Geological Society. 317 



GEOLOGICAL SOCIETY. 



[Continued from p. 71.] 



April 17, 1867. — Sir Gharles Lyell, Bart., M.A., F.R.S., 



Vice-President, in the Chair. 



The following communication was read : — 



" On the Physical Structure of North Devon, and on the Palae- 

 ontological Value of the Devonian Fossils." By Robert Etheridge, 

 Esq., F.R.S., F.G.S., Palaeontologist to the Geological Survey of 

 Great Britain. 



The Lower, Middle, and Upper groups of sandstones and shales of 

 West Somerset and North Devon were described in this paper as oc- 

 curring in a regular and unbroken succession from north to south, 

 namely from the sandstones comprising the promontory of the Fore- 

 land, at the base, to the grits and slates &c. overlying the Upper Old 

 Red Sandstone of Pickwell Down to the south. The author was unable 

 to see any traces of a fault of sufficient magnitude to invert the 

 order of succession,, or that would cause the rocks of the Foreland at 

 Lynton to be upon the same horizon as those south of a line of 

 high ground that passes across the county from Morte Bay on the 

 west to Wiveliscombe on the east. 



The Foreland grits and sandstones are overlain by the Lower or 

 Lynton slates, and form a group equal in time to the Lower Old 

 Red Sandstone of other districts, but deposited under purely marine 

 conditions. 



The author then showed that above the Lower or Lynton slates 

 there is an extensively developed series of red, claret-coloured, and 

 grey grits, from 1500 to 1800 feet thick; these form a natural and 

 conformable base to the Middle Devonian or Ilfracombe group. The 

 highest beds, containing Myalina and Natica, insensibly pass into 

 the gritty and calcareous slates of Combe Martin, Ilfracombe, &c. ; 

 this Middle group Mr. Etheridge unhesitatingly regarded as the 

 equivalent of the Torquay and Newton Bushel series of South 

 Devon. 



Mr. Etheridge gave detailed Tables of the organic remains of the 

 two groups (the Lower, or Lynton, and the Middle or Ilfracombe), 

 and collated with them those species found in equivalent strata in 

 Rhenish Prussia, Belgium, and France. He was inclined to believe 

 that these two marine fossiliferous groups represent in time the 

 unfossiliferous Old Red Sandstone (Dingle beds) of Kerry, and the 

 GlengarifF and Killarney Grits of the south-west of Ireland. 



The author then endeavoured to prove that the Pickwell Down 

 beds are the true Upper Old Red Sandstone only, not the whole of 

 the formation, as was lately proposed. 



Arguments were also brought forward to show the probability of 

 the Carboniferous slate (in part) and Coomhola grits being the 

 equivalent of the English Upper Old Red Sandstone, or Upper 

 Devonian, and that the North Devon beds only are to regarded 

 as the true type (to which the Irish must be compared), and not 

 vice versa. 



