~ ~ J •. I 

Tertiary Marine Pelecypods of 

California and Baja California: 

N uculidae through Malleidae 

BUREAU OF MIN.ES 

UBR.ARY 

SPOKANl:.. #ASH. 

MAR 3 0 1983 

· i.ltA5E Q.ETUR:t'-4 

to LtSRAR~. 

G E 0 L 0 G I C A L SURVEY P R 0 FE S S I 0 N A L PAPER 1 2 2 8- A(j?) 
Tertiary Marine Pelecypods of 

California and Baja California: 

Nuculidae through Malleidae 

By ELLEN JAMES MOORE 

PALEONTOLOGY OF CALIFORNIA AND BAJA CALIFORNIA 

GEOLOGICAL SURVEY PROFESSIONAL PAPER 1228-A 

A total of 233 species of 

pelecypods are illustrated, original 

descriptions quoted, taxonomy revised 

and updated, con1.parisons made with other 

species, geographic and geologic ranges 

given, occurrence by geologic forrnation 

cited, and habitat included when it can 

be confidently inferred 

.I 

UNITED STATES GOVERNMENT PRINTING OFFICE, WASHINGTON 1983 
UNITED STATES DEPARTMENT OF THE INTERIOR 

JAMES G. WATT, Secretary 

GEOLOGICAL SURVEY 

Dallas L. Peck, Director 

Library of Congress Cataloging in Publication Data 

Moore, Ellen James, 

Tertiary marine mollusks of California and the Baja California Peninsula 

(Geological Survey Professional Paper 1228-A) 

Bibliography: p. A91-A98 

Includes index 

Supt. of Docs. no.: I 19.16:1228-A 

1. Lamellibranchiata, Fossil. 2. Paleontology-Tertiary. 3. Paleontology-California. 4. Paleontology-Mexic~Baja California. 

I. Title. II. Series: United States Geological Survey Professional Paper 1228-A 

QE811.M63 564'.11'09794 81-6067879 

AACR2 

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

Washington, D.C. 20402 
CONTENTS 

Abstract ......................................................................................... . 

Introduction .................................................................................................................... . 

Purpose and scope .................................................................. . 

Procedure .............................................................................................................. . 

Acknowledgments ................................................................ . 

Abbreviations ........................................................................... . 

Systematics: Pelecypods ..................................................... . 

Family N uculidae ........................................................................................ . 

Genus Nucula .................................... . 

Genus Nucula? ................................................................... . 

Genus Acila ........................... . .................................. . 

Family Malletiidae .............................................................................. . 

Genus Malletia .......................................................... . 

Family Nuculanidae .......................................... . 

Genus Nuculana ....................... . 

Genus Led ina ....................................... . 

Genus Hilgardia .................................................................... . 

Genus Hilgardia? .............................. . ................... . 

Genus Litorhadia ................................................... . 

Genus Yoldia ..................................................................................... . 

Genus Yoldia? ............................................................................... . 

Genus Portlandia .......................................................................... . 

Family Solemyidae ............. : ................................................ . 

Genus Acharax ........................ ......................... . 

Genus Acharax? ....................................................................... . 

Family Arcidae ........................................................................ . 

Subfamily Arcinae ................. . 

Genus Area ................................................ .. 

Genus Barbatia ....................................................................... . 

Subfamily Anadarinae ..................................................... . 

Genus Anadara ............................................ . 

Genus Grandiarca ........................ . 

Genus Larkinia ............................................... . 

Genus Scapharca .............................. . 

Genus Scapha rca? ........................................... . 

Indeterminate species ..................................... . 

Family Parallelodontidae ....................... . 

Subfamily Grammatodontinae ................. . 

Genus Porterius ............................................................ . 

Family Cucullaeidae ................................................................ . 

Genus Cucullaea ..................................... . 

Family Noetiidae ................................................ . 

Subfamily Striarcinae ................................................................. . 

Genus Arcopsis .......................................................... . 

Subfamily Trinacriinae ........................ . .......................... . 

Genus Pachecoa ....................................... . 

Page 

A1 

1 

1 

5 

5 

6 

6 

6 

7 

8 

13 

13 

13 

13 

22 

22 

22 

23 

23 

28 

29 

30 

30 

31 

31 

31 

31 

34 

36 

36 

42 

42 

43 

44 

46 

46 

46 

46 

47 

47 

47 

47 

47 

48 

48 

Family Limposidae. 

Genus Limopsis .. 

Family Glycymerididae .. 

Subfamily Glycymeridinae .... . 

Genus Glycymeris ................................. . 

Genus Felicia .. . ........................ . 

Family Manzanellidae? .. 

Genus Huxleyia .. 

Family Mytilidae ... . .................... . 

Genus Mytilus ........... . 

Genus Brachidontes 

Genus Brachidontes? 

Genus Mytella . 

Genus Perna 

Genus Septifer 

Subfamily Crenellinae .................................. . 

Genus Crenella 

Genus Gregariella 

Genus Musculus ... 

Page 

. .. A49 

··························· 49 

49 

49 

49 

58 

59 

59 

59 

........................... 59 

·································· 66 

································ 67 

70 

70 

70 

71 

71 

72 

72 

Subfamily Lithophaginae ................................................................ . 73 

73 

73 

74 

74 

74 

78 

78 

Genus Lithophaga ...... . 

Genus Adula ......... . 

Genus Adula? ... 

Subfamily Modiolinae 

Genus Modiolus .. . ............................... . 

Genus Modiolus?. 

Genus Idasola ....... . 

Genus Idasola? .. ... .... . .•.........................•..••••.•••••... 

Family Pinnidae ........................ . 

Genus Pinna 

Genus Atrina .. 

Family Pteriidae ... 

Genus Pteria 

Genus Pinctada .............................. . 

Family Isognomonidae 

Genus Isognomon 

Genus Pachyperna 

Genus Pachyperna? .. 

Family Pulvinitidae ... 

Genus Pulvinites. 

Family Malleidae ......... . 

Genus Nayadina . ...................................... . 

Genus Vulsella. ................................ . .................... . 

Genus Vulsella? .. 

Fossil localities ................................ . 

Geologic formations cited for occurrence of pelecypods ... 

References cited ..................... . . ..................... . 

Index ............ _............ ·---... - .......... . 

III 

78 

78 

78 

80 

81 

81 

83 

84 

84 

85 

85 

85 

85 

86 

86 

87 

87 

87 

90 

91 

99 
IV CONTENTS 

ILLUSTRATIONS 

!Plates follow index] 

PLATE 1. Nuculidae. 

2, :3. N uculanidae. 

4. Nuculanidae, Solemyidae. 

5-·9. Arcidae. 

10. Cucullaeidae, Noetiidae, Limopsidae, Glycymerididae. 

11, 12. Glycymerididae. 

1:3. Glycymerididae, Mytilidae. 

14--20. Myti lidae. 

21. Mytilidae, Pinnidae. 

22, 2:3. Pinnidae. 

24. Pteriidae. 

25. Pteriidae, Isognomonidae. 

26. Isognomonidae, Pulvinitidae, Malleidae. 

27. Pinnidae. 

FIGUHE 1. Map showing divisions used for geographic range of species of pelecypods, Nuculidae to Malleidae, 

reported from California . 

2. Map showing divisions used for geographic range of species of pelecypods, Nuculidae to Malleidae, 

reported from Baja California Peninsula 

TABLES 

TABLES 1-8. Geologic and geographic distribution of large families: 

1. N uculidae ... . .................................................. . 

2. N uculanidae ...... . 

3. Arcidae ..... . 

4. Glycymerididae .. 

5. Mytilidae .... 

6. Pinnidae . 

7. Pteriidae .. 

8. Isognomonidae .. 

Page 

A3 

4 

Page 

A6 

14 

32 

50 

60 

79 

81 

84 
PALEONTOLOGY OF CALIFORNIA AND BAJA CALIFORNIA 

TERTIARY MARINE PELECYPODS 

OF CALIFORNIA AND BAJA CALIFORNIA: 

NUCULIDAE THROUGH MALLEIDAE 

By ELLEN JAMES IVIOORE 

ABSTRACT 

Marine mollusks are the principal means of dating and correlating the shallow-water facies that have persisted in Cenozoic 

marine basins along the Pacific coast of North America. This 

study focuses on California, the standard of reference for Cenozoic 

sequences of the northeast sector of the Pacific Ocean basin. 

Approximately 2,500 species of Tertiary marine mollusks were 

originally described from California, and about 50 from the Baja 

California Peninsula. A few additional species occur in the Californias that were originally described from other west coast localities. 

Descriptions of these species are spread through some 200 papers 

that span about 125 years of study. Some of these species are 

synonyms, and many are of doubtful status, never having been 

adequately illustrated. Consequently, research and practical utilization of Tertiary mollusks in geologic-age determination and biostratigraphy has often been difficult. 

In this synthesis, all Tertiary marine mollusks from the Californias are illustrated, the original description quoted, the taxonomy 

revised and updated, comparisons made with other species, geographic and geologic ranges given, the occurrence by formation in 

the Californias cited, and the habitat described when known from 

living specimens of the species or inferred from related species. 

Tables for the larger families are incorporated to show geographic 

and age ranges of the included species. 

This study is intended to improve the utility of marine mollusks 

in Cenozoic biostratigraphy of the Pacific coast of the conterminous United States and northern Mexico and, to a lesser extent, of 

Alaska, Kamchatka, and northern Japan. 

The compilation begins with the pelecypods; this chapter describes 233 species of the families Nuculidae, Nuculanidae, 

Solemyidae, Arcidae, Parallelodontidae, Cucullaeidae, Noetiidae, 

Limposidae, Glycymerididae , Manzanellidae, Mytilidae, Pinnidae, 

Pteriidae, Isognomonidae, Pulvinitidae, and Malleidae. Other 

chapters will follow in systematic order. 

INTRODUCTION 

PURPOSE AND SCOPE 

The literature pertaining to the Tertiary marine 

mollusks of California and the Baja California :peninsula spans about 125 years and includes descriptions 

of approximately 2,500 species in several hundred 

papers published in various journals. Many of these 

species have never been adequately illustrated. 

This synthesis brings together systematically all 

the descriptions of species originally named from, or 

subsequently found in, the marine Tertiary rocks of 

California and the Baja California Peninsula and, to 

the extent that is practical, illustrates the holotypes 

of these species. Taxonomy is revised and updated; 

supplementary descriptions and comparisons are 

included; geographic, geologic-age, and ecologic ranges recorded; and rel?orted occurrences in geologic 

formations in the Californias given. The goal is to 

improve the effectiveness and accuracy of utilizing 

mollusks in Cenozoic biostratigraphy. 

The compilation is being published as a series of 

separate chapters of a Professional Paper. The arrangementis biologically systematic and the families are 

arranged as cited in the Treatise On Invertebrate 

Paleontology (Moore, 1969), beginning with the 

family Nuculidae. Subsequent chapters will deal with 

the remaining pelecypods and the gastropods, scaphopods, and cephalopods. 

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. If a species is not 

positively identified or is questioned or only compared, it is generally not included. In genera that are 

extremely rare in the fossil record, however, 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). Within the systematic groups, species are arranged by geologic age, 

Al 
A2 PALEONTOLOGY OF CALIFORNIA AND BAJA CALIFORNIA 

beginning with the oldest species and ending with 

the youngest. The order in which families are arranged and the generic and subgeneric catergories 

have generally not been modified, except in a few 

cases. Most modifications made reflect either definitive papers published after publication of the Treatise 

in 1969 or works published earlier but not cited in it. 

Some of the names of genera and subgenera used 

in the Treatise and adopted in this paper have not 

been used before for west coast 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), in 

Keen (1971), and in Olsson (1961). For genera and 

subgenera that are not included in the Treatise, 

complete descriptions are given in the text. 

For large families, a distribution table is included 

to show graphically the geographic and geologic 

distribution of species within the 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, with 

particular emphasis on papers published after the 

checklist of Keen and Bentson (1944). The accuracy 

of identifications cited in subsequent references in 

the synonymy has not been verified. No attempt is 

made to include all references to a species, but the 

reader is referred to any citations that include extensive synonymies. 

The original description is quoted from the author 

of the species and is not modified; nor is it translated 

if in a language other than English. 

The type is usually that of the author of the 

original description or of later workers who selected a 

lectotype or neotype. In some instances, where syntypes or cotypes are cited but only one figured, I have 

herein designated the figured specimen as the lectotype. Lectotypes have also been designated for species 

originally based on many unfigured syntypes. Where 

any confusion exists concerning the type specimen, 

the most logical specimen is selected as the lectotype. 

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 where this information 

adds to the original description of the species. Where 

such information is not available or inclusive, I have 

supplemented the original description 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. Range 

extensions into Alaska are based on written communications from Scott McCoy, Jr., Amoco Production Co., 

and Richard C. Allison, University of Alaska, on 

data not previously published. I am deeply indebted 

to them for making their material available to me. 

Age ranges have not been refined within epochs. 

Where a stage name the same as a formation name is 

used, it is placed in quotation marks 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 1-8). 

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 a 

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 curently used by the U.S. Geological Survey. 

(See "Geologic Formations Cited for Occurrence of 

Pelecypods" at end of paper.) If the age of a formation 

is more than one epoch and a species is known to 

occur in only one part of that formation, this information is added. Except for the type locality of the 

species, 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 occurrences reported will 

serve as a framework upon which the true distribution 

of each species can be built. 

Most of the data on habitat have been compiled 

from Abbott (1974);Burch (1974), Hertlein and Grant 

(1972), Keen (1971), Smith and Gordon (1948), Stanley 

(1970), and Yonge and Thompson (1976). 

The type specimens were all photographed by Kenji 
z 

a: 

w 

:I: 

1-

a: 

0 

z 

UJ 

...J 

0 

0 

~ 

z 

a: 

UJ 

:I: 

1-

::;:) 

0 

(/) 

"'0 

~ 

("') 

0 

I 

~ 

so 

I 

TERTIARY MARINE PELECYPODS: NUCULIDAE THROUGH MALLEIDAE 

0 

100 

I 

'Z 

150 

I 

Santa Cruz: 

Island • San Miguel Island 4~ ~) 

Santa Rosa Island ____ ..," I 

I 

I 

I 

I 

I 

/Santa~ 

1 Catalina~ 

San Nicolas Island~. j Island 

200 KILOMETERS 

I 

I 

San Cleme~te Island~ SAN DIEGO 

A3 

IMPERIAL 

F'IGlJHE ].-Divisions used for geographic ranges of species of pelecypods, Nuculidae to Malleidae, reported from California. Heavy solid 

lines indicate Northern, Middle, and Southern divisions; dashed lines within southern region divide Channel Islands area. 
A4 

32° 

30° 

., 

PALEONTOLOGY OF CALIFORNIA AND BAJA CALIFORNIA 

116° 

San Diego 

CALIFORNIA 

Tij:=.;--,--------

112° 

ARIZONA 

28o Isla Cedros!) 

0 

26° 

24° 

50 

I 100 

I 150 I 

San Ignacio 

200 KILOMETERS 

I 

no• 

FIGURE 2.-Divisions used for geographic ranges of species of pelecypods, Nuculidae to Malleidae, 

reported from Baja California Peninsula. 
TERTIARY MARINE PELECYPODS: NUCULIDAE THROUGH MALLEIDAE A5 

Sakamoto, U.S. Geological Survey, with the exception 

of those housed in the National Museum of Natural 

History, which were photographed by Robert H. 

McKinney. Owing to the fact that the specimens 

photographed by Sakamoto were borrowed from other 

institutions, he did not use his usual technique of 

opaquing specimens for photography (Sakamoto, 

1973). Photographs of a few specimens were furnished 

by other individuals or institutions; credit is given 

them on the plate explanations. The holotype of each 

Tertiary species is figured if the type is extant. Some 

Holocene type specimens retained in museums outside 

the United States have not been figured; specimens 

considered to be of the same species by authors such 

as Keen (1971) or Hertlein and Grant (1972), or 

Holocene specimens from the type locality, are used 

for these illustrations, and this information is included in the plate explanation. A few substitutions are 

made for missing Tertiary types, as noted in the 

plate explanations along with their source. 

ACKNOWLEDGMENTS 

Warren 0. Addicott, U.S. Geological Survey, originally suggested this project, and since its inception 

has given me his wholehearted support, as has Louie 

Marincovich, also of the U.S. Geological Survey. 

They both also reviewed the manuscript, and their 

pertinent suggestions were most helpful. 

A. Myra Keen, Stanford University, made available 

the files of the late Prof. Hubert G. Schenck, which 

contain many original descriptions of species and 

copies of original photographs. Professor Keen also 

gave generously of her time with many problems, in 

addition to reviewing the manuscript, and I owe her a 

debt of gratitude. 

John G. Vedder, U.S. Geological Survey, assisted 

in pointing out pertinent references that included 

faunal lists and kindly checked all the sections on 

occurrence of species. Wendell P. Woodring, National 

Museum of Natural History, counseled me on the 

format to be used; his suggestions were most helpful. 

Vida C. Kenk, San Jose State University, assisted 

me with generic and subgeneric allocation of the 

Mytilidae, and I am indebted to her for her advice. 

Takeo Susuki, University of California at Los 

Angeles, gave his faunal list from the Topanga 

Canyon Formation, Barry Roth, California Academy 

of Sciences, his faunal lists from the Wildcat Group, 

and William J. Zinsmeister, Ohio State University, 

his faunal list from the Paleocene of Simi Hills, Calif. 

I am indebted to them for letting me use their unpublished data. 

The following individuals made available or loaned 

type material or made arrangements for photography; 

Barbara A. Bedette, U.S. Geological Survey; Frederick 

J. Collier, National Museum of Natural History; 

William C. Cummings, San Diego Natural History 

Musuem; Victoria Kohler, Harvard Museum of Comparative Zoology; Jack D. Mount, University of California at Riverside; Katherine V. W. Palmer, Paleontological Research Institute. Ithaca, New York; Joseph 

E. Peck, University of California at Berkeley; Joseph 

Rosewater, National Museum of Nat ural History; 

Barry Roth, California Academy of Sciences; LouElla 

Saul, University of California at Los Angeles; Elizabeth V. Scott, Academy of Natural Sciences of 

Philadelphia; Judith T. Smith, Palo Alto, Calif.; T. A. 

Demere and J. W. Tobiska, San Diego Natural History 

Museum; and Edward C. Wilson, Los Angeles 

Museum of Natural History. 

Mildred P. James made up cards for each species 

and its occurrences as noted on faunal lists. This was 

a time-consuming task, and I thank her for her 

patience and support. 

ABBREVIATIONS 

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

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

CAS: California Academy of Sciences, San Francisco, 

Calif. 

LAM: Los Angeles Museum of Natural History, Los 

Angeles, Calif. 

MCZ: Harvard Museum of Comparative Zoology, 

Cambridge, Mass. 

SDNM: San Diego Museum of Natural History, San 

Diego, Calif. 

CAS/SU: Stanford University, Stanford, Calif. (The 

Stanford University collections are now housed at 

the California Academy of Sciences.) 

CIT: California Institute of Technology, Pasadena, 

Calif. (The California Institute of Technology type 

collections are now housed at the Los Angeles 

Museum of Natural History.) 

SU: Stanford University, Stanford, Calif. 

UC: University of California, (Berkeley) 

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

UCR: University of California at Riverside. 

USCB: University of California at Santa Barbara. 

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

Cenozoic locality register. 

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

Cenozoic locality register. 

USNM: National Museum of Natural History, 

Washington, D. C. 

UW: University of Washington, Seattle, Wash. 
A6 PALEONTOLOGY OF CALIFORNIA AND BAJA CALIFORNIA 

SYSTEMATICS: PELECYPODS 

Family NUCULIDAE Gray 

Ovate; beaks opisthogyrate; internal ligament in a resilifer; 

inner shell material nacreous. 

Habitat.-Cold-water forms in general, mostly offshore; tropical 

species apt to occur in very deep bathyal water; burrows superficially, living just beneath the sediment surface; moves slowly 

and sporadically. · 

Genus NUCULA Lamarck, 1799 

Subgenus NUCULA s.s. 

Inner margin of shell with small denticles. 

Geologic range.-Cretaceous through Holocene (table 1). 

Habitat.-Greatest number of species in temperate and boreal 

regions, intertidally (Marincovich, 1973, p. 7) to more than 3,660 m. 

Nucula (Nucula) capayensis Schenck 

Plate 1, figures 1, 2 

Nucula (Nucula) capayensis Schenck, 1939, p. 34-35, pl. 6, figs. 

16-18, 20. 

Original description.-"Shelllarge for subgenus; dorsal margin 

gently convex; anterior extremity bluntly pointed dorsal to the 

convex ventral margin; posterior side truncate, but slightly inclined, 

giving a weak rostrate appearance to shell; numerous radial ribs 

up to about 560 microns in width, separated by narrow interspaces; 

inner ventral margin crenulate; chondrophore oblique, about 12 

posterior, 26 anterior teeth; escutcheonal area set off by low sunken 

area; beaks opisthogyrate; length (dorsal margin horizontal), 32 

mm, height, 22.5 mm, semithickness, 6.8 mm, umbonal angle, 

115°." 

Holotype.-UCMP 30196. 

Type locality.-UC A-1319. Yolo County, Calif. Capay Formation, Eocene. 

Comparisons.-This, species has the general profile and sculpture 

of the smaller Nucula cooperi Dickerson, but the flat radial ribs of 

N. cooperi are much narrower, about 130 microns in width, and are 

separated by narrow interspaces. The largest reported specimen of 

N. cooperi is only 12.0 mm in length and even that individual may 

be immature. (Schenck, 1939, p. 35) 

Comments.-Concentric ridges are fairly prominent near the 

anterior margin on the holotype; the radial ribs are barely perceptible near the ventral margin. 

Geographic range.-Northern California. 

Geologic range.-Eocene. 

Occurrence in California.-Capay Formation. 

N ucula (N ucula) coo peri Dickerson 

Plate 1, figures 3, 4 

Nucula cooperi Dickerson, 1913, p. 290, pl. 14, figs. 2a, 2b. Vokes, 

1939, p. 40, pl. 1, figs. 1, 2. 

Original description.-"Shell small, rounded triangular; small 

rather prominent beaks located about a third of the length from 

the anterior end and inclined forward. Cardinal margin nearly 

straight, sloping rapidly to the posterior margin; anterior end 

truncated, excavated under the beaks, slightly concave and united 

with the basal margin by a sharp angle; basal margin evenly 

rounded; posterior end narrowly rounded. Surface marked by 

many minute lines of growth and by small radiating ribs. Hinge 

robust, pit, very small." 

Lectotype.-UCMP 11754a, herewith designated. Two specimens 

are in the type collection. The largest fits the dimensions of the 

specimen figured by Dickerson, although the valve has a large 

borehole not shown; this specimen is the lectotype. 

Type locality.-UC 1853. Sutter County, Calif. Capay Formation, 

Eocene. 

Supplementary description.-"The hinge of the left valve has 9 

or 10 teeth in the posterior row and 16 or 17 in the anterior row, the 

rows being separated by a ligamenta} pit which is small, elongatetrigonal and directed anteriorly. The first tooth of the posterior row 

is large and trigonal in shape; the other teeth are straight. The 

inner margins of the valve are crenulate, and the muscle scars 

moderately large and rather deeply set; the pallial line is entire." 

(Vokes, 1939, p. 40) 

TABLE I.-Geologic and geographic distribution of the family Nuculidae in the eastern Pacific region 

[H =Holocene; Pie= Pleistocene; PI= Pliocene; M =Miocene; 0 =Oligocene; E =Eocene; Pa =Paleocene) 

Alaska British Washington Oregon California Baja Species Columbia California 

Genus Nucula: 

Subgenus Nucula: 

capayensis Schenck ........................... . cooperi Dickerson. . .. uitis Anderson and Hanna . Subgenus Leionucula: 

balboana Hertlein and Grant birchi Keen .................... . postangulata Clark .... . Subgenus Lamellinucula: 

exigua Sowerby ... Genus Nucula?: 

bifida Clark .............. . Genus Acila: 

Subgenus Acila: 

gettysburgensis (Reagan) . . ..... 0 and M 0 and M 

semirostrata (Grant and Gale) 

Subgenus Truncacila: castrensis (Hinds) ....... .................................... H H conradi (Meek) ........................ M' dalli (Arnold) ........................ . .............................. . decisa (Conrad).. ....................... E1 

deci~a, u~naHmed form, Vokes .. ................................... Pi·;··· 

emptrensts owe ........................ . 

;h'::::u~;.~rro~Hi ...................... ·· ········· ······a··· 

'Scott McCoy, written commun., 1978 

E?to M 

H 

M . ......... E 

PI 

0 

Oand 

M 

H 

M 

E 

Northern Middle Southern Norte Sur 

E ............... . Pa and E Pa and E E 

M? 

E 

PI 

M 

....... PI and Pie 

M? 

a~?j~ ............ M and PI M to Pie 

PI to H M to H M E and 0 Pa Pa and E 

MtoH M 

0 

E 

H 

H 

.................... Pa and E E M PI and Pie ............... . ................ M? 0 

0 E and 0 E and 0 E and 0 

Central and/or 

South 

America 

H 
TERTIARY MARINE PELECYPODS: NUCULIDAE THROUGH MALLEIDAE A7 

Comparisons.-Nucula cooperi closely resembles Nucula solitaria 

Gabb of the Cretaceous Chico Group, but is readily distinguished 

from it by radiating ribs (Dickerson, 1g13). N. cooperi has the 

general profile and sculpture of the larger Nucula capayensis but 

has radial ribs that are much narrower (Schenck, 1g3g, p. 35). N. 

cooperi is smaller than Nucula vitis and has broader radial 

threads (Anderson and Hanna, 1g25, p. 176). 

Geographic range.-Northern and middle California. 

Geologic range.-Paleocene and.Eocene. 

Occurrence in Cali{ornia.-Paleocene: Marysville (Keen and 

Bentson, 1g44) and Meganos (Clark, 1g21) Formations; Paleocene 

and Eocene: Cerros Shale Member, Lodo Formation (Keen and 

Bentson, 1g44); Eocene: Avenal Sandstone, Capay (Merriam and 

Turner, 1g37), and Domengine (Vokes, 1g3g) Formations. 

Nucula (Nucula) vitis Anderson and Hanna 

Plate 1, figure 5 

"Nucula cooperi Dickerson" of Dickerson, 1g15, p. 42. Not Nucula 

cooperi Dickerson, 1g13, p. 2go, pl. 14, figs. 2a, 2b. 

Nucula vitis Anderson and Hanna, 1g25, p. 175, pl. 2, fig. 14, text 

fig. 8. 

Original description.-"Shell trigonal in outline, rounded below; 

beaks full, turned gently backward; anterior slope convex, joining 

the basal margin with rounded angle; posterior slope flattened, 

almost straight, joining basal margin with abrupt angle of a little 

more than goo, sculptured only with rather coarse lines of growth; 

remainder of surface marked by distinct lines of growth and 

numerous radiating threads which are very narrow, only about 

one-third as wide as the flat-bottomed grooves; boundary of posterior slope carinated, slightly convex when viewed horizontally; 

length 8.2 mm; height 6.g mm." (Anderson and Hanna, 1g25) 

Holotype.-CAS 788. 

Type locality.-CAS 245. Kern County, Calif. Tejon Formation, 

Eocene. 

Comments.-In the original description, anterior and posterior 

are reversed. 

Comparisons.-"The Tejon species is larger than N. cooperi 

Dickerson, in which the posterior slope is not convex; radial 

threads are broader in the last and are separated by narrow 

grooves as shown somewhat diagrammatically•••. 

• 2 a a 

a a 

(a) Diagrammatic cross section of Nucula vitis near center of 

marginal area, showing sculpture; (b) Nucula cooperi. In Nucula 

vitis the posterior and anterior slopes meet at the beak in an angle 

of goo, whereas inN. cooperi the angle is 110°. All references toN. 

cooperi in the Type Tejon locality appear to have been based upon 

mistaken identity." (Anderson and Hanna, 1g25, p. 176) 

Geographic range.-Southern California. 

Geologic range.-Eocene. 

Occurrence in California.-Type Tejon Formation. 

Genus NUCULA? 

Nucula? bifida Clark 

Plate 1, figures 6, 7 

Nucula bi{ida Clark, 1g18, p. 122, pl. 12, figs. 10-12. 

Original description.-"Shellsmall, subtrigonal in outline; beaks 

inconspicuous, recurved. Anterior dorsal slope gently convex; posterior dorsal slope very steep; apical angle a little more than goo. 

Anterior end broadly and regularly rounded; ventral edge rather 

strongly and reg~larly arcuate. Surface of type sculptured by 22 

fairly heavy, rounded, radiating ribs, a few of which are bifid or 

split near their lower ends; interspaces between the radiating ribs 

about equal to the width of the ribs. Escutcheon only very slightly 

depressed, but marked off by oblique radiating ribs which branch 

off from the last rib of the general surface; some of these are bifid 

distally. Lunule not depressed but marked by a sculpturing similar 

to that of the escutcheon. Hinge plate unknown. Length, 6 mm.; 

height, 4.5 mm.; greatest diameter of both valves, 3 mm." 

Holotype.-UCMP 11184. 

Type locality.-UC 331. Contra Costa County, Calif. San Ramon 

Sandstone, Miocene(?). 

Comparisons.-"This beautiful species appears to be quite 

unique; the writer found nothing on the West Coast, either fossil or 

recent, with which to compare it. Though the hinge plate is not 

known, yet the general outline and sculpturing of the shell would 

seem to place it under the genus Nucula." (Clark, 1g18, p. 122) 

Comments.-If this species is indeed a Nucula, it probably can 

be assigned to Nucula s.s., as it has radial ribs and therefore 

presumably has a crenulate inner margin. The shell is nuculid in 

outline, but the radial ribs are very heavy for a nuculid; a few are 

dichotomous on both valves near the ventral margin. 

Geographic range.-Middle California. 

Geologic range.-Miocene(?). 

Occurrence in Cali{ornia.-Miocene(?). San Ramon Sandstone 

(Keen and Bentson, 1g44). 

Subgenus LEIONUCULA Quenstedt, 1930 

Inner margin of shell smooth. 

Geologic range. -Cretaceous through Holocene (table 1). 

Habitat.-15 to 2,275 m. 

Nucula (Leionucula) birchi Keen 

Plate 1, figures 8, g 

Nucula (Ennucula) birchi Schenck and Keen, 1g40, p. 10, pl. 4, figs. 

6, 7 [nomen nudum]. 

Nucula (Ennucula).birchi Keen, 1g43, p. 41, pl. 3, figs. g-12 . 

Original description.-"Shell small, solid, ovate, beaks low, 

opisthogyrate; lunule and escutcheon not marked; sculpture of 

incremental lines only; posterior end truncate, anterior produced 

and rounded, base arched; interior nacreous, adductor and auxiliary muscular impressions present, faint, basal margin smooth; 

hinge strong, chondrophore oblique, anterior teeth 15, posterior 6." 

(Keen, 1g43) 

Holotype.-CASISU 7527. 

Type locality.-SU 2121. Kern County, Calif. Lowermost part of 

Round Mountain Silt, Miocene. 

Comparisons.-From Nucula nuculana (Dall) of the Astoria 

Formation, Washington and Oregon (Moore, 1g63, p. 52-53), the 

only other described West American Miocene Nucula, Keen (1g43, 

p. 4) distinguishes this species by its smaller diameter, its more 

ovate outline, and its lack of impressed escutcheon. She adds that 

Nucula postangulata Clark is less attenuated anteriorly and has 

an impressed escutcheon, according to the original description. 

Comments.-Nucula postangulata is similar toN. birchi Keen 

but is slightly flattened along the shell edge just below the anterior 

dorsal margin, is slightly less produced, and is more evenly 

rounded near the posterior ventral margin than N. birchi. 
AB PALEONTOLOGY OF CALIFORNIA AND BAJA CALIFORNIA 

Geographic range.-Southern California. 

Geologic range. -Miocene. 

Occurrence in California.-Upper part ofthe Olcese Sand (Addicott, 1956) and lowermost part of the Round Mountain Silt. 

Nucula (Leionucula) postangulata Clark 

Plate 1, figure 12 

Nucula postangulata Clark, 1918, p. 122, pl. 13, figs. 2-5. 

Original description.-"Shell small, equivalved, inequilateral; 

subtrigonal to subovate in outline; beaks rather inconspicuous, 

opisthogyrous. Posterior dorsal slope abrupt, being a little more 

than at right angles to the anterior dorsal slope. Anterior end 

regularly rounded; posterior end subangulate. Escutcheon depressed 

and well-defined, lanceolate to subcordate, extending nearly to the 

posterior end, pouting rather sharply along its entire length. 

Lunule absent. Surface smooth except for fine, somewhat irregular 

incremental lines. Hinge plate unknown. Type 6.25 mm long; 4.75 

mm high." 

Holotype.-UCMP 11260. 

Type locality.-UC 2754. Contra Costa County, Calif. San 

Ramon Sandstone, Miocene(?). 

Comparisons.-See Nucula (Leionucula) birchi. 

Geographic range.-Middle California. 

Geologic range.-Miocene(?). 

Occurrence in California.-San Ramon Sandstone. 

Nucula (Leionucula) balboana Hertlein and Grant 

Plate 1, figure 10 

Nucula (Ennucula) balboana Hertlein and Grant, 1972, p. 145-146, 

pl. 27, figs. 1-4. 

Original description.-"Shell ovately triangular, smooth, beaks 

opisthogyrate, placed near posterior end, a lanceolate depressed 

area beneath them; the posterior margins of the valves slightly 

projecting; a narrow area along the anterior dorsal margin slightly 

depressed; anterior margin broadly rounded, the anterior end 

elliptically rounded, the posterior end slightly round and abruptly 

truncated; surface of valves with fine concentric lines of growth, 

toward the anterior margin with occasional minute constrictions; 

inner margin of shell smooth and devoid of denticles. Portions of 

two paratypes reveal the presence of about 18 teeth in the anterior 

series and about 8 or 9 in the posterior series. The chondrophore 

projects obliquely anteriorly. Dimensions of holotype: length, 13.4 

mm; height 10.7 mm; convexity (both valves together slightly 

gaping due to enclosed sediment), 7.2 mm." 

Holotype.-CAS 59684. 

Type locality.-CAS 12099, San Diego County, Calif. San Diego 

Formation, Pliocene. 

Comparison.-This species closely resembles the living species 

Nucula (Leionucula) quirica Dall but differs in that the shell is 

relatively more elongate and the anterior margin correspondingly 

less broadly rounded, and so far as known, there is no trace of fine 

radial striae on the interior of the valves. (Hertlein and Grant, 

1972, p. 145-146) 

Geographic range.-Southern California. 

Geologic range.-Pliocene. 

Occurrence in California.-Niguel (J. G. Vedder, written 

commun., 1978) and San Diego Formations. 

Subgenus LAMELLINUCULA Schenck, 1944 

Inner margin with small denticles; strong incised concentric 

sculpture; weak radial ribs. 

Geographic range.-Europe, North America, South America, 

and Africa. 

Geologic range.-Eocene through Holocene (table 1). 

Habitat.-5 to 220m, possibly deeper. 

Nucula (Lamellinucula) exigua Sowerby 

Plate 1, figure 13 

Nucula exigua Sowerby, 1833, p. 198. 

Nucula (Nucula) exigua Sowerby. Schenck, 1939, p. 36, pl. 6, figs. 

1-8, 11. 

Nucula (Nucula) exigua Sowerby. Hertlein and Grant. 1972, 

p. 146-147, pl. 27, figs. 5, 6. 

Original description.-"Nuc. testa parva, oblique ovata, albicante, pellucida, concentrice sulcata; latere postico longiore·, subacuminato, antico brevissimo: long. 0.2, lat. 0.1, alt. 0.15 poll." 

Holotype.-BM(NH). 

Type locality.-Bay of Caracas, probably the island of Curacao, 

west Colombia, South America (Schenck, 1939, p. 36). Holocene. 

Supplementary description.-"This small trigonal species has 

strong, uniform concentric sculpture***" (Grant and Gale, 1931, 

p. 111). 

"One left valve and two imperfect right valves*** retain traces of 

radial striae, crossing the stronger ribbing, over most of the 

surface of the valves. This feature, however, varies in a series of 

Recent specimens of this species as does the amount of escutcheonal projection." (Hertlein and Grant, 1972, p. 146) 

Comparisons.-Nucula suprastriata Carpenter in Arnold (1903, 

p. 96, pl. 18, fig. 6), a similar species or subspecies, is said to differ 

from N. exigua by having a more impressed lunule and escutcheon 

and by radial sculpture that usually is present only near the base 

of the valves. (Hertlein and Grant, 1972) 

Geographic range.-Living: Bahia T6rtolo, Baja California Sur, 

to the Golfo de California, and south to Ecuador; fossil: southern 

California. 

Geologic range.-Pliocene through Holocene. 

Occurrence in California.-Pliocene: San Diego Formation 

(Hertlein and Grant, 1972); Pliocene and Pleistocene: Fernando(?) 

Formation (Kennedy, 1975); Pleistocene: unnamed strata in 

southern California (Kanakoff and Emerson, 1959). 

Habitat.-16 to 1,895 m (Hertlein and Grant, 1972, p. 146). 

Genus ACILA Adams and Adams, 1858 

Shells with chevronlike sculpture. 

Habitat.-Marine, does not occur in estuaries. Below intertidal 

zone to 1,465 m, usually at depths less than 915 m. Most abundant 

in cool and cold water with greatest diversity in temperate water 

between 4° and 20°C; in deep water, only south of the equator. 

Prefers mud or fine sand bottom; fossils abundant in siltstone, 

shale, and fine-grained sandstone. (Schenck, 1936, p. 9, 31-33) 

Subgenus ACILA Adams and Adams 

Shell with rostral sinus from umbo to ventral margin; usually 

one or more bifurcations of radial ribs in addition to primary one. 

Geographic range.-Living off Hokkaido, Japan, to the Bay of 

Bengal and Arabian Sea. 

Geologic range.-Eocene(?); Oligocene through Holocene (table 

1). 
TERTIARY MARINE PELECYPODS: NUCULIDAE THROUGH MALLEIDAE A9 

Acilia (Acilia) gettysburgenis (Reagan) 

Plate 1, figure 11 

Nucula (Acila) gettysburgensis Reagan, 1909, p. 171, 175, 177, pl. 1, 

fig. 3. Clark, 1932, p. 804, pl. 14, fig. 12. 

Nucula (Acila) gettysburgensis alaskensis Clark, 1932, p. 804-805, 

pl. 14, fig. 15. 

Acila (Acila) gettysburgensis (Reagan). Schenck, 1936, p. 78-81, pl. 

12, figs. 1-15; pl. 13, fig. 7; text fig. 8; not figs. 4, 7. Addicott, 

Kanno, Sakamoto, and Miller, 1971, p. C20, fig. 3, g, k, m. 

Addicott, 1976b, p. 121-123, 3 figs. 

Original description.-"""""'Shell trigonal, convex, medium thickness; umbones considerably posterior to center, turned posteriorly, 

posterior end 16, anterior extremity 24.5 from umbones; posterior 

end short, truncated, concave back of umbones; anterior end 

rounded to arcuate, forming an acute angle with the anterior 

extremity; ventral and cardinal margins subparallel; lunule area 

large, slightly scooped out, sculptured same as rest of shell; a low 

ridge fronts each valve back of the lunule area, back of which there 

is a wide, flat, curved sinus extending from the umbo to the ventral 

margin, widening as it approaches that margin; surface divaricately sculptured, also ornamented with about seven concentric 

low ridges; inside of shell not seen. Dimensions: Lat, 28, alt, 19.5." 

Holotype.-USNM 328302. 

Type locality.-Clallam County, Wash., in sea cliffs near Gettysburg. Twin River Formation, Eocene to Miocene. 

Supplementary description.-Shells smaller than 6 mm in 

length, truncate, primary bifurcation only, radial ribs about 200 

microns wide, no rostral sinus. Shells 10 mm long have a welldeveloped sinus and show four or more concentric lines of growth. 

Shells 10-15 mm long are rostrate; secondary bifurcation sometimes present, radial ribs about 250 microns wide. Shells 15-20 mm 

long have distinct rostral sinus; secondary bifurcation present on 

some specimens. Specimens 25-30 mm long with rostral sinus, 11 

or more well-defined concentric lines of growth; secondary bifurcation in area posterior to sinus generally present, on several a 

double bifurcation along line of primary bifurcation; radial ribs 

about 300 microns wide, interspaces narrower. Specimens between 

30-36 mm long (the maximum length) may be gerontic individuals; 

14 well-defined concentric lines of growth, narrow area of obsolete 

radial ribbing rarely present; secondary bifurcation posterior to 

sinus such that the trough ofthe sinus is the "V" of the bifurcating 

lines; radial ribs to 460 mincrons wide, separated by narrower interspaces.(Schenck, 1936,p. 79) 

Comparisons.-Acila gettysburgensis typically has a stronger 

posterior sulcation, a larger apical angle, and a more prominent 

pout on the posterior area than A. semirostrata, a Pliocene species 

and the only other species in the eastern North Pacific Tertiary 

assigned to the subgenus Acila. (Grant and Gale, 1931, p. 115) 

Geographic range.-Gulf of Alaska to San Francisco Bay area, 

California; possibly also in Japan, Kamchatka, and Sakhalin in 

the western north Pacific (Kristofovich, 1964). 

Geologic range.-Eocene(?); Oligocene to Miocene(?) (Addicott, 

1976b, p. 123). Peak abundance during Zemorrian Age. 

Occurence in California.-Eocene and Oligocene: San Lorenzo 

Formation (Clark, 1918); Oligocene: Concord Formation of Clark 

(1918), Kirker Tuff; Miocene(?): San Ramon Sandstone. 

Acila (Acila) semirostrata (Grant and·Gale) 

Plate 1, figures 23, 25 

Nucula (Acila) semirostrata Grant and Gale, 1931, p. 113-115, 

text figs 2a, 2b, 3a, 3b. 

Acila (Acila) semirostrata (Grant and Gale). Schenck, 1936, p. 94 

pl. 13, figs. 2, 8, 10, text fig. 8. 

Acila (Acila)gettysburgensis (Reagan). Schenck, 1936, p. 78-81, pl. 

13, figs. 4, 9; not fig. 7. Not Nucula (Acila) gettysburgensis 

Reagan, 1909. 

Original description.-"Shell relatively large, abruptly truncated 

posteriorly; ventral and dorsal margins broadly curved, anterior 

margin strongly curved, the ventral margin slightly and broadly 

insinuated about three millimeters from the abruptly curved posterior ventral end of the shell; posterior area rather broad, slightly 

concave and very little flared or pouted where the two valves meet; 

umbonal angle about 88 or 90 degrees; valves sculptured with 

numerous raised radial riblets which divaricate along an axis 

somewhat anterior to the lateral medial line of the valves; hinge 

with about 19 anterior and about 10 posterior teeth, those near the 

umbo closely appressed, the two series slightly separated by a 

small resilial pit; adductor scars prominent, variable in shape." 

Holotype.-SDNM 370. 

Type locality.-SDNM 442. Boundary line between Los Angeles 

and Ventura Counties, Calif. Pico(?) Formation, Pliocene. 

Supplementary description.-Height is 80 percent or more of 

length (Schenck, 1935, p. 4). Rostral sinus weakly developed; about 

15 concentric growth lines; primary bifurcation appears before 

3-mm stage; secondary bifurcation especially noticeable on disk 

posterior to sinus; radial ribs separated by equal interspaces; 

escutcheonal area ofholotype (a worn right valve) shows indistinctly on an area not crossed by radial ribs; area of obsolete radial ribs 

conspicuous. Largest right valve measures: length, 30.3 mm; height, 

23.7 mm; semithickness, 9.6 mm; unbonal angle, 88°; number of 

anterior teeth about 19, posterior teeth about 10 (hinge worn). 

(Schenck, 1936,p.94) 

"A moderately large, shortAcila. Posterior end truncated, slightly prolonged at the ventral margin. Posterior sinus moderately 

strong. The apex ofthe main chevron extends downward in an arc 

from the umbo. An inverted chevron lies in the posterior sinus, and 

a minor chevron on the rostrum back ofthe sinus""""'· The inverted 

chevron in the sinus and the minor chevron behind it are not 

mentioned in the original description and do not show on the 

figure"'"""(Woodring, 1938, p. 28) 

Comparisons.-Acila gettysburgensis typically has a stronger 

posterior sulcation, a larger apical angle, and a more prominent 

pout on the posterior area than A. semirostrata (Grant and Gale, 

1931, p. 115). The similarity of these two species, though, has led to 

misidentification. (Addicott, 1976b) 

"The Recent Japanese A. mirabilis (Adams and Reeve) has an 

inverted chevron and minor chevron, but large specimens have a 

double or multiple main chevron. This species also is larger, more 

elongate, and more strongly rostrate than semirostrata." 

(Woodring, 1938, p. 28) 

Geographic range.-Middle and southern California. 

Geologic range.-Miocene to Pleistocene. 

Occurrence in California.-Miocene: Santa Cruz Mudstone; Miocene and Pliocene: Capistrano Formation (Vedder, 1974); Pliocene: 

Pico(?)Formation; Pliocene and Pleistocene: Fernando Formation 

(Vedder, 1972). 

Subgenus TRUNCACILA Schenck, 1931 

Lacking the well-defined rostral sinus that characterizes Acila 

s.s.; one or more bifurcations of the radial ribs. 

Geographic range.-Living from east Africa to the Bay of 

Bengal, the Philippine Islands, and Japan, and along the west 

coast of North America from Alaska to San Diego. 

Geologic range.-Cretaceous through Holocene (Table 1). 

Habitat.-Prefers a cool temperate habitat and depths of 10-915 

m (Schenck, 1936, p. 9, 33-35). 
AlO PALEONTOLOGY OF CALIFORNIA AND BAJA CALIFORNIA 

Aeila (Truncacila) decisa (Conrad) 

Pl~te 1, figure 14 

Nucuia decisa Conrad, 1855, p. 11, 12; 1856, p. 322, pl. 3, fig. 19 Not 

Nucula decisa Dall, 1898, p. 573. 

Acila (Truncacila) decisa (Conrad). Schenck, 1936, p. 53-56, pl. 3, 

figs. 1-9, 11-.15; pl. 4, figs. 1, 2; text figure 7 (22, 23, 25). ·, 

Acila gabbiana Dickerson, 1916, p. 481, pl. 36, fig. 1. 

Nucula (Acila) stillwaterensis Weaver and Palmer, 1922, p. 6, pl. 8, 

fig. 8. 

Acila lajollaensis M.A. Hanna, 1927, p. 270, pl. 25, figs. 1, 3, 5, 7, 8, 

12, 15. 

Original descriptions.-"Suboval or subrhomboidal, posterior 

'margin obliquely truncated; disk with divaricating striae." (decissa) 

. "Shell small, oval with straight anterior dorsal margin which 

slopes steeply to a sharp angle***broadly rounded ventral margin; 

posterior dorsal margin gently convex; posterior end, narrowly 

rounded; decoration consisting of delicate divaricate sculpture 

crossed by incremental lines; lunule fairly definite; escutcheon 

long and narrow." (gabbiana) 

"Left valve: Shell of medium size, of moderate thickness, well 

inflated; beak nearly posterior; dorsal margin only slightly rounded; 

posterior slightly concave in outline except for a central convexity 

due to a ridge in the escutcheon; ventral straight near the posterior 

but rounded anteriorly; anterior rather sharply rounded to the 

dorsal and ventral margins; surface divaricately sculptured by 

prominent, elevated, rounded ribs which are separated by deep, 

round-bottomed interspaces of about the same width as the ribs; 

the shell is divided into nearly equal parts by this sculpturing; 

surface concentrically sculptured by growth lines which are most 

prominent in the interspaces, giving the interspaces a pitted 

appearance, a few growth lines are prominent over the whole 

surface; escutcheon large, sculpturing similar to the remainder of 

the shell except for more numerous ribs; a large prominent ridge 

runs through the center of the escutcheon causing a concavity on 

either side due to the inflation of the ridge; lunule not distinct 

except for change in direction of the ribbing, and a flattening ofthe 

surface; inner surface of the type not seen. 

"Inner margin of paratype no. 31134 crenulate; muscle scars 

very unequal in size, the posterior the larger; hinge plate not wide; 

anterior surface bears about twenty large teeth which decrease in 

size toward the beak; posterior surface bears about ten large teeth, 

also decreasing in size toward the beak; pit under the beak 

elongate anteriorward. Dimensions: Altitude 8 mm., length 11 

mm." (lajollaensis) 

Neotype.-UCMP 31132, designated by Schenck (1936, p. 55), 

formerly the holotype of Acila lajollaensis Hanna. (The holotype of 

Nucula decisa Conrad is lost fide Dall, 1909.) 

Type locality.-Five km north of La Jolla, San Diego County, 

Calif. Ardath Shale, Eocene. 

Supplementary description.-"Shell small, ovate-quadrangular, 

compressed; anterior dorsal margin straight; anterior extremity 

broadly rounded; ventral margin ~convex, not parallel to dorsal 

margin; posterior margin straight, giving truncate profile to shell; 

umbones inconspicuous; radial ribs 100± microns wide, separated 

by equal interspaces; no secondary bifurcation; concentric lines 

present, not conspicuous; no area of obsolete radial ribbing; interior 

nacreous, smooth; pallial line entire; teeth not available; no rostral 

sinus. Length up to 8 millimeters; height up to 6.8 millimeters; 

semithickness, 2.2 millimeters; umbonal angle, estimated, 98 

degrees; angle of bifurcation, estimated, 65 degrees." (Schenck, 

1936, p. 56) 

Comments.-Concentric ridges are fairly prominent on part of 

the shell of the neotype. These ridges produce slight irregularities 

on the radial ribs. 

Geographic range.-Kamchatka, Alaska to southern California. 

Geologic range.-Paleocene and Eocene. In California, from the 

late Paleocene Meganos Stage to the late Eocene Turritella schencki 

delaquerrae Zone of Kleinpell and Weaver (Givens, 1974, p. 38). 

Occurrence in California.-Paleoc~ne: Martinez Formation (Weaver, 1949), Marysville Formation of Schenck (1936), Paleocene and 

Eocene: Santa Susana Formation (W. J. Zinsmeister, written 

Commun., 1978); Meganos Formation (Schenck, 1936), and Cerros 

Shale Member of Lodo Formation (Keen and Bentson, 1944); 

Eocene: Ardath Shale (M. A. Hanna, 1927), Avenal Sandstone 

(Stewart, 1946), Capay Formation (Merriam and Turner, 1937), 

Coldwater Sandstone, Domengine Formation (Schenck, 1936), 

Juncal Formation (in Turritella uvasana infera and Turritella 

uvasana applinae faunas, Givens, 1974), lower part of Llajas 

Formation of Schenck (1936), Muir Sandstone (Weaver, 1953), 

Tejon Formation (Schenck, 1936), and unnamed strata, San Nicolas 

Island (Vedder and Norris, 1963). 

Acila (Truncacila) decisa (Conrad), unnamed form 

Plate 1, figure 17 

Acila (Truncacila) decisa (Conrad), var. Vokes, 1939, New York 

Acad. Sci., v. 38, p. 41, pl. 1, figs. 7-8. 

Original description.-"Only four specimens referable to the 

genus Acila have been found in the collections from the Domengine 

[A venal] formation. They all differ from the typical Acila decisa 

(Conrad) in being more inflated and in possessing a shallow 

groove bounding the edge of the lunule. Similar forms occur in 

beds of contemporaneous age in the Eocene of Oregon." 

Figured specimen.-UCMP 15477. 

Locality.-UC A-1165. Kings County, Calif. Avenal Sandstone, 

Eocene. 

Comments.-The radial ribs on this form are separated by 

interspaces almost twice as wide as those on the neotype of Acila 

decisa and concentric ridges are not preserved. 

Geographic range.-Oregon to southern California. 

Geologic range.-Paleocene and Eocene. 

Occurrence in California.-Paleocene: Meganos Formation; 

Eocene; Avenal (Keen and Bentson, 1944) and Capay Formations, 

La Jolla Group, lower part of Llajas and Tejon Formations. 

Acila (Truncacila) shumardi (Dall) 

Plate 1, figures 15, 16 

Nucula (Acila) decisa Conrad. Dall, 1898, p. 573. Not Nucula 

decissa (Conrad), 1855. 

Nucula (Acila) shumardi Dall, 1909, p. 103. 

Acila (Truncacila) shumardi (Dall). Schenck, 1936, p. 64-67, pl. 4, 

figs. 5-7, 9; pl. 6, figs. 1-11, text fig. 7 (18). Moore, 1976, p. 

42-43, pl. 8, figs. 1-9, 11, 12, 14, 15, 18. 

Original description.-"***Conrad described from the Eocene 

(called by him Miocene) of San Diego Mission, California, a 

Nucula decisa which he figured (very badly) and afterwards united 

with his Miocene Astoria species. In this he was followed by Gabb 

and others. None of the figures or descriptions of this decisa are 

sufficient to identify the species. A fine large species from the 

Eocene of Pittsburg, Oreg., collected by Diller, was identified by me 

with decisa. This identification was made because of the Eocene 

age of both, there being usually only one species of Acila in a 

single horizon. However, inasmuch as Conrad's original type 

specimen seems lost, and his figure and description are worthless, 
TERTIARY MARINE PELECYPODS: NUCULIDAE THROUGH MALLEIDAE All 

it is probably best to apply a new name to the Oregonian Eocene 

species, which may be called Nucula (Acila) shumardi Dall." 

Holotype.-USNM 406405. 

Type locality.-USGS 2714. Columbia County, Oreg. Pittsburg 

Bluff Formation, Oligocene. 

Supplementary description.-"Acila shumardi is large to moderate in size (largest specimen: 30 mm long, 22 mm high, and 16 mm 

thick) and is sculptured with many narrow ribs separated by small 

spaces which on some specimens are barely discernible and could 

be described as incised lines. Secondary bifurcation ofthe ribs may 

be present at the ventral margin either in the midportion of the 

anterior half of the shell or along the anterior side of the primary 

bifurcation. On one specimen (USGS 18681) the ribs split near the 

dorsal margin on the anterior portions of both valves of an 

articulated specimen. Although areas of secondary bifurcation, if 

present, usually occur on the largest specimens, such bifurcation 

has also been seen on specimens of only small to moderate size. 

The beaks are located at the sharply truncated posterior margin. 

The hinges exposed on two left valves*"""show 7-10 posterior teeth 

and 16-22 anterior teeth. The hinges exposed on six right 

valves"""*show 7-11 posterior teeth and 17-20 anterior teeth. One 

specimen"""*, at the anterior end of the posterior series of teeth, 

shows a deep irregular socket with an irregular toothlike projection 

at the ventral anterior edge. The number of teeth varies with the 

size of the individual shell, and the larger specimens have more 

teeth than the smaller ones." (Moore, 1g76, p. 42-43) 

Geographic range.-Alaska to middle California. 

Geologic range.-Eocene and Oligocene. 

Occurrence in California.-Eocene and Oligocene: Kreyenhagen 

(Watkins, 1g74), San Emigdio (DeLise, 1g67), and San Lorenzo 

Formations (Clark, 1g18); Oligocene: Alegria Formation of Dibblee 

(1g50), Concord Formation of Clark (1g18), Kirker Tuff (Clark, 

1g18), Pleito Formation, and Tumey Formation of Atwill (1g35). 

Acila (Truncacila) dalli (Arnold) 

Plate 1, figure 18 

Nucula (Acila) dalli Arnold, 1g08, p. 364-365, pl. 33, fig. 15. 

Acila (Truncacila) dalli (Arnold). Schenck, 1g36, p. 67-73, pl. 5, figs. 

2, g, 13; pl. 14, figs. 4, 6, 7,; text fig. 8. 

Original description.-"Shell trigonal in outline, nearly as broad 

as long, large for a member of this genus, sometimes attaining a 

length of over 30 mm., rather compressed, strongly divaricately 

sculptured. Umbones prominent and turned backward, placed very 

near the posterior end, which is abruptly truncated and depressed, 

and forms a straight or slightly inwardly curved line from the 

umbones to the base, with which it makes a sharp angle of about 

goo; base rounded becoming more and more so toward the anterior 

extremity, which region exhibits the sharpest curvature of any of 

the anterior portion of the shell; anteriol' dorsal margin nearly 

straight for a considerable distance in front of the umbones; a faint 

carina extends from the umbo to the posterior ventral angle; 

surface sculptured by numerous rounded, raised, divaricating 

lines; margins crenulate. Hinge as in other members of this 

genus." 

Holotype.-USNM.165452. 

Type locality.-On the headwaters of south fork of Waddell 

Creek, Big Basin, Santa Cruz q~adrangle, Santa Cruz County, 

Calif. San Lorenzo Formation, Eocene and Oligocene. 

Supplementary description.-"quadrangular, compressed; anterior dorsal margin gently sloping to rounded anterior extremity; 

ventral margin convex; straight posterior margin gives truncate 

appearance to profile; radial ribs 350± microns wide, separated by 

equal interspaces 200± microns deep; escutcheonal area crossed by 

radial ribs; primary bifurcation distinct, sometimes somewhat 

anterior to middle of shell at ventral margin; concentric lines of 

growth clearly shown on some specimens; secondary bifurcation, 

when present, situated near middle of disk; area of obsolete radial 

ribbing rarely present, never conspicuous; weakly developed rostral 

sinus present, but not conspicuous***. An imperfect specimen***shows a nuculid hinge with 15± anterior teeth." (Schenck, 

1g36, p. 67). 

Comparisons.-Acila (Truncacila) dalli does not have the welldeveloped rostral sinus of A. (A) gettysburgensis, but the two 

species may be closely related and the postulation that A. dalli is 

ancestral to A. gettysburgensis may be a reasonable one. Acila 

dalli is also similar to A. (T.) nehalemensis Hanna but the shell of 

A. nehalemensis is more inflated than the compressed shell of A. 

dalli. (Schenck, 1g35, p. 5, 68) 

Geographic range.-Middle to southern California. 

Geologic range.-Eocene and Oligocene. 

Occurence in California.-Eocene and Oligocene: Rices Mudstone 

Member of San Lorenzo Formation (Brabb, 1g64); Oligocene: Pleito 

Formation. 

Acila (Truncacila) muta Clark 

Plate 1, figures 1g, 20 

Acila muta Clark, 1g18, p. 11g-120, pl. 13, figs. 6, 12, 13. 

Acila muta var. markleyensis Clark, 1g18, p. 121, pl. 13, fig. 3. 

Acila (Truncacila) muta B. L. Clark. Schenck, 1g36, p. 74, 75, pl. 8, 

figs. 4, 11; text fig. 7, nos. 20, 21. Addicott, 1g73, p. 22, pl. 1, figs. 

4-15. 

Original description.-"Shell subovate to subtrigonal, moderately 

convex; beaks strongly inturned; posterior end abruptly truncated, 

subangulate at point of junction between the posterior dorsal and 

the ventral edges. Anterior dorsal slope long and gently convex, 

posterior dorsal slope straight; apical angle about goo; anterior end 

evenly rounded; posterior ventral edge regularly arcuate. Lunule 

obsolete, escutcheon large, well-defined by a circumscribed line, 

pouting in the middle. Surface of shell covered by fine, divaricating 

threads which extend onto the escutcheon; the line at which the 

divaricating threads cross, is near the middle of the shell; on some 

of the larger specimens, a duplication of the divarication may be 

seen near the ventral edge. Seventeen or eighteen fairly prominent 

cardinals anterior, and about ten posterior to the beaks, resilium 

pit narrow and deep, rather long." 

Holotype.-UCMP 111g6. 

Type locality.-UCMP 1131. Contra Costa County, Calif. San 

Ramon Sandstone, Miocene(?). 

Supplementary description·.-:-"The radial ribs on the holotype 

(17.2 millimeters long) are 350± microns wide, separated by interspaces about half as wide. The smallest specimen (4.5 millimeters 

long) is ovate in profile; its broadly convex radial ribs are 220± 

mi('rons wide, interspaces less than half as wide. The specimens 

have no marked area of obsolete radial ribbing. There is no rostral 

sinus. The interior of the holotype is sufficiently free of matrix to 

disclose nuculid dentition." (Schenck, 1g36, p. 74) 

Comparison.-"As indicated by Schenck (1g36), the species that 

most closely resembles Acila muta is the middle Miocene A. 

conradi from the Temblor Formation ("Temblor Stage") of California and from the Astoria Formation of Oregon and Washington. 

Schenck differentiated these two species on the relatively greater 

thickness ofthe two valves of A. muta. They are differentiated here 

by the significantly smaller angle of bifurcation of A. muta evident 

from Clark's (1g18) and Schenck's (1g36) illustrated specimens. 

This difference is relfected by the fact that the primary line of 

bifurcation on specimens of A. conradi intersects the ventral 
A12 PALEONTOLOGY OF CALIFORNIA AND BAJA CALIFORNIA 

margin in a more anterior position than on specimens of A. muta." 

(Addicott, 1973, p. 22) 

Geographic range.-California. 

Geologic range.-Oligocene and Miocene(?). 

Occurrence in California.-Oligocene: Wygal Sandstone Member 

of Temblor Formation (Addicott, 1973); Miocene(?): San Ramon 

Sandstone. 

Acila (Truncacila) conradi (Meek) 

Plate 1, figures 21, 22 

Nucula divaricata Conrad, 1848, p. 432, figs. 1a, 1b, Not Nucula 

divaricata Hinds, 1843. 

Nucula (Acila) conradi Meek, 1864, p. 27, new name. 

Acila (Truncacila) conradi (Meek). Schenck, 1936, p. 82-85, pl. 8, 

figs. 1-3, 5-10, 12-14, text fig. 7. Moore, 1963, p. 54-55, pl. 12, 

figs. 2-4, 6-9. 

Original description.-"Subovate, convex, with divaricating 

striae, extremities rounded, ligament margin very oblique, slightly 

curved; basal margin curved; beaks near the anterior extremity." 

Neotype.-VSNM 3526. (Moore, 1963, p. 55) 

Type locality.-Astoria, Columbia County, Oreg. Astoria Formation, Miocene. 

Supplementary description.-"Shell lacking a rostral sinus or 

possessing only an incipient sinus; no area of obsolete radial 

ribbing or such an area only weakly developed; usually less than 

10 mm thick when more than 17 mm long." (Schenck, 1935, p. 4-5) 

"Radial ribs about 220-350 microns wide, separated by narrower 

interspaces; line of primary bifurcation anterior to center of shell 

at ventral margin; angle of bifurcation 50 to 72 degrees; secondary 

bifurcation common; no rostral sinus; no apparent area of obsolete 

ribbing; interior ventral margin not markedly crenulate." (Schenck, 

1936, p. 83) 

"Young specimens have bifurcated radial ribs which extend to 

the ventral margin, whereas on mature specimens these ribs may 

be obliterated by concentric lines. Fine concentric lines are numerous on the entire surface of the shell and form concentric ridges 

when they are crowded together at irregular intervals." (Moore, 

1963, p. 55) 

Comparisons.-Acila (Truncacila)conradi resembles A. (T.) muta 

but is differentiated by the significantly greater angle of the 

bifurcation. The primary line of bifurcation intersects the ventral 

margin in a more anterior position on A. conradi than on A. muta. 

(Addicott, 1973, p. 22) 

Geographic range.-Washington to southern California. 

Geologic range.-Miocene. Occurs in Washington with Vertipecten fucanus (Dall), which is re~tricted to the Pillarian Stage, 

Miocene (Addicott, 1976d, p. 99). Occurs in Oregon and California 

with Patinopecten propatulus (Conrad), which is restricted to the 

Newportian Stage, Miocene, in Oregon (Addicott, 1976d, p. 102). 

Occurs in Kern County with foraminiferal assemblages of early 

Saucesian age (Addicott, 1970, p. 27). 

Occurrence in California.-Cierbo Sandstone (Hall, 1960), 

Freeman Silt (Addicott, 1970), Neroly Sandstone (Hall, 1960), and 

upper part of the Temblor Formation (Stewart, 1946). 

Acila (Truncacila) empirensis Howe 

Plate 1, figure 26 

Acila empirensis Howe, 1922, p. 96, pl. 9, figs. 4, 5, 8. 

Acila (Truncacila) empirensis Howe. Schenck, 1936, p. 85-87, pl. 9, 

figs. 3, 4, 6-10, 12; text fig. 7. Weaver, 1942, p. 30-31, pl. 6, figs. 

6, 16, 17. 

Original description.-"Shell ovate, moderately convex, with 

fairly prominent adjacent beaks, lunule long, lanceolate, and 

separated from the rest of the shell by a distinct ridge, sculpture of 

lunule coarser than that of adjacent parts of shell; escutcheonal 

area not sharply defined, but separated from the rest ofthe shell by 

subangulation, on the anterior side of which, extending from the 

beaks to ventral margin, is a broad depression. Sculpture of 

escutcheon immediately below beaks tends to become obsolete; 

sculpture of escutcheon finer than rest of shell, and on some 

specimens tends to bifurcate. 

"Ventral margin regularly arcuate; posterior dorsal edge convex, 

anterior dorsal edge fairly long and nearly straight; anterior end 

obliquely subtruncate; sculptured with coarse radial ribs, the 

sculpture being coarser on the posterior than on the anterior half of 

shell. Incremental lines heavy and irregular; the line of bifurcation 

meets the ventral edge anterior to the middle of shell; extending 

from beaks to posterior end and between ventral angulation and 

escutcheon, parallel to same, is a broad shallow depression which 

is more marked in adult specimens. Hinge teeth inaccessible. 

Length, 16 mm.; alt., 12 mm.; diam., 9 mm." 

Holotype.-VCMP 30032. 

Type locality.-VC 3323. Coos County, Oreg. Coos Conglomerate 

member of Empire Formation, Miocene. 

Supplementary description.-Shelllarge for subgenus, truncatequadrate, inflated; anterior dorsal margin straight, but profile 

changes abruptly toward the bluntly rounded anterior extremity; 

ventral margin convex; posterior margin straight except for a 

pouting in escutcheonal region; inturned beaks closely appressed; 

primary bifurcation distinct in umbonal area; secondary bifurcation 

on all shells; radial ribs to about 500 microns wide, separated by 

equal interspaces; concentric lines to about 12; no rostral sinus; 

area of obsolete radial ribbing well developed, to 5 millimeters in 

width; escutcheonal area indistinctly defined, crossed by radial 

ribs; lunule sometimes defined by an abrupt termination of radial 

ribs, producing the appearance of a lanceolate depression; interior 

poorly preserved, one specimen about 24 anterior, about 12 posterior 

teeth; shell nacreous, ventral margin lacks marginal plications. 

(Schenck, 1936,p.86) 

Comparison.-"This species is differentiated from its nearest 

relative, Acila (Truncacila) conradi (Meek), by the area of obsolete 

radial ribbing, generally larger size, and greater degree of inflation." (Schenck, 1936, p. 86) 

Comments.-Faustman (1964) and Roth (1979) cite Acila 

castrensis, rather than A. empirensis, as occurring in the Wildcat 

Group. 

Geographic range.-Alaska; Washington to northern California. 

Geologic range.-Miocene to Pleistocene. 

Occurrence in California.-Pliocene and Pleistocene: Wildcat 

Group (Ogle, 1953). 

Acila (Truncacila) castrensis (Hinds) 

Plate 1, figure 24 

Nucula castrensis Hinds, 1843, p. 98 

Acila (Truncacila) castrensis (Hinds). Schenck; 1936, p. 96-99, pl. 

10, figs. 1-5, text fig. 7 (2-5). Hertlein and Grant, 1972, 

~ 147-14~pl.2~fig&7-1Q 

Original description.-"Nuc. testa elliptica, antice rotundata, 

epidermide olivacea induta; lineis divaricatis; marginibus ventralibus crenulatis; cardine antice dentibus 5, postice 11. Long 3; lat 

ll/2; alt. 2 lin." 

Holotype.-Location unknown; not in British Museum fide Keen 

(1966a, p. 267). 
TERTIARY MARINE PELECYPODS: NUCULIDAE THROUGH MALLEIDAE A13 

Type locality.-Sitka, Alaska. A single specimen was dredged in 

the harbor, from 13m, sand. (Hinds, 1843) 

Supplementary description.-"Adult shell of medium size for 

subgenus, ovate-trigonal, compressed; anterior dorsal margin convex, sloping away from beaks to sharply rounded anterior extremity; ventral margin convex; posterior margin nearly straight, giving 

shell the 'abruptly truncated' appearance that has struck the 

attention of most writers; immediately below beaks, escutcheonal 

area outlined by a slight groove extending from beaks; inside this 

groove, which is crossed by radial ribs, is a slight pouting, giving 

posterior margin a gently convex outward profile; no rostral sinus; 

when shells are 1 to 2 millimeters in height, smooth, but with 

growth undulations; at height of 6.0 millimeters radial ribs well 

developed; when shells 12.0 millimeters high, radial ribs tend to 

become obsolete distally and concentric lines are more crowded; 

larger specimens show at least 18 annular growth undulations, 

area of obsolete radial ribbing well developed; radial ribs attain 

width of 400 ± microns, separated by interspaces about half as 

wide, crossed by concentric ribs about 10 microns wide; 60 percent 

of 50 specimens displayed secondary bifurcation; interiors• .. smooth; muscle scars slightly impressed; ventral margin 

smooth, except on small specimens; pallial line generally not 

clearly defined; posterior teeth vary in number from 7 (rare) to 12; 

anterior from about 14 to 20." (Schenck, 1936, p. 97) 

Comparisons.-A. castrensis differs from A. blancoensis Howe 

by its more abruptly truncate posterior margin. 

Geographic range.-Living: From Sitka, Alaska, to Isla de 

Cedros, Baja California Norte; fossil: northern to southern California and possibly on the Schmidt Peninsula, Kamchatka 

(Khomenko, 1938, p. 30, 66, 73, pl. 3, figs. 5-7) and in east Sakhalin 

(Simonova, 1941, p. 12, pl. 1, figs. 4, 4a). Fossil: northern to middle 

California. 

Geologic range.-Miocene through Holocene. 

Occurrence in California.-Miocene and Pliocene: Capistrano 

(Vedder, 1974), Etchegoin (Arnold, 1909), Purisima (Arnold, 1908), 

Tahana Member of the Purisima (Addicott, 1969), and Towsley 

(Kern, 1973) Formations; Pliocene: Lomita Marl Member, San 

Pedro (A. Clark, 1931), Niguel (J. G. Vedder, written commun., 

1978), and Ohlson Ranch (Peck, 1960) Formations, Pomponio Mudstone Member of the Purisima (Cummings and others, 1962), Rio 

Dell (Faustman, 1964), San Diego (Hertlein and Grant, 1972), and 

San Joaquin (Acila zone) Formations; Pliocene-Pleistocene: 

Fernando (English, 1914; Durham and Yerkes, 1964), Merced 

(Woodring and others, 1940) and Pico (W. 0. Addicott and J. G. 

Vedder, written commun., 1978) Formations, and Wildcat Group 

(Roth, 1979); Pleistocene: Timms Point Silt Member of the San 

Pedro Formation (A. Clark, 1931). 

Habitat.-Dredged in sandy mud from 7 to 1,280 m. Off California 

coast in 28 to 426 m (Woodring and others, 1946, p. 90). 

Family MALLETIIDAE 

Genus MALLETIA Des Moulins, 1832 

No resilifer; ligament predominantly external. 

Two Tertiary species, "Malletia" chehalisensis Arnold and "M." 

packardi Clark, were formerly assigned to the genus Malletia. "M." 

chehalisensis has been assigned to Yoldia because it has a 

resilifer, "M." packardi to Portlandia. Therefore, no Tertiary 

species representing this genus are known to occur in the Californias. 

Family NUCULANIDAE 

Geologic range.-Devonian through Holocene. 

Habitat.-Most Holocene species are common on muddy bottoms. 

Genus NUCULANA Lirtk, 1807 

Resilifer narrow, oblique; posterior end produced; concentric 

sculpture. 

Geologic range.-Triassic through Holocene (table 2). 

Habitat.-Abundant in cool water, usually on muddy bottom 

from 5 to 3,600 m. 

Subgenus NUCULANA 

Nuculana (Nuculana) fossa (Baird) 

Plate 2, figures 1, 2 

Leda fossa Baird, 1863, p. 71. Arnold, 1903, p. 96-97, pl. 17, fig. 7. 

Nuculana fossa Baird. I. S. Oldroyd, 1924, p. 19, pl. 5, fig. 6. Grant 

and Gale, 1931, p. 120. 

Original description.-"Shell small, elongate, convex, thin, 

umbones anterior, turning slightly toward the posterior end, which 

is elongated, narrow and truncated; anterior end short and evenly 

rounded, sculpture nearly obsolete, a few concentric lines discernible; escutcheon long, smooth and deep-set; an elongate process on 

the middle of interior of posterior end; hinge with a small internal 

cartilage-pit, and numerous teeth on each side. Length, 11; height, 

6; diameter, 3.8 mm." 

Holotype.-BN(NH) (A. M. Keen, oral commun., 1978). 

Type locality.-Vancouver Island, British Columbia. Holocene. 

Supplementary description.-1.8 to 2.5 em in length; elongate, 

moderately fat and smooth except for small pronounced concentric 

ribs at the anterior end and on the beaks. Dorsal area of rostrum 

rather smooth, depressed, and bounded by two weak radial ribs. 

(Abbott, 1974, p. 414) 

Comparison.-According to Arnold (1903, p. 97) Nuculana fossa 

is distinguished by its lack of sculpture. The escutcheon is wider on 

N. fossa than on N. pernula. 

Geographic range.-Living: Alaska to Puget Sound, Washington; 

fossil: Alaska and southern California. 

Geologic range.-Pliocene through Holocene. 

Occurrence in Cali{ornia.-Pliocene: Rio Dell Formation 

(Faustman, 1964); Pliocene and Pleistocene: Fernando (J.D. Mount, 

written commun., 1971) and San Pedro (Arnold, 1903) Formations. 

Habitat.-Dredged offshore in shallow water from 25 to 135 m. 

Nuculana (Nuculana) fossa sculpta (Dall) 

Plate 2, figures 3, 4 

Leda fossa sculpta Dall, 1916, p. 396. 

Original description.-"This form has regular concentric ripples 

on the beaks, behind a faint depressed ray near the anterior end 

and on the keels on either side of the escutcheon." 

Holotype.-USNM 107688. 

Type locality.-ALBATROSS sta. 2855, southeast of Alaska 

Peninsula, Alaska, in mud at 110m. 

Comments.-Concentric ridges are prominent posterior to the 

depressed area and on the keel, as noted by Dall (1916); the rest of 

the shell is almost smooth. 

Geographic range.-Living: southeast of Alaska Peninsula; fossil: southern California. 

Geologic range.-Pliocene through Holocene. 

Occurrence in California.-Pliocene and Pleistocene: Fernando 

Formation (J. D. Mount, written commun., 1971). 

Habitat.-110 to 125m. 
A14 PALEONTOLOGY OF CALIFORNIA AND BAJA CALIFORNIA 

Nuculana (Nuculana) minuta praecursor (Arnold) 

Plate 2, figure 5 

Leda minuta Fabr. var. praecursor Arnold, 1903, p. 97-98, pl. 17, 

fig. 6. 

Original description.-"Shell small, trigonal, convex, thin; 

umbones anterior to middle and turning slightly· toward the 

posterior side; anterior portion from umbones short and rounded; 

posterior portion longer, slightly depressed, produced and slightly 

truncated; surface sculptured by prominent, raised concentric 

lines; escutcheon long, narrow, slightly striated with continuation 

of concentric ridges; a flat sculptured band runs around escutcheon 

from umbo to posterior end, and on the interior of the shell at the 

posterior end of this band is a little elongate ridge or process; hinge 

with prominent internal cartilage cup and about fifteen prominent 

sharp teeth on each side; pallial sinus small, narrow." 

Holotype.-Alleged to be in USNM but not found. 

Type locality.-Lower part of San Pedro Formation, Deadman 

Island, Calif. Pleistocene. 

Geographic range.-Southem California. 

Geologic range.-Pliocene and Pleistocene. 

Occurrence in California.-Pliocene and Pleistocene: Fernando 

(J.D. Mount, written commun., 1971) and San Pedro (Arnold, 1903) 

Formations. 

TABLE 2.-Geologic and geographic distribution of the family Nuculanidae in the eastern Pacific region 

[H = Holocene; Pie= Pleistocene; PI= Pliocene; M =Miocene; 0 =Oligocene; E =Eocene; Pa =Paleocene] 

Species 

Genus Nuculana: 

Subgenus Nuculana: 

Alaska British 

Columbia 

fossa Baird ................ . . ................... Ple 1 and H H fossa sculpta (Dall) .................. . minuta praecursor (Arnold) 

pernula (Miiller) ..... . Subgenus Nuculana? .............. . elongorostrata (Clark) .. Subgenus Costelloleda?: ... powersi Dickerson .. Subgenus Saccella: ...... . alaeformis (Gabb) .. cahillensis (Arnold) 

cellulita (Dall) .. chaneyi Vokes .................... . chehalisensis (Weaver) .. furlongi (Trask) 

gabbii (Gabb) ....... . hondana Vokes ......... . hindsii (Hanley) .......... . markleyensis (Clark) .. . merriami (Dickerson) ........................ . ochsneri (Anderson and Martin) .. orcutti (Arnold) ............................................. . pulchrisinuosa (Clark) .. . taphria (Dall) .................. . uvasana (Dickerson) .................. . washingtonensis (Weaver) . Subgenus Saccella? ................ . denomino.ta Hanna .. fabata (Nelson) ......... . packardi (Dickerson) ramonensis (Clark) . Subgenus Thestyleda:............ . ............................ . hamata (Carpenter) ..... Genus Ledina: 

duttonae (Vokes) .......... . fresnoensis (Dickerson) Genus Hilgardia?: 

parkei (Anderson and Hanna) .. parkei coosensis Turner .. Genus Litorhadia: 

astoriana (Henderson) . Genus Yoldia: 

Subgenus Yoldia?: ............................................. . temblorensis Anderson and Martin .. Subgenus Kalayoldia: .. cooperi Gabb ........................................ . oregona (Shumard) ............ . submontereyensis Arnold ... . .................. . supramontereyensis Arnold tenuissima Clark ... . Subgenus Kalayoldia?: ............... . carnarosensis (Clark) ..... . gesteri Dickerson ......... . Subgenus Megayoldia: .... . beringiana Dall .................. . thraciaeformis (Storer).. . . .................... . Subgenus Cnesterium: . ensifera Dall ... scissurata Dall seminuda Dall .. strigata Dall Genus Yoldia?: 

gala Woodring .. Genus Portlandia: 

Subgenus Portlandia: .......... . chehalisensis (Arnold) ........ . markleyensis (Clark) ................................ . mortuasusensis (Clark and Woodford) mosesi (Palmer) .. packardi (Clark) .. rosa (Hanna) ... 

1R. C. Allison, written commun., 1977. ~scott McCoy, writtep commun., 1978. 

H 

H 

········M:.;··· 

H 

·········ir· 

·········ir 

0 

........ if' ........ '''if' 

H 

M 

H PI to H2 

M 

H 

H 

pp 

H 

M 

H 

H 

H 

H 

H 

Washington 

H 

H 

................ "i-1'' 

'i'vf' 

················ic 

·······a·· 

H 

M 

''i\1'" ................ i\1 ... 

M 

H 

H 

H 

H 

H 

M 

EtoM 

Oregon 

·········ir·· 

·········E···· 

'il'''' 

H 

..... E .. 

......... E .... 

M 

H 

H 

H 

H 

M 

California 

Northern Middle Southern 

PI and Pie 

Pa 

....... "i-1 

········Pa·· 

········"i-c 

H 

H 

PI to H 

PI to H PI to H PI 

0 

Pa 

Pa 

E 

H 

E 

M 

M Pa and E Pa and E H 

M? 

'"ji,f"" 

E toM? 

MtoH 

··"E·a·~~i"o-· 

Pa 

M? 

H 

Pa Pa and E 

E 

E 

EtoM 

M 

Mto H 

'"i\1'" 

M E toM? 

M 

H M and PI 

H MtoH? H M to Pie 

E and 0 

E 

Pa 

E? E toM? 

PI and Pie PI and Pie PI and Pie PI and Pie 

PI to H E OandM 

··p-~-t:~·of 

Pti;-; .. H 

··E·~-~d-·6"· 

M M and PI 

''''O"i~'ii''' 

E 

Plto H 

·········E···· 

E 

Oand M 

M 

Mto H Oand M M 

M 

E toM 

PI to H 

H PI and Pie PI and Pie 

M and PI 

Baja California 

Norte Sur 

H 

H 

H H 

H H 
TERTIARY MARINE PELECYPODS: NUCULIDAE THROUGH MALLEIDAE A15 

Habitat.-The living species Nuculana (Nuculana) minuta minuta (Fabricus) occurs in mud at depths of 35 to 265m. 

Nuculana (Nuculana) pernula (Muller) 

Plate 2, figure 6 

Area pernula Muller, 1779, p. 57. Oldroyd, 1924, p. 19, pl. 19, figs. 7, 

7a. 

Nuculana pernula Muller. Abbott, 1974, p. 413-414, fig. 4848. 

Description.-"Shell oblong, rostrate, thick, olivaceous, sculptured with numerous raised concentric striae, more dense in the 

middle and slightly interrupted anteriorly; posterior side rostrated 

with a slight curve, depressed area circumscribed, inflated in the 

middle, apex obtuse; posterior side rather short, with an obscure 

ray, subacuminately rounded. Length, 17; height 10; diameter, 5.5 

mm. of a specimen from Etah, Greenland." (Oldroyd, 1924, p. 19) 

Holotype.-Location unknown. 

Type locality.-North Sea. 

Supplementary description.-1.2 to 2.5 em in length, elongate 

and truncate posteriorly, moderately fat, slightly gaping at the 

rounded anterior end. Interior of rostrum (posterior end of shell) 

reinforced by a strong radial roundish low rib. Lunule long, 

prominent, with a sharp edge. (Abbott, 1974, p. 414) 

Comparison.-"N. conceptionis Dall is much more elongate and 

smoother." (Abbott, 1974, p. 414) 

Geographic range.-Living: northern Alaska to Chatlum Sound, 

British Columbia, and Arctic Ocean to Cape Cod, Mass.; fossil: 

Alaska and southern California. 

Geologic range.-Pliocene through Holocene. 

Occurrence in California.-Pliocene and Pleistocene: Fernando 

Formation (J.D. Mount, written commun., 1971). 

Habitat.-Cold water at depths of 15 to 100m in clay. 

Subgenus NUCULANA? 

Nuculana (Nuculana?) elongorostrata (Clark) 

Plate 3, figure 1 

Leda elongorostrata Clark, 1918, p. 123, pl. 13, fig. 16. 

Original description.-"Shellsmall, thin, elongate-ovate, narrow 

and abruptly attenuated. Anterior end rather narrow but regularly 

rounded; beaks inconspicuous, anterior to the middle; posterior 

dorsal margin long, straight, only sloping very slightly; anterior 

dorsal edge gently convex; ventral edge long and gently arcuate. 

Lunule and escutcheon both elongate-lanceolate. Surface covered 

by fine concentric, somewhat irregularly spaced lines of growth. 

On the rostrate end a shallow, rather broad sulcus extends from 

the beak to the lower side of the posterior end. Internal character of 

shell unknown." 

Holotype.-UCMP 11206. 

Type locality.-UC 2755. Contra Costa County, Calif. Kirker 

Tuff, Oligocene. 

Comments.-On the basis of the outline of the holotype, this 

form is tentatively assigned to Nuculana s.s. Sixteen anterior teeth 

are preserved on the mold, but presumably there were more 

originally. This form is inflated and very elongate in proportion to 

its height (18 mm high; 7 mm long). The fine concentric sculpture 

described by Clark is not preserved on the holotype. 

Geographic range.-Middle California. 

Geologic range. -Oligocene. 

Occurrence in California.-Kirker Tuff(Keen and Bentson, 1944). 

Subgenus COSTELLOLEDA Hertlein and Strong, 1940 

Shell elongate with strong concentric sculpture. 

Geographic range.-North America. 

Geologic range.-Paleocene(?); Holocene (table 2). 

Subgenus COSTELLOLEDA? 

Nuculana (Costelloleda?) powersi (Dickerson) 

Plate 4, figures 4, 5 

Yoldia(?) powersi Dickerson, 1919, p. 124-125, pl. 7, fig. 6. 

Original description.-"Shell small, thin, elongated, slightly 

curved, shaped like a pruning knife. Beak, situated a fifth of the 

length from the anterior end, prominent. Anterior end, broadly 

rounded; posterior end, pointed sharply. Anterior dorsal margin, 

convex, short; posterior dorsal edge, concave, long. An impressed 

groove extends on the cast from the beak to the posterior end 

parallel to and just below the posterior dorsal edge. This groove 

divides the sharply pointed posterior end. Surface marked by 

rounded concentric lines which do not show in the type." 

Holotype.-UCMP 11724. 

Type locality.-UC 1556. Contra Costa County, Calif. Martinez 

Formation, Paleocene. 

Comparison.-Nuculana powersi is readily distinguished from 

"Yoldia" gesteri Dickerson by its more prominent beaks, its concave dorsal posterior margin, and its short anterior margin; the 

knifelike form identifies it readily. (Dickerson, 1914) 

Comments.-The holotype of this species is a mold, 10 mm long 

and 4 mm high. Its outline somewhat resembles the living Panamic 

species Nuculana (Costelloleda) marella Hertlein and Strong, as 

figured by Keen 1971, p. 28, fig. 17). Costelloleda has not been 

recorded in the fossil record. I have tentatively assigned this form 

to Costelloleda to call attention to its uniqueness and its similarity 

to that subgenus. 

Geographic range.-Middle California. 

Geologic range.-Paleocene. 

Occurrence in California.-Martinez Formation. 

Subgenus SACCELLA Woodring, 1925 

Rostrate, rostrum pointed; strong concentric rugae; posterior and 

anterior series of teeth mostly equal; resilifer triangular and 

symmetrical. A shallow groove extends from umbo to ventral 

margin at both ends of valve. 

Geologic range.-Paleocene through Holocene (table 2). 

Habitat.-Off southern California in shallow water (found in 

fish stomachs off Monterey) and off the west coast of America 

from Alaska south to Chile; in 7 to 1,000 m. 

Nuculana (Saccella) alaeformis (Gabb) 

Plate 2, figures 9, 10 

Corbula alaeformis Gabb, 1869, p. 177, pl. 29, fig. 63. Not Corbula 

aliformis Conrad, 1866. 

Corbula gabbii Dall, 1898, p. 840., new name for Corbula alaeformis 

Gabb. Leda polynominata Hana, 1924, p. 169, new name for 

Corbula gabbi Dall, not Leda gabbii Gabb, 1869. 

"Leda" alaeformis (Gabb). Stewart, 1930, p. 58-59, pl. 7, fig. 13. [It 

seems from Article 58 of the International Code, Stoll and 

others, 1961, p. 55, item 1, that C. alaeformis and C. aliformis 
Al6 PALEONTOLOGY OF CALIFORNIA AND BAJA CALIFORNIA 

are not homonyms and therefore the specific name alaeformis 

is reinstated following Stewart, 1930, p. 58]. 

Original description.-"Shelllarge, broadly rounded in advance, 

narrow, produced, and truncated behind; beaks about a third of the 

length from the anterior end, high; posterior cardinal margin 

nearly straight, bordered by a broad, deep groove, extending from 

the beaks to the posterior end; base prominently and broadly 

rounded in the middle, sinuous behind. Surface marked by small, 

regular, concentric ribs." 

Type material.-Holotype missing and presumed lost. The specimen illustrated by Stewart (1930, pl. 7, fig. 13), MCZ 15049, has not 

been found. A specimen labelled, "paratype, UCMP 32515," is 

figured herein as well as a specimen originally figured by Stanton 

(1896, pl. 64, fig. 6, 7). 

Type locality.-Near Lower Lake Village [NE 1/1 sec. 11, T. 12 N., 

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

Supplementary description.-"The escutcheon is very long and 

much impressed. The concentric lines are prominent and there are 

six to the two mm. interval near the posterior ventral margin. The 

posterior margin is sharply truncated but seems to be intact. Two 

taxodont teeth are visible on the cardinal region just anterior to the 

umbo. The ventral margin is incomplete." (Stewart, 1930, p. 58) 

Geographic range.-Northern California. 

Geologic range.-Paleocene. 

Occurrence in California.-Las Virgenes Sandstone (W. J. 

Zinsmeister, written commun., 1978),Martinez Formation (Arnold, 

1906; Waring, 1917). 

Nuculana (Saccella) gabbii (Gabb) 

Plate 2, figures 7, 8 

Nuculana gabbii Conrad, 1866, p. 3, nomen nudum. 

"Leda gabbii Conrad" of Gabb, 1869, p. 197-198. 

Leda protexta? Gabb, 1869, p. 199. 

Saccella gabbii (Gabb). Stewart, 1930, p. 55-58, pl. 7, fig. 3; pl. 10, 

fig. 4. 

Nuculana (Saccella) gabbii (Gabb). Givens, 1974, p. 39, pl. 1, fig. 3. 

Leda uogdesi Anderson and Hanna, 1925, p. 177, pl. 2, figs. 8, 9. 

Original description.-"Shell small, elongated, narrow; anterior 

end produced, rounded; posterior end long, narrow, curved upwards; 

base broadly and pretty regularly convex; beaks small, subcentral, 

not prominent, with the cardinal margin somewhat convex in 

front, excavated behind. Surface marked by numerous, regular, 

concentric ribs." (Gabb, 1869) 

Lectotype.-ANSP 4476 (Stewart, 1930). 

Type locality.-Martinez, Contra Costa County, Calif. Tejon 

Formation of some authors, Eocene. 

Supplementary description.-"there is considerable variation in 

length with an average slightly shorter than the length indicated 

in Gabb's figure***. The concentric sculpture is, in every case 

except one, that of ribs regularly overlapping toward the beak. At 

the posterior end, this type of ribbing may gradually grade into 

one of equilateral ribs***. The lunule and escutcheon are very long 

and well developed. The escutcheon is double***, being divided by 

a ridge on each valve. The outer escutcheon shows prominent 

divergent sculpture as though a feather had been distended and 

distorted by the insertion of an unsculptured area long its median 

line." (Clark and Woodford, 1927, p. 86) 

Comparison.-Nuculana gabbii is much more slender than N. 

alaeformis Gabb, and the posterior cardinal margin is usually 

produced to a point where it joins the broadly convex basal 

margin. The surface is marked by many concentric lines, much 

finer than inN. alaeformis. (Waring, 1917, p. 76) 

Geographic range.-Kamchatka; Southern Oregon and middle 

California. 

Geologic range.-Paleocene to Oligocene(?). Turritella delaguerrae Zone of Kleinpell and Weaver (1963). 

Occurrence in California .. -Paleocene: Las Virgenes Sandstone 

(W. J. Zinsmeister, written commun., 1978), Martinez (Wilson, 

1944) and Meganos Formations (Clark, 1921); Eocene: Avenal 

Sandstone (Stewart, 1946), Domengine (Wilson, 1944) and Llajas 

(Vokes, 1939) Formations, Matilija Sandstone (Dibblee, 1966), 

Muir Sandstone of Weaver (1953), Tejon Formation (Anderson and 

Hanna, 1925); Eocene and Oligocene: undifferentiated Sacate and 

Gaviota Formations of Weaver and Kleinpell (1963). 

Nuculana (Saccella) hondana Vokes 

Plate 2, figure 42 

Nuculana (Saccella) hondana Vokes, 1939, p. 42-43, pl. 1, figs. 9, 

10. Givens, 1974, p. 39, pl. 1, fig. 4. 

Original description.-"Shell small, elongate, subtrigonal, 

moderately inflated; umbo nearly central; anterior and ventral 

margins broadly and regularly rounded; posterior margin rounded 

to the bluntly angulate rostrum; anterior dorsal margin varying 

from slightly concave to straight; posterior ventral margin slightly 

concave, the shell appearing distinctly:equilateral; sculpture consisting of narrow, widely and regularly spaced concentric lines; a 

shallow, smooth groove extending from the beaks to the posterior 

point of the rostral margin; lunule and escutcheon long, narrow 

and well defined, the escutcheon crossed by a diagonal ridge." 

Holotype.-VCMP 15561. 

Type locality.-VC 1817. Fresno County, Calif. Cerros Shale 

Member, of the Lodo Formation, Paleocene. 

Comparisons.- "Nuculana hondana may be distinguished from 

N. gabbii, with which it has heretofore been confused, by the 

bluntly rostrate posterior margin, the more equilateral outline, the 

straight rather than convex anterior dorsal margin, and the 

sculpturing of impressed lines rather than concentric ribbing; from 

N. parkei (Anderson & Hanna) by differences in shape and 

sculpturing, and in the absence of small, sharp ridges on the 

impressed area." (Vokes, 1939, p. 42) 

Geographic range.-Southern California. 

Geologic range.-Paleocene and Eocene. 

Occurrence in California.-Paleocene: Cerros Shale Member, 

Lodo Formation (Keen and Bentson, 1944); Eocene: Capay Formation, Juncal Formation (in Turritella uuasana infera fauna, Givens, 

1974). 

Nuculana (Saccella) chaneyi Vokes 

Plate 2, figures 12, 13 

Nuculana (Saccella) chaneyi Vokes, 1939, p. 43, pl. 1, figs. 11, 12. 

Original description.-"Shell small, elongate; beaks low, opisthogyrate, slightly anterior; anterior dorsal margin slightly convex, 

sloping to the sharply rounded anterior end; ventral and posterior 

margins broadly rounded to the acute posterior end; posterior 

dorsal margin concave; escutcheon broad, incised, marked by a 

diagonal ridge from the beak nearly to the posterior end; lunule 

incised, narrower, and less well marked than the escutcheon; 

surface sculptured by broad, low, rounded ribbing separated by 

narrow incised interspaces; posterior area depressed, bounded by a 

well marked umbonalline to the posterior ventral margin, smooth 

except fo,r coarse lines of growth." 

Syntypes.-VCMP 15745 and 15746. 

Type locality.-VC A-1165 and A-976. Kings County, Calif. 

A venal Sandstone, Eocene. 

Comparison.- "N. chaneyi somewhat resembles N. hondana in 

outline but differs in the depressed posterior area; it differs from N. 
TERTIARY MARINE PELECYPODS: NUCULIDAE THROUGH MALLEIDAE A17 

parkei (Anderson and Hanna) and N. parkei coosensis Turner in 

lacking posterior umbonal ridges; from N. gabbii it may be 

separated by shape and sculpturing." (Vokes, 1939, p. 43) 

Comments.-The concentric sculpture on Hilgardia? parkei coosensis, discussed below under Hilgardia?, is slightly stronger and 

more prominent on the posterior depressed area than on N. 

chaneyi. 

Geographic range.-Middle to southern California. 

Geologic range.-Eocene. 

Occurrence in Cali{ornia.-Avenal Sandstone, Domengine Formation and Muir Sandstone (Weaver, 1953). 

Nuculana (Saccella) uvasana (Dickerson) 

Plate 2, figures 11, 41 

Leda uvasana Dickerson, 1915, p. 51-52, pl. 1, figs. 2a, 2b. 

