216 Bulletin American Museum of Natural History. [Vol. XXVII, 



Molars degenerate, greatly reduced, haplodout, variable in number. 

 Tongue elongate, protrusile. 

 Tarsipes. 

 Phascolarctin.e (Crescent-toothed Phalangers and Koala). 

 Arboreal. 



Size and habits variable. Pseudochirus phalanger-like, Petau- 

 roides, large Flying Phalanger, Phascolarctos (Koala) Sloth- 

 like. 

 Tip of tail naked [Pseudochirus, Petauroides) or tail absent 



(Phascolarctos) . 

 Pes with fully opposable hallux. 

 Pes strongly syndactylous. 

 Herbivorous. 



Diprotodont. 



Molars with strongly crescentic cusps. 

 Macropodid.e. 



Terrestrial. 



Size variable. The Rat Kangaroos are rabbit-like, the Giant 

 Kangaroos (Palorchestes) of the Pleistocene, had a skull as 

 big as that of a horse. 

 Tail non-prehensile, used as a secondary support. 

 Pes becoming elongate, hallux reduced (Hypsiprymnodon) , 



usually wanting. 

 Pes strongly syndactylous, digits II and III becoming vestigial, 



digit IV greatly enlarged. 

 Plantar pads reduced {Hypsiprymnodon) to wanting (Macropus). 

 Gait hopping; smallest forms partly fossorial. 

 Herbivorous (food: roots, grass), grazing. 



Diprotodont. Incisors sharp and cutting, lower incisors with 



scissors-like effect (i. c, with slight transverse motion). 

 Molars bilophodont; brachyodont to hypsodont; posterior upper 

 and lower premolars enlarged, grooved (Potoroinse, Bet- 

 tongiinse) or reduced (Macropodinse) . 

 Phascolomyid.e. 



Terrestrial-fossorial. 

 Size beaver-like. 

 Tail reduced. 



Pes broad, with large claws, hallux reduced. 



Of syndactylous derivation but digits II and III secondarily en- 

 larged. 

 Plantar pads degenerate. 

 Gait plantigrade, shuffling. 

 Herbivorous. 



Diprotodont. I-} , Incisors much enlarged, rodent-like, but 



motion of jaw vertical. 

 Molars strongly bilobate, hypsodont, curved. 

 Phascolomys, ^Phascolonus. 



