1863.] SALTEE UPPER OLD RED SANDSTONE. 475 



In the measured sections given by Sir H. De la Beche in the 

 ' Memoirs of the Geological Survey'*, those of East and West Pem- 

 brokeshire show a clear succession from the Upper Old Red Sand- 

 stone to the Carboniferous Shales. The most complete of these sec- 

 tions are those from Caldy Island and Skrinkle Haven, Tenby, 

 where the whole mass of the Mountain Limestone is underlain by 

 shales and limestones, and these again by the upper beds of the Old 

 Red Sandstone, in unbroken succession. About 150 feet of the latter 

 formation is given in detail. Twenty miles to the west another sec- 

 tion, different in detail, but in the main similar, is exhibited in 

 the wild coast-line of West Angle Bay, Pembrokeshire f. The dis- 

 crepancies, and agreements too, between the different parts of these 

 sections are very striking. I examined them all, and then, crossing 

 the Bristol Channel, took up the corresponding sections on the Barn- 

 staple river and the coast at Croyde Bay. A single fossil in the 

 collections made by Prof. Phillips in West Pembrokeshire gave me 

 the hope of identifying the lowest beds of the limestone-shale with 

 the uppermost Devonian beds, nor was I at all disappointed. 



The detailed examinations are written, and wait for publication 

 in the Memoirs of the Geological Survey. I will here confine myself 

 to general statements, somewhat different from those made, on my 

 evidence, in the Anniversary Address of the President of the Geological 

 Society in 1855. In that year I visited the South of Ireland, and, in 

 company with Mr. Jukes, saw ample confirmation of the succession 

 observed in the North Devon and Pembroke sections. The results 

 obtained are correctly stated in ' Siluria,' 2nd ed., pp. 299, 300. In 

 Mr. Hamilton's Address I had, however, ventured prematurely to 

 identify the Lower Limestone- shales of Pembrokeshire with the 

 Pilton group (uppermost Devonian) of North Devon; and this in 

 the teeth of palaeontological evidence which was fully stated, and 

 which ought to have weighed more heavily with me. So exactly 

 similar, however, are the two sections physically, and so exactly does 

 the fauna of one represent the fauna of the other, that I allowed 

 myself to believe that two sets of species, closely allied but actually 

 different, had lived at one and the same time on either side of a 

 barrier so narrow as the width of the Bristol Channel ! 



This idea, which was backed by the strong conviction and pub- 

 lished opinion of Sir H. De la Beche, was in accordance too with the 

 doctrine of marine provinces lately advocated by Prof. Edward 

 Porbes, and there is no wonder that I embraced it. 



In the meantime I was enabled to see, in 1857, the Cornish sec- 

 tion, and was satisfied that the Upper Devonian group in Britain 

 was divisible into two series %• And I had in Ireland seen the up- 

 permost of these in its true place — beneath the Limestone-shale — 

 and forming, or resting immediately on, the uppermost portion of 



* Vol. i. pp. 61, 108, 111, &c. 



t These sections are unrivalled for extent and completeness. The vertical 

 beds exposed to the coast-waves are worn by them in a manner to clear them of 

 all detritus, and exhibit the whole series in a remarkably distinct manner. 



J ' Siluria,' 2nd ed. p. 300. 



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