It is evident that Australia is the country which has been least changed in the later geological time, being now in the main as it was in the early part of the tertiary period. It has also been called a land forgotten in the cretaceous period by the development of the earth. This “ land of the dawning “ reveals to us a corresponding primitive and peculiar animal life, as well as flora with its proteaceas, leafless casuarinas, and acacias, which remind us of the vanished vegetation of the elder tertiary period. The major part of Australia's mammals consists of the remarkable marsupials, which belong to the very oldest and lowest organisation of all known mammals, and which have, without doubt, survived from an earlier geological period, during which they were also found in Europe. Among birds the country has some remarkable species (Megapodida), the only ones in the world that do not hatch their eggs themselves but, like reptiles, bury them in earth-mounds, whose elements of fermentation produce heat and thus hatch the eggs. The two coursers, the emu and the cassowary, when we except the kiwi-kiwi of New Zealand, have more rudimentary wings than any now existing ostrich.

In the tertiary period Australia is supposed to have been much larger than it now is. It is thought to have included New Guinea and Tasmania, and possibly to have extended eastward to the Fiji Islands. According to the celebrated naturalist Mr. A. R. Wallace, this hypothesis is absolutely necessary in order to explain certain facts connected with the Australian fauna. As already stated, remains of remarkable gigantic marsupials have been found.