Original description.-"Shell of medium size, elongate, with a 

very small inconspicuous central beak; anterior dorsal margin 

slightly convex with a slight slope to a narrowly rounded anterior 

extremity; posterior dorsal margin concave, ending in a sharply 

pointed rostrum; ventral margin very broadly rounded; escutcheon 

lanceolate, distinct; lunule indistinct." 

Holotype.-CAS 250. 

Type locality.-CAS 244. Kern County, Calif. Tejon Formation, 

Eocene. 

Comparison.-"This species has less thickness than L. gabbi 

Conrad and quite a different shape. Its ribbing is somewhat finer." 

(Dickerson, 1915, p. 52) 

Comments.-The beak on Nuculana uvasana is slightly posterior to the midpoint of the shell. The escutcheon is divided by a 

ridge beginning at the beak and curving toward the dorsal margin 

where it terminates. 

Geographic range.-Southern California. 

Geologic range.-Eocene. 

Occurrence in California.-Tejon Formation. 

Nuculana (Saccella) cahillensis (Arnold) 

Plate 2, figure 34 

Leda cahillensis Arnold, 1908, p. 375-376, pl. 34, fig. 9. 

Original description.-"Shell attaining a length of only 6 or 7 

mm, width about seven-ninths of length, oval, rounded in front, 

attenuate behind; well inflated, margin smooth; umbo small, 

subcentral, turned backward; anterior dorsal margin nearly 

straight, sloping steeply from umbo; anterior extremity regularly 

rounded; posterior dorsal margin concave, prominently excavated 

behind umbo; posterior extremity very attenuate; surface sculptured 

by numerous, equal, rounded concentric ribs, separated by moderately wide impressed lines; a trace of poorly developed carina 

extending from the umbo to the posterior extremity is discernible 

in the type." 

Holotype.-CASISU 5386 (Keen and Bentson, 1944, p. 55). 

Type locality.-Santa Cruz quadrangle, San Mateo County, 

locality No. 57, on road to Kings Mountain House, 3 km west of 

Woodside, in rather coarse, brownish-yellow sandstone. Butano(?) 

Sandstone, Eocene. 

Comparison.-"This gibbous little Leda is easily distinguished 

from associated fossil forms by its small size, great convexity, 

broad outline, sharply attenuate posterior extremity, excavated 

margin posterior to umbo, and rather coarse sculpture. It resembles 

L. acuta Conrad (recent) in size but is relatively broader and more 

excavated behind. Distinguishable from the closely allied L. taphria 

Dall by much smaller size, more excavated dorsal posterior margin, 

and finer concentric sculpture." (Arnold, 1908, p. 376) 

Comments.-This small form is very inflated, the posterior 

dorsal margin markedly concave, and the posterior extremity very 

rostrate. 

Geographic range.-Middle California. 

Geologic range.-Eocene. 

Occurrence in Cali{ornia.-Butano(?) Sandstone. 

Nuculana (Saccella) merriami (Dickerson) 

Plate 2, figures 14, 15 

Leda merriami Dickerson, 1917, p. 166, pl. 72, figs. la, lb. 

Nuculana merriami (Dickerson). Weaver, 1942, p. 37, pl. 8, figs. 21, 

30. 

Original description.-"Shell inflated, resembling Leda alae· 

{ormis Gabb in general shape; acutely rostrate, very inequilateral, 

very convex; beak prominent, high; anterior slope convex, ascending; posterior slope concave; anterior end bluntly rounded; base 

arcuate; escutcheon wide, nearly flat; incremental lines numerous, 

rounded; anterior teeth, 24; posterior teeth, 20 to 23; chondrophore 

sub-umbonal, not projecting. Dimensions: Length, 30 mm.; height, 

22 mm.; convexity, 4.5 mm." 

Holotype.-CAS 381. 

Type locality.-UW 239. Cowlitz County, Wash. Gries Ranch 

Formation, Oligocene. 

Comparison.-"N. merriami from the Gries Ranch beds***differs 

from N. washingtonensis of the Lincoln formation***in the proportionally lesser length of the area posterior to the umbo, the greater 

height, and the more pronounced concavity of the posterior dorsal 

margin. It is relatively higher and shorter than N. cowlitzensis of 

the***Cowlitz formation." (Weaver, 1942, p. 37) 

Comments.-This form is very high in proportion to its length 

and also is acutely rostrate, as Dickerson has noted. It differs from 

N. (S.) cowlitzensis by having a more pronounced concave posterior 

dorsal margin. 

Geographic range.-Southwestern Washington; southern California. 

Geologic range.-Eocene and Oligocene. 

Occurrence in Cali{ornia.-San Emigdio Formation (DeLise, 

1967). 

Nuculana (Saccella) washingtonensis (Weaver) 

Plate 2, figures 16, 17 

Leda washingtonensis Weaver, 1916, p. 34, pl. 3, fig. 25, 26. 

Nuculana washingtonensis (Weaver). Weaver, 1942, p. 38-39, pl. 8, 

figs. 18, 20, 26. Watkins, 1974, p. 263-264, fig. 8. 

Leda lincolnensis Weaver, 1916, 1916, p. 35, pl. 3, figs. 23, 24. 

Original description.-"Shell of medium size, elongate and narrow; anterior dorsal margin two-fifths the length of shell, nearly 

straight and sloping downwards at an angle of 10° from the beaks; 

anterior end sharply rounded and merging into a slightly arcuate 

base; posterior dorsal margin slightly concave and deeply excavated; posterior end rostrate and obliquely truncate. On both 

valves a narrow but distinct groove extends from beaks to posterior 

end which becomes more deeply impressed near the latter. Surface 

of shell is sculptured by well marked concentric ribs which are flat 

topped and with interspaces of about equal width. Radiating ribs 

are absent. Beaks not very prominent; lunule linear and marked by 

very faint incised lines; escutcheon sunken, elongate-lanceolate, 

extending from beaks to posterior end and obliquely grooved with 

rounded outer edges. Hinge with 26 anterior and 21 posterior V-
A18 PALEONTOLOGY OF CALIFORNIA AND BAJA CALIFORNIA 

shaped teeth. Chondrophore small and subumbonal. Adductor 

muscle scars small; pallial sinus short. Dimensions: Altitude 8 

mm.; longitude 20 mm.; thickness 7 mm." 

Lectotype.-CAS 451 (Moore, 1976); paratypes-CAS 450A-B. 

Type locality.-UW 256. Lewis County, Wash. Lincoln Creek 

Formation, Eocene to Miocene. 

Supplementary description.- "Nuculana washingtonensis is an 

elongate species terminating posteriorly in a sharply-pointed rostrum. The beaks are characteristically located two-fifths of the 

distance from the anterior end of the shell. The anterior dorsal 

margin is convex, and the anterior end is regularly curved. The 

ventral margin is long and broadly arcuate***. This sinus varies 

in prominence. There is also some variation in shape, degree of 

inflation, and relative position of the umbos. One of the most 

constant features is the sculpture, which consists of closely-spaced, 

well-developed, flat-topped concentric ridges***. Within the escutcheonal area the shell is produced at the dorsal margins. There 

is a slight posterior gape. The anterior hinge on a wellpreserved***specimen contains about 26 V-shaped teeth, and the 

posterior hinge contains 20***." (Hickman, 1969, p. 27) 

Comments.-This form is not as high in proportion to length as 

is Nuculana (Saccella) uvasana. 

Geographic range.-Alaska to middle California. 

Geologic range .. -Eocene to Miocene. 

Occurrence in California.-Eocene and Oligocene: Kreyenhagen 

Shale (Condit, 1930) and Rices Mudstone Member of San Lorenzo 

Formation (Cummings and others, 1962). 

Nuculana (Saccella) pulchrisinuosa (Clark) 

Plate 2, figures 18, 19 

Leda pulchrisinuosa Clark, 1918, p. 123--124, pl. 11, figs. 5, 6. 

Original description.-"Shell small, subovate; beaks near the 

middle. Dorsal slopes nearly equal, the posterior one, which is 

slightly the longer, being gently concave; anterior slope nearly 

straight. Anterior end regularly rounded; posterior end acutely 

rostrate. Lunule narrow, elongate--lanceolate, extending a little 

over half the length of the anterior dorsal edge. Escutcheon well 

defined, strongly depressed, lanceolate, extending from the beaks 

to the posterior end and enclosing a secondary escutcheon which is 

more sharply limited and more strongly depressed than the primary 

one. Surface of shell sculptured by numerous fine concentric ribs. 

On the surface near the posterior dorsal edge there is a shallow 

groove which extends from the beaks to a little anterior to the 

posterior end. Hinge plate unknown." 

Holotype.-UCMP 11109. 

Type locality.-UC 3081. Contra Costa County, Calif. San Ramon 

Sandstone, Miocene(?). 

Comparison.-Nuculana pulchrisinuosa is somewhat like Nuculana taphria (Dall) but differs from that species in that it is slightly 

more elongate and the concentric sculpturing somewhat finer. The 

most important difference, however, is the presence of the double 

escutcheon; on N. taphria, the escutcheon is single (Clark, 1918, p. 

124) 

Nucula (Saccella) pulchrisinuosa somewhat resembles N. gabbii 

(Gabb). It differs from that species principally in that it is not so 

acute and elongate posteriorly, also in that the sculpturing is 

somewhat finer. (Clark, 1918, p. 124) 

Nuculana pulchrisinuosa is also somewhat similar toN. ochsneri 

(Anderson and Martin). N. ochsneri differs from it by being more 

acute anteriorly and posteriorly; the sculpturing is coarser, and the 

lunule and escutcheon are larger. The escutcheon of N. ochsneri 

has the double area seen on N. pulchrisinuosa, but its secondary 

escutcheon is larger. (Clark, 1918, p. 124) 

Comments.-The shell of the species has a poutlike escutcheonal 

margin. 

Geographic range.-Middle California. 

Geologic range.-Eocene to Miocene(?). 

Occurrence in California.-Eocene: Muir Sandstone of Weaver 

(1953); Eocene and Oligocene; San Lorenzo Formation; Miocene(?): 

San Ramon Sandstone. 

Nuculana (Saccella) chehalisensis (Weaver) 

Plate 2, figures 20, 21 

Leda chehalisensis Weaver, 1912, p. 56, pl. 12, figs. 104, 105. 

Nuculana chehalisensis (Weaver). Weaver, 1942, p. 39, pl. 8, figs. 

11, 15-17. Addicott, 1976a, p. 27. 

Original description.-"Shell small, moderately convex, equivalve and nearly equilateral; beaks slightly elevated and curved 

forwards; lunule very large; cordate elongate and fairly deeply 

impressed; escutcheon long and narrow; anterior margin of shell 

concave, at first sloping steeply for a short distance from the 

beaks, and then straight to the anterior end; anterior end bluntly 

truncated upward; base broadly rounded; posterior margin very 

slightly convex and sloping downwards at a low angle; posterior 

end acutely rounded. Sculptured by equally spaced closely set 

concentric ribs with deeply grooved interspaces equal in width to 

the ribs. Dimensions: Altitude 10 rom.; longitude 15 rom.; thickness 

3.5mm." 

Holotype.-CAS 539 (Weaver, 1942). 

Type locality.-UW 63. Grays Harbor County, Wash. Astoria 

Formation, Miocene. 

Comparison.- "Nuculana" epacris Moore is more elongate, more 

pointed at the posterior end, and more finely sculptured than 

Nuculana chehalisensis (Moore, 1963, p. 55). 

Geographic range.-Alaska to Baja California Sur. 

Geologic range.-Oligocene and Miocene. 

Occurrence in California and Baja California Sur.-Oligocene 

and Miocene: Temblor Formation (Loel and Corey, 1932); Miocene: 

Briones Sandstone, Monterey Group, Sobrante Sandstone (Lutz, 

1951), Tortugas Formation (Minch and others, 1976). 

Nuculana (Saccella) markleyensis (Clark) 

Plate 3, figure 2 

Leda markleyensis Clark, 1918, p. 123, pl. 14, fig. 7. 

Original description.-"Shell small, acutely rostrate posteriorly; 

beaks opisthogyrous, anterior to middle; posterior dorsal margin 

strongly concave, longer than anterior dorsal margin, which is 

gently convex; posterior end sharply pointed; anterior end regularly 

rounded. Surface covered by medium-fine, regular incremental 

lines; escutcheonal area flat, fairly broad, depressed nearly at right 

angles to the main outer surface of shell. Lunule and hinge plate 

not exposed." 

Holotype.-UCMP 11272. 

Type locality.-UC 3081. Contra Costa County, Calif. San 

Ramon Sandstone, Miocene(?). 

Comparison.-Nuculana markleyensis resembles Nuculana 

gabbii (Gabb) in outline, but differs in being somewhat higher in 

proportion to the length; the beaks are more anterior, and the 

escutcheonal area is different. (Clark, 1918, p. 123) 

Geographic range.-Middle California. 

Geologic range.-Miocene(?). 
TERTIARY MARINE PELECYPODS: NUCULIDAE THROUGH MALLEIDAE A19 

Occurrence in Cali{ornia.-San Ramon Sandstone. 

Nuculana (Saccclla) furlongi (Trask) 

Plate 2, figures 35, 36 

Leda furlongi Trask, 1922, p. 147, pl. 1, figs. la, lb. 

Original description.-"Shell small, subovate, moderately ventricose; beaks obscure, nearly central; slightly opisthogyrous; posterior dorsal edge gently concave; anterior dorsal edge nearly straight; 

anterior end regularly rounded; posterior end subacutely rostrate; 

lunule and escutcheon elongate, lanceolate, extending almost the 

entire length of the dorsal margins, and rather strongly pouting; 

surface sculptured with numerous fine regular concentric lines; 

hinge plate unknown." 

Holotype.-UCMP 12362. 

Type locality.-UC 15. Contra Costra County, Calif. Briones 

Sandstone, Miocene. 

Comparison.-Nuculana furlongi somewhat resembles Nuculana 

taphria but differs from it by being narrower and more elongate 

posteriorly, by having finer concentric sculpturing, and by the 

lunule and escutcheon being more strongly pouting. It differs from 

Nuculana ochsneri by being less acutely elongate posteriorly, the 

posterior dorsal slope being less concave and the concentric ribs 

finer. It differs from Nuculana whitmani (Dall), described from the 

Empire Formation, Oregon, in that the ribs over the entire surface 

are finer and more evenly distributed, the posterior dorsal edge is 

less concave, and the shell appears much narrower. (Trask, 1922, 

p. 147) 

Comments.-Nuculana furlongi is of moderate size and the 

margins of both the lunule and escutcheon pout markedly. Although the holotype is imperfectly preserved, neither the lunule 

nor the escutcheon is as wide or as well demarcated as on 

Nuculana ochsneri and Nuculana taphria; N. taphria is also more 

rostrate. 

Geographic range.-Middle California. 

Geologic range.-Miocene. 

Occurrence in Cali{ornia.-Briones Sandstone (Weaver, 1953; 

Hall, 1958). 

Nuculana (Saccclla) ochsneri (Anderson and Martin) 

Plate 2, figures 24, 25 

Leda ochsneri Anderson and Martin, 1914, p. 53, pl. 3, figs. 8a-8c. 

Saccella ochsneri (Anderson and Martin). Moore, 1963, p. 55, 57, pl. 

13, figs. 1-3, 7. 

Original description.-"Shell small, slightly arcuate anteriorly, 

excavated behind the beaks, rostrate and acute with valves closed 

at the posterior extremity; basal margin strongly and regularly 

arcuate, or sometimes slightly truncated at the rear; surface 

marked with strong concentric lines, polished; posterior ends 

bearing a shallow oblique groove extending downward from the 

beaks. Length, 16 to 20 mm.; altitude, 9 to 10 mm.; thickness, 8 

mm." 

Holotype.-CAS 103. 

Type locality.-CAS 68. Kern County, Calif. Round Mountain 

Silt, Miocene. 

Comparisons.-Nuculana ochsneri elmana Etherington is more 

finely sculptured and has a second incised line on the escutcheon. 

Nuculana ochsneri "***resembles Leda taphria Dall, of which it 

may be the precursor, but it is relatively thicker, less elevated, and 

less clearly truncated behind." (Anderson and Martin, 1914, p. 53) 

"Nuculana" epacris Moore [Astoria Formation, Oregon] is higher 

in proportion to length and also more pointed at the posterior end 

than N. ochsneri and lacks the flattened area bordered by a slight 

ridge present at the posterior dorsal margin of N. ochsneri. (Moore, 

1963, p. 55) 

Nuculana (Saccella) amelga (Moore), described from the Astoria 

Formation, Oregon, differs from N. ochsneri by having sharp 

concentric ridges, not flattened as on N. ochsneri and more widely 

spaced. N. amelga is shorter anteriorly, the beaks are closer to the 

anterior margin, and it lacks the deeply incised, ridgelike lunule of 

N. ochsneri. (Moore, 1963, p. 57) 

Geographic range.-Middle and southern California. 

Geologic range.-Miocene. 

Occurrence in California.-Buttonbed Sandstone Member of the 

Temblor, Castaic (Stanton, 1966), and McLure Shale Member of 

Monterey (Adegoke, 1969) Formations, Olcese Sand (Addicott, 

1956), Round Mountain Silt (Keen, 1943), Sobrante Sandstone 

(Lutz, 1951), Tice Shale (Hall, 1958), and Topanga Formation 

(Takeo Susuki, written commun., 1978). 

Nuculana (Saccella) taphria (Dall) 

Plate 2, figures 22, 23 

Leda taphria Dall, 1896, p. 70. New name for Nucula coelata 

Hinds, 1843, not Nucula coelata Conrad, 1833. 

Saccella taphria (Dall). Moore, 1968, p. 50, pl. 23, figs. e-g. 

Nuculana (Saccella) taphria (Dall). Hertlein and Grant, 1972, p. 

150-151, pl. 27, figs. 11-13, 16-18. 

Original description.-"Nuc. testa luteo-virente, oblonga, argute 

sulcata; antice arcuate rostrata, sulcis paululum obliteratis; umbonibus prominulis. Long 7; lat 3; alt 4 lin." 

Holotype.-Missing (Keen, 1966a, p. 267; Hertlein and Grant, 

1972, p. 150). 

Type locality.-"Califomia, between 38°18' and 34°24' north 

latitude; namely, at Russian Bodegas, San Francisco, and Santa 

Barbara, in from six to ten fathoms [11 to 18m]." Holocene. 

Supplementary description.-"The umbos of Nuculana taphria 

are nearly centrally situated, the rostrum is bluntly pointed and 

the exterior is sculptured with well developed, uniform, sharp, 

raised, concentric ribbing. A narrow lunular area is present and 

there is a long, narrow escutcheon concentrically striated. A 

narrow, shallow, depressed area extending from the umbos to the 

ventral margin is usually present just anterior to the dorsal 

margin. There are two gently curved rows (the anterior slightly the 

longer) of chevron-shaped teeth, about 20 in each series. A shallow 

pallial sinus is present. A typical specimen from off San Martin 

Island, Lower California, is 18 mm long, 11.2 mm high, convexity 

(both valves together), 8.9 mm***. Larger shells tend to be more 

globose with the posterior end more pointed and upturned. Some of 

these have been bored on the umbo by a gastropod." (Hertlein and 

Grant, 1972, p. 150) 

Comparison.-"The shell of this species is less elongate, more 

inflated, and the surface is less polished than that of Nuculana 

callimene Dall from Panama and it has much coarser sculpture 

than that of N. pontonia Dall, originally described from the 

Galapagos Islands. The presence of an anterior lunular area on N. 

taphria serves to separate it from the similar N. balboae Brown 

and Pilsbry from mid-Miocene strata of Panama. Furthermore, the 

Panamanian species has a much greater number ofteeth, 28 in the 

anterior and 18 in the posterior series." (Hertlein and Grant, 1972, 

p. 151) 

Nuculana (Saccella) taphria resembles N. calkinsi (Moore, 1963, 

p. 56-57, pl. 13, figs. 10-13), described from the Astoria Formation, 

Oregon, but the rostrum of N. calkinsi is not as strongly recurved, 

and the escutcheon is longer, narrower, and has a secondary ridge. 
A20 PALEONTOLOGY OF CALIFORNIA AND BAJA CALIFORNIA 

In addition, the lunule of N. taphria is wider and more ovate in 

outline. (Moore, 1963, p. 57) 

Geographic range.-Living: Bodega Bay, Calif., to Blanco de 

Arena, Golfo de California, Mexico; fossil: middle and southern 

California. 

Geologic range.-Oligocene through Holocene. 

Occurrence in California.-Oligocene and Miocene: Temblor 

Formation (Winterer and Durham, 1958); Miocene: Briones Sandstone (Hall, 1958), Santa Margarita Formation (Adegoke, 1969); 

Miocene and Pliocene: Capistrano· (Vedder, 1974), Etchegoin 

(Adegoke, 1969), and Towsley (Kern, 1973) Formations; Pliocene: 

Cebada Member of Careaga Sand (Woodring, 1950), Niguel (J. G. 

Vedder, written commun., 1978), Ohlson Ranch (Peck, 1960), Pancho 

Rico (Durham, 1966), Purisima (Arnold, 1906), and San Diego 

(Hertlein and Grant, 1972) Formations; Pliocene and Pleistocene: 

Fernando (English, 1914), Pico (Winterer and Durham, 1958), 

Santa Barbara (Waterfall, 1929, as upper Pico), and Saugus (Waterfall, 1929) Formations; Pleistocene: lower part of San Pedro Series 

of Arnold (1903). 

Habitat.-Occurs in sand and clay at depths of 5 to 145m; found 

in fish stomachs off Monterey. 

Nuculana (Saccella) orcutti (Arnold) 

Plate 2, figures 28, 29 

Leda orcutti Arnold, 1907b, p. 435, pl. 55, fig. 9. 

Saccella orcutti (Arnold). Woodring, 1950, p. 80, pl. 8, figs. 5, 7, 8, 

13; pl. 10, fig. 3 

Original description.-"Shell averaging about 7 millimeters in 

longitude, solid, equivalve; beaks slightly anterior; anterior end 

rounded, shorter; posterior end rostrate, subacute; base arcuate; 

lunule long and very narrow, separated from shell by deeply 

impressed line; escutcheon much broader than lunule, its surface 

prominently concave and its carina well developed, especially 

toward the posterior end, sculpture consisting of several (7 in type) 

prominent wide spaced, narrow concentric riblets, this sculpture 

confined to the main portion of shell; lunule, escutcheon, and 

carinae ornamented only by fine concentric incremental lines; 

incremental lines also visible between the concentric riblets. Hinge 

and interior similar in a general way to L. minuta Fabr." 

Holotype.-USNM 165271. 

Type locality.-USGS 4473. Santa Barbara County, Calif. Careaga Sandstone, Pliocene. 

Supplementary description.-Nuculana orcutti is characterized 

by its coarse, widely spaced concentric riblets. The umbones are 

nearly in the center of the dorsal margin, both anterior and 

posterior dorsal margins being approximately equal in length and 

nearly straight. The rostrum is not attenuated and comes to a 

blunt point. (Grant and Gale, 1931, p. 125). 

"Twenty specimens are in collections from the type locality. 

They are elongate and strongly and coarsely sculptured except 

one, which is almost smooth aside from sculpture near the ventral 

margin. The few Careaga fossils also are elongate. The more 

numerous Sisquoc shells***show a greater range of variation. The 

outline varies from short***, the usual form, to elongate***. Some 

immature shells are coarsely sculptured***, but most immature 

and mature shells have strong moderately coarse sculpture. One 

immature shell, however, is almost smooth***." (Woodring, 1950, 

p. 80) 

Comparison.-"The short form of S. orcutti resembles closely the 

Recent northern S. penderi, but has coarser and generally stronger 

sculpture." (Woodring, 1950, p. 81) N. (S.) hindsii has finer sculpture 

than N. (S.) orcutti. 

Geographic range.-Southern California. 

Geologic range.-Miocene and Pliocene. 

Occurrence in Cali{ornia.-Miocene and Pliocene: Sisquoc Formation (Woodring, 1950); Pliocene: Cebada Member ofCareaga Sandstone and Foxen Mudstone. 

Nuculana (Saccella) cellulita (Dall) 

Plate 2; figures 26, 27 

Leda cellulita Dall, 1896, p. 1. Dall, 1987, p. 7, pl. 2, figs. 5, 7. 

Nuculana cellulita (Dall). Grant and Gale, 1931, p. 122. 

Saccella cellulita (Dall). Woodring, 1950, p. 80, pl. 15, figs. 3, 26. 

Original description.-"Shell solid, with a dull olive-gray epidermis, moderately convex, with subcentral, not prominent beaks, 

base profoundly arcuate, anterior dorsal slope rounded, posterior 

straight or slightly concave; posterior extreme bluntly pointed; 

escutcheon large, transversely striate; lunule not differentiated but 

similarly striate; sculpture of fine sharp, concentric grooves with 

wider interspaces, less arcuate than the incremental lines; chondrophore small, triangular, not projecting, with 22 anterior and 16 

posterior hinge teeth on the cardinal border. Height 10.5; diameter 

7.2; length 15.5 mm." 

Lectotype.-USNM 107436a, here designated [from the syntypic 

lot] as the double-valved syntype figured by Dall (1897, pl. 2, fig. 7). 

Type locality.-Puget Sound, near Port Orchard, Wash. Holocene. 

Supplementary description.-The irregular Acila-like radial sculpture on the lunule and escutcheon is the most characteristic feature 

of N. cellulita. (Woodring, 1950, p. 80) 

Comparison.-The shell of this species is less elongate and more 

bluntly pointed posteriorly than Nuculana taphria. The sculpture 

is not quite coincident with the growth lines (Grant and Gale, 1931, 

p. 123) The outline of N. cellulita suggests that of N. taphria, but 

the concentric rugae are finer. (Woodring, 1950, p. 80) 

Geologic range.-Pliocene through Holocene. 

Geographic range.-Living: Craig, Alaska to Redondo Beach, 

Calif.; fossil: southern California. 

Occurrence in California.-Pliocene: Cebada Member of Careaga 

Sandstone (Woodring, 1950), lower part of San Pedro (Grant and 

Gale, 1931), and upper part of Sisquoc Formations; Pliocene and 

Pleistocene: Pica Formation (Winterer and Durham, 1958). 

Habitat.-55 to 75 m, sandy mud. 

Nuculana (Saccella) hindsii (Hanley) 

Plate 2, figures 30, 31 

Leda hindsii Hanley, 1860a, p. 440; 1860b, p. 135, sp. 51, pl. 229, fig. 

102. 

Nuculana redondoensis Burch, 1944, p. 9; text fig. p. 10. 

Saccella redondoensis Burch. Woodring, 1950, p. 81, pl. 16, fig. 18. 

Original description.-"Very small, subequilateral, pointed, ovateoblong, more or less ventricose, only gaping at the hinder tip, with 

a conspicuous broad anterior indented ray and fold, white, concentrically castellated, except a smooth upper space before the keeled 

or sharply angulated umbonal ridge; riblets regular and numerous, 

scarcely as broad as their intervals, which are everywhere traversed 

by minute radiating lyrae. Anterior extremity attenuatedly rounded: posterior side, if either, the longer, simply and sharply acuminated, the tip subcentral, acutangular, scarcely, if at all, recurved. 

Dorsal slopes moderate; front one convex; hinder one straightish 

or subretuse. Ventral margin arcuated in the front and middle, 

rising at both ends, straighter behind. Lunule small, narrow, 

subgranosely cross-barred: escutcheon large, concave, crowded 

with longitudinal costellar striae, whose intervals appear punctulate either side of the minute cartilage-pit." 

Holotype.-Location unknown. 
TERTIARY MARINE PELECYPODS: NUCULIDAE THROUGH MALLEIDAE A21 

Type locality.-Probably from the Gulf of Nicoya, Costa Rica, 

Holocene. 

Supplementary description.-***Most of the fossils show microscopic punctae on the ventral side of the concentric rugae on the 

dorsal part of the shell, possibly due to slight corrosion, but not on 

the umbo. A few of the Recent shells examined show similar 

punctae***." (Woodring, 1950, p. 81) 

Comparison.-"***N. acuta Conrad, a name often given to this 

Pacific Coast species, has its rostral rib crossed by concentric ribs. 

N. penderi Dall and Bartsch is twice as fat, with a very ovate 

lunule and is more rounded at the ventral margin***." (Abbott, 

1974, p. 415) 

Nuculana hindsii is more pointed posteriorly than its Atlantic 

twin, N. acuta (Keen, 1971, p. 31). Nuculana hindsii has finer 

sculpture than N. orcutti and is shorter and more globose than N. 

penderi. 

Geographic range.-Living: Nazan Bay, Alaska, to Panama; 

fossil: southern California to Baja California Norte. 

Geologic range.-Pliocene through Holocene. 

Occurrence in California and Baja California.-Pliocene: Cebada 

Member of the Careaga Sandstone (Woodring, 1950, as N. redondoensis); Pliocene and Pleistocene: Fernando Formation (Zinsmeister, 

1970, as N. acuta); Pleistocene: unnamed sediments, San Quintin 

Bay, Baja California Norte (Jordan, 1926). 

Habitat.-Dredged off the west coast of North America from 30 

to 3,700 min gravel, sand, sandy mud, mud, and shells. 

Subgenus SACCELLA? 

Nuculana (Saccella?) fabata (Nelson) 

Plate 2, figure 39 

Leda fabata Nelson, 1925, p. 404, pl. 49, fig. 1. 

Original description.-"Shell small, suboval, moderately convex; 

beaks almost central, low. Anterior dorsal margin slightly concave, 

gently sloping; posterior dorsal margin almost straight, meeting 

anterior dorsal margin at beaks in very wide angle; ventral margin 

regularly and strongly arcuate, joining anterior dorsal margin in a 

rounded angle, merging into truncated posterior extremity; posterior extremity a trifle convex, meeting posterior dorsal margin in 

an angle slightly greater than 90°. Shell with maximum inflation 

just below beaks, slightly depressed toward anterior extremity, 

with broad, faint sulcation extending from behind beaks to posterior extremity. Surface of shell with fine concentric ribbing. 

Character of lunule and escutcheon obscure. Length of type specimen, 5 mm; height, 3.2 mm." 

Holotype.-VCMP 30717. 

Type locality.-VC 3752. Ventura County, Calif. Martinez Formation, Paleocene. 

Comments.-The comparatively straight dorsal margin and 

near-central location of the beaks distinguish this species. 

Geographic range.-Southern California. 

Geologic range.-Paleocene. 

Occurrence in California.-Martinez Formation. 

Nuculana (Saccella?) denominata G D. Hanna 

Plate 2, figure 40 

Leda milleri Dickerson, 1914, p. 123-124, pl. 7, fig. 4. NotNuculana 

milleri Gabb, 1881. 

Leda denominata G D. Hanna, new name, 1924, p. 169. 

Original description.-"Shell small, moderately convex; beak, 

prominent, located one-third of the distance from anterior end. 

Posterior dorsal edge straight with a very slight slope to a blunt 

pointed posterior end. Anterior dorsal edge straight with a slightly 

greater slope than posterior dorsal edge. Ventral margin gently 

convex. This margin curves sharply toward the two pointed 

extremities of the shell." 

Holotype.-VCMP 11663. 

Type locality.-VC 1556. Contra Costa County, Calif. Martinez 

Formation, Paleocene. 

Comparison.-This form resembles N. packardi but is much 

lower, its beak is more anterior and its length greater. It somewhat 

resembles Yoldia chehalisensis (Arnold) in shape. (Dickerson, 

1914, p. 214) 

Comments.-Nuculana denominata is more elongate in proportion to its height than Portlandia chehalisensis, and the holotype, 

though poorly preserved, resembles Saccella in outline. 

Geographic range.-Middle California. 

Geologic range.-Paleocene. 

Occurrence in California.-Martinez Formation. 

N uculana (Saccella?) packardi (Dickerson) 

Plate 2, figure 32 

Leda packardi Dickerson, 1914, p. 123, pl. 7, figs. 3a, 3b. 

Original description.-"Shell thin, marked by fine rounded concentric lines, short, convex; beaks central, small but prominent; 

anterior dorsal margin, slightly sloping; posterior, straight; anterior 

end rounded; posterior end bluntly pointed with apex of point at 

end of straight posterior dorsal margin; base rounded from anterior 

to middle of posterior ventral margin; from this point the slightly 

curving posterior margin slopes abruptly upward to the posterior 

extremity. This species differs from all the other California led as 

in shape and in the central position of its beaks. The oddly blunted 

rostrum is another distinguishing feature." 

Holotype.-VC 11725. 

Type locality.-VC 784. Lake County, Calif. Martinez Formation, 

Paleocene. 

Comments.-The outline of this species is unique; it is quadrate 

and the apex of the posterior end is parallel with the dorsal 

margin. 

Geographic range.-Northern California. 

Geologic range .-Paleocene. 

Occurrence in California.-Martinez Formation. 

Nuculana (Saccella?) ramonensis (Clark) 

Plate 2, figure 33 

Leda ramonensis Clark, 1918, p. 124-125. 

Original description.-"Shell small; beaks nearly central, rather 

inconspicuous; angle of dorsal slopes fairly low, almost equal; both 

dorsal slopes straight and nearly equal in length. Posterior end 

acutely rostrate; anterior end regularly rounded. Lunule lanceolate, 

narrow and not very long; escutcheon elongate-lanceolate, reaching over two-thirds the length of the posterior dorsal edge, slightly 

pouting. Surface of shell covered by regular, well-marked concentric 

lines." 

Holotype.-VCMP 11167. 

Type locality.-VC 1131. Contra Costa County, Calif. San Ramon 

Sandstone, Miocene(?). 

Comments.-Concentric ridges are preserved near the ventral 

margin of the holotype. 

Geographic range.-Middle California. 

Geologic range.-Miocene(?). 

Occurrence in California.-San Ramon Sandstone. 
A22 PALEONTOLOGY OF CALIFORNIA AND BAJA CALIFORNIA 

Subgenus THESTYLEDA Iredale 1929 

Posterior end drawn out into a spoutlike rostrum; strong concentric sculpture that curves at rostral sinus. Posterior end truncate, 

commonly with a keel at inflection of concentric ribs; chondrophore 

large. 

Geographic range.-Western America. 

Geologic range.-Pliocene through Holocene. 

Nuculana (Thestyleda) hamata (Carpenter) 

Plate 2, figures 37, 38 

Leda hamata Carpenter, 1846b, p. 612, 644. 

Nuculana (Thestyleda) hamata (Carpenter). Palmer, 1958, p. 61-62, 

pl. 2, figs. 4-6. 

Original description.-"Santa Barbara; Cat. Is., 20-60 fms.; 

common. Like Steenstrupi and pernuloides, but very hooked, 

sculpture strong. 20-60 fm. c.Cp. ,, 

Lectotype.-USNM 107420 (Palmer, 1958, p. 62). 

Type locality.-Catalina Island, southern California, 35-110 m. 

Holocene. 

Supplementary description.-"The long posterior rostrum is 

squarely cut off at the end, and the shell is strongly concentrically 

sculptured." (Keen, 1971, p. 31) 

Geographic range.-Living: Puget Sound, Wash., to Baja California Sur; fossil: southern California. 

Geologic range.-Pliocene through Holocene. 

Occurrence in California.-Pliocene: Niguel Formation (J. G. 

Vedder, written commun., 1978); Pliocene and Pleistocene: 

Fernando (Moody, 1916) and San Pedro (Arnold, 1903) Formations. 

Habitat.-35 to 1,490 m, in mud and sand. . 

Genus LEDINA Dall, 1898 

Ends of shell evenly rounded, valves smooth, equilateral.. 

Geographic range.-North America. 

Geologic range.-Paleocene and Eocene. 

Ledina duttonae (Vokes) 

Plate 3, figure 3 

Jupiteria (Ledina) duttonae Vokes, 1939, p. 44-45, pl. 1, fig. 6 

Original description.-"Shell small, elongate, subtrigonal, moderately inflated; umbos central, high, prominent; anterior, posterior, 

and ventral margins broadly and regularly rounded; slightly 

rostrate posteriorly with the rostrum barely ridged; lunule and 

escutcheon prominent, long, narrow, high, smooth, set off from the 

rest of the shell by a shallow groove; surface sculptured by fine, 

regularly spaced, concentric striae, nine to the one mm. interval on 

the center of the valve; hinge consisting of a slightly convex 

anterior and a slightly concave posterior series of chevron-shaped 

teeth." 

Holotype.-UCMP 15564. 

Type locality.-UC 1817. Fresno County, Calif. Cerros Shale 

Member of the Lodo Formation, Paleocene and Eocene. 

Comparison.-This unique little species is not likely to be confused with any previously described from the Western American 

Eocene. The high, centrally located umbos and the broad, rounded 

shape are distinctive. (Vokes, 1939, p. 44) 

Comments.-The very high, central umbos are indeed distinctive, 

but this form is not as strongly inflated or corbuloid in shape as 

Jupiteria. 

Geographic range.-Middle California. 

Geologic range.-Paleocene to Eocene. 

Occurrence in California.-Paleocene: Cerros Shale Member of 

the Lodo Formation (Keen and Bentson, 1944) 

Ledina fresnoensis (Dickerson) 

Plate 3, figures 4, 5 

Leda fresnoensis Dickerson, 1916, p. 483, pl. 36, figs. 2a, 2b. 

Calorhadia (Litorhadia) {resnoensis (Dickerson). Vokes, 1939, 

p. 43-44, pl. 1, fig. 5 

Ledina fresnoensis (Dickerson). Givens, 1974, p. 39-40, pl. 1, fig. 2. 

Original description."Shell long, rather robust for this genus; 

beak prominent and situated two-fifths of the length from the 

anterior end. Anterior dorsal margin straight with moderate slope; 

the posterior dorsal margin slightly concave with a gentle slope to 

a narrowly rounded rostrum; posterior end, narrowly rounded; 

ventral margin, broadly convex. Very fine growth lines decorate 

the shell. Dimensions.-Height of broken specimen, the type, 13 

mm.; length, 22 mm." 

Holotype.-UCMP 11790. 

Type locality.-DC 1817. Fresno County, Calif. Lodo Formation, 

Paleocene and Eocene. 

Supplementary description.-"The hinge of this species is that 

oftypical Calorhadia; the anterior tooth-row is the shorter, containing 18+ chevron-shaped, narrow teeth, smaller near the umbo; the 

posterior row has 24 chevron-shaped teeth which are smaller near 

the beak but more robust than the teeth of the anterior row. The 

ligamenta} pit is trigonal in shape, moderately wide and symmetrically placed between the two rows of teeth. The impressed lunule is 

wide and long, extending to the anterior dorsal extremity; the 

escutcheon is wide and long and extends to the posterior dorsal 

extremity, being divided by a diagonal ridge from beneath the 

umbos to the posterior dorsal edge near the posterior end." (Vokes, 

1939, p. 44) 

"This species is referred to Ledina on the basis of its nearly 

smooth shell, equilateral shape, and evenly rounded anterior and 

posterior margins." (Givens, 1974, p. 40) 

Geographic range.-Southern Oregon to southern California. 

Geologic range.-Paleocene and Eocene: "Capay" to "Domengine" megafossil Stages (Givens, 1974, p. 40) 

Occurrence in California.-Paleocene: Cerros Shale Member of 

the Lodo (Keen and Bentson, 1944) and Meganos (Clark, 1921) 

Formations; Eocene: Capay and Juncal (in Turritella uuasana 

infera fauna, Givens, 1974) Formations and lower part of Uajas 

Formation. 

Genus HILGARDIA Harris and Palmer, 1946 

Shell with radial ribs intersecting concentric sculpture as crenulations and nodes. 

Geographic range.-North America. Nuculana (Hilgardia) multilineata (Conrad), the type species of the genus Hilgardia, occurs in 

the Eocene of Mississippi, Louisiana, and Arkansas. Hilgardia has 

not been reported from the Tertiary of the Western United States. 

Geologic range.-Eocene (table 2). 

Genus HILGARDIA? 

Hilgardia? parkei (Anderson and Hanna) 

Plate 3, figures 6, 7 

Leda parkei Anderson and Hanna, 1925, p. 179-180, pl. 2, figs. 10, 

11. 

Nuculana (Saccella) parkei (Anderson and Hanna). Givens, 1974, 

p. 39. 
TERTIARY MARINE PELECYPODS: NUCULIDAE THROUGH MALLEIDAE A23 

Original description.-"Shell sculptured with· uneven lines of 

growth, and therefore without the regular concentric ornamentation usually found in members of this genus; anterior end and 

basal margin gently rounded; posterior dorsal slope concave, 

bounded by an impressed area which is relieved by small sharp 

ridges, and crossed by distinct concentric sculpturing. The posterior 

dorsal margin and the basal margin meet in a sharp angle and 

point." 

Holotype.-CAS 782. . 

Type locality.-CAS 244. Kern County, Calif. Tejon Formation, 

Eocene. 

Comparison.-"The irregular sculpture and peculiar posterior 

slope distinguish this species from any other known to us. Only 

two specimens were found." (Anderson and Hanna, 1925, p. 180) 

Hilgardia? parkei is distinguished from Hilgardia? parkei 

coosensis (Turner) by having a third intercalated umbonal line 

(Turner, 1938, p. 42, pl. 5, fig. 5). 

Comments.-Hilgardia? parkei is higher in proportion to its 

length and not as coarsely or regularly sculptured concentrically 

as H.? parkei coosensis. The escutcheonal ridges of H.? parkei are 

slightly nodose. 

Geographic range.-Southern California. 

Geologic range.-Eocene. 

Occurrence in Cali{ornia.-Domengine Sandstone (M.A. Hanna, 

1927), Juncal Formation (in Turritella uvasana infera and T. 

uvasana applinae faunas, "Capay" to "Tejon" megafossil Stages, 

Givens, 1974), La Jolla Group, Poway Group, and type Tejon 

Formation (M.A. Hanna, 1927). 

Hilgardia? parkei coosensis (Turner) 

Plate, 3, figure 8 

Nuculana parkei (Anderson and Hanna), subsp. coosensis Turner, 

193~p.4~pl.~fig.5 

Calorhadia? parkei coosensis (Turner). Stewart, 1946, table 1 (in 

pocket). 

Original description.-"Shell small, elongate; beaks low, subcentral; anterior dorsal margin sloping; anterior sharply rounded; 

ventral margin gently convex; posterior extremity acute; posterior 

dorsal margin concave; ornamented by two posterior umbonal 

ridges, the upper terminating at the posterior extremity, and heavy 

concentric ribbing." 

Holotype.-UCMP 33205. 

Type locality.-UC A-838. Coos County, Oreg. Lower part of 

Umpqua Formation, Eocene. 

Comparison.-Hilgardia? parkei coosensis does not have the 

third intercalated umbonal line that distinguishes Hilgardia? 

parkei. (Turner, 1938, p. 42) [See also Nuculana (Saccella) chaneyi.] 

Comments.-The very heavy concentric ribs that continue across 

the posterior depressed area are distinctive. 

Geographic range.-Southern Oregon to middle California. 

Geologic range.-Eocene. 

Occurrence in California.-A venal Sandstone (Stewart, 1946). 

Genus LITORHADIA Stewart, 1930 

Shell with shape of Nuculana but hinge of Calorhadia; with 

wide ligamenta} pit. 

Geologic range.-Eocene to Miocene (table 2). 

Litorhadia astoriana (Henderson) 

Plate 3, figure 9 

Nucula impressa Conrad, 1849, p. 726, atlas pl. 18, figs. 7a-7c. 

Yoldia (Portlandia) astoriana Henderson, 1920, p. 122, new name 

for Nucula impressa Conrad. NotNucula impressa J. Sowerby, 

1824. 

Litorhadia astoriana (Henderson). Moore, 1963, p. 56, pl. 12, figs. 

11, 14, 17, 21 [see for synonymy]. 

Original description.-"Oblong ovate, convex, with regular concentric impressed lines. Anterior extremity rostrate, slightly recurved, extremity truncated; ligament margin arcuate, slightly 

declining; rounded behind. Beaks submedial. Basal margin arcuate, slightly contracted near the anterior extremity. Astoria, Oreg. 

(Length 1 inch; breadth very nearly half an inch. Apical angle 

155° to 160°. The fine lines of the surface are neat, but closely 

crowded)." 

Lectotype.-USNM 3490 (Grant and Gale, 1931, pl. 32, fig. 46). 

Type locality.-Astoria, Columbia County, Oreg. Astoria Formation, Miocene. 

Supplementary description.-"The lectotype of Litorhadia as toriana (USNM 3490) is a double-valved specimen with the valves 

together and hinged but not completely closed. The shell of the 

right valve is broken along the ventral margin and covered by 

matrix at the posterior margin; only small patches of the original 

shell remain on the left valve. The anterior end is rounded, the 

posterior end is pointed and abruptly terminated; the beaks are 

slightly anterior of the middle of the shell. The lunule is long, 

incised, and flat; the escutcheon is wide, long, and deeply impressed, and the shell is produced at the dorsal margin within the 

escutcheonal area. There are concentric grooves on the shell 

separated by slight ridges. These grooves are particularly noticeable on the middle of the shell and near the ventral margins, but 

they seem to be missing from the umbonal area and the anterior 

and posterior ends of the shell. The type specimen is more than 

18.9 mm long (posterior end covered), more than 9 mm high 

(ventral margin broken), and 6.7 mm wide***." (Moore, 1963, p. 56) 

Geographic range.-Oregon to southern California. 

Geologic range.-Eocene to Miocene. 

Occurrence in California.-Eocene and Oligocene: San Lorenzo 

Formation (Arnold, 1906); Oligocene and Miocene: Temblor (Loel 

and Corey, 1932) and Vaqueros (Arnold, 1909) Formations; Miocene: Monterey Formation (Arnold, 1908). 

Genus YOLDIA Moller, 1842 

Somewhat similar to Nuculana but with thinner, subovate shell, 

slightly rostrate, usually gaping posteriorly; exteriorly sculptured 

by growth lines on concentric striae; hinge consists of two subequal 

series of small chevron-shaped teeth; resilifer large, symmetrically 

underlapping both rows of teeth; pallial sinus deep and wide, the 

apex broadly U-shaped. 

Geologic range.-Cretaceous through Holocene (table 2). 

Habitat.-Chiefly in boreal and temperate waters from 0 to 5,300 

m; common in shallow water in the north Pacific; burrows vertically. 

Subgenus YOLDIA? 

Yoldia (Yoldia?) temblorensis Anderson and Martin 

Plate 4, figure 14 

Yoldia temblorensis Anderson and Martin, 1914, p. 54, pl. 3, fig. 3. 

Original description.-"Shell small, oblong ovate, thin, arcuate 

on lower margin, nearly straight above; beaks central, inconspicuous; hinge margin bent only six degrees from a straight line; 

anterior end well rounded; posterior end rostrate, almost pointed, 

slightly open, angulated by an impressed line extending from the 
A24 PALEONTOLOGY OF CALIFORNIA AND BAJA CALIFORNIA 

beaks downward to the posterior end below the siphonal opening; 

anterior end similarly crossed by an impressed zone extending 

from the beaks obliquely downward and forward; surface sculptured by regular lines of growth." 

Holotype.-CAS 106 

Type locality.-CAS 68. Kern County, Calif. Round Mountain 

Silt, Miocene. 

Comments.-The very straight anterior dorsal margin distinguishes this form. 

Geographic range.-Western Washington, middle and southern 

California. 

Geologic range.-Miocene. 

Occurrence in California.-Monterey Formation, Olcese Sand 

(Addicott, 1956), Round Mountain Silt (Keen, 1943), Sobrante 

Sandstone, and Temblor Formation (Adegoke, 1969). 

Subgenus KALAYOLDIA Grant and Gale, 1931 

Posterior part of valves short, narrowed, recurved; strongly 

oblique resilifers, very deep pallial sinus; strong concentric sculpture. 

Geologic range.-Eocene to Holocene (table 2). 

Habitat.-Kalayoldia is restricted to western North America. 

The single living species, Yoldia (Kalayoldia) cooperii Gabb, ranges 

from middle California to Baja California Norte and Mexico, at 

depths of 10 to 25 mm. 

Yoldia (Kalayoldia) tenuissima Clark 

Plate 3, figure 10 

"Yoldia cooperii Gabb," ofGabb, 1869, p. 31, pl. 9, fig. 4. Not Yoldia 

cooperii Gabb, 1865, p. 189. 

Yoldia cooperi tenuissima Clark, 1918, p. 125-126, pl. 11, fig. 10; pl. 

12, figs. 8, 14. 

Yoldia (Kalayoldia) tenuissima Clark. Hickman, 1969, p. 32-33, pl. 

1, fig. 18. Addicott, 1973, p. 22-23, pl. 1, figs. 2, 3, 5, 8. 

Original description.-"This variety differs from the species Y. 

cooperi Gabb principally in that the distance from the beak to the 

anterior end is shorter in proportion to the length of the shell; also 

there is a less number of teeth in the hinge plate; in other respects 

the species and the variety are very similar. This difference, 

however, appears to be constant and when better and more 

specimens of the variety are obtained it may be found that the 

variety should be listed as a distinct species." 

Holotype.-UCMP 11110. 

Type locality.-UC 798. [No locality data available.] Lat 37.2° 

N., long 122.1 o W., San Ramon Sandstone, Miocene(?) (Addicott, 

1973, p. 23). 

Geographic range.-Washington to southern California. 

Geologic range.-Eocene to Miocene. 

Occurrence in California.-Eocene and Oligocene: San Emigdio 

Formation (DeLise, 1967), San Lorenzo Formation (Clark, 1925); 

Oligocene: upper part of Gaviota Formation of Weaver and Kleinpell (1963), Wygal Sandstone Member, Temblor Formation (Addicott, 1973); Miocene: Gould Shale Member, Monterey Formation 

(Addicott, 1972), Olcese Sand (Addicott, 1956), Round Mountain 

Silt (Addicott, 1973); Miocene(?): San Ramon Sandstone (Weaver, 

1953). 

Yoldia (Kalayoldia) oregona (Shumard) 

Plate 3, figures 11, 12 

Leda oregona Shumard, 1858, p. 121-122 (reprinted in Dall, 1909, p. 

187). 

Yoldia (Portlandia) oregona (Shumard). Weaver, 1942, p. 49, pl. 9, 

figs. 8, 16. 

Yoldia (Kalayoldia) oregona (Shumard). Trumbull, 1958, p. 900-901, 

pl. 115, figs. 2, 3. Hickman, 1969, p. 31-32, pl. 1, figs. 14, 15. 

Original description.-"Shell rather large, ovate, compressed, 

convex; anterior extremity strongly arched; posterior extremity 

rostrate, slightly recurved, truncated; basal margin forming a 

broad curve, slightly contracted near the posterior extremity; 

ligament margin slightly concave; beaks situated a little in advance 

of the middle; surface neatly ornamented with regular, concentric, 

impressed lines, becoming more approximate above; hinge with a 

line of closely set oblique teeth on each side ofthe beak. Length 20 

lines; height, 10 lines." 

Lectotype.-USNM 562470 (Trumbull, 1958, p. 900). 

Type locality.-A few kilometers south of Oregon City, Oreg. 

Scappoose(?) Formation, Oligocene and Miocene. 

Supplementary description.-"The lectotype of Yoldia (Kalayoldia) oregona is of moderate size, slightly inflated, and the 

impression shows faint traces of concentric lines. The umbos are 

slightly anterior to the middle of the shell. The anterior end is 

evenly rounded; the posterior end is attenuated and recurved. The 

posterior hinge line is concave and consists of about 20 teeth; the 

anterior hinge line, which is convex, of about 25 teeth." (Trumbull, 

1958, p. 900). 

Comparisons.- "Y. oregona is easily distinguished from other 

Tertiary nuculid taxodonts. Its closest relative is probably the 

Recent species Y. cooperi Gabb of the southern California coast. 

The beaks of Y. cooperi are much more posterior in their placement, 

and hence the rostrum is shorter. Consequently the anterior dorsal 

margin has a much more prominent convex curve. Y. tenuissima 

Clark has a rostrum intermediate in length between that of Y. 

oregona and Y. cooperi, although it is probably more closely 

related to Y. cooperi." (Hickm_an, 1969, p. 32) 

Geographic range.-Alaska to southern California. 

Geologic range.-Oligocene and Miocene. 

Occurrence in California.-Miocene: Temblor "Horizon" (Loel 

and Corey, 1932) and Round Mountain Silt (Keen, 1943). 

Yoldia (Kalayoldia) submontereyensis Arnold 

Plate 3, figure 13 

Yoldia submontereyensis Arnold, 1908, p. 376-377, pl. 34, fig. 8. 

Original description.-"Shell attaining a length of 32 mm., 

width about two-thirds of length, oblong, rounded in front, somewhat attenuated, angular, and slightly gaping behind, compressed; 

margin smooth; umbo central; anterior dorsal margin nearly 

straight, anterior extremity broad and evenly rounded; posterior 

dorsal margin concave, curving upward at posterior extremity, but 

not prominently excavated immediately in rear of umbo; basal 

margin curving up sharply behind and meeting dorsal margin in a 

right angle, although the extreme end is slightly posterior to the 

angle; a faint carina, separated from dorsal margin by impressed 

line or lunule, extends from umbo to posterior extremity; surface 

sculptured by numerous regular, narrow, incremental lamellae, 

which are abruptly truncated on the edge toward the umbo, slope 

off gently on the side toward the periphery, and become narrower 

posteriorly." 

Holotype.-USNM 165459. 

Type locality.-On San Francisquito Creek [below dam], 0.4 km 

below its confluence with Los Trancos Creek, Santa Cruz quadrangle [on San Mateo County line, 2 km southwest of Stanford 

University, Palo Alto quadrangle], California. Unnamed Miocene 

sandstone of Dibblee (1966). 

Comparison.- Yoldia submontereyensis is closely allied to "Nucu-
TERTIARY MARINE PELECYPODS: NUCULIDAE THROUGH MALLEIDAE A25 

lana" whitmani Dall from the Miocene and Pliocene of Oregon but 

differs from it by being less attenuate posteriorly and broader in 

outline; the excavation behind the umbo in "N." whitmani Dall is 

also more pronounced. Yoldia submontereyensis is smaller and 

less attenuated posteriorly than Y. oregona Shumard; is much 

smaller and much longer, but narrower posteriorly, than Y. cooperi 

Gabb; is much larger, broader and more closely sculptured than Y. 

impressa Conrad; is shorter and broader at the posterior end than 

Y. supramontereyensis. (Arnold, 1908, p. 376-377) 

Geographic ranges.-Middle and southern California. 

Geologic ranges.-Miocene. 

Occurrence in Cali{ornia.-Upper part of Temblor Formation 

(Loel and Corey, 1932); unnamed Miocene sandstone near Stanford 

University of Dibblee (1966). 

Yoldia (Kalayoldia) supramontereyensis Arnold 

Plate 3, figure 14 

Yoldiu supramontereyensis Arnold, 1908, p. 382, pl. 35, fig. 9. 

Addicott, 1976a, p. 27, pl. 3, figs. 7, 15. Addicott and others, 

1978, p. 58, pl. 1, fig. 5. 

Yoldia cooperii supramontereyensis Arnold. Stewart, 1930, p. 62-64, 

pl. 15, fig. 2. 

Original description.-"Shell attaining a length of 32 mm., 

width about two-thirds length, oblong, rounded in front, somewhat 

attenuated, angular and slightly gaping behind, compressed; margin smooth; umbo not prominent, curving backward, anterior, 

being about 48 percent of the length of the shell from the exterior 

extremity; anterior dorsal margin slightly convex, anterior extremity quite evenly rounded; posterior dorsal margin slightly concave 

and turned up at the extremity, meeting the ventral margin in a 

right angle slightly above and anterior to the curved extremity; a 

very faint carina, separated from the dorsal margin by a faint 

groove, extends from the umbo to the posterior extremity. Surface 

sculptured by numerous, regular, narrow, incremental lamellae, as 

in Y. submontereyensis"'**. Hinge and teeth similar in a general 

way to Y. coo peri." 

Holotype.-CASISU 5362 (Keen and Bentson, 1944, p. 122). 

Type locality.-Tusk Gully, near road, 4 km south of Mayfield 

[now part of Palo Alto] near Stanford University, Santa Cruz 

quadrangle, Santa Clara County, Calif. Unnamed Miocene sandstone of Dibblee (1966). 

Comparison.-"¥. supramontereyensis is closely allied to Y. 

submontereyensis"'"""but is easily distinguishable by its long posterior extremity." (Arnold, 1908, p. 382) 

"The beaks tend to be situated medially which permits this 

species to be differentiated from""""' Y. tenuissima Clark." (Addicott, 

1976a, p. 27) 

Geographic range.-Washington and middle and southern California. 

Geologic range.-Miocene. The record of Yoldia supramontereyensis in the Clallam Formation, Washington, "constitutes a 

range extension into the provincial lower Miocene; the holotype is 

from the unnamed sandstone of Dibblee (1966) which overlies the 

Page Mill Basalt that has been dated as 14.4±2.4 m.y. (Turner, 

1970, p. 106). Benthonic foraminifers from this sandstone are of 

provincial middle Miocene (Relizian or Luisian) age (Clark, 1968, 

p. 177)." (Addicott, 1976a, p. 27) 

Occurrence in California.-Hambre Sandstone (Hall, 1958), 

Monterey Formation (Lutz, 1951; Addicott and others, 1978), 

Oursan Sandstone, San Ramon Sandstone (Weaver, 1953), Sobrante Sandstone (Lutz, 1951), and Temblor Formation (Stewart, 1946); 

unnamed sandstone near Stanford University of Dibblee (1966). 

Yoldia (Kalayoldia) cooperii Gabb 

Plate 3, figures 19, 20 

Yoldia cooperii Gabb, 1865, p. 189. Gabb, 1866, p. 31 (in part), pl. 9, 

fig. 54. 

Yoldia (Kalayoldia) cf. Y. (K.) cooperi Gabb. Hertlein and Grant, 

1972, p. 151-152 [See for synonymy]. 

Original description.-"Shell thin, somewhat compressed, very 

inequilateral, beaks placed about a third of the length from the 

anterior end, minute; anterior end narrow, sub-acuminate, posterior 

end broadly rounded; base most prominent just posterior to the 

middle of the shell; surface sculptured by numerous small concentric ribs, rarely dichotomous or anastomosing on the widest part of 

the shell; these ribs are flat and abruptly truncated on the side 

nearest the beak, giving the surface, under a glass, the appearance 

of an overlapping. Epidermis shining, olivaceous; internally a 

bluish white; muscular scars large, the anterior triangular, posterior a third the largest, broadly suboval. Long. 1.25, lat. 2.6, alt .. 25 

[inches]." 

Holotype.-UCMP 30613. 

Type locality.-"A single left valve was found on the beach at 

Santa Cruz, Cal., by Dr. Cooper." Santa Cruz County, Calif., 

Holocene. 

Supplementary description.-"Shelllarge, ***greatest height (distance between dorsal and ventral margins) anterior to the median 

line of the shell and far anterior to the umbones; anterior portion of 

valves broadly, evenly curved; posterior portion attenuated, produced into a rostrum concavely curved on its dorsal margin; 

posterior dorsal area somewhat depressed, definitely set off from 

adjacent surface ofvalves;***anterior dorsal margin curving gently 

into the regular anterior curve. Hinge a long, gently curving, 

anterior row of rather long, somewhat upcurved teeth, chevronshaped at their bases, a depressed, somewhat roundly-trigonal 

ligament pit, and a short, slight-curved anterior [sic: posterior] row 

of teeth. Pallial sinus deep, u-shaped. Sculpture of concentric 

lamellae, occasionally slightly irregular in respect to incremental 

lines on portions of the valve but not regularly oblique. A large 

Recent specimen from Santa Cruz, California, in the Stanford 

collection, measures as follows: Total length, 76 mm.; umbo to end 

of rostrum 26 mm.; umbo to anterior margin of valve, 53 mm.; 

height (greatest dorsal-ventral distance), 37 mm.; thickness of one 

valve, about 7 mm." (Grant and Gale, 1931, p. 128) 

Comparison.-"Compared to Yoldia oregonensis Conrad***the 

beaks of Y. cooperii are more posteriorly situated and the rostrum 

is shorter. 

"Yoldia supramontereyensis Arnold*"'"'is less attenuated posteriorly than typical Y. cooperii. 

"Yoldia cooperii tenuissima Clark"'"'"'has the beak more anteriorly 

situated and a longer rostrum than Y. cooperii." (Hertlein and 

Grant, 1972, p. 152) 

Geographic range.-Living: from Point Reyes, Calif., to Todos 

Santos Bay, Baja California Sur; fossil: middle and southern 

California. 

Geologic range.-Miocene through Holocene. 

Occurrence in Cali{ornia.-Miocene: Briones Sandstone (Weaver, 

1953; Hall, 1958), San Pablo (Smith, 1912), Santa Margarita 

(Smith, 1912), and upper part of Temblor (Loel and Corey, 1932) 

Formations; Miocene and Pliocene: Etchegoin (Nomland, 1917a), 

Purisima (Addicott, 1969), and Tahana Member, Purisima (Addicott, 1969) Formations; Pliocene and Pleistocene: Fernando (English, 1914), Merced (Glen, 1959), San Pedro (Arnold, 1903), and 

Saugus (Waterfall, 1929) Formations, and Wildcat Group (Roth, 

1979). 

Habitat.-Usually in sand, from 10 to 125m. 
A26 PALEONTOLOGY OF CALIFORNIA AND BAJA CALIFORNIA 

Subgenus KALA YOLDIA? 

\'oidia (Kalayoldia?) gesteri Dickerson 

Plate 4, figure 8 

Yoldia gesteri Dickerson, 1914, p. 124, pl. 7, fig. 5 

Original description. "Shell thin, very compressed; anterior end, 

the shorter, and equally rounded above and below; posterior end, 

slightly longer, pointed; posterior dorsal margin very slightly 

concave; escutcheon, long, narrow; base, rounded and most prominent beneath beak, from which point it curves regularly to the 

pointed, posterior end; beaks, inconspicuous; sculpture consists of 

fine, rounded concentric threads." 

Holotype.-UCMP 11685. 

Type locality.-DC 790. Lake County, Calif. Martinez Formation, 

Paleocene. 

Comparison.-"This species is not as convex as Y. cooperi Gabb 

of the Miocene, its posterior dorsal margin is not as concave as 

that of Y. cooperi, and the decoration is much finer." (Dickerson, 

1914, p. 124) 

Geographic range.-Northern California. 

Geologic range.-Paleocene. 

Occurrence in California.-Martinez Formation. 

\'oidia (Kalayoldia?) carnarosensis (Clark) 

Plate 4, figure 17 

Yoldia carnarosensis Clark, 1915, p. 446, pl. 48, fig. 6 

Original description.-"Shell medium in size, beaks low and 

inconspicuous, situated about two-thirds the distance from the 

anterior to the posterior end. Anterior dorsal edge long and very 

gently convex; posterior dorsal edge gently concave. Posterior 

extremity subtruncate to bluntly rounded, the blunt subtruncate 

end being subangulate at the junction with the posterior dorsal 

edge and indistinctly separated from the ventral edge. Surface 

sculptured by somewhat irregular incremental lines or concentric 

ribs. On the surface near the posterior end there is a distinct sulcus 

which reaches from the beak to a little below the angulation on the 

posterior end. Hinge plate unknown." 

Holotype.-UC 11539. 

Type locality.-Carneros Creek [NW 1/2, sec. 4, T. 4 N., R. 4 W.], 

Napa County, Calif. Neroly Sandstone, Miocene. 

Comparison.~ "Y. carnarosensis***somewhat resembles Y. 

cooperi Gabb, a recent West Coast species. It differs in the following 

respects: the posterior end is not so attenuated, the concentric 

ribbing is ·not so regular, the distinct sulcus on the posterior 

extremity is lacking on Y. cooperi." (Clark, 1915, p. 446). 

Comments.-The bluntly rounded posterior end of this form is 

distinctive. 

Geographic range.-Middle California. 

Geologic range.'-Miocene. 

Occurrence in California.-Briones, Cierbo, and Neroly Sand-· 

stones (Hall, 1958). 

Subgenus MEGA YOLDIA Verrill and Bush, 1897 

Broad, compressed, rostrum indefinite, with posterior marginal 

lobe; resilifer large, concave, striate within; pallial sinus large; 

ligament external, strongly developed. 

Geologic range.-Oligocene through Holocene (table 2). 

Habitat.-10 to 1,900 m, in sand and mud. 

\'oidia (Megayoldia) beringiana Dall 

Plate 3, figures 15, 16 

Yoldia beringiana Dall, 1916, p. 399. 

Original description:-"Shelllarge, thin, smooth, except for lines 

of growth, brilliantly polished, inequilateral, hardly rostrate, 

rounded at each end, less compressed behind than . Y. secunda; 

color a rich yellowish brown, slightly olivaceous near the umbones; 

valves closing completely; escutcheon striated, narrower than in 

secunda; beaks very low, 24 anterior and 17 posterior teeth, the 

resilifer ample, cup-shaped, projecting. The pallial sinus is rather 

large and rounded. Length, 40; height, 22; diameter, 16 mm." 

Lectotype.-USNM 226195a. The double-valved specimen from 

the syntypic lot, one valve of which is figured herein, is here 

designated the loctotype. 

Type locality.-Bering Sea, off the Pribilof Islands, Alaska, in 

1,805 m. Holocene. 

Comparison.-Posterior end more evenly rounded and not turned 

upward as in Megayoldia thraciaeformis. 

Geographic range.-Living: Bering Sea, off Pribilof Islands, 

Alaska, to Anacapa Island, southern California; fossil: southern 

California. 

Geologic range.-Pliocene through Holocene. 

Occurrence in California.-Pliocene and Pleistocene: Pico Formation (Winterer and Durham, 1958). 

Habitat.-280 to 1,905 m, in sand and mud. 

\'oidia (Megayoldia) thraciaeformis (Storer) 

Plate 3, figures 17, 18 

Nucula thraciaeformis Storer, 1838, p. 122, text fig. 

Yoldia thraciaeformis (Storer). Oldroyd, 1924, p. 27, pl. 5, fig. 1. 

Grant and Gale, 1931, p. 127-128, pl. 1, figs. 12a, 12b. 

Yoldia (Megayoldia) thraciaeformis (Storer). Abbott, 1974, p. 418. 

Original description.-"Shell ovate, transverse, equivalve, inflated, gaping at both extremities, with numerous, very distinct, 

concentric lines of increment, covered with a yellowish-green, 

polished epidermis in young specimens, concealed under a black 

pigment, which readily rubs off in the recent specimen, giving a 

sooty appearance to the fingers. In the adult shell the epidermis is 

rather a dirty brown. Beaks slightly prominent over hinge margin. 

An obtuse angle, more elevated and wider at its lower half, runs 

obliquely from the umbones to the posterior base of the shell, 

serving as a boundary to the anterior inflated portion. Posterior 

portion of the shell much compressed, its epidermis is of a lighter 

color, and the striae of increase are much more apparent, than 

upon the anterior portion. Anterior margin rounded; posterior 

somewhat truncated. Within perlaceous. Teeth, numerous and 

peculiar; those contiguous to hinge, small, those farther removed 

from fosset, very strong, sharp, angulated, higher than wide; the 

teeth of one valve shutting very closely into the excavated teeth of 

the opposite valve, form a very powerful hinge. Length, 57; height, 

35mm." 

Holotype.-BM(NH). 

Type locality.-OffPoint Race, Atlantic [presumably Race Point, 

Mass.]. Holocene. 

Supplementary description.-3. 7 to 5.0 em in length, oblong. 

Characterized by its squarish, upturned posterior end; large circular 

chondrophore; and the coarse, oblique rib running from beak to 

posterior ventral margin. (Abbott, 1974, p. 418.) 

Geographic range.-Living: Greenland tCl South Carolina, Alaska 

to Puget Sound, Wash.; fossil: Alaska and middle California, 
TERTIARY MARINE PELECYPODS: NUCULIDAE THROUGH MALLEIDAE A27 

Pliocene; Japan, Oligocene to Pliocene (Masuda and Noda, 1976); 

possibly also in Kamchatka, USSR. 

Geologic range.-Oligocene through Holocene. 

Occurrence in California.-Miocene and Pliocene: Tahana Member of Purisima Formation (Addicott, 1969); Pliocene: Pomponio 

Mudstone Member of Purisima Formation (Cummings and others, 

1962). 

Habitat.-65 to 90 m; also found in fish stomachs. 

Subgenus CNESTERIUJ\f Dall, 1898 

With oblique secondary incised sculpture, especially on anterior 

end. 

Geographic range.-Living: eastern Pacific and Japan; fossil: 

Japan, Sakhalin Island, USSR, and west coast of the United 

States. 

Geologic range.-Miocene through Holocene. 

Habitat.-At depths of 15 to 250 m in mud and fine and coarse 

sand; common in fish stomachs off Pacific Grove, Calif. 

\'oidia (Cncstcrium) strigata Dall 

Plate 4, figure 3 

Yoldia (Cnesterium) strigata Dall, 1909, p. 104-105, pl. 14, figs. 9, 

9a. 

Yoldia scissurata Dall var. strigata Dall. Weaver, 1942, p. 51, pl. 9, 

figs. 14, 20. 

Not Yoldia scissurata strigata Dall. Faustman, 1964, p. 114. 

Original description.-"Shell thin, compressed, equivalve, inequilateral, polished; anterior end longer, equally arcuate above and 

below, anteriorly somewhat attenuated; posterior end a little 

shorter, subtruncate, slightly recurved, dorsal slope slightly concave, with the apposed margins compressed and projecting in the 

middle of the narrow escutcheon; lunule linear or nearly so; 

tuncate end a little concavely flexuous; posterior basal margin 

evenly convexly arcuate; base a little prominent toward the middle; 

beaks inconspicuous, flattish, not raised above the general arch of 

the dorsum; surface smooth except for obscure incremental lines, 

and numerous sharp, slightly elevated, somewhat flexuous, oblique, 

distant ridges with the long slope extending basally and the short 

slope abrupt and almost undercut; these ridges vary slightly. in 

individuals but in general cover the sides of the shell nearly to the 

beaks, and are usually obsolete on the anterior dorsal areas and on 

the rostrum; the shell gets proportionately broader, vertically, with 

age. Longitude of figured specimen, 37 mm.; altitude, 19.5 mm.; 

diameter, 5.5 mm. An older but less perfect individual measures, 

longitude, 43.5 mm.; altitude, 23.0 mm.; diameter, 7.5 mm." 

Holotype.-USNM 153951. 

Type locality.-Coos Bay, Coos County, Oreg. Empire Formation, Miocene. 

Supplementary description.-"a worn specimen indicates that 

there are at least 28 anterior and 22 posterior teeth on the hinge 

margin***." (Dall, 1909, p. 104-105) 

Comparison.-"Y. scissurata Dall occurs in the lower Pleistocene 

of San Pedro, Cal.; it is a much smaller and proportionately more 

convex shell, with 20 anterior and about 14 posterior hinge 

teeth***." (Dall, 1909, p. 105) 

Yoldia strigata is characterized by a more bluntly truncated 

posterior end than in Y. scissurata and the upward bending of the 

concentric growth lines is better developed on the posterior portion 

of the shell. (Weaver, 1942, p. 51) 

Geographic range.-Alaska to northern California. 

Geologic range.-Miocene to Pleistocene. 

Occurrence in California.-Miocene and Pliocene: Tahana Memher, Purisima Formation (Durham and Morgan, 1978); Pliocene: 

Falor Formation (Manning and Ogle, 1950); Pliocene and Pleistocene: Merced Formation (Glen, 1959). 

Habitat.-The living species Yoldia scissurata occurs from the 

Arctic Ocean to San Diego, Calif., at depths of 15 to 135 m. 

\'oidia (Cncstcrium) cnsifcra Dall 

Plate 4, figure 21 

Yoldia ensifera Dall, 1897. p. 9, pl. 2, fig. 4. 

Yoldia scissurata Dall. I. S. Oldroyd, 1924, pl. 5, fig. 2. Not Yoldia 

scissuratci Dall, 1897. 

Original description.-"Shelllarge, thin compressed, with a brilliant olivaceous periostracum, usually showing darker and lighter 

zones; valves nearly equilateral, moderately convex, rostrate, subarcuate; sculpture of fine lines of growth more or less evident, and 

on the anterior two-thirds of the shell numerous irregularly fluctuating, distant, incised grooves (like those of Y. scissurata) which 

are absent on the posterior third; base, arculate, anterior dorsal 

profile rounded evenly from·the beaks; a slight inward wave of the 

margin is visible anteriorly near the pedal gape; lunule absent; the 

escutcheon impressed, and the posterior dorsal margins of the 

valves, projecting vertically, blade-like and slightly pouting; rostrum pointed, slightly recurved, beaks low, inconspicuous; valves 

internally whitish; pallial sinus deep, rounded; chondrophore wide, 

hardly projecting; teeth narrow, "A"-shaped, slender, about 30 in 

front of and 24 behind the chondrophore. Length, 35; height, 16; 

diameter, 6 mm." 

Holotype.-USNM 107644. 

Type locality.-Vancouver Island, British Columbia, 245 m. 

Holocene. 

Comparison.-All of the specimens from Vancouver Island, B. 

C., south "which hitherto had been referred to Y. scissurata Dall, 

prove on examination to belong to this species. It differs from 

scissurata in being more equilateral, in having the grooved sculpture sparser and less extended, in being more compressed and 

more pointed but less recurved behind, and in the greater length, 

height and prominence ofthe blade-like extensions of the posterior 

dorsal margin." (Dall, 1897, p. 9) [See also Yoldia scissurata.] 

Comments.-This species was placed in the synonymy of Yoldia 

scissurata Dall by Grant and Gale (1931, p. 131) and Abbott (1974, 

p. 418), but recent work by Barry Roth (1979) has led him to 

separate the two species _following MacGinitie (1959, p. 154-155). 

Geographic range.-Living: Vancouver Island, British Columbia, to San Diego, Calif.; fossil: Alaska and northern California. 

Geologic range.-Miocene (Arley, 1978); Pliocene through Holocene. 

Occurrence in California.-Pliocene: Rio Dell Formation (Roth, 

1979). 

Habitat.-55 to 245 m. 

\'oidia (Cncstcrium) scissurata Dall 

Plate 4, figures 1, 2 

Nucula arctica Broderip and Sowerby, 1829, p. 359-360, pl. 9, fig. 1, 

Not Yoldia arctica Gray, 1824. 

Yoldia scissurata Dall, 1895, p. 595, new name. Dall, 1897, p. 8, 

Arnold, 1903, p. 99-100, pl. 17, fig. 13. Not I. S. Oldroyd, 1924, 

pl. 5, fig. 2. 

Original description.-"N. testa oblanga, postice subrostrata, 

antice subrotundata; epidermide crassa, olivacea; valvis striatis, 

striis obliquis lineas incrementi decussantibus; long. 1 5/8, alt. 6/8, 

lat. 7/16, poll." 
A28 PALEONTOLOGY OF CALIFORNIA AND BAJA CALIFORNIA 

Holotype.-Location unknown. 

Type locality.-"Hab. in Oceano Arctico." "Two or three specimens were obtained in Vatcha Bay, Kamtschatka." [Vatyna Bay, 

Kamchatka] 

Supplementary description.-"One of the largest of the 

Nuculae***. It is of an oblong shape, the anterior being longer 

than the posterior side; it is covered with a strong, shining 

olivaceous epidermis: the anterior side is somewhat rounded, and 

the posterior produced into a slightly recurved beak. The surface of 

each valve is covered with delicate concentric lines of growth, 

which are crossed on the central part, and towards the posterior 

side of the valves by stronger oblique striae. When the valves are 

closed, the upper posterior edge forms a sharp elevated ridge. The 

oblique striae are distinct on the epidermis as well as on the shell." 

(Broderip and Sowerby, 1829, p. 360) 

"Shell rather small, oval***very thin, translucent, only slightly 

narrowed posteriorly; umbones minute, slightly anterior to middle, 

the anterior margin is evenly convex; a thin lamina runs along the 

anterior margin from the umbo to the end of the shell; a much 

narrower one also occurs on the posterior margin; surface sculptured concentrically as in Y. cooperi except that this incised 

sculpture is not in harmony with the incremental lines; hinge and 

teeth similar to Y. coo peri." (Arnold, 1903, p. 99-100) 

Comparison.- Yoldia ensi{era "differs from scissurata in being 

more equilateral, in having the grooved sculpture sparser and less 

extended, in being more compressed and more pointed but less 

recurved behind, and in the greater length, height and prominence 

of the blade-like extension of the posterior dorsal margin." (Dall, 

1897, p. 9) 

"Y. scissurata is higher anteriorly and is proportionately longer 

from the umbos to the anterior end and proportionately shorter 

from the umbos to the posterior end than Y. ensi{era. The posterior 

dorsal blades of the valves are longer and much higher in Y. 

ensi{era than in Y. scissurata, so that a line from the beaks to the 

end of the rostrum always cuts across the blades in Y. ensifera but 

seldom does in Y. scissurata. The rostrum is more upturned in. Y. 

scissurata. Even in specimens only 5 to 10 mm. long, these 

differences are apparent and consistent." (MacGinitie, 1959, p. 

154-155) 

Comments.-The specimen figured (pl. 4, figs. 1, 2) is one that 

was apparently handled by Dall (Joseph Rosewater, written commun., 1978). 

Geographic range.-Living: Arctic Ocean to Monterey Bay, 

Calif.?; V atyna Bay, Kamchatka; fossil: California. 

Geologic range.-Miocene through Holocene. 

Occurrence in California.-Miocene and Pliocene: Purisima Formation (Arnold, 1906); Pliocene: Niguel (Vedder, 1972) and Rio Dell 

(Roth, 1979) Formations; Pliocene and Pleistocene: Fernando 

(Moody, 1916) and San Pedro (Arnold, 1903) Formations. [Some of 

the southern records may actually represent Y. ensi{era.] 

Habitat.-In coarse and fine sand and mud at depths of 15 to 255 

m; common in fish stomachs. 

Yoldia (Cnesterium) seminuda Dall 

Plate 4, figures 7, 18, 19 

Yoldia seminuda Dall, 1871, p. 153. 

Yoldia imleri Waterfall, 1929, p. 85-86, pl. 5, fig. 7. 

Yoldia scissurata strigata Dall. Faustman, 1964, p. 114. Not Yoldia 

strigata Dall, 1909. 

Original description.-"Shell obscurely lozenge-shaped, elongate, 

covered with a polished, glossy, olivaceous epidermis. Valves 

compressed, umbones inconspicuous; lunule long, narrow, just 

evident; escutcheon long, narrow, indented, well defined. Ventral 

'·t 

margin arcuated, widest about the middle of the shell; a slight 

obsolete groove or channel anteriorly bordered by two obscure 

ridges, terminates in a slight waved indentation in the anterior 

ventral margin, about the middle of the anterior fourth. Posterior 

end rising obliquely, rounded truncate posteriorly, forming an 

angle of90° with the hinge margin, and slightly upturned. Posterior 

dorsal slope concave, anterior slightly upturned. Posterior dorsal 

slope slightly concave, anterior slightly convex, evenly rounded to 

the anterior end. Ligament pit large, roundly triangular. Teeth 

(anterior) 37, (posterior) 17. Pallial sinus reaching before the 

umbones, which are 14/35 of the whole length from the posterior 

end. Interior bluish white, with fine radiating lines. Exterior 

marked by lines of growth and obsolete radiating lines; sculptured 

by sharp grooves, which, beginning near the middle of the shell 

with a slight wave toward the umbones, pass backward and 

downward across the lines of growth, rising a little and ceasing 

abruptly at a distance of about 4/35 of the whole length from the 

posterior end. Long., 1.74; alt., .82; diameter, 7.2 in." 

Holotype.-VSNM 107678; holotype of Y. imleri UCMP 31420. 

Type locality.-St. Paul's Harbor, Kodiak Island, Alaska, 30m. 

Holocene. 

Comments.-! am indebted to Barry Roth, California Academy 

of Sciences, who, during the course of his study of the fauna of the 

Wildcat Group, determined that Yoldia imleri Waterfall (pl. 4, fig. 

7) is a synonym of Y. seminuda Dall. 

Geographic range.-Living: Bering Sea to Monterey, Calif., 35 

m; fossil: northern and southern California. 

Geologic range.-Pliocene to Holocene. 

Occurrence in California.-Pliocene: Rio Dell Formation (Roth, 

1979); Pliocene and Pleistocene: Pico Formation (Waterfall, 1929). 

Habitat.-40 m off Monterey, Calif., in sand; 15 to 90 m off 

Alaska. 

Genus YOLDIA? 

Yoldia? gala Woodring 

Plate 4, figure 6 

Yoldia gala Woodring, 1950, p. 81, pl. 8, figs. 1, 2; pl. 9, figs. 9, 10. 

Original description.-"Yoldia gala***, a new species, is the 

most characteristic megafossil in the diatomaceous strata of the 

Sisquoc formation. It is moderately large, elongate, and weakly 

sculptured, the sculpture consisting of low concentric rugae of 

varying width on the ventral half or less. Though this species is 

represented by numerous well-preserved molds, the only shell 

material consists of patches on a left valve***. The sculpture is 

generally impressed on internal molds. This Yoldia is the 'Nuculana sp.' of the preliminary report on the Santa Maria district. The 

outline suggests Yoldia and the chondrophore is long and symmetrical, like that of Yoldia. It is not certain, however, that the 

chondrophore is as wide as that of Yoldia. The pallial sinus is not 

discernible on any of the fossils." · 

Holotype.-VSNM 560024. 

Type locality.-VSGS 15020. Santa Barbara County, Calif. Todos 

Santos Claystone Member of the Sisquoc Formation, Miocene and 

Pliocene. 

Comparison.- "Yoldia gala is perhaps related to Yoldia astoriana, from the Miocene Astoria formation of Oregon, but is larger 

and more elongate, its posterior end is not so abruptly upturned, 

and it evidently lacks the impressed lunule and escutcheon of Y. 

astoriana***Yoldia gala is also larger and more elongate than 

'Leda' subimpressa, from the Pliocene(?) Empire formation of 

Oregon. 'Leda' subimpressa appears to be closely related to Yoldia 

astoriana and may be the same species, as had been claimed. 
TERTIARY MARINE PELECYPODS: NUCULIDAE THROUGH MALLEIDAE A29 

Arnold's Yoldia impressa, from the Monterey shale of the Santa 

Cruz Mountains, has strong regular concentric rugae and is 

probably a Nuculana. No recent California allies of Yoldia gala are 

recognized in the U.S. National Museum collections. Y. limatula, 

which has been dredged as far south as San Diego in deep water 

(417 fathoms), has a shallow ventral notch near the anterior end of 

the shell. Northern specimens of Y. limatula are much larger than 

Y. gala, but those from British Columbia to San Diego are not 

larger***." (Woodring, 1950, p. 81) 

Geographic range. -Southern California. 

Geologic range.-Miocene and Pliocene. 

Occurrence in California.-Todos Santos Member of the Sisquoc 

Formation. 

Genus PORTLANDIA Morch, 1857 

Inflated, somewhat rostrate. 

Subgenus PORTLANDIA 

Posterior end set off by indistinct furrow. 

Geologic range.-Paleocene through Holocene. 

Habitat.-Living in boreal waters only; reported from 5 to 45 m. 

[Note that fossil species indentified as Portlandia occur in the 

Eocene of southern California.] 

Portlandia (Portlandia) mortuasusenis (Clark and Woodford) 

Plate 4, figure 15 

Yoldia mortuasusensis Clark and Woodford, 1927, p. 86, pl. 14, fig. 

3. 

Original description.-"Shell short, plump, with moderately 

prominent, strongly inturned beaks which are anterior to the 

median line; anterior dorsal margin almost straight; posterior 

dorsal edge gently concave; anterior end broadly and regularly 

rounded; posterior end narrow and bluntly rounded. Lunule apparently absent; escutcheon long, narrow, slightly depressed. Surface 

of shell smooth and glistening, marked by very fine and fairly 

numerous faint concentric incremental lines; also the internal 

layer of the shell is covered by numerous very fine radial lines 

which can be seen only with the aid of a lens. Dimensions: Length 

8.5 mm., height 5 mm., thickness of one valve about 2 mm." 

Holotype.-UCMP 31337. 

Type locality.-UC 3577. Contra Costa County, Calif. Meganos 

Formation, Paleocene. 

Supplementary description.-"The type, which is very beautifully 

preserved, is the only specimen of this species found in our 

collection." (Clark and Woodford, 1927, p. 86) 

Geographic range.-Middle California. 

Geologic range.-Paleocene. 

Occurrence in California.-Meganos Formation. 

Portlandia (Portlandia) markleyensis (Clark) 

Plate 4, figure 16 

Yoldia markleyensis Clark, 1938, p. 692, pl. 1, figs. 21, 22. 

Original description.-"Shell smooth with beaks anterior to the 

median line and strongly in turned; anterior end regularly rounded; 

posterior dorsal edge straight or nearly so; escutcheon elongatelanceolate in outline, smooth and somewhat depressed below the 

main surface of the shell; a somewhat smooth obscure lanceolate 

lunule; chrondrophore fairly large for this genus; taxodont teeth 

fairly high and peg-like, about twenty on each of the dorsal 

margins. Dimensions: holotype***30833, length 22.5 mm., height 

12.6 mm., width of both valves 7.5 mm.; paratype, right valve, 

30834, length 17.4 mm., height 10.3 mm." 

Holotype.-UCMP 30833. 

Type locality.-UC A-1297. Solano County, Calif. Markley Sandstone Member, Kreyenhagen Formation, Eocene. 

Comparison.-The only form which Portlandia markleyensis 

closely resembles is "Y." duprei (Weaver and Palmer) from the 

Cowlitz Formation (Eocene) of southwestern Washington. "Y." 

duprei differs in that it is thicker than P. markleyensis, and, 

according to the description of Weaver and Palmer, the posterior 

end joins the posterior dorsal edge in a point-apparently meaning 

an angle-whereas on P. markleyensis the two edges merge 

gradually into one another. The two species are similar in outline, 

and future work may show that P. markleyensis should be considered a subspecies of "Y." duprei. (Clark, 1938, p. 692) 

Comments.-This form has no pedal or siphonal gape and is 

moderately inflated in proportion to its size. 

Geographic range.-Middle California. 

Geologic range.-Eocene. 

Occurrence in California.-Markley Formation. 

Portlandia (Portlandia) rosa (1\f. A. Hanna) 

Plate 4, figure 9 

Leda rosa M.A. Hanna, 1927, p. 271, pl. 25, figs. 4, 6, 9, 16. 

Portlandia (Portlandia) rosa (Hanna). Givens, 1974, p. 40. 

Original description.-"Left valve; shell of medium size, moderately inflated, thin; ventral margin regularly broadly rounded; 

posterior dorsal margin nearly regularly concave to the rather 

sharply rounded rostrum; anterior dorsal margin straight to the 

broadly rounded anterior end; beak central, opisthogyrate, slightly 

anterior to the center; surface ornamented only by growth lines; no 

keel present; lunule narrow, linear; escutcheon linear, deep, wide, 

circumscribed by a ridge. Dimensions. Type: Altitude 8.5 mm., 

length 14.5 mm. Paratype 31092: Altitude 9.0 mm., length 15.5 

mm." 

"Hinge of paratype***narrow, twenty-one slightly V-shaped 

teeth present posterior to the large chondrophore, sixteen teeth 

remaining on the broken anterior portion of the hinge margin; 

interior of the shell not seen." 

Holotype.-UCMP 31090. 

Type locality.-UC 3993. San Diego County, Calif. Ardath Shale, 

Eocene. 

Supplementary description.-Portlandia rosa "is characterized 

by its wide shallow chondrophore, though it is not quite so 

extensive as shown in the original figure, for it has peen slightly 

crushed downward away from the hinge. The chondrophore also 

shows***radiating lines." (Stewart, 1930, p. 62) 

Comparison.-Portlandia rosa is closely related to P. japonica 

(Adams and Reeve), a living species, "which is so similar to it that 

it seems to be a direct descendant of the Eocene form. The posterior 

end of the Eocene species is a trifle higher, but considering the 

difference in time, they are remarkably alike." (Stewart, 1930, p. 

62) Portlandia rosa does not have as straight a dorsal margin asP. 

mosesi. 

Comments.-This species is the type of the genus Portlandella 

Stewart, (1930), now considered a synonym of Portlandia. 

Geographic range.-Southern California. 

Geologic range.-Eocene. 

Occurrence in California.-Juncal Formation in the Turritella 

uuasana applinae fauna (Givens, 1974) and the Ardath Shale 

(Hanna, 1927). 
A30 PALEONTOLOGY OF CALIFORNIA AND BAJA CALIFORNIA 

Portlandia (Portlandia) mosesi (Palmer) 

Plate 4, figure 10 

Yoldia mosesi Palmer, 1923, p. 301, pl. 55, fig. 2. 

Original description.-"Shell small, thin; beaks anterior to middle, moderately prominent. Anterior dorsal margin short, straight; 

posterior dorsal margin slightly concave just under beak but 

nearly straight, and almost in line with anterior dorsal margin. 

Anterior end broadly and regularly rounded with only a very 

slight indication of an angulation at anterior end of dorsal margin. 

Posterior end bluntly rostrate. Ventral edge gently arcuate. Shell 

slightly inflated near middle. Hinge not exposed. Surface smooth 

except for occasional irregular growth lines. Dimensions of type (a 

left valve): Length 13.9 mm.; height 8.5 mm." 

Holotype.-UCMP 30704. 

Type locality.-DC 3573. Solano County, Calif. Capay(?) Formation, Eocene. 

Comparison.-Portlandia mosesi has a straighter dorsal margin 

than Portlandia rosa. 

Geographic range.-Middle California. 

Geologic range.-Eocene(?). 

Occurrence in California.-Capay(?) Formation. 

Portlandia (Portlandia) chehalisensis (Arnold) 

Plate 4, figures 12, 13 

Malletia chehalisensis Arnold, 1908, p. 365-366, pl. 33, figs. 9, 9a. 

Portlandia (Portlandella) chehalisensis (Arnold). Hickman, 1969, 

p. 30-31, pl. 1, figs. 9, 12, 13. 

Original description.-"Shell attaining a length of 25 mm., oval, 

compressed, smooth; umbones rather inconspicuous, slightly anterior to middle, turned backward; anterior dorsal margin sloping 

straight from umbo; anterior extremity regularly rounded; posterior 

dorsal margin straight, depressed immediately in rear of umbones; 

posterior extremity above medial line, more attenuated than the 

anterior; posterior portion of base near extremity nearly straight, 

otherwise quite regularly curved. Surface smooth, except for faint 

concentric lines. Hinge consists of a row of sharp teeth flexed 

toward the umbo on each side of a prominent, projecting umbonal 

pit. Pallial sinus large and deep." 

Holotype.-USNM 165447. 

Type locality.-Porter, Chehalis County, Wash. Lincoln Creek 

Formation, Eocene to Miocene. 

Supplementary description.-"Some of the specimens of this 

species from the type locality show distinct incised concentric 

sculpturing." (Clark, 1925, p. 79) 

"Portlandia chehalisensis is a short, bluntly rostrate form with a 

relatively smooth shell. The inconspicuous and slightly opisthogyrous beaks are located slightly anterior-about 55 percent of the 

distance from the posterior end of the shell. The anterior end of the 

shell is evenly rounded, merging gradually with the broadly 

arcuate ventral margin. The posterior dorsal margin is slightly 

concave, almost forming a right angle with the abruptly truncate 

posterior margin. The ratio of length to width is about 1. 7." 

(Hickman, 1969, p. 30) 

Comparison.-[See Portlandia packardi.] 

Geographic range.-Alaska to middle California. 

Geologic range.-Eocene to Miocene. 

Occurrence in California.-Eocene and Oligocene: Rices Mudstone Member of the San Lorenzo Formation. 

Portlandia (Portlandia) packardi (Clark) 

Plate 4, figure 11 

Malletia packardi Clark, 1918, p. 125, pl. 12, fig. 3; pl. 14, figs. 5, 6. 

Yoldia (Portlandia) packardi (Clark). Clark, 1925, p. 77, pl. 9, fig. 7. 

Weaver, 1942, p. 44-45, pl. 8, figs. 33, 34. 

Original description.-"Shell rather small to medium in size; 

beaks anterior to the middle, opisthogyrous. Anterior dorsal slope 

straight; posterior dorsal slope rather strongly excavated; anterior 

end regularly rounded; posterior end regularly rounded but narrower than anterior end, the ventral margin sloping up more obliquely 

to it than to the anterior end. Surface smooth except for somewhat 

irregular incremental lines. As shown on one of the specimens 

obtained from the diatomaceous shale of the Markley formation 

(fig. 6), the escutcheon is well defined, long and narrow and 

depressed almost at right angles to the main outer surface of the 

shell. Lunule apparently absent. No well-defined chondrophore. 

Almost eighteen taxidont [Sic: taxodont] teeth posterior and about 

twenty-one anterior to the beak, the posterior and anterior rows of 

teeth meeting at the apex of the beaks." 

Holotype.-UCMP 11154. 

Type locality.-UC 2033. Contra Costa County, Calif. Kirker 

Tuff, Oligocene. 

Comparison.-Portlandia packardi bears a very close resemblance toP. chehalisensis (Arnold) but the "umbones of the former 

are situated about 40 per cent of the length of the shell from the 

anterior end while in the latter they are nearly central. The 

anterior end of the former is more evenly rounded and the posterior 

dorsal margin more deeply concave, especially just below the 

umbo." (Weaver, 1942, p. 45) 

Geographic range.-Western Washington to middle California. 

Geologic range.-Eocene to Miocene(?). 

Occurrence in California.-Eocene: Markley Sandstone Member 

of the Kreyenhagen Formation (Clark, 1918); Oligocene: Kirker 

Tuff; Miocene(?): San Ramon Sandstone (Clark, 1918). 

Family SOLEMYIDAE 

Geologic range.-Devonian through Holocene. 

Habitat.-Shallow to deep water; moves by clapping valves 

together. 

Solemya velum Say, a species living along the west Atlantic 

coast, lives in an open-ended, U-shaped burrow, in sandy mud, in 

shallow subtidal environments (Stanley, 1970, p. 120). 

Genus ACHARAX Dall, 1908 

Elongate-oval or subrectangular, compressed; umbones level 

with hinge margin, placed well toward posterior end of shell; valve 

margins with narrow anterior and posterior gapes; ligament 

wholly external, internal resilifer absent. Sculpture of irregularly 

arranged, depressed radial ribs; periostracum polished, consisting 

of radial sectors alternating in thickness and varying in width 

according to ribbing of shell; periostracum extends well beyond 

margins of calcareous part of valves, forming frill which, on death 

of animal, cracks along thinner sectors, producing series of rectangular or tonguelike projections separated by fissures. 

Geographic range.-Eastern and western Pacific; Indian Ocean, 

western Atlantic. 

Geologic range.-Miocene through Holocene, Japan and United 

States. (Probably also fossil from Devonian onward, if considered 

to include all Solemya-like forms with external ligament and 

without internal rib.) 
TERTIARY MARINE PELECYPODS: NUCULIDAE THROUGH MALLEIDAE A31 

Habitat.-Predominantly in deep water, although depth may be 

controlled by water temperature. Acharax johnsoni Dall has been 

found at 110 m in Puget Sound, 1,840 m off Baja California, and 

3,180 m off northern Ecuador near the equator (Vokes, 1955, 

p. 537-538). 

