206 
GEOGRAPHICAL ZOOLOGY. 
[part IV. 
communication with the ocean, leaving an inland sea with its seals. 
Lake Baikal, however, offers much greater difficulties ; since it is 
not only a fresh-water lake, but is situated in a mountain district 
nearly 2,000 feet above the sea level, and entirely separated from 
the plains by several hundred miles of high land. It is true that 
such an amount of submergence and elevation is known to have 
occurred in Europe so recently as during the Glacial period; but 
Lake Baikal is so surrounded by mountains, that it must at that 
time have been filled with ice, if at anything like its present 
elevation. Its emergence from the sea must therefore have taken 
place since the cold epoch, and this would imply that an enormous 
extent of Northern Asia has been very recently under water. 
W e are accustomed to look on Seals as animals which exclu- 
sively inhabit salt water ; but it is probably from other causes 
than its saltness that they usually keep to the open sea, and 
there seems no reason why fresh- water should not suit them quite 
as well, provided they find in it a sufficiency of food, facilities for 
rearing their young, and freedom from the attacks of enemies. 
As already remarked in vol. i. p. 218, Mr. Belt’s ingenious 
hypothesis (founded on personal examination of the Siberian 
Steppes), that during the Glacial period the northern ice-cap 
dammed up the waters of the northward flowing Asiatic rivers, 
and thus formed a vast fresh-water lake which might have risen as 
high as Lake Baikal, seems to offer the best solution of this 
curious problem of distribution. 
Range of Carnivora in Time . — Carnivora have been found in 
all the Tertiary deposits, and comprise a number of extinct 
genera and even families. Several genera of Canidae occur in 
the Upper Eocene of Europe ; but the most remarkable fact is, 
that even in the Lower Eocene are found tw T o well-marked 
forms, Palmonyctis , one of the Yiverridae, and Arctocyon, form- 
ing a distinct family type of very generalized characters, but 
unmistakably a carnivore. This last has been found at La Fere, 
in the north-east of France, in a deposit which, according to 
M. Gaudry, is the very lowest of the Lower Eocene formation 
in Europe. Arctocyon is therefore one of the oldest, if not the 
very oldest, of the higher forms of mammal yet discovered. 
