The distribution of animal life in America proves by itself what was probable on geologic and physiographic grounds, that the proper division between the two continents is not at the Isthmus of Panama, but at either Nicaragua or Tehuantepec, and that the junc tion was relatively late. Zoologically considered South America includes also not only Central America and the Antilles, but the Mexican plains and coasts east, west and south of the plateau of Anahuac. The fauna of the two continents have almost no common feature. Furthermore, the North American species are in many respects closely allied to the North Asiatic, while the South American mammalia and birds have but slight affinities to those of any other section of the world, and those of the most general kind, fully four-fifths of its species being unknown outside its own limits. North America, with this proviso, in Sclater's and Wallace's classification, is Palabarctic in the Arctic regions and for some distance south of the northern ocean and west of Hudson Bay, and Nearctic through the rest of its bulk; while South America, thus extended, is Neotropic. Some authorities, however, from the close affinities of the first two, group them together into one as Holarctic or Triarctic.
In North America, for instance, the fur animals are not very different from the Siberian kinds; the reindeer, moose (called elk in Europe) and bighorn are closely akin to Asiatic congeners; the bison belongs to the buffalo fam ily; the cat family is represented by the panther and wildcat ; the wolf family by various classes of wolves and probably by the Eskimo dog; the bear family by several distinct sorts. The white goat has close foreign relatives; so have the beaver, marmot, rabbit, squirrel and of the other rodentia, the weasels, insectivora, bats and others. The birds, reptiles and am phibia are nearly all identical in family with Old World groups and often in species. fresh-water fish and mollusks of the cold re gions of both are generally akin and sometime, the same, though in the great rivers of the southern half many new forms have developed. the river mollusks being much more numerom and specialized in the United States than in any other part of the world. But there are very notable individual forms. The North American cat" variously called panther, catamount cougar, puma, mountain lion, American lion. etc., has long been specialized in this region: the musk-ox and the skunk are our own, as are the pronghorn and the gopher. And there are still more striking absences where ar analogy would lead us to expect strong repre sentation. The horse, camel and rhmoceros originated in North America as late as Tertiary times, but have entirely disappeared. There L but one marsupial, the opossum, no antelope& and but onegenus of native swine (in Texas and Arkansas).
South America shows a new world. Out of 10 orders of mammalia with 33 families which it contains, 13 families are confined exclusively to it. All its families in two orders, the Pri mates (monkeys) and Edentates sloths and ant-eaters), are its own, and five of its nine families of rodents; while of the Chiroptera (bats), one family, the Phyllostovin de, which includes the vampire bats or blood suckers, is peculiar to it. Its deficiencies are equally notable, though less so in some respects than of the northern continent, as it lacks none which originated there. The horse family group
is represented only by the tapir, the ruminants only by the llama and the bears only by the Andean bear of Chile and Peru. There are Ungulates but a small deer and one genus of swine, no members of the weasel or civet fam ilies and only two small genera of insectivores. The birds, instead of having a wider range at might be thought, are still more individual: 23 families, including hundreds of genera, are exclusively South American, while only three out of its 118 genera of humming-birds, one of its 43 genera of tanagers, eight of its 70 genera of tyrant flycatchers, one of its 14 genera of macaws, four of its 13 genera of pigeons, one of its 12 genera of Cracidce (cnrassows, etc.), two of its 11 species of goatsuckers, etc., have any habitat beyond itself. Of its wading and swimming birds, 18 of its 24 genera are peculiar to it. The reptiles are much less specialize& only four out of 60 genera being entirely inch vidual, and those of lizards; the species, how ever, are more peculia. than this would indicate. the boas and scytales being distinctively South American, and the iguana practically so, though known somewhat north of this region. The waters naturally are much less specialized. 0' the amphibians only three out of 16 genera are local. The fishes have four families and 17 genera, of which one family with its one gem!, and a genus of another, are peculiar to the South American, the resemblances being mainly to the African families. The sirenoids repre sent extremely ancient forms. The insects are also not so different in form as might be antia pated. But this view understates the specific variations, for South America is a zoological land apart.
Consult 'The Standard Natural History' (Boston 1885) ; Wallace's 'The Geographic Distribution of Animals' (1876); Merriam's 'Geographic Distribution of Life in America' (in Proceedings of the American Biological Society, Vol. VIII). For special portions, Cope's 'Crocodiles, Lizards and Snakes of North America> (in United States National Museum Report 1898) ; Apgar's 'Birds of the United States> (1898) ; Beebe's 'Our Search for a Wilderness> (1910) ; Edwards' Butter flies of North America> (1868-88) ; Goode's 'American Fishes' (1888) • Zahm's 'Through South America's Southland' (1916).
Political Divisions.-- The independent States of both North and South America are all republican in government, though it was only in 1889 that Brazil became a republic. The con tinent is politically divided as follows: The foregoing table shows, for America as a whole, though with the omissions mentioned at the beginning of this article, an area of 15,807,404 square miles; the number of inhabi tants in 1916 appears as 186,106,036. It must be understood that these figures are, from the very nature of the subject, approximations only, and that the utmost care and diligence cannot pro duce at present (when great regions of both North and South America remain still unsur veyed, and in part still unexplored) figures of areas, etc., which should be called °exact.* Most earnest efforts have been made, however, to reduce the margin of error and to secure as nearly as possible essential accuracy.