ranges from Patagonia to Mendoza, and on the east coast to 37½° S. latitude. _Myopotamus_ (1 sp.), the coypu (Echimyidæ), 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 Muridæ, are also confined to Temperate South America; _Tolypeutes_ and _Chlamydophorus_, two genera of armadillos, the latter very peculiar in its organization and sometimes placed in a distinct 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" (Otariidæ), is confined to the coasts of this sub-region and the antarctic islands. Deer of American groups extend 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 Magellan, those marked * extending into Tierra del Fuego: {38}*_Pseudalopex_ (two wolf-like foxes), _Felis_ (the puma), _Mephitis_ (skunks), _Cervus_ (deer), *_Auchenia_ (guanaco), *_Ctenomys_ (tucu-tucu), *_Reithrodon_ and *_Hesperomys_ (American mice). _Birds._--Three families of Birds are confined to this sub-region,--Phytotomidæ (1 genus, 3 sp.), inhabiting Chili, La Plata, and Bolivia; Chionididæ (1 genus, 2 sp.) the "sheath-bills," found only at the southern extremity of the continent and in Kerguelen's Island, which with the other antarctic lands perhaps comes best here; Thinocoridæ (2 genera, 6 species) an isolated family of waders, ranging over the whole sub-region and extending northward to the equatorial Andes. Many genera are also peculiar: 3 of Fringillidæ, and 1 of Icteridæ; 9 of Dendrocolaptidæ, 6 of Tyrannidæ, 3 of Trochilidæ, and 4 of Pteroptochidæ,--the last four South American families. There is also a peculiar genus of parrots (_Henicognathus_) in Chili; two of pigeons (_Metriopelia_ and _Gymnopelia_) confined to the Andes and west coast from Peru to Chili; two of Tinamous, _Tinamotes_ in the Andes, and _Calodromus_ in La Plata; three of Charadriidæ, _Phægornis_, _Pluvianellus_, and _Oreophilus_; and _Rhea_, the American ostriches, inhabiting all Patagonia and the pampas. Perhaps the Cariamidæ have almost as much right here as in the last sub-region, inhabiting as they do, the "pampas" of La Plata and the upland "campos" of Brazil; and even among the wide-ranging aquatic birds, we have a peculiar genus, _Merganetta_, one of the duck family, which is confined to the temperate plateau of the Andes.