fauna thus dates from the period when Australia was still attached by Antarctica to South America, that is, between the lower Jurassic (the breaking away of India) and the Eocene (the separation of Australia from Antarctica). As the present position of Australia no longer affords isolation to these forms, they gradually encroach further and further into the Sunda Archipelago, so that Wallace had to lay his limits for the mammals between the Islands of Bali and Lombok and through the Straits of Macassar.
The third fauna of Australia is the most recent; emigrating from the Sunda Islands, it has made its home in New Guinea and has already conquered North-eastern Australia. The dingo (wild-dog), rodents, bats, and others were post-Pleistocene immigrants to Australia. The recent genus Pheretima of the earth-worms, which has displaced most of the older genera by its greater vitality on the Sunda Islands, and on the coastal areas of South-east Asia from the Malay Peninsula to China and Japan, has also completely conquered New Guinea, and has already obtained a firm foothold in the northern point of Australia. All this indicates a rapid exchange of fauna and flora which began in recent geological time.
This threefold division of the Australian fauna is in most beautiful agreement with the displacement theory. It is only necessary to glance at the three reconstructed
coast-line—in the estuarine area of a great river—from which the distribution of land and water must have been exactly the reverse of that of to-day. Simroth (vide supra), Andrée (“Das Problem der Permanenz der Ozeane und Kontinente,” Petermann’s Mitt., 63, p. 348, 1917), Diener, and Sörgel have rejected this continent of Burckhardt, and Arldt himself, one of the few adherents, had to allow that it was based on very slight evidence (“Die Frage der Permanenz der Kontinente und Ozeane,” Geogr. Anzeiger, 19, pp. 2–12, 1918). Quite another explanation must therefore be sought for Burckhardt’s observations.
