194 PROCEEDINGS OF THE ACADEMY OF [April, 



Pecten uselmae n. sp. 



Peden incequalis Sowerby, Guppy, Q. J. Geol. Soc, XXII, 1866, p. 294, 

 PL 18, fig. 6. Not of Sowerby. 



The shell is inequilateral, inequivalve, the left valve is larger, 

 conspicuously surpassing the right throughout the lower margin and 

 ends It is strongly convex; the right valve weakly so. Sculpture 

 of 17 rounded ribs. In the left valve these are wider than the 

 intervals, which are deeply cut, with concave bottoms, which are 

 closely sculptured with delicate transverse threads. In the right 

 valve the ribs are lower, and not quite as wide as the intervals, in 

 which the transverse striation is often weak. The submargins are 

 smooth. Ears with several ribs. Ctenolium is very short, of three 

 teeth, which are small in adult shells. Cardinal crura strong, 

 vertically striate. 



Length of left valve 28, alt. 27.3, diam. 8.25 mm. 



Type No. 11124, A. N. S. P., from Bowden, Jamaica, collected 

 by Mr. Uselma C. Smith. 



This species is noticed here because it has been identified as P. 

 incequalis Sowb. of Santo Domingo. It differs from that by having 

 fewer, stronger ribs in the left valve and more strongly ribbed ears. 

 The left valve is more convex, and the form more inequalateral. 

 Having seen large series of both, we find these differences constant. 

 It is not represented in our Santo Domingan collections. 



Pecten (Amusium ?) correctus n. sp. 



Pecten opercularis Gabb, Trans. Amer. Philos. Soc, XV, 1873, p. 256. 



The shell is orbicular, weakly convex, with sculpture of 21 extremely 

 low, weakly convex ribs, over which growth-lines are visible. Ears 

 plain, subequal, separated from the rest of the valve by undercut 

 grooves. 



Alt. 52, semidiameter about 6.5 mm. 



Type No. 2781, A. N. S. P. 



Pecten ischnon n. sp. 



The shell is delicate, very thin, much compressed, inequilateral, 

 the right valve slightly more convex. Sculpture of 19 very low 

 rounded ribs, and extremely delicate, fine and close concentric 

 striation, strongest between the ribs. Ears rather large, with a few 

 delicate riblets in the right valve. The left valve has 5 strong, 

 crenulated ribs on the posterior ear. Ctenolium w^ell developed. 

 Both valves are strongly furrowed radially inside, the edges of the 

 intervening elevations a little raised, thickened. 



