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CARDIIDAE 399
I to 2 inches in size, squarish in outline, thick, inflated, with 33 to 36
strong radial ribs which are covered with close-set, chevron-shaped plates.
External color whitish with mottlings of reddish brown. Interior usually
white, or may be flushed with orange, rose-brown or purple. The posterior
slope is pushed in somewhat and is slightly concave. A relatively common
species found in shallow to moderately deep water.
The Western Strawberry Cockle, T. biangiilata Sowerby, is the Cali-
fornian counterpart of the above species. It is iVi inches in length, with
about 30 strong ribs; exterior yellowish white, interior reddish purple.
Moderately common.
Subjavnly PROTOCARDIINAE
Genus Nemocardium Meek 1876
Nemocardhnn centifilomin Carpenter Hundred-lined Cockle
Alaska to Lower California.
% to % inch in length, almost circular; posterior third of shell with
cancellate sculpturing and separated from the finely ribbed anterior two
thirds of the shell by a single raised rib. Edge minutely serrate. Exterior
with gray, greenish gray or brownish gray, thin, fuzzy periostracum. Interior
dull-white. Fairly common.
Genus Microcardiwn Thiele 1934
Microcardiwn peramabile Dall Eastern Micro-cockle
Rhode Island to southeast Florida and the West Indies.
% to % inch in length, thin, inflated, subquadrate, white, but may be
mottled tan on the anterior slope. Sculpture prominent on the posterior
third of the valve. It consists of about 90 closely packed, radial ribs (spinose
posteriorly) which are crossed by minute concentric threads. The anterior
two thirds is separated from the rest of the shell by a single, crested, spinose,
radial rib. Very commonly dredged off eastern Florida.
Microcardium tinctu?n Dall, found with the above species, is % inch
in length, stained with rose-red and has more than 150 minute, radial ribs.
Uncommon.
Siibjainily LAEVICARDIINAE
Genus Laevicardimn Swainson 1840
Laevicardium laevigatum Linne Common Egg Cockle
North Carolina to both sides of Florida and the West Indies.
Plate 39k