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LIBRARY

UNIVERSITY OF CALIFORNIA
DAVIS



MANUAL



OP



ONCHOLOGY;



STRUCTURAL AND SYSTEMATIC.



WITH ILLUSTRATIONS OF THE SPECIES.



BY GEORGE W. TRYON, JR.

CONTINUED BY

HENRY A. PILSBRY.



Vol. XIII.

ACMJEIVAL, LEPETID^, PATELLIDyE, TITISCANIID^E.



PHILADELPHIA :
Published by the Conchologieal Section,

ACADEMY OF NATURAL SCIENCES, COR. igTH AND RACE STS.
1891.



LIBRARY

UNIVERSITY OF CALIFORNIA
DAVIS



In the present volume the important and difficult of group Doco-
glossate Gastropods, the Limpets, is monographed, and in addition a
small group not heretofore included. The material studied in
the families Acmceidce and PatellidcK is exceptionally extensive. A
large number of forms are herein for the first time figured and
adequately described. The value of the work has been enhanced
by the liberality of Dr. W. H. Ball, of Washington, who placed at
the author's disposal for study the magnificent collection of the
Smithsonian Institution, a collection especially rich in species from
the west coast of America, and containing the types of species
described by GOULD, CARPENTER and DALL, many of which have
not before been figured. No effort has been spared to make the
synonymy and references complete and reliable ; and it is hoped
that conchologists will find the labor of classifying their collections
of these intricate groups decidedly lightened.

Philadelphia, June, 1891. H. A. P.



MANUAL OF CONCHOLOGY.



Monographs of the Acmceidce, Lepetidce, Patellidce and Titiscaniidce.



Family A CMjEID^E Cpr.

Acmceidce CPR., Maz. Cat. p. 202, 1856. Tecturidce GRAY and
authors. Lottiadce GRAY. Patellidce, in part, of authors.

Shell patelliform, conical, the apex more or less anterior, the
embryonic shell conical, not spiral. Animal having a free branchial
plume above the neck on the left side ; radula without median teeth.

Animals of this family differ mainly from the Patellidce and Lep-
etidce in having a cervical branchial plume.

The shells may generally be known from Patellidce by their dif-
ferent texture and the more or less distinct internal border of the
aperture. They are never iridescent within.

They live on rocks and sea weeds, generally at very moderate
depths. One species, Acmcea fluviatilis, is known to inhabit brackish
water, and a few, like Pectinodonta arcuata, are abyssal.

The shells are excessively variable, as is usually the casein seden-
tary mollusks.

The author has examined very large suites of specimens, including
nearly every species and variety described from the waters of North
and South America, both east and west, and of Japan, Polynesia and
Europe. The Australian and New Zealand forms are known to me
by fewer specimens, and a number of the species of those regions I
have not seen.

In the treatment of species I have aimed to be strictly conserva-
tive, reducing no described form to a variety or synonym without
the most ample evidence of identity or intergradation of characters ;
and on the other hand, I have refrained from burdening science
with new names for the vast number of transitional or divergent
forms in the collections examined.

No characters diagnostic of the genera of Acmseidse can be found
in the shells.

(5)



6 PECTINODONTA.

Synopsis of genera.

I. Radula with a single lateral tooth on each side ; no uncini,

PECTINODONTIN^E.

Genus PECTINODONTA Ball, 1882.

Animal blind; having a cervical branchial plume but no
branchial cordon.

II. Radula having three lateral teeth on each side, ACM^EIN^E.

Genus ACM^EA Eschscholtz, 1830.

Animal having a cervical branchial plume but no branchial cor-
don ; eyes present.

Genus SCURRIA Gray, 1847.

Animal having a cervical branchial plume and a complete or
interrupted branchial cordon.



Subfamily PECTINODONTIN^E.
Genus PECTINODONTA Dull, 1882.

Pectinodonta DALL, Proc. U. S. Nat. Mus. 1881, p. 409, 1882;
Blake Gastrop. p 411.

Shell resembling Scutellina but with a blunt subcentral apex.
Soft parts resembling Acmsea except in the following details : Ani-
mal blind, with the front part of the head between the tentacles and
above the muzzle much produced upward and forward, extending
considerably farther forward than the end of the muzzle, which is
marginated with lappets at the outer corners. Jaw thin, translu-
cent. Gill exactly as in Acmsea; sides of foot and mantle edge
simple, nearly smooth. Dental formula (1.0.1.) 0; teeth large,
with transverse pectinated or denticulated cusps, the serrated edge of
which is turned toward the median line. The number of teeth is
the smallest in any known limpet. (Dall.)

