296 Thirty-fifth Report on the State Museum. 



cardinal expansions, and very obscure on the ear and umbonal 

 region or the right valve. Concentric strias regular, sharp. Liga- 

 mental area narrow, and marked by one or two longitudinal furrows. 

 The sharp stride in their extension over the hinge-margin give the 

 exterior a crenulated appearance. 



A left valve has a length of 25 mm., height 22 mm., hinge-line 

 30 mm. A right valve has a length of 36 mm., height 28 mm., 

 hinge-line 37 mm. 



This species differs from Pterinopecte?i Vertumnus by its compara- 

 tively longer hinge-line, more extended ear, less distinctly curving, • 

 narrower and more abruptly elevated radii on the left valve ; and 

 stronger, not undulating, duplicating radii of the right valve. The 

 form and proportions are similar to Pterinopecten Icetus, but it is a 

 larger and coarser form, with the right valve convex. The geological 

 positions of the two species are quite different. The character of the 

 surface ornamentation distinguishes it from Pterinea prora and Pter- 

 inea avis. 



Formation and locality. In shales of the Chemung group, 600 feet 

 above the base of the formation, at Ithaca, N". Y. 



ACTINOPTEBIA, Hall. 



ACTINOPTERIA EXIMIA. 



Actinopteria eximia, Hall. Pal. N. Y., vol. v, pt. 1. Plates and Explanations: 

 PI. 25, fig. 1, Jan., 1883. 



Shell small, rhomboidal; body falciform, very oblique ; length more 

 than one-third greater than the height ; margin broadly curved 

 along the ventral side and abruptly recurved over the posterior end. 

 Left valve convex. Eight valve unknown. Hinge-line straight, 

 less than the length of the valve. Beak acute, directed forward. 

 Umbonal angle about 60°. Ear short, oblique, limited by a dis- 

 tinct sulcus; margin convex; extremity rounded. Wing .imper- 

 fectly preserved in the specimen described, apparently joining the 

 body near the middle of the post-cardinal slope, and very strongly 

 defined; margin concave, extending acutely backward; extremity 

 acute . 



Test marked by about twenty strong, elevated slender rays, with 

 regular lamella of growth which are extended and bent backward 

 on crossing the rays, producing strong semi-tubular spines. The 

 cardinal expansions preserve only the lines of growth. 



