_Palamedea_ | 1 | Equatorial America | _Chauna_ | 2 | Columbia, Brazil, and| | | La Plata | | | | ANSERES. | | | ANATIDÆ. | | | _Cairina_ | 1 | Tropical S. America | _Merganetta_ | 3 | Andes | _Micropterus_ | 1 | Temperate S. America | | | | SPHENISCIDÆ. | | | Eudyptes | 6 | Temperate S. America| Antarctic shores Aptenodytes | 2 | Falkland Islands | Antarctic shores | | | STRUTHIONES. | | | STRUTHIONIDÆ. | | | 685. _Rhea_ | 3 | S. Temperate America | {114}CHAPTER XV. THE NEARCTIC REGION. This region consists almost wholly of Temperate North America as defined by physical geographers. In area it is about equal to the Neotropical region. It possesses a vast mountain range traversing its entire length from north to south, comparable with, and in fact a continuation of, the Andes,--and a smaller range near the east coast, equally comparable with the mountains of Brazil and Guiana. These mountains supply its great river-system of the Mississippi, second only to that of the Amazon; and in its vast group of fresh-water lakes or inland seas, it possesses a feature unmatched by any other region, except perhaps by the Ethiopian. It possesses every variety of climate between arctic and tropical; extensive forests and vast prairies; a greatly varied surface and a rich and beautiful flora. But these great advantages are somewhat neutralized by other physical features. It extends far towards the north, and there it reaches its greatest width; while in its southern and warmest portion it suddenly narrows. The northern mass of land causes its isothermal lines to bend southwards; and its winter temperature especially, is far lower than at corresponding latitudes in Europe. This diminishes the available area for supporting animal life; the amount and character of which must be, to a great extent, determined by the nature of the least favourable part of the year. Again, owing to the position of its mountain ranges and the direction of prevalent winds, a large extent of its interior, east of the Rocky Mountains, is bare and arid, and often almost desert; while the most favoured districts,--those east of the Mississippi and west of the Sierra Nevada, bear but a small proportion to its whole area. Again, we know that at a very recent period geologically, it was subjected to a very severe Glacial epoch, which wrapped a full half of it in a mantle of ice, and exterminated a large number of animals which previously inhabited it. Taking all this into