28 PALAEONTOLOGY OF NEW YORK. 



AviCULOPECTEN CONVEXUS. 



PLATE VII, FIGS. 22, 23 



/'( ten .' convextts, Hall. Geolog. Surv. N. Y. : Rep. Fourth Disk, p. 265. 1843. 



Avieulopeeten convexus, Hall. Pal. N. V., vol. v, pt. 1. Plates and Explanations: PI. 7, tip*. 22, 23. 



Jan., 1883. 



Shell small, sub-orbicular, not oblique ; heiglit 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 strire 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 

 Braehiopods, but its pectinoid character is well marked. 



Formation and locality. In the shales of the Chemung group at Rockville, 

 Alleghany county, N. Y. 



