President's Address. 47 



another. At the same time tliere are otlier genuine species 

 in our beds which have never been described. 



These so-called species have, with few exceptions, been 

 placed haphazard in the genus AviciclojJeden, simply from 

 their general resemblance to M'Coy's type. It is, however, 

 possible, and even probable, that many of them may belong 

 to types, at least subgenerically distinct from Aviculopeden. 

 We probably possess one Pecten, if not more ; we certainly 

 have an Entolium, and perhaps a EucJwndria or Pernopecten. 

 Lastly, I see no reason why the genus StreUopteria, proposed 

 by Professor M'Coy,* should not be made more use of than 

 it has been. 



In England at least, two species of Avicidopcctcn occur in 

 the Coal Measures, — A. iKipyraceus (Sby.), in the Gannister 

 coal, near 01dham,-(- and A. fihrillosiis (Salter), in a marine 

 bed at Ashton-under-Lyne, over the great main seam. \ 



Now, in Scotland, A. p)ctpyraccus, which is a typical Coal 

 Measure species elsewhere, so far as I am aware, does not 

 occur in the Coal Measures proper, but is confined to the 

 limestones, and the INIiddle Coal and Iron series. § A full list 

 of the Scotch Aviculopectens will be found in both the 

 *' Catalogues " by Messrs Armstrong and Young, but space 

 forbids our making anything like a descriptive reference to 

 them. 



The family Aviculida3 or Pteriidce, as it is now usually 

 called, II contains the genera Avicida, Pterinea, Posidonomya, 

 Myalina, and Pteronites. The first and last of these genera 

 are well represented by species in Scotch Carboniferous 

 rocks, but do not call for detailed notice. 



Myalina is an excellent genus possessing terminal beaks, 

 a thickened flat hinge margin with longitudinal cartilage 

 grooves, and sometimes septiferous beaks. As the British 

 type we may select Myalina crassa (Fleming), a very gregari- 

 ous shell, which sometimes grows to large proportions.^ It 



* Brit. Pal. Fos.s., p. 482. 



t Mem. Geol. Survey, Gt. Britain, country around Oldham, 1864, p. 61. 



t Ibid., p. 64. 



§ See Etheridge, Annaly Nat. Hist., 1875, xv., p. 4-27 



II Ibid. 11 Ibid. 



