geol. Survey, 4th ser., 

Bull. G26, 36 p., 4 pis., 3 text figs.

Chronic, Halka, 1952, Molluscan fauna from the Permian 

Kaibab formation, Walnut Canyon, Arizona: Geol. Soc. 

America Bull., v. 63, no. 2, p. 95-165, 11 pis., 15 text figs.

Conrad, T. A., 1842, Descriptions of new species of organic 

remains belonging to the Silurian, Devonian, and Carboniferous systems of the United States: Acad. Nat. Sci. 

Philadelphia Jour., v. 8, pt. 2, p. 235-280, pis. 13-17.

Darton, N. H., 1906, Geology of the Bighorn Mountains: 

U.S. Geol. Survey Prof. Paper 51, 129 p., 47 pis., 14 

text figs.

Driscoll, E. G., 1964, Accessory muscle scars, an aid to 

protobranch orientation: Jour. Paleontology, v. 38, no. 1, 

p. 61-66, pi. 16.

 1965, Dimyarian pelecypods of the Mississippian 

Marshall sandstone of Michigan: Palaeontographica 

Americana, v. 5, no. 35, 64-128, pis. 7-18. 

-1966, Morphology and evolution of certain Paleozoic

Nuculanidae from the mideontinental United States: 

[Czechoslovakia] Narod. Muz. Praze Sbornik, ser. B, v. 

22b, no. 1, p. 1-26, pis. 1-4.

Easton, W. H., 1962, Carboniferous formations and faunas 

of central Montana: U.S. Geol. Survey Prof. Paper 348, 

126 p., 14 pis.

French, E. M., Jr., 1940, Characteristic fossils of Maryland: 

Compass, v. 20, no. 4, p. 323-339, 8 pis.

Gabb, W. M., 1859, Descriptions of two new species of Carboniferous fossils, brought from Fort Belknap, Texas, by 

Dr. Moore: Acad. Nat. Sci. Philadelphia Proc., v. 11, 

1859, p. 297 [I860].

 1860, in Conrad, T. A., and Gabb, W. M., Illustrations 

of some fossils described in the Proceedings of the 

Academy of Natural Sciences: Acad. Nat. Sci. Philadelphia Proc., v. 12, 1860, p. 55, pi. 1 (plate numbered 7) 

[1861].

Girty, G. H., 1903, The Carboniferous formations and faunas 

of Colorado: U.S. Geol. Survey Prof. Pap^r 16, 546 p., 

10 pis.

 1909, Paleontology of the Manzano grovo of the Rio
PELECYPODA AND ROSTROCONCHIA OF THE AMSDEN FORMATION OF WYOMING E21

Grande valley, New Mexico: U.S. Geol. Survey Bull. 

389, p. 41-136, 12 pis., 9 text figs.

 1911, The fauna of the Moorefield shale of Arkansas: 

U.S. Geol. Survey Bull. 439, 148 p., 15 pis.

 1915a, The fauna of the Batesville sandstone of northern Arkansas: U.S. Geol. Survey Bull. 593, 170 p., 11 pis.

 1915b, Fauna of the Wewoka formation of Oklahoma: 

U.S. Geol. Survey Bull. 544, 353 p., 35 pis.

 1927, The generic characters of Astartella Hall: 

Washington Acad. Sci. Jour., v. 17, no. 16, p. 417-423, 

11 text figs.

Hall, James, 1852, Geology and paleontology, in Stansbury, 

Howard, Exploration and survey of the valley of the 

Great Salt Lake of Utah, including a reconnaissance of 

a new route through the Rocky Mountains (U.S. 32d 

Congress special session, March 1851, Senate Executive 

Document 3) : Philadelphia, p. 401-414, pis. 1-4.

 1858a, Description of new species of fossils from the 

Carboniferous limestones of Indiana and Illinois: Albany Inst. Trans., v. 4, p. 1-36.

 1858b, Lamellibranchiata of the Coal Measures, in 

Hall, James, and Whitney, J. D., Report on the geological survey of the State of Iowa, embracing the results 

of investigations made during portions of the years 

1855, 1856, and 1857, v. 1, pt. 2 Paleontology, p. 715- 

717, pi. 29 [Albany, N.Y.].

 1883, Nat. History New York, Geol. Survey New York, 

Palaeontology, v. 5, pt. 1, Lamellibranchiata Plates and 

Explanations, 20, p., pis. 1-34, 36-41, and 43-80: Albany, 

N.Y. 

