New Species and Xezc Stnicdiral Parts of /''ossils. 8i 



at the beak on eacli valve, and is directed ol^liquely downward 

 and backward, lieaks at the anterior end of the shell and ex- 

 tending beyond the hinge line. Umbones of moderate size 

 and nmbonal ridge gradually enlarging until it passes the 

 middle of each valve and then tapering to the postero-basal 

 margin. Posterior end wedge shaped. vSurface of each valve 

 marked by a rather broad furrow that arises at the cardinal 

 line behind the beaks and extends in an oblique line to the 

 postero-basal margin, and above this, near the middle of the 

 shell another furrow arises and extends to the posterior end of 

 the shell, and above this within the posterior third of the .shell 

 another furrow arises and extends to near the postero-cardinal 

 margin. Below the finst described furrow, the sHell is ribbed 

 in slightly curving lines to the basal margin, where they are 

 most strongl)^ defined. A few obscure concentric lines are 

 seen on the cast behind the commencement of the principal 

 oblique furrow. The muscular impression and external shell 

 unknown. 



This species is di.stinguished by its subelliptical outline, and 

 by three oblique furrows on each valve. This latter pecul- 

 iarity we have never observed on any other species in this 

 genus. 



Found by Charles Faber, in the Hudson River Group, on 

 the hills, at Cincinnati, and now in his collection. 



AviCL'LOPECTKN (;ERM.\NUS, U. Sp. 



Plate /, Fi^. (j, left valve, natural size. 



Shell small, a little higher than long ; inequilateral ; oblique; 

 base regularly rounded ; antero-basal and po.stero-basal mar- 

 gins rounded. Hinge oblique, nearly straight, not quite equal- 

 ing the greatest length of the valves below. Posterior ear 

 extends to the lateral border, with which it forms nearly a 

 right angle ; it graduates into the .shell below, without the 

 presence of a sinus. Anterior ear rather shorter than the pos- 

 terior one, angular at the extremity and rounding on the mar- 

 gin below into a notch, and arching from the wing into a deep 

 and distinct sinus that separates it from the posterior margin 

 of the shell. Umbo tumid and umbonal slopes diverging 



