PHALANGISTIDJE. 251 



gistidce we find certain modifications both in their 

 dentition and external characters, upon which genera, 

 and subgenera have been founded. They are divided 

 into three genera : those which have a large mem- 

 brane extended from the sides of the body, arid joined 

 to the fore and hind-legs, as in the flying Squirrels, 

 and which enables them to sail in the air like a para- 

 chute (but not to fly) constitute the genus Petaurus. 

 To those which have no such membrane, and have 

 a prehensile tail, the generic term Phalangista* 

 (Geofroy Saint-Hilaire,)is now restricted; and thirdly, 

 we have the genus Phascolarctos, containing only one 

 species, (the Koala) which is at once distinguished 

 by its want of tail. 



The constant teeth in the genus Phalangista are : 

 Incisors, |:| ; canines, ;J; false molars, \'.\ ; true 



SIDE VIEW OF TEETH OF UPPER AND LOWER JAW OF A 

 BPKuifiS OK 1'hula/tyWta. 



The anterior pair of incisors of the upper jaw are 

 longer than the rest, separated at the base, and meet 



* The same group is called Balantia by Illiger, and Cuscvs 

 by Lacepede. 



