396 Thirty-fifth Eeport on the State Museum. 



Pteronites rostratus. 



Pteronites rostratus, Hall. Pal. N. Y., vol. v, pt. 1. Plates and Explana- 

 tions : PL 22, fig. 24. Jan., 1883. 



Shell of medium size, broadly semi-ovate; body oblique at an angle 

 of about 45 ° to the hinge-line ; length nearly twice the height ; 

 ante-byssal margin oblique, gently curving into the broadly rounded 

 basal margin ; posterior margin somewhat obliquely truncate. 

 Left valve depressed-convex below, convex in the middle, and some- 

 what gibbous above. Eight valve unknown. Hinge-line straight ; 

 length greater than the greatest length of the shell. Beak sub-an- 

 terior, sub-acute, prominent. Umbonal region moderately gibbous, 

 subtending an acute angle. Anterior end nasute. Wing not de- 

 fined, in direct continuation of the convexity of the body, extend- 

 ing to the posterior extremity; margin very slightly concave, oblique 

 to the cardinal line, slightly produced at the extremity. 



Test ornamented by fine, elevated, concentric striae, which are 

 continued over the body and wing without interruption, becoming 

 crowded and somewhat fasciculate on the anterior side and on the 

 nasute extension in front. The umbonal region shows a few con- 

 centric undulations, which are not continued to the middle of the 

 length of the valve. 



The specimen described has a length of 29 mm., height 16 mm., 

 and hinge-line 31 mm. 



This species is much smaller than P. profundus, less elongate and 

 less gibbous in its proportions. The beak is apparently more elevated 

 and angular, but the angularity of the umbonal region is not con- 

 tinued along the body as in the preceding form. 



Formation and locality. In the shales of the Chemung group at 

 Rockville, Alleghany county. N. Y, 



Pteronites inoptatus. 



Pteronites inoptatus , Hall. Pal. N. Y., vol. v, pt. 1. Unpublished. 



Shell of medium size, broadly semi-ovate ; body ovate, oblique, mak- 

 ing an angle of about 25° with the cardinal line ; ventral and basal 

 margins broadly rounded ; post-basal extremity abruptly recurved. 

 Left valve regularly convex, slightly gibbous above. Right valve 

 unknown. Hinge-line straight, less than the greatest length of 

 the shell. Beak sub-anterior, directed forward, prominent and 



