64 
PALAEONTOLOGY 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 Aviculopecten 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- 
natus, 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. 
Pterinopecten Hermes, Hall. Pal. N. Y., vol. v, pt. 1. Plates and Explanations: PI. 17, figs. 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. 
