520 H. HICKS ON THE PRE-CAMBRIAN 
by an anticlinal fold, the centre of which is indicated along a line 
almost midway between the Dimetian ridge and Ramsey Sound. I 
fail to recognize that any evidence whatever has been given by him 
to prove this, and a full acquaintance with the rocks in this area 
tends certainly to show that the idea is devoid of foundation. 
The evidence that the sequence is a continuous one from the Dime- 
tian axis to the coast on the west will be fully given when treating 
further on of the special areas. Yet it may be stated here that 
I have paid very much attention to this question throughout the 
district, and that in my papers of 1871 and 1875, before the Pebidian 
rocks had been clearly differentiated, a section with an isoclinal 
condition of the beds was given curiously like that shown in the 
recent sections by the Director-General, and along the same line 
of country. This question, therefore, is in no respect a novel 
one, but merely the revival of a discarded one—originally suggested 
by myself, but found to fail on further examination *. 
VIII. Derainep Descrtetions or AREAS NEAR St. Davin’s. 
Having, in the foregoing remarks, referred generally to the Pre- 
Cambrian groups in Pembrokeshire, and to some of the various 
points at issue between the officers of the Geological Survey and 
myself, it will now be necessary for me to describe in detail the 
several areas in the more immediate neighbourhood of St. David’s 
to which the Director-General in his paper calls special attention. 
Others will also be added which seem to furnish any important 
evidence. 
1. Caerbwdy Valley and Area 8.E. of St. David's. 
a. Cambrian Conglomerates.—The basal Cambrian conglomerates 
which everywhere in the district, when not dropped by faults, mark 
the boundary line between the Cambrian and the Pre-Cambrian 
rocks, stand out very conspicuously in the face of the hill on the 
west, side of the valley immediately to the north of the mill, and 
are exposed also on the opposite side. The thickness of the more 
conglomeratic portion of the basal beds at this place is about 60 ft. 
The pebbles vary in size up to some quite a foot in diameter. The 
majority are well rolled, especially those of a compact or quartzose 
character. The schistose and ashy fragments are more angular, in 
accordance with their peculiar tendencies. The matrix is usually a 
mixture of particles of ashy materials, and of an arkose in which 
much of the felspar has become so decomposed that it is now only 
recognizable under the microscope. Sometimes the ashy material 
predominates, as in the case of the bands supposed by Prof. Geikie 
and his assistants to be conten:poraneous tuffs ; in other parts of the 
same series the matrix isa nearly pure admixture of quartz and de- 
composed felspar--atrue arkose, Ofcourse the more general condi- 
tion is an admixture of all these with some other materials; but the 
* See Quart. Journ. Geol. Soc. vol. xxvii. p. 888, and vol. xxxi. pl. viii. fig, 2. 
