15G 



MR. ST. GEORGE MIVART ON MICRORHYNCHUS. [Mar. 13, 



It may be said to have eight cusps, as, beside the four large nor- 

 mal prominences, there are three small ones developed from the very 

 strongly marked external eingulum, also one very small one between 

 the two anterior large cusps. The three small external cusps are 

 placed one in front of, one between, and one behind tbe external 

 pair of the four large normal cusps. These last-mentioned cusps are 

 not connected together by transverse ridges, as in Indris ; but a 

 slightly marked ridge runs from the postero-external to tbe antero- 

 intemal one. The two external normal cusps are longer and larger 

 than are the two inner ones. There is no internal eingulum. 



This tooth differs widely from its homologue in all the other Le- 

 muroids except Indris, with which it entirely corresponds, except as 

 regards the oblique ridge. 



Fig. 3. 



Basis cranii. Scale, nat. size. 



The second upper molar is in all respects like the first one, except 

 only that it is slightly smaller in all dimensions except vertical 

 extent, that the minute cusp between the anterior large ones has dis- 

 appeared, and that the oblique ridge from the postero-external to 

 the antero-internal cusp is rather more marked. 



This tooth has the same resemblance to its representative in Indris, 

 and exhibits the same differences from the corresponding molar of 

 all other genera, as in the case of the first upper molar. 



The third molar has two anterior cusps — one external, and the 

 other internal — like the other true upper molars. Behind these the 

 margin of the tooth developes three subequal and minute cusps, 

 which are arranged in a semicircle, and appear to be developed from 

 the eingulum, which is elsewhere rudimentary. No other Lemuroid, 

 except Indris, has a third upper molar so formed. 



The two inferior incisors have the narrow elongated form so com- 



