Sculptural - j^ - ,,„ Variation ,, . of the Pliocene

Pelecypod Patinopecten healeyi (Arnold)
Sculptural Variation of the Pliocene 

Pelecypod Patinopecten healeyi (Arnold)

By ELLEN JAMES MOORE

GEOLOGICAL SURVEY PROFESSIONAL PAPER 1103

Primary sculpture and microsculpture described

and illustrated; includes stratigraphic occurrence and ecology

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

CECIL D. ANDRUS, Secretary

GEOLOGICAL SURVEY 

H. William Menard, Director

Library of Congress Cataloging in Publication Data

Moore, Ellen James.

Sculptural variation of the Pliocene pelecypod Patinopecten healeyi (Arnold)

(Geological Survey professional paper ; 1103)

Bibliography: p. 12-13.

Includes index.

Supt. of Docs, no.: I 19.16:1103

1. Patinopecten healeyi. 2. Paleontology-Pliocene. 3. PaleontologyCalifornia. I. Title. II. Series: United States. Geological Survey. 

Professional paper ; 1103.

QE812.P4M66 564M1 79-607097

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

Washington, D.C. 20402

Stock Number 024-001-03225-2
CONTENTS

Abstract ______.

Introduction ____. 

Purpose and scope 

Abbreviations __.

Page 

1 

1 

__________________________ 1

__________________________ 1

Acknowledgments ________________________ 2

Patinopecten healeyi (Arnold) _______________ 2

Synonymy ____________________________ 2

Primary sculpture ________________________ 2

Right valve _________________________ 2

Left valve _____________________ 3

Auricles, byssus, and ctenolium ___________ 4

Hinge area _______________________ 5

Page

Patinopecten healeyi (Arnold)—continued

Microsculpture ____________—___ ————— _______ 5

Comparison with other species __—___ ——— ——— __— 6 

Geographic and stratigraphic distribution of 

Patinopecten healeyi (Arnold) and P. lohri 

(Hertlein) _______________________——— 7 

Ecology _________________—______ ———— _——— 10

Conclusion _____________—_———__ —— —— ___ H

Fossil localities (Pliocene, California) ________ — _____ 11

References cited ________ ————— ______ ——— — —— _— 12

Index ___________________——_——————————— 15

ILLUSTRATIONS

[Plates follow index] 

PLATES 1-12. Patinopecten healeyi (Arnold).

13. Patinopecten lohri (Hertlein) and Patinopecten healeyi (Arnold). 

14, 15. Patinopecten yessoensis (Jay) and Patinopecten healeyi (Arnold).

FIGURE 1. Index map showing geographic distribution of Patinopecten healeyi (Arnold) and Patinopecten lohri (Hertlein)

Page

III

SCULPTURAL VARIATION OF THE PLIOCENE

PELECYPOD PATINOPECTEN HEALEYI

(ARNOLD)

By ELLEN JAMES MOORE

ABSTRACT

The sculptural variation of both right and left valves of 

Patinopecten healeyi (Arnold) is more extreme than has been generally known and has led to difficulty in distinguishing P. healeyi 

from other species, especially Patinopecten lohri (Hertlein) and even 

in the identification of the species itself. Variants of this common 

Pliocene species, which occurs in California and Baja California, include a smooth form with subdued dichotomous ribs on the right 

valve and closely spaced, fine ribs on the left valve with some intercalaries that are as wide as the primary ribs; right valves with flat, 

widely spaced, dichotomous ribs and right valves with high, 

rounded, closely spaced, dichotomous ribs; and left valves with high 

square ribs and rounded intercalaries and left valves with smooth 

interspaces and no intercalaries.

Scanning electron micrographs of the imbricated microsculpture 

that is found only on left valves of P. healeyi show the development 

of this sculpture. The same microsculpture is present on both the 

left and the right valves of the living species Patinopecten yessoensis 

(Jay) of Japan. When more data are available, this microsculpture 

may prove to be taxonomically significant.

P. healeyi is generally more common in southern California than 

P. lohri and occurs as far south as Vizcaino Peninsula, Baja California.

Ecological data concerning the closely related living species 

Patinopecten caurinus (Gould) include the observations that it lives 

at depths of 15 to 275 m, is not an active swimmer, is byssally attached until it has grown to about 4 cm in shell diameter, and that 

its predators are Octopus, the large sun-star Pycnopodia, and crabs.

INTRODUCTION

PURPOSE AND SCOPE

The problem of identifying sculptural variants of 

Patinopecten healeyi (Arnold) became apparent when 

specimens of right valves of this species that on cursory inspection looked like Amusium were found in 

unnamed Pliocene strata on San Clemente Island, 

Calif. (Vedder and Moore, 1976). This form has now 

been named Patinopecten healeyi sanclementensis by 

Suzuki and Stadum (1978).

Patinopecten healeyi (Arnold) was originally described from the San Diego Formation (Pliocene), 

Pacific Beach, Calif., asPecten expansus Ball (1878, p. 

14) but later renamed Pecten (Patinopecten) healeyi 

Arnold (1906, p. 103-105, pi. 36, figs. 1, la; pi. 37, 

figs. 1, la, 2) because the older name was preoccupied. 

Although variation in the sculpture of P. healeyi has

been noted (Arnold, 1906, p. 103-105; Woodring and 

Bramlette, 1950, p. 84; Hertlein and Grant, 1972, p. 

185), the variation is more diversified than has been 

generally understood. Right valves that are smooth to 

a height of 30 mm have been figured (Hertlein and 

Grant, 1972, pi. 33, fig. 9; pi. 36, fig. 9), but none so 

large as those collected from San Clemente Island (pi. 

2, figs. 3-7), from unnamed Pliocene strata, had been 

previously illustrated (Suzuki and Stadum, 1978). In 

addition to the smooth form, the right-valve sculpture 

varies from flat, widely spaced, dichotomous ribs that 

become obsolete near the ventral margin to high, 

rounded, closely spaced, dichotomous ribs. The leftvalve sculpture ranges from closely spaced, fine ribs of 

nearly equal size to high, wide, flat square ribs alternating with one or two rounded secondary ribs. These 

extremes in sculptural variation have not been clearly 

illustrated or described, and this range of variation 

has led to confusion between named species.

Comparisons made with the similar species 

Patinopecten lohri (Hertlein), with which P. healeyi 

has been confused, include geographic and stratigraphic distribution. Observations on the habitat of 

the closely related Holocene species Patinopecten 

caurinus (Gould) concern depth of occurrence, swimming, attachment, and predators. Scanning electron 

micrographs of the imbricated microsculpture of P. 

healeyi show its development, which may prove to be 

useful taxonomically.

Approximately 400 specimens of Patinopecten 

healeyi from the San Diego Formation and about 100 

each from the Fernando Formation in the Newport 

Beach area and the Niguel Formation in the San Juan 

Capistrano area were examined in the course of this 

study.

ABBREVIATIONS

CAS—California Academy of Sciences, San Francisco,

Calif. 

LAM—Natural History Museum of Los Angeles

County, Los Angeles, Calif.

SU—Stanford University, Stanford, Calif. [These

1
SCULPTURAL VARIATION OF THE PELECYPOD PATINOPECTEN HEALEYI (ARNOLD)

types are now deposited in the California Academy 

of Sciences.]

UCMP—University of California Museum of Paleontology, Berkeley, Calif.

USGS-M—U.S. Geological Survey, Menlo Park, 

Calif., Cenozoic locality register.

USNM—National Museum of Natural History, 

Washington, D.C.

ACKNOWLEDGMENTS

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

specimens of Patinopecten healeyi (Arnold) that he had 

collected from Pliocene strata in southern California 

and furnished stratigraphic information. F. R. Bernard, Pacific Biological Station, Nanaimo, British 

Columbia, kindly provided information on the living 

habits of Patinopecten caurinus (Gould). Barry Roth, 

California Academy of Sciences, searched the 

Academy collections and loaned specimens of P. 

healeyi. Judith T. Smith, Palo Alto, California, Louie 

Marincovich, Jr., U.S. Geological Survey, and J. W. 

Durham, University of California, assisted with discussions and the loan of specimens. W. O. Addicott, 

U.S. Geological Survey, and T. R. Waller, Smithsonian Institution, read the manuscript and improved 

its technical quality.

The scanning electron micrographs were taken by 

Robert Oscarson, the photographs by Kenji Sakamoto, 

both of the U.S. Geological Survey, and I thank them 

for their patience and attention to detail.

To E. C. Wilson, Curator, Natural History Museum 

of Los Angeles County, Los Angeles, Calif., I express 

my special gratitude for the loan of about 400 specimens of P. healeyi from the San Diego Formation and 

for other courtesies he graciously extended to me.

PATINOPECTEN HEALEYI (ARNOLD)

Pecten expansus Dall, 1878, U.S. Natl. Mus. Proc., v.

1, p. 14 [1879]. 

Not Pecten expansus Smith, 1847, Geol. Soc. London

Quart. Jour., v. 3, p. 413, 419, pi. 18, fig. 21. 

Pecten (Patinopecten) expansus Dall, 1898, Wagner

Free Inst. Sci. Trans., v. 3, pt. 4, p. 706, pi. 26, fig. 1.

Arnold, 1903, California Acad. Sci. Mem., v. 3, p.

108. 

Pecten (Patinopecten) healeyi Arnold, 1906, U.S. Geol.

Survey Prof. Paper 47, p. 103, pi. 36, figs. 1, la; pi.

37, figs. 1, la, 2. Arnold and Anderson, 1907, U.S.

Geol. Survey Bull. 322, p. 154, pi. 26, figs. 1, 2.

Grant and Gale, 1931, San Diego Soc. Nat. History

Mem., v. 1, p. 196, pi. 6, figs. 2a, 2b. Hertlein and

Grant, 1972, San Diego Soc. Nat. History Mem. 2

(pt. 2b), p. 183-185, pi. 31, figs. 1, 4, 6, 7; pi. 33, fig.

9; pi. 36, figs. 8, 9; text fig. 9.

Patinopecten healeyi (Dall), Vedder and Moore, 1976, 

p. 122, pi. 3, figs. 2-6, 8.

Pecten (Patinopecten) healeyi Arnold sanclementensis 

Suzuki and Stadum, 1978, Nat. Hist. Mus., Los 

Angeles Co., Contrib. Sci. 299, p. 10-11, figs. 18, 19. 

Holotype. USNM 148012.

Type locality. San Diego Formation (Pliocene), 

San Diego County, Calif.

A complete synonymy is given in Hertlein and 

Grant (1972, p. 183-184). The elevation of Patinopecten to generic rank does not make it possible to use 

the specific name expansus for this species, because 

Pecten expansus Dall is a junior primary homonym.

PRIMARY SCULPTURE

RIGHT VALVE

Plate 1, figures 1-4, 6-8; plate 2, figures 1-3, 5-7; plate 3, figures 

1-6; plate 4, figures 1-4, 8; plate 14, figure 3

The typical sculpture of the right valve (Arnold, 

1906, p. 103-105; Hertlein and Grant, 1972, p. 185) 

consists of 18 to 21 prominent squarish, subequal ribs 

that branch to become dichotomous and on a few individuals trichotomous, after 30 to 40 mm in height (pi. 

1, fig. 1). The medial sulcus of the rib may be as deep 

as the interspace, completely dividing the primary rib. 

The interspaces are subequal, much narrower than 

the ribs, deeply channeled, and on some specimens ornamented by a small rounded intercalary riblet.

Patinopecten healeyi is easily recognized by the 

flat-topped sulcated radial ribs on the right valve. 

Juvenile specimens are smooth in the early stage; radial undulations of the anterior margin typically 

begin to form after the shell has attained a height of 3 

to 5 mm (pi. 1, figs. 4, 6). Some specimens remain 

smooth 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. 

The ribs on some large specimens bear two sulcations 

that 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). A narrow 

unsculptured band may be present at the anterior and 

posterior margins, usually wider at the posterior side 

(pi. 1, fig. 8).

A smooth form of P. healeyi (pi. 2, figs. 3-7) that 

tends to be relatively thin shelled occurs only in unnamed Pliocene strata on San Clemente Island, 

southern California (Vedder and Moore, 1976, p. 122, 

pi. 3, figs. 2-6, 8; Suzuki and Stadium, 1978, figs. 18, 

19). A fragment of a large right valve shows the disk
PRIMARY SCULPTURE

to be smooth to about 30 mm, at which point strong 

dichotomous ribs with very narrow interspaces appear 

(pi. 2, fig. 3). An incomplete right valve that is nearly 

100 mm high has the disk smooth in the midportion of 

the shell to a height of about 40 mm, the rest of the 

shell being sculptured by very low, closely spaced, 

dichotomous and trichotomous ribs (pi. 2, fig. 7). A 

large incomplete worn right valve, originally more 

than 145 mm long, has a smooth disk to a height of 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; traces of the same rib pattern seen 

on the other right valves from San Clemente Island 

are visible in low-angle reflected light (pi. 2, fig. 6). 

