Changes in Geography and Climate. 35 



all that I have seen, and, as these might well have drifted 

 across the Atlantic with the Gulf Stream, they are of no 

 value for our present inquiry; the rolled fragments of 

 phosphatised or silicified palm-wood in museums do not 

 really belong to the period of the Crag, they are washed 

 out of the underlying London Clay. 



During the earlier stages of the Newer Pliocene Period 

 the climate was still somewhat warmer than at the present 

 day, as is indicated by both the marine and the land 

 mollusca. Britain then seems to have taken somewhat its 

 present shape, for we find in our eastern counties traces 

 of a shore-line, parallel to the existing one, and of an 

 adjoining area of dry land, on which flourished various 

 mammals and mollusca. Of the associated plants we as 

 yet know nothing, mainly, I believe, because collectors 

 who examine the Red Crag desire to obtain mollusca or 

 mammals, and do not look for the fruits and seeds, which 

 moreover in a marine deposit, even of littoral origin, are 

 usually rare and badly preserved. The land and fresh- 

 water mollusca of the lower part of the Red Crag are 

 mainly south- European ; those of the Upper Red Crag 

 and of later Crag Deposits are more northern — there is 

 still a slight admixture of extinct forms, even in the newest. 



Only in the latest deposits belonging to the Pliocene 

 Period can we find a copious land fauna and flora, and, as 

 far as the plants now inhabiting Britain are concerned, 

 history begins with the Cromer F'orest-bed; all before is 

 prehistoric and speculative. The so-called Forest-bed 

 consists of a series of estuarine and lacustrine strata, laid 

 down apparently by the ancient Rhine, which at that 

 period seems to have crossed a low area now occupied by 

 the shallow southern half of the North Sea.* 



* 'Geology of the Country around Cromer' (1882); 'Pliocene 

 Deposits of Britain' (1890), Memoirs Geological Survey. 



