Marine Jurassic 

Pelecypods from 

Central and Southern 

Utah

GEOLOGICAL SURVEY PROFESSIONAL PAPER 483-C
 I I
Marine Jurassic 

Pelecypods from 

Central and Southern 

Utah

By RALPH W. IMLAY

CONTRIBUTIONS TO PALEONTOLOGY

GEOLOGICAL SURVEY PROFESSIONAL PAPER 483-C

Descriptions and illustrations of 

marine pelecypods of Jurassic age

UNITED STATES GOVERNMENT PRINTING OFFICE, WASHINGTON : 1964
UNITED STATES DEPARTMENT OF THE INTERIOR 

STEWART L. UDALL, Secretary

GEOLOGICAL SURVEY 

Thomas B. Nolan, Director

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

Washington, D.C. 20402
CONTENTS

Abstract. _ __-_--___-___-_. 

Introduction. _____-_-_.__-

Biologic analysis___ ________

Stratigraphic considerations. 

Ages and correlations___ _.

Carmel Formation.

Arapien Shale._______.

Cl 

1

1

2

3

3

5

Faunal associations and comparisons. 

Geographic distribution__ _ _ _______

Summary of results. _______________

Systematic descriptions.____________

Literature eited____________________

Index.___________________________

Page

06

8

22

23

38

41

ILLUSTRATIONS

[Plates follow index]

PLATE 1. Nucula, Mytilus, Lopha, Idonearcal, Plicatula, Modiolus, Gervillia, Anomial, Inoceramus, Ostrea (Liostrea), and Isognomon.

2. Camptonectes and Lima.

3. Trigonia, Vaugonia, Myophorella (Haidaia), and Myophorella (Promyophorella).

4. Astarte (Coelastarte), Quenstedtia, Myopholas, Pronoella, Cyprinal, Hamulusl, Cercomya, Thracia, Goniomya, and 

Pholadomya.

Page 

FIGURE 1. Index map showing marine Jurassic localities in central and southern Utah.________________________________ C14

TABLES

Page

TABLES 1. Relative abundance of marine Jurassic pelecypods in central and southern Utah___ ________________________ C2

2. Regional distribution of marine Jurassic megaf ossils in central and southern Utah_ 

3-8. Geographic distribution of marine Jurassic megafossils in Utah.

3. Juab, San Pete, Piute, and Beaver Counties_____-__-_______--___-__---_-

4. Iron County __ ___-__________________________________________-________

5. Washington County. _________________________________________________

6. West side of San Raf ael Swell, Emery County. _______________________-__

7. East side of San Raf ael Swell, Emery County. __ ________________________

8. Wayne, Garfield, and Kane Counties. __________________________-_---_--

9

10

11

12

in

CONTRIBUTIONS TO PALEONTOLOGY

MARINE JURASSIC PELECYPODS FROM CENTRAL AND SOUTHERN UTAH

By RALPH W. IMLAY

ABSTRACT

The pelecypod faunule in the marine Jurassic beds of central 

and southern Utah includes 31 genera and 44 species. The most 

common genera, in order of decreasing abundance, are Camptonectes, Ostrea, Pronoella, Vaugonia, Myophorella, and Lima. 

These genera include 80 percent of the specimens collected.

Pelecypods are more common than any other megafossils in 

the marine Jurassic rocks of central and southern Utah. They 

are most common in a belt about 40 miles wide that extends 

southwestward from the west side of the San Rafael Swell. 

Eastward they become less common as the limy unit wedges out 

into red siltstone of littoral origin. Westward the pelecypods 

become less common as the limy unit thickens greatly. To the 

west, deposition of calcareous muds was apparently too rapid 

for benthonic organisms to thrive. Nevertheless, all parts of 

the Jurassic sea were fairly shallow, as shown by the presence 

of such pelecypods as Ostrea, Lopha, Mytilus, Modiolus, Plicatula, 

and Isognomon, the absence of such pelecypods as Gryphaea and 

foeleagrinella, and an absence of ammonites except at the northwest end of the San Rafael Swell.

Studies of the pelecypods from the limy lower unit of the 

Carmel Formation show that the lower part of that unit is of 

Middle Jurassic (Bajocian) age, that the entire unit is probably of 

Bajocian age, at least locally, and that the highest beds of that 

unit are not younger than earliest Late Jurassic (early Callovian). 

The unit is correlated with the lower part of the Twin Creek 

Limestone of northern Utah, western Wyoming, and southeastern 

Idaho.

The gypsiferous claystone and siltstone upper unit of the 

Carmel Formation has furnished a few fossils but only in southwestern Utah, and these belong to long-ranging species of 

Bajocian to Callovian age. This unit is considered to be of 

early Callovian age on the basis of stratigraphic position and 

of regional stratigraphic considerations.

The pelecypods from the Twelvemile Canyon Member of the 

Arapien Shale in central Utah show that it is the equivalent of 

the Twin Creek Limestone and of the Carmel Formation and 

ranges in age from Bajocian to early Callovian.

INTRODUCTION

This study of the marine Jurassic pelecypods from 

central and southern Utah is based on 176 collections 

made by 47 geologists. The oldest collection was made 

by C. D. Walcott in 1879 and the next oldest by T. W. 

Stanton in 1892. All other collections have been made 

between 1907 and 1961. The study was undertaken 

at the request of J. C. Wright of the Geological Survey as an aid in solving correlation problems concerning the formations and members of the San Rafael 

Group. The study does not include pelecypods from 

the Curtis Formation and equivalent beds.

Thanks are due to J. C. Wright for checking the 

geographic descriptions and locations of the collections 

from the Carmel Formation and for furnishing stratigraphic data concerning the Carmel Formation. C. T. 

Hardy kindly supplied data concerning collections from 

the Twelvemile Canyon Member of the Arapien Shale.

The index map of localities in central and southern 

Utah does not show the locations of many small creeks, 

washes, springs, and seeps that are mentioned in the 

locality descriptions. The positions of such geographic 

features may be found in the quadrangle maps of 

Utah and in the publications of Baker, Dane, and 

Reeside (1936); Gilluly (1929); Gregory (1950, 1951); 

Hardy (1952a, 1962); and Spieker (1946).

BIOLOGIC ANALYSIS

The marine Jurassic pelecypods from central and 

southern Utah that have been studied during preparation of this paper number about 1,700 specimens. 

Their distribution by genera and families is shown in 

table 1. The genera Camptonectes and Ostrea are by 

far the most common and could easily have been collected in much larger numbers. Vaugonia and Pronoella 

are a little less common but likewise represent a mere 

sampling of the numbers present in the outcrops. 

Nucula was found in abundance only near Cedar City 

and Thracia only at one place on Deep Creek north 

of Escalante. The number of specimens of the other 

genera, as shown in table 1, represent all that have 

been obtained by many geologists during more than 

60 years. The 17 genera and subgenera represented 

by 1-6 specimens may be considered scarce. Eight 

genera and subgenera are represented by 14-37 specimens and, therefore, are not very common. Only 8 

genera and subgenera are represented by more than 64 

specimens, and of these only 6 genera are widespread.

Cl
C2 CONTRIBUTIONS TO PALEONTOLOGY

Consequently most fossil collections from central 

and southern Utah are dominated by only a few genera, which in order of decreasing abundance include 

Camptonectes, Ostrea, Pronoella, Vaugonia, Myophorella 

(Promyophoretta), and Lima (Plagiostoma).

TABLE 1. Relative abundance of marine Jurassic pelecypods in 

central and southern Utah

Family

Pholadidae... .....................

Laternulidae. __ __ ______

Genus or subgenus

Cercomya. ____ __ ____ - __

Number of 

specimens

100

14

5

33

4

4

37

4

6

>450

18

77

3

>300

21

5

36

>210

90

1

1

30

>230

4

3

3

6

31

2

6

2

3

64

Other megafossils are less common than pelecypods 

in the marine Jurassic beds of central and southern 

Utah. Gastropods are about half as common but are 

fairly widespread. Only four ammonites have been 

found, and all these are from the northwestern part of 

the San Rafael Swell. Crinoid columnals have been 

obtained from 41 localities in various parts of central 

and southwest Utah, but only one occurrence is known 

in Emery County. Echinoid fragments have been 

obtained at eight localities in San Pete, Beaver, Washington, Iron, and Garfield Counties. One starfish has 

been found near Teasdale in Wayne County. The 

worm tube Hamulus? subquadratus (Meek and Hayden) 

(pi. 4, fig. 26) has been obtained at three localities in 

Emery County. Other less distinctive worm tubes are 

known from Kane and Beaver Counties. Some colonial 

corals, probably including Astrocoenia, have been found 

in Garfield, Kane, and Iron Counties.

STRATIGRAPHIC CONSIDERATIONS

The fossils described herein were obtained from the 

lower limy unit of the Carmel Formation of eastcentral, south-central, and southwestern Utah and 

from the Arapien Shale of central Utah. The overall 

characteristics and distribution of the Carmel Formation have been described by Baker, Dane, and Reeside 

(1936, p. 6, 45, 54, 58) and have been summarized 

recently by Wright and Dickey (1958, p. 174, 175; 1963). 

The characteristics and distribution of the Arapien 

Shale have been described by Spieker (1946, p. 123- 

125), Hardy (1952a), Hardy and Zeller (1953, p. 1264- 

1266), and Willard and Callaghan (1962).

The Carmel Formation, as discussed by Wright and 

Dickey (1958, p. 174), is readily divisible into two major 

units over its entire area of distribution. The lower 

unit consists mostly of gray limestone and shale. The 

upper unit consists of claystone, siltstone, and gypsum 

but locally in southern Utah contains considerable 

sandstone. It is generally red in its eastern areas of 

exposure and generally green to gray in its western 

areas. Westward the Carmel Formation thickens 

considerably (Wright and Dickey, 1958, p. 175) from 

0 to at least 700 feet. In its westernmost exposures in 

Iron and Washington Counties it shows great resemblances lithologically to the Arapien Shale of central 

Utah and to the Twin Creek Limestone of north-central 

Utah. These resemblances probably are the basis for 

Spieker's (1946, p. 123) suggestion that the Arapien 

Shale may be recognized over a large area in southern 

and southwestern Utah.

In general, the Carmel Formation shows many of the 

same changes westward as are shown by equivalent 

beds exposed along the south side of the Uinta Mountains (Imlay, 1953, p. 58). The Carmel Formation 

along the east side of the San Rafael Swell consists of 

about 130 feet of sparsely fossiliferous limestone and 

silty limestone in the lower unit and about 175 feet of 

red siltstone containing some gypsum in the upper 

unit. It is comparable with the Carmel Formation 

exposed between White Rocks Canyon and Vernal 

in the Uinta Mountains.

The Carmel Formation on the west side of the San 

Rafael Swell consists of 135-200 feet of moderately 

fossiliferous oolitic limestone and interbedded elastics 

in the lower unit and 250-450 feet of greenish-gray 

clayey siltstone containing interbedded gypsum in the 

upper unit. It is comparable with the Carmel Formation exposed between Lake Fork and White Rocks 

Canyon in the Uinta Mountains.

The Carmel Formation exposed near Teasdale in 

Wayne County, on Deep Creek and Antimony Creek in 

Garfield County, and in western Kane County consists 

of 250-550 feet of moderately fossiliferous limestone 

and limy shale in the lower unit and 400-550 feet of 

clastic rocks containing interbedded gypsum in the 

upper unit. The lower unit shows resemblances to the 

Twin Creek Limestone exposed between Lake Fork and 

Duchesne River in the Uinta Mountains.
PELECYPODS FROM CENTRAL AND SOUTHERN UTAH C3

Finally, the lower part of the Carmel Formation in 

Iron and Washington Counties consists of about 500-950 

feet of red beds and shaly to medium-bedded limestone 

that show some resemblances to the lower part of the 

Twin Creek Limestone (members A-E) exposed near 

Peoa at the west end of the Uinta Mountains and at 

Monks Hollow in the Wasatch Range.

The Arapien Shale consists of a lower gray calcareous 

shale and limestone unit, named the Twelvemile Canyon 

Member, and an upper red siltstone and shale unit, 

named the Twist Gulch Member. The Arapien Shale 

is underlain by the Navajo Sandstone along Red Canyon 

about 1% miles northeast of Nephi, Utah (Johnson, 

1959, p. 19, pi. 8) and along the west side of the Sevier 

Valley from 8 to 10 miles southwest of Marysvale, 

Utah (Willard and Callaghan, 1962). It is overlain by 

beds assigned questionably to the Morrison Formation 

in Salina Canyon east of Salina (Spieker, 1946, p. 125; 

Hardy, 1952a, p. 23, 76-78) and along the southeastern 

part of the Gunnison Plateau (Hardy, 1962, p. 54). In 

Salina Canyon, however, 177 feet of beds in the upper 

part of the Twist Gulch Member of the Arapien Shale 

consists of fossiliferous glauconitic sandstone, grit, and 

shale that lithologically resembles the Curtis Formation 

(Hardy, 1952a, includes units 31-35 on p. 78) and 

contains the pelecypod Meleagrinella curta (Hall) which 

is common in the Curtis Formation of Utah and which 

has not been found elsewhere in any part of the 

Arapien Shale or in the Carmel Formation. For 

lithologic and faunal reasons, therefore, the 177 feet of 

beds in question in Salina Canyon is herein considered 

to be a western extension of the Curtis Formation.

The remainder of the Twist Gulch Member of the 

Arapien Shale consists mostly of unfossiliferous red siltstone and sandstone and attains thicknesses ranging 

from 1,265 feet to at least 1,910 feet (Hardy, 1952a, 

p. 23; 1952b, p. 94; 1962, p. 53). It is lithologically 

similar to and occupies the same stratigraphic position 

as the Preuss Sandstone of north-central Utah (Baker, 

1947; Imlay, 1952a, p. 1736-1739) and the Entrada 

Sandstone of central and southern Utah (Hardy, 1952a, 

p. 27, 28; Hardy and Zeller, 1953, p. 1266; Imlay, 

1952b, p. 1736).

The Twelvemile Canyon Member of the Arapien 

Shale is divisible lithologically into two parts. The 

lower part consists mostly of thin- to thick-bedded limestone that is locally oolitic but includes some shale. It 

is about a thousand feet thick southwest of Marysvale 

(Willard and Callaghan, 1962) and at least 800 feet 

thick in the northern part of the Gunnison Plateau 

(Hardy, 1952a, p. 16, 18, 19; Hardy and Zeller, 1953 

p. 1264; Johnson, 1959, p. 23, 24). The upper part

consists of gray calcareous shale and siltstone that is in 

part gypsiferous and red, locally includes salt beds at 

its top, and is commonly much contorted. This upper 

part is about 1,140 feet thick southwest of Marysvale 

(Willard and Callaghan, 1962). It is some thousands 

of feet thick on the west side of the Wasatch Plateau 

and near the Gunnison Plateau (Spieker, 1946, p. 125; 

Hardy, 1952a, p. 16, 17; Johnson, 1959, p. 22, 23, 24, 41; 

Hardy, 1962, p. 53), but the thicknesses cannot be 

determined because of complex distortion of beds. 

Estimates of thicknesses for the entire member in the 

Wasatch and Gunnison Plateaus areas range from 4,400 

to 10,000 feet (Johnson, 1959, p. 22).

AGES AND CORRELATIONS 

CARMEL FORMATION

The age of the limy lower unit of the Carmel Formation, based on the pelecypods described herein, is 

Middle Jurassic to possibly early Late Jurassic. The 

Middle Jurassic age is shown by the presence in the 

lower part of the Carmel Formation of certain species 

of pelecypods that are known elsewhere in the western 

interior region only in beds that contain middle to 

upper Bajocian ammonites, such as Stemmatoceras, 

Stephanoceras, Zemistephanus, and Chondroceras. 

These pelecypods include the following:

Gervillia montanaensis Meek

Myophorella (Haidaia) yellowstonensis Imlay, n. sp.

Astarte (Coelastarte) livingstonensis Imlay, n. sp.

Goniomya montanaensis Meek

Thracia weedi Stanton

Most of these species have been obtained only in the 

lower fourth of the limy lower unit of the Carmel 

Formation at positions ranging from 15 to 30 feet above 

the top of the Navajo Sandstone. Thracia weedi 

Stanton has been obtained, however, throughout most 

of the limy lower unit. For example, at Deep Creek 

north of Escalante it occurs only 12-15 feet above the 

Navajo Sandstone (Mesozoic Iocs. 25671, 28468). 

At Mount Carmel it occurs from 20 to 30 feet below the 

top of the limy unit (Mesozoic Iocs. 28494, 28495). 

Near Pintura in Washington County it occurs 75 feet 

below the top of the 520-foot thick limy unit (Mesozoic 

loc. 27466). Evidently, if Thracia weedi Stanton is 

indicative of the Middle Jurassic, then essentially all of 

the limy unit is of that age.

Most of the pelecypods found in the limy lower unit 

of the Carmel Formation belong to species, or are closely 

similar to species, that elsewhere in the western interior 

region occur with ammonites of Bajocian age but also 

range higher into beds containing ammonites of early
C4 CONTRIBUTIONS TO PALEONTOLOGY

Callovian age, such as Cadoceras and Kepplerites. 

These pelecypods include the following:

Modiolus subimbricatus Meek 

Mytilus of. M. whitei (Whitfield) 

Pinna kingi Meek

Isognomon of. I. perplana (Whitfield) 

Camptonectes stygius White

platessiformis White

Lima (Plagiostoma) occidentalis Hall and Whitfield 

Ostrea (Liostrea) strigilecula White 

Trigonia americana Meek

elegantissima Meek 

Vaugonia conradi (Meek and Hay den) 

Myophorella (Promyophorelld) montanaensis (Meek) 

Astarte of. A. meeki Stanton 

Pronoella of. P. cinnabarensis Stanton 

Pleuromya subcompressa (Meek) 

Pholadomya kingi Meek

inaequiplicata Stanton 

Cercomya punctata (Stanton)

The species of pelecypods in the preceding list have 

not been collected from all parts of the limy lower unit 

of the Carniel Formation (table 2). Four have been 

collected only from the lower part of that unit, four 

from both lower and middle parts, two from both 

middle and upper parts, and seven from all parts. 

The species that range throughout the unit are represented by many specimens. The species that have 

been found only in the lower part of the unit are, with 

one exception, represented only by a few specimens. 

Most of the other species listed are represented by a 

moderate number of specimens.

These relationships suggest that the apparent stratigraphic ranges of these pelecypod species within the 

limy lower unit may not be the real ranges but may 

reflect some environmental factor that influenced their 

development or some depositional factor that controlled 

their preservation after burial. Their stratigraphic 

distribution within the unit appears, therefore, to show 

only that the upper part of the unit cannot be younger 

than early Callovian and is not necessarily younger 

than Bajocian.

A Middle Jurassic age for the limy lower unit is 

supported by other organisms, including corals, nerineid gastropods, and ammonites. Of these, corals 

have been collected at eight localities from the lower 

and middle parts of the unit. They are all poorly 

preserved but belong in part to the genus Astrocoenia, 

which in Montana and Wyoming has been found only 

in beds of Bajocian age (Wells, 1942; Imlay, 1956b, 

p. 577, 578, 583, 584). The only other recorded occurrences of corals in the Jurassic of the western 

interior are (1) in southeastern Idaho in the Wolverine 

Canyon Limestone Member of the Preuss Sandstone 

(Imlay, 1952a, p. 1740-1742) and (2) in southwestern 

Montana as pebbles in the basal part of the Stump

TABLE 2. Regional and stratigraphic distribution of marine 

Jurassic megafossils in central and southern Utah

[X indicates that strattgraphic position is unknown]

Fossils

Mytilus cf. M. whitei (Whitfield). .......... ...... .

Lima (Plagiostoma) occidentalis Hall and Whitfield.

Myophorella (PnmyophoTella) montanaensis (Meek).

Quenstedtia aff. Q. bathonica (Morris and Lycett). ..

Western 

area

Arapien 

Shale, Twelvemile 

Canyon 

Member

X 

X 

X

X 

X

X 

X 

X

X 

X

X 

X

X 

X

X 

X 

X

X

Middle 

area

Eastern 

area

Carmel Formation^ 

Limy lower unit

j XXXXX

 

X

 

^MMM«

immm

^^^MM

~~ X 

X

X X

Sandstone exposed in the Centennial Range. The 

corals in the Stump Sandstone were derived from older 

Jurassic beds of unknown age, but the corals in the 

Preuss Sandstone are evidence that corals existed in 

the western interior sea after Middle Jurassic time. 

Nevertheless, as most of the occurrences of corals in the 

western interior are in Middle Jurassic beds, their 

presence in the Carmel Formation favors a Middle 

Jurassic age for that part of the formation in which 

they occur.

The age value of the nerineid gastropods in the Carmel Formation is similar to that of the corals. In the 

writer's experience they are fairly common in Middle 

Jurassic beds in Wyoming and Idaho and are unknown 

in younger Jurassic beds, except for an occurrence in
PELECYPODS FROM CENTRAL AND SOUTHERN UTAH C5

the Wolverine Canyon Limestone Member of the Preuss 

Sandstone in southeastern Idaho (1952a, p. 1742). 

By comparison the occurrence of such gastropods in 

moderate abundance in all parts of the limy lower unit 

of the Carmel Formation is suggestive of a Middle 

Jurassic age for that unit.

Somewhat stronger evidence for the Bajocian age 

of the lower unit of the Carmel Formation is furnished 

by four poorly preserved ammonites (Mesozoic Iocs. 

12555, 20351, 25678) found in the lower 5-40 feet of the 

formation in the northwestern part of the San Rafael 

Swell. These ammonites belong to the genus Zemistephanus which occurs elsewhere in beds of Bajocian 

age in the northern part of the western interior region 

in the Cook Inlet region, Alaska, and in the Queen 

Charlotte Islands, Alaska. The ammonites do not 

resemble any from beds of Callovian age in the same 

regions.

In summation, the limy lower unit of the Carmel 

Formation contains many pelecypod species that elsewhere in the western interior region occur only in beds 

of Bajocian to early Callovian age. In addition, the 

lower part of that unit contains a few pelecypod species 

and some ammonites that have been found elsewhere 

only in beds of Bajocian age. A Bajocian age for the 

upper part of the unit locally, as at Mount Carmel and 

near Pintura, is suggested by the presence of the pelecypod Thracia weedi Stanton, which has been found 

only in beds of Bajocian age. A Bajocian age for the 

entire lower unit is suggested likewise by the presence 

of corals and of nerineid gastropods, as those organisms 

have been found mostly in beds of Bajocian age elsewhere in the western interior. Evidently the fossil 

evidence is very strong for a Bajocian age for the lower 

part of the lower unit, favors a Bajocian age for the 

upper part of lower unit, and shows that no part of 

the unit is younger than early Callovian.

This general age assignment for the lower unit of the 

Carmel Formation is also favored by lithologic and 

stratigraphic resemblances to members of the Twin 

Creek Limestone of northern Utah (Imlay, 1953, p. 

55-59, fig. 3). If correlations based on the comparison 

are apt, then the lowest beds of the limy lower unit of 

the Carmel in the San Rafael Swell should be of Bajocian 

age, and the highest limy beds of the lower unit should 

be of earliest Callovian age. A Callovian age for the 

highest limy beds cannot be proved, however, because 

those beds have furnished few fossils, and the pelecypods 

present belong to species that range from Bajocian into 

the Callovian.

Similarly, in southwestern Utah between Gunlock 

and Cedar City, the limy lower unit of the Carmel 

Formation above the basal Red beds resembles members B-D, or possibly E, of the Twin Creek Limestone

as exposed in north-central Utah. There is no definitive 

lithologic or faunal evidence, however, that the upper 

part of this unit in southwest Utah correlates directly 

with members D or E of the Twin Creek. In fact, the 

presence of such pelecypods as Thracia weedi Stanton 

and Qervillia cf. G. montanaensis Meek near the top of 

the limy lower unit suggests that no part of that unit 

is younger than member C of the Twin Creek Limestone.

The above remarks concerning the age of the Carmel 

Formation apply only to the limy lower unit of the 

formations as defined by Wright and Dickey (1958, p. 

174). The overlying unit of gypsiferous claystone and 

siltstone on the San Rafael Swell has furnished no fossils, 

but its age is considered to be early Callovian on the 

basis of stratigraphic position and of regional stratigraphic relations (Imlay, 1952b, p. 963). The approximately equivalent beds in southwestern Utah that 

Gregory (1950, p. 94-98; 1951, p. 27-33) referred to 

the Entrada Sandstone, Curtis Formation, and Winsor 

Formation are now included in the upper part of the 

Carmel Formation (Wright and Dickey, 1963). Their 

age is probably Callovian on the basis of stratigraphic 

position. A few fossils have been found, however, in 

limy beds associated with gypsum that Gregory referred 

to his Curtis Formation (Mesozoic Iocs. 15498, 18867, 

20353). These fossils include the pelecypods Ostrea, 

Modiolus, Pronoellaf, and Camptonectes, a neritid 

gastropod, and the crinoid columnals named Pentacrinus 

asteriscus Meek and Hayden. These merely show that 

the beds are of Jurassic age.

ARAPIEN SHALE

All the fossils from the Arapien Shale that are described or listed herein are from the Twelvemile Canyon 

Member. The exact stratigraphic positions of many of 

the fossil localities in the Twelvemile Canyon Member 

are not well known because of structural and stratigraphic complications, because of the thousands of feet 

of beds involved, and because in many places the base of 

the formation is not exposed. The thin- to thick-bedded 

limestone in the lower part of the member has, however, 

furnished all the collections from southwest of Marysvale in Piute County and has probably furnished the 

collections from near Mineral Gap in Beaver County 

(table 3). In addition, some oolitic limestone from 250 

to 450 feet above the base of the member exposed on 

the first ridge south of Red Canyon, 2% miles northeast 

of Nephi, has furnished crinoid columnals, echinoid 

spines, Camptonectes, and Pinna (Johnson, 1959, p. 

23, 24, 41).

Most of the remainder of the collections listed in 

table 3 are from the calcareous shale and siltstone in 

the upper part of the Twelvemile Canyon Member.
C6 CONTRIBUTIONS TO PALEONTOLOGY

TABLE 3. Geographic distribution of marine Jurassic megafossils in Juab, San Pete, Piute, and Beaver Counties, Utah 

[Nos. 1-15 refer to numbers on fig. 1. All five-digit numbers refer to Qeol. Survey Mesozoic Iocs.]

