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 ( Sfimpson) ; 

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

 (^Cooper} ; Labrador {Packard} ; Fishing Banks, and Halifax, 

 common ( Willis) ; Gulf St. Lawrence {Bell) ; Sandy Hook, one 

 specimen {Cooper) ; Gardiner's Bay, Long Island {Smith). 



The shape 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. tridentata, 

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

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



Family ARCADE. 



Teeth 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 ; series 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. — riiiLippi, Abhilil. pi. I, fig. 4. — Stimpsox. Shells of New 

 England, 8. — S. Smith, Shell- of Lonijc Island, I.t, and in Ann. N. Y. Lye. vii. 



Argina pexata, Adams, Gen. ii. 540, pi. 125, figs. 1,1a. — Chenu, Man. de Conch, ii. 175, 

 fig. 873. 



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

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

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



