·" 4·~ ~~ '\, ·~·: ~ ~~ " \\ \. 

'~ ,.. . ~ ' 

\C L . "'" . . •.:·:.·c.l -· ' ' . ' . ', • •t...-. ~ • 

\\" 

" ',•'. 0 

rl "~:~:l'I.'''t···l~ ,-l·ry M· '.'a· c'1!'1l'l~ n,:·-'e·- " ~ ( __ ;7 • • • ". -· c/ . . . . . . ., -- , . l, • : ,! b : - . __ if? 

P(~It'l(·"'!,,.r·.c·>··C-1. • s <-">· f.~ C· _,'a---_ 1·: ·r~ fr~~)-r···. ·rl·-- I·~ a-- . r ; ~' '-~ ' ' y J) . _· ' > ~· - . --~- .. . " , \.._ · __ . . - . -•_ 

,-1-· l'tl ('-j~· ·B-· a· J~ ':l -c~=,aol~ ·1·., f:·o· rn· · 1~ a··-- Q C: " ' ' . . .. . C:l . .A . . . . . ' • . - . _· ... r_ • I . . . ., 

Pr()pearrllissiidae and 

P

. . . l 

. -- ectiiliuae 

C ~ I< t ) l , ( ) ( -~ 1 (: i\ :r , S l J Jt V l~ Y !'* R () }' J: S S I () N A I, l' A 1~ I< :R 1 2 2 K ~- l\ 
Tertiary Marine 

Pelecypods of California 

and Baja California: 

Propeamussiidae and 

Pectinidae 

By ELLEN JAMES MOORE 

PALEONTOLOGY OF CALIFORNIA AND BAJA CALIFORNIA 

GEOLOGICAL SURVEY PROFESSIONAL PAPER 1228-B 

A total of 139 species of 

Pectinacea (Propeamussiidae 

and Pectinidae) are illustrated, 

original descriptions quoted, 

taxonomy revised and updated, 

comparisons made with other 

species, geographic and geologic 

ranges given, occurrence by 

geologic ranges given, 

occurrence by geologic 

formation cited, and habitat 

included when it can be 

confidently inferred 

UNITED STATES GOVERNMENT PRINTING OFFICE~ WASHINGTON 1984 
UNITED STATES DEPARTMENT OF THE INTERIOR 

WILLIAM P. CLARK, Secretary 

GEOLOGICAL SURVEY 

Dallas· L. Peck, Director 

Library of Congress Cataloging in Publication Data 

Moore, Ellen James 

Tertiary marine pelecypods of California and Baja California Peninsula. 

(Paleontology of California and Baja California) (Geological Survey Professional 

Paper 1228-B) 

Bibliography: p. B91-B99 

Supt. of Docs. no.: I 19/16:1228-B 

Includes index. 

1. Lamellibranchiata, Fossil. 2. Paleontology-Tertiary. 3. PaleontologyCalifornia. 4. Paleontology-Mexico-Baja California. I. Title. II. Seryes. 

III. Series: Geological Survey. Professional Paper 1228-B. 

QE811.M64 1983 564'.11 83--{)00022 

For sale by the Distribution Branch, U.S. Geological Survey, 

604 South Pickett Street, Alexandria, VA 22304 
·CONTENTS 

Page 

A bstr·act ................................................... B1 

Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 

Purpose and scope . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 

Procedure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 

Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 

Abbreviations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 

Systematics: Pelecypods-Continued from Chapter A . . . . . . . . . 6 

Family Propeamussiidae . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 

Genus Propeaimuss·ium . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 

Genus Cyclopecten . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 

Genus Cyclopecten?. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 

Genus Pa,rva.muss·ium . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 

Family Pectinidae ...................................... 12 

Delectopecten group ................................. 13 

Genus Delectopecten ............................. 13 

Chlam.ys group . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18 

Genus Chlam.ys ................................. 18 

Genus Chla.1nys? ................................ 29 

Genus Leochla:mys .............................. 30 

Genus Leochlmnys? .............................. 30 

Genus Na.na.ochla.m.ys ........................... 31 

Genus Aequ·ipecten .............................. 31 

Genus A1·gopecten ............................... 32 

Genus Argopecten? ............................... 42 

Genus Anl'ipecten ............................... 42 

Genus Ant·ipecten? .............................. 42 

Page 

Genus Leptopecten . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43 

Genus Pa.c·ipecten . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 44 

Genus Ly1·opecten . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49 

Genus Ma.c1·ochlanL1:s ............................ 56 

Genus Nod1:pecten............................. 57 

Genus Sw1jtopecten............................ 58 

Genus Stmftopecten?........................... 60 

Genus Vertipecten . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 60 

Genus H1:n·m:tes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 65 

Pecten group...................................... 66 

Pecten subgroup . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 66 

Genus Amusium . . . . . . . . . . . . . . . . . . . . . . . . . . 66 

Genus Pecten . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 67 

Genus Amussiopecten . . . . . . . . . . . . . . . . . . . . . 69 

Genus Euvola.............................. 70 

Genus Fla.bellipecten . . . . . . . . . . . . . . . . . . . . . . 71 

Genus Flabell?:pecten? . . . . . . . . . . . . . . . . . . . . . 74 

Genus Oppenheimopecten . . . . . . . . . . . . . . . . . . 75 

Pa.tinopecten subgroup . . . . . . . . . . . . . . . . . . . . . . . . 78 

Genus Pa.t?:nopecten . . . . . . . . . . . . . . . . . . . . . . . 78 

Genus Leopecten . . . . . . . . . . . . . . . . . . . . . . . . . . 84 

Genus L1:tuya.pecten . . . . . . . . . . . . . . . . . . . . . . . 86 

Fossil localities .......................... ·................. 88 

Geologic formations cited for occurrence of pelecypods . . . . . . 90 

References cited . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 91 

Index ..................................................... 101 

ILLUSTRATIONS 

PLATE 1. 

2. 

3. 

4-5. 

6. 

7. 

8. 

9. 

10. 

11-12. 

13. 

14. 

15. 

16-19. 

20. 

21. 

22-23. 

Pl·opea:nt.uss·t:um., Cyclopecten, Pa.rva.mussium. 

Pairvmnus,.rhtm, Delectopecten, A mus1:um. 

Delectopecten, Chla.mys. 

Chla.mys. 

Chla.mys, Nod·t:pecten. 

Chla.mys, Chla.mys? 

Leochla.mys ?, Nanaochlamys 

A rgopecten, A equ.1:pecten. 

A ·rgopecten .. A 1·gopecten? 

A ·rgopecten. 

A ·rgopecten, A nt·ipecten ?, Leptopecten. 

Pa.c·t:pecten. 

Pa.c·t:pecten, Leptopecten. 

Ly·ropecten. 

Ly1·opecten, Pa.c1:pecten. 

Ly1·opecten, Ve·rt·ipecten, Ma.c·rochlamis. 

N od·ipecten, Sw·tftopecten. 

[Plates follow index] 

24. 

25. 

26-27. 

28. 

29. 

30. 

31. 

32. 

33. 

34. 

35-36. 

37. 

38. 

39. 

40. 

41-42. 

Vertipecten, Swijtopecten? 

Vertipecten. 

Hinnites, Vertipecten. 

Lyropecten, Pecten, Vertipecten. 

Pecten, A mussiopecten. 

A muss1:opecten, Euvola. 

Fla.bellipecten., Flabellipecten ? 

Fla.bellipecten, Flabell?.pecten?, Oppenheimopecten. 

Flabellipecten?, Oppenheimopecten. 

Pa.tinopecten, Oppenheimopecten. 

Patinopecten. 

Lituya.pecten, Pa.tinopecten. 

Patinopecten. 

Patinop\ecten, Leopecten, Ve1·tipecten. 

Patinopecten, Leopecten. 

Lituya.pecten, Patinopecten. 

III 
IV CONTENTS 

Pag•~ 

FtC. liRE 1. Map showing divisions used in California. for geographic range of species of pelecypods, 

Propeamussiidae and Pectinidae ................................................................................ B3. 

2. Map showing divisions used in Baja California Peninsula for geographic ranges of species of pelecypods, 

Propeamussiidae and Pectinidae ............................. .' ................................................... 4. 

TABLES 

Page 

TABLE 1. Geographic distribution of genera in the families Propeamussiidae and Pectinidae in the eastern Pacific region . .' .... ~ ... B2 

2. Geologic distribution of genera in the families Propeamussiidae and Pectinidae based exclusively on Tertiary and 

Pleistocene species in the Californias . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 

3-20. Geologic and geographic distribution of large genera: 

3. Cyclopecten . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 

4. Parvamussium . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 

5. Delectopecten . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14 

6. Chlamys . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18 

7. A rgopecten . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32 

8. Leptopecten ........................ ·. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43 

9. Pacipecten . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 44 

10. Lyropecten ................................................................................................ 49 

11. Nod1:pecten ............................................................................................... 57 

12. Sw1'jtopecten .............................................................................................. 59 

13. Vertipecten . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 61 

14. Pecten (Pecten) ............................................................................................ 67 

15. Euvola ....... ·. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 70 

16. Flabellipecten ............................................................................................. 71 

17. Oppenhe1:mopecten ......................................................................................... 75 

18. Patinopecten .............................................................................................. 78 

19. Lenpecten ................................................................................................. 84 

20. Lituyapecten . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 86 
PALEONTOLOGY OF CALIFORNIA AND BAJA CALIFORNIA 

TERTIARY MARINE PELECYPODS OF CALIFORNIA 

AND BAJA CALIFORNIA: 

PROPEAMUSSIIDAE AND PECTINIDAE 

By ELLEN jAMES MOORE 

ABSTRACT 

The description of the mollusks in the Tertiary formations of 

California and Baja California is continued from Chapter A. One 

hundred and thirty-nine species in the families Propeamussiidae 

and Pectinidae, representing 27 genera, are cov~red in this chapter; 

other chapters will follow in systematic order. Three genera are in 

the Family Propeamussiidae; the remainder are in the family 

Pectinidae. 

The holotypes of all species are illustrated when feasible, 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 or 

inferred from related species. Tables for the larger genera are 

incorporated to show geographic and age ranges of the included 

species. 

Of the 27 included genera, one occurs in the Paleocene, 6 in the 

Eocene, 9 in the Oligocene, 20 in the Miocene, 20 in the Pliocene, 11 in 

the Pleistocene. and 10 in the Holocene of the included geographic 

area. Eleven genera are extinct or locally extinct. 

Most of the species formerly assigned to Aequipecten are placed 

here in A1·gopecten and many of those that were assigned to Leptapecten and also to Aequ:ipecten, are placed in Pacipecten. 

Ant'ipecten, a Miocene genus in France, may be represented by 

Ant'ipecten? JWa.eva.l'idus (Jordan and Hertlein) from the Almejas 

Formation (Pliocene) of Baja California Sur. Ncma.ochla.mys is 

repot·ted for the first time outside of Japan and is represented by the 

species No.naochla,?nys mtlte'ri (Arnold) from Miocene to Pleistocene 

strata in middle and southern· California. 

INTRODUCTION 

PURPOSE AND SCOPE 

The description and illustration of the Tertiary 

marine mollusks of California, Baja California Norte, 

and Baja California Sur started in Chapter A is continued in this chapter, which treats the families Propeamussiidae and Pectinidae (tables 1, 2). A total of 

139 species occur in the geographic area covered. For 

convenience of reference, the figures showing the geographic divisions used for the Californias are reproduced (figs. 1, 2). 

Hertlein (1969) chose a conservative approach and 

placed supraspecific units in groups within the Pectinidae. These "groups" are retained here to show his 

interpretation of the relations between genera. However, most subgeneric categories used by Hertlein are 

elevated to generic rank for simplicity and ease of 

usage. This is a pragmatic approach and not a biological revision of the subgenera so treated. 

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). The order in which 

families are arranged and the generic and subgeneric 

categories have generally not been modified, except in 

a few cases. Most modifications made reflect either 

definitive papers published after publication of the 

Treatise in 1969 or works published earlier but not 

cited in it. Within the systematic groups, species are 

arranged by geologic age, beginning with the oldest 

species and ending with the youngest. 

Some of the names of genera and subgenera used in 

the Treatise and adopted in this paper have not been 

Bl 
B2 PALEONTOLOGY OF CALIFORNIA AND BAJA CALIFORNIA 

TABLE 1. ------Geograph·£c d?:stn:b-ution of genera 1:n the fa1n1:L1:es Propeam-ussiidae and Pect1:nidae in the eastern Pac1j1:c Tegion 

[F =Tertiary and Pleistocene species in the Californias; H =living species] 

Genus *=extinct or locally extinct 

Family Propeamussiidae: 

PTopeam,-uss?:-um -------------------------------------- Cyclopecten ------------------------------------------------ Paruam-ussiwn ---------------------------------------- Family Pectinidae: 

Delectopecten -------------------------------------------- Chlamys ---------------------------------------------------- Leochlamys?* -------------------------------------------- Nanaochlamys* ---------------------------------------- Aeq-uipecten ---------------------------------------------- A Tgopecten ------------------------------------------------ Ant·£pecten? ------------------------------------------------ Leptopecten ------------------------------------------------ Pac·£pecten _________________________________________________ _ 

Ly1·opecten* ---------------------------------------------- MacTochlamys ------------------------------------------ Nodipecten ------------------------------------------------ Sw?jtopecten* --------------------------------------------

J';~:~,.,~~:ec;_~~~-~--:::::::::::::::::::::::::::::::::::::::::::::: A 1n-us?:-u1n * ------------------------------------------------ Pecten*--------------------------------------------------------

A m-ussiopecten * ---------------------------------------- E-uvola * ________ .. ____________________ .... ___________________ _ Flabellipecten ___________________________________________ _ 

Oppenheim.opecten ---------------------------------- Patinopecten _____________________________________________ _ 

Leopecten* -------------------------------------------------- L?:t-uya pecten* ______ ...... ____ --------------- ____________ _ 

Alaska British Washington Oregon California 

H 

H 

F,H 

F,H 

F 

F 

F,H 

F,H 

F 

Columbia 

H 

F,H 

F,H 

F 

F,H 

F,H 

H 

F,H 

F,H 

F 

F,H 

F,H 

H 

F,H 

F,H 

F 

F,H 

F,H 

Northern Middle Southern 

H 

F,H 

F,H 

F 

F 

F 

F,H 

H 

F,H 

F 

F 

F 

F,H 

F,H 

F,H 

F 

F,H 

F,H 

F 

F 

F 

F 

F 

F,H 

F 

F 

F.H 

F p"" 

F 

F,H 

F,H 

F,H 

F,H 

F 

F 

F,H 

F,H 

F 

F 

F 

F 

F 

F 

F,H 

F 

F 

F 

F 

F.H 

F 

F 

F 

Baja California 

Norte Sur 

H 

H 

H 

F.H 

F,H 

F,H 

F 

F 

F 

F 

F,H 

F 

F 

F 

F.H 

F 

F 

F 

H 

H 

H 

F,H 

F 

F,H 

F 

F,H 

F,H 

F 

F,H 

F 

F,H 

F 

F 

F 

F,H 

F,H 

F 

F 

F 

TABLE 2.-Geologic distTib-ut?:on of genera in the families Propeam.-ussiidae and Pect?:m:dae based excl-us1:vely 

on TeTt?:aTy and Pleistocene species in the CalifoTnias 

(x =reported occurrence; 0 =no reported occurrence; ? =generic assignment uncertain] 

Genus Paleocene Eocene Oligocene Miocene Pliocene Pleistocene Holocene 

Family Propeamussiidae: 

Propeam-ussi-um -------------------------------------- Cyclopecten ------------------------------------------------ PaTvassi-um ---------------------------------------------- Family Pectinidae: 

Delectopecten -------------------------------------------- Chlamys ---------------------------------------------------- Leochlam.ys? ---------------------------------------------- N anaochlam.ys ------------------------------------------ Aeq-uipecten ---------------------------------------------- A Tgopecten ------------------------------------------------ Anti pecten? __ ---------------------------------------------- Leptopecten ------------------------------------------------ Pacipecten -------------------------------------------------- LyTopecten ------------------------------------------------ MacTochlamis ------------------------------------------ Nodipecten ------------------------------------------------ Swiftopecten ----------------------------------------------

ki~,.,~~:e~-~~~--:::::::::::::::::::::::::::::::::::::::::::::::: A m.-usi-u1n -------------------------------------------------- Pecten----------------------------------------------------------

A m.-ussiopecten ------------------------------------ _____ _ 

Euvola -------------------------------------------------------- Flabellipecten ------------------------------------------

~==e-~-~-~--:::::::::::::::::::::::::::::::::: uopecten; -------------------------------------------------- Lituyapecten --------------------------------------------

X 

X 

X 

X 

X 

X 

X 

0 

X 

X 

X 

X 

X 

X 

X 

X 

X 

X 

X 

X 

X 

X 

X 

X 

X 

X 

X 

X 

X 

X 

X 

X 

X 

X 

X 

X 

X 

X 

X 

X 

X 

X 

X 

X 

X 

X 

X 

.. 

X 

X 

X 

X 

X 

X 

X 

X 

X 

X 

X 

X 

X 

X 

X 

X 

X 

X 

X 

X 

X 

X 

X 

X 

X 

X 

X 

X 

X 

X 

X 

X 

X 

X 

X 

X 

X 

X 

X 

X 

X 

X 

Central 

and (or) South 

America 

H 

H 

H 

H 

F 

F.H 

H 

H 

F,H 

H 

F 

F.H 

H 
42° 

390 

34° 

125° 

z 

a: 

w 

J: 

1-

cr: 

0 

z 

w 

....1 

0 

0 

~ 

z 

a: 

w 

J: 

I-

:> 

0 

(/) 

~ 

'l> 

~ 

0 

I 

"'T\ 

50 

I 

TERTIARY MARINE PELECYPODS: PROPEAMUSSIIDAE AND PECTINIDAE 

0 

100 

I 

150' 

I 

120° 

Santa Cruz: 

Island I 

San Miguel Island 4~ ~) 

Santa Rosa Island ----"" 

I 

I 

I 

I 

I 

I f Santa~ 

1 Catalina~ 

San Nicolas Island ~. f Island 

200 KILOMETERS 

I 

I 

San Cleme~te Island~ SAN DIEGO 

B3 

115° 

IMPERIAL 

F!GUHE !.·~Divisions used in California for geographic ranges of species of pelecypods, Propeamussiidae, and Pectinidae. Heavy solid lines 

indicate Northern, Middle, and Southern Divisions; dashed lines within southern region divide Channel Islands area: 
B4 

32" 

30° 

28" 

26" 

24" 

PALEONTOLOGY OF CALIFORNIA AND BAJA CALIFORNIA 

116° 

Isla Cedros!) 

0 

50 

I 100 I 150 

I 

...... ............. ... , 

San Ignacio 

200 KILOMETERS 

I 

....... !f!!,.,..~ ... () 

At.'~l'-1 ~"'"c' .,..~s 0'" 

112" 1111" 

ARIZONA 

..... , ...... ....... .. _______ . _ 

FIGURE 2:- Divisions used in Baja California Peninsula for geographic ranges of species of pelecypods, Propeamussiidae and Pectinidae .. · 
TERTIARY MARINE PELECYPODS: PROPEAMUSSIIDAE AND PECTINIDAE B5 

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 originally figured, I have 

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

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 avaihtble to me. 

Age ranges have not been refined within epoclls. 

Where a stage name the same as a formation name is 

used, it is placed in quotes to distinguish it from the 

rock unit. 

The divisions used here to indicate the approximate 

geographic range of species within California based on 

county distribution are northern, middle, and southern (fig. 1); the divisions for the Baja California Peninsula, norte and sur (fig. 2) (tables 1-7). 

An attempt has been made to include all citations to 

a species that are unqualified and every geologic formation in which it is reported to occur in the Californias. The assumption has been made that all identifications of species are correct unless there is strong 

evidence to the contrary. The stratigraphic nomenclature used herein is that of the author(s) cited and does 

not necessarily agree with that of the U.S. Geological 

Survey. The age given for the stratigraphic units follows the classification of geologic time currently used 

by the U.S. Geological Survey. (See "Geologic Formations Cited for Occurrence· of Pelecypods" at end of 

paper.) 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 ofpublicationoftheworkfrom 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 occurr,:ence 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 (1944), 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 

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

of those housed in the National Museum of Natural 

History, which were photographed by Robert H. 
B6 PALEONTOLOGY OF CALIFORNIA AND BAJA CALIFORNIA 

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 

Barry Roth, California Academy of Sciences, and 

Thomas R. Waller, National Museum of Natural History, reviewed the manuscript and their pertinent 

suggestions and consultation were most helpful. 

Judith T. Smith loaned me photographs and specimens and gave generously of her time and advice concerning Lyropecten, Macrochlamis, Nodipecten, and 

Vertipecten, and' I am indebted to her. 

The following individuals made available or loaned 

type material or made arrangements for photography, 

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

Geological Survey; Federick J. Collier, National 

Museum of National History; Vickie Kohler, Museum 

of Comparative Zoology; Joseph E. Peck, University of 

California at Berkeley; Barry Roth, California Academy of Science; LouElla Saul, University of California, Los Angeles; Elizabeth V. Scott, Philadelphia 

Academy of Sciences; Frederick R. Schram, San 

Diego Natural History Museum; and Edward C. Wilson, Los Angeles Natural History Museum. 

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 N atural.Sciences of Philadelphia, Philadelphia, Pa. 

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

CAS: California Academy of Sciences, San Francisco, 

Calif. 

LAM: Los Angeles Museum of Natural History, California. 

MCZ: Harvard Museum of Comparative Zoology, Cambridge, Mass. 

SDNM: San Diego Natural History Museum, California. 

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

Stanford University collections are now housed at 

the California Academy of Sciences.] 

SU: Stanford University, Stanford, Calif. 

UC: University of California, Berkeley. 

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

UCR: University of California at Riverside. 

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

SYSTEMATICS: PELECYPODS-CONTINUED 

FROM CHAPTER A 

Family PROPEAMUSSIIDAE 

"Byssate or free Pectinacea with outer simple-prismatic calcitic 

layer on right valve present on main portion of disk throughout 

ontogeny; crossed-lamellar aragonite extending outside of pallial 

line, in some cases nearly to distal margins, and commonly covering 

hinge plate. Byssal notch without ctenolium even in early growth 

stages. Mantle curtains commonly without guard tentacles." 

(Waller, 1978, p. 353) 

Waller (in Bernard, 1978, p. 65) states that he includes Cyclopecten 

Verrill in his expanded concept of the Family Propeamussiidae, 

whereas Delectopecten Stewart remains a member of the family 

Pectinidae. 

"Dissection of propeamussiids reveals that there are numerous 

anatomical surprises, only some of which have been reported by 

.previous investigators. [In Propeamussium} There is a total lack of 

ocelli; there are no guard tentacles on the edges of the velum; and 

there is no trace of any pedal retractor insertion on the left valve. 

These, and other features as yet undescribed, are unknown in the 

common Pectinidae. 

"Shell microstructure and soft-part anatomy * * * provide ample 

evidence for the separation of the Propeamussiidae and the Pectinidae. The Propeamussiidae, today largely restricted to waters of the 

continental slopes and abyssal regions, most closely resemble the 

Pernopectinidae of the Paleozoic, and available evidence strongly 

suggests that the living forms may actually be surviving relicts of 

the group thought to have been extinct for 225 million years." 

(Waller, 1971, p. 7) 
TERTIARY MARINE PELECYPODS: PROPEAMUSSIIDAE AND PECTINIDAE B7 

Genus PROPEAMUSSIUM de Gregorio, 1884 

Valves rather flattened, usually gaping along lateral margins; 

byssal notch slight; internal ribs extend about halfway (farther in 

some) to ventral shell margin. 

Geolo{J'I:c ·m:nge.-Jurassic through Holocene. 

Ha.lritnl .. -275-2,740 m (Waller, 1971). 

Propeamussium interradiatum (Gabb) 

Plate I, figure I 

Pecte-n ·i·nte·r·ra.d·ia.tu .. o.; Gabb, 18(:)9, p. 199-200, pl. 33, fig. 98; not? fig. 

98a. Dickerson, 1914, p. 108. 151, pl. 9, fig. 5. 

Pecten(Pro1Jea:m?.!.ss·iu:n1.) 'l>nte·rrad·ia.tus Gab b. Arnold, 1906, p. 53-54, 

pl. 2, figs. 9-11. G. D. Hanna and Hertlein, 1943, fig. 62-28. 

Pro1Jea:n1:U .. ':!S'1:u:m. ·inte'l"''nd·ia.twm. (Gabb). Stewart, 1930, p. 123-124, 

pl. 8, fig. 10. Stewart. 1946, pl. 12, figs. 8, 9. Schenck and Keen, 

1950, pl. 7, figs. 4, 5. 

Propea:m:II .. '>S'I>u:m. (P.ropea:m:uswiun1.) ·inte·rmd·iatmn (Gab b). Addicott, 

1971. p. 229, figs. 6. 11. 

Pecte-n (Propea:m:uss·iu:m.) ·ua.ca:u·illens1:s Palmer, 1923, p. 301, pl. 55, 

figs. 3, 4a. 4b, 5. 

Orim>nal desc·ri1Jt·ion.-"Shell small, subcircular, equivalve, equilateral. compressed, thin; upper [left] valve, ears equal, moderately 

large: lower [right] valve, right ear long, deeply and narrowly 

emarginate. Surface marked by very numerous fine radiating lines, 

and obscure lines of growth. Internal surface of both valves bearing 

eight straight, equidistant, large ribs, of variable length among 

themselves, extending from the beaks to near the middle of the shell, 

and ending abruptly." 

Lectotype.-ANSP 4652 (Stewart, 1930). [Inadvertently cited by 

Stewart as ANSP 4442.] Holotype .of Pecten (Propeamuss·ium,) vaca.-

'lrillens·is Palmer, UCMP 30596. 

Type locah:t-y.-Of Propea:musshtm 'l:nte·rra.d·ia.t·unt: East of New 

ldria [Priest Valley quad., San Benito County], Calif. Kreyenhagen 

Shale, Eocene and Oligocene; of Pecten (Propeam.uss·ium) vacavUlen .. -;·,:s: UC 3573, Solano County, Calif. Capay Formation, Eocene. 

Supplwm.enta:ry desc·ription.-Addicott (1971, p. 229) notes that 

whereas the ears and the length of the internal ribs on one of the 

original hand-drawn illustrations representing a left valve of P. 

·inte'l"''tuhatu:m (Gabb, 1869. pl. 33, fig. 98) indicate reference to 

Proww:n1:u .. o.;wiu·m. (Propeu:nl:ttss·iwm.), the other illustration of a portion 

of the dor·sal margin of a right valve (figure 98a) indicates a deep 

byssal notch and an extremely narrow right anterior ear, suggesting 

that the figures are of entirely different taxa. 

Co·rn1w:rison.-Propea:m:uss·iu:m. ·1>nte·rm.d·iatwm (Gab b) differs from 

P.leohwrthn>n:1: Addicott (1971), described from the Eocene of Alaska, 

in having a relatively smooth exterior and fewer internal ribs-8 

rather than 10. (Addicott, 1971, p. 227) 

"It seems doubtful that Propeamussium stanfordens,is [Arnold, 

1906] represents young specimens of the well-known Eocene species 

P. inte1Ta.d1:a.tum (Gab b) as was suggested by Grant and Gale (1931). 

The shorter, consistently fewer internal ribs-8 rather than 10 or 

more-and the weaker, much finer concentric sculpture of P. 1:nter1·a.d·ia.tum * * *permit differentiation." (Addicott, 1971, p. 229) 

Com.m.ents.-The lectotype of P. inte?Ta.dia.tum., presumably a left 

valve, does not have the external shell preserved. It bears eight 

internal ribs; three posterior ribs are straight, the remaining five 

curve toward the anterior margin. The holotype of Pecten (Propeamuss?>um) va.ca.V1:Uens1:s is a juvenile specimen (1.4 mm high and 

1.4 mm wide), broken subsequent to its original illustration, that 

was distinguished from P. interm.d1:atum. by Palmer (1923, p. 301) as 

follows: "P. vaca:villens1:s differs from P. ·interra.dia.tus Gabb in that 

the internal ribbing occupies only the ventral two-thirds of the shell 

instead of the dorsal half as indicated in the original figure." 

As noted by Stewart (1930, p. 124), on small specimens of P. 

1:nte1Tad1:a.tum the internal ribs reach almost to the ventral shell 

margin. 

Geogm.p/n:c nt.nge.-MiddJe California. 

Geolog1:c range.-Eocene. 

Occw·rence in Ca.lijm·m:a .. - Eocene: Butano(?) Sandstone (Add icott, 1971), Capay Formation (Palmer, 1923), lower part of Kreyenhagen Shale (Addicott, 1971), and-Tejon Formation (Arnold, 1906). 

Genus CYCLOPECTEN Verrill, 1897 

Small, thin, not gaping, right valve flexible and upturned at margin in some forms; sculptured with concentric lamellae or nearly 

smooth, left valve with radial rows of arched scales or pustules; 

auricles well delimited; cardinal crura single, commonly feebly 

developed, hinge generally bearing vertical transverse striae; byssal 

notch large, without a ctenolium. 

Geolom:c nmge.-Paleocene(?); Miocene through Holocene 

(table 3). 

Ha.bita.t.-5 to 2,325 m. 

Cyclopec~en lompicoensis (Arnold) 

Plate I, figure 2 

Pecten (Pseuda.musium) lompicoensis Arnold, 1906, p. 89, pl. 23, fig. 

5; pl. 27, fig. 8. 

On:ginal descript1:on.-"AduJt shell averaging about 11 millimeters in altitude, subcircular, inequivalve, thin, compressed, margins smooth. Right valve ornamented externally by numerous sharp, 

elevated, equal, equidistant, imbricating, concentric lamellae; hinge 

.line equal to one-half length of disk; ears unequal; anterior nearly 

twice as long as the posterior, arcuately truncated and sculptured by 

regular sharp, imbricating, concentric lamellae and 6 or 7 faint 

TABLE 3.-Geolog·ic and geographic d1:stribut1:on of the genus Cyclopecten in the eastern Pacific region 

[H =Holocene; Pie= Pleistocene; PI =Pliocene; M =Miocene; Pa =Paleocene] 

Species 

Genus Cyclopecten: 

·inconm·uus (Dall) ................................... . lomp1:coens·1:s (Arnold) ........................... . pe1'1Wmus (Hertlein) ............................... . Genus Cyclopecten?: ma. 1·ti nezens·is (Gab b) ............................. . 

• 

California 

Northern Middle S~uthern 

M 

Pa 

Pl,Ple 

PI 

Baja California 

Norte Sur 

H 

H H 

Central 

and (or) South 

America 

H 
B8 PALEONTOLOGY OF CALIFORNIA AND BAJA CALIFORNIA 

radials; posterior ear short, somewhat obliquely truncated and 

sculptured by concentric lamellae; byssal notch only faintly indicated. Left valve sculptured by concentric lamellae similar to those 

of the right, and, in addition, having numerous fine radiating striae, 

which usually become obsolete near the periphery in the adult shell; 

ears similar to those of the right valve, except that in the specimens 

examined no radials were noted on the anterior one. Hinge similar to 

that of P. randolph1:." 

Holotype.-USNM 164931. 

Type locality.-Head of Lompico Creek [NW~ sec. 24, T. 9 S., R. 2 

W., Santa Cruz Quad.], Santa Cruz County, Calif. Monterey Formation, Miocene. 

Comparison.-Arnold (1906, p. ·89) says that C. lompicoensis can 

be distinguished from Delectopecten peckhami by its much more 

prominent and regular concentric lamellae, and well-defined ears. 

Comments.-The right posterior auricle of C.lompicoensis is delineated, excluding it from Delectopecten, and no trace of internal ribs 

can be seen, excluding it from Propeamussium and Parvamussium. 

The only sculpture preserved is strong, almost equally spaced, concentric ridges on the right valve. The left posterior auricle seems not 

to be delineated. 

I am indebted toT. R. Waller (written commun., 1979) who examined the holotype of this species and said that it "is definitely a 

member of the Propeamussiidae as evidenced by the presence of a 

prismatic structure over the entire right valve and lack of a ctenolium. I think that it can best be placed in Cyclopecten for the 

present." 

Geographic range.-Middle California. 

Geologic range.-Miocene. 

Occurrence in Calijornia.-Monterey Formation. 

Cyclopecten pernomus (Hertlein) 

Plate 1, figures 3-6 

Pecten (Cyclopecten) rotundatus Dall, 1908, p. 404. Not Pecten rotundus von ·Hagenow, 1842. · 

Pecten (Cyclopecten) pernomus Hertlein, new name, 1935, p. 320, pl. 

18, figs. 11-13. 

Cyclopecten pernomus (Hertlein). Grau, 1959, p. 32-34, pl. 11. 

Hertlein and Grant, 1972, p. 213-214, pl. 33, figs. 7, 11. 

Amusium (Cyclopecten) pernomus Hertlein. Olsson, 1961, p.168-169, 

pl. 21, fig. 6. 

On:ginal description.-"Shell very small, thin, white, suborbicular, with subequal ears, both valves nearly equally convex; right 

valve polished, minutely regularly concentrically striated, which 

sculpture is barely visible under a hand lens; posterior ear smooth, 

anterior finely radially threaded, with a narrow but clean-cut byssal 

sulcus and fasciole; left valve finely sharply radially striated, the 

anterior ear finely reticulated, the posterior apparently nearly 

smooth; hinge line short, straight; interior smooth, a pair of small 

auricular crura present; the hinge line with a minute central pit and 

two relatively large transversely sharply striated, elongate areas 

representing a permanent provinculum. Height and length, 3; hinge 

line, 2.5; diameter, 1.0 mm. A single valve from near the Straits of 

Magellan, apparently the same species, measures 7 mm. in height." 

Syntypes.-USNM 110708; two left and one right valve. 

Type locality.-Panama Bay, Panama, Albatross Station 2799, in 

54m. 

Supplementary description.-"The right valve is slightly smaller 

than the left. Its anterior auricle has concentric as well as radial 

striae; its posterior auricle is not 'smooth,' having 7 to 11 fairly 

prominent radial threads and finer concentric threads. The posterior auricle of the left valve is not 'nearly smooth,' having both fine 

radial and finer concentric threads. * * *" (Grau, 1959, p. 33) 

"The ears have a large, impressed, flattened inner surface which is 

finely vertically grooved or striated along the hinge, these groovings 

often interlock so well that the valves do not separate easily without 

breaking the shell." (Olsson, 1961; p. 169) 

Comparison.-"Cyclopecten pernomus lacks the distinct posterior 

flexure which is present on the right valve of C. cocosensis Dall. The 

auricles of C. pernomus are much less acutely pointed than those of 

C. acutus Grau from West Colombia * * *" (Hertlein and Grant, 

1972, p. 214) 

Comments. -Cyclopecten pernomus is smaller than C. incongruus. · 

The left valve has fine radials, whereas on C. incongruus the left-

·valve radials are scabrous and more prominent on the posterior half 

and the shell has strong concentric lamellae. ·The right valve of C. 

pernomus is smooth; C. 1:ncongruus is sculptured by prominent concentric lines. 

Geographicrange.-Living: Cedros Island·, Baja California Norte, 

Gulf of California, to La Libertad, Ecuador; also Guadalupe Island 

and Galapagos Islands; fossil: southern California. 

Geologic range.-Pliocene through Holocene. 

Occurrence in California.-PI iocene: San Diego Formation (Hertlein and Grant, 1972). 

Habitat.-Usually on mud bottoms, occasionally sandy mud or 

sand; sometimes associated with eel grass; 2 to 344 m (Grau, 1959). 

Cyclopecten incongruus (Dall) 

Plate 1, figures 7, 8 

Pseudamusium incongru'U'm Dall, 1916, p. 403. 

Cyclopecten incongruus (Dall). Grau, 1959, p. 36, pl. 13. 

Original description-"Shell small, white suborbicular, left valve 

rather flat with short straight hinge line, ears concentrically scaly, 

sculpture of disk concentric continuous low sharp lamellae, crossed 

by slightly raised radial lines, conspicuous only at the intersections 

which form in the middle of the disk square reticulations with a 

small conspicuous pustule at each intersection; laterally these are 

.more crowded; right valve concave near the margin, closely regularly concentrically lamellose; anterior ear with five radial lines, 

coarsely lamellose with a shallow notch and serrate margin. Height, 

14; breadth, 15; diameter, 3 mm." 

. Holotype.-USNM 207273. 

Type locality.-"*** Station 2986, N.W. ofCerros [sic: Isla Cedros] 

Island, Lower California." (Grau, 1959, p. 36) 

Supplementary description.-"This is the largest eastern Pacific 

.Cyclopecten, none of the other species exceeding 10 mm in height." 

(Grau, 1959, p. 36) 

Comments. -See C. pernomus. 

Geographic range.-Living: Isla Cedros, Baja California Norte; 

fossil: southern California. 

Geologic range.-Pliocene through Holocene. This s'pecies may be 

restricted to the Pleistocene through Holocene, depending upon its 

stratigraphic position within the Fernando Formation. 

Occurrence in California.-Pliocene and Pleistocene: Fernando 

Formation (Zinsmeister, 1970). 

Habitat.-The holotype was collected at 1,250 m from fine gray 

sand and broken shell. 

Genus CYCLOPECTEN? 

Cyclopecten? martinezensis (Gabb) 

Plate 1, figures 9, 10 

Pectenmartinezensis Gabb, 1869, p. 198, pl. 33, fig. 96. Stewart 1930, 

117-118, pl. 7, fig. 10 
TERTIARY MARINE PELECYPODS: PROPEAMUSSIIDAE AND PECTINIDAE B9 

On:m:na.l descn:pt1:on.-"Shell minute, thin, elongate, equivalve, 

equilateral; sides straight above, below forming with the base a 

regular curve. Lower valve, right auricle deeply emarginate, narrow; left smaller. Upper valve, right auricle small; left large, margin slightly sinuous. Surface ornamented by fine radiating ribs." 

Lectotype.-MCZ 15026a. 

Type loca.f:ity.-Martinez [Contra Costa County], Calif. Martinez 

Formation, Paleocene. 

Com:ments.-On the basis of the lectotype and two remaining specimens in the type lot, this species is small, thin shelled, and has fine 

radiating ribs or striations. The lectotype is an internal mold that 

retains no shell. It is presumably a left valve and is moderately 

inflated for its size. Faint traces of ribs or striations are preserved 

near the ventral posterior margin. The anterior auricle is small and 

squarely truncated; the posterior auricle is incomplete but may have 

been slightly smaller. 

One specimen remaining in the type lot, also apparently a left 

valve, shows traces of fine ribs over the entire surface of the internal 

mold. The auricles are incomplete, retain patches of the internal 

shell layer, and are of the same size and proportions as those on the 

lectotype. 

The last remaining specimen in the type lot is an incomplete 

specimen that shows the interior of the shell. It seems to be a right 

valve and, if so, the anterior auricle was narrow and perhaps not 

very long. 

None of the specimens in the type lot show internal ribs. Thus the 

species is presumably neither Pseuda.n~ussiu:m nor Pa.rvmnussiitm, 

and the valves do not show the posterior obliquity of Delectopecten. 

The fine radial ribs and outline of the auricles suggest Cyclopecten. 

Geom·a.1Jh1:c m.nge.-Middle California. 

Geolog·ic 1·a.nge.-Paleocene. 

Occu?Tence ·1:n Ca.hfo·rnia..-Martinez Formation. 

Genus PARVAMUSSIUM Sacco, 1897 

Differs from Propea.muss·,:um in its usually more rounded shape, 

lack of lateral gape, presence of well-developed byssal notch, and 

internal ribs extending to or almost to the ventral margin. Differs 

from Cyclopecten in possessing internal ribs. 

According toT. R. Waller (oral commun., 1979), Parvamussium 

belongs in the family Propeamussiidae. 

Geolog·ic 1·a.nge.-Cretaceous through Holocene (table 4). 

Parvamussium mideocenicum (Vokes) 

Plate I, figure II 

Propea.muss?:u.m?m:deocem:cum Vokes, 1939, p. 55-56, pl. 3, figs. 2, 3; 

not? pl. 3. fig. 4. 

0?"im:na.l desc1·ipt1:on.-"Shell small, thin, slightly higher than 

long; ventral margin evenly rounded, th'e anterior and posterior. 

margins straight to the umbos; surface of left valve ornamented with 

10 to 12low, rounded ribs separated by flat-bottomed inters paces of 

. varying width, widest on the center of the valve but never less than 

twice the width of the ribs; both ribs and interspaces marked by 

faint lines of growth; surface of right valve not seen; ears smooth, 

subequal, the byssal notch well-defined, small; interior of both 

valves with 10 to 12 ribs extending from the umbo to the ventral 

margin and directly opposite the ribbing on the exterior of the valve. 

"Propeamussium mideocenicum may be distinguished by the fact 

that the ribbing on the surface of the left valve is directly opposite 

that on the interior of the valve, which extends from the umbo to the 

ventral margin." 

Syntypes.-UCMP 15584 and 15586; not? 15585 which may be 

Parvamussium stanfordensis. 

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

Member, Lodo Formation (Keen and Bentson, 1944), Paleocene. 

"One of the early Eocene specimens of Propeamussiumm?:deocenicum Vokes, 1939, UCMP 15585 from the Arroyo Hondo Shale 

Member of the Lodo Formation in the San Joaquin basin, California, 

might be P. sta.njordens1:s. The ears, number and configuration of 

internal ribs, and size of this syntype are similar toP. stanfordensis. 

The other syntypes (both left valves) are quite distinct; they probably 

represent an entirely different species than P. stanfordensis judging 

by the occurrence of external ribbing and by the fact that these ribs 

,are much more numerous than on the right valve-12 instead of 9." 

(Addicott, 1971, p. 229) 

Comparison.-"P. inte1-radiatum (Gabb) has but 8 internal ribs 

which extend only half way down the valve from the umbo. * * * 

P. la.jollaense (M.A. Hanna) from the La Jolla formation, has about 

65 ribs on the exterior of the valve." (Vokes, 1939, p. 56) 

Parvamussium leohertle1:ni, from the Eocene of Alaska, differs 

from P. mideocenicum principally in lacking a well-defined byssal 

notch. The left valve of P. mideocenicum can be differentiated from 

P. leohertleini by its .Prominent, sharp external ribs. Further, but 

minor, differences are the relatively shorter internal ribs and the 

prominent, but very fine, growth striae of P. leohertleini. (Addicott, 

1971, p. 227) 

· Comments.-The exterior of the left valve bears 12 preserved 

well-defined, small ribs but may have had originally about 15; the 

shell is glossy white. The left valve auricles seem to have been equal 

in size. 

Geographic range.-Middle California. 

Geologic range.-Paleocene. 

Occurrence in Calijornia.-Paleocene: Cerros Shale Member, 

Lodo Formation (Keen and Bentson, 1944). 

Parvamussium lajollaense (M. A. Hanna) 

Plate l,.figures 12, 13 

Pecten lajollaensis M.A. Hanna, 1927, p. 277, pl. 32, figs. 1, 3-6. 

Original descr1:ption.-"Shells quite small, thin; length and altitude about equal; slightly convex; base evenly rounded; sid.es nearly 

TABLE 4.-Geolog1:c and geographic distn:bution of the genus Parvamussium in the eastern Pac1jic region 

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

Species 

Alaska British Washington Oregon California Baja Columbia 

Northern Maddie ~ali(2[Dill- Southern Norte Sur 

Genus Pa.rva.mussiunt: 

a.la.skense (Dall) ....................................... . H H H H H H PI to H H H 

la:jolla.ense (M. A. Hanna) ..................... . E E 

m:ideocenicum (Vokes) ........................... . Pa 

?'1:0ve1·s1: (Arnold) ....................................... . st£tn/o?·dense (Arnold) ........................... . M,Pl Pl,Ple 

E 
BlO PALEONTOLOGY OF CALIFORNIA AND BAJA CALIFORNIA 

straight to the beaks, forming an angle of about ninety degrees; left 

valve: hinge line three-fourths the length of the disc; ears sub-equal, 

the anterior the larger, radially ornamented by fifteen to twenty fine 

rounded ribs which are crossed by growth lines; disc ornamented by 

about sixty-five nearly equal sized, fine, rounded linear ribs which 

are crossed by fine indistinct growth lines; right valve: ears unequal 

in size, posterior the smaller, anterior much produced, crossed by 

growth lines but not radial lines; surface of the disc sculptured by 

fine, prominent, equally spaced, concentric growth lines; radial 

sculpturing not present; internal ribbing of the right valve consists 

of ten prominent, narrow, rounded ribs separated by very much 

wider flat-bottomed interspaces. 

"Pecten lajollaensis n. sp. differs from Pecten inteTradiata Gabb in 

not having the same sculpturing. The heavy internal ribs of the new 

species extend to the perifery [periphery] of the shell, rather than 

only a short way down from the umbones." 

Syntypes.-UCMP 31106, 31107, 31108, 31109, 31110. 

Type locality.-UC 5062. San Diego County, Calif. Ardath Shale, 

Eocene. 

Connnents.-The left valve (UCMP 31108) is sculptured by many 

(about 65) small, fine, almost equidimensional ribs; on the basis·of 

type material, this characteristic separates P. lajollaense from the 

other described Tertiary species of PaTvamussium. The interior of 

the right valve (UCMP 31108) bears 10 prominent ribs that extend 

almost to the ventral shell margin. 

Geograph1:c Tange.-Middle to southern California. 

Geologic range.-Eocene. 

Occu?Tence in California.-Eocene: Ardath Shale and Muir 

Sandstone (Weaver, 1953). 

Parvamussium stanfordense (Arnold) 

Plate I, figures 14, 15, 17 

Pecten(PTopeamussium)stanjoTdensis Arnold, 1906, p. 91-92, pl. 23, 

fig. 4. 

PTopeamussium (Parvamussiwn) stanfordensis (Arnold). Addicott, 

1971, p. 228-229, figs. 3, 5, 8, 10. 

?PTopeamuss?:um mideocen?:cum Vokes, 1939, p. 55-56, pl. 3, fig. 4; 

not pl. 3, figs. 2, 3. 

On:g1:nal description.-"Shell averaging about 9 millimeters in· 

altitude, subcircular, equivalve, equilateral, thin, only slightly ventricose, and with smooth margins. Right valve with the exterior 

surface ornamented by numerous fine concentric undulations and, 

in some cases, microscopic radiating striae; interior with 10 to 12 

prominent, rounded, equidistant ribs extending from the umbo to or 

near to the periphery of the disk, those ribs nearest the center of the 

shell being straight, while those near the sides are somewhat arcuate 

toward the central rib; hinge line slightly longer than one-half the 

length of the disk; ears equal in length, and ornamented by the fine 

concentric undulations; anterior ear with a small byssal notch. Leff 

valve similar to right, except that its anterior ear lacks the byssal 

notch." 

Holotype.-CAS/SU 12. 

Type locality.-Burke [Webb] Ranch, 0.5 km south [west] of Los 

Trancos Creek, near Stanford University, San Mateo County, Calif. 

Butano(?) Sandstone, Eocene (Addicott, 1971). 

SupplementaTy descTiption.-"a virtual topotype ***has a*** 

preserved external surface showing relatively strong, regularly 

spaced concentric undulations. * * * the anterior ear of the right 

valve has a rather strong byssal notch that is reflected in the curvature ofthe growth lines. Moreover, the internal ribs extend almost to 

the margins of the valves. Accordingly, placement in the subgenus 

PaTvamussium is clearly indicated. 

"One of the early Eocene specimens of Propea,mus.•n:um ?nideocen:icum Vokes, 1939, UCMP llQSB§ from the Arroyo Hondo Shale Member of the Lodo Formation in the San Joaquin basin, California, 

might be P. stanjoTdens1:s. The ears, number and configuration of 

internal ribs, and size ofthis syntype are similar toP. stnnjo·rdens1:s. 

The other syntypes (both left valves) are quite distinct; they probably 

represent an entirely different species than P. stctnjoTdens?:sjudging 

by the occurrence of external ribbing and by the fact that these ribs 

are much more numerous than on the right valve-12 instead of 9 

[sic: 10]." (Addicott, 1971, p. 228-229) 

' Cmnparison.-"It seems doubtful that Propeamuss1:wn sta.nfm·-

densis represents young specimens of the well-known Eocene species 

P. interradintuni-(Gabb) as was suggested by Grant and Gale (1931). 

The shorter, consistently fewer internal ribs-8 rather than 10 or 

more-and the weaker, much finer concentric sculpture of P. ·inte?'-

radiatum permit differentiation." (Addicott, 1971, p. 229) 

. Propemnussium. leohe1·tle1>ni, from exposures on Adak Island, is 

very similar toP. stanfm·densis (Arnold). It differs, however, in the 

configuration of the right anterior ear and in minor sculptural 

detail. (Addicott, 1971, p. 227) 

GeogTaphic range.-Middle California; Japan? (Kobayashi, 1926). 

Geologic ra,nge.-Eocene. 

"Arnold (1906, p. 92) originally classified the stratigraphic occurrence of this species as middle Miocene, apparently believing the 

light-colored shale exposure from which it was collected to be part of 

the Monterey Shale. Consequently, subsequent treatments of Tertiary Propeamussium (Slodkewitsch, 1938; Weaver, 1942) have considered species, and phylogenies, in the context of a Neogene stratigraphic occurrence of this taxon. * * * It was found that the type 

locality is in an area of upper Eocene rather than middle Miocene 

rocks, according to recent geologic mapping and related micropaleontologic studies. 

"Two of the specimens of Propemnuss1:um stanfm·denrn:s figured in 

this report * * * can be regarded as topotypes. They are from a 

locality on the north wall of the same drainage from which the 

holotype was collected by Ralph Arnold, possibly on strike from his 

locality. They occur with a diverse foraminiferal assemblage of late 

Eocene Narizian age according toM. C. Israelsky (in written communication to E. H. Pampeyan, April 16, 1963; USGS microfossil 

locality Mf707). The occurrence is about 45 m stratigraphically 

below the base of middle Miocene rocks in a unit mapped by Dibblee 

(1966) and by Pampeyan (1969) as by Page and Tabor (1967) as 

unnamed Eocene rocks." (Addicott, 1971, p. 228) 

OccurTence in California.-Butano(?) Sandstone and lower part of 

Kreyenhagen Shale (Addicott, 1971). 

Parvamussium riversi (Arnold) 

Plate I, figures 16, 18 

Pecten (PTopeamussium) riversi Arnold, 1906, p. 126-127, pl. 44, 

figs. 8, 9. · 

Original description.-"Shell averaging about 14 millimeters in 

altitude, about as long as high, circular in outline, equilateral, compressed, white, translucent; margins smooth. Right valve much 

compressed; surface smooth except for numerous very fine, regular, 

imbricating lamellae; hinge line one-half length of disk; ears distinctly separated from disk by impressed line, subequal in length; 

the anterior arcuate in front and with about 12 subequal prominent 

radials and numerous fine, regular, imbricating, incremental 

lamellae; the posterior slightly obliquely truncated and sculptured 

similarly to the anterior, except that the radials are nearly obsolete; 

byssal notch of medium prominence. Interior of disk smooth until an 

altitude of 15 millimeters is reached, when about 20 to 22 small, 
TERTIARY MARINE PELECYPODS: PROPEAMUSSIIDAE AND PECTINIDAE Bll 

round, radiating ribs appear and continue to the periphery. Left 

valve somewhat more convex than the right, and ornamented externally by numerous unequal prominently imbricated ribs, the alternate ones being intercalated between slightly larger ones; whole 

surface sculptured by fine imbricating lamellae; anterior ear similar to that of the right valve, except that it is more strongly radially 

ribbed and is less sinuated; posterior ear similar to that of right 

valve, except that it is more strongly ribbed; interior of left valve 

similar to that of the t·ight, and having the radial ribs developed only 

after attaining an altitude of about 15 millimeters." 

HolotmJe.-CAS/SU 33. 

Type locu.l-!:ty.-Los Angeles County, Calif. Fernando Formation, 

Pliocene and Pleistocene. 

Conl-1)(t:rison .. -"This species is very closely allied toP. alasken.'n:s, 

of which it is undoubtedly the precursor. It differs from the latter in 

having the external ribs on the left valve more prominently imbricated above, and in having the internal ribs of both valves appearing 

only after an altitude of about 15 millimeters has been attained." 

(Arnold, 1906, p. 127) 

Cmn:nwnts.-The right valve (holotype) is smooth except for fine 

concentt·ic lines. The right anterior auricle is broken but was longer 

than the posterior auricle. The internal ribs are visible only near the 

ventral shell margin. Pa1·vmnuss·ium n>venn: was synonymized with 

P. alaskense by Grau (1959, p. 18). The differences in the sculpture of 

the right valves of the holotypes of these two species is such that P. 

·n>ue·r.<;·i is here reinstated. The exterior of the right valve (holotype) of 

P. ·n>ue·rs-i is smooth; that of P. alaskense bears many fine ribs. The 

interior of the right valve of P. ?"ive·rs·i shows internal ribs near the 

ventral margin; on P. alaskense the internal ribs are stronger and 

cover a greater proportion of the shell. It is possible that the variation of P. alaskense is sufficient to include P. 1·1:vwrs1:. 

Georrraph:ic nt:nge.-Middle to southern California. 

Geolo{J'I:c nt.nge.-Miocene to Pleis.tocene. 

Occu:1Tence ·1:n Ca.l·1jon1:ia .. -Miocene and Pliocene: Purisima 

Formation (Arnold, 1906); Pliocene and Pleistocene: Fernando, 

Merced (At·nold, 1906), and San Pedro Formations (Arnold, 1906). 

Parvamussium alaskensis (Dall) 

Plate 2, figures 1-7 

Pecten (Pseuda:m:us.<rimn?) alaskens·is Dall, 1871, p. 155, pl. 16, fig. 4. 

Dall, 1898, p. 711. 

Propea·m.usshtm (Pm·vctmuss?:~tm) a.la.skense (Dall). Grau, 1959, p. 

18-20, pl. 3. 

Polyn.ema:muss·1:um. nlaskense (Dall). MacNeil, 1967, p. 6-7, pl. 5, 

figs. 2-4. 

Pecten (Propea.m.us·i~tnl.) le·V?:s Moody, 1916, p. 56-58, pl. 2, figs. 2a-2d. 

Not Pecten lnev·is Pennant, 1777. 

Pecten calnn1:1:tus G· D. Hanna, 1924, p. 176, new name for Pecten 

(Propea.mu .. <;.•n>u:m) le'ltis Moody, 1916, not P. leavis Maton and 

Rackett, 1807. 

Or·i{J'I>na.l descn:pt1:on.-"Shell nearly equilateral, inequivalve, 

flesh-color with a blush of salmon-color on the umbo of the superior 

valve. Internally white, the salmon-color showing through the valve. 

Shell su borbicular, barring the auricles, which are wide and prominent. Lower [right] valve flattened, .1 in. smaller than the upper one; 

sculpture of fine, close, equal, concentric ridges, sharply defined and 

separated by narrow non-canaliculated grooves. Valve covered with 

a fine velvety epidermis, ashy and very finely radiately striate. 

Surface of the valve, except for the ridges, smooth. Anterior auricle 

long, pt·ominent, with a deep sinus. Posterior auricle small; both 

with strong elevated lines of growth, which rise into scales on the 

eight or nine fine ribs with which the anterior auricle is furnished. 

Hinge line straight, smooth. Inside of the valve polished, furnished 

with twenty-one rounded, radiating ribs, with traces of others intercalated near the margin; nodulous or swollen at the more prominent 

ridges of growth and at the margin. 

"Upper [left] valve similar, inside; anterior auricle shorter, not so 

deeply sinuated. Valve more convex than the under one, and a little 

larger. Dorsal areas finely granulate. Umbo smooth; half way 

toward the margin the striae of increase become more conspicuous, 

and about thirty-five pseudo-ribs radiate toward the margin. These 

are formed by the elevation of the concentric lines of growth like 

ruffles, in such a way that the edge of one fluting of the ruffle 

overhangs the beginning of the next, and so on. These are very 

fragile, and when broken away show the nearly smooth surface of 

the valve underneath, without any true rib at all. Faint grooves are 

intercalated between the pseudo-ribs toward the margin. Lon .. 76, 

alt. 76, diam .. 22 in., width of hinge line .34 in. Angle at the umbones, 

100°." (ala.sken.'n:s) 

"Shell small, ·thin, transfucent, nearly circular in outiine, equilateral, compressed, slightly inequivalve. Right valve is smooth 

except for numerous very fine incremental lines, which occasionally 

are enlarged and roughened; traces of submicroscopic radiating 

striae are to be seen. Hinge line is about five-eighths the width of the 

shell; ears sharply set off from the disc by equal impressed lines 

which are nearly straight and slope evenly from the umbone; anterior ear arcuate, coarsely sculptured by about fourteen subequal 

ridges which radiate from the beak, and by about thirty-five prominent, regular, imbricating lines of growth which curve outward, 

following the anterior margin; posterior margin makes a rightangle 

with the hinge-line; byssal notch almost obsolete; posterior ear 

ornamented with a similar number of incremental laminae which 

are only slightly curved and are nearly vertical, the radiating ridges 

being indistinct. Interior surface of the valve marked by twenty-two 

rounding ridges which radiate from the apex but are partially obscured in the upper portions by a callus growth which covers onethird the area of the disc; a single adductor scar appears on the 

anterior dorsal margin of the callus. Left valve slightly less convex 

than the right; externally sculptured by fourteen prominent, smooth, 

rounded ribs which radiate from the apex; in the interspace appear 

one or sometimes two inter-ribs of varying length, which never 

reach the beak; anterior ribs and inter-ribs slightly imbricated; 

incremental lines quite fine and uniform on the posterior threefourths of the surface. Ears of the left valve subequal; both slightly 

arcuate below the hinge line, the anterior more coarsely sculptured 

by twelve radiating striae and thirty or more roughened incremental lines which are vertical on the hinge-line and broadly recurved 

below; beak sharp and straight and slightly raised above the hingeline. Interiorly the valve is sculptured by about twenty distinct, 

rounded ribs radiating from the umbone, which are independent of 

the external ornamentation and do not reach the ventral margin; 

internal ribs slightly obscured, as in the right valve, by a callus 

growth." (levis) 

Holotype.-Location unknown. Thomas R. Waller, Smithsonian 

Institution, searched the collections at the National Museum of Natural History and did not find any specimen that resembled Dall's 

(1871, pl. 16, figs. 4a, 4b) original illustrations of Pecten (Propeamusium) levis Moody, UCMP 11084. 

Type locality . ...:...Port Etches, western Hinchinbrook Island, Prince 

William Sound, Alaska, Holocene; of P. levis Moody, UC 3030, Los 

Angeles ~ounty, Calif. Fernando For.mation, Pliocene and Pleistocene. 

Supplementary description.-"Both the right and left valves of 

this species have weak internal rib lets that become stronger distally, 

but only the left valve has riblets on the exterior. The number of 

external riblets is variable, ranging usually from 24 to 30. Some of 
B12 PALEONTOLOGY OF CALIFORNIA AND BAJA CALIFORNIA 

the riblets tend to become weakly beaded or scabrous toward the · 

margin. The riblets have little relief and tend to merge with the 

interspaces; usually they are lighter colored than the remainder of 

the disc. All the ears have weak radial riblets, but such riblets are 

stronger on the anterior ear of the right valve." (MacNeil, 1967, p. 6) 

The count of 21 ribs given by Dall (1871, p. 155) is low for the 

species (T. R. Waller, written commun., 1979). 

Comparison.-"This species is easily dis~inguishable from the 

Miocene and older species on the Pacific coast by its more numerous 

internallirations. The writers tried to distinguish riversi from the 

living P. alaskensis Dall on the basis of the still more numerous 

internal lirations on the living specimens, until they noticed that 

Dall's original description calls for only 21. The form renamed by 

Hanna is exactly like riversi. P. (Propeamussium) davidsoni Dall, a 

species living in Alaska, ***has much the same shape; but it has 

fewer and stronger external ribs on the left valve, and after it is a 

little more than half grown it develops ribs on the outside of the right 

valve also." (Grant and Gale, 1931, p. 234) 

"Polynemamussium intuscostatum (Yokoyama) (Masuda, 1962b, 

p. 156), a related species from the early Pliocene to Recent of Japan, 

is more coarsely sculptured than P. alaskense and the riblets are 

more beaded. 

"Pecten (Propeamusium) riversi Arnold*** is closely related toP. 

alaskense; according to Arnold's figures the internal riblets are 

weaker and more closely restricted to the marginal area, and the 

external riblets of the left valve are stronger." (MacNeil, 1967, p. 6) 

Comments.-Parvamussium calamitus was considered to be conspecific with P. alaskense (Dall) by Grant and Gale (1931, p. 234) and 

Grau (1959, p. 18) but not by MacNeil (1967, p. 6-7). On the basis of 

examination of primary type material, the left valve auricles of P. 

calamitus are of almost equal length and height; the anterior left 

auricle of P. alaskense is both markedly longer and higher than the 

left posterior auricle. The left valve of P. alaskense has poorly delineated ribs; the left valve of P. calam1:tus has well-defined, narrow 

ribs extending almost to the beak and equally strong secondary ribs 

that appear when the shell has reached a height of about 5 mm. The 

ribs on the interior of the left valve of P. calam1:tus are fewer in 

number (about 20 rather than 30) and are less prominent than on P. 

alaskense. The auricles on the right valve holotype of P. calamitus 

are broken but seem to have been almost equal; the left posterior 

auricle is slightly higher than the left anterior auricle. The variability of P. alaskense may be sufficient to include P. calmm:tus. 

Geographic range.-Living: Japan, Korea; Bering Sea to Baja 

California Sur; fossil: Japan; Alaska to southern California. 

Geologic range.-Pliocene through Holocene. 

Occurrence in Calijornia.-Pliocene: Lomita Marl Member, San 

Pedro Formation (Woodring, 1946); Pliocene and Pleistocene: Fernando Formation (J. D. Mount, written commun., 1971) and San 

Pedro Sand (Arnold, 1906; Woodring, 1946). 

Habitat.-Recorded in 18 to 365m (Grau, 1959, p. 20). 

Family PECTINIDAE 

"Byssate, cemented, or unattached Pectinacea with outer, simpleprismatic calcitic layer on right valve generally present only in early 

growth stages, rarely absent altogether; crossed-lamellar aragonite 

restricted to area inside of pallial line or absent. Byssal notch with 

ctenolium, at least at early growth stage. Mantle curtains bearing 

guard tentacles." (Waller, 1978, p. 353) 

"Shell varying in size, orbicular to oval, valves of some shells. 

equally convex but usually one valve more inflated than other, mar-· 

gins usually, but not invariably closed; umbos central, on either side 

of which are triangular auricles (ears), anterior one on RV usually 

with distinct byssal notch or inden-tation below it; surface smooth or 

with radial ribs or folds, some species with concentric sculpture of 

raised lamellae; interior smooth or with fine radial riblets; hinge 

line straight; external ligament obsolete or nearly so, resilium internal, amphidetic, in triangular pit below umbones; young shells with 

small taxodont teeth which become obsolete later; cardinal crura or 

laminae commonly present, diverging from either side of ligamenta! 

pit; rounded laminae (auricular crura) present on interior of some 

shells where auricles join valves; adults monomyarian, with posterior adductor only; free, attached by byssus, or cemented by RV; 

upper (L) valve, usually more brightly colored***." (Hertlein, 1969, 

p. N348) 

"The shape and sculpture of the shells of pectens, usually differing 

in detail on the two valves, are often quite constant, and * **species 

may often be recognized from fragments.*** when riblets arise in 

the interspaces between the ribs they always appear first on the left 

valve. Dall (1898, p. 692, 693) pointed out that when ribbing tends to 

become obsolete, the radial sculpture is retained on the left valve 

after the right valve has become nearly smooth. Furthermore, that 

the right anterior ear usually, is the last to lose its radial sculpture. 

"An interesting characteristic of the sculpture of these bivalves is 

that rarely, if ever, do they possess concentric ribbing although some 

species such as Chlamys (Swijtopecten) swijtii Bernardi and C. condylomatus Dall have concentric thickening and undulations or '!edging'*** of the shell and others have coarse annular growth lamellae 

such as are present in the subgenus Camptochlamys Arkell. The 

geologic range of supraspecific units as well as of species is fre-

·quently short. Furthermore, apparently because of the composition 

and microstructure of the shell (which is made up of irregular 

foliated layers of calcite with a thin median prismatic layer of aragonite), pectens often occur abundantly as fossils where other mollusks (except some other genera such as Ostrea) are represented only 

by casts and moulds. From a consideration of the features here 

enumerated in connection with pectens, it is obvious why this group 

has furnished some of the most reliable index fossils used in deciphering the age and correlation of strata. 

"A striking feature of the Tertiary Pectinidae * * * is the great 

increase in size during Miocene time. Most specimens from strata of 

Eocene or Oligocene age do not exceed 50 mm in diameter. Very 

large species described from the late Tertiary are: M1:zuhopecten 

kamagai Nagasawa, probably of Pliocene age, in Japan, 280 mm 

long; Pecten dregeri von Teppner of Miocene age in Austria, 240 mm 

long; Pecten healeyi Arnold in the San Diego Formation, Pliocene, 

222 mm long; and Chlamys (Nod1:pecten) arnoldi Aguerrevere, of 

late Miocene or Pliocene age in Venezuela, 218 mm long. The greatest size reported for a living species is that of Pecten (Pat1:nopecten) 

caurinus Gould, 288 mm long and 198 mm high. 

"Some living species of this family especially valuable as food, 

have received intensive study. An interesting feature of the shell is 

the presence of concentric rings formed by offsets, or by color 

changes, during growth, and best observed on the upper valve. 

These rings*** are a result of a quiescent period of growth during 

the spawning season. It is generally believed that these rings are 

formed annually, but this is not always the case because, as pointed 

out by Gutsell, rings sometimes are present on young shells which 

have not reached maturity. 

"Several thousand species of pectens have been described as fossils. About 350 to 400 species are now living in the seas, the greater 

number in Indo-Pacific waters." (Hertlein and Grant, 1972, p. 172) 

"Pectinid bivalves are perhaps the most useful indices for age. 

determination and correlation of the shallow-water marine Neogene 

sequences of the marginal eastern North Pacific." (Add icott, 1978, p. 

11) 

In his discussion of the Family Pectinidae, Hertlein (1969, N348) 
TERTIARY MARINE PELECYPODS: PROPEAMUSSIIDAE AND PECTINIDAE B13 

states: "Although many supraspecific units greatly resemble others 

in shell structure, their close relationship generally has not been 

proved. The similarities appear to confirm Philippi's theory of iteration of shell form in this group of mollusks. For this reason it seems 

best to adopt a conservative course in arranging supraspecific units 

in groups within the Pectinidae. To define such groups as subfamilies or to separate them as families would imply relationships and 

distinctions based chiefly on supposition only." 

DELECTOPECTEN group 

Delectopecten was placed in theAmusiumgroup by Hertlein. Subsequent study of shell microsculpture by Waller (1971, 1972) presents evidence for eliminating that group and placing Amus1:wm in 

the Pecten group. Delectopecten is here placed in ·a group of its own. 

As stated in the "Introduction," Hertlein's "groups" are used with 

some modification herein, but his subgenera are elevated to generic 

rank. 

Genus DELECTOPECTEN Stewart, 1930 

Small, thin, hyaline; posterior auricle on right valve not delineated. Differs from Hyalopecten in that undulations are subdued or 

lacking, and sculpture commonly develops reticulate pattern or may 

be almost lacking. 

Geolog·ic m.nge.-Triassic to Holocene. 

Ha.b?:ta.t.-Some swim freely, others are attached by a byssus; 

t•at·ely they become cemented and irregular in form as in H1:nn1:tes. 

Coat·se, thick-shelled forms live in shallow temperate and tropical 

waters, but thin-shelled forms usually occur in deep water, up to at 

least 4,500 m. The largest forms, with the exception of Pa.t1:nopecten 

and Pla.co1Jecten, live in tropical marine water. The shells of species 

inhabiting temperate water tend to be less convex and the ribs more 

rounded in the northern part of their range. (Hertlein and Grant, 

1972, p. 172) Pectinids consistently lie with the right valve downward, against the attachment surface, and most exhibit a distinctive · 

ovet·turning t·eaction when placed upside down. (Waller, 1976, p. 11) 

"Delectopecten differs from Cyclopecten s.l. in the shape of the 

auricles, the unflexed right valve (except in Cyclopectengreenlandicus), the absence of concentric lamellae or ridges on that valve 

(except in C. vitreus ), the always-present ctenol i u m, and the trans) ucency of all species." (Grau, 1959, p. 39) 

Name 

PIII(Ji!mtmnlt pcdro1r.nu Tr·nsk. 

i:olll(lio,,fomll nnnulut.u., Trnsk. 

Plu(li!mlomnt.runc!rln 

'l'!'llsk. 

Peden 'JII!I:khmni Gabb 

Per.te1! (P.,I;udumu.,ium) r:ancouvcr- en.''·' Wlutcnvcs. 

P1!den l'andolphi Dall. 

l'l't:len (Psl'l!dtl'lllu.,iwm) poly/epltm Dall. 

Pet:!l!n (P.,cudamu."'um) nn:e,, Dnll. 

Pet:lt!ll (Pseudmnu.,iwm) ullernililwlll.us Clark. 

l'et:lt!ll (P.,eudmnusium) t:aueoum:ren- ,,;,, ·'ltlljllt/IWII.,;,, Clnrk nnd A r·nold. 

Type locality 

Snn Pedro [east coast of Palos Verdes Hills]. Cnlif. Cretaceous [Miocene]. 

........ do ....................................................... . 

........ do ....................................................... . 

Ojai ranch, Santa Barbara [now 

Ventura) County, Calif. Bitumi- nous sha[eof upper Miocene [Monterey shale of some geologists and Modclo formation of others]. 

Forwnrd Inlet, Quatsino Sound, Van- couver· Islnnd; depth 10 to 20 fath- oms. 

Off Destruction Island. Wash.-; depth 516 fnthoms. 

Off Tillamook Bay, Oreg.; depth 786 fathoms. 

Off Hood Island. Galapagos; depth 300 fathoms. 

Santa Bm·bara Channel. Calif .. off Santa Cruz Island; depth 534 fath- oms. 

Presumably a locality ncar Walnut Creek, Contra Costa County, Calif. (sec Clark. table opp. p. 80). San Ramon sandstone, assigned to Ol- igocene. 

Vancouver Island, British Columbia. Sookc fori-nation, assigned to Oligocene. 

Geographic range.-Western North America, Japan, northern 

Europe, and Australia. 

Geologic range.-Eocene through Holocene (table 5). 

"Delectopecten is represented on the Pacific coast from the Eocene 

to the Recent. The following names have been proposed: 

Characters 

Large; length about 35 mm [apparently exaggerated 

by deformation]. Concentric undulations strong. 

Right anterior ear sculptured with about 13 radial ribs. (Fide Trask.) 

Large; length about 32 mm [apparently exaggerated 

by deformation]. Concentric undulations strong. Left anterior ear sculptured with about 12 radial ribs. (Fide Trask.) 

Large; length about 28 mm [apparently slightly exag- gerated by deformation]. Concentric undulations strong. (Fide Trask.) 

Small; length of 3 specimens in lectotype lot 12 to 14.8 mm. Concentric undulations weak. Lectotype sculp- tured with weak, relatively widely spaced radial ribs on main part of shell. Right anterior ear sculp- tured with a few radial ribs (6 or 7: fide Arnold). 

Small; length 8.5 to 10 mm. Concentric undulations weak or absent. Main part of shell sculptured with weak to strong radial ribs; absent on some speci- mens. Right anterior ear sculptured with 5 to 7 radial ribs. 

Large: length 28 to 30.8 mm. Concentric undulations moderately strong or weak. Right anterior ear sculptured with 5 to 8 radial ribs. 

Large: length 29 to 32.5 mm. Concentric undulations moderately strong or weak. Type sculptured with weak radial ribs on main part of shell. In other specimens this radial sculpture varies from a few faint ribs to strong ribs covering entire shell. Some left valves that lack radial sculpture are paired with faintly sculptured right valves. Right anterior ear sculptured with 5 to 8 radial ribs. 

Small; length 9.6 to 10 mm. Concentric undulations weak or absent. Main part of shell sculptured with weak radial ribs, mainly in form of vaulted scales. Right anterior ear sculptured with 4 or 5 radial ribs. 

Moderately large: length 19.5 to 23 mm (type lot). Concentric undulations moderately strong or weak. Main part of shell sculptured with strong radial ribs. Right anterior ear sculptured with 5 to 7 radial ribs. 

Small; length 5 to 5.5 mm. [Concentric undulations apparently weak or absent.] Main part of shell sculptured with radial ribs. Right anterior ear sculptured with about 5 radial ribs. (Fide Clark.) 

Small: length 7 mm. Concentric undulations moder- ately strong. Main part of shell sculptured with radial ribs. (Fide Clark and Arnold.) 

Remarks 

Large number of ribs on right anterior ear needs confirmation. 

Considered same as pedroanu.,, Radial ribs on left anterior ear suggest that well-pre- served specimens may show radial ribs on main part of shell. 

Considered same as pedroa.nus . 

On many specimens that appear to represent 

peckha.mi radial ribs are not discernible, 

except on right anterior ear. Forms resem- bling peckhami have been recorded from horizons ranging from Eocene to Miocene. 

Radial sculpture very variable in lots assigned to this form. Apparently ranges from south- ern Alaska to San Diego in shallow to mod- erately deep water (12 to 200 fathoms). 

Apparently ranges from Bering Sea to Cape 

Blanco, Oreg., in deep water (225 to 1.064 fathoms). 

Considered a sculptured varietyofrandolphi, as described by Arnold. Radial sculpture very variable in suites of shells assigned to this variety. Apparently ranges ~!'om Ber- ing Sea to San Diego, generally in deep water (30 to 1.084 fathoms). 

Represented in two lots from depths of 300 and 392 fathoms ncar GalaJ)a~os. Apparently closely allied to H. fiC nt.mosus (Ma- bille and Rochebrune), a larger form from southern South America. 

Considered a synonym of t.i/lamookensi.,: 

strongly sculptured form. 

Apparently allied to r:rlltcotwerensis. 

Apparently allied to vancowr:erensis. 
B14 PALEONTOLOGY OF CALIFORNIA AND BAJA CALIFORNIA 

Name Type locality Characters Remarks 

Pecten (Pseudamusium) vancouveren- sis ferna.ndoensi.~ Hertlein. Ventura River, ~mile south of Tay- lor well no. 1 and 1 Yz miles north of 

Ventura, Calif. Fernando, Pliocene 

[upper Pliocene]. 

Of medium size to moderately large; length 12.5 to 22.7 mm. Concentric undulations moderately strong to weak; main part of shell sculptured with radial 

ribs of varying strength. Right anterior ear sculp- tured with 5 to 7 radial ribs. 

Apparently closely allied to tillamookensis. Pliocene specimens from Los Angeles Basin are smaller than tillamookensi.~. and some have stronger concentric undulations. 

Pecten (Pseudamusimn) Ul/isi Hertlein. 

Crow Creek road, Stanislaus County, Calif. Kreyenhagen shale, upper Eocene or lower Oligocene [appar- ently from part of Kreyenhagen shale now assigned to Eocene]. Small; length 9 to 15.6 mm. Concentric undulations 

weak or moderately strong. Main part of shell sculp- tured with a few or many radial ribs, especially on right valves. Right anterior ear sculptured with 4 to 

8 radial ribs. 

Relations to pecklw:mi. to which this form was formerly assigned. not determined. Some 

specimens have stronger undulations than 

peckha:mi. 

Pecten (Delectopecten) zacae Hertlein. Gulf of Panama; depth 322 fathoms. Moderately large; length 19 to 22 mm. Concentric 

undulations weak. Main part of shell sculptured with a few or many weak radial ribs. Right anterior ear sculptured with 4 to 6 radial ribs. 

Specimens in collection of U.S. National Mu- seum more obliquely elongate than those of 

other recent species of comparable size." 

"The presence or absence of radial ribs on parts of the shell other 

than the right anterior ear appears to be of doubtful value for 

specific differentiation. Large suites of specimens agreeing in other 

characters show gradations from strong sculpture to none. This 

gradation is well shown in the modern forms (vancouverensis, randolphi, and t1:llamookensis), in the Oligocene and Miocene forms 

assigned to peckhami, and in the form from the Eocene part of the 

Kreyenhagen shale formerly assigned to peckham1: and recently 

named lillisi. The radial ribs vary from strong. beaded or scaly ribs 

covering the entire shell to weak ribs confined to a small part or 

parts of the shell. Many right valves that elsewhere lack radial ribs, 

aside from those on the anterior ear, have a few at the anterior 

margin of the shell. Some left valves that are paired with weakly 

sculptured right valves lack radial ribs entirely or they are restricted to the anterior ear. 

"The size of the shell and the strength of the concentric undulations appear to offer grounds for specific differentiation. The possible value of these characters, however, is undetermined in many of 

the forms. The outline of the shell may be a characteristic feature in 

some Recent forms, but many fossil specimens are deformed." 

(Woodring, 1938, p. 36-38) 

Delectopecten lillisi (Hertlein) 

Plate 3, figures 1-3 

Pecten (Pseudamusium) lillisi Hertlein, 1934, p. 5-6, pl. 1, fig. 1; pl. 

2, figs. 2, 3. 

Hyalopecten (Delectopecten) lillisi (Hertlein). Woodring, 1938, p. 38. 

Original description.-"Shell small, of general form of Pectenpedroanus Trask; right valve, the anterior ear well defined, set off from 

the rest of the shell by a well defined groove, a well developed byssal 

notch is present; anterior ear ornamented by six or seven riblets, 

which are crossed by imbricating lines of growth; posterior ear 

unornamented except by fine lines of growth; the anterior portion of 

the valve ornamented by about ten fine spinose riblets; the posterior 

portion of the valve unornamented except by fine lines of growth; 

entire surface of valve covered by fine submicroscopic camptonectes 

striations which cross the radiating riblets. Measurements of holotype, altitude 14.1 mm.; length (approximately) 13 mm.; length of 

hinge line 9.2 mm." 

Holotype.-CAS 6062. 

Type locality.-CAS 184. Stanislaus County, Calif. Kreyenhagen 

Formation, Eocene and Oligocene. 

Supplementary description.-"Left valve (paratype), the anterior 

ear is ornamented by about six to eight fine radial ribs; the surface of 

the valve is ornamented by fine radiating riblets; entire surface 

covered by camptonectes striations similar to the right valve." (Hertlein, 1934, p. 6) 

"Small; length 9 to 15.6 mm. Concentric undulations weak or 

moderately strong. Main part of shell sculptured with a few or many 

radial ribs, especially on right valves. Right anterior ear sculptured 

with 4 to 8 radial ribs." (Woodring, 1938, p. 38) 

"A few right valves have ribs over the entire valve;· others have 

ribs on the greater part of the anterior half of the valve * * *Ribs 

were observed on only one left valve." (Woodring, 1938, p. 40) 

Comparison.-"Pecten lillisi may be distinguished from P. pedroanus Trask and other fossil and Recent species of small pectens on 

the west coast of North America, by the small number of delicate 

spinose ribs which ornament the anterior portion of the right valve, 

and by the fine submicroscopic camptonectes striations which cover 

the surface of the shell." (Hertlein, 1934, p. 6) 

"Relations to peckhami, to which this form was formerly assigned, 

not determined. Some specimens have stronger concentric undulations than peckhami." (Woodring, 1938, p. 38) 

Comments.-The radial ribs are longer and more prominent along 

TABLE 5.-Geologic and geographic distribution of the genus Delectopecten in the eastern Pacific region 

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

Alaska British Washington Oregon California Baja Species Columbia Califo[nia Northern . Middle Southern Norte Sur 

Genus Delectopecten: 

alternilineatus (Clark) M? -------------------------- harfordus (Davis) .................................... M? 

lillisi (Hertlein) ........................................ E,O 

peckhami (Gabb) of Arnold .................. M E toM E toM 

randolphi tillamookensis (Arnold) ...... H H H H H H Pl,H H 

vancouverensis fernandoensis 

(Hertlein) Pl,Ple -----------------------------------------·---- vancouverensis vancouverensis 

(Whiteaves) ............................................ H H H H H H PI to H H H 
TERTIARY MARINE PELECYPODS: PROPEAMUSSIIDAE AND PECTINIDAE B15 

the anteriot· margin of the left valve but also extend across the disk. 

The right valve is sculptured anteriorly by slightly nodose, radial 

ribs that extend to the ventral shell margin. 

Georrra.ph:ic ·ra:nge.-Middle California. 

Geolom:c ·ro.nge.-Eocene and Oligocene. 

Occu:/Tence ·in Cal·1jm·n:ia.-Eocene and Oligocene: Kreyenhagen 

Formation. 

Delectopecten P.eckhami (Gabb) of Arnold 

Plate 3, figures 4, 5 

Pecte·n (Pse'Uclo.musiuni.) pecklw:m:1: Gab b. Arnold, 1906, p. 56-57, pl. 

3, fig. 8. 

Delectopecten peclclw:m:i (Gabb) of Arnold. Moore, 1963, p. 67-68, pl. 

18, figs. 2, 3; plate 20, figs. 1. 3-5; pl. 21, fig. 2. 

?Pecte·n 1)ecklw:n1:i Gabb, 1869, p. 59-60, pl. 16, figs. 6-8. 

?Pall·iolu:m, (Delectopecten) pecklw.m·1: (Gabb). Stewart, 1930, p. 119-

120, pl. 13, fig. 4. 

?Delectopecten, pecklw:n1:1: (Gabb). Watkins, 1974, p. 251-252, fig. 6A. 

Orim>na.l clesc·n:pt·1:on.-"Shell averaging about 20 millimeters in 

altitude, subcircular, subequivalve, slightly inequilateral, thin, 

·usually compressed, and with smooth margins. Right valve with the 

disk showing several small, more or less obsolete, irregular concentric undulations. numerous fine incremental lines arid numerous 

fine obsolete radiating lines; hinge line about two-thirds of the longitude of the disk; anterior ear produced, separated from the body of 

the shell by a marked groove and a deep, narrow sinus, and prominently sculptured by 6 or 7 radiating ridges and numerous concentric elevated incremental lines; posterior ear not separated by any 

distinct line from the disk surface and ornamented only by concentric lines and obsolete undulations. Left valve similar to right except 

that the anterior ear is flat, the swell of the shell commencing with 

nearly a right angle with the ear-surface; surface of anterior ear 

usually sculptured only by incremental lines, but occasionally with 

radiating striae also." (Arnold, 1906, p. 56) 

Lectotype.-At·nold's usage based on USNM 164839 is followed 

here. The lectotype of P. peckha?m: Gabb, MCZ 15045 (Stewart, 

1930), is presumed lost. 

'l'mJe loca.l·ity.-Of Arnold's (1906, pl. 3. fig. 8) specimen, USGS 

2593. Contra Costa County, Calif. Monterey Shale, Miocene. 

Su.pplementa:ry desc?"'l:pt·ion.-"As a rule only the molds of casts of 

this species at·e found in the shales in which they occur, and for this 

reason some of the characteristics of sculpture of the species are 

generally lacking. For example, in a large series of specimens examined, only two or three of the shells showed the radiating sculpture. 

The disks are generally obliquely distorted and often compressed, 

but the sculpture on the anterior ear of the right valve is almost 

always present and is quite characteristic." (Arnold, 1906, p. 56) 

"A squeeze of the lectotype of peckham1: is available***. It is a left 

valve that has a length of about 12 millimeters, weak concentric 

undulations, and weak, relatively widely spaced radial ribs which 

are absent in most of the area extending downward from the umbo. 

These ribs are not well shown on the photograph of the lectotype, the 

radial lines of which appear to have been added by retouching. The 

other two specimens in the lectotype lot also are available * * *. 

One-a left valve exposed in interior view-has a length of 13 millimeters; the other-a right valve that lacks the shell aside from 

small patches of inner layers-has a length of 14.8 millimeters. Both 

specimens have weak concentric undulations, and neither shows 

radial ribs, with the exception of traces on the right anterior ear. 

"H. peckham:i seems to be a small species that has weak concentric 

undulations and weak, relatively widely spaced radial ribs. In many 

specimens the ribs are apparently absent. They are absent on the 

specimens from the Monterey group of the San Francisco Bay region 

figured by Arnold. On some specimens the apparent absence of ribs 

may be a matter of preservation, as the shell itself is generally not 

preserved, and preservation in the form of impressions is generally 

needed to show such weak ribs." (Woodring, 1938, p. 39) 

"Delectopecten peckhmni (Gabb) of Arnold is thin shelled, small, 

and possesses very weak to moderately strong concentric undulations. The concentric undulations are most apparent on specimens 

preserved in shale and subsequently flattened. Specimens collected 

from limestone and not flattened have barely discernable concentric 

undulations. The entire surface of the left valve has camptonectes 

sculpture; most of the specimens of right valves in the collections 

seem to have smooth shells, but patches of camptonectes sculpture 

are preserved on a few specimens. A few left valves have radial ribs 

0.5 to 1 mm apart, which apparently disappear near the anterior and 

posterior margins of the shell. Four right valves were found to 

possess radial ribs crowded together at the anterior margin. The 

maximum number of such ribs counted was eight, and they seem to 

have been slightly spinose." (Moore, 1963, p. 67) 

Geog?·a.phic range.-Japan; Kamchatka and Sakhalin, U.S.S.R.; 

Oregon to southern California. 

Geologic 1·mzge.-Eocene to Miocene. 

Occun·ence 1:n California.-Eocene and Oligocene:· Kreyenhagen(?) (Watkins, 1974) and San Lorenzo Formations (Arnold, 1906); 

Oligocene: Tumey Formation (A twill, 1935); Miocene: lower Capistrano (White, 1956), Modelo (Hudson and Craig, 1929), Los Laureles 

Sandstone Member (Hertlein, 1966) and "lower muddy phase," Monterey (Dickinson, 1969), Antelope Shale Member (Weddle, 1965), 

Monterey, Maricopa Shale of Howard (1935), Puente (Eldridge and 

Arnold, 1907), and Santa Margarita (Howard, 1935) Formations, 

Woodhams Member, Monterey Formation (Cummings and others, 

1962), Temblor "Horizon" (Loel and Corey, 1932), and Topanga 

Formation (J. G. Vedder and W. P. Woodring, written commun., 

1953). 

Delectopecten alternilineatus (Clark) 

Plate 2, figures 8, 9 

Pecten (Pseudomuseum) [sic: Pseudamusiu:m] alte1·nil1:neatus Clark, 

1918, p. 132-133, pl. 13, figs. 14, 15. 

Hyalopecten (Delectopecten) alternilineatus (Clark). Woodring, 1938, 

p. 38. 

Original description.-"Shell small, thin, subcircular, compressed, equivalved, nearly equilateral. Apical angle close to 90. 

Surface covered by numerous fine, radiating, raised, bifurcated 

lines, which are nearly obsolete on most of the specimens examined, 

.interspaces between the lines averaging a little wider than the width 

of the lines. Posterior ear of right valve not separated by a ·welldefined line from main surface of shell; posterior edge of ear 

straight, sloping outward; surface smooth on specimens at hand but 

probably originally radially sculptured, similar to that on the main 

surface of shell. Anterior ear of right valve very distinct, with a 

rather deep and acutely angular byssal notch; surface of ear covered 

by about five subnodose to spinose radiating lines. Ears of left valve 

similar to those of right except that anteriorly there is no byssal 

. not~h." 

Holotype.-UCMP 11203. 

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

Sandstone, Miocene(?). 

Comparison.-"Pecten alternilineatus is about the same size and 

belongs to the same general type asP. vancouverensis Whiteaves, 

from which it differs in the following respects: The radiating lines on 

the main surface of the shell are not so numerous nor so closely 
B16 PALEONTOLOGY OF CALIFORNIA AND BAJA CALIFORNIA 

crowded; the ears are larger and the radiating sculpturing is not so 

coarse; the hinge line is longer in proportion to the width of the shell, 

and the margins below the ears are less convex than on P . . 

vancouverensis. 

"Pecten alternilineatus resembles rather closely P. peckhami 

Gabb, a common species in the Lower Miocene of the West Coast, 

from which it differs as follows: On the left valve the ears are 

considerably narrower in a dorsal-ventral direction, and in the vicinity of the anterior ear the swell of the main surface of the shell 

commences as an inclined slope rather than at right angles, as is the 

case on P. peckhami as described by Gabb; the anterior edge of the 

anterior ears comes out practically flush with anterior edge of the 

shell, while on P. peckhami this edge is considerably back of the edge 

of the shell; also on the former the byssal notch is deeper than on the 

latter." (Clark, 1918, p. 132-133) 

Comments.-The right valve of the holotype is smooth except for 

slightly nodose, radial ribs (about 13) at the anterior dorsal margin. 

Although described by Clark (1918, p. 132), the right anterior auricle is missing on the holotype. The left valve is smooth except for 

slightly nodose radial ribs (about 10) that cover the posterior auricle 

and the depressed area below. The radial ribs on the left valve cover 

approximately one-half of the area that is ribbed on the right valve. 

Geographic range.-Middle California. 

Geologic range.-Miocene(?). 

Occurrence in California.-San Ramon Sandstone. 

Delectopecten harfordus (Davis) 

Plate 3, figures 6-9 

Pecten(Camptonectes) harfordus Davis, 1913, p. 456-457, figs. 3, 5, 6. 

Original descn:ption.-"A small thin pecten; form ovate, nearly 

smooth, and marked with fine almost microscopic groovings which 

radiate from the umbo and are deflected laterally from a median 

line on each valve. The shell is marked also by fine concentric lines, 

every fifth or sixth of which is more distinct. The anterior auricle is 

large; the anterior edge forms a right angle with the cardinal margin, and rounds sharply into the deep byssal sinus. The left auricle is 

small and obliquely trunkated [truncated]. The beaks are sharp and 

stop at the hinge-line." 

.Syntypes.-CAS/SU 406, 408. . 

Type locality.-Ten kilometers north of Port Harford [sic: Port 

San Luis], San Luis Obispo County, Calif. "Jurassic"; [possibly Miocene, teste N. L. Taliaferro in Keen and Bentson (1944). No Delectopecten have been found in valid Franciscan strata in the type area 

according to B. M. Page (oral commun., 1979).]. Monterey(?) Formation, Miocene. 

Comparison.---="This pecten is compared by Stanton to Pecten pedroanus, but the latter differs from these specimens in having 

stronger radial markings especially on the auricles, and in general 

outline. It is like P. bellistriatus in its sculpture but is smaller; it has 

finer markings than P. extenuatus Meek." (Davis, 1913, p. 457) 

Comments.-A left valve (syntype SU 406) retains small patches of 

the internal shell layer and shows strong concentric undulations. 

Two syntypes (SU 408) are right valves. One incomplete specimen 

(broken off along the ventral margin) bears patches of the internal 

shell layer and shows the outline of the anterior auricle and a deep 

byssal sinus. The shell seems to have had concentric undulations. 

The complete specimen is also poorly preserved and no sculpture of 

the external shell is preserved. 

The paraty.pe (SU 9819) is a double-valved specimen, opened and 

lying flat on the matrix, but still attached along the hinge margin. 

The two valves are poorly preserved but show some strong concentric undulations. The right anterior auricle bears 3 preserved mod- · 

.erately large riblets. 

Geographic range . .;_Southern California. 

Geologic range.-Miocene(?). 

Occurrence in California.-Monterey(?) Formation. 

Delectopecten vancouverensis fernandoensis (Hertlein) 

Plate 3, figure 10 

Pecten (Pseudamusium) vancouverens1:s var.jernandoens1:s Hertlein, 

1925b, p. 43, pl. 4, figs. 6, 7. 

Hyalopecten (Delectopecten) fernandoensis (Hertlein). Woodring, 

1938, p. 38. 

Original description.-"Shell small, somewhat compressed, 

pearly. Right valve sculptured by numerous submicroscopic radiating ribs which are crossed by concentric lines forming crosshatched 

sculpture on the shell, at each intersection a tiny node is developed; 

the anterior ear is well developed and ornamented by about 5 or 6 

radiating ribs crossed by concentric lines of growth, posterior ear 

·ornamented by radiating riblets crossed by concentric lines of 

growth. Left valve with sculpture similar to that of right, the ears of 

the left valve are well developed and sculptured similar to thatofthe 

right valve. There are about 7 to 9 slight, concentric undulations 

·which are more noticeable on the interior casts of the valves than on 

the exterior of the valves. Height 16 mm.; length 14 mm.; diameter of 

left valve approximately 3 mm.; length of hinge line of left valve 

·approximately 10 mm.; apical angle of left valve approximately 

goo." 

Holotype.-CAS/SU 16. 

Type locality.-SU 155. Ventura County, Calif. Fernando Formation, Pliocene and Pleistocene. 

Supplementary description.-"Of medium size to moderately 

large; length 12.5 to 22.7 mm. Concentric undulations moderately 

strong to weak; main part of shell sculptured with radial ribs of 

varying strength. Right anterior ear sculptured with 5 to 7 radial 

ribs." (Woodring, 1938, p. 38) 

Comparison.-" Pecten vancouverensis fernandoensis Hertlein is 

distinguished from P. vancouverensis Whiteaves, by more distinct 

crosshatched sculpture and usually larger size. P. vancouverensis 

fernando.ensis is distinguished from P. vancouverensis sanfuanens?:s 

Clark, by finer sculpture and larger size in the present species. P. 

vancouverensisfernandoensis differs from P. pedroan~ts Trask, in its 

characteristic crosshatched sculpture. P. vancouverensis fenwndoensis differs from P. randolphi var. tillamookensis Arnold, in that 

the present species has small nodes developed at the intersection of 

the crosshatched sculpture, while the variety described by Arnold 

has finer striae ornamentation on the valves." (Hertlein, 1925b, p. 

43) 

"The fossils [fernandoensis] from the Los Angeles Basin are considerably smaller than large shells of Wlamookensis. Some of the 

fossils have stronger concentric undulations than Recent shells, but 

the strength of the undulations is variable in both fossil and Recent 

specimens." (Woodring, 1938, p. 44) 

Comments.-The left posterior auricle of D. v. jernandoens1:s is 

larger and higher than the left posterior auricle of D. randolph1: 

tillamookensis. The angle that the left posterior auricle makes where 

it joins the shell is about 40 on D. v. fernandoen.'n:s com pared to about 

25 on D. r. tillamookensis. Grau (1959, p. 41) considered D. v.fernandoensis to be a valid species. 

Geogrraphic range.-Southern California. 
TERTIARY MARINE PELECYPODS: PROPEAMUSSIIDAE AND PECTINIDAE. B17 

Geolog1:c 1·ange.-Piiocene to Pleistocene. 

Occu?Tence ·1:n Cal1fm·m:a.-P1iocene and Pleistocene: Fernando 

Formation. 

Delectopecten vancouverensis vancouverensis (Whiteaves) 

Plate 3, figures 11, 16 

Pecten (P.•w·u.da.mus1:um.) va.ncouveren.<n:s Whiteaves, 1893, p. 133, pl. 

1. figs. 1, 1a. Arnold, 1906, p. 140, pl. 52, figs. 3, 3a. 

Hya.l01Jecten 'IJancouve?·ens?:s (Whiteaves). Woodring, 1946, p. 81, pl. 

33, figs. 2, 3. 

Cyclopecten (Delectopecten) vancmwe1·ensis (Whiteaves). Grau, 1959, 

p. 40-42, pl. 15. 

On:m:nal descn:pt·1:on.-"Shell small, equivalved, compressed lenticular, both valves being equally convex, ovately subcircular in 

outline apart from the ears and rather oblique; valves extremely 

thin and fragile, transluce11:t and almost transparent, pale horn color 

with a slightly yellowish hue. Beaks placed a little behind the 

midlength; hinge line straight and very long; ears unequal in size, 

the posterior pair, which are much smaller than the anterior, alike, 

indistinctly defined and merging gradually and imperceptibly into 

the general convexity and marginal contour of that side of each 

valve; anterior ears large, suotriangular, prolonged laterally and 

longer than high, distinctly defined, that of the left valve somewhat 

convex in outline above and concave below, that of the right valve 

with a deep and acutely angular byssal sinus at its base. 

"Surface marked by densely crowded and exceedingly minute, 

irregular and rarely continuous, but on the whole radiating, simple 

o1· bifurcating raised lines, also by comparatively large, regularly 

disposed and distant squamose radii. In the center of each valve the 

minute and nonsquamose raised lines are essentially parallel to the 

larger squamose radii, but on the sides the former are disposed 

obliquely to the latter. The surface of the anterior ear of each valve is 

minutely cancellated with extremely minute raised lines, which are 

almost parallel to the hinge line, in addition to the coarser cross lines. 

The whole sculpture of the exterior of the test is far too minute to be 

clearly seen without the aid of a microscope or powerful simple lens, 

but under either of these a few faint concentric lines of growth are 

also visible." 

Holotypl~.-Location unknown. 

Type locab:ty.-Forward Inlet, Quatsino Sound, Vancouver Island, 

British Columbia, Canada, in 18-37 m. 

Su.pplementa.1·y desc1·£pt·ion.-"Radia1 sculpture very variable in 

lots assigned to this form." (Woodring, 1938, p. 37) 

"Although not mentioned in Whiteaves' very thorough description, a ctenolium of 3 to 6 teeth is present. Many specimens have 

shallow concentric undulations of the umbonal portion of the disk. 

On some specimens the squamose sculpture is almost absent and the 

radii more prominent. Very young shells are frequently nearly 

smooth." (Grau, 1959, p. 42) 

Com.pa:rison.-Delectopecten vancouveren.<n:s is smaller [8.5 to 10.5 

mm] than D. t·Wamooken.<n:s [29 to 32.5 mm] and usually has weaker 

concentric undulations. (Woodring, 1938, p. 37) 

"The squarish angle of the posterior auricles and the longer hinge 

line distinguish this species from the related Cyclopecten randolph1: 

and C. nw.dolph:i t1:llamooken.•n:s, the presence of sculpture on the 

disks also separating it from the former." (Grau, 1959, p. 42) 

Delectopecten. va?wo·twe?·en.•i1:s sanjuanens1:s (Clark and Arnold, 

1923, p. 140), from the Sooke Formation, Vancouver Island, B. C., 

differs from D. ·v.va.ncou.1Je?·en.•n:s in having shorter anterior ears and 

major concentric undulations. 

Geogra.phic range.-Living: Bering Sea to southern end of Baja 

. California Sur, and north in the Gulf of California to Isla San Ildefonso Island; fossil: southern California. 

Geologic range.-Pliocene through Holoce~e. 

Occurrence in Calijornia.-Pliocene: Lomita Marl Member, San 

Pedro Formation (Woodring, 1946); Pliocene and Pleistocene: Fernando Formation (J.D. Mount, written commun., 1978); Pleistocene: 

Timms Point Silt Member, San Pedro Formation (Woodring, 1946). 

Habitat.-Usually on mud or sand bottoms, occasionally rock, 

shale or gravel; often attached to calcareous algae; often associated 

with brachiopods, crinoids, coralline or sponge; 18 to 384m; rarely 

less than 90 m. (Grau, 1959, p. 42) 

Delectopecten randolphi tillamookensis (Arnold) 

Plate 3, figures 13, 14 

Pecten (Pseudam.us1:um) randolph1: Dall var. tillamookensis Arnold, 

1906, p. 139, pl. 48, figs. 3, 3a. Woodring, 1938, p. 37. 

Cyclopecten (Delectopecten) randolph?: tillamookensis (Arnold). Grau, 

1959, p. 45-47, pl. 17 (see for synonymy). 

On:g1:nal descr1:ption.-"Shell resembling P. randolphi in outline 

and general characteristics. Disk ornamented by numerous more or 

less prominent fine, radiating ridges, microscopic radiating striae, 

and incremental lines of varying prominence. The radiating ridges 

are narrow and thread-like, and appear to be more prominent anteriorly and near the lines of interrupted growth; the ribs are affected 

similarly to the disk by the interruptions in growth. The microscopic 

striae cover the whole surface of the disk and ribs and in a general 

way radiate from the umbo, but are seldom parallel to the ribs; on. 

the portion of the disk and ear posterior to the umbo the striae are 

perpendicular to the lines of growth and are thus nearly parallel and 

not radiating. The right anterior ear has from 6 to 12 prominently 

imbricated radials." 

Holotype.-USNM "t50233. 

Type locality.-UFSC station 3346, off Tillamook Bay, Oreg. 

·Depth 1.572 m. 

Supplementary descript1:on:-"Radial sculpture very variable in 

suites of shells assigned to this variety." (Woodring, 1938, p. 37) 

· "Disk circular in some specimens, higher than long in others; left 

valve more convex than right. Small and narrow concentric undulations of disk often present either in umbonal region only or recurring 

nearly to ventral margin. Radial ridges of disk prominently spinose, 

continuing over both auricles of left valve and posterior of right; 

'incremental lines' actually low concentric ridges covering disk and 

less prominent than radials; on some specimens both ladial and 

concentric ridges present only at margins. Anterior auricle of right 

valve with usually 5 to 7 but occasionally as many as 12 imbricated 

radii; wide fasciole, shallow byssal notch and ctenolium of 4 to 6 

teeth. Interior surface of fold of posterior auricle of left valve angulate and ridged." (Grau, 1959, p. 46) 

Comparison.-"The subspecies can be distinguished from the typical by the sculpture of the disk, the latter being totally unsculptured 

except for the anterior auricle of the right valve; the ridge inside of 

the posterior auricle of the left valve also separates the subspecies." 