Aeharax johnsoni (Dall) 

Plate 4, figures 20, 23 

Solemya johnsoni Dall, 1891, p. 189; 1895, p. 712, pl. 25, fig. 1. 

Solemya (Acharax) johnsoni Dall. Olsson, 1961, p. 52-53 [See for 

synonymy]. Keen, 1971, p. 24. 

Original description.-"Shell resembling S. macrodactyla 

Mabille and Rochenbrune, from Orange Harbor, Tierra del Fuego, 

but larger, longer in proportion, the shorter end more tapering and 

the opposite end more rounded. Length of shell 115, height 48, 

diameter 18, mm. The cartilage pit is 30 mm behind the shorter 

end, and the greatest length of the digitate epidermis beyond the 

edge of the shelly valve is 23 mm." 

Holotype.-USNM 106886. 

Type locality.-Albatross station 3010, 1,840 m, Baja California 

Norte. Holocene. 

Supplementary description.-"The type lot of Solemyajohnsoni 

Dall**"'labeled johnsoni in Dall's writing, consists of four paired 

shells that have a virtually intact periostracum. One that appears 

to agree with the figure is regarded as the holotype. The valves of 

this specimen are cracked, and a small part of the anterior end of 

the periostracum is missing. This shell has a length including the 

periostracum of about 112 millimeters. A lot of three paired shells, 

two of which have the periostracum intact, from Albatross station 

3399 (off northern Ecuador, depth 1,740 fathoms) is labeled 'types' 

of johnsoni in Dall's writing (alcholic collection No. 3175). The 

largest of these shells has a length including a periostracum of 

about 73 millimeters." (Woodring, 1938, p. 27). 

Comparison.-((Solemya agassizi Dall,***which was given a 

range from the Gulf of California to Peru, was differentiated from 

johnsoni on the grounds that it has 6 or 7 anterior radial channels, 

as compared with 9 to 12 on S.johnsoni, and that the periostracum 

of johnsoni has a subtriangular outline. The type of agassizi is a 

large shell (U.S. Nat. Mus. 106885) that has a length exclusive of 

the periostracum of about 143 millimeters and was dredged off 

Panama at a depth of 1,672 fathoms. The basal part has been 

broken since the drawing was made, or the drawing is a restoration. 

The anterior part of the shell has six grooves; some sculpture on 

the umbonal part of the shell is not shown on the drawing. It 

appears doubtful whether two species are represented in the 

National Museum collections. All the specimens in the dried 

collection, representing localities from Oregon to Ecuador, are 

labeled agassizi in Dall's writing, or were so labeled under his 

direction. They have five or six grooves bordered by flat or slightly 

raised edges, but on some there is a transition from deep grooves to 

shallow grooves and ribs, and the number of grooves is a matter of 

individual judgment. No specimen has the entire periostracum 

preserved. The specimens in the type lot of johnsoni have seven 

distinct grooves; those from station 3399 have seven to nine." 

(Woodring, 1938, p. 27) 

Geographic range.-Living: Forbes Island, British Columbia, to 

Peru; fossil: northern and southern? California. 

Geologic range.-Pliocene through Holocene. 

Occurrence in California.-Pliocene: Rio Dell Formation (Roth, 

1979); Pliocene and Pleistocene: Fernando(?) Formation (Woodring, 

1938). 

Habitat.-This species has been found at 110m in Puget Sound, 

Wash., 1,840 m off Baja California, and 3,180 m off northern 

Ecuador. The depth of occurrence may be controlled by water 

temperature (Vokes, 195, p. 537-538). In Panama Bay at 3,270 m 

(Keen, 1971, p. 24). 

Genus ACHARAX? 

Aeharax? dunnensis Palmer 

Plate 4, figure 22 

Solemya? dunnensis Palmer, 1923, p. 302, pl. 55, fig. 1 

Solemya dunnensis Palmer. Vokes, 1955, p. 540. 

Original description.-"Shell small, thin; dorsal margin slightly 

crushed. Elongate in outline. Beaks posterior to center. Posterior 

dorsal margin straight; anterior dorsal margin appears to be 

slightly concave; ends rounded; ventral edge evenly rounded. 

Hinge not exposed. Surface sculptured by very faint concentric 

growth lines and indistinct, rounded, rather widely spaced radiating ribs. Dimensions: Length 14.8 mm.; height 6.6 mm." 

Holotype.-UCMP 30690. 

Type locality.-UC 3573. Solano County, Calif. Capay(?) Formation, Eocene. 

Geographic range.-Middle California. 

Geologic range.-Eocene, "Capay" megafauna} Stage. 

Occurrence in Cali{ornia.-Capay(?) Formation. 

Family ARCIDAE 

Geologic range.-Triassic(?); Jurassic through Holocene. 

Habitat.-"Abundant in shallow, tropic, subtropic and warm 

temperate marine waters, but two genera, Senila [sic: Senilia] Gray 

and Scaphula Benson, occur in brackish water, the latter also 

occurs in fresh water." (Hertlein and Grant, 1972, p. 152) Burrows 

but employs a weak byssus for increased stability. (Stanley, 1970, 

p. 8) 

Subfamily ARCINAE 

Habitat.-Nestling or rock-boring forms. Epifaunal arcids, anchored by a byssus, have markedly thinner shells than infaunal 

species in which a byssus is weak or absent. (Stanley, 1970, p. 68) 

Genus ARCA Linne, 1758 

Elongate, subtrapezoidal to subrectangular, very inequilateral, 

commonly expanded or auriculate posteriorly; cardinal area broad; 

dental series long and nearly straight; surface sculpture radial, 

fine. 

Geologic range.-Middle Jurassic through Holocene (table 3). 

Habitat.-"Worldwide in tropical and subtropical marine waters, 

but some species ranging into the boreal zone. Mostly in intertidal 

zone to shallow neritic zone, occasionally to a depth of 146 

meters***or deeper. Area tetragona Poli reported from a depth of 

2655 meters." (Hertlein and Grant, 1972, p. 153) Byssally attached. 

Subgenus ARCA 

Teeth small, numerous, transverse across middle of shell, becoming longer and convergent terminally. 

Geologic range.-Late Cretaceous through Holocene (table 3). 

Area (Area) hawleyi Reinhart 

Plate 5, figure 1 

Area (Area) hawleyi Reinhart, 1943, p. 21-22, pl. 2, figs. 19-22. 

Original description.-"Narrow and elongate in outline, narrow-
A32 PALEONTOLOGY OF CALIFORNIA AND BAJA CALIFORNIA 

TABLE 3.-Geologic and geographic distribution of the family Arcidae 

[H =Holocene; Pie= Pleistocene; PI= Pliocene; M =Miocene; 0 =Oligocene; E =Eocene; Pa =Paleocene] 

Alaska British Washington Oregon California Baja Central and/or South 

America Species Columbia California 

Genus Area: Subgenus Area: hawleyi Reinhart ...... . leptogrammica Hall ........................ . santamariensis Reinhart ...... . sisquocensis Reinhart ....................... . terminumbonis Grant and Gale . Genus Barbatia: 

Subgenus Barbatia: morsei Gabb ............... ..... . ................... . Subgenus Cucullaearca: 

bramkampi Durham .... cliffensis M. A. Hanna ............................. .. reeueana (Orbigny) .. Subgenus Fugleria: illota (Sowerby) .......... .. pseudoillota Reinhart .................... .. Genus Anadara: 

Subgenus Anadara: 

calcarea (Grant and Gale) ...................... .. canalis (Conrad) ...................... . 

Northern Middle Southern Norte Sur 

E E M M and PI PI and Pie M to Pie 

E E 

E 

PI M to Pie 

PI 

....... i.f.... Pl .. t~ H 

H Pie and H 

M PI and Pie. M and PI PI 

H 

Pie and H 

carrizoensis Reinhart .......... . deuincta (Conrad) ..... M? ... M ..... M ...... .. .... M MorPI ... M 

M 

M 

lakei (Wiedey) .............. .. 

:~~~~~r::;~~s(o~c~~:£> ................ .. .... r~i'~ .. . montesanoana (Etherington) .. osmonti (Dall) ................... . ..... 6'~-;;d M2 

submontereyana (Clark) ..... .. topangaensis Reinhart ...... . trilineata (Conrad) ... Subgenus Anadara?: 

strongi (Loel and Corey) . Genus Larkinia: 

camuloensis (Osmont) ..... .. multicostata (Sowerby) ........................ . santana santana (Loel and Corey) .. Santana weddlei (Loel and Corey) ..................... . Genus Grandiarca: 

grandis (Broderip and Sowerby) .. Genus Scapharca?: 

Subgenus Scapharca?: 

obispoana obispoana (Conrad) .... .. obispoana perdisparis (Wiedey) .. . Subgenus Cunearca: hamelini (Wiedey) ........ . riuulata (Wiedey) ................................ . santaclarana (Loel and Corey) .. uanderhoo{i Durham . 

1 Hiroshi Noda, oral commun., 1978. •Scott McCoy, written commun., 1978. 

......... M ... 

M 

M? 

ing posteriorly, strongly inflated. Anterior margin evenly rounded, 

meeting dorsal margin at right angles; ventral margin indented by 

large byssal gape; posterior margin broken. (On paratype 5344, 

however, posterior margin is preserved; it is nearly straight, 

rounding sharply into the ventral margin, and meeting the dorsal 

margin at an angle of 50°.) Surface ornamentation poorly preserved; a few radial ribs visible on posterior slope, and above 

byssal gape are several prominent, indented growth lines. Ligamenta} area wide and flat, sculptured with three indistinct, chevronshaped grooves, forming right angles under the beak. Dentition 

concealed on holotype. The paratype shows four posterior teeth 

lying transverse to the hinge line. Interior of shell not exposed." 

Holotype.-CASISV-5343. 

Type locality.-SV 834. Santa Barbara County, Calif. Tejon 

Formation, Eocene. 

Comparison.-"Although it resembles in general Area washingtoniana Dickerson from the Oligocene, this new species may be 

easily distinguished by its more elongate outline and relatively 

wider ligamenta} area." (Reinhart, 1943, p. 22) 

Geographic range.-Southern California. 

Geologic range.-Eocene. 

Occurrence in California.-Tejon and lone(?) Formations and 

Cozy Dell Shale (Weaver and Kleinpell, 1963). 

Area (Area) leptogrammiea Hall 

Plate 6, figure 4 

Area (Area) leptogrammica Hall, 1964, p. 87-88, pl. 22, figs. 9, 10. 

M? 

M 

M 

..... M? ... 

M·t:o'i>i~ 

M ... 

0 

M M toP! 

M 

M M 

M 

Oand M M OandM 

M 

M 

H 

PI to H M to H 

0 

Original description.-"Moderately large, rhombic in outline, 

anterior extremity broadly rounded, ventral margin nearly straight, 

small byssal gap'e slightly posterior of center, and posterior margin 

sharply rounded below, gently rounded above. Numerous thin 

radial ribs crossed by extremely faint concentric growth lines. Ribs 

closely spaced, interribs approximately 4/10 mm. wide, ribs slightly 

bunched posteriorly. Hinge narrow." 

Holotype.-VCLA 34997. 

Type locality.-VCLA 4180. San Luis Obispo County, Calif., 

Phoenix Member of Hall (1962), Santa Margarita Formation, 

Miocene. 

Comparison.- "Area washingtoniana Dickerson, from the Oligocene of Washington and Oregon, is more elongate and the area 

dorsal of the prominent posterior ridge extending from the umbo to 

the ventral margin is more pronounced. A. leptogrammica is 

nearly two to four times larger than A. washingtoniana. The 

Pliocene Area santamariensis Reinhart, although possessing fine 

radial ribs above the ridge from umbo to ventral margin, is 

smaller, has a depression at each end of the posterior slope, 

centrally located umbones, and a rounded posterior slope in comparison with Area leptogrammica. 

"Area sisquocensis Reinhart is much smaller than A. leptogrammica and it has beaded and moderately coarse ribs for its size. 

Although the beaks of A. mutabilis are more centrally located, as 

they are in A. leptogrammica, the posterior ribs are distinctly 

coarser than those in the central portion of the shell. The only 

species, fossil or living, that seems to resemble A.leptogrammica is 

the Pliocene to Recent Japanese species A. boucardi Jousseaume. 
TERTIARY MARINE PELECYPODS: NUCULIDAE THROUGH MALLEIDAE A33 

However, the umbones of A. boucardi are more anterior and the 

shells are smaller. The bundles of ribs on the posterior slope of A. 

boucardi are more pronounced than those of A. leptogrammica." 

(Hall, 1964, p. 88) 

Geographic range.-Southern California. 

Geologic range.-Miocene. 

Occurrence in Cali{ornia.-Phoenix Member of Hall (1962), Santa 

Margarita Formation. 

Area (Area) terminumbonis Grant and Gale 

Plate 5, figures 3, 4 

Area (Navicula) terminumbonis Grant and Gale, 1931, p. 142-143, 

pl. 1, figs. 18a-c, 19a-c, not 20a-c, 22. 

Area (Area) terminumbonis Grant and Gale. Reinhart, 1943, p. 

24-25, pl. 3, figs. 1-3. 

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

elongately trigonal; beaks near or at the extreme anterior end of 

the shell where the straight hinge line makes an acute angle with 

the area along the ventral margin; teeth divided near the middle 

by a slight internal thinning of the shell wall, outer teeth of the 

posterior series becoming rapidly elongated and very oblique, 

almost horizontal at the end of the hinge, continuing a short 

distance around the corner, teeth of the anterior series showing the 

same tendency but to a much less degree; cardinal area high, long, 

sculptured by many oblique grooves; beaks twisted forward but not 

sharply overhanging as in Area noae; from the beaks an oblique 

fold running out the posterior ventral corner, dividing into two 

broad branches as it goes, separated from the cardinal area by a 

depression; shell near the ventral margin of the valve nearly 

perpendicular to the plane of the valve margins; ventral margin 

arched around a very large byssal gape; sculpture consisting of 

many fine wavy radial striations and a few concentric ripples." 

Holotype.-SDNM 79 .. 

Type locality.-SDNM 207. Los Angeles County, Calif. Fernando 

Formation, Pliocene and Pleistocene. 

Supplementary description.-Arca (Area) terminumbonis "has a 

distinctive, wedgelike form, with the broad end at the posterior, 

and an extremely large byssal gape. These features distinguish it 

from any other species of the genus." (Reinhart, 1943, p. 24). 

Geographic range.-Southern California. 

Geologic range.-Miocene to Pleistocene. 

Occurrence in California.-Miocene and Pliocene: Towsley Formation (Kern, 1973); Pliocene and Pleistocene: Fernando Formation. 

Area (Area) santamariensis Reinhart 

Pia te 5, figures 2, 5 

Area (Area) santamariensis Reinhart, 1937b, p. 183-184, pl. 28, 

figs. 4, 5, 7, 8, 11. Reinhart, 1943, p. 26, pl. 3, figs. 7-11. 

Area santamariensis Reinhart. Woodring, 1950, p. 81, pl. 14, figs. 6, 

7. 

Original description.-"Both valves offairly well-preserved specimen, moderately large, elongate, equilateral, inflated. Profile of 

anterior margin evenly rounded; ventral margin roughly parallel 

to hinge; notched at center by byssal gape; posterior margin 

irregular, truncating ventral margin; umbones centrally placed, 

fairly large, but broken at top. Slightly curved umbonal ridge 

extends from umbo to posterior ventral margin; above this ridge is 

a groove. Medial sulcus extends upward a short distance from 

byssal gape. Sculpture, approximately 100 radial ribs, irregular in 

size and spacing, and having tendency to dichotomize; ribs larger 

at anterior and posterior ends of shell than elsewhere. Nodes on 

ribs inconspicuous, arranged in concentric bands; most prominent 

on posterior slope. Growth lines fairly prominent, following outline 

of shell. Ligamenta} area, with both valves together, resembles an 

arrowhead***, pointing anteriorly when viewed from above; inclined at anterior end, but nearly flat and wider toward posterior; 

four or five chevron-shaped grooves between beaks; in addition, 

ligamenta} area sculptured on exterior with a number of longitudinal lines, continuations of concentric growth lines. Hinge narrow, 

straight, slightly wider at extremities than at center; teeth about 44 

in number; a few anterior and posterior teeth are V-shaped or 

curved; teeth converge ventrally at extremities of hinge. Muscle 

scars distinct, oval-shaped, nearly equal in size. Inner margin of 

shell nearly smooth, with feeble crenulations at posterior end; 

small byssal gape. Pallial line simple, prominent." 

Holotype.-LAM 4072 (CIT 1381). 

Type locality.-Pliocene asphalt beds at Fugler Point, 10.2 km 

southwest of Santa Maria, Santa Barbara County, Calif. Cebada 

Member of the Careaga Sandstone, Pliocene. 

Supplementary description.-The posterior slope of this smallshelled species has a depression at each end, the intervening area 

being swollen. (Woodring, 1950, p. 81) 

Comparison.-Arca santamariensis is somewhat similar to the 

living species A. mutabilis (Sowerby) from the Gulf of California 

and Panama, but the two species differ in ornamentation as well 

as in the shape of the ligamenta} area. (Reinhart, 1937b, p. 184) 

Area santamariensis "resembles***A. mutabilis, which lacks 

the depressions on the posterior slope." (Woodring, 1950, p. 81) 

Geographic range.-Southern California. 

Geologic range.-Miocene and Pliocene. 

Occurrence in California.-Miocene and Pliocene: Capistrano 

Formation (Vedder, 1974); Pliocene: Cebada Member of the Careaga 

Sandstone (Woodring, 1950). 

Area (Area) sisquoeensis Reinhart 

Plate 5, figures 6, 8 

Area (Area) sisquocensis Reinhart, 1937b, p. 182-183, pl. 28, figs. 

1-3. Reinhart, 1943, p. 25, pl. 2, figs. 10-12. Hall, 1964, pl. 22, 

figs. 1, 2 

Area sisquocensis Reinhart. Kennedy, 1973, p. 124-125, fig. 3f. 

Original description.-Small, well-preserved right valve, elongate 

in outline, moderately inflated, slightly inequilateral. 

"Profile: Anterior margin evenly rounded; ventral margin 

straight, nearly parallel to hinge margin; posterior margin straight, 

forming acute angle where it intersects ventral margin, and 

meeting hinge margin at angle of 45°. Umbo located just anterior 

to center of shell, projecting slightly. An unusually sharp ridge 

extends from umbo to posterior ventral corner; above this ridge, 

shell is concave. A faint medial sulcus extends from byssal gape, 

upward a short distance toward umbo." 

"Sculpture: About 40 radial ribs, with occasional small interribs. 

On posterior slope, ribs are large and dichotomizing; elsewhere, 

simple and ornamented with closely-spaced nodes. The five anteriormost ribs are as large as the posterior ones, but do not dichotomize. 

Concentric growth-lines are not prominent, but two distinct concentric bands may be distinguished, and several less distinct ones. 

Ligamenta} area narrow in front of umbo, wide behind, there 

becoming noticeably excavated. About two right-angled, chevronshaped grooves directly beneath umbo. Hinge straight, narrow 

only slightly wider at extremities than at center; thirty-two teeth, 

small and granular at center, increasing regularly in size toward 

extremities of hinge; teeth converge ventrally, the anterior more 

sharply than the posterior. Muscle scars distinct, notable because 

of a raised flange bordering inner side of each scar, the posterior 

flange being the larger***. Inner margin of shell crenulated, 

especially at extremities. Narrow byssal gape near center. Pallial 

line simple; within this line, inner side of shell faintly striated by 

radial lines." 
A34 PALEONTOLOGY OF CALIFORNIA AND BAJA CALIFORNIA 

Holotype.-LAM 4073 (CIT 1382). 

Type locality.-Pliocene asphalt beds at Fulger Point, 10.2 km 

southeast of Santa Maria, center of NE 114 sec. 35, T. 10 N., R. 33 

W., S.B., Santa Barbara County, Calif. Cebada Member of the 

Careaga Sandstone, Pliocene. 

Supplementary description.-The posterior slope of A. sisquocensis is practically flat or slightly concave. (Woodring, 1950, p. 81) 

"Area sisquocensis Reinhart is much smaller than A. leptogrammica and it has beaded and moderately coarse ribs for its size." 

(Hall, 1964, p. 88) 

A fragment, which represents an individual probably 30 mm 

long, has about seven ligamenta} grooves on the cardinal area. 

This larger number of grooves is, no doubt, a result of the greater 

size of this shell in comparison to the holotype. (Hertlein and 

Grant, 1972, p. 154) 

Comparison.-Arca sisquocensis "has no known Recent allies 

on the Pacific coast, but is closely related to the Recent Japanese 

A. kobeltiana. Adult shells of A. sisquocensis have a wider posterior 

slope than that of A. kobeltiana, the posterior ridge being more 

strongly curved. Both species have a flange on the muscle scars, 

indicating that they do not represent Area in the restricted sense." 

(Woodring, 1950, p. 81) 

Area sisquocensis is similar in its general features to A. washingtoniana Dickerson from the Oligocene Gries Ranch Formation, 

Washington. In A. washingtoniana all of the ribs dichotomize and 

concentric growth lines are prominent, whereas in A. sisquocensis, 

only the ribs at the posterior end dichotomize and concentric bands 

are only feebly developed. (Reinhart, 1937b, p. 183) 

Geographic range.-Southern California. 

Geologic range.-Piiocene to Pleistocene. 

Occurrence in California.-Piiocene: Foxen Mudstone, Cebada 

Member of the Careaga Sandstone (Woodring, 1950), and Niguel 

Formation (J. G. Vedder, written commun., 1978); Pliocene and 

Pleistocene: Fernando (Zinsmeister, 1970) and Santa Barbara 

Formations, and unnamed late Pliocene or early Pleistocene strata 

of Anacapa Island (Valentine and Lipps, 1963); Pleistocene: Lindavista Formation (Kennedy, 1973), unnamed strata of San Nicolas 

Island (Vedder and Norris, 1963) and of San Pedro. 

Genus BARBATIA Gray, 1840 

Shell small, elongate, ovoid, inequilateral; ornamentation costellate, commonly fine. 

Geologic range.-Triassic(?); Jurassic through Holocene. 

Habitat.-Living worldwide in tropical and subtropical water, 

some forms ranging into the warm temperate zone. From the 

littoral zone to 183 m; occasionally deeper. (Hertlein and Grant, 

1972, p. 157). Byssally attached; characteristically live wedged in 

among coral colonies or rocks. (Stanley, 1970) 

Subgenus BARBA TIA 

Cardinal area low, ligamenta} grooves closely spaced, costellae 

numerous, in some forms obsolescent. 

Barbatia (Barbatia) morsei Gabb 

Plate 5, figure 7 

Barbatia morsei Gabb, 1864, p. 216, pl. 32, fig. 286. 

Barbatia (Obliquarca) morsei Gabb. Vokes, 1939, p. 49-50, pl. 1, 

figs. 25, 26, 28, 29. Reinhart, 1943, p. 30-32, pl. 1, fig. 4 [See for 

synonymy]. 

Barbatia (Barbatia) morsei Gabb. Givens, 1974, p. 40-41. 

Original description.-"Shell small, thin, subcompressed, oblique, broadest posteriorly; beaks small, approximate, anterior; 

area long and very narrow, shorter than the shell; anterior end 

short and broad; posterior end oblique above, rounded below; base 

sinuous, slightly gaping. Surface depressed in the middle and 

towards the ends, ornamented by numerous fine radiating ribs, 

alternating pretty regularly in size in the middle of the shell. Hinge 

slender, composed of numerous small, oblique teeth." 

Lectotype.-UCMP 11984 (Reinhart, 1943, p. 31) 

Type locality.-San Diego County, Calif. La Jolla Group, Eocene. 

M. A. Hanna (1927, p. 398) records Barbatia morsei Gabb from 

three stratigraphic units in the type area now designated the 

Torrey Sandstone, Delmar Formation, and Ardath Shale. 

Supplementary description.-"Eiongate***higher posteriorly 

than anteriorly; inequilateral, with umbo placed very near anterior 

extremity; umbonal ridge extends from beak to posterior ventral 

margin, in front of which is a shallow medial depression; in profile, 

hinge margin straight, scarcely interrupted by umbo, which projects slightly; anterior margin, partly concealed by matrix, slopes 

down immediately in front of umbo; ventral margin slightly 

broken in front, but growth lines show it to have been concave, 

with byssal gape at anterior third; posterior margin incomplete. 

Sculpture of numerous closely spaced radial ribs, inconspicuous 

posterior to umbonal ridge; more widely spaced in medial depression than elsewhere, in places separated by small inter-ribs; small 

nodes present on ribs on anterior half of shell; concentric growth 

lines fairly prominent posterior to umbonal ridge, but inconspicuous 

anterior to it. 

"Although the entire ligamenta} area is not shown on any of the 

original specimens that I have seen, examination of other specimens from the type area shows the ligament to be restricted to the 

posterior of the umbo, the ligamenta} grooves extending up to the 

umbo, where they stop; the short dorsal margin anterior to umbo 

shows no trace of a ligamenta! area." (Reinhart, 1943, p. 31) 

Comparison.-"Of the Pacific Slope species, B. morsei might be 

confused with B. landesi and B. suzzalloi (Weaver and Palmer), but 

differs from these by having the beaks placed farther anteriorly 

with the resulting anterior restriction of the ligament. Furthermore, 

B. suzzalloi possesses dichotomizing ribs, which B. morsei lacks." 

(Reinhart, 1943, p. 32) 

Geographic range.-Middle and southern California. Reported 

occurrences in Washington and Oregon are probably B. landesi 

and B. suzzalloi (Reinhart, 1943, p. 31) 

Geologic range.-Eocene. 

Occurrences in California.-Ardath Shale, Delmar (M.A. Hanna, 

1927), Domengine (Clark, 1929), lone (Dickerson, 1916), and Juncal 

(in Turritella uvasana applinae fauna, Givens, 1974) Formations. 

Subgenus CUCULLAEARCA Conrad 1865 

Subequivalve but generally much distorted, dorsal margin deeply 

sinuated by large byssal gape; sculpture of fine to coarse, subequal 

costae. 

Geologic range.-Cretaceous through Holocene. 

Habitat.-ln warm seas. 

Barbatia (Cucullaearca) diffensis M. A. Hanna 

Plate 5, figures 9, 12 

Barbatia cliffensis M.A. Hanna, 1927, p. 272, pl. 26, figs. 1-6. 

Barbatia (Cucullaearca) cliffensis M.A. Hanna. Reinhart, 1943, p. 

32-33, pl. 1, figs. 5-7. 

Original description.-"Shelliarge, moderately inflated; anterior 

and posterior fairly regularly rounded; ventral slightly concave 

upward, due to a depression near the center of the shell; dorsal 

margin slightly convex; posterior dorsal somewhat expanded; 

beak prominent, nearly central; concentrically striated by growth 

lines; radially ornamented by prominent round-topped ribs, distinctly noded where crossed by the growth lines so that a rib may 
TERTIARY MARINE PELECYPODS: NUCULIDAE THROUGH MALLEIDAE A35 

appear throughout its length; central depression in the shell 

shallow, extending from the beak to the ventral margin; interior of 

the shell radially ribbed, a reflection from the outer surface; inner 

margin not distinct in the cotypes; hinge margin moderately wide; 

cardinal area widely triangular, bearing well defined ridges and 

grooves which meet at the center to form an inverted 'V'; teeth 

more definite near the margins, three to eight at either end, more or 

less V-shaped toward the beak, inclined near the hinge extremities 

but not parallel to the hinge line. Dimensions. Cotype 31076: 

Altitude 26 mm., length 47 mm. Cotype 31077: Altitude 30 mm., 

length 52 mm." 

Lectotype.-UCMP 31077 (Reinhart, 1943). 

Type locality.-UC 5062. San Diego County, Calif. Ardath Shale, 

Eocene. 

Supplementary description.-"Shell fairly large, inequilateral, 

subcompressed; in profile, anterior end rounded, ventral margin 

sloping downward posteriorly, posterior margin broadly rounded, 

meeting hinge margin at angle of 40°; large byssal gape just 

anterior to center of ventral margin; umbones broadly rounded, 

not conspicuous, variable in postition; in the lectotype***umbones 

are at anterior fourth, while in paratype***they are only slightly 

anterior to center. This last specimen is also more quadrate in 

outline than lectotype, which widens noticeably toward posterior 

end***. Although some of this widening is only apparent, due to 

part of the anterior ventral margin being broken, the actual 

widening, as shown by growth lines, is nevertheless considerable. 

A broad ridge extends from beak to posterior ventral margin; 

anterior to this ridge is a broad, shallow depression. Sculpture of 

about 40 ribs as wide as interspaces, ribs fairly uniform over most 

of surface except on and posterior to umbonal slope, where they are 

larger and more widely spaced than elsewhere; ribs crossed by 

numerous growth lines, accentuated by nodes on ribs which give 

surface of shell an imbricate appearance. Ligamenta} area narrow, 

triangular, highly inclined, bearing six chevron-shaped grooves, 

on the lectotype. Hinge wide at extremities, but very narrow at 

center; longer posteriorly than anteriorly, curved into a gentle arc; 

in the lectotype the posterior third of hinge bears 8 large teeth, 

straight at posterior end of hinge and V-shaped at anterior end, 

strongly convergent; anterior part of hinge of lectotype has about 6 

somewhat smaller teeth, not V-shaped. Teeth in medial part of 

hinge small, granular. Muscle scars indistinct. Inner margin of 

shell crenulated, posteriorly at least; within pallial line these 

crenulations continue faintly toward the umbo; pallial line slightly 

impressed." (Reinhart, 1943, p. 33) 

Comparison.-"This species may be distinguished from the 

other known species by its larger size, the concavity near the 

center of the shell, the noded character of the ribs, and by the 

general character of the hinge." (M.A. Hanna, 1927, p. 272) 

Geographic range.-Southern California. 

Geologic range.-Eocene. 

Occurrence in Cali{ornia.-Ardath Shale. 

Barbatia (Cucullaearca) bramkampi Durham 

Plate 5, figures 10, 11 

Barbatia (Cucullaearca) bramkampi Durham, 1950, p. 55, pl. 1, 

7, 9. 

Original description.-"Shelllarge, rather flattened, beaks low, 

shape more or less irregularly subquadrate, similar in outline to B. 

reeueana (d'Orbigny); a low rounded angulation from the beak to 

ventral part of posterior margin; dorsal margin straight; posterior 

margin straight, making an angle of about 135° with dorsal 

margin, then rounding evenly into slightly curved ventral margin 

which slopes upward anteriorly to short rounded anterior margin; 

radial sculpture of 90-100 fine radial ribs, somewhat coarser and 

more nodose on anterior half of shell, posteriorly every fourth or 

sixth rib may be coarse, occasional fine secondaries intercalated; 

radial ribs crossed by fine growth lines which produce small nodes 

on anterior ventral margin; ligamenta} area with numerous inverted V-shaped chevrons; hinge with 5 coarse teeth and 10 finer ones 

inside them anteriorly, then a smooth area, followed by about 5 

small teeth and 7 large ones posteriorly-on some specimens the 

smooth central area is also covered with fine teeth, and there may 

be 10 large ones posteriorly." 

Holotype.-UCMP 15552. 

Type locality.-UC A3519. Baja California Sur. Marquer Formation, Pliocene. 

Comparison.-"The outline of different specimens varies considerably. B. bramkampi may readily be distinguished from B. 

reeueana by its finer and more numerous radial ribs, particularly 

on the anterior and posterior dorsal margins where the radial ribs 

on that species are rather coarse." (Durham, 1950, p. 55) 

Geographic.-Baja California Sur. 

Geologic range.-Pliocene. 

Occurrence in Baja California Sur.-Marquer Formation. 

Barbatia (Cucullaearca) reeveana (Orbigny) 

Plate 6, figures 1, 2 

Area reeueana Orbigny, 1846, p. 635. 

Barbatia (Cucullaearca) reeueana subsp. reeueana (d'Orbigny). 

Reinhart, 1943, p. 33-34, pl. 15, figs. 1-3. 

Barbatia (Cucullaearca) reeueana (d'Orbigny). Durham, 1950, p. 

56, pl. 1, figs. 3, 4, 8. 

Original description.-"A. testa ovato-oblonga, compressa, radiatum inequaliter costata; epidermide squamosa versus marginem 

induta; latere buccali brevi, oblique rotundato; latere anali producto, 

externe arcuato, angulato; latere palleali hiante, alba, striis analibus duplicibus; area ligamenti angustata, sulcata." 

Cotypes.-BM(NH) 54.12.478b (Keen, 1966b, p. 5). 

Type locality.-Payta [sic: Paita], Peru. Holocene. 

Supplementary description.-"Recent specimens of this subspecies***from the Galapagos Islands, show a large byssal gape, 

well-developed ligamenta} area, and hinge divided by a broad 

central edentulous gap, features which are characteristic of Cucullaearca." (Reinhart, 1943, p. 34) 

"This is a fairly large, coarsely reticulate form, with a habit of 

attaching between rocks, so that the shell may be much distorted 

in shape or even worn smooth in spots by friction with its 

surroundings." (Keen, 1971, p. 40). 

Geographic distribution.-Living: Laguna Manuela, Baja California Norte, Golfo de California, south to Zorritas, Peru; fossil: Baja 

California Sur. 

Geologic range.-Pliocene though Holocene. 

Occurrence in Baja Cali{ornia.-Pliocene: Marquer Formation 

(Durham, 1950); Pleistocene: unnamed strata, Gulf of California 

(Durham, 1950). 

Habitat.-Intertidally to 120m. 

Subgenus FUGLERIA Reinhart, 1937a 

Ovoid; cardinal area very narrow; sculpture of uniform costellae. 

Geographic range.-Florida, California, and Central America. 

Geologic range.-Pliocene through Holocene. 

Habitat.-In tropical and subtropical seas. 

Barbatia (Fugleria) pseudoillota Reinhart 

Plate 6, figures 3, 5 

Barbatia (Fugleria) pseudoillota Reinhart, 1937, p. 184-185, pl. 28, 
A36 PALEONTOLOGY OF CALIFORNIA AND BAJA CALIFORNIA 

figs. 6, 9, 10. Reinhart, 1943, p. 36, pl. 3,'figs. 4-6. Woodring, 

195~p.8~pl. 1~figs. 1~ 1& 

Original description.-"Fairly well-preserved right valve, elongate-oval in outline, inequilateral, little inflated. Beak placed near 

anterior end, prosogyrate. Profile of anterior margin of shell 

rounded; ventral margin nearly straight; byssal gape inconspicuous if present; posterior margin sharply-rounded ventrally, straighter dorsally; dorsal margin formed by large umbo, beyond which 

hinge margin projects only slightly on either side. A broad ridge 

extends from umbo to posterior ventral margin; in front ofthis is a 

very shallow medial depression. Sculpture of about 95 radial ribs, 

coarser on posterior slope than elsewhere; ribs spaced with fair 

regularity; small inter-ribs occasionally developed. Five prominent 

concentric growth lines present, as well as many inconspicuous 

ones. Ligamenta! area narrow, confined mainly to posterior of 

umbo, although extending slightly in front; about four chevronshaped ligamenta! grooves present, of which the upper two do not 

extend anterior to beak. Hinge arched, very narrow; about 7 small, 

granular teeth, at anterior end of hinge only; no posterior teeth 

either on holotype or paratype. Interior of shell of holotype is 

mainly concealed by· matrix, but in para type (no. 1384), a young 

specimen, the interior of the shell is entirely exposed; this appears 

smooth, but under magnification is seen to have numerous fine 

radial striations. Muscle scars indistinct. Inner margin of shell 

smooth. Pallial line slightly indented." 

Holotype.-LAM 4075 (CIT 1383). 

Type Locality.-Pliocene asphalt beds at Fugler Point, 10.2 km 

southeast of Santa Maria, Santa Barbara County, Calif. Cebada 

Member, Careaga Formation, Pliocene. 

Comparison.-Barbatia pseudoillota "is related to Barbatia illota 

(Sowerby), a Recent tropical Pacific Coast species***. However, 

although the posterior teeth on this species are not strongly 

developed, they are at least present." (Reinhart, 1943, p. 185) 

Barbatia pseudoillota is less elongate than B. illota (Woodring, 

1950, p. 82). 

Geographic range.-Southern California. 

Geologic range.-Miocene to Pleistocene. 

Occurrence in California.-Miocene and Pliocene: Towsley Formation (Kern, 1973); Pliocene: Cebada Member of the Careaga Sandstone (Woodring, 1950): Pliocene and Pleistocene: Fernando Formation (Vedder, 1972). 

Barbatia (Fugleria) illota (Sowerby) 

Plate 6, figures 6, 7 

Byssoarca illota Sower by, 1833, p. 18. 

Fugleria illata (Sowerby). Olsson, 1961, p. 83-84, pl. 6, figs. 1, 1a, 

lb. 

Barbatia (Fugleria) illota Sowerby. Hertlein and Grant, 1972, p. 

157-158, pl. 27, figs. 35, 36, 38-40. 

Original description.-"Byss. testa ovata, alba, radiatim costata, 

costis numerosis, decussatis; epidermide fusca, foliacea induta; 

latere antico breviore, rotundato, postico declivi; area ligamenti 

angusta, brevi: long. 1.5, lat. 0.75, alt. 1, poll." 

Holotype.-BM(NH) (A.M. Keen, oral commun., 1978). 

Type Locality.-Found under stones in the Gulf of Nocoiyo 

[Nicoya, Costa Rica], Holocene. 

Supplementary description.-"The shape is somewhat variable. 

On small specimens teeth are present along the entire hinge but on 

large specimens the posterior portion of the hinge is devoid of teeth 

except for four or five at the end***the teeth are striated. The 

ligamenta! grooves on small specimens are posterior to the beak, 

but larger specimens (35 mm long) have as many as seven 

ligamenta! grooves, the upper ones not extending beyond the beak 

but the three lower ones forming asymmetric angles extending 

anterior to the umbo. The largest Recent specimen which we have 

seen***is 39 em long, 25 mm high, the convexity (both valves 

together), 18.6 mm." (Hertlein and Grant, 1972, p. 158) 

"On fully. adult shells of B. illota a narrow band of ligament 

extends in front of the umbo, as on small specimens of Area 

barbata, the type of Barbatia. On such shells of B. illota the hinge 

is edentulous, except at the extremities." (Woodring, 1950, p. 82) 

Comparison.-Barbatia pseudoillota Reinhart is a very similar 

species. The type specimen, a right valve, is 33.5 mm long and 31 

mm high; the convexity is 9 mm. It was described as less elongate 

than B. illota and as having about seven granular teeth anteriorly 

but completely lacking teeth on the hinge posteriorly. Our observations on the hinge of adult Holocene specimens of B. illota show 

that although there is a long edentulous area in the subumbonal 

area, there are a few teeth at the posterior end. Perhaps a large 

series of B. pseudoillota may reveal specimens with teeth on the 

posterior end of the hinge but none have been reported. (Hertlein 

and Grant, 1972, p. 158) 

Geographic range.-Living: Isla Angel de la Guarda, Golfo de 

California to Lobitos, Peru; fossil: southern California, to Panama 

and Ecuador. 

Geologic range.-Pliocene through Holocene. 

Occurrence in California and Baja California Sur.-Pliocene: 

Niguel (J. G. Vedder, written commun., 1978) and San Diego 

(Hertlein and Grant, 1972) Formations; Pleistocene: unnamed 

strata, Golfo de California (Durham, 1950). 

Habitat.-Intertidal zone, attached to rocks; dredging records 

show an offshore occurrence to depths of 70 m. (Keen, 1971, p. 40) 

Subfamily ANADARINAE Reinhart, 1935 

Genus ANADARA Gray, 1847 

Rotund, moderately heavy, sculptured with strong costae that 

correspond to interlocking crenulations of shell margins; equivalve 

in shape and sculpture; cardinal area elongate; dental series only 

slightly arched. 

Geologic range.-Late Cretaceous through Holocene. 

Habitat.-Littoral zone to 128m but usually in less than 75 m. 

(Hertlein and Grant, 1972, p. 454) Usually burrowing but may 

attach by a weak byssus. (Stanley, 1970, p. 22-23) 

Subgenus ANADARA 

Subtrapezoidal; dental series continuous, consisting of similar 

and uniformly graded teeth. 

Anadara (Anadara) osmonti (Dall) 

Plate 6, figures 10, 11 

"Area microdonta Conrad" of Osmont, 1905, p. 90-91, p. 8, figs. 

1-2; not fig. 3. Not Area microdonta Conrad, 1855. 

Area osmonti Dall, 1909, p. 110, new name. 

Anadara (Anadara) osmonti (Dall). Reinhart, 1943, p. 50-53, pl. 4, 

figs. 9, 11, 16; pl. 10, figs. 12, 15. [See for synonymy]. 

Area barkeriana Clark, 1918, p. 128. 

Area impravida Wiedey, 1928, p. 130-131, pl. 14, figs. 2, 3. 

Description of holotype.-"Large, subquadrate, inflated, equivalve, inequilateral. Anterior margin regularly and broadly convex 

in profile, ventral margin straight and almost parallel to hinge 

margin, posterior portion of shell mostly broken away, the upper 

part of posterior margin still remaining; umbones large and full, 

beaks prosogyrate; hinge margin projects scarcely at all in front of 

umbo, but does project a short distance behind it. Curvature of 
TERTIARY MARINE PELECYPODS: NUCULIDAE THROUGH MALLEIDAE A37 

shell fairly uniform, except from umbo to posterior ventral margin 

where it is greater, forming a broadly rounded ridge, from which, 

to posterior dorsal margin, shell is slightly concave. Twenty-eight 

radial ribs, badly worn so that on casual inspection they appear 

flat and unornamented; closer examination, however, shows, in 

the better preserved portions, a central longitudinal groove on each 

rib, on each side of which is a smaller secondary groove. Ribs 

uniform in size and distribution over surface; interspaces flat, 

narrower than the ribs; closely spaced growth lines cross ribs and 

interspaces. Cardinal area moderately wide and inclined. A few 

grooves may be seen on area, but these are very poorly preserved. 

Dentition and interior of holotype not visible." (Reinhart, 1943, p. 

51) 

Holotype.-UCMP 11927; of A. barkeriana UCMP 11924; of A. 

imprauida CAS/SU 5162. 

Type locality.-Unknown. Probably from Devils Den, Kern 

County, southern California (Reinhart, 1943, p. 50). 

Supplementary description.-"Attention should especially be 

called to the variation in shape. Number of ribs is fairly uniform; 

an examination of many other specimens from Barker's ranch and 

Devils Den shows the number to range from 27 to 32, with 29 to 31 

ribs on most of the mature specimens." (Reinhart, 1943, p. 51) 

Comparison.-"From A. deuincta***(Conrad), A. osmonti differs 

by having the umbones placed farther anteriorly and by possessing 

beaded ribs, whereas those of A. deuincta usually are not beaded. 

In addition, when viewed dorsally, the anterior end of most 

specimens of A. osmonti is more bluntly pointed than that of A. 

deuincta, although some specimens of A. osmonti, particularly 

immature ones, are rather sharply pointed. 

"A. mediaimpressa***(Clark) greatly resembles A. osmonti but 

differs by having a slightly flattened area in the umbo, extending 

a short distance down toward the ventral margin. A. mediaimpressa, furthermore, has a sharply concave area on the dorsal posterior 

part of the shell which is not conspicuous in A. osmonti. 

"Andara lcikei (Wiedey), although similar in form to A. osmonti, 

has only about 25 ribs, which are broader and more deeply 

grooved." (Reinhart, 1943, p. 52-53) 

Geographic range.-Alaska; southern California. 

Geologic range.-Oligocene and Miocene. 

Occurrence in California.-Miocene: Branch Canyon Sandstone 

(Vedder, 1973), Olcese Sand and Round Mountain Silt (Addicott, 

1956), Saltos Shale Member of the Monterey (Repenning and 

Vedder, 1961), and Topanga (Takeo Susuki, written commun., 

1978) Formations. 

Anadara (Anadara) submontereyana (Clark) 

Plate 6, figure 12 

Area (Scapharca) submontereyana Clark, 1918, p. 128-129, pl. 16, 

fig. 2. 

Anadara (Anadara) mediaimpressa subsp. submontereyana 

(Clark). Reinhart, 1943, p. 40-41, pl. 4, fig. 7. 

Anadara (Anadara) submontereyana (Clark). Addicott, 1972, p. 

23-24, pl. 1, figs. 6, 7, 11, 16, 17. 

Original description.-"Shell plump, medium in size, fairly heavy, rhombic in outline; beaks rather prominent and anterior to the 

middle of the shell. Posterior end broadly rounded; anterior end 

regularly rounded, sloping down rather obliquely to the ventral 

edge. Ventral edge gently convex. Surface of shell radially sculptured by about twenty-three flat-topped ribs with interspaces 

averaging about the width of the tops of the ribs; on some 

specimens, there is a groove or channel down the middle of some of 

the ribs; this, however, appears to be due to weathering, not being 

apparent on the best preserved specimens. Incremental lines 

rather fine. Cardinal area large, crossed by well-defined multivincular grooves." 

Holotype.-UCMP 11186. 

Type locality.-UC 52. Contra Costa County, Calif. San Ramon 

Sandstone, Miocene(?). 

Supplementary description.-"ventral margin broadly rounded, 

posterior margin rounded below, straight dorsally;***ribs nearly 

flat-topped, straight-sided, separated by interspaces slightly narrower than ribs; medial groove present on lower extremity of 

several posterior ribs of holotype. Concentric growth lines closely 

spaced, preserved only in interspaces***inner ventral margin 

crenulated." (Reinhart, 1943, p. 41) 

"The number of ribs varies from as few as 21 or 22 to as many as 

25. Both the ribs and interspaces are seen to be very finely noded 

on a few of the better preserved specimens." (Addicott, 1972, p. 23) 

Comparison.- "A. submontereyana is not so large or inflated as 

A. osmonti and the number of radial ribs is not so great. The type 

specimen of A. osmonti Dall has twenty-seven ribs; the maximum 

number on any of the specimens of A. submontereyana examined 

by the writer is twenty-three." (Clark, 1918, p. 129) 

Anadara submontereyana is "closely related to typical A. mediaimpressa, from which it differs in being slightly less convex and in 

having possibly fewer ribs. Typical A. mediaimpressa has 27 to 29 

ribs, whereas on the holotype of A. submontereyana 24 can be 

counted, a number which would be increased if a well-preserved 

specimen were available." (Reinhart, 1943, p. 41) 

"A. submontereyana differs from A. strongi, a somewhat similar 

species of early Miocene age, in having a few more radial ribs that 

are not strongly grooved." (Addicott, 1972, p. 24) 

Geographic range.-Middle California. 

Geologic range.-Oligocene and Miocene.(?). 

Occurrence in California.-Oligocene: Wygal Sandstone Member 

of the Temblor Formation (Addicott, 1972); Miocene(?): San Ramon 

Sandstone. 

Anadara (Anadara) lakei (Wiedley) 

Plate 6, figures 8, 9 

Area lakei Wiedey, 1928, p. 127-128, pl. 13, figs. 4, 5. 

Anadara (Anadara) lakei (Wiedey). Reinhart, 1943, p. 55-56, pl. 9, 

figs. 1-3, pl. 12, figs. 7, 8. 

Original description.-"Shell subquadrate in outline and of 

moderate size, but distinctly inequilateral and quite gibbose. The 

anterior dorsal margin short and straight, gently sloping. The 

anterior dorsal extremity broadly rounded to the basal margin, 

which is less convexly rounded. The posterior dorsal extremity is 

quite sharply rounded, more narrowly below than above. Posterior 

dorsal margin short and straight to gently sloping. Umbones 

prominent, large, elevated, and incurved. The beaks are of moderate 

size, anteriorly situated, quite sharp, incurved and close-set. The 

cardinal area is not large and is only gently depressed. Sculpture 

consists of twenty-five ribs which are low and flattened. The ribs 

generally have on their surface three longitudinal striations which 

present the appearance of dividing the ribs into riblets, separated 

by thread-like channels. The interspaces between the ribs are 

slightly narrower than the ribs and are flatly channeled. Concentric 

lines of growth apparent but not prominent. Length, 38 mm.; 

breadth, 33 mm.; height of both valves, 32 mm." 

Holotype.-SDNM 19. 

Type Locality.-SU 432. San Luis Obispo County, Calif. Saltos 

Shale Member of the Monterey Formation, Miocene. 

Comparison.-"The species with which Anadara lakei might be 

confused is A. osmonti (Dall), which it resembles in general form 
A38 PALEONTOLOGY OF CALIFORNIA AND BAJA CALIFORNIA 

and ornamentation. In A. lakei, however, the ribs are fewer in 

number (25 instead of about 29-31), and are broader and more 

deeply grooved. Until more specimens of A. lakei have been 

studied, it is not possible to decide whether this is a distinct species 

or merely a variety of A. osmonti." (Reinhart, 1943, p. 56) 

Geographic range.-Southern California. 

Geologic range.-Miocene. 

Occurrence in California.-Saltos Shale Member of the Monterey 

Formation. 

Andara (Anadara) devincta (Conrad) 

Plate 6, figures 15-17; plate 7, figure 1 

Area devincta Conrad, 1849, p. 726; atlas pl. 18, figs. 10, lOa. 

Anadara (Anadara) devincta subsp. devincta (Conrad). Reinhart, 

1943, p. 43-45, pl. 16, figs. 6, 8. 

Anadara (Anadara) devincta (Conrad). Moore, 1963, p. 59-61, pl. 

13, figs. 14, 15; pl. 14, figs. 1-13. 

Area (Scapharca) microdonta Conrad. Dall, 1909, p. 110. Not A. 

microdonta Conrad in Blake, 1855. 

Arcaprocumbens Wiedey, 1928, p. 132, pl. 13, figs. 9-11. 

Original description.-"Rhomboidal, ribs narrow, flattened, and 

little prominent anteriorly; on the posterior side wider, slightly 

convex, and longitudinally striated. Beaks distant." 

Lectotype.-USNM 3499 (Moore, 1963). 

Type locality.-Astoria, Columbia County, Oreg. Astoria Formation, Miocene. 

Supplementary description.- "Anadara devincta includes forms 

quadrate to posteriorly elongate in outline, thin to highly inflated, 

possessing a narrow to very wide cardinal area, and forms that 

have smooth ribs, ribs medially split, or smooth ribs split at the 

ventral margin. On specimens preserved with the valves articulated 

and closed, the left valve is seen to overlap the right valve slightly 

along the ventral margin. The variations in outline, inflation, and 

ribbing bear no correlation to the size of the specimens, except that 

the thin forms become inflated as they mature and the cardinal 

area is coincidentally widened. 

"There are three forms of Anadara devincta in the Astoria 

formation in Oregon; a thin, an inflated, and a split-rib form***. 

"Young specimens of the split-rib form***are quadrate in shape 

(length 2.5 to 5 em), thin to moderately inflated (thickness, 1.5 to 3 

em), have a narrow cardinal area, and have ribs split by one deep 

center groove. The mature forms are posteriorly elongated (length, 

6 to 6.5 em), are moderately to greatly inflated (thickness, 3.5 to 4.5 

em), have a wide cardinal area, and have ribs split by three 

grooves. The beaks are situated about two-thirds the distance from 

the posterior margin. 

"The thin form***is usually moderate in size (length, 3 to 3.5 

em), subquadrate in shape, and thin (thickness, 1.5 to 2.5 em) and 

has a narrow cardinal area and ribs split by 1 or 3 grooves. 

"The inflated form***is subovate when young (length, 2.5 to 5 

em) and posteriorly elongated when mature (length, 5.5 to 7 em), it 

is moderately to greatly inflated when small (thickness, 2 to 4 em) 

and greatly inflated when large (thickness 4.5 to 5.5 em). The beaks 

are three-fourths the distance from the posterior margin on young 

specimens and two-thirds this distance on mature specimens. The 

ribs are smooth on young specimens and split by 1 or 3 grooves at 

the ventral margin on large specimens." (Moore, 1963, p. 59-60) 

Comparison.-A. osmonti (Dall) differs from A. devincta, on the 

basis of the poorly preserved topotype material available for 

comparison, by having a flattened ridge beginning beneath the 

anterior edge of the beak and extending to the anterior margin 

along the upper edge of the cardinal area. The cardinal area is 

inequilateral on all specimens, including the smallest, which 

possess a narrow cardinal area. The larger specimens of A. 

osmonti have a wide inequilateral cardinal area and resemble 

Anadara devincta, inflated form, in outline. However, the anterior 

cardinal ridge of A. osmonti is not found on A. devincta, inflated 

form; and the ribs of A. osmonti are split by 1 groove on small 

specimens and 3 grooves on larger specimens, whereas the ribs are 

smooth on A. devincta, inflated form, except on the ventral margin 

of large specimens. 

"Anadara trilineata (Conrad) of Arnold (Woodring, Stewart, and 

Richards, 1940, p. 89)***differs from A. devincta by generally 

maintaining a moderately inflated shell throughout its growth, by 

usually having a fairly narrow cardinal area which is however 

wide on some large specimens, and by being higher usually in 

proportion to length. The ribs are grooved like A. devincta, split-rib 

form, but they seem to be consistently fewer in number A. trilineata 

averaging about 25 and A. devincta, split-rib form, about 32. 

"Anadara (Anadara) devincta montesanoana (Etherington, 

1931)***is trigonal rather than quadrate in outline and seems to be 

allied more closely to Anadara (Anadara) trilineata (Conrad) than 

to A. devincta." (Moore, 1963, p. 61) 

Geographic range.-Alaska(?) to southern California and Japan(?). 

Geologic range. -Miocene. 

Occurrence in California.-Briones Sandstone (Hall, 1958; Moore, 

1963), Monterey Group (Weaver, 1949), Sobrante Sandstone (Lutz, 

1951; Weaver, 1953), and upper part of Temblor Formation (Loel 

and Corey, 1932; Adegoke, 1969). 

Anadara (Anadara) mediaimpressa (Clark) 

Plate 7, figures 2, 3 

Area (Scapharca) mediaimpressa Clark, 1918, p. 126-127, pl. 7, 

figs. 7, 8; pl. 16, figs. 5-7. 

Anadara (Anadara) mediaimpressa (Clark). Schenck and Reinhart, 

1938, p. 34-37, pl. 1, figs. 1a-1d. 

Anadara (Anadara) mediaimpressa subsp. mediaimpressa (Clark). 

Reinhart, 1943, p. 39-40, pl. 4, figs. 1, 5, 6. 

Original description.-"Shell small to medium in size, rhombic 

in outline. Umbones rather broad, strongly inturned and anterior 

to middle of shell, depressed medially, the depression on the 

smaller specimens extending from the beak well down to the 

ventral edge; this character is best seen on the smaller specimens, 

being less noticeable on the larger ones. Posterior end broadly 

subtruncate to gently rounded, anterior end evenly rounded, narrower than posterior end. Surface sculptured by twenty-seven to thirty 

flat-topped, radial ribs with interspaces about as wide as the ribs. 

On one ofthe specimens figured***most of the ribs show a medium 

groove beginning about halfway from the beaks and extending to 

the ventral edge; this groove is similar to that seen on Area 

montereyana Osmont and on Area trilineata Conrad. On this last, 

there is often a second and third groove bordering on each side of 

the medium groove which begin lower down from the beaks than 

does the medium groove. It is very possible that iflarger specimens 

of Area mediaimpressa are found, the second and third grooves 

may also appear on the lower part of the ribs. Apparently the ribs 

were originally somewhat spinose, due to the sharp, imbricating, 

incremental lines; this is to be seen on a few of the better preserved 

specimens. Surface rather strongly depressed posteriorly. Cardinal 

area very narrow; ligamenta! grooves obscure. Hinge plate narrow, 

slightly curved, with about thirty-five taxodont cardinals, which, 

beneath the beaks, are very small; distally they become larger and 

converge ventrally." 

Holotype.-UCMP 11174. 

Type locality.-UC 1131. Contra Costa County, Calif. San Ramon 
TERTIARY MARINE PELECYPODS: NUCULIDAE THROUGH MALLEIDAE A39 

Sandstone, Miocene(?). 

Supplementary description.-"Sculpture of 27 to 29 radial ribs 

crossed by concentric growth lines; ribs flat-topped, beaded on 

anterior half of shell***ribs and interspaces crossed by closelyspaced concentric growth lines; medial groove present on ribs near 

ventral margin, becoming distinct at distance of 10 to 15 mm. from 

umbo***(on] a relatively large individual, an additional groove is 

present near ventral margin, on each side of medial groove; 

ligamenta} area, long, nearly flat, rather narrow, wider in front of 

than behind beaks, bearing three chevron-shaped grooves, only 

the posterior halves of which are well preserved; hinge exposed 

only on holotype***shorter anteriorly than posteriorly, wider at extremities than in medial area; teeth strong, regular, vertical at center, 

con verging ventrally at extremities of hinge; inner margin of shell 

crenulated***" (Schenck and Reinhart, 1938) 

Comparison.-"This species resembles Anadara osmonti 

(Dall)***. This comparison is based upon a small number of 

specimens of [A.] mediaimpressa and a large number of probable 

topotypes of [A.] os monti ranging in length from 20 to 55 mm. and 

exhibiting considerable variation in outline and convexity. The 

similarity***is so great as to suggest the possibility that one rather 

than two species is present, but the meager representatives of [A.] 

mediaimpressa do not warrant making a definite decision as to 

specific identity." (Schenck and Reinhart, 1938, p. 37) 

"Area mediaimpressa differs from the typical A. montereyana***in the following respects: The beaks are more prominent 

and broader, the latter lacking the depressed area just below the 

beaks, and the truncated posterior margin being more oblique; A. 

montereyana is the longer and is more strongly produced posteriorly, also the surface is not so strongly depressed near the posterior 

truncated end." (Clark, 1918, p. 127) 

Geographic range.-Middle and southern California. 

Geologic range.-Miocene. 

Occurrence in California.-Miocene: Round Mountain Silt 

(Schenck and Reinhart, 1938) and upper part of Temblor Formation 

(Schenck and Reinhart, 1938); Miocene(?): San Ramon Sandstone. 

Anadara (Anadara) montereyana (Osmont) 

Plate 7, figure 4 

Area montereyana Osmont, 1905, p. 96-98, pl. 9, fig. 5; not figs. 5a, 

5b. 

Area deuincta var. montereyana (Osmont). Etherington, 1931, 

p. 69-70, pl. 3, figs. 1-5, 7, 8. 

Anadara (Anadara) montereyana (Osmont). Reinhart, 1943, 

p. 47-49, pl. 10, figs. 1, 3, 4, 9. 

Original description.-"Rhomdoidal, inequilateral, nearly twothirds of the length being behind the beak, posterior margin 

making a very obtuse angle with hinge-line. Ratio of length to 

height about 1-112 to 1. Average size of adult about 51x33 mm. 

Beaks not prominent, turned rather sharply forward, narrow and 

close together, ligament area narrow. Hinge line long and straight. 

Basal margin nearly parallel to hinge line. Ribs 26-32, usually 27, 

prominent, square, flattened, a little wider than the interspaces 

and marked with a median groove. Occasionally, in the older 

specimens, two subsidiary grooves may appear toward the margin, 

as in A. trilineata. More or less distinct lines of growth often 

roughen the shell, especially in the larger individuals, and when 

these are fine and numerous they approach closely the beaded 

effect of A. trilineata." 

Holotype.-UCMP 11925. 

Type locality.-SU 1166. Selby, Contra Costa County, Calif. 

(Reinhart, 1943, p. 48). Monterey Group, Miocene. 

Supplementary description.-"Moderately large, compressed*** 

elongate; dorsal margin straight, interrupted by umbo; anterior 

margin evenly rounded, merging into ventral margin which is 

gently convex, nearly parallel to dorsal margin; posterior margin 

sharply rounded below and nearly straight higher up, meeting 

hinge margin at angle of nearly 40°; umbo located one third of 

distance from anterior end; gentle ridge extends from umbo to 

posterior ventral margin, above which shell is slightly concave; no 

byssal gape apparent. Sculpture of 31 radial ribs, separated by 

nearly flat, narrower interspaces; ribs divided longitudinally by 

central grooves, which did not develop until shell had reached a 

length of about 30 mm; ribs and interspaces crossed by numerous, 

closely spaced growth lines***; ribs wider and more prominent on 

posterior part of shell than elsewhere; ligamenta} area, hinge, and 

interior of holotype concealed by matrix." (Reinhart, 1943, p. 49) 

Comparison.-"This species resembles Anadara deuincta*** 

(Conrad) closely. The two species may be distinguished by the fact 

that A. montereyana is more elongate and more compressed than 

A. deuincta, and typically has less deeply incised longitudinal 

grooves on the ribs. 

"A. montereyana also resembles A.*** montesanoana (Etherington), but differs in being more elongate and compressed, and in 

having 29 to 31 ribs whereas Etherington's subspecies has 25 to 28. 

"The resemblance of A. montereyana to A. osmonti is fairly 

close, but A. osmonti is more inflated than A. montereyana and its 

umbones are located farther anteriorly. 

"From A. trilineata*** A. montereyana may be distinguished by 

being more elongate, with more bluntly rounded umbones, more 

ribs (A. trilineata usually has only 25 to 27), and by lacking the 

distinct beaded ornamentation of the ribs which characterizes A. 

trilineata ***. 

"A. montereyana has been confused with A. obispoana, probably 

because A. obispoana is usually found as an internal mold, 

whereas A. montereyana is commonly better preserved, retaining 

its shell material. It is thus difficult to compare the two species, 

preserved differently; but if internal molds of A. obispoana are 

compared with internal molds of A. montereyana, the two are at 

once seen to be distinct because in the molds of A. montereyana the 

radiating ribs extend only for a short distance toward the umbo, 

while in A. obispoana they extend all the way up to the umbo. 

Other differences separate the two species, such as number of ribs. 

A. obispoana has about 26, fewer than A. montereyana." (Reinhart, 

1943, p. 49) 

Geographic range.-Alaska; Washington, middle California and 

Baja California Sur. 

Geologic range.-Miocene. 

Occurrence in California and Baja California Sur.-Briones 

Formation of Reinhart (1943), Monterey Formation (Ham, 1952), 

Oursan (Hall, 1958) and Sobrante (Lutz, 1951; Weaver, 1953), 

Sandstones and Tortugas Formation (Minch and others, 1976). 

Anadara (Anadara) montesanoana (Etherington) 

Plate 7, figures 6, 10 

Area deuincta montesanoana Etherington, 1931, p. 69-70, pl. 3, 

figs. 1-5, 7, 8. 

Anadara (Anadara) deuincta subsp. montesanoana (Etherington). 

Reinhart, 1943, p. 45-46, pl. 11, figs. 13, 14. 

Original description.-"Shell thick, subquadrate in outline; beaks 

elevated, subcentral; surface of the shell with 25-28 flattish channeled ribs varying in width from one-half to twice the width of the 

interspaces. Where the ribs are narrow they are bifurcated only 

once but usually develop four fine radial lines. On the adult the 
A40 PALEONTOLOGY OF CALIFORNIA AND BAJA CALIFORNIA 

cardinal area is wide, with four or five chevron-shaped threads; 

muscle scars deep; border coarsely crenate." 

Holotype.-UCMP 31922. 

Type locality.-VC 9069. Grays Harbor County, Wash. Montesano Formation of Weaver (1912), Miocene. 

Comparison.-Anadara deuincta has 29 to 32 ribs and A. montesanoana 26 to 28. This species approaches A. trilineata (Conrad) in 

outline and is similar in other respects, such as number of ribs, 

dentition, and ligamenta! area. A. trilineata is less convex, has a 

sharper umbo than A. montesanoana, and has beading on the 

ribs, which Etherington's species usually lacks. (Reinhart, 1943, 

p. 46) 

Geographic range.-Washington and middle California. 

Geologic range.-Miocene. 

Occurrence in California.-San Pablo Formation (Etherington, 

1931). 

Anadara (Anadara) topangaensis Reinhart 

Plate 8, figures 5, 6 

Anadara (Anadara) topangaensis Reinhart, 1943, p. 53-54, pl. 10, 

figs. 10, 13, 14 [See for synonymy]. 

Area microdonta Conrad. Osmont, 1905, p. 90-91, 100, pl. 8, figs. 

3a-b, not figs. 1-2. Not Area microdonta Conrad, 1855. 

Original description.-"Moderate in size, ventricose, slightly 

inequilateral; in profile, anterior margin evenly rounded, ventral 

margin nearly straight, sloping upward slightly toward rear, 

posterior margin abruptly rounded ventrally, but straight above, 

meeting hinge margin at angle of 45°; distinct ridge extends from 

umbo to posterior ventral margin, above which shell is concave; 

beaks prosogyrate, located at anterior third; ventral margin without byssal gape. Ribs 28 to 30 in number, ornamented with distinct 

nodes; ribs not divided centrally by longitudinal groove; interspaces slightly concave, nearly as wide as ribs; concentric growth 

lines crossing ribs and inters paces at periphery of shell, but higher 

up, present only in inters paces. Cardinal area fairly wide, inclined, 

bearing 4 to 6 grooves, chevron-shaped on paratype 3259, but 

curved on holotype. Hinge straight, much wider at extremities 

than at center; teeth numerous and fine, ventrally convergent at 

extremities. Inner margin of shell crenulated; interior of shell not 

exposed on any available specimens." 

Holotype.-VCMP 3258. 

Type locality.-VCLA 391. Los Angeles County, Calif. Topanga 

Formation, Miocene. 

Comparison.-"This species resembles Anadara osmonti in 

general form, but whereas the ribs of A. osmonti are divided 

centrally by longitudinal grooves, those of A. topangaensis are 

not; furthermore, the nodes on A. topangaensis are much more 

prominent than on A. osmonti." (Reinhart, 1943, p. 54) 

Geographic range.-Alaska; southern California to Baja California Norte. 

Geologic range.-Miocene. 

Occurrence in California.-Rosarito Beach (Minch and others, 

1970) and Topanga Formations. 

Anadara (Anadara) carrizoensis Reinhart 

Plate 7, figures 5, 11 

Anadara (Anadara) carrizoensis Reinhart, 1943, p. 56-57, pl. 5, 

figs. 1, 4, 10. 

Original description.-"Large and thick-shelled, strongly inflated, inequilateral, equivalve, beaks prosogyrate, situated at 

anterior third of shell; shell elongate in outline, hinge margin long 

and straight, interrupted by prominent broad umbones, ventral 

margin broadly curved, anterior margin curved upward, meeting 

dorsal margin at angle of 90°; posterior margin sharply curved 

below, straight above, meeting dorsal margin at angle of about 

45°. Sculpture similar on right and left valves, consisting of 40 

radial, rather flat-topped ribs, each ornamented with three to four 

linear grooves; interspaces between ribs slightly concave, about 

half as wide as ribs; wavy concentric growth lines traverse ribs 

and interspaces, conspicuous toward ventral margin of shell. 

Ligamenta! area large, with about six ligamenta! grooves on each 

valve, not chevron-shaped, but curved under beaks. Hinge straight, 

rather narrow, slightly wider at extremities than at center of shell; 

taxodont teeth small and numerous; only a portion of dentition 

preserved on holotype, which has about 40 teeth***; these diverge 

ventrally near center of hinge, and converge at posterior extremity; 

anterior teeth not preserved on type specimens. Muscle scars not 

preserved. Inner margin of shell strongly crenulated." 

Holotype.-LAM 4069 (CIT 3248). 

Type locality.-CIT 738. Imperial County, Calif. Imperial Formation, Miocene or Pliocene. 

Comparison.-"This species bears a strong resemblance to the 

Rec~nt Anadara formosa (Sowerby), but differs from that species 

in profile and in lacking the medially sulcate anterior ribs of A. 

formosa. The Recent Atlantic Coast species Anadara secticostata 

(Reeve) likewise resembles A. carrizoensis, but is slightly inequivalve, and all of its ribs are medially sulcate." (Reinhart, 1943, p. 

57) 

Geographic range.-Southern California. 

Geologic range.-Miocene or Pliocene. 

Occurrence in California.-Miocene or Pliocene: Imperial 

Formation. 

Anadara (Anadara) trilineata (Conrad) 

Plate 7, figures 7-9 

Area trilineata Conrad, 1857a, p. 314. 

Anadara (Anadara) trilineata subsp. trilineata Conrad. Reinhart, 

1943, p. 57-60, pl. 5, fig. 9; pl. 6, figs. 1-3, 5, 7; pl. 7, fig. 1. 

Anadara trilineata Conrad. Woodring and Stewart, 1940, p. 89-90, 

pl. 11, fig. 10, 19-24; pl. 14, fig. 7; pl. 20, figs. 15-17; pl. 29, figs. 2, 6. 

Woodring, 1950, p. 82, pl. 9, figs. 2, 5; pl. 11, fig. 4; pl. 16, fig. 19. 

Hertlein and Grant, 1972, p. 154-156, pl. 28, figs. 1-4, 6 [See for 

synonymy]. 

Original description.-"Trapezoidal, somewhat produced, inequilateral, ventricose; ribs 22-24, scarcely prominent, square, wider 

than the intervening spaces, ornamented with three impressed or 

four raised lines; disks concentrically wrinkled; summits prominent; beaks approximate. Length 3 inches." 

Holotype.-Location unknown; presumed lost. 

Type locality.-"Arca trilineata was said to have been collected 

by Newberry at Santa Barbara, but according to Newberry's 

itinerary he was nowhere near Santa Barbara, and this species 

has never been found near Santa Barbara. Area trilineata, Area 

canalis, and Mulinia densata, described at the same time and said 

to have been collected at Santa Barbara by Newberry, may have 

been collected at some locality farther north in the coastal region 

of California. It is possible but unlikely that they were collected by 

Blake in the Kettleman Hills or nearby; Blake mentioned only the 

Area." (Woodring, 1938, p. 31) 

Supplementary description .. -"We have had a large number of 

specimens available for study including several hundred valves 

varying in length from 5 mm to*** 79 mm long. These specimens 
TERTIARY MARINE PELECYPODS: NUCULIDAE THROUGH MALLEIDAE A41 

vary somewhat in proportion of length to height but all are 

decidedly longer than high. The number of ribs varies, usually 

from 25 to 28,...*. The ribs on the anterior half of the shell are often 

deeply sulcated or almost bifid, those on the posterior half usually 

bear two, three, or occasionally four shallow grooves. The ribs 

usually begin to develop a medial sulcation after the shell attains a 

height of about 8 to 10 mm, occasionally earlier. The ribs are 

usually at least partially beaded." (Hertlein and Grant, 1972, 

p. 155) 

Comparison.-"The fewer ribs as well as their beaded ornamentation and the slender umbos are features which serve to separate 

Anadara trilineata from two somewhat similar Miocene species, A. 

deuincta Conrad*** and A. montereyana Osmont***. The less 

convex valves and more sharply projecting umbos as well as the 

usually beaded character of the ribs are shell characters differing 

from those of A. deuincta montesanoana Etherington." (Hertlein 

and Grant, 1972, p. 156) 

Geographic range.-Kamchatka and Sakalin; British Columbia 

to southern California. 

Geologic range.-Miocene to Pleistocene. 

Occurrence in Cali{ornia.-Miocene: Briones Sandstone (Trask, 

1922), Castaic Formation (Stanton, 1966), Cierbo Sandstone (i-Iall, 

19580, Santa Margarita Formation (Adegoke, 1969); Miocene and 

Pliocene: Capistrano (Vedder, 1974), Tahana Member of Purisima 

(Addicott, 1969), Towsley (Kern, 1973) Formations; Pliocene: 

Cebada Member, Careaga Sandstone (Woodring, 1950), Etchegoin 

(Anderson, 1908) and Falor (Manning and Ogle, 1950) Formations, 

Foxen Mudstone (Keen and Bentson, 1944), Neroly (Weaver, 1949), 

Niguel (Vedder, 1960), Ohlson Ranch (Peck, 1960), Pancho Rico 

(Durham and Addicott, 1965), Pomponio Mudstone Member, 

Purisima (Cummings and others, 1962), Pullen (Roth, 1979), 

Tinaquaic Sand tone Member of the Sisquoc (Woodring, 1950), San 

Diego (Hertlein and Grant, 1972), and San Joaquin (Woodring and 

others, 1940) Formations; Pleistocene: Scotia Bluffs Sandstone 

(Roth, 1979). 

Anadara (Anadara) trilineata calcarea (Grant and Gale) 

Plate 8, figures 1, 2 

Area (Area) trilineata var. calcarea Grant and Gale, 1931, 

p. 140-141, pl. 2, figs. 6a, 6b. 

Anadara (Anadara) trilineata subsp. calcarea (Grant and Gale). 

Reinhart, 1943, p. 61-62, pl. 9, figs. 6-8. 

Anadara trilineata calcarea Grant and Gale. Hertlein and Grant, 

1972, p. 156, pl. 28, figs. 5, 7-10. [See for synonymy.] 

Original description.-"Shelllike that of typical Area trilineata 

Conrad, but larger, much thicker, and with more numerous cardinal grooves." 

Holotype.-CASISU 436. 

Type locality.-Well in Balboa Park, San Diego, San Diego 

County, Calif. San Diego Formation, Pliocene. 

Comparison.-"This subspecies differs from typical A. trilineata 

by having a larger, heavier shell and more grooves on the ligamenta} area. In addition, when viewed from above the anterior end 

of the shell of A. trilineata calcarea is bluntly pointed, differing 

from typical A. trilineata, which is sharply pointed. This blunt 

point was acquired at a late stage in the growth of the shell of A. 

trilineata calcarea, as shown by the growth lines." (Reinhart, 1943, 

p. 61) 

Comments.-The holotype is a disarticulated, double-valved 

specimen. 

Geographic range.-Middle to southern California. 

Geologic range.-Miocene to Pleistocene. 

Occurrence in California.-Miocene: Briones Sandstone (Weaver, 

1953); Pliocene: Niguel (Vedder, 1960) and San Diego (Hertlein and 

·Grant, 1972) Formations; Miocene and Pliocene: Capistrano Formation (Vedder, 1974); Pliocene and Pleistocene: Fernando Formation 

(Schoellhamer and others, 1981). 

Anadara (Anadara) trilineata canalis (Conrad) 

Plate 8, figure 4 

Area canalis Conrad, 1847a, p. 314. 

Anadara (Anadara) trilineata subsp. canalis (Conrad). Reinhart, 

1943, p. 60-61, pl. 7, figs. 3, 4. [See for synonymy.] 

Original description.-"Subtrapezoidal, ventricose; ribs 24-26, 

flattened, scarcely prominent, divided by a longitudinal furrow; 

disk concentrically wrinkled; umbo ventricose; summits prominent, 

remote from the center. Length 2 118 inches; height 1 3/4 inches." 

Holotype.-Location unknown; presumed lost. 

Type locality.-"Santa Barbara, Calif." The same uncertainty 

pertains to this locality as for A. trilineata. 

Comparison.-"This subspecies differs from the typical subspecies in form; the subspecies A. trilineata canalis is almost 

equidimensional in profile, its height nearly the same as the 

length, whereas A. trilineata trilineata is elongate." (Reinhart, 

1943, p. 60) 

Geographic range.-Japan? (Reinhart, 1943, p. 60); northern to 

southern California. 

Geologic range.-Miocene to Pleistocene. 

Occurrence in Cali{ornia.-Miocene. Pancho Rico Formation 

(Durham and Addicott, 1965); Miocene and Pliocene: Etchegoin 

(Arnold, 1909) and Purisima (Arnold, 1908; McLaughlin and 

Waring, 1915) Formations: Pliocene: Careaga Formation (Reinhart, 

1943) and upper part of Towsley Formation (Winterer and Durham, 

1962); Pliocene and Pleistocene: Fernando (W. 0. Addicott and J. 

G. Vedder, written commun., 1968) and Pico (Winterer and Durham, and 1962) Formations. 

Anadara (Anadara?) strongi (Loel and Corey) 

Plate 6, figures 13, 14 

Area (Barbatia) strongi Loel and Corey, 1932, p. 183, pl. 7, fig. 11 

Anadara (Anadara?) strongi (Loel and Corey). Reinhart, 1943, 

p. 42, pl. 12, fig. 6. 

Original description.-"Shell small, thin, somewhat elongate; 

valves inequilateral, ovate-quadrate in outline, moderately convex; 

umbones low, moderately inflate [sic; inflated] and well anterior, 

beaks closely proximate, overhang above hinge line, area narrow 

and long; sculptured by about twenty pairs of narrow, sharply 

rounded double ribs between which pairs interspaces are about 

width of single rib. Length, about 17 mm.; width about 10 mm." 

Lectotype.-UCMP 31762 (Reinhart, 1943). 

Type locality.-UC A527. Orange County, Calif. Uppermost part 

of Vaqueros Formation, Miocene. 

Supplementary description. -"umbones located at anterior third; 

shell evenly rounded, lacking medial depression or umbonal ridge; 

apparently no byssal gape. Ribs*** broad, flat, deeply grooved in 

center, grooves extending from margin to about 5 millimeters from 

beak; ribs separated by nearly flat interspaces slightly narrower 

than ribs; spacing and size of ribs fairly uniform over surface of 

shell. Sculpture appears to be equal on both valves. Ligamenta} 

area narrow*** an internal mold of three anterior teeth is preserved, showing these to converge ventrally; interior of shell not 
A42 PALEONTOLOGY OF CALIFORNIA AND BAJA CALIFORNIA 

known***. This species is assigned to Anadara on the basis of its 

regular, strong, Anadara-like radial ribs, which serve to separate it 

from Barbatia, as it was originally described. Preservation is not 

sufficiently good to permit its assignment to Anadara s.s., however, 

except questionably, as it may be a Scapharca." (Reinhart, 1943, 

p. 42-43) 

Comparison.-"This species is somewhat similar to Anadara 

media-impressa*** which differs in having more ribs, in being 

more inflated, and in not possessing such well-developed longitudinal grooves on the ribs as A. strongi." (Reinhart, 1943, p. 43) 

Geographic range.-Southern California. 

Geologic range.-Miocene. 

Occurrence in Cali{ornia.-Uppermost part of Vaqueros 

Formation. 

Genus GRANDIARCA Olsson, 1961 

"Shell large, high trigonal, equivalve, solid, often becoming 

heavy and ponderous in the adult. Umbones wide and prominent, 

central, and usually feebly sulcate, bordered posteriorly by the 

umbonal ridge at first relatively sharp or angled, later becoming 

lower and rounded. Beaks small, curved in over a wide, triangular 

cardinal area. Ligament coarse and heavy, covering the cardinal 

area completely, the surface of the cardinal area striated with 

faint, vertical lines and marked with few to many deep, triangular 

to lozenge-shaped ligamenta} grooves. Ribs strong, rectangular in 

section between deeply grooved interspaces, the summit ofthe ribs 

smooth or concentrically wrinkled except on the most anterior ones 

which are crudely noded. Interior of shell widely and deeply fluted 

by the ribs around the ventral margin. Hinge teeth small, vertical, 

in a continuous series. Surface of shell protected by a thick, 

smooth, black periostracum. 

"Like Larkinia but differing by its less truncated posterior side 

and fewer, plainer ribs." (Olsson, 1961). 

Type species.-Arca grandis Broderip and Sowerby. 

Comments.-This genus is reinstated following Keen (1971, 

p. 46), who says that Grandiarca is more oblique and massive than 

Larkinia and has fewer ribs. 

Geographic range.-Magdalena Bay, Baja California Sur to 

Peru. 

Geologic range.-Miocene to Holocene. 

Grandiarca grandis (Broderip and Sowerby) 

Plate 9, figures 8, 9 

Area grandis Broderip and Sowerby, 1829, p. 365 

Anadara (Larkinia) grandis (Broderip and Sowerby). Reinhart, 

1943, p. 65-66, pl. 13, figs. 4-6. 

Anadara (Grandiarca) grandis (Broderip and Sowerby). Keen, 

1971, p. 46, 48, fig. 89. 

Original description.-"A testa oblique subquadrata, crassa, 

alba, radiatim costata, laevi, costis rotundatis, anticis crenulatis, 

reliquis muticis, epidermide coriacea; long 4 3/16, lat 3 3/40, alt 3 

5/10, poll." 

Holotype.-Location unknown. 

Type locality.-None given. 

Supplementary description.-The shell has about 26 ribs and 

thickens with age until it becomes impressively massive. A single 

valve, 145 mm long, weighs 680 grams. (Keen, 1971) 

Comparison.-"The largest species of Area we remember to have 

seen, growing even to a larger size than A. sinilis, which it also 

resembles very much; it is, however, longer, and the number of ribs 

greater." (Broderip and Sowerby, 1829, p. 365) 

Geographic range.-Living: Magdalena Bay and the Golfo de 

California to Peru; fossil: Golfo de California to Ecuador. 

Geologic range.-Miocene through Holocene. 

Occurrence in Baja California.-Pliocene: unnamed strata, 

Carmen Island, Golfo de California (Hanna and Hertlein, 1927). 

Habitat.-Found at extreme low tide on sand bars; common in 

mud around mangrove roots. 

Genus LARKINIA Reinhart, 

Subtrigonal, nearly as high as long, heavy with prominent, 

elevated umbones and small beaks; cardinal area high; costae 

narrow, steep-sided, smooth or beaded with coarse or scabrous 

nodes. 

Geographic range.-Eastern Pacific; Caribbean. 

Geologic range. -Oligocene through Holocene. 

Habitat.-One species reported on sand bars at very low tide; to 

depths of 128m. 

Larkinia santana santana (Loel and Corey) 

Plate 8, figures 3, 7 

Area (Anadara) santana Loel and Corey, 1932, p. 185, pl. 8, figs. 

1a-3,2,3a,3b. 

Anadara (Larkinia) santana subsp. santana (Loel and Corey). 

Reinhart, 1943, p. 63-64, pl. 8, figs. 7, 8. 

Anadara santana Loel and Corey. Squires and Fritsche, 1978, 

p. 17, pl. 3, fig. 1. 

Original description.-"Shell heavy and rugose, fairly ventricose, equivalve, of medium size, exterior bell-shaped in outline, 

almost equilateral, interior subquadrate inequilateral, umbones 

very high and inflate [sic: inflated], medial; beaks prominent, 

strongly inturned, only slightly prosogyrous, and not greatly 

distant, just anterior to middle; cardinal area fairly broad, impressed, with inequal anterior-posterior lines; hinge plate narrow, 

straight, with about 30 fine slender teeth, vertical anteriorly, 

oblique posteriorly. The margins, which are fluted entirely around, 

are evenly rounded on the type specimen; (on most others the 

posterior extremity is more abruptly rounded and posterior margin 

is gently rounded). Surface sculptured by about 22 coarse, evenly 

rounded ribs with interspaces of almost equal width; prominent 

lines of growth give an irregularly constricted appearance to the 

shell which is of a dull brown color. Height, 40 mm.; length, 38 

mm.; length of hinge plate, 30 mm.; diameter of valve, 20 mm." 

Holotype.-UCMP 31768. 

Type loclity.-UC 6128. Orange County, Calif. Vaqueros Formation, Oligocene and Miocene. 

Supplementary description.-''Ligamental area broad, concave, 

indented at posterior end, sculptured by several indistinct grooves. 

Due to concavity, this area would appear U-shaped with both 

valves attached, if viewed end-on***. Hinge*** fairly heavy; teeth 

numerous, long and slender, converging slightly at extremities, 

but tending to diverge just posterior to center of hinge. Inner 

margin crenulated; no byssal gape." (Reinhart, 1943, 

p. 64) 

Comparison.-"This species belongs to the subgenus Larkinia, 

resembling, in a general way, Anadara chiriquiensis toroensis 

(Spieker)***from the***Zorritos Formation,***Miocene, of Peru. 

The Peruvian species, however, may easily be distinguished by 

being more elongate in outline, and by having more ribs." 

(Reinhart, 1943, p. 64) 

Geographic range.-Southern California; Baja California Norte? 

Geologic range.-Oligocene and Miocene. 
TERTIARY MARINE PELECYPODS: NUCULIDAE THROUGH MALLEIDAE A43 

Occurrence in California and Baja California Norte.-Oligocene 

and Miocene: Vaqueros Formation (Loel and Corey, 1932), upper 

Sespe and Vaqueros Formations, undifferentiated (Schoellhamer 

and others, 1981); Miocene: questionably in unnamed Miocene 

strata near Purisima Nueva, Baja California Norte (Loel and 

Corey, 1932). 

Larkinia santana weddlei (Loel and Corey) 

Plate 9, figures 1, 2 

Area (Anadara) santana var. weddlei Loel and Corey, 1932, p. 185, 

pl. 8, figs. 4a, 4b. 

Anadara weddlei (Loel and Corey). Schenck and Keen, 1940, pl. 31, 

figs. 1, 2. 

Anadara (Larkinia) santana subsp. weddlei (Loel and Corey). 

Reinhart, 1943, p. 64-65, pl. 8, figs. 5, 6. 

Original description.-"In the type section of the Vaqueros 

formation, Vaqueros Creek, Monterey County, occurs an Area 

similar in all characters to Area (Anadara) santana except that 

the umbones are less inflate [sic: inflated] and the ribs less 

prominent. These characters are constant in the eight specimens 

collected. Height of figured specimen, 39 mm.; length, 39 mm; 

diameter (both valves), 37 mm.; length of hinge plate, 34 mm." 

Holotype.-UCMP 31771. 

Type locality.-UC 3675. Monterey County, Calif. Vaqueros 

Formation, Oligocene and Miocene. 

Comparison.-"This subspecies differs from typical Anadara 

santana only in having less inflated umbones, so that, when 

viewed from either side, the hinge margin projects noticeably 

beyond the umbo, whereas in the typical A. santana the hinge 

margin projects only slightly. The holotype of A. santana weddlei 

is equivalve; the beaks are prosogyrate, as in typical A. santana." 

(Reinhart, 1943, p. 64-65) 

Geographic range.-Middle California. 

Geologic range.-Oligocene and Miocene. 

Occurrence in California.-Oligocene and Miocene: Vaqueros 

Formation. 

Larkinia camuloensis (Osmont) 

Plate 8, figures 8, 9 

Area camuloensis Osmont, 1905, p. 98, pl. 10, figs. 6, 6a; pl. 11, figs. 

6b, 6c. 

Area (Area) multicostata Sowerby var. camuloensis Osmont. Grant 

and Gale, 1931, p. 139, pl. 2, figs. 5a-c. 

Anadara camuloensis (Osmont). Woodring, 1938, p. 29-30, pl. 6, 

figs. 10, 13-16. 

Anadara (Larkinia) camuloensis (Osmont). Reinhart, 1943, p. 65, 

pl. 7, figs. 2, 8, 9. 

Original description.-"Shell quadrate to circular, height only 

slightly less than length, (adult 90x98 mm.), almost equilateral, 

thickness through closed shell nearly equal to height. Beaks not 

widely separated, very slightly turned forward, and greatly 

incurved over a wide and flaring ligament area. Ribs about 32 in 

number, rounded and without grooves, considerably wider than 

the interspaces, and crossed by regular ridges, which give them a 

beaded structure. At about the ninth rib from the posterior end is a 

very distinct shoulder, from which there is a steep concave slope to 

the posterior margin." 

Holotype.-UCMP 12006. 

Type locality.-1.5 km north ofCamulos, Ventura County, Calif. 

Fernando Formation, Pliocene and Pleistocene. 

Supplementary description.-"A large, thick-shelled, moderately 

short Anadara. Sculpture consisting of strong ribs bearing heavy 

concentric ridges ('beads') that appear to be strongest on the 

anterior part of the shell and are not uniformly developed. Ribs 

and interspaces show indistinct radial threads. Cardinal area wide 

(from umbo to lower margin.)" (Woodring, 1938, p. 29) 

Comparison.-"A. camuloensis is closely related to A. multicostata (Sowerby), but differs by possessing heavily beaded ribs, 

whereas those of multicostata are usually beaded slightly or not at 

all." (Reinhart, 1943, p. 65) 

Geographic range.-Middle and southern California. 

Geologic range.-Miocene to Pleistocene. 

Occurrence in California.-Miocene: Pancho Rico Formation 

(Durham and Addicott, 1965); Pliocene: Niguel Formation (J. G. 

Vedder, written commun., 1978); Pliocene and Pleistocene: 

Fernando (Arnold. 1907a; Durham and Yerkes, 1964) and Pico 

(Winterer and Durham, 1962) Formations. 

Larkinia multicostata (Sowerby) 

Plate 9, figures 4, 5 

Area multicostata Sowerby, 1833, p. 21 

Anadara (Larkinia) multicostata (Sowerby). Reinhart, 1943, p. 66, 

pl. 8, figs. 9-11. Durham, 1950, p. 54, pl. 1, figs. 15-17. Keen, 

1971, p. 48, fig. 90. 

Original description.-"Shell squarely rhomboid, solid, equivalve; sides attenuated and angulated at the upper part, anterior 

side shorter, ventricosely rounded beneath, posterior angularly 

extended downward; ivory white, covered over with a brown horny 

epidermis, which is a little velvety between the ribs; radiately 

ribbed, ribs about six-and-thirty in number, rather narrow, 

rounded, smooth, anterior ribs slightly granulous; area of the 

ligament rather broad; umbones somewhat approximated. Length, 

100; height, 80; diameter, 76 mm." 

Holotype.-In BM(NH)? 

Type locality.-Gulf ofTehuantepec, Central America. Holocene. 

Supplementary description.-"This species varies greatly. There 

may be a sharp posterior ventral angle, or it may be nearly square, 

the chevrons for attachment of the ligament may be few or many, 

although they are commonly few. The specimens may attain a 

height of more than 85 mm." (Durham, 1950, p. 54) 

Comparison.-"This has more ribs than A. grandis (31 to 36 

rather than 25 to 27). The shell is thinner and more quadrate. 

Unlike A. grandis, it is a little inequivalve, the left valve overlapping the right, as in Cunearca and Scapharca." (Keen, 1971, p. 48) 

Geographic range.-Living: Newport Bay, Calif., west coast of 

Baja California, Golfo de California, and south to Panama and the 

Galapagos Islands; fossil: Baja California Sur. 

Geologic range.-Pliocene through Holocene. 

Occurrence in Baja California Sur.-Pliocene: Carmen and 

Marquer Formations (Durham, 1950); Pleistocene: unnamed strata 

San Nicholas Island, Calif. (Vedder and Norris, 1963) and Bahia 

San Quintin, Baja California Norte (Jordan, 1926). 

In regard to supposed Pliocene localities in the Puente Hills, 

Orange County, and the Third Street Tunnel, Los Angeles County, 

L. camuloensis, not L. multicostata, has been found. It therefore 

seems doubtful that L. multicostata occurs in the Pliocene. 

(Reinhart, 1943, p. 66) 

Habitat.-In tropical waters in depths to 128m; rarely, on sand 

bars at very low tide. 

Genus SCAPHARCA Gray, 1847 

Shell relatively thin, moderately convex; valves discordant, left 
A44 PALEONTOLOGY OF CALIFORNIA AND BAJA CALIFORNIA 

valve being larger, its margin overlapping that of right valve. 

Geologic range.-Oligocene through Holocene (table 3). 

Subgenus SCAPHARCA 

Elongate, umbones flattened or slightly sulcate; sculpture similar 

on both valves, consisting of smooth or nodose, simple or bifurcating costae that are rectangular in cross section and separated 

by flattened interspaces; cardinal area narrow, elongate. 

Genus SCAPHARCA? 

Subgenus SCAPHARCA? 

Scapharca? (Scapharca?) obispoana obispoana (Conrad) 

Plate 9, figure 3 

Area obispoana Conrad, 1857c, p. 192, pl. 5, fig. 1. Grant and Gale, 

1931, p. 955, pl. 32, fig. 49. 

Anadara (Scapharca?) obispoana subsp. obispoana (Conrad). 

Reinhart, 1943, p. 70-72, pl. 10, figs. 6, 7, 11 [See for synonymy]. 

Anadara obispoana (Conrad). Addicott and others, 1978, p. 59, 

pl. 1, fig. 3. 

Original description.-"Oblong, or trapezoidal; very inequilateral, ventricose; ribs about 26, little prominent, flattened; sides 

rectangular with the back; transversely rugose, or subcrenulated." 

Lectotype.-USNM 13330 (Grant and Gale, 1931, p. 955; explanation of pl. 32, fig. 49). 

Type locality .-A few kilometers southwest of San Luis Obispo, 

San Luis Obispo County, Calif. Santa Margarita(?) Formation, 

Miocene. 

Supplementary description.-"Moderate in size, flat, *** 

quadrate in outline; hinge margin straight, slightly interrupted by 

umbones; ventral margin broadly rounded; anterior and posterior 

margins sharply rounded; umbones inconspicuous, located at 

anterior third. Ribs*** nearly flat, with a medial longitudinal 

groove faintly visible in each rib; ribs wider toward posterior than 

toward anterior part of shell; interspaces about as wide as ribs on 

anterior half of shell, but narrower in posterior half; concentric 

growth lines especially noticeable toward margins. Ligamenta} 

area apparently narrow; *** teeth *** strongly convergent." 

(Reinhart, 1943, p. 71) 

Comparison.-"A. obispoana s.s. differs from A. (A) montereyana by having fewer ribs and in being more compressed." 

(Reinhart, 1943, p. 72) 

Geographic range.-Kamchatka(?); Washington(?) (Weaver, 

1942); middle and southern California. 

Geologic range.-Oligocene and Miocene. 

Occurrence in California.-Miocene: Monterey Formation 

(Arnold, 1908; Martin, 1912; Addicott and others, 1978), Oursan 

Sandstone (Hall, 1958), and Santa Margarita(?) Formations and 

upper part of Temblor Formation (Stewart, 1946; Adegoke, 1969). · 

Scapharca? (Scapharca?) obispoana perdisparis (Wiedey) 

Plate 9, figure 6 

Area perdisparis Wiedey, 1928, p. 131-132, pl. 13, fig. 6; pl. 14, fig. 1. 

Anadara (Scapharca?) obispoana subsp. perdisparis (Wiedey). 

Reinhart, 1943, p. 72-73, pl. 10, fig. 8. 

Original description.-"Shell moderately small, elliptical in outline, with the posterior end broader than the corresponding anterior 

end. It is very inequilateral and only slightly convexly inflated. 

Anterior dorsal margin very short, passing in a gently rounded 

manner to the basal margin, which is very long and nearly 

straight, forming a low angle with the hinge line. Posterior dorsal 

extremity quite broadly rounded to the margin, ~hich is but 

slightly rounded. Umbo narrow, distinctly elevated above the 

main body of the shell in a long, regularly rounded ridge. Beak 

small, sharp, but prominent, very near the anterior end of the shell 

and perceptibly prosogyrous. The shell is sculptured by about 

twenty-eight flattened ribs, of equal or of lesser width than the 

interspaces. The nbs apparently have little tendency to split. The 

hinge line is about two-thirds the length of the shell. Length, 36 

mm.; breadth, 19 mm.; thickness of a single valve, 5 mm." 

Holotype.-SDNM 23. 

Type locality.-SD 443. Santa Cruz County, Calif. Monterey 

Formation, Miocene. 

