FAUNA OF THE NEOTROPICAL KEALM. 77 



is composed should, in their habitats, be separated by one-half of 

 the circumference of the globe; and that, further, while the one 

 genus, Camelus, belongs strictly to the Northern Hemisphere, the 

 other, Auchenia, is restricted to the Southern. But these are not 

 the only peculiarities distinguishing this singularly discontinuous 

 family, for, while the Eastern representatives are specially adapted 

 to an existence in the hot and parched surfaces characteristic of 

 desert lands, those of the Western Hemisphere, on the contrary, 

 are habituated to the rugged and snow-covered slopes of the South 

 American Cordilleras.* The tapir, which, with the exception of 

 the peccary, is the only pachydermatous South American mammal, 

 presents us with an example of a discontinuous family no less 

 marked than that of the Camelidse. Its four to six members are, 

 with one exception, all confined to South and Central America, in- 

 habiting the lofty mountain regions of from eight to twelve thou- 

 sand feet elevation, as well as the lowland equatorial forests. The 

 only extra-limital representative of the family is the Tapirus Malay- 

 anus, or white-banded Malay tapir, whose home, the Malay Penin- 

 sula, Sumatra, and Borneo, is separated from that of its American 

 congener by an interval of nearly one-half the earth's equatorial 

 circumference. 



The bird-fauna of the Neotropical realm is no less striking by 

 its diversity than the mammalian. It comprises representatives of 

 upwards of six hundred and eighty genera of land -birds, of which 

 some five hundred and seventy, or just five-sixths of the entire num- 

 ber, are peculiar to it. 26 The vernal migration naturally tends to 

 spread many of the South American avian types northward, and 

 thus a large number of even the more strictly Neotropical forms 

 have what might in a measure be considered North American or 

 Holarctic representatives. Of the humming-birds (Trochilidse), a 

 distinctively South American family, comprising about one hundred 

 and twenty genera, and upwards of four hundred species, no less 



* The vicuna is rarely found at a lower level than thirteen thousand feet ; 

 the llama descends to three thousand. It has already been remarked, when 

 treating of the influence of climate upon distribution, that, while the camel is 

 more properly an animal of the warm country, it yet winters, with apparent 

 comfort, as far north as the region of Lake Baikal, in latitude 52 to 53. 

 Again, while most suitably adapted to a desert region, the animal, it appears, 

 can conveniently accommodate itself also to rugged mountain-slopes. 



