LAMELLIBRANCHIATA. 27 



This small species somewhat resembles A. squama in the form of the body 

 ami surface markings, but the beak is less acute and the anterior ear compara- 

 tively smaller, without distinct sinus. 



Formation and locality. In the arenaceous shales of the Chemung group at 

 Philipsburg, Alleghany county, N. Y. 



AviCDLOPECTEN SQUAMA. 



PLATE VII, F1U. 20. 



Arii-iilii/itrhii squama, Hall. Pal. N. Y., vol. v, pt. 1. Plates and Explanations.: PI. 7, fig. 20, Jan., 1883. 



Shell transversely broad-elliptical, slightly oblique; height about nine-tenths 

 of the length. 



Right valve moderately convex. Left valve not known. 



Hinge-line straight, length two-thirds the length of the shell, extending in 

 front as far as the anterior margin of the valve. 



Beak rounded, not rising above the hinge-line, situated posterior to the 

 centre; umbonal angle 90°. 



Posterior ear small, triangular, narrow, with concave margin; not stronglj 

 defined; extremity angular. Anterior ear large, convex, broad-triangular ; 

 extremity obtuse; margin convex ; separated from the body by a deep rounded 

 sinus, and from the sides of the umbo by a distinct sulcus. 



Test marked by very fine radiating stria) and Irregular lines of growth. 

 These surface characters extend also over the ears. 



Internal characters not known. 



The specimen described is 11 mm. in height, 1 !?.•"> nun. in length, and 

 hinge-line 8 mm. 



This species diners from A. dolahriformis in its more acute beak, absence 

 of regular concentric stria\ and much larger anterior ear. 



Formation and locality. In the Chemung group at Philipsburg, AUeghanj 

 county, N. Y. 