Compatison.-"This subspecies is similar-to Anadara obispoana 

obispoana (Conrad), agreeing with it in the number of ribs *** 

dentition, and convexity. A. obispoana perdisparis, however, is 

more elongate than typical A. obispoana. No sharp line may be 

drawn between the subspecies and the typical species, both of 

which are variable in profile." (Reinhart, 1943, p. 73) 

Geographic range.-Middle California. 

Geologic range.-Miocene. 

Occurrence in California.-Monterey Formation. 

Subgenus CUNEARCA Dall, 1898 

Subtrigonal, inflated, with full umbones and small, submedial 

beaks, high triangular cardinal area; sculpture of valves discrepant, costae ofleft valve larger and more coarsely nodose. 

Geologic range.-Oligocene through Holocene (table 3). 

Scapharca (Cunearca) vanderhoofi Durham 

Plate 9, figure 7 

Anadara (Cunearca) vanderhoofi Durham, 1950, p. 53, pl. 1, figs. 1, 

2. 

Anadara vanderhoofi Durham. Wilson, 1979, p. 25, fig. 

Original description.-"Shell usually moderately thin, beaks 

rather high, of medium size, not too well preserved; dorsal margin 

straight, posterior margin slanting obliquely down and out, ventral 

margin evenly convex rounding into the decidedly convex anterior 

margin; right valve (holotype) with 28 medium-sized, square-sided 

ribs, interspaces of equal width; ribs apparently not noded; other 

right and left valves with about 24 ribs; all left valves with ribs 

wider than interspaces; ligamenta! area apparently with two 

broadly inverted V-shaped chevrons, widest anterior to beak but 

longest posterior; teeth eroded from all hinges available." 

Holotype.-UCMP 30548. 

Type locality.-UC A3595. Baja California Sur. San Gregorio 

Formation, Oligocene. 

Geographic range .. -Baja California Sur. 

Geologic range .. -Oligocene. 

Occurrence in Baja California Sur.-San Gregorio Formation. 

Scapharca (Cunearca) santaclarana (Loel and Corey) 

Plate 9, figures 10, 11 

Area (Anadara) santaclarana Loel and Corey, 1932, p. 184, pl. 7, 

figs. 8, 9, lOa, lOb. 

Anadara (Scapharca) santaclarana (Loel and Corey). Reinhart, 

1943, p. 66-67, pl. 12, figs. 12-14. 
TERTIARY MARINE PELECYPODS: NUCULIDAE THROUGH MALLEIDAE A45 

Original description.-"Shell small, gibbose, fairly convex, subtrigonal and but slightly oblique, with prominent high umbones 

which are just posterior; beaks distant and only slightly prosogyrous; a strong angular posterior umbonal ridge extends to the 

posterior extremity; cardinal area wide, slightly concave, posterior 

margin straight to acute posterior extremity, ventral margin 

gently rounded to anterior, which is evenly curved to the hinge; 

surface sculptured by 18 flat ribs (prominently nodose as seen on 

other specimens) crossed by evenly spaced concentric lines. Height, 

20 mm.; length, 22mm. On other specimens from same locality the 

hinge line is long, straight, with about 30 oblique teeth, the 3 

extremities being almost horizonal. Diameter (both valves) 21 

mm." 

Holotype.-UCMP 31765. 

Type locality.-UC A252. Ventura County, Calif. Vaqueros 

Formation, Oligocene and Miocene. 

Comparison.-"This species resembles Anadara (Cunearca) 

riuulata (Wiedey) *"'*but differs in having broader umbones, wider 

ligamenta} area, and fewer ribs. A. santaclarana is a Cunearca, as 

shown by its short, high, inflated form. Better specimens than the 

ones available will probably show the species to be slightly 

inequivalve, as is typical Cunearca." (Reinhart, 1943, p. 67) 

Geographic range.-Southern California. 

Geologic range. -Oligocene and Miocene. 

Occurrence in California.-Vaqueros Formation. 

Scapharca (Cunearca) hamelini (Wiedey) 

Plate 9, figure 12 

Area hamelini Wiedey, 1928, p. 126, pl. 13, fig. 2 

Anadara (Cunearca) hamelini (Wiedey). Reinhart, 1943, p. 67-68, 

pl. 12, fig. 9. 

Area sespeensis Wiedey, 1928, p. 125, pl. 13, fig. 1. 

Area (Anadara) sespeensis Wiedey. Loel and Corey, 1932, p. 184, 

pl. 7, fig. 6. 

Original description.-"Shell small, subtrapezoidal, distinctly inequilateral, equivalve, and convexly inflated. The anterior dorsal 

margin not long, moderately straight with the anterior extremity 

bluntly rounded. The basal margin is quite long and has a 

tendency toward parallelism with the hinge line. The posterior 

extremity more broadly rounded above than below. The posterior 

dorsal margin is short and nearly straight. The umbones are 

prominent, large, angular, and elevated, with the umbonal ridge 

quite well defined. Beak small, well anterior, prominent, sharply 

pointed, incurved, elevated, prosogyrous, and widely separated in 

combined valves. The sculpture consists of about sixteen ribs 

which are high, narrow, and rounded, separated by flattened 

channels which are distinctly much broader. Where the growth 

lines cross the ribs there is a tendency to form rugose sculpture, 

more markedly toward the extremity of the disk. The cardinal area 

is large, prominent, and moderately depressed. Length, 28 mm.; 

breadth, 20 mm.; height of one valve, 13 mm." (hamelini) 

"Shell moderately small, trapezoidal, quite inequilateral and 

somewhat gibbose. Posterior dorsal margin short, dropping nearly 

straight down from under beak. It is quite sharply rounded at the 

extremity, and has a long, gently convex ventral margin. The 

posterior extremity is sharply rounded to the anterior dorsal 

margin which slopes approximately straight down from the beak. 

Umbo large, prominent, rather broad, and flattened. The beak is 

large, posterior, blunt, incurved, and pointed anteriorly. Cardinal 

area of moderate size, only gently depressed. Sculpture consisting 

of about nineteen ribs which are prominently elevated and sharply 

rounded. Concentric growth lines faint and indistinct. Length, 32 

mm.; breadth, 25 mm.; height of one valve, 13 mm." (sespeensis) 

Holotype.-A. hamelini, SDNM 18; A. sespeensis, SDNM 17. 

Type locality.-SDNM 407. Ventura County, Calif. Vaqueros 

Formation, Oligocene and Miocene. 

Supplementary description.-A broad, rounded, inconspicuous 

ridge extends from umbo to posterior ventral margin. Ligamenta} 

area wide and flat. Anadara sespeensis is considered conspecific 

with A. hamelini because the holotypes of both species, collected 

from the same locality, are similar in size, number of ribs (17 ribs 

on the holotype of each), and shape, if one allows for distortion due 

to crushing, especially of the holotype of A. sespeensis. The beak of 

that specimen is crushed such as to appear opisthogyrate, this 

appearance is probably the reason for its being originally described 

as a right valve, although it is actually a left valve. Since A. 

sespeensis can hardly be considered recognizable, the name A. 

hamelini is used for this species. (Reinhart, 1943, p. 67) 

Geographic range.-Southern California. 

Geologic range. -Oligocene and Miocene. 

Occurrence in California.-Vaqueros Formation. 

Scapharca (Cunearca) rivulata (Wiedey) 

Plate 9, figure 13 

Area riuulata Wiedey, 1928, p. 128, pl. 13, fig. 3. 

Anadara (Cunearca) riuulata (Wiedey). Reinhart, 1943, p. 68-69, 

pl. 5, figs. 3, 5-8. 

Area galei Wiedey, 1928, p. 129-130, pl. 13, fig. 8. 

Original description.-"Shell of small size, subquadrate in outline, quite inequilateral and rather convex. Anterior dorsal margin 

short, sloping quickly to the extremity, which is sharply rounded 

above, more so below. The basal margin gently convexly rounded 

to the posterior dorsal extremity which appears to be quite sharply 

rounded to its adjacent margin. The latter is moderately long and 

slopes down quite straight from the beak. Umbo prominent, 

elevated, and incurved. The beak is small, prominent, situated 

anteriorly, sharp, and distinctly prosogyrous. The sculpture consists of about twenty ribs which are rounded, prominently elevated, 

and separated by slightly narrower, flatly channeled interspaces. 

Ribs quite regularly rilled by concentric waves which do not 

sculpture the interspaces. Rilling is more marked toward the 

margins of the disk. The cardinal area is apparently small and 

only slightly depressed. Length, about 15 mm.; breadth, 13 mm.; 

height of a single valve, 7 mm." (riuulata) 

"Shell of moderate size, subtrigonal in outline, distinctly inequilateral and quite convexly inflated. The anterior dorsal margin 

short and gently convexly curved to the anterior dorsal extremity, 

which is very sharply rounded to the basal margin. The latter is 

broadly convexly rounded. Posterior dorsal extremity angularly 

truncated to the posterior dorsal margin which is nearly straight 

and slopes abruptly. Umbo large, prominent, angular, elevated, 

and situated anteriorly. Beak slightly incurved, sharp, and prosogyrous. A distinct shoulder is formed at the posterior side of the 

umbo, extending from the beak to the posterior extremity, which 

causes the posterior dorsal area to be separated from the main 

body of the shell at nearly a right angle. The upper part of the 

posterior dorsal area appears distinctly folded under the beak. The 

sculpture consists of about twenty strong ribs, separated by narrower channeled interspaces. The ribs are rippled by concentric 

waves which are not apparent in the interspaces. Cardinal area 

inaccessible but apparently not large, sunken deeply below the 

beak. Length, 25 mm.; breadth, 18 mm.; thickness of a single valve, 

9 mm." (galei) 

Holotype.-A. riuulata: SDNM 20; A. galei: SDNM 21. 

Type locality.-SU 432. San Luis Obispo County, Calif. Saltos 

Shale Member of the Monterey Shale, Miocene. 

Supplementary description.-"Shell inequivalve, the right valve 

smaller than the left; sculpture of the two valves quite discrepant, 
A46 PALEONTOLOGY OF CALIFORNIA AND BAJA CALIFORNIA 

all of the ribs of the left valves nodulous, whereas, on right valve, 

only the anterior 10 are nodulous, the remaining ones being 

smooth; number of ribs on the two valves is the same-22. 

Ligamenta} area nearly flat, sculptured with two chevron-shaped 

grooves. Hinge straight, a little narrower at center than at extremities; about 36 small, closely spaced teeth interrupted by only a 

slight gap under the beak; these teeth are vertical at the center, but 

converge slightly at the extremities. Interior of the shell concealed 

by matrix, but enough of the inner margin is visible to show that it 

is strongly crenulated." (Reinhart, 1943, p. 69) 

Comparison.-"This species resembles Anadara (Cunearca) 

alcima (Dall) *** from the Pliocene of Florida, but differs in having 

more prominent nodes and fewer ribs. A. rivulata is much closer to 

Anadara (Cunearca) thalia (Olsson)*** a Peruvian lower Miocene 

species***. Although the similarity between these two species is 

great, A. thalia differs in having two to three more ribs and in 

being slightly more elongate. 

"This species also somewhat resembles A. santaclarana (Loel 

and Corey)*** but A. rivulata differs in having narrower umbones 

and ligamenta! area, and more ribs." (Reinhart, 1943, p. 69) 

Geographic range.-Southern California. 

Geologic range.-Miocene. 

Occurrence in Cali{ornia.-Upper part of Temblor Formation 

(Reinhart, 1943) and Saltos Shale Member of the Monterey Shale. 

INDETERMINATE SPECIES 

"Area" clarki Dickerson 

Area clarki Dickerson, 1916, p. 481, pl. 37, fig. 12. 

"Having exposed the hinge of the holotype, I find that this 

species does not belong to the Arcidae. The dentition consists of 

two heavy, ventrally-converging teeth on each side of the hinge 

plate; in the center of the hinge, directly beneath the beaks, is a 

deep central depression. The hinge, so far as can be seen, somewhat 

resembles that of Limposis, but externally this specimen resembles 

Pteria or Pecten." 

Comments.-On the basis of the outline and poorly preserved 

hinge, I believe this species may be a young cardiid, and it will be 

illustrated in the chapter that includes that group. 

"Anadara congesta (Conrad)'' 

Area congesta Conrad, 1857a, p. 314 

Anadara congesta (Conrad). Reinhart, 1943, p. 83. 

"This name is evidently based upon an immature specimen; and 

since the type locality is unknown and the original figure and 

description are inadequate, this species must remain unrecognizable. As noted by Osmont, Anadara congesta might be the 

young of any one of half a dozen species. The holotype appears not 

to be in the U.S. National Museum***." (Reinhart, 1943, p. 83) 

"Anadara (Anadara?) microdonta (Conrad)'' 

Area microdonta Conrad, 1855, p. 13 

Anadara (Anadara?) microdonta (Conrad). Reinhart, 1943, 

p. 46-47, pl. 6, figs. 9, 10. 

"The type of Area microdonta Conrad*** is a well-preserved 

right valve*** (***[USNM] 1844), said to be from the 'Tulare 

Valley(?)'***. California fossils have been identified as Area 

microdonta, but no fossil or living species now known from 

California agrees with it, and whether it came from California is 

very doubtful. It shows no characters to differentiate it from 'nonwinged' specimens of the Recent West Indian species identified by 

Dall as Area auriculata Lamarck. Perhaps Blake collected it from 

Pleistocene deposits on the Atlantic coast of Panama near Colon 

(Aspinwall of Blake's time), where the species identified as A. 

auriculata is known to occur. Blake collected from the Miocene 

Gatun formation, but nothing is mentioned about other localities 

in Panama." (Woodring, 1938, p. 31) 

Family PARALLELODONTIDAE 

Subfamily GRAMMATODONTIN AE 

Genus PORTERIUS Clark, 1924 

Ovoid, costellate, externally similar to Barbatia but with posterior lateral teeth and cardinals that converge ventrally. 

Geographic range.-Western United States, Europe, and 

Japan. 

Geologic range.-Eocene through Holocene. [Two species have 

been found in the Tertiary of the Western United States, one in the 

Eocene of southern California and one in the Oligocene of Washington and Oregon. The genus is not known to be living now off 

the coast of North or South America.] 

Porterius woodfordi (Hanna) 

Plate 10, figure 3, 4 

Barbatia woodfordi M. A. Hanna, 1927, p. 273, pl. 27, figs. 1, 6, 

8, 10. 

Porterius wood{ordi (Hanna). Reinhart, 1937a, p. 176-178. 

Vokes, 1939, p. 45, pl. 1, fig. 13. 

Original description.-"Left valve; shell small, subrhomboidal, 

fairly thick, moderately inflated, inequilateral; beak fairly prominent, anterior to the center, projects a short way above the hinge 

margin; ventral margin regularly rounded; anterior regularly 

rounded; posterior rounded to obliquely truncated; hinge margin 

straight, about one-half the length of the shell; no umbonal ridge, 

surface slopes away regularly, being wider at the posterior; surface 

concentrically striated by fairly prominent growth lines; radially 

striated by fifty-five to sixty prominent rounded ribs which are 

separated by narrower interspaces; cardinal area short, narrow; 

hinge margin narrow, bearing at least four teeth anteriorly and six 

posteriorly, the portion directly below the beak broken away; teeth 

nearly parallel to the hinge line at either end; interior of the shell 

not seen. Dimensions. Type: Altitude 2.5 mm., length 3.5 mm. 

Paratype 31063: Altitude 9.0 mm., length 13.0 mm." 

Holotype.-UCMP 31062. 

Type locality.-UC 5062. San Diego County, Calif. Ardath Shale, 

Eocene. 

Supplementary description. -"Description of holotype (a young 

left valve): Shell minute, suboval ***moderately inflated, delicate. 

Umbo moderately prominent, located one-fourth of length of shell 

from anterior end; beak prosogyrate. In profile the anterior, ventral, and posterior margins are gently rounded; hinge margin 

nearly straight, except for interruption of umbo. 

"Sculpture consists of about 58 radial ribs separated by narrower 

inters paces. Ribs simple throughout most of their length, but near 

ventral margin divided longitudinally by shallow grooves into two 

parts *** (In paratype no. 31063 *** a much larger specimen, this 

dichotomizing takes place at nearly the same distance from tip of 

umbo as in the small holotype; but in the larger specimen it is still 

high up in the umbo, so that throughout most of its length each rib 

is divided into two parts by a longitudinal groove. Toward the 

ventral margin each part resembles a separate rib. Hanna's figure 

does not show this detail.) Ribs are evenly spaced over most of 

shell, but the anterior and posterior ribs are larger and more widely 
TERTIARY MARINE PELECYPODS: NUCULIDAE THROUGH MALLEIDAE A47 

spaced. Regular concentric growth lines cut across the ribs. 

"Ligamenta} area narrow, not well preserved, located posterior 

to umbo. Hinge exposed in holotype, but the remainder of interior 

of shell is unknown. Hinge gently arched, posterior part longer 

than anterior; wider at extremities than in mesial region *** three 

strong, regular, inclined anterior teeth, and five posterior teeth, the 

posteriormost three lying parallel to hinge." (Reinhart, 1937a, p. 

177) 

Comparison.-"this species resembles Porterius gabbi (Dickerson) in hinge structure; and inasmuch as these two species are also 

similar in shape and ornamentation (both species possess dichotomizing radial ribs), it seems evident that P. woodfordi likewise 

belongs to Porterius. The two species may be distinguished by the 

fact that the radial ribs are much coarser and more distinct on P. 

gabbi than on P. wood{ordi." (Reinhart, 1937a, p. 178) 

Geographic range.-Middle and southern California. 

Geologic range. -Paleocene and Eocene. 

Occurrence in California.-Paleocene: Cerros Shale Member of 

the Lodo Formation (Keen and Bentson, 1944); Eocene: Ardath 

Shale, Domengine (Vokes, 1939) and Juncal (Turritella uvasana 

infera fauna, Givens, 1974) Formations. 

Family CUCULLAEIDAE 

Genus CUCULLAEA Lamarck, 1801 

Subtrigonal, subtrapezoidal to ovoid, heavy shells, posterior 

margin obliquely truncated, surface radially sculptured with 

strong costae; middle series of teeth and crenulations of inner shell 

margin becoming obsolete in mature and old individuals; pseudolaterals diverging downward in adults. 

Geographic range.-Living: Indo-Pacific; fossil: Europe and 

United States. 

Geologic range.-Jurassic through Holocene. 

Cucullaea mathewsonii Gabb 

Plate 10, figures 1, 2 

Cucullaea mathewsonii Gabb, 1864, p. 195, 235, pl. 31, fig. 266. 

Dickerson, 1914, p. 151, pl. 7, figs. 7a, 7b. Stewart, 1930, 

p. 77-78, pl. 8, fig. 8. Schenck and Keen, 1950, p. 27, pl. 19, 

fig. 4. 

Area biloba Weaver, 1905, p. 115, pl. 12, fig. 4 Not Nucula biloba 

Roemer, 1839. 

"Area" biloba Weaver. Reinhart, 1937a, p. 176, pl. 27, fig. 5. 

Original description.-"Shelllarge, thin, gibbous, subquadrate, 

rounded in front and on the base, and truncated behind; beaks 

large, prominent, subcentral, incurved, and somewhat remote; 

area long, narrow; hinge-line nearly as long as the greatest length 

of the shell. Surface marked by a large number of small, regular 

ribs, rounded on the surface, sometimes grooved longitudinally 

and with acute interspaces; posterior to the umbonal angle these 

ribs are much smaller than on the rest of the surface; the whole 

surface is crossed by fine lines of growth. Inner margin of the 

valves crenulated; inner plate well marked, but not very elevated." 

Lectotype.-ANSP 4559 (Stewart, 1930). 

Type locality.-Martinez, Contra Costa County, Calif. Martinez 

Formation, Paleocene. 

Supplementary description.-"basal margin of large specimens 

are truncated and marked by coarse lines of growth, probably due 

to age." (Waring, 1917, p.75) 

Comments.-The preserved characters of the holotype bear 

resemblance to the Jurassic and Cretaceous subgenus ldonearca. 

Geographic range.-Middle California to Baja California Sur. 

Geologic range. -Paleocene and Eocene. 

Occurrence in California and Baja California Sur. -Paleocene: 

Dip Creek Formation of Taliaferro (1944), Locatelli (Clark, 1968), 

and Martinez Formations; Paleocene and Eocene: Lodo (Smith, 

1975) and Tepetate (Beal, 1948) Formations. 

Cucullaea morani Waring 

Plate 10, figures 5, 6 

Cucullaea morani Waring, 1914, p. 784. Waring, 1917, p. 92, 

pl. 14, figs. 12-13. 

Original description.-"Shell thick, oblique, very convex; beaks 

large, broad, prominent, and about one-third the distance from the 

anterior, incurved and somewhat remote; area oval in shape and 

about two-thirds the length of the shell. Altitude 36 mm.; longitude 

60 mm. Anterior margin broadly rounded and more prominent 

above; base nearly straight; posterior produced and sharply 

rounded; umbonal ridge prominent and runs to posterior margin; 

cardinal margin sloping at an angle of about 45 degrees. Surface 

marked by alternating single and double radiating ribs which are 

crossed by fine to coarse lines of growth." 

Holotype.-CASISU 166. 

Type locality.-East of McCray wells 2.5 km. [Llajas Canyon, 6 

km northeast of Santa Susana, Simi Valley, Camulos quadrangle], 

Ventura County, Calif. Llajas Formation, Eocene. (Keen and 

Bentson, 1944) 

Geographic range.-Southern California. 

Geologic range.-Paleocene and Eocene. 

Occurrence in California.-Paleocene: Meganos Formation 

(Clark, 1921); Eocene: Llajas Formation. 

Family NOETIIDAE 

Geologic range. -Cretaceous through Holocene. 

Habitat.-Widespread in shallow seas. 

Subfamily STRIARCINAE MacNeil, 1938 

Geologic range.-Late Cretaceous through Holocene. 

Genus ARCOPSIS Koenen, 1885 

Barbatia-like costellate shells with ligament short, confined to 

shallow, triangular resilifer below beaks. 

Geographic range.-Europe, North America, Indo-Pacific. 

Habitat.-Attached to hard surface by byssus. 

Subgenus ARCOPSIS 

Surface costellate. 

Geologic range.-Paleogene through Holocene. 

Arcopsis (Arcopsis) eba (Hanna) 

Plate 10, figures 17, 18 

Area eba M.A. Hanna, 1927, p. 271-272, pl. 26, figs. 7-13. 

Arcopsis (Arcopsis) eba (Hanna). Reinhart, 1943, p. 37-38, pl. 11, 

figs. 15, 16. 

Original description.-"Left valve. Shell small, rhomboidal, moderately heavy, fairly well inflated; ventral margin nearly straight 

to very broadly rounded; anterior moderately sharply rounded; 

posterior straight, obliquely truncated; dorsal margin straight; 

beak prominent, anterior to the center, incurved; posterior surface 

steeply inclined from an umbonal ridge which extends from the 
A48 PALEONTOLOGY OF CALIFORNIA AND BAJA CALIFORNIA 

beak to the posterior ventral point; surface concentrically banded 

by prominent flat placoid ridges of equal width; radial sculpturing 

consists of numerous rows of prominent rounded nodes which are 

steeply inclined on their upper surface and nearly normal to the 

shell on the side toward the margin; usually rows of larger and 

smaller nodes alternate; only one node of each radial row to each 

concentric ridge; nodes break off rather easily so the surface may 

appear to have been smooth; posterior slope noded in accordance 

with the general surface; inner margin smooth, bordered inside by 

a groove; cardinal area rather wide, nearly smooth; hinge margin 

narrow, bent downward at either end, bears about twenty prominent elongate teeth which are much inclined toward the hinge line 

at either end but not parallel with it. Dimensions: Altitude 3.25 

mm., length 7.25 mm." 

Holotype.-UCMP 31047. 

Type locality.-DC 3990. San Diego County, Calif. Ardath Shale, 

Eocene. 

Supplementary description.-"In profile, anterior margin of shell 

rounded; ventral margin nearly straight; posterior margin sharply 

truncated, meeting dorsal margin at an angle of 45°, in holotype***numerous concentric growth lines, about 113 mm. apart, 

cover surface; these are crossed by radial ribs, formed of nodes (one 

node between each two growth lines)***. Nodes are larger (and 

consequently the radial ribs are more prominent) on the umbonal 

ridge than elsewhere. Spacing of ribs not uniform, but in most 

cases they are separated by interspaces wider than the ribs. About 

a quarter of the distance upward from the ventral margin, in the 

holotype, is a prominent growth line***; a similarly strong growth 

line, slightly higher up, is present on paratype***. Cardinal area 

long, narrow,***flat; two longitudinal grooves may be seen 

on***paratype***which join prominent growth lines at the extremities of cardinal area. Ligament apparently occupied only a small 

space between beaks, indicated by a shallow, transverse groove. 

Hinge slightly arched, thin in medial region; dentition observed in 

only two specimens, both imperfectly preserved***. 

"On the holotype, the five posterior teeth and two anteriormost 

teeth converge ventrically; the intervening teeth are poorly preserved; an edentulous area is present beneath beak. Muscle scars 

not observed. Inner margin of shell smooth; pallial line simple, 

impressed. Inner surface of shell lacks radial striations." (Reinhart, 

1943, p. 37-38) 

Comparison.- "Area eba***may be separated from Area hornii 

Gabb by shape, and in having a longer hinge line as well as a 

greater ratio of length to altitude. The sculpturing of the two is 

entirely different. Area hornii is the only species with which Area 

eba might be confused." (Hanna, 1927, p. 272) 

Geographic range.-Southern California. 

Geologic range.-Eocene. 

Occurrence in California.-Ardath Shale. 

Subfamily TRINACRIINAE 

Geographic range.-Europe, North America. 

Geologic range.-Cretaceous to Eocene. 

Genus PACHECOA Harris, 1919 

(=HALOANUS Stewart, 1930) 

Cardinal area small, situated entirely behind beaks; differs from 

Noeti~ in that sculpture consists of a few bifurcating costae, inner 

margm crenulate. 

Geographic range.-North America. 

Geologic range.-Eocene. 

Subgenus P ACHECOA 

Elongate ovoid, cardinal area well defined. 

Geographic range.-Southeast United States and California. 

Geologic range.-Eocene. 

Pachecoa (Pachecoa) hornii elusa (Clark and Woodford) 

Plate 10, figure 8 

Area hornii elusa Clark and Woodford, 1927, p. 87, pl. 14, fig. 6 

Trigonodesma hornii (Gabb) elusa (Clark and Woodford). Vokes, 

1939, p. 49, pl. 1, fig. 22. 

Original description.-"Shell small, gibbous, subequilateral; 

beaks_ central and very prominent; area short and narrow mostly 

anten?r to the beaks. Anterior dorsal margin short and straight; 

postenor dorsal margin sharply curved down; anterior end broadly 

rounded; posterior end truncated, making a sharp angle with the 

ventral margin which is straight posteriorly and broadly rounded 

anteriorly. A large posterior escutcheon-like depression separated 

from the main surface of the shell by a distinct ridge, this 

depressed area pouting at the junction of the two valves. Surface 

ornamented by numerous radial ribs, with broader flat inters paces. 

~urfac~ also covered by fine rounded incremental lines which give 

It a reticulated appearance. On the unweathered specimens, the 

rounded incremental lines are more prominent than the radial 

ribbing. The type***is a complete though immature specimen. 

Dimensions: Length 2.8 mm., height 2.3 mm., thickness of both 

valves 17 mm." 

Type material.-The holotype, UCMP 31428, is missing and 

presumed lost. A hypotype, UCMP 15594 (Vokes, 1939, pl.1, fig. 22) 

is figured herein. 

Type locality.-UC 3579. Contra Costa County, Calif. Meganos 

Formation, Paleocene. 

Comparison.-This form differs from the typical Pachecoa hornii 

(Gabb) in that the hinge line is shorter and the cardinal area is not 

so well developed. These differences seem to be constant on all the 

specimens at hand. (Clark and Woodford, 1927) 

Geographic range.-Middle California. 

Geologic range.-Paleocene. 

Occurrence in California.-Paleocene: Cerros Shale Member of 

the Lodo (Keen and Bentson, 1944) and Meganos Formations. 

Pachecoa (Pachecoa) hornii (Gabb) 

Plate 10, figure 7 

Area hornii Gabb, 1864, p. 194, pl. 30, fig. 263. 

Holonanus hornii (Gabb). Stewart, 1930, p. 79-80, pl. 10, fig. 6. 

Trigonodesma hornii (Gabb). Vokes, 1939, p. 49, pl. 1, figs. 24, 27. 

Pachecoa (Pachecoa) hornii (Gabb) s.s. Givens, 1974, p. 41. 

Original description.-"Shell minute, subequilateral; beaks subcentr~l, approximated; anterior end broadly rounded; basal most 

pro~ment below, or a little in advance of the beaks, nearly 

straight posteriorly, and inclined upwards towards the posterior 

which is obliquely truncated; posterior side abruptly truncated 

behind the umbonal angle; area short and very narrow. Surface 

marked by very fine, radiating striae, somewhat undulated laterally and crossed by still finer lines of growth, with an occasional 

coarser line formed by a slight interruption in the growth." 

Holotype.-ANSP 4460. [Holotype figured by Stewart, 1930, pl. 

10, fig 6, is missing.] 

Type locality.-Fort Tejon [NW 1/2 sec. 29, T. 10 N., R. 19 W., San 

Bernardino Base and Meridan, Kern County.] Calif. Tejon Formation, Eocene (Keen and Bentson, 1944). 
TERTIARY MARINE PELECYPODS: NUCULIDAE THROUGH MALLEIDAE A49 

Supplementary description.-The radiating lines on the holotype 

were about six per millimeter on the central region of the shell. The 

cardinal area is short and narrow, and the ligamenta) groove is 

apparently anterior to the umbo. Just enough of the hinge is 

exposed to show the taxodont character of the teeth. (Stewart, 

1930,p. 79-80) 

"The relative prominence of the radial and concentric striations 

on the surface of the shell varies somewhat in different specimens. 

Generally, but not always, the radial striations are slightly more 

prominent than the concentric ones on the right valve, and slightly 

less so on the left. On some specimens the concentric and radial 

sculpture seem about equal. The hinge is slightly arched, with 

small, convergent teeth. The ligamenta) area is transversely striated, and inclined, located anterior to the beak; the small posterior 

part of the cardinal area smooth, devoid of ligamenta! striations. 

The umbones are prominent, the beaks very slightly opisthogyrate." (Reinhart, 1943, p. 80-81) 

Comparison.-The ventral margin of Pachecoa hornii elusus 

curves upward posteriorly instead of extending almost straight as 

in P. hornii. (Reinhart, 1943, p. 81) 

Geographic range.-Middle and southern California. 

Geologic range.-Eocene. 

Occurrence in California.-Domengine, Juncal, and Matilija 

Formations (in Ectinochilus supraplicatus and E. canalifer faunas, 

Givens, 1974), La Jolla Group (Reinhart, 1943), Muir Sandstone of 

Weaver (1953), and Tejon Formation. 

Family LIMOPSIDAE 

Geologic range.-Triassic through Holocene. 

Genus LIMOPSIS Sassi, 1827 

Orbicular, nearly equilateral, commonly with slight forward 

obliquity. 

Geologic range.-Jurassic through Holocene. 

Subgenus LIMOPSIS 

Surface without radial ornamentation; inner margins not crenulate. 

Habitat.-Mostly cold water forms found in deep water, 35 to 

7,350 m. 

Limopsis (Limopsis) marysvillensis (Dickerson) 

Plate 10, figures 9, 10 

Glycimeris marysuillensis Dickerson, 1913, p. 290, pl. 14, figs. 1a, 

1 b; 1916, pl. 40, figs. 9a, 9b. 

Limopsis (Limopsis) marysuillensis (Dickerson). Givens, 1974, p. 

41, pl. 1, fig. 7. 

Original description.-"Shell, small, subglobose, almost equilateral; beak small, incurved and central. Cardinal margin, straight; 

the anterior and posterior margins, regularly rounded. Surface 

marked by prominent concentric ribs. Hinge marked by eleven 

teeth. Area trigonal, small." 

Holotype.-UCMP 11766. 

Type locality.-UC 1853. Sutter County, Calif. Marysville Claystone Member of the Meganos Formation, Paleocene. 

Geographic range.-Northern to southern California. 

Geologic range.-Paleocene and Eocene. 

Occurrence in California.-Paleocene: Marysville Claystone Member of the Meganos Formation; Eocene: Capay (Merriam and 

Turner, 1937) and Juncal (in Turritella uuasana in{era fauna, 

Givens, 1974) Formations. 

Family GLYCYMERIDIDAE 

Geologic range.-Cretaceous through Holocene (greatest development in Miocene.) 

Habitat.-In tropical to temperate marine water from 0 to 640 m 

(one species collected at 1,846 m), usually at depths less than 110 

m; probably restricted to coarse permeable substrata; strong tendency to lie on one si~e. 

Subfamily GLYCYMERIDINAE 

Geologic range.-Cretaceous through Holocene. 

Genus GL YCYMERIS Da Costa, 1778 

Subcircular to subquadrate, beaks orthogyre to opisthogyre, 

surface smooth or costate; ventral margins internally fluted. 

Geologic range.-Early Cretaceous through Holocene. 

Subgenus GLYCYMERIS 

Subcircular, subequilateral, with small umbones and beaks; 

teeth relatively short, transverse, becoming obsolescent medially; 

surface smooth or costate. 

Geologic range.-Early Tertiary though Holocene (table 4). 

Glycymeris (Giycymeris) rosecanyonensis M. A. Hanna 

Plate 10, figures 12, 13 

Glycymeris rosecanyonensis M.A. Hanna, 1927, p. 273-274, pl. 27, 

figs. 4, 5, 9, 11. Givens, 1974, p. 42. 

Original description.-"Shell small; general outline as figured; 

beak prominent, central; shell considerably inflated; outer surface 

ornamented by about forty rounded radial ribs which are approximately uniform in size except at the posterior and anterior extremities, separated by narrower rounded interspaces; outer surface also 

bears many concentric growth lines which are more prominent in 

the interspaces, giving the interspaces a pitted appearance; hinge 

line curving; cardinal area small, elongate trigonal; teeth separated 

from the cardinal area by a change in the surface; teeth arranged 

along the arc of a circle of smaller diameter than the diameter of 

the shell; teeth fourteen in number, seven to either side of a median 

line, nearly of uniform size, elongate, parallel sided, prominent, 

separated by sockets of equal width; long axes of the teeth not 

parallel to the radii of the circle of which they form an arc but to a 

point considerably above; ventral three-fourths ofthe inner margin 

prominently denticulate with some thirty teeth, denticulations do 

not correspond to the ribs of the outer surface, muscle scars large, 

pallial line distinct. Dimensions. Type: Altitude 5. 75 mm., length 

6.25 mm., diameter 2. 75 mm. Paratype: Altitude 5.25 mm., length 

5.5 mm., diameter 2.65 mm." 

Holotype.-UCMP 30989. 

Type locality.-DC 3990. San Diego County, Calif. Ardath Shale, 

Eocene. 

Comparison.-"Glycymeris rosecanyonensis***differs from G. 

sagitatta [sic; sagittata] ***which it most closely resembles, in size 

and shape. G. sagitatta flares·out in front like two wings while G. 

rosecanyonensis slopes up forming an angle of slightly more than 

ninety degrees, and with only very narrow wings. Also the number 

of teeth is different. There are seven to nine teeth to the side of the 

median line in the new species while in Gabb's species there are 

fourteen. The row of teeth form an arc in the new species and not a 
A 50 PALEONTOLOGY OF CALIFORNIA AND BAJA CALIFORNIA 

TABLE 4.-Geologic and geographic distribution of the family Glycymerid idae 

[H = Holocene; Pie= Pleistocene; PI= Pliocene; M = Miocene; 0 = Oligocene; E ·=.Eocene; Pa = Paleocene] 

Alaska British Washington Oregon Calif~rnia Baja California Central and/or South 

America Species 

Genus Glycymeris: 

Subgenus Glycymeris: 

branneri Arnold ... . buwaldi Clark ........................ . 

Columbia 

Northern Middle Southern 

OandM M? M 

Norte Sur 

eocenica (Weaver) ............... . ······i\,i("" 

M 

E E E E 

"ii.f~~-pj" gabbi Dall ........... . .............................. . M M PI gigantea (Reeve) ................ . maculata (Broderip) .... . rosecanyonensis Hanna subobsoleta (Carpenter) ....... . viticola Anderson and Hanna .. Subgenus Glycymeris? swartsi Hertlein and Jordan ..................... . whaleyi Nicol ............. . Subgenus Glycymerita: 

major (Stanton) ........................................................ . major meganosensis Clark and Woodford .. sagittata (Gabb) ....... . ...................... . Subgenus Glycymerita?: 

ree(ensis Vokes tecolotensis Hanna Subgenus Tucetona: 

H PI toH 

Pa 

M or PI ·······if····· PltoH H PI to H H 

E 

H Pie and H Pie E 

M? M 

Pa and E Pa Pa ··E··· E and 0? 

E ·····E·--···· 

evermanni Anderson and Hanna. fresnoensis Dickerson ....................... . Pa a~(i"E E 

"""pj"""""" 

···E··· E. 

multicostata (Sowerby) ....... . perrini Dickerson ......... . ruckmani Dickerson .... . teniumbricata Clark ....................... . verticordia Anderson and Hanna Subgenus Tuc;:etonif?: 

maccray1 Wanng ......................... . septentrionalis (Middendorf) . Subgenus Axinola: 

grewingki Dall . 

profunda (Dall) .. Genus Felicia: 

phrear (Woodring) .. 

1Scott McCoy, written commun., 1978. 

M? and ..... Pi' 

line bent down at either end. The radial ribs are crossed by narrow 

prominent growth lines. The radial ribs of G. sagitatta are flat and 

separated by narrow interspaces, while in G. rosecanyonensis they 

are rounded and separated by interspaces of nearly equal width. 

"Glycymeris rosecanyonensis***differs from G. viticola***in the 

presence of the narrow wings, narrower but more prominent radial 

ribs, in the arrangement of the teeth, and in the much smaller size. 

The new species differs from G. verticordia***in the less prominent 

and more uniform sculpturing. If differs from G. evermanni***in 

the larger size, shape (presence of the narrow wings), and fine 

growth lines rather than flat-topped growth lines. If differs from G. 

perrini***in that the radial sculpturing consists of only regular 

equal-sized ribs. It differs from G. fresnoensis***in the much finer 

radial ribs. It differs from G. hannibali***in the smaller apical 

angle as well as in sculpturing. It differs from G. marysvillensis in 

the presence of the prominent radial sculpturing. It differs from G. 

ruckmani***in shape as well as sculpturing." (Hanna, 1927, p. 724) 

Geographic range.-Southern California. 

Geologic range.-Eocene. 

Occurrence in California.-Ardath Shale and Juncal Formation 

(in Turritella uvasana applinae and Ectinochilus supraplicatus 

faunas, Givens, 1974, p. 42). 

Glycymeris (Giycymeris) viticola Anderson and Hanna 

Plate 10, figures 14, 15 

Glycymeris viticola Anderson and Hanna, 1925, p. 182-183, pl. 1, 

fig. 5; pl. 3, fig. 1. 

Glycymeris (Glycymeris) viticola Anderson and Hanna. Givens, 

197~p.4~pl. 1,fig.& 

Original description.-"Shell small, equilateral, not inflated, 

E 

M and PI 

Pa·a~"ii"E Pa and E 

E 

M M 

E 

······M··· .. PI a:d Pie 

M and PI M to Pie 

M MtoH 

......... PI and Pie ........ . 

H 

with umbones rather low; apical angle about 95°; surface sculptured 

with 35 radial ribs, flattened on top, with interspaces crossed by 

fine lines of growth and by concentric grooves showing rest 

periods; hinge with seven anterior and seven posterior lateral 

teeth, and with four less distinct teeth in the median area; ligamenta! area marked by six inverted V-shaped ridges; basal margin 

bearing crenulations corresponding to the intercostal grooves; 

length of shell, 21.5 mm.; altitude, 21.5 mm." 

Holotype.-CAS 777. 

Type locality.-CAS 245. Kern County, Calif. Tejon Formation, 

Eocene. 

Supplementary description.-"Several specimens are contained 

in the collections of the Academy of Sciences. They show that in its 

younger stages, the apical angle is greater than 95°, and that the 

ribs in unworn specimens are noded, due to the crossing of 

regularly spaced concentric grooves." (Anderson and Hanna, 1925, 

p. 183) 

Comparison.-"ln the details of its ornamentation this species 

does not closely resemble any other western form" (Anderson and 

Hanna, 1925, p. 183). [See G. rosecanyonensis.] 

Geographic range.-Southern California. 

Geologic range.-Eocene. 

Occurrence in California.-Matilija Sandstone (Ectinochilus 

canalifer fauna, Givens, 1974, p. 42) and type Tejon Formation. 

Glycymeris (Giycymeris) eocenica (Weaver) 

Plate 12, figure 23 

Pectunculus eocenica Weaver, 1912, p. 28, pl. 5, figs. 52, 53. 

Glycymeris eocenica (Weaver). Clark, 1938, p. 693, pl. 1, figs. 1, 6, 

10, 13, 18. Weaver, 1942, p. 56-57, pl. 10, figs. 2, 3, 8. 

\ 
TERTIARY MARINE PELECYPODS: NUCULIDAE THROUGH MALLEIDAE A51 

Original description.-"Shell subcircular, thin, equivalve, and 

nearly equilateral; base regularly convex; sides sloping down 

directly from the beak, the anterior side much more steeply 

rounded than the posterior, the latter being regularly convex; 

junction of the posterior end and the base very slightly truncated. 

Surface marked by forty broad nearly flat-topped radiating ribs 

with very narrow interspaces, between which are raised threads; 

four or five very prominent lines of interrupted growth are present 

with fainter intervening concentric lines. Hinge robust with radiating teeth; pallial line very distinct, inner margin coarsely crenulated. Dimensions.-Alt 23 mm.; long 25.; thickness 7 mm." 

Holotype.-CAS 476. [The holotype is missing. The specimen 

figured, pl. 12, fig. 23, is the paratype according to Weaver (1942, pl. 

10, fig. 2).] 

Type locality.-VW 345. Cowlitz County, Wash. Cowlitz Formation, Eocene. 

Geographic range.-Washington to southern California. 

Geologic range.-Eocene. 

Occurrence in Cali{ornia.-Markley (Clark, 1938) and type Tejon 

(Dickerson, 1914) Formations. 

Glycymeris (Glycymeris) branneri Arnold 

Plate 10, figures 11, 16 

Glycymeris branneri Arnold, 1908, p. 377-378, pl. 34, fig. 1. Loel 

and Corey, 1932, p. 182, pl. 7, figs. 5a, 5b. Nicol, 1947, p. 

346-347, pl. 50, figs. 12-15. 

Original description.-"Shell averaging nearly 70 mm. in length, 

about as wide as long, suborbicular, equivalve, bilaterally unsymmetrical, considerably convex for one of this genus, thick and 

heavy; umbo somewhat anterior to center, protruding beyond 

hinge line and turned slightly toward the front; anterior dorsal 

margin straight, sloping steeply from umbo; anterior extremity 

quite sharply rounded, and located above center line of shell; 

posterior dorsal margin straight, sloping less steeply than anterior; 

posterior extremity protruding obliquely downward and backward, 

regularly rounded, located below center line of shell; posterior 

dorsal and ventral margins join in a faintly defined angle considerably above and in front of the extreme end of the shell. Surface 

sculptured by numerous flat to concave-topped, close-set, radiating 

ribs (about 55 discernible in the type), relatively much broader 

toward the middle of the shell and becoming narrower and less 

well defined toward either end; in the later stages of growth a 

raised beaded intercalary line occupies the interspace and (in the 

type) rises above the level of the ribs; prominent incremental 

lamallae cross the ribs, bowing convexly upward toward the umbo; 

they are straight on the sides and across the top of the ribs, and 

become less prominent and more closely set toward the periphery 

in the adult shell. Hinge with 5 or 6 boomerang-shaped teeth, with 

angle toward the umbo, on either side of a centrally divaricately 

striated broad ligamenta} area; the teeth in the young form a 

semicircle below and extending on either side beyond the ligamenta} area, but in the later stages of growth the centrally situated 

teeth are obliterated by encroachment of the ligament. Interior 

unknown, but interior of margins appear to be smooth." 

Holotype.-VSNM 165455. 

Type locality.-Mindego Creek, 1.5 km above confluence with 

Alpine Creek, [sec. 24, T. 7 S., R. 4 W.] Santa Cruz quadrangle, San 

Mateo County, Calif. Vaqueros Formation, Oligocene and Miocene. 

Supplementary description.-"Arnold's specimen was eroded so 

that he did not have a correct impression of some of the features of 

the shell, especially the ornamentation. The radial ribs are flat and 

are separated by lines or grooves. Secondary superimposed radial 

ribs do occur but are weakly developed and are only seen in certain 

areas of the shell. On some specimens***the shell is so eroded that 

the primary radial ribs are faintly marked, but the superimposed 

secondary radials are much more prominent. No concentric ornamentation is present. 

"The interior ventral border is crenulated. The crenulations are 

long and slender with pointed ends and sunken centers. 

"Contrary to Arnold's observation, the specimens seen by the 

writer usually have orthogyrate beaks; occasionally the beaks are 

slightly opisthogyrate. 

"The ligamenta} area is large, and on well-preserved specimens 

the ligamenta} chevrons number from 6 to 9, are large, and are 

strongly marked." (Nicol, 1947, p. 347) 

Comparison.-"This magnificent species is apparently one of 

the largest of the west coast forms, equaling in size but not in 

convexity the Cretaceous Glycymeris ueatchii Gabb and its Eocene 

variety G. ueatchii major Stanton. It also lacks the prominent 

groove which separates the dorsal posterior angle from the rest of 

the shell in the earlier forms. It is distinguishable from Glycymeris 

gabbi Dall from Coos Bay, Oregon, the next largest Miocene 

species, by its unsymmetrical outline, its much greater size, relatively greater convexity, closer set ribs, and peculiar wavy incremental sculpture." (Arnold, 1908, p. 378) 

"The only closely related fossil species is Glycymeris swartsi 

Hertlein and Jordon [sic; Jordan] from lower Miocene beds of 

Lower California. G. branneri is a larger species, the crenulations 

on the inner ventral border are larger and have sunken centers, 

and the hinge teeth are larger and fewer in number than in G. 

swartsi. 

"Glycymeris gigantea (Reeve)***is a close analogue to G. branneri, but the former is larger and has more prominent superimposed 

secondary ribs. The two species resemble each other in shell 

outline, ligamenta} area, and crenulations on the inner ventral 

border." (Nicol, 1947, p. 347) 

Geographic range.-Middle and southern California. 

Geologic range.-Oligocene and Miocene. 

Occurrence in Cali{ornia.-Oligocene and Miocene. Vaqueros 

Formation (Turritella inezana zone); Miocene: Olcese Sand (Addicott, 1956) and Tierra Redonda Formation (Durham, 1970). 

Glycymeris (Giycymeris) buwaldi Clark 

Plate 12, figures 13, 14 

Glycymeris buwaldi Clark, 1918, p. 129, pl. 7, figs. 10, 11. 

Original description.-"Shell small, subcircular in outline; anterior dorsal slope gently convex; posterior dorsal slope short; posterior 

end subtruncated. Surface covered by fairly coarse, irregular incremental lines; also sculptured by numerous obscure radiating ribs, 

with interspaces which possibly average somewhat less than the 

width of the ribs; extending from the beak to the lower angle of the 

subtruncated end is an .indistinct ridge, the narrow margin posterior to which is rather strongly depressed. Hinge plate heavy; 

cardinal area very narrow; posterior to the beak there are eight, 

and anterior to it, seven cardinals. A large part of the hinge plate is 

not covered by the cardinals both below and on the sides; ventral 

margin denticulate." 

Holotype.-VCMP 11150. 

Type locality.-VC 1131. Contrfi Costa County, Calif. San Ramon 

Sandstone, Miocene(?). 

Comparison.-Glycymeris buwaldi is very similar in outline and 

sculpturing to G. intermedia Broderip, a Recent West Coast 

species, in fact so much so that the writer would have hesitated to 

separate the two had it not been that a good hinge plate was 
A 52 PALEONTOLOGY OF CALIFORNIA AND BAJA CALIFORNIA 

obtained on the former, which is quite different from that of the 

latter. It is heavier; there is a less number of cardinals; there is a 

narrow interspace below the beak between the anterior and posterior cardinals, which is not present on G. intermedia; also the 

cardinal area on G. buwaldi is much smaller." (Clark, 1918, p. 130) 

Geographic range.-Middle California. 

Geologic range.-Miocene(?). 

Occurrence in California.-San Ramon Sandstone (Weaver, 

1953). 

Glycymeris (Giycymeris) gabbi Dall 

Plate 13, figures 3, 4 

Glycymeris gabbi Dall, 1909, p. 108, pl. 11, fig. 5. Weaver, 1942, p. 

62, pl. 10, fig. 18. 

Original description.-"Shell large, rather thin, compressed, 

suborbicular, nearly equilateral; beaks defective, probably rather 

elevated, separated by a narrower ligamenta! area with about half 

a dozen angular sulci divaricating from the vertical of the umbones; 

dorsal slopes straight, nearly smooth, the posterior slope somewhat 

flattened; disk uniformly sculptured with about 34 narrow, flat 

radial ribs, separated by somewhat narrower channeled interspaces, the interspaces wider and the ribs narrower toward the 

ends of the shell; concentric sculpture of narrow, flat ridges, 

narrower and closer together toward the basal margin, but on the 

central part of the disk forming with the radial ribs nearly square 

reticulations; interior, as in other cases, filled with a refractory 

matrix. Altitude of shell, 51 mm.; latitude, 53 mm.; diameter, about 

20mm." 

Holotype.-VSNM 153949b. 

Type locality.-Coos Bay, Coos County, Oreg. Empire Formation, 

Miocene. 

Comparison.-"lt is possible***that this species may be synonymous with G. grewingki Dall. The differences in radiating and 

concentric sculpture are in part the result of weathering***. There 

seem to be differences in the number of radiating ribs and in their 

cross-sections as well as in the interspaces***. G. gabbi is more 

equilateral than G. grewingki." (Weaver, 1942, p. 62) 

Geographic range.-Southern Oregon to middle California. 

Geologic range.-Miocene and Pliocene. 

Occurrence in California.-Pliocene. Lower part of Merced Formation (Weaver, 1949). 

Glycymeris (Giycymeris) gigantea (Reeve) 

Plate 11, figures 1, 3 

Pectunculus gigantea Reeve, 1843, pl. 1, figs. 3a, 3b. 

Glycymeris gigantea (Reeve). Durham, 1950, p. 56, pl. 2, figs. 1, 8. 

Glycymeris (Glycymeris) gigantea (Reeve). Olsson, 1961, p. 106. pl. 

11, fig. 1. 

Original description.-[Figured only.] 

Holotype.-BM(NH) (A. M. Keen, oral commun., 1978). 

Type locality.-Guaymas, West Mexico (Olsson, 1961, p. 106). 

Supplementary description.-"One of the largest forms in the 

whole familiA large specimen may attain a height of 100 mm. 

The nearly smooth surface shows radial striae and the white 

ground color is mottled with reddish brown in zigzag patterns. 

There are about 30 hinge teeth." (Keen, 1971, p. 55) 

Comparison.-The long oblique teeth of G. gigantea distinguish 

it from G. maculata, which has short, nearly vertical teeth. 

(Durham, 1950, p. 56) 

Geographic range.-Living: Bahia de la Magdalena, Baja California Sur, to Acapulco, Mexico; fossil: southern California and 

both Pacific and Gulf sides of Baja California. 

Geologic range.-Miocene through Holocene. 

Occurrence in California and Baja California Sur.-Miocene or 

Pliocene: Imperial Formation (Hanna, 1926); Pliocene: Marquer 

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

Pleistocene: unnamed strata of Laguna San Ignacio and Santa 

Rosalia, Baja California Sur (Minch and others, 1976). 

Habitat.-Dredged in depths of 7 to 13 m. 

Glycymeris (Giycymeris) maculata (Broderip) 

Plate 11, figures 2, 4 

Pectunculus maculatus Broderip, 1832, p. 126. 

Glycymeris maculata (Broderip). Grant and Gale, 1931, p. 136. 

Keen, 1971, p. 55, fig. 112, Durham, 1950, p. 56, pl. 2, figs. 3, 5. 

Glycymeris (Glycymeris) maculata (Broderip). Olsson, 1961, p. 106, 

pl. 11, figs. 2, 5. 

Original description.-"Pect. testa orbiculata, subaurita, subaequilatera, convexa, albente castaneo-maculosa, striis radiantibus 

subdecussatis creberriensis; intus alba, marginibus crenatis; epidermide fusca villosa; long. 2 %, alt. 2 3fs, lat. 1 %poll." 

Holotype.-BM(NH) (A. M. Keen, oral commun., 1978). 

Type locality.-"Portu Portrero." [South America?; north of 

Zorritos, Peru.] 

Supplementary description.-"This species attains a large size 

and has a strong, thick, very convex shell. The umbo protrudes 

prominently above the dorsal margin of the shell. The radial 

ribbing is reduced to very low relief or is obsolete, but the surface is 

finely and evenly radially striated. The hinge plate is heavy, with 

a curved series of stout chevron-shaped teeth which may be 

interrupted in the middle by the basal line of the ligamenta! 

area***. The variations in shape noticed in a series of specimens is 

partly due to the influence of a rocky habitat." (Grant and Gale, 

1931, p. 136) 

"The shell is often large (length 80 mm.), convex, heavy, nearly 

circular, the posterior side with a low, obscure angulation. Surface 

smoothish but when fresh showing a submicroscopic sculpture of: 

low, rounded riblets on the umbones crossed by small, equidistant 

concentrics becoming gradually replaced ventrally by fine, raised 

radial threadlets which are evenly distributed and not bunched 

together in riblike groups. Hinge plate solid, the teeth relatively 

few, the laterals large, the middle series continuous or broken." 

(Olsson, 1961) 

Geographic range.-Living: Northern Gulf of California and 

Bahia de Ia Magdalena, Baja California Sur, to Zorritos, ·Peru; 

fossil: southern California to Baja California Sur. 

Geologic range.-Miocene through Holocene. 

Occurrence in California and Baja California Sur.-Miocene or 

Pliocene: Imperial Formation (Hanna, 1926); Pliocene: Marquer 

Formation (Durham, 1950); Pleistocene: unnamed strata Gulf of 

California and Laguna San Ignacio, Baja California Sur (Minch 

and others, 1976). 

Habitat.-The holotype was found in fine gravel at a depth of20 

m. 

Glycymeris (Giycymeris) subobsoleta (Carpenter) 

Plate 12, figures 15, 16 

Axinea (? septentrionalis, Midd. var.) subobsoleta Carpenter, 

1864b, p. 644. 
TERTIARY MARINE PELECYPODS: NUCULIDAE THROUGH MALLEIDAE A 53 

Glycymeris subobsoleta (Carpenter). Palmer, 1958, p. 63-64, pl. 1, 

figs. 8-10 [See for synonymy]. 

Original description.-"Shell similar to G. septentrionalis, 

slightly inequilateral, not tumid, umbones obtuse, broad, quite 

prominent; ash-colored, variegated with reddish chestnut; epidermis thick, somewhat laminated; ventral and posterior margins 

quite rounded, anterior margin produced, dorsal straight, sculptured by subobsolete radiating grooves, often disappearing dorsally; ventral margin strongly, and anterior and posterior internal 

margns slightly crenulated; cardinal plate subangular, with a few 

strong, compressed teeth; adductor scar chestnut colored; ligament 

furrowed." (Translation from Packard, 1918, p. 250) 

Syntypes.-USNM 15594 (two; both figured). 

Type locality.-Neah Bay, Wash. Holocene. 

Supplementary description.-Ligament area short. Radial ribs 

flat with narrow interspaces. The flattest and most thin-shelled 

Glycymeris of the Pacific coast. (Abbott, 1974, p. 427) 

Geographic range.-Living: Aleutian Islands, Alaska, to southern California [not living south of California, Keen, 1978, oral 

commun.]; fossil: California to Baja California Norte. 

Geologic range.-Pliocene through Holocene. 

Occurrence in California and Baja California.-Pliocene and 

Pleistocene: Wildcat Group (Ogle, 1953); Pleistocene: unnamed 

strata on San Nicolas Island (Vedder and Norris, 1963) and in 

Baja California Norte (Valentine, 1957). 

Habitat.-10 to 25 m off Pacific Groove, middle California, in 

coarse granitic sand. 

Subgenus GLYCYMERIS? 

Glycymeris (Glycymeris?) whaleyi Nicol 

Plate 11, figures 5, 6 

Glycymeris whaleyi Nicol, 1947, p. 347-349, pl. 50, figs. 7-11. 

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

outline of valves subcircular, with posterior side slightly produced; 

ratio of convexity to height 0.70; beaks orthogyrate and median in 

position; ligamenta} area amphidetic, short and high, with 6 to 8 

delicate, distinct, chevron-shaped grooves; hinge teeth about 20 in 

number, central teeth may be absent on large specimens; hinge 

plate strongly arched; denticulations on inner ventral border large, 

few in number with sunken centers and blunt ends." 

"The radial ribbing of this species varies with the size of the 

shell. On small specimens, or on the umbonal region and at either 

end of the shell, the radial ribs are raised, with well-rounded crests, 

separated by narrower interspaces. Toward the ventral margin on 

larger specimens these ribs become much wider and flatter and are 

secondarily grooved so that each rib may be divided into three 

parts. The interspaces remain linear. The number of radial ribs 

varies from 18 to 25, not including the secondary splitting of the 

ribs. No concentric ornamentation is present." 

Holotype.-CAS 8584. 

Type locality.-N. 71° W. 1.8 km from intersection of 119°45' 

meridan and 35°00' parallel as shown on U.S. War Department 

map of Caliente Mountain quadrangle [Caliente Mountain quadrangle, 1959], Caliente Mountain Range, San Luis Obispo County, 

Calif. Saltos Shale Member of the Monterey Shale, Miocene. 

Comparison.-"The nearest related fossil species are all found in 

rocks of Miocene age in Columbia [Sic; Colombia] and Venezuela. 

Glycymeris whaleyi resembles G. lloydsmithi Pils.bry and Brown 

from the Miocene of Columbia but differs from the latter by having 

the chevron-shaped ligamenta} grooves present and by having 

flatter and more distinctly split radial ribs. G. democraciana F. 

and H. Hodson from the Miocene of Venezuela differs from the 

California species by having a higher arched hinge plate and by 

being more produced posteriorly. G. whaleyi differs from G. usiacurii Anderson from the Miocene of Columbia in lacking secondary 

intercalated ribs in the interspaces. The remainder of the splitribbed species described from rocks of Miocene age in the Caribbean 

region generally have stronger ribs than G. whaleyi. 

"The closest related living analogue to Glycymeris whaleyi is G. 

bicolor (Reeve) from the Gulf of California. G. bicolor has more 

numerous, narrower, and more prominent ribs; also more numerous 

and smaller denticulations on the inner ventral border of the 

shell." (Nicol, 1947, p. 348) 

Geographic range.-Southern California. 

Geologic range.-Miocene. 

Occurrence in California.-Saltos Shale Member of the Monterey 

Shale. 

Glycymeris (Glycymeris?) swartsi Herltein and Jordan 

Plate 11, figures 7, 8 

Glycymeris swartsi Hertlein and Jordan, 1927, p. 620, pl. 17, figs. 1, 

2. 

Original description.-"Shell fairly large, obliquely ovate, rather 

strongly inflated; umbos high, subcentral, sculpture consisting of 

fine concentric lines of growth, and faint radial lines noticed on 

only a few unweathered parts of the shell and apparently developed 

mostly near base of shell; valves rounded in front, somewhat 

produced behind. Length approximately 40 mm.; height 38.2 mm.; 

width 29.8 mm." 

Holotype.-CAS 5132. 

Type locality.-SU 60. West side of Elephant Mesa, Laguna 

Scammon quadrangle, Baja California Sur. Isidro(?) Formation, 

Miocene. 

Supplementary description.-"This species is unlike any other 

west coast Glycymeris. A row oftaxodont teeth is present in one of 

the paratypes. The shape and sculpture of the valves and the 

circular row of teeth lead the authors to place this species under the 

genus Glycymeris although the shape is not similar to most other 

western North American species of that genus." (Hertlein and 

Jordan, 1927,p.620) 

Geographic range.-Baja California Sur. 

Geologic range.-Miocene(?). 

Occurrence in Baja California Sur.-Isidro(?)Formation. 

Subgenus GLYCYMERITA Finlay and Marwick, 1937 

Subquadrate, posterior subtruncate, with prominently projecting 

umbones, anterior and posterior teeth moderately elongate, curved 

or chevron-shaped with convexity directed toward beaks, medial 

teeth small, transverse, exterior costate. 

Geographic range.-Europe, New Zealand, and California. 

Geologic range.-Cretaceous to Oligocene(?) (table 4). 

Glycymeris (Glycymerita) major meganosensis Clark and Woodford 

Plate 11, figures 11, 12 

Glycymeris major meganosensis Clark and Woodford, 1927, p. 

86-87, pl. 14, figs. 4, 5. 

Original description.-"Shell heavy, fairly large, ventricose, 

subcircular in outline; beaks prominent, strongly inturned; dorsal 

margins straight or nearly so, approximately at right angles to 
A 54 PALEONTOLOGY OF CALIFORNIA AND BAJA CALIFORNIA 

vertical between the beaks and the ventral edge; posterior dorsal 

margin strongly depressed, or flexed. Main surface of shell sculptured by about 30 broad, flat-topped, low ribs with interspaces 

much narrower than the ribs. The ribbing becomes obsolete on a 

narrow, anterior dorsal margin, on the flexed posterior dorsal 

margin it is somewhat finer than on the main surface of the shell, 

becoming obsolete near the posterior dorsal edge. On the larger 

uneroded specimens the ribbing near the ventral edge tends to 

become obsolete and covered over by the heavy lines of growth. On 

adult specimens the ligamenta} area is wide and narrow, and there 

are about 20 taxodont teeth which extend continuously across the 

hinge plate and for about two-thirds the distance in the middle 

they are in a straight line curving gently downward on each end. 

Dimensions.- Type: Length 44 mm., height 43 mm., thickness of 

one valve 21 mm." 

Holotype.-VCMP 31289. 

Type locality.-VC 3152. Contra Costa County, Calif. Meganos 

Formation, Paleocene. 

Comparison.-"The subspecies meganosensis differs from the 

typical form principally in the type of ribbing. On the majority of 

specimens of the latter the ribbing is more prominent and the 

interspaces are wider, and on the adult specimens the ribbing does 

not become obsolete as on meganosensis. Weathered specimens of 

the typical form are often hard to distinguish from the subspecies." 

(Clark and Woodford, 1927, p. 87) 

Geographic distribution.-Middle California. 

Geologic distribution.-Paleocene. 

Occurrence in California.-Meganos Formation. 

Glycymeris (Giycymerita) major (Stanton) 

Plate 11, figures 9, 10 

Pectunculus veatchi var. major Stanton, 1896, p. 1040, pl. 64, figs. 

2, 3. 

Glycymeris veatchii major (Stanton). Dickerson, 1914, p. 151, pl. 

10, fig. 5. 

Original description.-"Compared with the typical form of the 

species this variety is larger, less convex and proportionately 

longer; the ribs are broader than the interspaces and the posterior 

end is more sinuous. Length of a large specimen, 65 mm, height, 64 

mm, convexity of one valve, about 22 mm." 

Syntypes.-VSNM 157830. [Not 157827 as cited by Keen and 

Bentson, 1944.] 

Type locality.-One and one-half kilometers southeast of Lower 

Lake [NE 14 sec. 11, T. 12 N., R. 7 W.] Lake County, Calif. Martinez 

Formation, Paleocene. 

Comparison.-[See G. major meganosensis.] 

Geographic range.-Northern to southern California. 

Geologic range.-Paleocene to Eocene. 

Occurrence in California.-Paleocene: Martinez and Silverado 

(Woodring and Popenoe, 1945) Formations; Paleocene and Eocene: 

Lodo Formation (Smith, 1975). 

Glycymeris (Giycymerita) sagittata (Gabb) 

Plate 12, figure 17 

Axinaea (Limopsis?) sagittata Gabb, 1864, p. 197, 235, pl. 31, fig. 

267, 267a. 

Glycymeris sagittata (Gabb). Stewart, 1930, p. 71-73, pl. 12, fig. 10. 

Vokes, 1939, p. 45-46, pl. 1, figs. 18-20. Clark, 1938, p. 693. 

Stewart, 1946, table 1, pl. 12, fig. 3. Kleinpell and Weaver, 1963, 

p. 196-197, pl. 28, fig. 10; pl. 29, figs. 1, 2. 

Glycymeris (Glycymerita) sagittata (Gab b). Givens, 1974, p. 42-43. 

Glycimeris hannibali Dickerson, 1916, p. 483, pl. 36, figs. Sa, 8b. 

Original description.-"Shell subcircular, thin, equivalve, very 

slightly inequilateral; base regularly convex, sides unequally so, 

the posterior being a little the most prominent. Surface marked by 

numerous faint, radiating lines, which, on weathered surfaces, 

develop into strongly impressed grooves; along these lines are 

small pits, from which proceed downwards fine, impressed diverging lines. Hinge composed of robust, radiating teeth. Inner margin 

finely crenulated." [sagittata] 

"Shell of moderate size, inflated, with broadly rounded ventral 

margin and prominent beak. The anterior and posterior dorsal 

margins are practically straight and parallel to the axis of the 

shell. The anterior end is nearly straight except for a very slight 

central concavity at the end of a broad umbonal groove. The 

posterior end is broadly rounded with greatest arcuity near the 

dorsal margin. The decoration consists of about thirty flat radial 

ridges equal in width to their interspaces. The interspaces are 

decorated by arrow-like marks as in G. sagittata Gabb. Area long, 

narrow; interior of ventral margin dentate." [hannibali] 

Lectotype.-ANSP 4422 (Stewart, 1930, p. 71). 

Type locality.-Near Fort Tejon [N1/2 sec. 29. T. 10 N., R. 19 W., 

SB, Kern County], Calif. Tejon Formation, Eocene. 

Supplementary description.-The hinge is exposed on one paratype, showing ten prominent widely spaced taxodont teeth anterior 

and eight posterior. The six central teeth are smaller and closer 

together and almost vertical, although the anterior three slope 

slightly posteriorly and the posterior three slope anteriorly. The 

coarse crenulations of the margin gradually disappear dorsally 

and are entirely absent at the extremities of the hinge. (Stewart, 

1930,p. 71) 

"The shell is smooth, radial ribbing on the surface being absent; 

upon weathering, the interspaces first appear as minute pitting, 

which rapidly deepens so that the radial ribs become prominent 

surface-features. The outline of the valves is variable; the most 

characteristic variations are figured. 

"There seems to be a slight progressive loss of ribs during the 

evolution of this species. A count of several specimens from 

various Eocene horizons in California shows: 

Horizon 

Tejon ............................................. . 

Domengine. 

Capay ................................... . 

(Vokes, 1939, p. 46) 

Auerage number 

of ribs 

44 

48 

49 

Minimum No. 

39 

43 

46 

Maximum No. 

48 

52 

52 

"The hinge is almost, but not quite straight, with the line of the 

teeth bent downward at each end. There are 12 well-defined teeth 

on each side of the central area; in this they are small and 

indistinct. The ligamenta} area is long and narrow and contains 

about five wide-spreading, inverted V-shaped ridges. The outer 

surface is usually smooth to the unaided eye, but is marked on the 

umbones with about 35 narrow radiating grooves. These disappear 

above the margin of the shell in well grown specimens, while the 

flat ribs between the grooves, 12 in number, do not extend to the 

margin. The ribs are crossed by concentric lines of growth of equal 

size, which gives the surface a delicate cross-hatched appearance 

under the lens. The incised V-shaped lines shown in Gabb's figure 

appear on some specimens as pits caused by the wavy lines of 

growth around marginal crenulations." (Anderson and Hanna, 

1925, p. 181-182) 

"The specimens from the Santa Ynez Mountains have about 13 

or 14 anterior and 12 posterior taxodont teeth. The disc is well 

preserved and has about 50-53 radiating ribs, considerably more 

than have been listed for this species; however, the types which the 

authors have been able to examine indicate that the previous 

literature cited may give too low an estimate because of poor 
TERTIARY MARINE PELECYPODS: NUCULIDAE THROUGH MALLEIDAE A 55 

preservation of specimens. The posterior is sharply truncated and 

has a weak umbonal groove typical of this group of Glycymeris in 

its stratigraphically uppermost occurrences***." (Kleinpell and 

Weaver, 1963, p. 196-197) 

Geographic range.-Washington to southern California. 

Geologic range.-Eocene; Oligocene(?). 

Occurrence in California.-Eocene: Avenal Sandstone (Stewart, 

1946), Capay, Domengine (Vokes, 1939), and Llajas Formations, 

Markley Sandstone Member ofthe Kreyenhagen Formation (Clark, 

1938), Muir Sandstone of Weaver (1953), Tejon (Anderson and 

Hanna, 1925), Juncal, and Matilija (in Turritella uvasana applinae, 

Ectinochilus supraplicatus, and E. canali{er faunas; Givens, 1974) 

Formations; Eocene and Oligocene: undifferentiated Sacate and 

Gaviota Formations (Weaver and Kleinpell, 1963). 

Subgenus GL YCYMERIT A? 

Glycymeris (Giycymerita?) reefensis Vokes 

Plate 12, figure 1 

Glycymeris ree{ensis Vokes, 1939, p. 47-48, pl. 1, fig. 21. 

Original description.-"Shell small, inflated; umbos central, 

prominent; cardinal area straight, slightly more than half the 

length of the shell; anterior, posterior, and ventral margins regularly and evenly rounded; posterior area not defined; surface 

smooth except for minute arrow-shaped pittings similar to those 

found in G. sagittata; interior of shell not seen." 

Holotype.-UCMP 15571. 

Type locality.-UC A-1165. Kings County, Calif. Avenal Sandstone, Eocene. 

Comparison.- "Glycymeris ree{ensis may be distinguished from 

G. sagittata by its round outline and shorter cardinal area; from all 

other described West Coast Eocene species it may distinguished by 

its smooth shell with arrow-like pittings." (Vokes, 1939, p. 48) 

Comments.-The somewhat quadrate outline and prominent 

high umbones suggest Glycymerita. 

Geographic range.-Middle California. 

Geologic range.-Eocene. 

Occurrence in Cali{ornia.-Avenal Sandstone (Keen and Bentson, 

1944). 

Glycymeris (Giycymerita?) tecolotensis M.A. Hanna 

Plate 11, figures 13, 14 

Glycymeris tecolotensis M.A. Hanna, 1927, p. 274-275, pl. 27, figs. 

2, 3, 7. 

Original description.-"Shell of medium size, heavy, rounded 

except for the projection of the prominent centrally located beak 

beyond the margin of the general outline; hinge line slightly 

straightened as viewed from the outside, a character more prominent in smaller specimens; shell moderately inflated; outer surface 

ornamented by fine concentric growth lines, and numerous fine 

round-topped'parallel-sided radial ribs which are separated by flatbottomed interspaces of three to four times the width of the ribs; 

radial ribs become obscure. near the perifery of the shell due to the 

increased prominence of the growth lines; outer surface of the type 

is weathered to some extent so the surface characters are not too 

clear in the figure; hinge of moderate width; cardinal area large, 

slightly impressed, trigonal, straight on its ventral side, crosses 

parallel to the anterior and posterior edges by fine ridges which 

meet in a depressed line in the center; six prominent teeth to each 

side separated by eight smaller teeth (four posterior and four 

anterior); dorsal margin of the toothed area is straight due to the 

truncation by the cardinal area, cardinal area and the toothed area 

are separated only by a cessation of the teeth and not by a line of 

any kind; inner margin crenulate; inner surface Qf the type not 

exposed." 

Holotype.-UCMP 30987. 

Type locality.-UC 5091. San Diego County, Calif. Ardath Shale, 

Eocene. 

Supplementary description.-Hinge margin greater in proportion 

in smaller individuals. (Hanna, 1927, p. 275) 

Comparison.- "Glycymeris tecolotensis***differs from the heretofore described species [sic: G. rosecanyonensis] in the presence of 

the large cardinal area, straight hinge line with few teeth, and in 

the presence of the very fine radial sculpturing." (Hanna, 1927, p. 

275) 

Comments.-This species was placed in the synonymy of G. 

perrini Dickerson by Stewart (1930, p. 73). 

Geographic range.-Southern California. 

Geologic range.-Eocene. 

Occurrence in Cali{ornia.-Ardath Shale. 

Subgenus TUCETONA Iredale, 1931 

Radial ribs well developed, interspaces narrow to moderately 

wide, ribs sometimes dividing terminally. 

Geographic range.-Baja California to Ecuador; Australia. 

Geologic range.-Paleocene through Holocene (table 4). 

Comments.-Tucetona is reinstated as a subgenus following 

Keen (1971, p. 55). 

Glycymeris (Tucetona) fresnoensis Dickerson 

Plate 12, figures 2, 3 

Glycimeris {resnoensis Dickerson, 1916, p. 483, pl. 36, fig. 7. 

Glycymeris {resnoensis Dickerson. Turner, 1938, p. 44, pl. 5, fig. 9. 

Vokes, 1939, p. 48, pl. 1, fig. 17. 

Original description.-"Shell small, cordate, with beak decidedly 

twisted; anterior and posterior dorsal margins nearly straight with 

steep slope to arcuate ventral margin; decoration consisting of 

sharp dichotomous ribs." 

Holotype.-UCMP 11795. 

Type locality.-UC 1817. Fresno County, Calif. Lodo Formation, 

Paleocene and Eocene. 

Supplementary description.-"The type is an immature specimen 

in which the ribbing is sharper than is characteristic on adult· 

individuals. The statement that the 'beak is decidedly twisted' is 

not borne out by a study of the type material, nor is it indicated in 

the figure accompanying the original description." (Vokes, 1939, p. 

48) 

Comparison.-[See G. verticordia.] 

Geographic range.-Washington to middle California. 

Geologic range.-Paleocene and Eocene. 

Occurrence in Cali{ornia.-Paleocene and Eocene: Cerros Shale 

Member of the Lodo Formation (Keen and Bentson, 1944); Eocene: 

Capay Formation. 

Glycymeris (Tucetona) perrini Dickerson 

Plate 12, figures 4, 5 

Axinea cor Gabb, 1864, p. 198, 235, pl. 31, fig. 268. Not Pectunculus 

cor Lamarck, 1805. 

Glycymeris instabilis Anderson and Hanna, 1925, p. 185, new 

name. 

Glycimeris perrini Dickerson, 1916, p. 482-483, pl. 36, figs. 6a, 6b, 

6c. Stewart, 1930, p. 73-74, pl. 7, fig. 5 [see for synonymy]. 

Turner, 1938, p. 44-45, pl. 5, figs. 10-12. 

Glycymeris perrini Dickerson instabilis Anderson and Hanna. 
A 56 PALEONTOLOGY OF CALIFORNIA AND BAJA CALIFORNIA 

Vokes, 1939, p. 47, pl. 1, figs. 14, 16. 

Original description.-"Shell medium in size, nearly equilateral, 

cordate; beak small, prominent, slightly incurved, area very small; 

base broadly rounded; anterior end straight and slightly shorter 

than the posterior end. The base is denticulated on interior. Shell is 

decorated by numerous fine rounded radiating ribs which vary 

greatly in strength over various portions of the shell. Some of the 

ribs are dichotomous. Interspaces are very narrow. Concentric 

lines of growth cross these ribs and on weathered specimens are 

very prominent." 

Holotype.-VCMP 11792. 

Type locality.-VC 672. Fresno County, Calif. Domengine Formation, Eocene. 

Supplementary description.-"This species is characterized by 

the presence of 'double ribs' which appear as ribs only after 

weathering; on unweathered specimens the ribbing appears as a 

difference in shell-texture on an almost smooth surface." (Vokes, 

1939, p. 47) 

Comparison.-The trigonal form of G. perrini is sufficient to 

distinguish it from G. sagittatus. (Dickerson, 1916, p. 483) 

Geographic range.-Southern Oregon to southern California. 

Geologic range.-Paleocene and Eocene. 

Occurrence in California.-Paleocene: Cerros Shale Member of 

the Lodo (Keen and Bentson, 1944) and Martinez Formations; 

Eocene: Avenal Sandstone (Stewart, 1946), Llajas Formation 

(Vokes, 1939), and Muir Sandstone of Weaver (1953). 

Glycymeris (Tucetona) evermanni Anderson and Hanna 

Plate 12, figures 6, 7 

Glycymeris evermanni Anderson and Hanna, 1925, p. 184-185, pl. 

15, figs. 1-3. 

Original description.-"Shell minute, circular, moderately inflated; umbones central; surface marked by about 26 rounded radial 

ribs which are closest together at the sides; in the center of the 

margin the interspaces are slightly wider than the ribs; ribs and 

interspaces crossed by coarse, equidistant, concentric grooves 

which extend uniformly form the beak to the lower margin, about 

16 in number on the type specimen; hinge line curved, having only 

three teeth on each side of the beak in the best para type; length 3.0 

mm.; altitude 3.0 mm." 

Holotype.-CAS 964. 

Type locality.-CAS 711. Kern County, Calif. Tejon Formation, 

Eocene. 

Supplentary description.-"This little species is beautifully cancellated on the outer surface. Three well-preserved specimens were 

extracted from very hard rock and the inner margin of one shows 

crenulations." (Anderson and Hanna, 1925, p. 185) 

Comparison.-[See G. rosecanyonensis.] 

Geographic range.-Southern California. 

Geologic range.-Eocene. 

Occurrence in California.-Type Tejon Formation. 

Glycymeris (Tucetona) ruckmani Dickerson 

Plate 12, figures 8, 9 

Glycimeris ruckmani Dickerson, 1915, p. 52-53, pl. 1, figs. 5a, 5b. 

Anderson and Hanna, 1925, p. 184. 

Original description.-"Shell of moderate size with acutely 

pointed beaks; dorsal margins sloping steeply to join a broadly 

rounded ventral margin; the posterior dorsal margin slightly 

convex and with a gentler slope than the straight anterior dorsal 

margin; decoration consisting of about 28 rounded radial ribs 

crossed by concentric growth lines; area semilunar and marked by 

impressed lines curving outward from the altitude line." 

Holotype.-VCMP 11051. 

Type locality.-VC 458. Kern County, Calif. Tejon Formation, 

Eocene. 

Comparison.-"This species differs from Glycimeris cor [ = Glycymeris perrini] in having a more pointed beak, in lack of hinge teeth 

in the central portion of its hinge and in general shape." (Dickerson, 1915, p. 53). 

G. ruckmani has a smaller apical angle than G. viticola and also 

has fewer ribs. [See G. rosecanyonensis.] 

Geographic range.-Southern California. 

Geologic range.-Eocene. 

Occurrence in California.-Type Tejon Formation. 

Glycymeris (Tucetona) verticordia Anderson and G D. Hanna 

Plate 12, figures 10, 11 

Glycymeris verticordia Anderson and Hanna, 1925, p. 183-184, pl. 

2, fig. 5; pl. 11, fig. 1. 

Original description.-"Shell small, sub-triangular, lower margin 

rounded; beak nearer the anterior than the posterior end; surface 

sculptured with 16 high, slightly rounded ribs, with slightly 

rounded interspaces of about equal width; only the seventh rib 

from the posterior end dichotomous; hinge broad and flat, with 

seven strong teeth on each side of the central area; ligament area 

very narrow, and beak elevated but little above the hinge line. 

Length, 8 mm.; altitude, 7.5 mm." 

Holotype.-CAS 776. 

Type locality.-CAS 245. Kern County, Calif. Tejon Formation, 

Eocene. 

Comparison.-"The beak in G. fresnoensis is centrally located, 

but in G. verticordia is much nearer the anterior end. In the former 

the anterior and posterior margins are almost straight, but in the 

latter they are much curved. Furthermore, the ribs in G. verticordia 

are more regular, sharper, and single, whereas, in G. fresnoensis 

they are irregular in size, and are often, but not always 

dichotomous." (Anderson and Hanna, 1925, p. 183-184) [See G. 

rosecanyonensis] 

Geographic range.-Southern California. 

Geologic range.-Eocene. 

Occurrence in California.-Tejon Formation. 

Glycymeris (Tucetona) tenuimbricata Clark 

Plate 12, figures 24, 25 

Glycimeris tenuimbricata Clark, 1918, p. 130, pl. 16, figs. 4, 8, 9, 10. 

Original description.-"Shell subtrigonal, somewhat variable in 

outline and diameter, medium in size, equivalved, nearly equilateral, valves moderately convex. Apical angle about 90°; dorsal slopes 

straight, the anterior slope being a little the shorter; ventral edge 

strongly and regularly convex; posterior dorsal margin, as a rule, 

slightly more depressed than anterior dorsal margin. Surface 

sculptured by twenty-three to twenty-nine radiating ribs which 

become obsolete near the dorsal edges; ribs separated by interspaces 

which generally average a little less than their width; surface also 

covered by heavy incremental lines which, on unweathered specimens, are very strongly and beautifully imbricated. Hinge plate 

fairly heavy, with seven or eight teeth anterior to the beak, and ten 
TERTIARY MARINE PELECYPODS: NUCULIDAE THROUGH MALLEIDAE A57 

or eleven posterior to it. The teeth do not reach the ventrai margin 

of the hinge plate; they are noticeably long and heavy near the 

ligamenta} area, which is narrow and ventrally is wedged in 

between the anterior and posterior rows of teeth; ligamenta} 

grooves numerous and well marked. Muscle impr~ssions equal and 

fairly heavy." 

Holotype.-UCMP 11183. 

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

Sandstone, Miocene. 

Geographic range.-Middle California. 

Geologic range.-Miocene(?). 

Occurrence in Cali{ornia.-Miocene: Olcese Sand (Addicott, 1956) 

and San Pablo Formation; Miocene(?). San Ramon Sandstone 

(Clark, 1918) 

Glycymeris (Tucetona) multicostata (Sowerby) 

Plate 12, figures 18, 19 

Pectunculus multicostatus Sowerby, 1933, p. 195-196. 

Glycymeris multicostata (Sowerby). Grant and Gale, 1931, p. 133. 

Glycymeris (Tucetona) multicostata (Sowerby). Keen, 1971, p. 57, 

fig. 116. 

Original description.-"Pect. testa suborbiculari, alba, castaneo 

rubiginosa cinereoque variegata; costellis numerosis, ex umbone 

radiantibus, transversim striatis: long. 1.5, lat. 1.2, alt. 1.5 poll." 

Holotype.-BM(NH) (A.M. Keen, oral commun., 1978). 

Type locality.-Isla de Muerte, Golfo de Guayaquil, Ecuador. 

Supplementary description.-"There are 35 to 40 flat-topped ribs 

on the grayish shell, and· in occasional individuals these may 

divide, especially at the ends, into numerous riblets***. In the 

southern part of the range the shells seem to have fewer ribs, and 

some have been confused in collections with G. canoa***." (Keen, 

1971, p. 47) 

"It is remarkable that in the young shells some of the radiating 

ribs are more prominent than others in the proportion of two large 

to one small." (Sowerby, 1833, p. 195-196) 

Geographic range.-Living: Punta Penasco, Sonora, Mexico, to 

Guayaquil, Ecuador; fossil: Baja California Peninsula and Golfo 

de California. 

Geologic range.-Pliocene through Holocene. 

Occurrence in Baja California Peninsula.-Pliocene: Marquer 

Formation (Durham, 1950); Pleistocene: Bahia de San Quintin 

(Minch and others, 1976). 

Subgenus TUCETONA? 

Glycymeris (Tucetona?) maccrayi Waring 

Plate 12, figure 12 

Glycimeris maccrayi Waring, 1917, p. 93, pl. 5, fig. 1. 

Original description.-"Shell small, of medium thickness and 

moderate convexity; umbone prominent, central, incurved; cardinal 

margin slightly convex and flared; anterior margin slightly produced above, broadly rounded below; basal margin broadly convex; 

posterior slightly produced above, broadly rounded below; surface 

marked by medium-size rounded, radiating ribs, which are crossed 

by lines of growth." 

Holotype.-CASISU 167. 

Type locality.-SU B. Ventura County, Calif. Llajas Formation, 

Eocene. 

Comments.-The hinge area is not exposed on the holotype but 

the sculpture of rounded ribs suggests Tucetona. 

Geographic range.-Southern California. 

Geologic range.-Eocene. 

Occurrence in California.-Llajas Formation (Keen and Bentson, 

1944). 

Glycymeris (Tucentona?) septentrionalis (Middendorf£) 

Plate 13, figures 1, 2 

Pectunculus septentrionalis Middendorff, 1849, p. 67, pl. 21, figs. 

1-3. 

Glycimeris septentrionalis Middendorf{. Clark, 1915, pl. 48, fig. 4. 

Original descriptjon.-((Pectunculus septentrionalis n. sp. Taf. 

XXI, fig. 1-3. Testa alba, extus maculis intense rubido-fuscis, intus 

macula ejusdem coloris magna ad impress. muse. antic.; subcordiformi, subaequilaterali, latitudine longitudinem aequante, gibbosa, 

umbonibus nonnihil antice inflexis; costis interstitia, ob incrementi 

strias squamulosa, latitudine his ad ter superantibus, rotundoapplanatis, 37 (7 21 9); dentibus cardinis 22 ad 23; margine medio, 

dentibus subbifidis grosse dentato. 

"Die Massverhaltnisse sind: Long., 29 m.; Latit.; 30 m.; Diam. 

ventr., 20m." 

"Etwa 37 Rippen kommen vor, von denen ich 21 ausgebildetere 

auf dem Mittelfelde, nebst 7 und 9 etwas schwacheren auf dem 

sehr undeutlich begrenzten Vorder-und Hinterfelde zahlte. Die 

rundriickigen scharfbegrenzten Rippen sind etwas flach, kaum 

halb so hoch als breit, und durch Furchen untereinander 

geschieden, welche zwei his drei Mal schmaler sind; als die Rticken 

der Rippen. Den Rippen des Mittelfeldes entsprechend ist der Rand 

mit groben, der Lange nach gefurchten Zahnen besetzt." 

Holotype.-Zoological Institute Leningrad, USSR. 

Type locality.-Arctic. 

Supplementary description.-"Shell of medium size, nearly circular, convex, thick; umbones central, not prominent; surface sculptured with rather faint ridges of growth and radiating grooves, 

which are more or less interrupted by the ridges; triangular 

ligamenta} area between umbones divaricately striated; hinge 

with a semi-circular row of transverse teeth; muscle impressions 

subequal; interior of margin crenulated. Length, 30; height, 32.2; 

diameter, 22 mm." (Arnold, 1903, p. 101) 

Comparison.-Differs from G. septentrionalis subobsoleta by 

having a larger, thicker shell, greater convexity, and more pronounced sculpture. (Arnold, 1903, p. 101) 

Geographic range.-Living: Aleutians to Forrester Island, 

Alaska; fossil: middle and southern California. 

Geologic range.-Miocene through Holocene. 

Occurrence in California.-Miocene: Neroly (Weaver, 1949) and 

Santa Margarita (Gale, 1931) Formations; Miocene and Pliocene: 

Etchegoin (Anderson, 1905); Pliocene: San Joaquin Formation 

(Adegoke, 1969); Pliocene and Pleistocene: Fernando (Zinsmeister, 

1970), San Pedro (Arnold, 1903), and Saugus (Kew, 1924) Formations. 

Subgenus AXINOLA Hertlein and Grant, 1972 

"Shell small to moderate size (5 to 50 mm long), subtrigonal to 

suborbicular in outline, often produced posteriorly, convexity of 

valves slight, thin, sometimes chalky, the Recent species covered 

with a velvety periostracum; the exterior is smooth or with faint 

rather narrow, flat-topped radial ribs which become strongly 

accentuated by erosion; beaks usually opisthogyrate but in some 
A 58 PALEONTOLOGY OF CALIFORNIA AND BAJA CALIFORNIA 

species orthogyrate; cardinal area short, high, with ligamentary 

grooves forming asymetrical [asymmetrical] triangles, the anterior 

side the longer; hinge arcuate, the central teeth much finer than 

those at either end or sometimes nearly obsolete; interior ventral 

margin of valves crenulated, the crenulations with blunt ends." 

(Hertlein and Grant, 1972, p. 159) 

Geographic range.-N ortheastern Pacific; living from Baja California to Japan. 

Geologic range.-Eocene through Holocene (table 4). 

Glycymeris (Axinola) grewingki Dall 

Plate 12, figure 20 

Glycymeris grewingki Dall, 1909, p. 107, pl. 2, fig. 13. Stewart, 

1940, p. 90, pl. 29, figs. 10, 11; pl. 33, figs. 7, 8. 

Glycymeris (Axinola) grewingki Dall. Hertlein and Grant, 1972, 

p. 159-160. 

Glycymeris coalingensis Arnold, 1909, p. 80, pl. 19, fig. 3. 

Original description.-"Shell solid, suborbicular, subequilateral, 

equivalve; beaks prominent, moderately convex, slightly separated 

by the area, which is narrow, in each valve forming a wide, very 

obtuse triangle with deeply incised angular sulci, radiating from 

the vertical of the beak; anterior slope slightly shorter and more 

rounded than the posterior, which is somewhat produced toward 

the lower portion; there is no distinct lunule or escutcheon; but a 

feebly differentiated anterior dorsal area is characterized by radial 

threads much finer than those on the anterior half of the disk; on 

the latter are about a dozen flat, little-elevated, radial ribs, separated by much narrower, channeled sulci, the whole with more or 

less obsolete fine radial striation; these radial ribs are distinct 

when the surface of the shell is intact; the anterior half of the disk, 

except when decorticated, nearly smooth except for close-set uniform numerous radial threads which cover the entire surface; 

when decorticated the internal structure shows ribs much like 

those normally exposed on the anterior half of the disk. Altitude of 

figured specimen, 38 mm.; longitude, 38 mm.; diameter 20 mm:: 

Holotype.-VSNM 107784. Holotype of Glycymeris coalingensis 

Arnold, USNM 165526. 

Type locality.-Coos Bay, Coos County, Oreg. Empire Formation, 

Miocene. 

Supplementary description.-"the incremental lines are imbricating, sharp and wavy, and where the surface is slightly worn, 

loop downward in more pr less regular festoons in the interspaces, 

this being one of the unique characteristics of the species***" 

(Arnold, 1909, p. 80; as G. coalingensis) 

Comparison.-G. grewingki differs from the living species G. 

subobsoleta Carpenter by having "higher umbos and correspondingly wider (dorsal-ventral) ligamenta! area and less prolongation 

posteriorly." (Hertlein and Grant, 1972, p. 160) [See also G. gabbi.] 

Geographic range.-Alaska to southern California. 

Geologic range.-Miocene to Pleistocene. 

Occurrence in California.-Miocene: Briones Sandstone (Weaver, 

1953), Castaic (Stanton, 1966), Cierbo (Hall, 1960), and McLure 

Shale Member of the Monterey (Adegoke, 1969) Formations, Neroly 

Sandstone (Weaver, 1949), Oursan Sandstone (Hall, 1958), San 

Pablo (Clark, 1915) and Santa Margarita (Clark, 1915) Formations; 

Pliocene: Etchegoin (Woodring and others, 1941) and San Diego 

(Hertlein and Grant, 1972) Formations; Pliocene and Pleistocene: 

Fernando Formation (J.D. Mount, written commun., 1971); Pleistocene: Pico Formation (Waterfall, 1929; upper part of the Pico or 

basal Santa Barbara Formation of modern usage). 

Glycymeris (Axinola) profunda (Dall) 

Plate 12, figures 21, 22 

Axinea profunda Dall, 1878, p. 11, 13. 

Glycymeris (Axinola) profunda Dall. Hertlein and Grant, 1972, p. 

160-161, pl. 27, figs. 15, 20, 21, 23, 25, 28-30, 34, 37, [See for 

synonymy]. 

Original description.-"Shell subtriangular, ventral margin 

rounded, umbos erect, rather small. Area narrow, deep; marked by 

five or six lines meeting at an angle in the vertical of the umbo, one 

above another; anterior lines somewhat the shortest; exterior 

marked by twenty-five or thirty flattened ribs, separated by deep 

channels one-fourth as wide as the ribs, and by which the interior 

margin is crenulated. The ribs are crossed by thread-like close lines 

of growth, which may be elevated or obsolete on the ribs, but are 

sharply defined in the channels, which they partially fill up in 

some specimens. Toward the anterior and posterior margins, the 

sculpture is nearly obsolete. In eroded examples, this sculpture 

may be entirely altered, and such are hardly striate, with a 

tendency to an elevated narrow ridge behind the anterior scar; 

hinge with teeth placed as if radiating from the centre of the valve, 

six to nine anteriorly, and ten to fourteen posteriorly, with some 

ten or twelve small, crowded teeth between the two radiating sets, 

and placed perpendicularly and parallel with one another. Height, 

32 mm; length 30 mm; thickness, 20 mm; the last proportionally 

greater in the young." 

Lectotype.-From type lot USNM 7935 (Woodring, 1946, p. 79). 

[The two remaining specimens in the original type lot have been 

assigned different USN~ catalogue numbers.] 

Type locality.-"The type material was collected evidently from 

the Pleistocene strata overlying the Pliocene San Diego Formation 

at Pacific Beach [San Diego County, Calif.]." (Woodring, 1946, p. 

79) 

Comparison.- "Glycymeris subobsoleta Carpenter***has a thin 

shell which is elongated posteriorly and has a narrow cardinal 

area. The shell characters of some young specimens of G. profunda 

approach those of G. subobsoleta and G. grewingki. 

"Glycymeris tenuimbricata Clark***, a species with high slender 

umbos,***has an apical angle of about 90° and bears a general 

resemblance to some specimens of G. profunda, but it has a much 

narrower cardinal area. 

"Glycymeris keenae Willett***from Alaska was described as a 

small (13.5 mm long) white shell with concentric sculpture and an 

angular hinge plate. Its general features are similar to those of G. 

profunda and allied species." (Hertlein and Grant, 1972, p. 161) 

The specimens illustrated by Arnold (1903) as G. barbarensis (pl. 

18, fig. 9) and G. septentrionalis (pl. 18, fig. 10) should be assigned 

to G. profunda (Hertlein and Grant, 1972, p. 161). 

Geographic range.-Living: off Redondo and Catalina Island, 

California; fossil: middle and southern California. 

Geologic range.-Miocene through Holocene. 

Occurrence in California.-Miocene: Cierbo and Neroly Sandstones (Hall, 1960); Miocene and Pliocene: Towsley Formation 

(Kern, 1973); Pliocene: Lomita Marl Member of the San Pedro Sand 

(Woodring, 1946), Niguel (J. G. Vedder, written commun., 1978) 

and San Diego Formations (Hertlein and Grant, 1972); Pliocene 

and Pleistocene: Fernando Formation (Zinsmeister, 1970). 

Habitat.-At depths of 45 to 365 m off southern California 

(Willett, 1944, p. 112). 