Worm tubes _ __

Echinoid fragments

Crinoid columnals

Modiolus isonemus (Meek)

Isognomon sp

Pinna kingi Meek

sp _ _ _ _

Camptonectes stygius White

platessiformis White _

sp _ _

Plicatula sp

sp

Ctenostreon sp __

Ostrea strigilecula White

Vaugonia utahensis Imlay, n. sp

ef. V. conradi (Meek)

Astarte sp __ _

cf. A. (C.) interlineata (Lycett)

uintahensis Imlay, n. sp

ef. P. uintahensis Imlay, n. sp

Quenstedtia? sp

Pholadomya kingi (Meek)

Juab 

County

1

1

X

v

v

V

2

tc 

1

v

X

v

3

o

2N

X

v

San Pete County

4

S

v

v

5

1

S

v

6

00

1

X

So o«

X

8o o«

X

t^ * <*

IN

X

00

3<M

X

X

v

X

7

r1<M

X

X

X

X

8

<M

X

X

X

X

9

o

1

X

X

X

X

X

Piute County

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These include in particular the collections made by 

C. T. Hardy and E. M. Spieker and associates in areas 

near Mayfield and Gunnison. Four of these collections 

are labeled as probably from, the upper 600 feet of the 

member (USGS Mesozoic Iocs. 21447-21450) and two 

as probably about 1,800 feet below its top (USGS 

Mesozoic Iocs. 21646, 21647).

Most of the fossils found in the Twelvemile Canyon 

Member of the Arapien Shale are identical specifically 

with those in the Twin Creek Limestone and in the 

limy lower unit of the Carmel Formation. The presence of Astarte (Coelastarte) livingstonensis Imlay, n. sp. 

(USGS Mesozoic loc. 17269) indicates that part of the 

Arapien Shale is as old as Bajocian because that species 

elsewhere in the western interior region has been found 

only in beds of that age. Most of the species found in 

the Twelvemile Canyon Member, however, range 

throughout most of the Twin Creek Limestone and by 

comparison could be as young as early Callovian or as 

old as Bajocian.

Stratigraphically, correlation of the Twelvemile 

Canyon Member of the Arapien Shale with the Twin 

Creek Limestone seems reasonable, considering that 

both are underlain by the similar appearing Navajo,

or Nugget Sandstone, and both are overlain by saltbearing red beds. Furthermore, the lower part of 

Twelvemile Canyon Member exposed on the south 

side of Red Canyon, northeast of Nephi, shows many 

resemblances to the lower part of the Twin Creek Limestone. Thus, the basal 50-80 feet of oolitic limestone 

of the Tweivemile Canyon Member exposed at and near 

the bottom of Red Canyon could correspond with Member B of the Twin Creek Limestone, the overlying 1 GO200 feet of shaly limestone with Member C, the ridgecapping 200 feet of oolitic to dense limestone beds with 

Members D and E, and the overlying splintery limestone with Member F.

FAUNAL ASSOCIATIONS AND COMPARISONS

The distribution, abundance, and variety of marine 

megafossils in the Carmel Formation and Arapien 

Shale of central and southern Utah are related to a 

gradual northwestward thickening of the associated 

limestone and calcareous shale from 0 in southeastern 

Utah to as much as 700 feet in Washington County, 

2,140 feet in Piute County, and at least 3,000 feet in 

San Pete and Juab counties. This northwestward 

increase in calcareous rocks reflects a change from
PELECYPODS FROM CENTRAL AND SOUTHERN UTAH C7

littoral deposition on the east and southeast to shallow 

marine deposition on the northwest (Wright and 

Dickey, 1958, p. 174, 175) and to progressively more 

rapid subsidence of the sea floor, toward the northwest. 

Furthermore, the westernmost marine Jurassic calcareous rocks that are preserved are comparable in 

thickness and lithologic features to the Twin Creek 

Limestone of north-central Utah and adjoining areas 

(Imlay, 1950, 1953), are probably a southern extension 

of that limestone, and similarly appear to havs been 

formed in the open sea at a considerable distance from 

its western shore.

The relations of these lithologic changes to the associated fossils may be illustrated by considering all 

fossil occurrences in three areas (table 2) that trend 

northeastward and eastward roughly parallel to the 

eastern and southern shoreline of the Jurassic sea and 

that are partly separated by uplifts and plateaus on 

which Jurassic rocks are not exposed. The eastern 

area, thus selected, includes all fossil-collecting localities 

on the eastern side of the San Rafael Swell in Emery 

County as well as a few localities in central and eastern 

Wayne County east of Capitol Reef. The middle area 

includes all fossil-collecting localities in Washington, 

Iron, and Kane Counties, in western Garfield County 

east of Antimony and north of Escalante, in western 

Wayne County near Teasdale and Bicknell, and on 

the western side of the San Rafael Swell in Emery 

County. The western area includes all fossil-collecting 

localities in Beaver, Piute, San Pete, and Juab Counties.

Inspection of the fossils listed in table 2 shows that 

all three areas contain typical shallow-water attached 

pelecypods such as Ostrea, Modiolus, Plicatula, and 

Isognomon. All three contain the bottom-dwelling 

pelecypods Vaugonia, Pronoella, and Quenstedtia and 

the free-swimming pelecypod Camptonectes, and all 

contain gastropods. The middle area contains the 

greatest variety of organisms and the eastern area the 

least. Such organisms as worm tubes, echinoids, and 

crinoids have been found only in the middle and western 

areas and corals only in the middle area. Ammonites 

have been found only at the northwest end of the San 

Rafael Swell and starfish only near Teasdale, both in 

the middle area.

Table 2 does not show, however, that decrease in 

variety away from the middle area is accompanied by a 

great decrease in the abundance of individuals of most 

of the species or that the decrease in abundance is 

particularly striking between the Jurassic beds exposed 

on the west side of the San Rafael Swell in Emery 

County and the Jurassic beds west of the Wasatch 

Plateau in San Pete, Juab, and Piute Counties. This 

westward change is quite comparable to that occurring

in the Twin Creek Limestone between western Wyoming and southeastern Idaho (Imlay, 1957, p. 496, 497). 

In the Twin Creek Limestone, as in the Carmel Formation, the most fossiliferous beds occur where the 

formation is of moderate thickness and contains 

interbeds of thin-bedded limestone and calcareous shale. 

Both formations become less fossiliferous northwestward as they thicken and as thin beds become less 

common. Both formations contain such shallow-water 

pelecypods as Ostrea, which shows that the relatively 

less fossiliferous thicker sequences to the west were not 

deposited in deep water.

The Jurassic megafossils in the Carmel Formation 

include many species in common with the Twin Creek 

Limestone of north-central Utah, southeastern Idaho, 

and western Wyoming, and with equivalent beds in 

the Yellowstone National Park area of Montana and 

Wyoming (Stanton, 1899, p. 600-640; Imlay, 1956a; 

1956b, p. 576, 577, 583, 584, 591). The most striking 

difference is the absence in the Carmel Formation of 

the pelecypod genera Gryphaea and Meleagrinella and 

a near absence of ammonites, except in one small area 

along the northwest side of the San Rafael Swell. The 

presence of a fair number of gastropods suggests faunal 

comparisons with the lower part of the Twin Creek 

Limestone and with the Gypsum Spring Formation of 

north-central Wyoming. The presence of corals suggests comparisons with the Middle Jurassic assemblages 

in north-central Wyoming and south-central Montana 

(Imlay, 1956b, p. 577, 578, 583, 584).

The few Jurassic megafossils that have been obtained 

from the Arapien Shale are mostly from its upper part 

and most belong to species that occur in the Twin 

Creek Limestone and in the Carmel Formation. The 

shale may have been deposited in slightly deeper water 

than the Carmel Formation, but the presence of such 

pelecypods as Ostrea and Modiolus indicate that the 

water was fairly shallow.

In summation, the megafossils of the Jurassic formations in central and southern Utah are closely similar 

to those in beds of Middle Jurassic age in southeastern 

Idaho, southwestern Wyoming, and southern Montana. 

They occur in greatest variety and numbers in a middle 

area or belt about 45 miles wide extending southwestward from the west side of the San Rafael Swell roughly 

parallel to a former shoreline that lay to the southeast 

and south. In this middle area the Jurassic calcareous 

sequence is of moderate thickness and consists mostly of 

thin-bedded limestone interbedded with calcareous 

shale. Southeastward, fossils become less common as 

the calcareous sequence wedges out into red siltstone 

and claystone of probable littoral origin (Wright and 

Dickey, 1958, p. 174). Northwestward, fossils become
C8 CONTRIBUTIONS TO PALEONTOLOGY

less common as the calcareous sequence thickens 

enormously, presumably owing to rapid subsidence 

accompanied by equally rapid sedimentation. Apparently both southeastward and northwestward from 

the middle area, conditions on the sea bottom became 

less favorable for benthonic organisms.

GEOGRAPHIC DISTRIBUTION

The occurrences by county and locality of the fossils 

described herein are shown in tables 3-8. The general 

position of each locality is shown in figure 1. Detailed 

descriptions of each locality are given in the following 

table.

TABLE 4. Geographic distribution of marine Jurassic megafossils in Iron County, Utah 

[Nos. 16-25 refer to numbers on fig. 1. All five-digit numbers refer to Geol. Survey Mesozoic Iocs.]

Iron County

Corals_____ _ _____ ___ ___ ____ __ _ _ _ ___

Echinoid fragments.-.. _ ___ ___ ________

Crinoid columnals _______________

Nucula sp____ _ ________

Grammatodon? sp __ _ ___ _____________

Modiolus subimbricatus (Meek) _ _ _ _ __________

Isognomon cf . I. perplana (Whitfield) _ _ _

?sp_ _______________________________________

Camptonectes stygius White. __ _____

platessiformis White ________

cf. C. platessiformis White _

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Plicatula sp. _ _ _______________

Lima (Plagiostomd) occidentalis Hall and Whitfield

ziona Imlay, n. sp_ _ _ ______ _____ ___ _

sp

Ctenostreon sp __ _ _______

Ostrea (Ldostrea) strigilecula White _ _

Trigonia americana Meek _ _ _ _ _

sp. undet _____ _ ______________

elegantissima Meek _ _ _ _ __

Vaugonia conradi (Meek and Hay den) _ _ ____

cf. V. conradi (Meek and Hayden) _

utahensis Imlay, n. sp _ _ ______ ___ _ __ __

Myophorella (Promyophorella) montanaensis (Meek)__

Astarte cf. A. meeki Stanton __ _________ ___ __

sp_____ _____ _ _________ ____ _____

(Coelastarte) n. sp. undet

Pronoella cf. P. cinnabarensis (Stanton) _ _ _ _

uintahensis Imlay, n. sp_ ___ ___

cf. P. uintahensis Imlay, n. sp _ _ __

Gastropods undetermined __ _________

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PELECYPODS FROM CENTRAL AND SOUTHERN UTAH C9

TABLE 5. Geographic distribution of marine Jurassic megafossils in Washington County, Utah 

[Nos. 2&-42 refer to numbers on fig. 1. All five-digit numbers refer to Qeol. Survey Mesozoic Iocs.]

Echinoid fragments. __ _ __ __ _ _ ___ _ __ _ _ _

Crinoid columnals __________

Mytilus cf . M. whitei ( Whitfield) ________ __

Gervillia cf . G. montanaensis Meek ___ _ ______

Isognomon cf. /. perplana (Whitfield) __ _ _ __ __

Camptonectes stygius White _ __ _ _

cf. C. platessiformis White____ __ _ ___ ____

sp_ ____ ___ _______ ___ _ ______ ________

Lima (Plagiostoma) occidentalis Hall and Whitfield- __ 

cf. L. (P.) occidentalis Hall and Whitfield ___

ziona Imlay, n. sp_ _ _ _ ___ __ ___ ___ ____

sp_ ________________________________________

Ostrea (Liostrea) strigilecula White_ ________

Lopha aff. L. engelmanni (Meek) _ __ _

Trigonia americana Meek _____ __ _______

sp. undet______ ____ __ _ _______ ____ _

Vaugonia conradi (Meek and Hay den) .____ _______

Astarte cf. A. meeki Stanton. ___ ___ ___ ___

sp_____________ __ ______ ______________

(Coelastarte) cf. (C.) livingstonensis Imlay, n. sp__ ___

(C.) n. sp. undet. ________ _________

Pronoella cf . P. cinnabarensis (Stanton) __ _____

uintahensis Imlay, n. sp _____ __ ___

cf. P. uintahensis Imlay, n. sp _ _ _ _

? sp_ ______________________________________

? sp_______ _ ______ _

Pholadomya inaequiplicata Stanton _______ ___

Mactromya? sp_ __ ____ _ _______ ___ ___

Thracia weedi Stanton. __ _ ___ _ _________ ____

Gastropods undetermined. ____ _. _

Washington County

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Meek. elegantissima ________ ... _______ conradi (Meek Hayden).... Vaugonia and ___.._(Meek and Hayden).. aff. V. conradi ____ cf. conradi (Meek and Hayden)-. V. ________ Myophorella (Promyophorella) montanaensis 

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(Haidaia) Imlay, yellowstonensis sp. n. _______ (Coelastarte) livingstonensis Imlay, Astarte n. sp.. 

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PELECYPODS FROM CENTRAL AND SOUTHERN UTAH Cll

TABLE 7. Geographic distribution of marine Jurassic megafossils on the east side of the San Rafael Swell in Emery County, Utah 

[Nos. 59-71 refer to numbers on fig. 1. All five digit numbers refer to Qeol. Survey Mesozoic Iocs.]

Mytilus cf. M. whitei ( Whitfield) . . _ __

Isognomon cf. 1. perplana (Whitfield) _

a-rj

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sp____________ _____ ___ _ _____

Plicatus sp __ _____ _____ ____

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Pronoella cf . P. cinnabarensis (Stanton) _ 

uintahensis Imlay, n. sp - _

Tancrediat sp __ ____ ____

Quenstedtia aff. Q. bathonica (Morris and

? sp____________________________

Gastropods undet _ ____

East side of San Rafael Swell, Emery County

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C12 CONTRIBUTIONS TO PALEONTOLOGY

TABLE 8. Geographic distribution of marine Jurassic 

[Nos. 72-94 refer to numbers on fig. 1. All fiveCorals__

Worm tubes __ _ _ _________

E chin oid fragments. ___ _______ _ _ _ _

Grin old columnals _______ _ ___

Starfish, __ ____ __ _____

Idonearca? sp_ ____ ____ ___

Modiolus subimbricatus (Meek) _ _ _ ___

Mytilus cf. M. whitei (Whitfield) _ _ ______

Isognomon cf. I. perplana (Whitfield) __ _ _

?sp__________________________ ______

Pinna kingi Meek_ _ _ _

sp_____ _____________________ ___

Plicatula sp____ _ ______ _ _______

Anomia sp____ _ _

Lima (Plagiostoma) occidentalis Hall and 

Whitfield. ___ __________ _ ___________

Ostrea (Liostrea) strigilecula White. _ _ _ _

sp. undet ____ _______ ____

Vaugonia conradi (Meek and Hayden)____

cf. V. conradi (Meek and Hayden) _

cf. V. utahensis Imlay, n. sp _ _ ______

Myophorella (Promyophorella') montanaensis

(Meek)___ _______ __ __

Astarte cf. A. meeki Stanton__ ______ _ __

(Coelastarte) cf. (C.) livingstonensis 

Imlay, n. sp____ _____ _______

uintahensis Imlay, n. sp_ _ _ __ ____

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? sp__ _ _ ___ ___ ________________

Lucina sp ______

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Lycett) ______

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Pholadomya inaequiplicata Stanton. _ _ _ _ _ _ _

Mactromya? sp

Thracia weedi Stanton ___ ______

Gastropods undetermined. ___ _________

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PELECYPODS FROM CENTRAL AND SOUTHERN UTAH C13

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diget numbers refer to Geol. Survey Mesozoic Iocs.]

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113' 112° 111°

COUNTY,,

MIDDLE AREA

FIGURE 1. Index map showing marine Jurassic localities in central and southern Utah. (Numbers on map refer to those given in tables 3-8.)
PELECYPODS FROM CENTRAL AND SOUTHERN UTAH 015

Localities at which marine megafossils of Jurassic age have been 

collected in central and southern Utah

No. 

(fig1)

1

?,

3 

4

5

5

6

6

6 

6

7

Geological Survey 

Mesozoic 

localities

17269

13756

21450 

961

21449

17028

17029

21447

21448 

17018

21647

Collector's 

field 

numbers

S-F5.._.___

1 ___ _ __

18-7, 8, 23..

13-17_____.

S30F15_.___

S30F16__.-_

8-8 

9-2, 9, 10, 

17, 18

S31F2__.___

10-___._._.

Collector, year of collection, description of 

locality, and stratigraphic assignment

S. L. Schaff, 1936. Red Creek.

SE>i sec. 9, T. 12 S., R. 2 E., 

Juab County, Utah. Arapien 

Shale. 

W. T. Thorn, Jr., 1925. Hills

north of road and opposite dam., 

about 1 mile east of Nephi plaster mill on road from Nephi to 

Manti, Juab County, Utah. 

C. T. Hardy, 1948. About 3 

miles east of Levan, on the north 

side of Pigeon Creek in the 

Gunnison Plateau. SEJ4SWJ4 

sec. 27, T. 14 S., R. 1 E., Juab 

County, Utah. Arapien Shale. 

About 430 ft below base of 

Twist Gulch Member. 

T. W. Stanton, 1892. Levan

Canyon, west of Wales, San 

Pete County, Utah. Arapien 

Shale. 

C. T. Hardy, 1948; 5.6 miles northnortheast of Gunnison and north 

of Gunnison-Manti road, U.S. 

Highway 89, SEtfNWtf sec. 8, 

T. 19 S., R. 2 E., San Pete 

County, Utah. Arapien Shale. 

About 500 (?) ft below base of 

Twist Gulch Member. 

E. M. Spieker, 1930. Hogback

north of U.S. Highway west olE 

Mayfield road junction, Wasatch 

Plateau, San Pete County, Utah. 

Arapien Shale. 

S. L. Schoff and E. M. Spieker,

1930. Hills south of road at 

locality of S30F15 (Mesozoic 

loc. 17028), San Pete County, 

Utah. Arapien Shale. 

C. A. Reutinger, 1947; 2.7 miles

northwest of Mayfield, Utah, 

south of Twelvemile Creek, 

SEtfNWft sec. 19, T. 19 S-, R. 

2 E., San Pete County, Utah. 

Arapien Shale, 600 (?) ft below 

base of Twist Gulch Formation. 

C. T. Hardy, 1948; 2.7 miles 

northwest of Mayfield, south 

of Twelvemile Creek. gE^NW^ 

sec. 19, T. 19 S., R. 2 E., San 

Pete County, Utah. Arapien 

Shale, about 600 (?) ft below 

Twist Gulch Member. 

E. M. Spieker, 1931. Crest of

anticline on divide northwest of 

Mayfield in west central part 

of T. 19 S., R. 2 E., Wasatch 

Plateau, San Pete County, Utah. 

Arapien Shale "Gray" Member; 

probably near top. 

R. W. Imlay, John Mclntyre, and

C. T. Hardy, 1949; 2.5 miles 

northwest of Mayfield, Utah, 

south of Twelvemile Creek, SEJ4- 

SW}£ sec. 19, T. 19 S., R. 2 E., 

San Pete County, Utah. Twelvemile Canyon Member of Arapien 

Shale, about 1,800(?) ft below 

base of Twist Gulch Member.

Localities at which marine megafossils of Jurassic age have been 

collected in central and southern Utah Continued

No. 

(fig.

8 

9

10

10

11

1?

12

13

14

15

15

15

16

17

17

Geological Survey 

Mesozoic 

localities

21446 

17030

7890

7891

17464

16395

17462

17463

26310

18670

18671

18672

18211

19423

25674

Collector's 

field 

numbers

7-21, 25, 30_ 

S30F17_._._

45 

27__. ______

122 . ______

220_.__-_-_

Collector, year of collection, description of 

locality, and stratigraphic assignment

C. T. Hardy, 1948; 1.9 miles northwest of Mayfield, NEJ4NWJ4 sec. 

30, "T. 19 S., R. 2 E., San Pete 

County, Utah. Arapien Shale, 

about 1,800(7) ft below base of 

Twist Gulch Member. 

E. M. Spieker, 1930. Near Mayfield-Gunnison road about 1 mile 

from Mayfield, Wasatch Plateau, 

San Pete County, Utah. Arapien 

Shale. 

B. S. Butler, 1912. Cottonwood

Canyon, Marysvale district, Piute 

County, Utah. Float, upper 

limestone. 

B. S. Butler, 1912. Cottonwood

Canyon, Marysvale District, Piute 

County, Utah. 

Eugene Callaghan, 1937. Tushar

Mountains, near the north side of 

sec. 24, T. 28 S., R. 4 W., Piute 

County, Utah. From a gray 

well-bedded limestone outcrop. 

J. W. Young, 1933. Limestone

Gulch, 8 miles south of Marysvale, sec. 20, T. 28 S., R. 4 W., 

Piute County, Utah. Arapien 

Shale. 

Eugene Callaghan, 1937. From

Limestone Gulch in sec. 30, T. 

28 S., R. 3 W., Piute County, 

Utah. Approximately at edge of 

Delano Peak No. 2 quadrangle. 

Eugene Callaghan, 1937. From

exposures near the road on south 

side of Cottonwood Creek canyon 

in sec. 26 [probably error for sec. 

23], T. 28 S., R. 4 W., Tushar 

Mountains, Piute County, Ut ah 

R. W. Imlay, 1956. About 3-miles

up Cottonwood Creek, southwest 

of Marysvale, sec. 20, T. 28 S., 

R. 4 W., Piute County, Utah. 

Limestone float on road, probably 

derived from just above Navajo 

Sandstone. 

P. E. Dennis, 1941. Near Minersville, Beaver County, Utah. 

P. E. Dennis, 1941. Near Minersville, Beaver County, Utah. 

P. E. Dennis, 1941. Northeast of

Minersville, Beaver County, 

Utah. 

H. E. Thomas, 1940. Iron Springs

quadrangle, SEtfNWtf sec. 21, 

T. 35 S., R. 12 W., Iron County, 

Utah. Carmel Formation. 

Dense blue limestone mapped by 

Leith and Harder as the Homestake limestone. 

G. C. Selfridge, 1943. From east

side of Iron Mountain in the Iron 

Springs area. T. 35 S., R. 12 W., 

Iron County, Utah. Carmel 

Formation. 

R. W. Imlay and Hector Ugalde,

1955. From one-half mile east of 

Iron Springs on paved highway 

to Cedar City, Iron County, 

Utah. Carmel Formation.
C16 CONTRIBUTIONS TO PALEONTOLOGY

Localities at which marine megafossils of Jurassic age have 

collected in central and southern Utah Continued

No. 

(fig.

18

19 

19

19

19

20

21 

21

21 

21

21

21

Geological Survey 

Mesozoic 

localities

18213

19428 

19429

19431

19432

18660

25672 

26309

27470 

27471

27472

27473

Collector's 

field 

numbers

C-36-ll_____

121-bed23._ 

122-A___-._

123-_.____.

122__.___ .

1-55-7-1 9A.

SS-II-A____ 

S-I-E......

S-I-D__._-

S-I-C__-__

Collector, year of collection, description of 

locality, and stratigraphic assignment

H. E. Thomas, 1940; 2 miles north

of Cedar City, NEtfNEft sec. 2, 

T. 36 S., R. 11 W., Iron County, 

Utah. Buff to brown limestone 

of the Carmel Formation. Position uncertain. 

H. J. Bissell, 1944. Sec. 1, T. 36 

S., R. 11 W., northeast of Cedar 

City, Iron County, Utah. Carmel Formation. Main Pentacrinus unit. From lower part of 

23 ft of fossiliferous limestone 

lying 231 ft above base of Carmel. 

H. J. Bissell, 1944. Sec. 1, T. 36

S., R. 11 W., northeast of Cedar 

City, Iron County, Utah. Carmel Formation, 203 ft above base. 

H. J. Bissell, 1944, Sec. 1, T. 36

S., R. 11 W., northeast of Cedar 

City, Iron County, Utah. Carmel Formation, from 331 to 369 

ft above base. 

H. J. Bissell, 1944. Sec. 1, T. 36

S., R. 11 W., northeast of Cedar 

City, Iron County, Utah. Carmel Formation. Bed 24 of Bissell's measured section. Main 

Nucula-bearing unit, 11 ft of 

limonitic to yellow-brown limestone and siltstone lying about 

254 ft above base of formation. 

H. E. Gregory, 1941. Coal Creek

Canyon, sec. 15(?) T. 35 S., R. 

10/2 W. East of Cedar City, 

Iron County, Utah. Carmel 

Formation. 

R. W. Imlay, Paul Averitt, and 

Hector Ugalde, 1955. North 

side of Shurtz Creek about 6 

miles south of Cedar City, sees. 

11 and 14, T. 37 S., R. 11 W., 

Iron County, Utah. Carmel 

Formation. From pebbly oolitic 

limestone in lower part of formation about 235 ft above base. 

R. W. Imlay, 1956. Along Shurtz

Creek Road in sec. 11, T. 37 S., 

R. 11 W., Iron County, Utah. 

Carmel Formation, oolitic sandy 

limestone overlying cliff-forming 

limestone whose top is 235 ft 

above top of Navajo Sandstone. 

J. C. Wright and R. P. Snyder, 1959- 

On crest line of north pyramid 

near Shurtz Creek. SW^SW}4 

sec. 11, T. 37 S., R. 11 W., Iron 

County, Utah. Carmel Formation, 458 ft above base. 

J. C. Wright and R. P. Snyder,

1959. 314 ft above base of 

Carmel Formation. Same locality as 27470. 

J. C. Wright and R. P. Snyder,

1959. Shurtz Creek, 307-310 ft 

above base of Carmel Formation. 

Same locality as 27470. 

J. C. Wright and R. P. Snyder,

1959. Shurtz Creek, 287 ft above 

base of Carmel Formation. Same 

locality as 27470.

Localities at which marine megafossils of Jurassic age have been 

collected in central and southern Utah Continued

No. 

(fig. 

1)

31

?,1

91

?,1

?,1

?,?,

?,?,

23

24 

94

?,5

?,5

?,5

Geological Survey 

Mesozoic 

localities

27474

27475

27476

28461

28462

19424

19425

19427

5261 

5263

5268

27468

27469

Collector's 

field 

numbers

S-I-B_.____

S-I-A_...._

S-I-O______

G.B.R. 5_.__ 

HG-13__.__

HG-11_.._-

K-2.______

Collector, year of collection, description of 

locality, and stratigraphic assignment

J. C. Wright and R. P. Snyder,

1959. Shurtz Creek, 272-282 ft 

above base of Carmel Formation. Same locality as 27470. 

J. C. Wright and R. P. Snyder,

1959. Shurtz Creek, 262-272 ft 

above base of Carmel Formation. Same locality as 27470. 

J. C. Wright and R. P. Snyder,

1959. Shurtz Creek, 257 ft above 

base of Carmel Formation. Same 

locality as 27470. 

R. W. Imlay and N. F. Sohl, 1961.

North side of Shurtz Creek about 

6 miles south of Cedar City. 

