540 Geological Society. 



Palceontological Results. — On making a census of the Mollusean 

 and other fossils from the various stages above that of the Carboni- 

 ferous Limestone (Stage B) as determined by the Palaeontologist 

 of the Geological Survey, some interesting results were obtained, 

 showing the prevalence of marine conditions up into stage E, and a 

 general change in the character of the fauna in the succeeding 

 stages. Including only the area of the British Islands, it was 

 found that no fewer than 37 genera, with 74 species, of decidedly 

 marine forms, occur in the Gannister-beds (Stage E), of which all 

 the genera and about 40 species were known in the stage of the Car- 

 boniferous Limestone. The series includes Phillvpsia, which has been 

 found by Dr. F. Homer in the representatives of Stage E in Silesia. 



On the other hand, of the whole number of species in stage E 

 (Gannister beds) only 6 are known in the overlying stages E and G, 

 these being characterized by the prevalence of bivalves of supposed 

 lacustrine or estuarine habitats, variously called " Unio " and " An- 

 ihracosia" Of the few species of marine genera known in stage E 

 (Middle Coal-measures), about 5 or 6 species are peculiar to itself, 

 according to the determination of the late Mr. Salter. 



Such a remarkable difference in the fauna of the Upper and 

 Middle Coal-measures, as compared with that of the Gannister beds, 

 constituted, in the author's opinion, sufficient grounds for drawing 

 a divisional line between these two divisions of the Carboniferous 

 series. Of the several existing methods of classification adopted by 

 different authors, none of them appeared sufficiently to recognize 

 the palseontological distinctions and characteristics of the several 

 formations. The large number of genera and species which are now 

 known to range up from the Carboniferous Limestone into the Gan- 

 nister beds, and no higher, indicated the proper horizon for a divi- 

 sional line, in fact a palaeontological break at the top of the Gan- 

 nister beds. 



On the other hand, the mineral and palseontological differences 

 between the Carboniferous Limestone and the overlying Yoredale 

 series* were sufficient to justify their separation into distinct divi- 

 sions ; while the Yoredale, Millstone-Grit, and Gannister series are 

 related by close mineral and palseontological resemblances. 



With a view, therefore, of bringing the classification of the Car- 

 boniferous series into harmony with the character of the representa- 

 tive faunas, and the physical features of the successive stages, the 

 author suggests that stages C, D, and E, composed of essentially 

 marine beds, should be united into a Middle Carboniferous group ; 

 while stages F and G would remain as at present, in the Upper 

 Carboniferous, their fauna being essentially of freshwater. The 

 series, as thus amended, would be as follows : — 



Upper Carboniferous Group. 



Stage G. Upper Coal-measures ) Essentially 



„ E. Middle Coal-Measures | freshwater. 



* In the south of Ireland there is strong evidence that the Yoredale beda 

 ("Shale-series") are unconformable to the Carboniferous Limestone. 



