FOSSILS OF THE CARBONIFEROUS. 229 
Aviculopecten affinis, n. sp. 
Plate xix, figs. 1, la. 
Shell of medium size. Left valve, exclusive of the ears, suborbicular 
in outline, depressed convex; hinge-line varying from two-thirds to five- 
sixths of the greatest width below; posterior margin most prominent at the 
transverse center of the shell from where it curves gently and nearly per- 
pendicularly downward to the somewhat abruptly rounded basal margin, 
and upward to the sinus beneath the ear; anterior margin most prominent 
above the center, from which it curves nearly as the opposite margin to the 
base, and above, more abruptly; ears subequal, subtriangular in form, and 
defined by a sinus that varies in depth and shape on different shells; beak 
subcentral, pointed, and extending above the hinge-line. 
Surface of both ears and the body of the valve ornamented with num- 
erous fine radiating coste, every third or fourth one of which is raised 
above the intervening costee, the latter usually running out before reaching 
the umbo; fine concentric strize cross the radiating striz on the ears and 
body of the valve, being more strongly marked on the anterior ear. 
Right valve nearly flat, with a stronger sinus under the anterior ear, and 
the surface marked by numerous simple radiating striz and concentric striz 
on the ears. 
An examination of many specimens in all conditions of preservation 
fails to show any crenulations on the hinge margin, although the interior is 
well preserved in several examples. 
This species varies considerably in the outline of the valves; some are 
longer than wide and others with length and width subequal In the latter 
case the left valve is somewhat like that of Crenipecten Winchelli Meek, of 
the Waverly Group of Ohio. (See Pal. N. Y., vol. v, pt. 1, plate ix, figs. 
1, 2, 4, 25-30.) The right valve, however, is finely but strongly striate 
longitudinally, while that of C. Winchelli is nearly smooth, except on the 
ears. 
This is a very abundant species in two localities, almost filling some 
of the layers on the little conical hill on the east side of Secret-cation-road 
Cation, where it is associated with A. Haguei, A. peroccidens, and A. Eurekensis. 
