CHAP, xiv.] THE NEOTROPICAL REGION. 37 



from 11,000 to 16,000 feet altitude; and Layostomus (1 sp.), the 

 <; viscacha," confined to the pampas between the Uruguay and 

 Rio Negro. Many important genera are also confined to this sub- 

 region. Auchenia (4 sp.), including the domesticated llamas 

 and alpacas, the vicugna which inhabits the Andes of Peru and 

 Chili, and the guanaco which ranges over the plains of Patagonia 

 and Tierra del Fuego. Although this genus is allied to the Old 

 World camels, it is a very distinct form, and its introduction from 

 North America, where the family appear to have originated, may 

 date back to a remote epoch. Ursus ornatus, the " spectacled 

 bear " of the Chilian Andes, is a remarkable form, supposed to be 

 most allied to the Malay bear, and probably forming a distinct 

 genus, which has been named Tremarctos. Four genera of Octo- 

 dontidoe are also peculiar to this sub-region, or almost so; Habro- 

 comus (1 sp.) is Chilian ; Spalacopus (2 sp.) is found in Chili and 

 on the east side of the southern Andes ; Octodon (3 sp.) ranges 

 from Chili into Peru and Bolivia ; Ctenomys (6 sp.) from the 

 Straits of Magellan to Bolivia, with one species in South Brazil. 

 Dolichotis, one of the Cavies, ranges from Patagonia to Mendoza, 

 and on the east coast to 37^ S. latitude. Myopotamus (1 sp.), 

 the coypu (Echimyidse), ranges from 33 to 48 S. latitude on 

 the west side of the Andes, and from the frontiers of Peru to 

 42 S. on the east side. Reithrodon and Acodon, genera of 

 Muridse, are also confined to Temperate South America; Toly- 

 peutes and Chlamydophorus, two genera of armadillos, the latter 

 very peculiar in its organization and sometimes placed in a dis- 

 tinct family, are found only in La Plata and the highlands of 

 Bolivia, and so belong to this sub- region. Otaria, one of the 

 " eared seals " (Otariidae), is confined to the coasts of this sub- 

 region and the antarctic islands. Deer of American groups ex- 

 tend as far as Chiloe on the west, and the Straits of Magellan on 

 the east coast. Mice of the South American genera Hesperomys and 

 Reithrodon, are abundant down to the Straits of Magellan and 

 into Tierra del Fuego, Mr. Darwin having collected more than 20 

 distinct species. The following are the genera of Mammalia 

 which have been observed on the shores of the Straits of Magel- 

 lan, those marked * extending into Tierra del Fuego : 



