EBIDIAjS - ROCKS OF PEMBROKESHIRE. 157 



pass over other and larger areas with simply mentioning their pre- 

 sence there. This was particularly the case with the area to the 

 west of the St.-David's axis, which I propose more especially to 

 refer to now. J 



This area also reaehes beyond the point indicated in my former map 

 and may roughly be made to include all the so-called altered Cambrian 

 beds and most of the intruded masses associated with them within 

 a line marked as running from the S.W. point in Ramsey Sound, 

 by Ehosson, to the south-east corner in Whitesand Bay, called Ogof 

 Golchfa, and bounded beyond by the great fault running in a NE 

 direction from that point to Tretio, at which place they are* 

 dropped by the fault extending here from east to west. This area 

 is in length about seven miles, and it has an average width of about 

 a mile and a half: nearly all the beds contained in it are higher in 

 the succession than those mentioned as immediately flanking the 

 Dimetian axis in my former paper ; and hence they will now require 

 a special description. 



As, however, the lowest beds of the Pebidian are nowhere well 

 shown in this area, and in the line of the section across it (which 

 I propose to describe) they have been cut off by the fault marked as 

 occurring at the junction of the Pebidian with the Dimetian, I 

 must refer to these again and describe them as they occur on the 

 east side of the axis, especially as several additional facts of interest 

 have been observed in regard to their lithological characters, &c. 



In Section IT. (fig. 2, p. 166), which is in reality but a continua- 

 tion towards the south-east of Section I., the Pebidian rocks, are 

 observed to lie unconformably upon the Dimetian axis. The lowest 

 beds as (1) seen on the hillside and in the valley (Caerbwdy), 

 where the road from St. David's to Solva crosses it, are made up of 

 an agglomerate in which large masses of a spherulitic felstone lava, 

 angular pieces of green shale, bits of chloritic schist and quartz rock 

 are imbedded in a sea-green felsitic matrix, studded with smaller 

 fragments of similar rocks, and broken and sometimes perfect crystals 

 of felspar (vide Appendix, § 1). 



(2) Conglomerates of the same materials as No. 1. 



(3) Light-green thin-bedded banded shales, usually highly indu- 

 rated, or porcellanitic in character, with a conchoidal fracture. 



(4) This series is for the most part hidden by the Cambrian con- 

 glomerates, which overlap it on this side of the axis. In some 

 places also it is cut off by faults. 



In Section I. (fig. 1) a few of the beds of this series (No. 4) are 

 seen directly beyond the fault in the hill on the east side of the 

 St.-David's valley to the north of the Cathedral. They consist for 

 the most part of greenish and purplish felspathic breccias, weathering 

 white on the surface, but often stained of a yellowish-red colour 

 from the iron contained in them. These rocks readily decompose 

 on exposure, and are much used in road-making for binding the 

 rougher road-materials. 



(5) Alternations of silvery-white schists, purple shales, and light- 



