522 Notices of Memoirs — Geology of Ramsey Island. 



the tendency for an unloaded area to rise ; it merely assigns to such 

 agents a subordinate part in the shaping of the greater features of the 

 Earth's crust. 



It is probable also that an analysis of a series oi gravity measure- 

 ments which may be taken' hereafter in Australasia would reveal the 

 existence therein of gravity anomalies, and it is probable also that 

 the disposition of these would be other than those which might have 

 been inferred from a mere inspection of the topography. 



(6) Geology OF Ramsey Island, Pembrokeshire. Final Report of the 

 Committee, consisting of Dr. A. Btrahan (Chairman), Dr. Herbert 

 H. Thomas (Secretary), Mr. E. E. L. Dixon, Dr. J. W. Evans, 

 Mr. J. E. N. Green, and Professor 0. T. Jones. 



I^HE Committee have to report that the grant made to them in 

 1913 to aid Mr. J. Pringie in continuing his researches in tlie 

 west of Pembrokeshire has been spent. They have also to report 

 that the detailed mapping of the island has been completed. The 

 examination of the rocks and fossils which have been collected will 

 be proceeded with. 



For the purpose of description the island can be divided conveniently 

 into two areas — a northern area composed of Lingula Flags, Arenig 

 Mudstones and Shales, Lower Llanvirn, and the intrusive mass of 

 Carn Ysgubor; and a southern area of Lower Llanvirn Shales with 

 interbedded tuffs and rhyolites, and a thick mass of intrusive 

 quartz-porphyry. To the latter area belongs the mass of rhyolitic 

 and brecciated tuffs of Carn Llundain. 



iN'oRTHERN Area. 



Lingula Flags. — The Lingula Flags consist of bluish-grey, flaggy, 

 micaceous shales with ribs of hard grey close-grained sandstone, some 

 of which reach a thickness of 2 feet. They occupy the headland 

 of Trwyn Drain-du, and they extend eastwards to Bay Ogof Hen, 

 while on the eastern side of the island they form the cliffs from 

 the north-east corner to Eoad Uchaf. The Flags also occur in the 

 headland to the south of Abermawr. They are highly fossiliferous, 

 and yield Lingulella davisi in great abundance. 



Arenig. — All the zones of the Arenig are present. The lowest beds 

 are bluish-grey sandy mudstones and shales with Ogygia sehcyni, 

 Orthis proava, and 0. menapim. They are confined to the north-east 

 corner of the island, and are faulted against the Lingula Flags. The 

 mudstones are followed by bluish-black shales belonging to the 

 Extensus zone, and are well displayed in the cliffs at Eoad Uchaf 

 and Road Isaf. Similar shales belonging to the Hirundo zone are 

 present in Abermawr. 



Lower Llanvirn. — The base of the Lower Llanvirn is seen only in 

 the cliffs in Abermawr, where the shales of the Hirundo zone are 

 succeeded by a thick series of hard dark and light-coloured tuffs of 

 fine texture, which yield Didgmograptus bifidus in their highest 

 beds. The tuffs are followed by fossiliferous blue-black shales, but 

 their full thickness is not seen in the northern area. 