These smooth right valves have a wide unsculptured 

band at both the anterior and posterior margins (pi. 

2, figs. 3, 7).

Three right valves from the San Diego Formation at 

Pacific Beach, Calif. (GAS 105, 547), have a smooth 

disk to a height of 20 mm and ribs somewhat subdued 

for an additional interval of about 10 mm (pi. 2, fig. 

1); one right valve (CAS 105) has closely spaced low 

ribs that are not dichotomous on the midportion of the 

shell (pi. 2, fig. 2).

Woodring (in Woodring and Bramlette, 1950, p. 84) 

noted that the interspaces on many right valves of P. 

healeyi from the Santa Maria basin are much narrower than the interspaces on right valves of P. 

healeyi 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 (pi. 

3, figs. 1, 5), as do some individuals from the Niguel 

Formation (pi. 3, fig. 4) 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 (USGS 

M2753), right valves with dichotomous and 

trichotomous ribs (pi. 4, fig. 2), right valves with narrow rather subdued ribs (pi. 4, fig. 1), and right valves 

with smooth disks to a height of about 50 mm followed 

by low subdued ribs (pi. 4, fig. 4), occur together. In 

another collection from the same area (USGS M5040), 

fragments of right valves include the smooth form (pi. 

3, fig. 2), some with narrow, widely spaced, dichotomous ribs (pi. 3, fig. 6), and others with very closely 

spaced, dichotomous and trichotomous ribs (pi. 3, fig. 

3). 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 (pi. 6, fig. 7). A similar difference 

between valves has been noted on Patinopecten 

caurinus (Gould), the Holocene genotype of Patinopecten, which has been collected from sedimentary rocks 

as old as Pliocene (Grau, 1959, p. 147; Moore, 1963, p. 

63).

LEFT VALVE

Plate 2, figure 4; plate 4, figure 5; plate 5, figures 1-3, 6; plate 6,

figures 3, 7; plate 7, figures 1, 2, 4, 5; plate 8, figures 1, 3, 4, 6; plate

9, figures 4, 7; plate 10, figures 1, 3, 4; plate 15, figure 3

Arnold (1906, p. 103-105) described the left valve of 

P. healeyi as much compressed and the ribs as narrow 

and rounded on some individuals with a narrow peak 

along which there may be a narrow, slightly raised 

line. The interspaces are wide and each is ornamented 

by a more or less prominent, rounded intercalary riblet.

Although the typical left valve sculpture has been 

described as primary ribs with interspaces invariably 

bearing a secondary rib (Arnold, 1906, p. 104; Hertlein and Grant, 1972, p. 185), 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 (pi. 5, fig. 2). 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°; 115° 

is the most common, and on inequilateral specimens 

with a very enlarged anterior ear, 120°.

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 (pi. 5, fig. 1) to wide square ribs 

that may bear a fine rib along the top (pi. 8, fig. 1) 

and that may have some interspaces that do not bear 

an intercalary. The square-ribbed forms typically 

begin with a sculpture of narrow rounded ribs that become flat when the shell reaches a height of about 60 

mm (pi. 6, fig. 4). On some square-ribbed forms, the 

intercalaries are fine and rounded (pi. 7, fig. 5); on 

others, the intercalaries, though rounded, are much 

wider (pi. 8, fig. 4). On some left valves, the ribs tend 

to become obsolete near the ventral margin (pi. 9, fig. 

7), a feature seen on P. caurinus (Moore, 1963, p. 65). 

Some left valves are markedly thinner than others 

that bear the same primary rib pattern.

Left valves from the Niguel Formation (Pliocene) in 

the San Juan Capistrano quadrangle (USGS M2096, 

M2098) show the same marked variation of narrow 

rounded ribs to square flat ribs as seen on specimens 

from the San Diego Formation. One fragment of a 

large left valve has two secondary ribs (or a split secondary) between the primary ribs near the anterior 

margin (pi. 9, fig. 4).
SCULPTURAL VARIATION OF THE PELECYPOD PATINOPECTEN HEALEYI (ARNOLD)

Left valves in a collection (USGS M2753) from the 

Fernando Formation (Pliocene) in the Newport Beach 

quadrangle include one fragment with multiple secondary ribs at the anterior margin (pi. 7, fig. 2).

Four left valves were collected from unnamed 

Pliocene strata on San Clemente Island (USGS 

M6503) with right valves of the smooth form. Although no articulated specimens were found, it is assumed that these left valves represent the smooth 

form. The ribs are unusually fine, narrow, and a bit 

more closely spaced than is common; some of the intercalaries are as wide as the primary ribs (pi. 5, fig. 

3). 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, perhaps 

in response to pressure from the larger right valve. 

On most specimens, this extension of the left valve is 

exceptionally thin and ribs are obsolete; the extension 

is rarely preserved and may be more common than its 

preservation indicates.

In his discussion of the Argopecten gibbus stock, 

Waller (1969, p. 31) stated that

In the description of plicae, only features of the right valve are 

discussed because the interlocking of plicae along the distal margin 

produces a complimentarity***. Thus plicae that are distinctly 

broader than the interspaces on the right valve will likely be distinctly narrower than the interspaces on the left valve.

Grant and Gale (1931, p. 192), in their description 

of Patinopecten, stated that the left valve will have 

intercalaries if the right valve primary ribs are 

dichotomous.

In the course of this study, I have found that if the 

right-valve primary ribs are strongly dichotomous, in 

essence producing another interspace, the usual leftvalve 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 be larger than average and square rather than 

rounded. If the right-valve disk is smooth and followed by low primary ribs that are only shallowly 

dichotomous, the left valve will usually respond with 

small rounded primaries and with secondaries of 

nearly equal size. On articulated specimens, one can 

usually predict the sculpture of either valve by simply 

examining the opposing valve.

Variation in the sculpture of Holocene specimens of 

Patinopecten caurinus (Moore, 1963, p. 63-65) is not 

as extreme as seen on P. healeyi. The ribs on the right 

valves of large specimens of P. caurinus may become 

obsolete near the margins, as may the ribs on large 

left valves. Fine intercalaries are irregularly spaced 

on parts of the left valve. On some individuals, intercalaries are occasionally present on the right valve 

but without a regular pattern or spacing.

AURICLES, BYSSUS, AND CTENOLIUM

Plate 1, figures 5, 6; plate 4, figures 6, 7; plate 5, figure 5; plate 6, 

figures 1, 2; plate 7, figure 3; plate 13, figures 1, 2; plate 15, figure 2

The right anterior auricle (ear) is slightly longer 

than the left anterior auricle, arcuate in front, and 

ornamented by several faint radial ridges; the byssal 

notch is prominent. The posterior auricle is slightly 

obliquely truncated and ornamented by sharp incremental lines and, on some specimens, by obsolete 

radiating ridges. The left-valve auricles are obliquely 

truncated and similarly sculptured (Arnold, 1906, p. 

104).

On large specimens (pi. 14, fig. 3), the left anterior 

auricle is larger than the right anterior auricle. The 

byssal notch is convexly folded and elevated above the 

rest of the auricle (pi. 7, fig. 3; pi. 13, fig. 1), a feature 

noted on P. caurinus, and the left anterior auricle is 

concavely folded toward the right, opposite the byssal 

notch, bringing the auricles closer together (pi. 6, figs. 

1, 2; pi. 13, fig. 2). The fold on the left anterior auricle 

typically becomes more pronounced as the shell grows 

larger such that on very large specimens the byssal 

opening is nearly closed.

Strong evidence suggests that the byssus on P. 

healeyi was functional at least during the early stages 

of growth. Several specimens, generally of small size, 

have been found that show a well-developed ctenolium 

(comblike row of teeth) below the anterior auricle (pi. 

1, figs. 5, 6; pi. 4, figs. 6, 7); others have been seen 

that are large in size with the shell corroded in such a 

way as to show the ctenolium along the entire attachment margin of the auricle. The presumed function of the ctenolium is to separate the byssal threads 

and keep them from twisting (Ball, 1898, p. 691). Waller (1969, p. 20), noting that the presence of a 

ctenolium is correlated with the presence of a deep 

byssal notch, assumed that a deep byssal notch indicates the presence of a byssus or, for earlier growth 

stages, an active extrudible foot. Ball (1898, p. 691) 

said that the growth of the margin of the valve and 

auricle does not always coincide with the development 

of the ctenolium and that a species that normally 

shows this feature may have stages when the valve 

margin has grown over the old ctenolial set and the 

new set has not yet formed.

Waller (1972a, p. 245) later stated

***the absence of a ctenolium and byssal gape on mature shells 

indicates that the species may lie free at this stage rather than attach bysally. Young individuals, which have a distinct ctenolium 

and byssal gape, are probably bysally attached.

The ctenolium is present on small specimens of P. 

healeyi and is well developed, which probably indicates that it was not an obsolete character during the 

early stages of growth when the byssal opening was of
MICROSCULPTURE

good size and not yet almost completely closed by the 

enlarged, strongly folded left anterior ear. The 

Holocene species Patinopecten caurinus is byssally attached in early life to a size of about 3 to 4 cm in shell 

diameter; above this size the byssus is no longer present (F. R. Bernard, written commun., 1976).

The left-valve anterior auricle of P. healeyi may be 

higher as well as longer than the posterior auricle (pi. 

5, fig. 5; pi. 6, fig. 1; pi 7, fig. 5; pi. 8, fig. 6). Marked 

enlargement of the left anterior auricle, typically 

characteristic of large specimens, is seen on some 

juvenile shells (pi. 10, fig. 3). The enlargement is generally coincident with the increased flexure of the auricle and the resultant closing of the byssal gap. Some 

examples of the difference in size between left-valve 

auricles are:

Anterior auricle

23 mm long and 20 mm high

34 mm long and 22 mm high

35 mm long and 27 mm high 

38 mm long and 27 mm high 

44 mm long and 27 mm high

Posterior auricle

20 mm long and 13 mm high 

27 mm long and 9 mm high 

30 mm long and 19 mm high 

32 mm long and 18 mm high 

37 mm long and 19 mm high

On complete specimens, the difference in length of 

right-valve auricles is found to be about the same as 

the left-valve auricles, but the height of the rightvalve auricles remains equal.

HINGE AREA

Plate 1, figure 5; plate 6, figures 4-6; plate 8, figures 2, 5; plate 9, 

figures 1-3, 5, 6; plate 10, figure 2

The resilial pit on the right valve is bordered on 

each side by a narrow, sharp, projecting ridge (pi. 9, 

figs. 5, 6). The resilial pit on the left valve may be 

bordered by a ridge that is followed by a groove and a 

second shorter ridge (pi. 8, fig. 5) or may be bordered 

by only one ridge (pi. 9, fig. 1). On one articulated 

specimen, the right-valve resilial ridges rested in 

grooves between the left-valve resilial ridges. On all 

specimens, the inner shell is thickened parallel to the 

line of attachment of the ears.

On the anterior portion of the right valve, although 

the shell is thickened, producing a strong smoothly 

rounded ridge (pi. 9, fig. 6), the ridge does not end in a 

denticle. On some specimens, however, the ridge ends 

in a slightly prominent node which on a few specimens could perhaps be considered an auricular denticle. At the posterior side of the right valve, the distal 

portion of the thickened shell ends in a rounded to 

somewhat pointed denticle (pi. 9, figs. 5, 6).

On the anterior portion of the left valve, the thickened ridge usually terminates in a rounded denticle or 

a somewhat triangular ridge (pi. 8, fig. 2); on some 

specimens, however, no auricular denticle can be distinguished. The thickened ridge on the left-valve 

posterior side is somewhat larger than the anterior

ridge at the distal end and may terminate in a subdued denticle (pi. 6, fig. 4).

MICROSCULPTURE

Plate 5, figure 4; plate 6, figure 2; plate 10, figures 1, 3-5; plate 11,

figures 1-3; plate 12, figures 1-3; plate 13, figure 5; plate 14, figures

1, 2; plate 15, figure 1

Small patches of an imbricated microsculpture similar to that found on many different pectinids such as 

Vertipecten (Moore, 1963, p. 63), Chlamys ( Verrill, 

1899, p. 73), and on some, if not all, species referred to 

Yabepecten by Masuda (1963, pi. 22, fig. 4) are preserved on some left valves of P. healeyi (pi. 10, figs. 1, 

3. 4); one juvenile specimen shows the entire surface 

to be so sculptured (pi. 10, fig. 4).

