Zoological Regions

This then is the true fauna of Neogaea, made up entirely of animals which arose within the area and whose evolutionary history can to some extent be traced in still earlier Tertiary horizons. It includes three groups which have been believed to have had relatives in other parts of the world. These are Necrolestes, originally described as an insectivore, but really of uncertain affinities. Coenolestes and its allies supposed to be diprotodont marsupials but which are certainly aberrant didelphids ; and the carnivorous marsupials such as Borhyaena, which present a re markable resemblance to the Tasmanian wolf. It has been held by many writers that these forms are indeed closely allied and that their occurrence in such widely separated localities is to be explained by the former existence of a practicable land-bridge over the Antarctic continent. Additional evidence in support of this view will be discussed at a later stage in this article, but it seems on the whole most probable that Borhyaena represents the result of a course of evolution starting from a didelphid which has been remarkably parallel to the independent process which produced Thylacinus from a dasyurid stock.

The remaining realm, Arctogaea, is much more extensive and less compact than those which we have considered, and it is most convenient to begin its discussion by a consideration of the exist ing distribution of animals in the various regions of which it is composed.

Nearctic Region.—Covering as it does the whole of North America except the lowlands of Mexico, the Nearctic region ex hibits extreme variations in geographical qualities. In the extreme north there is a completely snow-covered arctic area, to the south of which there is a continuous belt of coniferous forest extending from Alaska to New England. In the extreme south lies the Sonoran region which has a warm temperate climate and is largely composed of great tree-less plains, although at the mouth of the Mississippi it includes much forest, and in California passes into deserts where the day temperature may be extraor dinarily high, reaching in the Mohave desert i 2o° F.

In the Arctic zone there are polar bears, arctic foxes, musk oxen, reindeer, lemmings and arctic hares, all of these animals extending round the North Pole over the northern lands of Asia and Europe as well as those of North America.

The wooded region includes shrews and the American moles among insectivores ; the Canadian porcupine, chipmunks, musk rats, woodchucks, lemmings, beavers and tail-less hares amongst rodents. The carnivores are represented by pumas and lynx, the grey wolf, foxes, bears, otters, skunks, raccoons, wolverines, marten, weasels and the American badger. The artiodactyls are deer of types found in Asia and in Europe—the wapiti, moose and woodland reindeer; mountain sheep, and the peculiar Rocky Mountain goat ; bison extremely close to those of Europe, and in certain regions the American deer.

The Sonoran region of the south includes opossums and arma dillos, which are immigrants from South America. American types of shrews and moles represent the Insectivora. The rodents in clude prairie dogs, pocket gophers, cotton rats and kangaroo rats, true and flying squirrels, whilst ground squirrels and rabbits occur throughout the region. Amongst the Carnivora are pumas, lynx, bears, American badgers, raccoons, skunks, coyotes, timber wolves, etc. The characteristic artiodactyls are pronghorned antelopes, plains bison, and American deer, together with peccaries. The region is characterized by the absence of all perissodactyls, Pro boscidea, and Primates, of "edentates" and marsupials (other than the few immigrants from South America), of antelopes, true pigs and hippopotami.

Palaearctic Region.—The Palaearctic region greatly resembles the Nearctic in the general character of its mammalian fauna. It contains no monotremes, marsupials, edentates, hyracoids, Proboscidea, or Primates over the greater part of its area, though representatives of the last three groups occur in the Mediterranean region, which forms a transition between the Palaearctic and the Ethiopian regions. The following groups of animals are common to Palaearctic and Nearctic areas :—hares and picas, beavers, marmots, susliks, voles and lemmings; martens and weasels, wolverines, brown bears, wolves and foxes; elk, reindeer, wapiti, bison, big-horned sheep and musk ox either in identical or closely allied species. On the other hand the Palaearctic area includes cer tain wild sheep, goats, saiga antelope, chamoix, many peculiar deer, camels and true pigs, which are not known in America. It pos sesses also a number of horses and asses, though no other perisso dactyls. The desmans and some other insectivores are peculiar to the Old World, as are the dormice, hamsters and jerboas amongst the rodents, and the tiger and panda amongst the carnivores.

Africa.—The fauna of Africa is on the whole strikingly unlike that of the Palaearctic region, and the intervening Mediterranean area does comparatively little to bridge the gap. The mammal fauna is remarkable in that it includes a great variety of species and probably a greater number of individuals of large animals than that of any other region. There are no monotremes or mar supials. The aardvark and the pangolin (Manis) are curious forms, often classified as edentates, but probably not closely re lated to one another nor to the South American forms included in that order. The Insectivora include amongst the Zalambdodonta the golden moles and the Potamogalidae known from no other re gions of the world, and also the elephant shrews and the Macro scelididae, representative of a group, the Menotyphla, of which the other forms are the tree-shrews of the Malayan sub-region. There are many peculiar rodents, jumping hares (Pedetes), mole rats (Bathyergidae), crested rats (Lophiomys) and cane-rats, to gether with many members of the Muridae and true hares. The Carnivora include true dogs, the hunting dog (Lycaon) and the long-eared fox (Otocyon), spotted hyaenas and the Manhaar jackal (Proteles), etc. There are several mongooses and civets. The cats are represented by the lion, leopard and cheetah in addi tion to very numerous smaller forms; ratels, zorillas and otters represent the Mustelidae. There are elephants belonging to the sub-order Loxodon, and hyraxes, of two genera which spread northwards into Syria but are otherwise exclusively Ethiopian. The perissodactyls are represented by zebras and wild asses, to gether with two species of rhinoceroses. Amongst the artiodactyls there are found true pigs together with the forest and wart-hogs. The hippopotamus is widely distributed throughout the region, whilst a dwarf form is restricted to the west coast in the neigh bourhood of Liberia. The Giraffidae, including true giraffes and okapis, are restricted to the region ; the chevrotains of the genus Dorcatherium are similar to those found in Malaysia. Deer are completely absent but the hollow-horned ruminants include not only buffaloes but also an extraordinary number of peculiar genera of antelopes. Sheep and goats penetrate into the region only in the mountains of Abyssinia.