1866.] MR. ST. GEORGE MIVART ON MICRORHYNCHUS. 155 



Externally there is a mere rudiment of a cingulum ; but internally 

 it is exceedingly developed both in front and behind, but especially 

 the latter, where it constitutes a distinct, though small, basilar pro- 

 cess, or talon, almost as marked, indeed, as in the two premolars 

 behind it. 



Fig. 2. 



Inside of left upper canine and premolars. Scale, twice nat. size. 



From the middle of the internal surface a strong vertical promi- 

 nence is developed, which extends from the cingulum down to the 

 apex of the tooth ; in front of this is the small anterior process, 

 which projects forwards from the middle of the anterior margin of 

 the tooth, greatly increasing its antero-posterior diameter, and pre- 

 senting a character absolutely peculiar to this species of the Lemu- 

 roidea. 



In Hapalemur it is rather longer relatively, and considerably ex- 

 ceeds the most anterior premolar in size. In Indris the canine is 

 even slightly more prolonged as compared to the premolar than in 

 Hapalemur, and decidedly so in Propithecus. 



In M. laniger the canine and most anterior premolar are more 

 equal than in any other Lemuroid*, or indeed than in any other 

 Primate except Man. 



This canine is exceedingly like the first premolar of Lemur. 



The anterior upper premolar is unicuspidate, and resembles the 

 canine, except that it is less vertically extended ; while the process 

 from its anterior margin is much larger. The cingulum also is 

 rather more marked externally. This tooth differs from the corre- 

 sponding one of every other species of the suborder ; but most re- 

 sembles the homologous one of Indris, which, however, has the an- 

 terior process rudimentary. It slightly resembles the second pre- 

 molar of Lemur and Hapalemur, but is more antero-posteriorly and 

 less transversely extended. 



The posterior upper premolar is like the preceding, except that 

 it is smaller in all dimensions except width from within outwards, 

 and that the posterior basilar process is shorter, while the internal 

 cingulum is much more marked. This tooth has the same resem- 

 blances and differences to its homologue in Indris as that last de- 

 scribed has to its representative in that genus. It resembles the 

 second premolar of Lemur and Hapalemur more than the anterior 

 premolar does ; and it much more resembles the second than it does 

 the third premolar of any Lemuroid. 



The first upper molar is very different from the premolars, and is 

 the largest grinding-tooth in the upper jaw. There is more differ- 

 ence in size between it and the posterior premolar than there is be- 

 tween any other contiguous grind ing-teeth of the upper jaw, as 

 also is the case in Indris. 



* I. e. any uther species of the suborder Lemuroidea. 