(Grau, 1959, p. 46) 

Delectopecten vancouverens1:s tillamookens1:s is larger than D. v. 

vancouverensis and usually has stronger concentric undulations. 

(Woodring, 1938, p. 37) 

Geographic range.-Living: Bering Sea to Cedros Island, Baja 

California; fossil: southern California. 

Geologic range.-Pliocene through Holocene. 
B18 PALEONTOLOGY OF CALIFORNIA AND BAJA CALIFORNIA 

Occurrence in Calijorm:a.-Pliocene: lower Pico Formation (Wissler, 1941); Pliocene and Pleistocene: Fernando Formation (Zinsmeister, 1970). 

Hab1:tat.-Usually found on mud bottoms, occas.ionally on and (or) 

in sponge; depth 55 to 2,010 m, rarely less than 550 m. (Grau, 1959, p. 

47) 

Delectopecten pedroanus (Trask), nomen dubium 

Plagiostoma pedroana Trask, 1856, p. 86, pl. 3, fig. 1 [pedrona in 

text]. 

Hyalopecten (Delectopecten) pedroanus (Trask). Woodring, 1938, p. 

37-39. 

Not Pecten (Pseudamusium) pedroanus Trask. Arnold, 1906, p. 

90-91, pl. 28, figs. 4, 5. 

Plagiostoma annulatus Trask, 1856, p. 86, pl. 3, fig 2. 

Plag1:ostoma truncata Trask, 1856, p. 86, pl. 3, fig. 3. 

Original description.-"Shell compressed, subtriangular, with 

eight or nine flatly rounded concentric annulations, which are 

nearly as distinctly marked on the interior of the valve for about half 

the height from the ventral margin; beaks acute at the apex, and as 

high as the line of the auricles; anterior auricle rounded in front, and 

has a small, thin fold extending from the umbone to the center of its 

anterior margin, and is covered with about thirteen small, rounded, 

radiating striae, which converge at the beak; beaks at the anterior 

third; subacute; anterior margin rounded, and somewhat produced; 

ventral margin smoothly arched; posterior margin rounded, becoming slightly arcuate toward the dorsum of the shell; posterior auricle 

angulate and obtusely truncate posteriorly." 

Holotype.-Missing and presumed lost. 

Type locality.-San Pedro [east coast of Palos Verdes Hills], Los 

Angeles County, Calif. Trask's specimens evidently came from the 

lower part of the Valmonte Diatomite or the upper part of the 

Altamira Shale (Woodring, 1940, p. 39). 

Com'ments.-The holotype of Delectopecten pedroanus has not been 

found nor have any specimens been found in the type area that are as 

large as that illustrated by Trask (pl. 3, figs. 1-3) with ribs on the 

right anterior auricle. Gabb (1869, p. 60) examined Trask's specimens and said they were casts that did not preserve the sculpture. 

Woodring (1938, p. 39) examined specimens from the Valmonte 

Diatomite Member, Monterey Shale, near the type locality of D. 

pedroanus, and thought they probably represented D. peckhami. 

CHLAMYS group 

Both valves convex, left valve usually more so than right valve; 

with large byssal notch below right anterior ear; sculpture of radial 

elements fine to coarse, commonly crossed by concentric imbricating lamellae. 

Geologic range.-Triassic through Holocene. 

Genus CHLAMYS 

Usually higher than long, anterior auricle markedly longer than 

posterior one; sculpture of numerous, generally grooved or striated 

and spinose, radial ribs; inner margin commonly with rounded, 

grooved, weak riblets; cardinal crura weak or nearly obsolete. 

The characters I have found to be consistently useful in discriminating species of Chlamys are: 

(1) The umbonal angle and ratio of length to height-species with a 

small umbonal angle are higher than long; those with a wide umbonal angle are equidimensional. 

(2) The sculpture of the auricles, the extent to which the anterior 

auricles exceed the posterior auricles in length, and the size of the 

byssal sinus. 

(3) Whether the valves are equilateral or inequilateral, exclusive 

of the auricles. 

(4) Sculpture of the valves. This criterion is useful in separating 

TABLE 6.-Geologic and geographic distn:bution of the genus Chlamys 1:n the eastern Pac'lfic region 

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

Alaska British Washington Oregon California Baja 

Species Columbia California Northern M1ddle Southern Norte Sur 

Genus Chlamys: 

anapleus Woodring ··············------------------ Pl,Ple 

bartschi (Arnold) ...................................... PI 

branneri (Arnold) .................................... O,M 

calkins?: (Arnold) ...................................... E 

corteziana Durham -------------------------------- M?,Pl PI 

egregius (Nomland) ·······------------------------- PI PI 

hastata ellis1: Hertlein and Grant ........ PI 

hastata hastata (Sowerby) .................... MtoH MtoH PI 

hastata hericius (Gould) ........................ H H H H H MtoH MtoH 

hastata pugetensis (Oldroyd) ................ H H H H H Ple,H PI to H 

hertleini (Loel and Carey) -------------------- O,M O,M 

hodgei (Hertlein) ...................................... M M 

jordani (Arnold) ...................................... Pl,Ple ·M to Pie Pl,Ple 

opuntia (Dall) .......................................... M to Pie Pl,Ple PI PI 

picoens1:s (Waterfall) --------------··········------ PI? to Pie 

proavus (Arnold) ...................................... Pa? 

rubida (Hinds) .......................................... Ple,H Ple,H H H H MtoH M to Pie 

sanct?:ludovici (Anderson and 

Martin) .................................................. M 

sespeens1:s (Arnold) of Loel 

and Corey .............................................. O,M E toM 

sespeensis hydei (Arnold) ...................... O,M O,M 

Genus Chlamys? 

mediacostata grew1:ngki (Hertlein) PI ---- med1:acostata mediacostata 

(G D. Hanna) ........................................ M or PI PI 
TERTIARY MARINE PELECYPODS: PROPEAMUSSIIDAE AND PECTINIDAE B19 

species that are very different; for example, those with many closely 

spaced fine ribs from those with wide, heavy ribs. However, the 

variability of this sculpture within species lots is such that this 

character is the least reliable. Bifurcation of the ribs seems to be a 

somewhat helpful distinguishing character as is the spacing of the 

ribs and interribs. 

Geolog·ic ·ra.noe.-Triassic through Holocene (table 6). 

Ho,ln:tnt.-Byssus present in some species (Yonge, 1962, p. 116); 

some capable of swimming; found under rocks and in rock crevices 

from low tide to 1,540 m (Abbott, 1974). 

"The ecological relationship of the Chlnmys and the sponge is very 

interesting. The flagellate choanocytes lining the chambers of 

sponges maintain a constant water current through the animal and 

extract the smallest particles from the current for food. It seems 

likely that the Chla:m,ys utilizes this current for respiration and 

excretion, and uses as food the particles that have not already been 

extracted from the current by the sponge. This constant supply of 

food may be the reason for the sponge-encrusted Chlamys growing 

larger than any others. The Chlamys must also receive almost perfect protection when in the sponge, and altogether seems to have a 

gr·eat ecological advantage over unencrusted specimens. It is likely 

that the sponge obtains initial benefit from the association in using 

the Chla,m,ys as a substratum to grow on. It is also possible that the 

sponge is able to utilize part of the lamellibranch's 'excretory products as food." (Beu, 1965, p. 95) · 

Chlamys proavus (Arnold) 

Plate 3, figure 15 

Pecten (Chla:m.ys) 1J'roa:vus Arnold, 1906, p. 52-53, pl. 2, figs. 6-8. 

Or'ig·inal descn:pt·,:on.-"She11 averaging about 50 millimeters in · 

altitude, much higher than long, compressed, subequivalve, and 

equilateral, except for the ears; base regularly rounded; margins 

smooth; sides straight and forming an acute angle at the umbo. Left 

valve with numerous more or less unequal, narrow, thread-like, 

imbricated ribs, between which are occasionally much finer intercalaries; interspaces about as wide as ribs, channeled and flat bottomed; whole surface of disk and ears ornamented by numerous, 

sharp, imbricating lamellae of growth, which appear more prominently on the anterior portion of the disk; posterior ear short, slightly 

obliquely truncated, and sculptured by numerous radials and 

imbricating lamellae; anterior ear unknown, but probably much 

longer than posterior." 

Holotype.-VSNM 164930. 

Type local·1:ty.-SV 2694. San Mateo County, Calif. Locatelli(?) 

Formation, Paleocene. 

Arnold (1906 •. p. 53) thought that Chlamys proavus came from 

strata of "Martinez" age; Keen and Bentson (1944, p. 231) considered 

the type locality to be Oligocene or Miocene. Cummings and others 

(1962) named the Locatelli Formation, Paleocene, with a type locality in T. 9 S., R. 3 W., not too distant from SU 2694, T. 8 S., R. 3 W. I 

suggest that Arnold was correct in assigning the small, poorly preserved fauna that occurs with C. p?·oavus to the Paleocene. 

Su,pplementaTy descn:ption.-"A fragment of a much larger specimen than the type of P. p?·oo,·vus, from the same beds and probably 

the same species, shows, near the periphery, narrow ridge-like ribs 

separated by -rather wide interspaces in each of which are two or 

three fine thread-like riblets." (Arnold, 1906, p. 53) 

Cmnpa:rison.-"This species is closely allied to P. traski Gabb, 

from the Cretaceous of the Pacific coast. It differs from the latter, · 

however, in not having the diagonal microscopic sculpture so characteristic of that species." (Arnold, 1906, p. 53) 

Conmwnts.-The holotype is an incomplete left valve retaining 

only small patches of shell. It is higher than long and seems to have 

been equilateral. The shell patches .have small, rounded, closely 

spaced ribs bearing strong, concentric ridges. The interspaces are 

narrower than the ribs on the larger shell patch and some of these 

spaces have interribs. The left posterior auricle is small and has a 

few small riblets preserved on it; the left anterior auricle is not 

preserved. 

Geogmphic range.-Middle California. 

Geologic range.-Paleocene(?). 

Occun·ence 1:n Cali/o?·nia.-Locatelli(?) Formation. 

Chlamys calkinsi (Arnold) 

Plate 3, figure 12 

Pecten (Chlamys) calkinsi Arnold, 1906, p. 51, pl. 2, figs 1, 2. 

Original descn:pt?:on.-"Shell averaging about 35 millimeters in 

altitude, subcircular, equivalve or nearly so, equilateral, rather thin, 

somewhat ventricose, and with only slightly serrate margins. Right 

valve with the exterior surface ornamented by about 55 small, squarish, slightly imbricated ribs, which show a tendency to become 

dichotomous near the end in some specimens; interspaces channeled 

and about one-half as wide as the ribs; hinge line about three-fifths 

the length of the disk; ears equal in length, flat and with the swell of 

the disk commencing at right angles to them; anterior ear sculptured by 4 or 5 imbricated radiating ridges; byssal notch distinct; 

posterior ear sculptured in a similar manner to the anterior. Left 

valve similar to the right except that in the former the ribs are 

slightly more rounded and the anterior ear has no notch." 

Holotype.-VCMP 12076. 

Type locality.-Sisar Valley, Santa Paula quadrangle [SY2 sec. 12, 

T. 4 N., R. 22 W.], Ventura County, Calif. Coldwater Sandstone, 

Eocene. 

· Compan:son.-"So far as known this species has no closely allied 

forms in any of the other California Tertiary for.mation~. and for that 

reason is admirable as a diagnostic form for the Tejon." (Arnold, 

1906, p. 51) 

Comments.-The holotype of C. calkinsi, a left valve, is almost 

. equidimensional, and the preserved portions of the auricles are of · 

equal length. The shell bears closely spaced ribs, many' of them 

V-shaped. The sculpture on the auricles is not preserved. The shell is 

ventricose near the ventral margin. This species differs from other 

Chlamys in the seemingly equal.auricles and in sculpture. 

Geographic range.-Southern California. 

Geological range.-Eocene. 

OccuTrence in California.-Coldwater Sandstone (Keen and Bentson, 1944) and Cozy Dell Shale (Bailey, 1947). 

Chlamys branneri (Arnold) 

Plate 4, figure I 

Pecten (Chlamys) branneri Arnold, 1906, p. 55-56, pl. 3, figs. 9-11. 

Original description.-"Adult shell averaging about 80 millimeters in altitude, higher than long, equivalve, slightly convex, and 

equilateral, except for ears; sides only slightly concave above; base 

regularly rounded below. Right valve with from 20 to 22 prominent, 

narrow, more or less scaly or spinose ribs, which ·in the adults are 

sometimes medially sulcated or di~hotomous; interspaces generally 

much\ broader than the ribs, channeled and usually containing a 

spiny or scaly intercalary rib; whole surface sculptured by imbricating in.crementallines, often also by microscopic reticulations; hinge 

line about two-thirds length of disk; anterior ear much produced and 

sculptured by 6 to 10 imbricated ridges, which are separated by 
B20 PALEONTOLOGY OF CALIFORNIA AND BAJA CALIFORNIA 

equally wide reticulated interspaces; byssal notch profound; posterior ear about three-fifths of anterior, and sculptured similarly. Left 

valve similar to right." 

Holotype.-CAS/SU 358. 

Type locality.-Tuff Hill, near Stanford University [hill357, 3 km 

southwest of Stanford University], Santa Clara County, Calif. 

Unnamed Miocene sandstone of Dibblee (1966). 

Supplementary description.-:-"This species varies considerably in 

the degree of importance of the minor sculpture, such as reticulation, imbrication, and size of the sulcations and intercalaries. 

Although unquestionably allied to the Chlamys group, it has larger 

posterior ears than other species of the group * * *." (Arnold, 190, 

p. 55) 

Comparison.-"P. branneri resembles P. islandicus in size, outline, and general sculpture, but is distinguishable by having only· 

about one-half as many ribs and much larger posterior ears." 

(Arnold, 1906, p. 55) 

Comments.-The holotype is a mold of a left valve with the auricles 

and about half of the shell preserved. The ribs are narrower than the 

interspaces which may have a small interrib and which also may 

have imbricated microsculpture. The left anterior auricle has 12 

riblets, slightly spinose, and heavier than the 10 on the posterior 

auricle which are also slightly spinose. Imbricated microsculpture 

is preserved on the left anterior auricle. 

Geographic range.-Middle California. 

Geologic range-Oligocene and Miocene. 

Occurrence in California.-Oligocene and Miocene: Temblor Formation (Curran, 1943), Vaqueros Formation (Arnold, 1906; Brabb, 

1964); Miocene: unnamed sandstone (Dibblee, 1966). 

Chlamys sespeensis (Arnold) of Loel and Corey 

Plate 4, figures 2, 3 

Pecten (Chlamys) sespeensis Arnold, 1906, p. 69, pl. 8, figs. 2, 2a, 3. 

Loel and Corey, 1932, p. 196-197, pl. 21, figs. 1-5. Weaver and 

Kleinpell, 1963, p. 197, pl. 29, figs. 7, 9, 10; pl. 30, figs. 1, 2, 5. 

Vertipecten sespeensis (Arnold). MacNeil, 1967, p. 38, 40. 

Original description.-"Shell averaging about 50 millimeters in 

altitude, higher than long, inequivalve but both valves equally 

slightly convex, rather thin, and equilateral, except for ears. Right 

valve with about 9 pairs of narrow, rounded, nearly smooth ribs, 

each pair being separated from the adjacent ones by interspaces, 

which are generally slightly wider than the interspace between the 

members of the pair; surface sculptured by incremental lines; hinge 

line about two-thirds length of disk; anterior ear much produced, 

sculptured by several prominent radials and numerous incremental 

lines; posterior ear over one-half as long as anterior, and sculptured 

similarly; byssal notch prominent. Left valve with about nine prominent, narrow, squarish, somewhat convex-topped ribs separated by 

much broader interspaces, along the bottom of which run one or 

more thread-like intercalaries of greater or less prominence; ears 

similar to those of the right valve." 

Holotype.-California State Mining Bureau 12480. Missing and 

presumed lost, fide Keen and Bentson (1944). 

Type locality.-Sespe Oil District, Piru quadrangle, Ventura 

County, Calif. Vaqueros Formation, Oligocene and Miocene. 

Supplementary description.-"Individual variation in P. sespeen-

.<n:s is remarkable. In any locality the number of strong ribs may vary 

from 18 to 29. The ribs' development is most variable in number, 

spacing, and strength of.intercalary ribs. The valve (which is usually 

thin) varies considerably in outline and is frequently constricted 

near periphery." (Loel and Corey, 1932, p. 197) 

Comments.-On the basis of a specimen figured by Weaver and 

Kleinpell (1963, pl. 29, fig. 10; pl. 30, fig. 1) MacNeil (1967, p. 38) 

considered Chlamys sespeensis to be "very close to the boundary 

between ChlartJys and Vertipecten, morphologically." The hypotypes 

of Loel and Corey (1932) are typical Chlamys, and sespeensis is here 

retained in that genus. A few of the left-valve ribs are more prominent than others, but this is true for other Chlamys. The valves are 

equilateral, and the figured right valve has about 25 low rounded 

ribs with equal interspaces, some bearing an interrib. The right 

anterior auricle has six fine riblets and a moderately large byssal 

sinus. The smaller right posterior auricle is smooth. The left valve 

figured has 27 rounded to subrounded ribs, some higher than others, 

separated by slightly wider inters paces bearing 1 or 2 interribs. The 

left-valve auricles seem to have been smooth. 

The valves of Chlamys hodgei are more inequilateral and the left 

valve much more finely sculptured than C. sespeensis. Chlamys 

branneri has almost square ribs on the left valve and strongly sculptured left anterior auricle, which differentiate it from C. sespeensis. 

Geographic range.-Oregon (Durham and others, 1942); Southern 

California. 

Geologic range.-Eocene to Miocene. 

Occurrence in Calijornia.-Eocene: Coldwater Sandstone (Weaver 

and Kleinpell, 1963); Oligocene: upper part of Gaviota Formation 

(Weaver and Kleinpell, 1963); Oligocene and Miocene: Rincon Shale 

(Avila and Weaver, 1969) and Vaqueros Formation (Kew, 1924; Loel 

and Corey, 1932; Dibblee, 1950; Squires and Fritsche, 1978). 

Chlamys sespeensis hydei (Arnold) 

Plate 4, figures 4, 6 

Pecten (Chlamys) sespeensis var. hydei Arnold, 1906, p. 69-70, pl. 5, 

figs. 3, 3a, 3b. Arnold, 1907b, p. 24, pl. 53, fig. 3. 

Original description.-"Shell averaging about 45 millimeters in 

altitude, much higher than long, subequivalve, slightly convex, and 

subequilateral, except for ears; anterior sides more concave than 

posterior; base regularly rounded; umbonal angle comparatively 

small. Right valve with about 20 subequal, prominent, rounded, 

somewhat imbricated ribs, which increase gradually in number by 

division and intercalation as the shell grows; interspaces somewhat 

narrower than ribs and often containing one or two thread-like 

intercalaries; ears as in P. hastatus var. hericius except less imbricated, and the posterior relatively larger left valve similar in every 

respect to right." 

Holotype.-CAS/SU 10. 

Type locality.-Lynch's Mountain, Monterey County, Calif. 

Vaqueros Formation, Oligocene and Miocene. 

Supplementary desc1·1:pt1:on.-"This variety is characterized by 

the nearly uniform size of its ribs and interspaces. The shell has a 

tendency to contract somewhat upon reaching an altitude of about 35 

or 40 millimeters." (Arnold, 1906, p. 70) 

Comparison.-"P. var. hyde1: is closely allied to the typical P. 

sespeensis, but may usually be distinguished by its more nearly 

equal ribs, which are generally more strongly imbricated." (Arnold, 

1906, p. 70) 

Cmnments.-The sculpture of the right and left valves of the holotype is the same: rounded ribs with slightly narrower interspaces 

that may bear an interrib. The shell is high in proportion to length. 

Chlamys sespeensis hydei differs from C. 8espeensi8 in that it is 

higher in proportion to length, equilateral, and the valves bear 

similar sculpture. 

Geographic range.-Middle and southern California. 

Geologic range.-Oligocene to Miocene. 
TERTIARY MARINE PELECYPODS: PROPEAMUSSIIDAE AND PECTINIDAE B21 

Occu?Tence ·1:n Ca.lifont?:a.-Oligocene and Miocene: Vaqueros 

Formation (Arnold, 1906, 1907b; Arnold and Anderson, 1907; Bailey, 1952; Kew, 1924). 

Chlamys hertleini (Loel and Corey) 

Plate 4, figures 7, 8 

Pecten (Chlamys) he1·tle·1:n:1: Loel and Corey, 1932, p. 195-196, pl. 20, 

figs. 4, 6-8. · 

Chlo:mys he·rtle·1:n:1: Loel and Corey. Addicott, 1965, fig. 3e. Addicott, 

1967b, fig. 4, B, D. 

On:m>na.l descn:pt1:on.-"Shell medium thin, about as long as high; 

valves subequal, slightly convex and subequilateral except for ears; 

anterior sides concave, posterior straight, base regularly rounded; 

umbonal angle 80 degrees. Right valve ornamented by many fine, 

evenly spaced, minutely noded ribs which number about 60 at the 

periphery. These ribs are progressively added to outwardly by the 

strengthening of intercalary ribs, all being of equal strength at the 

margin; fine incremental lines form the nodes on the ribs and also in 

the interspaces which are about as wide as ribs. Anterior ear long, 

ornamented by seven fine riblets, the concentric incremental lines 

strong forming nodes on ribs and strong lines between ear and 

margin; byssal notch deep. Left valve similar in all characters save 

fot· shallower byssal notch. Height, 4 m.; length, 40 mm.; diameter, 

10 mm. (both valves)." · 

Holotype.-UCMP 31725. 

Type loca.l·1:ty.-UC A316, Santa Barbara County, Calif. Vaqueros 

Formation, Oligocene and Miocene. ' 

Su.mJlenwnta:ry desc1"1:pt·1:on.-"This distinctive Pecten (Chlamys) 

is different from all others in the Tertiary of the West Coast. On 

another specimen from the same locality, the posterior ears are seen 

to be ornamented in the same manner as the posterior [sic: anterior] 

ears and squarely truncate. Specimens from the Vaqueros of the 

western Santa Ynez Mountains*** are all small with rib number at 

the periphery generally less than the type or larger form. The rib 

number is prop01·tional to the size of the individual." (Loel and 

Corey, 1932, p. 196) 

Com.7Ja:rison .. -"Pecten (Chlam.ys) he1·tle1:m:, n. sp. differs from P. 

IWS1Jeen1-ris Arnold in its distinctively uniform and greater number of 

ribs-adult specimens of the latter species never have more than 

about 30 ribs and those are unevenly developed." (Loel and Corey, 

1932, p. 196) 

Com:ments.-The holotype is a poorly preserved, double-valved 

specimen with a small umbonal angle. The right-valve auricles are 

broken, but the byssal notch is wide. Both valves are similarly 

sculptured. 

Geog·ra.ph1:c nw.ge-Middle and southern California. 

Geolog·ic ·ra:nge.-Oligocene to Miocene. 

Occu:rren.ce ·1:n Ca.i'l/o·rn:l:a .. -Oligocene: Quail Canyon Sandstone 

Member, Vaquet·os Formation (Loel and Corey, 1932; Vedder,1973); 

Oligocene and Miocene: Rincon Shale (Avila and Weaver, 1969), 

Soda Lake Shale Member, Vaqueros (Vedder, 1973) and Temblor 

(Page and others, 1951) Formations; Miocene: Jewett Sand (Addicott, 1965 and 1967b), Monterey Formation (Avila and Weaver, 

1969), Painted Rock Sandstone Member, Vaqueros Formation 

(Vedder, 1973), and Skooner Gulch Formation (Addicott, 1967b). 

Chlamys hodgei (Hertlein) 

Plate 4, figures 5, 9; plate 5, figure 2 

Pecten (Chla:mys) hodge1: Hertlein, 1925b, p. 42, pl. 4, figs. 1, 2. 

Stanton, 1966, p. 27, pl. 5, figs. 4, 5. 

Chlamys durhami Adegoke, 1969, p. 97-98, pl. 2, fig. 5. 

Original descn:ption.-"Shell of medium size, higher than long, 

slightly compressed, equilateral. Right valve ornamented by over 19 

radiating ribs which are largely bifid and often have a small riblet 

on each side of the large ribs, the ribs toward the margins, become 

finer, interspaces somewhat rounded, showing very fine pitted surfaces, sculptured by a small intercalary riblet, ribs and riblets bearing fine, scattered, sharp, imbricating spines; sides of valve nearly 

straight, ventral margin regularly rounded; ears unequal, the anterior much larger than the posterior, anterior ear ornamented by 

about 5or 6 coarse, radiating rib lets which are crossed by concentric 

lines of growth, byssal notch large; posterior ear small in proportion 

to the large anterior ear, ornamented by about 9 small, radiating 

riblets which are crossed by concentric lines of growth. The ornamentation of the left valve consists of alternating large and small 

ribs but the ribbin.g is much finer than on the right valve. Height 47 

mm.; length 40 mm.; diameter of right valve approximately 8 mm.; 

length of hinge line of right valve 25 mm.; apical angle of right valve 

approximately 87°." (hodgei) 

"Shell small, thin, equilateral, gently and evenly convex, slightly 

higher than long; anterior and posterior dorsal margins moderately 

long, about half length of shell, subequal and straight, merge into 

very convex ventral margin with broad angle; umbonal angle about 

90°; cardinal area straight and long, about three-fourths length of 

shell; shell ornamented by about 20-22 dichotomously branching 

ribs; branching occurs at different levels along individual ribs; rib 

profile rounded near cardinal area, wide and flat-topped near ventral margin; shell surface sculptured by numerous faint incremental 

lines of growth; posterior ear short and inconspicuous; anterior ear 

long, sculptured by 4 or 5 axial riblets and numerous faint lines of 

growth; byssal notch deep." (durhami) 

Holotype.-CAS/SU 20; of Chlamys du·rhami Adegoke, UCMP 

33615. 

Type locality.-SU F-6. Fresno County, Calif. Santa Margarita 

Formation, Miocene; of Chlamys du.rhami Adegoke, UC D1099, 

Kern County, Calif. Santa Margarita Formation, Miocene. 

Supplementary descn:ption.-"The right valves are ornamented 

with about 20 bifid ribs; interspaces contain a median riblet, and, in 

a few instances, one or two tertiary riblets. The left valves bear about 

22 flatly rounded ribs; interspaces contain a median ribletone-third 

to one-fourth as wide as the primary rib and in some interspaces 

tertiary ribs lie along the sides of the primary ribs. The sculpture of 

the right valve is variable. On one specimen all the ribs are bifid; on 

another, only a few are bifid; and on the third, most ribs are bifid but 

the two parts of the ribs are not equally wide." (Stanton, 1966, p. 27) 

Compan:son.-"Pecten hodgei appears to be closely related toP. 

· halimensis Makiyama from the Pliocene of Japan, but it differs in 

that it has less numerous ribs which are more distinctly bifid, than in 

the species described by Makiyama. From P. opunt1:a Dall, P. hodgei 

differs in having the ribs bifid and arranged in pairs, rather than 

numerous, closely but irregularly spaced, rounded, and not bifid; the 

margins of P. opunt1:a are rounded and. not straight as in the present 

species. From P. J·ordani Arnold, P. hodge1: differs in having more 

numerous, rounder ribs, which on the right valve become bifid much 

earlier in the growth of the shell. From P. hen:cius Gould, P. hodgei 

differs in having less numerous ribs, narrower,less high, and generally finer, and the shell possesses straighter margins in the present 

species. From P. egregius Nomland, P. hodgei is distinguished by 

having more numerous ribs which are differently ornamented in the 

present species." (Hertlein, 1925b, p. 42) 

"Chlmnys durhami [=C. lwdgei] ***is closely similar in outline 

and ornamentation to Chlamys)·ordani Arnold from the upp·er Pliocene and Pleistocene of San Pedro and Santa Barbara. It may be 

readily distinguished from the latter by its smaller size, fewer ribs, 
B22 PALEONTOLOGY OF CALIFORNIA AND BAJA CALIFORNIA 

wider interspaces between ribs and the fact that bifurcation of ribs 

begin much earlier in the new species than in Arnold's species. 

"From Chlamys egregius Nomland ***may be distinguished by 

its less elongate oval outline and its bifurcating ribs." (Adegoke, 

1969, p. 97 -98) 

Comments.-The holotype of Chlamys hodgei is an inequilateral 

right valve with wide ribs that may bifurcate when the shell is 10 

mm high and that are separated by narrower interspaces that have 

an interrib. Remnants of spines are present on the ribs near the 

ventral margin. The right anterior auricle has six riblets; the left 

anterior auricle about eight, which are finer. 

The paratype of Chlamys hodgei is a markedly inequilateral left 

valve that has much finer ribs than the right valve. The ribs are 

closely spaced, and the narrow inters paces bear 1 or 2 interribs. The 

left anterior auricle has 13 riblets of almost equal size. 

On the basis of the holotypes, I can find no characters to differentiate Chlamys durhami from Chlamys hodgei. Chlamys durham1: is 

probably a juvenile specimen of C. hodgei, which was also collected 

from the Santa Margarita Formation. 

Geographic range.-Middle and southern California. 

Geologic range.-Miocene. 

Occurrence in California.-Castaic (Stanton, 1966) and Santa 

Margarita Formations. 

Chlamys sanctiludovici (Anderson and Martin) 

Plate 5, figures I, 3 

Pecten sanct?:-ludovici Anderson and Martin, 1914, p. 55, pl. 3, figs. 

lOa, lOb. 

NotPectensancti-ludoviciAnderson and Martin. G D. Hanna, 1926a, 

p. 4 73, pl. 22, figs. 1-3. 

Original description . ..:___"Shell of moderate size, equivalve, inequilateral, strongly ribbed, moderately inflated; umbones narrow and 

acute; each valve with nineteen or twenty ribs, rounded on the back 

and separated by narrow V-shaped interspaces; ribs ornamented by 

about six rib lets forming fasciculi more or less beaded or roughened, 

not spiny; ears unequal, the anterior being nearly twice the length of 

the posterior, and on the right valve coarsely ribbed; posterior ear 

smaller and ornamented with wavy radial threads." 

Holotype.-CAS 107. 

Type locality.-0.8 km'above the mouth of Navajoa Creek, San 

Juan River [NW~ sec. 16, T. 28 S., R. 16 E., La Panza quadrangle], 

San Luis Obispo County, Calif. Santa Margarita Formation, 

Miocene. 

Comparison. -"This species differs from Pecten hastatus Sower by, 

by having uniform riblets." (Anderson and Martin, 1914) 

Comments.-The holotype and paratype have a moderately shallow byssal sinus, nearly equal auricles, and no bifurcated ribs. A 

delicate scalelike sculpture is preserved on the ribs, which are 

broadly rounded and covered with fine riblets, as are the interspaces. The right anterior auricle has 5 heavy riblets; the right 

posterior auricle 11 much finer riblets. In sculpture, C. sanctiludovici resembles Aequipecten. 

Geographic range.-Middle California. 

Geologic range.-Miocene. 

Occurrence in Calijornia.-Santa Margarita Formation. 

Chlamys corteziana Durham 

Plate 5, figure 5 

Chlamys corteziana Durham, 1950, p. 64-65, pl. 10, figs. 2, 3, 6. 

Pecten sancti-ludovici Anderson and Martin. Hanna, 1926a, p. 473, 

pl. 22, figs. 1-3; not Pectensancti-ludov1:c1:Anderson and Martin, 

1914. 

Original description.-"Shell of medium size, right valve slightly 

more inflated than left; sculpture discrepant on the two valves; right 

valve with 17-18 low rounded ribs with interspaces about equal in 

size, ribs and inters paces each bearing equally spaced finely beaded 

riblets with an occasional tertiary riblet present; near umbo the 

primary ribs are higher and nearly square-sided but as shell 

becomes larger ribs spread out and become low and rounded; anterior ear of right valve with about 12 fine beaded riblets; riblets on 

posterior ear .Jess distinct than on anterior; left valve with a corresponding number of high, square-sided and noded ribs about two 

thirds as wide as flat-bottomed inters paces, occasionally a secondary 

beaded, flat-sided riblet is developed on sides of primary rib." 

Holotype.-UCMP 30564. 

Type locality.-DC A3579. Baja California Sur. San Marcos Formation, Pliocene. 

Cmnparison.-"This species somewhat resembles Chlan~ys lowe1: 

(Hertlein) living in the Gulf of California but may easily be separated by the large posterior ear and more rounded inters paces on the 

·right valve. Pecten (Chlamys) buchivacoanus F. and H. Hodson and 

its subspecies from the Miocene of Venezuela is another closely 

related species, but its left valve has many more secondary and 

tertiary riblets." (Durham, 1950; p. 64) 

Comments.-The holotype is a poorly preserved mold of a right 

valve that is more inflated than is usual for Chlamys and has 17 

subrounded ribs without equal interspaces. The ribs and the interspaces have secondary riblets. 

Geographic range.-Southern California to Baja California Sur. 

Geologic range.-Miocene to Pliocene. 

Occurrence 1:n the Calijornias.-Miocene or Pliocene: Imperial 

Formation; Pliocene: Gloria (Stump, 1979) and San Marcos Forma-

. tions and unnamed strata near San Felipe, Baja California Norte. 

Chlamys hastata hastata (Sowerby) 

Plate 5, figures 4, 6 

P[ecten] hastatus Sowerby, 1842, p. 72, pl. 20, fig. 236. 

Pecten(Chlamys) hastatus Sower by. Arnold, 1906, p. 108-110, pl. 41, 

fig. 4; pl. 42, figs. 1, la, 2, 2a. 

Pecten (Pecten) hastatus Sower by. Grant and Gale, 1931, p. 166-168, 

pl. 11, figs. 6a, 6b. 

Chlamys (Chlamys) hastata Sowerby. Hertlein and Grant, 1972, p. 

188-189, pl. 33, figs. 4-6. Vedder and Moore, 1976, pl. 4, fig. 2. 

Chlamys hastata (Sowerby). Grau, 1959, p. 84-87, pis. 27, 28. 

Pecten (Chlamys) lawsoni Arnold, 1906, p. 117-118, pl. 45, figs. 3, 4. 

Original description.-"Oval, inclining to triangular, rather elongated, rough; with very unequal ears, the posterior ones being very 

small; the upper valve has eight unequal, elevated, angular ribs, 

with numerous erect, slightly curved sharp spines, and several 

smaller spinose ribs in the interstices. The lower valve has 22 more 

nearly equal ribs with more numerous and smaller spines on the 

angles." (hastata) 

"Adult shell averaging about 70 millimeters in altitude, not as 

long as high, inequivalve, only slightly convex, equilateral, ears 

unequal; base regularly rounded; sides only slightly concave above; 

margins somewhat serrate. Right valve with about 18 to 20 subequal, prominent, narrow, round-topped, rugose ridges, separated 

by somewhat wider inters paces, in each of which runs a single more 

or less rugose riblet; some of the ribs are occasionally medially 

sulcated or dichotomous; surface sculptured by numerous irregular 

incremental lines, which give the ribs a squamose appearance when 

they are unworn; ears unequal, the anterior with three or four rather 
TERTIARY MARINE PELECYPODS: PROPEAMUSSIIDAE AND PECTINIDAE B23 

prominent rugose radials and numerous incremental lines; the posterior with several less prominent radials, and incremental sculpture; byssal notch rather profound. Left valve with 9or 10 prominent 

narrow, t·ound-topped, rugose major ribs, between each two of which 

there is a single minor t·ib similar to and almost equaling in prominence the major ribs; a single thread-like intercalary is visible in 

most of the inters paces; surface sculptured as in the right valve; ears 

similar to those of right valve except that there is no prominent notch 

between the anterior one and the disk." (lo:wsoni) 

Holotype.-B.M. (N.H.); of P.lawson·i, lost in San Francisco fire of 

1906. 

'TmJe loco.loi:ty.-San Diego, Calif., by subsequent designation 

(Grau, 1959, p. 85), Holocene. Of P. lawsom:, USGS 4473, Santa 

Barbara County, Calif. Careaga Formation (Keen and Bentson, 

1944), Pliocene. 

Supplenwnto:ry clescn:pt·ion.-"Shell averaging about 64 millimeters in altitude, slightly shorter than high, inequivalve, equilateral 

(except fot· ears), compressed and with serrate margins; base evenly 

rounded below; sides slightly concave above. Right valve with 9 

pairs of narrow, elevated, spiny ribs, along the sides of which are a 

pair of smaller spiny riblets; major interspaces much wider than 

ribs. concave-bottomed and ornamented by 1 or 3 thread-like, spiny, 

intercalat·y riblets; whole surface sculptured by microscopic imbricating lines. of which the spines on the ribs and riblets are only 

modifications; hinge line equal to one-half length of disk; ears 

unequal, the anterior being about two and one-half times the length 

of the posterior; anterior ear with 7 or 8 prominently spiny radials 

and minor riblets, and imbricating incremental lines; byssal notch 

deep and almost as wide as ear; posterior ear small, and sculptured 

by fine, spiny radials and imbt·icating inct·ementallines. Left valve 

with about 9 nan·ow, very prominently spiny ribs; interspaces wide, 

concave-bottomed, and ornamented by a single prominent, central, 

imbricated rib let, on each side of which are minor threadlike rib lets; 

whole surface of disk with fine incremental sculpture as in right 

valve; ears similar to those of t•ight valve except that the anterior one 

has more ribs and riblets and no byssal notch. Hinge with almost 

obsolete cardinal crura." (Arnold, 1906, p. 109) 

"Valves moderately inflated, left valve with about 10 strong spinose t•ibs, right valve with nine strong double or paired ribs, paired 

ribs well spaced, both valves with fine intercalary ribs and fine 

imbricate sculpture throughout." (McLean, 1978, p. 69) 

Com.po:rison.-"Both fossil and Recent shells show perfect gradation between C. hastatus proper, characterized by well-differentiated primary ribs that bear well-developed scaly lamellae, and C. 

heoric·1>us, which lacks those characters." (Woodring, 1946, p. 80) 

"Young specimens of 15 mm or les~ in height resemble theyoungof 

Nin.n:ites ·m:l.l.lt·i·rugosus (Gale), but those of the latter can be distinguished by the following differences in structure: the disk equilateral (or nearly so), the ribs of the right valve divaricating, the 

postet·ior auricles larger and squared, the inters paces of both valves 

concentrically lamellose." (Grau, 1959, p. 86) 

Chlo:mys hastata. pugetens·is "is distinguishable from Chlwmys hasta.ta and Chlo:m.ys lw.stato. he·ricia by its rib-structure, sculpture of 

disk, obliquely truncated posterior auricles and internal coloring; 

juveniles 12 mm in height or less are only distinguishable by the 

punctate sculpture of the disk." (Grau, 1959, p. 91) 

"Eroded specimens of this species are often difficult to separate 

ft·om similar specimens of the subspecies C. hastata hericius. In 

general, the major ribs on C. hastata are rather sharply defined 

whereas on C. h. lw·n:c·1:us these are composed of a fascicule of riblets 

the whole with a convex outline. The right valve of C. hastata is 

sculptured with 9 or 10 paired, high, steeply sloping ribs, each 

bearing a row of long spines. There are 1 to 3 thread-like spiny 

t·iblets in the inters paces. Very fine, incised groovings are present on 

the surface in the inters paces between the ribs. On the right valve of 

C. h. hericius, a generally more northern, larger form, there are 

·three riblets of nearly equal size (although the central one is slightly 

larger) on each major rib which lend a rounded appearance to the 

ribs. The ribs on the left valve of C. hastata, 9 or 10 in number, are 

narrower and more steeply sloping than are those of C. h. hen:cius 

(Hertlein and Grant, 1972, p. 189) 

Geographic range.-Living: Bolinas Bay to San Diego, Calif.; fossil: middle California to Baja California Norte. 

Geologic Tange.-Miocene through Holocene. 

Occur1·ence in the Calijo1·nias.-Miocene: Santa Margarita Formation (Nomland, 1917b; Addicott and Vedder, 1963); Miocene and 

Pliocene: Etchegoin (Adegoke, 1969), Purisima (Arnold, 1906), and 

Sisquoc (Woodring, 1950) Formations; Pliocene: Almejas Formation 

(Minch and others, 1976), Cebada Member, Careaga Sandstone 

(Woodring, 1950), Foxen Mudstone (Woodring, 1950), Lomita Marl 

Member, San Pedro Formation (Woodring, 1946), Niguel (J. G. 

Vedder, written commun., 1978), Ohlson Ranch (Peck, 1960), and 

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

strata on San Clemente Island (Vedder and Moore, 1976); Pliocene 

and Pleistocene: Fernando (Woodring, 1930), Merced (Arnold, 

1906), Pico (W. 0. Addicott and J. G. Vedder, written commun., 

1968), Santa Barbara (MacNeil, 1967), and Saugus (Kew, 1924) 

·Formations; Pleistocene: upper member, Fernando Formation (Durham and Yerkes, 1964), Timms Point Silt (Woodring, 1946), and 

unnamed strata on San Nicolas Island (Vedder and Norris, 1963) 

and at San Diego (Glibert and Van de Poel, 1965). 

Habitat.-18 to 90 m (Hertlein and Grant, 1972, p. 189); on rocky 

bottoms (McLean, 1978, p. 69); in sand and on shale or corallines, 

sometimes encased in sponge (Smith and Gordon, 1948). 

Chlamys hastata hericius (Gould) 

Plate 5, figures 7, 8 

Pecten hericius Gould, 1850, p. 345. 

Pecten (Chlamys) hastatus Sowerby var. hericius Gould. Arnold, 

' 1906, p. 110-111, pl. 43, figs. 3, 3a. 

Chlamys hastata hericius (Gould). Grau, 1959, p. 87-90, pl. 29. 

Chlamys (Chlamys) hastata hericius Gould. Hertlein and Grant, 

1972, p. 189-190, pl. 33, fig. 2 [See for synonymy]. 

On:ginal desc1·iption.-"T. rotundato-triangularis, equilateralis, 

equivalvis; val vis convex is, sub-tumid us: valva superior rosea, lineis 

exilibus concentricis exasperata, et costis ad 24 angulatis, alternis 

majoribus et spin is erectis fornicatis insculpta: valva inferior pallidior colore saturatiori zonata, costis sub-equalibus spiniferis armata; 

natibus acutis, prominentibus; auribus obliquis valde inequalibus 

radiatim squamoso-striatis; intus porcellana; marginibus crenulatis, rosaceis. Long. 4Yz; alt. 1~; lat. 4 3/4 poll." 

Holotype.-USNM 5955. 

Type locality.-Strait of Juan de Fuca, Washington, Holocene. 

Supplementary description.-"Aduit shell averaging about 70 

millimeters in altitude, not quite as long as high, both valves compressed, equilateral (except for ears), which are decidedly unequal; 

margins finely serrate; sides markedly concave above; umbo acute. 

Right valve with 9 or 10 pairs of spiny fasciculi, the middle rib of 

each fascicule being the most prominent; inters paces about as wide 

as the fasciculi, ·and ornamented by several more or less spiny 

riblets; spaces between the riblets of the fasciculi and large inter.-

·s paces channeled and ornamented by fine imbricating incremental 

lines, but free from any reticulations whatever; hinge line a 'little 

.over one-half the length of the disk; anterior ear about two and 

one-half times longer than the posterior, ornamented by imbricating 

concentric lines, and above the notch by several subequal spiny 
B24 PALEONTOLOGY OF CALIFORNIA AND BAJA CALIFORNIA 

riblets; byssal notch wide and deep; posterior ear small, and ornamented by numerous fine spiny riblets. Left valve with about 9or 10 

elevated fascicule, the middle rib of each fascicule being quite prominently spinose; the spaces between the major fasciculi each occupied 

by a minor fascicule of more or less scaly riblets; interspaces between 

riblets channeled and with imbricating incremental 

sculpture; ears sculptured as in right valve except that the riblets 

are smaller and more numerous on the anterior ear. Hinge weakly 

developed." (Arnold, 1906, p. 110) 

Comparison.-"The more extreme variants of typical C. hastata 

have high, sharp crested ribs with moderately large spinel ike scales, 

whereas the opposite extreme of C. hastata hericius has low bundles 

or fascicles of rib lets with all the rib lets finely and equally scabrous. 

Some intermediate specimens might be difficult to assign to either 

subspecies. If living individuals of these forms do not constitute an 

entirely continuous series of variation, they come very close to it." 

(MacNeil, 1967, p. 14-15) 

"Chlamys hastata hericius * * *differs from typical C. hastata in 

the generally larger size, less spinose ribs and in that the ribs of the 

right valve are composed of a fascicule consisting of three nearly 

equal, spiny riblets, the middle one slightly more prominent, the 

whole more convex in outline than the corresponding fascicule on C. 

hastata. There is usually a rib let in the middle of each interspace and 

between this and the major fascicule there are usually two smaller 

threads and occasionally also a finer pair of intercalaries. The ribs 

on the left valve also consist of a fascicule of riblets which is more 

convex than that of C. hastata. The surface in the interspaces 

between the ribs of C. h. hericius is usually sculptured with very fine 

oblique.grooves or scratches similar to those on C. hastata. Grau 

pointed out that the shell of C. hastata often is oblique, whereas that 

of C. h. hericius seldom is. 

"The form originally described as Pecten islandicus pugetensisi. . 

S. Oldroyd is similar to C. h. hericius but it is generally smaller, the 

interspaces and sometimes the entire valve bears fine honeycomblike sculpture. 

"Masuda [1956, p. 249] suggested that Chlamys miyatokoensis 

Nomura and Hatai ***,which occurs in beds of early Miocene age in 

Japan, may be an ancestral form of C. hastata hericius. The riblets 

forming the major ribs of the Japanese form are said to be divided 

into three subequal parts by radial grooves and there are but two or 

three rib lets in the inters paces. Judging from the illustrations given 

by Masuda, the radial fasciculi appear to be less elevated into raised 

ribs lending an appearance of nearly equal, spiny, radial rib lets over 

all the right valve. The anterior ears also are smaller than those on 

the west American form. The medial sulcation giving rise to the 

paired character of the ribs mentioned by Masuda also is noticeable 

on some west American specimens * * *. Some of the illustrations 

given by Masuda [1956] bear a decided resemblance to some forms of 

C. h. hericius (see especially his plate 35, figure 9a) and his suggestion that C. miyatokoensis may be an ancestral form of C. h. hericius 

is plausible. The two, however, are apparently distinct forms." (Hertlein and Grant,_l.Jt_72, p. 190) 

Geographic range.-Living: Port Althorp, Alaska, to Santa Barbara, Calif.; fossil: middle to southern California. 

Geologic range.-Miocene through Holocene. 

Occurrence in California.-Miocene: San Pablo and Santa Margarita Formations (Arnold, 1906); Miocene and Pliocene: Capistrano 

(Kern and Wicander, 1974), Etchegoin, and Purisima Formations 

_(Arnold, 1906); Pliocene: Lomita Marl Member, San Pedro Formation (Valentine and Meade, 1961); Pliocene and Pleistocene: Fernando (Moody, 1916; Soper and Grant, 1932), Merced (Arnold, 1906), 

San Pedro (Arnold, i906), ·santa Barbara (Waterfall, 1929: 

as Pico), and Saugus . (Kew. 1924) Formations: , Pleistocene: 

unnamed Pleistocene strata at Baldwin Hills (Willett, 1937) and 

Capistrano Beach (Willett, 1938). 

Habitat.-"Chlamys hastata hericius is a generally more northern 

form, at the present time occurring abundantly in Puget Sound 

often embedded in sponges. It has been recorded as occurr·ing from 

Port Althorp, Alaska, south toN ewport Bay, California, but we have 

not seen specimens from southern California." (Hertlein and Grant, 

1972, p. 190) From low tide line·to 145m. 

Chlamys (Chlamys) hastata ellisi Hertlein and Grant 

Plate 5, figure 9 

Chlamys (Chlamys) hastata ellisi Hertlein and Grant, 1972, p. 

190-191, pl. 3, figs. 2, 3; pl. 34, fig. 6. 

Original description.-"Shell characters similar to those of 

Chlamys hastata but differing in the presence of fine honeycomblike tesselations covering the interspaces and sides of the ribs, but 

obscured on the tops of the ribs where covered by strong imbricating 

spinose sculpture. Length, 66 mm; height, 68.5 mm." 

Holotype.-LAM 4483. 

Type locality.-LAM 305. San Diego County, Calif. San Diego 

Formation, Pliocene. 

Supplementary description.-"The entire surface of left valves is 

covered with minute tesselations. This sculpture, composed of a 

layer of minute scaly imbrications, is usually preserved in the 

interspaces but sometimes covers the ribs as well. Often the scaly 

honeycomb-like material is mostly gone and the interspaces retain 

only a pattern of minute reticulation. This type of sculpture * * * is 

present on C. islandica and allied forms. It also occurs on many 

species in other groups of scallops, including Manupecten, Patinapecten and Swiftopecten. It may be a primitive character. This minute sculpture may easily disappear with erosion and it is quite 

possible that some fossil specimens lacking perfect preservation in 

the present as well as in other collections, and referred to Chlamys 

hastata or C. h. hericius, may represent C. h. ellisi * * *." 

"It appears that since Pliocene time the members of the Chlamys 

hastata group bearing honeycomb-like tesselations have been reduced to one subspecies, which is smaller, less numerous, and in 

general has become restricted to cooler waters." (Hertlein and 

Grant, 1972, p. 191) 

Comparison.-"The only reliable basis for separating C. hastata 

ellisi ***from C. hastata rests entirely on the presence and recognition of the surficial tesselated sculpture. 

"The minute sculpture of the present subspecies is similar to that 

of the form described as Pecten islandicus pugetensi.'5 * * *The ribs of 

C. hastata pugetensis are more rounded than those of C. hastata, 

those on each valve are nearly equal in size, and the fasciculi are 

minutely spinose. * * * 

"Chlamys hastata pugetensis is generally reported to be smaller 

than C. hastata, C. h. ellisi n. subsp., and C. h. hericius." (Hertlein 

and Grant, 1972, p. 191) 

Geographic distribution.-Southern California. 

Geologic range.-PI iocene. 

Occurrence in California.-San Diego Formation. 

Chlamys egregius (Nom land) 

Plate 6, figure 5 

Pecten egregius Nomland, 1917a, p. 231-232, pl. 6, figs. 3, 3a, 3b. 

Chlamys egregius (Nomland). Peck, 1960, pl. 21, fig. 8. Adegoke, 

1969, p. 98. 

Original description.-"Shell equilateral, equivalve, thin, rather 

compressed; with smooth, regularly rounded base. Dorsal margins 

long; umbonal angle about 70 degrees. Right valve with about 22-23 

moderately strong, rounded ribs; in each interspace there is one 
TERTIARY MARINE PELECYPODS: PROPEAMUSSIIDAE AND PECTINIDAE B25 

small, often invisible, rounded riblet; anterior ear long, arcuate in 

front, ornamented above byssal notch by about six distinct, radiating ridges and numerous incremental lines; byssal notch well 

defined; posterior ear very small, sculptured by low radiating ridges 

and inconspicuous incremental lines. Left valve with about 22 subequal ribs, which are not so prominent as those of the right valve, but 

with auxiliary riblets more distinct; anterior ear large, with sculp-. 

ture consistingoffaint incremental lines and about.twelve radiating 

ridges; posterior ear similar to that on the right valve. Dimensions of 

type, which is a rather small specimen; height,,31 m width, 24 mm.; 

width of hinge, 13 mm." 

Holotype.-UCMP 11090. 

TmJe loca.hty.-UC 2991. Fresno County, Calif. Upper part of 

Etchegoin Formation, Pliocene. 

Compa:n:son.-"This species differs markedly from Chlamys bartsell:/: (Arnold) with which it was synonymized by Grant and Gale. C. 

f~m·eg·1:~u~ has an elongate oval shell ornamented by 22-23 rounded 

ribs while C. bartsch1: has a more oval outline and about 40 narrow, 

threadlike ribs." (Adegoke, 1969, p. 98) 

Comments.-The holotype, a right valve, has a small umbonal 

angle and 22 subrounded scaly ribs with narrower interspaces bearing a secondary rib. The right anterior auricle has 6 ribs and a 

moderately deep byssal sinus. The valve is equilateral. 

Geog·ra.ph:1:c range.-Middle to southern California. 

Geolog·ic ·range.-Pliocene. 

Occu-rrence ·in Cal1'jon1.1:a.-Upper part of Etchegoin (Nomland, 

1917a), Ohlson Ranch (Peck, 1960), and San Joaquin (Adegoke, 1969) 

Formations. 

Chlamys bartschi (Arnold) 

Plate 6, figure 6 

Pecten (Chlmnys) ba.?·tsch?: Arnold. 1906, p. 107-108, pl. 41, fig. 3. 

Pecten (Pecten) ba:rtsch:1: Arnold. Grant and Gale, 1931, p. 168-169. 

On:m:na.l descn:pt·1:on.-"Adult shell averaging about 60 millimeters in altitude, somewhat shorter than high, convex, slightly inequilateral; base regularly rounded; margins smooth. Valves with about 

40 prominent (more or less unequal) narrow threadlike ribs, ornamented on top by numerous short imbricating spines; interspaces 

deep, narrow, and channeled; lateral areas rather narrow, perpendicular to disk, and slightly concave. Ears similar to those of P. 

'l:sla.ncl-icus." 

Holotype.-USNM 164841. 

Type local-!:ty.-South side of Light-House Point, north of wharf, 

Crescent City, Del Norte County, Calif. St. George Formation, 

Pliocene. 

Su.pplementa.?·y descr£pt1:on.-"Shell of medium size, with the 

shape and general characters of hasta.tus except that the byssal ear is 

somewhat longer and the primary ribs do not have the paired arrangement (if paired, it is because the primary ribs have split, and 

the ribs are twice as numerous), the primary ribs varying from 20 to 

25 in number, with sometimes prominent intercalaries appearing 

irregularly and increasing the number considerably, secondary 

riblets on the sides of the primaries sometimes developed, especially 

in the fewer ribbed varieties, main ribs each with a single row of 

short, stout prickles. 

"Dimensions: Altitude, 50 mm.; length, 45 mm.; length of hinge, 

27.5 mm.; convexity of the two valves, 23 mm." (Grant and Gale, 

1931, p. 168-169) 

Com.7Jarison.-"This species, of which only two or three rather 

poorly preserved specimens are known, is quite closely related toP. 

01Jnnt·ia., but is readily distinguishable by its much larger size when 

adult, lack of concentric constriction in the later stages of growth, 

and relatively shorter disk." (Arnold, 1906, p. 107) 

Comments.-The holotype is an incomplete valve; the auricles are 

·not preserved. It looks as though it was equilateral and higher than 

long. 

Geographic range.-Northern California. 

Geologic range.-Pliocene. 

Occurrence in California.-St. George Formation. 

Chlamys jordani (~rnold) 

Plate 6, figures 3, 7 

Pecten (Chlamys) jordani Arnold, 1903, p. 111, pl. 12, figs. 6, 7. 

Arnold, 1906, p. 114-115, pl. 44, figs. 1, 1a, lb. 

Pectenjordani Arnold. McLaughlin and Waring, 1914, pl. 1, fig. 49. 

Chlamys (Chlamys) rubidaJ·ordani (Arnold). MacNeil, 1967, p. 22, 

pl. 22, fig. 3; pl. 24, fig. 5. 

Chlamys (Chlamys) J·ordani Arnold. Hertlein and Grant, 1972, 

p. 191-192, pl. 30, fig. 10; pl. 32, figs. 5, 6, 10, 12, 13. 

Not Pectenjordani Arnold. I. S. Oldroyd, 1924, p. 55-56, pl. 28, figs. 

5, 6. 

Not Chlamys islandicus jordani (Arnold). Woodring, 1946, pl. 32, 

fig. 16. 

Not Chlamys rubidajordan~ (Arnold). Grau, 1959, p. 79-81, pl. 25. 

Original description. -"Shell of medi urn size, shape of P. hericeus, 

inequivalve, rather thin; right valve with twenty-five to thirty angular, smooth-topped, imbricated ribs, which become dichotomous 

after reaching a length of about 30 mm; interspaces deeply channeled and narrower than ribs; anterior ear imperfectly radially 

ribbed with six ridges, and showing elevated, concentric, incremental lines; posterior ear nearly obsolete, showing four ribs; byssal 

notch not deep; left valve shows twenty-five to thirty narrow, convex 

ribs, showing imbrications only slightly; inters paces as large as ribs; 

after ad iameter of about 30 mm has been reached by the shell, small 

· riblets appear in the widening interspaces; anterior ear shows five 

narrow, imbricated ridges, with wide interspaces; both valves show 

a tendency to contract suddenly at the basal m!lrgin upon nearing 

completion of growth; surface of both valves covered with a minute, 

lattice-like sculpture, which is generally worn off on exposed portions of the shell." 

Holotype.-USNM 162522. 

Type locality.-Deadman Island, San Pedro, Los Angeles County, 

Calif. San Pedro Formation, Pleistocene. 

Supplementary description.-"Typical specimens of Chlamys)·ordani are quite rare. The type specimen from beds of late Pliocene or 

early Pleistocene age at San Pedro, California, was described as 45 

mm high, 42 mm long; the umbonal angle approximately 95°. The 

. valves are sculptured with 25-30 ribs which become dichotomous 

·after reaching a length of about 30 mm. The ribs on the left valve are 

rather coarse and a short midrib appears in the inters paces after the 

valve has reached an altitude of about 30 mm. Both valves tend to 

contract toward the base. 

"One right and one left valve, the larger one 27.3 mm high, "'"'"'are 

smaller than the type of C.jordani and the ribs become dichotomous 

following a constriction of the shell when 20 mm high. One right and 

two small left valves, the largest one 17.5 mm high, "' "' "'develop a 

constriction when 16 mm high. The ribs and interspaces of all these 

valves are covered with very fine honeycomb-like reticulate 

sculpture. 

"One right and two left valves"'"'"' are typical of C. jordani except 

for their larger size. The right valve is 47 mm high and has two 

constrictions in shell growth, one at 30 mm, and one at 42 mm. One 

left valve 34 mm high has a constriction at 20 mm, the other is 42 mm 

. high (incomplete) and is gently contracted at a height of 29 mm. The 

ribbing on these left valves is dichotomous after the first constriction 

and, following this, the splitting of the ribs and the development of 
B26 PALEONTOLOGY OF CALIFORNIA AND BAJA CALIFORNIA 

strong riblets in the interspaces result in more numerous finer ribs. 

Another feature on these left valves is a decided depression on the 

anterior ear where it joins the disk." (Hertlein and Grant, 1972, p. 

192) 

Compan:son.-"Typical specimens of this species are higher than 

long and the general appearance is of a more slender shell than that 

of Chlamys rubida. As mentioned by Arnold, the right valve of C. 

jordani is similar to that of C. rubida but the ribs on the left valve are 

quite different. These reach to a height of about 20 to 30 mm, consist 

of simple nonfasciculated, moderately coarse ribs covered with fine 

lattice-like sculpture but with only slight concentric imbrication. 

"The smaller apical angle and consequently less elongate, less 

discoidal shape as well as the constriction followed by splitting of the 

ribs are characteristic features of C. jordani as shown on Arnold's 

illustrations of the type specimen. These shell characters, in otir 

opinion, differ sufficiently from those of the form described as kincaidi to justify separation of the two." (Hertlein and Grant, 1972, p. 

192) 

Chlamys jordani may be distinguished from the Miocene Japanese species Chlamys hataii "by the greater number of radial ribs 

(23 to 25), absence of intercalary threads in the right valve, lack of 

bifurcation of the radial ribs of the left valve." (Masuda and Akutsu, 

1956) 

Comments.-The holotype is a double-valved specimen and the 

valves are equilateral. The right valve has wide, closely spaced ribs 

that are all bifurcate near the ventral margin; a few bifurcate when 

the shell reaches a height of about 10 mm. The inters paces are much 

narrower than the ribs and do not bear interribs; imbricated 

microsculpture is preserved over the entire shell surface near the 

ventral margin. The right anterior auricle has five riblets, a rather 

shallow byssal sinus, and imbricated microsculpture; the left auricle 

is very small and bears four riblets and imbricated microsculpture. 

The left-valve ribs are smaller than the right, only a few are slightly 

bifurcate near the ventral margin, and interribs appear in most of 

the interspaces near the ventral margin. The left anterior auricle 

has seven riblets and imbricated microsculpture; the small left posterior auricle, four riblets and imbricated microsculpture. 

Geographic range.-Northern to southern California (MacNeil, 

1969, p. 22; Hertlein and Grant, 1972, p. 192). · 

Geologic range.-Miocene through Pleistocene. [Not a Holocene 

species (MacNeil, 1969, p. 22) as reported by some other authors 

(Oldroyd, 1924; Woodring, 1946; Grau, 1959).] 

Occurrence 1:n California.-Miocene and Pliocene: Purisima Formation (Arnold, 1906); Pliocene: Niguel (J. G. Vedder, written 

commun., 1978) and San Diego (Hertlein and Grant, 1972) Formations; Pliocene and Pleistocene: Fernando (Arnold, 1907b; Vedder, 

1960), Merced (Arnold, 1906), Rio Dell Formation, Wildcat Group 

(Faustman, 1964), Pico (Kundert, 1952), Santa Barbara (Arnold, 

1906), and San Pedro and Saugus(?) (Waterfall, 1929) Formations; 

Pleistocene: Anchor Silt (Rodda, 1957) and Timms Point Silt 

Member, San Pedro Formation (McLaughlin and Waring, 1914; A. 

Clark, 1931). 

Chlamys opuntia (Dall) 

Plate 6, figure 2 

Pecten (Chlamys) opuntia Dall, 1898, p. 707, pl. 29, fig. 6. Arnold, 

1906, p. 118, pl. 41, fig. 2. 

Chlamys (Chlamys) opuntia Dall. Hertlein and Grant, 1972, p. 

192-193, pl. 30, figs. 5, 6 [See for synonymy]. Vedder and Moore, 

1976, pl. 1, fig. 5. 

Original description.-"Allied toP. hericeus var. navarchus Dall, 

from which it differs by its smaller and not fasciculated radial ribs, 

more elongated anterior ear, more densely radially costate posterior 

ear, small size when adult, and by a tendency to be suddenly contracted at the basal margin on the completion of growth, somewhat 

as in P. pesfelis. Alt. 35 mm, lat. 32.5 mm." 

Holotype.-USNM 107752. 

Type locality.-Pacific Beach, San Diego, San Diego County, 

Calif. San Diego Formation, Pliocene. 

Supplementary description.-"Shell averaging about 35 millimeters in altitude, slightly shorter than high, subequivalve, equilateral 

(except for ears), both valves nearly flat until altitude of about 20 to 

25 millimeters is reached, when they grow more convex; contracted 

at basal margin when adult; sides only slightly concave above. Right 

valve with 40 to 60 subequal, narrow, imbricated, more or less 

dichotomous ribs, which are separated by channeled interspaces 

about equal in width to the ribs; hinge line about two-fifths as long as 

disk; anterior ear much produced, sculptured by about six prominent, sharply imbricated radials, and imbricating incremental 

lines; byssal notch quite prominent; posterior ear nearly obsolete, 

radially and concentrically sculptured; whole surface of disk and 

ears sometimes microscopically checkered or tessellated. Left valve 

similar to right." (Arnold, 1906, p. 118) 

"The fine, uniform, non-fasciculated radial ribs are quite different 

from any other west American Pliocene species." (Hertlein and 

Grant, 1972, p. 193) 

Comparison.-"Some authors have considered this species to be a 

member of the Chlamys islandica group. It somewhat resembles 

some fine-ribbed variants of that group but the San Diego fossil is 

easily separable by its finer, even ribbing, slightly smaller umbonal 

angle, generally smaller size and tendency to constriction toward 

the ventral margin of adult forms. These features serve to separate it 

from forms of C. rubida and its close relatives. 

"The ribbing and the umbonal angle of C. opunt1:a are similar to 

those features on C. hertleini Loel and Corey * * *. One decided 

difference in the two species is in the outline of the posterior ears. 

The posterior ears on C. opuntia slope obliquely downward from the 

. hinge line whereas those on C. hertleini are squarely truncated. 

"Chlamys tamurae Masuda and Sawada * * *, compared by its 

authors with C. opuntia, differs in that the surface of the left valve 

(and to a less degree the right valve) is folded forming low, broad 

corrugations. Furthermore, the illustration * * * shows that the 

major ribs are divided toward the ventral margin of the right valve, 

a feature only occasionally present on C. opuntia." (Hertlein and 

Grant, 1972, p. 193) 

Comments.-The fine, even ribbing on the shell of C. opuntia is 

distinctive. The holotype is a right valve complete except for a small 

portion of missing shell at the anterior dorsal edge of the anterior 

ear. The ribs on the disk have strong, slightly spinose lamellae and 

imbricated micrqsculpture. The anterior auricle has 7 lamellose 

riblets and a moderately wide byssal sinus; the posterior ear has 10 

or more fine, lamellose riblets. The shell is equilateral and of about 

equal length and height. 

Geographic range.-Middle California to Baja California Sur. 

Geologic range.-Miocene to Pleistocene. 

Occurrence in the Californias.-Miocene and Pliocene: Purisima 

Formation (Arnold, 1906); Pliocene: Almejas (Minch and others, 

1976), Lomita Marl Member, San Pedro (Woodring, 1946), Niguel 

(J. G. Vedder, written commun., 1978), and San Diego(Arnold, 1906; 

Hertlein and Grant, 1972) Formations, unnamed Pliocene strata on 

San Clemente Island (Vedder and Moore, 1976; Susuki and Stadum, 

1978); Pliocene and Pleistocene: Fernando (Arnold, 1907b; Moody, 

1916; J.D. Mount, written commun., 1971), Merced (Arnold, 1906), 

Pico (Winterer and Durham, 1962) and Saugus(?) (Waterfall, 1929) 

Formations. 
TERTIARY MARINE PELECYPODS: PROPEAMUSSIIDAE AND PECTINIDAE B27 

Chlamys hastata pugetensis (Oldroyd) 

Plate 6, figures I, 9 

P(~cten ·islo.nd·icus pugetenwis I. S. Oldroyd, 1920, p. 136, pl. 4, figs. 5, 

6. 

Pectm1. (Pecten) ha.sta.tus Sower· by variety pugetens1:s Oldroyd. Grant 

and Gale, 1931, p. 168. 

Chla.m.ys Jw.sta.to. 1n1.getenwis (Oldroyd). Grau, 1959, p. 90-91, pl. 30. 

Chla:m.ys ("Chlo:m.ys") 1mgetenwis (Oldroyd). MacNeil, 1967, p. 15, pl. 

22, figs. 4, 5. 

Chla.?nys P'l.l,getwn,<;'l:.<:: (Oldroyd). Roth, 1979, p. 257-260, pl. 2, fig. 9. 

On:m>nal desc·r£pt·ion.-"Shell much smaller than the typical C. 

'l:slo:nd·icus. Sculpture coarser in proportion to the size. Shell more 

elongate and the ribs spinose. Ribs 17, with a very fine one in the 

interspaces. Length, 29; height 31; diameter 11; hinge line, 16 mm." 

Holotype.:_CAS/SU 95 (missing and presumed lost.) 

'Type lowl·1:ty.-Off San Juan Island, Puget Sound, Wash. Holocene. . 

SIIP1Jlem.ento:ry desc·l"ipt·1:on.-"Shell rather small, averaging 33 

mm in height; higher than long and moderately convex, right valve 

more so than left. Hinge 1/2 to 2/3length of disk. Right valve with 17 

to 21 rounded fasciculate ribs, often arranged in pairs; riblets of 

fasciculi minutely spinose when not worn smooth; interspaces as 

wide as ribs or wider, with small riblets irregularly disposed; fine 

punctate sculptur·e covering disk. Anterior auricle moderately long, 

with 5 or 6 imbricated riblets, wide fasciole, rounded byssal notch 

and ctenolium of 5 to 7 teeth; posterior auricle quite small, obliquely 

truncated, and with 7 or 8oblique imbricated riblets. Left valve with 

fasciculated ribs more angulated and usually more profusely spinose; interspaces of varying width and with fine imbricated riblets 

irregularly disposed; punctate sculpture covering disk as in right 

valve; anterior auricle large, with shallow byssal sinus, 9 to 11 

imbricated riblets, and with small intercalary riblets often present; 

posterior auricle same as that of right. valve." (Grau, 1959, p. 90-91) 

"Anterior ears large; anterior ear of right valve may be very long 

and straight; byssal sinus may be well rounded or angulate. Anterior 

dor·sal mar·gin usually a little longer than posterior dorsal margin. 

Ribs usually show a weak differentiation into primary, secondary, 

and even tertiary series. Ribs of right vaive are bluntly rounded, but 

ribs of left valve tend to have a narrow rounded crest; small upright 

scales may be present. Primary ribs, and some other ribs, tend to 

become tr·ipartite near the margin by the addition of minor rib lets or 

ridges on the sides. The microsculpture is reticulate or metal lathelike and usually covers all the interspaces." (MacNeil, 1967, p. 15) 

"Chlo.m.ys pugetenwis shows considerable variation from place to 

place, but the characters of a given population are quite constant. 

The principal variables in a large lot of C. pugetensis ***are the 

extent to which concentric frilling obscures or interferes with the 

latticed microsculpture, the predominance on the left valve of cer- · 

tain (usually alternate) major radial ribs over others, and the degree 

to which major ribs on the right valve tend to fall in pairs. On some 

specimens the microsculpture appears to cease at or near a growth 

rest; on others it ceases on one part of the disk but continues outward 

on other parts as far as the margin." (Roth, 1979, p. 258) 

Compo:n:son.-"This subspecies is distinguishable from Chlamys 

hasto.to. and C. hasta.ta he?"ic?:a by its rib-structure, sculpture of disk, 

obliquely truncated posterior auricles and internal coloring; juveniles 12 mm in height or less are only distinguishable by the punctate 

sculpture of the disk." (Grau, 1959, p. 91) 

"Chlo.m.ys pugetenwis shows a greater tendency toward 'ledging'-

concentrically disposed breaks-in-slope associated with growth 

rests-than C. hastata or C. h. hen:cius, and the shell is more frequently irregular." (Roth, 1979, p. 258) 

Comments.-The valves of the specimen figured (pl. 6, figs. 1, 9) 

are equilateral but the anterior auricles are greatly enlarged in both 

height and length and the posterior auricles are greatly reduced. 

The right valve has 20 low r.ounded ribs covered with scaly, imbricated microsculpture and numerous fine ribs. The interspaces are 

narrower than the ribs and also have scaly interribs. The right 

anterior auricle has 7 riblets; the posterior auricle about 9. 'rhe left 

valve has 21 rounded ribs, every other one slightly higher than the 

rest, and all bearing secondary ribs and scaly imbricated microsculpture. The left anterior auricle has about 16 riblets with some 

· interspaces bearing a secondary riblet; the posterior auricle has 

about 10 riblets. 

Geographic range.-Living: Sitkalidak Island, off Kodiak Island, 

Alaska, to Newport Bay, Calif.; fossil: middle and southern California. 

Geolog1:c range.-PI iocene to Holocene. 

Occurrence in Califon~ia.-Piiocene and Pleistocene: Fernando 

Formation (J. D. Mount, written commun., 1971); Pleistocene: 

unnamed strata near PointAiio Nuevo, San Mateo County (MacNeil, 

1967). 

Habitat.-Low tide to 90 m; on rocks at minus tide, and in rocky, 

sandy, or muddy bottoms; often associated with algae; occasionally 

encased in sponge. 

Chlamys picoensis (Waterfall) 

Plate 7, figures I, 2 

Pecten ( Chlamys) ·islandicus picoensis Waterfall, 1929, p. 83-84, pl. 5, 

figs. 2, 4. 

Chlamys (Chlamys) picoensis (Waterfall). MacNeil, 1967, p. 28. 

Pecten (Chlamys) venturaensis Waterfall, 1929, p. 84-85, pl. 6, fig. 4. 

On:ginal description.-"Shell subcircular, somewhat longer than 

high; valve convex, equilateral except for ears; of medium thickness; 

sides slightly concave above; base evenly rounded; left valve with 

about 90 (at basal margin) prominent, square, flat-topped, imbricated, radiating ribs which multiply by division and by intercalation; interspaces generally narrower than ribs, channeled, and minutely reticulated; hinge line over half the length of the shell; 

anterior ear much produced, nearly twice as long as posterior, sculptured with eleven radiating ribs similar to those on disk; byssal 

notch distinct, rounded; posterior ear with about eight radiati'ng 

ribs; right valve very similar; judging from the similarity in the two 

valves of P. island1:cus." 

Holotype.-UCMP 31419; of venturaensis UCMP 31416. 

Type locality.-UC 7100. Ventura County, Calif. U11per part of 

Pico Formation, Pleistocene (may actually be from San Pedro Formation, Pleistocene); of venturaensis, UC 7097, Ventura County, 

CaJif. Upper part of Pico Formation, Pleistocene. 

Comparison.-"This differs from the living Pecten islandicus 

Muller by being relatively longer, and by having a greater apical 

angle." (Waterfall, 1929, p. 84) 

Grau (1959, p. 76) put C. picoensis in synonymy with C. rubida. 

MacNeil (1967, p. 28) considered C. picoensis to be more closely 

related to C. islandica than to C. rubida, and to be more intimately 

related to the Japanese forms C. chinkopensis Masuda and Sawada 

(1961), from the Pliocene, and C. kinoshitai Kubota (1950), from the 

Holocene. 

Hertlein and Grant (1972, p. 194) said that the radial sculpture on 

some valves of Chlamys rubida from the San Diego Formation is 

similar to that of C. picoensis. 

CO?mmints.-The holotype of C. picoensis is a right valve sculptured with moderately heavy, dichotomous rubs separated by 

interspaces that are half as wide and in which an interrib may 
B28 PALEONTOLOGY OF CALIFORNIA AND BAJA CALIFORNIA 

appear when the shell has reached a height of about 30 mm. Imbricated microsculpture is preserved in some of the interspaces. The 

right anterior auricle has four coarse ribs; the right posterior auricle 

five somewhat finer ribs. The ventral margin is strongly and 

abruptly turned in towards the body. 

The holotype of C. venturaensis is a left valve sculptured with 

rounded ribs narrower than the interspaces and in which an interrib· 

may appear when the shell is about 15 mm high. Imbricated microsculpture is preserved in many of the inters paces. The left anterior 

auricle has 9 riblets, the left posterior 7 of about equal size. 

Chlamys picoensis is equidimensional with a wide apical angle 

which distinguishes it from related species. It presumably does not 

occur in strata older than Pleistocene but is included here because of 

the doubt concerning the age of the type locality. 

Geographic range.-Southern California. 

Geologic range.-Pliocene? or Pleistocene. 

Occurrence in California.-Pliocene and Pleistocene: San Pedro(?) 

Formation (Waterfall, 1929); Pleistocene: upper part of Pico(?) 

Formation. 

Chlamys rubida (Hinds) 

Plate 7, figures 3, 5 

Pecten rubidus Hinds, 1844, p. 61, pl. 17, fig. 5. Not Pecten rubidus 

Martyn, 1784, nomenclatorially unavailable. [See Opinion 456, 

International Commission Zoological Nomenclature.] 

Pecten hindsii Carpenter, 1864, p. 606, 645. 

Pecten hericeus var. navarchus Dall, 1898, p. 708-709, new name for . 

Pecten rubidus Hinds, 1844. 

Pecten (Chlamys) hastatus Sowerby var. hindsii Carpenter. Arnold, 

1906, p. 111-112, pl. 43, figs. 1, 2, 2a. 

Pecten (Chlamys) rubidus Hinds. Palmer, 1958, p. 69-70, pl. 3, figs. 

4-6. 

Chlamys rubida (Hinds). Grau, 1959, p. 76-79, pl. 24. 

Chla,mys (Chlamys) rubida (Hinds). MacNeil, 1967, p. 21-22, pl. 20, 

figs. 7, 9; pl. 22, figs. 7, 8. Hertlein and Grant, 1972, p. 193-195, 

pl. 35, figs. 6, 8. 

On:g1:nal description.-"Testa subtrigono-orbiculari, inaequaliter 

duplo-convexa, inaequiauriculata subtenui; valva sinistra convexa, 

costis parvis numerosissimis, serratis, in fasciculos duarum triumve 

,alternate aggregatis, rufis, interstitiis, pallescentibus; valva dextra 

subconvexa, albida, costis majusculis, aggregatis; auriculus sulcatis, postica parva, obliqua; intus alba." (rubidus) 

"'Pecten rubidus, Hds.' Vane. Is:, Lyall. [Hinds's type in Br. Mus. 

appears the ordinary form, of which P. hastatus = hericeus is the 

highly sculptured var. This shell, which is more allied to Islandicus 

may stand asP. Hindsii.] * * * 

"Pecten (?var.) Hindsii. Broader; ribs close, small, smooth, bifurcating. Passes from hastatus towards Jslandicus." (hindsii) 

Holotype.-Missing and presumed lost (Palmer, 1958, p. 70); three 

para types are present (MacNeil, 1967, p. 22), in the British Museum 

of Natural History; of Pecten hindsii, missing and presumed lost. 

Type locality.-Alaska at a depth of 60 m, Holocene; of Pecten 

hindsii, Vancouver Island, B.C., Holocene. 

Supplementary description.-"The original illustration of Pecten 

rubidus is that of the exterior of a left valve, the ribs of which are 

fasciculated and crossed by fine concentric imbrications. 

"The right valve of C. rubida is sculptured with about 26 radial 

ribs which are wider than the interspaces, flattish-topped, smooth, 

and usually dichotomous. The interspaces are narrow, channeled, 

and sculptured with fine reticulate honeycomb-like tesselations. The 

left valve is sculptured with narrow, fasciculated ribs which are 

crossed by fine concentric imbrications, the interspaces are sculptured similar to those on the right valve. The ribs on the right valve 

increase by bifurcation, those on the left, at later stages of growth, by 

intercalation. The sculpture of this species is quite variable. 

"Recent specimens of C. rubida are often about 60 mm high but we 

have seen fossil specimens 70 mm high." (Hertlein and Grant, 1972, 

p. 194) 

"Adult specimens averaging 50 millimeters in height and slightly 

higher than long; left valve more convex than right, and hinge line 

about half length of disk. Right valve with extremely variable rib 

structure; 21 to 28low, smooth, broad and rather flat primary ribs, 

becoming dichotomous at about 10 to 15 mm from hinge line and 

occasionally imbricated near ventral margin; ribs frequently narrower, obscurely fasciculated and almost entirely imbricated. Riblets often develop in interspaces, usually starting at 15 to 20 mm 

from hinge margin and occasionally imbricated. Interspaces narrower than ribs and with minute reticulations present in either 

upper or lower portion or throughout. Anterior auricle large and 

with 6 or 7 riblets having fine concentric imbrications; byssal notch 

prominent, and ctenolium of 5 to 7 teeth. Posterior auricle small, 

with 8 to 11 small spinose riblets; hinge margin tapering gently 

downward from beak. Left valve also variable in rib structure; 

primary ribs simple at first, later fasciculated; each fascicle consisting of three (occasionally two) imbricated ridges, often worn smooth 

at maturity; imbricated secondary rib usually present in center of 

each interspace, often flanked by two very small rows of spines. 

Interspaces wider than ribs and minutely reticulated from umbo to 

center of disk. Anterior auricle large and with moderately deep 

byssal notch; 10 to 12 small rib lets with nearly as many intercalaries, 

all imbricated. Posterior auricle small, hinge margin tapered as in 

right valve; 10 to 15 fine imbricated riblets ***margin delicately 

fluted." (Grau, 1959, p. 78-79) 

Comparison.-"Typical specimens of C. rub?:da differ from C. 

islandica in the generally smaller size, often less numerous primary 

ribs, and especially in the smaller posterior ears. 

"The shell of C. rubida differs from that of C. jordam: in the 

fasciculate rather than simple ribs on the left valve, usually the lack 

of honeycomb-like tesselation on the tops of the ribs, and usually 

greater size. 

"According to Palmer the type specimens of both P. rub?:d,us and P. 

hindsii cannot be found. Considerable variation in sculpture is 

revealed in a series of specimens of this species complex and the 

relationship of the two is not definitely known at the present time. 

The specimens identified by Carpenter as "Pecten h1:nds1:1:," illustrated by Palmer, furnish some justification for retaining this form 

as a subspecies of C. rub1:da and this interpretation of Carpenter's 

species was proposed by MacNeil (1967). The two forms apparently 

represent extreme variants in the fine and coarse character of the 

ribs. The variation in sculpture of the fossils from the San Diego 

Formation is such that we assign to them the earliest name proposed 

for this group, at least until the relationship of the variants of this 

species complex is better known. . 

"The larger shell and flattish radial ribs on the right valve which 

are broader than their inters paces are features separating C. rubida 

from C. imanishii Masuda and Sawada * * * which was described 

from beds of Pliocene age in Japan." (Hertlein and Grant, 1972, p. 

195) 

Geographic range.-Living: Bering Sea to Monterey, Calif.; fossil: 

Alaska to southern California. 

Geologic range.-Miocene through Holocene. 

Occurrence in Calijornia.-Miocene and Pliocene: Etchegoin 

(Nomland, 1917a), Purisima (Arnold, 1906), and Towsley (Winterer 

and Durham, 1962) Formations; Pliocene: Lomita Marl Member, 

San Pedro Formation (Woodring, 1946), Niguel (J. G. Vedder, written commun., 1978), Ohlson Ranch (Peck, 1960), and San Diego 
TERTIARY MARINE PELECYPODS: PROPEAMUSSIIDAE AND PECTINIDAE B29 

(Hertlein and Grant, 1972) Fo.rmations, and unnamed strata on San 

Clemente Island (Vedder and Moore, 1976); Pliocene and Pleistocene: Fernando (Arnold, 1907a; Willett, 1946), Merced (Arnold, 

1906), Pico (Winterer and Durham, 1962), San Pedro (Woodring, 

1946), and Saugus (Kew, 1924) Formations; Pleistocene: Timms 

Point Silt Member, San Pedro Formation (A. Clark, 1931). 

· Ha.lrita.t.-Usually found off rocky shores. Shell usually encased in 

one of two species of symbiotic sponge: most often Ectyodo?'1JX pa.Ta.-

wl:t·l:ca. (Lambe). but occasionally Myca.le a.dheTens Lambe. Both species of sponges are said to live only on Chla.mys ntbida., C. Tubida. 

.io·rda.n:1:, C. ha.sta.ta.. C. lw.sta.ta. hen:c1:a and C. h.a.sta.ta. pugeten.c:n:s, and 

to be the only species of sponge so restricted. Large barnacles, up to 

25or 30 mm in altitude, are often attached. Just below low tide to 185 

m, possibly deeper. (Grau, 1959; Hertlein and Grant, 1972) 

Chlamys anapleus Woodring 

Plate 7, figures 4, 6 

Pecten (Chla.m.ys) ho.sta.tus Sowerby var. st1·a.tegus Dall. Arnold, 

1906, p. 113, pl. 44, figs. 2, 2a, 3. 4. Not Pecten hen:ceus var. 

stnt.tegus Dall, 1898. 

Chla.m.y.~ a.na.pleus Woodring, 1946, p. 81. pl. 34, fig. 15. 

On:gino.l desc·n:pt·ion.-"The new name Chla:mys a.na.pleus ***is 

proposed for a small Chla.m.ys represented by a valve from the 

Lomita marl*"'* and another from the San Pedro sand***. It has 10 

or 11 wide primary ribs, a weak secondary riblet in most of the 

interspaces. and is sculptured with microscopic punctuation. The 

ventral margin of the type is bent, perhaps to form at a later stage a 

swelling, as in C. 7Ja.nnelee1:. On the imperfect Lomita specimen· 

some of the ribs are grooved. This Chla.?nys also might be considered 

a form of the C. '1:sla.nd·1:cus group at the opposite extreme from C. 

07nt.nt·1:a. in width of ribs. It was identified by Arnold as Pecten 

(Chla:mys) lw·n:ceus var. stm.tegus. 'P.' st?·a.tegus, from Alaska, is 

considered a synonym of C. ·isla.ndicus ben>nm:a.nus, a wide-ribbed 

A la.skan variety of C. 'l:sla.nd·icus. The ribs of C. a.napleus do not 

enlarge so rapidly as in C. 1:sla.nd1:cus be1·1:ng1:a.nus, and secondary 

t•ibs are weak or absent. The Pliocene C. pa.nnelee1: and its close 

Pliocene relative C. etchego·in:1: have only half as many primary ribs. 

C. a.na.7Jleus is not known to be living." 

Holotype.-USNM 498642. 

Type loca.t-~:ty.-USGS 12530. Los Angeles County, Calif. Basal 

part of San Pedro Sand, Pliocene. 

Ccnnments.-Chla:m.ys a.na.pleus is higher in proportion to length, 

the ribs are smaller on the disk, the right-valve ribs are not bifurcate, and fewer and weaker secondary ribs are present in the interspaces than in Chlmnys beh:n:ng·ia.na (Middendorf), a species living 

in Alaska. These two species somewhat resemble Na.na.ochla.mys in 

sculpture. 

Georrra.ph:ic ·ra.nge.-Southern California. 

Geolom:c ,.,·a.nge.-Pliocene to Pleistocene. 

Occ·u.rrence ·1:n Ca.l?jon1.1:a..-Pliocene: Lomita Marl Member, San 

Pedro Fot·mation: Pliocene and Pleistocene: San Pedro Sand (Woodt·ing, 1946). 

Genus CHLAMYS? 

Chlamys? mediacostata mediacostata (G D. Hanna) 

Plate 7, figure 7 

Pecten ·rnecha.costo.tus G D. Hanna, 1926a, p. 472, pl. 22, fig. 6; pl. 24, 

fig. 2. Mansfield, 1932, p. 46, pl. 16, fig. 2. 

L?J'I'01Jectennl.echa.costo.tu.s(Hanna). Durham, 1950, p. 65, pl. 7, fig. 4. 

On:m:na.l descn:pt·1:on.-"Shell small, altitude a little greater than 

length, equilateral and equivalve, not noticeably inflated. Surface 

sculptured with· 23 (in the type specimen) ribs which are regularly 

rounded and are largest in the center of the valve. These ribs are 

strong at the ventral margin of the shell but are scarcely visible 

within 18 mm. of the beak; interspaces occupied· by riblets, one to 

each, about one-third the size of the major ribs; in the better preserved specimens there is a fine even concentric sculpture of lirulae 

looped over the ribs, appearing as though cut with an engraving tool; 

anterior ear marked with five (in cotype) radiating rib lets while the 

posterior (in the type) is smooth except for fine even concentric 

sculpture. Measurements of type specimen, a single right ,valve, 

altitude 37.2 mm.; length 30 mm. (slightly compressed longitudinally); thickness 8.5 mm." 

Holotype.-CAS 1830. 

Type loca.lity.-CAS 681. Imperial County, Calif. Imperial Formation, Miocene or Pliocene. 

Compa1·ison.-"There is only one west coast species with which 

the sculpture of this can be compared, Pecten estTella.nus (Conrad) of 

Miocene and lower Pliocene strata. That species is more inflated, 

longer than high, and the ribs extend entirely to the beak; moreover, 

the ribs are squarish and interspaces channeled on each side of the 

smaller riblet." (G D. Hanna, 1926a, p. 472) 

"Pecten 1:nteTl1:nea.tus aide1: Harris * * *from the Miocene of Venezuela is closely related but may be distinguished by the much heavier interribs in the interspaces." (Durham, 1950, p. 65) 

Chla.mys mediacosta.ta. g1·ewingk1: Hertlein differs from Chlamys 

med1:a.costa.ta. med1:a.costa.ta. in having fewer ribs (17 or 18 rather 

than 23 or 24) and in the smaller apical angle. (Hertlein, 1966a, p. 

276) 

Comments.-Although the secondary sculpture of a riblet bordered by deep grooves and filling the interspace is similar to LyTopecten, this species is assigned to Chla.mys? on the basis of its hinge, 

outline, and small umbonal angle. 

GeogTa.ph1:c Tange.-Southern California to Baja California Sur. 

Geologic Ta.nge.-Miocene to Pliocene. 

OccuTTence in the Ca.l1fonn:as.-Miocene or Pliocene: Imperial 

Formation; Pliocene: Boleo (Stump, 1979) and San Marcos Formations (Durham, 1950). 

Chlamys? mediacostata grewingki (Hertlein) 

Plate 7, figure 8 

Chla.mys mediacosta.ta gre101:ngk1: Hertlein, 1966, p. 276, 278, fig. 12. 

OTig1:na.l descn:ption.-"Shell, a right valve, higher than long, 

nearly equilteral, gently convex; with about 17 or 18low, rounded, 

radial ribs widest at the middle of the ventral margin and sep::trated 

by interspaces narrower than the ribs; surfaces of the ribs with 

traces of concentric imbricating lines of growth which loop upward; 

each interspace on the ventral half of the shell with a well developed 

riblet; the ears are imperfectly preserved but the direction of the 

lines of growth on the posterior ear indicate a nearly square truncated posterior margin, a well developed notch is present under the 

. remnant of the anterior ear. No sculpture is visible on the ears; if 

originally present, it has been eroded. Dimensions: length 34.2 mm., 

height 39.6 mm., apical angle 81.5°." 

Holotype.-CAS 12812. 

Type loca.t?:ty.-CAS 39413. Rancho El Refugio, Baja California 

Sur. Salada Formation, Pliocene. 

Pecten (Ly1·opecten) tmm:a1m:ens1:s Mansfield (1932, p. 47, pl. 1b, 

figs. 3, 5) has the same secondary sculpture as C.? g1·e~m:ngk1: and has 

been placed in "Chla.mys" (Judith T. Smith, oral commun., 1979). 

Comparison.-"The shell of this new subspecies bears a decided 

resemblance to Pectenmediacostatus Hanna***. It differs from that 
B30 PALEONTOLOGY OF CALIFORNIA AND BAJA CALIFORNIA 

species in the less nu-merous ribs (17 or 18 rather than 23 or 24) and in 

the narrower apical angle. All the specimens of C. mediacostata in 

the collections of the California Academy of Sciences, many rather 

imperfectly preserved, have more numerous ribs than the present 

specimen." (Hertlein, 1966, p. 276) 

Comments.-The holotype is a small (length 35 mm; height 40 

mm), flat, moderately thick shelled right valve with about half of the 

anterior auricle missing. The interspaces are almost completely 

filled by the secondary rib lets, but the rib lets are separated from the 

primary ribs by deep grooves. On the basis of the holotype only, this 

species is assigned to Chlamys?. The secondary sculpture of a riblet 

filling the interspace distinguishes C.? grewingki from other described Tertiary species of Chlamys described from the western 

United States, except C.? mediacostata; this sculpture is found on 

some species of Lyropecten. 

Geographic range.-Baja California Sur. 

Geologic range.-PI iocene. 

Occurrence in Baja Calijorn1:a Sur.-Salada Formation. 

Genus LEOCHLAMYS MacNeil 

Leochlamys MacNeil, 1967, p. 9-10. 

Type species.-Chlamys (Leochlamys) tugidakensis MacNeil, Pliocene, Alaska. 

Original description.-"Shell of medium to moderately large size, 

moderately inflated, right valve more inflated than left valve; elongate dorsoventrally. Ears moderately large; recessed, the dorsal 

slope wider on left valve, anterior ear of right valve elongate and 

narrow, byssal sinus wide and deep with a moderately strong ctenolium. Ribs strong on both valves, interstitial ribs; present or absent; 

weakly to very strongly scabrous; many ribs have thick curved 

spines. Microsculpture reticulate or metal lathelike in juveniles, 

particularly on left valves, but consisting of fine continuous closely 

set raised lirations with a fanlike pattern in adults. Provinculum 

broad and gaping, extending nearly to the end of the ears; crurae 

moderately strong and weakly inclined. Muscle scars and umbonal 

callus inconspicuous. 

"The most distinguishing characters of Leochlamys are its long 

anterior ear, its deep, broad byssal notch, and its coarse, usually 

spiny ribs." 

Geologic range.-Jurassic(?); Oligocene through Holocene. 

Habitat.-In temperate and cool seas; perhaps some attach to 

rocks and stones by means of their spines. (MacNeil, 1967, p. 9, 10) 

Genus LEOCHLAMYS? 

Leochlamys? columbiana (Clark and Arnold) 

Plate 8, figure 3 

Pecten columbianum Clark and Arnold, 1923, p. 139, pl. 23, figs. 1, 2. 

Pecten (Chlamys) columbiana Clark and Arnold. Weaver, 1942, p. 

84, pl. 15, fig. 3; pl. 16, fig. 1. 

Original description.-"Shell fairly large, height greater than 

length, dorsal slopes long and straight; apical angle less than 90 

·degrees, ears prominent, anterior ears about a third longer than 

posterior. Anterior right ear long and narrow, sculptured by four or 

five fairly heavy radiating ribs with interspaces slightly less than 

width of ribs; byssal notch deep and broad and on its dorsal edge are 

a number of fairly prominent ctenidial teeth, ten of these teeth on 

type. Posterior ear broad; four heavy radial ribs on posterior ear of 

type with interspaces somewhat wider than width of ribs with a 

finer riblet in at least two of interspaces. Main surface of shell 

sculptured by about 24 bifurcated fairly heavy, round radiating ribs 

which are slightly less prominent near the dorsal margins and tend 

to pair, each pair separated by a wider interspace than that separating the individual members of pair; most of these pairs might be 

described as individual bifurcating ribs, the bifurcation taking 

place well up toward the beaks; some of the pairs, however, may be 

traced as distinct ribs up to the beaks. Irregularity of interspacing 

between pairs is noticeable and some of the individual ribs are 

bifurcated. Fine interrib in some inters paces. Surface of shell sculptured by fairly heavy concentric lines of growth which produce 

rather coarse imbrications where they cross ribs. Imbrications 

probably appeared as spines on uneroded specimens. Left valve 

unknown. Dimensions of type specimen (smaller of two specimens 

figured): Height 82.5 mm.; length probably about 75 mm.; length of 

hinge line about 47 mm. Dimensions of cotype: Height 96 mm.; 

length about 85 mm." 

Holotype.-UCMP 30056. 

Type locality.-SV 130. Vancouver Island, British Columbia. 

Sooke Formation, Oligocene and Miocene. 

Comparison.-Leochlamys? columbiana is very similar to L.? pm·-

terensis Weaver but the character of the ribbing is quite different in 

the details of the bifurcations and spacing; on L.? porteTen.'n:s the ribs 

are finer and more numerous along the dorsal margins. The ribs on 

the ears of L.? poTterensis are finer and more numerous, and the 

concentric lines of growth are finer, the result being a much more 

finely imbricated surface. (Clark and Arnold, 1923, p. 139) 

Comments.-The holotype is a very thick shelled right valve, lacking the anterior auricle and most of the disk. The ribs are large, 

subrounded, ·and lamellose. The preserved portions of the valve 

indicate it was inequilateral. The anterior auricle is missing, but 10 

ctenolial teeth are preserved. The right posterior ear has 5 large 

riblets and 2 small ones. 

Geographic range.-British Columbia; southern California. 

Geologic range.-Eocene to Miocene. 

Occurrence in Calijornia.-Eocene and Oligocene: San Emigdio 

(Eocene and Oligocene) and Pleito (Oligocene) Formations, undifferentiated (Hammond, 1958). 

Leochlamys? erici (Wiedey) 

Plate 8, figures 1, 2 

Pecten (Chlamys) erici Wiedey, 1928, p. 137-138, pl. 16, fig. 1. 

Original description.-"Shell of large size, subovoid in outline, 

subequivalve and equilateral, moderately inflated, with the right 

valve apparently the more convex. The anterior dorsal margin is not 

long and is straight to the extremity, where it is rounded to the basal 

margin. The latter portion of the shell is evenly and regularly 

rounded. Posterior dorsal extremity a little more sharply convexly 

curved than the corresponding anterior portion. Posterior dorsal 

margin short and nearly straight, or slightly concave in outline. 

Umbones narrow and very convexly inflated. The sculpturing on the 

left valve consists of about thirty prominent ribs, which are rounded 

and closely spaced. They curve irregularly anti a few divide near the 

basal margins of the shell. The ribs exhibit incremental sculpture 

only near the basal margins of the disk. The right valve appears to 

have a few less ribs but is similarly sculptured. The anterior ear is 

small; the posterior ear is the more extended. The umbonal angle is 

less than 90 degrees. Length, 58 mm.; breadth, 65 mm.; thickness of 

the attached valves, about 20 mm." 

Holotype.-SDNM 27. 

Type locality.-SU 406. Ventura County, Calif. Vaqueros Formation, Oligocene and Miocene. 

Comparison.-"Among the fossil Pectens this new species is most 

closely resembled by P. sespeensis, var. hydei Arnold, but the latter 

is distinctive in possessing much longer anterior and posterior dorsal margins, which form a smaller umbonal angle. The varietal form 
TERTIARY MARINE PELECYPODS: PROPEAMUSSIIDAE AND PECTINIDAE B31 

is sculptured by nearly ten less ribs which are more subequal. The 

characteristic paired ribbing of P. sespee?tS'I:s Arnold, about nine 

pairs in all, readily serves to distinguish it from the new species, 

which shows many more individual ribs." (Wiedey, 1928, p. 138) 

Com:ments.-The holotype is an incompletely preserved doublevalved specimen. It may have been equilateral and it is somewhat 

higher than long. The right valve has coarse, subrounded ribs, some 

of them bifurcated. The inters paces are narrower than the ribs, and' 

some of them have an interrib. 

Geom·a.ph:1:c ·m:nge.-Southern California. 

Geolom:c ·mnge.-Oligocene to Miocene. 

OccwTence ·1:n Ca.l?jO?·m:a.-Vaqueros Formation. 

Genus NANAOCHLAMYS Hatai and Masuda 

Differs from Sunjto1Jecten. in having more numerous, bifid ribs, 

shorter anterior auricle, and more rounded outline. 

Geortrn1Jh:ic ra:nge.-Japan; California. 

Geolom:c ·ra:nge.-Oligocene to Pleistocene. 

Co·m:nwnts.-This genus is here reported for the first time, outside 

of Japan, and is represented by the species Nanaochlamys nutter?:. 

Chlmnys ·isla.nd1:ca beh:n:nm:ana (Middendorf) of Grau (1959, pl. 23, 

fig. 2) and Chlamys (Chlmnys) be?"inm:ana (Middendorf).of MacNeil 

(1967, pl. 23, fig. 3) also bear a marked resemblance to Nanaochla:mys, and, to a lesser extent. so does Chla:mys anapleus Woodring. 

Grant and Gale (1931. p. 174) reported N. nutte-ri from the Pliocene 

of Japan, synonymizing Pecten hete·roglyptus Yokoyama (1926, p. 

304, pl. 33, figs. 1-6). 

Nanaochlamys nutteri (Arnold) 

Plate 8, figures 4, 5 

Pecte·n (Chla:mys) 'lmtten: Arnold, 1906, p. 67-68, pl. 11, figs. 3, 4, 4a. 

Pecte·n n:utten: Arnold. Arnold, 1909, p. 160, pl. 27, figs. 3, 4. 

Pect(fn etche{JO'I:n:l: var. n:utten: Arnold. Nom land, 1917a, p. 219, pl. 7, 

figs. 4, 5: pl. 8, figs. 2a, 2b. 

Pecten (Pnll-1>um.) S'1.mjt·1: Bernard variety nutten: Arnold. Grant and 

Gale, 1931, p. 174. 

}Jecten (S'I.Injtopecten) etchegm:m: Anderson subsp. watt.<n: Arnold. 

Faustman, 1964, p. 116, pl. 2, fig. 1; not Pecten (Chlamys) watt.'n: 

Arnold, 1906. 

Orig·inal desc·ript1:on.-"Shell averaging about 65 millimeters in 

altitude, slightly higher than long, inequivalve, equilateral, more or 

less ventricose, and often showing several constrictions or undulations of interrupted growth; margins somewhat coarsely serrate; 

base regularly rounded; sides straight, and forming an acute angle 

at the umbo. Right valve with about 8 to 10, unequal, rather prominent, flat-topped ribs, each of which is channeled by one or more 

deep, narrow, concave sulcations which divide the primary rib from 

umbo to margin into two or more generally unequal but evenly 

convex riblets; interspaces somewhat narrower than the ribs, and 

containing from 1 to 3 prominent rounded rib lets; the rib lets become 

more numerous and the major ribs less prominent anteriorly and 

posteriorly; the minor sculpture consists of squamose lines of 

growth, which are more prominent on the ribs, and beautiful 

microscopic checkered tessellation which is best developed in the 

major and minor interspaces; hinge line from two-fifths to nearly 

one-half length of disk; anterior ear prominent and sculptured by 5 

or 6 elevated radiating ridges and imbricating concentric lamellae; 

byssal notch moderately deep; posterior ear rectangularly truncated, a little less than one-half length of anterior, and similarly but 

less prominently sculptured. Left valve with unequal, rather narrow, convex ribs, the alternate ones being more prominent than 

those intermediate; extremities of the ribs sometimes ornamented 

by longitudinal riblets; inters paces of about equal width to the ribs, 

. and ornamented by one or three alternately prominent intercalaries; 

surface sculptured by imbricating incremental lines; the constric-

. tions, when present, are more pronounced in this valve; ears sculptured similarly to those of the right valve. Hinge with a pair of 

prominent cardinal crura adjacent to the umbonal pit in the right 

valve." 