Genus FELICIA Mabille and Rochebrune, 1889 

Oblique, with anterior end narrowly rounded; posterior slightly 
TERTIARY MARINE PELECYPODS: NUCULIDAE THROUGH MALLEIDAE A 59 

quadrangular; exterior and inner margin smooth; dental series 

straight. 

Geographic range.-Living: California to South America; fossil: 

California. 

Felicia phrear (Woodring) 

Plate 13, figures 5-7 

Limopsis (Felicia) phrear Woodring, 1938, p. 31, pl. 5, fig. 9. 

Original description.-"A large Limopsis allied to dalli and 

other deep-water species from the west coast of Central America 

and southern Chile. Obliquely elongate; some specimens, probably 

distorted, are short. Sculpture consisting of radial pits, between 

some of which faint or distinct narrow radial grooves extend. Near 

the upper posterior margin the grooves are generally replaced by 

narrow faint threads. Growth lines interrupt the grooves. Cardinal 

area and hinge plate moderately narrow. Hinge apparently symmetrical." 

Holotype.-USNM 496077. 

Type locality.-USGS 13900. Los Angeles County, Calif. Fernando Formation, Pliocene and Pleistocene. 

Comparison.-"This species is closely allied to three large deepwater species from the west coast of Central America and southern 

Chile-'compressus' Dall (= dalli Lamy; southern Mexico, Panama), 

zonalis Dall (Panama); and jousseaumi (Mabille and Rochebrune) 

(Strait of Magellan) These three species were differentiated by Dall 

principally on characters of the periostracum. L. phrear is so far as 

now known smaller than these three species, elongate specimens 

are more elongate, and the radial grooves and pits are more widely 

spaced, except on the holotype. L. zonalis generally has a wider 

ligament area and hinge plate, andjousseaumi has slightly fainter 

sculpture. The fossils appear to be most closely allied to dalli." 

(Woodring, 1938, p. 32) 

Geographic range.-Southern California. 

Geologic range.-Pliocene and Pleistocene. 

Occurrence in Cali{ornia.-Pliocene and Pleistocene: Fernando 

Formation. 

Habitat.-The three living forms to which this species has been 

compared were dredged from 223 to 4,081 m (Woodring, 1937, p. 32). 

"Giycymeris barbarensis (Conrad)" 

Axinaea barbarensis Conrad, 1857a, p. 314; 1857b, p. 71, pl. 3, fig. 

11. Not Axinea barbarensis Conrad, 1857b, p. 194, pl. 6, fig. 3. 

Glycymeris barbarensis Conrad. Dall, 1909, p. 108-109. Hertlein 

and Grant, 1972, p. 161. 

Original description.-"Lentiform, subequilateral, concentrically 

wrinkled; ribs about 37, scarcely prominent, flat, defined by an 

impressed line, wanting on the submargins and obsolete toward 

the base; summits slightly prominent. Length 1% inches; height 

rather more than 11A inches." 

Holotype.-Presumed lost at ANSP (Woodring, 1946, p. 79). 

Type locality.-Coast near Santa Barbara, Calif. Holocene. 

Supplementary description.-"The high full umbo of Arnold's 

figure of G. "barbarensis" from the Palos Verdes sand suggests G. 

profunda, but the relative height is not great for the typical form. 

The specimen of G. barbarensis figured in volume 7 of the Pacific 

Railroad Reports is in theN ational Museum (13358). It is imperfect 

and poorly preserved in a matrix of hard sandy limestone and is 

probably a small specimen of the species Gabb later described as 

G. ueatchii. It therefore is probably Paleocene (Eocene of Dall's 

nomenclature), as Dall thought, or Upper Cretaceous. A label glued 

to the rock reads 'Glossus (Pectunculus) collinus Con., shore 

betwe~n San Luis and Santa Barbara.' Antisell, however, recorded 

it from· the Simi Hills. The figured G. barbarensis of volume 6 of 

the Pacific Railroad Reports is not know to be exant [sic, extant]. It 

was listed from Santa Barbara, is presumably not conspecific with 

the G. barbarensis of volume 7, as Dall thought, and is presumably 

from the Pleistocene Santa Barbara formation. It has the relative 

dimensions of the Recent G. subobsoleta. The geologic reports, 

including the paleontology, of both volumes bear the date 1856. 

Volume 6 was transmitted for publication, however, May 6, 1857, 

and volume 7 February 9, 1857. Both were issued probably sometime during 1857. Until evidence establishing priority is found, the 

G. barbarensis of volume 6 is herewith arbitrarily given precedence. This action may dispose of the troublesome name, as the G. 

barbarensis of volume 6 is a probable synonym of G. subobsoleta, 

and the G. barbarensis of volume 7 is automatically a homonym." 

(Woodring, 1946, p. 79) 

Family MANZANELLIDAE? Chronic 

Geologic range.-Permian through Holocene. 

Genus HUXLEYIA A. Adams, 1860 

Ligamenta} fossette large and round, impinging on cardinal 

area; lateral tooth smaller than in Nucinella. 

Geologic range.-Pliocene through Holocene. 

Geographic range.-Living: Japan, Australia, Africa, western 

America; fossil: southern California. 

Huxleyia munita (Dall) 

Plate 13, figures 8-10 

Cyrilla munita "Carpenter" Dall, 1898, p. 602. 

Cyrilla munita (Dall). Schenck, 1939, pl. 6, figs. 14, 15. 

Huxleyia munita (Dall). Keen, 1971, p. 36, fig. 65. 

Original description.-"In this species the fossette has become 

still larger than in Cyrilla sulcata. None of the anterior cardinal 

teeth is left. The four posterior cardinals are of the bent or Vshaped variety, and the cardinal plate and shell have become more 

solid and heavy. The ligament is wholly internal and the cardinal 

plate solid and flat. The wing-like expansions of its outer margin, 

so notable in all true species of Pleurodon are gone." 

Syntypes.-USNM 23243. 

Type locality.-Off Catalina Island, Calif. Holocene. 

Geographic range.-Living: southern California (records from 

Golfo de California are in error, Keen, 1971, p. 36); fossil: southern 

California. 

Geologic range.-Pliocene through Holocene. 

Occurrence in Cali{ornia.-Pliocene and Pleistocene: Fernando 

Formation (Vedder, 1960, as "unnamed sandstone"); may be 

restricted to upper part. 

Family MYTILIDAE 

Subfamily MYTILINAE 

Geologic range.-Devonian through Holocene. 

Genus MYTILUS Linne, 1758 

Wedge-shaped, elongate, beaks terminal; margins not crenulated, 

surface smooth or with radial ribs which are not bent dorsalward. 

Geologic range.-Jurassic through Holocene. 

Habitat.-Intertidal zone to about 90 m; attached by highly 

developed byssus to hard substrata, most commonly rocks, in 

areas of strong wave action; some clumps of Mytilus bind together 

.pebbles and cobbles that serve as anchors for colonies. 
A60 PALEONTOLOGY OF CALIFORNIA AND BAJA CALIFORNIA 

TABLE 5.-Geologic and geographic distribution of the family Mytilidae 

[H = Holocene; Pie= Pleistocene; PI= Pliocene; M = Miocene; 0 = Oligocene; E = Eocene; Pa = Paleocene) 

Alaska British Washington Oregon California Species Columbia Baja California 

Subfamily Mytilinae: Genus Mytilus: 

Subgenus Mytilus: 

californianus Conrad . condoni Dall edulis Linne Subgenus Mytilus?: 

H 

arnoldi Clark.. ............ . ...................................... . ascia Gabb loeli Grant ................ . Subgenus Crenomytilus: 

coalingensis Arnold . expansus Arnold kewi Nomland ........... . mathewsonii Gabb ...................... . sternbergi Hertlein and Grant .. trampasensis Clark ..... Subgenus Crenomytilus?: 

perrini Clark ................................................... . schencki G D. Hanna and Hertlein .... . Subgenus Plicatomytilus: 

middendorffi Grewingk ...... . Genus Brachidontes: 

Subgenus Brachidontes: 

cowlitzensis (Weaver and Palmer) 

cooperi Moore, n. n. Genus Brachidontes?: 

Subgenus Brachidontes?: 

altiobliquus (Nelson) ......... . dichotomus (Gab b) 

kirkensis (Clark). 

lawsoni (Nelson) ............ . susanaensis (Nelson) . Genus Brachidontes: 

Subgenus Scolimytilus?: 

margaritana (Nomland) ..... . multiradiatus (Gabb) 

subconvexus (Trask) .. Subgenus Aeidimytilus: 

adamsianus (Dunker) ... gabbi (Clark) ......... . Genus Mytella: 

inezensis (Conrad) Genus Perna: 

montana Conrad .. Genus Septi{er 

bi{urcatus (Conrad) .... coalingensis Arnold . elegans Waring ......................... . Subfamily Crenellinae: Genus Crenella: 

decussata (Montagu) ..... . inflata Carpenter ........ . Genus Gregariella: 

chenui (Recluz) ... Genus Musculus: 

Subgenus Musculus: 

stalderi (Martin) .. Subfamily Lithophaginae: Genus Lithophaga: 

Subgenus Lithophaga: 

clarki M. A. Hanna .. Subgenus Diberus: 

plumula (Hanley) ... Genus Adula?: 

mcknighti M.A. Hanna. Subfamily Modiolinae Genus Modiolus: 

Subgenus Modiolus: capax Conrad .... carpenteri Soot-Ryen .. contract a Conrad .. 

directus Dall ......... . eugenensis Clark ....... . garzaensis Adegoke 

lagunanus Loel and Corey ........ . ................... . rectus Conrad ........................................... . veronensis temblorensis Adegoke ... . veronensis veronensis Trask ynezianus Arnold ... Subgenus Modiolus?: merriami Weaver ............. . pittsburgensis Clark .. . Genus Modiolus?: 

Subgenus Modiolus?: 

clarki Moore, n.n ........................................... . meganosensis Clark and Woodford ... . sacculifer (Berry) . Genus Idasola?: 

bakeri Dickerson . 

1Scott McCoy, written commun., 1978. 

.. 0? and M 

H H 

H 

PI 

H 

E 

E 

H 

M 

H 

MtoH 

M 

H 

M and PI 0 

·······i'c 

Northern Middle Southern Norte Sur 

PI to H PI to H Pie to H Pie PI and PlePI and Pie PI to H 

H 

H 

PI 

Mto H PI to H H 

0 and M? 0 

Q"~-;.;d .. M E OandM 

M to Pie M to Pie OandM Oand M M and PI M Mto PI OtoM 

. .. M PI PI 

M 

M o-~·;;d .. M 

M M 

Pa and E E and 0 E E 

Pa 

..... M?"··· E 

Pa ··p~··· 

Pa 

M 

Pa E--~~~1"6 

M 

······M··· PI to H H 

E and 0 

M? 

H PI to H Pie and H M and PI . .. E .. 

H PI to H ....... ii PI toH 

H PI to H H 

E? 

PI and Pie 

E 

MtoH MtoH H MtoH PltoH M?and 

PI? 

M and PI E .. ~~d-·O . ..... M 

o-~·;;d·M ............... . ·"1\1"~-~.( M to H Pie and H 

M 

E a~d o O"~·;;;(M 

Pa 0 and M? 

M 

Pa 

H 

Pa 

H 

················ 

..... M? 

H 

H 

·······ii 

H 

H 

H 

Pie 

H 

Central and/or South 

America 

............................ 

······················ 

···························· 

............................ 

. .......................... 

. .. ···················· 

H 

H 

H 

H 

H 
TERTIARY MARINE PELECYPODS: NUCULIDAE THROUGH MALLEIDAE A61 

Subgenus MYTILUS 

Smooth or with radial ribs, margins smooth. 

Geologic range.-Oligocene(?); Miocene through Holocene (table 

5). 

Habitat.-Temperature and boreal seas. 

Mytilus (Mytilus) edulis Linne 

Plate 13, figures 11, 12 

Mytilus edulis Linne, 1758, p. 705. Soot-Ryen, 1955, p. 19-22, pl. 1, 

figs. 1-2; text figs. 1, 2, 10, 11 [see for.synonymy]. Abbott, 1974, 

p. 428-429, fig. 5039. Hertlein and Grant, 1972, p. 162-163. 

Mytilus (Mytilus) edulis Linnaeus. Grant and Gale, 1931, 

p. 244-245. 

Mytilus ficus Dall, 1909, p. 113, pl. 9, figs. 1, 4. 

Original description.-"M. testa laevinscula violacea, valvulis 

obliquis postice acuminatis." 

Holotype.-In collection of Linnean Society, London, England 

(A. M. Keen, oral commun., 1978). 

Type locality.-North Atlantic. Holocene. 

Supplementary description.-"Relatively thin shelled, nearly 

smooth"'"'* three small teeth at beaks. Length 70-100 mm." 

(McLean, 1978, p. 66) 

Geographic range.-Living: Arctic Ocean to Baja California 

Sur; North Atlantic, South America, and Australia; fossil: Alaska 

to southern California. 

Geologic range.-Miocene through Holocene. 

Occurrence in California.-Miocene: Sobrante Sandstone (Lutz, 

1951); Pliocene: Falor Formation (Manning and Ogle, 1950); Pliocene and Pleistocene: Fernando (Hertlein and Grant, 1972, p. 163), 

Merced (Glen, 1959), and Pico (Addicott and Vedder, written 

commun., 1968) Formations. 

Habitat.-Usually found in intertidal zone attached in masses to 

pilings and rocks; at some places in deeper water to at least 35 m. 

Mytilus (Mytilus) condoni Dall 

Plate 13, figures 13, 14 

Mytilus condoni Dall, 1890, p. 88-89. Addicott, 1974, p. 355-356, 

figs. 3-9. Yancey, 1978, figs. 5c, 5d. 

Mytilus highoohiae Mandra, 1949, p. 104-105, fig. 1. 

Mytilus aff. middendorfi Grewingk, n. sp. Manning and Ogle, 

1950, pl. 8, fig. A. 

Original description.-"The most remarkable, and only new 

form in this bed [at Shoalwater Bay, Washington] is a fine Mytilus 

as large as M. californicus but distinguished from all other species 

of the genus by its surface which resembles that of M. edulis 

superimposed upon which are a few strong divaricating ridges 

extending from about the middle ofthe valves toward the posterior 

extreme. Many species have the surface covered with fine divari· 

eating lines but I believe there is none known in which there are a 

few strong distant ridges, perhaps not exceeding half a dozen on 

the surface of a shell six inches in length, and having otherwise 

the form and aspect of a giant M. edulis. For this interesting 

species I propose the name of M. condoni in honor of its discoverer." 

Neotype.-USNM 647272 (Addicott, 1974, p. 355). Holotype of 

Mytilus highoohiae Mandra, UCMP 35518. 

Neotype locality.-USGS M5219. Pacific County, Wash. 

Unnamed Pliocene strata. 

Supplementary description.-"Mytilus condoni is characterized 

by a network of moderately fine, divaricating ri}?s that bifurcate 

along the median line of the valves. The ribs are of variable 

strength but are best developed on the medial and dorsal parts of 

the valves and tend to reach the ventral margin at a much later 

stage of growth than the dorsal margin. The ribs are relatively 

flat-topped and are much broader than the interspaces"'"'"'· The 

early growth stages are characterized by a smooth surface; the 

divaricate rib pattern develops after a length of about 25 mm is 

attained. On a few specimens, however, the smooth surface is 

maintained until a much later stage in growth***. The shell 

margin is smooth except for the development of a few teeth in the 

umbonal region. 

"Assignment to Mytilus is suggested by the similarity of internal 

morphology to that of the cosmopolitan species M. edulis. On the. 

anterior part of the valve, the dentition, position of the anterior 

adductor muscle scar, and outline and position of the posterior 

retractors are all remarkably similar to M. edulis***." (Addicott, 

197 4, p. 355) 

Comparison.-"Mytilus condoni is characterized by a pattern of 

moderately fine divaricate ribbing, whereas M. middendorffi has a 

few rugose plicae that produce undulatory deflections of the plane 

of commissure. The sculpture of M. middendorffi consists of two 

main folds and, usually, finer folds that branch off of the main 

dorsal fold in the posterior dorsal area of the valves." (Addicott, 

1974, p. 355) 

Geographic range.-Washington to middle California. 

Geologic range.-Pliocene and Pleistocene. 

Occurrence in California.-Pliocene: Falor Formation (Manning 

and Ogle, 1950); Pliocene and Pleistocene: Carlotta (Ogle, 1953) 

and Merced (Addicott, 1974) Formations. 

Habitat.-Presumed to have lived at low intertidal or uppermost 

inner sublittoral depths in em bayed or otherwise protected environ· 

ments (Addicott, 1974). 

Mytilus (Mytilus) californianus Conrad 

Plate 13, figures 15, 16 

Mytilus californianus Conrad, 1837, p. 242, pl. 18, fig. 15. Oldroyd, 

1924, p. 66, pl. 27, fig. 2. Soot-Ryen, 1955, p. 22-23, pl. 1, figs. 

3-4, text figs. 3, 12 [see for synonymy]. 

Mytilus (Mytilus) californianus Conrad. Grant and Gale, 1931, 

p. 245, pl. 12, fig. 6. 

Mytilus (Crenomytilus) californianus Conrad. Abbott, 1974, p. 429, 

fig. 5042. 

Original description.-"Shell ovate elongated, inflated; anterior 

margin straight; posterior side emarginate; ribs not very numerous, 

slightly prominent, broad, rounded; lines of growth very prominent. 

Length, 2 118 inches." 

Holotype.-In the Gould Collection, MCZ. 

Type locality.-Off San Diego, Calif. Holocene. 

Supplementary description.-"Thick shelled**"'showing strong 

radial ribs and irregular growth lines, the surface usually worn**"' 

Length, 80-130 mm." (McLean, 1978, p. 66) 

This species is usually easy to recognize by the radiating ribs. In 

shape, however, it varies from the broad bay form to the elongate 

irregular and worn form living in the surf. Some large specimens 

attain a length of 225 mm. (Soot-Ryen, p. 22) 

Comments.-No posterior ligamenta! teeth are present on this 

form; it is therefore retained in Mytilus s.s. 

Geographic range.-Living: Unalaska Island, Aleutian Islands, 

Alaska, to southern California [not living south of California, A. 

M. Keen, oral commun., 1978]; fossil: northern California to Baja 

California Norte. 

Geologic range.-Pliocene to Holocene. 

· Occurrence in California and Baja California Norte.-Pliocene: 

Rio Dell Formation (Faustman, 1964); Pliocene and Pleistocene: 

Merced Formation (Arnold, 1906) and Wildcat Group (Ogle, 1953); 

Pleistocene: unnamed strata on San Nicolas Island (Vedder and 
A62 PALEONTOLOGY OF CALIFORNIA AND BAJA CALIFORNIA 

Norris, 1963) and at Bahia de San Quintin, Baja California Norte 

(Jordan, 1926). 

Habitat.-Rocky intertidal zone to 38 m; seamounts (Paine, 

1976). Especially common along the exposed coast in the intertidal 

zone (Soot-Ryen, 1955) 

Subgenus MYTILUS? 

The species here assigned to the subgenus Mytilus? could be 

placed in Crenomytilus?, as on the basis of external shell characters alone, the subgenera cannot be separated. 

Mytilus (Mytilus?) ascia Gabb 

Plate 14, figure 1 

Mytilus ascia Gabb, 1864, p. 183, pl. 30, fig. 259. Anderson and 

Hanna, 1925, p. 186. 

?Mytilus humerus Conrad, 1855, p. 10. 

Original description.-"Shell long, narrow, oblique, convex; 

anterior margin nearly straight, abruptly truncated parallel with 

the border; cardinal margin slightly arched; anterior and posterior 

margins parallel, basal truncated somewhat convexly and at right 

angles to the two adjoining sides, uniting with them by rounded 

angles. Surface marked only by a few indistinct lines of growth." 

Holotype.-UCMP 11989 is accepted as the holotype. It is the 

exact size of the original illustration and bears an old printed 

paper number indicative of the California State Survey collections. 

Type locality.-Fort Tejon, Kern County, Calif. Tejon Formation, 

Eocene. 

Comments.-The holotype is an internal mold with only patches 

of the inner shell layer preserved. 

The holotype of M. humerus (Conrad) [see below] is missing and 

presumed lost. The original drawing is of a small (18-mm long) 

form that could have been an immature specimen of M. ascia. 

Geographic range.-Southern California. 

Geologic range.-Eocene. 

Occurrence in California.-Tejon Formation. 

Mytilus (Mytilus?) humerus Conrad, nomen dubium 

Mytilus humerus Conrad, 1855, p. 10. Conrad, 1857b, p. 2, fig. 10. 

Anderson and Hanna, 1925, p. 186, text fig. 9 [See for 

synonymy]. 

Original description.-"Ovate, ventricose, summit acute; anterior 

margin rectilinear; basal margin rounded; anterior extremity 

obtusely rounded; posterior extremity less obtuse; disk with minute 

radiating lines." 

Holotype.-Not in USNM; missing and presumed lot. 

Type locality.-Grapevine Canyon, Tejon quadrangle, Kern 

County, Calif. Tejon Formation, Eocene. 

Comments.-Inasmuch as the holotype of this species is lost and 

the original drawing inadequate for identification, M. humerus is 

here considered to be a nomen dubium. Mytilus humerus may have 

been an immature specimen of M. ascia. 

Mytilus (Mytilus?) arnoldi Clark 

Plate 14, figure 2 

Mytilus arnoldi Clark, 1918, p. 135, pl. 12, fig. 1. 

Original description.-"Shell medium in size; beaks subacute; 

posterior end rather narrow, somewhat acutely rounded; base 

straight or nearly so; posterior dorsal margin straight, extending 

not quite to the middle of the shell; posterior to this, the margin 

converges very strongly to the posterior end, the converging 

margin being gently convex; the change from the posterior dorsal 

margin to the converging posterior margin is not marked by an 

angulation but by a broad, regular curve. Convexity of surface 

rather broad, the posterior slope being gentle, with the anterior 

slope slanting steeply though being considerable from vertical. 

Surface smooth except for medium coarse, somewhat irregular 

lines of growth." 

Holotype.-UCMP 11153. 

Type locality.-UC 78. Contra Costa County, Calif. Kirker Tuff, 

Oligocene. 

Geographic range.-Middle California. 

Geologic range.-Oligocene and Miocene(?). 

Occurrence in Cali{ornia.-Oligocene: Kirker Tuff, lower part of 

Pleito and upper part of San Emigdio (Wagner and Schilling, 1923) 

Formations, and upper part of San Juan Bautista Formation of 

Addicott (1973); Miocene(?): San Ramon Sandstone (Weaver, 1949). 

Mytilus (Mytilus?) loeli Grant 

Plate 14, figure 3 

Mytilus kewi Wiedey, 1949, p. 281, pl. 31, fig. 2 Not Mytilus kewi 

Nomland, 1917b, p. 314, pl. 14, fig. 1. 

Mytilus loeli Grant, 1930, new name, p. 419. 

Mytilus hamlini Loel and Corey, 1932, p. 205, pl. 34, fig. 3. 

Original description.-"Shell of large size, highly inflated, with 

a prominent high, rounded elevation passing from beak to posterior 

extremity of shell; posterior margin long, evenly rounded, sharply 

so near beak with tendency toward straightening near extremity; 

beak low and sharply projected forward; entire shell of scimitershaped appearance; external surface sculptured only by inconspicuous lines of growth; interior unknown; in combined valves 

anterior dorsal portions form a broad flat area which merges into 

elevated portion, which is nearly vertical above suture. Height, 102 

mm.; breadth, 53 mm.; thickness, single valve, 22 mm." 

Holotype.-CASISU 515. 

Type locality.-SU 200. Monterey County, Calif. Vaqueros Formation, Oligocene and Miocene. 

Supplementary description.-"Mytilus loeli Grant••• is a broad, 

strongly arcuate species which may be related toM. (Mytiloconcha) 

coalingensis Arnold, a larger, less arcuate species •••. The latter 

belongs to the group with the umbo internally greatly thickened. 

The hinge. characters of Wiedey's renamed species is••• as yet 

unknown and it may prove to be subgenerically different from 

Arnold's species." (Grant, 1930, p. 419) 

Comparison.-"The sharp and pointed beaks, together with the 

generally highly arcuate shape distinguish M. kewi from M. 

mathewsonii Gabb and M. mathewsonii var. expansus Arnold, M. 

coalingensis A~nold is less arcuate than this new species." (Wiedey, 

1929, p. 281) 

"This species is quite constant in the characters outlined and 

apparently is the precursor of Mytilus mathewsoni Gabb***to 

which species it is nearest related. It is different from the species in 

its more pronounced crescentic form and greater breadth. FromM. 

expansus Arnold***it differs in its more crescentic form and in the 

lack of posterior angulation and ventral expansion." (Loel and 

Corey, 1932; as M. hamlim) 

Geographic range.-Middle California. 

Geologic range.-Oligocene and Miocene. 

Occurrence in California.-Oligocene and Miocene: Vaqueros 

and Temblor (Eaton and others, 1941) Formations. 

Subgenus CRENOMYTILUS Soot-Ryen, 1955 

Margins minutely serrated. 
TERTIARY MARINE PELECYPODS: NUCULIDAE THROUGH MALLEIDAE A63 

Geographic range.-Living: Japan and Philippines; fossil: 

western North America. 

Geologic range.-Oligocene through Holocene (table 5). 

Mytilus (Crenomytilus) expansus Arnold 

Plate 15, figure 5 

Mytilus mathewsonii Gabb var. expansus Arnold, 1907a, p. 528, 

pl. 43, fig. 2. Arnold, 1909, p. 116, pl. 5, fig. 3. Loel and Corey, 

1932, p. 205, pl. 34, fig. 1. 

Original description.-"Shell wedge-shaped, rounded behind, 

curved; posterior margin curved, semiangular in middle, anterior 

margin more nearly straight; beaks terminal, blunt; surface sculptured by irregular concentric lines and ridges of growth and by fine 

radiating striae." 

Holotype.-USNM 164968. 

Type locality.-Near Torrey Canyon oil wells, southwest ofPiru 

[Piru quad.], Ventura County, Calif. Vaqueros Formation, Oligocene and Miocene. 

Comparison.-"This variety differs from the typical form in 

being somewhat smaller, relatively broader, and with straighter 

anterior margins. The fine radial striation is also said to be lacking 

in the typical form." (Arnold, 1907a, p. 528) 

Geographic range .. -Middle to southern California. 

Geologic range.-Oligocene and Miocene. 

Occurrence in California.-Oligocene: Wygal Sandstone Member 

of Temblor Formation (Addicott, 1973); Oligocene and Miocene: 

upper part of Sespe and Vaqueros Formations, undifferentiated 

(Schoellhamer and others, 1981), Vaqueros Formation (Loel and 

Corey, 1932; Bereskin and Edwards, 1969); Miocene: Buttonbed 

Sandstone Member of Temblor (Addicott, 1972), Los Tularicitos 

Member of Chamisal, McLure Shale Member of Monterey 

(Adegoke, 1969), Tierra Redonda (Durham, 1970), and Topanga 

(Takeo Susuki, written commun., 1978) Formations. 

Mytilus (Crenomytilus) mathewsonii Gabb 

Plate 14, figure 6 

Mytilus mathewsoni Gabb, 1866, p. 30, pl. 8, fig. 51. Stewart, 1930, 

p. 96, pl. 13, fig. 2 [See for synonymy]. 

Mytilus (Mytiloconcha) mathewsonii Gabb. Clark, 1918, p. 135, 

pl. 18, figs. 1, 2. Clark and Arnold, 1923, p. 142, pl. 27, fig. 1. 

Weaver, 1942, p. 106, pl. 23, figs. 1, 10. 

Original description.-"Shell very large, thick, curved, width 

and thickness about equal in center, flatter towards the base; 

beaks terminal, blunt. Surface marked only by lines of growth and 

irregular concentric undulations." 

Lectotype.-ANSP 4500 (Stewart, 1930). 

Type locality.-South of Martinez [Conrad quadrangle, Contra 

Costa County], Calif. San Ramon Sandstone, Miocene(?). 

Supplementary description.-"M. mathewsonii is distinguished 

by its comparatively large size, smooth surface, blunt beaks and 

straight base. The shell is noticeably high, rather narrow; the 

slopes from the line of highest convexity are steep both anteriorly 

and posterioly*"'*the hinge plate just under the beak is thick and 

on this thickened area is a broad, deep, V-shaped groove. The 

ligamenta} groove is long, farily deep and heavy." (Clark, 1918, p. 

135) 

Comparison.-[See Mytilus (Crenomytilus?) perrini.] 

Geographic range.-Aiaska to Baja California Sur. 

Geologic range.-Oligocene to Pliocene. 

Occurrence in California and Baja California Sur.-Oligocene 

and Miocene: Temblor (Anderson, 1905) and Vaqueros Formations 

(Arnold, 1906); Miocene: McLure Shale member, Monterey Formation (Adegoke, 1969), Sobrante Sandstone (Merriam and Clark, 

1914), Topanga Canyon (Takeo Susuki, written commun., 1978) 

and Isidro(?) (Beal, 1948) Formations; Miocene(?): San Ramon 

Sandstone (Clark, 1918; Weaver, 1953); Miocene and Pliocene: 

Purisima Formation (Arnold, 1906). 

Mytilus (Crenomytilus) trampasensis Clark 

Plate 14, figures 7, 8 

Mytilus (Mytiloconcha) trampasensis Clark, 1915, p. 457-458, 

pl. 42, figs. 2, 3. 

Crenomytilus trampasensis (Clark). Soot-Ryen, 1955, p. 23. 

Original description.-"Shell medium to large, slender; beaks 

acute, not twisted; base nearly straight, on some specimens gently 

concave. Cardinal angle near the middle of the elongate axis. 

Posterior end evenly rounded; anterior slope steep; surface of shell 

posterior to the steep anterior slope slightly convex, with a very 

gentle posterior slope. Surface smooth except for fine incremental 

lines of growth. Hinge plate below the beaks heavy, with a deep 

groove anterior to the ligamenta} groove." 

Syntypes. UCMP 11545, 11546. 

Type locality.-UC 402. Contra Costa County, Calif. Neroly 

Sandstone, Miocene. 

Comparison.-"This species differs from Mytilus coalingensis 

Arnold in being more slender, not so broad posteriorly; the beaks 

are not twisted; the surface is not so high or convex, the anterior 

slope not being so high but possibly steeper." (Clark, 1915, p. 458) 

Geographic range.-Middle California. 

Geologic range.-Miocene. 

Occurrence in California.-Cierbo (Hall, 1960), Neroly (Hall, 

1960), and Orinda (Richey, 1943) Formations. 

Mytilus (Crenomytilus) kewi Nomland 

Plate 15, figure 4 

Mytilus kewi Nomland, 1916, p. 206, pl. 9, fig. 1. Not Mytilus kewi 

Wiedey, 1929, p. 281, pl. 31, fig. 2 [=Mytilus loeli Grant, 1930, 

p. 419]. 

Crenomytilus kewi (Nomland). Soot-Ryen, 1955, p. 23. 

Original description.-"Shell elongate ovate, of moderate thickness. Surface sculptured by numerous unequal incremental lines 

and minute radiating striae. A wide depressed area passes from 

slightly above the beak to about middle of base. Beak terminal, 

somewhat curved. Posterior end regularly rounded. Posterior dorsal 

margin slightly arcuate, with small angulation a little more than 

one-half of the distance from the beaks to the anterior end. Base 

straight except slight arch where it meets the depressed area. 

Dimensions of type, which is a small specimen: length, 86 mm:; 

height, 45 mm.; maximum diameter, 34 mm." 

Holotype.-UCMP 12061. 

Type locality.-UC 2680. Fresno County, Calif. Etchegoin Formation, Miocene and Pliocene. 

Comparison.-"This species seems to be rather closely allied to 

Mytilus expansus Arnold***. M. expansus Arnold has, however, a 

broader posterior outline and the depressed area is not .as well 

marked. M. kewi*** differs from M. coalingensis Arnold*** by 

being smaller, having less acute and not as much thickened beak, 

and in the depression extending from beak to basal margin." 
A64 PALEONTOLOGY OF CALIFORNIA AND BAJA CALIFORNIA 

(N omland, 1916) 

Geographic range.-J a pan, Sakhalin, and Kamchatka; middle 

and southern California. 

Geologic range.-Miocene and Pliocene. 

Occurrence in Cali{ornia.-Miocene: Santa Margarita Formation 

(Grant and Gale, 1931; Adegoke, 1969); Miocene and Pliocene: 

Etchegoin Formation (Wilson, 1944; Adegoke, 1969). 

Mytilus (Crenomytilus) coalingensis Arnold 

Plate 15, figures 1-3 

Mytilus (Mytiloconcha) coalingensis Arnold, 1909, p. 73, pl. 19, 

fig. 5, pl. 22, fig. 6. Grant and Gale, 1931, p. 246 [See for 

synonymy]. 

Mytilus coalingensis Arnold. Stewart, 1940, p. 90, pl. 32, figs. 3, 4. 

Crenomytilus coalingensis (Arnold). Soot-Ryen, 1955, p. 23. 

Original description.-"Shell attaining an enormous size over 

200 millimeters in length, elongate-ovate in outline, falcate toward 

beaks, gibbous, equivalve; surface comparatively smooth; shell 

moderately thick; beaks prominent, terminal, acute, curved sharply 

forward; posterior margin gently and regularly curved except for a 

faint suggestion of an angle a little above middle; base only very 

slightly curved; anterior margin gently and regularly concave; 

surface convex, the angle or region of greatest convexity being 

somewhat anterior to the middle of the shell, thus causing the 

anterior slope of the surface to be much steeper than the posterior; 

surface sculptured by numerous fine lines of growth, radiating 

striae, and more or less conspicuous concentric irregularities. 

Apical region thickened, extended; cardinal area exceedingly long, 

its width being two-thirds of its length, and carrying two ridges on 

the left valve and one on the right, each ridge representing teeth in 

the younger stages of growth; hinge area concentrically and 

radially sculptured; a deep triangular, longitudinally sulcated pit 

occupies the space immediately back of the ridged hinge area; a 

well-defined groove on the interior of the shell corresponds to the 

angle on the surface." 

Holotype.-VSNM 165551. 

Type locality.-VSGS 4656. Fresno County, Calif. Etchegoin 

Formation, Miocene and Pliocene. 

Supplementary description.-"Fine transverse rows of pustules 

on the exterior of the anterior ventral end of M. coalingensis 

***suggest that the inner margin of the valves of that species is 

crenulated." (Hertlein and Grant, 1972, p. 163) 

Comparison.-"This magnificent species is easily recognized by 

its elongate falcate and longitudinally grooved and ridged apical 

region, where this is visible. It is closely allied to the type of the 

subgenus, M. (M.) incuruus Conrad***but may be distinguished 

from the latter by its greater size, broader outline, and prominent 

muscle pit just anterior to the beaks***. M (M.) coalingensis is 

broader and more falcate toward the beaks than Mytilus mathewsonii Gabb***, is relatively narrower and more falcate than M. 

mathewsonii var. expansus Arnold***, and lacks the corrugations 

of M. californicus Conrad***." (Arnold, 1909, p. 73) 

"Specimens of M. coalingensis are as large as the living M. 

cali{ornianus Conrad but may be distinguished from the living 

species by the thicker hinge plate and by the absence of radiating 

ridges. The nearest living relative of M. coalingensis seems to be 

the large Japanese species M. crassitesta Lischke***, which, 

however, does not have so thick a hinge plate and the teeth oflarge 

specimens of which are more distinctly formed. Specific criteria 

distinguishing M. coalingensis from the many California Miocene 

forms that have been named have not yet been worked out." 

(Stewart, 1940, p. 90) 

Geographic range.-Kamchatka; middle to southern California. 

Geologic range.-Miocene to Pleistocene. 

Occurrence in California.-Miocene: Castaic (Stanton, 1966) and 

Pancho Rico (Durham and Addicott, 1965) Formations; Miocene 

and Pliocene: Etchegoin (Arnold, 1906; Adegoke, 1969) and Towsley 

(Kern, 1973) Formations; Pliocene: Niguel (Vedder, 1960) and San 

Joaquin Formations (Woodring and others, 1940); Pliocene and 

Pleistocene: Fernando (Zinsmeister, 1970) and Merced (Martin, 

1916; Yancey, 1978) Formations. 

Mytilus (Crenomytilus) sternbergi Hertlein and Grant 

Plate 16, figure 1 

Mytilus (Crenomytilus) coalingensis sternbergi Hertlein and 

Grant, 1972, p. 163-164, pl. 41, figs. 10, 14 [See for synonymy]. 

Original description.-"Shell large, resembling Mytilus coalingenesis in general shape and trace of the line of growth. It differs 

from that species in that the valves are less convex. Dimensions: 

length, 238 mm, width, 134 mm, convexity near the umbonal area, 

59mm." 

Holotype.-LAM 4470. 

Type locality.-LAM 107. San Diego County, Calif. San Diego 

Formation, Pliocene. 

Supplementary description.-"The presence of a large anterior 

adductor impression on some of the present specimens is similar to 

that on the type species of Crenomytilus. Minute crenulations on 

the anterior ventral margin, characteristic of Crenomytilus are not 

visible on our specimens." (Hertlein and Grant, 1972, p. 163) 

Comparison.-"The shell of Mytilus coalingensis sternbergi is 

broader posteriorly and it is more curved toward the beaks than is 

that of M. mathewsoni Gabb***. The anterior ventral margin of 

the new subspecies is more curved than that of M. mathewsonii 

expansus Arnold***and Mytilus kewi Nomland***. Mytilus 

schencki Hanna and Hertlein*** is very much more broadly 

expanded posteriorly." (Hertlein and Grant, 1972, p. 164) 

Geographic range.-Southern California to Baja California 

Norte. 

Geologic range.-Pliocene. 

Occurrence in California and Baja California.-Careaga Sandstone, Foxen Mudstone, and Niguel Formation (Vedder, 1960); San 

Diego Formation (Hertlein and Grant, 1972) and unnamed Pliocene 

strata between Ensenada and San Quintin, Baja California Norte 

(Hertlein and Grant, 1972). 

Subgenus CRENOMYTILUS? 

Mytilus (Crenomytilus?) schencki G D. Hanna and Hertlein 

Plate 16, figure 2 

Mytilus schencki G D. Hanna and Hertlein, 1938, p. 106, pl. 21, 

fig. 11. 

Original description.-"Shell rather flat with the anterior part 

somewhat constricted, curved, but very broadly rounded and 

expanded posteriorly. Length (incomplete), about 138 mm." 

Holotype.-CAS 4686. 

Type locality.-In the southwest corner of the NW14SW14 sec. 23, 

T. 23 S., R. 13 E., Mount Diablo Base and Meridian, San Miguel 

quadrangle, Monterey County, Calif. Santa Margarita(?) Formation, Miocene. 

Comparison.-"The broad expanded posterior part of this species 

is quite distinct from any of the described species from western 
TERTIARY MARINE PELECYPODS: NUCULIDAE THROUGH MALLEIDAE A65 

America, such as M. expansus Arnold*** and M. loeli Grant*** 

from the Vaqueros of California. Arnold's species bears a decided 

resemblance to M. aquitanicus Mayer***. Somewhat the same 

general shape of the new species seems to be indicated in the figure 

of the type of M. uancouuerensis Clark and Arnold*** but it 

appears to be much less expanded." (Hanna and Hertlein, 1938, p. 

106) 

Supplementary description.-"Mytilus schencki*** is probably 

referable to the subgenus Crenomytilus but we have not seen 

specimens in which uneroded margins could be observed." 

(Hertlein and Grant, 1972, p. 163) 

Geographic range. -Middle to southern California. 

Geologic range.-Oligocene and Miocene. 

Occurrence in Cali{ornia.-Oligocene and Miocene: Temblor 

Formation of Page and others (1951); Miocene: Santa Margarita(?) 

Formation. 

Mytilus (Crenomytilus?) perrini Clark 

Plate 14, figures 4, 5 

Mytilus perrini Clark, 1915, p. 456-457, pl. 42, figs. 5, 6. 

Original description.-"Shell medium in size, somewhat variable 

in outline, elongate subovate; beaks subactue, slightly twisted; 

base straight or slightly concave. Posterior cardinal angle as a rule 

slightly anterior to the middle of the elongate axis, the angle being 

obscured on some of the larger specimens, the margin posterior to 

the point of angulation being nearly straight and parallel or 

slightly diverging from the anterior edge. Ventral edge broadly 

rounded to subtruncate. Surface of shell covered by heavy irregular 

undulations with finer incremental lines. Anterior slope of surface 

fairly abrupt; posterior slope gentle. There is a tendency for the 

surface of the shell to be depressed and flattened just in front of the 

posterior dorsal edge. Hinge plate heavy below the beak; on some 

specimens the thickened hinge plate resembles somewhat the 

myaphoric septum of a Septi{er or Dreissensia; the anterior edge of 

the smaller specimens is denticulate immediately below the beaks; 

on the smaller specimen figured at least ten of these minute teeth 

may be counted. Ligamenta! groove broad and fairly heavy; 

anterior adductor scar long and narrow." 

Holotype.-UCMP 11548. 

Type locality.-UC 1617. Contra Costa County, Calif. Neroly 

Sandstone, Miocene. 

Comparison.-"M. perrini***.differs from M. mathewsonii Gabb 

in that the latter is a larger form; the general outlines of the two 

shells are different; the highest point of convexity on the surface of 

M. mathewsonii Gabb is near the middle of the shell, on M. perrini 

it is in front of the middle; further, the posterior slopes of M. 

mathewsonii Gabb ·are steeper than on M. perrini. M. perrini 

***resembles M. cali{ornicus Conrad in the fairly coarse concentric 

undulations; it lacks the heavy radial sculpture of M. californicus; 

the hinge plate and outline are also quite different. M. perrini 

differs from M. expansus Arnold***in that it is a smaller form; the 

posterior dorsal margin is shorter; the surface lacks the fine 

radiating striae seen on M. expansus Arnold. In other respects the 

two forms seem to be quite similar; both have a broad, subtruncate 

ventral edge and usually a straight base, the anterior slope of the 

surface being quite abrupt, with the highest point of convexity well 

in front of the middle of the shell." (Clark, 1915, p. 457) 

Comments.-On the basis of Clark's statement (1915, p. 456) 

that the anterior edge below the beak is denticulate on small 

specimens of this species, it is tentatively assigned to Crenomytilus. 

Geographic range.-Middle California. 

Geologic range. -Miocene. 

Occurrence in California-Briones (Weaver, 1953) and Neroly 

Sandstones. 

Subgenus PLICATOMYTILUS Allison and Addicott, 1976 

Geographic range.-Kamchatka, USSR, Alaska Peninsula, and 

Kodiak Island, Alaska, to middle California. 

Geologic range.-Oligocene(?); Miocene (table 5). 

Original description.-"Shell moderate to large, heavy, mytiliform; beaks terminal; lunule grooved and sometimes incurved, 

forms two large teeth and several smaller ones; margins smooth; 

shell surface smooth, marked only by concentric growth lines and 

irregular undulations of growth; shell strongly plicate toward 

posterior and posterior ventral margin with two or three major 

plicae that strongly fold the plane of commissure; posterior dorsal 

area with or without irregular seminodulose divaricate branches of 

main posterior dorsal plica, little affecting plane of commissure; 

margin often alate at change in slope between anterior and 

posterior dorsal margins; resilial ridge compact; anterior adductor 

long, thin, and deeply sunken into shell, primarily on anterior 

ventral margin; posterior adductor and posterior byssal retractor 

continuous, may be poorly defined on shell; posterior byssal 

rectractor usually narrow, continues to thin line near mid-dorsal 

break in margin slope where it occasionally is more deeply incised; 

foot retractor not continuous with posterior byssal retractor but 

placed inside pallial line and posterior byssal retractor at or near 

change in slope of dorsal margin; foot retractor large and elongate, 

but not usually deeply impressed into shell***anterior byssal 

retractor small, divided into two or possibly three well-separated 

circular points of attachment on dorsal slope of umbo well above 

resilial ridge." 

Mytilus (Plicatomytilus) middendorffi Grewingk 

Plate 16, figures 3-6 

Mytilus middendorffi Grewingk, 1850, p. 360-361, pl. 7, figs. 3a-c. 

Addicott, 1974, p. 355, figs. 1, 2. 

Mytilus (Plicatomytilus) middendorf{i Grewingk. Allison and 

Addicott, 1976, p. 3-9, pl. 1, figs. 1-10; pl. 3, figs. 2, 4, 6 [See for 

synonymy]. 

Original description.-"Testa subrhomboidali, tumida; valva 

altera plicis radialibus late et profunda plicato-sulcata; sulco 

maximo totam fere tumiditalis carinam summan concomitante, 

paullatim increscente et denique in ultimum marginem ventralem 

ob plicas hasce valde sinuatum, exeunte; sulcis reqliquis duobus 

multo minoribis, submarginalibus in ultimum marginem dorsalem, 

rectiusculum excurrentibus; valva altera obsoletissime plicatosulcata." 

Holotype.-Missing. 

Type locality.-Probably at Narrow Cape, Kodiak Island, 

Alaska. Narrow Cape(?) Formation, Oligocene(?) and Miocene 

(Allison and Addicott, 1976, p. 5). 

Supplementary description.-"Mytilus middendorffi is characterized by the broad plications of the shell that strongly deflect the 

plane of commissure. The sulcus of one valve meets the fold of the 

opposite valve producing two or three undulatory deflections of the 

plane of commissure posteriorly. The species may reach a fairly 

large size (largest specimen at hand is about 102 mm long) and 

may become strongly inflated (one articulated individual measuring about 95 mm long has a height of about 51 mm). The shell is 

always elongate, usually with a gentle arch in the longitudinal 
A66 PALEONTOLOGY OF CALIFORNIA AND BAJA CALIFORNIA 

profile***. The dorsal margin is frequently alate at the break in 

slope between the anterior and posterior dorsal margins. The shell 

is typically mytiliform but readily distinguished by the several 

strong plications. 

"In addition to the mai~ folds, smaller irregular folds or ribs that 

branch off of the main dorsal fold may occur along the posterior 

dorsal area. This posterior dorsal area particularly displays 

marked variation. Most well-preserved individuals have two or 

three poorly defined irregular nodulose branches in this area. The 

posteriormost of these dorsal secondary ribs, usually the most 

clearly defined, branches off in a dorsal direction near the terminus 

of the main rib. These secondary dorsal ribs do not seriously 

deflect the plane of commissure, although they may cause mild 

undulations of it. A few individuals have only one secondary rib 

branching dorsally near the terminus of the main dorsal rib. On 

several individuals, the main dorsal rib is crowded against the 

dorsal margin, and the secondary terminal rib is directed ventrally 

off of it into the sinus between the two main folds. A few 

individuals have little or no development of secondary ribs along 

the posterior dorsal margin." (Allison and Addicott, 1976, p. 4, 5) 

Comparison.-Mytilus (Plicatomytilus) gratacapi Allison and 

Addicott (1976), described from the Bear Lake Formation, Alaska, 

"May be readily distinguished from M. middendorffi: (1) the adult 

M. gratacapi possesses a large ribbed lunule with beaks situated 

well above the plane of commissure and has a sharp groove 

running posterodorsally from beneath the beaks, whereas the 

lunule of M. middendorffi is small, externally indistinct, and 

turned under to form the hinge teeth; (2) M. middendorffi usually 

possesses secondary folds on the posterodorsal surface that branch 

off of the main dorsal fold; M. gratacapi does not possess secondary 

branch folds; (3) M. middendorffi has a regular elongate mytiliform 

shell, whereas adult M. gratacapi typically has a strongly arched 

and twisted shell that has a trapezoidal or subquadrate shape; (4) 

the main shell folds of M. gratacapi are usually more sharply bent 

ventrally toward the posteroventral margin than those of M. 

middendorffi; this bend may accompany a posteroventral production of the shell margin by giving it a broader blunter aspect than 

that of M. middendorf{i; (5) the main fold and sinuses of M. 

gratacapi are weaker and, accordingly, deflect the plane of commissure less severely than those of M. middendorffi; (6) M. gratacapi 

usually bears well-marked semiregular constrictions along growth 

lines (rugae) that tend to give the main folds of the shell an 

indistinct nodose appearance; such constrictions are not as common or well marked on shells of M. middendorf{i, and as a result 

the main folds do not appear nodose, and; (7) M. gratacapi usually 

has three primary folds; if present, the third fold develops posterodorsally of the main folds, whereas in M. middendorffi, the third 

fold, if present, apparently develops anteroventrally of the main 

folds." (Allison and Addicott, 1976, p. 11-12) 

Geographic range.-Alaska to middle California. 

Geologic range.-Oligocene(?); Miocene. 

Occurrence in California.-Oursan and Sobrante Sandstones, 

and upper part of the Temblor Formation (Allison and Addicott, 

1976, p. 6-7). 

Genus BRACHIDONTES Swainson, 1840 

Mytiliform, beaks terminal or nearly so; radially sculptured with 

bifurcating ribs. 

Geologic range.-Jurassic through Holocene (table 5). 

Subgenus BRACHIDONTES 

Umbones subterminal, radial sculpture on ventral part simple or 

regularly bifurcating. 

Habitat.-Intertidal on rocks and pilings to 30 m; some forms 

prefer slightly brackish water; both epifaunal and infaunal; some 

species with weak byssal attachment, partly or entirely buried in 

soft sediment; some species gregarious. 

Brachidontes (Brachidontes) cowlitzensis (Weaver and Palmer) 

Plate 17, figure 1 

Modiolus (Brachydontes) cowlitzensis Weaver and Palmer, 1922, 

p. 16-17, pl. 9, fig. 9. 

Brachidontes cowlitzensis? (Weaver and Palmer). Stewart, 1930, 

p. 100-104, pl. 8, fig. 12 (See for synonymy]. 

Brachidontes (Brachidontes) cowlitzensis (Weaver and Palmer). 

Givens, 1974,p.43. 

Volsella (Brachidontes) cowlitzensis (Weaver and Palmer). Weaver, 

1942, p. 113-114, pl. 26, fig. 4. 

Modiola ornata Gabb, 1864, p. 184,234, pl. 24, fig. 166. Not Mytilus 

ornatus Orbigny, 1843. 

Original description .. -"Shell medium in size; subovate in out, 

line; dorsal line straight, curving regularly into the posterior end 

which extends almost vertically downward; posterior end broad 

and inflated; anterior end short; beaks low; umbonal slope prominent and arching downward, convex above with a prominent 

concavity beneath; surface ornamented with radiating ribs which 

over the posterior and umbonal regions are large and flat with 

narrow inters paces; on the middle portion of the shell the ribs are 

very fine and delicate; on the anterior end of the shell, there are 

five or six radiating ribs which are enlarged with wide spaces 

between, the interspaces equal to the width of the ribs; cardinal 

margin denticulate, the series of teeth are larger on the anterior 

margin, diminishing in size beneath the beaks and becoming 

obscure on the posterior end; shell very thin and fragile. 

Dimensions.-Length 15 mm.; thickness, 7 mm." (Weaver and 

Palmer, 1922) 

"Shell thin, b_road, deep; beaks small, anterior, subterminal; 

anterior end narrow, rounded, produced; cardinal margin nearly 

straight, uniting by a broad curve with the posterior extremity; 

anterior basal edge broadly emarginate; umbonal ridge prominent, 

rounded, curved downwards and widening out posteriorly, until it 

becomes lost in the general swell of the surface. In advance of this 

the surface is gently concave; behind, it is nearly flat. Surface 

marked by numerous, fine dichotomous ribs, except on a small 

space under the beaks, where they sometimes become obsolete. 

Internal edge minutely crenulated. Figure, natural size, from an 

unusually large specimen. Generally from an inch to an inch and a 

quarter long." (Gabb, 1864) 

Holotype.-CAS 7406. Lectotype of Modiola ornata Gabb, ANSP 

4450, Stewart, 1930. 

Type locality.-VW 329. Lewis County, Wash. Cowlitz Formation, Eocene. 

Supplementary description.-"This species may be distinguished 

by its sharp umbonal ridge which is sharply deflected downward 

with less than one-fifth of the area of the surface of the shell 

beneath the ridge and the area above only very slightly swelled. 

The radial ribs are more marked above the umbonal ridge than 

below it." (Weaver, 1942, p. 113-114) 

Comments.-A specimen from the Cowlitz Formation, when 

cleaned, showed no shelf in the umbonal cavity. Therefore, this 

species is indeed a Brachidontes. 

Geographic range.-Washington to southern California. 

Geologic range.-Paleocene to Oligocene. 

Occurrence in California.-Paleocene: Martinez (Weaver, 1949) 

and Meganos (Clark, 1921) Formations; Eocene: Delmar (Hanna, 
TERTIARY MARINE PELECYPODS: NUCULIDAE THROUGH MALLEIDAE A67 

1927), Domengine (Clark and Woodford, 1927), Juncal, and Matilija 

(Ectinochilus supraplicatus and E. canali{er faunas, Givens, 1974) 

Formations, Poway Group (Hanna, 1927), and Tejon Formation 

(Anderson and Hanna, 1925); Eocene and Oligocene: Gaviota 

Formation (Turritella uariata Lorenzana zone, Weaver and Kleinpell, 1963). 

Brachidontes (Brachidontes) cooperi Moore, new name 

Plate 18, figure 8 

Mytilus dichotomus Cooper, 1894, p. 49, pl. 5, fig. 64. Vokes, 1939, 

p. 58-59, pl. 3, fig. 14. Weaver, 1942, p.107-108, pl. 23, fig. 14; pl. 

26, fig. 10. Not Septi{er dichotomus Gabb, 1864. 

Septi{er dichotomus Cooper. Stewart, 1946, tbl. 1 [in pocket]. 

Original description.-"Very similar to 'Septi{er dichotomus' 

Gabb, but without any trace of a septum inside the beaks. Outside 

also sculptured, as in Modiola ornata Gabb, and in several Tertiary 

or living species of this family. (Unfortunately the umbonal end of 

the specimen figured was broken off after it was arranged for 

drawing.) I illustrate this shell to show that such a Mytilus existed 

in the latest stage of the California coal-epoch, with a strong 

suspicion that it has already one or two names. Gabb's Septi{er 

was described from one young specimen found at Tejon, very 

nearly in the same strata, and it is not unlikely that he was 

mistaken in the general character, but if proved correct the specffic 

name suits this species as well. There is also Conrad's Mytilus 

inezensis, assigned to the Miocene Tertiary, which prima facie 

seems most probable, though there is some room for doubt. This 

has not lately been confirmed among large numbers of Miocene 

fossils handled by me, and if found in the Miocene will probably be 

found to be living M. bi{urcatus, which also has its Septi{er 

bi{urcatus coexisting. In doubt as to the true value of the slight 

distinction between the two genera, I leave their correct names to 

be decided by future discoveries." 

Holotype.-CAS 613. 

Type locality.-California Coal Mine, near Huron [N1/2 sec. 16, T. 

20 S., R. 17 E.], Fresno County, Calif. Domengine Formation, 

Eocene. 

Supplementary description.-"This species is small, moderately 

inflated with a nearly straight ventral margin. The dorsal margin 

is strongly convex with a tendency to angulation about two-fifths 

the length of the shell from the anterior end. The posterior end is 

narrow, nearly straight, and forms rough angular junctions with 

both dorsal and ventral margins. The greatest thickness of the 

valves is attained about one-third the length of the shell from the 

anterior end. The radial sculpture is well marked and exhibits 

dichotomous branching on the posterior part ofthe shell." (Weaver, 

1942, p. 107-108) 

Comparison.-" A specimen in the collections of the University 

of California labelled Septi{er dichotomus Gabb from the Tejon 

agrees with themiginal figure in size and shape and is presumably 

the holotype of that species. It is certainly a Septifer, and the form 

described by Cooper is distinct and differs from Gabb's species in 

having much finer sculpturing." (Vokes, 1939, p. 58) 

Comments.-On the basis of Cooper's statement that this species 

has no septum inside the beaks, it is here assigned to Brachidontes. 

Geographic range.-Washington to southern California. 

Geologic range.-Eocene. 

Occurrence in Cali{ornia.-Avenal Sandstone (Stewart, 1946), 

Domengine (Keen and Bentson, 1944), and Tejon (Anderson and 

Hanna, 1952) Formations. 

Genus BRACHIDONTES? 

Subgenus BRACHIDONTES? 

Brachidontes (Brachidontes?) susanaensis (Nelson) 

Plate 17, figure 2 

Septi{er susanaensis Nelson, 1925, p. 409, pl. 49, fig. 10 

Original description.-"Shell small; beaks inconspicuous, terminal, semigyrate. Angle of margins at beaks about 50°. Base 

slightly concave; posterior dorsal edge almost straight for a trifle 

less than half the length of shell, posterior to which the edge is 

arcuate and approximately parallel to base; posterior extremity 

rounded with maximum curvature at junction with base. Rounded 

umbonal ridge extends from beaks to base of posterior extremity, 

most prominent near beaks. Posterior slope broad; anterior slope 

very steep. Surface of shell ornamented by about 40 radiating ribs. 

Many of these merge into a single rib near the beaks while some 

are bifid near the edge of the shell. Posterior edge internally 

crenulated. Length of type specimen, 8 mm.; width, 4 mm.; diameter 

of one valve, about 2.5 mm." 

Holotype.-UCMP 30501. 

Type locality.-UC 3776. Ventura County, Calif. Martinez 

Formation, Paleocene. 

Comparison.-Septi{er elegans Waring is less curved than 

"Septi{er" susanaensis and differs somewhat in sculpture (Nelson, 

1925, p. 409). 

Comments.-Brachidontes? altiobliquus is somewhat more produced at the anterior dorsal margin and has a higher umbonal 

ridge and deeper ventral concavity than .B.? susanaensis. These 

characters may not be sufficient to separate the two species. The 

radial ribs on B.? susanaensis are of almost equal width over the 

entire shell, which presumably distinguishes it from B. cowlitzensis. 

Geographic range.-Southern California. 

Geologic range.-Paleocene. 

Occurrence in Cali{ornia.-Martinez Formation. 

Brachidontes? (Brachidontes?) altiobliquus (Nelson) 

Plate 17, figures 3, 4 

Modiolus altiobliquus Nelson, 1925, p. 408, pl. 49, fig. 5. 

Original description.-"Shell small, subtrigonal; beaks inconspicuous. Posterior dorsal margin straight; posterior angle well 

developed, about halfway between beak and posterior extremity; 

posterior extremity broadly arcuate; basal margin regularly concave. Surface of shell with well-marked, rather sharp umbonal 

angulation extending in an almost straight line from beaks to 

juncture of posterior and ventral margins; posterior slope broad, 

gentle; anterior slope abrupt, slightly concave. Surface of shell 

ornamented by numerous small radiating ribs extending entire 

length of shell; ribs less conspicuous below umbonal angulation. 

Length of the type specimen, normal to dorsal margin, 13.2 mm.; 

length of dorsal margin 11.2 mm.; diameter of one valve, about 4.2 

mm." 

Holotype.-UCMP 30587. 

Type locality.-UC 3809. Ventura County, Calif. Martinez Formation, Paleocene. 

Comments.-This form has somewhat more prominent ribs 

along the ventral margin than B. cowlitzensis and is not as widely 

expanded on the posterior side. I do not know if the range in 

variation of B. cowlitzensis is sufficient to include this form, nor do 

I know if it is a Brachidontes or a Septi{er. 
A68 PALEONTOLOGY OF CALIFORNIA AND BAJA CALIFORNIA 

Geographic range.-Southern California. 

Geologic range.-Paleocene. 

Occurrence in California.-Martinez Formation. 

Brachidontes? (Brachidontes?) lawsoni (Nelson) 

Plate 17, figure 5 

Modiolus lawsoni Nelson, 1925, p. 408, pl. 50, figs. 3, 4. 

Brachidontes lawsoni (Nelson). Keen and Bentson, 1944, p. 68. 

Original description.-"Shell narrow, elongate, crescent-shaped 

rather high; beak almost terminal. Dorsal mar~in short, slightly 

convex; posterior lateral margin broadly arcuate, merging into a 

narrow, convex, subtruncate posterior extremity; base concave, 

with sharply reversed curvature at juncture with posterior extremity. Shell with prominent rounded umbonal ridge rising abruptly 

from beaks, curving backward and downward to juncture of 

posterior and basal margins, pinched at beaks, widening slightly 

posteriorly. Shell regularly rounded above and posterior to umbonal 

ridge; area below umbonal angulation steeply sloping, with a 

decrease in slope in anterior third above a line between beak and 

umbonal ridge. Surface of shell ornamented by numerous radiating 

ribs, uniform spacing of ribs maintained by insertion of new ribs 

as margin of shell is approached. Internal margin crenulated. 

Greatest length of type specimen (posterior extremity reconstructed 

from cotype 30652), 26.5 mm.; greatest width, 10.5 mm.; diameter of 

single valve, about 6 mm." 

Holotype.-VCMP 30651. 

Type locality.-VC 4004. Ventura County, Calif. Martinez Formation, Paleocene. 

Comparison.-The almost terminal position of the beak of B. 

lawsoni is enough to separate it from B. cowlitzensis, which is also 

much wider. (Nelson, 1925, p. 408) 

Comments.-The range in variation of B. cowlitzensis may be 

sufficient to include this form. 

Geographic range.-Southern California. 

Geologic range.-Paleocene. 

Occurrence in California.-Lower part of the Lodo (Smith, 1975) 

and Martinez Formations. 

Brachidontes? (Brachidontes?) dichotomus (Gabb) 

Plate 17, figures 6, 7 

Septi{er dichotomus Gabb, 1864, p. 186, pl. 30, fig. 261. Arnold, 

1909, p. 106, pl. 2, fig. 3. Anderson and Hanna, 1925, p. 

187-188, pl. 1, fig. 2. Weaver, 1942, p. 115, pl. 25, fig. 6. 

Original description.-"Shell small, oblique, subquadrate; cardinal margin straight, anterior and posterior margins subparallel, 

basal irregularly convex; anterior side abruptly truncated at an 

acute angle to the rest of the surface. Surface marked, posterior to 

this angle by a few large, irregular, radiating ribs, dichotomous, or 

with smaller ones interpolate." 

Holotype.-VCMP 11993. 

Type locality.-Fort Tejon, Tejon quadrangle, Kern County, 

Calif. Tejon Formation, Eocene. 

Comments .-On the basis of the placement of the keel and the 

large radiating ribs, this species is assigned to Brachidontes?; the 

diagnostic internal characters are not exposed on the holotype. 

Geographic range.-Washington; southern California. 

Geologic range.-Eocene. 

Occurrence in California.-Avenal Sandstone (Stewart, 1946) 

and Tejon Formation. 

Brachidontes? (Brachidontes?) kirkerensis (Clark) 

Plate 17, figure 9 

Modiolus kirkerensis Clark, 1918, p. 133, pl. 9, fig. 8. 

Original description.-"Shell medium in size; base straight or 

nearly so, on some specimens being slightly concave; anterior end 

rather strongly produced; posterior margin angulated back of 

middle of shell; posterior to this margin slopes in rather obliquely 

to the posterior end, which is regularly rounded but not very wide. 

Umbones prominent; umbonal ridge distinct but not extending to 

the posterior end of the shell. Surface rather acutely arched in the 

anterior third of the shell but gently rounded near the posterior 

end; anterior slope steep, slightly ex~avated in front of the umbonal 

ridge. Posterior slope not so steep as anterior; in the vicinity of the 

posterior angle, the surface is depressed or flattened, giving the 

shell an alate appearance similar to that seen on Modiolus rectus 

Conrad, a common Recent West Coast species. Surface, except for 

an elongate, smooth, triangular space between the base and the 

umbonal ridge, sculptured by numerous fine radiating dichotomous 

ribs, with interspaces averaging less than the width of the ribs. 

The dichotomous character of the ribbing is more marked toward 

the posterior margin." 

Holotype.-VCMP 11121. 

Type locality.-VC 3081. Contra Costa County, Calif. San 

Ramon Sandstone, Miocene(?). 

Comparison.- "M. multiradiatus differs quite decidedly from M. 

kirkensis , both in outline and sculpturing; the anterior end is not 

produced as strongly as that of M. kirkerensis and there is no 

well-marked posterior angle; also the sculpturing is much coarser." 

(Clark, 1918,p. 133) 

Geographic range.-Middle California. 

Geologic range.-Miocene(?). 

Occurrence in California.-San Ramon Sandstone (Weaver, 

1953). 

Subgenus SCOLIMYTILUS Olsson, 1961 

Original descrption.-"Shell small, mytiliform or modioliform, 

the beaks placed almost terminal, the valves elongated with the 

longer, oblique axis lying along the convex or sharply arched 

umbonal slope, the ventral side commonly flattened or deeply 

impressed. The surface sculpture is formed by radial riblets which 

may be weak or coarse. The posterior adductor scar is fused with 

that of the retractor and with a part of the pallial impression 

forming a single, large, lobate-shaped or ribbon-like band within 

the posterior margin. Ligament, as in Hormomya, is nearly as long 

as the posterior-dorsal margin. Hinge with one to three, fairly 

large, strong, dysodont teeth under the beak. The valve margin is 

crenulated throughout except for a short space along the impressed 

ventral side where the fluting of the riblets is weak or obsolete." 

Type species.-Modiolus (Brachydontes) playasensis Pilsbry and 

Olsson. 

Geographic range.-California? to Peru. 

Geologic range.-Paleocene(?) to Miocene(?); Holocene (table 5). 

Subgenus SCOLIMYTILUS? 

The forms here assigned to Scolimytilus? resemble that subgenus externally, but the internal shell characters of the fossil forms 

are not know. 
TERTIARY MARINE PELECYPODS: NUCULIDAE THROUGH MALLEIDAE A69 

Brachidontes? (Scolimytilus?) multiradiatus (Gabb) 

Plate 17, figure 12, 17 

Modiola multiradiata Gabb, 1866, p. 30, pl. 8, fig. 52. 

Mytilus(?) multiradiatus (Gabb). Stewart, 1930, p. 96-97, pl. 14, fig. 

3. 

Original description.-"Shell moderate in size, variable in form, 

more or less curved; cardinal margin arched; posterior curved and 

descending more or less abruptly; anterior margin sinuated, more 

or less deeply excavated; beaks very small, subterminal. Surface 

marked by numerous fine radiating lines except on the anterior 

fourth, which is only marked by lines of growth." 

Holotype.-ANSP 4482. 

Type locality.-Martinez, Contra Costa County, Calif. Martinez 

Formation, Paleocene. 

Supplementary description.-"The radial ribs are not wellpreserved [on holotype]. They are absent and probably never were 

present on the anterior portion of the shell and they become very 

fine posteriorly and were apparently not developed on the posterior 

dorsal region•••. The umbones and anterior ends of this specimen 

are too poorly preserved to permit an exact identification but teeth, 

suggesting Mytilus, are evident on the right valve and while the 

radial ribs suggest Brachidontes, they do not meet the dorsal 

posterior border at an angle as on that genus." (Stewart, 1930, p. 

97) 

Comments.-The right valve has heavy, slightly nodose ribs on 

the ventral half and much finer, somewhat nodose ribs on the 

dorsal half. The left valve has moderately heavy ribs on the midposterior region with much finer ribs closer to the ventral margin. 

Although no posterior ligamenta! teeth are visible on the exposed 

inner shell of the holotype, externally it resembles the subgenus 

Scolimytilus. 

Geographic range.-Middle California. 

Geologic range.-Paleocene to Oligocene. 

Occurrence in California.-Paleocene: Martinez Formation; Eocene and Oligocene: S.cm Emigdio and Pleito Formations, undifferentiated (Hammond, 1958). 

Brachidontes? (Scolimytilus?) margaritana Nomland 

Plate 17, figure 13 

Septifer margaritana Nomland, 1917, p. 308-309, pl. 19, fig. 5. 

Septifer margaritanus Nomland. Grant and Gale, 1931, p. 248. 

Original description.-"Shelllong, cuneate, rather thick; beaks 

pointed, terminal; with well-developed umbonal ridge extending to 

posterior ventral margin. Anterior dorsal margin slightly concave; 

posterior dorsal margin regularly convex; posterior end evenly 

rounded; ventral margin a little concave at middle but becoming 

convex about one-third oflength of shell from anterior end. Surface 

ornamented by a large number of fine radiating ridges and welldeveloped growth lines. Dimensions: Length, 52 mm.; height, 22." 

Holotype.-VCMP 11310. 

Type locality.-VC 2276. Fresno County, Calif. Santa Margarita 

Formation, Miocene. 

Comparison.-"This species is much larger than the Recent 

Septifer bi{urcatus Conrad, the radiating ridges are more numerous, and the umbonal ridge is more marked." (Nomland, 1917, p. 

309) 

Geographic range.-Middle California. 

Geologic range.-Miocene. 

Occurrence in California.-Santa Margarita Formation. 

Brachidontes? (Scolimytilus?) subconvexus (Trask) 

Plate 17, figure 14 

Modiolus gabbi subconvexus Trask, 1922, p. 149, pl. 3, fig. 2. 

Original description.-"Shell very similar to M. gabbi 

Clark•••but differs from the latter in that the umbonal ridge is less 

prominent; the shell is more convex, narrow, and tumid; the 

striations are slightly narrower and less prominent; and on the 

posterior slope the striations become much finer, closer together 

and more numerous." 

Holotype.-VCMP 12372. 

Type locality.-VC 793. [No locality data available. Trask (1922, 

p. 149) says that it is a common species in the Briones Formation.] 

Geographic range.-Middle California. 

Geologic range.-Miocene. 

Occurrence in California.-Briones Sandstone. 

Subgenus AEIDIMYTILUS Olsson, 1961 

Original description.-"Shell small, mytiliform with ribbed sculpture, usually divided, the ribs on the posterior-dorsal side of the 

umbonal ridge much coarser. Ventral side usually strongly impressed resulting in a high, angular umbonal ridge and often a 

distorted appearance to the whole shell. Adductor and pallial 

impressions united, but smaller and narrower than in Scolimytilus." 

Type species.-Mytilus adamsiana Dunker. 

Geologic range.-Miocene through Holocene (table 5). 

Habitat.-In temperate and tropical seas, predominantly intertidal; reported to a depth of 90 m. 

Comments.-This genus was omitted by Soot-Ryen (1969) and 

was placed in synonymy with Brachidontes by Keen (1971). 

Aeidimytilus was used by Hertlein and Grant (1972) and seems to 

me, on the basis of external shell characters only, to be a useful 

category. Admitting that the classification of the mytilids needs to 

be resolved on the basis of soft-part anatomy and internal shell 

characters also, I feel that since these forms are different in 

external shell characters, they should be separated. 

Brachidontes (Aeidimytilus) gabbi (Clark) 

Plate 17, figure 8 

Modiolus gabbi Clark, 1915, p. 458-459, pl. 48, fig. 1. 

Original description.-"Shell medium to large, elongate, anterior 

end extending only slightly beyond the beak. Posterior dorsal edge 

subangulate posterior to the midlength of the valve. Base nearly 

straight with a tendency to concavity; posterior end evenly rounded. 

Surface sculptured by rather broad, flat-topped, dichotomous ribbing, except for an elongate, smooth, subtriangular space above 

the base near the anterior end; the dichotomous ribbing is more 

marked toward the posterior margin, while anteriorly the ribs are 

split only at their lower ends; interspaces slightly narrower than 

the tops or the ribs. Surface quite strongly convex, usually with a 

well-defined ridge marking the line of greater convexity extending 

from the beak toward the basal side of the posterior extremity; on 

the larger specimens this ridge is not so pronounced, the surface 

being more evenly rounded." 

Holotype.-VCMP 11550. 

Type locality.-VC 2040. Contra Costa County, Calif. San Pablo 

Group, Miocene. 

Comparison.-"The radial ribbing on M. multiradiatus is much 

finer and closer together than on M. gabbi; also, on the former the 

anterior and extends much further beyond the beak than on the 

latter." (Clark, 1915, p. 459) 
A70 PALEONTOLOGY OF CALIFORNIA AND BAJA CALIFORNIA 

Geographic range.-Middle California. 

Geologic range.-Miocene. 

Occurrence in California.-Cierbo (Hall, 1958) and Neroly Sandstones (Weaver, 1949; Hall, 1958). 

Brachidontes (Aeidimytilus) adamsianus (Dunker) 

Plate 17, figures 10, 11 

Mytilus adamsianus Dunker, 1856, p. 360. 

Aeidimytilus adamsianus (Dunker). Hertlein and Grant, 1972, p. 

164-165, pl. 42, figs. 4, 5 [See for synonymy]. 

Original description.-"M. testa ovato-trigona, utrinque obtuse 

carinata, solidula, costis mature bifidis eleganter granosis sculpta, 

fusco-purpurascente et albida; epidermide cornea vestita; umbonibus terminalibus; margine crenato." 

Holotype.-Type lot in British Museum (Hertlein and Grant, 

1972, p. 164). 

Type locality.-lsthmus of Panama, Holocene. 

Supplementary description.-"The beaks are small and nearly 

terminal and the umbonal ridge is high. The ribbing and general 

shell characters of the present valves agree exactly with specimens 

from west Mexico and Central America. The ribs on typical 

specimens of Aeidimytilus adamsianus are coarse on the dorsal 

area; they increase posteriorly by divarication or by addition. They 

are granulated as a result of successive step-like resting stages. 

The ribs on the ventral area are much finer. The dorsal area is 

brownish purple, the ventral area yellowish white. Interiorly the 

dorsal margin above the ligamenta! groove is strongly crenulated. 

The external appearance of this shell is remarkably similar to that 

of Septifer bifurcatus. Some specimens are sculptured with fine 

ribs but such forms agree in all other shell characters with the 

coarsely ribbed ones." (Hertlein and Grant, 1972, p. 165) 

Geographic range.-Living: Santa Barbara, Calif., to Puerto 

Callo, Ecuador, and the Galapagos Islands; fossil: southern California. 

Geologic range.-Pliocene through Holocene. 

Occurrence in California.-Pliocene: San Diego Formation 

(Hertlein and Grant, 1972). 

Genus MYTELLA Soot-Ryen, 1955 

Mytiliform to modioliform or elongate; smooth or concentrically 

striated, rarely finely striated radially. 

Geographic range.-Western North America to South America. 

Geologic range.-Eocene through Holocene (table 5). 

Mytella inezensis (Conrad) 

Plate 17, figures 15, 16 

Mytilus inezensis Conrad, 1857c, p. 194, pl. 8, figs. 2, 3. Woodring, 

1931 b, p. 380. 

Mytella inezensis (Conrad). Soot-Ryen, 1955, p. 48 

Original description.-"Subovate-oblong? ventricose anteriorly; 

compressed posteriorly ; ribs radiating, numerous, bifurcated, and 

trifurcated near the inferior margins." 

Syntype.-VSNM 13319 (Woodring, 1931b). 

Type locality.-Santa Ynez Mountains and Santa Ynez River, 

Santa Barbara County, Calif. Gaviota Formation, Eocene and 

Oligocene. 

Geographic range.-Southern California. 

Geologic range.-Eocene and Oligocene. 

Occurrence in California.-Eocene and Oligocene: Gaviota Formation of Keen and Bentson (1944). 

Genus PERNA Retzius, 1788 

Like Mytilus but without anterior adductor except in young 

specimens; surface and margins smooth. 

Geologic range.-Eocene through Holocene (table 5). 

Subgenus PERNA 

Resilial ridge pitted, posterior retractor scars widely separated. 

Habitat.-In tropic and subtropic seas. 

Perna (Perna) montana Conrad 

Plate 18, figure 4 

Perna montana Conrad, 1857c, p. 195 [unfigured]. [Reprinted in 

Dall, 1909, p. 184.] 

Original description.-"Elevated, anterior margin nearly 

straight; hinge line slightly incurved." 

Holotype.-VSNM 13329. 

Type locality.-Santa Buenaventura, Santa Barbara County 

[Ventura, Ventura County], Calif. Formation and age unknown. 

[From the Eocene to Miocene sequence of the eastern Santa Ynez 

Mountains; presumably from the Miocene as stated by Conrad 

(1857c, p. 189).] 

Supplementary description.-"An imperfect cast, about 4112 

inches [11 em] in height, allied to P. marillata of Virginia, from 

which it differs in having a straighter front and incurved cardinal 

margin." (Conrad, 1857c, p. 195) 

Geographic range.-Southern California. 

Geologic range.-Not known. Miocene?. 

Occurrence in California.-Formation unknown. 

Genus SEPTIFER Reduz, 1848 

Externally similar to Brachidontes (Brachidontes), anterior adductor placed on internal septum beneath beaks. 

Geologic range.-Triassic through Holocene (table 5). 

Habitat.-In tropic and subtropic seas; from intertidal zone to 

about 55 m; attached by byssus; found on boulqers at low tide. 

Subgenus SEPTIFER 

Radial sculpture strong, margins crenulated. 

Septifer (Septifer) elegans Waring 

Plate 18, figure 11 

Septifer elegans Waring, 1917, p. 79, pl. 14, fig. 2. 

Original description.-"Shell small, oblique, subquadrate; cardinal margin straight, anterior and posterior submargins subparallel, 

base irregularly convex; anterior side abruptly truncated, at an 

acute angle, to rest of surface; surface marked, posterior to this 

angle, by many fine radiating ribs. This species differs from S. 

dichotomus Gabb in having fine radial sculpture." 

Neotype.-Here designated as CAS/SU 322. In the Stanford 

University type collection, there are two specimens of S. elegans. 

One is a small shell fragment in rock (CAS/SU 156) labelled 

"holotype?"; the other an entire specimen in rock (CAS/SU 322) 

labelled "paratype." This specimen labelled "paratype" is selected 

as the neotype. 

Type locality.-SV 322. Ventura County, Calif. Llajas Formation, Eocene. 

Geographic range.-Southern California. 
TERTIARY MARINE PELECYPODS: NUCULIDAE THROUGH MALLEIDAE A71 

Geologic range.-Eocene. 

Occurrence in California.-Llajas Formation (Keen and Bentson, 

1944). 

Septifer (Septifer) coalingensis Arnold 

Plate 18, figure 10 

Septifer coalingensis Arnold, 1909, p. 58-59, pl. 5, fig. 4. 

Original description.-"Shell averaging about 45 millimeters in 

length, wedge-shaped, slender, convex, radially striate. Beaks 

subterminal, curved, sharp, anterior margin moderately concave, 

slightly angular at about middle; posterior margin considerably 

more curved than the anterior, slightly angulated opposite angle in 

the anterior margin; base slightly convex, moderately abruptly 

truncated at right angles to margins on both sides. Surface 

sculptured by numerous regular, close-set small rounded radiating 

ribs and a considerable number of prominent lines of growth; all of 

the specimens examined are more or less decorticated and show 

the radial sculpture around the periphery only; the sculpture in the 

younger stages of growth is believed to be coarser than that in the 

later stages. Hinge without teeth, furnished with a lamellar septum; 

ligamenta} pits linear, marginal." 

Holotype.-VSNM 165580. 

Type locality.-VSGS 4634. Fresno County, Calif. Etchegoin 

Formation, Miocene and Pliocene. 

Supplementary description.-"This unique species is characterized by its slender form, regularly convex surface, and fine radial 

sculpture." (Arnold, 1909, p. 58) 

Comparison.-Septifer coalingensis "is closely allied to the recent 

S. bifurcatus Reeve•••but is narrower, more falcate, and more 

regularly but less markedly convex. It is much larger, narrower, 

less angulate, and finer sculptured than•••s. dichotomus Gabb." 

(Arnold, 1909, p. 58) 

Comments.-Arnold (1909) says that S. coalingensis has a 

lamellar septum; thus it does belong in Septifer s.s. 

Geographic range.-Middle California. 

Geologic range.-Miocene and Pliocene. 

Occurrence in California.-Etchegoin Formation (Keen and 

Bentson, 1944). 

Septifer (Septifer) bifurcatus (Conrad) 

Plate 18, figures 7, 9 

Mytilus bifurcatus Conrad, 1837, p. 241, pl. 18, fig. 14. 

Septifer bifurcatus Conrad. Soot-Ryen, 1955, p. 41-42, pl. 4, figs. 

19, 20; text fig. 33. Hertlein and Grant, 1972, p. 165-166, pl. 42, 

figs. 6, 12, [See synonymy]. 

Original description.-"Shell narrowed, slightly arcuate; anterior 

margin much flattened; ribs narrow, prominent, bifurcated toward 

the base; color dark purple. Height 1 1/2 inches." 

Holotype.-ANSP 57920. 

Type locality.-Vnknown; believed to be California (Hertlein 

and Grant, 1972, p. 165). Age: Holocene. 

Supplementary description.- "Septifer bifurcatus is here reported 

for the first time from strata of Pliocene age. One valve, somewhat 

eroded [is] 18.2 mm long and 10.8 mm wide•••. The largest Recent 

specimen in the collections of the California Academy of Sciences 

[from]***San Diego, California, is 41.5 mm long and 18 mm high. 

Some large valves become partially or almost entirely smooth after 

attaining a length ~f about 25 mm. Shells similar to these with 

obsolete radial sculpture were described as Septifer bifurcatus var. 

obsoletus Dall." (Hertlein and Grant, 1972, p. 166) 

"The outer form of this species is as variable as that of other 

intertidal mytilids. The keel from umbo to posteroventral angle is 

generally very pronounced and the ventral part flattened. The 

radiating sculpture is strong posterior to the keel, with the upper 

ribs bent dorsalward; the ventral ribs are weaker; all ribs are 

irregularly furcating. The periostracum is dark, blackish. The 

anteriorly placed umbones are strongly twisted, with the lunule 

bent inward, at least in large specimens, and furnished with 

radiating furrows which form the teeth. Generally there is a single 

strong tooth more or less furrowed; but the teeth seem to be so 

variable that it is nearly impossible to give an adequate description 

of them. The margins are crenulated, with especially strong 

crenulations behind the ligament. The crenulations on the posterior 

margins are extremely variable." (Soot-Ryen, 1955, p. 41-42) 

Comparison.- "Septifer margaritana Nomland•••was described 

as larger (52 mm long, 22 mm high) than S. bifurcatus, with more 

numerous radiating riblets and with a more acute umbonal angulation. We have examined a cast of the holotype which reveals the 

shell characters mentioned by N omland." (Hertlein and Grant, 

1972, p. 166) 

Geographic range.-Living: Crescent City, Calif., to Cabo San 

Lucas, Baja California Sur; fossil: southern California and Baja 

California Norte. 

Geologic range.-Pliocene through Holocene. 

Occurrence in California and Baja California Norte.-Pliocene: 

San Diego Formation (Hertlein and Grant, 1972); Pleistocene: 

unnamed strata on San Nicolas Island (Vedder and Norris, 1963), 

Newport Bay area (Kanakoff and Emerson, 1959), San Pedro, 

Santa Barbara, and San Diego (Arnold, 1903), and in Baja California Norte (Valentine, 1957). 

Habitat.-Vsually intertidal and attached to underside of rocks; 

to 20m. 

Subfamily CRENELLINAE 

Genus CRENELLA Brown, 1827 

Small, round to ovate, beaks anterior; radiating sculpture, usually 

unilaterally bifurcate anteriorly and posteriorly, bifurcate or simple 

in middle; margins crenulate. 

Geologic range.-Cretaceous through Holocene (table 5). 

Habitat.-Most of the living species are found in cool seas but a 

few occur in tropical seas; 2 to 4,190 m (Hertlein and Grant, 1972, p. 

170). 

Crenella decussata '(Montagu) 

Plate 18, figures 1, 2 

Mytilus decussata Montagu, 1808, p. 69. 

Crenella decussata (Montagu). Grant and Gale, 1931, p. 254. 

Original description.-"Shelllongitudinally ovate, with the umbo 

at the smaller end; sides equal. It is very thin, pellucid, of a pearly 

white when divested of the epidermis, which is of a pale olive 

brown; and is finely striated longitudinally, crossed by more 

minute striae in a transverse direction, that give it a decussated 

appearance when examined under a microscope. The inside is 

smooth with a nacred gloss; at the hinge is a slight indenture, the 

margin contiguous and slightly denticulated; near the front margin 

is a singular, reflected transverse ridge, but whether this is a 

constant character, or accidental, cannot be determined; indeed 

only one valve of this curious little shell has come under examination, and that through the favor of Mr. Laskey, who found it in 

sand on the Scottish coast. Length about 1/s of an inch; and not 

quite so broad." 
A72 PALEONTOLOGY OF CALIFORNIA AND BAJA CALIFORNIA 

Holotype.-In British Museum? 

Type locality.-Scottish coast, British Isles. Holocene. 

Geographic range.-Living: Bering Sea to San Pedro, Calif.; 

Greenland toN orth Carolina; British Isles; fossil: southern California. 

Geologic range.-Pliocene through Holocene. 

Occurrence in California.-Pliocene and Pleistocene: Fernando 

Formation (J. D. Mount, written commun., 1971; J. G. Vedder, 

written commun., 1978), San Pedro Formation (Oldroyd, 1924). 

Habitat.-In sand or mud from 10 to 265m. 

Crenella inflata Carpenter 

Plate 18, figures 3, 5, 6 

?Crenella inflata Carpenter, 1864a, p. 313. 

Crenella inflata Carpenter. Hertlein and Grant, 1972, p. 171, pl. 41, 

fig. 11 [See for synonymy]. 

Original description.-"C. testa valde inflata, minuta, albida, 

subrhomboideo-orbiculari; diagonaliter parum producta; marginibus subquadrangulatim rotundatis; umbonibus prominentibus, 

valde antice intortis; tota superficie ut in C. decussata sculpta, 

costulis crebris radiantibus aequidistantibus, hie et aliis intercalatis· lirulis concentricis decussantibus: intus margine dorsali brevissi~o, arcuato, dentato; ligamento curtissimo, in fossa omnino 

interna, celata, lamina definiente, sito; lamina cardinali sub 

umtonibus intus porrecta, dentibus validis instructa; marginibus 

internis omnino crenatis; cicatr. adduct. subaequalibus, ventraliter 

sitis. Long .. 1, lat .. 2, alt .. 09 poll." 

Holotype.-USNM 3988 is considered to be the holotype (Hertlein 

and Grant, 1972, p. 171). 

Type locality.-Cabo San Lucas, Baja California Sur. Holocene. 

Comparison.-The shell of Crenella decussata is more symmetrical and the beaks more centrally located than on C. inflata. 

Geographic range.-Living: Huntington Beach and San Miguel 

Island, Calif., to Golfo de California and south to Callao, Peru; 

fossil: southern California. 

Geologic range.-Pliocene through Holocene. 

Occurrence in California.-Pliocene: San Diego Formation. 

Habitat.-4 to 90 m. 

Genus GREGARIELLA Monterosato, 1884 

Elongated, inflated, beaks incurved, umbonal keel angulated; 

radially striated anteriorly and posteriorly where striae end along 

oblique line, median part concentrically striated; margins crenulated. 

Geologic range.-Miocene through Holocene (table 5). 

Habitat.-Living in 49 to 90 m; burrows in rocks and large 

shells. 

Gregariella chenui (Reduz) 

Plate 19, figures 1, 2 

Mytilus (Modiola) chenui Recluz, 1842, p. 306. 

Gregariella chenui Recluz. Hertlein and Grant, 1972, p. 168-169, pl. 

41, figs. 1, 5; pl. 42, figs. 1, 8 [See for synonymy]. 

Original description.-"Soquille transverse, ovale, renflee, mince, 

marquee d'um angle obtus des sommets au bord posterieur et plane 

en dessus, arrondie, etroite et plus courte anterieurement qu'au cote 

posterieur, lequel est plus retreci et presque anglueux. Sommets 

petits, saillants, obtusement arrondis, places tres-pres du bord 

anterieur et decortiques; l'exterieur est sculpte de tres petits sillons 

longitudinaux, partant des crochets et rayonnant vers la base des 

valves: les sillons sont finement stries en dedans et ont un aspect 

presque onduleux; les anterieurs sont arques et obliquent fortement 

en avant; les posterieurs ont une direction anterieure plus droit 

dans leur cours. Ces sillons et ces stries sont effaces sur le tiers 

anterieur des valves ou a'peine apparents, et a cette place regne 

une depression qui part des crochets, ou elle est peu sensible et se 

continue en augmentant graduellement d'intensite jusqu'a la base 

des valves, qu'elle retrecit legerement dans leur longeur. La couleur 

de cette couquille est roussatre, peinte longitudinalement d'une 

large fascie marron sur la partie deprimee et lisse. Toute la portion 

posterieure est couverte de poils jaunatres, comme agglutines entre 

eux, et dont les posterieurs sont disposes en trois ou quatre 

filaments roides, vel us et saillants d'un a deux millimetres. Interieur 

nacre et legerement irise. Charniere formee d'une serie de denticules 

ou crenelures qui, tres-saillantes anterieurement, se continuent sur 

toute la region superieure des valves, et viennent finir sur le milieu 

du cote posterieur, en s'affaiblissant graduellement dans leur 

cours.-Larg. 16, diam, 10, convex. 10 mill." 

Holotype.-Location unknown. 

Type locality.-"Hab. les cotes du Bresil, province de Bahia." 

Supplementary description.-"The radial sculpture on both the 

fossil and on the Recent shells is well developed and beaded 

posteriorly where crossed by coarse concentric lines of growth. The 

largest valve***from off Catalina Island is 0.4 mm long and 4.6 

mm high." (Hertlein and Grant, 1972, p. 169) 

"Shell***small, with the umbones anteriorly placed, of a broadly 

oval form with sloping curved anterior and posterior margins, 

broadest in the posterior half***. Sculpture consisting of a few 

radial anterior striae, a median part without radial sculpture, and 

distinct radial striae on the posterior part, the first not reaching to 

the ventral margin, the dorsal ones bent backward. The radiating 

striae crossed by distinct but somewhat irregular concentric lines, 

giving the posterior part a decussated sculpture. The anterior 

dorsal margin somewhat thickened and crenulated; the posterior 

dorsal margin with strong crenulations which become smaller on 

the posterior margin and hinder part of the ventral margin; the 

middle part of the ventral margin smooth. The ligament internal 

and descending backward, supported by a distinct nymphae." 

(Soot-Ryen, 1955, p. 78) 

Comparison.-"The sculpture on the shell of G. chenui is much 

coarser, the posterior end more rounded and the umbonal slope is 

less angulated than that of G. coarctata Dunker in Carpenter***. 

Specimens of G. coarctata which we have seen are larger than 

those of G. chenui." (Hertlein and Grant, 1972, p. 169) 

Geographic range.-Living: Monterey Bay, Calif., to Bahia de la 

Independencia, Peru; also Brazil and Caribbean region; fossil: 

southern California. 

Geologic range.-Pliocene. 

Occurrence in California.-Pliocene: San Diego Formation (Hertlein and Grant, 1972). 

Habitat.-Living in 2 to 90 m. 

Genus MUSCULUS Roding, 1798 

Modioliform with broadly rounded mnbonal keel, posterodorsal 

part usually separated from remainder of valve by furrow, radiate 

sculpture separated in middle by concentrically striated area; 

margins crenulate. 

Geologic range.-Jurassic through Holocene. 

Habitat.-Moderately deep water; 10 to 230 m; some species 

occupy a bysally formed nest within shells or holdfasts or embedded within the nest of ascidians (sea-squirts). 

Subgenus MUSCULUS 

Shell rather flat. 

Geologic range.-Jurassic through Holocene (table 5). 
TERTIARY MARINE PELECYPODS: NUCULIDAE THROUGH MALLEIDAE A73 

Musculus (Musculus) stalderi (Martin) 

Plate 19, figures 3, 4 

Modiolus stalderi Martin, 1914, p. 182-183, pl. 22, figs. 6a, 6b. 

Volsella (Brachiodontes) stalderi (Martin). Grant and Gale, 1931, 

p. 252. 

Original description.-"Shell small, thin, subelliptical, sculptured 

with numerous radiating ridges which are crossed by very fine 

concentric lines, producing a fine tessellated surface; valves nearly 

equal, very inequilateral; umbones conspicuous, almost terminal; 

umbonal ridge, prominent anteriorly broadening and less prominent posteriorly; hinge line nearly straight, about one-fourth the 

length of the shell; upper posterior margin broadly arcuate; posterior extremity sharply and evenly rounded; ventral margin nearly 

straight, slightly concave at the middle in some specimens; anterior 

end blunt, excavated in front of the beaks." 

Holotype.-UCMP 12354. 

Type locality.-UC 1859. Humboldt County, Calif. Rio Dell 

Formation, Pliocene. 

Comparison.-"This species differs from the Recent Brachidontes 

· demissus (Dillwyn), which has been introduced into San Francisco 

Bay from the Atlantic on seed oysters, in being less pointed 

anteriorly and less incurved ventrally." (Grant and Gale, 1931, p. 

252) 

Geographic range.-Northern California. 

Geologic range.-Pliocene. 

Occurrence in Cali{ornia.-Rio Dell Formation (Roth, 1979). 

Subfamily LITHOPHAGJN AE 

Genus LITHOPHAGA Roding, 1798 

Cylindrical, usually tapering posteriorly, beaks near anterior 

end; smooth or with vertical striae; hinge edentulous; margins 

smooth. 

Geologic range.-Carboniferous(?); Eocene(?); Miocene through 

Holocene (table 5). 

Habitat.-Mainly in tropical and subtropical seas; a few species 

extend into the temperate zone. Boring into calcareous rocks, coral, 

and shells, by means of a chemical process that is effective only in 

calcareous media; retains byssus. 

Subgenus LITHOPHAGA 

Shell with vertical striations. 

Lithophaga (Lithophaga) clarki M. A. Hanna 

Plate 19, figures 5, 6 

Lithophaga clarki M.A. Hanna, 1927, p. 278-279, pl. 33, figs. 3-6, 9. 

Original description.-"Shell small, very heavy, cylindrical, 

bluntly rounded in front, wedge-shaped behind, greatest altitude 

some distance behind the beaks, posterior margin somewhat 

sharply rounded; beaks not prominent, located near the anterior 

end, projecting only slightly above the bluntly rounded anterior; 

surface ornamented by small rounded growth lines; valves fit very 

closely together. Dimensions: Altitude 6 mm., length 13 mm., 

diameter of two valves 5 mm." 

Holotype.-UCMP 31031. 

Type locality.-UC 3981. San Diego County, Calif. Delmar 

Formation, Eocene. 

Comments.-Fossiliferous marine sand of the Pleistocene Bay 

Point Formation unconformably overlies the Eocene Delmar Formation in the type locality of Lithophaga clarki. Fossil bivalve 

borings of Pleistocene age are associated with the wave-cut platform eroded into the Eocene Delmar Formation. The holotype of L. 

clarki is so well p"reserved that I suggest it may have been a 

Pleistocene species that burrowed into Eocene strata and shells. 

This suggestion is perhaps substantiated by Hanna's (1927, p. 279) 

comment that: "Some of the individuals lived in the soft sand 

which has since been cemented and consolidated." Lithophaga is 

not known from unconsolidated sediment. 

Geographic range.Southern California. 

Geologic range.-Eocene or Pleistocene. 

Occurrence in Cali{ornia.-Delmar(?) Formation. 

Subgenus DIBERUS Dall, 1898 

Two or more posterior sulci with plumelike incrustation distinctly 

projecting beyond valves. 

Geographic range.-Living: Western North America and IndoPacific; fossil: Florida and California. 

