DIPROTODONTIA. 747 



markedly resembles the Cape golden mole. It is thus a good 

 illustration of "convergence," i.e. the appearance of similar 

 characters in forms not nearly related, apparently in indirect 

 response to similar conditions of life. 



4. Family Peramelidae. The burrowing bandicoots, all small in size, 

 insectivorous or omnivorous in diet. In the fore-feet two or 

 three of the middle toes are well developed and clawed, the 

 others being rudimentary ; in the hind-feet the hallux is small or 

 absent, the second and third toes are very slender and united 

 in the same fold of skin, the fourth toe is very large, the fifth 

 smaller, the whole foot suggesting that of the kangaroo. The 

 stomach is simple ; the caecum not large. Clavicles are absent 



in the adult but present in the foetus. Dentition, 4 or 5T34 . 



' 3 134 



Examples. The true bandicoot (Perameles}, remarkable for its 

 allantoic placenta ; the native rabbit (Peragale lagotis] ; the 

 rat-like Chceropus. 



B. DIPROTODONTIA 



1. Family Epanorthidae. The selvas, a family of S. American forms, 



till recently believed to be entirely extinct. The existing forms 

 are included in the genus Ccenolestes, with two species. They 

 are remarkable in having, the upper jaw of the polyprotodont 

 type, and the lower distinctly diprotodont ; and also in having 

 all the digits of the hind-foot free, whereas in all other living 

 Diprotodonts certain of these are united by skin (syndactylous). 

 They are probably primitive forms, and their presence in S. 

 America is highly important. There seems little doubt that 

 the Diprotodonts have been evolved in the Australian area from 

 a primitive widely-spread polyprotodont stock. If, therefore, the 

 Epanorthidae are really allied to the Diprotodonts, their exist- 

 ence in S. America seems to indicate a former connection 

 between that continent and Australia. 



2. Family Phascolomyidae. The wombats, terrestrial, vegetarian, 



nocturnal Marsupials, somewhat bear-like in appearance. The 



dentition is rodent-like, ^^, the teeth have persistent pulps, the 



incisors are chisel-edged, there being no enamel except in front. 

 In the embryo, however, there are four upper incisors, of which 

 the first persists, and five lower incisors, of which the third 

 persists. The fore-feet have five distinct toes, with strong nails ; 

 the hind-feet have a small nailless hallux, the second, third, and 

 fourth toes partly united by skin, the fifth distinct. The tail is 

 very short. The stomach is simple ; the caecum very short. 



There is but one living genus Phascolomys, with three 

 species. 



3. Family Phalangeridae. Small woolly arboreal nocturnal Marsupials, 



with vegetarian or mixed diet. The fore -feet have five distinct 

 toes ; the hind -feet have a large, nailless, opposable hallux, the 



