Notices of Memoirs — Pleistocene Vale of Clwycl. 509 



Continental series, is still sufficiently marked and important in this 

 count}' and elsewhere to make it a distinctive and independent forma- 

 tion. 



VIII. — On the Silurian Eocks of North Wales. By Professor T. 

 M'Kenny Hughes, M.A., F.G.S. 



THE author begins by describing some sections in the Silurian rocks 

 of North "Wales. Some of them are in the lower part, some in 

 higher beds. He gives lists of fossils from the various horizons in each. 

 He then, by means of these and by what he calls syntelism, that is, 

 the occurrence of similar sequences of beds of the same characters, 

 lithological or other, points out the corresponding parts of the various 

 sections described. 



He then does the same for the Silurian of the eastern borders of the 

 Lake district, and, having in this manner constructed a vertical section 

 of each, compares the two districts and shows that there is an identical 

 series in each, with all the important zones of one represented in the 

 other, except that in the part of North Wales which he has worked 

 out he has not yet detected beds as high as the newer part of the series 

 in the Lake district. 



IX. — NOTES ON" SOME SECTIONS IN THE ARENIG SERIES OF NORTH 



Wales and the Lake District. By Professor T. M'Kenny 

 Hughes, M.A., F.Gr.S. 



IN this paper the author describes a number of sections which cross 

 the Arenig series in different parts of England and Wales, and 

 endeavours to explain some apparent discrepancies in what is generally 

 a remarkably constant set of beds. 



He starts with the Portmacloc section, where he considers that the 

 chief differences of opinion have arisen from mistakes in the explana- 

 tion of the geological structure of the district, especially from the 

 wrong identification of some grit bands on opposite sides of important 

 faults. 



Following the series to the north he shows that, although they vary 

 in thickness, the principal zones are still represented near Carnarvon ; 

 and, discussing the question of the unconformity of these beds on the 

 Lower Cambrian, he points out that the Lower Cambrian rocks are 

 seen to vary so much both in character and thickness within short 

 distances in the neighbourhood of the existing outcrop of the Archaean 

 that any argument founded upon their thinning-out or their different 

 texture must be received with distrust in an area where they are known 

 to have been deposited on the flanks of mountain ranges of pre-Cam- 

 brian age. 



He then describes some localities in the Lake district where the 

 occurrence of the same zones has been determined, and points out the 

 difficulty of getting rid of such great thicknesses of deposits of fine 

 mud as would be implied in the usual interpretation of those areas. 



X. — On the Pleistocene Deposits of the Vale of Clwtd. By 



Professor T. M'Kenny Hughes, M.A., F.G.S. 

 npHE author cautions observers against inferring too hastily the 

 J_ glacial origin of beds from their containing glaciated boulders. 



