Nonmarine Ostracodes in 

the Lakota Formation 

(Lower Cretaceous) 

From South Dakota 

and Wyoming

GEOLOGICAL SURVEY PROFESSIONAL PAPER 1069
Nonmarine Ostracodes in 

the Lakota Formation 

(Lower Cretaceous) 

From South Dakota 

and Wyoming

By I. G. SOHN

GEOLOGICAL SURVEY PROFESSIONAL PAPER 1069

Revision of nonmarine Lower Cretaceous 

ostracode genera from the Black Hills, 

and description of two new genera 

and four new species. On the 

basis of this revision, the Lakota 

Formation is considered 

to be pre-Aptian in age

UNITED STATES GOVERNMENT PRINTING OFFICE, WASHINGTON : 1979
UNITED STATES DEPARTMENT OF THE INTERIOR 

CECIL D. ANDRUS, Secretary

GEOLOGICAL SURVEY

H. William Menard, Director

Library of Congress Cataloging in Publication Data

Sohn, Israel Gregory, 1911-

Nonmarine ostracodes in the Lakota Formation (Lower Cretaceous) from South Dakota and Wyoming.

(Geological Survey professional paper ; 1069)

Supt. of Doc. No. : SD 119.16:1069

Bibliography: p.

Includes index.

1. Ostracoda, Fossil. 2. Paleontology Cretceous. 3. Paleontology Black Hills, S. Dak. and Wyo. I. Title.

II. Series: United States. Geological Survey. Professional paper ; 1069. 

QE817.Q8S583 565'.33 77-608326

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

Washington, D.C. 20402 

Stock Number 024-001-03155-6
CONTENTS

Page

Abstract _______________________________________________ 1

Introduction _________________________________________— 1

Acknowledgments ____________________________———————————— 2

Age of the rocks __________________________—————————————— 2

Paleoecology ____________________________________———————— 4

USGS Mesozoic collection localities _______________———————————— 5

Systematic descriptions __________________________————————— 8

Family Trapezoidellidae, n. fam. ______________———————————— 8

Key to the genera ______________——————————————————— 8

Genus Trapezoidella n. gen. _______________———————— 8

Trapezoidella trapezoidalis (Roth, 1933) _____———————— 9

T. rothi n. sp. ____________________——————————— 9

Genus Limnocypridea Lubimova, 1956 ________————————— 10

Key to the species ____________________———————— 11

Limnocypridea morrisonensis (Roth, 1933) __———————— 11

L.I albertensis (Loranger, 1951) ________———————— 12

Family Cyprideidae Martin, 1940 _________________________——— 12

Key to the genera _______________________—————————— 12

Genus Cypridea Bosquet, 1852 ______________—————————— 12

Subgenus Cypridea Bosquet, 1852 __________———————— 13

Subgenus Pseudocypridina Roth, 1933 _____————————— 13

Cypridea (Pseudocypridina) piedmonti Roth, 1933 ._—— 15

Cypridea (P.) inornata (Peck, 1941) _____._____— 15

Cypridea (P.) laeli n. sp. _____________________ 16

Cypridea (P.) henrybelli n. sp. _______-____—— 17

New genus undescribed _______________________—______ 18

"Cypridea" sp. 1 ______________________________ 18

Genus Longispinella n. gen. _________________________ 18

Longispinella asymmetrica n. sp. ___________________ 18

L. longispina (Peck, 1941) ______________________ 19

References cited _________________________________________ 20

Index _________________________________________________ 23

ILLUSTRATIONS

	[Plates follow index]

PLATE 1. Trapezoidella, Limnocypridea.

2. Limmocyprideal, Trapezoidella.

3. Cypridea (Pseudocypridina), Limnocypridea, Candona.

4. Longispinella.

5. Longispinella.

6. Cypridea (Pseudocypridina).

1. Cypridea (Pseudocypridina), Longispinella, "Cypridea.

8. Cypridea (Pseudocypridina).

FIGURE 1. Probable stratigraphic position of the Lakota Formation

2. Map showing the collection localities ________________

3. Shell morphology of Cyprideidae __________________

Page

3

7

13

in
IV CONTENTS

TABLE

Page 

TABLE 1.—USGS Mesozoic collections represented by each number

on the locality map ________________—_-_———————— 8
NONMARINE OSTRACODES IN THE LAKOTA FORMATION (LOWER 

CRETACEOUS) FROM SOUTH DAKOTA AND WYOMING

By I. G. SOHN

ABSTRACT

The stratigraphic age of the Early Cretaceous Lakota 

Formation in the Black Hills of South Dakota and Wyoming 

is Barremian or older rather than late Aptian as previously 

considered. This age is based on the study of certain ostracodes in 46 collections and the revision of several previously 

described taxa in North America.

The new genera Trapezoidella and Longispinella. and the 

new species T. rothi and L. asymmetrica, as well as Cypridea (Pseudocypridina) laeli and C. (P.) henrybelli, are described and illustrated. "Cypridea" sp. 1 is illustrated as an 

example of an as-yet-undescribed genus to which many of 

the species previously referred to Cypridea s.l. should be 

referred. Subgenera of Cypridea Bosquet, 1852, are elevated 

to generic status except Cypridea (Cypridea) and C. (Pseudocupridina) Roth, 1933. Species previously referred to the 

Paleozoic marine subgenus Bythocypris (Bairdiocypris) 

Kegel, 1932, are illustrated and referred to the new family 

Trapezoidellidae in the genera Trapezoidella and Limnocypridea Liibimova, 1956. Dimorphism similar to that in 

the living genus Candona Baird, 1845, is proposed for 

Limnocypridea morrisonensis (Roth, 1933), which, unlike 

most nonmarine ostracodes, is demonstrated to be variable 

in lateral outline. A lectotype is designated for Bairdiocypris albertensis Loranger, 1951, from the Blairmore Formation (Aptian-Albian) in Alberta, Canada, and one for 

Limnocypridea. equalis (Harper and Sutton, 1935), from the 

Lakota Formation, South Dakota. The Canadian species is 

reillustrated and questionably referred to Limnocypridea.

INTRODUCTION

Because of the presence of uranium, the Mesozoic sedimentary deposits in the southern Black 

Hills, S. Dak. and Wyo. (Gott, Wolcott, and Bowles, 

1974, and references therein), have been mapped by 

the U.S. Geological Survey in cooperation with the 

U.S. Atomic Energy Commission. Nonmarine ostracodes are the most common fossils in the Upper 

Jurassic (Morrison Formation) and in the Lower 

Cretaceous sedimentary rocks (Robinson, Mapel, 

and Bergendahl, 1964, and references therein). I received ostracode collections during the early stages 

of field work, and I joined the field parties in 1957 

to obtain additional collections.

The nonmarine ostracodes from the Black Hills

were described and illustrated as faunules from the 

Morrison Formation of Late Jurassic age by Roth 

(1933) and later by Harper and Sutton (1935). 

Roth (1933) described, among other species, 

Bythocypris (Bairdiocypris) morrisonensis, B. (B.) 

trapezoidalis, and Pseudocypridina piedmonti as 

part of the nonmarine fauna. Harper and Sutton 

(1935, p. 627) added to the faunule from a second 

locality, B. (B.) celtiformis, B. (B.) morrisonensis 

var. equalis, and Darwinula dakotensis. Loranger 

(1951, p. 2360; 1954, p. 286) described Bythocypris 

(Bairdiocypris) albertensis from the Lower Cretaceous Blairmore Formation in central and southern 

Alberta, Canada. Howe and Laurencich (1958, p. 

79) stated that Loranger's description does not fit 

Bairdiocypris.

I demonstrated that the sedimentary rocks in 

South Dakota from which Roth, and also Harper 

and Sutton, described the ostracodes are actually 

from the Lower Cretaceous Lakota Formation 

(Sohn, 1957, 1958). In that study I was able to 

differentiate between the Jurassic and Lower Cretaceous sedimentary rocks in the Black Hills, because 

the Jurassic Morrison Formation contains Theriosynoecum Branson, 1936, and does not contain 

notched forms that belong in the Cyprideidae Martin, 1940. In contrast, the Lower Cretaceous sedimentary rocks do not contain Theriosynoecum and 

do contain notched forms. I was not able, however, 

at that time to correlate the Lower Cretaceous rocks 

in the Western United States with the cosmopolitan 

stratigraphic scheme which is based primarily on 

marine faunas.

During the past two decades, publications on 

Lower Cretaceous stratigraphy of the Black Hills 

and on nonmarine Early Cretaceous ostracodes 

abroad (see references cited) have made it possible 

to suggest a tentative correlation. On the basis of 

selected taxa discussed in this paper, the Lakota 

Formation is inferred to be pre-Aptian in age.

When Post and Bell (1961) defined the Chilson 

Member of the Lakota Formation in the southern
NONMARINE OSTRACODES, LAKOTA FORMATION, SOUTH DAKOTA AND WYOMING

Black Hills, they recognized the Minnewaste Limestone Member above the Chilson Member and below 

the Fuson Member of the Lakota Formation. The 

Minnewaste Limestone Member is present only in 

the southern and southeastern Black Hills in Custer 

and Fall River Counties, S. Dak. (Waage, 1959, fig. 

7), and where it is absent, the Chilson Member is 

disconformably overlain by the Fuson Member 

(Post and Bell, 1961, figs. 349.1, 349.2). Rocks 

equivalent to the Chilson Member of the Lakota 

Formation thin westward and pinch out beneath 

rocks equivalent to the Fuson Member west of a 

line that approximately bisects R. 63 W. in Crook 

and Weston Counties, Wyo. (Post and Bell, 1961, 

p. D178, fig. 349.2; Robinson, Mapel, and Bergendahl, 

1964, p. 25). For this reason, Mapel and Pillmore 

(1963, p. M17, pi. 1) mapped the rocks in Wyoming 

as Lakota Formation.

Map localities 5-7 of this report are in Wyoming 

in rocks considered to be equivalent to the Fuson 

Member of the Lakota Formation in the southern 

Black Hills in South Dakota (Post and Bell, 1961, 

p. D178), rather than to the Chilson Member. However, the ostracodes in eight collections from the 

Fuson Member in Fall River and Custer Counties, 

S. Dak., although low in diversity (three genera), 

differ on the generic level from the high-diversity 

(eight genera) ostracodes in the Chilson Member of 

South Dakota (Sohn, 1958, unpublished reports on 

referred collections, MD-57-60, MD-57-61), and 

also from those in Wyoming. The ostracodes from 

map localities 5-7 in Wyoming (pis. 1, 3, 7, and 8), 

as well as some not included in this report, are 

identical on the species level with those from the 

Chilson Member. Because of the short period of 

absolute time involved, the ostracodes of the Chilson 

member may have extended into the Fuson Member 

during similar environmental conditions northwest 

of Inyan Kara Creek in Wyoming, and the difference on the generic level between the ostracodes of 

the two members in South Dakota may have been 

due to different environments. It cannot be stated 

with certainty that the similarity of ostracodes on 

the species level between the Lakota Formation 

undifferentiated in Wyoming and the Chilson Member of the Lakota Formation in South Dakota indicates a time equivalence. All the previously described ostracode species (Roth, 1933; Harper and 

Sutton, 1935) and the newly described species, with 

the possible exception of those from Wyoming, are 

from the Chilson Member of the Lakota Formation.

The Mesozoic nonmarine species previously referred to Bythocypris (Bairdiocypris) are redescribed, ireillustrated, and referred to Mesozoic 

genera, and the Middle Devonian marine genus 

Bairdiocypris Kegel, 1932 (see Sohn, 1960, p. 83), 

is restricted to Paleozoic rocks: Silurian (Lundin, 

1965, p. 37; Pranskevichius, 1972, p. 139), Carboniferous (Green, 1963, p. 99; Buschmina, 1965, p. 

83; 1968, p. 94; 1970, p. 28), and questionably Permian (Willey, 1970, p. 130).

ACKNOWLEDGMENTS

I wish to thank the following colleagues in the 

U.S. Geological Survey for guiding me in the field 

and (or) sending me collections from the Black 

Hills: Henry Bell III, M. H. Bergendahl, W. R. 

Braddock, J. J. Connor, W. J. Mapel, C. L. Pillmore, 

C. E. Price, C. S. Robinson, D. E. Walcott, and V. 

R. Wilmarth. Prof. K. M. Waage, Yale University, 

guided me to some critical localities, Prof. R. E. 

Peck, University of Missouri, donated specimens 

of Cypridea longispina Peck, 1941, and Dr. D. M. 

Loranger made available the types of Bairdiocypris 

albertensis Loranger, 1951. Without the aid of these 

scientists, this study could not have been made.

AGE OF THE ROCKS

The nomenclatural history of the Lower Cretaceous formations was discussed by Waage (1959, 

p. 18) and later by Wolcott (1967, p. 433). The 

Lakota Formation consists, in ascending order, of 

the Chilson Member, the Minnewaste Limestone 

Member, and the Fuson Member. Post and Bell 

(1961, p. D173) divided the Chilson Member into 

two units. The lower (Unit 1) consists mostly of 

fine-grained yellowish-gray sandstone interbedded 

or interfingered with highly carbonaceous siltstone 

and mudstone layers and ranges in thickness from 

zero to about 400 feet (122 m). Unit 2 unconformably overlies the older unit. It consists of lenticular bodies of grayish-yellow or reddish-orange 

to reddish-brown fine-grained well-sorted sandstones that are interbedded with and finger laterally into varicolored siltstone or claystone. Unit 2 

ranges in thickness from zero to 437 feet (133 m). 

The mudstone and sandstone are calcareous in 

many places; consequently, it is inferred that Roth's 

as well as Harper and Sutton's collections came from 

this unit.

The exact stratigraphic position of the Lower 

Cretaceous continental deposits in the Western Interior of the United States in terms of the European 

stages is as yet uncertain. I (Sohn, 1958, p. 122) 

suggested that the basal part of the Lakota Forma-
AGE OF THE ROCKS

TIME

M.Y.

121-

1 OC

I O I

138.5- 

141 5

EUROPEAN

FACEOUS

HI

<r 

u

<r

O

JURASSIC 

(PART)

STAGES SUBSTAGES

ALBIAN

APTIAN

BARREMIAN

NEOCOMIAN

TITHONIAf (VOLGIAN

HAUTERIVIAN

VALANGINIAN

BERRIASIAN

PORTLANDIAN

KIMMERIDGIAN

SOHN, 1958

7

LAKOTA FORMATION

MORRISON 

FORMATION

THIS PAPER

LAKOTA FORMATION

FIGURE 1.—Probable stratigraphic position of the Lakota Formation. Absolute scale from van Hinte (1976b).

tion may prove to be older than Aptian (1958, fig. 

2, p. 124). Lane (1963, p. 232) summarized the 

previous work on the Lower Cretaceous of the

Western Interior and concluded that the boundaries 

within the formations were still highly conjectural. 

Anderson (1973, fig. 1) extended the Lower Cre-
NONMARINE OSTRACODES, LAKOTA FORMATION, SOUTH DAKOTA AND WYOMING

taceous of South Dakota to the approximate base 

of the Middle Valanginian but noted that the North 

American ages are subject to considerable revision. 

Cook and Bally (1975, p. 206) showed the Lakota 

Formation of South Dakota as starting in the 

Middle Aptian(?), extending through the Barremian, and questionably terminating at the top of 

the Hauterivian.

Because the Early Cretaceous ostracodes in the 

Black Hills of South Dakota and Wyoming are endemic, all the known species and those described 

here as new offer no clues to intercontinental correlation. However, some idea as to the probable 

stratigraphic position of the rocks might be obtained 

by recording the ranges of related species in 

Europe, Asia, and South America. Figure 1 shows 

the probable stratigraphic position of the Lakota 

Formation on the basis of such a comparison.

The Lakota Formation contains, among other 

species, Cypridea (Pseudocypridina) piedmonti 

Roth, 1933, C. (P.) henrybelli n. sp., and C. (P.) 

laeli n. sp. The resemblance of C. (P.) piedmonti to 

C. (P.) unicostata Galeeva, 1955, from the Barremian of Mongolia, as shown in the discussion of 

the species, suggests that the Lakota Formation is 

probably not younger than the Barremian. C. (P.) 

henrybelli is shown in the discussion of the species 

to belong, on the basis of lateral outline and rostrum, to the Cypridea parallela-lme of Wolburg 

that has a stratigraphic range of Wealden 4 to 

Wealden 6 Beds in Germany. The Wealden Beds 4 

to 6 were considered to be Valanginian in age by 

Anderson (1973, fig. 1) but van Hinte (1976b) regarded these beds as Berriasian in age. The lateral 

nodes relate this species to C. (P.) binodosa (Martin, 1940) from the middle Purbeckian of Germany, 

and to C. (P.) salvadorensis nodifer (Krb'mmelbein, 

1962) as well as to C. (P.) subtilis (Krommelbein, 

1965), both from Brazil. The Brazilian species are 

considered to be at least partly younger than the 

Wealden Beds of Germany, and are probably of 

approximate Valanginian Age. C. (P.) laeli is shown 

in the discussion of the species to resemble the 

Purbeckian Cypridea fasciculata-group of Wolburg 

and also the late Purbeckian-Berriasian C. altagroup of Wolburg. Certain structures on the surface of the carapace could have developed from 

similar structures on species described from Purbeckian through Berriasian Ages. On the basis of 

the resemblances and postulated evolutionary 

stages of development in relation to the known 

species outside of North America, C. (P.) henrybelli and C. (P.) laeli suggest that the plausible age

for the Lakota Formation is younger than Berriasian and possibly also younger than early Valanginian.

According to van Hinte's proposed absolute time 

scales for the Jurassic (1976a) and for the Cretaceous (1976b), the time involved between the underlying Morrison Formation (Kimmeridgian) and the 

base of the Aptian is approximately 26 m.y., of 

which 6 m.y. are in the Jurassic and the remaining 

20 m.y. in the Early Cretaceous. On the basis of the 

estimates of the timespan in the standard section, 

the Lakota Formation should fall somewhere within the 16-m.y. span between the Berriasian and the 

base of the Aptian. As the ostracodes dealt with in 

this paper are from the Chilson Member, the lowest 

of three members of continental deposits, I estimate 

the timespan of the rocks represented by the ostracodes to be less than 10 m.y., somewhere between 

118 m.y. and 128 m.y. before the present.

PALEOECOLOGY

The Lower Cretaceous sedimentary rocks in the 

Black Hills represent limnic and fluviatile deposits, 

and the ostracodes in those rocks belong to genera 

described from nonmarine environments in other 

parts of the world. The one possible exception is 

presented in a study by Alien and others (1973) on 

the basis of isotopic ratios of the carbonate in fossils from the Lower Cretaceous Wealden clay in 

Europe (England and Germany). They concluded 

that two species of Cypridea: C. bispinosa suttingenis [sic] = C. bispinosa suthringensis Anderson, 1967, and C. recta tillsdenensis Anderson, 1967, 

"might be marine" (Alien and others, 1973, p. 619), 

and that other species of Cypridea used in their 

study may be freshwater. It is known that nonmarine ostracodes have been transported into 

brackish and also marine environments. I have recovered from the same samples (Sohn, 1967, p. 123) 

Cypridea specimens and charophytes associated 

with typically marine ostracodes as well as the 

foraminifer Chofatella decipiens Schlumberger, 

1905.

However, the paleogeographic framework of the 

European Lower Cretaceous differs from that in the 

Black Hills. In Europe, the Lower Cretaceous sediments were deposited during a marine-freshwater 

transgressive and regressive sequence (Anderson 

and others, 1967, p. 174-175), whereas no evidence 

exists in North America of a marine incursion in 

Wyoming and South Dakota during Early Cretaceous time (Lane, 1963, fig. 2).

