38 THE NOTOG^IC REALM. [CHAP. 



tooth in question has an elongated cutting-blade, adapted to work 

 against its fellow in the opposite jaw with a scissor-like action, 

 somewhat after the fashion of the carnassial teeth of a tiger ; but 

 the other cheek-teeth were all relatively small, although the tusks 

 were large. The giant among the marsupials was the extinct 

 Diprotodon of the Australian Plistocene, a creature rivalling in size 

 the extinct South American Megalotherium, and allied on the one 

 hand to the kangaroos, and on the other to the phalangers. It 

 was not, however, endowed with the leaping powers of the former, 

 and doubtless walked on the ground in the ordinary manner, its 

 toes having apparently been covered with structures intermediate 

 between hoofs and nails. Nearly related, but likewise repre- 

 senting a family by itself, is the somewhat smaller, but still 

 gigantic Nototherium, which in the conformation of its limb-bones 

 appears to approximate to the wombats, and may consequently 

 have been, like those animals, of fossorial habits. 



The last Notogaeic family of the Diprotodont section is that of 

 the wombats (Phascolomyidcz\ distinguished from all the preceding 

 forms by the presence of only a single pair of incisor teeth in both 

 the upper and lower jaws ; canines being absent, and the whole 

 dentition thus curiously simulating that of the rodents among 

 the higher mammals. All the three existing species, which 

 are included in the single genus Phascolomys, are confined to 

 Australia and Tasmania; and, except certain extinct species 

 belonging to the same genus, the only other member of the 

 family is the extinct Phascolonus (Sceparnodoti) from the Australian 

 Plistocene, distinguished by the peculiarly flattened and chisel- 

 like form of the upper incisor teeth. This, the only known 

 species, attained much larger dimensions than either of the 

 existing wombats. 



The Polyprotodonts likewise include three existing families 

 found within the limits of the Australian region, none of the mem- 

 bers of which stray either into the Austro- Malay an or Polynesian 

 regions, although the separate family of the opossums (Didelphyidcz} 

 inhabits the New World. In the family of the bandicoots (Pera- 

 melidtz}, the two species of rabbit-bandicoot (Peragale) are ex- 

 clusively Australian, whereas the true bandicoots (Perameles] have 

 both Papuan and Australian representatives ; the third genus 



