58 THE LESSON OF EVOLUTION 



the Condylarthra, the early ungulate or hoofed mam- 

 mals, which gave rise to the Artiodactyla (pigs, 

 camels, and ruminants), and to the Perissodactyla 

 (rhinoceros, tapir, and horse). 



The Condylarthra and Creodonta are almost iden- 

 tical ; and both were plantigrade, that is, they walked 

 on the soles of their feet, and not merely on their 

 toes, as do all the Ungulates and most of the Carni- 

 vora at the present day. But in the Creodonta the 

 teeth are sharper, and the toes appear to have carried 

 sharp claws, while they are flattened in the Condy- 

 larthra. The Tillodontia are the primitive Eodents, 

 which are connected by Typotherium with the 

 Condylarthra. 



We must, therefore, suppose that the Creodonta 

 gave rise to the Carnivora, the Ungulata, and the 

 Eodentia. The Insectivora and the Creodonta pro- 

 bably had a common origin in the primitive Insecti- 

 vora ; from which stock the Lemuroidea also appears 

 to have been derived ; but as all these orders appear 

 together in the lower Eocene, their actual lines of 

 descent are doubtful. 



In the upper Eocene nearly all the existing mam- 

 malian groups are clearly separated from each other. 

 True Carnivora, true Insectivora, true Eodentia, and 

 Chiroptera (bats) appear, as also do the Cetacea. 

 But among the Carnivora there is as yet no distinc- 

 tion between bears, dogs, hyaenas, and cats; these 

 were only separated off in the Miocene. The 

 Chiroptera are flying insectivora. 



Of the Primates, the Lemuroidea are known in 

 the lower Eocene ; the Simiidsc in the middle Mio- 