The population dynamics of the limnic ostracodes
USGS MESOZOIC COLLECTION LOCALITIES

in the Black Hills area must have been such as to 

induce an unusual variety in the shell morphology. 

The development of lateral ridges on the valves, 

asymmetrical on the carapace as on Trapezoidella 

(pi. 1, figs. 5, 8, 16; pi. 2, figs. 14, 16, 18, 20-24, 28, 

30, 36), and on Cypridea (Pseudocypridina) (pi. 3, 

figs. 1, 4, 9, 10, 13; pi. 6, figs. 1, 5, 8, 10, 13, 16, 21, 

23, 32, 41, 42; pi. 8, figs. 29, 30) on which they are 

developed only on the left valves, and the asymmetrical structure on the left valve only in Longispinella 

(pi. 4, figs. 9, 13, 16, 17, 18; pi. 5, figs. 7, 13, 20, 21; 

pi. 7, figs. 5, 7) probably reflects some functional 

response to their ecology.

Sohn (1962) and Sohn and Anderson (1964) 

demonstrated that the presence and position of 

every spine and node in the Mesozoic freshwater 

cypridacean ostracode Theriosynoecum Branson, 

1936, are genetically controlled, and later workers 

(Benson, 1972; Liebau, 1975) showed that the 

same is true for marine cytheraceans. Some of the 

species in the Black Hills show a variation contrary 

to this, principle, as illustrated in this paper in 

Cypridea (Pseudocypridina) henrybelli (pi. 3, figs. 

14-17; pi. 8, figs. 1-25). Although similar structures have been recorded on other limnic cypridaceans, nobody has proposed an explanation for their 

presence. At the present state of knowledge, such 

structures cannot be ascribed to a definite ecological 

factor.

USGS MESOZOIC COLLECTION LOCALITIES

[Map locality numbers refer to figure 2]

USGS 25460. Chilson Member of Lakota Formation. Unit 

2, Buck Canyon, SEU, sec. 15, T. 8 S., R. 4 E., Flint 

Hill quadrangle, Fall River County, S. Dak. Colln. H. 

Bell, 1954, (MD-55-11, field No. HBP-70-54). Map loc. 

17.

USGS 25643. Lakota Formation, NE% sec. 9, T. 50 N., R. 64 

W., Crook County, Wyo. Colln. W. J. Mapel, 1956 (F56-32, field No. MP-41-23). Map loc. 6.

USGS 25644. Lakota Formation, NW*4 sec. 21, T. 51 N., 

R. 65 W., Crook County, Wyo. Colln. W. J. Mapel, 1956 

(F-56-32, field No. MP-48-19). Published in error as 

USGS 24644 by Robinson, Mapel, and Bergendahl (1964, 

p. 37, unit 13), see USGS 31001. Map loc. 5.

USGS 25645. Same locality as USGS 25644. Colln. W. J. 

Mapel, 1956 (F-56-32, field No. MP-48-20). Published 

in error as USGS 24645 by Robinson, Mapel, and Bergendahl (1964, p. 37, unit 14), see USGS 31001. Map loc. 5.

USGS 25646. Lakota Formation, approximately 80 feet (24.4 

m) above base. Sec. 16, T. 6 N., R. 4 E., Lawrence 

County, S. Dak., vicinity of Sturgis. Colln. W. J. Mapel, 

1956 (F-56-32, field No. MP-119-9). Map loc. 2.

USGS 25647. Lakota Formation, N% sec. 30, T. 6 N., R. 5 

E., Meade County, S. Dak., Colln. W. J. Mapel, 1956 

(F-56-32, field No. MP-119-10). Map loc. 4.

USGS 26098. Chilson Member of Lakota Formation, Unit 2,

Buck Canyon measured section, 56 to 63 feet (17 to 22 

m) above base. SE%, sec. 15, T. 8 S., R. 4 E., Flint Hill 

quadrangle, Fall River County, S. Dak. Colln. H. Bell, 

1954 (MD-56-6, field No. HBP-51-54). Map loc. 17.

USGS 26100. AEC Diamond Drill Hole RE-17 (Bell and 

Post, 1971, p. 557, pi. 32), same as USGS 30988, core at 

267.0 feet (81 m). Colln. H. Bell, 1955 (MD-56-6, field 

No. RE-17B). Map loc. 16.

USGS 26468. Lakota Formation, measured section in SE% 

sec. 1, T. 8 S., R. 3 E., elevation 4,170 feet (1,271 m), 

Fall River County, S. Dak. Colln. V. R. Wilmarth, 1956 

(MD-57-11, field No. MK-S-56). Map loc. 10.

USGS 26469. Same locality and section as USGS 26468 at 

elevation 4,200 feet (1,280 m). Colln. V. R. Wilmarth, 

1956 (MD-57-11, field No. MK-T-56). Map loc. 10.

USGS 26939. Lakota Formation, 20 feet (6 m) above base, 

SW% sec. 9, T. 50 N., R. 64 W., Crook County, Wyo. 

Colln. W. J. Mapel and C. L. Pillmore, 1957 (F-57-31, 

field No. 213-6). Map loc. 6.

USGS 26940. Lakota Formation, basal part, sec. 29, T. 50 

N., R. 64 W., Crook County, Wyo. Colln. W. J. Mapel 

and C. L. Pillmore, 1957 (F-57-31, field No. 216-1). Map 

loc. 7.

USGS 26941. Lakota Formation, limestone bed, 1 foot (0.30 

m) above USGS 26940. Colln. W. J. Mapel and C. L. 

Pillmore, 1957 (F-57-31, field No. 216-2). Map loc. 7.

USGS 30985. Chilson Member of Lakota Formation, upper 

part, mudstone, dark greenish gray, somewhat sandy, 

Unit 2, SEi4 sec. 11, T. 8 S., R. 3 E., Flint Hill quadrangle, Fall River County, S. Dak. Colln. H. Bell, 1954 

(field No. HB-l-54 = Station B-136). Map loc. 13.

USGS 30986. Chilson Member of Lakota Formation, upper 

part, thin sandstone in Unit 2 (Bell and Post, 1971, p. 

520), SWi/i sec. 12, T. 8 S., R. 3 E., Flint Hill quadrangle, Fall River County, S. Dak. Colln. H. Bell, 1954 

(MD-55-11, field No. HB-2-54). Map loc. 13.

USGS 30987. Chilson Member of Lakota Formation, white 

clay, Unit 2, 1.8 miles (2.9 km) southeast of 30986. Flint 

Hill quadrangle, Fall River County, S. Dak. Colln. H. 

Bell, 1953 (MD-53-55, field No. HB-14-53). Map loc. 16.

USGS 30988. Chilson Member of Lakota Formation, Unit 2, 

AEC Diamond Drill Hole RE-17 (Bell and Post, 1971, 

p. 557, pi. 32), corner common to sees. 14, 15, 22, 23, 

T. 8 S., R. 3 E., Flint Hill quadrangle, Fall River 

County, S. Dak. Core at 289.5 feet (88 m) interbedded 

mudstone and sandstone. Colln. H. Bell, 1955 (MD-56-6, 

field No. RE-171). Map loc. 16.

USGS 30989. Chilson Member of Lakota Formation, Unit 2. 

AEC Diamond Drill Hole RE-14 (Bell and Post, 1971, 

p. 555, pi. 32), SW^SWi/i sec. 11, T. 8 S., R. 3 E., Flint 

Hill quadrangle, Fall River County, S. Dak. Core at 

346.0 feet (105 m), siltstone, dark-gray, carbonaceous; 

some dark-greenish-gray claystone. Colln. H. Bell, 1955 

(MD-56-6, field No. RE-14J). Map loc. 13.

USGS 30990. Chilson Member of Lakota Formation, Unit 1, 

mudstone about 10 feet (3 m) above base of section, 

Upper Chilson Canyon, Marty's Ranch, T. 8 S., R. 3 E., 

Flint Hill quadrangle, Fall River County, S. Dak. Colln. 

I. G. Sohn and H. Bell, 1957, field No. 8/15/10/57. Map 

loc. 14.

USGS 30991. Chilson Member of Lakota Formation, Unit 1, 

same locality as above, limestone below and between 

paper shale sequence. Colln. I. G. Sohn and H. Bell, 1957, 

field No. 8/15/18/57. Map loc. 14.
6 NONMARINE OSTRACODES, LAKOTA FORMATION, SOUTH DAKOTA AND WYOMING

USGS 30993. Lakota Formation, core in NE 1^ sec. 33, T. 7 

S., R. 3 E., Edgement quadrangle, Fall River County, 

S. Dak. Colln. W. B. Braddock, 1953 (MD-53-33, field 

No. BB-45-33). Map loc. 9.

USGS 30994. Chilson Member of Lakota Formation, mudstone below typical Lakota sandstones and above the 

Unkpapa Sandstone. Sec. 4, T. 8 S., R. 4 E., Minnekahta 

quadrangle, Fall River County, S. Dak. Colln. H. Bell, 

1953 (MD-53-33, field No. HB-9-53a). Map loc. 11.

USGS 30995. Lakota Formation, 95 feet (29 m) below top, 

center NW% sec. 17, T. 8 N., R. 1 E., Butte County, S. 

Dak. Colln. W. J. Mapel, 1957 (F-57-35, field No. 253- 

13a). Map loc. 1.

USGS 30996. Lakota Formation, gray silty claystone, carbonaceous, approximately 150 feet (45.7 m) below top 

of formation, 4,300 feet (1,311 m) N. 35° E. from common corner sees. 11, 12, 13, 14, T. 8 S., R. 5 E., Cascade 

Springs quadrangle, Fall River County, S. Dak. Colln. 

J. J. Conner, 1957 (MD-57-60, field No. AS-58). Map 

loc. 15.

USGS 30997. Chilson Member of Lakota Formation, probably 

Unit 2, coquina at Roth's (1933) type-locality, sec. 28, 

T. 4 N., R. 6 E., Meade County, S. Dak., 3 miles (4.8 

km) north of Piedmont. Colln. I. G. Sohn, 1957 (field No. 

8/10/2/57). Map loc. 8.

USGS 30998. Lakota Formation, laminated ostracodal clay, 

Harper and Sutton's (1935) type-locality, NW1^ sec. 29, 

T. 6 N., R. 4 E., Lawrence County, S. Dak. Colln. I. G. 

Sohn and H. Bell, 1957 (field No. 8/11/2/57) Map loc. 3.

USGS 30999. Lakota Formation, shale with ostracodes, about 

3 feet (0.9 m) below the sandstone, same locality as 

above. Colln. I. G. Sohn and H. Bell, 1957 (field No. 

8/11/4/57). Map loc. 3.

USGS 31001. Lakota Formation, near top, shale above limestone, near Corral Creek, NE% sec. 20 and NW1^ sec. 

21, T. 51 N., R. 65 W. Crook County, Wyo. Colln. I. G. 

Sohn and W. J. Mapel, 1957 (field No. 8/20/21/57), same 

as USGS 24645 = 25655 (see Robinson, Mapel, and Bergendahl, 1964, p. 37, unit 14). Map loc. 5.

USGS 31002. Chilson Member of Lakota Formation, Unit 2, 

mudstone, gray to green calcareous, core at 314.5 feet 

(96 m) in same drill hole as USGS 30989. Colln. H. Bell, 

1955 (MD-56-6, field No. RE-14A). Map loc. 13.

USGS 31003. Same unit, formation and drill hole as above, 

core at 321.8 feet (98.1 m). Colln. H. Bell, 1955 (MD56-6, field No. RE-14D). Map loc. 13.

USGS 31004. Same unit, formation and drill hole as above, 

core at 334.0 feet (102 m). Colln. H. Bell, 1955 (MD56-6, field No. RE-14G). Map loc. 13.

USGS 31005. Same unit, formation and drill hole as above, 

siltstone, dark-gray, carbonaceous, core at 345.0 feet 

(105 m). Colln. H. Bell, 1955 (MD-56-6, field No. RE141). Map loc. 13.

USGS 31006. Chilson Member of Lakota Formation, Unit 2. 

Same drill hole as USGS 30988. Mudstone, dark-olivegray, carbonaceous, core at 283.5 feet (86 m). Colln. H. 

Bell, 1955 (MD-56-6, field No. RE-17H). Map loc. 16.

USGS 31007. Chilson Member of Lakota Formation, Unit 2, 

Buck Canyon, SE 1^ sec. 15, T. 8 S., R. 4 E., Flint Hill 

quadrangle, Fall River County, S. Dak. Mudstone, 

brownish gray, silty; bedding irregular, unit 10 of Bell 

and Post (1971, p. 531), 52 feet (15.8 m) above base.

Colln. H. Bell, 1955 (MD-56-6, field No. HB-23-54). 

Map loc. 17.

USGS 31008. Same unit as above, slightly higher. Colln. 

H. Bell, 1955 (MD-56-6, field No. HB-24-54). Map loc. 

17.

USGS 31009. Lakota Formation, variegated clay just below 

USGS 30998. Colln. I. G. Sohn and H. Bell, 1957 (field 

No. 8/11/3/57). Map loc. 3.

USGS 31129. Chilson Member of Lakota Formation, Unit 1, 

same location as USGS 30990, about 5 feet (1.5 m) below 

USGS 30990, Fall River County, S. Dak. Colln. I. G. 

Sohn and H. Bell, 1957 (field No. 8/15/11/57). Map loc. 

14.

USGS 31130. Chilson Member of Lakota, Unit 1, sandy layer, 

just above USGS 31129. Fall River County, S. Dak. 

Colln. I. G. Sohn and H. Bell 1957, (field No. 8/15/12/ 

57). Map loc. 14.

USGS 31153. Lower part of the Lakota Formation, shale, 

sec. 32, T. 7 S., R. 6 E. Channel sample of upper onehalf of 15-foot (4.6-m) lens in cut on north side of Fall 

River Road, 3.2 miles (5.1 km) southeast of city limits 

(1940) of Hot Springs, Fall River County, S. Dak. 

Same locality as Peck (1957, p. 11) loc. D286. Colln. I. G. 

Sohn, D. E. Wolcott, and C. E. Price, 1957 (field No. 

8/16/1/57). Map loc. 12.

USGS 31154. Same locality as above, channel sample of lower 

one-half of the same lens to contact with underlying 

Unkpapa Sandstone (Upper Jurassic). Colln. I. G. Sohn, 

D. E. Wolcott, and C. E. Price, 1957 (field No. 

8/16/2/57). Map loc. 12.

USGS 31171. Chilson Member of Lakota Formation, probably 

Unit 2, shale, about 3 feet (0.9 m) above USGS 30997, 

and approximately 33 feet (10 m) above base. Sec. 28, 

T. 4 N., R. 6 E., Meade County, S. Dak. Colln. I. G. Sohn, 

1957 (field No. 8/10/1/57). Map loc. 8.

USGS 31172. Chilson Member of Lakota Formation, probably Unit 2 shale, about 25 feet (7.6 m) below USGS 

30997, and approximately 5 feet (1.5 m) above base. Sec. 

28, T. 4 N., R. 6 E., Meade County, S. Dak. Colln. I. G. 

Sohn, 1957 (field No. 8/10/3/57). Map loc. 8.

USGS 31237. Chilson Member of Lakota Formation, same 

locality as USGS 30990, shale, Unit 1, about 3 feet (0.9 

m) lower in the section than USGS 31129. Colln. I. G. 

Sohn, and H. Bell, 1957 (field No. 8/15/13/57). Map loc. 

14.

USGS 31238. Same locality as above, 2 feet (0.6 m) below 

USGS 31237. Colln. I. G. Sohn and H. Bell, 1957 (field 

No. 8/15/14/57). Map loc. 14.

USGS 31239. Lakota Formation, gray, silty claystone approximately 150 feet (45.7 m) below top, 5,400 feet 

(1,646 m) N. 45 E. from common corner of sees. 11, 12, 

13, 14, T. 9 S., R. 5 E., Cascade Springs quadrangle, Fall 

River County, S. Dak. Colln. J. J. Conner, 1957 (MD57-60, field No. AS-33). Map loc. 18.

The geographic location of the samples in Wyoming and South Dakota is shown in figure 2. Collection localities that are too close to each other to 

be shown on the map are lumped under one number. 

Table 1 shows the USGS Mesozoic localities under 

each of the location numbers on the map.
USGS MESOZOIC COLLECTION LOCALITIES

105'

! L A W R'E N € E

F A Li L , R ! 1 V, E1 - \F

Base from U.S. Geological Survey State bases 

Wyoming, 1964 and South Dakota, 1961, 1:500,000

FIGURE 2.—Map showing the location of the collection localities in South Dakota and Wyoming.
NONMARINE OSTRACODES, LAKOTA FORMATION, SOUTH DAKOTA AND WYOMING

TABLE 1.—USGS Mesozoic collections represented by each 

number on the locality map (fig. 2)

Map location Xo. I'SGft Menogoir collection 2Vo.

1 30995

2 25646

3 30998, 30999, 31009

4 25647

5 25644, 25645, 31001

6 25643, 26939

7 26940, 26941

8 30997, 31171, 31172

9 30993

10 26468, 26469

11 30994

12 31153, 31154

13 30985, 30986, 30989, 31002, 31003, 31004,

	31005, 31129

14 30990, 30991, 31129, 31130, 31237, 31238

15 30996

16 26100, 30987, 30988, 31006

17 25460, 26098, 31007, 31008

18 31239

SYSTEMATIC DESCRIPTIONS

Class OSTRACODA Latreille, 1802 emend. 1804

Order PODOCOPIDA Sars, 1865

Superfamily CYPRIDACEA Baird, 1845

Family TRAPEZOIDELLIDAE Sohn, n. fam.

Diagnosis.—Medium to large (between 0.75 mm 

and 2 l/2 mm or larger), thick walled, with straight 

to curved dorsal margin. Surface smooth or tuberculate, with or without ventrolateral ridge or node on 

larger valve. Overlap strong along dorsal and ventral margins, variable on end margins. Duplicature 

wide on end margins, hingement ridge and groove, 

with or without anterior toothlike widening on 

ridge. Dimorphism unknown.

Discussion.—Galeeva (1955, p. 26) described 

Limnocypridae Mandelstam, 1948, for the genera 

Dsunbaina Galeeva, 1955, Cypridea Bosquet, 1850, 

Mongolianella "Mandelstam in litt. 1948," and 

"Cyprideamorphella" but did not describe, illustrate, or cite a reference to Limnocypridea, the typegenus. Because Limnocypridea Liibimova, 1956, had 

not been validated in 1955, the family Limnocypridae is a nomen nudum, and does not compete with 

the Trapezoidellidae. Howe (1962, p. 134) discussed 

the Limnocypridae, and stated that "As used this 

family is more or less equivalent to the Cyprideinae 

Martin, 1940 * * * ."

Liibimova (1956b, p. 9) transferred Limnocypridea Liibimova, 1956, and Mongolianella Mandelstam, 1955, to the Cyprideinae, and Mandelstam and 

Schneider (1963, p. 106) added to the subfamily 

the genera Latonia Mandelstam, 1963, Zefaina Mandelstam, 1963, and Ilyocypromorpha Mandelstam,

1955. The Cyprideinae were elevated to family 

status, the Cyprideidae Martin, 1940, by Hartmann 

and Puri (1974, p. 57) who stated that all the 

genera in this family possess a "rostrum-like" incisure at the border of the anterior and ventral 

margins. Because none of the genera except Cypridea discussed above has an anteroventral incisure, 

I am referring them to the new family Trapezoidellidae.

