PELECYPODA 



593 



Fig. 934 



Cardium 



pinnulatum 



(Gould). 



near the center of the shell ; siphons very short, and separate ; 1 or 2 car- 

 dinals, 1 or 2 posterior laterals and 2 anterior laterals in the right valve, 

 and 2 cardinals, 1 anterior and 1 posterior lateral in the left valve; 

 mantle margin with papillae : 100 species. 



Key to the species of Cardium here described: 



! Shell large. 



6j Occurs north of Cape Cod C. ISLANDICUM 



6 2 Occurs in the southern states C. MAGNUM 



a a Shell small C. PINNULATUM 



C. islandicum L. Shell large, rounded, with about 36 ribs sepa- 

 rated by deep grooves, and with concentric lines of growth; periostracum 

 yellowish-brown, forming a stiff fringe on the edges of the 

 ribs, but often absent in the dead shell; length 5 cm.; 

 height somewhat less; width 25 mm.: circumpolar, south 

 to Cape Cod and Puget Sound, in 5 to 50 fathoms; 

 Europe. 



C. pinnulatum Conrad (Fig. 934). Shell round, small, 

 thin, with about 26 ribs with a row of arched scales on 

 each, inside with furrows corresponding to the ribs; length 11 mm.; 

 height 10 mm.; width 7.5 mm.; color white, interior white or pink: 

 Cape Cod to Labrador, in 1 to 200 fathoms. 



C. magnum Born. Shell large, with about 35 ribs; color yellowish- 

 brown, with transverse rows of brown spots; length 10 cm.; height 

 11 cm.; width 75 mm.: Virginia to Texas, in shallow water; West 

 Indies. 



2. LJEVICARDITTM Swainson. Shell oval, oblique; umbo nearly cen- 

 tral, surface smooth or with slight radial striations : 20 species. 



L. mortoni (Conrad) (Fig. 935). Shell small, thin, 

 globular, pale fawn color sometimes with brown spots, 

 within bright yellow, with a purplish blotch pos- 

 terially; surface smooth, without ribs; length 25 mm.; 

 height 22 mm.; width 17 mm.: Nova Scotia to west 

 coast of Florida, in shallow water; very common south 

 of Cape Cod on sandy flats. 



3. SERRIPES Beck. Shell nearly round, com- 

 pressed, rather thin; umbo nearly central, prominent; 

 surface smooth or slightly radiated; cardinals and 

 laterals obtuse, almost wanting: 1 species, on both 

 coasts. 



S. grcenlandicus (Gmelin). Shell 70 mm. long, 55 mm. high, and 

 30 mm. wide; white or drab in color; margin slightly crenulated; foot 

 serrated : circumpolar, south to Cape Cod and Puget Sound, 



cardium mortoni 

 (Gould). 1, liga- 

 ment ; 2, cloacal 

 siphon ; 3, bran- 

 chial siphon ; 4, 

 foot. 



