Page:American Seashells (1954).djvu/555

% 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