Key to the genera in the Trapezoidellidae

1 Left valve larger than right __————————— 2 

la Right valve larger than left _—————————— 5 

2(1) Ventrolateral ridge and dorsolateral groove on

left valve ________________ Trapezoidella 

2a Without ventrolateral ridge and dorsolateral

groove on left valve __________—————— 3 

3(2a) Dorsal margin overreaches right valve _————

_______________________ Limnocypridea 

3a Dorsal margin does not overreach right valve — 4 

4(3a) Dorsoposterior margin pointed _____— Zefaina 

4a Dorsoposterior margin rounded __ Mongolianella 

5(la) Dorsal margin round ________————— Latonia 

5a Dorsal margin straight ——_—————————— 6 

6(5a) Lateral surface tuberculate ____ Ilyocyprimorpha 

6a Lateral surface not tuberculate Cyprideamorphella

Genus TRAPEZOIDELLA Sohn, n. gen.

Type-species.—Bythocypris (Bairdiocypris) trapezoidalis Roth, 1933.

Diagnosis.—Large, to 1.6 mm in greatest length, 

trapezoidal, with straight or convex dorsal margin. 

Surface smooth, with ventrolateral ridge near ventral margin, and dorsolateral thin groove subparallel to dorsal margin of left valve. Overlap and 

overreach of left valve over right. End outline subtriangular, ridge and overlap forming almost 

straight base, dorsal outline subelliptical, greatest 

width at approximate midlength, posterior wider 

than anterior.

Discussion.—This genus is established for the 

type-species, T. trapezoidalis (Roth, 1933), and T. 

rothi n. sp., both from the Lower Cretaceous Lakota Formation in the Black Hills. Harper and Sutton (1935, p. 627) stated in their discussion of 

Bythocypris (Bairdiocypris) morrisonensis Roth, 

1933 (= Limnocypridea), "A semi-false keel paralleling the dorsal margin of the left valve is the only 

surface ornament," and Loranger (1951, p. 2360) 

stated in her description of Bairdiocypris albertensis Loranger, 1951 (= Limnocypridea^.), "Surface 

ornamentation commonly consists of straight ridge 

or false keel on left valve parallel with the ventral 

margin." Both of the above species do not have the 

diagnostic ventrolateral ridge and are discussed 

under Limnocypridea Liibimova, 1956. Krommelbein (1963, p. 387) described and illustrated Salvo-
SYSTEMATIC DESCRIPTIONS

doriella redunca subsp. comitans from the upper 

part of the Ilhas Formation of Bahia, Brazil, that is 

trapezoidal in lateral outline and has a ventrolateral 

ridge on both valves, which, combined with the 

lateral outline, differentiates it from the nominate 

subspecies, the type-species of Salvadoriella. Because Krommelbein did not mention a dorsolateral 

groove, I do not know whether the Brazilian taxon 

belongs in the new genus. Salvadoriella Krommelbein, 1963 (type-species Candonat redunca Krommelbein, 1962) differs from Trapezoidella in having 

a concave ventroanterior, is smaller in size, has a 

relatively narrow overlap, and lacks the ventrolateral ridge and dorsolateral groove on the larger 

left valve.

Stratigraphic range.—Lower Cretaceous.

Trapezoidella trapezoidalis (Roth, 1933)

Plate 1, figures 6-9, 12-17; plate 2, figures 30-32

Bythocypris (Bairdiocypris) trapezoidalis Roth, 1933, Jour. 

Paleontology, v. 7, no. 4, p. 402, pi. 48, figs. 6a-d. Lakota 

Formation, Meade County, S. Dak.; Harper and Sutton, 

1935, Jour. Paleontology, v. 9, no. 8, p. 628, pi. 76, figs. 

16, 17 (orientation reversed 180°). Lakota Formation, 

Lawrence County, S. Dak.

Diagnosis.—Straight backed, with straight ventrolateral ridge near middle of larger valve.

Discussion.—The holotype (USNM 74470) is a 

young individual about one-half the size of available 

specimens (compare pi. 1, figs. 6-9 with figs. 16, 17). 

The species is distributed in the Chilson Member of 

the Lakota Formation in South Dakota and Wyoming.

Geographic distribution.—South Dakota; Butte 

County; map loc. 1, USGS colln. 30995, USNM 

242910.

Meade County; map loc. 4, USGS colln. 25647, 

USNM 242921; map loc. 8, Roth's type-locality, pi. 

1, figs. 6-9, and USGS colln. 30997, USNM 242911, 

associated with Limnocypridea morrisonensis 

(Roth, 1933) and Cypridea (Pseudocypridina) 

piedmonti (Roth, 1933).

Lawrence County; map loc. 3, Harper and Sutton's type-locality and USGS colln. 30998, USNM 

242912, associated with Cypridea (Pseudocypridina) piedmonti (Roth, 1933) ; USGS colln. 30999, 

USNM 242913, associated with Limnocypridea 

morrisonensis (Roth, 1933) ; USGS colln. 31009, 

USNM 242914.

Fall River County; map loc. 13, USGS colln. 

30986 (? identification), USNM 242915, associated 

with Cypridea (Pseudocypridina) piedmonti (Roth, 

1933) ; map loc. 17, USGS colln. 31007, USNM 

242916, associated with T. rothi. n. sp., and

Cypridea (Pseudocypridina) henrybelli n. sp.; map 

loc. 16, USGS colln. 30987, USNM 242916.

Wyoming, Crook County; map loc. 6, USGS colln. 

25643, pi. 1, figs. 12-17, USNM 242917; USGS 

colln. 26939 (? identification), USNM 242918; map 

loc. 7, USGS colln. 26940, USNM 242919; 26941, 

pi. 2, figs. 30-32, USNM 242920.

Trapezoidella rothi Sohn, n. sp.

Plate 1, figures 1-5, 10; plate 2, figures 7-29, 33, 34-36

Name.—In honor of Dr. Robert Roth, Wichita 

Falls, Tex., who was the first to describe the Mesozoic ostracodes from the Black Hills, S. Dak.

Holotype.—USNM 242861.

Paratypes.—USNM 242836-242838, 242851- 

242860, 242862-242864.

Type-locality.—Map loc. 13, SE^ sec. 11, T. 8 

S., R. 3 E., Flint Hill quadrangle. Fall River 

County, S. Dak.

Other localities.—See geographic distribution.

Type level—Upper part of the Chilson Member 

of the Lakota Formation, USGS colln. 30985.

Diagnosis.—Convex dorsal margin and gently 

curved lateroventral ridge on left valve, smaller 

right valve with shallow horizontal lobe below and 

subparallel to straight hingeline, delineated ventrally by a horizontal shallow sulcus.

Description.—The lateral outline of the carapace 

is subhemicircular, with a convex dorsal margin, a 

straight to slightly concave ventral margin, curved 

end margins with the posterior margin more broadly rounded than the anterior margin. The left valve 

overlaps the right, and overreaches it along a 

straight-hinge margin; it bears a gently curved 

ridge near its ventral margin, and a narrow groove 

subconcentric to the curved dorsal outline. This 

groove gives the impression of the dorsal margin 

having been pinched along its perimeter. The 

smaller right valve is subtrapezoidal in lateral outline, with a straight-hinge margin that is overreached by the left valve, and with a shallow horizontal lobe below the hinge margin. This lobe has 

below it a shallow sulcus that sets it off from the 

convexity of the valve.

Discussion.—This species was called "Genus F" 

in my reports to the field geologists who were mapping in the Black Hills and appears as such in their 

faunal lists.

Geographic distribution.—South Dakota, Fall 

River County; map loc. 9, USGS colln. 30993, pi. 1, 

figs. 1, 2, pi. 2, figs. 34-36; map loc. 10, USGS colln.

26468. pi. 2, fig. 21, USNM 242922; USGS colln.

26469. USNM 242923; map loc. 11, USGS colln. 

30994, pi. 2, fig. 23, associated with Cypridea
10 NONMARINE OSTRACODES, LAKOTA FORMATION, SOUTH DAKOTA AND WYOMING

(Pesudocypridina) piedmonti (Roth, 1933) ; map 

loc. 13, USGS colln. 30985, pi. 2, figs. 7-9, 22, 24-29, 

33, USNM 242924; USGS colln. 30989, USNM 

242025; USGS colln. 31002, USNM 242928; USGS 

colln. 31003, USNM 242929, associated with C. (P.) 

henrybelli n. sp.; USGS colln. 31004, USNM 242930; 

USGS colln. 31005, USNM 242987, associated with 

C. (P.) inornata (Peck, 1941) ; map loc. 14, USGS 

colln. 30990, pi. 2, figs. 10, 11, USNM 242926; 

USGS colln. 30991, USNM 242927; USGS colln. 

31237, USNM 242959, associated with C. (P.) inornata (Peck, 1941), and C. (P.) henrybelli n. sp.; 

USGS colln. 31238, USNM 242960, associated with 

C. (P.) inornata (Peck 1941) ; map loc. 16, USGS 

colln. 26100, USNM 242933, associated with C. (P.) 

inornata (Peck, 1941) ; USGS colln. 30988, pi. 2, 

figs. 12-15, USNM 242934; USGS colln. 31006, pi. 

2, figs. 16, 17, USNM 242935; map loc. 17, USGS 

colln. 31007, pi. 2, fig. 20, associated with T. trapezoidalis (Roth, 1933) and C. (P.) henrybelli n. sp.; 

USGS colln. 31008, USNM 242932.

Genus LIMNOCYPRIDEA Lubimova, 1956

Limnocypridea Lubimova, 1956a, in Kiparisova, Markovsky, 

and Radchenko, Materialy po paleontologii, VSEGEI, 

Materialy, new ser., no. 12, p. 106; Lubimova, 1956b, 

VNIGRI, Trudy, no. 93, p. 9; Lubimova, Mandelstam, 

and Schneider, 1960, Osnovy paleontologii, v. 8, p. 353; 

Swain and others, in Moore, 1961, Treatise on invertebrate paleontology, Part Q, Arthropoda 3, Crustacea, 

Ostracoda, p. Q237; Mandelstam and Schneider, 1963, 

VNIGRI, Trudy, no. 203, p. 112.

Bythocypris (Bairdiocypris) Kegel. Roth, 1933, Jour. 

Paleontology, v. 7, p. 401; Harper and Sutton, 1935, 

Jour. Paleontology, v. 9, p. 627; Loranger, 1951, Am. 

Assoc. Petroleum Geologists Bull., v. 35, no. 11, p. 2359; 

Loranger, 1954, Western Canada sedimentary basin—A 

symposium, p. 286.

Type-species (original designation).—Limnocypridea abscondida Lubimova, 1956a, p. 108, pi. 26, 

figs. 2a-c, text figs. 27a, b. Dzunbain Formation 

(Barremian), SE Mongolia, U.S.S.R., nonmarine.

Diagnosis.—Carapace thick walled, subtriangular, 

suboval or trapezoidal, with rounded ends, greatest 

convexity in middle or ventral part of valves. Left 

valve overlaps right, greatest overlap along venter, 

dorsal margin overreaches; hingeline approximately 

straight, of variable length. Vestibule large, radial 

pore canals straight or slightly curved; surface 

smooth or pitted, with or without elongate nodes 

on ventral part.

Discussion.—The following description is modified from the original description and discussion, 

which has been translated from Lubimova (1965a, 

p. 106), and from that given in Moore (1961, p. 

Q237).

Carapaces large (length 1.2 to 1.8 mm), thick walled, 

suboval to trapezoidal with rounded corners, with the 

greatest convexity in the middle or posteroventral part of 

the valve. The left valve markedly larger than right and 

overlaps the latter all around: particularly strong overlap 

is expressed on the dorsal and ventral margins. Occasionally the dorsal part of the left valve is noticeably raised 

above the dorsal margin of the right valve and markedly 

overlaps [overreaches] longitudinally the entire dorsal 

margin.

Anterior and posterior margins of equal height or the 

anterior is slightly higher than the posterior. Both ends are 

bevelled in their upper part and are roundly curved below, 

somewhat lower downward. Dorsal margin straight. Ventral 

margin concave in the middle. Valves pitted, with one or 

two [nodes] protuberances in the ventral part, sometimes 

smooth. Inner margin of the valves does not coincide with 

the outer. Pore-canal zone wide, well developed on anterior 

and posterior ends, and on the ventral side. Pore canals 

straight or somewhat curved, extend [from the] sinuous line 

of concrescence. Sometimes branched pore canals are observed. On the anterior and posterior ends are well developed 

structureless plates [calcified part of the inner lamella].

Hinge straight-ridged, equaelemental, of sufficiently simple 

construction. The right valve has a ridge, widening towards 

the ends [particularly toward the front] and curving in its 

own marginal parts, tapers [merges] imperceptibly to anterior and posterior ends. Hinge of left valve has the opposite 

structure, i.e., consists of a shallow groove, also slightly 

widening towards the ends and dying out at the anterior and 

posterior where it flattens out.

Reason for separating genus: Hinge of described genus is 

generally similar to the hinge of the genus Cyprideamorphella erected by Mandelstram for Lower Cretaceous representatives from eastern Zabaikal. Differs from it in simpler 

construction, namely: absence in the anterior portion of the 

ridge, the thickened curved tooth, and in the anterior portion 

of the groove and expanded socket that opens into the groove. 

In addition, the arrangement of the hinge elements of the 

described genus are reversed: ridge on right valve and groove 

on left, and in the related genus Cyprideamorphella the ridge 

on the left valve and the groove on the right. The overlap is 

also different in the two genera.

Members of the genus Limnocypridea are characterized by 

left overlapping valves, well-developed pore-canal zone, 

peculiar hinge structure, and also characteristic trapezoidal 

outline of the carapace and elevated margin of the dorsal 

part of the valve, which characterize the new genus.

The type-species, L. abscondida Lubimova, 1956, 

is nonreticulated and has no nodes or ridges; in 

the same year, Lubimova (1956b) described four 

additional species, two of which, L. tumulosa, and 

L. bitumulosa, have subventral nodes and are finely 

reticulated, and two, L. subplana and L. grammi, 

are smooth. Several species in North America that 

belong to Limnocypridea conform with the original 

concept of the genus as defined in the U.S.S.R. 

There are, however, additional species that do not 

fit within the genus as originally defined. This situation is not unique because, in practice, genera are
SYSTEMATIC DESCRIPTIONS 11

usually erected before all the species that belong 

to the taxon are known.

Van Morkhoven (1963, p. 61) considered Limnocypridea as a synonym of Lineocypris Zalanyi, 1929. 

The two genera differ in type and amount of overlap on the dorsal margin and in details of the 

muscle-scar pattern.

Key to the species of Limnocypridea

1 Lateral surface with nodes or ridges ——__— 2 

la Lateral surface without nodes or ridges ________ 3

2(1) One subventral node on each valve ________

___________ tumulosa Liibimova, 1956b

2a Two subventral nodes on each valve ________

____________ bitumulosa Liibimova, 1956b

3(la) Dorsal margin straight ____________ 4

3a Dorsal margin curved ___________ 8

4(3) Ventral margin concave ____________--

_____________ abscondida Liibimova, 1956a

4a Ventral margin straight _____________ 5

5(4a) Height of left valve one half or less greatest

length ________ albertensis (Loranger, 1951)

5a Height of left valve more than one half greatest

length __________________________ 6 

6(5a) Greatest height of right valve anterior to midlength _________________________ 7 

6a Greatest height of right valve at midlength __

______________ grammi Liibimova, 1956b

7(6) Anterior margin of right valve broader than

posterior margin ______________________

______ celtiformis (Harper and Sutton, 1935)

7a Anterior margin of right valve narrower than

posterior margin ___ subplana Liibimova, 1956b 

8(3a) Greatest height behind midlength ____________

_____________ morrisonensis (Roth, 1933)

8a Greatest height in front of midlength __________

______________ equalis (Harper and Sutton, 1935)

The divisions shown in the key are tentative because some of the species described from Mongolia 

may be conspecific. Cypridopsis parallela Hanai, 

1951, from the Middle and Upper Cretaceous of central Manchuria may belong in Limnocypridea but 

is not included in the key because of the uncertainty.

L. equalis (Harper and Sutton, 1935) is recognized here as a valid species, and the variation in 

lateral outline of L. morrisonensis (Roth, 1933), is 

described and illustrated.

Limnocypridea morrisonensis (Roth, 1933)

Plate 1, figures 11, 18-30; plate 3, figures 26-29

Bythocypris (Bairdiocypris) morrisonensis Roth, 1933, Jour. 

Paleontology, v. 7, no. 4, p. 401, pi. 48, figs. 4a-c; Harper 

and Sutton, 1935, Jour. Paleontology, v. 9, p. 627.

Bythocypris (Bairdiocypris) morrisonensis var. equalis 

Harper and Sutton, 1935 (part), Jour. Paleontology, 

v. 9, no. 8, p. 627, pi. 76, figs. 22 23 (not fig. 21 = L. 

equalis).

Diagnosis.—Large, as much as 2.7 mm or more in 

greatest length; smooth; lateral outline of left valve

varies from subtriangular to subovate, dorsal margin curved to acuminate; greatest height behind 

approximate midlength, greatest length below midheight; hingeline straight, one-half or less greatest 

length, closer to posterior than anterior end, below 

overreaching left valve; anterior margin always 

narrower than posterior, dorsoanterior margin always longer than dorsoposterior, ventral margin 

straight to gently concave; dorsal margin coincides 

with hingeline.

Discussion.—Harper and Sutton (1935, p. 627) 

described the new variety equalis because "Roth 

did not mention variations in B. morrisonensis 

* * *." They illustrated three specimens, the first of 

which (pi. 76, fig. 21) is here designated as the 

lectotype of L. equalis (Harper and Sutton, 1935), 

and the other two (pi. 76, figs. 22, 23) are synonyms of L. morrisonensis. Specimens from Roth's 

type-locality (topotypes) (pi. 1, figs. 18, 24) that are 

undoubtedly conspecific with the holotype (pi. 1, 

figs. 22, 25-28) are 2.3 mm in greatest length. 

Other topotype specimens range in greatest length 

from 2.2 mm (pi. 1, fig. 21) to 2.7 mm (pi. 1, fig. 20). 

The smallest representative of this species that I 

found is 1.8 mm long in a group of nested valves 

(pi. 1, fig. 11).

I cannot explain the absence of younger instars 

because the nesting indicates quiet water that would 

preclude size sorting by currents. Specimens of T. 

trapezoidalis (Roth, 1933) as small as 0.85 mm are 

associated with this species.

I consider all the specimens illustrated on plate 

1, figures 11, 18-30, to be conspecific. The variation 

in lateral outlines of the specimens illustrated on 

figures 18-29 is gradational; the specimen illustrated on figure 30, and the one on plate 3, figures 

26-29, differ from the rest in lateral outline and are 

considered to be males of the species. This inference 

is based on the dimorphism found in living Candona Baird, 1845 (McGregor and Kesling, 1969a, 

b) in which the valves of the females as determined 

by soft parts have a dorsoposterior truncation (pi. 

3, fig. 30). This truncation is similar to the specimens illustrated on plate 1, figures 18-29. The valves 

of male Candona have a rounded posterior (pi. 3, 

fig. 31) similar to those specimens of L. morrisonensis illustrated on plate 1, figure 30; plate 3, figures 

26-29. The magnification of plate 1, figure 28, is 

approximately X 30 in order to compare the size 

of this species with the sizes of the other species 

illustrated on this plate that are also approximaely 

X 30.

Geographic distribution.—South Dakota, Meade
12 NONMARINE OSTRACODES, LAKOTA FORMATION, SOUTH DAKOTA AND WYOMING

County; map loc. 4, Roth's type-locality, pi. 1, figs. 

