{ { (_a_) Indian Province { 1. _Indo-Malay Sub-Region_ { (_b_) Siamese Province =Oriental Region= { { (_c_) Malay Province { { (_d_) Philippine Province { { { (_a_) Chinese Province { 2. _Chinese Sub-Region_ { (_b_) Japanese Province The Indo-Malay fauna spreads eastward from its metropolis, but has practically no westward extension, or only such as may be traced on the eastern coasts of Africa and the off-lying islands. There appears to exist no other case in the world where the metropolis of a fauna is so plainly indicated, or where it lies, not near the centre, but at one of the ends of the whole area of distribution. Comparing the two sub-regions, the Chinese is distinguished by the great predominance of _Helix_, while in the Indo-Malay sub-region _Nanina_ and the related genera are in the ascendancy. In India itself there are only 6 genera of true Helicidae, poorly represented in point of numbers; in China there are at least three times this amount, most of them abundant in species. The Indo-Malay sub-region, on the other hand, is the metropolis of the Naninidae, which abound both in genera and species. In the Chinese sub-region _Clausilia_ attains a development almost rivalling that of S.E. Europe, while in India there are scarcely a dozen species. A marked feature of the Indo-Malay sub-region is the singular group of tubed land operculates (_Opisthoporus_, _Pterocyclus_, etc.). In China the group is only represented by stragglers of Indian derivation, while the land operculate fauna, as a whole, is distinctly inferior to the Indian. Another characteristic group of the Indo-Malay region is _Amphidromus_, with its gaudily painted and often sinistral shell; the genus is entirely absent from China proper and Japan, where its place is taken by various small forms of the _Buliminus_ group. Fresh-water Mollusca, especially the bivalves and operculates, are far more abundant in the Chinese sub-region than in the Indo-Malay. (1) The =Indo-Malay Sub-region=.--(_a_) _The Indian Province_ proper includes the peninsula of Hindostan, together with Assam and Upper and Lower Burmah. To the east and extreme north-east, the boundaries of the province are ill-defined, and the fauna gradually assimilates with the Siamese on the one hand and the Chinese on the other. Roughly speaking, the line of demarcation follows the mountain ranges which separate Burmese from Chinese territory, but the debatable ground is of wide extent, and Yunnan, the first Chinese province over the border, has many species common with Upper Burmah.