Gastropoda, Cephalopoda, and Trilobita 

of the Amsden Formation (Mississippian 

and Pennsylvanian) of Wyoming 

GEOLOGICAL SURVEY PROFESSIONAL PAPER 848-F 

Gastropoda, Cephalopoda, and Trilobita 

of the Amsden Formation (Mississippian 

and Pennsylvanian) of Wyoming 

By MACKENZIE GORDON, JR., and ELLIS L. YOCHELSON 

THE AMSDEN FORMATION (MISSISSIPPIAN AND PENNSYLVANIAN) 

OF WYOMING 

GEOLOGICAL s·uRVEY PROFESSIONAL PAPER 848-F 

Descriptions and illustrations of 44 taxa 

of gastropods) 4 of cephalopods) and 2 of 

trilobites) 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-

Gastropoda, Cephalopoda, and Trilobita of the Amsden Formation (Mississippian and Pennsylvanian) of Wyoming. 

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

Includes bibliographical references and index. 

Supt. of Docs. no.: I 19.16:848-F 

1. Gasteropoda, Fossil. 2. Cephalopoda, Fossil. 3. Trilobites. 4. Paleontology-Carboniferous. 5. PaleontologyWyoming. I. Yochelson, Ellis Leon, 1928- joint author. II. Title. III. Series: The Amsden Formation (Mississippian and Pennsylvanian) of Wyoming. IV. Series: United States. Geological Survey. Professional 

paper ; 848-F. 

QE808.G67 564'.3'09787 74-32014 

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

Washington, D.C. 20402 

Stock Number 024-001-02632-5 
Abstract _______________________________________ _ 

Introduction ------------------------------------

Acknowledgments ----------------------------· 

Previous work -----------------------------------

Present investigation -----------------------------

Fossil localities ----------------------------------

Composition and distribution of gastropod fauna ___ _ 

Stratigraphic considerations ----------------------

CONTENTS 

Page 

Fl 

1 

1 

1 

2 

2 

2 

4 

Stratigraphic and geographic occurrence of the 

gastropods --------------------------------

Mississippian fauna --------------------------

Pennsylvanian fauna -------------------------

Cephalopods -------------------------------------

Trilobites ---------------------------------------

Systematic paleontology --------------------------

References cited ---------------------------------

Index -------------------------------------------

ILLUSTRATIONS 

[Plates follow index] 

PLATE 1. Gastropods and trilobites. 

2. Gastropods and cephalopods. 

Page 

FIGURE 1. Cross section of Bellerophon? sp. indet ------------------------- FlO 

2. External suture of Cravenoc.eratoides sp. indet ----------------- 23 

TABLES 

Page 

TABLE 1. Taxonomic relationships and relative abundance of gastropods in 

the Amsden Formation of Wyoming ------------------------- F3 

2. Gastropods, cephalopods, and trilobites of the Amsden Formation 

of Wyoming --------------------------------------------- 5 

3. Checklist of gastropod, cephalopod, and trilobite collections ------ 6 

III 

Page 

F5 

6 

7 

8 

8 

9 

27 

2-9 

THE AMSDEN FORMATION (MISSISSIPPIAN AND PENNSYLVANIAN) OF WYOMING 

GASTROPODA, CEPHALOPODA, AND TRILOBITA 

OF THE AMSDEN FORMATION 

(MISSISSIPPIAN AND PENNSYLVANIAN) OF WYOMING 

By MACKENZIE GoRDoN, JR., and ELLIS L. YocHELSON 

ABSTRACT 

The study of the gastropod fauna of the Amsden Formation is based upon 288 specimens, of which 233 are idenrbifiable and assigned to 27 genera and 38 species or species 

groups, probably totaling 44 taxa. Although most of this material is poorly preserved, this relatively large fauna from 

beds of latest Mississippian and Early Pennsylvanian age 

fills a gap in the existent literature. The gastropods have 

not been used, however, to differentiate Mississippian and 

Pennsylvanian beds in the Amsden. 

Bellerophontaceans account for nearly half the number of 

individuals. Euomphalaceans constitute the second most abundant group, accounting for slightly more than one-sixth of 

the generically identifiable specimens. The remaining onethird of the fauna is distributed among nine superfamilies. 

Because of the poor quality of the material, an extremely 

open nomenclature is necessitated. Only two species are compared with previously known forms, and two others, Straparollus (Euomphalus) calix and Dictyotomaria carlbransoni, are described as new. Euphemites sacajawensis C. 

Branson is redescribed and reillustrated, and a new genus, 

possibly allied to Colpites, is described but not named. 

One additional specimen is added to the four sp·ecimens of 

ce.phaJ.opods previously reported from the Amsden. A previously mentioned specimen is described and illustrated as 

Cravenoceratoides sp. indet., a genus restricted to the upp·er 

part of the Eumorphoceras bisulcatum (E2) Zone of early 

Namurian Age. 

Two species of trilobites are also included here because the 

material is too sparse to warrant a separate chapter. Paladin 

moorei (C. Branson) is redescribed and reillustrated. It is 

limited to the Mississippian part of the Amsden. Another 

species of Paladin occurs in the Pennsylvanian part. 

INTRODUCTION 

This report is concerned principally with the mollusks of the Amsden Formation of Wyoming other 

than pelecypods. Among the material under study 

are about 44 gastropods and 4 cephalopods. Like 

the pelecypods, the gastropods are rather few in 

number but rich in variety. With the exception of 

the bellerophonta~ceans and the euomphalaceans, 

Amsden gastropod species are rarely represented in 

our collections by as many as five specimens. Most of 

the gastropods occur together with pelecypods at the 

few mollusk-rich localities in the formation. 

Two species of trilobites occur in the Amsden 

and are included here because the relative sparseness of the material does not warrant treatment in 

a separate chapter. 

ACKNOWLEDGMENTS 

We are indebted to workers at other institutions 

who kindly have lent us material for study. We 

thank A. G. Unklesbay, J. A. Wolleben, R. L. Ethington, R. E. Peck, and J. H. Stitt of the University of 

Missouri, D. W. Boyd of the University of Wyoming, 

and Copeland MacClintock of Yale University. We 

are also indebted to Roger Batten of the American 

Museum of Natural History for helpful comments 

and review of the gastropod part of this report and 

to our colleague Michael E. Taylor for his review of 

the trilobite part. 

Photographs were prepared by Robert McKinney 

and Haruo Mochizuki. 

PREVIOUS WORK 

The record of Amsden gastropods is exceedingly 

sketchy. Only three authors have previously dealt 

with this part of the fauna. The earliest paper on 

Amsden fossils, that of Branson and Greger (1918, 

p. 322-324), mentioned and figured three gastropods 

from the Mississippian part of the formation. C. C. 

Fl 
F2 THE AMSDEN FORMATION (MISSISSIPPIAN AND PENNSYLVANIAN) OF WYOMING 

Branson (1937, p. 658, 659) mentioned six species 

and listed a seventh; these included those previously 

recorded by Branson and Greger. He figured two 

species: one was Euphemites sacajawensis C. Branson, a new species, and the other a shell that he 

identified as Ptychomphalus wortheni Weller, but 

which is here described as Dictyotomaria carlbransoni n. sp. 

The only Pennsylvanian gastropods recorded from 

the Amsden Formation are in faunal lists. The most 

noteworthy of these lists six forms identified by 

Girty; it was published by Darton (1906, p. 34) in 

his original description of the Amsden Formation. 

These gastropods are included in the present study. 

Cephalopods have received only passing mention 

by previous authors. Two orthoconic nautiloids were . 

cited by Branson and Greger (1918, p. 324), and a 

goniatite was mentioned by Burk ( 1954, p. 15) and 

identified by Sadlick (1960, p. 1211) as a Cravenoceras. A trilobite was mentioned as Phillipsia sp.? 

by Branson and Greger (1918, p. 324), and a new 

species was described as Grifjithides moorei C. 

Branson (1937, p. 659). 

PRESENT INVESTIGATION 

No monographic treatment exists of Mississippian (Chesterian) gastropods or of Early and Middle Pennsylvanian (Morrowan and Atokan) species. 

The Amsden gastropods documented on these pages, 

therefore, fill a gap in the existing literature. For 

this reason, the writers have attempted to describe 

them in as much detail as possible. 

The poor preservation of the gastropod material 

cannot be overemphasized. Were it not for the fact 

that this is part of a comprehensive treatment of 

the principal components of the Amsden fauna, the 

gastropods would hardly warrant systematic description. Nevertheless, the painstaking examination of each specimen and fragment required by the 

unsatisfactory preservation has in part been responsible for our recognition of the diversity of the 

fauna. 

Cephalopoda are exceedingly rare in the Amsden 

Formation, and for this reason have not been assigned a special chapter in this report. No representatives of three other molluscan classes, Hyolitha, 

Monoplacophora, or Polyplacophora have been found 

in the Amsden. 

The one remaining class to consider is Scaphopoda. Although C. C. Branson (1937, p. 659) noted 

the presence of abundant internal molds referred 

by him to Plagioglypta? sp., we are unable to confirm this identification. Several short segments of 

tapering smooth steinkerns or internal molds have 

been seen, but they are nondescript in character and 

might belong to any of several nonmolluscan phyla. 

Accordingly, we prefer not to perpetuate the record 

of the occurrence of scaphopods in the Amsden 

Formation, though this is largely a matter of subjective opinion. 

FOSSIL LOCALITIES 

For the purpose of simplification, the collections 

studied during our investigations of the Amsden 

Formation and its faunas have been given numbers 

from 1 to 160. Material is included from U.S. Geological Survey (USGS) and U.S. National Museum 

(USNM) collections and collections in the University of Wyoming (UW), University of Missouri 

(UM), and Yale University's Peabody Museum 

(YPM). The permanent numbers of these collections, locality descriptions, and complete lists of 

identified fossils are given in the first report in this 

series on the Amsden Formation (Sando and others, 

in press) . A ,checklist of the g1ast.ropod, cephalopod, 

and trilobite collections is given in table 3. 

COMPOSITION AND DISTRIBUTION OF 

GASTROPOD FAUNA 

In spite of a relatively limited number of individuals as compared with the brachiopods, the gastropod fauna of the Amsden Formation is remarkably diverse. Twenty-seven genera representing at 

least 20 families are included under Systematic 

paleontology. A minimum of 38 species has been 

recorded. When one takes into account poorly preserved material in which more than one species of a 

given genus has been recognized but not differentiated and several specimens too poor to include in the 

systematic discussion, 44 Amsden gastropod species 

are probably represented in our collections. 

In table 1, the families and genera of gastropods 

recorded in the Amsden Formation are listed in the 

first two columns. In the third column, the number 

of specimens of Mississippian age for each genus is 

recorded and in the fourth, the percentage that this 

represents of the identifiable gastropods. In the fifth 

and sixth columns, the same data are recorded for 

the Pennsylvanian specimens. Totals for the specimens of both systems are shown in the seventh and 

eighth columns. In addition to the shells listed in 

table 1, we have examined and found unidentifiable 

another 55 specimens, 44 from the Mississippian 

part of the formation and 11 from the Pennsylvanian 

part. 
GASTROPODA, CEPHALOPODA, AND TRILOBITA OF THE AMSDEN FORMATION F3 

TABLE 1.-Taxonomic relationships and relative abundance af gastropods in the Amsden Formation of Wyo1ning 

Mississippian specimens Pennsylvanian specimens Totals 

Family Genus Number 

Bellerophontidae ----- Belle'rophon -------------- 10 

Euphemites -------------- 8 

Knightites (Retispira) 11 

Euomphalidae -------- Straparollus (Euomphalus) 15 

Sinuopeidae ---------- Colpites ----------------- ? ----------- New genus aff. Colpites --- 2 

Lophospiridae ------- Worthenia? -------------- 1 

Phymatopleuridae ---- Borestus ----------------- Dictyotomaria ------------ 4 

Raphistomatidae ----- Bc~ylea? ------------------ Eotomariidae -------- Mourlonia --------------- Gosseletinidae ------- Goosseletina -------------- 2 

Portlockiellidae Shansiella --------------- Holopeidae ---------- Yunnania? -------------- Platyceratidae ------- Strophostylus ------------ 2 

Microdomatidae ------ Microdoma? ------------- Elasmonematidae ---- Anematina -------------- Neritopsidae -------- Naticopsis --------------- 5 

M urchisoniidae ------ Goniasma? ---------------- Murchisonia? ------------ Pseudozygopleuridae _ Palaeost1Jlus (Pseudozygopleura ------------- 4 

Turritellidae --------- Orthonema --------------- Subulitidae ---------- Ianthinopsis ------------- 5 

Soleniscus? -------------- Meekospiridae ------- M eekospira? ------------- Girtyspi1·a --------------- 5 

Streptacidae --------- Donald ina --------------- 15 

Total ----------------------------------- 89 

Considering the number of individuals at the 

superfamily level, the Bellerophontacea make up 

nearly half the gastropod fauna. The Euomphalacea 

account for slightly more than one-sixth. The remaining one-third of the fauna, in decreasing order 

of abundance, is distributed among the Pleurotomariacea (9 percent), Subulitacea (7 percent), Pyramidellacea (7 percent), Neritacea (31;2 percent), 

Loxonematacea (21f2 percent), Murchisoniacea (2 

percent), Platyceratacea (1%t percent), Microdomatacea (11,4 percent), and Cerithiacea (0.9 percent). In more general terms, essentially five-sixths 

of the individual specimens are referrable to the 

Archaeogastropoda. 

Gastropods occur in 25 of the collections from the 

Amsden Formation, but this figure is misleading because many of these records are based upon sporadic 

occurrences of one or two specimens. Only three 

collections can be said to be predominantly molluscan, all of them from the Pennsylvanian part of the 

formation. In these, gastropods are as common as 

or slightly more numerous than pelecypods. The 

fossils in these beds occur either as molds in fine 

granular chert or recrystallized in tan porous limestone. One chert faunule (colln. 52) consists mainly 

of Bellerophon and St'raparollu.~ (Euomphalus) toPercentage of total Number Percentage of total Number Percentage of total 

identifiable identifiable identifiable 

gastropods gastropods gastropods 

4.29 61 26.17 71 30.46 

3.43 8 3.43 

4.72 22 9.44 33 14.16 

6.44 25 10.73 40 17.17 

6 2.58 6 2.58 

.86 2 .86 

.43 1 .43 

2 .86 2 .86 

1.72 4 1.72 

2 .86 2 .86 

1 .43 1 .43 

.86 2 .86 

1 .43 1 .43 

2 .86 2 .86 

.86 2 .86 

1 .43 1 .43 

2 .86 2 .86 

2.15 3 1.29 8 3.44 

3 1.29 3 1.29 

2 .86 2 .86 

1.72 2 .86 6 2.58 

2 .86 2 .86 

2.15 5 2.15 

1 .43 1 .43 

2 .86 2 .86 

2.15 3 1.29 8 3.44 

6.44 1 .43 16 6.87 

38.22 144 61.82 233 100.04 

gether with some murchisoniids and rare pleurotomariaceans. The other chert collection ( colln. 40) 

and the one from the impure limestone (colin. 50) 

have a more varied fauna, Knightites (Retispira) 

replacing Bellerophon as the most common form. 

Pleurotomariaceans are even rarer than in collection 52. 

Four more collections, three of which are Pennsylvanian in age, can be regarded as brachiopodmollusk assemblages, the pelecypods being by far 

the most common of the mollusks. In contrast to the 

predominantly gastropod collections, these brachiopod-pelecypod assemblages occur in gray fine- to 

medium-grained limestone. Gastropods are so scarce 

that comparisons are not warranted. 

The Mississippian part of the formation has 

yielded almost as many specimens ( 46 percent of 

the total gastropod collection) as the Pennsylvanian part, but a larger proportion of them are indeterminate as to genus. Most of the Mississippian gastropods are from the Little Popo Agie River drainage, including Cherry Creek. Here the mollusks occur in limonite probably derived from replacement 

of limestone layers in shale. Limonitic coating of 

many gastropods renders them unidentifiable. In 

this area, high-spired gastropods predominate, 
F4 THE AMSDEN FORMATION (MISSISSIPPIAN AND PENNSYLVANIAN) OF WYOMING 

pleurotomariaceans are rare, and bellerophontaceans are uncommon. 

At the only other place where a significant 

Mississippian gastropod faunule occurs (colin. 137), 

the badly recrystallized specimens are in a limestone 

bed. This faunule resembles the Pennsylvanian collections in the greater number of bellerophontaceans, although here Knightites (Retispira) and rare 

Bellerophon occur together. 

Of the 27 genera differentiated, 14 are in the 

Mississippian part of the Amsden. Twenty are present in the Pennsylvanian. The 7 genera that are 

"exclusively Mississippian" are based on 24 specimens, 4 of them on a total of 9 specimens. The 13 

genera that are "exclusively Pennsylvanian" are 

represented by 27 specimens; 11 of these are based 

on only 18 specimens. Obviously, the chance finding 

of an additional gastropod locality in the Mississippian or the failure to discover one in the Pennsylvanian would have a profound effect on the relative 

percentages of the genera in either system. 

In broader perspective, on the basis of studies 

from other areas, it is difficult to point to any genus 

that is significant for age dating within the interval 

under consideration. Most of the genera listed are 

known from both systems. A few have been occasionally reported from one or the other and are not 

exclusive indicators of age. 

STRATIGRAPHIC CONSIDERATIONS 

Four members are recognized within the Amsden 

Formation, three of them extending throughout its 

outcrop area in Wyoming. The three are, in descending order: 

Ranchester Limestone Me·mber 

Horseshoe Shale Member 

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, 

separating in this manner a thin Horseshoe Shale 

Member from the overlying Ranchester. The lithology and biostratigraphy of the Amsden Formation 

are discussed in some detail by Sando, Gordon, and 

Dutro. (In pres.s.) 

The Amsden and its individual members are 

transgressive in a general west-to-east direction. 

For this reason, we speak of the Mississippian and 

Pennsylvanian parts of the Amsden in general 

terms without always identifying the member or 

members. Nevertheless, all the fossil collections are 

referred to their respective members in the data on 

occurrence that follows the descriptions. 

No fossils have been found in the Darwin Sandstone Member, but available dat.a indicate that it is 

Late Mississippian in age throughout its are,a of outcrop. The coraliferous Moffat Trail Limestone lViember has been determined to be Late Mississippian 

(Chesterian) in age throughout. The Horseshoe 

Shale Member in western and west-central Wyoming is Mississippian in age from bottom to top ; in 

eastern-most east-central Wyoming the same member is Pennsylvanian (Morrowan) in age from bottom to top; in between, it is part Mississippian and 

part Pennsylvanian. 

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 probably early Atokan). In 

west-central and east-central Wyoming this member is Pennsylvanian (Morrowan and early 

Atokan). 

