LIFE HABITS AND DENTITION 



71 



marked canines, the triangular transversely elongated upper 

 molars and the typical tuberculo-sectorial lower molars indi- 

 cate its primitive character. The characters of the molars re- 

 call at once the appearance of Jurassic Trituberculates. The 

 sharp needle-pointed cusps and the presence of pronounced 

 styles upon the upper molars (Fig. 18) proclaim its insectiv- 

 orous diet. Nevertheless there are certain features which sug- 

 gest that even in this animal some specialization occurs. The 

 incisors on each side of each jaw are one less in number than 

 in the American Opossums which in this respect are still more 

 primitive. Again the third lower premolar is smaller than the 

 second indicating that the former tooth is undergoing reduc- 



Fig. 18. — Lateral aspect of skull of Marsupial Mouse (Phascoiogale flavipes, 9.211-2). 

 Note the typical needle-like insectivorous cusps and the forceps-grip between the pro- 

 cumbent lower incisors and the median upper incisors. Very plainly shown are the 

 two-rooted condition of the upper premolars and the deep groove analogous to sub- 

 division on the upper canine root (see p. 3). 



tion. In the main however Phascoiogale may be said fairly to 

 represent a very primitive type of Marsupial. 



Reference to Fig. 18 shows that all the lower incisors are 

 procumbent and form a forceps-like occlusion with the simi- 

 larly procumbent upper median incisors, a trait characteristic 

 of the insectivorous dentition. The upper median incisors have 

 their tips approximated though their bases are set widely 

 apart. 



Regarding the molars it should be remembered that the pro- 

 tocone of the upper tooth fits into the talonid of the correspond- 



