LAMELLIBRANCHIATA. 85 



Crenipecten glaber. 



PLATE IX, FIGS. 20, 22? 



Lhiia fflaber, Hall (xeolog. Siirv. N. Y. : Rep. F<mrth Dist., p. 255. 1843. 



Crenipecten glaber. Hall. Pa!. N. Y. vol. v, pt. 1. Plate.=! and Explanations: P!. 9, fig-s. 20, 22? 



Jan., 1883. 



Shell small, ovate, erect, very slightly oblique ; height about one-fifth greater 

 than the length ; pallial margins regularly rounded, more extended on the 

 posterior side. 



Left valve moderately convex above, and depressed-convex below. Right 

 valve unknown. 



Hinge-line straight, length equal to about one-half the length of the valve. 



Beak acute, erect, somewhat prominent, not elevated above the hinge. 

 Uniljonal region well defined by the sulci, subtending an acute angle. 



Ears triangular, nearly equal, separated from the body of the shell by 

 shallow sulci ; margins straight or slightly concave : posterior ear a little 

 the larger. Byssal sinus not distinct. 



The cast is marked only by fine concentric striae. 



Interior unknown. 



The crenulations of the ligamental area are obscure in the specimen. 



The original of this species is 12 mm. in length, 16 mm. in height, and 

 hinge-line G mm. 



This specimen is embedded vertically to the lines of rock bedding, and the 

 proportions of length and height may have been changed. The species is 

 known by its erect form, conspicuous ears and great comparative height. 



The specimen of figure 22 is referred with doubt to this species; the erect 

 form is similar ; the proportional length is slightly greater. 



Formation and localities. In shales of the Chemung group at Philipsburg and 

 Rockville, Alleghany county, N. Y. 



