THE MAMMALIA. 35 



This theory is highly satisfactory till we examine into the his- 

 tory of the Marsupials in their own island-continent, Australia. 

 Australia was cut off from the rest of the world before the Creta- 

 ceous period and before the placental mammals had had time to 

 arrive on its soil. Here the Marsupials were the masters of all 

 they surveyed. What happened ? They flourished and developed 

 in all possible ways. They became differentiated into vegetable- 

 feeders, into insect- and root-eaters, into formidable carnivorous 

 animals ; they lived in trees, flew after the fashion of bats, bur- 

 rowed in holes ; and, in short, mimicked most of the great animal 

 orders in other parts of the world. Some attained a gigantic size, 

 and must have been as much as sixteen feet high, the largest 

 existing kangaroo measuring about five feet. The Hving genus, 

 Macropus (the kangaroo), was represented in the Post-Tertiary 

 deposits by species in all essential respects agreeing with the 

 recent forms, but of immense size, one species being as large as 

 the rhinoceros. Diprotodoii had a skull more than a yard in 

 length, and was about sixteen feet in height. It was, says Owen, 

 a giant kangaroo, but without the power of leaping. Thylacoleo 

 was named by Owen the Marsupial Lion, which animal it rivalled 

 in size. The dentition was not the same as that of the carnivo- 

 rous marsupials of the present day, but was of so powerful and 

 formidable a character as irresistibly to suggest the habits of a 

 beast of prey. 



The Wombats are represented by fossil species, partly cor- 

 responding with them in size and partly far exceeding them. 

 Nototherium^ for instance, far exceeded the living species in 

 size, and had the most hideous skull imaginable — very nearly as 

 broad as it was long. The living Marsupials of Australia are 

 evidently, therefore, but diminished and scattered survivals of the 

 Marsupials of the past.'^ All these fossil Marsupials, too, belong 

 to the most recent geological period. On the Darling Downs, 

 Leichhard collected bones which were so little like fossils that he 

 expressed a hope that he would find living specimens of the same 

 animals further in the interior of the Continent. Here, in 

 Australia, the Marsupials had no rivals. There was no Glacial 



* Schmidt. 