The dentition is figured on pi. 33, fig. 74.

P. ARCUATA Dall. PI. 33, figs. 74, 75, 76.

Shell white, elongate-ovate, moderately elevated, with a blunt
polished apex, on which in young specimens, remain traces of the
disk-like, chalky, embryonic shell ; the slopes from the apex to the
ends both convexly arched ; margin simple or slightly denticulated
by the radiating sculpture ; within polished ; scars as in Acmsea ;



ACM^EA. 7

epidermis none ; sculpture externally of fine, uniform, rounded,
closely set threads, radiating from near the apex to the margin and
reticulated by the fine, rather prominent, regular, concentric ridges
of growth, both ridges and threads averaging near the margin about
three and a half to the millimeter. Length., from end to end, 14'5
mm. ; from apex to anterior end 5*5 mrn. ; lat. 10*0 mm. ; alt. 5'5 mm.
(Dall}

Off St. Lucia, 226 fms. ; off Dominica, 333 fms. ; off Guadelupe,
583 fms.; and off St. Thomas.

P. arcuata BALL, Proc. IT. S. Nat. Mus. 1881, p. 409, 1882 ; Blake
Rep. p. 411, t. 25, f. 3, 3a, 3b.

Subfamily ACM^EIN^E.

Genus ACM^EA Eschscholtz, 1830.

Acmcea ESCH., in append. Kotzebue's Neue Reise, ii, p. 24, 1830,
type A. mitra Esch. FORBES & HANLEY, Brit. Moll., ii, p. 433.
CPU., Mazat. Catal. p. 202. DALL, Amer. Journ. Conch, vi, p.
237. WATSON, Challenger Gastr. p. 28. FISCHER, Manuel, p.
865. Tecture AUD. & MILNE-EDW., in Cuvier's Rapport sur trois
Mmoires, etc., Annales des Sci. Nat. xxi, 1830, p. 326, published
not before 1831, type P. virginea. Tectura of GRAY, H. & A.
ADAMS, JEFFREYS, et al. Patelloidea QUOY & GAIMARD, Voy.
Astrol. iii, p. 349. Type P. fragilis (Chemn.) Q. & G., 1834.
Lottia GRAY, in pare, Philos. Trans. 1833, p. 800. Lottia of GOULD,
et al. Erginus JEFFREYS. Ann. Mag. N. H. 4th ser., xix, p. 231,
March, 1877. Type Tectura rubella Fabr. Collisella DALL, Amer.
Journ. Conch, vi, p. 245, 1871. Type A. pelta Esch. Collisellina
DALL, I. c., p. 154, type A. saccharina. L.

Shell conical, patelliform, apex more or less anterior. Animal
with a branchial plume at the left side of the neck above; no
branchial cordon. Dentition, see below.

The shells may generally be distinguished from Patella by the
different texture and marginal border of the inside.

The thorough discussion of the generic name of this group con-
tained in the various papers of Dr. Dall and others, renders any
justification of the view of its nomenclature here taken, unnecessary.

Tectura and Erginus must be regarded as absolute synonyms of
Acmcea s. sir. ; Patelloidea Q. & G. will probably be found to differ
somewhat anatomically, and may then be utilized for a subgeneric
group. The subgenera Collisella and Collisellina are defined below.



8 ACM^EA.

Species of the genus Acmsea are found in the littoral and lamin-
arian zones of nearly all seas, except the waters adjacent to the con-
tinent of Africa.

The shells are subject to even greater mutations than the Patel-
lidse, and species are correspondingly difficult to define and limit.
More than any other shells, these must be studied with constant
reference to not only habitat geographically, but station as well.
For an exact knowledge of the group we must therefore wait until
observations on the species are made with especial reference to their
modes of life and surroundings. Such data should be attached to
every limpet collected.

Acmcea has been divided by Dr. W. H. Dall into a number of
groups which may be tabulated as follows :

A. Muzzle with lappets ; no uncini ; formula of teeth (3.0.3) 0,

Acmcea s.s.

B. Muzzle without lappets, uncini present, Collisella Dall.

a. formula of teeth 1 (3.0.3) 1 Collisella s.s.

b. formula of teeth 2 (3.0.3) 2 Collisellina Dall.
The type of Acmcea is A. mitra Esch., dentition pi. 42, fig. 82 ; of

Collisella, A. pelta Esch., dentition pi. 42, fig. 8J ; and the type
of Collisellina is A. saccharin a L., dentition pi. 42, fig. 83.