-1885, Lamellibranchiata, II, Descriptions and figures

of the Dimyaria of the Upper Helderberg, Hamilton, 

Portage, and Cheniung groups: New York Geol. Survey, 

Palaeontology 5, pt. 1, p. 269-561.

Heath, Harold, 1937, The anatomy of some protobranch 

mollusks: Mus. Royale Histoire Nat. Belgique Mem., 

ser. 2, pt. 10, 26 p., 10 pis.

Herrick, C. L., 1887, A sketch of the geological history of 

Licking County [Ohio] : Denison Univ. Sci. Lab. Bull., 

v. 2, pt. 1, p. 5-70, pis. 1-7; pt. 2, p. 143-148, pi. 14.

Hind, Wheelton, 1899, A monograph of the British Carboniferous Lamellibranchiata, v. 1, pt. 4; Palaeontographical 

Soc. London, p. 277-360, pis. 26-39.

 1900, A monograph of the British Carboniferous 

Lamellibranchiata, v. 1, pt. 5, Palaeontographical Soc. 

London, p. 361-476, pis. 40-54.

Kauffman, E. G., 1969, Form, function, and evolution, in 

Moore, R. C., ed., Treatise on invertebrate paleontology, 

pt. N, Mollusca 6, Bivalvia, v. 1: New York, Geol. Soc. 

America and Kansas Univ. Press, p. N129-N205.

Keyes, C. R., 1891, Fossil faunas in central Iowa: Acad. 

Nat. Sci. Philadelphia Proc. 1891, p. 242-265.

 1894, Paleontology of Missouri, part 2: Missouri Geol.

Survey, v. 5, 266 p., pis. 33-56. 

Koninck, L. G. de, 1841-44, Description des animaux fossiles

qui se trouvent dans le terrain Carbonifere de Belgique,

p. 59-146, pis. 1-5, H: Liege, H. Dessain. 

Lintz, Joseph, Jr., 1958, The fauna of the Ames and Brush

Creek shales of the Conemaugh formation of western

Maryland: Jour. Paleontology, v. 32, no. 1, p. 97-112, pi.

16. 

McChesney, J. H., 1859, Descriptions of new species of fossils

from the Paleozoic rocks of the Western States: Extract from Chicago Acad. Sci., Trans., v. 1, 76p. [I860]. 

[Plates illustrating in part the new species of fossils 

from the Palaeozoic rocks of the Western States and 

two new species noticed March, 1860, pub. 1865, 11 pis.]. 

-1867, Description of fossils from the Paleozoic rocks

of the Western States, with illustrations: Chicago Acad. 

Sci. Trans. 1, p. 1-57, pis. 1-9 [1868].

McCoy, Frederick, 1844, A synopsis of the characters of the 

Carboniferous limestone fossils of Ireland: Dublin Univ. 

Press, 207 p., 29 pis. 

 1851, Descriptions of some new Mountain Limestone

fossils: Annals and Mag. Nat. History, 2d ser, v. 7, p. 

167-175.

Mamet, B. L., 1974, Foraminifera and algae of the Airsden 

Formation (Mississippian and Pennsylvanian) of Wyoming: U. S. Geol. Survey Prof. Paper 848-B. (In press.)

Mark, C. G., 1911, The Mercer limestone and its associated 

rocks in the Newark-Zanesville region: Denison Univ. 

Sci. Lab. Bull. 16, p. 267-308, pis. 8-10, 5 text figs

Meek, F. B., 1864, Remarks on the family Pteriidae (-Aviculidae) with descriptions of some new fossil genera: 

Am. Jour. Sci., ser. 2, v. 37, p. 212-220. 

-1875, A perort on some of the invertebrate fossils of

the Waverly group and Coal Measures of Ohio: Ohio

Geol. Survey Rept. 2, pt. 2 Paleontology, p. 269-347,

pis. 10-20. 

Meek, F. B., and Hayden, F. V., 1865, Palaeontology of the

upper Missouri invertebrates: Smithsonian C ontr.

Knowledge, v. 14, art. 5 (no. 172), 135 p., 5 pis. 

Morgan, G. D., 1924, Geology of the Stonewall quadrangle,

Oklahoma: [Oklahoma] Bur. Geology Bull. 2, 248 p.,

53 pis. 