The distribution of the gastropods, cephalopods, 

and trilobites in the Mississippian part of the Amsden equates with the coral and brachiopod zones that 

have been recognized in this study. The Pennsylvanian ones, however, are not as well equated with 

these zones. The coral and brachiopod zones are as 

follows: 

Pennsylvanian: 

M esolobus Zone 1 

N eokoninckophyllum hamaUlis Zone 1 

A ntiquatonia blackwelderi Zone 2 

Mississippian : 

Anthracospirifer welleri-shawi Zone 2

• 3 

Composita poposiensis Subzone 3 

Carlinia amsdeniana Subzone 3 

Caninia Zone 2 

Gastropods occur in both Mississippian zones and 

subzones but are moderately common only in the 

Carlinia amsdeniana Subzone. They are even more 

common in the early Morrowan part of the formation in east-central Wyoming, but in this region 

A ntiquatonia blackwelderi is not present. One occurrence, near the top of the Amsden on the east 

slope of the Bighorn Mountains, may be as young 

as the Mesolobus Zone of Atokan Age but cannot be 

dated so precisely. Cephalopods have been found 

only in the A nthracospirifer welle1·i-shawi Zone and 

at the base of the Pennsylvanian in west-central 

Wyoming. Trilobites are known from the Caninia 

1 East-central Wyoming. 2 Western Wyoming. a West-central Wyoming. 
GASTROPODA, CEPHALOPODA, AND TRILOBITA OF THE AMSDEN FORMATION F5 

Zone, Carlinia anusdeniana Subzone, and the Morrowan of east-central Wyoming, including the N eokoninckophyllurn, hamatilis Zone. 

STRATIGRAPHIC AND GEOGRAPHIC 

OCCURRENCE OF THE GASTROPODS 

The gastropod collections are discussed below under two main headings : those from beds of Mississippian age and those from beds of Pennsylvanian 

age. This should not imply, however, that the gastropods have been of any use in identifying the 

containing beds as either Mississippian or Pennsylvanian. Recognition of the ages of the strata has 

been based almost exclusively on evidence from 

foraminifers and brachiopods. 

Most of the gastropod genera are so long ranging 

that their usefulness is precluded for distinguishing 

Upper Mississippian from Lower Pennsylvanian 

rocks. However, in genera present in both the 

Mississippian and Pennsylvanian parts of the Amsden, we have noted that they are represented by 

different species in each part. This suggests that 

with better material derived from more exhaustive 

collecting, it might be possible to distinguish Mississippian from Pennsylvanian Amsden on the basis of 

gastropods alone. 

All the Pennsylvanian gastropod-bearing collections are from the west-central and east-central 

regions of Amsden outcrop. The Mississippian gas.-

tropod collections are from the central and western 

regions. In table 2 the distribution of the gastropods 

by collection and by stratigraphic member is shown, 

and table 3 is the checklist of collecting localities. 

TABLE 2.-Gastropods, cephalopods, and trilobites of the Amsden Formation of Wyoming 

Gastropoda: 

Betlerophon cf. B. crassus 

Horseshoe Shale Member Moffat Trail Limestone Member 

3 8 30 31 34 35 36a 36c 36d 36e 45 48 53 116 137 159 E 76 77 78 79 92 93 105 109 

Ranchester 

Limestone 

Member 

40 50 62 

Meek and Worthen --------- ___ ___ X ___ ___ ___ ___ ___ ___ ___ ___ ___ ___ ___ ___ ___ X _________________________________ --- X 

Beu:io~h~~?-~"P~-i~d.~t--_-_--:::: ::: ::: ::: ::: ::: -~ ::: ::: ::: ::: ::: ::: ::: ::: ::: -~ ::: ::: -X -X -X- -X- -X- ::: -X- -X ::: ::: ::: -~ Buphemites sacajawensis C. 

