TEETH AND THEIR VARIATIONS. 



2OI 



In the great majority of Eeptiles the whole of the 

 teeth are of the same pattern, although in some cases 

 as the Crocodiles and Alliga- 

 tors one or more of the teeth 

 in either jaw may be much 

 larger than the others ; and in 

 a few extinct types (Fig. 62) 

 the teeth are divided into three 

 distinct series. As one tooth FIG - 61 - ~ The crown of a tooth of 



an extinct Reptile, with a mag- 



COmeS illtO USe it is Succeeded nifled view of the notches on 



the margin. 



trom below by the germ or 



another, which gradually grows up and absorbs its 

 roots till the old tooth finally drops out, this process 

 going on without intermission during the whole life of 

 the animal, so that a practically endless succession of 

 teeth is developed. Some of the varieties assumed by 



FIG. 62. Skull and teeth of an extinct South African Reptile. 



the teeth of extinct reptiles are noticed and figured in 

 Chapter VIII., among which we may especially call 

 attention to the fluted and serrated type obtaining in 

 the Iguanodon (Fig. 32), and the spatulate modification 

 seen in the Hoplosaur (Fig. 34). Other extinct reptiles 

 have flattened and pavement-like teeth adapted for 



