24 PALEONTOLOGY OF NEW YORK . 
sinus, and from the sides of the umbo by a sulcus ; the byssal sinus is deep and 
rounded. 
Test marked by fine alternating filiform radiating striae, which are absent 
on the ears, except as two or three alternating undulations. Fine lines of 
growth mark the test and extend over the ears. 
Ligamental area linear and marked by an inflection of the hinge-margin. 
The specimen has a height of 15 mm. and a length of 13 mm., hinge¬ 
line 10 mm. About 13 rays occupy the space of 5 mm., measured near the 
basal margin. 
This form may be distinguished by its equilateral proportions, acute, 
straight apex, the non-obliquity of the transverse axis to the hinge-line, the 
broad, triangular ears and the alternating surface striae. These characters sepa¬ 
rate it from A. striatus, to which it is most nearly allied. 
Formation and locality. In sandstone of the conglomerate, associated with 
the upper Chemung group, at Salamanca, Cattaraugus county, N. Y. 
Aviculopecten patulus. 
PLATE VII, PIGS. 32, 33. 
Aviculopecten patulus, Hall. Pal. N. Y., vol. v, pt. 1. Plates and Explanations: PI. P, ligs. 32, 33. 
Jan., 1883. 
Shell large, longitudinally broadly elliptical; height about five-sixths as great 
as the length. The axis of greatest height is at right angles to the hinge, 
and the line of greatest length is parallel to the hinge and across the middle 
of the shell. Basal margin convex, somewhat flattened in the middle. 
Lateral margins very full, and curving rapidly to the ears. 
Valves convex, the convexity equal to one-fourth the length of the hinge¬ 
line. The right and left valves do not differ conspicuously in character, so 
far as observed. 
Hinge-line apparently straight, equalling nearly two-thirds the length of 
the shell, central, not extending as far as either lateral margin. 