K!~~~it~~ (R;t~pi;~)--sP.-"A:: ::: ::: ::: ::: ::: ::: ::: ::: _:_ ~ ::: ::: ::: ::: ::: -X- ::: ::: ::: ::: ::: ::: ::: ::: ::: ::: ::: ::: ::: ::: sp. H -------------------- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- X X --- ?Knightites (Retispira) sp. 

~~~~t n:-s·p-::::::::::::::::: --- --- --- --- --- --- --- --- --- --- --- --- X --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- ---

affKn~~h\E·~-~~~~~~~~----- ___ ___ ___ ___ ___ ___ ___ ___ ___ ___ ___ ___ ___ ___ ___ ___ x ______________________________________ _ 

sp. indet ----------------- X X --- --- --- --- --- --- --- --- --- ___ --- --- --- --- ___ --- --- --- ___ --- --- --- --- --- --- --- X X 

~~[~ft~:o~~~ 1E_~~rr_:~~~z~_ ! _____ ::: ::: ::: ::: ::: ::: ::: ::: ::: ::: ::: ::: ::: -~ ::: ::: ::: ::: ::: ::: ::: ::: ::: ::: ::: ::: ::: -x -x -x ~~tfe~~; ~~: ;;;~t~~ ~~-~~-= ::: ::: ::: ::: ::: ::: ::: ::: ::: ::: ::: ::: ::: ::: ::: -X- ::: -~- ::: ::: ::: ::: ::: ::: ::: ::: ::: ::: ::: ::: Borestus sp. indet ------------ __________________________________________ ~-- ___ ___ ___ ___ ___ ___ ___ ___ ___ ___ ___ ___ X --- __ _ Borestus? sp ----------------- ____________________________________________________________________________________ --- X 

Baylea? sp. indet ------------- ___________________________ X ________________________________________________ --- X --- X 

g~i:~~!:::~~pi.~~~i;~========== === === === === === === =~ ::: ::: ::: ::: ~~ ::: :;: === === === === ::: ::: ::: ::: ::: ::: ::: ::: ::: ::: ::: ::: Dictyotomaria carlbrwnsoni n. 

sp ------------------------- --- --- --- --- --- --- --- --- --- X --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- Shansiella sp. indet ----------- ___ ___ ___ ___ ___ ___ ___ ___ ___ ___ ___ ___ ___ ___ ___ ___ ___ ___ ___ ___ ___ ___ ___ ___ ___ ___ ___ ___ ___ X 

Yunnania? sp. indet ---------- ___ ___ ___ ___ ___ ___ ___ ___ ___ ___ ___ ___ ___ ___ ___ ___ ___ ___ ___ ___ ___ ___ ___ ___ ___ ___ ___ ___ X __ _ 1£j:ophosty~us sp: indet _____ ___ ___ ___ ___ ___ ___ ___ ___ ___ X ______________________________________________________ --- --- • wrodoma. sp. 1ndet --------- ___ ___ ___ ___ ___ ___ ___ ___ ___ ___ ___ ___ ___ ___ ___ ___ ___ ___ ___ ___ ___ ___ ___ ___ ___ ___ ___ X --- --- Anematina sp. indet ---------- ___ ___ ___ ___ ___ ___ ___ ___ ___ ___ ___ ___ ___ ___ ___ ___ ___ ___ ___ ___ ___ ___ ___ ___ ___ ___ ___ X _____ _ 

Naticopsis (Naticopsis) spp. indet ----------------------- ___ ___ ___ ___ ___ ___ ___ ___ ___ ___ ___ ___ ? ______ X ____________________________________ X __ _ 

(Jedria?) sp. indet ------ --- ___________________________ --- X __________________________________________ --- --- --- ---

~~::,:::~i:f"s~~dl~d~t-:::::::: ::: ::: ::: ::: ::: ::: ::: ::: ::: ::: ::: ::: ::: ::: ::: ::: ::: ::: ::: ::: ::: ::: ::: ::: ::: ::: ::: ::: ~ ::: Palaeostylus ( Pseudozygo- pleura) spp. indet ---------- ___ ? ___ ___ ___ ___ ___ X ___ X ___ ___ ___ ___ ___ ___ ___ ___ ___ ___ ___ ___ ___ ___ ___ ___ ___ X _____ _ 

Orthonema sp. indet ---------- X X __ _ lanthinopsis spp. indet -------- ::: ::: ::: ::: ::: ::: ::: ::: ::: --? -X- ::: --? ::: ::: ::: ::: ::: ::: ::: ::: ::: ::: ::: ::: ::: ::: --- --- --- Soleniscus? sp. indet ---------- ___ ___ ___ ___ ___ ___ ___ ___ ___ ___ ___ ___ ___ ___ ___ ___ ___ ___ ___ ___ ___ ___ ___ ___ ___ ___ ___ ___ X __ _ Meekospira? sp. indet --------- ____________________________________________________________________________________ X __ _ 

::~:~=~ a~:::p;g~~~~::::: ::: ::: ::: ::: ::: ::: ::: -~ ::: _:_ ::: ::: ::: ::: ::: ::: ::: ::: ::: ::: ::: ::: ::: ::: ::: ::: ::: ::: -X ::: 

(Weller) ------------------ ___ ___ ___ ___ ___ ___ ___ ___ ___ X --- --- --- --- _________ --- --- ______ --- ______ --- --- --- --- --- ---

Cephalo:~da~ndet ----------------- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- X 

Reticycloceras? sp. indet ____________________________________ -- ___ ___ ___ ___ ___ ___ ? _________________________________ ---

Orthoconic nautiloid, gen. and 

c:!e~~~:;aio-id~;-~p:-i~d;t-::: === ::: === === === ::: -x- ::: ::: ::: ==--~=- -::_ -_-:_ -_-_-_ -_-_-_ -_-_-_ --~ === ::: === === === === =-- === ::: ::: ::: ::: Goniatitacean, gen. and sp. --

TriJobl::.~et ---------------------- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- X --- ---

Paladin moorei (C. Branson)_ ___ ___ ___ X X ____________ X ___ ___ ___ ___ ? ___ ___ ___ ___ ? _________ X _________________ _ 

sp ----------------------- --- X --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- X ? ---
F6 

Collection No. in report 

1 

THE AMSDEN FORMATION (MISSISSIPPIAN AND PENNSYLVANIAN) OF WYOMING 

TABLE 3.-Checklist of gastropod, ~ephalopod, and trilobite collections 

Permanent 

institutional 

locality No. 

Name of locality Mountain Range County 

USGS 5441-PC ---- Cherokee Spring_ Rawlins hills ----- Carbon 

Location 

Probably in SW1,4 sec. 11, 

T. 21 N., R. 88 W. 

3 ----- USGS 3139-PC _______ do ______________ do _________________ do NW%SW% sec. 11, T. 

21 N., R. 88 W. 

8 ----- USGS 21728-PC __ Meadow Ranch ____ do _________________ do SW1.4NE1.4 sec. 25, T. 

22 N., R. 88 W. 

30 ---- UW 3199/19B4 ---- Cherry Creek ___ Wind River Range_ Fremont __ SE%NW1.4 sec. 19, T. 31 

N., R. 99 W. 

31 ---- UW 3199/19B5 _______ do ______________ do __________ • ______ do _________ do ------------------- 34 ---- UW 3199/19B8 _______ do ______________ do _________________ do _________ do -------------------

35 ---- UW 3199/19A ________ do ______________ do _________________ do ------ NWl~ "''ee. 19, T. 31 N., R. 

99 w. 36a --- UM :;:pecimer1s ________ do ______________ do _________________ do ______ Sec. 19, T. 31 N., R. 99 W. 

36c --- ___ do ------------- Near Lander _______ do _________________ do ------ Not known exactly ------ 36d --- ___ do ------------- Little Popo Agie ___ do _________________ do _________ do -------------------

River. 

36e --- USNM 487A ______ Cherry Creek ______ do _________________ do ______ Sec. 19, T. 31 N., R. 99 W. 

40 USGS 21676-PC ___ Bull Lake Creek ____ do _________________ do ------ SW1.4 sec. 2, T. 2 N., R. 

45 USGS 21719-PC ___ Livingston Washakie Range ______ do 

Ranch. 

48 YPM 20101-20110 _ Wiggins Fork ______ do _________________ do 

4 w. 

SW% SW% sec. 29, T. 43 

N., R.106 W. 

SW% sec. 7, T. 42 N., R. 

105 w. 

50 ---- USGS 19187-PC ___ Trout Creek ____ Bighorn Mountains_ Washakie _ Sec. 19, T. 41 N., R. 88 W. 

52 USGS 2461-PC, North Fork, ___ do -------------- Johnson ___ SE1,4 sec. 28 orNE% sec. 2461A-PC. Crazy Woman 33, T. 49 N., R. 83 W. 

Creek. 

53 USGS 19241-PC --- South Fork, ___ do _________________ do ______ SW1.4 sec. 25, T. 52 N., R. 

Rock Creek. 84 W. 

76 USGS 22987-PC ___ Moffat Trail ____ Salt River Range __ Lincoln ___ NW1,4NE1,4 sec. 3, T. 33 

N., R. 117 W. 

77 USGS 6960A-PC _____ do ______________ do _________________ do _________ do ------------------- 78 USGS 6960B-PC _____ do ______________ do _________________ do _________ do ------------------- 79 USGS 22981-PG ______ do ______________ do _________________ do _________ do ------------------- 92 ---- USGS 6965-PC ___ Covey Cutoff _______ do _________________ do ______ NW%,NE:14 sec. 27, T. 34 

N., R.ll7 W. 

93 ---- USGS 6951-PC ______ do ______________ do _________________ do _________ do ------------------- 105 --- USGS 17907-PC ___ Haystack Peak _____ do _________________ do ______ Center sec. 19, T. 34 N., 

R. 117 W. 

109 --- USGS 23002-PC ___ South Indian Snake River Range ____ do ______ NE1.4 sec. 14, T. 38 N., R. 

Creek. 118 w. 

116 --- USGS 18798-PC ___ Hoback Canyon _ Hoback range ______ Teton ____ _ Sec. 3, T. 38 N., R. 115 W. 

137 --- USGS 6191-PC ___ Darwin Peak ___ Gros Ventre Range ____ do ______ Slh sec. 28, T. 40 N., R. 

112 w. 

159 --- USGS 24050-PC ___ Elk Ridge ______ Teton Range _________ do ______ SW1.4 sec. 26, T. 47 N., R. 

116 w. 

E ----- USNM Epecimens __ Near Lander ___ Wind River Range _ Fremont __ Not known -------------

Member 

Horseshoe 

Shale 

Member 

Do. 

Do. 

Do. 

Do. 

Do. 

Do. 

Do. 

Do. 

Do. 

Do. 

Ranchester 

Limestone 

Member. 

Horseshoe 

Shale 

Member. 

Do. 

Ranchester 

Limestone 

Member. 

Do. 

Horseshoe 

Shale 

Member. 

Moffat Trail 

Limestone 

Member. 

Do. 

Do. 

Do. 

Do. 

Do. 

Do. 

Do. 

Horseshoe 

Shale 

Member. 

Do. 

Do. 

Do. 

MISSISSIPPIAN FA UN A 

In the Mississippian parts of the Amsden only two 

areas have yielded gastropod faunules: 1) the area 

south of Lander, Fremont County, including the 

Cherry Creek and Amsden Hill exposures, which 

have been exhaustively collected over a long period; 

and 2) a unique collection from the Darwin Peak 

section in Teton County. 

identified as Bellerophon? sp. indet. This shell, invariably poorly preserved, is found in association 

with corals of the Caninia Zone; it commonly is 

overgrown with chaetetiform bryozoans. This species was recorded in seven collections made in Lincoln County, in the Moffat Trail, Covey Cutoff, Haystack Peak and South Indian Creek sections ( collns. 

76-79,92,105, 109). 

Lincoln County.-A single gastropod species has 

been recorded in the Moffat Trail Limestone Member. It is a moderately large bellerophontacean, here 

Teton County.-In the Darwin Peak section, a 

brachiopod-mollusk assemblage was collected by 

Blackwelder and its fossils identified first by Girty 
GASTROPODA, CEPHALOPODA, AND TRILOBITA OF THE AMSDEN FORMATION F7 

(in Blackwelder, 1918, p. 422). The gastropods from 

this locality (colln. 137) have been reidentified as 

follows: 

Bellerophon sp. 

Knightites (Retispira) sp. A 

Straparollus? sp. indet. (too poorly preserved 

to include in systematic paleontology) 

W orthenia? sp. indet. 

Naticopsis (Natico.psis) sp. indet. 

At Berry Creek in the Teton Range, a limestone 

bed in the Horseshoe Shale Member of latest Mississippian age ( colln. 159), the following species were 

recorded: 

Bellerophon cf. B. crassus Meek and Worthen 

Straparollus (Euomphalus) calix n. sp. 

The age determination at this locality was by foraminifers and in part by brachiopods. Like some of 

the brachiopods, these snails suggest Pennsylvanian 

affinities, as the Bellerophon is widespread elsewhere in Wyoming in beds of Pennsylvanian (Morrowan) age. 

Fremont County.-Gastropods from the Anthracospirifer welleri-shattvi Zone in the Horseshoe Shale 

Member are known from the Lander area, which 

includes Cherry Creek and Amsden Hill. Most of 

these collected were weathered out from shale, and 

their stratigraphic position is not certain, but the 

striking limonitic preservation is characteristic of 

the CarUnia amsdeniana Subzone in this region. The 

following species have been recorded (collns. 34, 35, 

36a, 36c-e, E) : 

Bellerophon sp. 

Euphemites sacajawensis C. Branson 

Knightites (Retispira) sp. A 

New genus aff. Colpites sp. 

Dictyotomaria carlbransoni n. sp. 

Gosseletina? sp. indet. 

Strophostylus sp. indet. 

Palaeostylus (Pseudozygopleura) sp. indet. 

Ianthinopsis sp. indet. 

Girtyspira sp. A 

Donaldina aff. D. pygmaea (Weller) 

In the Washakie Range, beds that contain brachiopods of the Carlinia amsdeniana Subzone have provided the following gastropod species at Livingston 

Ranch (colin. 45) : 

Gosseletina sp. indet. 

Naticopsis (Jedria.?) sp. indet. 

At approximately the same level at Wiggins Fork, 

also in the Washakie Range ( colln. 48) , are these 

species: 

?Knightites (Retispira) sp. indet. 

?Naticopsis (Naticopsis) sp. indet. 

I anthinopsis? sp. indet. 

PENNSYLVANIAN FAUNA 

Gastropods were found in beds of Pennsylvanian 

age at seven localities-four of them in the Horseshoe Shale Member and three in the Ranchester 

Limestone Member. These provided most of the 

Amsden species. 

Fremont County.-The westernmost occurrence 

of gastropods of Pennsylvanian age in the Amsden 

Formation was at Bull Lake Creek (colin. 40) in 

the Wind River Range. Here the mollusks occur as 

molds in a chert bed in the basal 2 feet of the 

Ranchester Limestone Member. These include external molds of high-spired gastropods too poor to 

identify even as to family. The following gastropods 

are recorded : 

Knightites (Retispira) sp. B 

Colpites sp. A 

Borestus sp. indet. 

Baylea? sp. indet. 

M icrodom,a? sp. indet. 

A nematina sp. indet. 

Palaeostylus (Pseudozygopleura) sp. indet. 

Orthonema sp. indet. 

Washakie County.-On the west slope of the Bighorn Mountains, on Trout Creek, a mollusk-bearing 

marl in the Ranchester Limestone Member (colin. 

50) yielded the following species : 

Knightites (Retispira) sp. B 

Straparollus (Euomphalus) aff. S. (E.) plummeri Knight 

Colpites sp. A 

Moderately high-spired pleurotomariacean indet. (too poorly preserved to include in systematic paleontology) 

Yunnania? sp. indet. 

N aticopsis (N aticopsis) sp. indet. 

Orthonema sp. indet. 

M eekospira? sp. indet. 

Gi1·tyspira sp. B 

Soleru'scus? sp. indet. 

Johnson County.-One of the earliest collections 

made in the Amsden Formation, mentioned by Darton (1906, p. 34), has provided the largest single 

gastropod faunule among our collections. It came 

from near the top of the Ranchester Limestone 

Member on the North Fork of Crazy Woman Creek 

(colln. 52). The fossils occur as molds in a granular 

chert bed. The following species have been 

identified: 
FS THE AMSDEN FORMATION (MISSISSIPPIAN AND PENNSYLVANIAN) OF WYOMING 

Bellerophon cf. B. cra.ssus Meek and Worthen 

sp. 

Straparollus (Euomphalus) aff. S. (E.) plummeri Knight 

Colpites sp. A 

Borestus? sp. 

Bay lea? sp. indet. 

Shansiella sp. indet. 

Goniasma? sp. indet. 

Murchisonia? sp. indet. 

Donaldina sp. indet. 

A collection from the base of the Horseshoe Shale 

Member at South Fork of Rock Creek, on the eastern flank of the Bighorn Mountains (colin. 53), contained the following species: 

Bellerophontacean indet. (too poorly preserved 

to include in systematic paleontology) 

Straparollus (Euomphalus) sp. indet. 

M ourlonia sp. indet. 

Carbon County.-Three collections from limestone beds in the Horseshoe Shale Member made in 

the Rawlins hills region at Cherokee Spring and 

Meadow Ranch ( collns. 1, 3, 8), yielded the following species in brachiopod-mollusk assemblages: 

Bellerophon cf. B. crassus Meek and Worthen 

Straparollus (Euomphalus) aff. S. (E.) plummeri Knight 

?Palaeostylus (Pseudozygopleura) sp. indet. 

Nearly all these collections of gastropods from the 

Pennsylvanian part of the Amsden Formation come 

from beds dated by other fossils as Morrowan in 

age. The prime exception to this statement is the 

large faunule from Crazy Woman Creek (colin. 52). 

The bed in which these fossils occur is near the top 

of the formation and might be either Morrowan or 

Atokan in age. The fauna is largely molluscan, and 

although some of the same species occur in it that 

are present in beds of known Morrowan age, the 

ranges of the molluscan species are not well enough 

known at present to be used for precise dating. 

CEPHALOPODS 

Four different cephalopods have been recognized 

in the Amsden Formation, on the basis of five specimens, three of which cannot presently be located in 

the University of Missouri collections. None has 

been figured previously, In the course of our investigation only one new specimen was found, an indeterminate juvenile ammonoid (USNM 173621) 

preserved as an internal mold in a gastropod-bearing chert bed of Pennsylvanian age (colin. 40), in 

the Bull Lake Creek section, Fremont County. 

The rest came from what is now called the Horseshoe Shale Member in the Little Popo Agie River 

drainage southwest of Lander. These include two 

orthoconic nautiloids cited by Branson and Greger 

(1918, p. 324), which seem not to have been deposited in the University of Missouri collection. 

These were originally identified as Orthoceras sp? 

and Cycloceras sp? 

The best preserved cephalopod, a specimen from 

Cherry Creek (colin. 35) in the collection of the 

University of Wyoming (IT-243), is here identified as Cravenoceratoides sp. indet. This genus is 

restricted to the middle and upper parts of the 

Eumorphoceras bisulcatum Zone in northwest 

Europe. 

TRILOBITES 

Thirty-four parts and fragments of trilobites 

from the Amsden Formation have been available 

for study. These include, in addition to the holotype, 

5 cranidia, 3 librigenae, 2 broken genal spines, and 

18 whole or fragmental pygidia; 3 other genal 

spines mentioned by Branson (1937, p. 659) are 

indeterminate fragments. All of them are referred 

to Paladin and probably represent two species, one 

in the Mississippian part of the formation and the 

other in the Pennsylvanian part. 

The Mississippian species is Paladin nworei (C. 

Branson). Most of the specimens of P. moo1·ei are 

from the Horseshoe Shale Member in the Little Popo 

Agie River drainage (collns. 30, 31, 36d) and Twin 

Creek, Wind River Range, Fremont County. The 

same species is rare in the Moffat Trail Limestone 

Member in the Moffat Trail and Covey Cutoff sections (collns. ?77, 93) in the Salt River Range, 

Lincoln County. 

The Pennsylvanian form has not been identified 

with any previously described species, though it 

probably is related rather closely to P. pyriformis 

Chamberlain. It occurs in the eastern region of 

Amsden outcrop in the Horseshoe Shale Member 

(colin. 3) and Ranchester Limestone Member 

(collns. 50, ?52). 
GASTROPODA, CEPHALOPODA, AND TRiLOBITA OF THE AMSDEN FORMATION F9 

SYSTEMATIC PALEONTOLOGY 

Pbyllum MOLLUSCA 

Class GASTROPODA 

Subclass PROSOBRANCHIA 

Order ARCHAEOGASTROPODA 

Suborder BELLEROPHONTINA 

Superfamily BELLEROPHONTACEA M'Coy 

Family BELLEROPHONTIDAE M'Coy 

Genus BELLEROPHON Montfort, 1808 

Belleropbon cf. B. crassus Meek and Worthen 

Plate 1, figures 1-4 

Bellerophon crassus Meek and Worthen, 1860, p. 458; 1866, 

p. 385, pl. 31, figs. 16a, b. 

Description.-Bellerophontacean having inflated 

conch; whorl profile moderately well rounded, lessening slightly in curvature on lateral slopes so as 

to appear subglobose. Early whorls unknown. Apertural margin normal to axis of growth, straight 

across dorsum and essentially straight along lateral 

slopes, but curving back abruptly along umbilical 

slopes to attach to preceding whorl; growth lines 

faint to absent. Selenizone obscure, very slightly 

raised above rounded dorsum. Slit narrow and short, 

its depth equal to approximately one-eighth length 

of body whorl; junction of outer lip with slit emargination being virtually at right angles with no appreciable rounding. Slight depression present within aperture on areas below lateral slopes. Inductural boss not prominent and possibly absent. Shell 

of moderate thickness throughout, thinning abruptly at margin. 

Discussion.-The bellerophontaceans are a rather 

difficult group because characters that distinguish 

the species are relatively few. Perhaps the two most 

commonly used names for late Paleozoic species of 

the genus Bellerophon in North America are B. sublaevis Hall, described originally from beds of Mississippian (Meramecian) age, and B. c1·assus Meek 

and Worthen, from beds of Middle Pennsylvanian 

age. The two species are closely related and differ 

principally in that B. crassus is slightly more 

globose. 

No comprehensive review has been made of these 

and other closely related American Carboniferous 

gastropods. Until such a study is available, no practical purpose would be served in adding yet another 

name to this species group. Despite the fact that 

our material is sufficiently abundant and well preserved to show nearly all the salient characters of 

this Amsden form, the rather limited taxonomic 

characters are not well enough understood to warrant proposal of a new specific name. 

This bellerophontacean is common as poorly to 

moderately well preserved internal and external 

molds at Crazy Woman Creek in the Bighorn Mountains. It is associated with other mollusks and 

brachiopods that include the orthotetid Pulsia delira Gordon, n. sp., in a granular chert bed of Pennsylvanian age near the top of the formation. The 

figured specimens are from that locality. It also is 

present in beds of latest Mississippian age at Berry 

Creek in the Teton Range. Five steinkerns from a 

locality at Meadow Ranch in the Rawlins hills are 

also included here and another steinkern from the 

Gros Ventre Range. 

Figured specimens.-USNM 168460-168463. 

Occurrence and number of specimens.-Horseshoe Shale Member: collections 8 (5), Carbon 

County; 159 ( 4), Teton County. Ranchester Limestone Member : collection 52 (50+ ) , Johnson 

County. 

!Selleropbon spp. 

Plate 1, figure 5 

A specimen from the Pennsylvanian molluskbearing bed at Crazy Woman Creek, preserved as 

an incomplete external mold, differs from the common form in the greater rounding of the dorsum, 

giving the whorl a higher arched, narrower profile. 

The lateral slopes are somewhat compressed, and 

the umbilicus immediately behind the thickened lip 

of the apertural margin is marked by a prominent 

shallow dimple. The margin swings slightly forward 

to attach to the preceding whorl, as figured. 

A slightly compressed small steinkern, 10 mm in 

length, from the Mississippian Carlinria amsdeniana Subzone at Darwin Peak is questionably referred here, though there is no doubt as to its generic 

assignment. Another poorly preserved specimen, 16 

mm in diameter, from the Cnmposita poposiensis 

Subzone at Cherry Creek agrees with the previous 