22, 25-28, and map loc. 8, USGS colln. 30997, pi. 1, 

figs. 11, 18-21, 23, 24, 29, 30; pi. 3, figs. 26-29, 

USNM 242936, associated with Trapezoidella trapezoidalis (Roth, 1933), and Cypridea (Pesudocypridina) piedm,onti (Roth, 1933).

Lawrence County; map loc. 3, Harper and Sutton's type-locality and USGS colln. 30999, USNM 

242937, associated with T. trapezoidalis (Roth, 

1933).

Limnocypridea? albertensis (Loranger, 1951)

Plate 2, figures 1-6

Bairdiocypris albertensis Loranger, 1951, Am. Assoc. Petroleum Geologists Bull., v. 35, no. 11, p. 2360, pi. 2, figs. 

7, 8, 16, 17, 21, 28, 36, 37. Blairmore Formation (AptianAlbian), Alberta, Canada; Loranger, 1954, Western 

Canada sedimentary basin—A symposium, p. 286, pi. 

2, figs. 7, 8, 16, 17, 21, 28, 36, 37; Howe and Laurencich, 

1958, Introduction to the study of Cretaceous Ostracoda, 

p. 78.

Diagnosis.—Small, less than 0.9 mm in greatest 

length, smooth, dorsoanterior margin longer than 

dorsoposterior margin.

Discussion.—Loranger included in her description 

of this species the following: "Surface ornament 

commonly consists of straight ridge or false keel 

on left valve parallel to the ventral margin." She 

very kindly sent me four out of the five illustrated 

specimens. The four syntypes that I examined do 

not have a ventrolateral ridge; consequently, this 

species is referred here to Limnocypridea'? rather 

than to Trapezoidella.

The original of Loranger's figure 28 (pi. 2, figs. 

4-6) is here designated as the lectotype; it and the 

three paralectotypes are deposited in the Geological 

Survey of Canada (nos. 48735-48738). I am grateful to Dr. F. L. Staplin, Imperial Oil Limited, for 

permission to deposit these specimens with the Geological Survey of Canada.

According to Stelck (1975, p. 438, fig. 10), the 

Blairmore Formation is late Aptian-early Albian 

in age.

Family CYPRIDEIDAE Martin, 1940

I agree with Hartmann and Puri (1974, p. 57) 

in elevating the Cyprideinae to family category. 

My discussion of this subfamily (Sohn, 1969, p. 

B3) would now be applicable to the family. More 

than 300 species have been recorded in the genus 

Cypridea Bosquet, 1852, and its subgenera, making 

this an unwieldy taxon with which to deal. For 

practical purposes, it would be easier to deal with 

this group if it were divided into smaller taxonomic

units; the elevation of some of the subgenera to 

generic category would accomplish this.

In a previous study (Sohn, 1969, p. B4), I proposed a key to the subgenera of Cypridea in which 

I differentiated the subgenus Pseudocypridina from 

the subgenus Cypridea on the basis of the presence 

of a ventrolateral ridge on the left valve of the 

former and the absence of such a ridge on the 

latter. I now know that this was not a valid criterion. Although some species that I now refer to 

Cypridea (Pseudocypridina), do have a ventrolateral ridge in common with the type-species, C. (P.) 

piedmonti Roth, 1933, other species do not have 

that ridge. The other subgenera in that key are 

here elevated to generic status.

Key to the genera in the Cyprideinae

1 Nonsulcate _________________————— 2 

la Sulcate ____________.._____————— 6

2(1) Left valve larger _____________ — _— 4

2a Right valve larger ____________———— 3

3(2a) Lateral outline ovoid, rostrum insignificant,

alveolus obsolescent, surface without nodes or 

spines _________ Paracypridea Swain, 1946 

3a Lateral outline subtriangular, rostrum and

alveolus well developed ___________——_

______________ Ulwellia Anderson, 1939 

4(2) Lateral outline subovoid _______________ 5

4a Lateral outline subrectangular or subtriangular, 

rostrum, alveolus, and cyathus well developed, 

surface with subcentral spine, with or without tubercles ___________________ 8

5(4) Surface with or without nodes or ridges, without 

tubercles or spines, rostrum reflexed, alveolus 

obsolescent, cyanthus lunate ___________

_____ Cypridea (Pseudocypridina) Roth, 1933 

5a Surface with tubercles or spines, without nodes 

or ridges, rostrum, alveolus, and cyathus 

usually well developed _________________

________ Cypridea (Cypridea) Bosquet, 1852 

6(la) One sulcus ______________________ 7

6a Two sulci _______ Bisulcocypridea Sohn, 1969

7(6a) With two nodes _____ Morinia Anderson, 1939 

7a With three nodes _ Morrninoides Krommelbein, 1962 

8(4a) Lateral outline subrectangular, surface with

tubercles or small spines ______________

______________ n. gen. ("Cypridea" sp. 1) 

8a Lateral outline subtriangular, surface without

tubercles or small spines __ Longispinella n. gen.

Genus CYPRIDEA Bosquet, 1852

Cypridea Bosquet, 1852, Belgium, Acad. Royale Sci., Lettres, 

Beaux-Artes, Mem. Courrones et Mem. Savantes 

Etrangers, v. 24, p. 47; Sylvester-Bradley, 1949, 

Geologists' Assoc. Proc., v. 60, pt. 2, p. 130.

Cypridea (part) of authors.

Type-species (subsequent designation).— Cypris 

granulosa Sowerby, 1836, by Sylvester-Bradley 

1947, p. viii.
SYSTEMATIC DESCRIPTIONS 13

Discussion.—Sylvester-Bradley (1949) redefined 

the genus and designated a neotype for Cypridea 

granulosa (Sowerby, 1836), the type-species, from 

the lower part of the middle Purbeckian of England. On the basis of Sylvester-Bradley's description and illustrations, Cypridea is closer to Pseudocypridina Roth, 1933, than to a large number of 

species that have been described as or referred to 

the genus Cypridea. His assignment of both as subgenera is accepted in this study. The major differences between the two subgenera are: (1) welldeveloped rostrum, and alveolus in Cypridea, and 

reflexed rostrum, obsolescent alveolus in Pseudocypridina; and (2) the presence of relatively large 

tubercles on the lateral surface of Cypridea and of 

fewer and smaller tubercles on Pseudocypridina. 

Most of the species that have been assigned to 

Cypridea differ from Cypridea as redefined by 

Sylvester-Bradley in size, lateral outline, surface 

ornament, and sculpture, and in the development of 

the alveolus and the cyathus (fig. 3).

In this paper I am illustrating in open nomenclature as "Cypridea sp. 1" a carapace from the 

Lakota Formation that shows many of the above 

differences. The reason for the open nomenclature 

is that I have found only one good carapace in one 

collection and five very poorly preserved carapaces 

in a second collection.

Although I had previously stated (Sohn, 1969, p. 

B2) that dimorphism in Cypridea is unknown, I 

have since observed dimorphism in width of posterior in cypridinid ostracodes (this paper, pi. 5, 

figs. 9, 12). Hanai (1951, p. 411, figs. 2-7) discussed 

and illustrated males and females of Cypridea subvaldensis Hanai, 1951, from the Middle Cretaceous 

of Manchuria, and Andreev (in Andreev and Mandelstam, 1968, p. 80) illustrated dimorphism in 

Cypridea gissarensis Andreev, 1968, from the upper 

Aptian of Tadzhikistan.

Anderson (in Anderson, Bazley, and ShephardThorn, 1967, p. 202) established the basis for discriminating between the genera in the Cyprideinae 

by naming and illustrating characters in the shell 

morphology of "Cypridea" (fig. 3). This major contribution provides criteria to split the taxon into 

component genera. Such a revision, however, is beyond the scope of this paper.

Subgenus CYPRIDEA Bosquet, 1852 emend. SylvesterBradley, 1949

Type-species.—Same as the genus. 

Diagnosis.—Relatively large cypridinids, to about 

2 mm in greatest length, subovoid, with or without

Alveolus

Rostrum

FIGURE 3.—Some of the characters in the shell morphology 

of Cyprideidae used in this paper, modified from Anderson (in Anderson, Bazley, and Shephard-Thorn, 1967, p. 

202).

distinct angulation at junction of dorsal and anterior margins; surface finely punctate, with large 

tubercles, without reticulations or large spines; 

rostrum well developed, cyanthus usually lunate; 

hinge margin incised.

Stratigraphic range.—Upper Jurassic-Upper Cretaceous.

Subgenus PSEUDOCYPRIDINA Roth, 1933

Pseudocypridina Roth, 1933, Jour. Paleontology, v. 7, no. 4, 

p. 404; Howe and Laurencich, 1958, Introduction to the 

study of Cretaceous Ostracoda, p. 480.

Langtonia Anderson, 1939, Annals Mag. Nat. History, ser. 

11, v. 3, no. 15, p. 304.

Cypridea (Pseudocypridina) Roth. Sylvester-Bradley, 1949, 

Geologists' Assoc. Proc., v. 60, pt. 2, p. 146; Swain 

in Moore, 1961, Treatise on invertebrate paleontology, 

Part Q, Arthropoda 3, Crustacea, Ostracoda, p. Q242; 

Kneuper-Haack, 1966, Beih. Geol. Jahrb., v. 44, p. 187.

Type-species (monotypy). — Pseudocypridina 

piedmonti Roth, 1933, Lakota Formation (Lower 

Cretaceous), South Dakota.

Diagnosis.—Relatively large cypridinids, to about 

2 mm in greatest length, subovoid, without distinct 

angulation at junction of dorsal and anterior margins on larger left valve; surface finely punctate, 

with or without scattered tubercles, smaller than 

combined diameters of two punctae, usually near 

end margins, never with large spines or tubercles; 

with or without nodes or lateral ridges; rostrum 

poorly developed, alveolus obsolescent, cyanthus
14 NONMARINE OSTRACODES, LAKOTA FORMATION, SOUTH DAKOTA AND WYOMING

lunate or indistinct; hinge margin incised.

Stratigraphic range.—Upper Jurassic-Upper Cretaceous.

Discussion.—The holotype of P. piedmonti Roth, 

1933, is probably a male; it is here reillustrated 

(pi. 6, figs. 23-27). Many of the species assigned 

to Cypridea Bosquet, 1852, should be referred to 

the subgenus C. (Pseudocypridina). The following 

species have been described in, referred to, or are 

here referred to Pseudocypridina:

Cypridea acutituberculata Galeeva, 1955, Barremian (Lower

Cretaceous), Asia. 

Cypridea (Pseudocypridina) alacaramwe Kneuper-Haack,

1966, upper Purbeckian (Upper Jurassic), Europe. 

Cypridea alto, alia Wolburg, 1959, upper Purbeckian and

Valanginian (Upper Jurassic-Lower Cretaceous), Europe. 

C. alto, formosa Wolburg, 1959, middle and upper Wealden

3 (Upper Jurassic-Lower Cretaceous), Europe. 

C. altissima Martin, 1940, Wealden (Lower Cretaceous),

Europe. 

C. altissima rotunda Wolburg, 1959, lower to middle Wealden

2 (Upper Jurassic), Europe.

C. amisia Wolburg, 1959, Wealden 2 (Upper Jurassic), 

Europe.

C. baidarensis Bischoff, 1963, probably Hauterivian- Barremian (Lower Cretaceous), Asia Minor.

C. binodosa Martin, 1940, Purbeckian (Upper Jurassic), 

Europe.

C. brevirostrata Martin, 1940, Wealden (Lower Cretaceous), 

Europe.

C. consiilta Mandelstam in Liibimova, Kaz'mina, and 

Reshetnikova, 1960, Barremian (Lower Cretaceous), Asia.

C. (Pseudocypridina) demandae Kneuper-Haack, 1966, upper Purbeckian (Upper Jurassic), Europe.

C. dolabrata angulata (Martin). Wolburg, 1959, Wealden

3 (Upper Jurassic), Europe. 

C. dolabrata dolabrata (Anderson). Wolburg, 1959, Wealden

3 (Upper Jurassic), Europe.

1C. (Pseudocypridina) ellipseloides Hou, 1958, Lower Cretaceous, China.

1C. (P.) extenda Hou, 1958, Lower Cretaceous, China. 

C. fasciata Anderson, 1967, Wealden (Lower Cretaceous),

Europe. 

C. fasciculata (Forbes in Lyell). Wolburg, 1959, Wealden 1

& 2 (Upper Jurassic), Europe.

C. inaequalis Wolburg, 1959, Wealden 2 & 3 (Upper Jurassic), Europe. 

C. laevis Galeeva, 1955, Barremian (Lower Cretaceous),

Asia. 

C. laevigata fairlightensis Anderson, 1967, Wealden (Lower

Cretaceous), Europe. 

C. laevigata hawkhurstensis Anderson, 1967, Wealden

(Lower Cretaceous), Europe. 

C. laevigata leonardi Anderson, 1967, Wealden (Lower

Cretaceous), Europe. 

C. laevigata philpottsi Anderson, 1967, Wealden (Lower

Cretaceous), Europe. 

C. laevigata subquadrata Anderson, 1967, Wealden (Lower

Cretaceous), Europe. 

C. laevigata wadhurstensis Anderson, 1967, Wealden (Lower

Cretaceous), Europe.

C. lata Martin, 1940, Purbeckian-Wealden (Upper JurassicLower Cretaceous), Europe.

C. (Cyamocypris) latiovata Hou, 1958, Lower Cretaceous, 

China.

C. (C.) sp. A Hou, 1958, Lower Cretaceous, China.

C. (C.) sp. B Hou, 1958, Lower Cretaceous, China.

C. (Pseudocypridina) magna Hou, 1958, Cretaceous, China.

C. (P.) moneta Kneuper-Haack, 1966, upper Purbeckian 

(Upper Jurassic), Europe.

C. (P.) moneta logronana Kneuper-Haack, 1966, upper 

Purbeckian (Upper Jurassic) Europe.

C. nannorostrata Krommelbein, 1962, Lower Cretaceous, 

South America.

1C. obesa Peck, 1951, Cleverly Formation (Lower Cretaceous), Wyoming, U.S.A.

C. (Cyamocypris) ovatiformis Hou, 1958, Lower Cretaceous, 

China.

C. parallela Martin, 1940, Wealden (Lower Cretaceous), 

Europe.

C. (Pseudocypridvna) parallela Hou, 1959 (not Martin, 

1940) Lower Cretaceous, China.

C. posticalis Jones, 1885, Purbeckian (Upper Jurassic), 

Europe.

C. prognata Liibimova, 1956, Barremian (?) (Lower Cretaceous), Asia.

C. profusa Liibimova, 1956, Upper Cretaceous, Asia.

1C. qiiadrata Peck, 1951, Cloverly Formation (Lower Cretaceous), Utah and Wyoming, U.S.A.

C. rotundata Anderson, 1967, Wealden (Lower Cretaceous), 

Europe.

C. salvadorensis nodifer Krommelbein, 1962, Wealden 

(Lower Cretaceous), South America.

C. salvadorensis salvadorensis Krommelbein, 1962, Wealden 

(Lower Cretaceous), South America.

Pseudocypridina sambaensis Grekoff, 1957, Wealden (Lower 

Cretaceous), Africa.

Cypridea (Pseudocypridina) setina (Anderson, 1939), upper 

Purbeckian (Upper Jurassic), Europe.

C. (P.) setina acerata Anderson, 1962, Wealden 5 (Lower 

Cretaceous), Europe.

C. (P.) setina camelodes Anderson, 1962, lower and middle 

Wealden 4 (Upper Jurassic), Europe.

C. (P.) setina dotica Anderson, 1962 Wealden 3 (Upper 

Jurassic), Europe.

C. (P.) setina erumna Anderson, 1962, Wealden 3, (Upper 

Jurassic), Europe.

C. (P.) setina fiteriensis Kneuper-Haack, 1966, middle Purbeckian (Upper Jurassic), Europe.

C. (P.) setina rectidorsata Sylvester-Bradley, 1949, upper 

Purbeckian (Upper Jurassic), Europe.

C. sowerbyi Martin, 1940, Purbeckian (Upper Jurassic), 

Europe.

1C. spinigera Liibimova, 1956 ( = C. lubimovae Sohn, 1969), 

Barremian (Lower Cretaceous), Asia.

C. (Pseudocypridina) subcentrinoda Hou, 1958, Cretaceous, 

China.

C. subtilis Krommelbein, 1965, Wealden (Lower Cretaceous), 

South America.

C. subvaldensis Hanai, 1951, Cretaceous, Manchuria.

C. tennis Anderson, 1967, Wealden (Lower Cretaceous), 

Europe.

C. trita Liibimova, 1956, pre-Barremian (Lower Cretaceous), Asia.
SYSTEMATIC DESCRIPTIONS 15

C. unicostata Galeeva, 1955, Barremian (Lower Cretaceous) , Asia.

C. (Cypridea) uninoda Hou, 1958, Lower Cretaceous, China.

C. valdensis (Sowerby, 1836). Anderson, 1967, Wealden 

(Lower Cretaceous), Europe.

C. vidrana Wolburg, 1959, Wealden 2 (Upper Jurassic), 

Europe.

C. vitimensis Mandelstam in Liibimova, 1956, Barremian and 

older (Lower Cretaceous), Asia.

C. (Cypridea) yumenensis Hou, 1958, Lower Cretaceous, 

China.

C. (Pseudocypridina) spp. Hou, 1958, Lower Cretaceous, 

China.

Some of these species may be synonyms of each 

other, but without comparative specimens, it would 

be imprudent to classify them as such.

Cypridea (Pseudocypridina) piedmonti Roth, 1933

Plate 6, figures 1-47

Psendocypridina piedmonti Roth, 1933, Jour. Paleontology,

v. 7, no. 4, p. 404, pi. 48, figs. 7a-h; Peck, 1951, Jour.

Paleontology, v. 25, no. 3, p. 319, pi. 48, figs. 16-18; Sohn,

1958, Wyoming Geol. Assoc., Guidebook, Thirteenth Ann.

Field Conf., p. 123, pi. 1, figs. 5-8. 

Cypridea piedmonti (Roth). Harper and Sutton, 1935, Jour.

Paleontology v. 9, no. 8, p. 625, pi. 76, figs. 12-15. 

not Cypridea (Pseudocypridina) piedmonti Roth. Swain,

1946, Jour. Paleontology, v. 20, no. 6, p. 550, pi. 83, figs.

10-12 — Ci/prideal salvadorensis salvadorensis Krommelbein, 1962. 

not Ci/pridea (Psendocypridina) piedmonti (Roth). Wicher,

1959, Geol. Jahr., v. 77, p. 47, pi. 9, fig. 6 (juvenile? of

indet. sp.).

Diagnosis.—A species of Psendoci/pridina with a 

ventrolateral ridge on left valve, with few, small 

(less than twice the diameter of punctae), subdued, 

scattered tubercles, near end margins.

Disc?(ssion.—This species is similar to C. (P.) 

unicostata (Galeeva, 1955), described from the 

Barremian of Mongolia, from which it differs in 

having a higher posterior margin, and a less defined rostrum. The holotype of P. piedmonti has a 

narrower posterior in dorsal outline than Galeeva's 

species. Although I do not consider the two species 

to be conspecific, this feature is interpreted to 

represent a male carapace and Galeeva's specimen, a female carapace. A ventrolateral ridge on 

the overlapping valve is present in several other 

species in the subgenus Psettdocypridina as well as 

in some species belonging to other taxa in the 

Cypridininae. All the ventrolateral ridged species in 

Pseudocypridina differ from C. (P.) piedmonti and 

C. (P.) unicostata in lateral outline and lack the 

scattered small tubercles. Three species from the 

Barremian of Mongolia and Siberia have small 

tubercles but lack the ventrolateral ridge: C. (P.) 

acutitubercidata (Galeeva, 1955), C. (P.) consulta

(Mandelstam) in Liibimova, Kaz'mina, and Reshetnikova, 1960, and C. (P.) vitimensis (Mandelstam) 

in Liibimova, 1956b.

