IGTJANODON. 191 



In this curious pieCe of animal mechanism, we find a varied 

 adjustment of all parts and proportions of the tooth, to the 

 exercise of peculiar functions ; attended by compensations 

 adapted to shifting conditions of the instrument, during dif- 

 ferent stages of its consumption. And we must estimate 

 the works of nature by a different standard from that which 

 we apply to the productions of human art, if we can view 

 such examples of mechanical contrivance, united with so 

 much economy of expenditure, and with such anticipated 

 adaptations to varying conditions in their application, with- 

 out feeling a profound conviction that all this adjustment 

 has resulted from design and high intelligence. 



SECTION XI. 



AMPHIBIOUS SAURIANS ALLIED TO CROCODILESi 



The fossil reptiles of the Crocodilean family do not de- 

 viate sufficiently from living genera, to require any descrip- 

 tion of peculiar and discontinued contrivances, like those we 

 have seen in the Ichthyosaurus, Plesiosaurus, and Pterodac- 

 tyle ; but their occurrence in a fossil state is of high import- 

 ance, as it shows that whilst many forms of vertebrated 

 animals have one after another been created, and become 

 extinct, during the successive geological changes of the 

 surface of our globe ; there are others which have survived 

 all these changes and revolutions, and still retain the leading 

 features under which they first appeared upon our planet. 



If we look to the state of the earth, and the character of 

 its population, at the time when Crocodilean forms were 

 first added to the number of its inhabitants, we find that the 

 highest class of living beings were reptiles, and that the only 

 other vertebrated animals which then existed were fishes ; 

 the carnivorous reptiles at this early period must therefore 



