404 A MANUAL OF DENTAL ANATOMY. 



correspond to it, but to be the first premolar (cf. page 283). 

 The premolars are compressed from side to side, and are 

 very sharp : the molars are armed with long sharp cusps, 

 which are worn down in old animals. 



The upper molars in many lemurs are armed with four 

 cusps, connected by an " oblique ridge " like those of man 

 and the anthropoid apes. 



There is a very aberrant lemur, the Aye-aye (Cheiromys), 

 which in its dentition imitates the rodents. 



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In both upper and lower jaws the incisors form a single 

 pair of large curved teeth, growing from persistent pulps, 

 and wearing obliquely so as to constantly preserve a sharp 

 cutting edge. The enamel is very much less thick, if not 

 altogether absent, upon the backs of these incisors. 



After a considerable interval, which is devoid of teeth, 

 there follow four upper and three lower teeth, which are 

 not of persistent growth, but have definite roots, .and re- 

 semble the molars of many omnivorous rodents. 



Being a somewhat rare and strictly nocturnal animal, 

 little is known of its food ; some have believed that it made 

 use of its rodent incisors to cut away portions of wood in 

 order to get at the grubs contained in it, drawing them out 

 of their hiding place by means of its curiously elongated 

 finger, whilst others believe that it gnaws the sugar cane. 

 But whatever the nature of its food may be, it is certain 

 that its scalpriform incisors arc put to hard work, and so 

 kept worn down, for in a specimen kept for a time in the 

 Zoological Gardens, which was supplied with soft food, 

 the incisor teeth grew to an excessive length, and ultimately 

 caused the animal's death by the points of its lower incisors 

 perforating the palate. The accompanying figure represents 

 the muzzle of this specimen, and although the upper teeth 



