The Australian and Indian regions of Zoology are very strongly contrasted. In one the Marsupial order constitutes the great mass of the mammalia,--in the other not a solitary marsupial animal exists. Marsupials of at least two genera (_Cuscus_ and _Belideus_) are found all over the Moluccas and in Celebes; but none have been detected in the adjacent islands of Java and Borneo. Of all the varied forms of _Quadrumana_, _Carnivora_, _Insectivora_ and _Ruminantia_ which abound in the western half of the Archipelago, the only genera found in the Moluccas are _Paradoxurus_ and _Cervus_. The _Sciuridæ_, so numerous in the western islands, are represented in Celebes by only two or three species, while not one is found further east. Birds furnish equally remarkable illustrations. The Australian region is the richest in the world in Parrots; the Asiatic is (of tropical regions) the poorest. Three entire families of the Psittacine order are peculiar to the former region, and two of them, the Cockatoos and the Lories, extend up to its extreme limits, without a solitary species passing into the Indian islands of the Archipelago. The genus _Paloeornis_ is, on the other hand, confined with equal strictness to the Indian region. In the Rasorial order, the _Phasianidæ_ are Indian, the _Megapodiidæ_ Australian; but in this case one species of each family just passes the limits into the adjacent region. The genus _Tropidorhynchus_, highly characteristic of the Australian region, and everywhere abundant as well in the Moluccas and New Guinea as in Australia, is quite unknown in Java and Borneo. On the other hand, the entire families of _Bucconidæ_, _Trogonidæ_ and _Phyllornithidæ_, and the genera _Pericrocotus_, _Picnonotus_, _Trichophorus_, _Ixos_, in fact, almost all the vast family of Thrushes and a host of other genera, cease abruptly at the eastern side of Borneo, Java, and Bali. All these groups are _common birds_ in the great Indian islands; they abound everywhere; they are the characteristic features of the ornithology; and it is most striking to a naturalist, on passing the narrow straits of Macassar and Lombock, suddenly to miss them entirely, together with the _Quadrumana_ and _Felidæ_, the _Insectivora_ and _Rodentia_, whose varied species people the forests of Sumatra, Java, and Borneo.