1867.] MR. ST. GEORGE MIVART ON INDRIS DIADEMA. 249 



the description before given of the dentition and skull of /. laniger, 

 except where the contrary is stated. 



Of the two incisors in each proemaxilla, the anterior one is very 

 considerably larger than the posterior one. 



The upper canine is not yet in place in the skull transmitted by 

 Dr. Peters ; but from the mounted specimens in the British Museum it 

 has already been determined to decidedly exceed the incisors in length. 



The vertical prominence on the internal surface of the tooth is 

 (unlike that of the canine of/, laniger, and more like that of /. brevi- 

 caudotus) very much nearer to the anterior margin of the tooth than 

 to its posterior edge. 



The anterior upper premolar is quite like that of /. laniyer, and 

 has the anterior process more developed than is the case in the cor- 

 responding tooth of /. brevicaudatus. 



Fig. 1. 



Inside of left dental series. Scale, nat. size. 



The posterior upper premolar differs from the anterior one just as 

 in /. laniger, and the internal cingulum is very marked indeed. It 

 also, of course, more resembles the second than it does the third 

 premolar of any Lemuroid*. 



The first upper molar, as in /. laniger, is the largest grinding- 

 tooth in the upper jaw. The difference in size, however, between it 

 and the posterior premolar is not quite so great as that between the 

 second and third upper molars. 



It may be said to have seven cusps, as, beside the four principal 

 ones, there are three developed from the external cingulum and 

 placed as in /. laniger. The posterior one of these three, however, 

 is (as in /. brevicaudatus) much smaller relatively than in the Woolly 

 Lemur, and much smaller than the two anterior ones ; also the small 

 cusp, which in /. laniger exists between the two large anterior ones, 

 is here wanting. 



In other respects this tooth agrees with its homologue in the 

 Woolly Lemur, and has a similar slightly marked ridge running 

 from the postero-external cusp to the antero-internal onef . 



The second upper molar quite resembles the corresponding tooth 



* Dr. Peters, in his very interesting memoir on the Aye-Aye (in the 'Ab- 

 handlungen der Konigl. Akad. der Wissenschaften zu Berlin,' 1805), in a note 

 (p. 87), observes that it is not always the homologues of the most anterior pre- 

 molars of one genus which are the first to disappear in another in which the 

 number is less. lie refers, as examples, to the I'hyllostomata and Ehhiolophi. 



t In the immature dentition of Indris diadema, which is represented by 

 DeBlainville in his ' Osteographie, Primates, Lemur' (pi. 11), the first upper 

 molar is represented with the posterior cusp of the external cingulum quite ru- 

 dimentary. There is also an indication of the oblique ridge extending between 

 the postero-external and the antero-internal principal cusps. 



