U.S. GEOLOGICAL SURVEY PROFESSIONAL PAPER 1228-C
Tertiary Marine Pelecypods of 

California and Baja California: 

Plicatulidae to Ostreidae

By ELLEN JAMES MOORE

PALEONTOLOGY OF CALIFORNIA AND BAJA CALIFORNIA

U.S.GEOLOGICAL SURVEY PROFESSIONAL PAPER 1228-C

A total of 68 species representing 23 genera 

in the families Plicatulidae, Spondylidae, 

Anomiidae, Limidae, Gryphaeidae, and Ostreidae 

are illustrated, taxonomy revised and updated, 

geographic and geologic ranges given, 

occurrence by geologic formation cited, 

and habitat included when it can 

be confidently inferred

UNITED STATES GOVERNMENT PRINTING OFFICE, WASHINGTON : 1987
DEPARTMENT OF THE INTERIOR 

DONALD PAUL HODEL, Secretary

U.S. GEOLOGICAL SURVEY 

Dallas L. Peck, Director

Library of Congress catalog card no, 86-600557

For sale by the Books and Open-File Reports Section, 

U.S. Geological Survey, Federal Center, Box 25425, Denver, CO 80225
CONTENTS

Page

Abstract __________________________________Cl

Introduction _______________________________ 1

Purpose and scope ________________________ 1

Procedure _ ____________________ 1

Acknowledgments ________________________ 4

Abbreviations ____________________________ 4

Systematics: Pelecypods Continued from Chapter B ______ 5

Superfamily Pectinacea _______ _ _________ 5

Family Plicatulidae ___________________ __ 5 

Genus Plicatula ______________________ 5

Family Spondylidae ____________________ 6

Genus Spondylus _________ ___________ 6

Superfamily Anomiacea ___________________ 9

Family Anomiidae _______________________ 9 

Genus Anomia _________________________ 9

Genus Anomia ? ________________________11 

Genus Placunanomia __________ __________ 11 

Genus Pododesmus _______________________ 13

Superfamily Limacea ________________________13 

Family Limidae __ ______ _______ 13

Genus Lima _________________________13

Genus Acesta _______________________14

Genus Limaria ______________________ 16

Genus Limatula ___ _____ _______ 17 

Genus Limea __ ____________________ 17 

Genus Limea? ________________________ 17

Superfamily Ostreacea _______________________ 17

Family Gryphaeidae ______________________ 17

Subfamily Exogyrinae __________________ 18

Genus Gryphaeostrea _____ ___18

Subfamily Pycnodonteinae _______________ 18 

Genus Pycnodonte __________________ 18

Systematics: Pelecypods Continued from Chapter B 

Superfamily Ostreacea Continued 

Family Gryphaeidae Continued

Subfamily Pycnodonteinae Continued

Genus Pycnodonte? _________________C20

Genus Hyotissa ____________________22

Genus Neopycnodonte _____ 23 

Genus Neopycnodonte? _______________23

Family Ostreidae _____ 24

Subfamily Lophinae _ 24

Genus Lopha __ 24

Genus Lopha? _ 24

Genus Dendostrea __________________25

Genus Dendostrea? _______ 25

Subfamily Ostreinae _ 27 

Genus Ostrea __ 27 

Genus Ostreola ____________________28

Genus Ostreola? ___________________29

Subfamily Ostreinae, incertae sedis __________29

Subfamily Crassostreinae 30 

Genus Acutostrea 30

Genus Acutostrea? __________________32

Genus Saccostrea _______ 32

Genus Striostrea _ 32 

Genus Striostrea? ___________________33

Genus Crassostrea __________________35

Genus Crassostrea? _________________38

Fossil localities 40 

Geologic formations cited for occurrence of pelecypods 41 

References cited __________ 42 

Index __________________________________ 49

ILLUSTRATIONS

	[Plates follow index]

PLATE 1. Plicatula, Spondylus.

2 4. Spondylus.

5. Spondylus, "Spondylus", Anomia.

6. Anomia, Placunanomia.

7-8. Anomia, Placunanomia, Lima, Pododesmus.

9. Spondylus, Limatula, Lima, Pododesmus, Acesta.

10. Lima, Limea?, Acesta, Limaria.

11. Pycnodonte, Dendostrea?.

12. Pycnodonte, Dendostrea?, Striostrea?.

13. Pycnodonte, Dendostrea?, Acutostrea.

14. Pycnodonte?, Dendostrea?, Acutostrea.

15. Pycnodonte?, Dendostrea?.

16. Hyotissa, Acutostrea, Pycnodonte?, Striostrea?, Dendostrea?.

17. Lopha, Pycnodonte?.

18. Saccostrea, Pycnodonte?.

19. Gryphaeostrea, Crassostrea?, Pycnodonte?.

20. Crassostrea?.

21. Pycnodonte?, Crassostrea?.

22. Crassostrea?, Striostrea?.
IV CONTENTS

PLATE 23. Crassostrea.

24. Crassostrea, Crassostrea?.

25. Striostrea?, Crassostrea?.

26-27. Crassostrea, Crassostrea?, Striostrea?.

28. Crassostrea.

29. Crassostrea, "Ostrea", Acutostrea, Striostrea?.

30. Ostreola, Acutostrea, Ostrea.

31. Dendostrea?, Ostreola?.

32. Dendostrea?, Ostreola?, Neopycnodonte?, Acutostrea

33. Acutostrea, Acutostrea?, Ostreola?.

34. Ostreola?, Dendostrea?, Acutostrea.

FIGURE 1. Map showing divisions used in California for geographic range of species of pelecypods, Plicatulidae to Ostreidae C2 

2. Map showing divisions used in Baja California peninsula for geographic range of species of pelecypods,

Plicatulidae to Ostreidae ________________ 3

TABLES

	Page

TABLES 1-10. Geologic and geographic distribution:

1. Plicatula _________________________________________________ C5

2. Spondylus _ _________________ 6

3. Anomia, Anomia? __________________ _ 9

4. Placunanomia, Pododesmus ______ 12

5. Lima, Acesta, Limaria, Limatula, Limea? 14

6. Gryphaeostrea, Pycnodonte, Pycnodonte? ___________ 18

7. Hyotissa, Neopycnodonte?, Lopha?, Dendostrea? ______ 23

8. Ostrea, Ostreola, Ostreola?, "Ostrea", Acutostrea, Acutostrea? 27

9. Saccostrea, Striostrea ? ___________________ 33

10. Crassostrea, Crassostrea? _____ 36
PALEONTOLOGY OF CALIFORNIA AND BAJA CALIFORNIA

TERTIARY MARINE PELECYPODS

OF CALIFORNIA AND BAJA CALIFORNIA:

PLICATULIDAE TO OSTREIDAE

By ELLEN JAMES MOORE

ABSTRACT

The description of the mollusks in the Tertiary formations of California and Baja California is continued from Chapter B. The families 

Plicatulidae, Spondylidae, Anomiidae, Limidae, Gryphaeidae, and 

Ostreidae, which represent 23 genera and 68 species, are covered in 

this chapter; other chapters will follow in zoologically systematic 

order.

All the Tertiary species that were described from or are known to 

occur in the Californias are included, along with their original descriptions and their distribution by formation. The holotype is illustrated 

where feasible, and tables show the geologic and geographic occurrence of the species in each genus.

Of the 23 genera studied, the Gryphaeidae and Ostreidae were most 

in need of taxonomic revision, and only 1 of the 39 species originally 

assigned to Ostrea is retained in that genus.

The marked response of oysters to their particular habitats causes 

more variation in shell character within individual species than in any 

other group of bivalves. The size, shape, and sculpture are all affected 

by substrate, by crowding, and even by the intensity of available light.

The abundance and gigantic size of Crassostrea and Striostrea 

during Miocene time in California parallels that of the pectinids 

during the same time period, just prior to the well documented cooling 

trend that reached its nadir during the Pleistocene. This population 

and gigantism explosion may be related to shallow, restricted seaways 

fed by rivers and streams rich in nutrients, in addition to the known 

relationship to the temperature of the seas.

INTRODUCTION

PURPOSE AND SCOPE

The description and illustration of the Tertiary 

marine mollusks of California and Baja California 

started in Chapter A is continued in this chapter, which 

treats the families Plicatulidae to Ostreidae.

A total of 68 species assigned to the included families 

occur in the geographic study area. For convenience of 

reference, the figures showing the geographic divisions 

used for the Californias are reproduced (figs. 1, 2).

PROCEDURE

All Tertiary marine mollusks originally described 

from California and the Baja California peninsula, and 

all species originally described from other geographic 

localities but known to occur in the Tertiary of the Californias, are included in this study. All positively identified species that have been found on faunal lists are also 

included. In genera that are extremely rare, I have 

included species that are only questionably identified.

In this work, species are arranged systematically following the order of families, genera, and subgenera 

given in the Treatise (Moore, 1969; 1971). The order in 

which families are arranged and the generic and subgeneric categories have generally not been modified, 

except in a few cases. Most modifications made reflect 

either definitive papers published after publication of 

the Treatise or works published earlier but not cited in 

it. Within the systematic groups, species are arranged 

by geologic age, beginning with the oldest species and 

ending with the youngest.

Some of the names of genera and subgenera adopted 

in this paper have not been used before for eastern 

Pacific Tertiary species. Brief synopses of generic and 

subgeneric characters are given in the appropriate 

places; more complete synopses will be found in the 

Treatise (Moore, 1969; 1971), in Keen (1971), in Hertlein 

and Grant (1972), and in Olsson (1961). For genera and 

subgenera that are not included in the Treatise, complete descriptions are given in the text.

Distribution tables are included to show graphically 

the geographic and geologic distribution of species 

within each family. To facilitate finding a specific taxon, 

the species are listed alphabetically under genus and 

subgenus in the tables.

The synonymy for each species includes the original 

citation and subsequent substantive references. The

Ci
C2 PALEONTOLOGY OF CALIFORNIA AND BAJA CALIFORNIA

> SAN FRANCISCO 

O

SANTA CRUZ

- 

San Miguel Island

Santa Rosa Island

San Nicolas Islan

150 

I

200 KILOMETERS _ . . San Clemente Island

FIGURE 1. Divisions used for geographic ranges of species of pelecypods, Plicatulidae to Ostreidae, reported from California. Heavy solid lines 

indicate no rthern, middle, and southern divisions; dashed lines within southern region divide Channel Islands area.
TERTIAEY MARINE PELECYPODS: PLICATULIDAE AND OSTREIDAE

116° 114° 112° 110°

C3

Isla Santa Magdalena

Bahia Magdalena

0 50 100 150 200 KILOMETERS 

I I I I

26° _

FIGURE 2. Divisions used for geographic ranges of species of pelecypods, Plicatulidae to Ostreidae, reported

from Baja California peninsula.
C4 PALEONTOLOGY OF CALIFORNIA AND BAJA CALIFORNIA

accuracy of identifications cited in subsequent references in the synonymy has not been verified.

The type is usually that of the author of the original 

description or of later workers who selected a lectotype 

or neotype. Where the original locality description is so 

vague that it is of little use, the type locality is described 

as corrected or modified by other workers such as Keen 

and Bentson (1944) and the modifications given within 

brackets. All other localities are cited as originally 

described except that the formation given is that currently used.

Previously published supplementary descriptions 

and comparisons are included and I have supplemented 

this in the section headed "Comments". For most 

descriptions, my comments are based only on examination of primary type material.

All available published data for each species have 

been included in the section on geographic and geologic 

age range, including that contained in faunal lists when 

the identification is unqualified. Age ranges have not 

been refined within epochs. Where a stage name the 

same as a formation name is used, it is placed in quotes 

to distinguish it from the rock unit.

The divisions used here to indicate the approximate 

geographic range of species within California based on 

county distribution are northern, middle, and southern 

(fig. 1); the divisions for the Baja California peninsula, 

Norte and Sur (fig. 2) (tables 1-10).

An attempt has been made to include all citations to a 

species that are unqualified and every geologic formation in which it is reported to occur in the Californias. 

The assumption has been made that all identifications 

of species are correct unless there is strong evidence to 

the contrary. The stratigraphic nomenclature used 

herein is that of the author(s) cited and does not necessarily agree with that of the U.S. Geological Survey. The 

age given for the stratigraphic units follows the classification of geologic time currently used by the U.S. Geological Survey. (See "Geologic Formations Cited for 

Occurrence of Pelecypods" at end of paper.) Each formation listed is followed by the name of the author and date 

of publication of the work from which it was obtained. 

More than one reference to a formation is given where it 

might be useful to the reader. The list of formations 

given for species occurrence should not be considered 

complete or necessarily accurate. Many western American Tertiary faunas have not been monographed, and 

their species content is not fully known. It is hoped that 

the list of formational occurrence reported will serve as 

a framework upon which the true distribution of each 

species can be built.

The type specimens were all photographed by Kenji 

Sakamoto, U.S. Geological Survey. Owing to the fact 

that the specimens photographed were borrowed from

other institutions, Sakamoto did not use his usual technique of opaquing specimens for photography 

(Sakamoto, 1973). The holotype of each Tertiary species 

is figured if the type is extant. Holocene type specimens 

have not been figured; specimens considered to be of the 

same species by authors such as Durham (1950) and 

Hertlein and Grant (1972) are used for these illustrations, and this information is included in the plate explanation.

ACKNOWLEDGMENTS

Kiyotaka Chinzei, University of Tokyo, Japan, A. 

Myra Keen, Santa Rosa, Calif., and John G. Vedder, U.S. 

Geological Survey, reviewed the manuscript, and their 

pertinent suggestions were most helpful. Harold W. 

Harry, Bellaire, Texas, read the section on oysters, suggested generic revisions based on his studies of soft part 

anatomy and shell characters, and furnished ecologic 

data for the group.

The following individuals made available or loaned 

type material or made arrangements for photography, 

and I am indebted to them: Barbara A. Bedette, U.S. 

Geological Survey; Frederick J. Collier, National 

Museum of National History; Vickie Kohler, Museum of 

Comparative Zoology; Carole J. Hickman, University of 

California at Berkeley; Barry Roth, California Academy 

of Sciences; Lou Ella Saul, University of California, Los 

Angeles, Charles L. Powell, II, U.S. Geological Survey, 

Menlo Park, Calif., Carol C. Jones, Philadelphia Academy of Sciences; Frederick R. Schram, San Diego Natural History Museum; Druid Wilson, Smithsonian 

Institution; and Edward C. Wilson, Los Angeles County 

Natural History Museum.

Mildred P. James made up cards for each species and 

its occurrences as noted on faunal lists. This was a timeconsuming task, and I thank her for her patience and 

support.

ABBREVIATIONS

ANSP: The Academy of Natural Sciences of Philadelphia, Philadelphia, Pa.

BM (NH): British Museum of Natural History, London, 

England.

CAS: California Academy of Sciences, San Francisco, 

Calif.

LAM: Los Angeles County Museum of Natural History, 

California.

MCZ: Harvard Museum of Comparative Zoology, 

Cambridge, Mass.

SDNM: San Diego Natural History Museum, California.

CAS/SU: Stanford University, Stanford, Calif. [The
TERTIARY MARINE PELECYPODS: PLICATULIDAE AND OSTREIDAE C5

Stanford University collections are now housed at the 

California Academy of Sciences.]

SU: Stanford University, Stanford, Calif.

UC: University of California, Berkeley.

UCMP: University of California, Museum of Paleontology, Berkeley.

UCR: University of California at Riverside.

USGS: U.S. Geological Survey, Washington, B.C., 

Cenozoic locality register.

USGS M: U.S. Geological Survey, Menlo Park, Calif, 

Cenozoic locality register.

USNM: National Museum of Natural History, Washington, B.C.

UW: University of Washington, Seattle, Wash.

SYSTEMATICS: PELECYPODS CONTINUED 

FROM CHAPTER B

Superfamily PECTINACEA

Family PLICATULIDAE 

Genus PLICATULA Lamarck, 1801

Subequivalve or with right valve usually more convex, cardinal area 

small, resilium pit acutely triangular, adductor scar in relatively posterior position.

Subgenus PLICATULA

Auricles absent or ill-defined, most species with radial sculpture 

and imbricating concentric lamellae; short spines common.

Geographic range. Living: restricted to tropics; fossil: cosmopolitan.

Geologic range, Triassic to Holocene (table 1).

Habitat. At depths from intertidal zone to 140 m in the eastern 

Pacific (Bernard, 1983, p. 24).

Plicatula ostreiformis Stanton 

Plate 1, figures 1-3

Plicatula ostreiformis Stanton, 1896, p. 1038, pi. 63, figs. 5-6.

Plicatula ostreaformis Stanton. Dickerson, 1914, p. 151, pi. 9, fig. 12 

[error for ostreiformis].

Original description. "Shell large, irregularly ovate in outline, but 

varying considerably in this respect; valves subequal, the right one 

being usually slightly convex and the left flattened or a little concave in 

the middle; test unusually thick; surface with obscure radiating plications and irregular pits."

Syntypes. USNM 157838.

Type locality. One mile [1.6 km] southeast of Lower Lake [NE1/4, T. 

12 N., R. 7 W.], Lake County, Calif.. Martinez Formation, Paleocene.

Supplementary description. "An average specimen measures 52 

mm. in length, 39 mm. in breadth, and 19 mm. in greatest convexity of 

the two valves united.

"Internal casts show impressions of the characteristic hinge of 

Plicatula." (Stanton, 1896, p. 1038)

Geographic range. Northern California.

Geologic range. Paleocene.

Occurrence in California. Paleocene: Martinez Formation 

(Dickerson, 1914).

Plicatula penicillata Carpenter 

Plate 1, figures 4, 6, 8, 9

Plicatula penicillata Carpenter, 1857, p. 155-156. Durham, 1950, p. 69, 

pi. 13, figs. 2,5. Olsson, 1961, p. 154-155. Keen, 1971, p. 94, fig. 208.

Original description. "P. t. alba, brunneo saepe tenue penicillata, 

elongata, haud valde costata, margine plerumque plicata; dentibus 

cardinalibus elongatis, rugosis, externis magnis valde extantibus; 

intermis angustis, ligamentum minimum tabulatum amplectentibus; 

cicatrice musculari subcirculari seu subovali."

Holotype. BM(NH) Tablet 701; missing?

Type locality. Mazatlan, Mexico.

Supplementary description. "A very young valve .15 across is not 

plicated: a larger flat specimen on Crepidula is ribbed, but scarcely 

plaited at the margin: a still larger one is but very indistinctly ribbed. 

A swollen short specimen, grown on a spine of Murex nigritus, is 

rather strongly plicated; while the largest ***, grown between two 

folds of Chama, scarcely displays crenations, except near the hinge. 

The finest grown specimen displays the following characters: margin 

scarcely plicate, internally finely crenated on each side of the hinge: a 

deep hollow in each valve running up inside the umbos: central teeth 

(on the attached valve) joined together for more than half their height,

TABLE 1. Geologic and geographic distribution of the genus Plicatula in the eastern Pacific region 

[H=Holocene; Pl=Pliocene; Pa=Paleocene]

Species California

Northern Middle Southern

Baja California

Norte Sur

Central 

or South 

America

Genus Plicatula

ostreiformis Stanton............

penicillata Carpenter...........

spondylopsis Rochebrune.....

Pa

PI 

PI toH
C6 PALEONTOLOGY OF CALIFORNIA AND BAJA CALIFORNIA

holding the ligament, which is extremely small, tubular, only exposed 

at the extremities, and running up to the umbos, though not exposed 

(or scarcely covered) as in Spondylus, but nearer the interior of the 

shell. In the free valve, the ligamental tube rises up separating the pits 

of the inner teeth. In this specimen the muscular scar is almost round; 

in another, rather oval. The valves are held together by the interlocking of the large rugose teeth.' (Carpenter, 1857, p. 156)

"Shell variable in size and shape from nearly circular, flattened 

forms to irregularly humped, elongate-ovate types, the lower valve is 

usually broadly attached over most of its surface. Upper valve may 

show a few, irregular, ill-defined riblets around the margin or the 

whole surface may be flat and plain or with an occasional short, hollow, 

spinelike elevation rising above it." (Olsson, 1961, p. 154).

Geographic range. Living: Galapagos Islands and Ecuador; fossil: 

Baja California Sur.

Occurrence in Baja California Sur. Pliocene: Marquer Formation 

(Durham, 1950).

Habitat. Intertidal zone (Bernard, 1983, p. 24) in rock crevices or 

inside dead shells (Keen, 1971).

Plicatula spondylopsis Rochebrune

Plate 1, figures 7, 10

Plicatula spondylopsis Rochebrune, 1895, p. 242. Hertlein, 1934a, p. 

62, pi. 21, fig. 9. Durham, 1950, p. 69, pi. 15, fig. 2. Olsson, 1961, p. 

155. Keen, 1971, p. 94, 96, fig. 209.

Original description. "Testa transverse ovato rotundata, 

crassissima, affixa; valvis radiatim costato sulcatis, costis squamis 

imbricatis ornatis; marginibus intense dentatis; extus sordide 

lilacina, intus alba."

Holotype. In Paris Museum.

Type locality. Laguna des Isles de San Jose, Golfo de California.

Supplementary description. "Shell roughly trigonal in shape, 

ornamented by coarse radial plaited sculpture, which, however, may 

be partially or almost wholly absent on some specimens; two hinge 

teeth in each valve *** Muscles scar nearer the posterior margin." 

(Olsson, 1961, p. 155)

Comparison. "Differs from P. penicillata by its smaller area of 

attachment, usually thicker, vaulted shell, and strong ribs. Some 

specimens of Plicatula in the U.S. National Museum, probably belonging to this species are sharply plicated and resemble P. gibbosa 

Lamarck of the Western Atlantic." (Olsson, 1961, p. 155).

Geographic range. Living: Golfo de California to Ecuador and 

Galapagos Islands; fossil: Baja California Sur.

Occurrence in Baja California Sur. Pliocene: Marquer Formation 

(Durham, 1950); Pleistocene: Isla Maria Magdalena (Durham, 1950). 

Habitat. Intertidal zone to 5 m (Bernard, 1983, p. 24).

Family SPONDYLIDAE

"Cemented Pectinacea lacking simple, prismatic calcite; crossedlamellar aragonite prominent, extending well outside pallial line 

nearly to distal margins and covering hinge plate, which bears prominent dysodont teeth. Byssal notch generally present in early growth 

stages and lacking a ctenolium. Mantle curtains without guard tentacles.

"The early ontogeny of the spondylid ligament is precisely like that 

of pectinids, with the central, lamellar portion of the resilium being 

continuous with the anterior and posterior outer ligaments, which 

continue throughout ontogeny along the straight hinge. The lateral 

fibrous pads originate as in the Pectinidae. The grooves, which arise 

late in ontogeny and in many cases become multiple, appear to be 

nothing more than crenulations of the resilium possibly resulting 

from confinement to a narrow space." (Waller, 1978, p. 354).

Geologic range. Jurassic through Holocene.

Genus SPONDYLUS Linne, 1758

Well inflated, mostly with strong radial sculpture, many forms 

spiny or foliaceous; cardinal area of right valve large, triangular; 

crural teeth short, heavy, smooth, or with weakly crenulated edges.

Geologic range. Jurassic through Holocene (table 2).

Geographic range. Living: restricted to the tropics; fossil: cosmopolitan.

Habitat. Spondylus attaches to a rock surface by cementation of 

the right valve, with the exception of the species Spondylus regius 

Linne which is not ordinarily attached. The right valve shows great 

variation depending upon the shape of the object chosen for attachment and the size of the area of the shell attached (Dodge, 1952, p. 125). 

Spondylus is commonly attached to littoral boulders which are usually 

covered by fine growths of algae extending equally over the rock and 

over the shell (Purchon, 1977, p. 178-179).

Spondylus carlosensis Anderson

Plate 1, figure 5

Spondylus carlosensis Anderson, 1905, p. 194, pi. 13, fig. I.Arnold, 1909 

[1910], p. 13, pi. 2, figs. 6, 7. Yokes, 1939, p. 57, pi. 3, figs. 10,13.

TABLE 2. Geologic and geographic distribution of the genus Spondylus in the eastern Pacific region 

[H Holocene; Ple=Pleistocene; Pl=Pliocene; M=Miocene; O=Oligocene; E=Eocene]

Species California

Northern Middle Southern

Baja California

Norte Sur

Central 

or South 

America

Genus Spondylus

bostrychites Guppy..........

calcifer Carpenter............

carlosensis Anderson......

cliffensis M.A. Hanna.....

perrini Wiedey.................

princeps Broderip............

MorPl

M or PI and Pie 

E E 

E 

O and M O and M

PI to H Pie and H

Pie PI toH

H

H
TERTIARY MARINE PELECYPODS: PLICATULIDAE AND OSTREIDAE C7

Original description. "Shell of medium size, sub-circular or obliquely ovate, radially ribbed, convex; costae granulated or obscurely 

spinose; ears and hinge rather broad. The costae radiate in graceful 

sinuous lines from the beak to the margins, and occur in pairs or 

triplets, every second or third rib being more elevated than the others."

Holotype. CAS 56.

Type locality. West and north of Coalinga [NW1/4, sec. 35; T. 20 S., 

R. 14 E.], Fresno County, Calif. Domengine Formation, Eocene.

Supplementary description. "The left valve figured is irregular in 

outline. There is a well-marked regular umbonal area of development 

during the period preceding attachment. The sculpture consists of 

irregular, sharp, round-topped ribs of varying strength, usually large 

ribs alternating with smaller ones, with approximately nine more 

prominent noded ribs subequally spaced over the surface of the valve. 

The ears have been broken.

"The hinge shows long auricular crurae, buttressed ventrally by two 

ridges. The ligamental groove is long and narrow, extending to the 

apex; the crural sockets are subtriangular, set beneath the umbonal 

ends of the crurae." (Yokes, 1939, p. 57)

Comparison. "Spondylus cliffensis *** is a smaller species and 

appears to be characterized by the possession of a longer hinge-line." 

(Yokes, 1939, p. 57).

Geographic range. Middle and southern California.

Geologic range. Eocene.

Occurrence in California. Eocene: Avenal Sandstone (Stewart, 

1946), Domengine and Tejon Formations (Yokes, 1939), and Cozy Dell 

Shale (Weaver and Kleinpell, 1963).

Spondylus cliffensis M. A. Hanna 

Plate 2, figure 3

Spondylus cliffensis M. A. Hanna, 1927, p. 278, pi. 32, figs. 2, 7.

Original description. "Shell small, inequilateral, subcircular, only 

slightly inflated; beaks not prominent or central; hinge line straight; 

surface distorted; ornamented by many small prominent sharp roundtopped ribs of various sizes; usually large ribs alternate with smaller 

ones, every third to fifth large rib more prominent, some of the very 

large ribs appear to be noded; surface crossed by a few indistinct 

growth lines. Dimensions: Altitude 25.5 mm, length 29 mm."

Holotype. UCMP 31025.

Type locality. UC 5062. San Diego County, Calif. Rose Canyon 

Shale (Hanna, 1926), Eocene.

Comparison. Spondylus cliffensis is smaller and seems to have a 

longer hinge line than S. carlosensis (Yokes, 1939, p. 57).

Geographic range. Southern California.

Geologic range. Eocene.

Occurrence in California. Eocene: Rose Canyon Shale (Hanna, 

1927).

Spondylus perrini Wiedey 

Plate 2, figures 1, 4-7; plate 9, figure 1

Pecten (Hinnites)giganteus Gray. Eldridge and Arnold, 1907, pi. 32, fig.

1. Not Pecten (Hinnites) giganteus Gray, 1825. 

Spondylus perrini Wiedey, 1928, p. 138, pi. 17, figs. 6, 7. Loel and Corey,

1932, p. 203, pi. 32, figs, la, lb, Ic, 2. Avila and Weaver, 1969, p. 59,

pi. 34, figs, lla, lib. 

Spondylus inezana Wiedey, 1928, p. 139, pi. 16, figs. 2, 3.

Original description. "Shell large, variable in shape, narrowly 

ovoid, very inequivalve, slightly inequilateral, and very strongly inflated. Anterior dorsal margin not long, quite straight, sharply truncated at the extremity, curving into the broadly rounded basal margin, 

which varies in the degree of curvature owing to the irregularity of

outline of the shell. Posterior dorsal margin short, curving slightly 

from its gently rounded extremity to the hinge line. Umbo of the left 

valve of much greater size than the umbo of the right valve. It is long, 

narrow, highly arched, and projected very markedly over the corresponding feature of the right valve. Umbo of the right valve, if elevated, 

is broadly inflated and quite blunt. The beaks are strongly incurved, 

sharp, and prominent. The sculpturing consists of about twelve or 

more prominent ribs, which are rendered rugose by having small 

spines, which evidently projected sharply forward, now broken away. 

Two or more smaller ribs sculpture the very wide interspaces. Incremental sculpture prominent. The hinge line is very short and the ears 

are very subdued and not prominent. The areas adjacent to the ears 

under the umbones in the combined valves are deeply depressed. 

Length, 85 mm.; breadth, 59 mm.; thickness of the combined valves, 

60 mm.; the left valve projects as much as 20 mm. over the right valve 

in some individuals." (perrini)

"Shell very large, of variable shape, generally subcircular, inequivalve to a large degree, inequilateral, and slightly to moderately 

inflated in most individuals. Anterior dorsal margin often long and 

nearly straight to broadly rounded, more sharply curved at its 

extremity. Basal margin broadly rounded to the posterior dorsal 

extremity, which is a little more sharply rounded. The posterior dorsal 

margin is quite broadly curved but may be straight and long. Umbones 

of subequal size, with the left valve possessing the more prominent 

umbo, which is generally moderately elevated and projected slightly 

over the umbo of the right valve. Beaks in most forms obscured, but 

apparently distant, situated in the anterior portion of the shell and not 

prominent. The left valve is the more strongly convex with occasional 

individuals possessing a nearly flat right valve. Valves sculptured by 

about fifteen prominent radiating ridges, which are narrow and 

appear to have supported numerous small spines, projecting obliquely 

forward. The ribs are more prominent on the central parts of the 

valves and less distinct toward the dorsal margins. Between the heavier ribs is another system of ribbing in the wide interspaces, consisting 

of a rather fine median rib flanked by a varying number of finer threadlike riblets, generally four or more. Concentric wavy lines of growth 

become very prominent on the older parts of the shell and assume the 

character of wavy folds in some of the old individuals. Hinge line not 

long; ears vary in size, projecting moderately on either side of the 

beaks. Length, 72 mm.; breadth, 60 mm.; thickness of the combined 

valves, 45 mm." (inezana)

Holotype. SDNM 28 [SDNM 438 in original text is in error]; of S. 

inezana Wiedey, SDNM 29.

Type locality. SDNM and SU 437. Head of Wiley Canyon [SVz, sec. 

12, T. 3 N., R. 19 W, S.B. Piru quad.], Ventura County Calif. Vaqueros 

Formation, Oligocene and Miocene; of S. inezana, the same locality.

Supplementary description. "Wiedey describes two species, S. perrini and S. inezana, from the same locality and same bed. He states 

that both are very variable and that S. inezana differs in being less 

convex and more circular in outline.

"Study of a large number of specimens from the type and other 

localities in the region has shown that there is but one species present Spondylus perrini Wiedey by priority. The characters of convexity, valve equality, and height of umbo in the left valve are all 

differential in development, variability being of course due to the 

attached mode of habitat. It is the inequivalve variant form described 

by Wiedey as S. perrini, with the lower valve largest, which is usually 

comparatively less convex, not the reverse case as Wiedey states.

"The variant described as 'S. inezana,' in which individual valves 

are more nearly equivalve owing to position of attachment, is usually 

much more convex (the reverse of Wiedey's observations)." (Loel and 

Corey, 1932, p. 203)

Geographic range. Middle and southern California.

Geologic range. Oligocene and Miocene.
C8 PALEONTOLOGY OF CALIFORNIA AND BAJA CALIFORNIA

Occurrence in California. Oligocene and Miocene: Rincon Shale 

(Avila and Weaver, 1969) and Vaqueros Formation (Loel and Corey, 

1932); Miocene: Monterey Shale (Avila and Weaver, 1969).

Spondylus bostrychites Guppy 

Plate 2, figure 2; plate 3, figure 2; plate 9, figures 3, 9

Spondylus bostrychites Guppy, 1867, p. 176. Woodring, 1925, p. 76-77, 

pi. 9, figs. 5-7. G D. Hanna, 1926a, p. 477, pi. 24, figs. 3, 4. Palmer, 

1938, p. 152-155, pi. 1, figs. 1,2; pi. 2, figs. 1, 3, 5; pi. 3, figs. 1-5.

Original description. "Testa subregularis, totondata, ventricosa, 

margine latiusulco, valide denticulateo; extus radiatim costata, costa 

5 and 6 spiniferis; area cardinal! alterius valvae angustissima, 

alterius latiori."

Lectotype. BM(NH) R12833 (Palmer, 1938).

Type locality. Dominican Republic, Gurabo Formation, Miocene.

Supplementary description. " *** specimens *** show that S. 

bostrychites may have concentric ribs over the umbonal portion of the 

right valve. One of the right valve paratypes has conspicuous, concentric ribs on the attached area. The factor of concentric lamellae is 

taken up in detail because authors have used the presence or absence 

of concentric ribs in specific determination. When concentric foliations 

do not occur below the point of adherence they may be present or 

absent and are not of specific value in such species as S. bostrychites 

Guppy.

"Large spines project from the radiating ribs of S. bostrychites. The 

spines are common on the primary ribs but by no means limited to the 

primary ribs as has usually been described by writers. Numerous 

spines may be seen on secondary ribs on paratypes 3 and 4 ***. The 

lectotype has incipient spines on secondary ribs The whole surface of 

the shell is sculptured with scaly, concentric lines giving the radiating 

ribs a lamelliform appearance. Specimens Nos. 3 and 4 have the 

posterior end produced in both valves. Specimen No. 5 shows a slight 

posterior production. Specimen No. 2 has conspicuous, concentric ribs 

on the umbonal region." (Palmer, 1938, p. 152,153).

Geographic range. Southern California; Dominican Republic, 

Jamaica? (Palmer, 1938).

Geologic range. Miocene or Pliocene.

Occurrence in California. Miocene or Pliocene: Imperial Formation (G D. Hanna, 1926a).

Spondylus calcifer Carpenter 

Plate 4, figures 1, 2, 4, 5

Spondylus calcifer Carpenter, 1857, p. 152-155. G D. Hanna, 1926a, p. 

477. Jordan, 1936, p. 112. Olsson, 1961, p. 153. Emerson and 

Hertlein, 1964, p. 350. Keen, 1971, p. 96, fig. 210.

Original description. "S. t. maxima, ponderosa, solida, plerumque 

orbiculari; rubropurpureo; valva superiore costis minimis aculaetis 

creberrimis tecta, hue et illuc costis irregularibus squamosis; squamis 

curtis, ad basim arcuatis, supra foliatis; valva inferiore plerumque 

foliata; area ligamenti magna, ligamenta haud tecto; intus subnacrea, 

limbo lato toto purpureo, seu nonnumquam flavesco-rubente; margine 

extremo creberrime et minute crenulato; dentibus validis; fossa ligamenti canalibus 2-6 parallelis, decussatis; muse. imp. suborbiculari, 

magna."

Syntypes. BM(NH) Tablet 692 to 699.

Type locality. Bay of Panama.

Supplementary description. "Shell of medium or large size, often 

becomes coarse and heavy, rounded or much deformed due to fixation 

and growth, the valves then unsymmetrical in shape and in details of 

sculpture. Attachment is usually by a major part of the surface of the 

lower valve, often along one side of the umbonal slope, the free surface

covered with foliated concentrics which aid in fixation. Surface of the 

upper valve sculptured with numerous rows of radial spines, short or 

of medium length; on the middle of the disk, these spines are largest 

and of uniform size (not divided into sets of primary, secondary, or 

tertiary strength) but diminish in strength towards the sides and may 

be wholly absent from the anterior slope. Radial spaces between the 

ribs is usually wide and plainly marked with fine and coarse threads, 

the middle one sometimes bearing small spines." (Olsson, 1961, p. 153)

Comparison. Young shells of S. calcifer may be hard to distinguish 

from those of Spondylus princeps Broderip; generally the spines are 

more numerous and evenly distributed on S. calcifer (Keen, 1971, p. 

96).

Geographic range. Living: Golfo de California to Ecuador; fossil: 

southern California to Baja California Sur.

Geologic range. Miocene or Pliocene through Holocene.

Occurrence in the Californias. Miocene or Pliocene: Imperial Formation (G D. Hanna, 1926a); Pliocene: Almejas Formation (Jordan and 

Hertlein, 1926b); Pliocene and Pleistocene: Fernando Formation (J. D. 

Mount, written commun., 1971); Pleistocene: unnamed strata at Bahia 

Magdalena (Jordan and Hertlein, 1926b).

Habitat. At a depth of 2-55 m in the eastern Pacific (Bernard, 1983, 

p 27).

Spondylus princeps Broderip 

Plate 3, figures 1, 3-10; plate 4, figures 3, 6; plate 5, figure 6

Spondylus princeps Broderip, 1833, p. 4. Hertlein and Strong, 1946, p.

62- 63. Hertlein, 1957, p. 66-67. 

Spondylus princeps princeps Broderip. Olsson, 1961, p. 152, pi. 22, figs.

4, 8; pi. 86, figs. 1, la. Keen, 1971, p. 96, fig. 211. 

Spondylus crassisquama Lamarck of authors; not Lamarck, 1819. 

Spondylus victoriae Sowerby. Durham, 1950, p. 68, pi. 15, fig. 3; not 

Spondylus victoriae Sowerby, 1859.

Original description. "Spond. testa rotundata, 6-costata, rubra 

spinosa, spinis lingulatis, latis; costis interstitialibus 5 spinosis, 

spinis brevioribus; intus alba, limbo lato profunde plicato, rubro: long. 

5Vs, alt. 5, lat. 3 poll, (spinis haud inclusis)."

Holotype. BM(NH).

Type locality. Isla la Plata, Ecuador. Found attached to coral rocks 

at the depth of 17 fathoms.

Supplementary description. "Shell usually regular in shape, the 

valves seldom showing much distortion, the attachment area usually 

small. Valves not strongly convex. Sculpture of crowded, or close-set, 

short or medium-length, spikelike spines. Primary and secondary 

spines set in six rows, the tertiary in pairs of two in the space between 

the primary and central secondary (four in the larger interspaces 

between the primaries). Inner marginal band wide and deeply colored. 

*** The subspecies is readily distinguished by its crowded, spikelike 

spines, showing no open spaces between them." (Olsson, 1961, p. 152)

Geographic range. Living: Laguna de Scammon to Negritos, Peru, 

and Golfo de California; fossil: Baja California Sur.

Geologic range. Pliocene through Holocene.

Occurrence in Baja California Sur. Pliocene: Almejas (Minch and 

others, 1976) and San Marcos (Durham, 1950) Formations; 

Pleistocene: unnamed strata on Isla Coronados (Emerson and 

Hertlein, 1964).

Habitat. At depth of 2-40 m (Bernard, 1983, p. 27).

"Spondylus estrellanus Conrad" 

Plate 5, figure 2

Spondylus estrallensis Conrad, 1857a, p. 315 [error for estrellanus]. 

Spondylus estrellanus Conrad, 1857c, p. 191, pi. 1, fig. 3.
TERTIARY MARINE PELECYPODS: PLICATULIDAE AND OSTREIDAE C9

Original description. "Obtusely ovate; both valves ventricose; ribs 

17, not very prominent, rounded, rugose; valves with radiation striae."

Type. A specimen (USNM 13312) is in the U.S. National Museum 

type collection labelled, presumably by Conrad, from Estrella Valley, 

Calif., and catalogued in 1884 (pi. 5, fig. 2). It does not compare well 

with the specimen figured by Conrad (1857c, pi. 1, fig. 3) that is missing 

and presumed lost. This specimen (USNM 13312) is not a Spondylus; it 

is Lyropecten estrellanus (Conrad, 1857a). Conrad did not describe the 

hinge area of Lyropecten estrellanus in his original description, and I 

assume that the hinge was not exposed. However, the specimen he 

described as Spondylus estrellanus did have the hinge exposed, and he 

described the hinge as having lateral tubercles or teeth that are 

prominent, conical, and very robust (1857c, p. 191). Perhaps the strong 

crura led him to believe that the species was Spondylus rather than 

Lyropecten. The original illustration of Spondylus estrellanus (Conrad, 1857c, pi. 1, fig. 3), which resembles Lyropecten estrellanus somewhat, shows none of the characters of Spondylus. All available 

evidence points to the conclusion that Conrad did not have a Spondylus in his collections from Estrella Valley and mistakenly identified 

some specimens of Lyropecten estrellanus as Spondylus. The description of "Pallium" estrellanus is on page 313 and that of "Spondylus" 

estrellanus on page 315 (Conrad, 1857a), thus giving page priority to 

Lyropecten estrellanus.

Type locality. Estrella Valley [T. 26 S., R. 13 E., San Luis Obispo 

County], Calif. Santa Margarita Formation, Miocene.

Superfamily ANOMIACEA 

Family ANOMIIDAE

Genus ANOMIA Linne, 1758

Shell thin, partially attached, foramen in right valve, left valve with 

three muscle scars on central area.

The left (upper) valve of Anomia has one large and two small muscle 

impressions; the same valve of Pododesmus has one large and one 

small muscle impression.

Geologic range. Jurassic to Holocene (table 3).

Geographic range. Cosmopolitan, except not in the Arctic and 

Antarctic.

Habitat. "The species of this genus are attached to rocks, shells or 

other objects and often acquire sculpture corresponding to that of the 

object to which they are attached. Often only upper valves are found 

*** as fossils, because those become loose and are washed away, 

whereas the lower valve remains attached *** the byssal plug of

members of this genus apparently corrodes surfaces to which it is 

attached and as a result the shell often lies sunk into a pit of its own 

making." (Hertlein and Grant, 1972, p. 223).

The animals arrange themselves in the plane of least resistance, 

thus indicating the direction of strongest current. (Jackson, 1890, p. 

354).

Intertidal zone to 130 m in the eastern Pacific (Bernard, 1983, p. 27).

Anomia inomatus (Gabb) 

Plate 6, figure 2; plate 7, figure 3

Placunanomia inornata Gabb, 1864, p. 217, pi. 32, figs. 288, 288a.

Arnold, 1909 [1910], p. 108, pi. 3, figs. 1,10. Arnold and Anderson,

1910, p. 70, pi. 25, figs. 1,10. Anderson and Hanna, 1925, p. 190.

"Placunanomia" inornata Gabb. Stewart, 1930, p. 66, pi. 8, fig. 4.

Pododesmus (Monia) inornatus (Gabb). Vokes, 1939, p. 57-58, pi. 3,

figs. 6, 7, 9,11.

