TUPAIID^ 115 



The milk incisor is a long tooth, more or less compressed laterally, with a crown 

 resembling the anterior cusp of the first premolar. The second incisor is more pointed 

 than the canine, but preserving to a certain extent the same character of crown. 

 The first incisor is cylindrical, with its crown slightly outwardly divergent, as in 

 Crocidura. The canine and the two incisors are curved downwards, forwards, and 

 backwards. 



These deciduous teeth are succeeded by the permanent teeth in the following 

 order. The third premolar supplants its molar-like predecessor by having its large 

 and strong cutting edge wedged in between the outer fangs — a space which it com- 

 pletely fiUs. The second premolar has its long cusp wedged in in a similar way 

 between the long, slender, external fangs of its antecedent. The large cusps of the 

 foregoing teeth are more external to the fangs of the deciduous teeth than equally 

 between or internal to them. In the first premolar, however, the permanent cusp is 

 internal to the fangs of the deciduous teeth rather than between them. The perma- 

 nent canine is placed right in front of the tooth it supplants, whilst this arrangement 

 is reversed in the case of the first and second incisors. 



The third permanent premolar presents two prominent cusps, one corresponding 

 to the median cusps of the mofars, and the other to the internal cusp of these teeth. 

 The cingulum is continuous along the outer surface of the base of the crown, and is 

 prolonged into a cusp at its anterior and posterior extremities. The large cusp 

 is conical and twice as large as any of the corresponding cusps of the molars : it is 

 convex on its internal and external surfaces, but hollowed out or deeply concave on 

 its postero-external aspect. The second premolar has not the cingulum continuous 

 externally, for it occurs only along the posterior half of the external surface, where 

 it developes a cusp nearly as large as in the preceding tooth. The cingulum is 

 continuous internally from the posterior to the anterior margin, and in the latter 

 situation it terminates in a small prominence. The central conical cusp which 

 forms the bulk of the tooth is nearly as large, but slightly more pointed than in 

 the previous tooth, and viewed internally is a little concave from above downwards, 

 while it is pronouncedly convex from before backwards. This tooth and the 

 former have three fangs, as in the deciduous teeth. The first premolar has a 

 conical cusp resembling those of the third and second premolars ; but there is no 

 trace of a cingulum, and it wants the postero-external concavity or groove : there 

 are very obscure prominences on the anterior and posterior margins corresponding 

 to the anterior and posterior cusps of the third molar : two fangs correspond to 

 these prominences. The internal aspect of the tooth is markedly convex, and the 

 internal surface, especially near the tip, is flattened from above downwards, and 

 slightly concave ; however, it is strongly convex from before backwards. This is the 

 smallest of all the teeth, and has the least vertical extension of the premolar and 

 incisor teeth. 



The canine has a straight posterior margin, and the anterior margin is parallel 

 to it throughout the upper half of its extent, but below that it is bevelled off from 

 before backwards to the posterior margin. It is slightly compressed from side to 



