698 PROCEEDINGS OF THE GEOLOGICAL SOCIETY. 



fail to clearly determine that south and south-west of Lynmouth, after 

 passing the anticlinal, an entirely new marine fauna sets in, accom- 

 panied by an equally new set of physical conditions, the species 

 comprising the fauna in this North Devon area having but one form 

 in common with all the Silurian species, viz. Atrypa reticularis. We 

 are therefore, I believe, from our knowledge of the structure of the 

 country, justified in assuming that along its now northern borders, 

 washed by the waters of the Bristol Channel, and somewhere south 

 of the Mendip Hills, an axis of movement or a barrier of some kind 

 existed, stretching under what are now the secondary rocks of Somer- 

 set, Dorset, Hampshire, Sussex, and Kent, on to the French, Belgian, 

 and Rhenish areas, over which we have one and the same kind of 

 physical conditions, one and the same fauna, one and the same re- 

 cognizable and adapted general succession. 



The accompanying Table of equivalent strata in different areas has 

 been drawn up with the view of endeavouring to coordinate the groups 

 one to the other, taking their physical structure, and the distribu- 

 tion of the fossils of North and South Devon as the types of the Devo- 

 nian system, adapting the European and Irish series to them as the 

 type. It is still a matter of great doubt as to whether the true Old Red 

 Sandstone series of England, Wales, and Scotland can in any way 

 be really coordinated with the marine Devonian of Devonshire. 

 All that can be said is, that they both occupy a place above the 

 Silurian and below the Carboniferous, and that they are not found 

 together in any area. The barren Foreland sandstones at the base 

 of the Lynton slates I have, as before stated, placed as Lower Devo- 

 nian sandstone. The red grits and sandstones which succeed these 

 (the Hangman grits), and on which repose the Combe-Martin and 

 Ilfracombe slates, I have placed at the base of, and classified with, 

 the Middle Devonian series as Middle Devonian sandstone, and the 

 equally well-defined and (to these) conformable red sandstones of 

 Pickwell Down I have placed at the base of the Upper Devonian 

 strata as Upper Devonian sandstone, which is the whole of the Old 

 Red Sandstone of Prof. Jukes*. The groupings of the Rhenish 

 Prussian, Belgian, and French series are correlated with our Devon- 

 shire beds, the whole of which I believe belong to and were depo- 

 sited in and over one general area, and contemporaneously. 



* Neither of these three Sandstones contains any organic remains, except the 

 uppermost beds of the Hangman G-rits near Combe Martin, in which occur 

 Myalina and Natica, &c., as before stated. 



