The region which we are about to study is not really a continent in its usual sense consisting mainly of land, but a continent in which the land surface may be looked upon as fragmented into thousands of islands, large and small, with water masses separating them so as to combine the effects of a continent and an ocean over a vast geographical area lying between the continents of Asia and Australia and between the Indian and the Pacific oceans. It covers a wide area of land and ocean extending longitudinally from about 100°E to the dateline or even beyond, and latitudinally from about 10°S to about 20°N (see Fig.6.1