It is practically impossible at present to group the species of the
entire world according to anatomical characters, or to decide to what
extent these divisions will prove applicable to the entire series.

The most convenient and in most cases the most natural division
of the genus is geographic. Thus considered, the species fall into
six groups :

I. North Atlantic and Arctic.

II. Western coast of North America.

III. Western coast of South America.

IV. West Indies.

V. Japan.

VI. Indo-Pacific.

(VII. Species of unknown habitat.)

Of these groups, the second has great affinity to the first and fifth ;
the fourth may be regarded as derived from the second during the
early tertiary period.

I. SPECIES OF EUROPEAN SEAS AND THE NORTH ATLANTIC.

Many specimens of all of the species of this region have been
examined by me.



ACM^EA. 9

A. RUBELLA Fabricius. PL 42, figs. 79, 80.

Shell small, rounded-oval, conical, apex elevated, situated at the
anterior fourth of the shell's length ; front slope steep, straight or
concave, posterior slope convex. Surface smooth, showing faint
lines of growth. Color reddish-buff or orange ; inside of the same
color, the border flesh-colored. Length 5, breadth 4, alt. 2| mill.

Finmark, Norway ; Greenland, 5-40 fms.

Patella rubella FABR,, Fauna Gronl., p. 386, 1780. Tectura
(Erginus) rubella JEFFREYS, Ann. Mag. N. H., Mar., 1877, xxi,
p. 231. SARS, Moll. Arct. Norv. p. 121, t. 8, f. 5 ; t. ii, f. 11
(dentition), 1878. Pilidium fulvwn, in part, DALL, Am. Journ.
Conch, v, 1869. Acmcea rubella DALL, Proc. U. S. Nat. Mus.
1879, p. 337.

This little shell is of a more erectly conical form than Pilidium
fulvum, and lacks radiating sculpture. It is smaller than A. vir-
ginea and not radiately painted, besides having the summit more
anterior and more elevated. The specimens before me are from
Greenland. It has been reported from the New England coast, but
I am not sure of the correctness of the determination.

A. VIRGINEA Miiller. PL 10, fig. 13, 14.

Shell small, oval, conical ; apex at or a little back of the anterior
fifth of the shell's length. Surface having delicate, almost obsolete
radiating striae and delicate growth lines. Color a delicate pink, with
numerous (about 13) pink rays. Upper part of the cone buffish-
white.

Inside pink or white, center flesh-colored or opaque white.

Length 9-10, breadth 6|-9, alt. 31-4 mill.

Mediterranean and Adriatic Seas ; Atlantic from Nonvay and Ice-
land to the Canaries, Azores and Cape Verde Is., low water to 60 fms.

Patella virginea MULL., Zool. Dan. Prodr. i, p. 43, 1776. GMEL.,
Syst. Nat. xiii, p. 3711. Acmcea virginea HANLEY, Br. Mar. Conch,
p. 32, 1844. FORBES & HANLEY, Hist. Brit. Moll, ii, p. 437, t. 61,
f. 1, 2. DALL, Am. Journ. Conch, vi, p. 243, 1871. BUQUOY,
DAUTZ, & DOLLF., Moll, du Rouss. p. 478, t. 51, f. 12, 13. Tectura
virginea JEFFR., Brit. Conch, iii, p. 248 ; v, p. 200, t. 58, f. 4.
SARS, Moll. Reg. Arct. Norv. p. 121, t. ii, f. 10 (dentition). Patella
parva DA COSTA, Brit. Conch, p. 7. t. 8, f. 11, 1778, of DONOVAN
and MONTAGU. Lottia unicolor FORBES, Rep. JEg. Invert, pp. ] 35,
188,1844. L. pulchella FORBES, I. c., p. 137. Lottia pellucida



10 ACMJEA.

WKINKAUFF (not Linne) Journ. de Conchyl. x, p. 334, 1862.
Patelloidea virginea COLBEAU, Moll. viv. de la Belg., p. 14. Patella
cequalis Sow., Min. Conch, t. 139. Patella astensis BONELLI.

A small and delicate species, pink rayed on a pale ground. It is
widely distributed in European seas. The following mutations
have received names:

Form cornea Jeffr. Smaller than the type, more conical, summit
more elevated, nearly central. This form is figured by Wood,
Crag Moll. pi. 18, f. 60.