Meek (1864, p. 26-27), in describing Patinopecten 

propatulus (Conrad) from the Miocene of Oregon, said

***it shows, under a magnifier, a very peculiar and beautiful style 

of sculpture resembling somewhat the regularly disposed asperities 

on the surface of a rasp***.

In 1899 Verrill (p. 73-74, pi. 16, figs. 4, 5, 5a, 5b) 

named a new variety of Chlamys and illustrated a 

microsculpture similar to that on P. healeyi, which he 

described as follows:

The concentric and divergent laminae and smaller riblets cross 

each other in such a way that a peculiar decussated sculpture is 

formed between the primary ribs on the early part of the shell, 

while on the older parts the interspaces are covered with elevated 

scales.

Ball (1878, p. 14) said, in describing the upper (left) 

valve of Pecten expansus (= Patinopecten healeyi):

The entire surface is covered with fine, slightly raised, sharp 

lamellae, which are waved in some places so regularly as to produce 

the appearance of a delicate reticulation, which, however, does not 

really exist***.

Waller (1972a, p. 229) used the term shagreen for a 

similar microsculpture that he defined as a screenlike 

pattern of openings between projecting lamellae on 

the shell exterior. On the caption for his figure 12 (p. 

229), he described the specimen illustrated as showing 

uneroded areas with strongly projecting, cell-forming 

flanges and eroded areas forming the typical shagreen 

pattern.

MacNeil (1961, p. 227) noted that

No specimens of Lituyapecten yet observed show any suggestion of 

the imbricating microsculpture, resembling the surface of metal 

lath, that characterizes left valves of Chlamys, Vertipecten, Fortipecten, and some species of Patinopecten such as P. yessoensis, P. 

propatulus (Conrad), and P. ibaragiensis Masuda ***, imbricating 

microsculpture occurs rarely in small patches on specimens of P. 

caurinus.

A right valve from the Pliocene Koshiba Formation 

of Japan referred to Yabepecten tokunagai (Yokoyama) by Masuda (1963, pi. 22, fig. 4) shows an imbricated microsculpture. The right valve of the Holocene 

west Pacific species Patinopecten yessoensis (Jay) also 

shows an imbricated microsculpture (pi. 14, fig. 1). Al-
SCULPTURAL VARIATION OF THE PELECYPOD PATINOPECTEN HEALEYI (ARNOLD)

though this microsculpture is fairly common on the 

left valve of east Pacific Patinopecten, it has not been 

found on the right valve.

One well-preserved juvenile left valve of P. healeyi 

(pi. 10, figs. 4, 5) was found that had the imbricated 

microsculpture well preserved and was small enough 

to be mounted for the scanning electron microscope 

without destruction. 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 (pi. 11, 

figs. 1-3; pi. 12, figs. 1-3). This imbricated microsculpture has been found on young portions of the left 

valve of P. healeyi but has not been seen on the mature parts of the shell. The fact that it develops on 

only a small portion of the shell and is fragile and 

easily abraded makes its preservation fortuitous. Waller (written commun., 1977) said that on some 

Chlamys this microsculpture can appear, disappear, 

and reappear more than once during ontogeny and 

that this uneven occurrence is primary and not the 

result of erosion.

On an especially well-preserved left valve from unnamed Pliocene strata on San Clemente Island, 

closely spaced concentric lamellae are preserved (pi. 5, 

fig. 3); these lamellae are seen to be parallel and not 

imbricated on the electron micrograph of a shell 

fragment broken off the ventral edge (pi. 5, fig. 4).

During examination of specimens of the Holocene 

species Patinopecten yessoensis (Jay), it was noted that 

imbricated lamellae merge to form a pseudosurface, 

apparently leaving a honeycomblike structure beneath. This outer layer is loosely cemented to the underlying shell, rarely preserved, and when removed by 

abrasion leaves a barely traceable pattern on the shell 

(Moore, 1963, p. 63).

Imbricated microsculpture may prove useful in determining the evolutionary trend of the Patinopecten 

bearing it, as it is seen only on left valves in the east 

Pacific but is also found on right valves of Patinopecten yessoensis and Yabepecten tokunagai (Yokoyama) 

in the west Pacific.

Because this paper is intended to call attention to 

specific variation, and I have not dealt extensively 

with genera other than Patinopecten, I have chosen a 

conservative approach and used the genus Patinopecten for species that have been assigned by others to 

Mizuhopecten (Masuda, 1963) but have considered 

Yabepecten (Masuda and Addicott, 1970) to be a valid 

genus. I do wish to emphasize, however, that the microsculpture on the west Pacific species of Patinopecten 

is different from the sculpture on the east Pacific 

species. It seems plausible to me that as more data are 

accumulated, using the scanning electron microscope,

microsculpture may prove to be useful in the 

taxonomy of the pectinids. In the course of this study, 

I have found that large specimens unsuitable for 

mounting for the scanning electron microscope can be 

coated with a plastic spray, covered with a thick coat 

of liquid latex, the coating then removed and filled 

with colorless fingernail polish and the hardened 

polish mounted for the scanning electron microscope. 

This technique proved quite successful and should 

make it possible to study the microsculpture on 

specimens of any size.

COMPARISON WITH OTHER SPECIES

Patinopecten healeyi is closely similar to P. lohri 

(Hertlein) and sometimes confused with that species. 

Patinopecten lohri (Hertlein) (1928, p. 93) was originally described as Pecten (Patinopecten) oweni Arnold 

(1906, p. 63, pi. 8, figs. 1, la, Ib), a name that was 

preoccupied. The holotype of P. lohri (pi. 13, figs. 3, 4, 

6), according to Woodring (in Woodring and Bramlette, 1950, p. 83-84), was presumably collected from 

the Tinaquaic Sandstone Member (early and middle 

Pliocene) of the Sisquoc Formation somewhere near 

Foxen Canyon, Calif. In his discussion of Patinopecten 

lohri from the Santa Maria basin of California, 

Woodring (in Woodring and Bramlette, 1950, p. 83) 

said that

The ribs on large left valves of P. lohri are wide and divided, 

whereas on P. healeyi 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. lohri generally have 

a strong secondary rib in the space between the primary ribs, 

whereas on right valves of P. healeyi secondary ribs are absent or, if 

present, generally 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. lohri, right and left valves are difficult to distinguish unless the ears are preserved, whereas right and left valves of 

P. healeyi are readily differentiated.

The right valve of the holotype (UCMP 12081) of P. 

lohri (pi. 13, figs. 3, 4) is more inflated than is typical for P. healeyi; the primary ribs are higher, 

dichotomous at an earlier stage, fewer in number (14), 

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 holotype, 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. healeyi. A narrow 

unsculptured band is present along the posterior margin of the shell. The right anterior auricle is poorly
GEOGRAPHIC AND STRATIGRAPHIC DISTRIBUTION

preserved but seems to be sculptured by subdued riblets and to have a byssal notch similar to P. healeyi. 

The posterior auricle bears a shallow groove bordered 

by low ridges; this feature is discernible on about 

two-thirds of the auricle 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 an angle of about 25°.

The left valve of the holotype of P. lohri (pi. 13, fig. 

6) bears fewer (12) 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 typical 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 

specimens of P. healeyi 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, and the posterior shell margin, excluding the 

ear, forms an angle of 25° with the hinge and with 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. As discussed, a similar inequilateralty is 

seen on large specimens of P. healeyi.

Arnold, in describing P. lohri (1906, p. 63) asPecten 

(Patinopecten) oweni Arnold, said that it may be distinguished from P. healeyi by its smaller size, greater 

convexity, fewer and stronger ribs, more prominent 

intercalary riblets on the right valve, and relatively 

much longer hinge line.

The smooth form of P. healeyi is surprisingly similar in external sculpture*to Yabepecten condoni (Hertlein, 1925, p. 41, pi. 4, figs. 8, 9) from the Montesano 

Formation (Miocene) of Washington, as figured by 

Masuda and Addicott (1970, figs. 1, 3-9). The rightvalve primary ribs on P. healeyi are typically dichotomous, whereas they are rarely so on Y. condoni. The left-valve sculpture of Y. condoni seems to 

consist of small fine primaries with only occasional 

secondaries, whereas secondaries are commonly present in the left-valve interspaces on P. healeyi. According to Masuda and Addicott (1970, p. 154), the hinge 

of Y. condoni has simple cardinal crura and a wide 

and shallow resilial pit, both characters that would 

separate it from P. healeyi.

Hertlein (1925, p. 41), in describing Y. condoni, said 

that it has about 16 smooth faint ribs that broaden 

rapidly as the shell grows and are about two or three 

times as wide as the very slight interspaces at the 

ventral margin. He also noted that the right valve 

bears concentric lines of growth that are very prominent on some specimens and almost lacking in others, 

that the right-valve auricles are small, and that the 

anterior auricle bears a very slight byssal notch. The 

left-valve sculpture is similar to that of the right. The 

slight byssal notch on the right-valve auricle and the 

similarity of sculpture of the right and left valves are 

other characters that separate Y. condoni from P. 

healeyi.

Lituyapecten turneri (Arnold) differs from P. healeyi 

by having very narrow, high, medially sulcated ribs 

and wide interspaces on the right valve and high narrow ribs on the left valve with no intercalaries (Arnold, 1906, p. 106, pi. 34, fig. 4; pi. 35, figs. 2, 3; Peck, 

1960, pi. 21, figs. 15, 16).

Yabepecten tokunagai (Yokoyama) differs from P. 

healeyi in right-valve sculpture, having low, rounded, 

closely spaced ribs. In addition, an imbricated microsculpture is present on the right valve (Masuda, 1963, 

pi. 12, fig. 4), and this sculpture has been found only 

on left valves of P. healeyi.

The marked consistent dichotomy of the right-valve 

ribs separates P. healeyi from other Patinopecten with 

the exception of P. lohri, already discussed. Although 

several species such as Patinopecten oregonensis 

(Howe), Patinopecten coosensis (Ball), and Patinopecten oregonensis cancellosus Moore may have a few 

dichotomous ribs at the anterior and posterior margins of the right valve, none bear low, flat, dichotomous ribs over the entire shell surface.

GEOGRAPHIC AND STRATIGRAPHIC DISTRIBUTION OF

PATINOPECTEN HEALEYI (ARNOLD) AND

P. LOHRI (HERTLEIN)

Patinopecten lohri is restricted to the Pliocene of 

California, and Patinopecten healeyi to the Pliocene of 

California and Baja California. Both species first appear in the early Pliocene and, as unique split-ribbed 

giant pectinids, are of significance in the interpretation of Neogene zoogeography and age determination 

(Addicott, 1974, p. 191). The base of the Jacalitos 

Stage 1 is defined by the lowest occurrence of the 

split-ribbed species of Patinopecten, P. healeyi and P. 

lohri (Addicott, 1972, p. 15-16). Although most 

Patinopecten have one or two split ribs on the right 

valve, none show the unique sculpture of P. healeyi 

and P. lohri, which typically have all of the rightvalve primary ribs split.

'Epoch assignments used herein follow the West Coast provincial usage outlined by 

Weaver and others (1944).
SCULPTURAL VARIATION OF THE PELECYPOD PATINOPECTEN HEALEYI (ARNOLD)

124° 122° 120° 118° 116° 114° 112°

ORGON i D_ A »JL_ O__L

San Gregorio

Monterey

\ARIZONA

•n Diego__-5" ) UtyT^

-.-- Me\ica\if -~~i{ED $T Tnuana / »3>;>-.^-'-

A Patinopecten lohri (Hertlein) 

• Patinopecten healeyi (Arnold) 

XS Southernmost reported modern occurrence

of Patinopecten caurtnus (Gould) 

N Northernmost reported occurrence of species 

S Southernmost reported occurrence of species

34° -

32° -

30 -

28° -

FIGURE 1.—Geographic distribution of Patinopecten healeyi (Arnold) and Patinopecten lohri (Hertlein) and southern modern occurrence of Patinopecten caurinus (Gould). (Compiled from Cummings and others, 1962; Dibblee, 1950; 

Durham and Addicott, 1965; Durham and Yerkes, 1964; Faustman, 1964; Glen, 1959; Hawkins and others, 1971; 

Hertlein and Grant, 1972; Jordan and Hertlein, 1926; Kern, 1973; Martin, 1916; Minch and others, 1976; Ogle, 1953; 

Stanton and Dodd, 1976; Vedder and Moore, 1976; Weaver and Meyer, 1969; Winterer and Durham, 1962; Woodring, 

1930; Woodring and others, 1940; Woodring and Bramlette, 1950.)
GEOGRAPHIC AND STRATIGRAPHIC DISTRIBUTION 9

The northernmost occurrences of P. healeyi are in 

the Eureka and Cape Mendocino areas of northern 

California (Ogle, 1953, pi. 5), the northernmost of P. 

lohri in the Point Reyes area (fig. 1). Specimens from 

the Falor Formation (Pliocene) on the bank of Boulder 

Creek, Blue Lake quadrangle, were loaned to me 

through the kindness of J. W. Durham, University of 

California; these specimens are typical P. healeyi. A 

concretion containing P. healeyi, also loaned me by 

Durham, was collected from beach drift at the base of 

the Cliff House in San Francisco. Presumably it came 

from the Merced Formation (Pliocene) offshore; this 

formation is known on land to the south. P. lohri has 

been found no farther south than the Santa Maria 

basin northwest of Los Angeles (Woodring and Bramlette, 1950, p. 65), whereas P. healeyi occurs as far 

south as the Vizcaino Peninsula of Baja California 

Sur (Jordan and Hertlein, 1926, p. 417; Minch and 

others, 1976, p. 176).

