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This general conclusion is of great importance in the study of the geographical distribution of animals, because it bids us avoid the too hasty assumption that the countless anomalies we meet with are to be explained by great changes in the distribution of land and sea, and leads us to rely more on the inherent powers of dispersal which all organisms possess, and on the union or disruption, extension or diminution, of existing lands
—but always in such directions and to such a limited extent as not to involve the elevation of what are now the profoundest depths of the great oceans.
Zoological Regions. We will now proceed to sketch out the zoological features of the six great biological regions; and will afterwards discuss their probable changes during the more recent geographical periods, in accordance with the principles here laid down.
The Pulæarctic Region. The Palæarctic, or North Temperate region of the Old World, is not only by far the most extensive of the zoological regions, but is the one which agrees least with our ordinary geographical divisions. It includes the whole of Europe, by far the largest part of Asia, and a considerable tract of North Africa; yet over the whole of this vast area there prevails a unity of the forms of animal life which renders any primary subdivision of it impossible, and even secondary divisions difficult. But besides being the largest of the great zoological regions, there are good reasons for believing this to represent the most ancient, and therefore the most important centre of the development of the higher forms of animal life,—and it is therefore well to consider it first in order.
In enumerating the most important animal groups characteristic of this and other regions, it must be clearly understood that such groups are not always absolutely confined to one region. Here and there they will often overlap the boundaries, while in other cases single species may have a wide distribution in one or more of the adjacent regions ; but this does not at all affect the main fact, that the group as a whole is very abundant and very widely spread over the region in question, while it is very rare, or confined to a very limited area in adjacent regions, and is therefore specially characteristic of the one as compared with other parts of the world. Bearing this in mind, we shall find that the Palæarctic region is well characterized by a considerable number of typical groups, although, as we shall presently sce, it has in recent geological times lost much of its ancient richness and variety of animal
Among Mammalia the groups most characteristic of this region are the moles (Talpida), a family consisting of eight distinct genera which range over the whole region, but beyond it barely enter the Oriental region in North India, and the Nearctic region in North-West America ; camels, confined to the deserts of North Africa and Asia ; sheep and goats (Capra), only found beyond the region in the Nilgherries and Rocky Mountains ; several groups of antelopes, and many peculiar forms of deer; hamsters (Cricetus), sand rats (Psammomys), mole rats (Spalas), and pikas (Lagomys), with several other forms of rodents. Wolves, foxes, and
bears, are also very characteristic, though by no means confined to the region.
Among birds the most important group is certainly the small-sized, but highly-organized warblers (Sylviidae), which, although almost universally distributed, are more numerous, and have more peculiar and characteristic genera here than in any other region. Most of our song-birds, and many of the commonest tenants of our fields, woods, and gardens, belong to this family; and identical or representative species are often found ranging from Spain to China, and from Ireland to Japan. The reedlings (Panuridae), the tits. (Paridæ), and the magpies (Pica), are also very characteristic; while among the finches (Fringillida), a considerable number of genera are peculiar. A large number of peculiar groups of grouse (Tetraonidae), and pheasants (Phasianidae) are also characteristic of this region. Although the reptiles and fresh-water fishes are comparatively few, yet many of them are peculiar. Thus, no less than 2 genera of snakes, 7 of lizards, and 16 of batrachia, are confined to the Palæarctic region, as well as 20 genera of fresh-water fishes.
The insects and land-shells offer their full proportion of peculiar types; but it would lead us beyond our special object to enter into details with regard to these less known groups of animals.'
1 Details will be found in the Author's work on The Geographiccl Distribution of Animals.
The Ethiopian Region. The Ethiopian region, consisting of Africa south of the Tropic of Carcer with Madagascar, is of very small area compared with the Palæarctic region ; yet owing to the absence of extreme climates, and the tropical luxuriance of a considerable portion of its surface, it supports a greater number and variety of large animals than any other part of the globe of equal extent. Much of the speciality of the region is, however, due to the rich and isolated fauna of Madagascar, the peculiarities of which may be set aside till we come to discuss the past history of the Ethiopian region.
Considering then, first, the zoological features of tropical and southern Africa alone, we find a number of very peculiar forms of mammalia. Such are the golden moles, the Potamogale, and the elephant-shrews among Insectivora ; the hippopotami and the giraffes, among Ungulata ; the hyæna-like Proteles (Aard-wolf), and Lycaon (hyæna-dog), among Carnivora; and the Aard-varks (Orycteropus) among Edentata. These are all peculiar; but among highly characteristic forms are the baboons, and several genera of monkeys and apes ; several peculiar Lemurs; a great variety of the civetfamily (Viverridae), and of rodents ; peculiar genera of swine (Potamochærus and Phacochærus), and a greater abundance and variety of antelopes than are to be found in all the other regions combined. But the Ethiopian region is strikingly distinguished from all others, not only by possessing many peculiar forms, but by the absence of a number of common and widely distributed
groups of mammalia. Such arc—the bears, which range over the whole northern hemisphere, and as far south as Sumatra in the eastern and Chili in the western hemisphere, yet they are totally wanting in Tropical and South Africa ;—the deer, which are still more widely distributed, ranging all over North and South America, and over all Asia to Celebes and the Moluccas, yet they are totally absent from the Ethiopian region ; goats and sheep, truc oxen (Bos), and true pigs (Sus), are also absent; though as to the last there is some doubt, certain wild pigs having been observed, though rarely, in various parts of Tropical Africa, but it is not yet determined whether they are indigenous, or escaped from domestication. The absence of such wide-spread families as the bears and deer is, however, most important, and must be taken into account when we come to consider the geographical changes needed to explain the actual state of the Ethiopian fauna.
The birds are not proportionately so peculiar, yet there are many remarkable forms. Most important are the plantain-caters, the ground-hornbills, the colies, and the anomalous secretary-bird ;—while among characteristic families there are numbers of peculiar genera of Aycatchers, shurikes, crows, sun-birds, weaver-birds, starlings, larks, francolins, and the remarkable subfamily of the Guinea-fowls. There are not such striking deficiencies among birds as among mammals, yet there are some of importance. Thus, there are no wrens, creepers, or mut-hatches, and none of the widespread group comprising the true pheasants and jungle fowl-a deficiency almost comparable with that of the bears er the deer. Among the lower vertebrates there