Sees. 11 and 14, T. 37 S., R. 11 

W., Iron County, Utah. Carmel 

Formation. 

R. W. Imlay and N. F. Sohl, 1961.

Iron County, Utah, 229-255 ft 

above base of Carmel Formation. 

Same locality as collection loc. 

28461. 

G. C. Self ridge, 1943. Just east of

contact of porphyry and sedimentary deposits on Pilot Creek 

side of spur at Pilot Creek and 

Moody Wash, sec. 31, T. 36 S., 

R. 13 W., Iron County, Utah. 

Carmel Formation. Slabby gray 

oolitic limestone., 

G. C. Selfridge, 1943. Pink oolitic

limestone from the Moody Wash 

side of the spur at same locality 

as loc. 19424. 

G. C. Selfridge, 1943. Granite

Mountain, just east of the Armstrong ore body. SW>£ sec. 32, 

T. 35 S., R 12 W., Iron County, 

Utah. Carmel Formation. 

Dense dark-gray impure limestone. 

G. B. Richardson, 1907. Road from 

Kanarraville to coal mine, Utah. 

Near NW# cor. sec. 29, T. 37 S., R. 

11 W., Iron County, Utah. Altitude 7,000 ft. Carmel Formation. 

G. B. Richardson and H. Graff,

1907. WH sec. 32, T. 37 S., R. 

11 W., Iron Co., Utah. Carmel 

Formation, 1 mile southwest of 

Union coal mine, Kanarraville. 

H. Graff, 1907; 1 mile east of

Kanarraville, sec. 1, T. 38 S., R. 

12 W., Iron County, Utah. Carmel Formation. 

J. C. Wright and R. P. Snyder

1959. NEJ4 sec. 7, T. 38 S., R. 

1 1 W. On southwest spur of knoll 

southwest of Sweetwater Spring 

about 4 miles southeast of Kanarraville. Gray dense limestone 

from 555 to 575 ft above base of 

Carmel Formation, Iron County, 

Utah. 

J. C. Wright and R. P. Snyder,

1959; 4 miles southeast of Kanarraville, NE}4 sec. 7, T. 38 S., R. 

11 W., Iron County, Utah; 260- 

305 ft above base of Carmel Formation.
PELECYPODS FROM CENTRAL AND SOUTHERN UTAH C17

Localities at which marine megafossils of Jurassic age have been 

collected in central and southern Utah Continued

No. 

(fig. 

1)

26

27

28

29

30

31

32

33 

34

34

34

35

35

36

Geological Survey 

Mespzoic 

localities

18281

17196 

17349

17352

17354

18282

19426

17495 

27465

27466

27467

16700

16701

16702

Collector's 

field 

numbers

7a._. ______

F.G.W. 35- 

35.

7b_________

8 No. 41...

P-2___ ____

P-l___ ___

4__

Collector, year of collection, description of 

locality, and stratigraphic assignment

H. E. Gregory, 1940. Horse Ranch

Mountain, near E.J4 cor. sec. 23, 

T. 38 S., R. 12 W. Washington 

County, Utah, Carmel Formation. 

F. G. Wells, 1935. Limestone on 

hogback in SW#SW# sec. 26, 

T. 38 S., R. 12 W., Washington 

County, Utah, Carmel Formation. 

H. E. Gregory, 1936. Jolly Gulch,

Zion Park. Head of La Verkin 

Creek, Washington County, 

Utah. Carmel Formation, topmost bed, 100 ft below "Dakota" 

Sandstone. 

H. E. Gregory, 1936. Horse Pasture flats, \% miles northwest of 

road near Blue Springs, sec. 10, 

T. 39 S., R. 11 W., Washington 

County, Utah. Near top of Carmel Formation. 

H. E. Gregory, 1936; 2J_ miles south

of Blue Springs near limestone 

sinks, overlaid by lava. Sec. 15, 

T. 39 S., R. 11 W., Washington 

County, Utah. Carmel Formation about 200 ft above base. 

H. E. Gregory, 1940. Deep Creek

near junction with North Fork, 

Virgin River, Washington County, Utah. Carmel Formation. 

G. C. Selfridge, 1943. First main

canyon to the east of Echo Spring 

Canyon, sec. 35, T. 40 S., R. 10 

W., Washington County, Utah. 

Carmel Formation, pinkish-gray 

oolitic limestone. 

H. E. Gregory, 1937. West of 

Pintura, sec. 32, T. 39 S., R. 13 

W., Washington County, Utah, 

Carmel Formation. 

J. C. Wright and R. P. Snyder,

1959. Just north of Mill Creek 

at Red Seep, 3.3. miles along road 

from east boundary of National 

Forest, sec. 29, T. 39 S., R. 13 

W., Washington County, Utah. 

Carmel Formation. Yellowish 

silty limestone about 10 ft below 

top. 

J. C. Wright and R. P. Synder,

1959. Same as USGS loc. 27465. 

Washington County, Utah. 

Carmel Formation, about 75 ft 

below top. 

J. C. Wright and R. P. Snyder,

1959. Same location as USGS 

loc. 27465. Washington County, 

Utah. Carmel Formation, about 

250-350 ft above base. 

C. E. Dobbin, 1934. Sec. 22, T. 41

S., R. 13 W., Washington County, 

Utah. Carmel Formation. 

C. E. Dobbin, 1953. Sec. 22, T. 41

S., R. 13 W., Washington County, 

Utah. Carmel Formation. 

C. E. Dobbin, 1934. NE}£ sec. 34,

T. 40 S., R. 14 W., Washington

Localities at which marine megafossils of Jurassic age have been 

collected in central and southern Utah Continued

No. 

(fig. 

1)

36

36

37

37

38 

39

40

41

42

42

42

Geological Survey 

Mesozoic 

localities

16703

28493

28475

28477

17198 

17197

15878

10622

15877

28463

28464

Collector's 

field 

numbers

5_. _.___-__

F.G.W. 

138-35.

F.G.W. 

138-35.

Collector, year of collection, description of 

locality, and stratigraphic assignment

County, Utah. Carmel Formation. 

C. E. Dobbin, 1934. NE}£ sec. 34,

T. 40 S., R. 14 W., Washington 

County, Utah. Carmel Formation. 

R. W. Imlay and N. F. Sohl, 1961.

Danish Ranch section, NE. cor. 

sec. 34, T. 40 S., R. 14 W., Washington County, Utah. Carmel 

Formation, 60 ft above base of 

limestone. 

R. W. Imlay and N. F. Sohl, 1961.

Cottonwood Canyon, sec. 3, T. 

41 S., R. 15 W., Washington 

County, Utah. Carmel Formation. Oolitic and crinoidal limestone float, probably from 170 ft 

above base of limestone member, 

but possibly from a unit 240 ft 

above base. 

R. W. Imlay and N. F. Sohl, 1961.

Sec. 3, T. 41 S., R. 15 W., Cottonwood Canyon, Washington County, Utah. From oolitic limestone 

zone about 140 ft above base of 

limestone member. 

F. G. Wells, 1935. NEJ4NWK sec. 

25, T. 38 S., R. 17 W., Washington County, Utah. Carmel Formation. 

F. G. Wells, 1935. Limestone on 

ridge on south side of sec. 27, T. 

38 S., R. 17 W., Washington 

County, Utah. Carmel Formation. 

H. E. Gregory, 1931. "Mount

Jackson" near Nevada line west 

of Gunlock on the Santa Clara 

River, about 60 ft below "Dakota" Sandstone. Washington 

County, Utah. Carmel Formation. 

Robert Anderson, 1910. Santa

Clara River \}i miles below 

Gunlock on northeast side of 

creek and northeast of Gunlock 

field. Washington County, 

Utah. Carmel Formation. 

H. E. Gregory, 1931; 2 miles south

of Gunlock, Santa Clara River. 

Washington County, Utah. Carmel Formation. About middle 

of 300 ± ft of thin-bedded limestone. 

R. W. Imlay and N. F. Sohl, 1961.

West side of Santa Clara River, 

\% miles south of Gunlock near 

center of sec. 32, T. 40 S., R. 

17 W., Washington County, 

Utah. Carmel Formation, 287 

ft above base. 

R. W. Imlay and N. F. Sohl, 1961;

\Yz miles south of Gunlock, west 

side of Santa Clara River, Washington County, Utah. Carmel 

Formation, 50 ft below base of 

Upper Cretaceous basal conglomerate.
CIS CONTRIBUTIONS TO PALEONTOLOGY

Localities at which marine megafossils of Jurassic age have been 

collected in central and southern Utah Continued

No. 

(fig. 

1)

42

42

42

43

43

44

45

45

45

45

45

46

Geological Survey 

VIesozoic 

localities

28465

28466

28467

25826

25827

28470

10098

20351

20359

20364

25684

25670

Collector's 

field 

numbers

JCW10

JCW13

1-46-9-1 IB.

1-46-9-1 IB.

1-46-9-11 A

1-55-6-25 _.

I-55-6-28A

Collector, year of collection, description of 

locality, and stratigraphic assignment

R. W. Imlay and N. F. Sohl, 1961;

\Yi miles south of Gunlock on

west side of Santa Clara River;

near center sec. 32, T. 40 S.,

R. 17 W., Washington County,

Utah. Carmel Formation, float

from oolitic sandstone capping

ridge about 350 ft above base

of limestone member of Carmel

Formation.

R. W. Imlay and N. F. Sohl, 1961;

ll/z miles south of Gunlock,

Washington County, Utah.

Carmel Formation about 5 ft

above loc. 28464.

R. W. Imlay and N. F. Sohl, 1961;

\% miles south of Gunlock,

Washington County, Utah; 430

ft above base of limestone member of Carmel Formation.

J. C. Wright and D. D. Dickey,

1955. At Cedar Mountain, San

Rafael Swell, sec. 10, T. 19 S.,

R. 11 E., Emery County, Utah.

Carmel Formation, 30 ft above

base.

J. C. Wright and D. D. Dickey,

1955. At Cedar Mountain, San

Rafael Swell, sec. 10, T. 19 S.,

R. 11 E., Emery County, Utah.

Carmel Formation, 30 ft above

base.

R. W. Imlay and N. F/Sohl, 1961.

Tributary on northeast side of

Buekhorn Wash at crossing of

road from Woodside to Castle

Dale, Utah. Sec. 8, T. 19 S.,

R. 11 E., Emery County, Utah.

Carmel Formation.

W. M. Small, 1917. San Rafael

Swell at point where Buckhorn

Wash goes down from the lower

Buckhorn Flat, SE}£ sec. 13,

T. 19 S., R. 10 E., Emery County,

Utah. Carmel Formation.

J. B. Reeside, Jr., and R. W.

Imlay, 1946. Head of Buckhorn

Wash, sec. 13, T. 19 S., R. 10 E.,

Emery County, Utah. Carmel

Formation, platy limestone about

25 ft above base.

J. B. Reeside, Jr., and R. W. Imlay,

1946. Head of Buckhorn Wash,

sec. 13, T. 19 S., R. 10 E.,

Emery County, Utah, Carmel

Formation, platy limestone about

25 ft above base.

J. B. Reeside, Jr., and R. W. Imlay,

1946. Head of Buckhorn Wash.

T. 19 S., R. 10 E., Carmel

Formation, from red beds about

10 ft above the base.

R. W. Imlay, 1955. SW>4 sec. 18,

T. 19 S., R. 11 E., to SE_K see.

13, T. 19 S., R. 10 E., Emery

County, Utah. Carmel Formation, 20-40 ft above base.

R. W. Imlay, 1955. On small

ridge just south of road in

NEtfNWtf sec. 17. T. 19 S., 

R. 11 E., Emery County Utah.

Localities at which marine megafossils of Jurassic age have been 

collected in central and southern Utah Continued

No. 

(fig. 

1)

46

46

47

48

48

48

49

50

50

51

51

51

51

Geological Survey 

Mesozoic 

localities

25678

25680

25687

25681

25679

25682

25686

12555

12556

12557

12558

12560

12574

Collector's 

field 

numbers

I-55-6-28B.

1-55-6-29 A.

1-55-6-26 ._

I-55-6-29B.

I-55-6-23B.

1-55-6-23 A121_____._.

Collector, year of collection, description of 

locality, and stratigraphic assignment

Carmel Formation, about 75 ft

above base.

R. W. Imlay, 1955. Near head of

small gully draining west into

southwest-trending tributary of

Buckhorn Wash. NE}4 sec. 18,

T. 19 S., R. 11 E., Emery County,

Utah. Carmel Formation, ledgeforming sandy limestone about

40 ft above base.

R. W. Imlay, 1955. On northwest

side of gulch in northeast and

central parts of sec. 18, T. 19 S.,

R. 11 E., Emery County, Utah.

Carmel Formation, ledge of sandy

limestone from 20 to 30 ft above

base.

R. W. Imlay, 1055. W/i sec. 24, T.

19 S., R. 10 E., Emery County,

Utah. Carmel Formation, lower

20-40 ft.

R. W. Imlay, 1955. West side of

gulch in SW#SE# sec. 36, T. 19

S., R. 10 E., Emery County,

Utah. Carmel Formation, from

15 to 25 ft above base in sandy

limestone.

R. W. Imlay, 1955. NWX sec. 1,

T. 20 S., R. 10 E., Emery

County, Utah. Carmel Formation, about 40 ft above base.

R. W. Imlay, 1955. NWtf sec. 1,

T. 20 S., R. 10 E., Emery County,

Utah. Carmel Formation, lower

20ft.

R. W. Imlay, 1955. Northeast

part of sec. 31, T. 19 S., R. 11 E.,

Emery County, Utah. Carmel

Formation, about 20 ft above

base.

W. H. Newhouse, 1924. The

Wedge, about 2 miles south of

Fullers Bottom along San Raf ael

River, San Raf ael Swell, Emery

County, Utah. Carmel Formation, 6-12 ft above Navajo

Sandstone.

D. J. Fisher, 1924. The Wedge,

between Buckhorn Wash and San

Rafael River, Emery County,

Utah. Carmel Formation, 8-10

ft above base.

W. H. Newhouse, 1924. San Rafael

River below Fullers Bottom, San

Rafael Swell, Emery County,

Utah. Carmel Formation, 18 ft

above Navajo Sandstone.

W. H. Newhouse, 1924. San Rafael

River, San Rafael Swell, Carmel

Formation, 15 ft above base.

W. H. Newhouse, 1924. Below

Fullers Bottom on San Rafael

River, Emery County, Utah.

Carmel Formation, 17 ft above

the Navajo Sandstone.

W. H. Newhouse, 1924. Below

Fullers Bottom on San Rafael

River. San Rafael Swell, Emery

County, Utah. Carmel Formation, 2-8 ft above Navajo Sandstone.
PELECYPODS FROM CENTRAL AND SOUTHERN UTAH C19

Localities at which marine megafossils of Jurassic age have been 

collected in central and southern Utah Continued

No. 

(fig.

52

52

53

54

54

55

56

56 

56

56

56

57

58

Geological Survey 

Mesozoic 

localities

12841

12842

6941

6944

7341

6281

13529

25673 

27592

28472

28480

6282 

13531

Collector's 

field 

numbers

No. L______

M_. ._._.._

F-33.__.___

No. ABCD. 

I-55-7-8A...

No. 3Cc.__. 

B-l. _______

Collector, year of collection, description of 

locality, and stratigraphic assignment

James Gilluly, 1924. Salt Wash

Canyon, sec. 25, T. 20 S., R. 9 E., 

San Rafael Swell, Emery County, 

Utah. Carmel Formation, J16 

ft above Navajo Sandstone. 

James Gilluly, 1924. Salt Wash

Canyon, sec. 25, T. 20 S., R. 9 E., 

San Rafael Swell, Emery County, 

Utah. Carmel Formation, 21 ft 

above Navajo Sandstone. 

Robert Forrester, 1910. Near

mouth of Salt Wash, Emery 

County, Utah. Carmel Formation. 

Robert Forrester, 1910. Coal

Wash, about 2 miles above 

Leaking Springs, Emery County, 

Utah. Carmel Formation. 

C. T. Lupton, 1911. About 2

miles above spring on Coal Wash 

east of Ferron, Emery County, 

Utah. Carmel Formation, just 

above massive Navajo Sandstone. 

Robert Forrester, 1909. Coal

Wash, sec. 10, T. 21 S., R. 9 E., 

Emery County, Utah. Carmel 

Formation, in lower 30 ft. 

James Gilluly, and E. T. McKnight, 

1925. Rim of Eagle Canyon, 

just below road from Rochester 

to Horn Silver Prospect, approximately sec. 33, T. 22 S., R. 9 E. 

(unsurveyed), Emery County, 

Utah. Basal limestone of Carmel 

Formation. 

R. W. Imlay, 1955. On divide 

between Eagle Canyon and 

Devil's Canyon, NE% sec. 33, 

T. 22 S., R. 9 E., Emery County, 

Utah. Carmel Formation, about 

15 ft above base. 

J. S. Wright and D. D. Dickey,

1956. On high flatiron just 

south of Eagle Canyon near 

road on west side of San Rafael 

Swell. NEJi sec. 33, T. 22 S., 

R. 9 E., Emery County, Utah. 

Carmel Formation, limestone 

member. 

R. W. Imlay and N. F. Sohl, 1961.

Justensen Flats, NWJ4 sec. 3, 

T. 23 S., R. 9 E., Emery County, 

Utah. Limestone ledges between 

switchbacks of road, 14-21 ft 

above base of Carmel Formation. 

R. W. Imlay and N. F. Sohl, 1961.

Eagle Canyon Lookout, sec. 33, 

T. 22 S., R. 9 E., Emery County, 

Utah. About 20 ft above base 

of Carmel Formation in bed 

of limestone with very abundant 

fossil fragments just below green 

shale. 

Robert Forrester, 1909. Devil's 

Canyon, sec. 14, T. 23 S., R. 

8 E., Emery County, Utah. 

Carmel Formation, in lower 

30ft. 

James Gilluly, 1925. Muddy

Creek, south bank, 2}£ miles

Localities at which marine megafossils of Jurassic age have been 

collected in central and southern Utah Continued

No. 

(fig. 

1)

58

59

59

60

61

61 

61

6?

63

64

Geological Survey 

Mesozoic 

localities

13532

12839

12840

12835

20352

20356 

20358

19422

22656

15551

Collector's 

field 

numbers

B-2._._.__.

No. F_____

No. G______

No. B.__.._

1-46-9-1 OC_

1-46-9-1 OBI-46-9-1 OA_

No. !__-__-

Collector, year of collection, description of 

locality, and stratigraphic assignment

below mouth of Salt Gulch on 

west flank of San Rafael Swell, 

Emery County, Utah. Carmel 

Formation, 17 ft above base. 

James Gilluly, 1925. South bank

of Muddy Creek, 1% miles below 

mouth of Salt Gulch, San Rafael 

Swell, Emery County, Utah. 

Limestone bed 32 ft above base 

of Carmel Formation. 

D. J. Fisher, 1924. Cottonwood

Springs Draw, sec. 33, T. 19 S., 

R. 13 E., San Rafael Swell, 

Emery County, Utah. Carmel 

Formation, 40 ft above Navajo 

Sandstone. 

James Gilluly, 1924. Cottonwood

Springs Draw, sec. 33, T. 19 S., 

R. 13 E., San Rafael Swell, 

Emery County, Utah. Carmel 

Formation, immediately above 

Navajo Sandstone. 

James Gilluly, 1924. Cottonwood

Springs Draw, sec. 10, T. 20 S., 

R. 13 E., San Rafael Swell, 

Emery County, Utah. Carmel 

Formation, 68 ft above Navajo 

Sandstone. 

J. B. Reeside, Jr., and R. W. 

Imlay, 1946. Near Smith's 

Cabin, 5}^ miles west of highway 

on road to Saleratus Wash, 

Emery County, Utah. Carmel 

Formation, sandstone bed at top 

of lower limestone member just 

below red beds. 

J. B. Reeside, Jr., and R. W. 

Imlay, 1946. Near Smith's 

Cabin, 5% miles west of highway 

on road to Saleratus Wash, 

Emery County, Utah. Carmel 

Formation, about 60 ft above 

base. 

J. B. Reeside, Jr., and R. W. 

Imlay, 1946. Near Smith's 

Cabin, about 5*4 miles from highway on road to Saleratus Wash, 

east side of San Rafael Swell, 

Emery County, Utah. Carmel 

Formation, about 25 ft above 

base. 

H. E. Yokes, 1943; 1 mile south of

Black Dragon Canyon, northeast 

side of San Rafael Swell, sec. 6, 

T. 22 S., R. 14 E., Emery 

County, Utah. Carmel Formation. 

L. C. Craig and V. L. Freemen,

about 1950. W/l 2 sec. 13, T. 22 

S., R. 13 E., Emery County, 

Utah. Carmel Formation, 20 ft 

above base. 

L. G. Henbest and A. A. Baker,

1930. Side of road on east side 

of Iron Wash in SEtf sec. 34, T. 

23 S., R. 13 E., Green River 

Desert, Emery County, Utah. 

Carmel Formation, about 96 feet 

above base.
C20 CONTRIBUTIONS TO PALEONTOLOGY

Localities at which marine megafossils of Jurassic age have been 

collected in central and southern Utah Continued

No. 

(fig. 

1)

65

65 

66

67

67

68

69

70

71

72

73

73 

73

Geological Survey 

Mesozoic 

localities

12581

16202 

9111

8597

12570

11137

17412

10116

27591

24258

24259

24260 

25669

Collector's 

field 

numbers

No. H51..._

No. 80_.___

Lot 2._____

No. !!_____

SF-1_______

CR-108___.

CR-110_--_

CR-115___. 

1-55-7-13 __

Collector, year of collection, description of 

locality, and stratigraphic assignment

J. B. Reeside, Jr., 1924. About 15

miles southwest of Green River, 

\% miles west of Lost Spring, San 

Rafael Swell, Emery County, 

Utah: Carmel Formation, 104 ft 

above top of Navajo Sandstone. 

L. G. Henbest, 1930. Green River 

Desert, NE}4 sec. 19, T. 24 S., 

R. 13 E., Emery County, Utah. 

Carmel Formation. 

B. S. Butler, 1914. Lost Spring

just east of San Rafael Swell, sec. 

29, T. 24 S., R. 13 E., Emery 

County, Utah. Carmel Formation. 

C. T. Lupton, 1913. Green River

Desert, sees. 23, 24, 26, 35 T. 

24 S., R. 12 E., Emery County, 

Utah. Carmel Formation. 

J. B. Reeside, Jr., 1924. West of

Lost Spring, sees. 23, 24, 26, 35, 

T. 24 S., R. 12 E., Emery County, 

Utah. Carmel Formation, uppermost limestone (oolite), 100 ft 

above base. 

C. J. Hares, 1921. East side of San

Rafael Swell, near Temple Mountains, sec. 34 T., 24 S., R. 12 E., 

Emery County, Utah. Carmel 

Formation, limestone at bottom. 

A. A. Baker, 1930. About 500 feet

east of Swazey's Seep, Green 

River Desert, Emery County, 

Utah. Upper part of Carmel 

Formation. 

W. B. Emery, 1917. Hanksville

road, 2 miles south of Straight 

Wash, Green River Desert, SEJ4 

sec. 6, T. 24 S., R. 13 E., Emery 

County, Utah. Carmel Formation. 

J. C. Wright, 1955. Little Wild

Horse Mesa, SE# sec. 35, T. 25 

S., R 10 E., Emery County, 

Utah. Carmel Formation; 42- 

44J^ ft above base. 

J. F. Smith, 1952. About }i mile 

west of Sun Glo Park (in Fish 

Lake National Forest) Capitol 

Reef area, SW# sec. 31, T. 28 S., 

R. 4 E., Wayne County, Utah. 

Carmel Formation, about 40-60 

ft above base. 

J. F. Smith, 1952. Approximately 

% mile west of Teasdale, Capitol 

Reef area, sec. 17 T. 29 S., R. 4 

E., Wayne County, Utah. Carmel Formation, 40-60 ft above 

base. 

J. F. Smith, 1952. Approximately 

% mile west of Teasdale, Capitol 

Reef area, sec. 17, T. 29 S., R. 

4 E., Wayne County, Utah. Carmel Formation. 

R. W. Imlay, 1955. One-half mile 

west of Teasdale, sec. 17, T. 29 S., 

R. 4 E., Wayne County, Utah. 

Carmel Formation. Oolitic limestone, about 44 ft above top of 

Navajo Sandstone, or 7 ft above 

top of red unit at base of Carmel.

Localities at which marine megafossils of Jurassic age have been 

collected in central and southern Utah Continued

No. 

(fig. 

1)

73

74

75

75

76

77

78

78

78

79

80

Geological Survey 

Mesozoic 

localities

28456

18076

10436

25685

9112

9113

18920

18922

26308

28492

25671

Collector's 

field 

numbers

No. 4______

No. 5______

155-7-1 5 A. _

Collector, year of collection, description of 

locality, and stratigraphic assignment

R. W. Imlay and N. F. Sohl, 1961.

West of Teasdale, between town 

and Bullberry Creek, SEtfSEtf 

sec. 18, T. 29' S., R. 4 E., Wayne 

County, Utah. Carmel Formation. 

H. E. Gregory, 1937. In Fremont

River Canyon, 4 miles below 

Fruita, west-central part of sec. 

17, T. 29 S., R. 7 E., Wayne 

County, Utah. Carmel Formation. 

E. F. Davis, 1920. East side of the

Water Pocket fold just north of 

Capitol Wash, NWtf sec. 10, T. 

30 S., R. 7 E., Wayne County, 

Utah. Carmel Formation. 

R. W. Imlay, 1955. North side

of mouth of Capitol Wash, at east 

end of Capitol Reef Monument, 

NW}1 sec. 10, T. 30 S., R. 7 E., 

Wayne County, Utah. Carmel 

Formation. Oolitic bed at top 

of limestone ledge, about 81 ft 

above top of massive Navajo 

Sandstone and 28 ft above gypsum bed. 

B. S. Butler, 1914. On trail about

midway between Hanksville and 

Robbers Roost just above Navajo Sandstone, NEJ4 sec. 31, 

T. 28 S., R. 13 E., Wayne 

County, Utah. Carmel Formation. 

B. S. Butler, 1914. Boulder

Mountain, near head of Pleasant 

Creek, T. 31 S., R. 5 E., Garfield County, Utah. Carmel Formation. 

H. E. Gregory, 1943. Antimony

Canyon, sec. 20, T. 31 S., R. 

1 W., Garfield County, Utah. 

Carmel Formation, 10 ft above 

Navajo Sandstone. 

H. E. Gregory, 1943. Antimony

Creek, sec. 20, T. 31 S., R. 1 W., 

Garfield County, Utah. Carmel 

Formation. 

