OUR ANCIENT RELATIVES 



jaw the principal tooth-bearing bone, or dentary, 

 one on each side of the head, was relatively larger 



smx 



6 



Fig. 20. Skulls of Earlier and Later Mammal-like 

 Reptiles from South Africa. 



(Data from Broom, Watson, Houghton.) 

 For details, see p. xvi. 



as compared with the other bony plates of the jaw 



lying behind it, than it had been in earlier stages. 



35 



