SOME EARLY MAMMALS 239 



researches on the history of camels as illustrated from fossil 

 remains have brought to light another line of evolution equally 

 interesting if not quite so complete. According to the latter 

 palaeontologist, the very earliest ancestor of all the hoofed 

 animals (and therefore of the horse) was the Eocene Phenacodus, 

 with five toes. But this conclusion is not generally accepted 

 now. 



We pass on to consider the true fossil horses, as worked 

 out by Professors Huxley and Marsh, and others. The modern 

 horse, and that which was known to man in the days before 

 history was written, we may regard as a product of the latest 

 geological period the Pleistocene. The development of the 

 horse from a primitive five-toed ancestor seems to have taken 

 place along two separate lines, one in Europe and one in America. 

 The latter is the most complete ; for it so happens in that country 

 the physical conditions which prevailed throughout nearly the 

 whole of the Tertiary Era were singularly favourable to the 

 preservation of the skeletons of those creatures which lived on 

 land. The various members of the horse tribe that roamed over 

 North America all through these long ages of the past were 

 specially numerous in what is now the Eocky Mountain region, 

 and their remains are sealed up in the strata of these regions. 



Here in Wyoming and Utah is found one of the oldest direct 

 ancestors of the horse, the Orohippus of Marsh. During the 

 middle Tertiary, or Miocene period, two other lakes existed on 

 either side of the great Eocene basin. The largest of these, to 

 the east of the Kocky Mountains, extended over portions of 

 what are now Dakota, Nebraska, and Colorado. The clays 

 deposited in this lake form the " Bad Lands " of that region, 

 so well known for their fossil treasures. The other Miocene 

 lake was west of the Blue Mountains, where eastern Oregon 