Morning-star, Helen, 1922, Pottsville fauna of Ohio: Ohio

Geol. Survey Bull. 25, ser. 4, 312 p., 16 pis.

Morse, W. C., 1931, Pennsylvanian invertebrate fauna: Kentucky Geol. Survey, ser. 6, v. 36, p. 293-348, 10 pis., 

2 text figs.

Mudge, M. R., and Yochelson, E. L., 1962, Stratigraphy and 

paleontology of the uppermost Pennsylvanian and lowermost Permian rocks in Kansas: U.S. Geol. Survey Prof. 

Paper 323, 213 ps., 17 pis.

Newell, N. D., 1937, Late Paleozoic pelecypods. Pectinacea: 

Kansas Geol. Survey [Rept.], v. 10, pt. 1, 123 p., 20 

pis. [1938].

 1942, Late Paleozoic pelecypods, Mytilacea: Kansas 

State Geol. Survey [Rept.], v. 10, pt. 2, 115 p., 15 pis.

Newell, N. D., and LaRocque, Aurele, 1969, Family Grammysiidae, in Moore, R. C., ed., Treatise on invertebrate 

paleontology, pt. N, Mollusca 6, Bivalvia, v. 2: New 

York, Geol. Soc. America and Kansas Univ. Press, p. 

N819-N823.

Nicol, David, 1955, Morphology of Astartella, a primitive 

heterodont pelecypod: Jour. Paleontology, v. 29, no. 1, p. 

155-158, 4 text figs.

Plummer, F. B., 1950, The Carboniferous rocks of the Llano 

region of central Texas: Texas Univ. Pub., no. 4329, 

170 p., 22 pis., 4 charts, 14 figs.

Plummer, F. B. and Moore, R. C., 1921, Stratigraphy of the 

Pennsylvanian formations of north-central Texas: Texas 

Univ. Bull., no. 2132, 237 p., 27 pis., 19 text figs.

Pojeta, John, Jr., 1969, Revision of some of Girty's inverte-
E22 THE AMSDEN FORMATION (MISSISSIPPIAN AND PENNSYLVANIAN) OF WYOMING

brate fossils from the Fayetteville Shale (Mississippian) 

of Arkansas and Oklahoma Pelecypoda: U.S. Geol. Survey Prof. Paper 606-C, p. 15-24, pis. 3, 4. 

-1971, Review of Ordovician pelecypods: U.S. Geol.

Survey Prof. Paper 695, 46 p., 20 pis.

Pojeta, John, Jr., Runnegar, Bruce, Morris, N. J., and Newell, N. D., 1972, Rostroconchia a new class of bivalved 

mollusks: Science, v. 177, no. 4045, p. 264-267, 3 text figs.

Price, W. A., 1914, Notes on the paleontology of Preston 

County fossil fauna of the Conemaugh rocks: West 

Virginia Geol. Survey, Preston County, Rept., p. 472- 

553, pis. 42, 43.

 1916, Notes on the paleontology of Raleigh, Wyoming, 

McDowell, and adjacent counties: West Virginia Geol. 

Survey, Raleigh County, Rept., p. G63-734, pis. 30, 31. 

-1921, Notes on the paleontology of Nicholas County 

Invertebrate fossils from the Pottsville series: West Virginia Geol. Survey, Nicholas County, Rept, p. 751-788, 

2 pis., 1 text fig.

Puri, H. S., 1969, Family Nuculanidae, in Moore, R. C., ed., 

Treatise on invertebrate paleontology, pt. N, Mollusca 6, 

Bivalvia, V. 1: New York Geol. Soc. America and Kansas 

Univ. Press, p. N235-N241.

Raymond, P. E., 1910, A preliminary list of the fauna of the 

Allegheny and Conemaugh series in western Pennsylvania: Carnegie Mus. Annals, v. 7, no. 1, p. 144-158, 

pis. 24-28.

 19.11, A preliminary list of the fauna of the Allegheny 

and Conemaugh series in western Pennsylvania: Pennsylvania Topog. Geol. Survey Comm. Rept. 1908-10, p. 

81-98, pis. 3-6.

Sando, W. J., Gordon, Mackenzie, Jr., and Dutro, J. T., Jr., 

1974, Stratigraphy and geologic history of the Amsden 

Formation (Mississippian and Pennsylvania!!) of Wyoming: U.S. Geol. Survey Prof. Paper 848-A. (In press.)

