474 PKOCEEDJNGS OF THE GEOLOGICAL SOCIETY. [May 20, 



3. On the Upper Old Red Sandstone and Upper Devonian Rocks. 

 By J. W. Salter, Esq., F.G.S., A.L.S. 



Contents. 

 I. Introduction. 



2. South Pembrokeshire. 



3. North Devonshire. 



4. Somersetshire, Gloucestershire, and 



Shropshire. 



5. South Ireland. 



6. Foreign Equivalents. 



7. General Conclusions. 



8. Appendix. 



§ 1. Introduction. 



I was engaged for three summer months in 1854, and again for a 

 short time last year, in examining carefully the lower beds of the 

 Mountain Limestone and the uppermost beds of the Old Red Sand- 

 stone, with a view to establish, if possible, the correlation between the 

 Upper Old Red and the corresponding portion of the Devonian series 

 — a relation which has been called in question by good observers. 



The memoir of Sedgwick and Murchison* was, indeed, a full state- 

 ment of the identification of the Old Red Sandstone, as a mass, with 

 the Devonian ; a comparison first suggested by Lonsdale from a con- 

 sideration of the fossil evidence, and ably supported by Godwin- Austen 

 from his Rhenish explorations, though afterwards called in question 

 by him. The identification is repeated in the later edition of ' Siluria.' 

 Yet, over the North-European districts, there is a singular deficiency 

 of proof of the superposition of the Devonian to the Upper Silurian 

 rocks, and more especially of the gradual passage, at any one point, 

 of the Old Red Sandstone into rocks of the Devonian type. 



It has been argnied, and with reason, by Sharpef that in Belgium 

 Old Red Sandstone of the ordinary type underlies the whole of the 

 Devonian rocks with marine fossils. The opposite case occurs in the 

 red conglomerates of the Catskill group in America, which themselves 

 overlie the Devonian. But it has been much overlooked that, in the 

 latter country, the whole Devonian mass, distinguished by its fossils, 

 is clearly superposed on Upper Silurian rocks ; while it has been by 

 no means certain what part of our great Old Red Sandstone group 

 is represented by the red conglomerates either of America or of Bel- 

 gium. Nor has it been decisively shown that the Old Red Sandstone 

 passes conformably into the strata above or below it ; all that could 

 be said with certainty was this— that the Devonian rocks contain 

 fossils of a newer type than the Silurian and overlie them, and that 

 the Old Red Sandstone holds some intermediate place between the 

 Silurian and the Carboniferous rocks. 



In this state of the question, the positive identification of any one 

 part of the Old Red series with any one portion of the Devonian 

 became of paramount consequence ; since, if we could know the true 

 succession of the Old Red beds as accurately as that of the Devonian 

 rocks has been already traced, we might be able to prove or disprove 

 the correlation of the two series. I have tried to do this, and have, 

 I hope, succeeded. 



* " On the Devonian Rocks of the Rhenish Provinces," Trans. Geol. Soc. 2nd 

 ser. vol. v. pp. 633 &c. 

 t Quart. Journ. Geol. Soc. vol. ix. p. 18. 



