96 Mr. R. Etheridge on Carboniferous LamellibrancUata. 



X.— Notes on Carhomferous Lamellihranchiata. 

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



[Plate IV.] 



Class LAMELLIBRANCHIATA. 



Genus AvicuLOPECTEN, M'Coy, 1851 

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

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

 Sp. char. Ovato-orbicular in^quivalve. Anterior side 

 romfded: posterior side slightly produced. Left valve the 

 r^ore convex of the two, with the beak larger, more inflated 

 Td more abruptly separated from the ears by a s ope on each 

 Se TnteU L of the right valve almost triangular, de- 

 fined from the body of the shell by a deep notch with several 

 radiaUng ridges, crossed by strong scale-like striae ; anterior 

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

 deeply defined, ornamented by many radiating ridges crossed 

 bv stH^ parallel to its margin. Posterior ears pointed, falcate, 

 marked with radiating ridges crossed by striee parallel to the 

 ma g^^^^ radiating ridges of the left posterior ear pei-- 



haps^ stronger and mo?e numerous than those of the right 

 mnUline long. Cartilage-area (in casts) wel defined, and 

 wffo the sife of the shell. Body of the shell ornamented 

 wth radiating ribs, larger and smaller alternately m the left 

 valve; broader, flattei" and more nearly equal m the right 



^%bs. The slightly extended posterior side convexity of the 

 left valve, and'sep'aration of the body of the Bhell from the 

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

 S M^Coy*. But in this species the ears are said to be 

 "to equal, slightly pointed . . . and withou radiating 

 strS-'' the r ght valve"^ is not specially mentioned; and the 



adfat'lng strilof the shell are " equal." In a later descnp- 

 tkm Piof. M'Coy only refers to the posterior _ ear t- The 

 ornamented condition of the ears and the varymg nature of 

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

 larjr rbs of the left valve of A. suhconoideus bx^ sharper 



n the umbonal region, and become gradually broader and 

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

 flaf as those of the right valve. The intermediate smaller 



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

 t Brit. Pal. Foss. p. 485. 



