1863.] 



SALTER UPPER OLD RED SANDSTONE. 



479 



stones, calcareous layers, and argillaceous shales, are only (on a 

 much larger scale) the limestone, shale, and sandstone we have left 

 in South Pembrokeshire. 



Neglecting then the purple Morte slates, which, being destitute 

 of fossils, cannot yet be safely paralleled with any special division of 

 the Old Red*, I may, however, say that they pass up by insensible 

 gradations and loss of colour into the Marwood series. 



In ascending order we have : — 



1. Purple slates and sandstones of Morte Bay. 



2. A band of pale, nearly white slate, with a few Bivalves, 



3. A thick series of greenish-grey grits, with bands of Cu- 

 cullcea and Avicula Damnoniensis, in abundance, and with much 

 olive shale, in which a new Lingida occurs abundantly. 



1 4. An alternating series of calcareous sandstone, grey shales with 

 thin nodular bands of limestone, and grey cleaved slate full of 

 fossils, and many hundred feet thick. Avicula Damnoniensis and 

 Hhynchonella laticosta, with numerous Lamellibranchiata, occur in 

 the lower part ; and Strophalosia caperata with Spirifer Barumensis 

 throughout. 



The series No. 4 is the upper part of the "Pilton group" of 

 Phillips ; and its aspect in the grand coast- section of Baggy Point 

 and Croyde Bay is exactly like that assumed by the Carboniferous 

 Slates of Pembrokeshire, as they lie, in the section before noticed, 

 upon the fossiliferous beds of the Upper Old Bed. 



So like are the two sections, and so exactly does the succession 

 appear to correspond, that my faith in fossil-evidence gave way, in 

 1854, before this apparent identity. The grey sandstone and inter- 

 vening Plant-beds of Baggy are so like those of West Angle (on a 

 larger scale), and the overlying calcareous and shaly series so like 



Fig. 1. — Generalized Section in Pembrokeshire and North Ireland, 



Upper Old Red 

 (1,2,3). 



Carboniferous Slate 

 (4? &5). 



Carboniferous 

 Limestone (6). 



Fig. 2. — Generalized Section in Devonshire and South Ireland, 



Carboniferous 

 Limestone (6). 



(1,2) 



Upper Devonian [Marwood (3) and Piltoa Group (4)]. 



Carboniferous 

 Slate (5). 



the bottom part of the Carboniferous Slate of Angle — having a very 

 similar set of fossils and a few even identical, — that an older geologist 



* Professor Jukes admits, as I do, these reddish-purple slates to be the equi- 

 valents of the Old Red of the South of Ireland, and in the same mineral condition. 



