THE TEETH OF MARSUPIALIA. 



427 



the'r cutting edges, are calculated to effect the same objects 

 as those attained by the incisors of a rodent ; a still closer 

 resemblance would be brought about by the dwindling 

 (which occurs in other genera) and final disappearance of 

 the second and third upper incisors, and a compensating 

 extra development of the first pair. 



The canines are not large ; yet they are not so small as 



to be termed rudimentary ; in the lower jaw they are 

 absent. 



Only one premolar exists in the adult, and this is a very 

 peculiar tooth ; its crown is very long from back to front 

 (at least twice as long as any of the molars, and in some 

 species as long as three of the molars), and consists of a 

 finely furrowed blade with a sharp edge ; the blades of the 

 upper and lower teeth slide over one another. Behind this 

 there are four true molars, with square quadricuspid crowns, 

 which become much worn down by use. 



The third premolar, the tooth to which attention has 



( J ) Upper and lower teeth of Hypsiprymnus (Bettongia) (Graii ?). The 

 dentition represented is that of the adult animal, the permanent premolar 

 (pm 3) being already in place. 



