MAMMALIA. 407 



any now existing liave l)c-en found botli in Nortli and South 

 America. This cireunistanco has ehcited from 31r. JJurwin 

 the remark — " It is a marvellous event in the history of ani- 

 mals, that a native kind should have disappeared, to be suc- 

 ceeded after ages by the countless herds introduced with the 

 Spanish colonist."* The wild Asses extend from Siberia to 

 Egypt ; and the different species of Zebra {Fig. 321) through- 

 out central and southern Africa, some inhabiting the plains, 

 others selecting the mountains. 



Fig. G'21.— Zekha. 



Having briefly given the geographical distribution of the 

 leading groups of the present order, we turn to the Elephant, 

 the "half-reasoning Elephant," as he has been termed by the 

 poet. We do so, not for the purpose of bringing forwai'd 

 anecdotes illustrative of his strength, docility, or sagacity ; his 

 inofl'ensive habits, or his utility to man ; but that we may ad- 

 vert to certain peculiarities of structure, and to the interest 

 which attaches to him in reference to species which have passed 

 away, but which have left scattered over Europe the memorials 

 of their former existence. 



The food of the Elephant consists not merely of leaves, but 

 of the twigs and branches of trees. It is needful, therefore, 

 that he should have teeth fitted to grind down the woody fibre, 

 and with some principle of renovation which would make up 

 for the continual wearing away. The teeth are composed of 

 three substances of different degrees of hardness ; the " den- 



• Voya^:^ of the Adventure and Beagle, vol. \vl p. IJO. 



