During the _Primary Epoch_ our globe would appear to have been chiefly
appropriated to beings which lived in the waters--above all, to the
Crustaceans and Fishes; during the _Secondary Epoch_ Reptiles seem to
have been its prevailing inhabitants. Animals of this class assumed
astonishing dimensions, and would seem to have multiplied in a most
singular manner; they were, apparently, the kings of the earth. At the
same time, however, that the animal kingdom thus developed itself, the
vegetation lost much of its importance.
Geologists have agreed among themselves to divide the Secondary epoch
into three periods: 1, the _Cretaceous_; 2, the _Jurassic_; 3, the
_Triassic_--a division which it is convenient to adopt.