520 
The case of the II ip par ion is an instructive one. The bones of 
this animal differ so widely that M. Gaudry says, it is difficult at 
first to refer them to one species ; but an examination of a large 
number of specimens renders it as difficult to draw the line which 
should separate them. There are two distinct races of Hipparion, 
one light and the other heavy, but they do not differ more, inter se, 
than do the different breeds of our domestic horse, of which, were 
only a few fossil specimens known, a number of good species could 
no doubt be made. 
M. Gaudry says, with reference to the deposits lie has himself 
investigated, that where they are of no great thickness, representing 
a comparative^ short period of time, he does not find in the 
mammalian fossils they contain, evidence of change of character ; 
but where the contrary is the case, as in some phosphate beds at 
Quercy, which, he says, represent a succession of geological periods, 
he has found forms which have very different degrees of development. 
It has long been known that the Rhinoceros connects itself 
through the Acarotherium, which is a rhinoceros without a horn, 
with the Palceotherium of the Eocene. M. Gaudry’s researches 
have enabled him to show further how the different existing species 
of Rhinoceros can be traced back through different fossil forms till 
they meet in Acerotlierium and Palceotherium. He has also been 
able in like manner to construct genealogical tables, one of which 
shows a similar connection between the three different existing 
types of Ilpcena , through various Pleistocene forms, with the Miocene 
animals, Hpnnictis and Ichtitherium ; and others, the mutual 
relationship which recent and fossil Elephants, recent and fossil 
Horses, and recent and fossil Pigs, bear to one another. 
Among the ruminants, he alludes to the fact that the earliest 
known forms, such as the Xiphodon from the Eocene, and the 
D remotlierium from the lower Miocene, were hornless ; that horned 
ruminants did not make their appearance until the middle Miocene, 
and that the earliest antelopes of the period had very small horns. 
The antelopes of the upper Miocene, on the contrary, had larger 
horns ( des comes considerables). lie points out that just as the 
antlers of the existing red doer, Cervus ElapJws, increase in number 