The two species are reported to occur geographically 

together at only three areas in California: the northern Santa Cruz Mountains (Cummings and others, 

1962, pi. 24), the Kettleman Hills area (Stanton and 

Dodd, 1976, p. 91, fig. 4), and the Santa Maria basin 

(Woodring and Bramlette, 1950, p. 65). As will be 

shown, nowhere do the two species cooccur in one locality, and, in general, P. lohri occurs stratigraphically lower than P. healeyi.

Patinopecten healeyi and P. lohri are reported near 

each other from the same stratigraphic interval in 

only one area, the Jacalitos Canyon area near Kettleman Hills (Stanton and Dodd, 1976, p. 91, fig. 4). In 

the Santa Maria basin, P. lohri is found stratigraphically below P. healeyi, but in the Santa Cruz Mountains, it is reported to be stratigraphically above. The 

Santa Cruz Mountains occurrence may be in error, as 

the forms collected could well be a new species of 

Patinopecten (Clark, 1966) that closely resembles P. 

healeyi and is known to occur in the Santa Cruz 

Mountains. Unfortunately, the material collected by 

Cummings, Touring, and Brabb (1962) is missing and 

presumed to be lost.

Arnold (1906, p. 63) found P. lohri in the lower part 

of the Purisima Formation, where, he stated, P. lohri 

seems to grade into P. healeyi, the form occurring at 

Lobitas and Purisima identified as P. healeyi serving 

as the link between the two species. Arnold (1906, p. 

104, pi. 37, fig. 2) illustrated a specimen of P. healeyi 

from San Gregorio in San Mateo County and said that 

the right-valve specimens of P. healeyi from this area 

generally have natter, more deeply dichotomous ribs 

than are typical of this species and left valves with 

secondary ribs nearly equal in size to the primary 

ribs. But he noted also that similar variation occurs in 

specimens from San Diego County and therefore concluded that these differences are not of taxonomic significance. Specimens that I have collected from San 

Gregorio certainly all fall within the range of 

sculptural variation of P. healeyi.

The Patinopecten identified as P. (P.) cf. P. (P.) 

healeyi in the Santa Margarita Formation in the Felton quadrangle of the Big Basin area in San Mateo 

County by Clark (1966) is here assigned to Lituyapecten purisimaensis (Arnold).

In the northern Santa Cruz Mountains, Patinopecten lohri is found in the Pomponio and San Gregorio 

Members of the Purisima Formation, as used by 

Cummings, Touring, and Brabb (1962), pi. 24), 

stratigraphically above the occurrence of Patinopecten 

healeyi in their Tahana Member of the Purisima Formation in the same area. As stated, P. healeyi may 

have been confused with P. n. sp. Clark in this area.

Grant and Gale (1931, p. 198) said that P. lohri and 

P. healeyi commonly occur together but that at some 

places P. lohri is more common in older horizons. 

Stewart (in Woodring, Stewart, and Richards, 1940, p. 

91-92) noted that the specimen from Elsmere Canyon 

in Ventura County figured by Grant and Gale (1931, 

pi. 6, figs, la, Ib) as P. lohri probably is P. healeyi, 

and I concur. Stewart identified P. lohri in the Etchegoin Formation of the Kettleman Hills, where he 

found it to be especially common in the Patinopecten 

Zone. Kern (1973, p. 13, 74) recorded P. lohri in the 

Towsley Formation in the San Fernando quadrangle.

Woodring (in Woodring and Bramlette, 1950, p. 83), 

in discussing the occurrence of Patinopecten in the 

Santa Maria district, said that P. lohri is found in the 

oldest formation containing marine Pliocene fossils, P. 

healeyi in the youngest, and Lituyapecten dilleri in intervening strata, and that although their ranges overlap, the three species are stratigraphically useful. He 

added that P. lohri is present in the Tinaquaic 

Sandstone Member of the Sisquoc Formation and a 

comparable form in diatomaceous strata of the Sisquoc; a variety of L. dilleri in diatomaceous strata of 

the Sisquoc and L. dilleri proper in the Foxen 

Mudstone and the Cebada Member of the Careaga 

Sandstone; and P. healeyi in the Foxen Mudstone and 

the Careaga. P. healeyi and P. lohri do not occur 

within the same stratigraphic interval in the Santa 

Maria district, although both are associated with L. 

dilleri.

Stanton and Dodd (1976, p. 90-91) noted that P. 

lohri is more common in the upper part of the 

Jacalitos Formation of former usage, as it was originally mapped in the Zapato Chino section of the 

Jacalitos Canyon area, and that the fauna contained 

in this section is strongly suggestive of zones low in 

the Etchegoin Formation as exposed in North Dome in 

the Kettleman Hills. They collected P. lohri from the
10 SCULPTURAL VARIATION OF THE PELECYPOD PATINOPECTEN HEALEYI (ARNOLD)

middle upper part of the so-called Jacalitos and the 

upper middle part of the San Joaquin Formations and 

P. healeyi from the middle part of the San Joaquin 

Formation. In the Jacalitos Canyon sections then P. 

healeyi and P. lohri occur within the same stratigraphic interval; even there, they were not collected 

together at the same locality (Stanton and Dodd, 

1976, p. 91, fig. 4).

Patinopecten lohri has not been found in the Niguel, 

Fernando, or San Diego Formations in southern California, where P. healeyi is commonly collected, presumably because these areas are beyond the southernmost range of P. lohri.

It is apparent that part of the stratigraphic range of 

P. healeyi and P. lohri, as well as part of the geographic range, is the same. Yet the two species seem 

never to have been collected together from one locality 

despite reports to the contrary. P. lohri is more common in middle California, P. healeyi more common in 

southern California; P. lohri is less common generally 

and much more restricted in its geographic occurrence. Of a total of approximately 135 species of mollusks that occur with P. lohri (Durham and Addicott, 

1965, table 1, p. A12-A14), about 40 species are not 

found with P. healeyi, although the same genera occur 

with both species. The reported stratigraphic occurrence of the two species, assuming all identifications 

to be correct, precludes the possibility sometimes 

suggested that P. healeyi was the descendant of P. 

lohri (Arnold, 1906, p. 63; Hertlein, in Hertlein and 

Grant, 1972, p. 185). Perhaps the explanation for the 

distribution of P. healeyi and P. lohri lies in ecologic 

parameters not yet apparent from the fossil record.

ECOLOGY

On the basis of what we know about the living 

habits of modern pectinids, especially Patinopecten, 

some speculations can be made on the ecology of P. 

healeyi.

Fitch (1953, p. 44) stated that the geographic range 

of the modern Patinopecten caurinus (Gould) is from 

Wrangell, Alaska, to Eureka, Calif., and that the 

species is frequently taken in considerable numbers 

by flatfish trawlers at depths of 58 to 88 m. Grau (1959 

p. 147-148) gave the geographic range of P. caurinus 

as Channel Inlet, Orca Inlet, Cordoba, Alaska, to 

Point Reyes, Calif., the bathymetric range as 37 to 

183 m, or possibly deeper. F. R. Bernard (written commun., 1976) says that P. caurinus lives at depths of 15 

to 275 m and that in British Columbia its maximum 

population density occurs at about 35 m on a mixed 

sand and mud 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.

P. caurinus, off British Columbia, is not an active 

swimmer (F. R. Bernard, written commun., 1976). It 

remains in the same place and moves only when directly threatened by contact with a starfish. The typical pattern of movement consists of vigorous valvepumping, moving the animal upward at an angle of 

about 45° for 2 meters or so, then a cessation of activity and fall through the water. At all times, the right 

valve is downmost. Although all individuals move, the 

smaller of the nonsessile animals are more active.

P. caurinus is bysally attached to a size of about 3 to 

4 cm in shell diameter (F. R. Bernard, written commun., 1976) and has a ctenolium during its young 

stage.

The predators of P. caurinus are Octopus and the 

large sun-star Pycnopodia; juveniles are attacked by 

crabs (F. R. Bernard, written commun., 1976). Fleming (1957, p. 14) noted that fossil pectinids under 30 

mm long are much rarer than large individuals and 

believes that predatory benthic fish probably eat more 

young pectinids than adults.

Waller (1972b, p. 55) suggested that radial ribs of 

pectinid shells serve to buttress the thin growing 

edges of the shells against crushing forces exerted by 

predators and to stabilize the living position in shifting sediment. As noted earlier, the right valve of P. 

healeyi, presumed to be the lower, may extend beyond 

the left valve by as much as 10 mm. This extension 

may help keep silt from being washed up onto the soft 

parts of the animal when it is at rest with the valves 

open. It may also produce a closure less accessible to 

the possible predators of P. healeyi, such as Octopus 

and Pycnopodia, for rather than being able to approach the interlocked margin of both valves, it would 

be necessary for them to pry up the left valve or break 

off the extension of the right valve. Specimens of P. 

healeyi in the collections show repeated breakage and 

subsequent repair to the shell (pi. 1, fig. 8; pi. 7, fig. 

1; pi. 8, figs. 3, 6), and this breakage is more common 

on the left valve. Many shells also show nonrepaired 

breakage and chipping at the margins, but this damage could have occurred after the animal died.

Cahn (1951, p. 56) noted that Patinopecten yessoensis (Jay) has the following growth rate:

1 year: 3.0 cm.

2 years: 7.0 cm

3 years: 10.3 cm

4 years: 13.0 cm

5 years: 14.8 cm

Masuda (1962, p. 213) reported that the shells of 

Patinopecten yessoensis (Jay) of Japan are rather large 

in size in calm seas and that the convexity of the right
FOSSIL LOCALITIES 11

valve is low and the left valve rather inflated, 

whereas those living in less calm water have thick 

shells with a more convex right valve and a nearly 

flat left valve.

Waller (1973, p. 46) collected thin specimens of Argopecten gibbus (Linne) in Harrington Sound, Bermuda, that he felt were within the range of variation 

of that form. He thought that these specimens might 

be the offspring of shallow-water populations that had 

entered the Subthermocline Zone as larvae, where 

there was little mixing of water, resulting in cooler, 

oxygen-poor water (Waller, 1973, p. 35). Subsequent 

growth might then have been modified by the conditions present in the subthermocline environment. 

Clark (1976, p. 607, 610) found that the convexity of 

the shell of Argopecten gibbus, in Harrington Sound, 

Bermuda, changed with depth from markedly convex 

in shallow water (7 m) to only slightly convex in 

deeper water (21 m) and concluded that turbulence was 

most likely to be the environmental variable affecting shell convexity. It is possible that the smooth form 

of P. healeyi is a response to some such unusual ecologic condition.

Rowland (1972, p. 27) noted that the fauna in the 

San Diego Formation exposed at Pacific Beach indicates a sand-cobble open coast environment, whereas 

the fauna in the San Diego Formation exposed on the 

San Diego Mesa, about 10 km to the northwest, represents quiet water. It has been suggested that the San 

Diego Formation exposed at Pacific Beach and the San 

Diego Formation exposed in the San Diego Mesa may 

represent different times of deposition (Woodring and 

Bramlette, 1950, p. 104-107; Rowland, 1972, p. 27). 

Recent geologic mapping in San Diego County (M. P. 

Kennedy in Kennedy and Peterson, 1975, p. 29, 

49-50) has shown, however, that these two areas are 

not significantly different in age. The fauna that occurs in the San Diego Formation in northwestern Baja 

California, near Tijuana, Mexico, is believed to represent three environments: littoral-sublittoral rocky 

coast, sublittoral open coast with sand substrate, and 

sublittoral open coast with fine mud or mud-sand substrate (Rowland, 1972, p. 27-28). P. healeyi is found at 

all these localities in all of these proposed environments but may have been transported into certain environments, such as the rocky coast, rather than have 

lived in them.

