116 PALEONTOLOGY OF NEW YORK. 



county, Lb probablj from the Hamilton shales at Fultonham; and the only 

 species from this locality, answering the description given, is A. Boydii, in 

 a condition in which the radii and elevated concentric lamellae are more con- 

 spicuous than in any specimens from Cazenovia, Hamilton, or any other locality 

 in Central New York. 



Formation and localities. In the shales of the Hamilton group; abundant at 

 numerous places in the eastern and central portions of the State. 



ACTINOFTERIA PER0BLIQUA. 

 l'LATK XIX, PIG. 31; PLATE LXXXIV, PIG. 14. 



Arirnlu perubliqua, Conrad. Jour. Acad. Nat. s L -i.. Phila., vol. viii, p. 235. pi. 12, fig. 1. 1842. 

 Actirwpteria perobliqiia, (Conrad) Ball. Pal. N. V., vol. v, pt. 1. Plates and Explanations : PI. lit. fig. 31. 



Jan.. 1SS3. 



Shell of medium size, sub-rhomboidal ; body very oblique, narrow-ovate; length 

 one-third greater than the height ; anterior margin truncate or slightly con- 

 cave ; basal margin regularly arched and acutely rounded over the post-basal 

 side. 



Valves very convex. Left valve gibbous in the upper part, angular along 

 the post-cardinal slope. Right valve somewhat less convex. 



Hinge-line straight, about two-thirds the length of the shell. 



Beak anterior, acute, prominent, inclined forward. Umbonal region 

 gibbous, subtending an acute angle. 



Ear a small lobe, defined by a distinct sulcus and shallow, elongate, bvssal 

 sinus. Wing large, triangular, limited by the angular post-cardinal slope 

 of the valves ; margin moderately concave, sloping forward ; extremity 

 angular. 



Test (as seen in the specimen, which is a partial cast of the interior), 

 marked bv irregular concentric striae, which become fasciculate on the wing; 

 the surface apparently without rays. 



Muscular impression large, sub-quadrangular below the middle of the post- 

 cardinal slope, from which, the pallial line curving downward below the 



