Lamelllbkanchiata. 235 



AVICULOPECTEN DOLABHIFORMIS. 



Pecten? dolabriformis, Hall. Geolog. Surv. N. Y.: Rep. Fourth Dist., p. 265. 

 1843. 



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

 planations : PI. 7, fig. 21. Jan., 1883. 



Shell small, sub- orbicular, slightly oblique ; height nearly equal to 

 the length ; margins regularly rounded, becoming more inflated and 

 convex posteriorly. Right valve moderately convex. Left valve 

 unknown. Hinge-line straight, central, more than two-thirds the 

 length of the shell. Beak central, straight, obtuse, rounded, not 

 rising above the hinge-line ; umbo well defined by the rapid slope 

 of the sides and the flatness of the ears. Ears triangular, flat ; 

 margins slightly concave ; extremities obtuse-angular. Posterior 

 ear of the right valve about one-third larger than the anterior. 

 Byssal sinus not marked. 



Test cancellate, marked by line radii and concentric striae, which 

 characters are also preserved on the ears. 



A right valve has a height of 11 mm., length 12 mm., and hinge- 

 line 8 mm. 



This small species somewhat resembles A. squama in the form of 

 the body and surface markings, but the beak is less acute and the 

 anterior ear comparatively smaller, without distinct sinus. 



Formation and locality. In the arenaceous shales of the Chemung 

 group at Philipsburg, Alleghany county, N. Y. 



AVICULOPECTEN SQUAMA. 



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

 tions : PI. 7, fig. 20. Jan., 1883. 



Shell transversely Jproad-elliptical, slightly oblique; height about 

 nine- tenths of the length. Right valve moderately convex. Left 

 valve not known. Hinge-line straight ; length two-thirds the length 

 of the shell, extending in front as far as the anterior margin of the 

 valve. Beak rounded, not rising above the hinge-line, situated 

 posterior to the center; umbonal angle 90°. Posterior ear small, 

 triangular, narrow, with concave margin; not strongly defined; 

 extremity angular. Anterior ear large, convex, broad-triangular 

 extremity obtuse ; margin convex ; separated from the body by a 

 deep rounded sinus, and from the sides of the umbo by a distinct 

 sulcus. 



