L06 PALAEONTOLOGY OF NEW YORK. 



Pterins \ ( Vertumni \) reproba; q. sp. 



PL \ I I. I.W \M. FIGS. [9, ." 



Shell of medium size, rhomboidal; body oblique; Length somewhat greater than 

 the heighi ; pallia! margin regularly rounded, becoming produced behind and 

 extending thence in a nearly direct line to the hinge. 



Valves depressed-convex, the right valve the more convex ; very similar 

 in form and surface markings. 



Hinge-line straight, length greater than the greatest length of the shell, 

 extended anteriorly considerably beyond the margin of the valve. 



Beaks obtuse, not prominent, directed forward, anterior to the middle. 

 I'lnbonal region undefined. 



Ear defined by a shallow sulcus ; margin concave ; extremity acute. Byssal 

 sinus moderate, marked in the right valve by a partial reflexion of the mar- 

 gin. Wing large, triangular and undefined; margin nearly straight below, 

 slight!) concave toward the extremity, which is acute. 



Surface marked by numerous strong, rounded rays, which alternate on the 

 left valve, and duplicate on the right valve. The interspaces are equal to, 

 or greater than, the radii ; the rays are finer on the cardinal expansions, and 

 very obscure on the ear and unibonal region of the right valve. Concentric 

 striae regular, sharp. 



Interior not known. 



Ligameutal area narrow, and marked by one or two longitudinal furrows. 

 The sharp stria' in their extension over the hinge-margin give the exterior 

 a crenulated appearance. 



A left valve has a length of 25 mm., height 22 mm., hinge-line 30 mm. 

 A right valve has a Length of 36 mm., heighi 28 mm., hinge-line 37 mm. 



This species differs from Ptoinopecten Vertumnus by its comparatively 

 Longer hinge-line, more extended ear, less distinctly curving, narrower, and 

 more abruptly elevated radii on the Left valve; and stronger, not undulating, 

 duplicating radii of the right valve. The form and proportions are similar to 



