68 PALEONTOLOGY OF NEW YORK. 



Beaks obtuse, anterior to the middle of the valve, directed forward, not 

 well denned. Unibonal region not strongly marked. 



Ears unequal. Posterior ear wide-triangular, extending as far as the mar- 

 gin of the shell, its limits undefined ; margin nearly straight ; extremity rec- 

 tangular. Anterior ear small, limited by a strong sulcus ; margin concave ; 

 extremity obtuse. Byssal sinus in the left valve moderate; in the right 

 valve well-marked. 



Test of right valve thin, marked by fine filiform radii, with much wider 

 interspaces which are marked by finer rays ; the same character continuing 

 on the posterior ear, with more equal rays. The entire surface is marked 

 by fine, close, concentric lines of growth, with lamellose elevations at unequal 

 intervals. 



Hinge-ligament marked by several parallel grooves. 



A right valve measures approximately 35 mm. in length, and 29 mm. in 

 height. 



In general form this species resembles P. conspectus, but is proportionally 

 longer, and the surface markings are different. 



Formation and localities. In the Hamilton group near Cardiff, Onondaga 

 county, and from a bowlder of Hamilton shale at Pine Valley, Chemung 

 county, N. Y. 



Pterinopecten tntermedius, n. sp. 



PLATE XVII, FIG. 19; AND PLATE LXXXIII, FIGS. 4, 5 



Pterinopecten conspectus, in part, Hall. Pal. N. V., vol. v, pt. 1. Plates and Explanations: PI. 17, tig-. 19, 



.Ian.. 1883. 



Shell of medium size, sub-rhomboidal, oblique ; length one-fourth greater than 

 the height ; margins regularly rounded, more convex on the post-basal side. 



Left valve convex, greatest convexity below the umbo. Right valve 

 unknown. 



Hinge-line straight, somewhat anterior ; length greater than the length of 

 the valve. 