Shaw, A. B., 1955, The Amsden formation in southwestern 

and south-central Wyoming in Wyoming Geol. Assoc.

Guidebook 10th Ann. Field Conf. 1955: p. 60-63, 1 correlation chart.

Shimer, H. W., and Shrock, R. R., 1944, Inder fossils of 

North America; New York, John Wiley and Sons, 837 p.

Stanley, S. M., 1968, Post-Paleozoic adaptive radiation of 

infaunal bivalve molluscs a consequence of mantle fusion and siphon formation: Jour. Paleontology, v. 42, no. 

1, p. 214-229, 13 figs.

 1970, Relation of shell form to life habits of the Bivalvia (Mollusca) : Geol. Soc. America Mem. 125, 296 p., 

40 pis. 

-1972, Functional morphology and evolution of byssally

attached bivalve mollusks: Jour. Paleontology, v. 46, no. 

2, p. 165-212, 34 figs.

Verneuil, P. E. P. de, and Murchison, R. I., 1844, Note sur 

les equivalents du systeme permien en Europe, suivie 

d'un coup d'oeil general sur 1'ensemble de ses fossiles, 

et d'un tableau des especes: Soc. Geol. France Bull., 2d 

ser., v. 1, p. 505.

Weller, Stuart, 1916, Description of a Ste. Genevieve limestone fauna from Monroe County, Illinois: Chicago 

Univ. Walker Mus. Contr., v. 1, no. 10, p. 243-264, pis. 

15-19.

Wilson, R. B., 1959, Wilkingia gen. nov. to replace Allorisma 

for a genus of upper Paleozoic lamellibranchs: Palaeontology, v. 1, pt. 4, p. 401-404, pi. 71.

Winchell, Alexander, 1865, Descriptions of new species of 

fossils, from the Marshall group, and its supposed 

equivalent in other States * * *: Acad. Nat. Sci. Philadelphia Proc. 1865, p. 109-133.

Worthen, A. H., 1890, Description of fossil invertebrates: 

Illinois Geol. Survey, v. 8, p. 69-154, pis. 10-28.

Worthen, A. H., 1884, Descriptions of two new species of 

Crustacea, fifty-one species of Mollusca, and three species of crinoids, from the Carboniferous formations of 

Illinois and adjacent states: Illinois State Mus. Nat. 

History, Bull. 2, 27 p.
INDEX

[Italic page numbers indicate both major references and descriptions]