Holotype.-CAS/SU 6. 

Type locality.-South 0.8 km of mouth of San Gregorio Creek, 

Santa Cruz quadrangle, San Mateo County, Calif. Purisima Formation, Pliocene. 

Comparison.-"This species is allied toP. parmeleei and P. wattsi 

but is distinguishable by having a larger number of ribs, which are 

also narrower and more coarsely radially sculptured. The Miocene 

forms of P. nutteri have more prominent and deeply sulcated ribs on 

the right valve, are generally more convex and more prominently 

constricted, and have relatively longer posterior ears than the later 

forms." (Arnold, 1906, p. 68) 

Comments.-The holotype of N. nutteri is strongly and crudely 

sculptured. The ribs preserved on the right valve are deeply and 

almost evenly bifurcated and some of the inters paces have one or two 

interribs. The right anterior auricle is broken but seems to have 

been large, perhaps with only a shallow byssal sinus, and sculptured 

with moderate ribs. The right posterior auricle is also broken but 

·was perhaps only one-fourth as long as the right anterior auricle. 

The left valve is more strongly and crudely sculptured than the right 

valve. The ribs are unevenly and shallowly divided into two or three 

parts, and no consistent pattern is apparent on the preserved shell. 

The median rib and the secondmost ribs toward the dorsal and 

ventral margins are elevated above the others, similar to Vert?:-

pecten. Preserved barnacles are attached to the left valve. 

Geographic range.-Middle to southern California. 

Geologic range.-Miocene to Pleistocene. 

Occurrence in Calijornia.-Miocene: unnamed strata near Mount 

Hamilton; Miocene and Pliocene: Etchegoin (Nomland, 1917a; 

Woodring and others, 1940) and Purisima (Arnold, 1906) Formations; Pliocene: San Joaquin Formation (Adegoke, 1969); Pliocene 

and Pleistocene: Merced Formation (Arnold, 1906) and Rio Dell 

Formation, Wildcat Group (Faustman, 1964). 

Genus AEQUIPECTEN Fischer, 1886 

Differs from Chlamys in more rounded outline, nearly equal auricles, smaller byssal notch, fewer, usually not bifurcating radial ribs, 

and flattened, marginally pointed internal riblets near margin; pair 

of cardinal crura and auricular denticles (or weak auricular crura) 

present. Argopecten has more highly inflated valves, no secondary 

radial riblets, and large auricles. Argopecten also has concentric 

sculpture in looped lamellae and a tendency to oblique growth in 

adult stage, additional characters that separate it from Aequipecten. 

Geologic range.-Jurassic(?); Cretaceous through Holocene. 

Aequipecten dallasi (Jordan and Hertlein) 

Plate 9, figures 10, 12 

Pecten (Chlamys) dallasi Jordan and Hertlein, 1926, p. 213, pl. 23, 

figs. 2, 5, 6, 8. Grant and Gale, 1931, p. 169-170. 

Chlamys dallasi (Jordan and Hertlein). Durham, 1950, p. 65; pl. 6, 

fig. 2. 

Original description.-"Shell of medium size, moderately thick, in 

several specimens with strong lines of restricted growth; valves 

mildly arched, and slightly extended posteriorly; hinge line a little 
B32 PALEONTOLOGY OF CALIFORNIA AND BAJA CALIFORNIA 

over half the total length of the disk. Right valve ornamented by 

about 15 to 19 almost flat-topped radiating ribs, separated by 

siightly rounded interspaces almost as wide as the ribs, the summit 

of the ribs smooth, the sides and interspaces sculptured by fine, 

sharp, subequal radiating ridges and grooves, the shoulder of each 

rib on either side marked by a deeper groove; anterior dorsal and 

posterior dorsal areas of disk smooth; ears unequal, the anterior with 

a well developed byssal notch and sculpture consisting of about six 

radiating rib lets crossed by concentric lines of growth; posterior ear 

obliquely truncated behind, and ornamented by four or five radiating rib lets between which the inters paces bear fine incised radiating 

lines. Left valve sculptured much as right; anterior dorsal and posterior dorsal margins of disk sloping more abruptly to base of ears 

than on right valve; anterior ear indented by a rounded byssal notch 

and ornamented by five radiating rib lets between which are minute 

sharp radiating grooves; posterior ear obliquely truncated and 

sculptured much as anterior, the radiating riblets, however, much 

more subdued and less prominent. Height 42 mm.; length 43 mm.; 

diameter 13 mm.; apical angle approximately 105°." 

Holotype.-CAS 1862. 

Type locality.-Canons 1.5 or 3 km from Punta San Antonio, east 

coast of Baja California Sur. Salada Formation, Pliocene. 

Supplementar-y descr-iption.-"Pecten dallasi is easily recognized 

by the peculiar minor radiating sculpture superimposed on the 

major ribs and interspaces. The number of ribs varies considerably,· 

as does the obliquity of the valves." (Jordan and Hertlein, 1926a, p. 

214) 

Cmnpar-ison.-"This species resembles somewhat P. islandicus 

var. k1:ncaidi, and P. sancti-ludovici, but is distinguished by greater 

length, shallower ears, shallower byssal notch, and regular ribs with 

superimposed striations. It approaches closely the typical form of 

Aeqw:pecten, and should, perhaps, be assigned to that subgenus." 

(Grant and Gale, 1931, p. 170) 

Comments.-The holotype is subrounded in outline and slightly 

oblique, with nearly equal auricles and no bifurcated ribs. The 

byssal notch is extremely small. Aequipecten dallasi differs from 

Chlamys sanctiludovici in being less inflated, in having a more 

rounded outline, less elongate and more finely sculptured right 

anterior auricle, and a less elongate left anterior auricle. 

Geogr-aphic range.-Baja California Sur to Mexico. 

Geologic r-ange.-PI iocene. 

Occur-r-ence in BaJ·a Califor-nia Sur-.-Carmen (Durham, 1950), 

Gloria (Stump, 1979), and Salada Formations. 

Genus ARGOPECTEN Monterosato, 1889 

Auricles about equal in length, right anterior with distinct byssal 

notch; concentric sculpture in looped lamellae well developed in 

interspaces, rarely projecting strongly over radial ribs; tendency to 

oblique growth in adult stage. Differs from Aequipecten in having 

more highly and nearly equally inflated valves that usually lack 

secondary radial riblets and that have larger auricles. 

Geologic r-ange.-Miocene through Holocene (table 7). 

Habitat.-Living in tropic, subtropic, and warm temperate seas 

(Hertlein, 1969, p. N357). 

For a discussion of Tertiary species of A r-gopecten in eastern North 

America, see Waller (1969). 

Argopecten diminutivus (Hertlein and Jordan) 

Plate 9, figures 3, 6 

Pecten (Plagioctenium) diminutivus Hertlein and Jordan, 1927, p. 

623-624. 

Pecten (Plagioctenium) calli Hertlein, 1925a, p. 16, pl. 4, figs. 5, 7. 

Not pl. 4, fig. 6. 

Or-iginal descr-iption.-"She1Lsmall, right valve fairly flat and 

ornamented by 16 flattish topped to broadly rounded ribs which are 

separated by flattish bottomed interspaces which are very slightly 

narrower than the ribs; right ear well developed with strong byssal 

TABLE 7.-Geologic and geogr-aph1:c distr-ibution of the genus Argopecten in the 

easter-n Pac1jic r-egion 

[H =Holocene; Pie= Pleistocene; PI= Pliocene; M =Miocene] 

California 

Species Middle Southern 

Genus A r-gopecten: 

abietis abbott?: (Hertlein and Grant) ..... . Pl,Ple 

abietis abietis (Jordan and Hertlein) ... . antonitaensis (Durham) ........................... . callidus (Hertlein) ..................................... . Pl,Ple 

cir-cular-is br-amkarnpi (Durham) ......... . MorPl 

cir-cular-is calli (Hertlein) ....................... . cir-cular-is cir-cular-is (Sowerby) ............. . ciTculaTis eldTidgei (Arnold) .................. PI 

M to Pie 

M,Pl 

ciTculaTis imposter- (G D. Hanna).......... PI PI 

cTistobalensis (Hertlein) ........................... . deseTt?: (Conrad) ......................................... . Mor PI 

dirninutivus (Hertlein and Jordan) ..... . M 

eTicellus (Hertlein) ................................... . PI 

evennanni (Jordan and Hertlein) ......... . hakei (Hertlein) ......................................... . PI 

1:nval1:dus (G D. Hanna) ............................ M,Pl 

mendenhalli (Arnold) ................................ M to Pie 

Pl,Ple 

Mor PI 

peTcarus (Hertlein) ................................... . Tevellei (Durham) ....................................... . subdolus (Hertlein) ................................... . Pl,Ple 

sveTdTupi (Durham) ................................. . MorPl 

Genus Ar-gopecten?: 

cTassiTadiatus (Clark).............................. M 

Baja California 

Nort~ Sur 

PI 

PI 

PI PI 

PI 

PI 

PI to H PI to H 

PI 

PI PI 

M 

PI 

PI 

PI 

PI 

PI 

PI 

PI 

PI 

Central 

and (or) South 

America 

PI 

PI 

H 

PI 
TERTIARY MARINE PELECYPODS: PROPEAMUSSIIDAE AND PECTINIDAE B33 

notch. Left valve convex with fairly high and rather sharp umbo, 

and ornamented by 15 to 16 ribs. Altitude 8 mm.; longitude 8 mm.; 

thickness 2.1 mm.; apical angle, approximately 98°." 

Holotype.-CAS/SU 125. 

Type local1:ty.-SU 60. Baja California Sur. Isidro Formation, 

Miocene. 

Supplementa:ry desc1·1:1Jtion.-"The "' "' "'Miocene species figured 

by Hertlein cannot be referred to Pecten calli Hertlein. It is small 

and may possibly be the young form of some described species, but 

several specimens have been found, and it seems best to refer to them 

with a definite name; Pecten (Plag1:octen1:unt) d1>minutivus is proposed. 

"The species differs from other west coast Plagiocteniums in its 

small size and flattish right valve." (Hertlein and Jordan, 1927) 

Comments.-The holotype is a very small, moderately heavyshelled, double-valved specimen. The right valve is almost flat; the 

left valve is moderately inflated, and the left umbo projects above the 

hinge. The ribs and interspaces on both valves are smooth, with no 

concentric sculpture. 

Geogm.pkic ?'ange.-Southern California to Baja California Sur. 

Geolorric 1·a.nge.-Miocene. 

Occu:rrence 1:n the Cal?jo?·m:as.-Temblor "Horizon" (Loel and 

Corey, 1932) and Isidro Formation (Stump, 1979). 

Argopecten mendenhalli (Arnold) 

Plate 9, figures I, 4 

Pecten (Plag·iocten:1:um.) cerrosensis Gabb var.? mendenhall?: Arnold, 

1906, p. 84-85, pl. 25, figs. 2, 2a, 2b. 

Pecten (Pla{J'I:octem:um) cen·osen.'n:s mendenhalli Arnold. Hertlein, 

1925a, p. 16, pl. 1, fig. 5. 

Pectenm.en.denha.ll-1: Arnold. G D. Hanna, 1926a, p. 473, pl. 25, figs. 4, 

5. 

Pecten (Pla{J'I:octen·imn) mendenhall?: Arnold. Jordan and Hertlein, 

1926b. p. 442. 

Ori{J'I:nal desc·n:pt·ion.-"Shell, when adult, averaging about 75 

millimeters in altitude. Similar toP. ce1·rosensis in shape, convexity, 

·and ribbing, but differing from the latter in being much smaller 

when adult. having fewer ribs (about 19 in the former, while the 

latter has usually 21 or more), much less prominent incremental 

lines, and a relatively longer hinge line." 

Holotype.-USNM 164849. 

Type local·ity.-Santa Rosalia, Baja California Sur. Salada Formation, Pliocene. 

S·upplementa.?·y desc1·ipt1:on.-"A few specimens in the collection 

appear to belong to this species. They agree with Arnold's figure of 

the type of P. mendenhall?: in possessing an unusually long hinge line, 

valves which are little inflated and are unusually long in proportion 

to their height and right valves which are evenly rounded at the 

umbo, and broadly rounded on the ventral margin. They can be 

distinguished from P. 1:nval1:d1).s and P. calliclus by these characters. 

None of our specimens has quite as broadly rounded ribs as is shown 

by Arnold's figure of the type of P. mendenhall?:. 

"Examination of many specimens of true P. cerrosensis Gabb 

proves that P. mendenhalli is not related to that species, but it is far 

closer to P .. ,:n:val?:d·us, P. callidus, P. subdolus, and P. circularis." 

(Jordan and Hertlein, 1926b, p. 442) 

Compwrison.-The ribs on Lyropecten ce1-rosens1:s are 18 to 20 in. 

number and not 21 or more as on A. mendenhalli (Hertlein, 1925a, p. 

16). 

Cmn:m.ents-The holotype is double valved and slightly inequilateral, with a long hinge. Both valves have low, subrounded ribs 

separated by slightly narrower interspaces and have looped concentric lamellae. The finer sculpture of the auricles separates 

A. mendenhallifrom A. callidus. The heavier ribs, longer hinge line, 

and shallower left anterior byssal notch distinguishes A. mendenhalli from A. subdolus. A. invalidus has wider ribs that are not as 

rounded as those on A. mendenhalli. A. antonitaens1:s has smaller 

anterior auricles with a deeper left anterior byssal notch than 

A. mendenhalli. 

Geographic range.-Middle California to Baja California Sur. 

Geologic range.-Miocene to Pleistocene. 

Occu?-rence in the Caliform:as.-Miocene or Pliocene: Imperial 

Formation (G D. Hanna, 1926a; Stump, 1979); Miocene and Pliocene: 

Purisima Formation (Arnold, 1906); Pliocene: Almejas (Minah and 

others, 1976), Boleo (Stump, 1979), and Salada (Arnold, 1906) Formations; Pliocene and Pleistocene: Merced Formation (Arnold, 

1906). 

Argopecten deserti (Conrad) 

Plate 9, figure 2 

Pecten deserti Conrad, 1855, p. 15. Conrad, 1857b, pl. 5, fig. 41. 

Nom land, 1917a, p. 242, pl. 6, figs. 1, 1a, lb. G D. Hanna, 1926a, 

p. 4 70, pl. 25, figs. 1-3. 

Pecten (Plagioctenium) deserti Conrad. Arnold, 1906, p. 85, pl. 26, 

fig. 3; not? pl. 26, figs. 1, 2, 4. 

Pecten (Lyro7Jecten) deserti Conrad. Mansfield, 1931, p. 46, pl. 17, 

figs. 3, 6. 

Aequipecten dese1·ti (Conrad). Durham, 1950, p. 63, pl. 11, figs. 5, 6. 

Chlamys (Argopecten) desert1: (Conrad). Hertlein and Grant, 1972, 

p. 198. 

Original descript1:on.-"Suborbicular, both valves convex; ribs 

about 23, rounded, somewhat flattened toward the base, about as 

wide as the interstices; [in the lower valve much wider than the 

interstices,] and the valve more convex than the opposite one; ears 

equal in the upper valve; left ear of lower valve extended downward 

and very obliquely striated; cartilage pit profound; a submarginal 

channel parallel with the upper margin." 

Holotype.-USNM 8398. 

Type local1:ty.-Carrizo Creek, Colorado Desert[Imperial County], 

Calif. Imperial Formation, Miocene or Pliocene. 

Supplementary description.-"Shell averaging about 32 millimeters in altitude, about as long as high, biconvex, equivalve, subequilateral, and with serrate margins; sides straight and sloping at a 

steep angle. Right valve with 22 or 23 high, narrow, close-set, 

smooth, rounded ribs, which sometimes show looped incremental 

lines on their tops near extremities; interspaces deep, narrow, 

slightly concave bottomed, and ornamented on the bottom by 

numerous fine, sharp, straight, incremental lines; hinge lin~ about 

three-fourths length of disk; ears subequal; the anterior slightly 

convex and ornamented by 4 radiating ridges and numerous incremental lines, while the posterior is ornamented by 6 or 7 radials and 

numerous concentric lines; byssal notch rather small. Left valve 

similar to the right, except possibly that the ribs are relatively 

slightly taller. Hinge strong, with a deep resilial pit and a submarginal channel parallel with the upper margin; numerous parallel 

microscopic lines perpendicular to the hinge line visible in the crural 

grooves. 

"This species is distinguishable from allied forms by its strong 

hinge, tall, narrow, close-set ridges and straight incremental sculpture in the bottoms of the interspaces." (Grant and Gale, 1931, p. 85) 

"Grant and Gale (1931, p. 212) cited the number of ribs on the 

deserti group 'usually 18 or 19,' and on typical deserti 15 to 19. 

Woodring and Stewart (1941, p. 91) stated that C. deserti had fewer 

. ribs than P. impostor which originally was described as possessing 
B34 PALEONTOLOGY OF CALIFORNIA AND BAJA CALIFORNIA 

21 to 24. It appears obvious that some of the specimens attributed to 

C. dese'rt'i are not referable to it. Judging from the original description given by Conrad, the left valve illustrated by Arnold (1906, 

pl. 26, fig. 3), the illustrations of Nom land (1917, pl. 6, figs. 1, 1a, 1b), 

those of Hanna (1926, pl. 25, figs. 1, 2, 3), and of Durham (1950, pl.11, 

figs. 5, 6) correctly delineate typical specimens of Conrad's species." 

(Hertlein and Grant, 1972, p. 198) 

CmnpaTison.-Argopecten ci1·cularis in the San Diego Formation 

is more elongate than typical A. deserti, has fewer ribs, wider submargins that are not sculptured with riblets, and more concave 

auricles. (Hertlein and Grant, 1972, p. 198) 

Geographic range.-Southern California to Baja California Sur. 

Geolog'ic 1·ange.-Miocene(?) to Pliocene. 

Occurrence r:n the Calrfm·nias.-Miocene or Pliocene: Imperial 

Formation; Pliocene: Almejas (Minch and others, 1976), Salada 

(Beal, 1948), and San Marcos (Durham, 1950) Formations. 

Argopecten sverdrupi (Durham) 

Plate 9, figure 9 

Aequipecten sver·drupi Durham, 1950, p. 64, pl. 8, figs. 2, 5; pl. 9, 

fig. 7. 

Orig-~:nal descriptr:on.-"Shell of medium size, fairly heavy, resembling A. r:mpostor (Hanna) but having only 17 or 18 heavy rounded 

ribs; obliqueness of valves varying considerably, some specimens 

being markedly oblique to posterior; ribs rounded, inters paces about 

half as wide; in one small specimen the younger half of shell, after a 

heavy constriction representing a marked pause in growth, shows 

very high ribs on right valve with relatively narrow interspaces, 

while on left valve the ribs are high but with wide interspaces; 

anterior ears missing from all six valves at hand; however, the traces 

of byssal notch present indicate that it was deep and fairly sharply 

angled, like that of A. circularis." 

Holotype.-UCMP 15995. 

Type local'ity.-UC A3583. Baja California Sur. Salada Formation, Pliocene. 

Supplementary descn:ption.-"The 17-18 heavy rounded ribs appear to be characteristic of this species." (Durham, 1950, p. 64) 

Comments.-The holotype is a very thick shelled, moderately 

inflated right valve with a small umbonal angle. It has 17 wide, 

subrounded ribs and shallow, narrower interspaces. The auricles 

are broken but the right posterior auricle was very high. 

Geographic range.-Southern California to Baja California Sur. 

Geologic range.-Miocene to Pliocene. 

Occurrence in the Calijornias.-Miocene or Pliocene: Imperial 

Formation; Pliocene: Salada and San Marcos Formations. 

Argopecten circularis circularis (Sowerby) 

Plate 9, figures 7, 8 

Pecten tumr:dus Sowerby, 1835, p. 109. Not Pecten tumidus Turton, 

1822. 

Pecten cinularis Sowerby, 1835, p. 110. 

Pecten (Plagioctenium) drcularis Sowerby. Arnold, 1906, p. 125-

126, pl. 43, figs. 3-6; pl. 44, figs. 6, 6a, 6b, 7. Hertlein, 1935, p. 

311-316. 

Aequipecten circularis (Sowerby). Durham, 1950, p. 63, pl. 10, figs. 

1, 5. 

Aequipecten (Plagr:octenium) circularis (Sowerby). Olsson, 1961, p. 

163, pl. 19, figs. 2, 2b. 

Chlamys (Argopecten) circularis Sowerby. Grau, 1959, p. 97-100, pl. 

32. Hertlein and Grant, 1972, p. 197-198, pl. 32, figs. 4, 15, 16. 

Argopectencircularis (Sower by). Waller, 1969, p. 46-48, pl. 5, fig.12; 

text figs. 8-10; tables 20, 21. 

Pecten (Pecten) compactus Dall, 1898, p. 707, pl. 34, fig. 5. 

Original descn:ption.-"Pect. testa suborbiculari, tumida, subaequivalvi, aequilaterali, fusco alboque varia, auriculis magnis, subaequalibus; costis radiantibus octo-decim interstitiis latioribus, arcuatim striatis; valva altera sulcis profundioribus: long. 1.5, lat. 0.8, 

alt. 1.4 poll." 

Holotype.-BM(NH) 1950-11-14.18.19. 

Type locality.-Guaymas, Mexico. Holocene. 

Supplementary descriptr:on.-"ln the smaller valves, there is much 

variation in the convexity, the width of the inters paces between the 

ribs and in the height and degree of rounding or flattening of the tops 

of the ribs. Many of the valves to a height of about 35 mm are very 

convex, the ribs are high and flat-topped and rather closely spaced. 

These closely resemble Arnold's illustration (1906, pl. 44, fig. 7) of 

the type of Pecten compactus Dall which is now generally placed in 

the synonymy of C. circularis. Other larger ones resemble Arnold's 

illustration of C. circularis (on his plate 42, fig.' 3). Large specimens 

of C. cr:rcularis from the Gulf of California are about 66 mm long." 

(Hertlein and Grant, 1972, p. f97-198) 

"Mature individuals of moderate size in southern part of range, 

commonly attaining heights of 40 to 60 mm; of moderate to large size 

in northern part of-range, commonly 50 to 70 mm, a few as high as 95 

to 100 mm; equiconvex to right-convex. Outline of disk oblique, with 

posterior margin extended; disk flanks very steep, commonly turned 

inward near bases of auricles, and curved in plane perpendicular to 

commissure and to disk flank. Disk gapes absent or very narrow in 

southern part of range, narrow to rather wide in northern part. 

"Right auricles with dorsal margins dorsal to outer ligament and 

diverging slightly from outer ligament away from beak; free margins of right auricles forming 9()0

• or acute angles at junctures with 

outer ligament. Free margins of posterior auricles moderately to 

rather deeply sigmoidal in plane of commissure, with central portion of sigmoidal curve forming acute angle with dorsal margins. 

Right anterior auricle with broadly rounded a'nterior margin; byssal 

notch of mature individuals rather deep, with apex pointed, 

rounded, or truncate; ctenolium generally present except on largest 

individuals; byssal fasciole planar to strongly arched adjacent to 

suture with disk. 

"Plicae of right valve 18 to 23 in number * * *, with external 

surfaces high and rectangular or subrectangular in cross section 

proximally, becoming low and subrounded with upper surfaces flattened distally; width generally considerably greater than that of 

inters paces. Concentric lamellae on both valves generally projecting 

only in interspaces (although commonly absent from bottoms of 

interspaces) and on sides of plicae, extending to or slightly over 

edges of plica crests and commonly demarcating a bald band down 

crest; trend of l'amellae across central region of either valve at 

heights greater than 30 mm distally convex across inters paces, sloping rathe> strongly up sides of plicae in proximal direction, and 

distally concave across crests of plicae; spacing of lamellae close in 

central region of mature right valve. Disk flanks noncostate or with 

very faint, incipient costae." (Waller, 1969, p. 46-47) 

"Hinge structure strong; cardinal crura very pronounced on right 

valve and interlocking tightly with left valve; strong transverse 

striae on crura and provinculum; cardinal margin of right valve 

well folded over; prominent nodules at base of each auricle on both 

valves." (Grau, 1959, p. 99) 

Comparison.-"Recent adult specimens of C. (A.) circularis 

aequisulcata differ from typical C. (A.) circularis in the larger, 

· flatter, and thinner shell as well as in the narrower ribs and less 

brightly colored shell. 

"Some of the fossils from the San Diego formation closely resemble 

some specimens of the form described as Pecten (Plagioctenium) calli 

Hertlein * * *from beds of Pliocene age at 'Bahfa. T6rtolo (Turtle 
TERTIARY MARINE PELECYPODS: PROPEAMUSSIIDAE AND PECTINIDAE B35 

Bay), Lowet· California. The record of this form from the San Diego 

Pliocene, mentioned by E. K. Jordan and Hertlein, is referred by us 

to juvenile C. c·1>rculo.?"is. Typical specimens of the form C. c. call?: 

possess very highly arched umbos, squarish ribs on the right valve 

and fine, high ribs on the left valve. There is also a tendency for the 

valves to develop a length greater in proportion to the height. * * * 

The valves of C. C'l:rcu.la?"l:s call1: are more elongated and the ribs are. 

more numerous and narrower than those of C. c?:rcula?"l:s b1·amkampi 

Durham*** described from the Carrizo Creek region in Imperial 

County, which has about 19 ribs. 

"In general appearance and in degree of globosity, some of the 

smaller specimens from San Diego resemble C. eldn:dge?: Arnold 

* * * which was described from beds of late Pliocene age in San 

J.oaquin Valley, California. The fossils from San Diego have thinner 

shells, which lack constrictions, the ribs are more numerous, often a 

little more widely spaced and the crenellations along the ventral 

margin of the interior are less consistently and deeply grooved than 

those of C. eld·n:dge-i. The ribs on some of the left valves of C. eldn:dgei 

are shallowly medially grooved toward the ventral margin but this 

feature is lacking on the valves from San Diego. 

"The species described as Pecten (Plag·1:octem:1·nn) neahen.'n:s by 

Arnold (1906, p. 87, pl. 15, fig. 2, 2a, 2b) from beds of Miocene age at 

Neah Bay, Washington, has narrower ribs and a longer hinge line 

than C. c·irculo:ris." (Hertlein and Grant, 1972, p. 198) 

"A. c·1>rcu.lo:n:s differs from A. m:bbus in being more generally 

right-convex and from both A. g·ibbus and A. nucleus in having a 

more oblique shell with higher and more angular right plicae." 

(Waller, 1969. p. 47) 

Geognt,ph:ic ·range.-Living: Cedros Island, Baja CaliforniaN orte, 

to Peru and Galapagos Islands; fossil: southern California to 

Ecuador. 

Geolo{}'l:c ·ro.nge.-Miocene through Holocene. 

Occu:rrence ·in the Cal?jo?·m:as.-Miocene and Pliocene: Towsley 

Formation (Winterer and Durham, 1962); Pliocene: Almejas (Minch 

and others, 1976), Gloria (Wilson, 1948; Stump, 1979), Infierno (Wilson, 1948; Stump, 1979), Marquer (Durham, 1950), Niguel (J. G. 

Vedder, written commun., 1978), and San Diego (Hertlein and 

Grant, 1972) Formations; Pliocene and Pleistocene: Fernando (J.D. 

Mount, written commun., 1971), Pico (Kundert, 1932), and Saugus 

(Kew, 1924) Formations; Pleistocene: Palos Verdes Sand (Woodring, 

1946). 

Haln:tat.-On rock, gravel, sand, and sandy mud bottoms from 1 to 

135m; associated with kelp, corallines, or gorgonians (Grau, 1959, 

p. 100). 

"Seemingly, a geographic change in the habitat preference of the 

species [A1·gopecten c?>rcula·n:s sensu lato] may occur, the northern 

forms [A. aequ·isulco.t.us] being found more commonly in bays and 

estuaries than the southern forms, which seem to be more common in 

open marine waters. (Waller, 1969, p. 47) 

Argopecten circularis calli (Hertlein) 

Plate 10, figure 2 

Pecten (Pla.g-~:octen:1:mn) call1: Hertlein, 1925a, p. 16-18, pl. 4, fig. 6. 

Not pl. 4, figs. 5, 7 [.= A1·gopecten diminutivus Hertlein and 

Jordan, 1927]. Jordan and Hertlein, 1926b, p. 436-437, pl. 27, 

fig. 5. 

Chlo.m.ys (A·rgopecten) c·i1·cularis call1: (Hertlein). Hertlein and 

Grant, 1972, p. 198. 

0?"ig-~:nal desc?"ipt?:on.-"Shell small, inequivalve. Right valve 

slightly arched, ornamented by about 16 or 17 rather high, narrow, 

rounded, radiating ribs separated by interspaces of about the same 

width as the ribs; anterior ear with a large byssal notch and sculpture consisting of about five radiating riblets crossed by concentric 

lines of growth; posterior ear sculptured by radiating rib lets crossed 

by concentric lines of growth. Left valve slightly prolonged posteriorly, much more highly arched than right, and sloping rather 

abruptly from the umbos, sculptured by about 19 well developed, 

rather sharp, rounded, radiating ribs separated by interspaces 

about as wide as the ribs, ribs and interspaces crossed by fine concentric lines; ears slightly concave, the anterior with a small notch 

and ornamentation consisting of five or six radiating riblets crossed 

by concentric lines of growth; posterior ear slightly prolonged at the 

hinge line, sculptured as right. Altitude 24 mm.; longitude 24 mm.; 

diameter of left valve approximately 7 mm.; apical angle approximately 90°." 

Holotype.-CAS/SV 68. 

Type local1:ty.-SU 53. First arroyo east of Santiago, Baja Cal ifornia Sur. Salada Formation, Pliocene. 

Supplementa1·y descn:ption.-"Right valves of this species vary 

considerably in convexity; usually they are moderately convex, and 

markedly so at the umbo. The hinge line is about two-thirds as long 

as the shell. They bear 18-21 ribs, which are rather high and prominent, squarish in early stages of growth and usually square in the 

adult forms, but in a few individuals later becoming slightly 

rounded. The ribs are separated by interspaces that are not quite as 

wide as the ribs and, in unweathered specimens their sides are 

ornamented by fine concentric lamellae. The posterior ear is well 

developed, and shows a very faint, broad notch. The ear is ornamented by five or six faint radiating riblets crossed by concentric 

lines of growth. The anterior ear is well developed, and is cut by a 

well defined byssal notch; the anterior margin of the ear is rounded, 

and the surface is ornamented by four to six radiating rib lets crossed 

by incremental lines." (Jordan and Hertlein, 1926b, p. 436-437) 

"Typical specimens of the form C. c. calli possess very highly 

arched umbos, squarish ribs on the right valve and fine, high ribs on 

the left valve. There is also a tendency for the valves to develop a 

length greater in proportion to the height. Durham [1950] men-

. tioned this tendency in C. c1:rcularis occurring in Pliocene beds in 

the Gulf of California region." (Hertlein and Grant, 1972, p. 198) 

Comparison.-"Pecten calli differs from P. andersoni Arnold, In 

its narrower ribs and more highly arched left valve. From P. d1:scus 

Conrad, and P. raymondiClark, the present species is distinguished 

by the differently shaped ribs and less circular outline of the valves. 

From P. desert?: Conrad and P. impostor Hanna, P. calli is distinguished by its high narrow, rounded ribs and only slightly arched 

right valve. From P. santa1·osanus Bose, P. call?: is distinguished by 

the fewer higher ribs and by the presence of a profou·nd rounded 

notch in the posterior ear of the left valve of the prese11.t species, 

which notch is lacking in P. santarosanus." (Hertlein, 1925a, p. 17) 

"The valves of C. circularis call1: are more elongated and the ribs 

are more numerous and narrower than those of C. circulan:s branl--

kampi * * *."(Hertlein and Grant, 1972, p. 198) 

Comments.-The holotype is a small, moderately thick-shelled left 

valve with narrow, subtriangular ribs that are separated by 

U-shaped interspaces of equal size that have imbricated concentric 

lamellae. 

Geographic range.-Baja California Sur to Mexico. 

Geologic range.-PI iocene. 

Occurrence in Haja California Su1·.-Pliocene: Salada Formation. 

Argopecten circularis bramkampi (Durham) 

Plate 9, figure 5 . 

Aequipectenc1:rcularissubsp. bramk::L?npi Durham, 1950, p. 63, pl. 9, 

figs. 2, 4, 8. 

Original description.-"Shell of medium size, resembling A. cir-

. cularis in general outline, but with high, prominent beaks; 19 ribs, 
B36 PALEONTOLOGY OF CALIFORNIA AND BAJA CALIFORNIA 

wide and rounded, interspaces narrow and channeled at bottom; 

beaks laterally compressed and slightly overhanging hinge line, 

with ears sharply delimited by an impressed area; anterior ear of 

right valve with about four radial ribs; byssal notch deep and 

sharply pointed; posterior ear of right valve with extremely faint 

and fine radial ribs. Both ears of left valve with 6-8 fine radial ribs." 

Holotype.-VCMP 30035. 

Type locality.-VC A1268. Imperial County, Calif. Imperial Formation, Miocene or Pliocene. 

Comparison.-The high, overhanging, laterally compressed beaks 

separate A. circularis bramkampi from the typical form. (Durham, 

1950, p. 63) 

"The valves of C. circularis calli are more elongated and the ribs 

are more numerous and narrower than those of C. circularis bramkampi * * *." (Hertlein and Grant, 1972) 

Comments.-The holotype is a moderately thick-shelled, inequilateral, right valve with a very inflated umbonal area. The ribs are 

rounded and separated by small, deeply rounded interspaces that 

have imbricated, concentric lamellae; both the ribs and interspaces 

are crossed by looped, concentric lamellae near the ventral margin. 

Geographic range.-Southern California to Baja California Sur. 

Geologic range.-Miocene to Pliocene. 

Occurrence 1:n the Calijornias.-Miocene or Pliocene: Imperial 

Formation; Pliocene: San Marcos Formation. 

Argopecten circularis eldridgei (Arnold) 

Plate 9, figure II 

Pecten (Plagioctenium) eldr1:dgei Arnold, 1906, p. 87, pl. 25, figs. 3, 

3a, 3b, 4, 4a, 4b, 5, 5a, 5b. Howard, 1935, pl. 6, fig. 3. 

Pecten (Aequipecten) eldridgei Arnold. Grant and Gale, 1931, p. 214. 

Aequipecten circularis eldridgei (Arnold). Woodring and others, 

1940, p. 53, 54, pl. 24, figs. 10-13. 

On:g1:nal descript1:on.-"Shell averaging about 20 millimeters in 

altitude, nearly as high as long, equivalve, somewhat oblique (the 

posterior portion being the longer), very thick and heavy, very ventricose, and with serrate margins; base unequally rounded; sides 

somewhat concave above and sloping at a moderately steep angle. 

Right valve with 19 or 20 small, rather low but sharply defined, 

squarish ribs; inters paces about one-half as wide as ribs, channeled, 

and with flat bottoms; surface of disk ornamented by numerous 

sharp concentric lines which loop back over the ribs; more or less 

prominent constrictions, indicating interrupted growth, are common on most specimens; hinge line equal to about three-fourths 

length of disk; anterior ear slightly longer than posterior, deeply 

notched, and ornamented by 3 or 4 prominent radiating ridges and 

numerous imbricating incremental lines; posterior ear rectangularly truncated and ornamented by 8 or 10 radiating ridges and 

incremental sculpture. Left valve similar to right, except that the 

ribs are slightly narrower and more rounded; ears similar to those of 

right valve except that the anterior one is not as deeply notched. 

Hinge similar to that of P. circularis except stronger and with the 

auricular crura much more highly developed. Adductor impressions 

very deep." 

Holotype.-USNM 164580 (paratypes also so numbered). 

Type local1:ty.-McKittrick district (NYz sec. 22, T. 30 S., R. 22 E.), 

Kern County, Calif. Etchegoin Formation, Miocene and Pliocene. 

Comparison.-"This species is similar in many respects toP. c?:rcularis, but is characterized by its smaller size, greater ventricosity, 

thicker and heavier shell, deep adductor impressions, and more or 

less prominent constrictions. It sometimes attains an altitude of 45 

millimeters, as shown by fragments collected at the type locality." 

(Arnold, 1906, p. 87) 

Comments.-The holotype is a small, inequilateralleft valve with 

closely spaced, subrounded ribs and shallow interspaces; looped, 

concentric lamellae cross both the ribs and the interspaces near the 

ventral margin. The left anterior auricle is deeply notched. 

Geograph1:c range.-Middle to southern California. 

Geologic range.-Miocene to Pliocene. 

Occurrence in Calijornia.-Miocene and Pliocene: Etchegoin 

Formation; Pliocene: Cascajo Conglomerate Member, San Joaquin 

Formation (Woodring and others, 1940). 

Argopecten circularis impostor (G D. Hanna) 

Plate 10, figure I 

Pecten proteus Nomland, 1917a, p." 232, pl. 6, figs. 2, 2a-c. Not Pecten 

proteus Sowerby, 1847. 

Pecten impostor G D. Hanna, 1924, p. 177. new name. 

Aequipecten c1:rcularis 1:mpostor (Hanna). Woodring and others, 

1940, p. 91, pl. 13, figs. 3, 4, 6-9. 

Aequipecten 1:mpostor (Hanna). Adegoke, 1969, p. 99, pl. 2, fig. 12. 

?Pecten deserti Conrad. Arnold, 1909, p. 76, pl. 26, figs. 1, 2, 4. Not 

Pecten deserti Conrad, 1855a. 

Original description.-"Shell thin, equilateral, equivalve, compressed, with smooth regularly convex margins. Dorsal margins 

slightly concave; apical angle about 95 degrees. Right valve ornamented externally by 21-24 wide, moderately high, rounded ribs; on 

each side of major ribs is usually a faint auxiliary rib let; inters paces 

between major ribs less than width of ribs; anterior ear slightly 

longer than posterior, sculptured by about five low radial ridges and 

indistinct incremental lines; posterior ear ornamented with about 

seven low, radial ridges and nearly invisible incremental lines. Left 

valve in general similar to right, but has higher, more strongly 

rounded, major ribs with narrow interspaces; anterior ear with 

about seven radiating lines. Dimensions of rather small left valve of 

type: height, 37 mm.; width, 33 mm.; width of hinge line, 17 mm." 

Holotype.-VCMP 11089. 

Type locality.-VC 2991. Fresno County, Calif. Upper Etchegoin 

Formation, Pliocene. 

Comparison.-"Specimens of this species found in the Coalinga 

region have heretofore been identified as Pecten dese1·t1: Conrad. On 

comparison of P. deserti from the type locality at Carrizo Mountain, 

San Diego County, with P. proteus, n. sp., several marked differences 

may be observed. In P. deserti the ribs are higher, flatter above, with 

more nearly vertical sides; on the left valve the ribbing continues 

without interruption from ears over the outer depressed dorsal 

margins, while in P. proteus, n. sp., the corresponding areas have no 

ribs. The ears of P. deserti are larger, more strongly curved, and 

have less depression where ears join dorsal margins of shell; also the 

dorsal margins show less marked concavity." (Nomland, 1917a, p. 

232) 

Argopecten circularis im,postm· differs from the living California 

A. circularis Sowerby and its allies in having a smaller thinner shell 

and smaller ears. Argopecten desert1: appears to have not quite so 

many ribs, and at least some specimens have ribs on the lateral 

areas; on A. c. impostor the lateral areas are smooth. A. c1:rculan:s 

eldridgei is smaller than A. circularis 1>rnpostor and has a thicker 

shell. (Woodring and others, 1940, p. 91) 

Comments.-The holotype is a small, moderately thick-shelled, 

slightly inequilateralleft valve. The left valve ribs are grooved along 

the edges, and they, and the narrower inters paces, seem to have been 

covered by imbricated microsculpture. 

Geograph1:c range.-Middle and southern California. 

Geologic range.-Pliocene. 

Occurrence in Calijornia.-Cascajo Conglomerate Member, San 

Joaquin and upper part of Etchegoin (Woodring and others, 1940) 

Formations. 
TERTIARY MARINE PELECYPODS: PROPEAMUSSIIDAE AND PECTINIDAE B37 

Argopecten ericellus (Hertlein) 

Plate 12, figure 2 

Pecten (Plo.m:octeniu.m) en:cellus Hertlein, 1929, p. 215, pl. 24, figs. 

10, 11. 

Chla:m.ys (ATg01Jecten) en:cellus Hertlein. Hertlein·and Grant, 1972, 

p. 199, pl. 32, fig. 7. 

On:m:na.l (lesc?"ipt·,:on.-"Shell small, moderately convex; hinge 

line straight. Right valve ornamented by about 22 subrounded, 

fairly low radiating ribs which are separated by narrower interspaces; two tiny midribs are present along the base of the sides of the 

major ribs; ribs and interspaces crossed by concentric lines of 

growth; anterior and posterior margins ornamented by concentric 

lines of growth; ventral margin rounded; ears unequal, the anterior 

with a well-defined byssal notch, and sculpture of about five or six 

radiating riblets crossed by incremental lines; the posterior ear 

sculptured by about four or five radiating riblets crossed by lines of 

growth, no notch present. Altitude 28 mm.; longitude 29.1 mm.; 

diameter of right valve approximately 7.5 mm.; apical angle in right 

valve approximately 94°." 

Holot.ype.-CAS 2998. 

Type loca.l·1:ty.-CAS 1132. San Diego County, Calif. San Diego 

Formation, Pliocene. 

S?l.1Jplementa.?·y (lescn:pt·ion.-"The shell of this species is characterized by its narrow, subrounded ribs, narrow interspaces, and by 

the presence of two tiny ri blets, one at the base of each side of most of 

the major ribs. In some of the inters paces toward the lateral margins 

only one riblet, or in some cases, none is present." (Hertlein and 

Grant, 1972, p. 199) 

Ccnn1Ja.n:son. -"This form appears to be a member of the Chlamys 

cin~u.la:ris group. It differs from C. c1:?"Cula·r£s in the smaller posterior ear, more numerous, narrower ribs and interspaces, and in the 

presence of the rib lets in the inters paces toward the ventral margin. 

"Grant and Gale (1931, p. 219) stated that this form could be 

matched by juvenile specimens of Chlamys c?:TculaTis aequisu.lca.ta. 

Carpenter. However, they cited it with question in the synonymy of 

'Pecten (Aeqw1:pecten) gibbus variety ci?·culan:s Sowerby.' Comparison of the type specimen of C. (A.) eTicellus with a series of specimens 

of C. c·1>rcu.la.n:s and its subspecies C. c1:1·culan:s aequ1:sulca.ta. of comparable size, reveals differences sufficient in our opinion to justify 

assignment of specific status to C. (A.) en:cellus." (Hertlein and 

Grant, 1972, p. 199) 

Ccnnment.<~.-lmbricated, looped lamellae cross both the ribs and 

interspaces near the ventral margin, but only the interspaces on the 

rest of the disk. The right anterior auricle is half again as long as the 

right posterior auricle. 

Geogmph:ic m.nge.-Southern California. 

Geolom:c ?'a,nge.-PI iocene. 

Occu.n·ence ·in Ca.l-ifontia .. -San Diego Formation. 

Argopecten invalidus (G D. Hanna) 

Plate 10, figure 5 

Pecten (Plom:octeni·um) coopen: Arnold, 1906, p. 124, pl. 49, figs. 2-4. 

Not Pecten coope1·£ E. A. Smith, 1903. 

Pecten '1:nva.l1:dus G D. Hanna, 1924, p. 177, new name. 

Chla.mys (A ·rgopecten) ?:Onval'l:da. Hanna. Hertlein and Grant, 1972, p. 

200-201, pl. 33, figs. 1, 3, 8 (see for synonymy). 

01"ig-~:na.l desc?"I:1Jtion.-"Shell averaging about 30 millimeters in 

a~titud~, slightly lon~er than high, both valves moderately convex, 

d tsks slightly obliquely produced posteriorly, moderately thick; disk 

generally characterized by several more or less prominent concentric zones of interrupted growth, which show as color bands even on 

the fossil shells; sides nearly straight; margins serrate. Right valve 

with 18 to 20 flat-topped, squarish ribs, which tend to flatten out and 

become more convex topped in the later stages of growth; interspaces narrower than the ribs, and crossed on the bottom by numerous, fine, sharp, incrementallirulae, which hecome obsolete on the 

ribs excepting in the later stages of growth; hinge line somewhat· 

more than one-half length of disk; anterior ear slightly produced and 

ornamented by 4 or 5 prominent radials and numerous incremental 

lines; byssal notch deep and sharply defined; posterior ear slightly 

truncated, and sculptured by obsolete radials and fine incremental 

lines. Left valve similar to right, except that the ribs are •narrower 

and the interspaces correspondingly broader. Dimensions: Alt. 30 

mm; long. 31 mm; hinge line 17 mm; diameter 12 mm; umbonal 

. angle 95°." 

Holotype.-CAS/SU 8. 

Type locality.-Pacific Beach, San Diego, San Diego County, 

Calif. San Diego Formation, Pliocene. 

S·upplementaTy descT?:ption.-".Valves of this species are characterized by their low convexity and by the character of the ribs, 18 to 

20, which are square in the early stages but which widen out and 

become more convex toward the ventral margin. The interspaces 

often are ornamented with well developed concentric imbrications. 

"***Two large right valves***, the larger 47.9 mm long and 46.8 

mm high, agree with valves of Chlamys invalida except that they 

are larger and have a greater number of ribs, 21 to 22. These valves 

appear to be referable to large gerontic forms of C. 1:nvalida." (Hertlein and Grant, 1972, p. 201) 

CompaTison.-"The smaller shell, more rounded outline, fewer 

ribs which become broader and more rounded toward the ventral 

margin, occasional concentric zones of interrupted growth, and 

smaller umbonal angle are features which serve to separate this, 

species from Chlamys callida. 

"The generally smaller more orbicular shell and fewer ribs which 

become decidedly broader and more convex but not obsolete near the 

margin are characteristics which serve to separate C. 1:nva.l?:da from 

'Aequipecten' antonitaensis Durham. 

"Chlamys (A 1·gopecten) coopen:cellus Ferreira*** described from 

strata of early Miocene age in Brazil, was compared by its aut.hor 

with 'C. (A.) coope1·i (Arnold, 1906)' [=Pecten inval1:dus Hanna]. A 

small riblet is present in the interspaces between the ribs of the 

Brazilian species and in this and in other details it is quite distinct 

from C. 1:nvalida." (Hertlein and Grant, 1972, p. 201) 

Comments.-The holotype is a right valve with square to subrounded ribs separated by U-shaped interspaces half as wide as the 

ribs. The interspaces have imbricated, concentric lamellae; near the 

ventral margin, looped concentric lamellae also cross the ribs. 

GeogTaph1:c Tange.-Southern California to Baja Califo;nia Norte. 

Geologic Tange.-Miocene to Pleistocene. 

OccuTrence in the Calijcn·m:as.-Miocene and Pliocene: Purisima 

Formation (Arnold, 1906); Pliocene: Almejas (Minch and others, 

1976), Niguel (Vedder, 1972), and San Diego (Hertlein and Grant, 

1972) Formations; Pliocene and Pleistocene: Fernando (J.D. Mount, 

written commun., 1971), Merced (Arnold, 1906), and Pico (Grant 

and Gale, 1931) Formations. 

Argopecten subdolus (Hertlein) 

Plate 10, figures 3, 4 

Pecten (Plag1:octenium) subdolus Hertlein, 1925a, p. 20-21, pl. 5, figs. 

2, 4, 7. Jordan and Hertlein, 1926b, p. 443. 

Pecten (Aequipecten) purpuTatus Lamarck variety subdolus Hertlein. Grant and Gale, 1931, p. 211, pl. 5, fig. 1. 

Pecten (ATgopecten) subdolus Hertlein. Moore, 1968, p. 50, pl. 23, figs. 

a, b. 
B38 PALEONTOLOGY OF CALIFORNIA AND BAJA CALIFORNIA 

Chlamys (A rgopecten) subdola Hertlein. Hertlein and Grant, 1972, p. 

201-202, pl. 30, figs. 7, 8; pl. 35, figs. 2, 5, 9. 

Original description.-"Shell of medium size, the valves moderately convex. Right valve ornamented by about 21 rounded, radiating ribs which become broader toward the ventral margin, the ribs 

separated by round-bottomed, narrower inters paces, the whole surface ornamented by very fine radial striations and by concentric 

lines of growth; anterior and posterior margins sculptured only by 

concentric incremental lines; ventral margin rounded; ears unequal, 

the anterior with a well defined byssal notch, and sculpture of about 

six radiating riblets crossed by incremental lines; the posterior also 

sculptured by about six or seven slight radiating riblets crossed by 

lines of growth, a very slight notch present. Left valve more arched 

than right and somewhat one-sided in appearance, ornamented by 

about 21 rounded, radiating ribs separated by round-bottomed interspaces about as wide as the ribs, the whole surface finely longitudinally striate and crossed by concentric lines of growth; ears slightly 

concave, the posterior sculptured by very slight radiating riblets 

and concentric lines of growth, the anterior with a rounded notch, 

the surface sculptured by a few very slight radiating riblets and by 

concentric growth lines, the ornamentation indistinct on weathered 

specimens. Altitude 50 mm.; longitude 50 mm.; diameter approximately 17 mm.; apical angle in each valve approximately 105°." 

Holotype.-CAS/SU 51. 

Type locality.-SU 115. San Diego County, Calif. San Diego Formation, Pliocene. 

· Comparison.-"The shell of Chlamys subdola resembles that of C. 

callida, with which it occurs, in outline and in general pattern of 

sculpture. It differs from the latter species in possessing a thinner 

shell, in the low rounded ribs, the presence of radial striae on the 

disk, and weaker sculpture on the ears. 

"Specimens of Chlamys subdola closely resemble some individuals 

of Chlamys impostor Hanna. We have examined a large series of C. 

impostor and it is evident that there is considerable variation in that 

species with respect to number of ribs (20 to 24), the elevation and 

degree of roundness of the ribs and in the umbonal angle. The largest 

specimens usually do not exceed 46 mm in altitude. 

"In comparison to Chlamys impostor, the shell of Chlamys subdola 

is thinner, it attains a greater size (altitude 50 to 61 mm), the ribs, of 

which there are usually fewer, are flatter and become broader 

toward the ventral margin, the ears are a little larger, and the ribs 

on the left valve are finer. 

"Grant and Gale (1931, p. 214) considered Chlamys impostor to be 

a variety of Chlamys deserti Conrad, whereas Woodring and Stewart 

considered it to be a subspecies of Chlamys circularis Sowerby. 

Whatever the true relationship may be, there is a striking resemblance between specimens of Chlamys impostor and those of C. 

subdola. However, the differences observed in series of the two lead 

us, at least for the present, to retain C. subdola as a species rather 

than a subspecies of C. impostor. 

·~ 'Aequipecten' revellei Durham * * * described from strata of 

PI iocene age on Monserrate Island, in the Gulf of California, bears a 

resemblance to C. subdola, but differs in the more rounded outline 

and proportionally longer hinge line." (Hertlein and Grant, 1972, p. 

202) 

Comments.-The holotype is a double-valved specimen, with 

slightly inequilateral disks; the posterior end is larger than the 

anterior. The right valve has low, subrounded, radial ribs and shallow interspa(!es about half as wide. Fine, concentric, looped lamellae 

cross the inters paces and ribs on the ventral two-thirds of the right 

disk. The left valve is more inflated than the right, and strong, 

concentric lamellae cross the interspaces on the dorsal one-third of 

the disk, and both the ribs and interspaces on the remaining 

two-thirds. 

Geographic range.-Southern California to Baja California Norte. 

Geologic range.-Pliocene to Pleistocene. 

Occurrence in the Californias.-Pliocene: Almejas (Minch and 

others, 1976), Infierno (Wilson, 1948; Vokes, 1955), and San Diego 

(Hertlein and Grant, 1972) Formations; Pliocene and Pleistocene: 

Pico Formation (Grant and Gale, 1931). 

Argopecten callidus (Hertlein) 

Plate 10, figures 7, 9 

Pecten (Plagiocteniwn) callidus Hertlein, 1925a, p. 22, pl. 5, figs. 1, 3, 

5, 6. Jordan and Hertlein, 1926b, p. 437. 

Pecten (Aequipecten) purpuratus Lamarck variety callidus Hertlein. 

Grant and Gale, 1931, p. 211, pl. 5, fig. 4. 

Chlamys (Argopecten) callida Hertlein. Hertlein and Grant, 1972, p. 

198-199, pl. 32, figs. 9, 11. 

Original description.-"Shell of medium size, the valves moderately arched. Right valve ornamented by about 21 or 22 rather high, 

flat-topped, radiating ribs separated by narrower interspaces, tops 

of ribs smooth, but sides and interspaces sculptured by fine, sharp 

lamellae; anterior and posterior margins sculptured by concentric 

lines of growth only; ventral margin rounded; ears unequal, the 

anterior with a large byssal notch and ornamented by about five or 

six radiating rib lets crossed by concentric lines of growth; the posterior sculptured by several radiating riblets. Left valve more convex 

than right and somewhat one-sided in appearance, with sculpture 

quite similar to that of right valve except that the interspaces are 

slightly wider; anterior ear carrying a small, rounded notch and 

ornamentation consisting of small, radiating riblets and concentric 

lines of growth; posterior ear sculptured much as the anterior. Altitude 55 mm.; longitude 55 mm.; diameter 19 mm.; apical angle of 

valves approximately 105°." 

Holotype.-CAS/SU 53. 

Type locality.-SU 116. Cedros Island, Baja California Norte. 

Almejas Formation, Pliocene. 

· Supplementary description.-"The shell of this species is characterized by the gently convex right valve and sculpture consisting of 

21 to 22 well developed flat-topped ribs which are separated by 

narrower interspaces. The left valve is more convex than the right, 

but is similarly sculptured except that the ribs are narrower and 

separated by wider interspaces." (Hertlein and Grant, 1972, p. 199) 

Comparison.-"The outline and general sculpture of this species is 

similar to that of Chlamys subdola, but it differs from that species in 

the much higher flat-topped ribs which retain this character to the 

ventral margin. 

"The greater size, greater number offlat-topped ribs which retain 

this character to the margin, the lack of interrupted concentric 

zones of growth and the greater umbonal angle, are features which 

serve to separate C. callida from C. invalida." (Hertlein and Grant, 

1972, p. 199) 

Comments.-The holotype is a double-valved specimen, of moderate size, with moderately inflated valves. The posterior portions of 

the disks are slightly larger than the anterior. The right valve 

inters paces -have imbricated, concentric lamellae; near the ventral 

margin the ribs and interspaces are crossed by looped concentric 

lamellae. The left valve has imbricated, concentric lamellae that lap 

up onto the sides of the ribs but are absent on the tops. Near the 

ventral margin looped, concentric lamellae cross both the ribs and 

the interspaces. 

Geographic range.-Southern California to Baja California Sur. 

Geologic range.-Pliocene to Pleistocene. 

Occurrence in the Californias.-Pliocene: Almejas (Minch and 

others, 1976), Gloria (Vokes, 1955), Infierno (Wilson, 1948; Vokes, 
TERTIARY MARINE PELECYPODS: PROPEAMUSSIIDAE AND PECTINIDAE B39 

1955), Niguel (J. G. Vedder, written commun., 1978), and San Diego 

(He1·tlein and Grant, 1972) Formations; Pliocene and Pleistocene: 

Fernando (Hertlein and Grant, 1972) and Pi co (Jordan and Hertlein, 

1926b) Formations. 

Argo pecten evermanni (Jordan and Hertlein) 

Plate 13, figure 7 

Pecte-n (Plo.rriocten:iu:m.) wue?"m.a.n:m: Jordan and Hertlein, 1926b, p. 

439-440. pl. 27. fig. 1. 

Pect(~·n (Ae(pl:i1Jecten) w1;e·rma.nn:i Jordan and Hertlein. Grant and 

Gale, 1931, p. 207. 

On:m>na.l desc·ript·ion .. -"Shell large, thick, moderately inflated. 

Right valve omamented by 30or 31, flattish topped, equal, radiating 

ribs, separated by narrow, slightly rounded interspaces crossed by 

concentric lines of growth and the sides of ribs fringed by concentric 

lamellae; anterior ear sculptured by about four radiating ribs, a 

ve1·y prominent thickening at base of ear; posterior ear somewhat 

simila1· to anterior in omamentation, but without any large ridge at 

base. Length about 125 mm.; height 115 mm.; apical angle 108°." 

Holotype.-CAS 2108. 

TmJe loco.t-1:ty.-CAS 928. Baja California Norte. Almejas Formation, PI iocene. 

C(nnpa:r·ison .. -"P. eve?·m.o.nm: differs from P. ha.kei Hertlein in 

possessing more numerous ribs which are flatter and much closer 

together. From P. 1J'WI'1J'I.I:mtus Lamarck, P. evenno.nni can be distinguished by the much greater nuf!1ber of ribs in the new species." 

(Jordan and Hertlein. 1926b. p. 440) 

CO'In:nwnts.-The holotype is an incomplete, very thick, right 

valve. The ribs are closely spaced, separated by narrow, deep, Vshaped inte1·spaces, and crossed by loopeJ:l, concentric lamellae. The 

auricles are incomplete. 

Georrro.ph:ic ·mn.ge.-Baja California Norte. 

Geolo(J'I:c ·ra.nge.-PJiocene. 

Occu:rren.ce ·in Ba;ja. Ca.l-ifon1:1:a .. -Almejas Formation. 

Argopecten percarus (Hertlein) 

Plate 10, figure 6; plate 12, figure 4 

Pecten(Aequ:ipecten) pe·rca:rus Hertlein, 1925a, p. 13-14, pl. 2, figs. 2, 

5. Jo1·dan and Hertlein, 1926b, p. 435. 

Pecten (Aequ:ipecten) purpu1·a.tus Lamarck var. pe?·ca.·rus Hertlein. 

G1·ant and Gale. 1931. p. 210. 

Or£m:no.l descn:pt'ion.-"Shell moderately large, equilateral, subequivalve, moderately thin, somewhat compressed, the outline 

round. Right valve ornamented by about 22 moderately strong, 

I'Ounded ribs, separated ·by round-bottomed interspaces which are 

not quite as wide as the ribs; ribs and interspaces sculptured by 

regular, wavy, incremental lines, and, at irregular intervals, by 

stronger lines of growth; hinge line about one-half as long as the disk 

and slightly indented at the beaks; ears unequal, the anterior with a 

large byssal notch and sculpture consisting of about six or seven 

radiating riblets, the posterior ear ornamented by about seven 

radiating riblets, both ears sculptured by incremental lines. Left 

valve more arched and sharper at umbo than right, and somewhat 

one-sided in appearance, the disk ornamented by about 25 or 26 

rounded, radiating ribs, and also concentrically sculptured much as 

on· right valve; ears ornamented by about six or seven radiating ribs, 

crossed by concentric incremental lines; ears slightly concave, anterior with a slight byssal notch. Altitude 82 mm.; longitude 91 mm.; 

diameter approximately 12 mm.; apical angle of valves approxi- · 

mately 118°." 

Holotype.-CAS/SV 42. 

Type loca.lity.-SV 48. Baja California Sur. Almejas Formation, 

Pliocene. 

C01npa1·ison.-"Pecten percarus is distinguished from other west 

American Aequipectens by its large size, number of ribs, and its 

clear concentric incremental lines." (Hertlein, 1925a, p. 14) 

Comments.-The holotype is a large, thin-shelled, almost flat, 

inequilateral right valve. It has 20 low, rounded ribs separated by 

rounded, somewhat narrower interspaces. Prominent, looped, concentric lamellae cross both the ribs and interspaces. The left-valve 

paratype is moderately inflated, inequilateral, and has 24low, subrounded ribs separated by rounded, narrower inters paces. The valve 

bears concentric, looped, lamellae. In addition to the characters 

mentioned by Hertlein (1925a, p. 14), this species is distinguished by 

the almost flat right valve. 

Geog1·aphic 1·ange.-Baja California Peninsula. 

Geologic range.-PI iocene. 

Occurrence in BaJ·a Calijornia.-AJmejas Formation (Minch and 

others, 1976). 

Argopecten hakei (Hertlein) 

Plate 11, figure 6 

Pecten (Pla.gioctenimn) hakei Hertlein, 1925a, p. 18-19, pl. 4, figs. 1, 

3. Jordan and Hertlein, 1926b, p. 440-441, pl. 31, figs. 1, 2. 

Pecten (Aequ1:pecten) purpu?·atus Lamarck variety hake1: Hertlein. 

Grant and Gale, 1931, p. 209, pl. 8, fig. 3. 

Chlmnys (A1·gopecten) ha.kei Hertlein. Hertlein and Grant, 1972, p. 

199-200, pl. 33, fig. 10. 

On:g1:nal description.-"SheJJ moderately arched, coarse and 

thick, slightly longer than high. Right valve ornamented by about 23 

or 24 rounded to slightly flat-topped ribs, separated by narrower, 

round-bottomed interspaces, both the interspaces and ribs crossed 

by concentric incremental lines, and, in some cases, by rather strong 

lines of growth; anterior ear with a large byssal notch, and sculpture 

consisting of about five or six radiating rib lets, crossed by concentric 

incremental lines; anterior and posterior margins of valves smooth 

except for concentric incremental lines; ventral margin rounded;, 

posterior ear ornamented by about eight radiating riblets and by 

lines of growth, the posterior edge of the ear forming nearly a right 

angle with the hinge line. Left valve convex, higher at the umbo than 

the right valve, and ornamented by about 24 or 25 squarish, flat-

, topped, rounded ribs, separated by narrower, round-bottomed interspaces, the whole valve sculptured by concentric lines of growth; 

ears slightly concave, ornamented by about six or seven rad-iating 

rib lets. Altitude 90 mm., longitude 95 mm.; diameter of right valve· 

approximately 15 mm.; apical angle of right valve approximately 

114°." 

Holotype.-CAS/SV 40. 

Type locality.-SV 47. Baja California Sur. Almejas Formation, 

Pliocene. 

Supplementary description.-"This species is characterized by its 

large, thick, coarse valves which are sculptured with 24 to 27 subrounded radial ribs." (Hertlein and Grant, 1972, p. 200) 

Comparison.-"The shell of this species can be separated from 

other somewhat similar west American species of Argopecten by its 

large size when adult and by the more numerous subrounded radial 

ribs. In the number of ribs it is exceeded by Chlmnys (Argopecten) 

evennanni E. K. Jordan and Hertlein*** which has 30 to 31 flattish 

topped ribs separated by very narrow interspaces. Chlamys hakei 

differs from C. cristobalensis Hertlein in the much wider and less 

elevated ribs. Chlamys hakei differs from C. purpurata Lamarck 

now living from Paita, Peru, to Valparaiso, Chile, in the generally 
B40 PALEONTOLOGY OF CALIFORNIA AND BAJA CALIFORNIA 

larger size, larger ears, generally more numerous, rounded ribs 

which are separated by narrower inters paces. The ribs on the right 

valve of C. purpurata are flat-topped and on both valves the ribs are 

separated by rather deeply grooved interspaces, those on large left 

valves often with an interstitial riblet. 

"Chlamys hake1: can be easily separated from Chlamys (Lyrapecten) cerrosensis by the more numerous ribs, lack of coarse hinge 

teeth, lack of midrib in interspaces and also by the fact that the ears 

on the left valve slope downward from the margin rather than 

forming a right angle." (Hertlein and Grant, 1972, p. 200) 

Connnents.-The right valve holotype is large, heavy-shelled, and 

has low subrounded radial ribs separated by rather shallow interspaces, half the width of the ribs; both the ribs and the interspaces 

are crossed by looped concentric lamellae. 

Geographic range.-Southern California to Baja California Sur. 

Geologic range.-PI iocene. 

Occurrence in the Calijornias.-Almejas (Minch and others, 1976) 

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

Argopecten revellei (Durham) 

Plate II, figures I, 3 

Aequipecten revellei Durham, 1950, p. 63-64, pl. 9, figs. 3, 6, 9. 

Chlamys revellei Durham. Emerson and Hertlein, 1964, p. 345-346, 

349. 

Chlamys (Argopecten) revellei Durham. Hertlein, 1966, p. 280, 282, 

fig. 10. 

Orig1:nal description.-"Shell of medium size [57 mm long, 55 mm 

high], equivalved, beaks low, not prominent, very similar to A. 

subdolus (Hertlein); right valve with 22-23 low rounded ribs with 

very narrow V-shaped interspaces; left valve with corresponding 

ribs but wider inters paces; anterior ear of right valve with a moderately developed byssal notch and about four fairly wide radial ribs; 

posterior ear with numerous fine radial ribs, becoming obsolete near 

hinge line; ears of left valve correspondingly ornamented; hinge line 

between seven-twelfths and two-thirds the length of the shell, thus 

separating this species from A. subdolus (Hertlein) which has a 

hinge line only very slightly over half as long as the length of the 

shell." 

Holotype.-UCMP 15510. 

Type locality.-UC A3566. Isla Monserrate, Baja California Sur. 

Salada Formation, Pliocene. 

Comparison.-"This species is very similar to the species described as Pecten (Plagioctenium) subdolus Hertlein * * *. It differs 

from that species chiefly in the more circular outline and in that the 

hinge line (41 mm.long) is longer in proportion to the length of the 

valves." (Hertlein, 1966, p. 282) 

Comments.-The holotype is a moderate-sized, thick-shelled, double valve. The right valve has 22 almost flat ribs separated by 

narrow grooves, and the surface is sculptured by looped, concentric 

lamellae. The left valve is inequilateral and has slightly higher ribs, 

a few subtrigonal, and some grooved along the sides, and narrow 

interspaces. The left valve has strong, concentric, looped lamellae. 

The right-valve ribs on A. revellei are wider and fewer in number (22 

rather than 29) than on A. evermanni. The right valve of A. revellei is 

much more inflated than is A. subdolus, and the left valve has wider 

and more closely spaced ribs than A. subdolus. 

Geographic range.-Baja California Sur to Mexico. 

Geologic range.-PI iocene. 

Occurrence in BaJa Calijornia.-Carmen (Durham, 1950), Gloria 

(Stump, 1979), and Salada Formations. 

Argopecten cristobalensis (Hertlein) 

Plate 13, figure I 

Pecten (Plagioctenium) cristobalensis Hertlein, 1925a, p. 19-20, pl. 3, 

figs. 1, 2, 5. 

Chlamys (Argopecten) cristobalens1:s Hertlein. Hertlein and Grant, 

1972, p. 200. 

Original description.-"Shelllarge, fairly thick, in several specimens with strong lines of restricted growth; valves moderately 

arched. Right valve ornamented by about 24 flat-topped, squarish, 

radiating ribs, separated by flat-bottomed, slightly narrower, interspaces, the whole surface crossed by well defined, wavy, concentric 

lines of growth; anterior and posterior margins of valve smooth 

except for concentric incremental sculpture; ventral margin evenly 

rounded; ears unequal, the anterior ear with a large byssal notch, 

and ornamented by about five radiating riblets crossed by concentric lines of growth; the posterior ear also bearing about five or six 

radiating riblets crossed by growth lines. Left valve slightly more 

convex than right and sculptured much as the latter, the anterior 

and posterior margins with concentric lines of growth only; ears 

ornamented by about eight or nine radiating rib lets, the anterior ear 

with a slight notch. Altitude 117 mm.; longitude 135 mm.; diameter 

right valve approximately 17 mm.; apical angle of right valve 

approximately 100°-110°." 

Holotype.-CAS/SU 36. 

Type locality.-SU 49. Baja California Sur. Almejas Formation, 

Pliocene. 

Supplementary description.-"P. cn:stobalensis is easily recognized by its numerous, high, rather narrow, square ribs, separated 

by deep, square inters paces, and by the presence of unusually strong, 

sharp concentric lamellae ornamenting the bottoms of the interspaces and the sides of the ribs." (Jordan and Hertlein, 1926b, p. 439) 

Coniparison.-"Pecten cristobalensis is distinguished from P. cerrosensis mendenhalli Arnold [Lyropecten], by its squarish, more 

numerous ribs. The greater number of radial, squarish ribs, separated by narrower interspaces, and the less strong development of 

concentric incremental lines, distinguish the present species from P. 

cerrosensis Gabb proper. P. cristobalensis has a large byssal notch in 

the anterior ear of the right valve, and the ears are more strongly 

sculptured by radiating riblets than in P. cerrosensis in which the 

byssal notch is very slight, and, except for lines of growth, the ears 

are smooth. From P. callidus Hertlein, P. cristobalens1:s differs in 

the more numerous ribs, different ears, and rounder outline. The 

distinction between the present species and P. purpuratus Lamarck 

is based largely upon· the character of the radial ribs and of the 

anterior ear of the right valve. The ribs of P. purpuratus are wider 

and lower than those of P. c1·istobalensis; and conversely, the interspaces are narrower in P. pm·puratus; furthermore the ribs of the 

latter species expand much more rapidly toward the ventral margin 

than do those of P. cristobalensis. The lateral serrations on the radial 

ribs, so strongly developed in Lamarck's species, are very slight in 

the present form. The presence of three very strong ribs on anterior 

ear of right valve of P. purpuratus with only a vestige of a fourth, 

rather than five less strong riblets as in P. cristobalensis, is also an 

evident and apparently constant difference." (Hertlein, 1925a, p. 20) 

"Chlan1-ys hakei differs from C. cristobalensis * * * in the much 

wider and less elevated ribs." (Hertlein and Grant, 1972, p. 200) 

Comments.-The holotype is a moderately large, thick-shelled, 
TERTIARY MARINE PELECYPODS: PROPEAMUSSIIDAE AND PECTINIDAE B41 

right valve that has heavy, square ribs and square interspaces that 

are half as wide. Looped, concentric lamellae cross the ribs and 

interspaces on the ventral half of the disk. 

Geog·raph·1:c 1·ange.-Isla Cedros to Bahia Tortugas, Baja California Peninsula. 

Geolog1:c ra.nge.-PI iocene. 

Occu?Tence 1:n BaJa Cal1jo·rnia.-Almejas Formation (Minch and 

others, 1976). 

Argo pecten abietis abietis (Jordan and Hertlein) 

Plate II, figure 2; plate 12, figure 3 

Pecten (Plag-~:octem:u.m) ab1:et1:s Jordan and Hertlein, 1926a, p. 214-

215, pl. 23, figs. 1. 3, 7. 

Aequ:1:1Jecten a.lriet1:s (Jordan and Hertlein). Durham, 1950, p. 62, pl. 

10, figs. 4, 7; pl. 11, fig. 4. 

Chla:m.ys (A·rgo1Jecten) a.ln:et·1:s E. K. Jordan and Hertlein. Emerson 

and Hertlein, 1964, p, 349,354, figs. 4a-e. Hertlein, 1966, p. 278, 

280. fig. 15. 

On:g·ina.l desc?·i1Jt'1:on.-"Shell averaging about 45 millimeters in 

altitude. about as long as high, fairly thick and solid, somewhat 

produced posteriorly. Right valve ornamented by 19-21 subtriangular ribs, in adults becoming flattened toward the margin, separated by sharp, narrow-bottomed interspaces, the sides of the ribs 

and interspaces decorated by sharp, close-set fringing lamellae; 

hinge line about two-thirds the length of disk; ears about equal in 

length, rather large, the anterior ear ornamented by about four. 

r·ather faint radial ribs crossed by concentric lines of growth, the 

byssal notch well defined; posterior ear faintly radially and concentrically sculptured. Left valve with the ribs more pronouncedly 

triangular in cross-section, the sides densely fringed with lamellae; 

ears similar to those of right valve, but the byssal notch on anterior 

ear less developed: hinge strong; cardinal crura well developed. 

Altitude 45 mm.; longitude 46 mm.; diameter of left valve about 32 

mm.: apical angle about 100°." 

HolotmJe. -CAS 2079. 

TmJe loca.l-ity.-CAS 937. Isla Maria Madre, Mexico. Unnamed 

PI iocene str·ata. 

SumJlementa.ry descn:pt1:on.-"The radial ribs of this species are 

triangular to subtriangular in cross-section, especially in the early 

stage of growth. These are separated by narrow interspaces and the 

sides of the ribs and the inters paces are covered with a dense fringe 

of concentric lamellae." (Hertlein, 1966, p. 280) 

"In some well-preserved specimens * * * the byssal notch is 

extremely shallow, in others it is of the normal type. Two individuals 

* * * have much higher ribs than the average. * * * many small 

specimens have the V-shaped ribs flat-topped, but on the larger 

individuals these ribs grade into those of the typical form." (Durham, 1950. p. 62) 

Com.1)(1:1"1:son.-"This species is closely related toP. c1>rcula?·is, but 

is distinguishable by the character of the ribbing. The ribs of P. 

a.b·iet·1:s ar·e wide at the base. and are triangular or subtriangular in 

cross-section. The interspaces are very narrow, and the sides of the 

ribs and interspaces are covered by a dense fringe of concentric 

lamellae. The ribs of P. c1:?·cu.la.n:s are distinctly rounder and much 

nar·rower in cross section, and the interspaces are much wider." 

(Jordan and Hertlein, 1926a, p. 214) 

"The byssal notch varies somewhat in depth but is never so deep as 

in the living Pecten puTpu.?·atus or Pecten cinula.r1:s; further, the 

anterior ear is not so produced in proportion to its width as in those 

two species. The ribs normally have a low V-shaped profile, thus 

differing from the two aforementioned living forms in which the 

sides of the ribs are nearly vertical. 

"A few specimens*** are very close to Pecten mendenhall1: Arnold, 

but the rest are more typical of A. abietis. It is possible that additional collecting at Santa Rosalia (type locality for P. mendenhalli) 

may show that the two species are the same." (Durham, 1950, p. 62) 

Argopecten abietis abbotti differs from A. abbotti "in the deeper 

notch under the right anterior ear, in the more widely spaced ribs 

and by the more flattened character of the ribs toward the ventral 

margin of the left valve." (Hertlein and Grant, 1972, p. 196-197) 

Comments.-The holotype is a thick-shelled left valve with 19 

triangular ribs separated by narrow, shallow interspaces bearing 

looped, concentric lamellae. The right-valve paratype, tigured 

herein, is thick shelled and has 19 subrounded ribs with narrow, 

shallow interspaces. Looped, concentric lamellae can be seen on the 

ribs and interspaces near the ventral margin. 

Geograph1:c range.-Baja California Sur to Isla Maria Madre, 

Mexico. 

Geologic range.-PI iocene. 

Waller (196, p. ·55) notes that his Argopecten species a, from the 

Miocene in Florida, is similar to A. abietis and says that: "Because 

faunal interchange between the Atlantic-Caribbean and Pacific is 

generally accepted during the Miocene and Pliocene, Argopecten 

species a may be conspecific with a Pacific form." 

Occurrence in Baja California.-Carmen (Durham, 1950), Gloria 

(Stump, 1979), Infierno (Stump, 1979), Marquer, and San Marcos 

Formations (Durham, 1950). 

Argopecten antonitaensis (Durham) 

Plate 11, figures 4, 5 

Aequipecten antonitaensis Durham, 1950, p. 62, pl. 9, figs. 1. 5. 

01·ig1:nal descr1:ption.-"Shell small, resembling A. percarus 

(Hertlein); moderately convex, nearly equivalved; ornamented by 22 

moderately high, rounded ribs with nearly vertical sides; on right 

valve interspaces about half as wide as ribs, on left valve equal in 

width to ribs; radial ribs crossed by fine concentric growth lines; 

extreme lateral margins smooth; hinge line 0.6length of shell; ears 

unequal, elongate, anterior slightly longer than posterior; a large 

byssal notch in right valve; anterior ear of left valve decidedly alate; 

posterior ears slightly drawn out; anterior ear with about 7 radial 

ribs, posterior ear with about 8." 

Holotype.-CAS 5957. 

Type local1:ty.-CAS 795. Baja California Sur. Carmen Formation, Pliocene. 

S,upplementary descript1:on.-"The long narrow anterior efl.r with 

that of the left valve being drawn out is very characteristic." 

(Durham, 1950, p. 62) 

Comparison.-"The ears [of A. antonitaensis]suggestA. pe1·carus 

(Hertlein) but are longer in proportion to length of shell. It is also 

similar to some specimens of A. 1:m.postor (Hanna) but may be separated by the more produced posterior ears of the present species." 

(Durham, 1950, p. 62) 

Comments.-The holotype is a rather small, inequilateral, doublevalved specimen with a moderately thick shell. The right valve has 

imbricated, concentric lamellae on both the ribs and inters paces and 

looped concentric lamellae near the ventral margin; the left valve is 

·sculptured like the right. The left anterior auricle is long and deeply 

notched. 

Geographic range.-Baja California Sur. 

Geologic range.-Pliocene. 

Occun·ence in BaJ·a Calijornia.-Carmen Formation. 
B42 PALEONTOLOGY OF CALIFORNIA AND BAJA CALIFORNIA 

Argopecten abietis abbotti (Hertlein and Grant) 

Plate 12, figures I, 5 

Chlamys (Argopecten) abietis abbotti Hertlein and Grant, 1972, p. 

196-197, pl. 34, fig. 5; pl. 36, figs. 1, 6. 

Original description.-"Shelllarge, thick, both valves highly convex, somewhat elongated posteriorly; hinge_lim~ long, a little over 

two thirds the length of the valves. Right valve with 21 radial ribs 

which are high, narrowly flat-topped and steeply sloping until the 

valve is about 70 mm high, then becoming lower and broadly 

rounded; the sides of the ribs and the interspaces are ornamented 

with close-set fringing lamellae; anterior ear sculptured with 4 or 5 

fine radial riblets, a well developed byssal notch present; posterior 

ear faintly radially striated and with lines of growth which reveal a 

shallow sinuation. Left valve with a ribbing similar to that of the 

right except that the ribs are narrower and more triangular, the 

anterior··ear with a shallower notch and with faint traces of fine 

riblets. Inner margin of valves scalloped by the corresponding ribs 

and interspaces on the exterior. Dimensions: length 129.0 mm; 

height 118.0 mm, convexity (both valves together), 64.0 mm, length 

of hinge line 88.0 mm." 

Holotype.-SDNM 04334. 

,Type locality.-From cut in exposure at Frontier Housing Project, 

Lorna Portal, San Diego, San Diego County, Calif. San Diego Formation, Pliocene. 

Comparison. -"The shell characters of this new subspecies appear 

to be intermediate between those of Chlamys(Argopecten) abietis E. 

K. Jordan ana Hertlein * **and those of C. (A.) aequisulcata Carpenter * * *. This new subspecies differs from C. (A.) abietis in the 

deeper notch under the right anterior ear, in the more widely spaced 

ribs and by the more flattened character of the ribs toward the 

ventral margin of the left valve. It differs from C. (A.) circular1:s · 

aeqU1:sulcata in the larger, thicker shell, longer hinge line, more 

triangular shape of the ribs in the early stages of growth but which 

become rounded and flattened toward the ventral margin on the 

right valve, and also in the more highly convex left valve with 

narrower interspaces between the ribs. 

"The rotund appearance of large specimens of this new subspecies 

lends a general resemblance to C. (A.) hakei Hertlein but it may be 

separated from that species by the fewer ribs (21 or 22 rather than 24 

to 27) which are triangular until the shell is about 70 mm high and 

then become broader and flatter toward the ventral margin." 

(Hertlein and Grant, 1972, p. 196-197) 

Geograph1:c range.-Southern California·. 

Geologic range.-Pliocene to Pleistocene. 

Occurrence in Calijornia.-Pliocene: San Diego Formation; Pleistocene: Las Posas Formation (Hertlein and Grant, 1972). 

Genus ARGOPECTEN? 

Argopecten? crassiradiatus (Clark) 

Plate 10, figure 8 

Pecten (Plag1:octeniurn?) crass1:radiatus Clark, 1915, p. 450, pl. 47, 

fig. 7. 

On:g1:nal description.-"Shell medium in size; fairly heavy; apical 

angle about 98\ height about equal to the length; dorsal edges 

nearly straight. Hinge plate over half the length of the shell. Right 

valve sculptured by sixteen heavy, broadly rounded, radiating ribs, 

which become somewhat narrower near the margins; interspaces 

very narrow and deep. Dorsal margins rather strongly depressed, 

the depressed area being narrow and without ribs. Anterior ear 

longer than posterior, deeply notched with anterior edge gently 

convex, sculptured by four fairly heavy radiating ribs. Left valve 

unknown." 

Holotype.-UCMP 11584. 

Type locality.-UC 367. Contra Costa County, Calif. [Locality description not available.] Cierbo Sandstone, Miocene. 

Comments.-The holotype is a thick-shelled, incomplete, slightly 

inflated right valve with 14 wide, smooth, closely spaced radial ribs, 

separated by very narrow, deep interspaces. The rigpt anterior 

auricle bears 4 riblets; the right posterior auricle is missing. The 

ribs on A.? crassiradiatus are more closely spaced than on A. cn:stobalensis, higher and more closely spaced than on A. hake1:, and 

higher than on A. evermanni. 

Geographic range.-Known only from the type locality, middle 

California. 

Geologic ra,nge.-Miocene. 

Occurrence in Calijorm:a.-Cierbo Sandstone. 

Genus ANTIPECTEN Cossmann, 1914 

Right valve nearly flat, left valve convex; auricles very large, 

hinge line oblique. 

Differs from Aequipecten in the obliquity of the hinge line, larger 

auricles, and in the unequal size of the ribs of the left valve. Differs 

from Leptopecten in having a thick shell, higher ribs, and secondary 

riblets on both the ribs and interspaces of the left valve and on the 

ribs of the right valve. Differs from Pacipecten in having higher 

posterior auricles and secondary riblets on the ribs and interspaces 

of the left valve and on the ribs of the right valve. Differs from 

Fortipecten in having an oblique hinge line and in that the umbo of 

the right valve does not overhang the left valve. 

Geographic range.-France; Baja California Sur? 

Geologic range.-Miocene; PI iocene(?). 

Genus ANTIPECTEN? 

Anti pecten? praevalidus (Jordan and Hertlein) 

Plate 13, figures 2, 4, 5 

Pecten (Leptopecten) praevalidus Jordan and Hertlein, 1926b, p. 

435-436, pl. 29, figs. 2, 3. 

Pecten (Aequipecten) praeval1:dus Jordan and Hertlein. Grant and 

Gale, 1931, p. 206. 

On:ginal descn:pt?:on. -"Shell of moderate size, somewhat inflated, 

elongated posteriorly giving an oblique outline, the hinge line fourfifths the length of the shell. Right valve nearly flat, ornamented by 

about 13 or 14 flat-topped radiating ribs which are often longitudinally sculptured by one or two slight sulci; ribs separated by interspaces about as wide as the ribs, the bottoms ofsomeofthe inters paces 

lightly, longitudinally striate; anterior ear large, cut by a large 

byssal notch, and ornamented by four or five radiating ribs crossed 

by concentric lines of growth; left ear larger than right, sloping 

acutely from hinge line to posterior margin of shell, ornamented by 

six to nine unequal radiating riblets. Left valve somewhat more 

arched than right, ornamented by 15 or 16 moderately rounded 

radiating ribs some of which show a fairly well defined medial 

sulcus; interspaces as wide as ribs; both ribs and interspaces finely 

longitudinally striate, and crossed by concentric lines of growth; 

ears much as those of right valve, and similarly ornamented, except 

that the anterior ear of the left, carries six or seven radiating rib lets 

between which are intercalated minute raised lines. Length 50 mm.; 

height 48 mm.; diameter approximately 15 mm.; length of hinge line 

approximately 40 mm.; apical angle 103°." 

Holotype.-CAS 2101. 
TERTIARY MARINE PELECYPODS: PROPEAMUSSIIDAE AND PECTINIDAE B43 

Type locab:ty.-CAS 945. Baja California Sur. Almejas Formation, Pliocene. 

SnmJlenwnta:ry desc·ript·ion.-"The large size, the flattish right 

valve, the flat-topped ribs of the right valve and the striations of the 

ribs of both valves characterize this large Leptopecten. Some specimens attain a length of about 70 mm., and a height of about 60 mm., 

or more." (Jordan and Hertlein, 1926b, p. 436) 

Cmn1J0:r'1:son.-"Like typical Pecten lat1:au:ratus Conrad but about 

twice as large and with distinct radial striation on the ribs and 

inter·spaces: ears as in tu:m.bezen.s·is." (Grant and Gale, 1931, p. 206) 

Com:nwn.ts.-Ant·ipecten? p·raevab:dus does not resemble any of the 

other· pectinids described from the eastern Pacific. It resembles 

Aequ:1:1Jecten.only in 'the secondary sculpture of rib lets on the ribs and 

interspaces of the left valve and on the ribs of the right valve. It 

resembles Le1Jtopecten only in the obliquity of the shell and the high 

posterior auricles. It has a moderately thick shell like Pac1:pecten but 

is more oblique and bears secondary riblets. It differs from Antipecten in having a straight hinge line that is shorter, but in other 

characters it is surprisingly similar. Hertlein and Grant (1972, 

p. 203) noted the "remarkable" resemblance of this species to 

Chla:m.ys sa,cy·i Cossmann and Peyrot, the type species of Ant1:pecten 

from the Miocene of France. I have placed A.? 1n-aevab:dus tentatively in Ant·i1u~cten to call attention to its similarity to that genus 

and to its uniqueness. 

Georrraph:1:c ·ra:nge.-Baja California Sur. 

Geolog·,:c 1·a:nge.-Pliocene. 

Occu:rrence ·in Bo:in Co.l·I/O?"'n:ia .. -Almejas (Minch and others, 

1976) and Glor·ia (Stump, 1979) Formations. 

Genus LEPTOPECTEN Verrill, 1897 

Small. thin. very oblique. only slightly convex, ribs narrow with 

wider· interspaces; cardinal crura small. hinge plate crossed by fine 

transverse grooves. Pcw·iw~cten is more equilateral in form and has a 

thicker shell than Leptopecten. 

Geog·ra1Jh:ic ·ro:nge.-North and South America. 

Geolom:c rnnge.-Miocene through Holocene (table 8). 

Leptopecten bellilamellatus (Arnold) 

J>Jatc 13, figures 3, 6 

Pecte-n (Chla:mys) bell-Ua:m.ellatus Arnold, 1906, p. 108, pl. 41, figs. 6, 

6a. 7, 7a. 

Pecten (Aequ:ipecten) belh:lamwllat'!ts Arnold. Grant and Gale, 1931. 

p. 205. 

Chlo:m.ys (Leptopecten) belh:la:mellata Arnold. Hertlein and Grant, 

1972, p. 203. pl. 32. figs. 1, 2. 8. 

Orirtina.l clesc·ri1Jt·ion.-"Shell averaging about 18 millimeters in 

altitude, about as long as high, equivalve. both valves moderately 

convex. inequilateral: sides nearly straight; margins not serrate. 

Right valve with 15or 16 prominent narrow, sharply convex-topped 

ribs with sloping sides; interspaces much wider than ribs, with 

narrow, flat bottoms; surface sculptured by numerous, regular, 

equidistant, thin, concentric, imbricating lamellae, which cut 

squarely across the bottoms of the interspaces, curve convexly 

toward the umbo on the sides of the ribs, and loop gracefully downward away from the umbo on the tops; hinge line equal to the length 

of the disk; ears equal in length; anterior ear convexly truncated, 

separated from the disk by a deep, sharply defined, byssal notch, and 

sculptured by fine, regular, incremental lamellae and five or six 

subequal radials; posterior ear acutely pointed, radially striate, and 

with incremental sculpture similar to but not quite as prominent as 

that of the anterior. Left valve similar to right; anterior ear more 

prominently sculptured, both radially and concentrically, than the 

posterior." 

Holotype.-CAS/SU 35. 

Type locality.-Pacific Beach, San Diego, San Diego County, 

Calif. San Diego Formation, Pliocene. 

Compm·ison.-The small size, lon·g hinge line, narrow, sharply 

topped ribs. and beautifully curved incremental lamellae are characters which separate L. bellilamellatus from L. lat?:am·ata. and L. 

delmn: (Arnold). (Arnold, 1906, p. 108) 

Comments.-The holotype is a very small, thin-shelled, doublevalved specimen. The hinge line is almost as long as the valve. The 

entire surface of the right-valve disk bears imbricated, concentric 

lamellae. The lamellae are at right angles to the ribs in the bottom of 

the interspaces, loop up toward the dorsal margin on the sides of the 

ribs, and then loop down toward the ventral margin on the tops of the 

ribs. A ctenolium is exposed along the junction of the right auricle 

and the disk. The left valve ribs are identical to those on the right 

valve, but the microsculpture is barely visible. 

Geom·aph1:c range.-Middle California to Baja California Sur. 

Geolog1:c 1·ange.-Miocene to Pleistocene. 

OccmTence in the Cal?/o?·m:as.-Miocene and Pliocene: Purisima 

Formation (Arnold, 1906); Pliocene: Almejas (Minch and others, 

1976) and San Diego (Hertlein and Grant, 1972) Formations; Pliocene and Pleistocene: Merced Formation (Arnold, 1906). 

Leptopecten latiauratus (Conrad) 

Plate 15, figures 7, 9 

Pecten lahaw·atus Conrad, 1837, p. 238, pl. 18, fig. 9. 

Leptopecten la.t?:a.u?·atus (Conrad). Woodring, 1946, p. 81. Clark, 

1971, p. 269-272, figs. 0369, 0372, 0373, 0380, 0459. 

Chlamys (Leptopecten) lat1:a1tTata (Conrad). Grau, 1959, p. 107-110, 

pl. 35, fig. 1. 

Not? Chlam,ys (Leptopecten) lat1:aw·ata Conrad. Hertlein and Grant, 

1972. p. 203-204, pl. 35, figs. 1, 3. 

On:m:nal descn:pt?:on.-"Shell inequilateral, thin, compressed; 

ribs fourteen, flattened on the back, slightly sulcated; interstices 

TABLE 8.-Geolom:c and {Jeogmph:1:c d?:stn:lni.t·ion of the genus Leptopecten 1:n the easten~ 

Pac1}1:c 1·em:on 

11·1 =Holocene: Pic= Pleistocene: PI= Pliocene: M =Miocene] 

Species 

Genus Le1Jtopecten: 

bell·ilmnellatu.s (Arnold)····--··········-··········· 

lnt·ia:u.?·atus (Conrad)·-··-··-····················-····· 

California 

Northern Middle Southern 

M to Pie PI 

M to H PI to H 

Baja 

California 

Norte Sur 

PI 

H PI to H 
B44 PALEONTOLOGY OF CALIFORNIA AND BAJA CALIFORNIA 

transversely striated; ears very wide, unequal, both acutely angulated at the extremity; colour reddish brown and white, variegated 

or spotted." 

Syntypes.-BM (NH) 55.3.14.53 and 61.5.20.89 (Keen, 1966). 

Type locality.-"Inhabits below the efflux of the tide near Sta. 

Diego and Sta. Barbara." The type locality has been cited as "San 

Diego, California" by some authors, such as Grant and Gale (1931, p. 

203) and Grau (1959, p. 109), but none formally designated. 

Supplementary description.-"P. latiauritus is found living attached to kelp, those specimens inhabiting the deeper, quieter 

waters being less strongly sculptured than those which are subjected 

to a more strenuous existence nearer the shore." (Arnold, 1906, p. 

116) 

"Shell rather thin, slightly oblique and moderately convex; equilateral or nearly so; adult specimens averaging 20 mm in height and 

length. Hinge line almost always longer than disk in juvenile stage; 

in adult stage infrequently longer, usually slightly shorter. Both 

valves )Vith 12 to 16 rounded ribs (actually corrugations of disk), 

rather flat on top and occasionally with a central groove; inters paces 

about same width as ribs and in some specimens having one or two 

low radial ridges; concentric lamellae covering disk, quite profuse in 

juvenile stage but less prominent in adult. Anterior auricles longer 

than posterior, former projecting beyond margin of disk, latter 

seldom reaching to margin; anterior auricle of right valve having 4 

to 7 imbricated riblets, other auricles having 4 to 8 riblets and fine 

concentric lamellae. Reverse surfaces of interspaces flat and angulated." (Grau, 1959, p. 109) 

"A series of specimens reveals that the number of ribs may vary 

from 12 to 16. Some ofthese may be faintly medially sulcated. A faint 

intercalary riblet may be present in the interspaces especially on 

large specimens." (Hertlein and Grant, 1972, p. 204) 

Cornparison.-"Chlarnys (Leptopecten) latiaurata differs from C. 

(L.) rnonotirneris Conrad in the squarish ribs rather than rounded 

undulations of the shell." (Hertlein and Grant, 1972, p. 204) 

"This species differs from its subspecies rnonotirneris in having a 

thicker shell, longer hinge line, acutely pointed auricles, less pronounced obliquity, higher and narrower ribs, and concentric lamellae on the disks." (Grau, 1959, p. 110) 

"The variety L. latiauratus cerritensis ('jragilis'), based on material from the Palos Verdes sand, has fewer and wider ribs than L. 

latiauritus proper. The variety L.latiauratus delosi, based on material from the San Pedro sand, has strong concentric lamellae." 

(Woodring, 1946, p. 81) 

Cornrnents.-The specimen figured by Hertlein and Grant (1972, 

pl. 35, figs. 1, 3) as Chlarnys (Leptopecten) latiaurata is similar to 

Pacipecten tU?nbezensis. It differs from L. latiaura,ta in not being 

oblique and in having a shorter right anterior auricle and smaller 

right posterior auricle than is common for L. latiaurata. 

Geographic range.-Living: Point Reyes, Calif., to Cabo San 

Lucas, Baja California Sur and Guadalupe Island; fossil: middle 

California to Baja California Sur. 

Geologic range.-Miocene through Holocene. 

Occurrence in the Californias.-Miocene and Pliocene: Purisima 

Formation (Arnold, 1906); Pliocene: Almejas Formation (Minch and 

others, 1976), Lomita Marl Member, San Pedro Formation (Woodring, 1946), and unnamed Pliocene strata of northern Santa Clara 

County (Addicott, 1969); Pliocene and Pleistocene: Fernando (Woodring, 1931; Kennedy, 1975) and Merced (Arnold, 1906) Formations; 

Pleistocene: Timms Point Silt Member, San Pedro Formation 

(Woodring, 1946), and unnamed strata of Baja California Norte 

(Valentine, 1957). 

Hab1:tat.-"Found attached to rocks or pilings in shallow water; in 

deeper water on rock, shale, gravel or sand bottoms, often attached 

to calcareous algae." (Grau, 1959, p. 110) 

"Leptopecten * * * latiaurata, commonly known as 'kelp-pecten,' 

occurs at many places along the coast of southern California attached by its byssus to vegetable growths, pilings, or rocks. It occurs 

in shallow water but it has been taken at a depth of 229 meters. * * * 

It reaches maturity in about 9 to 12 months and in that period of time 

attains a length of about 32 mm. 

"Formerly it flourished in the still, warm waters of Mission Bay, 

San Diego Co., where it lived attached to Zostera." (Hertlein and 

Grant, 1972, p.204) 

Clark (1971, p. 271-272) says that "there seems to be little doubt 

that environmental factors can have a profound influence on the 

morphological characteristics of the shell of a bivalved mollusk" and 

that, although far from definitive, his observations "strongly suggest 

that the difference in temperature is the major cause of the differences in morphology" between L. latiauratus and L. monotime'ris. 

Genus PACIPECTEN Olsson, 1961 

Shell with rounded, flat-topped, or triangular ribs; interspaces as 

wide or wider. Auricles large, posterior ones spreading, the right 

anterior long and narrow with a deep byssal notch bordered by a few 

ctenolial teeth. Differs from Leptopecten in its more equilateral 

form, longer anterior auricle with deeper byssal notch, and heavier 

.shell. 

Geographic range.-Eastern Pacific. 

Geologic range.-Miocene through Holocene (table 9). 

TABLE 9.-Geologic and geographic distribution of the genus Pacipecten in the eastern Pac1]1:c region 

[H =Holocene; PI= Pliocene; M =Miocene; 0 =Oligocene] 

California 

Species Northern Middle 

Genus Pacipecten: 

andersoni andersoni (Arnold) ............... . M 

andersoni barkerianus (Arnold) .......... .. O,M 

andersoni subandersoni 

(Loel and Corey) .................................... .. bilineatus (Clark) ....................................... . M 

discus (Conrad) .................................... : ...... . M M 

pabloensis (Conrad) of Arnold .............. .. M 

tolrnani (Hall and Ambrose) .................. .. M 

tumbezensis (Orbigny) ............................ .. weaveri (Clark) .......................................... .. M 

Southern 

M 

O,M 

O,M 

. ..... 

M 

M 

Baja California 

Norte Sur 

M M 

M 

PI to H 

Central and (or) South 

America 

H 
TERTIARY MARINE PELECYPODS: PROPEAMUSSIIDAE AND PECTINIDAE B45 

Pacipecten andersoni subandersoni (Loel and Corey) 

Plate 14, figure 6 

Pecten (Pla.rriocten:iu:m) a.nde·rsom: Arnold subanderson1: Loel and 

Corey, 1932, p. 202. pl. 21. figs. 7, 8. 

A eq·1.t:1:pecten a.nde·rson:1: (Arnold) suba:ndenwm: (Loel and Corey). 

Adegoke, 1969. p. 98, pl. 1. fig. 11. 

Ori{J'I:na.l desc·n:pt·1:on .. -"Pectens of the phylum of P. andersoni 

Arnold which have been collected from many localities in the 

Vaqueros horizon have consistently fewer ribs than the typical form 

which has 17, and fewer than those from all collections examined 

fr·om the Temblor horizon. Rarely is a specimen found in the Vaqueros with 16 ribs: the average number on hundreds counted is 15, 

many having but 14 well defined ribs. Some individuals from the 

Temblor horizon have 16 ribs. Since there is an apparent stratigraphic significance in the rib number in P. andersom: it is thought 

that this Vaqueros form (including variants in outline and rib character as in the case of P. ande·rsoni Arnold) shouJd be given a subspecific or· varietal designation. It should be noted that the type of P. 

a.ncle-l·.c::on:l: Arnold (1906) was found in sandstones a few feet below 

the Monterey shale of Santa Cruz County, according to Arnold, and 

is therefore Temblor in age, in accord with the Temblor faunule 

associated." 

Holotype.-UCMP 31741. 

'Type loca.l·1:ty.-UC A572. San Luis Obispo County, Calif. Vaqueros Formation, Oligocene and Miocene. 

Com.nwnts.-Pcwipecten a.ncle?·som: su.bancle?·som: can only be differentiated from P. o:ncle·rson:1: by the number of ribs: P. ande?·son?: 

usually has 17 and P. a. su.bancle·rsom: usually has 15. 

Geogro.1Jh:ic ·ro.nge.-Southern California to Baja California Sur. 

Geolog·ic 'l'o,nge.-Oiigocene to Miocene. 

Occu:rnmce ·1:n Cal·ij'o?·n:io .. -Oiigocene and Miocene: Temblor 

(Adegoke. 1969) and Vaqueros Formations: Miocene: Isidro (Stump, 

1979) and Tierra Redonda (Durham, 1970) Formations. 

Pacipecten andersoni barkerianus (Arnold) 

Plate 20, figures 2, 5 

Pecten (Pla.rrl:oct(m:l:?.t?n) a.ncle?·son:i var. ba·rke?'?:anus Arnold, 1906, p. 

83-84, pl. 26, fig. 9. 

Chla:m.ys ba:rke?"l:a.no, (Arnold). Schenck and Keen, 1940, pl. 39, fig. 5. 

On:rrhwl clesc·ript·ion.-"Shell averaging about 40 millimeters in 

altitude, somewhat longer than high, equilateral, somewhat ventricose. and with serrate margins; base regularly rounded; sides nearly 

stntight, sloping at a moderately low angle. Left valve with 17rather 

narTow, prominent rounded ribs, each with a rounded, thread-like 

riblet running longitudinally along its top; at more or less regular 

intervals small obsolete spines protrude from the riblet: inters paces 

wider than the ribs. with sloping sides, and flat bottoms; whole 

surface of disk cr·ossed by very fine incremental lines; hinge line 

longer than one-half length of disks; ears subequal, rectangularly 

truncated, and sculptured by radiating ridges and incremental 

lines." 

Holotype.-Missing and presumed destroyed in the San Francisco 

fire of 1906. 

TmJe locob:ty.-Barker's Ranch [NX!, T. 29 S., R. 29 E.], Kern 

County, Calif. Temblor Formation, Oligocene and Miocene. 

Supplenwnta:ry cle.•w·n:pt·ion.-"This variety * * *is characterized 

by the thread-like riblet along each primary rib on the left valve 

"' "' *" (Arnold. 1906, p. 84) 

Geogm.ph:ic 'l'ange.-Middle and southern California. 

Geologic range.-Oligocene to Miocene. 

Occurrence in Califon~ia.-Oligocene and Miocene: Temblor 

Formation; Miocene: Modelo Formation (Hudson and Craig, 1929) 

and Olcese Sand (Schenck and Keen, 1940). 

Pacipecten andersoni andersoni (Arnold) 

Plate 14, figure I 

Pecten (Plagioctenium) anclenoni Arnold, 1906, p. 82-83, pl. 26, figs. 

5, 5a, 6, 7, 8, Sa. Loel and Corey, 1932, pl. 21, fig. 6. 

Pecten (Aequipecten) andersom: Arnold. Grant and Gale, 1931, p. 

202-203, pl. 4, figs. 4, 5. 

Pecten anclersom: Arnold. Hanna and Hertlein, 1943, fig. 63-1 and 

63-2. 

