ITS NEAEEST EXISTING RELATIONS. 71 



oped to a remarkable extent of complexity, These 

 characters cannot be clearly nnderstood until the 

 details of the structure of the teeth, to be explained 

 in the next chapter, are known ; but they are suffi- 

 cient to enable any one conversant with them to 

 recognize a single molar of an hipparion from that 

 of any of the existing species, and to show that the 



Fig. 10. — Section of upper molar tooth of hipparion, 

 from the Red Crag of Suffolk, a.i, anterior inter- 

 nal column completely isolated from the main mass 

 of dentine ; p.i, posterior internal column. The 

 uncolored portion is the dentine, the shaded part 

 the cement, and the black line separating these 

 two the enamel. Compare with Fig. 21 , c, p. 125. 



horse-like teeth found occasionally among the debris 



of former Miocene or Pliocene formations in the 



Red Crag of Suffolk belong to animals of this group. 



These dental characters, and also details in the 



structure of the bones of the feet, have led even 



more conclusively than the presence of the suborbital 



depression to the view that the hipparion, or, at all 



events, the European Htppotherium gracile, was not 

 6 