Original description. "Shell thin, irregular, inequivalve; upper 

valve convex, usually narrowest near the beaks, broad towards the 

base; hinge-margin thickened; surface marked by fine radiating lines; 

hinge-line but little, if at all, thickened; foramen small, bordered on 

one side by a thickened margin."

Holotype. Missing and presumed lost. ANSP 4442 is here designated the lectotype (Stewart, 1930, p. 66, pi. 8, fig. 4).

Type locality. Corral Hollow [T. 3 or 4 S., R. 3 E., Tesla quadrangle, 

Alameda County], Calif. Domengine Formation, Eocene.

Supplementary description. "Recent collections from Corral Hollow have furnished abundant material representing Gabb's species. 

Among the specimens is a right valve through the byssal notch of 

which projects a portion of a somewhat calcified byssus. There is a 

single prominent muscle-scar on the disk. The valve embraces but 

does not join about the foramen, which is bordered posteriorly by the 

ventral buttress of the posterior ligamental platform. The right valve 

is flattened; the left moderately to well inflated. The umbos are prominent, and there is a well developed cardinal area.

"The Domengine specimens show a range in coarseness of sculpturing which fully embraces both Gabb's and Hanna's species. The interior of Anomia mcgoniglensis is not sufficiently well known to allow 

determination of its true generic position." (Vokes, 1939, p. 58)

"The cardinal area is wide and the ligamental attachment was 

presumably beneath this platform in the umbos." (Stewart, 1930, p. 66, 

pi. 8, fig. 4)

Comparison. According to Vokes (1939, p. 58) the sculptural variation of A. inornatus is sufficient to include A. mcgoniglensis, based on

TABLE 3. Geologic and geographic distribution of the genus Anomia in the eastern Pacific region 

(H=Holocene; Pl=Pliocene; M=Miocene; O=OHgocene; E=Eocene]

Species Oregon California

Northern Middle Southern

Baja California

Norte Sur

Central 

or South 

America

Genus Anomia

hannai Wiedey.............................

inconspicua Clark........................

inornatus Gabb............................

peruviana Orbigny.......................

subcostata Conrad.......................

vaquerosensis Loel and Corey..... 

Genus Anemia!

mcgoniglensis M.A. Hanna..........

O and M

M?

E

H

M and PI 

O and M

M or PI to H 

MorPl 

O and M

E

H PI toH H
CIO PALEONTOLOGY OF CALIFORNIA AND BAJA CALIFORNIA

that character alone, but the lack of a well preserved interior of A. 

mcgoniglensis leaves its generic allocation in doubt.

Geographic range. Middle California.

Geologic range. Eocene.

Occurrence in California. Domengine Formation (Stewart, 1930).

Anomia hannai Wiedey 

Plate 5, figures 4, 5

Anomia hannai Wiedey, 1929b, p. 280-281, pi. 31, fig. 1.

Original description. "Shell quite large, not thick, subovoid, 

rather convex near beak, flattened toward basal margin, more pointed 

and angular in umbonal area; surface sculptured by about ten coarse, 

low, irregularly radiating ribs, which tend to split; interior surface 

irregular, deep in vicinity of beak; ligamental pit apparently broad, 

deep, but not high. Height, 67 mm.; breadth, 57 mm.; thickness, single 

valve, 18 mm."

Holotype. CAS/SU 514.

Type locality. SU 449. Monterey County, Calif. Vaqueros Formation, Oligocene and Miocene.

Comparison. "The fewer ribs and larger form serve to distinguish 

this new species from Anomia peruviana d'Orbigny, living in the Gulf 

of California. A. hannai is more triangular and less gibbose than the 

average form of A. subcostata Conrad of the Carrizo Creek beds, lower 

Pliocene in age, of Imperial County, California." (Wiedey, 1929b, p. 281)

Anomia hannai is higher in proportion to length than A. 

vaquerosensis. The two species are so similar otherwise that additional material may very well show them to be conspecific.

Geographic range. Middle California.

Geologic range. Oligocene and Miocene.

Occurrence in California. Oligocene and Miocene: Vaqueros Formation (Wiedey, 1929b).

Anomia vaquerosensis Loel and Corey 

Plate 5, figure 7; plate 6, figures 9, 12

Anomia vaquerosensis Loel and Corey, 1932, p. 203-204, pi. 33, figs, la, 

Ib, 2a, 2b, 3, 4.

Original description. "Shell thin, medium size, subtrigonal, 

longer than high, inequilateral, of a silvery-nacreous platy material; 

left valve moderately innate [inflated] flattening outwardly, umbone 

[umbo] strongly inflate with inconspicuous beak twisted to posterior; 

distinct notch in posterior dorsal margin, rest of periphery irregularly 

crenulate though evenly rounded. Shell is folded or fluted from 

umbone to ventral margin posterior to middle and ornamented by 

about eight narrow irregular and discontinuous crenulations which 

become stronger and divergent outwardly, annulations very irregular. 

Hinge margin is thickened, strongly incurving, roughened; interior of 

shell uneven, ligament pit covered directly under beak, triangular in 

shape. Muscle scar area is above the center and inclined anteriorly; 

major byssal adductor scars in a vertical line, minor byssal scar below 

and to anterior, below which is the smallest byssal scar. Right 

(attached, or lower) valve not found whole. Length, 57 mm.; height, 50 

mm."

Holotype. UCMP 31758.

Type locality. UC A-336. Ventura County, Calif. Vaqueros Formation, Oligocene and Miocene.

Supplementary description. "Other specimens are three times the 

size of the one described. The species is very irregular in shape because 

of its habit of attached growth. In many specimens the outline and 

inflation of beak is almost brachiopod-like, usually with deep radial 

folds as well as a varying number of plications (usually 6-8). ***It is 

easily identifiable by its thin, silvery shell even when incomplete and

should be recognized as one of the best of Vaqueros index fossils. 

Anomia vaquerosensis, n. sp. has frequently been reported as 'Ostrea 

sp.' " (Loel and Corey, 1932, p. 204)

Comparison. "Anomia vaquerosensis is distinct from any of the 

few described North American species." (Loel and Corey, 1932, p. 204) 

See also Anomia hannai Wiedey described above.

Geographic range. Middle and southern California.

Geologic range. Oligocene and Miocene.

Occurrence in California. Oligocene and Miocene: Vaqueros Formation (Eaton and others, 1941; Durham, 1968; Dickinson, 1969; 

Squires and Fritsche, 1978).

Anomia inconspicua Clark 

Plate 6, figure 8

Anomia inconspicua Clark, 1918, p. 133, pi. 13, figs. 19-20.

Original description. "Shell small, thin, subcircular and somewhat variable in outline; beaks inconspicuous, subcentral in position, 

on some specimens slightly twisted but on others not; left valve convex; right valve flat, with a large byssal notch. Surface smooth except 

for rather heavy, irregular incremental lines. Muscle area, as seen on 

left valve, with one fairly large, distinct scar which is slightly posterior 

to the beak; other scars indistinct. Hinge line very thin, with a small, 

deeply sunken resilifer."

Holotype. UCMP 11205.

Type locality. UC 1131. Contra Costa County, Calif. San Ramon 

Sandstone, Miocene(?).

Comparison. "This species appears to be quite distinct from anything described from the West Coast. Possibly the form that is nearest 

is Anomia linatula [limatula] Dall, from which it differs in being much 

smaller, in the hinge not being so heavy, and in lacking the faint 

radiating lines seen on the latter." (Clark, 1918, p. 133)

Geographic range. Middle California.

Geologic range. Miocene(?).

Occurrence in California. Miocene(?): San Ramon Sandstone 

(Clark, 1918).

Anomia subcostata Conrad 

Plate 6, figures 7, 10, 13; plate 7, figure 5; plate 8, figure 1

Anomia subcostata Conrad, 1855, p. 267. Conrad, 1857b, pi. 5, fig. 34. 

Conrad, 1857e, p. 161, pi. 19, figs, la, Ib. GD. Hanna, 1926a, p. 460, 

pi. 23, figs. 3-5. Grant and Gale, 1931, p. 241.

Original description. "Obtusely ovate from base to back; lower 

valve thick, with interrupted somewhat tubercular radii; upper valve 

thin, radii obsolete or wanting. Height, 1V2 in."

Lectotype. USNM 1865 is here designated the lectotype (pi. 6, fig. 

7). The holotype was cited previously (Keen and Bentson, 1944, p. 25) 

as USNM 13345a. Two specimens are numbered USNM 13345a (pi. 6, 

figs. 10, 13) but neither of these specimens agrees with Conrad's two 

illustrations. The lectotype agrees very well with the specimen illustrated by Conrad (1857b, pi. 5, fig. 34), but not with the other specimen 

illustrated by him (Conrad, 1857e, pi. 19, figs, la, Ib). The line drawing 

(Conrad, 1857b, pi. 5, fig. 34) shows the same breaks in the shell and 

the same radial sculpture as is seen on the lectotype.

Type locality. [Carrizo Creek], Colorado Desert, [Imperial 

County], Calif. Imperial Formation, Miocene or Pliocene.

Supplementary description. "Obtusely ovate, rather thick; umbo 

of larger valve ventricose; hinge thickened, surface of the valve 

obtusely undulated concentrically, and marked with waved, wrinkled, 

interrupted ribs, much raised, except towards the base, where they are 

larger and somewhat tuberculiform; upper valve entire, or with
TERTIARY MARINE PELECYPODS: PLICATULIDAE AND OSTREIDAE Cll

obsolete radii towards the base." (Conrad, 1857e, p. 161, pi. 19, figs, la, 

lb)

"Among this large number [100] there is exhibited great variation in 

shape, sculpture and weight. The radial sculpture ranges from very 

decided ribs to none at all ***" (G D. Hanna, 1926a, p. 460)

Geographic range. Southern California.

Geologic range. Miocene and Pliocene.

Occurrence in California. Miocene or Pliocene: Imperial Formation (Grant and Gale, 1931); Miocene and Pliocene: Etchegoin Formation (Smith, 1912).

Anomia peruviana Orbigny 

Plate 6, figures 1, 4, 6

Anomia peruviana Orbigny, 1846, p. 673. Grant and Gale, 1931, p. 240, 

pi. 12, figs. 2, 5. Olsson, 1961, p. 177, pi. 24, figs. 2-2f. Hertlein and 

Grant, 1972, p. 223-224, pi. 40, fig. 2; pi. 41, fig. 8. Keen, 1971, p. 101, 

fig. 223.

Original description. "Coquille presque arrondie, un peu carree 

plus longue que large, tres-deprimee, marquee en dessus de quelques 

indices de cotes rayonmantes peu prononcees, nombreuses. Sa couleur 

est verdatre tres-pale ou rosee; son interieur est verdatre, le ligament 

entierement vert. La valve inferieure a ses bords desunis sur une 

grande largeur. Diametre, 33 millimetres."

Holotype. BM(NH).

Type locality. Paita, Peru. Holocene.

Supplementary description. "Recent specimens of Anomia peruviana vary in shape and in sculpture. They may be smooth exteriorly 

or they may bear well developed radial ribs occasionally bearing very 

short spines. Exterior sculpture of the shell of Anomia may simulate 

that of the object to which it is attached. Partly because of the multiplicity of forms resulting from such situs this species has received a 

number of names in the literature. The following are generally considered to be synonyms: Anomia hamillus Gray, A. larbas Gray, A. 

alectus Gray, A. lampe Gray, A. pacilus Gray, Anomya' simplex 

Mabille." (Hertlein and Grant, 1972, p. 224)

Geographic range. Living: middle California to Paita, Peru; fossil: 

southern California to Ecuador.

Geologic range. Miocene or Pliocene through Holocene.

Occurrence in the Californias. Miocene or Pliocene: Imperial Formation (C. L. Powell, oral commun., 1983) Pliocene: Almejas (Minch 

and others, 1976) and Infierno (McFall, 1968) Formations; Pliocene and 

Pleistocene: Fernando (Soper and Grant, 1932) and Saugus (Waterfall, 

1929) Formations; Pleistocene: unnamed strata in southern California 

(Valentine, 1960), and in Baja California Sur (Emerson, 1980).

Habitat. "Common on clam shells and rock off exposed beaches 

along the open coast." (McLean, 1978, p. 71)

"*** lives in quiet bays where it is attached to rocks or to empty 

shells by a byssus which extends through a notch in the lower valve. 

The pearly upper valves, which may be white, green or yellow, are 

often found upon the beaches where the species occurs. The lower 

valves often are not found, or occur but sparsely among empty shells. 

This is probably a result of the method of attachment." (Hertlein and 

Grant, 1972, p. 224). Intertidal zone to 130 m (Bernard, 1983, p. 27).

Genus ANOMIA?

Anomia? mcgoniglensis M. A. Hanna 

Plate 5, figures 1, 3

Anomia mcgoniglensis M. A. Hanna, 1927, p. 278, pi. 31, figs. 1, 2, 5, 7. 

Turner, 1938, p. 46, pi. 6, figs. 4-6. Weaver, 1942, p. 100, pi. 22, figs. 

4, 5.

Original description. "Shell of medium size and thickness, only 

moderately inflated, slightly distorted, shape varying from ovate to 

elongate, of irregular outline; surface striated by rough, prominent, 

concentric growth lines and scales; whole surface radially sculptured 

by many ribs; radial ribs are rounded, slightly nodulose where crossed 

by growth lines, vary in direction due to distortion of the shell, separated by regularly concave shallow interspaces which vary in size 

about like the ribs; surface of the inner margin irregular, smooth; 

muscle scar very large, central, and just below the beak.

Dimensions. Cotype No. 31011: Altitude 29 mm., length 34 mm., 

diameter 9 mm. Cotype 31012: Altitude 30 mm., length 28 mm., diameter 9 mm."

Syntypes. UCMP 31009-31012.

Type locality. UC 3981. San Diego County, Calif. Delmar Formation, Eocene.

Comparison. Anomia? mcgoniglensis differs from A. inornata 

(Gabb) in the coarser sculpturing, both concentric and radial. (M. A. 

Hanna, 1927, p. 278)

Yokes (1939, p. 58) said that the range in coarseness of sculpture of 

Anomia inornatus (Gabb) is sufficient to include A.? mcgoniglensis, 

but the lack of well preserved interiors made generic allocation uncertain.

Geographic range. Oregon; southern California.

Geologic range. Eocene.

Occurrence in California. Eocene: Delmar Formation (M. A. 

Hanna, 1927; Givens and Kennedy, 1976).

Genus PLACUNANOMIA Broderip, 1832

With about three strong radial plications; byssal foramen obsolete 

in adult; interior with one retractor scar.

Geographic range. Eastern and western North America; western 

Central America.

Geologic range. Miocene through Holocene (table 4).

Placunanomia granti Hertlein 

Plate 6, figure 3

Placunanomia granti Hertlein, 1928, p. 148, pi. 23, figs. 7-9. Loel and 

Corey, 1932, p. 204, pi. 33, figs. 5, 6a, 6b.

Original description. "Shell moderately small, subcircular in outline, inequivalve, compressed. Upper valve slightly convex; surface 

irregularly wrinkled. Lower valve slightly concave, sculpture similar 

to right. A short depressed groove is present on the beak. Altitude, 34 

mm.; length, 29 mm."

Holotype. CAS4139.

Type locality. CAS 1150. Santa Barbara County, Calif. Vaqueros 

Formation, Oligocene and Miocene.

Comparison. "This small and rather irregularly faintly plicated 

species does not resemble closely any other west coast Placunanomia. 

It does not show the radial striations of P. californica Arnold and is 

smaller and more corrugated than P. hannibali Jordan and Hertlein." 

(Hertlein, 1928, p. 148)

Geographic range. Southern California.

Geologic range. Oligocene and Miocene.

Occurrence in California. Oligocene and Miocene: Rincon Shale 

(Avila and Weaver, 1969) and Vaqueros Formation (Hertlein, 1928).

Placunanomia californica Arnold 

Plate 6, figures 5, 11

Placunanomia californica Arnold, 1909, p. 75-76, pi. 24, figs. 2, 2a, 3. 

Grant and Gale, 1931, p. 243. Adegoke, 1969, p. 106, pi. 10, fig. 4.
C12 PALEONTOLOGY OF CALIFORNIA AND BAJA CALIFORNIA

TABLE 4. Geologic and geographic distribution of the genera Placunanomia and Pododesmus in the eastern Pacific region 

[H Holocene; Ple=Pleistocene; Pl=Pliocene; M=Miocene; O=Oligocene]

Species Alaska British Washington Oregon 

Columbia

California

Northern Middle Southern

Baja California

Norte Sur

Genus Placunanomia

calif arnica Arnold.........................

granti Hertlein...............................

hannibali Jordan and Hertlein..... 

Genus Pododesmus

Subgenus Mania

macroschisma (Deshayes).........

M and PI PI

O and M

PI

H H H H H M to H PI to H Pie to H H

Original description. "Shell averaging about 65 millimeters in 

length, subcircular in outline, inequivale [inequivalve], compressed. 

Right valve irregular, somewhat convex, the surface sculptured by 

numerous small, thread-like, rugose, radiating ridges and several 

laminae of growth; byssal foramen, though closed, leaves an oblique 

semicovered pit near the beak; two strong elevated rough crests the 

auricular crura diverge from the beak at a very acute angle; immediately behind the auricular crura is the broadly V-shaped scar of the 

byssal muscle, on each side of which is a deeply impressed groove, and 

in the middle of which is an oblique V-shaped pit which was once 

connected with the external pit forming the byssal foramen; adductor 

scar subcircular to irregular and equal in diameter to over one-third 

the length of shell. Left valve flat to slightly concave; surface sculpture 

similar to but less prominent than that of right valve; a broad V-- 

shaped socket, into which the crura of the right valve fits, occupies the 

area below the beaks; adductor scar same as in right valve.

"Dimensions. Altitude 66 mm.; latitude 60 mm.; diameter of both 

valves 33 together, 17 mm."

Holotype. USNM165546 (right valve).

Type locality. USGS 4715. Kern County, Calif. Etchegoin Formation, Miocene and Pliocene.

"This rare shell, of which the type, paratype, and a fragment are the 

only specimens so far known, is characterized by the elevated 

auricular crura of the right valve and V-shaped socket of the left. Its 

external sculpture is quite similar to certain specimens of 

Pododesmus (Monia) macroschisma Deshayes, found Recent and fossil on the Pacific coast. The only other member of the genus 

Placunanomia on the Pacific coast is the Recent P. cumingi Reeve, of 

the Recent Gulf of California province, which is characterized by one 

or two very strong plications. P. californica is thinner and more nearly 

circular in outline than P. plicata Tuomey and Holmes, of the upper 

Miocene of the Carolinas; it also has radial sculpture, which is lacking 

in the latter." (Arnold, 1909, p. 75-76)

Comparison. "This rare species differs from P. cumingii in the 

presence of radial riblets and the very low, almost obsolete plications. 

P. hannibali Jordan and Hertlein is very closely related, but has finer 

radial sculpture and the byssal scar is not sub-triangular as in 

Arnold's species." (Grant and Gale, 1931, p. 243)

Geographic range. Middle and southern California.

Geologic range. Miocene and Pliocene.

Occurrence in California. Miocene and Pliocene: Etchegoin Formation (Arnold, 1909); Pliocene: San Joaquin Formation (Adegoke, 

1969).

Placunanomia hannibali Jordan and Hertlein

Plate 7, figures 2, 6, 7; plate 8, figures 2, 5

Placunanomia hannibali Jordan and Hertlein, 1926b, p. 443-444, pi. 

28, figs. 2-4. Grant and Gale, 1931, p. 243. Smith, 1984, p. 206, pi. 

205, figs. 2, 3.

Original description. "Shell large, thin, subcircular to suboval in 

outline, usually very flat, compressed and more or less regular in 

growth; most specimens with no evidence of radial plication but a few 

more or less profoundly, radially plicate; surface sculptured by concentric growth lines, and by very fine, wavy, minutely prickly, radial 

striations. Right valve slightly arched; byssal foramen closed or nearly 

so, but leaving an elongate oblique semi-triangular pit near the beak, 

which almost communicates with the interior; auricular crura very 

strong, diverging from the beak at an acute angle varying somewhat in 

different specimens. Left valve flat or concave, never convex as is the 

right; without byssal foramen, but usually broken slightly at the beak; 

interiorly with two strong ribs radiating from the umbo, but fitting 

outside of the auricular crura," and hence diverging at a somewhat 

greater angle. Length 114 mm.; width 95 mm.; thickness 15 mm."

Holotype. GAS 2110.

Type locality. GAS 945. Baja California Sur. Almejas Formation, 

Pliocene.

Comparison. "Placunanomia hannibali is related to P. californica 

Arnold *** but is distinguished by having a generally flatter and more 

regular shell with very fine rather than heavy radial sculpture. P. 

cumingii Broderip, from the recent fauna of western Mexico and the 

upper Pliocene of Maria Madre Island is very strongly radially plicate, 

and lacks all radial sculpture. P. hannibali is most nearly related to P. 

lithobleta Dall, of the Miocene of the Caribbean region, but seems to 

attain a larger size than that species, and to be fitted with larger and 

heavier auricular crura." (Jordan and Hertlein, 1926b, p. 443-444)

"This species is closely related to P. californica Arnold, but *** 

appears to attain a larger size and the byssal scar does not have the 

subtriangular shape of the type of californica." (Grant and Gale, 1931, 

p. 243)

Geographic range. Baja California Sur.

Geologic range. Pliocene.

Occurrence in Baja California Sur. Pliocene: Almejas (Minch and 

others, 1976), Gloria (Wilson and Rocha, 1955), and Infierno (Wilson 

and Rocha, 1955) Formations.
TERTIARY MARINE PELECYPODS: PLICATULIDAE AND OSTREIDAE C13

Genus PODODESMUS PhiHppi, 1837

Sculpture of irregular corrugations; shell attached, byssal foramen 

large, small, or even obsolete; left valve with one large and radially 

striate byssal retractor scar.

Pododesmus "***differs from Placunanomia in possessing an open 

byssal foramen in the lower valve, although small or sealed over in the 

type species, and in lacking large, well developed cardinal crura. It 

differs from Anomia in possessing only one muscle impression (in 

addition to the byssal impression), rather than two." (Hertlein and 

Grant, 1972, p. 225)

Geographic range. North and South America, Europe, Australia, 

and Japan.

Geologic range. EoceneC?); Oligocene through Holocene (table 4).

Subgenus MONIA Gray, 1850

Byssal retractor scar large; foramen of moderate to large size.

The shell ofMonia differs from Pododesmus (Pododesmus) "in possessing a large byssal opening and in that the large perforation of the 

lower valve only slightly embraces the large thin plug." (Hertlein and 

Grant, 1972, p. 225)

Geographic range. New Zealand, North America, and Europe.

Geologic range. Oligocene through Holocene.

Pododesmus (Monia) macroschisma (Deshayes) 

Plate 7, figure 4; plate 8, figures 4, 7; plate 9, figure 7

Anomia macrochisma Deshayes, 1839, p. 359. (Specific name later

emended by Carpenter, fide Keen, 1971, p. 103). 

Pododesmus (Monia) macroschisma (Deshayes). Arnold, 1903, p. 

116-117. Hertlein and Grant, 1972, p. 225-226, pi. 40, fig. 3; pi. 41, 

figs. 9,12,13. 

Monia macroschisma Deshayes. Arnold, 1909, p. 134, pi. 14, fig. 1.

Vedder and Moore, 1976, pi. 1, fig. 3. 

Pododesmus macroschisma (Deshayes). Grant and Gale, 1931, p.

241-242, pi. 12, figs. 3,4a, 4b. Adegoke, 1969, p. 106. 

Placunanomia cepio Gray, 1850. Kern, 1973, p. 74. 

Pododesmus (Monia) cepio (Gray, 1850). Keen, 1971, p. 103, fig. 227. 

Pododesmus cepio (Gray, 1850). McLean, 1978, p. 71-72, fig. 39.3. 

IPododesmus newcombei Clark and Arnold, 1923, p. 141, pi. 21, figs. 

3-6.

Original description. "Testa irregulariter ovata, inaequivalvi, 

albo-viridula, irregulariter plicata; valvaii superiore convexa, 

inferiore plana, suprene late perforata, foramine integro, marginibus 

acutis plicatis, valvis intus submargaritaceis, superiore maculamagna satirata viridi ornata." (macroschisma)

"Scars 2, far apart; upper very large, ovate, longitudinal, central; 

lower smaller, oblong, oblique, rather behind the upper *** Plug large, 

flat, broad. Notch large wide." (cepio) 

Holotype. Location unknown; of cepio, BM(NH). 

Type locality. "Kamtschatka;" of cepio, California. 

Supplementary description. "The thickness of the shell and the 

development of coarse or fine radial sculpture (occasionally obsolete) 

varies greatly depending upon the situs." (Hertlein and Grant, 1972, p. 

226)

Authors have most recently separated P. (M.) macroschisma as the 

Pododesmus living in the north and western Pacific and P. (M.) cepio as 

the southern species. Pododesmus cepio has been distinguished from 

P. macroschisma chiefly on the basis of a thinner shell, sculpture, and 

a larger byssal foramen. Hertlein and Grant (1972, p. 226) stated that 

"the variation in a large series is so great that there appear to be no

criteria to rely upon for separating the shells *** unless certain forms 

are arbitrarily selected to represent various species. *** Burch, after 

studying a large series of specimens of Pododesmus from Puget Sound 

and from Monterey, California, stated that he could find no basis for 

the recognition of more than one species." On the basis of these 

statements, I have synonymized P. cepio.

Geographic range. Living: Japan; Alaska to Baja California Sur; 

fossil: middle California to Baja California Norte.

Geologic range. Miocene to Holocene.

Occurrence in the Californias. Miocene: Pancho Rico (Durham 

and Addicott, 1965) and Santa Margarita (Addicott and Vedder, 1963) 

Formations; Miocene and Pliocene: Etchegoin (Adegoke, 1969) and 

Towsley (Kern, 1973) Formations; Pliocene: Careaga Sandstone (Woodring and Bramlette, 1950), Niguel (J. G. Vedder, written commun., 

1978) and San Diego (Hertlein and Grant, 1972) Formations and 

unnamed Pliocene strata on San Clemente Island (Vedder and Moore, 

1976); Pliocene or Pleistocene: Fernando (Arnold, 1907c) and Potato 

Harbor (Weaver and Meyer, 1969) Formations; Pliocene and 

Pleistocene: Merced (Arnold, 1909; Glen, 1959), Pico (Waterfall, 1929), 

and Saugus (Kew, 1924) Formations; Pleistocene: SanPedro Formation 

(Eaton, 1928), Timms Point Silt Member, San Pedro Formation (A. 

Clark, 1931), and unnamed strata in Southern California and in Baja 

California Norte (Valentine, 1960).

Habitat. Common on shells of abalone, submerged reefs, breakwater rocks, and inside dead shells (Smith and Gordon, 1948, p. 170; 

McLean, 1978, p. 72). Intertidal to 90 m (Bernard, 1983, p. 27, 28).

Superfamily LIMACEA

Family LIMIDAE 

Genus LIMA Bruguiere, 1797

Subtrigonal, higher than long, with rather short hinge margin; 

auricles relatively well differentiated, anterior one slightly the 

smaller; anterior umbonal ridge not strongly marked; inflation only 

moderate; gapes of valve margins only slight; hinge edentulous or with 

weak denticles near ends of hinge margin; ornament of scaly radial 

ribs.

"Many species are superficially alike and the external ornamentation may vary with habitat. Useful distinguishing characters are 

found in the comparative height of the umbones and the length of the 

cardinal area just below the beaks." (Bernard, 1979, p. 31)

Geographic range. Cosmopolitan.

Geologic range. Triassic to Holocene (table 5).

Habitat. "*** most often found in deep and cold waters. Individuals are able to move and sometimes swim, by pulsating the extremely 

long tentacular fringe of the mantle edges. More usually, species are 

byssally attached, often in 'nest' of matted byssal threads that may 

serve as a protection for the exposed tissues and delicate shell." (Bernard, 1979, p. 31)

According to Purchon (1977, p. 149) Lima lima is byssally attached 

under boulders and has a heavily built shell whereas Lima fragilis, 

which can swim, has a small, fragile shell. Thus, the thickness of the 

shell of fossil limids may indicate whether they lived byssally attached 

or were free moving.

Subgenus LIMA

Lima (Lima) vedderi Moore

Plate 10, figures 1, 3

Lima vedderi Moore, 1977, p. 277, figs. 2, 6, 7, 9,10.
C14 PALEONTOLOGY OF CALIFORNIA AND BAJA CALIFORNIA

Original description. "The shell of Lima vedderi is moderately 

thick, and the preserved part bears 20 prominent slightly rounded 

ribs that are separated by rounded interspaces about half as wide as 

the ribs of the anterior and posterior margins, but as wide as the ribs 

on the central part of the shell. Assuming a normal positioning of the 

beaks, the holotype is about 45 mm high and 50 mm long. Distinctive 

bulbous nodes are preserved along the entire length of the surface of 

the ribs; no part of the ribs is smooth. The nodes are massive and 

shaped like very shallow cups with their dorsal surfaces convex and 

smooth and their ventral surfaces concave. The nodes are about evenly 

spaced; the distance between the mid-points ranges from 2.2 to 2.8 

mm. Although the general configuration of the nodes is regular, some 

nodes are more nearly semispherical and thicker than others. No 

minor sculpture similar to that on L. vedderi has been noted on any 

described Lima, nor, for that matter, on any other pelecypod genus. 

The uniqueness of the sculpture makes identification of even small 

fragments feasible. The outline, shape, and ribbing of L. vedderi are 

sufficient to make assignment to the genus Lima reasonably certain. 

Holocene specimens of Lima tetrica Gould from Baja California, the 

only similar northeast Pacific species, * * * differs from L. vedderi in 

sculpture; the ribs on L. tetrica bear spines and lamellae rather than 

nodes."

Holotype. USNM 240060.

Type locality. USGS M3220. Orange County, Calif. Monterey 

Shale, Miocene.

Geographic range. Southern California.

Geologic range. Miocene.

Occurrence in California. Miocene: Monterey (Moore, 1977) and 

Santa Margarita (Addicott and others, 1978) Formations and 

unnamed Miocene strata on San Clemente Island (Moore, 1977).

Genus ACESTA H. and A. Adams, 1858

Large, thin-shelled, ovate, inequilateral, with moderate byssal 

gape; anterior umbonal ridge ill defined; anterior auricle reduced;

ligament pit broad, curved. Cardinal area narrower than that of Lima 

s.s.

Geologic range. Jurassic through Holocene (table 5).

Geographic range. Cosmopolitan.

Habitat. Living in cold water or at great depths (to 2,550 m).

Subgenus ACESTA

Sculpture of superficial, rather irregular, radiating riblets that are 

more strongly developed on anterior and posterior portions of valves.

Geographic range. Living: California to Chile. Hertlein (1952) 

described a new species ofAcesta collected offCalifornia between 1260 

and 1465 m from Mulberry Seamount, thus extending the northern 

range of the genus.

The scarcity of collections from deep water no doubt directly relates 

to the known geographic distribution of living Acesta as well as fossil 

species. (Yokes, 1963, p. 75)

Acesta (Acesta) multiradiata (Gabb) 

Plate 10, figures 5, 8

Lima multiradiata Gabb, 1869, p. 201-202, pi. 33,'fig. 101. Stanton, 1896, 

p. 1038, pi. 63, figs. 7,8. Dickerson, 1914, p. 151, pi. 8, fig. 1. Stewart, 

1930, p. 125, text fig. 2.

Original description. "Shell (right valve) large, oblique, compressed subelliptical; anterior side forming a regular curve to the 

middle of the base, very slightly sinuous above, under the ear; posterior portion of the basal margin much more narrowly rounded than 

in advance, uniting by a broad curve above, with the posterior side, the 

upper half of which seems to have been nearly straight; the anterior 

ear seems to have been long and narrow. Surface convex a little behind 

the middle, the anterior slope being broad and nearly flat; the entire 

surface covered by very numerous, slightly wavy, somewhat irregular,

TABLE 5. Geologic and geographic distribution of the genera Lima, Acesta, Limaria, Limatula, and

Limea? in the eastern Pacific region

[H=Holocene; Ple=Pleistocene; Pl=Pliocene; M=Miocene; E=Eocene; Pa=Paleocene]

Species California Baja California

Northern Middle Southern Norte

Central 

 or South 

Sur America

Genus Lima 

Subgenus Lima

vedderi Moore................................

Genus Acesta 

Subgenus Acesta

hamlini (Dall).................................

multiradiata (Gabb).......................

Subgenus Plicacesta

haseltinei (Dickerson)....................

Genus Limaria 

Subgenus Limaria

clarki (Nelson)...............................

hemphilli (Hertlein and Strong).....

orcutti (Hertlein and Grant).........

Genus Limatula

aff. subauriculata (Montagu).............

Genus Limeal

Subgenus Isolimea"!

claytonensis (Dickerson)................

Pa Pa 

Pa

H

M

PI 

E

Pa

Pa

MtoH 

PI

PI

Pa

Pie and H H H

Pa
TERTIAEY MARINE PELECYPODS: PLICATULIDAE AND OSTREIDAE C15

radiating ribs of small size, and with narrow interspaces; on the 

younger portion of the shell, the spaces between the ribs are mere 

impressed lines, the ribs being convex; near the base, however, the ribs 

become proportionally smaller, the spaces are wider than the ribs, and 

are concave, and the whole are crossed by minute subsquamose lines 

of growth."

Holotype. MCZ15016.

Type locality. Near Lower Lake Village [NEV4, sec. 11, T. 12 N., R. 7 

W.], Lake County, Calif. Martinez Formation, Paleocene.

Supplementary description. "The holotype *** is very poorly preserved. The right margin is unknown and the left dorsal region has 

been worn away while the ventral margin is entirely broken away. 

Unfortunately, the growth lines are not well exposed so that it is 

impossible to obtain the true outline of the shell. It has been possible to 

expose part of the left side, showing that the shell is more convex than 

the original figure suggests. The radial ribs are irregular and somewhat wavy." (Stewart, 1930, p. 125)

Geographic range. Northern California to Baja California Norte.

Geologic range. Paleocene and Eocene.

Occurrence in the Californias. Paleocene: Martinez (Weaver, 

1905; Dickerson, 1914) and Sepultura(?) (Gardner in Barton, 1921) 

Formations; Eocene: Tejon Formation (Stanton, 1896; Arnold, 1906).

Acesta (Acesta) hamlini (Dall) 

Plate 10, figures 4, 7

Lima hamlini Dall, 1900, p. 16. Arnold, 1907a, p. 527. Dall, 1925, p. 18,

pi. 29, fig. 6.

Lima (Acesta) hamlini Dall. Woodring, 1938, p. 47-49, pi. 8, figs. 5,7,10, 

11.

Original description. "Several specimens, more or less crushed, of 

a large Lima are among the forms collected. This species belongs to 

the general type of Lima excavata Fabr, L. goliath Sby, etc., and 

reaches to a length of four and a half inches. The valves are brilliantly 

polished, and in the middle part unsculptured, the anterior and posterior thirds are finely radially grooved with shallow grooves of which 

the outer slopes are less steep than the inner; the incremental lines, 

obsolete elsewhere, appear in the channel of the grooves and cross 

striate it here and there, giving the effect of obsolete punctation. I may 

add that close to the impressed area of the shell there are two or three 

coarser, deeper radial grooves. The species differs from the South 

Pacific and all other forms of its group known to me in its much finer 

and more delicate sculpture and brilliant polish. I await more perfect 

specimens before trying to figure it, but would propose the name of 

Lima hamlini for the species in honor of Mr. Homer Hamlin C. E., 

Asst. City Engineer of Los Angeles, who is much interested in the 

geology and paleontology of the region, and has made valuable studies 

of the southern California Tertiary. The specimen in hand was kindly 

forwarded for examination by Dr. R. E. C. Stearns."

Holotype. USNM 495186.

Type locality. USGS 3426. Los Angeles County, Calif. Fernando 

Formation, Pliocene and Pleistocene (from the Pliocene part of the 

Fernando Formation, John G. Vedder, written commun., 1983).

Supplementary description. 'A giant Lima allied to the modern 

Panamanian agassizii. Depressed area at anterior end and posterior 

auricle sculptured with relatively strong radial ribs that are more 

closely spaced toward the center of the shell, the interspaces being 

gradually transformed into narrow grooves, microscopically punctuated by concentric threads. On some specimens subdued grooves continue over the central part of the shell, except in the umbonal region, 

but in most specimens they are absent on a central area of varying 

width." (Woodring, 1938, p. 47).

Comparison. Acesta hamlini is higher in proportion to length 

than Acesta mori (Hertlein), a species living off central California 

(Hertlein, 1952, p. 379).

Geographic range. Southern California.

Geologic range. Pliocene.

Occurrence in California. Pliocene: upper part of Capistrano 

(Vedder, 1972) and lower part of Fernando (Arnold, 1907c; Woodring, 

1938) Formations.

Subgenus PLICACESTA Yokes, 1963

Radial ribs strong on the plicate shells, not exclusively surficial as 

on Acesta, and characteristically they are larger on the middle of the 

valves than on the valve margins. Cardinal area and ligamental pit 

similar to Acesta; relatively thin to very thick shelled.

Geologic range. Eocene through Holocene (table 5).

Geographic range. Living: Japan and southern California; fossil: 

Asia, California, and Washington. 

Habitat. 90 to 185 m, Japan; 455-550 m, southern California.

Acesta (Plicacesta) haseltinei (Dickerson) 

Plate 9, figure 10; plate 10, figures 10,11

Lima(?) haseltinei Dickerson, 1914, p. 126-127, pi. 8, fig. 2; pi. 9, fig. 11. 

"Lima" haseltinei Dickerson. Woodring m Hoots 1931, p. 92. 

Lima perrini Waring, 1914, p. 782-783. Waring, 1917, p. 76-77, pi. 10, 

figs. 1, la, 2.

Original description. "Shell large, slightly oblique, nearly equivalve, moderately convex; beak prominent, pointed, anterior, prosogyrate; hinge, edentulous, long, straight; ears not markedly set off from 

rest of shell, the posterior one being the larger; anterior end broadly 

rounded; posterior, slightly truncated; ventral margin, arcuate; decoration consists of numerous squarish radial ribs with very narrow 

interspaces." (haseltinei)

"This giant circular lima has a thick shell with nacreous, and outer 

prismatic layer. The diameter is about 160 mm. The umbones are small 

and the cardinal margin slopes gradually to the posterior where it 

becomes rounded and grades into the circular margin below. The 

beaks are slightly excavated in front, and the margin slopes at a 35- 

degree angle into the rounded anterior margin. The hinge is very thick 

and has a deep wedge-shaped ligament pit sloping from the interior 

edge of the shell to the exterior edge at the anterior end of the hinge 

line. A single large sub-posterior muscle impression marks the interior of the shell. The surface is ornamented by many fine radiating 

lines, and the prismatic shell layer gives the surface a silken 

appearance. It belongs to the subgenus Acesta." (perrini)

Holotype. UCMP 11676; of perrini CAS/SU 303.

Type locality. UC 1540, Contra Costa County, Calif. Martinez Formation Paleocene; of perrini, Simi Hills [1.6 km N. 68° W of Hill 2150, 

southwest of Santa Susana, Camulos quadrangle], Ventura County, 

Calif. Santa Susana Formation, Paleocene (Zinsmeister, 1983).

Dickerson described Acesta haseltinei in May, 1914, and Waring 

described Acesta perrini in November-December, 1914. Subsequently, 

Waring (1917, p. 77) believed the two species to be distinct, although he 

did say that when more specimens were found of each this might be 

disproven. Because neither specimen is complete, the original outline 

of each can be misconceived, but on the basis of the holotypes, I can find 

no characters to separate the two species. It is unfortunate that the 

specific name haseltinei precedes perrini by a few months as the 

holotype of perrini is much better preserved.

Both A. haseltinei and A. perrini have very thick shells; the thick 

shells may have been a characteristic of fossil representatives of the 

subgenus Plicacesta and may indicate that they were byssally 

attached.

Geographic range. Middle and southern California.

Geologic range. Paleocene.
C16 PALEONTOLOGY OF CALIFORNIA AND BAJA CALIFORNIA

Occurrence in California. Paleocene: Martinez (Dickerson, 1914; 

Waring, 1914) and Santa Susana (Zinsmeister, 1983) Formations.

Genus LIMARIA Link, 1807

Shell medium-sized, ovate, auricles small, subequal; radial ribs fine, 

not scaly.

Promantellum Iredale differs but little fromLimaria, but the valves 

of Promantellum may be more widely gaping. Submantellum differs 

from Limaria in the greater inflation of the valves and the lack of any 

posterior gape. (Hertlein and Grant, 1972, p. 215).

Geologic range. Eocene through Holocene (table 5).

Geographic range. Cosmopolitan.

Habitat. Species of this genus live today in temperate and tropical 

waters (Hertlein and Grant, 1972, p. 215).

Subgenus LIMARIA

Somewhat oblique, rather strongly inflated with wide posterior 

gape; narrow radial riblets.

Geologic range. Miocene to Holocene. 

Geographic range. Cosmopolitan.

Limaria (Limaria) clarki (Nelson) 

Plate 10, figure 6

Lima(?) clarki Nelson, 1925, p. 407, pi. 49, fig. 2.

Original description. "Shell small, moderately oblique, ovate, 

compressed; beak inconspicuous. Posterior dorsal margin straight; 

anterior margin slightly convex, rounding evenly into ventral margin; 

ventral margin rounded, with decrease in curvature toward posterior 

extremity; character of posterior end unknown. Anterior ear small; 

posterior ear unknown. Surface of shell with 20 or more rounded 

radial ribs which are widest spaced in midportion of shell and indistinct toward each margin, spacing uneven in posterior third of shell. 

Greatest length of shell in type specimen, 12 mm; width, 8.3 mm.

"The type for this species is a cast from which a small portion of the 

posterior end has been broken."

Holotype. UCMP 30494.

Type locality. \JC 3752. Ventura County, Calif. Martinez Formation, Paleocene.

Comparison. "Lima(?) clarki can be distinguished from L.(?) 

claytonensis Dickerson by its obliqueness and finer ribbing. It resembles L. packardi Weaver and Palmer, from which it can be distinguished by its greater elongation and more widely spaced ribbing." 

(Nelson, 1925, p. 407)

Geographic range. Southern California.

Geologic range. Paleocene.

Occurrence in California. Paleocene: Martinez Formation 

(Nelson, 1925).

Limaria (Limaria) hemphilli (Hertlein and Strong) 

Plate 7, figure 1; plate 8, figures 3, 6, 8

Lima (Limaria) hemphilli Hertlein and Strong, 1946, p. 66-67, pi. 1, 

figs. 3, 4.

