CHAP. Ill] THE MAMMALIAN ORDER PRIMATES 



37 



scheme (Fig 15) by Professor Gregory is well worthy of study 

 since it indicates the earlier ancestral stages in relation to the 



Permian ' 



Cotylosaviria- 



Tkerocej>kalia 



AnovnodcmUa 



~ *■ Monotremata 

 Dif>votokoutia 

 Polyfrotodontia 



'XenavtKva 

 Rodcvitia 



Deryno\>lera \ 



Megac^^.lvo()tevQ , 



MicrocKifof" 



Fie. 15. 



several geological horizons. Moreover the Metatherian and Proto- 

 therian forms also appear. Starting with the Permian horizon, 

 the first point to notice is that the stem begins with the 



