78 PALEONTOLOGY OF NEW YORK. 



Pterinopecten crenicostatus. 



PLATE VIII, KR;s, 3, 4; ani> PLATE LXXXII, FIG. 14. 



Pterino]>e<tiii crenulatiut (by error), Hai.l. Pal. N. Y., vol. v, pt. 1. Plates and Ex]>lanatioiis : PI. 8, figs. 



:!. 4. .Jan., 1S8S. 



Shell larj!;e, suh-orbicular, sli;:litly ol)li(jVK' ; length somowhat greater than the 

 height ; pallial margins reguhirl}- curved, l)roadly rounded from the antero- 

 hiteral to the basal margin ; post-lateral margin less convex. 



Left valve very moderately convex. Kight valve not known. 



Hinge-line straight, length one-fifth less tliaii the length dl' the shell, 

 exteiiilrd anteriorly, but not as far as the anterior mai'gin of the valve. 



l')eak obtuse, rounded, scarcely directed forward, prominent, anterior to 

 tlic iniddlc. Uml)onal region wide, indistinctly defined on the jwsterior 

 sitle, more distinctly limited anteriorly, subtending an angle somewhat 

 gi-eater than 90°. 



Ears triangular. Hat. Posterior ear five times as large a.s the anterior, 

 undefined ; margin straight or slightly concave ; extremity abruptly acute. 

 Anterior ear small ; margin deeply concave from the byssal sinus; defined by 

 a distinct sulcus ; extremity acute. 



Test apparently thick, marked by al)()ut fifty strong, roimded rays which 

 are simple oi- bifurcating, always with liner intermediate rays. Concentric 

 striae strong, elevated, conspicuously crenulating the radii. The radii mark 

 the ears, and on tli(> posterior ear are simple and distant. 



Internal characters not known. 



The two specimens figured give about the following respective dimensions : 

 length 50, 57 mm., height 47, 53 mm., and length of hinge-line 52 and 

 40 mm. 



This species differs from P. suborbicularis in being more inequilateral, with 

 longer hinge, and stronger and less frequent radii. It differs from P. Neptunus, 

 pi. 8, fig. G, by its more erect form, extended hinge-line, distant and elevated 

 radii, with stronger and more elevated concentric strife. 



Formation and localities. In ibe .-bales of tlu' Cheinuug gi-ouj) at Angelit'a and 

 Conewango, N. Y., and at Mansfield, Tioga county, Pa. 



