Fam. 14.] NATURAL HISTORY SOCIETY. 97 



ribs ; cardinal teeth two in each valve ; ligament external, short 

 and prominent ; pallial line entire or with a slight sinus. 



Animal with usually short-fringed siphons ; gills two on each 

 side, thick ; foot long, curved. 



* Shall with distmct radiating ribs Cardium. 



* Without prominent radiating lines Lioeardium. 



1. Cardium, L. 



Shell with prominent radiating ribs. 



Animal with the siphons clothed with tentacular filaments ; 

 incurrent orifice fringed, excurrent with a tubular valve; foot 

 long, sickle-shaped. 



1. Cardium pinnulatum, Con. Shell small, fragile, nearly or- 

 bicular; umbones small, slightly elevated ; surface with about 26 

 rounded, radiating ribs separated by deep, linear grooves ; ribs 

 rendered rough by equidistant, arched scales ; inside with radi- 

 ating grooves. Dingy white ; interior white or flesh colored, 

 sometimes with a posterior, brownish blotch. L. 11 ; H. 10 ; 

 W. 7J; U. |.— New York and north. 



2. Cardium Mandicum, L. Shell large, rather thin, rounded 

 ovate ; umbones rather large, prominent, approximate ; surface 

 with about 36, three sided, sharp-edged, radiating ribs, the fur- 

 rows rounded, and regularly wrinkled by the lines of growth ; 

 inside with radiating grooves. Epidermis of live shells lax, and 

 bristling into a stiff" fringe on the sharp edges of the ribs, yellow- 

 ish-brown color ; straw color within, somewhat pearly. L. 50 ; 

 H. 42 ; W. 25 ; U. i.— Cape Cod and north. Only dead shells 

 rarely thrown upon the beach from deep water. 



3. Cardium magnum, Born. Shell very large, obliquely cordate, 

 ventricose, posterior side somewhat angularly depressed ; surface 

 with about 35 flattened, close set, radiating ribs, the front ones 

 crenulated. Yellowish-brown, painted with transverse rows of 

 purple-brown spots, the depressed posterior area entirely purple 

 brown. L. 100 ; H. 110 ; W. 75 ; U. f ; An. 105°.— Virginia and 

 south, 



2. LlOCARDIUM, Sw. 



Shell oval, elongated, oblique; umbo about central; surface 

 smooth or lightly radiately striate. 



1. Lioeardium Mortoni, Con. Shell thin, inflated, globular; um- 

 bones large and prominent; surface smooth, glossy, with no ribs, 