Lima hemphilli Hertlein and Strong. Kern, 1973, p. 74.

Original description. "Shell obliquely elliptical equivalve, inequilateral, moderately convex, broadly gaping especially along the 

anterior dorsal margin, posteriorly narrowly gaping hinge short, 

anterior ear the larger, pointed and beneath which a notch is present; 

the maximum width of the anterior margin is above the middle of the 

shell; between the widest portion and the hinge the margin shows two

vague angulations; ventral margin elliptical, posterior margin very 

gently rounded; the anterior umbonal slope of the valves is gentle, the 

posterior slope is rather abrupt; valves ornamented by fine irregular 

radial ribs which are crossed by very fine imbricating lirae; anterior 

and posterior submargins smooth. Height 23 mm., length 16.4 mm., 

convexity (both valves) approximately 12 mm."

Syntypes. CAS 9174, 9174A.

Type locality. GAS 5955. San Diego, Calif. Holocene.

Supplementary description. "The shell gapes a little more on the 

anterior than on the posterior side." (Keen, 1971, p. 98)

Comparison. Lima orcutti somewhat resembles L. hemphilli, but 

it has fewer, coarser, more widely spaced ribs; the hinge plate is 

relatively broader; and the posterior ear is much less acutely pointed 

(Hertlein and Grant, 1972, p. 215).

Geographic range. Living: Monterey Bay, California to Acapulco, 

Mexico; fossil: southern California to Baja California Norte.

Geologic range. Miocene to Holocene.

Occurrence in California. Miocene and Pliocene: Towsley Formation (Kern, 1973); Pleistocene: Palos Verdes Sandstone and San Pedro 

Sand (Arnold, 1903); unnamed strata in southern California (Valentine, 1956; Kanakoff and Emerson, 1959) and unnamed strata in Baja 

California Norte (Valentine and Rowland, 1969).

Habitat. On rock bottoms, 15 to 100 m (Bernard, 1983, p. 22). In 

swimming they carry the hinge behind, in the manner ofPecten (Baily, 

1950, p. 112).

Limaria (Limaria) orcutti Hertlein and Grant

Plate 9, figures 4-6, 8

Lima (Limaria) orcutti Hertlein and Grant, 1972, p. 215, pi. 35, fig. 11; 

pi. 49 36, figs. 2-5; pi. 57, fig. 10.

Original description. "Right valve, shell obliquely elliptical in outline, inequilateral, moderately convex; greatest length (anterior-posterior) about halfway between beak and ventral margin, gaping along 

the posterior dorsal margin; hinge short, oblique, the posterior ear 

pointed, a shallow sinus immediately below it; the anterior margin 

nearly straight above, but below it is gently rounded into the ventral 

margin, the outline of the posterior and ventral margin forms a broad 

arc; anterior umbonal slope rather steep, the posterior slope rather 

gentle; the valves are sculptured with about 35 to 40 fine, radial 

riblets, some vaguely paired, all separated by wider interspaces, ribs 

and interspaces widest on medial portion of the valve, the whole 

crossed by fine imbricating lines of growth; hinge elongately triangular, with a broad shallow, triangular ligamental pit, a triangular 

pit under the posterior ear, a shallow depression under the anterior 

one; the interior smooth, in some places the external ribbing is visible. 

Dimensions of holotype: Height (beak to ventral margin) 43 mm, 

length approximately 35.5 mm (posterior side imperfect), convexity 

(left valve) approximately 9.6 mm."

Holotype. LAM 4509.

Type locality. LAM 305c. San Diego County, Calif. San Diego Formation, Pliocene.

Comparison. "This new species bears a general resemblance to 

Lima hemphilli Hertlein and Strong which now lives in adjacent 

waters but the new species has fewer, coarser, more widely spaced ribs, 

the greatest length of the valves (anterior-posterior) is at a point about 

midway between the beak and the ventral margin rather than above 

the middle, the hinge plate is relatively broader and the posterior ear 

is much less acutely pointed.

"The general features of the hinge are more like that of Lima 

orbignyi Lamy, but the shell of the new species is much more elongated, less inflated and the valves gape posteriorly.

"The general outline of this new species is somewhat like that of 

Lima auaua Ball, Bartsch, and Rehder, from Hawaii, but the 

character of the ribbing appears to be quite different." (Hertlein and 

Grant, 1972)
TERTIARY MARINE PELECYPODS: PLICATULIDAE AND OSTREIDAE C17

Geographic range. Southern California. 

Geologic range. Pliocene.

Occurrence in California. Pliocene: Niguel (J.G. Vedder, written 

commun., 1983) and San Diego (Hertlein and Grant, 1972) Formations.

Genus LIMATULA Wood, 1839

Small, oval, strongly inflated; auricles small, subequal; margins not 

gaping; hinge edentulous; sculpture of fine radial riblets, most conspicuous toward center of valves and absent from posterior end.

Geologic range. Triassic through Holocene (table 5).

Geographic range. Cosmopolitan.

Habitat. Most living species in the eastern Pacific are found at 

depths of 10-350 m, but one species is found as deep as 2,200 m 

(Bernard, 1983, p. 23).

Limatula aff. L. subauriculata (Montagu) 

Plate 9, figure 2

Limatula aff. subauriculata (Montagu). Woodring, 1938, p. 49, pi. 8, fig. 

6.

Although not positively identified, this species is included because it 

is the only known fossil representative of Limatula in the Californias. 

It is described by Woodring (1938) as follows:

"A small moderately elongate valve represents a species of Limatula. The sculpture consists of fine radial ribs, slightly roughened by 

microscopic concentric threads. Two median ribs are heavier than the 

others and modify the interior outline. On the interior of the lower 

part of the shell, where the exterior is missing, a narrow midrib lies 

between the heavy ribs.

"This species is probably the Recent form known as Lima (Limatula) subauriculata (Montagu). Recent shells attain a height of 16.4 

millimeters and a length of 10.4 millimeters. They have one to three 

relatively heavy median ribs that are differentiated by strong interspaces on the interior, even though the ribs are not conspicuously 

differentiated on the exterior, a characteristic feature of Limatula 

shown by the fossil."

Geographic range. Southern California.

Geologic range. Pliocene.

Occurrence in California. Pliocene: lower part of Fernando Formation (Woodring, 1938).

Genus LI ME A Bronn, 1831

Small; cardinal area narrow; hinge with series of short denticles on 

either side.

Geographic range. Cosmopolitan.

Geologic range. Triassic through Holocene (table 5).

Subgenus ISOLIMEA Iredale, 1929

Suborbicular; sculpture of strong radial ribs with wide interspaces. 

Geographic range. Australia; California(?). 

Geologic range. Holocene; Paleocene(?).

Genus LIMEA? 

Subgenus ISOLIMEA?

Limea? (Isolimea?) claytonensis (Dickerson) 

Plate 10, figures 2, 9

Limad) claytonensis Dickerson, 1914, p. 126, pi. 7, figs. 9a, 9b.

Original description. "Shell inflated, with radial sculpture; 

rounded and almost symmetrical. Ratio of length to height about .65 to 

1. Beak prominent, acute, and in some specimens compressed. Hinge

line short and straight with about twelve small striations perpendicular to hinge line. These striations may be plications within the 

shell wall, revealed by th [the] breaking away of the inner shell layer. 

Area, narrowly elliptical and central. Basal margin, rounded. Ribs 

about thirteen in number are acute-angled and beaded; the interspaces are the same in width as the ribs."

Syntypes. UCMPin20, 11721.

Type locality. UC 1592. Contra Costa County, Calif. Martinez Formation, Paleocene.

Dickerson said that he had four specimens all from shale 30 m above 

the base of the Martinez Formation at the type locality.

Geographic range. Middle California.

Geologic range. Paleocene.

Occurrence in California. Paleocene: Martinez Formation 

(Dickerson, 1914).

Superfamily OSTREACEA

Stenzel's (19 71) classification, in his scholarly volume on the oysters, 

is generally followed and I have relied heavily upon his work. Revisions reflect subsequent studies of the anatomy and shell characters of 

oysters by Harold W Harry (1981,1983; written commun., 1983,1984). 

In the Tertiary of the Californias, 8 genera are represented by 40 

species. Only three of these genera have been used by other workers 

for Tertiary species of oysters in the eastern Pacific. As noted by 

Stenzel (1971, p. N1095), classification of oysters at the generic level 

seems extraordinarily difficult and open to divergent opinions. For 

example, Woodring (1982, p. 607), who based his classification on that 

of Stenzel's (1971), assigned one Tertiary species of oyster from the La 

Boca Formation, early Miocene, Panama, to "Hyotissa", and he said 

that this species, "Hyotissa" tryoni (Gabb), was by no means a typical 

Hyotissa but might be a link between Pycnodonte and Hyotissa. Harry 

(in Harry and Dockery, 1983) described two vesicular species of oysters 

from the Oligocene in Mississippi, and he said that they did not fit well 

in any of the four subgenera of pycnodontine oysters recognized by 

Stenzel(1971).

Harry (in Harry and Dockery, 1983) said that the three subfamilies 

of Ostreidae are more sharply differentiated from each other and from 

the Pycnodonteinae by the anatomy of their flesh, reproductive habits, 

and environmental preference than by the characteristics of the 

highly variable shells.

The classification used here for eastern Pacific Tertiary oysters is 

preliminary. Future work on large suites of oysters from stratigraphically controlled sections, and study of variation within large 

collections of single living species, will improve and refine the classifications suggested by me and also improve the utility of oysters as a 

tool in correlation.

The oysters as a group show a great range of variability within a 

single species. Among factors causing variation are the substratum to 

which they are attached, the toppling over of specimens as the shell 

grows and becomes too heavy for a small, light-weight object to which 

it has attached, the crowding of individuals versus uncrowding, and 

even whether the shell grew in sunlight or in shade (Stenzel, 1971, p. 

N1019). Taking these factors into consideration, it is unwise to propose 

new specific or subspecific names for oysters based on one or a few 

specimens, especially if another species of oyster assigned to the same 

genus has already been described from the same stratigraphic 

horizon.

Family GRYPHAEIDAE

Muscle scar subcircular. Posterior adductor muscle orbicular in 

cross section and placed closer to hinge than to opposite valve margin, 

ventral border of its insertion on left valve sometimes elevated above 

general surface of valve. Valves highly unequal in most genera to 

subequal in others.

Geologic range. Triassic to Holocene.
CIS PALEONTOLOGY OF CALIFORNIA AND BAJA CALIFORNIA

Habitat. Most genera never form true oyster reefs in which conspecific individuals grow mainly on one another.

Subfamily EXOGYRINAE

Chomata commonly present, varied; commissural shelf variable, 

often well defined; chalky deposits not vesicular; umbo of left valve 

inflated, opisthogyrous, coiled in several planes, right valve flat or 

nearly so; posterior bourrelet (posterior-most of three divisions of ligamental area) much reduced, commonly merely a narrow ridge.

Genus GRYPHAEOSTREA Conrad, 1865

Left valve highly convex and capacious; deep umbonal cavity overhung by hinge plate; anterior wall of left valve spirally curved and 

rising up obliquely or vertically from substratum; angular to spoonshaped shelly claspers growing out periodically from growth squamae 

of left valve to provide additional attachments. Right valve flat; outline 

oval to spatulate or triangular; growth squamae simple and spaced 

regularly apart starting close to umbo. Right valve considerably 

smaller than left valve, leaving wide (as much as 0.7 cm) margin on left 

valve uncovered in bivalved fossil specimens.

Geographic range. Worldwide.

Geologic range. Cretaceous to Miocene (table 6).

Gryphaeostrea aviculiformis (Anderson) 

Plate 19, figures 1, 2, 6

Ostrea aviculiformis Anderson, 1905, p.194-195, pi. 13, figs. 3-5. Arnold, 

1909, p. 50, pi. 2, fig. 12. Yokes, 1939, p. 55.

Original description. "Shell small, very inequivalve, quadrate, 

oblique, laminated; inferior valve convex and strongly arched; superior valve thin, often concave, and sharply laminated in thin concentric 

folds; hinge broad and somewhat straight. The surface of the convex 

valve is marked only by concentric lines of growth. The margin is more 

or less ragged or irregular."

Holotype. CAS 21. The type was recovered after the San Francisco 

fire of 1906 but was considerably broken (Yokes, 1939, p. 55).

Type locality. West and north of Coalinga [NW^, sec. 35, T. 20 S., 

R. 14 E., Fresno County], California. Domengine Formation, Eocene.

Supplementary description. "The upper valve *** was strongly 

laminated, with laminae which were approximately one eighth of an 

inch apart." (Yokes, 1939, p. 55)

Comments. The anterior portion of the left valve is auricular and 

has a terebratuloid sinus. The right valve is operculiform with evenly 

spaced, thick laminae made up of prismatic shell layers.

Geographic range. Middle California.

Geologic range. Eocene.

Occurrence in California. Eocene: Domengine Formation (Weaver, 

1949) and Avenal Sandstone (Yokes, 1939).

Subfamily PYCNODONTEINAE

Commissural shelf usually well defined, delimited proximally by 

circumferential curb. Chomata generally present, vermiculate near 

ligament; divisions of ligamental area of equal size; shell vescicular.

Geologic range. Cretaceous to Holocene.

Genus PYCNODONTE Fischer de Waldheim, 1835 

Subgenus PYCNODONTE

Left valve umbo rising barely above long straight dorsal margin. 

Auricles present; outline subcircular to semicircular. Radial ribs 

absent to low, short, and gently undulatory; no. well-defined radial 

riblets.

Geographic range. Cosmopolitan.

Geologic range. Cretaceous to Pleistocene (table 6).

Pycnodonte (Pycnodonte) ynezana (Loel and Corey) 

Plate 11, figures 1, 3, 4, 6

Ostrea eldridgei Arnold. Arnold and Anderson, 1907, pi. 16, fig. 2; not 

pi. 18, figs. 6a, 6b (=O. eldridgei}. Not Ostrea eldridgei Arnold, 

1907a.

Ostrea eldridgei (Arnold) var. ynezana Loel and Corey, 1932, p. 188-189, 

pi. 11, fig. 3; pi. 12, figs, la-lc; pi. 13, figs. 1, 2a, 2b.

TABLE 6. Geologic and geographic distribution of the genera Gryphaeostrea and Pycnodonte in the

eastern Pacific region

[Ple=Pleistocene; Pl=Pliocene; M=Miocene; O=Oligocene; E=Eocene]

Species California Baja California

Northern Middle Southern Norte

Central 

 or South 

Sur America

Genus Gryphaeostrea

aviculiformis (Anderson)..........

Genus Pycnodonte 

Subgenus Pycnodonte

erici (Hertlein)......................

ynezana (Loel and Corey)..... 

Genus Pycnodonte"! 

Subgenus Pycnodontel

heermanni (Conrad).............

howelli (Wiedey)...................

loeli (Hertlein).......................

wiedeyi (Hertlein).................

Subgenus Crenostreat

eldridgei (Arnold).................

stewarti (M.A. Hanna)..........

O and M

O and M

M to Pie 

O and M

MorPl 

O and M 

O and M 

O and M

O and M 

E

PI

PI 

M

PI

PI 

M

M

PI?
TERTIARY MARINE PELECYPODS: PLICATULIDAE AND OSTREIDAE C19

Ostrea eldridgeiynezana Loel and Corey. Addicott, 1965, p. C104, fig. 3f.

Crassostrea eldridgeiynezana (Loel and Corey). Addicott, 1973, p. 27,

pi. 2, 57 figs. 2,10. Squires and Fritsche, 1978, p. 19, pi. 3, fig. 5.

Original description. "Shell medium, moderately thin; beaks 

twisted posteriorly; left or lower valve moderately convex, obliquely 

ovate, irregularly crenulate shell layers smoothly appressed except 

where protruded as plicated edges; beak pointed; posteriorly 

extended, margin thin; upper valve concave and foliated. Interior of 

left valve deep, muscle scar round, central; ligament pit tapering, 

rounded; upper valve interior convexo-concave with lateral ridges and 

flat, wide margins, dorsally truncate with deep, round ligament pit. 

Height, 115 mm.; length, 103 mm.; diameter (thickness through both 

valves), 40 mm."

Holotype. UCMP 31745.

Type locality. UC A-317. At west end of hill that is poorly defined on 

the topographic map about 0.8 km northwest of Rancho Atascoso 

house. 1.9 km S 80° E from 603-ft bench mark on road, Santa Barbara 

County, Calif. Vaqueros Formation, Oligocene and Miocene.

Supplementary description. "Specimens of Crassostrea eldridgei 

ynezana are characterized by their relatively thin valves, the left being 

moderately convex and somewhat larger than the right. The largest 

specimen is about 100 mm in height. During an early stage of growth 

the axis of the valve undergoes a gradual rotation through about 45°, 

the result being posteriorly situated beaks and, on many specimens, a 

subquadrate outline." (Addicott, 1973, p. 27)

Comparison. "This variety of Ostrea eldridgei is gradational in all 

characters to O. eldridgei Arnold ***.It is characterized by its comparative thinness of valves, lesser convexity of the lower valve and 

usual crenulation of the margins in a peculiar curtain-like (ruffle) 

effect. In many specimens the convex valve exhibits strong development of these crenulations, especially toward the margins. The 

umbones are often blunt or truncate." (Loel and Corey, 1932, p. 190)

"This species is similar to Crassostrea sookensis (Clark and Arnold, 

1923, p. 138, pi. 17, figs. 1,2) from the early Miocene(?) Sooke Formation 

of southern Vancouver Island, British Columbia. The northern species 

has a thicker shell in general and a less quadrate outline than specimens of C. eldridgei ynezana, but the holotype is too poorly preserved 

to determine possible relationships confidently." (Addicott, 1973, p. 27)

"The species is differentiated from O. howelli by the presence of low, 

fluted corrugations on the shell, in place of the larger, higher, more 

angular ribs of O. howelli." ( Squires and Fritsche, 1978)

Comments. Although no vesicular shell structure was seen on P. 

ynezana, it is placed in Pycnodonte because it has a long straight hinge 

line, the dorsal margin is produced into a wing, and the interior of the 

right valve has a prominent commissural shelf and its exterior bears a 

few radial gashes.

Geographic range. Middle and southern California.

Geologic range. Oligocene and Miocene.

Occurrence in California. Oligocene: Wygal Sandstone Member, 

Temblor Formation (Addicott, 1973); Oligocene and Miocene: Vaqueros 

Formation (Bereskin and Edwards, 1969; Addicott, 1965; Squires and 

Fritsche, 1978); Miocene: Jewett Sand (Addicott, 1965).

Pycnodonte (Pycnodonte) erici (Hertlein)

Plate 12, figures 1, 4, 7, 8

Ostrea tayloriana Gabb. Jordan and Hertlein, 1926b, p. 428, pi. 33, fig.

3. Not Ostrea tayloriana Gabb, 1869. 

Ostrea erici Hertlein, 1929, p. 295. Durham, 1950, p. 59, pi. 4, fig. 2.

Woodring m Woodringand Bramlette, 1950, p. 85, pi. 8, figs. 17,18;

pi. 9, figs. 1,3,4. Hertlein and Grant, 1972, p. 217-218, pi. 38, figs. 4,

6, 8, 9.

Original description. "Shell moderately thick; sub-oval in outline; 

beaks sub-terminal; ligament pits sub-triangular. Right valve moderately convex, shell slopes obliquely from the umbones to the anterior 

margin, smooth except for projecting edges of shell lamellae; margins 

of shell rather thin. Left valve moderately heavy, ovate in outline, 

slightly concave; edges of shell layers give a rather rough appearance 

to the shell, otherwise without ornament. Height, 94 mm.; width, 71 

mm.; thickness, 36 mm."

Holotype. AS 2094.

Type locality. Mouth of large arroyo northwest of Mesa de Elefante, Laguna Scammon [Laguna Ojo de Liebre, fide Woodring, 1950, 

in Woodring and Bramlette, 1950, p. 85], Baja California Sur. Almejas 

Formation, Pliocene.

Supplementary description. "This species is sculptured with 

lamellae of varying strength. The umbonal part of the shell is thick 

and composed of numerous shell lamellae. On the attached (left) valve 

the outer lamellae form a more or less distinct 'wing5 adjoining the 

attachment area. The ligamental groove is narrow and gradually 

tapering. The inner margin below the ligament area is smooth on 

large shells and smooth or faintly denticulate on small shells." (Woodring in Woodring and Bramlette, 1950, p. 85)

"Shell moderately large, elongately to roundly trigonal, sometimes 

slightly expanded posteriorly; lower valve arched, right (upper) valve 

flat, both valves composed of rather coarse overlapping shell laminae; 

ligamental pit on both valves elongately trigonal, rather small for the 

size of the shell; hinge plate at end of pit rounded and very slightly 

overhanging a shallow cavity; a small flat-topped indentation, corresponding to the lines of growth, occurs on each side of the ligamental 

pit; interior of shell smooth, large adductor impression rounded to 

semi-lunar, situated on the posterior side dorsally a little over one half 

the distance from the ventral margin to to the beak; body cavity often 

bounded on each side by smooth, steep walls beyond which the shell 

tapers to a thin edge; margins smooth, no denticles present." (Hertlein 

and Grant, 1972, p. 217-218)

Comparison. "No similar Recent species is known in California or 

adjoining areas." (Woodring in Woodring and Bramlette, 1950, p. 85)

Comments. The left valve is suboval in outline and the anterior 

dorsal margin is produced into a wing, with the shell layers folded and 

projecting upward. The exterior of the left valve is smooth except for 

paper-thin extensions of the shell laminae that are most noticeable at 

the margins of the shell. The interior of the left valve body cavity is 

bounded by a steep shelf posteriorly near the dorsal margin and a less 

prominent shelf in the same position anteriorly. Vesicular shell structure is visible on the ventral side where the shell is broken or worn.

The right valve is ovate, convex near the dorsal margin and concave 

near the ventral. The exterior of the right valve is smooth except for 

radial gashes and imbricated shell lamellae, thinner at the ventral 

margin and showing thick (as much as 3 mm) vesicular layers where 

broken near the dorsal margin.

Vesicular shell structure is characteristic of the Pycnodonteinae 

and, on the basis of the prominent commissural shelf, auricle, concentric puckers, and radial gashes, this species is assigned to Pycnodonte.

Pycnodonte erici, which closely resembles P. ynezana, differs in that 

the shell is thicker on P. ynezana and markedly produced at the 

posterior ventral margin. The left valve of the holotype of P. ynezana 

has worn, thick extensions of the shell lamellae that probably were 

more spoon-shaped than hyote.

Geographic range. Southern California to Baja California Sur; 

Mexico? (Hertlein and Grant, 1972, p. 218)

Geologic range. Miocene to Pleistocene.

Occurrence in the Californias. Miocene and Pliocene: Sisquoc Formation (Woodring and Bramlette, 1950); Pliocene: Almejas (Minch and 

others, 1976; Smith, 1984), Boleo (Wilson and Rocha, 1955), Carmen 

(Durham, 1950), Cebada Member of the Careaga Sandstone and Foxen 

Mudstone (Woodring and Bramlette, 1950), Gloria (Wilson and Rocha, 

1955), Purisima (Cummings and others, 1962), and Niguel (Vedder, 

1972) Formations; Pliocene and Pleistocene: Fernando Formation 

(Willett, 1946).
C20 PALEONTOLOGY OF CALIFORNIA AND BAJA CALIFORNIA

Genus PYCNODONTE? 

Subgenus PYCNODONTE?

The placement of the species that follow in Pycnodonte? is not based 

on objective criteria. On the basis of shell characters, it does not seem 

possible at this time to determine critically where Pycnodonte ends 

and Hyotissa begins. Harold W. Harry (written commun., 1984) suggested that these thick plicate species might be assigned to Hyotissa?. 

Woodring (1982, p. 607), in describing "Hyotissa" tryoni (Gabb), said 

that: "This species is by no means a typical Hyotissa but may be a 

connecting link between Pycnodonte andHyotissa." On the basis of the 

specimens that I have examined, I prefer at the present time to assign 

the species under discussion to Pycnodonte? (Pycnodonte?). The variability of O. heermanni in collections from the Imperial Formation, for 

example, is considerable; some specimens resemble Hyotissa and others Pycnodonte, but more seem to me to resemble Pycnodonte.

Pycnodonte? (Pycnodonte?) howelli (Wiedey) 

Plate 14, figures 1, 3, 5, 7

Ostrea howelli Wiedey, 1928, p. 135-136, pi. 15, figs. 1, 2. Squires and 

Fritsche, 1978, p. 19, pi. 2, figs. 1-6; pi. 3, figs. 3, 4.

Original description. "Shell of moderate size. Variable outline, but 

most forms exhibit a subcircular to subovoid contour. It is very inequivalve and is seldom equilateral. The left valve is the more convex and 

thick-shelled. In some specimens the dorsal portion is the narrower 

part of the shell while the basal end is often wider and more broadly 

rounded. Umbo of the left valve is found in some individuals to preserve the small subcircular shell of the young stages, showing about 

six prominent, radiating, irregular ribs as the principal sculpturing. 

Sculpturing on the adult consists of about six prominently elevated, 

radiating ridges, separated by narrower channels. Ribs show a tendency to divide at different stages of growth in some specimens. Strong, 

concentric, incremental growth lines become very coarse toward the 

basal margin. The interior is smooth with the muscle impression very 

deep, round, and situated in the posterior portion near the dorsal 

margin. The ligamental pit is robust, moderately long, roundly and 

deeply channeled. Length from the margin at the hinge to the distant 

periphery 90 mm.; breadth, about 60 mm.; thickness of a single valve, 

40 mm."

Syntypes. SDNM 26; CAS 2981,2982; CAS/SU 422 [missing; Keen 

and Bentson, 1944].

Type locality. S\J and SDNM 446. Ventura County, Calif. Vaqueros 

Formation, Oligocene and Miocene.

Comparison. "This new species of Ostrea may not be easily confused with any other known fossil forms because of its very distinctive 

characteristics. It bears external similarity of outline most closely to 

Ostrea vespertina Conrad, but the latter species is much thinner 

shelled. This new form also possesses a much more powerful hinge and 

greater arching of the shell than Conrad's species. It shows a slight 

similarity to O. titan Conrad and O. titan Conrad, var. corrugata 

Nomland. The latter may be separated by its broader resilial pit, 

relatively smaller muscle impression, and much less prominent sculpture of the shell than found in the new species. Among the living forms 

there is very little resemblance to this species. So, apparently, it 

belonged to a group of forms of which there are no, or rare, living 

representatives." (Wiedey, 1928, p. 136)

"Loel and Corey( 1932) synonymized Ostrea wiedeyi with O. loeli, but 

did not note their similarity with O. howelli. O. loeli was distinguished 

by a few, low, broadly rounded ribs, O. wiedeyi by many, prominent, 

elevated ribs, and O. howelli by a few, prominent, elevated ribs. At 

localities where specimens are abundant, however, all three forms 

occur together and are clearly variants of a single species.

"The shell of O. howelli is thicker, the hinge is thicker and stronger, 

and the ligament area longer than in O. vespertina." (Squires and 

Fritsche, 1978, p. 19)

Comments. No vesicular shell structure preserved; deeply 

impressed suboval muscle impression. Pycnodonte? howelli somewhat 

resembles both P.? loeli and P.? wiedeyi but differs from P.? loeli in 

having a narrower shell with more ribs and from P. ? wiedeyi in having 

a much thicker shell with fewer radial ribs.

Geographic range. Southern California.

Geologic range. Oligocene and Miocene.

Occurrence in California. Oligocene and Miocene: Vaqueros Formation (Carson, 1965; Squires and Fritsche, 1978).

Pycnodonte? (Pycnodonte?) wiedeyi (Hertlein) 

Plate 15, figures 1, 4, 5, 8

Ostrea wiedeyi Hertlein, 1928, p. 147, pi. 23, figs. 1,10. 

Ostrea vespertina Conrad. Avila and Weaver, 1969, pi. 34, figs. 8a, 8b. 

Not Ostrea vespertina Conrad, 1854.

Original description. "Shell moderately large, oblong, moderately 

thick, flattish; surface marked by 10 to 15 deep radiating plications 

which have a tendency to become nodose, some of the ribs arise at or 

near the beaks, others branch from the earlier ones or are interpolated 

between them; interspaces angular; the ribs internally show only 

toward the margin. Hinge subtriangular, fairly broad, moderately 

impressed. Muscle scar large, suboval to subquadrate. Altitude 151 

mm.; length 69 mm.; thickness of lower valve 31.5'mm."

Holotype. CAS 4129.

T^pe locality. CAS 1154. Santa Rosa Island, Calif. Vaqueros Formation, Oligocene and Miocene.

Supplementary description. "Ostrea wiedeyi is extremely variable 

from a subovate form ornamented by 12 to 15 radial, nodose plications 

to a long narrow shell with six to eight plications. The ligament pit also 

varies with the shape of the shell; in the subovate forms it is a short, 

turned up triangular pit and in the long shells it is a broad fairly deep 

and slightly depressed scar. These forms all occur in the same zone 

and apparently the great variation is due to differences in the 

swiftness of the water currents in which they grew." (Hertlein, 1928, p. 

147)

Comparison. Pycnodonte? wiedeyi *** differs from O. heermanni 

Conrad by its elongate form, thinner shell and longer ligament pit. 

From O. howelli Wiedey it differs in being a much larger shell, ornamented by more numerous branching corrugations rather than the 

few straight corrugations on Wiedey's species.

The small ovate forms of O. wiedeyi resemble O. vespertina Conrad 

but the shell usually has a thicker and larger shell and a greater 

tendency to adopt an elongate form; also the ligament pit in the 

present species is often quite depressed, narrowly triangular and 

longer." (Hertlein, 1928, p. 147)

"Ostrea wiedeyi Hertlein *** bears a strong resemblance exteriorly 

to O. veatchii. The shell of this Miocene species [O. wiedeyi] is much 

thicker and on some specimens the growth lines loop upward to some 

extent on each side of the ligamental area. Another feature noticed on 

the interior of these fossils is the presence of a depression just below 

the hinge on the posterior side of the body cavity.

"Loel and Corey considered O. wiedeyi to be identical with O. loeli 

Hertlein which they placed as a variety of O. vespertina. The thick 

shell, shape of body cavity, and muscle impression, as well as the shape 

of the hinge line of O. wiedeyi bear a greater resemblance to O. heermanni than to typical O. vespertina. Ostrea wiedeyi bears a close 

resemblance to Ostrea haitensis Sowerby *** from the late Miocene of 

Trinidad but the west coast species differs in lacking the transverse 

vermiculate threads on the margin just below the hinge." (Hertlein 

and Grant, 1972, p. 220-221)
TERTIAEY MARINE PELECYPODS: PLICATULIDAE AND OSTREIDAE C21

Comments. Vesicular shell structure was not found on the type 

specimens but other shell characters seem pycnodontine. The holotype (pi. 15, figs. 5,8) is a large, spatulate right valve with a thick shell 

bearing narrow, rounded, dichotomous ribs on the dorsal half. A few of 

these ribs continue to the ventral margin as wide, low folds of the shell. 

The ribs on the entire valve seem to have had hyote spines, subsequently broken off.

One paratype (pi. 15, figs. 5, 8) is a double-valved specimen; the 

interior is not accessible. The body cavity of the left valve is somewhat 

larger than the right. Both valves with rounded (at the margins) to 

knife-shape (on the midportion), irregular, dichotomous, spinose ribs 

that continue to the shell margins. The commissure is plicate.

The upper (right) valve ofDendostrea? uespertina is flatter than the 

same valve of P.? wiedeyi and bears fewer ribs that are more regular 

and narrower. Externally the paratype of P.? wiedeyi resembles 

Hyotissa haitensis (Sowerby) of Woodring (1982, pi. 98, fig. 2).

Geographic distribution. Southern California.

Geologic distribution. Oligocene and Miocene.

Occurrence in California. Oligocene and Miocene: Vaqueros Formation (Hertlein, 1928).

Pycnodonte? (Pycnodonte?) loeli (Hertlein) 

Plate 18, figures 7, 8

Ostrea loeli Hertlein, 1928, p. 144, pi. 22, figs. 2, 3. 

Ostrea vespertina (Conrad) loeli (Hertlein). Loel and Corey, 1932, p. 

193-194, pi. 16, figs, la, 2; pi. 17, figs, la, Ib, 2a, 2b, 3.

Original description. "Shell quadrate, thick, slightly arched; 

made up of many layers of shell material; shell shows about 6 coarse, 

radial, corrugations which are but little developed or absent in the 

early part of shell but which are pronounced in the adult. Ligament pit 

broad, prominent, distinctly depressed; body cavity sharply depressed 

on one side; muscle scar large, depressed, situated on posterior side of 

shell about one third the length of shell from ventral margin. Height, 

130 mm.; length, 100 mm.; thickness, lower valve, 38 mm."

Holotype. GAS 4117.

Type locality. GAS 1153. Santa Rosa Island, Santa Barbara 

County, Calif. Vaqueros Formation, Oligocene and Miocene.

Comparison. "This heavy oyster resembles Ostrea heermanni 

Conrad from the Pliocene of Imperial County, California but it is more 

quadrate in outline, thicker, and it possesses fewer and heavier plications which are prominent only on the ventral part of the shell; it also 

has a distinctly depressed body cavity and longer hinge line." 

(Hertlein, 1928, p. 144)

"O. loeli Hertlein is a less common variant in the Vaqueros horizon 

which differs from O. wiedeyi Hertlein mainly in degree of sharpness 

of plications. It may be considered to be of varietal value. Most specimens of the latter form show the six primary plications on the younger 

part of the shell. 'O. loeli Hertlein,' in retaining these into the adult 

form, shows a tendency toward O. heermanni Conrad (1885) of the 

Lower Pliocene." (Loel and Corey, 1932, p. 194)

"Loel and Corey considered O. wiedeyi to be identical with O. loeli 

Hertlein which they placed as a variety of O. vespertina. The thick 

shell, shape of body cavity, and muscle impression, as well as the shape 

of the hinge line of O. wiedeyi bear a greater resemblance to O. heermanni than to typical O. vespertina." (Hertlein and Grant, 1972, p. 

220-221)

Comments. No vesicular shell structure was found on the type, but 

other shell characters are pycnodontine. See also Pycnodonte? howelli 

above.

Geographic range. Southern California to Baja California Sur.

Geologic range. Oligocene and Miocene.

Occurrence in the Califomias. Oligocene and Miocene: Rincon 

Shale (Avila and Weaver, 1969) and Vaqueros Formation (Dickinson,

1966; 1969; Vedder, 1973); Miocene: Comondu (Mina, 1956), Topanga 

(J.G. Vedder, written commun., 1978) and Tortugas (Minch and others, 

1976) Formations.

Pycnodonte? (Pycnodonte?) heermanni (Conrad)

Plate 13, figures 1, 4, 6, 7; plate 14, figure 4; plate 16, figure 4; plate 

17, figs. 6, 7

Ostrea heermanni Conrad, 1855, p. 267. GD. Hanna, 1926a, p. 467, pi.

22, figs. 7, 8; pi. 23, figs. 1, 2.

Ostrea veatchii Gabb, 1869, p. 60-61, pi. 17, figs. 21-21a. Not Ostrea 

veatchii Gabb, 1869, p. 34-35, pi. 11, fig. 59.

Original description. "Very irregular in form, thick, ovate and 

often dilated; lower valve shallow; exterior very irregular, with large 

distant angular radiating ribs and with pits, irregular cavities; cartilage pit broad and oblique; upper valve flat or concave, with a profoundly irregular surface. Length, 5.75 inches; height, 6.5 inches."

Holotype. ANSP13367 (Woodring, 1938, p. 46); 4 specimens in type 

lot all are numbered 13367.

Type locality. Colorado Desert, Imperial County, Calif. Imperial 

Formation, Miocene or Pliocene.

Supplementary description. "Although this species has not been 

previously figured, so far as I have been able to determine, there is no 

mistaking the fact that Conrad had specimens of the only large circular oyster of the Coyote Mountain region. It is excessively abundant 

in many places and also excessively variable. Uneroded specimens, 

however, show clearly that it is an irregularly ribbed species." (G D. 

Hanna, 1926a, p. 467)

Comparison. "Small shells varying in outline from circular-ovate 

to ovate-falcate are associated with large specimens of heermanni and 

some of intermediate size *** from the lower part of the Imperial 

Formation. Some of these small specimens (length 37.8 to 44.4 millimeters) have fewer and broader plications than vespertina, but some 

ovate-falcate specimens (length 27.3 to 40.7 millimeters) are indistinguishable from that form in outline, plication, fluting of the inner 

margin, and character of the ligament area. The possibility that two 

species of plicate oysters are represented at this locality seems to be 

remote. These small specimens indicate that vespertina from the 

upper part of the Imperial Formation is a form of heermanni and that 

heermanni should be treated as a nomenclatural variety of vespertina. 

Nevertheless, it does not seem desirable to unite heermanni with 

vespertina, for typical heermanni is readily distinguishable from any 

lot of small oysters from the upper part of the Imperial Formation." 

(Woodring, 1938, p. 46)

Comments. A left valve of P. ? heermanni, collected from the Imperial Formation by Charles L. Powell, U.S. Geological Survey, clearly 

shows vesicular shell structure on the inside of the valve near the 

commissure; this structure was not seen on the specimens in the type 

lot. The shell is thick, mostly smooth with a few irregular subdued 

plications and a very small attachment area. Two fragments seem to 

have had auricles, and the largest specimen in the type lot (pi. 13, figs. 

6, 7), a right valve, is produced at the anterior margin. The chomata 

are vermiculate, the chomatal trough well defined, and the commissural shelf is prominent. These characters combined place heermanni in the subfamily Pycnodonteinae (Stenzel, 1971, p. N1105), yet 

the species does not fit satisfactorily into any of the described genera in 

that subfamily.

Geographic range. Southern California to Baja California Sur.

Geologic range. Miocene(?); Pliocene.

Occurrence in the Califomias. Miocene or Pliocene: Imperial Formation (G D. Hanna, 1926a); Pliocene: Almejas(?) (Minch and others, 

1976), and Infierno (McFall, 1968) Formations and unnamed strata at 

San Felipe (Hertlein, 1968).
C22 PALEONTOLOGY OF CALIFORNIA AND BAJA CALIFORNIA

Subgenus CRENOSTREA Marwick, 1931

Left valve umbo prominent, rising well above hinge line; no auricles; 

outline vertical oval; posterodorsal valve margin not geniculate; 

chomata strong, straight, most not branching; radial ribs short, gently 

undulatory; many variable prominent concentric puckers and welts.

Geographic range. New Zealand, California(?).

Geologic range. Eocene(?); Oligocene and Miocene (table 6).

Subgenus CRENOSTREA?

Pycnodonte? (Crenostrea?) stewarti (M. A. Hanna) 

Plate 19, figures 4, 7, 8

Ostrea stewarti M. A. Hanna, 1927, p. 276, pi. 28, fig. 1; pi. 29, fig. 3; pi. 

30, fig. 3.

Original description. "Species of medium size, massive, pyriform 

to subcircular in outline, beak straight; surface bears only prominent 

partially overlapping growth scales; one valve nearly flat, the other 

moderately inflated; hinge area massive; central depression of hinge 

concave, nearly parallel-sided, much deeper in the convex valve; area 

to either side of the depression flat, and about equal in width to the 

depression; just posterior to the hinge the margin is denticulate with 

narrow sharp teeth, which are separated by round-bottomed interspaces, teeth best developed in the flat valve; adductor scars large, 

subcircular, nearly central and just below the hinge; adductor in the 

convex valve located in a deep pit. Dimensions: Altitude from the beak 

to the ventral 115 mm., length 115 mm., width of the hinge 45 mm., 

thickness of the shell of the convex valve 30 mm., diameter of the 

convex valve 50 mm."

Syntypes. UCMP 30921, 30922.

Type locality. UC 5062. San Diego County, Calif. Rose Canyon 

Shale (M.A. Hanna, 1926), Eocene.

Comparison. "The massiveness of the shell, the position and the 

shape of the adductor scars, and the general character of the hinge 

may be used to distinguish Ostrea stewarti n. sp. from other West 

Coast species." (M. A. Hanna, 1927, p. 276)

Comments. The syntypes are a right and a left valve. Although the 

valves seem to fit together at the ventral margin, they gape markedly 

at the dorsal margin and the ligamental areas are widely separated. 

The left valve is almost ovate, the right valve pyriform. The muscle 

impressions are large and subcircular and positioned near the ligamental areas. The left-valve muscle impression is in a deep pit, unlike 

any I have seen on other Eastern Pacific Tertiary oysters. Both valves 

are thick for their size; the left more so than the right. Chomata are 

preserved on the right valve; no vesicular shell structure was seen. The 

left valve may have had a radial posterior sulcus, has no radial ribs, 

but does have concentric puckers. The exterior shell of the right valve 

is not preserved.

Geographic range. Southern California.

Geologic range. Eocene.

Occurrence in California. Eocene: Rose Canyon Shale (M. A. 

Hanna, 1927) and unnamed strata in the Transverse Ranges (Squires, 

1977).

Pycnodonte? (Crenostrea?) eldridgei (Arnold) 

Plate 21, figures 1, 4

Ostrea eldridgei Arnold, 1907a, p. 528, pi. 42, figs. 2, 2a. Arnold and 

Anderson, 1907, pi. 18, figs. 6a, 6b; not pi. 16, fig. 2 (= O. eldridgei 

ynezana). Loel and Corey, 1932, p. 188, pi. 11, figs, la, Ib, 2. Hertlein 

and Jordan, 1927, p. 622. Hanna and Hertlein, 1943, p. 174, fig. 

63-16. Squires and Fritsche, 1978, p. 19, pi. 4, fig. 1.

Original description. "Shell about 150 mm. in length, inequivalve, 

the left very convex, the right flat or slightly concave. Left valve with 

incurved umbo; a prominent, falcate, evenly convex ridge extends from 

near the umbo to the margin of the left valve posteriorly; surface of this 

valve and ridge foliaceous and more or less inclined to be fluted. Left 

valve approximately flat, with foliaceous surface."

Holotype. USNM164966 [erroneously cited as 164968 in Keen and 

Bentson, 1944].

Type locality. [Oak Ridge], Elkins Ranch, east of Grimes Canyon, 

near Fillmore [sec. 7, T. 3 N., R. 19 W., Piru Quad.], Ventura County, 

Calif. Vaqueros Formation, Oligocene and Miocene.

Supplementary description. "Ostrea eldridgei Arnold is most variable in thickness and ornamentation. The collections examined indicate the existence of two major forms or variants, often found in 

association, with perfect intergradation. One or the other form is 

usually in dominance of numbers in any single zone. Arnold figured 

both forms, the heavier thicker form, lacking plications or 'frills' was 

the first figured and the one described by him." (Loel and Corey, 1932, 

p. 189.)