Form rotundata Monts. More rounded than the type.

Form depressa Wood. Crag Moll. pi. 18, f. GA.

Form unicolor Forbes. Of a uniform rosy color, without rays ;
small.

Form lactea Jeffr. Milky-white.

A. TESTUDINALIS Muller. PI. 9, figs. 25, 26, 27, 28, 29.

Shell conical, oval, the apex a little in front of the middle ; pos-
terior slope slightly convex, other slopes straight ; surface more or
less distinctly, finely radiately striated ; color yellowish-gray, with
numerous blackish-brown stripes, generally broken into a coarse
network, or tessellated pattern.

Inside white, with a large dark brown central area, the border
tessellated brown and white. Length 38, breadth 28, alt. 13 mill.

North Atlantic and Arctic Oceans, southeast to the English Channel,
southwest to Long Island Sound; North Pacific from Sitka (and
Yesso f) to the Arctic Ocean.

Patella testudinalis MULL., Prodr. Zool. Dan. p. 237, 1766.
REEVE, Conch. Icon. f. 70. Tectura testudinalis JEFFREYS, Brit.
Conch, iii, p. 246 ; v, p. 200, t. 58, f. 3. OLD., Invert, of Mass.,
Binney's edit., p. 267, f. 529. Acmasa testudinalis FORBES & HAN-
LEY, Hist. Brit. Sh. ii,' p. 434, t. 62, f. 8, 9 ; t. AA, f. 2 (animal).
DALL., Amer. Journ. Conch, vi, p. 249, t. 14, f. 13 (dentition) ;
Proc. U. S. Nat. Mus. 1878, p. 339. SARS, Moll. Reg. Arct. Norv.
p. 120, t. ii. f. 9 (dentition). Lottia testudinalis FORBES, Malac.
Monensis p. 34. GLD., Invert, of Mass., 1st edit., p. 153, f. 12.-
Patella testudinaria and P. tessellata MULL. P. clealandi SOWB.,
Trans. Linn. Soc. xi, p. 621. P. amcena SAY, Journ. Acad. N. S.
Phila. ii, p. 223. DE KAY, N. Y. Moll. p. 162, t. 9, f. 196. P. cly-
peus BROWN, 111. Conch. Gt. Br. t. 37, f. 9, 10. Patella alveus CON-
RAD, Journ. Acad. N. S. Phila. vi, p. 267, t. 11, f. 20, 1831. Patel-



ACM.EA. 11

loidea alveus COUTH., Best. Journ. N. H, ii, p. 177. Lottia alveus
GLD., Inv. of Mass., p. 154, f. 13. lectura alveus BINNEY in
GOULD, Inv. of Mass., 2d edit., p. 269, f. 530. Acmcea testudinalis
var. alveus DALL, Proc. U. S. Nat. Mus. 1878, p. 340.

Atlantic specimens of this well-known shell, although very vari-
able in size and coloration, are readily distinguished from the other
forms, the only considerable divergence being found in var. alveus.
Specimens from the Aleutian Is., according to Dr. Dall, completely
bridge the gap between testudinalis and patina. I have retained
the latter separate, simply as a matter of convenience ; but I do not
doubt that it must be regarded as a geographic race of testudinalis.

American specimens are generally larger than European ; figs.
27-29 represent specimens from Maine, figs. 25, 26 from England.

Var. ALVEUS Conrad. PI. 42, figs. 90, 91.

Small, thin, compressed at the sides; apex acute and a little
hooked forward. Surface delicately striated, interruptedly striped
or tessellated with brown. Inside showing the markings of the
exterior.

Massachusetts to Arctic Ocean ; Sitka northward.

Numerous transitions occur between this and typical testudinalis.
The narrow form is caused by the residence of individuals on sea-
weed or Zostera fronds.

** *
II. SPECIES OF THE WESTERN COAST OF NORTH AMERICA.

The author has examined specimens of all of the species of this
region, including many original types. Of most species many
hundreds of shells have been studied. The elaborate papers of
Dr. P. P. Carpenter, and of Dr. Win. H. Dall have been freely
used.

A. PATINA Eschscholtz. PL 2, figs. 34, 35, 36, 37 ; pi. 9. figs. 6-14.

Shell large, oval or rounded-oval, depressed-conic, the apex
rounded and near the middle; slopes slightly convex. Surface
obsoletely radiately striated, olive-gray, tessellated, or more rarely
striped, with black.