one in being compressed so that the maximum width 

is equal to about four-fifths of the diameter. 

The specimen from the Heath Formation of 

Montana figured as Bellerophon sp. by Easton (962, 

p. 98, pl. 13, fig. 7) is similar but slightly wider. It 

is a steinkern, preserving a patch of the shell. Owing 

to the poor preservation we cannot be sure whether 

or not the Mississippian shells are properly assigned 

here or even represent the same taxon. 

Figured specimen.-USNM 168464. 

Occurrence and number of specimens.-Horseshoe Shale Member: collection 34 ( 1), Fremont 

County; 137 (1), Teton County. Ranchester Limestone Member: collection 52 (1), Johnson County. 
FlO THE AMSDEN FORMATION (MISSISSIPPIAN AND PENNSYLVANIAN) OF WYOMING 

Bellerophon? sp. indet. 

Figure 1 

This group consists of some poorly preserved 

shells, all of them from the Caninia Zone in western 

FIGURE 1.-Cros:s section of Bellerophon? sp. indet., X 1%, 

from specimen USNM 16846,5, collection 78. 

Wyoming. They have, in addition to basic bilateral 

symmetry, the following characters in common: 

closed umbilici, subglobose shape, and rather large 

size, being more than 2.5 em in length. Random 

sections suggest that no spiral lirae are present on 

the surface and that the inductural boss is rather 

thin and located far within the whorl. Although 

several species of Euphemites cannot be eliminated 

as a possibility, the available characters suggest 

that this form is a typical Bellerophon. The specimens at one locality (colln. 105) are overgrown by 

a chaetetiform bryozoan, a relationship noted by 

Gordon and Duncan (1970, p. A41) in the Canin,ia 

Zone of the Oquirrh Mountains, Utah. 

Most of the specimens are fairly uniform in 

shape, but the one from collection 76 (USNM 

173616) may be somewhat narrower than the others; however, it is preserved as a steinkern rather 

than in cross section. One from collection 109 

(USNM 168465) has in cross section a low dorsal 

ridge on the shell surface. Preservation is much too 

poor to determine whether these forms are taxonomically distinct or represent variation within one 

species. 

Figured specimen.-VSNM 168465. 

Occurrence and number of specim,ens.-Moffat 

Trail Limestone Member: collections 76 (1), 77 (1), 

78 (1), 79 (1), 92 (1), 105 (2), 109 (1), Lincoln 

County. 

Genus EUPHEMITES Warthin, 1930 

Euphemites sacajawensis C. Branson 

Plate 1, figure 6-9, 11-13 

?Bucanopsis or Bellerophon. Branson and Greger, 1918, p. 

324, pl. 19, figs. 9, 10. 

Euphemites sacajawensis C. Branson, 1937, p. 658, 659, pl. 

89, figs. 24, 25, 33; ?Eas,ton, 1962, p. 98, pl. 13, figs. 9, 

10. 

Descript.ion.-Shell globose, not geniculate, having infundibuliform umbilical depressions that occuPY about one-quarter of total length of shell, set off 

from flanks by obscure angulation. Flanks and dorsum well inflated, essentially following semicircular 

arc between umbilical areas. Surface ornamented by 

raised thick longitudinal cords (lirae) totaling approximately 22 on shell, closely spaced near umbilical area but more widely spaced on slopes and dorsum where interspaces are as much as two times 

greater than width of cords. Cords dying out abruptly anteriorly; mature part of whorl and aperture 

unknown. 

Dimensions.-Holotype: length 6.5 mm and width 

6.0mm. 

Discussion.-This description is based on a restudy of Branson's holotype. The specimen is relatively small, slightly crushed on one side, and partly 

coated with limonite, as are many of the fossils of 

the Horseshoe Shale Member of the Amsden. A tiny 

patch of smooth inductura remains in front of the 

lirate part of this shell, but no other details of the 

apertural part remain. The broken section of the 

inner lip does not seem to be thickened, and it may 

not extend far out from the main body of the shell, 

but this is conjectural. 

Branson's two figured paratypes are refigured 

here on plate 1, figures 6, 11-13. These give details 

of an adult shell but are omitted from our redescription because we feel that they may represent another species. They differ from the holotype in 

having a narrower shell, lacking prominent umbilical depressions, and are ornamented by fewer and 

finer lirae, having proportionally wider interspaces. 

It seems to us very unlikely that these differences 

could be ontogenetic changes, as the more complete 

paratype measures 8.5 mm long and 7.0 mm wide, 

which is not a great deal more than the holotype. 

Nevertheless, with the paucity of material at our 

disposal, we feel that splitting E. sacajawensis into 

two species at this time is not warranted. 

Easton (1962, p. 98) quite properly questioned 

C. C. Branson's referral to this species of the steinkern figured by Branson and Greger (1918, pl. 19, 

figs. 9, 10) as "Bucanopsis or Bellerophon," because 

so few characters are available on it for comparison 

with the more complete type lot. After studying the 

bellerophontid steinkerns from the Little Popo Agie 

River region, we are inclined to agree with Branson 
GASTROPODA, CEPHALOPODA, AND TRILOBITA OF THE AMSDEN FORMATION F11 

that this is a steinkern of Euphemites, but cannot 

be certain if it is E. sacajawensis. 

Several Mississippian species of Euphemites have 

been described from North America. The Wyoming 

species is similar to E. incarinattts Easton, from the 

Pitkin Limestone of Arkansas, in its globose shape, 

but that form differs in its ornamentation of finer, 

more abundant lirae. The Redoak Hollow species, E. 

compressus Elias, a.s illustrated, has similar ornamentation, but the shape is somewhat less globose 

and the umbilical depressions deeper than in E. 

sacajawensis. The Oklahoma species was established 

on an incomplete juvenile shell and is poorly known. 

As noted by Elias (1958, p. 2), both E. nautiloides (Winchell) and E. galericulatus (Winchell) 

from the Marshall Formation in Michigan also are 

poorly known species; both seem to be galeiform in 

outline and thus distinct from E. sacajawensis. 

Euphemites subglobosus Hyde from the Logan Formation of Ohio differs in having a more compressed 

shell than E. sacajawensis, its width equal to threefourths of its length, the "umbilicus closed," and in 

having a greater number of longitudinal cords (25 

to 30). 

Euphemites lentiformis (Weller) from the Ste. 

Genevieve Limestone in Illinois is easily distinguished by the extreme compression of its shell. 

Types.-Holotype and paratypes UM 6631. 

Occurrence and number of specimens.-Horseshoe Shale Member: collections 36c (1), 36d (7), 

Fremont County. 

Genus KNIGHTITES Moore, 1941 

Subgenus KNIGHTITES (RETISPIRA) Knight, 1945 

Knigbtites (Retispira) sp. A 

Plate 1, figures 14, 15 

Bucanopsis sp. C. Branson, 1937, p. 659. 

Amsden specimens referred to this subgenus are 

not sufficiently complete or well enough preserved 

to describe in detail. Two or possibly three species 

occur in the formation. Perhaps the most distinctive 

of them is represented in part by a lot of three steinkerns (UM 6627) from the Carlinia amsdeniana 

Subzone in the Popo Agie River area, referred by 

C. C. Branson ( 1937, p. 659) to Bucanopsis sp. 

(Branson, however, mentioned only two specimens.) 

The two largest ones are figured here. 

This species expands in width fairly rapidly and 

has a low arched dorsum bearing a slightly raised 

selenizone bounded by two shallow grooves. The 

opening in the umbilical region of the steinkern is 

moderately small. Surface sculpture, seen on two 

patches of shell adjacent to the umbilical opening 

at either side of one of Branson's specimens, consists of closely spaced uniformly fine lirae. The fine 

even ornament of this form indicates that it belongs 

in the group of Knightites (Retispira) tenuilineata 

(Gurley). 

In addition to Branson's material, seven specimens from the same subzone at Darwin Peak are 

referred here. Although it is difficult to equate limonitic steinkerns with partly recrystallized calcareous specimens, the size and overall shape are approximately the same. One fragmental specimen 

preserves the outer lip and shows that the fine longitudinal lirae are crossed by growth lines bowed 

slightly forward at either side of the selenizone, 

which is gently rounded on top and bordered by an 

almost imperceptible longitudinal depression at 

either side. 

Figured specimens.-UM 6627. 

Occurrence and nutnber of specimens.-Horseshoe Shale Member: collections 36d (3), Fremont 

County; 137 (7), Teton County. 

Knigbtites (Retispira) sp. B 

Plate 1, figure 10 

Another species referable to K. (Retispira) occurs at two localities in the Pennsylvanian part of 

the Amsden. The shell expands in width less rapidly 

than K. (R.) sp. A, and the umbilical opening is 

proportionately larger. Its broadly convex dorsum 

bears a slightly raised, flattened selenizone. The 

slit extends backward for about one-fifth of the 

whorl circumference. The surface lirae are fine, 

somewhat variable in strength; they are crossed by 

growth lines shallowly convex toward the aperture 

on either side of the selenizone and narrowly concave across the selenizone. 

The fine sculpture, like that of K. (R.) sp. A suggests to some degree the group of K. (R.) tenuilineata (Gurley). However, inK. (R.) sp. B the variable size and strength of the longitudinal lirae and 

their interruption by fairly strong growth lines are 

features suggestive of K. (R.) textilis (Gurley), 

and they differentiate it from the Mississippian 

form. 

Figured specimen.-USNM 168466. 

Occurrence and number of specimens.-Ranchester Limestone Member: collections 40 (2), Fremont County; 50 (20), Washakie County. 

?Knigbtites (Retispira) sp. indet. 

Love (1939, p. 28) mentioned a Bellerophon? sp. 

in a list of Amsden fossils from Wiggins Fork Can-
F12 THE AMSDEN FORMATION (MISSISSIPPIAN AND PENNSYLVANIAN) OF WYOMING 

yon. We have reexamined the cited specimen (YPM 

20101), which is a s.mall steinkern 11.0 mm wide. 

No trace of shell or impression of ornamentation is 

preserved. The umbilical areas show small depressions, and the rate of expansion of the shell is rather 

low. This specimen is too poorly preserved to assign with confidence to any generic taxon, but its 

overall ·character suggests Retispira as a somewhat 

more likely placement than either the Euphemites 

or the various species of Bellerophon noted above. 

Occurrence.-Horseshoe Shale Member: collection 

48, Fremont County. 

Suborder MACLURITINA 

Superfamily EUOMPHALACEA deKoninck 

Family EUOMPHALIDAE deKoninck 

Genus STRAPAROLLUS deMontfort, 1810 

Subgenus STRAPAROLLUS (EUOMPHALUS) J. Sowerby, 1814 

Straparollus (Euompbalus) calix n. sp. 

Plate 1, figures 20-22 

Description.-Conch depressed, discoidal, having 

steep rounded outer surface. Earliest whorls unknown. Sutures distinct, not impressed. Upper whorl 

face rising directly from suture, very shallowly inclined upward and outward, abruptly rounded 

where it meets outer face; upper whorl surface 

steepening somewhat with age so that mature specimens are very slightly steplike in profile. Outer 

whorl face gently convex in profile, periphery just 

above midwhorl. Basal angulation sharp. Umbilicus 

infundibuliform, deep and prominent, its sutures 

distinct but not incised. Inner whorl face having 

steep wall near basal angulation, bending slightly 

but abruptly inward so that basal angulation mimics 

but does not constitute circumbilical angulation; 

most of .inner whorl face slightly convex, area of 

maximum curvature about one-third of distance 

from suture. 

Growth lines obscure on upper face of whorl, apparently nearly orthocline, exact course on outer 

face unknown; in contrast, growth lines on basal 

face prominent, closely spaced and distinctly incised, prosocline near angulation, but gradually 

curving to ol'ithocline on inner half of face adjacent 

to suture. Faint irregularities seem to be present 

along upper shoulder of whorl, though not actual 

nodes or serrations. Shell thick, especially at upper 

shoulder and basal angulation, as steinkern is well 

rounded. 

Dimen..~ions.-Holotype: width 19.5 mm, height 

7mm. 

Discussion.-This species has a distinctly wider 

(deeper) whorl than Straparollus (Euomphalus) 

a:ff. S. (E.) plummeri Knight. Its most striking feature is the smooth broadly funnel-shaped (infundibuliform) umbilicus which, even on incomplete 

specimens, distinguishes this species from S. (E.) 

plummeri and related forms having shallower more 

steplike umbilici. Among the more common Mississippian and Pennsylvanian species of Straparollus, 

the combination of a sharp basal angulation and 

smooth funnel-shaped umbilicus is unique, approached only by S. (Amphiscapha) hollingsworthi 

(Knight) from the Boggy Shale (Des Moinesian) 

of Oklahoma. In that species, the whorl is narrower 

and the umbilicus correspondingly shallower. 

The largest specimen in the type lot is 21 mm 

wide. Easton (1962, p. 99) described a Strapa1·ollus 

(Euomphalus) sp. A from the Upper Mississippian 

Heath Formation of Montana. This specimen has a 

width of about 31 mm. It is crushed so that no comparison of the umbilical area is possible, though it 

appears to be a narrower shell. The rugose character of the upper angulation readily distinguishes 

that form from S. (E.) calix. 

Types.-Holotype, USNM 168467; paratypes, 

USNM 168468. 

Occurrence and number of specimens.-Horseshoe Shale Member : collection 159 ( 15) , Teton 

County. 

Straparollus (Euompbalus) aff. S. (E.) plummeri Knight 

Plate 1, figures 16-19 

Description.-Conch depressed, discoidal, having 

steep curved outer whorl face and slightly but distinctly rounded sloping umbilical walls. Early 

whorls poorly known, possibly with mere incipient 

angulation at boundary between top and outer surfaces of whorl; early part of shell slightly but distinctly sunk below overall level of upper surface. 

Sutures distinct, becoming incised and somewhat 

channeled at maturity and thus gradually modifying upper surface of whorl. Early whorls shallowly 

steplike, sloping outward and upward from suture 

with rather flat profile, but becoming concave just 

inside angulation; top of whorl sloping inward at 

angle of approximately 20° to horizontal. Mature 

whorl profile lacking concave zone inside angulation, rising even more abruptly from suture than 

early whorls, curving more rapidly toward horizontal, and continuing convex in cross section to 

juncture with outer surface, which it meets at 

approximately right angles. Outer whorl face uniformly gently arched; periphery below midwhorl; 

juncture of outer and basal surfaces not shown in 
GASTROPODA, CEPHALOPODA, AND TRILOBITA OF THE AMSDEN FORMATION F13 

our specimens, but presumably meeting approximately at right angles. 

Umbilicus wide and relativel'Y shallow, having 

curved steplike profile; basal whorl surface horizontal at outer edge, curving gradually upward so 

that inner edge is nearly vertical, most of curvature occurring on inner half of surface; sutures 

distinct and slightly incised. Upper angulation irregularly and weakly serrated. Growth lines orthocline on upper surface and outer face, poorly known 

at upper angulation, but seeming to have small shallow sinus; gently curved on basal surface so that 

juncture with suture is most anterior point of aperture; trough of broad shallow basal sinus corresponding to area of maxim urn change in slope of 

surface. Shell moderately thick. Average-sized specimen is 13.5 mm wide and 4 mm high. 

Discussion.-This species is common and well preserved in a chert bed near the top of the formation 

on the east slope of the Bighorn Mountains (colin. 

52) ; all the illustrated specimens are from this 

locality. One specimen shows the early whorls less 

depressed and the ridged angulation of the early 

whorls less prominent than in the others. Because 

this difference may in part be due to diagenetic 

changes in the external mold, rather than to actual 

morphologic characters of the organism, we are not 

inclined to separate it as a distinct taxon. 

The review by Knight ( 1934) of the Pennsylvanian euomphalid gastropod species is the only 

summary paper on these forms. The Amsden species 

is readily distinguished from those described and 

illustrated by Knight, with the single exception of 

Straparollus (Euomphalus) plummeri Knight, from 

the Upper Pennsylvanian rocks of Kansas and 

Texas. Although that species is much larger than 

our material, its configuration at the same size is 

very similar; at maturity, the body whorl of S. (E.) 

plummeri is produced slightly downward. The early 

whorls of the Amsden species seem to be a little 

more deeply depressed. The upper surface of the 

early whorls of S. (E.) plummeri slope inward at 

approximately 30° from the horizontal. The basal 

surface of the same species appears to have slightly 

less curvature than in the Amsden shells. 

The Mississippian species of this group have not 

been subject to monographic treatment and are 

therefore not as well understood as the Pennsylvanian forms. The Amsden species can be distinguished from most of the known Mississippian 

forms by its lack of an elevated spire. Straparollus 

(Euomphalus) utahensis (Hall and Whitfield) from 

beds now assigned to the Gardison Formation of 

Early Mississippian (Osagean) age is the closest 

Mississippian species to the Amsden form. Its spire 

is distinctly depressed, and the angulation is more 

acute at all stages than in the Amsden shell. 

The form described by Easton (1962, p. 99, pl. 

13, fig. 15) from the Cameron Creek Shale of Montana as Straparollus (Euomphalus) n. sp. B is similar in general size to S. (E.) plummeri. It is readily 

distinguished by its higher whorl and steeper slopes 

in both the umbilical region and the depressed upper surface. Furthermore, in the Montana form the 

sutures are not incised. 

Figured specimens.-USNM 168469-168472. 

Occurrence and number of specimens.-Horseshoe Shale Member: collection 3 ( 1), Carbon County. Ranehester Limestone Member: collections 50 

( 9) , Washakie County ; 52 ( 10), Johnson County. 

Straparollus (Euomphalus) sp. indet. 

A third species of Straparollus (Euomphalus) occurs in a bed of Pennsylvanian age at the base of 

the Horseshoe Shale Member on the South Fork of 

Rock Creek in the Bighorn Mountains, but, owing 

to poor preservation of the material, it cannot be 

assigned to a species. The conch is depressed and 

discoidal, the upper surface stepped. The upper 

face of the whorl is flat and nearly horizontal initially but appears somewhat tilted inward on the later 

whorls; the angulation at the juncture between top 

and outer faces is marked by a distinct ridge well 

within the periphery of the whorl. The outer whorl 

face is poorly known because of partial crushing but 

seems to be rather narrow. The umbilicus is shallow, its walls flat; details of the umbilical suture 

have not been observed. Growth lines are steeply 

prosocline on the lower part of the outer face and 

continue this same course into the umbilicus. 

The best of our available specimens (USNM 

168473) is moderately crushed and is partly covered 

with matrix; a cross section shows that the initial 

whorls are badly crushed. Nevertheless, it can be 

determined that the whorl is narrower and the umbilicus shallower than in S. (E.) calix n. sp. The 

ridge emphasizing the angulation along the juncture 

of the top and outer faces distinguishes this form 

from S. (E.) aff. S. (E.) plummeri. It is unlikely 

that this ridge might be the product of crushing of 

the shell because cross sections of even badly 

crushed whorls seem to show that the shell is thickened at the top and the base. 

The shell that Easton (1962, p. 99, pl. 13, fig. 14) 
F14 THE AMSDEN FORMATION (MISSISSIPPIAN AND PENNSYLVANIAN) OF WYOMING 

denoted as Straparollus (Euomphalus) n. sp. A 

from the Heath Formation of Montana shows some 

similarities to this taxon, but they are due entirely 

to crushing. Both are so poorly preserved that proper comparison cannot be made. 

Occurrence and number of specimens.-Horseshoe Shale Member: collection 53 ( 5), Johnson 

County. 

Suborder PLEUROTOMARIINA 

Superfamily PLEUROTOMARlACEA Swainson 

Family SlNUOPEIDAE Wenz 

Genus COLPITES Knight, 1956 

Colpites sp. A 

Pia te 2, figures 1-5 

Description.-Shell extremely low spired, having 

nodose subsutural ornament; body whorl embracing 

high on side of penultimate whorl. Early whorls 

very poorly known, but probably including flattened 

protoconch. Sutures obscure. Whorl profile slightly 

flattened near suture but otherwise following 

smooth inflated curve; periphery just below midwhorl; ibas.e anomphalous. Shell surface smooth, ornament consisting only of subsutural nodes, which 

are elongate, steeply prosocline, closely and uniformly spaced; interspaces approximately same 

width as nodes ; 18 to 20 nodes present on each 

whorl. Growth lines unknown but possibly represented by faint opisthocline markings on lower half 

of shell. 

The most complete shell, a paratype lacking part 

of the spire, measures 5.2 mm long and 7.0 mm wide. 

Discussion.-The six specimens included in this 

species, with one exception, are external molds that 

do not preserve the lower half of the shell. Several 

specimens are partly exfoliated or the mold is partly filled with secondary drusy calcite; at least two 

