286 
POPULAR SCIENCE REVIEW. 
hollow-horned ruminants are immigrants of recent date from 
other lands ; and it is probable that the deer have been simi- 
larly derived, though at a somewhat older period, which will 
account for their being more varied and wider spread in surface 
distribution, extending down almost to the southern extremity 
of the continent, while the hollow-horned ruminants are entirely 
confined to the north. 
Scarcely any group to which the term “ Order ” is applied is 
so limited in the number of its existing species as that called, 
from one of the most striking external characteristics of the 
animals composing it, tc Proboscidean The two species of 
elephant, that of Asia and Africa, the largest and in some 
respects the strangest of all land animals, are its sole represent- 
atives. Between these two animals and all others now existing 
there is a wide gap in numerous essential structural characters, 
so that really, in the world as we now see it, they have no near 
relatives. 
But this was not always so. Leaving the existing condition 
of the earth’s surface, and passing back to the last well-marked 
stage before our own, the Pleistocene period, we find abundant 
remains of elephants, imbedded in alluvial gravels, or secreted 
in the recesses of caves, into which they have been washed by 
streams or floods, or where, in many cases, they have been 
dragged in as food by hyaenas or other predacious inhabitants of 
these subterranean dens. 
We find these remains of elephantine animals extensively 
distributed over regions of the earth where no such creatures 
have existed within the memory of man. We find, moreover, 
that the elephants of the Pleistocene period, judging from their 
bones, and especially their teeth, do not in most cases exactly 
correspond in form or size to either of the existing kinds. We 
certainly find remains undistinguishable from those of the 
existing African elephant, in the north of Africa and southern 
parts of Europe ; but the majority of these remains not only 
differ among themselves, but differ more or less from either the 
African or Indian species, and hence have had many different 
appellations bestowed upon them, as belonging to what are 
considered to be different species. 
But not only in the Pleistocene period did elephants abound. 
Animals which must come within any definition which will 
include both Elephas Indicus and Elephas Africanus are also 
found in the European Pliocenes ; and even earlier in Asia, the 
deposits of the Sivalik Hills, belonging to a transition between 
the Pliocene and Miocene age, are rich with the remains of ele- 
phants of varied form, in some cases presenting a considerable 
departure from our better-known types. Further back in time, 
however, we search in vain for true elephants. In the Miocene 
