232 Thirty-fifth Eeport on the State Museum. 



AVICULOPECTEN STRIATUS . 



Pecten striatus, Hall. Geolog. Surv. N. Y. : Rep. Fourth Dist. 1843. 

 Aviculopecten striatus, Hall. Pal. N. Y., vol. v, pt. 1. Plates and Explana- 

 tion's : PL 10, figs. 3, 4. Jan., 1883. 



Shell transversely ovate, scarcely oblique, nearly equilateral; width 

 somewhat greater than the length. Hinge-line straight, two- thirds 

 the length of the shell, situated centrally in regard to the body of 

 the shell, not extending as far as the margin. Beak central to the 

 hinge-line, well-defined, arching over the hinge; umbo prominent, 

 the sides subtending a right angle. Ears sub-equal, triangular, 

 defined by the rapid slope of the sides of the umbo. Anterior ear 

 the larger, limited by a broad sinus ; margins slightly convex ; ex- 

 tremity rounded. Posterior ear acute at the extremity ; margins 

 concave. 



Test ornamented with fine, rounded, closely arranged, regular radi- 

 ating striae, from 12 to 14 in the space of 5 mm. at the pallial mar- 

 gin. Some specimens show a slight flattening of the rays and also line 

 lines of growth. The ears present the same surface characters. 



Ligamental area narrow, well-marked • its width is 5 mm. in a 

 specimen of 20 mm. in height. 



The original specimen of this species is 20 mm. in height, 18 mm. 

 in length, and the hinge-line 13 mm. Another specimen is 13 mm. 

 in height, 11 mm. in length, hinge-line 8 mm. The largest specimen 

 found has a height of 22 mm. 



This species resembles A. celsus more nearly than any other form 

 here described ; it differs from that one by its much smaller ears with 

 concave margins, more obtuse umbo, regular, equal striae, and com- 

 paratively shorter form. The two species agree in the non-obliquity 

 of the body of the shell to the hinge-line. This species has a vertical 

 range from the middle to the upper members of the Chemung group, 

 but is not abundant. 



Formation and localities. In the Chemung group at Painted Post, 

 Steuben county; Chemung Narrows, Tioga county, N". Y., and in 

 Bradford, Tioga and Warren counties, Pa. 



AVICULOPECTEN CELSUS. 



Aviculopecten altus, Hall. Pal. N. Y., vol. v, pt. 1. Plates ana Explanations : 



PI. 7, figs. 29, 30. Jan., 1883. 

 Not Aviculopecten altus, White. Bull. U.S. Geolog. Surv., vol. v, p. 110. 1879. 



Shell small, ovate cuneiform, sub-equilateral, not oblique ; height 

 one-fifth greater than the length ; pallial margin rounded to near 



