64 PALEONTOLOGY OF NEW YORK. 



wrinkled from the apex to below the middle of the valve. The surface 

 markings are finer and sub-equal over the posterior ear. A small space on 

 the umbo, as in Aviculopeden bellus, is destitute of radii. 

 Internal characters not known. 



This species differs from P. Hermes in its less oblique form, shorter hinge- 

 line, less ample umbo, and in having no regular alternation in the rays, which 

 are closer and more rounded. It is associated with, and closely allied to, P. dig- 

 naius, but differs by its more obtuse beak, longer outline, and comparatively 

 more frequent and smaller rays, without the regular concentric striae. 



Formation and locality. In the Marcellus shale at Bloomfield, Ontario 

 county, N. Y. 



Pterinopecten Hermes. 



PLATE XVII, FIGS. 13-15. 



Pterinopeettn Hermes, Hall. Pal. N. Y., vol. v, pt. 1. Plates and Explanations: PI. 17. tigs. 13-15. 



Jan., 1883. 



Shell less than medium size, sub-rhomboidal, obliquely sub-ovate ; length and 

 height about as three to four ; pallial margins regularly rounded, becoming 

 straight on the post-cardinal slope at the junction with the ear. 



Left valve moderately convex. Right valve not determined. 



Beak acute, prominent, anterior to the middle of the shell directed forward. 

 Umbonal region ample, subtending an angle of about 80°. 



Ears very unequal, triangular. Posterior ear much the larger, scarcely 

 defined ; margin concave ; extremity acute. Anterior ear small, slightly 

 convex, defined by a distinct sulcus ; margin convex ; extremity rounded. 

 Byssal sinus deep. 



Test marked by regular, rounded striae, with wider interspaces which, on 

 the posterior part of the valve, show finer intermediate rays. The ears 

 have essentially the same surface characters as the body of the valve. The 

 entire surface is marked by fine concentric striae. Umbo with concentric 

 wrinkles. Partial casts of the interior show the same characters as the 

 exterior, but show no muscular or pallial markings. 