Geologic range.-Miocene through Holocene (table 5). 

Lithophaga (Diberus) plumula (Hanley) 

Plate 19, figures 7, 8 

Lithodomus plumula Hanley, 1844, p. 17. 

Lithophaga plumula (Hanley). Arnold, 1903, p. 121. 

Lithophaga (Diberus) plumula (Hanley). Grant and Gale, 1931, p. 

253. Keen, 1971, p. 68, fig. 138. 

Original description.-"Lit. testa L. canalifero simillima, sed 

extremitate antice minus obtusa; tegmine calcareo antico, crassiore, 

atque in parietibus confertis, subparallelis ordinato; parietibus 

corrugatis et (plumulae haud dissimilibus) versus marginem et 

marginem anticum utroque latere radiantibus." 

Holotype.-BM(NH)? (A.M. Keen, oral commun., 1978). 

Type locality.~Panama. Holocene. 

Supplementary description.-" Anterior end rounded, two grooves 

extending from beaks to the tapered posterior end of the shell, area 

between the grooves bearing a ridged, feathery encrustation 

extending posteriorly beyond end of shell, encrustation is also 

thinly spread over the rest of shell***Length, 40-55 m." (McLean, 

1978) 

Comments.-Lithophaga plumula kelseyi Hertlein and Strong 

(1946), a species living along the coast of California, has been 

reported from the Pleistocene of Newport Bay, Calif., by Kanakoff 

and Emerson (1959). 

Geographic range.-Living: Gulf of California to Peru; fossil: 

southern California. 

Geologic range.-Pliocene through Holocene. 

Occurrence in Cali{ornia.-Pliocene and Pleistocene: Fernando 

(Willett, 1946) and San Pedro (Arnold, 1903) Formations. 

Habitat.-Specimens may be found boring into calcareous shale, 

into the pelecypod Spondylus or other large shells, or into masses 

of coral; low tide to 37 m. 

Genus ADULA H. and A. Adams, 1857 

Elongate, cylindrical, beaks behind anterior margin, anterodorsal margin thickened, surface smooth or with irregular wrinkles. 

Geographic range.-Pacific. 

Geologic range.-Eocene(?); Holocene (table 5). 

Habitat.-Usually boring in soft rocks with the exception of 

Adula diegensis (Dall), which is free-living on mud flats or pilings. 
A74 PALEONTOLOGY OF CALIFORNIA AND BAJA CALIFORNIA 

Genus ADULA? 

Adula? mcknighti (M.A. Hanna) 

Plate 19, figures 9, 10 

Lithophaga mcknighti M.A. Hanna, 1927 p. 279, pl. 33, figs. 2, 7, 8, 

10, 11 [Figure 2 is not of the holotype. I assume it was an 

impression of the mold not' retained with the type specimen.] 

Original description . ....,...."Shell of moderate size, elongate, well 

inflated, heavy; beaks anterior, elongate due to the length of the 

shell, prominent; ventral margin straight to slightly concave; 

anterior short, rounded to the beak; posterior somewhat flattened, 

well rounded; posterior dorsal margin broadly rounded; only concentric sculpturing present, which consists of heavy placoid ridges 

which project out over the later formed ones for a considerable 

distance; both the concentric ribs and the interspaces sharp. 

Dimensions: Altitude 8 mm., length 19 mm., diameter of the two 

valves 9 mm." 

Holotype.-VCMP 31151. 

Type locality.-VC 5062. San Diego County, Calif. Delmar 

Formation, Eocene. 

Comparison.-"Lithophaga mcknighti***d.iffers from Lithophaga 

clarki***not only in shape and size but also in the coarse placoid 

character of the concentric sculpturing." (Hanna, 1927, p. 279) 

Comments.-The strong placoid ridges illustrated by Hanna 

(1927, pl. 33, fig. 2) and the overall outline of this form exclude it 

from the lithophagids. The shell is mytiloid in shape with large, 

rounded umbos and somewhat resembles the living species Adula 

diegensis (Dall). If it is indeed Adula, this is the only known fossil 

species. 

Geographic range.-Southern California. 

Geologic range.-Eocene. 

Occurrence in California.-Delmar Formation. 

Subfamily MODIOLINAE 

Genus MODIOLUS Lamarck, 1799 

More or less inflated, rounded anteriorly, umbones obtuse, distinctly behind anterior end. 

Geologic range.-Devonian through Holocene (table 5). 

Habitat.-Intertidal zone to 3,270 m (Knudsen, 1970); most 

abundant at depths less than 90 m; usually semi-infaunal or 

infaunal in marsh grass, sand, and gravel, but some species live 

attached to piling; some species gregarious. 

Subgenus MODIOLUS 

Inflated, smooth. 

Modiolus (Modiolus) eugenensis Clark 

Plate 19, figure 12 

Modiolus eugenensis Clark, 1925, p. 86, pl. 9, fig. 4. Hickman, 1969, 

p. 34, pl. 2, figs. 1-5. 

Volsella eugenensis (Clark). Weaver, 1942, p. 111-112, pl. 24, fig. 8. 

Original description.-"Shell fairly large; base usually slightly 

concave; anterior end moderately produced; posterior margin 

angulated well back of middle of valve; posterior to angulation, the 

edge turns in rather abruptly to posterior end, which is broadly 

rounded; umbones only moderately prominent; umbonal ridge very 

prominent; distinct to the posterior end. Surface of shell strongly 

arched; posterior and anterior slopes about equal in width, both 

fairly steep. Surface, except for a smooth elongated triangular 

space between base and umbonal ridge, sculptured by fairly 

coarse, radial ribbing, which apparently does not extend on to 

depressed anterior dorsal margin. Dimensions: Greatest length, 

about 67 mm.; greatest width, 33 mm." 

Holotype.-VCMP 30319. 

Type locality.-VC 4182. Eugene, Lane County, Oreg. Eugene 

Formation, Oligocene. 

Supplementary description.-"Modiolus eugenensis is a large, 

elongate form ranging from 48 to 95 mm in length and from 23 to 

39 mm in altitude. The rounded anterior end extends for a short 

distance in front of the small inconspicuous beaks. The hinge 

margin is longer than the posterior dorsal margin, and the two 

meet to form an angle of about 125°. The posterior ventral margin 

is straight to broadly convex, and the area of maximum convexity 

corresponds to the angulation in the posterior dorsal margin. The 

umbonal ridge, which distinguishes this genus from Mytilus, is 

prominent and convex, extending obliquely from the beaks to the 

rounded posterior end. The posterior dorsal and ventral slopes are 

slightly depressed on either side of the umbonal ridge. Surface 

sculpture is formed by threads radiating from the beak. These 

threads are prominent dorsal to and along the umbonal ridge and 

are only faintly developed ventrally. Generally only the pearly 

inner shell layers are preserved, but fragments of the outer layer 

indicate that the surface was a go~den brown." (Hickman, 1969, 

p. 34) 

Comparison.-"M. eugenensis*** is closely related to M. 

sookensis (Clark and Arnold) from the upper Oligocene of Vancouver Island. M. sookensis may be distinguished by a less 

prominent umbonal ridge, lack of prominent radial ornamentation, 

and by the equal length of the posterior and dorsal slopes on either 

side of the angulation." (Hickman, 1969, p. 34) 

Geographic range.-Oregon; southern California. 

Geologic range.-Eocene and Oligocene. 

Occurrrence in California.-Eocene and Oligocene: San Emigdio 

Formation (Delise, 1967). 

Modiolus (Modiolus) ynezianus Arnold 

Plate 19, figure 11 

Modiolus ynezianus Arnold, 1907b, p. 429, pl. 52, fig. 2. Arnold and 

Anderson, 1907, p. 132, pl. 15, fig. 2. Loel and Corey, 1932, 

p. 206, pl. 33, figs. 7, 9. 

Original description.-"Shell averaging about 60 mm in altitude, 

elongate-ovate in outline, convex, equivalve; beaks nearly terminal, 

protruding forward and slightly beyond margin; base not regularly 

rounded, curving sharper anteriorly; anterior margin curving 

sharply around attenuate extremity just in front of beak and then 

straight for nearly entire length of shell, with the exception of a 

slight contraction near middle caused by a sulcation extending 

obliquely backward from beaks; posterior dorsal margin straight, 

bending around a moderately angular extremity into the slightly 

arcuate ventral margin; the shell bulges in the middle in such a 

way as to suggest a broad rounded ridge bowing over obliquely 

backward from the anterior part of the base to the beak; surface 

sculpture consists of fine incremental lines." 

Holotype.-VSNM 165324. 

Type locality.-VSGS 4504. Santa Barbara County, Calif. 

Vaqueros Formation, Oligocene and Miocene. 

Supplementary description.-"This species attains much larger 

size than is indicated by Arnold's figured specimen. When the 

beaks and part of the umbones are missing, it is difficult to 

separate from Mytilus expansus Arnold." (Loel and Corey, 1932, 

p. 206). 
TERTIARY MARINE PELECYPODS: NUCULIDAE THROUGH MALLEIDAE A75 

Geographic range.---Southern California. 

Geologic range.-Eocene to Miocene. 

Occurrence in California.-Eocene and Oligocene: San Lorenzo 

Formation (Arnold, 1908); Oligocene and Miocene: Vaqueros 

Formation. 

Modiolus (Modiolus) lagunanus Loel and Corey 

Plate 19, figures 13, 14 

Modiolus ynezianus (Arnold) lagunanus Loel and Corey, 1932, 

p. 206, pl. 34, fig. 2. 

Original description.-"Shell elongate-quadrate bowed in outline; 

very convex; beaks blunt, nearly terminal; anterior and posterior 

margins nearly parallel, tapering suddenly dorsally and rounded 

sharply to the ventral margin, the anterior margin being evenly 

concave and the posterior evenly convex; a prominent, broad 

umbonal ridge extends from anterior extremity obliquely bowing 

to the umbone. Surface marked by fine incremental lines. Height, 

1.10 mm.; width (or antero-posterior length at widest point), 

40 mm.; diameter (single valve), 36 mm." 

Holotype.-UCMP 31788. 

Type locality.-UC A543. Orange County, Calif. Vaqueros 

Formation, Oligocene-Miocene. 

Comments.-This form is distinctive in being very slender with 

almost no posterior enlargement and very wide and in having a 

strong umbonal ridge and concave anterior ventral surface. 

Geographic range. -Sou them California. 

Geologic range.-Oligocene and Miocene. 

Occurrence in California.-Oligocene and Miocene: Vaqueros 

Formation. 

Modiolus (Modiolus) ynezianus garzaensis Adegoke 

Plate 20, figure 1 

Modiolus ynezianus Arnold garzaensis Adegoke, 1969, p. 93, pl. 1, 

figs. 5, 7. 

Original description.-"Shell small, thin, relatively short and 

wide, roughly triangular in outline; beak prominent, subacutely 

pointed; anterior end extends only slightly beyond beaks; umbonal 

ridge well developed, its main axis runs from posterior dorsal 

margin of beak to posterior edge of 'straight' anterior dorsal 

margin; shell sloping with high angle from top ofumbonal ridge to 

anterior dorsal margin but more gradually to posterior dorsal 

margin; posterior dorsal margin straight, about two-thirds length 

of shell, merges sharply into the rounded basal margin at an angle 

of about 50°; anterior dorsal margin slightly convex, more than 

three-fourths length of shell; surface of shell ornamented by 

concentric lines of growth, often accompanied by overlap of shell 

layers giving a distinct banded appearance especially near ventral 

margin." 

Holotype.-UCMP 36601. 

Type locality.-UC D-1065. Fresno County, Calif. Upper part of 

Temblor Formation, Miocene. 

Comparison.-"This species may be readily distinguished from 

other described Miocene species of Modiolus by its relatively small 

size. It is smaller, less crescentic in shape, and has a straighter and 

more prominent umbonal ridge than in typical Modiolus ynezianus 

Arnold••• and has a gently convex, straight, or slightly concave 

anterior dorsal margin whereas this margin is markedly concave 

in M. ynezianus, s.s. FromM. veronensis Trask, the new subspecies 

is separated by its smaller size, its higher umbonal ridge and its 

'convex' anterior dorsal edge." (Adegoke, 1969, p. 93) 

Comments.-The small size ofthis form is not especially distinctive. The umbonal ridge on the holotype of M. veronensis temblorensis is higher and more arcuate than on M. ynezianus garzaensis 

Adegoke, but the variation within living species is so great that I 

believe M. ynezianus garzaensis and M. veronensis temblorensis 

may be conspecific. 

Geographic range.-Middle California. 

Geologic range.-Miocene. 

Occurrence in California.-Upper part of Temblor Formation. 

Modiolus (Modiolus) veronensis veronensis Trask 

Plate 20, figure 3 

Modiolus veronensis Trask, p. 150, pl. 3, fig. 4 

Original description.-"Shell small to medium in size, flat and 

elongate; anterior end extending only slightly beyond beak; posterior dorsal edge straight and not separated from the posterior end 

by any well defined angle; anterior dorsal edge slightly concave; 

base evenly rounded; surface smooth, except for concentric lines of 

growth." 

Holotype.-UCMP 12373. 

Type locality.-UC 3529. Alameda County, Calif. Briones Sandstone, Miocene. 

Comments.-The holotype is moderately inflated in proportion 

to its size. 

Geographic range.-Middle California. 

Geologic range.-Miocene. 

Occurrence in California.-Briones Sandstone. 

Modiolus (Modiolus) veronensis temblorensis Adegoke 

Plate 20, figure 2 

Modiolus veronensis Trask temblorensis Adegoke, 1969, p. 94, pl.1, 

figs. 6, 8. 

Original description.-"Shell small, narrow, elongate, convex 

anteriorly, less so in posterior half; lateral profile arcuate; anterior 

end extends slightly beyond beaks; posterior dorsal margin 

straight, about half the length of shell, gently merging into the 

rounded ventral margin; anterior dorsal margin slightly concave; 

conspicuous umbonal ridge on anterior third of shell; surface 

smooth except for concentric lines of growth." 

Holotype.-UCMP 36606. 

Type locality.-UC D-1065. Fresno County, Calif. Upper part of 

Temblor Formation, Miocene. 

Comparison.-"This subspecies differs from Modiolus ynezianus 

Arnold and Modiolus ynezianus Arnold garzaensis Adegoke••• by 

its narrower and more elongate outline, evenly rounded ventral 

margin and shorter and less inflated umbonal ridge. From typical 

Modiolus veronensis Trask, the new subspecies can be distinguished by its greater convexity and higher and more distinct 

umbonal ridge." (Adegoke, 1969, p. 94) 

Comments.-It is doubtful that the higher umbonal ridge and 

greater convexity ofthis form are characters sufficiently unique to 

warrant separating it from either M. ynezianus garzaensis or M. 

veronensis veronensis. 

Geographic range.-Middle California. 

Geologic range.-Miocene. 

Occurrence in California.-Upper part of Temblor Formation. 
A76 PALEONTOLOGY OF CALIFORNIA AND BAJA CALIFORNIA 

Modiolus (Modiolus) contracta Conrad 

Plate 20, figure 5 

Modiola contracta Conrad, 1855, p. 14. Conrad, 1857c, pl. 5, fig. 35. 

Original description.-"Elongated, narrowed anteriorly, contracted submedially, basal margin widely contracted; disk with 

numerous minute radiating lines." 

Holotype.-VSNM 1853. 

Type locality.-Twenty-five or thirty km south of Tres Pinos, 

Monterey County, Calif. Etchegoin(?) Formation. 

Geographic range.-Middle California. 

Geologic range.-Miocene(?) and Pliocene(?). 

Occurrence in California.-Etchegoin(?) Formation. 

Modiolus (Modiolus) directus Dall 

Plate 20, figure 4 

Modiolus directus Dall, 1909, p. 113-114, pl. 12, figs. 11, 12. Clark, 

1915, pl. 42, fig. 4. Etherington, 1931, p. 73, pl. 4, fig. 4. 

Original description.-"Shell thin, elongate, covered with a 

brown periostracum of which the remaining portions show alternating zones of darker and lighter color; umbones low, inconspicuous, not very close to the posterior end of the valves, as figured; 

dorsal margin straight anteriorly, arcuate posteriorly, obliquely 

descending to the hinder end ofthe shell, which is bluntly rounded; 

umbonal ridge broad, prominent, extending from the beaks to the 

lower posterior end of the shell, the part of the disk immediately in 

front of it slightly excavated; basal margin slightly concave, 

arching anteriorly toward the subangulate anterior extremity, surface smooth or distally slightly concentrically wrinkled. Longitude, 

105 mm.; altitude, 40 mm.; diameter, 26 mm." 

Lectotype.-VSNM 153947, here designated. (Figured by Dall, 

1909, pl. 12, figs. 11, 12.) 

Type locality.-Coos Bay, Coos County, Oreg. Empire Formation, Miocene and Pliocene. 

Comparison.-According to Dall (1909, p. 114), the anterior end 

of Modiolus directus is proportionately much shorter than that of 

M. rectus, the posterior end even more so. 

Geographic range.-Washington to middle California. 

. Geologic range.-Miocene and Pliocene. 

Occurrence in California.-Miocene: Cierbo and Neroly (Hall, 

1960) Sandstones; Miocene and Pliocene: Etchegoin (Arnold, 1909) 

and Tahana Member, Purisima (Cummings and others, 1962) 

Formations. 

Modiolus (Modiolus) capax (Conrad) 

Plate 20, figure 6 

Modiola capax Conrad, 1837, p. 242. 

Modiolus capax (Conrad). Keen, 1971, p. 72, fig. 149. 

Volsella capax (Conrad). Grant and Gale, 1931, p. 249 [See for 

synonymy]. 

Original description.-"Shell much inflated; anterior margin 

slightly retuse in the middle; umbo broad; summit obtusely 

rounded; posterior margin salient in the middle; epidermis chestnut 

brown, fibrous at base; within bluish, tinged with yellow. Length, 3 

inches.'' 

Holotype.-Not found at Philadelphia Academy of Natural 

Sciences; missing and presumed lost. 

Type locality.-San Diego, Calif. Holocene. 

Comparison.-Modiolus capax has a rounded, bulbous dorsal 

margin that distinguishes it from M. recta; the nearly straight 

ventral margin distinguishes it from M. flabellata. Modiolus capax 

differs from both M. recta and M. flabellata by having umbos at, 

but separate from, the anterior end. (Fitch, 1953, p. 47) 

This species is similar toM. modiolus, but heavier shelled and 

more inflated and has a more depressed region between the 

umbones. (Grant and Gale, 1931, p. 249) 

Geographic range.-Living: Santa Cruz, Calif. to Paita, Peru; 

fossil: middle California to Baja California Sur. 

Geologic range.-Miocene through Holocene. 

Occurrence in California and Baja California Sur.-Miocene: 

Briones (Hall, 1958), Cierbo (Hall, 1960), Neroly (Weaver, 1949), 

and Santa Margarita Formations (Grant and Gale, 1931); Miocene 

and Pliocene: Etchegoin (Clark, .1915) Formation; Pliocene: 

Marquer Formation (Durham, 1950); Pliocene and Pleistocene: 

Fernando (J. D. Mount, written commun., 1971) and Saugus(?) 

[upper part of Pi co of Waterfall, 1929] Formations. 

Habitat.-Intertidally on rocks or boulders or in mud to 45 m. 

Solitary individuals occur in protected areas along the open coast. 

Modiolus (Modiolus) rectus Conrad 

Plate 20, figure 9 

Modiola recta Conrad, 1837, p. 234, pl. 19, fig. 1. 

Modiolus rectus Conrad. Arnold, 1903, p. 120-121. Arnold, 1909, 

p. 146, pl. 20, fig. 4. Hertlein and Grant, 1972, p. 166-167, pl. 42, 

fig. 7 [See for synonymy]. 

Mytilus (Modiola) flabellatus Gould, 1850, p. 343. 

Original description.-"Shell produced, smooth, thin; anterior 

margin elevated; posterior side cuneiform; color brown, with a 

broad pale stripe extending from the beak toward the posterior 

margin; within very glossy and irridescent. Length, 2 inches." 

Holotype.-In Gould Collection, MCZ. 

Type locality.-Sandy shores near Santa Barbara, Calif. 

Holocene. 

Supplementary description.-"Specimens are often found that 

are 120 mm to 130 mm in length but huge forms are reported to 

at~ain a length of 230 mm." (Hertlein and Grant, 1972, p. 167) 

Comparison.-Modiolus rectus is always more elongate than M. 

neglectus Soot-Ryen (1955) and never shows the distinct posterodorsal angle of that species. The straight dorsal margin extends 

over to the posterior margin in a long arch without angulation. 

(Soot-Ryen, 1~55, p. 63) [SeeM. directus Dall.] 

Geographic range.-Living: Vancouver Island, British Columbia, to Bahia Concepcion east coast of Baja California Sur; fossil: 

middle California to Baja California Norte. 

Geologic range.-Miocene to Holocene. 

Occurrence in California and Baja California Norte.-Miocene: 

Pancho Rico (Durham and Addicott, 1965) and Santa Margarita 

(Nomland, 1917) Formations; Miocene and Pliocene: Etchegoin 

(Arnold, 1909); Nomland, 1971a; Wilson, 1944), Purisima (Martin, 

1916), and Towsley (Kern, 1973) Formations; Pliocene: San Diego 

Formation (Hertlein and Grant, 1972); Pliocene and Pleistocene: 

Merced (Martin, 1916; Glen, 1959), San Pedro (Arnold, 1903), Santa 

Barbara (Arnold, 1903), and Saugus (Waterfall, 1929) Formations; 

Pleistocene: unnamed Pleistocene strata, San Diego, Calif. (Arnold, 

1903), and Bahia de San Quintin, Baja California Norte (Jordan, 

1926). 

Habitat.-"At the present time this mollusk lives on a muddy 

bottom with the anterior portion embedded in a nest in the mud but 

with the posterior portion of the shell exposed above the surface of 

the bottom. (Hertlein and Grant, 1972, p. 167) 

Living singly on mud flats at low water or submerged with the 

posterior end slightly protruding. Intertidal to about 45 m. 
TERTIARY MARINE PELECYPODS: NUCULIDAE THROUGH MALLEIDAE A77. 

Modiolus (Modiolus) carpenteri Soot-Ryen 

Plate 20, figures 7, 8 

Modiola fornicata Carpenter, 1846b, p. 643. Not Modiola fornicata 

F. A. Roemer, 1836. 

Modiolus fornicatus (Carpenter). Palmer, 1958, p. 73, pl. 4, figs. 

10-12 [See for synonymy]. 

Modiolus carpenteri Soot-Ryen, new name, 1963, p. 127. 

Original description.-"Short, swollen, like large M. marmorata; 

but smooth, not crenated." 

Holotype.-Redpath Museum 3133. 

Type locality.-Santa Barbara, Santa Barbara County, Calif. 

Holocene. 

Supplementary description.-"In this species the beaks curve 

strongly forward, downward and backward so that a portion of 

their curve projects considerably beyond the anterior margins of 

the valves**"' a Recent specimen from Monterey which is unusually 

large and swollen**"' has the following measurements: extreme 

anterior-posterior length, 32 mm.; dorsal-ventral height, 16 112 

mm.; thickness of both matched valves together 20 mm." (Grant 

and Gale, 1931, p. 251) 

Comparison.-[See M. sacculifer.] Modiolus trinominata "is 

much larger, does not have such a pronounced curvature of the 

umbones, is less ventricose, and is broader posteriorly." (Grant 

and Gale, 1931) 

Geographic range.-Living: Monterey to San Pedro, Calif.; fossil: 

middle California to Baja California Sur. 

Geologic range.-Miocene through Holocene. 

Occurrence in California and Baja California Sur.-Miocene 

and Pliocene: Etchegoin Formation (Nomland, 1917a); Pliocene 

and Pleistocene: Santa Barbara Formation (Arnold, 1903); Pleistocene: unnamed strata, Bahia de Ia Magdalena, Baja California Sur 

(Jordan, 1924). 

Habitat.-25 to 45 m. 

Subgenus Modiolus? 

Modiolus (Modiolus?) merriami Weaver 

Plate 21, figure 2 

Modiolus merriami Weaver, 1905, p. 114-114, pl. 12, fig. 2. 

Modiolus merriami Weaver. Dickerson, 1914, p. 151, pl. 9, fig. 7. 

Original description.-"The shell is thin, elongated, and 

moderately convex. The beaks are broad and not very prominent. 

The umbonal ridge is prominent, rounded, and curved only slightly 

downward. The surface is marked by several rather prominent 

concentric wrinkles. There is no radial ornamentation." 

Holotype.-UCMP 11892. 

Type locality.-UC 333. Contra Costa County, Calif. Martinez 

Formation, Paleocene. 

Comments.-The holotype is very small (28 mm long) with only 

patches of the internal shell layer preserved. The mold from which 

it came does not reveal the external shell characters, but it is 

modiolid in outline. 

Geographic range.-Middle California. 

Geologic range.-Paleocene. 

Occurrence in California.-Paleocene: Martinez Formation. 

Modiolus (Modiolus?) pittsburgensis Clark 

Plate 21, figures 3, 4 

Modiolus pittsburgensis Clark, 1918, p. 134, pl. 9, fig. 9. 

Original description.-"Shell rather small, thin; umbones not 

prominent; umbonal ridge indistinct, unseen in the anterior third 

of the shell; anterior end strongly produced beyond the beaks; base 

straight; posterior margin long, with no distinct posterior angulation; posterior end broad and regularly rounded, the base and the 

posterior margin diverging in approaching the posterior end. 

Surface rather strongly arched, the highest point of convexity 

being posterior to the middle of the shell. Anterior slope broad and 

fairly steep; posterior slope shorter but more steep than the 

anterior. Surface smooth except for medium fine incremental 

lines." 

Holotype.-VCMP 11122. [The specimen illustrated herein is a 

plaster cast of the two-part mold.] 

Type locality.-VC 1895. Contra Costa County, Calif. Kirker 

Tuff, Oligocene. 

Comparison.-"This species appears to be quite distinct in 

outline from any ofthe known Recent or fossil species of the West 

Coast. In outline it somewhat resembles Modiolus inflatus Dall; 

both have the broadly rounded posterior end; on the former the 

anterior end is more strongly produced and the shell is more 

slender just back of the beaks." (Clark, 1918, p. 134) 

Comments.-The cast is small, inflated, and the posterior end 

enlarged. 

Geographic range.-Middle California. 

Geologic range.-Oligocene and Miocene(?). 

Occurrence in California.-Oligocene: Kirker Tuff; Miocene(?): 

San Ramon Sandstone (Weaver, 1949). 

Modiolus (Modiolus?) sacculifer (Berry) 

Plate 21, figure 1 

Volsella sacculifer Berry, 1953, p. 407, pl. 28, figs. 1, 2, text fig. 1. 

Modiolus sacculifer (Berry). Hertlein and Grant, 1972, p. 167-168, 

pl. 41, fig. 2-4 [See for synonymy]. 

Original description.-"Shell of but moderate size for the genus, 

in outline broadly almond-shaped; highest at about the mid-point, 

thin, smooth, moderately inflated; hinge-line nearly straight to 

very slightly arcuate. Valves well rounded behind, more or less 

distinctly swollen ventrally in the byssal region and produced 

abruptly into a small obtuse lobe-like flare or pocket just under the 

umbones, the rounded angle of this pocket forming the anterior 

end of the shell; postero-dorsal area subalate, its angle obtuse. 

Hinge toothless except for a short, sharply conical, posteriorly 

directed process set off by a notch at the anterior insertion of the 

ligament. Periostracum light to deep brown (near Buckthorn 

Brown to Mummy Brown), smooth, polished, under the more or 

less dehiscent traces of some fairly considerable posterior 

shagginess." 

Holotype.-CASISV 7853. 

Type locality.-San Pedro Harbor, Los Angeles County, Calif. 

Holocene. 

Supplementary description.-"The anterior lunular part, so characteristic in most of the specimens, is not so well defined in small 

specimens, which often look very like small M. modiolus. The 

lunule is dull and usually distinctly set off from the rest of the 

shell. The inside is margaritaceous, white or reddish-white; the 

shell is thin compared toM. capax and M. fornicatus. The ligament 

is short, and the umbones nearly touch in the middle." (Soot-Ryen, 

1955,p.66) . 

Comparison.-"The shell of M. sacculifer is readily separable 

from that of Modiolus carpenteri Soot-Ryen""""'a new name for 

Modiola fornicata Carpenter""""', in that the lobe-like anterior end 

extends beyond the beaks whereas in Soot-Ryen's species it does 

not." (Hertlein and Grant, 1972, p. 167) 
• ~ ,t •• • • 

A78. PALEONTOLOGY OF CALIFORNIA AND BAJA CALIFORNIA 

Geographic range.-Living: Monterey to Long Beach and 

Beechers Bay, Santa Rosa Island, and San Clemente Island, 

Calif.; fossil: southern California. 

Geologic range.-Pliocene through Holocene. 

Occurrence in California.-Pliocene: San Diego Formation . 

. Habitat.-Living in nests of sand or among holdfasts; low 

intertidal zone to 100m. 

Genus MODIOLUS? 

Subgenus MODIOLUS? 

Modiolus (Modiolus?) meganosensis Clark and Woodford 

Plate 21, figure 5 

Modiolus? meganosensis Clark and Woodford, 1927, p. 88, pl. 14, 

fig. 9. 

Original description.-"Shell elongate subtrapezoidal in outline; 

beaks rather prominent, strongly inturned. Anterior end broadly 

rounded, posterior dorsal edge long and straight, separated from 

the posterior end by a fairly well developed angulation; base long 

and straight, parallel with the posterior edge; a well-defined 

umbonal ridge between the beaks and the point of junction of the 

base and posterior end; slope of surface between this ridge and the 

posterior dorsal edge rather abrupt; anterior slope broader and 

more gentle, slightly depressed between the beaks and the middle 

of the ventral edge. Dimensions: Greatest length 15 mm.; greatest 

width about 7 mm." 

Holotype.-VCMP 31363. 

Type locality.-VC 3155. Contra Costa County, Calif. Meganos 

Formation, Paleocene. 

Supplementary description.-"Only one specimen of this species 

was found in our collection; a cast but fairly well preserved. It 

appears to be referable to the genus Modiolus, and if so it is very 

different in outline from any of the other known species from the 

west coast of North America." (Clark and Woodford, 1927, p. 88) 

Geographic range.-Middle California. 

Geologic range.-Paleocene. 

Occurrence in Cali{ornia.-Meganos Formation. 

Modiolus? (Modiolus?) clarki Moore, new name 

Plate 21, figures 8, 9 

Mytilus merriami Clark, 1915, p. 455-456, pl. 48, figs. 7, 8. Not 

Modiola merriami Weaver, 1905. 

Original description.-"Shell thick, very ventricose. Beaks 

heavy, bluntly pointed. Hinge plate below the beaks very heavy. 

Base sometimes straight, sometimes gently concave. Posterior 

edge angulated, the point of angulation being situated anterior to 

the middle. Posterior extremity evenly rounded. Surface of shell 

covered by irregular coarse incremental undulations. Highest 

point of convexity of surface anterior to the middle of the valve; 

anterior slope high and nearly perpendicular; posterior slope steep, 

dropping at an angle of nearly 30° as measured at the point of 

angulation on the posterior edge; to the rear of this point the shell 

is not so convex; no teeth on thickened hinge plate. Thickened area 

below the beaks obscurely grooved; deep elongate anterior adductor 

muscle scar just below the thickened hinge plate." 

Holotype.-VCMP 11544. 

Type locality.-VC 118. Contra Costa County, Calif. Neroly 

Sandstone, Miocene. 

Comments .-On the. basis of the position of the umbonal ridge, 

strong inflation, and assumed beak location, this species is tentatively assigned to Modiolus. The holotype has an exceptionally 

thick shell perhaps indicating response to wave shock. The assignment of this species tv Modiolus necessitates a new name owing to 

the prior existence of Modiola merriami Weaver, 1905. 

Geographic range.-Middle California. 

Geologic range. -Miocene. . 

Occurrence in Cali{ornia.-Neroly Sandstone (Weaver, 1949). 

Genus IDASOLA Iredale, 1915 

Small, thin-shelled, with rounded anterior and posterior margins, 

beaks in front of middle. 

Geographic range. -Atlantic; California? 

Geologic range.-Paleocene(?); Holocene (table 5). · 

Habitat.-In bathyal water. 

Genus IDASOLA? 

Idasola? bakeri (Dickerson) 

Plate 21, figures 6, 7 

Modiolus bakeri Dickerson, 1914, p. 128, pl. 9, fig. 8. 

Original description.-"Shell medium in size, thick; beak small 

but prominent, about a sixth of the length from the anterior end, 

which is narrowly. rounded; posterior end, broadly rounded; cardinal margin, straight; ventral margin, slightly rounded; umbonal 

ridge prominent, rounded, and extending to the posterior end 

below its center. A marked concavity in larger specimen figured 

extends from the beaks to the middle of the ventral margin. 

Surface marked by lines of growth." 

Holotype.-VCMP 11686. 

Type locality.-VC 1556. Contra Costa County, Calif. Martinez 

Formation, Paleocene. 

Comments.-The holotype is an internal mold of a left valve 

with the beak broken off and only patches of internal shell 

preserved. It is markedly inflated in proportion to its size with 

prominent beaks, is not elongate or modiolid in shape, and is 

somewhat enlarged posteriorly. On the basis of the holotype, I am 

not even certain that this form should be assigned to the Mytilidae; 

it could be an arcid. Within the mytilids, it somewhat resembles 

ldasola, a bathyal form. 

Geographic range.-Middle California. 

Geologic range.-Paleocene. 

Occurrence in Cali{ornia.-Martinez Formation. 

Family PINNIDAE 

Genus PINNA Linne, 1758 

Equivalve, wedge- to ham-shaped; umbones at extreme anterior 

end; valves carinate medially, at least in early growth stages; 

mostly with radial ribs, some forms with growth undulations on 

ventral region; nacre of interior divided medially into two lobes. 

Geologic range.-Carboniferous through Holocene (table 6). 

Subgenus PINNA 

Wedge-shaped, ventral margin straight to concave; median ridge 

well defined; sculpture of radial ribs or rows of scales. 

Habitat.-Living worldwide in tropical or subtropical shallow 

seas. Sedentary, generally found buried, with the rounded posterior 

margins above the sediment surface, in mud, sand, or gravel with 
TERTIARY MARINE PELECYPODS: NUCULIDAE THROUGH MALLEIDAE A79 

TABLE 6.-Geologic and geographic distribution of the Family 

Pinnidae . IPI =Pliocene; M =Miocene; 0 =Oligocene; E =Eocene; Pa =Paleocene) 

California Species Middle Southern 

Genus Pinna: 

Sub~~~~~~t1ioi~kcrson .................. Pa 

~~:~.~~~~~ri~g ~~-~-~-~:::::::::::::::: :::::::::::::::::::: 

mendenhalli G D. Hanna ......................... . stock toni Loci and Corey ........................... . n. sp. Vokes ................................ E Genus Atrina: 

alamedensis (Yates) ................ 0 and M bicuneata (Nomland) .............. M stephensi G D. Hanna ............................... . uenturensis (Yates) ..................................... . 

""M""~~-pj""" 

E M or PI Oand M 

M 

···M"·~~-?i" .. Oand M 

Baja 

Norte Sur 

the anterior end downward and anchored in a vertical position by 

the byssus; occasionally found epifaunally attached to hard substrata. (Olsson, 1961, p. 143; Yonge and Thompson, 1976, p. 171) 

Lives buried in the mud of a quiet bay. (Keen, p. 74) 

Pinna (Pinna) barrowsi Dickerson 

Plate 22, figures 5, 6 

Pinna barrowsi Dickerson, 1914, p. 125, pl. 8, fig. 3. Anderson and 

Hanna, 1925, p. 189. 

Original description.-"The shape of the shell is elongatecuneate. The cross section of the shell is quadrate-oval. The valves 

meet on their dorsal margins at a sharp angle which increases 

from sixty degrees near the base to ninety degrees near the beak. 

The ventral portions of the valves are rounded. Each valve 

presents two slopes; a flat, dorsal and a slightly convex, ventral 

which meet along a radial line. This line divides the shell so that 

the flat dorsal slope is one-third and the rounded ventral, twothirds of the total surface. The rounded ventral slope is marked in 

its central half by approximately eight compressed and slightly 

elevated radial ribs whose interspaces are twice their width, and 

by eight to ten concentric rounded ribs in its marginal portion as 

well as radial ribs, thus further dividing the convex slope into 

equal parts. These ribs do not show on figured specimen. The flat 

dorsal slope of the shell is ornamented by about ten compressed 

radial ribs which are separated by interspaces two times as wide. 

The nearly straight posterior end makes a right angle with the 

ventral margin." 

Holotype.-UCMP 11728. 

Type locality.-UC 1547. Contra Costa County, Calif. Martinez 

Formation, Paleocene. 

Comparison.-According to Waring, (1917, p. 94), Pinna barrowsi 

has a narrower apical angle than Eocene species P. lewisi Waring 

and has fewer radiating ribs. 

Geographic range.-Middle California. 

Geologic range.-Paleocene. 

Occurrence in Cali{ornia.-Martinez Formation. 

Pinna (Pinna) lewisi Waring 

Plate 21, figure 10 

Pinna lewisi Waring, 1917, p. 94, pl. 15, fig. 24. 

Original description.-"Shell thin, pearly, mytiliform, equivalve, 

truncate and wholly open behind; hinge line long; valves triangular, the apical angle being about 45 degrees; convex along the 

center line and flaring at the margins; base of shell notched in the 

middle and convex on either side; surface marked by fine indistinct 

radiating ribs and concentric lines of growth." 

Holotype.-CASISU 5194. 

Type locaility.-SU 2696. Ventura County, Calif. Llajas Formation, Eocene. 

Comparison.-"Differs from Pinna barrowsi Dickerson***by 

having a wider apical angle and fewer radiating ribs." (Waring, 

1917, p. 94) 

Geographic range.-Southern California. 

Geologic range.-Southern California. 

Occurrence in California.-Llajas Formation. 

Pinna (Pinna) n. sp. Vokes 

Plate 22, figure 1 

Pinna n. sp. Vokes, 1939, p. 50, pl. 2, fig. 14. 

Original description.-"A single crushed individual representative of the genus Pinna occurs in the collections. The shell is 

elongate-cuneate, ornamented with 23 rounded radial ribs separated by interspaces of approximately equal width." 

Figured specimen.-UCMP 32595. 

Locality.-UC 2287. Fresno County, Calif. Domengine Formation, Eocene. 

Geologic range.-Eocene. 

Occurrence in California.-Domengine Formation. 

Pinna (Pinna) stocktoni Loel and Corey 

Plate 22, figures 2, 3 

Pinna (Pinna) stocktoni Loel and Corey, 1932, p. 186, pl. 8, figs. 5, 6. 

Original description.-"Shell large, very convex, elongatecuneate in outline, subdiamond shape in cross-section; valves 

flattened and gaping ventrally, umbonal shoulder subangular to 

rounded, extending almost to ventral margin, carina about onethird of height in width, flat or concave; dorsal margin being 

evenly, broadly arcuate, and the ventral part of shell somewhat 

flattened near this margin; dorsal surface ornamented by 5 or 6 

longitudinal round ribs with a longitudinal groove above shoulder, 

ventral portion with about 14 weaker ribs which become concentric 

on the posterior third. Length (incomplete), 85 mm.; width, 105 

mm.; diameter (both valves), 55 mm. Cotype, length (incomplete), 

63 mm.; width, 36 mm.; diameter (both valves), 22 mm." 

Syntypes.-UCMP 31778 and 31779. 

Type locality.-UC A-252. Ventura County, Calif. Vaqueros 

Formation, Oligocene and Miocene. 

Geographic range.-Southern California. 

Geologic range.-Oligocene and Miocene. 

Occurrence in California.-Oligocene and Miocene: Vaqueros 

Formation. 

Pinna (Pinna) latrania G D. Hanna 

Plate 22, figure 4 

Pinna latraniaG D. Hanna, 1926, p. 475, pl. 27, fig. 1, text fig. 1. 

Pinna (Pinna) latrania Hanna. Grant and Gale, 1931, p. 145. 

Original description.-"Shell thin, long and slender, apical 

angle acute (27°); surface apparently unmarked externally by 

ridges, ribs or spines, except for a heavy longitudinal mid-rib in 

each valve; this is rounded convex, internally and apparently 

sharply carinate externally and divided longitudinally, the two 

parts being united by cartilage; the length of this rib is unobtainable from available material, but in other species it does not extend 

entirely to the beak; each valve is deeply sulcate at the mid-rib so 

that in looking down upon it, it is double-looped. Length of type 

specimen, 135 mm.; width from hinge line down, 63 mm.; gape 
ABO PALEONTOLOGY OF CALIFORNIA AND BAJA CALIFORNIA 

posteriorly, 51 mm.; length of hinge line, 116 mm.; length ofbyssal 

scar, 85 mm." 

Holotype.-USNM 324593. 

Type locality .. -USGS 3922. Imperial County, Calif. Imperial 

Formation, Miocene or Pliocene. 

Comments.-See Pinna mendenhalli below. 

Geographic range. -Southern California and Baja California 

Sur. 

Geologic range.-Miocene to Pliocene. 

Occurrence in California and Baja California.-Miocene or 

Pliocene: Imperial Formation; Pliocene: unnamed strata, Baja 

California Sur (Durham, 1950). 

Pinna (Pinna) mendenhalli G D. Hanna 

Plate 23, figure 1 

Pinna mendenhalli G D. Hanna, 1926, p. 476, pl. 27, fig. 2. 

Pinna (Pinna) mendenhalli Hanna. Grant and Gale, 1931, p. 146. 

Original description.-"Shell thick and heavy; apical angle 

obtuse (47°); outer surface without sculpture or distinct ribs; there 

is a low longitudinal ridge, however, on the ventral half of each 

valve; mid-rib exceedingly heavy (7 mm. thick in a fragment 

preserved on one specimen); rounded on the interior and apparently 

sharply carinate on the exterior. Each valve appears to be divided 

through this rib for at least a portion of its length because in the 

remnants of the shell preserved on the casts, there are ligament 

scars as shown in the figure. The gape extends the full length of 

the shell and the byssal scar appears to do the same; beak and 

posterior margins not seen. Greatest length of type, 167 mm.; 

greatest breadth, 98 mm.; thickness, 58 mm.; full dimensions were: 

length about 200 mm. and breadth 100 mm.; thickness of the 

paratype is 66 mm." 

Holotype.-USNM 324593a. 

Type locality.-USGS 3922. Imperial County, Calif. Imperial 

Formation, Miocene or Pliocene. 

Comments.-Pinna latrania is distinguished from P. mendenhalli primarily on the basis of its smaller apical angle: 27° 

compared to 47°. The holotypes of both species, collected from the 

same locality in the Imperial Formation, are poorly preserved. I 

am not certain that two species are actually represented. 

Geographic range. -Southern California. 

Geologic range.-Miocene or Pliocene. 

Occurrence in California.-Miocene or Pliocene: Imperial Formation. 

Genus ATRINA Gray, 1842 

Equivalve, ham-shaped, posterior end rounded, no median ridge; 

smooth or with radial rows of ribs or scales; internal nacre not 

divided into two lobes. 

Geologic range .. -Jurassic through Holocene (table 6). 

Habitat.-Living in tropical and warm-temperate, shallow seas; 

vertically embedded in the substratum. 

Atrina venturensis (Yates) 

Plate 23, figure 2; plate 27, figure 2 

Pinna venturensis Yeates in Cooper, 1888, p. 259 

Pinna venturensis Yates. Cooper, 1894, p. 56, pl. 4, fig. 54. 

Pinna (Atrina) venturensis Yates. Dall, 1898, p. 665. 

Original description.-"From the hinge side about two thirds of 

the width of this shell is marked by nine well-developed, narrow 

ribs, radiating from the apex to the basal margin; the other portion 

shows rounded, concentric inequidistant ribs, extending only to 

the line of the radiating ribs, so that about two thirds of the surface 

is covered by the radiating smaller ribs, and one third by the 

curved, concentric, rounded ribs or wrinkles, very like Pinna 

pectinata, figured in 'Bro~n's Recent Conchology.' Pinna 

venturensis is short and thick compared with its length. The 

largest specimen found was about five and one half inches long, 

three and one half in width, and one and three fourths in thickness, 

the hinge side considerably shorter than the other. Locality, 

several specimens collected by the writer in Casitas Pass, Ventura 

County." 

Holotype.-UCSB-Y3096. 

Type locality.-Casitas Pass [Ventura quadrangle], Ventura 

County, Calif. Vaqueros Formation (Keen and Bentson, 1944). 

A specimen of Atrina venturensis (pl. 27, fig. 2) was found in the 

collections at the University of California at Santa Barbara by 

Eugene V. Coan (oral commun., 1979). This specimen is presumably the holotype described by Yates in 1888. It is not the 

specimen subsequently illustrated (pl. 4, fig. 54) in 1894 (pl. 23, fig. 

2 in this report). The specimen was surely handled by Yates as his 

signature is on the old label as well as a notation, also in his own 

hand, stating, "Described in 7th Annual Report of Cal. State 

Mineralogist for 1889. Illustration in same Report for 1891-2." 

Camp (1963, p. 384) briefly discussed A. venturensis and Atrina 

alamedensis and said that, "The University of California, Santa 

Barbara, has what are presumably the types of these shells." 

Geographic range.-Southern California. 

Geologic range.-Oligocene to Miocene. 

Occurrence in California.-Oligocene and Miocene: Vaqueros 

Formation. 

Atrina alamedensis (Yates) 

Plate 23, figure 3; plate 27, figures 1, 3 

Pinna alamadensis Yates in Cooper, 1888, p. 259 [Lapsus for P. 

alamedensis ]. 

Pinna alamed·znsis "Yates." Cooper, 1894, p. 56, pl. 4, fig. 53. Clark, 

1915, p. 446-447, pl. 48, fig. 3. ' 

Pinna alamedensis Yates. Clark, 1915, p. 446-447, pl. 48, fig. 3. 

Pinna (Atrina) alamedensis Yates. Grant and Gale, 1931, p. 146. 

Original description.-"This species has nine concentric inequidis- _ 

tant rounded wrinkles emanating from the open side, and turning 

toward the hinge at nearly right angles, the entire shell marked by 

longitudinal narrow ribs (about forty), which, radiating from apex, 

extend to the basal margin, becoming more indistinct as they 

approach the lower margin. These ribs, at their intersection with 

the lines of growth, are ornamented by slight elevations, forming 

zigzag markings along the lines of growth~_ The hinge side is 

straight the entire length, the opposite side running parallel for 

about one half the distance from base to apex, where it makes a 

sharp curve, thence at an angle of about forty-five degrees to the 

apex. Length nine, width five, and thickness about two inches. 

Locality, Alameda Creek, Alameda County. Only one specimen 

found, and that a very fine one, in the center of a round sandstone 

bowlder. Miocene." 

Holotype?.-UCSB-Y 474. 

Type locality.-ln sandstone boulder, Alameda Creek, Alameda 

County, Calif. San Pablo(?) Group, Miocene. 

A specimen of Atrina alamedensis (pl. 27, figs. 1, 3) was found in 

the collections at the University of California of Santa Barbara by 

Eugene V. Coan (oral commun., 1979). This specimen is presumably the holotype described by Yates in 1888. It is not the specimen 

subsequently illustrated (pl. 4, fig. 53) in 1894 (pl. 23, fig. 3 in this 

report). It is the approximate size given by Yates and better fits 

Yates' (1888, p. 259) statement that it was "a very fine one" than 

does the less complete specimen figured later (1894, pl. 4, fig. 53). 
TERTIARY MARINE PELECYPODS: NUCULIDAE THROUGH MALLEIDAE A81 

Supplementary description.-Pinna alamedensis "is noticeable 

for its large size and the thickness of the prismatic outer layer. 

Some of the specimens collected have a maximum antero-posterior 

length often inches, with a maximum width at right angles to that 

of about five and one-half inches." (Clark, 1915, p. 447) 

Comparison.-[See A. bicuneata.] 

Geographic range.-Middle and southern California. 

Geologic range.-Oligocene to Miocene. 

Occurrence in California.-Oligocene and Miocene: Vaqueros 

Formation (Arnold, 1908); Miocene: Monterey Formation 

(Nomland, 1917b, Cierbo and Neroly Sandstones (Hall, 1960), and 

Santa Margarita Formation (Nomland, 1917b). 

Atrina bicuneata (Nomland) 

Plate 23, figure 4 

Pinna bicuneata Nomland, 1917b, p. 308, pl. 15, figs. la, lb. 

Pinna (Atrina) bicuneata Nomland. Grant and Gale, 1931, p. 146. 

Original description.-"Shell elongate-cuneate; in cross-section 

thin, acutely elliptical. Hinge line long, nearly straight; ventral 

margin slightly concave near beaks; posterior end evenly rounded. 

Sculptured by approximately ten distinct radiating ridges which 

appear to be absent on lower one-third of shell." 

Holotype.-UCMP 11307. 

Type locality.-UC 2284. Fresno County, Calif. Santa Margarita 

Formation, Miocene. 

Comparison.-"This form may be distinguished from Pinna 

alamedensis Yates, which also occurs in the same beds, by its 

smaller size, long, straight hinge-line and ventral margin, less 

number of radiating ridges, and in being thinner in cross-section." 

(Nomland, 1917b, p. 308) 

Geographic range.-Middle California. 

Geologic range.-Miocene. 

Occurrence in California.-Santa Margarita Formation and San 

Pablo Group (Nomland, 1917b). 

Atrina stephensi G D. Hanna 

Plate 24, figure 4 

Atrina stephensi G D. Hanna, 1926, p. 461, pl. 27, figs. 3, 4. 

Original description.-"Shell robust, inflated, beaks acutely 

pointed; both margins concave toward beaks; growth ridges rough 

but not scaled or spinose; radial ndges on posterior two-thirds of 

shell; these are wavy in cross section, but not spinose; byssal area 

flat, the opening 3.5 mm. wide; valves gape broadly. Length 200 

mm.; thickness, 60 mm.; width, 112 mm." 

Holotype.-SDNM 2. 

Type locality.-S. 1/2 sec. 10, T. 16 S., R. 10 E., SB, Coyote 

Mountain, Imperial County, Calif. Imperial Formation, Miocene or 

Pliocene. 

Comparison.-"This species appears to be more closely related 

to A. oldroydi than any other; comparison has been made with the 

type of that species in Stanford University and it is found to have a 

convex swelling on the ventral margin; the radial ridges do not 

extend on the ventral half of the shell and the byssal area is not so 

flattened." (Hanna, 1926, p. 461) 

Geographic range.-Southern California. 

Geologic range.-Miocene or Pliocene. 

Occurrence in California.-Miocene or Pliocene: Imperial Formation. 

Family PTERIIDAE 

Genus PTERIA Scopoli, 1777 

Obliquely ovate, moderately inflated, slightly inequivalve; 

elongate posterior wing commonly present; exterior commonly 

smooth except for growth lines, but with radial rows of lamellar 

processes in some species. 

Geographic range.-Triassic through Holocene (table 7). 

Habitat.-Living in warm seas, most common in sandy sediment; on mud flats and in shallow subtidal water, seldom more 

than a few meters deep; byssally attached; some species gregarious 

on alyconarians (octocoral). 

Pteria howei Nelson 

Plate 24, figure 2 

Pteri howei Nelson, 1925, p. 406, pl. 49, figs. 6, 7. 

Original description.-"Shell medium-sized, thin, submytiliform, 

oblique; beaks fairly prominent, anterior; hinge line long, straight. 

Anterior ear almost one-third the length of posterior ear, margin of 

ear convex below hinge; posterior ear narrow, rear margin straight, 

curved to meet posterior margin of shell. Posterior margin of shell 

produced, rounded, with greatest curvature at junction with ventral 

margin; ventral margin broadly arcuate, roughly parallel to hinge 

line; anterior extremity continuous with ventral margin with 

reversed curvature where joined to anterior ear. Anterior ear joined 

to body in a rounded angle along a convex line between the 

anterior extremity and front of beak; posterior ear similarly joined 

along a slightly concave line between posterior end of shell and 

rear of beak. Byssal notch in right valve rather large, rounded, 

corresponds to a depression between ear and body of shell. Surface 

of shell smooth. Length of type specimen, 33 mm.; height, 13 mm. 

Length of cotype specimen, 19 mm.; height, 8.4 mm.; diameter of 

one valve, about 3.3 mm." 

Holotype.-UCMP 30515. 

Type locality.-UC 3767. Ventura County, Calif. Martinez 

Formation, Paleocene. 

Comparison.- "Pte ria howei is more elongate and has a less 

TABLE 7.-Geologic and geographic distribution of the family Pteriidae 

[H = Holocene; Pie= Pleistocene; PI= Pliocene; M =Miocene; 0 =Oligocene; E =Eocene; Pa = Paleooene] 

California Species 

Middle Southern 

Genus Pteria: berryi Adegoke ............................................................................................................................. ......................... M hertleini Wicdey ............................................................................................................... ............................... 0 and M howei Nelson..................................................................................................................... . ...................... . jordani Wicdey ........................................................................................................................... . ................................... . pellucid a (Gobb) ............................................................................................................... ........................ E rositae Hertlein........................................................................................................ ......................... . ........................... . sp. Clork and Woodford ............................................................................. ................................. Pa Genus Pinctada: mazatlanica (Honley) ............................................................................................. . 

Oand M Pa 

M 

E Oand M 

Baja California 

Norte Sur 

H PI to H 

Central and/or South 

America 

H 
A82 PALEONTOLOGY OF CALIFORNIA AND BAJA CALIFORNIA 

prominent beak than P. pellucida (Gabb), and is much lower than 

Pteria clarki Weaver and Palmer." (Nelson, 1925, p. 406) 

Geographic range.-Southern California. 

Geologic range.-Paleocene. 

Occurrence in California.-Martinez Formation. 

Pteria sp. Clark and Woodford 

Plate 24, figure 1 

Pteria sp. Clark and Woodford, 1927, p. 88, pl. 14, fig. 7. 

Description.-"An imperfect specimen of a Pteria, not determinable specifically." 

Figured specimen.-VCMP 31321. 

Locality.-VC 3152. Contra Costa County, Calif. Meganos 

Formation, Paleocene. 

Geographic range.-Middle California. 

Geologic range.-Paleocene. 

Occurrence in California.-Meganos Formation. 

Pteria pellucida (Gabb) 

Plate 24, figure 3 

Avicula pellucida Gabb, 1864, p. 186, pl. 25, fig. 172. 

Pteriapellucida (Gabb). Anderson and Hanna, 1925, p. 188-189, pl. 

1, fig. 1. Vokes, 1939, p. 50-51, pl. 2, figs. 1, 4, 7, 8. Kleinpell and 

Weaver, 1963, p. 197, pl. 29, fig. 5. Givens, 1974, p. 43, pl. 1, fig. 

10. 

NotPteriapellucida (Gabb).Anderson and Hanna, 1925, p.l88-189, 

pl. 1, fig. 1. 

Original description.-"Shell oblique, subcompressed, broadlingulae-form; ears very unequal; beaks moderate, anterior; cardinal line straight; anterior ear short angular, posterior ear broad, 

acuminate; anterior and posterior margins nearly parallel for a 

short distance below the ears; base forming an excentric curve, 

most produced behind; there is no distinct division between the 

body of the shell and the ears. Surface polished, and exhibiting 

only faint, concentric undulations, corresponding to lines of 

growth, and a few microscopic, radiating lines, posteriorly." 

Lectotype.-VCMP 11983 (Vokes, 1939, p. 50) 

Type locality.-Near Martinez, Contra Costa County, Calif. 

Domengine(?) Formation, Eocene (Keen and Bentson, 1944). 

Comparison.-"The specimen figured by Anderson and Hanna 

(1925: pl. 1, f. 1) as Pteria pellucida differs from Gabb's species in 

having the dorsal edge of the anterior ear at an angle to the hingeline rather than forming a straight line, and in the umbonal ridge 

forming an angle of approximately 55 degrees with the hinge-line." 

(Vokes, 1939, p. 51) 

Geographic range.-Middle and southern California. 

Geologic range.-Eocene. 

Occurrence in California.-Avenal (Stewart, 1946) and Coldwater (Weaver and Kleinpell, 1963, p. 197) Sandstones, Domengine 

Formation, Matilija Sandstone (Ectinochilus canalifer fauna, 

Givens, 1974), and Tejon Formation (Anderson and Hanna, 1925). 

Pteria hertleini Wiedey 

Plate 24, figure 6 

Pteria hertleini Wiedey, 1928, p. 133. pl. 2, fig. 1. Loel and Corey, 

1932, p. 188, pl. 10, figs. 1, 4. 

Original description.-"Shell large, very oblique, lingulaeform, 

nearly equivalve, very inequilateral, and highly inflated. Anterior 

dorsal margin quite straight and nearly vertical to the hinge line. 

This dorsal extremity is terminated in a sharp curve. The basal 

margin is broadly rounded and seems generally somewhat parallel 

to the hinge line. The posterior dorsal extremity is more sharply 

rounded; being quite distant from the beaks, it accentuates the 

oblique form of the shell. The posterior dorsal margin is very long 

and nearly straight. The umbones are very prominent, highly 

elevated, very regularly rounded, and acutely angular. The beaks 

are small, sharp, not conspicuous, and quite distant from one 

another. The hinge length is about three-fourths the width of the 

shell and is straight with a broad, moderately deeply excavated 

ligamenta! area. The anterior ear is the sharper and the more 

extended. Length, about 110 mm.; breadth, about 99 mm.; thickness 

of combined valves, about 70 mm.; length of hinge line, about 75 

mm." 

Holotype.-CASISV 5160. 

Type locality.-SV 200. Monterey County, Calif. Vaqueros 

Formation, Oligocene and Miocene. 

Supplementary description.-"This species is distinct in its 

inflation and acute umbonal angle. The shell is thin and not 

commonly preserved. On a few specimens the surface is seen to be 

smooth, with faint concentric incremental lines, strongest on 

umbos." (Loel and Corey, 1932, p. 188) 

Comparison.-"This new species is very distinctive and is 

resembled but slightly by any of the yet recorded West Coast 

Tertiary forms of this genus. From Pteria jordani Wiedey~**it 

differs in being more convexly inflated, more elongate and extended in outline, and in possessing higher, sharper, and more 

prominent umbones***" (Wiedey, 1928) 

Comments.-See Pteria rositae. 

Geographic range.-Middle and southern California. 

Geologic range.-Oligocene and Miocene. 

Occurrence in Cali{ornia.-Oligocene and Miocene: Vaqueros 

Formation (Eaton and others, 1941); Miocene: Temblor "horizon" 

(Loel and Corey, 1932), Topanga Formation (Takeo Susuki, written 

commun., 1978). · 

Pteria berryi Adegoke 

Plate 24, figure 5 

Pteria berryi Adegoke, 1969, p. 95-96, pl. 1, figs. 10, 12. 

Original description.-"Shell moderately large, oblique, nearly 

equivalve, inflated, inequilateral; anterior dorsal margin fairly 

long, nearly straight, merges into broadly rounded ventral margin 

with sharp angulation; posterior dorsal margin very long, nearly 

straight, merges into ventral margin with no marked angulation; 

extreme ventral margin broadly rounded; umbones prominent, 

convexly rounded; beaks small, acutely pointed and bent anteriorly; hinge line straight, about two-thirds length of shell; posterior 

ventral margin of shell conspicuously depressed and flattened 

behind hinge line; shell surface smooth." 

Holotype.-VCMP 36611. 

Type locality.-VC D-1063. Fresno County, Calif. Upper part of 

Temblor Formation, Miocene. 

Comparison.-"This new species is closely similar to Pteri 

hertleini Wiedey from the Vaqueros Formation but may be distinguished from it by its relatively smaller size, its shorter and more 

broadly rounded posterior ventral margin and by the more prominent depression and flattening of the posterior dorsal margin. It 

differs from P. jordani Wiedey from the Temblor of Santa Monica 

Mountains by its wider and more convexly inflated valves, and by 

the more prominent umbones." (Adegoke, 1969, p. 96) 

Geographic range.-Middle California. 

Geologic range. -Miocene. 

Occurrence in California.-Upper part of Temblor Formation. 
TERTIARY MARINE PELECYPODS: NUCULIDAE THROUGH MALLEIDAE A83 

Pteria jordani Wiedey 

Plate 25, figure 1 

Pteria jordani Wiedey, 1928, p. 134-135, pl. 4, fig. 4; pl. 15, fig. 3. 

Original description.-"Shell quite large, moderately oblique, 

lingularform, slightly inequivalve, inequilateral, and well inflated. 

Anterior dorsal margin above the hinge line rounded concavely, 

the anterior dorsal extremity very broadly convexly rounded. The 

basal margin is a little more sharply rounded toward the posterior 

dorsal extremity, which is but gently rounded. The posterior dorsal 

margin slopes nearly straight and is only slightly re-entrant into 

the main body of the shell adjacent to the hinge line. Umbones 

large, prominent, broad, convexly well inflated with a poorly 

defined umbonal ridge passing from the beaks toward the base of 

the shell, about 45° to the hinge line. Beaks situated at the anterior 

end of the shell, small, sharp, slightly elevated, and incurved. 

Since most of the shell has been broken away, the external 

sculpture is unknown. The hinge line is generally about the length 

of the shell and is straight, marked in the ligamenta} area by long, 

narrow, longitudinal grooves. The posterior ear is the broader, 

while the anterior ear appears to be the more extended and 

sharper, being very acutely angular. The shell attains a length of 

over 100 mm.; a breadth of over 95 mm, and a thickness in 

combined valves of over 55 mm." 

Holotype.-SDNM 25. 

Type locality.-SU 425. Los Angeles County, Calif. Topanga Formation (Keen and Bentson, 1944), Miocene. 

Comparison.-"This new species differs from other known fossil 

forms in its very much greater size and in its more rounded and 

regular outine. It is approached in similarity by**"' Pte ria hertleini 

Wiedey"'"'*The latter species is of similar size, but shows greater 

sharpness of the umbones, which are themselves much more 

inflated. In some respects it is resembled by Pteria peruuiana Reeve, 

which ranges from the Gulf of California to Ecuador. The fossil 

species has not the subquadrate outline nor the short posterior ear 

much separated from the shell found in the living form." (Wiedey, 

1928, p. 135) 

Geographic range.-Southern California. 

Geologic range.-Miocene. 

Occurrence in California.-Topanga Formation (Takeo Susuki, 

written commun., 1978). 

Pteria rositae Hertlein 

Plate 24, figure 7 

Pteria rositae Hertlein, 1928, p. 150, pl. 25, fig. 3. Loel and Corey, 

1932, p. 188, pl. 9, fig. 3. 

Original description.-"Shell oblique triangular, with long produced wing; hinge line long and straight; surface ornamented by 

incremental lines of growth. Beak near anterior fourth, prominent, 

oblique; shell slopes rather rapidly posteriorly from beak; anteriorly 

the beak slopes abruptly to a small byssal fold, forming a groove 

which separates the anterior auricle from shell; auricle triangular, 

obliquely truncate; byssal notch small, but pronounced. Height, 

26.9 mm; length of hinge line (incomplete at both ends), 43 mm." 

Holotype.-CAS 4142. 

Type locality.-CAS 1156. Santa Barbara County, Calif. Rincon 

Shale, Oligocene and Miocene. 

Comparison.-"This species differs from P. sterna Gould in that 

the anterior ventral part of the shell drops abruptly and is directly 

in line with the byssal sinus while in P. sterna Gould, the anterior 

ventral part of the shell extends broadly anterior and the byssal 

groove runs obliquely anterior from the beak. It is much broader 

ventrally and much more extended posteriorly than P. peruuiana 

Reeve." (Hertlein, 1928, p. 150) 

"The small form figured and described by Hertlein may possibly 

be a young specimen of P. hertleini Wiedey•••, to the young of 

which it is very similar in outline." (Loel and Corey, 1932, p. 188) 

Comments.-The anterior margin of P. rositae is nearly straight, 

as is a groove that continues to the dorsal edge. P. hertleini Wiedey, 

though much larger, has a deeply concave anterior margin, and, in 

proportion to its size, a shorter dorsal margin. P. rositae has a 

short posterior wing and a large anterior ear. The living species, 

Pteria sterna (Gould), includes a short-winged form that occurs in 

clusters on mud flats (Keen, 1971, p. 77). 

Geographic range.-Southern California. 

Geologic range.-Oligocene and Miocene. 

Occurrence in California.-Rincon Shale. 

Genus PINCT ADA Roding, 1798 

Less oblique and usually thicker shelled than Pteria, subquadrate, commonly slightly higher than long, nearly equivalve; 

posterior wing and indentation lacking or nearly so; surface 

lamellose. 

Geographic range.-Pantropic, especially Indo-Pacific. 

Geologic range.-Miocene through Holocene (table 7). 

Habitat.-Attached by byssal threads; the flattened shell is 

usually secured almost at right angles to the surface but always 

inclined somewhat to the right. (Yonge and Thompson, 1976, 

p. 173) 

Pinctada mazatlanica (Hanley) 

Plate 25, figure 2 

Meleagrina mazatlanica Hanley, 1855, p. 388, pl. 24, fig. 40. 

Pteria (Pinctada) mazatlanica (Reeve). Grant and Gale, 1931, 

p. 148 [See synonymy]. 

Pinctada mazatlanica Hanley. Hertlein and Strong, 1943, 

p. 164-165. 

Pinctada mazatlanica (Hanley). Durham, 1950, p. 58, pl. 2, fig. 6. 

Keen, 1971, p. 79, fig. 162. 

Original description.-"Large, solid, subventricose, more or less 

oblique, more or less projecting behind ventrally, longer than 

broad, squarish above in front; rounded ventrally, yellowish olive, 

with rather faint pallid rays; the rather distant concentric lamellae 

somewhat closely fringed with moderately large peaked concave 

vandyked scales; ventral edge much arcuated, rising in front; 

anterior margin not retuse, but either straightish or convex, 

forming nearly a rectangle with the rather short straight and 

rising dorsal line; hinder gape ample, the posterior dorsal incurvation being full, and the auricle rather large and deep; nacre 

bluish white, broadly edged with the external colouring. 5"'"'"'41/2. 

Mazatlan. Distinguished from margaritifera by its scales, obliquity, colour, and by not being retuse in front." 

Holotype.-Location unknown; not in BM(NH) (A.M. Keen, oral 

commun., 1978). 

Type locality.-Mazatlan, Mexico. 

Geographic range.-Living: Pacific coast of Baja California and 

Golfo de California to Peru; fossil: Baja California Sur. 

Geologic range.-Pliocene through Holocene. 

Occurrence in Baja California Sur.-Pliocene: Carmen and 

Marquer Formations (Durham, 1950); Pleistocene: unnamed strata 

Punta San Telmo and Isla Carmen, Baja California Sur (Durham, 

1950). 

Habitat.-In shallow water offshore; attached by byssus. 
A84 PALEONTOLOGY OF CALIFORNIA AND BAJA CALIFORNIA 

Family ISOGNOMONIDAE 

Genus ISOGNOMON Lightfoot, 1786 

Shell subequivalve, usually higher than long, more or less compressed, of various shapes; urn bo directed anteriorly and not 

protruding above hinge margin; ligamenta! area broad and flat, 

scarcely undercut; ligamenta! grooves numerous, regularly 

arranged; narrow byssal gape present below beaks with corresponding reflection of anterior margin. 

Geologic range.-Triassic through Holocene (table 8). 

Habitat.-Attached to byssus that passes between the two 

valves; commonly wedged in among coral colonies, mangrove 

roots, or rocks with a distorted shell conforming to the constricting 

cavity. 

Subgenus ISOGNOMON 

Rhomboidal to pyriform, beak at anterior end of hinge margin, 

produced and pointing anteriorly; lower part of anterior margin in 

some species strongly convex and extending well forward of beak, 

entire margin in other species straight or almost so and inclined so 

as to form a slightly acute angle with hinge margin; hinge margin 

rather short, posterior wing obtuse and seldom well differentiated; 

ligamenta! grooves subequal, intervals between them lying in 

general plane of ligamenta! area; surface lamellose. 

Isognomon (lsognomon) panzana (Loel and Corey) 

Plate 25, figures 3, 6 

Pedalion panzana Loel and Corey, 1932, p. 187, pl. 9, figs. 1a, 1b, 

2-6. 

Original description.-"Shelllarge, rugose and thick, of a dark 

brown material, valves equivalve, very inequilateral and high, 

fairly convex, and subquadrate in outline; umbones prominentproduced beyond anterior margin in continuation of dorsal margin, 

beaks acute, proximate, inturned; dorsal margin gently curved, 

joining posterior margin in a short curve (in paratype this extremity is angular) ventral margin evenly rounded to the anterior 

which is gently convex in lower half and gently concave in upper 

part of beak. The upper part of the anterior margin is deeply 

inturned; a fairly prominent ridge extends along this convexity 

from the beak, inside of which ridge is a groove, deepest under 

beaks. Interior of valves quadrate, produced toward beaks; cardinal 

area straight, broad, with deep straight, perpendicular pits which 

are wider posteriorly. No byssal notch on right valve. Muscle scars 

not seen. Surface ornamented by a number of irregular, divaricateradial plications, triangular in shape, which become more numerous and stronger toward the crenulate posterior ventral margins." 

Holotype.-UCMP 31780. 

Type locality.-UC A-498. San Luis Obispo County, Calif. 

Vaqueros Formation, Oligocene and Miocene. 

Supplementary description.-"This interesting species is the 

first Pedalion found in the Post-Eocene Tertiary of the West Coast. 

It occurs in large numbers at the type locality, forming a hard reef 

bed." (Loel and Corey, 1932, p. 187) 

Geographic range.-Southern California. 

Geologic range.-Oligocene and Miocene. 

Occurrence in California.-Oligocene and Miocene: Vaqueros 

Formation. 

Isognomon (lsognomon) janus Carpenter 

Plate 25, figures 4, 5 

Isognomonjanus Carpenter, 1857, p. 151-152. Keen, 1971, p. 79, fig. 

163. 

Pedalion janus (Carpenter). Durham, 1950, p. 58, pl. 3, figs. 1, 4. 

Original description.-"!. t. rhomboidea, tenui, planatA, pallida; 

valva inferiori laevi, superiori coatis gracillimis, interdum 

obsoletis, testa juniore spinis semitubulis imbricatA; haud aurita, 

angulo ad umbones acuto; marginibus ant. et post. subparallelis, 

subrectis: cardine ligamento ut in Avicula Iongo, fossibus perpaucis, minimis, irregulariter dispositis; imp. muse. haud magno." 

Holotype.-BM(NH), Carpenter collection, tablet 690. 

Type locality.-Off Mazatlan, Mexico. 

Comparison.-"The principal distinction that Carpenter noticed 

in this shell was that there are fewer pits along the hinge marginas many as 10 to 12 in I. recognitus, only 7 to at most 9 in I. 

janus. ***The shell tends to be higher for the length or more tongueshaped. Radial sculpture may be more pronounced in I. janus, and 

concentric lamellae are lacking. Perna anomoides Reeve was 

described as from 'California,' but the present label on the type 

specimen in the British Museum says 'Torres Straits' (i.e. northern 

Australia). Reeve's figure does not resemble I. janus in outline." 

(Keen, 1971, p. 79) 

Geographic range.-Living: Laguna San Ignacio, Baja California Sur, to Oaxaca, Mexico; fossil: Baja California Sur. 

Geologic range.-Pliocene through Holocene. 

Occurrence in Baja California Sur.-Pliocene: Marquer Formation (Durham, 1950). 

Habitat.-"on I. chemnitzii and Spondylus calcifer***" (Carpenter, 1857, p. 152) 

Isognomon sp. (Clark and Woodford) 

Plate 26, figure 3 

Pedalion sp. Clark and Woodford, 1927, p. 88, pl. 14, fig. 8. 

Description.-"Two fragmentary specimens are referred to this 

TABLE B.-Geologic and geographic distribution of the family Isognomonidae. 

[H = Holocene; PI = Pliocene; M = Miocene; 0 = Oligocene; E = Eocene; Pa = Paleocene.J. 

Species 

Genus lsognomon: 

Subgenus /sognomon: 

janus Carpenter .......................................................... . panzana (Loel and Corey) .. . ............................ . Subgenus lsognomon?: n. sp.? Givens ... sp. (Clark and Woodford) ......... . Genus Pachyperna?: 

goniglensis (M.A. Hanna) 

joaquinensis (Vokes) 

California 

Middle Southern 

E Pa 

................. E ........ E 

Baja California 

Norte Sur 

PI to H 

South 

America 

H 
TERTIARY MARINE PELECYPODS: NUCULIDAE THROUGH MALLEIDAE A85 

genus, one of which is figured. The material is not good enough for 

specific identification." 

Figured specimen.-UCMP 31301. 

Locality.-UC 3609. Contra Costa County, Calif. Meganos Formation, 

Paleocene. 

Geographic range.-Middle California. 

Geologic range.-Paleocene. 

Occurrence in California.-Meganos Formation. 

lsognomon n. sp.? Givens 

Plate 26, figure 1 

Isognomon n. sp.? Givens, 1974, p. 43-44, pl. 2, fig. 6. 

Description.-"Five poorly preserved specimens of a large 

Isognomon were collected from locality 4752. They represent the 

first record of this genus in the Eocene of the Pacific Coast and, 

therefore, probably represent a new species. The small size of the 

sample and poor preservation of the specimens, however, do not 

justify the naming of a new species at this time. The description of 

the figured specimen is as follows: shell subquadrate in outline, 

about 6 in high and 4 in long, moderately convex, equivalve, 

inequilateral; umbo situated at anterior end of hinge margin, 

produced and directed anteriorly; anterior margin of shell nearly 

straight, becoming concave near the beak and forming an acute 

angle with the hinge margin; posterior and ventral margins of 

shell evenly rounded; narrow byssal gape present below beaks; 

hinge area with at least 11 narrow, subequal ligament grooves; 

surface of shell concentrically lamellose." 

Figured specimen.-VCR 4752/61. 

Locality.-UCR 4752. Ventura County, Calif. Juncal Formation, 

Turritella uuasana applinae fauna, Eocene. 

Comparison.-" 'Perna' goniglensis Hanna***and 'Pedalion' 

joaquinensis Vokes***from the middle Eocene ('Domengine Stage') 

of California are distinguished from Isognomon n.sp.? by their 

much smaller size and by the presence of only 3-5 ligament 

grooves on the hinge area. These species appear to be referable to 

Pachyperna Oppenheim***of the European middle Eocene." 

(Givens, 1974,p.44) 

Geographic range.-Southern California. 

Geologic range.-Eocene. 

Occurrence in California.-Juncal Formation (Turritella 

uuasana applinae fauna, Givens, 1974). 

Genus PAC~YPERNA Oppenheim, 1900 

Moderately small, ovate, higher than long, not oblique, subequivalve, strongly convex; shell wall very thick; with small 

anterior auricle but with no differentiated posterior wing; umbones 

ill-defined, not protruding; anterior face with broad, shallow lunule 

but without byssal gape; ligamenta} area broad with not more 

than five ~elatively wide pits. 

Geographic range.~France, northern Italy, California? 

Geologic range.-Eocene (table 8). 

Genus PACHYPERNA? 

Pachyperna? goniglensis (M. A. Hanna) 

Plate 26, figure 4 

Perna goniglensis M.A. Hanna, 1927, p. 275, pl. 27, figs. 12-14. 

"Perna" goniglensis Hanna. Givens, 1974, p. 44. 

Original description.-"Shell of medium size, moderately inflated; dorsal edge straight to gently rounded; posterior side 

straight to slightly rounded; ventral margin regularly rounded to 

the deep indentation on the anterior side; beak sharply rounded; 

outer surface evidently smooth; shell chalky, fairly heavy; ligamenta} grooves elongate normal to the ligamenta! surface, three to 

four grooves separated by flat-topped ridges of various widths, but 

wider than the grooves; character of the interior not evident. 

Dimensions: Altitude 30 mm, length 25 mm." 

Holotype.-UCMP 30912. 

Type locality.-UC 4233. San Diego County, Calif. Ardath Shale, 

Eocene. 

Geographic range.-Southern California. 

Geologic range.-Eocene. 

Occurrence in California.-Ardath Shale. 

Pachyperna? joaquinensis (Vokes) 

Plate 26, figure 5 

Pedalionjoaquinensis Vokes, 1939, p. 52-53, pl. 2, figs. 3, 6, 10, 12, 

15. 

"Pedalion" joaquinensis Vokes. Givens, 1974, p. 44. 

Original description.-"Shell of medium size, compressed; dorsal 

margin straight, the posterior and ventral rounded, the anterior 

slightly concave; a small anterior ear angulate to the dorsal 

margin; umhos anterior, sharply prosogyrate; shell laminated, 

iridiscent; surface smooth except for growth-lines; ligamenta} 

grooves four or five, narrow-elongate, separated by interspaces 

equal in width to the grooves at the beak and becoming progressively wider posteriorly." 

Holotype.-UCMP 15577. 

Type locality.-UC 7177. Fresno County, Calif. Domengine 

Formation, Eocene. 

Comparison.-"This species differs from P. goniglensis M. A. 

Hanna***in lacking the deep anterior indentation characteristic of 

the San Diego species; the anterior margin, ventral to. the byssal 

notch, does not project as far forward in the Coalinga species. The 

dorsal margin is never rounded, and the ear, characteristic of P. 

joaquinensis, is not well developed on P. goniglensis." (Vokes, 

1939, p. 53) 

Geographic range.-Middle California. 

Geologic range.-Eocene. 

Occurrence in California.-Domengine Formation. 

Family PULVINITIDAE 

Genus PULVINITES Defrance, 1824 

Orbicular or broadly trigonal; right valve flat or slightly concave, with byssal foramen below middle of ligamenta! area. 

Geographic range.-France, Lebanon, North America. 

Geologic range.-Jurassic to Paleocene; Holocene of Australia: 

Habitat.-Attached by byssus through foramenal opening. 

Pulvinites californica Zinsmeister 

Plate 26, figure 6 

Puluinites californica Zinsmeister, 1978, p. 568, pl. 1, figs. 7-10 

[erroneously cited in text as figs. 5, 6]. 

Original description.-"Shell small orbicular, compressed. Right 

valve flat to slightly concave with small slightly elliptical foramen 

located immediately below hinge, a short suture extends from 

foramen to anterior edge of shell below hinge; left valve weakly 

convex with faint, irregular undulations. Small, subcentrally 

located adductor muscle scar in each valve. Hinge edentulous with 

narrow ligamenta} area, 4 to 5ligamental grooves." 

Holotype.-UCR 6821119. 
A86 PALEONTOLOGY OF CALIFORNIA AND BAJA CALIFORNIA· 

Type locality.-UCR 6821. Ventura County, Calif., Paleocene. 

Comparison.-"This small species is distinguished from Puluinites pacifica by the convex left valve and small size. The two 

species have never been found together." (Zinsmeister, 1978, p. 568) 

Geographic range.-Southern California. 

Geologic range.-Paleocene. 

Occurrence in California.-Lower part of Santa Susana Formation~ 

Pulvinites pacifica Zinsmeister 

Plate 26, figures 2, 7 

Pedalion sp. Nelson:, 1925, p. 405, pl. 49, figs. 8. 9. 

Puluinites pacifica Zinsmeister, 1978, p. 569, pl. 1, figs. 5, 6 

[erroneously cited in text as figs. 7-10]. 

Original description.-"Shell orbicular, compressed, lamellose. 

Right valve flat to slightly concave with moderately large slightly 

elliptical foramen, located 4 mm ventrally from the dorsal edge of 

valve, anterior to foramen, the laminar shell layers are closely 

packed. Moderately large adductor muscle medially located in each 

valve, left valve slightly convex, with centrally located adductor 

muscle scar with a faint radiating retractor scar. Hinge edentulous, 

with approximately 5ligamental grooves." 

Holotype.-UCR 7342/1 (not 6900/101; J. D. Mount, written 

commun., 1978). 

Type locality.-UCR 7342. (Not UCR 6900; J.D. Mount, written 

commun., 1978). Ventura County, Calif. Paleocene. 

Supplementary description.-"Specimens of Puluinites are 

generally poorly preserved because of the hard matrix and laminar 

nature of the shell structure. No suture is immediately obvious, but 

the close bunching of the laminar shell constrictions anterior to 

the foramen probably represents the location of the suture. 

"The occurrence of Puluinites in the Paleocene of California is 

the first recognized occurrence of the genus in the Tertiary. Nelson 

(1925) found poorly preserved fragments of Puluinites, but because 

the foramen was not preserved in his material, he did not recognize 

that it was a pulvinitid and referred it to the genus Pedalion." 

(Zinsmeister, 1978, p. 569) 

Comparison.-"The large foramenal opening (4 to 5 mm.), 

narrow hinge, and ventrally located suture separates Puluinites 

pacifica from other known Paleocene species of Puluinites. 

Puluinites californica which also occurs in the Simi Hills is 

considerably smaller with a more convex left valve." (Zinsmeister, 

1978, p. 569) 

Geographic range.-Southern California. 

Geologic range.-Paleocene. 

Occurrence in California.-Lower part of Santa Susana 

Formation. 

Family MALLEIDAE 

Genus NAYADINA Munier-Chalmas, 1864 

Subequivalve of various shapes, commonly elongate and equilateral; valves with or without narrow, simple gape; ligamenta} 

area well exposed to exterior, with broad, deeply concave ligamenta} pit occupying most of its width. 

Geographic range.-Europe, North America, North Africa, 

southwest Asia. 

Geologic range. -Cretaceous to Eocene. 

Subgenus EXPUTENS Clark, 1934 

Elongate, oblong, inequilateral, with posterior end extended; 

subauriculate anteriorly; valve margins not gaping; umbones 

commonly pointed and prominent; ligamenta! area broad, overhanging platform extending posterior from umbones; surface 

smooth except for well-marked growth lines. 

Geographic range.-California and Jamaica. 

Geologic range.-EI)cene. 

Nayadina (Exputens) alexi (Clark) 

Plate 26, figures 8, 9 

Exputens alexi Clark, 1934, p. 271-272, pl. 37, figs. 19-24. Vokes, 

· 1939, p. 51, pl. 2, figs. 2, 5, 9. 

Original description.-"Shell moderately thick for the size, 

elongate subquadrate to subtrapezoidal in outline; beaks inconspicuous, in the anterior third of the shell; anterior end broad and 

bluntly rounded; posterior end narrower than anterior and regularly rounded; the anterior ear stands up prominently above the 

beaks as though this portion of the shell had been twisted upward 

and backward. A large triangular ligamenta! area, only moderately depressed. The line of greatest convexity of the surface of the 

shell extends from the beak . to the posterior end. The general 

surface of an unweathered specimen is sculptured by somewhat 

irregular concentric undulations. The large posterior adductor scars 

are close to the ventral edge and only slightly posterior to the 

beaks. The small anterior scars are just below the beaks and 

somewhat obscure on some of the specimens." 

Holotype.-UCMP 32386. 

Type locality.-UC A-1007. Fresno County, Calif. Domengine 

Formation, Eocene. 

Comparison.- "Exputens ale xi may be distinguished from E. 

llajasensis by the position of the ears, which on the former stand 

out above the beaks whereas on the latter they are in the normal 

position in front of the beaks. Another character, in which the two 

species differ, is the ligamenta! pit; on the former it is much less 

depressed than on the latter. Apparently E. llajasensis is a more 

variable form than E. alexi. None of the specimens of the latter 

species is as large as the average size of the former." (Clark, 1934, 

p. 272) 

Geographic range.-Middle and southern California. 

Geologic range.-Eocene. 

Occurrence in California.-Avenal Sandstone (Stewart, 1946) 

and Domengine Formation. 

Nayadina (Exputens) llajasensis (Clark) 

Plate 26, figures 10, 13 

Exputens llajasensis Clark, 1934, p. 270-271, pl. 37, figs. 11-18. 

Vokes, 1939, p. 51 [Designated as genotype]. 

Nayadina (Exputens) llajasensis (Clark). Givens, 1974, p. 44, pl. 1, 

fig. 9. 

Original description.-"Shell thin, variable in outline, roughly 

elongate, subquadrate in outline; surface smooth except for fairly 

heavy, irregular lines of growth; beaks in the anterior third of the 

shell, variable in prominence, inconspicuous on the type. Anterior 

ears defined and in front of the beak; ligamenta} area broad 

triangular in outline and situated on a chrondrophore-like platform 

which stands out almost at right angles to the main surface of the 

shell; posterior muscle scar large near the ventral edge and a little 

posterior to the beak; anterior scar small and situated below the 

beak and the anterior edge of the ligamenta} platform, obscure on 

some specimens." 

Holotype.-UCMP 32391. 

Type locality.-UC 7004. Ventura County, Calif. Uajas Formation, Eocene. 
TERTIARY MARINE PELECYPODS: NUCULIDAE THROUGH MALLEIDAE A87 

Supplementary description.-"There are several distinct 

variants of this species as found at the type locality***variety 

A ***is a perfect specimen showing both valves; it is long and 

narrow and has well-developed anterior ears; the beaks are only 

moderately conspicuous***. 

"variety B. On this specimen the beaks are so inconspicuous as 

to be hardly discernible. The ear is larger than on variety A and 

the anterior end is broadly rounded, sloping down from the outer 

angle of the ear almost at right angles to the posterior dorsal 

margin and giving a subquadrate appearance to the shell. 

"variety C, a form in which the beaks are conspicuous and 

opisthogyrous. The ear is almost obsolete; this is brought about by 

the fact that the upper margin of the ear slopes abruptly downward 

and joins the anterior edge of the shell without any break such as 

is seen in varieties A and B***. 

"Most of the specimens of this species show irregularities in the 

surface of the shell. This, together with the variability in outline, 

the general elongate shape, and the lack of any well-defined byssal 

notch, suggests that the species was a nestler." (Clark, 1934, p. 271) 

Comparison.-[See N. (E.) alexi.] 

Geographic range.-Southern California. 

Geologic range.-Eocene. 

Occurrence in Cali{ornia.-Juncal (Turritella uuasana infera 

fauna, Givens, 1974) and Llajas (Keen and Bentson, 1944) Formation. 

Genus VULSELLA Roding, 1798 

Shell elongated dorsoventrally, linguiform, subequivalve, compressed, gaping anteriorly and posteriorly; ears absent or small;· 

surface concentrically lamellose, radial ribbing present in some 

forms; not byssiferous. 

Geologic range.-Cretaceous through Holocene. 

Habitat.-Living forms commonly commensal in sponges; no 

byssus. 

Genus VULSELLA? 

Vulsella? clarki Vokes 

Plate 26, figures 11, 12 

Vulsella(?) clarki Vokes, 1939, p. 53-54, pl. 3, fig. i. 

Original description.-"Shell ostreiform, moderately large, elongate posteriorly, inflated, attached; surface, other than area of 

attachment, marked by coarse lines of growth; ligamenta! groove 

external, elongate, triangular; shell thin at area of attachment, 

thick elsewhere; muscle-scar subcentral, moderately large." 

Holotype.-UCMP 15743. 

Type locality.-UC 1817. Fresno County,Calif. Lodo Formation, 

Paleocene and Eocene. 

Supplementary description.-"According to Reeves the genus 

occurs principally in association with sponges, and none of the 

figured species shows any indication of an area of attachment. The 

generic determination ofthe new species is therefore questioned, as 

a prominent area of attachment is visible on all the specimens in 

the collection. 

"One large specimen appears to have been attached to a large 

flat surface (possibly an Aturia) and, as a result, tends to be 

elongated ventrally rather than posteriorly.".(Vokes, p. 53-54) 

Comparison.-" Vulsella(?) clarki may be distinguished from all 

described West American species by its ostreiform shape and the 

externalligamental pit." (Vokes, 1939, p. 53) 

Geographic range.-Middle California. 

Geologic range.-Paleocene to California. 

Occurrence in California.-Paleocene and Eocene: Cerros Shale 

Member of the Lodo Formation (Keen and Bentson, 1944). 

FOSSIL LOCALITIES 

[Corrections and information not in the original description are in brackets; miles and 

feet are converted to metric units; formations are cited as emended by later work where 

pertinent] 

California Academy of Sciences: 

CAS 68. North bank of Kern River, about 1 km west of the 

power plant and 5 km east of the Rio Bravo Ranch House 

[Caliente quadrangle], Kern County, Calif. Temblor 

Formation. 

CAS 119. East bank of Eel River, 2 km north of Scotia, 

Humboldt County, Calif. Upper part of Rio Dell Formation 

or lower part of Scotia Bluffs Sandstone. 

CAS 244. In east bank of Live Oak Creek. 1.2 km from mouth, 

4.8 km due east of mouth of Grapevine Canyon, Tejon 

quadrangle, Kern County, Calif. Tejon Formation. 

CAS 245. Along east bank of a small gulch 0.4 km east of 

pumping plant at mouth of Grapevine Canyon, 56 km south 

of Bakersfield, Tejon quadrangle, Kern County, Calif. Tejon 

Formation. 

CAS 711. East side of Grapevine Creek near point where it 

enters valley floor, Tejon quadrangle, Kern County, Calif. 

Tejon Formation. 

CAS 788. Along east bank of gulch 400 m east of pumping 

plant at mouth of Grapevine Canyon, 56 km south of 

Bakersfield, Tejon quadrangle, Kern County, Calif. Tejon 

Formation. 

CAS 1156. About 0.4 km southeast of spring on ridge south of 

San Augustine Canyon, east of dike near top of hill, Santa 

Rosa Island, Santa Barbara County, Calif. Rincon Shale. 

CAS 12099. Well in Balboa Park, San Diego, San Diego 

County, Calif. San Diego Formation. 

CAS 53043. Rio Dell side of Eel River, 730-825 m downstream 

from Scotia-Rio Dell bridge, Humboldt County, Calif. Rio 

Dell Formation. 

California Institute of Technology: 

CIT 738. South slope of Carrizo Mountain, crest of ridge 1,120 

m northeast of mouth of Alverson Canyon, Imperial County, 

Calif. Imperial Formation. 

Los Angeles Natural History Museum: 

LAM 107. Thirty-meter bluff with fossiliferous concretions in 

clay quarry at end of Arroyo Drive, San Diego, Calif. San 

Diego Formation. 

San Diego Natural History Museum: 

SDNM 207. Near Elsmere Canyon, in ridge, sec. 8, T. 3 N., R. 

15 W., SB [San Fernando quadrangle], Los Angeles County, 

Calif. Fernando Formation. 

SDNM 407. South wall of Little Sespe River, just above its 

junction with Big Sespe River, Ventura County, Calif. 

Vaqueros Formation. 

SDNM 432. [See SU 432.] 

SDNM 442. On a spur in a small canyon about 2 km west of 

San Martinez Grande Canyon, north side of Santa Clara 

Valley, approximately on the boundary line between Los 

Angeles and Ventura Counties, Calif. Pico(?) Formation. 

SDNM 443. Near center of south line ofSE1

/2 sec. 36, T. 9 S., R. 2 

W., Santa Cruz quadrangle, California. On old road, about 1/2 

km southwest of Zayante R. R. station. Elevation about 300 

m. Monterey Shale. 
A88 PALEONTOLOGY OF CALIFORNIA AND BAJA CALIFORNIA 

Stanford University [These collections are now housed in the 

California Academy of Sciences]: 

SU 111. Two Bar Creek, 0.4 km above junction with San 

Lorenzo River, Santa Cruz County, Calif., about 185 m 

above base. Vaqueros Formation. 

SU 200. East side of Vaqueros Creek, SE1A sec. 9, T. 20 S., R. 6 

E., Junipero Serra quadrangle, Monterey County, Calif. 

Vaqueros Formation. 

SU 425. Head of small canyon trending westward from head 

of Dry Canyon at base of east-west ridge forming divide, 3 

km south of Calabasas, Santa Monica Mountains [sec. 34, T. 

1 N., R. 17 W., Calabasas quadrangle], Los Angeles County, 

Calif. Topanga Formation. 

SU 432. East slope of first ridge west of Syncline Hill, 3 km 

west of Simmler [SW1A sec. 35, T. 29 S., R. 17 E., La Panza 

quadrangle], San Luis Obispo County, Calif. Temblor 

Formation. 

SU 834. 19 mm west and 82 mm south of the intersection of 

lines indicating lat 34°40' N. and long 129°10' W. on Lompoc 

quadrangle (1905 ed.), east side ofNojoqui Creek, due east of 

the letter "R" of the word "Creek," just 5 km north of 

Gaviota Pass, Santa Barbara County, Calif. Gaviota Formation of some authors. 

SU 2121. Near center of SW1A sec. 6, T. 29 S., R. 30 E., Caliente 

quadrangle, Kern County, Calif. Lowermost part of Round 

Mountain Silt. 

SU 2696. McCray Wells [Oil Canyon, 5 km N. 20° E. of B.M. 

961 at Santa Susana, Santa Susana quadrangle], Ventura 

County, Calif. Llajas Formation. 

University of California at Berkeley: 

UC 15. N1/2 sec. 23, T. 1 N., R. 3 W., Concord quadrangle, 

Contra Costa County, Calif. Briones Sandstone. 

UC 52. South of town of Walnut Creek 2 km, near top of first 

ridge west of creek, long 122°3'30" W., lat 37°52'44" N. 

[Concord quadrangle], Contra Costa County, Calif. San 

Ramon Sandstone .. 

UC 78. About 5 km south of Pittsburg, close to west edge of 

SW1A sec. 30, T. 2 N., R. 1 E., Contra Costa County, Calif. 

Kirker Tuff. 

UC 118. Southeast side of prominent hill at elevation of about 

305 m, near center of NW1ANW1A sec. 9, T. 1 S., R. 1 W. 

[Contra Costa County], Calif. Neroly Sandston~. 

UC 331. On first ridge north of Sobrante Ridge, southeast of 

west fork of Bear Creek, long 122° 12'22" W., lat 37°55'58" N., 

Contra Costa County, Calif. San Ramon Sandstone. 

UC 333. 16.5 em east, 7 em south of northwest corner of map 

sheet, Concord quadrangle, Contra Costa County, Calif. 

Martinez Formation. ' 

UC 402. [To south of Pittsburg] a little east of saddle southwest 

of 198m hill near west side of NW% sec. 30, T. 2 N., R. 1 E. 

[Contra Costa County], Calif. Cierbo Sandstone. 

UC 458. West side of Grapevine Creek, 7.2km S., 6° W. ofB.M. 

1058, Tejon quadrangle, Kern County, Calif. Tejon 

Formation. 

UC 672. South part of crest of Parson's Peak, SW1ANW1A T. 18 

S., R. 14 E., Coalinga quadrangle [Fresno County], Calif. 

Domengine Formation. 

UC 784. Near Lower Lake, at old brick yard, 0.4 km east of 

village NW1ANE1A sec. 11, T. 12 N., R. 7 W., Lake County, 

Calif. Martinez Formation. 

UC 790. East of Lower Lake village 1 km 365 m south of 

Herndon Creek Bridge, SE1ANE1A sec. 11, T. 12 N., R. 7 W., 

Lake County, Calif. Martinez Formation. 

UC 798. Lat 37.2° N., long 122.1° W., Santa Cruz County, 

Calif. San Ramon Sandstone. 

