ARCA. 147 



distinct. Length, one inch; height, one inch ; width, seven tenths 

 of an inch. 



Found along the whole coast of Massachusetts, and is one of the 

 most common shells found in fishes. It is a more northern shell, 

 and is found along the coast of Maine, and in the Arctic seas, of 

 a very large size. Grand Manan, large and common {Slinipsoii) ; 

 St. George's Banks, thirty fathoms ( Tufts) ; at Eastport, plentiful 

 (Cooper) ; Labrador {Packard) ; Fishing Banks, and Halifax, 

 common ( Wi/Iis) ; Gulf St. Lawrence (Bell) ; Sandy Hook, one 

 specimen (Cooper) ; Gardiner's Bay, Long Island (S»iUh). 



The shajjc of the shell is much varied by age. In the young the 

 beaks are nearly central, very little elevated, and scarcely recurved ; 

 but the posterior portion, advancing in growth faster than the an- 

 terior, produces the ol)liquity of the old shell. [C. veslita is an 

 elongated, middle-aged variety.] It is closely allied to C. tridentaia, 

 Say, but it grows to a much larger size, is more incquipartite, and 

 has two teeth in the right valve, while that shell has but one. 



Family ARCAD^E. 



Teetpi small, numerous, disposed in a line along the hinge-mar- 

 gin of each valve. 



Genus ARCA, Lix. 1758. 



Shell elongated, beaks separated by a diamond-shaped area for 

 the ligament ; scries of teeth in a straight line. 



Area pexata. 



Fig. 60. 



Shell oblong ; beaks prominent, very oblique ; the ligamentary space very nar- 

 row ; surface with about thirty-two radiating ribs, covered with a shaggy brown 

 epidermis. 



Area pexata, Say, Journ. Acad. Nat. Sc. ii. 268 (1822). — De Kay, Nat. Hist. New York, 

 176, pi. 12, fig. 211. — Philippi, Abbikl. pi. 1, fig. 4. — Stimpson, Shells of New 

 England, 8. — S. Smith, Shells of Long Island, 1.5, and in Ann. N. Y. Lye. vii. 



Argina pexata, Adams, Gen. ii. 540, pi. 125, figs. 7, 7 a. — Chenu, Man. de Conch, ii. 175, 



fig. 87.3. 



Shell thick and heavy, oblong, somewhat ovate ; very incquipar- 

 tite ; the beaks are ventricose and prominent, directed very obliquely 

 forwards, terminating in points which are nearly in contact over the 



