330 TROPICAL NATURE, AND OTHER ESSAYS. 



mammalia of North America are not very numerous ; 

 and they can be for the most part divided into two 

 groups, the one allied to the Palsearctic, and the other 

 to the Neotropical fauna. The bears, the wolves, the 

 cats, the bison, sheep and antelope, the hares, the mar- 

 mots, and the pikas, resemble Palsearctic forms ; while 

 the racoons, skunks, opossum, and vesper-mice are now 

 more peculiarly Neotropical. There are also many 

 genera which are altogether peculiar and characteristic 

 of the region, as the prong-horn antelope (Antilocapra), 

 the jumping-mouse (Jaculus), five genera of pouched 

 rats (Saccomyidae), the prairie dogs (Cynomys), the tree 

 porcupines (Erethizon), and some others. 



Birds present the same mixture of the two types ; but 

 the wild turkeys (Meleagris), the passenger pigeon (Ec- 

 topistes), the crested quails (Lophortyx, &c.), the ruffed 

 grouse (Cupidonia), and some other groups of less 

 importance, are peculiar ; while the family of the wood 

 warblers (Mniotiltidae) is so largely developed that it 

 may claim to be more characteristic of North than of 

 South America. 



Eeptiles and Amphibia present a number of peculiar 

 types ; while no less than five peculiar families of fresh- 

 water fishes would alone serve to mark out this as 

 distinct from every other part of the world. 



Considering the evident afiinity between the Nearctic 

 and Palsearctic regions, there are here some curious 

 deficiencies of groups which are common and widely- 

 spread in the latter. Thus hedgehogs, wild horses and 

 asses, swine, true oxen, goats, dormice, and true mice 

 are absent ; while sheep and antelopes are only repre- 

 sented by solitary species in the Eocky Mountains. 



