182 
CROMER FOREST-BED. 
of the older and newer deposits; but any definite conclusions 
are at present rendered somewhat unsafe, through the deficiency 
of our knowledge of the contemporaneous mammals of the 
various parts of the Crag. 
Distribution 
of the 
Land 
Mammals. 
Total 
Species. 
Living. 
Extinct. 
Nodule Bed 
_ 
28 
3 
25 
Norwich Crag - 
. 
- 
13 
1(?) 
12 
Forest-bed - - 
. 
45 
24 
21 
^Pleistocene 
. 
. 
49 
41 
8 
Living British (exclusive of 
Bats) 
- 
29 ■ 
29 
— 
At first it does not seem clear why the Glacial Epoch should 
have exterminated so many large mammals and left the smaller 
species ; but a more minute examination of the fauna shows that 
most of the forms which did not survive till Pleistocene times 
were highly specialized herbivora which would die out through 
the gradual change in the vegetation as the climate became colder. 
The surviving forms, on the other hand, are principally the 
omnivorous voles, mice, and shrews, and the carnivora. All 
these can accommodate themselves without difficulty to a change 
of diet, and would probably be able to exist through the Glacial 
Epoch north of the Alps, or at least to pass that barrier, and 
return when the climate ameliorated. 
The occurrence of the glutton, now an exclusively northern 
species, might be thought to imply greater cold during the for¬ 
mation of the Forest-bed than is now felt in Norfolk ; but the 
great climatic range of many living carnivora, which seem limited 
more by want of food, competition, or human agency than by 
temperature, renders the occurrence of a species now confined to 
northern latitudes of very little value in evidence, when counter¬ 
balanced by the numerous ungulata. One ungulate only, the 
musk ox, has at the present day an exclusively northern habitat. 
In analyzing the mammalian fauna of the Forest-bed, the first 
thing that strikes one is the marked contrast, long since pointed 
out by Lyell, between the familiar character of the plants, most 
of which are now living in Norfolk, and the strange appearance 
of the mammals. We can point to no part of the world where 
a similar assemblage is now living; for though South Africa 
shows an equally varied fauna of large species, the deer of the 
Forest-bed (Figs. 45, 46) are there replaced by antelopes. Of 
30 large land mammals found in the Forest-bed, only three are 
now living in Britain, or have been living there within the 
historic period, and only six still exist in any part of the world. 
The small inconspicuous mammals, which are also the lowest 
* On the authority of Prof. Boyd Dawkins, Quart. Journ. Geol. Soc.t vol. xxxv., 
p. 895. (1880.) 
