Mr. J. Prestwich on the Crag of Norfolk and associated Beds, 137 



denudation which furnished the materials for the formation of the 

 conglomerate at different levels, in which he recognized two great 

 periods of oscillation, the first witnessing a downward movement of 

 the Palaeozoic lands and lasting throughout the deposition of the 

 New Bed marl and sands, and the second, during which the accu- 

 mulations of the former were again, at least partly, denuded. With 

 regard to the time at which the remains of Thecodont Reptiles were 

 imbedded in the conglomerate, the author inferred from the evidence 

 that this took place late in the period of the Keuper. 



2. " On the Superficial Deposits of portions of the Avon and 

 Severn Yalleys and adjoining Districts." By T. G. B. Lloyd, Esq., 

 C.E., F.G.S. 



The author, after describing the general characters of what he 

 termed the Drifts of the Upper and Lower series, and the fresh- 

 water gravels of the Lower Avon, comprised within the district 

 of the Avon valley between Tewkesbury and Bugby, and of the 

 Severn valley above and below the town of Worcester, endeavoured to 

 show that there was a balance of evidence in favour of the existence 

 of an upper and lower platform of drift in the main valley of the 

 Lower Avon, the upper one being of marine origin, and probably 

 belonging to the same epoch as the stratified beds of gravel in the 

 neighbourhood of Worcester, which contain marine shells and mam- 

 malian remains, whilst the lower one, of freshwater origin, had been 

 derived from the former by fluviatile action, as supposed by the 

 late Prof. Strickland. Further, that there was no evidence to warrant 

 the supposition of the existence of high- and low-level river-gravels 

 in those portions of the Severn and Avon valleys under review, and 

 that the apparent absence of any freshwater shells in the gravels of 

 the Severn valley between Bridgnorth and Tewkesbury led to the 

 inference that the freshwater gravels of the Avon were not repre- 

 sented in the adjoining portions of the Severn valley, although re- 

 mains of some of the same species of Mammalia occurred in both 

 localities. After stating his opinion that the time had not yet ar- 

 rived for indulging in theoretical speculations concerning the pheno- 

 mena of the Drifts of the Upper and Lower series exhibited in so 

 small an area as the one under consideration, the author concluded 

 by expressing hopes that the facts which he had brought forward 

 would contribute their share of help to the further elucidation of 

 the question. 



3. " On the Surface-deposits in the neighbourhood of Bugby." 

 By J. M. Wilson, Esq., F.G.S. 



January 26th, 1870.— Prof. T. H. Huxley, LL.D,, F.R.S., 



President, in the Chair. 



The following communication was read : — 



" On the Crag of Norfolk and associated Beds." By Joseph 

 Prestwich, Esq., E.B.S., F.G.S. 



The author commenced by referring to his last paper, in which 



