Lamellibranchiata. 395 



PTERONITES, McCoy. 



Pteronites profundus. 



Pteronites profundus, Hall. Pal. N. Y., vol. v,pt. 1. Plates and Explanations : 

 PI. 22, figs. 25-27. Jan., 1883. 



Shell large, longitudinally semi-ovate ; body semi-elliptical, arcuate, 

 oblique to the hinge-line at an angle of about 30°; length about 

 twice the height ; anterior margin very oblique, slightly concave 

 beneath the beak and gradually curving into the broadly rounded 

 basal margin; posterior margin obliquely truncate, slightly curving 

 below. Left valve convex in the lower part, gibbous from the mid- 

 dle upwards. Eight valve unknown. Hinge-line straight ; length 

 more than the greatest length of the shell. Beak sub-anterior, ob- 

 tuse, rising but little above the hinge-line, and apparently not in- 

 curved. Umbonal region very gibbous, subtending an acute angle. 

 Anterior end produced into an acute extension, which is limited by 

 a very shallow byssal depression. Wing not defined, extending from 

 the beak the entire length of the shell, and produced beyond the 

 posterior extremity of the body ; margin very slightly concave, ex- 

 tending at nearly right angles to the axis of the body. 



Test of moderate thickness, marked by concentric striae. The 

 casts show distant, irregular, concentric undulations. Hinge with 

 a single continuous groove. The pallial line extends parallel to the 

 ventral margin, from a point anterior to the beak to "below the mid- 

 dle of the length of the body. 



A large left valve has a length of 78 mm., with a height of 38 

 mm., and hinge-line 90 mm. A smaller example has a length of 

 37 mm., height 23 mm., and hinge-line 40 mm. 



All the specimens of this species are casts of the interior, with the 

 single exception of an individual which preserves the test very imper- 

 fectly. The concentric undulations of the cast are often a conspicu- 

 ous feature, and the umbonal slope is occasionally obtusely sub- 

 angular. The wing follows the general contour and convexity of the 

 valve. 



Formation and localities. In the Upper Chemung group, associated 

 with SpiriferaVemeuili near Olean, Cattaraugus county ; in the vicin- 

 ity of East Randolph, and other places in Cattaraugus county, N. Y. 



