Page:Encyclopædia Britannica, Ninth Edition, v. 7.djvu/287

269 ANIMAL.] DISTRIBUTION 269 of all that is most characteristic of the tropics, and their limits form the dividing lines between very distinct faunas. Rivers, when very large, also determine the range of many species, but this is probably because their valleys have been once arms of the sea separating districts with some what different faunas. Mountains, when rising to a great height in unbroken ranges, form an impassable barrier to many groups; but their geological age is also an important factor, and they are seldom so ancient and so continuous as to form absolute barriers. Climate, whether determined by latitude or by elevation above the sea, is also a very effective barrier, though probably its action is indirect, and is determined by its influence on vegetation, and by bring ing diverse groups into competition. The limits of the tropical and temperate zones, generally marked out by more or less extensive deserts, form the boundary between regions or sub-regions all round the globe. Oceans are, however, by far the most important barriers ; and this is due not only to their great extent and general impassability to land animals, but also to their enormous antiquity, so that for countless ages they have separated the faunas of remote continents from each other. In accordance with these principles, it is found, that continents separated by the widest and deepest oceans differ most radically in the entire series of their animals ; while those which are less completely separated, or which are only divided by climatal differences or by mountain ranges, are less unlike in their chief forms of life. Thus are con stituted zoological regions, which represent the most permanent geographical features of the globe, and afford us an indication of that permanence in the isolation and pecu liarity of their animal inhabitants. Zoological Regions. Although there is some difference of opinion as to the number and limits of the primary divisions of the earth termed regions, the following are now generally admitted to be the most satisfactory. They are nearly identical with those first proposed by Mr P. L. Sclater in 1857. 1. The Paltearctic Region, which includes all Europe to the Azores and Iceland, all temperate Asia from the high Himalayas and west of the Indus, with Japan, and China from Ningpo and to the north of the watershed of the Yang-tse-kiang ; also North Africa and Arabia, to about the line of the tropic of Cancer. This may be popularly called the European region, Europe being the richest and most varied portion of it and containing representatives of all the more important types ; but it must not be forgotten that the region includes a much larger area in Asia, and that there are many peculiar North Asiatic animals. 2. The Ethiopian Region, which includes all Africa south of the tropic of Cancer, as well as the southern part of Arabia, with Madagascar and the adjacent islands. It may be popularly termed the African region. 3. The Oriental region, which is comparatively sinall, including India and Ceylon, the Indo-Chinese countries and southern China, and the Malay Archipelago as far as the Philippines, Borneo, and Java. It may be popularly called the South Asiatic or Indian region. 4. The Australian Region, which is composed of the remainder of the Malay Archipelago, Australia, New Zealand, and all the tropical islands of the Pacific, as far east as the Marquesas and the Low Archipelago. 5. The Neotropical Region, which comprises the whole of South America and the adjacent islands, the West Indies or Antilles, and the tropical parts of Central America and Mexico. It may be well called the South American region. 6. The Nearctic region, which consists of all temperate and arctic North America, with Greenland, and is thus well described as the North American region. These six regions, although all of primary importance f rom.their extent, and well marked by their total assemblage of animal forms, vary greatly in their zoological richness, their degree of isolation, and their relationship to each other. The Australian region is the most peculiar and the most isolated, but it is comparatively small, and poor in the higher animals. The Neotropical region comes next in peculiarity and isolation, but it is extensive and excessively rich in all forms of life. The Ethiopian and Oriental regions are also very rich, but they have much in common. The Paloearctic and Nearctic regions, being wholly temperate, are less rich, and they too have many resem blances to each other ; but while the Nearctic region has many groups in common with the Neotropical, the Palaearctic is closely connected with the Oriental and Ethiopian regions. The cause of these various resem blances and differences depends on the past history of the earth, and will be better understood when we have sketched the zoological features of each region and the changes they have undergone in the latest geological periods. I. The Palcearctic Region. This extensive region, though varied in physical aspect, and often covered with luxuriant vegetation, is poor in animal life when compared with the great tropical regions of the Old and New Worlds. This is no doubt due mainly to climate, but also in part to so much of its surface being densely populated and highly cul tivated. It contains, however, a number of characteristic and not a few altogether peculiar animal forms. Beginning with the Mammalia, we have first the sheep and goats with such allied forms as the chamois and saiga-antelope, which are especially characteristic ; deer are abundant and varied ; the smaller cats, the wolves, the foxes, and the bears abound, with a variety of smaller groups, as weasels, badgers, and some otters. Seals are plentiful on the northern coast, and even in the Black and Caspian Seas ; wild horses and asses abound in Asia, as they once did in Europe ; there are many peculiar forms of mica, voles, and hamsters ; while dormice, squirrels, marmots, hares, and pikas are well-marked features of the region. The insectivorous family of the moles is almost peculiar, as are the curious mole-rats (Spalax). The genera which are peculiar to the Palrearctic region belong to the following families : to the moles (Talpidce) 7 genera ; to the dogs (Canidce) 1 genus ; to the weasels (Mustelidce) 3 genera; to the pandas (jEluridce) 1 genus ; to the seals (Phocidce) 1 genus ; to the camels (Camelidce) 1 genus ; to the deer (Gervidce) 6 genera ; to the hollow-horned ruminants (Bovidae) 7 genera ; to the rats (Muridce) 6 genera ; to the mole-rats (Spalacidce) 2 genera ; to the Octodontidce, a peculiar group of rat-like animals only found in South America, Abyssinia, and North Africa, 1 genus. In birds, the Palcearctic region is pre-eminently rich in thrushes, warblers, titmice, jays and magpies, sparrows, and buntings. It also abounds in grouse, and in its eastern half in magnificent pheasants. Water-birds are plentiful, and its northern districts produce many fine ducks and divers. The following enumeration of the families of which the Palaearctic region possesses peculiar genera will help to give an idea of the characteristic features of its ornithology : Of the warblers (Sylviidce) 15 genera, many of which, however, migrate into tropical Africa and India in winter ; of babblers (Timaliidcc) 1 genus ; of reedlinga (Panuridce) 4 genera ; of creepers (Certhiidce) 1 genus ; of tits (Paridce) 1 genus ; of the crow family (Corvidce) 4 genera; of finches and buntings (Fringillidae) 12 genera ; of starlings (Sturnidce) 1 genus ; of larks (Alaudidce) 2 genera ; of sand-grouse (Pterodidce) 1 genus : of grouse (Tetraonidce) 4 genera ; of pheasants (Phasianidce) 5 genera ; of vultures ( Vulturidce) 1 genus ; of rails (Rallidce) 1 genus ; of snipes (Scolopaddce) 4 genera ; of coursers (Glareolidce) 1 genus ; of bustards (Otididce) 1 genus. Of the remaining groups less accurate information is obtainable, and their distribution is less generally interest ing. Reptiles, being heat-loving animals, are comparatively scarce, yet in the desert regions they are more plentiful and furnish a considerable number of peculiar types, there