166 FOSSIL SAURIANS. 
of any animals we discover in deposits preceding 
or succeeding the secondary series.* 
The species of fossil Saurians are so numer- 
ous, that we can only select a few of the most 
remarkable among them, for the purpose of 
exemplifying the prevailing conditions of animal 
life, at the periods when the dominant class of 
animated beings were reptiles ; attaining, in 
many cases, a magnitude unknown among the 
living orders of that class, and which seems to 
have been peculiar to those middle ages of geo- 
logical chronology, that were intermediate be- 
tween the transition and tertiary formations. 
During these ages of reptiles, neither the car- 
nivorous nor lacustrine Mammalia of the tertiary 
periods had begun to appear ; but the most for- 
midable occupants, both of land and water, were 
Crocodiles, and Lizards ; of various forms, and 
often of gigantic stature, fitted to endure the 
turbulence, and continual convulsions of the 
unquiet surface of our infant world. 
When we see that so large and important a 
range has been assigned to reptiles among the 
* The oldest strata in which any reptiles have yet been found 
are those connected with the magnesian-limestone formation. 
(PI. 1, Sec. 16). The existence of reptiles allied to the Monitor 
in the cupriferous slate and zechstein of Germany, has long been 
known. In 1834, two species of reptiles, allied to the Iguana 
and Monitor, were discovered in the dolomitic conglomerate, on 
Durdham Down, near Bristol. 
