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 
stilla 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 Forest-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. 
