PHENACODUS, 



297 



Proceeding still further down in our search, we find in the 

 early Eocene the Phenacodus prtmcevusy which is supposed to 

 have been the ancestor, or one of the very early ancestors, of 

 all hoofed animals. Fig 394 shows how it appears in a fossil 

 condition. It was about twenty-one inches high. From the 

 form of the third phalanx of its digits, we may conclude that 

 each of them carried a hoof. We may also see that each 



Fig 392 — {After Gaudry) Left Fokl 

 Foot of Broniotherium (^th leal length). 



Fig. 393 — {Afiu Gaud}y ) 

 Lfft Hind Fooi or Bronto 

 THERIUM (|tli real length). 



of its digits had three phalanges. As I am considering the 

 genealogy only of hoof-bearing animals, I shall not go fur- 

 ther back than the Phenacodus. Having now arrived at an 

 animal with five toes, I may point out that in no case do 

 the digits of any normal mammal (an animal which suckles its 

 young) exceed that number The digits, I may remark,«3re 

 numbered from within, outwards. Thus, the thumb on our 

 hand is termed the first digit , the little finger, the fifth digit 

 Among the ancestors of the horse, the first digit was; the first 

 to disappear ; and after it, the fifth digit. In the Hyraco- 

 therium, the first digit has gone from all four feet. The fifth 

 has vanished from the hind ones, and has begun the process 

 of doing so in the front feet. The Orohippus has also 

 lost its first digit. The Anchitherium (like the rhinoceros) 



