150 DISTRIBUTION OF EXTINCT ANIMALS. [PART II. 
time since these changes took place is, geologically, minute. 
The time of the whole of the Post-Pliocene period, as measured 
by the amount of physical and general organic change known to 
have taken place, is exceedingly small when compared with the 
duration of the Pliocene period, and still smaller, probably, as 
compared with the Miocene. Yet during these two periods we 
meet with no such break in the continuity of the forms of life, no 
such radical change in the character of the fauna (though the 
number of specific and generic changes may be as great) as we 
find in passing from the Post-Pliocene to recent times. For 
example, in Central Europe numerous hyzenas, rhinoceroses, and 
antelopes, with the great Machairodus, continued from Miocene 
all through Pliocene into Post-Pliocene times; while hippo- 
potami and elephants continued to live through a good part of 
the Pliocene and Post-Pliocene periods,—and then all suddenly 
became extinct or left the country. In North America there has 
been more movement of the fauna in all the periods; but we 
have similar great felines, horses, mastodons, and elephants, in 
the Pliocene and Post-Pliocene periods, while Rhinoceros is com- 
mon to the Miocene and Pliocene, and camels range continuously 
from Miocene, through Pliocene, to Post-Pliocene times ;—when 
all alike became extinct. Evenin South America the evidence is, 
as far as it goes, allthe same way. We find Machairodus, Equus, 
Mastodon, Megatherium, Scelidotherium, Megalonyx, and numerous 
gigantic armadillos, alike in the caves and in the stratified 
tertiary deposits of the Pampas ;—yet all have since passed away. 
It is clear, therefore, that we are now in an altogether 
exceptional period of the earth’s history. We live in a zoologi- 
cally impoverished world, from which all the hugest, and fiercest, 
and strangest forms have recently disappeared ; and it is, no 
doubt, a much better world for us now they have gone. Yet it 
is surely a marvellous fact, and one that has hardly been suffi- 
ciently dwelt upon, this sudden dying out of so many large 
mammalia, not in one place only but over half the land surface 
of the globe. We cannot but believe that there must have been 
some physical cause for this great change; and it must have 
been a cause capable of acting almost simultaneously over large 
