32 
PALEONTOLOGY OF NEW YORK. 
directed slightly forward, depressed. Umbonal region moderately prominent, 
subtending an angle a little less than 90°. 
Ears triangular, flat, extremities acute. Anterior ear smaller, defined by 
a sulcus; margin nearly straight. Posterior ear with the margin concave, 
extremity acuminate; having no strong radiating striae. 
Test, as indicated in an exfoliated specimen, marked by a few fine radiating 
striae, with wider interspaces which are marked by finer radii. Anterior 
ear showing the same characters. Posterior ear free from rays. Fine con¬ 
centric striae cross the rays, and stronger concentric wrinkles interrupt them 
and produce a slight crenulation of the radii. 
The specimen is 10.5 mm. in length, 10 mm. in height, with hinge-line a 
little more than 11 mm. 
This species resembles in form the young of Pterinopeden dignatus, but differs 
in the finer radiating lines on the body of the shell, the concave margin, and 
absence of rays on the posterior ear. 
Formation and locality. In the black Marcellus shale at Cherry Yalley, Otsego 
county, N. Y. 
AviCULOPECTEN (PTERINOPECTEN?) TERMINALIS. 
PLATE X, FIG. 3. 
Pterinopecten terminalis, Hall. Pal. N. Y., vol. v, pt. 1. Plates and Explanations: PL 1, fig. 3. Jan., 1883. 
Shell small, rhomboidal; body of the shell obliquely ovate; length a little 
greater than the height; margins regularly rounded, somewhat extended 
behind. 
Left valve very convex. Right valve unknown. 
Hinge-line straight, central, equal to the length of the shell. 
Beak acute, prominent, directed a little forward, arching over the hinge¬ 
line. Umbo elevated, subtending a right angle. 
Ears triangular; margins concave; extremities acute. Posterior ear larger, 
undefined. Anterior ear limited by a shallow sulcus. Byssal sinus moderate. 
