' 
Clement Reid—Pliocene and Pleistocene Beds. 549 
Above this is found the ‘Forest Bed Series,” consisting of two 
fresh-water beds, with an intervening estuarine deposit (the “ Forest 
Bed” of Norfolk geologists), containing large bones and abundance 
of drift wood and tree stumps. These divisions appear to be inti- 
mately connected. 
Next comes the “Leda myalis” Bed, previously described. This 
having yielded a very small fauna, may ultimately be found to belong 
to the Pleistocene; at present it is left with the Crags. 
At this point I should draw the line between Pliocene and Pleisto- 
cene, for the next deposit, the Arctic Fresh-water Bed, shows a 
marked change of conditions. Trees have entirely disappeared, and 
the plants include the dwarf arctic birch and arctic willow. The 
fauna and flora show the first incoming of arctic land species, and 
indicate a lowering of the temperature by about twenty degrees, a 
difference as great as that between the South of England and the 
North Cape at the present day. 
The classification I have been led to adopt is founded upon the 
great oscillations of temperature, and corresponding changes in the 
animals and plants. Changes in the physical geography have also 
been taken into account, as they must always cause changes in the 
fauna and flora; but this branch of the subject I hope to deal with 
in the Geological Survey memoir. 
It appears to be commonly felt that Lyell’s classification, in which 
the Pliocene extends into the middle of the Glacial deposits, is very 
inconvenient; and in talking with geologists I find that they insen- 
sibly speak of Pleistocene as equivalent to the whole of the Glacial 
and Paleolithic periods. Professor Boyd Dawkins, on the other 
hand, wishes to separate the Forest Bed from the Crag, and class it 
with the Pleistocene, but it certainly is much more naturally con- 
nected with the older deposits. 
For these reasons I think the classification here suggested will be 
the simplest, though it necessitates a slight alteration in Lyell’s test, 
founded on the per-centage of extinct mollusca. 
Glacial deposits of the North of England? and ay | Namen aU lanteuens 
\ deposits of the south, newer than the Chalky Mab iiek Gece col 
Boulder-clay (Paleolithic period). 
Chalky Boulder- clay. 2 
Stratified beds (including Middle Glacial of Yarmouth.) | Older Pleistocene. 
Till. + Commencement and great 
Arctic Fresh-water Bed. (First appearance of Arctic | increase of cold. 
land species.) Jj 
Leda myalis Bed. WiWowertPhocens 
Upper Fresh-water Bed. 
Forest Bed (estuarine). 
Lower Fresh-water Bed. 
Weybourn Crag. 
Chillesford Crag. 
Fluvio-marine Crag. 
(Upper or Fluvio-marine 
i Crag.) Climate cold- 
> temperate and probably 
| 
nearly uniform during 
the whole period. Sea 
Red Crac. j open to the north only. 
Coralline Crag ) Older Pliocene. (L. Crag.) 
Black Crag of Antwerp. j Climate Mediterranean. 
Most of the details of thie above classification will, of course, be 
only applicable to the Hast Anglian District. 
