HJS PALEONTOLOGY OF NEW YORK. 



Beak anterior, acute, prominent, inclined forward, rising above the hinge. 

 I'lnhonal region gibbons, abruptly limited on the anterior side bv the sulcus, 

 and on the posterior side sloping rapidly to the wing. 



A\'ing large, tlat, triangular, joining the body of the vahe below the 

 middle of the height, limited by the gently retral curve of the striae ; margin 

 moderately concave ; extremity acute or iniu iduatc 



Surface marked by regular, ecpiiilistaiit, uiuliilating, lanu'llilnnii. concentric 

 expansions, which become crowded, finer, and to some extent less undulated 

 on the wing, stronger and very much crowded on the anterior of the shell. 

 The undulations extend forward in an abrupt curve, bending gently back- 

 ward, and being thus opposite and slightly imliricating, they give an 

 appearance of radiation. 



Interior unknown. 



The specimen described has a length of oG mm., height '61 mm., and hinge- 

 line about 29 mm. 



In general aspect, this species resembles Actinopteria Boydi, but the body is 

 much less oblique and wider below ; the surface is without proper rays ; the 

 wing has only fine, crowded, concentric stria;; while in that sjjecies the wing is 

 marked with strong radii and a lew lines of gi'owth. 



These comparisons are made from similar casts of the interior of both species. 



Formation and locality. In the coarse grits of the upjier part of the Hamilton 

 group, ill the northern part of Schoharie county, N. Y. 



LeIOPTERIA LeAI, 11. .-^p. 



PLATE LXXXVIII, FKJS. 2t, '.i 



Shell small, sub-rhomboidal ; body broadly ovate, very moderately ol)li{pie; 

 height much greater than the length ; margin regularly rounded from aliove 

 the middle on the anterior side, to a similar point on the ojjposite side of tlie 

 valve ; post-basal margin slightly produced. 



Left valve very convex; gibbous from below tlie middle ti) tlie umbo. 

 Right valve unknown. 



