28 
PALAEONTOLOGY OF NEW YORK. 
Aviculopecten convexus. 
PLATE VII, FIGS. 22, 23. 
Pecten? convexus, Hall. Geolog. Surv. N. Y.: Rep. Fourth Dist., p. 265. 1843. 
Aviculopecten convexus. Hall. Pal. N. Y., vol. v, pt. 1. Plates and Explanations: PI. 7, figs. 22, 23. 
Jan., 1883. 
Shell small, sub-orbicular, not oblique; height somewhat greater than the 
length; margins regularly rounded. 
Left valve very convex, convexity equal to about one-third the length of 
the shell. Right valve not known. 
Hinge-line straight, central, length three-fifths the length of the shell. 
Beak prominent, straight, central, rounded, arching over the hinge-line; 
the sides of the umbo subtend a right angle. 
Ears broad-triangular, extremities obtuse-angular. Posterior ear of left 
valve smaller than the anterior, defined by the abrupt slope of the umbo; 
margin slightly concave. Anterior ear convex; margin straight; separated 
from the umbo by a very deep and narrow sulcus. Byssal sinus small. 
Test marked by fine irregular radiating striae and finer regular concentric 
lines; the same surface characters are continued over the ears. The speci¬ 
men is exfoliated and the radii represented in the figure are partially restored. 
Interior characters unknown. 
The original of this species has a height of 12.5 mm., length 12 mm., and 
hinge-line 8 mm. 
The remarkable convexity of the left valve distinguishes this species from 
all the other forms here described. Its orbicular outline, prominent beak and 
deep anterior sulcus are also characteristic. In general appearance the body 
of the shell resembles some forms of Athyris and Meristina among the 
Brachiopods, but its pectinoid character is well marked. 
Formation and locality. In the shales of the Chemung group at Rockville, 
Alleghany county, N. Y. 
