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usual dividing line of the Palæarctic and Oriental regions. The causes of such a phenomenon are not difficult to conceive. Even now, that portion of the Palearctic region between Western Asia and Japan is, for the most part, a bleak and inhospitable region, abounding in desert plateaus, and with a rigorous climate even in its most favoured districts, and can, therefore, support but a scanty population of snakes, and of such groups of insects as require flowers, forests, or a considerable period of warm summer weather; and it is precisely these which are represented in Japan and North China by tropical forms. We must also consider, that during the Glacial epoch this whole region would have become still less productive, and that, as the southern limit of the ice retired northward, it would be followed up by many tropical forms along with such as had been driven south by its advance, and had survived to return to their northern homes.

It is also evident that Japan has a more equable and probably moister climate than the opposite shores of China, and has also a very different geological character, being rocky and broken, often volcanic, and supporting a rich, varied, and peculiar vegetation. It would thus be well adapted to support all the more hardy denizens of the tropics which might at various times reach it, while it might not be so well adapted for the more boreal forms from Mongolia or Siberia. The fact that a mixture of such forms occurs there, is then, little to be wondered at, but we may rather marvel that they are not more predominant, and that even in the extreme south, the most abundant forms of mammal, bird, and insect, are modifications of familiar Palæarctic types. The fact clearly indicates that the former land connections of Japan with the continent have been in a northerly rather than in a southerly direction, and that the tropical immigrants have had difficulties to contend with, and have found the land already fairly stocked with northern aborigines in almost every class and order of animals.

General Conclusions as to the Fauna of the Palearctic Region.-From the account that has now been given of the fauna

of the Palearctic region, it is evident that it owes many of its deficiencies and some of its peculiarities to the influence of the Glacial epoch, combined with those important changes of physical geography which accompanied or preceded it. The elevation of the old Sarahan sea and the complete formation of the Mediterranean, are the most important of these changes in the western portion of the region. In the centre, a wide arm of the Arctic Ocean extended southward from the Gulf of Obi to the Aral and the Caspian, dividing northern Europe and Asia. At this time our European and Siberian sub-regions were probably more distinct than they are now, their complete fusion having been effected since the Glacial epoch. As we know that the Himalayas have greatly increased in altitude during the Tertiary period, it is not impossible that during the Miocene and Pliocene epochs the vast plateau of Central Asia was much less elevated and less completely cut off from the influence of rain-bearing winds. might then have been far more fertile, and have supported a rich and varied animal population, a few relics of which we see in the Thibetan antelopes, yaks, and wild horses. The influence of yet earlier changes of physical geography, and the relations of the Palearctic to the tropical regions immediately south of it, will be better understood when we have examined and discussed the faunas of the Ethiopian and Oriental regions.

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TABLES OF DISTRIBUTION.

IN constructing these tables showing the distribution of various classes of animals in the Palearctic region, the following sources of information have been chiefly relied on, in addition to the general treatises, monographs, and catalogues used in compiling the fourth part of this work.

Mammalia.-Lord Clement's Mammalia and Reptiles of Europe; Siebold's Fauna Japonica; Père David's List of Mammalia of North China and Thibet; Swinhoe's Chinese Mammalia; Radde's List of Mammalia of South-Eastern Siberia; Canon Tristram's, Lists for Sahara and Palestine; Papers by Professor Milne-Edwards, Mr. Blanford, Mr. Sclater, and the local lists given by Mr. A. Murray in the Appendix to his Geographical Distribution of Mammalia.

Birds.-Blasius' List of Birds of Europe; Godman, On Birds of Azores, Madeira, and Canaries; Middendorf, for Siberia; Père David and Mr. Swinhoe, for China and Mongolia; Homeyer, for East Siberia; Mr. Blanford, for Persia and the high Himalayas; Mr. Elwes's paper on the Distribution of Asiatic Birds; Canon Tristram, for the Sahara and Palestine; Professor Newton, for Iceland and Greenland; Mr. Dresser, for Scandinavia; and numerous papers and notes in the Ibis; Journal für Ornithologie; Annals and Mag. of Nat. History; and Proceedings of the Zoological Society.

Reptiles and Amphibia.-Schreiber's European Herpetology. VoL. I-17

TABLE I.

FAMILIES OF ANIMALS INHABITING THE PALÆARCTIC REGION.

EXPLANATION.

Names in italics show families peculiar to the region.

Names inclosed thus (..............) barely enter the region, and are not considered properly to belong to it.

Numbers are not consecutive, but correspond to those in Part IV.

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