Inside white with an irregular brown central area and a rather
wide dark or tessellated border. Length 53, breadth 46, alt. 18 mill.

Aleutian Is. to San Diego, California.



12 ACM^EA.

A. patina ESCH., Zool. Atlas, edit. Rathke., p. 19, t. 24, f. 7, 8.
MIDD., Sib. Reise, p. 187, t. 16, f. la-d, 2a-c, 3. CPU., Mazat. Cat.
p. 207; Araer. Journ. Conch, ii, p. 333. A. scutum ESCH., not
Orb. P. mammillata NUTT., Jay's Catal. no. 2839. RVE., Conch.
Icon f. 140. P. tessellata NUTT., Jay's Cat. no. 2885. P.fenestrata
NUTT., Rve. Conch. Icon. f. 121. P. verrieulata RVE., I. c., f. 87.
P.nuttalliana, RVE., /. c., f. 81. P. cumingii RVE., 1. c., f. 37. Lot-
tiapintadina GOULD, U. S. Expl. Exped. t. 29, f. 455. Collisella
patina DALL, Amer. Journ. Conch, vi, p. 247, 1. 14, f. 4 (dentition).
A. testudmalis var. patina DALL, Proc. U. S. Nat. Mus. i, p. 340.

P. cinis Rv., considered a synonym of patina by Cpr., belongs to
A.pelta. P. strigillata Nutt. mss. is a form of fascicularis, judging
from the suite deposited by Nuttall in the Academy collection.

This is the commonest of all western limpets. Although it has
been shown to intergrade with A. testudmalis on the Alaskan coast,
yet I cannot rank it as a variety of that species in the sense in
which alveus is a variety. It is thoroughly differentiated from testu-
dinalis throughout most of its range. The two forms vary in quite
diverse directions, patina having no form corresponding to the var.
alveus of testudmalis, but having its own peculiar mutations, not
found in the other species.

It would be an advantage if we were to use the term " form "
(forma) for such mutations as alveus, nacelloides, etc., reserving the
rank of "variety" for true geographic subspecies.

The principle mutations of A. patina are as follows:

Var. PINTADINA Gld. (pi. 9, fig. 6). Large, flat, open, apex
subcentral ; tessellated white and dark. P. cumingii Rv. (pi. 42,
fig. 87) and tessellata Nutt. belong here as synonyms. This form
passes into the striped form nuttalliana Rve. (pi. 2, figs. 32, 33, and
also f. 36, 37). The last figures correspond to Reeve's verrieulata.

Another mutation is the form fenestrata Nutt. (pi. 9, figs. 10, 11,
12, 13, 14), of which eribraria Gld. mss. is a synonym. This shell
when young is dark olive closely dotted all over with white, the
eroded apex black ; when adult it is usually uniform dull slate-color
outside with a ring of light around the black apical spot ; inside it
has a wide dark border, a large, irregular central dark patch', and
generally is suffused with dark brown all over. Sculpture obsolete.
This form is from San Francisco, Santa Cruz, etc.

Var. OCHRACEA Dall (pi. 9, figs. 7, 8, 9). Externally of a very
light yellowish-brown, without spots or rays ; internally white with



ACM^EA. 13

the characteristic dark brown stain of patina in the visceral area.
The exterior is covered with fine, regularly radiating, close, equal,
thread-like riblets, which pass from apex to margin without bifur-
cation, imbrication or asperities of any kind. These riblets will
serve to distinguish it from any of the other limpets of the coast ;
otherwise it approaches very close to some varieties of scabra and
can be traced right into some varieties of patina. (Dall.)

This variety was described from Monterey, Cal. ; it has also been
found on Vancouver Id.

A. DALLIANA Pilsbry. PI. 7, figs. 57, 58, 59, 60.

Shell large, oblong, depressed, rather thin. Apex low, curving
forward ; length of front slope contained about 3? times in the
length of the shell ; posterior slope gently convex. Surface covered
with close, slightly unequal radiating riblets, each rendered rasp-like
by very close, regular and erect delicate lamellae ; interstices narrow,
having growth-strise but no lamellae.

The color is chestnut-brown, becoming dark umber in places,
having short streaks and spots of white, forming a sparse tessellation.
Inside light blue, with a small brown spot at the cavity of apex,
and showing the color-pattern of the outside faintly through. Bor-
der wide, deep brown with white spots.

Length 46, breadth 32, alt. 6i mill.

