230 
ORIGIN OP LIFE IN AMERICA 
into North America, while the monkeys (Primates) disappear 
for ever from the continent. 
In his restoration of Oligocene conditions in North 
America, Professor Schuchert still depicts North America 
as being joined in the far north by wide land bridges with 
Asia and Europe, while practically submerging the whole of 
the West Indies. As we shall learn later on, an intimate 
relationship exists between the shallow water marine forms 
of early Tertiary European and Antillean deposits, and this 
has given rise to the suggestion that a land bridge must then 
have united Europe and the Antilles. If my view should be 
substantiated, that the resemblance in the Oligocene faunas of 
Europe and south-western North America is due to the exis¬ 
tence in Oligocene times of a mid-Atlantic land bridge, the 
West Indian area, of course, could not have been submerged 
at that time. 
After a short phase of independent evolution, during which 
the Oligocene deposits of western North America insensibly 
pass into Miocene ones, the succeeding Middle Miocene beds 
are characterised by the appearance of a large number of new 
forms, among which the elephants (Proboscidea) deserve 
special mention. Some of these new immigrants are, ap¬ 
parently, of African, others of Eurasiatic origin. The 
Miocene beds of Europe and of America are remarkable for 
the similarity of their fauna. The conclusion deduced from 
this fact by Professor Osborn * is that the North American 
middle Miocene formations contain animals which first appear 
in the lower Miocene of Europe, just as the American lower 
Miocene contains animals that first appear in the upper 
Oligocene of Europe. 
Now it is quite possible that while the faunistic inter¬ 
change between western Europe and western North America 
took place by means of one land connection during early 
Tertiary times, this land bridge was replaced later on by an 
entirely different one. Professor Deperet f had some such 
idea in his mind in expressing the view that the Miocene and 
Pliocene migrations from Europe to America probably 
arrived by way of Asia and the Bering Strait, while the earlier 
* Osborn, H. F., “ Cenozoic Mammal Horizons,” p. 76. 
t Depbret, C., “Transformations of the Animal World,” p. 314. 