Comparison. "This species is distinguished from the other Tertiary oysters of the California Tertiary by the prominent posterior ridge 

and incurved umbo of the left valve. The species has the external 

appearance of a Gryphaea." (Arnold, 1907a, p. 528)

Comments. The shell characters of P.? (C?) eldridgei seem pycnodontine, but it is not known if the species has vesicular shell structure. 

The posterior radial sulcus indicates placement in Crenostrea.

Geographic range. Middle California to Baja California Sur.

Geologic range. Oligocene and Miocene.

Occurrence in the Californias. Oligocene and Miocene: Soda Lake 

and Quail Canyon Sandstone Members of the Vaqueros Formation 

(Vedder, 1973), Vaqueros Formation (Addicott, 1972; Squires and 

Fritsche, 1978; Dickinson, 1969); Miocene: Isidro(?) Formation 

(Hertlein and Jordan, 1927) and Monterey Shale (Weaver, 1949).

Genus HYOTISSA Stenzel, 1971

Valves similarly sculptured, left valve slightly more convex; attachment area large to very large; commissure plicate in free-growing 

individuals; ribs crude, irregularly dichotomous, tops mostly rounded 

and crossed by prominent nonappressed growth squamae.

Noninterlocking, adjacent, vermicular ridges, occurring only near 

the ligament in both valves, are regularly present in Hyotissa. 

Hyotissa s.s. may have a few lath chomata below the vermiculate 

chomata.

For variation within one species of Hyotissa, see H. haitensis 

(Sowerby) figured by Woodring (1982, pi. 98, fig. 2; pi. 103, fig. 7; pi. 105, 

figs. 10,11; pi. 109, figs. 6,9-12) from the Emperador Limestone Member, 

La Boca Formation, Miocene, Panama.

Geographic range. Worldwide.

Geologic range. Cretaceous to Holocene (table 7).

Habitat. The genus is euhaline, stenohaline, and stenothermal, a 

member of the compound-coral biocoenosis (Stenzel, 1971, p. N1108).

Hyotissa hyotis (Linne) 

Plate 16, figures 1, 2

Mytilus hyotis Linne, 1758, p. 704, no. 217. Linne, 1767, p. 1155, no. 244. 

Ostreajacobaea Rochebrune, 1895, p. 241. Not Ostreajacobaea Linne,

1758.

Ostrea fisheri Ball, 1914, p. 1, new name. Hertlein, 1957, p. 65-66. 

Ostrea fischeri Ball. Burham, 1950, p. 59, pi. 6, figs. 1,4. Olsson, 1961, p.

173-174, pi. 23, fig. 6.

Original description. "M. testa plicata imbricata squamis compressis patulis, labro utroque laevi." (hyotis)
TERTIARY MARINE PELECYPODS: PLICATULIDAE AND OSTREIDAE C23

TABLE 7. Geologic and geographic distribution of the genera Hyotissa, Neopycnodonte?, Lopha?, ana"

Dendostrea? in the eastern Pacific region

[H=Holocene; Ple=Pleistocene; Pl=Pliocene; M=Miocene; O=Oligocene]

Species California

Northern Middle

Baja California

Southern Norte

Central 

 or South 

Sur America

Genus Hyotissa

hyotis (Linne )......................................

Genus Neopycnodontet

cf. cochlear (Poli). ...............................

Genus Lophat

Subgenus "Lopha"

veatchii (Gabb)..................... ..........

Genus Dendostreal

angelica (Rocheb rune).. ......................

angertnanni (Hertlein and Jordan).....

vespertina (Conrad)............................

PI and Pie

M and PI

OtoPl?

M and PI M and PI

PltoH

PI

PI PI

PI PI to H

M

PI PI

PI toH

PI

"Testa sublibera, apice inferior! tantummodo adherens; 

crassiuscula subrotundata, complanata, ad marginem plicato crenata; 

umbonibus rectis, abbreviatis, pyramidatis; ligamento elongate, subangustato, longe arcuato; valvis subaequalibus, transverse nodoso 

undulatis et radiatim late plicato costatis, plicis irregularibus, obscure 

squamatis, obtusis, interruptis; impressione subcentrali, rotundate 

evato; extus violacca et sordide luteo tincta; intus albonitida, vel cereo 

subpurpureoque peruncta; fuscoviolaceo late marginata." (fisheri)

Holotype. Missing. According to Dodge (1952, p. 206), unmarked 

specimens of the species are found in the Linnaean collection, but 

none can be used as the type, because the name hyotis does not appear 

on Linne's list of owned species, thus raising the probability that the 

specimens were added later and possibly by someone else. Of Ostrea 

fisheri, in Museum Nationale d'Histoire Naturelle de Paris.

Type locality. In Pelagi Gorgoniis; of fisheri, lies de la Baie de la 

Paz.

Supplementary description. "Shell large (length 120 mm), subcircular to obliquely oblong, thick, generally strongly plicated with six or 

more heavy ribs and sharp folds, heaviest near the margin, similar in 

both valves. These ribs occasionally develop irregular hollow tubular 

extensions. *** Adductor scars large, placed slightly posterior of the 

middle. Cardinal area wide and heavy. Substance of the shell is thick, 

made up of porcellaneous layers interfingered with porous and cellular seams.

"Typical specimens have a round, thick shell with strong ribs *** 

Other specimens which have grown attached to smooth piling will 

have a flat or curved surface and a relatively thin shell without ribs." 

(Olsson,1961,p.l73,174)

"*** an extremely variable species, especially in the degree of 

development of the tubular processes arising from the imbricate 

layers of the upper valve, and the available figures are confusing in 

that they usually represent the most highly developed form in this 

respect, a form that is rarely seen" (Dodge, 1952, p. 206).

Comparison. Hyotissa quercinus (Sowerby), a species living at 

Bahia de los Angeles, differs from H. hyotis in being smaller with 

radial plicae rare, small, and local. The left promyal passage is closed 

in H. quercinus whereas it is open in H. hyotissa. (Harold W. Harry, 

written commun., 1983).

Comments. Hyotissa hyotis has vesicular shell structure, irregularly dichotomus ribs with hyote spines, and prominent nonappressed growth squamae.

Geographic range. Living: East Africa and Madagascar to southern Japan; Golfo de California to Ecuador and Galapagos Islands; 

fossil: Baja California Sur to Mexico.

Geologic range. Pliocene through Holocene.

Occurrence in Baja California. Pliocene: Carmen (Durham, 

1950). Infierno (Wilson and Rocha, 1955), Marquer (Durham, 1950), 

and San Marcos (Durham, 1950) Formations and unnamed strata at 

Rancho El Refugio and Isla Cerralvo (Hertlein, 1966); Pleistocene: 

Santa Rosalia Formation (Wilson, 1948) and unnamed strata on Isla 

Carmen (Hertlein, 1957).

Genus NEOPYCNODONTE Stenzel, 1971

Shell walls very thin, outline variable, many individuals auriculate. 

Left valve deep and capacious, posterior half rising vertically from 

substratum attachment so that the hinge axis is at 45°. Left valve 

mostly smooth but older individuals have paper-thin foliaceous 

imbrications near ventral margin and some may be drawn out into 

long hyote or spoon-shaped extensions. Auricles on either side of hinge 

common, foliaceous, and imbricated. Commissural shelf on left valve 

only in dorsal half. Adductor muscle imprint large, diameter about 

one-fourth that of valve height. Right valve flat to concave with a few 

radial gashes. Commissural shelf on right valve nearly complete 

around periphery.

Geographic range. Worldwide.

Geologic range. Oligocene to Holocene (table 7).

Habitat. The type species, Ostrea cochlear Poli, is stenohaline and 

euhaline in oceanic waters of 12-14 °C and at depths of 27-1500 m. 

(Stenzel,1971,p.Nllll).

Genus NEOPYCNODONTE?

Neopycnodonte? cf. N. cochlear (Poli) 

Plate 32, figures 3, 7

Two specimens were figured by Durham (1950, pi. 5, figs. 4, 6) as 

Ostrea cumingiana Dunker. The specimen illustrated in figure 6 is 

Dendostrea? angelica (Rochebrune), and it is included herein in that 

synonymy and illustrated in plate 34, figure 2. The specimen Durham 

(1950) illustrated in figure 4 resembles Neopycnodonte cochlear (Poli,
C24 PALEONTOLOGY OF CALIFORNIA AND BAJA CALIFORNIA

1795, p. 179) and is illustrated in plate 32, figures 3,7.1 have included it 

to call attention to the probable presence of Neopycnodonte in the 

eastern Pacific.

Geographic range. Baja California Sur.

Geologic range. Pliocene.

Occurrence in Baja California Sur. Pliocene: Marquer Formation 

(Durham, 1950).

Family OSTREIDAE

Adductor muscle scar usually concave dorsally or flattened. 

Chomata of pustules in right valve with or without pits to receive them 

in left valve. Chomata absent in some genera throughout postlarval 

life or occasionally in larger specimens of a few genera. Chalk deposit 

when present not vesicular. Commissural shelf rarely well defined.

Subfamily LOPHINAE

Attachment area medium size to large; some genera with shelly 

claspers that grow out at intervals from plicae of left valve to lock onto 

substrate. Valves subequal, with similar rib patterns of regular, subequal, fairly sharp-crested plicae producing a regularly plicate valve 

commissure.

Chomata are minute pustules that usually form a moderately 

broad, usually interrupted submarginal band completely around both 

valves. Pits to receive the pustules are absent in the opposite valve. 

The chomata are aligned on the protochomata with none to three on 

adjacent bands. Other chomata may be present as a single row of 

pustules in right valve with pits to receive them in left. Chalk deposits 

are lacking, and there are many chambers. (Harry, 1983, p. 90)

Genus LOPHA Roding, 1798

Attachment area medium to large. Some species often have shell 

claspers that grow out at intervals on plicae of left valve to lock onto 

substrate. Valves subequal in size and convexity with similar rib 

patterns of regular, subequal, fairly sharp-crested plicae with flat 

sides which produce a regularly plicate valve commissure.

Geographic range. Worldwide in the tropics and partly in the 

subtropics. (Restricted to tropical Indo-Pacific in Holocene.)

Geologic range. Triassic(?) to Holocene (table 7).

Genus LOPHA? 

Subgenus "LOPHA"

Lopha? ("Lopha") veatchii (Gabb) 

Plate 17, figures 1-5

Ofstrea] veatchii Gabb, 1866, p. 34-35, pi. 11, fig. 59; not 1869, p. 60-61,

pi. 17, figs. 21, 21a [ = Ostrea heermanni Conrad]. 

Ostrea veatchii Gabb. Heilprin, 1884, p. 316, pi. 72, fig. 1. Hertlein and

Grant, 1972, p. 219-221, pi. 39, fig. 4; pi. 40, figs. 1, 4-6. 

Ostrea haitensis Sowerby subsp. vespertina Conrad. Stewart, 1930, pi.

14, fig. 4. Not Ostrea vespertina Conrad, 1854. 

"Ostrea" veatchii Gabb. Smith, 1984, p. 206, pi. 4, fig. 6.

Original description. "Shell large, subequivalve, varying from 

nearly equilateral to very oblique, the obliquity being always to the left 

side. Surface marked by ten or a dozen large, angular, radiating ribs, 

some of which arise at or near the beaks, the others branching from 

the first, or interpolated between them; the interspaces are angular, 

and the ribs are marked by more or less squamose plates, and occasionally these plates assume almost the character of spines; internally 

the ribs show only towards the margins. Hinge short, very broad and 

shallow; no crenulations or denticulations near the margin. Muscular 

scar large, suboval to subquadrate."

Holotype. ANSP 4502.

Type locality. Cerros [CedrosJIsland, Baja California Norte. Almejas Formation, Pliocene.

Supplementary description. "The type is a comparatively thin 

(about 4 mm) lower valve, 75 mm high and 68 mm long, the upper 

anterior margin incomplete. The exterior is sculptured with about 10 

angular, radiating ribs which at intervals develop into spines. Interiorly there is no recessed area under the hinge, the muscle impression is fairly large and rounded, and as mentioned by Gabb, there are 

no denticles along the margin of the valve. An upper valve, about the 

same size, gently convex, sculptured similar to the type, is in the type 

lot." (Hertlein and Grant, 1972, p. 220)

Comparison. "The gently arched upper valve, more numerous, 

spinose ribs which deeply interlock along the ventral margin and the 

smooth margins totally lacking denticles are shell characters quite 

different from those of O. vespertina from its type locality.

"Exteriorly some specimens of O. angelica bear a close resemblance 

to O. veatchii. *** The shell of O. angelica is usually thicker, the 

flutings usually do not extend to the dorsal third of the valves and do 

not develop into spines, interiorly the margins below the ligamental 

pit are finely denticulate, and the muscular impression is semicircular 

in outline.

"Examination of about 50 specimens from Pliocene strata on Cedros 

Island, the type locality of O. veatchii, and of additional specimens 

from Bahia Tortolo (Turtle Bay), Lower California, reveals considerable variation. Some of these agree exactly with Gabb's type and lack 

denticles on the margin. Others, usually smaller, more trigonal or 

falcate forms have very fine denticulation only along the upper portion 

of the margin, others have denticulation similar to that on O. vespertina. Also occurring at Cedros Island are specimens agreeing in every 

way with O. angelica. The variation in this series from Cedros Island is 

such as might lead one to question whether perhaps some of these are 

hybrids between O. veatchii and O. angelica. For the present we believe 

it desirable to retain O. veatchii as a separate taxon at least until the 

relationships of west American oysters are better known.

"Ostrea wiedeyi Hertlein described from early Miocene strata on 

Santa Rosa Island, California, bears a strong resemblance exteriorly 

to O. veatchii. The shell of this Miocene species is much thicker and on 

some specimens the growth lines loop upward to some extent on each 

side of the ligamental area. Another feature noticed on the interior of 

these fossils is the presence of a depression just below the hinge on the 

posterior side of the body cavity.

"Ostrea veatchii, at times, has been placed in the synonymy of O. 

haitensis Sowerby, a species occurring in strata of Miocene age in the 

Caribbean region. The west American shell represents a similar but 

distinct species with a thinner shell and without denticles or transverse threads on the margin." (Hertlein and Grant, 1972, p. 220-221) 

Comparison. Pycnodonte? wiedeyi (Hertlein) is thicker shelled 

and has more radial plicae, which are not as sharp-crested nor as high 

as the plicae on L.? veatchii, and the hyote spines are smaller.

Comments. Lopha? veatchii has irregular ribs that are rarely 

dichotomous, hyote spines on young individuals, and very prominent 

nonappressed growth squamae.

The specimen (holotype) first described as O. veatchii (Gabb, 1866) 

and later figured by Gabb (1869, p. 34-35, pi. 11, fig. 59) is thin shelled 

and moderate in size. It has strong, sharp, radial plicae, some with 

hyote spines, a plicate commissure, no commissural shelf, and no 

vesicular shell structure. Because it has lophine characteristics, it is 

here assigned to Lopha?. Subsequently, Gabb (1869, p. 60-61, pi. 17, 

figs. 21, 21a) described and figured another specimen (hypotype) that
TERTIAEY MARINE PELECYPODS: PLICATULIDAE AND OSTREIDAE C25

he identified as O. veatchii. This specimen is a very thick shelled left 

valve with numerous irregularly placed, rough-topped ribs, a strong 

commissural shelf, and vesicular shell structure. It is identified here 

as Ostrea heermanni Conrad, a species that has pycnodontine characters, and is assigned toPycnodonte?. Hertlein and Grant (1972, p. 220) 

noted that this specimen resembled O. heermanni.

Stewart (1939, p. 128-130) placed O. veatchii and O. heermanni into 

synonymy with O. vespertina, an example of the difficulty that workers 

have had differentiating fossil oysters. Ostrea vespertina is assigned 

here toDendostrea ?. The specimen illustrated by Stewart (1930, pi. 14, 

fig. 4) as an example of O. vespertina is the holotype of O. veatchii.

Lopha ? veatchii differs from Lopha chiefly by the absence of fine 

pustules in crowded rows on the extensions of both valves (H. W. Harry, 

written commun., 1984).

Geographic range. Southern California to Baja California Sur.

Geologic range. Pliocene and Pleistocene.

Occurrence in the Californias. Pliocene: Almejas (Mina, 1957), 

Cantil Costero (Hertlein and Allison, 1959), Carmen (Durham, 1950), 

Marquer (Durham, 1950), Niguel (J.G. Vedder, written commun., 

1978), San Diego (Hertlein and Grant, 1972) and San Marcos 

(Durham, 1950) Formations and unnamed strata on Isla Tres Marias 

(Hertlein and Emerson, 1959); Pliocene and Pleistocene: Fernando 

(Arnold, 1907c; English, 1914), PicoCKew, 1924), and Saugus (Kew, 1924) 

Formations.

Genus DENDOSTREA Swainson, 1835

Small (as much as 8.5 cm high); both valves convex, equivalve, shape 

lanceolate to ovate, usually with many rounded to sharp radial plicae. 

Surface without any pustules, but with many fine, closely set growth 

squamae. Hollow recurved hyote spines arise intermittently from 

crests of plicae of left valve; several of them serve as claspers for left 

valve embracing stem of coral and gorgonaceans, but clasper spines 

are usually not present. Dendostrea is highly variable in size, shape, 

and plications. Usually the marginal commissure is finely zigzag, at 

least in some sections. Chomata are variable, being ostreine usually, 

sometimes both ostreine and lophine, and rarely only lophine. (Harold 

W. Harry, written commun., 1984)

The exterior surface of Dendostrea is never pustular as that of Lopha 

s.s., and there are no fingerprintlike markings inside as in 

Alectryonella. Ostreola is about the same size as Dendostrea, but 

plications are generally present only on the left valve. (Harold W. 

Harry, written commun., 1984)

Geographic range. Worldwide. The eastern Pacific Tertiary species are all questionably assigned to Dendostrea.

Geologic range. Miocene to Holocene (table 7).

Habitat. Tropical and partly subtropical; usually attached to 

stony coral, often attached to gorgonians (sea fans).

Genus DENDOSTREA?

Dendostrea? angermanni (Hertlein and Jordan) 

Plate 31, figures 1-6, 8

Ostrea angermanni Hertlein and Jordan, 1927, p. 621, pi. 17, figs. 3,6. 

Clark, 1929, p. 21, pi. 19, fig. 3.

Original description. "Right valve rather small, subquadrate in 

outline, moderately arched; an unornamented area covers beak and 

umbonal region, remainder of shell ornamented by 15 to 20 medium 

fine, well developed radial plications. Interior of valve moderately 

deep, sloping from margins of shell to point of greatest concavity at 

center; hinge shows narrow ligament pit running to anterior dorsal

edge of shell; dorsal and parallel to this another longer, narrow pit 

follows posterior dorsal edge of shell; margins of shell marked with 

small crenulations. Height 46.2 mm.; length 38.9 mm.; greatest diameter of shell 13.1 mm."

Holotype. CAS/SU 5137.

T^pe locality. SU 59. Baja California Sur, Isidro(?) Formation, 

Miocene.

Comparison. "Ostrea angermanni differs from O. vespertina Conrad in possessing a different hinge in which the pits are narrow and 

run obliquely across hinge to anterior dorsal margin of shell; furthermore, the present species possesses many more and much finer radial 

plications on the exterior of the valve. From Ostrea (Alectryonia) 

plicata Chemnitz and O. edulis Linnaeus, O. angermanni can be 

distinguished by the more numerous and finer radial plications ornamenting the right valve. O. angermanni differs from O. sellaformis var. 

thomasii Conrad, in that the lower valve of the present species is more 

quadrate in outline, it is apparently more highly arched and is ornamented by finer ribs." (Hertlein and Jordan, 1927, p. 621)

Comments. The right valve is very inflated compared to the size of 

the shell. Although this species seems to belong in the subfamily 

Lophinae, its characters don't fit well into any of the genera assigned 

to that subfamily by Stenzel (1971, p. N1157).

Geographic range. Southern California to Baja California Sur.

Geologic range. Oligocene to Pliocene(?).

Occurrence in the Californias. Oligocene and Miocene: Vaqueros 

Formation (Clark, 1929); Miocene: Isidro(?) Formation (Hertlein and 

Jordan, 1927); Miocene or Pliocene: Imperial Formation (Bramkamp, 

1935).

Dendostrea? vespertina (Conrad)

Plate 11, figures 2, 5; plate 12, figures 2, 5, 6; plate 13, figure 5; plate 

14, figure 2; plate 15, figures 2, 3, 6, 7; plate 16, figures 6, 7

Ostrea vespertina Conrad, 1854, p. 300. Conrad, 1857d, p. 325, pi. 5, 

figs. 36-38. Arnold, 1909, p. 77, pi. 24, figs. 4,5. G D. Hanna, 1926a, 

p. 468, pi. 26, figs. 1-3. Grant and Gale, 1931, p. 152, pi. 12, figs, la, Ib. 

Woodring, 1938, p. 42-47, pi. 8, figs. 1-4,89; pi. 9, fig. 5. Woodring in 

Woodring and Bramlette, 1950, p. 85, pi. 16, figs. 4,17. Hertlein and 

Grant, 1972, p. 218-219, pi. 39, figs. 1-3, 5-9. Addicott in Addicott 

and Galehouse, 1973, p. 511, 513, fig. 3a-c, h, 1- n. 

Ostrea vespertina Conrad var. sequens Arnold, 1909, p. 79-80, pi. 29, 

figs. 5, 6. Woodring in Woodring and others, 1940, p. 92, pi. 8, figs. 

10-14; pi. 10, figs. 1-5. 

Ostrea haitensis Sowerby subsp. vespertina Conrad. Stewart, 1930, p.

128-130, pi. 14, fig. 4. 

Not Ostrea vespertina Conrad. Durham, 1950, p. 59, pi. 5, figs. 1, 2,5, 7

84 [ = Ostrea angelica Rochebrune].

Original description. "Ovato-subfalcate, lower valve plicated or 

ribbed; hinge long and wide, sharp and somewhat pointed; ligament 

cavity wide, profound, minutely wrinkled; margins abrupt, cavity not 

very deep; muscular impressions large, impressed; upper valve flat, 

irregular; pallial impression crenulated throughout its whole extent, 

profoundly crenulated on the upper half of the shell. From beak to base 

l7/s; transversely IVz." (vespertina)

"Shell averaging about 42 mm., in length, subcircular in outline, 

irregular, plaited, usually with three major plaits, each of these sometimes sulcate or divided into minor plaits; foliaceous lines of growth 

not as prominent as in many species of Ostrea; beak prominent, 

curved toward right when viewed from exterior. Right valve nearly flat 

or only slightly folded, the plaits practically obsolete; incremental 

laminae as in left valve; hinge not strong, subdentate laterally in left 

valve; muscle scars prominent." (vespertina sequens)
C26 PALEONTOLOGY OF CALIFORNIA AND BAJA CALIFORNIA

Lectotype. Ofvespertina ANSP13366 (Woodring, 1938, p. 43); holotype ofvespertina sequens USNM 165545.

Type locality. Ofvespertina, near San Diego [Carrizo Creek, Imperial County fide Woodring, 1938, p. 43], Calif. Imperial Formation, 

Miocene or Pliocene; ofvespertina sequens USGS 4728, Kings County, 

Calif. San Joaquin Formation, Pliocene.

Supplementary description. "Left valves are strongly to moderately plicate; right valves are moderately plicate to warped, some 

small right valves being practically flat. The ligamental groove is 

shallow, relatively wide, and rapidly tapering. The inner margin below 

the ligament area is generally strongly denticulate, but is weakly 

denticulate to smooth, or practically smooth, on a few valves. With few 

exceptions, the umbo is twisted in a counterclockwise direction when 

the shells are viewed in attached position." (Woodring, in Woodring 

and Bramlette, 1950, p. 85)

"The lower valve is usually convex, bearing 5 to 10 plications, and the 

upper valve is flattish and fits down into the fluting around the margin. The margin below the ligamental area bears denticulations which 

sometimes occur along the margin for half the length of the valve." 

(Hertlein and Grant, 1972, p. 218-219)

Comparison. "O. vespertina is smaller, relatively narrower, and 

usually more falcate in outline and carries plaits more regular in size 

and generally fewer in number than O. haitensis." (Arnold, 1909, p. 78)

"Perhaps the average Recent specimen [Ostrea palmula Carpenter, 

1856] has the upper margins a little more fluted and the excavation 

under the beak of the lower (left) valve a little deeper but these 

features are variable in a large series.

"The large oyster from Imperial Co., California, named Ostrea heermanni by Conrad has an ovate, flattish, very thick shell. The body 

cavity is fairly deep on the anterior side and the exterior flutings are 

reflected interiorly along the margins of rather thin valves, but not on 

thick valves. The growth lines are decidedly looped upward on each 

side of the ligamental area, distinctly different from those of O. vespertina which are but slightly or not at all looped upward.

"Some authors have considered a close relationship to exist between 

O. vespertina, O. haitensis Sowerby, O. heermanni Conrad, and O. 

wiedeyi Hertlein. The latter three species bear a greater resemblance 

to O. veatchii Gabb * * * Studies of the type lot of O. vespertina and other 

specimens from the type locality, also the selection of a lectotype by 

Woodring, have furnished a basis for separating this species from 

typical O. veatchii with which it has been united by some authors." 

(Hertlein and Grant, 1972, p. 219)

Comments. I have not seen hyote spines or vesicular shell structure on D. ? vespertina. I place the species in Dendostrea? on the basis 

of its plicate margin, crude, irregularly dichotomous plicae, and rather 

large attachment area. Mostly the muscle scar is prominent, rounded 

medially and pointed peripherally, and distinctly concave on dorsal 

margin.

Addicott (in Addicott and Galehouse, 1973, p. 510-511) considered 

Ostrea vespertina sequens to be a small, weakly sculptured form of O. 

vespertina, a decision with which I concur.

Geographic range. Middle California to Mexico (Hertlein and 

Grant, 1972, p. 219).

Geologic age. Miocene and Pliocene.

Occurrence in the Californias. Miocene: Castaic (Stanton, 1966) 

and Santa Margarita (Nomland, 1917; Adegoke, 1969; Addicott and 

others, 1978) Formations; Miocene and Pliocene: Etchegoin Formation 

(Adegoke, 1969); Miocene or Pliocene: Imperial Formation (G D. 

Hanna, 1926a; Stump, 1979); Pliocene: Almejas (Emerson and 

Hertlein, 1960), Boleo (Wilson, 1948), Cantil Costero (Hertlein and 

Allison, 1959), upper part of Capistrano (Kern and Wicander, 1974), 

Carmen (Durham, 1950), Fernando (Woodring, 1938; Durham and 

Yerkes, 1964; Vedder, 1972), Gloria (Wilson, 1948), Infierno (Wilson, 

1948), Marquer (Durham, 1950); Niguel (Vedder, 1972), upper part of 

Paso Robles (Addicott and Galehouse, 1973), Pico (Winterer and

Durham, 1958), Purisima (Alien, 1946; Wilkinson, 1963), San Diego 

(Hertlein and Grant, 1972), San Ignacio (Mina, 1957), San Joaquin 

(Woodring and others, 1940), San Marcos (Durham, 1950), lower part of 

Saugus (Squires and White, 1983), and Towsley (Winterer and 

Durham, 1958) Formations.

Dendostrea? angelica (Rochebrune) 

Plate 32, figures 1, 8, 9; plate 34, figures 2, 7, 9, 10

Ostrea angelica Rochebrune, 1895, p. 241-242. Keen, 1971, p. 82, fig. 

167. Emerson and Hertlein, 1964, p. 353, figs. 3a-3c. Hertlein and 

Grant, 1972, p. 216-217, pi. 38, figs. 2, 3. 

Lopha angelica (Rochebrune, 1895). Bernard, 1983, p. 24. 

?Ostrea cumingiana Dunker. Durham, 1950, p. 58, pi. 5, fig. 6. Not

Ostrea cumingiana Dunker, 1846.

Ostrea vespertina Conrad. Durham, 1950, p. 59, pi. 5, fig. 7; not pi. 5, 

figs. 1, 2, 5. Not Ostrea vespertina Conrad, 1854.

Original description. "Testa aggregata, plerumque irregulariter 

ovoideo rotundata, apice plus minusive attenuata, ad marginem undulato dentala; umbonibus arcuatis, ligamento obliquo; valvis inaequalibus; valva inferiore subprofunda, intense adherens, circulariter 

radiatim costata; costis crassis subangulosis; valva superiore plana, 

centraliter corrugata, circulariter radiatim costata, costis irregularibus, obtusis plicatis, plicis imbricatis latis; extus albo viridula, 

intus albo nitida virescente; impressione subcentrali albo, trapezoideo; marginibus lateralibus prope umbonibus, minutissime denticulatis."

Holotype. In Musee Nationale d'Histoire Naturelle de Paris.

7\pe locality. Bahia de Los Angeles, east coast of Baja California 

Sur. Holocene.

Supplementary description. "Recent specimens of O. angelica are 

usually oblong or rounded and the shell is rather thick. The lower 

valve is decidedly convex, the upper one only gently so. Both valves are 

sharply plicated over the distal half or one third of their surfaces which 

interlock along the margin, but the plications usually do not extend 

much beyond the pallial line on the interior of the valves. *** Denticles 

or transverse vermiculations are present on the margins from the 

ligamental pit usually to about a third the distance to the ventral 

margin. The muscle impression is posterior to the center, trapezoidal 

in shape." (Hertlein and Grant, 1972, p. 217)

Comparison. "Small specimens of O. angelica differ from O. lurida 

laticaudata Carpenter in the greater thickness of the shell, the more 

convex upper valve which is more deeply plicated and along the margin interlocks downward with the lower valve rather than turning 

upward along the margin and fitting into the scalloped margin of the 

lower valve. Adult shells of O. angelica attain a much greater size and 

thickness than forms of O. lurida.

"These same shell characters serve to separate O. angelica from O. 

palmula Carpenter, with which it occurs in the Gulf of California.

"The valves of O. angelica are generally larger, thicker, and more 

deeply plicated than those of O. vespertina. The plications on the 

exterior of the valves usually are present only on the distal half or 

third of the valves of O. angelica. On the lower valve these plicae extend 

from the margin to the broad unplicated area of attachment. The 

corresponding area of attachment on O. vespertina is usually much 

smaller. Furthermore the upper valve of O. angelica is more convex, 

the plications interlock downward along the margin, whereas on O. 

vespertina the upper valve is almost flat and fits into the scalloped 

edges of the lower valve similar to that of O. lurida laticaudata and O. 

palmula." (Hertlein and Grant, 1972, p. 217)

Comments. The posterior half of the left valve of Dendostrea? 

angelica rises vertically from the substrate, a generic character used 

by Stenzel (1971, p. N1109-N1110) to differentiate the genus Neopycnodonte. In other characters, however, D. ? angelica is closest to
TERTIARY MARINE PELECYPODS: PLICATULIDAE AND OSTREIDAE C27

Dendostrea. According to Harold W. Harry (written commun., 1983), 

its anatomy is distinctly lophine.

Geographic range. Living: Golfo de California; fossil: southern 

California to Mexico.

Geologic range. Miocene or Pliocene to Holocene.

Occurrence in the Californias. Miocene or Pliocene: Imperial Formation (Stump, 1979); Pliocene: Almejas (Minch and others, 1976), 

Carmen (Durham, 1950), Infierno (McFall, 1968), Marquer (Durham, 

1950), and San Diego (Hertlein and Grant, 1972) Formations; 

Pleistocene: unnamed strata in Baja California Sur (Durham, 1950) 

and Mexico (Stump, 1979).

Habitat. At the mouths of estuaries and bays that are sheltered 

from breakers but which have a current (Hertlein and Grant, 1972, p. 

217). From 1-5 m and 13-32 °C (Bernard, 1983, p. 24).

Subfamily OSTREINAE

Left valve often plicate, right valve usually less so, with much 

variation among individuals. Chomata are a single band of pustules in 

the right valve with pits to receive them in the left valve (Harry, 1983, 

p. 90). Chomata are small, few, generally present in small shells, often 

absent in larger ones. Chalk deposits usually present, not vesicular. 

Attachment small to large; no hyote or clasper spines. (Harold W. 

Harry, written commun., 1983)

As restricted by Harold W. Harry (written commun., 1983), Ostrea s. 

s. includes those species that have smooth surfaces or closely spaced, 

thin, fragile imbricated lamellae on the flat right valve which has no 

radial ribs. The left valve has fewer growth rests than the right valve, 

the lamellae are fewer and thicker and narrower but more elevated.

The left valve has numerous, closely spaced, small radial plicae, more 

or less continuous at growth rests. The attachment area is small to 

large.

Genus OSTREA Linne, 1758

Very compressed circular shells with no plications along valve margins. Chomata often absent in large specimens (Harry, 1983, p. 90). 

Genus here restricted to those species which have numerous, closely 

spaced, thin, fragile imbricated lamellae on the right valve. The right 

valve is flat and lacks radial ribs; the left valve has numerous closely 

spaced, small radial plicae. Chalk deposits are usually present. 

(Harold W. Harry, written commun., 1983)

Geographic range. Eastern Atlantic, Indo-West Pacific, Japan and 

adjacent Asiatic coast. No species of Ostrea s. s., as here restricted, is 

known living in the northern hemisphere of the eastern Pacific or 

western Atlantic. Ostrea edulis (Linne) is present in the eastern 

Atlantic and Ostrea denselamellosa Lischke is present off Japan and 

the adjacent asiatic coast. Besides the typical subgenus, a second one, 

Eostrea Ihering, 1907, is represented by a single living species, O. (E.) 

puelchana Orbigny, circum-mundane between 35° and 50° S. latitude. 

Adult shells of the two subgenera are practically the same, and only 

differences in larval form and period of incubation distinguish the two. 

(Harold W. Harry, written commun., 1983)

Geologic range. Cretaceous through Holocene (table 8).

Habitat. In cool, temperate waters, most populations live at a 

depth of several meters, but a few specimens are found at very low 

tides. (Harold W. Harry, written commun., 1983) Open sea and bays in 

salinity of 22-41 parts per thousand (Oyama, 1952, p. 338).

TABLE 8. Geologic and geographic distribution of the genera Ostrea, Ostreola, "Ostrea," and Acutostrea in the eastern Pacific region 

[H=Holocene; Ple=Pleistocene; Pl=Pliocene; M=Miocene; O=Oligocene; E=Eocene; Pa=Paleocene]

Species Alaska British Wash- Oregon 

Columbia ington

California Baja California

Northern Middle Southern Norte Sur

Central 

or South 

America

Genus Ostrea 

Subgenus Ostrea 

atwoodii Gabb.. 

Genus Ostreola 

conchaphila 

(Carpenter)......

Genus Ostreolat 

venturana (Loel 

and Corpy).......

megodon

(Hanley)...........

Genus "Ostrea" 

weaveri 

Dickerson.........

Genus Acutostrea 

idriaensis fettkei 

(Weaver)..........

idriaensis 

idriaensis 

(Gabb).........

simiensis

(Zinsmeister)... 

Genus Acutostreal 

miguelensis 

(Hertlein).........

M and PI M and PI

H H H H H PltoH PI toH PI to H H H

O and M 

M or PI to Pie PI and Pie PI to H PI to H

Pa Pa

Pa and E

E E

E

E 

Pa

O and M
C28 PALEONTOLOGY OF CALIFORNIA AND BAJA CALIFORNIA

Subgenus OSTREA

Ostrea (Ostrea) atwoodii Gabb 

Plate 30, figures 7, 9

Ostrea atwoodii Gabb, 1866, p. 33-34, pi. 10, figs. 58,58a; pi. 11, fig. 58b. 

Arnold, 1909, p. 140, pi. 17, figs. 1, 2. Woodring in Woodring and 

others, 1940, p. 92, pi. 29, figs. 1,13. Durham and Addicott, 1965, p. 

A13, pi. 3, figs. 3, 7. Addicott in Addicott and Galehouse, 1973, fig. 

3p, r.

Original description. "Shell broad, irregular, thin; partly 

attached, sometimes by nearly the whole of the lower surface; free 

surface of lower valve marked by numerous irregular radiating ribs 

crossed by lines of growth; upper valves more squamose and not 

radiated (in the only specimen I have seen). Hinge broad at the base, 

triangular, not deep, and sometimes slightly oblique; inner margin of 

the shell not denticulated. Muscular scar broad."

Holotype. Missing (Keen and Bentson, 1944).

Type locality. San Lorenzo Creek, Monterey County, Calif. Pancho 

Rico Formation, Miocene.

Comments. The smooth, flat right valve and the finely ribbed left 

valve serve to distinguish O. atwoodii.

Geographic range. Middle and southern California.

Geologic range. Miocene and Pliocene.

Occurrence in California. Miocene: Pancho Rico Formation 

(Durham and Addicott, 1965); Miocene and Pliocene: Etchegoin Formation (Woodring and others, 1940; Adegoke, 1969); Pliocene: Paso 

Robles Formation (Addicott and Galehouse, 1973).

Genus OSTREOLA Monterosato, 1884

Stenzel (1971, p. N1138) placed Ostreola in synonymy with Ostrea. 

Ostreola is reinstated here and the information concerning the genus 

was furnished by Harold W. Harry (written commun., 1983).

Shells smaller than those of Ostrea, as restricted herein; generally 

subcircular to slightly elongate dorso-ventrally. The right valve is flat, 

or nearly so, without radial plicae, and the prismatic layer is continuous as a smooth sheet with few growth rests from which no lamellae 

project. Left valve often broadly cemented to substrate, but upturned 

part usually has prominent plications. Ostreine chomata prominent, 

extensive, and persistent in older shells.

Geographic range. Mediterranean and probably southward in the 

eastern Atlantic at least to the equator; western Atlantic from North 

Carolina to Argentina; eastern Pacific from Alaska to Panama.

Geologic range. Oligocene (?); Pliocene to Holocene (table 8).

Habitat. Stenohaline, oceanic salinity. Of the three species known 

living, two extend from the tropics to the cool temperate zone and the 

third may have the same range, but its distribution is poorly known. 

Occasionally found at very low tide level, but optimum populations are 

found subtidally at a depth of a few meters.

Ostreola conchaphila (Carpenter) 

Plate 30, figures 1-4, 6, 8

Ostrea conchaphila Carpenter, 1857, p. 161-163. Palmer, 1958, p. 66 [see

for synonymy]. 

Ostrea lurida Carpenter, 1864, p. 645. Arnold, 1909, p. 167, pi. 30, fig. 12.

Oldroyd, 1924, p. 50, pi. 37, figs. lOa, lOb. Howard, 1935, pi. 7, fig. 5.

Palmer, 1958, p. 66-67, pi. 5, figs. 4-6. Hertlein, 1959, p. 6-7, pi. 2,

figs. 1-3, 6-9,11.

Original description. "O.t. plerumque parva, tenui, subovali, testis variis affixa; purpurea saepe aurantia tincta, interdum radiis una

vel duabus; cardine parvo, utroque latere denticulis crenato; area 

ligamenti augusta, triangulari, saepius sulco denticulate utraque 

parte extus ornata; plerumque tota valva affixa, margine integro, sed 

interdum subiter ascendente, margine undato, vix plicato; intus subnacreo, cicatrice modico, irregulari." (conchaphila)

"T. omnino planata, per totum superficiem affixa; extus, marginem 

versus laminata, purpureo radiata; intus, olivaceo-rufa, ligamento 

parvo, in medio undato, solidiore.

"Animal flavore cupreo tinctum.

"Var. laticaudata, Nutt. ms.: t. omnino purpurea, margine producto, 

undato; cardinem versus, denticulis conspicuis instructo." (lurida)

Holotype. BM(NH); of lurida, syntypes Redpath Museum 125.

T^pe locality. Mazatlan, Mexico, of lurida, Shoalwater, Willapa 

Harbor, Washington (Palmer, 1958, p. 67).

Supplementary description. "Ordinarily it is a very small purple 

shell, frequenting other shells even when living, and often interfering 

with their growth. It is known by the very small triangular ligament 

area, with very fine denticles on each side. In addition to these, there 

are generally (in the attached valve) two lines of denticles situated in 

furrows running outside the area to the umbos. It begins life as a 

swollen regularly formed body, of the shape of Astarte compressa. A 

specimen from S. W. Mexico, in a dead Cypraea, retains this regularity 

and general form: it is smooth, white, and convex. The hinge of the 

attached valve, when extremely young, reminds one of Mesodesma; 

the ligament being internal between two raised processes followed by 

pits; the processes afterwards developing into the ligamental area. 

Sometimes the shell becomes rather thick, and, after continuing 

smooth and flat, suddenly rises, and waves (almost plicating) the outer 

margin." (Carpenter, 1857, p. 162)

"This is a rather small species of an irregular ellipsoidal or elongate 

shape, sculptured with crude, low, irregular plications, or almost 

smooth except for irregularities of growth." (Grant and Gale, 1931, p. 

151)

"Valves thin, irregular in shape, usually circular or elongate, sometimes scalloped at the edges. Surface of both valves flat though may 

conform to contours of substrate." (Fitch, 1953, p. 38)

"The lower (left) valve, shallowly concave, may be attached by a 

small area beneath the umbo or attached by the entire surface. The 

upper (right) valve is flat and fits into slightly raised margins of the 

opposite valve. Several small denticles are present along the margin 

just anterior to the hinge area ***." (Hertlein, 1959, p. 6)

Comparison. "Adult shells of O. angelica Rochebrune attain a 

much greater size and thickness than forms of O. lurida." (Hertlein 

and Grant, 1972, p. 217)

"The smaller size is the only apparent character that distinguishes 

elongate, weakly plicate left valves, and most right valves, of Ostrea 

vespertina sequens Arnold from moderately elongate shells of O. 

lurida." (Woodring, 1938, p. 44)

Geographic range. Living: Alaska to Panama, especially common 

in Willapa Bay and Puget Sound, Washington; fossil: middle California to Baj a California Norte.

Geologic range. Pliocene to Holocene.

Occurrence in the Californias. Pliocene: Almejas (Hertlein, 1933; 

Minch and others, 1976) and San Joaquin (Howard, 1935; Adegoke, 

1969) Formations; Pliocene and Pleistocene: Fernando (Kennedy, 

1975), Merced (Martin, 1916; Glen, 1959), and Saugus (Kew, 1924) Formations; Pleistocene: Anchor Silt (Rodda, 1957), Bay Point Formation 

(Kern and others, 1971), Carlotta Formation (Ogle, 1953), Medill Sand 

(Rodda, 1957), Palos Verdes and San Pedro Sands (Woodring and 

others, 1946), Timms Point Silt (Woodring and others, 1946), and 

unnamed strata in coastal southern California (Valentine, 1956), on 

San Nicolas Island (Vedder and Norris, 1963), and in Baja California 

Norte (Valentine, 1957).