of the specimens show impressions of small rounded 

oblique subsutural nodes. All the specimens included 

here are from beds of Early Pennsylvanian age. 

Two American Pennsylvanian species of Colpites 

have been previously described. The type species C. 

moniliferus (White) is readily distinguished by its 

higher spire. Colpites minutus (Sayre) is similar to 

C. sp. A but has a very slight spire and is even more 

globose. Furthermore, the subsutural ornament consists of elongate ribs rather than nodes, and their 

inner edges are closer to the suture. 

The Late Mississippian (late Chesterian) form 

illustrated by Easton (1942, pl. 11, figs. 10, 11) from 

the Pitkin Limestone of northern Arkansas as Col-~ 

pites? sp. has a flattened outer whorl face and is 

almost lenticular in profile. If it is a Colpites, it is 

not at all typical. No top view of the specimen was 

provided, and we cannot suggest a substitute 

assignment. 

Figured specimens.-USNM 168474-168477. 

Occurrence and number of specimens.-Ranchester Limestone Member: collections 40 (2), Fremont 

County; 50 (holotype and two para types), Washakie County; 52 (1), Johnson County. 

Family uncertain 

New genus af. "Colpiles" sp. 

Plate 2, figures 6, 7 

Description.-Shell turbiniform, body whorl embracing penultimate whorl at periphery. Suture not 

impressed; upper whorl surface narrow, approximately horizontal and ramplike; outer whorl face 

convex, periphery approximately at mid whorl; 

curvature lessening below periphery but continuing 

smoothly to edge of umbilicus. Umbilicus narrowly 

phaneromphalus, without circumbilical angulation. 

Surface of shell elaborately ornamented by numerous spiral lirae with subequal interspaces ; at 

least 12 occur on outer whorl face and additional 

lirae on bottom. Juncture of ramp and outer face 

bearing 3 additional more prominent lirae, slightly 

wider spaced and interrupted by 21 to 23 prominent 

smooth nodes elongated normal to suture; spaces 

between nodes equal to 1 V2 times width of nodes. 

Growth lines unknown. 

Discussion.-Specimens in the U.S. National Museum collected by I. A. Keyte near Lander are the 

basis for the description above. These specimens, 

like all known specimens in the vicinity of Lander, 

are believed to have come from the Anthracospirifer welleri-shawi Zone of Late Mississippian age. 

The ramplike upper surface and elaborate spiral 

ornament of this species is not typical of any species 

of Colpites known to us. Very likely, a new genus 

will have to be erected for this form, but in the absence of growth lines or any indication pointing to 

the presence or absence of a selenizone, the material 

does not provide an adequate basis for erecting such 

a genus. The assumption of affinity to Colpites is on 

the basis of shape and presence of prominent subsutural nodes. 

Figured specimen.-USNM 168479. 

Occu'rrence and number of specimens.-Horseshoe Shale Member: collection E (2), Fremont 

County. 
GASTROPODA, CEPHALOPODA, AND TRILOBITA OF THE AMSDEN FORMATION F15 

Family LOPHOSPIRIDAE Wenz 

Genus WORTHENIA deKoninck, 1883 

W ortbenia? sp. indet. 

Plate 2, figure 8 

This identification is based on poorly preserved 

material from the Darwin Peak section, consisting 

of a steinkern partly covered by recrystallized shell 

material and matrix. Enough of the whorl profile 

can be seen to show. that this is a moderately high 

spired shell. A distinct upper whorl face slopes 

downward at an angle of about 30° to the horizontal 

(observed on middle whorl) ending at an upper 

angulation; the details of this face are unknown. 

The outer whorl face of the steinkern is inclined 

slightly inward from vertical and terminates below 

in a broad obscure basal angulation. The basal surface is gently inclined and slightly inflated; the base 

appears anomphalous, though the presence of an 

umbilical chink cannot be ruled out. No growth lines 

or details of ornament are preserved. The ridge 

marking the upper angulation is bordered by two 

shallowly concave zones; it resembles the selenizone 

in W orthenia. 

Figured specimen.-USNM 168480. 

Occurrence.-Horseshoe Shale Member: collection 137, Teton County. 

Family PHYMATOPLEURIDAE Batten 

Genus BORESTUS Thomas, 1940 

Borestus sp. indet. 

Plate 2, figure 9 

A moderately high spired turbiform gastropod 

preserved as a mold in chert at Bull Lake Creek in 

the Wind River Range is assigned this identification. Its early whorls are unknown. The suture is 

not prominent. The upper whorl surface is gently 

concave in profile, having a general inclination of 

approximately 45°. The outer whorl face is virtually 

vertical but also very slightly concave in profile; its 

curvature is accentuated by the sharp upper and 

lower angulations, both of which protrude beyond 

the general curvature of this face. The outer part of 

the basal surface is flattened and inclined downward, but other details of it are unknown. 

No growth lines are preserved. On the body whorl 

at one point, two obscure parallel markings suggest 

lirae along the outer face, the area between them 

occupying about one-third of the width. A reasonable interpretation is that these border a selenizone. 

The material at hand has a general shape closely 

similar to that of the type species of Borestus, B. 

wrig hti Thomas ; the lack of preserved ornamentation precludes identification as to species. 

Figured specimen.-USNM 168481. 

Occurrence.-Ranchester Limestone Member: collection 40, Fremont County. 

Borestus? sp. 

Plate 2, figure 10 

Description.-Shell turbiform, steplike, and elaborately ornamented; nucleus and early whorls unknown; body whorl embracing penultimate whorl at 

basal surface; suture distinct but not impressed. 

Upper surface of whorl sloping outward and downward, divided into two equal segments by fairly 

prominent, elevated sharp spiral cord along angulate juncture of two segments ; inner segment above 

spiral cord sloping at approximately 50° to vertical 

and likewise divided in two b~ smaller subcentral 

raised spiral lira; outer segment sloping downward 

at approximately 30° to vertical, concave in profile, 

terminating below at another sharp spiral lira. 

Outer face of whorl very steeply inclined, almost but 

not quite vertical, gently concave overall in profile, 

its lower edge protruding to form shell periphery; 

smooth curve of face interrupted by two rounded 

spiral lirae almost equidistant from upper and lower 

angulations, area bordered by these lirae occupying 

central half of outer face, appearing slightly flattened and depressed relative to gentle curvature 

above and below it; periphery accentuated by 

rounded cord. All details of base unknown. 

Growth lines prominent, raised, nearly the 

strength of spiral lirae; interspaces approximately 

twice as wide as growth lines. Growth lines normal 

to suture, but after crossing cord in middle of inner 

segment bending slightly opisthocline to central 

cord, where they turn slightly prosocline to upper 

angulation; on upper part of outer whorl face, 

growth lines become more strongly prosocline; central band between lirae apparently constitutes a 

selenizone, but no lunulae can be observed; on lower 

part of outer face, faint opisthocline growth lines 

present. 

Discussion.-One very well preserved but incomplete specimen, 7 mm high, consisting of parts of 

four whorls, is assigned to this genus. This specimen, preserved as an external mold, is from a bed 

on the east flank of the Bighorn Mountains. It 

represents an unnamed species and clearly has most 

of its salient characters, yet this material is not 

regarded as sufficient for the formal proposal of a 

name. This Amsden species differs from typical 

Borestus in the preservation of two fairly strong 

nodose cords on a convex upper whorl slope and 
F16 THE AMSDEN FORMATION (MISSISSIPPIAN AND PENNSYLVANIAN) OF WYOMING 

possibly could belong in an undescribed genus. It 

resembles Ptychomphalus similis deKoninck which 

Batten (1966, p. 50, pl. 5, fig. 18) has assigned to 

Borestus. 

Figured specimen.-VSNM 168482. 

Occurrence.-Ranchester Limestone Member: 

collection 52, Johnson County. 

Genus DICTYOTOMARIA Knight, 1945 

Dictyotomaria carlbransoni n. sp. 

Plate 2, figures 19-21 

Ptychomphalus wortheni Weller. C. Branson, 1937, p. 658, 

65-9, pl. 89, figs. 26, 27. 

Description.-Low-spired narrow-whorled turbiform pleurotomariacean having five rather prominent spiral Iirae on upper whorl surface. Nucleus 

and early whorls unknown. Shell broadly steplike in 

profile; body whorl embracing penultimate whorl at 

base; suture not accentuated. Upper slope of whorl 

straight in profile from suture to angulation, inclined about 30° to horizontal; outer face narrower 

than upper ~slope, almost vertical,. with periphery at 

basal angulation; basal surface gently convex, nearly 

flat and inclined strongly inward for approximately 

two-thirds of its length and then, after crossing an 

obscure subangulation, curving smoothly into a narrow umbilicus or umbiHc~al chink. 

Surface of shell ornamented by fairly strong 

spiral lirae, of which three occur on upper slope, a 

fourth at angulation, and a finer thread at suture; 

outer face having a fine lira a little below upper 

angulation, two lirae bordering selenizone, and a 

strong lira accentuating lower angulation; basal 

surface covered with closely spaced lirae, exact number unknown but no less than eight visible on outer 

half of this surface. Selenizone of moderate width, 

flat in profile between bordering lirae, occupying 

slightly less than half of outer whorl face and situated slightly above middle of that face. Growth lines 

orthocline on upper slope, minutely beading spiral 

lirae where they cross them, not visible on outer face 

and on base, except for closely spaced symmetrical 

lunulae within selenizone. Shell probably thin. 

The holotype has a height of 6.3 mm and a diameter of 7.3 mm. 

Discussion.-The holotype of this species is the 

shell of Late Mississippian age illustrated by C. C. 

Branson (1937, pl. 89, figs. 26, 27) as Ptychomphalus wortheni Weller. The '\tVyoming shell came 

from Little Popo Agie River in the Wind River 

Range. A second specimen in the same lot, consisting of part of the spire of a gastropod of similar 

size and shape, preserved in a limonitic crust, cannot be identified even as to genus. Questionably included in this species are three immature shells from 

the Little Popo Agie River (UM 6616) referred by 

C. C. Branson with question to Ptychompha,lus wortheni. All are depressed turbinate in shape and bear 

spirallirae. 

Although Branson (1937, p. 659) considered his 

material to agree in minute detail with Weller's 

species from the Ste. Genevieve Limestone of Illinois, several differences can be noted. The Amsden 

species has a proportionately lower whorl, one more 

lira on the upper slope of the whorl, and finer and 

more closely spaced lirae on the base. These basal 

lirae probably are also more numerous on the Amsden species, which has about as many on the outer 

half of the basal surface as P. wortheni has on the 

entire base. They have not been preserved, however, 

on the inner part of the base of the holotype of our 

new species. Dictyotomaria carlbransoni also appears to have a lower spire than the Ste. Genevieve 

shell, but partial wear on the spire of the holotype 

precludes a definite statement on this point. 

Batten (1958, p. 210) suggested that Dictyotomaria be reduced to the rank of a subgenus under 

Glyptotomaria Knight, 1945. He based this suggestion on the presence in the Pennsylvanian of species 

which seemed to him to bridge the gap between the 

strikingly different shapes of the two type species. 

However, upon examining specimens of the type 

species, we note that in Glyptotomaria apiarum 

Knight the growth lines are sweepingly prosocline 

from the suture to the upper edge of the selenizone. 

In Dictyotomaria scitula (Meek and Worthen) 

growth lines are nearly vertical below the suture 

and across several spiral Iirae; they are obliquely 

inclined for only a short distance from the lowest 

of the upper set of lirae to the edge of the selenizone. We believe this difference to be at least as 

significant as the presumed intergradation in shape 

and prefer to regard the geologically older Dictyotomaria as a full genus. 

Dictyotomaria carlbransoni is readily distinguished from D. scitula, because its upper whorl 

face is gently inclined and upper angulation fairly 

abrupt, whereas on the type species this surface is 

nearly horizontal and the upper angulation is 

strongly convex. D. scitula is far more steplike than 

in our species. The selenizone of D. carlbransoni is 

both slightly wider and slightly higher on the outer 
GASTROPODA, CEPHALOPODA, AND TRILOBITA OF THE AMSDEN FORMATION F17 

whorl face than in the type species. Some differences in the ornament are apparent, that of D. 

scitula being more elaborate, but the more subdued 

ornamentation of D. carlbransoni may be the result of poor preservation of the holotype in a limestone matrix. Other species assigned to the genus by 

Knight are markedly different in shape and need 

not be compared. 

Type.-Holotype UM 6626. 

Occurrence and number of specimens.-Horseshoe Shale Member: collection 36d ( 1, ?3), Fremont 

County. 

Family RAPHISTOMATIDAE Koken 

Genus BA YLEA deKoninck, 1883 

Baylea? sp. indet. 

Plate 2, figure 11 

This form, occurring as an internal mold in chert 

of Pennsylvanian age, is angulated turbiform in 

shape. Sutures are obscure but are set off by a very 

narrow ramp bordered by a prominent angulation. 

A concave area inclined outward and downward lies 

between this upper angulation and a lower, more 

ridgelike one. A slightly wider concave area, inclined almost vertically, forms the outer face; the 

angulation at its base protrudes to form the periphery. On the lower side of the periphery, the profile is 

concave and curves smoothly into the umbilical area. 

The shell is anomphalous. 

No growth lines are preserved. Generic assignment is therefore entirely arbitrary and based on 

gross similarity of shell form. 

Figured specimen.-VSNM 168483. 

Occurrence and number of specim,ens.-Ranchester Limestone Member : collection 40 ( 1) , Fremont 

County; 52 (1), Johnson County. 

Familv EOTOMARIIDAE Wenz 

Genus MOURLONIA deKoninck, 1883 

Mourlonia sp. indet. 

Plate 2, figures 12, 13 

A small specimen from a silty limestone bed of 

Pennsylvanian age on the east slope of the Bighorn 

Mountains is referred to this genus with considerable confidence. The shell has a spire of moderate 

height, the whorls embracing some distance below 

the periphery. The upper part of the whorl profile 

is flattened and ramplike at the suture, but otherwise slopes outward and gently downward, with increasing curvature in the outer part of this segment. The selenizone forms the outer face and appears as a flattened band slightly raised above the 

rounded whorl; although the selenizone is mainly 

vertical, its upper edge forms the periphery. Below 

this raised band the whorl profile curves inward for 

a short distance, but details of the lower part of the 

whorl and the base are not preserved. Growth lines 

are prosocline at an angle approximating 45° about 

midway between suture and selenizone, but their 

course cannot be traced on other parts of the shell ; 

several asymmetrical lunulae are preserved on the 

selenizone. The specimen, consisting of parts of five 

whorls, is 4.3 mm high and 4.5 mm in diameter. 

Although the presence of a broad selenizone on 

the periphery is a feature similar to that on the 

outer whorl face of Dictyotomaria, carlbransoni n. 

sp., the two shells have little in common and are 

readily distinguished. In D. carlbransoni the selenizone is flat and sunk between bordering lirae, rather 

than raised. Moreover, the shape of the two shells 

is different, the rounded profile of Mourlonia sp. 

indet. contrasting with the more angulated outline 

of the Dictyotomaria; the Mourlonia is also slightly 

narrower at a comparable whorl height. 

Figured specimen.-USNM 168484. 

Occurrence.-Horseshoe Shale Member: collection 5,3, Johnson County. 

Family GOSSELETINIIDAE Wenz 

Genus GOSSELETINA Fischer, 1885 

Gosseletina sp. indet. 

Plate 2, figures 14-16 

A specimen from the Carlinia amsdeniana Subzone at Livingston Ranch in the Washakie Range is 

assigned to this genus. The shell is littoriniform, its 

otherwise rounded-subconical profile slightly indented at the suture. No ramp is present, but the 

upper part of the outer face is more gently inclined 

than most of the length of this face. The periphery 

is low on the whorl, and below it the whorl curves 

smoothly inward so that no flattened basal area is 

present. The specimen appears anomphalus_ but may 

have a shallow umbilical chink. On the final part of 

the body whorl, markings on the steinkern suggest 

a broad shallow band bordered by grooves about 

one-third of the distance from suture to periphery. 

An even more obscure pair of lirae can be distinguished just above the periphery at the broken edge 

of the shell. Recrystallized calcite on the outer surface, which may be a remnant of the original shell, 

obscures all other details. 

The assignment of this species is based on general 

shape and the assumption that the band high on the 

whorl constitutes a selenizone. 

Figured specimen.-USNM 168485. 
F18 THE AMSDEN FORMATION (MISSISSIPPIAN AND PENNSYLVANIAN) OF WYOMING 

Occurrence.-Horseshoe Shale Member: collection 45, Fremont County. 

Gosseletina 1 sp. indet. 

Plate 2, figures 17, 18 

Naticopsis sp. Burk, 1954, p. 15. 

This record is based on a poorly preserved specimen that Burk (1954) assigned to Naticopsis. 

Three whorls are present, and their rate of expansion is significantly less than in naticopsids of comparable size. The whorl profile also is not typical of 

N aticopsis; it is steeply arched outward near the 

suture; then the curvature lessens so that the slope 

is flatter to the periphery, which is well below midwhorl; beyond the periphery the curvature follows 

a semicircle to complete the lower part of the whorl. 

The steinkern is not umbilicate, though a very narrow umbilical chink may be present. No shell is 

preserved. The presumed vertical striations noted 

by Burk appear to be vertical alinements of secondary calcite cryst·als and thus may be secondary 

features due to recrystallization of the shell. 

This specimen, not identifiable with certainty 

even as to genus, is questionably assigned to Gosseletina on the basis of its general shape. It is 

readily separable from Gosseletina sp. indet. by its 

more rounded whorl profile and its slightly narrower whorl. 

Figured specimen.-UW IT-242. 

Occurrence.-Horseshoe Shale Member: collection 35, Fremont County. 

Family PORTLOCKIELLIDAE Batten 

Genus SHANSIELLA Yin, 1932 

Shansiella sp. indet. 

Plate 2, figure 22 

An incomplete external mold of the upper part of 

a very low turbiniform shell is tentatively referred 

to Shansiella. At least six whorls are preserved; the 

first three are well rounded and smooth ; the rest are 

ornamented by prominent narrow spiral lirae, of 

which five are present and nearly equally spaced on 

the upper part of each whorl between the sutures. 

The suture is obscure, bounded by a ramp that ends 

at the first lira; the areas between each pair of lirae 

are increasingly steep downward, the one bordering 

the next suture being vertical. The greater part of 

the body whorl is not preserved. Growth lines and 

all other details are not known. 

This specimen is slightly higher spired than typical Shansiella carbonaria (Meek and Worthen), the 

common Pennsylvanian species. 

Figured specimen.-USNM 168486. 

Occurrence.-Ranchester Limestone Member: 

collection 52, Johnson County. 

Suborder TROCHINA 

Superfamily PLA TYCERA T ACEA Hall 

Fa:mily HOLOPEIDAE Wenz 

Genus YUNNANIA Mansuy, 1912 

Yunnania 1 sp. indet. 

Plate 2, figure 27 

Shells from Trout Creek on the west flank of the 

Bighorn Mountains are referred with question to 

this genus on the basis of shape somewhat. com~arable to Yunnania and the presence of spiral hrae. 

They are moder·ately high spired, of few whorls, a~d 

resemble modern Littorina. The whorl profile IS 

fairly well rounded and somewhat inflated, though 

a slight flattening is present on the upper half of 

the whorl. The sutures are deep. Few details can be 

seen of the shell surface. Spiral lirae occur near the 

periphery and extend onto the base; at least 10 of 

them can be counted. The columellar area is not 

known nor have any growth lines been observed. A 

faint depression at the aperture just above midwhorl may mark a selenizone between the spiral 

lirae but as it is not preserved on the rest of the 

shell' one can with equal reason assume no selenizone' is present and that a nonpleurotomarian she~l like Yunnania is represented. The incomplete specimen figured, consisting of about 2¥2 whorls, is 9.0 

mm high and 7.3 mm in diameter. 

Figured specimen.-USNM 168487. 

Occurrence and number of specimens.-Ranchester Limestone Member: collection 50 (3), Washakie 

County. 

Family PLATYCERATIDAE Hall 

Genus STROPHOSTYLUS Hall, 1859 

Strophostylus sp. indet. 

Plate 2, figures 31, 32 

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