Stratigraphic age.—Roth (1933) assumed that 

the ostracode assemblage that includes P. piedmonti was from rocks in the Morrison Formation. 

However, as previously indicated, the faunule is 

from Lower Cretaceous rocks and belongs in the 

Chilson Member of the Lakota Formation, probably Unit 2.

Geographic distribution.—South Dakota, Mead 

County; map loc. 8, Roth's type-locality, pi. 6, figs. 

23-27, and USGS colln. 30997, pi. 6, figs. 5-7, 10-13, 

USNM 242938, associated with Trapezoidella trapezoidalis (Roth, 1933), and Limnocypridea morrisonensis (Roth, 1933) ; USGS colln. 31171, pi. 6, 

figs. 1-4, 8, 9, USNM 242939; 31172, USNM 242940.

Lawrence County; map loc. 3, Harper and Sutton's type-locality and USGS colln. 30998, USNM 

242957, associated with T. trapezoidalis (Roth, 

1933).

Fall River County; map loc. 13, USGS colln. 

30986, USNM 242041, associated with T. trapezoidalis (Roth, 1933) ; map loc. 11, USGS colln. 

30994, USNM 242958, associated with T. rothi n. 

sp.; map loc. 17, USGS colln. 26098, pi. 6, figs. 28-37, 

41-47, USNM 242942, associated with Cypridea 

(Pseudocypridina) inornata (Peck, 1941), "Cypridea" sp. 1, and Longispinella asymmetrica n. sp.

Cypridea (Pseudocypridina) inornata (Peck, 1941)

Plate 3, figures 18-23; plate 7, figures 2-4

Cypridea inornata Peck, 1941, Jour. Paleontology, v. 15, no. 

3, p. 301, pi. 44, figs. 33-36. Kootenai Formation, 

Montana.

Pseudocupridina inornata (Peck). Peck, 1951, Jour. Paleontology, v. 25, no. 3, p. 319, pi. 48, figs. 8-11. Minnewaste 

Limestone Member of the Lakota Formation, Fall River 

County, S. Dak., and Kootenai Formation, Montana.

Cypridea inornatal Peck. Sohn, 1958, Wyoming Geol. Assoc. 

Guidebook, 13th Ann. Field Conf., pi. 1, figs. 17, 18. 

Lakota Formation, Crook County, Wyo.

Diagnosis.—Differs from C. (P.) piedmonti Roth, 

1933, in lacking a ventrolateral ridge on the larger 

valve.

Discussion.—Peck (1951, pi. 48, fig. 9) illustrated 

a carapace from the Lakota Formation of South 

Dakota that differs from the carapace that I am 

illustrating (pi. 3, fig. 22) in that the anterodorsal 

curvature on Peck's specimen meets the dorsal margin at a point farther back from the anterior margin than in my specimen, but the holotype, from the 

Kootenai Formation of Montana, illustrated by Peck 

(1941, pi. 44, fig. 33), more closely resembles the 

same view of my specimen (pi. 3, fig. 23).
16 NONMARINE OSTRACODES, LAKOTA FORMATION, SOUTH DAKOTA AND WYOMING

Geographic distribution.—South Dakota, Fall 

River County; map loc. 13, USGS colln. 30985, 

USNM 242968, associated with T. rothi n. sp.; USGS 

colln. 31005, USNM 242988, associated with T. rothi 

n. sp.; map loc. 14, USGS colln. 31237, USNM 

242964, associated with T. rothi n. sp. and Cypridea 

(Pseudocypridina) henrybelli n. sp.; USGS colln. 

31238, USNM 242965, associated with T. rothi n. 

sp.; map loc. 15, USGS colln. 30996. USNM 242982; 

map loc. 16, USGS colln. 26100, USNM 242963, associated with T. rothi n. sp.; map loc. 17. USGS 

colln. 26098, USNM 242962, associated with C. (P.) 

piedmonti (Roth, 1933), "Cypridea" sp. 1, and 

Longispinella assymetrica n. sp.; USGS colln. 25460, 

USNM 242976, associated with C. (P.) henrybelli 

n. sp., "Cypridea" sp. 1, and L. assymetrica n. sp.; 

map loc. 18, USGS colln. 31239, USNM 242983, associated with L. longispina (Roth, 1941).

Lawrence County; map loc. 2, USGS colln. 25646, 

USNM 242986.

Wyoming, Crook County; map loc. 5, USGS colln. 

25645, pi. 3, figs. 18-23, pi. 7, figs. 2-4, USNM 

242961, associated with C. (P.) laeli n. sp.; USGS 

colln. 25644, USNM 242968, associated with L. 

longispina (Peck, 1941).

Cypridea (Pseudocypridina) laeli Sohn, n. sp.

Plate 3, figures 1-13, 24, 25, 32; plate 7, figure 1; 

plate 8, figures 26-30

Name.—In honor of Master Lael Schooler. Washington, D.C.. a budding young scientist.

Holotype.—USNM 129644

Parati/pes.—USNM 242865-242871, 242908

Type-locality.—Map loc. 5. USGS colln. 25645. 

NEi/i sec. 20, and NWVj. sec. 21. T. 51 N.. R. 65 W., 

Crook County, Wyo.

Other localities.—See geographic distribution.

Type level.— Lakota Formation, shale near top.

Diagnosis.—Subovate. with arched dorsal margin, 

ventrolateral ridge and dorsoanterior node on larger 

left valve; right valve with curved irregular ridge 

subparallel and slightly removed from dorsal margin. Surface finely punctate, with scattered minute 

spinelets more common on anterior and posterior 

quarters than on center.

Description.—The carapace is subovate, with an 

arched dorsal margin, gently convex ventral margin, 

broadly rounded end margins, and a distinct rostral 

incisure on both valves. The left valve has a distinct 

ridge near the ventral margin that starts behind 

the rostrum and expands posteriorly along the 

valve surface for about three-fourths of the greatest 

length, and a distinct but low moundlike subelliptical node at the dorsoanterior. In ventral view, this 

ridge has an abrupt posterior termination (pi. 3, 

fig. 13). In most specimens, the surface of the valve 

is smooth along the dorsal margin; in some, a crude 

delineation of a thin ridge borders the dorsal edge 

of the valve (pi. 3, figs. 2. 11). The right valve has 

an irregular ridge subparallel and slightly removed 

from the hinge contact. In some specimens, this 

| ridge is variable and starts as a subelliptical node 

approximately opposite the node on the left valve 

and becomes stronger as it extends backward to just 

before the approximate junction of the posterior 

and dorsal margins. In other specimens, it has a 

series of constrictions along its backward route. The 

hingeline is slightly incised; a straight double ridge 

on the right valve fits into a groove and ridge on 

the left valve (pi. 3. fig. 32). The surface is finely 

punctate. The left valve overlaps on all margins. 

The overlap along the venter is straight along the 

posterior two-thirds of the length; at that point it 

has a distinct bend towards the rostrum. Dorsal 

and ventral outlines are subelliptical; the greatest 

width is at or slightly behind the midlength. The 

end outlines are subelliptical, truncated along the 

venter by the ridge on the left valve, and along the 

dorsum by the ridge and incised hinge; the greatest 

width is at the approximate midheight.

Discussion.—C. (P.) laeli resembles in lateral 

outline and surface ornament the Cypridea fasciculata-group of Wolburg (1959, p. 243) from the 

middle and upper Purbeckian, and also the Cypridea 

alto-group of Wolburg (1959, p. 262) from the 

upper Purbeckian-Berriasian, both from Germany. 

The node on the left valve and dorsal ridge on the 

right valve could have evolved from similar structures on C. (P.) alto formosa (Wolburg. 1959) of 

Purbeckian age (Wolburg, 1959, p. 264, pi. 3, figs. 

2a-c, 11, 12). The ventrolateral ridge on the left 

valve is present on a specimen illustrated by Wolburg (1959. pi. 2, fig. 5) as a tuberculate variety of 

C. (P.) dolabrata angulata (Martin, 1940) from 

the lower or middle Wealden 3 (Purbeckian). This 

specimen differs from C. (P.) laeli in having the 

ridge closer to the rostrum and in tapering backwards. An almost identical dorsal ridge on the right 

valve is present on C. (P.) fasciculata (Forbes in 

Lyell. 1855), illustrated by Wolburg (1959. pi. 1. 

fig. 3) from the middle Purbeckian; this species has 

nodes that are much larger than the spinelets on 

C. (P.) laeli scattered on the anterior and posterior 

surfaces of the punctate valves.

Wolburg (1962, pi. 29) illustrated a gradational 

series beginning with the tuberculate C. (P.) fasci-
SYSTEMATIC DESCRIPTIONS 17

culata in the Jurassic Wealden 1, through less 

tuberculated individuals of the same species in 

Wealden 2, to a nontuberculated species in Wealden 

2, which he identified as Cypridea altissima Martin. 

He illustrated two specimens (pi. 29, figs. 7, 8) that 

are not conspecific with C. (P.) altissima (Martin, 

1940, pi. 4, figs. 45, 47) recorded by Martin from 

the Lower Cretaceous (Martin, 1940, pi. 13). The 

reduction in number and ultimate loss of nodes 

through time in this species group and the affinities 

of C. (P.) laeli enumerated above suggest that C. 

(P.) laeli may be younger than the lower Valanginian.

Geographic distribution.—Wyoming, Crook County; map loc. 5, USGS colln. 31001, pi. 3, figs. 1-9, 

24, 25, 32; pi. 7, fig. 1; pi. 8, figs. 26-30, USNM 

242966; USGS colln. 25645, pi. 3, figs. 10-13, USNM 

242967.

Cypridea (Pseudocypridina) henrybelli Sohn, n. sp.

Plate 3, figures 14-17; plate 8, figures 1-25

Name.—In honor of Henry Bell III, U.S. Geological Survey, who introduced me to the ostracodes 

from the Black Hills.

Holotype.—USNM 129645.

Paratypes.—USNM. 242901-242907.

Type-locality.—Map loc. 17, Buck Canyon, SEi/i 

sec. 15, T. 8 S., R. 4 E., Flint Hill quadrangle, Fall 

River County, S. Dak. USGS colln. 25460.

Other localities.—See geographic distribution.

Type-level.—Chilson Member of Lakota Formation, Unit 2, about 5 feet (1.5 m) above the base.

Diagnosis.—Straight backed, with anterodorsal 

angulation, finely punctate; commonly with distinct 

nodes at midheight on anterior and posterior quarters of each valve; sometimes one or both nodes may 

be smaller, more subdued, or entirely missing on the 

right valve.

Description.—The carapace is elongate-ovate, 

with a straight dorsal margin that is one-half or 

slightly less than one-half the greatest length, a 

gently convex ventral margin, a distinct beak, a 

rounded anterior margin that is higher than the 

rounded posterior margin and that meets the dorsal margin at a distinct angulation at about onethird the greatest length. The hinge is incised. The 

dorsal outline is elliptical with the greatest width at 

approximately midlength; the lateral nodes, when 

present, cause the dorsal outline to have a hexagonal 

appearance, with convex lateral sides. The left valve 

overlaps on all margins except the hingeline. The 

lateral surface is finely punctate. The lateral nodes 

vary in size, shape, and height among specimens

(compare pi. 8, figs. 1, 4, 7, 10, 12, 21) ; the right 

valve of some specimens does not have any nodes.

Discussion.—On the basis of the lateral outline 

and rostrum C. (P.) henrybelli belongs in the 

parallela-line of the Cypridea valdensis-parallelagroup of Wolburg (1959, p. 267). The Cypridea 

parallela-]me was recorded by Wolburg (1959, p. 

227, fig. 2) as ranging stratigraphically from Wealden 4 to Wealden 6 (Berriasian-lower Valanginian). 

The lateral nodes relate C. (P.) henrybelli to C. 

(P.) binodosa (Martin, 1940) from the middle 

Purbeckian of Germany, and to C. (P.) salvadorensis nodifer (Krommelbein, 1962) from the upper 

part of the Candeias and the lower part of the 

Ilhas Formations of Brazil. The species differs from 

C. (P.) binodosa in lacking a ventrolateral ridge on 

the left valve (Martin, 1940, pi. 3, fig. 42), and from 

C. (P.) salvadorensis nodifer in that the nodes are 

closer to the end margins and in having a more distinct rostrum. C. (P.) subtilis (Krommelbein, 

1965) from the middle to upper part of the Candeias Formation of Brazil also has two lateral 

nodes and a well-developed rostrum, but the nodes 

on C. (P.) henrybelli are closer to the end margins 

as well as to the ventral margin. Krommelbein 

(1966, p. 115) considered the Candeias and Ilhas 

Formations to be at least partly younger than the 

Lower Cretaceous Wealden Beds of Europe.

It may be significant that C. (P.) salvadorensis 

nodifer (Krommelbein, 1962) is associated with C. 

(P.) salvadorensis salvadorensis (Krommelbein, 

1962), from which it differs only in having lateral 

nodes, and that the type-series of C. (P.) henrybelli 

contains specimens without nodes on the right valve. 

C. (P.) baidarensis (Bischoff, 1963), from the 

Lower Cretaceous (probably pre-Hauterivian to 

Hauterivian-Barremian) of southern Lebanon, was 

described and illustrated as having a single node 

near the posterior of the left valve. These morphologically related species suggest an age younger than 

lower Valanginian for the new species.

Geographic distribution.—South Dakota, Fall 

River County; map loc. 13, USGS colln. 31003, 

USNM 242971, associated with Trapezoidella rothi 

n. sp.; map loc. 14, USGS colln. 31129, USNM 

242985; USGS colln. 31130, pi. 8, figs. 1-25, USNM 

242970, associated with Longispinella asymmetrica 

n. sp.; USGS colln. 31237, USNM 242973, associated with T. rothi n. sp. and Cypridea (Pseudocypridina) inornata (Peck, 1941) ; map loc. 17, 

USGS colln. 25460, pi. 3, figs. 14-17, USNM 242975, 

associated with C. (P.) inornata (Peck, 1941), 

"Cypridea" sp. 1, and L. asymmetrica n. sp.; USGS 

colln. 31007 (? identification), USNM 242972, asso-
18 NONMARINE OSTRACODES, LAKOTA FORMATION, SOUTH DAKOTA AND WYOMING

elated with T. trapezoidalis (Roth, 1933) and T. 

rothi n. sp.

New genus undescribed 

"Cypridea" sp. 1

Plate 7, figures 8-12

Discussion.—A single well-preserved carapace 

(USNM 242900) about 0.9 mm in greatest length 

was found in a collection from the Lakota Formation, Fall River County, S. Dak. (USGS colln. 

26098, map loc. 17). This specimen is reticulated, 

has a large subcentral spine, numerous surface 

tubercles, and resembles Cypridea (C.) propunctata 

Sylvester-Bradley, 1949, in lateral outline and in 

the development of the rostrum, alveolus, and cyathus. Although five additional, poorly preserved 

carapaces were found in the same area (USGS 

colln. 25460 (USNM 242978)), the available material is inadequate to describe the taxon. This taxon 

differs markedly from Cypridea Bosquet, 1852, as 

represented by Cypridea granulosa (Sowerby, 

1836), and also from Pseudocypridina Roth, 1933, as 

illustrated in this paper. Species described in 

Cypridea that are similar to "Cypridea" sp. 1 

should be segregated in a separate genus. The specimens described and illustrated by Swain and Brown 

(1972, p. 14, pi. 1, figs. 19, 20; pi. 3, fig. 1) as 

Cypridea (C.) Wyomingensis Jones, 1893, from the 

Lower Cretaceous of the Atlantic Coastal region are 

referable to this genus, probably as a new species.

Genus Longispinella Sohn, n. gen.

Type-species.—Longispinella asymmetrica Sohn 

n. sp.

Name.—For the long lateral spine on each valve.

Diagnosis.—Relatively small, to 1 mm in greatest 

length, subtriangular in lateral outline; surface 

punctate, with one subcentral large spine, without 

nodes, small spines or ridges; rostrum and alveolus 

well developed, cyathus usually subtriangular. Dimorphic in width of posterior.

Discussion.—This genus is established for those 

species previously referred to Cypridea Bosquet, 

1852, that have a robust lateral spine on each valve 

and that do not have accessory smaller spines. The 

following additional species are here assigned to 

Longispinella:

C. armnta Krommelbein, 1962, Lower Cretaceous, Brazil. 

C. longispina Peck, 1941, Kootenai Formation, Lower Cretaceous, Montana. 

C. tucanoensis Krommelbein, 1965, Lower Cretaceous, Brazil.

Stratigraphic range.—Lower Cretaceous.

Longispinella asymmetrica Sohn, n. sp.

Plate 4, figures 7-20; plate 5, figures 1-7, 13-16

Name.—Asymmetrical ornament on left valve.

Holotype.—USNM 242882

Paratypes.—VSNM 242877-242881, 242883

Type-locality.—Map locality 14, Upper Chilson 

Canyon, T. 8 S., R. 3 E., Flint Hill quadrangle, Fall 

River County, S. Dak. USGS colln. 31130.

Other localities.—See geographic distribution.

Type-level.—Sandy layer above paper shale in 

Chilson Member of Lakota Formation, about 5 feet 

(1.5 m) above base of member.

Diagnosis.—Subtriangular, with well-developed 

rostrum, alveolus, and triangular cyathus; with 

robust lateral spine in approximate center of posterior third of each valve; short perpendicular shallow sulcus bounded anteriorly by a rounded ridge at 

approximate midheight, just behind the upper part 

of the alveolus on left valve.

Description.—The carapace is small, less than 

0.9 mm in greatest length. The lateral outline is 

subtriangular; the anterior and dorsoanterior margins form a continuous curve from the tip of the 

rostrum to the approximate mid-length. The hinge 

line is straight, incised; it slopes downward to a 

point about halfway between the curve of the posterior margin and the lateral spine. The posterior 

margin is gently curved; it extends as the outside of 

the triangular downward-pointing cyathus. The 

ventral margin of the right valve is straight; the 

ventral margin of the left, overlapping, valve is 

gently curved to straight. The dorsal outline is subelliptical, with the posterior end wider than the 

anterior end, but the greatest width is subcentral. 

The rostrum is well defined; it points straight down 

to below the ventral margin, and it is separated 

from the valve surface by a subdeltoid-shaped alveolus. The alveolus extends upwards about halfway to the curve of the anterior margin; it has a 

horizontal ridge at its base. This rounded ridge connects the rostrum to the valve surface.

A single robust lateral spine is about one third 

of the greatest length from the posterior margin, 

and about halfway between the ventral and dorsal 

margins. The valves are punctate, except the areas 

of the rostrum and alveolus. The left valve has a 

smooth, shallow, vertical, short sulcus, whose bottom is at approximately the same distance above 

the ventral margin as the spine. This sulcus is separated from the alveolus by a rounded smooth ridge. 

The right valve does not have this sulcus and ridge, 

but the area in that position is smooth. The left
SYSTEMATIC DESCRIPTIONS 19

valve overlaps the right along all the margins except the incised hinge margin.

Discussion.—This species belongs in a group of 

species previously assigned to Cypridea that have in 

common a robust lateral spine and a subtriangular 

lateral outline. It differs from L. longispina (Peck, 

1941) by having the peculiar sulcus bounded by a 

ridge on the left valve. Peck (1951, pi. 48, fig. 12) 

illustrated a specimen from the lower 15 feet of the 

Lakota Formation, Fall River County, S. Dak. as 

C. longispina. The illustration of this specimen 

suggests that it does not belong in L. longispina, 

but because the right side of the carapace is illustrated, it cannot be referred to L. asymmetrica. 

