206 
THE TERTIARY AGE, AND 
with thicker hair or fur But I think the sim- 
pler and more natural reason for their existence 
throughout the North is to be found in the differ- 
ence of climate ; and I am the more inclined to 
this opinion because the Tertiary animals gener- 
ally, the Fishes, Shells, etc., in the same regions, 
arc more closoly allied in character to those now 
living in the Tropics than to those of the Tem- 
perate Zones. The Tertiary age may be called 
the geological summer ; we shall see, hereafter, 
how abruptly it was brought to a close. 
One word more as to the relation of the Terti- 
ary Mammalia to the creation which preceded 
them. I can only repeat here the argument used 
before: the huge quadrupeds characteristic of 
these epochs make their appearance suddenly, 
and the deposits containing them follow as im- 
mediately upon those of the Cretaceous epoch, in 
which no trace of them occurs, as do those of the 
Cretaceous upon those of the Jurassic epoch. I 
would remind the reader that in the central basin 
of France, in which Cuvier found his first Palse- 
otherium, and which afterwards proved to have 
been thickly settled by the early Mammalia, the 
deposits of the Jurassic, Cretaceous, and Tertiary 
epochs follow each other in immediate, direct, 
uninterrupted succession ; that the same is true 
of other localities, in Germany, in Southern Eu- 
rope, in England, where the most complete col- 