Aequipecten anclersom: (Arnold). Stewart, 1946, pl. 17, figs. 1-3. 

Woodring, 1946, p. 27, pl. 28, fig. 11. Adegoke, 1969, p. 98, pl. 1, 

fig. 13; pl. 2, fig. 2. 

Leptopecten ande?·som: (Arnold). Addicott, 1972, pl. 3, figs. 11, 20. 

01·iginal desc?·iption.-"Shell averaging about 35 millimeters in 

altitude, generally somewhat longer than high, both valves convex, 

more or less inequivalve and inequilateral; margins smooth; base 

regularly rounded; sides concave above. Right valve with 14 to 18 

prominent rounded ribs, separated by flat-bottomed interspaces, 

which are generally of about equal width to, but sometimes narrower than, the ribs; surface sculptured by numerous, sharp, imbricating, incremental lines, and sometimes, at irregular intervals, by 

more or less prominent lines of interrupted growth; hinge line more 

than one-half length of disk; ears subequal; anterior ear with 3 or 4 

sharp radials and numerous fine concentric lines: byssal notch quite 

pronounced; posterior ear sculptured similarly to anterior, and 

truncated nearly rectangularly. Left valve more convex than the 

right, sculptured similarly and with similar ears, except that the 

notch in the anterior is not so pronounced." 

Holotype.-USNM 164932. 

Type locality.-Zayante Creek, Santa Cruz County, Calif. Monterey(?) Formation, Miocene. 

Supplementa?·y clescription.-"characterized by subcircular flat 

valves with about 16 to 18 rounded ribs and relatively wide, flatbottomed interspaces." (Adegoke, 1969, p. 98) 

Compa?·ison.-"Large specimens ·of P. andersoni very closely 

resemble some specimens of P. discus but differ from the latter in 

the fewer number (14 to 18) of their ribs, P. discus having 18 to 21. 

"A prominent characteristic of this species is that the left is decidedly the more convex of the two valves. In this respect it is similar to 

P. latiauritus and varieties. In fact, the young of P. andersoni is 

almost indistinguishable, in some instances, from small specimens 

of P. lat1:auritus var. monotimer1:s. The young of P. andersoni are 

·equilateral, are relatively more convex, and have more prominent 

'ribs than the adult forms." (Arnold, 1906, p. 82) 

Pacipecten ande1·soni andersoni consistently has fewer ribs (14 to 

18) than P. discus (17 to 20). (Vedder and Moore, 1976) 

Geog1·aphic range.-Middle California to Baja California Sur. 

Geologic range.-Miocene. ":restricted·. in stratigraphic occurrence 

to the 'Temblor' Stage of the California molluscan sequence, a unit 

that is of latest early Miocene and middle Miocene age in terms of 

European series-epoch terminology." (W. 0. Addicott, written 

commun., 1978) 

Occurrence in the Californias.-Altamira Shale Member, Monterey Shale (Woodring, 1946), Branch Canyon Sandstone (Vedder, 

'1968), Buttonbed Sandstone Member, Temblor (Addicott, 1972), 

Chamisal (Bowen, 1966), Gould Shale Member, Monterey (Addicott, 
B46 PALEONTOLOGY OF CALIFORNIA AND BAJA CALIFORNIA 

1972), Hames Member, Monterey (Addicott and others, 1978), Isidro 

(Stump, 1979), Los Tularcitos Member, Chamisal (Hertlein in 

Bowen, 1966), McLure Shale Member, Monterey (Adegoke, 1969), 

Media Shale Member, Temblor (Anderson and Land, 1969), Modelo 

(Hudson and Craig, 1929), and Moreno (Page and others, 1951) 

Formations, Olcese Sand (Addicott, 1965), Round Mountain Silt 

(Addicott, 1965), Saltos Shale Member, Monterey (Vedder, 1973; 

Addicott and others, 1978), San Pablo (Arnold, 1906), Tierra 

Redond'a (Durham, 1970), Topanga (Vedder and Woodring, written 

commun., 1953), Tortugas (Minch and others, 1976), and Twisselman Sandstone Member, Monterey (Addicott, 1972) Formations, 

and unnamed Miocene sandstone of Dibblee, 1966 (Arnold, 1906). 

[This subspecies does not occur in the Vaqueros Formation, and 

citations to that effect are in error.] 

Pacipecten tolmani (Hall and Ambrose) 

Plate 14, figure 2 

Pecten tolmani Hall and Ambrose, 1916, p. 82. Trask, 1922, pl. 3, figs. 

1, 3. Wiedey, 1929, p. 23, pl. 1, fig. 2. Hall, 1958, p. 51, pl. 2, fig. 1. 

"Pecten" tolmani Hall and Ambrose. Schenck and Keen, 1950, pl. 44, 

figs. 5, 6. 

On:g1:nal description.-"Both valves convex, left more convex of 

two, inequilateral, base regularly rounded; margins smooth. Right 

valve with 16 to 18 prominent rounded ribs, separated by rounded 

interspaces, narrower than the ribs; ribs on left valve more prominent and irregularly spaced; surface sculptured by numerous, fine, 

imbricating, regular lines of growth; hinge line less than one-half 

length of disk; ears subequal; anterior ear of other specimens show 5 

or 6 sharp radial lines emanating from beak, crossed by fine, faint, 

concentric lines; sculpture of posterior ear less distinct but truncated at right angles." 

Holotype.-CAS/SU 23. 

Type locality.-[Mouth of Welch Creek, Sunol], Pleasanton quadrangle, Alameda County, Calif. Briones Sandstone, Miocene. 

Comparison.-"This species resembles an enlarged P. andersoni 

but* * *is much larger than P. andersoni, the hinge (proportional to 

size) much shorter, and the umbonal angle much larger. 

"It is possible this form is a descendant of P. andersoni, of Monterey times. The young are very similar to P. andersoni, and it is not 

certain that the forms classified as P. andersoni in the Briones are 

not the young of P. tolmani." (Hall and Ambrose, 1916, p. 82) 

Comments.-The holotype is a large (for the genus), moderately 

inflated left valve. The umbonal angle is small, the umbo inflated, 

and the beak higher than the hinge line. Although the umbonal 

angle is small and the line of attachment of the auricles to the disk 

steeply concave, the shell then flares outward toward the anterior 

and posterior margins in a line subparallel to the hinge, and in this 

character resembles P. weaveri. The ribs on P. tolmani are subrounded, not prominent, and are separated by wider interspaces at 

the ve'\tral margin. The anteriormost and posteriormost margins of 

the shell bear only faint traces of ribs. The valve seems to have been 

inequilateral with the anterior portion larger than the posterior. 

The left valve holotype of P. tolmani is twice as large as the left 

valve syntype of P. weaveri and has 17low rounded ribs. Pacipecten 

weaveri has 14 ribs on the left valve syntype and these ribs are higher 

and mor,e ridgelike than those on P. tolmani. In addition, P. weaveri 

does not have the slightly sculptured areas at the anterior and posterior margins. Pacipecten we a veri has fine concentric lamellae on the 

left valve that may be bunched together giving a roughness to the 

ribs; P. tolmani has an almost smooth left valve with barely perceptible concentric lines. 

Geograph1:c range.-Middle California. 

Geologic range.-Miocene. 

Occurrence in California.-Briones (Hall, 1958) and Cierbo (Huey, 

1948) Sandstones. 

Pacipecten weaveri (Clark) 

Plate 15, figures 4, 5 

Pecten (Patinopecten) weaver1: Clark, 1915, p. 454-455, pl. 45, figs. 1. 

2. 

"Pecten" weaveri Clark. Schenck and Keen, 1950, pl. 42, fig. 2. 

Original description.-"Shell discoidal, broader than high, equilateral, nearly equivalved; apical angle about 90°, dorsal edges 

gently concave; hinge line about half the length of the shell. Right 

valve sculptured by about fourteen low, broad-topped, squarish ribs, 

the interspaces between which are flat-bottomed and about as wide 

as the tops of the ribs. Surface concentrically sculptured by rather 

coarse, somewhat irregular incremental lines. Anterior ear slightly 

longer than posterior, deeply notched, sculptured by three medium 

coarse, radiating ribs. Posterior ear marked by two or three faint 

radiating riblets. Left valve sculptured by fourteen fairly prominent, rounded, radiating ribs with interspaces about equal to the 

width of the ribs; the ribs next to the dorsal edges are not so promi-

. nent as the others. Surface also covered by fine, sharp, incremental 

lines. Anterior and posterior ears each marked by three medium 

fine, radiating rib lets; anterior edge of anterior ear slightly notched." 

Syntypes.-UCMP 11575, 11576. 

Type locality.-UC 407. Contra Costa County, Calif. Cierbo Sandstone, Miocene. · 

Supplementary description.-"The differences in the sculpturing 

on the two valves is quite noticeable; the left valve, with fairly 

prominent rounded ribs and the sharp incremental lines, contrasts 

quite strongly with the right valve, with its low, squarish ribs and 

·coarser incremental lines." (Clark, 1915, p. 455) 

Comments.-The right valve syntype is inequilateral with the 

posterior side of the disk larger than the anterior. The umbonal 

angle is small, but at a distance about 5 mm below the hinge line the 

anterior portion of the shell margin turns abruptly outward toward 

the anterior; the posterior margin is less concave, with a more even 

slope. The right anterior auricle is long and narrow and has three 

strong riblets; the right posterior auricle is low and has two fine 

riblets. The right valve has 14 ribs that are subrounded and rather 

flat near the ventral margin but subtrigonal on the rest of the shell. 

Bunched concentric threads form irregular bumps on the ribs. 

The left valve syntype is like the right valve in outline. It has 13 

prominent ribs with strong concentric lamellae in the interspaces 

and also on the ribs near the ventral margin. The concentric lamellae 

are bunched to form irregular bumps on the ribs at random intervals, mostly near the ventral margin. The left anterior auricle has 

three riblets, the left posterior two. [SeeP. tolmani for comparison 

with that species.] 

Geographic range.-Middle California. 

Geologic range.-Miocene. 

Occurrence in Calijornia.-Cierbo and Neroly (Hall, 1960) Sandstones. 

Pacipecten discus (Conrad) 

Plate 14, figures 3-5; 7-9 

Pecten discus Conrad, 1857c, p. 190-191, pl. 3, fig. 1. [Reprinted in 

Dall, 1909, p. 181.] 
TERTIARY MARINE PELECYPODS: PROPEAMUSSIIDAE AND PECTINIDAE 

Pecten (Plo.g·,:octen·l:1.t.m,) d·iscus Conrad. Arnold, 1906, p. 86-87, pl. 27, 

figs. 1. la, 2-4. 

Pecten (Aetru:ipecle'n) d-iscu.s Conrad. Grant and Gale, 1931, p. 200-

201, pl. 4, fig. 7. 

l.A~1)t01Jl~cten d·iscus (Conrad). Vedder and Moore, 1976, p. 121, pl. 1, 

figs. 4, 8, 11. Addicott and others, 1978, pl. 4, fig. 18. 

Chla:mys d·iscus (Conrad). Stanton, 1966, p. 27. 

Aettlt:i1)ecten ch<;cus (Conrad). Squires and Fritsche, 1978, p. 21, pl. 4, 

fig. 7. 

Pecte·n (Pecten.) ·ra.ynwnch: Clark, 1915, p. 450-452, pl. 46, figs.l, 2; pl. 

47, figs. 1, 2. 

Al~({'l.t:0Jecwnra:ynunuli(Clark). Adegoke, 1969, p. 99, pl. 2, figs. 7, 10, 

11. 

Pet;ten (Pecten) c·ie·rboen.wis Clat·k, 1915, p. 449, pl. 47, fig. 6. 

Pectwn (Pectwn) ·ra.ynunuli lJ'n:on:io.nus Trask, 1922, p. 148-149, pl. 1, 

figs. 2, 3. 

Pecte·n ·ro.ynwncl-1: b?-·,:on·ia.n:u.s Trask. Hall, 1958, p. 51, pl. 3, fig. 1. 

A etru:ipecten. ·rayni.O'Iuh: (Clark) b·rion:1:a.nus (Trask). Adegoke, 1969, p. 

99, pl. 2, fig. 1. 

Pectwn (Pecten) ancle·rson:1: rwnicosta.tus Trask, 1922, p. 149, pl. 1, fig. 

5. 

On:rrin.al desc'l"l:1)t·ion .. -"Suborbicular, slightly oblique, profoundly 

compressed or discoidal, thin; ribs about 17, rather distant, not very 

prominent, narrow, subtriangular, slender, and more distant toward 

the latet·al margins: ears very unequal, rather small." 

Holotype.-USNM 13335; of P. ·ra.ymond·1:, UCMP 11581; of P. 

b·rion:ia:n:u..':/, UCMP 12368; of P. c·ie1·boen.s·1:s, UCMP 11585: of P. 

gon:1:costo.tu.s, UCMP 12370. 

'l'ype loca.l·dy.-Between La Purisima and Santa Ynez [T. 7 N., R. 

32 W .. SB. Santa Barbara County], Calif. Monterey(?) Formation, 

Miocene. Of P. ra.ynwnd·1:, UC 1492, Contra Costa County, Calif., San 

Pablo Group, Miocene: of P. b·rion:1:a.nus. UC 3532, Alameda County, 

Calif., Briones Sandstone. Miocene: of P. c·1:e·rboens·is, UC 14, Contra 

Costa County, Calif., Briones Sandstone, Miocene; of P. gom:costa.tus, 

UC 1176, Contra Costa County, Calif., Briones Sandstone, Miocene. 

Su.ppltmwnto:ry desc'l"l:pt·,:on .. -"Leptopecten d·1:scus (Conrad) is a 

small, moderately thin-shelled species. * * *The right valve * * * 

bears 17 to 19 ribs that are rounded on the umbonal disk and flattened at the ventt·al margin; the interspaces are flat and slightly 

narrower than the ribs. The right valve is almost flat with an inflation of about 3 mm on the disk. The left valve * * * bears 18 to 20 

sharply rounded ribs; the interspaces are slightly rounded and 

somewhat wider than the ribs. The left valve is more inflated than 

the right valve, with a maximum inflation of 4 to 5 mm. The right 

anterior ear is narrow and bears 4 strong riblets; the byssal notch is 

narrow and deep. The right posterior ear bears as many as four very 

weak rib lets, usually difficult to discern without magnification. The 

left anterior ear bears 5 to 7 rib lets, the left posterior ear 3 to 5; these 

riblets are of moderate strength on both ears. The umbonal angle is 

about 120°. 

"The type specimen of L. chscus * * *is an internal mold of a left 

valve showing the internal ribbing, which reflects the character of 

the external ribs * * *. The valve is very flat with less than 5 mm 

inflation and the umbonal angle is 130°. The valve bears 16 prominent ribs, 1 weak posterior rib, and 2 or 3 weak anterior ribs. 

Eighteen ribs. almost as wide as the interspaces, can be counted at 

the beak. The specimen is 53 mm long and 47 mm high; the hinge is 

20.5 mm long. A small (20 mm wide) external mold on the slab 

containing the type specimen bears 18 ribs, one bifurcated (W. 0. 

Addicott, wt·itten commun., 1969)." (Vedder and Moore, 1976, p. 

121) 

"Shell averaging about 50 millimeters in altitude, about as long as 

high, equivalve, equilateral, thin, rather compressed, and with 

smooth margins; umbonal angle large, averaging about 108°; sides 

somewhat concave above. Right valve with 17 to 20 moderately 

strong, rounded ribs, separated by rather flat interspaces about 

equal in width to the ribs; surface sculptured by regular, elevated, 

wavy, incremental lines and, at irregular intervals, generally by 

more or less prominent lines of interrupted growth; hinge line about 

one-half length of disk; ears unequal, the anterior showing several 

strong radials, while on the posterior the radials are obsolete; both 

ears sculptured by fine concentric lines. Left valve similar to right; 

ears more or less distinctly radially ridged and obliquely truncated. 

"This species, of which the type is a poor specimen, being preserved as a cast in indurated clay, is characterized by its moderately 

strong, convex ribs, compressed disk, and strikingly unequal ears on 

the right valve. Specimens of P. discus having the shell material 

preserved always show moderately high, convex ribs; the internal 

casts (in which form the species is generally found) have the ribs 

more or less squarish, and low. The specimens having the fewest 

number of ribs have the widest lateral areas or submargins. The 

type does not show the radial sculpture found in most cases on the 

ears of the left valve." (Arnold, 1906, p. 86) 

Compa.rison.-"P. discus is closely allied toP. pa.bloensis but has 

the constant difference of larger size when adult and stronger 

rounded ribs instead of weak squarish ones." (Arnold, 1906, p. 86) 

"Shells referable to C. ra.ymondi have been found in this study but 

appear to be part of a gradational series encompassing both C. 

ra.ymondi and C. discus and grouped most closely around the typical 

C. d1:scus." (Stanton, 1966, p. 27) 

"Leptopecten a.nderson1: (Arnold), a species similar to L. discus, 

consistently has fewer ribs (14 to 18). Leptopecten pa.bloen.'n:s (Conrad) has a thinner shell; the ribs become obsolete at the ventral 

margins* * *,and the byssal notch on the right anterior ear is twice 

as wide as the byssal notch on L. d1:scus." (Vedder and Moore, 1976, p. 

121) 

Geograph1:c 1·ange.-Northern (Roth, 1979) to southern California. 

Geolog1:c 1·ange.-Miocene. 

"Leptopecten d1:scus is restricted to the 'Margaritan' Stage of the 

California molluscan sequence, a unit that is the time equivalent of 

the Mohnian benthic foraminiferal stage." (Warren 0. Addicott, 

written commun., 1979) 

Occurrence in Ca.hjm·m:a.-Branch Canyon Sandstone (Vedder, 

1973), Briones Sandstone (Trask, 1922; Weaver, 1953; Hall, 1958), 

Castaic Formation (Stanton, 1966), Cierbo Sandstone (Weaver, 

1949), McLure Shale Member, Monterey Formation (Adegoke, 

1969), Modelo Formation (Oakeshott, 1958), Neroly Sandstone (Hall, 

1960), Santa Margarita (Arnold, 1906; Vedder, 1973; Addicott and 

others, 1978; Squires and Fritsche, 1978), upper part of Temblor 

(Adegoke, 1969), and Wimer (Roth, 1979) Formations, and unnamed 

Miocene strata on San Clemente Island (Vedder and Moore, 1976). 

Pacipecten pabloensis (Conrad) of Arnold 

Plate 15, figures I, 3 

Pecten pabloensis Conrad, 1857b, p. 71, pl. 3, fig. 14. Hertlein, 1951, 

p. 190, fig. 2, no. 14. 

Pecten (Pla.giocteniwn) pabloensis Conrad. Arnold, 1906, p. 88-89, pl. 

27, figs. 5-7. 

Pecten (Chlmnys) pa.bloensis Conrad. Clark, 1915, p. 452-453, pl. 47, 

fig. 8, pl. 48, fig. 2. 

Pecten (Aequipecten) pa.bloensis Conrad. Grant and Gale, 1931, p. 

199-200. 

Leptopecten pa.bloensis (Conrad). Vedder and Moore, 1976, pl. 1, figs. 

1, 2. 

Original description.-"Orbicular, compressed, thin, concentri-
B48 PALEONTOLOGY OF CALIFORNIA AND BAJA CALIFORNIA 

cally wrinkled; ribs 18-20, slender; little prominent, with an intermediate radiating line." (Conrad, 1857b) 

"Shell averaging about 35 millimeters in altitude, about as high as 

long, equivalve, equilateral, thin, only slightly ventricose, and with 

smooth margins; sides sloping at a low angle and quite prominently 

concave above. Right valve with 18 to 20 square, flat-topped, radiating ribs, which are narrower and less distinct laterally and become 

more feeble as the periphery of the disk is approached; interspaces 

about as wide as the ribs, flat bottomed and often separated from the 

principal ribs by impressed lines which give the interspaces the 

appearance of bearing intercalary riblets; whole surface of disk 

sculptured by fine concentric lines and, in some instances, more or 

less prominent lines showing interrupted growth; hinge line somewhat longer than one-half length of disk; anterior ear slightly longer 

than posterior, deeply notched, and ornamented by 4 or 5 coarse 

radiating ridges and sharp, raised incremental lines; posterior ear 

slightly concave behind,- and covered by numerous incremental lines 

and several obsolete radiating ribs. Left valve similar to the right 

except that in some cases the ribs are slightly more rounded above, 

and the looped or wavy concentric lines are more conspicuous; ears 

similar to those of the right valve except that the anterior one lacks 

the deep byssal notch. Hinge as in P. circularis except that the 

cardinal crura are very faint, while the auricular crura are quite 

prominent." (Arnold, 1906) 

Holotype.-Missing and presumed lost; hypotypesof Arnold (1906, 

pl. 27, figs. 5-7), CAS/SU 302 and 302a, 302b. 

Type locality.-San Pablo Bay [Contra Costa County], Calif. San 

Pablo Group, Miocene; of Arnold (1906, p. 88-89), the same. 

Supplementary description.-"The prominence of the ribs seems 

to be the most variable factor in this species. As a rule the ribs are 

sharp and well defined until the shell attains an altitude of 10 or 15 

millimeters, when they broaden out and become low, those near the· 

sides almost losing their identity in some specimens. One specimen 

examined retained the elevated and sharply defined ribs up to an 

altitude of over 25 millimeters * * *."(Arnold, 1906, p. 89) 

"The most interesting character of P. pabloensis is its possession of 

strong Amusium-like internal lirae, which are stronger than the 

external ribbing, and which cause on internal casts the two lines of 

bUineatus." (Grant and Gale, 1931, p. 200) 

Comparison. -..:."This species appears to be a degenerate offshoot of 

P. discus, with which it occurs and with which it intergrades. The 

humped-up form may have been caused by the influx of more or less 

fresh water, and this suggestion is strengthened by the fact that 

pabloensis sometimes occurs very abundantly all by itself in beds 

two or three feet thick." (Grant and Gale, 1931, p. 199) 

Pacipecten pabloensis has a thinner shell, the ribs become obsolete 

at the ventral margins, and the byssal notch on the right anterior ear 

is twice as wide as on P. discus. (Vedder and Moore, 1976, p. 121) 

Comments.-The right valve figured by Arnold (1906, pl. 27, figs. 

6, 6a) is moderately inflated and has 19 ribs that are narrow and 

subrounded and prominent until the shell reaches a height of about 

10 mm at which point they begin to broaden and become flat. At the 

ventral margin the ribs are broad and flat and demarcated by a 

deep, incised groove on both sides. Three barely perceptible interribs appear near the ventral anterior margin. The right anterior 

auricle has five slightly nodose riblets; the right posterior auricle 

has six faint riblets. The anterior dorsal margin is concave; the 

posterior is almost straight. 

The left valve figured by Arnold (1906, pl. 27, figs. 5, 5a) is almost 

flat and has 23 very·narrow ribs separated by interspaces up to four 

times as wide, which commonly have an interrib near the ventral 

margin. The left anterior auricle has seven riblets crossed by concentric lamellae which produce small nodes where bunched on the 

riblets. The left posterior auricle has six riblets sculptured as they 

are on the left anterior auricle. 

Pacipecten pabloensis resembles P. b1:tineatus (Clark) in sculpture 

but can be distinguished by the outline of the shell. In Pacipecten 

bilineatus the shell flares outward at an angle slightly subparallel to 

the hinge on both the anterior and posterior sides; on P. pabloensis 

the posterior margin slopes evenly toward the ventral edge. 

Geographic range.-Middle to southern California. 

Geologic range.-Miocene. 

Occurrence in California.--:-Briones Sandstone (Weaver, 1953), 

Cierbo Sandstone (Clark, 1915; Hall, 1960), Modelo Formation 

(Hudson and Craig, 1929), Neroly Sandstone (Hall, 1960), and San 

Pablo Formation (Hertlein, 1951). 

Pacipecten bilineatus (Clark) 

Plate 15, figure 6 

Pecten (Plagioctenium) bilineatus Clark, 1915, p. 448-449, pl. 64, 

figs. 3, 4. 

Original description.-"Shell thin, medium in size, equivalved 

and equilateral, usually longer than high. Dorsal edges gently concave, the anterior dorsal edge usually being shorter than the posterior; ventral edge quite strongly and regularly arcuate. Apical angle 

averaging about 102°. Hinge plate about half as long as the length of 

the shell. Both valves gently convex and similarly sculptured by 18 

to 20 low, flat-topped, radiating ribs with interspaces little wider 

than the tops of the ribs. In each interspace and almost filling it there 

is a low, broad, flat-topped in terri b. On some specimens these broad 

interribs become almost as prominent as the ribs themselves; this is 

more especially noticeable near the dorsal edges, where the ribbing 

becomes finer. Anterior ear of right valve notched, bearing three to 

four fine, radiating riblets; posterior edge of posterior ear slightly 

oblique, bearing very faint, almost obsolete, radiating riblets. Ears 

of left valve similar to those of the right, valve, except that the 

anterior ear is not notched." 

Holotype.-UCMP 11579. 

Type locality.-UC 1632. Contra Costa County, Calif. Cierbo 

Sandstone, Miocene. 

Comparison.-"P. bilineatus differs from P. pabloensis Conrad in 

that the ribs are wider and not so far apart, they do not show the 

tendency to split as in the other species, the interrib is much broader. 

The concentric sculpturing is different, on P. pabloensis Conrad it is 

distinctly imbricated, the species belonging to the same subgenus as 

Pecten hastatus Sowerby-that is, Chlamys; on P. bilineatus it is not 

imbricated. 

"P. bilineatus resembles P. raymondi in the number and width of 

the ribs, in the. width of the interspaces, and in general outline; it 

differs from that species in the following respects: it has a thinner 

shell, the ribs are not so prominent;. on P. raymond?: there is no 

interrib; the two valves of the latter are unequal, the right valve 

being flat and the left valve convex, thus belonging to the subgenus 

Pecten; the valves of P. bilineatus are both convex* * *"(Clark, 1915, 

p. 449) 

Comments.-In Pacipecten bilineatus the shell flares outward at 

an angle slightly subparallel to the hinge on both the anterior and 

posterior sides; on P. pabloensis the posterior margin slopes evenly 

toward the ventral edge. 

Geographic range.-Middle California. 

Geologic range.-Miocene. 

Occurrence in Calijornia.-Briones (Weaver, 1953) and Cierbo 

Sandstones. 
TERTIARY MARINE PELECYPODS: PROPEAMUSSIIDAE AND PECTINIDAE B49 

TABLE 10.-Geolog1:c and geog·raph1:c d1:st1·1:but?:on of the genus 

Lyropecten 

!PI= Pliocene; M =Miocene; 0 =Oligocene] 

Species 

Genus Ly1·opecten: 

cata.l'inae (Arnold) ........................... . ce·rrosens1:s (Gabb) ........................... . cntss1:ca.1·do (Conrad) ....................... . estTello.nus (Conrad) ......................... . go.lle{Jo:cri (Jordan and Hertlein) ... . m:i{Juelens·,:s (Arnold) ....................... . modulo.tus (Hertlein) ....................... . p1·et1:osus (Hertlein) ......................... . subm·iguelens1:s 

(Loel and Corey) ........................... . term:inus (Arnold) ............................. . ·uo.u{Jiw.n·i (Arnold) ........................... . 

Pacipecten tumbezensis (Orbigny) 

Plate 15, figures 2, 8 

Pecte·n t'U:m.bezen:·n:s Ot·bigny, 1846, p. 663. 

Pecte·n (Ae(ru:i1Jecten.) tun1.bezenwis d'Orbigny. Grant and Gale, 1931, 

p. 206. 

Pecten.(Po.c·i1Jecten) t·wrnbezens·1:s (d'Orbigny). Olsson, 1961, p. 164, pl. 

21, figs. 2-2c. 

Ch.la:m.ys (Lepto7Jecten) tu.mbezens·is (d'Orbigny). Grau, 1959, p. 118-

120, pl. 40. 

On:m:nnl de.<w·ript·1:on.-"Pect. testa suborbiculari, depressiuscula, 

subaequivalvi. aequilaterali, auriculis inaequalibus, dextra majuscula; valvarum altera radiatim costata, pallescente seu alba, costis 

quatuordecim majoribus, rotundatis, laevibus, altera radiatim costata, costis quindecim acutioribus, fuscis, punctulis caerulescentibus aspersis, interstitiis tenuissime transversim striatis, pallescentibus; long. 1.4, lat. 0.5, alt. 1.3 poll." 

Holotype.-Location unknown. Not found at BM (NH) (Keen, 

1966, p. 6). 

'Pype local·ity.-Tumbez, Peru. Holocene. 

Su.pplenwn.to:ry desc1"'1:pt1:on.-"Shell small or of medium size, seldom above 35 mm. in height, subequivalve. Ribs number from 13 to 

15: those of the right valve are nearly square in section between 

deeply grooved inters paces; those of the left valve narrowly triangular between wider interspaces. Surface is nearly smooth except for 

minute concentrics and still finer radial striae.* **Anterior right 

ear with a deep, byssal notch." (Olsson, 1961. p. 164-165) 

"Shell of moderate size, adult specimens averaging 32 mm in 

height. Both valves moderately convex; left one slightly shallower 

and often depressed. between umbo and ventral margin. Beak closer 

to anterior of shell, resulting in anterior auricles and submargins of 

shorter length than posterior. Right valve with 14 or 15 rounded ribs 

and interspaces of same width; interspaces having fine concentric 

lamellae in juvenile stage, smooth when adult; anterior auricle with 

4 strong ridges covered with prominent concentric lamellae; posterior auricle with 4 to 6 ridges crossed by fine lamellae; byssal notch 

small and ctenolium having 3 or 4 teeth. Left valve with 14 or 15 

usually rounded but occasionally triangular ribs; inters paces slightly wider and usually smooth, but occasionally having fine concentric 

lamellae." (Grau, 1959, p. 119-120) 

Geogm.ph:ic ·ra.nge.-Living: Gulf of California to Peru; fossil: Baja 

California Sur. 

California Baja California 

Middle 

M,Pl 

M,Pl 

M 

M 

O,M 

O,M 

Southern 

PI 

M,Pl 

M 

M,Pl 

······ 

O,M 

Mor PI 

M 

O,M 

M,Pl 

O,M 

Norte 

PI 

PI 

Sur 

PI 

PI 

M 

Geologic range.-Pliocene through Holocene. 

Occurrence in BaJa California Sur.-Pliocene: Infierno (Stump, 

1979) and Salada (Hertlein, 1966) Formations. 

Hab1:tat.-Just below low tide level to 130 m, usually in mud, 

occasionally in sandy mud or sand. (Grau, 1959, p. 120) 

Genus LYROPECTEN Conrad, 1862 

"Shell large, thick, valves usually nearly equally inflated, sometimes undulated in the vicinity of the umbos, sometimes strongly 

constricted at various stages of growth; ears nearly equal in size, a 

byssal notch present under right anterior ear; ribs large and undivided; entire shell covered with radial striae and fine concentric 

imbrications; hinge with large coarse cardinal crura or teeth." (Hertlein and Grant, 1972, p. 208, 209) 

Geographic range.-Eastern Pacific. 

Geolog1:c range.-Oligocene(?); Miocene to Pliocene (table 10). 

Habitat.-Perhaps subtropical (Hertlein and Grant, 1972). 

"Lyropecten appears on the Pacific coast in the lower Miocene 

(Vaqueros formation), and the large shells of this genus are used by 

field geologists as a readily recognized aid in distinguishing th~ late 

Tertiary from the early Tertiary. There are large Pectens in the late 

Eocene and Oligocene of the Pacific coast (ynez1:anus Arnold, porterensis Weaver), but they belong to an·endemic genus, Vertipecten, 

which became extinct in the Miocene and is not directly related to 

Lyropecten * **The Pacific coast Lyropecten has been considered a 

migrant from the West Indies and Central America, or from the 

Atlantic coast through Central America, but Lyropecten proper has 

not certainly been recognized in the West Indian and Central American Miocene." (Woodring, 1938, p. 35) 

Lyropecten miguelensis (Arnold) 

Plate 16, figures I, 2, 4 

Pecten (Lyropecten) miguelensis Arnold, 1906, p. 79-80, pl. 22, figs. 1, 

1a, 1b; pl. 23, fig. 1. Hertlein, 1928, p. 151, pl. 24,fig. 1. Loel and 

Corey, 1932, p. 199-200, pl. 29, figs. 2, 3; pl. 30, fig. 2. 

Original description.-"Shell averaging about 110 ':'lillimeters in 

altitude, about as long as high, inequivalve, subequilateral, rather 

thin, and with margins more or less serrate; base rounded; sides 

slightly concave above, the posterior being slightly longer than the 

anterior. Right valve more convex than the left, with 17 or 18 promi-
B50 PALEONTOLOGY OF CALIFORNIA AND BAJA CALIFORNIA 

nent rounded ribs, each sculptured by several (10 or 11 at extremity 

of ribs in type) distinct radiating raised rib lets and numerous sharp, 

minutely wavy, incremental lines; interspaces narrower than ribs, 

and containing by a prominent radial auxiliary rib, which is ornamented by the incremental sculpture, and toward the periphery of 

the disk, by two or more radiating riblets as in the large ribs; hinge 

line somewhat longer than one-half the length of the disk; anterior 

ear arcuate in front, with small byssal notch, and sculptured by 5 or 

6 prominent, rounded, radiating ridges and numerous sharp, concentric lines; posterior ear with 10 or 11 radiating riblets and fine 

incremental sculpture. Left valve less ventricose than the right, but 

otherwise similar to it, except that the ribs are slightly narrower and 

the inters paces relatively broader; ears similar to those of the right 

valve except that the anterior one lacks the byssal notch." 

Holotype.-UCMP 12079. 

Type local?:ty.-San Miguel Island, Calif. Vaqueros Formation, 

Oligocene and Miocene. 

Cmnpm·ison.-"This species is distinguishable from P. estrellanus 

and others of the same group by its larger size, inequality of valves 

(which are more or less inequilateral), and radially striate surface 

from umbo to periphery. It sometimes shows the constrictions common toP. estrellanus." (Arnold, 1906, p. 80) 

"This form is intermediate in general characters between Pecten 

magnijicus variety crassicardo and P. est'rellanus, having 17 or 18 

prominent rounded ribs which are wider than the interspaces, both 

the ribs and the inters paces being ornamented by longitudinal striae 

as on crassicm·do, and having a prominent mid-rib as on estrellanus. 

The left valve of the type is depressed behind the umbones, but this 

feature is probably not a characteristic of the species. P. miguelensis 

is distinguished from crassicardo by the wider ribs and narrower 

interspaces on the right valve and by the mid-rib. From estrellanus 

it is distinguished by stronger striation, higher, rounder ribs, and 

larger size." (Grant and Gale, 1931, p. 178) 

Lympecten 1niguelens'1:s does not have the feather-like microsculpture that distinguishes L. estrellanus. 

Geog1·aphic 1·ange.-Middle to southern California. 

Geolog'ic range.-Oligocene to Miocene. 

Occur1·ence in Calijm·nia.-Oligocene and Miocene: Rincon Shale· 

(Avila and Weaver, 1969), Soda Lake Shale Member, Vaqueros 

Formation (Vedder, 1973), and Vaqueros Formation (Repenning 

and Vedder, 1961; Eaton, 1965; Addicott, 1968; Avila and Weaver, 

1969; Bereskin and Edwards, 1969); Miocene: Carneros Sandstone 

Member, Temblor Formation (Addicott, 1972), Painted Rock Sandstone Member, Vaqueros (Vedder, 1973), Saltos Shale Member, 

Monterey (Vedder, 1973), and Tierra Redonda (Durham, 1968) 

Formations. 

Lyropecten submiguelensis (Loel and Corey) 

Pia te 16, figures 3, 5; pia te 17, figure 1 

Pecten (Lyropecten) miguelensis (Arnold) submiguelensis, n. var. Loel 

and Corey, 1932, p. 200, pl. 29, fig. 1; pl. 30, fig. 1; pl. 31, figs. 1a, 

1b, 1c. 

Original desc1·iption.-"Shell medium in size, similar to type of P. 

rm:guelensis Arnold in characters of shape, except in being nearly 

equivalve; valves fairly thin, ornamented alike by 15 low, flattish 

ribs with rounded sides, each with seven or eight rib lets; interspaces 

slightly concave, with four or five riblets; anterior ears with eight or 

nine riblets (P. m'iguelensis has fewer). Height, 69 mm.; length, 72 

mm.; diameter (both valves), 34 mm." 

Holotype.-UCMP 31737. 

Type locaWy.-UC A311. Santa Barbara County, Calif. Vaqueros 

Formation, Oligocene and Miocene. 

Cmnparison.-"This variety is similar in all characters to P. 

1niguelensis Arnold ( 1906) save for t.he constant comparative thin ness 

of shell and valves and the lack (or faint development) of the intercalary ribs which is accompanied by lower height of the major ribs. 

Owing to this lower height of the main ribs there appear to be one or 

two fewer ribs. The valves are more nearly equal in convexity than in 

the type form of the species." (Loel and Corey, 1932, p. 200) 

In a series of specimens of L. condylomatus from the type San 

Fernando Formation, Tamaulipas, Mexico, some are 70 mm high, 

considerably larger than the holotype, nearly devoid of nodes, and 

resemble some specimens of L. miguelens'is submJguelen.'n:sof similar 

size. (Hertlein and Grant, 1972, p. 209) 

Geographic range.-Middle to southern California. 

Geolog1:c range.-Oligocene to Miocene. 

Occun·ence in Cal?jm·nia.-Oligocene and Miocene: Rincon Shale 

(Avila and Weaver, 1969) and Vaqueros Formation (Kleinpell and 

Weaver, 1963). 

Lyropecten vaughani (Arnold) 

Plate 17, figures 2-4 

Pecten (Lyropecten) vaughan1: Arnold, 1906, p. 81-82, pl. 23, figs. 3, 

3a, 3b. Loel and Corey, 1932, p. 201-202, pl. 21, fig. 9. 

Pecten (Ly1·opecten) nodosus (Linnaeus) variety vaugiWn'l: Arnold. 

Grant and Gale, 1931, p. 180-181. 

Lyropectencrass1:cm·dovaughani(Arnold). Addicott, 1972, p. 9, pl. 2, 

fig. 6. 

01·iginal description.-"Shell averaging about 40 millimeters in 

altitude, slightly longer than high, inequivalve, equilateral, convex, 

and showing constrictions with consequent undulations on the right 

valve and nodose ribs on the left; base regularly rounded; sides 

nearly straight above; margins smooth. Right valve with 12 prominent convex ribs separated by concave-bottomed interspaces somewhat narrower than the ribs; surface of ribs and interspaces sculptured by numerous fine, imbricated, threadlike, radial lines, 

between which are fine imbricating concentric lirae, the lines multiplying by intercalation toward the periphery of the disk; hinge line 

about five-eighths length of disk; ears unequal, the anterior much 

elongated, rather narrow, and ornamented by 4 very prominent, 

rounded, sharply imbricated radials and numerous fine imbricating 

incremental lirae; byssal notch deep; posterior ear about one-half 

length of anterior, somewhat concave behind, and ornamented by 

about 6 radial and numerous fine incremental lirae. Left valve 

similar to right, but with narrower, sharper ribs and correspondingly broader interspaces; the second, fourth, seventh, tenth, and 

twelfth ribs from the posterior end are more prominent than the 

others, and are subnodose at the lines of undulation of the disk; 

anterior ear similar to that of the right valve but with 2 or 3 more 

radials, which are less prominent; posterior ear like that of right." 

Holotype.-CAS/SU 9 [Probably a late juvenile form according to 

Judith T. Smith (written commun., 1979)]. , 

Type locality.-Ojai Valley, Ventura County, Calif. Vaqueros 

Formation, Oligocene and Miocene. 

Compm·ison.-Though allied to L. magnol1:a and L. c1·assimrdo, L. 

vaughani is distinguishable by its small size, obviously unequal ears, 

long and strongly radially sculptured right anterior ear, deep byssal 

notch, undulating disk, and finely striated, concave-bottomed interspaces. This form seems to combine the number of ribs of L. 1nagnolia (L.1nagnol1:a generally has one to three less), with the sculpture of 

L. crassicardo var. han1-Utoni, the undulations of L. cras.'n:ca,,.,·do, and 

the long, strongly sculptured, right anterior ear of the typical 

Chlamys. It appears to be a connecting link between the typical 

Chlamys and Lyropecten. (Arnold, 1906, p. 82) 
TERTIARY MARINE PELECYPODS: PROPEAMUSSIIDAE AND PECTINIDAE B51 

Goorrra.1Jh'1:c nl:l1.fJO.-Southern California. 

Geolorric ·ro:nue.-Oiigocene to Miocene. 

Occu:rnnu;e ,,:·n CaLifonl:ia..-Oiigocene and Miocene: Vaqueros 

Formation (Arnold, 1906; Loel and Corey, 1932); Miocene: Cameros 

Sandstone Member. Temblor For·mation (Addicott, 1972). 

Lyropecten pretiosus (Hertlein) 

Pia tc 17, figures 5, 8 

Pecte·n (L?J'I'01Jecten,) p·ret·,:osu.i:i Hertlein, 1925a, p. 12-13, pl. 2. fig. 6; 

pl. 3. fig. 4. Grant and Gale. 1931, p. 185. 

Or·im>nnl clesc'l"l:pt·l:on.-"Sheii small. Right valve moderately 

arched, and ornamented by about 17 or 18 rounded, radiating ribs, 

separ·ated by somewhat narrower interspaces; ribs and interspaces 

sculptured by fine, radiating lines and crossed by fine, concentric 

lines of growth; anterior and posterior margins turning down 

abruptly, and smooth except for incremental striae; ventral margin 

rounded and turned down abruptly; anterior ear with a distinct 

byssal notch, and a slight groove also present between ear and 

margin of shell; about five radiating riblets crossed by incremental 

lines ornament the ear; posterior ear sculptured by about six or 

seven radiating riblets. crossed by incremental striae, the ear sloping downward and slightly posteriorly from the hinge line. Left 

valve ornamented by about 14 or 15 radiating ribs, the whole surface 

with sculpture similar to that of right valve; ears sculptured much as 

on right valve. Altitude 27 mm.; longitude 29 mm.; diameter of right 

valve approximately 10 mm.; apical angle of right valve approximately 87°." 

Holotype.-CAS/SU 38. [Juvenile right valve (Judith T. Smith, 

written commun .. 1979).] 

Type locab:ty.-SU 59. Baja California Sur, Isidro Formation, 

Miocene. 

Cmnpo:n:so·n.-"The characteristic shape, sculpture, and shape of 

ears distinguish this beautiful little Pecten from other species." 

(Hertlein, 1925a, p. 13) 

"This species appears to be closely related toP. conclyloma.tus Dall 

but can not be definitely assigned to that species. It differs from 

specimens of the latter"' "' "'in smaller size, the right valve is higher 

at the umbo and the ribs are lower, evenly rounded and ornamented 

by numerous fine striae." (Hertlein and Jordan, 1927, p. 624) 

Georrraph:ic ·ra:nge.-Southern California to Baja California Sur. 

Geolog·ic ·ran{]e.-Miocene. 

Occu.?Tence 'l:n the Cal?jm·m:a.s.-Temblor "Horizon" (Loel and 

Corey, 1932) and Isidro Formation (Beal, 1948). 

Lyropecten crassicardo (Conrad) 

Plate 17, figures 6, 7; plate 18, figures 1-3, 5; 

plate 21, figure 3; plate 28, figure 1 

Pa.lhu:m. C'/'O.i:IS'ica.nlo Conrad, 1857a, p. 313 [reprinted in Dall, 1909, 

p. 173]. 

Pecte-n (Ly·ropecten) c·m .. <:~1:n:ca:rclo Conrad. Arnold, 1906, p. 71, pl. 16, 

figs. 1. 1a; pl. 17, figs. 1. 1a, 1b; pl. 18, figs. 1, 2, 2a. Arnold, 

1907a, pl. 44, fig. 1. Hanna and Hertlein, 1941, fig. 63-8. 

Pecte·n c·ra .. <:~w1:ca:rclo Conrad. Clark, 1915, pl. 45, fig. 3. 

Pecten (Ly1·opecten) c?·a.ss·1:ca.nlo Conrad nov. var.? Clark, 1915, pl. 

46, fig. 3. 

Pecten (Ly1·opecten) ?na.omfl:cus Sowerby variety cra.ss1:cm·do (Conrad). Grant and Gale, 1931, p. 183-184, pl. 9, figs. 4, 5. 

L?J'I'01Jecten c·ra.swl:ca,?·do (Conrad). Addicott. 1965, fig. 3b. Vedder 

and Moore, 1976. p. 121. pl. 2, figs. 1, 7, 10. 

Pecten (Ly·ropecten) c·ra.swicm·do Conrad var. hmniltom: Arnold, 1906, 

p. 73-74, pl. 11, figs. 5, 6. 

Pecten (Ly1·opecten) ma.gmj1:cus Sowerby variety hmniltom: Arnold. 

Grant and Gale, 1931, p. 184-185. 

Pecten (Pa.ll1:wn) holwa.y1: Clark, 1915, p. 454, pl. 47, fig. 5. 

Pecten c?·a.ssica,?·do b1/onna.t1:s Nom land, 1917b, p. 307, pl. 18, figs. 1. 

1a, 1b; pl. 19, fig. 4. 

Pecten c?·ass?:ca.?·do nomla.ndi Hertlein, 1931, p. 369, new name. Not 

Pecten b1jonna.tus Bittner, 1899. 

Ly1·opecten c1·a.ss1:cm·do (Conrad) nomla.nd1: (Hertlein). Adegoke, 

1969, p. 100-101, pl. 2, fig. 8. 

Pecten (Ly1·opecten) 1·ice1: Trask, 1922, p. 148, pl. 2, figs. 1-2. 

Pecten (Ly1·opecten) V1:cke1·y·i Trask, 1922, p. 148, pl. 4, fig. 1. 

Sw1jtopecten a.dekunb1:a.na. Adegoke, 1969, p. 104, pl. 6, figs. 3, 5. 

On:g1:na.l desc?"l:ption.-"Obtuseiy ovate or suborbicular, thick; 

lower valve ventricose; ribs 15-16, elevated, back rounded, sides 

flattened, disks radiato-striate, 9 or 10 on the ribs, intervals of ribs 

;concave, umbo or whole disk at wide intervals having a tendency to 

be humped and nodose; upper valve convex or slightly ventricose; 

ears large, equal; hinge thick, with prominent, acute, oblique teeth; 

fosset profound; muscular impression very large. Height 5 inches." 

( c?·a.ss1:ca.1·do) 

"Adult shell averaging about 60 millimeters in altitude, subequivalve, equilateral, convex; sides concave above; margins smooth. 

Right valve with 15 to 17 prominent convex-topped ribs, separated 

by interspaces narrower than the ribs; surface of ribs and interspaces sculptured by rather coarse radiating lines and imbricating 

incremental lamellae; anterior ear longer than the posterior, and 

with 4 prominent, finely imbricated radials; byssal notch rather 

deep; posterior ear rectangularly truncated, and with radial and 

concentric sculpture. Left valve similar to right, except with slightly 

wider interspaces. The disk of this variety is generally contracted 

after reaching an altitude of 40 millimeters or more." (ha.miltoni) 

"Shell large, equilateral; posterior, anterior, and ventral margins 

strongly depressed; surface of shell with a marked step-like depression, indicating a former depressed ventral margin, situated not 

· quite one third the distance from the ventral edge to the beak. 

Surface sculptured by three heavy rounding ribs; these ribs are very 

prominent between the step-like depression and the ventral depressed margin, but very faint and almost d isa ppeari ng between the 

step and the beak. Surface also sculptured by fine, regular, radial 

striae or riblets, which cover both the interspaces and the ribs, and 

by fine imbricate concentric lines. Shell feebly I irate internally, the 

lirations being most prominent on the depressed area along the 

ventral edge. Adductor muscle scar prominent." (holwa.yi) 

"Shell equilateral, equivalve, thin, rather compressed; with more 

or less serrate, regularly convex, basal margins. Right valve with 

about fifteen high, squarish, rather narrow ribs; inters paces considerably wider than ribs, both being ornamented by numerous fine 

· radiating lines; surface sculptured by fine, almost invisible, imbricate lines; the larger specimens frequently show abrupt constrictions or undulations at later stages of growth. Anterior ear ornamented with incremental growth lines and about six radiating 

ridges; posterior ear smaller but otherwise similar to anterior. Left 

·valve with about fifteen-seventeen high squarish ribs. These are 

wider than the interspaces or than the ribs of the other valve, ornamented with fine incremental lines; byssal notch well developed. 

Dimensions of type: Height, 92 mm.; length, 114 mm.; length of 

hinge line, about 65 mm.; umbonal angle, 110 degrees." (nomla.ndi) 

"Shell medium in size; about as long as high, equilateral; apical 

angle about 89°; anterior and posterior dorsal margins strongly 

depressed; surface of left valve with fourteen low flat topped to 

broadly rounded ribs; inters paces flat, about equal in width to ribs, 

and possessing from three to four, almost invariably three, small 

riblets, which have a tendency to become bifurcated near the ventral 

margin." (ricei) 
B52 PALEONTOLOGY OF CALIFORNIA AND BAJA CALIFORNIA 

"Shell large, slightly more wide than high; ears about one-half the 

width of the shell; dorsal margins strongly depressed and quite long, 

being about three-fourths the height of the shell; surface with sixteen prominent ribs; every third rib being higher and more strongly 

developed than the others; interspaces about as wide as ribs; both 

ribs and interspaces ornamented with numerous fine riblets; ears 

with five to six small ribs." (vickery1:) 

"Shell medium sized, thin, subcircular, length approximately 

equal to height; ornamented by 5 very prominent major ribs separated by very wide interspaces; major ribs prominently elevated at 

each of the numerous concentric constrictions in ventral half of shell; 

between each adjacent pair of major ribs are 2 minor ribs of approximately same diameter as major ribs but less prominently elevated; 

minor ribs and interspaces ornamented by numerous fine radial 

riblets; major ribs generally less ornate than minor ribs; anterior 

ear longer and more prominent than posterior ear; both ears ornamented by fine radial riblets." (adekunb1:ana) 

Holotype.-Missing and presumed lost. ANSP 30745a is herewith 

designated the lectotype. It is one of three specimens labelled by 

Gabb as having been given to him by Conrad. Of hamiltoni USNM 

164845; of holwayi UCMP 11580; of nomlandi UCMP 11308; of ricei 

UCMP 12364; of vickeryi CAS/SU 26; of adekunbiana UCMP 36639. 

Type locality.-Monterey County, Calif. Subsequent field work 

restricts the locality to the La Panza Quadrangle, where L. crassicardo is abundant in the Santa Margarita Formation, Miocene 

(Judith T. Smith, oral commun., 1979). Of hamiltoni, Alum Rock 

Canyon [San Jose Quad.], Santa Clara County, Calif., Briones Sandstone, Miocene; of holwayi, UC 1632, Contra Costa County, Calif., 

Cierbo Sandstone, Miocene; of nomlandi, UC 3029, Kern County, 

Calif., Santa Margarita Formation, Miocene; of ricei, UC 3535, 

Alameda County, Calif., Briones Sandstone, Miocene; of vickeryi, 

vicinity of McGuire Peaks, Pleasanton Quad., Alameda County, 

Calif., Briones Sandstone, Miocene; of adekunbiana, UC D1088, 

Fresno County, Calif., Santa Margarita Formation, Miocene. 

Supplementary description.-"Adult, shell averaging about 130 

millimeters in altitude, about as long as high, inequivalve, convex, 

equilateral (except for ears), thick, and generally prominently and 

abruptly constricted or undulated one or more times near the umbo 

and sometimes at later stages of growth; sides nearly straight; base 

regularly rounded; margins smooth. Right valve with 14 to 17 prominent, perpendicular-sided, convex-topped ribs, which are separated 

by more or less deeply channeled, flat-topped, convex-bottomed 

interspaces somewhat narrower than the ribs; whole surface of ribs 

and interspaces sculptured by numerous radial striae and fine, minutely wavy, imbricating, concentric lines; hinge line about foursevenths length of disk; anterior ear somewhat produced, subarcuate laterally and sculptured by about 5 prominent radial ridges and 

numerous fine imbricating incremental lines; posterior ear about 

three-fourths length of anterior, sculptured similarly, but slightly 

less prominently, and rectangularly truncated. Left valve similar to 

right, except that the ribs are narrower, and the interspaces correspondingly broader; ears similar to posterior one of right valve. 

Hinge with a deep resilial pit, on each side of which are several 

prominent lateral crura or teeth. 

"The tops of the ribs sometimes overhang the interspaces and also 

sometimes appear smooth. Great variation is shown in regard to the 

number, abruptness, and prominence of the constrictions on the 

disk. One or two are generally present near the umbo in most specimens, and some show as many as six or seven at different periods of 

growth. The specimens of this species from Orange County are 

generally freer from constrictions and the disks are usually more 

compressed than in the forms from central California; otherwise the 

former are normal types." (Arnold, 1906, p. 72) 

"Lyropecten crassicardo (Conrad) in collections from Lemon Tank 

Reservoir [unnamed Miocene strata on San Clemente Island] ranges 

from 26 mm wide and 26 mm high * * * to 160 mm wide and about 

145 mm high***. The right valve bears 12 to 13 primary ribs***, 

the left valve 12 to 14 * * *. Of nine right valves, one has 12 ribs, the 

remaining eight 13; of six left valves, one has 12 ribs, four 13 ribs, 

and one 14 ribs. Judith T. Smith (oral commun., 1975) has found 15 

ribs on the right valve and 14 ribs on the left valve to be more 

common on L. crassicardo elsewhere in the Californias. 

"The anterior ear is longer than the posterior ear on both valves. 

The left posterior ear is truncated at a right angle to the hinge; the 

left anterior ear is enlarged just below the hinge. The right anterior 

ear bears 5 to 6 riblets, the right posterior ear 8 to 12; the left 

posterior ear bears 8 to 12 rib lets, the left anterior, 7 to 10. The first 2 

or 3 riblets below the hinge on the ears are usually largest. On both 

right and left valves of large specimens, additional rib lets are present near the margins of the posterior ears but do not cross them. 

"Fine striations and lyrae are present on the entire surface of both 

right.and left valves of L. crassicardo, these striations are of equal 

strength on the specimens from San Clemente Island." (Vedder and 

Moore, 1976, p. 121-122) 

Comparison.-"P. crass1:cardo is characterized by its comparatively few ribs, which, with the interspaces, are more or less prominently striated. It is distinguishable from * * * P. 1nagnolia, with 

which it is often confused, by its more numerous and much narrower 

ribs, relatively shorter hinge line, more prominently striate ears, 

and its tendency to become constricted; distinguishable from P. 

estrellanus, with which it is often associated, by its fewer and rather 

finely striate ribs and lack of a major intercalary rib let (the bottoms 

of the inters paces of P. crassicardo being striate rather than containing a riblet). Some of the lateral ribs and inters paces, and the surface 

near the periphery of the disk in adults of P. estrellanus generally 

show sculpture similar to that characteristic of P. cras.'n:ca?·do." 

(Arnold, 1906, p. 72) 

"On most left valves of L. cra88icardo, the middle rib and the third 

rib from the middle toward both the anterior and posterior margins 

are elevated above the other ribs. On left valves of Lyropecten ce'rro-

.<;ens?:s (Gabb), three ribs rather than two are present between the 

elevated ribs. This feature, when preserved serves to separate L. 

cerrosen81:8 from L. crassicardo (Judith T. Smith, oral commun., 

1975)." (Vedder and Moore, 1976, p. 121-122) 

According to Judith T. Smith (written commun., 1979) L. c?·as.'n:-

cardo has 14 to 15 ribs whereas L. estrellanus has 16 to 17. The 

juvenile valves of L. estrellanus are commonly more convex than 

those of L. crassicardo, which are flat. L. C?'a8s?:cardo may have 

elongate incipient nodes; L. estrellanu.<; does not. Left valves of L. 

cra8.'n:cardo commonly have the central rib raised and the third next 

rib toward both the anterior and posterior margins. 

Comments.-Arnold (1906, pl. 18, fig. 1) figured a specimen 

(ANSP 30745) which he considered to be the holotype of L. c?·as.<n:-

cardo. That specimen is a left valve with the auricles missing and on 

the shell is written "Pres. by Dr. Wilson." For two reasons I believe 

this specimen is not the holotype: (1) The auricles are missing and 

they were described by Conrad; (2) Conrad (1856, p. 313) cites A. S. 

Taylor as the collector, and this specimen was presented by Dr. 

Wilson. The specimen is one of three labelled by Gabb as "dupl. 

types-Given me by Mr. Conrad." I have selected as the lectotype the 

best preserved specimen of the three, and it is not the one figured by 

Arnold. 

The lectotype is a left valve with the anterior auricle missing and 

only a portion of the posterior auricle preserved. It has 16 square, 

slightly undercut ribs and both the ribs and the slightly narrower to 

as wide interspaces have fine riblets. At two-thirds the distance 

from the beak to the ventral margin the shell is constricted, producing a marked ledge; near the ventral margin is another less pronounced ledge. 

The holotype of Swijtopecten adekunbiana Adegoke (1969, p. 104) 
TERTIARY MARINE PELECYPODS: PROPEAMUSSIIDAE AND PECTINIDAE B53 

is a fragment of a much larger left valve of L. crass1:cardo. The 

holotype of Pecten holwa.y·1: Clark (1915, p. 454) is a worn left valve 

with no auricles preserved, but it is !edged and has raised ribs in the 

same position as L. c?·ass?:ca:rdo. (Judith T. Smith, written commun., 

1979) 

Geog·m1Jh?:cm.nge.-Middie to southern California. [The records of 

L. c?·as.•n:ca:rdo in Baja California are in error and the species represented is probably L. sufnniguelensis (Judith T. Smith, written 

commun., 1979).] 

Geolog·ic ra.nge.-Miocene. 

Occu.n·ence 1:-n Ca.l·ijo·rn1:a .. -Branch Canyon Sandstone (Vedder, 

1973), Briones Sandstone (Weaver, 1953), Buttonbed Sandstone 

Member, Temblor Formation (Addicott, 1972), Castaic Formation 

(Stanton, 1966), Cierbo Sandstone (Eaton and others, 1941), Cold 

Creek Member. Gould Shale Member, Monterey Formation (Addicott, 1972). Topanga Formation (Takeo Susuki, written commun., 

1978), McLure Shale Member, Monterey (Adegoke, 1969), "middle 

sandy phase," Monterey (Dickinson, 1969). Modelo(?) (Kew, 1924), 

Neroly Sandstone (Eaton and others. 1941), Obispo (Hall and others, 

1966), Saltos Shale Member. Monterey (Vedder, 1973). San Onofre 

Breccia (Bereskin and Edwards, 1969). San Pablo (Arnold, 1906; 

Clark, 1915), and Santa Margarita (Arnold, 1906; Addicott, 1965; 

Adegoke, 1969; Dickinson, 1969) Formations; unnamed Miocene 

strata on San Clemente Island (Vedder and Moore, 1976). 

Lyropecten ca~alinae (Arnold) 

Plate 18, figures 4, 6 

Pecten (Ly·ropecten) est1·ellanus Conrad var. cata.lina.e Arnold, 1906, 

p. 76-77, pl. 20, figs. 3, 3a, 4. Grant and Gale, 1931, p. 186. 

On:m:nal de.•;c?"i1Jt'l:on.-Shell averaging about 65 millimeters in 

altitude, considerably longer than high, equivalve, equilateral, of 

medium thickness, only slightly ventricose, and with margins more 

or less serrate; base evenly rounded; sides only slightly concave 

above. Right valve with 19or 20square, flat-topped ribs, all of which 

are sculptured by incremental lines and the 3or 4outer ribs on each· 

side by more or less prominent radial lines; interspaces narrower 

than ribs and ornamented by a prominent squarish riblet; hinge line 

over one-half length of disk; anterior ear arcuate in front, with 

rathe·r small byssal notch, and ornamented by concentric lines and 5 

or 6 t·ather pt·ominent radiating ridges; posterior ear with concave 

end and ornamented by numerous fine radiating ridges and incremental lines. Left valve similar to right except that the ears are both 

like the posterior one of the right valve and the int.erspaces are 

relatively a little wider." 

Holot1me.-CAS!SV 30. 

Ttme loco.l·1:ty. -Near Isthmus, Santa Catalina Island, Los Angeles 

County, Calif. San Onofre(?) Breccia, Miocene. [Subsequent field 

work and comparison of holotype matrix with that of other specimens suggests that the type locality is near the saddle on the north 

side of Mt. Banning (Judith T. Smith, written commun., 1979).] 

Su.ppleuwnta:ry desc·n:pt·ion.-"According to the figure, the type of 

cat.ah>nae from Santa Catalina Island has a strong midrib fi IIi ng the 

interspaces, as in est-rellanu.s s.s. Material from the Pliocene at 

Temescal Canyon mentioned by Arnold as representing cata.l?:nae is 

not recognized in the National Museum collection. This record is 

probably an error, as cata.l·inae is not mentioned in Arnold's later 

lists ft·om this locality." (Woodring, 1938, p. 34) 

Ccnnpa?'ison .. -"This species is similar in general characteristics 

to the typical P. est·rella.nus, but differs from it in being much flatter, 

having a relatively much longer hinge, and, on the average, more 

ribs. The characteristic constriction of P. est-rella:nus is also lacking 

in this variety, so far as known." (Arnold, 1906, p. 77) 

Geogm.1Jh:icnm.ge.-Middle and southern California. According to 

Judith T. Smith (written commun., 1979) L. catal1:nae is restricted to 

Catalina Island and the Ventura Basin and probably is restricted to 

the Miocene. 

Geolog1:c range.-Miocene. 

Occurrence 1:n California.-Miocene: Modelo Formation (Judith 

T. Smith, written commun., 1979) and San Onofre Breccia. 

Lyropecten estrellanus (Conrad) 

Plate 19, figure 2 

Pallium estrellanum Conrad, 1857a, p. 313. Conrad, 1857b, p. 71, pl. 

3, fig. 15. 

Pecten (Lyropecten) estrellanus Conrad. Arnold, 1906, p. 74-76, pl. 

19, figs. 1, 1a; pl. 20, figs. 1, 2, 2a; pl. 21, figs. 1, 1a, 1b, 2, 2a, 2b. 

Grant and Gale, 1931, p. 185-186, pl. 8, fig. 4. G D. Hanna and 

Hertlein, 1941, fig. 63-7. 

Lyropectenestrellanus(Conrad). Woodring, 1938, p. 33-34. Addicott, 

1972, pl. 4, fig. 1. Addicott and others, 1978, pl. 1, fig. 4; pl. 4, fig. 

11. 

Ly1·opectenvolaejonm:s Conrad, 1862, p. 291. New name for Pnll1:um. 

estrellanum Conrad, 1857b, pl. 3, fig. 15 = L. estrellanus fide 

Arnold, 1906, p. 74. 

Original descript1:on.-"Suborbicuiar; lower valve ventricose, 

slightly undulated; ribs 17, broad, little prominent, convex, with an 

intermediate linear rib, from which the larger ribs are separated by 

an impressed line; upper valve convex, somewhat undulated, ribs 

flattened and the intermediate small ribs with a longitudinal 

impressed line on the lower part of the valve. Height 2~ inches." 

Lectotype.-VSNM 13317 (Woodring, 1938; neoholotype, TuckerRowland, 1938). 

Type locality.-Estrella Valley [San Luis Obispo County], Calif. 

Santa Margarita Formation, Miocene. 

Supplem.enta.Ty descTiption.-"Shell averaging about 90 millimeters in altitude, somewhat longer than high; equivalve, equilateral, of medium thickness, generally quite ventricose, and with 

margins more or less serrate; base evenly rounded; sides sloping, 

slightly concave above. Right valve with 16 to 20 prominent, squarish ribs separated by channeled interspaces which are narrower 

than the ribs; interspaces each with one sharply outlined, squarish 

riblet in the middle; surface sculptured by fine raised incremental 

lirulae which loop back over the ribs and riblets, and, on the anterior 

and posterior portions of the disk, by radiating striae, which 

increase in number as the periphery of the disk is approached; hinge 

line straight and nearly equal to one-half length of disk; ears equal; 

anterior ear arcuate in front and ornamented above byssal area by 

three or four radiating ridges and numerous incremental l'ines; 

byssal notch sharply defined; byssal area with incremental sculpture only; posterior ear with slightly concave end and ornamented by 

5 or 6 radiating ridges and more or less prominent incremental lines. 

Left valve with the ribs narrower and having more sloping sides and 

rounded tops than those of the right; interspaces wider; auxiliary 

riblets inclined to be dichotomous near the ends in the more mature 

specimens; the looping incremental lirulae and the secondary 

·radiating lines apparently more highly developed in this valve than 

in the right; ears similar to the posterior ear of the right valve. 

"This is a most variable species in size, shape, and sculpture, the 

above description applying to the most common form. One peculiar 

characteristic sometimes shown by this species is a contraction or 

interruption in the growth at different stages. * * *Up to the first 

interruption the sculpture is generally simple and quite constant, 

but afterwards it (especially the radial) becomes more complex, the 

riblets in the interspaces becoming dichotomous and the radiating 

lines becoming more numerous and prominent. 

"The variety of this species described as Ly1·opecten volaefonnis by 
B54 PALEONTOLOGY OF CALIFORNIA AND BAJA CALIFORNIA 

Conrad is the extremely convex type. Conrad thought that the valves 

were unequal in the very convex shell, but in all the specimens of this 

sort examined by the writer, both valves show an equal amount of 

convexity. * * * 

"Specimens of this species from Catalina Island show more ribs 

(right valves, 19 to 21) than the average, and also appear to be 

slightly inequivalve, the left valve being the more ventricose. The 

characteristic interruption and constriction took place on most of the 

Catalina specimens at an altitude of about 55 millimeters. 

"A specimen of this species from San Benito County * * * is very 

convex, and shows beautiful equal, equidistant, looped lamellae over 

the surface of the valve. The intercalary riblets on this specimen are 

sharply defined." (Arnold, 1906, p. 75) 

In the type Jot of L. estrellanus "the lectotype and two others, on 

which the number of ribs is discernible, have 17 ribs; the inters paces 

are occupied by a strong midrib, which is split toward the margin, 

and the two branches may be flanked by a riblet. The anterior ear of 

a right valve has four relatively strong ribs." (Woodring, 1938, p. 33) 

"Arnold's figured right valve from the Santa Margarita sandstone 

of the Coalinga region (1909, pl. 10, fig. 3) ***is strongly inflated; is 

sculptured with 17 ribs; has a strong midrib that is not split toward 

the margin but in some interspaces is not stronger than riblets 

added near the margin; and has four relatively strong ribs on both 

ears. Strongly marked 'resting stages,' possibly induced by unfavorable conditions, produce humps in the profile." (Woodring, 1938, 

p. 34) 

Comparison.-"This species is distinguished from P. miguelensis 

by its lower, smoother, squarer ribs. From crassicardo it can also be 

told by its mid-rib." (Grant and Gale, 1931, p. 185) 

"In some interspaces one secondary rib is stronger than others, but 

it does not completely fill the interspace as in the smaller Miocene L. 

estrellanus. Lyropecten terminus, from the Pliocene of the Salinas 

Valley, is smaller than L. cerrosensis and has a relatively strong 

secondary rib. It evidently is more closely related to L. estrellanus 

than is L. cerrosensis, which may be descended from the Miocene L. 

crassicardo." (Woodring, 1950, p. 85) 

Lyropecten estrellanus can be distinguished from L. miguelensis 

by its feather-like microsculpture. 

Geographic range.-Middle to southern California. 

Geologic range.-Miocene to Pliocene. 

Occurrence in California.-Miocene: Branch Canyon Sandstone 

(Vedder, 1973), Buttonbed Sandstone Member, Temblor (Addicott, 

1972), Castaic (Stanton, 1966), Cierbo Sandstone (Hall, 1960), Cold 

Creek Member, Topanga (Takeo Susuki, written commun., 1978), 

McLure Shale Member, Temblor (Adegoke, 1969), Media Shale 

Member, Temblor (Anderson and Land, 1969), Modelo (Oakeshott, 

1958), and Monterey (Arnold, 1906; Mandra, 1963) Formations, 

Neroly Sandstone (Eaton and others, 1941; Hall, 1960), Pancho Rico 

(Addicott and others, 1978), and Santa Margarita (Arnold, 1906; 

Durham and Addicott, 1964; Adegoke, 1967; Durham, 1968; Vedder, 

1973) Formations, Topanga Group (Takeo Susuki, written commun., 

1978), and Tranquillon Volcanics (Dibblee, 1950); Miocene and Pliocene: Towsley (Kern, 1973) and Etchegoin (Arnold, 1906; Adegoke, 

1960) Formations; Pliocene: Morales Formation (Hill and others, 

.. 1958). 

Lyropecten terminus (Arnold) 

Plate 19, figures 1, 5 

Pecten (Lyropecten) estrellanus Conrad var. terminus Arnold, 1906, 

p. 77, pl. 23, figs. 2, 2a. Grant and Gale, 1931, p. 186. 

Lyropecten terminus (Arnold). Addicott, 1974, pl. 1, fig. 5. 

Original description.-"Shell averaging about 70 millimeters in 

altitude, somewhat longer than high, ventricose, subequivalve, equilateral; margins coarsely serrate. Right valve with about 15 prominent, squarish ribs, separated by narrower channeled interspaces, 

in each of which runs a prominent intercalary; surface of ribs and 

interspacesobsoletely radially striate; hinge line more than one-half 

length of disk; ears subequal, the anterior strongly radially ribbed, 

the posterior with finer sculpture; byssal notch deep and rather 

narrow. Left valve similar to right, except that the ribs are relatively 

narrower." 

Holotype.-UCMP 11662. 

Type locality.-Monterey County, Calif. Pancho Rico Formation, 

Pliocene. Subsequent work by Durham and Addicott (1965) suggests 

that the type locality is in terraces on east side of Salinas Valley or in 

tributary canyons to the valley between King City and San Lucas 

(Judith T. Smith, written commun., 1979). 

Comparison.-Lyropecten terminus is distinguishable from L. 

estrellanus by its fewer and broader ribs, relatively longer hinge 

line, and finer obsolete radial striation; and from L. catab>nae by its 

fewer ribs and greater convexity. (Arnold, 1906, p. 77) 

· "This species is probably a direct descendant of Lyropecten est?·ellanus (Conrad). It is distinguished from the latter by the usually 

fewer ribs with numerous radial striations, and the vertical sides of 

the primary ribs. In L. estrellanus the ribs are slightly more numer-

·ous and have a uniformly rounded profile." (Adegoke, 1969, p. 101) 

Lyropecten cerrosensis has more numerous ribs (17 to 19) that are 

usually more rounded than those on L. terminus which has but 15 

flat-topped ribs. (Hertlein and Grant, 1972, p. 211) 

Geographic range.-Southern California. 

Geologic range.-Miocene to Pliocene. 

Occurrence in Calijornia.-Miocene: Pancho Rico Formation 

(Addicott, 1974); Miocene and Pliocene: Etchegoin Formation 

(Arnold, 1906; Adegoke, 1969; Addicott, 1972). [According to Judith 

T. Smith (written commun., 1979) L. terminus is restricted to the 

Pliocene, and the records of Arnold (19,06) in the San Pablo and 

Santa Margarita Formations are in error.] 

Lyropecten gallegosi (Jordan and Hertlein) 

Plate 19, figure 3 

Pecten (Lyropecten) gallegosiJordan and Hertlein, 1926, p. 434-435, 

pl. 29, fig. 1. 

Original description.-"Shelllarge, and of the same general outline asP. cerrosensis Gabb, but flatter. Right valve ornamented by 

21 to 23, narrow, square, flat-topped and often T-rail shaped radiating ribs; inters paces flat-bottomed, with a well defined midrib, their 

bottoms and walls also finely, radially striate; ribs and interspaces 

crossed by concentric lines of growth; anterior dorsal and posterior 

dorsal margins of the valve bearing several sharp, radiating ri blets; 

anterior ear large, with a well defined byssal notch, the ear ornamented by six to eight strong, radiating rib lets which are crossed by 

lines of growth; posterior ear smaller than anterior, and sloping 

obliquely, posteriorly and downward from posterior termination of 

hinge line to edge of disk, the ear scul,ptured by 10 to 12 sharp, 

strong, radiating riblets crossed by growth lines. Height 125 mm.; 

length 138 mm.; apical angle 116°. Left valve more highly arched 

than right, and similarly sculptured; at intervals every fifth rib is 

slightly raised, as is the case on occasional specimens of P. cerrosensis Gabb." 

Holotype.-CAS 2096. 

Type locality.-CAS 946. Baja California Norte, Almejas Formation, Pliocene. 

Comparison.-"It is recognized that intergradation may ultimately be proved with P. cerrosensis Gabb, which itself is rather 
TERTIARY MARINE PELECYPODS: PROPEAMUSSIIDAE AND PECTINIDAE B55 

variable, but the type and paratypes of P. ga.llegos-1: present such 

striking characters as to merit a separate designation. From P. 

ce'l"l'o.•w·n:,-is, the present form is distinguished mainly by having a 

much flattet· shell, and by a greater intensity of sculpture. The 

slightly greater number of ribs, which are in nowise rounded, the 

sharp riblets on the anterior dorsal and posterior dorsal margins of 

the shell, and the strong sculpture on the ears are distinguishing 

characters. From P. hake·1: Hertlein, P. gallegosi differs in having the 

strong hinge teeth characteristic of a Ly1·opecten, in the presence of a 

midt·ib between the major radial ribs, and in other less important 

particulars." (Jordan and Hertlein, 1926b, p. 434-435) 

"The stt·ong midrib indicates that Pecten (Ly1·opecten) gallegmn: 

Jordan and Het·tlein, from Cedros Island, where it is associated with 

ce·n·os(m,.<;·is, is allied to est·rello:n:u.s." (Woodring, 1938, p. 34) 

Ly·ropecten {Ja.llegos·l: has more rectangular ribs and stronger 

radial mict·osculpture than L. ce·rrosens·is (Judith T. Smith, written 

commun., 1979). 

Geortraph:ic ·ro:n{j(~.-Baja California Norte. 

Glwlorric ·ro.nge.-Piiocene. 

Ocl;'I.I!I"I'Wn.ce ·in. Bodo. Cahj(J'/''11:/:a.-Aimejas Formation (Minch and 

others, 1976). 

Lyropecten modulatus (Hertlein). 

Plate 19, figure 4 

Pecten.(Lyropecten.)'lll.odulatu.s Hertlein, 1925a, p.11-12, pl. 3, fig. 6. 

Pecten .. •ofu.bn.odosus Sowerby. G D. Hanna, 1926a, p. 474, pl. 25, fig. 6. 

Not Pecten su.bnodosus Sowerby, 1835. 

Not Ly'l'lJpecten ·m.odulo.tu,.o.; (Hertlein). Durham, 1950, p. 65, pl. 11, 

fig. 7. [= Nod·i1Jecten. subnodosus (Sowerby).] 

01"irrina.l desc·r·ipt?:on.-"Shell moderately convex, fairly heavy, 

showing slight areas of constricted growth. Right valve ornamented 

by about 14 longitudinally sculptured radiating ribs, which are 

rounded in the eal'lier part of the shell, but which, toward the ventral 

margin. show a tendency to become flattened; i nterspaces of varying 

width but all nan·ower than the ribs, all containing a small midrib; 

anterior and posterior margins of shell ornamented by fine longitudinalt·iblets; ears unequal, the anterior ear large, with large byssal 

notch and sculpture consisting of about seven well defined radial 

t·iblets and concentric growth lines, the left ear small in comparison 

with the large right, its posterior edge sloping down almost vertically to the margin of shell, the surface of the ear ornamented by 

about eight ot· more radiating riblets over which are superimposed 

fine longitudinal and concentric lines. Altitude 58 mm.; longitude 60 

mm.; diameter of right valve approximately 14 mm.; apical angle, 

right valve approximately 92°." 

HolotmJe.-CAS/SV 39. 

Type local·,:ty.-SV 43. Baja California Sur. Almejas Formation, 

Pliocene. · 

Su.1)1Jlmnentary desc'/"1:pt·1:on.-The left valve has 10 to 11 ribs, 3 of 

which are nodose and separated by 2lesser ribs; the right-valve ribs 

have no nodes (Judith T. Smith, written commun., 1979). 

C(nnpo:n:son.-"Pecten nwdulatus bears some resemblance toP. 

vo:u.glw:n:i Arnold, but is much larger and also has sculptured margins and prominent midriblets in the interspaces, while in P. 

'1;o:u.glw.n:1: the interspaces bear fine striae only." (Hertlein, 1925a, p. 

12) 

Geortra.1Jh:1:c ·ro:nge.-Southern California to Baja California Sur. 

Geologic ·ra:nge.-Miocene to Pliocene. 

Occu:rrence h1. the Cal·1jon~ias.-Miocene or Pliocene: Imperial 

Formation (Judith T. Smith, written commun., 1979); Pliocene: 

Almejas (Minch and others, 1976), Salada, and San Marcos (Durham, 1950) Formations. 

Lyropecten cerrosensis (Gabb) 

Plate 20, figures I, 3, 4; plate 2I, figure I 

Pecten ce?Tosensis Gabb, 1866, p. 32. Gabb, 1869, pl. .9. figs. 55, 55a. 

Pecten (Plagioctem>um) cerrosensis Gabb. Hertlein, 1925a, p. 15-16, 

pl. 6, fig. 1. 

Pecten (Ly1·opecten) ce1·rosensis Gab b. Jordan and Hertlein, 1926b, p. 

432-433, pl. 32, fig. 4. Moore, 1968, p. 44, pl. 20, figs. a, b. 

Pecten (Ly1·opecten) est?·ellanus (Conrad) var. cerrosen:n:s Gabb. 

Grant and Gale, 1931, p. 187, pl. 8, figs. la, lb, 2a, 2b; pl. 9, fig. 2. 

Ly1·opectencerrosensis(Gabb). Woodring, 1938, p. 32-34, pl. 7, figs. I, 

2. Woodring, 1950, p. 85, pl. 21, fig. 1. 

Chlamys (Ly1·opecten) ce1·rosensis Gab b. Hertlein and Grant, 1972, p. 

209-211, pl. 34, figs. 1-4; pl. 36, fig. 7. 

.Pecten (Ly1·opecten) ashleyi Arnold, 1906, p. 122-123, pl. 47, figs. 1, 

la; pl. 48, fig. 1. 

Not Pecten (Plag1:octem:um) cerrosens1:s Gabb. Arnold, 1906, p. 

123-124, pl. 44, fig. 5; pl. 49, figs. 1, la, lb.[= A1·gopecten.] 

Original description.-"Shell equivalve, subcircular, broader than 

long, convex; beaks small; sides sloping concavely above, rounded 

below; ears small, subequal, roughened and irregular, sinus very 

small. Surface marked by eighteen or twenty flat ribs, with flat or 

slightly concave interspaces; margins undulated, the ends of the ribs 

being deeply emarginated, and the interspaces being prolonged into 

tongue-like processes." (cerrosensis) 

"Adult shell averaging about 150 millimeters in altitude, much 

longer than high, subequivalve, convex, inequilateral, the posterior 

portion of the disk being obliquely produced; sides concave above. 

Right valve with about 18 or 19 prominent, rather squarish, flattopped (convex-topped near umbo) ribs which are more or less prom-

. inently sculptured by numerous thread-like, somewhat imbricated, 

radial ridges; interspaces narrower than ribs, channeled and ornamented by an intercalary riblet and, in the later stages of growth, by 

several imbricated radial lines; hinge line about one-half length of 

disk; anterior ear somewhat produced, prominently notched and 

sculptured by numerous imbricating incremental lines and several 

more or less prominent unequal radials; posterior ear slightly shorter than anterior, and similarly sculptured except with more,1

but less 

conspicuous, radials. Left valve slightly more convex than right and 

similar to it except that the ribs are slightly narrower and more 

convex, and the interspaces are correspondingly wider and generally have the bottom entirely sculptured with subequal radial lines, 

with the prominent intercalary lacking; ears subequal, rectangularly truncated and sculptured in a similar manner to the posterior 

ear of the right valve." (ashley1:) 

Holotype.-UCMP 32669 (formerly UCMP 1091); of L. ashley1:, 

UCMP 12082. 

Type local?:ty.-lsla Cedros, Baja California Norte. Almejas Formation, Pliocene; of L. ashleyi, same locality. [Subsequent collecting 

by Frank Kilmer restricts the type locality to the beach cliffs below 

Cedros Village and the canyons just south of it (Judith T. Smith, 

written commun., 1979).] 

Supplementary descript?:on.-"Fragments of an exceptionally 

large valve from San Diego * * * have a riblet stronger than the 

others in the inters paces some distance from the margin of the valve, 

in the middle of the interspaces or a short distance from the middle. 

Hertlein's figure of the type of cerrosensis shows a riblet slightly 

stronger than others in inters paces on the middle of the righfvalve 

about halfway between the umbo and lower margin ***."(Woodring, 1938, p. 33) 

"The entire shell is radially striated with fine threads as are other 
B56 PALEONTOLOGY OF CALIFORNIA AND BAJA CALIFORNIA 

species of Lyropecten. The inters paces bear four or five striations or 

threads of which the central one is stronger than the others and 

forms a midrib." (Hertlein and Grant, 1972, p. 210) 

Some left valves, especially juvenile or young adult parts, have the 

central rib and the fourth anterior and posterior lateral ribs raised 

(Judith T. Smith, written commun., 1979). 

Comparison.-"£. cerrosensis is larger than L. estrellanus, estrellanus catalinae, and estrellanus terminus but is not much larger 

than * * * gallegos1:; it also lacks the strong midrib of estrellanus and 

its allies, those on the young shell figured by Jordan and Hertlein 

being weaker than in estrellanus. It is almost as large as the Miocene 

L. crassicardo (Conrad), ***but*** the ears are sculptured with 

fewer riblets. On some specimens of crassicardo a riblet in some of 

the interspaces is stronger than the others." (Woodring, 1938, p. 34) 

"In some inters paces one secondary rib is stronger than others, but 

it does not completely fill the interspace as in the smaller Miocene L. 

estrellanus. Lyropecten terminus, from the Pliocene of the Salinas 

Valley, is smaller than L. cerrosensis and has a relatively strong 

secondary rib." (Woodring, 1950, p. 85) 

"The general characters of the shell of the present species closely 

resemble those of C. (L.) estrellanus ***.A midrib is present in the 

interspaces between the ribs of C. (L.) cerrosensis as it is in C. (L.) 

estTellanus and its subspecies. However, the midrib is usually decidedly finer than it is on the shells of the C. (L.) estrellanus group. Some 

young specimens of C. (L.) cerrosens1:s have a well developed midrib 

and in this respect closely resemble some specimens of C. (L.) estrellanus. Compared to typical C. (L.) estrellanus Conrad*** the valves 

of C. (L.) cerrosensis are less inflated, generally larger, more elongated posteriorly, the midrib in the interspaces is usually smaller 

and not split at the margin, there are more numerous riblets on the 

ears and often there are more and coarser radial threads and rib lets 

on the posterior submargin. Chlamys (L.) cerrosensis has more 

numerous ribs which are usually more rounded than those on C. (L.) 

estrellanus terminus Arnold which has but 15 flat-topped ribs. The 

valves of C. (L.) cermsens1:s are more convex and the midribs are 

usually finer than are those of C. (L.) estrellanus catalinae Arnold. 

Chlamys (L.) gallegosi E. K. Jordan and Hertlein bears a close 

resemblance to C. (L.) cerrosensis but the former species has flatter, 

squarer, and much more closely spaced ribs, the riblet in the interspaces is much coarser and the radial threads on the shell are generally coarser. 

"In general outline and sculpture C. cerrosensis bears a similarity 

to C. (L.) crassicardo Conrad but differs in possessing a midrib in the 

inters paces between the major ribs, in the usually greater number of 

ribs, 17 to 19or 20 in comparison to 14 to 17, also in lacking constrictions which often are present on the shell of Conrad's species." (Hertlein and Grant, 1972, p. 210-211) 

Cmnments.-The largest specimen known is 190 mm long and 175 

mm high (Moore, 1968, p. 44, pl. 20, figs. a, b). 

Geographic Tange.-Southern California to Baja California Sur. 

Geologic range.-Miocene and Pliocene. This species is the last 

known Lyropecten to have lived in California seas (Woodring, 1950, 

p. 85). 

Occurrence in the Calijornias.-Miocene: Pancho Rico Formation 

(Durham and Addicott, 1965); Miocene and Pliocene: Etchegoin 

Formation (Smith, 1912); Pliocene: Almejas Formation (Arnold, 

1906; Minch and others, 1976), Cebada Member, Careaga Sandstone 

(Woodring, 1950), lower member, Fernando Formation (Durham 

and Yerkes, 1964), Foxen Mudstone (Woodring, 1950), Niguel 

(Vedder, 1960), lower part of Pico (Kew, 1924; Winterer and Durham, 1962), Salada (Beal, 1948), and San Diego (Hertlein and Grant, 

1972) Formations; Pliocene: Gragg and Squire Members, Pismo 

Formation (Hall, 1973). 

Genus MACROCHLAMIS Sacco, 1897 

Differs from Lyropecten in that the left valve is usually more 

convex than the right valve (but this character is variable), the 

byssal notch shallower, and the cardinal crura weaker. 

Geographic range.-Eurasia, western Atlantic, and eastern 

Pacific. 

Geologic range.-Oiigocene to Pliocene. 

Macrochlamis magnolia (Conrad) 

Plate 21, figures 4, 5 

Pecten magnolia Conrad, 1857c, p. 191, pl. 1, fig. 2. 

Pecten (Lyropecten) magnolia Conrad. Arnold, 1906, p. 77-79, pl. 24, 

figs. 1, 2; pl. 25, fig. 1. Loel and Corey, 1932, p. 198-199, pl. 25, 

figs. 1-4; pl. 26, figs. 1a, 1b; pl. 27, figs. 1, 2; pl. 28, fig. 1. 

Lyropecten magnolia (Conrad). Addicott, 1965, fig. 3, i. J. T. Smith, 

1975, pl. 1, figs. 3-5, 7. 

Pecten (Lyropecten) vaughani emigdioensis Wagner and Schilling, 

1923, p. 253, pl. 45, fig. 2. 

Macrochlamis magnolia (Conrad). Addicott, 1972, pl. 2, fig. 8. 

Original description.-"Suborbicular, ribs 11, very large, prominent, convex-depressed on the back, laterally angulated, longitudinally rugoso-striate. Locality, Santa Ynez Mountains, S. B. C." 

(magnolia) 

"Shell small; equilateral; convex; slightly longer than high; base 

regularly rounded, dorsal margins slightly concave; left valve with 

10 prominent ribs, rail-shaped and flat to rounded on top; interspaces nearly equal to ribs in width; bottoms rounded; surface of ribs 

and interspaces covered with very fine radial striae; incremental 

lines not prominent; anterior ear sculptured by 5 distinct riblets; 

byssal notch shallow; posterior ear (imperfect type) ornamented by 1 

rounded and 3 sharp ribs. Dimensions: length, 23 mm.; height, 21 

mm.; convexity of left valve, 5.5 mm." (emigd1:oensis) 

Type.-Lectotype USNM 13325 (Keen and Bentson, 1944); holotype of M. emigdioensis, UCMP 11417. 

Type locality.-Santa Inez [Ynez] Mountains [T. 5 N., R. 30 W., 

S.B., Santa Barbara County], Cal if. Vaqueros Formation, 0 I igocene 

and Miocene. Of M. emigdioensis: UC 3224, Kern County, Calif., 

Vaqueros Formation, Oligocene and Miocene. 

Supplementary description.-"Shell averaging about 150 millimeters in altitude, slightly longer than high, subequivalve, equilateral, rather thick, somewhat ventricose, and with smooth margins; base regularly rounded; sides sloping above, and slightly 

concave. Right valve slightly more convex than left, with about 9 to 

11 broad, flat-topped, equal, equidistant ribs; interspaces slightly 

narrower than ribs and flat-bottomed; whole surface of ribs and 

interspaces covered by imbricated radiating riblets (about 10 on 

each rib) and fine, concentric incremental lines; hinge line about 

two-thirds the length of the disk; anterior ear slightly longer than 

the posterior, with arcuate end and fine concentric incremental 

sculpture, but obsolete radiating ridges; posterior ear with no radial 

sculpture whatever; byssal notch relatively small. Left valve quite 

similar to right but with narrower, more rounded ribs; sculpture of 

radiating riblets and fine wavy incremental lines; interspaces 

bro"ader than in right valve; ears almost identical to those of right." 

(Arnold, 1906, p. 78) 

"The umbone of the right valve is commonly higher and more 

convex than that of the left, projecting above the hinge line. 

"In one zone of the type region***, Pecten magnolia Conrad has 

developed 10 to 12 ribs in a large percentage of individuals. A count 

of all specimens in the collections and in the field gives an average 
TERTIARY MARINE PELECYPODS: PROPEAMUSSIIDAE AND PECTINIDAE B57 

TABLE 11.-Geolog1:c and geog·raphic distribution of the 

genus Nodipecten 

[H =Holocene: Pie= Pleistocene: PI =Pliocene: M =Miocene] 

Species 

Genus Nod·ipecten: 

subnodosus 1:ntennedius 

California 

Southern 

Baja California 

Norte Sur 

Central 

and (or) South 

America 

(Conrad) .......................................... Pie to H PI to H PI to H 

subnodosus subnodosus 

(Sowerby) ........................................ Pie PI to H PI to H 

veatch1:i (Gabb) ................................. . 

rib number of 9 and a range of 6 to 13." (Loel and Corey, 1932, p. 198) 

Cmn1m.n:.•wn.-"P. nwgnolia is somewhat closely allied toP. c·ras-

. c;·ica:rdo ***.It is distiM"uishable· from the latter by its fewer (9 to 11, 

instead of 14 to 17). broader, more square-cut and more coarsely 

radially sculptured ribs, and the obsolete radial sculpture on its 

ears." (Arnold, 1906, p. 78) 

Commwnts.-Pecten (L1J?'01Jecten) vaugham: e1n1:gd1:oensic; is a juvenile specimen of M. magnob:a(Judith T. Smith. oral commun.,1978): 

Geog·raph·ic ?'a.nge.-Middle to southern California. 

Geolog·ic ·ro:nge.-Oligocene and Miocene. 

Occu:1"/'e1we ·in Cahjont·ia.-Oligocene: Agua Sandstone Member, 

Temblor (Dibblee, 1973) and Quail Canyon Sandstone Member, 

Vaqueros (Dibblee. 1973) Formations: Oligocene and Miocene: Mindego Basalt (Cummings and others, 1962), Rincon Shale (Bailey, 

1952). Soda Lake Shale Member. Vaqueros (Vedder, 1973; Squires 

and Fritsche, 1978). Temblor (Nilsen and others. 1973), and Vaquer·os (Arnold. 1906; Kew, 1924; Loel and Corey, 1932; Dibblee, 1950; 

Repenning and Vedder, 1961: Addicott, 1968) Formations; Miocene: 

Painted Rock Sandstone Member. Vaqueros Formation (Vedder, 

1973), Pyramid Hill Sand Member. Jewett Sand (Addicott, 1974), 

and Tranquillon Volcanics (Dibblee, 1950). 

Genus NODIPECTEN Dall, 1989 

Ctenolium well developed; imbricated surface layer in some species very marked. Differs from Ly1·opecten in that ribs are intermittently nodose (hollow nodes) and posterior auricle is smaller than 

anterior. 

Geom·aph:ic ·ra:nge.-Western Atlantic; eastern Pacific. 

Geolog·ic ·ro.nge.-Miocene through Holocene (table 11). 

Nodipecten subnodosus subnodosus (Sowerby) 

Plate 6, figures 4, 8 

Pectm1. W/.1.lnwdosu.s Sowerby, 1835. p. 109. 

Pectm1. (Noch:1Jecten) snbnodosus Sowerby. Arnold, 1906, in part, p. 

128-129. pl. 52, fig. 1; not pl. 53, figs. 1, 1a. 

Pecten (L?J'f01Jecten) .c;u.bnodosus Sower by. Hertlein, 1935, p. 317-318. 

L?J'f01)(Wtm1.S'I.dnwdowu.s(Sowerby). Durham,1950, p. 65, pl.11. fig.l. 

Nod·1:1mcten S'/.l.bnodosu.s (Sowerby). Grau, 1959, p. 128-132, pl. 43. 

Not Pecten S'l.drnodosus Sowerby. G D. Hanna, 1926a, p. 474, pl. 25, 

fig. 6 [= /.i!J?'01Jecten m.odulatus Hertlein]. 

Ori{J'I:nal descn:1Jt·ion.-"Pect. testa subqequivalvi, aequilaterali, 

auriculus inaequalibus; striis radiantibus numerosissimis, radiisque 

decem, crass is, rotundatis. alternatim nodoso-vesicularibus vel subnodosis; intus plerumque purpureo signata; long. 5.25,lat. 2.75, alt. 

5. poll." 

PI 

Holotype.-In BM (NH). 

Type locality.-lsla La Plata, Ecuador. Holocene . 

Supplementary description.-"Shell large and thick, averaging 

130 mm in height when adult, and usually longer than high; left 

valve usually more concave than right; hinge line from almost half to 

slightly more than half length of disk. Right valve often concentrically undulated; 10 ribs (occasionally 11), those next to submargins 

being almost obsolete; ribs rounded and with 7 to 15 thin radial 

ridges; interspaces with 5 to 8 ridges of same size; fine concentric 

imbricating lamellae between all ridges. Anterior auricle short for 

size of disk, of varying height, and concentrically lamellose; from 8 

to 12 radiating riblets, those next to disk being much smaller; byssal 

·notch rather shallow and either rounded or angled; ctenolium of 5 to 

10 teeth in young shells, later only 3 or 4 obscurely present. Posterior 

auricle shorter, also lamellose, and with 10 to 18 radial riblets. Left 

valve often concentrically undulated; usually 9 but occasionally 10 

ribs, those next to submargin being almost obsolete; ribs rounded 

and having 8 to 16 thin radial ridges; central rib and alternate one or 

two either side often having hollow nodules, with degree of prominence varying in individuals; interspaces with 6 to 8 radial ridges; 

entire disk profusely covered with fine imbricating lamellae which 

is nearly always worn off tops of ribs on mature specimens. Anterior 

auricle concentrically lamellose and with 10 to 15 radial ridges of 

varying size; byssal sinus shallow. Posterior auricle same as that of 

right valve. Hinge line with strong diagonal crura adjoining resilial 

pit. * * * heavy white callus covering umbonal area, surrounding 

muscle scar, and reaching to from one-thirds to two-thirds of distance to ventral margin. 

"Specimens from western Lower California and the Gulf of California to southern West Mexico are usually larger at maturity*** 

with 10 ribs on the right valve and 9 on the left, while those from 

central West Mexico (overlapping the above) to Peru are usually 

smaller * * * with 11 ribs on the right valve and 10 op the left. 

Conrad's Pecten 1:ntermedius was based on the northern 'form'; he 

commented, 'It differs from subnodosus ***in having much finer 

striae, numbering nearly double as many between each rib.' The 

finer striae are actually found only on occasional specimens, and the 

features of the northern 'form' mentioned above would not be of 

specific or infraspecific significance even if they were constant." 

(Grau, 1959, p. 130-131) 

"Both valves are similar, not strongly convex. Most specimens of 

the typical form have 10 ribs in the left valve and 11 ribs in the right, 

counting the deep furrows around the ventral margin. The ribs are 

as wide as their intervals, both covered with a series of close-set, 

coarse, slightly scabrous radial cords; there are usually a scattering 

of small or coarse, sometimes hollow nodes or humplike swellings 

along the summit of the ribs, best developed on the left valve. * * * 

Ears unequal in size, the anterior larger and longer, that of the right 

valve with a deep notch." (Olsson, 1961, p. 161) 
B58 PALEONTOLOGY OF CALIFORNIA AND BAJA CALIFORNIA 

Comparison.-"Grant and Gale (1931, p. 179-182) united this species with Pectennodosus (Linnaeus). However, the two may easily be 

separated by the fewer interribs (usually 3 or 4) of that species 

compared to 6 or 8 on Sowerby's species. Further, L. subnodosus is 

usually more inflated. A large specimen*** has much less than the 

normal degree of inflation but still retains the greater number of 

interribs. Many of the specimens * * * are similarly less inflated, a 

condition that has not been noted in any of the recent specimens." 

(Durham, 1950, p. 65) See also comparison below in section on Nodipecten subnodosus intermedius. 

Geographic range.-Living: Isla Tres Marias to Peru; fossil: southern California to Oaxaca, Mexico. 

Geologic range.-Pliocene to Holocene. 

Occurrence 1:n the Calijor·nias.-Pliocene: unnamed strata on Isla 

Cerralvus; Pleistocene: Palos Verdes Sand (Woodring, 1946). The 

record in the Imperial Formation (G D. Hanna, 1926a) is in error; 

the species is Lyropecten modulatus (Judith T. Smith, written commun., 1979). 

Habitat.-From low tide to 110m. Found in shallow depressions 

in sand at low tide; in deeper water on rock, sand or mud bottoms, 

associated with red algae, nullipores, corraline and coral; vermetids, 

bryozoans and barnacles often commensal. 

Nodipecten subnodosus intermedius (Conrad) 

Plate 22, figure 1; plate 23, figure 5 

Lyr·opecten 1>ntermedius Conrad, 1867, p. 7. 

Pecten (Nodipecten) subnodosus Sowerby. Arnold, 1903, p. 108. Not 

Pecten subnodosus Sowerby, 1835. 

Pecten (Nodipecten) subnodosus Sowerby. Arnold, 1906, in part, p. 

128-129, pl. 53, fig. 1, not pl. 52, fig. 1. 

Pecten subnodosus Sowerby. Jordan, 1924, p. 148. 

Pecten (Lyropecten) subnodosus Sowerby. Jordan and Hertlein, 

1926b, p. 418. Hanna and Hertlein, 1927, p. 141. 

Pecten (Lyropecten) nodosus (Linnaeus) variety intermedius (Conrad). Grant and Gale, 1931, p. 181-182. 

Original description.-"Rounded-oval, ventricose; ribs 9-10 

nodose, as wide as the intersti'ces; with numerous closely scaled 

striae covering the whole surface, and numbering about ten between 

each rib. Purple, within purple, with a large white central deposit of 

callus." 

Holotype.-The holotype is missing and presumed lost. 

Type locality.-Cabo San Lucas, Baja California Sur. 

Comparison.-Right valves of Holocene specimens of Nod1:pecten 

subnodosus intermedius differ from N. subnodosus subnodosus in 

having the ribs evenly distributed; right valves of N. subnodosus 

subnodosus have ribs grouped in 5 about a wider central space. 

Holocene specimens of Nodipecten nodosus nodosus h~ve_more bulbous or flared nodes, sometimes on all ribs of both .right and .left 

valves, and a slightly coarser, striate, lyrate microsculpture than N. 

subnodosus intermedius (Judith T. Smith, written commun., 1980). 

Geographic range.-Living: Santa Catalina Island, Calif., to Baja 

California Sur and in Golfo de California; fossil: Baja California 

Norte to Mexico. 

Geologic range.-P!iocene through Holocene. 

Occurrence in the Calijornias.-Pliocene: Almejas (Minch and 

others, 1976), Carmen (Durham, 1950), lnfierno(?) (McFall, 1968), 

Marquer (Durham, 1950), and San Marcos (Durham, 1950) Formations; Pleistocene: unnamed strata at San Pedro and San Diego, Isla 

de Cedros, and Golfo de California. 

Nodipecten veatchii (Gabb) 

Plate 22, figure 4; plate 23, figure 2 

Pecten veatchii Gabb, 1869, p. 32, pl. 10, fig. 56. 

Pecten (Nod1:pecten) veatchi1: Gabb. Arnold, 1906, p. 106-107, pl. 40, 

figs. 1, 1a. 

Pecten (Lyropecten) ·veatchii Gabb. Jordan and Hertlein, 1926b, p. 

418. 

Pecten (Lyropecten) nodosus (Linnaeus) variety veatchi·i Gab b. Grant 

and Gale, 1931, p. 182. 

Original description.-"Shell large, equivalve, a very little 

broader than long; base regularly rounded; sides sloping above, with 

a slight concavity; ears unequal; sinus in the right ear of the lower 

valve moderately deep; surface of ears covered by small radiating 

ribs and fine imbricating lines of growth; surface of valves ornamented by about 8 broad, flat, subnodose ribs, arranged in pairs, and 

a few small linear ribs on the side; besides the ribs, the whole surface 

is covered by small radiating lines, and crossed by very irregular 

lines of growth, and very fine imbricating concentric lines." 

Holotype.-UCMP 12078. 

Type locality.-ls!a de Cedros, Baja California Norte. Almejas 

Formation, Pliocene. 

Supplementary descn:ption.-"Shell averaging about 130 millimeters in altitude*** subequivalve, equilateral, of medium thickness, somewhat ventricose, and with margins finely serrate * * *. 

