4 CARBONIFEROUS LAMELLIBRANCHIATA. 



The species of certain families of Carboniferous Lamellibranclis — Cavhonicola 

 (Anthracosia) , Anthracomya, and Naiadltes [Anthraco'ptera) — having been fullj 

 described in a former Monograph, will be only briefly alluded to in the present 

 work ; but it is deemed inadvisable to omit them altogether, as these genera form 

 intermediate links between other Palaeozoic groups. 



The greatest systematic work on the subject of this Monograph is that by 

 L. de Koninck, a brief synopsis of which will be found hereafter. I have had the 

 opportunity of personal examination of all the specimens in the collection of types 

 in the Musee de I'Histoire Naturelle at Brussels, which formed the material for 

 that work, owing to the kindness of Professor Dupont. These specimens are all 

 from the " Calcaire Carbonifere " of Belgium, and as a fauna differ very markedly 

 from that which obtains in British rocks of Carboniferous age, only about 8 per 

 cent, of all the species described beiug recognised as occurring in British rocks. 



This difference is, I think, largely due to differences in the deposits in the 

 two areas. In Great Britain the larger number of our Carboniferous bivalves 

 are obtained from the shales and argillaceous deposits which were probably laid 

 down contemporaneously with the great " Massif " of limestone in Belgium, and 

 with the smaller masses in Derbyshire, Somersetshire, Wales, and Ireland. But 

 these English deposits, judging from many collections, do not appear to contain a 

 fauna by any means rich in Lamellibranchs. In Ireland, however, conditions were 

 somewhat more favorable to the growth of bivalves, for M'Coy described 195 

 species from the Carboniferous Limestone; a number which is probably far in 

 excess of the truth, as many species were founded on mere variations of shape and 

 size ; and it is probable that in the case of the PectinidsD, of which genus sixty-nine 

 species were described, the varied ornament and sculpture of the right and left 

 valves served to separate the two halves of a shell into two species. 



Mr. G. H. Morton,^ in a careful and exhaustive work on the Carboniferous 

 Limestone of North Wales and its fauna, only mentions twenty-four species of 

 Lamellibranchs as occurring within the district in which he laboured, and these 

 only very sparingly. 



The Brachiopoda are by far the most common fossils in the Carboniferous 

 limestones of England and Wales, both as regards numbers and wideness of 

 distribution. They are by no means evenly distributed throughout the mass, or 

 even in the same bed ; certain portions of limestone are almost wholly made up of 

 fossil shells, others are almost free from them ; but the fossiliferous pockets are 

 comparatively rare, and the shells are almost all broken and the valves separated, 

 affording evidence that the shells are not exactly in the place where they lived. 

 'I'his is not the case where the shells are obtained from the shales intercalated 

 between the thin beds of limestone in the Northumbrian Scottish area. 

 1 'Proc. Liverpool Geol. Soc.,' 1876— 1878, and 1886. 