Page

abruptus, Schizodus depressus -------- E15

affinis, Schizodus ___ . ---- 5, 7, 15; pi. 3

Allorisma subcuneatum . -____-_ ._--_ 19

terminate ...........- ----------- 2,19,20

terminalis .... - ----------- _-_ 19

alpina, Dolabra . - - - ----------- 16

Schizodus ......................... 16

alpinus, Schizodus ..........- 5,7, 16; pi. 3

Ambonychiacea 11

amsdenensis, PaleoneUo .... ......... 1, 9

Paleyoldia ........... 1, 5, 7, 8, 9, 10; pi. 1

Anomalodesmata --- __________ 2, 18

Anthracospirifer iveller-shawi Zone _-_ 4 

Antiquatonia blackwelderi Zone ___. 4, 7 

Astartella ........------.............. 3,18

concentrica .............-. 5, 7, 8, 18; pi. 4

sp __________------__ 5, 6, 18; pi. 4

Astartidae 3,18 

aviculatum, Entolium ................. 13

Aviculopecten ................. 3,6,13,14,16

gravidus .......... ....... 5, 8, 13; pi. 3

sp. A ._--.- . 5, U;pl. 3

sp. B _____________ 5, 7, 14; pis. 2, 3

sp ___-__ . --- 5, 7, Ik, pi. 3

Aviculopectinidae --- 3,13

Aviculopectininae 13

Aviculopinna ............-------------- 3,12

peracuta .......................... 12

sp __________________ 5, 7, 12; pi. 2

Bighorn Mountains _-_ .__________ 13,18

Bloyd Shale ______________________ 9

Brentwood Limestone Member _____ 9

Caney Shale of Oklahoma ... 12 

Caneyella ........................... 3,12,17

percostata ........................ 12

sp ... . _ 5, 7, 12; pi. 2 

Caninia Zone _---__--__________ 4, B, IB

Carditacea __________-_.-___-_________ 16

Carlinia amsdenia.no,

Subzone --._ 4, 7, 11, 12, 13, 15, 19 

Composite poposiensis Subzone __._... 4 

Composition of the fauna __._______ 2

concentrica, Astartella ....._ 5, 7, 8, 18; pi. 4

Edmondia ......._____________ 18

Nuculites .................._____ 18

Conocardiidae -__.__ ._____ 20

Conocardium _______.____________ 20

orientate .......................... 2, 8

sp 5, 20; pi. 4 

Covey Cutoff section --____--_.__ 5

Crassatellacea _.__-___..____.__ 17 

Crassatellidae ...______________ 3,17 

Cypricardella ..................... 3, 8, 17, 18

oblonga ........................_._ 17

sp ___ 1, 5, 7, 17, 18; pi. 4

Page

Darwin Peak section--- ____- E6

Darwin Sandstone Member -- 4

depressus, Schizodus __--_ 2, 5, 7, 15, 16; pi. 3

abruptus, Schizodus ______-__- ___ 15

Diaphragmus nivosus - __-_ ________ 6

Dolabra alpina ....-------- ____.--_____ 16

E

Edmondia ......................... 2,3,8,18

concentrica ...--,-.......-........ 18

nebrascensis ...... 18

sp ______________ 5, 7, 8, iS;pl. 4 

Edmondiacea _________________________ 18

Edmondiidae --_----__-_----_ -- 3, 18

Entoliidae _____________ - 3,13

Entolium ___._--____-.-__ ___-_ 2

aviculatum _______________________ 13

Faunal diversity

Geographic and stratigraphic occurrence

of the pelecypods __ k 

Grammysiidae -____ __ -__ 3, 19 

gravidus, Aviculopecten ........ 5, 8, 13; pi. 3

H

Hale Formation of Arkansas . _ 16 

Heath Formation _______--_-- 17

Heath Shale of Montana _.__ ______ 6

Heteroconchia ______________ 2, 15 

Hoback Canyon _--_-.-----_-__ _._ 5, 7

Horseshoe Shale Member ___.________ 4,5,6

inflata, Phestia ...._______________ 9

Isofilibranchia ______________ 2,11

Isofilibranchian _.._______ 3, 5, 7, 11; pi. 2

Leptodesma ................._________ 3, 12

sp _ _____ 5, 7, 12; pi. 2

Lingula .............................. 7, 12

M

Mesolobus Zone ____________ 4 

Microdon __________________________ 8

oblongus .........----.-.......... 1,8,17

Mississippian fauna -_____________ 5

Mississippi-Pennsylvanian boundary__ 3 

Moffat Trail Limestone Member ____ 4, 5, 6

Moffat, Trail section 

Mollusca ----

moorei, Posidonia ....-.. _--- ______

morroivensis, Schizodus ....--...- 

Myalina ......--------- -- -- 3

sancti-ludovici ........-..- ------

(Myalina) ......------- ---------

sp _ _ - B,8.«

Myalinidae _-- -- --- 

Myophoriidae ___-___--___ - -- 

N

nebrascensis, Edmondia ..........--...