Patinopecten healeyi most likely lived at a depth of 

15 to 275 m, perhaps with its greatest concentration 

around 35 to 85 m, depending on the water temperature, as the greatest density of P. caurinus is around 

35 m in British Columbia (F. R. Bernard, written 

commun., 1976) and between 55 and 85 m in more 

southern waters (Fitch, 1953, p. 44). During the Pleistocene, P. caurinus lived as far south as San Pedro in 

the Los Angeles area (Arnold, 1903, p. 37, 107); the 

southernmost modern occurrence of P. caurinus is 

Point Reyes, Calif., north of the known Pliocene distribution of P. lohri and P. healeyi; this suggests that 

P. caurinus may prefer cooler water than did its possible predecessors. The Pliocene mollusks and other 

invertebrates that occur with P. healeyi indicate shallow water, intertidal to 50 m.

Patinopecten healeyi was presumably attached by a 

byssus when young. Mature individuals probably 

could swim in the sense that they could make a dart 

up off the bottom and then resettle when directly 

threatened by their predators, which may have been 

Octopus and starfish.

CONCLUSION

It is my opinion that the different sculptural forms 

of P. healeyi may represent responses to the environment. The sculptural variation within single lots of 

specimens from the same locality shows that the variation is not of stratigraphic significance.

Imbricated microsculpture found on the left valve of 

P. healeyi occurs only on the left valves of other 

Patinopecten in the east Pacific. In the west Pacific, 

this microsculpture is found on both the right and left 

valves of pectinids assigned to the genera Mizuhopecten and Yabepecten by other workers. Use of the scanning electron microscope in the study of microsculpture may prove useful in the separation of genera or subgenera of pectinids and in the study of the 

evolution of the group.

FOSSIL LOCALITIES (PLIOCENE, CALIFORNIA)

U.S. Geological Survey:

M2096: San Juan Capistrano 7.5-minute quadrangle (1949 ed.). 

Between Aliso Creek and U.S. Highway 101 in gully wall 

about 4.8 km south of El Toro town; 235 m south and 45 m 

east of NW cor. sec. 11, T. 7 S., R. 8 W., altitude about 120 m. 

Niguel Formation. J. G. Vedder, 1953 and 1962.

M2098: San Juan Capistrano 7.5-minute quadrangle (1949 ed.). 

About 4.8 km south of San Juan Capistrano; 505 m south and 

775 m west of NW cor. sec. 24, T. 7 S., R. 8 W., altitude about 

105 m. Niguel Formation. J. G. Vedder, 1954.

M2753: Newport Beach 7.5-minute quadrangle. Approximately 

785 m southeast and 775 m southwest of north corner Irvine 

Block 52. Altitude about 30 m. In artificial cut near top of 

bluff overlooking upper Newport Bay. Fernando Formation. 

J. G. Vedder, 1966.

M3627: La Jolla 7.5-minute quadrangle. North end of Pacific 

Beach, collected from north end of pumping station off Wilbur Street to a point about 60 m north. San Diego Formation. 

J. G. Vedder, 1961.

M3628: La Jolla 7.5-minute quadrangle. South end of Pacific 

Beach, off Law Street, slightly south of dead end. San Diego 

Formation. J. G. Vedder, 1961.
12 SCULPTURAL VARIATION OF THE PELECYPOD PATINOPECTEN HEALEYI (ARNOLD)

M5040: Newport Beach 7.5-minute quadrangle, Orange 

County. Approximately 900 m northeast and 775 m northwest of south corner Irvine Block 52 in new cut trending N. 

84° E. Altitude about 10 m. Fernando Formation. J. G. Vedder, 1972.

M6502: San Clemente Island. 610 m east and 135 m north of 

BM 554, San Clemente Island North 7.5-minute quadrangle 

(1950 ed.). Altitude approximately 50 m in resistant limy 

outcrop high on east side of steep gully draining northeast 

side of island. Unnamed Pliocene rocks. J. G. Vedder, 1975.

M6503: San Clemente Island. 615 m east and 25 m north of BM 

553, San Clemente North 7.5-minute quadrangle (1950 ed.). 

Altitude approximately 70 m in new road cut not shown on 

map, about 160 m southwest of lighthouse on seacliff 4,020 m 

southeast of Wilson Cove. Unnamed Pliocene rocks. J. G. 

Vedder, 1975. 

California Academy of Sciences:

CAS 105: Sea cliffs at Pacific Beach, La Jolla 7.5-minute quadrangle. San Diego Formation. 

Natural History Museum Los Angeles:

LAM 107: Quarry at end of Arroyo Drive, known locally as 

Clay Canyon or Clay Quarry. San Diego Formation. G. P. 

Kanakoff.

LAM 122: Pacific Beach, La Jolla 7.5-minute quadrangle. Exposure at shore bluff at bend at end of Loring Street. San 

Diego Formation. G. P. Kanakoff.

LAM 305: North of Mexican border, San Ysidro 7.5-minute 

quadrangle. From 30 m of exposure, 1.5 to 4 m thick, exactly 

530 m from Mexican border fence. "K" Ranch, Palm City. San 

Diego Formation. G. P. Kanakoff.

LAM 305A: West side of next gully east of LAM 305, same elevation. G. P. Kanakoff.

LAM 485: National City 7.5-minute quadrangle (1953 ed.). 

From 6 m thick, mostly unconsolidated, yellow, medium- to 

coarse-grained sandstone on 30° bulldozed slope at locality 

north of Market Street and east of Euclid Avenue. Projected 

intersection of arrows on edges of NW 1/4 of map marked "2.6 

mi. to U.S. 101" and "0.6 mi. to U.S. 80" mark this locality. 

San Diego Formation. E. C. Wilson, 1967.

LAM 4902: Pacific Beach, La Jolla 7.5-minute quadrangle. 

South-facing exposure on north side of lot on northeast corner 

of Edgeworth Road and Belloc Court. Collected from a 

yellow-tan fine- to medium-grained sandstone, unindurated, 

1 to 3 m up bank. San Diego Formation. G. L. Kennedy, 1965, 

1966.

LAM 5108: A general locality number for LAM localities 20, 

107, 108, 122, and 180, which were mixed, but all from San 

Diego Formation.

Stanford University:

SU 1605. Rikuoku (Japan).

REFERENCES CITED

Addicott, W. O., 1972, Provincial middle and late Tertiary molluscan stages, Temblor Range, California, in Symposium on 

Miocene biostratigraphy of California: Soc. Econ. Paleontologists and Mineralogists, Pacific Sec., Bakersfield, Calif., 

March 1972, p. 1-26, pis. 1-4.

———1974, Giant pectinids of the eastern north Pacific margin— 

Significance in Neogene zoogeography and chronostratigraphy: 

Jour. Paleontology, v. 48, no. 1, p. 180-194.

Arnold, Ralph, 1903, The paleontology and stratigraphy of the 

marine Pliocene and Pleistocene of San Pedro, California: California Acad. Sci. Mem., v. 3, 419 p., 37 pis.

———1906, The Tertiary and Quarternary pectens of California:

U.S. Geol. Survey Prof. Paper 47, 264 p., 53 pis., 2 figs.

Cahn, A. R., 1951, Clam culture in Japan: Supreme Commander for 

the Allied Powers, General Headquarters, Tokyo, Nat. Resources Sec. Rept. 146, 103 p., 38 figs., 13 tables.

Clark, G. R., 2d, 1976, Shell convexity in Argopecten gibbus— 

variation with depth in Harrington Sound, Bermuda: Bull. 

Marine Sci., v. 26, no. 4, p. 605-610, 3 figs.

Clark, J. C., 1966, Tertiary stratigraphy of the Felton-Santa Cruz 

area, Santa Cruz Mountains, California: Stanford Univ., Stanford, Calif., Ph.D. thesis, 184 p.

Cummings, J. C., Touring, R. M., and Brabb, E. E., 1962, Geology of 

the northern Santa Cruz Mountains, California, in Bowen, O. 

E., ed., Geologic guide to the gas and oil fields of northern California: California Div. Mines and Geology Bull. 181, p. 179- 

222, 21 photos, pis. 20-24, 4 figs., 1 table.

Dall, W. H., 1878, Fossil mollusks from later Tertiaries of California: U.S. Natl. Mus. Proc., v. 1, p. 10-16 [1879].

———1898, Contributions to the Tertiary fauna of Florida, with 

especial reference to the Miocene silex beds of Tampa and the 

Pliocene beds of the Caloosahatchie River: Wagner Free Inst. 

Sci. Trans., v. 3, pt. 4, p. 571-947, pis. 23-35.

Dibblee, T. W., Jr., 1950, Geology of southwestern Santa Barbara 

County, California, Point Arguello, Lompoc, Point Conception, 

Los Olivos, and Gaviota Quadrangles: California Div. Mines 

Bull. 150, 95 p., 17 pis., 6 figs.

Durham, D. L., and Addicott, W. O., 1965, Pancho Rico Formation, 

Salinas Valley, California: U.S. Geol. Survey Prof. Paper 

524-A, 22 p., 5 pis.

Durham, D. L., and Yerkes, R. F., 1964, Geology and oil resources of 

the eastern Puente Hills area, southern California: U.S. Geol. 

Survey Prof. Paper 420-B, p. B1-B62.

Faustman, W. F., 1964, Paleontology of the Wildcat Group at Scotia 

and Centerville Beach, California: California Univ. Pubs. Geol. 

Sci., v. 41, no. 2, p. 97-160, 3 pis., 7 figs.

Fitch, J. E., 1953, Common marine bivalves of California: California Dept. Fish and Game Fish Bull. 90, 102 p., 63 figs.

Fleming, C. A., 1957, The genus Pecten in New Zealand: New Zealand Geol. Survey Paleontology Bull. 26, 69 p., 15 pis.

Glen, William, 1959, Pliocene and lower Pleistocene of the western 

part of the San Francisco Peninsula: California Univ. Pubs. 

Geol. Sci., v. 36, no. 2, p. 147-198, pis. 15-17, 5 text figs.

Grant, U. S., 4th, and Gale, H. R., 1931, Catalogue of the marine 

Pliocene and Pleistocene Mollusca of California and adjacent 

regions: San Diego Soc. Nat. History Mem., v. 1, 1036 p., 32 

pis., 15 figs., 3 tables.

Grau, Gilbert, 1959, Pectinidae of the eastern Pacific: Los Angeles, 

Univ. Southern California, Allan Hancock Pacific Exped., v. 23, 

308 p., 57 pis.

Hawkins, J. W., Allison, E. C., and MacDougall, Doug, 1971, Volcanic petrology and geologic history of Northeast Bank, southern California borderland: Geol. Soc. America Bull., v. 82, no. 1, 

p. 219-228, 4 figs.

Hertlein, L. G., 1925, New species of marine fossil mollusca from 

western North America: Southern California Acad. Sci. Bull., v. 

24, pt. 2, p. 39-46, pis. 3, 4.

———1928, Pecten (Patinopecten) lohri, new name for Pecten oweni 

Arnold, a Pliocene species from California: The Nautilus, v. 41, 

no. 3, p. 93-94.

Hertlein, L. G., and Grant, U.S., IV, 1972, The geology and paleontology of the marine Pliocene of San Diego, California (Paleontology: Pelecypoda): San Diego Soc. Nat. History Mem. 2, pt. 2b, 

p. 143-409, 57 pis.

Jordan, E. K., and Hertlein, L. G., 1926, Contributions to the geology and paleontology of the Tertiary of Cedros Island and adja-
REFERENCES CITED 13

cent parts of Lower California, in Expedition to the Revillagigedo Islands, Mexico, 1925: California Acad. Sci. Proc., ser. 

4, v. 15, no. 14, p. 409-464.

Kennedy, M. P., and Peterson, G. L., 1975, Geology of the San Diego 

metropolitan area, California: California Div. Mines and Geology Bull. 200, 56 p., 6 pis., 8 photos, 12 figs., 3 tables.

Kern, J. P., 1973, Early Pliocene marine climate and environment 

of the eastern Ventura Basin, southern California: California 

Univ. Pubs. Geol. Sci., v. 96, 117 p., 27 figs., 10 tables.

MacNeil, F. S., 1961, Lituyapecten (new subgenus of Patinopecten) 

from Alaska and California: U.S. Geol. Survey Prof. Paper 

354-J, p. 225-239, pis. 35-46 [1962].

Martin, Bruce, 1916, Pliocene of middle and northern California: 

California Univ. Pub. Geol. Sci. Bull., v. 9, no. 15, p. 215-259.

