206 GEOGKAPHICAL 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. 



"We 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. 



Bange 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 Canidai occur in 

 the Upper Eocene of Europe ; but the most remarkable fact is, 

 that even in the Lower Eocene are found two well-marked 

 forms, Palceonyctis, one of the Viverridse, and Arctocyon, form- 

 ing a distinct family type of very generalized characters, but 

 unmistakably a carnivore. This last has been found at La Eere, 

 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. 



