OF THE WOMBAT, KOALA, AND PHALANGERS. 



889 



PhasGolarctos and Pluiscolomys the gland patch alone could not 

 be employed as a test of affinity. 



The liver also possesses distinguishing chai-acters. In the 

 Phalangeridfe the caudate lobe is present, but the main lobes are 

 not complicated by secondarj'- sulci. In the Phascolarctidse, on 

 the other hand, there is no caudate lobe, and many secondary 

 sulci subdivide the main lobes. 



Phascolarctos predominates over Phascolomys in the size of 

 the cheek-pouches, the complexity of the gland patch, the sub- 

 division of the main hepatic lobes, and the length of the gall- 

 bladder. 



As regards the dentition, Waterhouse (17) pointed out long ago 



Text-figure 42. 



The hard palate in Fhascolomys mitclielli.* 



that "■ the approximation to the Rodent-like dentition which is 

 exhibited by the Wombat is perceptible in the Koala, in the 

 smaller development of the postei'ior incisors and canines of 

 the upper jaw, and the total absence of those premolars which, 

 in the typical Phalangers, intervene between the canine and 

 the five molars of the upper jaw, and the incisor and corre- 

 sponding teeth in the lower jaw." Bensley (1) has shown, 

 however, that the dental characters which would point to a 

 resemblance between Phascolarctos and Phascolomys are probably 

 due to convergent evolution, and Forbes (3) rightly considered 

 that the dental characters in Phascolomys are adaptive in 



* Compare with Plate V in my paper on the Koala (10). 



