20 GEOGRAPHICAL DISTRIBUTION OF ANIMALS. 






























continents. Even those few species which are common to q 
the temperate regions of both oceans or the shores of both — 
continents, and not now found in the intermediate northern — 
regions, may have been driven in the same manner south- q 
ward, until the intervening continent or ocean left the rem- 
nants of the old cireumpolar fauna widely separated in more — 
southern regions. Why call to the aid of modern theories 4 
the mythical Atlantis to bear species across the ocean, when 
known climatic changes can have led them gradually from a 
common home at the north? 1 
The marine fossils of the latest Tertiary of Europe, and 
doubtless of North America also, are very largely living — 
species ;* and at that time, the climate of the North Atlantic 3 
was nearly like that of the present. In the absence of any — 
knowledge of fossil deposits contemporaneous with the earlier ~ 
Glacial period, it is impossible to arrive at any definite con- 
clusions in regard to the geographical distribution of the 
species at that time.t Still, the number of species which 
continued to live on through the Glacial epoch, the absence 
of well marked and extensive glacial phenomena from mid 
latitudes, and the appearance, in the decline of the Glacial 
period, of species near their present habitats, are good nega- 
tive evidence that there was no very extensive southern 
migration of marine life during that period. 
iari, i in the “Origin of Species,” supposes the cold of 
the Glacial period sufficient to have driven the species from 
the arctic and from the antarctic to the equator, and thus 
accounts for the similarity of the living species of those re- 
gions. Such intense cold would have been sufficient to 
destroy all life in the North Atlantic; and it can scarcely be 
supposed that species would travel iee far north to the 
ED es 

D i a a i a tee ich Crag, 

Lyel 
. Bog 2 an slate fer cent or more Primeiples o! Geology, Amer. Edit., p. M3. 
l ter Tertiary we its compar 
isor Gi d d bat Ce aiá yee P T R nio a 
Gai. ill 




epoch. 
