112 MAMMALIAN DENTITION 



The approximating tips of the upper median incisors and the 

 fenestration of the palate are marsupial-like but the student 

 should not mistake the animal for a Marsupial. The upper 

 canine is not prominent and the last upper premolar is bicuspid. 

 The upper molars, sub equal in size, show a trigon similar to 

 that of Tarsius, but in addition, there is an incipient hypo- 

 cone upon the internal cingulum in the first and the second 

 molars. In association with this the lower molars have lost 

 their paraconid and in all of them the metaconid lies upon a 

 plane somewhat distal to the protoconid, a situation primitive 

 in Primates. The hypoconulid on the last lower molar is large. 



Lemur catta, the Ring-tailed Lemur of Madagascar (Fig. 

 36), is a much larger animal than Microcebus but more retro- 

 gressive. It is a species which has recently (geologically speak- 

 ing) forsaken an arboreal existence for a life among the rocks 

 and stunted bushes. Its principal food is iioav the prickly pear 

 probably supplemented in the summer by bananas and figs. It 

 will not eat meat. It is perhaps because this change in diet 

 is of recent occurrence that the dentition shows insectivorous- 

 omnivorous features, although certainly more degenerate than 

 those of Microcebus. The dental formula is the same but the 

 teeth exhibit many specialized and retrogressive characters. 

 The upper incisors are vestigial, the lower first premolar in- 

 creasingly caniniform, the internal cingulum of the first and 

 second upper molars is now represented by two tubercles, one 

 in front (Carabelli's tubercle, see page 161), the other behind 

 the protocone. The last upper molar is the smallest, the first 

 and second are subequal. The hinder ends of the elongated 

 upper dental arch are much less divergent than in Microcebus 

 and the palate does not extend back to the third molar. In 

 the mandible the third molar is the smallest, lacks the hypo- 

 conulid and its axis tends to converge backwards toward that 

 of its fellow. 



The purely herbivorous Lemurs or Indrisinae all exhibit cres- 

 centic cusps on the molars, but like other Lemurs are a degen- 

 erate and specialized group. As a representative species we 



