78 
PALAEONTOLOGY OF NEW YORK. 
Pterinopecten crenicostatus. 
PLATE VIII, FIGS. 3, 4; and PLATE LXXXXI, FIG. 14. 
Pterinopecten crenulatus (by error), Hall. Pal. N. Y., vol. v, pt. 1. Plates and Explanations: PI. 8, figs. 
3, 4. Jan., 1883. 
Shell large, sub-orbicular, slightly oblique; length somewhat greater than the 
height; pallial margins regularly curved, broadly rounded from the antero¬ 
lateral to the basal margin; post-lateral margin less convex. 
Left valve very moderately convex. Right valve not known. 
Hinge-line straight, length one-fifth less than the length of the shell, 
extended anteriorly, but not as far as the anterior margin of the valve. 
Beak obtuse, rounded, scarcely directed forward, prominent, anterior to 
the middle. Umbonal region wide, indistinctly defined on the posterior 
side, more distinctly limited anteriorly, subtending an angle somewhat 
greater than 90°. 
Ears triangular, flat. Posterior ear five times as large as 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 about fifty strong, rounded rays which 
are simple or bifurcating, always with finer intermediate rays. Concentric 
striae strong, elevated, conspicuously crenulating the radii.- The radii mark 
the ears, and on the posterior ear are simple and distant. 
Internal characters not known. 
The two specimens figured give about the following respective dimensions: 
length 56, 57 mm., height 47, 53 mm., and length of hinge-line 52 and 
46 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. 6, by its more erect form, extended hinge-line, distant and elevated 
radii, with stronger and more elevated concentric striae. 
Formation and localities. In the shales of the Chemung group at Angelica and 
Conewango, N. Y., and at Mansfield, Tioga county, Pa. 
