OP THE WOMBAT, KOALA, AND PHALANGERg. 891 



regards the manus and pes, it is necessary to consider both the 

 external appearances and the internal structure. Pocock (9) and 

 other's have ah'eady described the external appearances, and the 

 following conclusions can be drawn from their accounts : — 



1 . The fore foot possesses no special modifications in Tricho- 

 surus. 



2. The conditions in Phascolomys, which are adapted for a 

 fossorial and ambulant life, have some resemblance to those of 

 Trichosurus, but difier in many ways from those in Phascolarctos 

 and the Phalangeridpe. Among these are the length of the 

 digits, the shortness and bluntness of the claws ; and there is no 

 division of the digits into two opposing groups. The pads are 

 reduced. 



3. In Phascolarctos and the Phalangeridse the pollex and index 

 can be opposed to the long a,xis of the manus, and Young regarded 

 these two digits as constituting one group, the remaining three 

 digits forming a second. These conditions are slightest in 

 Phcdanger, intermediate in Pseudochirus, and most highly 

 developed in Phascolarctos. The latter differs from all Phalangers, 

 except Trichosurus, in the appearance of the pads. In Phalanger 

 and Pseicdochirics the pads are striated, but they are granular in 

 Phascolarctos and Phascolomys. Moreover, myological literature 

 shows that Phascolarctos is peculiar in many ways. I agree with 

 Pocock's scheme, which shows that the characters of the manus in 

 Phascolomys differ from those in the other animals. And although 

 the others iiave features in common, there are sufficient characters 

 to distinguish Phascolarctos from the Phalangeridse. 



Bensley (1) described and figured the pes of the Diprotodonts, 

 and drew important conclusions as regards the affinities of the 

 animals. He pointed out that the pes in Dromicia is prototypal 

 for the Phalangeridpe, and those of Phalanger and Pseudochirus 

 conforiTi more or less closely to it. But the conditions in 

 Phascolarctos show no close relation to those in PseudoGhh-i(,s. 

 The general conformation of the digits is the same, but the pads 

 are all reduced, the sole being covered with soft, granular skin as 

 in Phascolomys. The hallux is much farther back than in 

 Pseudochir-tis, so it is more perfectly opposable. A slightly 

 greater displacement would put its axis in line with that of the 

 fourth digit, which it opposes. The foot differs in Phascolarctos 

 and Phascolomys both in external appearance and internal 

 structure. 



Although the pes of Phascolarctos differs liom that in Pseudo- 

 chirus the dental characters are similar, but reach a higher degree 

 of development in the former. Bensley (1) showed that these 

 genera have qiiadrituberculate molars with selenoid cusps. The 

 upper teeth have reduced external styles, with or without 

 intermediate conules. In Phalanger and Trichosurus the quadri- 

 tuberculate molars have bunoid cusps. And the upper teeth have 

 neither external styles nor intermediate cusps. Moreover, as 



