74 Geological Society : — 



In this paper the author gave the results obtained by him during 

 a recent visit to N.W. Pembrokeshire. He stated that he had further 

 examined some of the sections referred to in his previous papers, as 

 well as others not therein mentioned, and that he had obtained many 

 additional facts confirmatory of the views expressed by him in those 

 papers. The lower Cambrian conglomerates and grits, he said, con- 

 tained pebbles of nearly all the rocks in that area which he had 

 claimed as of pre-Cambrian age ; and the fragments of the granitoid 

 rocks, the felsitic rocks, the halleflintas, and of the various rocks of 

 the Pebidian series which he had found, showed unmistakably that 

 those rocks had assumed, in all important particulars, their peculiar 

 conditions before the fragments were broken off. 



Moreover, he stated that there was abundant evidence to show that 

 the very newest of the pre-Cambrian rocks of the area had been 

 greatly crushed, cleaved, and porcellanized, before any of the Cam- 

 brian sediments were deposited; hence he maintained that there 

 was in the area a most marked unconformity at the base of the 

 Cambrian. At Chanter's Seat, near St. David's, he found that the 

 lower Cambrian grits and conglomerates were, in parts, almost 

 wholly made up of fragments of characteristic varieties of the 

 Granitoid rocks which form the Dimetian ridge near by. 



The so-called granite of Brawdy, Hayscastle, and Brimaston, he 

 said, there was good evidence to show, was probably of the age of 

 the Granitoid rocks of St. David's. The mass of so-called granite 

 near Newgale, he stated, was composed of rhyolites and breccias, 

 undoubtedly of pre-Cambrian age. 



The Roch Castle and Trefgarn rocks, he stated, could not possibly 

 be intrusive in Cambrian and Silurian strata, but belonged to a 

 series of pre-Cambrian rocks. He referred to the important evidence 

 bearing on the age of these rocks given in a paper communicated to 

 the Society, since his last paper was read, by Messrs. Marr & 

 Roberts. These authors showed that in a quarry near Trefgarn 

 Bridge a Cambrian conglomerate, overlain by Olenus-shales, is to be 

 seen resting on the eroded edges of the Trefgarn series. The author 

 examined this section lately, and obtained from the Conglomerate 

 some very large pebbles of the characteristic rocks called halleflintas, 

 and of the ash-bands, both of which are found in situ in the quarry. 

 He therefore maintained that there was the most ample evidence to 

 show that there was a great group of pre-Cambrian rocks exposed in 

 N.-~W. Pembrokeshire, and hence that he had proved conclusively 

 that Dr. Geikie's views in regard to these rocks, as given in his 

 paper and more recently in his text-book, are entirely erroneous. 



2. " On some Rock-specimens collected by Dr. Hicks in North- 

 western Pembrokeshire." By Prof. T. G. Bonney, D.Sc, LL.D., 

 F.R.S., P.G.S. 



The author stated that he had examined microscopically a series 

 of specimens collected by Dr. Hicks, and compared them with those 

 described by Mr. T. Davies, in vol. xl. of the Quarterly Journal, and 

 with some in his own collection. He agreed with Mr. Davies's 

 conclusions in all important matters. 



