234 Thikty-fifth Report cm the State Museum. 



from the body of the shell by a broad, deep sinus; margins concave 

 below, becoming convex above the middle ; extremities rounded. 



Test ornamented by regular, sharp radii, with broader concave in- 

 terspaces, and some finer radii, crossed by irregular crenulating lines 

 of growth. Near the basal margin of a large specimen, there are 

 five of these rays in the space of 10 mm. A smaller specimen has 

 eleven rays in the same space. 



The measurements of one individual are : height 55 mm., length 

 69 mm., hinge-line 41 mm. ; of another specimen, height 26 mm., 

 and length 30 mm. 



This species nearly resembles in form A. ellipticus, and differs by its 

 sharp, crenulated radii, while that species is marked by strong, rounded, 

 continuous plications ; and the hinge-line is comparatively somewhat 

 longer. These two forms differ from others in their broad longitu- 

 dinally elliptical outlines, and the amplitude of the umbones. 



Formation and localities. In conglomerate and sandstone, associated 

 with the Upper Chemung group, at Eock City, near Salamanca, Cat- 

 taraugus county, N. Y. 



Ayiculopecten" ellipticus. 



Aviculopecten ellipticus, Hall. Pal. N. Y., vol. v, pt. 1. Plates and Explana- 

 tions : PI. 7, fig. 31. Jan., 1883. 



Shell large, longitudinally broadly elliptical, equilateral, not oblique; 

 height equal to about four-fifths of the length ; margins regularly 

 convex and rapidly curving to the beak. Left valve capacious, con- 

 vex. Right valve not observed. Hinge-line straight, central, length 

 equal to about one-half the length of the shell. Beak straight, 

 central, obtuse, rounded; umbonal angle about 110°. Ears sub- 

 equal, broad-triangular, flat; margins slightly convex; extremities 

 rectangular, defined by a gentle sinus, which is deeper below the 

 anterior ear. 



Test marked by about 35 strong, rounded, radiating continuous 

 plications which are wider than the interspaces. These radii are 

 absent on the ears. The striae of growth are irregular and mark the 

 entire surface of the shell. 



A large specimen has a height of 53 mm., length 66 mm., hinge- 

 line 34 mm. 



This species differs from A. patulus in its shorter hinge-line, and 

 the strong, rounded, radiating plications. 



Formation and locality. In the sandstone of the upper part of the 

 Chemung group at Meadville, Crawford county, Pa. 



