ITS NEAREST EXISTING RELATIONS. 67 



by the French palaeontologist Christol ; * the latter 

 by Kaup of Darmstadt. t Although Christol's ap- 

 pears to have the actual priority, and has been ex- 

 tensively used, especially in France and England, it 

 does not seem to have been accompanied when first 

 brought out by any clear description, and is therefore 

 not acknowledged by many zoological authors, espe- 

 cially in Germany and America, where Hippotherium 

 takes its place. Protoh ippus and various other names 

 have been proposed for other modifications (differing 

 chiefly in tooth structure) of animals in the same gen- 

 eral phase of evolution. The great variety of these 

 forms may be gathered from the fact that in a recent 

 memoir Professor Cope has described fifteen spe- 

 cies of Hippotherium, which he considers to be quite 

 distinct from each other, from North America alone. f 

 The term " Hipparion " has become so well known, 

 even beyond the limits of strictly scientific literature, 

 that it may be conveniently used as a common name 

 for all the three-toed horse-like animals which im- 

 mediately precede the existing Hqidce, reserving 

 Hippotherium, Protohippus, etc., for generic modifica- 

 tions capable of exact zoological definition. 



* Ann. Sci. Indust. Mid. France, vol. i. p. 180 (1832). 

 t Jahrbuch fur Mineralogie, etc., 1833, p. 327. 

 X "A Review of the North American Species of Hippothe- 

 rium," Proc. American Philosophical Society, 1889. 



