406 



A MANUAL OF DENTAL ANATOMY. 



are to be seen at once, but the large size of the permanent 

 incisors causes the speedy loss of the milk incisors. 



No known rodent has so many milk teeth, nor indeed any 



FIG. 178 ('). 



milk incisors at all ; the aye-aye thus affords an excellent 

 example of a milk dentition preserving characters which arc 

 lost in the extremely modified adult dentition. 



The special interest which attaches to the dentition of 

 Cheiromys has been already alluded to (see page 271) ; to 

 briefly recapitulate, it is this : in Madagascar, an isolated 

 area separated by a wide tract of deep sea from other areas, 

 true rodents are almost absent, but lemurs abundant. But 



i 1 ) Upper and lower jaws of Cheiromys. A. Milk dentition, witli the 

 permanent incisors just emerging, i, I. Upper and lower permanent in- 

 cisors. i2, 12. Upper and lower milk incisors, c. Milk canines, dl, 

 d 2, da, d b. Upper and lower milk molars. (Twice natural size.) B. 

 Reduced figure of permanent teeth (after Peters). 