NeokoninckophyUum hamatUis

Zone -- 4,8,11, 

nivosus, Diaphragmus _-- --- 

Nucula sp. C ------ -----_____

sp _ _____-_____------_-_-___----_

Nuculacea .-___- _-- 

Nuculanacea ---- ----------

Nuculanidae ___ _____

Nuculidae --- ___ --- -- 

Nuculites concentrica ......... - - 

Nuculoida _-_- --- -- 

Nuculopsis ............-------------- 3

sp. A ______----- 1,2,5,7,5,9

sp. B -_ 5,7,9

Page

E5

8

18

16

,5,11

1,11

11

;pl. 2 

3, 11 

3,15

18

13, 15

6

3, 8

18

8

8,18

pi. 1

oblonga, Cypricardella -............... 17

oblongus, Microdon .................. 1,8,17

orientale, Conocardium .............. 2, 8

Otter Shale 17

Palaeotaxodonta 2, 8 

PaleoneUo amsdenensis ................ 1, 9

Paleyoldia ...-....................... 3,9,10

amsdenensis ......... 1, 5, 7, 8, 9, 10; pi. 1

sp _________________ 5, 7, 10; pi. 1 

Parallelodontidae __ __ 3 

Pectinacea __- __ - 13

Pelecypoda -_ -- .-_--_-.. 5, 8 

Pennsylvanian fauna ----- . ----- 7

peracuta, Aviculopinna ... __ _____ 12

percostata, Caneyella - - _._-_______ 12

Permophoridae ------ . __ _____ 3,16

Permophorus ______ .-_-_____- 2,3,16,17

sp. A ___________ 3, 5, 7, 8, 16; pi. 3 

Pernopecten ............ _--_-_-.-_ 2,3,13

sp ____--._________.. 5, 8, IS; pi. 2 

Phestia .............................. 3,9,10

inflata ..................... ..... 9

sp --. _-_ 5, 7, 9; pi. 1

Pholadomyacea _------___-------_ 19

Pholadomyidae _--________.__-_-__ 3, 19

Pholadomyoida ---------_-..-__..___ 18

Pinnacea __-_____________ 12

Pinnidae _____________-_.____ 3, 12

Pleurophorus ........__.____________ 2,17

sp ________________________ 16,17

E23
E24 INDEX

Page

Posidonia __-__ E3, 12 

moorei _________ ._ -________ 18

wapanuckensis _____________________ 12

sp _________________ 5, 1, 12; vl. 2 

Posidoniidae 3, 12

Promytttus ... ......... ...... - 11

Pseudomonotidae _______--___________ 3, 13

Pseudomonotis ...................... 3, 13, 14

sp __________________ 5, 8, 13; pi. 2 

Pteriacea -__-_______ _.___ 12

Pterineidae ___________-._____ 3,12 

Pterioida ____________________ 11

Pteriomorpha ________ _______ 2

Ptefriomorphia _-___-__-__________ 11

R

Ranchester Limestone Member _ 4, 7 

Rawlins hills ________________ 11, 15 

Relation to Mississippian-Pennsylvanian

Boundary _.________. 3

Rostroconchians ______ __ __ 2,5,3,20

sancti-ludovici, Myalina __._.-. -- 1,11

Page

Sanguinolites .......... .... -.._ E3, 19

sp _______________ 2, 5, 7, 19; pi. 4

Schizodus .......................... 3 ,15, 16

affinis .-.-..------__ ---- 5, 7, 15; pi. 3

alpina -------------------- ------ 16

alpinus .................... 5, 7, 16; pi. 3

depressus ............. 2, 5, 7, 15, 16; pi. 3

abruptus ...................... 15

morrowensis .. ---------- ------ 16

sp. A ______-_ _____ 6, 7, ifi;pl. 8

sp. B --___---- --_--.- 5, 8, 16; pi. 3

sp _________-__ -__ __ 2,15 

Sedgwickia ------ 3, 19

sp - _._________-___ 5, 8, i9;pl. 4 

Septimyalina .....................___ 3, 11

sp. A __-_____________ 5,7, 11; pi. 2

sp _________ ____ 1,5, 7, 11; pi. 2

Sphenotus ............................ 3,19

sp _____.___________ 5, 7, 19; pi. 4 

Ste. Genevieve Limestone --._-__.-_ 15 

Stratigraphic considerations .__ ----- 4

Streblochrondriinae ---_ -__-___ 13 

Streblopteria ....................... 3, 12,13

sp ._________________ 5, 1,13; pi. 2

subcuneatum. Allorisma ............... 19

Page

terminate, Allorisma .............. E2,19, 20

terminalis, Allorisma .................. 19

Wilkingia .......__ 2, 3 5, 7, 8, 19; pi. 4

Trigoniacea ____ _________ _.___-_--_ 15

Trigonioida -_-_---.--_----- __._ 15

Veneroida 16

W

wapanuckensis, Posidonia ............. 12

Washakie Range __-____._____ 12

Wilkingia ... ________________ 3,19,20

terminalis ________ 2, 3 5, 7, 8, 19; pi. 4

sp __________________ 5, 7, 20; pi. 4

Yoldia 10

U.S. GOVERNMENT PRINTING OFFICE: 19VB -5S5 474/93
PLATES 1-4

Contact photographs of the plates in this report are available, at cost, from U.S. 

Geological Survey Library, Federal Center, Denver, Colorado 80225.
PLATE 1

FIGURES 1-5. Nuculopsis sp. A (p. E8).

