22 I'ALjEONTOLOCY OF NEW YORK. 



Ill loriii. tliis species lie;irs considcriililr rcscniljlance to A. duplicatus ; l)iit 

 the siiil'ace markings are quite diflereiit, and the extremities of the hinge line 

 are more acute in tliis species. In A. scabridus the beak is not so well defined, 

 tlic cars 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 obli(|uity of the shell and form ol' the ears. 

 It differs from A. Idas in the iiiorc rotund form, more numerous and elevated 

 rays, and larger ears. 



The single valve described appears to Ijc 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 ol" the middle Chemung group, 

 near Elmira, X. Y. 



AviCULOPECTEN STKIATUS. 

 PLATE X, FIGS. 3, 4. 



Pectim, striatu.1. Hall. Geulop. Siirv. N. Y. : R(>ii. Fcnirtli l)i.«t. 1S4;^. 



ABiatlopectnt. xtrlatu.^. Hall. Pal. N. Y., vul. v, \>t. 1. Plat<'s and l';x]ilaii.iticiii.« : PI. 10. tig-s. 3, 4. 



.Jan., 1SS8. 



Shell trans\ersely ovate, scarcely oblique, nearly equilateral, width some- 

 what greater than the length. 



Ilinge-line straight, two-thinls the leiiuth of the shell, situated centrally 

 in regard to the body of the shell, not I'xtending as far as the margin. 



Beak central to the liiiige-line, well-defined, arching over the hinge; 

 uiiilio prominent, the sides subtending a right angle. 



Ears sub-equal, triangular, ilefniei] l)y the rapid slope of the sides of the 

 und)o. Anterior ear the larger, limited by a broad sinus; mai'gius slightly 

 convex; extremity rounded. Posterior ear acute at the extremity : margins 

 concave. 



Test ornamented with line, rounded, clo.sely arrangetl, regular radiating 

 striai, 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. 



