100 THE WHITE RIVER BADLANDS 



the Big Badlands, all belonging to the genus Protapirus, are 

 believed to be in the direct line of ancestry from the modern 

 tapirs. (Plate 14). All of the specimens secured have 

 come from within or near the Big Badlands. The material 

 is not abundant and consists chiefly of skulls, lower jaws, 

 and certain limb bones. 



Prof. Scott suggests that the scarcity of the remains is 

 probably because tapirs have always been forest-haunting 

 animals, hence their habits must have kept them in places 

 remote from areas where the accumulation of sediments was 

 in progress and thus only occasional stragglers were buried 

 and preserved. 



EQUIDAE 



Of all the fossils of the White Kiver badlands perhaps 

 none have elicited more genuine interest than those of the 

 Equidae, or horse family. The ancestry of the horse is in 

 full harmony with the proud position he holds among present 

 day animals. No other mammal displays such a lengthy, 

 well connected lineage, nor discloses a more beautiful handi- 

 work in the well-ordered development of structure and habits. 

 For perhaps three million years or more, members of the 

 family have roamed the hills and dales of the earth, molding 

 their nature to an ever changing environment, discarding 

 many things inherited from their evident Cretaceous five- 

 toed progenitors, and taking on new features leading to the 

 exquisite relation of organs and actions in the finely-built 

 horse of today. 



The earliest known members of the family is the little 

 Hyracotherium, or Eohippus of the Eocene, less than one 

 foot in height, with four well developed toes on each front 

 foot, and three on each hind foot. Splint bones indicate the 

 earlier presence of five toes on the front foot and four on the 

 hind foot, and there is good reason for believing that at some 

 still earlier stage the pentadactyl nature was complete. In 

 connection with the progressive enlargement of the middle 

 toe, profound alteration also took place in other parts of 

 the anatomy, particularly the lengthening of the jaws, in- 

 creasing complexity of the teeth, pronounced elongation of 

 the lower part of the limbs, and the degeneration of the 

 ulna and fibula. 



