486 PROCEEDINGS OF THE GEOLOGICAL SOCIETY. [May 20, 



mixed with shale, come close down upon the yellow sandstones, as 

 is the case at Clydach in Monmouthshire in even a more striking- 

 way*. 



The well-known Clifton section also gives the same results, with 

 the great advantage of being all visible along the Avon. Mr. D. H. 

 Williams gives f, below the thick alternating series of shales and 

 limestone, crowded from top to bottom, as I have myself seen, with 

 the same Mountain-limestone species as those common at Tenby, 



Grey shale and red marl (thin limestones). 



Light quartzose sandstone and conglomerates. 



Red and claret- coloured marls and sandstones. 



Light grey and brown sandstones and shales. 



Red marls and light-grey sandstones, &c. &c. 



I must by no means omit to notice the careful section of the Far- 

 low beds X by Messrs. Roberts and Morris. In this compact paper, 

 the passage upward from 



1. Red sandstone, with cornstone, to 



2. Yellow sandstone and conglomerate, containing Eoloptychius 

 giganteus, Pterichthys meter oceplialus, and a larger species, and 

 then to 



3. Grey oolitic limestones, bearing Fish, or Crinoids, or Bra- 

 chiopods in the several bands, and these interstratified again 

 with clays of various colour, 



is completely in accordance with the Pembroke sections. The Bra- 

 chiopods are mostly identical with those from Tenby. Spirifer cus- 

 pidatus, and the varieties which seem to connect this species with 

 S. distans, Sow., together with Aihyris, Rhynchonella, and other 

 fossils, completely recall to mind the Tenby sections. 



The Fish too, though far more numerous and better preserved, 

 are in the main identical. Orodus, Psammodus, Helodus, and Cla- 

 dodus, among them, are excellent types for the Lower Limestone- 

 shales. 



But the measured thickness of this section gives us no idea of the 

 masses to be seen in Pembrokeshire ; and we have only the general 

 accordance — of red sandstones surmounted by yellow grits full of 

 characteristic Upper Devonian types — to assure us that the Upper 

 Old Red is here, as in the sections above described, gradually losing 

 its colour before being overlain by the deeper-water sediments of the 

 Carboniferous series. 



In the Mendips a valuable section by Mr. D. H. Williams § shows 

 the same alternations of impure limestone and shale, at the base 

 interstratified, as at Caldy Island, with red limestones and oolitic 

 bands ; and a thick series of brown calcareous sandstones which can 

 be exactly paralleled with Nos. 77 to 80 of the Skrinkle Bay section || . 



Then a few alternations of red shale and cherty limestone at the 

 base conduct us to hard light-grey sandstones, which here form the 



* Mr. Eees's Section, Geol. Surv., Vertical Section No. 12. 



f Geol. Surv., Vertical Sections Nos. 11 & 12. 



X Quart. Journ. Geol. Soc. vol. xviii. p. 95. 



§ Geol. Surv., Vertical Section No. 12. || Ibid. No. 12. 



