114 



MAMMALIAN DENTITION 



with the type of diet, thus recalling the condition in the marsu- 

 pial Koala. The paraconid has disappeared from each of the 

 lower molars and the third presents only a small hypoconulid 

 but although very specialized there are traces left of a primi- 

 tive feature in the occurrence on the first and second upper 

 molars of the three outer styles which are utilized as in the 

 Koala for the conversion of paracolic and metacone into cres- 

 centic cusps. Indeed the molars of the purely herbivorous 



Fig. 37. — Dentition of Woolly Demur (Dichanotus laniger, Gmelin; 9.811-2). This 

 purely herbivorous Primate presents crescent-cusped molars. The upper incisors have 

 been lost in the specimen but their sockets are plainly seen and indicate the vestigial 

 nature of the teeth. Compare this figure with Fig. 24. 



lemur and the correspondingly herbivorous Koala present a 

 striking instance of convergent evolution. The general pat- 

 tern of the molars of Tupaia affords an indication of the type 

 from which the molars of Lichanotus originated. 



The most aberrant of the Indrisinae is the rodent-like Aye- 



*The dental formula of the Indrisinse is in dispute. Some give it thus: 



M 



total 30. 



Such an interpretation would indicate that the lower incrsiform tooth in Dauben- 

 tonia is really an incisor. 



