282 report — 1865. 



that within the boundary of these two faults we have an exposed section of 

 all the Lower Cambrian beds, the whole of the Lower Lingula-flags, and a 

 part of the Middle Lingula-flags, following one another in true succession. 



I have taken three parallel sections across the hue of strike, as follows : — 



1st. Caerbwddy section, to the west of Porth-y-rhaw, including nearly the 

 whole of the Lower Cambrian beds exposed in this neighbourhood, and above 

 400 feet of the Lower Lingiila-flags. 



2nd. Porth-y-rhaw section runs along the east side of that creek, and in- 

 cludes the uppermost beds of the Lower Cambrians, and nearly the whole of 

 the Lower Lingula-flags. 



3rd, or Cradle Rock section, includes the remaining beds of the Lower Lin- 

 gula-flags, and the Middle Lingula-flags as far as they are exposed here in 

 true succession. It extends from a point inland of Porth-y-rhaw to the 

 Cradle Rock — the latter an islet about midway from Porth-y-rhaw to the 

 mouth of Solva Harbour. The first, or Caerbwddy section, cuts across the 

 beds in a direction from N."W. by N. to S.E. by S., and includes about 1980 

 feet of conformable strata, comprising, in ascending order, — 



Syenite. 



Fine-grained shales, altered. 



feet. 



1. Some Conglomerates (chiefly quartz pebbles in a purple ( kq 



base) | 



2. Greenish sandstones in thin beds 280 



3. Purple sandstones, massive 8(30 



[ A variable series. Yellowish sandstone and ) > Lower 



4. Upper Grey J shale in thin beds, and grey grit, with ( ,~ Cambrian. 



series . . 1 purple bands in thick beds, a few beds f ' 

 ( of purple slate among them J 



)a. Hard grey compact beds 100^ 

 

 b. Black and dark grey striped shales, with I Upper 

 interbedded trap 330 ( Cambrian. 



1980 



The lowest third, or base of the fossilifcrous scries, is especially worth 

 notice, as resembling very nearly in lithological character the immediately 

 underlying Lower Cambrian beds, and distinguished from them only by the 

 absence of the purple bands. It must be understood also that the absence 

 of these bands by no means contradicts us in assigning these fossiliferous 

 beds (No. 5 a) to the upper portion of the true Lower Cambrian or " Harlech 

 Grit" series, since many beds of the immediately underlying series are as free 

 from purple colour as are any of these. Purple and red beds, moreover, are 

 not found to be favourable for the exhibition of organic traces. In the true 

 purple beds (No. 3), and, indeed, in the whole of the Lower Cambrians of this 

 district, worm tracks only have as yet been found, though it is to be hoped 

 that the presence and true position of the Ohlhamia will also be determined 

 here ere long. 



As we ascend from the coarse-grained compact beds already mentioned, 

 the beds gradually become darker in appearance, of a finer grain, and more 

 flag-like ; the dip is very high, and often vertical. 



The 2nd, or Porth-y-rhaw section, extends along the east side of that 

 creek, in a direction from N. by E. to S. by W., includes about 700 feet of 

 strata, nearly all fossiliferous, and shows the most perfect section of the Lower 

 Lingula-flags anywhere exposed in this neighbourhood. 



It begins in the Grey grit, or lowest fossiliferous beds (5 a), and upon 



