420 DEVONIAN SERIES. !"Ch. XXVI 



racy, the true place in the geological series of these slate-rocks and 

 limestones of South Devon, had not Messrs. Sedgwick and Murchison, 

 in 1836 and 1837, discovered that the culmiferous or anthracitic shales 

 of North Devon belonged to the Coal, and not, as preceding observers 

 had imagined, to the " transition " period. 



As the strata of South Devon here alluded to are far richer in organic 

 remains than the red sandstones of contemporaneous date in Herefordshire 

 and Scotland, the new name of the " Devonian system " was proposed as 

 a substitute for that of Old Red Sandstone. 



The link supplied by the whole assemblage of imbedded fossils, con- 

 necting as it does the paleontology of the Silurian and Carboniferous 

 groups, is one of the highest interest, and equally striking whether we 

 regard the genera of the corals or of the shells. The species are mostly 

 distinct, except in the upper group. 



The rocks of this group in South Devon consist, in great part, of green 

 chloritic slates, alternating with hard quartzose slates and sandstones. 

 Here and there calcareous slates are interstratified w r ith blue crystalline 

 limestone, and in some divisions conglomerates, passing into red sand- 

 stone. But the whole series is much altered and disturbed by the intru- 

 sion of the granite of Dartmoor and other igneous rocks. 



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 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. 



f (a. Calcareous brown slates ; with fossils, many of them common to 

 T1 - J 1. ■< the Carboniferous group. (Barnstaple, Pilton, <fec.) 



PP J (6. Brown and yellow sandstone, with shells and land-plants — Stiff- 

 (_ maria, Knorria, and others. (Baggy Point, Marwood, &a.) 



Hard gray and reddish sandstones and micaceous flags, without 

 fossils, resting on soft greenish schists of considerable thickness. 

 (Morte Bay, Bull Point, <fcc.) 

 Calcareous slates, with eight or nine courses of limestone, full of 

 corals and shells like those of the Plymouth limestone. (Combe 

 Martin, Ilfracombe Harbor, &c.) 



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

 Spirifers, &c (Linton, North Foreland, &c.) 

 5. Soft chloritous slates, with some sandstones ; Orthis, Spirifer, and 

 some Corals. (Valley of Rocks, Lynmouth, &c.) 



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 Prof. 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 Rhenish Provinces, Central Germany, and Amer- 



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

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

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



Middle 



