Teeth in the Centetida?. 541 



occupies the entire breaJtli of tiic tooth. Lastly, a sli^^lifc 

 internal tubercle (" nietaconid ") also occurs. P. 2 differs 

 from P.d. 2 to a not inconsiderable extent ; the latter is elon- 

 gated, with a strongly develu|)ed anterior basal cusp, and 

 possesses an accessory cusp situated on the same level as the 

 " nietaconid " (but on the outer side of the main cusp), than 

 which it is sometimes rather more, sometimes rather less 

 strongly develupcd. The dimensions of P.d are variable, 

 Init this tooth is always smaller than P. 2; an anterior basal 

 cusp is indicated now and then, and sometimes an accessory 

 cusp in addition, behind and below the main cusp. Tiie 

 latter is on P.d. '6 sometimes of really considerable bulk, and 

 almost as strongly developed as on P.d. 2 ; on other specimens 

 no trace of it is to be seen. Occasionally, even on perfectly 

 fresh teeth, there is no vestige whatever of an anterior basal 

 cusp in the case of I'.d. '6 {cf. Leclie, he. cit. p. 519). 



These variations, as well as the similar ones in teeth 

 belonging to the upper jaw, suggest the idea that we have to 

 deal with more than one species. I may add that I assume 

 the existence of two species of Centetes for reasons other than 

 those advanced by Bardeleben, but I cannot here enter further 

 into this question, — All three milk-incisors show, as do their 

 successors, a posterior basal cusp. 



MicrogaJe. — P. 1 alone is molariform, and consequently 

 provided with an internal cusp (" nietaconid "), which is 

 wanting in the case of the two anterior premolars, but, in 

 the majority of species at any rate, is still present on P.d. 2, 

 P. 2 is somewhat larger than P. 3, but in other respects the 

 two teeth are alike : they are secodont, with a median main 

 cusp, an anterior and posterior basal cusp, and two roots. It 

 is only in the case of M. jmsilla that P. 3 has a single root 

 and is similar in build to the C, /. e. not elongate, but 

 shortened and inclined obliquely forwards ; the anterior cusp 

 is indicated only by a slight indentation in the margin, which 

 occurs high up near the main cusp. As regards the form of 

 P. 3, M. longicaudata forms a transition between M. pusilla 

 and the remaining species (J/. Dohsoni^ Thomasi, Cowani, 

 gracilis J and longirostris). 



Oryzoryctes. — In the build of the lower premolars this 

 genus agrees essentially with Microgale. In comparison with 

 P. 2, P. 3 is somewhat simplified, owing to the fact that the 

 basal cusp is absent or scarcely indicated. A characteristic 

 feature in the dentition of Oryzoryctes is the unusually large 

 and powerful C in both upper and lower jaws ; in the case of 