R. W. Imlay, 1956. On west side

of gulch draining south into 

Antimony Creek in west-central 

part of sec. 20, T. 31 S., R. 1 W., 

Garfield County, Utah. Carmel 

Formation, 20-30 ft above base. 

N. F. Sohl, 1961. Devils Backbone, approximately sec. 5, T. 

33 S., R. 3 E., Garfield County, 

Utah. About 200 yds south of 

pre-1961 Devils Backbone Bridge 

on west side of road. Carmel 

Formation, about 15-20 ft above 

base. 

R. W. Imlay, 1955. Deep Creek, 

about 1 mile southeast of road to 

Hell's Backbone Ridge and about 

15 miles north of Escalante, 

Garfield County, Utah. Carmel Formation, from basal bed 

of 15-ft limestone ledge about 

20 ft above top of Navajo 

Sandstone.
PELECYPODS FROM CENTRAL AND SOUTHERN UTAH C21

Localities at which marine megafossils of Jurassic age have been 

collected in central and southern Utah Continued

No. 

(fig. 

1)

80

SO

81

8?

83

83

83

83

84

85

86

Geological Survey 

Mesozoic 

localities

26307

28468

25676

20353

964

16624

28473

28496

963

5278

15498

Collector's 

field 

numbers

HG-19_____

Collector, year of collection, description of 

locality, and stratigraplric assignment

R. W. Imlay, J. D. Strobell, Jr.,

J. C. Wright, D. D. Dickey, 

1956. On Deep Creek, onehalf mile southeast of road to 

Hell's Backbone, east-central part 

of sec. 15, T. 33 S., R. 2 E., Garfield County, Utah, Carmel Formation, shaly limestone about 

12 ft above Navajo Sandstone. 

R. W. Imlay and N. F. Sohl, 1961.

East side of Deep Creek 4,000 

ft downstream from road crossing of Deep Creek by the road to 

Devil's Backbone, sec. 15, T. 

33 S., R. 2 E., Garfield County, 

Utah. Same as loc. 26307. Carmel Formation. 

R. W. Imlay, 1955. In Paria

Valley, about 5 miles south of 

Cannonville, Kane County, Utah. 

Carmel Formation about 12 ft 

above base of formation in gray 

sbaly limestone. (See Gregory, 

1951, p. 58.) 

H. E. Gregory, 1946. Averitt

Hollow, probably NW>£ sec. 23, 

T. 38 S., R. 3 W., Kane County, 

Utah. From the calcareous 

sandstone above the thick bed of 

gypsum in the "Curtis" Formation of Gregory. 

T. W. Stanton, 1892. Upper part

of Kanab Creek, sec. 3, T. 41 S., 

R. 6 W., Kane County, Utah. 

Carmel Formation. 

C. D. Walcott, 1879. Upper end

of box canyon below volcano, 

Kanab Creek, W# sec. 3, T. 

41 S., R. 6 W., Kane County, 

Utah. Carmel Formation. 

R. W. Imlay and N. F. Sohl, 1961.

Kanab Creek, west fork at Box 

Canyon just below Glendale 

Road and below lava flow, WJ4 

of sec. 3, T. 41 S., R. 6 W., Kane 

County, Utah. Carmel Formation, about 10-15 ft below top of 

limestone member. 

R. W. Imlay and N. F. Sohl, 1961.

Kanab Creek, west fork at Box 

Canyon just below Glendale 

Road and below lava flow, W% 

of sec. 3, T. 41 S., R. 6 W., Kane 

County, Utah. Carmel Formation, about 10-15 ft below top of 

limestone member. 

T. W. Stanton, 1892. NW# sec.

25, T. 40 S., R. 7 W., Glendale 

area, Kane County, Utah. 

G. B. Richardson, 1907. About

2!/2 miles southeast of Orderville, 

From limestone on top of "Sevier 

Fault," Kane County, Utah. 

Carmel Formation. 

J. B. Reeside, Jr. and others, 1930.

West of bridge at south end of 

Mount Carmel. WJ4 sec. 18, 

T. 41 S., R. 7 W., Kane County, 

Utah. Carmel Formation, 15 ft

Localities at which marine megafossils of Jurassic age have been 

collected in central and southern Utah Continued

No. 

(fig. 

1)

86

86

87

87

87

87

87

87

87

88

89

Geological Survey 

Mesozoic 

localities

12749

12753

11438

11439

25675

25683 

28469

28471

28474

17353

5273

Collector's 

field 

numbers

Lot 4______

Lot 8___.__

No. !___._.

No. 2______

I-55-7-21A.

Collector, year of collection, description of 

locality, and stratigrapMc assignment

above gypsum bed at Mount 

Carmel. 

H. E. Gregory, 1924. Mount

Carmel, Kane County, Utah. 

Carmel Formation, 76 ft above 

Navajo Sandstone. (See Gregory, 1950, p. 126.) 

H. E. Gregory, 1924. Mount

Carmel, Kane County, Utah. 

Carmel Formation, bed 8 of 

published section. (See Gregory, 1950, p. 126.) 

H. E. Gregory, 1922. East bank

of Virgin River, about 3 miles 

south of Mount Carmel, sec. 30, 

T. 41 S., R. 7 W., Kane County, 

Utah. Carmel Formation. 

H. E. Gregory, 1922. East bank

of Virgin River, about 3 miles 

south of Mount Carmel, sec. 30, 

T. 41 S., R. 7 W., Kane County, 

Utah. Carmel Formation, 25 ft 

above Navajo Sandstone. 

R. W. Imlay and Hector Ugalde,

1955. In NW>4 sec. 30, T. 41 S., 

R. 7 W., Kane County, Utah. 

Carmel Formation. From base 

of unit 10 of Gregory's published 

section (Gregory, 1950, p. 127). 

R. W. Imlay and Hector Ugalde, 

1955. Just southeast of bridge, 

in SE}£ sec. 31, T. 41 S., R. 7 W., 

Kane County, Utah, Carmel Formation, top bed. Unit 15 of Gregory's published section (Gregory, 

1950, p. 127). 

R. W. Imlay and N. F. Sohl, 1961.

Just east of highway and south 

of pre-1960 bridge, sec. 30, T. 41 

S., R. 7 W., Kane County, Utah. 

Carmel Formation, about 20 ft 

below top of limestone member. 

R. W. Imlay and N. F. Sohl, 1961.

On east side of U.S. Highway 89 

just south of pre-1960 bridge, 

sec. 30, T. 41 S., R. 7 W., Kane 

County, Utah. Carmel Formation, about 93 ft above base of 

limestone member (at top of 

"Lower lime"). 

R. W. Imlay and N. F. Sohl, 1961.

On east side of U.S. Highway 89 

just south of pre-1960 bridge, sec. 

30, T. 41 S., R. 7 W., Kane 

County, Utah. Carmel Formation, about 35 ft below top of 

limestone member. 

H. E. Gregory, 1936. Escarpment

south of Zion-Mount Carmel 

road. Approximately sec. 18, 

T. 41 S., R. 8 W., Kane County, 

County, Utah. Carmel Formation. 

G. B. Richardson, 1907. Valley of

North Fork of Virgin River about 

1% miles west of Walkers Ranch, 

sec. 33, T. 39 S., R. 9 W., Kane 

County, Utah. Carmel Formation.

711-164 O 64-
C22 CONTRIBUTIONS TO PALEONTOLOGY

Localities at which marine megafossils of Jurassic age have been 

collected in central and southern Utah Continued

No. 

(fig.

89

89 

90

91 

92 

93

94

Geological Survey 

Mesozoic 

localities

28494

28495 

28479

17351 

17054 

28491

17494

Collector's 

field 

numbers

Collector, year of collection, description of 

locality, and stratigrapMe assignment

R. W. Imlay and N. F. Sohl, 1961. 

South side of canyon of Virgin 

River at cabin. Orderville quadrangle, sec. 33, T. 39 S., R. 9 W., 

Kane County, Utah. Carmel 

Formation, 20-30 ft below top 

of limestone member and 8-18 

ft above top of oolitic ledge 

former. 

R. W. Imlay and N. F. Sohl, 1961. 

South side of Virgin River, sec. 

33, T. 39 S., R. 9 W., Kane 

County, Utah. Carmel Formation, 20-30 ft below top of 

limestone member. 

R. W. Imlay, 1961. Orderville 

Canyon near SE cor. sec. 19, 

T. 40 S., R. 9 W., Kane County, 

Utah. Thin-bedded creamweathering limestone in uppermost 10 ft of Carmel Formation 

below gypsum bed. 

H. E. Gregory, 1936. Jolly Gulch, 

Zion Park, approximately SW}4 

sec. 8 T. 41 S., R. 9 W., Kane 

County, Utah. Carmel Formation, top limestone below red 

sandstone. 

H. E. Gregory, 1934. East entrance Zion Park. Approximately W# sec. 18, T. 41 S., 

R. 9 E., Kane County, Utah. 

Carmel Formation, near top of 

Navajo Sandstone. 

R. W. Imlay and N. F. Sohl, 1961. 

Co-op Creek borrow pit, % mile 

north of Utah highway 15 on 

west side of road to Orderville 

Canyon, sec. 15, T. 41 S., R. 9 

W., Kane County, Utah, Carmel 

Formation. 

H. E. Gregory, 1937. Box Mesa, 

near Parunuweap Canyon, north 

of Virgin River in NEJ4 sec. 31, 

T. 41 S., R. 9 W., Kane County, 

Utah. Carmel Formation.

SUMMARY OF RESULTS

1. The marine Jurassic pelecypods from central and 

southern Utah available for study comprise about 

1,700 specimens, are more common than other 

megafossils, and are divisible into 31 genera and 

44 species. The dominant genera in order of 

decreasing abundance are Camptonectes, Ostrea, 

Pronoella, Vaugonia, Myophorella (PromyophoreVa), and Lima (Plagiostoma). Numerically these 

compose 80 percent of the specimens available 

for study. Nucla and Thracia are locally common 

but are not widespread. Grammatodon?, Modiolus, 

Isognomon, Plicatula, Lopha, Trigonia, Astarte 

(Coelastarte), and Pholadomya are fairly widespread but are not common. Seventeen genera 

occur rarely.

The limy lower unit of the Carmel Formation is of 

Bajocian to possible early Callovian age. The 

lower part of this unit contains pelecypods and 

some ammonites that are found elsewhere in the 

western interior region only in beds of Bajocian 

age. A Bajocian age for the upper part of the 

unit locally is suggested by the presence of the 

pelecypod Thracia weedi Stanton. The presence 

of corals and nerineid gastropods likewise favors 

a Bajocian age for the lower limy unit, as those 

organisms are uncommon above beds of that age 

elsewhere in the western interior.

This age assignment for the limy lower unit of the 

Carmel Formation is also favored by stratigraphic 

resemblances with the members of the Twin Creek 

Limestone of northern Utah.

The age of the gypsiferous claystone and siltstone 

composing the upper unit of the Carmel Formation is not as well established because it has 

furnished few fossils. It is considered to be of 

early Callovian age on the basis of regional 

stratigraphic relations.

The fossils found in the Twelvemile Canyon Member 

of the Arapien Shale are identical with those in the 

Twin Creek Limestone and in the limy lower unit 

of the Carmel Formation. One of the species 

present in the Twelvemile Canyon Member 

indicates a Bajocian age, but most of the species 

have a longer range elsewhere in the western 

interior region. Stratigraphically the Twelvemile 

Canyon Member is a southward extension of the 

Twin Creek Limestone, is overlain and underlain 

by nearly identical-appearing beds, and differs 

mainly by being more shaly and more contorted.

Marine Jurassic megafossils in central and southern Utah occur in greatest abundance and variety 

in a broad belt extending south westward from the 

west side of the San Rafael Swell and become less 

common southeastward and northwestward from 

that belt. This condition is related to a gradual 

northwestward thickening of the associated limy 

beds from 0 in southeastern Utah to at least 

3,000 feet in San Pete and Juab Counties. It 

reflects a change from slow littoral deposition on 

the southeast to rapid shallow marine deposition 

on the northwest. The shallowness of the sea 

to the northwest is attested by the presence of 

the pelecypods Ostrea, Lopha, and Mytilus. The 

scarcity of megafossils to the northwest in the 

Twelvemile Canyon Member of the Arapien Shale 

is probably related to rapid subsidence accompanied by equally rapid sedimentation.
PELECYPODS FROM CENTRAL AND SOUTHERN UTAH C23

SYSTEMATIC DESCRIPTIONS

Genus NUCULA Lamarck, 1799

Nucula sp. 

Plate 1, figures 1-3

The genus Nucula has been found in the Jurassic of 

the western interior region only at several localities 

near Cedar City, Utah. At these localities it occurs 

in thin beds of yellow oolitic slightly sandy pebbly 

limestone lying from 230 to 255 feet above the base of 

the Carmel Formation. It is commonly associated 

with small oysters, crinoid columnals, and small 

gastropods. Less commonly it occurs with trigonias 

and Camptonectes.

The species is small, subtrigonal, and moderately 

convex. The umbones are prominent and are situated 

about one-third of the length of the shell from the 

anterior end. The ventral margin curves evenly into 

the anterior margin and more sharply into the posterior 

margin. The surface is marked by weak concentric 

growth lines. The interior of the shell has a taxodont 

hinge and simple palial line.

Figured specimens: TJSNM 131917.

Occurrences in southern Utah: USGS Mesozoic Iocs. 18213, 

19428, 19432, 25672, 28461.

Genus IDONEARCA Conrad, 1862

Idonearca1? sp. 

Plate 1, figures 10-12

This species is represented by five specimens that 

retain considerable shell material. The shell is moderate in size, inflated, equivalve, inequilateral, elongate, 

subrhomboidal in outline. The dorsal margin is 

straight and makes an angle of about 135° with the 

nearly straight posterior margin. The anterior margin 

is regularly rounded. The ventral margin is slightly 

convex and rounds acutely into the posterior margin. 

The beaks are widely separated, incurved, fairly 

prominent, situated near the middle of the ligamental 

area, and about one-third of the length of the shell 

from the anterior end. A prominent angular ridge 

curves backward from the beak to the postero-ventral 

end. It is bordered dorsally by a deep depression and 

ventrally by a shallow depression. The surface of the 

cardinal area is marked by at least five chevron-shaped 

ligamental grooves, but the exact number cannot be 

ascertained. The hinge line is straight and about 

two-thirds as long as the length of the shell, inclined 

slightly obliquely to the hinge margin and is exposed 

on the anterior part of one specimen. The surface of 

the shell is ornamented with strong concentric growth 

lines. Radiating striae are not visible, but their 

absence may be due to corrosion. The figured specimen has a length of 42 mm, a height of 29 mm, and a 

convexity of 28.5 mm.

This species compares in shape with Cucullaeat 

elongata Warren (1932, p. 12, pi. 1, fig. 15) from beds 

of Bajocian age near Blairmore, Alberta, but has a more 

angular umbonal ridge, and the area above the ridge is 

more depressed. Idonearcat haguei Stanton (1899, 

p. 623, pi. 73, figs. 11-13) is much higher, is trigonal in 

outline, and has much more prominent umbones.

Figured specimen: USNM 131918.

Occurrences in southern Utah: USGS Mesozoic Iocs. 26307, 

28468, 28461.

Genus MODIOLUS Lamarck, 1799

Modiolus subimbricatus (Meek)

Plate 1, figures 16-20

Modiola (Vulsella) subimbricata Meek, 1873, U.S. Geol. Survey

Terr. (Hayden) 6th Ann. Rept., 1872, p. 472. 

Volsella subimbricata (Meek). White, 1880, U.S. Geol. Survey

Terr. (Hayden), 12th Ann. Rept., 1878, pt. 1, p. 145,

146, pi. 37, figs. 2 a-c. 

Modiola subimbricata (Meek). Stanton, 1899, U.S. Geol.

Survey Mon. 32, pt. 2, p. 617.

This species is characterized by its imbricating 

concentric sculpture. As noted by Meek (1873, 

p. 472), it is similar to Modiolus imbricatus (Sowerby) 

as illustrated by Morris and Lycett (1853, pi. 4, fig. 2) 

except "* * * that its anterior ventral portion, in 

front of the umbonal ridges, is more prominent, and its 

posterior basal extremity more produced and narrowed."

Modiolus sphenoproratus Crickmay (1930, p. 56, 

pi. 7b) from the Bajocian Opuntia Formation of 

southwestern British Columbia appears to have a 

weaker umbonal ridge than M. subimbricatus (Meek), 

but it could be an immature representative of that 

species. M. rosii McLearn (1924, p. 53, pi. 8, fig. 1, 

pi. 9, fig. 12) is distinguished by its author from M. 

subimbricatus (Meek) by being larger, not as strongly 

arched, and less elongated posteroventrally. It appears, also, to have a longer hinge line.

Modiolus subimbricatus (Meek) is fairly common in 

the western interior region in beds of Bajocian to 

early Callovian age. The Geological Survey collections from central and southern Utah contain 31 

specimens of the species.

The original collection studied by Meek was obtained 

from the Lower Canyon of the Yellowstone River 

about 2 miles south of Livingston, Mont. It contains 

8 specimens of which 1 was illustrated by White 

(1880, pi. 37, fig. 2a). This specimen is herein designated the lectotype of Modiolus subimbricatus (Meek) 

and is re-illustrated.

Types: Lectotype USNM 131919; syntypes USNM 131920, 

131921, 7818; plesiotypes USNM 131922, 131923.
C24 CONTRIBUTIONS TO PALEONTOLOGY

Occurrences in central and southern Utah: USGS Mesozoic 

Iocs. 963, 964, 7341, 11438, 11439, 12840, 15877, 16624, 17054, 

27467, 27470, 28461-28463, and 28491.

Modiolus isonemus (Meek)

Plate 1, figure 22

Volsella scalprum var. isonema Meek, 1877, U.S. Geol. Explor. 

40th Parallel (King), v. 4, pt. 1, p. 132, 133, pi. 12, figs. 

4, 4a.

This species is characterized by its fine regularly 

spaced concentric ribs. M. subimbricatus (Meek) 

differs by having coarser imbricate ribs and a much 

more highly arched form. M. pertinuis (Meek and 

Hayden) (1858, p. 51; 1865, p. 86, pi. 3, figs. 5, 5a), 

whose type specimen is probably lost, has similar 

fine regular concentric ribbing but appears to differ 

by its less arcuate form, less prominent umbonal ridges, 

and less inflated anterior end.

The holotype was obtained from Weber Canyon 

in the Wasatch Range of north-central Utah, presumably from the Twin Creek Limestone. In central 

Utah the species is represented by one external and 

one internal mold from the Arapien Shale of San Pete 

County. The species has not been reported elsewhere 

from the western interior region.

Type: Holotype USNM 12545.

Occurrence in central Utah: USGS Mesozoic loc. 21450.

Genus MYTILTJS Linne, 1758

Mytilus cf. M. whitei Whitfleld

Plate 1, figures 4-6

The genus Mytilus is represented in southern Utah 

by four internal molds that are similar in shape to 

M. whitei Whitfield (1877, p. 18; 1880, p. 360, pi. 5, 

figs. 9-12) from the Jurassic of the Black Hills but 

appear to lack the rugose irregular concentric ribs of 

that species. Their smoothness, however, may be due 

to the absence of shell material.

Figured specimens: USNM 131924, 131925. 

Occurrences in central and southern Utah: USGS Mesozoic Iocs. 

6941, 15551, 25675, and 28477.

Genus GERVILLIA Defrance, 1820 

Gervillia montanaensis Meek

Plate 1, figure 21

Gervillia montanaensis Meek, 1873, U.S. Geol. Survey Terr.

(Hayden), 6th Ann. Rept., 1872, p. 472. 

Gervillia sparsilirata Whitfield, 1876, in Ludlow, Wm., Report

of a reconnaissance from Carroll, Montana Territory * * *

to the Yellowstone National Park and return * * * p. 142,

pi. 2, fig. 8. 

Gervillia montanaensis Meek. White, 1880, U.S. Geol. Survey

Terr. (Hayden), 12th Ann. Rept., 1878, pt. 1, p. 145,

pi. 37, figs, la, b.

Gervillia montanaensis Meek, i Stanton, 1899, U.S. Geol. Survey 

Mon. 32, pt. 2, p. 617.

This species is represented in southern Utah by an 

external mold at USGS Mesozoic loc. 26308 and is 

probably represented by internal molds at Mesozoic 

Iocs. 20359 and 28464.

Genus ISOGNOMON Solander, 1786

Isognomon perplana (Whitfield)

Plate 1, figures 32-34

Myalina? (Gervillia) perplana Whitfield, 1876, in Ludlow, Wm., 

Report of a reconnaissance from Carroll, Montana Territory * * * to the Yellowstone National Park and return 

* * *, p. 143, pi. 1, fig. 8.

tMytilus whitei White (not Whitfield), 1880, U.S. Geol. Survey 

Terr. (Hayden), 12th Ann. Rept. 1878, pt. 1, p. 147, 

pi. 37, fig. 9a.

The holotype is a left valve that lacks part of the 

ventral margin and is not sufficiently well preserved to 

show the amount of prolongation of the umbones. It 

was obtained near the south end of the east side of 

the Bridger Range about 6 miles north of Fort Ellis, 

Mont. It is reported to have been obtained from about 

60 feet of "firm blue compact limestone" and to be 

associated with other Jurassic fossils that include Gryphaea planoconvexa Whitfield. Actually the holotype 

is embedded in a brownish-gray fine-grained limestone 

matrix that matches very well with limestone in the 

middle part of the Piper Formation exposed on the 

north side of Bridger Creek at the south end of the 

Bridger Range.

The best preserved specimens of Isognomon perplana 

(Whitfield) have been found in beds of Bajocian age in 

and near Yellowstone National Park. These show that 

the shell is high, elongated obliquely, and is gently inflated in the umbonal region. The umbones are fairly 

prolonged. The anterior margin is gently concave in its 

dorsal half and gently convex in its ventral half. The 

ventral margin is narrowly rounded. The posterior 

margin is nearly straight and forms an obtuse angle 

with the hinge line. The surface of the shell bears 

variably spaced irregularly weak growth lamellae. 

The ligamental area bears narrow vertical ligamental 

pits.

Isognomon perplana (Whitfield) is similar in shape 

and ornamentation to Isognomon promytiloides Arkell 

(1933, pi. 27, figs. 2, 3, 3a, text figs. 49-52) from the 

Upper Jurassic of Europe, but its umbones appear to 

be less projected. I. weelaupensis McLearn (1926, p. 

93, pi. 19, figs. 1, 2) from the Bajocian beds of western 

British Columbia likewise has much more projected 

umbones as well as more vigorous ribbing.

The genus Isognomon is moderately common in beds 

of Bajocian age in the western part of the western
PELECYPODS FROM CENTRAL AND SOUTHERN UTAH C25

interior region. Most of the specimens, however, are 

fragmentary molds that have been assigned commonly 

to Gervillia or Perna and are probably not identifiable 

specifically. The Geological Survey collections from 

the Jurassic beds of southern Utah contain 33 specimens of Isognomon (pi. 1, figs. 30, 31, 35, 36) of which 

all are fragmentary. They show resemblances to 

Isognomon perplana (Whitfield) and possibly belong to 

that species. Several show the narrow vertical ligamental pits that are characteristic of the genus.

Types: Holotype, Yale Peabody Museum 21280; plesiotypes 

USNM 131926, 131927. Figured specimens of Isognomon cf. I. 

perplana (Whitfield), USNM 8177, 131928, 131929.

Occurrences of Isognomon in southern Utah: USGS Mesozoic 

Iocs. 963, 10116, 10436, 12581, 16202, 16624, 17054, 19422, 19429, 

19431, 20358, 25680, 27469, 27591, 28461, 28469, 28473, and 

28496.

Genus INOCERAMUS J. Sowerby, 1814

Inoceramus crassalatus White 

Plate 1, figures 24, 25

Inoceramus crassalatus White, 1877, U.S. Geog. Surveys West 

100 Meridian (Wheeler), Rept., v. 4, pt. 1, p. 166, pi. 

13, figs. 4a-c.

The original description of the species is as follows:

Shell rather small, thin; valves subequal, moderately convex, 

subovate or obscurely tetrahedral in marginal outline; hinge-line 

rather short, forming an angle with the axis of the shell of about 

seventy degrees; beaks small, not very prominent. Left valve 

more capacious than the right, having an indistinct auricular 

furrow extending, from just behind the beak to the postero-basal 

border, obscurely defining a thick posterior wing; but the right 

valve has little or no trace of a similar furrow.

Surface of both valves marked by the usual lines of growth, 

and also by more or less numerous, slightly raised, concentric 

folds.

Greatest length of an average example in the collection, about 

thirty millimeters; thickness, both valves together, about fifteen 

millimeters.

This species is characterized by the valves being 

markedly unequal, by the left valve bearing a conspicuous furrow, and by the concentric ornamentation 

consisting of both broad folds and fine ribs. The type 

collection includes four specimens which, judging by 

their size, are probably immature.

This species is of particular interest because it is 

represented to date only by the four type specimens, 

because no other specimen of Inoceramus has been 

found in the Jurassic of central and southern Utah, and 

because Inoceramus is extremely rare in the Jurassic 

of the western interior region south of central Montana. 

Furthermore, the type specimens bear weak concentric 

ribs and folds that are quite different from the coarse 

ribs on specimens of Inoceramus from the Jurassic of 

Alberta (McLearn, 1924, p. 41, pi. 3, fig. 9; Warren, 

1932, p. 15, pi. 2, figs. 1-3) and northern Montana. 

These facts suggest the possibility that the type

specimens of Inoceramus crassalatus White may be 

from Cretaceous instead of Jurassic rocks.

The specimen illustrated by White on his plate 13, 

figure 4a is herein selected as lectotype of /. crassalatus 

White.

Types: Lectotype USNM 131929; syntypes USNM 131930, 

8585.

Occurrence: The type lot is labeled "Jurassic North Fork of 

Virgin River, Utah." This would be in either northeastern 

Iron County or westernmost Kane County.

Genus PINNA linne, 1758 

Pinna kingi Meek

Pinna kingi Meek, Meek, 1877, U.S. Geol. Explor. 40th Parallel 

(King), v. 4, pt. 1, p. 131, 132, pi. 12, figs. 9, 9a.

Pinna kingi Meek. Stanton, 1899, U.S. Geol. Survey Mon. 32, 

pt. 2, p. 618.

Pinna kingi Meek. Veatch, 1907, U.S. Geol. Survey Prof. 

Paper 56, pi. 6, figs. 11, lla.