Right valve slightly less ventricose than left, * * * [and] the whole 

surface is covered by several more or less prominent concentric 

undulations and numerous fine, squarish, imbricated, raised rib lets; 

hinge line a little more than one-half the length of the disk; anterior 

ear about one and two-thirds length of posterior, ornamented by 

about 12 radiating riblets and numerous fine, sharp, imbricating, 

incremental lines; byssal notch about one-fourth length of ear in 

depth; posterior ear much smaller than anterior, but sculptured in a 

similar manner. Left valve with about 7 broad, flat, round-cornered 

ridges of unequal size, which are separated by interspaces of 

unequal width, there being 3 or 5 prominent ribs, between each pair 

of which is a smaller one; the surface of this valve is sculptured 

similarly to that of the right, except that the concentric undulations 

on the ribs become more or less prominent nodes toward the apex of 

the shell; ears similar to those of the right valve, except that the 

anterior one has a simple arcuate end and no notch." (Arnold, 1906, 

p. 106-107) 

Comparison.-"This species is quite similar to and is no doubt the 

precursor of P. subnodosus, from which it differs by attaining a 

larger size and having fewer and broader ribs. Like the living form, 

it is quite variable as regards the number and rugosity of its ribs." 

(Arnold, 1906, p. 107) 

Geographic 1·ange.-Baja California Sur. [According to Judith T. 

Smith (written commun., 1979) N. veatchi1: does not occur north of 

Baja California, and the records of Arnold (1906) and Smith (1912) 

are in error.] 

Geologic range.-PI iocene. 

Occurrence in Baja Calijornia.-Almejas Formation (Minch and 

others, 1976). 

Genus SWIFTOPECTEN Hertlein, 1936 

Higher than long, nearly equivalve, auricles nearly equal and 

with well-developed byssal notch and ctenolium in adult; four, five, 

or more folded radial ribs (paired in some shells), thickened where 
TERTIARY MARINE PELECYPODS: PROPEAMUSSIIDAE AND PECTINIDAE B59 

TABLE 12.-Geolom:c a.nd geogmph:1:c d1:stribution of the genus Swiftopecten 

!Pic= Pleistocene; PI= Pliocene; M =Miocene] 

Species 

Genus S·unftopecten: po:nnelewi etchegoin·1: 

(Ander·son) ..................................... . pa:nnelee·i 1Ja.nnelee·i (Dall) ............. . Genus Swiftopecten.?: 

ha:m.l·in·1: (Arnold) ............................... . 

Alaska 

PI 

crossed by concentr·ic undulations, commonly with nodes at intersections on left valve, entire surface with coarse radial striae and 

microscopic tesselations; hinge with strong cardinal crura. one on 

each side of ligamenta! pit. 

Mo:n:upecten has radial ribs rather than folds and no constricted 

radial ribs on the left valve. 

Geog·mph:ic 1·a.nge.-Japan and eastern Pacific. 

Geologic ·ra.nge.-Miocene through Holocene (table 12). 

Ha.ln:tat.-In 1 to 145m. 

Swiftopecten parmeleei parmeleei (Dall) 

Plate 23, figures I, 3, 4 

Pecten (Chlmnys) 1Ja:nnelee·1: Dall, 1898, p. 708, pl. 37, figs. 14, 14a. 

Arnold, 1906, p. 119, pl. 41, figs. 1, 1a; not? 5, 5a [= S. sw1}t1:dide 

Masuda, 1972]. 

Chlo:m,ys 1W:1"melee·1: (Dall). Woodring, 1950, p. 83, pl. 16; fig. 20. 

Chlo:m.ys (S·wifto1Jecten) pa:rm.elee·1> Dall. Hertlein and Grant, 1972, 

p. 206-208, pl. 31, fig. 5; pl. 37. figs. 1-10; text fig. 10 (see for 

synonymy). 

Pecten (Chlo.mys) wo.ttwi Arnold, 1906, p. 120, pl. 11, figs. 1. 1a. 

On:rrhw.l clesc·ript·ion.-"This species is close to P. S1.m}ti1: Bernhardi [sic: Bernardi] of Japan (J. de Conchyl., vii., plates 1 and 2, 

1858) but smaller, and differs by the smooth top surface of the ribs, 

which in P. Surijt·1:·i are more or less striated or coarsely threaded, 

and by the not alternated radial riblets on the right posterior ear; 

also, especially, by the profuse coalescent microscopically checkered 

squamation, which makes a complete external coating to the valve. 

Alt. 45, lat. 38 mm." (Dall, 1898) 

"Shell averaging about 65 millimeters in altitude, slightly higher 

than long, equilateral, of medium thickness, decidedly ventricose, 

and with margins slightly finely serrate; base regularly rounded; 

sides sloping above, with slight concavity. Left valve with 5 high, 

rather narrow, rounded, almost smooth ribs, which are made prominently nodose by several very pronounced concentric undulations, 

or constrictions; interspaces much wider than ribs and each ornamented by about 5 small, subequal, rounded, imbricated riblets; 

whole surface of disk with a profuse, coalescent, microscopically 

checkered squamation; hinge line about two-fifths length of disk; 

anter·ior ear with arcuate end, and with surface sculptured by about 

5 prominent imbricated riblets and several concentric undulations; 

poster·ior ear obsolete. Right valve about equal to left in convexity, 

with broad, flat-topped ribs and narrower interspaces, both being 

longitudinally sculptured by subequal riblets; ears similar to left; 

byssal notch not prominent; surface sculpture microscopic; constrictions less pronounced than in left valves." (wattsi) 

Holotype.-USNM 154479; of P. wo.tts1: missing and presumed. 

destroyed in San Francisco fire of 1906; lectotype CAS 5945 (G D. 

California 

Northern Middle Southern 

PI.Ple M,PI 

PI,Ple M to Pie 

M? 

PI 

M,PI 

Baja .California 

Norte Sur 

PI 

Hanna and Hertlein, 1941, p. 176, fig. 65-18). 

Type local?:ty.-San Diego [San Diego County], Calif. San Diego 

Formation, Pliocene; of S. watts1:, USGS 4712, Fresno County, Calif., 

Etchegoin Formation, Miocene and Pliocene. 

Supplementary desc1·1:pt1:on.-"A fine series**'* collected * * * 

from near the Mexican boundary [San Diego Formation, Pliocene] 

* * *of various sizes, from 4 to 79 mm high***. Some attain a height 

of 32 mm with only a trace of undulation of the shell. Some have 

three, others as many as five, constrictions in the shell. These undulations where they cross the ribs, lend a nodose appearance to the 

ribs. 

"The ribs are large, convex and consist of folds in the shell, those of 

the right valve corresponding to the inters paces of the left. There are 

four broad ribs on the right valve and often in addition a narrow, 

minor one near the anterior and posterior margins. The ribs on this 

valve are separated by narrower interspaces than those on the left. 

There are five on the left valve which is more convex than the right. 

The ribs and interspaces of both valves are sculptured with nearly 

equal, coarse, radial threads. The anterior ears are much larger 

than the posterior ones and are sculptured with 5 to 9 riblets, those 

on the left po~terior ear are fine and nearly equal in size." (Hertlein 

and Grant, 1972, p. 207) 

"Po.rmelee1: is characterized by its small shell which is contorted 

posteriorly in the young stage but tends to become rounded with 

growth * * *."(Masuda, 1972, p. 401) 

Comparison.-"The dorsal (umbonal) part of the shell ofdarge 

specimens of C. parmeleei is more inflated than that of C. sw1jti1:and 

is more strongly set off from the ears * * *. C. parmeleei has concentric swellings, whereas C. parmelee1: etchego1:ni lacks the swellings." 

(Woodring, 1950, p. 83) 

"Po.rmelee1: differs from the closely related Swijtopecten sw1}t1:1: in 

having smaller shell which tends to become rounded ~ith growth 

and somewhat larger apical angle." (Masuda, 1972) 

"A comparison of large specimens of Chlmnys (Swijtopecten) parmelee?: with C. (S.) swijtii from Japan reveals that on C. (S.) pm·tneleei and its subspecies the left posterior ear is generally sculptured 

with finer more nearly equal riblets. The radial ribs on both valves of 

the Japanese species tend to bifurcate toward the ventral margin 

whereas those on C. (S.) parmelee1: only rarely show this feature. 

Furthermore the west American forms do not reach the size of C. (S.) 

swijtii which attains a height of at least 108 mm." (Hertlein and 

Grant, 1972, p. 208) 

Geog1·aphic ;ange.-Aiaska; middle to southern California. 

Geologic range.-Miocene(?); PI iocene; Pleistocene(?). 

Occurrence in Calijornia.-Miocene: Castaic Formation (Stanton, 

1966); Miocene and Pliocene: Capistrano (Kern and Wicander, 1974), 

Etchegoin (Arnold, 1906; Woodring and others, 1940), Purisima 

(Arnold, 1906), and Tahana Member, Purisima (Cummings and 

others, 1962~ Durham and Morgan, 1978) Formations; Pliocene: 
B60 PALEONTOLOGY OF CALIFORNIA AND BAJA CALIFORNIA 

Cebada Member, Careaga Sandst9ne (Woodring, 1950), lower member, Fernando (Durham and Yerkes, 1964), Niguel (Vedder, 1960), 

Pico (Addicott and Vedder, written commun., 1968), San Diego 

(Hertlein and Grant, 1972), San Joaquin (Woodring and others, 

1940) Formations; Pliocene and Pleistocene: Merced Formation 

(Arnold, 1906) and Wildcat Group (Arnold, 1906). 

Swiftopecten parmeleei etchegoini (Anderson) 

Plate 22, figures 2, 3 

Pecten etchegoini Anderson, 1905, p. 198, pl. 18, figs. 92, 93. Hanna 

and Hertlein, 1943, p. 172, fig. 63, 1-2. 

Pecten (Pallium) swijtii Bernard variety etchegoini Anderson. Grant 

and Gale, 1931, p. 173-17 4, pl. 1, figs. 3a, 3b. 

Swijtopecten etchegoini (Anderson). Adegoke, 1969, p. 104-105. 

Chlamysetchegoini(Anderson). Woodring, Stewart, and Bramlette, 

1940, pl. 13, fig. 5; pl. 32, fig. 1. 

Chlamys (Swijtopecten) parmeleei etchegoini (Anderson). Hertlein 

and Grant, 1972, p. 208. 

Pecten(Chlamys)watts1:var. moraniArnold, 1906, p.121-122, pl.10, 

figs. 3-6. 

Original description.-"Shell rather large, thick, and ovate in 

outline; ears nearly equal, costate; ribs strong and grouped in sets of 

3 or 4, forming radial undulations in the shell, seen both within and 

without; margin of valve fluted within. The grouping of the ribs is a 

variable feature of the shell. In some specimens the depressions are 

wider, in others narrower than in the one figured. Concentric lines 

are usually visible on the shell." (Anderson, 1905) 

"Adult shell averaging about 65 millimeters in altitude, much 

shorter than high, inequivalve, equilateral, moderately convex, and 

with slightly serrate margins. Right valve less convex than the left, 

ornamented by 4 very broad, prominent, flat-topped ridges, each of 

which carries from 5 to 7 strong, squarish, elevated, subequidistant 

· riblets; interspaces narrow and rather deep, each ornamented by 1 

or 2 squarish riblets; hinge line about one-third length of disk; 

anterior ear much more prominent than the posterior, regularly 

arcuate-ended and sculptured by 5 or 6 radials; byssal notch only 

slightly developed; posterior ear very short, obliquely truncated and radially 

striate. Left valve more convex than right, and usually more or less 

undulated by constrictions; disk with 5 subequal, narrow, ridge-like 

ribs, separated by wide interspaces, in each of which are from 2 to 5 

subequal, prominent, squarish rib lets; whole surface ornamented by 

a superimposed tessellation, which is usually worn off in the adult 

shells; ears similar to those of the right valve, there being nearly as 

pronounced a· byssal notch in the anterior ear of the left valve as in 

the anterior one of the right." (Arnold, 1906) 

Holotype.-CAS 55. Of S. morani, USNM 164929. 

Type locality.-Kreyenhagen Ranch on Zapata [Zapato] Chino 

Creek [Mt. Diablo Range, Fresno County], Calif. Upper part of 

Etchegoin Formation, Pliocene. Of S. moran1:, Mr. Moran's place, 

Priest Valley [SW~ sec. 14, T. 20 S., R. 12 E., Monterey County], 

Calif. Etchegoin Formation, Miocene and Pliocene. 

Comparison.-"This species can be distinguished from S. nutteri 

(Arnold), S. wattsi (Arnold), and S. parmeleei Dall by the absence of 

concentric swellings and the tendency for the major ribs to bifurcate 

at an earlier age than in the other species." (Adegoke, 1969, p. 105) 

C:hlamys parmeleei parmeleei has concentric swellings whereas C. 

parmeleei etcheg01>ni does not. (Woodring, 1950, p. 83) 

Geographic range.-Northern California to Baja California Sur. 

Geologic range.-Miocene to Pleistocene. 

Occurrence in the Calijornias.-Miocene and Pliocene: Etchegoin 

Formation (Anderson, 1905; Arnold, 1906; Woodring and others, 

1940); Pliocene: Almejas Formation (Hertlein and Grant, 1972), 

Cantil Costero (Hertlein and Allison, 1959), Careaga Sandstone 

(Woodring, 1950), Foxen Mudstone (Woodring, 1950), San Diego 

(Hertlein and Allison, 1959), and San Joaquin (Woodring and others, 

1940; Adegoke, 1969) Formations; Pliocene and Pleistocene: Rio Dell 

Formation (Faustman, 1964). 

Genus SWIFTOPECTEN? 

Swiftopecten? hamlini (Arnold) 

Plate 24, figure 5 

Pecten ( Chlamys) hamlini Arnold, 1906, p. 67, pl. 11, fig. 2. 

Pecten (Pallium) hamlini Arnold. Grant and Gale, 1931, p. 171. 

Chlamys (Swijtopecten?) hamlini (Arnold). Hertlein and Grant, 

1972, p. 205. 

Original descript1:on.-"Type somewhat distorted but originally 

about 60 millimeters in altitude, and probably somewhat shorter 

than high; moderately convex; base evenly rounded;· sides nearly 

straight. Right valve with 4 broad, squarish ribs, each ornamented 

above by about 5 prominent imbricated radiating ridges, and separated by relatively narrow interspaces; hinge line more than one-half 

length of disk; anterior ear much longer than posterior and ornamented by several imbricated radiating ridges; byssal notch quite 

prominent; posterior ear short and radially ridged." 

Holotype.-USNM 164844. 

Type locality.-USGS 3851. Monterey County, Calif. Santa Margarita(?) Formation, Miocene. 

Supplementary descr1:ption.-"A specimen, which is probably a 

left valve of P. hamlini, was found associated with Pecten branneri in 

the lower Miocene at Tuff Hill, near Stanford University, Santa 

Clara County. This specimen has three widely separated, narrow, 

ridge-like ribs, and the interspaces are ornamented by a number of 

rather coarse radiating riblets; altitude 31 millimeters." (Arnold, 

1906, p. 67) 

"The type, a right valve, is*** a distorted specimen. It possesses 4 

broad ribs each of which are radially grooved forming 5 radiating 

ridges. This rare species may be related to the Swijtopectengroup or 

it may be referable to some other group with radially grooved ribs** 

* The relationship, if any, of P. hamhn1: with other Californian 

species is not known at the present time." (Hertlein and Grant, 1972) 

Compar1:son.-"This species is closely allied to P. watts1:, but is 

distinguishable from the latter species by its relatively broader (?) 

disk and longer hinge line. The characteristics of sculpture are 

approximately the same in the two species." (Arnold, 1906, p. 67) 

"The original specimen of this species is very poor and badly 

distorted. Specimens in the collection at Stanford University show 

that it is a form of the P. swijtii type, distinguishable from the 

variety parmeleei of that species not by its shape but by its fewer, 

, coarser secondary ribs." (Grant and Gale, 1931, p. 171) 

Comments.-Judith T. Smith (oral commun., 1979) examined the 

holotype and felt that this species could be a distorted Lyropecten. 

Geographic range.-Middle California. 

Geologic range.-Miocene(?). 

Occurrence 1:n Cal1jornia.-Santa Margarita(?) Formation (Keen 

and Bentson, 1944). 

Genus VERTIPECTEN Grant and Gale, 1931 

Left valve usually strongly convex, right valve nearly flat; right 

anterior auricle narrow and elongate with large byssal notch as wide 

as auricle; hinge practically smooth with shallow ligament pit. 

Differs from Athlopecten in that ribs of left valve are not paired and 

about every third one is elevated. Differs from Pat1:nopecten in that 

" [ 
TERTIARY MARINE PELECYPODS: PROPEAMUSSIIDAE AND PECTINIDAE B61 

TABLE 13.-Geologic and geographic distribution of the genus Vertipecten 

[M =Miocene; 0 =Oligocene; E =Eocene] 

Northern M1ddle Southern Alaska Washington Oregon California Species 

Genus Ve1·tipecten: 

a.lexclm·ki Addicott ........ , .................................. . bowenn: (Arnold) ................................................. . d?:a.bloen,cn:s (Clark) ............................................. . jucanus (Da11) .................................... 0 

k.ernens1:s (Hertlein) ........................................... . pe1·n:m: (Arnold) ................................................. . ?J1WZ1:a.na. subynez1:a.na. (Weaver 

and Kleinpell) ................................................. . ynezia.na. ynezia.na. (Arnold) ........................... . 

both the right and left valves have imbricated microsculpture. Pati-

?W1Jecten has this sculpture only on the left valve: This microsculpture is most commonly found on the right valve of Vert1:pecten at the 

posterior edge of the disk and on the posterior ear. 

Geogm.ph1:c ?·a.nge.-Western North America and Japan. 

Geologic m.nge.-Oligocene to Miocene (table 13). 

Vertipecten yneziana yneziana (Arnold) 

Plate 25, figures 2, 3 

Pecten (Chla.m.ys) (?) ynezia.na. Arnold, 1907b, p. 8-9 [separate pagination], pl. 51, figs. 6a, 6b; not pl. 50, fig. 4. 

Pecten ( Ve·rt1:1Jecten) ynez·1:a.nus Arnold. Grant and Gale, 1931, p. 191. 

Pecten ( Ve1·t·1:pecten) ynez1:a.na. ?J?Wz?:ana. Arnold. Weaver and Kleinpel1, 1963. p. 198, pl. 30, figs. 6, 7; pl. 31, figs. 1, 4. 

Ve?·tipecten ynez·1:a.na. (Arnold). J. T. Smith, 1975, pl. 1, fig. 6. 

On:m:na.l de.~cn:ption.-"Shell averaging 60 to 70 mi11imeters in 

altitude; slightly higher than long, moderately convex, practica1ly 

equivalve and equilateral, rather thin; base regularly rounded; dorsal margins concave; margins somewhat serrate. Surface of disk · 

ornamented by from 30 to 45 irregular, inequidistant rounded, more 

or less imbricated ribs; in some instances the ribs occur quite regularly, every alternate one being prominent, with lesser ones (appearing as intercalaries) between; in others the ribs are irregularly 

disposed, although there is a tendency for the alternate ones to be 

larger and sometimes dichotomous. Ears radia11y striate in addition 

to incremental imbricating sculpture; anterior ear of right valve 

with deep byssal notch and we11 isolated byssal area." 

Holotype.-USNM 165313a. 

11JJ1)e loca.l-ity.-USGS 4507. Santa Barbara County, Calif. Gaviota 

Formation, Eocene and Oligocene. [According to Wilson (1954, p. 

147) the type locality is in the middle member of Dibblee (1950, pl.1).] 

C0'1n1Ja.n:son.-"The imperfect fragments which furnish the characters described above represent a species apparently a11ied to P. 

pe1Tini Arnold, although it is sma11er and has more numerous and 

less imbricate ribs than the latter." (Arnold, 1907b, p. 426) 

"Pecten 1J1Wz?:a.na."' "'"'can usua11y be distinguished [from sespeens·l:s] by the greater umbonal angle (ca.. 75° for P. sespeensis vs. ca.. 

110° for P. 1J?Wz?:a.na., though with extreme variation) and by the 

greater number and prominence of the bifurcation of the ribs, especially near the margins of the disc." (Weaver and Kleinpel1, 1963, p. 

198) 

Geogmphic m.nge.-Southern California. 

Geolog·ic ra.nge.-Eocene to Oligocene. 

Occu.?Tence ·1:n Cahj0'1"11.1:a .. -Eocene and Oligocene: Gaviota (Dibblee, 1950; Weaver and Kleinpell, 1963; J. T. Smith, 1975) and 

Sacate and Gaviota Formations, undifferentiated (Weaver and 

0 

O,M 

M 

M M M 

M 

O,M 

E,O 

E,O 

Kleinpe11, 1963); Oligocene: Alegria Formation (Dibblee, 1950; 

Smith, 1975). 

Vertipecten yneziana subyneziana (Weaver and Kleinpell) 

Plate 24, figure 3 

Pecten ( Vertipecten) ynezia.na subyneziana. Weaver and Kleinpel1, 

1963, p. 198, pl. 31, figs. 2, 3, 7. 

Original description.-"This form is a11 but indistinguishable 

from P. ynezia.na. yneziana. except for its much sma11er size. Young 

forms of P. ynezia.na yneziana are not available for comparison. 

However, where known to date, the two morphological varieties 

seem to occupy separate stratigraphic intervals in the column." 

Holotype.-CAS/SU 9265. 

Type locality.-UC B6940. Santa Barbara County, Calif. Cold{ 

water Sandstone, Eocene. 

Supplementary description.-"With this previously undescribed 

subspecies the very phylogenetic radicle of the subgenus Vert?:-

pecten, as described by Grant and Gale (1931, pp. 188-189), is now 

recognized. In fact, one faces the problem of whether to classify this 

'connecting link' with its immediate ancestors of Chla.m.ys, as its 

sma11 size alone would seem to dictate, or with its larger and more 

robust descendants of Vertipecten, from which it is all but indistinguishable except for the very sma11 size." (Weaver and Kleinpel1, 

1963, p. 198) 

Geographic ra.nge.-Southern California. 

· Geologic range.-Eocene to Oligocene. 

Occurrence in Calijornia..-Eocene: Coldwater Sandstone; Eocene 

and Oligocene: Sacate and Gaviota Formations undifferentiated 

(Weaver and Kleinpel1, 1963). 

Vertipecten alexclarki Addicott 

Plate 24, figures 1, 2, 4 

Vert1:pecten a.lexclarki Addicott, 1973, p. 26-27, pl. 1, figs. 9, 10, 13; 

pl. 2, figs. 1, 3, 5, 8, 9; pl. 3, figs. 1. 4. Smith, 1975, pl. 1, fig. 7. 

On:gina.l description.-"Moderately large, reaching as much as 

115 mm in height, higher than long. Apical angle narrow, averaging 

about 70°. Right valve relatively flat; has 20 to 30 or more flattopped, scaly ribs that tend to be dichotomous in the central portion 

of the disk but more irregular in development toward the sides. 

Scales are fine and closely spaced near the beak but become coarser 

and more widely spaced toward base. Secondary riblets usua1ly 

developed in the inters paces between the paired ribs. Anterior auricle long, set off by deep byssal notch. Auricle sculptured by five 

strong ribs bearing heavy flanges. Left valve convex and has rather 
B62 PALEONTOLOGY OF CALIFORNIA AND BAJA CALIFORNIA 

uniform sculpture of primary, secondary, and tertiary rounded ribs 

bearing strong, rather widely spaced flanges toward the base. 

Medial primary and two lateral primaries that tend to divide the 

disk into quadrants are somewhat stronger than other primary 

ribs." 

Lectotype.-USNM 646531. 

Type locality.-USGS M3281. Kern County, Calif. Wygal Sandstone Member, Temblor Formation, Oligocene. 

Supplementary description.-"This species is assigned to Vert1:-

pecten because ~fthe distinct inequality of the valves, the right valve 

being relatively flat and the left being moderately convex***, and 

because of the relatively greater strength of the central and two 

lateral primary ribs on the left valve, the three of which tend to 

divide the valve into quadrants. In sculptural detail and in the size of 

the right anterior ear, the species resembles Chlamys. 

"The right valve of Vertipecten alexclarki ***is characterized by 

narrow, flat-topped ribs that are highly irregular in their development, whereas the left valve has a more or less orderly development 

of rounded primary, secondary, and tertiary ribs. The ribs of both 

valves are scaly." (Addicott, 1973, p. 26) 

Comparison.-"This species seems to be a lineal antecedent of the 

early and middle Miocene species Vertipecten perrini (Arnold). The 

Miocene species differs, however, by having fewer, much coarser 

ribs on the right valve that also tend to be smooth and generally are 

not dichotomous. The medial portion of the right valve of V. perrini 

also has a depression coinciding with an interspace and reflecting a 

relatively much more strongly raised medial rib on the left valve. 

"The sculpture of the right valve of Chlamys branneri * * * is 

similar to that on the Vertipecten alexclarki. ***Although the type 

material of C. branneri is poorly preserved, it is an equivalved 

species and, therefore, is properly assigned to Chlamys and not to the 

subsequently proposed genus Vertipecten, which is characterized by 

a relatively flat right valve and a convex left valve * * *. Other 

differences are the similar sculpture of both valves of C. branneri, 

the lack of an accentuated medial rib on the left valve, and the 

greater number of radial ribs on the auricles of this species-6 to 10 

rather than 5. It is possible that specimen, or specimens, identified 

by Arnold (1906, p. 56) as C. branneri from the lower part of what is 

now mapped as Vaqueros Sandstone*** on Twobar Creek in the 

Santa Cruz Mountains, may represent V. alexclarki n. sp. The material is from rocks of approximately the same age. C. branneri, on the 

other hand, is from unnamed rocks of middle Miocene age from 

Coyote Hills near the Stanford University campus***" (Addicott, 

1973, p. 26) 

Geographic range.-Southern California. 

Geologic range.-Oligocene. 

Occurrence in California.-Wygal Sandstone Member, Temblor 

Formation. 

Vertipe«;:ten bowersi (Arnold) 

Plate 24, figure 6; plate 25, figure 1 

Pecten (Lyropecten) bowersi Arnold, 1906, p. 70-71, pl. 12, figs. 1, 2; 

p.l. 13, figs. 1, 1a. Loel and Corey, 1932, p. 198, pl. 22, fig. 1. 

Pecten ( Vertipecten) bowersi Arnold. Hanna and Hertlein, 1943, p. 

176, fig. 64-20. 

Original description.-"Shell averaging about 150 millimeters in 

altitude and length, inequivalve, equilateral, rather thick, ventricose, and with smooth margins; base regularly rounded; sides sloping, the anterior ones slightly concave upward. Right valve considerably less ventricose than left, the surface of the disk being almost 

flat until an altitude of 50 or 60 millimeters is reached, when it 

begins to be more or less convex; surface ornamented with about 18 

subequal, prominent, rounded ribs, which, with the interspaces, are 

obsoletely radiately striate and crossed by fine wavy incremental 

lines; the ribs tend to become smaller toward the sides of the disk, 

there being a varying number of riblets near the sides in different 

specimens; inters paces subequal, round bottomed, about as wide as 

the ribs, and sometimes containing an auxiliary riblet; hinge line 

about three-fifths length of shell; ears about equal in length, anterior 

ear divided into two nearly equal parts by a line radiating from the 

apex, the part above the dividing line being ornamented by 3 or 4 

radiating ribs and concentric lines while the lower part (byssal area) 

is ornamented by imbricating incremental lines which are convex 

toward the apex; byssal notch wide and of medium depth; posterior 

ear rectangularly truncated, radiately ribbed, and crossed by concentric incremental lines. Left valve prominently and evenly ventricose; sculptured the same as the right valve except that most of the 

interspaces contain an auxiliary riblet; anterior ear arcuate ended, 

radiately ribbed, and with concentric incremental sculpture; posterior ear as in right valve." 

Holotype.-UCMP 12075. 

Type locality.-Santa Inez [Ynez] Canyon [Santa Ynez Quad.], 

Santa Barbara County, Calif. Topanga(?) Formation, Miocene. 

Supplementary description.-"This species is distinguishable by 

its large size, almost smooth rounded ribs, and the greater convexity 

of the left valve. The flat surface of the right valve near the apex is 

also a very noticeable characteristic." (Arnold, 1906, p. 71) 

Comparison.-Lyropecten bowersi "is distinguishable from P. 

perrini Arnold (1906) by its fewer and more rounded ribs, and the 

usual convexity and similarity of both valves-unlike P. pen·im:." 

(Loel and Corey, 1932, p. 198) 

Lyropecten bowersi has simple microsculpture and the inters paces 

bear one riblet, features that distinguish it from L. perrim:(Judith T. 

Smith, written commun., 1979). 

Geographic range.-Southern California. 

Geologic range.-Oligocene to Miocene. 

Occurrence in California.-Oligocene and Miocene: Vaqueros 

Formation (Arnold, 1907b); Miocene: upper part of Topanga Canyon 

Formation (Judith T. Smith, written commun., 1980), Painted Rock 

Sandstone Member, Vaqueros Formation (Judith T. Smith, written 

commun., 1980), and Saltos Shale Member, Monterey Formation 

(Judith T. Smith, written commun., 1980). 

Vertipecten perrini (Arnold) 

Plate 25, figu~es 4-6 

Pecten (Lyropecten) perr-ini Arnold, 1906, p. 80-81, pl. 14, figs. 1, 1a; 

pl. 15, fig. 1. Loel and Corey, 1932, p. 202, pl. 23, fig. 1; pl. 24, fig. 

1. 

Pecten ( Vertipecten) nevadanus Conrad var. perrin'i Conrad. Grant 

and Gale, 1931, p. 190. 

Vertipecten perrini (Arnold). Addicott, 1974, pl. 1, figs. 3, 4; J. T. 

Smith, 1975, pl. 1, figs. 4, 5. 

Original description.-"Shell averaging about 150 millimeters in 

altitude, somewhat longer than high, inequivalve, equilateral, of 

medium thickness, ventricose, and with smooth margins; base regularly rounded; sides sloping and decidedly concave above. Right 

valve nearly flat, with about 23 unequal, narrow, more or less 

rounded, and often prominently imbricated, radiating ribs, which 

are sometimes dichotomous; inters paces unequal, narrow, and occasionally ornamented by a small auxiliary riblet; surface sculptured 

by fine incremental lamellae which are much more prominent in 

some specimens than in others; hinge line about one-half length of 
TERTIARY MARINE PELECYPODS: PROPEAMUSSIIDAE AND PECTINIDAE B63 

disk: ears about equal in length; anterior ear wide, ornamented by 

concentric incremental sculpture; byssal notch wide and deep; posterior ear ornamented by several prominent, more or less imbricated radiating ridges, and concentric sculpture. Left valve quite 

prominently ventricose, otherwise similar to the right, except that 

the ribs seem to vary even more in relative size and spacing; anterior 

ear lacking notch, otherwise ears similar to those of the right valve." 

Holotype.-CAS/SU 13. 

Type locaJ1:ty.-Between Morro and Toro Creeks [W~ sec. 4, T. 29 

S .. R. 11 E.], San Luis Obispo County, Calif. Vaqueros Formation, 

Oligocene and Miocene. 

Su.1>plem.enta:ry clesc·r·ipt·ion.-"This is a most variable species, 

ther·e being no two specimens sculptured in exactly the same manner 

in a series of over fifty specimens examined. The convexity of the 

valves is almost constant, the variable factors being the number and 

relative importance of the intercalary ribs, and the prominence of 

the incremental sculpture." (Arnold, 1906, p. 80) 

Con1.pa.n:son.- Ve1·t·1:pecten pen·£n:1: is like V. neva.cla.nus of authors 

[now called V. ke-rnenS'is] "but with the ribs smaller, more flattened, 

and more numerous, multiplying by irregular bifurcation on the 

right valve and by irregular accentuation of the intercalaries on the 

left: also with more minor radial riblets than is usual in the typical 

variety." (Grant and Gale, 1931, p. 190) 

"This large form, sometimes difficult to differentiate from Pecten· 

bo·we·rwi Arnold, is perhaps the most variable species of the Lyropectens. In some specimens the more convex valve is almost identical 

to that of P. b0'1.oe·rs·1:. The characteristically flatter P. pe?·rini has a 

possible"'"'"' ancestr;ll form"'"'"' which was described by Arnold as 

P. ·1:neza:na.. The two for·ms are almost. if not, identical. P. pe·rn:m: is 

distinct from other similar species in its usual flatness of the right 

valve and irregular scaly ribbing." (Loel and Corey, 1932, p. 201) 

Geortra.ph:l:c nw.ye.-Southern California. 

Geoloy·ic ?"a.nge.-Oligocene to Mi6cene. 

Occwrnm.ce ·in Ca.l·ljo?"'n:ia.-Oligocene: Agua Sandstone Member, 

Temblor Formation (Addicott, 1972); Oligocene and Miocene: Temblor (Loel and Corey, 1932: Dickinson. 1963) and Vaqueros (Arnold, 

1906: Hoots. 1930; Loel and Corey, 1932) Formations; Miocene: 

Pyramid Hill Sand Member, Jewett Sand (Addicott, 1974). 

Vertipecten fucanus (Dall) 

Plate 26, figures 3, 4; plate 27, figure I 

Pecten (Chla:m.ys) fuca:nus Dall, 1898, p. 704, pl. 26, fig. 7. Arnold, 

1906, p. 66-67. pl. 10, figs. 1. 2, 2a. 

Pecten ( Ve·rt·1:pecten) neva.clanus Conrad var.fucanus Dall. Grant and 

Gale, 1931. p. 190, [not? pl. 7, figs. 1a, 1b]. 

Ve·rt·1:1>ecten,fuca:nus (Dall). Moore, 1963, p. 66-67, pl. 19, figs. 1, 2; pl. 

20, fig. 8: pl. 21, figs. 1, 3; pl. 22. figs. 1, 4. Addicott, 1976a, p. 29, 

pl. 4, figs. 1, 2, 5, 7, 10, 12. Addicott, 1976b, pl. 1. fig. 1. 

Ve·rt·1:pecten cf. p1·opatulus (Conrad). Stewart, 1946, pl. 17, fig. 4. 

Pecten(Pa.t·ino1>ecten) propatulus Conrad. Arnold, 1906, pl. 9, figs. I, 

1a. 2. 2a [not pl. 7, fig. 1]. Not Pecten p·ropatulus Conrad, 1849. 

Orirrinal desc·ript·1:on. -"This is a rather large species of the type of 

P. N1:nds·1>i var. stnttegus, both valves moderately convex and with a 

fine subsidiary surface tessellation: sixteen squarish ribs, of which 

the median one in the left valve is stronger than the rest and surmounted by prominent imbricated scales; the others .are simply 

radially striated, as are the interspaces, which carry a mesial elevated thread; the submargins are radially threaded, as are the subequal ears, which also bear marked concentric lamellae; the resilial 

pit is of moderate size and the cardinal edge is deeply grooved 

parallel to and just below the margin; the interior reflects the external ribbing. Alt. 85, lat. 80, convexity of left valve 16 mm." 

Holotype.-USNM 107790. 

Type locaWy.-USGS 2464. Clallam County, Wash. Clallam Formation, Miocene. 

Supplementary description.-"Adult shell averaging nearly 100 

millimeters in altitude, about as long as high, inequivalve (the left 

being the more convex), equilateral, moderately thin, and with 

nearly smooth margins. Right valve with from 14 to 17 more or Jess 

unequal, prominent, rather squarish, radiately striate ribs, between 

which (especially the anterior and posterior ones) are occasionally 

intercalated small riblets; inters paces unequal and averaging somewhat narrower than the ribs; whole surface of disk sculptured by 

rather prominent lines of growth and a fine subsidiary tessellation; 

hinge line longer than one-half length of disk; ears equal in length; 

the anterior rather narrow and sculptured by 4 prominent radials 

and fine, imbricating, incremental lamellae; the posterior rectangularly truncated and sculptured by more, but less prominent radials 

and fine concentric lamellae; byssal notch profound. Left valve usually having 15 or 16 unequal, prominent, convex-topped ribs, the 

median one generally being stronger than the rest, with the second 

or third one from it on each side only a little Jess prominent; the 

prominent ribs, especially the median one, is generally surmounted 

by elevated imbricating scales; the other ribs are simply radially 

striated, as are the interspaces, which often carry one or more elevated riblets; the submargins are radially threaded, as are the subequal ears, which are rectangularly truncated, and also bear 

marked concentric lamellae "' "' *."(Arnold, 1906, p. 66) 

"The median rib on the left valve of Vertipectenfucanus is always 

elevated above the others; the fourth rib on either side may also be 

elevated, but to a lesser degree, and in some places the second rib on 

the anterior and posterior side of the median rib is elevated. The ribs 

on the left valve are usually strong, narrow, and rounded, and the 

median rib is Jess rounded than the others. An imbricated, lamellar 

microsculpture is often pr,eserved on the left valve and is usually 

·particularly apparent on the elevated median rib."'"'"' This microsculpture may be seen also on some places on the left valve ears of V. 

fucanus. There is usually one interrib in each interspace on the left 

valve, but there may be as many as 2 or 3. On the right valve of V. 

fucanus there are about 15 or 16 slightly rounded flat-topped finely 

striated ribs in some places with a median groove. The interspaces 

seem to be smooth, without any interribs." (Moore, 1963, p. 6&) 

"Specimens in the collections average about 80-90 mm in greatest 

diameter. These averages are misleading because the relatively 

small specimens are easiest to collect: In the field, most specimens 

exceed 100 in maximum diameter, and there are several specimens 

in the stratigraphic collections that are as large as 110.:.]20 mm. The 

right valves have 17 or 18somewhat irregular flat-topped ribs. This 

valve also has a reticulate, or honeycombed, microsculpture that 

covers both the ribs and interspaces. There are usually 15 or 16 

crested ribs on the left valves; the medial rib is much stronger than 

any of the others and most are scaly or imbricated. Both valves have 

fine, irregular lateral ribs." (Addicott, 1976a, p. 29-30) 

Comparison.-"V. fuca nus may be closely related to V. nevadan us 

(Conrad). On the basis of a comparison of the type and topotype 

specimens of V. fucanus with specimens of V. nevadanus possibly 

, from near the type locality, they are considered separate species. 

The right valve <;>f V. nevadanus is usually much more highly sculptured and has numerous interribs. The left valve of V. nevaclanus 

seems to have more ribs and more interribs than .V. fucanus." 

(Moore, 1963, p. 66) 

"The ears of V.fucanus"' "'"'are relatively much larger than those 

of P. propatulus. Specifically, the length of the ears on specimens of 

V. fucanus is considerably more than half the width of the valves 

whereas on P. propatulus the ears are less than half the width of the 

valves. A second difference is the initially flat or slightly concave 
B64 PALEONTOLOGY OF CALIFORNIA AND BAJA CALIFORNIA 

profile of right valves of V.fucanus during early growth stages. This 

profile contrasts with the regularly convex profile of P. propatulus. 

In adult specimens of V. jucanus, the initially flat profile of V. 

fucanus usually develops into a gently convex profile similar to that 

of P. propatulus. Finally, the ribbing in right valves of V.jucanus is 

much more irreg.ul~r than on P. propatulus, especially in the lateral 

areas. Many specimens of V.jucanus have one or more irregular ribs 

in the medial part of the disk and most specimens have a widening 

and deepening of the medial interrib corresponding to the strongly 

raised opposing rib of the left valve." (Addicott, 1976a, p. 29) 

Geographic range.-Washington to southern California. 

Geologic range.-Miocene. 

"Vertipectenfucanus seems to be a very useful species in biostratigraphic correlation of Miocene formations in the Pacific Northwest 

States. Its restricted stratigraphic occurrence in the Nye Mudstone 

of western Oregon and the Jewett Sand of central California is 

indicative of provincial early Miocene age." (Addicott, 1976a, p. 30) 

Occurrence in Calijornia.-Jewett Sand (Addicott, 1976a). 

Vertipecten diabloensis (Clark) 

Plate 21, figure 2; plate 39, figure 4 

Pecten gabbi Clark, 1918, p. 131, pl. 15, figs. 1, 2. Not Pecten gabbi 

Dall, 1898. 

Pecten diabloensis Clark in G D. Hanna, 1924, p. 176, new name. 

Original description.-"Shell fairly large, heavy, equivalved; 

right valve flat; left valve convex. Apical angle about 100°; dorsal 

edges very nearly straight; ventral edge rather strongly convex. Left 

valve sculptured by about nineteen prominent and variable, rounded 

radiating ribs; on the type specimen, a left valve, seven of these ribs 

are he a vier than the others; one radiating from the beak down to the 

middle of the ventral edge, three of the other ribs being anterior and 

three posterior to this; in each interspace between these major ribs is 

a less prominent and narrower rib, and in the interspaces between 

this narrower rib and the major ribs on each side of it is a still less 

prominent and more narrow rib; besides this, in some of the interspaces, there is a fourth set of ribs still less prominent than the 

others. The valve originally had strong and beautiful imbricated 

sculpturing, which does not show on the type specimen but is seen on 

some of the external casts. Ears large and heavy. One specimen of a 

cast of the anterior ear shows eight or nine radiating ribs; the ones 

next the dorsal margin being much finer than the others; surface of 

ear strongly imbricated. Right valve flat, sculptured by nineteen or 

twenty fairly heavy, rather broadly rounded, radiating, somewhat 

variable ribs; as on the left valve there is a tendency for some of the 

ribs to be heavier than the others, but this difference is not so great 

nor is the distribution of the heavy ribs so regular; apparently there 

were no rib lets in the inters paces. Surface of right valve sculptured 

by imbricated incremental lines, which are coarser than on the left 

valve. Sculpturing of ears of right valve not preserved." 

Holotype.-VCMP 11138. 

Type locality.-VC 1311. Contra Costa County, Calif. San Ramon 

Sandstone, Miocene. 

Comparison.-"P. perrini is a very variable species, the sculpturing being more irregular than on P. gabbi [= P. diabloensis]; it has 

about the same number of ribs, and on some specimens certain of the 

ribs stand out more prominently than others, as is the case with P. 

gabbi. The imbricated concentric sculpturing appears to be much 

stronger on the former, is more irregular, and the inter-ribbing and 

striations are heavier." (Clark, 1918, p. 131) 

Geographic range.-Middle California. 

Geologic range.-Miocene(?). 

Occurrence in Calijornia.-San Ramon Sandstone. 

Vertipecten nevadanus (Conrad), nomen dubium 

Pecten nevadanus Conrad, 1855a, p. 19, pl. 8, fig. 77. 

Original description.-"Ovate, flat or slightly concave; ribs 17?, 

large, flattened on the back; interstices strongly wrinkled transversely." 

Holotype.-Missing and presumed lost. 

Type locality.-Ocoyo Creek [Pozo Creek, NEY.; sec. 12, T. 28 S., 

R. 28 E., Kern County], Calif. 

Neotype.-CAS/SV 431 (Grant and Gale, 1931). 

Neotype locality.-Uncertain; McKittrick district or Santa Monica Mountains, Calif. Miocene(?). 

Comments.-According to the International Code of Zoological 

Nomenclature (Article 75), for a neotype to·be validly designated it 

must come "as nearly as practicable from the original type-locality, 

and where relevant, from the same geological horizon * * *." Grant 

and Gale (1931, p. 190) in describing the locality for their neotype say 

that it is "reported to have come from the lower Miocene of the 

McKittrick district, but*** may have come from the Santa Monica 

Mountains." The imprecision of the locality data for the neotype 

invalidates the designation and Pecten nevadanus Conrad may be 

considered a nomen dubium. 

According to Judith T. Smith (oral commun., 1979) Vert1:pecten 

nevadanus has been confused with Vertipecten bowe'rsi for many 

years. In addition, the holotype is missing, the original illustration 

poor, and no good material is available for either a lectotype or a 

neotype. She therefore feels that the specific name should no longer 

be used. 

Vertipecten nevadanus of authors is now called Vertipecten 

kernensis (Hertlein). 

Vertipecten kernensis (Hertlein) 

Plate 28, figure 6 

Pecten (Patinopecten) kernensis Hertlein, 1925b, p. 40, pl. 4, fig. 3. 

Schenck and Keen, 1940, pl. 28, figs. 1-3. · 

Vertipecten nevadanus (Conrad) of authors; not Pecten nevadanus 

Conrad, 1855. 

Pecten catill1jormis Conrad, 1855a, p. 20. Conrad, 1857b, pl. 9, fig. 

83 .. 

On:ginal description.-"Shell large, slightly arched, moderately 

thick. Right valve ornamented by about 22 to 24 fairly high, flattish 

topped, round edged, radiating ribs of unequal size, separated by 

slightly rounded interspaces which are narrower than the ribs, 

many of the interspaces sculptured by a tiny midrib, whole surface 

ornamented by fine concentric lines of growth; anterior ear large, 

bearing a large byssal notch, ear ornamented by about 4 or 5 radiating riblets crossed by concentric lines of growth; posterior ear 

ornamented by about 6 radiating riblets crossed by concentric lines 

of growth. Height approximately 93 mm.; length approximately 

93 mm.; length of hinge line 57 mm.; apical angle approximately 

100°." 

Holotype.-CAS/SV 128; of catillijormis, described from drawings, no type extant (Arnold, 1906, p. 141). 

Type locality.-SV 150. Kern County, Calif. Jewett Sand, Miocene. 

Comparison.-"Pecten kernensis differs from P. propatulus Conrad, and P. oregonensis Howe, in the more numerous, unequal ribs, 

and less numerous, coarser ribs on the posterior ear of the present 

species. From P. caurinus Gould, P. kernensis is distinguished by the 

narrower ribs and strongly sculptured ears." (Hertlein, 1925b, p. 40) 

Vertipecten kernensis has a wider byssal notch, smaller right posterior auricle with larger rib lets, and more closely spaced ribs on the 

right valve than V. jucanus. 
TERTIARY MARINE PELECYPODS: PROPEAMUSSIIDAE AND PECTINIDAE B65 

Geogm.phic range.-Southern California. 

Geolog·ic ra:nge.-Oiigocene to Miocene. [This species is an index 

fossil of the middle "Vaqueros" megafauna) stage (Judith T. Smith, 

written commun., 1980).] 

Occu?Tence 1:n Cal?Jo?·m:a.-Oiigocene: upper part of the Pleito 

Formation (Judith T. Smith, written commun., 1980); Oligocene and 

Miocene: Vaqueros Formation (Loel and Corey, 1932; Judith T. 

Smith, written commun., 1980); Miocene: Carneros Sandstone 

Member, Temblor Formation (Judith T. Smith, written commun., 

1980), Freeman Silt(Schenck and Keen,l950; Addicott,1956),1ower 

part of Jewett Sand (Addicott, 1956), Olcese Sand (Addicott, 1956), 

and Topanga Formation (Takeo Susuki, written commun., 1978). 

Genus HINNITES De France, 1821 

Free in early stages similar to Chlamys, but later cemented by 

right valve which becomes irregular. 

Geolom:c 1·a.nge.-Eocene to Holocene. 

Ha.b·1:to.t.-Warm-temperate to tropic. 

Hertlein (1969) placed H1:nm:tes in the H1:nm:tes group. Hinnites is 

here placed in the Chla?nys group because of recent studies by 

Waller (Thomas R. Waller, written commun., 1979) that show that 

the cementing habit is polyphyletic and that living "H1:nnites" pusio 

shows a geographic cline ranging from uncemented typical Chlamys 

to cemented typical H1:nnites. 

Hinnites benedicti Adegoke 

Plate 26, figure 2 

fl-inn·1:tes benecl?:ct·i Adegoke, 1969, p. 103-104, pl. 3, figs. 3, 5. 

On:m:nal clescn:ption.-"Shell medium sized, thin, similar to H1:nn:itl~s m:u.lt·,:-rugosu.s c?·aswl:pt·icatu.s (Gale); outline oblong-oval, much 

higher than long; ornamented by over 40 low, rounded, subequally 

prominent ribs: frequently 1 riblet in each interspace: ribs only. 

slightly spinose, become more prominent, more irregular and more 

spinose toward ventral margin; anterior ear longer than posterior 

ear: byssal notch deep." 

Holotype.-VCMP 36638. 

Type loca.b:ty.-VC D702. Fresno County, Calif. Santa Margarita 

Formation, Miocene. 

Com.po.n:.'!on.-"This species may be readily distinguished from 

N1:nn:ites ·mu.lt·int.gosus c?·aswipt?:co.tu.s (Gale)[= H1:nm:tes g1:ganteus], 

which occurs in the same beds, by the more elongate and oval outline 

and the more numerous but less prominent radial ribs. The 'Chla.mys 

stage' lasts longer (28-34 mm) in the new species than it does in 

c·rass·i1Jhcntu.s. Additionally, the ribs are remarkably uniform and 

are only slightly spinose." (Adegoke, 1969, p. 104) 

Com.nwnts.-A slight shell irregularity can be seen on the holotype 

at about 35 mm, the maximum size given by Adegoke (1969, p. 104) 

for the Chlmnys stage. 

Geognt.1Jh:ic 1·ange.-Middle California. 

Geolom:c ?'o.nge.-Miocene. 

OccmTence ·in Cobjo·rm:o .. -Santa Margarita Formation. 

Hinnites giganteus (Gray) 

Plate 26, figures I, 5; plate 27, figures 2-4 

I./1:nw. g·igo.ntea Gr·ay, 1825, p. 139. 

Pecten (H1:nn:1:tes) g·iga.nteu.s (Gray). Arnold, 1903, p. 115. Arnold, 

1906, p. 93, pl. 29, figs. 1, 2, 2a. 

N1:nn:ites m:ga.nteu .. ~ (Gray). Oldroyd, 1924, p. 63, pl. 25, figs. la, lb. 

Hertlein and Grant, 1972, p. 211-212, pl. 41, fig. 16. Roth and 

Coan, 1978, p. 297. Addicott and Galehouse, 1973, fig. 30. Addicott and others, 1978, pl. 4, fig. 19. 

Pecten (Chlamys) multirugosus Gale, 1928, p. 92-93. 

Pecten (Pecten) multirugosus (Gale). Grant and Gale, 1931, 

p. 159, pl. 11, figs. 5a, 5b. 

Hinnites multirugosus (Gale). Fitch, 1953, p. 41, fig. 7. Grau, 1959, 

p. 134-137. 

Hinnita poulsoni Conrad, 1834, p. 182, pl. 14. Not Pecte?t poulsoni 

Morton, 1834. 

H1:nnites crassa Conrad, 1857c, p. 190, pl. 2, figs. 1, 2. Hertlein and 

Grant, 1972, p. 212. 

Pecten (Chlamys) mult1:rugosus variety crassiplicatus Gale, 1928, 

p. 93, new name for Hinnites crassa Conrad, 1857c. 

Pecten (Pecten) multirugosus variety crassiplicatus Gale. Grant and 

Gale, 1931, p. 160-161. 

H1:nnites multirugosus var. crassiplicatus (Gale). Stanton, 1966, 

pl. 5, fig. 6. 

Hinnites mult1:rugosus subsp. crassiplicatus (Gale). Adegoke, 1969, 

p. 103, pl. 3, figs. 1, 2. 

Original description.-"Testa crassa, ponderosa, subauriculata. 

Albido-rosea, irregulariter radiata costata striata; intus alba, rufo 

maculata. Lat. 15-4, long. 18-4 unc." (giga.nteus) 

"Pecten multirugosus is virtually a new name for the common 

Pliocene to Recent West Coast species formerly known as Pecten 

(H1:nnites) giganteus (Gray); but in order to avoid any questions about 

the location or identity of the original types, the species is described 

as new and a new type is cited. The type is a Recent specimen from 

San Diego and is now No. 5 in the type collection of the San Diego 

Society of Natural History. There are also two paratypes (Nos. 2978 

and 2979) at the California Academy of Sciences, and another in the 

Oldroyd Collection at Stanford University." (multirugosus) 

"Ovate or subovate, thick, irregular, with large, rounded, unequal, 

radiating, irregular ribs, squamose, and with foliated spines on the 

lower part of the valves or near the base; intervals of the ribs with 

three or four squamose, prominent lines; hinge profoundly thickened; fosset profoundly excavated, angular; muscular impression 

very large." (crassa) 

Holotype.-In BM (NH); of H. mult1:rugosus, SDNM 5; of 

H. crassa., USNM 13336 (also lectotype of Keen and Bentson, 1944). 

Type locality.-None originally cited; of H. mult1:rugosus, San 

Diego, Calif., Holocene; of H. crassa, Salinas Valley [T. 29 S., R. 13 

E., San Luis Obispo County], Calif. Santa Margarita Formation, 

Miocene. 

"***Gray's (1825) name gigantea. was available when proposed 

and has remained available throughout its nomenclatural history. 

Gale's (1928) rejection of it was invalid because he did not contend 

that the two species-group taxa, 'Lima' g1:gantea Gray and Plagiostoma g1:ganteum Sower by, were congeneric. Pecten ( Chlamys) mult?:rugosus Gale, 1928, is therefore a junior synonym of H1:nm:tes 

g1:ganteus (Gray, 1825), and the latter is the valid name for the 

Pacific Coast rock scallop." (Roth and Coan, 1978, p. 297) 

Supplementary description.-"Shelliarge, heavy, and irregular in 

outline when adult; averaging 105 to 150 mm in height, occasionally 

much larger; ratio of height to length variable, but almost always 

higher than long. 

"Juvenile form (up to from 20 to 30 mm in height): identical with 

Chlamys; slightly higher than long; valves of nearly equal convexity; 

hinge line from 2/3 to 3/41ength of disk. Right valve with numerous 

low and finely imbricated ribs, which become dichotomous early 

and appear to be paired, particularly near ventral margin; specimens up to about 15 mm in height have distinct intercostal concentric lamellae, which disappear soon thereafter. Anterior auricle 

long, often produced as far as anterior margin of disk; 6 to 11 concentrically 

lamellated radial riblets; deep byssal notch and ctenolium of 5 teeth. 
B66 PALEONTOLOGY OF CALIFORNIA AND BAJA CALIFORNIA 

Posterior auricle 1/3 to 1/2length of anterior and with faint, oblique, 

imbricated radial riblets. Left valve with 10 or 11 ribs, moderately 

to prominently spinose; between them 3 to 5 imbricated riblets, with 

either center one of three or second and fourth of five slightly larger. 

Anterior auricle large, with 12 to 20 imbricated radial riblets of 

irregular size; byssal sinus usually shallow; posterior auricle same 

as that of right valve. * * * 

"Adult form: large, heavy and irregular; juvenile Chlarnys stage 

preserved intact on each valve, succeeding growth being much heav-. 

ier and coarser. Shell attached by right valve to rock (or other 

foreign object), by means of shell substance secreted by outer lobe of 

mantle of that valve; moderately to greatly distorted (both laterally 

and horizontally) as result of conformation to surface of fixed object 

and, in many cases, restriction of space in which to grow. Right valve 

quite convex, with adult ribs (below Chlarnys stage) straight or 

irregularly waved and moderately to heavily imbricated; ribs actually low ridges on outer surface of valve, no trace of them being 

visible from interior. Auricles usually have margins obliterated by 

surrounding shell deposit; no ctenolium. Left valve flattish and usually slightly smaller than right; structure of ribs and auricles same 

as on right valve. Hinge line straight when growth of shell not 

hampered; when growth is restricted (as in narrow rock crevices), 

new hinge lines are formed successively lowerso valves can continue 

to open; in such cases hinge line tapers downward on each side of 

ligament, more so posteriorly.*** 

"In the juvenile stage this species is quite constant. Adolescent and 

adult specimens vary greatly in convexity and outline, but are easily 

recognizable. * * *" (Grau, 1959, p. 136-137) 

"This species attains a large size in northern waters. * * * a 

specimen from the San Juan Islands in Puget Sound*** was 222 

mm ***long, 168 mm ***wide, and near the byssal plug the valve 

was 64 mm * * *thick. The lower valve weighed 3 pounds and 1 

ounce.*** A huge specimen 230 mm long, was reported*** from 

Santa Cruz Island, California. * * *" 

"Attachment to the substratum takes place when the shell is 

between 2.2 and 4.2 em high." (Hertlein and Grant, 1972, p. 212) 

Cornpa'rison.-"Young specimens of [Chlarnys hastata] 15 mm or 

less in height resemble the young of Hinnites rnultirugosus (Gale) [ = H. giganteus], but those of the latter can be distinguished by the 

following differences in structure: the disk equilateral (or nearly so), 

the ribs of the right valve divaricating, the posterior auricles larger 

and squared, the interspaces of both valves concentrically lamellose." (Grau, 1959, p. 86) 

Geographic range.-Living: Aleutian Islands, Alaska to Baja California Sur; fossil: northern California to Baja California Sur. 

Geologic range.-Miocene through Holocene. 

Occurrence 1:n the Californias.-Miocene: Branch Canyon Sandstone (Vedder, 1973), Castaic (Stanton, 1966), Monterey (Arnold, 

1906), Painted Rock Member, Vaqueros (Vedder, 1973), Pancho 

Rico (Durham and Addicott, 1965), San Pablo (Arnold, 1906), and 

Santa Margarita (Nomland, 1917b; Adegoke, 1969; Addicott and 

others, 1978) Formations, and unnamed strata on San Clemente 

Island (Vedder and Moore, 1976); Miocene and Pliocene: Capistrano 

(Kern and Wicander, 1974), Etchegoin (Nomland, 1917a), and Purisima (Arnold, 1906) Formations; Pliocene: Niguel (J. G. Vedder, 

written commun., 1978), San Diego (Hertlein and Grant, 1972), and 

Salada (Beal, 1948) Formations, and unnamed strata on San Clemente Island (Vedder and Moore, 1976); Pliocene and Pleistocene: 

Fernando (Moody, 1916; Zinsmeister, 1970), Merced (Arnold, 1906), 

Paso Robles (Addicott and Galehouse, 1973), Pico (Addicott and 

Vedder, 1963), San Pedro (Arnold, 1906), and Saugus (Kew, 1924) 

Formations; Pleistocene: Timms Point Silt (A. Clark, 1931), and 

unnamed Pleistocene strata on San Nicolas Island, Calif., and in 

Baja California Norte (Valentine, 1957). 

Habitat.-"Free-swimming juveniles often found on gravel bottoms; byssal attachment to a fixed object occurs when shell is 

anywhere from 15 to 25 mm. high, cementation beginning soon 

thereafter; one or more of the following are often commensal on the 

left valve of adult specimens: hydroids, barnacles, bryozoa, boring 

sponges." (Grau, 1959, p. 137) 

"***In sheltered waters from high tide to a depth of 55 meters. In 

northern waters it lives close to shore and in shallower water." 

(Hertlein and Grant, 1972, p. 222) 

PECTEN group 

Right valve decidedly convex, left valve gently convex, flat, or 

concave; auricles nearly equal; radial ribs usually fairly broad; 

hinge with cardinal crura or almost lacking armature. 

Geologic range.-Eocene through Holocene. 

PECTEN subgroup 

Byssal notch very shallow. 

Geolog1:c range.-Eocene through Holocene. 

Genus AMUSIUM Roding, 1798 

Fairly large, thin, valves slightly convex and gaping along margins below auricles; trace of byssal notch present; internal lirae 

commonly in pairs; hinge with pair of short ridges diverging from 

shallow ligamenta! pit and extending toward margins; auricular 

crura present. 

Geologic range.-Miocene to Holocene. 

Habitat.-In temperate seas but most abundant in tropic and 

subtropic water. 

"The type species of A 1nusiurn, A. pleuronectes, strongly resembles 

true Pecten in shell microsculpture. The internal ribs of Amus1>um 

are the result of crenulations of the foliated calcite layer, as are the 

external costae and deep radial plicae of Pecten, Chlamys, and other 

Pectinidae." (Waller, 1971, p. 6) 

Based on study of shell microsculpture by Waller (1971, 1972), 

Arnusiurn is here placed in the Pecten subgroup. 

Amusium lompocensis (Arnold) 

Plate 2, figures 10, 11 

Pecten (Amusium) lompocensis Arnold, 1906, p. 92-93, pl. 28, figs. 

1-3. 

Arnusium lornpocensis (Arnold). Addicott, 1974, pl. 1, fig. 2. 

Pecten (Amussiopecten) lompocensis Arnold. Susuki and Stadum, 

1978, p. 11-12, figs. 12-17. 

Original descr1:ption.-"Adult shell averaging about 100 millimeters in altitude, somewhat longer than high, compressed, subequivalve, equilateral, and thin; base regularly rounded; sides 

straight, or nearly so; margins smooth. Right valve with external 

surface smooth except for very fine and numerous concentric and 

nearly obsolete radiating striae; internal surface sculptured by 

about fourteen pairs of rather prominent rounded radiating lirae, 

the members of each pair being separated by flat spaces usually of 

about two-thirds the width of the major interspaces (in one case the 

spaces between the members of each pair were as wide as the interspaces); hinge line about two-fifths the length of the disk; ears subequal, obliquely truncated, and finely concentrically sculptured; 

anterior with a faint suggestion of abyssal notch; ctenolium absent. 

Left valve similar in all respects to the right except that the anterior 
TERTIARY MARINE PELECYPODS: PROPEAMUSSIIDAE AND PECTINIDAE B67 

ear has a straight, rather than an arcuate end." 

HolotmJe.-CAS 81. 

'Type locnl'ity.-Six kilometers south of Lompoc, Santa Barbara 

County, Calif. Tranquillon(?) Formation, Miocene. 

Cmnpa:n:son.-"This very unique species, of which there are no 

closely allied forms in the Tertiary or living faunas of the west coast, 

so far as known, is somewhat analogous toP. (A·m.us1:~nn) uw1·tom:. 

Ravenel of the Miocene and Pliocene of eastern America. It is distinguishable from the latter species, however, by the smaller number, 

greater prominence, and more regular arrangement of the internal 

t·ibs. P. lon1.pocenS'is is included in Amw:r1>um because it appears to 

show stronger affinities for this than for any other group." (Arnold, 

1906, p. 92) 

A m:1t.swio1Jecten 'IJa.nvleck·i has been confused with A m.wn:~nn lmnpocen:·n:s. An1:u .. <;.'riopecten va.nvleck-1: may be distinguished from A. lompocen.S'is by its prominent, flat, wide ribs. A.lompocens1:s lacks radial 

surface ribs. Both species are usually found preserved as casts, but 

even so their ribbing is different in that A. va.nvleck1: has raised rib 

molds whereas in A. lom.pocens1:s only the interior riblets are represented by grooves in the cast. (Loel and Corey, 1932, p. 195) 

"On the right valve of P. (A.) loutpocen:ris, the external radial ribs 

are poorly defined and the ribs are paired internally. On the left 

valve, the external ribs are better developed and the internal ribs 

are not paired but equally spaced with the interspaces. 'In P. (A.) 

va:n:ulec/m:, the external ribs on both valves are better developed but 

internally, the paired ribs occur on the left valve and they are 

equally spaced in the right valve." (Susuki and Stadum, 1978, p. 12) 

Com:nwnts.-The holotype of A. lompocens·is was broken after it 

was originally illustrated, perhaps as a result of the San Francisco 

fire in 1906, and now consiPts of the posterior half of the left valve. No 

shell remains on the specimen but the paired internal lirae are 

clearly visible and are more closely spaced near the posterior 

margin. 

Georrra.ph:ic ·ra:nge.-Middle to southern California. 

Geolo{)'l:c ·ra:nge.-Miocene. 

Occu:rrence ·in Ca.l·1jm·m:a..-Miocene: Branch Canyon Sandstone 

(Hill and others, 1958; Vedder, 1973), Monterey Shale (Kieinpell and 

Weaver, 1963), Obispo Formation (Hall and others, 1966), San 

Onofre Bt·eccia (Addicott, 1974), Temblor "Horizon" (Loel and 

Corey, 1932), and Tierra Redonda (Durham, 1970) Formations, 

Tranquillon Volcanics (Dibblee, 1950); unnamed Miocene strata 

north of Bald Mountain in Santa Barbara County (Vedder and 

others, 1967), and unnamed Miocene strata, San Clemente Island 

(Susuki and Stadum, 1978). 

Genus PECTEN Muller, 1776 

Radial ribs well dev.eloped, usually flat topped, commonly radially 

striated or grooved; concavity present in many shells on left valve 

u m bona! area. 

Geolo{)'l:c 1·a,nge.-Eocene through Holocene (table 14). 

Ha.b1:ta.t.-In warm temperate and tropical seas from 10 to 1,845 m 

(Hertlein and Grant, 1972). 

Subgenus PECTEN 

Pecten (Pecten) aletes Hertlein 

Plate 28, figures 3, 4 

Pecten (Pecten) a.letes Hertlein, 1925a, p. 8, pl. 2, figs. 1, 4. Hertlein, 

1966, p. 268. 

Pecten (Ja.niTa.) hmnph1·eysii Conrad variety a.letes Hertlein. Grant 

and Gale, 1931, p. 222. 

Orig1:na.l descript1:on.-"Shell of medium size. Right valve moderately convex, ornamented by about 11 rather broad, flat-topped 

radiating ribs, which anteriorly and posteriorly decrease in size, 

each rib with one to four narrow, slight, radial sulcations; interspaces flat-bottomed, narrower than the ribs, occasionally bearing a 

tiny radiating riblet, the whole surface of valve sculptured by fine, 

close, concentric striae; ears subequal, marked by growth lines, but 

lacking all radial sculpture. Left valve slightly concave, with a 

pronounced depression toward the beak; about nine flat-topped 

radial ribs, separated by interspaces about as wide as the ribs, the 

ribs and interspaces both covered by fine, sharp, concentric sculpture; ears subequal, and somewhat concave, ornamented only by fine 

incremental lines. Altitude 62 mm,; longitude 65 mm.; diameter of 

right valve approximately 13 mm.; apical angle of right valve 

approximately 100°." 

Holotype.-CAS/SU 44. 

Type loca.lity.-SU 50. Baja California Sur, Salada Formation, 

Pliocene. 

Cmnpm·1:son.-"Pecten aletes differs from P. bellus Conrad in the 

smaller number of ribs, which are finely sulcate. It differs from P. 

la.queatus Sowerby, from Japan, to which it is most closely related, in 

the fewer ribs; also in that the ears on the right valve of the present 

species appear to be straighter and not quite as arcuate as those of P. 

laqueatus." (Hertlein, 1925a, p. 8) 

Comments.-Pectenaletes has fewer wider ribs than other eastern 

Pacific Tertiary species. The right valve holotype has seven primary 

ribs that are wide, flat, slightly undercut, and separated by interspaces slightly narrower than the ribs at the ventral margin. Three 

secondary ribs are present on the anterior end of the shell and two on 

the posterior end. Some of the ribs have radial riblets and grooves, 

and the entire shell surface has slightly imbricated, concentric 

sculpture. The portion of the anterior auricle exposed nas no rib lets; 

the posterior auricle is missing. The left valve paratype,. has seven 

wide, flat ribs separated by slightly wider interspaces. A secondary 

rib appears in some of the inters paces near the ventral margin. The 

entire shell has imbricated, concentric lamellae. The posterior auricle has one small riblet; the anterior auricle none. 

The ribs on P. aletes are fewer in number, broader, and flatter 

than on P. bellus. 

TABLE 14.-Geolog?:c and geog?·aphic distribution of the genus Pecten (Pecten) 

[Pie= Pleistocene; PI= Pliocene; M =Miocene] 

California Species Middle Southern 

Genus Pecten: 

Subgenus Pecten: 

aletes Hertlein ........................... . bellus (Conrad) ............................ M to Pie Pl,Pie 

leconte1: Arnold .......................... M,Pl 

Baja 

Caljforoja Norte Sur 

PI 

PI 

PI 

PI 
B68 PALEONTOLOGY OF CALIFORNIA AND BAJA CALIFORNIA 

Geograph1:c range.-Baja California Sur. 

Geologic range.-Pliocene. 

Occurrence in Baja Calijornia.-Salada Formation (Beal, 1948). 

Pecten (Pecten) lecontei Arnold 

Plate 28, figures 2, 5 

Pecten (Pecten) lecontei Arnold, 1906, p. 98, pl. 33, figs. 4, 4a, 4b. 

Original description.-"Shell averaging about 60 millimeters in 

altitude, longer than high, plano-convex, equilateral, and with 

smooth margins; base evenly rounded; sides concave above. Right 

valve convex, and ornamented by about 18 prominent round-topped, 

perpendicular-sided, smoothish ribs, separated by interspaces, 

which are narrower than the ribs and have nearly flat bottoms; 

surface sculptured by fine wavy incremental lines, which are generally worn off from the tops of the ribs; hinge less than one-half the 

length of the disk; ears somewhat convex; the anterior with 2 or 3 

broad, nearly obsolete, radiating ridges, imbricating incremental 

lines, and a rather small byssal notch; the posterior rectangularly 

truncated, and with fine incremental sculpture. Left valve flat or 

slightly concave, ornamented by about 17 prominent rounded ribs, 

which are separated by interspaces about equal in width to the ribs; 

surface sculptured by numerous fine, sharp, regular, raised, incremental lines; ears concave, rectangularly truncated, and covered by 

fine sharp incremental lines." 

Holotype.-CAS/SU 4. 

Type locality.-Isla Cedros, Baja California Norte. Almejas Formation, Pliocene. · 

Comparison.-"This species is distinguishable from P. diegensis, 

P. bellus, P. stearnsii and other members of this group by the 

number and convexity of the ribs on the right valve. The left valves of 

P. lecontei and P. diegensis are somewhat similar, although the 

former has fewer ribs and is generally slightly more concave." 

(Arnold, 1906, p. 98) 

"Pecten (Pecten) lecontei ***is quite distinct from P. bell us and its 

variants. The ribs, about 18 on the right valve and 17 on the left, are 

round-topped. Those on the right valve usually quite smooth, separated by flat-bottomed interspaces which are narrower than the 

ribs. The left valve is usually slightly concave and the rounded ribs 

are quite different from the high usually flat-topped ribs of P. bellus." (Hertlein and Grant, 1972, p. 177) 

Comments.-The holotype is a double-valved specimen and has 

imbricated concentric lamellae on the left valve. 

Geographic range.-Middle California to Baja California Norte. 

Geologic range.-Miocene to Pliocene. 

Occurrence in the Calijornias.-Miocene and Pliocene: Purisima 

Formation (Arnold, 1906); Pliocene: Almejas Formation (Minch and 

others, 1976). 

Pecten (Pecten) bellus (Conrad) 

Plate 29, figures 1-4 

Janira bella Conrad, 1857a, p. 312 [reprinted in Dall, 1909, p. 173]. 

Conrad, 1857b, p. 71, pl. 3, fig. 16. 

Pecten (Pecten) bell us (Conrad). Arnold, 1903, p. 103-104, pl. 21, figs. 

1, 2. Arnold, 1906, p. 95-96, pl. 31, figs. 1, la. Jordan and 

Hertlein, 1925b, p. 430-431, pl. 32, fig. 2; pl. 33, figs. 1, 2; pl. 34, 

figs. 2-4. Jordan and Hertlein, 1926b, p. 430-431. Hertlein and 

Grant, 1972, p.l74-177, pl. 30, figs. 1, 2, 3, 4, 9; pl. 32, fig.14; text 

fig. 7. 

Pecten hemphillii Dall, 1878, p. 15. Woodring, 1950, p. 82-83, pl. 16, 

figs. 15, 16; pl. 21, fig. 8. 

Pecten (Pecten) hemphillii Dall. Dall, 1898, p. 706. Arnold, 1903, p. 

105-106. Arnold, 1906, p. 97, pl. 33, figs. 3, 3a, 3b. 

Pecten (Janira) bellus (Conrad) variety hemphillii Dall. Grant and 

Gale, 1931, p. 226, pl. 3, figs. la, lb. Durham, 1950, p. 60, pl. 7, 

figs. 3, 5. 

Pecten (Pecten) auburyi Arnold, 1906, p. 94, pl. 33, figs. 2, 2a; pl. 34, 

figs. 2, 2a. 

Original description.-"Subtriangular; inferior valve convex, ribs 

14 or 15, square, about as wide as the intervening spaces, very 

prominent, some of them with one or two longitudinal obsolete lines; 

disk finely wrinkled cqncentrically; upper valve flattened, deeply 

depressed toward the apex; ribs rather narrower than those of the 

opposite valve, obscurely bicarinated above, disk ornamented with 

close, fine, squamose, concentric wrinkles. Length 4 inches, height 3 

3/4 inches." (bellus) 

"This species has a strong general resemblance to the last, and is 

best described by comparison with it. P. Hemphillii is smaller, with 

sixteen ribs, as against twenty-six in a P. Stearns1:i of the same size, 

with which throughout it will be compared; the lateral margins of 

the ears are perpendicular and straight, instead of outwardly 

rounded; the hinge-line is perfectly straight, not slightly concave; 

the ribs on the lower valve are flattened above, with symptoms of a 

groove on the top surface, instead of beautifully roundly vaulted; the 

interspaces are of course wider; the raised concentric lamellae 

toward the periphery become long, coarse, and very crowded; on the 

lower valve, the shell is more vaulted, with hardly any traces of the 

raised lamellae, and with larger, rude, hardly flattened, radiating 

ribs, which show no trace of grooving or riblets; the ears and byssal 

notch are smaller and more coarsely sculptured. Height, 56 mm; 

breadth, 63 mm; breadth of hinge-line, 28 mm; thickness, 15 mm." 

(hemphillii) 

"Adult shell averaging about 60 millimeters in altitude, somewhat 

longer than high, inequivalve, plano-convex, equilateral, and with 

smooth margins. Right valve convex and ornamented by about 16 or 

17 prominent, rather narrow, convex-topped ribs; interspaces 

slightly narrower than the ribs, and with concave bottoms; whole 

surface sculptured by prominent, fine, sharp, subequal incremental 

lines; hinge line less than one-half length of disk; ears subequal and 

convex; anterior ear with two or three obsolete radiating ridges, 

prominent concentric sculpture, and small byssal notch; posterior 

ear with concentric sculpture only. Left valve flat or slightly concave, ornamented by 16 or 17 prominent, narrow, convex-topped 

ribs, which are separated by deep, almost flat-bottomed interspaces 

slightly wider than the ribs; whole surface sculptured by prominent, 

fine, sharp, equal, concentric lines; ears slightly concave, rectangularly truncated, and sculptured by fine, sharp, concentric lines." 

(auburyi) 

Neotype.-ANSP 960 (Stewart, 1930); holotype of P. hemph1:lli1: 

USNM 7943; neotype of P. auburyi CAS 87 (Keen and Bentson, 

1944). 

Type locality.-Santa Barbara, Santa Barbara County, Calif. 

Santa Barbara Formation, Pliocene and Pleistocene; of P. hemph1:U1:i 

San Diego, San Diego County, Calif., San Diego Formation, Pliocene; of P. auburyi Puente Hills, Los Angeles County, Calif., Pico(?) 

Formation, Pliocene and Pleistocene. 

Supplementary description.-"Shelllarge, thin, inequivalve, elegantly, radiately ribbed. Left (upper) valve slightly convex, the 

point of greatest convexity being generally about one-fourth the 

distance from the apex toward the ventral margin; between this 

point of greatest convexity and the apex there is a deeply depressed 

area, the depression generally not affecting the two outer ribs on 

each side, which inclose the depression on the sides; surface of left 

valve ornamented by 13 or 14 prominent, flat-topped, sometimes 

faintly bicarinated, radiating ribs, which have flat, sloping sides; 
TERTIARY MARINE PELECYPODS: PROPEAMUSSIIDAE AND PECTINIDAE B69 

these ribs become broader, less elevated, and less sharply angulated 

near the periphery in the adult: interspaces slightly wider than the 

tops of the ribs, with slightly rounded bottoms; whole surface of left 

disk covered with fine, sharp, concentric, regular lamellae; ears 

rather small, subequal, slightly concave, finely concentrically lamellated, separated from the disk by an impressed line. Right (lower) 

valve prominently convex, the point of greatest convexity being 

about one-third the distance from the apex to the ventral margin of 

the disk; the umbo in this valve curves sharply and meets the plane of 

the ears at an angle of about 90 degrees; surface of right valve 

ornamented by 14 or 15 prominent, nearly flat-topped, square, 

radiating ribs. some of them with one or two longitudinal obsolete 

lines: the ribs become somewhat less elevated and the sides more 

sloping as the periphery is approached in the adult; surface of right 

disk ornamented with close, fine, squamose, concentric wrinkles; 

ears subequal, arched, covered with crowded, elevated lamellae; 

byssal notch small." (Arnold, 1906, p. 95-96) 

"We have examined over 600 specimens, the greater number single valves, varying in size from 8 mm to 78.8 mm high. The number 

of ribs vary from 12 to 18 but the average is about 15. The ribs on the 

ventral portion of large forms tend to become broad, flat-topped, the 

sides slope rather steeply to the interspaces. The ribs on smaller 

specimens are higher, narrower and more rounded. The tops of ribs 

on large specimens sometimes bear one or more faint longitudinal 

grooves. The ribbing on the interior of valves, which is well defined 

on the right valve, extends to the umbonal area, on the left valve to 

the muscle impression. Low flanges are present on the ribs near the 

ventral margin of large valves. There are usually two pairs of rather 

weakly developed cardinal crura but these are not prominent. 

Auricular crura are well developed on the left valve but Jess pronounced on the right valve." (Hertlein and Grant, 1972, p. 176) 

Cmnpa:n:son.-"Pecten (Pecten) leconte'i Arnold described from 

Cedros Island, Lower California, is quite distinct from P. bellus and 

its variants. The ribs, about 18 on the right valve and 17 on the left, 

are round-topped. Those on the right valve usually quite smooth, 

separated by flat-bottomed interspaces which are narrower than the 

ribs. The left valve is usually slightly concave and the rounded ribs 

are quite different from the high usually flat-topped ribs of P. bellus. 

"Pecten (Pecten) sleV?:m: Dall and Ochsner described from strata of 

Pliocene age on the Galapagos Islands differs from P. bellu.<; and its 

variants by the narrower, rounded ribs on the right valve which are 

separated by wider interspaces and by the wider apical angle. * * * 

"The shell of Pecten bell us bears a general resemblance to that of P. 

a.lln:r:a:ns Schroter and toP. exca.va.tus Anton, which have fewer ribs. 

but close relationship with these Japanese species has not been 

demonstrated." (Hertlein and Grant, 1972, p. 177) 

"Collections of P. (P.) hemph1:lli from the San Diego Formation, 

Pacific Beach, California, and of P. (P.) bellus from the Santa Barbara Formation, Santa Barbara, California, have been examined 

and no consistently useful characters have been found for separating 

specimens of these two forms that are of similar size. The only 

consistent difference is that P. (P.) bellus from Santa Barbara usually reaches a greater maximum size than the form that has been 

called P. (P.) hem.ph1:lli from Pacific Beach. This is in agreement 

with the findings of Hertlein and Grant (1972, p. 176-177), who 

examined more than 600 specimens of P. (P.) hemph:illi from the San 

Diego Formation and placed that species in synonymy with P. (P.) 

bdlus." (Vedder and Moore, 1976, p. 124) 

Com:nwnts.-The neotype is a double-valved specimen. The right 

valve has 16 ribs that are flat-topped, unequal in size, and separated 

by interspaces ranging in width from half as wide to wider than the 

ribs. Secondary ribs are in some of the subrounded interspaces. The 

right anterior auricle has a narrow, shallow byssal notch and one 

rib let; the right posterior auricle has no riblets. The left valve has 14 

ribs subrounded at the anterior and posterior ends of the shell but 

flat topped on the rest of the shell. One rib is split close to the umbo. 

The interspaces are wider than the ribs and do not have secondary 

rib lets. The entire shell has imbricated, concentric lamellae, and the 

auricles have no riblets. 

Geographic ra.nge.-Middle California to Baja.California Sur. 

Geologic ra.nge.-Miocene to Pleistocene. · 

Occurrence in the Ca.lijornias.-Miocene and Pliocene: Purisima 

Formation (Arnold, 1906); Pliocene: Almejas (Minch and others, 

1976), Carmen (Durham, 1950), Cebada and Graciosa Members, 

Careaga Sandstone(Woodring, 1950), Niguel (Vedder, 1960), Salada 

(Beal, 1948), and San Diego (Arnold, 1906: Hertlein and Grant, 1972) 

Formations, unnamed Pliocene on San Clemente Island (Vedder 

and Moore, 1976; Susuki and Stadum, 1978); Pliocene and Pleistocene: Fernando (Arnold, 1907a; Moody, 1916; Soper and Grant, 

1932; Zinsmeister, 1970), Merced (Arnold, 1906), Pico (Waterfall, 

1929; Winterer and Durham, 1962), Potato Harbor (Weaver and 

Meyer, 1969), and Saugus (Kew, 1924) Formations; Pleistocene: 

Lindavista Formation (Kennedy, 1973). 

Pecten (Pecten) slevini Dall and Ochsner 

Pecten (Pecten) slevini Dall and Ochsner, 1928, p. 118, pl. 3, fig. 9; pl. 

4, fig. 4. Hertlein and Grant, 1972, p. 177. 

Com.ments.-Pecten slevini was described from Pliocene strata on 

the Galapagos Islands. The specimen illustrated by Grant and Gale 

(1931, p. 227, pl. 2, fig. 3) as P. slevini, from the Pliocene of Los 

Angeles County, was incorrectly identified. It is probably a distorted 

· specimen of P. bellus (Hertlein and Grant, 1972, p. 177). Therefore, 

P. slevini does not occur in the Californias and is not illustrated in 

this report. 

Genus AMUSSIOPECTEN Sacco, 1897 

Differs from Flabellipecten in its nearly obsolescent radial ribs 

with correspondingly stronger internal radial riblets similar to 

A 1nusutm; cardinal margin of hinge commonly more angulated with 

high angulated auricles. 

Geolog1:c ra.nge.-Oligocene to Miocene. 

Amussiopecten vanvlecki (Arnold) 

Plate 29, figure 5; plate 30, figure 1 

Pecten (Pecten) vanvlecki Arnold, 1907b, p. 428, pl. 53, figs. 1, 2. Loel 

and Corey, 1932, p. 195, pl. 20, figs. 3, 5. 

Amuss1:opectenvanvleck1:(Arnold). Masuda, 1971b, p. 210-21'1, pl. 25, 

figs. 1a, 1b, 2-4. Addicott, 1974, pl. 2, fig. 2. 

On:g1:na.l description.-"Shell averaging about 70 mm. in altitude, 

length and height about equal, outline circular; both valves convex, 

the right slightly more so than the left, equilateral, thin; base regularly rounded; sides only very slightly concave above; margins 

smooth. Right valve somewhat convex, the region of greatest convexity being just below the beak; surface ornamented with 13 or 14 

rather prominent ribs, these being quite rounded in the younger 

stages of growth, but gradually becoming flatter and lower toward 

the periphery; interspaces rounded near umbos, but shallower and 

flatter below; equal, fine, sharp, raised incremental lines, separated 

by interspaces as wide as the lines, cover the surface of the disk and 

ears; hinge line longer than half length of disk; ears subequal, anterior with a shallow byssal notch; posterior rectangularly truncated. 

Left valve slightly less convex than right, flat to concave immediately below umbo; ribs regularly rounded throughout entire 
B70 PALEONTOLOGY OF CALIFORNIA AND BAJA CALIFORNIA 

length, becoming flatter and sometimes almost obsolute toward the 

periphery; minute sculpture as in right valve; ears flat, the anterior 

one showing two or three faint radial rib lets. Interior of both valves 

reflecting the external ribbing very prominently." 

Holotype.-USNM 165305. 

Type locality.-USGS 4478. Santa Barbara County, Calif. Vaqueros Formation, Oligocene and Miocene. 

Supplementary description.-"Shell slightly inflated, subequivalve, though right valve a little more convex than slightly inflated 

left valve which is sometimes nearly flat in younger stage but tends 

to become slightly inflated with growth; radial ribs of right valve 

flatly round-topped, more or less squarish in profile, rather distinctly separated from their interspaces and varying in number 

from about 13 to 18 * * *. Hinge with simple cardinal crura with a 

distinct provinculum and distinct cardinal crura terminating distally in an oblong denticle. Paired internal ribs well developed near 

ventral margin." (Masuda, 1971b, p. 210) 

Comparison.-"Pecten vanvlecki has frequently been confused 

with Pecten (Amusium) lompocensis Arnold (1906), described from 

the Temblor Miocene in Southern California, as already pointed out 

by Loel and Corey (1932), but the former is easily distinguishable 

from the latter by its rather thick shell, squarish, low, flatly roundtopped radial ribs tending to become obsolete towards the ventral 

and lateral margins, paired internal ribs developed at lower part 

and larger and a~gulated auricles. * * *However, because of the 

state of preservation sometimes the two can not be distinguished 

from one another." (Masuda, 1971b, p. 210-211) 

Comments.-Flabellipecten? hawleyi was placed in synonymy with 

A. vanvlecki as an immature form by Masuda (1971b, p. 210-211). 

The left valve holotype of F.? hawleyi is almost flat and has 18 

narrow, round ribs separated by slightly wider interspaces. Both 

auricles are smooth, but the rest of the shell bears imbricated, 

concentric lamellae. The left valve paratype of A. vanvlecki is somewhat convex and has 13 ribs; the anterior auricle has three faint 

riblets. I believe that F.? hawleyi is not an immature form of A. 

vanvlecki and concur with Hertlein and Grant (1972, p. 178) in 

tentatively assigning it to Flabellipecten. 

Geographic range.-Southern California to Baja California Sur. 

Geologic range.-Oiigocene and Miocene. 

Occurrence in the Calijornias.-Oiigocene and Miocene: Soda 

Lake Shale Member, Vaqueros (Vedder, 1973) and Vaqueros 

(Arnold, 1907b; Loel and Corey, 1932; Dibblee, 1950; Avila and 

Weaver, 1969) Formations; Miocene: Branch Canyon Sandstone 

(Vedder, 1968), Button bed Sandstone Member, Temblor Formation 

(Addicott, 1972), Isidro (Stump, 1979), Obispo Formation (Hall, 

1973), Painted Rock Sandstone Member, Vaqueros Formation. 

(Vedder, 1973), and Saltos Shale Member, Monterey Shale (Vedder, 

1973). 

Genus EUVOLA Dall, 1898 

Valves smooth except for radial grooves which are more prominent on umbonal portion; interior with narrow, rounded riblets 

corresponding to exterior radial sculpture. 

Geographic range.-West Atlantic, Caribbean, southern California, and Baja California Sur. 

Geologic range.-Miocene through Holocene (table 15). 

Euvola keepi (Arnold) 

Plate 30, figures 5, 6 

Pecten (Pecten) keepi Arnold, 1906, p. 60-61, pl. 5, fig. 1; pl. 6, figs. 1, 

1a. 

Pecten keepi Arnold. G D. Hanna, 1926a, p. 471. 

Pecten (Janira) keep1: Arnold. Grant and Gale, 1931, p. 229. 

Pecten (Euvola) keepi Arnold. Durham, 1950, p. 61, pl. 6, figs. 5, 6. 

Original description.-"Shell averaging about 75 millimeters in 

altitude, longer than high, plano-convex, equilateral, and with 

smooth margins; sides concave above; lateral area very broad. Right 

valve ventricose and ornamented by about 20 low, broad, rounded 

ribs, separated by shallow interspaces in which are low, broad intercalaries; the sulcation on the interior of the valve corresponding to 

the intercalary is often quite prominent; whole surface sculptured 

by inconspicuous incremental lines; hinge line more than one-half 

length of disk; ears equal, somewhat convex, rather obliquely truncated and turned up slightly at the corners; sculpture of ears consists 

of fine incremental lines; byssal notch rather small. Left valve flat, 

with a slight tendency toward concavity near the umbo, with broad 

lateral areas and with 18 or 19 low, rather flat-topped ribs; interspaces somewhat wider than the ribs; surface sculptured by fine 

incremental lines; ears concave, obliquely truncated and sculptured 

by more or less irregular concentric lines." 

Holotype.-CAS/SU 5. 

Type locality.-Carrizo Creek district [NYzsec. 14, T. 15 S., R. 8 E., 

S.B.], San Diego County, Calif. Imperial Formation, Miocene or 

Pliocene. 

Comparison.-"The ears of the left valve are more concave and 

more definitely set off than on P. refugioensis Hertlein; further, the 

apical angle is greater." (Durham, 1950, p. 61). 

Comments.-The holotype is a double-valved specimen. The right 

valve is strongly convex and seems to have been inequilateral, with 

the posterior end the largest. This valve has about 17 very low, flat, 

almost obsolete wide ribs with narrow, slightly rounded inters paces. 

The auricles are smooth and strongly convex. The left valve is flat 

except near the umbos and ventral margin where it is concave. It has 

15 narrow flat ribs separated by slightly wider inters paces, a few of 

which have one or two secondary riblets. The auricles are smooth 

and markedly concave. The right valve of E. refugioensis is smooth 

except on the umbo which has narrow, somewhat rounded, closely 

spaced ribs. The rest of the shell shows barely perceptible obsolete 

ribs a few of which can be seen and felt as slight protuberances on the 

shell. The auricles are only slightly convex. The left valve of E. 

rejugioensis has almost obsolete ribs which are wider and not as 

strongly demarcated as on E. keepi. The auricles are smooth and 

only slightly concave. All of these characters serve to distinguish E. 

keepi from E. rejug1:oensis, and I do not concur with Grant and Gale 

(1931, p. 229) that the species are the same. 

TABLE 15.-Geologic and geographic distribution of the genus Euvola 

[PI= Pliocene; M =Miocene] 

Species 

Genus Euvola: 

California 

Southern 

keepi (Arnold) ··---------------------------------- M or PI 

refugioensis (Hertlein) .................... .. 

Baja Ca!jfornja Norte Sur 

M,Pl 

PI 
TERTIARY MARINE PELECYPODS: PROPEAMUSSIIDAE AND PECTINIDAE B71 

Geog·ra.ph:ic ·mnge.-Southern California to Baja California Sur, 

and Santa Rosalia, Mexico. 

Geolo(J1:c 1·ange.-Miocene(?) to Pliocene. 

Occ·wtTence ·in the Ca.l·ijo·rn·,:as.-Miocene: Isidro Formation 

(Stump, 1979); Miocene or Pliocene: Imperial Formation (Arnold, 

1906; G D. Hanna, 1926a); Pliocene: Salada (Beal, 1948) and San 

Marcos (Durham, 1950) Formations. 

Euvola refugioensis (Hertlein) 

Plate 30, figures 2-4 

Pecte·n (Pecten) ·refug·ioens-i.':l Hertlein, 1925a, p. 7, pl. 1, fig. 2; pl. 5, 

fig. 9. 

Pecten (Euvola.) ·refu(J'I:oen.'n:s Hertlein. Durham, 1950, p. 61, pl. 6, fig. 

3. Het·tlein, 1966, p. 274, figs. 16, 17. 

Ori(}'l>na.l desc·n:pt·,:on.-"Shell of medium size. Right valve practically smooth, ornamented, however, by fine concentric lines of 

growth, and close to the beaks also by fine, faint, radiating ribs 

which, however, disappear at the umbo; ventral margin smooth; 

interior of the shell ornamented by about 19 dichotomous ribs; ears 

about equal and concentrically sculptured; a slight groove showing 

where the ears meet the margins of the shell; a slight byssal notch 

present on the anterior ear. Left valve fairly smooth, ornamented 

intet·iorly much as right, a depressed area which is lower than the 

mat·gins extends from the beaks to about one-half the height of the 

shell; ears slightly concave, ornamented by concentric lines of 

growth. Altitude 56 mm.; longitude 57 mm.; diameter of right valve 

approximately 14 mm.; apical angle of right valve approximately 

97°." 

Holotype.-CAS/SU 49. 

Type loco.l-ity.-SU 50. Baja California Sur. Salada Formation, 

Pliocene. · 

Su.pplem.enta:ry desc?"'ipt?:on. -"The largest*** left valve*** is 88 

mm. high and 95 mm. long (slightly imperfect on one end). The 

smallest is a left valve 29 mm. high and 27.6 mm. long. The largest 

right valve*** is a fragment 75 mm. high." (Hertlein, 1966, p. 274) 

Co·m1Ja:rison.-"The shell of this species differs from that of Pecten 

( Euvola.) keep·i Arnold usually in the lack of radial ribbing on the 

ventral half of the valves or if ribbing is present it is much more 

weakly developed." (Hertlein, 1966, p. 274) 

Cmmnents.-See E. keep·i for the description of the right-valve 

holotype of E. rejug1:oensis, the left-valve paratype, and comparison 

of the two species. 

Georrmph:ic ·mnge.-Baja California Sur. 

Geolo(J'I:c ·range.-PI iocene. 

Occu:tTence ·1:n BaJ·a Cahfontia.-Carmen (Durham, 1950) and 

Salada (Beal, 1948) Formations. 

Genus FLABELLIPECTEN Sacco, 1897 

Differs from Pecten (Pecten) in the less highly arched right valve, 

greater apical angle, and more numerous and usually lower radial 

ribs. The character of the umbonal area (Hertlein, 1969, p. N369) 

does not differentiate Flabell?:pecten from Pecten (Pecten), because 

some species of Flabellipecten also have a depression there. 

Geog·raphic range.-Eurasia, southeastern and western United 

States, and Panama. 

Geologic range.-Miocene through Holocene (table 16). 

Flabellipecten carrizoensis (Arnold) 

Plate 31, figures 4, 6 

Pecten (Pecten) carrizoensis Arnold, 1906, p. 59-60, pl. 4, figs. 1, 1a, 

1b, 2, 3, and 3a. Durham, 1950, p. 61, pl. 8, figs. 1, 3. 

Pecten carn:zoens1:s Arnold. G D. Hanna, 1926a, p. 470. 

Pecten (Janira) stearnsi1: variety carrizoensis Arnold. Grant and 

Gale, 1931, p. 224. · 

01·iginal description.-"Shell averaging about 42 millimeters in 

altitude, longer than high, inequivalve, plano-convex, equilateral, 

and with smooth margins; base evenly rounded; sides concave above. 

Right valve convex, ornamented by about 18 or 19 prominent, 

square, flat-topped medially sulcated ribs; interspaces channeled 

and slightly narrower than ribs; whole surface sculptured by fine, 

regular, concentric incremental lines; hinge line less than one-half 

length of disk; ears subequal, convex, and ornamented by concentric 

lines. Left valve flat or slightly concave, ornamented by about 17 

prominent, equal, equidistant, narrow, convex-topped ribs, which 

are separated by flat-bottomed interspaces much wider than the 

ribs; surface sculptured by numerous fine, regular, wavy, concentric 

lines; ears concave and sculptured by concentric lines." 

Holotype.-CAS/SU 11. 

Type locality.-Head of Garnet Canyon [NYz sec. 13, T. 15 S., R. 8 

E., S.B.], San Diego County, Calif. Imperial Formation, Miocene or 

Pliocene. 

Supplementary description.-Flabellipecten carrizoensis differs 

from the type species of Flabellipecten in the fairly high, medlally 

sulcated ribs, but it is believed to be allied toP. diegens1:s and should 

be included in the same supraspecific taxonomic category. (Hertlein 

and Grant, 1972, p. 178) 

Com.parison.-"This species belongs to the group of which P. diegensis is the living member. P. carrizoensis, P. stearnsii, and P. 

cf:iegensis taken in chronologie order as above may represent a 

genetic series. The three species are alike in most respects: They are 

all plano-convex, have squarish, more or less sulcated or longitudiTABLE 16.-Geologic and geographic distribution of the genus Flabellipecten 

[H =Holocene: Pie= Pleistocene: PI= Pliocene; M =Miocene; 0 =Oligocene] 

California Baja California 

Species Northern Middle Southern. Norte Sur 

Genus Flabell1:pecten: 

beat?: (Hertlein) .................................. PI 

boese·i (Hanna and Hertlein) .......... PI 

carrizoensis (Arnold) ........................ Mor PI PI 

d·iegens1:.':1 (Dall) .................................. H H PI to H Pie 

stea·rnsii (Dall) .................................. M to Pie Pl,Ple PI 

Genus Flabell1:pecten?: 

hawley1: (Hertlein) ............................ O,M 

uw1·n:ami (Arnold) ............................ M,Pl Pl,Ple 

Central 

and (or) South ·America 

PI 
B72 PALEONTOLOGY OF CALIFORNIA AND BAJA CALIFORNIA 

nally ridged ribs, convex ears on the right valve, and rather narrow, 

rounded ribs and concave ears on the left. 

"P. carrizoensis differs from the other two members of the group 

in the smaller number and less prominence of its ribs and in its 

relatively much shallower and narrower interspaces." (Arnold, 

1906, p. 60) 

"Pecten (Pecten) lecontei Arnold from Cedros Islanc~ is very similar 

except that the left valve is usually entirely concave instead of first 

concave and then convex as in P. carrizoensis." (Durham, 1950, p. 61) 

Comments.-The holotype is a small, incomplete, double-valved 

specimen. The right valve has 18 flat-topped ribs, some of which are 

grooved, and interspaces as wide as the ribs. The auricles are missing. The left valve has 16 rounded ribs separated by slightly wider 

interspaces and retains small patches of imbricated, concentric 

microsculpture on a few ribs. The umbonal area is depressed. The 

anterior auricle seems to have been smooth and the posterior auricle 

to have two riblets. 

Geographic range.-Southern California to Baja California Sur. 

Geolog1:c range.-Miocene(?) to Pliocene. 

Occurrence in the Cahfornias.-Miocene or Pliocene: Imperial 

Formation (G D. Hanna, 1926a); Pliocene: Boleo (Stump, 1979), 

Salada (Beal, 1948) and San Marcos (Durham,1950) Formations. 

Flabellipecten bosei (Hanna and Hertlein) 

Plate 32, figures I, 2 

Pecten (Pecten) bosei Hanna and Hertlein, 1927, p. 153-154, pl. 5, figs. 

2, 3. Durham, 1950, p. 60, pl. 7, fig. 1. 

Orig1:nal description.-"Shell fairly large; right valve convex,· 

ornamented by about 24 to 25 rather low, flattish-topped ribs which 

seldom show sulcation; intersp,aces narrower than ribs, flattish but 

slightly rounded at edges; ribs and inters paces crossed by fine concentric incremental lines; ears fairly large, subequal; anterior shows 

a faint byssal notch, above which the anterior ear slopes to hinge line 

forming an oblique angle; this ear possesses a fold near base; posterior ear slopes fairly abruptly to shell; ears set off from shell by sharp 

line and both ears ornamented by fine incremental lines of growth. 

Left valve slightly convex, ornamented by about 24 to 25 radiating, 

rounded ribs and interspaces, crossed by fine concentric incremental lines; ears slope from hinge line obliquely toward margin of shell. 

Length of right valve 74 mm.; height 66 mm.; apical angle, approximately 100°; hinge length, 28 mm." 

Syntypes.-CAS 2215 and 2216. 

Type locality.-CAS 795. Baja California Sur. Salada Formation, 

Pliocene. 

Comparison.-"This species differs from P. stearnsii Dall and P. 

diegensis Dall in possessing much lower ribs and these are usually 

broader and seldom show sulcation." (Hanna and Hertlein, 1927, p. 

154) 

"This species may be distinguished from P. baker1: by the right 

valve being much more convex than the left which is but slightly 

convex, and by the nondevelopment of the secondary riblets on the 

primaries of the left valve when the specimen is over 60 mm high." 

(Durham, 1950, p. 60) 

Comments.-The left valve syntype(CAS 2216) is depressed in the 

umbonal area. 

Geographic range.-Baja California Sur. 

Geologic range.-Pliocene. 

Occurrence in Baja California Sur.-Gloria (Stump, 1979), Infierno (Stump, 1979) and Salada (Beal, 1948) Formations and 

unnamed Pliocene strata on Carmen and Monserrate Islands. 

Flabellipecten stearnsii (Dall) 

Plate 31, figures 7, 8 

Janiraflorida Hinds. Dall, 1874, p. 297. Not Pectenfloridus Hinds, 

1844 =Pecten diegensis Dall, 1898. 

Pecten stearns1:i Dall, 1878, p. 11, 14. Woodring, 1946, p. 80, pl. 30, 

figs. 9, 11; pl. 32, figs. 14, 15. 

Pecten (Pecten) stearnsii Dall, 1898, p. 706, pl. 26, fig. 5. Arnold, 

1903, p. 106, pl. 12, fig. 3. Arnold, 1906, p. 100, pl. 32, figs. 1, 1a. 

Moore, 1968, p. 48, pl. 22, figs. a, b. 

Pecten (Janira) stearnsii variety stearnsi1: Dall. Grant and Gale, 

1931, p. 223, pl. 3, figs. 2a, 2b. 

Pecten (Flabellipecten) stearnsii Dall. Hertlein and Grant, 1972, p. 

178-180, pl. 29, figs. 2, 4; pl. 35, fig. 10; text fig. 8. 

Or1:ginal description.-"Shell moderately large, thin, regular; 

elegantly radiately ribbed. Upper valve flattened or even a little 

concave, with about twenty-four regularly rounded, vaulted, even 

ribs, separated by slightly wider channeled interspaces; the whole 

surface covered with fine, sharp, concentric, regular lamellae, a 

little looped backward over the top of the ribs, but showing no 

appearance of reticulation anywhere; ears small, nearly symmetrical, covered with more elevated, crowded, concentric lamellae, especially near the margins; hinge-margin straight, or even a little 

concave toward the umbo; peripheral margins ofthe valves strongly 

and regularly crenulated and interlocking; interior regularly deeply 

grooved, to correspond with the external ribs; lower valve slightly 

convex, with about twenty-six regular even ribs, separated by channelled inters paces somewhat narrower than the ribs; the top surface 

of each rib is flattened with a broad, shallow groove in the middle, 

with one or two faint riblets on each side of the groove; the whole 

surface is covered with concentric lamellae, like those of the upper 

valve, but less sharp, and about twice as crowded. Ears subequal, 

arched, covered with crowded, elevated lamellae; byssal notch very 

small. Height of shell, 90 mm; breadth, 100 mm; breadth of hingeline, 34 mm; thickness, 15 mm." 

