198 



DE. B. A. BENSLET OX THE EVOLUTION 



that its divergence as a teiTestrial type must have taken place, as in the case of tlie latter 

 family, at a comparatively early stage. (d) Its Central-Australian range and the 

 probability of a Papuan origin of the Peramelidse do not favour the view of a very 

 intimate relationship with the latter family. 



PHALANGERIDiE. 



The phylogenetic position of this family may be estimated as follows : — (a) By the 

 retention in foot-structure of the second arboreal stage through which all the remaining 

 members of the second or syndactylous line have passed ; (b) by the appearance of the 

 diprotodont modification of the antemolar teeth ; {c) by the loss of the insectivorous 

 characters of the molar cusps ; (d) by the retention of a number of dental characters 

 ancestral to those of the Macropodidoe, Diprotodontidte, and Phascolomyidse. In respect 

 to character a the family is prototypal. In characters b and c it is more advanced 

 than the Peramelidse and Notoryctidse. 



Pliascolarctus. 



Tricliosurus. 



Dactylopsila. 



Petanrus. 



Pseud ocldrus 



rsipes. 



Properamclida; (hyp.). 



The PhalangeridEe are the derivatives of minute insectivorous or incipient omnivorous 

 i^rototypes combining the dental characters of the moi*e primitive of the Peramelidse with 

 the type of pes at present characteristic of the group. The diprotodont modification was 

 developed in these forms as an insectivorous adaptation primarily affecting the median 

 lower incisors. 