This species appears to have much stronger ribs 

and growth lines than Pinna jurassica Whitfield and 

Hovey (1906, p. 392, pi. 44, pi. 45, fig. 1) from the 

Black Hills, South Dakota. The type specimens of 

P. jurassica Whitfield and Hovey occur in a slab of 

glauconitic sandstone suggestive of sandstones near the 

base of the Redwater Shale Member of the Sundance 

Formation. This member is correlated with the upper 

part of the Oxfordian stage. The type specimen of 

Pinna kingi Meek was obtained as float in Weber 

Canyon, Utah. Presumably it was derived from the 

Twin Creek Limestone. The species is fairly common 

in the western part of the western interior region in 

beds of Bajocian age. It is represented by five fragmentary specimens from southwestern Utah.

Occurrences in Utah: USGS Mesozoic Iocs. 18670, 25669, 

26308, and 28472.

Genus CAMPTONECTES Meek, 1864

Camptonectes stygius White 

Plate 2, figures 1-10

Camptonectes stygius White, 1874, U.S. Geog. and Geol. Surveys

West 100th Meridian (Wheeler), p. 23. 

Camptonectes stygius White, 1877, U.S. Geog. Surveys West

100th Meridian (Wheeler), v. 4, pt. 1, p. 164, 165, pi. 13,

figs. 2a-c. 

Camptonectes stygius White. Butler and others, 1920, U.S.

Geol. Survey Prof. Paper 111, pi. 10, fig. 19.

The shell is medium in size, suborbicular, moderately 

convex. The left valve is more convex than the right. 

The hinge line is about half as long as the width of the 

shell. The auricles are moderate in size for the genus 

and are covered with fine growth lines. The anterior auricles are much larger than the posterior auricles. A deep 

byssal notch occurs beneath the right anterior auricles.
C26 CONTRIBUTIONS TO PALEONTOLOGY

The surface of the shell is covered mostly with fine 

concentric growth lines. Faint radiating striae are 

barely visible near the margins of the best preserved 

shells and appear to be slightly stronger on left valves 

than on right valves.

This species is very common in the western interior 

region in beds of Bajocian to early Callovian age. It is 

represented by several hundred specimens in the Geological Survey collections from central and southern 

Utah.

The specimen illustrated by White (1877, pi. 13, 

fig. 2a) is herein selected as lectotype of the species. 

The type specimens are from two widely separated 

localities described as "* * * east of Aquarius Plateau, 

fifteen to twenty miles south of Dirty Devil River, and 

also at the North Fork of Virgin River, Utah."

Types: Lectotype USNM 131931; syntypes USNM 131932- 

131934, 8580; plesiotypes USNM 131935-131938.

Occurrences in central and southern Utah: USGS Mesozoic Iocs. 

963, 964, 5261, 7341, 7890, 7891, 8597, 10098, 10116, 10436, 11137 

11438, 11439, 11445, 12555, 12841, 13756, 16202, 16700, 16701, 

16703, 17054, 17269, 17353, 17412, 17462, 17494, 18281, 18282, 

19422, 19424, 19426, 19429, 20358, 20364, 21448, 22656, 24258, 

24260, 25670, 25678, 25679, 25682, 25686, 25826, 25827, 27465, 

27466, 27468, 28461, 28462, 28472, 28491, and 28495.

Gamptonectes platessiformis White 

Plate 2, figures 11-14

Camptonectes platessiformis White, 1880, U.S. Geol. Survey Terr.

(Hayden) 12th Ann. Rept., 1878, pt. 1, p. 143, 144, pi.

37, fig. 5a. 

Camptonectes platessiformis White. Stanton, 1899, U.S. Geol.

Survey Mon. 32, pt. 2, p. 615. 

Camptonectes extenuatus Whitfield (not Meek and Hayden).

Whitfield, 1880, U.S. Geog. and Geol. Survey Rocky Mtn.

Region, p. 353, pi. 4, fig. 4.

This species is subovate in shape and higher than 

wide. The hinge line is about two-thirds as wide as the 

shell. The auricles are large for the genus and have the 

shape of right-angle triangles. The anterior ear is 

considerably larger than the posterior ear. The surface 

of the shell is marked by fairly coarse fan-wise radiating 

crenulated obliquely curved branching ribs. The ribs 

are much wider than the interspaces, are flattopped and 

broad on the umbones but become broadly rounded and 

slightly narrower toward the margins of the shell. The 

interspaces are punctate. Fine concentric growth lines 

produce a cancellate pattern near the margins of the 

larger shells.

This species may be distinguished from Camptonectes 

bellistriatus (Meek) (Meek and Hayden, 1865, p. 77, 

78, text figs, a-d) by its more slender shape, much 

smaller size in the adult, much longer hinge line, and 

broader coarser ribs. C. distans Stanton (1899, p. 614,

pi. 72, fig. 13) differs by having much broader ribs and 

a broader shell (pi. 2, figs. 15, 16). It is associated 

with C. platessiformis White in the western interior 

region but is much less common. C. platessiformis 

White in the Yellowstone National Park area of 

Wyoming and Montana occurs in beds that contain 

ammonites of Bajocian to early Callovian age. C. 

bellistriatus (Meek) occurs higher stratigraphically in 

beds of Oxfordian age, such as the Stump Formation 

and the Upper Sundance Formation.

C. platessiformis White is represented in central and 

southern Utah by about 60 specimens of which most 

are fragmentary and poorly preserved.

Types: Holotype USNM 8179; plesiotypes USNM 131939, 

131940.

Occurrences in central and southern Utah: USGS Mesozoic 

Iocs. 963, 964, 11438, 15878, 16395, 16624, 17054, 17198, 17462, 

17463, 18670, 18922, 19431, 21450, 24258, 24260, 25669, 25672, 

25673, 25675, 25682, 26308, 26309, 27469, 27474, 25682, 28461, 

28472, 28477, 28479. Specimens comparable with C. platessiformis White occur at USGS Mesozoic Iocs. 7341, 12555, 13529, 

18671, 27466, 27475, and 27476.

Genus PLICATULA Lamarck, 1801

Plicatula sp. 

Plate 1, figures 13-15

The genus Plicatula is represented in central and 

southern Utah by 18 specimens that show considerable 

variation in fineness of ribbing and in spinosity. Finely 

ribbed specimens occur at U.S. Geological Survey 

Mesozoic localities 7341, 10116 and 13756. More 

coarsely ribbed specimens occur at U.S. Geological 

Survey Mesozoic localities 12555, 17462, 21446, 21448, 

25672, 27470, 28461, and 28495. The coarser ribbed 

specimens resemble P. peregrina d'Orbigny from the 

Callovian beds of India (Cox, 1952, p. 40, pi. 4, figs. 

2-6).

Figured specimens: USNM 131941, 131942.

Genus ANOMIA Linne, 1758 

Anemia? sp.

Plate 1, figure 23

The genus is represented in the Carmel Formation 

of southern Utah by five specimens that are very 

small, ovate in outline, and highly convex. The beak 

appears to be near the dorsal margin, but its tip is 

broken. The surface bears broad faint concentric folds 

and microscopic radiating flexuous striae.

Figured specimen: USNM 131943.

Occurrence in southern Utah: USGS Mesozoic Iocs. 18922 and

28472.
PELECYPODS FROM CENTRAL AND SOUTHERN UTAH C27

Genus LIMA Bruguiere, 1797 

Subgenus PLAGIOSTOMA J. Sowerby, 1814

Lima (Plagiostoma) occidentalis Hall and Whitfleld

Plate 2, figures 17-20

Lima occidentalis Hall and Whitfield, 1877, U.S. Geol. Explor.

40th Parallel (King), v. 4, pt. 2, p. 292, 293, pi. 7, fig. 23. 

Lima occidentalis Hall and Whitfield. Butler and others, 1920,

U.S. Geol. Survey Prcf. Paper 111, pi. 10, fig. 16.

This species was based on a single left valve from 

Jurassic beds exposed in the Flaming Gorge southeast 

of Manila in northeast Utah. The valve lacks most 

of the umbonal region. It is subovate in outline and 

slightly oblique. It has a height of about 45 mm, a 

length of 42 mm, and a convexity of about 12 mm. 

The anterior umbonal ridge is well defined. The 

lunule is fairly deep and long. The posterior auricle 

is small, only partly preserved, bears fine radial ribs, 

and merges with the body of the shell. The ornamentation of the valve consists of about 60 rounded radial 

ribs that are about twice as wide as the intervening 

grooves. Both ribs and grooves near the ventral 

margin are crossed by very fine concentric growth 

striae that are most conspicuous in the grooves. The 

grooves are not punctate on the parts of the shell that 

are preserved.

Other specimens of this species show that punctae 

are present in grooves on the umbonal region but that 

ventrally the punctae are replaced by fine striae. 

Also, the width of the radial ribs in some specimens 

may be three times greater than that of the grooves. 

The anterior auricle is much smaller than the posterior 

auricle.

This species is uncommon in the western interior 

region outside of Utah. A few specimens have been 

found, however, in western Wyoming and southeastern Idaho in beds of Bajocian to early Callovian 

age. In Utah the species is moderately common in 

the lower part of the Carmel Formation. It is represented by 37 specimens from central and southern Utah.

Types: Holotype USNM 12539; plesiotypes USNM 131944- 

131946.

Occurrences in central and southern Utah: USGS Mesozoic Iocs. 

5278, 6941, 16624, 16700, 17349, 19429, 26309, 27469, 27474, 

27475, 28461, 28475, 28477, and 28479. Fragments that 

possibly belong to the species occur at Mesozoie Iocs. 17495, 

18213, and 27476.

Lima (Plagiostoma) ziona Imlay, n. sp.

Plate 2, figures 21-26

This species differs from Lima (Plagiostoma) occidentalis Hall and Whitfield by having only about half 

as many ribs. Also, the ribs are much broader, are 

flat topped on the umbonal region, and tend to split 

toward the ventral margin. The left valve of the

holotype has about 30 ribs. The left valve of the 

larger paratype, shown on plate 2, figure 26, has 32 

ribs of which 7 ribs near the posterior auricle are much 

smaller than the others. The ornamentation near the 

beak consists of widely separated rows of punctae. 

Ventrally on the umbones these rows of punctae 

develop into narrow punctate grooves that separate 

very broad flat-topped ribs. On the largest specimens 

the punctae are gradually replaced ventrally by fine 

transverse markings, the radial grooves become a little 

broader and deeper, and the ribs become broadly 

rounded. The left valve of the holotype has a length 

of 42 mm and a width of 40 mm. The largest paratype 

has a length of 48 mm and a width of 43 mm.

This species is represented by 35 specimens from 

central and southern Utah. It is also fairly common in 

northern Utah but has not yet been identified elsewhere 

in the western interior region. Most of the specimens 

in the Geological Survey collections are from Washington and Iron Counties and the western part of Kane 

County. All the specimens from these counties are 

from parts of the Carmel Formation that have furnished 

Lima, (Plagiostoma} occidentals Hall and Whitfield, but 

surprisingly the two species have been found in association only near Cedar City (USGS Mesozoic loc. 27469). 

This suggests that the two species lived under slightly 

different environmental conditions.

Types: Holotype USNM 131947; paratypes USNM 131948- 

131950.

Occurrences in central and southern Utah: USGS Mesozoic Iocs. 

961, 12749, 18281, 25672, 25675, 25682, 26308, 27467, 27469, 

28471, and 28491.

Genus CTENOSTREON Eichwald, 1862 

Ctenostreon sp.

This genus is represented in southern Utah by three 

fragments that are similar in size and in strength of 

ribbing to Ctenostreon gikshanensis McLearn (1926, p. 

91, pi. 19, figs. 3, 4) from Bajocian beds in British 

Columbia.

Occurrence in southern Utah: USGS Mesozoie Iocs. 18670 and 

26309.

Genus OSTREA Linne, 1758 

Subgenus LIOSTREA Douville, 1904

Ostrea (Liostrea) strigilecula White

Plate 1, figures 26-29

Ostrea strigilecula White, 1877, U.S. Geog. Surveys West 100th

Meridian (Wheeler), v. 4, pt. 1, p. 163, 164, pi. 13, figs.

3a-d. 

Ostrea strigilecula White. Whitfield, 1880, U.S. Geog. and Geol.

Survey Rocky Mtn. Region, p. 348, 349, pi. 3, figs. 8-12. 

Ostrea strigilecula White, 1884, U.S. Geol. Survey 4th Ann. Rept.,

p. 289, 290, pi. 35, figs. 9, 11.
C28 CONTRIBUTIONS TO PALEONTOLOGY

Ostrea strigilecula White. Stanton, 1899, U.S. Geol. Survey

Mon. 32, pt. 2, p. 610. 

^Ostrea strigilecula White. Logan, 1900, Kansas Univ. Quart.,

v. 9, no. 2, ser. A, p. 120, 121, pi. 28, figs. 1-6. 

Ostrea strigilecula White. Butler and others, 1920, U.S. Geol.

Survey Prof. Paper 111, pi. 10, figs. 8, 9.

This species is small, subovate in outline, and the 

axis of shell is curved slightly posteriorly. The right 

valve is flat to slightly concave. In some right valves 

the umbonal part is slightly convex and the ventral 

part slightly concave. The left valve is strongly swollen, much larger than the right valve, bears ordinary 

lines of growth, and is marked by an attachment scar 

of variable size. Many left valves have a weak winglike 

expansion of the posterior margin. The left valves do 

not bear radiating plications, although White (1877, p. 

164) thought that there were a few faint indications of 

plications.

The primary types were obtained from the Carmel 

Formation south of the Dirty Devil River in eastcentral Utah, presumably from Wayne County. The 

species has been found subsequently in enormous numbers at many places in the Carmel Formation of Utah, 

and the name has been applied to similar small nondescript hump-shaped oysters from the marine Jurassic 

beds throughout the western interior region.

The specimen figured by White (1877) on his plate 

13, figures 3. a-c is herein selected as lectotype of Ostrea 

strigilecula White.

Types: Lectotype USNM 131951; syntypes USNM 131952 

8581; plesiotype USNM 131953.

Occurrences: As noted on tables 3-8.

Genus IOPHA Bolt en, 1798

Lopha aff. I. engelmanni (Meek)

Plate 1, figures 7-9

Twenty-one specimens of a small ovate oyster have 

been obtained in Iron and Kane Counties in southern 

Utah. These specimens are characterized by a few 

broad irregular radial plications that are somewhat 

stronger on the left valve than on the right valve. The 

left valve is slightly to moderately convex; the right 

valve is flat to slightly concave.

This species differs from "Ostrea" dowlingi McLearn 

(1924, p. 43, pi. 3, figs. 6-8) from the Callovian beds of 

Alberta by being more elongate and by having fewer 

and coarser ribs. Its rib pattern is more similar to that 

on "Ostrea" engelmanni Meek (1860, p. 311; Meek and 

Hayden, 1865, p. 73, 74, figs. A, B; Meek, 1876, p. 355, 

pi. 3, fig. 6; White, 1884, p. 289, pi. 34, figs. 3, 4) from 

the Upper Sundance Formation of eastern and central 

Wyoming, but it is much smaller than that species.

Figured specimens: USNM 131954, 131955. 

Occurrence in southern Utah: USGS Mesozoic Iocs. 5261, 5263, 

17353, 18281, 18660, 28462, and 28494.

Genus TRIGONIA Bruguiere, 1789

Tiigonia americana Meek

Plate 3, figures 8-13

Trigonia americana Meek. 1873, U.S. Geol. Survey Terr.

(Hayden) 6th Ann. Rept., 1872, p. 472. 

Trigonia americana Meek. White, 1880, U.S. Geol. Survey

Terr. (Hayden), 12th Ann. Kept., 1878, pt. 1, p. 148, pi.

38, figs, la, b. 

Trigonia americana Meek. Stanton, 1899, U.S. Geol. Survey

Mon. 32, pt. 2, p. 618.

The original description by Meek (1873, p. 472) is 

as follows:

A fine species of the type of T. costata of the Old World, but 

differing from that and the other allied forms, in having the 

radiating costae of the corselet, or posterior dorsal region, all of 

uniform size.

The description by White (1880, p. 148) is as follows:

Shell subtetrahedral in marginal outline, gibbous in front of 

the umbonal ridge and compressed behind it; the margin from 

the beak all the way to the postero-basal angle forming a continuous and almost regular curve; posterior margin nearly 

straight, truncating the shell downward and backward; dorsal 

margin gently concave; beaks somewhat elevated and having 

the appearance of being directed slightly backward; umbonal 

ridge forming a somewhat prominent crenulated carina, which 

very gradually increases in size towards and ending at the posterobasal angle. Surface in front of the umbonal ridge marked by 

15 to 18 sharply-raised concentric varices, which become suddenly obsolete just before reaching the umbonal ridge. The 

surface behind that ridge is marked by numerous raised, radiating, finely crenulated lines, which are nearly uniform in size; 

but the spaces separating the five and six lower ones are a little 

wider than the others.

Length from front to posterior margin, 34 mm; heights from 

base to beaks, 31 mm.

Both White and Meek noted that T. americana Meek 

was characterized by the uniform character of the 

radiating riblets on the area posterior to the marginal 

carina. The area is divided into two parts, however, 

by a weak groove. The general appearance of the 

species is similar to that of T. denticulata Agassiz as 

figured by Lycett (1877, p. 152, pi. 29, figs. 1-3) except 

for somewhat sparser ribbing. In this respect it resembles 

T. costata Sowerby (Lycett, 1877, pi. 30, figs. 3, 3 a, b, 

6; Cox, 1952, p. 109, pi. 12, figs. 3, 4, 7), but its posterior area bears much finer radial riblets and is not 

divided by a prominent median carina, its posterior 

carina bears much finer crenulations, and its shell is 

much less elongate. T. guhsani McLearn (1926, p. 94, 

pi. 20, figs. 2, 3), from middle Bajocian beds in British 

Columbia, differs from T. americana Meek by being 

much larger, by having denser concentric ribs, fewer 

riblets on the posterior area, and by being more elongated posteriorly.

This species is fairly common in the western interior 

region in beds of Bajocian to early Callovian age. The
PELECYPODS FROM CENTRAL AND SOUTHERN UTAH C29

type specimens are from the middle of the Piper Formation exposed at the mouth of Yellowstone Canyon 

about 2% miles south of Livings ton, Mont. The beds 

from which they were obtained have furnished the 

Bajocian ammonite Zemistephanus (USGS Mesozoic 

Iocs. 19214, 15635). Near Lower Slide Lake, Teton 

County, Wyo. (Imlay, 1956a, p. 70), Trigonia americana 

Meek occurs with ammonites of Bajocian to Callovian 

age. The species is represented in the U.S. Geological 

Survey collections from the Carmel Formation of Utah 

by 9 adult specimens and probably also by 9 immature 

specimens.

The specimen illustrated by White (1880, pi. 38, 

fig. 1) is herein selected as lectotype of the species.

Types: Lectotype USNM 131956; syntypes USNM 131957, 

7794, 7819; plesiotype USNM 131958.

Occurrences in central and southern Utah: Carmel Formation 

at USGS Mesozoic Iocs. 7341, 24258, 25669, 25684, 27469. The 

species is probably represented by some small immature specimens at Mesozoic Iocs. 16624, 25670, 25672, 25673, and 26308.

Trigonia elegantissima Meek 

Plate 3, figures 1-7

Trigonia elegantissima Meek, 1873, U.S. Geol. Survey Terr.

(Hayden) 6th Ann. Rept., 1872, p. 474. 

Trigonia elegantissima Meek. Stanton, 1899, U.S. Geol. Survey

Mon. 32, pt. 2, p. 619, pi. 73, fig. 2.

The original description by Meek (1873, p. 474) is as 

follows:

A small species of the type of T. costata, but having the concentric or horizontal costae on the sides of the valves very delicate, 

closely arranged, and but slightly larger than the radiating ones 

on the posterior dorsal region, or corselet. The valves are rather 

compressed, about one-fourth longer than wide, and have the 

posterior umbonal slopes acutely angular.

The description by Stanton (1899, p. 619) is as 

follows:

Shell small, subtrigonal in outline, moderately convex, with 

prominent, acute, recurved beaks; posterior umbonal ridge 

prominent, angular, and curved; anterior end broadly rounded; 

posterior end subangular below at the extremity of the umbonal 

ridge and forming a convex slope to the beak above; escutcheon 

not distinctly marked; posterior area depressed and bearing 

numerous equal, fine radiating lines; remainder of surface with 

regular, closely arranged, small concentric ribs that show a 

tendency to bend downward toward the front.

Length of figured specimen, 21 mm; height, 14 mm; convexity 

of single valve, 4 mm.

This species is closely related to T. americana, from which it 

differs in outline, and more especially in having much smaller and 

more numerous concentric ribs. In specimens of T. americana 

no larger than the type of this species the spaces between the ribs 

are at least a millimeter wide.

Trigonia elegantissima Meek differs from T. americana 

Meek, with which it is commonly associated, by its less 

erect form, much smaller adult size, much finer and 

denser ribbing, and by its ribbing becoming denser 

ventrally instead of sparser. The species shows some

variation in the coarseness of its ribbing, but even the 

most coarsely ribbed specimens have much finer ribbing 

than on T. americana Meek. The downward bending 

of the concentric ribs near the anterior margin, described 

by Stanton, occurs on only some of the more finely 

ribbed variants. The marginal carina is nearly smooth, 

but on the best preserved specimens bears faint crenulations. The radiating lines or fine riblets on the area 

are crossed by finer threads.

The specimen from the Devils Slide area, Montana, 

illustrated by Stanton (1899, p. 73, fig. 2) is the most 

finely ribbed of the specimens available. Somewhat 

less finely ribbed specimens from the north side of Lower 

Slide Lake, Teton County, Wyoming, are herein illustrated for comparison (pi. 3, figs. 4, 5). In collections 

from the Carmel Formation of Utah, most of the specimens of T. elegantissima Meek represent medium to 

coarsely ribbed variants, but some are as finely ribbed 

as the specimen illustrated by Stanton.

Among American species, T. elegantissima Meek is 

most similar to Trigonia poststriata Whitfield and Hovey 

(1906, p. 396, pi. 48, figs. 4-6) obtained 4 miles southwest of Hulett, Wyo., but differs by being considerably smaller, less elongate posteriorly, and by its 

concentric ribs remaining distinct instead of fading on 

the posterior part of the area.

Among foreign species, T. elegantissima Meek is similar in shape and fineness of ribbing to T. hemisphaerica 

Lycett (1877, p. 174-178, pi. 31, figs. 4-8) from the 

Inferior Oolite of England, differing mainly by its 

much smaller size, sparser ribbing near the beak, and 

weaker crenulations on the area and marginal carina.

Trigonia elegantissima Meek in the western interior 

is associated with such species of the Trigoniidae as 

T. americana Meek, Myophorella (Promyophorella) conradi (Meek and Hayden), and Vaugonia montanaensis 

(Meek) but is much less common. It is represented 

in the Carmel Formation of Utah by only 15 specimens 

and is similarly poorly represented in collections from 

Montana and Wyoming. Its range, based on associated ammonites found with it in Wyoming and Montana, is from Bajocian to basal Callovian. For example, in the Jurassic section near Lower Slide Lake, 

Wyoming (Imlay, 1956a, p. 70, 71), it ranges from the 

lower part of unit 10 into unit 19. In unit 10 it is 

associated with an ammonite of Bajocian age (USGS 

Mesozoic loc. 20967). In unit 19 it is associated with 

the ammonites Arcticoceras and Cadoceras of earliest 

Callovian age (USGS Mesozoic loc. 22112). A similar 

range is shown by occurrences of the species in northcentral Wyoming and south-central Montana (Imlay, 

1956b, p. 576, 577, 583, 584, 591).

Types: Plesiotypes USNM 28935, 131959-131964. The holotype was never figured. The specimen mentioned by Stanton
C30 CONTRIBUTIONS TO PALEONTOLOGY

(1899, p. 619) as probably being the type has not been located. 

Occurrences in central and southern Utah: Carmel Formation 

at USGS Mesozoic Iocs. 11439, 12555, 15878, 19422, 20351, 

25686, and 27472.

Genus VAUGONIA Ciickmay, 1930 

Vaugonia conradi (Meek and Hayden) 

Plate 3, figures 14-21

Trigonia conradi Meek and Hayden, 1860, Acad. Nat. Sci.

Philadelphia Proc. 1860, p. 183, 184. 

Trigonia conradi Meek and Hayden, 1865, Smithsonian Inst.,

Smithsonian Contr. Knowledge, v. 14, no. 172, p. 83,

84, pi. 3, fig. 11. 

Not Trigonia quadrangularis Hall and Whitfield, 1877, U.S.

Geol. Explor. 40th Parallel (King), v. 4, pt. 2,

p. 293, 294, pi. 7, fig. 22. 

Trigonia quadrangularis Hall and Whitfield. Veatch, 1907, U.S.

Geol. Survey Prof. Paper 56, pi. 6, fig. 8. 

Not Trigonia quadrangularis Hall and Whitfield. Butler and

others, 1920, U.S. Geol. Survey Prof. Paper 111, pi. 10,

fig. 18. 

Not Trigonia quadrangularis Hall and Whitfield. Mansfield,

1927, U.S. Geol. Survey Prof. Paper 152, pi. 31, fig. 18.

The original description of the species (Meek and 

Hayden, 1860, p. 183, 184) is as follows:

Shell rather small, subtrigonal, moderately convex; anterior 

side truncate; base rounded; posterior side sloping obliquely 

from the beaks above, and apparently vertically truncate at the 

extremity; beaks elevated, narrow, incurved, and located in 

advance of the middle; posterior umbonal slopes distinctly 

angular; surface ornamented by rather small, obscure concentric 

costae, which on the posterior side of the valves, descend at 

first perpendicularly, after which they are deflected forward 

parallel to the basal and anterior borders. Length and height, 

each about 0.97 inch; convexity 0.58 inch.

The type specimen, obtained from the southwest 

base of the Black Hills, is preserved in a fine-grained 

light grayish-yellow sandstone and is associated with 

Trigonia americana Meek and Myophorella (Promyophorella) cf. M. montanaensis (Meek).

The holotype is so corroded that the ornamentation 

is not well shown. Much better preserved specimens 

have been obtained subsequently in the southwestern 

part of the Black Hills from the upper part of the 

Canyon Springs Sandstone Member of the Sundance 

Formation (USGS Mesozoic Iocs. 20499, 20497), from 

the same member in the Hartville uplift in southeastern 

Wyoming (USGS Mesozoic loc. 20501), and from 

equivalent oolitic limestones near the base of the 

Sundance Formation near Cody, Wyoming (USGS 

Mesozoic loc. 20362). These are the beds characterized 

by Arcticoceras codyense Imlay. The species has also 

been found at many places in western Wyoming, 

southeastern Idaho, and western Montana in beds of 

Bajocian age containing such ammonites as Zemistephanus and Stemmatoceras.

Some of the specimens from these areas show that 

the species had a shape and ornamentation similar to 

that on Vaugonia veronica Crickmay (1930, p. 53, pi. 7f) 

and V. mariajosephinae Crickmay (1930, p. 54, pi. 7g) 

from the Middle Jurassic of Canada. The shape is more 

elongate posteriorly than is suggested by the holotype 

because the posterior end of the holotype is not preserved. 