Holotype.-USNM 7942. 

Type locality.-Well at San Diego, San Diego County, Calif. San 

Diego Formation, Pliocene. 

Supplementary description.-Flabellipecten stearnsi1: differs from 

the type species of Flabellipecten in the fairly high, medially sulcated 

ribs but is believed to be allied toP. diegensis and should be included 

in the same supraspecific taxonomic category. (Hertlein and Grant, 

' 1972, p. 178) 

Comparison.-"Pecten stearnsi1: is an extinct species and, as mentioned by Dall and by Arnold, it is the precursor of P. diegensis Dall, 

a Recent species which occurs at the present time in waters off San 

Diego. 

"Pecten stearnsii differs from the Recent species in the greater 

number of ribs, 23 to 26 on the right valve and about 24 on the left 

valve in comparison to 19-21 on the right valve of P. diegensis and 

20-21 on the left one. Furthermore, the hinge line of P. stearns1:1: is 

shorter, the ribs are usually more deeply medially sulcated and the 

i nterspaces between the ribs are narrower than those of P. d1:egens1:s. 

·Woodring, Bramlette, and Kew (1946, p. 80) called attention to the 

fact tha:t near the margin of the interior'of the right valve of Pecten 

d1:egensis a flange occurs along each edge of the projection corresponding to the interspace on the exterior. Similar flanges appear to 

be lacking or but slightly developed near the anterior and posterior 

ends of the right valve of P. stearnsii. 

"The two forms are very similar but in our opinion the differences 

are sufficient to justify recognition of each as a separate species. 

"Pecten ser1:ceus Hinds, a Recent species originally described from 

I ..... 
TERTIARY MARINE PELECYPODS: PROPEAMUSSIIDAE AND PECTINIDAE B73 

Panama, differs from P. stea.rnsi1: and P. d1:egensis in that the ribs, 

especially toward the ventral margin on adult right valves, often 

develop a low, median, tricarinate ridge. 

"Three fossil forms of Pliocene age in the Gulf of California region 

are closely allied toP. stearns1:i. 

"Pecten caTr-izoens1:s Arnold*** has fewer (18 or 19 on right, 17 on 

the left valve) and less prominent ribs, which are. separated by 

narrower interspaces than those on P. stearnsii. 

"Pecten beab: Hertlein*** differs from P. stearnsii in that the ears 

of the right valve bear radial riblets and in that a fine radial riblet 

occurs in each interspace between the radial ribs on the left valve.** 

"Pecten bose·i Hanna and Hertlein*** differs from P. stea·rnsii in 

possessing lower, nonsulcated, often almost smooth ribs. Specimens 

from Pliocene beds in the Gulf of California region referred toP. 

stenrnwi1: by Hanna and Hertlein (1927) are not typical of that species, but are more nearly allied to P. bOsei." (Hertlein and Grant, 

1972, p. 179-180) 

Geograph·ic ·ra.nge.-Middie California to Islas Tres Marias, 

Mexico. · 

Geolom:c ·mnge.-Miocene to Pleistocene. 

Occu-rrence 1:n the Cal1jo-rnias.-Miocene and Pliocene: Purisima 

Formation (Arnold, 1906); Pliocene: Almejas Formation (Minch and 

others. 1976), Lomita Marl Member, San Pedro Formation (Woodring, 1946), Niguel (J. G. Vedder, written commun., 1978) and Sa11 

Diego (Arnold, 1906; Hertlein and Grant, 1972) Formations; Pliocene and Pleistocene: Fernando (Eldridge and Arnold, 1907) and 

Merced (Arnold, 1906) Formations; Pleistocene: Timms Point Silt 

Member, San Pedro Formation (A. Clark, 1931; Woodring, 194S). 

Flabellipecten beali (Hertlein) 

Pia te 31, figures 3, 5 

Pecten(Pecten) beal-1: Hertlein, 1925a, p. 10-11, pl. 2, fig. 3; pl. 5, fig. 8. 

On:ginal descn:pt·ion.-"Shell inequivalve, plano-convex, equilateral, the ventral margin evenly rounded. Right valve convex, ornamented by about 23 or 24 prominent, square, flat-topped, strongly 

medially sulcate radial ribs, with in some cases, fainter radial 

grooves superimposed; interspaces flat-bottomed and slightly narrower than the ribs, the whole surface sculptured by fine, regular, 

concentric lines; posterior ear sculptured by about four radial 

riblets, and by fine incremental lines. Left valve flat or slightly 

concave. ornamented by about 21 radiating ribs separated by flatbottomed interspaces, each of which bears a single small intercalated riblet, the ribs and interspaces crossed by fine concentric 

lines; a somewhat depressed area is found just below the beak; 

margins of shell somewhat concave, b.earing four or five radiating 

ribs and fine concentric imbricating lines; ears somewhat concave, 

ornamented by three or four radiating rib lets and by fine concentric 

lines of growth. Altitude 55 mm.; longitude 56 mm.; diameter of 

right valve approximately 10 mm.; apical angle of right valve 

approximately 114°." 

Holotype.-CAS/SU 55. 

'P!me locahty.-SU 64. Baja California Sur, Salada Formation, 

Pliocen~. 

Cmn1Jwn:.<wn.-"Pecten beab appears to be related toP. carn:zoen-. 

wis Arnold, but is larger, and the ribs are more numerous and more 

deeply sulcate. On the left valve the radial interspaces are ornamented by small midribs which are lacking in Arnold's species .. 

P. cn?Tizoen.'H:s also is longer in proportion to the height than P. 

bettl·i." (Hertlein, 1925a, p. 11) 

"Pecten beat?: * * *differs from P. stearnsi1: in that the ears of the 

right valve bear radial riblets and in that a fine radial riblet occurs 

in each interspace between the radial ribs on the left valve." (Hertlein and Grant, 1972, p. 180) 

Flabellipecten beali differs from the type species of Flabelhpecten 

in the fairly high, medially sulcated ribs but is believed to be allied to 

P. diegensis and should be included in the same supraspecific category. (Hertlein and Grant, 1972, p. 178) 

Geographic -range.-Baja California Sur. 

Geologic -range.-PI iocene. 

Occu-r-rence in BaJ·a Califo-rnia.-Salada Formation. 

Flabellipecten diegensis (Dall) 

Plate 31, figure 2; plate 32, figure 4 

Pecten jloridu.s Hinds, 1845, p. 60, pl. 17, figs. 6, 6a. Not Ost-rea 

florida Gmelin, 1791. 

Pecten(Pecten) diegensis Dall, 1898, p. 710, new name. Arnold, 1903, 

p. 106, pl. 12, .fig. 5. Arnold, 1906, p. 127, pl. 51, figs. 1, la, lb. 

Oldroyd, 1924, p. 51-52, pl. 29; fig. 5; pl. 41, fig. 3. Grau, 1959, p. 

143-145, pis. 52, 53. 

Pecten (Jani-ra) stearnsii Dall variety diegensis Dall. Grant and 

Gale, 1931, p. 223-224, pl. 3, fig. 4. 

Or1:g1:nal desc-ription.-"Testa orbiculari, plano-subconvexa, 

aequiauriculata; valva sinistra planulata, prope medium subelevata, rufescente sparsim albo maculata, costis viginti-duo ad latera 

compressis, superne rotundatis cum interstitiis laminis minimis 

epidermidis transversim striatis; valva dextra subconvexa, pallescente, costis quadratis, medio sulco impressis; auriculis aequalibus, 

rectis, laevibus, epidermide indutis; intus alba, versus auriculas et 

margines saturate fusca." 

Holotype.-BM (NH) 79.2.26.241 (1 specimen, probably holotype 

fide Keen, 1966a). 

Type locality.-San Diego, San Diego County, Calif. Holocene, 

(Depth 10m.) 

Supplementa-ry descn:ption.-"Shell averaging about 60 millimeters in altitude, longer than high, inequivalve, plano-convex, or 

nearly so, equilateral and with smooth margins; base evenly 

rounded; sides slightly concave above. Right valve somewhat convex 

(more pronounced near the umbo), and ornamented by about 22 or 23 

prominent T-rail-shaped ribs, flattened, and generally longitudinally ridged or sulcated on top, which overhang deep, narrow, flatbottomed interspaces; whole surface sculptured by numerous fine, 

sharp, incremental lines; hinge line slightly less than one-half length 

of disk; ears equal, slightly convex, rectangularly truncated, sculptured by fine, sharp, incremental lines; anterior ear with small 

byssal notch. Left valve flat or nearly so, generally concave near 

apex, ornamented by 21 or 22 prominent, narrow conv~x-topped 

ribs, which are separated by concave-bottomed interspaces about 

equal in width to the ribs; whole surface prominently sculptured by 

numerous regular, fine, sharp, concentric, raised lines; ears concave, 

convexly truncated, and ornamented by the same concentric sculpture as the disk." (Arnold, 1906, p. 128) 

"The average adult specimen is 90 mm in height, 110 in length and 

20 in diameter.*** Although Arnold said the right valve has 22 or 

23 ribs and the left 21 or 22, such specimens must be quite uncommon; all that the author has ever seen had 18 to 21 on the right valve 

and 17 to 20 on the left." (Grau, 1959, p. 144) 

Compa-rison.-" Although closely related to Pecten se-riceus Hinds, 

this species is quite diStinct and differs in the following respects: less 

orbicular (length considerably greater than height); ribs of right 

valve always squarish, flat-topped, and often longitudinally ridged; 

ribs of left valve wider and rounded; interspaces of both valves 

narrower (especially left); auricular margins perpendicular (or 
B74 PALEONTOLOGY OF CALIFORNIA AND BAJA CALIFORNIA 

nearly so) rather than oblique; hinge line relatively longer; concentric lamellae on disks and auricles only half as numerous." (Grau, 

1959, p. 144) 

"Pecten stearnsi1: differs from the Recent species [F. diegensis] in 

the greater number of ribs, 23 to 26 on the right valve and about 24 

on the left valve in comparison to 19-21 on the right valve of P. 

diegen.'n:s and 20-21 on the left one. Furthermore, the hinge line of P. 

stearns1:1: is shorter, the ribs are usually more deeply medially sulcated and the inters paces between the ribs are narrower than those 

of P. d1:egensis. Woodring, Bramlette, and Ke~ (1946, p. 80) called 

attention to the fact that near the margin of the interior of the right 

valve of Pecten diegensis a flange occurs along each edge of the 

projection corresponding to the interspace on the exterior. Similar 

flanges appear to be lacking or but slightly developed near the 

anterior and posterior ends of the right valve of P. stearnsi1:. 

"The two forms are very similar but in our opinion the differences 

are sufficient to justify recognition of each as a separate species." 

(Hertlein and Grant, 1972, p. 180) 

Geographic range.-Living: Northern California to Guadelupe 

Island, Mexico; fossil: southern California to Baja California Norte. 

Geologic range.-Pliocene(?); Pleistocene through Holocene. 

Occu?Tence in the Cal1jornias.-Pliocene and Pleistocene: Santa 

Barbara Formation (Pico Formation of Waterfall, 1929); Pleistocene: unnamed strata of southern California (Kanakoff and Emerson, 1959) and Baja California Norte (Valentine, 1957). 

Habitat.-10 to 365m. 

"Usually found on * * * the following varieties of bottom: shale, 

rock, gravel, gray sand, green sand, mud; associated with coralline, 

nullipores, kelp, sponge. * * *The commensal gastropod Capulus 

calijornicus Dall is often attached to the anterior side of the umbo of 

the right valve." (Grau, 1959, p. 144, 145) 

Genus FLABELLIPECTEN? 

Flabellipecten? hawleyi (Hertlein) 

Plate 31, figure I 

Pecten (Pecten) hawleyi Hertlein, 1925b, p. 40, pl. 4, figs. 4, 5. Loel 

and Corey, 1932, p. 194, pl. 20, figs. 1, 2. 

Original description.-"Shell small, moderately thick, inequival ve. Right valve moderately convex, the point of greatest convexity 

being about one-third the distance from the apex to the ventral 

margin of the disk, the umbos gently rounded to the plane of the ears; 

surface ornamented by 17 to 18 prominent, sharply rounded ribs 

with nearly flat inters paces, toward the posterior extremity the ribs 

become flattened, and broader, and the interspaces broader proportionately; toward the periphery of the disk the ribs become somewhat less elevated and the sides of the ribs are more sloping to the 

flattened interspaces, in addition the surface of the right valve is 

ornamented by closely spaced, very fine, concentric lines, which are 

most prominent near the periphery of the disk; ears ornamented by 

concentric lines of growth, the anterior with a small byssal notch. 

Left valve slightly convex, slightly depressed near the anterior and 

posterior dorsal margins, ornamented by 16 to 17 very narrow, 

round ribs which expand but slightly towards the periphery of the 

disk, and are separated by interspaces wider than the ribs, the 

surface also sculptured by numerous fine, concentric growth lines 

which are more prominent than those on the right valve; ears crossed 

by very fine lines of growth. Height 32 mm.; length 34 mm.; apical 

angle of left valve approximately 125°." 

Holotype.-'-CAS/SU 19. 

Type locality.-SU 860. Santa Barbara County, Calif. Vaqueros 

Formation, Oligocene and Miocene. 

Comparison.-"Pecten hawley1: Hertlein resembles P. sanctaecruzensis Arnold, but the present species is smaller, has a greater 

number of ribs, and has more prominent concentric sculpture on 

both valves than P. sanctaecruzens1:s." (Hertlein, 1925b, p. 40) 

Comments.-For a description of the left valve holotype of F.? 

hawleyi and comparison see A1nuss1:opecten vanvleck1:. 

Geographic 1·ange.-Southern California. 

Geolog1:c Tange.-Oligocene to Miocene. 

OccuTrence in Calijornia.-Oligocene and Miocene: Vaqueros 

Formation (Hertlein, 1925b; Loel and Corey, 1932). 

Flabellipecten? merriami (Arnold) 

Plate 32, figure 5; plate 33, figure I 

Pecten (Pecten) merriam,i Arnold, 1906, p. 99, pl. 30, figs. 1, 1a, 2. 

Pecten (?Patinopecten) me?·Tianu: Arnold. Hertlein and Grant, 1972, 

p. 185-186. 

On:ginal desc1·iption.-"Shell averaging about 115 millimeters in 

altitude, longer than high, inequivalve, equilateral, of medium 

thickness, and with smooth margins; base evenly rounded; sides 

straight or only slightly concave above, sloping at a rather low angle. 

Right valve decidedly ventricose, with 18 or 19 subequal, strong, 

square ribs, some of which show faint medial sulcations near their 

extremities; interspaces flat-bottomed and somewhat narrower 

than ribs; whole surface of disk sculptured by more or less prominent lines of growth; hinge line more than one-half length of shell; 

ears about equal in length; anterior ear with faint byssal notch, 

obsolete radiating ridges and fine incremental sculpture; posterior 

ear rectangularly truncated, and with faint radial and fine concentric sculpture. Left valve flat to concave, with a more or less prominent bulge just below the umbo, as in P. bellus; ribs prominent and 

rounded, relatively flatter and broader as the periphery of the disk is 

approached; interspaces about as wide as the ribs, round-bottomed, 

and some of them showing a faint intercalary riblet; surface sculptured by fine, sharp, looped, concentric lines; ears ornamented by 5 

or 6 rather prominent radiating ridges and numerous fine concentric lines." 

Holotype.-UCMP 12086. 

Type locality.-From light-colored shale under the conglomerate 

on San Felician Creek, near Piru, Ventura County, Calif. Pico Formation, Pliocene and Pleistocene. 

Comparison.-"?. merriami is distinguishable from P. bellus, to 

which it is allied, by its much larger size when adult, more numerous 

ribs (18 to 19 in the former, 14 to 15 in the latter), relatively longer 

hinge line (the hinge line of the former being about 60 per cent of the 

length of the disk, while that of the latter is only about 45 per cent), 

and the radial ridging of the ears." (Arnold, 1906, p. 99) 

Comments.-The holotype is a large, incomplete, double-valved 

specimen with the umbonal areas and auricles of both valves missing. The right valve has about 18 square ribs, a few of them grooved, 

and interspaces slightly narrower than the ribs. The right valve is 

convex, more so than would be expected for Patinopecten. The left 

valve has about 15 rounded ribs separated by interspaces of about 

equal width. The umbonal area is missing, but the shell is slightly 

convex below it, then flattens out, and is markedly concave at the 

ventral margin. 

The paratype illustrated by Arnold (1906, pl. 30, fig. 2), which is 

missing and presumed lost (Keen and Bentson, 1944, p. 90), was a 

large specimen with a wide apical angle, long hinge, and two riblets 

on the anterior auricle and about three on the posterior auricle. 

Geographic range.-Southern California. 

Geologic range.-Miocene to Pleistocene. 
TERTIARY MARINE PELECYPODS: PROPEAMUSSIIDAE AND PECTINIDAE B75 

TABLE 17.-Geolog·ic and geognLph1:c d1:stribution of the genus Oppenheimopecten 

[H =Holocene: Pie= Pleistocene; PI= Pliocene; M =Miocene: 0 =Oligocene] 

Species Northern 

Genus Oppenh~1:mopecten: 

coa.hngen.'ns (Arnold) ....................... . /w,?·t?na:nn1: (Hertlein) ....................... . he·int:i (Hertlein) ............................... . fuanen.'rt:s (Grant and 

Stevenson) ....................................... . sanctaec1·uzens1:s (Arnold) ............. . 1;ogdes-1: (Arnold) ............................... . 

Occu.?Twrwe ·in Cahfm·nia.-Miocene and Pliocene: Purisima Formation; Pliocene and Pleistocene: Pico Formation (Keen and Bentson, 1944). 

Genus OPPENHEIMOPECTEN von Teppner, 1922 

Right valve very strongly convex; beak strongly incurved and 

overhanging that of left valve; ribs rounded to subrectangular, auricles squarely terminated. Left valve flat to concave, ribs low and 

wide but narrower than interspaces. 

Geog·ra,ph:ic 1·ange.-Living in Indo-Pacific, Australia, Japan, 

Hawaii, and eastern Pacific. 

Geolog·ic ·ra:nge.-Oiigocene through Holocene (table 17). 

Haln:tat.-In shallow tropical and subtropical seas. 

Oppenheimopecten sanctaecruzensis (Arnold) 

Plate 32, figure 3; plate 33, figure 2 

Pecten (Pecten) sa.nctaec·ruzenwis Arnold, 1906, p. 54-55, pl. 3, figs. 

12, 13. Addicott, 1973, p. 24-25, pl. 2, figs. 4, 7. 

Pecten (Pecten) d·t:ckenwm: Wagner and Schilling, 1923, p. 253, pl. 45, · 

fig. 1. 

Orim>na,l desc·n:pt·t:on.-"Shell averaging about 50 millimeters in 

altitude, slightly longer than high, planoconvex, equilateral, rather 

thin; base regularly rounded; sides only slightly concave above; 

margins smooth. Right valve quite convex and ornamented with 

about 12 prominent, perpendicular-sided, slightly convex-topped 

ribs, separated by flat-bottomed, channeled inters paces about equal 

in width to the ribs; surface sculptured by small, almost imperceptible, obsolete, radiating striations and numerous fine sharp concen-· 

tric lines; hinge line considerably longer than one half length of disk; 

ears subequal; anterior with shallow byssal notch and fine, sharp. 

concentric lines: posterior similarly sculptured, but rectangularly 

truncated. Left valve flat, with slight concavity near umbo; lateral 

areas rather prominent; ribs squarish, with slightly convex tops 

narrower than those of the right valve and with proportionally wider 

inter[s]paces; ears subequal, rectangularly truncated, and with surface sculptured by numerous fine, sharp incremental lines." (Arnold, 

1906) 

"Small in size; convex; equilateral; dorsal margins slightly concave; base evenly rounded; on the type specimen there are 14 ribs on 

the right valve; ribs rail-shaped being somewhat larger on top than · 

near the base; tops of ribs slightly rounded; wider than interspaces; 

bottom of interspaces flat; each rib sculptured by a faint groove 

running down the center but nearly obsolete on some; hinge line at 

least two-thirds the length of the disc; anterior and posterior ears 

fairly large, ornamented by about five fairly coarse and irregular 

ribs; left valve unknown, probably flat. Dimensions: length, 19 mm.; 

California Baja Central 

California and (or) South 

Middle Southern Norte Sur America 

M,Pl M,Pl 

PI 

PI 

M 

0 O,M 

Pl,Ple PI to H H 

height, 19 mm.; convexity of right valve, 8 mm." (Wagner and Schilling, 1923) 

Holotype.-CAS/SU 360•; of P. dicke?·sO?u:, UCMP 11416. 

Type locaWy.-SU 111. Santa Cruz County, Calif. Vaqueros Formation, Oligocene and Miocene; of P. dicke?·som:, UC 3231, Kern 

County, Calif., Pleito Formation (Addicott, 1973, p. 25), Oligocene. 

Supplementary descn:ption.-"Right valves of the pectinid range 

from about 45 to 85 mm (millimeters) in length. They have 12 or 13 

strong ribs which have gently rounded upper surfaces and vertical 

sides. The interspaces are deep, relatively flat bottomed, and somewhat narrower than the ribs. On two of the larger specimens, there is 

a suggestion of fine radial ;culpture on a few of the ribs. 

"Two left valves*** are relatively flat. The interior of the better 

preserved valve is characterized by strong cardinal crura that 

extend almost to the ligamenta! pit. Each valve has 12 prominent 

radial ribs that are much sharper than those of the right valve and 

that are separated by relatively wide interspaces. These valves measure about 48 and 73 mm long." (Addicott, 1973, p. 25) 

Comparison.-"This species is allied toP. bellus and may be its 

precursor,· as it is very similar to the latter in most respects. P. 

sanctaecruzensis may be distinguished from P. bellus by its fewer 

ribs (11 instead of 14) and relatively smaller size when adult." 

(Arnold, 1906, p. 54-55) 

Study of several topotypes indicates that the pattern and number 

of ribs on P. dickersoni are identical to P. sanctaecntzens1:s. (Addicott, 1973, p. 25) 

Com:ments.-The auricles on the left-valve holotype are deeply 

concave. 

Geograph1:c 1·ange.-Middle to southern California. 

Geologic range.-Oiigocene to Miocene: Possibly..early Zemorrian 

of Kleinpell (Addicott, 1973, p. 25). According to Burchfiel (1964, p. 

405) 0. sanctaecruzensis "is, as far as known, limited to the Zemorrian Stage, and can be used as an index fossil to the Vaqueros 

Sandstone." 

Occurrence in Calijornia.-Oiigocene: Pleito (Addicott, 1973) and 

Wygal Sandstone Member, Temblor (Addicott, 1973) Formations; 

Oligocene and Miocene: Vaqueros Formation (Keen and Bentson, 

1944). 

Oppenheimopecten juanensis (Grant and Stevenson) 

Plate 33, figure 5 

Pecten (Pecten)fuanensis Grant and Stevenson, 1948, p. 804-805, pl. 

124, figs. 1-4. 

Pecten ( Oppenheimopecten)Juanensis Grant and Stevenson. Hertlein 

and Grant, 1972, p. 180, 182. 

Original descr1:ption.-"Shell of moderate size; right valve highly 

ventricose; left valve flattish (none well preserved); right valve 
B76 PALEONTOLOGY OF CALIFORNIA AND BAJA CALIFORNIA 

sculptured with 18 to 21 rounded ribs which are less-convex near 

their medial portions though not flat, with evenly rounded interspaces which are somewhat narrower than the ribs; no interribs nor 

radial striations present on type material; ears of right valve about 

equal in length, smooth, with occasional subdued growth lines; 

byssal notch under right anterior ear slightly developed; hinge 

apparently similar or identical to that of Pecten coalingaensis. 

Dimensions of type: Height, 2 1/8 inches (54 mm.); width, 2 1/4 

inches (57 mm.); ventricosity of right valve, 15/16 inch (24 mm.); 

length of hinge, 13/32 inch (27 mm.)." 

Holotype.-UCLA 10441. 

Type locaWy.-UCLA 435. San Luis Obispo County, Calif. Neroly 

Sandstone, Miocene. 

Comparison.-"This new species differs from Pecten coalingaensis Arnold of the upper Pliocene in its lack of ribs on the ears of the 

right valve, in its lower, broader, less convex ribs with narrower 

interspaces, and in its greater ventricosity. Both species appear to 

have the same average number of ribs, which is about 20 on the right 

valve. 

"From Pecten vogdesi Arnold, the new Miocene species differs in 

its smaller size, less ventricosity and smooth ears. P. vogdesi has 3 or 

4 strong ribs on the right anterior ear with more, slightly less 

prominent ribs on the posterior ear. Both ears of the new Miocene 

species are smooth. 

"The similarities between the new species and P. coalingaensis 

Arnold*** is greater than the similarities between the new species 

and Pecten bellus Conrad * * *. We believe that P. }uanensis, P. 

coalingaensis and P. vogdesi are genetically related and form a clan 

to which P. bellus is only related as a possible off-shoot from the 

upper Miocene species here described, or from an earlier common 

ancestor*** the apical angle of the umbones*** in the new species 

is about 90 degrees, but in P. vogdesi is about 95 to 100 degrees. * * * 

Pecten he1:mi Hertlein * * * has but weakly sculptured ears. In 

general appearances it closely resembles the new Miocene species 

which, however, has unsculptured ears. Possibly the relationship of 

the new species is closer to P. heimi than toP. vogdesi." (Grant and 

Stevenson, 1948, p. 805) 

The apical angle of 0. Juanensis is about 90° rather than 95° to 

100° as in P. vogdesi. (Hertlein and Grant, 1972, p. 182) 

Geographic range.-Middle California. 

Geolog1:c range.-Miocene. 

Occurrence in California.-Neroly Sandstone. 

Oppenheimopecten coalingaensis (Arnold) 

Plate 33, figure 3 

Pecten coalingaensis Arnold in Anderson, 1905, p. 197, pl. 18, figs. 

94-98. Arnold, 1909, p. 158, pl. 26, figs. 1, 2. Stewart, 1940, p. 

90-91, pl. 13, figs. 1, 2, 17, 18; pl. 16, fig. 4. Woodring, 1946, p. 80. 

G D. Hanna and Hertlein, 1941, fig. 65-10. Grant and Stevenson, 

1948, pl. 124, figs. 5, 6. 

Pecten (Pecten) coal1:ngaensis Arnold, 1906, p. 97, pl. 4, figs. 4, 4a, 5. 

Adegoke, 1969, p. 96-97, pl. 1, figs. 1, 14. 

Pecten (Janira) bellus (Conrad) variety coalingaensis Arnold in 

Anderson. Grant and Gale, 1931, p. 227, pl. 2, fig. 2. 

Pecten (Oppenheimopecten) coalingaensis Arnold. Hertlein and 

Grant, 1972, p. 180. 

Ortginal description.-"Shell about 45 millimeters in altitude, 

longer than high, plano-convex, or nearly so, equilateral, and with 

smooth margins. Right valve ventricose and ornamented by about 20 

ribs which have narrow, somewhat convex tops, and sides which 

slope at angles of about 45°; interspaces quite deeply impressed, 

channeled, and flat bottomed; surface sculptured by fine incremental lines; hinge line slightly longer than one-half length of disk; ears 

equal, convex, and ornamented by 2 or 3 obsolete radiating ridges 

and numerous fine incremental lines. Left valve flat, with 19 prominent convex ribs, a surface sculpture of fine regular incremental 

lines, and concave ears which are slightly obliquely truncated." 

Lectotype.-CAS/SU 7 is here designated the lectotype. The specific name coalingaensis was first used by Arnold in Anderson ( 1905, 

p. 197, pl. 18, figs. 94-98), and the specimens illustrated in that paper 

would therefore be the primary types. The specimens, however, are 

missing from the California Academy of Sciences and presumed 

lost. In 1906 (p. 97, pl. 4, figs. 4, 4a) Arnold described coal1:ngaens1:s 

as a "new species," illustrated a right and a left valve and called the 

right valve the "type" and the left valve the cotype. The left valve is 

missing and presumed lost in the San Francisco fire of 1906. The 

right valve illustrated by Arnold (1906, pl. 4, figs. 4, 4a) is the 

specimen selected as the lectotype. 

Type locality.-Coalinga [sec. 36, T. 20 S., R. 14 E.], Kreyenhagen 

Ranch on Zapata [Zapato] Chino Creek [Fresno County], Calif. 

Etchegoin Formation, Pliocene. 

Supplementary description.-On 150 valves of this species the 

number of ribs ranges from 15 to 23; three-fourths of the inflated 

valves have 19 to 21 ribs, and three-fourths of the flatter valves have 

18 to 20 ribs." (Stewart, 1940, p. 90-91) 

Comparison. -"The nearest living relative of P. coalingaensis is P. 

cataractes Dall [= 0. vogdesi], from the Gulf of California. The living 

species may be distinguished from P. coalingaensis by the presence 

of secondary radials in the inters paces on the flatter valve. All of 150 

valves of P. coalingaensis lack secondary radials except 5, which 

have a radial in one or two interspaces, but only 1 of 29left valves of 

P. cataractes lack the radials, and that valve is small (height, 22 

millimeters). P. coalingaensis and its allies may be distinguished 

from P. bellus Conrad * * *and its allies, by the greater number of 

ribs, the greater inflation of the inflated valve, and the shorter 

internal channels-corresponding to the external ribs-on the flatter valve. The cross section of the ribs of the inflated valve also differ 

in the two groups: P. bellus has square-topped ribs, whereas P. 

coalingaensis has round-topped ribs." (Stewart, 1940, p. 91) 

Oppenhe1:mopecten coalingaensis is distinguished from 0. vogdes1: 

by the lack of secondary riblets on the left valve. (Woodring, 1946, p. 

80) 

Comments.-The lectotype is a slightly distorted right valve with 

20 ridgelike to subrounded ribs separated by deep, slightly narrower interspaces. 

Geographic range.-Middle to southern California. 

Geologic range.-Miocene and Pliocene. 

Occurrence in California.-Miocene and Pliocene: Etchegoin 

(Arnold, 1906; G D. Hanna and Hertlein, 1943) and Purisima 

(Arnold, 1906) Formations; Pliocene: San Joaquin Formation 

(Stewart, 1940; Adegoke, 1969). 

Oppenheimopecten hartmanni (Hertlein) 

Plate 33, figure 4 

Pecten (Pecten) hartmanni Hertlein, 1925a, p. 8-9, pl. 1, figs. 4, 6. 

Pecten (Jan1:ra) hartmanm: Hertlein. Grant-and Gale, 1931, p. 229. 

Pecten(Oppenheimopecten) hartmanni Hertlein. Hertlein and Grant, 

1972, p. 180. 

Original description.-"Right valve excessively arched, ornamented by about 16 or 17 rounded radiating ribs which become 

flattened toward the ventral margin of the shell; anterior and posterior margins highly arcuate, smooth except for faint lines of growth; 

ears somewhat convex and turned up slightly at the ends, the anterior sculptured by about four poorly defined radiating riblets which 
TERTIARY MARINE PELECYPODS: PROPEAMUSSIIDAE AND PECTINIDAE B77 

are crossed by concentric incremental lines, and cut by a slight 

byssal notch; left ear with a few faint radial riblets and slight 

concentric striae. Altitude 75 mm.; longitude 65 mm.; diameter of 

right valve approximately 30 mm.; apical angle of right valve 

approximately 88°." 

Holotype.-CAS/SV 48. 

11!J1)e loca.lity.-SV 54. Baja California Norte. Almejas Formation, 

Pliocene. 

Compm·ison.-"Pecten ha.'rtrna,nm: differs from P. hernphilli Dall 

in possessing a more highly arched right valve and in the shape of the 

ears. which in the present species are somewhat more concave. It 

differs from P. ca.tm·a.ctes Dall in having fewer ribs, and in that the 

margins of the shell descend abruptly rather than expanding laterally, as in the case in Dall's species, and also in P. vogdes1: Arnold." 

(Hertlein. 1925a, p. 9) 

Com:ments.-The holotype is a thick-shelled right valve with 17 

ribs that enlarge rapidly, are wide and almost flat at the ventral 

margin, and are separated by very narrow interspaces. 

Geom·a,ph1:c ?'a.nge.-Baja California Norte. 

Geolom:c ?'a,nge.-Pliocene. 

Occu.?Tence 'in Baja, Ca,l'ljO?·n,ia,.-A I mejas Formation (M ina, 1956). 

Oppenheimopecten heimi (Hertlein) 

Plate 33, figure 6 

Pecten (Pecten) he1:m,1: Hertlein, 1925a, p. 9-10. pl. 1, fig. 3; pl. 3, fig. 3 .. 

Pecten (Op1Jenhe1:m.opecten) he1:rn1: Hertlein. Hertlein and Grant, 

1972. p. 182. 

Or'ig-~:na.l de.wm:pt1:on.-"Shell concavo-convex, equilateral, inequivalve. Right valve highly arched, and ornamented by about 20or 21 

rounded, radiating ribs which become flattened toward ventral 

margin, these separated by round-bottomed interspaces about onehalf as wide as the ribs; ribs and interspaces crossed by concentric 

incremental lines of growth; ventral margin of shell rounded; ears 

somewhat convex: a distinct groove on right ear close to margin of 

shell, and byssal notch also present; anterior margin of right ear 

somewhat convex: ear ornamented by about four or five radiating 

rib lets and by concentric incremental lines. Left valve slightly concave and ornamented by about 17 or 18 radiating ribs which are 

separated by r·ound-bottomed interspaces, the ribs and interspaces 

crossed by fine concentric incremental lines; a depressed area present just below the beaks; anterior and posterior margins of valve 

flattened, higher than the depressed inner area near beak, sloping 

abruptly to ears; ears concave and sculptured by fine incremental 

lines only. Altitude 75 mm.; longitude 85 mm.; diameter of right 

valve approximately 25 mm.; apical angle of right valve approximately 97°." 

Holotype.-CAS/SV 46. 

Type loca.l·,:ty.-SV 65. Southern part of Arroyo San Gregorio, 

Baja California Sur. Salada Formation, Pliocene. 

Com1Ja.n:1wn. -"Pecten he1:m.1: differs from P. hemph1:lli1: Dall in the 

number of ribs. which is greater in the P. he1:rn1:, and in the ears 

which are smooth, and more convex in the present species than in P. 

hem.ph:,:U·,:-,:. From P. coa.l1:ngens1:s Arnold and P. a.u.bury1: Arnold it is 

distinguished by its larger size and the more rounded shape of its 

ribs; from P. vogdes-i Arnold, by the fact that the shell in P. hei1m: 

does not flatten out at the ventral margin as does P. vogdes1:, and P. 

hm:m:1: has a greater number of ribs than Arnold's species. P. he1:rni 

differs from P.lw.?·tnwnm: Hertlein, in being longer in proportion to 

the altitude, less inflated, and in possessing differently shaped ears. 

From P. a.ztecus Bose, P. lw·1:mi is distinguished by the fewer, more 

rounded, broader ribs, in the present species; furthermore, P. hei1m: 

is larger and apparently more convex." (Hertlein, 1925a, p. 10) 

The auricles of the type specimen of 0. heirni, a right valve, are 

weakly sculptured, and the auricles of the left valve are smooth, 

whereas the auricles of 0. vogdesi have well-defined riblets. (Hertlein and Grant, 1972, p. 182) 

Cornrnents.-The holotype is a thick-shelled right valve with 20 

ribs that are moderately large and flat at the ventral margin and are 

separated by narrow interspaces of different widths. The umbonal 

area of the right valve of 0. juanensis is more inflated than on 

0. he1:rni, and 0. juanensis has smooth auricles. The right valve of 

0. keepi is less inflated, and the ribs are wider and lower than on 

0. heirni The right valve of 0. hartrnanni is much more inflated than 

0. heirni, and the ribs are wider and more closely spaced. •The right 

valve of 0. vogdesi is less inflated than 0. he1:rn1:, and the byssal notch 

is wider. 

Geograph1:c range.-Baja California Sur. 

Geologic range.-PI iocene. 

Occurrence in BaJ·a Calijornia.-Salada Formation. 

Oppenheimopecten vogdesi (Arnold) 

Plate 34, figure 5 

Pecten dentatus Sowerby, 1835, p. 109. Not Pecten dentatus 

J. Sowerby, 1829. 

Pecten (Pecten) dentatus Sowerby. Arnold, 1903, p. 104, pl. 12, 

figs. 1, 1a. 

Pecten (Euvola) ca.taractes Dall, 1914, p. 121, new name for Pecten 

denta.tus G. B. Sowerby, not Pecten denta.tus J. Sowerby. 

Pecten (Pecten) vogdes1: Arnold, 1906, p. 100-101, pl. 33, figs. 1, 1a; pl. 

34, fig. 1. Hertlein, 1935, p. 304-305. Olsson, 1961, p. 158, pl. 20, 

figs. 4-4b. 

Pecten (Oppenhe1:rnopecten) vogdes1: Arnold. Grau, 1959, p. 149-152, 

pl. 55. Hertlein and Grant, 1972, p. 181-182, pl. 29, figs. 1, 3, 5, 6. 

Orig1:nal description.-"Shell similar toP. excava.tus, except averaging larger and with the following differences: Right valve, somewhat less convex, has 19 or 20 broader, flatter ribs, which are 

separated by relatively broader interspaces that occasionally show 

faint intercalary riblets or faint longitudinal striations. Left valve 

with fewer ribs than P. excava.tus, and having no intercalary rib lets, 

or faint ones, which become obsolete near the periphery of the disk; 

ears slightly less concave than in P. excava.tus." 

Holotype.-CAS/SV 4. 

Type loca.lity.-San Pedro, Los Angeles County, Calif. Upper part 

of San Pedro Formation, Pleistocene. 

Supplernentary descr1:pt1:on.-"Shell inequivalve and longer than 

high; average fully adult specimen about 110 mm high and 100 mm 

long; left valve smaller than right and recessed into latter,at ventral 

margin to depth of 6 to 8 mm, hinge line slightly more than half 

length of disk. Right valve deeply convex; umbo strongly inflated 

and projecting above hinge margin (starting to do so when shell 

reaches height of from 35 to 44 mm); hinge recurved at maturity, 

with contact surfaces of cardinal crura at right angle to left valve; 

19 to 21 rounded ribs, strongly produced ventrally and resulting in 

prominently dentate margin; interspaces about half as wide as ribs; 

surface of disk covered by very minute growth striae which become 

stronger near ventral margin. Interior of disk with deep grooves 

near ventral margin, resulting from external ribs; reverse surfaces 

of inters paces flat and ridged. Anterior auricle very slightly longer 

than posterior; strong convex fold 2 or 3 mm above disk; upper 

portion of auricle flat, angled at about 45° from perpendicular, 

finely concentrically lamellose and with 4 or 5 riblets; byssal notch 

shallow and ctenolium absent after shell reaches height of 40 to 45 

mm. Posterior auricle convex and with 6 to 11 faint riblets covered 
B78 PALEONTOLOGY OF CALIFORNIA AND BAJA CALIFORNIA 

by fine concentric lamellae. Left valve shallowly concave; 18 to 20 

rather flat ribs, with 4 or 5 small riblets next to submargins; ribs 

having one to three grooves near ventral margin; interspaces 

slightly wider than ribs, having a low central rib let and being finely 

concentrically lamellose. Interior of disk grooved near ventral margin as result of external ribs, grooves becoming shallower toward 

umbonal area; reverse surfaces of interspaces flattened and ridged; 

low rounded ridge parallel to submargin at base of each auricle and 

terminating in small white knob at lower end; cardinal crura prominent and with contact surfaces at right angle to disk. Both auricles 

concave, concentrically lamellose, and often slightly longer than 

those of right valve; 2 or 3 prominent rib lets adjoining hinge margin, 

with occasionally 2 or 3 indistinct riblets below them." (Grau, 1959, 

p. 151) 

"Shell large. (altitude 70 to 100 mm.), slightly longer than high, 

inequivalve, the right valve being convex, its umbone projecting 

above the hinge line, the left valve concave, equilateral, and with 

more or less serrate margins. Ribs in the right valve about 20; these 

are wide, low and rounded, broader than high, separated by narrower inters paces, their surface smooth except for incremental lines 

which loop across them. Ribs in the left valve about 19; these are 

narrow, squarish, flat-topped, about equal in width to their interspaces, sometimes longitudinally sulcated or ridged, interspaces 

flat-bottomed, usually with a well-developed mid-rib, the surface 

sculptured by numerous fine, sharp concentric lines, more marked 

in the interspaces. Ears subequal, the right anterior with abyssal 

notch." (Olsson, 1961, p. 158) 

"The observable shell characters of the Pliocene P. vogdesi do not 

differ from Recent specimens. On some left valves the interspaces 

lack a radial riblet but on others it is present. This feature varies in 

both fossil and Recent specimens. The hinge of juvenile specimens 

has but one pair of crura but adults have two pairs." (Hertlein and 

Grant, 1972, p. 181-182) 

Comparison.-"Pecten (Pecten) heimi Hertlein * * * is a similar 

species but that it is identical toP. vogdesi, as believed by Grant and 

Gale, is open to question. The ears of the type specimen are weakly 

sculptured and the ears of the left valve are smooth, whereas the ears 

of Recent P. vogdesi are ornamented with well defined riblets. 

"Pecten (Pecten)juanensis Grant and Stephenson*** has smooth 

ears and the apical angle is about 90° rather than 95° to 100° in 

P. vogdes1:. Grant and Stephenson suggested that P.J·uanensis might 

be the precursor of P. coalingaensis Arnold in Anderson and 

P. vogdesi. 

"Pecten ( Oppenheimopecten) hancocki Grau, a Recent species from 

Cocos Island, has only 16 to 17 ribs and the right valve is much less 

convex than that of P. vogdesi and it differs in other details. 

"In general appearance P. vogdesi bears a general resemblance to 

some members of the P. benedictus group and especially the 

P. aduncus group in the Miocene of the Mediterranean region but 

there are differences in the shape of the ribs and in other details." 

(Hertlein and Grant, 1972, p. 182) 

Geographic range.-Living: Baja California Sur to Gulf of California and to Peru; fossil: southern California to Mexico. 

Geologic range.-Piiocene through Holocene. 

Occurren-ce in the Calijorm:as.-Piiocene: Gloria (Stump, 1979), 

Infierno (Stump, 1979), San Diego (Hertlein and Grant, 1972), and 

San Marcos (Durham, 1950) Formations: Pliocene and Pleistocene: 

Palos Verdes Sand (Woodring and others, 1946) and San Pedro 

Formation (Arnold, 1906). 

Habitat._:_4 to 420 m; usually in sand, sandy mud, or mud; associated with coral or sponge. (Grau, 1959, p. 152) 

PATINOPECTEN subgroup 

Byssal notch deep, cardinal crura weak. 

Genus PATINOPECTEN Dall, 1898 

Large, round, gently convex valves, left valve nearly flat; radial 

ribs sulcate in some species. 

Yabepecten (Masuda, 1963) has a shallower byssal notch in right 

valve and more numerous, rounded radial ribs. 

Mizuhopecten (Masuda, 1963) was questionably placed in synonymy with Patinopecten by Hertlein (1969). Mizuhopecten (type: 

PectenyessoensisJay) has imbricated microsculpture on both valves 

(pl. 40, fig. 3); Patinopecten has this sculpture only on the left valve 

(pl. 41, fig. 5; pl. 43, fig. 2). I do not know at this time how meaningful 

microsculpture is in the pectinids, but the fact that its preservation 

is usually fortuitous makes it an unreliable character for differentiating fossil species. 

Geographic range.-North and northeastern Pacific. 

Geologic range.-Oiigocene through Holocene (table 18). 

Habitat.-Patinopecten caurinus (Gould), the only Patinopecten 

now living in the eastern Pacific, is found from Alaska to northern 

California at depths of 15 to 275 m. It is taken in considerable 

numbers by flatfish trawlers at depths of 58 to 88 min California. In 

British Columbia its maximum population density occurs at about 

35m, on a mixed sand and inud bottom. In the natural habitat the 

species has been observed lying in small depressions that are presumed to be a result of current scour around the shell. It is byssally 

attached to a size of about 3 to 4 em in shell diameter and has a 

ctenolium during its young stage. 

Masuda (1962, p. 213) reported that the shells of Patinopecten 

yessoensis (Jay), of Japan, are rather large in size in calm seas, with 

the convexity of.the right valve low and the left valve rather inflated, 

whereas those living in less calm water have thick shells with a more 

TABLE 18.-Geologic and geographic distribution of the genus Patinopecten 

[H =Holocene; Pie= Pleistocene; PI= Pliocene; M =Miocene; 0 =Oligocene] 

Alaska British Washington Oregon California Species Columbia Northern M1ddle Southern 

Genus Patinopecten: 

calaverasensis (Hall)------------------------

caurinus (Gould)--------------------------------

haywardensis (Lutz) ------------------------ healeyi (Arnold) --------------------------------

lohri (Hertlein) ---------------------------------- propatulus (Conrad) _________________________ _ 

H H H H PI toH 

PI 

M M 

M 

Pl,Ple Pie 

M 

M? to M? to 

Pie? Pie? 

M,Pl M,Pl 

M O,M 

Baja California Norte Sur 

PI PI 
TERTIARY MARINE PELECYPODS: PROPEAMUSSIIDAE AND PECTINIDAE B79 

convex right valve and a nearly flat left valve. 

The pt·edators of P. ca:u:n:nus are Octopus and the large sun-star 

Pycnopo(l'/:a.; juveniles are attacked by crabs. 

Golikov and Scarlato (1970) note that P. yessoens1:s in the Sea of 

Japan "inhabits mainly depths of 0.5 to 25m on the sand and siltsand bottom (often with stone and shell admixtures). In summer 

time, when surface water layers warm to 15°-20° C. the scallops are 

found at depths of 0.5 to 12 m and are most abundant in a depth 

nwgi ng from 1.5 to 4 m: their young settle at the same depths on the 

ft·onds of seaweed. In autumn, before the first frosts, the molluscs 

leave the shallow inshore waters and move to depths of 3 to 25 m, 

being most abundant at 6 to 8 m. By this time, their quantity considerably decreases. due mainly to elimination of the young. In winter, 

their activity is greatly reduced and they accumulate at 3.5 to 6.5 m 

depths. Their number decreases still more a.t the beginning of spring 

due to a generalt·ise in the death-rate***. When spring approaches 

and the surface layers of the water warm to 6°-8° C, the molluscs 

become active and spread to depths from 0.5 to 8 or 9 m, being found 

usually at depths of 3 to 7 m. Because of the prespawning aggregations of mature individuals in the most favourable plots their population density somewhat increases at this time." 

Patinopecten propatulus (Conrad) 

Pia tc 34, figures 1, 4, 6; pia te 35, figures 1, 2 

Pecten 1J'r01Ht.tu.lus Conrad. 1849, p. 726. atlas pl. 18, figs. 13, 13a. 

Meek, 1864, ~2aConrad, 186~ p. 154. 

Pectwn (Pah>nopecten) p·ro1Ht.t·ulus Conrad. Dall, 1898, p. 699. Arnold, 

1906. p. 64-75, pl. 7, fig. 1 [not pl. 9, figs. 1, 1a, 2, 2a = Ve1·t1:pecten 

fu.ca:nus (Dall)]. Dall, 1909. p. 112, pl. 16, fig. 1 [not pl. 15, figs. 1, 

la, 2. 2a = Ve?·t·ipectenfuca:nus (Dall)]. Grant and Gale, 1931. p. 

192-193, pl. 22. fig. 5. Weaver. i942, p. 91, pl. 19, fig. 6, pl. 20, fig. 

2. 

Vwrt·i1Jecten. cf. V. 1J'ropatu.lus (Conrad). Stewart, 1946, pl. 17, fig. 4. 

Pat·,:·no1Jecten 1J't"01Ja,tu.lus (Conrad). Moore, 1963, p. 64-65, pl. 16, 

figs. 1-4: pl. 17. figs. 2-5, 7. 

Orim>na.l desc·n:pt·,:on.-"Large, subequivalve, suborbicular, compressed: costae about 17, rounded, narrow, interstices much wider 

than the ribs: ears unequal." 

Lectotype.-USNM 3504 (Moore, 1963). 

'J1ype loca.h:ty.-Astoria [Columbia County], Oreg. Astoria Formation, Miocene. 

Supplem.enta:ry (/.esc·n:pt·ion.-"Patinopecten p1·opat·ulus is of moderate size and the valves are slightly and equally inflated. There are 

16 to 22 flat-topped to slightly rounded or flattened finely striated 

ribs on the right valves and 15 to 18 evenly rounded or ridgelike ribs 

on the left valves.' The right anterior ear has a moderately deep 

byssal sinus and the surface of the ear above the sinus is ribbed; the 

right posterior and left valve ears are finely ribbed. The right and 

left anterior ears are folded. Well-preserved left valves show the 

surface to be sculptured by an imbricated lamellar microsculpture 

***:this sculpture may also be present on the left valve ears; it has 

not been found on right valves. 

"The lectotype is an internal mold of both valves and only fragments of the innermost shell layer remain. The specimen was contained in a concretion and apparently only the right valve was 

exposed when Conrad described the species; the specimen was 

removed from the concretion at some later date, and both valves are 

now exposed. There are 16 flat-topped to slightly rounded ribs on the 

right valve and the inters paces are flat to slightly rounded and wider 

than the t•ibs. The left valve has probably more than 13 rounded ribs 

and the interspaces are slightly rounded and wider than the ribs. 

The lectotype is approximately 10.3 em high and 10.2 em wide 

(broken along margins). 

"The number and configuration of the ribs and inters paces on both 

valves of Patinopecten propatulus is variable. The right valve has 16 

to 22 ribs; 19 ribs are most common. The interspaces may be narrow, 

less than a third the width of the rib, or more commonly as wide or 

somewhat wider than the rib. Both the ribs and the interspaces are 

usually flat, but they may be slightly rounded. The ribs are often 

square but may be moderately undercut, and show fine radial striations on well-preserved specimens. There is occasionally an interrib 

. in some of the interspaces especially near the anterior and posterior 

margins of the shell. There may also be as many as five threadlike 

ribs on the anterior or posterior margin of the shell; these fine ribs 

were not included in the rib counts. 

"The anterior ear on the right valve has a moderately deep byssal 

sinus covering more than a third of the total area of the ear and 3 to 

perhaps more than 5 imbricated ribs on the upper part of the ear. 

The posterior right ear has 5 to 10 ribs usually about half as wide as 

those on the anterior ear. These ribs may be of equal width and may 

alternate with very fine threadlike ribs. 

"The left valve has 15 to 18 ribs which are usually evenly rounded, 

but which may rise abruptly to a narrow ridge or may be flat-topped. 

Both types of ribs may be present on the same specimen. The interspaces may be flat, slightly rounded, or moderately round and may 

contain a fine interrib. The interribs when present are usually centered in the interspace but may be crowded close to the posterior side 

of the rib. Flange! ike lamellae are present near the dorsal end of the 

first few posterior ribs on two left valves * * *. 

"The left anterior ear has 5 to 8or more ribs, similar in size to those 

on the posterior ear of the right valve, and it usually has fine threadlike interribs. On all but immature specimens, the posterior ear is 

depressed medially. The left posterior ear is sculptured by 6 to 8 ribs, 

similar in weight to those on the anterior ear but without the fine 

interribs that are often present on the anterior ear. 

"An imbricated lammelar microsculpture may be present on the 

left valve of P. propatulus ***.This microsculpture is on a thin now 

chalky shell layer that flakes off leaving no trace of the presence of 

the microsculpture and the remaining shell seems to be perfectly 

preserved." (Moore, 1963, p. 64-65) 

Compa·rison.-"P. propatulus is allied toP. caun:nus (Gould) of the 

Recent, which has been collected from sedimentary rocks as old as 

Pliocene*** in age. Recent specimens of P. caun:nus reach a much 

larger maximum size than P. p1·opatulus. The ribs on the right valve 

of P. caurinus tend to disappear near the margins on large specimens, and the ribs on both ears of the right valve are poorly developed, being barely discernible on some specimens. The ribs on the 

left valves of P. caun:nus are usually flat topped Whereas on 

P. propatulus this is rare, although they may be rounded similar to 

those of P. p·ropatulus. The ribs on the left valve also tend to disappear along the margins of large specimens of P. caun>nus. The ribs 

on the ears of the left valve of P. caurinus tend to be finer than those 

on P. propatulus. Interribs are less frequently present on both the 

right and left valves of P. caurinus. The umbonal angle on 

P. p1·opatulus is narrower than on P. caur1:nus, P. propatulus averaging about 100° and P. caurinus averaging about 125°." (Moore, 1963, 

p. 65) 

Patinopectenhealey1: has more ribs (mostly more than 20) than P. 

propatulus, arid Patinopecten lohri has stronger intercalaries and 

deeper interspaces than P. propatulus. (Arnold, 1906, p. 65) 

"Poorly preserved specimens of P. propatulus, or specimens of 

only the right valve, are difficult to separate from Ve·rt?:pectenfucanus (Dall). The shell of P. propatulus is usually thinner: the ribs on 

the right valve are often. flatter; and the byssal sinus somewhat more 

shallow. Ribs on the right valve of V. fucanus may be split, whereas 
B80 PALEONTOLOGY OF CALIFORNIA AND BAJA CALIFORNIA 

they commonly are not on P. propatulus and may be more conspicuous, narrower, and more closely and irregularly spaced; and in some 

specimens unevenly split, with one part half the width of the other." 

(Moore, 1963, p. 65) 

Comments.-Patinopectenhaywardensis lias a wider apical angle, 

wider byssal notch, and narrower ribs with wider inters paces than 

P. propatulus. Patinopecten calaverasensis has the ribs more closely 

spaced, not as evenly distributed by width, and has wider riblets 

than P. propatulus. 

Geographic range.-Washington to southern California. 

Geologic range.-Oligocene to Miocene. 

Occurrence in Calijornia.-Oligocene and Miocene: Temblor 

Formation (Adegoke, 1969); Miocene: Briones Sandstone (Crittenden, 1951) and Monterey Formation (Hall, 1973). 

Patinopecten haywardensis (Lutz) 

Plate 35, figure 4; plate 36, figure I 

Pecten (Patinopecten) haywardensis Lutz, 1951, p. 386-387, p. 17, 

figs. 9, 10. 

On:g1:nal description.-"Shell of large size, suborbicular, compressed, equivalve; apical angle about 115 degrees for specimen 60 

mm. high, about 130 degrees if measurements taken tangential to 

dorsal slope of specimen 120 mm. high; dorsal slope slightly concave; 

hinge margin less than half width of shell; right valve with 17 or 18 

square, flat-topped, radiating ribs, some with slight medial sulcus; 

interribs as wide or slightly wider than ribs, square, with vertical 

side walls, some with medial interriblets; entire surface ornamented 

with numerous fine growth lines; anterior ear longer than posterior 

ear, nearly flat, ventral half slightly convex, dorsal half covered with 

from 5 to 6 well-defined radiating riblets crossed by numerous 

growth lines; byssal notch slightly less deep than in P. caurinus, 

deeper than in P. propatulus; posterior ear slightly and evenly concave, ornamented by 7 or 8 radiating riblets, posterior edge sloping 

at about 110 degrees from hinge margin; left valve with about 17 

V-shaped ribs; anterior ear like P. caurinus, possibly with more 

concave ventral half of anterior edge; posterior ear slightly and 

evenly convex. (Left valve notations from internal cast.)" 

Holotype.-UCMP 34133. 

Type locality.-UC A-4566. Alameda County, Calif. Sobrante 

Sandstone, Miocene. 

Compan:son.-"This species may be distinguished from P. caurinus by its much better developed rib lets on the right posterior ear, a 

greater angle between the hinge margin and the posterior edge of 

the posterior ear, and also by its more squarely shaped ribs and. 

interspaces which have vertical side walls, its slightly less deep 

byssal notch, a shorter hinge line in proportion to the width of the 

shell, and a greater number of ribs. (Grant and Gale, 1931, p. 195, 

have given the rib count of more than 25 Recent and Pliocene specimens of P. caurinus in the collections of Stanford University as 

between 16 and 20. Mr. E. J. Wilson and the author counted the ribs 

of the Recent specimens in the Stanford stratigraphic collection and 

found them to have not less than 20 and as many as 23.) P. haywardensis may be distinguished from P. propatulus by its larger apical 

angle, greater width of the hinge line in proportion to the width of 

the shell (P. propatulus has a hinge line proportionally much smaller 

than that of P. caurinus), a deeper byssal notch, and a greater 

number of riblets on the anterior ear. The ribs of P. propatulus are 

much higher than those of either P. caurinus or P. haywardens1:s, 

especially in the intermediate growth stage." (Lutz, 1951, p. 386-387) 

Comments.-The holotype and paratype of P. haywarden.c;is are 

·molds from which the figured latex impressions were made. Patinopecte.n haywardensis may be distinguished by the narrow, high, 

square, widely spaced ribs on the right valve; none of the ribs are 

sulcated. 

Geographic range.-Middle California. 

Geologic range.-Miocene. 

Occurrence in Cal1fornia.-Sobrante Sandstone. 

Patinopecten calaverasensis (Hall) 

Plate 35, figures 5, 6 

Pecten (Patinopecten) haywardens'is calaverasensis Hall, 1958, p. 

51-52, pl. 2, fig. 2; pl. 3, fig. 4; pl. 4, fig. 3. 

Original description. -"Shell of moderate to large size; right valve 

convex, with 20 or 21 flat-topped ribs; ribs approximately twice as 

wide as interribs; bifurcating ribs common; small riblets common; 

left valve slightly flatter than right valve; growth lines well developed on left valve; bifurcating ribs not as frequent as on left valve; 

byssal notch well-developed; anterior ear longer than posterior ear 

and slightly convex; riblets on anterior ear crossed by growth lines; 

posterior ear nearly flat, with no well-defined riblets and with welldefined growth lines." 

Holotype.-CAS/SU 8442. 

Tupe localitu.-SU 3252. Contra Costa County, Calif. Oursan 

Sandstone, Miocene. 

Comparison.-"This subspecies may be distinguished from Pecten 

hauwardens1:s Lutz by its greater number of ribs. Lutz (1951, p. 386) 

gives the rib count of P. haywardens1:s as 17. P. haywardensis calaverasensis has 20 or 21 ribs. The related P. propatulus has 15 or 16 

ribs." (Hall, 1958, p. 52) 

Comments.-Patinopecten propatulus has 16-22 ribs on the right 

valve, 19 being most common. The right valve of P. calaverase?un:s 

has 20 or 21 ribs, and this feature does not distinguish it from P. 

propatulus. The right-valve ribs of P. calave1·asens1:s are mostly 

lower, wider, and more closely spaced than on P. propatulus. In 

addition, the interribs are wider than on P. propatulus, and the right 

posterior auricle is longer and much higher than the right anterior 

auricle; on P. propa,tulus the auricles are equal in length, and the 

right posterior auricle only slightly higher than the right anterior 

auricle. The right-valve ribs of P. calaverasens1:s are unevenly distributed by width and in this character somewhat resemble a specimen from the Astoria Formation, Oregon, identified as Vert?:pecten? 

cf. V. fucanus (Moore, 1963, pl. 21, fig. 4). 

On the underside of the holotype a portion of a left valve, presumably the same species, is preserved. The shell has narrow ribs that 

rapidly widen toward the ventral margin, interspaces as wide or 

wider each bearing a fine riblet, and preserved patches of imbricated microsculpture. The left valve was apparently almost flat. 

Geograph1:c range.-Middle California. 

Geologic range.-Miocene. 

Occurrence 1:n California,.-Sobrante Sandstone. 

Patinopecten lohri (Hertlein) 

Plate 34, figure 2; plate 36, figures 2, 3 

Pecten (Pat1:nopecten) oweni Arnold, 1906, p. 63-64, pl. 8, figs. 1, la, 

lb. Not Pecten owem: De Gregorio, 1884. 

Pecten (Pa,tinopecten) lohri Hertlein, 1928, p. 93, new name. G D. 

Hanna and Hertlein, 1943, fig. 65-1. 

Pecten (Pat·inopecten) healeyi Arnold variety lohri Hertlein. Grant 

and Gale, 1931, p. 197-198, pl. 6, figs. la, lb. 

Patinopecten lohn: (Hertlein). Woodring, Stewart, and Richards, 

1940, pl. 32, figs. 2-5. Woodring, 1950, p. 83-84, p. 7, figs. 7, 9. 

Adegoke, 1969, p. 103, pl. 2, figs. 6, 7. Addicott, 1974, pl. 2, fig. 4. 
TERTIARY MARINE PELECYPODS: PROPEAMUSSIIDAE AND PECTINIDAE B81 

Addicottand others.1978. p. 82, text fig. Moore, 1979, p. 6-7, pl. 

13, figs. 3, 4, 6. 

On:m>na.l descn:pt·1:on.-"Shell averaging about 85 millimeters in 

altitude. slightly longer than high, inequivalve, equilateral, and 

with more or less serrate margins; base regularly rounded; sides 

somewhat concave above. Right valve much more convex than the 

left, with 15 of 16 subequal, strong, elevated, squari.sh ribs, which 

become more or less deeply medially sulcated after about 40 or 50 

millimeters in length; interspaces about as wide as ribs. channeled 

and ornamented with more or less prominent rounded intercalary 

riblets; whole surface of disk sculptured by fine lines of growth; 

hinge line considerably longer than length of disk; anterior ear 

slightly longer than posterior. obsoletely radially ribbed, and with 

sharp incremental sculpture; byssal notch quite prominent and 

equal in width to about one-third width of ear; posterior ear 

rectangularly truncated and with promine·nt incremental, but 

nearly obsolete, radial sculpture. Left valve less ventricose than 

right; ribs quite high. narrow, and rounded; interspaces much wider 

than ribs, with round bottoms, and each ornamented by a prominent 

r·otmded intercalary rib; surface sculptured by numerous sharp, 

regular, concentric lines; ears slightly truncated and sculptured as 

those of right valve. Hinge as in P. ca.m"inus." 

Holotype.-VCMP 12081. 

Type locnl·ity.-Foxin's Ranch [WY2 sec. 28, 'I'. 9 N .. R. 32 W.], 

Santa Barbara County, Calif. Tinaquaic Sandstone Member, Sisquoc 

Formation (Woodring, 1950. p. 83-84). Pliocene. 

C0'1npa:ri1wn.-Pat·inopecten lohri may be distinguished from P. 

lwa.ley·1: by its smaller size. greater convexity, fewer and stronger 

ribs. more prominent intercalary riblets on the right valve, and 

relatively much longer hinge line." (Arnold, 1906. p. 63) 

"The ribs on large left valves of P. lohn: are wide and divided, 

whereas on P. lwnley·i they are narrow and not divided. or on some 

very large left valves are moderately wide and faintly divided by one 

or more shallow grooves. Right valves of P. loh1·£ generally have a 

strong secondary rib in the space between the primary ribs, whereas 

on right valves of P. healey·i secondary ribs are absent or, if present 

gener·ally are weak. Some right valves of P. lohri, however, lack 

secondary ribs or have weak secondaries. Left valves of both species 

have secondaries. Owing to the presence of divided ribs on both 

valves of P. loh:ri, right and left valves are difficult to distinguish 

unless the ears are preserved. whereas right and left valves of P. 

lwa.leyi are readily differentiated." (Woodring, 1950, p. 83) 

The right valve of the holotype of P. lohn: is more inflated than is 

typical for P.lwaley·i; the primary ribs are higher. dichotomous at an 

earlier stage. fewer in number, and therefore more widely spaced. 

Each interspace bears a wide secondary rib that first appears when 

the shell has reached a height of about 30 mm. The primary ribs are 

deeply dichotomous. the first division of a rib taking place when the 

shell is about 15 mm in height. the last at about 55 mm. At the 

ventral margin of the holotye, which is about 90 mm in height, the 

primary ribs. except two at each of the margins of the shell. are 

dichotomous. and two near the posterior margin are completely 

divided. Both sides of the split ribs are more rounded than on P. 

lwa.ley·i. A nan·ow unsculptured band is present along the posterior 

margin of the shell. The right anterior auricle is poorly preserved 

but seems to be sculptured by subdued riblets and to have a byssal 

notch similar to P. lwaleyi. The posterior auricle bears a shallow 

groove bordered by low ridges; this feature is discernible on about 

two-thirds of the auricule but seems to disappear before reaching the 

posterior edge. The right anterior auricle is broken at the margin but 

was possibly not as high as the left anterior auricle. The right valve 

is noticeably inequilateral, and the anterior margin, excluding the auricle, forms an angle of about 40° with the hinge; the posterior margin 

forms an angle of about 25°. 

The left valve of the holotype of P. lohri bears fewer primary ribs 

than P. healeyi, and these ribs are therefore more widely spaced. The 

ribs are also higher, especially on the younger portion of the shell, 

than is common for P. healeyi. Each interspace has a strong 

secondary rib, and three of the interspaces closest to the posterior 

margin .bear two secondary ribs. The shell is worn, but traces of 

concentric lamellar sculpture, similar to that seen on some P. henley1: 

are visible under magnification. A few of the primary ribs near the 

central portion of the shell have subdued shell protuberances that 

seem not to be primary structures but rather to be related to a time of 

breakage and subsequent repair of the shell. The left, valve is 

strongly inequilateral; the posterior shell margin, excluding the ear, 

forms an angle of 25° with the hinge, the anterior margin, 40°. The 

ears are markedly inequilateral, the posterior being about 26 mm 

long and 13 mm high and the anterior about 30 mm long and 22 mm 

high. A similar inequilaterality is seen on large specimens of P. 

healey1: (Moore, 1979, pl. 8, figs. 1, ,3, 4, 6). 

Geographic range~-Middle to so\lthern California. 

Geologic range.-Miocene to Pliocene. 

Occurrence in Cal1jornia.-Miocene: Pancho Rico (Durham and 

Addicott, 1964; Addicott and others, 1978) and San Pablo (Arnold, 

1906) Formations; Miocene and Pliocene: Edna Member, Pismo 

(Hall, 1973), Etchegoin (Arnold, 1906; Woodring and others, 1940; 

Durham and Wolfe, 1958; Adegoke. 1969; Bertholf, 1962; Anderson· 

and Land, 1969; Addicott, 1974) and Towsley (Kern, 1973) Formations; Pliocene: Pomponio Mudstone and San Gregorio Sandstone 

Members, Purisima Formation (Cummings and others, 1962) and 

Tinaquiac Sandstone Member. Sisquoc Formation (Woodring, 1950). 

Patinopecten healeyi (Arnold) 

Plate 34, figure 3; plate 35, figure 3; plate 36, figure 4; plate 37, figure 3; 

plate 38, figures 2-5 plate 39, figure 1; plate 40, figure 5; plate 41, figure 2; 

plate 42, figures 1-3 

Pecten expansus Dall, 1878. p. 14. Not Pecten expansus Smith, 1847, 

p. 413, 419, pl. 18. fig. 21. 

Pecten (Pat·inopecten) expansus Dall, 1898, p. 706, p. 26, fig. 1. 

Arnold, 1903, p. 108. 

Pecten (Pat1:nopecten) healeyi Arnold, 1906, p. 103, p. 36, figs. 1, la; 

pl. 37, figs. 1, 1a, 2. Arnold and Anderson, 1907, p. 154, pl. 26. 

figs. I. 2. Grant and Gale,1931, p.196, pl. 6, figs. 2a, 2b. Hertlein 

and Grant, 1972, p. 183-185, pl. 31, figs. 1, 4, 6, 7; pl. 33, fig. 9; pl. 

36, figs. 8, 9; text fig. 9. Susuki and Stadum, 1978, figs. 20, 21. 

Pat£nopecten healey1: (Arnold). Woodring, 1950, p. 19, fig. 9; pl. 21, 

fig. 9. Vedder and Moore, 1976, p. 122. pl. 3, figs. 2-6, 91 Moore, 

1979, p. 2-7, pls. 1-15. 

Pecten (Patinopecten) healey£ Arnold sanclementensis Susuki and 

Stadum, 1978, p. 10-11. figs. 18, 10. 

On:g1:nal de.~cr1:ption.-"Shell averaging 130 millimeters in altitude, length about equal to height. inequivalve (the right slightly 

more ventricose than the left), equilateral, and with smooth margins; base evenly rounded; sides only slightly concave above. Right 

valve somewhat ventricose, and ornamented by 18 to 21 strong, 

squarish, subequal primary ribs, which become more or less dichotomous, and sometimes trichotomous, after 30 or 40 millimeters in 

length; medial sulcus of rib more or less deep, in some cases being as 

deep as the interspaces near the ends, thus completely dividing the 

primary rib; interspaces subequal, much narrower than the ribs, 

quite deeply channeled, and often ornamented by a small, rounded 

intercalary riblet; whole surface crossed by numerous fine lines of 

growth; hinge line less than one-half length of disk; anterior ear only 

slightly longer than left, arcuate in front, and ornamented by several 

obsolete radial ridges and numerous sharp incremental lines; byssal 
B82 PALEONTOLOGY OF CALIFORNIA AND BAJA CALIFORNIA 

notch quite prominent; posterior ear slightly obliquely truncated, 

and ornamented by sharp incremental lines and sometimes by 

obsolete radiating ridges. Left valve much compressed; ribs narrow 

and rounded, more or less sharply toward the top (there being in 

some cases a narrow, slightly raised line along the top); interspaces 

wide, and each ornamented by a more or less prominent, rounded, 

intercalary riblet; whole surface striated concentrically by fine, 

sharp, wavy lines; ears obliquely truncated and sculptured similarly 

to those of the right valve." (healey?:) 

"Distinguishable by the much finer and greater number of closely 

and equally spaced ribs on the left valve; ribs narrow, flat, interspaces shallow and narrow on right valve; right valve gently but 

evenly convex; left valve slightly convex with anterior and posterior 

margins flat to somewhat concave; poorly developed ribbing on 

umbonal area of both valves." (sanclementensis) 

Holotype.-USNM 148012; of P. sanclementens'£s, syntypes UCLA 

38790, 38791. 

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

Formation, Pliocene; of P. sanclenwntens·£s, unnamed Pliocene 

strata, San Clemente Island, California. 

Supple'menta'ry descr·iption. -Pat1:nopecten healeyi is easily recognized by the flat-topped medially sulcated radial ribs on the right 

valve. Juvenile specimens are smooth in the early stage, but radial 

undulations of the anterior margin usually begin to form after the 

shell has attained a height of 3 to 5 mm. Some specimens remain 

smooth up to a height of 23 mm. The ribs on the right valve, especially those toward the anterior and posterior margins, begin to 

develop a slight medial sulcus after the shell has attained a height of 

10 mm, but such sulcations on the medial ribs are well developed 

only after a height of 30 to 40 mm has been attained. Occasionally the 

ribs on large specimens may bear two sulcations which thus divide 

the major ribs into three small riblets, but such forms, so far as 

known, have no taxonomic significance. (Hertlein and Grant, 1972, 

p. 185) 

Although intercalaries may be present in the right-valve inter-, 

spaces, they are not common, and a narrow unsculptured band may 

be present at the anterior and posterior margins of the right valve 

that is usually wider at the posterior side. 

A smooth form of P. healey?:, described as Pecten (Patinopecten) 

healey'/: Arnold smwlementensis Susuki and Stadum, tends to be 

relatively thin-shelled and has been found only in unnamed Pliocene 

strata on San Clemente Island, southern California (Vedder and 

Moore, 1967, p. 122, pl. 3, figs. 2-6, 8; Susuki and Stadum, 1978, p. 

10-12, figs. 18, 19). A fragment of a large right valve shows the disk 

to be smooth to about 30 mm, at which point strong dichotomous ribs 

appear with very narrow interspaces. An incomplete right valve 

that is almost 100 mm high has the disk smooth in the mid portion of 

the shell to about 40 mm, with the rest of the shell sculptured by very 

low, closely spaced dichotomous and trichotomous ribs. A large, 

incomplete, worn right valve, that was originally more than 145 mm 

long, has a smooth disk to 55 mm and shows subdued dichotomous 

ribs near the posterior margin; the largest specimen obtained was 

about 160 mm high, with the hinge about 75 mm long. A,small 

complete right valve that is 50 mm high is essentially smooth, 

although traces of the same rib pattern seen on the other right valves 

from San Clemente Island are visible in low-angle reflected light. 

These smooth right valves also have a wide unsculptured band at 

both the anterior and posterior margins. 

Three right valves from the San Diego Formation at Pacific 

Beach, Calif. (CAS 105, 547), have a smooth disk to 20 mm and the 

ribs somewhat subdued for an additional interval of about 10 mm, 

and one right valve has closely spaced low ribs that are not dichotomous on the midportion of the shell. 

·Woodring (in Woodring and Bramlette, 1950, p. 84) noted that the 

i nterspaces on many right valves of P. healeyi from the Santa Maria 

district are much narrower than the interspaces on right valves of P. 

healey1: from the San Diego Formation and that the right valves are 

more inflated. A few specimens from collections now available from 

the San Diego Formation show this same sculpture and valve inflation, as do some from the Niguel Formation of Pliocene age in the 

San Juan Capistrano quadrangle (USGS M2096, M2098). 

In one collection from the Fernando Formation (Pliocene), in the 

Newport Beach quadrangle, right valves with dichotomous and 

trichotomous ribs, right valves with narrow subdued ribs, and right 

valves with smooth disks to about 50 mm followed by low subdued 

ribs occur together. In another collection from the same area (USGS 

M5040) fragments show right valves of the smooth form, some with 

very closely spaced dichotomous ribs, and others with very closely 

spaced dichotomous and trichotomous ribs. On some specimens of 

right valves from this locality there is no unsculptured band at the 

posterior shell margin. 

The right valve of P. healeyi may extend as much as 10 mm beyond 

the left valve along the entire distal margin of the disk. A similar 

discrepancy between valves has been noted on Pai£nopecten cnun:-

nus (Gould), the Holocene genotype of Pat·£nopecten, which has also 

been collected from sedimentary rocks as old as Pliocene in age 

(Grau, 1959, p. 147; Moore, 1963, p. 63). 

Although the typical left-valve sculpture has been described as 

primary ribs with interspaces always bearing a secondary rib, it is 

common to find specimens that have a few smooth interspaces without a secondary rib, and even specimens with no secondary ribs are 

occasionally found. The left valve may bear 17 to 21 primary ribs; 18 

is the most common number. The umbonal angle, measured on the 

disk between ears. is between 110° and 120°, with 115° being the 

most common; a 120° umbonal angle is found on inequilateral specimens with a very enlarged anterior ear. 

The left-valve sculpture of specimens of P. healeyi from the San 

Diego Formation ranges from narrow rounded ribs with wide 

interspaces that each bear a fine intercalary riblet to left valves with 

wide square ribs that may bear a fine rib along the top and that may 

have some interspaces that do not bear an intercalary. The squareribbed forms usually begin with a sculpture of narrow rounded ribs 

that become flat when the shell reaches a height of about 60 mm. On 

some square-ribbed forms the intercalaries are fine and rounded, 

but on others, although the intercalaries are rounded, they are much 

wider. On some left valves the ribs tend to become obsolete near the 

ventral margin, a feature also seen on P. caur-inus (Moore, 1963, p. 

65). Some left valves are noticeably thinner than others that bear the 

same primary rib pattern. 

Four left valves were collected from unnamed Pliocene strata on 

San Clemente Island with right valves of the smooth form. Although 

no articulated specimens were found, it is assumed that these left 

valves represent the smooth form. They have unusually fine, narrow 

ribs, a bit more closely spaced than· is common, with some of the 

intercalaries as strong as the primary ribs (Moore, 1979, p. 5, fig. 3; 

Susuki and Stadum, 1978, fig. 19). One of these left valves is about 

160 mm high. 

On some left valves the shell curves upward along the ventral 

margin away from the soft parts, probably in response to pressure 

from the larger right valve. This extension of the left valve is usually 

exceptionally thin, with obsolete ribs, rarely preserved, and may be 

more common than its preservation indicates. 

If the right-valve primary ribs are strongly dichotomous, in 

essence producing another interspace, the usual left-valve response 

is to produce a strong secondary rib about equal in size to that of the 

space produced by the dichotomy. On these left valves the primary 

ribs will also be larger than average and square rather than 

rounded. If the right-valve disk is smooth followed by low primary 

ribs that are only shallowly dichotomous, the left valve will usually 

respond with small rounded primaries and with secondaries of 
TERTIARY MARINE PELECYPODS: PROPEAMUSSIIDAE AND PECTINIDAE B83 

almost equal size. On articulated specimens one can usually predict 

the sculpture of either valve by simply examining the opposing 

valve. 

The left anterior auricle is larger than the right anterior auricle 

on large specimens. The byssal notch is convexly folded and elevated 

above the rest of the auricle, a feature also noted on P. ca:w·inus, and 

the left anterior auricle is concavely folded toward the right anterior 

auricle opposite the byssal notch thus bringing the auricles closer 

togethet·. The fold on the left anterior auricle usually becomes more 

pt·onou need as the shell grows larger so that on very large specimens 

the byssal opening is almost closed and presumably not functional 

for byssal attachment. 

The left-valve anterior auricle of P. healey·i may be higher as well 

as longer than the posterior auricle. Marked enlargement of the left 

anterior auricle is usually characteristic of large specimens, but it is 

sometimes seen on juvenile shells. The enlargement is usually coincident with the increased flexure of the auricle and the resultant 

closing of the byssal gap. 

The resilial pit on the right valve is bordered on each side by a 

nart·ow, sharp pt·ojecting ridge. The resilial piton left valves may be 

bordered by a ridge that is followed by a groove and a second shorter· 

ridge or may be bordered by only one ridge. 

Small patches of an imbricated microsculpture, si~ilar to that 

found on many different pectin ids such as Ve1·t·ipecten (Moore, 1963, 

p. 63) and Chla:m.y.'{ (Verrill, 1897, p. 73). and on some, if not all 

species referred to Yabepecten by Masuda (1963, p. 22, fig. 4), are 

pt·eserved on some left valves of P. healey·i, and one juvenile specimen 

shows the entire surface to be so sculptured (pl. 40, fig. 5). Both the 

right (pl. 40, fig. 3) and the left valves of Pat?:nopecten yessoen.,n:s bear 

this microsculpture. 

One well-preserved juvenile left valve of P. hea.ley·1: was found that 

had the imbricated microsculptu're well preserved and was also 

small enough to be mounted without destruction for the scanning 

electron microscope. The specimen was scanned from the dorsal to 

the ventral margin in the center of the disk between the same two 

ribs, and the progressive development of the microsculpture can be 

seen (Moore, 1979, p. 11, figs. 1-3; pl. 12, figs. 1-3). 

Com.1)(l:l"l:son .. -"The ribs on large left valves of P. lohn: are wide 

and divided, whereas on P. healey£ they are narrow and not divided, 

or on some very large left valves are moderately wide and faintly 

divided by one or mot·e shallow grooves. Right valves of P. loh1·i 

generally have a strong secondary rib in the space between the 

primary ribs. whereas on right valves of P. heale1ri secondary ribs 

are absent or, if present generally are weak. Some right valves of P. 

loh:n:, however, lack secondary ribs or have weak secondaries. Left 

valves of both species have secondaries. Owing to the presence of 

divided ribs on both valves of P. lohn:, right and left valves are 

difficult to distinguish unless the ears are preserved, whereas right 

and left valves of P .. heale?J'I: are readily differentiated." (Woodring, 

1950, p. 83) 

The right valve of the holotype of P. lohn: is more inflated than is 

usual for P. healey·i; the primary ribs are higher, dichotomous at an. 

earlier stage, fewer in number (14), and therefore more widely 

spaced. 

The left valve of the holotype of P. lohn: bears fewer (12) primary 

ribs than P. hea.ley·i, and these ribs are therefore more widely spaced. 

The ribs are also higher, especially on the younger portion of the 

shell, than is common for P. healeyi. 

Yabepecten. tokwnaga·i (Yokoyama) differs from P. healey?: in rightvalve sculpture, having low, rounded, closely spaced ribs. In addition, an imbricated microsculpture is present on the right valve 

(Masuda, 1963, pl. 12, fig. 4), and this sculpture has been found only 

on left valves of P. healey?:. 

The marked consistent dichotomy of the right-valve ribs separates 

P. healey·1: from other Pat·inopecten, with the exception of P. lohri, 

which has already been discussed. Although several species such as 

Pat·inopecten m·egonensis (Howe), Pat?:nopecten coosensis (Dall), and 

Pat1:nopecten m·egone?un:s cancellosus Moore may have a few dichot-

.omous ribs at the anterior and posterior margins of the right valve, 

none bear low, flat dichotomous ribs over the entire shell surface. 

(Moore, 1979, p. 7) 

"YabepectencondondHertlein)(Hertlein, 1925, p. 41, pl. 4, figs. 8, 

9; Masuda and Addicott, 1970, p. 153-156, figs. 1, 3-9) has a large 

smooth area on the umbonal disk and therefore somewhat resembles 

the smooth form of P. healeyi * * *. Y. condoni differs by having a 

deeper byssal notch than the smooth form of P. healeyi and radial 

ribs that are less distinct and rarely divided." (Vedder and Moore, 

1976, p. 122) 

"Pecten healey·i is quite distinct from P. p1·opatulus and differs in 

the more numerous and more deeply sulcated ribs on the right valve, 

finer ribs on the left valve and smaller byssal fasciole beneath the 

.right anterior ear." (Hertlein and Grant, 1972, p. 185) 

Geograph1:c range.-Northern California to Baja California Sur. 

Geologic range.-Miocene(?) to Pleistocene(?). 

Occun·ence in the Caliform:as.-Miocene and Pliocene: Capistrano 

(Kern and Wicander, 1974), Etchegoin (Nomland, 1917a; Barbat 

and Galloway, 1935), and Purisima (Arnold, 1906) Formations, and 

Tahana Member, Purisima Formation (Cummings and others, 1962; 

Kern, 1973; Durham and Morgan, 1978); Pliocene: Almejas Formation (Minch and others, 1976), Falor Formation (Moore, 1979), 

Foxen Mudstone (Woodring, 1950), Cebada and Graciosa Members, 

Careaga Sandstone (Woodring, 1950), Niguel (Vedder, 1960), San 

Diego (Arnold, 1906; Hertlein and Grant, 1972) and San Joaquin 

(Stanton and Dodd, 1976) Formations, and unnamed Pliocene strata, 

San Clemente Island (Vedder and Moore, 1976; Susuki and Stadum, 

1978); Pliocene and Pleistocene: Fernando (Arnold, 1907a; Moody, 

1916; Soper and Grant, 1932; Vedder, 1972), Merced (Moore, 1979), 

Pico (Winte~er and Durham, 1962), and Saugus (W. 0. Addicott, 

written commun., 1978) Formations: Pleistocene(?): basal Las Posas 

Formation (Hall and Redin, 1967). 

Habitat.-"This species lived in warm water unlike its northern 

relative Pecten caun:nus Gould * **"(Hertlein and Grant, 1972, p. 

185). 

Patinopecten ca·urinus (Gould) 

Plate 38, figure I; plate 39, figure 5 

Pecten caur1:nus Gould, 1850, p. 345. 

Pecten (Patinopecten) caurhms Gould. Arnold, 1906, p. 101-103, pl. 

38, figs. 1, 1a, 1b; pl. 39, figs. 1, 2. Grant and Gale, 1931, p. 

195-ioo, pl. 6, fig. 4. Grau, 1959, p. 145-148, pl. 54 (see for 

synonymy). 

Pat?>nopecten cau1·inus (Gould). Woodring, 1946, p. 81, pl. 32, fig. 17; 

pl. 33, fig. 1. Addicott, 1974, pl. 1, fig. 6. 

Pat1:nopecten (Patinopecten) caurinus (Gould). Roth, 1979, p. 248-

252, pl. 2, figs. 1, 2, 8; pl. 3, figs. 5, 9. 

Pecten heermannii Conrad, 1855b, p. 267. 

Pecten meeki1:_Conrad, 1857a, p. 313. 

Orig1:nal descript1:on.-"T. trigono-orbicularis, haud crassa, inequivalvis, sub-equilateralis; valva superior convexiuscula, rubra, 

striis concentricis tenuibus insculpta, costis humilibus rotundatis 

vel interdum subduplicatis ad 20 ornatis; valva inferior convexa, 

alba, versus marginem rubricans, radiis ad 22 elevatis, quadratis, 

longitrorsum stria tis;· natibus rosaceis compress is; auribus transversis, sub-equalibus, radiatim striatis: intus lactea, rosaceo fimbriata. Long. 2%; !at 2~; alt. 1 poll [68.8 mm, 56.3 mm, 25 mm]." 

Holotype.-USNM 5954; of heermanni1: ANSP 14446; of meeldi 

USNM 13333. 
B84 PALEONTOLOGY OF CALIFORNIA AND BAJA CALIFORNIA 

Type locality.-Puget Sound, Wash. Holocene; of heermannii, 

unknown; of meekii, San Rafael Hills [T. 8 N., R. 29 W., Santa 

Barbara County]; of merriami, San Felician Creek, near Piru [Santa 

Susana quadrangle], Ventura County, Pico Formation, Pliocene and 

Pleistocene. 

Supplementary descn:ption.-"Shell averaging about 150 millimeters in altitude, slightly longer than high, valves much compressed (the right generally slightly more convex than the left), 

equilateral, and with smooth margins; sides straight or only slightly 

concave above. Right valve with 20 to 25 strong, flat-topped squarish 

ribs, which, in some well-preserved specimens, show faint obsolete 

radial striae; inters paces flat-bottomed and about equal in width to 

the ribs; whole surface of disk sculptured by fine incremental lines; 

hinge line less than one-half length of disk; anterior ear only very 

slightly longer than posterior, ornamented with fine, sharp, incremental lines, but generally having no radial sculpture whatever; 

byssal notch prominent; posterior ear rectangular behind, and with 

sculpture similar to anterior. Left valve slightly less ventricose than 

right, with narrow rounded ribs and wide concave-bottomed interspaces; surface ornamented by fine, regular, raised, wavy, concentric 

lines, and sometimes more or less tesselated; ears obliquely truncated 

and sculptured with sharp incremental lines and sometimes by obsolete radiating ridges." (Ar!told, 1906, p. 102) 

"Specimens of this species show considerable variation in the ratio 

of the width of the ribs to the width of the interspaces; this seems to 

be especially true in the Scotia area, although this may be a result of 

the large number of specimens collected. The writer feels that these 

differences reflect the normal variation within the species.". 

(Faustman, 1964, p. 116) 

"Shell large, average adult specimens measuring 150 mm in altitude, slightly oblique, inequivalve and compressed; auricles nearly 

equal. Right valve larger than left and having 18 to 22 squarish 

flat-topped ribs which occasionally show faint radial striae and/or 

longitudinal ridges; inters paces flattish and becoming wider toward 

ventral margin; fine concentric growth lines covering disk. Posterior auricle flat, with perpendicular margin and strong incremental 

lines; anterior auricle rather narrow, with faint (often obsolescent) 

radial ridges, sharp incremental lines and a prominent convex fold 

next to the disk; byssal notch moderately deep and no ctenolium. Left 

valve smaller than right and slightly less convex; 18 to 22 low and 

gently-rounded ribs; fine concentric lamellae covering disk. Posterior auricle having strong incremental lines and sometimes faintly 

ridged; anterior auricle having an oblique margin, a prominent 

concave fold and strong incremental lines. 

"The holotype was a young shell. In 1918 W. J. Eyerdam dredged a 

specimen outside of Wrangell Narrows, Alaska, having some of the 

ventral margin broken off but still measuring 288 mm in length and 

198 mm in height, the largestso far recorded." (Grau, 1959, p. 147) 

Comparison.-"The Japanese subspecies Pecten caurinus yessoen-

,<n:s (Jay) differs from P. caurinus in the following respects: right 

valve considerably more convex, auricles higher and longer, byssal 

notch much less pronounced * * *" (Grau, 1959, p. 147) 

The marked consistent dichotomy of the right-valve ribs separates 

P. healey1: from P. caurinus. (Moore, 1979, p. 7) . 

Geographic Tange.-Living: Off Sand Point, Shumagin Islands, 

Alaska, to Point Sur, Calif.; fossil: northern to southern California. 

Geologic Tange.-Miocene through Holocene. 

Occurrence in Calijorn1:a.-Miocene and Pliocene: Purisima 

Formation (Arnold, 1906); Pliocene: Lomita Marl Member, San 

Pedro Formation (Woodring, 1946), and Ohlson Ranch Formation 

(Peck, 1960); Pliocene and Pleistocene: Fernando (Arnold, 1906; 

Moody, 1916; Soper and Grant, 1932; V citder, 1972), Merced 

(Arnold, 1906), and Pico (Grant and Gale, 1931) Formations, Rio 

Dell Formation, Wildcat Group (Faustman, 1964), San Pedro Sand 

(Woodring, 1946), Santa Barbara Formation (Waterfall, 1929); 

Pleistocene: Anchor Silt Member, San Pedro Formation (Rodda, 

1957) and Timms Point Silt Member, San Pedro Formation (A. 

Clark, 1931; Woodring, 1946). 

Habitat.-PatinopectencauTinus lives at depths of 15 to 275m and 

in British Columbia its maximum population density occurs at about 

35 m on a mixed sand and mud bottom (F. R. Bernard, written 

commun., 1976). In more southern waters the greatest density is 

between 55 and 85 m (Fitch, 1953, p. 44). In the natural habitat the 

species has been observed lying in small depressions that are presumed to be a result of current scour around the shell. P. caun>nus is 

byssally attached to a size of about 3 to 4 em in shell diameter (F. R. 

Bernard, written commun., 1976) and has a ctenolium during its 

younger stage. The predators of P. cauTinus are Octopus and the 

large sun star Pycnopodia; juveniles are attacked by crabs (F. R. 

Bernard, written commun., 1976). (Moore, 1979, p. 10-11) 

Genus LEOPECTEN Masuda, l97la 

Genotype.-Pecten (Patinopecten) bakeri Hanna and Hertlein, 

1927. Pliocene, Baja California Sur. 

Original description.-"Shell large, gently inflated, of medium 

thickness, longer than high, equilateral, subequivalve, right valve a 

little more inflated than left valve which is nearly flat in younger 

stage but tends to become inflated with growth; right valve with 

distinct, perpendicular sided, flatly round-topped radial ribs which 

are sculptured with sometimes faint, fine radial threads, fine intercalary threads and fine, rugose incremental lines; left valve with 

distinct but low, narrow radial ribs usually sculptured with a few 

faint, fine radial threads, a few fine intercalary threads, and raised, 

regularly spaced, rugose, fine incremental lines; auricles large; 

right anterior auricle angulated at end, with very wide and shallow 

byssal notch; hinge with very simple, low, fine cardinal crura with 

fine provinculum and wide and shallow resilial pit; auricular crura 

well developed, terminating distally in a distinct oblong denticle at 

each extremity; interior surface with distinct paired internal ribs at 

lower part." 

SupplementaTy description.-Leopecten "resembles Pat1:nopecten 

externally but Pat1:nopecten lacks paired internal ribs and has a well 

developed byssal notch below the right anterior auricle. A ?nu.<;,<n:opecten ***is distinguishable from Leopecten by its radial ribs which 

tend to become obsolete towards the ventral and lateral margins, 

lack of radial threads on the surface of the radial ribs and no intercalary threads in the interspaces between the radial ribs. * * * 

Flabellipecten * * * is distinguishable from the present one [Leopecten] by its rather more inflated right valve, plano-convex left 

valve, rather small auricles and more distinct and complicated cardinal crura." (Masuda, 1971a, p. 171) 

Geograph1:c range.-Baja California Sur. 

Geolog1:c range.-Pliocene (table 19). 

Habitat.-Considered from the standpoint of the associated fauna, 

Leopecten may have been a tropical or subtropical genus (Masuda, 

1971a, p. 171). 

TABLE 19.-Geologic and geogra,ph1:c d1:stn:but1:on of the genus 

Leo pecten 

[PI= Pliocene] 

Species 

Genus Leopecten: 

bakeTi bakeTi (Hanna and Hertlein) ............. . bakeTi diazi (Durham) .................................... .. marqueTensis (Durham) .................................. .. 

Baja California 

NOrte Sur 

PI 

PI 

PI 
TERTIARY MARINE PELECYPODS: PROPEAMUSSIIDAE AND PECTINIDAE B85 

Leopecten bakeri bakeri (Hanna and Hertlein) 

Plate 40, figure 4 

Pecte·n (Pat·inopecten) bake?"'/: Hanna and Hertlein, 1927, p. 153, pl. 5, 

fig. 1. 

Pecten (Ja,?rint,) stea,?'?1..'i1>1: var. baken: Hanna and Hertlein. Grant and 

Gale, 1931, p. 224-225, in part; not pl. 4, figs. la, lb. 

Pat·inopecten baken: (Hanna and Hertlein). Durham, 1950, p. 66, pl. 

12, fig. 1; pl. 13, fig. 7. 

Leo1Jecten bake·r£ (Hanna and Hertlein). Masuda, 1971a, p. 171-172, 

pl. 20, figs. 1, 2. Addicott, 1974, pl. 2, fig. 1. 

Orim:nal de.'W?"'ipt·imi.-"Left valve, large, subcircular, moderately 

convex, moderately thick; about 23 to 25 radiating square sided ribs 

separated by interspaces a little wider than the ribs, each rib ornamented with three small riblets, one on each shoulder and a middle 

riblet which is a little higher than the two other riblets; inters paces 

ornamented by three small riblets, the middle one usually slightly 

more prominent than the other two; ribs and interspaces both 

covered by fine, fairly sharp concentric lines of growth; ears subequal, setoff from beak by sharp squarish shoulders, ornamented by 

about eight or nine radiating rib lets which are crossed by concentric 

incremental lines. Length approximately 150 mm.; height approximately 132 mm.; apical angle approximately 123°." 

Holotype.-CAS 1865. 

'Pype loca.hty.-CAS 794. Baja California Sur. San Marcos Formation (Masuda, 1971a), Pliocene. 

Su.p1Jlenwnta:ry dm;c·rl:pt?:on.-"Sheiiiarge, longer than high, equilateral, nearly equivalve but right valve a little more convex than 

left; surface with distinct radial ribs and raised, regularly spaced, 

distinct incr·emental lines; right valve with about 23 rather low, 

flat-topped, square sided radial ribs which are broader than their 

inter·spaces and with a few faint, fine radial threads on their surface 

near ventral margin; radial threads on surface of radial ribs appear 

at about middle part of shell and tend to become somewhat distinct 

towards ventral margin; interspaces between radial ribs with an 

intercalary thread, appearing at about middle part of disc and 

tending to become distinct towards ventral margin, also with secondary intercalary threads near ventral margin; auricles rather large, 

with a very shallow byssal notch below anterior one, provided with 

rather distinct concentric lines and rarely with a few faint, fine 

radial threads; inter·ior surface provided with paired internal ribs 

that are distinct near ventral margin; hinge with very low, simple, 

fine cardinal crura, wide and shallow resilial pit with very fine, flat, 

intemal ridges which diverge downward, and auricular crura 

which terminate distally in a distinct, oblong denticle at each 

extremity." (Masuda, 197la, p. 172) 

Com,1Ja:rison.-"This species may easily be distinguished from 

Pecte·n lwa,ley·1: A mold by the less prominent ribs and by the greater 

apical angle. It is obviously of the same stocks asP. cau-rinus Gould, 

rather than the P. :-;tea:rnwi?: Dall stock to which Grant and Gale 

assigned it. Their· figured specimen appears to be P. bake?"'/: subsp. 

cb:az·i n. subsp. P. bake·n: may be separated from the subspecies d·iaz1: 

by having the interspaces and ribs of the right valve of approximately the same width." (Durham, 1950, p. 66) 

Geognt,1Jh:ic ·mnge.-Baja California Sur. 

Geolom:c ·ra,nge.-Piiocene. 

Occu:rrence 'h1, Baia Cahjo?·m:a.-Gioria (Stump, 1979), Infierno 

(Stump, 1979), and San Marcos (Masuda, 1971a) Formations. 

Leopecten bakeri diazi (Durham) 

Plate 39, figure 2; plate 40, figure 2 

Pa.t-hwpecten baken: d·ia,z·1: Durham, 1950, p. 66, pl. 12, fig. 2; pl. 13, 

fig. 4. 

Leopecten baken:diazi(Durham). Masuda, 1971a, p. 172-173, pl. 20, 

figs. 3, 4. 

Pecten (Janira) stearnsii Dall var. bakeri Hanna and Hertlein. 

Grant and Gale, 1931, 1:n part, pl. 4, figs. la, lb. 

On:ginal descript1:on.-"At a number of localities Patin.opectens of 

the P. baken: stock may be separated from the typical form by the 

partial or complete obsolescence of the anterior and posterior areas 

of fine ribbing and by the squarer sides of the major ribs of the left 

valve. On the same valve, the secondary rib lets on the primary ribs 

are commonly entirely absent or very feeble, and the tertiary intercalaries in the interspaces are missing. In the central ar~as of the 

right valve the primary ribs are 1~-lYz times as wide as the interspaces, whereas in the typical form they are approximately of equal 

width." 

Holotype.-UCMP 15968. 

Type locality.-UC A3566. Baja California Sur. Carmen Formation, Pliocene. 

Supplementary description.-"This subspecies is characterized by 

its large, compressed, subequivalved shell which is longer than high, 

right valve with squarish, distinct radial ribs with very faint, fine 

threads on surface of radial ribs near ventral and lateral margins, 

an intercalary thread between radial ribs in adult specimens, and 

raised, rugose, regularly spaced incremental lines; somewhat angulated auricles with a wide, shallow byssal notch below anterior 

auricle. It is sculptured with fine concentric lines and several faint, 

fine radial threads; the left valve having somewhat square sided 

radial ribs in younger stage, with three fine radial threads, and an 

intercalary thread in interspaces between radial ribs, crossed by 

raised, rugose, regularly spaced, fine incremental lines; simple cardinal crura; shallow resilial pit; and paired internal ribs and distinct 

auricular crura which terminate distally in an oblong denticle at 

each extremity." (Masuda, 1971a, p. 172-173) 

Compan:son.-"Leopecten bakeri (Hanna and Hertlein) differs 

from the present subspecies in having the right valve with many fine 

radial threads at lateral margins and the left valve with perpendicular sided major radial ribs, distinct radial threads on surface of 

radial ribs and tertiary intercalary threads in interspaces between 

radial ribs." (Masuda, 197la, p. 172-173) 

Geograph1:c 1·ange.-Baja California Sur. 

Geolog·ic m.nge.-PI iocene. 

Occurrence 1:n Baja California.-Carmen Formation. 

Leopecten marquerensis (Durham) 

Plate 39, figure 3; plate 40, figure 1 

Pat?:nopecten marque1·en1n:.~ Durham, 1950, p. 67, pl. 14, figs. 1, 2. 

Leopecten nw?·queren.'n:s (Durham, 1950). Masuda, 197la, p. 173-17 4, 

pl. 21, figs. 1, 2. 

On:g1:nal descript?:on.-"Sheiiiarge; in general outline, ornamentation, and size very similar toP. baken:. Right valve with about 20 

prominent primary ribs, lYz times as wide as the interspaces. Anterior and posterior to these are several finer ribs. Inters paces without 

intercalaries. Left valve with an equivalent number of low inverted 

V-shaped primary ribs, with three secondary riblets, one on each 

side and one at apex of V. Interspaces with a single intercalary 

riblet. On an unworn specimen the posterior margin has an area of 

fine ribbing similar to that on typical P. baken:." 

Holotype.-UCMP 15475. 

Type locality.-UC A3518. Baja California Sur. Marquer Formation, Pliocene. 

Supplementa·ry descr1:pt1:on.-"This species is characterized by its 

subequivalved shell, in which the right valve is a little more inflated 

than the left valve; with a very wide and shallow byssal notch below 

the right anterior auricle; several fine radial threads on the auricles 
B86 PALEONTOLOGY OF CALIFORNIA AND BAJA CALIFORNIA 

TABLE 20.-Geologic and geographic distribut1:on of the genus Lituyapecten 

[Pie= Pleistocene: PI= Pliocene: M =Miocene] 

California 

Species Northern Southern 

Baja Cali Cornia Norte Sur 

Genus L1:tuyapecten: 

dilleri (Dall) ---------------------------------------- falorensis (MacNeil) ------------------------

Pl,Ple 

PI 

PI.Ple 

M, PI 

M,Pl 

M(?),Pl PI 

pun:simaensis (Arnold) ___________________ _ 

turneri (Arnold) --------------------------------

of the left valve but those of the right valve with only concentric lines; 

radial ribs on right valve without radial threads on their surface." 

(Masuda, 1971a, p. 173) 

Comparison.-"The inverted V-shaped ribs with three secondaries on the left valve together with the absence of any intercalaries on. 

the right valve, and the central primary ribs of the right valve being 

half again as wide as the interspaces separates this species from P. 

bakeri and its subspecies diazi." (Durham, 1950, p. 67) 

"This species differs from the other species of Leopecten in having 

no radial threads on the surface of the radial ribs and in the interspaces between the radial ribs of the right valve." (Masuda, 1971a, p. 

173) 

Geographic range.-Baja California Sur. 

Geolog1:c range.-PI iocene. 

Occurrence in Baja California.-Marquer Formation. 

Genus LITUYAPECTEN MacNeil, 1961 

Differs from Patinopecten in having one to several rows of frill-like 

flanges on the rounded to flat-topped ribs of the left valve. 

Geographic range.-Alaska to Baja California Sur. 

Geologic range.-Oligocene to Pliocene (table 20). 