Habitat. "In the Pacific Northwest it is found in beds on the surface of mud flats and gravel bars near the mouths of rivers or streams.
TERTIARY MARINE PELECYPODS: PLICATULIDAE AND OSTREIDAE C29

In other localities it is found in most sheltered inlets and bays along 

the entire coast, attached to the shells of previous generations of 

oysters or any firm surface that will hold it out of the mud. These beds 

may cover several acres and are usually exposed at low tide. Often 

when not in beds these oysters are found singly or in small clusters 

attached to rocks, cement pilings and particularly to metal buoys, 

floats, etc." (Fitch, 1953, p. 38)

Spawns at minimum temperatures of about 14 to 16 °C (Hopkins, 

1936, p. 460). Intertidal to 50 m (Bernard, 1983, p. 23).

Genus OSTREOLA? 

Ostreola? venturana (Loel and Corey)

Plate 31, figure 7; plate 33, figure 5

Ostrea venturana Loel and Corey, 1932, p. 193, pi. 15, fig. 2; pi. 18, figs. 

1,2.

Original description. "Shell small, thin, ovate-pointed; lower 

valve moderately convex with no ornamentation other than fine incremental lamellae. In another specimen the interior of the lower valve is 

seen to be deep, muscle scar central and reniform, margins thin and 

finely serrate, and hinge area is triangular with narrow, deep ligament pit. Upper valve of another individual is convexo-concave or flat, 

with broad hinge area lower than in lower or right valve. Height, 12 

mm.; width, 6 mm."

Holotype. UCMP31751.

Type locality. UC A-321. Santa Barbara County, Calif. Vaqueros 

Formation, Oligocene and Miocene.

Comparison. "Ostrea venturana *** resembles O. lurida *** in 

form, and may be ancestral to it, but is distinct in its constant smaller 

size and ovate-pinnate shape, lack of ornamentation, elongatereniform muscle scar, and serrate margins. The present discussed 

species is distinct in shape and in its lack of medial ridge from O. 

miguelensis Hertlein, the only other small Ostrea known from the 

Vaqueros horizon." (Loel and Corey, 1932, p. 193)

Geographic range. Southern California.

Geologic range. Oligocene and Miocene.

Occurrence in California. Oligocene and Miocene: Vaqueros Formation (Loel and Corey, 1932; Weaver and Kleinpell, 1963).

Ostreola? megodon (Hanley) 

Plate 32, figure 2, 5; plate 34, figures 1, 3, 6, 8

Ostrea megodon Hanley, 1846, p. 106. Jordan and Hertlein, 1926b, p.

427-428, pi. 28, fig. 1. Durham, 1950, p. 59, pi. 5, fig. 3. 

Ostrea (Lopha) megodon Hanley. Keen, 1971, p. 84, fig. 173. 

Ostrea (Agerostrea) megodon Hanley. Hertlein and Grant, 1972, p.

221-222, pi. 38, figs. 1, 5, 7. Smith, 1984, p. 206, pi. 4, figs. 1, 2. 

Agerostrea megodon (Hanley, 1846). Bernard, 1983, p. 23. 

Ostrea cerrosensis Gabb, 1866, p. 35, pi. 11, fig. 61. 

Ostrea megodon Hanley subsp. cerrosensis Gabb. Stewart, 1930, p. 130,

pi. 14, fig. 1. 

Not Ostrea (Alectryonia) megodon Hanley of Olsson, 1964, p. 39, pi. 1,

figs. 1-lb [ = O. messor Maury, 1925].

Original description. "Ost. Testa falcata, glabra, solida, subaequivalvi, pallide livido-purpurascente, margines versus plicata; plicis 

anticis 5 aut 6, maximis, subangulatis; posticis minimis, angulatis, 

paucis sub-obsoletis; margine valde plicato, intusque magis minusve 

scabro; natibus incurvatis; superficie interna albo-virescente, nunquam margaritacea; cicatrice satis magna, reniformi. Long. 5 poll." 

(megodon)

"Shell small, subequivalve, very oblique, strongly falcate, variable 

in form, upper edge entire, concave; lower margin very strongly undulated, each valve bearing four or five rounded, tongue-like processes, 

which alternate in the two valves; the margin, on each valve, between 

these processes, is very much thickened, and presents the squamose 

edges of successive layers of growth. Surface smooth, or marked only 

by rather indistinct lines of growth. Hinge long and very oblique, 

slightly curved. Muscular scars small, rounded subtriangular." (cerrosensis)

Holotype. BM(NH). Lectotype of Ostrea cerrosensis ANSP 4494.

Type locality. Peru. Of O. cerrosensis, Isla Cedros, Baja California 

Norte, Almejas(?) Formation, Pliocene.

Supplementary description. "Shell elongate arcuate, (length up to 

100 mm), the two valves nearly alike, ventral margin folded into three 

or four large, sharp but short plications, attached generally by a small 

area on the extreme umbone of the left valve. The dorsal side is concave 

or excavated, often finely corrugated on the margin. Surface smoothish 

or roughened by concentric growth incrementals." (Olsson, 1961, p. 

173).

Hertlein and Grant (1972, p. 222) noted variation in the development 

of denticles on the shell margins and in the width and depth of fluting 

of Holocene specimens of O. ? megodon.

Comments. The shells of the fossil specimens identified as O.? 

megodon are half the size of Holocene specimens. Although this species bears a striking resemblance to the Cretaceous genus Agerostrea 

Vyalov, 1936 (Stenzel, 1971, p. N1158-N1160)), it differs from that presumedly lophine genus in having fewer marginal undulations; moreover these undulations are all limited to the antero-ventral margin 

and more rounded than those onAgerostrea. The anatomy of Ostreola ? 

megodon is ostreine, not lophine. (Harold W. Harry, written commun., 

1984)

Geographic range. Living: Baja California Sur to Peru; fossil: 

southern California to Mexico.

Geologic range. Miocene or Pliocene through Holocene.

Occurrence in the Californias. Miocene or Pliocene: Imperial Formation (Stump, 1979); Pliocene: Almejas (Minch and others, 1976), 

Carmen (Durham, 1950), Gloria (Wilson and Rocha, 1955), Lomita 

Marl (Woodring and others, 1946), San Diego (Hertlein and Grant, 

1972), San Marcos (Durham, 1950) Formations and unnamed Pliocene 

strata on Isla Tres Marias (Jordan and Hertlein, 1926a); Pleistocene: 

unnamed strata in southern California (Kanakoff and Emerson, 1959) 

and in Baja California Norte (Valentine, 1957).

Habitat. From 5-20 m and 10-31 °C (Bernard, 1983, p. 23).

Subfamily OSTREINAE, incertae sedis

"Ostrea" weaveri Dickerson

Plate 29, figure 2

Ostrea weaveri Dickerson, 1914, p. 127-128, pi. 9, fig. 3.

Original description. "Shell medium in size, subequivalve, irregularly oval, contorted near the beaks, unattached. Surface marked by 

regular squamose lines of growth. Beak twisted and terminating at 

the anterior dorsal margin. The upper half is subglobose while the 

lower half is flat or slightly concave. These two portions are very deeply 

set off and the species is readily determined by this characteristic. In 

the lower valve, the bulging of the upper portion is less prominent. The 

growth lines are remarkably even for this genus."

Holotype. UCMP 32624.

Type locality. UC 781. Vicinity of Lower Lake, SEV4 , NEVi, T. 12 N., 

R. 7 W, Lake County, Calif. Martinez Formation, Paleocene.

Comments. The holotype is a single worn valve with only the 

exterior exposed. It is smooth and much inflated for its size on the 

dorsal half and flat to concave on the ventral half with prominent
C30 PALEONTOLOGY OF CALIFORNIA AND BAJA CALIFORNIA

concentric shell lamellae. "Ostrea" weaveri in profile somewhat resembles "Quadriostrea"Vya\ov (1936, p. 18), from the Cretaceous in Africa, 

which Stenzel (1971, p. N1169) considered an uncertain genus.

Geographic range. Northern and middle California.

Geologic range. Paleocene.

Occurrence in California. Paleocene: Martinez Formation 

(Dickerson,1914).

Subfamily CRASSOSTREINAE

Though the three genera included here tend to be elongate dorsoventrally, they are often oval or even round. The right promyal passage 

is open but smaller than it is in Pycnodonteinae. They tend to live in 

shallower water than all the other oysters. Their shells are very 

erodable but they are thickened in several ways. Chalk and conchyolin 

deposits are common. Plication of left valve is rare (except in Saccostrea) and even more rare on right valve. Ostreine chomata are 

usually present, but absent throughout life in Crassostrea. Attachment absent throughout life in Crassostrea. Attachment area small to 

large; hyote spines absent, except in juveniles of Saccostrea, where 

they are variably present. Left valves sometimes enormously thickened, especially in Saccostrea and Striostrea. (Harold W. Harry, written commun., 1983)

Genus ACUTOSTREA Vyalov, 1936

Medium-sized (as much as 9 cm. high); outline variable, mostly 

elongate-spatulate, straight, or more commonly falcate; subequivalve 

to inequivalve. Left valve beak commonly pointed, straight or variously curved, projecting beyond that of right valve; ligamental area 

acuminate, high triangular, length of resilifer commonly twice that of 

adjoining bourrelet; deep umbonal cavity overhung by hinge plate. 

Left valve commissural shelf with rounded gutter in which pits of 

chomata are located. Left valve with many undulatory growth 

squamae and in some individuals few (about 6) wide low weak radial 

costae. Right valve lacks costae but has concentric growth squamae. 

(Stenzel, 1971)

Kiyotaka Chinzei (written commun., 1983) first suggested that I 

consider the genus Acutostrea for the included species. The genus 

previously was known only from the Upper Cretaceous.

Geographic range. Europe and North America.

Geologic range. Cretaceous to Eocene; Oligocene and Miocene(?) 

(table 8).

Acutostrea simiensis (Zinsmeister) 

Plate 34, figures 4, 5

Ostrea simiensis Zinsmeister, 1983, p. 1286-1287, fig. 1E-G.

Original description. "Shell medium to small gryphaeiform; left 

valve narrow, but occasionally moderately broad; beaks mediumsized, blunt, prosogyral to nearly orthogyral; somewhat enrolled with 

small attachment area; left valve smooth with infrequent low concentric undulations; poorly developed radial sulcus; right valve flat to 

slightly concave with faint squamae."

Holotype. UCR 6899/101.

Type locality. UCR 6899. Ventura County, Calif, Simi Conglomerate, Paleocene.

Supplementary description. "This species is easily recognized by 

its narrow, elongated outline and small to medium size." (Zinsmeister, 

1983)

Comparison. "O. simiensis n. sp. is similar to O. haleyi Hertlein 

from the Eocene, but is not quite as narrow and the beak is more 

prosogyral. The close similarity of the two species suggest that O.

simiensis n. sp. may be ancestral to O. haleyi. The only other oyster (O. 

weaveri Dickerson) occurring in the upper Paleocene of the Simi Hills 

can easily be distinguished by its larger size and coarse, evenly spaced 

squamae." (Zinsmeister, 1983)

Geographic range. Southern California.

Geologic range. Paleocene.

Occurrence in California. Paleocene: Simi Conglomerate 

(Zinsmeister, 1983).

Acutostrea idriaensis fettkei (Weaver) 

Plate 30, figure 5; plate 32, figures 4, 6; plate 33, figures 1-3, 8

Ostrea fettkei Weaver, 1912, p. 30, pi. 4, figs. 37, 39.

Ostrea idriaensis (?var. ) fettkei Weaver. Yokes, 1935, p. 291.

Ostrea idriaensis Gabb var. fettkei Weaver. Yokes, 1939, p. 54-55, pi. 2,

figs. 11,13.

Ostrea crandalli M. A. Hanna, 1927, p. 275, pi. 29, figs. 1, 2. 

Ostrea buwaldana Dickerson, 1914, p. 127, pi. 9, fig. 4.

Original description. "Shell small, thin, somewhat curved, right 

valve nearly flat, left valve convex; hinge deflected to the left and 

median groove very well marked; internal margins in both old and 

young forms are pitted; shell inequivalve and slightly inequilateral; 

left valve ornamented by a marked median ridge extending from beak 

to basal margin; anterior to this ridge are two radiating ribs becoming 

obsolete toward the beaks; posterior surface with six radiating ribs 

extending to the beak; these are crossed by a large number of concentric ribs and lines of growth." (fettkei)

"Shell of medium size or less, roughly trigonal to pyriform, as 

figured; beak acute, not curved; thin, with six large well rounded 

unequal sized ribs which are separated by deep round-bottomed interspaces; crossed by prominent growth lines which become rough laminae on the ribs; valve slightly distorted below the beak; inner margin 

crenulate, corresponding to the ribs and interspaces of the outer 

surface; hinge margin trigonal, slightly rounded internally, central 

depression narrow, relatively shallow, bordered on either side by an 

area which appears rough due to the presence of three rounded toothlike elevations; submargins not denticulate; interior smooth; adductor 

scar marginal, more sub-circular than the figure would indicate. 

Dimensions: Altitude 30 mm., length 43 mm., diameter 15 mm." (crandalli)

"Shell, medium, with thick shell substance, only slightly oblique, 

elliptical; upper valve flat; lower valve deep, convex and marked by 

rough, squamose growth lines and about six strong radiating ribs. 

Muscular scar is reniform, nearly central. Internal margins of some 

specimens distinctly pitted on both sides of beaks in casts of this 

species. Occasionally small tooth-like projections are seen on the shell 

itself on both sides of the beaks." (buwaldana)

Holotype. CAS 479; of crandalli UCMP 31072; of buwaldana 

UCMP11719.

Type locality. One and one-half miles east of Vader on north bank 

of Cowlitz River in sec. 27, T 11 N., R. 2 W, Cowlitz County, Washington. Cowlitz Formation, Eocene; of crandalli UC 3981 San Diego 

County, Calif, Delmar Formation, Eocene; of buwaldana UC 790, 

Lake County, Calif, Martinez Formation, Paleocene.

Comparison. "Ostrea fettkei Weaver represents a variety of Ostrea 

idriaensis bearing definite ribs which are of primary strength and not 

interrupted by the growth-lines . The specimens from the New Idria 

region are all larger than those from the Washington localities." 

(Yokes, 1939, p. 54-55)

Comments. The holotype of Ostrea buwaldana is a badly worn 

specimen and is assumed to be a left valve. Only the internal shell 

layers are preserved and they show fairly large, radial ribs. Yokes 

(1935, p. 292), in his description of idriaensis, said that there is a 

tendency toward the development of a radial type of ribbing but that
TERTIARY MARINE PELECYPODS: PLICATULIDAE AND OSTREIDAE C31

this is always a secondary feature superimposed upon and interrupted 

by the lamellae.

Geographic range. Washington to southern California; 

KamchatkaC?) (Pleshakov, 1939).

Geologic range. Paleocene and Eocene.

Occurrence in California. Paleocene: Martinez Formation 

(Dickerson, 1914); Eocene: Avenal Sandstone (Yokes, 1939), Delmar 

(M. A. Hanna, 1927) and Domengine (Yokes, 1939; Weaver, 1949) Formations, and La Jolla Group (Yokes, 1939).

Acutostrea idriaensis idriaensis (Gabb)

Plate 13, figures 2, 3; plate 14, figure 6; plate 16, figure 3; plate 29, 

figures 3-5

Ostrea idriaensis Gabb, 1869, p. 203, pi. 33, figs. 103b, c, d; pi. 34, figs. 

103,103a. Arnold, 1909, p. 106, pi. 2, figs. 4,5. M. A. Hanna, 1927, 

p. 276, pi. 30, figs. 1,2; pi. 31, figs. 3,4. Stewart, 1930, p. 126, pi. 8, 

fig. 3; pi. 17, fig. 1. Yokes, 1935, p. 291-295, pis. 22-24. Turner, 

1938, p. 46, pi. 6, fig. 9. Yokes, 1939, p. 54. Givens, 1974, p. 44. 

Ostrea columbiana Weaver and Palmer, 1922, p. 13, pi. 8, figs. 15,16. 

Ostrea oregonensis Packard, 1923, p. 4-6, pis. 1-4. 

Ostrea haleyi Hertlein, 1933, p. 277, pi. 18, figs. 5, 6. 

?Odontogryphaea? haleyi (Hertlein). Givens, 1974, p. 45, pi. 1, figs.

11-13.

Original description. "Shell moderately large, oblique, often 

curved, heavy; lower valve usually deep, more oblique than the upper; 

hinge straight or deflected to the left, median groove pretty strongly 

marked; internal margins in the young shell, finely crenulated or 

pitted towards the beak, this character disappearing to a great extent 

in the adult. Surface of both valves roughly and very irregularly 

squamose. Muscular scar reniform to semicircular, and placed distinctly to one side of the middle." (idriaensis)

"Shell large and elongate in outline; right valve very convex and 

irregular; left valve flat or concave with the anterior end straight 

dorsally, swinging into the ventral margin with a broad curve which 

continues ventrally to the posterior ventral end; posterior end with a 

more or less deep concave area at about one-third of the distance from 

the dorsal line; shell very thick; surface of the left valve rough and 

irregular with overlapping laminae; surface of the right valve 

smoother, the growth lines more regular than those of the left valve; 

left valve with a glossy, corneous outer layer over which are fine yet 

conspicuous radiating lines; beaks deflected posteriorly; anterior and 

posterior margins internally or laterally with coarse transverse 

grooves." (columbiana)

"Shell large, very thick and irregular; subcircular to subovate in 

outline; left valve very convex, tumid; right valve opercular-form. 

Anterior dorsal margin of left valve of type and cotype very regularly 

rounded, for nearly 180 degrees from the beak; base sloping upwards 

to the slightly attenuated but evenly rounded posterior end. Umbone 

of type very prominent, strongly curved inward and backward and 

terminating in a sharply pointed, slightly twisted beak. In both specimens the beaks lie well within the margin of the shell. The beak of the 

cotype is deformed by a large, linear scar of attachment which shows 

the external mold of a gastropod. An indistinct umbonal ridge extends 

in a curve, anteriorly, for about half the distance to the anterior 

extremity. The outline of the flat upper valve of the type is nearly 

elliptical, much thinner, than the lower one and only slightly convex. 

Umbone depressed; beak small, twisted slightly posteriorly and situated well within, but not far from the margin of the shell. Surface of left 

valve marked by heavy concentric imbricating growth lamellae which 

are irregularly nodose, tending to be radially arranged on the umbone. 

The growth lamellae of the right valve are thin, ridge-like and lack the 

nodose character of the left except at the very apex where faint radiating costae may be seen.

"Interior of left valve with a broad shallow irregular ligamental 

groove, slightly depressed near and parallel to the margin of the shell; 

lateral margins of hinge and valve pitted or crenulated, the crenulations extending on either side nearly to the base. Adductor scar 

impressed, situated posterior to the center." (oregonensis)

"Shell elongate, rounded umbos, broader toward the base; beak 

curved inward and backward; a shallow groove extends from near the 

beaks to the ventral margin of the shell where it is more pronounced; a 

well-defined ligament pit is present beneath the beak. Altitude 45.5 

mm.; approximate longitude (shell not complete) 32.5 mm." (haleyi)

Holotype. Lectotype of idriaensis MCZ 15048 (Stewart, 1930); of 

columbiana, missing and presumed lost; of oregonensis UO 20; of 

haleyi GAS 5526.

Type locality. About 3 km east of Hacienda at the New Idria [Priest 

Valley Quad., NV2 sec. 15, T. 17 S., R. 12 E., San Benito County, Calif], 

Domengine Formation, Eocene. Of columbiana UW 160A, Cowlitz 

County, Wash. Cowlitz Formation, Eocene; of oregonensis UO 130, 

Douglas County, Oregon, Umpqua Formation, Eocene; of haleyi Canada del Pozo, Santa Cruz Island, Santa Barbara County, Calif. Canada(?) Formation, Eocene.

Supplementary description. "The characters which appear to be 

diagnostic for Ostrea idriaensis Gabb are:

1. Valves discrepant in size; the lower much larger than the upper.

2. Shape variable; umbos generally straight or twisted to the left ,but 

may be slightly twisted to the right.

3. Valves elongate and broader near the base.

4. Lower valve with rugose, coarse, concentric lamellae of growth, a 

superimposed radial ribbing commonly present; upper valve 

with finer lamellae of growth, ribbing not present.

5. Lines on the sides of the upper valves near the umbos, reflecting 

the denticulations present on the lateral margins of the body 

area of the shell.

6. Ligamental area of the lower valve consisting of a well-marked 

median groove with two prominent ridges, one on each side, 

which are bounded by small, linear, lateral grooves at the edges 

of the area.

7. Ligamental area of the upper valve with a median groove, and two 

lateral grooves complementary to the ridges of the ligamental 

area of the lower valve.

8. Ligamental area commonly twisted to the left, but may be 

straight or slightly twisted to the right.

9. Denticulations present on the lateral margins of the body area of 

the upper valve near the ligamental region, fitting into pits on 

the lateral margins of the body area of the lower valve.

10. Left margin of the lower valve commonly with an impressed area 

into which a corresponding protuberance on the upper valve is 

fitted.

11. Muscle scar reniform to subcircular; situated approximately onesixth of the distance across the body area from the left side." 

(Yokes, 1935, p. 295)

Adult specimens show a great variation in size. Yokes (1935, p. 

292) noted that adult left valves range from 65 to 92 mm in height, 50 

to 61 mm in length, and 26 to 34 mm in thickness; adult right valves 

range from 61 to 64 mm in height, 50-53 mm in length, and 14 to 21 mm 

in thickness.

Comparison. In O. idriaensis radial ribbing may develop but it is a 

secondary feature superimposed upon and interrupted by lamellae, 

whereas in O. idriaensis 'fettkei some of the radial ribs become a 

primary sculptural feature and are little interrupted by growth 

lamellae. (Yokes, 1935, p. 292-293)

The two linear lateral grooves in the ligamental area of O. idriaensis 

are never as strongly developed as they are on O. stewarti M. A. Hanna, 

and the muscle scar on the left side of the body area is never so circular 

as on O. stewarti. (Yokes, 1935, p. 293, 294)

Geographic range. Washington to southern California.
C32 PALEONTOLOGY OF CALIFORNIA AND BAJA CALIFORNIA

Geologic range. Eocene.

Occurrence in California. Eocene: Avenal Formation (Yokes, 

1939), Canada Formation (Doerner, 1969), Coldwater Sandstone 

(Weaver and Kleinpell, 1963), Delmar (M. A. Hanna, 1927), Domengine 

(Yokes, 1939; Givens, 1974), and Juncal (Givens, 1974) Formations, La 

Jolla Group (M. A. Hanna, 1927), Matilija Sandstone (Givens, 1974), 

Sacate (Dibblee, 1950), and Tejon (Givens, 1974) Formations.

Genus ACUTOSTREA?

Acutostrea? miguelensis (Hertlein) 

Plate 33, figures 4, 6, 7, 9

Ostrea miguelensis Hertlein, 1928, p. 146, pi. 23, figs. 3-6. Loel and 

Corey, 1932, p. 191, pi. 10, figs. 2a, 2b, 3a, 3b.

Original description. "Shell small; obliquely subovate, beaks 

pointed; shell fairly thick. Lower valve convex, a slight groove runs 

from beak to umbo, two or three irregular projections of shell material 

are irregularly scattered on valve, ornamentation consists of fine 

lamellar edges of shell. Upper valve gently concave with a small raised 

median ridge which runs from the beak for one third the length of 

shell, otherwise ornamented only by the incremental shell lamellae. 

Height from beak to base, 21.5 mm.; greatest anterior-dorsal width, 21 

mm.; convexity of valves, 9.1 mm."

Holotype. CAS 4121.

Type locality. CAS 1163. San Miguel Island, Calif. Vaqueros Formation, Oligocene and Miocene.

Comparison. "Ostrea miguelensis is distinct through its possession of a narrow medial plication effecting [sic] both valves." (Loel and 

Corey, 1932, p. 191)

"This small oyster *** in many of its features seems to resemble O. 

idriaensis Gabb, from the Upper Eocene but it is much smaller and 

commonly possesses a median ridge on the upper valve. O. miguelensis 

resembles the early part of O. bourgeoisii Remond, from the Upper 

Miocene of California but is more ovate and does not attain a large size; 

many of the specimens are not ornamented except for the incremental 

lines of growth. In some specimens the beaks turn anteriorly, in others 

posteriorly; apparently the direction depends upon the position 

assumed at the time of attachment. The raised median ridge on the 

upper valve appears to be an unusual feature in this interesting little 

shell." (Hertlein, 1928, p. 146)

Comments. Although I am reasonably satisfied with the generic 

placement of miguelensis, I have queried the generic assignment 

because neither of the small double-valved syntypes has the interior of 

the valves exposed.

Geographic range. Southern California.

Geologic range. Oligocene and Miocene.

Occurrence in California. Oligocene and Miocene: Vaqueros Formation (Hertlein, 1928; Loel and Corey, 1932).

Genus SACCOSTREA Dollfus and Dautzenberg, 1920

Small to medium-sized, outline variable. Left valve with large 

attachment area; radial ridges on upturned part. Umbonal cavity 

usually very deep. Right valve flat, free of folds, but has many scaly 

growth squamae. Both valves usually have strong chomata which 

commonly encircle entire valve. Conchyolin deposits abundant. Exterior usually very eroded; contour pattern usually present on right 

valve.

Differs from Crassostrea in its deeper umbonal cavity, strong 

chomata, and tendency to conical rudistiform or cornucopialike 

shapes.

Geographic range. Nearly circumglobal in the tropics; but absent 

among living oysters in the western Atlantic.

Geologic range. Miocene to Holocene (table 9).

Habitat. Chiefly intertidal, mostly on noncalcareous rocks in surf 

zone. Occasionally on mangrove in high salinity zone.

Saccostrea palmula (Carpenter) 

Plate 18, figures 1-6

Ostrea ?? conchaphila, var. palmula Carpenter, 1857, p. 163-164, 550. 

Ostrea palmula Carpenter. Keen, 1971, p. 84, fig. 174.

Original description. O. ?? conchaphila t. satis magna, margine 

subito ascendente, valva inferiore superante, undulato, limbo purpureo scu olivaceo irregulariter tessellato; linea pustularum valva 

superiore, in parte nacrea a margine remota, circumeunte, in puncta 

convenientia valva inferiore aptante; pagina interna subnacrea, 

aurantio seu purpureo tincta; rarissine spinis ramosis paucis, tabulis 

ad marginum exteriorem arborescentibus.

Holotype. BM(NH).

Type locality. Mazatlan.

Supplementary description. "Remarkable for the palmated foliations in the outer margin, which has a distinct limb mottled with 

purple and olive; and for the row of denticles within this limb and 

within the nacreous border, fitting into corresponding depressions in 

the other valve." (Carpenter, 1857)

"One of the most variable of the Panamic province oysters, this may 

be recognized by the flat or even concave upper valve that fits down into 

the plicate margins of the cup-shaped lower valve'*** ." (Keen, 1971, p. 

84)

Comparison. "Modern shells *** of O. palmula Carpenter, resemble ovate or ovate-falcate specimens of the coastal vespertina in size, 

but they have an exceptionally long strongly fluted area on the inner 

margin." (Woodring, 1938, p. 44-45)

According to Woodring (in Woodring and Bramlette, 1950, p. 85) S. 

palmula has more numerous plications and is considerably smaller 

than Dendostrea vespertina.

Comments. Saccostrea palmula has an exceptionally large attachment area, obliterating all but the commissure on some left valves, 

and the posterior half of the left valve rises vertically from the attachment area. The unattached valve fits snugly down into the attached 

valve.

Geographic range. Living: eastern Pacific tropics and Galapagos 

Islands; fossil: southern California to Baja California Sur.

Geologic range. Miocene or Pliocene to Holocene.

Occurrence in the Californias. Miocene or Pliocene: Imperial Formation (Stump, 1979); Pliocene: Pico (Waterfall, 1929) and Salada 

(Beale, 1948) Formations.

Genus STRIOSTREA Vyalov, 1936

The hinge line ofStriostrea is usually long relative to that of other 

oysters; the left beak often very large. The shell interior is subnacreous and the right valve peculiarly brittle, with flaky splinters left 

at the fractures. Juveniles have prominent ostreine chomata which 

are usually reduced or even absent in larger specimens. The numerous 

fragile, appressed lamellae of the right valve have peculiar fine radial 

striae on them, but this is best seen on small shells, as the valves 

become much eroded as they grow. The shells generally grow to ponderous size (as much as 20 cm high) and usually attach by most of the 

left valve to firm rocks. The left valve often becomes very thick, by 

continuous secretion of the foliar layer, and the specimens may be 

raised thus on pedicels, as high as the maximum dimensions of the 

shell in profile. Much brown conchyolin is produced in the process, but
TERTIARY MARINE PELECYPODS: PLICATULIDAE AND OSTREIDAE C33

chalk formation is not as common as in Crassostrea. (Harold W. Harry, 

written commun., 1983)

Differs from Crassostrea by having chomata, a nacreous and iridescent interior, a very foliaceous shell structure, and a rudistiform 

growth pattern.

Geographic range. North America, east and south Africa, 

Madagascar, Central America, west coast of Baja California. The 

eastern Pacific Tertiary species are all questionably assigned to Striostrea.

Geologic range. Eocene to Holocene (table 9).

Habitat. In shallow subtidal waters where there is strong surf and 

constant oceanic salinity. (Harold W. Harry, written commun., 1983)

Genus STRIOSTREA?

Striostrea? tayloriana (Gabb) 

Plate 29, figures 7, 8

Ostrea tayloriana Gabb, 1869, p. 34, pi. 12, figs. 60, 60a. Grant and 

Gale, 1931, p. 153. Weaver and Kleinpell, 1963, p. 197, pi. 29, figs. 6, 

8.

Not Ostrea tayloriana Gabb. Jordan and Hertlein, 1926b, p. 428, pi. 33, 

fig. 3 [ = Ostrea erici Hertlein, 1929].

Original description. "Shell large, thick, irregularly subtriangular, resembling somewhat some of the more massive forms of O. 

virginica; not attached. Surface covered by heavy, irregular, subsquamose plates, showing more or less of a faint undulation on their 

edges. Interior unknown. Hinge broad and short(?)."

Holotype. UCMP12005.

Type locality. San Marcos Pass, near Santa Barbara [NVfc sec. 21, T 

5 N., R. 28 W., Santa Ynez Quadrangle]. Santa Barbara County, Calif. 

Gaviota(?) Formation, Eocene and Oligocene.

Comments. The supposed relationship of S. ? tayloriana to 

Crassostrea was first suggested by Gabb, when he commented on its 

similarity to Crassostrea virginica, and later by Dall (1909, p. Ill), 

when he erroneously synonymized it with Crassostrea titan titan. The 

holotype is a double-valved specimen with the valves together and 

closed, thus making the hinge inaccessible. Weaver and Kleinpell 

(1963, pi. 29, fig. 8) illustrated a left valve of tayloriana, assumed to be 

correctly identified, and their specimen shows the interior of the shell.

Geographic range. Southern California.

Geologic range. Eocene and Oligocene.

Occurrence in California. Eocene: Coldwater Sandstone (Bailey, 

1952); Eocene and Oligocene: Gaviota Formation (Dibblee, 1950); 

Oligocene: Alegria Formation (Dibblee, 1950; Weaver and Kleinpell, 

1963).

Striostrea? appressa (Gabb) 

Plate 12, figure 3; plate 16, figure 5

Ostrea appressa Gabb, 1869, p. 203-204, pi. 34, figs. 104,104a. Stewart, 

1930, p. 127-128, pi. 13, fig. 1.

Original description. "Shell thin, flat, more or less equilateral, 

valves nearly equal, usually about two-fifths longer than wide. Surface covered by numerous, thin, squamose plates. Hinge flat, large; 

margins simple, sometimes subsquamose. Muscular scar small, 

oblique."

Syntype. MCZ15013 [The best of four specimens labelled in Gabb's 

handwriting, according to Stewart, 1930, p. 127]. Missing and presumed lost.

Type locality. On one of the branches of Eel River, at the mouth of 

Salt Creek, southwest of Round Valley, Mendocino County, Calif. Tejon 

Formation of Gabb (1869) or Temblor Formation of Samuel G. Clark 

(1940).

Supplementary description. "The species is remarkable for its 

thin, flat shell, often distorted, and for its broad, flat hinge." (Gabb, 

1869, p. 204)

"The free valve is convex externally, near the hinge, and concave in 

the central part *** One specimen retains radial ribs on the external 

central portion of the valve." (Stewart, 1930, p. 128)

Geographic range. Northern California.

Geologic range. Eocene(?) or Oligocene and Miocene.

Gabb (1869, p. 203) wrote, "I found this shell forming a stratum 

several feet thick, adjoining a bed of coal, and in associated strata were 

familiar species characteristic of the Tejon Group.

"The locality is on one of the branches of Eel River, at the mouth of 

Salt Creek, southwest of Round Valley ***."

Samuel G. Clark (1940, p. 135) placed Gabb's type locality (Middle 

Fork of the Eel River at the mouth of Salt Creek, NEVi sec. 11, T. 21 N., 

R. 13 W.) in the Temblor Formation. He said that in the shale above the

TABLE 9. Geologic and geographic distribution of the genera Saccostrea and Striostrea? in the

eastern Pacific region

[H=Holocene; Pl=Pliocene; M=Miocene; O=Oligocene; E=Eocene]

Species California

Northern Middle Southern

Baja California Central

 or South

Norte Sur America

Genus Saccostrea

palmula (Carpenter)...................................

Genus Striostreat

appressa (Gabb).........................................

bourgeoisii bourgeoisii (Remond)..............

bourgeoisii perrini (Hall and Ambrose).....

freudenbergi (Hertlein and Jordan)...........

subtitan (Loel and Corey)..........................

tayloriana (Gabb).......................................

E?, O, and M

M 

M

M? and PI

M

O and M 

O and M 

Band O

H

M

PltoH

M

H
C34 PALEONTOLOGY OF CALIFORNIA AND BAJA CALIFORNIA

coal seam were some oysters and gastropods that F E. Turner said 

could be either Miocene or Eocene and that the nearest strata equivalent to Gabb's Tejon was 2.2 km up the river.

Because Gabb (1869, p. 203) said that he found appressa adjoining a 

bed of coal, it seems reasonably certain that the type locality is indeed 

in the Temblor Formation as mapped by S. G. Clark (1940; locality 56). 

A Desmostylus tooth was collected, presumably at this same locality, 

and is in the collections of the California Academy of Sciences (VanderHoof, 1937). The oldest known geologic record for Desmostylus is 

late Oligocene, and the genus is common in the Temblor Formation. It 

seems more likely that C. ? appressa was collected from the Temblor 

Formation than from Gabb's Tejon, yet it is puzzling that Gabb (1869, p. 

203) said he found "familiar species characteristic of the Tejon Group" 

in associated strata with C. ? appressa.

Occurrence in California. Oligocene and Miocene: Temblor(?) Formation (Clark, 1940).

Striostrea? freudenbergi (Hertlein and Jordan)

Plate 26, figure 3; plate 27, figure 3

Ostrea freudenbergi Hertlein and Jordan, 1927, p. 622, pi. 17, fig. 9; pi. 

18, fig. 4. Loel and Corey, 1932, p. 190-191, pi. 14, figs, la, Ib; pi. 15, 

figs, la, Ib.

tOstrea freudenbergi Hertlein and Jordan. Adegoke, 1969, p. 108, pi. 4, 

fig. 7; pi. 5, fig. 7.

Original description. "Shell elongate, thickness medium, right 

valve moderately arched, narrow at beak but widening ventrally, made 

up of flattish layers of shell material which is ornamented by faint, 

rather small radial plications. Interior of valve under beak possesses a 

ligament pit which is rather prominent, long, fairly broad and moderately impressed; concavity of shell moderately deep, just ventral to 

ligament pit but becoming flatter toward the ventral margin; ventral 

muscle scar fairly large, impressed and located on the anterior side of 

the shell about a third of the length of shell from the ventral margin. 

Height 88.5 mm.; length 61.1 mm.; greatest diameter 21.1 mm."

Holotype. CAS/SU 5138.

Type locality. CAS/SU 59. "Turritella bed above San Gregorio 

Lagoon, 120 miles [190 km] north of Magdalena Bay *** on the trail 

from Arroyo Mesquital to La Purisima." Baja California Sur, Isidro(?) 

Formation, Miocene.

Comparison. "Ostrea freudenbergi can be distinguished from O. 

chilensis Philippi and other west coast Ostreas by its only moderately 

high right valve, elongate shape, faint radial ornamentation, differently shaped ligament pit and long, narrow beaks." (Hertlein and 

Jordan, 1927, p. 622)

Comments. One method suggested by Stenzel (1971, p. N995) for 

distinguishing the right from the left valve on oysters is to draw the 

mid-axis on a valve. The center of the adductor muscle then falls to the 

left side on the inner face of the left valve and to the right side on the 

right valve. If this is done on the holotype of S. ? freudenbergi, it is seen 

to be a left valve, although it was described as a right valve (Hertlein 

and Jordan, 1927, p. 622).

The left valve holotype of S.? freudenbergi is small, relatively thick 

with faint traces of radial ribs. It is narrow for about half the height of 

the shell and then widens. The muscle impression is deep and 

subquadrate. The ligamental area is moderately narrow and the 

resilifer shallow. The faint radial ribs suggest Striostrea.

Geographic range. Southern California to Baja California Sur.

Geologic range. Oligocene and Miocene.

Occurrence in the Californias. Oligocene and Miocene: Vaqueros 

Formation (Loel and Corey, 1932; Vedder, 1973); Miocene: Isidro(?) 

Formation (Hertlein and Jordan, 1927), Saltos Shale Member, Monterey Shale (Vedder, 1973), and Tortugas Formation (Minch and others, 

1976).

Striostrea? subtitan (Loel and Corey)

Plate 22, figures 3-5

Ostrea titan Conrad. Arnold, 1907a, pi. 40, fig. 2. Not Ostrea titan

Conrad, 1853.

Ostrea new species near titan Conrad. Arnold, 1907b, p. 32. 

Ostrea titan (Conrad)subtitan Loel and Corey, 1932, p. 192, pi. 18, fig. 3.

Original description. "There occurs in the Vaqueros horizon an 

Ostrea species which is identical in all characters with O. titan Conrad 

except in its constant comparatively greater length in proportion to 

height ('wider' valves) and smaller size. Arnold (loc. cit.) noted this 

from the Vaqueros of the western Santa Ynez Mountains, where it is 

associated with a typical Vaqueros assemblage. An Ostrea of very 

similar form occurs in the Oligocene in this same region. This form is 

probably ancestral to O. titan Conrad (1853) of Middle and Upper 

Miocene. The specimen figured is from Univ. Calif, loc. A326, San 

Antonio Creek, Ventura County, found associated withPecten magnolia, Rapana vaquerosensis, and others characteristic of Vaqueros, 

Lower Miocene."

Holotype. UCMP 31750.

Type locality. UC A-326. Ventura County, Calif. Vaqueros Formation, Oligocene and Miocene.

Comments. The holotype is a double-valved specimen with the 

valves separated. The specimen, poorly preserved, has few distinguishing features except that it has a rounder outline than C. titan 

and is smaller. The adductor muscle impression is somewhat 

reniform, suggesting Striostrea.

Geographic range. Southern California.

Geologic range. Oligocene and Miocene.

Occurrence in California. Oligocene and Miocene: Vaqueros Formation (Loel and Corey, 1932); Miocene: Beechers Bay Member 

(Weaver and Doerner, 1969) and Saltos Shale Member (Vedder, 1973) of 

the Monterey Formation.

Striostrea? bourgeoisie bourgeoisii (Remond)

Plate 25, figure 1; plate 26, figure 5

Ostrea bourgeoisii Remond, 1863, p. 13. Gabb, 1866, p. 33, pi. 11, figs. 57, 

57a. Clark, 1915, p. 447-448, pi. 43. Eaton, Grant, and Alien, 1941, 

p. 240, pi. 3, fig. 1. Hertlein, 1951a, p. 188, fig. 1, no. 1.

Original description. "Shell suboval, higher than long, strongly 

contracted near the cardinal area, sub-rounded on the ventral margin; 

inferior valve comparatively thin, convex, irregular exteriorly, with 

remote, somewhat rugose plaits of growth. Ligament fossa long, profound, minutely wrinkled and finely striated, oblique and turned 

downwards; muscular impression very large, oblique, and sub-central, somewhat prominent."

Holotype. Location unknown. Remond (1863, p. 13) said that he 

was describing "two lower valves, from the collections of Mr. 1 'Abbe 

Bourgeois (Pont-Levoy, France) and Mr. Bioche (San Francisco)".

Type locality. Vicinity Kirker's Pass [NJ/2, sec. 9, T. 1 N., R. 1 W.], 

Contra Costa County, Calif. Briones Sandstone, Miocene.

Supplementary description. Takeo Suzuki (written commun., 

1982) says that Striostrea? bourgeoisii bourgeoisii is characterized by 

a thick left valve, which is arched and has a long, narrow, slightly 

curved resilifer trough, and that the right valve is much flatter than 

the left and has a narrow, long resilifer.

"O. bourgeoisii Remond somewhat resembles O. titan Conrad in its 

size and thickness, though it is never as large. The maximum length as 

measured from the beak through the muscle impression is about eight 

to ten inches, with a maximum width at right angles to this of about 

five inches. Both valves vary considerably in thickness; sometimes the 

shell of the ventral valve has a thickness of from two to three inches.
TERTIARY MARINE PELECYPODS: PLICATULIDAE AND OSTREIDAE C35

The ventral valve is usually only slightly more convex than the upper 

valve but is usually somewhat thicker. The fine radiating ridges on the 

surface, described by Remond, are not constant, appearing on only a 

few specimens that the writer has seen.

"O. bourgeoisii Remond differs from O. titan Conrad in that the 

ligamental pit is narrower and the ligamental callus is heavier; on 

Ostrea titan Conrad the ligamental pit extends nearly across the 

anterior end of the shell; the muscle impression on O. bourgeoisii 

Remond is much smaller and is nearer the posterior end of the shell 

than on O. titan Conrad; on the latter species the muscle impression is 

sometimes nearly half the width of the shell; the ventral valve of O. 

titan Conrad is usually more strongly convex. A large number of 

specimens of both species were examined and these differences were 

found to be constant." (Clark, 1915, p. 448)

One of the oldest oysters, in terms of its life span, as seen by Stenzel 

(1971, p. N1016), is a specimen of S. ? bourgeoisii bourgeoisii from the 

Temblor Formation (CAS 33269). The ligamental area is 2 cm long and 

13 cm high; the apex is missing but the remainder has 43 annual 

layers.

