370 GEOGRAPHICAL AKD GEOLOGICAL DISTRIBUTION. 



caballus) was the only living representative of the caballine section 

 of the family, and that no truly wild stock any longer existed on 

 the surface of the earth. Whether Przevalski's horse proves to 

 be a good species or not, there can be little or no question as to 

 the normally wild state in which it occurs. The domestic animal 

 has been spread through the agency of man over the greater part 

 of the globe, where in nearly all localities it has flourished to a 

 remarkable degree. That America was wholly, or in great part, 

 deficient in horses at the time of the Spanish conquest, is proved 

 beyond doubt, but at the same time it is equally proved, from the 

 number of fossil remains that have been found between Escholz 

 Bay in the north and Patagonia in the south, that the animal not 

 only inhabited, but abounded on, the continent during a period com- 

 paratively recent preceding. There is, further, very little question 

 as to the contemporaneity of the horse and man on the American 

 continent, and, indeed, it would appear not exactly improbable, 

 from certain references contained in old narratives, that at least in 

 South America the animal still lingered on even after the advent of 

 the Europeans. What led to its general extermination, when under 

 apparently similar physical conditions the introduced animal has 

 been able to thrive to such a wonderful degree, is a problem which 

 still awaits solution. 



The species of ass appear to be more numerous than those of 

 the horse, although not unlikely one or more of the forms usually 

 considered distinct will have to be classed as mere varietal types. 

 Zoologists are practically agreed that the domestic animal (E. asi- 

 nus) is either identical with, or only a feebly modified derivative 

 from, the wild ass of Abyssinia (E. tseniopus), the only African 

 species, which it very closely resembles. Three generally recog- 

 nised species of ass roam over the wilds of West-Central Asia, the 

 Syrian ass (E. hemippus), the onager (E. onager), from Persia and 

 Northwest India, and the kiang or dziggetai (E. hemionus), the 

 most horse-like in appearance, which inhabits the high table-lands 

 of Thibet, at elevations of 15,000 feet and upwards. Two species 

 of zebra the quagga (E. quagga) and dauw or Burchell's zebra 

 (E. Burchellii) inhabit the plains of South Africa, while a third 

 species, the mountain zebra (E. zebra), frequents the mountainous 

 districts of the same region. A fourth form (E. Grevyi) has re- 

 cently been described by Milne-Edwards from the land of Shoa, 



