536 DEVONIAN SERIES. [Ch. XXVI. 



In North Devon, on the contrary, the Devonian group has been less 

 changed, and its relations to the overlying carboniferous rocks or 

 " Culm Measures " are somewhat more clearly seen. The following 

 sequence is exhibited in the coast section on the Bristol Channel 

 between Barnstaple and the North Foreland.* 



Devonian Series in North Devon. 



(a. Calcareous brown slates ; with fossils, some of them 

 1. J common to the Carboniferous group, but most of 



Upper or Pilton 1 them distinct. (Barnstaple, Pilton, &c.) 



' Brown and yellow sandstone, with marine shells and 

 land-plants — Stigmaria, Sagenaria, and others. Bag- 

 gy Point, Marwood, &c. 

 f 2. Hard gray and reddish sandstones and micaceous flags, with- 

 out fossils, resting on soft greenish schists of consider- 

 able thickness. (Morte Bay, Bull Point, &c.) 

 Calcareous slates, with eight or nine courses of limestone, 

 full of corals and shells like those of the Plymouth lime- 

 stone, viz., Cyathophyllum ccespitosum, see fig. 606, Fa- 

 vosites polymorplia, see fig. 605, &c. (Combe Martin, 

 Ilfracombe Harbor, &c.) 

 C 4. Hard, greenish, red, and purple sandstones ; with occasional 

 Lower or Linton J fossils, Spirifers, &c. (Linton, North Foreland, &c.) 



group. j 5. Soft chloritous slates, with some sandstones ; Orthis, JSpiri- 



fer, and Corals. (Valley of Rocks, Lynmouth, &c.) 



group. 



Middle or Hfra 

 combe group. 



!■■ 



The successive beds of this section have been compared with those 

 of South Devon and Cornwall both by the authors of the "Devonian" 

 system and by other observers. And Professor Sedgwick has again 

 lately brought them into closer comparison.f Other geologists at 

 home and abroad have successively identified them with the Devonian 

 series in France, Belgium, the Khenish Provinces, Central Germany, 

 and America.]; I shall proceed first to treat of the main divisions 

 which have been established in Europe. 



Upper Devonian RocJcs. 



Pilton Group. — The slates and sandstone of Barnstaple (No. 1, a, b, 

 of the preceding section) were formerly considered to be represented 

 in Cornwall by the limestones of Petherwyn, which rise from under 

 the Culm Measures, constituting the Petherwyn group of Professor 

 Sedgwick. But later researches § have rendered it probable that these 

 beds overlie the Petherwyn group; they contain the shell Spirifer 



* Sedgwick and Murchison, Trans. Geol. Soc, New Series, vol. v. p. 644. De la 

 Beche, Geol. Report, Devon and Cornwall, pi. 3. Murchison's Siluria, p. 256. 



f Quart. Journ. Geol. Soc, vol. viii. p. 1, et seq. 



% See Dr. Fridolin Sandberger on the Devonian Rocks of Nassau (Geol. Verhalt. 

 Nassau) ; Fried. A. Romer, on the Hartz Devonian Rocks, in Dunker and Von 

 Meyer's Paheontographica, 3d vol. pt. 1. 



§ See Murchison's Siluria, 2d ed., p. 247. 