Two steinkerns were referred to this genus by C. 

C. Branson but not illustrated. The more complete 

one is figured here merely for documentation. It is 

depressed lenticular in shape and expands rapidly. 

No external characters are preserved. 

Figured specimen.-UM 6645. 

Occurrence.-Horseshoe Shale Member: collection 36d, Fremont County. 

Superfamily MICRODOMA T ACEA Wenz 

Family MICRODOMATIDAE Wenz 

Genus MICRODOMA Meek and Worthen, 1867 

Microdoma 1 sp. indet. 

Plate 2, figure 36 

A small incomplete external mold is referred with 

question to this genus. The sutures are impressed, 
GASTROPODA, CEPHALOPODA, AND TRILOBITA OF THE AMSDEN FORMATION F19 

the whorl embracing on the base a little below the 

periphery. The outer face is flat in profile and inclined steeply downward to an expanded rounded 

periphery clearly delimited from the upper surface; 

below the periphery the whorl curves abruptly into 

the flattish base. Details of the base are not preserved. The periphery is ornamented by a row of 

nodes, elongated upward, separated by interspaces 

about as wide as the nodes ; an estimated 20 nodes 

occur on each whorl. The nodose periphery is on a 

raised ridge set off from the general inclination of 

the whorl face. 

Typical Microdoma has three rows of nodes on 

each whorl. The single row on the Amsden form 

combined with a complete lack of evidence as to the 

course of the growth lines is responsible for our 

questioning the generic assignment. However, no 

closely related genus is known. 

Figured specimen.-USNM 168488. 

Occurrence.-Ranchester Limestone Member: 

collection 40, Fremont County. 

Family ELASMONEMA TIDAE Knight 

Genus ANEMA TINA Knight, 1933 

Anematina sp. indet. 

Plate 2, figure 28 

Two small external molds in chert, one preserving 

at least five whorls, are referred to this genus. The 

shell is high subconical in shape, its sutures distinctly impressed, and the periphery at the base of 

the slope narrowly rounded. The whorls embrace on 

the outer edge of the basal surface. The outer whorl 

face below the overhanging preceding whorl is 

steeply inclined and principally flat, sloping at an 

angle of 60° to the vertical axis of the shell. Growth 

lines on the surface are straight and steeply prosocline at an angle of about 20° to the vertical. 

Figured specimen.-USNM 168489. 

Occurrence and nutnber of specimens.-Ranchester Limestone Member: collection 40 (2), Fremont 

County. 

Suborder NERITOPSINA 

Superfamily NERIT ACEA Rafinesque 

Family NERITOPSIDAE Gray 

Genus NA TICOPSIS M'Coy, 1844 

Naticopsis (Naticopsis) spp. indet. 

Plate 2, figures 23, 24 

A Mississippian species is readily identified as 

Naticopsis s.s. by its exceedingly low spire, globose 

shape, and rapid expansion of the whorl. The shell 

material is not preserved, and the early growth 

stages are therefore obscure. No more than two 

complete whorls seem to be present in the best preserved of three specimens in a collection from the 

Darwin Peak section. Patches of calcite adhere to 

the steinkern; these almost certainly result from 

recrystallization of the shell. Recrystallization of 

shells preserved in a limestone matrix is common in 

N aticopsis and may be a consequence of their thickness and aragonitic composition. 

The illustrated specimen is the only one complete 

enough to be identified with certainty. The other two 

are comparable in size and show part of the whorl 

and similar crystallization of the shell material. Another shell, from Wiggins Fork, may belong here 

but is too poorly preserved for one to be certain even 

of its generic assignment. 

Three poorly preserved specimens from a bed of 

Pennsylvanian age on the west side of the Bighorn 

Mountains are also referred here, but represent a 

different species as they are slightly higher spired. 

They differ in overall shape from Colpites sp. A, 

with which they are associated. These shells expand 

more rapidly and have a higher, less well rounded 

whorl than C. sp. A. 

The specimen listed by Burk (1954, p. 15) as 

N aticopsis sp. is assigned here to Gosseletina? sp. 

indet. 

Figut·ed specimen.-USNM 173606. 

Occurrence and number of specimens.-Horseshoe Shale Member: collections ?48 (1), Fremont 

County; 137 (3), Teton County. Ranchester Limestone Member: collection 50 (3), Washakie County. 

Subgenus NA TICOPSIS (JED RIA) Yochelson, 1952 

Naticopsis (Jedria ?) sp. indet. 

Plate 2, figures 25, 26 

Another Mississippian N aticopsis present in the 

Amsden fauna differs from the typical subgenus in 

having the aperture produced strongly downward. 

Shells of this shape are generally referred to the 

subgenus N. (Jedria) Yochelson. Specimens of both 

subgenera are comparable in size. On the single 

specimen from Livingston Ranch, a slight suggestion of a subsutural shoulder is present, and some 

indication of impressed growth lines can be seen in 

this area. The poor preservation, however, precludes 

positive demonstration of these features, and therefore the subgeneric assignment is questioned. Naticopsis ( J edria) has not previously been illustrated 

from North American beds of Mississippian age. 

Figured specimen.-USNM 173607. 

Occurrence.-Horseshoe Shale Member: collection 

45, Fremont County. 
F20 THE AMSDEN FORMATION (MISSISSIPPIAN AND PENNSYLVANIAN) OF WYOMING 

Order ARCHAEOGASTROPODA? 

Suborder MURCHISONIINA 

Superfamily MURCHISONIACEA Koken 

Family MURCHISONIIDAE Koken 

Genus GONIASMA Tomlin, 1930 

Goniasma? sp. indet. 

Plate 2, figure 30 

High-spired gastropods with an angulation near 

but slightly below midwhorl are assigned with question to Goniasma. These occur as molds in a granular chert bed of Pennsylvanian age near the top of 

the formation on the east flank of the Bighorn 

Mountains. The suture of this form occurs at the 

narrowest part of the whorl but does not indent the 

shell profile in any way. About three-fifths of the 

whorl is above the angulation and is gently concave 

in profile; the other part below the angulation is 

very gently convex. No growth lines are preserved, 

and although there is a high probability that a 

selenizone was present, its position on the surface 

of the whorl cannot be determined. 

Figured specimen.-USNM 173608. 

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

County. 

Genus MURCHISONIA d' Arcbiac and de Verneuil 

Murcbisonia? sp. indet. 

Plate 2, figure 37 

Another high-spired gastropod occurs with Goniasma? sp. indet. but lacks its distinctly keeled profile. Instead, the whorls are broadly subangular to 

subrounded in profile. The pleural angle is slightly 

narrower than in Goniasma? sp. indet., and the 

individual whorls are correspondingly wider. The 

sutures also are not deeply incised. No growth lines 

are preserved, and no spiral ornament is present to 

even suggest the position of the selenizone. 

Figured specimen.-USNM 173609. 

Occurrence and number of specimens.-Ranchester Limestone Member: collection 52 (2), Johnson 

County. 

Order CAENOGASTROPODA 

Superfamily LOXONEMA T ACEA Koken 

Family PSEUDOZYGOPLEURIDAE Knight 

Genus PALAEOSTYLUS Mansuy, 1914 

Palaeostylus (Pseudozygopleura} spp. indet. 

Plate 2, figure 38 

Loxonema wortheni Weller. Branson and Greger, 1918, p. 

324, pl. 18, fig. 6. 

Solenospira pygmaea Weller. C. Branson, 1937 [part], p. 

658. 

Distinction between Loxonema and some of the 

pseudozygopleurids is difficult, particularly if the 

characteristic nuclear whorls are missing. Both 

Palaeostylus (Pseudozygopleura) and Loxonema 

have prominent collabral costae ornamenting the 

shell surface. Reassignment to P. (Pseudozygopleura) of Branson and Greger's specimen from 

Cherry Creek, which they illustrated (at approximately .natural size, not x 2 as indicated in the plate 

description) as Loxonema wortheni Weller, is based 

on characters of the ribs. The specimen is not refigured here. In this specimen, the costae, where 

present, are virtually orthocline and die out abruptly just below the periphery, whereas in Loxonema 

the costae tend to continue across the entire width 

of the whorl and to be sinuate. Three more specimens of this same form, broken but preserving the 

axial costae, were found in a lot collected by C. C. 

Branson from the same region and labeled "Solenospira pygmaea" (UM 6628). 

In addition, the figured specimen, preserved as a 

mold in a chert bed of Pennsylvanian age, is also 

assigned to this subgenus. Its costae are straight 

and stronger than in the Cherry Creek form, so that 

one cannot ascertain whether or not they die out 

below the periphery. Easton (1962, p. 100, pl 13, 

fig. 11) has figured a similar though not identical 

specimen from the Cameron Creek Formation of 

central Montana. 

Probably three distinct species are represented 

by the Mississippian Cherry Creek specimens, the 

Pennsylvanian mold, and Easton's Cameron Creek 

shell. None of the material is complete enough to 

warrant erecting a new name. 

The basal part of a steinkern with a small worn 

patch of shell on the base is also referred here but 

with considerable question. Its shape agrees with 

that of P. (Pseudozygopleura), but no sculpture ran 

be seen. The specimen i~ from beds of Pennsylvanian age in the Rawlins hills. 

Figured specimen.-USNM 173610. 

Occurrence and number of specimens.-Horseshoe Shale Member: collections ?3 ( 1) , Car.bon 

County; 36a (1), 36d (3), Fremont County, Ranches,ter Limestone Member: collection 40 ( 1), Fremont County. 

Superfamily CERITHIACEA 

Family TURRITELLIDAE 

Genus ORTHONEMA Meek and Worthen. 1862 

Ortbonema sp. indel. 

Plate 2, figure 29 

Among the high-spired gastropods Orthonema i!s 

rather easily recognized. No other form is known 

that combines a nearly vertical flattened whorl, 
GASTROPODA, CEPHALOPODA, AND TRILOBITA OF THE AMSDEN FORMATION F21 

somewhat turreted on top, with weak spiral sculpture. The turreting, in which individual whorls protrude abruptly and distinctly for a short distance 

adjacent to the suture, produces the effect of an 

extremely narrow high staircase. Details of the 

growth lines are not preserved in our specimens, 

one of which is an external mold and the other an 

incomplete steinkern. 

Figured specimen.-USNM 173611. 

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

County; 50 (1), Washakie County. 

Superfamily SUBULITACEA Lindstrom 

Family SUBULITIDAE Lindstrom 

Genus IANTHINOPSIS Meek and Worthen, 1866 

Ianthinopsis spp. indet. 

Five specimens from beds of Mississippian age 

are tentatively assigned to this genus. One, from 

Cherry Creek (USNM 173612) is a limonitic steinkern that has been crushed flat and thus shows no 

meaningful details. Four whorls are present, showing embracement rather high on the outer whorl 

face, well above the periphery. The broken aperture 

seems to be produced downward in a siphonlike 

extension. The associated silicified brachiopods are 

typical of the Composita poposiensis Subzone. 

Three additional limonitic steinkerns were found 

in a lot of 67 gastropods labeled "Solenispira pygmaea" in the University of Missouri collection (UM 

6628) and are referred with some question to this 

genus. These were collected at Little Popo Agie 

River. They are partly crushed and resemble specimens referred here to Girtyspira sp. A, but are 

slightly more tumid and shorter spired. 

Finally, a steinkern from the collection of Yale 

University's Peabody Museum (YPM 20105) collected at Wiggins Fork is referred here with some 

question. Although this specimen is uncrushed, it is 

not complete, showing only part of the globose, 

slightly elongate body whorl. This shell is twice the 

size of the Cherry Creek specimen. Because of 

differences in preservation, comparison between the 

specimens is not possible. None of the specimens 

warrants illustration. 

Occurrence and number of specimens.-Horseshoe Shale Member: collections ?36d (3), 36e (1), 

?48 (1), Fremont County. 

Genus SOLENISCUS Meek and Worthen, 1861 

Soleniscus? sp. indet. 

Plate 2, figures 40, 41 

A steinkern showing the body and penultimate 

whorls is referred with question to this genus. The 

body whorl is inflated elongate with little constriction at the suture. The columellar lip is produced 

downward but is broken, so that we cannot determine whether or not a columellar fold is present. 

This specimen is higher spired than those that have 

been assigned to Ianthinopsis spp. indet. but wider 

than those referred to Girtyspira. 

Figured specimen.-USNM 173613. 

Occurrence.-Ranchester Limestone Member: 

collection 50, Washakie County. 

Family MEEKOSPIRIDAE 

Genus MEEKOSPIRA Ulrich 

Meekospira? sp. indet. 

Plate 2, figure 39 

The presumedly advanced Paleozoic gastropods 

of the Order Caenogastropoda commonly are less 

well preserved than those of the Order Archaeogastropoda. The Wyoming material is no exception 

to this generalization. Possibly this is a reflection of 

shell architecture, which may be more susceptible to 

recrystallization or solution in the caenogastropods. 

This particular species is represented by a steinkern and a poorly preserved external mold which is 

illustrated. Flattened whorls and an absence of ornament combined with relatively high whorls and a 

narrow pleural angle are the characters upon which 

the tentative assignment to M eekospira is based. 

This shell is much more slender and has more whorls 

than the more common Mississippian ones assigned 

to Girtsyspira sp. 

Figured specimen.-USNM 173614. 

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

County. 

Genus GIRTYSPIRA Knight 

Girtyspira sp. A 

Plate 2, figures 42, 43 

Bulimorpha canaliculata, (Hall). Branson and Greger, 1918, 

p. 322, 323, pl. 19, fig. 15. 

Soleniscus (Bulimorpha) bulimiformis (Hall). C. Branson, 

1937, p. 658. 

The specimen from Cherry Creek figured by 

Branson and Greger (UM 2659) is a flattened 

limonitic steinkern indeterminate as to species; because of its distortion, it has not been refigured. 

The shells figured here are from material collected 

later by C. C. Branson in the same region and provide more details. This lot (UM 6629) was referred 

by him (C. C. Branson, 1937, p. 658) to Soleniscus 

(Bulimorpha) bulimiformis (Hall). 

The shell is high spired, the whorls higher than 

wide. The suture is impressed, but most of the whorl 

profile is gently convex, the periphery occurring near 
F22 THE AMSDEN FORMATION (MISSISSIPPIAN AND PENNSYLVANIAN) OF WYOMING 

mid whorl. The body whorl is moderately long; the 

columellar lip is very slightly reflexed and produced 

downward. The shell surface is polished except for 

fine growth lines, most of which are striae; they are 

very steeply prosocline, approaching orthocline in 

course. 

This species is higher spired and has more whorls 

for its size than Girtyspira canaliculata (Hall), to 

which the first specimen was referred by Branson 

and Greger (1918). It differs also from Bulimorpha 

bulimiformis (Hall), to which the Amsden form was 

referred by C. C. Branson, in having a proportionately longer body whorl and a higher spire. 

Although these shells do not seem to be referrable 

to any previously described species, the lack of complete information as to the shape of the aperture 

causes us to feel that no formal name should be proposed for it at this time. 

Figured specimens.-UM 6629. 

Occurrence and num,ber of specimens.-Horseshoe Shale Member : collections 36a ( 1) , 36d ( 4) , 

Fremont County. 

Girtyspira sp. B 

Another species of Girtyspira is represented by 

three broken and very incomplete steinkerns from 

a bed of Pennsylvanian age. The whorl is very 

slightly wider than in the Mississippian form, with 

greater curvature and less development of a shoulder in the sutural area. The proportion of height to 

width is mainly the same as in Girtyspira sp. A but 

is very difficult to estimate. The specimens do not 

warrant figuring. 

This species, like Girtyspira sp. A, differs from 

M eekospira? sp. indet. in having a wider pleural 

angle. 

Occurrence and number of specimens.-Ranchester Limestone Member: collection 50 (3), Washakie 

County. 

Order uncertain 

Superfamily PYRAMIDELLACEA 

Family STREPTACIDAE 

Genus DONALDINA Knight, 1933 

Donaldina aff. D. pygmaea (Weller) 

Plate 2, figure 44 

Solenospira pygmaea Weller. C. Branson, 1937 [part], p. 658. 

Donald ina sp. cf. D. tenuis (de Koninck). Elias, 1958, p. 20, 

21, pl. 2, fig. 5, text fig. 1. 

This rec.ord is based on 15 specimens from a lot of 

64 gastropods, no. 6628 in the University of Missouri collection, labeled "Solerwspira pygmaea" and 

collected by C. C. Branson at Little Popo Agie River~ 

These are presumably the specimens cited under 

this name by Branson (1937). One of them is 

figured here. The lot also contains several specimens 

referrable to Palaeostylus (Pseudozygopleura) and 

I anthinopsis and numerous unidentifiable small 

high-spired snails covered with a limonitic coating. 

The better shells of Donaldina in this lot have 

apical angles approximating 20°, gently convex 

whorls, and rather deeply impressed sutures; spiral 

lirae and finer threads provide the main ornamentation. Most of the shells have six or seven moderately strong lirae ornamenting the lower three fourths 

of the whorl, becoming more closely spaced downward. The best preserved specimen, which is illustrated, also shows three finer, closely spaced faint 

threads on the upper one-fourth of the whorl, above 

the highest of the stronger lirae. As many as five 

similar fine lirae are present on the base, becoming 

weaker toward the umbilical area. This specimen, 

lacking parts of base and spire, is 8.2 mm long. 

Comparison of our specimens with the description and figures of Donaldina cf. D. tenuis (de 

Koninck), described by Elias 1958) from the Redoak Hollow Formation of southern Oklahoma, suggests that the Amsden and Redoak Hollow forms 

are conspecific, agreeing in shape, apical angle, and 

number of both coarse and fine lirae on the whorls. 

On the other hand, direct comparison of the Amsden specimens with topotypes of Donaldina pygmaea 

(Weller) from the Ste. Genevieve Limestone at 

Waterloo, Ill., which Elias (1958) placed in synonymy with the Redoak Hollow form, convinces us that 

the Illinois species is distinct from the Wyoming and 

Oklahoma one. D. pygmaea has a smaller shell, each 

whorl bearing four or five lirae on the lower threefourths of the whorl; no fine lirae have been distinguished. Both the American species are closely 

related to but not regarded as conspecific with 

Donaldina tenuis (de Koninck) from the Tournaisian of Belgi urn. 

The Amsden material is not complete enough nor 

well enough preserved to serve as a basis for erecting a new name for this late Chesterian species. 

Figured specimen.-UM 6628. 

Occurrence and nnmber of specimens.-Horseshoe Shale Member: collection 36d (15), Fremont 

County. 

Donaldina sp. indet. 

Plate 2, figure 45 

This rec'Ord is based on a specimen from the ea:st 

slope of the Bighorn Mountains. In spite of the 

coarseness of its preservation in granular chert, at 
GASTROPODA, CEPHALOPODA, AND TRILOBITA OF THE AMSDEN FORMATION F23 

least five closely spaced spiral lirae can be observed 

on one whorl. This feature and the slender shape, 

the flattened whorl profile, and the slightly impressed sutures support the identification of the 

specimen as a Donaldina, even though the specimen 

lacks the characteristic heterostrophic nucleus. 

Figured specimen.-USNM 173615. 

Occurrence.-Ranchester Limestone Member: 

collection 52, Johnson County. 

Class CEPHALOPODA 

Sublcass NAUTILOIDEA 

Order ORTHOCERIDA 

Superfamily PSEUDORTHOCERA TACEA Flower and Caster 

Genus RETICYCLOCERAS Gordon, 1960 

Reticycloceras 1 sp. indeL 

Cycloceras sp.? Branson and Greger, 1918, p. 324. 

Branson and Greger (1918) reported collecting a 

fragment of a cyclocerid nautiloid resembling the 

species now known as Reticycloceras sequoyahensis 

(Snider), which occurs in the Fayetteville Shale and 

Pitkin Limestone of Arkansas and Oklahoma. Unfortunately, the Amsden specimen was never figured 

and was not placed in the collection at the University of Missouri, so we have not been abe to study it. 

Superfamily unknown 

Family unknown 

Ortboconic nautiloid, gen. and sp. indet. 

Orthoceras sp.? Branson and Greger, 1918, p. 324. 

Two fragments of an orthocerid nautiloid were 

also recorded by Branson and Greger (1918). These 

are not in the collection at the University of Missouri and have not been studied. 

Subclass AMMONOIDEA 

Superfamily GONIA TIT ACEA deHaan 

Family HOMOCERATIDAE Spath 

Genus CRAVENOCERATOIDES Hudson, 1941 

Cravenoceratoides sp. indet. 

Plate 2, figures 33-35; figure 2 

Goniatite, Burk, 1945, p. 15. 

Cravenoceras [sp.]. Sadlick, 1960, p. 1211. 

Description.-Conch subglobose, moderately involute, diameter of umbilicus equal to slightly less 

than one-third shell diameter; venter broadly convex, rounding gradually into steep but narrow 

flanks; umbilical shoulder narrowly rounded. Surface of internal mold ornamented by low flat transverse lirae, either faintly but distinctly dichotomous 

or increasing by intercalation on flanks between umbilical shoulder and ventrolateral zone; course of 

lirae nearly straight but bulging very slightly orad 

ventrolaterally and similarly bowed almost imperceptibly apicad over venter. Outer shell surface not 

known. 