Peck (1941, p. 301) related C. longispina with C. 

brevicornis Peck, 1941, from the Draney Formation 

(upper Aptian) of Idaho and Wyoming and to C. 

spinigera (Sowerby, 1836) from the Wealden (Lower Cretaceous) of England. The latter two species 

are not subtriangular in lateral outline; consequently, they are not included in Longispinella.

Geographic distribution.—South Dakota, Fall 

River County; map loc. 12, USGS colln. 31153, 

USNM 242979, associated with L. longispina (Peck, 

1941) ; map loc. 14, USGS colln. 31130, pi. 5, figs. 

1-7, 13-16, associated with L. longispina (Peck, 

1941) ; map loc. 17, USGS colln. 26098, pi. 4, figs. 

7-20, USNM 242974, associated with Cypridea 

(Pseudocypridina) piedmonti (Roth, 1933), C. (P.) 

inomata (Peck, 1941), and "Cypridea" sp. 1; 

USGS colln. 25460, USNM 242977, associated with 

C. (P.) inornata (Peck, 1941), C. (P.) henrybelli 

n. sp., and "Cypridea" sp. 1.

Longispinella longispina (Peck, 1941)

Plate 4, figures 1-6; plate 5, figures 8-12, 17-23; 

plate 7, figures 5-7

Cypridea longispina Peck, 1941, Jour. Paleontology, v. 15, 

p. 300, pi. 43, figs. 69. Kootenai Formation, Montana; 

Peck, 1951, Jour. Paleontology, v. 25, p. 312, pi. 48, figs. 

12-15. Lakota Formation, Fall River County, S. Dak., 

Cloverly Formation, Fremont County, Wyo.

Cypridca longispinal Peck. Sohn, 1958, Wyoming Geol. Assoc. Guidebook, 13th Ann. Field Conf., pi. 1, figs. 1-4. 

Lakota Formation, Crook County, Wyo.

Diagnosis.—Differs from L. asymmetrica in 

smaller and narrower size, in more pointed end in 

dorsal outline, and in either having a smaller perpendicular shallow sulcus bounded anteriorly by a 

rounded ridge behind the alveolus of the left valve, 

or not having that structure.

Discussion.—Peck (1941) illustrated the left 

view of the holotype, and two right views and the 

ventral view of three paratypes. The same view of

the holotype was republished by Peck (1951, pi. 48, 

fig. 15), as well as a right view of a carapace from 

the Lakota Formation and the right and ventral 

views of a carapace from the Cloverly Formation. 

I obtained from Dr. Peck three specimens from the 

type-locality in Montana and am illustrating two 

presumed males mainly to show the dorsal and ventral outlines and the poor state of preservation (pi. 

4, figs. 1-6). One of these specimens (pi. 4, fig. 4) 

has a faint suggestion of the ridge and sulcus on 

the left valve, although Peck's drawing of the holotype does not show that feature. The specimens 

illustrated here from Crook County, Wyo. (pi. 7, 

figs. 5, 7), and from Peck's locality in Fall River 

County, S. Dak. (pi. 5, figs. 20, 21), have that structure, which is smaller than that on L. asymmetrica. 

Other specimens, however, do not have that structure (pi. 5, figs. 11, 18).

Dimorphism in width of posterior in dorsal and 

ventral outlines is inferred in this species because 

the specimen illustrated by Peck in 1941 (pi. 43, 

fig. 9) is narrower in ventral outline than is the 

carapace illustrated by him in 1951 (pi. 48, fig. 14) ; 

likewise, the carapaces illustrated here in pi. 4, figs. 

3, 5; pi. 5, figs. 9, 19; pi. 7, fig. 6 are narrower in 

dorsal and ventral outlines than are the specimens 

illustrated herein on pi. 5, figs. 12, 22. Presumably 

the ones with the wider posteriors represent females, and those with narrower posteriors represent 

males.

It is noteworthy that the left valve of the holotype from the Kootenai Formation, Montana, has a 

knoblike structure near the posterior end of the 

left valve and that a somewhat similar structure, 

not quite as well defined, can be seen on the left 

valve of the specimen from the Lakota Formation, 

Wyoming, illustrated here (pi. 5, figs. 18 and 20). 

This structure is absent on all the other specimens 

illustrated; consequently, it is probably of no diagnostic significance, but it lends a certain amount of 

credence to my identification of this species.

I have no data to confirm that the stratigraphic 

age of the Kootenai Formation in Montana and the 

Cloverly Formation in Wyoming, both of which 

have been assigned to the Aptian, are older than 

Aptian, although I now consider the Lakota Formation to be pre-Aptian in age.

Geographic distribution.—Montana, Cascade 

County; Peck's (1941, p. 288) loc. 23.

South Dakota, Fall River County; map loc. 12, 

USGS colln. 31154, pi. 5, figs. 8-12, USNM 242980; 

USGS colln. 31153, pi. 5, figs. 17, 23, USNM 242981, 

associated with L. asymmetrica n. sp.; map loc. 18,
20 NONMARINE OSTRACODES, LAKOTA FORMATION, SOUTH DAKOTA AND WYOMING

USGS colln. 31239, USNM 242984, associated with 

Cypridea (Pseudocypridea) inornata (Peck, 1941).

Wyoming, Crook County; map loc. 5, USGS colln. 

25644, pi. 7, figs. 5-7, associated with C. (P.) inornata (Peck, 1941).

Wyoming, Fremont County; Peck's (1951, p. 

310) loc. 32.

REFERENCES CITED

Alien, P., Keith, M. L., Tan, F. C., and Deines, P., 1973, 

Isotopic ratios and Wealden environments: Palaeontology, v. 16, pt. 3, p. 607-621, 2 figs.

Anderson, F. W., Bazley, R. A. B., and Shephard-Thorn, 

Annals Mag. Nat. History, ser. 11, v. 3, no. 15, p. 

291-310.

———— 1973, The Jurassic-Cretaceous transition: the nonmarine ostracod faunas, in Casey, R., and Rawson, P. F., 

eds., The Boreal Lower Cretaceous: Geol. Jour., Spec. 

Issue 5, p. 101-110.

Anderson, F. W., Bazley, R. A. B., and Shephard-Thorn, 

E. R., 1967, The sedimentary and faunal sequence of the 

Wadhurst Clay (Wealden) in boreholes at Wadhurst 

Park, Sussex: Great Britain Geol. Survey Bull. 27, p. 

171-235, pis. 9-15, 4 figs.

Andreev, Yu, N., and Mandelstam, M. N., 1968, Ostracody 

semeistva Cyprididae iz melovykh otlozhenii Tadzhikskoi 

Depressii: Akad. Nauk Tadzhik. SSR, Izv., Otdeleniye 

Fiz.-Mat. i Geol.-Khim. Nauk, v. 2, no. 28, p. 69-82.

Bell, Henry III, and Post, E. V., 1971, Geology of the Flint 

Hill quadrangle, Fall River County, South Dakota: U.S. 

Geol. Survey Bull. 1063-M, p. 505-586.

Benson, R. H., 1972, The Bradleya problem, with descriptions of two new psychrospheric ostracode genera, 

Agrenocythere and Poseidonamicus (Ostracoda: Crustacea) : Smithsonian Contr. Paleobiology, no. 12, 138 p., 

14 pis., 66 figs.

Bischoff, Gunther, 1963, Ostracoden-Studien im Libanon, 2: 

Die Gattung Cypridea in Aptien inferieur: Senckenbergiana lethaea, v. 44, no. 4, p. 301-319, pis. 42-44, 

1 fig.

Buschmina, L. S., 1965, Ostrakody Abyshevskogho gorizonta 

(Nizhnii Karbon) Kuzbassa, in Sokolov, B. S., ed., 

Stratigrafiya i paleontologiya Paleozoya Aziatskoi chasti 

SSSR: Moscow, Akad. Nauk SSSR, Sibirsk. Otdeleniye, 

Inst. Geologii i Geofiziki, p. 64-98, 8 pis.

———— 1968, Rannekamennougol'nyye ostrakody Kuznetzkogho Basseina: Moscow, Akad. Nauk SSSR, Sibirsk. 

Otdeleniye, Inst. Geologii i Geofiziki, 127 p., 25 pis.

1970, Kamennougol'nyye Ostrakody nizov'yev r.

Leny: Akad. Nauk SSSR, Sibirsk. Otdeleniye, Inst. 

Geologii i Geofiziki, Trudy, no. 125, 72 p., 15 pis.

Cook, T. D., and Bally, A. W., eds. 1975, Stratigraphic atlas 

of North and Central America: Princeton, N.J., Princeton University Press, 272 p.

Galeeva, L. L, 1955, Ostrakody melovykh otlozhenii 

MongoFskoi Narodnoi Respubliki: Moscow, Vses. 

Nauchno-Issled. Geol-Razved. Neft. Inst. (VNIGNI), 94 

p., 15 pis. (Gostoptechizdat).

Gott, G. B., Wolcott, D. E., and Bowles, C. G., 1974, Stratigraphy of the Inyan Kara Group and localization of 

uranium deposits, southern Black Hills, South

Dakota and Wyoming: U.S. Geol. Survey Prof. Paper 

763, 57 p., 4 pis 23 figs.

Green, Robert, 1963, Lower Mississippian ostracodes from 

the Banff Formation, Alberta: Research Council Alberta Bull. 11, 237 p., 17 pis., 23 figs.

Hanai, Tetsuro, 1951, Cretaceous non-marine Ostracoda from 

the Sungari Group in Manchuria: Tokyo Univ. Fac. 

Sci. Jour., sec. 2, v. 7, pt. 9, p. 403-430, 2 pis. 13 figs.

Harper, Frances, and Sutton, A. H., 1935, Ostracodes of 

the Morrison Formation from the Black Hills, South 

Dakota: Jour. Paleontology, v. 9, no. 8, p. 623-628, pi. 76.

Hartmann, Gerd, and Puri, Harbans, 1974, Summary of 

neontological and paleontological classification of Ostracoda: Hamburg. Zool. Mus. Inst. Mitt., v. 70, p. 7-73.

Hinte, J. E. van, 1976a, A Jurassic time scale: Am. Assoc. 

Petroleum Geologists Bull., v. 60, no. 4, p. 489-497, 4 figs.

———— 1976b, A Cretaceous time scale: Am. Assoc. Petroleum Geologists Bull., v. 60, no. 4, p. 498-516, 9 figs.

Hou, Y. T., 1958, Jurassic and Cretaceous nonmarine ostracods of the Subfamily Cyprideinae from north-western 

and north-eastern regions of China: Acad. Sinica, Inst. 

Palaeontology Mem., 103 p., 13 pis.

Howe, H. V., 1962, Ostracod taxonomy. Baton Rouge, 

Louisiana State Univ. Press, 366 p.

Howe, H. V., and Laurencich, Laura, 1958, Introduction to 

the study of Cretaceous Ostracoda. Baton Rouge, 

Louisiana State Univ. Press, 536 p.

Kneuper-Haack, Friederun, 1966, Ostracoden aus dem 

Wealden der Sierra de los Cameros (Nordwestliche 

Iberische Ketten) : Geol. Jahrb. Beih., v. 44, p. 165-209, 

8 pis., 2 figs.

Krommelbein, Karl, 1962, Zur Taxonomie und Biochronologie stratigraphisch wichtiger Ostracoden-Arten aus der 

oberjurassisch?-unterkretazischen Bahia-Serie (Wealden-Facies) NE-Brasiliens: Senckenbergiana lethaea, 

v. 43, no. 6, p. 437-528, pis. 53-63.

———— 1963, Ilhasina n.g. und Salvadoriella n.g., zwei neue 

Ostracoden-Gattungen aus der Bahia-Serie (nichtmariner Oberjura?-Unterkreide, NE-Brasilien) : Zool. 

Anzeiger, v. 171, nos. 9-10, p. 376-390, 2 pis., 1 fig.

———— 1965, Neue, fur Vergleiche mit West-Afrika wichtige 

Ostracoden-Arten der brasilianischen Bahia-Serie (OberJura?/Unter-Kreide in Wealden-Fazies) : Senckenbergiana lethaea, v. 46a, p. 177-213, pis. 11-15.

———— 1966, On "Gondwana Wealden" Ostracoda from NE

Brazil and West Africa: West African Micropaleontological Colloquium, 2d, Ibadan, 1965, Proc., p. 

113-119.

Lane, D. W., 1963, Sedimentary environments in Cretaceous 

Dakota Sandstone in northwestern Colorado: Am. Assoc. 

Petroleum Geologists Bull., v. 47, no. 2, p. 229-256, 9 figs.

Liebau, Alexander, 1975, The left-right variation of the 

ostracode ornament, with discussion, in Swain, F. M., 

Kornicker, L. S., and Lundin, R. F., eds., Biology and 

paleobiology of Ostracoda: Bulls. Am. Paleontology, 

v. 65, no. 282, p. 76 86, 1 pi., 5 figs.

Loranger, D. M., 1951, Useful Blairmore microfossil zone in 

central and southern Alberta, Canada: Am. Assoc. 

Petroleum Geologists Bull., v. 35, no. 11, p. 2348-2367, 

3 pis., 2 figs.

———— 1954, Useful Blairmore microfossil zone in central 

and southern Alberta, Canada, in Clark, L. M., ed., 

Western Canada sedimentary basin—A symposium: 

Tulsa, Okla., Am. Assoc. Petroleum Geologists, Ralph
REFERENCES CITED 21

Leslie Rutherford Memorial Volume, p. 279-296, 3 pis., 

2 figs. [Reprinted with revisions of 1951 paper]. 

Lubimova [Lyubimoval, P. S., 1956a, Lymnocypridea, Pyrocytheridea, and Mandelstamia, in Kiparisova, L. D., 

Markovsky, B. P., and Radchenko, G. P., eds., Materialy 

po paleontologii, novye semeistva i rody: Vses. NauchnoIssled. Geol. Inst. (VSEGEI), Materialy, new ser., no. 

12, Paleontology, p. 106-109, 139-142, pi. 26.

———— 1956b, Ostrakody melovykh otlozhenii vostochnoi 

chasti Mongol'skoi Narodnoi Respubliki i ikh znachenie 

dlya stratigrafii: Vses. Neft. Nauchno-Issled. Geologorazv. Inst. (VNIGRI), Trudy, no. 93, 174 p., 25 pis., 

10 figs. (Leningrad, Gostoptechizdat).

Lubimova [Lyubimova], P. S., Kaz'mina, T. A., and Reshetnikova, M. A., 1960, Ostrakody Mezozoiskikh i Kainozoiskikh otlozhenii Zapadno-Sibirskoi nizmennosti: Vses. 

Neft, Naucho-Issled. Geologorazv. Inst. (VNIGRI), 

Trudy, no. 160, 427 p., 24 pis.

Lubimova [Lyubimova], P. S., Mandelstam, M. I., and 

Schneider, G. F., 1960, Superfamily Cypracea in Chernysheva, N. E., ed., Osnovy paleontologii; spravochnik dlya 

paleontologov i geologov SSSR; [v. 8|, Chlenistonogie, 

trilobitobraznye i rakobraznye: Moscow, Gosudar. 

Nauch.-Tekh. Izdat. Lit. Geol. i Okhrane Nedr., p. 347- 

365, figs. 898 993.

Lundin, R. F., 1965, Henryhouse ostracodes: Oklahoma Geol. 

Survey Bull. 108, 104 p., 18 pis., 45 figs.

Mandelstam, M. L, and Schneider, G. F., 1963, Iskopaemie 

ostrakody SSSR, Semeistvo Cyprididae: Vsesoyuz. Neft. 

Nauch.-Issled. Geologorazv. Inst., (VNIGRI), Trudy, no. 

203, 331 p., 42 pis., 113 figs. (Leningrad, Gostoptechizdat.)

Mapel, W. J., and Pillmore, C. L., 1963, Geology of the 

Inyan Kara Mountain quadrangle, Crook and Weston 

Counties, Wyoming: U.S. Geol. Survey Bull. 1121-M, 

56 p., 3 pis., 9 figs.

Martin, G. P. R., 1940, Ostracoden des norddeutschen Purbeck und Wealden: Senckenbergiana, v. 22, no. 5-6, p. 

275-361, 13 pis.

McGregor, D. L., and Kesling, R. V., 1969a, Copulatory 

adaptations in ostracods-part I. Hemipenes of Candona: 

Michigan Univ., Mus. Paleontology Contr., v. 22, no. 13, 

p. 169-191, 3 pis., 16 figs.

———— 1969b, Copulatory adaptations in ostracods-part II. 

Adaptations in living ostracods: Michigan Univ., Mus. 

Paleontology Contr., v. 22, no. 17, p. 221-239, 17 figs.

Moore, R. C., ed., 1961, Treatise on invertebrate paleontology, Part Q, Arthropoda 3, Crustacea, Ostracoda: New 

York and Lawrence, Kans., Geol. Soc. America and Univ. 

Kansas Press, 422 p., 334 figs.

Morkhoven, F. P. C. M. van, 1963, Post-Paleozoic Ostracoda: 

Amsterdam-London-New York, Elsevier Publishing Co., 

v. 2, 478 p., 763 figs.

Peck, R. E., 1941, Lower Cretaceous Rocky Mountains nonmarine microfossils: Jour. Paleontology, v. 15, no. 3, p. 

285-304, pis. 42-44.

———— 1951, Nonmarine ostracodes—The subfamily 

Cyprideinae in the Rocky Mountain area: Jour. Paleontology, v. 25, no. 3, p. 307-320, pis. 48-50, 1 fig.

Post, E. V., and Bell, Henry III, 1961, Chilson Member of 

the Lakota Formation in the Black Hills, South Dakota 

and Wyoming: U.S. Geol. Survey Prof. Paper 424 D, 

p. D173-D178, figs. 349-1, 349-2.

Pranskevichius, Antanas, 1972, Ostracody silura Yuzhnoi 

Pribaltiki [South Baltic Silurian Ostracoda): Litovskii 

Nauch.-Issled. Geol. Razv. Inst., Trudy, no. 15, 280 p., 

42 pis. 17 figs.

Robinson, C. S., Mapel, W. J., and Bergendahl, M. H., 1964, 

Stratigraphy and structure of the northern and western 

flanks of the Black Hills uplift, Wyoming, Montana and 

South Dakota: U.S. Geol. Survey Prof. Paper 404, 134 p., 

5 pis. 8 figs.

Roth, Robert, 1933, Some Morrison Ostracoda: Jour. Paleontology, v. 7, no. 4, p. 398-405, pi. 48.

Sohn, I. G., 1957, Upper Jurassic-Lower Cretaceous 

Cyprideinae (Ostracoda) in the Black Hills [abs.|: Geol. 

Soc. America Bull., v. 68, no. 12, p. 1798.

———— 1958, Middle Mesozoic nonmarine ostracodes of the 

Black Hills: Wyoming Geol. Assoc. Guidebook, 13th Ann. 

Field Conf., p. 120-126, 1 pi., 1 fig.

———— 1960, Paleozoic species of Bairdia and related genera: 

U.S. Geol. Survey Prof. Paper 330-A, 105 p., 6 pis., 15 

figs. [1961].

———— 1962, Genetic control of surface ornaments in an 

ostracode species [abs.]: Geol. Soc. America Spec. Paper 

68, Abstracts for 1961, p. 276.

———— 1967, Paleogeographical implications of nonmarine 

Lower Cretaceous Cyprideinae in Israel, and Metacytheropteron parnesi n. sp. (Ostracoda, Crust.) : Israel 

Jour. Earth Sci., v. 16, no. 3, p. 120-131, 1 pi., 1 fig. 

