TEETH OF DIPHYODONTS. 



289 



and prey upon the smaller quadrupeds and birds ; but they have 

 a more omnivorous diet, feeding on reptiles and insects, and 

 even fruits. One large species (Did. cancrivora) prowls about 

 the sea-shore, and lives, as its name implies, on crabs and other 

 crustaceous animals. Another species, the Yapock, frequents 

 the fresh water, and preys almost exclusively on fish : it has the 

 habits of the Otter, but the dentition does not differ from that 

 of ordinary Opossums. 



In the genus Tarsipes the molars soon begin to fall ; the 

 small canines are also deciduous ; the two procumbent incisors of 

 the lower jaw remain the longest. The inferior incisors are 

 opposed to six minute incisors above, which are succeeded by 

 a small canine and some small molars ; but these are reduced 

 perhaps old, individuals, to a single tooth on each 



n some 



side. 



The Phalangers, being provided with hinder hands and pre- 

 hensile tails, are strictly arboreal animals, and have a close 

 external resemblance to the Opossums. They differ chiefly in 

 their dentition, and in accordance therewith their diet is more 

 decidedly of a vegetable kind. The interspace between the 

 functionally developed incisors and molars in both jaws always 

 contains teeth of small size and little functional importance, and 

 variable not only in their proportions but their number. The 

 constant teeth are the -i^i true molars, and the i^s. incisors. 



4 -t 1 - 1 



The canines, c, fig. 228, are constant in regard to their presence, 

 but variable in size ; they are always very small in the lower jaw : 

 the functional premolars, p 3, are always in contact with the 



298 



229 



Dentition of Piiaiangista vulpiua. 



Dentition of Cook's Phalanger. 



molars and their crowns reach to the same grinding level ; some- 

 times the second premolar is similarly developed in the upper 

 jaw, as in the Phal Cookii, p 2, fig. 229, but it is commonly 

 absent; the first premolar, p i, is a very minute tooth, shaped 



VOL. III. U 



