FOSSILS OF THE CARBONIFEROUS. 



229 



Aviculopecten affinis, n. sp. 

 Plate xix, figs. 1, 1 a. 



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 costae, every third or fourth one of which is raised 

 above the intervening costae r the latter usually running out before reaching 

 the umbo; fine concentric striae cross the radiating striae on the ears and 

 body of the valve, being more strongly marked on the anterior ear. 



Eight valve nearly flat, with a stronger sinus under the anterior ear, and 

 the surface marked by numerous simple radiating striae and concentric striae 

 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 Winchetti 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. Winchetti 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-canon-road 

 Canon, where it is associated with A. Haguei, A.peroccidens, and A. EureJcensis. 



