MARSUPIALS 841 



B. DiPROTODONTIA 



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



till recently believed to be entirely extinct. The existing forms 

 are included in the genus CcBnolestes, 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 

 betv/een 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 Phalangerid.'e. — 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 

 second and third toes are narrow and bound together by skin, 

 the fourth and fifth free. The tail is generally long and pre- 

 hensile. The stomach is simple, the caecum usuallj' large. 



Average dental formula, 



3. I, 2-3, 3-4 



I, o, 0-2, 3-4 



Examples. — The grey Cuscus {Phalanger orientalis) ; Tarsipes, a 

 small mouse-like animal which feeds on honey, and is remark- 

 able in having no inflection of the angle of the mandible and 

 no caecum ; the flying phala.ns,eT?,'\Petaurns), with a parachute 

 of skin extending from the little finger to the ankle ; the Koala, 

 or " native bear " [Phascolarctos cinereus), a relatively large 

 form, about 2 ft. in length. An extinct form Thylacoleo, of 

 the late Tertiary period of Australia, is interesting in its ex- 

 traordinary dentition, the functional teeth being reduced to 

 large front incisors and the third premolars, both adapted 

 for sharp cutting. 



4. Family Macropodidae. — Kangaroos, herbivorous terrestrial Marsupials. 



Dentition, - °-h^^^ The incisors are sharp, and suited for 

 J, o, 2, 4. ^ ' 