Comparison. "Fragment of lower (left) valve, showing the characteristic narrow, commonly curved ligamental pit and uneven, wavy 

growth lamellae which differentiate this species from O. titan and O. 

titan var. prior. Average adult is about 7 inches long. No specimen 

observed has much more than half the length of an adult O. titan; has 

commonly the length but only about half the mass of O. titan var. prior. 

Differs from O. ligminuta of somewhat similar average length in its 

much thinner valves, relatively large body cavity, longitudinally 

curved shell, and uneven growth lamellae. From O. cierboensis in 

being highly elongate instead of sub-rounded in outline, in having a 

narrow, round, and elongate instead of a wide, flattish, and extremely 

short ligamental pit, and in lacking the broad, somewhat even radial 

plications of the latter." (Grant and Eaton in Eaton, Grant, and Alien, 

1941.)

Comments. The fine riblets on some specimens and patches of 

nacreous shell suggest assignment to Striostrea.

Geographic range. Middle and southern California.

Geologic range. Miocene.

Occurrence in California. Miocene: Briones Formation (Trask, 

1922), Branch Canyon Sandstone (Hill, Carlson, and Dibblee, 1958), 

Cierbo Sandstone (Huey, 1948), Neroly (Hall, 1960), San Pablo Formation (Clark, 1915), and Santa Margarita (Addicott and Vedder, 1963), 

and Topanga (Kew, 1924) Formations.

Striostrea? bourgeoisii perrini (Hall and Ambrose) 

Plate 26, figure 4; plate 27, figure 5

Ostrea titan Conrad var. perrini Hall and Ambrose, 1916, p. 80-81. 

Wiedey, 1929a, p. 22, pi. 3, fig. 1.

Original description. "Lower valve. Shell irregularly elliptical, 

contracted at beak; beak curved toward right when viewed from exterior; right valve very ventricose; extremely laminated, giving rough 

plaited surface; left valve almost flat, laminated; muscle-scars distinct; hinge long, narrowing at beak, viewed from interior curves to 

left; cavity of hinge deep, coarsely wrinkled, with wrinkles running up 

onto either side of hinge; interior of hinge ends abruptly, cutting at 

right angles toward interior of shell, although not characteristic of all 

forms."

Holotype. CAS/SU 502.

Type locality. Pleasanton Quadrangle, Alameda County, Calif. 

Briones Sandstone of San Pablo Group, Miocene.

Comparison. "This species greatly resembles O. titan Conrad, the 

main difference between the two being in the hinge. This variety has a 

long curved pointed hinge, while the O. titan has a much shorter hinge, 

about as wide as long. Also the summit of this variety does not rise

above the beak of the opposite valve. All forms do not have as curved a 

hinge as this one figured. It is generally elongate, and seldom, if ever, 

has the subcircular shape the O. titan often has." (Hall and Ambrose, 

1916, p. 81)

Comments. The characters given by Hall and Ambrose (1916, p. 81) 

to distinguish perrini from titan are basically the same as those used 

to distinguish S. ? bourgeoisii bourgeoisii from Crassostrea titan titan. 

Certainly the relationship of perrini is with bourgeoisii rather than 

with titan, and additional material may well prove perrini to be conspecific with bourgeoisii.

Geographic range. Middle California.

Geologic range. Miocene.

Occurrence in California. Miocene: Briones Sandstone, San Pablo 

Group (Hall and Ambrose, 1916).

Genus CRASSOSTREA Sacco, 1897

Small to very large (to 60 cm high), outline very variable among 

individuals, but high, slender, spatulate forms with subparallel anterior and posterior margins seem most common. Surface rough, right 

valve with many nonappressed, irregularly spaced growth squamae, 

simple or frilled along free edges; left valve with poorly developed, 

discontinuous plicae. Shells very erodable and thickened in several 

ways. Umbonal cavity usually small. No chomata in post-larval shells. 

Adductor muscle imprint close to posterior valve margin and closer to 

ventral margin than to hinge; its outline has two fairly sharp corners 

and a nearly straight or concave dorsal margin.

The validity of the many specific and subspecific names proposed for 

Crassostrea, especially Miocene forms of C. titan titan, needs special 

attention. In this work, based almost wholly on type material, the 

validity of the many names proposed is not always challenged nor are 

they synonymized. Large collections of Crassostrea from as many 

different environments as are represented in a single formation spanning a short time interval need to be carefully studied and compared 

with living populations of Crassostrea. Logic as well as observation 

dictates that oysters crowded together will respond to that crowding in 

their growth form. Stanton (1966, p. 26) has discussed the variability 

in morphology of C. titan from north to south within the Miocene 

Castaic Formation.

Geographic range. Living along the shores of most continents and 

of larger islands nearby (Antilles, Borneo, Philippines, Japan) but not 

south of the equator (Harold W. Harry, written commun., 1983).

Geologic range. Cretaceous to Holocene (table 10).

Habitat. Mostly in constant brackish water but may live in hypersaline conditions in the tropics. Usually in shallower water than all 

other oysters. Intertidal zone and to shallow depths in estuarine 

conditions, protected from strong wave action but with strong tidal 

currents. The living species, although essentially tropical, do not seem 

to live south of the equator, and C. gigas and C. virginica extend into 

temperate and even into cool waters. (Harold W. Harry, written commun., 1983)

Crassostrea titan (Conrad)

Plate 23, figures 1-7; plate 24, figures 1, 3, 4, 6; plate 27, figure 4; 

plate 28, figures 3, 5; plate 29, figures 1, 6

Ostrea titan Conrad, 1853, p. 199-200. Conrad, 1857b, p. 72, pi. 4, fig. 17; 

pi. 5, fig. 17a. Arnold, 1907a, p. 543, pi. 45, fig. 2. Arnold, 1909, pi. 5, 

fig. 1; pi. 10, fig. 5; pi. 11, fig. 2. Clark, 1915, pi. 44, fig. 1. Grant and 

Eaton in Eaton, Grant, and Alien, 1941, pi. 4, fig. 2. Hanna and 

Hertlein, 1943, fig. 63-14. Addicott, 1965, p. C103, fig. 3a.

Ostrea titan titan Conrad. Adegoke, 1969, p. 109, pi. 5, figs. 1, 8.

Ostrea (Crassostrea) titan Conrad. Ball, 1909, p. 111.
C36 PALEONTOLOGY OF CALIFORNIA AND BAJA CALIFORNIA

TABLE 10. Geologic and geographic distribution of the genus Crassostrea in the eastern Pacific region 

[H=Holocene; Pl=Pliocene; M=Miocene; O=Oligocene]

Species California

Northern Middle Southern

Baja California

Norte Sur

Central 

or South 

America

Genus Crassostrea

columbiensis (Hanley)....................

titan (Conrad)................................

Genus Crassostreat

ashleyi (Hertlein)............................

englekyi (Hertlein)..........................

eucorrugata (Hertlein)....................

californica osunai (Hertlein)..........

vaquerosensis (Loel and Corey).....

M or PI 

M M

O and M M

O? and M 

M M

PI toH

PI

O and M M

Crassostrea titan (Conrad). Stanton, 1966, p. 26-27. Stenzel, 1971, p.

N973,figs.J14,la-lc.

Ostrea subjecta Conrad, 1857c, p. 193, pi. 2, fig. 3. 

Ostrea panzana Conrad, 1857c, p. 193, pi. 2, fig. 4. 

Ostrea ligminuta Grant and Eaton in Eaton, Grant, and Alien, 1941,

pi. 4, fig. 1. 

Ostrea titan prior Grant and Eaton in Eaton, Grant, and Alien, 1941,

pi. 4, fig. 2. 

Ostrea titan Conrad andersoni Adegoke, 1969, p. 110, pi. 5, figs. 2, 3,6;

pi. 6, fig. 1.

Not Ostrea titan Conrad. Arnold, 1907a, pi. 40, fig. 2 [ = Ostrea titan 

subtitan Loel and Corey].

Original description. "Elliptical or oblong; extremely thick and 

ponderous, contracted toward the hinge; ligament cavity profound; 

upper valve slightly arched; surface coarsely laminated. Length 10V2 

inches. Locality, San Luis Obispo, Cal." (titan titan)

"Very irregular, valves sometimes subplicated; cardinal area broad 

and carinated laterally; cartilage pit but slightly impressed. Locality, 

between Santa Clara River and Los Angeles Valley, on the Sierra 

Monica. Height, 2 inches, (in pi. 2 this fossil is improperly included 

under the O. panzana)." (subjecta)

"Ovate, thick, lower valve with a few lateral distant radiating plicae; 

upper valve thick, concentrically undulated and rugose; hinge area 

wide and carinated on the margins. Localities, Panza and Estrella 

valleys. Height, 2% inches. The hinge of this shell resembles that of 

the preceding [subjecta]; and possibly, it may be the old shell of that 

species, the specimens of which, in the collection, are evidently all 

young shells. At Gaviote [Gaviota] Pass specimens of O. panzana occur 

twice the size of those from the above localities." (panzana)

"This species, where previously found, has probably been classified 

as either an immature O. titan or an unusually thick-shelled O. bourgeoisii. Averages 6 or 7 inches in length; some specimens attain 9 

inches. Ligamental pit, minute in proportion to the exceedingly thick 

equal valves, averages about % inches in width, and ranges from 1 to 3 

inches in length. O. ligminuta differs from O. titan in its relatively 

much narrower, in some individuals curved, ligamental pit, even more 

prodigiously thick valves, commonly thicker than wide, and normally 

smaller size. Also, the laminae or shell layers as seen in cross section 

are strongly curved instead of relatively straight, which gives it its 

extreme thickness in proportion to width. Then too, the beak is thick, 

massive, broadly rounded, and in most specimens protrudes beyond 

the ligamental pit. From O. bourgeoisii of somewhat similar over-all 

length and ligamental pit it differs in its extremely thick and massive 

valves, which are essentially straight instead of curved, its remarkably small body cavity, and relatively smooth growth lamellae. It has no

resemblance whatever to the ornate, plicated, thin-shelled, largecavitied O. cierboensis having a broad, short flattish ligamental pit, 

but is the opposite in all of these attributes. The range of O. ligminuta 

overlaps that of O. titan var. prior, which latter form, less massive, has 

the broad, straight ligamental pit, relatively flat laminae, and other 

characteristics of O. titan. The average specimen, which is near the 

holotype in size and medial thickness, has a heavier, more protruding 

beak than is exhibited by the somewhat worn type. Known range: late 

upper Briones, and lower and middle Cierbo." (ligminuta)

"Fragment of upper (right) valve showing convex ligamental callous 

of O. titan character, and even, flattish growth lamellae at the margins. 

In nearly all observed respects except size O. titan. Presumably 

ancestral to that gigantic Neroly form. Averages 6 or 7 inches in 

length. Differs from O. titan in having little more than half the length, 

and thus only a fraction of the mass, of the latter. Since both typical O. 

titan and this ancestral variety are commonly found in quantity, the 

markedly smaller size is quite diagnostic. Where previously observed 

has presumably been classified as the young of O. titan. Known range: 

late middle and upper Cierbo." (prior)

"Shell medium, thin, sub-trigonal; composed of many thin, platy 

calcite layers; valve relatively long, extremely narrow at cardinal area, 

becomes progressively broader ventrally; shell surface flat or gently 

concave; ligamental groove and ridge long and relatively narrow, bordered by narrow margins." (andersoni)

Holotype. Missing and presumed lost; of panzana USNM13338; of 

subjecta USNM 13338; of ligminuta UCLA 8985; of prior UCLA 8991; 

of andersoni UCMP 36661.

Type locality. San Luis Obispo [County], Calif., Santa Margarita 

Formation, Miocene; of panzana, Panza and Estrella Valleys, San Luis 

Obispo County, Calif, Miocene; of subjecta, between Santa Clara 

River and Los Angeles Valley, on the Sierra Monica; of ligminuta, 

UCLA 1795, Santa Barbara County, Calif, Branch Canyon Sandstone, 

Miocene; of prior, UCLA 1745, Santa Barbara County, Calif., Branch 

Canyon Sandstone, Miocene; of andersoni, UC-D701, Fresno County, 

Calif, Santa Margarita Formation, Miocene.

Supplementary description. "Produced from beak to base, 

straight or slightly curved, substance very thick, coarsely laminated; 

upper valve flat, very thick, somewhat gibbous; lower valve profoundly 

ventricose, umbonated, the summit rising above beak of the opposite 

valve." (Conrad, 1857b, p. 72)

According to Takeo Suzuki (written commun., 1982), specimens of C. 

titan in the Topanga Formation vary considerably in outline. They are 

high, narrow, and thick valved in reef-type occurrence and thick valved but not so elongate as when they grow in an uncrowded environment. The valves are usually unequal; one is flat or nearly flat and the
TERTIARY MARINE PELECYPODS: PLICATULIDAE AND OSTREIDAE C37

other thick and arched. Crassostrea titan has a broad, straight, somewhat half-cylinder shaped resilifer with an accompanying resilifer 

trough. Striostrea? bourgeoisii bourgeoisii (Remond) has a narrow 

slightly curved resilifer in the early growth stage which changes 

abruptly into the broad, straight form.

"The species varies considerably in abundance and morphology 

from north to south within the Castaic Formation. In the northern 

part of the formation, the species is more abundant and individuals 

are much larger than in the southern part. The average dimensions of 

specimens from north of San Francisquito Canyon are: length 30 cm., 

width 10 cm., and valve thickness 3 cm. The average dimensions of 

specimens from the southern part of the formation are: length 15 cm., 

width 8 cm., valve thickness 2 cm. Some valves from the southern part 

bear three to five irregular, round-crested ribs which may be discontinuous between laminae. Ribbing is more prevalent on left valves and 

particularly on those that are deeply cupped. Right valves are generally flat without ribbing." (Stanton, 1966, p. 26)

"C. titan has been reported from middle and upper Miocene strata of 

central and southern California. Eaton, Grant, and Alien (1941) 

describe from Miocene strata of the Caliente Range [Cuyama Valley] a 

number of new species and a new subspecies of C. titan from material 

that would have been grouped previously under C. titan. In addition, 

three other varieties or subspecies of C. titan have been described. In 

the Castaic Formation, in strata that are contemporaneous, morphologic variability is so great that, according to the illustrations and 

descriptions of type specimens, several of the previously described 

species and subspecies could be identified among the Castaic specimens. Most shells found in the northern part of the formation correspond to typical C. titan; some thick specimens could be classified as 

the species C. ligminuta. The largest specimens from the southern 

part of the outcrop area of the Castaic Formation are eight to ten 

inches long and thus would correspond to C. titan var. prior, which 

differs from C. titan only in being about half the size, and in being 

presumably ancestral to it. Ribbed specimens differ from the species 

C. bourgeoisii, as described and illustrated by Clark (1915, p. 447, pi. 

43) and by Eaton, Grant and Alien (1941, pi. 3, fig. 1) in lacking the 

elongate narrow ligamental pit. They differ from the species C. cierboensis in having ribs that are narrow rather than broad and rounded. 

Ribbing, along with decrease in size and abundance, presumably 

reflects an environment to the southeast less hospitable for the species 

than to the northwest. The morphologic changes coincide with the 

change in environment from embayment in the north to open coast in 

the southeast." (Stanton, 1966, p. 27)

Comments. Stanton (1966, p. 27) and Takeo Suzuki (written commun., 1982) have called attention to the fact that C. titan shows 

marked variability in ribbing, maximum size, thickness, and shape 

and that this variability relates to the environment in which they 

grew. In addition, John G. Vedder (written commun., 1983) said that he 

had seen literally thousands of specimens of C. titan along the south 

side of Cuyama Valley and that no two specimens were alike. He added 

that the same is true for myriads of specimens in the San JuanEstrella Creek area. Variability of Crassostrea is discussed under the 

generic heading above.

The holotypes ofOstrea subjecta Conrad and Ostrea panzana Conrad both have the same catalogue number, USNM13338. They are both 

poorly preserved, have generalized locality data, and neither name 

has been used subsequently, to my knowledge. Woodring (1931, p. 386) 

said that the holotype of Ostrea panzana is free of matrix and probably 

represents a small specimen of Crassostrea titan Conrad. I see no 

reason for burdening the literature with these two specific names so I 

have synonymized them with C. titan.

The holotype of O. ligminuta is a worn, sponge-bored valve, 150 mm 

high, 170 mm long, and 170 mm thick. It has no distinctive shell 

chambers. Ostrea titan prior is distinguished from Ostrea titan only 

on the basis of size; it is the young of O. titan.

The holotype and paratype of Crassostrea titan andersoni Adegoke 

are worn, incomplete right valves. The holotype is poorly preserved 

and at least half of the original shell is missing. The paratype is not so 

poorly preserved as the holotype, but much of its shell is missing also. 

Adegoke (1969, p. 110) distinguished his subspecies from C. titan and 

other described subspecies on the basis of its relatively longer, narrower shell. The two right valves are not longer than right valves of C. 

titan: they only seem narrower because so much of the shell is missing. 

On the basis of the type material, C. titan andersoni is here synonymized with C. titan. Stenzel (1971, p. 127) placed titan in 

Crassostrea.

Geographic range. Middle and southern California.

Geologic range. Miocene.

Occurrence in California. Miocene: Branch Canyon Sandstone 

(Vedder, 1973), Castaic Formation (Stanton, 1966), McLure Shale 

Member, Monterey Formation (Adegoke, 1969), Modelo Formation 

(Dehlinger and Jennings, 1952; Oakeshott, 1958), Neroly Sandstone 

(Eaton, Grant, and Alien, 1941; Weaver, 1949), Round Mountain Silt 

(Addicott, 1965), San Pablo Formation (Clark, 1915), Santa Margarita 

Formation (Fairbanks, 1904; Hill, Carlson, and Dibblee, 1958; Adegoke, 1969; Squires and Fritsche, 1978; Addicott and others, 1978), 

Sobrante Sandstone (Weaver, 1953), and Topanga Formation (Arnold, 

1907c; Vedder, written commun., 1978).

Crassostrea columbiensis (Hanley)

Plate 24, figure 2; plate 26, figure 2; plate 28, figures 1, 2, 4

Ostrea columbiensis Hanley, 1846, p. 187.

Ostrea (Crassostrea) columbiensis Hanley. Olsson, 1961, p. 172, pi. 23,

figs. 4, 4a. 

Ostrea corteziensis Hertlein, 1951b, p. 68-73, pi. 24, figs. 1,2; pi. 25, fig.

7. Keen, 1971, p. 82, fig. 170. 

Ostrea chilensis Phillipi. Durham, 1950, p. 58, pi. 4, fig. 1; not Ostrea

chilensis Phillipi, 1844.

Crassostrea corteziensis (Hertlein). Bernard, 1983, p. 23. 

Ostrea iridescens Gray. G D. Hanna, 1926a, p. 468, pi. 26, figs. 4-7. Not

Ostrea iridescens Gray, 1854. 

Ostrea californica Marcou. Hanna and Hertlein, 1927, p. 46. Grant

and Gale, 1931, p. 149. Not Ostrea californica Marcou, 1858. 

Original description. "Ost. testa subinequivalvi, subtenui, 

lamellosa, albida, purpureo radiata, subcompressa; valvula inferiore 

magis convexa; superficie interna albida, submargaritacea; cardine 

denticulis nullis munito; cicatrice satis magna reniformi." (columbiensis)

"Shell elongately ovate to subtrigonal in outline, moderately thick, 

beaks turned posteriorly; lower (left) valve moderately convex, upper 

valve flattish or gently convex; early portion of upper valve with 8-10 

weak, scaly, radiating costae ending about 75 mm. from the beak, the 

remainder of the shell concentrically lamellose with faint traces of 

superficial radial sculpture, colored grayish-white to brownish-white, 

the brownish color more pronounced on juvenile shells; interior of 

lower valve with a large rather broad, ligamental area which is lightly 

transversely grooved, about 4 of these coarser than the others, the 

ligamental area is bordered on each side by a narrow groove; the 

anterior portion of the ligamental area centrally overhangs the body 

cavity; adductor muscle impression posteriorly situated, broadly 

semi-crescentic above, white with traces of purplish-brown concentric 

bands or lines; the remainder of the interior white with occasional 

traces of purplish-brown. Upper (right) valve usually flat or nearly so, 

exteriorly it is similar to the lower valve in coloration but it lacks the 

indistinct radiating furrows; interiorly the anterior portion of the 

ligamental area is raised centrally; adductor impression a little larger 

than that of the lower valve and truncated above by white shell mate-
C38 PALEONTOLOGY OF CALIFORNIA AND BAJA CALIFORNIA

rial. Holotype: height, 153 mm.; width (maximum), 98 mm.; convexity 

(both valves together), approximately 56 mm." (corteziensis)

Holotype. In Museum Cuming; of corteziensis CAS 4288.

Type locality. St. Elena, west Columbia; of corteziensis CAS 28186. 

Bahia Kino, Golfo de California, Sonora Mexico. Holocene.

Supplementary description. "Elongate, somewhat triangular, 

with a wide ligamentary area, rather flat. The surface shows faint 

radial furrows. *** This species *** was long known as O. chilensis 

Philippi, 1844, a mis-identification; for Chilean specimens show a 

rounded shape and denticles along the hinge margin." (Keen, 1971, p. 

82)

"All the specimens I have seen are attached by the entire surface of 

the lower valve. The shape varies from oblong to suborbicular, and the 

valves are of equal length, but the shelly substance of the shallow 

upper valve fits into the lower one, and is only continued to the margin 

by the lamellae, which, when the habitat permits, branch into wavy 

foliations." (Hanley, 1846, p. 187)

"This species [O. corteziensis] has generally been referred by various 

authors to Ostrea chilensis Philippi. That species was originally 

described from Chile. *** 9 to 10 denticles or traces of such, are present 

on specimens of O. chilensis from Calbuco, Chile. *** No trace of such 

denticles has been observed on any of the specimens studied from the 

Gulf of California. The base of the hinge of the upper valve of the 

Chilean shells does not possess such a large transverse ridge." 

(Hertlein, 1951b, p. 68-69)

"Shell relatively small (length to about 90 mm.), very irregular, the 

attached valve deep, cup-shaped, the upper valve smaller and generally flattened. Sculpture smooth or with crudely formed ribs." (Olsson, 

1961,p.l72.)

Comments. Harold W. Harry (written commun., 1983) called my 

attention to the fact that O. corteziensis is a junior synonym of O. 

columbiensis.

Geographic range. Living: Golfo de California to Ecuador; fossil: 

southern California to Baja California Sur.

Geologic range. Miocene(?); Pliocene to Holocene.

Occurrence in the Californias. Miocene or Pliocene: Imperial Formation (Stump, 1979); Pliocene: Gloria (Stump, 1979) and San Marcos 

(Durham, 1950) Formations.

Habitat. Generally attached to roots of mangroves; adhering to 

rocks at low tide.

Genus CRASSOSTREA?

Crassostrea? vaquerosensis (Loel and Corey) 

Plate 21, figure 2; plate 25, figure 2

Ostrea vaquerosensis Loel and Corey, 1932, p. 192, pi. 19, figs, la, Ib. 

Addicott, 1965, p. C104, fig. 3g.

Original description. "Shell large and heavy, nearly round or 

slightly higher than long, nearly equivalve, upper valve more convex 

than lower; beaks rounded and slightly curved, exterior of shell without ornamentation other than concentric, fairly prominent growth 

ridges; muscle scar round, located posteriorly. Height, 190 mm.; width 

170 mm.; diameter (through both valves), 90 mm."

Holotype. CAS/SU 617; missing and presumed lost; paratypes 

CAS 6789, 6790.

Type locality. Jeff Harris Ranch, west of Pleyto [T. 24 S., R. 9 E.], 

Bryson Quad., Monterey County, Calif. Vaqueros Formation, 

Oligocene and Miocene.

Comparison. "This species is distinct from O. titan in its constant 

roundness and equality of valves." (Loel and Corey, 1932, p. 192)

Geographic range. Middle and southern California.

Geologic range. Oligocene and Miocene. Eaton and others (1941, p. 

199) said that C. vaquerosensis is restricted to the uppermost 

Vaqueros and aids in zoning the Vaqueros substage.

Comments. The generic assignment is uncertain and C.? 

vaquerosensis may be a variant of C. titan.

Occurrence in California. Oligocene and Miocene: Mindego Basalt 

(Cummings and others, 1962); Miocene: Jewett Sand (Addicott, 1965), 

Painted Rock Sandstone Member, Vaqueros Formation (Loel and 

Corey, 1932), Pyramid Hill Sand Member, Jewett Sand (Park and 

others, 1963).

Crassostrea? englekyi (Hertlein)

Plate 20, figure 1; plate 22, figure 1

Ostrea englekyi Hertlein, 1928, p. 143-144, pi. 25, fig. 1. Loel and Corey, 

1932, p. 190, pi. 15, fig. 3. Bereskin and Edwards, 1969, p. 77, pi. 32, 

figs. 4a, 4b.

Original description. "Shell elongate triangular. Lower valve 

thick, made up of flattish layers of shell material, thickest in middle 

part of valve; sides of valve fairly straight. Left valve thinner but 

otherwise similar to right valve. Altitude 143.4 mm.; width of ventral 

margin of shell 86 mm."

Holotype. CAS 4116.

Type locality. CAS 1156. Santa Barbara County, Calif. Temblor 

[upper part of Vaqueros] Formation of Loel and Corey, 1932; San 

Onofre Breccia of Bereskin and Edwards, 1969, Miocene.

Comparison. "The hinge of Ostrea englekyi isnot fully exposed but 

it apparently belongs to the Ostrea virginica Gmelin group. It differs 

from that species in its extremely triangular shape, straight sides and 

thick shell. From O. freudenbergi Hertlein and Jordan, O. englekyi 

differs in its larger size, greater thickness and straight sides and 

different hinge. The present species is apparently not close to O. 

chilensis Philippi in the early part of shell nor in general shape. O. 

englekyi most closely resembles a species of recent Ostrea which is 

found in the Gulf of California apparently differing only in minor 

details. The triangular shape, narrower ligament pit and wider anterior margin distinguish O. englekyi from O. californica Marcou, a 

species once reported by Hanna [1926a, p. 468] as O. iridescens Gray 

but later [M. A. Hanna and Hertlein, 1927, p. 45-47] recognized as 

distinct from Gray's recent species." (Hertlein, 1928, p. 143-144)

Comments. The holotype of C.? englekyi is a double-valved specimen with the valves together and closed. The specimen is worn and 

was originally somewhat wider at the umbonal end and thus not 

"extremely triangular" as stated by Hertlein (1928, p. 143). The 

straight steep sides of the left valve are distinctive and may not simply 

relate to where it grew. The edges of the shell layers on the left valve 

may have been fluted. The right valve is smooth and flat to concave. On 

the basis of the holotype, the generic assignment is uncertain.

Geographic range. Southern California.

Geologic range. Oligocene(?); Miocene.

Occurrence in California. Oligocene and Miocene: Vaqueros Formation (Bereskin and Edwards, 1969); Miocene: Temblor Formation 

(Hertlein, 1928) and upper part of Vaqueros Formation (Loel and 

Corey, 1932).

Crassostrea? ashleyi (Hertlein)

Plate 19, figures 3, 5; plate 20, figures 2-6; plate 21, fig. 3; plate 22, 

fig. 2; plate 24, fig. 5.

Ostrea ashleyi Hertlein, 1934b, p. 1, 3, pi. 1, figs. 2, 3; pi. 2, fig. 1. 

Adegoke, 1969, p. 107-108, pi. 4, fig. 5. Addicott, 1965, p. C106, fig. 

4q.
TERTIARY MARINE PELECYPODS: PLICATULIDAE AND OSTREIDAE C39

Ostrea altatemblorensis Grant and Eaton in Eaton, Grant, and Alien,

1941, pi. 2, fig. 2 [described in plate explanation]. 

Ostrea arnoldi Adegoke, 1969, p. 106-107, pi. 4, figs. 1,2,6,9; pi. 5, fig. 5. 

Ostrea hertleini Adegoke, 1969, p. 108, pi. 4, figs. 3,4; pi. 5, fig. 4; pi. 6, 

fig. 9.

Original description. "Lower valve narrowly oblong, wider at 

base; exteriorly ornamented by numerous fluted ribs; area of attachment near beak unornamented. Interior of margin not folded; muscle 

scar fairly large; ligament groove long and fairly wide. Upper valve 

long and narrow; on the interior beneath the beak a long narrow 

elevated area is present which fits into the groove of the lower valve. 

Height of shell (beak to base, incomplete); 216 mm.; width of shell (at 

base) 108 mm." (ashleyi)

"Lower (left) valve. Average length about 6 inches; width commonly 

from a third to a half of this. Lower valve moderately thick, with 5-8 

characteristically narrow, somewhat angular, rather evenly spaced, in 

many specimens almost knife-edge, radial ribs separated by rounded 

trough-like interspaces which may bear minor riblets. Upper (right) 

valve thinner, flattish, with irregular, concentric growth rugosities, 

but without definite continuous radial sculpture. Ligamental pit of 

lower valve concave, elongate, tapering, and ordinarily curved. Differs 

from O. wiedeyi of the older Miocene in its fewer, narrower plications, 

and the wide, rounded troughs between these. Differs from the 

Pliocene species O. vespertina in all of the foregoing attributes, and in 

its more elongate shape, larger size, and thicker valves." 

(altatemblorensis)

"Shell medium sized, oval to subcircular, not constricted at hinge 

area, valves moderately thick, composed of several thin flat laminae; 

outer surface rather smooth, often faintly corrugated or with rather 

indistinct ornamentation; ligamental groove ralatively short, often 

less than one-sixth length of shell, rather broad, with broad raised 

margins; interior of shell evenly concave, except in area immediately 

adjacent to ligamental groove where it is deep; muscle scar large, 

impressed, with a semicircular outline, ventral margin broadly 

rounded, anterior margin almost straight; muscle scar located on 

anterior edge of shell about a third of length from the ventral margin, 

displaced toward 'dorsal' margin; both valves equally inflated." 

(arnoldi)

"Shell long, narrow, only slight change in diameter from anterior to 

posterior end; left valve heavy, thick, convexly arched; right valve thin, 

flat anteriorly, concave posteriorly; growth lines more distinct on right 

than on left valve; ligamental groove short, narrow, bounded by relatively wide, flat margins; ligamental groove narrow but fairly deep, 

deeper on left valve; adductor muscle scar not very distinct, subcircular in outline, centrally placed, about midway in valve; shell straight 

to slightly curved, ventral margin gently rounded, anterior margin 

bluntly acute; dorsal margin almost straight." (hertleini)

Holotype. CAS 6065; of altatemblorensis UCLA 8970; of arnoldi 

UCMP 36646; of hertleini UCMP 36654.

Type locality. CAS 933. Kern County, Calif. Temblor Formation, 

Oligocene and Miocene; of altatemblorensis UCLA 512, San Luis 

Obispo County, Calif. Branch Canyon Sandstone, Miocene; of arnoldi 

UC D-1075. Fresno County, Calif. Temblor Formation, Oligocene and 

Miocene; of hertleini UC D-1057. Kings County, Calif. Temblor Formation, Oligocene and Miocene.

Comparison. "This long narrow oyster with pronounced ribs ornamenting the lower valve, which bears a long ligament groove, internally, is quite distinct from any other species from western North 

America. These features of the lower valve as well as the long narrow 

upper valve with the internally raised area below the beak, easily 

distinguish the species from other lower Miocene forms such as O. loeli 

Hertlein, O. wiedeyi Hertlein, and O. howelli Wiedey." (Hertlein, 

1934b, p. 1-2)

"Ostrea ashleyi Hertlein is characterized by an elongate, narrow 

ligamental groove, similar to that of O. bourgeoisii to which it has been 

referred by several workers. It differs from O. bourgeoisii by its much 

smaller size, thin valves, and relatively large semicircular muscle scar. 

It was described from the Temblor of Kern County. The species occurs 

abundantly in an 8-foot oyster bed in the middle of the Temblor 

Formation of the Coalinga region." (Adegoke, 1969, p. 108)

Comments. The holotype of C. ? ashleyi is a fairly large, somewhat 

worn left valve. The exterior is sculpted by irregular ribs that are 

somewhat fluted. The muscle impression is semiovate and the ligamental area is large. The deep resilifer is bordered anteriorly by a 

prominent bourrelet (area flanking resilifer) and posteriorly by a 

bourrelet projecting upwards at an angle of about 45°. The body cavity 

is shallow.

The left valve holotype of O. altatemblorensis has narrow, sharpedged plicae or folds that are irregularly nodose and separated by 

shallow, U-shaped interspaces.

The right valve holotype of Ostrea arnoldi is small and the exterior 

very worn. Some of the exposed shell layers show traces of fine, radial 

ribs, suggesting Striostrea. The left valve paratype of O. arnoldi is 

small and badly worn; it does not have traces of radial ribs as are 

present on C. ? ashleyi.

The holotype of Ostrea hertleini is a double-valved specimen with 

the valves together and closed. It is small and relatively narrow. The 

left valve, although very worn with the outer shell layers missing, 

seems to have had fluted ribs. The left valve is smooth, worn, and flat to 

concave.

Geographic range. Middle and southern California.

Geologic range. Oligocene and Miocene.

Occurrence in California. Oligocene and Miocene: Temblor Formation; Miocene: Branch Canyon Sandstone (Hill and others, 1958; 

Vedder, 1973; Adegoke, 1969) and Olcese Sand (Addicott, 1965).

Crassostrea? eucorrugata (Hertlein)

Plate 25, figures 3-5; plate 26, figure 1; plate 27, figure 1

Ostrea titan corrugata Nomland, 1917, p. 306, pi. 16, fig. 1; pi. 17, fig. 1. 

Not Ostrea corrugata Brocchi, 1814; not Ostrea corrugata Hutton, 

1873.

Ostrea titan eucorrugata Hertlein, 1934b, p. 5, new name. 

Ostrea titan Conrad eucorrugata Hertlein. Adegoke, 1969, p. 109. 

Ostrea cierboensis Grant and Eaton in Eaton, Grant, and Alien, 1941, 

pi. 3, fig. 2.

Original description. "Shell large, very heavy, when full grown 

sub-ovate but in earlier stages of very irregular outline. Surface sculptured by well marked growth lines which at the edges are irregularly 

folded into prominent radiating ridges. Ligamental groove wide, triangular, extending nearly across anterior end of shell. Muscular 

impression large, rectangular, almost invisible in type. Dimensions of 

lower valve: length 235 mm.; width, 150 mm.; height, 120 mm." (corrugata)

"View showing lower (left) valve. Averages 5-6 inches in length and 

about 4 in width. Differs from all other known large upper Miocene 

oysters of California in being nearly as wide as long, and in having 

broad, somewhat regular radial plications on the lower valve. Upper 

(right) valve thin and flattish. Moderately thin-shelled, large-cavitied 

with a broad, very short, flattish ligamental pit commonly about 1 inch 

wide and 1/2 inch long. Well preserved specimens normally occur as 

matched valves. Has probably previously been erroneously identified 

as the smaller and younger species O. vespertina (Pliocene). Differs 

from the latter species in its larger size, thicker shell and fewer, 

broader plications." (cierboensis)
C40 PALEONTOLOGY OF CALIFORNIA AND BAJA CALIFORNIA

Holotype. UCMP 11309; of cierboensis UCLA 8980.

Type locality. UC 2284. Fresno County, Calif. Santa Margarita 

Formation, Miocene; ofcierboensis UCLA 1751, Santa Barbara County, 

Calif., Cierbo Formation [Branch Canyon Sandstone], Miocene.

Comparison. "Distinguishable from the typical Ostrea titan Conrad which is also found in the Santa Margarita Formation by the 

prominent folds on surface and the greater convexity of lower valve." 

(Nomland, 1917, p. 306)

Comments. The growth lamellae are fluted at their edges, thick at 

their base but almost paper thin at their free margin, and where 

broken across are seen to be built of thick, prismatic calcite crystals. 

On the basis of the growth lamellae (Stenzel, 1949, p. 35-36), the 

holotype specimen was at least 8 years old. Almost the entire exterior 

and interior surfaces of the left-valve holotype show pseudovesicular 

structure. Stenzel (1971, p. N987) illustrated true honey-comb vesicular structure and used this character to identify the Pycnodonteinae. Cross sections of the prismatic shell layer produced at shell 

breaks show only the vertical prismatic crystals and no internal vesicular layers. Thus the pseudovesicular structure, which is believed to 

be a solution artifact, consists of small pits conforming to the size of 

the sand grains, some of which are still attached. The pits were caused 

by leaching of the shell.

Shell characters of C. ? eucorrugata that make assignment of the 

species to Crassostrea dubious are: the ligamental area of the left 

valve is longer than high and the left valve has thick, prismatic shell 

layers. These two characters suggest Fleminostrea, but C.? eucorrugata has a beaked left valve umbo, the left valve is highly convex, 

and the valves are not nearly equal in size. No vesicular shell structure 

was seen, but C. ? eucorrugata may belong in the subfamily Pycnodonteinae.

Geographic range. Middle and southern California.

Geologic range. Miocene.

Occurrence in California. Miocene: Branch Canyon Sandstone 

(Eaton, Grant, and Alien, 1941; Vedder,1970) and Santa Margarita 

Formation (Nomland, 1917; Wilson, 1944; Addicott and Vedder, 1963).

Crassostrea? californica osunai (Hertlein) 

Plate 27, figure 2

Ostrea californica osunai Hertlein, 1966, p. 272-273, figs. 2-6, 8, 9.

Original description. "Shell, a left valve, elongated, longer than 

wide, thick with uneven, wavy growth laminae; exterior flattish, lacking ornamentation; interior with a shallow body cavity; ligamental pit 

rather wide, concave, elongate, the laminae of growth form a nearly 

straight line across the pit; muscle impression on the type specimen 

indistinct, apparently at about one third the length of the shell from 

the ventral margin. Dimensions: Length (apex lacking), 393 mm., 

maximum width, 140 mm., maximum thickness, 84 mm.

"Right valve, a paratype, ventral portion lacking; a raised, convex 

ridge corresponds to the ligamental pit of the opposite valve. Dimensions; length (ventral portion lacking), 238 mm., maximum width, 133 

mm., maximum thickness, 53 mm."

Holotype. AS 12823.

Type locality. GAS 38855. From the southwest end of Punta Concepcion, Baja California Sur. Salada Formation, Pliocene.

Comparison. The dorsal half of two specimens of C. californica 

osunai, about 130 mm long, closely resemble specimens of C. californica s. s., differing only in the larger and thicker shell. One lower valve 

is recessed under the hinge, but other valves are not. Similar variability can be observed among specimens of C. californica s. s.. None of 

the valves of C. californica s. s. are as large and thick as those of C. 

californica osunai nor is the ligamental pit and corresponding ligamental ridge on the opposite valve as large as those on valves of C.

californica osunai. Some of the large valves of C. californica osunai 

resemble Crassostrea bourgeoisii Remond, as illustrated by Clark 

(1915, pi. 43), but differ from that species in their much more elongate, 

narrower outline, and broader ligamental pit. (Hertlein, 1966, p. 273)

Comments. The holotype is a double-valved specimen with the 

valves separated. The early portion (one-fourth) of the left valve is 

ribbed; the right valve is smooth.

Geographic range. Baja California Sur.

Geologic range. Pliocene.

Occurrence in Baja California. Pliocene: Salada Formation 

(Hertlein, 1966).

FOSSIL LOCALITIES

[Corrections and information not in the original description are in brackets; feet and miles 

are converted to the metric system; formations are cited as emended by later workers, where

pertinent]

California Academy of Sciences:

GAS 933. Center of sec. 32, T. 28 S., R. 29 E., Kern County, Calif.

Temblor Formation. 

GAS 945. Southeast of Bahia Tortola, Baja California Sur. Almejas Formation. 

GAS 1150. West of Arlington Canyon, Santa Rosa Island, Santa

Barbara County, Calif. Vaqueros Formation. 

GAS 1154. Oyster bed near spring on ridge to south of San

Augustine Canyon, about 1.6 to 2 km from mouth of canyon,

Santa Rosa Island, Calif. Temblor Formation. 

GAS 1156. About 0.4 km southeast of spring on ridge south San

Augustine Canyon, east of dike near top of hill, Santa Rosa

Island, Calif. Temblor Formation Miocene. 

GAS 1163. East of Crook Point, San Miguel Island, Santa Barbara

County, Calif. Vaqueros Formation. 

GAS 5955. San Diego, Calif. Holocene.

Los Angeles Natural History Museum:

LAM 305. 730 m east and 310 m south of NW cor. sec. 8, T. 19 S., R. 

2 W, San Ysidro Quad. (1943 edition), [San Diego County], 

Calif. San Diego Formation.

Stanford University [All these collections are now in the California

Academy of Sciences]: 

SU 59. Turritella bed above San Gregorio Lagoon, 190 km north of

Magdalena Bay, on the trail from Arroyo Mesquital to La

Purisima, Baja California Sur. Isidro(?) Formation. 

SU 446. Near Sespe Creek, 8.8 km northeast of Wheeler's Hot

Springs, [sec. 32, T. 6 N., R. 22 W], Mt. Pinos Quad.,

Ventura County, Calif. Temblor Formation. 

SU 449. Val Celico, a little west of Pleyto, Monterey County, Calif.

Vaqueros Formation. 

University of California at Berkeley:

UC 790. East of Lower Lake village 1.2 km, 365 m south of

Nerndon Creek bridge, SEVi, NEV4, sec. 11, T. 12 N., R. 7 W,

Lake County, Calif. Martinez Formation. 

UC 1131. Southwest of town of Walnut Creek 0.8 km, in creek bed,

Long. 122°4'8", Lat. 37°53'7" [Concord Quad.], Contra

Costa County, Calif. San Ramon Formation. 

UC 1540. South of Stewartville 1.6 km, NE cor. NWVi sec. 15, T. 1

N., R. 1 E., Mt. Diablo Quad., Contra Costa County, Calif.

Martinez Formation. 

UC 2284. Near middle of south boundary of NEV4, sec. 10, T. 19 S.,

R. 15 E., Fresno County, Calif. Santa Margarita Formation,

Miocene. 

UC 3752. Simi Valley, Santa Susana Quad., SE Vt, SEVi, sec. 7, T. 2

N., R. 17 W, Ventura County, Calif. Martinez Formation.
TERTIARY MARINE PELECYPODS: PLICATULIDAE AND OSTREIDAE C41

UC 3981. At 15 m above high tide level in small gully 0.4 m south of 

Soledad Valley, La Jolla Quad., San Diego County, Calif. La 

Jolla Group.

UC 5062. In sea cliff south of mouth of Soledad Valley, due west of 

midpoint between "P" and "u" of "Pueblo", La Jolla Quad., 

San Diego County, Calif. La Jolla Group, Eocene.

