I4 2 STRUCTURE OF KOALA CHAP. 



species of the genus, which extend through pretty well the 

 entire Australian region. The term " flying " as applied to these 

 and the other " flying " genera is of course an exaggeration. The 

 animals cannot fly upwards ; they can only descend in a skim- 

 ming fashion, the folds of skin breaking their fall. P. Ireviceps is 

 perhaps the best - known species. The body is 8, the tail 9 

 inches long. 



Petauroides seems to be chiefly distinguished from Petaurus 

 by the fact that, as in its ally Dactylopsila, the tail is partly 

 naked terminally. In Petaurus and Gymnobelideus the tail is 

 bushy to the very end, including its extreme tip below. 



A third genus of Flying Phalangers is the minute Acrobates, 

 which has a distichous tail like that of Distaechurus. It is not 

 more than 6 inches in length including the tail. As to these 

 Flying Phalangers it is exceedingly instructive to observe that 

 the same method of " flight " has been apparently evolved three 

 times ; for . the three genera are each of them specially related 

 to a separate type of non-flying Phalanger. The same observa- 

 tion can be made about the Flying Squirrels, Anomalurus and 

 Sciuropterus. The dental formula is I f C ^ Pm f M f. The 

 ears are thinly clad with hair. There are four teats. 



Sub-Fam. 2. Phascolarctinae. The Koala, or Native Bear, 

 Phascolarctos cinereus, is the only representative of its sub-family. 

 It is, like the Wombat, aberrant in the lack of an obvious tail. 

 The absence of this appendage is curious in an arboreal creature 

 whose near allies have a long and prehensile one. The structure 

 of the Koala .was investigated by the late Mr. W. A. Forbes. 1 

 There are some unexpected points of likeness to the Wombat : 

 thus they agree in the absence of the tail, in the structure of the 

 stomach, and in the great subdivision of the lobes of the liver. 

 The brain, however, is smooth, and the caecum is exceedingly large 

 and complicated in structure, that of the Wombat being short. 

 That both animals have cheek-pouches is perhaps due to similar 

 habits of temporarily storing masses of food. This animal has 

 only eleven pairs of ribs. The tail has only seven or eight verte- 

 bra, and these have no chevron-bones. 



A peculiarity of the skull is seen in the great size of the 

 alisphenoid bulla, which is comparable in size and appearance with 

 that of the Pig. As in the Kangaroos, the atlas is incomplete below. 

 1 "On some Points in the Anatomy of the Koala," Proc. Zool. Soc. 1881, p. 180. 