UC 1547. Just south of Arroyo del Hambre Creek, 12 km south 

of north edge of Concord quadrangle, Contra Costa County, 

Calif. Martinez Formation. 

UG 1556. A little more than 1.5 km south of Stewartville, 

NE1ANW1A sec. 15, T. 1 N., R. 1 E., Mount Diablo quadrangle, 

Contra Costa County, Calif. Martinez Formation. 

UC 1617. About 0.5 km east ofRodeo[NE1A sec. 13, T. 2 N., R. 

4 W.], Napa quadrangle, Contra Costa County, Calif. Neroly 

Sandstone. 

UC 1817. Opposite the place where Urruttia Canyon enters 

Salt Creek, 30 m up fourth small draw from west end of 

ridge, SW1

ANW% sec. 15, T. 18 S., R. 14 E., Coalinga 

quadrangle [Fresno County], Calif. Cerros Shale Member of 

the Lodo Formation. 

UC 1853. Marysville [Sutter] Buttes, Nlf2 sec. 28, T. 16 N., R. 1 

E., Marysville [Sutter] Buttes quadrangle, Sutter County, 

Calif. Capay Formation. 

UC 1859 and 1860. In seacliff at mouth of small gulch 0.5 km 

north of Guthrie Creek, 13 km southwest of Ferndale [SW1A 

sec. 13, T. 2 N., R. 3 W., H.], Humboldt County, Calif. Wildcat 

Group. 

UC 1895. About 4.5 km south of Pittsburg, north of Mount 

Diablo, near center of SE% sec. 29, T. 2 N., R. 1 E., Contra 

Costa County, Calif. Kirker Tuff. 

UC 2033. South of Hill 651 about 0.4 km, 0.8 km west of 

Kirker's Creek, near west edge of sec. 30, T. 2 N., R. 1 E., 

Mount Diablo quadrangle, Contra Costa County, Calif. 

Kirker Tuff. 

UC 2040. On southeast side of 285m hill at elevation of about 

100 m, near south edge of NE1A sec. 33, T. 2 N., R. 1 E., 

[Mount Diablo quadrangle, Contra Costa County], Calif." 

San Pablo Group. 

UC 2276. Northeast of Coalinga about 16 km, on hill near SW 

cor. SE1ANE% sec. 10, T. 19 S., R. 15 E. [Coalinga quadrangle], Fresno County, Calif. Santa Margarita Formation. 

UC 2284. Sixteen kilometers northeast of Coalinga, middle of 

south line of NE1A sec. 10, T. 19 S., R. 15 E., Fresno County, 

Calif. Santa Margarita Formation. 

UC 2287. West side of Domengine Canyon, SW cor. SW1ASE% 

sec. 29, T. 18 S., R. 15 E., Fresno County, Calif. Domengine 

Formation. 

UC 2680. Near top of ridge at center ofNW% sec. 8, T. 22 S., R. 

15 E., M.D.B.M., Fresno County, Calif. Etchegoin Formation. 

UC 2754. On Sobrante Ridge on branch of San Pablo Creek, 

northeast of California and Nevada Railroad, long 122°14.1" 

W., lat 37°56'54" N. [Concord quadrangle], Contra Costa 

County, Calif. San Ramon Sandstone. 

UC 2755. Valley north of Sobrante Ridge; on west fork of Bear 

Creek, long 122°12'35" W., lat 37°55'58" N., Contra Costa 

County, Calif. Kirker Tuff. 

UC 3080. East side of Markley Canyon opposite L. Loughrie's 

house; elevatfon 215 m, SW1

A sec. 34, T. 2 N., R. 1 E., Contra 

Costa County, Calif. Kirker Tuff. 

UC 3081. Near mouth of Markley Canyon on west side, 

opposite tunnel of Pittsburg Railroad, near SE cor~ NE 1

A sec. 

33, T. 2 N., R. 1 E., Mount Diablo quadrangle, Contra Costa 

County, Calif. San Ramon Sandstone. · 

UC 3152. [Deer Valley, NW1A sec. 20, T. 1 N., R. 2 E., Mount 

Diablo quadrangle], Contra Costa County, Calif. Meganos 

Formation. 

UC 3155. [NE1ASE1A sec. 7, T. 1 N., R. 1 E., Mount Diablo 

quadrangle], Contra Costa County, Calif. Meganos 

Formation. 

UC 3529. W1/2 sec. 4, T., 4 S., R. 1 E., Pleasanton quadrangle, 

Alameda County, Calif. Briones Sandstone. 
TERTIARY MARINE PELECYPODS: NUCULIDAE THROUGH MALLEIDAE A89 

UC 3573. Near Vacaville, banks of Ualtis Creek, just south of 

Dunn's Peak, Vaca Valley [sec. 19, T. 6 N., R. 1 W., Napa 

quadrangle], Solano County, Calif. Capay.(?) Formation. 

UC 3577. [Los Meganos Grant, north ofBriones Valley, east of 

crest of Hill 392, Brentwood quadrangle], Contra Costa 

County, Calif. Meganos Formation. 

UC 3579. [Southwest of ridge east of Marsh Creek, 0.4 km east 

of Hil~ 386, Bryon quadrangle], Contra Costa County, Calif. 

Meganos Formation. 

UC 3609. [Sec. 23, T. 1 N., R. 2 W., Bryon quadrangle], Contra 

Costa County, Calif. Meganos Formation. 

UC 3675. North of road and east of summit of Reliz-Vaqueros 

Creek Road, Junipero Serra quadrangle, Monterey County, 

Calif. Between 300 and 460 m below the top of the Vaqueros 

Formation. 

UC 3752. Simi Valley, Santa Susana quadrangle, SEtf.1SEtf.1 

sec. 7, T. 2 N., R. 17 W., SB, Ventura County, Calif. Martirtez 

Formation. 

UC 3771. Northeast cor. sec. 23, T. 2 N., R. 18 W., SB, Ventura 

County, Calif. Martinez Formation. 

UC 3776. West side of bottom of canyon, 1,615 m N. 3° W. of 

Hill 2150, Simi Hills, Calabasas quadrangle, Ventura 

County, Calif. Martinez Formation. 

UC 3809. SEcor. sec. 28, T. 2 N., R.18 W., Camulos quadrangle, 

Simi Hills, Ventura County, Calif. Martinez Formation. 

UC 3981. At 15m above high-tide level in small gully 0.4 km 

south of mouth of Soledad Valley, La Jolla quadrangle, San 

Diego County, Calif. Delmar Formation. 

UC 3990. On the east side of canyon in bottom of Rose Creek 

0.5 km east of "t" of "Soledad Mountain," La Jolla qu~drangle, San Deigo County, Calif. Ardath Shale. 

UC 3993. In bottom of Rose Creek where creek makes a strong 

bend to west, 0.8 km south ofB.M. 176, 3 km east of La Jolla, 

La Jolla quadrangle, San Diego County, Calif. Ardath 

Shale. 

UC 4004. In saddle 2,745 m N. 88° W. of Hill1926, Simi Hills, 

Camulos quadrangle, Ventura County, Calif. Martinez 

Formation. 

UC 4180. 105m north, 365m west from the northwest corner 

sec. 1, T. 32 S., R. 14 E., Nipoma quadrangle 91952 ed.), San 

Luis Obispo County, Calif. Phoenix Member, Santa 

Margarita Formation. 

UC 4182. At the new city reservoir, Eugene, Lane County, 

Oreg. Eugene Formation. 

UC 4233. In a creek, in the NEt;., sec. 12, T. 14 S., R. 3 W., La 

Jolla quadrangle, San Diego County, Calif. Ardath Shale. 

UC 5062. In sea cliff south of mouth of Soledad Valley,. due 

west of midpoint between "P" and "u" of "Pueblo," La Jolla 

quadrangle, San Diego County, Calif. Ardath Shale. 

UC 5091. Tecolote Creek about 0.5 km north of its junction 

with its largest tributary, La Jolla quadrangle, San Diego 

County, Calif. Ardath Shale. 

UC 6128. At base of bluff, west of south end of remnant hill on 

lower plain, west side of Plano Trabuco, Santa Ana Mountains, Corona quadrangle, Orange County, Calif. Vaqueros 

Formation. 

UC 7004. Branch of Las Llajas Canyon just north of northernmost extent of 1,500-foot contour, Simi Valley [Santa Susana 

quadrangle], Ventura County, Calif. Llajas Formation. 

UC 7100. Northwest cor. sec. 3, T. 3 N., R. 21 W., Ventura 

County, Calif. San Pedro(?) Formation. 

UC 7177. Upper fossiliferous ledge at San Joaquin coal mine, 

sec. 26, T. 20 S., R. 14 E., Coalinga quadrangle [Fresno 

County], Calif. Domengine Formation. 

UC 9069. In a cut on the Wynoochee River road about 135 m 

south of the railroad that goes up Black Creek, sec. 26, T. 18 

N., R. 8 W., Grays Harbor County, Wash. Montesano 

Formation. 

UC A-252. Along northeast-southwest ridge west of mouth of 

Wiley Canyon, south center of SEt;.; sec. 35, T. 4 N., R. 19 W., 

[Piru quadrangle], Ventura County, Calif. Vaqueros 

Formation. 

' UC A-527. On spur in large turn in Laguna Canyon (west side 

of canyon), San Joaquin Hills, Orange County, Calif. Uppermost Vaqueros Formation. 

UC A-543. At south end of long ridge, 4.2 km N. 21° E. of 

Abalone Point between forks of canyon, San Joaquin Hills 

[Corona quadrangle], Orange County, Calif. Vaqueros 

Formation. 

UC A-838. Bed of Middle Fork of Coquille River opposite 

Roseburg-Coos Bay Highway survey station 834 + 34, Coos 

County, Oreg. Lower part of Umpqua Formation. 

UC A-976. Big Tar Canyon, Reef Ridge, T. 23 S., R. 17 E., 

Cholame quadrangle [Kings County], Calif. Avenal Sandstone. 

UC A-1007. North bank of Los Gatos Creek, 90 m from mouth, 

NEt;.; sec. 10, T. 20 S., R. 14 E., Coalinga quadrangle [Fresno 

County], Calif. Domengine Formation. 

UC A-1165. East side of Big Tar Canyon at end of Eocene 

ridge, T. 23 S., R. 17 E., Cholame quadrangle [Kings County], 

Calif. Avenal Sandstone. 

UC A-1297. Sandstone cliff on northeast bank of Pleasants 

Creek opposite Brink Ranch House about 1 km east of B.M. 

257, 3 km south of Putah Creek, Wt/2 sec. 12, T. 7 N., R. 2 W., 

Napa quadrangle, Solano County, Calif. Markley Formation. 

UC A-1319. About 215 m south and 30 m west of the east 

quarter corner of sec. 26, T. 10 N., R. 3 E., Capay Valley 

quadrangle, Yolo County, Calif. About 185 m east of the 

contact between Cretaceous and Eocene rocks and about 60 

to 105m above base of Capay Formation, which here totals 

about 455 to 550 m. 

UC A-3519. Sea cliff near south end of bay. Coral reef exposed 

in cliff on north side of large southern arroyo at its junction 

with sea cliff. Rests on bed of calcareous algae and sandy 

marl with an irregular contact marked by boulders of 

volcanic material. Marquer Bay, Carmen Island, Gulf of 

California. Marquer Formation. 

UC A-3595. North of San Telmo Point, Baja California 

(approx. 25° N. lat). From sea cliff to north of large arroyo. 

In a massive calcareous pebbly sandstone carrying abundant areas, at top of thin-bedded cherty sands and shales. 

Approximately 45 m stratigraphically higher than Cornwallius teeth, but fragments of bone were noted scattered 

through section to about this level. San Gregorio Formation. 

University of California at Davis: 

UC D1063. Sec. 3, T. 33 S., R. 16 E., 345 m north, 220 m west, 

Reef Ridge quadrangle, Fresno County, Calif. Temblor 

Formation. 

UC D1065. Sec. 33, T. 22 S., R. 16 E. 185m north, 1,080 m west, 

Reef Ridge quadrangle, Fresno County, Calif. Temblor 

Formation. 

University of California at Los Angeles: 

UCLA 391. On Mulholland Drive, 3 km west, by road, from 

intersection of Laurel Canyon Road and Mulholland Drive. 

335m north, 215m west of SEcor. sec. 36, T. 1 N., R. 15 W. 

Road cut about 45 m north of a small basalt sill. Santa 

Monica Mountains, Los Angeles County, Calif. Topanga 

Formation. 

UCLA 4180. 105m north, 365m west ofNW cor. sec. 1, T. 32 S., 

R. 14 E., Nipoma quadrangle (1952 ed.), San Luis Obispo 
A90 PALEONTOLOGY OF CALIFORNIA AND BAJA CALIFORNIA 

County, Calif. Phoenix Member, Santa Margarita 

Formation. 

University of California at Riverside: 

UCR 4752 .. 185m S. 45° W. of UCR 4751, 535 m south, 745 m 

east of NW cor. sec. 32, T. 7 N., R. 21 W., Ventura County, 

Calif. Juncal Formation. 

UCR 6821. West side of Meier Canyon, 490 m north, 8 m east of 

hill1658, 269m due south ofhill1490, elevation 300m, Simi 

Hills, Ventura County, Calif. Upper part of Santa Susana . 

. Formation. 

UCR 7342. On low hill390 m NE 17° from hill3151 and 410 m 

NW 7° from hill 2160, Calabasas 7.5' quadrangle, Ventura 

County, Calif. Lower Santa Susana Formation. 

U.S. Geological Survey, Washington, D. C., register: 

USGS 2714. [Sec. 23, T. 5 N., R. 4 W., Vernonia quadrangle], 

Pittsburg, Columbia County, Oreg. Pittsburg Bluff 

Formation. 

USGS 3922. At head of Garnet Canyon on north side of Coyote 

Mountain [W1/2 sec. 3, T. 16 S., R. 10 E.], Imperial County, 

Calif. Imperial Formation. 

USGS 4473. Waldorf asphalt mine, 6 km south of Guadelupe 

[Guadelupe quadrangle], Santa Barbara· County, Calif. 

Careaga Sandstone. 

USGS 4504. San Julian Ranch, 16 km southeast of Lompoc, 

N1

/2 sec. 35, T. 6 N., R. 33 W., Santa Barbara County, Calif. 

Vaqueros Formation. 

USGS 4634. Hill south of oil well, 4.5 km southwest of Coalinga, 

in NE ~ sec. 12, T. 21 S., R. 14 E., Fresno County, Calif. 

Etchegoin Formation. 

USGS 4656. At northwest end of Anticline Ridge, 10 km northnortheast of Coalinga, SW ~ sec. 34, T. 19 S., R. 15 E. 

[Coalinga quadrangle, Fresno County, Calif.], Etchegoin 

Formation. 

USGS 15020. Solomon Hills, 5.4 km northeast of Los Alamos, 

275 m southeast of Pinal Dome Pezzoni 2 well, Santa 

Barbara County, Calif. Todos Santos Claystone member of 

the Sisquoc Formation. 

U.S. Geological Survey, Menlo Park, Calif. register: 

USGS M5219. Near base of cliff on north side of State Route 

105, 1,020 m S., 900 m W. ofNE cor. sec. 5, T. 14 S., R. 10 W., 

Bay Center 7W quadrangle, Pacific County, Wash., Mytilusbearing beds about 3.6 m thick overlying a 60-cm-thick 

Macoma bed. Unnamed formation of late Pliocene age. 

University of Washington [Seattle]: 

UW 63. East branch of Clemons logging road, south of 

Montesano, Grays Harbor County, Wash. NW ~ sec. 28, T. 

17 N., R. 7 W. Astoria(?) Formation. 

UW 239. East side of Cowlitz River 1.2 km above ferry near 

Gries Ranch, NE ~ sec. 25, T. 11 N., R. 2 W., Cowlitz County, 

Wash. Gries Ranch Formation. 

UW 256. In Union Pacific railway cut 400 m northwest of 

Galvin Station, sec. 27, T. 15 N., R. 3 W., Lewis County, 

Wash. Lincoln Creek Formation. 

UW 329. On north bank of the Cowlitz River at bend 1.5 to 2.5 

km east of Vader, sec. 28, T. 11 N., R. 2 W., Lewis County, 

Wash. Cowlitz Formation. 

UW 345. On Coal Creek, at large falls about 1 km below the 

schoolhouse, sec. 35, T. 9 N., R. 3 W., Cowlitz County, Wash. 

Cowlitz Formation. 

GEOLOGIC FORMATIONS CITED FOR 

OCCURRENCE OF PELECYPODS 

FAMILY NUCULIDAE TO FAMILY MALLEIDAE 

Name 

California: 

Alegria Formation 1 ..... . 

Ardath Shale... . ......... . Arroyo Hondo Shale Member, 

Lodo Formation 

A venal Sandstone. 

Branch Canyon Sandstone ......... . Briones Sandstone, San 

Pablo Group ....... . Butano Sandstone ............................... . Buttonbed Sandstone Member, 

Age 

. ...... Oligocene. . ........ Eocene. 

.................. Eocene. . ...... Eocene. 

. .... Miocene. 

. .. Miocene. 

. .... Eocene. 

Temblor Formation........... . ....................... Miocene. 

Capay Formation .......... : ......................................... Eocene. 

Capistrano Formation .......................................... Miocene and Pliocene. 

Careaga Sandstone .... . ...... Pliocene. 

Carlotta Formation ........ . ........ Pleistocene. 

Castaic Formation 1 ........................ . ...... Miocene. 

Cebada Member, Careaga 

Sand or Sandstone ...... ................................ ..Pliocene. 

Cerros Shale Member, 

Lodo Formation .............. . Chamisal Formation 1 ....... . 

Cierbo Sandstone, San 

Pablo Group .... Coldwater Sandstone and 

Coldwater Sandstone 

Member, 1 Tejon Formation .. Concord Formation 1 ..... . 

Cozy Dell Shale and Cozy 

Dell Shale Member, 1 

Tejon Formation ........... . Delmar Formation, La 

. .... Paleocene. ......... Miocene. 

. ... Miocene. 

. .... Eocene. . ..... Oligocene. 

. .... Eocene. 

Jolla Group ................................................................ Eocene. 

Dip Creek Formation 1 .......................................... Paleocene. 

Domengine Formation or Sandstone ............... . ................................. Eocene. 

'Etchegoin Formation ............................................ Miocene and Pliocene. 

Falor Formation ........................................................ Pliocene. 

Fernando Formation ............................................ Pliocene and 

Pleistocene. 

Foxen Mudstone ...................................................... Pliocene. 

Freeman Silt................ . ........................... Miocene. 

Gaviota Formation 1 ............................................ Eocene and Oligocene. 

Gould Shale Member, 

Monterey Formation ........................................ Miocene. 

Hambre Sandstone, Monterey 

Group .......................................................................... Miocene. 

Imperial Formation ................................................ Miocene or Pliocene. 

lone Formation .......................................................... Eocene. 

Juncal Formation .................................................... Eocene. 

Kirker Tuff ............. Oligocene. 

Kreyenhagen Shale or Formation .............................. Eocene and Oligocene. 

La Jolla Group......... . ................ Eocene. 

Las Virgenes Sandstone .................................... Paleocene. 

Lindavista Formation ............. Pleistocene. 

Llajas Formation....... . ........... Eocene. 

Locatelli Formation.................. . ............. Paleocene. 

Lodo Formation.. ........................... . .......... Paleocene and Eocene. 

Lomita Marl Member, 

San Pedro Formation ...................................... Pliocene. 

Los Tularcitos Member, 1 

Chamisal Formation .................... . . .... Miocene. 

Markley Sandstone Member, 

Kreyenhagen Formation .. , ......................... Eocene. 

Martinez Formation ........... . ............... Paleocene. 

Marysville Claystone Member, 

Meganos Formation.......... . ............... Paleocene. 

Matilija Sandstone ................................................ Eocene. 

'Stratigraphic nomenclature used is that of the reference cited in the text and does not necessarily accord with that of the U.S. Geological Survey. 
TERTIARY MARINE PELECYPODS: NUCULIDAE THROUGH MALLEIDAE A91 

McLure Shale Member, 

Monterey Formation ........................................ Miocene. 

Meganos Formation .............................................. Paleocene. 

Merced Formation .................................................... Pliocene and 

Pleistocene. 

Monterey Formation, Shale, 

M~irGs~~ast~~·~·i·::::::::::::::::::::::::::::::::::::::::::::::::::::::::~~~~~~~- N eroly Sandstone, San 

Pablo Group ............................................................ Miocene. 

Niguel Formation .................................................... Pliocene. 

Ohlson Ranch Formation 1 •.••••....•................... Pliocene. 

Olcese Sand .................................................................... Miocene. 

Orinda Formation, Contra 

Costa Group ............................................................ Miocene. 

Oso Member, Capistrano Formation .................................................................. Miocene. 

Oursan Sandstone, 

Monterey Group .................................................... Miocene. 

Palos Verdes Sand .................................................. Pleistocene. 

Pancho Rico Formation ...................................... Miocene. 

Paso Robles Formation ...................................... Miocene, Pliocene, 

and Pleistocene. 

Phoenix Member, 1 Santa 

Margarita Formation ...................................... Miocene. 

Pico Formation .......................................................... Pliocene and 

Pleistocene. 

Pleito Formation ........................................................ Oligocene. 

Pomponio Mudstone Member, 

Purisima Formation .......................................... Pliocene. 

~~rr:~ ¥~~~~t:i~~·::::::::::::::::::::::::::::::::::::::::::::::::::::::~li~~~~·e. Purisima Formation .............................................. Miocene and Pliocene. 

Rices Mudstone Member, San 

Lorenzo Formation ............................................ Eocene and Oligocene. 

Rincon Shale ................................................................ Oligocene and 

Miocene. 

Rio Dell Formation, Wildcat Group .......... Pliocene and 

Pleistocene. 

Round Mountain Silt ............................................ Miocene. 

Sacate Formation 1 .......•.••...•.•................................. Eocene. 

Saltos Shale Member, 

Monterey Shale .................................................... Miocene. 

San Diego Formation ............................................ Pliocene. 

San Emigdio Formation .................................... Eocene and Oligocene. 

San Joaquin Formation ...................................... Pliocene. 

San Juan Bautista Formation1 .................... Eocene and Oligocene. 

San Lorenzo Formation ...................................... Eocene and Oligocene. San Pablo Formation or Group .................... Miocene. 

San Pedro Formation ............................................ Pliocene and 

Pleistocene. 

San Ramon Sandstone ........................................ Miocene(?). 

Santa Barbara Formation ................................ Pliocene and 

Pleistocene. 

Santa Cruz Mudstone .......................................... Miocene. 

Santa Margarita Formation .......................... Miocene. 

Santa Susana Formation 1 ................................ Paleocene and Eocene. 

Santos Shale Member, 

Temblor Formation ............................................ Oligocene and 

Miocene. 

Saugus Formation .................................................. Pliocene and 

Pleistocene. 

Scotia Bluffs Sandstone ...................................... Pleistocene. 

Sespe Formation ........................................................ Eocene to Miocene. 

Silverado Formation .............................................. Paleocene. 

Sisquoc Formation .................................................. Miocene and Pliocene. 

Sobrante Sandstone .............................................. Miocene. 

Tahana Member, Purisima 

Formation .................................................................. Miocene and Pliocene. 

Tejon Formation ........................................................ Eocene. 

Tern blor Formation ................................................ Oligocene and 

Miocene. 

Tice Shale, Monterey Group ............................ Miocene. 

Tierra Redonda Formation .............................. Miocene. 

Timms Point Silt Member, 

San Pedro Formation ...................................... Pleistocene. 

Tinaquaic Sandstone Member, 

Sisquoc Formation ............................................ Pliocene. 

Todos Santos Claystone Member, 

Sisquoc Formation ............................................ Miocene and 

Pleistocene. 

Topanga Formation .............................................. Miocene. 

Towsley Formation ................................................ Miocene and Pliocene. 

Tumey Formation 1 ................................................ Oligocene. 

Twobar Shale Member, San 

Lorenzo Formation ............................................ Eocene. 

Vacaville Shale 1 .............................................•...•...•.. Eocene. 

Vaqueros Formation .............................................. Oligocene and 

Miocene. 

Wheatland Formation 1 ....................................... Eocene and Oligocene. 

Wildcat Group....................................... . .... Pliocene and 

Pleistocene. 

Wygal Sandstone Member, 

Temblor Formation ....................... . .. Oligocene. Baja California Peninsula: 

Almejas Formation................ . ..... Pliocene. 

Carmen Formation................... . ..... Pliocene. 

Gloria Formation........... . .. Pliocene. 

Infierno Formation... . ............................. Pliocene. 

Isidro Formation ................................... Miocene. 

Marquer Formation.. .......................... . .... Pliocene. 

Rosarito Beach Formation ......... Miocene. 

Salada Formation............... . .... Oligocene. 

San Gregorio Formation .......................... . ..... Pliocene. 

San Marcos Formation... . ..... Pliocene. 

Tepetate Formation.. . ..................................... Paleocene and Eocene. 

Tortugas Formation ..................................... Miocene. 

Oregon: 

Empire Formation ....... . ..................................... Miocene. 

Pittsburg Bluff Formation ............................... Oligocene. Washington: 

Gries Ranch Formation ..................................... Oligocene. 

Lincoln Creek Formation ................................. Eocene to Miocene. 

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TERTIARY MARINE PELECYPODS: NUCULIDAE THROUGH MALLEIDAE A93 

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1 pl., 1 text fig. 
A 

Aclwrnx. 30. 31 

dunnenxi.~. ,'JJ; pl. 4 

jolnwmi, 9/; pl. 4 

(Acharax)joh111wni, Solenl'ya, 31 

Acila, 8. 20 

blancoen.~i.~. 13 

caxtren.~in, 12, 13 

COnl'(l(/i, 11, 12 

dalli, 11 

dccixa, 10 

empiren.~ix, 12 

gabbimw, 10 

getlyxburgenxix, 9 

/ajo/laensis, 10 

miral!ilis, 9 

11111/n, 11. 12 

11111 rkleyensix, 11 

semiroxlrala, 9 

zone, 13 

(Aci/a), 8 

gel/ysbm·gell,qi.~. 6, 9, 11: pl. 1 

xemil'oxlrata, 6, !J; pl. 1 

(Truucaci/a), !J 

caxlreuxix, 6, /2: pl. 1 

COIII'adi, 6, /2; pl. 1 

dalli, 6. //:pl. 1 

decixn, 6. JO; pl. 1 

I!'IIIJJii'I!IIHiH, 6, /2; pl. 1 

mula, 6. 11. 12: pl. 1 

nehaie·11umHiH, 11 

HhiiiiHII'di, 6, /0', pl. 1 

(Aci/a), Acila, 8 

coul'ruli, Nucula, 12 

dalli, Nm:u/a, 11 

deci.•a. Nucu/a, 10 

getty,q/mr(JCIIHiH, Acila, 6, 9, 11: pl. 1 

NrtcJtla, 9. 

alankensis, Nucrtla, 9 

semirtmlmta, Acila, 6. 9: pl. 1 

Nrtcula, 9 

xllllllllll'di, N11c1tla, 10 

lllilill'alel'en,qi.~. Nltclt/a, 10 

IICI/111, IA?dll, 17 

N~tcu/ana, 21 

adamsimw. Mutil11s, 69 

adamsit1111111, Aeidimutil11x, 70 

/JI'acllidoutes (Aeidimyti/11.~). 60. 7(i; pl. 17 

MutiluH, 70 

Ad11/a, 79, 74 

diegt!nsiH, 73, 74 

mckwi[lhli, 60. 74: pl. 19 

Af!idimytiluH, adamsianus, 70 

(At!idimytiliiH), f)!} 

adrmrsir1111111, /Jmchidoule,q, 60, 70; pl. 17 

IJI'achidon/1?.~. 60 

gabbi, /Jmchidontes, 60, 69; pl. 17 

llfJIIHHizi. Solemya, 31 

a/aeformis, Corbula. 15 

/,eda, 15 

Nucult11w, 16 

(Sacr.elia), 14, 1 5; pl. 2 

a/a·mademdx, Pinna, 80 

a/amedenHiH, Atri1w. 79, 80; pis. 23. 27 

Pimw. 80, 81 

(Atrina), 80 

ala11ktmHi.•. Nucula (Acila) gelly.~bu·I'Oell.~i.~. 9 

a/cimu, Anada1·a (Cmwarca), 46 

Alegria Formation, 11 

alexi, Exputrms, 86 

Nauadina (Expulens), 86, 87: pl. 26 

aliformis, Col'hu/a, 15 

INDEX 

[Italic page numbers indicate major references] 

altiobliquus, BmchidouteH, 67 

Bmchidonles (Bmchidonles). 60, 67; pl. 17 

Modiolus, 67 

mne/ga, Nuculuuu (Sncce/la). 19 

Alladam,96 

camuloensis, 43 

chiriq11ie11.~is toroensi.~. 42 

co11gestu. 46 

deviucta, 37, 38, 39, 40, 41 

montesanoann, 41 

formosu, 40 

grandi.~. 43 

hamelini, 45 

lakei, 37. 38 

mediaimpressu, 37, 39 

media-impre.~su, 42 

mo11lereyana, 39. 41 

mun/e,qa IIOOIIa, 39, 40 

multico.•tatu, 43 

obispoanu, 39, 44 

obi.~poanu, 44 

perdi.~pari.•. 44 

o.•monti. 37, 38. 39, 40 

xaulac/aralla, 45, 46 

sn11tuna, 42, 43 

seclicoslata. 40 

sespeensis. 45 

.~inilis, 42 

submontereyana, 37 

topa11gaensi.•. 40 

trilineala. 38, 40, 41 

ca.lcarea, 41 

canalis, 41 

triliueata, 41 

mnderhoofi, 44 

weddlei, 43 

(Anudara), 32. 96 

calcarea, 32 

canalis, 32 

cal'rizoensis, 32, 40: pl. 7 

devine/a, 32. 38; pis. 6, 7 

devincta, 38 

montesanoana, 38, 39 

lakei, 32. 97; pl.6 

media impre.~sa, 32, 98; pl. 7 

mediaimpres.•a.. 38 

submontereyana., 37 

microdonta, 46 

montereynna. 32. 99, 44: pl. 7 

monte.•anoana, 32, 99; pl. 7 

o.~monti, 32. 96; pl. 6 

st·rongi, 32, 41: pl. 6 

submontereyana, 32. 37; pl. 6 

/opangaensis, 32, 40: pl. 8 

trilineata, 32. 38, 40: pl. 7 

calca.rea., 41: pl. 8 

canalis, 41: pl. 8 

tri/ineata.. 40, 41 

(CIIIIearcn), 44 

a/cima, 46 

hame/ini. 45 

rir:ula.ta. 45 

thalia, 46 

rmnder·hoo/i. 44 

(Graudiarca) grandi.•. 42 

(Larkin in) ca.muloensis, 43 

{jrandi,q, 42 

mltlticosta.ta., 43 

sa.nlana xa.ntana, 42 

weddlei, 43 

(Scapharca) obispoa.na obispoana, 44 

obispoana perdi.qparis, 44 

santacla.rana., 44 

(Anndara), Anadara. 96 

calcarea, A11adara, 32 

caua/i.•. Auadara, 32 

carrizoeusi,q, Auadara, 32, 40: pl. 7 

der·incla, Auadaru. 32. 38; pis. 6. 7 

der·incta, Anadara, 38 

montesuuouuu, Anadura, 39 

lukei, Auudara, 32. 37; pl. 6 

mediuimpre.•sa, Anadara, 32, .98; pl.7 

mediaimpre,q,qa, Auadara, 38 

submonlereyana, Anadara, 37 

microdonta. Anadara, 46 

monlereyanu, Aundara, 32, 99; pl. 7 

mo11tesauoann. Auudara, 32 . . 'J9; pl.7 

OMIIOIIIi, Anadara, 32, 96; pl. 6 

santac/urana, Arcu, 44 

suutanu, Area, 42 

lf'eddlei. Area, 43 

se.•peensi.•. A rca, 45 

.•trongi, Ana.dara, 32, 4/: pl. 6 

submontereyana, A1wdara, 32. 37; pl. 6 

topangaensis, Anndara, 32. 4(}; pl. 8 

trilineata, Anadara. 32. 40: pl. 7 

calcarea. Anadara, 41; pl. 8 

canalis, Auadara, 41: pl. 8 

triliueata, Anudara, 40 

Anadarinae, 96 

applinae, T11rritel/a 1/r:asrlllfl, 10. 23, 29, 34. 50. 55, 85 

aquifanica, Mytilus, 65 

Area, 31 

auriculata. 46 

hnrbata, 36 

barkeriarra, 36. 37 

biloba. 47 

boucurdi, 32, 33 

camuloeusis. 43 

en nal is, 40. 41 

c/a·rki, 46 

cougesta, 46 

der:irrcta, 38 

mo11tereyarra. 39 

moute.•arroana, 39 

eba. 47 

galei, 45 

graudi.~. 42 

lramelini. 45 

lrornii. 48 

el11sa, 48 

imprar:ida, 36, 37 

kobeltianu, 34 

lakei. 37 

/eptogrammica. 32, 33, 34 

111 icrodo:nta, 36, 38. 40, 46 

montereyunn. 39. 41 

multicostata, 43 

mutabilis, 33 

nuuicula termimmrboni.~. 33 

obi.•poana, 44 

osmonli, 36 

perdispari.~. 44 

perrrula, 15 

procumbens, 38 

reer:euna, 35 

rir:ulata, 45 

santamariensis. 32. 33 

sespeensis, 45 

,qisquocensis, 32, 33, 34 

trilineatct, 40 

waslringtoniana., 32. 34 

(Anadara) santaclarana. 44 

santana., 42, 43 

u:eddlei, 43 

sespeen,qis, 45 

A99 
AlOO PALEONTOLOGY OF CALIFORNIA AND BAJA CALIFORNIA 

Area-continued 

(Area), .'JJ 

hawleyi, 8 I. 32; pl. 5 

leplo[Jrammica, 82; pl.6 

multicostata camuloensis, 43 

santnmariensis, 32, .'J.'J; pl. 5 

sisquocen.~is, 32, 88; pl. 5 

termimnnhonis, 32 . .'J.'J; pl. 5 

trilineata calcarea, 41 

(Bm·hatia.) .~tmn[Ji, 41 

(Scaphwrca) media.impres.<a. 38 

mic1·odonta, 38 

suhmontereyana, 37 

(Area), Arw . .':Jl 

hatoleyi, Area, .'JI. 32; pl. 5 

leptoormnmica, A1·ea, 82; pl.6 

multieostatn cmnu./oensis, Area, 43 

santamnriensis, Area, 32. ,'J.'J; pl. 5 

.<i.<quocensi.<. Area, 32, 88; pl. 5 

tenninumhoni.<. Area, 32. 88; pl. 5 

tn'linenta calcarea. Area, 41 

Arcidae. I. .'1 I. 32 

Arcinae, .'JI 

Arcopsi.<, 4 7 

(Arcop.<i.<), 4 7 

eha. 4 7; pl. 10 

(Arcopsis). Arcop.~i.<, 47 

elw. A reo psis, 4 7; pl. 10 

arctica, Nncula, 27 

Yoldia, 27 

Ardath Shale, 10. 29. 34, 35. 46, 47, 48, 49, 50, 55. 85; 

pis. 1. 4, 5, 10. II. 26 

arnuldi, Mytihm, 62 

Mytilus (Mytilus), 60. 62; pl. 14 

ascia, Mytilus, 62 

Myti/u.< (MyW.us), 60, 6'2; pl. 14 

Astoria Formation, 12, 18, 19. 23. 38; pis. I. 2, 3. 6, 7 

asloriana, Litorhadia, 14, 28; pl. 3 

Yo/din. 28 

(Portlnndia). 23 

Atri11a, 80 

alameden.<is. 79. 80, pis. 23, 27 

bicuneata, 79, 81; pl. 23 

stephens/, 79, 81; pl. 24 

venturensis. 79. 80; pis. 23, 27 

(Atrina) alameden.<is, Pinna. 80 

hicuneata, Pinna. 81 

uenturenxis. Pinna. 80 

auriculata, Area, 46 

Avenal Sandstone, 7, 10, 16, 17, 23. 55, 56. 67. 68, 82. 

86; pis. I. 2. 12 

A uicula pellucida, 82 

AJ:inea har/)(lrensi.<, 59 

cur, 55 

profunda, 58 

.<eptentriomtlis suhohsoleta, 52 

(Limopsis) sa[Jittatn, 54 

(Axinola), Glycymeri.~ . .57 

grewin[Jki, Glycymeri.<. 50, .58; pl. 12 

profunda, Glycymeris, 50, .58; pl. 12 

B 

bakeri. ldasola. 60, 78; pl. 21 

Modiolus. 78 

balboae, Nuculana. 19 

balbomw. Nucula (Ennucula), 8 

Nucula (Leionucula). 6. 8; pl. 1 

barbaren.<i.~. Axi11eo, 59 

Glycymeris, 58. 59 

hm·bata, Area, 36 

Barhatia, 84. 47 

clljfen.<i.<, 34 

illota. 36 

landesi, 34 

mm·.<ei, 34 

pseudoillota. 36 

.<uzzalloi, 34 

wuodfordi, 46 

(Barbatia), 34 

morsei, 32, 34; pl. 5 

Barbatia.-continued 

( Cucu./ laearca.), 34 

hramkampi, 32, 8.5; pl. 5 

cliffensis, 32, 84; pl. 5 

reeveana, 32. 3.5; pl. 6 

reeveana, 35 

(Fu[Jleria), 35 

illota, 32. 86; pl. 6 

pseudoillota, 32, 8.5; pl. 6 

(Obliqua.rca) morsei, 34 

(Barba.tia), Barhatia, 84 

nwr.~ei, Barbatia, 32, .'14; pl. 5 

.<tron[Ji, Area, 41 

barkeriana, Area, 36. 37 · 

barrow.<i, Pinna, 79 

Pinna (Pinna). 79: pl. 22 

Bear Lake Formation. 66 

berinoiana, Yoldia., 26 

Yoldia (Mega.yoldia), 14. 26; pl. 3 

berryi, Pteria, 81. 82; pl. 24 

bicolor, G/ycymeris, 53 

bicuneata. Atrina, 79, 81; pl. 23 

Pinna, 81 

(Atrina), 81 

hi/ida. Nucula, 6. 7; pl. 1 

bljurca.tus, Mytilus, 67, 71 

ob~;oletus, 71 

Sept1jer, 60, 67, 69. 70, 71 

(Septi/er), 71; pl. 18 

biloba, Area, 47 

Nucu/a, 47 

birchi, Nucula, 7 

Nucula (Em111cula), 7 

(Leionucula), 6, 7, 8; pl. 1 

bhmcoen.<is. Acila, 13 

Brachidontes, 66. 67, 68. 69 

altiob/iquus. 67 

cowlitzensis, 66, 67. 68 

/au.·soni. 68 

.<usanaen.~is, 67 

(AeidimyWu.~). 69 

ndamsianus, 60, 70; pl. 17 

ga.bbi. 60, 69; pl. 17 

(Brachidontes), 66, 67, 70 

a.ltiobl iquus, 60, 67; pl. 17 

cooperi, 60, 67; pl. 18 

cowlitzensis, 60, 66; pl. 17 

d ichotumus, 60, 68; pl. 17 

kirkerensis, 60, 68; pl.l7 

lawsoni, 60, 68; pl. 17 

susanaensis. 60, 67; pl. 17 

(Scolimytilus), 68 

nwrgaritana, 60, 69; pl. 17 

multiradiatus, 60, 69; pl. 17 

subconvexu.<, 60, 69; pl. 17 

(Brachidontes) a.ltioh/iquu.<, Brachidontes, 60, 67; pl.l7 

Brachidontes, 66, 67, 70 

cooperi, Bra.chidontes, 60. 67; pl. 18 

cowl itzensis. Brach idontes, 60, 66; pl. 17 

Volsella, 66 

dichotomus, Brachidontes, 60. 68; pl. 17 

kirkerensis, Brachidontes, 60, 68; pl. 17 

Ia wson i. Brach idontes. 60. 68; pl. 17 

su.qanaensi.<. Brachidontes, 60. 67; pl. 17 

sta.lden·, Volsella, 73 

(Brachydontes) coll'litzen.<i,q, Modiolus. 66 

playasensis. Modiolus, 68 

bramkampi, Barbatia (Cucullaearca), 32. 3.5; pl. 5 

Branch Canyon Sandstone. 37 

bra nneri, Glycyme1·is, 51 

Glycymeris (Glycymeris). 50, .5I; pl. 10 

Briones Sandstone, 18. 19. 20, 25, 26. 38. 39. 41. 58. 65, 

69, 75, 76; pis. 2. 17, 20 

Butano(?) Sandstone. 17 

Buttonbed Sandstone Member, 19. 63 

bwcaldi, Glycimeris. 51 

Glycymeri.<, 51. 52 

(Glycymeris), 50, .51; pl. 12 

Byssoarca illota, 36 

c 

cahillensis. Leda, 17 

Nucu/ana (Sa.ccella). 14. I7; pl. 2 

calcarea, Anadara trilineata, 41 

A nadara (A nadara), 32 

(Anadara) trilineata. 41; pl. 8 

Area (Area.) trilineata, 41 

calcifer. Spondylus, 84 

ca./1jornianus, Myti/u.~. 61 

Mytilus (Crenom.ytilus), 61 

(Mytilu.~). 60. 61; pl. 13 

californica, Pulvinite.<. 8.5, 86; pl. 26 

ca/1/o'rllicus, Mytilus, 64, 65 

ca.lkinsi, Nucula.na. 19 

callimene, Nuculana, 19 

Calorhadia, 23 

parkei coosen.<is. 23 

(Litorhadia) fresnoen,qis, 22 

camuloensis, Anadara, 43 

Anadarr1 (Larkinia), 43 

Area, 43 

(Area) mu/t.icostata, 43 

Larkinia, 32. 48; pl. 8 

canal1jer. Ectinochilus, 49. 50, 55, 67. 82 

canalis, Anadara (Anadara), 32 

Anadara (Anadara) trilineata, 41; pl. 8 

trilineata, 41 

Area, 40. 41 

capa.x. Modiola. 76 

Modiolus, 76. 77 

(Modiolus), 60. 76; pl. 20 

Vol.<ella, 76 

Capay Formation, 6, 7. 10. 16. 22, 30. 31. 49. 55; 

pis. 1. 4 

Capay megafauna! Stage, 31 

Capay megafossil Stage, 22 

capayensis, Nucula, 7 

Nucula (Nucu/a), 6; pl. 1 

Capistrano Formation, 9. 13. 20. 33. 41 

Careaga Formation, 36. 41 

Careaga Sand, 20 

Careaga Sandstone, 20. 21. 33. 34, 36. 41. 64; pis. 2, 5. 6 

Carlotta Formation. 61 

Carmen Formation, 43. 83 

carnarowmsis, Yoldia, 26 

Yoldia (Kalayoldia), 14, 26; pl. 4 

carpenteri, Modiolus, 77 

Modiolus (Modiolus), 60. 77; pl. 20 

carrizoensis, Anadara (Anadara), 32, 40; pl.7 

Castaic Formation. 19. 41. 58. 64 

castrensis. Acila, 12. 13 

Acila (Tnmcacila). 6. I2; pl. I 

Nucula. 12 

Cebada Member, 20. 21. 33. 34. 36, 41; pis. 2. 5. 6 

cellulita, Leda, 20 

Nuculana, 20 

(Saccella), 14. 20; pl. 2 

Saccella, 20 

Cerros Shale Member, 7, 10. 16. 22. 47. 48. 55. 56, 87 

Chamisal Formation. 63 

chaneyi. Nuculana (Saccella), 14. 16, 23; pl. 2 

chehalisensis, Leda. 18 

Malletia, 13, 30 

Nuculana, 18 

(Saccella), 14, 18; pl. 2 

Portlandia, 21. 30 

(Portlandia), 14, 80; pl. 4 

Yoldia, 21 

chemnitzii, I.<ognomon, 84 

chenui, G1·eoariel/a, 60, 72; pl. 19 

Mytilus (Modiola), 72 

Chico Group, 7 

chiriquiensis toroensis, Anadara, 42 

Cierbo Formation, 58, 63, 76 

Cierbo Sandstone, 12. 26. 41. 58, 70, 76, 81 

Clallam Formation, 25 

c/a.rki, Area. 46 

Lithopha[Ja .. 73, 74 
clarki-continued 

J .. ilhopha(la-continued 

(l .. ithopha(ln), 60, 78; pl. 19 

Modio/u.~ (Modio/u,q), 60. 78; pl. 21 

Vut.~et/a, 87; pl. 26 

cliffen.~iH, Barbal.in, 84 

BUI·/)(1/.ia (Cueullrreal't:u), 82. 84; pl. 5 

(CneHierium) en.~ifem, Yoldia, 14. !!7; pl. 4 

Hci.~.~u·rala. Yoldia, 14. !!7; pl. 4 

Heminudu. Yoldia, 14. !!8; pl. 4 

.~lri(/nl.n, Yoldia, 14. 27; pl. 4 

Yoldia, 27 

r.oalint/l!ll.~i.~. Crenomut.i/u,q, 64 

GltiCfflllf!ri.~. 58 

Myti!ltH, 62. 68. (i4 

(C1·enomyt.i/u.~). 60, 64; pl. 15 

(Mytilocrmclw). 62. 64 

Septifm·. 60, 71 

(Seplifer). 71; pl. 18 

.~l.r!l'lthel'fli, Mytilu.~ (Crcnom!lti/u.~). 64 

coarc/al.a, Gn:(luriella. 72 

coe/ata, Nur:ula, 19. 

Coldwater Sandstone. 10. 82 

collillltH, Glo.~HitH (Per:tum:ul11s), 59 

COIIIJ!I'f!ll/111.~. /..~imop.~i.~. 59 

r:oncr.plioni11, Nur:ulana, 15 

Concord Formation. 9. 11 

r.rmdoni, Myl.i/u,q, 61 

M!lt.ilu,q (M!It.illl.~). 60. 61; pl. 18 

COII{/f!Hia. Anrrdara, 46 

Arr.rr. 46 

Clllll'adi, Ar:ilrr, 11. 12 

Ar:i/rr (7'nwcru:ila), 6. 12; pl. 1 

Nllcula(Ar:ila), 12 

r:on/rru:/n, Modioln, 76 

Modio/1111 (Modiolu.~). 60, 7(j; pl. 20 

r:rwpai lrmui.~.~tmrr. Yo/din, 24 

/Jmr:hidtlllles (IJnu:hidonlr.H), 60. 67; pl. 18 

Nur:ula, 6, 7 

(Nucllln), (j; pl. I 

)'oidia, 26,28 

(Knln!lolrlin), 14. 24 

COOJIIIri i .~upriiiiiOIIICrl!/ll?lll<i.~. }'o/rf in, 25 

lenuiH.~ima, }'oldirr, 25 

)'oldin, 24, 25 

(Krrlnyoldia), 25; pl. 3 

Coos Conglomerate Member. 12 

r.oo.~en.~in, Calorlwdia parkei, 23 

Hil(larrfirr parkrn', 14. 17. 28; pl. 3 

Nllcllltll/11 pnrkei. 17. 23 

cor, AJ:inen, 55 

Pr:ctuncu/u.~. 55 

Col'lmla alrufonnix, 15 

alifrwmiH. 15 

(lab/Ji, 15 

(lnbl!ii. 15 

(Crml.dlo/r:dn) mnn:lla. Nw:ulann, 15 

N11culana, 14. 15 

power.~i. Nuc11/ana, 14. 15; pl. 4 

Cowlitz Formation. 51. 66; pis. 12. 17 

cotditzenHiH, f:lrachidontc.q, 66, 67. 68 

/Jrachidrmlc.~ (BmchidrmtcH), 60. 66~ pl. 17 

Modio/u.~ (f:lrrrchydrmtex), 66 

Nuculr111a, 17 

(Sar:cr.llrr), 17 

Volxel/a (Bmchidrm/e.~). 66 

Cozy Dell Shale, 32 

cmx.~ilr.,qfa, MyliluH, 64 

Cre1wlla, 71 

rfet:UHHafa, 60, 7/, 72; pJ. 18 

inf/rrta, 60. 72; pl. 18 

Crenellinae. 60. 71 

Ct·tmomyliluH, 64, 65 

coalillfltmHi.~. 64 

kcu·i, 63 

f.l'aiiiJiCIHI?IIHill, 63 

(CI·enomyti/u.~) crrliforniamr.q, MyliluH, 61 

coaliii{/IIIIHiH, Mytil!tn. 60, 64; pl. 15 

.~lcl'ltbcl'(li, Mytilun, 64 

INDEX 

( Cre11omytilu.~ )-continued 

expal/.qlls, Myti/us, 60. 68; pl. 15 

kell'i, Mytilus, 60, 68; pl. 15 

matheu·,qonii, Myt.ilus, 60, 68; pl. 14 

Myti/u,q, 62. 64 

perrini. Mytilu,q, 60. 63. 65; pl. 14 

schencki, Mytilus, 60, 64; pl. 16 

xternber(li, Mytilu.q, 60. 64; pl. 16 

trriiiiJJasensis, Mytilus, 60, 68; pl. 14 

Cucullaea, 4 7 

mnlhe/l'sonii. 47; pl. 10 

morani, 47; pl. 10 

(Cucullaeurca), Ba.rbatia, 84 

bmmkampi, Ba.rba.tia. 32. 8.5; pl. 5 

cliffen.qi.~. Ba.rbatia, 32. 84; pl. 5 

reeveana, Barba.tia, 32. 8.5; pl. 6 

reeveana. Barbatia, 35 

Cucullaeidae, l. 4 7 

(Cu11earca) alcima, Anadara, 46 

hame/ini. Anadara, 45 

Scapha.rca. 32. 4.5; pl. 9 

rivulata,Anadara, 45 

Scapharca, 32. 45; pl.9 

santaclarana, Scapharca, 32. 44; pl. 9 

Scapharca, 44 

tlwlia, Anadura, 46 

t:rt.llderhoofi. A nada.rn, 44 

Scapharca, 32. 44; pl. 9 

Cyrillamunita. 59 .• 

D 

dalli, Aci/a, 11 

Acila (Tnwca.cilrr), 6, 11; pl. 1 

Limopsis. 59 

Nucu/a.(Acilrr), 11 

decisa. Acila, 10 

Acila (1'1'1/llcacila), 6. JO; pl. 1 

Nucula,1 

(Acila), 10 

decussata, Crenelln. 60. 71, 72; pl. 18 

Myti/us, 71 

de/aguerme zone, Turritella. 16 

de/rrquerrrrc zone, Turritella. schencki. 10 

Delmar Formation, 34. 66. 73. 74; pl. 19 

democracicma., Glycymeris, 53 

denominrr.ta. J .. eda. 21 

Nuculatw, 21 

(Srrccella). 14, 2/; pl. 2 

de11satrr. Mulinirr. 40 

det:inctu, Anadara, 37. 38. 39. 40. 41 

A11a.dura (Anadara), 32. 88; pis. 6. 7 

(Anudarrr) dellillcta, 38 

de1:incla. Anadrrrrt (Anada.ra). 38 

monlereya.na, Anadam, 41 

Arcu, 39 

mollleHanoa·llfl, Anadara, 41 

Anadara (Annda.ra). 39 

Area, 39 

Arcu, 38 

(Diberus). Lithophaga. 78 

plumula, Lithophaga. 60, 78; pl. 19 

dichotomus, Bmchidontes (B;·achidon/es), 60. 68; pl. 17 

Myti/us, 67 

Sepl.ifer, 67. 68. 71 

diegensi.q, Adulu, 73. 74 

Dip Creek Formation. 47 

direc/us, Modiolus, 76 

Modiolus (Modiolu.~). 60. 76; pl. 20 

di11aricata. Nucula, 12 

Domengine Formation, 7. 10. 16. 17, 34. 47, 49, 55. 56. 

67. 79, 82. 85. 86; pis. 12. 18. 22. 24. 26 

Domengine horizon. 54 

Domengine megafossil Stage. 22 

Domengine Sandstone. 23 

Dreissensia. 65 

dul/1/ellsis, Achamx. 81; pl. 4 

Solemya. 31 

duprei, Yoldia, 29 

duttonae, Ju.piteria. (Ledin a.), 22 

Ledina, 14. 22; pl. 3 

E 

eba. Area, 47 

Arcopsis (Arcop.~is), 1,7; pl. 10 

Ectinochilus caualifer, 49, 50, 55. 67, 82 

supmp/icatus, 49. 50. 55, 67 

edulis, Myti/u.~. 61 

Mytilus (Mytilus). 60. 61; pl. 13 

elegnns. Sept1jer, 60, 67, 70 

Sepl.ifer (Septifer). 70; pl. 18 

e/maua, Nuculana (Ochsneri), 19 

elon(lorostrata, Leda, 15 

Nuculana (Nucu/ana). 14. 15; pl. 3 

dusa., Area hornii. 48 

Pachecoa (Pachecoa.) hm·nii, 48; pl. 10 

Trigonodesma horuii, 48 

e/usus, Pachecoa hol'llii, 49 

AlOl 

Empire Formation, 12, 19, 27, 52. 58. 76; pis. l. 4. 12, 

13. 16, 20 

empire11sis, Acila, 12 

Acila (Truuca.cila). 6, 12; pl. 1 

(Ennucula) balboa.na., Nuculu., 8 

birchi. Nucula. 7 

ensifem, Yoldia, 27. 28 

Yoldia (Cnesterium). 14, 27; pl. 4 

eocenica, Glycymeris. 50 

Glycymeris (Glycymeris), .50; pl. 12 

Petu 1/Cidu.~. 50 

epacris, Nuculana. 18, 19 

Etchegoin Formation. 13. 20, 25. 41. 57. 58. 63. 64. 71. 

76. 77; pis. 15, 18 

Eugene Formation, 74; pl. 19 

eugeuensis, Modiolus, 74 

Modiolus (Modiolus). 60. 74; pl. 19 

Volsella. 74 

evermunni. Glycymeris, 50. 56 

Glycymeris (Tucetona), 50 . .56; pl. 12 

eJ:igurr. Nucula, 8 

Nucula (Lamellillucula.), 6. 8; pl. 1 

(Nucula), 8 

expr111sus. Myti/u.~. 63, 65. 74 

Mytilus (Creuomytilus), 60, 68; pl. 15 

Mytilus mathell'sonii. 63 

E:rpulens alexi, 86 

1/ajaseusis. 86 

(Exputens) alexi. Naya.dina. 86, 87; pl. 26 

1/ajasensis. Nayrulina, 86; pl.26 · 

Naya.diua, 86 

F 

fabata.. Leda. 21 

Nuculana (Sacce/la), 14. 2/; pl. 2 

Falor Formation. 27. 41. 61 

Felicia. 58 

phrear, 50, 59; pl. 13 

(Felicia) phreur, Limopsis, 59 

Fernando Formation. 8, 9. 13. 14. 15. 20. 21. 22. 25, 28. 

31, 33. 34. 36, 41. 43. 57. 59, 61. 64. 72. 73. 

76; pis. 2. 4. 5. 13. 18 

ficus. Mytilu.~. 61 

flabellata, Modiolus. 76 

flnbellatus, Mytilus (Modiola), 76 

formosa, Anadara, 40 

fornicata, Modiola, 77 

fornicatus, Modiolus. 77 

fossa, Leda, 13 

Nuculaua, 13 

·(Nuculana), 18. 14; pl. 2 

sculpla, Leda, 13 

Nuc111a11a (Nuculana). 1.'J. 14; pl. 2 

Fossil localities. 87 

Foxen Mudstone. 20. 34. 41. 64 

Freeman Silt. 12 

fresuoensis, Calorhadia (Lilorhadia), 22 
A102 

fre.~noen.~is-continued 

Glycimeris. 55 

Glycymeri.~. 50, 55. 56 

(Tucefonu), 50, 55; pl. 12 

Leda, 22 

Ledinu. 14. 22; pl. 3 

fucanu.~. Vertipecfen, 12 

Fugleria illota, 36 

(Fugleria), Barlwtia, 85 

illota, Barbatiu, 32 . .'J6; pl. 6 

p.~euduillota. Barbatia, 32 . .'J5; pl. 6 

furlongi. Leda, 19 

Nuculana. 19 

(Saccella), 14. JIJ; pl. 2 

G 

gubbi, Brachidontes (Aeidimytilus), 60, 69; pl. 17 

Corbula, 15 

Glycymeri.~. 51. 52. 58 

(Glycymeris), 50. 52; pl. 13 

Leda, 17 

Modio/u.~. 69 

Porteriu.~. 47 

subcu111:exus, Modiolu.~. 69 

gabbiana. Acila, 10 

gabbii, Corbulu, 15 

Ledu, 15. 16 

Nuculanu, 16, 18 

(Saeeel/a), 14, /6; pl. 2 

Suceellu, 16 

ga.la, Yoldia. 14, 28; pl. 4 

Yo/diu (Yo/diu), 14 

gu.lei, Area, 45 

garzaensi,q, Modio/u.~ (Modiolus), 60 

Modio/u.9 (Modiolus) ynezianus, 75; pl. 20 

ynezianus, 75 

Gaviota Formation, 16. 24, 55, 67, 70; pl. 17 

Geologic formations, pelecypod occurrences, 90 

gesteri, Yoldia, 15, 26 

Yoldia (Kalayoldiu), 14, 26; pl. 4 

gettysburgen.~is, Acila, 9 

Aeila (Acila), 6, 9, 11; pl. 1 

alaskenwis, Nuculu (Acilu), 9 

Nucula (Acila), 9 

gigunteu, Glycymeris, 52 

Glycymeri.~ (Glycymeris), 50, 52; pl. 11 

Pectunculu.~. 52 

Glossus (Pectunculus) eollinus, 59 

Glycim.eri.~ buwuldi, 51 

fresnoensis, 55 

hannibali. 54 

maccruyi, 57 

marysvillensi.~. 49 

perrini, 55 

ruckmani, 56 

septentrionalis, 57 

tenuimbricata, 56 

Glycymerididae, 1. 49, 50 

Glycymeridinae, 49 

Glycymeris, 49, 53 

barburensis, 58, 59 

bicolo1·, 53 

branneri, 51, 52 

buwuldi, 51 

coa/ingensis, 58 

democracia.na, 53 

eoeenica, 50 

evermann i, 50, 56 

fresnoen.sis, 50, 55. 56 

gabbi, 51. 52. 58 

gigantea., 51, 52 

grewingki, 52. 58 

hanniba.li, 50 

instabilis, 55 

intennedia, 51. 52 

keenae, 58 

1/oydsmithi, 53 

maculata. 52 

major meganosenwis, 53, 54 

marysvWensis, 50 

PALEONTOLOGY OF CALIFORNIA AND BAJA CALIFORNIA 

Glycymeris-continued 

multicostata, 57 

perrin i, 50, 56 

instabilis. 55 

profunda. 58, 59 

reefensis, 55 

rosecanyonensis, 49, 50, 55, 56 

ruclonani, 50, 56 

.~agitatta, 49, 50 

.~agittata, 54 

sagitta/us, 56 

.~eptentrionuli.~. 53, 58 

subobsoleta, 57 

subobsoletu, 53, 58, 59 

swartsi, 51. 53 

tecolotensis, 55 

tenuimbricata, 58 

veatchii, 51 

major, 51. 54 

/.'erticordia, 50, 55, 56 

viticola, 50 

!chaleyi, 53 

(Axinola). 57 

greU"ingki, 50. 58; pl. 12 

profunda, 50, 58; pl. 12 

(Glycymeri.q), 4Y. 53 

branneri, 50, 51; pl. 10 

buwaldi, 50, 51; pl. ~2 

eoeenica, 51); pl. 12 

gabbi, 50, 52; pl. 13 

gigantea, 50, 52; pl. 11 

maculata, 50, 52; pl. 11 

rosecanyonensis, 50, 49; pl. 10 

subobsoleta, 50, 52; pl. 12 

,qwartsi. 50, 53; pl. 11 

viticola, 51); pl. 10 

whaleyi, 50, 58; pl. 11 

(Glycymerita), 53, 55 

major, 50, 54; pl. 11 

meganosen.~is, 50, 53; pl. 11 

ree/ensis, 50, 55; pl. 12 

sagittata, 50, 5.4: pl. 12 

tecolotensis, 50, 55; pl. 11 

(Tucetona). 55, 57 

evennanni, 50, 56; pl. 12 

fre.~noensis, 50, 55; pl. 12 

maccrayi, 50, 57; pl. 12 

multicostata, 50, 57; pl. 12 

perrim', 50, 55; pl. 12 

ruckmani, 50, 56; pl. 12 

septentrionalis, 50, 57; pl. 13 

tenuimbricata. 50. 56; pl. 12 

uerticordia. 50, .56; pl. 12 

(Glycymeri.q) branneri, Glycymeris, 50, 51; pl. 10 

buwaldi, Glyeymeris, 50, .51; pl. 12 

eoeenica, Glycymeris, 51); pl. 12 

gubbi, Glycymeri,q, 50, 52; pl. 13 

gigantea., Glycymeris, 50, 52; pl. 11 

Glyeymeris, ,49, 53 

maculata, Glyeymeris, 50, 52; pl. 11 

roseeanyonensis, Glycymeris, 49, 51); pl. 10 

subobsoleta, Glycymeris, 50, 52; pl. 12 

swartsi, Glycymeris, 50. 53; pl. 11 

uiticola, Glyeymeri.~. 51); pl. 10 

whaleyi, Glycymeris, 50, 53; pl. 11 

Glyeymerita, 55 

(Glycymerita.), Glycymeris, 53, 55 

major, Glyeymeris, 50, 54; pl. 11 

meganosensis, Glycymeris, 50, 53; pl. 11 

reefensis, Glycymeris, 50, 55; pl. 12 

sagittata. Glycymeris, 50. 54; pl. 12 

teeolotensi.~. Glycymeris, 50, 55; pl. 11 

goniglensis. Pachyperna, 84, 85; pl. 26 

Perna, 85 

Gould Shale Member, 24 

Grammatodontinae, 46 

Grandiarea, .42 

grandis. 32, 42; pl. 9 

(Grandiarca) grandis, Anadara, 42 

grandis, Anadara, 43 

Anadara (Grandiarca.), 42 

(Larkinia), 42 

grandis-continued 

Area, 42 

Grandiarca, 32, ,42; pl. 9 

gmtacapi, Mytilus, 66 

Mytilus (Plicatomytilus), 66 

Gregariella, 72 

ehenui. 60. 72; pl. 19 

com·ctata. 72 

grewingki, Glycymeris, 52. 58 

Glyeymeris (Axinola), 50, 58; pl. 12 

Gries Ranch Formation, 17, 34; pl. 2 

Haloanus, 48 

hamata, Leda, 22 

H 

Nuculana (Thestyledu), 14. 22; pl. 2 

Hambre Sandstone. 25 

hamelini, Anadara, 45 

Anadara (Cunearca), 45 

Area, 45 

Mytilus, 62 

Seapharca (Cunearca), 32. ,45; pl. 9 

hann ibali, Glyeimeris, 54 

G/yeymeris, 50 

hau:/eyi, Area (Area), 31, 32; pl. 5 

hertleini, Pteria, 81, 82. 83; pl. 24 

highoohiae, Mytilu.~. 61 

Hilgardia, 17. 22 

parkei, 14. 22. 23; pl. 3 

eoosensis, 14, 17, 23; pl. 3 

(Hilgardia) multilineata., Nuculana, 22 

hindsii, Leda, 20 

Nueulana, 21 

(Saeee/la), 14. ZIJ; pl. 2 

Holonunu.~ hornii, 48 

hondana, Nueulana, 16 

Nuculana (Saeeella), 14. 16; pl. 2 

Hormomya. 68 

hornii, Area, 48 

e/usa, Area, 48 

Pachecou (Pachecoa), 48; pl. 10 

Trigonodesma, 48 

elusus, Pachecoa, 49 

Holonanus, 48 

Pachecoa, 48 

(Pachecoa), 48; pl. 10 

Trigonodesma, 48 

ho1cei, Pteria, 81; pl. 24 

humeru.q, Mytilus, 62 

Mytilus (Mytilus), 62 

Huxleyia, 59 

munita, 59; pl. 13 

Idasola, 78 

bakeri, 60, 78; pl. 21 

/donearca., 47 

illata, Barbatia, 36 

Barbatia (Fugleria). 32, 36; pl. 6 

Byssoarca, 36 

Fugleria, 36 

imleri, Yoldia, 28 

Imperial Formation, 40, 52, 80, 81; pis. 7, 22, 23, 24 

impravida, Area, 36, 37 

impressa, Nueula, 23 

Yoldia, 25, 29 

inezana zone, Turrite/la, 51 

inezensis, Myte/la., 60. 71); pl. 17 

Mytilus. 67, 70 

in/era, Turritella uvasana, 10, 16, 22, 23. 47. 49, 87 

inf/ata, Crenella, 60, 72; pl. 18 

inf/atus, Modiolus, 77 

instabili.~. Glyeymeris, 55 

Glyeymeris perrini, 55 

intermedia. Glycymeris, 51, 52 

lone Formation, 32. 34 

Isidro Formation. 53, 63; pl. 11 

lsognomon, 84, 85 

chemnitzii, 84 
/.~ognomon-continued 

janu.~. 84 

sp .. HJ.. 8.5; pl. 26 

(/.~o(lllomon), 81. 

janu.~. HJ.: pl. 25 

JHIIIZII/HI, 8J.; pl. 25 

(/SII{JnOmon), J.~ognonWn, 8J. 

janu.~. /.~oyno111on, 81.: pl. 25 

JWnZIIIHI, /.~O{JnOIIIOn, 8J.; pl. 25 

lsognomonidae. I. 81. 

janu.~. /.~ugnolllt!ll, 84 

[SO{JnOmOn (l.~ogno1110n), 8J.; pl. 25 

Pl'da/ion, 84 

japonica, Ptll'tlr111dia. 29 

joaqui1wn11i.~. Pru:hypet'IW, 84. 8.5: pl. 26 

Pr•da/ir111, 85 

joll/l.~rmi, Adw/'(lx, ,'J/; pl. 4 

Solemya, 31 

(Adwrru), :31 

jordr111i, Pteria, 81. 82. 8.'1: pl. 24 

jou.~.~l!llllmi, Umop.~i.~. 59 

Juncal Formation, 10. 16. 22. 2:3. 29, 34. 47, 49, 50, 55. 

67. 85. 87: pl. 26 

Jupiteria (Led ina) duttonae, 22 

K 

(Kalauuldia) crii'IIIII'O.~en.~i.~. Yoldia, 14. '.!6; pl. 4 

c:ooperi, }'oidia. 14. 24 

cooperii, Yoldia, '.!.5: pl. 3 

{Je.~teri, Yoldia, 14, '.!6~ pl. 4 

rJrr•(lona, Yoldia, 14. i'J.: pl. a .~ub11wntereye11.~i.~. Yoldia, 14. '.!4: pl. 3 

IIIIJ!I'OIIIIInlereyen.~i.~. Yoldia, 14. '.!.5: pl. 3 

tenui11.~ima, Yoldia, 14. i'J.: pl. 3 

Yoldia, !!4. 26 

keenrw. Gluctfllll'ri.~. 58 

kel11eyi. J .. ithoplwya (Piunmla), 73 

kewi, Ct·e11omytilu11, 63 

Mutilu.~. 62. 63 

(Cre/lomuti/u.~). 60. 69; pl. 15 

kit·ket'l!llllill, lJmchidontes (Bmchidonte.~). 60. fj8; pl. 17 

Modiolus, 68 

Kirker Turr. 9. II. 15. 30. 62. 77: pis. 3. 4. 14. 21 

Kreyenhagen Formation. II. 29. 30. 55 

Kreyenhagen Shale. 18 

L 

La Jolla Group, 10. 23. 49: pl. 5 

lri{JIIIUI/11111, Modio/u.~ (Modiolus), 60. 7.5: pl. 19 

Modio/u.~ unezianu.~. 75 

lnjol/nr•n.~is. Acila. 10 

lakei, Anadara, 37 

Anada/'(1 (Anadrll'a). 32. 97; pl. 6 

At'C(/, 37 

Lamellinw:ula. 8 

(/..rlllll'llinucula) exi{JIW, Nucula, 6. 8: pl. I 

Lnrkinin, 42 

cr11nuloen.~i.~. 32. J.,'J; pl. 8 

lllltllico.qfala, :32. J.,'J; pl. 9 

santana .~antr11w, 32. 4!!: pl. 8 

wedd/ei, 32. J..'J: pl. 9 

(l .. arkinia) camulor!n.~i.~. Anadara. 43 

(Jrrlluli.~. A nadara. 42 

multico.~lala. Anadara. 43 

srllllatlll .~1111fatw, A11adm·a, 42 

u•eddlei, AnrHfara, 4:3 

Las Virgenes Sandstone. 16 

laln111ia, Pinna. 79. 80 

Pimw (Pinna), 7!J; pl. 22 

law.~on i. Brachidonte.~. 68 

/Jrru:hidrmte.~ (IJI'(Ichidrmtes), 60. 68; pl. 17 

Modiolu.~. 68 

I .. eda ncula. 17 

alarformi.~. 15 

cahillr!nHill, 17 

cdlulita, 20 

INDEX 

Leda-continued 

chehalisellsis. 18 

de11omillala, 21 

e/ongorostrata, 15 

fabata, 21 

fo,qsa. 13 

.~culpta, 13 

fresnoensis. 22 

furlo11gi, 19 

(IO!Jbi, 17 

uabbii. 15. 16 

lwmata, 22 

hindsii. 20 

lincolnenllis. 17 

markleyensis, 18 

merriami. 17 

mille/'/·, 21 

mi11uta. 20 

praeCU/'HOr, 14 

ochs11eri. 19 

orcutti, 20 

ori'{/0/1(/, 24 

packordi, 21 

parkei, 22 

po!ynomi11alo, 15 

protexta. 16 

pulchrisinuo.~a. 18 

1'(1/no/lensis, 21 

rosa, 29 

su!Jimpressa, 28 

taphria, 19 

11/'all(/111/, 17 

vogdesi, 16 

u·ashin{llollensis, 17 

Ledi11a. '.!2 

rluttonae. 14, 2'.!: pl. 3 

jresnoe11sis. 14. 22: pl. 3 

(Ledi11a) dutlonae. Jupiteria. 22 

(Leionucula). ba/boana. Nucula, 6. 8; pl. 1 

birchi, Nucula, 6. 7. 8; pl. 1 

Nucula, 7 

postanuulata, Nucula. 6, 8; pl. 1 

quirico, Nucula. 8 

/eptogrammica, Area (Area), .'J2: pl. 6 

/ewisi. Pi11na, 79 

Pinna (Pin11a), 79; pl. 21 

Limopsidae. I. 49 

Limop.~i.q, 49 

com J!l'essu.q, 59 

dalli. 59 

jou.qseaumi, 59 

zona/is, 59 

(Felicia) ph rear. 59 

(Limopsi.~). 49 

morysville11sis. 49: pl. 10 

(Linwp.~is) 111aryst:il/ensis. Limopsi.~. 49: pl. 10 

Limopsis. 4.9 

sogitlala, An'nea, 54 

/imatula. Yoldia, 29 

Lincoln Creek Formation, 18. 30: pis. 2. 4 

lincolnensis, Leda, 17 

Lindavista Formation. 34 

Lithodomus p/umulo. 73 

Lithoplwuo. 7.'1 

clarki, 73. 74 

mckniuhli, 74 

plumula, 73 

ke/,qeyi, 73 

(Diberus), 73 

plumulo, 60, 7.'1; pl. 19 

(Lithoplwuo), 73 

clarki, 60, 73; pl. 19 

(Lithophauo) clorki, Lithophouo. 60. 7.'1; pl. 19 

Lithophaga, 7.'1 

Lithophaginae. 60. 78 

Litorhadia, 28 

astorianc1. 14. 2.'1: pl. 3 

(Litorhadio)fresnoensi,q, Cnlorhodia, 22 

Llajas Formation, 10. 16, 22. 47. 55, 56. 57, 70. 71. 79, 

86, 87: pis. 12. 18. 21. 26 

1/ajasensis, EJ:putens, 86 

Nayadino (Exputens), 86; pl. 26 

1/oydsmithi, Glycymeris, 53 

Locatelli Formation. 47 

A103 

Lodo Formation. 7, 10. 16. 22. 47, 48. 54. 55, 56, 68. 87: 

pis. 2. a. 12. 26 

/oeli. Mytilus, 62, 63, 65 

Mytilus (Mytilus), 60. 62; pl. 14 

Lomita Marl Member. 13. 58 

lore11zona zone, Turritello n1rioto, 67 

Los Tularicitos Member. 63 

M 

maccrayi, Glycimeris, 57 

Glycymeris (Tucetona), 50, .57: pl. 12 

mckllighli, Adu/a, 60. 74: pl. 19 

Lithophaua. 74 

McLure Shale Member. 19. 58. 63 

moculata, Glycymeri,q, 52 

Glycymeri,q (Giycymeris), 50, .52: pl. II 

mocu/otus, Pectunculus. 52 

major. Glycymeris (Giycumerita). 50 .. SJ.: pl. II 

Glycymeris l'eotchii, 54 

meganosensis, Glycymeris. 53, 54 

Glycymeris (Giycymerita). 50 . .5.'1: pl. 11 

Pectunculus reatchi, 54 

Malleidae, I. 86 

Mal/etia, 13 

chehalisensis, 13. 30 

packardi, 13. 30 

Malletiidae. 13 

Manzanellidae, I. 59 

morel/a, Nuculana (Costel/oleda), 15 

mar{loritano, Brachidonte.~ (Scolimutilus). 60, 69; 

pl. 17 

Sept1jer. 69. 71 

margarit1jera. Meleaurina, 83 

maril/a.ta, Perna, 70 

Markley Formation. 29, 51: pl. 4 

Markley Sandstone Member. 29. 30. 55 

morkleyensis, Acila mula, 11 

Leda, 18 

Nuculana, 18 

(Saccel/a), 14. 18; pl. 3 

Portlandia, 29 

(Portlandia). 14, 29; pl. 4 

Yoldia, 29 

Marquer Formation, 35. 43. 52, 57. 76, 83, 84: pis. 5, 25 

Martinez Formation. 10, 15. 16. 21. 26, 47. 54. 56, 66, 

67, 68, 69, 77, 78. 79, 81. 82; pis. 2, 4, 10, 

II. 17. 21. 22. 24, 26 

Marysville Claystone Member. 49: pl. 10 

Marysville Formation, 7. 10 

marysvillensi.~. Glycimen·s. 49 

Glycymeris, 50 

Limop.qi.~ (Limopsis), 1.9: pl. 10 

mathewsoni. Mytilus, 63 

mathewsonii expa.t1sus, Mytilus, 62. 63, 64 

Cucul/aea, 4 7; pl. 10 

Mytilus, 62. 64. 65 

(Crenomytilus), 60, 63; pl. 14 

(Myt.iloconcho), 63 

Matilija Formation, 49. 55, 67 

Matilija Sandstone, 16. 50, 82 

mazatlanica, Me/eaurina, 83 

Pinctoda, 81. 8.'1; pl. 25 

Pten·a (Pincla.da), 83 

media impressa, Anadara, 37. 39 

A nadara (A nadara). 32. 38; pl. 7 

(Anada.ra) media impressa, 38 

Area (Scapharca.). 38 

mediaimpressa. Anadara (Anada.ra), 38 

.~ubmonlereyana, Anadara (Anadom), 37 

media-impressa, Anadara, 42 

Meganos Formation, 7, 10, 16, 22. 29. 47. 48, 49. 54, 66, 

78, 82. 85: pis. 4. 10. 11, 21. 24, 26 

meuanosensis, Glycymeris (Glycymerita) m.ojor, 50 . .58; 

pl. 11 

Glycymeris major. 53. 54 

Modiolus (Modiolu.~). 60. 78; pl. 21 

Megayoldia thraciaeformis. 26 
A104 

(Megayoldia) beringia.na, Yoldia, 14, 26; pl. 3 

thmciaeforrni8, Yoldia, 14, 26; pl. 3 

Yoldia, 26 

Meleagrina margarilljera, 83 

mazatlanica, 83 

mendenhalli, Pinna, 80 

Pinna (Pinna), 79. 80; pl. 23 

Merced Formation, 13. 25. 27, 52. 61. 64, 76; pl. 13 

merriami. Leda, 17 

Modiola, 77, 78 

Modiolus, 77 

(Modiolu,q), 77; pl. 21 

Mytilu.q, 78 

Nuculana. 17 

(Saccella), 14, 17; pl. 2 

microdonta, Anadara. (Anadam). 46 

A 1'CU, 36. 38, 40. 46 

(Scaphm·ca.). 38 

middendorffi, Mytilus, 65 

Mytilu,q (Plica.tomytilu.~). 60. 6.5; pl. 16 

middendm'fi, Mytilus, 61 

milleri. Leda, 21 

Nuculmw, 21 

minuta, Leda. 20 

minuta, Nuculana (Nuculana), 15 

Nuculana (Nuculana) nu·nuta, 15 

praecur.qor. Leda, 14 

Nuculana (Nuculona), ll;; pl. 2 

mira!Jilis, Acila., 9 

Modiola capa.x, 76 

contracto, 76 

fornica.ta, 77 

merriami, 77, 78 

multiradiata, 69 

ornata, 66 

recta, 76 

(Modiola) chenui, Mytilus, 72 

flabella.tus. Mytilus, 76 

Modiolinae, 60, 74 

Modiolus, 74. 78 

altiobl iquus. 67 

bakeri, 78 

capax, 76, 77 

cm·penteri, 77 

directus, 76 

eugel/ell,qis, 74 

fla.bellata., 76 

fornicatu,q, 77 

yabbi, 69 

.~ubcrHu•e:w.~. 69 

in/lata, 77 

ki·rkeren.~i.~. 68 

lmcsoni. 68 

mega.nosensis, 78 

merria:mi, 77 

nwrliolus, 76, 77 

multiradiatus, 69 

neglectus, 76 

pittsbumensi.~. 77 

rectus. 76 

.~accul1jer, 77 

sookensi.~. 74 

stalderi, 73 

trinrnninota, 77 

l'eronensi.~. 75 

temblorensis, 75 

l.'eronensis, 75 

ynezia.tms, 74. 75 

{Jarzaensi.~. 75 

lagunanu.~. 75 

(Brachydontes), 66 

cowl itzen.qis, 66 

playa.~ensis, 68 

(Modiolus), 74, 76. 77, 78 

capax, 60. 7fj; pl. 20 

ca.rpenteri, 60. 77; pl. 20 

clarki, 60, 78; pl. 21 

contra.cta, 60, 76; pl. 20 

direcfu,q, 60, 76; pl. 20 

eugenensis, 60, 74: pl. 19 

garzaensis, 60 

PALEONTOLOGY OF CALIFORNIA AND BAJA CALIFORNIA 

Modiolus-continued 

(Modiolus)-contin~ed 

lagunanus, 60, 7.5; pl. 19 

mega.nosensis, 60, 78; pl. 21 

merria.mi, 77; pl. 21 

pitt.~burgensis, 77; pl.21 

rectus, 60, 76; pl. 20 

sacculifer, 60, 77; pl. 21 

veronenwis temblorensi.~. 60, 7.5; pl. 20 

veronensi.~. 60, 7.5; pl. 20 

ynezianu.~. 60. 74; pl. 19 

garzaensis, 7.5; pl. 20 

(Modiolus) capax, Modiohrs, 60, 76; pl. 20 

carpenteri, Modiolus, 60, n; pl. 20 

clarki, Modiolus, 60, 78; pl. 21 

contracta, Modiolus. 60, 76; pl. 20 

rlirectus, Modiolus, 60, 76; pl. 20 

eugenensis, Modiolu.~. 60, 74; pl. 19 

garzaensi,q, Modiolus, 60 

lagutw.nus, Modioi1rs, 60. 7.5; pl. 19 

meganosensis, Modiolus, 60, 78; pl. 21 

merrimni, Modio/u.~. 77; pl. 21 

Modiolus, 74, 76, 77, 78 

pittsbw·gensi.q, Morliol11s, 77; pl. 21 

rectus, Modiolu.~. 60. 76; pl. 20 

sacculifer, Modiolus, 60, 77; pl. 21 

veronensis temblorensi.~. Modiolus, 60, 7.5; pl. 20 

veronensis, Modiolus, 60, 7.5; pl. 20 

ynezianus, Modiolu.~. 60, 74; pl. 19 

garzaensis, Mod1:olus. 7.5; pl. 20 

modiolus, Modiolus, 76, 77 

montana, Perna (Perna), 60, 70; pl.18 

Monterey Formation. 19. 23, 24, 25, 37, 38, 39. 44, 58, 

63, 81; pl. 9 

Monterey Group. 18, 38, 39; pis. 7, 20 

Monterey Shale. 45. 46, 53; pl. 11 

montereyana, Anadara. 39 

Anadam (Anadam), 32. 3.9. 44; pl. 7 

Area, 39 

devincta, 39 

Montesano Formation, 40; pl. 7 

montesanuana. Anadara, 39, 40 

Anadara (Anadara), 32, 39; pl. 7 

(A nadara) devincta, 38, 39 

devincta. 41 

Area devincta. 39 

morani, Cucullaea, 47; pl. 10 

morsei, Barba.tia. 34 

Barbatia (Barbatia), 32, 84; pl. 5 

(Qbliq1,WI'Cll), 34 

_ mortuasusensi.~. Portlandia (Portland in), 14, 29; pl. 4 

Yoldia, 29 

mosesi. Portlandia, 29, 30 

Portlanrlia (Portlandia), 14, 30; pl. 4 

Yoldia. 30 

Muir Sandstone, 10, 16. 17, 18, 49. 55, 56 

Mulinia rlf!l!.~ata. 40 

multicostata. Anada.ra. 43 

Anadara (Larkinia), 43 

Area, 43 

camuloensis, Area (Area), 43 

Glycymeris, 57 

(Tucetona). 50, .57; pl. 12 

Larkinia, 32, 43; pl. 9 

multicostatus, Pectunculus, 57 

multilineata. Nuculana (Hilgardia). 22 

multiradiata, Modiola. 69 

multiradiatus, Brach idontes (Scolimytilus), 60. 69; pl. 17 

Modiolu.~. 69 

munita, Cyrilla., 59 

Hu:rleyia, .59; pl. 13 

Musculus, 72 

(Musculus), 72 

.~talderi. 60, 73; pl. 19 

(Musculus), Muscu/u.~. 72 

stalden·, Musculus. 60. 73; pl. 19 

muta. Acila, 11, 12 

Acila (Truncacila), 6, 11, 12; pl. 1 

markleyensis, Acila, 11 

mutabilis, Area, 33 

Mytella, 70 

i nezens is, 60, 70; pl. 17 

Mytilidae, 1, 59. 60 

Mytilinae. 59, 60 

(Mytiloconcha) coalingensis, Mytilus, 62. 64 

matheu•sonii, Mytilus, 63 

trampasensis, Mytilus, 63 

Mytilus, 59, 60, 61, 70 

adamsiana. 69 

adamwianus, 70 

aquitanicus, 65 

arnolrli. 62 

ascia, 62 

b1jurcatus. 67, 71 

cal ijm·n ianus. 61 

calijornic1rs, 64, 65 

coalingen.~is, 62. 63. 64 

condoni, 61 

crassitesta. 64 

decussata. 71 

dichotomus. 67 

edulis, 61 

expa nwu.~. 63. 65 7 4 

ficus, 61 

gratacapi. 66 

hamlini, 62 

highoohiae, 61 

humerus, 62 

inezen.~is, 67, 70 

kewi. 62, 63 

loeli. 62, 63, 65 

mathewsoni. 63 

mathewsonii. 62. 64. 65 

e:rpan.~us, 62, 63. 64 

merriami, 78 

middend01jji, 61. 65, 66 

middendorfi, 61 

multiradiatus. 69 

ornatus, 66 

perrini, 65 

schencki, 64, 65 

vancou t'e1·ensis, 65 

(Aeidimytilus), 69 

adamsia nus, 70; pl. 17 

gabbi, 69; pl. 17 

(Ct·enomytilus), 62, 64. 65 

cal1jornianus, 61 

coalingensis, 60, 64; pl. 15 

sternbergi, 64 

expansus, 60, 63; pl. 15 

kewi. 60. 63; pl. 15 

mathewsonii. 60. 63; pl. 14 

perrini. 60. 63, 65; pl. 14 

schencki. 60, 64: pl. 16 

sternbergi, 60, 64; pl. 16 

trampasensis, 60, 63; pl. 14 

(Modiola) chenui, 72 

flabellatu.~. 76 

(Mytiloconcha) coalingen.~is, 62, 64 

incunms, 64 

mathewson ii, 63 

trampasensi.~. 63 

(Mytilu.~). 61, 62 

arnoldi. 60, 62; pl. 14 

ascia, 60, 62; pl. 14 

ca.l1jornianus, 60. 61; pl. 13 

condoni. 60, 61; pl. 13 

edulis, 60. 61; pl. 13 

humerus, 62 

loeli. 60: 62; pl. 14 

(Plicatomytilus). 6.5 

gratacapi, 66 

middendorffi, 60, 6.5; pl. 16 

(Scolimytilus), 68 

(Mytilus) arnoldi, Mytilus. 60, 62; pl. 14 

ascia, Mytilus, 60, 62; pl. 14 

california nus, Mytilus, 60, 61; pl. 13 

condoni, Mytilus, 60, 61 

edulis, Mytilus, 60, 61; pl. 13 

humerus, Mytilus, 62 

loeli, Mytilus, 60, 62; pl. 14 

Mytilus. 61, 62 
N 

Narrow Cape Formation. 65 

(N11nicu/11) lennirlll'lllhoni,q, Area, 33 

N11y11dina, 8fi 

(f.':t:pllftlns), 8(j 

alt?:r:i, 8fi, 87: pl. 26 

1/aJII.w:n.~i.~. 86~ pl. 26 

nt•yleclux, Modiolus, 76 

nr!lwlt•mr:IIHiH, At:ila (Truncacila), 11 

Neroly Formation. 41. 57. 63. 76 

Neroly Sandstone. 12. 26. 58. 63. 65. 70. 76. 78. 81: pl. 21 

Newportian Stage. 12 

Niguel Formation, 13. 22. 28. 34. 36. 41. 43. 58. 64 

Nof?!i11, 48 

Noetiidae. I. 4 7 

Nm:inella. 59 

.Nucu/11. 6. 7 

11n:tiw .. 27 

/Jijid11. 6. 7: pl. I 

l>i/oiHr. 47 

/Jirchi. 7 

CIIJ!IIJJf!n,qi.~. 7 

t:rrsfrenHiH, 12 

crwlata, 19 

coopr:ri, 6. 7 

deci.~fl. 10 

dint~rit:fllfl, 12 

e~:iyrw, 8 

im J!l'f!.~Hfl, 23 

nm:u/llnll, 7 

ptmllln{lllllllll, 7. 8 

.~utit11riu, 7 

.~upru.~triutu, 8 

thrur.icwfm·mi.~. 26 

nili11, 7 

(Aci/n) conrudi, 12 

dulli, 11 

deci.~u. 10 

{/t:llylmr·yeu.qi.~. 9 

alrl.~ken.qi.~. 9 

semir·o,qf/'{1111, 9 

,qhumardi. 10 

,qf il/wutere11.~i.~. 10 

(f.'nriiiCII/11) /wl/roanu, 8 

ln'rchi, 7 

(/.AIInel/irllu:u/a), 8 

e:dyrw, 6. i:i; pl. I 

(/Jr:iunm:ula), 7 

/Jallwum1, 6. 8: pl. I 

llirchi, 6. 7. 8: pl. I 

po.~fllll(lldatu, 6. 8: pl. 1 

quin'cu, 8 

(Nuculu). fi 

CIIJifl/len.~i.~. (j, pl. I 

cooperi, 6~ pl. 1 

e:r.iyrw. 8 

r:iti,q, 6, 7; pl. I 

(Nm:ula) t:fiJifi/J!In.qi,q, Nucula, fi; pl. I 

cooper·i. Nm:ula, 6; pl. I 

exi{IIW, Nuculrr, 8 

Nm:ula,fi 

r:iti.~. Nm:ula, 6. 7: pl. 1 

Nm:ulu1w. /.'J, 15.23 

ru:ula. 21 

alaeformis, 16 

lml/10rw. 19 

wlkin.~i. 19 

cullirrwrw, 19 

t:t:llu/ita, 20 

cheha/i,qen.qi.~. 18 

r:mu:epl.ioni.~. 15 

curd itzen.~i.~. 17 

den0111inuta, 21 

f!JHII:ri.~. 18, 19 

/rmsu, 13 

furlull{li. 19 

{lflblrii. 16. 18 

hindxii, 21 

/lf)ll(/(111(1, 16 

rrwrk/eyellxi,q, 18 

INDEX 

Nuculana-continued 

merriami, 17 

milleri. 21 

ocl1.~neri. 18. 19 

elmana, 19 

orcutti, 20. 21 

paclwrdi, 21 

parkei coosensis, 17. 23 

penderi. 21 

perrwla, 13. i5 

JI01110niu, 19 

po11•ersi, 15 

pulchri.~illllosa.. 18 

redondoen.~ill, 20. 21 

taphria, 18, 19. 20 

1111(111(11/(1, 17 

ll•ashin{lfollensi.~. 17. 18 

whitmarri. 19. 24. 25 

(Costel/oleda), 14. /.5 

:ma rellr1, 15 

powersi, 14. /.5; pl. 4 

(Hii{Jardia) multilineata. 22 

(Nucu/arw). IS. 15 

e/orr{loro~<trata. 14, 15: pl. 3 

fo.~.qa, IS, 14: pl. 2 

llt:ulpla, 18, 14: pl. 2 

mirwtamimtta.l5 

pnrecursor, 14: pl. 2 

perrrula, 14. /5; pl. 2 

(Saccel/a), /5, 21 

a/aejonrri11, 14. 1.5: pl. 2 

amelrJa, 19 

calrillerr.~i.~. 14. I 7; pl. 2 

cel/ulita. 14. 20; pl. 2 

chaneyi, 14, 16. 23: pl. 2 

chehaliseusi,q, 14, 18; pl. 2 

COOSf!nHill, 17 

colt'lilzensi.~. 17 

denominuta, 14. 21: pl. 2 

fabata. 14. 21: pl. 2 

furlorr{li. 14. 19; pl. 2 

ua.bbii. 14. 16: pl. 2 

hindsii, 14. 20; pl. 2 

horrdarra, 14. 16; pl. 2 

markleyerrsis. 14. 18: pl. 3 

merriami. 14. 17: pl. 2 

och.qneri, 14. 19; pl. 2 

orculli, 14, 20: pl. 2 

paclwrdi, 14. 21: pl. 2 

parkei, 22 

cooserr11i.~. 17 

pulchrixirwoxa, 14. 18; pl. 2 

/'{111/f!llen.~is, 14, 2/; pl. 2 

taphria. 14. J!J; pl. 2 

llt:allanu. 14. 17. 18: pl. 2 

washinutonensi11. 14. /7; pl. 2 

(Thestyleda), 22 

hamata, 14. 22: pl. 2 

(Nuculana) elollffurostra.ta, Nuculana, 14. /.5: pl. 3 

jo11.qa, Nucularw, J.'J, 14: pl. 2 

sculpta, Nucularw. 13. 14; pl. 2 

rrri11uta min uta, Nucularw. 15 

praecursor, Nuculana, /4; pl. 2 

Nuculalla. IS. 1.5 

perrw/a, Nuculal/a, 14. 15; pl. 2 

nuculana, Nuculana, 7 

Nuculanidae. 1. J.'J. 14 

Nuculidae, 1. 6 

0 

obi,qpoana, Anada·ra. 39. 44 

Arwdara obispoana, 44 

(Scaplwrca) o/Jispoana, 44 

Area, 44 

o/Jispoana, Anadara, 44 

A rw darn (Sea ph a rca). 44 

Scapharca (Scapharca), 32. 1,4; pl. 9 

perdixparis. Arradan1, 44 

Anadara (Scapharca), 44 

Scapha rca (Scaplwrca), 32. 1,4; pl. 9 

A105 

ob i.qpoana -continued 

Scapha.rca (Scapharcu) obispoa.na., 32. 44; pl. 9 

(Obliquarca) mo·rsei, Ba.rbatia. 34 

ochsneri elma.rw, Nuculmra. 19 

Leda, 19 

Nucu/am1, 18, 19 

(Saccella), 14. l.'J; pl. 2 

Sacce/la, 19 

Ohlson Ranch Formation. 13, 20. 41 

Olcese Sand, 8. 19, 24, 37. 51. 57 

orcutti. Leda, 20 

Nucularw. 20. 21 

(Saccel/a), 14. 20; pl. 2 

Saccel/a, 20 

oreuor111. Ledo. 24 

Yoldia, 25 

(Kn/ayo/dia), 14, 24; pl. 3 

(Portlandia.), 24 

ore{lonensi,q, Yoldia, 25 

Orinda Formation. 63 

ornata, Modiola, 66 

ornotus, Mytilus, 66 

osmonti, A 1111dara. 37, 38. 39, 40 

Ar;adara (Arradnra), 32 . . 'J6; pl. 6 

Area, 36 

Oursan Sandstone, 25, 39. 44. 58, 66 

p 

Paclrecoa, 48 

lrornii. 48 

elusus, 49 

(Paclrecoo), 48 

lrornii, 1,8; pl. 10 

elusa, 1,8; pl. 10 

(Paclrecoa) lrorrrii, Paclrecoa, 1,8; pl. 10 

lronrii e/usa, Paclrecoa, 1,8; pl. 10 

Paclrecoa. 48 

Paclryperna, 8.5 

f}oniulensis, 84, 8.5; pl. 26 

Joaquinensis. 84, 8.5; pl. 26 

pac1jica, Puh:inites, 86; pl. 26 

packardi, Leda, 21 

Malletia, 13, 30 

Nuculamr. 21 

(Saccella), 14. 21; pl. 2 

Portlandia, 30 

(Portlandia), 14, ,'J(J; pl. 4 

Yoldia (Portlandia), 30 

Pancho Rico Formation. 20. 41. 43. 64. 76 

panzana, lsof}numon (l.~of}nomon), 84: pl. 25 

Pedalion, 84 

Parallelodontidae. 1. J,fi 

parkei coosensis, Calorlradia, 23 

coosensi.~. Hil{lardia. 14, 17. 28; pl. 3 

Nuculana, 17,23 

Hi/ga.rdia. 14. 22. 23; pl. 3 

Leda. 22 

Nuculana (Saccella). 22 

Patinopecten propatulus, 12 

Pectunculus cor, 55 

eocenica, 50 

uiuantea, 52 

mar:ulafu,q, 52 

rrlltlticostatus, 57 

septentrionalis, 57 

r:eatclri maJor. 54 

(Pectunculus) co/linus, G/ossus, 59 

Prda/ion Janus, 84 

Joaquinen.~is, 85 

pallZ0/1{1, 84 

sp .. 84. 86 

Pelecypod occurrences. geologic formations . .'.10 

pellucida, Ar:icula. 82 

Pteria. 81. 82; pl. 24 

· peruleri. Nuculm111, 21 

Saccel/a, 20 

perdisparis. Arwdara o/ri.~poana, 44 

Anadara (Scaplrarca) obispoana. 44 

Al"t'a, 44 

Scapha rca (Scapha rca) o/Jispoa1111, 32. 44: pl. 9 
A106 

Perna, 70 

yon iylensis, 85 

marillata, 70 

(Perna). 70 

montana, 60, 711; pl. 18 

(PI'nla). Perna. 711 

montana. Pen~rt, 60, 711; pl. 18 

pernula. Area, 15 

Nuculrtna, 13, 15 

(Nuculana), 14, !.5; pl. 2 

perrin i, Glycimet·i.~. 55 

Glycynwri.~. 50, 56 

(Tt~r·etona), 50 . .5.5; pl. 12 

i n.~tabil i.~. Gl !JC!JIIII'ris, 55 

Mytilu,,, 65 

(Crenomytilus), 60, 63, 6.5; pl. 14 

penll'illlw, Pteria, 83 

Phoenix Member, 32, 33 

phrea1·. Felicia, 50, .5.9; pl. 13 

LimuJmis (Ph rear). 59 

Pico Formation, 9. 13. 20. 26. 28. 41. 43, 58, 61. 76: 

pis. 1. 4, 8 

Pillarian Stage, 12 

Pinctada, 8.'1 

mazatlanica, 81. 8.'1; pl. 25 

(Pinctada) mazat/anica, Pteria, 83 

Pinna, 78 

alamadensis, 80 

1t!ameden.~is, 80, 81 

barrutcsi, 79 

bicuneata, 81 

latrania, 79, 80 

lewisi, 79 

mendenhalli. 80 

t·entu ren.~is. 80 

(Atrina) alamedensi.~. 80 

bicuneata, 81 

uenturensi.~. 80 

(Pinna), 78 

barrow.~i. 7.'1; pl. 22 

latrania. 7.'1; pl. 22 

lewisi, 7.9; pl. 21 

mendenlwlli. 79. 80; pl. 23 

.~tocktoni. 79; pl. 22 

sp., 7.'1; pl. 22 

(Pinna) barrow.~i. Pinna, 7.9; pl. 22 

latrania, Pinna, 7.9; pl. 22 

lewi.~i. Pinna, 7.'1; pl. 21 

mendenhalli. Pinna. 79. 80; pl. 23 

Pinna, 78 

.~tucktoni, Pinna, 79; pl. 22 

sp., Pinna. 7.9; pl. 22 

Pinnidae, 1. 78. 79 

Pittsburg Bluff Formation, pis. 1, 3 

pittsburyensi.~. Modiolu,q, 77 

Modiolu.q (Modiolu.,), 77; pl. 21 

playasensi.~. Modiolu.~ (Brachydontes), 68 

Pleito Formation, 11, 62, 69 

Pleurodon, 59 

Plicatomytilus, 65 

(Piiwtumytilus) [Jmtacnpi, Mytilus, 66 

rniddendorffi. Mytilus, 60, 6.5; pl. 16 

Mytihts, 6.5 

plmnula kelseyi, Lithophaya, 73 

Lithodomu.q, 73 

Lithophaga, 73 

(Dilterus), 60, 7.'1; pl.19 

po/ynominata, Leda, 15 

Pomponio Mudstone Member, 13, 27, 41 

pontonin, Nuculana, 19 

Porterius, 46 

gabbi, 47 

troodfordi, 1,6; pl. 10 

Portl(mde/la. 29 

(Portlandella) chehalisensis, Portlamlia. 30 

Portlandia, 13, 2!J 

chehal i.~en,qi,,, ·21. 30 

japonica., 29 

markleyenwi,q, 29 

mose,qi, 29, 30 

packardi, 30 

PALEONTOLOGY OF CALIFORNIA AND BAJA CALIFORNIA 

Portlandia-continued 

ro.~a. 29. 30 

(Portlandel/u) chehali.~ensi.~. 30 

(Port/andia), 29 

chehal isensis, 14, 30; pl. 4 

markleyensi.~. 14, 2.9; pl. 4 

11/0rfuasu.W'nsis, 14. 2.9; pl. 4 

1/IOSI'Si, 14, 80; pl. 4 

packardi, 14, .wr. pl. 4 

ru.~a. 14. 2.'1; pl. 4 

(Purtlandia) astoriana. Yo/din. 23 

chelwlisen,qis. Portlandia, 14. 80; pl. 4 

markleyensis, Portlandia, 14. 2.9; pl. 4 

mortuasusensis, Portlandia. 14. 2.'1; pl. 4 

mosesi, Port/andia, 14, 31r, pl. 4 

oreyuna, Yoldia. 24 

packardi, Portlandia. 14, 8U; pl. 4 

Yoldia. 30 

Purtlandia, 2.'1 

rosa, Portlandia, 14. 29; pl. 4 

postanyulata. Nucula. 7. 8 

Nucula (Leionucula), 6, 8; pl. 1 

Poway Group, 23. 67 

pou·er.qi, Nuculana, 15 

Nuculana (CostPllo/eda). 14. 1.5; pl. 4 

Yoldia. 15 

praecursor, Leda minuta. 14 

praecursor, Nuculana (Nuculana) mittula, Jl,; pl. 2 

procumben.~. Area. 38 

profunda, Axinea, 58 

G/ycymeri.9, 58, 59 

(Axinola), 50, .58; pl. 12 

propatulus, Patinopecten, 12 

protexta. Leda. 16 

p.~eudoillota, Barbatia. 36 

Barbatia (Fugleria), 32, .'].5; pl. 6 

Pteria, 81, 83 

berryi. 81, 82; pl. 24 

hertlein i. 81. 82. 83: pl. 24 

howei, 81; pl. 24 

jordani. 81, 82, 88; pl. 25 

pel/ucida, 81. 82; pl. 24 

J!e1'1tviana. 83 

I'IJ.~itae. 81. 82, 88; pl. 24 

sterna, 83 

sp., 81. 82; pl. 24 

(Pinctada) mazatlanica, 83 

Pteriidae. 1. 81 

pulchrisinuosa. Leda, 18 

Nucula.na, 18 

(Saccel/a), 14, 18; pl. 2 

Pullen Formation, 41 

Puh·inite.~. 85 

ca/ifornica, 8.5, 86,; pl. 26 

pacifica. 86; pl. 26 

Pulvinitidae, 1, 8.5 

Purisima Formation. 13, 20, 25. 27. 28, 41. 63. 76: 

pis. 7. 8 

Q.R 

quirica, Nucula (Leionucu/a.). 8 

ramonensi.~. Leda, 21 

Nuculana (Saccella), 14. 21: pl. 2 

recta, Modiola, 76 

rectus, Modio/u.~. 76 

Modiolu., (Modiolus), 60, 76; pl. 20 

redondoensis, Nuculana, 20, 21 

Saccella, 20 

reeje11.~i.,, Glycymeri.~. 55 

GlycymeriH (Glycymerita), 50. 55; pl. 12 

reevea11a. Area, 35 

Barbatia (Cucullaearca), 32, 3.5; pl. 6 

(Cucullaearca.) reeueana, 35 

1·eeveana, Barbatia (Cucul/aearca.). 35 

Rices Mudstone Member. 11. 18, 30 

Rincon Shale, 83: pl. 24 

Rio Dell Formation. 13. 27, 28. 31. 61. 73; pis. 4, 19 

rivulata. Anadara (Cunea.rca). 45 

Area, 45 

Scapharca (Cunearca), 32. 4.5: pl. 9 

rosa. Lrda. 29 

Purtlandia. 29, 30 

(Portlandia), 14, 2.'1; pl. 4 

Rosarito Beach Formation. 40 

ro.,ecanyonen.,is, Glycymeris, 49. 50. 55, 56 

Glycymeris (Giycymeri.~). 1,.9, 50; pl. 10 

rositae, Pteria, 81, 82. 88; pl. 24 

Round Mountain Silt. 7. 19. 24. 37. 39: pis. 1. 2. 4 

ruckmani. Glycimeris. 56 

Glycymeris, 50. 56 

(Tucetona). 50 . .56; pl. 12 

Sacate Formation. 16, 55 

Saccel/a cellulita, 20 

gabbii. 16 

ochsneri. 19 

0/'l'Uffi, 20 

j)('nderi. 20 

redondoen.~i.~. 20 

taphria, 19 

s 

(San·el/a) alaeformis, Nuculana, 14, 1.5; pl. 2 

ame/ga, Nuculana, 19 

cah il/en.,is. Nucu/ana, 14, I 7; pl. 2 

cellulita. Nuculana, 14, 20; pl. 2 

clwneyi, Nuculana, 14, 16, 23: pl. 2 

chehalisen.~is. Nuculana, 14, 18; pl. 2 

coli' I itzensis, Nucula11a, 17 

denominata. Nuculana, 14, 21; pl. 2 

fabata. Nucu/ana, 14, 21; pl. 2 

furlongi, Nuculana. 14. /9; pl. 2 

gabbii. Nucu/ana, 14, 16; pl. 2 

hindsii. Nuculana, 14, 20; pl. 2 

/tf)ndana, Nuculana, 14, 16; pl. 2 

markeleyensis, Nuculana, 14, 18; pl. 3 

merriami. Nuculana,14, 17; pl. 2 

Nuwlana, 1.5, 21 

och.~neri, Nuculana, 14, 1.9; pl. 2 

orcutti, Nuculana, 14. 20: pl. 2 

packat·di, Nuculana, 14. 21; pl. 2 

parkei, Nucu/ana, 22 

pulchrisinuosa, Nuculana. 14. 18; pl. 2 

ramonensis, Nuculana. 14, 21: pl. 2 

taphria. Nuculana. 14, 1.9; pl. 2 

ut·asana, Nuculana, 14, 17, 18: pl. 2 

1/'ashingtonensis, Nuculana, 14. 17; pl. 2 

saccultfe·r. Modiolus, 77 

Modio/u.~ (Modiolus), 60. 77; pl. 21 

Vol.~ella, 77 

sayitatta, Glycymeris, 49, 50 

.~agittata, Axinea (Limopsis), 54 

Glycymeris, 49, 54 

(Giycymerita), 50, 51,; pl. 12 

sagittatu.~. Glycymeris, 56 

Saltos Shale Member. 37. 38, 45. 46, 53; pl. 11 

San Ramon Sandstone. 7 

San Diego Formation, 8. 13. 20. 36. 41. 58. 64, 70, 71. 

