120 EVOLUTION IN THE PAST 



PHENACODUS Phenacodus affords a good example of what may be called 

 an omnibus animal that is, a highly generalised creature 

 containing in its anatomy several features, which in course 

 of time are not found combined in any one form. It had 

 affinities with deer, pigs, tapirs, horses, and apes, and was 

 tailed like a carnivore. 



Some members of the genus did not exceed small dogs 

 in size ; whilst some were as big as tapirs. The fore-limbs 

 had apparently some grasping power ; and the toes ter- 

 minated with sheaths of a mixed hoof and claw description. 

 The teeth were adapted to an omnivorous diet ; but they 

 were not of a powerful character. And as the skull indicates 

 but slight mental calibre, it is clear that these animals were 

 not forcibly endowed either in mind or body : and long 

 before the close of the Eocene they and closely allied forms 

 became extinct. 



Their great foes, no doubt, were the flesh-eaters, which 

 greatly increased in the course of the Period, and became of 

 more decided carnivorous type. Nature, however, does not 

 leave comparatively defenceless animals without resources ; 

 and the phenacodi when seriously threatened must frequently 

 have found salvation in flight. 



They were, no doubt, capable of speedy movements ; for 

 they were of slender build, and although they may have 

 walked in a more or less plantigrade manner, the limb- 

 construction shows that in running they no doubt raised 

 themselves well on the toes; and were, therefore, capable 

 of the digitigrade method characteristic of fleet-footed 

 mammals. 



LOPHIODONTS More or less closely related to the Phenacodi were other 

 animals known, on account of a peculiarity in tooth-structure, 

 as lophiodonts (" crest-tooth "). These were undoubtedly 

 hoofed creatures ; and when in motion the weight of the 

 body was thrown entirely on certain of the toes, with the 

 heel or hock high-raised. As a result of disuse some of the 

 shorter toes had become atrophied ; and the foot, thus 

 rendered more compact, was better adapted for fast running. 



The most notable of these animals were about the size of 

 HORSES fox-terriers ; and they probably roamed about in herds 



