rance in Great Britain in recent
geological times, _i.e._, during and since the deposition of the
Forest-Bed for example, the following species probably came direct from
Siberia across the plains of Europe, as already mentioned (p. 95):--

Canis lagopus.
Gulo luscus.
* Mustela erminea.
* " putorius.
* " vulgaris.
* Sorex vulgaris.
Lagomys pusillus.
* Castor fiber.
Spermophilus Eversmanni.
" erythrogenoides.
Cricetus songarus.
Myodes lemmus.
Cuniculus torquatus.
* Mus minutus.
* Arvicola agrestis.
* " amphibius.
" arvalis.
* " glareolus.
" gregalis.
" ratticeps.
Equus caballus.
Saiga tartarica.
Ovibos moschatus.
Alces latifrons.
" machlis.
Rangifer tarandus.

* Those marked with an asterisk still inhabit Great Britain,
or did so within historic times.

Of the arrival of many of these in Europe we have geological proof, as
they have left their bones in recent pleistocene deposits, and are
unknown from older European strata. The remote ancestors of others, such
as _Sorex_ and _Lagomys_, no doubt lived in Europe, but the recent
species probably had their original homes in Asia. It is evident that in
recent geological times there existed no active centre of origin for
mammals in Europe, and that our continent was largely dependent on the
neighbouring one for the supply of its mammalian fauna. A shifting of
the centre of development from Europe to Asia appears to have taken
place occasionally, as already mentioned (p. 45). Mr. Lydekker has drawn
attention to the fact that though the remote ancestors of the
_Elephantidae_ resided in Europe, neither the latter continent nor North
America was the home of the direct ancestor of any of the true
Elephants. Similarly, though we have had our _Sorex_ in Europe from the
Upper Eocene and _Lagomys_ from the Middle Miocene, the geographical
distribution of _Sorex vulgaris_ and _Lagomys pusillus_ does not support
the view that they are of European origin and have migrated to Asia.
Their absence from most of the European islands indicates either an
extremely recent origin or a recent immigration from Asia, and the
latter view seems to me much the more probable.

No less than twenty-six species of the Siberian mammals penetrated as
far west as the British Islands, and nine of these still inhabit Great
Britain. Some of the r