LAMELL1BRANCHIA TA. 
89 
Crenipecten Winchelli. 
PLATE IX, PIGS. 1, 2, 4, 25-30. 
Aviculopecten' Winchelli, Meek. Pal. of Ohio, vol. ii, p. 296, pi. 15, fig-s. 50, 56. 1875. 
Crenipecten ( Pecten) Winchelli (Meek), Hall. Pal. N. Y., vol. v, pt. 1. Plates and Explanations: PI. 9, 
fig-s. 1, 2, 4, 25-30. Jan., 1883. 
Shell larger than medium, flabelliform, equilateral, not oblique; length a little 
greater than the height; margins regularly rounded below. On the anterior 
side, from a point two-thirds the height of the valve., above the base, the 
antero-cardinal margin extends in a direct line to the beak; the posterior 
side, from a point a little above the middle, also slopes in a direct line to the 
beak. 
Left valve moderately convex; the greatest convexity about one-third the 
height of the shell from the beak. Right valve nearly flat, depressed-convex 
above. The right and left valves are unlike. 
Hinge-line straight, central, length about two-thirds the length of the 
shell. In several specimens referred to the right valve, the length of the 
hinge is nearly equal to the length of the valve. 
Beak of left valve acute, erect, prominent. Beak of right valve depressed, 
obtuse, not rising above the hinge-line. Umbonal region of left valve dis¬ 
tinctly defined, subtending a right angle. 
Ears of left valve triangular, defined by shallow but distinct sulci. Margin 
of anterior ear convex, with a shallow sinus at the base. Posterior ear the 
larger; margin concave, with a comparatively broad sinus. The extremities 
of the ears in the right valve are acute. Byssal sinus deeper and more 
angular in the right valve. 
Surface of left valve marked by numerous rounded or sub-angular, alter¬ 
nating rays, with somewhat wider interspaces, crossed by sharp, elevated, 
concentric striae; the ears show the same markings. Right valve marked 
by obscure radii, which are stronger on the ears. 
Ligamental area with numerous narrow cartilage-pits. 
A large left valve has a length of 47 mm., height 42 mm., hinge-line 29 
12 
