loG PALEONTOLOGY OF NEW YORK. 



Pterinea (Vertumnia) iu:i'K(ii!a; h. s}). 



IM.ATK I.XXXII, FIGS. 10,20. 



Shell of luediuiii j^izc, I'liomhoidal ; body ol)li(jiie ; Iciigtii soiiu'wliut p't-atcr lliaii 

 the height ; pallial margin reguhirly rounded, Ijecoming produced behind and 

 extending tlience 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 tliaii tlie greatest length of the sliell, 

 extended anteriorly considerably beyond the margin of the valve. 



Beaks obtuse, not jjrominent, directed forward, anterior to the iiiiildlc. 

 Umbonal region undefined. 



Ear defined by a shallow sulcus : uiariiin concave : extreniitv acute. T5yssnl 

 sinus moderate, marked in the rii^lit \al\i' hy a |)artial reflexion of the mar- 

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

 slightly concave toward the extremity, which is acute. 



Surface marked by numerous strong, rounded lays. which alternate on the 

 left valve, and (ln|ilicate on the right valve. The interspaces are e(iual to, 

 or greater tliau, the radii : the rays are liuer on the cnidinal expansions, and 

 very obscure on the ear and umbonal region ol' the right valve. Concentric 

 striae regular, sharp. 



Interior not known. 



Ligamental area narrow, and marked l)y 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., liiuge-line .'id mm. 

 A right valve has a length of 36 mm., height 28 mm., hinge-line 37 mm. 



This species differs from Pterinopeden Vertumnus hy its comparatively 

 longer hinge-line, more extended ear, less distinctly curving, narrower, anil 

 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 