[19681.

1969, Nonmarine ostracodes of Early Cretaceous age

from Pine Valley quadrangle, Nevada: U.S. Geol. Survey 

Prof. Paper 643-B, 9 p., 2 pis., 1 fig. [1970].

Sohn, I. G., and Anderson, F. W., 1964, The ontogeny of 

Theriosynoecum fittoni (Mantell) : Palaeontology, v. 7, 

pt. 1, p. 72-84, pi. 15, figs. 1-4.

Stelck, C. R., 1975, Basement control of Cretaceous sand 

sequences in western Canada, hi Caldwell, W. G. E., ed., 

The Cretaceous System of the Western Interior of North 

America: Canada Geol. Assoc. Spec. Paper 13, p. 427- 

440, 10 figs.

Swain, F. M., 1946, Middle Mesozoic nonmarine Ostracoda 

from Brazil and New Mexico: Jour. Paleontology, v. 20, 

no. 6, p. 543 555, pis. 83, 84, 1 fig.

Swain, F. M., and Brown, P. M., 1972, Lower Cretaceous, 

Jurassic (?), and Triassic Ostracoda from the Atlantic 

Coastal region: U.S. Geol. Survey Prof. Paper 795, 55 

p., 9 pis.

Sylvester-Bradley, P. C., 1949, The ostracod genus Cypridea 

and the zones of the upper and middle Purbeck: Geologists' Assoc. Proc., v. 60, pt. 2, p. 125-153, pis. 3, 4, figs. 

17-25.

Waage, K. M., 1959, Stratigraphy of the Inyan Kara Group 

in the Black Hills: U.S. Geol. Survey Bull. 1081-B, p. 

11 90, pi. 2, figs. 5-9.

Wicher, C. A., 1959, Ein Beitrag zur Altersdeutung des 

Reconcavo, Bahia (Brasilien) : Geol. Jahrb., v. 77, p. 

35-58, pis. 6-9.

Willey, E. C., 1970, Lower Devonian ostracodes: Revision 

of species described by Chapman (1904) from the Lilydale Limestone, Victoria: Royal Soc. Victoria, Proc., v. 

83, pt. 2, p. 121 136, pis. 7-9, 3 figs.

Wolburg, Johannes, 1959, Die Cyprideen des NW-deutschen 

Wealden; Senckenbergiana lethaea, v. 40, no. 3-4, p. 

223-315, 5 pis., 27 figs.

———— 1962, Artenumwandlung und Artenabspaltung an
22 NONMARINE OSTRACODES, LAKOTA FORMATION, SOUTH DAKOTA AND WYOMING

einem Beispiel aus der Ostracodengattung Cypridea: 

Palaont. Zeitschr., H. Schmidt-Festband, p. 254-265, 

pi. 29, 10 figs.

Wolcott, D. E., 1967, Geology of the Hot Springs quadrangle, Fall River and Custer Counties, South Dakota: 

U.S. Geol. Survey Bull. 1063-K, p. 427-442, pi. 28, fig. 85.
INDEX

Page

abscondida. Limnocrypridea -___--____ 10, 11 

acerata, Cypridca (Pscudocypridina)

setina -------------------- 14

acutituberculata, Cypridca _____________ 14

Cypridca (Pscudocypridina) _______ 15

Age of the rocks ______--------______ 2

ala.caram.ac Cypridca (Pscudocrypridina) ___-----_--_-_______ 14

albcrtcnsis, Bairdiocypris _____________ 12

alta, Cypridca _________________

Cypridca alta ______________

Cypridca (Pscudocypridina) 

alta, Cypridca ______-__--_.

formosa, Cypridca _________

16 

14 

17 

14 

14 

altissima. Cypridca ------------------- 14, 17

Cypridca (Pscudocypridino) ______

rotunda, Cypridca ________________

amisia, Cypridca ______________________

annulata, Cypridca dolabrata __________

Cypridca (Pscudocypridina) dolabrata _____________________

armatn, Cypridca ___--__-_____--______

17

14

14

14

16 

18

asymmctrica, Longispinclla _____ 15, 1G, 17, 78;

pis. 4, 5

B 

baidarcnsis, Cypridca _________________

Cypridca (Pscudocypridina) ______

Bairdiocypris albcrtcnsis ______________

(Bairdiocypris) morrisoncnsis, Bythocypris ____________________

morrisoncnsis cqualis, Bythocypris 

trapczoidalis, Bythocypris _________

Bythocypris ---_--________________

binodosa, Cypridca ____________________

Cypridca (Pscudocypridina) _______

Bisulcocypridca _______________________

bitumulosa, Limnocypridca __--__----._

brcvicornis, Cypridca _________________

brcvirostrata, Cypridca _______________

Bythocypris (Bairdiocypris) -.-_______

(Bairdiocypris) morrisoncnsis _____

morrisoncnsis cqualis __________

trapczoidalis __________________

camclodcs, Cypridca (Pseudocyridina) 

setina ____________________

Candona ____________________________ 11

rcdunca __________________________

Sp. _-_--_--__-____-_______________

ccltiformis, Limnocypridca _____________

comitans, Solvadoriclla rcdunca ________

consulta, Cypridca ____________________

Cypridca (Pscudocypridina) --____ 

(Cyamocypris) latiovata, Cypridca ____

ovatiformis, Cypridca _____________

Cyp ridacea ___________________________

Cypridca ________________________ 8, 7~',

acutituberculata __________________

10

14

17

12

11

11

8, 9

10

14

17

12

11

19

14

10

11

11

8, 9

14

;pl. 3

9

pi. 3

11

9

14

15

14

14

8

18, 19 

14 

Ifi

[Italic page numbers indicate major references]

Page 

alta _--__--_-_----—-_--___—_ 14

formosa _____________________ 14

altissima _________-__----__-_-_-__ 14, 17

rotunda ______

amisia -----------

armata ___________

baidarcnsis _______

binodosa _________

brcvicornis _______

brcvirostrata ______

consulta ____-___-.

dolabrata anfinlata

dolabrata ____ 

fasciata __________

14

14

18

14

14

19

14

14

14

14

14

gtssarcnsis _______________________

granulosa, __________-_---__--___.

inacqualis _____________--_------_

inornata ________________________

lacvifiata fairlightcnsis __________

haii'khurstensis _-----__--_--.

leonardi _____________________

pfc ilpottsi ____-_-__--___-____

subquadrata ________________

wadhurstcnsis ___-__-----___-

If avis ---------------------------

fata __________-____________

lonflispina __-___-_-----_______--__ 18, 19

lubimovac ________________________ 14

nannorostrata ____________________ 14

obcsa _____________________________ 14

parallcla --_____----_--_--_--__-__ 14, 17

picdmonti _____-__-_----__________ 15

posticalis _________________________ 14

profusa __________________________ 14

proc/nata _________________________ 14

iliiadrata ________________________ 14

rotundata ____--___----_------__-. 14

salvadorcnsis nodifcr ______________ 14

salvadorcnsis -____-___--______ 14,15

sovcrbyi _________________________ 14

spinificra ________________________ 14,19

subtilis _____-_-__-_----__--__-_-__ 14

subvnldcnsis ______________________ 13,14

trnuis ____-----_-_-_-_-_-_-_--_.__ 14

frrta, ____--____-.____________ 14

tucanocnsis ___--------___-________ 18

unirnstata _-_---__-_-___--________ 15

valdmsia _________________________ 15,17

vidrana __________________________ 15

vitimcnsis ___--_--_-_-----______-_ 15

sp. 1 _____________________ 13, 15, 16, 17,

78, 19; pi. 7 

(CyamocHpris) latiovata __________ 14

ovatiformis ___________________ 14

(Cupridcn) ______________________ 12,73

18 

15 

____________ 18

15 

____________ 14

14 

(Pscudoeypridina) ________________ 12,7.?

acMtitubrrculata ______________ 15

propttnctata _ 

uninodu _____

K't/ominr/cnsis 

yumcncnsis _. 

sp. A _______

sp. B _______

Page

alacaramae __ — __._______-,—— 14

a/ta formosa __ — __ — -------— 16

altissima ______— ____ —— _ — ___ 17

baidarcnsis __ — ____--_-------_ 17

binodosa __________—__—__—_ 17

consulta .__-__—--—_-------__ 15

dcmandac __ — __ — _______ — ___ 14

dolabrata angulata _____ — _-___ 16

c/lipscloidcs ______-_____---_-_ 14

cxtcnda ________________—____ 14

fasciculata ________--__-_ — ___ 16

hcnrybclU ___________—— 9, 10, 16,

77, 19; pis. 3, 8 

inornate ____-_-----_ 10, 75, 17, 19, 20;

pis. 3, 7 

_ac/j ________--___ 75; pis. 3, 7, 8

magna ----------------------- 14

moncta ______ — ___-____-____-_ 14

logronana __— __ — ________ 14

parallcla ________-___-_-_-__-_ 14

picdmonti _____----- 9, 12, 75, 16,

19; pi. 6 

salvadorcnsis nodifer __ — ______ 17

salvadorcnsis __— __ — _____ 17

setina _______---------_------- 14

acerata __—_-_----_--_---_ 14

camclodcs ________--_--___ 14

dotica ______—------_-_--_ 14

crumna ________-- — ______ 14

fitcricnsis ________________ 14

rcctidorsata ____--__--__-_ 14

subccntrinoda -___._- — _______ 14

subtilis _-_--. — __-_-___------- 17

unicostata -__-_-_------------_ 15

vitimcnsis ___-____--__---_--__ 15

spp ______-____---— ------ — __ 15

(Cypridca) propunctata, Cypridca ____ 18

uninoda, Cypridca __— _- — -_---___ 15 

u'yominricnsis, Cypridca _____--_--_ 18

yumcncnsis, Cypridca -__________-- 15

sp. A, Cypridca __-_-___---_-____-- 14

sp. B, Cypridca __________ — ______ 14

Cypridca ____________--------__ 12,73

Cypridcamorphclla -------------------- 8, 10

Cyprideidae __---_--------_-------_---- 12

Cyprideinae ______________ — __________ 8, 12

Cypridopsis parallcla ______-____-_----_ 11

Cypris (jranulosa _____________________ 12

D

dcmandac, Cyridca (Pscudocypridina)-- 14

dolabrata, Cypridca dolabrata _________ 14

anrjulala, Cypridca ________________ 14

Cypridca (Pscudocypridina) ___ 16

dolabrata, Cypridea _______________ 14

dotica, Cypridea (Pscudocypridina) setina ---------------------- 14

Dsiinbaina ---------------------------- 8

E

t'llipscloidcx, Cypridca (Pscudocypridina) 14 

ci/udlis, Hyihocijiiris (Bairdiocypris)

morrisoncnsis ______-__--_ 11

23
24 INDEX

Page

Limnocypridea __________________ 11

erumna, Cypridea (Pseudocypridina)

setina _._----_.__________ 14

extenda, Cypridea (Pseudocypridina)-- 14

fairlightensis, Cypridea laevigata ______ 14

fasciata, Cypridea ___________________ 14

fasciculata, Cypridea _________________ 14, 16

Cypridea (Pseudocypridina) ______ 16

fiteriensis, Cypridea (Pseudocyprindina)

setina ____________________ 14

formosa, Cypridea alta ________________ 14

Cypridea (Pseudocypridina) alta __ 16

gissarensis, Cypridea ------------------ 13

grammi, Limnocypridea --------------- 10, 11

granulosa, Cypridea ________________ 18

Cypris __________________ 12

H

hawkhurstensis, Cypridea laevigata ____ 14

lienrybelli, Cypridea (Pseudocypridina) 9, 10,

16, 17, 19; pis. 3, 8

Ilyocyprimorpha ___-___-_____________ 8

inaequalis, Cypridea _________________ 14

inornata, Cypridea ___________________ 15

Cypridea (Pseudocypridina) __ 10, 15, 17, 

19, 20; pis. 3, 7

Pseudocypridina __---_--_--_______ 15

laeli, Cypridea (Pseudocypridina) __ 16; pis. 3,

7, 8 

laevigata fairlightcnsis, Cypridea ______ 14

hawkhurstensis, Cypridea __---____ 14

leonardi, Cypridea _______________ 14

philpottsi, Cypridea __— _.-_._-____ 14

subquadrata, Cypridea ____________ 14

ivadhurstcnsis, Cypridea ___________ 14

lacvis, Cypridea ______________________ 14

Langtonia ._--._--_- — ________________ 13

lata, Cypridea __-__--_-_____--___.___ 14

latiovata, Cypridea (Cyamocypris) ____ 14

Latonia ------------------------------ 8

leonardi, Cypridea laevigata ___________ 14

Limnocypridae ____________________ 8

Limnocypridea ______-____._-.____ 8, 9, 10, 12

abscondida ______________________ 10, 11

albertcnsis __— __ — _____-_--_ 11, 12; pi. 2

bitumulosa _____________________ 10, 11

celtiformis ------------------------ 11

equalis ____.__________________ 11

grammi ________________________ 10, 11

morrisoncnsis __________ 9, 11, 15; pis. 1, 3

subplana ___________.__.______ 10, 11

tumulosa ______________________ 10, 11

Lincocypris ______ — __________________ 11

logronana, Cypridea (Pseudocypridina)

moncta __---____----_---_ 14

longispina, Cypridea ________________ 18, 19

Longispinella __________ 16, 19; pis. 4, 5, 7

Longispinella ___________________ 12, 18, 19

asymmetrica ______________ 15, 16, 17, 18;

pis. 4, 5 

longispina _. — _.------. 16, 19; pis. 4, 5, 7

lubimovae, Cypridea ______-_____--___ 14

M

magna, Cypridea (Pseudocypridina) .__ 14 

moncta, Cypridea (Pseudocypridina) __ 14 

logronana, Cypridea (Pseudocypridina) ____________________ 14

Page

Mongolianella -___--___--_

Morinia __-_-_--__ _ _____-

Morininoidcs ________-___--

morrisoncnsis, Bythocypris

cypris) -- —— __-_- 

Limnocypridea ___-____-- 9,

--__ — __ 12 

_--_- — _ 12 

(Bairdio-

-_.- —— _ 11 

, 15; pis. 1, 3

equalis, Bythocypris (Bairdiocypris) 11

N 

nannorostrata, Cypridea ______ — __ — __ 14

nodifcr, Cypridea (Pseudocypridina)

saluadorensis __-___---__-- 17 

Cypridea salvadorcnsis ____.____--- 14

O

obesa, Cypridea ___________________ — - 14

ovatiformis, Cypridea (Cyamocypris) __ 14

Paleoecology _________--_-_-_----____-- 4

Paracypridca ------------------------- 12

parallels, Cypridea ________________---- 14, 17

Cypridea (Pseudocypridina) ______ 14

Cypridopsis ____-___-_--.--------- 11

philpottsi, Cypridea laevigata __________ 14

picdmonti, Cypridea __----_-----_-_--- 15

Cypridea (Pseudocypridina) ___._- 9, 12,

15, 16, 19; pi. 6

Pseudocypridina ______ — _.__-_---_ 13,15

posticalis, Cypridea ------------------- 14

profusa, Cypridea ______-_-_---_---_-- 14

profinata, Cypridea _______--_---_____- 14

jiropunctata, Cypridea (Cypridea) _____ 18

Pseudocypridina ______-____-------- 12, JJ, 18

inornata __________-___-_---_--__- 15

picdmonti ------------------------ 13, 15

sambacMSfs ______________------_- 14

(Pseudocypridina) acutitubcrculata, Cypridea ____-__--_--__----- 15

alacaramac, Cypridea ------------- 14

a/ta formosa, Cypridea ------------ 16

altissima, Cypridea ___--_--___--__ 17 

baidarensis, Cypridea -------------- 17

binodosa, Cypridea ________________ 17

consults, Cypridea ____._--__---_-. 15

demandac, Cypridea _.--_--__-- — _ 14 

dolabrata angidata, Cypridea ______ 16

cllipscloidcs, Cypridea ------------- 14

extenda, Cypridea ---------------- 14

fasciculata, Cypridea ------------- 16

hcnrybelli, Cypridea ..-_-- 9, 10, 16, i?M9;

pis. 3, 8

inornata, Cypridea ___-___-_ 10, iS, 17, 19,

20; pis. 3, 7

fae.i', Cypridea ------------- 16; pis. 3, 7, 8

magna, Cypridea ------------------ 14

moncta, Cypridea _________________ 14

moneta logronana, Cypridea __ — ___ 14 

parallcla, Cypridea --------------- 14

picdmond, Cypridea _____--__ 9, 12, i5, 16,

19; pi. 6 

salvadorcnsis nodifcr, Cypridea ____ 17

salvadorensis, Cypridea _______ 17

scntina, Cypridea _________________ 14

accrata, Cypridea ------------- 14

camelodes, Cypridea __________ 14

dotica, Cypridea ______________ 14

eri.mna, Cypridea ------ ______ 14

fiteriensis, Cypridea _______ — __ 14

rcctidorsata, Cypridea ________ 14

subccntrinoda, Cypridea ___________ 14

subtilis, Cypridea ----------------- 17

unicostata, Cypridea -------------- 15

vitimcnsis, Cypridea ____----__.__ 15

spp __________ — --_---_---_--_ — __ 15

Cypridea ______-_.__-_______ 12, iJ

Q

quadrata, Cypridea 14

Page 

R

rectidorsata, Cypridea (Pseudocypridina) setina --------- _____ 14

redunca, Candona --------------------- 9

comitans, Salvadoriclla ------------ 9

rothi, Trapczoidella _____._ 8, 9, 15, 16, 17, 18;

pis. 1, 2 

rotunda, Cypridea altissima ___________ 14

rotundata, Cypridea ------------------- 14

salvadorcnsis nodifer, Cypridea ___._— 14 

nodifer, Cypridea (Pseudocypridina) 17 

salvadorcnsis, Cypridea ------------ 14

Cypridea (Pseudocypridina) __. 17 

Cypridea (Pseudocypridina) saladorcnsis __-__ — ___------_- 17

Cypridea salvadorcnsis ------------ 14, 15

Salvadoriclla -------------------------- 8, 9

redunca comitans ---------- — __ — - 9

sambaensis, Pseudocypridina ---------- 14

scntina, Cypridea (Pseudocypridina) __ 14 

accrata, Cypridea (Pseudocypridina) 14 

camelodes, Cypridea (Pseudocypridina) ------------------ 14

erumna, Cypridea (Pseudocypridina) -----------_--_--_-- 14

fiteriensis, Cypridea (Pseudocypridina) -------------------- 14

rcctidorsata, Cypridea (Pseudocypridina) -------------------- 14

sou-crbyi, Cypridea -------------------- 14

spinigira, Cypridea ------------------- 14,19

snbccntrinoda, Cypridea (Pseudocypridina) ---------------- — - 14

subplana, Limnocypridea -------------- 10, 11

subquadrata, Cypridea laevigata _--_._- 14 

siibtilis, Cypridea ------ — _____________ 14

Cypridea (Pseudocypridina) ______ 17

subvaldcnsis, Cypridea ---------------- 13,14

Systematic descriptions _--_---___----- 8

tennis, Cypridea --------- —— __-___---_ 14

trapczoidalis, Bythocypris (Bairdiocypris) --------...--------- 8,9

Trapezoidclla ------- 8, 9, 10, 11, 12, 15, 18;

pis. 1, 2 

Trapczoidella _________ —— __.__-__._ 8,12

rothi ----------- 8, 9, 15, 16, 17, 18; pis. 1, 2

trapezoidalis -------- 8, 9, 10, 11, 12, 15, 18;

pis. 1, 2 

Trapezoidellidae _______-___-_--_--— __ 8

trita, Cypridea _-_____- — __ — _________ 14

tucanocl^sis, Cypridea ----------------- 18

tumulosa. Limnocypridea _. —— __-_---. 10, 11

U 

Ulwcllia --- — - — ------ — .------ —— - 12

unicostata, Cypridea _.-__ —— ___.--._-_ 15

Cypridea (Pseudocypridina) ------ 15

uninoda, Cypridea (Cypridea) ___ — ____ 15

USGS Mesozoic collection localities _-__ 5

valdensis, Cypridea ------------------- 15, 17

vidrana, Cypridea --------------------

vitimensis, Cypridea -------------------

Cypridea (Pseudocypridina) ______

W

wadhurstensis, Cypridea laevigata _____ 

u-yomingcnsis, Cypridea (Cypridea) ___

yumcncnsis, Cypridea (Cypridea) _____

Z 

Zcfaina ------------- —— —— —— —— _.