Lituyapecten falorensis (MacNeil) 

Plate 41, figures I, 5 

Pecten oregonensis Howe var. Manning and Ogle, 1950, p. 23-24, pls. 

6, 7. 

Patinopecten (Lituyapecten) falorensis MacNeil, 1961, p. 234-235, 

pl. 38, figs. 1, 3; pl. 44, figs. 2, 4; pl. 45, figs. 2, 4; pl. 46, figs. 1-4. 

Original description.-"Shell moderately large; suborbicular to 

weakly extended posteriorly; valves moderately inflated; right valve 

slightly more inflated than left valve; shell moderately thin. Posterior dorsal margin moderately concave, and anterior margin nearly 

straight; left valve with low but sharp steplike submarginal slopes, 

and right valve slopes less sharp because of inflation of ears. Dorsal 

margin of ears straight. Ears sculptured by radial riblets with 

moderately strong beads, about seven riblets on posterior ear of left 

valve; posterior ears longer and with stronger radial riblets than 

anterior ears; ,no denticles along byssal sinus; dorsal margin of left 

ear of left valve with a weak swelling or fold. Ribs 21 to 23. Right 

valve often having a split rib, one segment having no counterpart on 

left valve; right valve ribs broad with undercut sides, interspaces 

narrow and deep; bottoms flattened; central ribs flattened or 

rounded on top; terminal ribs with a median sulcus which at the 

margin may be nearly as deep and wide as the primary interspaces. 

Left valve ribs moderately broad with a row of short flanges or 

denticles along each side; central area depressed and troughlike; 

M to Pie 

three terminal ribs on each side narrow and with a single row of 

short flanges on their crest; interspaces round-bottomed and narrower than the ribs on some specimens, wider on others, no interstitial riblets on any specimens observed. Juvenile microsculpture 

unknown." 

Holotype.-UCMP 34172. 

Type locality.-UC A4233. Humboldt County, Calif. Falor Formation, Pliocene. 

Comparison.-"The specimen figured by Manning and Ogle, 

refigured here and made the holotype of the species, is the only 

specimen of a yakatagensis-like Lituyapecten figured previously 

other than the type of yakatagens1:s itself. Its relationship to yakata,-

gensis was not recognized and instead, it was identified tentatively 

as a variety of P. oregonens1:s Howe, a species described from the 

Empire formation of western Oregon. * * * it is very difficult to 

identify right valves, even on specimens whose left valves are very 

dissimilar. 

"There are two specimens in the Manning and Ogle collection 

·besides the holotype. They are smaller than the type, but they appear 

to have narrower ribs than the corresponding stage on the type. In 

this respect they approach some of the typical specimens of P. purisimaensis. The left valves of these two specimens have narrow but 

definitely flat-topped ribs with denticulate margins***. Typical P. 

(L.) purisimaensis on the other hand, has narrow rounded ribs over 

most of its disk with two or three of the central ribs slightly wider 

and having a weak concavity along the crest. * * * The Purisima 

formation also contains a form that has wide ribs on the right valve 

and broad, flat-topped ribs with marginal denticles on the left valve 

* * *, and that compares favorably with the type of falorensis. 

"Although it is difficult to say how many species are involved here 

and, if they are distinct, just what the varietal range of each species 

is, it is fairly certain that purisimaensis and falore?un:s are very 

closely related. P. (L.) yakatagensis is a highly variable species if all 

the specimens here referred to it are really conspecific. The same 

range of variation has not been noted in lituyaensis, but possibly all 

variants of that species have not been found. If approximately the 

same range of variation could be demonstrated for lituya,ens·is, a 

strong case for considering falorensis·as a variety or, at most, a 

subspecies of purisimaensis could be made. To state the problem 

another way, it is not known whether purisimaensis and falorensis 

represent divergent stocks of common but not too distant ancestry or 

whether the three species, yakatagensis, lituyaensis, and pun:.'n:-

maensis (includingfalorensis) are linear elements of one very variable stock, no parts of it having been clearly set off by geographical 

isolation. If the latter were so, all the variants existing at any particular instant of time belonged to one species, whereas the mean of 

variation shifted sufficiently through time to make at least three 

distinct species recognizable." (MacNeil, 1961, p. 234) 

Geographic range.-Northern to middle California. 

Geologic range.-Miocene to Pliocene. 

Occurrence in California.-Miocene and Pliocene: Purisima 
TERTIARY MARINE PELECYPODS: PROPEAMUSSIIDAE AND PECTINIDAE B87 

Fot·mation (MacNeil. 1961), and Tahana Member, Purisima Formation (Durham and Morgan, 1978): Pliocene: Falor Formation (MacNeil, 1961). 

Lituyapecten purisimaensis (Arnold) 

Plate 41, figures 3, 4 

Pect.e·n (Pa.l'l>nopect.wn) P'l.l.'l"l:s·/:nw.en.'{·is Arnold, 1906, p. 105, pl. 34, fig. 

3; pl. 35. figs. 1. 1a. Grant and Gale, 1931, p. 194, pl. 6, fig. 3. 

MacNeil, 1961, p. 233, pl. 44, figs. 1, 3. 

Patinopecten (Lituyapecten) purisi~nsis (Arnold). Peck, 1960, pl. 

21. fig. 14. 

Orim>no.l desc·n:pt·ion .. -"Shell averaging about 125 millimeters in 

altitude, length same as height, valves both equally well compressed, 

equilateral, and with the margins smooth; base regularly rounded; 

sides t·elatively short, straight. sloping at a moderate angle. Right 

valve with about 24 prominent, T-rail-shaped ribs, flattened and 

sometimes faintly dichotomous above, overhanging deep, channeled, 

flat-bottomed interspaces, which are about equal in width to the 

ribs: whole surface of disk with incremental sculpture, which develops into prominent scales on the sides of the ribs; hinge line equal to 

about two-fifths length of disk; anterior ear only slightly longer than 

posterior, sculptured by about three prominent radiating ridges and 

numerous imbricating incremental lines; byssal notch prominent, 

but not deep, being equal in width to one-half width of ear; posterior 

ear obliquely truncated, and ornamented by about three prominent 

radiating ribs and imbricating incremental lines. Left valve with 

narrow, rather sharp, concave-sided ribs and wide concavebottomed interspaces; surface with fine incremental sculpture; ears 

obliquely truncated and sculptured similar to those of right, except 

that the radiating ridges are finer and more numerous." 

Holotype.-CAS/SV 3. . 

11!Jpe locab:ty.-North of mouth of Pescadero Creek [Santa Cruz 

quadrangle, San Mateo County), Calif. Purisima Formation, 

Pliocene. 

Su.1Jplenwn.ta.1·y de.•wript·1:on.-"The typical form of the species has 

rather narrow ribs on its right valve, and most of the ribs have short 

mat·ginal denticles or flares recalling those on the terminal ribs of P. 

(/..,.) l·1:l'u.yaens·is. * * * The left valve has narrow ribs with wide, 

round-bottomed interspaces. Two or three of the central ribs are 

slightly wider with a weak concavity along the crest, but most of the 

ribs are narrowly rounded on top and bear a single row of denticles 

or narrow flanges along their crest. They are broken or worn on most 

specimens observed, and even on the fairly well preserved specimen 

figured here, only their base is preserved." (MacNeil, 1961, p. 233) 

Com.po:l"ison .. -"Pat·in.opecten tu-rne?"l: Arnold from the Pliocene of 

the Tomales Bay region, California, was regarded by Grant and Gale 

* * *as a synonym o.f puris·imaens·1:s. If Grant and Gale were influenced by an error in ·Arnold's statements about his figured specimens they did not say· so. Arnold figured three specimens, two of 

them as right valves and ·one as a left valve; however, all three of 

Arnold's specimens are left valves. This gave him an erroneous 

concept of his supposed new species and made it appear to be very 

different from p·u:n:.cr1:ma.ens·is. Actually pun:.'n:ma.en.'n:s and turneri 

are closely related, but some good specimens of turneri ***show a 

well-defined sulcus on the right valve ribs that is not found in puriwinl.aen.'H:s. These species should probably be kept separate. 

"Pat·1:nopecten (L.) pu:riwinw.en.'n:s is related toP. (L.) dilleri (Dall), 

* * *. P. (L.) d·alen: usually has coarse flanges on both valves, those of 

the right valve being either single and crossing the ribs * * *, or 

divided and along the margins of the ribs * * *. The left valve has 

strong single flanges***. It is doubtful if d?:lle? .. ishould be regarded 

as a variety of coosenS'is as was done by Grant and Gale***. In view 

of the Alaskan forms now known, it seems more likely that dilleri 

and coosensis stem from different early Miocene forms; d1:llen: from ' 

poulc·reekensis, and coosen.cn:s from an early variant of yakatagens1:s. 

"In spite of its apparent close relation to dille1·i, pur1:shnaensis 

·appears to be more closely related to falm·ensis * * *. In fact, it is 

difficult to say from the known specimens whether two species are 

represented in the Purisima formation, purisim.aensis andfalo?·en-

.c;is, or whether all the specimens in question should be regarded as 

belonging to one greatly variable species. For the time being they 

are treated as two species although it may later be found preferable 

to treatfalm·ensis as a subspecies of pun:.'n:maens1:s. (MacNeil, 1961, 

,p. 233) 

Geogmph-ic m.nge.-Middle California. 

Geolog1:c 1·ange.-Miocene to Pliocene. 

OccmTence 1:n Cal?jornia.-Miocene and Pliocene: Purisima 

(Arnold, 1906), and Tahana Member, Purisima (Cummings and 

others, 1962; Durham and Morgan, 1978) Formation; Pliocene: Ohlson Ranch Formation (Peck, 1960). 

Lituyapecten turneri (Arnold) 

Plate 37, figures I, 2 

Pecten (Pat?:nopecten) tunw1·i Arnold, 1906, p. 106, pl. 34, fig. 4; pl. 

35, figs. 2, 3. 

Pat?:nopecten turne1·i (Arnold). Peck, 1960, pl. 21, figs. 15, 16. 

· Original desc1·ipt1:on.-"Shell averaging about 70 to 80 millimeters in altitude, length same as height, both valves equally compressed, equilateral, and with smooth margins; base regularly 

rounded; sides nearly straight and sloping at a rather low angle. 

Right valve with eighteen to twenty-two high, narrow, flat-topped, 

concave-sided ribs, which,· in most cases, show a distinct medial 

sulcus after reaching a length of 30 or 35 millimeters; interspaces 

much wider than ribs, round bottomed and sometirpes orn~mented 

near the end by a faint intercalary rib let; whole surface of disk finely 

concentrically striated; hinge line slightly longer than one-half 

length of disk; ears equal, rectangularly truncated; anterior ear 

sculptured by four or five prominent radiating ridges and numerous 

fine incremental lines; byssal notch shallow but distinct; post~rior 

ear with sculpture similar to anterior. Left valve with narrow 

rounded ribs, which are separated by round-bottomed and concavesided interspaces much wider than the ribs; surface sculptured by 

fine, distinct, wavy, concentric lines; ears as in right valve, except 

lacking by~sal notch. Hinge as in P. caurinus." 

Holotype.-CAS/SV 430. 

Type locaWy.-Arroyo San Antonio, Tomales Bay, Marin County, 

Calif. Merced Formation (Keen and Bentson, 1944), Pliocene. and 

Pleistocene. 

Comparison.-"Patinopecten turneri Arnold*** was regarded by 

Grant and Gale * * * as a synonym of purisimaensis. If Grant and 

Gale were influenced by an error in Arnold's statements about his · 

figured specimens they did not say so. Arnold figured three specimens, two of them as right valves and one as a left valve; however, all 

three of Arnold's specimens are left valves. This gave him an erroneous concept of h-is supposed new species and made it appear to be 

very different from purisimaensis. Actually puris1:maensis and turneri are closely related, but some good specimens of turneri ***show 

a well-defined sulcus on the right valve ribs that is not found in 

purisimaensis. These species should probably be kept separate." 

(MacNeil, 1961, p. 233) 

Geographic range.-Middle California. 

Geologic range.-Miocerie to Pleistocene. 
B88 PALEONTOLOGY OF CALIFORNIA AND BAJA CALIFORNIA 

Occurrence in Calijornia.-Miocene and Pliocene: Purisima 

(Arnold, 1906), and Tahana Member, Purisima (Durham and Morgan, 1978) Formation; Pliocene and Pleistocene: Merced Formation 

(Dickerson, 1922; Keen and Bentson, 1944). 

Lituyapecten dilleri (Dall) 

Plate 42, figure 4 

Pecten (Lyropecten) dilleri Dall, 1901, p. 117-118. 

Pecten (Patinopecten) dilleri Dall. Arnold, 1906, p. 62, pl. 5, fig. 2. 

Hertlein and Jordan, 1927, p. 431-432, pl. 30, fig. 1. 

Pecten (Patinopecten) coosensis Shumard variety dilleri Dall. Grant 

and Gale, 1931, p. 193-194. 

Patinopectendilleri(Dall). Woodring,1950, p. 84-85, pl.11, figs.1, 9. 

Pecten (Lituyapecten) dilleri Dall. MacNeil, 1961, p. 233, 235-236. 

Hertlein and Grant, 1972, p. 186-187, pl. 35, figs. 4, 7. 

On:ginal descript-ion.-"Shelllarge, averaging about 190 millimeters in altitude, rather compressed, nearly orbicular with a relatively short, straight, hinge line, dorsally rectangular, nearly 

smooth, subequal ears, the posterior with 3 small riblets; a wellmarked though shallow byssal fold; and moderately thick valves. 

The right valve is somewhat more convex and strongly sculptured, 

bearing 29 to 30 high, narrow, T-rail shaped ribs, flattened above, 

overhanging narrower, deep, nearly smooth channels; and with 

marked concentric imbrication, feeble on top of the ribs but articularly scaly at their sides. The sculpture of the left valve is less 

pronounced, hidden in the matrix, but apparently similar." 

Lectotype.-USNM 164846, which Arnold (1906, pl. 5, fig. 2) illustrated as a cotype, is here designated the lectotype. 

Type local?:ty.-Eel River, Humboldt County, Calif. Rio Dell Formation, Pliocene and Pleistocene. 

Supplementary description.-"The left valve of P. d1:lleri is large, 

subcircular in outline, and slightly arched. The anterior ear is rather 

sharply truncated at the anterior margin, and is ornamented by 

about six to eight radiating ribs which are crossed by concentric 

lines of growth and are roughened by raised scaly imbrications. The 

posterior ear slopes slightly from the posterior dorsal margin to the 

base; it bears about six radiating ribs and is otherwise sculptured 

similar to the anterior ear. 

"The left valve bears about 27 or 28 slightly rounded, high, prominent radiating ribs separated by interspaces that are a little wider 

than the ribs. The tops of the ribs are ornamented by strong, raised 

scaly concentric imbrications; the sides of the ribs and the interspaces are marked only by faint traces of rather widely spaced 

concentric lamellae." (Hertlein and Jordan, 1927, p. 431-432) 

"There seems to be little doubt that dilleri is a Lituyapecten. It is a 

highly variable species if all the specimens that have been referred 

to it are really conspecific. Among pectens of its own age, it appears 

to be most closely related to P. (L.) purisimaens1:s as numerous 

writers have claimed. However it has characters which link it 

unmistakably with both P. (L.) poulcreekensis and poulcreekensis 

var. * * *, both early Miocene forms. Its relation to purisimaensi.c; 

may be, therefore, one of parallelism rather than of direct intergradation, purisimaensis merely representing the varietal extreme of 

the purisimaensis-falorensis stock that perpetuated more of the 

characters that both it and the diller1: stock inherited from a common 

early Miocene ancestor." (MacNeil, 1961, p. 235-236) 

"One well preserved specimen found in the San Diego Formation 

is present in the collections of the University of California at Los 

Angeles. The record of Pecten dilleri from San Diego by Woodring 

was based upon this specimen. It is 88.7 mm long, 88.6 mm high 

(anterior margin slightly defective), convexity (both valves together), 

17 mm. There are 27 radial ribs of which two nearest the anterior 

margin on the right valve are medially grooved. The riblets on the 

anterior ears are fine but well defined, those on the posterior ears 

only faintly indicated. Scaly concentric lamellae are only faintly 

noticeable on the right valve but on the left valve these are well 

developed. * * * 

"On some specimens of this species from other formations, concentric lamellae may cross the ribs or only flanges may be present 

along the margins of the ribs on the right valve. On well preserved 

left valves, strong, elevated, concentric lamellae cross the ribs, or are 

occasionally interrupted and alternating, as shown on the illustrations of a left valve from northern Lower California by E. K. Jordan 

and Hertlein (1926, pl. 30, fig. 1)." (Hertlein and Grant, 1972, p. 186) 

Cmnparison.-"P. dilleri Dall is distinguished from P. pun:s?:-

maensis Arnold and from P. coosens1:s Shumard by having a larger 

number of ribs which, in the left valve of Dall's species, are fairly 

large, slightly rounded, and more distant than in the others. The 

great prominence of the raised scaly imbrications on the ribs is also 

characteristic of P. dilleri." (Hertlein and Jordan, 1927, p. 432) 

"Patinopecten (L.) purisimaensis is related toP. (L.) dUleri (Dall) 

* * *. P. (L.) dilleri usually has coarse flanges on both valves, those of 

the right valve being either single and crossing the ribs * * *, or 

divided and along the margins of the ribs***. The left valve has 

strong single flanges." (MacNeil, 1961, p. 233) 

"Pecten (Lituyapecten) puris1:maensis Arnold * * *, is characterized by fewer (22 to 24), usually broader ribs on the right valve and 

narrower, sharper ribs with correspondingly wider interspaces on 

the left valve. 

"Fossils cited as 'P. dillen: variety' by Woodring (1950, pl. 9, figs. 

6-8), from the Sisquoc Formation in the Santa Maria district are 

characterized by the presence of rib lets in the inters paces on the left 

valve and by minute riblets crossed by very fine lamellae in the 

interspaces on the right valve. 

"Pecten (Lituyapecten) coosensis Shumard bears a resemblance to 

P. (L.) dilleri in the slightly developed flanges on the ribs and in that 

the ribs bear one or more medial grooves toward the ventral margin, 

* * *"(Hertlein and Grant, 1972, p. 187) 

Geographic range.-Northern California to Baja California Sur. 

Geologic range.-Miocene(?) to Pleistocene. Patinopecten dilleri 

characterizes the Moclipsian Molluscan Stage of Addicott (1976b) 

and affords a basis for correlation between strata in southern California and Baja California. 

Occurrence in the Calijornias.-Miocene or Pliocene: Imperial 

Formation (Mount, 1974); Pliocene: Almejas (Minch and others, 

1976), Cebada Member, Careaga (Woodring, 1950), and Fernando 

(Durham and Yerkes, 1964; Vedder, 1972; Kern and Wicander, 

1974) Formations, Foxen Mudstone (Woodring, 1950), Niguel 

(Vedder, 1960) and San Diego (Hertlein and Grant, 1972) Formations; Pliocene and Pleistocene: Merced (Faustman, 1964) and Rio 

Dell (Faustman, 1964) Formations. 

FOSSIL LOCALITIES 

(Corrections and information not in the original description are in brackets; feet and 

miles are converted to the metric system; formations are cited as emended by later 

workers. where pertinent] 

California Academy of Sciences: 

CAS 681. Alverson Canyon, near source, Coyote Mountain, 

Imperial County, Calif. Imperial Formation. 

CAS 794. "Cuesta Blanca" on Arroyo de Area 24 km north of 

Loreto, Baja California Sur. San Marcos Formation. 

CAS 795. Punta San Antonita, Baja California Sur. Collected 

along a canyon about 0.8 km inland and which empties near 

point. Carmen Formation. 

CAS 928. Bernstein's abalone camp, Isla Cedros, Baja California 
TERTIARY MARINE PELECYPODS: PROPEAMUSSIIDAE AND PECTINIDAE B89 

Norte. Almejas Formation. 

CAS 937. Arroyo Hondo, Isla Maria Madre, Mexico. Unnamed 

Pliocene strata. 

CAS 945. Southeast of Bahia Tortola, Baja California Sur. 

Almejas Formation. 

CAS 946. [East coast of] Isla Cedros, Baja California Norte. [The 

section north of Gran Canon, about 15 km north of Pueblo 

Cedros, former site of Bernstein's Abalone Camp.] Almejas 

Formation. 

CAS 1132. Pacific Beach, San Diego, San Diego County, Calif. 

San Diego Formation. 

CAS 1874. From SE cor. sec. 35, T. 6 S., R. 7 E., M.D.M., 

Stanislaus County, Calif.; on the north side of Crow Creek 

road. Kreyenhagen Shale. 

CAS 27625. SEcor. sec. 31, T. 28 S., R. 20 E., Carneros Creek 

quad. Wygal Sandstone Member, Temblor Formation. 

CAS 39413. Along the trail about 200m to the southeast from 

CAS Joe. 39412, southeast of the ranch house, Rancho El 

Refugio, Baja California Sur. Salada Formation. 

Los Angeles Natural History Museum: 

LAM 305. 730 m east and 310m south of NW cor. sec. 8, T. 19 S., 

R. 2 W., S.B.M. (San Ysidro quad., 1943 ed.) [San Diego 

County], California. San Diego Formation. 

Stanford University [These collections are now all in the California 

Academy of Sciences]: 

SU 43. Mesa west of Mesa de las Auras, Laguna Scammon 

quad .. Ba.ia California Sur. Salada Formation. 

SU 47. Bahia T6rtola, Baja California Sur. Salada Formation. 

SU 48. Mouth of large arroyo northwest of Mesa de Elephant, 

Laguna Scammon quad., Baja California Sur. Salada 

Formation. 

SU 49. Slopes of Salada, 4.5 km southeast of Bahia T6rtola, 

uppermost beds, Bahia San Cristobal quad., Baja California 

Sur. Salada Formation. 

SU 50. Rancho Refugio, north of San Jose del Cabo, Baja California Sur. 

SU 53. First arroyo east of Santiago, Baja California Sur. Salada Formation. 

SU 54. Arroyo Mesquita), above the yellow silts which are well 

exposed in this arroyo. Baja California Norte, Almejas 

Formation. 

SU 59. 1\t?'?"itella. bed above Laguna San Gregorio, 190m north 

of Bahia de Magdalena, Baja California Sur, on the trail from 

Arroyo Mesquita) to La Purisima. Isidro Formation. 

SU 60. WestsideofMesade Elephant, Laguna Scammon quad., 

Baja California Sur. Isidro Formation. 

SU 64. Pebbly sandstone near Comondti-Salada contact, arroyo 

near La Palma, Baja California Sur. Salada Formation. 

SU 65. Southern part of Arroyo San Gregorio, Baja California 

Sur. Salada Formation. 

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 115. Pacific Beach, San Diego, San Diego County, Calif. San 

Diego Formation. 

SU 116. Isla Cedros, Baja California Norte. Salada Formation. 

SU 130. Sea cliffs at mouth of Fossil Creek, 3 km west of Sherringham Point, Jordan River, Vancouver Island, B.C. Sooke 

Formation. 

SU 150. Pyramid Hill, 5 km northwest of mouth of Kern River 

Canyon, Caliente quad. [sec. 10, T. 28 S., R. 29 E.], Kern 

County, Calif. Jewett Sand. 

SU 155. Drill core, depth 850 m, 1,300 m northwest of Signal 

Hill, 150m east of Orange Avenue, 230m north <;>f Willow 

Street, Long Beach [Los Angeles County], Calif. Fernando 

Formation. · 

SU 406. From the west end of South Mountain where it is 

truncated by the Santa Clara River, in a grayish-green, 

firmly indurated sandstone, but a few meters above the river 

bed; 3 km southwest of Santa Paula, Ventura County, Calif. 

Vaqueros Formation. 

SU 860. Santa Inez [Ynez] Mountains, Santa Barbara County, 

Calif. Vaqueros Formation. 

SU 2694. Between headwaters of San Lorenzo River and Pescadero Creek [off old dirt road running 180 to 275m west of 

new highway, between Saratoga Point and Boulder Creek, 

SE~ sec. 23, T. 8 S., R. 3 W., just west of Santa Cruz County 

line, Santa Cruz quad., San Mateo County], Calif. Locatelli(?) 

Formation. 

SU 3252. 100 millimeters east, 412 millimeters south, of 

northwest corner as measured on 1953 edition, La Costa Valley quad., Alameda County, Calif. Briones Sandstone. 

SU. F-6. Coalinga region, sec. 20, T. 19 S., R. 15 E. [Fresno 

County], California. Santa Margarita Formation. 

University of California at Berkeley: 

UC 14. In valley north of Sobrante Ridge, on west fork of Bear 

Creek, 0.8 km from source, long 122°12'35" W., lat 37°55'58" 

N. [Concord quad.], Contra Costa County, Calif. Briones 

Sandstone. 

UC 367. Locality description not available. 

UC 407. [On San Pablo Bay, near north mouth of tunnel on first 

point southwest of Selby Station, Napa quad., Contra Costa 

County'] California. Cierbo Sandstone. 

UC 1176. [NYz sec. 19, T. 2 N., R.. 3 W.] Carquinez quad., Contra 

Costa County, Calif. Briones Sandstone. 

UC 1311. 2.5 km southeast of Muir Station, long 122°6'8" W, lat 

37°58'14" N., Contra Costa County, Calif. San Ramon Sandstone. 

UC 1492. [South side of Mount Diablo, SE ~SW~ sec. 14, T. 1 S., 

R. 1 W.] Mount Diablo quad., Contra Costa County, Calif. San 

Pablo Group. 

UC 1632. On bay shore just west of town of Rodeo, a little south of 

Lone Tree Point, Napa quad., Contra Costa County, Calif. 

Cierbo Sandstone. 

UC 1817. Opposite the place where Urruttia Canyon enters Salt 

Creek, 30 m up fourth small draw from west end of ridge, 

SW~NW~ sec. 15, T. 18 S., R. 14 E., Coalinga quad. [Fresno 

County], California. Cerros Shale Member, Lodo Formation. 

UC 2991. [Near Zapato Creek]on top of ridge south of road near 

center SE~ sec. 17, T. 22 S., R. 16 E, [Coalinga quad., fresno 

County], California. Upper part of Etchegoin Formation. 

UC 3029. Tejon Hills, Caliente quad., sec. 13, T. 32 S., R. 29 E., 

Kern County, Calif. Santa Margarita Formation. 

UC 3030. Fourth and Broadway, Los Angeles [Los Angeles 

County], Calif. Fernando Formation. 

UC 3224 [not 3234]. East of Rock Springs, near Bee Spring 

Ridge, in SW cor. NW~ sec. 28, T. 10 N., R. 21 W., S.B. [Mount 

Pinos quad., Kern County], California. Vaqueros Formation. 

UC 3231. Westside of Salt Creek, near SW cor. sec. 21, T. 10 N., 

R. 20 W., S.B., Kern County, Calif. Pleito Formation. 

UC 3532. [NYz sec. 4, T. 4 S., R. 1 E.] Pleasanton quad., Alameda 

County, Calif. Briones Sandstone. 

UC 3535. [NE~ sec. 32, T. 4 N., R. 1 E.] Pleasanton quad., 

Alameda County, Calif. Briones Sandstone. 

UC 7100. Northwest cor. sec. 3, T. 3 N., R. 21 W., Ventura 

County, Calif. San Pedro(?) Formation. 

UC A311. In canyon east of pass between two high peaks on crest 

of island, Santa Rosa Island, Calif .. Vaqueros Formation. 
B90 PALEONTOLOGY OF CALIFORNIA AND BAJA CALIFORNIA 

UC A316. Along bluffs on south side of Santa Ynez River about 

1.5 km west of bridge on steep spur southwest of the "HG" 

ranch house [Lompoc quad., Santa Barbara County], California. Vaqueros Formation. 

UC A572. [Corner of San Luis Obispo, Cayucos, and Adelaida 

quads., T. 28 S., R. 11 E.] San Luis Obispo County, Calif. 

Vaqueros Formation. 

UC A1268. Upper part of basal sandstone and conglomerate 

series on northwest side of Carrizo Mountain. S. 5°30' E. of 

Carrizo Station. Oyster reef on ridge running west from east 

side of meander of stream in badland area. Imperial County, 

Calif. Imperial Formation. 

UC A3518. Marquer Bay, Carmen Island. In cliff facing bay, 

just south of northern arroyo. About 45 m above sea level 

(aneroid barometer reading). Same bed as at Joe. A3513 [yellow calcareous sands], and about 6 m below a coral-reef 

horizon. Marquer Formation. 

UC A3566. From Pecten bed in calcareous "sandstone" overlying 

algal sandstone which is in fault contact with breccia, on east 

side of southern tip of Isla Monserrate, Baja California Sur. 

Salada Formation. 

UC A3583. Bahia Santa Inez, Baja California Sur. From sandstones outcropping on a·beach west of Punta Santa Inez and 

unconformably overlain by Pleistocene terrace. Salada 

Formation. 

UC A4233. Bank of Boulder Creek from 90 m south to 180 m 

north of bridge near "Beckstine Ranch" (Wiggins Ranch), in 

about a 5-m stratigraphic interval, about 16 km southeast of 

Blue Lake, Humboldt County, Calif. Falor Formation. 

UC A4566. Approximately 25 mm due west of top of the capital 

"E" of Eden Creek on the 800-ft contour line, Hayward quad., 

0.6 km north of junction of Hollis Creek and Eden Creek, 25m 

below the base of the Claremont Chert, Alameda County, 

Calif. Sobrante Sandstone. 

UC B6940. Along Camino Cielo near Sacate-"Coldwater" contact, San Rafael Mountain quad., grid coordinates: 1113850-

1273370, Santa Barbara County, Calif. Coldwater Sandstone. 

UC D702. From approximately 2-m-thick oyster bed about 1 to 

1.5 m above locality D701 [sec. 15, T. 19 S., R. 15 E., 740 m 

north, 770 m west], Domengine Ranch quad., Kern County, 

Calif. Santa Margarita Formation. 

UC D1088. Sec. 28, T. 19 S., R. 15 E., 1,105 m north, 105m east, 

Coalinga quad. From oyster-pecten bed of the Santa Margarita Formation outcropping on hill slope about 35m north 

of Standard Oil well 184. Fossil bed is about 10 m stratigraphically below the unconformity at the base of the marine 

Etchegoin Formation, Kern County, Calif. Santa Margarita 

Formation. 

UC D1099. Along road cut between Shell oil wells 155-15 and 

254-15 from very well sorted, fine-grained, buff to brown, 

silty sandstone over 5 m thick; sec. 15, T. 19 S., R. 15 E., 760 m 

north, 750 m west, Domengine Ranch quad., Kern County, 

Calif. 

University of California at Los Angeles: 

UCLA 435. East side of valley of San Juan Creek, elevation 

approximately 2, 700 m, in west middle half of sec. 32, T. 28 S., 

R. 16 E., M.D.B.M., San Luis Obispo County, Calif. Neroly 

Formation. 

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

USGS 2464. Forty kilometers eastward from Cape Flattery, on 

the south shore of Fuca [Juan de Fuca] Strait, Wash. Clallam 

Formation. 

USGS 3851. Head of Slacks Canyon [Priest Valley quad., sec. 8, 

T. 22 S., R. 13 E.], Monterey County, Calif. Santa Margarita 

Formation. 

USGS 4478. South of Santa Ynez 3 km, on knoll just east of 

mouth of Ballard Canyon, west end of Santa Ynez Range 

[Lompoc quad.], Santa Barbara County, Calif. Vaqueros 

Formation. 

USGS 4507. Just above the San Julian ranch house, about 16 km 

southeast of Lompoc [Lompoc quad.], Santa Barbara County, 

Calif. Gaviota Formation. 

USGS 4712. East of Zapato Creek [1.2 km east of B.M. 922], 

SWY.;SEY.; sec. 8, T. 22 S., R. 16 E. [Coalinga quad., Fresno 

County], California. Etchegoin Formation. 

USGS 12530. Deadman Island, east side. (Same as CIT Joe. 130, 

now inaccessible.) Los Angeles County, Calif. Basal part of 

San Pedro Sand. 

U.S. Geological Survey, Menlo Park, Calif., register: 

USGS M3772. On southeast side of ridge paralleling Media 

Agua Creek about 60 m above dirt road, 315 m south, 60 m 

east of NW cor. sec. 23, T. 28 S., R. 19 E., Las Yeguas Ranch 

7Y2' quad., Kern County, Calif. Wygal Sandstone Member, 

Temblor Formation. 

USGS M3281. On south side of hill 2259 just below summit, 

2,000 ft N., 1,000 ft W. of SEcor. sec. 22, T. 28 S., R. 19 E., Las 

Yeguas Ranch 7Y2' quad., Kern County, Calif. Wygal Sandstone Member, Temblor Formation. 

GEOLOGIC FORMATIONS CITED FOR 

OCCURRENCE OF PELECYPODS 

Family Propeamussiidae and Fmnily Pectim:dae 

Name Age 

California: 

Agua Sandstone Member, 

Temblor Formation .............................. Oligocene. 

Alegria Formation1 ...............•.................... 0ligocene. 

Altamira Shale Member, 

Monterey Shale ...................................... Miocene. 

Anchor Silt Member 1, 

San Pedro Formation ............................ Pleistocene. 

Antelope Shale Member, 

Monterey Formation ............................ Miocene. 

Ardath Shale .............................................. Eocene. 

Branch Canyon Sandstone ...................... Miocene. 

Briones Sandstone, San 

Pablo Group ............................................ Miocene. 

Butano Sandstone ...................................... Eocene. 

Buttonbed Sandstone 

Member, Temblor Formation ............ Miocene. 

Capay Formation ........................................ Eocene. 

Capistrano Formation .............................. Miocene and Pliocene. 

Careaga Sandstone .................................... Pliocene. 

Carneros Sandstone Member, 

Temblor Formation .............................. Miocene. 

Cascajo Conglomerate Member, 

San Joaquin Formation ........................ Pl.iocene. 

Castaic Formation 1 •••••••••••••••••••••••••••••••••••• Miocene. 

Cebada Member, Careaga 

Sand or Sandstone .................................. Pliocene. 

Cerros Shale Member, 

Lodo Formation ...................................... Paleocene. 

Chamisal Formation1 ................................ Miocene. 

Cierbo Sandstone, San 

Pablo Group ............................................ Miocene. 

Cold Creek Member, Topanga 

Canyon Formation ................................ Miocene. 

Coldwater Sandstone and 

Coldwater Sandstone Member, 1 

Tejon Formation .................................... Eocene. 

Cozy Dell Shale and Cozy Dell 

Shale Member, 1 Tejon Formation .... Eocene. 

Edna Member, Pismo Formation .......... Miocene and Pliocene. 

1Stratigraphic nomenclature used is that of the references cited in the text and does not necessarily accord with that of the U.S. Geological Survey. 
TERTIARY MARINE PELECYPODS: PROPEAMUSSIIDAE AND PECTINIDAE B91 

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. 

Graciosa Member, Careaga 

Sand or Sandstone .................................. Pliocene. 

Gragg Member, Pismo For·mation ........ Pliocene. 

Hames Member, 

Monterey Formation ............................ Miocene. 

Imperial For·mation .................................. Miocene or Pliocene. 

Jewett Sand .................................................. Miocene. 

Kreyenhagen Shale or Formation ........ Eocene and Oligocene. 

Las Posas Formation 1 •••••••••••••••••••••••••••••••• Pleistocene. 

Lindavista Formation .............................. Pleistocene. 

Locatelli Formation .................................. Paleocene. 

Lomita Marl Member, 

San Pedro Formation ............................ PI iocene. 

Los Laureles Sandstone Member, 1 

Monter·ey Formation ............................ Miocene. 

Los Tularcitos Member, 1 

Chamisal Formation .............................. Miocene. 

Maricopa Shale 1 •••••••••••••••••••••••••••••••••••••••••• Miocene. 

Martinez Formation .................................. Paleocene. 

McLure Shale Member, 

Monterey Formation ............................ Miocene. 

Media Shale Member, 

Temblor Formation .............................. Miocene. 

Merced Formation .................................... Pliocene and 

Pleistocene. 

Mindego Basalt .......................................... Oligocene and Miocene. 

Modelo Formation ...................................... Miocene. 

Monterey Formation, Shale, or Group .................................................... Miocene. 

Mor·ales Formation .................................... Pliocene. 

Moreno Formation .................................... Miocene. 

Muir Sandstone 1 •••••••••••••••••••••••••••••••••••••••• Eocene. 

Ner·oly Sandstone, 

San Pablo Group .................................... Miocene. 

Niguel Formation ...................................... Pliocene. 

Obispo Formation ...................................... Miocene. 

Ohlson Ranch Formation 1 •••••••••••••••••••••••• Pliocene. 

Olcese Sand .................................................. Miocene. 

Oursan Sandstone, Monterey Group .... Miocene. 

Painted Rock Sandstone Member, 

Vaqueros Formation ............................ Miocene. 

Palos Verdes Sand .................................... Pleistocene. 

Pancho Rico Formation ............................ Miocene. 

Paso Robles Formation ............................ Miocene; Pliocene, 

and Pleistocene. 

Pico Formation .......................................... Pliocene and 

Pleistocene. 

Pleito Formation ........................................ Oligocene. 

Pomponio Mudstone Member, 

Purisima Formation .............................. Pliocene. 

Potato Harbor For·mation 1 •••••••••••••••••••••• Pliocene or Pleistocene. 

Puente Formation ...................................... Miocene. 

Pullen Formation, Wildcat Group ........ Pliocene. 

Purisima Formation .................................. Miocene and Pliocene. 

Pyramid Hill Sand Member, 

Jewett Sand .............................................. Miocene. 

Quail Canyon Sandstone Member, 

Vaqueros Formation ............................ Oligocene. 

Rincon Shale ................................................ Oligocene and Miocene. 

Rio Dell Formation, 

Wildcat Group ........................................ Pliocene and 

Pleistocene. 

Round Mountain Silt ................................ Miocene. 

Sacate Formation 1 •••••••••••••••••••••••••••••••••••••• Eocene. 

St. George Formation ................................ Pliocene. 

Saltos Shale Member, 

Monterey Formation ............................ Miocene. 

San Diego Formation ................................ Pliocene. 

San Emigdio Formation .......................... Eocene and Oligocene. 

San Gregorio Sandstone Member, 

Pu risi rna Formation .............................. PI iocene. 

San Joaquin Formation ............................ Pliocene. 

San Lorenzo Formation ............................ Eocene and Oligocene. 

San Onofre Breccia .................................... Miocene. 

San Pablo Formation or Group .............. Miocene. 

San Pedro Formation or Sand ................ Pliocene and 

Pleistocene. 

San Ramon Sandstone .............................. Miocene(?). 

Santa Barbara Formation ...................... Pliocene and 

Pleistocene. 

Santa Cruz Mudstone ................................ Miocene. 

Santa Margarita Formation .................. Miocene. 

Saugus Formation ...................................... Pliocene and 

Pleistocene. 

Sisquoc Formation .................................... Miocene and Pliocene. 

Skooner Gulch Formation ........................ Miocene. 

Sobrante Sandstone .................................. Miocene. 

Soda Lake Shale Member, 

Vaqueros Formation ............................ Oligocene and Miocene. 

Squire Member, Pismo Formation ...... Pliocene. 

Tahana Member, 

Purisima Formation .............................. Miocene and Pliocene. 

Temblor Formation .................................. Oligocene and Miocene. 

Tierra Redonda Formation .................... Miocene. 

Timms Point Silt Member, 

San Pedro Formation ............................ Pleistocene. 

Tinaquaic Sandstone Member, 

Sisquoc Formation ................................ Pliocene. 

Topanga Group .......................................... Miocene. 

Topanga Canyon Formation, 

Topanga Group ...................................... Miocene. 

Towsley Formation .................................... Miocene and Pliocene. 

Tranquillon Volcanics 1 ••........•.•.•••••••••••••• Miocene. 

Tumey Formation 1 •••••••••••••••.••••••••••.••••••••• Oligocene. 

Twisselman Sandstone Member, 1 

Monterey Formation ............................ Miocene. 

Valmonte Diatomite Member, 

Monterey Shale ...................................... Miocene. 

Vaqueros Formation ................................ Oligocene and Miocene. 

Wildcat Group ............................................ Pliocene and 

Pleistocene. 

Wimer Formation 1 •..••••••.••.••••••.......•••....... Miocene. 

Woodhams Member, 1 Monterey 

Formation ................................................ Miocene. 

Wygal Sandstone Member, 

Temblor Formation .............................. Oligocene. 

Baja California peninsula: 

Almejas Formation .................................... Pliocene. 

Boleo Formation ........................................ Pliocene. 

Cantil Costero Formation ........................ Pliocene. 

Carmen Formation .................................... Pliocene. 

Gloria Formation ........................................ Pliocene. 

Infierno Formation .................................... Pliocene. 

Isidro Formation ........................................ Miocene. 

Marquer Formation .................................. Pliocene. 

Salada Formation ...................................... Pliocene. 

San Marcos Formation ............................ Pliocene. 

Tepetate Formation .................................. Paleocene and Eocene. 

Tortugas Formation .................................. Miocene. 

Oregon: 

Astoria Formation .................................... Miocene. 

Empire Formation .................................... Miocene. 

Washington: 

Clallam Formation .................................... Miocene. 

Gries Ranch Formation ............................ Oligocene. 

Lincoln Creek Formation ........................ Eocene to Miocene. 

Sooke Formation ........................................ Miocene. 

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[1971]. 

A 

nbbott·i, A1·gopocton, 41 

A1'U01JOct.en abiet-is, 32, 41, .411; pl. 12 

Chlconys <A1'U01JOcton) abietis, 42 

Abbr·eviations, 6 

(l.biotis, Aoqni7Jocten, 41 

A·,·uo1Jecten, 41 

ctiJ·iotis, 32, .41; pis. 11, 12 

Chla.mys (A-I'U01JOctcn) 41, 42 

Pocton, 41 

(Plngiocteni·u.m) 41 

ctb·iof.'is ctblwtti, A-rgo7Jecton. 32. 41. .4£; pl. 12 

niJbott'i, Chln.m:ys <A1'001Jectcn), 42 

nll'iot.is, A·ruo110cten, 32, .41; pis. 11, 12 

Acknowledgments, 6 

cr.cu.tu.s, C11clopocton, 8 

o.clcku.nlrin:nn, Swijto7Jectcn, 51, 52; pl. 21 

nflhc·I'O'II.H, /111JC(I.{O, 29 

nchr:ncu.s, Pecten, 78 

Aeqni1Jccton, 2, 22, 91, 32, 39, 42, 43 

nlriot:iH, 41 

nnclc·rsoni, 45 

H'U.Inr:nclO'I'HO'Il:i, 45 

n:nton-ita.cnsis, 37, 41 

ch·cu.ln:l'iH, H4, 35 

lrt·nmknmpi, 35 

olcl·riclgoi, 36 

i111.1JOHtC1', 36 

dctllnsi, .'11; pl. 9 

cloHe'l'ti, 3H 

cl-ismr.s, 47 

·iiii.1JOHtO'I·, a6, 41 

1HJ1'C(I:I'ItH, 41 

'1'(1.1JIIW'II.d·i, 47 

IJ·ri on·i w11:u.s , 4 7 

·rovclloi, 38, 40 

H'IJO'I'Ch·u:p·i. 84 

(Plngioct.on:iu.m) ch·c·u.la:1·is, a4 

(Aoqu:i1Joct.on) wnde·rso11.i, Pecten, 45 

ltollila.mcllnt:ns, Pecten, 48 

cl·iHc·u.H, Pecten, 47 

clch·icl{JC'i, Pcct.on, a6 

O'IJO'I'IIt(l:n'll:i, Pecten, 39 

{J·iiJim.R ch·cu.la:t·is, Pecten, 37 

pnbloonsis, Pecten, 47 

1Hrrc;wrns, Pectc·it, 39 

7J'I'ne1Jrt./idu.s, Pecten, 42 

1J'II:I'1J'II:m.tu.s co.llidu.s, Pecten, 38 

hn.kC'i, Pcu;tcn, a9 

pe·,·en·ru.s, Pecten, 39 

sniHlolu.s, Pecten, 37 

tu.miJczcnwis, Pect.cn, 49 

ncqu:iwnlcn.t.n., Chlnm:ys (A·ruo1Jeet.en), 42 

Chlo.III.)JH (At'{J07JCCten) C'i·rcnln·l'is, a4, 42 

ch·cu.la:ri H, a 7 

o.ocrniwnlcntns, Ar{J01JCctcn, a5 

Agua Sandstone Member, Temblor· Formation, 

57, 6a, 90 

o:icloi, f'octcn ·inte·rUnenf:ttl!, 29 

!tletslwnsc, Pa:t·vnm:nssinm, 9, .11; pl. 2 

Pol1JnCIIt.a.m:nswiu.m, 11, 12 

P·ropen.m:nswi:twt. (Pn1·vam:nssinm), 11 

ctla.skenwis, Pwt"tmmnswinm, pl. 2 

Pecten, 11, 12 

(J'HO'Itcla.m:nswinm?), 11 

nlb·icnnH, Poet.en, 69 

Alegl'ia l<~ol'lnation, 61, 90 

nlet.os, Poet.e·''·· 67 

Pecten (Ja:t~:i·rn) hum7Jh·re1Jwii, 67 

(Pecten), 67; pl. 28 

o./c:1:Gla:rki, Vc·,·t.ipeetcn,61; pl. 24 

INDEX 

I Italic page numbers indicate major references) 

Almejas Formation, 23, 26, 83, 34, 35, a7, as, 39, 

40,41;48,44, 54,55, 56, 58, 60, 68,69, 

73, 77, sa, 88, 89, 91; pis. 10, 11, 12, 13, 

19, 20,21,22, 23,28,33 

Altamira Shale, 18 

Altamira Shale Member, Monterey Shale, 45, 90 

alternilineatus, Delectopecten, 14, 15; pl. 2 

Hyalopecten (Delectopecten), 15 

Pecten, 15, 16 

(Psettclamusium), 13 

(Psendonmseum), 15 

Amusium, 2, 48, 66, 69 

group, 13 

lompocensis, 66, 67; pl. 2 

pleuronectes, 66 

(Cyclopecten) pernonms, 8 

(Amusium) lompocensis, Pecten, 66, 67, 70 

mo1·toni, Pecten, 67 

vanvlecki, Pecten, 67 

Amussiopecten, 2, 69, 84 

vanvlecki, 67, 9, 74; pis. 29, 30 

(Amussiopecten) lompocensis, Pecten, 66, 67 

cma.pletts, Chlamys, 18, 29, 31; pl. 7 

Anchor Silt Member, San Pedro Formation, 26, 

84, 90 

ande1·soni, Aequipecten, 45 

Leptopecten, 45, 47 

Padpecten andersoni, 44,,45; pl. 14 

Pecten, 35, 45, 46 

(Aeqnipecten), 45 

(Plngioctenittm), 45 

andenwni, Pacipecten, 44, .45; pl. 14 

bn1·kerianus, Pacipecten, 44, ,45; pl. 20 

Pecten (Plagioctenium), 45 

gonicostatus, Pecten (Pecten), 47 

l!ubandersoni, Aequipecten, 45 

Padpecten, 44, 45; pl. 14 

Pecten (Plagioctenittm), 45 

ctnnulatus, Plagiostoma, 13, 18 

Antelope Shale Member, Monterey Formation, 

15,90 

Antipecten, 42, 43 

Anti7Jecten?, 2, 42 

prnevalidus, 42; pl. 13 

antonitaensis, Aequipecten, 37, 41 

A1'001Jecten, 32, 33, 41; pl. 11 

a1·ces, Pecten (Pseudamusium), 13 

Ardath Shale, 10, 90; pl. 1 

A-t·gopecten, 2, 31, 92, 39, 55 

abbotti, 41 

a.bietis, 41 

abbotti, 32, 41, 42; pl. 12 

a.bietis, 32, 41; pis. 11, 12 

aeqttisulca.tus, 35 

a.ntonitaensis, 32, 33,41; pl. 11 

ca.llidus, 32, 33,98; pl. 10 

ci·rcularis, 34, 35, 36 

bramknmpi, 32, 95; pl. 9 

call-i, 32, 95; pl. 10 

cinulm·is, 32, 94; pl. 9 

elcl·ridgei, 32, 96; pl. 9 

imposte·r, 32, 96; pl. 10 

sens1t Into, 35 

cristobalensis, 32, .40, 42; pl. 13 

cle.qe1·ti, 32, 99, 36; pl. 9 

cl·iminutivus, 92, 35; pl. 9 

e1·icell-t.ts, 32, 97; pl. 12 

e'Vennann·i, 32, 99, 40, 42; pl. 13 

geographic distribution, 32 

geologic distribution, 32 

gibbus, 35 

lwkei, 32, 99, 42; pl. 11 

imposte1·, 34 

Argopecten-continued 

invalidus, 32, 33, 97; pl. 10 

mendenhalli, 32, 99; pl. 9 

nucleus, 35 

percarus, 32, 99, 41; pis. 10, 12 

1·evellei, 32, 40; pl. 11 

subdolus, 32, 33, 97, 40; pl. 10 

sverdrupi, 32, 94; pl. 9 

species a, 41 

(Argopecten) abietis, Chlamys, 41, 42 

abietis abbotti, Chlamys, 42 

aequisulcata, Chlamys, 34, 42 

calli, Chlamys, 35 

circularis, Chlamys, 34 

aequisulcata, Chlamys, 34,42 

calli, Chlamys, 35 

cooperi, Chlamys, 37 

coope1·icelltt8, Chlamys, 37 

cristobalensis, Chlamys, 40 

deserti, Chlamys, 33 

ericellus, Chlamys, 37 

evennanni, Chlamys, 39 

hakei, Chlamys, 39, 42 

invalida, Chlamys, 37 

revellei, Chlamys, 40 

subdola, Chla.mys, 38 

subdolus, Pecten, 37 

Argopecten?, 42 

crassiradiatus, 32, 42; pl. 10 

arnoldi, Chlamys (Nodipecten), 12 

Arroyo Hondo Shale Member, Lodo Formation, 9, 

10 . 

ashleyi, Lyropecten, 55; pis. 20, 21 

Pecten, 55 

(Lyropecten), 55 

Astoria Formation, 79, '1; pis. 3, 27, 34, 35 

Athlopecten, 60 

auburyi, Pecten, 68, 77 

Pecten (Pecten), 68 

aztecus, Pecten, 77 

bake1·i, Leopecten, 85 

B 

Leopecten bake1·i, 84,854 pl. 40 

Patinopecten, 85, 86 

Pecten, 72, 85 

(Jani1·a) stearnsii, 85 

(Pntinopecten), 84, 85 

bake1·i, Leopecten, 84, 85; pl. 40 

diazi, Leopecten, 8.4, 8 5; pis. 39, 40 

Patinopecten, 85, 86 

Pecten, 85 

barke1·iana, Chlamys, 45 

barkerimuts, Paci.pecten andersoni, 44, 45; pl. 20 

Pecten (Plagiocteniwn) andersoni, 45 

ba1·tschi, Chlam1Js, 18, £5; pl. 6 

Pecten (Chlamys), 25 

(Pecten), 25 

beali, Flabellipecten, 71, 79; pl. 31 

Pecten, 73 

(Pecten), 73 

beh1·ingia.na., Chlam1JS, 29 

Chlamys (Chlamys), 31 

islandica, 31 

bella., Jan ira, 68 

bellilamellata, Chlam1Js (Leptopecten), 43 

bellilamellatus, Lepto11ecten, 49; pl. 13 

Pecten (Aequipecten), 43 

(Chlamys), 43 

bellistriatus, Pecten, 16 

bellus, Pecten, 67, 68, 69, 74, 75, 76 

BlOl 
B10_2 PALEONTOLOGY OF CALIFORNIA AND BAJA CALIFORNIA 

bell1Ls -continued 

Pecten (Pecten), 67, 68; pl. 29 

coalingaensis, PeCten (Janira), 76 

hemphillii, Pecten (Janira), 68 

benedicti, Hinnites, 65; pl. 26 

benedictus, Pecten, 78 

beriangiana, Chlamys (Chlamys), 31 

beringiamts, Chlamys islandicus, 29 

biformatis, Pecten crassicardo, 51 

bifonnatus, Pecten, 51 

bilineatus, Pacipecten, 44, 1,8; pl. 15 

Pecten, 48 

(Plagioctenium), 48 

boesei, Flabellipecten, 71 

Boleo Formation, 29, 33, 72, 91 

bosei, Flabellipecte'n, 72; pl. 32 

bose·i, Pecten, 73 

Pecten (Pecten), 72 

bowersi, Lyropecten, 62 

Pecten, 63 

(Lyropecten), 62 

(V ertipecten), 62 

Vertipecten, 61, 62, 64; pis. 24, 25 

bramkampi, Aequipecten circularis, 35 

Argopecten circularis, 32, 35; pl. 9 

Chlamys circ;_laris, 35, 36 

Branch Canyon Sandstone, 45, 47, 53, 54, 66, 67, 

70,90 

branneri, Chlamys, 18, 19, 62; pl. 4 

Pecten, 20, 60 

(Chlamys), 19 

Briones Sandstone, 46, 47, 48, 52, 53, 80, 89; pis. 

14, 17, 18 

San Pablo Group, 90 

brionianus, Aequipecten raymondi, 47 

Pacipecten, pl. 14 

Pecten, 47 

(Pecten) raymondi, 47 

raymondi, 47 

buchivacoanus, Pecten (Chlamys), 22 

Butano Sandstone, 7, 10, 90; pl. 1 

Buttonbed Sandstone Member, Temblor 

Formation, 45, 53, 54, 70, 90 

c 

calamitus, Parvamussium, 12; pl. 2 

Pecten, 11 

calaverasensis, Patinopecten, 78, 80; pl. 35 

Pecten haywardensis, 80 

(Patinopecten) haywardensis, 80 

californicus, Capulus, 74 

calkinsi, Chlamy's, 18, 19; pl. 3 

Pecten (Chlamys), 19 

calli, Argopecten circularis, 32, 35; pl. 10 

Chlamys (Argopecten) circularis, 35 

circularis, 35, 36 

Pecten, 33, 35 

(Plagioctenium), 32, 34, 35 

callida, Chlamys, 37, 38 

Chlamys (Argopecten), 38 

callidus, Argopecten, 32, 33, 38; pl. 10 

Pecten, 33, 40 

(Aequipecten) purpuratus, 38 

(Plagioctenium), 38 

Camptochlamys, 12 

(Camptonectes) harfordus, Pecten, 16 

cancellosus, Patinopecten oregonensis, 83 

Cantil Costero F.ormation, 60, 91 

Capay Formation, 7, 90 

Capistrano Formation, 15, 24, 59, 66, 83, 90 

Capulus californicus, 74 

Careaga Formation, 23 

Cebada Member, 88 

Careaga Sand, Cebada Member, 90 

Graciosa Member, 91 

Careaga Sandstone, 60, 90 

Cebada Member, 23, 56, 60, 69, 83, 90 

Graciosa Member, 69, 83, 91 

Carmen Formation, 32, 40, 41, 58, 69,7-1, 85, 88, 91; 

pis. 11, 39, 40 

Carneros Sandstone Member, Temblor 

Formation, 50, 51, 65, 90 

carrizoensis, Flabellipecten, 71; pl. ·31 

Pecten, 71, 72, 73 

(Janira)·stearnsii, 71 

(Pecten), 71 

Cascajo jconglomerate Member, San Joaquin 

Formation, 36, 90 

Castaic Forma~ion, 22, 47, 53, 54, 59, 66, 90 

catalinae, Chlamys (Lyropecten) est1·ellanus,. 56 

Lyropecten, 49, 53, 54; pl. 18 

estrellanus, 56 

Pecten, 53 

(Lyropecten) estrellanus, 53 

cataractes, Pecten, 76, 77 

Pecten (Euvola), 77 

catilliformis, Pecten, 64 

caurinus, Patinopecten, 78, 79, 82, 83; pis. 38, 39 

Patinopecten (Patinopecten), 83 

Pecten, 64, 80, 81, 83, 84, 85, 87 

(Patinopecten), 12, 83 

yessoensis ,.Pecten, 84 

Cebada Membe.r, Careaga Formation, 88 

Careaga Sand, 90 

Careaga Sandstone, 23, 56, 60, 69, 83, 90 

cerritensis fragilis, Leptopecten latiauratus, 44 

Cerros Shale Member, Lodo Formation, 9, 89, 90; 

pl. 1' 

cerrosensis, Chlamys, 56 

Chlamys (Lyropecten), 40, 55, 56 

Lyropecten; 33, 49, 52, 54, 55; pis. 20, 21 

Pecten, 33, 40, 54, 55 

(Lyropecten), 55 

estrellanus, 55 

(Plagioctenium), 55 

mendenhalli, Pecten, 40 

Pecten (Plagioctenium), 33 

Chamisal Formation, 45, 90 

Los Tularcitos Member, 46, 91 

chinkopensis, c'hlamys, 27 

Chlamys, 2, 18, 30, 31, 48, 50, 61, 62, 65, 66,83 

anapleus, U3, 29, 31; pl. 7 

barkeriana, 45 

bartschi, 18, 25; pl. 6 

behringiana, 29 

branneri, 18, 19, 62; pl. 4 

calkinsi, 18, 19; pl. 3 

callida, 37, 38 

cerrosensis', 6 

chinkopensis, 27 

circularis, . .34, 35, 37, 38 

aequis~lcata, 37 

bramk_ampi, 35, 36 

calli, 3?, 36 

group, 37 

condylomatus, 12 

corteziana, 18, 22; pl. 5 

crassiplicatus, 65 

cristobalensis, 39, 40 

dallasi, 31. 

deserti, 33, 34, 38 

group,33 

discus, 47 

durhami, 21, 22; pl. 5 

egregius, 18, 22, 21,; pl. 6 

eldridgei, 35 

etchegoini, 29, 60 

geographic distribution, 18 

geologic distribution, 18 

group, 18, 65 

hakei, 39, 40 

hastata, 22, 23, 24, 27, 29, 66 

Chlamys-continued 

hastata-continued 

ellisi, 18, 24 · 

group, 24 

hastata, 18, 22; pl. 5 

hericia, 23, 27, 29 

hericius, 18, 23, 27; pl. 5 

pugetensis, 18, 23, 24, 27, 29; pl. 6 

hastatus, 23 · · 

hataii, 26 . 

heTicius, 23 

hertleini, 18, 21, 26; pl. 4 

hodgei, 18, 20, 21; pis. 4, 5 

imanishii, 28 

impostor, 38 

invalida, 37, 38 

islandica, 24, 27, 28 

behring·iana, 31 

group, 26 

islandicus, 29 

beringianus, 29 

group,29 

jordani, 25 

jordani, 18, 21, 25, 28; pl. 6 

kincaidi, 26 

kinoshitai, _27 

lowei, 22 

mediacostata, 30 

grewingki,29 

mediacostata, 29 

miyatokoensis, 24 

opuntia, 18, 26, 29; pl. 6 

parmeleei, 29, 59 

etchegoini, 59, 60 

parmeleei, 60 

picoensis, 18, 27; pl. 7 

proavus,.18,19; pl. 3 

pugetensis, 27 

purpurata, 39, 40 

raymondi, 47 

revellei, 40 · 

rubida, 18, 26, 27, 28; pl. 7 

jordani, 25, 29 

sacyi, 43 

sanctiludovici, 18, $2, 32; pl. 5 

sespeensis, 18, 20; pl. 4 

hydei, 18, 20; pl. 4 

subdola, 38 

swiftii, 59 

tamurae, 26 

venturaensis, 27, 28; pl. 7 

(Argopecten)_abietis, 41, 42 

abietis abbotti, 42 

aequisulcata, 42 

callida, 38 

circularis, 34 

aequisulcata, 34, 42 

calli', 35 

cooperi, 37 

coopericellus, 37 

cristobalensis, 40 

deserti, 33 

ericellus, 37 

evermanni, 39 

hakei, 39, 42 

invalida, 37 

revellei, 40 

subdola, 38 

(Chlamys) beringiana, 31 

hastata, 22 

ellisi, 21,; pl. 5 

hericius, 23 

jordani, 25 

opuntia, 26 

picoensis, 27 

pugetens"is, 27 

rubida, 28 

jordani, 25 
G'hlctmys-continucd 

(/Awc;h/.(r.m.yH) tn[Jida.kcnwiH, 30 

(l.opt.opcc;l.on) llolril.a.molla.tn, 43 

lcr.t:ia:u:ra.ta., •13, 44 

lltO'/I.Of:i/1/.l!'l'iH, 44 

/."11.11/./li)ZIJ'II.H'iH, 4!) 

(/•1J'I'01UH;f,IJ'll.) (;()'l"l"OHOnRiH, 40, 55, 56 

C'/'(I,HRit;a:J:dO, 5(; 

oHI:rolla:nus, 56 

cnt.nl:i·Jw.o, 56 

(JnllO(JOHi; 5(; 

(Nodi}loc;t.o·JI.) a:J"nold·i, 12 

(S·IIri}~.01UH;I.on) pwnneloiJ'i, 59 

1!11:1' uwletri ot.cho{Jo·ini, HO 

Hwift.ii, 12, 59 

(Swifi.01liJI:I.on'?) lw.mNni, 60 

Chla.m1Jil'l, 18,1J!J 

(J'I'O'IIri'li[Jki., 2!), 30 

mo!Ucu;oHt.a.tn, i!O 

rrro·wi.nyld, 18, 21J; pl. 7 

uwdia.coHtnt.a., 18, 2!J; pl. 7 

(Chla.m:yH), Poct.on, 21 

lur:J'tHch:i., Poc;t.on, 25 

lioh:l"i:ntri.a:na., Chla.m·y11, 31 

/Jo/1-ila.mollnt:u.H, Pecten, 43 

IJo'l'inrria.na., Chla.myr<, 31 

/n·a.nno·ri, Pm;t.on, 19 

ll'nc;h:i'lla.coa:nnH, Pocton, 22 

ca.lldnwi, P(J(;/.on, 19 

c:ohw1.lria:na., Poet.en, 30 

da.lla.wi, Poot.on, 31 

trrit:i, P(J(;f,on, .38 

fu.c;a:/1:/I.H, Poct.on, (;3 

lw.m.l·ini, P(J(;ton, 60 

lw.r<t.nt.n, Chla.m:JJH, 22 

olliwi, Chlnm1JH, 21,; pl. 5 

ho·1·idnH, Chla.myH, 23 

lw.Ht.nt:u.H, Poeton, 22 

ho·1·it:onr<, Pocton, 28 

hindwii, Peot.on, 28 

Ht·ra.t.oynr<, Poet.on, 29 

lw·l'i.t;onH Hf;ra.l.o{JnH, Pecten, 29 

lw·rtlohl.'i, Poc;ton, 21 

hoiltJtl'i, Pt:cl.o·11., 21 

·iHla:ncUcnR 1J'i.coonwill, Pecten, 27 

jrn·dtr:11:i, Chla.myH, 25 

Pect.on, 25 

la:wHo·11:i, Poct.en, 22 

m:nlt.i·ru.{JOH'It.H, Pocton, 65 

c;·raHHi1ll-i.t;a.tnH, Poct.en, 65 

'll.'lr.t.t.o·ri, P(J(;f,on, 31 

01J'II:n.t.ia., ChlnmyH, 26 

Poct.on, 26 

1Jit.IJ/oonwis, Peet.on, 47 

1un·mol(J(ri, Pocton, 59 

1JiGOIJ'II.HiH, Chlll.ll/.1fH, 27 

1J'I'oa:unH, Pecten, 19 

1J'It.fJ e t.onHi H , C hla. m:y 11 , 2 7 

·ru.Mda., Chla.m1JH, 28 

jonlw11:i, Chla.m:yH, 25 

'l'n/ri<lnH, Pc.ct.en, 28 

HOH1Joenwis, Poeton, 20 

hudoi, Poctcm., 20 

·vonl:u:rcW'II.wis, Poc;ton, 27 

'IIHI.t.l.wi, Pocl.on, 31, 59 

11/.0'I'a:ll:i, Pect.on, 60 

·yne:d.a:11.11., Pocton, 61 

Cic•·bo Sandstone, 42, 46, 47, 48, 52, 53, 54, 89; pis. 

10, 15, 28 

San Pablo G1·oup, 90 

cio·r/ioonwiH, Pa.c·ipecton, pl. 14 

Pecten, 47 

(Poct.on), 47 

C'inula:l'iH, AotrnhJoct.on, H4, 35 

AoqnhuH:tcn (Pla.[J·ioetmdnm), 34 

ih'{J01JCGton, 84, 35, HG 

t;i·rw.la.·l"iH, 32, 91,; pl. 9 

INDEX 

circularis-continued 

Chlamys, 34, 35, 37, 38 

(A·rgopecten), 34 

Pecten, 33, 34, 36, 41 

(Aeq'ltipecten) gibbus, 37 

(Plagiocteniwn), 34 

aeqwis'ltlca.ta., Chla.mus, 37 

Chla.m.ys (A?'{JO]Jecten), 34, 42 

bnr.mkamp1~, Aeqnipecten, 35 

A1·gopecten,' 32, 95; pl. 9 

Chla.mys, 35, 36 

cctll-i, A·rgopecten, 32, 95; pl. 10 

Chlamus, 35, 36 

(A1·gopecten), 35 

drc'!t.laris, Argopecten, 32, 91,; pl. 9 

eld·ridge·i, Aeq1~ipecten, 36 

A1·gopecten, 32, 96; pl. 9 

group, Chla.mys, 37 

imposter, Aeq'ltipecten, 36 

ATgopecten, 32, 96; pl. 10 

sens·u. La. to, A ?'[JOJJecten, 35 

Clallam Formation, 63, 90, 91; pl. 26 

coalingaensis, Oppenheimopecten, 76; pl. 33 

Pecten, 76, 78 

(Ja.nim) bellu.s, 76 

(0JJpenheimopecten), 76 

(Pecten), 76 

coarin{}ai'mH"is·, Pecten, 78 

coa.lin{}enwis, Oppenheimopecten, 75 

Pecten, 77 

cocosensis, Cuclopecten, 8 

Cold Creek Member, Monterey Formation, 53 

Topanga Canyon Formation, 90 

Topanga Formation, 54 

Coldwater Sandstone, 19, 20, 61, 90; pis. 3, 24 

Coldwate•· Sandstone Membe1·, Tejon Formation, 

90 

col-lwtb·iana, Leochlcnnus?, 90; pl. 8 

Pecten (Chlam.ys), 30 

col·umb·ianum, Pecten, 30 

compactus, Pecten, 34 

Pecten (Pecten), 34 

concloni, Y abepecten, 83 

conclyloma.tus, Chlamys, 12 

Lyropecten, 50 

Pecten, 51 

coope1·i, Chlamys (A?·gopecten), 37 

Pecten, 37 

(Plagioctenimn), 37 

coope1·icellus, Chlamys (Argopecten), 37 

coosenB"is, Patinopecten, 83 

Pecten, 87, 88 

(Lituyapecten), 88 

dille?"i, Pecten (Patinopecten), 88 

c01·teziana, Chlamus, 18, 22; pl. 5 

Cozy Dell Shale, 19, 90 

Cozy Dell Shale Member, Tejon Formation, 90 

c·rassa, Hinnites, 65; pis. 26, 27 

c1·assicanlium, Pallium, 51 

c·1·a.ssicardo, Chlamys (Lyropecten), 56 

Lyropecten, 49, 50,51, 54, 56; pis. 17, 18, 21,28 

Pallium, 51 

Pecten, 50, 51, 52, 57 

(Ly1·opecten), 51 

magnificus, 51 

magnificus, 50 

bifonnatis, Pecten, 51 

hamiltoni, LyTopecten, 50 

Pecten CLyropecten), 51 

nomlandi, Ly1·opecten, 51 

Pecten, 51 

vaughani, LyTopecten, 50 

crnssiplicatus, Chlamys, 65 

Hinnites nmltirugosus, 65 

Pecten (Chlamys) nmltirugosus, 65 

(Pecten) nmltirugosus, 65 

m·assiradi~tus, Argopecten?, 32, 1,2; pl. }0 

eras siradiatus -continued 

Pecten (Plag·ioctenimn ?), 42 

c1·istobalensis, Argopecten, 32, 1,0, 42; pl. 13 

Chlamys, 39, 40 

(A1·gopecten), 40 

Pecten, 40 

(Plagiocteniwn), 40 

Cyclopecten, 2, 6, 7, 8, 9, 13 

act~tus, 8 

cocosensis, 8 

geographic distribution, 7 

geologic distribution, 7 

greenlandicus, 13 

incong?·nus, 7, 8; pl. 1 

lompicoensis, 7, 8; pl. 1 

pernonms, 7, 8; pl. 1 

randolphi, 17 

tilla mookensis, 17 

vitreus, 13 

B103 

(Delectopecten) ?'andolphi tillamooken.qis, 17 

vancotwerensis, 17 

(Cyclo]Jecten) pernomus, Amusium, 8 

pernomus, Pecten, 8 

rott~ndatus, Pecten, 8 

Cyclopecten?, 7, 8 

martinezensis, 7, 8; pl. 1 

D 

dallasi, Aequipecten, 91; pl. 9 

Chlamys, 31 

Pecten, 31 

(Chlamys), 31 

davidsoni, Pecten (Propeamussium), 12 

Delectopecten, 2, 6, 8, 9, 19, 14, 16 

altentilineatus, 14, 15; pl. 2 

geographic distribution, 14 

geologic distribution, 14 

group, 19 

harfordus, 14, 16; pl. 3 

lillisi, 11,; pl. 3 

peckhami, 8, 14, 15, 18; pl. 3 

pedToanus, 18 

mndolphi tillamookensis, 14, 16, 17; pl. 3 

tillamookensis, 17 

vancouverensis, 17 

fernandoensis, 14, 16; pl. 3 

sanjuanensis, 17 

tillamookensis, 17 

vanconverensis, 14, 17; pl. 3 

(Delectopecten) altentilineatus, Hyalopecten, 15 

fernandoensis, Hyalopecten, 16 

lillisi, Hyalopecten, 14 

peckhami, Palliolum, 15 

pedroantts, Hyalopecten, 18 

randolphi tillamookensis, Cyclopecten, 17. 

.vancouverensis, Cyclopecten, 17 

zacae, Pecten, 14 

delosi, Leptopecten, 43 

dentatus, Pecten, 77 

Pecten (Pecten), 77 

deserti, Aeqnipecten, 33 

Argopecte.n, 32, 99, 36; pl. 9 

Chlamys, 33, 34, 38 

(Argopecten), 33 

Pecten, 33, 35, 36 

(Lyropecten), 33 

(Plagioctenium), 33 

group, Chlamys, 33 

diabloensis, Pecten, 64 

Vertipecten, 61, 61,; pis. 21,39 

diazi, Liwpecten bakeri; 84, 85; pis. 39, 40 

Patinopecten bakeri, 85, 86 

Pecten bakeri, 85 

dickersoni, Pecten, 75 

Pecten (Pecten), 75 
B104 PALEONTOLOGY OF CALIFORNIA AND BAJA CALIFORNIA 

diegensis, Flabellipecten, 71, 79; pls. 31, 32 

Pecten, 68, 71, 72, 73, 74 

(Janira) stearnsii, 73 

(Pecten), 73 

dilleri, Lituyapecten, 86 .• 88; pl. 42 

Patinopecten, 88 

(Lituyapecten), 87, 88 

Pecten, 87, 88 

(Lituyapecten), 88 

(Lyropecten), 88 

(Patinopecten), 88 

coosensis, 88 

diminutivus, Argopecten, 92, 35; pl. 9 

Pecten (Plagioctenium), 32, 33 

discus, Aequipecten, 47 

Chlamys, 47 

Leptopecten, 47 

Pacipecten, 44, 46, 48; pl. 14 

Pecten, 35, 45, 46, 48 

(Aequipecten), 47 

(Plagioctenium), 47 

dregeri, Pecten, 12 

durhami, Chlamys, 21, 22; pl. 5 

E 

Ectyodoryx parasitica, 29 

Edna Member, Pismo Formation, 81, 90 

egregius, Chlamys, 18, 22, 24; pl. 6 

Pecten, 21, 24 

el dridgei, Aequipecten circularis, 36 

Argopecten circularis, 32, 96; pl. 9 

Chlamys, 35 

Pecten (Aequipecten), 36 

(Plagioctenium), 36 

ellisi, Chlamys (Chlamys) hastata, 24; pl. 5 

Chlamys hastata, 18, 24 

emigdioensis, Macrochlamis, 56; pl. 21 

Pecten, 56 

(Ly·ropecten) vaughan-!, 56, 57 

Empire Formation, 86, 91 

ericellus, Argopecten, 32, 97; pl. 12 

Chlamys (Argopecten), 37 

Pecten (Plagioctenium), 37 

erici, Leochlamys?, 90; pl. 8 

Pecten (Chlamys), 30 

estrellanum, Pallium, 53 

estrellanus, Chlamys (Lyropecten), 56 

Lyropecten, 49, 50, 52, 59, 56; pl. 19 

Pecten, 29, 50, 52, 53, 55 

(Lyropecten), 53 

catalinae, Chlamys (Lyropecten), 56 

Lyropecten, 56 

Pecten (Lyropecten), 53 

cerrosensis, Pecten (Lyropecten), 55 

terminus, Lyropecten, 56 · 

Pecten (Lyropecten), 54 

Etchegoin Formation, 23, 24, 25, 28, 31, 36, 54, 56, 

59, 60, 66, 76, 81, 83, 89, 90, 91; pls. 6, 9, 

10,22,23,33 

etchegoini, Chlamys, 29, 60 

Chlamys parmeleei, 59, 60 

(Swiftopecten) parmeleei, 60 

Pecten, 60 

(Pallium) swiftii, 60 

Swiftopecten, 60 

parmeleei, 59, 60; pl. 22 

nutteri, Pecten, 31 

wattsi, Pecten (Swiftopecten), 31 

Euvola, 2, 70 

keepi, 70, 71; pl. 30 

geographic distribution, 70 

geologic distribution, 70 

refugioensis, 70, 71; pl. 30 

(Euvola) cataractes, Pecten, 77 

keepi, Pecten, 70, 71 

(Euvola )-continued 

refugioensis, Pecten, 71 

evermanni, Argopecte·n, 32, 99, 40, 42; pl. 13 

Chlamys (Argopecten), 39 

Pecten, 39 

(Aequipecten), 39 

(Plagioctenium), 39 

excavatus, Pecten, 69, 77 

expansus, Pecten, 81 

Pecten (Patinopecten), 81 

extenuatus, Pecten, 16 

F 

Falor Formation, 83, 86, 87, 90, 91; pl. 41 

falorensis, Lituyapecten, 86; pl. 41 

Patinopecten (Lituyapecten), 86 

Pecten, 87 

Fernando Formation, 8, 11, 12, 16, 17, 18, 23, 24, 

26,27,29,35,37,39,44,56,60, 66, 69, 

73, 82, 83, 84, 88, 89, 91; pls. 1, 2, 3 

fernandoensis, Delectopecten vancouverensis, 14, 

16; pl. 3 

Hyalopecten (Delectopecten), 16 

Pecten, 16 

(Pseudamusium) vancouverensis, 14, 16 

vancouverensis, 16 

Flabellipecten, 2, 69, 70, 71, 84 

beali, 71, 73; pl. 31 

boesei, 71 

bosei, 72; pl. 32 

carrizoensis, 71; pl. 31 

diegensis, 71, 73; pls. 31, 32 

geographic distribution, 71 

geologic distribution, 71 

stearnsii, 71, 72; pl. 31 

Flabellipecten?, 74 

hawleyi, 70, 71, 74; pl. 31 

merriami, 71, 74; pls. 32,33 

(Flabellipecten) stearnsii, Pecten, 72; pl. 31 

florida, Janira, 72 

floridus, Pecten, 72, 73 

Fortipecten, 42 

Fossil localities, 88 

Foxen Mudstone, 23, 56, 6~ 83, 8~ 91 

fragilis, Leptopecten latiauratus cerritensis, 44 

Freeman Silt, 65, 91 

fucanus, Pecten (Chlamys), 63 

Pecten (V ertipecten) nevadanus, 63 

Vertipecten, 61, 69, 64, 79, 80; pls. 26, 27 

G 

gabbi, Pecten, 64 

gallegosi, Chlamys (Lyropecten), 56 

Lyropecten, 49, 54, 56; pl. 19 

Pecten, 55 

(Lyropecten), 54, 55 

Gaviota Formation, 20, 61, 90, 91; pl. 25 

gela.tinosus, Hyalopecten, 13 

Geographic distribution, Argopecten, 32 

Chlamys, 18 

Cyclopecten, 7 

Delectopecten, 14 

Euvola, 70 

Flabellipecten, 71 

Leopecten, 84 

Leptopecten, 43 

Lituyapecten, 86 

Lyropecten, 49 

Nodipecten, 57 

Oppenheimopecten, 75 

Pacipecten, 44 

Parvamussium, 9 

Patinopecten, 78 

Geographic distribution-continued 

Pecten (Pecten), 67 

Pectinidae, 2 

Propeamussiidae, 2 

Swiftopecten, 59 

Vertipecten, 61 

Geologic distribution, Argopecten, 32 

Chlamys, 18 

Cyclopecten, 7 

Delectopecten, 14 

Euvola, 70 

Flabellipecten, 71 

Leopecten, 84 

Leptopecten, 43 

Lituyapecten, 86 

Lyropecten, 49 

Nodipecten, 57 

Oppenheimopecten, 75 

Pacipecten, 44 

Parvamussium, 9 

Patinopecten, 78 

Pecten (Pecten), 67 

Pectinidae, 2 

Propeamussiidae, 2 

Swiftopecten, 59 

Vertipecten, 61 

Geologic formations containing pelecypods, 90 

gibbus, Argopecten, 35 

circularis, Pecten (Aequipecten), 37 

gigantea, Lima, 65 

giganteum, Plagiostoma, 65 

giganteus, Hinnites, 65, 66; pls. 26, 27 

Pecten (Hinnites), 65 

Gloria Formation, 22, 35, 38, 40, 41, 43, '/2, 78, 85, 

91 

gonicostatus, Pacipecten, pl. 14 

Pecten, 47 

(Pecten) andersoni, 47 

Gould Shale Member, Monterey Formation, 45, 

53, 91 

Graciosa Member, Careaga Sand, 91 

Careaga Sandstone, 69, 83, 91 

Gragg Member, Pismo Formation, 56, 91 

greenlandicus, Cyclopecten, 12 

grewingki, Chlamys mediacostata, 29 

Chlamys?, 29, 30 

mediacostata, 18, 29; pl. 7 

Gries Ranch Formation, 91 

H 

hakei,Argopecten, 32, 99, 41, 42; pl. 11 

Chlamys, 39, 40 

(Argopecten), 39, 42 

Pecten, 39, 55 

(Aequipecten) purpuratus, 39 

(Plagioctenium), 39 

halimensis, Pecten, 21 

Hames Member, Monterey Formation, 46, 91 

hamiltoni, Lyropecten, pl. 18 

Lyropecten crassicardo, 50 

Pecten, 52 

(Lyropecten) crassicardo, 51 

magnificus, 51 

hamlini, Chlamys (Swijtopecten?), 60 

Pecten, 60 

(Chlamys), 60 

(Pallium), 60 

Swiftopecten?, 59, 60; pl. 24 

hancocki, Pecten (Oppenheimopecten), 78 

harfordus, Delectopecten, 14, 16; pl. 3 

Pecten (Camptonectes ), 16 

Oppenheimopecten, 75, 76; pl. 33 

Pecten, 77 

(Janira), 76 

(Oppenheimopecten), 76 

(Pecten), 76 
hartmanni, Oppenheimopecten, 75, 76; pl. 33 

Pecten, 77 

(Janira), 76 

(Oppenheimopecten), 76 

(Pecten), 76 

hast1tta, Chlamys, 22, 23, 24, 27, 29, 66 

Chlltmys (Chlamys), 22 

hastata, 18, .!1.!1; pl. 5 

elliB'i, Chlamys, 18, 24 

Chlamys (Chlamys), .114; pl. 5 

gt·oup, Chlamys, 24 

hn11tata, Chlamys, 18, .!1.!1; pl. 5 

hericia, Chlam.y11, 23, 27, 29 

he1·iC'ius, Chlamys, 18, .119, 27; pl. 5 

Chlamy11 (Chlamys), 23 

Pecten, 20 

pu.getensis, Chlnmys, 18, 23, 24, .!17, 29; pl. 6 

hastatus, Chlamys, 23 

Pecten, 22, 25, 28, 48 

(Chlamys), 22 

(Pecten), 22 

hericins, Pecten, 20 

Pecten (Chlamys), 23 

hindsii, Pecten (Chlamys), 28 

pnget.ensis, Pecten (Pecten), 27 

stnttegns, Pecten (Chlamys), 29 

hatcd:i, Chlnmy11, 26 

lur.wleyi, 1-'lctbellipecten?, 70, 71,74; pl. 31 

Pecten, 74 

(Pecten), 74 

haytva:rdensis, Pati1w1Jecten, 78, 80; pis. 35, 36 

Pecten, 80 

(Pntinopecton), 80 

ca.lltverasensis, Pecten, 80 

Pecten (Pntinopecten), 80 

hectleyi, Pcttinopecten, 78, 79,81, 82, 84; pis. 34, 35, 

36, 37, 38, 39, 40, 41, 42 

Pecten, 12, 82, 83, 85 

(Patinopecten), 81 

loh·ri, Pecten (Patinopecten), 80 

sa.nclementensis, Pecten (Patinopecten), 81, 

82 

hee?'IIHtnnii, Pecten, 83, 84 

heim:i, 01J1Jenhe·imopecten, 75, 77; pl. 33 

Pect.en, 76, 77 

(01Jpenheimopect.en), 77 

(Pecten), 77, 78 

lwmphilU, Pecten, 77 

Pecten (Pecten), 69 

hemphillii, Pecten, 68; pl. 29 

Pllcten (Ja.ni1·a) bellus, 68 

(Pect.en), 68 

Hemphilli-i, Pecten, 68 

he·ricens, P oct en, 28 

nct1!Ct'l'chus, Pecten, 26, 28 

st·rcttegus, Pectun, 29 

Pecten (Chlctmys), 29 

hm·icict, Chlctmys hasta.tct, 23, 27, 29 

he·l'icius, Chlctmys, 23 

Chlctmys (Chlamys) hctstatct, 23 

ha.stcttct, 18, .119, 27; pl. 5 

Pecten, 21, 23 

(Chlctmys) hasta.tus, 23 

lw.statns, 20 

Hct·tlcin, I... G., cited, 1 

Hct·tlcin, I... G., quoted, 12, 13 

he·rtleini, Chlctmys, 18,.111, 26; pl. 4 

Pecten (ChlconyR), 21 

hete1·oglyptus, Pecten, 31 

h:inrlsii, Pecten, 28 

Pecten (Chlctmys) hastatus, 28 

Hinnitct 1J01.tlsoni, 65 

11-innites, 2, 13, 65 

/Jenecl-icti, 65; pl. 26 

C'I'U.BBCt, 65; pis. 26, 27 

gigcmte'!I.H, 65, 66; pis. 26, 27 

gt·oup, 65 

INDEX 

Hinnites-c.ontinued 

multirugosus, 23, 65, 66 

crassiplicatus, 65 

pusio, 65 

(Hinnites) giganteus, Pecten, 65 

hodgei, Chlamys, i8, 20, 21; pls. 4, 5 

Pecten, 21 

. (Chlamys), 21 

holtvayi, Pecten, 51, 52, 53; pl. 28 

Pecten (Pallium), 51 

humphreysii alete11, Pecten (Janira), 67 

Hyalopecten, 13 

gelatinosus, 13 

peckhami, 15 

vancouverensis, 17 

(Delectopecten) alternilineatus, 15 

fernandoensis, 16 

lillisi, 14 

pedroanus, 18 

hydei, Chlamys sespeensis, 18, 20; pl. 4 

Pecten, 20 

(Chlamys) sespeensis, 20 

sespeensis, 30 

I, J, K 

imanishii, Chlamys, 28 

Imperial Formation, 22, 29, 33, 34, 36, 55, 58, 70, 

71, 72, 88, 90, 91; pis. 7, 9, 30, 31 

impostor, Aeq1tipecten, 36, 41 

Aequipecten circularis, 36 

Argopecten, 34 

circularis, 32, 96; pl. 10 

Chlamys, 38 

Pecten, 33, 35; 36 

incongruum, Pseudamusium, 8 

incongruus, Cyclopecten, 7, 8; pl. 1 

inezana, Pecten, 63 

Infierno Formation, 35, 38, 41, 49, 58, 72, 78, 85,91 

interlineatus aidei, Pecten, 29 

intermedius, Lyropecten, 58 

Nodipecten subnodosus, 57, 58; pls. 22, 23 

Pecten, 57 

(Lyropecten) nodosus, 58 

interradiata, Pecten, 10 

inte·rradiatum, Propeamussium, 7, 9, 10; pl. 1 

Propeamussium (Propeamussium), 7 

interradiatus, Pecten, 7 

Pecten (Propeamussium), 7 

Introduction, 1 

intuscostatum, Polynemamussium, 12 

invalida, Chlamys, 37, 38 

Chlamys (A.rgopecten), 37 

·invctlidus, Argopecten, 32, 33, 97; pl. 10 

Pecten, 33, 37 

Isidro Formation, 33, 45, 46, 51, 70, 71, 89, 91; pls. 

9, 17 

islandica, Chlamys, 24, 27, 28 

behringiana, Chlamys, 31 

group, Chlamys, 26 

islandicus, Chlamys, 29 

Pecten, 20, 27, 28 

beringianus, Chlamys, 29 

group, Chlamys, 29 

jordani, Chlamys, 25 

kincaidi, Pecten, 32 

11icoensis, Pecten (Chlamys), 27 

pugeten11is, Pecten, 24, 27 

Janira bella, 68 

florida, 72 

(Janira) bellus coalingaensis, Pecten, 76 

bellus hemphillii, Pecten, 68 

hartmanni, Pecten, 76 

hmnphreysii aletes, Pecten, 67 

keepi, Pecten, 70 

(Janira)-continued 

stearnsii bakeri, Pecten, 85 

carrizoensis, Pecten, 71 

diegensis, Pecten, 73 

stearnsii, Pecten, 72 

Jewett Sand, 21, 64, 65, 89, 91 

Pyramid Hill Sand Member, 57, 63, 91 

jordani, Chlamys, 18, 21, 25, 28; pl. 6 

Chlamys (Chlamys), 25 

(Chlamys) 1·ubida, 25 

islandicus, 25 

rubida, 25, 29 

Pecten, 21, 25 

(Chlamys), 25 

B105 

juanensis, Oppenheimopecten, 75, 76, 77; pl. 33 

Pecten, 76, 78 

(Oppenheimopecten), 75 

(Pecten), 75, 78 

kamagai, Mizuhopecten, 12 

keepi, Euvola, 70, 71; pl. 30 

Oppenh.etmopecten, .77 

Pecten, 70 

(Euvola), 70, 71 

(Janira), 70 

(Pecten), 70 

kernensis, Pecten, 64 

Pecten (Patinopecten), 64 

Vertipecten, 61, 63, 61,; pl. 28 

kincaidi, Chlamys, 26 

Pecten islandicus, 32 

kinoshitai, Chlamys, 27 

Kreyenhagen Formation, 14, 15, 91; pl. 3 

Kreyenhagen Shale, 7, 10, 14, 89, 91; pl. 1 

La jolla Formation, 9 

laevis, Pecten, 11 

L 

lajollaense, Parvamussium, 9; pl. 1 

Propeamussium, 9 

lajollaensis, Pecten, 9, 10 

laqueatus, Pecten, 67 

Las Posas Formation, 42, 83, 91 

latiaurata, Chlamys (Leptopecten), 43, 44 

Leptopecten, 43, 44 

latiauratus, Leptopecten, 1,9; pl. 15 

Pecten, 43 

cerritensis fragilis, Leptopecten, 44 

latiauritus, Pecten, 44, 45 

monotimeris, Pecten, 45 

latvsoni, Pecten, 23 

Pecten (Chlamys), 22 

leavis, Pecten, 11 

lecontei, Pecten, 68· 

Pecten (Pecten), 67, 68, 69, 72; pl. 28 

Leochlamys, 90 

Leochlamys?, 2, 90 

columbiana, 90; pl. 8 

erici, 90; pl. 8 

porterensis, 30 

(Leochlamys) tugidakensis, Chlamys, 30 

leohertleini, Parvamussium, 9 

Propeamussium, 7, 10 

Leopecten, 2, 81, 

bakeri, 85 

bakeri, 84,85; pl. 40 

diazi, 84, 85; pls. 39,40 

geographic distribution, 84 

geologic distribution, 84 

marquerensis, 84, 8 5; pls. 39, 40 

Leptopecten, 2, 42, 1,9 

andersoni, 45, 47 

bellilamellatus, 49; pl. 13 

delosi, 43 

discus, 47 

geographic distribution, 43 
B106 PALEONTOLOGY OF CALIFORNIA AND BAJA CALIFORNIA 

Leptopecten-continued 

geologic distribution, 43 

latiau1·ata, 43, 44 

lrttiauratus, 43; pl. 15 

ceTritensis fragilis, 44 

monotimeTis, 44 

pa bloensis, 4 7 

(Leptopecten) bellilamellata, Chlamys, 43 

latiaurata, Chlamys, 43, 44 

monotimeT'is, Chlamys, 44 

praeval-id'tts, Pecten, 42 

tumbezensis, Chlamys, 49 

levis, Pecten, 11 

Pecten (Propeamusi'um), 11 

lillisi, Delectopecten, 14; pl. 3 

Hyctlopecten (Delectopecten), 14 

Pecten, 14 

(Pseudamusiwn), 14 

Lima giga,ntea, 65 

Lincoln Creek Formation, 91 

Lindavista Formation, 69, 91 

lituyaensis, Pecten, 86 

Pecten (Lituyapecten), 87 

Lit'uyapecten, 2, 86 

d-illeTi, 86, 88; pl. 42 

falorensis, 86; pl. 41 

geographic distribution, 86 

geologic distribution, 86 

purisimaensis, 86, 87; pl. 41 

turneri, 86, 87; pl. 37 

(Lituyapecten) coosensis, Pecten, 88 

dilleri, Patinopecten, 87, 88 

Pecten, 88 

falorensis, PaUnopecten, 86 

lituyaensis, Pecten, 87 

7Joulc1·eekensis, Pecten, 88 

p1t1·isimaensis, Patinopecten, 87, 88 

Pecten, 86, 88 

pu1·isimaensis-jalorensis stock, Pecten, 88 

yakatagensis, Pecten, 86 

Locatelli Formation, 19, 89, 91; pl. 3 

Lodo Formation, Arroyo Hondo Shale Member, 9, 

10 

Cerros Shale Member, 9, 89, 90; pl. 1 

lohri, Patinopecten, 78, 79, 80, 83; pis. 34, 36 

Pecten (Patinopecten), 80 

(Patinopeeten) healeyi, 80 

Lomita Marl Member, San Pedro Formation, 12, 

17, 23,24, 26, 28, 29,44, 73, 84,91 

lompicoensis, Cyclopecten, 7, 8; pl. 1 

Pecten (Pseudanmsium), 7 

lompocensis, A musium, 66, 67; pl. 2 

Pecten, 67 

(Amusium), 66, 67, 70 

(Amussiopecten), 66, 67 

Los Laureles Sandstone Member, Monterey 

Formation, 15, 91 

Los Tularcitos Member, Chamisal Formation, 46, 

91 

lowei, Chlamys, 22 

Lyropecten, 2,6, 29, 30,40,49, 50,55, 56,57 

ashleyi, 55; pis. 20, 21 

bowersi, 62 

catalinae, 49, 53, 54; pl. 18 

cerrosensis, 33, 49, 52, 54, 55; pis. 20, 21 

condylomatus, 50 

crassicardo, 49, 50,51, 54, 56; pis. 17, 18, 21, 28 

hamiltoni, 50 

nomlandi, 51 

vaughani,50 

estrellanus, 49, 50, 52, 53, 56; pl. 19 

catalinae, 56 

terminus, 56 

gallegosi, 49, 54, 56; pl. 19 

geographic distribution, 49 

geologic distribution, 49 

hamiltoni, pl. 18 

Lyropecten-continued 

i1itennedius, 58 

magnolia, 50, 56 

mediacostatus, 29 

miguelensis, 49, 50, 54; pl. 16 

submiguelens,i.~, 50 

modulatus, 49, .55, 57, 58; pl. 19 

nomlandi, pl. 17 

pretiosus, 49, 51; pl. 17 

ricei, pl. 18 

s1tbmiguelensis, 49, 50, 53; pis. 16, 17 

subnodosus, 57, 58 

terminus, 49, 54, 56; pl. 19 

vaughani, 49, 50; pl. 17 

vicke1·yi, pl. 17 

volaeformis, 53 

(Ly1·opecten) ashleyi, Pecten, 55 

bowersi, Pecten, 62 

cerrosensis, C hlaniys, 40, 55, 56 

Pecten, 55 

crassicardo, Chlamys, 56 

Pecten, 51 

hamiltoni, Pecten, 51 

deserti, Pecten, 33 

dille1·i, Pecten, 88 

est1·ellanu.q, Chlamys, 56 

Pecten, 53 

catalinae, Chlamys, 56 

Pecten, 53 , 

cerrosens'is, Pecten, 55 

terminus, Pecten, 54 

gallegosi, Chlamys, 56 

Pecten, 54, 55 

magnificus crassicardo, Pecten, 51 

hamiltoni, Pecten, 51 

magnol,ia, Pecten, 56 

miguelensis, Pecten, 49 

submig'uelensis, Pecten, 50 

modulat1ts, Pecten, 55 

nodosus intermediu:;, Pecten, 58 

va1tghani, Pecten, 50 

veatchii, Pecten, 58 

perrini, Pecten, 62 

pretiosus, Pecten, 51 

ricei, Pecten, 51 

subnodosus, Pecten, 57, 58 

tamiamiensis, Pecten, 29 

vaughani, Pecten, 50 

emigdiocnsis, Pecten, 56, 57 

veatchii, Pecten, 58 

vickeryi, Pecten, 51 

M 

Macrochlamis, 6, 56 

emigdioensis, 56; pl. 21 

magnolia, 56; pl. 21 

. Macrochlamys, 2 

nwgnificus. crassicardo, Pecten, 50 

crassicardo, Pecten (Lyropecten), 51 

hamiltoni, Pecten (Lyropecten), 51 

magnolia, Lyropecten, 50, 56 

Macrochlamis, 56; pl. 21 

Pecten, 52, 56, 57 

(Lyropecten), 56 

Man1tpecten, 24, 59 

Margaritan Stage, 47 

Maricopa Shale, 15, 91 

Marquer Formation, 35, 41, 58, 85, 86, 90, 91; pis. 

