| OCR Text |
Show 156 MR. ST. GEORGE MIVART ON MICRORHYNCHUS. [Mar. 13, It may be said to have eight cusps, as, beside the four large normal prominences, there are three small ones developed from the very strongly marked external eingulum, also one very small one between the two anteiior large cusps. The three small external cusps are placed one in front of, one between, and one behind the 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 the antero-internal one. The two external normal cusps are longer and larger than are the two inner ones. There is no internal cingulum. 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 disappeared, 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 cingulum, 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- |
