30 PALEONTOLOGY OF NEW YORK. 



Left valve convex, the convexity equal to about one-sixth of the longi- 

 tudinal diameter. Right valve unknown. 



Hinge-line straight, length three-fourths of the diameter, extending nearly 

 to the anterior margin of the shell. 



Beak obtuse, prominent, central, rising above the hinge. 



Ears triangular, nearly equal, separated from the umbo by distinct sulci. 

 Anterior ear with slightly convex margin ; extremity rounded. Byssal sinus 

 deep. Margin of posterior ear concave ; extremity abruptly mucronate. 



The test (as preserved on a partial cast of the interior) is marked by about 

 45 regular alternating, rounded rays with equal interspaces. The lines of 

 growth are fine and obscure on the specimen. The ears are marked by 

 from five to eight rays similar to those on the body of the shell. 



The ligamental area is a linear furrow along the hinge-line ; cartilage pit 

 small, situated under the beak. 



The left valve described has a height of 17 mm., and an equal length ; 

 hinge-line 13 mm. 



In the original description of this species mention is made of small, spinose 

 processes from the concentric stria? ; these do not exist in this specimen, 

 which is a partial cast of the interior.. 



This species is distinguished from A. striatus by its more circular form, 

 obtuse beak, and stronger radii. Compared with A. elongaiics, the wings are 

 smaller, and the height comparatively much less. 



Formation and locality. In the yellow sandstone of the Waverly group at 

 Newark, Ohio. 



AviCULOPECTEN (CrENIPECTEN ?) INCULTUS. 

 PLATE IX. KIG. 3. 



AvicuJi'prittii (I'rtn'iptftni .') iiiniltiui, 1 1 all. Pal. N. Y., vol. v, pt. l. Plates and Explanations: PI 9, fig. 



3. Jan.. 1883. 



Shell small, longitudinally very broad-elliptical, nearly circular, not oblique to 

 the hinge-line, sub-equilateral : height somewhat less than the longitudinal 

 diameter; basal margin regularly rounded. 



