Bkkde.] Carboniferous Invertebrates, 123 



This species differs from A. hertzeri Meek in being much 

 larger, in having a much more (20°) acute beak, which makes 

 it a more slender shell. Aside from the species just mentioned, 

 it can easily be distinguished from our other Coal Measures 

 species by its strongly reticulated surface. 



The specimen at hand agrees very well with Miller's descrip- 

 tion and figure, though there are a few minor differences, but 

 both are from the same locality, so there can be but little doubt 

 of their identity. 



Aviculopecten germanus. Plate XIII, fig. 4. 



Aviculopecten germanus Miller and Faber, Jour. Cino. Soc. Nat. Hist., 

 xv, pp. 81, 82, pi. i, f. 9, (1892.) 



Original description : " Shell small, a little higher than long ; 

 inequilateral ; oblique ; base regularly rounded ; antero- basal 

 and postero-basal margins rounded. Hinge oblique, nearly 

 straight, not quite equaling 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 posterior one, angular at the extremity and rounding 

 on the margin below into a notch, and arching from the wing 

 into a deep and distinct sinus that separates it from the poste- 

 rior margin of the shell. Umbo tumid and umbonal slopes 

 diverging to the margin. Beak high, pointed and projecting 

 beyond the cardinal margin a little forward of the middle of 

 the hinge line. There are two costa? on the posterior ear, and 

 three or more finer ones on the anterior ear. There are about 

 twelve principal radiating ribs on the body of the shell and 

 about as many rudimentary and intercalated shorter ribs be- 

 tween them ; they are separated by wider flattened spaces. It 

 is difficult to tell from our specimens whether or not there were 

 any concentric lines, though they are quite well preserved ; if 

 there were such lines they were very fine. 



"This species approaches more nearly to^l. rectilaterarins than 

 to any other, but it may be readily distinguished by the scarcity 

 of the radiating ribs and the wide flattened spaces between 



