22 
PALAEONTOLOGY OF NEW YORK. 
In form, this species bears considerable resemblance to A. duplicatus; but 
the surface markings are quite different, and the extremities of the hinge line 
are more acute in this species. In A. scabridus the beak is not so well defined, 
the ears usually more extended, and the coarser rugose radii of that species 
are characteristic. This form resembles some varieties of A. fasciculatus in the 
surface characters, but differs in the obliquity of the shell and form of the ears. 
It differs from A. Idas in the more rotund form, more numerous and elevated 
rays, and larger ears. 
The single valve described appears to be well distinguished from all the 
other species, and possesses characters too remote to be united with any of 
those described from right valves alone. 
Formation and locality. In arenaceous shales of the middle Chemung group, 
near Elmira, N. Y. 
Aviculopecten striatus. 
PLATE X, FIGS. 3, 4. 
Pecten striatus, Hall. Geolog. Surv. N. Y.: Rep. Fourth Dist. 1843. 
Aviculopecten striatus, Hall. Pal. N. Y., vol. v, pt. 1. Plates and Explanations: PI. 10, figs. 3, 4. 
Jan., 1883. 
Shell transversely ovate, scarcely oblique, nearly equilateral, width some¬ 
what greater than the length. 
Hinge-line straight, two-thirds the length of the shell, situated centrally 
in regard to the body of the shell, not extending as far as the margin. 
Beak central to the hinge-line, well-defined, arching over the hinge; 
umbo prominent, the sides subtending a right angle. 
Ears sub-equal, triangular, defined by the rapid slope of the sides of the 
umbo. Anterior ear the larger, limited by a broad sinus; margins slightly 
convex; extremity rounded. Posterior ear acute at the extremity; margins 
concave. 
Test ornamented with fine, rounded, closely arranged, regular radiating 
striae, from 12 to 14 in the space of 5 mm. at the pallial margin. Some 
specimens show a slight flattening of the rays and also fine lines of growth. 
The ears present the same surface characters. 