Suture at diameters of 6 to 8 mm (fig. 2) has 

ventral lobe of moderate width, with fairly straight 

FIGURE 2.-External suture of Cravenoceratoides sp. indet., 

X 8, at a diameter of slightly more than 6 mm. 

sloping sides diverging adorally and terminating 

adapically in short rounded prongs. First lateral 

saddle slightly wider than ventral lobe and broadly 

rounded adorally; first lateral lobe symmetrical, 

rounded adapically, and about same width as ventral lobe. Second lateral saddle fairly low and curving asymmetrically across umbilical shoulder; umbilical lobe not clearly distinguishable, but shallow 

and located on outer part of umbilical wall. Fifteen 

camerae present on final volution. 

Dimensions and proportions.-Although the only 

shell available is partly crushed from front to back, 

measurements (in millimeters) taken in plane of 

adoral end are reasonably undistorted: diameter 8.3, 

height of last whorl 4.0, width of last whorl 6.2, 

diameter of umbilicus 2.6 mm. These give the following shell ratios: U/D = 0.31, W /D = 0.75, and 

W/H=1.55. 

Discussion.-The unique specimen upon which 

this description is based is a small septate internal 

mold of a goniatite collected by C. A. Biggs in float 

60 to 90 feet above the base of the Amsden Formation at Cherry Creek. It was mentioned by Burk 

(1954) but not identified as to genus. Later, Sadlick 

(1960, p. 1211) identified it as a "Cra'oenoceras exhibiting coarse ornamentation similar to C1·avenocerras scotti Miller & Youngquist." 

This specimen is figured for the first time. Its 

assignment to the genus Cravenoceratoides is on the 

basis of its dichotomous transverse lirae that show 

faintly on the internal mold. Presumably, if the 

shell surface were preserved, the lirae would be seen 

to be rather prominent and elevated. This genus is 

typical of the upper part of the Eumo1·phoceras bisulcatum, (E2 ) Zone which occurs in the Namurian 

A Substage of Europe and its equivalents in other 

parts of the Northern Hemisphere. A related form, 

Cravenoceratoides cf. C. nititoides (Bisat), slightly 

more involute than the Amsden one and preserving 

the surface sculpture, has been reported from the 
F24 THE AMSDEN FORMATION (MISSISSIPPIAN AND PENNSYLVANIAN) OF WYOMING 

Rest Spring Shale (as Chainman Shale) of the Inyo 

Mountains, Inyo County, Calif., by Gordon (1964, 

p. A16, A17, pl. 4, figs. 18-23). The containing beds 

in California and in Wyoming are presumably of 

about the same age, very late Chesterian (latest 

Mississippian). 

Figured specimen.-VW IT-243. 

Occurrence.-Horseshoe Shale Member: collection 35, Fremont County. 

Family uncertain 

Goniatitacean, gen. and sp. indet. 

A small external mold in chert of an ammonoid 

(USNM 173621) preserving the protoconch and 

slightly more than 21f2 volutions of the shell is too 

immature to be assigned to a genus. The shell is 

thick discoidal at a diameter of 4 m.m. The whorl is 

rather rapidly expanding, oval in cross section, and 

wider than high; the greatest diameter is near midwhorl where the curvature is greatest. Faint growth 

lines on the final one-third volution are straight 

across the umbilical wall to the periphery, which is 

located at mid whorl. No sutural elements are 

preserved. 

The low, rapidly widening whorl of this form 

places it in the suborder Goniatitina rather than in 

Prolecanitina and indicate the superfamily Goniatitacea as the most likely major category for assignment of this early Pennsylvanian form from Bull 

Lake Creek in the Wind River Range. Its small size 

and lack of evidence as to the character of its suture 

preclude more precise assignment of this shell. 

Occurrence.-Ranchester Limestone Member: 

collection 40, Fremont County. 

Phylum ARTHROPODA 

Class TRILOBITA 

Order PTYCHOP ARIIDA 

Suborder ILLAENINA 

Superfamily PROET ACEA Salter 

Family PHILLIPSIIDAE Oehlert 

Genus PALADIN Weller, 1936 

Discussion.-This genus was erected by Weller 

(1936, p. 707) for Grifjithides morrowensis Mather 

and related species that have the cephalon bearing a 

flat marginal band anterior to the glabella, which is 

expanded in front. The eyes are large and the basal 

furrows only slightly curved. Following a thorax of 

nine segments, the pygidium is bordered by a distinct smooth flange without continuations of the 

interpleural furrows, except at the anterior end. 

Typically, 14 to 16 axial rings and 9 or 10 pleurae 

are present. 

Weller considered Paladin to differ from Kaskia, 

which he erected (Weller, 1936, p. 708) for K. 

chesterensis ( S. Weller and J. M. Weller) , and related species, in which the marginal band in front 

of the glabella is obsolete or lacking entirely. Subsequent workers (Whittington, 1954; Cisne, 1967; 

Chamberlain, 1969) have generally regarded Paladin and Kaskia as intergrading and therefore congeneric; Whittington used Weller's two taxa as subgenera. 

So far as the Amsden species are concerned, 

whether one includes the species of Weller's Kaskia 

in Paladin or not is academic, as both Amsden forms 

possess a distinct shelflike marginal band in front 

of the glabella and belong, therefore, in Paladin in 

Weller's more restricted sense. For other American 

species included in Paladin s.l., the reader should 

refer to the papers of Cisne ( 1967) and Chamberlain ( 1969) . 

Paladin moorei (C. Branson) 

Plate 1, figures 23-32 

Grijjithides moorei C. Branson, 1937, p. 659, 660, pl. 89, figs. 

28-31. 

Paladin moorei (C. Branson). Gordon, 1969, p. 38. 

Descrription.-Cranidium having moderately convex subparallel-sided glabella, slightly constricted 

medially, bordered by fairly distinct axial and preglabelar furrows and set off by deep occipital furrow; lateral preoccipital glabellar lobes set off by 

deep diagonal furrows; frontal lobe expanded laterally. Glabella 1.4 times longer than wide and 11.4 

times wider anteriorly than posteriorly; greatest 

height about one-quarter of way forward from posterior end. Three pairs of faint lateral glabellar furrows visible on holotype, in addition to the preoccipital pair. 

Anterior border gently convex on top forming 

frontal shelf, about one-eighth as long as glabella, 

rounded in front. Fixigenae widest opposite frontal 

lobe of glabella, narrow anterior to palpebral lobes, 

which are strongly posterior in location, centering 

on front part of preoccipital glabellar lobes. Palpebral lobes one-third to three-eighths as long as glabella; palpebral furrows moderately deep. Occipital 

ring moderately wide, convex in sagittal cross section, sloping anteriorly. Occipital furrow deep, 

particularly behind lateral preoccipit~l, lobes and 

posterior end of glabella, and subangular in cross 

section. 

Anterior border of cranidium ornamented by as 

many as 10 fine terrace lines. On posterior part of 

glabella, dorsum ornamented by fine to moderately 

coarse granules, granules largest near posterior end 
GASTROPODA, CEPHALOPODA, AND TRILOBITA OF THE AMSDEN FORMATION F25 

and bordering preoccipital glabellar furrows. About 

five granules occur at summit of each lateral preoccipital lobe; finer granules dorsally on palpebral 

lobes. Fairly prominent mesial tubercle just posterior to center of occipital lobe and about a dozen 

granules along posterior edge. 

Librigenae having steeply sloping lateral border 

marked by fine subparallel terrace lines; border 

forming obtuse angle with upper surface outside 

lateral furrow. Genal angle produced into moderately long spine; details of tip unknown. Slope between 

eye and furrow marked by fine granules. Visual surface of eye crescentic, relatively narrow for genus. 

Full details of thorax not known. First thoracic 

segment showing row of granules along posterior 

edge. 

Pygidium parabolic in outline, width equal to 

roughly 11;4 times length. Axis of moderate height, 

about one-third width of pygidium at anterior end, 

gently convex on top, having sloping, slightly concave sides; at maturity bearing 16 to 17 axial rings 

and 10 to 11 pleurae on each of pleural lobes. Axial 

rings narrow, rounded, ornamented by seven to nine 

tiny elongate granules along posterior edge. Pleurae 

moderately narrow, subrounded, their greatest elevation slightly posterior to middle, ornamented by 

scattered granules. Interpleural furrows subangular 

and moderately deep. 

Border of pygidi urn smooth, sloping less steeply 

than outer edge of pleural lobe and set off from 

pleural field by abrupt termination of pleurae at 

change in slope. Inner part of border flat to slightly 

concave; outer part steeper and slightly convex. 

Dimensions.-Cranidia of holotype and University of Wyoming specimen A57 measure, respectively: length 9.3 and 8.5 mm, width 8.0 and 7.0 mm. 

Three pygidia, two of them paratypes (UM 6625, 

USNM 173617, and UM 6592) measure: length 7.0, 

5.3, and 5.1 mm, width 8.8, 6.6, and 6.2 mm. 

Discussion.-The holotype is a cranidium crushed 

against an incomplete pygidium, probably belonging to the same individual. No librigena is preserved, but one crescentic section of the visual surface of the eye is fused, slightly out of place, to a 

palpebral lobe of the cranidium; a fragment of the 

first thoracic segment is fused to the occipital ring. 

The crushed pygidium is complete axially and bears 

17 axial rings and 11 pleurae. As the specimen does 

not appear to have changed since the original figures 

were made, the mention by Branson (1937, p. 659) 

of 8 thoracic segments as well as a pygidium of 18 

segments is puzzling. Reexamination of the specimen (pl. 2, figs. 29, 30) shows that, except for the 

fragment of the first thoracic segment fused to the 

occipital ring, the thorax is missing. 

Our description is based on Branson's type material and three additional specimens from the University of Wyoming collection, including an undistorted cranidium (A57) which is figured here (pl. 

1, fig. 26). Also referred to this species and figured 

here (pl. 1, figs. 23-25) is a pygidium having 17 

axial rings and 10 pleurae, from the Moffat Trail 

Limestone Member in western Wyoming. The lateral glabellar furrows mentioned in the description 

are seen not too distinctly on the two cranidia ; the 

positions of these weak furrows on the two glabellae 

indicate that at least three pairs may be present in 

addition to the deep basal or preoccipital pair. 

The specimen listed by Branson and Greger 

(1918, p. 324) as Phillipsia sp.? does not appear in 

the list of Sacajawea Formation fossils compiled by 

C. C. Branson ( 1937, p. 652-653). We have not 

found the specimen in the University of Missouri 

collection, and as Paladin moorei is the only species 

known from the Mississippian part of the Amsden, 

presumably it belongs here. 

Specimens from the Heath and "Cameron Creek" 

Shales of Montana described and figured by Easton 

(1962, p. 103, pl. 13, figs. 27-28b) as Ameura? sp. 

possibly belong in P. moorei. The pygidia have 16 to 

19 axial rings and 11 pleurae and are parabolic in 

outline; the axial rings each bear about 6 or 7 large 

granules along the posterior edge. One small cranidium illustrated by Easton from the "Cameron Creek" 

in the Delpine section clearly belongs in Paladin, 

but its somewhat worn dorsal surface seems to be 

somewhat more finely granular than the holotype 

of P. moorei. Sando, Gordon, and Dutro (in press) 

showed that the beds referred by Easton to the 

"Cameron Creek" at Delpine, Mont., are W·ell down 

in the Mississippian (Chesterian) and do not actually represent the true Cameron Creek unit of sections 

in the Big Snowy Range. Contrariwise, the specimen described and figured by Easton (1962, p. 103, 

pl. 13, fig. 29) as Paladin? sp. does indeed come 

from the Cameron Creek Member of the Tyler Formation (Maughan and Roberts, 1967, pl. 4) but is 

Pennsylvanian (Morrowan) in age and should be 

referred to Ditomopyge. 

Comparisons and affinities.-This species is 

among those that have a well-developed frontal lobe 

protruding as a narrow shelf bordering the glabella, 

which is slightly expanded in front. In this respect 

it is like P. helmsensis Whittington, P. morrowensis 
F26 THE AMSDEN FORMATION (MISSISSIPPIAN AND PENNSYLVANIAN) OF WYOMING 

(Mather), P. mucronatus (Girty), P. pyriformis 

Chamberlain, and P. retrolatus Chamberlain. 

The Wyoming species differs from nearly all the 

other species in this group in having 17 axial rings 

and 11 pleurae on the adult pygidium (most of the 

other species of Paladin having 14 to 16 axial rings 

and 9 or 10 pleurae), also in the relatively large 

number, possibly 4 pairs, of lateral glabellar lobes 

on the cranidium. Only one other species, P. helmsensis, has been reported to have so many axial rings 

and lateral glabellar lobes. 

P. helmsensis differs from P. moorei in having a 

slightly smaller, more depressed carapace. Although 

the cranidium of P. helmsensis bears 4 pairs of 

lateral glabellar furrows, the preoccipital pair is 

shallower and the preoccipital lobes lower than in 

P. rnoorei; also the glabella is less expanded anteriorly, its anterior width only 1.1 times the posterior 

width, instead of the 11,4 times in P. moorei. P. 

helmsensis commonly has only 15 or 16 axial rings 

on the pygidium and only exceptionally 17, but in 

P. moorei, the normal number is 17. Finally, the 

granules ornamenting the axis of both species are 

much finer and more closely spaced in P. helmsensis 

than in P. moorei. 

Types.-Holotype, UM 6605; paratypes, UM 6592 

(pygidium), 6600 (librigena), 6625 (pygidium and 

fragments of four pygidia, two genal spines, and 

three indet.); hypotypes UW A57 (cranidium) and 

USNM 173617 (pygidium). 

Occurrence and number· of specimens.-Moffat 

Trail Limestone Member: collections ?77 (1), 93 

(1), Lincoln County. Horseshoe Shale Member: 

collections 30 (2), 31 (1), 36d (13), Fremont County; ?116 (1), Teton County. 

Paladin sp. 

Plate 1, figures 33-37 

This species is fairly common in a collection of 

Pennsylvanian (Morrowan) age from the Rawlins 

hills (colin. 3). The figured cranidium (pl. 1, fig. 

34) is 8.4 mm long and 7.7 mm wide. The glabella 

is long and appears pyriform; it is about 1.6 times 

longer than wide and very slightly wider anteriorly 

than posteriorly; the frontal lobe is moderately expanded. Its highest point is at the posterior tip, 

which is lobelike and set off anteriorly by a shallow 

depression. Faint lateral glabellar furrows are 

visible opposite and just in front of the moderately 

large palpebral lobes. The frontal border projects 

to form a narrow flange in front of the glabella, 

about one-eighth as long as the glabella. The lateral 

preoccipital glabellar lobes are diagonally elongate, 

paralleling the short furrows, and are highest posteriorly. The preoccipital furrow is moderately deep 

and narrow at the bottom. The occipital lobe is convex in cross section and slopes forward as in P. 

mooreri. 

Surface ornament consists principally of scattered granules, coarsest over the posterior part of 

the glabella, sparse on the summits of the lateral 

preoccipital lobes, and fine on the palpebral lobes. 

Granules are also present scattered on the surface 

of the occipital lobe, but no mesial tubercle was 

observed. No terrace lines were observed on the 

frontal border. 

Librigenae are distinctive, the slightly convex 

lateral border being raised into a rim where it meets 

the upper surface at an acute angle. This rim is 

well shown by highlighting in the figure (pl. 1, fig. 

33). Three or four subparallel terrace lines are visible on the lateral border. The lateral furrow is modified into a rounded depression between the raised 

margin and the slope below the eye. The genal angle 

is produced into a moderately long genal spine. The 

visual surface of the eye is moderately large and 

somewhat globose. The figured librigena is 13 mm 

long. 

Thoracic segments have not been observed. The 

pygidia from this locality are all incomplete but in 

composite are parabolic in outline and have a moderately elevated axis, gently convex on top, with 

sloping, slightly concave sides. The most complete 

of these has about 15 axial rings and 10 pleurae. 

The pleurae are aiSymmetrical and have their greatest elevation posterior to the middle, and their distal 

parts are ornamented by scattered granules, which 

also can be seen on some of the axial rings. The 

smooth border is set off from the pleural shield by a 

shallow furrow and abrupt termination of the ribs. 

The border is gently convex and has about the same 

inclination as the outer part of each pleural lobe. 

The above description is based on 12 specimens 

from locality 3, incluling 4 cranidia, 3 librigenae 

and 5 pygidia. Three pygidia from other localities 

(collns. 50, 52) are included in this species. The 

figured pygidium (pl. 1, figs. 35-37) is a mold of 

the underside, measuring 9.2 mm long and 11.3 mm 

wide. The first three pleural ribs encroach rather 

far on to the border. Another pygidium from the 

same locality has the upper surface fairly well preserved but lacks most of the border. Both pygidia 

have 15 axial rings and 9 ribs. The last-mentioned 

pygidium (loc. 52) is the largest but is poorly preserved in sandstone and only referred with question 
GASTROPODA, CEPHALOPODA, AND TRILOBITA OF THE AMSDEN FORMATION F27 

to this species. The ring and rib count seems to be 

the same. 

This species differs from P. moorei in details of 

the cranidium which include the lobelike posterior 

tip and diagonally elongate lateral preoccipital lobes, 

in the distinctive raised margins of the librigenae, 

and in the lesser number of axial rings and ribs in 

the pygidi um. 

Chamberlain (196.9, p. 50) has listed 14 North 

American species of Paladin. Of these, three are 

from rocks of Pennsylvanian age-P. morrowensis 

(Mather), P. retrolatus Chamberlain, and P. pyriformis Chamberlain. Only the last mentioned is 

similar to P. sp. from the Amsden. According to 

Chamberlain ( 1969, p. 55), P. pyriformis likewise 

has an elongate pyriform glabella, the posterior end 

suggesting a partially developed medial preoccipital 

lobe and thus approaching the genus Sevillia. Its 

pygidium has 9 pleurae and 15 axial rings. Differences from the Pennsylvanian Amsden species, however, include a wider expansion of the frontal lobe 

of the glabella and the subpyramidal shape of the 

lateral preoccipital lobes. The librigenae, so distinctive in the Amsden form, are unknown in P. pyriformis. Because of insufficient material available to 

evaluate the characters and despite direct comparison with Chamberlain's type specimen, we cannot at 

this time determine whether or not Chamberlain's 

name is applicable to the Amsden species but are 

inclined to regard them as different species. 

Figured specimens.-USNM 173618-173620. 

Occurrence and number of specimens.-Horseshoe Shale Member: collection 3 (12), Carbon County. Ranchester Limestone Member: collections 50 

(2), Washakie County; ?52 (1), Johnson County. 

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figs. 

--- 1966, The lower Carboniferous gastropod fauna from 

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417-426. 

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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, 

p. 309-326, pls. 18, 19. 

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

in Wyoming: Jour. Paleontology, v. 28, no. 1, p. 1-16, 

pl. 1. 

Chamberlain, C. K., 1969, Carboniferous trilobites-Utah 

species and evolution in North America: Jour. Paleontology, v. 43, no. 1, p. 41-68, pls. 11-13. 

Cisne, J. L., 1967, Two new Mississippian trilobites of the 

genus Paladin: Jour. Paleontology, v. 41, no. 5, p. 1267-

1273, 2 figs. 

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

U.S. Geo1. Survey Prof. Paper 51, 129 p., 47 pls. 

Easton, W. H., 1942, Pitkin limestone of northern Arkansas: 

Arkansas Geol. Survey Bull. 8, 115 p., 12 pls. 

--- 1962, Carboniferous formations and faunas of central 

Montana: U.S. Geol. Survey Prof. Paper 348, 126 p., 

13 pls. 

Elias, M. K., 1958, Late Mississippian fauna from the Redoak Hollow formation of southern Oklahoma; Pt. 4, 

Gastropoda, Scaphopoda, Cephalopoda, Ostracoda, Thoracica, and Problematica: Jour. Paleontology, v. 32, no. 

1, p. 1-57, pls. 1-4. 

Gordon, Mackenzie, Jr., 1964, California Carboniferous 

cephalopods: U.S. Geol. Survey Prof. Paper 483-A, 27 

p., 4 pls. 

--- 1969, Revision of some of Girty's invertebrate fossils 

from the Fayetteville Shale (Mississippian) of Arkansas 

and Oklahoma-Trilobites: U.S. Geol. Survey Prof. 

Paper 606-E, p. 35-39, pl. 5. 

Hyde, J. E. (Marple, M. F., ed.), 1953, The Mississippian 

formations of central and southern Ohio: Ohio Div. 

Geol. Survey Bull. 51, 355 p., 54 pls. 

Knight, J. B., 1934, The gastropods of the St. Louis, Missouri, Pennsylvanian outlier; 7, The Euomphalidae and 

Platyceratidae: Jour. Paleontology, v. 8, no. 2, p. 139-

166, pls. 20-25. 

--- 1945, Some new genera of Paleozoic Gastropoda: Jour. 

Paleontology, v. 19, no. 6, p. 573-587, pls. 79, 80. 

Love, J. D., 1939, Geology along the southern margin of the 

Absaroka Range, Wyoming: Geol. Soc. America Spec. 

Paper 20, 134 p., 17 pls., 3 figs. 

Maughan, E. K., and Roberts, A. E., 1967, Big Snowy and 

Amsden Groups and the Mississippian-Pennsylvanian 

boundary in Montana: U.S. Geol. Survey Prof. Paper 

554-B, 27 p. 

