The Thick-Shelled Hearts - Family Crassatellidae

THE THICK-SHELLED HEARTS - FAMILY CRASSATELLIDAE.

Shell bivalve, oblong, posterior end produced; sculpture consists of concentric grooves; epidermis thick; hinge with few cardinal teeth; pit on each valve.

Genus CRASSATELLA, Lam.

Shell with thick, solid valves, ventricose; ligament internal; lunule distinct; epidermis dense, brown. Chiefly distributed in tropical regions; but few fossils found in the United States.

The West Indian Crassatella (C. Antillarum, Rve.) has a three-cornered outline, though the angles are found only at the umbones and at the limits of the narrow posterior area. The ventral and anterior margins are rounded. The brown surface is regularly grooved. The lining is stained with chocolate, except at the borders. Length, 4 to 5 inches.

C. Floridana,

DaII, replaces the last species from Cape Hatteras to Florida. Length, 2 to 3 inches.

The Chestnut Crassatella (C. castanea, Rye.) wears a bright horny coat of epidermis of a rich chestnut brown. It is characteristic of this covering to be worn off at the umbones, ex posing the paler brown or white shell. Brown also stains the lining. The outline is oval, drawn out posteriorly a little. Length, 5 inches.

Habitat.— New Holland.

C. marginata,

Cpr., yellow, with brown dots, or chevrons, and scarcely as large as a pea, is found on the coasts of southern California.

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