46 Proceedings of the lloyal Physical Society. 



subdivided the Pectinidce into two sections,* which I believe 

 must be accepted — thus : 



a. Pectinidce, or" scallop shells" proper — with a large 



anterior ear, and central cartilage pit. 



b. AvicidoiKctinidm — large posterior ear, no cartilage pit, 



but a grooved hinge area. 



It is quite possible that the typical genus Pecten occurs in 

 British Carboniferous rocks ; indeed, Professor M'Coy has so 

 referred one species.-]- Be this as it may, however, we un- 

 doubtedly have a member of the Pectinidce proper, and one 

 which is pretty extensively found in Scotland — the Entolium 

 Sowerhii (M'Coy, sp.). J This shell has been variously re- 

 ferred to at different times, but a fortunate discovery by Mr 

 Bennie of many well-preserved internal casts at Teasses 

 Quarry, Fife, enabled its affinity with Meek's genus PJntolium 

 to be made out. § Great interest is attached to E. Sowerhii, 

 from the evident manner in which it forecasts an Oolitic 

 type, represented by the Pecten demissum (Phill.). A few 

 years ago Mr Bennie found a badly preserved shell in the 

 east of Scotland with all the appearance of an ordinary 

 Avicidojjecten. The hinge line, however, bore traces of a 

 series of hinge pits rather than the usual striated area. 

 Two genera possessing this character have been described 

 from American Carboniferous rocks — Perno-pectcn (Win- 

 chell) II and Enchondria (Meek),1I to either of which the 

 shell in question may be referred so far as we know its 

 structure. 



The genus Aviculopecten is certainly the most prolific 

 genus of Bivalves in the Carboniferous system. No less than 

 44 species have been listed from Scotch Carboniferous 

 rocks, but it is not too much to say that quite a quarter of 

 these have no existence, in fact, being mere synonyms of one 



* Pal. Up. Missouri, 1864, p. 48. + Brit. Pal. Toss., \^. 477. 



tM'Coy, Synopsis Garb. Foss., 1844, p. 100; Etheridge, Gcol. Mag., 

 1874, i., p. 300; 1877, iv., p. 241. 



§ Etheridge, " On the Hinge Structure and Generic Aflinitics of Fcdcn 

 Sowerbii,^^ etc. (Annals Nat, Hist., 1878, ii., ]). 30). 



llProc. Acad. Nat. Science, riiihid., 1865, ]>. 125. 



U American Jour. Science, 1874, vii., p. 445. 



