THE EQUID.E, OR HORSES. 215 



Europe. In the Pliocene we have the last stage of 

 the series before reaching the horse, in the genus 

 Pliohippus, which has lost the small hooflets and 

 in other respects is very equine. Only in the 

 Upper Pliocene does the true Equus appear and 

 completes the genealogy of the horse, which in the 

 Post-Tertiary roamed over the whole of North and 

 South America, and soon after became extinct. 

 This occurred long before the discovery of the 

 continent by Europeans, and no satisfactory reason 

 for its extinction has yet been given.' l 



So far Marsh, and, owing to the quantity of his 

 discoveries, he proclaims the horse, above all the 

 other hoofed animals, to be clearly a native of 

 America. That the European line discussed above 

 is more incomplete is very evident ; however, it must 

 be assumed that with further discoveries the differ- 

 ence will be equalised. And, indeed, an important 

 beginning has already been made during the last 

 few years. The gap between Hipparion and Equus, 

 which clearly existed, and was filled up in the Ame- 

 rican line by Pliohippus, no longer exists in the Euro- 

 pean series either. For Forsyth-Major 2 has pointed 



1 Marsh, The Introduction and Succession of Vertebrate Life 

 in America (1877). 



2 Forsyth-Major, ' Rivista scientifica industriale, 1876,' 

 Kosmos, ii. 