The ribs on the disk form a sharp V. The ribs on the 

anterior part of the disk are high, thin, widely spaced, 

nontuberculate, and parallel to the ventral margin. 

The ribs on the posterior part of the disk are fairly 

thick, are weakly tuberculate transversely, and are 

vertical. During growth, the V formed by the junction 

of these vertical and nearly horizontal ribs tends to 

become more acute and eventually broken. Most shells 

have 1 or 2 more horizontal ribs than vertical ribs.

The marginal carina is sharp and weakly crenulated. 

The inner carina is less sharp. The area is about 

one-third as wide as the disk, is crossed transversely 

by weak riblets, and is marked medially by a groove 

dorsal to a weak carina. The escutcheon is narrow, 

depressed, and nearly smooth.

Vaugonia conradi (Meek and Hayden) shows some 

variation in the density and strength of the ribbing on 

the disk and in the sharpness of the V formed by the 

two sets of ribs on the disk. The specimens from the 

beds of Bajocian age in the Yellowstone National Park 

area are, in general, smaller and have denser ribbing 

(pi. 3, figs. 20, 21) than those in beds of Callovian age 

in the lower part of the Sundance Formation, although 

the specimen figured by Veatch (1907, pi. 6, fig. 8) 

from Bajocian beds west of Nugget, Wyo., is closely 

similar to specimens from the lower part of the Sundance 

Formation. The specimens from the Carmel Formation of central and southern Utah show similar 

variations in size and ribbing.

Most specimens of V. conradi (Meek and Hayden) in 

the Geological Survey collection have been misidentified 

as V. quadrangularis (Hall and Whitfield) (1877, p. 293, 

pi. 7, fig. 22) whose holotype is a fragmentary external 

mold preserved in a matrix of oolitic limestone obtained 

near Como Bluff, Wyo. Other specimens of V. 

quadrangularis have been found at that place by 

Pipiringos (1957, p. 23, 50) in an oolitic bed at the base 

of the Redwater Shale Member of the Sundance 

Formation. The holotype is a left valve that lacks 

part of its anterior margin (pi. 3, fig. 22). The remainder of the holotype indicates that the species is 

similar to V. conradi (Meek and Hayden), but differs 

by having broader, lower, and more closely spaced ribs 

on its disk. Such ribs are well shown on a specimen 

illustrated by Butler and others (1920, pi. 10, fig. 18) 

and Mansfield (1927, pi. 31, fig. 18) from the Stump 

Formation near Bear River City, Wyo. (Schultz, 1914,
PELECYPODS FROM CENTRAL AND SOUTHERN UTAH C31

p. 53), and contrast markedly with the high thin 

widely spaced ribs on V. conradi (Meek and Hay den).

Similarly, V. sturgisensis Whitfield and Hovey (1906, 

p. 394-396, pi. 47, 48, figs. 1-3, 7) from the Black Hills 

of Wyoming and South Dakota differs from V. conradi 

(Meek and Hayden) by having broad low closely 

spaced ribs on its disk, by being more elongate posteriorly, and by attaining much larger size. Also, it 

occurs at a higher stratigraphic position. The largest 

specimen illustrated by Whitfield and Hovey (1906, 

pi. 48, fig. 7) is from the Redwater Shale Member of 

the Sundance Formation. The other specimens illustrated are probably from the Hulett Sandstone Member 

of the Sundance Formation.

Much closer resemblances to V. conradi (Meek and 

Hayden) are borne by the Canadian species V. veronica 

Crickmay (1930, p. 53, pi. 7f) which, judging from the 

holotype, appears to have somewhat stronger transverse 

ribbing on the area and a less acute V formed by the 

ribs on the disk.

Compared with V. conradi (Meek and Hayden), V. 

praelonga (Gottsche) (1878, p. 26, pi. 6, figs. 2a, b) 

from the Bajocian of Argentina appears to be more 

elongate and to have stronger tubercles on the vertical 

ribs on the posterior part of the disk. V. v-costata 

(Lycett) (1874, p. 66, pi. 13, fig. 5, pi. 15, figs. 1-4) 

from the Inferior Oolite of England appears to develop 

the V on its disk ribs at a later growth stage.

This species is represented by about 210 specimens 

in collections from central and southern Utah.

Types: Holotype USNM 212; plesiotypes USNM 131965- 

131971.

Occurrences in central and southern Utah: USGS Mesozoic iocs. 

5268, 6281, 6282, 10116, 11137, 12556, 12570, 12581, 12835, 

12840, 13532, 16202, 19432, 20351, 20356, 20358, 20359, 22656, 

24259, '25669, 25670, 25671, 25673, 25681, 25684, 25685, 25686, 

26307, 26309, 28463, 28468, 28470, 28472, 28473, 28480, 28492, 

28493. Immature or fragmentary specimens that possibly belong 

to V. conradi (Meek and Hayden) occur at Mesozoic Iocs. 16395, 

21448, 24260, 25687, 27469, 27472, 27475, and 28491.

Vaugonia aff. V. conradi (Meek and Hayden) 

Plate 3, figure 37

One specimen from Emery County, Utah, differs 

from V. conradi (Meek and Hayden) by an abrupt 

geniculation of the ribs in the anterior part of the disk. 

This results in the formation of a V that is much more 

acute than on V. conradi but resembles that on V. 

(Hijitrigonia) geniculata Kobayashi and Mori (1955, 

p. 84, pi. 4, figs. 4-9). The Utah specimen differs, 

however, by lacking tubercles and by having widely 

spaced ribs on the anterior part of the disk.

Figured specimen: USNM 131972.

Occurrence in Utah: USGS Mesozoic loc. 13529

Vaugonia utahensis Imlay, n. sp. 

Plate 3, figures 23-26

The shell is subtrigonal, moderately convex, elongated posteriorly. The uinbo is located about onethird of the length of the shell from the anterior end. 

The disk is ornamented with ribs that form a V near 

its posterior side. The ribs on the posterior side of 

the disk are vertical, thicken considerably ventrally, 

and are finely crenulated transversely. The ribs on 

the anterior side of the disk are irregularly fine, closely 

to moderately spaced, wavy to geniculate, apparently 

nontuberculate, tend to fade out near the middle of 

the disk, outnumber the vertical ribs 2 or 3 to 1, and 

become very crowded and irregular near the ventral 

margin. The marginal carina is blunt. The area is 

about one-fourth as wide as the disk, is marked by a 

median groove, and is crossed transversely by striae. 

The escutcheon is depressed, is about half as wide as 

the area, and is crossed obliquely by striae.

The holotype, a right valve, is 25 mm long. 20 mm 

high, and 8 mm thick.

This species is distinguished from V. conradi (Meek 

and Hayden) by having much denser ribbing on the 

anterior side of the disk, by the anterior ribs being 

much more numerous than the posterior ribs of the 

disk, by having a blunt instead of a sharp marginal 

carina, and by having much weaker transverse markings 

on the area. The character of the ribbing on the disk 

of the Utah species shows some resemblance to that 

of Vaugonia (Hijitrigonia) kojiwa Kobayashi and Mori 

(1955, p. 85, pi. 4, figs. 2a, b, 3a, b) from the Lower 

Jurassic of Japan, but the marginal carina is blunt and 

rounded instead of prominent, and the shell is much 

more elongate posteriorly.

This species has been found only in southwest Utah 

and mostly in Kane, Iron, and San Pete Counties. 

About 85 specimens are available in the collections of 

the Geological Survey.

Types: Holotype USNM 131973; paratypes USNM 131974, 

131975.

Occurrences in Utah: USGS Mesozoic Iocs. 963, 16624, 17030, 

17353, 17494, 20356, 25672, 26309, 27473. The species probably 

occurs at Mesozoic Iocs. 11439, 19429, 25683, 25685, 25826, and 

28461.

Genus MYOPHORELLA Bayle, 1878 

Subgenus PROMYOPHORELLA Kobayashi and Tamura, 1955

Myophorella (Promyophorella) montanaensis (Meek) 

Plate 3, figures 33-36, 38-41

Trigonia montanaensis Meek, 1873, U.S. Geol. Survey Terr.

(Hayden), 6th Ann. Kept., 1872, p. 472. 

Trigonia montanaensis Meek. White, 1880, U.S. Geol. Survey

Terr. (Hayden), 12th Ann. Kept., 1878, pt. 1, p. 147,

148, pi. 38, fig. 2a.
C32 CONTRIBUTIONS TO PALEONTOLOGY

Trigonia montanaensis Meek. Stanton, 1899, U.S. Geol.

Survey Mon. 32, pt. 2, p. 619, 620. 

?'Trigonia ferrieri McLearn, 1924, Royal Soc. Canada Proc. and

Trans., 3d ser., v. 18, sec. 4, p. 45, 46, pi. 5, figs. 2, 10.

The original description by Meek (1873, p. 472) is as 

follows:

Of the type of T. signata Agassiz, but differing in its proportionally shorter form, with smaller nodiferous costae, while 

it has a row of nodes down the anterior lateral region of each 

valve, nearly as in T. navis Lamarck.

The species description by White (1880, p. 147, 148) 

is as follows:

Shell transversely elongate, somewhat arcuate and rudely subtetrahedral in marginal outline, gibbous anteriorly and narrowed 

and compressed behind; umbones elevated; from the umbo to 

the middle of the base the margin, as seen by side view, forms 

a continuous and almost true semicircular curve; from the middle 

of the base to the posterobasal angle the margin is slightly concave; posterior margin nearly straight or very slightly convex, 

forming, with the dorsal margin, a distinct slightly obtuse 

angle; dorsal margin concave, the appearance of concavity being 

increased by the elevation of the umbones; umbonal ridge 

distinct and prominent below, but becoming obsolete toward the 

beak. Surface in front of the umbonal ridge marked by ten 

or twelve curved varices, which start from the umbonal ridge 

and extend upward and forward. The first six or seven of 

these varices become broken up into distinct nodules a short 

space in front of the ridge. The forward ones of each varix or 

transverse row of nodules are larger than the others, and are 

arranged in a vertical row of strong nodules, which form a 

conspicuous feature of the shell. The corselet, a space behind 

and above the umbonal ridge, is marked only by numerous, 

distinct, nearly vertical, lines of growth.

The descriptions by Meek and White were based on 

the type figured by White and on one fragment consisting of the posterior three-fifths of a left valve. 

Both specimens are much corroded, and consequently, 

the ornamentation appears to be subdued as compared 

with other specimens of the species that are herein 

illustrated. In particular the umbonal ridge, or 

marginal carina, is distinct near the beak and bears 

prominent tubercles, and the postumbonal area bears 

a shallow median groove throughout its length and 

is bounded dorsally by a tuberculate carina. The 

escutcheon is about half as wide as the area, is 

depressed, and is nearly smooth but bears weak 

transverse riblets near the beak.

The specimen illustrated by White (1880, pi. 38, 

fig. 2a) is herein designated as the lectotype of 

Myophorella (Promyophorella) montanaensis (Meek).

This species is very similar in shape and ornamentation to "Scaphogonia" argo Crickmay (1930, p. 51, 

52, pi. 5, figs, a, b) from middle Ba]ocian beds in 

British Columbia. In both species the anterior part 

of the disk bears strongly arcuate tuberculate ribs 

that diverge from the marginal carina at an acute angle 

and that meet the anterior margin at nearly a right

angle. The tubercles on these ribs become stronger 

ventrally near the middle of the flank and then weaken 

slightly as the ribs curve anteriorly. Near the anterior 

margin the ribs weaken rather abruptly, or in some 

specimens are interrupted, but immediately anterior 

to the point of weakening or interruption, each rib 

bears a single prominent tubercle which is much stronger 

than the tubercles near the middle of the flanks. 

These prominent tubercles, as developed on successive 

ribs near the anterior margin, are almost in a row. 

They are generally followed anteriorly by from 1 to 3 

weaker tubercles.

In both species the ribs on the posterior part of the 

disk have only a slight forward curvature near the 

ventral margin, are not interrupted or weakened near 

the ventral margin, and gradually become more strongly 

tuberculate ventrally.

The characteristics of the postumbonal area are 

likewise similar on the two species except that on 

"Scaphogonia" argo Crickmay the median groove is 

bounded ventrally by a weak tuberculate median carina, 

until the shell attains about 15 mm in length. Thereafter, both groove and carina disappear, according to 

Crickmay (1930, p. 52), and the middle of the area is 

marked only by a row of weak tubercles. In contrast, 

on "Trigonia" montanaensis Meek the median groove 

persists in the adult and is not bordered by tubercles 

or by a median carina.

Trigonia trafalgarensis Warren (1932, p. 18, pi. 3, 

figs. 5, 6) and T. ferrieri McLearn (1924, p. 45, pi. 5, 

figs. 2, 10) from the Fernie Formation of Alberta, 

Canada, are referred to Myophorella (Promyophorella) 

by Kobayashi and Tamura (1955, p. 93, 94). They 

are based on poorly preserved specimens that are 

difficult to compare with "Trigonia" montanaensis 

Meek but are described as being much less tuberculate. 

T. ferrieri McLearn, however, has the same shape and 

rib pattern as "T" montanaensis Meek. Furthermore, 

some specimens of the species obtained from the type 

locality on Grassy Mountain near Blairmore, Alberta, 

are as strongly tuberculate as "T." montanaensis 

Meek. It is doubtful, therefore, that T. ferrieri 

McLearn is a valid species.

Myophorella, (Promyophorella} montanaensis Meek is 

common in the western interior region in beds of 

Bajocian to early Callovian age. The lectotype was 

obtained with the types of Trigonia americana Meek 

in beds of Bajocian age at the mouth of Yellowstone 

Canyon about 2^ miles south of Livingston, Mont.

The species is represented in the U.S. Geological 

Survey collections from the Carmel Formation of Utah 

by about 90 specimens.

Types: Lectotype USNM 131976; syntype USNM 7817; 

plesiotypes USNM 131977-131982.
PELECYPODS FROM CENTRAL AND SOUTHERN UTAH C33

Occurrences in central and southern Utah: Carmel Formation at 

USGS Mesozoic Iocs. 964, 6281, 6282, 6941, 7341, 12555, 12557, 

12560, 12842, 13532, 16700, 17269, 17462, 17492, 20364, 22170, 

24258, 24259, 25669, 25673, 25678, 25680-25682, 25687, 26308, 

26310, 27469, 28472, 28474, and 28480.

Subgenus HAIDAIA Crickmay, 1930

Myophorella (Haidaia) yellowstonensis Imlay, n. sp.

Plate 3, figures 27-32

The shell is subtrigonal in outline, a little longer than 

high. The anterior and ventral margins form a semicircle. The posterior margin is straight. The beak is 

small, curved backward, and located at %-}{ of the 

length of the shell from the anterior end.

The disk is gently convex, ornamented with 16-20 

finely crenulated arcuate ribs that diverge acutely from 

the marginal carina. These ribs are narrow, rounded, 

and are steepest on their umbonal side. The crenules 

are very fine and are most distinct on the posteroventral 

side of the ribs. The marginal carina is narrow, distinct 

curved, and tuberculate. The area is about one-third 

as wide as the disk, is divided medially by a groove, is 

bounded dorsally by a tuberculate carina that is 

broader than the marginal carina, and is ornamented by 

fine transverse riblets. These riblets are fairly widely 

spaced near the beak but become closely spaced posteriorly. Most of them terminate in the tubercles on the 

marginal and inner carinae, but some terminate between 

the tubercles. The escutcheon is depressed, is about 

half as wide as the area, and is crossed by fine widely 

spaced riblets. The holotype is 21 mm long and 15 mm 

high.

The species shows some variation in the strength of 

the tubercles on the carinae and in the density of the 

riblets on the area.

It differs from Myophorella (Haidaia) dawsoni 

(Whiteaves) (1884, p. 231, pi. 31, figs. 1, la) from 

western British Columbia by its much smaller size, 

more trigonal shape, finer ornamentation, and the lack 

of a row of tubercles in the middle of the area. It shows 

much more resemblance to M. (H.) crenulata Kobayashi 

and Tamura (1955, p. 100, pi. 5, figs. 8, 9a, b, 10) from 

the Upper Jurassic of Japan, but its carinae are 

tuberculate instead of crenulate, its area is less depressed, and the riblets on the area are more widely 

spaced near the beak.

This species is moderately common in western 

Montana, western Wyoming, southeastern Idaho, and 

northern Utah in beds of Bajocian age. In contrast, 

only one specimen has been found in Utah south of the 

Uinta and Wasatch Mountains.

Types: Holotype USNM 131983; paratypes USNM 131984- 

131988.

Occurrence in central Utah: Carmel Formation at USGS

Mesozoic loc. 13531. The holotype and one of the paratypes are 

from Mesozoic loc. 27624 in Montana. The other paratypes are 

from Mesozoic loc. 21385 in Montana, Mesozoic loc. 20967 in 

Wyoming, and Mesozoic loc. 13531 in Utah.

Genus ASTARTE Sowerby, 1816

Subgenus COEIASTARTE Boehm, 1893

Astarte (Coelastarte) livingstonensis Imlay, n. sp.

Plate 4, figures 1-4

The shell is very flat, elongate, subrectangular in outline, inequilateral. Posterior dorsal margin long, 

straight, gently inclined. Posterior margin straight, 

nearly vertical, rather short, meeting the dorsal margin 

sharply at a subobtuse angle, meeting the ventral margin rather abruptly at nearly a right angle. Ventral 

margin slightly convex on immature specimens but becoming nearly straight on adults. Anterior margin 

short, rounding evenly into ventral margin. Anterior 

dorsal margin slightly concave, shorter and steeper 

than the posterior dorsal margin, meeting the anterior 

margin at nearly a right angle. Beaks small, compressed, rising moderately above the hinge line, situated 

from % to % of the length of the shell from the anterior 

end. A low oblique ridge trends from the beak to the 

posteroventral angle.

The ornamentation consists mainly of narrowly 

rounded concentric ribs that follow the outline of the 

shell, bend sharply where they cross the oblique ridge, 

meet the posterior dorsal margin at nearly a right angle, 

and number from 17 to 20 on the largest specimens. 

The interspaces are broadly rounded and are wider 

than the ribs. On the largest adult the ribs tend to 

weaken near the posterior margin. Nearly microscopic 

growth lines cover the entire surface. The holotype 

has a length of 23 mm and a height of 12.5 mm.

This species is distinguished from most described 

species of Coelastarte by having a more salient beak 

farther from the anterior end of the shell and by a 

shorter posterior margin. One of the most similar is 

A. (C.) rectangula Arkell (1934, p. 248, pi. 33, fig. 16), 

from beds of late Oxfordian age in England, but that 

species evidently has a much longer posterior margin, 

a less salient beak, and a weakly concave ventral margin. A. (C.) aytonensis Lycett (not Bean) (Lycett, 

1863, pi. 40, fig. 13; Arkell, 1934, p. 246) from the Great 

Oolite of England is likewise similar to A. (C.} hvingstonensis Imlay, n. sp., but has a broader anterior margin, a longer posterior margin, and its beak is nearer 

the anterior end of the shell.

This species has been obtained in collections from the 

western part of the western interior region in beds of 

Bajocian age but is somewhat less common than other 

species of Astarte found in those beds. In the Geological
C34 CONTRIBUTIONS TO PALEONTOLOGY

Survey collections from southern Utah, it is represented 

by one specimen.

Types: Holotype USNM 131989; paratypes USNM 12220, 

131990, 131991.

Occurrences in Utah: USGS Mesozoic Iocs. 12558, 17269. The 

species is probably represented also at Mesozoic Iocs. 11438, 

28467, 28472.

Occurrences of type specimens: The large paratype shown on 

pi. 1, fig. 2, is in a collection made by A. C. Peale on the west 

side of the Lower Canyon of the Yellowstone River near Livingston, Mont. The other paratypes are from Mesozoic Iocs. 21385 

and 25866. The holotype is from Mesozoic loc. 25866. All these 

localities are in southwestern Montana.

Astarte (Coelastarte) n. sp. undet.

Plate 4, figures 6-8

This species is represented in central and southern 

Utah by about 25 molds. It differs from A. livingstonensis Imlay, n. sp. by having a higher rounder 

less elongate shell, by its beaks being nearer the anterior 

end of the shell, and by its ribbing fading toward the 

margins.

Figured specimens: USNM 131993, 132011, 132012. 

Occurrences in central and southern Utah: USGS Mesozoic 

Iocs. 17269, 27474, 28461, 28494, and 28495.

Astarte (Coelastarte) cf. A. (C.) interlineata (Lycett)

Plate 4, figure 5

One specimen of Coelastarte from southern Utah is 

comparable in shape and sparseness of ribbing to 

A. (C.) interlineata (Lycett) (Morris and Lycett, 1853, 

p. 87, pi. 9, figs. 14, 15a, b) from the Middle Jurassic 

of England. It appears to have a less rectangular 

outline and a slightly convex instead of a straight 

ventral margin.

Figured specimen: USNM 131992.

Occurrence in southern Utah: USGS Mesozoic loc. 17269.

Genus PRONOELLA Fischer 1887

Pronoella cinnabarensis (Stanton)

Plate 4, figures 27-30

Cyprinaf cinnabarensis Stanton, 1899, U.S. Geol. Survey Mon. 

32, pt. 2, p. 621, 622, pi. 72, figs. 7, 8.

The original description is as follows:

Shell of medium size, moderately convex, sub circular in outline, 

with prominent submedian beaks; dorsal margin excavated in 

front of the beaks, gently sloping behind, and in both cases 

passing gradually into the rounded ends; posterior end in some 

individuals slightly straightened, so as to become almost vertically subtruncate; ventral margin broadly rounded; surface 

sculpture unknown. There is a very obscure posterior umbonal 

ridge, and the muscular and pallial impressions are not clearly 

shown on the cast.

One cast showing impression of part of hinge has three strong 

cardinal teeth, of which the posterior one is very long and oblique.

The specimen is not in condition to show whether lateral teeth 

are present.

Height of an average shell, 28 mm; length 32 mm; convexity 

of two valves united 15 mm. The largest specimens in the collection the have corresponding dimensions about one-fifth greater.

The hinge described by Stanton is on a right valve 

and is illustrated herein. It bears an elongate posterior lateral tooth that is followed by a deep, fairly 

narrow pit. Beyond is a triangular shaped bifid 

posterior cardinal tooth. This is followed by a wide 

triangular-shaped pit beyond which is a moderately 

prominent tooth that occurs at the posterior end of a 

thin elongate anterior lateral tooth.

The presence of a bifid posterior cardinal tooth 

indicates that this species belongs to Pronoella rather 

than to Eocattista or Isocyprina (Cox, 1947, p. 144, 

145). The presence of a faint umbonal ridge also 

favors an assignment to Pronoella.

The specimen illustrated by Stanton is herein selected as lectotype of P. cinnabarensis (Stanton). 

This is from the ridge southwest of the second crossing 

of the Snake River, Yellowstone National Park. 

The specimen on which the hinge is exposed is from the 

ridge between Red and Basin creeks near Sheridan 

Peak.

Internal molds having the shape of P. cinnabarensis 

(Stanton) are fairly common in beds of Bajocian to 

early Callovian age in the western part of the western 

interior region and particularly near Yellowstone 

National Park. Lack of distinctive markings and poor 

preservation generally make specific identification 

difficult or uncertain. The Geological Survey collections 

from central and southern Utah contain about 40 internal molds comparable with the species. Such occur 

at USGS Mesozoic localities 6284, 6941, 12556, 12835, 

12839, 16624, 17462, 18076, 20351, 20358, 20359, 

25671, 25686, 27470, and 28493.

Types: Lectotype USNM 28939; syntype USNM 30648. 

Pronoella uintahensis Imlay, n. sp. 

Plate 4, figures 15-23

The shell is subovate, wider than high, moderately 

inflated. The umbones are broadly rounded, curved 

inward and forward, and are situated at %-% of the 

length of the shell from the anterior end. The posterodorsal margin is gently convex, gently inclined, and 

meets the posterior margin at an obtuse angle. The 

anterodorsal margin is slightly excavated. The anterior margin is rather sharply convex. The ventral 

margin is broadly convex, rounds evenly into the anterior margin and sharply into the posterior margin. 

The posterior margin is high and steeply inclined. 

The lunule is poorly defined. The escutcheon is long, 

narrow, deep and is bounded by a ridge. A weak
PELECYPODS FROM CENTRAL AND SOUTHERN UTAH C35

ridge curves downward from the limbo to the posteroventral corner. The shell surface is nearly smooth, 

but toward the margins it bears very weak growth 

lines and a few larger growth imbrications.

The hinge line is fairly well exposed on two silicified 

specimens from the Uinta Mountains (USGS Mesozoic 

loc. 20536). The hinge on the right valve bears an 

elongate posterior lateral tooth. The posterior cardinal tooth is triangular, thick, and bifid. It is separated 

by a deep pit from a less prominent median(?) cardinal 

tooth that occurs at the posterior end of a thin oblique 

lateral tooth. The hinge on the left valve bears a thick 

prominent median cardinal tooth. This is separated 

by a deep pit from a thin posterior cardinal tooth and 

by a smaller shallower pit from a moderately thin 

anterior cardinal tooth that bends abruptly into an 

anterior lateral tooth.

The paratype shown on plate 4, figures 20-22, has a 

height of 23 mm, a length of 26 mm, and a convexity 

(both valves) of 11.5 mm.

This species is distinguished from Cyprina! iddingsi 

Stanton (1899, p. 622, pi. 73, fig. 9) (pi. 4, figs. 24, 25) 

by having more prominent umbones that are nearer the 

anterior end and by its posterior margin being higher. 

Pronoella cinnabarensis (Stanton) (1899, p. 621, pi. 73, 

figs 7, 8) has a fainter umbonal ridge, and its umbones 

are nearer the middle of the shell. Among foreign 

species it shows considerable resemblance to Pronoella 

ravenscarensis Cox (1947, p. 175, 176, text figs. 56a, b, 

on p. 181, pi. 10, fig. 86) from the Middle Jurassic of 

England but has more prominent umbones, a higher 

posterior margin, and a weak postumbonal ridge.

This species is represented in the Geological Survey 

collections from southern and central Utah by 140 

specimens. Most of these are internal molds preserved 

in a limestone matrix, but about a dozen specimens from 

one locality (USGS Mesozoic loc. 25685) are silicified, 

and these show the external shape of the species very 

well. In addition, the species may be represented by 

another 65 specimens that are very poorly preserved.

The specimens showing the hinge features are from 

Uintah County, northeast Utah, and were collected 

from the base of the Carmel Formation in Steinaker 

Draw, near Vernal (USGS Mesozoic loc. 20536) in sec. 

26, T. 3 S., R. 21 E.