15
PLATES 1-8

Contact photographs of the plates in this report are available at cost, from 

U.S. Geological Survey Library, Federal Center, Denver, Colorado 80225
PLATE 1

FIGURES 1-5, 10. Trapezoidella rothi Sohn, n. sp. (p. 9).

1, 2. Outside and inside views of right valve approx. x 30. Paratype USNM 

242836, Lakota Formation, Edgemont quadrangle, Fall River County, S. 

Dak. USGS colln. 30993, map loc. 9.

3-5. Right, posterior, and left views of carapace approx. X 30. USNM 242837, 

Chilson Member of Lakota Formation, Flint Hill quadrangle, Fall River 

County, S. Dak. USGS colln. 30986, map. loc. 13.

10. Outside view of right valve approx. x 30. Paratype USNM 242838, same

collection as above. 

6-9, 12-17. Trapezoidella trapezoidalis (Roth, 1933) (p. 9).

6-9. Right, dorsal, left, and posterior views of juvenile carapace approx. X 30. 

Holotype USNM 74470. Lakota Formation, 3 miles (4.8 km) south of 

Piedmont, Meade County, S. Dak.

12-15. Right, dorsal, left, and posterior views of larger carapace approx. X 30. 

Figured specimen USNM 242839. Lakota Formation, Crook County, Wyo. 

USGS colln. 25643, map loc. 6. 

16, 17. Left and posterior views of still larger carapace approx. X 30. Figured

specimen USNM 242840. Same as collection above. 

11, 18-30. Limnocypridea morrisonensis (Roth, 1933) (p. 11).

11. Inside view of nested valves, approx. X 15. Figured specimen USNM 

242841. Probably topotypes from Roth's type-locality, USGS colln. 30997, 

map loc. 8.

18-21, 23, Right views of eight carapaces showing variation in lateral outlines ap24, 29, 30. prox. x 15. Figured specimens USNM 242842-242849. Lakota Formation, 

probably topotypes from Roth's type-locality, 3 miles (4.8 km) south of 

Piedmont, S. Dak. USGS colln. 30997, map loc. 8.

22, 25-28. Right, dorsal, ventral, and left views of holotype approx. X 10, and right 

view approx. x 30 for relative size to other species on plate. Holotype 

USNM 74469. Roth's type-locality.
GEOLOGICAL SURVEY PROFESSIONAL PAPER 1069-PLATE 1

TRAPEZOIDELLA, LIMNOCYPRIDEA
PLATE 2

[SEM means scanning electron micrograph]

FIGURES 1-6. Limnocypridea? albertensis (Loranger, 1951) (p. 12).

1-3. Ventral, left, and right views of carapace approx. X 30, original of Loranger's pi. 2, fig. 21. Paralectotype, Geol. Survey of Canada No. 48736. 

Blairmore Formation (Aptian-Albian), Imperial's Deville No. 1 well, 

3,402-3,416 feet (1,037-1,041 m).

4-6. Dorsal, right, and left views of carapace, approx. X 30, original of Loranger's pi. 2, fig. 28. Lectotype, Geol. Survey of Canada No. 48735. Blairmore Formation (Aptian-Albian), Imperial's Looma No. 1 well, core at 

3,947-3,978 feet (1,203-1,212 m). 

7-29, 33. Trapezoidella rothi Sohn, n. sp. (p. 9).

7-9. Dorsal, right, and left views of carapace, SEM approx. X 30. Paratype 

USNM 242851. Upper part of Chilson Member of Lakota Formation, Fall 

River County, S. Dak. USGS colln. 30985, map loc. 13.

10, 11. Inside and outside views of right valve, approx. X 30. Paratype, USNM 

242852. About 10 feet (3 m) above base of Chilson Member of Lakota 

Formation, Fall River County, S. Dak., USGS colln. 30990, map loc. 14.

12-15. Dorsal, right, left, and ventral views of carapace, approx. X 30. Paratype 

USNM 242853. Unit 2 of Chilson Member of Lakota Formation, AEC 

Diamond Drill Hole RE-17, core at 289.5 feet (88 m), Fall River County, 

S. Dak. USGS colln. 30988, map loc. 16.

16, 17. Left and right views of crushed carapace, approx. X 30. Paratype USNM 

242854. Same unit and drill hole as above, core at 283.5 feet (86.4 m). 

USGS colln. 31006, map loc. 16.

18, 19. Left and right views of partly broken carapace, approx. X 30. Paratype 

USNM 242855. Unit 2 of Chilson Member of Lakota Formation, Fall River 

County, S. Dak. USGS colln., 30986, map loc. 13.

20. Left view of crushed carapace, approx. X 30. Paratype USNM 242856. 

Unit 2 of Chilson Member of Lakota Formation, Fall River County, S. 

Dak. USGS colln. 31007, map loc. 17.

21. Left view of carapace, approx. X 30. Paratype USNM 242857, Lakota 

Formation, Fall River County, S. Dak. USGS colln. 26468, map loc. 10.

22. Left view of carapace, SEM approx. X 30. Paratype USNM 242858. Upper 

part of Chilson Member of Lakota Formation, Fall River County, S. Dak. 

USGS colln. 30985, map loc. 13.

23. Left view of carapace, approx. X 30. Paratype USNM 242859. Chilson 

Member of Lakota Formation, Fall River County, S. Dak. USGS colln. 

30994, map loc. 11. 

24, 25. Outside view of left valve SEM approx. X 30, hinge view, SEM approx.

X 100. Paratype USNM 242860. Same collection and locality as fig. 22. 

26-29. Posterior, dorsal, left, and right views of carapace, SEM approx. X 30.

Holotype, USNM 242861. Same collection and locality as fig. 22. 

33. Right view of carapace, SEM approx. X 75. Paratype USNM 242862. Same

collection and locality as fig. 22. 

30-32. Trapezoidella trapezoidalis (Roth, 1933) (p. 9).

Left, dorsal, and right views of carapace, approx. X 30. Paratype USNM 

242863. Lakota Formation, Crook County, Wyo. USGS colln. 26941, map 

loc. 7. 

34-36. Trapezoidella rothi Sohn, n. sp. (p. 9).

Detail of adductor muscle attachment scar, SEM approx. x 180, inside and 

outside views of fragment of left valve approx. X 30. Figured specimen 

USNM 242864. Lakota Formation, Fall River County, S. Dak. USGS 

colln. 30993, map loc. 9.
GEOLOGICAL SURVEY PROFESSIONAL PAPER 1069-PLATE 2

LIMNOCYPRIDEA?, TRAPEZOIDELLA
PLATE 3

[SEM means scanning electron micrograph)

FIGURES 1-13. Cypridea (Pseiidocypridma) laeli Sohn, n. sp. (p. 16).

1-4. Ventral (anterior to left) dorsal (anterior to right), right, and left views 

of four carapace approx. X 30. Paratypes USNM 242865-242868. Lakota Formation, Crook County, Wyo. USGS colln. 31001, map loc. 5. 

5-7. Dorsal (anterior to left), right, and ventral (anterior to left) views of 

carapace, SEM approx. X 30. Paratype USNM 242869. Same collection 

as above. 

8, 9. Dorsal (anterior to right), and left views of carapace, SEM approx. x 30.

Paratype USNM 242870. Same collection as above.

10-13. Left, dorsal (anterior to left), right, and ventral (anterior to right), 

views of carapace. Holotype USNM 129644. Lakota Formation, Crook 

County, Wyo. USGS colln. 25645, map loc. 5. Same specimen as Sohn, 

1958, p. 1, figs. 9-12. 

14-17. Cypridea (Pseudocypridi-na) henrybelli Sohn, n. sp. (p. 17).

Left, dorsal (anterior to right), right, and ventral (anterior to right) views 

of carapace, approx. X 30. Holotype USNM 129645. USGS colln. 25460, 

map loc. 17. Same specimen as Sohn, 1958, pi. 1, figs. 13-15. 

18-23. Cypridea (Pseiidocypridma)inornata (Peck, 1941) (p. 15).

18, 19. Dorsal (anterior to right) and right views of carapace, instar, approx.

X 30. Figured specimen USNM 242873. Same collection as figs. 1-9. 

20, 21. Dorsal and right views of carapace, adult, approx. X 30. Figured specimen 

USNM 129647. Same collection as figs. 10-13. Same specimen as Sohn, 

1958, pi. 1, figs. 17, 18. 

22, 23. Right and left views of carapace, approx. x 30. Figured specimen USNM

242874. Same collection as figs. 1-9. 

24, 25. Cypridea (Psendocypridina) laeli Sohn, n. sp. (p. 16).

Ventral (anterior to left), and left views of carapace, SEM approx. X 30.

Paratype USNM 242871. Same collection as figs. 1-9. 

26-29. Limnocypridea morrisonensis (Roth, 1933) (p. 11).

Dorsal (anterior to right), left, posterior, and right views of presumed 

male carapace, approx. x 15. Figured specimen USNM 242850. Lakota 

Formation, Roth's type locality, Meade County, S. Dak. USGS colln. 30997, 

map loc. 8. 

30, 31. Candona sp. (p. 11).

Left lateral views of female and male valves, approx. X 30. Figured specimens USNM Crustacea 168192, 168193. Collected alive in Kenilworth 

Aquatic Gardens, Washington, D.C. 

32. Cypridea (Psendocypridina) laeli Sohn, n. sp. (p. 16).

Left valve hinge approx. X 130. Paratype (broke during removal from stub) 

USNM 242872. Same collection as figs. 1-9.
GEOLOGICAL SURVEY PROFESSIONAL PAPER 1069-PLATE 3

CYPRIDEA (PSEUDOCYPRIDINA), LIMNOCYPRIDEA, CANDONA
PLATE 4

[Scanning electron micrographs (SEM) approx. X 90, except tig. 14 which is approx. 

X 200, reduced 1/3 for publication]

FIGURES 1-6. Longispinella longispina (Peck, 1941) (p. 19).

1-3. Left, right, and dorsal views of carapace, presumed male. Figured specimen, 

topotype USNM 242875. Kootenai Formation, T. 18 N., R. 4 E., Cascade 

County, Mont. Peck's colln. 23 (1941, p. 288).

4-6. Left, ventral, and right views of carapace, presumed male. Figured specimen, topotype USNM 242876. Same collection as above. 

7-20. Longispinella asymmetrica Sohn, n. gen., n. sp. (p. 18).

7-9. Right, ventral (anterior to left), and left views of carapace. Paratype 

USNM 242877. Unit 2 of Chilson Member of Lakota Formation, Fall 

River County, S. Dak. USGS colln. 26098, map. loc. 17. 

10-13. Posterior oblique, dorsal, right, and left views of carapace. Paratype USNM

242878. Same collection as above. 

14-17. Right, ventral, detail of left anterior, and left views of carapace. Paratype

USNM 242879. Same collection as above.

18-20. Left, dorsal, and right views of carapace converted to fluoride. Paratype 

USNM 242880. Same collection and locality as above.
GEOLOGICAL SURVEY PROFESSIONAL PAPER 1069—PLATE 4

LONGISPINELLA
PLATE 5

| Scanning electron micrographs approx. X 90, except iig. 20 which is approx. 

X 250, reduced 1/3 for publication 1

FIGURES 1-7. Longispmella asymmetrica Sohn, n. sp. (p. 18).

1-3. Dorsal, right, and ventral views of carapace. Paratype USNM 242881. Unit 

1 of Chilson Member of Lakota Formation, Fall River County, S. Dak. 

USGS colln. 31130, map loc. 14. 

4-7. Right, ventral, dorsal, and left views of carapace. Holotype USNM 242882.

Same collection as above. 

8-12. Longispinella longispina (Peck, 1941) (p. 19).

8-10. Left, dorsal, and right views of carapace, presumed male. Figured specimen USNM 242884. Lowermost part of Lakota Formation, Fall River 

County, S. Dak. USGS colln. 31154, map loc. 12. 

11, 12. Left and dorsal views of carapace, presumed female. Figured specimen

USNM 242885. Same collection as above. 

13-16. Longispinella asymmetrica Sohn, n. sp. (p. 18).

Left, ventral, dorsal, and right views of carapace. Paratype USNM 242883.

Same collection as figs. 1-7. 

17-23. LongispmeHa longispina (Peck, 1941) (p. 19).

17-19. Right, left, and dorsal views of carapace, presumed male. Figured specimen USNM 242886. Lower part of Lakota Formation, Fall River County, 

S. Dak. USGS colln. 31153, map loc. 12.

20-23. Detail of anterior of left valve, left, dorsal, and right views of carapace, 

presumed female. Figured specimen USNM 242887. Same collection as 

above.
GEOLOGICAL SURVEY PROFESSIONAL PAPER 1069—PLATE 5

LONGISPINELLA
PLATE 6

[Scanning electron micrographs (SEM) taken approx. x 60, 

and where indicated larger, reduced 1/2 for publication |

FIGURES 1-47. Cypridea (Pseudocypridina) piedmonti Roth, 1933 (p. 15).

1-4. Left, posterior, right, and dorsal (anterior to right) views of carapace.

Figured specimen USNM 242888. Probably Unit 2 of Chilson Member of

Lakota Formation, Meade County, S. Dak. USGS colln. 31171, map loc. 8.

5-7. Left, dorsal (anterior to right), and posterior views of carapace. Figured

specimen topotype USNM 242889. Probably Unit 2 of Chilson Member of

Lakota Formation, Meade County, S. Dak. USGS colln. 30997, map loc. 8.

8, 9. Left valve and posterior of carapace. Figured specimen USNM 242890.

Same collection as figs. 1-4.

10-13. Left, posterior, right, and ventral (anterior to left) views of carapace. 

Figured specimen, topotype USNM 242891. Same collection as figs. 5-7.

14-17. Right, dorsal (anterior to right), left, and posterior views of carapace. 

Figured specimen USNM 242892. Same collection as figs. 1-4.

18-20. Dorsal, posterior, and right views of carapace. Figured specimen USNM 

242893. Same collection as figs. 1-4.

21, 22. Left and posterior views of carapace. Figured specimen USNM 242894. 

Same collection as figs. 1-4.

23-27. Left (anterior imbedded in mounting medium), posterior, right, dorsal (anterior to left), and ventral (anterior to left) views of carapace. Holotype USNM 74473. Probably Unit 2 of Chilson Member of Lakota Formation, Meade County, S. Dak. Roth's type-locality, map loc. 8.

28-33. Detail of dorsoanterior approx. X 50, left, posterior, right, ventral (anterior to left), and dorsal (anterior to right) views of carapace. Figured 

specimen USNM 242895. Unit 2 of Chilson Member of Lakota Formation, 

Fall River County, S. Dak. USGS colln. 26089, map loc. 17.

34 37. Right valve, detail of hinge approx. X 50, inside, outside, and dorsal 

views. Figured specimen USNM 242896. Same collection as figs. 28-33.

38-40. Left valve, detail of hinge approx. X 75, outside and inside views. Figured 

specimen USNM 242897. Same collection as figs. 1-4.

41-47. Ventral oblique, left, posterior, dorsal oblique (anterior to left), right, ventral (anterior to left), and dorsal (anterior to right) views of carapace. 

Figured specimen USNM 242898. Same collection as figs. 28-33.
GEOLOGICAL SURVEY PROFESSIONAL PAPER 1069—PLATE €

CYPRIDEA (PSEUDOCYPRIDINA)
PLATE 7

[Scanning electron micrographs (SEM) uot wilm-ed for publication]

FIGURE 1. Cypridea (Pseudocypridina) laeli Sohn, n. sp. (p. 16).

Dorsal view of carapace, approx. X 75. Same specimen as pi. 3, figs. 24, 25.

Chilson Member of Lakota Formation, Crook County, Wyo. 

2-4. Cypridea (Pseudocypridina) momata (Peck, 1941) (p. 15).

Ventral (anterior to left), posterior, and right views of carapace, approx. 

X 60. Figured specimen USNM 242899. Lakota Formation, Crook County, 

Wyo. USGS colln. 25645, map loc. 5. 

5-7. Longispinella longispina (Peck, 1941) (p. 19).

Detail of anterior portion of left valve, approx. X 300, dorsal and left views 

of carapace, approx. X 90. Figured specimen, presumed male, USNM 

12943. Limestone near middle part of Lakota Formation, Crook County, 

Wyo. USGS colln. 25644, map loc. 5. The same specimen was illustrated 

by Sohn (1958, pi. 1, figs. 1-4). 

"Cypridea" sp. 1 (p. 18).

Dorsal, posterior, anterior, left, and right views of carapace, approx. X 90. 

Figured specimen USNM 242900. Unit 2 of Chilson Member of Lakota 

Formation, Fall River County, S. Dak. USGS colln. 26098, map loc. 17.
GEOLOGICAL SURVEY PROFESSIONAL PAPER 1069-PLATE 7

CYPRIDEA (PSEUDOCYPRIDINA), LONGISPINELLA, "CYPRIDEA"
PLATE 8

I All scanning electron micrographs (SEM), photographed approx. X 90, reduced 1/2 for publication]

FIGURES 1-25. Cypridea (Pseudocypridma) henrybelli Sohn, n. sp. (p. 17).

1-3. Left, dorsal (anterior to right), and right views of carapace with two nodes

on each valve. Paratype USNM 242901. Unit 1 of Chilson Member of

Lakota Formation, Fall River County, S. Dak. USGS colln. 31130, map

loc. 14.

4-6. Left, dorsal (anterior to right), and right views of carapace with two nodes

on each valve. Paratype USNM 242902. Same collection as above. 

7-9. Left, dorsal (anterior to left), and right views of carapace with two nodes

on each valve. Paratype USNM 242903. Same collection as above. 

10-12. Left, dorsal (anterior to right), and right views of carapace with two nodes

on each valve. Paratype USNM 242904. Same collection as above.

13-16. Left, dorsal (anterior to left), ventral (anterior to right), and right views 

of carapace with two nodes only on left valve. Paratype USNM 242905. 

Same collection as above.

17-20. Left, dorsal oblique (anterior to right), posterior, and right views of carapace with two nodes only on left valve. Paratype USNM 242906. Same 

collection as above.

21-25. Left, ventral (anterior to right), posterior, dorsal oblique (anterior to 

right), and right views of carapace with one node only on anterior part 

of left valve. Paratype USNM 242907. Same collection as above. 

26-30. Cypridea (Pseudocypridina) laeli Sohn, n. sp. (p. 16).

Right, posterior, dorsal (anterior to right), ventral (anterior to left), and 

left views of carapace. Paratype USNM 242908. Lakota Formation, Crook 

County, Wyo. USGS colln. 31001, map loc. 5.
GEOLOGICAL SURVEY PROFESSIONAL PAPER 1069—PLATE 8

CYPRIDEA (PSEUDOCYPRIDINA)

irU.S. GOVERNMENT PRINTING OFFICE: 1979 O— 281-359'12