EXTERNAL CHARACTERS OF THE KOALA. 607 



them to rank as a subfamily — and I see no reason for dissenting 

 from that view, — the characters of Sypsiprymnodon must be 

 given the higher rank of a family, the Hypsiprymnodontidse 

 ■equivalent to, and standing between, the Macropodidse and the 

 Phalangeridee, but not definitely assignable to either. 



From the tj^pical Phalangeridae constituting the subfamily 

 Phalangerinse, the genera, Pseudochirus andi Petauroides, character- 

 ized by the crescentic pattern of the molar teeth, may be separated 

 as the Pseudochirinfe as proposed by Winge. But it does not 

 appear to me that proper appreciation has been shown for the 

 characters of the very highly specialized genus Tarsipes *, which 

 differs profoundly from the Phalangeridae in the structure of the 

 skull, teeth, tongue, snout, and alimentary canal, as Thomas re- 

 corded. The genus seems to be at least as widely divergent fi'om 

 the Phalangeridae as are the Macropodidse. These two families, 

 indeed, are linked by the Hypsiprymnodontidse, and the 

 evolutionary stages by which the Kangaroos have been derived 

 from the Phalangerine stock may be traced with reasonable 

 certainty through living forms. Bvit all the hypothetical inter- 

 mediate genera between Tarsipes and the Phalangers have died 

 out, leaving that genus isolated. And since, in my opinion, it 

 differs more from the typical Phalangers than do the Pseudo- 

 chirines, it may be raised at least to the rank of a family — 

 Tarsipedidfe. 



Briefly, the existing genera of Diprotodonts may be classified 

 as follows : — 



Phalangeroidea. 



Fam. MACROPODIDiE. 



Subfam. Macropodin^. 



,, PoTOROINjE. 



Fam. Hypsiprymnodontid^. 

 Fam. Phalangerid^. 

 Subfam. Phalangerine. 



,, PSEUDOCHIRINE. 



Fam. Tarsipedide. 



Phascolarctoidea. 



Fam. Phascolarctide. 



Phas colomy oidea . 



Fam. Phascolomyide. 



* Winge and Beiisley even considered the characters of this genus to be of less 

 ■sj'stematic value than the concentric molars of Fsev.docJiirus. 



Proc. Zool. Soc— 1921 , No. XLI. 41 



