500 ZOOLOGY. 



those parts inhabited by the largest and most carnivorous of Carnivora. In 

 JSTortli America, where Carnivora are comparatively scarce, ruminants are 

 much less numerous. 



The genus Camelus is peculiar to the old continent, and the genus 

 Auchenia to the new; they are two equivalent groups. The aberrant 

 girafte is exclusively African. The antelopes proper are also absent from 

 the New World. A single species occurs in North America, the Rocky 

 ]\[ountain antelope {Antilocapra amencana). 



The rodents constitute the most numerous order of the class of mammals, 

 and are at the same time among the smallest. 



The family of Leporidoe has representatives both in the Old and New 

 Worlds, but they are chiefly confined to the northern hemisphere ; some, 

 like the Lepus glacialis, extend into the polar regions. About 35° south 

 latitude is the most southern range of the family in either hemisphere. 

 T^he great continent of South America has yielded but a single species, 

 and that does not occur south of the Eio de la Plata ; whilst, on the other 

 hand, it is in North America that the species are proportionally more 

 numerous. In the Old World, the group in like manner almost disappears 

 in the tropical portions ; it reappears, however, south of the tropics, there 

 being several species found at the Cape of Good Hope. But one species 

 has been discovered in the Indian islands, and in Australia there are no 

 hares; indeed, all Rodentia found in that continent belong to the family 

 Murida3. 



The hystricine rodents are essentially South American, and under that 

 head we include Hystricid^e, Dasyproctidse, Echimyidas, Octodontidse, Chin- 

 chillidfe, and Cavidte. Hystricida? has a wide geographical range, having 

 representatives in the four quarters of the globe, with the exception of two 

 species, Aulacodus swinderianus and Pteromys typicus ; the whole of the 

 species forming the five remaining sub-families are exclusively found in the 

 New World, being chiefly confined to South America. Two or three spe- 

 cies in the West India islands, and about the same number in Central 

 America, form the exceptions. The members of the Hystricidas, Dasy- 

 proctidoe, and Echimyidiis increase in number towards the tropical portion 

 of South America ; whilst in the southern part of that continent, the less 

 highly organized species only are found, these being members of the Octo- 

 dontidse, Chinchillidaj, and Cavida?. On the western side of the southern 

 Andes the Octodontidis alone have representatives. 



The Saccomyina are exclusively American, from the extreme north to 

 Colombia and Guiana, the greatest development of the group being in 

 Central America. 



The Bathyergina are African, three species constituting the group, 

 forming two genera. The Arvicolina are excluded from Africa and Aus- 

 tralia, but are found in North America, Northern Asia, and Europe. Ine 

 Spalacina are not found in the New World ; three species are European and 

 three African ; the remainder are Asiatic. The Alurina are common to 

 both hemispheres. The domestic mice and rats have spread all over the 

 world ; each country also possesses its own kinds. Furthermore, we 

 "704 



