THE FORERUNNERS OF THE HORSE 271 



of the individual teeth being accompanied by a 

 progressive increase of the premolars, till these, 

 with the exception of the first of the series (which 

 undergoes degeneration), in place of being small 

 and simple, become as large and complex as the 

 molars. 



It is noteworthy that in Europe the Hyraco- 

 theriidce appear to have died out at the close of 

 the Eocene epoch without leaving descendants ; 

 if, however, the palaeontology of Eastern Central 

 Asia were known, we might find a transition to 

 the Equidce as complete as in North America. 



The latest and most specialised member of 

 the Hyracotheriidce appears to be the imperfectly 

 known Epihippus of the Upper or Uinta Eocene 

 of Utah, where it is represented by the two species 

 E. gracilis and E. mutensis. From the other 

 American genera of the family Epihippus is dis- 

 tinguished by all the upper premolars, with the 

 exception of the first, being as complex as the 

 molars ; the cross-crests being nearly complete. 

 The lateral toes of both fore and hind feet are 

 relatively smaller than in the undermentioned earlier 

 genera, and would thus seem to have taken a 

 smaller share in supporting the weight of the body. 

 It is somewhat remarkable that in the matter of 

 size the two species mentioned above are a little 

 inferior to the representatives of the earlier genera. 

 Lophiotherium, of the Upper Eocene of Europe, 



