06 Mr. R. Etheridge o« Carboniferous LameUihrancliiata. 



X. — Notes on Carboniferous Lamellihranchiata. 

 By R. Etheridge, Jun., F.G.S. 



[Plate IV.] 



Class LAMELLIBRANCHIATA. 



Genus Aviculopecten, M'Coy, 1851 

 (Ann. & Mag. Nat. Hist. vii. p. 171). 



Aviculopecten subconoideus, sp. nov. PI. IV. figs. 1 & 2. 



Sp. char. Ovato-orbicular, insequivalve. Anterior side 

 rounded; posterior side slightly produced. Left valve the 

 more convex of the two, with the beak larger, more inflated 

 and more abruptly separated from the ears by a slope on each 

 side. Anterior car of tlie right valve almost triangular, de- 

 fined from the body of the shell by a deep notch, witli several 

 radiating ridges, crossed by strong scale-like strias ; anterior 

 ear of the left valve larger than the preceding, and not so 

 deeply defined, ornamented by many radiating ridges crossed 

 by strife parallel to its margin. Posterior ears pointed, falcate, 

 marked with radiating ridges crossed by sti-ise parallel to the 

 margins ; the radiating ridges of the left posterior ear per- 

 haps stronger and more numerous than those of the right. 

 Hinge-line long. Cartilage-area (in casts) w^ell defined, and 

 large for the size of the sliell. Body of the shell ornamented 

 with radiating ribs, larger and smaller alternately in the left 

 valve ; broader, flatter, and more nearly equal in the right 

 valve. 



Obs. The slightly extended posterior side, convexity of the 

 left valve, and separation of the body of the shell from the 

 ears by a slope intimately connect this species with A. conoi- 

 deus, M'Coy*. But in this species the ears are said to be 

 " large, equal, slightly pointed . . . and without radiating 

 striae ;" the right valve is not specially mentioned ; and the 

 radiating striae of the shell are " equal." In a later descrip- 

 tion. Prof. M'Coy only refers to the posterior earf. The 

 ornamented condition of the ears and the varying nature of 

 the ribs, however, tend to separate the two species. The 

 larger ribs of the left valve of A. subconoideus are sharper 

 in the umbonal region, and become gradually broader and 

 flatter towards the ventral margin, but in no case so broad or 

 flat as those of the right valve. The intermediate smaller 



• Synopsis Carb. Foss. Ireland, 1844, p. 91, t. 17. f. 2. 

 t Brit. Pal. Foss. p. 485. 