1,2. Left valve showing adductor muscle scars and dorsal view 

showing pedal muscle scars and trace of the taxodont dentition 

(X 3). UM 6630, collection 36d.

3-5. Right valve, dorsal view, and left valve showing adductor 

muscle scars, pedal muscle scars, and filling of resilifer (X 2). 

UM 2657, collection 36c. 

6-9. Nuculopsis sp. B (p. E9). 

Collection 50.

6. Right valve (X 2). USNM 174018.

7. Left valve (X 2). USNM 174019.

8. 9. Right valve showing anterior adductor muscle scar and dorsal view showing trace of taxodont dentition (X 3). USNM 

174020. 

10,11. Phestia sp. (p. E9).

10. Rubber cast of right valve mold showing ornament and shape 

of rostrum (X 4). USNM 174022, collection 50.

11. Right valve (X 2). USNM 174023, collection 50. 

12,13. Paleyoldia sp. (p. E10).

12. Left valve (X 1). USNM 174024, collection 50.

13. Right valve (X 2). USNM 174025, collection 53. 

14-31. Paleyoldia amsdencnsis (Branson and Greger) (p. E9).

14-16. Dorsal (anterior end up) (X 4), left valve, (X 2), and

right valve (X 2), views of lectotype. UM 2665, collection 36b. 

17-19. Left valve, dorsal (anterior end down), and right valve

views (X 2), of paralectotype. UM 2665, collection 36b. 

20. Left valve (X 3). UM 6639, collection 36d. 

21,22. Dorsal (anterior end up) (X 10), and right valve (X 5),

views. UM 6639, collection 36d. 

23,24. Left valve (X 3), and dorsal (anterior end Tip) (X 6),

views, showing some muscle scars and trace of the taxodont dentition. UM 6639, collection 36d.

25,26. Dorsal (anterior end up) (X 7), and left valve (X 9), 

views, showing trace of taxodont dentition, pallial line, pallial

sinus, and most other muscle scars. UM 6639, collection 36d. 

27,28. Dorsal (anterior end down) (X 3), and left valve (X 6),

views. UM 6639, collection 36d. 

29. Left valve (X 3). UM 6639, collection 36d. 

30,31. Right valve (X 5), and dorsal (anterior end down) (X 6),

views showing muscle scars. UM 6639, collection 36d.
GEOLOGICAL SURVEY PROFESSIONAL PAPER 848-E PLATE 1

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PALAEOTAXODONTA
PLATE 2

FIGURES 1,2. Isofilibranchian? gen. and sp. indet. (p. Ell).

1. Left valve (X 2), UW A1275, collection 31.

2. Right valve (X 2), UW A201, collection 28.

3. Posidonia sp. indet. (p. E12).

Left valve (X 4). USNM 174032, collection 46.

4. Caneyella sp. (p. E12).

Right valve (X 1). USNM 174029, collection 46.

5. Se-ptimyalinat sp. indet. (p. Ell).

Left valve (X 1). USNM 174028, collection 131. 

6,7. Myalina (Myalina) sp. (p. Ell). 

Collection 3 (X 1).

6. Rigth valve. USNM 174026.

7. Left valve. USNM 174027. 

8-15. Septimyalina sp. A (p. Ell).

8,9. Left valve and dorsal views (X 3). UM 6638, collection 36d. 

10, 11. Anterior and right valve views (X 2). UM 6638, collection

36d. 

12-15. Right valve, dorsal, left valve, and anterior views (X 2).

UM 2658, collection 36c. 

16-18. Aviculopecten sp. B (p. E14). 

Collection 50 (X 3). 

16. Left valve. USNM 174039.

17,18. Anterior view of rubber cast showing dorsal margin shelf 

extending from beak to commissure, and oblique lateral view also 

showing shelf. USNM 174040. 

19. Leptodesma sp. (p. E12).

Left valve (X 4). USNM 174030, collection 50. 

20-22. Avicuiopinna sp. (p. E12).

Dorsal (X 1), left valve (X 2), and dorsal (X 2) views. USNM 

174033, collection 67.

23. Pernopecten sp. indet. (p. E13).

Left valve (X 2). USNM 174034, collection 52.

24. Streblopteria sp. indet. (p. E13).

Left valve (X 2). USNM 174036, collection 46.

