THE PERISSODACTYL UNGULATES 219 



it is impossible to conceive their divergence from any common 

 stock later than the very dawn of mammalian life. We have 

 seen moreover that the Artiodactyla originated probably from 

 a carnivorous stock, the creodont Mesonychidae. As we fol- 

 low back the Horses, Rhinoceroses and Tapirs Ave find their 

 Basal Eocene forerunners obviously related to each other and 

 in addition Ave note close relationship betAveen their ancestors 

 and those of the Proboscidea and of Hyrax representing the 

 tAvo other Ungulate orders Avhich Ave have still to discuss, and 

 also with the ancestors of the Sirenia. It is probable then that 

 all the orders just enumerated, Avith the exception of the Artio- 

 dactyla, trace their ancestry back to a group of Cretaceous 

 Protungulata, claAved Mammals related to the Creodont-Insec- 

 tivore stock, forest dAvellers and possibly partly arboreal Avhich 

 in consequence of their mode of life escaped destruction by the 

 then existing Dinosaurs and the knoAvn Cretaceous Mammals 

 dAvelling near the sAvamps or on the plains. 