9, 39,40 

marquerensis, Leopecten, 84, 85; pis. 39, 40 

Patinopecten, 85 

Martinez age strata, 19 

Martinez Formation, 9, 91; pl. 1 

martinezensis, Cyclopecten?, 7, 8; pl. 1 

Pecten, 8 

McLure Shale Member, Monterey Formation, 46, 

47,53,91 

Temblor Formation, 54 

Media Shale Member, Temblor Formation, 46, 54, 

91 

mediacostata, Chlamys, 30 

Chlamys mediacostnta,, 29 

Chlamys?, 30 

medincosta,ta, 18, 29; pl. 7 

grewingki, Chlamys, 29 

Chlnmys?, 18, 29; pl. 7 

mediacosta.tn,. Chlnmys, 29 

Chlnmys?, 18, 29; pl. 7 

mediacostat1is, Dyropecten, 29 

Pecten, 29 

meekii, Pecten, 83, 84 

mendenhalli, Argopecten, 32, 33; pl. 9 

Pecten, 33, 41 

cer'rosensis, 40 

(Plagiocteni'ttln), 33 

ceTroscnsis, 33 

Merced Formation, 11, 23, 24, 26, 29, 31, 33, 37, 43, 

44, 60, 66, 69, 73, 83, 84, 87, 88, 91; pl. 37 

merrinmi, Flabellipecten?, 71, 74; pis. 32, 33 

Pecten, 74, 84 

(?Patinopecten), 74 

(Pecten), 74 

mideocenicum, Pa1·vam1tssium, 9; pl. 1 

P1·openmussi1mt, 9, 10 

miguelensis, Lyropecten, 49, 50, 54; pl. 16 

Pecten, 50, 54 

(Lyropecten), 49 

submiguelensis, Lyropecten, 50 

Pecten (Lyropecten), 50 

Mindego Basalt, 57, 91 

miyatokoensis, Chlamys, 24 

Mizuhopecten, 78 

knnwgai, 12 

Moclipsian molluscan stage, 88 

Modelo Formation, 13, 15, 45, 46, 47, 48, 53, 54, 91 

modulatus, Lyropecte,n, 49, 55, 57, 58; pl. 19 

Pecten, 55 

(Lyropecten), 55 

Mohnian benthic foraminiferal stage, 47 

Molluscan stage, Moclipsian, 88 

monotimeris, Chlamys (Leptopecten), 44 

Leptopecten, 44 

Pecten latinuritus, 45 

Monterey Formation, 8, 15, 16, 21, 45, 47, 53, 54, 

66, 80, 91; pis. 1, 3, 14, 28 

Antelope Shale Member, 15, 90 

Cold Creek Member, 53 

Gould Shale Member, 45, 53, 91 

Hames Member, 46, 91 

Los Laureles Sandstone Member, 15, 91 

McLure Shale Member, 46, 47, 53, 91 

Saltos Shale Mem her, 46, 50, 53, 62, 91 

Twisselman Sand:stone Member, 46, 91 

Woodhams Member, 15, 91 

Monterey Group, 91 

Oursan sandstone·, 91 

Monterey Shale, 10, 13, 15, 45, 67, 91; pl. 3 

Altamira Shale Member, 45, 90 

Saltos Shale Member, 70 

Valmonte Diatomite Member, 18, 91 

Morales Formation, 54, 91 

morani, Pecten (Chlamys) wattsi, 60 

Swiftopecten, 60; pl. 22 

Moreno Formation, 46, 91 

mortoni, Pecten (Am1tsium), 67 

Muir Sandstone, 10, 91 

multirugosus, Hinnites, 23,, 65, 66 

Pecten, 65 

(Chlamys), 65 

(Pecten), 65 

crassiplicatus, Hi'nnites, 65 

Pecten (Chlamys), 65 
nmltirugosus-continued 

crassiplicatus-continued 

Pecten-continued 

(Pect.en), 65 

Myt:a.lo culhe·1·en11, 29 

N 

Nn.nn.ochlnnl.yH, 2, 29, 9.1 

n:u.tt.e·l"i., .'11; pl. 8 

nn'IJII:I'chu.s, Pecten he·riceus, 26, 28 

IWrthenwiH, Pecten (Plctg·iocten·i-nm), 35 

Ncroly Fonnation, 90· 

Ncr·oly Sandstone, 46, 47, 48, 53, 54, 76; pl. 33 

San Pablo Gr·oup, 91 

neva.clctnuH, Pect.en, 64 

V e·rt·ipecten, 63, 64 

fu.cwn:ns, Pecten (V cwt·ipecten), 63 

11e'l"'ri-ld, Pecten (Vc·,.t·ipccten), 62 

Niguel Formation, 23, 26, 28, 35, 37, 39, 56, 60, 66, 

69, 73, 82, 83, 88, 91 

Nocl·ipect.en, 2, 6, 57 

gcogr·aphic distribution, 57 

geologic distribution, 57 

nocloH'lt.H nodowns, 58 

Hulmoclowns, 55, 57 

Hubnoclosns inte'l"lneclius, 57, 58; pis. 22, 23 

Hlt./nwclosns, 57; pl. 6 

vea.tcldi, 57, 58; pis. 22, 23 

(Nocl·ipect.en) ct·l·nolcl-i, Chla.mys, 12 

wu.bnoclowns, Pect.en, 57, 58 

tJea.t.ch-i-i, Pecten, 58 

noclowu.H, Nocl·ipect.en noclowu.s, 58 

Pecten, 58 

·intennecl·ius, Pecten ([Jy·ropecten), 58 

'IWclowu.s, Nocl·ipecten, 58 

·uaughcm·i, Pect.en (Ly·mpecten), 50 

ventch:ii, Pecten (Ly·ropecten), 58 

'ItO 1nln.ncl'i, I:.y·ropecten, pI. 17 

Dy·,·opecten c·rnssica1·clo, 51 

Pecten, 51, 52 

cntss-icnnlo, 51 

'/l:ncle·u.s, A·rgopecten, 35 

n-nttm··i, NctnctochlctlnyH, 91; pl. 8 

Pecten, 31 

(Chlctmyll), 31 

etchego·in·i, 31 

(Pctll-i·u.m) swift·i, 31 

Swiftopecten, 60 

Nyc Mudstone, 64 

0 

Obispo Fonnation, 53, 67, 70, 91 

Octopus, 79, 84 

Ohlson Ranch !''ormation, 23, 25, 28, 84, 87, 91 

Olccsc Sand, 45, 46, 65, 91 

Oppenlteimopecten, 2, 75 

eoctlingaensis, 76; pl. 33 

coctlingensis, 75 

gcogmphic distr·ibution, 75 

geologic distr·ibution, 75 

hartmanni, 75, 76; pl. 33 

lte·imi, 75, 77; pl. 33 

juctnenB'is, 75, 76, 77; pl. 33 

keepi, 77 

HanctlteC?"ItZenHiB 1 75 j piS. 32, 33 

vogclesi, 75, 76, 77; pl. 34 

(Oppenltoimopecten) coalingaensis, Pecten, 76 

hctncocki, Pecten, 78 

hwrtmctnni, Pecten, 76 

!teind, Pecten, 77 

juanonsis, Pecten, 75 

vogclosi, Pecten, 77 

opuntia, Cltlamys, 18, 1!6, 29; pl. 6 

Cltlamys (Citlamys), 26 

Pecten, 21, 25 

INDEX 

opttntia-continued 

Pecten-continued 

(Citlamys), 26 

o1·egonen.qis, Patinopecten, 83 

Pecten, 64, 86 

ca.ncellosus, Patinopecten, 83 

Ost1·ea, 12 

Oursan Sandstone, 80; pl. 35 

Monterey Group, 91 

oweni, Pecten, 80 

Pecten (Patinopecten), 80 

Oyster reef, 90 

Oyster-pecten bed, 90 

p 

pabloensis, Leptopecten, 47 

Pacipecten, 44, 4 7; pl. 15 

Pecten, 47, 48 

(Aequipecten), ·47 

(Chlamys), 47 

(Plagioctenittm), 47 

Pacipecten, 2, 42, 43, 44 

andersoni andersoni, 44, 45; pl. 14 

barkerianttB, 44, 45; pl. 20 

subanclerso1i.i, 44, 45; pl. 14 

bilineatus, '44, 48; pl. 15 

brion·ianus, pl. 14 

cierboensis, pl. 14 

discus, 44, 46, 48; pl. 14 

geographic distribution, 44 

geologic distribution, 44 

gonicostattts, pl. 14 

pabloensis, 44, 4 7; pl. 15 

raymondi, pl. 14 

tolmani, 44, 46; pl. 14 

t·twtbezensis, 44,49; pl.15 

weave1·i, 44, 46; pl. 15 

(Pacipecten) tumbezensis, Pecten, 49 

Painted Rock Member, Vaqueros Formation, 66 

Painted Rock Sandstone Member, Vaqueros 

Formation, .21, 50, 57, 62, 70, 91 

Palliolum (Delectopecten) peckltami, 15 

Pallium crassicardium, 51 

crassicardo, 51 

estrellanum, 53 

(Pallium) ltamlini, Pecten, 60 

ltolwayi, Pecten, 51 

swifti nutteri, Pecten, 31 

swiftii etchego·ini, Pecten, 60 

Palos Verdes Sand, 35, 58, 78, 91 

Pancho Rico Formation, 54, 56, 66, 81, 91; pl. 19 

parasitica, Ectyodoryx, 29 

parmeleei, Cltlamys, 29, 59 

Cltlamys parmeleei, 60 

(Swiftopecten), 59 

Pecten, 31, 60 

(Citlamys), 59 

Swiftopecten, 60 

parmeleei,59; pl. 23 

etcltegoini, Cltlamys, 59, 60 

Cltlamys (Stviftopecten), 60 

Swiftopecten, 59, 60; pl. 22 

panneleei, Cltlamys, 60 

Swiftopecten, 59; pl. 23 

Parvamussium, 2, 8, 9, 10 

alaskense, 9, 11; pl. 2 

alaskensis, pl. 2 

cala,;titus, 12; pl. 2 

geographic distribution, 9 

geologic distribution, 9 

lajollaense, 9; pl. 1 

leoltertleini, 9 

mideocenicum, 9; pl. 1 

riversi, 9, 10; pl. 1 

stanfordense, 9, 10; pl. 1 

stanfordensis, 9 

B107 

(Pa.1·vamttssi1on) alaskense, Propeam1tssium, 11 

stanfordensis, P1·opeamussium, 10 

Paso Robles Formation, 66, 91 

Pa.tinopecten, 2, 13, 24, 60, 61, 74, 78, 84, 86 

bakeri, 85, 86 

diazi, 85, 86 

calaverasensis, 78, 80; pl. 35 

caurinus, 78, 79, 82, 89; pis. 38, 39 

coosensis, 83 

dilleri, 88 

geographic distribution, 78 

geologic distribution, 78 

haywardensis, 78, 80; pis. 35, 36 

healeyi, 78, 79,81, 82, 84; pis. 34, 35, 36, 37, 38, 

39,· 40, 41, 42 . 

loh?-i, 78, 79, 80, 83; pis. 34, 36 

ma1·querensis, 85 

oregonensis, 83 

cancellosus,83 

propatuhts, 78, 79, 80; pis. 26, 34, 35 

p1trisa maensis; 87 

subgroup, 78 

t1trneri, 87 

yessoensis, 78, 79, 83; pl. 40 

(Lituyapecten) dilleri, 87, 88 

falorensis, 86 

purisimaensis, 87, 88 

(Patinopecten) caurinus, 83 

(Patinopecten) bakeri, Pecten, 84, 85 

ctturintts, Patinopecten, 83 

Pecten, 12, 83 

coosensis dilleri, Pecten, 88 

dilleri, Pecten, 88 

expansus, Pecten, 81 

haywardensis, Pecten, 80 

calaverasensis, Pecten, 80 

ltealeyi, Pecten, 81 

lohri, Pecten, 80 

sanclementensis, Pecten, 81, 82 

kernensis, Pecten, 64 

lohri, Pecten, 80 

oweni, Pecten, 80 

propatulus, Pecten, 63, 79 

purisimaensis, Pecten, 87 

turneri, Pecten, 87 

weaveri, Pecten, 46 

(?Patinopecten) merriami, Pecten, 74 

peckltami, Delectopecten, 8, 15, 18; pl. 3 

Hyalopecten, 15 

Palliolum (Delectopecten), 15 

Pecten, 13, 14, 15, 16 

(Pseudamusium), 14, 15 

Pecten,~30,4~49, 51,67 

abietis, 41 

adu1wus, 78 

alaskensis, 11, 12 

albicans, 69 

aletes, 67 

altentilineatus, 15, 16 

andersoni, 35, 45, 46 

asltleyi, 55, 68, 77 

auburyi, 68, 77 

aztecus, 77 

bakeri,· 72, 85 

diazi, 85 

beali, 73 

bed, 90 

bellistriatus, 16 

bellus,67,68,69,74,75,76,78 

benedictus, 78 

biformatus, 51 

bilineatus, 48 

bosei, 73 

bowersi, 63 

branneri, 20, 60 

brionianus, 4 7 

calamitus, 11 
B108 

Pecten-continued 

calli, 33, 35 

callidus, 33, 40 

carrizoensis, 71, 72, 73 

catalinae, 53 

cataractes, 76, 77 

catilliformis, 64 

caurinus, 64, 80, 81, 83, 84, 85, 87 

yessoensis, 84 

cerrosensis, 33, 4'0, 54, 55 

mendenhalli, 40 

cierboensis, 4 7 

circularis, 33, 34, 36, 41 

coalingaensis, 78 

coalingaensis, 76 

coalingensis, 77 

columbianum, 30 

compactus, 34 

condylomatus, 51 

cooperi, 37 

coosensis, 87, 88 

crassicardo, 50, 51, 52, 57 

biformatis, 51 

nomlandi, 51 

cristobalensis, 40 

dallasi, 32 

dentatus, 77 

deserti, 33, 35, 36 

dia bloensis, 64 

dickersoni, 75 

diegensis, 68, 71, 72, 73, 74 

dilleri, 87, 88 

discus, 35,45,46, 48 

dregeri, 12 

egregius, 21,24 · 

emigdioensis, 56 

estrellanus, 29, 50, 52, 53, 55 

etchegoini, 60 

nutteri, 31 

evermanni, 39 

excavatus, 69, 77 

expansus,81 

extenuatus, 16 

falorensis, 87 

fernandoensis, 16 

florid us, 72, 73 

gabbi, 64 

gallegosi, 55 

gonicostatus, 47 

group, 13, 66 

hakei, 39, 55 

hali mensis, 21 

hamiltoni, 52 

hamlini, 60 

hartmanni, 77 

hastatus,2~25,28,48 

hericius, 20 

hawleyi, 74 

haywardensis, 80 

calaverasensis, 80 

healeyi, 12, 82, 83, 85 

heermannii, 83, 84 

heimi, 76, 77 

hemphilli, 77 

hemphillii, 68; pl. 29 

Hemphillii, 68 

hericeus, 28 

navarchus, 26, 28 

strategus, 29 

hericius, 21, 23 

hetet·oglyptus, 31 

hindsii, 28 

Hindsii, 28 

hodgei, 21 

holwayi, 51, 52, 53; pl. 28 

hydei, 20 

impostor, 33, 35, 36 

PALEONTOLOGY OF CALIFORNIA AND BAJA CALIFORNIA 

Pecten-continued 

inezana, 63 

interlineatus aidei, 29 

intermedius, 57 

interradiata, 10 

interradiatus, 7 

invalidus, 33, 37 

islandicus, 20, 27, 28 

kincaidi, 32 

pugetensis, 24, 27 

jordani,21,25 

juanensis, 76, 78 

keepi, 70 

kernensis, 64 

laevis, 11 

lajollaensis, 9, 10 

laqueatus, 67 

latiauratus, 43 

latiauritus, 44, 45 

monotimeris, 45 

lawsoni, 23 

leavis, 11 

lecontei, 68 

levis, 11 

lillis~, 14 

lituyaensis, 86 

lompocensis, 67 

magnificus crassicardo, 50 

magnolia, 52, 56, 57 

martinezensis, 8 

mediacostatus, 29 

meekii, 83, 84. 

mendenhalli, 33, 41 

merriami, 74, 84 

miguelensis, 50, 54 

modulatus, 55 

multirugosus, 65 

nevadan us, 64 

nodosus, 58 

nomlandi, 51, 52 

nutteri, 31 

opuntia, 21, 25 

oregonensis, 64, 86 

oweni, 80 

pabloensis, 47, 48 

parmeleei, 31, 60 

peckhami, 13, 14, 15, 16 

pedroanus, 14, 16 

percarus, 39 

perrini, 62, 63, 64 

pesfelis, 26 

poulcreekensis, 87 

proavus, 19 

propa.tulus, 63, 64, 79, 80, 83 

proteus, 36 

purisimaensis, 86, 87, 88 

purpuratus,39, 40,41 

randolphi, 8, 13, 14, 17 

randolphi tillamookensis, 16 

raymondi, 35, 47, 48 

brionianus, 47 

refugioensis, 70 

ricei, 51, 52 

riversi, 12 

rotundus, 8 

rubidus, 28 

sanclementensis, 82 

sanctaecruzensis, 74, 75 

sancti-ludovici, 22, 32 

santarosanus, 35 

sericeus, 72, 73 

sespeensis, 20, 21, 31, 61 

hydei, 30 

slevini, 69 

stearnsii, 68, 71, 72, 73, 74, 85 

Stearnsii, 68 

strategus, 29 

Pecten-continued 

sub dolus, 33 

subgroup, 66 

subnodosus, 55,57,58 

swiftii, 59, 60 

tillamookensis, 13, 14, 16 

tolmani, 46 

traski, 19 

tumbezensis, 43, 49 

tumidus, 34 

vacavillensis, 7 

vancouverensis, 13, 14, 15, 16 

fernandoens·is, 16 

sanjuanensis, 16 

vanvlecki, 70 

veatchii, 58 

vickeryi, 52 

vogdesi, 76, 77, 78 

wattsi, 31, 59, 60 

weaveri, 46 

yakatagensis, 86, 87 

yessoensis, 78 

yneziana, 61 

yneziana, 61 

(Aequipecten) andersoni, 45 

bellilamellatus, 43 

discus, 47 

eldridgei, 36 

evermanni, 39 

gibbus circularis, 37 

pa bloensis, 4 7 

percarus, 39 

praevalidus, 42 

purpuratus callidus, 38 

hakei, 39 

percarus,39 

subdolus, 37 

tumbezensis, 49 

(Amusium) lompocensis, 66, 67, 70 

mortoni, 67. 

vanvlecki, 67 

(Amussiopecteti) lompocensis, 66, 67 

(Argopecten) subdolus, 37 

(Camptonectes) harfordus, 16 

(Chlamys), 21 

bartschi, 25 

bellilamellatus, 43 

branneri, 19 

buchivacoanus, 22 

calkinsi, 19 

columbiana·, 30 

dallasi, 31 

erici, 30 

fucanus, 63 

hamlini, 60 

hastatus, 22 

hericius, 23 

hindsii, 28 

strategJts, 29 

hericeus strategus, 29 

hertleini, 21 

hodgei, 21 

islandicus picoensis, 27 

jordani, 25 

lawsoni, 22 

multirugosus, 65 

crassip.li.cattts, 65 

ntttteri, 31 

opttntia, 26 

pabloensis; 47 

parmeleei, 59 

proavtts, lfl 

rubidus, 28 

sespeensis, 20 

hydei, 20 

ventttraensis, 27 

wattsi, 31, .59 
Pecten-continued 

(Chlttmys)-continued 

wattsi-con tin ued 

morttni, 60 

ynozia:ntt,'61 

(Cyclopct:f.on) po·t"IWtll:nll, 8 

rot:u:ndntu.11, 8 

(/)oloctopocton) znca.o, 14 

(/i,'u:vola.) ca.t.a:m.ct.tJII, 77 

kotJ}Ji, 70, 71 

n:fn(Jioonllill, 71 

(Fla./Jcl/.ipoct.o:n) 11tcn:rn11U, 72 

(Hinnit.oll) (Ji(Jil.ntt:nll, 65 

(Ja.nh·a.) IH:ll.n11 ooalin(Jtr.onwi11, 76 

bolln11 he 111.11hill ii, 68 

lw:t·tma:nn:i, 76 

h:nm:phro·/JRii a.lotos, 67 

kct:pi, 70 

11t.oa:t'n11ii lmlwri, 85 

C(l:/''l'iZOil'll.llill, 71 

(/j 0(/IJ'I/,11 iH, 73 

Hf.tlWI'nHii, 72 

(fAJpf.O/}()(Jton) 'JI'I'(I.e'Ua./itlnll, 42 

(l:.it:nJJII.7JCCten) COORO'II.RiH, 88 

tli/lcl'i, 88 

litu.yntrn11i11, 87 

'JIIHI.[CI'Cekvnllill, 88 

JIU.'I'iHiiiW.I)'I/,IIiH, 86, 88 

Jl'lt:J'i.Hiii/.(I.(J'JI.IIiH·fa/.o·t'O'/I.IIill stock, 88 

Jfll./w.f.II(JIJ'/I.H iH, 86 

(/J'/1'/'0JICCf.en) 11.11hloyi., 55 

IJOWO'I'Hi., 62 

CO'I"/'OHO'/I.HiH, 55 

C'/'U.HR j Cll.'/'1/0, 51 

/w.milt.oni, 51 

dOHO'I'f,i, 33 

dil/ori, 88 

Olltl'tJflii'I/:1/.H, 53 

t:n.tn.lina.t:, 53 

CO'/'I'OHO'IIRiR, 55 

t.ormin:nH, 54 

(111.1/tJ(JOHi, 54, 55 

1/W(J'II.ij'icu.H 1)/'(I.HIIitJ(I.'I'dO, 51 

ha.m:iltoni, 51 

1/I.II.(J'/I.o/.i.a., 56 

mitrnt:l.ont~iH, 49 

IIU.InnirrnolonwiH, 50 

1/l.od·u./a.t:n};, 55 

nodown11 into·nncdht.ll, 58 

'llll:n(Jiw.·ni., 50 

'U(J(I.f.t;hii, 58 

JIOrrini, 62 

p·rotiown11, 51 

ricoi, 5.1 

HnilnodoHu.H, 57,58 

tn./lt.ia.mionwill, 29 

'IJll.n{Jha:ni, 50 

allt.i{JdioonlliR, 56, 57 

1Jca.tahii., 58 

'Vit;kC'I''/Ii, SJ 

(Notlip()(;ton) 1m.lnwdown11, 57, 58 

'I!CII.f.chti, 58 

(0J)1Jonlwi.lll.opoct.cn) cotr.lin{Jnenwis, 76 

lw:nt:ocld, 78 

hn:rt.llw.nni, 76 

lwimi, 77 

ju.a:nonHiR, 75 

'IJO(JdOHi, 77 

(Pa.c:iJJOt:f.on) f.l/.1/l.iJCZIJnHiH, 49 

<Ptt.llilun) lw.mlini, 60 

holwnyi, 51 

H urij~. i ·11:u.tt.c·t·i, 31 

Hwift.ii ct.clw{Jnini, 60 

(Pntinopoct.cn) bn.ko·t·i, 84, 85 

· t:a:nrinnH, 12, 83 

COOHO'II.HiR di//c·t•i, 88 

dillcl'i, 88 

c:,:pa:nHnll, 81 

INDEX 

Pecten-continued 

(Patinopecten)-contin ued 

ha.ywa·rllensis, 80 

ca.la.ve·ra.sensis, 80 

healeyi, 81 

loh-ri, 80 

sttnclementens·is, 81, 82 

kontens·is, 64 

lohri, 80 

owen·i, 80 

p·t·opn.tul-Lt.H, 63, 79 

purisima.enwis, 87 

turne1·i, 87 

wea.ve·t·i, 46 

(?Pntinopecten) me·rrinm.i, 74 

(Pecten), 67, 71 

aletes, 67; pl. 28 

wnde·rson·i {Jowicostntus, 47 

a:u.buru·i, 68 

ba.1·tschi, 25 

benli, 73 

bell-u.s, 67, 68; pl. 29 

·!Ja.~ei, 73 

ctt1Tizoensis, 71 

cie·rboensis, 47 

coa.lin{Jnensis, 76 

compa.ctus, 34 

llentntns, 77 

llickenwn·i, 75 

die{Jensis, 7 3 

geographic distribution, 67 

geologic distribution, 67 

ha:rtma.nni, 76 

ha.Rta.tns, 22 

pngetenRi,q, 27 

/w.wleyi, 74 

hll'imi, 77, 78 

hemJJh-illi, 69 

hemph:illii, 68 

jna:neu.R'is, 75, 78 

keepi, 70 

lecontei, 67, 68, 69, 72; pl. 28 

IIW1"J'ia.tni, 74 

multint.gosns, 65 

e1·a.ss iplicntus, 65 

1·a.ymonlli, 47 

IJ'I''i.on:ia.n:ns, 4 7 

nfugioensis, 71 

snncta.ecnt.zenwis, 75 

slevini, 69 

stea.n1.s'ii, '72 

vnnvlecki, 69 

vogtle.~i, 77 

(Pla.gioetenhun) a.bietis, 41 

a:nlle·t·son·i, 45 

lmTke1·ia:nns, 45 

suba:nde1·soni, 45 

bilinea.tus, 48 

ca.lli, 32, 34, 35 

callidus, 38 

ce·rro.~enB'is, 55 

mendenha.lli, 33 

ci1'Cula.r·is, 34 

coope'l'i, 37 

cristo balens is, 40 

deseTti, 33 

diminutivn.q, 32, 33 

discus, 47 

eld1·idgei, 36 

e·t"icellus, 37 

evenna.nwi, 39 

ha.kei, 39 

1/l.endenha././.i, 33 

nea.hens·is ,· 35 

pa.IJ/oensis, 47 

snbdolns, 37, 40 

(Plagiocteninm?) c·mssirndiatus, 42 

(PTopea.m.ushq'n) levis, 11 

'l'iversi, 12 

Pecten-contined 

(P·ropeanmssium) davidsoni, 12 

inte1·rndiatus, 7 

1"iversi, 10 

stanj'oTdensis, 10 

vncavillensis, 7 

(Pseudamusium) a.lte1·nilineatus, 13 

arces, 13 

lillisi, 14 

lompicoensis, 7 

peckhami, 14, 15 

pedro anus, 18 

polyleptus, 13 

1'nndolphi tillnmookensis, 13, 17 

vnncouverensis, 13, 17 

fenwndoensis, 14, 16 

sa.njua.nenwis, 13 

(Pseuda.mussi'll.m?) a.laskensis, 11 

(Pseudomuseum) altentilineatus, 15 

(Swiftopecten) etchegoini wa.ttsi, 31 

(VertiJJecten) b~wm·si, 62 

nevntlanltB/1tcnnus, 63 

pen·ini, 62 

ynezinna subynezia.nb1, 61 

ynezin·ti.a., 61 

ynezianus, 61 

(Pecten), Pecten, 67, 71 

aletes, Pecten, 67; pl. 28 

ande·rsoni gonicostntu .. ~. Pecten, 47 

aubu1·yi, Pecten, 68 

bartschi, Pecten, 25 

benli, Pecten, 73 

bellus, Pecten, 67, 68; pl. 29 

bosei, Pecten, 72 

carrizoensis, Pecten, 71 

cierboensis, Pecten, 47 

coalinga,ensis, Pecten, 76 

compactus, Pecten, 34 

dentatns, Pecten, 77 

dicke1·soni, Pecten, 75 

diegensis, Pecten, 73 

hnrtmanni, Pecten, 76 

hastntus, Pecten, 22 

pugetensis, Pecten, 27 

hawleyi, Pecten, 74 

heimi, Pecten, 77, 78 

hemphilli, Pecten, 69 

hemphillii, Pecten, 68 

juanensis, Pecten, 75, 78 

keepi, Pecten, 70 

lecontei, Pecten, 67, 68, 69, 72; pl. 28 

merTinmi, Pecten, 74 

nmltirugosus, Pecten, 65 

crassiplica.tus, Pecten, 65 

1·aymondi, Pecten, 47 

i11·ionianus, Pecten, 47 

refu{Jioensis, Pecten, 71 

sanctaecntzensis, Pecten, 75 

slevini, Pecten, 69 

sten1·nsii, Pecten, 72 

vanvl.ecki, Pecten, 69 

vogdesi, Pecten, 77 

Pectinacea, 6, 12 

Pectinidae, 1, 2, 6, 12, 66, 90 

geographic distribution, 2 

geologic distribution, 2 

petl-l·oann, Pla.giostoma, 13, 18 

pedroanus, Delecto7Jecten, 18 

Hyalo71ecten (Delectopecten), 18 

Pecten, 14, 16 

(Pseuda.musium), 18 

Plagiostomn, 13 

pedrona, Plagiostoma, 18 

B109. 

Pelecypods, occurrence in geologic formations, 90 

systematics, 6 

pe1·cants, Aequipecten, 41 

AT(JOJJecten, 32, 39; pis. 10, 12 

Pecten, 39 
BllO PALEONTOLOGY OF CALIFORNIA AND BAJA CALIFORNIA 

percarus-continued 

Pecten-continued 

(Aeq·t~ipecten), 39 

purpuratus, 39 

penwmu8, Amnshun (Cyclopecten), 8 

C·yclo7Jecten, 7, 8; pl. 1 

Pecten (Cyclopecten), 8 

Pez·nopectinidae, 6 

pen·ini, Pecten, 62, 63, 64 

Pecten (Ly1·opecten), 62 

(Verti11ecten) nevadan1~s, 62 

Vert·ipecten, 61, 62; pl. 25 

pesfelis, Pecten, 26 

Pico Formation, 18, 23, 24, 26, 27, 28, 29, 35, 37, 

38, 39, 56, 60, 66, 68, 69, 74, 75, 83, 84, 

91; pis. 7, 32, 33 

picoensis, Chlamys, 18, 27; pl. 7 

Chla.mys (Chlam·ys), 27 

Pecten (Chlamys) ·island,icus, 27 

Pismo Formation, Edna Member, 81, 90 

Gragg Member, 56, 91 

Squire Member, 56, 91 

Placopecten, 13 

Plagioctenium, 33 

(Plag,iocteninm) abietis, Pecten, 41 

ande1·soni, Pecten, 45 

ba1·kerian1~s, Pecten, 45 

subandersoni, Pecten, 45 

bilineatus, Pecten, 48 

call-i, Pecten, 32, 34, 35 

callidus, Pecten, 38 

ce1Tosensis, Pecten, 55 

mendenlwlli, Pecten, 33 

c'i1"c1da?·is, Aequ·ipecten, 34 

Pecten, 34 

cooperi, Pecten, 37 

c1·istobalensis, Pecten, 40 

deserti, Pecten, 33 

dimin1~tivus, Pecten, 32, 33 

discus, Pecten, 47 

el£l1·idgei, Pecten, 36 

e1·icellns, Pecten, 37 

evennan1t'i, Pecten, 39 

hakei, Pecten, 39 

mendenhalU, Pecten, 33 

neahensis, Pecten, 35 

pabloens,is, Pecten, 47 

snbdolns, Pecten, 37, 40 

(Plagioctenium?) c1·assiTadiatus, Pecten, 42 

Plagio8toma annnlatus, 13, 18 

giganteum, 65 

pedroana, 13, 18 

ped1·oanus, 13 

tn~ncata, 13, 18 

Pleito Formation, 30, 65, 75, 89, 91; pl. 32 

ple1~1·onectes, Am1~si1tm, 66 

polylept1~s, Pecten (Pseudamusi1~m), 13 

Polynemam1~ssiwn alaskense, 11, 12 

int1~scostatnm, 12 

Pomponio Mudstone Member, Purisima 

Formation, 81, 91 

po·rterensis, Leochlamys?, 30 

Ve·1·t,ipecten, 49 

Potato Harbor Formation, 69, 91 

po1~lc1·eekensis, Pecten, 87 

Pecten (Lit1~yapecten), 88 

poulsoni, Hinnita, 65 

p1·aevalidns, A ntipecten?, 42; pl. 13 

.Pecten (Aeqnipecten), 42 

(Leptopecten), 42 

p1·etiosns, Lyropecten, 49, 51; pl. 17 

Pecten (Lyropecten), 51 

proavns, Chlamys, 18, 19; pl. 3 

Pecten, 19 

(Chlamys), 19 

Procedures, 1 

propatnlns, Patinopecten, 78, 79, 80; pis. 26, 34,35 

Pecten, 63, 64, 79, 80, 83 

propatnlns -continued 

Pecten-continued 

(Patinopecten), 63, 79 

Ve1·tipecten, 63, 79 

(P1·opettmnsium) levis, Pecten, 11 

riversi, Pecten, 12 

Propeamussiidae, 1, 2, 6, 8, 9, 90 

geographic distribution, 2 

geologic distribution, 2 

Propeamussi1~m, 2, 6, 7, 8, 9, 10 

inte1Tadiat1on, 7, 9, 10; pl. 1 

lajollaense, 9 

leohe·rtleini, 7, 10 

m·ideocenicum, 9, 10' 

stanfonlensis, 7, 9, 10 

(PnTVamussium) nlaskense, 11 

stnnfM·densi.~, 10 

(P1·opeamussium), 7 

interrndintwn, 7 

(Propeamussium), P1·opectm1~ss,i1~m, 7 

davidsoni, Pecten, 12 

inte1Tadiat1w1, Propenmussi1un, 7, 

inte1Tadintns, Pecten, 7 

river8i, Pecten, 10 

stanf01·densis, Pecten, 10 

vacavillensis, Pecten, 7 

p1·ote1~s, Pecten, 36 

Pse1tdnmussium, 9 

incongruum, 8 

(Pseudamusium) altentilinentus, Pecten, 13 

nrces, Pecten, 13 

lillisi, Pecten, 14 

lompicoensis, Pecten, 7 

peckhami, Pecten, 14, 15 

pedroanus, Pecten, 18 

polyleptus, Pecten, 13 

randolphi tillnmookensis, Pecten, 13, 17 

vancouve1·ensis·, Pecten, 13, 17 

fenwndoenwis, Pecten, 14, 16 

samjnanensis, Pecten, 13 

(Pseudnm1tssi1un?) alaskens·is, Pecten, 11 

(Pse!tdomnsenm) altern,ilineatus, Pecten, 15 

Puente Formation, 15, 91 

p11.getensis, Chla.mys, 27 

Chlamys (Chlamys), 27 

ha11tatn, 18, 23, 24, 27, 29; pl. 6 

Pecten islandicns, 24, 27 

(Pecten) hastntus, 27 

Pullen Formation, Wildcat Group, 91 

Purisima Formation, 11, 23, 24, 26, 28, 31, 33, 37, 

43, 44, 59,66,68, 69, 73, 75, 76, 83, 84, 

86, 87, 88, 91; pis. 8, 41 

Pomponio Mudstone Member, 81, 91 

San Gregorio Sandstone Member, 81, 91 

Tahana Member, 59, 83, 87, 88, 91 

pnrisimaensis, Lit1tyapecten, 86, 87; pl. 41 

Patinopecten, 87 

(Lituyapecten), 87, 88 

Pecten, 86, 87, 88 

(Lituyapecten), 86, 88 

(Patinopecten), 87 

purisimaensis-fnl01·ensis stock, Pecten 

(Lituyapecten), 88 

Purpose and scope, 1 

purpurata, Chlamys, 39, 40 

purpuratus, Pecten, 39, 40, 41 

callidus, Pecten (Aeqnipecten), 38 

hnkei, Pecten (Aeqnipecten), 39 

percarus, Pecten (Aequipecten), 39 

subdolns, Pecten (Aequipecten), 37 

pusio, Hinnites, 65 

Pycnopodia, 79, 84 

Pyramid Hill Sand Member, Jewett Sand, 57, 63, 

91 

Q,R 

Quail Canyon Sandstone Member, Vaqueros 

Formation, 21, 57, 91 

1·andolphi, Cyclopecten, 17 

Pecten, 8, 13, 14, 17 

tilla. mookensis, Cyclopecten, 17 

Cyclopecten (Delect.opecten), 17 

Delectopecten, 14, 16, 17; pl. 3 

Pecten, 16 

(Pseuda.mnwi,u.m), 13, 17 

rnymondi, Aeqwipecten, 47 

Chla.mys, 47 

Pncipecten, pl. 14 

Pecten, 35, 47, 48 

(Pecten), 47 

b'rionia.n:ns, A eqn,ipecten, 4 7 

Pecten, 47 

(Pecten), 47 

References cited, 91 

1·efngioensis, E-nvola, 70, 71; pl. 30 

Pecten, 70 

(Envola., 71 

(Pec.ten), 71 

1·evellei, Aequ.i]Jecten, 38, 40 

ATgopecten, 32,40; pl. 11 

Chlam.ys, 40 

(A?·go]Jecten), 40 

ricei, Ly1·opecten, pl. 18 

Pecten, 51, 52 

(Lyropecten), 51 

Rincon Shale, 20, 21, 50, 57, 91 

Rio Dell Formation, 60, 88; pl. 42 

Wildcat Group, 26, 31, 84, 91 

·rive1·si, Pwrvnm1tswium, 9, 10; pl. 1 

Pecten, 12 

(PTopea.muwium.), 12 

(P'I"O]Jea,m!t.ssinm), 10 

1·otwndatus, Pecten (Cyclopecten), 8 

rot,wnd!ts, Pecten, 8 

Round Mountain Silt, 46, 91 

1·ub,ida., Chla.mys, 18, 26, 27, 28; pl. 7 

Chlamys (Chla.my8), 28 

jordan,i, Chlamys, 25, 29 

Chlamys (Chla.mys), 25 

ntb·icl'tt.s, Pecten, 28 

Pecten (Chlnmys), 28 

s 

Sacate Formation, 61, 91 

sncyi, Chla.mys, 43 

St. George Formation, 25, 91; pl. 6 

Salada Formation, 29, 30, 32, 33, 34, 35, 40, 49, 55, 

56, 66, 67' 68, 69, 71, 72, 73, 77' 89, 90, 

91; pis. 7, 9, 10, 11, 28, 30, 31, 32, 33 

Saltos Shale Member, Monter·ey Fonnation, 46, 

50,53,62,91 

Monterey Shale, 70 

San Diego Formation, 8, 23, 24, 26, 27, 28, 34, 35, 

37,38,39, 40, 42, 43, 56, 59, 60,66,68, 

69, 72, 73, 78, 82, 83, 88, 89, 91; pis. 5, 6, 

10, 12, 13, 23, 29, 31, 34, 35, 36, 37, 38, 

39,40,42 

San Emigdio Formation, 30, 91 

San Fernando Formation, 50 

San Gregorio Sandstone Member, Purisima 

Formation, 81, 91 

San Joaquin Formation, 25, 31, 60, 76, 83, 91 

Cascajo Conglomerate Member, 36, 90 

San Lorenzo Formation, 15, 91 

San Marcos Foz·mation, 22, 29, 34, 36, 41, 55, 58, 

71, 72, 78, 85, 88, 91; pis. 5, 40 

San Onofre Breccia, 53, 67, 91; pl. 18 

San Pablo Formation, 24, 46, 48, 53, 54, 66, 81, 91; 

pl. 15 

San Pablo Group, 47, 48, 8·9, 91~ pl. 14 

Briones Sandstone, 90 
Sun Pnblo G•·oup-continued 

Cierbo Snndstone, 90 

Neroly Snnclstone, Ill 

San Pedt·o l~onnntion, I .I, 24, 25, 26, 27, 28, 29, 44, 

66, 77, 78, 8[), 91; pis. 6, 7, 34 

Anchor Silt Membet·, 26, 84, 90 

Lomitu Mal'l Membet·, 12, 17, 2::1, 24, 26, 28, 29, 

4<1, 7:1, 84, 91 

Timms Point Silt Member, 17, 26, 29, 44, 73, 

84, !ll 

San Pedt·o Sand, .12, 29, 84, 90, 91; pl. 7 

Sun Rnmon Sundstone, 1:.1, 15, W, 64, 89, 91; pis. 2, 

21. an Ha:nclom.rJ'II.t.o·II.H'ill, Poct.rJn, 82 

Per;l.on (Pnt.inoper;t.on) lwnloy·i., 81, 82 

llll:ncf,(I.IW'/'1/.ZIJ'II.H'i H, 01)1!0'1/./Wi 11/.0lJIJCI.en, 75; pis. 32, 

:~a 

P()(;l.on, 74, 75 

(PrH;I.on), 75 

Hu:ncl:ilndrruid, Chlniii:IJII, 18, !!2, Hl; pl. 5 

Ha:nr;l.i·lndr!'llioi, Per;t.on, 22, 81 

HWIIjna:nrJ'I/.II'iH, Doled.o·JHWtcn ·uu:nr;o·/1:/Je·ro·/ud.~, 17 

Prwt.on (PHmulnlll.'/l.winm.) 'lill:nciJ'II.'/ie'/'ensis, 13 

'/ii/.'IWO'//.'Iii)'/'0'1/.HiH, .I 6 

Snnta Bui'IHII'U Formntion, 2:3, 24, 26, 68, 7:3, 84, 

91; (>1. 29 

Snnta Cruz Mudstone, 91 

Santu Mat·garitu l~ot·mution, 15, 21, 22, 28, 24, 47, 

52, 58, 54, 60, 65, {16, 89, 90, 91; pis. 4, 5, 

17, 18, 19, 21, 24, 2{1, 27 

Santa Margal'itn Sandstone, 54 

Hll:nl.u:I'OHII:/1:/I.H, Per;lo~Jn, 35 

Suugus l''ol'llllltion, 23, 24, 26, 29, 35, {l{l, 69, 83, 91 

Hll'l'ioonH, P01;l.on, 72, 73 

HOHlJilO'/I.H'iH, ChlnmyH, .18, 20; pl. 4 

P()(;t.on, 20, 2.1, :n, 61 

(ChlnmJJH), 20 

V O'l'l.i·pru;I.IJ'/1., 20 

hJJdoi, ChlnmJJH, .18,20; pl. 4 

Por;t.on, HO 

(Chlniii:JJH), 20 

Sisquoc l~ormntion, 28, 88, 91 

Tinnqunic Sandstone Membet·, 81, 91; pis. 34, 

illi 

Skoonet· Gulch l~ormntion, 21,91 

HIO'II'i·11:i, Prwt.on, 69 

Pod.rJn (Prwton), (j9 

Sobrante Snndstone, 80, 90, 9.1; pis. 35, 36 

Soda Luke Shale Membet·, Temblot· l<~ormntion, 21 

Vaquet·os l~onnution, 21, 50, 57, 70, 91 

Sooke I~OI'Illlltion, 13, 17, 30, 89, 91; pl. 8 

Squire Membet·, Pismo l~ormntion, 56, 91 

Htwnfo'l'llenHo, Pn:I'VI/.11/.'/t.HHhl.'ln, 9, 10; pl. 1 

Hl.wlljirnlonwiH, Pu:/'1/II./II.'U.HH-i'u.m, 9 

Pocton (P·I'IJJ!OI/.111.'1/.HH'inm), 10 

P'l'fJlJ()(/.///.'/I.HHLU./11., 7, 9, 10 

(Pa:I"III/.111.'1/.HH'inm), 10 

Ht.ea:rnwU., Ji'lnlwlUpoct.en, 71, 7!!; pl. 31 

Pect.wn, 68, 71, 72, 73, 74, 85 

(Ji'lnboll-iJwcten),. 72 

(Ja:ll:i.·l·n) Hl.owi"II.R'i·i;. 72 

(Pocten), 72 

l!ltke·l'i, Pecten (Ja:ll:int), 85 

CM"rizoonwiH, Pocton (Ja:ll:i'l'lt), 71 

ri'iegonH'iH, Poct.cn (Ja:nh·n), 73 

Hl.ew1·nwi'i, Pect.en (Jrtni'l'lt), 72 

St.cn·I"II.H'i'i, Poct.en, 68 

Hl.'l'rttC{J'It.H, Pccte·i1., 29 

Pc1;tcn (Chlnm1JH) ha.HI.ntns, 29 

(ChlnmJJH) hc·riccns, 29 

ho·1·iccnH, 29 

H'U.IJII•ndc·I'Hon:i, A oq·u.-iJHwton nnde·rson·i, 45 

Pnc·i.lJocl.on u:ndo·I'HOn:i, 44, 1,5; pl. 14 

Poct.rm. (Plny·iocton·i'u.m) n:nde·I'Hon·i, 45 

wu.IJiloln, ChlnmJJH, 38 

ChlnmyH (A·I'fJ01JCcton), 38 

sniJilo/:u.H, A·rtJOlJOcton, 32, 33, 97, 40; pl. 10 

INDEX 

subdol1ts -continued 

Pecten, 33 

(Aeqn·ipecten) pwrpn·mtwl, 37 

(Argopecte'n), 37 

(Pla.giocte·n:inm), 37, 40 

snb11t'ignelenwis, LJJ'I'opecten, 49, 50, 53; pis. 16, 17 

Ly·ropecten 11t'ignelensis, 50 

Pecten (Ly·ropecten) m.ignelensis, 50 

subnodos11.s, Ly1·opecten, 57, 58 

Norlipecten, 55, 57 

snbnodosns, 57; pl. 6 

Pecten, 55, 57, 58 

(Ly·ropecten), 57, 58 

(Nod·ipecten, 57, 58 

intennedius, Nod·i.pecten, 57, 58; pis. 22,23 · 

wu.bnodowus, Nod·ipecten, 57; pl. 6 

wltbJJnez·icww, Pecten (Ve·rt-ipecten) ynezinna, 61 

Ve·1·t·ipecten yneziann, 61; pl. 24 

wuenlru.]J'i, Aeqnipccten, 34 

A'l'gopectcn, 32, 91,; pl. 9 

sw·ift-i nutte1·i, Pecten (Pnll-ium), 31 

sw-ift·i i, C hlct my s, 59 

Chlnm.JJS (Swiftopecten), 12, 59 

Pecten, 59, 60 

Sw·iftopecton,. 59 

etchego·in·i, Pecten (PnlUwn), 60 

Sw·iftopecten, 2, 24, 31, 58 

n.de'kunbiwna, 51, 52; pl. 21 

etchego·in:i, 60 

geogt·aphic distt·ibution, 59 

geologic distribution, 59 

group, 60 

1//.()'/'(/.'lt'i, 60; pl. 22 

nutte·1·i, 60 

pwl'lnelee·i, 60 

etchego·in:i, 59, (jQ; pl. 22 

panneleci, 59; pl. 23 

swift-i.i, 59 

wattsi, 60; pl. 23 

(Swiftopecten) etchegoini wa.ttsi, Pecten, 31 

pctnnelee·i, Chlam.ys, 59 

pnnneleei etchegoini, Chlamys, 60 

swijti·i, Chlnmys, 12, 59 

Sw·iftopecten?, 60 

hcunl·ini, 59, 60; pl. 24 

(Swijt07}(JCten?) haml-ini, Chlnmys, 60 

Systematics, pelecypods, (j 

T 

Tuhunu Member, Purisimu Formation, 59, 83, 87, 

88, 91 

tctmiamiensis, Pecten (Ly1·opecten), 29 

tannt?·ae, Chlamys, 26 

Tejon Formution, 7 

Coldwater Sandstone Member, 90 

Cozy Dell Shale Member, 90 

Temblor faunule, 45 

Temblor Formution, 20, 21, 45, 47, 57, 63, 80, 91 

Aguu Sundstone Member, 57, 63, 90 

Buttonbed Sandstone Member, 45, 53, 54, 70, 

90 

Carneros Sandstone Member, 50, 51, 65, 90 

McLure Shule Member, 54 

Media Shule Member, 46, 54, 91 

Sodu Luke Shale Member, 21 

Wygul Sandstone Member, 62, 75, 89, 96, 91; 

pl. 24 

Temblor horizon, 15, 33, 45, 51, 67 

Temblor Stuge, 45 

Tepetute Formation, 91 

termimts, Lyropecten, 49, 51,, 56; pl. 19 

Ly1·opecten est1·ellanus, 56 

Pecten (Lyropecten) estrellanus, 54 

Tierra Redonda Formation, 45, 46, 50, 67, 91 

tillamookensis, Cyclopecten (Delectopecten) 

randolphi, 17 

Cyclopecten rnndolphi., 17 

Delect'opeeten, 17 

rnndolphi, 14, 16, 17; pl. 3 

vancouve·rensis, 17 

Pecten, 13, 14, 16 

(Pseuclanmsimn) rnndolphi, 13, 17 

ranclolphi, 16 

Timms Point Silt Member, 23, 66 

Blll 

San Pedro Formution, 17, 26, 29, 44, 73, 84, 91 

Tinaquaic Sundstone Member, Sisquoc 

Formution, 81, 91; pis. 34, 36 

toknnaya·i, Y abepecten, 83 

tolmani, Pncipecten, 44, 1,6; pl. 14 

Pecten, 46 

Topunga Cunyon Formation, 62 

Cold Creek Member, 90, 91 

Topangu Formation, 15, 46, 53, 62, 65; pis. 24, 25 

Cold Creek Member, 54 

Topanga Group, 54, 91 

Topunga Canyon Formution, 91 

Tortugas Formation, 46, 91 

Towsley Formation, 28, 35, 54, 81, 91 

Tranquillon Formution, 67; pl. 2 

Tranquillon Volcunics, 54, 57, 67, 91 

trnski, Pecten, 19 

tntnca.ta, Plagiostoma., 13, 18 

tug·idakensis, Chlamys (Leochlam.ys ), 30 

tumbezensis, Chlamys (Leptopecten), 49 

Pacipecten, 44, 1,9; pl. 15 

Pecten, 43, 49 

(Aequipecten), 49 

(Pncipecten), 49 

Tumey Formation, 15, 91 

tnmidus, Pecten, 34 

tunte1·i, Lit1tyapecten, 86, 87; pl. 37 

Patinopecten, 87 

Pecten (Patinopecten), 87 

Turritella bed, 89 

Twisselmun Sandstone Member, Monterey 

Formation, 46, 91 

v 

vncavillen.~is, Pecten, 7 

Pecten (Propeam1tSS'ium), 7 

Valmonte Diatomite, 18 

Valmonte Diatomite Member, Monterey Shale, 

18, 91 

vancouverensis, Cyclopecten (Delectopecten), 17 

Delectopecten, 17 

vanconvercnsis, 14, 17;.pl. 3 

Hyalopecten, 17 

Pecten, 13, 14, 15, 16 

(Psendamnsinm), 13, 17 

fenwndoensis, Delectopecten, 14, 16; .pl. 3 

Pecten, 16 

(Pseudamusium), 14, 16 

sanjuanensis, Delectopecten, 17 

Pecten, 16 

(Psendamusi1tm), 13 

tillamookensis, Delectopecten, 17 

.vancouverensis, Delectopecten, 14, 17; pl. 3 

vanvleeki, Amnssiopecten, 67, 69; 74; pis. 29, 30 

Pecten, 70 

(Amusinm), 67 

(Pecten), 69 

Vaqueros Formation, 20, 21, 30, 31, 45, 46, 49, 50, 

51, 56,57, 62, 63, 65, 7~ 74, 75, 89, 9~ 

91; pis. 4, 8, 14, 16, 17, 21, 25, 29, 30, 31. 

33 

Painted Rock Sandstone Member, 21, 50, 57, 

62,66,70,91 

Quail Canyon Sandstone Member, 21, 57, 91 

Soda Lake Shale Member, 21, 50, 57, 70, 91 
B112 PALEONTOLOGY OF CALIFORNIA AND BAJA CALIFORNIA 

Vaqueros horizon, 45 

·Vaqueros megafaunal·stage, 65 

Vaqueros Sandstone, 75 

vaughani, Lyropecten, 49, 50; pl. 17 

Lyropecten crassicardo, .50 

Pecten (Lyropecten), 50 

(Lyropecten) no do sus, 50 

emigdioensis, Pecten (Lyropecten), 56, 57 

veatchii, Nodipecten, 57, 58; pis. 22, 23 

Pecten, 58 

(Lyropecten), 58 

nodosus, 58 

(Nodipecten), 58 

venturaensis, Chlamys, 27, 28; pl. 7 

Pecten (Chlamys), 27 

Vertipecten, 2, 6; 20, 31, 49, 60, 83 

alexclarki, 61; pl. 24 

bowersi, 61, 62, 64; pis. 24, 25 

diabloensis, 61, 64; pis. 21, 39 

fucanus, 61, 63, 64, 79, 80; pis. 26,27 

geographic distribution, 61 

. geologic distribution, 61 

kernensis, 61, 63, 64; pl. 28 

nevadanus, 63, 64 

perrini, 61, 62; pl. 25 

po1·terensis, 49 

p1·opatuhts, 63, 79 

sespeensis, 20 

yneziana, 61 

sttbyneziana, 61; pl. 24 

yneziana, 61; pl. 25 

ynezianus, 49 

(Vertipecten) bowersi, Pecten, 62 

nevadanus fucanus, Pecten, 63 

perrini, Pecten, 62 

yneziana subyneziana, Pecten, 61 

yneziana, Pecten, 61 

ynezianus, Pecten, 61 

vickeryi, Lyropecten, pl. 17 

Pecten, 52 

(Lyropecten), 51 

vitreus, Cyclopecten, 13 

vogdesi, Oppenheimopecten, 75, 76, 77; pl. 34 

Pecten, 76, 77, 78 

(Oppenheimopecten), 77 

(Pecten), 77 

volaeformis, Lyropecten, 53 

W, Y,Z 

wattsi, Pecten, 31, 59, 60 

Pecten (Chlamys}, 31, 59 

(Swiftopecten) etchegoini, 31 

Swiftopecten, 60; pl. 23 

morani, Pecten (Chlamys), 60 

weaveri, Pacipecten, 44, 46; pl. 15 

Pecten, 46 

(Patinopecten), 46 

Wildcat Group, 60, 91; pl. 23 

Pullen Formation, 91 

Rio Dell Formation, 26, 31, 84, 91 

Wimer Formation, 47, 91 

Woodhams Member, Monterey Formation, 15, 91 

Wygal Sandstone Member, Temblor Formation, 

62, 75, 89, 90; 91; pl. 24 

Yabepecten, 78, 83 

condoni,83 

tokunagai, 83 

yakatagensis, Pecten, 86, 87 

Pecten (Lituyapecten), 86 

yessoensis, Patinopecten, 78, 79, 83; pl. 40 

Pecten, 78 

caurinu11, 84 

yneziana, Pecten, 61 

. Pecten (Chlamys), 61 

(V ertipecten) yneziana., 61 

yneziana, 61 

V ertipecten, 61 

yneziana, 61; pl. 25 

subynezia.na, Pecten (V e1·tipecten), 61 

Ve1·tipecten, 61; pl. 24 

yneziana, Pecten, 61 

Pecten (V ertipecten), 61 

Vertipecten, 61; pl. 25 

ynezianu.s, Pecten (Vertipecten), 61 

Vertipecten, 49 

za.cae, Pecten (Delectopecten), 14 

Zemorrian Stage, 75 

Zostera, 44 
PLATES 1-42 

[Contact photographs of the plates in this report are available, at cost, from the U.S. Geological 

Survey Photographic Library, Federal Center, Denver, Colorado 80225] 
PLATE 1 

FIGURES 1. PropeamussiU1n interradiatum (Gabb) (p. ~7). 

Lectotype ANSP 4652 (x 2.0). Length 18 mm, height 19 mm. Kreyenhagen 

Shale, Eocene and Oligocene. 

2. Cyclopecten lompicoensis (Arnold) (p. B7). 

Holotype USNM 164931 ( X3.0). Height about 13 mm. Monterey Formation, 

Miocene. 

3-6. Cyclopecten pernomus (Hertlein I (p. B8). 

Syntypes USNM 110708 ( x 10.0). Panama Bay, Panama, Holocene. 

3. Exterior of right valve. Height 3.5 mm. 

4. Interior of right valve illustrated in figure 3. 

5. Exterior of left valve. Height 2.8 mm. 

6. Exterior of left valve. Height 3.0 mm. 

7, 8. Cyclopecten incongruus (Dall) (p. B8). 

Holotype USNM 207273 (x2.0). Length 15 mm, height 14 mm. Isla Cedros, 

Baja California Norte, Holocene. 

9, 10. Cyclopecten? martinezensis (Gabb) (p. B8). 

Martinez Formation, Paleocene. 

9. Lectotype MCZ 15026a ( x4.0). Height 9 mm. 

10. Paratype MCZ 15026 ( x4.0). Height 6 mm. 

11. Parvamussium mideocenicum (Vokes) (p. B9). 

Syntype UCMP 15584 (x4.0). Height 8 mm. Cerros Shale Member, Lodo 

Formation, Paleocene. 

12, 13. Parvamuss1>um la)·ollaense (M. A. Hanna) (p. B9). 

Ardath Shale, Eocene. 

12. Syntype UCMP 31108 ( x4.0). Height 3.8 mm. 

13. Syntype UCMP 31106 (x4.0). Height 3.8 mm. 

14, 15, 17. Parvamussium stanfordense (Arnold) (p. BlO). 

14. Topotype USNM 646446 (x3.0) (Addicott, 1971, fig. 5). Left valve (top). 

Length 8 mm, height 7.8 mm. USGS locality M1492. 

15. Syntype UCMP 15585 (x4.0) of Parvamussium mideocenicum (Vokes)= 

Parvamussium stanfordense (Arnold)? Height 6.2 mm. Cerros Shale Member, 

Lodo Formation, Paleocene. 

17. Holotype CAS/SU 12 (x 4.0). Length 7.2 mm, height 7.8 mm. Butano(?) 

Sandstone, Eocene. 

16, 18. Parvamussium riversi (Arnold) (p. BlO). 

Holotype CAS/SU 33 (X 3.0). Length 17 mm, height 17 mm. Fernando 

Formation, Pliocene and Pleistocene. 
GEOLOGICAL SURVEY PROFESSIONAL PAPER 1228-B PLATE 1 

XTO.O 

4 

X2.0 8 

13 

t 

X3.0 

16 17 18 

PROPEAMVSSIUM, CYCLOPECTEN, PARVAMVSSIUM 
PLATE 2 

FIGURES 1-7. Par-vamuss1:um alaskensis (Dall) (p. (Bll). 

1. Holotype of Parvmnussium calam1:tus (G D. Hanna), UCMP 11084 ( x 

3.0). Length 15 mm, height 16 mm. Fernando Formation, Pliocene and 

Pleistocene. 

2, 3. Paratype of Par-vanwss1:u1n calmnitus (G D. Hanna), UCMP 11779 ( x 

3.0). Length 15 mm, height 14 mm, hinge 9 mm. Fernando Formation, 

Pliocene and Pleistocene. 

4, 5. Hypotype USNM 149604 (X 2.0) (Arnold, 1906, pl. 53, figs. 2, 2a). Height 

22 mm (right valve); height 25 mm (left valve). Pribilof Islands, Bering 

Sea. Holocene, 145m. 

6, 7. Hypotype USNM 62343 (x2.0). Length 18 mm, height 18 mm, hinge 6 

mm. Port Etches, Alaska. Holocene. 

8, 9. Delectopecten alternil1:neatus (Clark) (p. B15). 

Holotype UCMP 11203 (x 4.0). Length 5 mm, height 6 mm, hinge 3 mm. San 

Ramon Sandstone, Miocene(?). 

10, 11. Amusium lompocens?:.c; (Arnold) !(p. B66)'. 

10. Holotype CAS 81. Height 105 mm. Tranquillon(?) Formation, Miocene. 

11. Paratype USNM 164852 (copied from Arnold, 1906, pl. 28, fig. 2). 
GEOLOGICAL SURVEY PROFESSIONAL PAPER 1228-B PLATE 2 

X3.0 

2 3 

PARVAMUSSJUM, DELECTOPECTEN, AMUSJUM 
FiGURES 

PLATE 3 

1-3. Delectopecten lillis1: (Hertlein) (p. B14). 

Kreyenhagen Formation, Eocene and Oligocene. 

1, 3. Holotype CAS 6062 (x 3.0). Length 13 mm, height 13 mm, hinge 

8mm. 

2. Paratype CAS 6063 (X 3.0). Hing-e 10 mm. 

4, 5. Delectopecten peckhami (Gabb) of Arnold (p. B15). 

4. Hypotype USNM 563246 (x 4.0) (Moore, 1963, pl. 20, fig .. 3). 

Astoria Formation, Miocene, Oregon. 

5. Hypotype USNM 164839 (X 1.5) (Arnold, 1906, pl. 3, fig. 28; 

Moore, 1963, pl. 21, fig. 2). Monterey Shale, Miocene. 

6-9. Delectopecten harfordus (Davis) (p. B16). 

Monterey(?) Formation, Miocene(?). 

6. Syntype CAS/SU 406 (X 2.0). Length 15 mm, height 13 mm, 

hinge 11 mm. 

7, 9. Syntype CAS/SU 408 (x 2.0). 

7. Hinge 9 mm. 

9. Length 14 mm, height 19 mm, hinge 10 mm. 

8. Paratype CAS 9819 (x 2.0). 

10. Delectopecten vancouverensisjernandoensis (Hertlein)(p. B16). 

Holotype CAS/SU 16 (X 3.0). Length 14 mm, height 15 mm, hinge 

10 mm. Fernando Formation, Pliocene and PleistoceP-e. 

11, 16. Delectopecten vancouverens1:s vancouverensis (Whiteaves) (p. B17). 

Hypotype USNM 126643 (X 8.0). Departure Bay, Vancouver Island, 

B.C. Holocene, 35m. Length 6 mm, height 6 mm, hinge 5 mm. 

12. Chlamys calkinsi (Arnold) (p. B19). 

Holotype UCMP 12076 (x 1.5). Height 45 mm. Coldwater Sandstone, 

Eocene. 

13, 14. Delectopecten randolphi tillamookensis (Arnold) (p. B17). 

Holotype USNM 150233 (Arnold, 1906, pl. 48, figs. 3, 3a). Height 

30 mm. Tillamook Bay, Oreg. Holocene, 1,437 m. 

15. Chlamys proavus (Arnold) (p. B19). 

Holotype USNM 164930. Height 38 mm. Locatelli(?) Formation, Paleocene. 
GEOLOGICAL SURVEY PROFESSIONAL PAPER 1228-B PLATE 3 

12 16 

DELECTOPECTEN, CHLAMYS 
FIGURES 

PLATE 4 

1. Chlamys brnnneri (Arnold) (p. B19). 

Holotype CAS/SU 358 (X 1.5). Photograph is of clay impression 

made from mold of holotype. Hinge 31 mm. Unnamed Miocene 

sandstone of Dibblee (1966), near Stanford University, California. 

2, 3. Chlamys sespeensis (Arnold) of Loel and Corey (p. B20). 

Vaqueros Formation, Oligocene and Miocene. 

2. Hypotype UCMP 31721 (Loel and Corey, 1932, pl. 21, fig. 5). 

Hinge 25 mm. Vaqueros Formation, Oligocene and Miocene. 

3. Hypotype UCMP 31722 (Loel and Corey, 1932, pl. 21, fig. 4). 

Length 39 mm, height 47 mm, hinge 24 mm. 

4, 6. Chlamys sespeensis hyde'/: (Arnold) (p. B20). 

Holotype CAS/SU 10 (X 1.5). Length 40 mm, height 46 mm. 

Vaqueros Formation, Oligocene and Miocene. 

5, 9. Chla,mys hodgei (Hertlein) (p. B21). 

Santa Margarita Formation, Miocene. 

5. Holotype CAS/SU 20 (X 1.5). Length 40 mm, height 45 mm, hinge 

25mm. 

9. ParatypeCAS/SU 21(x2.0). Length 24 mm, height32mm, hinge 

15mm. 

7, 8. Chla,mys he1·tlein1: (Loel and Corey) (p. B21). 

Holotype UCMP 31725 (X 1.5). Length 40 mm, height 46 mm. 

Vaqueros Formation, Oligocene and Miocene. 
GEOLOGICAL SURVEY PROFESSIONAL PAPER 1228-B PLATE 4 

2 

3 

6 

4 

9 

7 

CHLAMYS 
FIGURES 

PLATE 5 

1, 3. Chlamys sanct?:ludovic1: (Anderson and Martin) (p. B22). 

Santa Margarita Formation, Miocene. 

1. Holotype CAS 107 (x 1.5). Length 36 mm, height 40 mm, hinge 

25mm. 

3. Paratype CAS 108 (X 1.5). Length 40 mm, height 42 mm. 

2. Chlamys hodgei (Hertlein) (p. B21). 

Holotype of Chlamys durhami Adegoke, UCMP 36615 (X 2.0). 

Length 30 mm, height 36 mm, hinge 21 mm (estimated). Santa 

Margarita Formation, Miocene. 

4, 6. Chlamys hastata hastata (Sowerby) (p. B22). 

Copy of Arnold (1906, pl. 42, figs. 1, 1a). Height 64 mm. Monterey 

Bay, Calif. Holocene. 

5. Chlamys corteziana Durham (p. B2~b. 

Holotype UCMP 30564 (X 2.0). Photograph is of latex impression of 

holotype mold. San Marcos Formation, Pliocene. 

7, 8. Chlamys hastata heric1>us (Gould) (p. B23). 

Holotype USNM 5955. Length 60 mm, height 66 mm, hinge 28 mm. 

Strait of Juan de Fuca, Wash. Holocene. 

9. Chlamys (Chlamys) hastata ellisi Hertlein and Grant (p. B24). 

Holotype LAM 4483. Length 66 mm, height 69 mm. San Diego 

Formation, Pliocene. (Photograph courtesy of Barry Roth, California Academy of Sciences.) 
GEOLOGICAL SURVEY PROFESSIONAL PAPER 1228-B PLATE 5 

CHLAMYS 

-
FIGURES 

PLATE 6 

1, 9. Chlamys hastata pugetensis (Oldroyd) (p. B27). 

"Virtual paratype" CAS 12390 (X 1.5). Length 38 mm, height 

43 mm, hinge 24 mm. Puget Sound, Wash., Holocene. 

2. Chlamys opuntia (Dall) (p. B26). 

Holotype USNM 107752. Length 33 mm, height 35 mm. San Diego 

Formation, Pliocene. 

3, 7. Chlamys J·ordani (Arnold) (p. B25). 

Holotype USNM 162522. Length 43 mm, height 47 mm, hinge 

18 mm. San Pedro Formation, Pleistocene. 

4, 8. Nod1:pecten subnodosus subnodosus (Sowerby) (p. B57). 

Hypotype SDNM 78669. Length 93 mm, height 85. San Juan del Sur, 

Nicaragua, Holocene. 

5. Chlamys egregius (Nomland) (p. B24). 

Holotype UCMP 11090 (X 2.0). Length 24 mm, height 31 mm, hinge 

13 mm (estimated). Upper part of Etchegoin Formation, Pliocene. 

6. Chlamys bartschi (Arnold) (p. B25). 

Holotype USNM 164841. Length 50 mm. St. George Formation, Pliocene. 

•. 
GEOLOGICAL SURVEY PROFESSIONAL PAPER 1228-B PLATE 6 

8 

CHLAMYS, NOD/PECTEN 
FIGURES 

PLATE 7 

1-2. Chlamys picoensis (Waterfall) (p. B27). 

Upper part of Pico or San Pedro Formation, Pleistocene. 

1. Holotype UCMP 31419. Length 68 mm, height 69 mm, hinge 

30mm. 

2. Holotype of Chlamys venturaens1:s (Waterfall), UCMP 31416. 

Length 68 mm, height 68 mm, hinge 32 mm. 

3, 5. , Chlamys ntb1:da (Hinds) (p. B28). 

Hypotype USNM 150220 (MacNeil 1967, pl. 20, figs. 7, 9). Length 

50 mm, height 55 mm. South side of Alaska Peninsula, Holocene. 

4, 6. Chlamys anapleus Woodring (p. B29). . 

4. Holotype USNM 498642 (X 2.0). Length 23 mm, height 20. Basal 

part of San Pedro Sand, Pleistocene. 

6. Hypotype copied from Arnold (1906, pl. 44, fig. 4) (X 3.0). Height 

21 mm. San Pedro Formation, Pleistocene. 

7. Chlmnys? med1:acostata med1:acostata (G D. Hanna) (p. B29). 

Holotype CAS 1830. Length 30 mm, height 37 mm. Imperial 

Formation, Miocene or Pliocene. 

8. Chlamys? mediacostata grew1:ngk1: (Hertlein) (p. B29). 

Holotype CAS 12812 (X 1.5). Length 34 mm, height 40 mm. Salada 

Formation, Pliocene. 
GEOLOGICAL SURVEY PROFESSIONAL PAPER 1228-B PLATE 7 

2 

4 

3 5 

7 

8 

6 

CHLAMYS, CHLAMYS? 
FIGURES 

PLATE 8 

1, 2. Leochlamys? erici (Wiedey) (p. B30) .. 

Holotype SDNM 27 (x 1.5). Length 55 mm, height 63 mm, hinge 

28 mm (estimated). Vaqueros Formation. Olil!ocene and Miocene. 

3. Leochlamys? columbiana (Clark and Arnold) (p. P.JO). 

Holotype UCMP 30056. Length 75 mm, height 83 mm, hinge 47 mm 

(estimated). Sooke Formation, Oligocene and Miocene, British 

Columbia. 

4, 5. Nanaochlamys nutteri (Arnold) (p. B31). 

Holotype CAS/SU 6. Height 74 mm. Purisima Formation, Pliocene. 
GEOLOGICAL SURVEY PROFESSIONAL PAPER 1228-B PLATE 8 

5 

LEOCHLAMYS ?, NANAOCHLAMYS 
FIGURES 

PLATE 9 

1, 4. A rgopecten mendenhalli (Arnold) (p. B33). 

Holotype USNM 164849. Height 43 mm. Salada Formation, Pliocene. 

2. Argopecten deserti (Conrad) (p. B33). 

Holotype USNM 8398 (X 2.0). Imperial Formation, Miocene or 

Pliocene. 

3, 6. Argopecten d?>minutivus (Hertlein and Jordan) (p. B32). 

Holotype CAS/SU 125 (x 4.0). Length 9 mm, height 9 mm. Isidro 

Formation, Miocene. 

5. A1·gopecten circular1:s bramkamp1: (Durham) (p. B35). 

Holotype UCMP 30035. Length 43 mm, height 44 mm, hinge 23 mm. 

Imperial Formation, Miocene or Pliocene. 

7, 8. Argopecten circularis circularis (Sowerby) (p. B34). 

7. Hypotype UCMP 15706 (Durham, 1950, pl. 10, fig. 5). Length 

54 mm, height 52 mm, hinge 37 mm. Marquer Formation, 

Pliocene. 

8. UCMP 15740. Length 42 mm, height 50 mm, hinge 38 mm 

(estimated). Marquer Formation, Pliocene. 

9. Argopecten sverdrupi (Durham) (p. B34). 

Holotype UCMP 15995. Length 57 mm, height 55 mm, hinge 30 mm 

(estimated). Salada Formation, Pliocene. 

10, 12. Aequipecten dallasi (Jordan and Hertlein) . (p. B31) .. 

Holotype CAS 1862 (x 1.5). Length 43 mm, height 42 mm. Salada 

Formation, Pliocene. 

11. Argopecten circularis eld1·idgei (Arnold) (p. B36). 

Holotype USNM 164580 (X 1.5). Height 20 mm. Etchegoin Formation, Pliocene. 
. GEOLOGICAL SURVEY PROFESSIONAL PAPER 1228-8 PLATE 9 

10 12 

ARGOPECTEN, AEQUIPECTEN 
FIGURES 

PLATE 10 

1. Argopecten circularis imposter (G D. Hanna) (p. B36). 

Holotype UCMP 11089 (X 1.5). Length 33 mm, height 37 mm, hinge 

15 mm. Upper part of Etchegoin Formation, Pliocene. 

2. Argopecten cinularis calli (Hertlein) (p. B35). 

Holotype CAS/SU 68 (x 3.0). Length 24 mm, height 24 mm, hinge 

18 mm. Salada Formation, Pliocene. 

3, 4. Argopecten subdolus (Hertlein) (p. B37). 

Holotype CAS/SU 51. Length 50 mm, height 49 mm, hinge 25 mm. 

San Diego Formation, Pliocene. 

5. Argopecten inval1:dus (G D. Hanna) (p. B37). 

Holotype CAS/SU 8 (X 1.5). Length 37 mm, height 35 mm, hinge 

22 mm (estimated). San Diego Formation, Pliocene. 

6. Argopecten percarus (Hertlein) (p. B39). 

Holotype CAS/SU 42. Length 89 mm, height 79 mm, hinge 45 mm 

(estimated). Almejas Formation, Pliocene. 

7, 9. Argopecten callidus (Hertlein) (p. B38). 

Holotype CAS/SU 53. Length 54 mm, height 55 mm, hinge 28 mm. 

Almejas Formation, Pliocene. 

8. Argopecten? crass1:radiatus (Clark) (p. B42). 

Holotyr'" UCMP 11584. Height 45 mm. Cierbo Sandstone, 

Miocene. 
GEOLOGICAL SURVEY PROFESSIONAL PAPER 1228-B PLATE 10 

9 

ARGOPECTEN, ARGOPECTEN? 
FIGURES 

PLATE 11 

1, 3. A1·gopecten revellei (Durham) (p. B40). 

Holotype UCMP 15510. Length 60 mm, height 58 mm, hinge 36 mm 

(estimated). Salada Formation, Pliocene. 

2. A1·gopecten abietis abiet?:s (Jordan and Hertlein) (p. B41). 

Holotype CAS 2079. Length 55 mm, height 55 mm, hinge 37 mm 

(estimated). Unnamed Pliocene strata. Isla Maria Madre, Mexico. 

4, 5. Argopecten antonitaensis (Durham) (p. B41). 

Holotype CAS 5957 (x 1.5). Length 43 mm, height 41 mm, hinge 

24 mm. Carmen Formation, Pliocene. 

6. Argopecten hakei (Hertlein) (p. B39). 

Holotype CAS/SU 40 (X 0.8). Length 135 mm, height 116 mm, hinge 

90 mm (estimated). Almejas Formation, Pliocene. 
GEOLOGICAL SURVEY 

4 

PROFESSIONAL PAPER 1228-B PLATE 11 

6 

ARGOPECTEN 
FIGURES 

PLATE 12 

1, 5. Argopecten ab1:et?:s abbott1: (Hertlein and Grant) (p. B42). 

Holotype SDNM 04334 (X 0. 7). Length 129 mm, height 117 mm. San 

Diego Formation, Pliocene. 

2. A rgopecten er£ceil'us (Hertlein) (p. B37). 

Holotype CAS 2998 (X 2.0). Length 29 mm, height 28 mm, hinge 

19 mm. San Diego Formation, Pliocene. 

3. Argopecten ab£etis abietis (Jordan and Hertlein) (p. B41). 

Holotype CAS 2079. Length 66 mm, height 64 mm, hinge 39 mm 

(estimated). Unnamed Pliocene strata, Isla Maria Madre, Mexico. 

4. Argopecten percarus (Hertlein) (p. B39). 

Holotype CAS/SU 42. Length 91 mm, height 80 mm, hinge 43 mm. 

Almejas Formation, Pliocene. 
GEOLOGICAL SURVEY PROFESSIONAL PAPER 1228-B PLATE 12 

ARGOPECTEN 
FIGURES 

PLATE 13 

1. Argopecten cristobalensis (Hertlein) (p. B40). 

Holotype CAS/SU 36 (x 0. 7). Length 135 mm, height 117 mm, hinge 

50 mm (estimated). Almejas Formation, Pliocene. 

2, 4, 5. Antipecten? praeval1:dus (Jordan and Hertlein) (p. B42). 

Almejas Formation, Pliocene. 

2. Paratype CAS 2102. Length 65 mm, height 58 mm, hinge 40 mm 

(estimated). 

4, 5. Holotype CAS 2101. Length 51 mm, height 47 mm, hinge 39 mm. 

3, 6. Leptopecten bellilamellatus (Arnold) (p. B43). 

Holotype CAS/SU 35 (X 3.0). Length 18 mm, height 18 mm, hinge 

16 mm. San Diego Formation, Pliocene. 

7. Argopecten evermanni (Jordan and Hertlein) (p. B39). 

Holotype CAS 2108 (X 0.8). Length 125 mm, height 115 mm. 

Almejas Formation, Pliocene. 
GEOLOGICAL SURVEY PROFESSIONAL PAPER 1228-B PLATE 13 

6 7 

ARGOPECTEN, ANT/PECTEN ?, LEPTOPECTEN 
FIGURES 

PLATE 14 

1. Pac1:pecten anderson·1: ande1·som: (Anderson) (p. B45). 

Holotype USNM 164932. Length 43 mm, height 38 mm. Monterey(?) 

Formation, Miocene. 

2. Pac1:pecten tol1nmn: (Hall and Ambrose) (p. B46). 

Holotype CAS/SU 23. Length 72 mm, height 65 mm. Briones 

Sandstone, Miocene. 

3-5, 7-9. Pac1:pecten discus (Conrad) (p. B46). 

3. UCMP 11581, holotype of P. raymondi Clark. Length 43 mm, 

height 40 mm, hinge 21 mm. San Pablo Group, Miocene. 

4. UCMP 12370, holotype of P. gon1:costatus Trask (X 2.0). Length 

31 mm, height 29 mm. Briones Sandstone, Miocene. 

5. UCMP 11585, holotype of P. cierboens-is Clark (X 2.0). Length 

18 mm, height 20 mm. Briones Sandstone, Miocene. 

7. UCMP 12368, holotype of P. bn:onianus Trask (x 1.5). Length 

37 mm, height 37 mm. Briones Sandstone, Miocene. 

8. USNM 13335, holotype of P. d1:scu8. Length 53 mm, height 

47 mm, hinge 21 mm. Monterey(?) Formation, Miocene. 

9. UCMP 12371, paratype of P. 1·aynwndi. Length 57 mm, height 

53 mm, hinge 30 mm. San Pablo Group, Miocene. 

6. Pacipecten andersoni subander.c;oni (Loel and Corey) (p. B45). 

Holotype UCMP 31741 (x 1.5). Length 40 mm, height 35 mm 

(estimated), hinge 23 mm (estimated). Vaqueros Formation, 

Qligocene and Miocene. 
GEOLOGICAL SURVEY PROFESSIONAL PAPER 1228-B PLATE 14 

2 

7 9 

PACJPECTEN 
FIGURES 

PLATE 15 

1, 3. Pacipecten pabloens1:s (Conrad) of Arnold (p. B47). 

1. CAS/SU 302 (X 1.5). Hypotype (Arnold, 1906, pl. 27, figs. 5, 5a). 

Length 35 mm, height 35 mm, hinge 20 mm. San Pablo Formation, Miocene. 

3. CAS/SU 302a ( x 1.5). Hypotype (Arnold, 1906, pl. 27, figs. 6, 6a). Length 

32 mm, height 32 mm, hinge 17 mm (estimated). 

6. Pacipecten bilineatus (Clark) (p. B48). 

Holotype UCMP 11579. Length 48 mm, height 38 mm, hinge 20 mm. 

Cierbo Sandstone, Miocene. 

2, 8. Pacipecten tumbezensis (Orbigny) (p. B49). 

Tumbez, Peru, Holocene. 

2. Hypotype CAS 60361 (x 3.0). Length 24 mm, height23 mm, hinge 

18mm. 

8. Hypotype CAS 60360 (X 1.5). Length 39 mm, height 38 mm, hinge 

23mm. 

4, 5. Pacipecten weaveri (Clark) (p. B46). 

Cierbo Sandstone, Miocene. 

4. Syntype UCMP 11576 (X 1.5). Length 39 mm, height 34 mm. 

5. Syntype UCMP 11575 (X 1.5). Length 48 mm, height 40 mm, 

hinge 25 mm. 

7, 9. Leptopecten lat'iauratus (Conrad) (p. B43). 

Hypotype CAS 60358 (X 2.0). Length 28 mm, height 28 mm, hinge 

22 mm. San Diego, Calif., Holocene. 
GEOLOGICAL SURVEY 

7 

PROFESSIONAL PAPER 1228-B PLATE 15 

8 

PAC/PECTEN, LEPTOPECTEN 
FIGURES 

PLATE 16 

1, 2, 4. Lyropecten m1:guelensis (Arnold) (p. B49). 

Holotype UCMP 12079. Height 110 mm. Vaqueros Formation, 

Oligocene and Miocene. 

3, 5. Lyropecten submiguelens1:.c; (Loel and Corey) (p. B50). 

Holotype UCMP 31737. Length 70 mm, height 67 mm. Vaqueros 

Formation, Oligocene and Miocene. 
GEOLOGICAL SURVEY PROFESSIONAL PAPER 1228-B PLATE 16 

3 

5 

4 

LYROPECTEN 
FIGURES 

PLATE 17 

1. Ly1·opecten submiguelensis (Loel and Corey) (p. B50). 

Holotype UCMP 31737. Length 70 mm, height 67 mm. Vaqueros 

Formation, Oligocene and Miocene. 

2-4. Lyropecten vaughani (Arnold) (p. B50). 

Holotype CAS/SU 9. Height 37 mm. Vaqueros Formation, Oligocene and Miocene. 

5, 8. Lyropecten pretiosus (Hertlein)"(p. B51). 

Isidro Formation, Miocene. ' 

5. Holotype CAS/SU 38 (X 2.0). Length 29 mm, height 27 mm, hinge 

18mm. 

8. Paratype CAS/SU 89 (X 2.0). Leng-th 47 mm, height 32 mm. 

6, 7. Lyropecten cra.c;sicardo (Conrad) (p. B51). 

6. Holotype of Lyropecten nmnlandi (Hertlein), UCMP· 11308. 

Length 114 mm, height 92 mm, hinge 65 mm (estimated). 

Santa Margarita Formation, Miocene. 

7. Holotype of Lyropecten vickeryi (Trask), CAS/SU 26. Length 

106 mm (estimated), height 99 mm. Briones Sandstone, 

Miocene. 
GEOLOGICAL SURVEY PROFESSIONAL PAPER 1228-B PLATE 17 

2 3 4 

6 

7 

8 

LYROPECTEN 
FIGURES 

PLATE 18 

1-3, 5. Lyropecten crass-£cardo (Conrad) (p. B51). 

1. Holotype of Lyropecten Tice-i (Trask), UCMP 12364. Length 

53 mm (estimated), height 54 mm. Briones Sandstone, Miocene. 

2, 5. Lectotype of L. c1·assicaTdo, ANSP 30745a (X 0.7). Length 

135 mm, height 138 mm. Santa Margarita Formation, Miocene. 

3. Holotype of LyTopecten ham,£ltoni (Arnold), USNM 164845. 

Height 40 mm. Briones Sandstone, Miocene. 

4, 6. LyTopecten catal'£nae (Arnold) (p. B53). 

San Onofre(?) Breccia, Miocene. 

4. Paratype CAS/SU 561 (photograph copied from Arnold, 1906, 

pl. 20, fig. 4). Hinge 30 mm. 

6. Holotype CAS/SU 30. Length 74 mm, height 76 mm. 
GEOLOGICAL SURVEY PROFESSIONAL PAPER 1228-B PLATE 18 

4 

5 

LYROPECTEN 
FIGURES 

PLATE 19 

1, 5. · Lyropecten teTminus (Arnold) (p. B54). 

Holotype UCMP 11662. Height 70 mm. Pancho Rico Formation, 

Pliocene. 

2. LyTOpecten estTellanus (Conrad) (p. B53). 

Lectotype USNM 13317. Height 90 mm. Santa Margarita Formation, Miocene. 

3. LyTopecten gallegosi (Jordan and Hertlein) (p. B54). 

Holotype CAS 2096 (X 0. 7). Length 138 mm, height 125 mm. 

Almejas Formation, Pliocene. 

4. Ly1·opecten modulatus (Hertlein) (p. B55). 

Holotype CAS/SU 39. Length 60 mm, height 58 mm. Almejas 

Formation, Pliocene. 
GEOLOGICAL SURVEY PROFESSIONAL PAPER 1228-B PLATE 19 

5 

LYROPECTEN 
FIGURES 

PLATE 20 

1, 3, 4. Lyropecten cerrosetun:s (Gabb) (p. B55). 

1, 4. Holotype UCMP 32669 (X 0.5). Length 226 mm, height 210 mm. 

Almejas Formation, Pliocene. 

3. UCMP 12082, holotype of L. ashley1: (x 0.5). Almejas Formation, 

Pliocene. 

2, 5. Pac1:pecten a,nderson1: barker1:anus (Arnold) (p. B45)~ 

2. Photograph copied from Arnold (1906, pl. 26, fig. 9); specimen 

lost. Height 40 mm. 

5. Hypotype CAS/SU 6588 (Schenck and Keen, 1940, pl. 39, fig. 5) 

(X 2.0). 
GEOLOGICAL SURVEY PROFESSIONAL PAPER 1228-B PLATE 20 

4 5 

L YROPECTEN, PAC/PECTEN 
FIGURES 

PLATE 21 

1. Lyropecten cerrosens·1:s (Gabb) (p. B55). 

Holotype of L. ashley1:, UCMP 32669 (x 0.5). Height 155 mm. 

Almejas Formation, Pliocene~ 

2. Vertipecten d1:abloensis (Clark) (p. B64). 

Holotype UCMP 11138. Length 46 mm, height 55 mm. San Ramon 

Sandstone, Miocene. 

3. Lyropecten crassicardo (Conrad) (p. B51). 

Holotype of Swijtopecten adekunbiana Adegoke, UCMP 36639. 

Length 41 mm, height 43 mm. Santa Margarita Formation, Miocene. 

4, 5. Macrochlarnis rnagnolia (Conrad) (p. B56). 

4. Lectotype USNM 13325. Vaqueros Formation, Oligocene and 

Miocene. 

5. Holotype of M. ern1:gdioens·is, UCMP 11417 (X 2.0). Length 

23 mm, height 21 mm. Vaqueros Formation, Oligocene and 

Miocene. 
GEOLOGICAL SURVEY PROFESSIONAL PAPER 1228-B PLATE 21 

xo.s3 

5 

4 

L YROPECTEN, VERT/PECTEN, MACROCHLAMIS 
FIGURES 

PLATE 22 

1. Nodipecten subnodosus 'intenned?:u.c; (Conrad) (p. B58). 

Height 112 mm. West coast of Mexico, Holocene. Photograph copied 

from Arnold (1906, pl. 52, fig. 1). 

2, 3. Sw?}topecten parmelee?: etchegoini (Anderson) (p. B60). 

2. Holotype CAS 55. Etchegoin Formation, Pliocene., 

3. USNM 164929, holotype of S. nw1·ani. Height 63 mm. Etchegoi!l 

Formation, Pliocene. (Photograph copied from Arnold, 1906, 

pl. 10, fig. 3.) 

· 4. Nod1:pecten veatchii (Gabb) (p. B58). 

Holotype UCMP 12078 (x 0.6). Height 130 mm. Almejas Formation, 

Pliocene. 
GEOLOGICAL SURVEY PROFESSIONAL PAPER 1228-B PLATE 22 

4 

NODIPECTEN, SWIFTOPECTEN 
FIGURES 

PLATE 23 

1, 3, 4. Swijtopecten parmelee?: panneleei (Dall) (p. B59). 

1. USNM 164842, hypotype (Arnold, 1906, pl. 12, fig. 5). Height 

70 mm. Wildcat Group, Pliocene and Pleistocene. 

3. Photograph copy of Arnold (1906, pl. 41, fig. 1), holotype of 

S. watts1:, missing and presumed lost. Height 65 mm. Etchegoin 

Formation, Pliocene. 

4. Holotype USNM 154479 (x 1.5). Height 45 mm. San Diego 

Formation, Pliocene. 

2. Nodipecten 'Veatchii (Gabb) (p. B58). 

Holotype UCMP 12078 (x 0.6). Height 130 mm. Almejas Formation, 

Pliocene. 

5. Nodipecten subnodosus 1:ntermed,ius (Conrad) (p. B58). 

Height 112 mm. West coast of Mexico, Holocene, Photograph copied 

from Arnold (1906, pl. 53, fig. 1). 
GEOLOGICAL SURVEY PROFESSIONAL PAPER 1228-B PLATE 23 

5 

SWIFTOPECTEN, NOD/PECTEN 
FIGURES 

PLATE 24 

1, 2, 4. Vertipecten alexclarki Addicott (p. B61). 

1. Paratype USNM 646529. Length 63 mm, height 82 mm. Wygal 

Sandstone Member, Temblor Formation, Oligocene. 

2. Hypotype CAS 60682. Length 68 mm, height 75 em. Wygal Sandstone Member, Temblor Formation, Oligocene. 

4. Lectotype USNM 646531. Length 66 mm, height 69 mm. Wygal 

Sandstone Member, Temblor Formation, Oligocene. 

3. Vert?:pecten ynezr:ana subynezr:ana (Weaver and Kleinpell) (p. B61). 

Holotype CAS/SU 9265 (X 1.5). Photograph of rubber cast from 

holotype mold. Coldwater Sandstone, Eocene. 

5. SuJ?jtopecten? hamt?:ni (Arnold) (p. B60). 

Holotype USNM 164844. Height 50 mm. Santa Margarita(?) Formation, Miocene. 

6. Ver·tipecten bowersr: (Arnold) (p. B62). 

Holotype UCMP 12075 (X 0. 7). Height 150 mm. Topanga(?) Formation, Miocene. 
GEOLOGICAL SURVEY PROFESSIONAL PAPER 1228-B PLATE 24 

5 

VERT/PECTEN, SWIFTOPECTEN? 
FIGURES 

PLATE 25 

1. Vert1:pecten bowers1: (Arnold) (p. B62). 

Holotype UCMP 12075 (X 0.7). Height 150 mm. Topanga(?) Formation, Miocene. 

2, 3. Vertipecten ynez1:ana yneziana (Arnold) (p. B61). 

2. Paratype USNM 165313. Hinge 25 mm. Gaviota Formation, 

Eocene. 

3. Holotype USNM 165313a. Height 64 mm. Gaviota Formation, 

Eocene. 

4-6. Vert'ipecten pern>m: (Arnold) (p. B62). 

Holotype CAS/SU 13 (X 0.5). Height 150 mm. Vaqueros Formation, 

Oligocene and Miocene. 
GEOLOGICAL SURVEY PROFESSIONAL PAPER 1228-B PLATE 25 

VERT! PECTEN 
FIGURES 

PLATE 26 

1, 5. H1:nn-ites g1:ganteus (Gray) (p. B65). 

1. USNM 13336. Holotype of H. crassa Conrad. Height 110 mm. 

Santa Margarita Formation, Miocene. 

5. USNM 13336a. Paratype of H. cr·assa Conrad. Santa Margarita 

Formation, Miocene. 

2. H-inn?:tes bened?:ct?: Adegoke (p. B65). 

Holotype UCMP 36638. Length 36 mm, height 47 mm, hinge 22 mm. 

Santa Margarita Formation, Miocene. 

3, 4. Vertipectenjucanus (Dall) (p. B63). 

3. Latex cast of holotype mold (USNM 107790). Length 82 mm, 

height 84 mm. Clallam Formation, Washington, Miocene. 

4. USNM 3558, right valve. (Figured by Arnold, 1906, pl. 9, figs. 1, 

1a, as Patirwpecten p1·opatulus.) 
GEOLOGICAL SURVEY PROFESSIONAL PAPER 1228-B PLATE 26 

HINNITES, VERTIPECTEN 
FIGURES 

PLATE 27 

1. Ver-tipecten fuca nus (Dall) (p. B63). 

USNM 563250 hypotype (Moore, 1963, pl. 21, fig. 1). Length 

108 mm, height 111 mm. Astoria Formation, Oregon, Miocene. 

2-4. Hinm:tes giganteus (Gray)(p. B65). 

2, 3. USNM 74166 hypotype (Arnold, 1906, pl. 29, figs. 2, 2a). Height 

70 mm. San Diego, Calif., Holocene. 

4. USNM .13336, holotype of H. crassa Conrad. Height 110 mm. 

Santa Margarita Formation, Miocene. 
GEOLOGICAL SURVEY PROFESSIONAL PAPER 1228-B PLATE 27 

3 

HINNITES, VERT/PECTEN 
FIGURES 

PLATE 28 

1. Lyropecten crass1:cardo (Conrad) (p. B51). 

Holotype of Pecten holwayi Clark, UCMP 11580. Length 90 mm, 

height 85 mm. Cierbo Sandstone, Miocene. 

2, 5. Pecten (Pecten) Leconte-£ Arnold (p. B68). 

Holotype CAS/SU 4. Height 59 mm. Almejas Formation, Pliocene. 

3, 4. Pecten (Pecten) aletes Hertlein (p. B67). 

Salada Formation, Pliocene. 

3. Holotype CAS/SU 44. Length 65 mm, height 62 mm. 

4. Paratype CAS/SU 45 (x 1.5). Length 43 mm. 

6. Vertipecten kernen.<n:s (Hertlein) (p. B64). 

Holotype CAS/SU 128. Monterey Formation, Miocene. 
GEOLOGICAL SURVEY PROFESSIONAL PAPER 1228-B PLATE 28 

5 

L YROPECTEN, PECTEN, VERT/PECTEN 
FIGURES 

PLATE 29 

1-4. Pecten (Pecten) bellus (Conrad) (p. B68). 

1, 4. Neotype ANSP 960. Length 100 mm, height 94 mm. Santa 

Barbara Formation, Pliocene and Pleistocene. 

2, 3. USNM 7943, holotype of P. hemphUlii. Length 63 mm, height 

56 mm, hinge 28 mm. San Diego Formation, Pliocene. 

5. Amuss1:opecten vanvleck?: (Arnold) (p. B69). 

Holotype USNM 165305. Height 64 m. Vaqueros Formation, Oligocene and Miocene. 
GEOLOGICAL SURVEY PROFESSIONAL PAPER 1228-B PLATE 29 

5 

PECTEN, AMUSSIOPECTEN 
FIGURES 

PLATE 30 

1. A m/ussiopecten vanvleck1: (Arnold) (p. B69). 

Paratype USNM 165306. Height 72 mm. Vaqueros Formation, 

Oligocene and Miocene. 

2-4. Euvola rejug1:oensis (Hertlein) (p. B71). 

Salada Formation, Pliocene. 

2. Paratype CAS/SU 50. Length 82 mm, height 80 mm. 

3, 4. Holotype CAS/SU 49. Length 57 mm, height 56 mm. 

5, 6. Eu:vola keepi (Arnold) (p. B70). 

Holotype CAS/SU 5. Length 74 mm, height 75 mm. Imperial Formation, Miocene or Pliocene. 
GEOLOGICAL SURVEY PROFESSIONAL PAPER 1228-B PLATE 30 

3 

5 6 

AMUSSIOPECTEN, EUVOLA 
FIGURES 

PLATE 31 

1. Flabellipecten? hawleyi (Hertlein) (p. B74). 

Holotype CAS/SU 19 (X 1.5). Length 34 mm, height 32 mm. 

Vaqueros Formation, Olig-ocene and Miocene. 

2. Flabell1:pecten d1:egens1:s (Dall) (p. B73). 

Hypotype USNM 150980 (photograph copied from Arnold, 1906, 

pl. 51, fig. 1). Height 86 mm. San Pedro, Calif., Holocene. 

3, 5. Flabelhpecten beali (Hertlein) (p. B73). 

Holotype CAS/SU 55. Length 56 mm, height 55 mm. Salada Formation, Pliocene. 

4, 6. Flabell?:pecten carrizoen.':n:s (Arnold) (p. B71). 

Holotype CAS/SU 11 (x 1.5). Length 42 mm, height 36 mm. 

Imperial Formation, Miocene or Pliocene. 

7, 8. Flabellipecten stewrn.'n:?: (Dall) (p. B72). 

Holotype USNM 7942 (x 0. 7). Length 100 mm, height 90 mm, hinge 

34 mm. San Diego Formation, Pliocene. 
GEOLOGICAL SURVEY PROFESSIONAL PAPER 1228-B PLATE 31 

FLABELLIPECTEN 
FIGURES 

PLATE 32 

1, 2. Flabellipecten bosei (Hanna and Hertlein) (p. B72). 

Salada Formation, Pliocene. 

1. Syntype CAS 2215. Length 74 mm, height 66 mm, hinge 28 mm. 

2. Syntype CAS 2216. Length 82 mm, height 78 mm. 

3. Oppenhe'l:nwpecten sanctaecntzensis (Arnold) (p. B75). 

UCMP 11416, holotype of P. dicke'rsoni (X 2.0). Length 19 mm, 

height 19 mm. Pleito Formation. Oligocene. 

4. Flabell'ipecten diegenwis (Dall) (p. B73). 

Hypotype USNM 150980 (photograph copied from Arnold, 1906, 

pl. 51, fig. la). Height 86 mm. San Pedro, Calif., Holocene. 

5. Flabellipecten? 1ner~·imm: (Arnold) (p. B74). 

Holotype UCMP 12086, left valve (X 0.8). Height 120 mm. Pico 

Formation, Pliocene and Pleistocene. 
GEOLOGICAL SURVEY PROFESSIONAL PAPER 1228-B PLATE 32 

2 

5 

FLABELLIPECTEN, FLABELLIPECTEN ?, OPPENHEIMOPECTEN 
FIGURES 

PLATE 33 

1. Flabellipecten? meniam'l: (Arnold) (p. B74). 

Holotype UCMP 12086, right valve (X 0.8). Height 120 mm. Pico 

Formation, Pliocene and Pleistocene. 

2. Oppenhe1:mopecten sanctaecruzens'is (Arnold) (p. B75). 

Holotype CAS/SU 360 (x 1.5). Photograph of latex impression of 

holotype mold. Height 52 mm. Vaqueros Formation, Oligocene 

and Miocene. 

3. Oppenheimopecten coalingaens1:s (Arnold) (p. B76). 

Lectotype CAS/SU 7 (X 1.5). Length 54 mm, height 46 mm. 

Etchegoin Formation, Pliocene. 

4. Oppenhe1:mopecten ha'rt1nmnn: (Hertlein) (p. B76). 

Holotype CAS/SU 48. Length 65 mm, height 75 mm. Almejas Formation, Pliocene. 

5. Oppenhe'l>mopectenfuanensis (Grant and Stevenson) (p. B75). 

Holotype UCLA 10441. Length 57 mm, height 54 mm. Neroly Sandstone, Miocene. 

6. Oppenheimopecten he1>"mi (Hertlein) (p. B77). 

Holotype CAS/SU 46. Length 85 mm, height 75 mm. Salada Formation, Pliocene. 
GEOLOGICAL SURVEY PROFESSIONAL PAPER 1228-B PLATE 33 

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4 

5 6 

FLABELLIPECTEN ?, OPPENHEIMOPECTEN 
FIGURES 

PLATE 34 

1, 4, 6. Patinopecten propat'ulus (Conrad) (p. B79). 

Astoria Formation, Miocene, Oregon. 

1, 6. Lectotype USNM 3504. Length 102 mm, height 103 mm. 

4. Hypotype (Moore, 163 pl. 16, fig. 2) USNM 563234 (x 2.0). 

2. Pat?>nopecten lohn: (Hertlein) (p. B80). 

Holotype UCMP 12081. Height 85 mm. Tinaquaic Sandstone Member, Sisquoc Formation, Pliocene. 

3. Pat1:nopecten healey'!: (Arnold) (p, B81). 

Hypotype (Moore, 1979, pl. 13, fig. 2) LAM 5254 (x 0.7). Hinge 

95 mm. San Diego Formation, Pliocene. 

5. Oppenhe1>"mopecten vogde.'n: (Arnold) (p. B77). 

Holotype CAS/SU 4. Length 73 mm, height 69 mm. Upper part of 

San Pedro Formation, Pleistocene. 
GEOLOGICAL SURVEY PROFESSIONAL PAPER 1228-B PLATE 34 

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PA TINOPECTEN, OPPENHEIMOPECTEN 
FIGURES 

PLATE 35 

1, 2. Patinopecten propatulus (Conrad) (p. B79). 

Hypotype (Moore, 1963, pl. 17, fig. 3) USNM 563236 (x 2.0). Length 

75 mm, height 77 mm. Astoria Formation, Miocene, Oregon. 

3. Pat?:nopecten healey1: (Arnold) (p. B81). 

Hypotype (Moore, 1979, pl. 1, fig. 3) LAM 5221 (X 1.5). San Diego 

Formation, Pliocene. 

4. Patinopecten haywardens,is (Lutz), (p. B80). 

Plaster castofholotype mold UCMP 341133 (X 0. 7). Length 130 mm, 

height 112 mm. Sobrante Sandstone, Miocene. 

5, 6. Patinopecten cala:uerasensis (Hall) (p. B80). 

5. Holotype CAS/SU 8442. Length 88 mm, height 76 mm, hinge 

47 mm. Oursan Sandstone, Miocene. 

6. Specimen on underside of holotype, CAS/SU 8442. presumed 

left-valve fragment. 
GEOLOGICAL SURVEY PROFESSIONAL PAPER 1228-B PLATE 35 

PA TINOPECTEN 
FIGURES 

PLATE 36 

1. Pat1>nopecten haywm·dens1:s (Lutz) (p. BBO). 

Plaster cast of paratype mold UCMP 34134. Sobrante 

Sandstone, Miocene. 

2, 3. Pat?:nopecten lohri (Hertlein) (p. BBO). 

Holotype UCMP 12081. Length 88 mm, height 87 mm, hinge 47 mm. 

Tinaquaic Sandstone Member, Sisquoc Formation, Pliocene. 

4. Pat1:nopecten healeui (Arnold) (p. B81). 

Hypotype (Moore, 1979, pl. 14, fig. 3) LAM 5254 (x 0.5). Length 

210 mm, height 190m, hinge 95 mm. San Diego Formation, Pliocene. 
GEOLOGICAL SURVEY PROFESSIONAL PAPER 1228-B PLATE 36 

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PA TINOPECTEN 
FIGURES 

PLATE 37 

1, 2. L'duyapecten turnen: (Arnold) (p. B87). 

Merced Formation, Pliocene and Pleistocene. 

1. Paratype CAS/SU 430-A .. 

2. Holotype CAS/SU 430. Height 65 mm. 

3. Pat1:nopecten healeyi (Arnold) (p. B81). 

Paratype USNM 154162. Height 141 mm. San Diego Formation, 

Pliocene. 
GEOLOGICAL SURVEY PROFESSIONAL PAPER 1228-B PLATE 37 

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LITUYAPECTEN, PA TINOPECTEN 
FIGURES 

PLATE 38 

1. PaLinopecten cau1'inus (Gould) (p. B83). 

CAS 60359 (X 0.7). Length 155 mm, height 145 mm, hinge 74 mm. 

Puget Sound, Washington, Holocene. 

2-5. Patl:nopecten healey'£ (Arnold) (p. B81). 

2. Hypotype (Moore, 1979, pl. 1, fig. 2) LAM 5220 (X 2.0). Length 

30 mm, height 31 mm, hinge 16 mm. San Diego Formation, 

Pliocene. 

3. Hypotype (Moore, 1979, pl. 2, fig. 6) USNM 235592. Length 

50 mm, height 50 mm, hinge 23 mm. Unnamed Pliocene strata, 

San Clemente Island, Calif. 

4. Holotype USNM 148012. Height 121 mm. San Diego Formation, 

Pliocene. 

5. Hypotype (Moore,1979, pl. 1, fig. 4) LAM 5222 (X 3.0). Length 

13 mm, height 13 mrri, hinge 8 mm. San Diego Formation, 

Pliocene. 
GEOLOGICAL SURVEY PROFESSIONAL PAPER 1228-B PLATE 38 

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PA TINOPECTEN 
FIGURES 

PLATE 39 

1. Pat1:nopecten healeyi (Arnold) (p. B81). 

Hypotype (Moore, 1979, pl. 4, fig. 5) LAM 5228. Length 48 mm, 

height 50 mm, hinge 22 mm. San Diego Formation, Pliocene. 

2. Leopecten bake1·i d·iaz·i (Durham) (p. B85). 

Holotype UCMP 15968 (X 0.7). Length 135 mm, height 123 mm, 

hinge 53 mm. Carmen Formation, Pliocene. 

3. Leopecten nwr-que1·ensis (Durham) (p. B85). 

Holotype UCMP 15475 (X 0.5). Length 176 mm, height 155 mm, 

hinge 72 mm. Marquer Formation, Pliocene. 

4. Ver-tipecten ci'iabloens1:s (Clark) (p. B64). 

Paratype UCMP 11139 (X 1.5). Length 50 mm, height 51 mm. San 

Ramon Sandstone, Miocene. 

5. Pat1:nopecten caur-inus (Gould) (p. B83). 

CAS 60359 (X 0.8). Length 148 mm, height 137 mm. hinge 73 mm. 

Puget Sound, Washington, Holocene. 
GEOLOGICAL SURVEY PROFESSIONAL PAPER 1228-B PLATE 39 

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PA TINOPECTEN. LEOPECTEN, VERT/PECTEN 
FIGURES 

PLATE 40 

1. Leopecten rnm·qu£1·ensis (Durham) (p. B85). 

Holotype UCMP 15475 (x 0.5). Length 176 mm, height 155 mm, 

hinge 72 mm. Marquer Formation, Pliocene. 

2. Leopecten ba.ken: diazi (Durham) (p. B85). 

Holotype UCMP 15968 (X 0.8). Length 135 mm, height 123 mm, 

hinge 53 mm. Carmen Formation, Pliocene. 

3. Pat1:nopecten yessoens1:s (Jay)(p. B78). 

Hypotype (Moore, 1979, pl. 14, fig. 1) (X 1.5). Exterior of right valve 

enlarged to show imbricated' microsculpture. CAS 58773. 

4. Leopecten bake1·£ bakeri (Hanna and Hertlein) ,(p. B~). 

Holotype CAS 1865 (X 0. 7). Length 150 mm, height 130 mm, hinge 

66 mm. San Marcos Formation, Pliocene. 

5. Pat1:nopecten hea.leyi (Arnold) (p. B81). 

Hypotype (Moore, 1979, pl. 10, fig. 4) LAM 5253 (X 3.0). Length 

21 mm, height 21 mm, hinge 10 mm. San Diego Formation, 

Pliocene. 
GEOLOGICAL SURVEY PROFESSIONAL PAPER 1228-B PLATE 40 

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PA TINOPECTEN, LEOPECTEN 
FIGURES 

PLATE 41 

1, 5. Lituyapectenfalm·en.'n:s (MacNeil) (p. B86). 

Holotype UCMP 34172. Length 105 mm, height 99 mm. Falor 

Formation, Pliocene. 

2. Patinopecten healey1: (Arnold) (p. B81). 

Hypotype (Moore, 1979, pl. 4, fig. 7) LAM 5229 (X 3.0). Enlargement 

of right anterior auricle showing ctenolium. Right anterior 

auricle 17 mm long. _ 

3, 4. L1:tuyapecten pur?:.'n>maen.'n:s (Arnold) (p. B87). 

Holotype CAS/SU 3 (X 0.7). Length 121 mm, height 124 mm. 

Purisima Formation, Pliocene. 
GEOLOGICAL SURVEY PROFESSIONAL PAPER 1228-B PLATE 41 

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LITVYAPECTEN, PA TINOPECTEN 
FIGURES 

PLATE 42 

1-3. Pat1:nopecten healey1: (Arnold) (p. B81). 

San Diego Formation, Pliocene. 

1. Hypotype (Moore, 1979, pl. 5, fig. 1) LAM 5231 (X 0.8). Length 

106 mm, height 105 mm, hinge 52 mm. 

2. Hypotype (Moore, 1979, pl. 10, fig. 1) LAM 5250 (X 2.5). Length 

36 mm, height 37 mm. 

3. Hypotype (Moore, 1979, pl. 4, fig. 3) LAM 5228. Length 48 mm, 

height 50 mm, hing-e 22 mm. 

4. Lduyapecten ddlen: (Dall) (p. B88). 

Lectotype USNM 164846. Length 160 mm. Rio Dell Formation, 

Pliocene and Pleistocene. 
GEOLOGICAL SURVEY PROFESSIONAL PAPER 1228-B PLATE 42 

LITUYAPECTEN, PA TINOPECTEN