POUCHED MAMMALS. 205 



Australia. Unlike the opossums, which are comparatively recent immigrants 

 from the North, the selvas, like the edentates, belong to the original primitive 

 fauna of South America, which was first developed when that country was 

 completely cut off from North America by a sea occupying the site of the 

 Isthmus of Panama and Mexico. 



The bandicoots (Peramelidce) are the first representatives of the secotid 

 great subordinal division of the pouched mammals, technically known as the 

 Polyprotodontia. This name is assigned from the circum- 

 stance that these animals differ from the preceding group Bandicoot 

 by the larger number of incisor teeth, of which there are Tribe, 



never less than three pairs in each jaw, while more generally 

 there are four or five pairs of these teeth in the upper, and three or four in the 

 lower jaw. These incisors are always relatively small and of subequal size, 

 and they are flanked by large, tusk-like canines, close behind which are the 

 anterior cheek-teeth. Nearly always the cusps of the molars are numerous 

 and sharp ; and the whole dentition is of a markedly carnivorous type. In 

 all their characters, the Polyprotodonts are a less specialised group than the 

 Diprotodonts ; and they have at the present day a wide geographical 

 distribution, being represented not only in the Notogseic realm, but likewise 

 in South America, and, more sparingly, in North America. They were also 

 living in various parts of the world during the Tertiary and Secondary epochs. 

 In Australasia, and to a certain extent in South America, the members of the 

 present group all of which are either flesh or insect eaters take the place 

 of the Carnivora and Insectivora of other parts of the world. 



From the other three families included in the sub-order the bandicoots are 

 broadly distinguished by the circumstance that the second and third toes of 

 the hind-foot are reduced in size, and enclosed in a common skin in the same 

 manner as among the Diprotodonts. In addition to this very striking and 

 characteristic feature, the members of the present family have the hind-limbs 

 markedly longer than the front pair ; in the fore-limbs the three middle 

 toes, or occasionally only two, are long and furnished with claws, the others 

 being rudimental or wanting ; and the hind-foot has either four or five toes 

 of very unequal lengths, the first toe being rudimental or absent, the second 

 and third small and united, and the fourth, the stoutest. As in the 

 phalangers, the opening of the pouch of the female is directed backwards. 

 Internally, there is a caecum to the intestine ; and in the skeleton collar- 

 bones are lacking. In the upper jaw there may be either four or five pairs 

 of incisor teeth, whereas in the lower jaw there are invariably three. The 

 tail, which is always relatively long, is never prehensile. Bandicoots are 

 restricted to Australia, Tasmania, New Guinea, and certain of the adjacent 

 islands, such as the Aru, Kei, and Duke of York group. In habits they are 

 mainly fossorial and insectivorous, although a few are more or less completely 

 omnivorous. Among the more aberrant forms are the rabbit-bandicoots 

 (Peragale\ of which there appear to be two species, both restricted to the 

 A ustralian mainland. Their most distinctive feature, and the one from which 

 they derive their name, is the great length of the ears. In form these animals 

 are light and delicate, with a long and narrow muzzle. The three middle 

 toes of the fore-foot are long and furnished with stout, curved claws, and in 

 the hind-foot all trace of the first toe is wanting externally. The hind-limbs 

 greatly exceed the front ones in length ; the soles of the hind-feet are hairy ; 

 and there is a distinct crest of hair on the upper surface of the terminal half 

 of the tail. The upper jaw carries five pairs of incisor teeth; and the 