Angel Island, Porto Refugio, Gulf of California.

This is one of the finest American Acmceas. The oblong, some-
what parallel-sided and depressed contour, thin texture, and the
beautifully sharp and regular lile-like sculpture of the low, close
riblets, are its prominent features. It is allied to A. scabra, but the
enormous number of specimens of that species which I have exam-
ined in the Philadelphia and Washington collections, furnish no
forms leading toward the Dalliana. The species is named in honor
of Dr. Wm. H. Dall, who outlined the classification of the Acma3-
idse in essentially its modern form, twenty years ago.

A. SCABRA Reeve. P 1 . 3, figs. 38-49.

Shell thin, rounded-oval, depressed ; apex situated between the
center and the anterior third ; surface sculptured with close, fine,
minutely scaly riblets, of which larger ones are placed at regular
intervals. Color light yellow, indistinctly spotted (rarely striped in
divaricating pattern) with brown.



14 , ACM^EA.

Interior porcelain-white or blue-tinted, with sometimes a few faint
spots of brown in the cavity. Inside border transparent-yellowish
or showing faint brown markings.

Length 37, breadth 31, alt. 7-8 mill.

Vancouver's Island to Acapulco, western Mexico.

Patella scabra Rv., Conch. Icon. f. 119. Acmcea scabra CPU.,
Am. Journ. Conch, ii, p. 340. Collisella scabra DALL, /. c., vi, p.
251, t. 14, f. 12, 12a (dentition). Acmcea (scabra var.?) morchii
DALL, Proc. U. S. Nat. Mus. 1878, p. 47.

The typical form is easy to recognize by its light coloration and
the fine rasp-like riblets of the surface. Forms in which the outer
layer of the shell is deep brown instead of buff, and the inside bor-
der consequently blackish, are quite similar to some variations of
A. patina ; but sculpture and color-pattern will usually permit one
to separate them readily.

Two forms have been described :

Var. LIMATULA Cpr. PL 3, figs. 38, 39, 40.

Outer layer of the shell black, covered with an olive-green, or
sometimes light bluish, epidermis ; inside border black ; a deep
brown central spot. Distribution mainly southern, San Diego to
Acapulco.

A very beautiful color-pattern is shown in figs 45, 46, drawn from
San Diego specimens. White rays alternate with dark olive.

As an extreme form of this variety, Var. MORCHII of Dall (pi. 3,
figs. 47, 48, 49), must be ranked. It is typically much elevated, the
apex subcentral and curved forward, sculpture coarse. Otherwise
like var. limatula. Locality, Tomales Bay, Lower California. The
large suite of shells before me from Tomales Bay show every inter-
mediate stage between the high, cap-shaped forms and the normal
limatula. The former constitute a peculiar phase of development
attained by comparatively few individuals. Figures 47-49 are
drawn from Tomales Bay specimens.

A. SPECTRUM Reeve. PI. 1, figs. 7, 8, 9.

Apex rather anterior ; slopes rather straight ; sculptured with
very strong close rough ribs, with smaller intervening riblets ; cen-
ter of the inside white, with dark spots and bars.

Normally it is solid, rather depressed, with from 20-30 very
strong, rounded ribs not evanescent anteriorly, the interstices being
occupied by intercalary riblets. The color is white, with fine lines



ACM^A. 15

of brown (not striped as in pelta and persona) between the principal
ribs, which delicately dot the otherwise uniform white margin.
Sometimes the principal ribs are rather sharp, palmating the margin,
occasionally they are small and crowded, becoming faint at the mar-
gin, when the shell presents the internal aspect of A. mitella; at
other times assuming that of Patella pediculus.. Generally the apex
is at the anterior third ; rarely at the anterior fourth, with very
elongated outline ; but sometimes is nearly central, with a rounded
shell. In this species also there is occasionally found a var. iextilis;
when the ribs become faint and distant, the color-lines run into net-
work, and the shell is of a thinner texture. The young is extremely
inequilateral, and rapidly developes the characteristic ribs. Inside
the shell has a white callus, through which the dark irregular blotch
appears. This occasionally takes the form of irregular ghostly bars,
which gave the name to the species. ( Cpr.)
Length 34, breadth 24, alt. 12 mill.

Bodega Bay and San Francisco south to Lower California.

Patella spectrum Rv., Conch. Icon. f. 76. Acmcea spectrum CPU.,
Amer. Journ. Conch, ii, p. 339. Collisella spectrum DALL, Amer.


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