Masuda, Koichiro, 1962, Tertiary Pectinidae of Japan: Tohoku 

Univ. Sci. Repts., ser. Geology, v. 33, no. 2, p. 117-238, pis. 

18-27.

———1963, The so-called Patinopecten of Japan: Palaeont. Soc. 

Japan Trans. and Proc., n.s., no. 52, p. 145-153, pis. 22, 23.

Masuda, Koichiro, and Addicott, W. O., 1970, OnPecten (Amusium) 

condoni Hertlein from the west coast of North America: The 

Veliger, v. 13, no. 2, p. 153-156, figs. 1-9.

Meek, F. B., 1864, Check list of the invertebrate fossils of North 

America: Smithsonian Misc. Colln. 183, 32 p.

Minch, J. C., Gastil, Gordon, Fink, William, Robinson, John, and 

James, A. H., 1976, Geology of the Vizcaino Peninsula, in Howell, D. G., Aspects of the geologic history of the California continental borderland: Am. Assoc. Petroleum Geologists, Pacific 

Sec., Misc. Pub. 24, p. 136-195, 5 figs., 17 tables.

Moore, E. J., 1963, Miocene marine mollusks from the Astoria Formation in Oregon: U.S. Geol. Survey Prof. Paper 419, 109 p., 33 

pis., 9 figs., 3 tables [1964].

Ogle, B. A., 1953, Geology of Eel River Valley area, Humboldt 

County, California: California Div. Mines Bull. 164, 128 p.

Peck, J. H., Jr., 1960, Paleontology and correlation of the Ohlson 

Ranch Formation: California Univ. Pubs. Geol. Sci., v. 36, no. 4, 

p. 233-242, pi. 21.

Rowland, R. W., 1972, Paleontology and paleoecology of the San 

Diego Formation in northwestern Baja California: San Diego 

Soc. Nat. History Trans., v. 17, no. 3, p. 25-32, 2 figs., 2 tables.

Stanton, R. J., Jr., and Dodd, J. R., 1976, Pliocene biostratigraphy 

and depositional environment of the Jacalitos Canyon area, 

California, in Fritsche, A. E., Best, H. T., Jr., and Wornardt, 

W. W., The Neogene Symposium: Soc. Econ. Paleontologists 

and Mineralogists Pacific Sec., Ann. Mtg., p. 85-94, 5 figs., 2 

tables.

Suzuki, Takeo, and Stadum, C. J., 1978, A Neogene section, northeastern San Clemente Island, California: Los Angeles County 

Mus. Nat. History Contr. Sci. 299, 24 p., 29 figs.

Vedder, J. G., and Moore, E. J., 1976, Paleoenvironmental implications of fossiliferous Miocene and Pliocene strata on San 

Clemente Island, California, in Howell, D. G., Aspects of the 

geologic history of the California continental borderland: Am. 

Assoc. Petroleum Geologists, Pacific Sec., Misc. Pub. 24, p. 

107-127, 4 pis., 1 table, 9 figs.

Verrill, A. E., 1899, A study of the family Pectinidae with a revision 

of the genera and subgenera: Connecticut Acad. Arts and Sci. 

Trans., v. 10, pt. 1, p. 41-95, pis. 16-21.

Waller, R. R., 1969, The evolution of the Argopecten gibbus Stock 

(Mollusca: Bivalvia), with emphasis on the Tertiary and 

Quaternary species of eastern North America: Jour. Paleontology, v. 43, suppl. to no. 5, 125 p., 8 pis.

———1972a, the Pectinidae (Mollusca: Bivalvia) of Eniwetok Atoll, 

Marshall Islands: The Veliger, v. 14, no. 3, p. 221-264, 8 pis., 

22 text figs.

———1972b, Functional significance of some shell microsculptures 

in the Pectinacea (Mollusca: Bivalvia): Internat. Geol. Cong., 

24th, Montreal, Canada, 1972, sec. 7, Paleontology, p. 48-56, 3 

figs., 1 table.

———1973, The habits and habitats of some Bermudian marine

mollusks: The Nautilus, v. 87, no. 2, p. 31-52, 2 pis., 2 text figs.

Weaver, C. E., chm., and others, 1944, Correlation of the marine 

Cenozoic formations of western North America: Geol. Soc. 

America Bull., v. 55, no. 5, p. 569-598.

Weaver, D. W., and Meyer, G. L., 1969, Stratigraphy of northeastern Santa Cruz Island, in Weaver, D. W., and others, Geology of 

the northern Channel Islands: [Calif.] Am. Assoc. Petroleum 

Geologists and Soc. Econ. Paleontologists and Mineralogists, 

Pacific Sees., Spec. Pub., p. 95-104.

Winterer, E. L., and Durham, D. L., 1962, Geology of southeastern 

Ventura Basin, Los Angeles County, California: U.S. Geol. 

Survey Prof. Paper 334-H, p. 275-366, pis. 44-49, figs. 49-68, 

11 tables.

Woodring, W. P., 1930, Pliocene deposits north of Simi Valley, California: California Acad. Sci. Proc., ser. 4, v. 19, no. 6, p. 57-64.

Woodring, W. P., and Bramlette, M. N., 1950, Geology and paleontology of the Santa Maria district, California: U.S. Geol. Survey 

Prof. Paper 222, 185 p., 23 pis., 9 figs. [1951].

Woodring, W. P., Stewart, R. E., and Richards, R. W., 1940, Geology 

of the Kettleman Hills oil field, California: U. S. Geol. Survey 

Prof. Paper 195, 170 p., 57 pis., 15 figs.

INDEX

[Italic page numbers indicate major references] 

Page Page

Acknowledgments _______________-_--_______________—____ 2 Orca Inlet, Alaska -_______________________ _ ___ _—— __- — - — ----—— 10

Amusium _____________________________________________ 1 oregonensis, Patinopecten _______——____— _._ — — — — - — —— ____— _ — __-_ 7

Argopecten gibbus ______________________________________________ 4, 10, 11 cancellosus, Patinopecten _ — __ —— __ —————— ——— — __ —— ____ ——— -—— 7

Auricles __________________________________________________ 4 oweni, Pecten (Patinopecten) _________._______ —— — —————— _ ———— __ 6, 7

Baja California __________________________________________ 11 Pacific Beach, California _——————————————————————————————————— 3

Big Basin, California ______________________________________ 9 Patinopecten caunnus _____._ — —— _________ —— —— — ________ 1, 2, 3, 4, 5, 10, 11

Boulder Creek, California ___--__--_-________________________________ 9 coosensis __________________ —— ____—— —— __________ — _ — __-_ — ___- 7

Byssus ____________________________________________________ 4 healeyi sanclementensis ____________________ ———— ______ — _._ — ________ 1

lohri ___-_____——-—————————-— 1, 6, 7, 9, 10, 11, 12; pi. 13

cancellosus, Patinopecten oregonensis ____________________________________ 7 oregonensis _____. —— ——— __ — —— ___ —— ____________ —— __ —— — — __— 7

Cape Mendocino, California ______________________________________ 7 cancellosus ________ —— — _____ —— __________________ —— _____ — — — __ 7

Careaga Sandstone ______________________________________________ 9 propatulus ______ —— _______ —————. —— — — _ ——— ___- ———— _--- —— ---- 5

caurinus, Patinopecten ___________________________ 1, 2, 3, 4, 5, 10, 11 yessoensis ______________————————————————————— 5, 6, 10, 12; pis. 14, 15

Cebada Member __________________________________________ 9 (Patinopecten) expansus, Pecten ____ — __________ ——— — _ — __ — _ —— ._______--. 2

Channel Inlet, Alaska __________________________________________________ 10 healeyi, Pecten ______—_______________________________—_____________ 1,9, 11

Chlamys __________________________________________________ 5,6 sanclementensis, Pecten _________________ — ______ — _ — __ — — _ 2

Conclusion _______________________________________________ 11 oweni, Pecten _____________ — ______ — ________________ — — _____—— 6, 7

condoni, Yabepecten ______________________________________ 7 Pecten expansus _______ — — — —— __ — _____ — — — — —— — ____ — — — _— 1, 2, 5

coosensis, Patinopecten ___________________________________________ 7 (Patinopecten) expansus _________________ — — ___ — _________________ 2

Cordoba, Alaska ________________________________________ 10 healeyi ————— ———. ——— — —— ————————————————— -————— 1,2

Ctenolium ___________________________________________ 4 sanclementensis _____________ — ___ — — __ — — — _ — - — - — — - 2

oweni _____________ ——— —— __ — ____ ——— _________ — ______ — _-__ 6, 7

Dall, W. H., quoted ____________________________________________________ 5 Point Reyes, California ______________ —__________ _ _———______ 7,10, 11

dilleri, Lituyapecten ______________________________________ 9 Pomponio member _________________________ — — __ ——— ___ —— ——— __ 9

	Primary sculpture ________ —— —— -___ —— __ — -___ — — —— — _____ — __— 2

Ecology _____________________________________________ 10 Propatulus, Patinopecten __ ———————————— ————————— —————————————— 5

Etchegoin Formation _________________________________________ 9 Purisima Formation ____ ——— — ____ — ——— _ — __ —— _._— __________ — __ — ___ 9

Eureka, California ____________________________________________ 7, 10 purisimaensis, Lituyapecten ____ ——— ______ — — _______ — __________-------_— 9

expansus, Pecten _______________________________________________ 1, 5 Purpose ________ — _________ — — __________ — ______ — _ — _____ —— ___ ——— ___ 1

Pecten (Patinopecten) ______________________________________ 2 Pycnopodia. _______ —— _ —— -___ ——— ___———— __ — — ________ — _____ —— __— 10

Falor Formation ____________________________________________________________ 9 References cited ______________—___________________—_____.______— — — _— 12

Fernando Formation ________________________________________________ 1,3, 10, 11 Right valve ________________ — _______________________———_ ——— ______________ 2

Fossil localities ______________________________________________________________ 11 Rikuoka, Japan _____________——_____________________________ ____——— 12

Foxen Canyon, California _______________ _ ___ ___ __ _ _ ______ 6

Foxen Mudstone ________________________________________________________________ 9 San Clemente Island, California ________________________________ 1, 2, 3, 4, 6, 11, 12

sanclementensis, Patinopecten healeyi ____________________________.--_-_____ 1

Geographic distribution _________________________ _ _________ 7 Pecten (Patinopecten) healeyi ________________________________________________ 2

gibbus, Argopecten ______________________________________________________________ 4 $** DieS° Formation ____________________________________________ 1, 2, 3, 10, 11, 12

San Diego Mesa ________________________________________________ 11

Harrington Sound, Bermuda 11 San Gregorio, California ____ —— _—__________________ _ _______________________ 9

healeyi, Pecten (Patinopecten) ___________________ _ _________ 1,9 San Gregorio Member __________________________________________________________ 9

sanclementensis, Patinopecten _____________ 1 San Joaquin Formation __________________________________________________________ 9

Pecten (Patinopecten) __________________ ____ 1 San Juan Capistrano, California ____________________________________________ 1,3,11

Hinge area ____________________________________________________________________ 5 San Ysidro> California ________________________________________________________ 12

Santa Cruz Mountains ________________________._______________ 9

Introduction ____________________________________________________________________ 1 Santa Margarita Formation ______________________________________________________ 9

Santa Maria basin ______________________________________________ 3, 6, 9

Jacalitos Canyon, California ________________________________________________ 9 Scope ——--———————————— — — — ——————— _——_______ ——— ___ 1

Jacalitos Formation __________________________ _ _______ 9 Sisquoc Formation ____________________________________________________________ 6,9

Jacalitos Stage __________________ __ 7 Species comparison ______________________________________________________________ 6

starfish _______________________________________________ 11 

Kettleman Hills, California ______________________________________________________ 9 Stratigraphic distribution ________________________________________________________ 7

Koshiba Formation __________________________ ____________________ 5 , ,. Tahana Member .___________________________________ — _________— 9

T T ,. n i-r • 11 ir, Tinaquaic Sandstone Member——————_____ —————— __ ———————— ——— 6,9 La Jolla area, California _________________________________ 11, 12 , ^ _ „ _

T „, , tokunagai, Yabepecten __________ — _____________________________— o, b, 7

Left valve _____________________________________________________________ 3 , ' . Q

_ . Towsley Formation —————._ —————— —— ————— ——— — ————————————— 9

Lituyapecten dilleri ____________________________ ____ __ _ _ ________________ 9 _. _

... _ turneri, Lituyapecten __________ — ._______—_ —— _ — __ — _ — _ —— --.__— /

purisimaensis ________________________ _ _ __ __________________ 9 „ , „

Patinopecten __________________________-_..___________ — — ___ 7

turneri _______________________________________________ 7

lohri, Patinopecten ____________________________________________________ 1, 6, 7, 9, 11 ^^ A ^ quoted „ __. _ 5

MacNeil, F. S., quoted _____ _ _ ___ 5 ^pecto _______ _.____.._______________.__________ —— -___-_--_ 6

». , T, T, i r Vizcamo Peninsula, Baja California ——______————————————————————— 9 Meek, F. B., quoted _________________________________________ 5

Merced Formation ____________________________ _ __ __________________ 9 .„ ,, „ „ . , , Waller, R. R., quoted ____________________________________.__ 4 Microsculpture ______________________________________________________________ 5 „.,.„._., ,,

,,. , v Woodnng, W. P., quoted ___________________________________ 6

Mizuhopecten _____________________________ _ _ ___________ 6, 11 ,,. „ ., , ,_ ^ ———— — _ , Wrangell, Alaska ______________________________________ 10

Montesano Formation ____________________________________ 7

Yabepecten _______________._________________________ 5,6, 11

National City, California ___________________________________ 12 condoni ______ _ __ __ __ __ _ _ __ __ 7

Newport Beach, California ________________________________________________ 1, 3, 11 tokunagai ______________________________________________________________ 5, 6, 7

Niguel Formation ______________________________________________________ 1, 3, 10, 11 yessoensis, Patinopecten ________________________________________________ 5, 6, 12, 10

North Dome, California ________________________________________________ 9

Octopus ______________________________________________ 10, 11 Zapato Chino section —— — ————— — _ —————— _ ————— ——— ___———————— 9

15

PLATES 1-15

Contact photographs of the plates in this report are available, at cost, from U. S. 