72, 76, 77: pis. 1. 2. 6. 7. 8. 16. 17. 18 

San Emigdio Formation, 11, 17. 24. 62. 69, 74 

San Gregorio Formation. 44: pl. 9 

San Joaquin Formation. 13, 41. 57. 64 

San Juan Bautista Formation, 62 

San Lorenzo Formation, 9. 11. 18. 23. 24. 30. 75: pl. 1 

San Marcos Formation. 52 

San Nicolas Island. 10 

San Pablo Formation, 5, 40, 57. 58; pis. 4. 27 

San Pablo Group, 69, 80, 81; pis. 13. 14. 17. 23 

San Pedro Formation. 13, 14, 20. 22. 25. 28. 57. 72. 73, 

76; pl. 2 

San Pedro Sand, 58 

San Pedro Series, 20 

San Ramon Sandstone. 7. 8. 9, 11. 12. 18. 19. 21. 24. 25. 

30, 37, 38. 39. 51, 52, 57, 62, 63, 68, 77: 

pis. 1. 2. 3, 6. 7. 12. 14. 17 

Santa Barbara Formation. 20, 34, 58, 76, 77 

Santa Cruz Mudstone. 9 

Santa Margarita Formation. 20. 25, 32. 33. 41, 44, 57. 

58, 64, 65, 69. 76. 81; pis. 6, 9, 16, 23 

Santa Susana Formation. 10. 86: pl. 16 

santaelarana. Anadara. 45,46 
snu/nl'int'n/HI-continued 

Auudnm (Scnphnrcn). 44 

Arcn (Auru/nrn). 44 

Sr·nphurcn (Cunt'lll'l'n). 32. 44: pl. 9 

111111/nmnrieu.~is, Arcn, 33 

Arr·n (Arcn), 32 . .'J.'J; pl. 5 

111111/nun. Auru/nm, 42.43 

A unrlnrn (/Airkiuin) suu/aun. 42 

Arcn (Aunrlnrn). 42. 43 

/,urkiuin su11/nlln. 32. 42: pl. 8 

.~nu/nun. A11nrlnm (Lnrkiuin). 42 

/,nrkiuin, 32.42: pl. 8 

ll'l'ddlt•i. Aund111'n (Lnrkiuiu). 43 

Arr·n (Amulnrn). 43 

Lnrkiuin. 32. 4.'/: pl. 9 

Saugus Formation. 20. 25. 57. 76 

Scnplwt·r·n, 4.'/ 

(CIIIII'III'Cn). 44 

hnmt•li11i. 32. 4.5; pl. 9 

ri,·ulntn. 32. 4.5; pl. 9 

.~111/lnc/nl'(l/111."32. 44: pl. 9 

rnuderhoofi. 32. 44: pl. 9 

(Srnphni'Cn). 44 

ohi,qponnn ohispo111tn, 32. 44: pl. 9 

perdispnris. 32. 44: pl. 9 

(Scnpltrll'cn) medinimpreHsn. Area. 38 

mic:mrlrm/n, Arcn. 38 

obi,qporllw obispo111111, Aundnm. 44 

obi.•poll/111, St~npltiii'Cn, 32. 44: pl. 9 

pr•rdi.•JHII'i.•. Anndnra. 44 

Srnpltlll'cn. 32. 44: pl. 9 

Hllltlnr/nmun. Aundnrn, 44 

Smplwrcn, 49. 44 

.•ulllnoutereJJIII/11, Area. 37 

Scappoose Formation. 24: pl. 3 

schl'ucki delnqtwrt'nl' zone. Turritella. 10 

Myti/u.•. 64. 65 

(CI'I!IIOIII!Jii/u.•). 60, 64; pl. 16 

HeiH,quraln .~triynta, Yo/din. 27. 28 

Yo/din, 27 

(Cnes/rrium). 14. 27; pl. 4 

(Sco/imytiluH), !Jmcltidollte.~. 6H 

11111/'{JIII'ilnnn, !Jrnch ido11/es, 60. 69; pl. 17 

multimdinltr.~. !Jmcltidrmtr.•. 60. 69; pl. 17 

,quftco/1/'I'J'UH, Bmcltidonle.•. 60. 6!J; pl. 17 

Scotia Bluffs Sandstone. 41 

Hculptn. [,edn fossa. 13 

Nm:u/nun (Nuculnnn)/oH.WI, I.'J. 14: pl. 2 

sr•ctico.qfntn, Anndnrn. 40 

srmiuudn. Yolrlin. 28 

}'o/din (Cuesterium). 14. 28; pl. 4 

Hl'llliroHfrntn. Aciln. 9 

Aciln (Aciln). 6. 9; pl. 1 

Nuculn (Ar:i/n), 9 

sep/eutrionnlis .~u/)()/llwleta. A:rilll'll, 52 

subo/tso/1'/n, Glycymeris. 57 

Glycimrri.~. 57 

Glyi~JJIIWI'iH, 53, 58 

(Tuee/oun). 50 .. 57: pl. 13 

Pedtwculu.•. 57 

Srptifer, 65. 67, 70, 71 

bijUI'Cn/u,q, 60, 67, 69, 71 

conlin{JI!II,qi.•. 60, 71 

dichotomu.•. 67, 68, 71 

rleyn11.•. 60, 67, 70 

1/1(1/'{Jnrifnll(l, 69, 71 

nwr[JIII'itnnu.q, 69 

,,1/H(I//ni'IIHi,q, 67 

(Sr•p/i.fer), 70 

ltifu rcn(/1,,, 7I; pl. 18 

con/iuyeu.qi,q, 7I: pl. 18 

e/eya/1.~. 70; pl. 18 

(Septifer) lufurcnluH, Septifer, 7I; pl. 18 

conliii[JI'U.~i.q, Sept1/er, 7I; pl. 18 

elr'f/1111.~. Sepltfer, 70: pl. 18 

Septifer, 70 

Sespc Formation, 43. 63 

.~e.qpreusi,q, Aundara, 45 

At·cn, 45 

(Aundnrn), 45 

si/111/HII'di. Ar.·ila (TI'Iwcnr:i/n), 6, IO; pl. 1 

INDEX 

shumnrdi-continued 

Nuculn (Aciln), 10 

Silverado Formation, 54 

.•i11ili.•. A11ndnrn, 42 

Sisquoc Formation. 20. 28. 29, 41: pl. 4 

sisquocensis, A rcn, 33. 34 

A rca (A rcn), 32. 88; pl. 5 

Sobrante Sandstone, 18. 19, 25, 38, 39. 61. 63. 66 

Solemyn. 30 

n{lnssizi, 31 

dunuen.•is, 31 

johii .• OIIi. 31 

relum. 30 

(Ar·hnru.r)johllsolli. 31 

Solemyidae, 1. 80 

.wJ/itaria, Nuculn. 7 

.mokrusis, Modiolus. 74 

Spo11dy/us, 73 

cnlci/er. 84 

stnlderi, Modiolus, 73 

Musculus (Muscu/u.•). 60, 73: pl. 19 

Vo/selln (!Jrachiodollfi'H), 73 

s/epltr11si, Atri11a. 79, 8I; pl. 24 

.•trnw, Pteria. 83 

slrruheryi. Mytilus (Crei/OIII!Jii/us). 60, 64; pl. 16 

Mytilus (Crruomyti/us) conlill[lr.llsis, 64 

.•tillwatr.rrllsis, Nucu/a (Aciln). 10 

s/ocktoni. Piuun (Pinlla). 79; pl. 22 

Striarcinae. 4 7 

.•lriya/n, Yoldia, 27, 28 

Yo/din (CIIeHferium). 14. 27; pl. 4 

scis.•uratn, 27, 28 

.•lronyi, Anndnra (Anndnrn), 32, 4I: pl. 6 

Arcn (!Jarhntin), 41 

suhcont•erus. Brachidontes (Scolimytilus), 60, 69; pl. 17 

Modiolus [Jahbi, 69 

.•uhimpres.•n. Leda, 28 

HUhmontereyann, Aundnrn, 37 

Anadara (Anndnrn), 32, 87; pl. 6 

(Anadam) mediaimpressa, 37 

Arcn (Scapharca). 37 

submontereyeusis, Yo/din, 24, 25 

Yoldia (Kalayoldia), 14, 24: pl. 3 

suhobso/ela, A:rinea septentrionalis. 52 

Glycymeris. 53, 58. 59 

septentrional is. 57 

(Giycymeris), 50, .52; pl. 12 

supramun/ereyensi.•. Yoldia. 25 

Yoldia coopen'i, 25 

(Ka/ayoldia), 14. 2.5: pl. 3 

suprap/icatus fauna, Ectinochilus, 49. 50. 55, 67 

suprastriata, Nucu/a, 8 

susatwen.~i .•. Brachidon/es, 67 

!Jrachidonlrs (!Jracltidontes), 60, 67; pl. 17 

Septifer, 67 

swartsi, G/ycymeris, 51. 53 

Glycymeris (Giycymeris), 50, .58; pl. 11 

T 

Tahana Member, 13, 25, 27, 41, 76 

taphria. Ledn, 19 

Nuculana, 18, 19, 20 

(Saccel/a). 14, I9; pl. 2 

Saccella, 19 

tecolotensis. Glycymeris. 55 

Glycymeri.~ (Giycymerita). 50, .5.5; pl. 11 

Tejon Formation, 7, 10, 16, 17. 23, 32, 48. 49, 50, 51. 54, 

55, 56. 62, 67. 68, 82: pis. 1. 2, 3, 5, 12, 14, 

20. 17 

Tejon horizon, 54 

Temblor Formation, 12, 18, 19, 20, 23, 24, 25, 37. 38. 

39, 44, 46, 62. 63, 65, 66, 75, 82: pis. 6, 9, 

20,24 

Temblor horizon, 24, 82 

temh/orensis. Modiolus (Modiolus) toeronensis, 60, 7.5; 

pl. 20 

Modiolus t.·eronensis, 75 

Yoldia, 23 

(Yoldia), 14, 28; pl. 4 

lenuimhrica/a, Glycimeri.~. 56 

Glycyn1eri.~. 58 

(Tucelona), 50, .5fi; pl. 12 

le1111i.•sima, Yoldia. 25 

Yoldia cooperi. 24 

1'00/)Prii, 25 

Yoldia (Kalayo/dia). 14, :!4: pl. 3 

Tepetate Formation. 47 

lenniuumbonis. Area (Area). 32 . .'J.'I; pl. 5 

Area (Narirula), 33 

thalia, Anadara (Cunearca). 46 

(Thl'sly/edn) hamata, Nucu/ana, 14. 22; pl. 2 

Nucu/ann. 22 

lhral'iarfonnis, MP{Iayo/dia. 26 

Nucula. 26 

Yoldia, 26 

(MP[Jayoldia). 14. 2fi; pl. 3 

Tice Shale. 19 

Tierra Redonda Formation. 51. 63 

Timms Point Silt Member, 13 

Tinaquaic Sandstone Member. 41 

Todos Santos Claystone Member. 28. 29: pl. 4 

Topanga Canyon Formation, 63 

A107 

Topanga Formation, 19. 37. 40, 63, 82, 83: pis. 8, 25 

topaii[JaPnsis, A 1wda ra, 40 

Anadam (Anadarn), 32. 40; pl. 8 

loroPn.~is, Anadara chiriquiPn.qi.•. 42 

Torrey Sandstone. 34 

Tortugas Formation, 18, 39 

Towsley Formation, 13, 20, 33. 36. 41. 58, 64. 76 

/ramJw.•ensis, Creuomytilus. 63 

Myli/us (Crenomytilus). 60, 6.'1; pl. 14 

(Mytiloconclw), 63 

Tri{lmwdesmalwrnii. 48 

hornii e/u.~a. 48 

trilinPala. Anadara, 38, 40,41 

Anadara (Anadara), 32, 38, 40; pl. 7 

(Anadara) lrilineata. 40 

Area, 40 

ca./carea, Anadara, 41 

Anadara (Anndara), 4I: pl. 8 

Area (Area), 41 

canalis, Anadara. 41 

A1wdara (Anadara), 4/: pl. 8 

lrilineata. Anadara (Anadara), 40 

Trinacriinae. 48 

lrinominala, Modiolus. 77 

(Truncacila), Aci/a, 9 

cas/rensis, Acila, 6, I2; pl. 1 

conradi, Acila, 6, I2; pl. 1 

dalli, Aci/a, 6, II; pl. 1 

decisa, Acila, 6, IO; pl. 1 

empirensis. Acila, 6, I2; pl. 1 

mula. Acila, 6, II. 12; pl. 1 

nehaiPmPnsi.~. Acila, 11 

shumardi, Aci/a, 6, JO; pl. 1 

(Tuce/ona) e1·ermanni, Glycymeris. 50, .5fi; pl. 12 

fresnoensis, Glycymeri.•. 50, .5.5; pl. 12 

GI!JC!Jilleri.q, .5.5. 57 

maccrayi. Glycymeris, 50, .57; pl. 12 

multicos/ata. Glycymeri.~. 50, .57; pl. 12 

perrini, Glycymeri.~. 50 .. 5.5; pl. 12 

ruckmani. Glycymeris, 50, .56; pl. 12 

septenlrionali.~. Glycymet·i.•. 50, .57; pl. 13 

/Pnuim!Jricata, Glycymeris, 50, .56; pl. 12 

l'erlicordia, Glycymeris, 50, .56; pl. 12 

Tumey Formation. 11 

Turritelln dela{luerme zone, 16 

inezana zone, 51 

schencki delaquerrae zone, 10 

ut·asana applinae fauna, 10, 23. 29, 34, 50, 55, 85 

infera fauna, 10. 16. 22, 23, 47, 49. 87 

t·ariatalorenzana zone, 67 

Twin River Formation, 1, 9 

u.v 

Umpqua Formation, 23: pl. 3 

111'asa1w applinae fauna, Turrite/la, 10, 23. 29, 34, 50, 

55.85 

in/era fauna, Turitel/a, 10, 16, 22, 23, 47, 49, 87 
A108 PALEONTOLOGY OF CALIFORNIA AND BAJA CALIFORNIA 

uvasana-continued 

Leda, 17 

Nuculana, 17 

(Saccella), 14. 17. 18; pl. 2 

l'aiiCOIII!eren.qis, Mytilus, 65 

Nmderhoofi, Anadara, 44 

Anadara (Cunearca), 44 

Scapharca (Cunearca), 32. 44: pl. 9 

Vaqueros Formation, 23. 41. 42. 43, 45, 51. 62. 63, 74. 

75. 79. 80, 81. 82, 84; pis. 2. 3. 6, 8. 9. 10. 

14, 15, 19. 22. 23. 24. 25. 27 

rariata Iorenzana zone, Turritel/a, 67 

reatchi major, Pectunculus. 54 

veatchii. Glycymeri.q, 51 

major, Glycymeris, 51. 54 

l'efmn, Solemya, 30 

l'enturensis, Af'l·ina. 79. 80; pis. 23, 27 

Pinna, 80 

(Atrina), 80 

. reronen,qis, Modiolus. 75 

Modiofu,q (Modio/u,q) 1·eronensis. 60, 7.5; pl. 20 

/!C/'01/en,qis, 75 

tembtorensis, Modiolus, 75 

Modio/u,q (Modiolus), 60. 7.5; pl. 20 

veronensls, Modiolus, 75 

Modiolus (Modiolus). 60, 7.5; pl. 20 

l'erticordia, Glycymeris. ~0. 55. 56 

Glycymeris (Tucetona), 50 . .56; pl. 12 

Vertipecten fucanu.q, 12 

viticola. Glycymeris. 50 

Glycymais (Giycymeris), .50; pl. 10 

riti,q, Nucula, 7 

Nucula (Nucula), 6, 7; pl. 1 

I'Ogde,qi, Leda, 16 

Volsella capm·, 76 

eugenensis. 74 

sacculifer, 77 

(Brachiodonfe,q) cowlitzrnsi.q, 66 

,qfalderi. 73 

Vulsella, 87 

clarki. 87; pl. 26 

w 

u·ashingtonensis, Leda, 17 

Nuculana, 17. 18 

(Saccella), 14. 17; pl. 2 

u·a,q/n'ngtoniana, Area, 34 

u•eddlei, Anadara, 43 

Anadara (Larkinia) ,qantana, 43 

Area (Anadara) ,qantana, 43 

Larkinia santana, 32, 4.'1; pl. 9 

tdwleyi, Glycymeris, 53 

Glycymen's (Giycymeris), 50 . .5.'1; pl. 11 

1chitmani. Nuculana. 19. 24. 25 

Wildcat Group, 12. 13. 25. 28, 53. 61 

woodfordi. Barbatia, 46 

Porterius, 46; pl. 10 

Wygal Sandstone Member, 12. 24. 37. 63 

Y.Z 

ynezianus garzaensis, Modiolus. 75 

garzaensis. Modiolus (Modiolus). 7.5; pl. 20 

lagunanus. Modiolus, 75 

Modiolus, 74 

(Modiolu.q), 60. 74; pl. 19 

Yoldia, 13. 2.'1. 28 

arctica. 27 

a.qforiana. 28 

beringiana. 26 

canwrosensis, 26 

chehalisensi.q, 21 

cooperi, 26. 28 

tenuis,qima, 24, 25 

cooperii, 24. 25. 26. 28 

supramontrreyensis, 25 

tenuissima, 25 

duprei, 29 

ensifera, 27. 28 

gala. 14. 28; pl. 4 

gesteri. 15. 26 

imleri, 28 

impres,qa, 25. 29 

Yold ia-continued 

limatula. 29 

markleyensis, 29 

mortuasusensis. 29 

mosesi. 30 

oregona. 25 

oregonensis. 25 

JJOII'!'I'Si, 15 

sci.q,qu rata, 27 

strigata, 27. 28 

semimHia, 28 

sfn'gata, 27. 28 

submontereyensi.q, 24. 25 

supramontereyensis, 25 

temblorensis, 23 

tenuissima, 25 

thraciaeformis, 26 

(Cnestm·ium), 27 

en.q1jera. 14. 27; pl. 4 

scissurata, 14. 27; pl.4 

seminuda, 14. 28; pl. 4 

strigata, 14. 27: pl. 4 

(Kalayoldia). 24, 26 

carnarosensis, 14. 26; pl. 4 

cooperii, 14. 24. 2.5; pl. 3 

gesteri. 14. 26: pl. 4 

oregona, 14, 24: pl. 3 

,qubmontereyensis, 14, 24: pl. 3 

supramontereyensis, 14. 2.5; pl. 3 

lenui.qsima, 14, 24; pl. 3 

(Megayoldia), 26 

beringiana, 14. 26: pl. 3 

th--aciaejormi.~. 14. 26; pl. 3 

(Portlandia) astoriana, 23 

oregona. 24 

packardi, 30 

(Yoldia), 14, 2.'1 

temblorensi.~. 14. 23; pl. 4 

( Yoldia) temblorensis, Yoldia, 14. 2.'1; pl. 4 

Yoldia, 14, 23 

zona/is, Limopsis. 59 
PLATES 1-27 

[Contact photographs of the plates in this report are available from the 

U.S. Geological Survey Library, Federal Center, Denver, Colorado 80225] 
PLATE 1 

FIGURES 1, 2. Nucula (Nucula) capayensis Schenck (p. A6). 

Holotype UCMP 30196. Length 32 mm, height 24 mm, thickness 8 mm (one 

valve). Capay Formation, California, Eocene. 

3, 4. Nucula (Nucula) cooperi Dickerson (p. A6). 

Holotype UCMP 11754a (x 4.0). Length 9 mm, height 7 mm. Capay Formation, California, Eocene. 

5. Nucula (Nucula) vitis Anderson and Hanna (p. A 7). 

Holotype CAS 788 (x 4.0). Length 8 mm, height 7 mm. Tejon Formation, 

California, Eocene. 

6, 7. Nucula? bi{ida Clark (p. A 7). 

Holotype UCMP 11184 (x 6.0). Length 6 mm, height 5 mm, thickness 3 mm 

(both valves). San Ramon Sandstone, California, Miocene(?). 

8, 9. Nucula (Leionucula) birchi Keen (p. A 7). 

Holotype CAS/SU 7527 (x 3.0). Length 7 mm, height 5 mm, thickness 2 mm 

(one valve). Round Mountain Silt, California, Miocene. 

10. Nucula (Leionucula) balboana Hertlein and Grant (p. A8). 

Holotype CAS 59684 (x 1.5). Length 13 mm, height 11 mm, thickness 7 mm 

(both valves). San Diego Formation, California, Pliocene. 

11. Acila (Acila) gettysburgensis (Reagan) (p. A9). 

Holotype USNM 328302 (x 1.5). Length 26 mm, height 19 mm, thickness 8 

mm (one valve). Twin River Formation, Washington, Eocene to Miocene. 

12. Nucula (Leionucula) postangulata Clark (p. A8). 

Holotype UCMP 11260 (x 3.0). Length 7 mm, height 5 mm, thickness 3 mm 

(both valves). San Ramon Sandstone, California, Miocene(?). 

13. Nucula (Lamellinucula) exigua Sowerby (p. A8). 

Hypotype UCLA 48610 (x 4.0; Hertlein and Grant, 1972, pl. 27, figs. 5, 6). 

Length 5 mm, height 5 mm. San Diego Formation, California, Pliocene. 

(Photography courtesy of the California Academy of Sciences). 

14. Acila (Truncacila) decisa (Conrad) (p. AlO). 

Neotype UCMP 31132 (x 2.0). Length 12 mm, height 9 mm, thickness 3 mm 

(one valve). Ardath Shale, California, Eocene. 

15, 16. Acila (Truncacila) shumardi (Dall) (p. AlO). 

Holotype USNM 406405 (x 1.5). Length 24 mm, height 18 mm. Pittsburg Bluff 

Formation, Oregon, Oligocene. 

17. Acila (Truncacila) decisa (Conrad), unnamed form, Vokes (p. AlO). 

Hypotype UCMP 15477 (x 4.0). Length 8 mm, height 7 mm, thickness 5 mm 

(both valves). Avenal Sandstone, California, Eocene. 

18. Acila (Truncacila) dalli (Arnold) (p. All). 

Holotype USNM 165452. Length 35 mm, height 27 mm. San Lorenzo 

Formation, California, Eocene and Oligocene. 

19, 20. Acila (Truncacila) muta Clark (p. All). 

Holotype UCMP11196 (x 1.5). Length 18 mm, height 15 mm, thickness 6 mm 

(one valve). San Ramon Sandstone, California, Miocene. 

21, 22. Acila (Truncacila) conradi (Meek) (p. Al2). 

21. Neotype USNM 3526 (x 1.5; latex impression). Length 8 mm, height 10 

mm. Astoria Formation, Oregon, Miocene. 

22. Hypotype USNM 563204 (Moore, 1963, pl. 12, fig. 2). Length 21 mm, 

height 17 mm, thickness 10 mm (both valves). Astoria Formation, 

Oregon, Miocene. 

23, 25. Acila (Acila) semirostrata (Grant and Gale) (p. A9). 

Holotype SDNM 370. Length 27 mm, height 23 mm, thickness 9 mm (one 

valve). Pico(?) Formation, California, Pliocene. 

24. Acila (Truncacila) castrensis (Hinds) (p. Al2). 

Hypotype LAM 4448 (x 4.0); Hertlein and Grant, 1972, pl. 27, fig. 8). Length 

10 mm, height 8 mm. San Diego Formation, California, Pliocene. (Photography courtesy of the California Academy of Sciences.) 

26. Acila (Truncacila) empirensis Howe (p. Al2). 

Holotype UCMP 30032 (x 1.5). Length 14 mm, height 11 mm, thickness 8 mm 

(both valves). Empire Formation, Oregon, Miocene. 
GEOLOGICAL SURVEY PROFESSIONAL PAPER 1228-A PLATE 1 

2 X4.0 

4 

6 7 X3.0 

8 

5 

X3.0 9 X7.5 

10 X3.0 12 

X4.0 

11 13 

15 X7.5 16 

X7.5 19 X7.5 20 

18 

23 25 

X4.0 

24 

X7.5 

22 26 

NUCULANIDAE 
PLATE 2 

FIGURES 1, 2. Nuculana (Nuculana) fossa (Baird) (p. A13). 

Hypotype CAS 59924 (x 1.5). Length 25 mm, 

height 14 mm, thickness 9 mm (both valves). 

CAS/SU 1079, Unalaska, Alaska, Holocene. 

Depth 135m. 

3, 4. Nuculana (Nuculana) fossa sculpta (Dall) (p. A13). 

Holotype USNM 107688 (x 1.5). Length 20 mm, 

height 11 mm, thickness 8 mm (both valves). 

Southeast of Alaska Peninsula, Alaska, 

Holocene. 

5. Nuculana (Nuculana) minuta praecursor (Arnold) 

(p. A14). 

Hypotype UCR 7560/12 (x 2.0). Length 18 mm, 

height 8 mm. San Pedro Formation, California, Pliocene and Pleistocene. 

6. Nuculana (Nuculana) pernula Mi.iller (p. A15). 

UCR 4915/317 (x 2.0). Length 14 mm, height 7 

mm, thickness 3 mm (one valve). Fernando 

Formation, California, Pliocene and Pleistocene. 

7, 8. Nuculana (Saccella) gabbii (Gabb) (p. A16). 

7. Lectotype ANSP 4476 (x 2.0). Length 12 mm, 

height 7 mm. Tejon Formation of some 

authors, California, Eocene. 

8. Hypotype ANSP 4476a (Stewart, 1930, pl. 10, 

fig. 4) (x 2.0). Length 13 mm, height 7 mm. 

9, 10. Nuculana (Saccella) alaeformis (Gabb) (p. A15 ) 

Martinez Formation, California, Paleocene .. 

9. Hypotype, USNM 157829 (Stanton, 1896, pl. 

64, figs. 6, 7). Length 34 mm, height 18 

mm. 

10. Paratype? UCMP 32515. Length 29 mm, 

height 18 mm, thickness 5 mm (one valve, 

estimated). 

11, 41. Nuculana (Sacella) uvasana (Dickerson) (p. A17). 

11. Paratype CAS 251 (x 2.0). Exterior of right 

valve. Length 22 mm, height 12 mm, thickness 3 mm (one valve). Tejon Formation, 

California, Eocene. 

41. Holotype CAS 250 (x 1.5). Length 18 mm, 

height 9 mm. Tejon Formation, California, 

Eocene. 

12, 13. Nuculana (Saccella) chaneyi Vokes (p. A16). 

12. Syntype UCMP 15745 (x 6.0). Length 5 mm, 

height 3 mm, thickness 2 mm (both valves). 

A venal Sandstone, California, Eocene. 

13. Syntype UCMP 15746 (x 4.0). Length 6 mm, 

height 3 mm, thickness 3 mm (both valves). 

A venal Sandstone, California, Eocene. 

14, 15. Nuculana (Saccella) merriami (Dickerson) (p. A17). 

Holotype CAS 381. Length 31 mm, height 18 

mm, thickness 6 mm (one valve). Gries Ranch 

Formation, Washington, Oligocene. 

16, 17. Nuculana (Saccella) washingtonensis (Weaver) 

(p. A17). 

Paratype CAS 450A (x 2.0). Length 17 mm, 

height 8 mm, thickness 5 mm (both valves). 

Lincoln Creek Formation, Washington, 

Eocene to Miocene. 

18, 19. Nuculana (Saccella) pulchrisinuosa (Clark) (p. A18). 

Holotype UCMP 11109 (x 3.0). Length 9 mm 

(incomplete), height 5 mm (incomplete), thickness 4 mm (both valves). San Ramon Sandstone, California, Miocene. 

20, 21. Nuculana (Saccella) chehalisensis (Weaver) (p. A18). 

Holotype CAS 539 (x 1.5). Length 14 mm, height 

9 mm, thickness 7 mm. Astoria Formation, 

Washington, Miocene. 

22, 23. Nuculana (Saccella) taphria (Dall) (p. A19). 

Hypotype SDNM 77 (x 2.5; Moore, 1968, pl. 23, 

figs. e, g). Length 16 mm, height 10 mm, 

thickness 10 mm (both valves). San Diego 

Formation, California, Pliocene. 

24, 25. Nuculana (Saccella) ochsneri (Anderson and Martin) 

(p. A19). 

Holotype CAS 103 (x 1.5). Length 15 mm, 

height 8 mm, thickness 6 mm (both valves). 

Round Mountain Silt, California, Miocene. 

26, 27. Nuculana (Saccella) cellulita (Dall) (p. A20) 

26. Lectotype USNM 107436a (x 1.5); (figured by 

Dall, 1897, pl. 2, fig. 5). Length 15 mm, 

height 10 mm, thickness 7 mm (both 

valves). Port Orchard, Washington, Holocene. 

27. Paratype USNM 107436 (x 1.5); (figured by 

Dall, 1897, pl. 2, fig. 7). Length 15 mm, 

height 10 mm, thickness 4 mm (one valve). 

Port Orchard, Washington, Holocene. 

28, 29. Nuculana (Saccella) orcutti (Arnold) (p. A20). 

Holotype USNM 165271 (x 3.0). Length 7 mm, 

height 5 mm. Careaga Sandstone, California, 

Pliocene. 

30, 31. Nuculana (Saccella) hindsii (Hanley) (p. A20). 

Hypotype USNM 560096 (x 3.0; Woodring, 1950, 

pl. 16, fig. 18). Length 7 mm, height 4 mm, 

thickness 2 mm (one valve). Cebada Member 

of the Careaga Sandstone, California, Pliocene. 

32. Nuculana (Saccella ?) packardi (Dickerson) (p A21). 

Holotype UCMP 11725 (x 2.0). Length 12 mm, 

height 7 mm. Martinez Formation, California, 

Paleocene. 

33. Nuculana (Saccella ?) ramonensis (Clark) (p. A21). 

Holotype UCMP 11167 (x 2.0). Length 14 mm, 

height 7 mm. San Ramon Sandstone, California, Miocene(?). 

34. Nuculana (Saccella) cahillensis (Arnold) (p. A17). 

Holotype CAS/SU 5368 (x 3.0). Length 7 mm, 

height 5 mm, thickness 2 mm (one valve, 

estimated). Vaqueros Formation, California, 

Oligocene and Miocene. 

35, 36. Nuculana (Saccella) furlongi (Trask) (p. A19). 

Holotype UCMP 12362 (x 1.5). Length 20 mm, 

height 11 mm, thickness 8 mm (both valves). 

Briones Sandstone, California, Miocene. 

37, 38. Nuculana (Thestyleda) hamata (Carpenter) (p. A22). 

Lectotype USNM 107420 (x 3.0). Length 9 mm, 

height 5 mm, thickness 2 mm (both valves). 

Catalina Island, California, Holocene. 

39. Nuculana (Saccella ?) fabata (Nelson) (p. A21). 

Holotype UCMP 30717 (x 4.0). Length 5 mm, 

height 3 mm. Martinez Formation, California, 

Paleocene. 

40. Nuculana (Saccella?) denominata (G D. Hanna) 

(p. A21). 

Holotype UCMP 11663 (x 3.0). Length 10 mm, 

height 5 mm. Martinez Formation, California, 

Paleocene. 

42. Nuculana (Saccella) hondana Vokes (p. A16). 

Holotype UCMP 15561 (x 3.0). Length 9 mm, 

height 5 mm, thickness 3 mm (one valve). 

Lodo Formation, California, Paleocene and 

Eocene. 
GEOLOGICAL SURVEY PROFESSIONAL PAPER 1228-A PLATE 2 

3 

X1.5 X1 .5 2 X1.5 

X2.0 6 

X2.0 

8 9 

11 

X4.0 14 

X6.0 12 13 

X3.0 

15 X2.0 17 

16 

X3.0 

18 

X1.5 20 

X1.5 24 

""--

. a ' 

<A X2.5 X2.5 

X1.5 23 22 X1.5 21 25 

X3.0 30 C.> 

X1.5 

X1.5 26 27 29 X3.0 32 31 

X7.5 

X7.5 35 36 X3.0 

37 

X3.0 38 X3.0 

40 

42 

NUCULANIDAE 
PLATE 3 

FIGURES 1. Nuculana (Nuculana?) elongorostrata (Clark)(p. A15). 

Holotype UCMP 11206 (x 2.0). Length 18 mm, height 7 mm. Kirker Tuff, 

California, Oligocene. 

2. Nuculana (Saccella) markleyensis (Clark) (p. A18). 

Holotype UCMP 11272 (x 1.5). Length 15 mm, height 8 mm. San Ramon 

Sandstone, California, Miocene(?). 

3. Ledina duttonae (Vokes) (p. A22). 

Holotype UCMP 15564 (x 4.0). Length 6 mm, height 3 mm. Lodo Formation, 

California, Paleocene and Eocene. 

4, 5. Ledina fresnoensis (Dickerson) (p. A22). 

Holotype UCMP 11790 (x 1.5). Length 21 mm, height 12 mm, thickness 6 mm 

(one valve). Lodo Formation, California, Paleocene and Eocene. 

6, 7. Hilgardia? parkei (Anderson and G D. Hanna) (p. A22). . 

6. Holotype CAS 782 (x 3.0). Length 11 miri, height 6 mm, thickness 3 mm 

(one valve). Tejon Formation, California, Eocene. 

7. Paratype CAS 783 (x 3.0). Length 11 min, height 5 mm. Tejon Formation, 

California, Eocene. 

8. Hilgardia? parkei coosensis Turner (p. A23) 

Holotype UCMP 33205 (x 3.0). Length 9 mm, height 5 mm. Umpqua 

Formation, Oregon, Eocene. 

9. Lithorhadia astoriana (Henderson) (p. A23). 

Lectotype USNM 3490 (x 1.5). Length 19 mm, height 9 mm, thickness 7 mm 

(both valves). Astoria Formation, Oregon, Miocene. 

10. Yoldia (Kalayoldia) tenuissima Clark (p. A24). 

Holotype UCMP 11110. Length 45 mm, height 24 mm. San Ramon Sandstone, California, Miocene(?). 

11, 12. Yoldia (Kalay9ldia) oregona (Shumard) (p. A24). 

11. Lectotype USNM 562470. Length 41 mm, height 22 mm. Scappoose(?) 

Formation, Oregon, Oligocene and Miocene. 

12. Hypotype USNM 214094 (x 1.5); Moore, 1976, pl. 9, fig. 17). Length 41 

mm, height 23 mm. Pittsburg Bluff Formation, Oregon, Oligocene. 

13. Yoldia (Kalayoldia) submontereyensis Arnold (p. A24). 

Holotype USNM 165459. Length 32 mm, height 21 mm, thickness 3 mm (one 

valve). Vaqueros Formation, California, Oligocene and Miocene. 

14. Yoldia (Kalayoldia) supramontereyensis Arnold (p. A25). 

Holotype CAS/SU 5362. Length 35 mm, height 20 mm, thickness 8 mm (both 

valves). Unnamed Miocene sandstone of Dibblee (1966). 

15, 16. Yoldia (Megayoldia) beringiana Dall (p. A26). 

Lectotype USNM 226195a. Length 39 mm, height 23 mm, thickness 9 mm 

(one valve). Pribiloff Islands, Alaska, Holocene. 

17, 18. Yoldia (Megayoldia) thraciaeformis (Storer) (p. A26). 

Hypotype CAS 59925. Length 43 mm, height 27 mm, thickness 10 mm (one 

valve). Nahant, Mass., Holocene. 

19, 20. Yoldia (Kalayoldia) cooperi Gabb (p. A25). 

Holotype UCMP 30613. Length 65 mm, height 32 mm, thickness 7 mm. 

Santa Cruz, Calif., Holocene. 
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15 16 

17 

NUCULANIDAE 
PLATE 4 

FIGURES 1, 2. Yoldia (Cnesterium) scissurata Dall (p. A27). . 

Hypotype USNM 73669 (x 1.5). Length 29 nim, height 16 mm, thickness 4 

mm (one valve). Sea Horse Island, Arctic Ocean, Holocene. 

3. Yoldia (Cnesterium) strigata Dall (p. A27). 

Holotype USNM 153951. Length 37 mm, height 20 mm, thickness 6 mm 

(both valves). Empire Formation, Oregon, Miocene. 

4, 5. Nuculana (Costelloleda?) powersi (Dickerson) (p. A15). 

Holotype UCMP 11724 (x 3.0). Length 10 mm, height 4 mm. Martinez 

Formation, California, Paleocene. 

5. Tipped to show teeth. 

6. Yoldia? gala Woodring (p. A28). 

Holotype USNM 560024 (x 1.5). Length 26 mm, height 11 mm, thickness 3 

mm (one valve). Todos Santos Claystone Member of the Sisquoc Formation, 

California, Miocene and Pliocene. 

7, 18, 19. Yoldia (Cnesterium) seminuda Dall (p. A28). 

7. Holotype of Yoldia (Cnesterium) imleri Waterfall, UCMP 31420. Length 

39 mm, height 21 mm. Pica Formation, California, Pliocene and 

Pleistocene. 

18. Hypotype CAS 59920 (x 1.5). Length 36 mm, height 16 mm. Rio Dell 

Formation, California, Pliocene. 

19. Holotype USNM 197678. Length 44 mm, height 22 mm. Kodiak Island, 

Alaska, Holocene. 

8. Yoldia (Kalayoldia?) gesteri Dickerson (p. A26). 

Holotype UCMP 11685 (x 1.5). Length 29 mm, height 13 mm. Martinez 

Formation, California, Paleocene. 

9. Portlandia (Portlandia) rosa (M.A. Hanna) (p. A29). 

Holotype UCMP 31090 (xl.5). Length 15 mm, height 8 mm. Ardath Shale, 

California, Eocene. 

10. Portlandia (Portlandia) mosesi (Palmer) (p. A30). 

Holotype UCMP 30704 (x 2.0). Length 15 mm, height 9 mm. Capay(?) 

Formation, California, Eocene. 

11. Portlandia (Portlandia) packardi (Clark) (p. A30). 

Holotype UCMP 11154 (x 1.5). Length 17 mm, height 9 mm, thickness 5 mm 

(one valve, estimated). Kirker Tuff, California, Oligocene. 

12, 13. Portlandia (Portlandia) chehalisensis (Arnold) (p. A30). 

Holotype USNM 165447 (x 3.0). Length 7 mm, height 5 mm. Lincoln Creek 

Formation, Oregon, Eocene to Miocene. 

14. Yoldia (Yoldia?) temblorensis Anderson and Martin (p. A23). 

Holotype CAS 106 (x 2.0). Length 18 mm, height 8 mm, thickness 4 mm (both 

valves). Round Mountain Silt, California, Miocene. 

15. Portlandia (Portlandia) mortuasusensis (Clark and Woodford) (p. A29). 

Holotype UCMP 31337 (x 3.0). Length 9 mm, height 5 mm. Meganos 

Formation, California, Paleocene. 

16. Portlandia (Portlandia) markleyensis (Clark) (p. A29). 

Holotype UCMP 30833. Length 23 mm, height 13 mm, thickness 8 mm (both 

valves). Markley Formation, California, Eocene. 

17. Yoldia (Kalayoldia?) carnarosensis (Clark) (p. A26). 

Holotype UCMP 11539. Length 39 mm, height 21 mm (plaster cast). San 

Pablo Formation, California, Miocene. 

20. Acharax aff. johnsoni (Dall) (p. A31). 

Hypotype USNM 496070 (x 1.5); Woodring, 1938, pl. 5, fig. 14). Length 31 mm, 

height 16 mm. Fernando Formation, California, Pliocene and Pleistocene. 

21. Yoldia (Cnesterium) ensifera Dall (p. A27). 

Hypotype CAS 59927 (x 1.5). Length 40 mm, height 19 mm. Vancouver 

Island, British Columbia. Holocene. 

22. Acharax? dunnensis (Palmer) (p. A31) 

Holotype UCMP 30690 (x 3.0). Length 14 mm, height 7 mm. Capay(?) 

Formation, California, Eocene. 

23. Acharax johnsoni (Dall) (p. A31). 

Hypotype CAS 53043. Length 70 mm, height 23 mm. Rio Dell Formation, 

California, Pliocene. 
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NUCULANIDAE, SOLEMYIDAE 
PLATE 5 

FIGURES 1. Area (Area) hawleyi Reinhart (p. A31). 

Holotype CAS/SU 5343 (x 1.5). Length 42 mm, height 19 mm, thickness 14 mm 

(one valuve). Tejon Formation, California, Eocene. 

2, 5. Area (Area) santamariensis Reinhart (p. A33). 

Holotype LAM 4072 (CIT 1381) (x 3.0). Length 26 mm, height 19 mm, 

thickness 19 mm (both valves). Cebada Member of the Careaga Sandstone, 

California, Pliocene. 

3, 4. Area (Area) terminumbonis Grant and Gale (p. A33). 

Holotype SDNM 79. Length 70 mm, height 37 mm. Fernando Formation, 

California, Pliocene and Pleistocene. 

6, 8. Area (Area) sisquoeensis Reinhart (p. A33). 

Holotype LAM 4073 (CIT 1382) (x 4.0). Length 15 mm, height 8 mm, 

thickness 4 mm (one valve). Cebada Member of the Careaga Sandstone, 

California, Pliocene. (Photography courtesy of the Los Angeles Natural 

History Museum) 

7. Barbatia (Barbatia) morsei Gabb (p. A34). 

Lectotype UCMP 11984 (x 3.0). Length 19 mm, height 16 mm. La Jolla Group, 

California, Eocene. 

9, 12. Barbatia (Cueullaearea) cliffensis M.A. Hanna (p. A34). 

9. Paratype UCMP 31081 (x 1.5). Length 34 mm, height 22 mm. Ardath 

Shale, California, Eocene. 

12. Lectotype UMCP 31077. Length 48 mm, height 37 mm (plaster cast). 

Ardath Shale, California, Eocene. 

10, 11. Barbatia (Cucullaearca) bramkampi Durham (p. A35). 

Holotype UCMP 15552. Length 40 mm, height 24 mm, thickness 8 mm. 

Marquer Formation, Baja California Sur, Pliocene. 
GEOLOGICAL SURVEY PROFESSIONAL PAPER 1228-A PLATE 5 

ARCIDAE 
PLATE 6 

FIGURES 1-, 2. Barbatia (Cucullaearca) reeveana (Orbigny) (p. A35). 

Hypotype CAS/SU 6967 (Reinhart, 1943, pl. 15, figs. 1-3). Length 66 mm, 

height .38 mm, thickness 13 mm (one valve). Baja California, Holocene. 

3, 5. Barbatia (Fugleria) pseudoillota Reinhart (p. A35). 

Holotype LAM 4075 (CCIT 1381) (x 1.5). Length 34 mm. Cebada Member of 

the Careaga Sandstone, California, Pliocene. (Photography courtesy of 

Los Angeles Natural History Museum) 

4. Area (Area) leptogrammiea Hall (p. A32). 

Holotype UCLA 34977. Length 56 mm, height 34 mm. Santa Margarita 

Formation, California, Miocene. 

6, 7. Barbatia (Fugleria) illata (Sowerby) (p. A36). 

Hypotype LAM 4464 (x 2.0; Hertlein and Grant, 1972, pl. 27, figs. 38, 39). 

Length 20 mm, height 14 mm. San Diego Formation, California, Pliocene. 

8, 9. Anadara (Anadara) lakei (Wiedey) (p. A37). 

Holotype SDNM 19. Length 38 mm, height 34 mm, thickness 28 mm. Upper 

part of Temblor Formation, California, Miocene. 

10, 11. Anadara (Anadara) osmonti (Dall) (p. A36). 

Holotype UCMP 11927. Length 48 mm, height 42 mm, thickness 36 mm (both 

valves). Upper part of Temblor(?) Formation, California, Miocene. 

12. Anadara (Anadara) submontereyana (Clark) (p. A37). 

Holotype UCMP 11186 (x 2.0). Length 18 mm, height 14 mm. San Ramon 

Sandstone, California, Miocene(?). 

13, 14. Anadara (Anadara?) strongi (Loel and Corey) (p. A41). 

13. Lectotype UCMP 31762 (x 2.0). Length 16 mm, height 11 mm. Upper part 

of Vaqueros Formation, California, Miocene. 

14. Paratype UCMP 31762 (x 2.0; on same rock as lectotype). Length 15 mm, 

height 9 mm. Upper part of Vaqueros Formation, California, Miocene. 

15. Anadara (Anadara) devineta (Conrad), split-rib form (p. A38). 

Hypotype USNM 563220 (Moore, 1963, pl. 14, fig. 4). Length 35 mm, height 28 

mm, thickness 23 mm (both valves). Astoria Formation, Oregon, Miocene. 

16. Anadara (Anadara) devineta (Conrad), inflated form (p. A38). 

Hypotype USNM 563221 (Moore, 1963, pl. 14, fig. 5). Length 23 mm, height 25 

mm, thickness 27 mm (both valves). Astoria Formation, Oregon, Miocene. 

17. Anadara (Anadara) devineta (Conrad), thin form (p. A38). 

Hypotype USNM 56322 (Moore, 1963, pl. 14, fig. 6). Length 36 mm, height 

26 mm, thickness 4 mm (one valve). Astoria Formation, Oregon, Miocene. 
GEOLOGICAL SURVEY 

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ARCIDAE 

PROFESSIONAL PAPER 1228-A PLATE 6 

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PLATE 7 

FIGURES 1. Anadara (Anadara) devincta (Conrad) (p. A38). 

Lectotype USNM 3499 (x 1.5). Length 37 mm, height 29 mm, thickness 15 mm 

(one valve). Astoria Formation, Oregon, Miocene. 

2, 3. Anadara (Anadara) mediaimpressa (Clark) (p. A38). 

Holotype UCMP 11174 (x 2.0). Length 15 mm, height 12 mm, thickness 6 mm 

(one valve). San Ramon Sandstone, California, Miocene(?). 

4. Anadara (Anadara) montereyana (Osmont) (p. A39). 

Holotype UCMP 11925. Length 54 mm, height 37 mm, thickness 15 mm (one 

valve). Monterey Group, California, Miocene. 

5, 11. Anadara (Anadara) carrizoensis Reinhart (p. A40). 

Holotype LAM 4069 (CIT 3248). Length 98 mm, height 63 mm, thickness 

35 mm (one valve). Imperial Formation, California, Miocene or Pliocene. 

6, 10. Anadara (Anadara) montesanoana (Etherington) (p. A39). 

Holotype UCMP 31922. Length 48 mm, height 40 mm, thickness 18 mm. 

Montesano Formation, Washington, Miocene. 

7-9. Anadara (Anadara) trilineata (Conrad) (p. A40). 

7, 9. Hypotype LAM 4459 (Hertlein and Grant, 1972, pl. 28, fig. 1). Length 

67 mm, height 51 mm. San Diego Formation, California, Pliocene. 

8. Hypotype CAS/SU 5304 (Schenck and Keen, 1940, pl. 1, fig. 6). Length 

42 mm, height 37 mm, thickness 15 mm (one valve). Purisima Formation, 

California, Miocene and Pliocene. 
GEOLOGICAL SURVEY PROFESSIONAL PAPER 1228-A PLATE 7 

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6 

7 

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ARCIDAE 
PLATE 8 

FIGURES 1, 2. Anadara (Anadara) trilineata calcarea (Grant and Gale) (p. A41). 

Holotype CAS/SU 436. Length 78 mm, height 70 mm, thickness 70 mm (both 

valves). San Diego Formation, California, Pliocene. 

3, 7. Larkinia santana santana (Loel and Corey) (p. A42). 

Holotype UCMP 31768. Length 39 mm, height 40 mm, thickness 21 mm (one 

valve). Vaqueros Formation, California, Oligocene and Miocene. 

4. Anadara (Anadara) trilineata canalis (Conrad) (p. A41). 

Hypotype CAS/SU 5304 (Reinhart, 1943, pl. 7, figs. 3, 4). Length 42 mm, 

height 36 mm. Purisima Formation, California, Miocene ·and Pliocene. 

5, 6. Anadara (Anadara) topangaensis Reinhart (p. A40). 

Holotype UCMP 3258. Length 32 mm, height 25 mm, thickness 23 mm (both 

valves). Topanga Formation, California, Miocene. 

8, 9. Larkinia camuloensis (Osmont) (p. A43). 

Holotype UCMP 12006. Length 95 mm, height 90 mm, thickness 78 mm (both 

valves). Pico Formation, California, Pliocene and Pleistocene. 
GEOLOGICAL SURVEY 

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PROFESSIONAL PAPER 1228-A PLATE 8 

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ARCIDAE 
PLATE 9 

FIGURES 1, 2. Larkinia santana weddlei (Loel and Corey) (p. A43). 

Holotype UCMP 31771. Length 40 mm, height 37 mm, thickness 37 mm 

(both valves). Vaqueros Formation, California, Oligocene and Miocene. 

3. Scapharca? (Scapharca?) obispoana obispoana (Conrad) (p. A44). 

Lectotype USNM 13330 (x 1.5). Length 28 mm, height 17 mm. Santa 

Margarita(?) Formation, California, Miocene. 

4, 5. Larkinia multicostata (Sowerby) (p. A43). 

Hypotype CAS/SU 5294 (Reinhart, 1943, pl. 3, figs. 9-11). Length 59 mm, 

height 53 mm, thickness 44 mm (both valves). Gulf of California, Holocene. 

6. Scapharca? (Scapharca?) obispoana perdisparis (Wiedey) (p. A44). 

Holotype SDNM 23 (x 1.5). Length 33 mm, height 24 mm, thickness 4 mm 

(one valve; estimated). Monterey Formation, California, Miocene. 

7. Scapharca (Cunearca) vanderhoofi Durham (p. A44). 

Holotype UCMP 30548 (x 1.5). Length 18 mm, height 15 mm, thickness 7 mm 

(one valve). San Gregorio Formation, Baja California Sur, Oligocene. 

8, 9. Grandiarca grandis (Broderip and Sowerby) (p. A42). 

Hypotype CAS/SU 6964 (Reinhart, 1943, pl. 13, figs. 4-6). Length 96 mm, 

height 77 mm, thickness 42 mm. Ecuador, Holocene. 

10, 11. Scapharca (Cunearca) santaclarana (Loel and Corey) (p. A44). 

Holotype UCMP 31765 (x 1.5). Length 22 mm, height 20 mm, thickness 

21 mm (both valves). Vaqueros Formation, California, Oligocene and 

Miocene. 

12. Scapharca (Cunearca) hamelini (Wiedey) (p. A45). 

Holotype SDNM 18 (x 2.0). Length 25 mm, height 23 mm. Vaqueros 

Formation, California, Oligocene and Miocene. 

13. Scapharca (Cunearca) rivulata (Wiedey) (p. A45). 

Holotype SDNM 20 (x 3.0). Length 14 mm, height 15 mm, thickness 7 mm 

(one valve; estimated). Upper part of Temblor Formation, California, 

Miocene. 
GEOLOGICAL SURVEY PROFESSIONAL PAPER 1228-A PLATE 9 

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ARCIDAE 13 
PLATE 10 

FIGURES 1, 2. Cucullaea mathewsonii Gabb (p. A47). 

1. Lectotype ANSP 4559. Length 63 mm, height 58 mm, thickness 28 mm 

(one valve). Martinez Formation, California, Paleocene. 

2. Paratype? ANSP 4559 (also numbered 6125). Length 75 mm, height 

67 mm, thickness 37 mm (one valve). Martinez(?) Formation, California, 

Paleocene. 

3, 4. Porterius woodfordi (M.A. Hanna) (p. A46). 

Holotype UCMP 31062 (x 5.0). Length 4 mm, height 3 mm. Ardath Shale, 

California, Eocene. 

5, 6. Cucullaea morani Waring (p. A47). 

Holotype CAS/SU 166. Length 50 mm, height 30 mm (incomplete), thickness 

38 mm (both valves). Meganos Formation, California, Paleocene. 

7. Pachecoa (Pachecoa) hornii (Gabb) (p. A48). 

Paratype ANSP 4460a (x 7.0). Length 7 mm, height 6 mm, thickness 4 mm. 

Tejon Formation, California, Eocene. 

8. Pachecoa (Pachecoa) hornii elusa (Clark and Woodford) (p. A48). 

Hypotype UCMP 15594 (x 5.0; Vokes, 193, pl. 1, fig. 22). Length 4 inm, height 

3 mm. Meganos Formation, California, Paleocene. 

9, 10. Limopsis (Limposis) marysvillensis (Dickerson) (p. A49). 

Holotype UCMP 11766 (x 5.0). Length 6 mm, height 6 mm, thickness 3 mm. 

Marysville Claystone Member of the Meganos Formation, Paleocene. 

11, 16. Glycymeris (Glycymeris) branneri Arnold (p. A51). 

Holotype USNM 165455. Length 62 mm, height 62 mm, thickness 23 mm 

(one valve). Vaqueros Formation, California, Oligocene and Miocene. 

12, 13. Glycymeris (Glycymeris) rosecanyonensis M.A. Hanna (p. A49). 

Holotype UCMP 30989 (x 2.5). Length 7 mm, height 6 mm. Ardath Shale, 

California, Eocene. 

14, 15. Glycymeris (Glycymeris) viticola Anderson and Hanna (p. A50). 

Holotype CAS 777. Length 22 mm, height 21 mm, thickness 8 mm (one 

valve). Tejon Formation, California, Eocene. 

17, 18. Arcopsis (Arcopsis) eba (M.A. Hanna) (p. A47). 

Holotype UCMP 31047 (x 5.0). Length 7 mm, height 5 mm, thickness 3 mm 

(one valve). Ardath Shale, California, Eocene. 
GEOLOGICAL SURVEY PROFESSIONAL PAPER 1228-A PLATE 10 

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16 X5.0 18 

CUCULLAEIDAE, NOETIIDAE, LIMOPSIDAE, GLYCYMERIDIDAE 
PLATE 11 

FIGURES 1, 3. Glycymeris (Glycymeris) gigantea (Reeve) (p. A52). 

Holotype UCMP 30554 (Durham, 1950, pl. 2, figs. 1, 8). Length 65 mm, height 

64 mm, thickness 24 mm (one valve). Baja California Sur, unnamed 

Pliocene strata. 

2, 4. Glycymeris (Glycymeris) maculata (Broderip) (p. A52). 

Hypotype UCMP 30557 (Durham, 1950, pl. 2, figs. 3, 5). Length 60 mm, 

height 58 mm, thickness 21 mm (one valve). Baja California Sur, unnamed 

Pleistocene strata. 

5, 6. Glycymeris (Glycymeris?) whayleyi Nicol (p. A53). 

Holotype CAS 8584. Length 39 mm, height 38 mm, thickness 13 mm (one 

valve). Saltos Shale Member of the Monterey Shale, California, Miocene. 

7, 8. Glycymeris (Glycymeris?) swartsi Hertlein and Jordan (p. A53). 

7. Paratype CAS 2659. Length 42 mm, height 41 mm, thickness 15 mm (one 

valve). Isidro(?) Formation, Baja California Sur, Miocene. 

8. Holotype CAS 5132. Length 40 mm, height 39 mm, thickness 30 mm. 

Isidro(?) Forma~ion, Baja California Sur, Miocene. 

9, 10. Glycymeris (Glycymerita) major (Stanton) (p. A54). 

Syntype USNM 157830. Length 65 mm, height 57 mm. Martinez Formation, 

California, Paleocene. 

11, 12. Glycymeris (Glycymerita) major meganoensis Clark and Woodford (p. A53). 

Holotype UCMP 31289. Length 43 mm, height 44 mm (restored), thickness 

19 mm (one valve). Meganos Formation, California, Paleocene. 

13, 14. Glycymeris (Glycymerita?) tecolotensis M. A. Hanna (p. A55). 

Holotype UCMP 30987 (x 1.5). Length 24 mm, height 27 mm, thickness 

10 mm (one valve). Ardath Shale, Califomia, Eocene. 
GEOLOGICAL SURVEY 

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GLYCYMERIDIDAE 

PROFESSIONAL PAPER 1228-A PLATE 11 

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PLATE 12 

FIGURES 1. Glycymeris (Glycymerita?) reefensis Vokes (p. A55). 

Holotype UCMP 15571 (x 2.0). Length 12 mm, height 12 mm, thickness 5 mm 

(one valve). Avenal Sandstone, California, Eocene. 

2, 3. Glycymeris (Tucetona) fresnoensis Dickerson (p. A55). 

Holotype UCMP 11795 (x 3.0). Length 7 mm, height 8 mm. Lodo Formation, 

California, Paleocene and Eocene. 

4, 5. Glycymeris (Tucetona) perrin{Dickerson (p. A55). 

Holotype UCMP 11792 (x 1.5). Length 12 mm, height 12 mm, thickness 4 mm 

(one valve). Domengine Formation, California, Eocene. 

6, 7. Glycymeris (Tucetona) evermanni Anderson and Hanna (p. A56). 

Holotype CAS 964 (x 8.0). Length 3 mm, height 3 mm. Tejon Formation, 

California, Eocene. 

8, 9. Glycymeris (Tucetona) ruckmani Dickerson (p. A56). 

Holotype UCMP 11051 (x 1.5). Length 18 mm, height 20 mm, thickness 7 mm 

(one valve). Tejon Formation, California, Eocene. 

10, 11. Glycymeris (Tucetona) verticordia Anderson and G D. Hanna (p. A56). 

Holotype CAS 776 (x 3.0). Length 8 mm, height 8 mm, thickness 3 mm (one 

valve). Tejon Formation, California, Eocene. 

12. Glycymeris (Tucetona?) maccrayi Waring (p. A57). 

Holotype CAS/SU 167 (x 1.5). Length 17 mm, height 15 mm, thickness 5 mm 

(one valve). Llajas Formation, California, Eocene. 

13, 14. Glycymeris (Glycymeris) buwaldi Clark (p. A51). 

Holotype UCMP 11150 (x 2.0). Length 10 mm, height 9 mm. San Ramon 

Sandstone, California, Miocene(?). 

15, 16. Glycymeris (Glycymerjs) subobsoleta Cooper (p. A52). 

Syntypes USNM 15594 (two specimens; both figured). 

15. USNM 15594. Length 33m, height 31 mm, thickness 10 mm. Neah 

Bay, Wash., Holocene. 

16. USNM 15594. Length 28 mm, height 28 mm, Neah Bay, Wash., 

Holocene. 

17. Glycymeris· (Glycymerita) sagittata (Gabb) (p. A54). 

Lectotype ANSP 4422. Length 34 mm, height 31 mm, thickness 13 mm (one 

valve). Tejon Formation, California, Eocene. 

18, 19. Glycymeris (Tucetona) multicostata (Sowerby) (p. A57). 

Hypotype CAS/SU 385 (Keen, 1971, fig. 116). Length 37 mm, height 38 mm, 

thickness 12 mm (both valves). Gulf of California, Holocene. 

20. Glycymeris (Axinola) grewingki Dall (p. A58). 

Holotype USNM 107784. Length 38 mm, height 38 mm, thickness 20 mm 

(both valves). Empire Formation, Oregon, Miocene. 

21, 22. Glycymeris (Axinola) profunda (Dall) (p. A58). 

LectQtype USNM 7935. Length 30 mm, height 32 mm, thickness 20 mm (both 

valves). Unnamed Pleistocene strata, San Diego, California. 

23. Glycymeris (Glycymeris) eocenica (Weaver) (p. A50). 

Paratype CAS 476A (x 1.5). Length 17 mm, height 17 mm, thickness 9 mm 

(both valves). Cowlitz Formation, Washington, Eocene. 

24, 25. Glycymeris (Tucetona) teniumbricata Clark (p. A56). . 

Holotype UCMP 11183. Length 26 mm, height 28 mm, thickness 7 mm (one 

valve). San Ramon Sandstone, California, Miocene(?). 
GEOLOGICAL SURVEY 

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• 

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,.,-s ·-; '-' I ( 

-~ 

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19 

23 

GLYCYMERIDIDAE 

PROFESSIONAL PAPER 1228-A PLATE 12 

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25 
PLATE 13 

FIGURES 1, 2. Glycymeris (Tucetona?) septentrionalis (Middendorff) (p. A57). 

Holotype UCMP 11520 (x 1.5; Clark, 1915, pl. 48, fig. 4). Length 19 mm, height 

19 mm, thickness 5 mm (one valve). San Pablo Group, California, Miocene. 

3, 4. Glycymeris (Glycymeris) gabbi Dall (p. A52). 

Holotype USNM 153949b. Length 53 mm, height 52 mm, thickness 22 mm 

(both valves). Empire Formation, Oregon, Miocene. 

5-7. Felicia phrear (Woodring) (p. A59). 

5. Holotype USNM 496077 (x 1.5). Length 18 mm, height 15 mm. Fernando 

Formation, California, Pliocene and Pleistocene. 

6, 7. Paratype USNM 496079 (x 1.5). Length 18 mm, height 22 mm. Fernando 

Formation, California, Pliocene and Pleistocene. 

8-10. Huxleyia munita (Dall) (p. A59). 

Syntype USNM 23243 (x 10.0). Length 1.6 mm, height 1.9 mm. Off Catalina 

Island, California, Holocene. 

11, 12. Mytilus (Mytilus) edulis Linne(p. A61). 

11. Hypotype CAS 59916. Length 74 mm, height 40 mm, thickness 25 mm 

(both valves). Long Island, N.Y., Holocene. 

12. Hypotype CAS 59917. Length 97 mm, height 54 mm, thickness 23 mm 

(one valve). Long Island, N.Y., Holocene. 

13, 14. Mytilus (Mytilus) condoni Dall (p. A61). 

13. Hypotype UCMP 10928 (Addicott, 1974, fig. 9). 

Length 80 mm, height 45 mm. Merced Formation, California, Pliocene 

and Pleistocene. 

14. Neotype USNM 647272. Length 42 mm, height 33 mm. Willapa Bay, 

Washington, unnamed Pliocene strata. 

15, 16. Mytilus (Mytilus) californianus Conrad (p. A61). 

15. Hypotype CAS 59918. Length 85 mm, height 35 mm, thickness 33 mm 

(both valves). San Diego, Calif., Holocene. 

16. Hypotype CAS 59919. Length 78 mm, height 42 mm, thickness 31 mm 

(both valves). San Diego, Calif., Holocene. 
GEOLOGICAL SURVEY PROFESSIONAL PAPER 1228-A PLATE 13 / ., } . 

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15 16 

GLYCYMERIDIDAE, MYTILIDAE 
PLATE 14 

FIGURES 1. Mytilus (Mytilus?) ascia Gabb (p. A62). 

Holotype UCMP 11989 (x 2.0). Length 32 mm, height 18 mm. Tejon Formation, California, Eocene. 

2. Mytilus (Mytilus?) arnoldi Clark (p. A62). 

Holotype UCMP 11153. Length 64 mm, height 35 mm. Kirker Tuff, California, Oligocene. 

3. Mytilus (Mytilus?) loeli Grant (p. A62). 

Holotype CAS/SU 515. Length 101 mm, height 60 mm. Vaqueros Formation, 

California, Oligocene and Miocene. 

4, 5. Mytilus (Crenomytilus ?) perrini Clark (p. A65) 

Holotype UCMP 11548 (x 1.5). Length 55 mm, height 28 mm, thickness 

16 mm (both valves). San Pablo Group, California, Miocene. 

6. Mytilus (Crenomytilus) mathewsonii Gabb (p. A63). 

Lectotype ANSP 4500 (x 0.8). Length 157 mm, height 70 mm, thickness 

72 mm (both valves). San Ramon Sandstone, Miocene(?). 

7, 8. Mytilus (Crenomytilus) trampasensis (Clark) (p. A63). 

7. Syntype UCMP 11545. Length 80 mm, height 48 mm. San Pablo Group, 

California, Miocene. 

8. Syntype UCMP 11546. Length 64 mm, height 39 mm. San Pablo Group, 

California, Miocene. 
GEOLOGICAL SURVEY PROFESSIONAL PAPER 1228--A PLATE 14 

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MYTILIDAE 
PLATE 15 

FIGURES 1-3. Mytilus (Crenomytilus) coalingensis Arnold (p. A64). 

Etchegoin Formation, California, Miocene and Pliocene. 

1, 3. Holotype USNM 165551. Length 110 mm, height 52 mm, thickness 35 mm 

(one valve). 

2. Paratype USNM 165557. Length 99 mm, height 54 mm. 

4. Mytilus (Crenomytilus) kewi Nomland (p. A63). 

Holotype UCMP 12061. Length 84 mm, height 42 mm, thickness 33 mm (one 

valve). Etchegoin Formation, California, Miocene and Pliocene. 

5. Mytilus (Crenomytilus) expansus Arnold (p. A63). 

Holotype USNM 164968. Length 105 mm, height 50 mm, thickness 60 mm 

(both valves). Vaqueros Formation, California, Oligocene and Miocene. 
GEOLOGICAL SURVEY PROFESSIONAL PAPER 1228-A PLATE 15 

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MYTILIDAE 
PLATE 16 

FIGURES 1. Mytilus (Crenomytilus) sternbergi Hertlein and Grant (p. A64). 

Holotype LAM 4470. Length 238 mm, height 134 mm. San Diego Formation, 

California, Pliocene. 

2. Mytilus (Crenomytilus?) schencki G D. Hanna and Hertlein (p. A64). 

Holotype CAS 4686 (x 0.8). Length 130 mm, height 108 mm. Santa 

Margarita(?) Formation, California, Miocene. 

3-6. Mytilus (Plicatomytilus) middendorffi Grewingk (p. A65). 

3. Copy of original drawing (Grewingk, 1850, pl. 7, fig. 3a). 

4. Copy of original drawing (Grewingk, 1950, pl. 7, fig. 3b). 

5. Hypotype USNM 647060 (Allison and Addicott, 1976, pl. 1, fig. 6). Length 

102 mm. Lower part of Empire Formation, Oregon, Miocene. 

6. Hypotype USNM 647062 (Allison and Addicott, 1976, pl. 1, fig. 7). Length 

86 mm (a rubber cast). Lower part of Empire Formation, Oregon, 

Miocene. 
GEOLOGICAL SURVEY PROFESSIONAL PAPER 1228-A PLATE 16 

MYTILIDAE 
PLATE 17 

FIGURES 1. Brachidontes (Brachidontes) cowlitzensis (Weaver and Palmer) (p. A66). 

Holotype CAS 7406 (x 2.0). Length 18 mm, height 14 mm. Cowlitz Formation, 

Washington, Eocene. 

2. Brachidontes? (Brachidontes?) susanaensis (Nelson) (p. A67). 

Holotype UCMP 30501 (x 5.0). Length 8 mm, height 5 mm. Martinez 

Formation, California, Paleocene. 

3, 4. Brachidontes? (Brachidontes?) altiobliquus (Nelson) (p. A67). 

Holotype UCMP 30587 (x 3.0). Length 14 mm, height 10 mm. Martinez 

Formation, California, Paleocene. 

5. Brachidontes? (Brachidontes?) lawsoni (Nelson) (p. A68). 

Holotype UCMP 30651 (x 2.0). Length 25 mm, height 13 mm. Martinez 

Formation, California, Paleocene. 

6, 7. Brachidontes? (Brachidontes?) dichotomus (Gabb) (p. A68). 

6. Holotype UCMP 11993 (x 3.0). Length 16 mm, height 11 mm. Tejon 

Formation, California, Eocene. 

7. Rubber impression of mold from which holotype was removed. 

8. Brachidontes (Aeidimytilus) gabbi (Clark) (p. A69). 

Holotype UCMP 11550. Length 68 mm, height 28 mm. San Pablo Group, 

California, Miocene. 

9. Brachidontes? (Brachidontes?) kirkerensis (Clark) (p. A68). 

Holotype UCMP 11121 (x 1.5). Length 38 mm, height 18 mm. San Ramon 

Sandstone, California, Miocene(?). 

10, 11. Brachidontes (Aeidimytilus) adamsianus (Dunker) (p. A 70). 

Hypotype LAM 4473 (x 3.0; Hertlein and Grant, 1972, pl. 42, figs. 4, 5). Length 

19 mm, height 7 mm. San Diego Formation, California, Pliocene. (Photography courtesy of the California Academy of Sciences) 

12, 17. Brachidontes (Scolimytilus?) multiradiatus (Gabb) (p. A69). 

Holotype ANSP 4482. Length 71 mm, height 30 mm, thickness 22 mm (both 

valves). Martinez Formation, California, Paleocene. 

13. Brachidontes (Scolimytilus?) margaritana (Nomland) (p. A69). 

Holotype UCMP 11310. Length 52 mm, height 23 mm, thickness 13 mm (one 

valve; estimated). Santa Margarita Formation, California, Miocene. 

14. Brachidontes (Scolimytilus?) subconuexus (Trask) (p. A69). 

Holotype UCMP 12372 (x 1.5). Length 56 mm, height 25 mm. Briones 

Sandstone, California, Miocene. 

15, 16. Mytella inezensis (Conrad) (p. A70). 

Syntypes USNM 13319. Gaviota Formation of some authors, California, 

Eocene and Oligocene. 

15. Length 40 mm, height 32 mm. 

16. Length 35 mm, height 30 mm. 
GEOLOGICAL SURVEY PROFESSIONAL PAPER 1228-A PLATE 17 

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15 16 17 

MYTILIDAE 
PLATE 18 

FIGURES 1, 2. Crenella decussata (Montagu) (p. A 71). 

Hypotype LAM 5747 (x 7.0). Length 2 mm, height 2.5 mm. Fernando 

Formation, California, Pliocene and Pleistocene. 

3, 5, 6. Crennella inflata Carpenter (p. A 72). 

3. Hypotype LAM 4479 (x 9.0); (Hertlein and Grant 1972, pl. 41, fig. 11). 

Length 3 mm, height 2.3 mm. San Diego Formation, California, Pliocene. (Photography courtesy of the California Academy of Sciences) 

5, 6. Holotype USNM 3988 (x10.0). Length 2.4 mm, height 3.0 mm. Cabo San 

Lucas, Baja California Sur, Holocene. 

4. Perna montana Conrad (p. A 70). 

Holotype USNM 13329. Length 70 mm, height 110 mm. Formation unknown; 

southern California, Eocene(?). 

7, 9. Septifer (Septifer) bifurcatus (Conrad) (p. A 71). 

Hypotype SDNM 04319 (x 4.0); (Hertlein and Grant, 1972, pl. 42, figs. 6, 12). 

Length 18 mm, height 10 mm. San Diego Formation, California, Pliocene. 

(Photography courtesy of the California Academy of Sciences) 

8. Brachidontes (Brachidontes) cooperi Moore, new name (p. A67). 

Holotype CAS 613 (x 2.0). Length 26 mm, height 14 mm. Domengine 

Formation, California, Eocene. 

10. Septifer (Septifer) coalingensis Arnold (p. A 71). 

Holotype USNM 165580. Length 45 mm, height 19 mm, thickness 18 mm 

(both valves). Etchegoin Formation, California, Miocene and Pliocene. 

11. Septifer (Septifer) elegans Waring (p. A 70). 

Neotype CAS/SU 322 (x 2.0). Length 20 mm, height 13 mm. Llajas Formation, California, Eocene. 
GEOLOGICAL SURVEY PROFESSIONAL PAPER 1228-A PLATE 18 

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MYTILIDAE 
PLATE 19 

FIGURES 1, 2. Gregariella chenui (Recluz) (p. A 72). 

Hypotype CAS 59920 (x 3.0). Length 9 mm, height 7 mm, thickness 3 mm (one 

valve). Isthmus Cove, Catalina Island, Calif., Holocene. Depth 55-90 m. 

3, 4. Musculus (Musculus) stalderi (Martin) (p. A 73). 

Holotype UCMP 12354 (x 1.5). Length 34 mm, height 18 mm, thickness 

13 mm (both valves). Rio Dell Formation, California, Pliocene. 

5, 6. Lithophaga (Lithophaga) clarki M.A. Hanna(p. A73). 

Holotype UCMP 31031 (x 3.0). Length 13 mm, height 7 mm, thickness 5 mm 

(both valves). Delmar(?) Formation, California, Eocene(?). 

7, 8. Lithophaga (Diberus) plumula (Hanley) (p. A 73). 

Hypotype CAS 59921 (x 1.5). Length 42 mm, height 13 mm, thickness 13 mm 

(both valves). Panama, Holocene. 

9, 10. Adula? mcknighti (M.A. Hanna)(p. A74). 

Holotype UCMP 31151 (x 3.0). Length 19 mm, height 9 mm, thickness 9 mm 

(both valves). Delmar Formation, California, Eocene. 

11. Modiolus (Modiolus) ynezianus Arnold (p. A74). 

Holotype USNM 165324. Length 31 mm, height 8 mm, thickness 11 mm (one 

valve). Vaqueros Formation, Oligocene and Miocene. 

12. Modiolus (Modiolus) eugenensis (Clark) (p. A74). 

Holotype UCMP 30319. Length 120 mm, height 50 mm. Eugene Formation, 

Oligocene, Oregon. 

13, 14. Modiolus (Modiolus) lagunanus Loel and Corey (p. A75). 

Holotype UCMP 31788. Length 113 mm, height 44 mm, thickness 33 mm 

(one valve). Vaqueros Formation, California, Oligocene and Miocene. 
GEOLOGICAL SURVEY 

PROFESSIONAL PAPER 1228-A PLATE 19 

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MYTILIDAE 
PLATE 20 

FIGURES 1. Modiolus (Modiolus) ynezianus garzaensis Adegoke (p. A 75). 

Holotype UCMP 36601 (x 3.0). Length 19 mm, height 11 mm. Upper part of 

Temblor Formation, California, Miocene. 

2. Modiolus (Modiolus) veronensis temblorensis Adegoke (p. A 75). 

Holotype UCMP 36606 (x 2.0). Length 23 mm, height 12 mm, thickness 6 mm 

(one valve; estimated). Upper part of Temblor Formation, California, 

Miocene. 

3. Modiolus (Modiolus) veronensis veronensis Trask (p. A 75). 

Holotype UCMP 12373 (x 1.5). Length 40 mm, height 19 mm, thickness 

14 mm (both valves). Briones Sandstone, California, Miocene. 

4. Modiolus (Modiolus) directus Dall (p. A 76). 

Lectotype USNM 153947. Length 105 mm, height 40 mm, thickness 26 mm 

(both valves). Empire Formation, Oregon, Miocene. · 

5. Modiolus (Modiolus) contracta Conrad (p. A 76). 

Holotype USNM 1853. Length 63 mm, height 28 mm. Monterey(?) Group, 

California, Miocene(?). 

6. Modiolus (Modiolus) capax (Conrad) (p. A76). 

Hypotype CAS 59922. Length 95 mm, height 49 mm, thickness 44 mm (both 

valves). San Diego, Calif., Holocene. 

7, 8. Modiolus (Modiolus) carpenteri Soot-Ryen (p. A 77). 

Holotype Redpath Museum 3133. Length 36 mm, height 20 mm, thickness 

12 mm (one valve). Santa Barbara, Calif., Holocene. (Photographs courtesy 

of Katherine V. W. Palmer). 

9. Modiolus (Modiolus) rectus Conrad (p. A 76). 

Hypotype CAS 59923. Length 125 mm, height 43 mm, thickness 18 mm (one 

valve). San Diego, Calif., Holocene. 
GEOLOGICAL SURVEY PROFESSIONAL PAPER 1228-A PLATE 20 

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MYTILIDAE 
PLATE 21 

FIGURES 1. Modiolus (Modiolus) sacculifer (Berry) (p. A 77). 

Holotype CAS/SU 7853 (x 1.5). Length 37 mm, height 20 mm, thickness 

9 mm (one valve). San Pedro, Calif., Holocene. 

2. Modiolus (Modiolus?) merriami (Weaver) (p. A 77). 

Holotype UCMP 11892 (x 2.0). Length 28 mm, height 13 mm, thickness 8 mm 

(both valves). Martinez Formation, California, Paleocene. 

3, 4. Modiolus (Modiolus?) pittsburgensis Clark (p. A 77). 

Holotype UCMP 11122 (x 1.5; specimen illustrated is a plaster cast. Length 

33 mm, height 20 mm, thickness 13 mm, both valves). Kirker Tuff, 

California, Oligocene. 

5. Modiolus? (Modiolus?) meganosensis Clark and Woodford (p. A 78). 

Holotype UCMP 31363 (x 3.0). Length 16 mm, height 10 mm. Meganos 

Formation, California, Paleocene. 

6, 7. Idasola? bakeri (Dickerson) (p. A 78). 

Holotype UCMP 11686 (x 2.0). Length 26 mm, height 17 mm, thickness 

10 mm (one valve; estimated). Martinez Formation, California, Paleocene. 

8, 9. Modiolus? (Modiolus?) clarki Moore, new name (p. A 78). 

Holotype UCMP 11544. Length 102 mm, height 53 mm, thickness 49 mm 

(one valve). Neroly Sandstone, Miocene. 

10. Pinna (Pinna) lewisi Waring (p. A 79). 

Holotype CAS/SU 5194. Length 63 mm, height 50 mm, thickness 27 mm 

(both valves). Llajas Formation, California, Eocene. 
GEOLOGICAL SURVEY PROFESSIONAL PAPER 1228- A PLATE 21 

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MYTILIDAE, PINNIDAE 
PLATE 22 

FIGURES 1. Pinna (Pinna) n. sp. Vokes (p. A79). 

Hypotype UCMP 32595 (Vokes, 1939, pl. 2, fig. 14). Length 60 mm, height 

54 mm. Domengine Formation, California, Eocene. 

2, 3. Pinna (Pinna) stocktoni Loel and Corey (p. A 79). 

2. Syntype UCMP 31779. Length 62 mm, height 37 mm, thickness 18 mm 

(both valves). Vaqueros Formation, California, Oligocene and Miocene. 

3. Syntype UCMP 31778. Length 80 mm, height 100 mm, thickness 50 mm. 

Vaqueros Formation, California, Oligocene and Miocene. 

4. Pinna (Pinna) latrania G D. Hanna (p. A 79). 

Holotype USNM 324593. Length 135 mm, height 63 mm. Imperial Formation, 

California, Miocene or Piiocene. 

5, 6. Pinna (Pinna) barrowsi Dickerson (p. A 79). 

Holotype UCMP 11728. Length 75 mm, height 40 mm, thickness 17 m (both 

valves). Martinez Formation, California, Paleocene. 
GEOLOGICAL SURVEY PROFESSIONAL PAPER 1228-A PLATE 22 

PINNIDAE 
PLATE 23 

FIGURES 1. Pinna (Pinna) mendenhalli G D. Hanna (p. A80). 

Holotype USNM 324593a. Length 167mm, height 98 mm, thickness 58 mm 

(both valves). Imperial Formation, California, Miocene or Pliocene. 

2. Atrina venturensis (Yates) (p. A80). 

Hypotype CAS 622 (Cooper, 1894, pl. 4, fig. 54). Length 96 mm, height 60 mm, 

thickness 33 mm (both valves). Vaqueros Formation, California, Oligocene 

and Miocene. 

3. Atrina alamedensis (Yates) (p. A80). 

Hypotype CAS 5 (x 0.8; Cooper, 1894, pl. 4, fig. 53). Length 128 mm, height 

104 mm, thickness 59 mm (both valves). San Pablo(?) Group, California, 

Miocene. 

4. Atrina bicuneata (Nomland) (p. A81). 

Holotype UCMP 11307. Length 95 mm, height 42 mm, thickness 18 mm (both 

valves). Santa Margarita Formation, California, Miocene. 
GEOLOGICAL SURVEY PROFESSIONAL PAPER 1228-A PLATE 23 

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PINNIDAE 
PLATE 24 

FIGURES 1. Pteria sp. Clark and Woodford (p. A82). 

Hypotype UCMP 31321 (x 2.0). Length 23 mm, height 17 mm. Meganos 

Formation, California, Paleocene. 

2. Pte ria howei Nelson (p. A81). 

Holotype UCMP 30515 (x 2.0). Length 33 mm, height 14 mm. Martinez 

Formation, California, Paleocene. 

3. Pteria pellucida (Gabb) (p. A82). 

Lectotype UCMP 11983 (x 1.5). Length 33 mm, height 19 mm. Domengine(?) 

Formation, California, Eocene. 

4. Atrina stephensi G D. Hanna (p. A81). 

Holotype SDNM 2 (x 0.5). Length 205 mm, height 111 mm, thickness 60 mm 

(both valves). Imperial Formation, California, Miocene or Plicoene. 

5. Pteria berryi Adegoke (p. A82). 

Holotype UCMP 36611. Length 60 mm. Upper part of Temblor Formation, 

California, Miocene. 

6. Pteria hertleini Wiedey(p. A82). 

Holotype CAS/SU 5160 (x 0.7). Length 95 mm, height 100 mm, thickness 

70 mm (both valves). Vaqueros Formation, California, Oligocene and 

Miocene. 

7. Pteria rositae Hertlein (p. A83). 

Holotype CAS 4142 (x 1.5). Length of hinge line 43 mm, height 27 mm. 

Rincon Shale, Oligocene and Miocene. 
GEOLOGICAL SURVEY PROFESSIONAL PAPER 1228-A PLATE 24 

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PTERIIDAE 
PLATE 25 

FIGURES 1. Pteria jordani Wiedey (p. A83). 

Holotype SDNM 25. Length 95 mm, height 95 mm, thickness 41 mm (both 

valves). Topanga Formation, California, Miocene. 

2. Pinctada mazatlanica (Hanley) (p. A83). 

Hypotype UCMP 15965 (Durham, 1950, pl. 2, fig. 6). Length 73 mm, height 

79 mm, thickness 17 mm (one valve). Unnamed Pleistocene strata, Baja 

California Sur. 

3, 6. Isognomon (lsognomon) panzana Loel and Corey (p. A84). 

Holotype UCMP 31780. Length 52 mm, height 94 mm, thickness 23 mm (one 

valve). Vaqueros Formation, California, Oligocene and Miocene. 

4, 5. Isognomon (lsognomon) janus Carpenter (p. A84). 

Hypotype UCMP 30563 (x 2.0). Durham, 1950, pl. 3, fig. 4). Length 22 m. 

Marquer Formation, Baja California Sur, Pliocene. 
GEOLOGICAL SURVEY PROFESSIONAL PAPER 1228-A PLATE 25 

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~ 4 

3 

PTERIIDAE, ISOGNOMONIDAE 
PLATE 26 

FIGURES 1. Isognomon n. sp. Givens (p. A85). 

Hypotype UCR 4752/61 (x 0.7). Length 130 mm, height 118 mm. Juncal 

Formation, California, Eocene. 

2, 7. Pulvinites pacifica Zinsmeister (p. A86). 

2. Hypotype UCMP 30513 (Pedalion sp. Nelson, 1925, pl. 49, figs. 8, 9). 

Length 35 mm, height 35 mm. Martinez Formation, California, 

Paleocene. 

7. Holotype UCR 7342/1. Length 35 mm, height 40 mm. Lower part of Santa 

Susana Formation, California, Paleocene. 

3. Isognomon sp. (Clark and Woodford) (p. A84). 

Hypotype UCMP 31301 (x 3.0). Length 9 mm, height 12 mm. Meganos 

Formation, California, Paleocene. 

4. Pachyperna? goniglensis (M.A. Hanna) (p. A85). 

Holotype UCMP 30912 (x 1.5; plaster cast illustrated). Length 25 mm, height 

30 mm. Ardath Shale, California, Eocene. · 

5. Pachyperna? joaquinensis (Vokes) (p. A85). 

Holotype UCMP 15577 (x 2.0). Length 18 mm, height 20 mm. Domengine 

Formation, California, Eocene. 

6. Pulvinites californica Zinsmeister (p. A85). 

Holotype UCR 6821119 (x 2.0). Length 18 mm, height 20m. Lower part of 

Santa Susana Formation, California, Paleocene. 

8, 9. Nayadina (Exputens) alexi (Clark) {p. A86). 

Holotype UCMP 32386 (x 3.0). Length 18 mm, height 13 mm, thickness 5 mm 

(one valve). Domengine Formation, California, Eocene. 

10, 13. Nayadina (Exputens) llajasensis (Clark)(p. A86). 

Holotype UCMP 32391 (x 1.5). Length 52 mm, height 26 mm, thickness 

15 mm (both valves). Llajas Formation, California, Eocene. 

11, 12. Vulsella? clarki Vokes (p. A87). 

Holotype UCMP 15743 (x 2.0). Length 21 mm, height 17 mm, thickness 7 mm 

(one valve). Lodo Formation, California, Paleocene and Eocene. 
GEOLOGICAL SURVEY PROFESSIONAL PAPER 1228-A PLATE 26 

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ISOGNOMONIDAE, PULVINITIDAE, MALLEIDAE 
PLATE 27 

FIGURES 1, 3. Atrina alamedensis (Yates) (p. A80). 

Holotype? UCSB Y 474 (x 0.7). Length 200 mm, height 130 mm, width 56 mm. 

San Pablo Formation, California, Miocene. 

2. Atrina venturensis (Yates) (p. A80). 

Holotype? UCSB Y3096. Length 106 mm, height 60 mm, width 30 mm. 

Vaqueros Formation, California, Oligocene and Miocene. 
GEOLOGICAL SURVEY 

3 

PINNIDAE 

PROFESSIONAL PAPER 1228-A PLATE 27 

2