FOSSIL SAURIANS. 131 



ture and functions of these extinct families of reptiles ; and 

 not only enables us to infer from the restoration of their 

 skeletons, what may have been the external form of their 

 bodies ; but instructs us also as to their economy and habits, 

 the nature of their food, and even of their organs of di- 

 gestion. It farther shows their relation to the then existing 

 condition of the world, and to the other forms of organic 

 life with which they were associated. 



The remains of these reptiles bear a much greater re- 

 semblance to one another, than to those of any animals we 

 discover in deposites preceding or succeeding the secondary 

 series.* 



The species of fossil Saurians are so numerous, 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 ani- 

 mated beings were reptiles; attaining, in many cases, a 

 magnitude unknown among the living orders of that class, 

 ajid which seems to have been pecuUar to those middle 

 uges of geological chronology, that were intermediate be- 

 tween the transition and tertiary formations. 



During these ages of reptiles, neither the carnivorous 

 nor lacustrine Mammaha of the tertiary periods had begun 

 to appear ; but the most formidable 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 former population of 



* The oldest strata in which any reptiles have yet been found are those 

 connected with the magnesian-lirnestone formation. (PI. 1, Sec. 16.) The 

 existence of reptiles allied to the Monitor in the cupriferoHs slate and 

 zechstcin of Germany, has long^ been known. In 1834, two species of rep- 

 tiles, allied to the Iguana and Monitor, were discovered in the dolomitic con. 

 glomerate, on Durdham Down, near Bristol. 



