CHAPTER XXI: THE THICK-SHELLED HEARTS 



Family Crassatellid^ 



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, Aniillarum, 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, Dall, replaces the last species from Cape 

 Hatteras to Florida. Length, 2 to 3 inches. 



The Chestnut Crassatella (C casianea, Rve.) 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. Theoutlineisoval,drawnout posteriorly a little. Length, 

 5 inches. 



Hahitat. — 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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