UC A-321. About 0.5 m due south of end of Santa Ynez River 

bridge, south of Santa Ynez Mission, on east side of Alisal 

Creek [Lompoc Quad., Santa Barbara County], Calif. 

Vaqueros Formation.

UC A-326. Upper end of San Antonio Creek Canyon, northwest of 

mouth of Lion Canyon, on west side, Ventura Quad., Ventura County, Calif. Vaqueros Formation.

UC A-336. On long sharp northwest spur of Oak Ridge 1.6 km east 

of Grimes Canyon [NWVi sec. 8, T 3 N., R. 19 W., Piru 

Quad., Ventura County], Calif. Vaqueros Formation.

UC D-701. From 2 + m thick, prominent oyster and pecten "reef, 

the most prominent ledge-forming Ostrea-Pecten "reef on 

the slope of the hills a few feet northwest of Shell Oil well 

254-15. 2,460 feet north, 2,530 feet west, sec. 15, T. 19 S., R. 

15 E., Domengine Ranch Quad., Fresno County, Calif. 

Santa Margarita Formation.

UC D-1057.190 m north, 395 m west, sec. 3, T. 23 S., R. 16 E., Reef 

Ridge Quad., Kings County, Calif. Temblor Formation. 

From two prominent oyster beds about 3.5 m apart and 

from coarse sandstone bed below the lower oyster bed. 

Lateral extent of collection about 30 m.

UC D-1075. Sec. 21, T. 19 S., R. 15 E., 745 m north and 215 m east, 

Domengine Ranch Quad., Fresno County, Calif. From 

approximately 2.5 m oyster bed in light gray and buff 

colored, fragile, silty shale. Fossil bed crops out for considerable distance along road on the west slope of the hills. 

Temblor Formation.

U.S. Geological Survey, Menlo Park, Calif:

USGS 3220. 328 m north and 91 m west of SE cor. sec. 4, T. 7 S., R. 

8 W., San Juan Capistrano Quad. (1949 edition), altitude 

about 80 m. On east bank of Aliso Creek, base of Monterey 

Shale. Lat. 33° 35.3' N, long., 117° 47.7' W, Calif. Monterey 

Shale.

USGS 3426. Third Street Tunnel, Los Angeles, Los Angeles 

County, Calif. Repetto Formation.

USGS 4715. South end of Kettleman Hills in sec. 10, T. 25 S., R. 19 

E. [Lost Hills Quad., Kern County], Calif. Etchegoin Formation.

University of California at Los Angeles:

UCLA 512. Ridge between main and east Abbott Canyons, oyster 

bed 6 + m thick and 6 m conglomerate below. (Not found in 

bottom of canyon). [SWV4 sec. 11, T. 11 N., R. 27 W., McKittrick Quad., northeast slope of] Caliente Range, San Luis 

Obispo County, Calif. Upper Temblor Formation [Branch 

Canyon Sandstone].

UCLA 1745. Cuyama Valley, Branch Canyon, east of head of Discovery Gulch. On top of knoll, Zone 9, Santa Barbara 

County, Calif. Middle Cierbo Formation [Branch Canyon 

Sandstone].

UCLA 1751. About 350 m S 25° E from Branch Canyon along ridge 

west side Discovery Gulch. 18-22 m down the 16° slope from 

prominent white sandstone reef which forms the strike 

ridge N 25° W, along the weathered surface exposure of 

Ostrea cierboensis and Astrodapsis gregerseni. Oysters 

very abundant at southwest end of exposure above head of 

Discovery Gulch westward. South side Branch Canyon, 

Cuyama Valley, Santa Ynez Quad., Santa Barbara County, 

Calif. Cierbo Formation [Branch Canyon Sandstone].

UCLA 1795. Short Canyon branch of Bitter Creek. Reef at base of 

the Astrodapsis section exposed therein. Collected on west 

side of Short Canyon, from Ostrea reef interbedded withA 

cf. tumidus. About 70 m below upper shale of this locality. 

[South side Cuyama Valley, Santa Ynez Quad., Santa Barbara County, Calif] Cierbo Formation [Branch Canyon 

Sandstone].

University of California at Riverside:

UCR 6899. Light gray concretions with abundant oyster debris 

134 m due east of small hill 1461 m NW11° from hill 496 and 

748 m southwest 5° of hill 1331. 928 m above base of Simi 

Conglomerate, Calabasas Quad., California.

University of Oregon:

UO 130. Near Glide, Douglas County, Oregon. Umpqua Formation.

University of Washington:

UW160. Bluff at Porter Station in Northern Pacific Railroad cut, 

sec. 22, T. 17 N., R. 4 W., Grays Harbor County, Wash. 

Lincoln Creek Formation.

GEOLOGIC FORMATIONS CITED FOR 

OCCURRENCE OF PELECYPODS.

Family Plicatulidae to Family Ostreidae

California:

Alegria Formation1 

Anchor Silt1 

Avenal Sandstone 

Bay Point Formation 

Beechers Bay Member,

Monterey Formation1 

Branch Canyon Sandstone 

Briones Sandstone, San Pablo

Group

Canada Formation1 

Capistrano Formation 

Careaga Sandstone 

Carlotta Formation 

Castaic Formation1 

Cebada Member, Careaga Sand

or Sandstone 

Cierbo Sandstone, San Pablo

Group 

Coldwater Sandstone and

Coldwater Sandstone

Member1 , Tejon Formation 

Cozy Dell Shale and Cozy Dell

Shale Member1 , Tejon

Formation 

Delmar Formation, La Jolla

Group 

Domengine Formation or

Sandstone

Etchegoin Formation 

Fernando Formation

Foxen Mudstone

Age

Oligocene 

Pleistocene 

Eocene 

Pleistocene

Miocene 

Miocene

Miocene

Eocene

Miocene and Pliocene

Pliocene

Pleistocene

Miocene

Pliocene 

Miocene

Eocene

Eocene 

Eocene

Eocene

Miocene and Pliocene 

Pliocene and 

Pleistocene 

Pliocene

^tratigraphic nomenclature used is that of the references cited in the text and does not 

necessarily accord with that of the U.S. Geological Survey.
C42 PALEONTOLOGY OF CALIFORNIA AND BAJA CALIFORNIA

Gaviota Formation1

Imperial Formation

Jewett Sand

Juncal Formation

La Jolla Group

Lomita Marl Member, San

Pedro Formation 

Martinez Formation 

Matilija Sandstone 

Medill Sand1 

Merced Formation

Mindego Basalt

Modelo Formation

Monterey Formation, Shale, or

Group 

Neroly Sandstone, San Pablo

Group

Niguel Formation 

Olcese Sand 

Painted Rock Sandstone

Member, Vaqueros Formation 

Palos Verdes Sand 

Pancho Rico Formation 

Paso Robles Formation

Pico Formation

Potato Harbor Formation1 

Purisima Formation 

Pyramid Hill Sand Member,

Jewett Sand 

Quail Canyon Sandstone

Member, Vaqueros Formation

Rincon Shale

Rose Canyon Shale 1

Round Mountain Silt

Sacate Formation1

Saltos Shale Member, Monterey

Formation

San Diego Formation 

San Joaquin Formation 

San Pablo Formation 

San Pedro Formation or Sand

San Ramon Sandstone 

Santa Margarita Formation 

Santa Susana Formation1 

Santos Shale Member, Temblor 

Formation

Saugus Formation

Simi Conglomerate 

Sisquoc Formation 

Sobrante Sandstone 

Soda Lake Sandstone Member, 

Vaqueros Formation

Tejon Formation 

Temblor Formation

Eocene and Oligocene

Miocene or Pliocene

Miocene

Eocene

Eocene

Pliocene 

Paleocene 

Eocene 

Pleistocene 

Pliocene and 

Pleistocene 

Oligocene and 

Miocene 

Miocene

Miocene

Miocene 

Pliocene 

Miocene

Miocene

Pleistocene

Miocene

Miocene, Pliocene, and

Pleistocene 

Pliocene and

Pleistocene 

Pliocene 

Miocene and Pliocene

Miocene

Oligocene and

Miocene 

Oligocene and

Miocene 

Eocene 

Miocene 

Eocene

Miocene 

Pliocene 

Pliocene 

Miocene 

Pliocene and 

Pleistocene 

MioceneC?) 

Miocene 

Paleocene and Eocene

Oligocene and

Miocene 

Pliocene and

Pleistocene 

Paleocene

Miocene and Pliocene 

Miocene

Oligocene and

Miocene 

Eocene 

Oligocene and

Miocene

Timms Point Silt Member, San

Pedro Formation 

Tomales Formation 

Topanga Formation 

Towsley Formation 

Vaqueros Formation

Wygal Sandstone Member,

Temblor Formation 

Baja California peninsula:

Almejas Formation

Boleo Formation

Cantil Costero Formation

Carmen Formation

Comondu Formation

Gloria Formation

Infierno Formation

Isidro Formation

Marquer Formation

Salada Formation

San Marcos Formation

San Ignacio Formation

Santa Rosalia Formation

Sepultura Formation

Tortugas Formation 

Washington:

Cowlitz Formation 

Oregon

Umpqua Formation 

Dominican Republic:

Emperador Member, La Boca 

Formation

Gurabo Formation

Pleistocene 

Pleistocene 

Miocene

Miocene and Pliocene 

Oligocene and 

Miocene

Oligocene

Pliocene

Pliocene

Pliocene

Pliocene

Miocene

Pliocene

Pliocene

Miocene

Pliocene

Pliocene

Pliocene

Pliocene

Pleistocene

Paleocene

Miocene

Eocene 

Eocene

Miocene 

Miocene

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in Santa Rosalia area, Baja California, Mexico: American Association of Petroleum Geologists Bulletin, v. 32, no. 9, p. 1762-1807, 

3 this.

Wilson, I. F, and Rocha, V. S., 1955, Geology and mineral deposits of 

the Boleo Copper District, Baja California, Mexico: U.S. Geological Survey Professional Paper 273,134 p.

Winterer, E. L., and Durham, D. L., 1958, Geologic map of a part of the 

Ventura Basin, Los Angeles County, California: U.S. Geological 

Survey Oil and Gas Investigations Map OM-196, scale 1:24,000.

Woodring, W. P., 1925, Miocene mollusks from Bowden, Jamaica; pelecypods and scaphopods: Carnegie Institute of Washington Publication 366, 222 p., 28 pis.

 1931, Age of the orbitoid-bearing Eocene limestone and Turritella variata zone of the western Santa Ynez Range, California: 

San Diego Natural History Museum Transactions, v. 6, no. 25, p. 

371-387.

 1938, Lower Pliocene mollusks and echinoids from the Los 

Angeles basin, California and their inferred environment: U.S. 

Geological Survey Professional Paper 190, 67 p., 9 pis. 

-1982, Geology and paleontology of Canal Zone and adjoining

parts of Panama; description of Tertiary mollusks (Peiecypods: 

Propeamussiidae to Cuspidariidae) *** U.S. Geological Survey 

Professional Paper 306-F, p. 541-759, pis. 83-125, incl. geologic 

map.

Woodring, W. P., Bramlette, M. N., and Kew, W. S. W, 1946, Geology 

and paleontology of Palos Verdes Hills, California: U.S. Geological 

Survey Professional Paper 207,145 p., 37 pis.

Woodring, W. P., and Bramlette, M. N., 1950, Geology and paleontology 

of the Santa Maria District, California: U.S. Geological Survey 

Professional Paper 222,185 p., 23 pis., 9 figs.

Woodring, W. P., Stewart, Ralph, and Richards, R. W, 1940 [1941], 

Geology of the Kettleman Hills oil field, California: U.S. Geological Survey Professional Paper 195,170 p., 57 pis., 15 figs.

Zinsmeister, W. J., 1983, New late Paleocene molluscs from the Simi 

Hills, Ventura County, California: Journal of Paleontology, v. 57, 

no. 6, p. 1282-1303, 4 figs.
Abbreviations, 4 

Acapulco, Mexico, 16 

Acesta, 14

haseltinei, 15 

mori, 15 

perrini, 15 

Acesta, 14 

(Acesta), 14

hamlini, 14, 15; pi. 10 

multiradiata, 14; pi. 10 

Plicacesta, 14, 15

(Plicacesta), 15

haseltinei, 14, 15; pis. 9,10 

(Acesta), Acesta, 14

hamlini, Acesta, 14, 15; pi. 10 

Lima, 15

multiradiata, Acesta, 14; pi. 10 

Acknowledgments, 4 

Acutostrea, 30

idriaensis fettkei, 27, 30; pis. 30, 32, 33 

idriaensis, 27, 31; pis. 13,14,16, 29

simiensis, 27, 30; pi. 34 

Acutostrea?, 32

miguelensis, 27, 32; pi. 33 

Adegoke, O. S., cited, 37 

Africa, 30

east, 23, 33

south, 33

agassizii, Lima, 15 

Agerostrea, 29

megodon, 29

(Agerostrea) megodon, Ostrea, 29 

Alameda County, Calif, 35 

Alaska, 13, 28 

Alectryonella, 25 

(Alectryonia) megodon, Ostrea, 29

plicata, Ostrea, 25 

alect us, Anomia, 11 

Alegria Formation, 33 

Almejas Formation, 8,11,12,19, 21,24, 25, 26, 27,28,

29, 42; pis. 7, 8,12,17,32, 34 

altatemblorensis, Ostrea, 39; pis. 21, 24 

Anchor Silt, 28, 41 

andersoni, Crassostrea titan, 37

Ostrea, 36

titan, 36; pi. 24 

angelica, Dendostrea?, 23, 26; pis. 32, 34

Lopha, 26

Ostrea, 24, 25, 26, 28 

angermanni, Dendostrea?, 23, 25; pi. 31

Ostrea, 25 

Anomia, 9, 11,13

alectus, 11

hamillus,!!

hannai, 9, 10; pi. 5

inconspicua, 9, 10; pi. 6

inornata, 11

inornatus, 9, 11; pis. 6, 7

lampe, 11

larbas, 11

limatula, 10

linatula, 10

macrochisma, 13

mcgoniglensis, 9,10,11

pacilus, 11

peruviana, 9,10, 11; pi. 6

subcostata, 9, 10; pis. 6, 7, 8

vaquerosensis, 9, 10; pis. 5, 6 

Anomia ?, 9, 11

mcgoniglensis, 11; pi. 5 

Anomiacea, 9 

Anomiidae, 9 

Anomya simplex, 11 

Antilles, 35 

appressa, Crassostrea, 34

INDEX

[Italic page numbers indicate major references]

appressa Continued

Ostrea, 33

Striostrea?, 33; pis. 12,16 

Argentina, 28 

Arnold, Ralph, cited, 34 

arnoldi, Ostrea, 39; pis. 19, 20 

ashleyi, Crassostrea?, 36, 38, 39; pis. 19, 20, 21, 22, 24

Ostrea, 38, 39 

Asia, 15, 27 

Astarte compressa, 28 

Astrodapsis, 41

gregerseni, 41

tumidus, 41 

Atlantic, eastern, 27, 28

western, 27, 28, 32 

atwoodii, Ostrea, 28

Ostrea (Ostrea), 27, 28; pi. 30 

auaua, Lima, 16 

Australia, 13,17 

Avenal Formation, 32 

Avenal Sandstone, 7,18,31,41 

aviculiformis, Gryphaeostrea, 18; pi. 19

Ostrea, 18

B

Bahia de los Angeles, 23, 26

Bahia Kino, 38

Bahia Magdalena, 8

Baja California, 33

Baja California Norte, 13,15,16, 24, 28, 29

Baja California Sur, 6, 8,11,12,13,19, 21, 22,23, 24,25, 

26, 27, 29, 32, 34, 38, 40

Bay of Panama, 8

Bay Point Formation, 28, 29, 41

Beechers Bay Member, Monterey Formation, 34, 41

Boleo Formation, 19, 26, 42

Borneo, 35

bostrychites, Spondylus, 6, 8; pis. 2, 3, 9

bourgeoisii, Crassostrea, 37, 40 

Ostrea, 32, 34, 35, 36, 39 

Striostrea? bourgeoisii, 33, 34, 37; pis. 25, 26 

bourgeoisii, Striostrea?, 33, 34, 37; pis. 25, 26 

perrini, Striostrea?, 33,35, 37; pis. 26, 27

Branch Canyon Sandstone, 35, 36, 37, 39, 40, 41; pis. 21, 

24, 27, 28, 29

Briones Formation, 35; pis. 26, 27

Briones Sandstone, 34

San Pablo Group, 35, 41

buwaldana, Ostrea, 30; pi. 30

calcifer, Spondylus, 6, 8; pi. 4 

Caliente Formation, pis. 21, 24 

California, 13,14,15,17,22

middle, 7,10,11,12,13,15,17,18,19,22,26,28,30, 

31,35,37,38,39,40

northern, 5,15, 30

southern, 7,8,10,11,12,13,14,15,16,17,19,20,21, 

22, 25, 26, 28, 29, 30, 31, 32, 33, 34, 35, 

37, 38, 39, 40 

californica, Crassostrea, 40

Ostrea, 37, 38

Placunanomia, 11, 12; pi. 6

osunai, Crassostrea?, 36, 40; pi. 27

Ostrea, 40

Canada del Pozo, Calif, 31 

Canada Formation, 31, 32, 41; pi. 29 

Cantil Costero Formation, 25, 26, 42 

Capistrano Formation, 15, 26, 41 

Careaga Sandstone, 13,41

Cebada Member, 19,41 

carlosensis, Spondylus, 6., 7; pi. 1 

Carlotta Formation, 28, 29, 41 

Carmen Formation, 19, 23, 25, 26, 27, 29, 42 

Carrizo Creek, Calif, 10, 26 

Carrizo Creek beds, Calif., 10

Castaic Formation, 26, 35, 37, 41

Cebada Member, Careaga Sandstone, 19, 41

Cedros Island, 24

Central America, 11, 33

cepio, Placunanomia, 13

Pododesmus, 13 

(Mania), 13 

cerrosensis, Ostrea, 29, 30; pis. 32, 34

Ostrea megodon, 29 

Chile, 14, 38

chilensis, Ostrea, 34, 37, 38; pi. 24 

Chinzei, Kiyotaka, cited, 30 

Cierbo Formation, 40, 41; pis. 25, 26 

Cierbo Sandstone, 35

San Pablo Group, 41 

cierboensis, Crassostrea, 37

Ostrea, 35, 36, 39, 40, 41; pis. 25, 26 

Clark, S. G., cited, 33, 34 

clarki, Lima, 16

Limaria (Limaria), 14, 16; pi. 10 

claytonensis,Lima, 16,17

Limea? (Isolimea?), 14, 17; pi. 10 

cliffensis, Spondylus, 6, 7; pi. 2 

Coalinga, Calif, 7,18, 39 

cochlear, Neopycnodonte?, 23; pi. 32

Ostrea, 23

Coldwater Sandstone, 32, 33, 41 

Coldwater Sandstone Member, lejon Formation, 41 

Colorado Desert, 10,21 

columbiana, Ostrea, 31 

columbiensis, Crassostrea, 36, 37; pis. 24, 26, 28

Ostrea,37, 38

(Crassostrea), 37 

Comondu Formation, 21, 42 

compressa, Astarte, 28 

conchaphila, Ostrea, 28

Ostreola, 27, 28; pi. 30

palmula, Ostrea, 32 

Contra Costa County, Calif, 10,15,17 

Corral Hollow, Alameda County, Calif, 9 

corrugata, Ostrea, 39

Ostrea titan, 20, 39 

corteziensis, Crassostrea, 37, 38

Ostrea, 37, 38; pis. 26, 28 

Cowlitz County, Wash., 30, 31 

Cowlitz Formation, 30, 31, 42; pi. 33 

Coyote Mountain, 21 

Cozy Dell Shale, 7, 41

Cozy Dell Shale Member, lejon Formation, 41 

crandalli, Ostrea, 30; pi. 32 

crassisquama, Spondylus, 8; pi. 3 

Crassostrea, 30, 32, 33,35, 37, 40

appressa, 34

bourgeoisii, 37, 40

californica, 40

cierboensis, 37

columbiensis, 36, 37; pis. 24, 26, 28

corteziensis, 37, 38

eldridgei ynezana, 19

gigas, 35

ligminuta, 37

sookensis, 19

titan, 34, 35, 36, 37, 38; pis. 23, 24, 27, 28, 29 

andersoni, 37 

prior, 37 

titan, 33, 35

vaquerosensis, 38

virginica, 33, 35 

Crassostrea?, 36, 38

ashleyi, 36, 38, 39; pis. 19, 20, 21, 22, 24

californica osunai, 36, 40; pi. 27

englekyi, 36, 38; pis. 20, 22

eucorrugata, 36, 39, 40; pis. 25, 26, 27

vaquerosensis, 36, 38; pis. 21, 25 

(Crassostrea) columbiensis, Ostrea, 37

titan, Ostrea, 35 

Crassostreinae, 30

C49
C50 PALEONTOLOGY OF CALIFORNIA AND BAJA CALIFORNIA

Crenostrea, 22

iCrenostrea?/, Pycnodonte?, 22

eldridgei, Pycnodonte?, 18, 22; pi. 21

stewarh, Pycnodonte?, 18,22; pi. 19 

cumingi, Placunanomia, 12 

L-ummgiana, Ostrea, 23, 26; pis. 32, 34 

cumingh, Placunanomia, 12 

Cuyama Valley. Calif, 37 

Cypraea, 28

D

Dall, W. H , cited, 33

Delmar Formation, 11, 30, 31, 32; pis. 5, 32

La Jolla Group, 41 

Dendostrea, 25, 27 

Dendostrea?, 23, 25, 27

angelica, 23, 26; pis. 32, 34

angermanm, 23, 25; pi. 31

vespertma, 21, 23,25, 26, 32; pis. 11.12.13,14,15.16 

denselamellosa, Ostrea, 27 

Desmostylus tooth. 34 

Domengine Formation. 7. 9. 10, 18, 31, 32, 41: pis 1, 6, 7,

13,14.16.19

Domengine Sandstone. 41 

Dominican Republic. 8 

Douglas County, Oreg., 31

E

Eaton, J. E., cited, 38 

Ecuador, 6, 8,11, 23. 38 

eduhs, Ostrea, 25. 27 

Eel River, Calif, 33 

eldridgei, Ostrea, 18, 19, 22

Pycnodonte? (Crenostrea!'I, 18,22. pi 21

ynezana, Crassostrea, 19

Ostrea, 18,19, 22 

Emperador Limestone Member, La Boca Formation, 22,

42 

englekyi, Crassostrea'', 36, 38; pis. 20, 22

Ostrea, 38 

Eostrea. 27

lEnxti-m) puelchana, Ostrea, 27 

erici, Ostrea, 19, 33

Pycnodonte, 19

'Pycnodonte). 18, 19; pi. 12 

Estrella Valley, Calif. 9, 36 

estrallensis, Spondylus. 8 

estrellanus, Lyropecten, 9

Pallium, 9

Spondylus, 8; pi. 5

Etchegoin Formation, 11,12,13, 26, 28, 41; pis. 6, 9, 30 

eucorrugata. Crassostrea?, 36, 39, 40; pis. 25. 26. 27

Ostrea titan, 39 

Europe, 13, 30 

excavata. Lima, 15 

Exogyrinae, 18

Fernando Formation, 8,11,13,15,17,19, 25. 26. 28, 41;

pis. 9, 10 

fettkei, Acutostrea idriaensis, 27, 30; pis. 30, 32, 33

Ostrea, 30

idriaensis, 30, 31 

fischeri, Ostrea, 22 

fisheri, Ostrea, 22, 23 

Fleminostrea, 40 

Fossil localities, 40 

Foxen Mudstone, 19, 41 

fragihs, Lima, 13 

Fresno County, Calif, 36, 39, 40 

freudenbergi, Ostrea, 34. 38

Striostrea?, 33, 34; pis. 26, 27

G

Gabb, W. M., cited, 33, 34 

Galapagos Islands, 6, 23, 32 

Gaviota Formation, 33, 42; pi. 29 

Gaviota Pass, Calif, 36 

Geologic formations cited, 41

gibbosa, Plicatula, 6

giganteus, Pecten (Hinmtes), 1

gigas, Crassostrea, 35

Gloria Formation. 12,19, 26, 29, 38, 42

Golfo de California, 6, 8, 23, 27, 38

gohath, Lima, 15

granti, Placunanomia, 11, 12; pi 6

gregerseni, Astrodapsis, 41

Gryphaea, 22

Gryphaeidae, 17

Gryphaeostrea, 18

aviculiformis, 18; pi. 19 

Gulf of California. 38 

Gurabo Formation, 8, 42

H

haitensis, Hyotissa, 21. 22

Ostrea, 20, 24, 26

vespertma, Ostrea, 24, 25 

haleyi, Odontogryphaea, 31

Ostrea, 30, 31; pi. 29 

hamillus,Anomia, 11 

hamhm, Acesta (Acestai, 14, 75; pi. 10

Lima. 15

I Acesta I, 15

hannai. Anomia. 9, 10; pi 5 

hannibah, Placunanomia, 11, 12; pis 7, 8 

Harry, H W., cited, 17, 20, 28, 38 

haseltinei. Acesta. 15

Acesta (Phcacesta), 14. 15; pis. 9, 10

Lima, 15 

heermanm, Ostrea. 20, 21, 24, 25, 26

Pycnodonte''. 21

(Pycnodonte?). 18,21; pis. 13,14,16,17 

hemphilh, Lima, 16

Lima (Limarial, 16

Limaria I Limaria I. 14, 16; pis. 7, 8 

hertleim, Ostrea, 39; pis. 20, 22 

(Hinmtesl giganteus, Pecten, 1 

howelli, Ostrea, 19, 20, 39

Pycnodonte?, 20, 21

IPycnodonte?I. 18,20, pi. 14 

hyotis, Hyotissa, 22, 23; pi. 16

Mytdus, 22 

Hyotissa, 17,20.22

haitensis, 21. 22

hyotis. 22, 23; pi. 16

hyotissa, 23

quercmus. 23

tryoni, 17, 20 

hyotissa, Hyotissa, 23

I, J, K

idriaensis, Acutostrea idriaensis, 27, 31, pis 13,14,16, 

29

Ostrea. 30, 31, 32

fettkei. Acutostrea, 27, 30; pis 30, 32, 33 

Ostrea. 30, 31

idriaensis, Acutostrea, 27, 31; pis. 13, 14,16, 29 

Imperial County, Calif, 10, 21, 26 

Imperial Formation, 8. 10, 11, 21, 25, 26, 27. 29, 32, 38, 

42; pis. 2.3, 6, 7, 8.11,12,13,14,15,16, 31 

mconspicua, Anomia, 9, 10; pi. 6 

Indo-West Pacific, 27 

inezana. Spondylus, 7; pis. 2, 9 

Infierno Formation, 11,12, 21, 23, 26. 27, 42 

inornata, Anomia, 11

Placunanomia, 9 

inornatus. Anomia, 9, 11; pis 6,7

Pododesmus iMonial, 9 

Introduction, 1 

indiscens, Ostrea, 37. 38

Isidro Formation, 22, 25, 34, 40, 42; pis. 26, 27, 31 

Isla Carmen, 23 

Isla Cedros, 29 

Isla Cerralvo, 23 

Isla Coronados, 8 

Isla la Plata, Ecuador, 8 

Isla Maria Magdalena, 6 

Isla Tres Marias, 25, 29

(Isolimeat, Limea, 17 

(Isohmea?!, Limea?, 14, 17

claytonensis. Limea?, 14, 17; pi. 10 

jacobaea, Ostrea, 22 

Jamaica, 8

Japan, 13, 15, 23, 27, 35 

Jewett Sand, 19, 38, 42

Pyramid Hill Sand Member, 38, 42 

Juncal Formation, 32, 42 

Kamtschatka, 13, 31 

Kern County, Calif, 12, 39 

Kings County, Calif, 26, 39 

Kirker's Pass, Calif, 34

La Boca Formation, 17

Emperador Limestone Member, 22, 42 

Laguna de Scammon, 8,19

Laguna des Isles de San Jose, Golfo de California. 6 

La Jolla Group. 31, 32, 42 

Delmar Formation, 41 

Lake County, Calif, 5, 30 

lampe, Anomia, 11 

larbas, Anomia, 11 

laticaudata, Ostrea lurida, 26 

hgminuta, Crassostrea, 37

Ostrea. 35, 36, 37; pis. 28, 29 

Lima, 13,14, 15 

agassizu, 15 

auaua. 16 

clarki. 16

claytonensis, 16.17 

excavata. 15 

fragilis, 13 

gohath, 15 

hamhm, 15 

haseltinei, 15 

hemphilh, 16 

lima, 13

multiradiata, 14 

orbignyi. 16 

orcutti, 16 

packardi, 16 

pernni, 15; pis. 9, 10 

tetrica. 14 

vedderi, 13,14 

(Acestai hamhm. 15 

Lima. 13 

(Limal, 14

vedderi. 13. 14; pi. 10 

iLimanat hemphilh, 16

orcutti. 16

(Limatulal subauriculata. 17 

lima, Lima, 13 

/Limai, Lima, 13

vedderi. Lima, 13. 14; pi. 10 

Limacea, 13 

Limaria. 14, 16

Limaria, 14,16 

(Limarial, 16

clarki, 14, 16; pi. 10 

hemphilh. 14, 16; pis. 7, 8 

orcutti, 14, 16; pi. 9 

(LimariaI. Limaria, 16

clarki, Limaria. 14, 16; pi 10 

hemphilli. Lima, 16

Limaria, 14, 16; pis. 7. 8 

orcutti, Lima, 16

Limaria, 14. 16; pi. 9 

Limatuta, 14,17

subauriculata, 14, 17, pi. 9 

iLimatula) subauriculata, Lima, 17 

limatula, Anomia, 10 

Limea, 17

Isohmea, 17 

Limea?, 14,17

llsohmea?). 14,17

claytonensis. 14, 17; pi. 10 

Limidae, 13 

hnatula, Anomia, 10
INDEX C51

Lincoln Creek Formation, 41 

lithobleta, Placunanomia, 12 

loeli, Ostrea, 20, 21, 39

Ostrea vespertina, 21

Pycnodonte?, 20

iPycnodonte?), 18, 20, 21; pi. 18 

Lomita Marl, 29

Lomita Marl Member, San Pedro Formation, 42 

Lopha, 24. 25

angelica. 26 

Lopha?. '23,24

veatchii, 24, 25

"Lopha", 24

(Lopha), 23,24

veatchii, 23, 24; pi. 17 

(Lopha), Lopha?, 23, 24

megodon, Ostrea, 29

veatchii. Lopha, 23, 24; pi. 17 

Lophinae, 24, 25 

Los Angeles County, Calif, 15 

Lower Lake, Calif, 29 

Lower Lake Village, Calif, 15 

lurida, Ostrea. 26, 28, 29

laticaudata, Ostrea, 26 

Lyropecten, 9

estrellanus, 9

M

macrochisma, Anomia, 13

macroschisma. Mania, 13

Pododesmus, 13

(Moma), 12, 73; pis. 7, 8, 9 

Madagascar, 23, 33 

magnolia. Pecten, 34 

Maria Madre Island, 12 

Marquer Formation, 6, 23, 24, 25, 26, 27, 42; pis. 1,

34 

Martinez Formation, 5.15, 16,17, 29, 30, 31, 42; pis

10, 29, 30

Matilija Sandstone, 32, 42 

Mazatlan, Mexico, 5, 28, 32 

McLure Shale Member, Monterey Formation, 37 

mcgomglensis. Anomia, 9,10. 11 

mcgomglensis, Anomia?, 9, 11; pi. 5 

Medill Sand, 29, 42 

Mediterranean Sea, 28 

megodon, Agerostrea, 29

Ostrea, 29

lAgerostrea), 29 

(Alectryonial, 29 

(Lopha), 29

Ostreola?, 27, 29: pis. 32, 34

cerrosensis, Ostrea, 29 

Merced Formation, 13, 28, 42 

Mesodesma, 28 

messor, Ostrea, 29 

Mexico, 23, 26, 27, 29 

miguelensis, Acutostrea?, 27, 32; pi. 33

Ostrea, 29, 32 

Mmdego Basalt, 38, 42 

Modelo Formation, 37, 42 

Moma, 12, 13

macroschisma. 13 

/Monial cepio, Pododesmus, 13

mornatus, Pododesmus, 9

macroschisma. Pododesmus, 12, 13; pis. 7. 8, 9 

Monterey, Calif. 13 

Monterey Bay, Calif, 16 

Monterey County, Calif, 10, 28, 38 

Monterey Formation, 14, 42

Beechers Bay Member, 34, 41

McLure Shale Member, 37

Saltos Shale Member, 34, 42 

Monterey Group, 42 

Monterey Shale, 8, 14, 22, 42; pi. 10

Saltos Shale Member, 34, 42 

mon, Acesta, 15 

Mulberry Seamount, 14 

multiradiata, Acesta (Acesta), 14; pi. 10

Lima, 14

Mytilus hyotis, 22

N, O

32, 

1.9,

Negritos, Peru, 8 

Neopycnodonte, 23, 26

cochlear, 23 

Neopycnodonte?, 23, 26

cochlear, 23; pi. 32 

Neroly Formation, 35 

Neroly Sandstone, 37

San Pablo Group, 37, 42 

newcombei, Pododesmus, 13 

New Idria, Calif, 30, 31 

New Zealand. 13, 22 

Niguel Formation, 13,17,19, 25,26, 42 

North America, 11,13, 30, 33 

Odontogryphaea haleyi, 31 

Olcese Sand, 39, 42 

Orange County, Calif, 14 

orbignyl, Lima, 16 

orcutti, Lima. 16

Lima iLimaria), 16

Limaria (Limaria), 14, 16; pi. 9 

Oregon, 11

oregonensis, Ostrea, 31 

Ostrea, 20, 25, 27, 28, 29, 34, 38

altatemblorensis, 39; pis. 21, 24

andersoni, 36

angelica, 24, 25, 26, 28

angermanni, 25

appressa, 33

arnoldi. 39; pis. 19, 20

ashleyi, 38, 39

atwoodii, 28

aviculiformis, 18

bourgeoisii, 32, 34, 35, 36, 39

buwaldana, 30; pi. 30

cahformca. 37, 38 

osunai, 40

cerrosensis, 29, 30; pis. 32. 34

chilensis, 34, 37, 38; pi. 24

cierboensis. 35. 36, 39, 40, 41; pis. 25, 26

cochlear, 23

columbiana, 31

columbiensis, 37, 38

conchaphila, 28 

palmula, 32

corrugata, 39

corteziensis, 37, 38; pis. 26, 28

crandalli, 30; pi. 32

cumingiana, 23, 26; pis. 32, 34

denselamellosa, 27

edulis, 25, 27

eldridgei. 18,19, 22 

ynezana, 18,19, 22

englekyi, 38

erici, 19, 33

fettkei, 30

fischeri, 22

ftsheri, 22, 23

freudenbergi, 34, 38

haitensis, 20, 24, 26 

vespertina, 24, 25

haleyi, 30, 31; pi. 29

heermanm, 20, 21, 24, 25, 26

hertleim, 39; pis. 20, 22

howelli, 19, 20, 39

idriaensis, 30, 31, 32 

fettkei, 30, 31

iridescens, 37, 38

jacobaea, 22

tigminuta, 35, 36, 37; pis. 28, 29

loeh, 20, 21, 39

lurida, 26, 28, 29 

laticaudata, 26

megodon, 29

cerrosensis, 29

messor, 29 

miguelensis, 29, 32

oregonensis, 31

palmula, 26, 32

panzana, 36, 37; pi. 23 

prior, 36 

reef, 41

sellaformis thomasii, 25 

simiensis, 30 

stewarti, 22, 31 

subjecta, 36, 37; pi. 23 

tayloriana, 19, 33 

ft'tan, 20, 34, 35, 36, 37, 38, 40 

andersoni, 36; pi. 24 

corrugata, 20, 39 

eucorrugata, 39 

perrini, 35

prior, 35, 36, 37; pis. 27, 29 

subtitan, 34, 36 

titan, 35, 36 

vaquerosensis, 38 

veatchii, 20, 21, 24, 25, 26; pi. 17 

venturana, 29

vespertina, 20, 21, 24, 25, 26, 32, 39; pi. 34 

/oe/;, 21

sequens, 25, 26, 28; pi. 15 

virginica, 33, 38 

weaveri, 27, 29; pi. 29 

wiedeyi, 20, 21, 24, 26, 39 

sp., 10

lAgerostrea) megodon, 29 

'Alectryonia) megodon, 29

plicata, 25 

(Crassostreat columbiensis, 37

ritarc, 35

(Eostrea) puelchana, 27 

fLopha) megodon, 29 

Ostrea, 28 

' Ostrea), 27, 28

atwoodii, 27, 2#; pi. 30 

(Ostrea), Ostrea, 27, 28

atwoodii, Ostrea, 27, 28; pi. 30 

Ostrea-Pecten "reef, 41 

Ostreacea, 17 

ostreaformis, Plicatula, 5 

Ostreidae, 17,24 

ostreiformis. Plicatula. 5; pi. 1 

Ostreinae, 27, 29

incertae sedis, 29 

Ostreola. 25, 28

conchaphila, 27, 28; pi. 30 

Ostreola?, 27, 2«

megodon, 21,29; pis. 32, 34 

venturana. 27, 2.9; pis. 31, 33 

osunai, Crassostrea? californica, 36, 40; pi. 27

Ostrea cahformca, 40 

oysters, 17. 31

Pacific, eastern, 9, 27, 28, 32

pacdus, Anomia, 11

packardi, Lima, 16

Painted Rock Sandstone Member, Vaqueros Formation,

38,42

Paita, Peru, 11 

Pallium estrellanus, 9 

palmula, Ostrea, 26, 32

Ostrea conchaphila. 32

Saccostrea, 32, 33; pi. 18 

Palos Verdes Sand, 28, 29, 42 

Palos Verdes Sandstone, 16 

Panama, 17, 22, 28

Pancho Rico Formation, 13, 28, 42; pi. 30 

Panza Valley, Calif, 36 

panzana, Ostrea, 36, 37; pi. 23 

Paso Robles Formation, 26, 28, 42 

Pecten, 16

magnolia, 34

(Hinnites) giganteus, 7 

Pectinacea, 5. 6 

Pectinidae, 6 

Pelagi Gorgoniis, 23 

Pelecypods, 5 

penicillata, Plicatula, 5, 6; pi. 1
C52 PALEONTOLOGY OF CALIFORNIA AND BAJA CALIFORNIA

