548 Dr. J. W. Evans — Devonian Rocks of North Devon. 



plant-bearing beds of a fish-plate referred by Dr. Smith Woodward to 

 Coccosteus, a genus which is usually of Middle Old lied Sandstone and 

 Middle Devonian age, though it has been found in the Upper Old lied 

 Sandstone. The Staddon Grits of South Devon, on the other hand, 

 which are usually considered to be the equivalent of the Hangman 

 Grits, cannot extend upwards much above the base of the Eifelian or 

 Lower-Middle Devonian, as they are succeeded by dark-grey slates 

 and shaly limestones with Calceola sandalina. The succession in the 

 Middle Devonian of North Devon may be paralleled in the Boulonnais, 

 where micaceous sandstones with plant remains are overlaid by 

 marine beds with Stringocephalus burtini. 



The Hangman Grits are succeeded by the Combe Martin Beds, 

 grits with occasional ferruginous crinoidal limestones, and these by 

 the llfracombe Beds, shales and limestones with crinoids and corals. 

 Except for an alleged occurrence of Stringocephalus, which cannot now 

 be verified, no distinctive fossils have been found either in the Combe 

 Martin or Lower llfracombe Beds, and they may be either Upper- 

 Middle Devonian (Givetian) or Lower-Upper Devonian (Frasnian). 

 Unfortunately no goniatites have been found in the Devonian of 

 North Devon, so that exact correlation is difficult. In higher portions 

 of the llfracombe Beds Spirifer verneuili and Rhynchonella ( Wilsonia) 

 cuboides are found, which are sufficient to establish the Upper 

 Devonian (presumably Frasnian) age of the rocks. The highest 

 llfracombe Beds are less calcareous, and there seems no reason to 

 doubt that they pass upwards conformably into the Morte Slates, the 

 Upper Devonian age of which is completely established by the 

 occurrence of Spirifer verneuili (var. hamlingi), and they may well 

 represent the Schistes de Matagne, which form the highest beds of 

 the Frasnian in the Ardennes. Rocks of the same age appear to be 

 met with in the Boulonnais and in the boring in Tottenham Court 

 lload in London. The Morte Slates become more arenaceous at the 

 summit and are succeeded probably conformably by the Pickwell 

 Down Sandstones. The junction is usually faulted, but this is apt to 

 be the case in strongly folded areas where successive beds differ 

 considerably in physical characters and in the resistance they offer to 

 the forces to which the rocks have been subjected. The Pickwell 

 Down Sandstones have yielded the typical Upper Old Bed Sandstone 

 fish Holoptychius and Bothriolepis, and may be compared to the beds 

 with the same forms reached by a boring at Southall, west of London, 

 and to the Psammites de Condroz. They must therefore be referred 

 to the terrestrial or Old Red Sandstone type of the Famennian. 

 The Baggy and Marwood Beds that overlie the Pickwell Down 

 Sandstones and the lower portion of the succeeding Pilton Beds 

 represent a marine facies of the Upper Famennian, as well as the 

 Calcaire d'Etroeungt, which forms a passage to the Carboniferous in 

 the Ardennes. The Upper Devonian of the Turnford boring in the 

 Lea Valley, north-east of London, and the marine beds of the Upper 

 Old Red Sandstone of South Wales and the Coomhola Grits in South 

 Ireland are probably at about the same horizon as the Baggy and 

 Marwood Beds and the base of the Piltons. The Upper Pilton Beds 

 have now been shown to be of Carboniferous and not Devonian age, 



