238 
PALAEONTOLOGY OF NEW YORK. 
All the specimens of this species are casts of ‘the interior, with the single 
exception of an individual which preserves the test very imperfectly. The 
concentric undulations of the cast are often a conspicuous feature, and the 
umbonal slope is occasionally obtusely subangular. The wing follows the 
general contour and convexity of the valve. 
Formation, and localities. In the Upper Chemung group, associated with 
Spirifera Verneuili near Olean, Alleghany county; in the vicinity of East Ran¬ 
dolph, and other places in Cattaraugus county, N. Y. 
Pteronites rostratus. 
PLATE XXII, PIG. 24. 
Pteronites rostratus, Hall. Pal. N. Y., vol. v, pt. 1. Plates and Explanations^: PI. 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 somewhat 
gibbous above. Right valve unknown. 
Hinge-line straight; length greater than the greatest length of the shell. 
Beak sub-anterior, sub-acute, prominent. Umbonal region moderately 
gibbous, subtending an acute angle. 
Anterior end nasute. Wing not defined, in direct continuation of the 
convexity of the body, extending 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 some¬ 
what fasciculate on the anterior side and on the nasute extension in front. 
The umbonal region shows a few concentric undulations, which are not 
continued to the middle of the length of the valve. 