perrini, Acesta, 15

Lima, 15; pis. 9,10 

Ostrea titan, 35 

Spondylus, 6, 7; pis. 2, 9 

Striostrea? bourgeoisii, 33, 35, 37; pis. 26, 27 

Peru, 29

peruviana, Anomia, 9,10, 22; pi. 6 

Philippine Islands, 35 

Pico Formation, 13, 25, 26, 32, 42 

Placunanomia, 11, 12,13 

californica, 11, 12; pi. 6 

cepio, 13 

cumingi, 12 

cumingii, 12 

granti, 11, 12; pi. 6 

hannibali, 11,22; pis. 7,8 

inornata, 9 

lithobleta, 12 

plicata, 12 

Plicacesta, 15 

(Plicacesta), Acesta, 15

haseltinei, Acesta, 14,25; pis. 9,10 

plicata, Ostrea (Alectryonia), 25

Placunanomia, 12 

Plicatula, 5 

gibbosa, 6 

ostreaformis, 5 

ostreiformis, 5; pi. 1 

penicillata, 5, 6; pi. 1 

spondylopsis, 5,6; pl.l 

(Plicatula), 5 

(Plicatula), Plicatula, 5 

Plicatulidae, 5 

Pododesmus, 9,12,23 

cepio, 13

macroschisma, 13 

newcombei, 13 

(Monia) cepio, 13 

inornatus, 9

macroschisma, 12, 23; pis. 7, 8, 9 

(Pododesmus), 13 

(Pododesmus), Pododesmus, 13 

Potato Harbor Formation, 13, 42 

Powell, C. L., cited, 21 

princeps, Spondylus, 6, 8; pis. 3, 4, 5 

Spondylus princeps, 8 

princeps, Spondylus, 8 

prior, Crassostrea titan, 37 

Ostrea, 36

iitarc, 35, 36, 37; pis. 27, 29 

Procedure, 2 

Promantellum, 16 

puelchana, Ostrea (Eostrea), 27 

Puget Sound, Wash., 13, 28 

Purisima Formation, 19, 26, 42 

Purpose and scope, 2 

Pycnodonte, 17,2S, 20, 21 

erici, 19 

ynezana, 19 

Pycnodonte, 18 

(Pycnodonte) erici, 18, 29; pi. 12

yrcezarca.-ZS.ll 

Pycnodonte?, 18, 20 

heermanni, 21 

howelli, 20, 21 

foe/i, 20

wiedeyi, 20, 21, 24 

Crenostrea, 22 

(Crenostrea?), 22

eldridgei, 18,22; pi. 21 

stewarti, 18,22; pi. 19 

(Pycnodonte?), 18,20

heermanni, 18,22; pis. 13,14,16,17 

howelli, 18,20; pi. 14 

ZoeZt, 18,20,22; pi. 18 

wiedeyi, 18,20; pi. 15 

(Pycnodonte) erici, Pycnodonte, 18, 79; pi. 12

ynezana, Pycnodonte, 18; pi. 11 

(Pycnodonte?), Pycnodonte?, 18,20

heermanni, Pycnodonte?, 18,22; pis. 13,14,16,17 

howelli, Pycnodonte?, 18, 20; pi. 14

(Pycnodonte?) Continued

loeli, Pycnodonte?, 18,22; pi. 18

wiedeyi, Pycnodonte?, 18,20; pi. 15 

Pycnodonteinae, 17, 18, 19,21,30,40 

Pyramid Hill Sand Member, Jewett Sand, 38, 42

Q, R

Quadriostrea, 30

Quail Canyon Sandstone Member, Vaqueros Formation,

22,42

quercinus, Hyotissa, 23 

Rancho El Refugio, 23 

Rapana vaquerosensis, 34 

References cited, 42 

regius, Spondylus, 6 

Remond, Auguste, quoted, 34 

Repetto Formation, 41 

Rincon Shale, 8,11, 21, 42 

Rose Canyon Shale, 7, 22, 42; pis. 2,19 

Round Mountain Silt, 37, 42

Sacate Formation, 32, 42 

Saccostrea, 30, 32

palmula, 32, 33; pi. 18 

Saint Elena, Columbia, 38 

Salada Formation, 32, 40, 42; pi. 27 

Saltos Shale Member, Monterey Formation, 34, 42

Monterey Shale, 34, 42 

San Antonio Creek, Calif., 34 

San Clemente Island, 13,14 

San Diego, Calif, 16

San Diego County, Calif., 7,11,16, 22, 30 

San Diego Formation, 13, 16,17, 25, 26, 27, 29, 42; pi. 9 

San Felipe, Calif, 21 

San Francisquito Canyon, Calif, 37 

San Gregorio Lagoon, Calif, 34 

San Ignacio Formation, 26, 42 

San Joaquin Formation, 12, 26, 28, 42; pis. 15, 30 

San Lorenzo Creek, Calif, 28 

San Luis Obispo, Calif, 36, 39 

San Marcos Formation, 8, 23, 25, 26, 29, 38, 42 

San Marcos Pass, Calif, 33 

San Miguel Island, Calif, 32 

San Nicolas Island, 28 

San Onofre Breccia, 38, 39, 42 

San Pablo Formation, 35, 37, 42; pis. 23, 25, 26 

San Pablo Group, Briones Sandstone, 35

Neroly Sandstone, 37, 42 

San Pedro Formation, 13, 42

Lomita Marl Member, 42

Timms Point Silt Member, 13, 42 

San Pedro Sand, 16, 28, 29, 42 

San Ramon Sandstone, 10, 42; pi. 6 

Santa Barbara County, Calif., 11,19, 29, 36, 38, 40 

Santa Margarita Formation, 9,13,14, 26, 35, 36, 37, 40,

42; pis. 5, 23, 24, 25, 27 

Santa Rosa Island, Calif, 20, 21, 24 

Santa Rosalia Formation, 23, 42 

Santa Susana Formation, 15,16,42 

Santa Ynez Mountains, 34 

Santos Shale Member, Temblor Formation, 42 

Saugus Formation, 11,13, 25, 26, 28, 42 

sellaformis thomasii, Ostrea, 25 

Sepultura Formation, 15, 42 

sequens, Ostrea vespertina, 25, 26, 28; pi. 15 

Sierra Monica, Calif, 36 

Simi Conglomerate, 30, 42; pi. 34 

Simi Hills, Calif, 15, 30 

simiensis, Acutostrea, 27, 30; pi. 34

Ostrea, 30 

simplex, Anomya, 11 

Sisquoc Formation, 19, 42 

Sobrante Sandstone, 37, 42 

Soda Lake Sandstone Member, Vaqueros Formation, 22,

42

Sonora, Mexico, 38 

Sooke Formation, 19, 42 

sookensis, Crassostrea, 19

South America, 13 

Spondylidae, 6

spondylopsis, Plicatula, 5, 6; pi. 1 

Spondylus, 6, 9

bostrychites, 6, 8; pis. 2, 3, 9

calcifer, 6,8; pi. 4

carlosensis, 6, 7; pi. 1

cliffensis, 6, 7; pi. 2

crassisquama, 8; pi. 3

estrallensis, 8

estrellanus, 8; pi. 5

inezana, 7; pis. 2, 9

perrini, 6, 7; pis. 2, 9

princeps, 6, 8; pis. 3, 4, 5 

princeps, 8

regius, 6

victoriae, 8; pis. 3, 4 

Stanton, R. J., Jr., cited, 35, 37 

Stenzel, H. B., cited, 17, 34, 35, 37, 40 

stewarti, Ostrea, 22, 31

Pycnodonte? (Crenostrea?), 18, 22; pi. 19 

Striostrea, 30, 32, 34, 35, 39 

Striostrea?, 33

appressa, 33; pis. 12,16

bourgeoisii bourgeoisii, 33, 34, 37; pis, 25, 26 

perrini, 33, 35, 37; pis. 26, 27

freudenbergi, 33, 34; pis. 26, 27

subtitan, 33,34; pi. 22

tayloriana, 33; pi. 29 

subauriculata, Lima (Limatula), 17

Limatula, 14, 2 7; pi. 9 

subcostata, Anomia, 9, 20; pis. 6, 7, 8 

subjecta, Ostrea, 36, 37; pi. 23 

Submantellum, 16 

subtitan, Ostrea titan, 34, 36 

Striostrea?, 33, 34; pi. 22 

Suzuki, Takeo, cited, 34, 37, 38 

Systematics, 5

tayloriana, Ostrea, 19, 33

Striostrea?, 33; pi. 29 

Tejon Formation, 7,15, 32, 33, 42; pi. 10

Coldwater Sandstone Member, 41

Cozy Dell Shale Member, 41 

Tejon Group, 33, 34

Temblor Formation, 33, 34, 35, 38, 39, 42; pis. 12,16,19, 

20,22

Saltos Shale Member, 42

Wygal Sandstone Member, 19, 42 

tetrica, Lima, 14 

thomasii, Ostrea sellaformis, 25 

Timms Point Silt, 28, 29

Timms Point Silt Member, San Pedro Formation, 13, 42 

titan, Crassostrea, 34, 35, 36, 37, 38; pis. 23, 24, 27, 28, 

29

Crassostrea titan, 33, 35

Ostrea, 20, 34, 35, 36, 37, 38, 40 

(Crassostrea), 35 

titan, 35, 36

andersoni, Crassostrea, 37 

Ostrea, 36; pi. 24

corrugata, Ostrea, 20, 39

eucorrugata, Ostrea, 39

perrini, Ostrea, 35

prior, Crassostrea, 37

Ostrea, 35, 36, 37; pis. 27, 29

subtitan, Ostrea, 34, 36

titan, Crassostrea, 33, 35

Ostrea, 35, 36 

Tomales Formation, 42 

Topanga Formation, 21, 35, 36, 37, 42; pi. 23 

Tortugas Formation, 21, 34, 42 

Towsley Formation, 13,16, 26,42 

Transverse Ranges, 22 

Trinidad, 20 

tryoni, Hyotissa, 17, 20 

tumidus, Astrodapsis, 41 

Turritella bed, 34, 40 

Turtle Bay, 24
INDEX C53

U, V, W, Y

Umpqua Formation, 31, 42 

Vancouver Island, B.C., 19

Vaqueros Formation, 7, 8,10,11,19, 20,21, 22, 25, 29,32, 

34, 38, 42; pis. 2, 5,6,9,11,14,15,18, 20, 

21,22,25,31,33

Painted Rock Sandstone Member, 38, 42

Quail Canyon Sandstone Member, 22, 42

Soda Lake Sandstone Member, 22, 42 

vaquerosensis, Anomia, 9, 10; pis. 5, 6

Crassostrea, 38

Crassostrea?, 36, 38; pis. 21, 25

Ostrea, 38

Rapana, 34

veatchii, Lopha?, 24, 25

("Lopha"),23,24;pl. 17

Ostrea, 20, 21, 24, 25, 26; pi. 17 

Vedder, J. G., cited, 37 

vedderi, Lima, 13,14

Lima (Lima), 13,14; pi. 10 

Venture County, Calif., 10,16, 20, 22, 30, 34 

venturana, Ostrea, 29

Ostreola?, 27, 29; pis. 31, 33

vespertina, Dendostrea?, 21, 23, 25, 26, 32; pis. 11,12,13, 

14,15,16

Ostrea, 20, 21, 24, 25, 26, 32, 39; pi. 34 

haitensis, 24, 25

loeli, Ostrea, 21

sequens, Ostrea, 25, 26, 28; pi. 15 

victoriae, Spondylus, 8; pis. 3, 4

virginica, Crassostrea, 33, 35

Ostrea, 33, 38 

Vokes, H. E., cited, 30, 31 

Washington, 15,31 

weaveri, Ostrea, 27, 29; pi. 29 

wiedeyi, Ostrea, 20, 21, 24, 26, 39

Pycnodonte?, 20, 21, 24

(Pycnodonte?), 18, 20; pi. 15 

Wiley Canyon, Calif., 7 

Willapa Harbor, Wash., 28 

Woodring, W. P., cited, 17, 32, 37

quoted, 20

Wygal Sandstone Member, Temblor Formation, 19, 42 

ynezana, Crassostrea eldridgei, 19

Ostrea eldridgei, 18,19, 22

Pycnodonte, 19

(Pycnodonte), 18; pi. 11

PLATES 1-34

[Contact photographs of the plates in this report are available, at cost, from the U.S. Geological 

Survey Photographic Library, Federal Center, Denver, Colorado 80225]
PLATE 1

FIGURES 1-3. Plicatula ostreiformis Stanton (p. 5).

1, 3. Syntypes USNM 157838. Martinez Formation, California, Paleocene. 

2. Hypotype UCMP 11680 ( x 2.0; Dickerson, 1914, pi. 9, fig. 12).

Martinez Formation, California, Paleocene. 

4, 6, 8, 9. Plicatula pencillata Carpenter (p. 5).

4, 6. Hypotype UCMP 15927 ( x 3.0; Durham, 1950, pi. 13, fig. 5).

Unnamed Pleistocene strata, Isla Coronado, Baja California Sur. 

8, 9. Hypotype UCMP 15921 ( x 3.0; Durham, 1950, pi. 13, fig. 2).

Unnamed Pleistocene strata, Isla Coronado, Baja California Sur. 

5. Spondylus carlosensis Anderson (p. 6).

Holotype CAS 56. Domengine Formation, California, Eocene. 

7,10. Plicatula spondylopsis Rochebrune (p. 6).

Hypotype UCMP 14898 (Durham, 1950, pi. 15, fig. 2). Marquer Formation, 

Baja California Sur, Pliocene.
GEOLOGICAL SURVEY PROFESSIONAL PAPER 1228-C PLATE 1

10

PL/CA TULA SPOND YLUS
PLATE 2

FIGURES 1,4-7. Spondylus perrini Wiedey (p. 7).

1, 4, 5. Holotype SDNM 28. Vaqueros Formation, California, Oligocene

and Miocene.

6, 7. Holotype of Spondylus inezana Wiedey SDNM 29. Vaqueros 

Formation, Oligocene and Miocene.

2. Spondylus bostrychites Guppy (p. 8).

Hypotype UCMP 32279 (G D. Hanna, 1926a, pi. 24, figs. 3, 4). Imperial 

Formation, California, Miocene or Pliocene.

3. Spondylus cliffensis M. A. Hanna (p. 7).

Holotype (plaster cast) UCMP 31025 ( x 2.0). Rose Canyon Shale, 

California, Eocene.
GEOLOGICAL SURVEY PROFESSIONAL PAPER 1228-C PLATE 2

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SPONDVLUS
PLATE 3

FIGURES 1,3-10. Spondylus princeps Broderip (p. 8).

1, 6, 8. Hypotype CAS 057755 (x 0.8). Peru, Holocene. 

3, 4, 10. Spondylus victorias Sowerby of Durham

UCMP 15418 (x 0.8; 1950, pi. 15, fig. 3). Unnamed 

Pleistocene strata, Isla Coronado, Baja California Sur. 

5, 7, 9. Spondylus crassisquama Lamarck of Durham

Hypotype UCMP 15414 ( x 0.8; 1950, p. 68, pi. 15, fig. 1). 

Unnamed Pleistocene strata, Isla Carmen, Baja California

Sur. 

2. Spondylus bostrychites Guppy (p. 8).

Hypotype UCMP 32380 (G D. Hanna, 1926a, pi. 24, fig. 4). Imperial 

Formation, California, Miocene or Pliocene.
GEOLOGICAL SURVEY PROFESSIONAL PAPER 1228-C PLATE 3

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SPONDVLUS
PLATE 4

FIGURES 1, 2, 4, 5. Spondylus calcifer Carpenter (p. 8).

GAS 41999 (x 0.8). Isla Grassa, Sonora, Mexico, Holocene. 

3, 6. Spondylus princeps Broderip (p. 8).

3. GAS 40504 (x 0.9). Pira, Peru, Holocene. 

6. Spondylus victoriae Sowerby of Durham

(x 0.8; 1950, pi. 15, fig. 3). Unnamed Pleistocene strata, Isla Coronado, 

Baja California Sur.
GEOLOGICAL SURVEY PROFESSIONAL PAPER 1228-C PLATE 4

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SPONDYLUS
PLATE 5

FIGURES 1,3. Anomia? mcgoniglensis M. A. Hanna (p. 11).

1. SyntypeUCMP 31011 (x 2.0). Delmar Formation, California,

Eocene. 

3. Syntype UCMP 31011 ( x 2.0). Delmar Formation, California,

Eocene. 

2. "Spondylus estrellanus Conrad" (p. 8).

Holotype USNM 13312. Santa Margarita Formation, California, Miocene. 

4, 5. Anomia hannai Wiedey (p. 10).

Holotype CAS/SU 514. Vaqueros Formation, California, Oligocene and 

Miocene.

6. Spondylus princeps Broderip (p. 8).

UCMP 15417 (x 0.8). Unnamed Pleistocene strata, Isla Carmen, Baja 

California Sur.

7. Anomia vaquerosensis Loel and Corey (p. 10).

Holotype UCMP 31758 (x 1.5). Vaqueros Formation, California, 

Oligocene and Miocene.
GEOLOGICAL SURVEY PROFESSIONAL PAPER 1228-C PLATE 5

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SPONDYLUS, "SPONDYLUS", ANOMIA
PLATE 6

FIGURES 1, 4, 6. Anomia peruviana Orbigny (p. 11).

CAS/SU 39737. Guaymas, Sonora, Mexico, Holocene.

2. Anomia inornatus (Gabb) (p. 9).

Lectotype ANSP 4442 ( x 1.5). Domengine Formation, California, Eocene.

3. Placunanomia granti Hertlein (p. 11).

Holotype CAS 4139 (. x 2.0). Vaqueros Formation, California, Oligocene

and Miocene. 

5,11. Placunanomia californica Arnold (p. 11).

Holotype USNM 165546. Etchegoin Formation, California, Miocene and

Pliocene. 

7,10,13. Anomia subcostata Conrad (p. 10).

7. Lectotype USNM 1865. Imperial Formation, California, Miocene

or Pliocene. 

10,13. USNM 13345a (two specimens). Imperial Formation, California,

Miocene or Pliocene. 

8. Anomia inconspicua Clark (p. 10).

Holotype UCMP 11205 ( x 10.0) fThe specimen is glued to a slide and was 

photographed through glass. 1 San Ramon Sandstone, California, 

Miocene(?). 

9,12. Anomia vaquerosensis Loel and Corey (p. 10).

Holotype UCMP 31758. Vaqueros Formation, California, Oligocene and 

Miocene.
GEOLOGICAL SURVEY PROFESSIONAL PAPER 1228-C PLATE 6

13

ANOM/A, PLACUNANOMIA
PLATE 7

FIGURES 1. Limaria (Limaria) hemphilli Hertlein and Strong (p. 16).

Syntype CAS 9174A (x 2.0). San Diego, California, Holocene. 

2, 6, 7. Placunanomia hannibali Jordan and Hertlein (p. 12).

2. Paratype CAS 2111. Almejas Formation, Baja California Sur, Pliocene.

6. Holotype CAS 2110 (x 0.9). Almejas Formation, Baja California Sur, 

Pliocene.

7. Paratype CAS 2112. Almejas Formation, Baja California Sur, Pliocene.

3. Anomia inornatus (Gabb) (p. 9).

Lectotype ANSP 4442 (x 1.5). Domengine Formation, California, Eocene.

4. Pododesmus (Monia) macroschisma Deshayes (p. 13)

Hypotype CAS 42135. McCleod Harbor, Montague Island, Alaska, 

Holocene.

5. Anomia subcostata (Conrad) (p. 10).

Hypotype CAS 1814 ( x 1.5; G D. Hanna, 1926a, pi. 23, fig. 4). Imperial 

Formation, California, Miocene or Pliocene.
GEOLOGICAL SURVEY PROFESSIONAL PAPER 1228-C PLATE 7

ANOMIA, PLACUNANOMIA, LIMARIA, PODODESMUS
PLATE 8

FIGURES 1. Anomia subcostata Conrad (p. 10).

Hypotype CAS 1814 (x 1.5; G D. Hanna, 1926a, pi. 23, fig. 4). Imperial

Formation, California, Miocene or Pliocene. 

2, 5. Placunanomia hannibali Jordan and Hertlein (p. 12).

2. Paratype CAS 2111. Almejas Formation, Baja California Norte,

Pliocene. 

5. Paratype CAS 2112. Almejas Formation, Baja California Norte,

Pliocene. 

3, 6, 8. Limaria (Limaria) hemphilli Hertlein and Strong (p. 16).

3. Syntype CAS 9174 ( x 1.5). San Diego, California, Holocene. 

6, 8. Syntype CAS 9174A ( x 1.5). San Diego, California, Holocene. 

4, 7. Pododesmus (Monia) macroschisma Deshayes (p. 13)

Hypotype CAS 42135. McCleod Harbor, Montague Island, Alaska, 

Holocene.
GEOLOGICAL SURVEY PROFESSIONAL PAPER 1228-C PLATE 8

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ANOMLA, PLACaNANOMLA, L/MARLA, PODODESMUS
PLATE 9

FIGURES 1. Spondylus perrini Wiedey (p. 7).

Holotype of Spondylus inezana Wiedey SDNM 29. Vaqueros Formation,

California, Oligocene and Miocene. 

2. Limatula aff. L. subauriculata (Montagu) (p. 17).

Hypotype USNM 496096 (x 4.0; Woodring, 1938, pi. 8, fig. 6). Fernando

Formation, California, Pliocene. 

3, 9. Spondylus bostrychites Guppy (p. 8).

3. Lectotype BM(NH) R12833 (photograph copied from Palmer, 1938,

pi- 3, fig. 4). 

9. Paratype BM(NH) (photograph copied from Palmer, 1938, pi. 2, fig.

1). 

Limaria (Limaria) orcutti Hertlein and Grant (p. 16).

4. 8. Holotype LAM 4509 ( x 0.7). San Diego Formation, California, 

Pliocene.

5. 6. Paratype LAM 4511 (x 0.7). San Diego Formation, California,

Pliocene. 

7. Pododesmus (Monia) macroschisma (Deshayes) (p. 13).

Hypotype USNM 165602 (Arnold, 1909 [1910], pi. 14, fig. 1). Etchegoin

Formation, California, Miocene and Pliocene. 

10. Acesta (Plicacesta) haseltinei (Dickerson) (p. 15).

Holotype of Lima perrini Waring CAS/SU 303 (x 0.7). Martinez 

Formation, California, Paleocene.
GEOLOGICAL SURVEY PROFESSIONAL PAPER 1228-C PLATE 9

SPONDYLUS, LIMATULA, LIMARIA, PODODESMUS, ACESTA
PLATE 10

FIGURES 1, 3. Lima (Lima) vedderi Moore (p. 13).

Holotype USNM 240060. Monterey Shale, California, Miocene. 

1. (x 1.5). 

3. (x 3.0). 

2, 9. Limea? (Isolimea?) claytonensis (Dickerson) (p. 17).

2. SyntypeUCMP 11721 (x 10.0).MartinezFormation, California,

Paleocene.

9. SyntypeUCMP 11720 (x 10.0). Martinez Formation, California, 

Paleocene.

4. 7. Acesta (Acesta) hamlini (Ball) (p. 15).

Holotype USNM 495186. Fernando Formation, California, Pliocene.

5. 8. Acesta (Acesta) multiradiata (Gabb) (p. 14).

5. Latex impression of hypotype USNM 157826 (Stanton, 1896, pi. 63, fig.

7). Tejon Formation, California, Eocene. 

8. Holotype (photograph copied from Gabb, 1869, pi. 33, fig. 101).

Martinez Formation, California, Paleocene. 

6. Limaria (Limaria) clarki (Nelson) (p. 16).

Holotype UCMP 30494 (x 3.0). Martinez Formation, California,

Paleocene. 

10,11. Acesta (Plicacesta) haseltinei (Dickerson) (p. 15).

10. Holotype ofLimaperrini Waring CAS/SU 303 (x 0.5). Martinez 

Formation, California, Paleocene.

11. Holotype UCMP 11676 (x 0.7). Martinez Formation, California, 

Paleocene.
GEOLOGICAL SURVEY PROFESSIONAL PAPER 1228-C PLATE 10

11

LIMA, LIMEA?, ACESTA, LIMARIA
PLATE 11

FIGURES 1, 3, 4, 6. Pycnodonte (Pycnodonte) ynezana (Loel and Corey) (p. 18).

Holotype UCMP 31745. Figures 4, 6 ( x 0.9). Vaqueros Formation,

California, Oligocene and Miocene. 

2, 5. Dendostrea? vespertina (Conrad) (p. 25).

Paratype ANSP 13366e ( x 1.5). Imperial Formation, California, Miocene 

or Pliocene.
GEOLOGICAL SURVEY PROFESSIONAL PAPER 1228-C PLATE 11

*'

PYCNODONTE, DENDOSTREA?
PLATE 12

FIGURES 1, 4, 7, 8. Pycnodonte (Pycnodonte) erici (Hertlein) (p. 19).

Holotype CAS 2094. Almejas Formation, Baja California Sur, Pliocene. 

3. Striostrea? appressa (Gabb) (p. 33).

Paratype (photograph copied from Gabb, 1869, pi. 34, fig. 104a).

Temblor(?) Formation, California, Oligocene and Miocene. 

2, 5, 6. Dendostrea? vespertina (Conrad) (p. 25).

2. Paratype ANSP 13366d (x 1.5). Imperial Formation, California,

Miocene or Pliocene.

5, 6. Paratype ANSP 13366a (x 1.5). Imperial Formation, California, 

Miocene or Pliocene.
GEOLOGICAL SURVEY PROFESSIONAL PAPER 1228-C PLATE 12

PYCNODONTE, DENDOSTREA?, STRIOSTREA?
PLATE 13

FIGURES 1, 4, 6, 7. Pycnodonte? (Pycnodonte?) heermanni (Conrad) (p. 21).

Syntypes ANSP 13367 (6, 7 x 0.7). Imperial Formation, California,

Miocene or Pliocene. 

2, 3. Acutostrea idriaensis idriaensis (Gabb) (p. 31).

Photograph copied from Gabb (1869, pi. 33, figs. 103b, 103c), Domengine

Formation, California, Eocene. 

5. Dendostrea? vespertina (Conrad) (p. 25).

Paratype ANSP 13366a (x 1.5). Imperial Formation, California, Miocene 

or Pliocene.
GEOLOGICAL SURVEY PROFESSIONAL PAPER 1228 C PLATE 13

PYCNODONTE?, DENDOSTREA?, ACUTOSTREA
PLATE 14

FIGURES 1, 3, 5, 7. Pycnodonte? (Pycnodonte?) howelli (Wiedey) (p. 20).

1, 5. Syntype CAS 2981. Vaqueros Formation, California, Oligocene and

Miocene. 

3, 7. Syntype CAS 2982 (x 0.8). Vaqueros Formation, California,

Oligocene and Miocene. 

2. Dendostrea? vespertina (Conrad) (p. 25).

Hypotype of G D. Hanna (1926a, pi. 26, figs. 1-3) UCMP 33290. Imperial

Formation, California, Miocene or Pliocene. 

4. Pycnodonte? (Pycnodonte?) heermanni (Conrad) (p. 21).

Syntype ANSP 13367. Imperial Formation, California, Miocene or

Pliocene. 

6. Acutostrea idriaensis idriaensis (Gabb) (p. 31).

Photograph copied from Gabb (1869, pi. 33, fig. 103d). Domengine 

Formation, California, Eocene.
GEOLOGICAL SURVEY PROFESSIONAL PAPER 1228-C PLATE 14

6 7 

PYCNODONTE?, DENDOSTREA?, ACUTOSTREA
PLATE 15

FIGURES 1, 4, 5, 8. Pycnodonte? (Pycnodonte1?) wiedeyi (Hertlein) (p. 20).

1, 4. Paratype CAS 4130. Vaqueros Formation, California, Oligocene and

Miocene. 

5, 8. Holotype CAS 4129 (x 0.8). Vaqueros Formation, California,

Oligocene and Miocene. 

2, 3, 6, 7. Dendostrea? vespertina (Conrad) (p. 25).

2, 3. Syntypes ofOstrea vespertina sequens Arnold USNM 165545 (two 

specimens). San Joaquin Formation, California, Pliocene.

6. Paratype ANSP 13366a ( x 1.5). Imperial Formation, California, 

Miocene or Pliocene.

7. Hypotype of G D. Hanna (1926a, pi. 26, figs. 1-3). UCMP 32290. 

Imperial Formation, California, Miocene or Pliocene.
GEOLOGICAL SURVEY PROFESSIONAL PAPER 1228-C PLATE 15

PYCNODONTE?, DENDOSTRE4?
PLATE 16

FIGURES 1, 2. Hyotissa hyotis (Linne) (p. 22).

Hypotype of Durham (1950, pi. 6, figs. 1, 4) UCMP 15502 ( x 0.7). 

Unnamed Pleistocene strata, Isla Carmen, Baja California Sur.

3. Acutostrea idriaensis idriaensis (Gabb) (p. 31).

Photograph copied from Gabb (1869, pi. 34, fig. 103). Domengine 

Formation, California, Eocene.

4. Pycnodonte? (Pycnodonte?) heermanii (Conrad) (p. 21).

Syntype ANSP 13367b. Imperial Formation, California, Miocene or 

Pliocene.

5. Striostrea? appressa (Gabb) (p. 33).

Photograph copied from Gabb (1869, pi. 34, fig. 104). Temblor(?)

Formation, California, Oligocene and Miocene. 

6, 7. Dendostrea? vespertina (Conrad) (p. 25).

Lectotype of Woodring (1938) ANSP 13366. Imperial Formation, 

California, Miocene or Pliocene.
GEOLOGICAL SURVEY PROFESSIONAL PAPER 1228-C PLATE 16

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HYO77SSA ACUTOSTREA, PYCNODONTE?, STRIOSTREA?, DENDOSTREA?
PLATE 17

FIGURES 1-5. Lopha? ("Lopha") veatchii Gabb (p. 24)

1, 3, 5. Paratypes ANSP unnumbered. Almejas Formation, Baja

California Norte, Pliocene. 

2, 4. Holotype ANSP 4502. Almejas Formation, Baja California Norte,

Pliocene. 

6, 7. Pycnodontel (Pycnodonte?) heermanni (Conrad) (p. 21)

Hypotype of Ostrea veatchii Gabb (1869, pi. 17, figs. 21, 21a), ANSP 

unnumbered (x 0.8). Almejas(?) Formation, Baja California Sur, 

Pliocene.
GEOLOGICAL SURVEY PROFESSIONAL PAPER 1228-C PLATE 17

S^CrfE*^^"^'- tiP * V .r1 ''" -' , ' 

'^T SJ'iMifr'V^. / J. O 

LOPHA ?, PYCNODONTE?
PLATE 18

FIGURES 1-6. Saccostreapalmula (Carpenter) (p. 32).

Espiritu Santo, Golfo de California, Holocene.

1. 5. CAS 057756.

2. 3. CAS 057757. 

4. CAS 057758. 

6. CAS 057759. 

Pycnodontel (Pycnodontel) loeli (Hertlein) (p. 21).

Holotype CAS 4117 (x 0.8). Vaqueros Formation, California, Oligocene 

and Miocene.
GEOLOGICAL SURVEY PROFESSIONAL PAPER 1228-C PLATE 18

SACCOSTREA, PVCNODONTE?
PLATE 19

FIGURES 1, 2,6. Gryphaeostrea aviculiformis (Anderson) (p. 18).

Holotype CAS 21 (x 2.0). Domengine Formation, California, Eocene. 

3, 5. Crassostrea? ashleyi (Hertlein) (p. 38).

3. Holotype ofOstrea arnoldi Adegoke UCMP 36646. Temblor

Formation, California, Oligocene and Miocene. 

5. Paratype ofOstrea arnoldi Adegoke UCMP 36647. Temblor

Formation, California, Oligocene and Miocene. 

Pycnodonte? (Crenostrea?) stewarti (M. A. Hanna) (p. 22).

4. Syntype UCMP 30921 (x 0.8). Rose Canyon Shale, California,

Eocene.

7, 8. Syntype UCMP 30922 ( x 0.8). Rose Canyon Shale, California, 

Eocene.
GEOLOGICAL SURVEY PROFESSIONAL PAPER 1228-C PLATE 19

GRYPHAEOSTREA, CRASSOSTREA?, PYCNODONTE?
PLATE 20

FIGURES 1. Crassostrea? englekyi (Hertlein) (p. 38).

Holotype CAS 4116 (x 0.7). Vaqueros Formation, California, Oligocene

and Miocene. 

2-6. Crassostrea? ashleyi (Hertlein) (p. 38).

2. Holotype of Ostrea arnoldi Adegoke UCMP 36646. Temblor 

Formation, California, Oligocene and Miocene.

3. Paratype of Ostrea arnoldi Adegoke UCMP 36647. Temblor

Formation, California, Oligocene and Miocene. 

4, 5. Holotype CAS 6065 (x 0.5). Temblor Formation, California, 

Oligocene and Miocene.

6. Holotype of Ostrea hertleini Adegoke UCMP 36654. Temblor 

Formation, California, Oligocene and Miocene.
GEOLOGICAL SURVEY PROFESSIONAL PAPER 1228-C PLATE 20

t -

CRASSOSTREA?
PLATE 21

FIGURES 1,4. Pycnodonte? (Crenostreat) eldridgei (Arnold) (p. 22).

Holotype USNM 164966. Vaqueros Formation, California, Oligocene and 

Miocene.

2. Crassostrea? vaquerosensis (Loel and Corey) (p. 38).

Paratype CAS 6790. Vaqueros Formation, California, Oligocene and 

Miocene.

3. Crassostrea? ashleyi (Hertlein) (p. 38).

Holotype of Ostrea altatemblorensis Grant and Eaton, UCLA 8970. 

Branch Canyon Sandstone/Caliente Formation, Caiifornia, Miocene.
GEOLOGICAL SURVEY PROFESSIONAL PAPER 1228-C PLATE 21

PYCNODONTE?, CRASSOSTREA?
PLATE 22

FIGURES 1. Crassostrea? englekyi (Hertlein) (p. 38).

Holotype CAS 4116 (x 0.7). Vaqueros Formation, California, Oligocene

and Miocene. 

2. Crassostrea? ashleyi (Hertlein) (p. 38).

Holotype of Ostrea hertleini Adegoke UCMP 36654. Temblor Formation,

California, Oligocene and Miocene. 

3-5. Striostrea? subtitan (Loel and Corey) (p. 34).

Holotype UCMP 31750. Vaqueros Formation, California, Oligocene and 

Miocene.

3. Right valve (x 0.7). 

4, 5. Left valve (x 0.8).
GEOLOGICAL SURVEY PROFESSIONAL PAPER 1228-C PLATE 22

CRASSOSTREA?, STR/OSTREA?
PLATE 23

FIGURES 1-7. Crassostrea titan (Conrad) (p. 35).

1. Hypotype of Arnold (1907a, pi. 45, fig. 2) USNM 164987. Topanga 

Formation, California, Miocene.

2. 6. Hypotype of Clark (1915, pi. 44, fig. 1) UCMP 15565. San Pablo 

Formation, California, Miocene.

3. 7. Holotype of Ostrea panzana Conrad USNM 13338. Santa 

Margarita(?) Formation, California, Miocene.

4. 5. Holotype of Ostrea subjecta Conrad USNM 13338. Santa 

Margarita(?) Formation, California, Miocene.
GEOLOGICAL SURVEY PROFESSIONAL PAPER 1228-C PLATE 23

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\"tiif f- ._.-.--- "**

CRASSOSTREA
PLATE 24

FIGURES 1, 3, 4, 6. Crassostrea titan (Conrad) (p. 35).

1, 6. Paratype ofOstrea titan andersoni Adegoke UCMP 36662 (x 0.5).

Santa Margarita Formation, California, Miocene. 

3, 4. Holotype ofOstrea titan andersoni Adegoke UCMP 36661 (x 0.5).

Santa Margarita Formation, California, Miocene. 

2. Crassostrea columbiensis (Hanley) (p. 37).

Hypotype ofOstrea chilensis Phillipi of Durham (1950, pi. 4, fig. 1) UCMP

15505. Unnamed Pliocene strata, Isla Carmen, Baja California Sur. 

5. Crassostrea? ashleyi (Hertlein) (p. 38).

Holotype of Ostrea altatemblorensis Grant and Eaton UCLA 8970. 

Branch Canyon Sandstone/Caliente Formation, California, Miocene.
GEOLOGICAL SURVEY PROFESSIONAL PAPER 1228-C PLATE 24

CRASSOSTREA, CRASSOSTREA?
PLATE 25

FIGURES 1. Striostrea? bourgeoisii bourgeoisii (Remond) (p. 34).

Hypotype of Clark (1915, pi. 43) UCMP 11566 ( x 0.5). San Pablo

Formation, California, Miocene. 

2. Crassostrea? vaquerosensis (Loel and Corey) (p. 38).

Paratype CAS 6789 (x 0.8). Vaqueros Formation, California, Oligocene

and Miocene. 

3-5. Crassostrea? eucorrugata (Hertlein) (p. 39).

3. Holotype of Ostrea cierboensis Grant and Eaton, UCLA, 8980 (x

0.8). Cierbo Formation, California, Miocene. 

4, 5. Holotype UCMP 11309 (x 0.4). Santa Margarita Formation, 

California, Miocene.
GEOLOGICAL SURVEY PROFESSIONAL PAPER 1228-C PLATE 25

STR/OSTREA?, CRASSOSTREA?
PLATE 26

FIGURES 1. Crassostrea? eucorrugata (Hertlein) (p. 39).

Holotype ofOstrea cierboensis Grant and Eaton UCLA 8980. Cierbo 

Formation, California, Miocene.

2. Crassostrea columbiensis (Hanley) (p. 37).

Holotype ofOstrea corteziensis Hertlein CAS 4288 ( x 0.8). Bahia Kino, 

Golfo de California, Sonora Mexico, Holocene.

3. Striostreat freudenbergi (Hertlein and Jordan) (p. 34).

Holotype CAS/SU 5138. Isidro(?) Formation, Baja California Sur, 

Miocene.

4. Striostrea? bourgeoisii perrini (Hall and Ambrose) (p. 35).

Holotype CAS/SU 502 (x 0.7). Briones Formation, California, Miocene.

5. Striostrea? bourgeoisii bourgeoisii (Remond) (p. 34).

Hypotype of Clark (1915, pi. 43) UCMP 11566 (x 0.5). San Pablo 

Formation, California, Miocene.
GEOLOGICAL SURVEY PROFESSIONAL PAPER 1228-C PLATE 26

CRASSOSTREA, CRASSOSTREA?, STRIOSTREA?
PLATE 27

FIGURES 1. Crassostrea? eucorrugata (Hertlein) (p. 39).

Holotype UCMP 11309 ( x 0.4). Santa Margarita Formation, California, 

Miocene.

2. Crassostrea? californica osunai (Hertlein) (p. 40).

Holotype CAS 12823 ( x 0.5). Salada Formation, Baja California Sur, 

Pliocene.

3. Striostrea? freudenbergi (Hertlein and Jordan) (p. 34).

Holotype CAS/SU 5138. Isidro(?) Formation, Baja California Sur, 

Miocene.

4. Crassostrea titan (Conrad) (p. 35).

Holotype ofOstrea titan prior Grant and Eaton UCLA 8991. Branch 

Canyon Sandstone, California, Miocene.

5. Striostrea? bourgeoisii perrini (Hall and Ambrose) (p. 35).

Holotype CAS/SU 502. Briones Formation, California, Miocene.
GEOLOGICAL SURVEY PROFESSIONAL PAPER 1228-C PLATE 27

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, ti*

CRASSOSTREA, CRASSOSTREA?, STRIOSTREA?
PLATE 28

FIGURES 1, 2, 4. Crassostrea columbiensis (Hanley) (p. 37).

Holotype ofOstrea corteziensis Hertlein CAS 4288 (x 0.8). Golfo de

California, Sonora Mexico, Holocene. 

3, 5. Crassostrea titan (Conrad) (p. 35).

Holotype of Ostrea ligminuta Grant and Eaton, UCLA 8985 (x 0.8). 

Branch Canyon Sandstone, California, Miocene.
GEOLOGICAL SURVEY

"VK ?£f,

PROFESSIONAL PAPER 1228-C PLATE 28

fcV^l8^'^*V to^j^xjw. ; ; v\ %;&*#A-'i\ ^1A

CRASSOSTREA
PLATE 29

FIGURES 1,6. Crassostrea titan (Conrad) (p. 35).

1. Holotype ofOstrea titan prior Grant and Eaton, UCLA 8991. Branch

Canyon Sandstone, California, Miocene. 

6. Holotype of Ostrea ligminuta Grant and Eaton, UCLA 8985 (x 0.8).

Branch Canyon Sandstone, California, Miocene. 

2. "Ostrea" weaveri Dickerson (p. 29).

Holotype UCMP 32624. Martinez Formation, California, Paleocene. 

3-5. Acutostrea idriaensis idriaensis (Gabb) (p. 31).

3, 5. Holotype of Ostrea haleyi Hertlein CAS 5526. Canada Formation,

Santa Cruz Island, California, Eocene. 

4. Photograph copied from Gabb (1869, pi. 34, fig. 103a). 

7, 8. Striostrea? tayloriana (Gabb) (p. 33).

Holotype UCMP 12005. Gaviota Formation, California, Eocene and 

Oligocene.
GEOLOGICAL SURVEY PROFESSIONAL PAPER 1228-C PLATE 29

CRASSOSTREA, "OSTREA", ACLJTOSTREA, STRIOSTREA?
PLATE 30

FIGURES 1-4, 6, 8. Ostreola conchaphila (Carpenter) (p. 28).

1,3. CAS 057760 (x 1.5). Olympia, Washington, Holocene. 

2, 4. CAS 057761 (x 1.5). Olympia, Washington, Holocene. 

6, 8. Hypotype of Howard (1935, pi. 7, fig. 5) CAS 7044 (x 2.0). San 

Joaquin Formation or upper part of Etchegoin Formation, 

California, Pliocene. 

5. Acutostrea idriaensis fettkei (Weaver) (p. 30).

Holotype ofOstrea buwaldana Dickerson UCMP 11719. Martinez

Formation, California, Paleocene. 

7, 9. Ostrea (Ostrea) atwoodii Gabb (p. 28).

Hypotype of Durham and Addicott (1965, pi. 3, figs. 3, 7) USNM 649094. 

Pancho Rico Formation, California, Miocene.
GEOLOGICAL SURVEY PROFESSIONAL PAPER 1228-C PLATE 30

OSTREOLA, ACUTOSTREA, OSTREA
PLATE 31

FIGURES 1-6, 8. Dendostrea? angermanni (Hertlein and Jordan) (p. 25).

1-4, 6. Hypotype UCMP 37535 (x 1.5). Imperial Formation, California,

Miocene or Pliocene.

5, 8. Holotype CAS/SU 5137 (x 1.5). Isidro(?) Formation, Miocene. 

7. Ostreola? venturana (Loel and Corey) (p. 29).

Paratype UCMP 10035 (x 1.5). Vaqueros Formation, California, 

Oligocene and Miocene.
GEOLOGICAL SURVEY PROFESSIONAL PAPER 1228-C PLATE 31

DENDOSTREA?, OSTREOLA?
PLATE 32

FIGURES 1, 8, 9. Dendostreal angelica (Rochebrune) (p. 26).

1, 8. Hypotype CAS 057786. Golfo de California, Holocene.

9. Hypotype of Durham (1950, pi. 5, fig. 7) UCMP 15955. Marquer 

Formation, Baja California Sur, Pliocene.

2. 5. Ostreola? megodon (Hanley) (p. 29).

2. Hypotype of Jordan and Hertlein (1926b, pi. 28, fig. 1) CAS 2093.

Almejas Formation, Baja California Norte. 

5. Lectotype of Ostrea cerrosensis Gabb ANSP 4494. Almejas(?) 

Formation, Baja California Norte, Pliocene.

3. 7. Neopycnodonte? cf. N. cochlear (Poli) (p. 23)

Hypotype of Ostrea cumingiana Dunker of Durham (1950, pi. 5, fig. 4) 

UCMP 15425. Marquer Formation, Baja California Sur, Pliocene.

4. 6. Acutostrea idriaensis fettkei (Weaver) (p. 30).

Holotype of Ostrea crandalli M. A. Hanna UCMP 31072 (x 1.5). Delmar 

Formation, California, Eocene.
GEOLOGICAL SURVEY PROFESSIONAL PAPER 1228-C PLATE 32

DENDOSTREA?, OSTREOLA?, NEOPYCNODONTE?, ACUTOSTREA
PLATE 33

FIGURES 1-3, 8. Acutostrea idriaensis fettkei (Weaver) (p. 30).

1. 3. Holotype CAS 479 (x 3.0). Cowlitz Formation, Washington, Eocene.

2. 8. Paratype CAS 479a (x 3.0). Cowlitz Formation, Washington,

Eocene. 

4, 6, 7, 9. Acutostrea? miguelensis (Hertlein) (p. 32).

4, 6. Holotype CAS 4121 (x 3.0). Vaqueros Formation, California,

Oligocene and Miocene. 

7, 9. Paratype CAS 4122 (x 3.0). Vaqueros Formation, California,

Oligocene and Miocene. 

5. Ostreola? venturana (Loel and Corey) (p. 29).

Holotype UCMP 31751 (x 3.0). Vaqueros Formation, California, 

Oligocene and Miocene.
GEOLOGICAL SURVEY PROFESSIONAL PAPER 1228-C PLATE 33

ACUTOSTREA, ACUTOSTREA?, OSTREOLA?
PLATE 34

FIGURES 1, 3, 6, 8. Ostreola? megodon (Hanley) (p. 29).

1, 3. Hypotype of Jordan and Hertlein (1926b, pi. 28, fig. 1) CAS 2093. 

Almejas(?) Formation, Baja California Norte, Pliocene.

6. 8. Holotype ofOstrea cerrosensis Gabb ANSP 4494. Almejas(?)

Formation, Baja California Norte, Pliocene. 

2, 7, 9,10. Dendostrea? angelica (Rochebrune) (p. 26).

2. Hypotype ofOstrea cumingiana Dunker of Durham (1950, pi. 5, fig. 

6) UCMP 15424.

7. 9. Hypotype CAS 057762. Golfo de California, Holocene. 

10. Hypotype ofOstrea vespertina Conrad of Durham (1950, pi. 5, fig. 7) 

UCMP 15955. Marquer Formation, Baja California Sur, Pliocene. 

4, 5. Acutostrea simiensis (Zinsmeister) (p. 30).

4. Holotype UCR 6899/101. Simi Conglomerate, California, Paleocene.

5. Paratype UCR 6899/102. Simi Conglomerate, California, Paleocene.
GEOLOGICAL SURVEY PROFESSIONAL PAPER 1228-C PLATE 34

10

OSTREOLA?, DENDOSTREA?, ACUTOSTREA