25. Pseudomonotis sp. (p. E13).

Left valve (X 1). USNM 174035, collection 52.
GEOLOGICAL SURVEY PROFESSIONAL PAPER 848-E PLATE

22

23 24 25 

ISOFILIBRANCHIA? AND PTERIOMORPHA
PLATE 3

FIGURE 1. Aviculopecten sp. A (p. E14).

Two left valves (X 3). USNM 174037A, B, collection 118. 

2. Aviculopecten sp. B (p. E14).

Left valve (X 3). USNM 174038, collection 50. 

3,4. Aviculopecten spp. indet. (p. E14).

Enlargement showing ornament (X 2) and entire valve (X 1).

USNM 174045, collection 53. 

5-7. Aviculopecten gravidus n. sp. (p. E13). 

Collection 3 (X 1).

5. Holotype showing shape and ornament of left valve. USNM 

174041.

6. Paratype showing shape of right valve. USNM 174042.

7. Paratype showing left valve. USNM 174043. 

8, 9. Schizodus sp. A (p. E16) .

Right valve and dorsal (anterior end down) views (X 2). UM

6637, collection 36a. 

10-13. Schizodus cf. S. depressus Worthen (p. E15).

10,11. Dorsal (anterior end down) and right valve views (X 3). 

UM 6630, collection 36d.

12. Right valve (X 3). USNM 174048, collection 20.

13. Left valve (X 2). UW A11121, collection 28. 

14. Schizodus sp. B (p. E16).

Right valve (X 1). USNM 174052, collection 3. 

15,16. Schizodus aff. S. affinis Herrick (p. E15).

Two right valves (X 2). USNM 174049, 174050, collection 50. 

17. Schizodus alpinus (Hall)? (p. E16).

Right valve (X 1). USNM 174051, collection 53. 

18-23. Permophorus sp. A (p. E16). 

(X 2).

18. Left valve. USNM 174053, collection 53.

19. Right valve. USNM 174054, collection 52.

20. Right valve. USNM 174059, collection 159.

21. Right valve. USNM 174056, collection 50.

22. Left valve. USNM 174057, collection 50.

23. Left valve. USNM 174055, collection 52.
GEOLOGICAL SURVEY PROFESSIONAL PAPER 848-E PLATE 3

20 21 22 

PTERIOMORPHA AND HETEROCONCHIA
PLATE 4

FIGURES 1-3. Astartella sp. (p. E18).

Dorsal, anterior, and left valve views (X2). USNM 174063, collection 41.

4-7. Astartella concentrica (Conrad) (p. E18). 

Collection 50 (X 2).

4, 5. Right valve and dorsal views. USNM 174061. 

6, 7. External mold right valve and rubber cast of mold showing

ornament. USNM 174062. 

8-10. Cypricardellal sp. indet. (p. E18).

Right valve, anterior, and left valve views (X 3). USNM 174060,

collection 20. 

11. Cypricardella sp. (p. E17).

Left valve (X 2). UM 2657, collection 36c. 

12,13. Edmondia sp. (p. E18).

Left valve and dorsal views showing adductor muscle scars (X 2).

USNM 174066, collection 52. 

14,15. Edmondia sp. (p. E18).

14. Right valve (X 2). USNM 174065, collection 50.

15. Right valve (X 2). USNM 174064, collection 52. 

16. Edmondia sp. (p. E18).

Right valve (X 1). USNM 174067, collection 52. 

17,18. Sphenotus sp. (p. E19).

Left valve and dorsal views (X 2). USNM 174068, collection 137. 

19-21. Sanguinolites sp. (p. E19).

Left valve, dorsal, and right valve views (X 2). UW IT-237, collection 22. 

22. "Conocardium" sp. indet. (p. E20).

Fragment of left valve (X 3). USNM 182074, collection 139. 

23,24. Sedgwickial sp. indet. (p. E19).

Right valve and dorsal views (X 1). USNM 174069, collection 5. 

25. Wilkingia sp. (p. E20).

Left valve (X 2). UW IT-240, collection 22. 

26-30. Wilkingia terminal (Hall) (p. E19).

26. Left valve (X 1). USNM 174071, collection 50. 

27-30. Anterior, right valve, dorsal, and left valve views (X 1). 

USNM 174070, collection 5.
PROFESSIONAL PAPER 848-E PLATE 4

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HETEROCONCHIA, ANOMALODESMATA, AND ROSTROCONCHIA