﻿282 Reports and Proceedings- — 



Stage C. — Yoredale Beds. 3000 feet in Lancashire; Upper 

 Limestones and " Lower Coal and Ironstone series " of Scotland ; 

 Shale series of Kilkenny and Carlow ; Ironstone shales of Lough 

 Allen, with marine shells. 



Stage B. — Carhoniferous Limestone. Mountain Limestone of 

 Derbyshire ; " Scaur Limestone " in Yorkshire ; " Lower Lime- 

 stone " (Roman camp) of Scotland ; Carboniferous Limestone of 

 Ireland. 



Stage A. — Lower Limestone Shale of England. Calciferous Sand- 

 stone series ("Tuedian," Tate) of N. of England and Scotland; 

 Lower Carboniferous Sandstone, N. of Ireland ; Lower Carboni- 

 ferous slate, with Coomhola grits, with marine shells, S. of Ireland. 

 (In Scotland, estuarine or lacustrine.) 



PalcEontological BesuUs. — On making a census of the Molluscan 

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

 ferous Limestone (Stage B.) as determined by the palceontologist 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 or 75 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 

 Carboniferous Limestone.^ The series includes Pliilli'psia, which 

 has been found by Dr. F. Eomer, 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 F and G, 

 these being characterized by the prevalence of bivalves of supposed 

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

 thracosia." Of the few species of marine genera known in Stage F 

 (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 those two divisions of the Carboniferous 

 series. Of the several existing methods of classification adopted by 

 different authors, none of them ajDpeared sufficiently to recognize 

 the palceontological 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 pala^ontological break at the top of the Gan- 

 nister beds. 



On the other hand, the mineral and paleeontological differences 



1 In the discussion which followed the reading of Prof. Hull's paper, the author in 

 replying remarked that it seemed to him that sufficient importance had not 

 been given to the palieontological break above the Gannister beds; out of 74 species 

 of marine genera below this line not more than 6 pass upwards. 



