PROBLEMS OF DISTRIBUTION AND THEIR SOLUTION. 153 



the skunk and other two genera of weasels are found nowhere but in 

 Nearctic lands. Then there are the carnivorous racoons, which are 

 likewise special forms; and among the rodents, the pouched rats 

 (Sa&omyufa)) the jumping mouse, the tree porcupines, and prairie 

 dogs are peculiar. The Insectivora number three peculiar genera of 

 moles. The pronghorn antelope (fig. 18) and the mountain goat 

 are absolutely Nearctic. The opossums complete the list of 

 peculiar mammals of the region; whilst the absentees may be 

 summarised in the remark that the Nearctic region is chiefly 

 notable for its absence of wild horses and pigs, dormice, oxen, 

 and hedgehogs, and true mice and rats (Mtfs). The single native 

 sheep, as against the twenty species of sheep and goats of the 

 Palaearctic region, also typifies a remarkable deficiency of a widely 

 distributed quadruped family. 



The small birds of the Nearctic region are, as a rule, well marked 

 off from those of the Palsearctic 

 province. The North American 

 warblers belong to different families 

 from the Palsearctic forms ; the 

 Nearctic flycatchers belong like- 

 wise to different groups from those 

 at home; and the starlings are 

 really "hangnests," or Icteridce. 

 The birds peculiar to the Nearctic 

 region are in turn well defined. 

 The mocking-birds and blue-jays, 

 the special cuckoos and the 

 tanagers ; the humming-birds ; the 

 wild turkeys and turkey buzzards, 

 are all limited to this province. 

 The humming-birds of the New 

 World present certain extraordi- 

 nary limitations in their distribu- 

 tion within the limits of the two 

 regions comprising the Western Hemisphere. The peaks and valleys 

 of the Andes possess each its own species. On Pinchincha a 

 peculiar species occurs, 14,000 feet above the sea level, and nowhere 

 else ; another has been found only inside the crater of the extinct 

 volcano of Chiriqui in Veragua ; a third occurs only on Chimborazo ; 

 and of another species only one specimen has ever been seen, the 

 bird in question having been obtained, over forty years ago, in the 

 Andes of Northern Peru. Again, the presence of such distinct reptiles 

 as the rattlesnakes among serpents, and the true iguanas among lizards, 

 is highly characteristic of Nearctic lands. This region, lastly, may 

 be described as the home of the tailed amphibians or newt-tribe. 



FIG. 18. PRONGHORX ANTELOPE. 



