OF CREATION. 121 



represents the upper jaw of one species, with nipping 

 teeth in front, small grinding teeth on the sides, and 

 large crushing teeth in the palate. The form of this 

 fish is not known. 



Fig. 46 



PLACODUS. 

 (Lower Jaw and Teeth.) 



It would certainly be premature, in the existing 

 state of our knowledge of fossils, to assume the ab- 

 sence or even the great rarity of reptiles during the 

 earliest epoch of the earth's history, merely because 

 we have hitherto only found in the last formed rocks 

 of that epoch a few traces of reptilian existence. 

 These indeed are sufficient to indicate the presence 

 of a highly organized group of such animals, although 

 they are too few and imperfect to give us much 

 idea of their habits, their relative importance, or the 

 extent of their distribution. But, judging from analogy 

 and from the extreme prevalence of a group of fishes 

 organized like reptiles, and performing the part after- 

 wards taken by several species of this latter class, it is 

 hardly too much to assume, that the time of greatest 

 development of the reptilian fishes preceded that in 

 which the true reptiles themselves abounded. At 

 any rate, it is quite certain that while the remains 



G 



