236 Thirty-fifth Report on the State Museum. 



Test marked by very fine radiating striae and irregular lines of 

 growth. These surface characters extend also over the ears. 



The specimen described is 11 mm. in height, 12.5 mm. in length, 

 and hinge-line 8 mm. 



This species differs from A. dolabriformis in its more acute beak, 

 absence of regular concentric striae, and much larger anterior ear. 



Formation and locality. In the Chemung group at Philipsburg, 

 Alleghany county, N. Y. 



Ayiculopecten conyexus. 



Pectent cotton ms, Hall. Geolog. Surv. N. Y. : Rep. Fourth Dist., p. 265. 1843. 

 Aviculopecten convexus, Hall. Pal. N. Y., vol. v, pt. 1. Plates and Ex- 

 planations : PL 7, figs. 22, 23. Jan., 1883. 



Shell small, sub-orbicular, not oblique; height somewhat greater 

 than the length ; margins regularly rounded. Left valve very con- 

 vex ; convexity equal to about one-third the length of the shell. 

 Eight 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 sub- 

 tend 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. Ante- 

 rior 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 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 

 Eockville, Alleghany county, N. Y. 



