broken up into many small volcanic islets in which a limitel number of Malayan types alone survived. Such a condition of things will account for the very small variety of mammalia compared with the tolerably numerous genera of birds, that now characterise its fauna; while both here and in Celebes we find some of the old Malayan types preserved, which, in the extended area of the Sunda Isles have been replaced by more dominant forms.

The next important change would be the separation of Java; and here also no doubt a considerable submergence occurred, rendering the island an unsuitable habitation for the various Malay types whose absence forms one of its conspicuous features. It has since remained permanently separated from the other islands, and has no doubt developed some peculiar species, while it may have preserved some ancient forms which in the larger area have become changed. From the fact that a number of its species are confined either to the western or the eastern half of the island, it is probable that it long continued as two islands, which have become united at a comparatively recent period. It has also been subjected to the immigration of Indo-Chinese forms, as already referred to in the earlier part of this sketch.

We have thus shown how the main zoological features of the several sub-divisions of the Malayan sub-region may be accounted for, by means of a series of suppositions as to past changes which, though for the most part purely hypothetical, are always in accordance with what we know both of the physical geography and the zoology of the districts in question and those which surround them. It may also be remarked, that we know, with a degree of certainty which may be called absolute, that alternate elevation and subsidence is the normal state of things all over the globe; that it was the rule in the earliest geological epochs, and that it has continued down to the historical era. We know too, that the amount of elevation and subsidence that can be proved to have occurred again and again in the same area, is often much greater than is required for the changes here speculated on,-while the time required for such changes is certainly less than that necessitated by the changes

of specific and generic forms which have coincided with, and been to a large extent dependent on them. We have, therefore, true causes at work, and our only suppositions have been as to how those causes could have brought about the results which we see; and however complex and unlikely some of the supposed changes may seem to the reader, the geologist who has made a study of such changes, as recorded in the crust of the earth, will not only admit them to be probable, but will be inclined to believe that they have really been far more complex and more unexpected than any supposition we can make about them.

There is one other external relation of the Malayan fauna about which it may be necessary to say a few words. I have supposed the greatest westward extension of the Malayan area to be indicated by the Maldive islands, but some naturalists would extend it to include Madagascar in order to account for the range of the Lemurida. Such an extension would, however, render it difficult to explain the very small amount of correspondence with a pervading diversity, between the Malayan and Malagasy faunas. It seems more reasonable to suppose an approximation of the two areas, without actual union having ever occurred. This approximation would have allowed the interchange of certain genera of birds, which are common to the Oriental Region and the Mascarene islands, but it would have been too recent to account for the diffusion of the lemurs. which belong to distinct genera and even distinct families. This probably dates back to a much earlier period, when the lemurine type had a wide range over the northern hemisphere. Subjected to the competition of higher forms, these imperfectly developed groups have mostly died out, except a few isolated examples, chiefly found in islands, and a few groups in Africa.

In our discussion of the origin of the Ethiopian fauna, we have supposed that a close connection once existed between Madagascar and Ceylon. This was during a very early tertiary epoch; and if, long after it had ceased and the fauna of Ceylon and South India had assumed somewhat more of their present character, we suppose the approximation or union of Ceylon

and Malaya to have taken place, we shall perhaps be able to account for most of the special affinities they present, with the least amount of simultaneous elevation of the ocean bed; which it must always be remembered, requires a corresponding depression elsewhere to balance it.

Concluding Remarks on the Oriental Region.—We have already so fully discussed the internal and external relations of the several sub-regions, that little more need be said. The rich and varied fauna which inhabited Europe at the dawn of the tertiary period, as shown by the abundant remains of mammalia wherever suitable deposits of Eocene age have been discovered,— proves, that an extensive Palearctic continent then existed; and the character of the flora and fauna of the Eocene deposits. is so completely tropical, that we may be sure there was then no barrier of climate between it and the Oriental region. At that early period the northern plains of Asia were probably under water, while the great Thibetan plateau and the Himalayan range, had not risen to more than a moderate height, and would have supported a luxuriant sub-tropical flora and fauna. The Upper Miocene deposits of northern and central India, and Burmah, agree in their mammalian remains with those of central and southern Europe, while closely allied forms of elephant, hyæna, tapir, rhinoceros, and Chalicotherium have occurred in North China; leading us to conclude that one great fauna then extended over much of the Oriental and Palearctic regions. Perim island at the mouth of the Red Sea, where similar remains are found, probably shows the southern boundary of this part of the old Palearctic region in the Miocene period. Towards the equator there would, of course, be some peculiar groups; but we can hardly doubt, that, in that wonderful time when even the lands that stretched out furthest towards the pole, supported a luxuriant forest vegetation, substantially one fauna ranged over the whole of the great eastern continent of the northern hemisphere. During the Pliocene period, however, a progressive change went on which resulted in the complete differentiation of the Oriental and Palearctic faunas. The

causes of this change were of two kinds. There was a great geographical and physical revolution effected by the elevation of the Himalayas and the Thibetan plateau, and, probably at the same time, the northward extension of the great Siberian plains. This alone would produce an enormous change of climate in all the extra-tropical part of Asia, and inevitably lead to a segregation of the old fauna into tropical and temperate, and a modification of the latter so as to enable it to support a climate far more severe than it had previously known. But it is almost certain that, concurrently with this, there was a change going on of a cosmical nature, leading to an alteration of the climate of the northern hemisphere from equable to extreme, and culminating in that period of excessive cold which drove the last remnants of the old sub-tropical fauna beyond the limits of the Palearctic region. From that time, the Oriental and the Ethiopian regions alone contained the descendants of many of the most remarkable types which had previously flourished over all Europe and Asia; but the early history of these two regions, and the peculiar equatorial types developed in each, sufficiently separate them, as we have already shown. The Malayan sub-region is that in which characteristic Oriental types are now best developed, and where the fundamental contrast of the Oriental, as compared with the Ethiopian and Palearctic regions, is most distinctly visible.

TABLES OF DISTRIBUTION.

In constructing these tables, showing the distribution of various classes of animals in the Oriental region, the following sources of information have been chiefly relied on, in addition to the general treatises, monographs, catalogues, &c., used for the compilation of the Fourth Part of this work.

Mammalia.-Jerdon's Indian Mammalia; Kelaart's Fauna of Ceylon; Horsfield and Moore's Catalogue of the East India Museum; Swinhoe's Catalogue of Chinese Mammalia; S Müller's Zoology of the Indian Archipelago; Dr. J. E. Gray's list of Mammalia of the Malay Archipelago (Voyage of Samarang); and papers by Anderson, Blyth, Cantor, Gray, Peters, Swinhoe, &c.

Birds.-Jerdon's Birds of India; Horsfield and Moore's Catalogue; Holdsworth's list of Ceylon Birds; Schlegel's Catalogue of the Leyden Museum; Swinhoe on the Birds of China, Formosa, and Hainan; Salvadori on the Birds of Borneo; Lord Walden on the Birds of the Philippine Islands; and papers by Blyth, Blanford, Elwes, Elliot, Stoliczka, Sclater, Sharpe, Swinhoe, Verreaux, and Lord Walden.

Reptiles.-Günther's Reptiles of British India; papers by same author, and by Dr. Stoliczka.