68 A. Bell — Succession of the Later Tertiaries in Gt. Britain. 



by the Bure Valley Beds is not so satisfactory as might be desired. 

 I am more disposed to agree with Mr. H. B. Woodward in placing 

 these marine beds on the same level as the Wey bourne Sands, and as 

 constituting the very upper part of the newer Pliocenes, since I find 

 that, with the exception of Telliua balthica, 1 all the mollusca of these 

 beds are found in the Butley Crags. 



The Quaternary, if not a very sound division of the Tertiary, 

 is at least a very convenient one, and it is with the "Forest Bed" 

 rather than the preceding Passage beds that it may be said to com- 

 mence. 



Mr. H. B. Woodward takes the view that the lapse of time between 

 the Newer Crag and the Forest Bed may be inconsiderable ; but 

 there is not only the disappearance of the Mastodon to be accounted 

 for, but the variation in the Mammalia as a whole ; since, leaving 

 out nine species in the Norwich Crags still existing, only four pass 

 up to the Forest-bed, where at least 4.0 others occur for the first 

 time. (Is there any confirmatory evidence of the existence of 

 Mastodon in the later Thames gravel as recorded by Mr. Whitaker ? 

 Mem. Geol. Survey.) 



The fluviatile mollusca, except for LitlwgJyphus, 2 does not offer 

 much for comment. The splitting up of the very minute Hydrobia 

 by Sandberger into so many new species and a new genus will not 

 commend itself to Conchologists generally. 



Will Mr. Eeid allow me to set one of his quotations right? I am 

 represented as saying (Mem. Country around Cromer, p. 74) that 

 Mr. Prestwich's tfnio margaritifera in reality is TJnio littoralis. If 

 he will turn to the Geol. Mag. Vol. IX. 1872, p. 214, he will find 

 I said nothing of the hind, but that it was an Anodon, as he himself 

 assigns it. The specimen referred to is in the Norwich Museum. 

 Again, on what grounds does he transfer the Limax agrestis of my 

 Forest Bed list to L. modioliformis? The Forest Bed Mollusca I 

 collected myself. Silpha dispar may be also added to the Coleoptera. 



Inasmuch as Mr. Newton has rehabilitated in the Forest Bed 

 Hycena spelcea after having once rejected it, I hope he will be able 

 also to replace the other species he has excised from the Forest Bed 

 list compiled by my brother and myself. 



Between the temperate Forest Bed flora and the intensely Arctic 

 one above it the measure of time must be a long one to allow for 

 physical changes, as the Forest Bed must have been submerged at 

 least six or eight fathoms, that being the average depth at which the 

 Yoldias found in situ in the intervening beds inhabit our modern 

 seas, the Yoldia or Leda myalis beds being here 15 feet thick. 



One of the chief objections to the Myalis bed being synchronous 

 with the Bure Valley Beds is the fact that several of the species, Leda 



1 The presence of this shell seems to indicate that great hydrographical changes 

 had taken place, probably the influx of a heavy current setting in from the north, 

 bringing the Tellen in profusion. It sufficiently distinguishes the beds in which it 

 occurs from the immediately preceding Upper Crag or the Chillesford Series. 



3 This is the recent species figured in Forbes and Hanley's British Mollusca as 

 Natica Eingi, obtained in the rubbish of a fishing boat at Cullercoats. 