Geological Survey Library, Federal Center, Denver, Colorado 80225
PLATE 1

FIGURES 1-8. Patinopecten healeyi (Arnold), San Diego Formation, San Diego, Calif.

1. Exterior or right valve showing typical dichotomy of primary ribs. 95 mm 

high; 98 mm wide; hinge 45.5 mm long. LAM loc. 5108. LAM 5219.

2. Exterior of right valve showing complete dichotomy of rib on anterior portion of shell. 31 mm high; 30 mm wide; hinge 16 mm long. LAM loc. 485. 

LAM 5220, x2.

3. Exterior of incomplete right valve showing complete dichotomy of ribs on 

anterior portion of shell and riblets on posterior ear. 39 mm wide; hinge 

17.5 mm long. LAM loc. 107. LAM 5221, xl.50.

4. Exterior of juvenile right valve showing smooth disk and low rounded ribs. 

13.2 mm high; 13.0 mm wide; hinge 7.8 mm long, LAM loc. 4902. LAM 

5222, x3.

5. Interior of juvenile right valve showing hinge area and ctenolium. (Same 

specimen illustrated as fig. 4.)

6. Exterior of right-valve fragment showing smooth disk, low rounded ribs, 

and ctenolium. Hinge 10.5 mm long. LAM loc. 107. LAM 5223, x3.

7. Exterior of right valve showing smooth disk, complete dichotomy of ribs at 

both anterior and posterior margins, and fine striations on posterior ear. 

25 mm high; 24 mm wide; hinge 12.5 mm long. LAM loc. 107. LAM 

5224, x3.

8. Exterior of right valve showing wide unsculptured band at both anterior 

and posterior margins and dichotomy of all primary ribs. 153 mm high; 

165 mm wide; hinge 85 mm long. LAM loc. 107. LAM 5225, xO.60.
GEOLOGICAL SURVEY PROFESSIONAL PAPER 1103 PLATE 1

PA TINOPECTEN HEALEYI (ARNOLD)
PLATE 2

FIGURES 1-7. Patinopecten healeyi (Arnold).

1. Exterior of right valve of intermediate form showing smooth umbo and low 

subdued ribs. San Diego Formation, San Diego, Calif. 75 mm high; 80 

mm wide; hinge 36.5 mm long. CAS loc. 105. CAS 58250.

2. Exterior of right valve of intermediate form showing smooth rounded ribs 

over midportion of shell and dichotomous ribs at posterior margin and 

one near anterior margin. San Diego Formation, San Diego, Calif. 78 

mm high; 81 mm wide; hinge 35.5 mm long. CAS loc. 105. CAS 58251.

3. Fragment of right valve of smooth form showing large smooth disk succeeded by dichotomous but very closely spaced primary ribs. Unnamed 

Pliocene strata, San Clemente Island, Calif. USGS M6502. USNM 

235594. (Illustrated by Vedder and Moore, 1976, pi. 3, fig. 6.)

4. Exterior of juvenile left valve, presumed to be of smooth form. Unnamed 

Pliocene strata, San Clemente Island, Calif. 15 mm long; 16 mm high; 

hinge 8.7 mm long. USGS M6503. USNM 235590, x2. (Illustrated by 

Vedder and Moore, 1976, pi. 3, fig. 2.)

5. Fragment of right valve of smooth form showing dichotomous but very 

closely spaced ribs. Unnamed Pliocene strata, San Clemente Island, 

Calif. USGS M6503. USNM 235595. (Illustrated by Vedder and Moore, 

1976, pi. 3, fig. 8.)

6. Exterior of small right valve of smooth form showing faint trace of subdued rib sculpture. Unnamed Pliocene strata, San Clemente Island, 

Calif. 50 mm high; 50 mm wide; hinge 23 mm long. USGS M6503. 

USNM 235592. (Illustrated by Vedder and Moore, 1976, pi. 3, fig. 4.)

7. Exterior of right valve of smooth form showing large smooth area of disk 

succeeded by very closely spaced dichotomous ribs. Unnamed Pliocene 

strata, San Clemente Island, Calif. 100 mm high; 101 mm wide; hinge 

48 mm long. USGS M6503. USNM 235591. (Illustrated by Vedder and 

Moore, 1976, pi. 3, fig. 3).
GEOLOGICAL SURVEY PROFESSIONAL PAPER 1103 PLATE 2

PA TINOPECTEN HEALEYI (ARNOLD)
PLATE 3

FIGURES 1-6. Patinopecten healeyi (Arnold).

1. Exterior of right valve of many-ribbed form showing 22 closely spaced 

dichotomous ribs and unsculptured bands at anterior and posterior margins. San Diego Formation, San Diego, Calif. 132 mm high; 138 mm 

wide. LAM loc. 305A. LAM 5226, xO.66.

2. Fragment of exterior of right valve showing closely spaced ribs, smooth 

disk, and wide posterior unsculptured band. Fernando Formation, Newport Beach quadrangle, California. Posterior ear 27 mm long. USGS 

M5040. USNM 249742.

3. Fragment of exterior of right valve showing wide very closely spaced ribs. 

Fernando Formation, Newport Beach quadrangle, California. USGS 

M5040. USNM 249743.

4. Exterior of incomplete right valve showing narrow dichotomous and 

trichotomous ribs. Niguel Formation (Pliocene), San Juan Capistrano 

quadrangle, California. 107 mm wide. USGS M2096. USNM 249744.

5. Exterior of right valve of many-ribbed form showing 22 closely spaced 

dichotomous and trichotomous ribs and unsculptured bands at anterior 

and posterior margins. San Diego Formation, San Diego, Calif. 150 mm 

high; 158 mm wide; hinge 71 mm long. LAM loc. 107. LAM 5227, xO.60.

6. Fragment of exterior of right valve showing narrow widely spaced ribs. 

Fernando Formation, Newport Beach quadrangle, California. USGS 

M5040. USNM 249745.
GEOLOGICAL SURVEY PROFESSIONAL PAPER 1103 PLATE 3

PA TINOPECTEN HEALEYI (ARNOLD)
PLATE 4

FIGURES 1-8. Patinopecten healeyi (Arnold).

1. Exterior of incomplete right valve showing subdued deeply dichotomous 

ribs and wide unsculptured bands at anterior and posterior margins. 

Fernando Formation, Newport Beach quadrangle, California. 165 mm 

wide; hinge 70 mm long (incomplete). USGS M2753. USNM 249746,- 

xO.66.

2. Exterior of fragment of right valve showing wide closely spaced dichotomous and trichotomous ribs. Fernando Formation, Newport Beach quadrangle, California. USGS M2753. USNM 249747.

3. Exterior of right valve of double-valved specimen showing smooth ribs 

near anterior and posterior margins. San Diego Formation, San Diego, 

Calif. 50 mm high; 48 mm wide; hinge 21.5 mm long. LAM loc. 107. 

LAM 5228.

4. Exterior of right-valve fragment showing large smooth disk and subdued 

ribs. Fernando Formation, Newport Beach quadrangle, California. 

USGS M2753. USNM 249748.

5. Exterior of left valve of double-valved specimen, showing rounded primary 

ribs. (Same specimen illustrated as fig. 3.)

6. Enlargement (x3) of anterior auricle of right valve, illustrated in figure 3, 

showing ctenolium.

7. Enlargement (x3) of right anterior auricle showing ctenolium and auricle 

sculpture. San Diego Formation, San Diego, Calif. Entire specimen: 65 

mm high; 70 mm wide; hinge 32 mm long (incomplete); right anterior 

auricle 17 mm long. LAM loc. 305. LAM 5229.

8. Exterior of right valve of double-valved specimen showing dichotomous 

and trichotomous ribs and addition of secondary ribs near ventral margin. (Left valve illustrated, pi. 6, fig. 3.) San Diego Formation, San Diego, Calif. 112 mm high (incomplete); 123 mm wide (incomplete); hinge 

62 mm (incomplete). LAM loc. 122, LAM 5230, xO.75.
GEOLOGICAL SURVEY PROFESSIONAL PAPER 1103 PLATE 4

PA TINOPECTEN HEALEYI (ARNOLD)
PLATE 5

FIGURES 1-6. Patinopecten healeyi (Arnold).

1. Exterior of left valve showing typical sculpture of alternating primary and 

secondary ribs. San Diego Formation, San Diego, Calif. 105 mm high; 

106 mm wide; hinge 51.5 mm long. LAM loc. 5108. LAM 5231, xO.75.

2. Exterior of left valve of specimen that has rounded primary ribs but no 

secondary ribs. San Diego Formation, San Diego, Calif. 87 mm high; 85 

mm wide; hinge 35.5 mm long. LAM loc. 5108. LAM 5232.

3. Exterior of left valve of probable smooth form showing closely spaced fine 

primary and secondary ribs and concentric lamellae. Unnamed Pliocene 

strata, San Clemente Island, Calif. 100 mm long; 98 mm high; hinge 

47.4 mm long. USGS M6503. USNM 235593. (Illustrated by Vedder and 

Moore, 1976, pi. 3, fig. 5.)

4. Electron micrograph of concentric lamellae of left valve showing parallel 

rather than imbricated pattern. LAM loc. 305. LAM 5233, X100.

5. Exterior of left-valve auricles of double-valved specimen. (Right-valve auricles illustrated, pi.7, fig. 3). San Diego Formation, San Diego, Calif. 

Hinge 63 mm long. LAM loc. 5108. LAM 5234.

6. Exterior of left valve showing squaring of ribs toward ventral margin and 

fine concentric lamellae. San Diego Formation, San Diego, Calif. 94 mm 

high; 95 mm wide; hinge 42 mm long (incomplete). LAM loc. 5108. LAM 

5235.
GEOLOGICAL SURVEY PROFESSIONAL PAPER 1103 PLATES

PA TINOPECTEN HEALEYI (ARNOLD)
PLATE 6

FIGURES 1-7. Patinopecten healeyi (Arnold), San Diego Formation, San Diego, Calif.

1. Exterior of left-valve auricles showing anterior fold and subdued riblets. 

(Same specimen illustrated pi. 9, fig. 1). Hinge 94 mm long; anterior 

auricle 49 mm long; posterior auricle 45 mm long.-LAM loc. 122. LAM 

5236.

2. Exterior of left-valve anterior auricle showing fold, riblets, and concentric 

sculpture, and of anterior disk showing imbricated microsculpture. 

Hinge 44 mm long; anterior auricle 23.5 mm (maximum length). LAM 

loc. 122. LAM 5237, x3.

3. Exterior of left valve of double-valved specimen showing a small rib running down the center of some of the primary ribs and two secondary ribs 

in the interspaces near the anterior margin. 110 mm high; 118 mm 

wide; 60 mm high. LAM loc. 122. LAM 5230, xO.75. (Right valve illustrated, pi. 4, fig. 8.)

4. Interior of left-valve hinge area showing ridges bordering resilial pit and 

auricular denticles. Hinge 42 mm long. LAM loc. 5108. LAM 5238.