Meek, F. B., and Worthen, A. H., 1860, Descriptions of 

new Carboniferous fossils from Illinois and other Western States: Acad. Nat. Sci. Philadelphia Proc. 1860, p. 

447-472 [1861]. 

--- 1866, Descriptions of invertebrates from the Carboniferous system: Illinois State Geol. Survey, v. 2, p. 143-

411, pls. 14-20, 23-32. 

Sadlick, Walter, 1960, New name for Spirifer occidentalis 

(Girty) and its geologic history: Jour. Paleontology, v. 

34, no. 6, p. 1210-1214. 

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

in press, Stratigraphy and geologic history of the Amsden 

Formation: U.S. Geol. Survey Prof. Paper 848-A, in 

press. 

Tooker, E. W., and Roberts, R. J., 1970, Upper Paleozoic 

rocks in the Oquirrh Mountains and Bingham mining 
F28 THE AMSDEN FORMATION (MISSISSIPPIAN AND PENNSYLVANIAN) OF WYOMING 

district, Utah, with a section on Biostratigraphy and 

correlation, by Mackenzie Gordon, Jr., and H. M. Duncan: U.S. Geol. Survey Prof. Paper 629-A, 76 p. 

Weller, J. M., 1936, Carboniferous trilobite genera: Jour. 

Paleontology, v. 10, no. 8, p. 704-714, pl. 95. 

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122, no. 10, 16 p. 3 pls., 1 fig. 

Yochelson, E. L., and Saunders, B. W., 1967, A bibliographic 

index of North American late Paleozoic Hyolitha, Amphineura, Scaphopoda, and Gastropoda: U.S. Geol. Survey Bull. 1210, 271 p. 
INDEX 

fltalic page numbers indicate descriptions and major references] 

Page 

A 

Ameura sp F25 

Ammonoidea -------------------------- 23 

(Amphiscapha) hollingsworthi, 

Straparollus -------------- 12 

Anematina -------------------------'-- 3, 19 

sp ------------------------- 5, 7, 19; pl. 2 

Anthracospirifer welleri-shawi Zone __ 4, 7, 14 

Antiquatonia blackwelderi ------------- 4 

blackwelderi Zone ----------------- 4 

apiarum, Glyptotomaria --------------- 16 

Archaeogastropoda ------------------- 3, 9, 20 

Arthropoda --------------------------- 24 

B 

Baylea ------------------------------- 3, 17 

sp ----------------------- 5, 7, 8,17; pl 2 

Bellerophon --------------- 3, 4, 7, 8, 9, 10, 12 

crassus ------------------- 5, 7, 8, 9; pl. 1 

sublaevis ------------------------- 9 

sp --------- 5, 6, 7, 8, 9,10, 11; pl. 1; fig. 1 

Bellerophontacea --------------- 1, 3, 4, 6, 8, 9 

Bellerophontidae ---------------------- 3, 9 

Bellerophontina ----------------------- 9 

Bighorn Mountains ------------- 4, 7, 8, 9, 13 

blackwelderi, Antiquatonia ------------ 4 

Boggy Shale -------------------------- 12 

Borestus ------------------------------ 3, 15 

wrighti --------------------------- 15 

sp ----------------------- 5, 7, 8, 15; pl. 2 

Brachiopod zones --------------------- 4 

Bucanopsis --------------------------- 10 

sp. C ----------------------------- 11 

sp ------------------------------- 11 

bulimiformis, Soleniscus (Bulimorpha) _ 21 

Bulimorpha canaliculata --------------- 21 

(Bulimorpha) bulimiformis, Soleniscus _ 21 

c 

Caenogastropoda ---------------------- 20 

calix, Straparollus 

(Euomphalus) ___ 5, 7, 12, 13; pl1 

Cameron Creek Shale ----------------- 13 

canaliculata, Bulimorpha -------------- 21 

Girtyspira ------------------------ 22 

Caninia Zone ----------------------- 4, 6, 10 

carbonaria, Shansiella ----------------- 18 

carlbransoni, Dictyotomaria -------- 2, 5, 7, 16, 17; pl. 2 

Carlinia amsdeniana Subzone _ 4, 5, 7, 9, 11, 17 

Cephalopoda ---------------------- __ 2, 5, 23 

Cephalopods -------------------------- 8 

Cerithiacea --------------------------- 3, 20 

Chaetetiform bryozoans --------------- 6, 10 

Cherry Creek ------------------------- 9 

Colpites ------------------------------ 3, 14 

minutus -------------------------- 14 

moniliferus ----------------------- 14 

sp. A ---------------- 5, 7, 8, 14, 19; pl. 2 

sp ------------------------- 5, 7, 14; pl. 2 

Composita poposiensis Subzone ------- 4, 9, 21 

Composition and distribution of 

gastropod fauna ---------- 2 

Page 

comJJressus, Euphemites --------------- Fll 

Coral zones --------------------------- 4 

Covey Cutoff section ------------------ 6, 8 

crassus, Bellerophon ---------- 5, 7, 8, 9; pl. 1 

Cravenoceras ------------------------- 2, 23 

scotti ---------------------------- 23 

sp ------------------------------- 23 

Cravenoceratoides --------------------- 23 nititoides ___ _ ____ ___ ___ _ ____ _ _ ____ 23 

sp ------------------------- 5, 8, 23; pl. 2 

Crazy Woman Creek ------------------ 8, 9 

Cycloceras sp ------------------------- 8, 23 

D 

Darwin Peak ------------------------- 9, 11 

Daxwin Peak section ------------------ 6 

Darwin Sandstone Member ------------ 4 

delira, Pulsia ------------------------- 9 

Dictyotomaria ---------------------- 3, 16, 17 

carlbransoni ----------- 2, 5, 7, 16, 17;pl. 2 

scitula --------------------------- 16, 17 

sp ------------------------------- 5 

Distribution and composition of 

gastropod fauna ---------- 2 

Ditomopyge -------------------------- 25 

Donaldina -------------------------- 3, 22, 23 

pygmaea ------------------- 5, 7, 22; pl. 2 

tenuis ---------------------------- 22 

sp ------------------------- 5, 8, 22; pl. 2 

E 

Elasmonematidae --------------------- 3, 19 

Eotomariidae ------------------------- 3, 17 

Eumorphoceras bisulcatum Zone ------- 8, 23 

Euomphalacea ---------------------- 1, 3, 12 

Euomphalidae ---------------------- 3, 12 

(Euomphalus), Straparollus ---------- 3, 12 

(Euomphalus) utahensis, Straparollus _ 13 

( Euomphalus) calix, 

Straparollus ---- 5, 7, 12, 13; pl. 1 

plummeri, Straparollus -------- 5, 7, 8, 12, 13; pl. 1 

Euphemites --------------------- 3, 110, 11, 12 

compressus ----------------------- 11 

galericulatus --------------------- 11 

incarinatus ----------------------- 11 

lentijormis ----------------------- 11 

nautiloides 11 

sacajawensis ------------- 2, 5, 7, 10; pl. 1 

subglobosus ----------------------- 11 

F 

Fossil localities 2 

G 

galericulatus, Euphemites ------------- 11 

Gardison Formation ------------------ 13 

Gastropod fauna, composition and 

distribution ---------------

Gastropoda 

Gastropods, stratigraphic and 

2 

5, 9 

geographic occn>rrence --- _ 5 

Page 

Girtyspira --------------------------- F3, 21 

canaliculata ---------------------- 22 

sp. A ------------------ 5, 7, 21, 22; pl. 2 

sp. B --------------------------- 5, 7, 22 

Glyptotomaria ------------------------ 16 

apiarum -------------------------- 16 

Goniasma ---------------------------- 3, 20 

sp ------------------------- 5, 8, 20; pl. 2 

Goniatitacea -------------------------- 23 

Goniatitacean ------------------------ 5, 24 

Goniatite ---------------------------- 2, 23 

Gosseletina -------------------------~- 3, 17 

sp ------------------ 5, 7, 17, 18, 19; pl. 2 

Gosseletinidae ------------------------ 3, 17 

Griffithides moorei -------------------- 2, 24 

morrowensis ---------------------- 24 

H 

Haystack Peak section ---------------- 6 

Heath Formation ------------------ 9, 12, 14 

Heath Shales ------------------------- 25 

helmsensis, Paladin ------------------ 25, 26 

hollingsworthi, Straparollus 

(Amphiscapha) ---------- 12 

Holopeidae --------------------------- 3, 18 

Homoceratidae ------------------------ 23 

Horseshoe Shale Member ---------- 4, 6, 8, 10 

Hyolitha ----------------------------- 2 

Ianthinopsis ----------------------- 3, 21, 22 

sp ------------------------------ 5, 7, 21 

Illaenina ----------------------------- 24 

incarinatus, Euphemites -------------- 11 

K 

Kaskia ------------------------------- 24 

Knightites ---------------------------- 11 

(Retispira) --------------------- 3, 4, 11 

tenuilineata ------------------ 11 

textilis ----------------------- 11 

sp. A --------------------- 5, 7,11; pl. 1 

sp. B ---------------------- 5, 7, 11; pl 1 

sp ------------------------------ 5, 7,11 

L 

lentiformis, Euphemites ---------------

Littorina -----------------------------

Logan :~<'ormation ---------------------

Lophospiridae ------------------------

Loxonema ----------------------------

wortheni ------------------------- Loxonema tacea 

M 

Macluritina 

11 

18 

11 

3, 15 

20 

20 

3,20 

12 

Marshall Formation ------------------ 11 

Meekospira --------------------------- 3, 21 

sp --------------------- 5, 7, 21, 22; pl. 2 

Meekospiridae ------------------------ 3, 21 

Mesolobus Zone ----------------------- 4 

Microdoma ------------------------- 3, 18, 19 

sp ------------------------- 5, 7, 18; pl. 2 

F29 
F30 

Page 

Microdomatacea ---------------------- F3, 18 

Microdomatidae ---------------------- 3, 18 

minutus, Colpites --------------------- 14 

Mississippian (Chesterian) gastropods _ 2 

Mississippian fauna -------------------

Moffat Trail Limestone Member ___ 4, 6, 8, 10 

Moffat Trail section ------------------ 6, 8 

Mollusca ----------------------------- 9 

moniliferus, Colpites ------------------ 14 

Monoplacophora ---------------------- 2 

moorei, Griffithides ------------------- 2, 24 

Paladin ---------------- 5, 8, 24, 27; pl. 1 

morrowensis, Griffithides -------------- 24 

Paladin -------------------------- 25,27 

Mourlonia ---------------------------- 3, 17 

sp ------------------------- 5, 8, 17; pl. 2 

mucronatus, Paladin ------------------ 26 

Murchisonia -------------------------- 3, 20 

sp ------------------------- 5, 8, 20; pl. 2 

Murchisoniacea ----------------------- 3, 20 

Murchisoniidae ----------------------- 3, 20 

Murchisoniids ------------------------ 3 

Murchisoniina 20 

N 

Naticopsis ------------------------- 3, 18, 19 

(Jedria) ------------------------- 19 

sp --------------------- 5, 7, 19; pl. 2 

(Naticopsis) sp ----------- 5, 7, 19; pl. 2 

sp ------------------------------- 18 

Nautiloidea --------------------------- 23 

nautiloides, Euphemites --------------- 11 

Neokoninckophyllum hamatilis Zone ___ 4, 5 

Neritacea ---------------------------- 3, 19 

Neritopsidae -------------------------- 3,19 

Neritopsina -------------------------- 19 

nititoides, Cravenoceratoides ---------- 23 

0 

Orthoceras sp ------------------------ 8, 23 

Orthocerida --------------------------- 23 

Orthoconic nautiloid ----------------- 2, 5, 23 

Orthonema --------------------------- 3, 20 

sp ------------------------- 5, 7, 20; pl. 2 

p 

Paladin ------------------------------ 24 

helmsensis ----------------------- 25,26 

moorei ----------------- 5, 8, 24, 27; pl. 1 

morrowensis --------------------- 25, 27 

mucronatus ----------------------- 26 

pyriformis --------------------- 8, 26, 27 

retrolatus ------------------------ 26,27 

sp ----------------------- 5, 25, 26; pl. 1 

INDEX 

Page 

Palaeostylus -------------------------- F20 

(Pseudozygopleura) ------------ 3, 20,22 

sp ------------------ 5, 7, 8, 20; pl. 2 

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

Phillipsia sp ------------------------- 2, 25 

Phillipsiidae -------------------------- 24 

Phymatopleuridae -------------------- 3, 15 

Pitkin Limestone --------------------- 11 

Plagioglypta sp ---------------------- 2 

Platyceratacea ------------------------

Platyceratidae ------------- _ ----------

Pleurotomariacea ___ ------------------

Pleurotomariaceans ------ ___ ----------

Pleu,rotomariina ----------------------

plummeri, Straparollus (Euom3, 18 

3, 18 

3, 14 

3, 4 

14 

phalus) ------ 5, 7, 8, 12, 13; pl. 1 

Polyplacophora ----------------------- 2 

Portlockie!lidae ------------------------ 3, 18 

Proetacea ---------------------------- 24 

Prosobranchia ------------------------ 9 

Pesudorthoceratacea ------------------ 23 

(Pseudozygopleura), Palaeostylus ____ 3, 20,22 

Pseudozygopleuridae ------------------ 3, 20 

Pseudozygopleurids ------------------- 20 

Ptychomphalus similis ----------------- 16 

wortheni 

Ptychopariida 

Pulsia delira 

2, 16 

24 

9 

pygmaea, Donaldina ------------ 5, 7, 22; pl 2 

Solenospira ------------------- 20, 21,22 

Pyramidellacea ----------------------- 3, 22 

pyriformis, Paladin ---------------- 8, 26,27 

R 

Ranchester Limestone Member ____ 4, 6, 7, 11 

Raphistomatidae ---------------------- 3,17 

Rawlins hills ------------------------- 26 

Reticycloceras ------------------------ 23 

sequoyahensis --------------------- 23 

sp ------------------------------- 5, 23 

Retispira ----------------------------- 12 

(Retispira), Knightites ------------- 3, 4,11 

tenuilineata, Knightites ----------- 11 

textilus, Knightites --------------- 11 

retrolatus, Paladin 26,27 

s 

sacajawensis, Euphemites ---- 2, 5, 7, 10; pl. 1 

Ste. Genevieve Limestone ------------- 11, 16 

Scaphopoda -------------------------- 2 

scitula, Dictyotomaria ----------------- 16, 17 

scotti, Cravenoceras ------------------- 23 

sequoyahensis, Reticycloceras ___ _____ __ 23 

Shansiella ---------------------------- 3, 18 

Page 

Shansiella-Continued 

carbonaria ------------------------ F18 

sp ------------------------ 5, 8, 18; pl. 2 

similis, Ptychomphalus ---------------- 1o 

Sinuopeidae -------------------------- 3, 14 

Soleniscus ---------------------------- 3, 21 

(Bulimorpha) bulimiformis ------- 21 

sp ------------------------- 5, 7, 21; pl. 2 

Solenospira pygmaea -------------- 20, 21,22 

South Indian Creek section ------------ 6 

Straparollus -------------------------- 12 

(Amphiscapha) hollingsworthi ---- 12 

(Euomphalus) --·----------------- 3, 12 

calix --------------- 5, 7, 12, 13; pl. 1 

plummeri -------- 5, 7, 8, 12, 13; pl. 1 

utahensis --------------------- 13 

sp. A ----------------------- 12 

sp -------------------------- 5, 8, 13 

sp --------------------------- 7 

Stratigraphic considerations ----------- 4 

Stratigraphic and geographic occurrence 

of the gastropods --------- 5 

Streptacidae -------------------------- 3, 22 

Strophostylus ------------------------ 3, 18 

sp ------------------------ 5, 7,18; pl. 2 

subglobosus, Euphemites --------------- 11 

sublaevis, Bellerophon ----------------- 9 

Subu!itacea 

Subulitidae 

Systematic paleontology 

T 

tenuilineata, K nightites ( Retispira) 

textilis, Knightites (Retispira) --------

Trilobita 

Trilobites 

Trochina ___ - -------------------------

Turritellidae --- __ ------------------- _ 

u 

utahensis, Straparollus (Euomphalus) _ 

w 

Washakie Range 

3,21 

3,21 

9 

11 

11 

5,24 

8 

18 

3,20 

13 

7 

wortheni, Loxonema ------------------ 20 

Ptychomphalus ------------------- 2, 16 

Worthenia --------------------------- 3, 15 

sp ------------------------- 5, 7,15; pl. 2 

wrighti, Borestus --------------------- 15 

y 

Yunnania ---------------------------- 3, 18 

sp ------------------------ 5, 7, 18; p.J. 2 
PLATES 1, 2 

Contact photographs of the plates in this report are available, at cost, from the U.S. 

Geological Survey Library, F,ede,ral Cooter, Denver, Colorado 80225. 
PLATE 1 

[All figures enlarged; magnifications indicated on plate] 

FIGURES 1-4. Bellerophon cf. B. crassus Meek and Worthen (p. F9). 

Ranchester Limestone Member, collection 52. 

1, 2. Apertural views of two latex casts, USNM 168460 and 168461. 

3. Adapertural view of incomplete steinkern Eho,wing details of slit and lip, USNM 168462. 

4. Side view of steinkern coated with crystalline druse showing small axial hole normally filled with 

shell material, USNM 168463. 

5. Bellerophon sp. (p. F9). 

Side view of latex cast, USNM 168464, from Ranchester Limestone Member, collection 52. 

6-9, 11-13. Euphemites sacajawensis C. Branson (p. FlO). 

UM 6631, from Horseshoe Shale Member, collection 36d. 

6. Apertural view of paratype. 

7-9. Apertural, side, and adapertural views of holotype. 

11-13. Adapertural, side, and apertural views of another paratype. 

10. Knightites (Retispira) sp. B (p. Fll). 

Dorsal view showing sculpture and slit of a specimen, USNM 168466, from Ranchester Limestone Member, collection 50. 

14, 15. Knightites (Retispira) sp. A (p. Fll). 

14. Dorsal view of steinkern showing selenizone, U.M. 6627, from Horseshoe Shale Member, collection 

36d. 

15. Side view of another steinkern from same lot. 

16-19. Straparollus (Euomphalus) aff. S. (E.) plummeri Knight (p. F12). 

16. Bottom view of latex cast of external mold, USNM 168472, from Ranchester Limestone Member, 

collection 52. 

17-19. Top views of latex casts of three external molds, USNM 168470, 168471, 168469, from same 

collection. 

20-22. Straparollus (Euomphalus) calix n. sp. (p. F12). 

Bottom, side, and top views of holotype, USNM 168467, from Horseshoe Shale Member, collection 159. 

23-32. Paladin moorei (C. Branson) (p. F24). 

23-25. Side, back, and top views of pygidium, USNM 173617, from Moffat Trail Limestone Member collection 93. 

26. Top view of cranidium, UW A57, from Horseshoe Shale Member, collection 30. 

27, 28. Side and top views of pygidium, UM 6625, from same member, collection 36d. 

29, 30. Views of holotype a, specimen folded double, UM 6605, one showing cranidium and the other 

broken pygidium and part of thorax, from same member at Twin Creek, Wyo. 

31. Top view of pygidium of paratype UM 6592, collection 36d. 

32. Top view of free cheek paratype UM 6600, collection 36d. 

33-37. Paladin sp. (p. F26). 

33. Top view of free cheek, USNM 173619, from Horseshoe Shale Member, collection 3. 

34. Top view of cranidium, USNM 173620, from same collection. 

35-37. Side, back, and top views of pygidium, USNM 173618, from Ranchester Limestone Member, 

coUection 50. 
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1-5. Colpites sp. A (p. F14). 

1, 2. Top and side views of specimen, USNM 168474, from Ranchester Limestone Member, collection 50. 

3. Oblique ·top vie·w of specimen, USNM 168477, from Ranchester Limestone Member, collection 52. 

4, 5. Top views of two specimens, USNM 168475 and 168476, from Ranchester, Limestone Member, collection 50. 

6, 7. New genus aff. "Colpites" sp. (p. F14). 

Top and side views of steinkern, USNM 168479, from Horseshoe Shale Member, collection E. 

8. Worthenia? sp. indet. (p. F15). 

Side view of poorly preserved specimen, USNM 168480, from Horseshoe Shale Member, collection 137. 

9. Borestus sp. indet. (p. F15). 

Side view of latex cast, USNM 168481, from Ranchester Limestone Member, collection 40. 

10. Borestus? sp. (p. F15). 

Side view of latex cast, USNM 168482, from Ranchester Limestone Member, collection 52. 

11. Bay lea? sp. indet. (p. F17). 

Apertural view of latex cast, USNM 168483, from Ranchester Limestone .Member, collection 52. 

12, 13. Mourlonia sp. indet. (p. F17). 

Top and side views of specimen, USNM 168484, from Horseshoe Shale Member, collection 53. 

14- 16. Gosseletina sp. indet. (p. F17). 

Top, side, and bottom views of a steinkern, USNM 168485, from Horseshoe Shale Member, collection 45. 

17, 18. Gosseletina? sp. indet. (p. F18). 

Top and side viewsof steinkern, UW IT-242, from Horseshoe Shale Member, collection 35. 

19-21. Dictyotomaria carlbransoni n. sp. (p. F16). 

Top, side, and bottom views of holotype, UM 6626, from Horseshoe Shale Member, collection 36d. 

22. Shansiella sp. indet. (p. F18). 

Oblique top view of latex cast, USNM 168486, from Ranchester Limestone Member, collection 52. 

23, 24. Naticopsis (Naticopsis) sp. indet. (p. F19). 

Top and side views of specimen, USNM 173606, from Horseshoe Shale Member, collection 137. 

25, 26. Naticopsis (Jedria?) sp. indet. (p. F19). 

Top and side views of specimen, USNM 173607, from Horseshoe Shale Member, collection 45. 

27. Yunnania? sp. indet. (p. F18). 

Side view of specimen, USNM 168487, from Ranchester Limestone Member, collection 50. 

28. Anematina sp. indet. (p. F19·). 

Strongly oblique side view of latex cast, USNM 168489, from Ranchester Limestone Member, collection 40. 

29. Orthonema sp. indet. ( p. F20). 

Side view of latex cast, USNM 173611, from Ranchester Limestone Member, collection 40. 

30. Goniasma? sp. indet. ( p. F20) . 

Side view of latex cast, USNM 173608, from Ranchester Limestone Member, collection 52. 

31, 32. Strophostylus sp. indet. (p. F18). 

Apertural and top views of steinkern, UM 6645, from Horseshoe Shale Member, collection 36d. 

33-35. Cravenoceratoides sp. indet. ( p. F23). 

Back, side, and front views of unique internal mold showing sutures, UW IT-243, from Horeshoe 

Shale Member, collection 35. 

36. Microdoma? sp. indet. (p. F18). 

Side view of latex cast, USNM 168488, from Ranchester, Limestone Member, collection 40. 

37. Murchisonia? sp. indet. (p. F20). 

Side view of latex cast, USNM 173609, from Ranchester Limestone Member, collection 52. 

38. Palaeostylus (Pseudozygopleura) sp. indet. (p. F20). 

Side view of latex cast, USNM 173610, from Ranchester Limestone Member, collection 40. 

39. Meekospira? sp. indet. (p. F21). 

Side view of latex cast, USNM 173614, from Ranchester Limestone Member, collection 50. 

40,41. Soleniscus? sp. indet. (p. F21). 

Apertural and adapertural views of specimen, USNM 173613, from Ranchester Limestone Member, collection 50. 

42, 43. Girtyspira sp. A (p. F21). 

42. Side view of specimen retaining part of shell surface, UM 6629, from Horseshoe Shale Member, 

collection 36d. 

43. Apertural view of steinkern from same lot. 

44. Donaldina aff. D. pygmaea (Weller) (p. F22). 

Side view of incomplete specimen, UM 6628, from Horseshoe Shale Member, collection 36d. 

45. Donald ina sp. indet. ( p. F22). 

Side view of latex cast, USNM 173615, from Ranchester Limestone Member, collection 52. 
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* u.s. GOVERNMENT PRINTING OFFICE: 1975 0 - 585- 473/84