42 Reports and Proceedings — Geological Society of London. 



The general succession is argued to be the same in the isolated 

 portion east and south of Bangor as in the main mass. The existence 

 or otherwise of a base on the mainland is considei'ed to depend on 

 the age assigned to the Dinorwic felsite, and the presence of the 

 summit-beds to depend on whether the Bronllwyd Grit (stated to 

 belong to the overlying group) rests conformably or uncouformably 

 on the Cambrian rocks. 



It is argued that the rocks to the west of the Llyn Padarn felsite 

 belong to the lower part of the series and those to the east to the 

 upper, and that the felsite is a volcanic complex belonging to the 

 middle of the Cambrian period. 



A post-Cambrian age is assigned to the conglomerates of Moel 

 Tryfan and Llyn Padarn, thus causing the break at the base of the 

 Silurian system to assume an increased importance. 



2. " The Subterranean Denudation of the Glacial Drift, a probable 

 Cause of submerged Peat and Forest-beds." By W. Shone, Esq., 

 F.G.S. 



A description is given of a section at Upton, Cheshire, where 

 Boulder-clay rests upon the " mid-glacial sands." The Boulder- 

 clay sinks to a lower level in the small valleys which are cut through 

 into the sands ; and the author supposes that this is due to the 

 subterranean denudation of the sands, which would be greatest near 

 the valle3's, and become less at a distance from them. He considers 

 such denudation is capable of producing submerged peat and forest- 

 beds, and accounts for the splitting of peat-beds, as described by 

 Mr. G. H. Morton, by a somewhat similar action, which he believes 

 may have also operated in Carboniferous times, causing the splitting 

 of coal-seams. 



3. " High-Level Glacial Gravels, Gloppa, Cyrn-y-bwch, near 

 Oswestry." By A. C. Nicholson, Esq. Communicated by W. 

 Shone, Esq., F.G.S. 



These gravels are found at Gloppa, and are situated at a height 

 of from 900 to 1160 feet above sea-level, on the eastern slope of a 

 ridge of Millstone Grit which forms the western border of the 

 Cheshire and Shropshire plain. 



The beds present the appearance of having been abruptly cut off 

 on the north-eastern slope. The gravels are in places much contorted, 

 and false-bedding is frequent. They contain numerous striated 

 erratics. Amongst the boulders are Silurian grits and argillites, 

 granites like those of Eskdale, Criffel, etc.. Carboniferous rocks. Lias 

 shale, and Chalk flints. The shells are often broken, rolled, and 

 striated, but the bulk of them are in fairly good condition. 



A list of the shells is given, including nine Arctic and Scandina- 

 vian forms not now living in British seas, nine northern types, also 

 found in British seas, two southern types, and nearly fifty sj^ecies 

 of ordinary British forms. Comparative lists of the shells of Moel 

 Tryfan and of those now living in Liverpool Bay are placed side by 

 side with the list of shells from Gloppa. 



