442 



MAMMALIA. 



Protohippos in America, whose foot resembles that of Hip- 

 parion — the existing genus Equus not appearing until Post- 

 Pliocene times. 



3 ■ 3 3 3 



Fig. 209. — Skeleton of Foot in various forms of Equid^. 



A, Orohippos (Eocene) ; b, AncJntherium (Upper Eocene and Lower and Upper Mio- 

 cene) ; 0, Hipparion (Upper Miooeiie and Pliocene) ; r>, Eguus (Pliocene and Becent). 

 (Nicholson, after Marsh.) 



There seem to be two distinct lines of descent, one in America 

 and one in Europe. In America the stages are Eohippos, 

 Orohippos, Mesohippos, Miohippos, Protohippos, Pliohippos, 

 and Equus. In Europe, Hyracotherium, Palseotherium, Anchi- 

 therium, Hipparion, and Equus.^ 



^ The living and extinct horses are tabulated as follows by Dr Gadow : — 

 Eqwidce. Lovper naolara quadrituberculate, or with two transverse 

 ridges curved into two half -moons. Toes, f , f, or \. Since Eocene. 

 Lower Eocene, England. 

 Lower Eocene, Wyoming. 

 ■ Eocene to Miocene, Europe and U.S.A. 



Lower Miocene, Dakota. 

 . Upper Miocene of Europe = Miohippos, U.S.A. 

 Upper Miocene of Europe, Asia, and U.S.A. 

 Pliocene, U.S.A. 

 Pliocene, U.S.A. 

 Pleistocene, S. America. 

 Since Miocene in India ; since Pliocene in 

 Europe. During Pleistocene cosmopolitan, 

 excluding Australian region. 

 (' ClaBsification of Vertebrata,' p. 47.) 