5. Interior of left-valve hinge area showing ridges and grooves bordering resilial pit. Hinge 52.5 mm long. LAM loc. 5108. LAM 5239.

6. Interior of left-valve hinge area showing ridges and grooves bordering resilial pit. Hinge 68.3 mm long. LAM loc. 5108. LAM 5240.

7. Exterior of left valve of double-valved specimen showing anterior unsculptured band and overlap of larger right valve along ventral margin. 

(Right-valve auricles illustrated, pi. 13, fig. 1). 140 mm high; 150 mm 

wide; hinge 75 mm long (incomplete). LAM loc. 5108. LAM 5241, xO.66.
GEOLOGICAL SURVEY PROFESSIONAL PAPER 1103 PLATE 6

PA TINOPECTEN HEALEYI (ARNOLD)
PLATE 7

FIGURES 1-5. Patinopecten healeyi (Arnold).

1. Exterior of left valve showing square, ribbed primaries and two times of 

breakage and subsequent repair of shell. Niguel Formation, San Juan 

Capistrano quadrangle, California. 97 mm high; 103 mm wide; hinge 52 

mm long (incomplete). USGS M2098. USNM 249749.

2. Exterior of fragment of left valve showing multiple secondary ribs at anterior margin. Fernando Formation, Newport Beach quadrangle, California. USGS M2753. USNM 249750.

3. Exterior of right valve auricles of double-valved specimen showing 

sculpture and the enlargement of left anterior auricle opposing the right 

anterior auricle. (Left-valve auricles illustrated, pi. 5, fig. 5.) San Diego 

Formation, San Diego, Calif. Hinge 63 mm long. LAM loc. 5108. LAM 

5234.

4. Exterior of fragment of left valve showing wide square primaries and doubled secondaries. Niguel Formation, San Juan Capistrano quadrangle, 

California. USGS M2096. USNM 249751.

5. Exterior of left valve showing narrow ribs on disk that are flat and broad 

at the ventral margin and showing marked enlargement of anterior auricle. San Diego Formation, San Diego, Calif. 127 mm high (incomplete); 

130 mm wide (incomplete); hinge 60.4 mm long. USGS M3627. USNM 

249752, xO.75.
GEOLOGICAL SURVEY PROFESSIONAL PAPER 1103 PLATE 7

PA TINOPECTEN HEALEYI (ARNOLD)
PLATE 8

FIGURES 1-6. Patinopecten healeyi (Arnold), San Diego Formation, San Diego, Calif.

1. Exterior of left valve showing square primaries, some ribbed, and enlargement of anterior auricle. 128 mm high; hinge 66 mm long. LAM 

loc. 5108. LAM 5242, xO.75.

2. Interior of left valve showing hinge area and auricular denticles. Entire 

specimen 116 mm high; 120 mm wide; hinge 55 mm long. LAM loc. 

5108. LAM 5243.

3. Exterior of left valve showing multiple times of breakage and subsequent 

repair of shell. (Same specimen illustrated as fig. 5.) 140 mm high; 150 

mm wide; hinge 68 mm long. LAM loc. 5108. LAM 5244, xO.66.

4. Exterior of left valve showing ribbed primaries, some narrow and some 

round secondaries, one double secondary near anterior margin, and enlarged anterior auricle. 140 mm high; 147 mm wide; hinge 70 mm long. 

LAM loc. 5108. LAM 5245, xO.66.

5. Interior of left-valve hinge area. Note grooves and double ridges bordering 

resilial pit. (Same specimen illustrated as fig. 3.) Hinge 68 mm long 

(incomplete).

6. Exterior of left valve showing wide, ribbed primaries, narrow to widely 

rounded secondaries, fine ribs at anterior margin, breakage and repair 

of shell, and enlarged anterior auricle. 147 mm high; 159 mm wide; 

hinge 80 mm long. LAM loc. 5108. LAM 5246, xO.60.
GEOLOGICAL SURVEY PROFESSIONAL PAPER 1103 PLATE 8

PA TINOPECTEN HEALEYI (ARNOLD)
PLATE 9

FIGURES 1-7. Patinopecten healeyi (Arnold).

1. Interior of left valve showing hinge area and anterior auricular denticle. 

(Same specimen illustrated, pi. 6, fig. 1) San Diego Formation, San Diego, Calif. Hinge 92 mm long. LAM loc. 122. LAM 5236.

2. Interior of right-valve hinge area. San Diego Formation, San Diego, Calif. 

Hinge 77 mm long (incomplete). USGS loc. M3628. USNM 249753.

3. Interior of left-valve hinge area. San Diego Formation, San Diego, Calif. 

Hinge 78 mm long. USGS loc. M3628. USNM 249754.

4. Fragment of exterior of left valve showing wide flat primaries and some 

narrow and some wide flat secondaries. Niguel Formation, San Juan 

Capistrano quadrangle, California. USGS loc. M2096. USNM 249755.

5. Interior of right-valve hinge area showing thickened posterior ridge. San 

Diego Formation, San Diego, Calif. Hinge 55 mm long. LAM loc. 122. 

LAM 5247.

6. Interior of right-valve hinge area showing thickened posterior ridge. San 

Diego Formation, San Diego, Calif. Hinge 53 mm long. LAM loc. 122. 

LAM 5248.

7. Exterior of left valve showing subdued ribs near ventral margin and enlarged anterior auricle. San Diego Formation, San Diego, Calif. 120 mm 

high; 130 mm wide; hinge 59 mm long. LAM loc. 122. LAM 5249, xO.75.
GEOLOGICAL SURVEY PROFESSIONAL PAPER 1103 PL ATE 9

PA TINOPECTEN HEALEYI (ARNOLD)
PLATE 10

FIGURES 1-5. Patinopecten healeyi (Arnold), San Diego Formation, San Diego, Calif.

1. Exterior of small left valve enlarged to show imbricated microsculpture. 

Note also fine primary ribs and few secondary ribs. 37 mm high; 36 mm 

wide (incomplete). LAM loc. 107. LAM 5250, x2.50.

2. Interior of right-valve hinge area. Hinge 92 mm long. LAM loc. 122. LAM 

5251.

3. Exterior of small left valve enlarged to show imbricated and lamellar microsculpture and enlarged anterior auricle. Note also rounded primary 

ribs and few secondary ribs. 37 mm high; 38 mm wide; hinge 18.8 mm 

long. LAM loc. 107. LAM 5252, x2.50.

4. Exterior of juvenile left valve enlarged to show imbricated microsculpture 

(see also pis. 11-13 for electron micrographs of same specimen). 21.4 

mm high; 20.5 mm wide; hinge 10.1 mm high. LAM loc. 107. LAM 5253, 

x3.

5. Electron micrograph of imbricated microsculpture on specimen illustrated 

in figure 4. Note that lamellae are not imbricated where they cross ribs.
GEOLOGICAL SURVEY PROFESSIONAL PAPER 1103 PLATE 10

PA TINOPECTEN HEALEYI (ARNOLD)
PLATE 11

FIGURES 1-3. Patinopecten healeyi (Arnold), San Diego Formation, San Diego, Calif. Electron 

micrographs of left valve illustrated, pi. 10, fig. 4. The specimen was 

scanned from the dorsal to the ventral margin with fig. 1 showing the dorsal 

margin and fig. 3 the area about one-third the distance from the dorsal to 

the ventral margin (pi. 12 continues the scan).

1. The microsculpture consists of longitudinal ridges that are not parallel 

with the primary ribs.

2. The microsculpture now consists of longitudinal ridges that are nearly 

parallel with the primary ribs and of concentric ridges that cross the 

primary ribs.

3. Concentric ridges are prominent between ribs and are starting to become 

imbricated.
GEOLOGICAL SURVEY PROFESSIONAL PAPER 1103 PLATE 11

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PATINOPECTEN HEALEYI (ARNOLD)
PLATE 12

FIGURES 1-3. Patinopecten healeyi (Arnold), San Diego Formation, San Diego, Calif. Electron 

micrographs of left valve illustrated, pi. 10, fig. 4. The specimen was 

scanned from the dorsal to the ventral margin with fig. 1 representing the 

midportion of the shell and fig. 3 the shell near the ventral margin (pi. 11 

shows dorsal scan).

1. The concentric ridges are now loosely imbricated between the ribs.

2. The concentric ridges are loosely imbricated at the top of the picture but 

barely scalloped near the bottom of the picture.

3. The concentric ridges are tightly imbricated between the primary ribs.
GEOLOGICAL SURVEY PROFESSIONAL PAPER 1103 PLATE 12

PA TINOPECTEN HEALEYI (ARNOLD)
PLATE 13

FIGURES 1, 2, 5. Patinopecten heaieyi (Arnold), San Diego Formation, San Diego, Calif.

1. Right-valve auricles of double-valve specimen showing strong flexure of 

byssus. Note also the unsculptured band at both the anterior and posterior margins. (Left valve of same specimen illustrated, pi. 6, fig. 7.) 

Hinge 62.4 mm long. LAM loc. 5108, LAM 5241.

2. Dorsal view of hinge of double-valved specimen showing relative inflation 

of valves and strong flexure of left anterior auricle toward right anterior 

auricle byssus. (Same specimen illustrated, pi. 14, fig. 3; pi. 15, figs. 2. 

3.) Hinge 95 mm long. LAM loc. 107. LAM 5254, xO.66.

5. Electron micrograph of portion of anterior auricle of left valve, illustrated

pi. 10, fig. 4, and pis. 11 and 12, showing closely spaced lamellae. 

3, 4, 6. Patinopecten lohri (Hertlein), holotype (UCMP 12081). Tinaquaic Sandstone 

Member, Sisquoc Formation, near Foxen Canyon, Calif.

3. Right valve of holotype showing wide, high, dichotomous primary ribs 

with a wide rounded secondary rib in every interspace. 87 mm high; 88 

mm wide, hinge 47 mm long.

4. Dorsal view of holotype showing relative inflation of valves.

6. Left valve of holotype showing strong, rounded primary ribs that are

dichotomous near ventral margin, wide rounded secondary ribs, and

greatly enlarged anterior auricle.
GEOLOGICAL SURVEY PROFESSIONAL PAPER 1103 PLATE 13

PA TINOPECTEN HEALEYI (ARNOLD) AND PA TINOPECTEN LOHRI (HERTLEIN )
PLATE 14

FIGURE 1. Patinopecten yessoensis (Jay), Rikuoku, Japan. Exterior of right valve enlarged to show imbricated microsculpture. 140 mm high; 148 mm wide; 

hinge 77 mm long. SU loc. 1605. CAS 58773, xl.50. 

2, 3. Patinopecten healeyi (Arnold), San Diego Formation, San Diego, Calif.

2. Exterior of left valve enlarged to show imbricated microsculpture. 51.7 

mm high; 52.1 mm wide; hinge 22.9 mm long. LAM loc. 107. LAM 5255, 

x3.

3. Exterior of right valve of largest double-valve specimen seen in any collection showing folded byssus of right auricle and large overlap of left anterior auricle. (Left valve of same specimen figured, pi. 15, fig. 3; hinge 

figured, pi. 13, fig. 2; pi. 15, fig. 2.) 190 mm high; 210 mm wide (broken 

at margins); hinge 95 mm long. LAM loc. 107. LAM 5254, xO.75
GEOLOGICAL SURVEY PROFESSIONAL PAPER 1103 PLATE 14

PA TINOPECTEN YESSOENSIS (JAY) AND PA TINOPECTEN HEALEYI (ARNOLD)
PLATE 15

FIGURE 1. Patinopecten yessoensis (Jay), Holocene, Rijuoku, Japan. Exterior of left 

valve enlarged to show imbricated microsculpture. 140 mm high; 148 

mm wide; hinge 77 mm long. SU loc. 1605. CAS 58774, xl.5 

2, 3. Patinopecten healeyi (Arnold), San Diego Formation, San Diego, Calif.

2. Exterior of hinge of left valve showing fold of anterior auricle. (Same 

specimen illustrated as fig. 3; right valve illustrated, pi. 14, fig. 3.) 

Hinge 95 mm long. LAM loc. 107. LAM 5254, xO.75

3. Exterior of left valve of the largest double-valve specimen seen in any 

collection showing overlap of larger valve along the margins. (Right 

valve of same specimen illustrated, pi. 14, fig. 3.) LAM loc. 107. LAM 

5254. 185 mm high; 205 mm wide; hinge 95 mm long, xO.75.
GEOLOGICAL SURVEY PROFESSIONAL PAPER 1103 PLATE 15

PA TINOPECTEN YESSOENSIS (JAY) AND PATINOPECTEN HEALEYI (ARNOLD)

GPO 689-035