PELECYPODA 593 



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 M'ith papillae: 100 species. 



Key to the species of Cardium here described : 

 fli Shell large. 



6i Occurs north of Cape Cod C. islandicum 



6o Occurs iu the southern states C. magnum 



«2 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. Fig. 934 



. Cardium 



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



(Gould), 

 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. La:viCARDiTJM 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- 



3 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. 



Pig. 935 — L(Evi- 3. Serripes Beck. Shell nearly round, com- 



cardium mortoni i , i j i • ^ i , i • i 



(Gould). 1, liga- pressed, rather thin; umbo nearly central, prominent; 

 siphon; 3, bran- surface smooth or slightly radiated; cardinals and 

 foot. ^^'^ ^^' ' laterals obtuse, almost wanting: 1 species, on both 

 coasts. 

 S. groenlandicus (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. 



