128 CYPRINID^. 



Shell small, solid, ovate-triangular or broad kidney-shaped, the an- 

 terior portion being somewhat recurved ; beaks acute and elevated, 

 close upon each other, placed at the posterior third ; posterior mar- 

 gin convex and sweeping regularly into the ventral mar- 

 ^'^' '^ ' gin, which is semicircular ; anterior margin concave, but, 

 passing into the ventral margin, forms a well-rounded end, 

 so that the anterior portion is considerably less elevated 

 ^- ^"^^^'"^' than the posterior ; lunule narrow, elongated, shallow ; 

 surface smooth with the exception of fine incremental 

 strias, which under a magnifier appear rather coarse and broken ; 

 epidermis yellowish-brown ; interior smooth, dark-brown, inclining 

 to chocolate color. Hinge-margin thin, the posterior margin of the 

 left valve being sharp a little behind the beak, and received into a 

 corresponding groove in the right valve ; margins internally simjile. 

 Length, two fifths of an inch ; height, nine twentieths of an inch ; 

 breadth, one fifth of an inch. 



A single specimen was found in the stomach of a haddock, by Dr. 

 Mighels, in 1842. 



Genus GOULDIA, C. B. Adams. 1851. 



Shell equivalve, trigonal or sub-trigonal, with concentric ridges 

 or plates ; lunule distinct ; two cardinal teeth on one valve and only 

 one on the other ; two anterior marginal teeth on each valve ; pal- 

 lial impression simple or very slightly sinuate. 



Gouldia mactracea. 



Shell small, quadrant-shaped, anterior margin excavated, surface with fine con- 

 centric waves, and minute radiating lines between them. 



Astarte mactracea, Lii^SLET, Catal. Shells of Connecticut, in Sillim. Jouvn. xlviii. (name 

 only). — Gould, in Sillim. Journ. Sc. (Sept. 1848) 233. 



Shell small and solid, nearly quadrant-shaped ; the apex acute, 



somewhat behind the centre, with a divergence of the anterior 



and posterior marginal slopes of nearly a right angle, 



the posterior and ventral margins regularly curved, while 



the anterior margin is nearly a right line (rather con- 

 Ct. mac- cave), so as to form an obtuse angle when it joins the ven- 

 tral margin ; lunule long and deeply excavated. The sur- 

 face is undulated with about fourteen concentric, rib-like waves, and 

 is marked between the ribs with very minute, regular, radiating 



