108 



THE WHITE RIVER BADLANDS 



canines, one; pre-molars, four; molars, three. They were of 

 the crested or lophiodont type and show the intermediate 

 stage in the conversion of the short, round-knobbed and 

 enamel covered crown, into the long, sharp-crested crown 

 of cement, dentine, and enamel, as in the present day horse, 

 so arranged that the unequal density of these tissues pro- 

 duces a hard, uneven grinding surface at all stages of wear. 





AFRICA 

 ETHIOPIAN 



EURASIA 

 PALEARCTIC 

 •f ORIENTAL 



NORTH AMERICA 



NEARCTIC 



SOUTH AMERICA 

 NEOTROPIC | 



) 



t- 

 z 



o 



UJ 



Eqmis 

 Zebras 

 and ass 



\ 







I eral horses 



i ^ ' 



J 



Tarpan 

 kiang 

 and 

 asses 









Z 

 UJ 



O 



o 



te 



Q 

 a. 





\ 





Eitioct 

 Equus 



Extinct 

 EqwtS 



OnohippUllon 



z 



UJ 



O 

 O 





E 

 E* 

 Uip 





1 







dim 



tioct 



Virion 





Hipp 



/ 



0. 





\ 



rilohi)i}ms 

 t 



/ 









I/ippariQH J S 

 ^Protohippus^ 









Extinct 





UJ 



1 



2 





4>uJtllheriim 



T Exu'net" 









ilCTI/Ctl 



pptu> J 













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IS 





UJ 



z 



u 

 o 



o 

 Zi 

 o 







Ai'mhiinivs 



1 



.MesoMppiui 

 t 





UJ 



1 



UJ 





Hyraeotherluin.. 



Epihipput 

 Otolapput 



: ' ■ ■ > Eohippus 





Figure 47 — Phylogeny of the Horses. R. S. Lull Organic Evolution, 

 1917. Published by The Macmillan Company. Reprinted by 

 permission. 



The animal, unlike its present day representative evidently 



had to limit its food to soft vegetable tissue. Indeed it is of 



interest that the magnificent tooth battery of the horse 



developed pretty much in unison with the incoming of the 



hard grasses. 



The most striking feature is the tridactyl nature of the 



feet. There were three well-developed toes on each foot, fore 



