The geographical distribution of animals, with a study of the relations ...

chap, xiu.] THE AUSTRALIAN REGION. 465few observations will therefore suffice, on the supposed earlyhistory of the Australian region as a whole.It was probably far back in the Secondary period, that someportion of the Australian region was in actual connection withthe northern continent, and became stocked with ancestral formsof Marsupials ; but from that time till now there seems to havebeen no further land connection, and the Australian lands havethenceforward gone on developing the Marsupial and Monotrematetypes, into the various living and extinct races we now findthere. During some portion of the Tertiary epoch Australia probablycomprised much of its existing area, together with Papuaand the Solomon Islands, and perhaps extended as far east as theFiji Islands ; while it might also have had a considerable extensionto the south and west.Some light has recently been thrownon this subject by Professor McCoy's researches on the Palaeontologyof Victoria. He finds abundant marine fossils ofEocene and Miocene age, many of which are strikingly similarto those of Europe at the same period. Among these are Cetaceansof the genus Squaloclon ;European species of Plagiostomousfishes ; mollusea and corals closely resembling those ofEurope and North America of the same age,—such as numerousVolutes closely allied to those of the Eocene beds of the IsleofWight, and the genus Dentalium in great abundance, almost orquite identical with European tertiary species. Along withthese, are found some living species, but always such as nowlive farther north in tropical seas. The Cretaceous and Mesozoicmarine fossils are equally close to those of Europe.The whole of these remains demonstrate that, as in thenorthern so in the southern hemisphere, a much warmer climateprevailed in the Eocene and Miocene periods than at the presenttime. This is a most important result, and one which stronglysupports Mr. Belt's view, before referred to, that the warmerclimates in past geological epochs, and especially that of theMiocene as compared with our own, was caused by a diminution ofthe obliquity of the ecliptic, leading to a much greater uniformityof the seasons for a considerable distance from the equator, andgreatly reducing the polar area within which the sun would ever