44 LAND MAMMALS IN THE WESTERN HEMISPHERE 



tinguish the marsupial from the carnivore are no less clearly 

 displayed. Large herbivorous mammals too, though referable to 

 very different orders, bear a strong resemblance to one another, 

 the characteristic differences, so far as the living animal is 

 concerned, appearing chiefly in the head. It was this general 

 likeness that induced Cuvier to form his order, "Pachyder- 

 mata," which comprised elephants, rhinoceroses, hippopota- 

 muses, tapirs, etc., animals that are now distributed into no 

 less than three separate orders; aside from the head, all of 

 these forms are quite distinctly similar in appearance. 



Of course, the external features, such as ears, tail, skin and 

 hair, are most important factors in the general make-up of 

 any mammal; and, as to these matters, the fossils leave us 

 largely in the lurch, save in the all too rare cases, like the Si- 

 berian fMammoth, in which these external features are actually 

 preserved. Two artists may so restore the same animal as 

 to result in two very different pictures, and no one can posi- 

 tively decide between them; just as two modern mammals, 

 which are closely related and have very similar skeletons, may 

 yet differ markedly in outward appearance, because of the 

 different character of the skin, as do, for example, the Bornean 

 and Indian rhinoceroses. Yet even in dealing with purely 

 external features, we are not left altogether to conjecture. 

 Ears of unusual size or form frequently leave some indication 

 of this on the skull, and the presence or absence of a proboscis 

 can nearly always be inferred with confidence from the char- 

 acter of the bones of the nose and muzzle. The length and 

 thickness of the tail may be generally directly deduced from 

 the caudal vertebrae, but whether it was close-haired and 

 cylindrical, or bushy, or tufted at the end, or flat and trowel- 

 shaped, as in the Beaver, is not determinable from the bones 

 alone. 



Most uncertain of all the characters which determine 

 outward appearance are the hair and the pattern of colouration ; 

 the Horse and Zebra differ much more decidedly in the living 