This species is assigned to Pronoella rather than 

Eocallista because of the presence of a weak postumbonal ridge and of a bifid posterior cardinal tooth in 

the right valve. This bifid tooth is present on several 

right valves from USGS Mesozoic locality 20536 in 

northeast Utah. The hinge is not exposed on any of 

the specimens from central and southern Utah. Consequently the identification of P. uintahensis Imlay,

n. sp., in those parts of Utah is based solely on external 

shape.

Types: Holotype, USNM 131994; paratypes, USNM 131995- 

131999.

Occurrences in central and southern Utah: USGS Mesozoic Iocs. 

963, 964, 7341, 9113, 10116, 11439, 11445, 12581, 12840, 16624, 

16700, 16701, 17054, 14712, 17495, 19422, 21446, 20352, 25670, 

25685, 27469, 27474, 28469, 28470, 28491, 28494, and 28595. 

Poorly preserved specimens comparable to Pronoella uintahensis 

Tmlay, n. sp., occur at Mesozoic Iocs. 5263, 15498, 16702, 16703, 

17018, 17030, 17351, 17494, 18672, 24260, 25683, 25826, 26309, 

27475, and 28462.

Genus IUCINA Bruguiere, 1797 

Lucina sp.

The genus is represented in southern Utah by four 

poorly preserved specimens. These are orbicular in 

shape, bear fine concentric growth lines, and have a 

weak furrow extending backward from the umbo. The 

genus is rare in the Jurassic of the western interior 

region.

Occurrences in southern Utah: USGS Mesozoic Iocs. 963 and 

25671.

Genus QUENSTEDTIA Morris and Lycett, 1854

Quenstedtia aff. Q. bathonica (Morris and Lycett) 

Plate 4, figures 9-11

Three specimens from southern Utah resemble 

Quenstedtia bathonica (Morris and Lycett) (1854, p. 95, 

pi. 13, fig. 14; Cox, 1929, pi. 13, fig. 10) in shape and in 

the position of their umbones but differ by having a 

more distinct ridge extending from the umbo to the 

posteroventral angle and a less rounded posterior end.

Figured specimens: USNM 132000-132002.

Occurrences: USGS Mesozoic Iocs. 12835, 16701, and 17494.

Genus PLEUROMYA Agassiz, 1843

Pleuromya subcompressa (Meek)

Myacites (Pleuromya) subcompressa Meek, 1873, U.S. Geol.

Survey Terr. (Hayden) 6th Ann. Rept., 1872, p. 472. 

Myacites (Pleuromya) subcompressa Meek, 1877, U.S. Geol.

Explor. 40th Parallel (King), v. 4, pt. 1, p. 136, pi. 12,

figs. 6, 6a. 

Myacites (Pleuromya) subcompressa Meek. White, 1880, U.S.

Geol. Survey Terr. (Hayden) 12th Ann. Rept., 1878,

pt. 1, p. 151, pi. 38, figs. 5a-e. 

Pleuromya subcompressa (Meek). Stanton, 1899, U.S. Geol.

Survey Mon. 32, pt. 2, p. 627, pi. 74. figs. 8-11. 

Pleuromya subcompressa (Meek). Crickmay, 1936, Geol. Soc.

America Bull., v. 47, p. 556, pi. 1, fig. 6, pi. 2, figs. 5, 12,

pi. 3, fig. 10.

Both White and Stanton emphasized the high 

variability of this species in form and sculpture and 

illustrated a number of specimens to show the range in 

variation. In particular Stanton (1899, p. 626) noted
C36 CONTRIBUTIONS TO PALEONTOLOGY

that "Extreme variations approach the plicate 

Pleuromya weberensis Meek on the one hand and the 

nearly smooth Pleuromya newtoni Whitfield on the 

others."

Of these species, Pleuromya newtoni Whitfield (1880, 

p. 367, 368, pi. 5, figs. 19, 20) has much finer ribbing, 

is more elongate, has lower umbones, and occurs at 

a higher stratigraphic level in beds of late Oxfordian 

age in the Black Hills (Imlay, 1947, p. 262). The type 

of P. weberensis (Meek) (1877, p. 137, pi. 12, figs. 11, 

11 a) is from Weber Canyon, Utah, where it is associated 

with P. subcompressa (Meek) (1877, p. 136). It lacks 

the posterior end of its shell and is possibly only a finely 

ribbed variant of P. subcompressa (Meek).

Among Canadian species, the most similar is P. 

postculminata McLearn (1924, p. 55, pi. 9, fig. 6). This 

species is apparently differentiated by having a shallow 

sulcus that extends from the umbo to near the middle 

of the ventral margin where it produces an emargination. 

On P. subcompressa (Meek) an emargination of the 

ventral margin is generally less distinct and occurs 

nearer the anterior end.

P. subcompressa (Meek) is very common in beds of 

Bajocian to Callovian age in central and western Wyoming and Montana, in southeastern Idaho, and in 

northern Utah. The Geological Survey collections from 

central and southern Utah contain only six specimens of 

this species.

The original description of P. subcompressa (Meek) is 

in a footnote to a list headed "Near Lower Canyon of 

Yellowstone River." Consequently the primary types 

should include the specimens from the Lower Canyon 

of the Yellowstone River that Meek studied (see 

Crickmay, 1936, p. 557). These specimens were collected by A. C. Peale in 1872 and were illustrated in part 

by C. A. White in 1880 (pi. 38, figs. 5a-d). The original 

collection made by A. C. Peale includes seven specimens, all technically cotypes. Of these the writer selects 

as lectotype the specimen illustrated by White on his 

plate 38, figures 5c, d.

Types: Cotypes USNM 8061; plesiotypes USNM 8180, 

28958-28961. The specimen from Weber Canyon, Utah, figured 

by Meek (1877, pi. 12, figs. 6, 6a) is lost.

Occurrences in central and southern Utah: USGS Mesozoic Iocs. 

17462, 18922, 20351, 20364, and 25682.

Genus PHOLADOMYA G. B. Sowerby, 1823

Pholadomya kingi Meek

Plate 4, figure 36

Pholadomya kingi Meek, 1873, U.S. Geol. Survey Terr. (Hayden)

6th Ann. Kept., 1872, p. 473. 

Pholadomya kingi Meek. White, 1880, U.S. Geol. Survey Terr.

(Hayden) 12th Ann. Kept., 1878, pt. 1, p. 150, pi. 38,

figs. 3a, b.

Pholadomya kingi Meek. Stanton, 1899, U.S. Geol. Survey

Mon. 32, pt. 2, p. 624, pi. 74, figs. 1-3. 

Pholadomya kingi Meek. Butler-and others, 1920, U.S. Geol.

Survey Prof. Paper 111, pi. 10, figs. 1, 2.

This species is characterized by having from 8 to 

14 strong radial ribs that cover the middle part and most 

of the anterior part of the shell. It is moderately 

common in the western part of the western interior 

region in beds of Bajocian to early Callovian age. Four 

specimens have been found in central Utah.

Types: Holotype USNM 7815; plesiotypes USNM 28957, 

132003.

Occurrences in central Utah: USGS Mesozoic Iocs. 6941, 12558, 

and 17269.

Pholadomya inaequiplicata Stanton 

Plate 4, figures 37, 38

Pholadomya inaequiplicata Stanton, 1899, U.S. Geol. Survey 

Mon. 32, pt. 2, p. 625, pi. 74, fig. 4.

This species, as characterized by Stanton, differs 

from P. kingi Meek by being smaller, more ventricose, 

less elongate, and by having about 20 radiating ribs 

that cover more of the shell. Judging by the collections 

now available, P. inaequiplicata Stanton shows the 

same variation in shape as P. kingi Meek and differs 

only by having finer more numerous ribs. Both species 

have the same vertical range and are commonly 

associated.

Pholadomya inaequiplicata Stanton is represented by 

27 specimens in collections from central and southern 

Utah.

Types: Holotype USNM 28956; paratypes USNM 30668; 

plesiotypes USNM 132004, 132005.

Occurrences in central and southern Utah: USGS Mesozoic Iocs. 

6941, 7890, 25671, 25681, 26307, 28468, and 28493.

Genus GONIOMYA Agassiz, 1842

Goniomya montanaensis Meek

Plate 4, figures 34, 35

Goniomya montanaensis Meek, 1873, U.S. Geol. Survey Terr.

(Hayden) 6th Ann. Kept., 1872, p. 473. 

Goniomya montanaensis Meek. White, 1880, U.S. Geol. Survey

Terr. (Hayden) 12th Ann. Kept., 1878, p. 151, pi. 37,

fig. 8a.

In this species the ribs do not form a sharp V near the 

middle of the flanks as is common in Goniomya, but 

rather resemble a V whose apex is spread apart and 

connected by a horizontal bar. The anterior part of 

the shell bears strong ribs that are steeply inclined, the 

middle part of the shell bears weak horizontal ribs, and 

the posterior part of the shell bears strong vertical ribs. 

The junction of these ribs is rather abrupt on the upper 

part of the shell but becomes less abrupt near the ventral 

margin where all the ribs become weaker.
PELECYPODS FROM CENTRAL AND SOUTHERN UTAH C37

This species has a rib pattern similar to that on 

Goniomya hemicostata Morris and Lycett (1853, p. 120, 

pi. 12, fig. 3) from the Great Oolite of England, but its 

beaks are situated more anteriorly, and its anterior 

margin is more broadly rounded.

Goniomya montanaensis Meek is rare in beds of 

Bajocian age in the western interior region. The 

holotype was obtained from the middle of the Piper 

Formation on the west side of the Lower Canyon of the 

Yellowstone River near Livingston, Mont. A single 

external mold of the species occurs in the Geological 

Survey collections from central Utah.

Type: Holotype USNM 7814.

Occurrence in central Utah: USGS Mesozoie loe. 20351.

Goniomya? n. sp. undet. 

Plate 4, figure 39

This species is represented by a single highly convex 

left valve on which the umbo is situated about one-third 

of the length of the shell from the anterior end. The 

dorsal part of the valve bears strong ribs that are bent 

sharply twice to form two acute V-shaped folds of which 

the most anterior is the larger. Some of the ribs on 

the posterior part of the larger fold continue beyond the 

apex of the V as far as the anterior ventral margin as 

fairly strong ribs. The remainder of the ventral margin 

and all of the posterior margin are smooth except for 

growth lines. In addition, the anterior part of the shell 

anterior to the largest V bears 8 or 9 weak ribs directed 

obliquely downward and anteriorly at nearly a right 

angle to the axis of the V.

The zigzag rib pattern bears some resemblance to that 

on G. normanniana (d'Orbigny) as figured by Arkell 

(1935, p. 48, figs. 8, 9), but the large V-shaped fold as 

well as the umbo is much nearer the anterior end of the 

shell, and the apex of the V is not separated by a horizontal bar. The generic status of the species is questionable because of the unusual direction of the ribs at 

the anterior end of the shell.

Figured specimen: USNM 132006.

Occurrence in Utah: USGS Mesozoie loe. 6944.

Genus MYOPHOLAS H. Douville, 1907

Myopholas hardyi Imlay, n. sp.

Plate 4, figures 12-14

The genus Myopholas is represented by two fairly 

complete external molds and by several incomplete 

molds in the Arapien Shale of central Utah. These 

show that the shell is highly convex, elongate ovate, 

and nearly twice as long as high. The posterior end is 

more narrowly rounded than the anterior end and apparently is gaping. The umbones are broad, strongly 

incurved, and slightly anterior to the middle of the shell. 

The anterior part of the shell bears five strong sharp

widely spaced radial ribs. The medial part of the shell 

bears 6 or 7 less sharp closely spaced ribs. These ribs are 

bound posteriorly by a deep and broad sulcus that extends radially from the posterior side of the umbo to 

the ventral margin. The sulcus shows faint traces of 

radial ribbing, but the posterior end of the shell does not 

bear radial ribs. The entire surface of the shell is 

marked by weak concentric ribs.

The holotype has a length of 11.5 mm, a height of 

6 mm, and a convexity (one valve) of about 2.5 mm.

The Utah specimens of Myopholas are similar in appearance to M. acuticosta (J. de C. Sowerby) (1827, p. 

88, pi. 546, fig. 1; Arkell, 1935, p. 349, pi. 45, figs. 14-16; 

Lissajous, 1923, pi. 32, figs. 8, 8a) from the Bathonian 

and Callovian of Europe but have a broader deeper 

radial sulcus and lack radial ribs posterior to the sulcus.

Types: Holotype USNM 132007; paratype USNM 132008.

Occurrences in central Utah: USGS Mesozoie Iocs. 21448 and 

21449.

This species is named after C. T. Hardy, Utah State Agricultural College, who collected the type specimens.

Genus CERCOMYA Agassiz, 1843

Cercomya punctata (Stanton)

Plate 4, figure 31

Anatina (Cercomya) punctata Stanton, 1899, U.S. Geol.

Survey Mon. 32, pt. 2, p. 628, pi. 74, fig. 5. 

Anatina cf. A. punctata Stanton. MeLearn, 1924, Royal Soe.

Canada, Proc. and Trans., 3d ser., v. 18, see. 4, p. 56, pi. 9,

fig. 11. 

tAnatina (Cercomya) semiradiata Whiteaves, 1900, Canada

Geol. Survey, Mesozoie fossils, v. 1, pt. 4, p. 288, pi. 37,

fig. 4.

This species is distinguished from most species of 

Cercomya by being less elongate and by the presence of 

distinct granular radiating ribs on the middle of the 

posterior part of the shell. The specimen of Cercomya 

from the Callovian beds of Alberta (MeLearn, 1924, p. 

56, pi. 9, fig. 11) is nearly identical in appearance with 

the holotype of Stanton's species. Cercomya semiradiata Whiteaves (1900, p. 288, pi. 37, fig. 4) from the 

Callovian beds of the Queen Charlotte Islands compares closely with Stanton's species in shape and in the 

presence of fine radial ribs but may have a more 

swollen triangular area posterior to the narrow median 

sulcus that descends from the beak to the ventral 

margin. Among European species probably the most 

similar is C. striata Agassiz (1842, p. 149, pi. 11, figs. 

13-15; Loriol, 1872, p. 197, pi. 12, figs. 10, 11; Cottreau, 

1928, p. 95, 1929, pi. 52, fig. 14), but it is definitely 

much more elongate posteriorly, and the radial striae 

are not nearly as strong as the radial ribs on C. punctata 

(Stanton).

Cercomya punctata (Stanton) is moderately common 

in the western part of the western interior region in
C38 CONTRIBUTIONS TO PALEONTOLOGY

beds of Bajocian to early Callovian age. It is represented by three specimens from Garfield County, 

Utah, in the Geological Survey collections.

Types: Holotype USNM 28945; paratype USNM 30593 

plesiotype USNM 132009.

Occurrences in southern Utah: USGS Mesozoic Iocs. 25671 

and 26307.

Genus THRACIA Leach, 1823 

Thracia weedi Stanton 

Plate 4, figures 32, 33

Thracia weedi Stanton, 1899, U.S. Geol. Survey Mon. 32, pt. 2, 

p. 627, pi. 75, figs. 1-3.

The original description is as follows:

Shell of medium size, thin, compressed, elongate, subelliptical 

in outline; beaks rather prominent, submedium; dorsal margin 

sloping rather rapidly and almost equally before and behind the 

beaks; anterior end broadly rounded, most prominent below; 

posterior end subtruncate; ventral margin slightly convex, 

somewhat sinuous toward the posterior end; posterior umbonal 

ridge narrow and sharply defined; surface marked by irregular 

concentric undulations and by numerous growth lines.

The preceding description needs some modification. 

The beaks are actually slightly posterior to the median 

part of the shell and are directed slightly backward, 

the posterior dorsal margin is slightly concave, and on 

most specimens the right valve is distinctly larger than 

the left. The shape varies considerably from one 

specimen to another, but this is a characteristic of the 

genus (Arkell, 1936, p. 355).

This species differs from Thracia convexa Warren 

(1932, p. 26, pi. 1, fig. 19) from beds of Bajocian age 

near Blairmore, Alberta, by being much less convex and 

by its beaks being nearer the median part of the shell. 

Its umbones are much less prominent than in T. 

semiplanata Whiteaves (1884, p. 221, 222, pi. 29, 

figs. 5, 5a-c) from beds of Callovian age on the Queen 

Charlotte Islands. Among European species it shows 

more resemblance to T. lens Agassiz (1845, p. 267, 

pi. 36, figs. 1-15), but its beaks are smaller and more 

centrally situated and it is apparently more compressed.

Thracia weedi Stanton is fairly common in shaly beds 

of Bajocian age in and near Yellowstone National Park. 

In southern Utah it is represented by 64 specimens of 

which 60 are from a single spot in Garfield County.

The specimen illustrated by Stanton (1899) on his 

plate 75, figure 2, is herein selected as the lectotype of 

Thracia weedi Stanton. This specimen is from USGS 

Mesozoic locality 1145 from a streambed west of 

Little Quadrant Mountain in Yellowstone National 

Park.

Types: Lectotype USNM 28994; syntypes USNM 28943; 

plesiotype USNM 132010.

Occurrences in southern Utah: USGS Mesozoic Iocs. 16701, 

16703, 25671, 26307, 28468, 28494, and 28495.

LITERATURE CITED

Agassiz, Louis, 1840-45, Etudes critiques sur les mollusques 

fossiles: Neuchatel, 3 v. (v. 1. (1840) Les Trigonies du 

Jura et de la Craie Suisses; v. 2-3 (1842-45) Monographic 

des Myes).

Arkell, W. J., 1929-37, A monograph of British corallian Lamellibranchia: London, Palaeontographical Soc., 392 p., 56 pis.

Baker, A. A., 1947, Stratigraphy of the Wasatch Mountains in 

the vicinity of Provo, Utah: U.S. Geol. Survey Oil and Gas 

Inv. Prelim. Chart 30.

Baker, A. A., Dane, C. H., and Reeside, J. B., Jr., 1936, Correlation of the Jurassic formations of parts of Utah, Arizona, 

New Mexico and Colorado: U.S. Geol. Survey Prof. Paper 

183, 66 p., 33 pis., 16 figs.

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PELECYPODS FROM CENTRAL AND SOUTHERN UTAH C39

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 1950, Jurassic rocks in the mountains along the west 

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 1926, New Jurassic species from the Hazelton Group of 

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 1877, Report upon the invertebrate fossils collected in 

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C40 CONTRIBUTIONS TO PALEONTOLOGY

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INDEX

A Page 

ucuticosta, Myopholas.... .-.--------.-. C37

Ages and correlations....---...-.-..--.---..--. 3

americana, Trigonia... 4,8, 9,10,12,28,29,30,32; pi. 3 

Ammonites_.__.._.-.._.-.-----.-.__ 4,10

Anatina punctata......... . . 37

(Cercomya) punctata-........... ... __ 37

semiradiata................ .. ..... 37

Anemia.......................__._____ 2,56

sp..__ _..................... 4,10,12, 86; pi. 1

Anomiidae..._______._________ 2 

Arapien Shale......_...----.--...-.-..-.. 2,3,5,6

Arcticoceras...-------------------------------- 29

codyense. --------- ----------- 30

argo, Scaphogonia.-..-.........-...---....-..- 32

Astarte........... ________________ 2,33

Hvingstonensis..................___..-. 10,34

meeki-.............--....--......-.-. 4,8,9,12

(Codastarte)................. 4,8,12,22, 34; pi. 4

aytonensis--------... ...-_.__---_ 33

interlineata-... ____-._-. 4, 6,34; pi- 4 

Iwingstonensis- -.-- 3,4,6,10, 12,33; pl. 4 

rectangula...- __...______.. 33

sp._-..-._-.---._ ..---. -_ -.--.. 4,6,8,9 

Astartldae_____________________ 2 

asteriscus, Pentacrinus. --------------------- 5

aytonensis, Astarte (Coelastarte) ... _--.-.. 33

B 

bathonica, Quenstedtia............ 4,9,11,12, 35; pi. 4

bellistriatus, Camptonectes____..____ 26 

Biologic analysis_____....-______ ;

Cadoceras. -... . -. ...

Camptonectes____________ 1,2,5,7,22,

bellistriatus.-.-..........-_____.....

. _ .---..-.- 26;

--------- 4,6,8,9,10,12,26;

....... 4,6,8,9,10,11,12,25;

sp.-.-.------.---.-...--..---.--. 6,8,9,10,

Carmel Formation.-.__._..___.. 1,

Cercomya..........__.__..._.__.....

punctata-....................._ 4,12,37;

semiradiata.-.---------...-----------_--

striata.-------... ___-------_---.....

(Cercomya) punctata, Anatina ...... -----

semiradiata, Anatina ..... _--------_-

Chondroceras-...... ... --_-_---..----.-- -

cinnabarensis, Cyprina-...-__-_--------_-

Pronoella .--.-- 4, 6,8, 9,10,11,12, 34, 35;

codyense, Arcticoceras-..-.... .__...-____

Coelastarte ___._...___--.._.. 2, 

Hvingstonensis.__._ - _- - 

(Coelastarte)----..... .._.__--...._.-

(Coelastarte), Astarte ---------- 4, 8,12,22, 34: aytonensis, Astarte--.---_-_....___.

interlineata, Astarte - ............... 4.6,34

Hvingstonensis, Astarte-...- 3,4,6,10,12, 33, 

rectangula, Astarte-_..-..--. _-.--..-_- 

Coelastarte..--- ___-------__-_..-.

Colonial corals_____..___..._..--.

conradi, Myophorella (Promyophorella)..-..-.. 

Trigonia ...__...___.............

Vaugonia. ......... 4,6,8,9,10,11,12, 30, 31

4,29 

23, 8 5 

26

pi. 2 

26

pi. 2 

pi. 2 

11,12 

2, 3, 6 

2,37 

pi. 4 

37 

37 

37 

37 

3

34

pi. 4 

30

33,34 

9 

9

 pi. 4 

33

ipl. 4 

; pi. 4 

33 

9 

2

29

30 

pi. 3

[Italic page numbers indicate descriptions]

Page 

convexa, Thracia...-...____....____ C38

Corals._..............._---.-...----.. 4,8,10,12

costata, Trigonia--.... ..-.__--..- __-. 28,29

crassalatus, Inoceramus ................. 4,25; pi. 1

crenulata, Myophorella (Haidaia) ............ 33

Crinoid columnals_...._........ 4,5,6,8,9,10,12

Ctenostreon... ................. _._.. 2,57

gikshanensis.----------...._..-.___.. 27

sp.......-.-.................. .... 4,6,8,07

Cucullaea elongata............... 23

Cucullaeidae..._____.___________ 2 

curta, Meleagrinella ...... .. .. .- 3

Curtis Formation.....___._ __..... 1,3,5

Cyprina cinnabarensis..... . - 34

iddingsi- _________________ 35; pi. 4 

Cyprinidae -. - 2

D

dawsoni, Myophorella (Haidai)......------ - 33

denticulata, Trigonia--...---------_____.. 28

distans, Camptonectes...........--_____ 26; pi. 2

dowlingi, Ostrea... - . 28

E

Echinoid fragments_.. ________ 4,5,6,8,9,12 

elegantissima, Trigonia--.. 4,8,9,10,11,12,20; pi. 3 

elongata, Cucullaea.. _________________________ 23

engelmanni, Lopha __________ _ 4,8,9,12,28; pi. 1

Ostrea-.-.--.............................. 28

Entrada Sandstone____________... 5

Eocallista..................................... 34,35

extenuatus, Camptonectes..-..- ... - 26

Faunal associations and comparisons...__. 6 

ferrieri, Trigonia.. .............. ..........- 32

G 

Gastropods........................ 4,6,8,9,10,11,12

geniculata, Vaugonia (Hijitrigonia). .-.-_.-_. 31

Gersillia.. . ...-. . ...-. 2, $4,25

montanaensis .......... 3,4, 5,9,10,12, % pi. 1

sparsilirata _-----------_-------_-. 24; pi. 1

(Gervillia) perplana, Myalina. ..--.-_---__ 24 

gikshanensis, Ctenostreon...... ...------------- 27

Goniomya _______-______-. 2,36,37; pi. 4 

hemicostata------ ___ _...---.-___ 37

montanaensis.-........ .-._ 3,4,10, 56, 37; pi. 4

normanniana.------- _---------___-- 37

Grammatodon _.---____ -____... 2,22 

sp........................................ 4,8

Gryphaea. __.-..--.___.______-_ 7 

planoconvexa..--- ____-----___._- 24

guhsani, Trigonia-- ......___ ___..-.- 28

H

haguei, Idonearca.______ _-___ 23 

Haidaia. ................... ......... 2,3S

(Haidaia) crenulata, Myophorella.... ..___. 33

dawsoni, Myophorella-...----____._ 33

yellowstonensis, Myophorella---- 3,4,10,53; pi. 3

Hamulus subquadratus____. __ _. _.. 2,10; pi. 4

hardyi, Myopholas..................... 4, 6,57; pi. 4

Page 

hemicostata, Goniomya--...................... C37

hemisphaerica, Trigonia--------_ __.- 29

(Hijitrigonia) geniculata, Vaugonia--.....__ 31

kojiwa, \augonia......................... 31

iddingsi, Cyprina.......................... 35;

Idonearca.....................................

sp................................ 4,12,55;

imbricatus, Modiolus... .......................

inaequiplicata, Pholadomya..... 4,6,9,10,12,56;

Inoceramus-......... .........................

crassalatus.---- __________ _.__ 4,55;

interlineata, Astarte (Coelastarte)....... 4,6,54;

Introduction....______...___.__.

Isocyprina....................................

Isognomon........................ _____ 2,7,22,

.......... 4,8,9,10,11,12,54,25;

weelaupensis_....._....._.--..-.

SP....... . ....... . ......

Isognomonidae.-______________ 

isonema, \olsella scalprum................

isonemus, Modiolus.................... 4, <

6,8,

pi. 4 

2,55

23 

Pi. 1

23

pl. 4 

2,55 

Pl. 1 

pl. 4 

1

34

84,25 

pl. 1

24

24

11,12 

2

. 24 

Pl. 1

jurassica, Pinna.............................. 25

K

Kepplerites. ________ 4

kingi, Pholadomya.. ................ 4, 6,10, 56; pl. 4

Pinna.............................. .. 4,6,12,25

kojiwa, Vaugonia (Hijitrigonia)............ ._ 31

Laternulidae ____________ 

lens, Thracia_____________ 

Lima......__ ___.___.....

occidentalis- -. ___ .

ziona... __.. ____...........

(Plagiostoma).............................

occidentalis __________ 4,8,9,10,12,57;

ziona__.-___-.___--.

sp................................

Limidae..___________.._ 

Liostrea. ..........................-

Ostrea--_ _ ... .

strigilecula, Ostrea-. . 4,8,9,10,11,12,07, 

Hvingstonensis, Astarte-- __. ...

Astarte (Coelastarte)-.- . 3, 4, 6,10,12,55;

Coelastarte.- .......

