LAMELLIBRANCHIA TA. 
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Beaks obtuse, rounded; umbo prominent, straight, central, well-defined 
by its gibbous form and the rapid slope of the sides. Umbonal angle 110°. 
Ears broad-triangular, sub-equal, separated from the body of the shell by 
a broad, deep sinus; margins concave below, becoming convex above the 
middle; extremities rounded. 
Test ornamented by regular, sharp radii, with broader concave inter¬ 
spaces, and some finer radii, crossed by irregular crenulating lines of growth. 
Near the basal margin of a large specimen, there are five of these rays in 
the space of 10 mm. A smaller specimen has eleven rays in the same 
space. 
The interior is not preserved. 
The measurements of one individual are: height 55 mm., length 69 mm., 
hinge-line 41 mm.; of another specimen, height 26 mm., and length 30 mm. 
This species nearly resembles in form A. ellipticus, and differs by its sharp, 
crenulated radii, while that species is marked by strong, rounded, continuous 
plications; and the hinge-line is comparatively somewhat longer. These two 
forms differ from others in their broad longitudinally elliptical outlines, and 
the amplitude of the umbones. 
Formation and locality. In conglomerate and sandstone, associated with the 
Upper Chemung group, at Rock City, near Salamanca, Cattaraugus county, N. Y. 
Aviculopecten ellipticus. 
PLATE VII, FIG. 31. 
Aviculopecten ellipticus. Hall. Pal. N. Y., vol. v, pt. 1. Plates and Explanations: PI. 7, fig. 31. Jan., 1883. 
Shell large, longitudinally broadly elliptical, equilaterial, not oblique; height 
equal to about four-fifths of the length ; margins regularly convex and rapidly 
curving to the beak. 
Left valve capacious, convex. Right valve not observed. 
Hinge-line straight, central, length equal to about one-half the length of 
the shell. 
Beak straight, central, obtuse, rounded; umbonal angle about 110°. 
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