LIFE HABITS AND DENTITION 91 



I T' C ^' P T' M T- tota124 - 

 I U 1 4 



The gnawing character is seen in the scalpriform incisors in 

 which the enamel lies mainly upon the labial face and in the 

 double triangular appearance of the molars which like the 

 incisors, growing throughout life, have permanently open 

 roots. 



Nothing need be said concerning the single premolar since 

 it resembles half a molar. The molar bodies are curved, the 

 concavity of the upper teeth directed laterally and that of the 

 lowers facing toward the tongue. In this way grinding 

 pressure is not transmitted to the growing root but is sup- 

 ported upon the side of an arch. The crowns are worn obliquely 

 so that the sharp edge is lateral in the upper teeth and mesial 

 in the lower. The connected bases of the maxillary molars are 

 lateral; those of the mandibular series mesial. The upper 

 molars dimmish in size from the second backward; in the man- 

 dible the first three molars are subequal. In both jaws the 

 fourth molar is the smallest. 



A specimen with worn teeth like the one figured does not 

 greatly assist in the identification of the relationships of Phas- 

 colomys. For this a very young example is necessary. It then 

 appears that Phascolomys is very like Trichosurus in the pos- 

 session of pointed incisors and unworn molar crowns. In both 

 there occurs the same arrangement of bunodont cusps, ridges, 

 and ledges. Probably, therefore, Phascolomys had a phalan- 

 gerine ancestor and its burrowing habit is secondary being 

 readopted after a previous arboreal existence. 



The peculiar condyle and coronoid process and the remark- 

 able glenoid fossa should be noted. 



To complete fully an account of the Marsupials, some refer- 

 ence should be made to the aberrant forms Tarsipes, Myrmeco- 

 bius, and Notoryctes. 



Tarsipes is a long snouted phalanger which, having taken to 

 a diet of honey, exhibits a degenerate dentition. Myrmecobius, 

 the Banded Anteater, is an aberrant dasyure which possesses 



