132 MARSUPIALIA 



In certain species, as the Opossums, Dasyures, and Thylacine, 

 the incisors are numerous, small, and subequal in size, and the 

 canines large, as in the typical placental Carnivores (Fig. 35). 

 To these the term " polyprotodont " is applied, and they are all 

 more or less carnivorous in their habits. In others the central 

 incisors are very prominent, and the lateral incisors and canines 

 absent or subordinate in function (Fig. 36). These are called 

 " diprotodont," and they are all wholly or in great part vegetable 

 feeders. In one group of these, the Wombats, there are but two 

 incisors above and the same number below ; but all the others, in- 

 cluding the Kangaroos, Koalas, and Phalangers, have two functional 

 incisors below and as many as six above, three on each side, but 

 of these the first or central pair is the most fully developed. 



Some hesitation has frequently been expressed as to whether the 

 Polyprotodont and Diprotodont types are entitled to constitute 

 distinct primary groups, owing to the presence of syndactylism 

 among the Peramelidce in the former, as well as in the latter ; but if 

 Mr. 0. Thomas is right in regarding this feature as acquired 

 independently in the two groups we may safely adopt such a 

 division. Taking various combinations into consideration, the 

 existing Marsupials readily group themselves into six very natural 

 families, the leading characters of which may be summarised as 

 follows : 



Order MARSUPIALIA. 



A. POLTPBOTODONTIA. Incisors numerous, small, subequaL Canines 



larger than the incisors. Molars with sharp cusps. 



a. Incisors y. Hind feet with the four outer toes subequal, 

 distinct, and a well-developed opposable hallux. Didel- 

 phyidce. 



/3. Incisors ^. Hind feet with four outer toes distinct. Hallux 



small or rudimentary, rarely opposable. Dasyuridce. 



/4 g\ 



y. Incisors . Hind feet long and narrow. Fourth toe 



larger than the others. Hallux rudimentary or absent 

 Second and third toes very slender, and united in a 

 common integument (syndactylous). Perainelid(e. 



B. DIPROTODONTIA. Incisors not exceeding f , usually y, but occasion- 



ally -p Central (first) upper and lower incisors large and 

 cutting. Upper canines generally, and lower invariably, absent 

 or small Molars with bluntly tuberculated or transversely 

 ridged crowns. 



a. Teeth with persistent pulps. Incisors T , large, scalpriform, 

 with enamel on the outer surface only. No canines. 

 Hind feet with four subequal outer toes, partially 

 syndactylous, and with rudimentary hallux. Phascolo- 

 myidce. 



