Fam. 9.] NATURAL HISTORY SOCIETY. 93 



ribs or lines ; hinge with about two cardinal teeth in each valve ; 

 pallial line entire ; ligament external, strong. Animal with 

 mantle-lobes free except at the siphonal end ; gills rounded in 

 front, tapering behind and united together. 

 1. Venericardia, Lam. 



Shell suborbicular, radiately ribbed and covered by a rough 

 -epidermis; hinge with two robust teeth in the left valve, and 

 one in the right. 



1. Venericardia borealis, Con. Shell thick and strong, rounded 

 or somewhat heart shaped; umbones projecting well in front in 

 old shells, the rest of the shell evenly rounded ; surface raised 

 into about 20, rounded, radiating ribs, which are broader than 

 the grooves between them ; the ribs are roughened by coarse lines 

 of growth ; lunule rhomboidal, deep ; ligament small and sunken; 

 interior margin strongly crenulated. Epidermis strong, rusty 

 brown; interior white. L. 25; H. 25 ; W. 17 ; U.J. — Whole 

 extent. 



Var novangli^, Morse. A smaller more elongated and thin- 

 ner shell, the umbones not so projecting nor so far in front, 

 and the hinge plate much narrower ; the radiating ribs are about 

 17 in number. L. 21 ; H. 16 ; W. 14 ; U. J.— New England. 

 Family 9. ASTARTID£. 



Shell neaily as in the preceeding family except that there 

 are no radiating ribs, but the shell is either smooth or concen- 

 trically striated or furrowed. Animal with a moderate, tongue- 

 shaped foot ; lips large, palpi lanceolate ; gills nearly equal. 

 1. Astarte, J. Sowb. 



Shell suborbicular, compressed, thick, smooth or concentrically 

 furrowed; lunule impressed; ligament external; hinge teeth 

 strong, about 2 in each valve ; epidermis dark. 



Animal with mantle open ; margins plain or slightly fringed ; 

 siphonal openings simple ; foot moderate, tongue-shaped. 



1. Astarte undata, Gld. Shell thick, ovate-triangular, some- 

 what compressed ; anterior end shorter, concave, and with a 

 deep, smooth, lanceolate lunule; a still longer, lunule shaped 

 excavation found back of the umbones ; umbones in contact, 

 obtuse; surface covered with from 15-25, strongly developed 

 furrows and ridges ; the furrows a little wider than the ridges ; 