Lopha... 2,

engelmanni ---------....... 4,8,9,12,28,

Lucina... . .....

sp.._.... .. 4, 

Lucinidae __ - - . .-...

10,12 

2,22 

pl. 2 

,- Pl. 2 

J, 9,10

2 

57

2

, Pl. 1 

10,34 

pl. 4

9

22,08 

 pl. 1 

2,55 

12,55

2

M

Mactromya.-. _____._______.... 2 

sp....................................... 4,9,12

mariajosephinae, Vaugonia. _ _ . .-. . 30 

meeki, Astarte .......................... 4,8,9,12

C41
C42 INDEX

Page 

Meleagrinella..-..... - .. --- C7

curta. --..-...---..--------.--.-----..--_. 3

Modiola subimbricata.... . ------- .- 23

(\ulsella) subimbricata_.--__--------- 23

Modiolus............................... 2,5,7,22,23

imbricatus.. ... -. 23

isonemus__.___---------__... 4,6,24; pi. 1

pertinuis ....... ... .. . . 24

TOSM_-_________________-__ 23 

sphenoproratus_._.._ .. . 23 

subimbricatus........ 4,8,9,10,11,12, US;, 24; pi. 1

montanaensis, Oervillia....... 3,4,5,9,10,12, 24; pi. 1

Gmlomya.................... 3,4,10, 36, 37; pi. 4

Myophorella (Promyophorella).......... .. 4,

6,8, 9,10,12,30, 31, 32; pi. 3 

Trigonia.................................. 31,32

Vaugmia................................. 29

Morrison Formation_______.___... 3 

Myacites (Pleuromya) subcompressa........... 35

Myalina (Gervillia) perplana.................. 24

Myopholas.................................... 2,37

acuticosta........................ . 37

hardyi.............................. 4,6,37;pi. 4

Myophorella.................................. SI

(Haidaia) crenulata....................... 33

dawsoni.....__-_..._.---. .. 33

yellowstonensis.............. 3,4,10, 35; pi. 3

(Promyophorella)....................... 2,22,32

conradi............................... 29

montanaensis...4,6,8,9,10,12,30, 31, 32; pi. 3 

Mytilidae.. -.. .--.- .... -.-.- 2

Mytilus..................................... 2,22,84

whiteL ................. 4,9,10,11,12,24; pi. 1

Page

N

Navajo Sandstone___. 

navis, Trigonia...........

Nerineid gastropods.....

newtoni, Pleuromya......

normanniana, Goniomya.

............... 3

 -_ -- 32

 . .- - . 4

 36

 . ... - 37

Nucula................................... 1, 2, 22, 23

sp___...._____________ 4, 8, 25; pi. 1 

Nuculidae.._______________....._ 2

Nugget Sandstone.._______________ 6

0 

occidentalis, Lima............................ 8,9,27

Lima (Plagiostoma)........ 4, 8, 9,10,12, 27; pi. 2

Ostrea................................ 1, 2, 5, 7,22, 27

dowlingi.................................. 28

strigilecula.............................. 6,27,28

(Liostrea)_...-__..._.__.____ 2 

strigilecula.......... 4,8, 9,10,11,12,27; pi. 1

Ostreidae_____________________ 2

Parallelodontidae _. 

Pectinidae_____. 

Pentacrinus asteriscus. 

peregrina, PHcatula... 

Perna................

.................. 2

.................. 2

.................. 5

-----_--_.-------. 26

 25

perplana,, Isognomon--.-- 4,8,9,10,11,12,24,25; pi. 1

Myalina (Gervillia).. ____________ 24

pertinuis, Modiolus........................... 24

Pholadidae...________.._______ 2 

Pholadomya................................ 2,22,36

inaequiplicata.............. 4, 6,9,10,12, 56; pi. 4

kingi. ........................ 4,6,10, 36; pi. 4

sp..- - - 10

Pholadomyidae___________.__ 2

Pinna....................................... 2,5,25

jurassica.................................. 25

kingi-................................ 4,6,12,#5

sp._ ------..---....-..................... 6,10

Plnnidae..._____...._._______ 2

(Plagiostoma), Lima.......................... 2,22

occidentalis, Lima.......... 4, 8, 9,10,12, 27; pi. 2

ziona, Lima.......... _________ 6,27,- pi. 2

planoconvexa, Gryphaea....................... 24

platessiformis, Camptonectes.. 4,6,8,9,10,12,26; pi. 2 

Pleuromya_______...--------..- 2,35

newtoni__________ -- 36 

postculminata........................... 36

subcompressa-.. -.-- ------ 4, 6,10,12,35,36

(Pleuromya) subcompressa, Myacites.......... 35

Pleuromyacidae.__.___ 2 

Plicatula................................. 2,7,22,26

peregrina........................... .... 26

sp..._...___...-..---. 4,6,8,10,12,26; pi. 1 

Plicatulidae.--.. .- - - 2

Plicatus sp___________. - 11

postculminata, Pleuromya..................... 36

poststriata, Trigonia........................... 29

praelonga, Vaugonia.......................... 31

Preuss Sandstone___.... 4

Promyophorella............ ..... .... -- 2, 31

(Promyophoretta), Myophorella.............. 2,22,32

conradi, Myophorella....------------------ 29

montanaensis, Myophorella................ 4,

6,8,9,10,12,30,3.7,32; pi. 3 

promytiloides, Isognomon...................... 24

Pronoella.......................... 1,2,5,7,22,34,35

cinnabarensis...... 4, 6,8,9,10,11,12, 34, 35; pi. 4

ravenscarensis...... 35

uintahensis. -.. 4,6,8,9,10,11,12, 34, 35; pi. 4 

sp.............................. ..... 9,10,12

punctata, Anatina............................ 37

Anatina (Cercomya)...................... 37

Cercomya......................... 4,12,37; pi. 4

quadrangularis, Trigonia......-...-....---.... 30

Vaugonia.............................. 30; pi. 3

Quenstedtia.................................. 2,7,35

bathonica.................... 4,9,11,12,35,' pi. 4

sp.- .......... .. 6,9,11

Quenstedtiidae.________-____ 2

R

ravenscarensis, Pronoella........

rectangula, Astarte (Coelastarte). 

rosii, Modiolus..................

35

33

23

San Rafael Group.._____.._ .. ... 1 

San Rafael Swell.----.- ------------------ 2,5

scalprum isonema, Volsella...----------------- 24

Scaphogonia argo.... - 32

semiplanata, Thracia.......................... 38

semiradiata, Anatina (Cercomya).............. 37

Cercomya.......................... . 37

signata, Trigonia.............................. 32

sparsilirata, Oervillia....................... 24; pi. 1

sphenoproratus, Modiolus..................... 23

Starfish. . -- - 2,4,12 

Stemmatoceras................................ 3,30

Stephanoceras................ . 3

Stratigraphic considerations..__-------- - 2

striata, Cercomya.............................. 37

strigilecula, Ostrea.......................... 6,27,28

Ostrea (Liostrea)........ 4,8,9,10,11,12, 17; pi. 1

Stump Formation_______- 26 

Stump Sandstone.-..--.__ ... 4 

sturgisensis, Vaugonia..... 31

stygius, Camptonectes..... 4,6,8, 9,10,11,12,25; pi. 2

subcompressa, Myacites (Pleuromya)..-....... 35

Pleuromya........ . -..-- 4,6,10,12,35,36

subimbricata, Mcdiola ----------------------- 23

Modiola (Volsella)....-................... 23

Volsella................................... 23

Page

subimbricatus, Modiolus,C4, 8, 9,10,11,12,23,24; pi. 1 

subquadratus, Hamulus................... 2,10; pi. 4

Tancredia..... -.... ... . 2 

sp.. .............................. 4,11,12

Tancrediidae..._______-______-_ 2 

Thracia... .............._. . ..... 1,2,22,38

convexa.....................________ 38

lens.......____-.__ __.____ 38

semiplanata............................... 38

weedi ..... ..... 3,4, 5,9,12,22,38; pi. 4

Thraciidae_._..... ....._...._ ._ 2

trafalgarensis, Trigonia........................ 32

'Trigonia...................._______._ 2,22,28

americana......... 4,8,9,10,12,28,29,30,32; pi. 3

conradi................................... 30

costata ............ ....----- __... 28,29

denticulata................................ 28

elegantissima. 4,8,9,10,11,12,29; pi. 3 

ferrieri.. ............ _ ......_ 32

guhsani...............______.____ 28

hemisphaerica............................. 29

montanaensis............................. 31,32

navis..................................... 32

poststriata................................ 29

quadrangularis............................ 30

signata................................ .. 32

trafalgarensis.............................. 32

sp.- . 4,8,9,10,11,12

Trigoniidae - . 2

Twelvemile Canyon Member of the Arapien

Shale 1,3,5,6

Twin Creek Limestone____________ 2,3,5,6 

Twist Gulch Member...____._......_ 3

U

uintahensis, Pronoella.. 4,6,8,9,10,11,12, 34, 35; pi. 4 

utahensis, Vaugonia............ 4,6,8,11,12,3?; pi. 3

Vaugonia-- - -- ......... 1,2, 7,22,30

conradi.......... 4,6,8,9,10,11,12, 30, 31; pi. 3

mariajosephinae...------------------------ 30

montanaensis............................. 29

praelonga................................. 31

quadrangularis-........................ 30; pi. 3

sturgisensis............................... 31

utahensis.... .... .--- 4,6,8,11,12, 31; pi. 3

v-costata.................................. 31

veronica................................... 30,31

(Hijitrigonia) geniculata................... 31

kojiwa..........................---... 31

v-costata, Vaugonia__ - -_-------- 31

veronica, Vaugonia........................... 30,31

Volsella scalprum isonema.................... 24

subimbricata.............................. 23

(Volsella) subimbricata, Modiola.............. 23

W 

weedi, Thracia....... 3, 4, 5,9,12, 22,38; pi. 4

weelaupensis, Isognomon...................... 24

whitei, Mytilus... ....... 4,9,10,11,12,24; pi. 1

Winsor Formation_ 5 

Wolverine Canyon Limestone Member of the

Preuss Sandstone____ 4, 5 

Worm tubes 2,4,6,12

yellowstonensis, Myophorella (Haidaia) 3,

4,10, 33; pi. 3 

Z 

Zemistephanus.................. ...... 3,5,29,30

ziona, Lima 4,8,9,10 

Lima (Plagiostoma).....- . 6,27; pi. 2
PLATES 1-4
PLATE 1

[Figures natural size unless otherwise indicated]

FIGUEES 1-3. Nuculasp. (p. C23).

Figured specimens USNM 131917 from USGS Mesozoic loc. 19432. 

4-6. Mytilus cf. M. whitei Whitfield (p. C24).

4. Lateral view of figured specimen USNM 131925 from USGS Mesozoic loc. 15551.

5. 6. Lateral and dorsal views of figured specimen USMN 131924 from USGS Mesozoic loc. 6941. 

7-9. Lopha off. L. engelmanni (Meek) (p. C28).

7. Figured specimen USNM 131954 from USGS Mesozoic loc. 17353.

8. 9. Figured specimen USNM 131955 from USGS Mesozoic loc. 5263. 

10-12. Idonearca"? sp. (p. C23).

Figured specimen USNM 131918 from USGS Mesozoic loc. 26307. Fig. 2 shows internal cast of left valve. 

13-15. Plicatula sp. (p. C26).

13, 14. Finely ribbed specimens USNM 131941 from USGS Mesozoic loc. 13756.

15. Coarsely ribbed specimen USNM 131942 from USGS Mesozoic loc. 12555. 

16-20. Modiolus subimbricatus (Meek) (p. C23).

16. Syntype USNM 131920 from Lower Canyon of the Yellowstone River, Montana.

17. Plesiotype USNM 131922 from USGS Mesozoic loc. 17054.

18. Lectotype USNM 131919 from Lower Canyon of the Yellowstone River, Montana.

19. Syntype USNM 131921 from Lower Canyon of the Yellowstone River, Montana.

20. Plesiotype USNM 131923 from USGS Mesozoic loc. 16624.

21. Gervillia sparsilirata Whitfield (p. C24).

Lateral view of plaster replica of holotype 21281 in the Yale Peabody Museum. This species is a synonym 

of G. montanaensis Meek.

22. Modiolus isonemus (Meek) (p. C24).

Holotype USNM 12545 from Weber Canyon, Utah.

23. Anomiat sp. (p. C26).

Figured specimen USNM 131943 from USGS Mesozoic loc. 18922. 

24, 25. Inoceramus crassalatus White (p. C25).

24. Syntype USNM 131930 from North Fork of Virgin River, Utah.

25. Lectotype USNM 131929 from North Fork of Virgin River, Utah. 

26-29. Ostrea (Liostrea) strigilecula White (p. C27).

26. Left valve of plesiotype USNM 131953 from USGS Mesozoic loc. 16202.

27. Left valve of lectotype USNM 131951 from south of Dirty Devil River, Utah.

28. Interior of right valve of syntype USNM 8581 from same locality as the lectotype.

29. Interior of right valve of syntype USNM 131952 from same locality as the lectotype. 

30, 31, 35, 36. Isognomon cf. /. perplana (Whitfield) (p. C25).

30. 31. Internal casts showing ligamental areas of figured specimens USNM 131929 from USGS Mesozoic 

loc. 16624.

35. Internal mold of right valve of figured specimen USNM 131928 from USGS Mesozoic loc. 963.

36. Left valve of internal mold assigned by White to Mytilus whitei Whitfield. Figured specimen USNM

8177 from near Fontenelle Canyon on west side of Green River Basin, Wyoming. 

32-34. Isognomon perplana (Whitfield) (p. C24).

32. Right valve of plesiotype USNM 131926 from USGS Mesozoic loc. 1158 in Yellowstone National Park.

33. Left valve of holotype 21280 in the Yale Peabody Museum from the south end of the Bridger Range, 

Montana.

34. Left valve of plesiotype USNM 131927 from USGS Mesozoic loc. 1158 in Yellowstone National Park.
GEOLOGICAL SURVEY PROFESSIONAL PAPER 483-C PLATE 1

NUCULA, MYTILUS, LOPHA, IDONEARCA ?, PLICATULA, MODIOLUS, ANOMIA?, GERVILLIA, 

INOCERAMUS, OSTREA (LIOSTREA), AND ISOGNOMON

711-164 O 64 3
PLATE 2

[Figures natural size unless otherwise indicated]

FIGURES 1-10. Camptonectes stygius White (p. C25).

1. Right valve of lectotype, USNM 131931 from southern Utah.

2. Interior of right valve of syntype USNM 8580 from the type lot.

3. Right valve of syntype USNM 131932 from the type lot.

4. Small right valve of syntype USNM 131934 from the type lot.

5. Small right valve of syntype USNM 131933 from the type lot.

6. Right valve of plesiotype USNM 131936 from USGS Mesozoic loc. 17353.

7. Right valve of plesiotype USNM 131937 from USGS Mesozoic loc. 10436.

8. 9. Left valve and posterior view of plesiotype USNM 131935 from USGS Mexozoic loc. 18281.

10. Left valve of plesiotype USNM 131938 from USGS Mesozoic loc. 10436. 

11-14. Camptonectes platessiformis White (p. C26).

11. 12. Left valve of holotype USNM 8179 from north base of Aquarius Plateau, Utah. Fig. 11 is shown X 2.

13. Left valve of plesiotype USNM 131940 (X 2) from USGS Mesozoic loc. 16624.

14. Left valve of plesiotype USNM 131939 (X 2) from USGS Mesozoic loc. 25669. 

15, 16. Camptonectes distans Stanton (p. C26).

Right valve of holotype USNM 28933 from USGS Mesozoic loc. 1158 in Yellowstone National Park. 

17-20. Lima (Plagiostoma) occidentalis Hall and Whitfield (p. C27).

17. Left valve of plesiotype USNM 131946 from USGS Mesozoic loc. 26309.

18. Left valve of plesiotype USNM 131945 from USGS Mesozoic loc. 27474.

19. Right valve of plesiotype USNM 131944 from USGS Mesozoic loc. 16624.

20. Left valve of holotype USNM 12539 from the Flaming Gorge near Manila, Utah. 

21-26. Lima (Plagiostoma )ziona Imlay, n. sp. (p. C27).

21. Small left valve of paratype USNM 131950 from USGS Mesozoic loc. 25675.

22-24. Posterior view, left valve and right valve of holotype USNM 131947 from USGS Mesozoic loc. 12749.

25. Small right valve of paratype USNM 131949 from USGS Mesozoic loc. 25675.

26. Complete large left valve of paratype USNM 131948 from USGS Mesozoic loc. 27469.
PROFESSIONAL PAPER 483-C PLATE 2

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22

CAMPTONECTES AND

26
PLATE 3

[All figures are natural size]

FIGURES 1-7. Trigonia elegantissima Meek (p. C29).

1. Coarsely ribbed right valve of plesiotype USNM 131963 from USGS Mesozoic loc. 11439.

2. Finely ribbed left valve of plesiotype USNM 28935 from USGS Mesozoic loc. 1182, Cinnabar Mountain, 

Montana. This specimen was illustrated by Stanton.

3. Coarsely ribbed left valve of plesiotype USNM 131964 from USGS Mesozoic loc. 25686.

4. Moderately ribbed plesiotype USNM 131960 from USGS Mesozoic loc. 20974, Lower Slide Lake, 

Teton County, Wyo.

5. Plesiotype USNM 131959 from USGS Mesozoic loc. 20974, Lower Slide Lake, Wyoming.

6. Moderately ribbed plesiotype USNM 131961 from USGS Mesozoic loc. 19422.

7. Finely ribbed plesiotype USNM 131962 from USGS Mesozoic loc. 19422. 

8-13. Trigonia americana Meek (p. C28).

8. 13. Dorsal and lateral views of right valve of plesiotype USNM 131958 from USGS Mesozoic loc. 

25866 in sec. 35, T. 1 S., R. 9 E., Park County, Mont.

9. Lectotype USNM 131956 from mouth of Yellowstone Canyon near Livingston, Mont.

10. Syntype USNM 7794 from same locality as lectotype.

11. Syntype USNM 7819 from same locality as lectotype.

12. Syntype USNM 131957 from same locality as lectotype. 

14-21. Vaugonia conradi (Meek and Hayden) (p. C30).

14. Plesiotype USNM 131965 from USGS Mesozoic loc. 20362 near Cody, Wyo.

15. Holotype USNM 212 from the southwest .base of the Black Hills, Wyoming. The specimen is 

corroded and lacks posterior end but is comparable to specimen shown in fig. 14.

16. Corroded right valve of plesiotype USNM 131968 from USGS Mesozoic loc. 25669.

17. Corroded right valve of plesiotype USNM 131966 from USGS Mesozoic loc. 26309.

18. Corroded right valve of plesiotype USNM 131969 from USGS Mesozoic loc. 25669.

19. Corroded right valve of plesiotype USNM 131967 from USGS Mesozoic loc. 25686.

20. Left valve of plesiotype USNM 131971 from USGS Mesozoic loc. 20958 from Lower Slide Lake, 

Teton County, Wyo.

21. Right valve of plesiotype USNM 131970 from USGS Mesozoic loc. 20958, Wyoming. Compare 

sharpness of ribbing in internal molds shown in figs. 20 and 21 with corroded internal molds shown 

in figs. 15-19. 

22. Vaugonia quadrangular is (Hall and Whitfield) (p. C30).

Holotype USNM 12537 from Como Bluff, Wyo. Photograph made from rubber cast of an external

mold that lacks part of anterior end. 

23-26. Vaugonia utahensis Imlay, n. sp. (p. C31).

23, 24. Dorsal and lateral views of right valve of holotype USNM 131973 from USGS Mesozoic loc. 26309.

25. Left valve of paratype USNM 131975 from USGS Mesozoic loc. 27473.

26. Right valve of paratype USNM 131974 from USGS Mesozoic loc. 27473. 

27-32. Myophorella (Haidaia) yellowstonensis Imlay, n. sp. (p. C33).

27. Right valve of holotype USNM 131983 from USGS Mesozoic loc. 27624, near East Boulder River, 

Montana, sec. 23, T. 3 S., R. 12 W., about 165 ft below top of Piper Formation.

28. Paratype USNM 131984 from USGS Mesozoic loc. 27624, Montana.

29. Paratype USNM 131985 from USGS Mesozoic loc. 13531, Utah.

30. Paratype USNM 131987 from USGS Mesozoic loc. 20967, Lower Slide Lake, Teton County, Wyo., 

from unit 10 of published section (Imlay, 1956a, p. 70).

31. Paratype. USNM 131988 from USGS Mesozoic loc. 20967, Wyoming.

32. Paratype USNM 131986 from USGS Mesozoic loc. 21385, Madison Range, NEK SEtf sec. 35, T.

5 S., R. 1 E., Montana, Sawtooth Formation. 

33-36, 38-41. Myophorella (Promyophorella) montanaensis (Meek) (p. C31).

33. Plesiotype USNM 131978 from USGS Mesozoic loc. 13532.

34. Plesiotype USNM 131977 from USGS Mesozoic loc. 27628, 2}4 miles south of Livingston, Mont.

35. Plesiotype USNM 131979 from USGS Mesozoic loc. 6941.

36. Plesiotype USNM 131981 from USGS Mesozoic loc. 19622, 2}£ miles south of Livingston, Mont.

38. Lectotype USNM 131976 from Lower Canyon of the Yellowstone River, Montana.

39. Syntype USNM 7817 from same locality as the lectotype.

40. Plesiotype USNM 131982 from USGS Mesozoic loc. 12842.

41. Plesiotype USNM 131980 from USGS Mesozoic loc. 6941. 

37. Vaugonia aff. V. conradi (Meek and Hayden) (p. C31).

Figured specimen USNM 131972 from USGS Mesozoic loc. 13529.
GEOLOGICAL SURVEY PROFESSIONAL PAPER 483-C PLATE 3

39 40 41

TRIGONIA, VAUGONIA, MYOPHORELLA (HAIDAIA), AND 

MYOPHORELLA (PROMYOPHORELLA)
PLATE 4

[Figures natural size unless otherwise indicated]

FIGURES 1-4. Astarte (Coelastarte) livingstonensis Imlay, n. sp. (p. C33).

1. Holotype USNM 131989 from USGS Mesozoic loc. 25866 in sec. 35, T. 1 S., R. 9 E., Park County, Mont.

2. Paratype USXM 12220 from Lower Canyon of Yellowstone River near Livingston, Mont.

3. Paratype USNM 131990 from USGS Mesozoic loc. 21385 in NE#SW>£ sec. 35, T. 5 S., R. 1 E., Montana.

4. Paratype USNM 131991 from USGS Mesozoic loc. 25866, Park County, Mont. 

5. Astarte (Coelastarte) cf. A. (C.) interlineata Lycett (p. C34).

Figured specimen USNM 131992 from USGS Mesozoic loc. 17269. 

6-8. Astarte (Coelastarte) n. sp. undet. (p. C34).

6. Figured specimen USNM 132011 from USGS Mesozoic loc. 28494.

7. Figured specimen USNM 131993 from USGS Mesozoic loc. 17269.

8. Figured specimen USNM 132012 from USGS Mesozoic loc. 28495. 

9 11. Quenstedtia aff. Q. bathonica Morris and Lycett (p. C35).

9. Specimen USNM 132000 from USGS Mesozoic loc. 17494.

10. Specimen USNM 132001 from USGS Mesozoic loc. 16701.

11. Specimen USNM 132002 from USGS Mesozoic loc. 12835. 

12-14. Myopholas hardyi Imlay, n. sp. (p. C37).

12. View of rubber cast of external mold of paratype USNM 132008 from USGS Mesozoic loc. 21449.

13. 14. View of rubber cast of external mold of holotype USNM 132007 (X 1 and X 2) from USGS Mesozoic

loc. 21448. 

15-23. Pronoella uintahensis Imlay, n. sp. (p. C34).

15, 16. External and internal views of right valve of silicified holotype USNM 131994 from USGS Mesozoic

loc. 20536 in northeast Utah.

17. Internal cast of paratype USNM 131996 from USGS Mesozoic loc. 16624.

18. Silicified paratype USNM 131998 from USGS Mesozoic loc. 25685.

19. Silicified paratype USNM 131999 from USGS Mesozoic loc. 25685.

20-22. Posterior, lateral and anterior views of paratype USNM 131997 from USGS Mesozoic loc. 19422.

23. Silicified paratype USNM 131995 from USGS Mesozoic loc. 20356 in northeast Utah. Shows hinge features. 

24, 25. Cyprina? iddingsi Stanton (p. C35).

24. Internal cast of paratype USNM 30653 from USGS Mesozoic loc. 1160 in Yellowstone National Park.

25. Internal mold of holotype USNM 28940 from USGS Mesozoic loc. 1173 in Yellowstone National Park. 

26. Hamulus? subquadratus (Meek and Hayden).

Plesiotype USNM 132013 from USGS Mesozoic loc. 12555. 

27-30. Pronoella cinnabarensis (Stanton) (p. C34).

27-29. Lateral and ventral views of lectotype USNM 28939 from USGS Mesozoic loc. 1168 in Yellowstone

National Park.

30. Rubber cast of internal mold of syntype USNM 30648 from USGS Mesozoic loc. 1187 in Yellowstone National Park. 

31. Cercomya punctata (Stanton) (p. C37).

Internal mold cf. plesiotype USNM 132009 from USGS Mesozoic loc. 26307. 

32, 33. Thracia weedi Stanton (p. C38).

32. Left valve of lectotype USNM 28944 from USGS Mesozoic loc. 1145 in Yellowstone National Park.

33. Left valve of plesiotype USNM 132010 from USGS Mesozoic loc. 16701. 

34, 35. Goniomya montanaensis Meek (p. C36).

Dorsal views of holotype USNM 7814 shown under different lighting, from Lower Canyon of the Yellowstone

River near Livingston, Mont. 

36. Pholadomya kingi Meek (p. C36).

Left valve of plesiotype USNM 132003 from USGS Mesozoic loc. 6941. 

37, 38. Pholadomya inaequiplicata Stanton (p. C36).

37. Plesiotype USXM 132005 from USGS Mesozoic loc. 6941.

38. Plesiotype USNM 132004 from USGS Mesozoic loc. 6941. 

39. Goniomya? n. sp. undet. (p. C37).

Specimen USNM 132006 from USGS Mesozoic loc. 6944.

U.S. GOVERNMENT PRINTING OFFICE: 1964 O 711 -164
GEOLOGICAL SURVEY PROFESSIONAL PAPER 483-C PLATE 4

*^

31

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3b . ..£ V

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ASTARTE (COELASTARTE), QUENSTEDTIA, MYOPHOLAS, PRONOELLA, CYPRINA?, 

HAMULUS?, CERCOMYA, THRACIA, GONIOMYA, AND PHOLADOMYA