22 PALEONTOLOGY 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 Elinira, N. Y. 



AviCULOPECTEN STRIATDS. 

 PLATE X, FIGS. 3, 4. 



Peeten striata*. Hall. Geolog. Surv. N. Y. : Rh]>. Fourth Dist. 1*4;). 



Aoiculopecten striatus, Hall. Pal. N. V., vol. v, pt. 1. Plates and Explanations: PI. 10, figs. 8, 4. 



Jan.. 1SS3. 



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 

 stria-, from 12 to 14 in the space of 5 mm. at the pallia] margin. Some 

 specimens show a slight flattening of the rays and also fine lines of growth. 

 The ears present the same surface characters. 





