EOCENE PERIOD 121 



(Hyracotherium). The fore and hind limbs were four toed 

 and three-toed respectively ; but in a few cases there was 

 a rudimentary fifth digit or " thumb " on the fore-leg 

 (Eohippus). The teeth were not strongly crowned, and seem 

 to have been adapted only for succulent vegetation. In 

 appearance the creatures were somewhat horse-like ; and 

 indeed they are generally regarded as remote ancestors of 

 modern horses. 



In the course of the Period this branch of the lophiodont 

 family made distinct progress. The teeth became harder 

 and more like those of living horses ; and were capable, 

 therefore, of masticating a more varied vegetation. As a 

 result probably of an extended dietary, the animals in- 

 creased in size, and became as big as foxes (Pachynolophus, 

 Orohippus). The toes underwent no reduction in number. 

 The animals, however, were evidently rising more on the feet 

 in order to obtain greater speed : for the second toe the 

 central of the primitive five had become considerably 

 developed ; and the other toes had diminished in size. 



Other members of the highly-charged lophiodont family TAPIRS 

 were developing in the direction of tapirs (Systemodon). 

 Excepting as regards the teeth, they can have differed but 

 little from the equines. They had probably the same number 

 of toes as those animals (4-3) ; and that indeed is the 

 number possessed by modern tapirs. They had, it is true, 

 an atrophying digit on the hind-foot, and to that extent 

 possessed an " extra " toe. They had, moreover, two teeth 

 more than their now living descendants. These excesses, 

 however, were not serious obstacles in the path to modern 

 tapirism. 



In mid-Eocene times yet other members of the lophiodont RHINO- 

 family were, it would seem, diverging in the direction of CEROSES 

 rhinoceroses (Hyrachyus). These animals were confined to 

 North America. 



In late Eocene times there were certainly some big brutes 

 with rhinoceros-like skulls on that continent (Titanotheria). 

 Many of them were destitute of horns (Palaosyops) ; but 

 apparently the snouts of some were being prepared for those 

 weapons (Telmatotherium). Their later representatives, how- 



