88 TERTIARY SERIES. 
rated from one another, than those of any other 
Order of Mammalia, it is important to fill these 
vacant intervals with the fossil genera of a former 
state of the earth ; thus supplying links that 
appeared deficient in the grand continuous chain 
which connects all past and present forms of 
organic life, as parts of one great system of 
Creation . 
As the bones of all these animals found in the 
earliest series of the tertiary deposits are accom- 
panied by the remains of reptiles, such as now 
inhabit the fresh waters of warm countries, e. g. 
the Crocodile, Emys, and Trionyx (see PI. 1, 
Figs. 80, 81, 82), and also by the leaves and 
prostrate trunks of palm trees (PI. 1, Figs. 66, 
67, 68, and PL 56), we cannot but infer that the 
temperature of France was much higher than it 
is at present, at the time when it was occupied 
by these plants and reptiles, and by Mammalia 
alHed to families which are natives of some of 
the warmest latitudes of the present earth, e. g. 
the Tapir, Rhinoceros, and Hippopotamus. 
The frequent intrusion of volcanic rocks is 
a remarkable accompaniment of the tertiary 
strata of the Eocene period, in various parts of 
Europe ; and changes of level, resulting from 
volcanic agency, may partially explain the fact, 
that portions of the same districts became alter- 
nately the receptacles of fresh and salt water. 
The fresh- water calcareous deposits of this 
period are also highly important, in relation to 
