CHINCHILLAS, AGOUTIS, POECUPINES. 361 



The chinchillas comprise a limited number of species which are 

 restricted to the Alpine zones of the Peruvian and Chilian Andes 

 (the true chinchillas, C. lanigera, 8,000 to 12,000 feet; Alpine vis- 

 cachas, Lagidium Peruanum, 10,000 to 16,000 feet), and the pampas 

 between the Eio Negro and tlie Uruguay (true viscachas, Lagosto- 

 mus trichodactylus). All the agoutis and cavies (or Guinea-pigs) 

 are, as has already been stated, restricted to the Neotropical realm, 

 over which (principally east of the Andes) they are very extensively 

 distributed. The range of the agoutis proper (Dasyprocta) extends 

 from Mexico to Paraguay, one species (D. cristata) finding its way 

 into some of the smaller West Indian islands — St. Vincent, Santa 

 Lucia, Grenada; the paca (Cselogenys paca), the largest member of 

 the family, inhabits the river-bottom forests over almost the entire 

 tract covered by the remainder of the species. The cavies proper 

 (Cavia) are spread throughout nearly the whole of the South 

 American continent, from Guiana to the Strait of Magellan, and 

 from the lowlands to the plateau region of perpetual snow; one 

 or more doubtful species are said to occur west of the Andes. 

 Brazil is most favoured as to number of species, from one of which 

 (Cavia aperea) appears to have descended the domestic Guinea- 

 pig. The Patagonian cavy .(Dolichotis Patagonica), an animal 

 measuring nearly three feet in length, inhabits the plains between 

 Mendoza and the forty-ninth parallel. The capybara (Hydrochoerus 

 capybara), the largest of all living rodents, inhabits the whole of 

 South America east of the Andes and north of the Rio de la Plata, 

 wherever water is found ; its range at one time appears to have ex- 

 tended as far south as the Salado, or even farther. 



Of the remaining hystricomorphs the porcupines, of which some 

 authors recognise two distinct families, the true porcupines or por- 

 cupines of the Old "World (Hystricidse) and the tree-porcupines, or 

 the species of the New World (Cercolabidse), comprise a consider- 

 able number of forms, which though closely related to one another 

 in point of anatomical structure, affect most diverse conditions of 

 habit. The American species range from the northern limits of 

 trees to Paraguay, but the South American forms are generically 

 distinct from those inhabiting North America (except Mexico). 

 Two well-marked varieties of a single species, the Canada porcu- 

 pine (Erethizon dorsatus), inhabit the forest region of North 

 America. The eastern porcupine, or Canada porcupine proper. 



