92 THE AMERICAN NATURALIST. [VoL. XXXV. 
arvalis, * A. glareolus, A. gregalis, A. ratticeps, Equus caballus, 
Saiga tartarica, Ovibos moschatus, Alces latifrons, A. machiis, 
Rangifer tarandus. It will be noticed that this list contains 
species which have also been quoted as Arctic immigrants, 
in which case, however, Dr. Scharff regards them as having 
arrived at different times both from the north and from the 
east. It will also be observed that several species which from 
their present distribution are regarded as Arctic, — as, for 
instance, Canis lagopus and Ovibos moschatus, the Arctic fox 
and the musk ox, — are given as Siberian immigrants, the latter 
obviously because it has not been found in Norway, and conse- 
quently cannot have come by way of the latter country from 
Greenland. In discussing the route by which these animals 
arrived and their origin, Dr. Scharff returns to his preterea 
censeo, that a mild climate prevailed then in central Europe; 
and in reply to Nehring’s “steppe theory ” he states that we 
have really no idea under what precise climatic conditions the 
Siberian mammals lived in their original home, and offers evi- 
dence from other synchronous animals, such as the mollusks, 
to show that they afford no proof of a steppe character of the 
country at the time when they were alive. Additional support 
is derived from the evidence of a connection between the Cas- 
pian and the White Sea which would have prevented the 
Siberian fauna from spreading westward in Pliocene and early 
glacial times. But on disappearance of the marine connection 
a way would have been opened into central Europe. The 
marine character of the boulder clay is again reverted to, and 
the age of the English Forest Bed determined as interglacial, 
contemporaneous with the German interglacial beds also con- 
taining the bones of these Siberian migrants. 
While the so-called Siberian invaders came from the east, 
they entered Europe by a more northern route than a large 
number of animals which also came from Asia, 
but by way 
of Asia Minor. 
They compose what Dr. Scharff calls the 
Oriental migration, which is treated of in detail in Chapter VI, 
and of which he himself has given the following summary : 
. They originated in central, southern, and western Asia. 
It is not easy to discriminate in all cases between the Oriental 
