128 
SYSTEM OF NATURE. 
for the reception of animals. It is not for us to say by 
what means this change was effected, but doubtless an at- 
mosphere adapted to aerial respiration was one of the most 
essential changes : the creations of the former period were 
composed of animals capable of breathing water, but now 
another element was provided for this purpose. The 
almighty fiat again went forth, and the earth was peopled 
with reptiles. This seems to have been the era of mon¬ 
sters : the vast lguanodon, and those anomalous forms the 
Mosasaurus, Plesiosaurus and Ichthyosaurus, seem to have 
enjoyed uninterrupted dominion; and what appears a 
striking character of the age is, that its herbivora were of 
the reptile class. The lguanodon himself probably de¬ 
voured the tropical foliage that grew in rank abundance 
around his haunts. His bulk, or the thickness of his skin, 
might well protect him from attack; but, like the rhinoce¬ 
ros, he was furnished with a nasal horn, that must have 
proved a formidable weapon w'hen wielded with a power 
so prodigious. Synchronous with these huge reptiles were 
the earlier marsupials —* the opossums and pterodactyles. 
The creations of this epoch seem to fall principally on the 
terrestrial radius, but by no means to be exclusively terres¬ 
trial : not only were many of the reptiles, as Mosasaurus 
&c., wholly aquatic, but there were abundance of species 
added to the radiates, mollusks, articulates and fishes; 
and the pterodactyles were creatures furnished with long 
and powerful wings, well adapted for making their way 
through a damp and murky atmosphere. 
Lastly, during the deposition of the tertiary strata, a pe¬ 
riod further subdivided by Lyell, there was a purification 
of the atmosphere, and an intensity given to the light.— 
Coloured flowers adorned the trees, and were strewn upon 
