362 JOURNAL OF THE PLYMOUTH INSTITUTION. 
in which the shells are al] of living forms, whilst the Mammalia, 
in part, and often a considerable part, belong to extinct species, 
such as the Mammoth and his contemporaries, are called Pleistocene. 
The Recent and Pleistocene together, make up the Post-Tertiary, 
or as some term them, the Quaternary deposits. The beds next 
lower, that is the uppermost or more recent Tertiaries, are denomi- 
nated the Newer Pliocene, and are characterized by the fossil shells 
containing a small minority of extinct species. It is not necessary 
to go here into still more ancient times. 
The distinguished author just mentioned recognizes two distinct 
periods during the Pleistocene era when, at least, Western Europe 
stood at a level so much higher than at present that Britain formed 
a continuous portion of the continent. ‘‘In order,’’ he says, ‘to 
form a connected view of the most simple series of changes in 
physical geography which can possibly account for the phenomena 
of the glacial period, and the period of the establishment of the 
present provinces of animals and plants, the following geographical 
states of the British and adjoining areas may be enumerated. 
‘‘ First, a continental period, towards the close of which the 
forest of Cromer flourished: when the land was at least 500 feet 
above its present level, perhaps much higher... . . The remains 
of Hippopotamus major, and Rhinoceros etruscus, found in the beds’ 
of this period, seem to indicate a climate somewhat milder than 
that now prevailing in Great Britain.” [This was a Pre-glacial era. | 
‘Secondly, a period of submergence, by which the land north of 
the Thames and Bristol Channel, and that of Ireland, was generally 
reduced to an archipelago. . . . This was the period of great sub- 
mergence and of floating ice [in British waters], when the Scandi- 
navian flora, which occupied the lower [? higher] grounds [of 
Britain] during the first continental period, may have obtained 
exclusive possession of the only lands not covered with perpetual 
snow.” [This was a portion of the Glacial period, or perhaps, 
more correctly, it was one of the Glacial periods. | 
Thirdly, a second continental period, when the beds of the 
glacial sea [just described], with its marine shells and erratic 
blocks, was laid dry, and when the quantity of land equalled that 
of the first period. . . . During this period there were glaciers in 
the higher mountains of Scotland and Wales, and the Welsh 
glaciers . . . . pushed before them and cleared out the marine 
drift with which some valleys had been filled during the period of 
