THE OZARKIAN AND ITS SIGNIFICANCE 543 
begin until the Trias. Mammals were introduced in the Mesozoic, 
and even true mammals—eutheres—probably in the Laramie, 
but the reign of mammals did not begin until the Tertiary. So, 
also, man was introduced in the Quaternary and possibly even 
in the Pliocene, but for a long time he struggled doubtfully for 
mastery with the great beasts of that time. His supremacy was 
not established until after the Glacial epoch, 7. e., with the 
Psychozoic. 
All I insist on, however, is that the Quaternary, wherever it 
is put, must all go together. It must not be split and its most 
characteristic part separated and put inthe Tertiary. There may 
be, indeed, some good reasons for putting it @// in the Tertiary, 
and analogy will bear this out. For example, it is customary to 
make three periods in the Carboniferous, viz., the Mississipian, 
the Coal Measures, and the Permian, but there is a growing 
tendency to unite the Permian with the Coal Measures as its 
uppermost transitional stage. Again, we may divide the Mesozoic 
into Triassic, Jura, Cretaceous, and Laramie, but it is more 
usual and probably best to unite the Laramie with the Cretaceous 
as its uppermost transitional stage. So, also, it is customary to 
divide the Cenozoic into two periods, Tertiary and Quaternary, 
but it may possibly be better to regard the Quaternary as the final 
transitional stage of the Tertiary, and thus to divide the Tertiary 
into four epochs, the Eocene, Miocene, Pliocene, and Pleistocene. 
All I insist on is that its most characteristic part and that which 
determined the whole series of changes characteristic of this 
time should not be separated from the rest. 
A PLEA FOR PSYCHOZOIC AS AN ERA. 
I again take occasion to insist on the present, as the begin- 
ning of a new era—the Psychozoic—separated from the Cenozoic 
by the last great critical period, the Quaternary. This must 
be so if the Quaternary be indeed a critical period comparable 
with those that separated the previous eras. That it is such is 
shown by the fact that it has all the characteristics of such 
periods. It is characterized (1) by widespread oscillations of 
