THE AMERICAN FAUNA AND ITS ORIGIN. 
215 
Atlantis of Plato in Mid Atlantic, was it an Antarctic 
land or archipelago extending between the southern extremities 
of Africa and South America, and connecting these with New 
Zealand and Australia, was it a northern land uniting Labrador 
and Greenland to Europe, and Alaska and British Columbia to 
Asia, or were there more than one or even two terrestrial 
bridges for the passage to the New World of the ancestors of 
its present animals ? 
This question has been so much discussed that a large 
number of authors of eminence can be quoted who have 
written both tentatively and very decidedly on the subject. 
The affinities of the fauna of the northern parts of America 
and that of the northern parts of the Old World, or of the 
Nearctic and Pakearctic regions, are so many and so strong, 
and the fossil fauna of the two regions is so confirmatory, that 
a former land connection between them is a conclusion that, at 
once suggests itself. And when the present relative position of 
these two great land areas that are separated by but narrow 
seas, and the comparative shallowness of these seas, are 
considered, there is no difficulty in admitting this conclusion. 
Such land connections would be produced by elevations by 
no means greater than those we know to have taken place in 
Europe and Asia since Eocene, or indeed, since Miocene times. 
There is continuous sea-bottom of less than 2,000 fathoms depth 
between Labrador, Greenland, Iceland and Scotland, and the 
greatest depth between Siberia, Kamtchatka and Alaska, is also 
less than 2,000 fathoms, so that an elevation of the floor of 
the northern seas above its present level of 12,000 feet, would 
give these two great zoological bridges. 
Great elevations have taken place since Eocene times in 
Central Europe where the Alps show Tertiary rocks at 11,000 
feet above sea-level, and of much more than 12,000 feet in Asia 
where the Himalayas show Pliocene deposits at 14,000 feet 
above the level of the sea; and a change of level of 12,000 
feet in later geological times in one or more areas makes it 
difficult to refuse to admit possible similar changes of level in 
other areas. 
Nor would there be any climatal difficulty in animal 
migration by these northern lands. From the general mildness 
of the climate of the northern regions in pre-Glacial times, 
there would be no impediment to the spread of a temperate 
fauna that present boreal conditions would interpose. 
Thus we may regard it as established that the northern part 
of North America was joined on the east to Europe, and on the 
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