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CORBULIDAE 457
% of an inch in length, % as high, moderately thin-shelled and glossy.
Beaks high, curled under and pointing anteriorly. Right valve subtrigonal
in shape, very obese and with strong, concentric ridges. Left valve more
elongate, smaller, less obese and with numerous but weaker ridges. Color
white, but some may be tinted with rose near the margins. Uncommonly
dredged from 12 to 250 fathoms. Live specimens very rare. This is C. dis-
parilis of authors.
Genus Corbula Bruguiere 1792
Small, thick shells characterized by one valve (commonly the right)
being larger than the other. Posterior end commonly rostrate. Resilium
and ligament internal. The genus Aloidis Aliihlfeld was in current use until
recently.
Corhila contracta Say Contracted Corbula
Cape Cod to Florida and the West Indies.
^4 inch in length, oblong, moderately to strongly obese. Both valves
about the same size, except that the posterior, ventral margin of the right
valve overlaps that of the left. The numerous, poorly defined, concentric
ridges on the outside of the valves extend over the posterior, radial ridge on
to the posterior slope. The left valve has a V-shaped notch in the hinge
just anterior to the beak. Color dirty-gray. A common shallow-water
species.
Corbula dietziana C. B. Adams Dietz's Corbula
North Carohna to southeast Florida and the West Indies.
% to ^ inch in length, like contracta, but larger, thicker-shelled and
pinkish inside. The ventral margins are blushed or rayed with carmine-rose.
Microscopic threads numerous between the few coarse, concentric ridges.
Compare with the smaller and more comprecsed barrattiana. Commonly
dredged offshore in the Miami region.
Corbula nasuta Say Snub-nose Corbula
North Carolina to both sides of Florida and the West Indies.
%6 to % inch in length, oblong, obese and strongly rostrate at the pos-
terior end. The posterior end looks as if it had been severely pinched. Right
valve considerably larger than the left. Margins of valves with a thick border