THE TEETH OF INSECTIVORA. 397 



Shrews lies in the form of their incisors. The first upper 

 incisor is always very large indeed : it looks vertically 

 downwards, is a little hooked, and has a notch, and a second 

 low cusp behind the principal long pointed cusp. The tip 

 of the lower incisor fits into this notch. The lower incisor 

 is also very large ; it lies nearly horizontally, though the 

 point is bent a little upwards. Along its upper edge there 

 are, in most species, three or four small cusps, while its 

 lower border is curiously prolonged outside the bone of the 

 jaw, so as to in some measure encase this latter. The lower 

 incisor is at least one-third as long as the whole alveolar 

 border. The incisor teeth of the Shrew would appear to 

 form a very efficient pair of pincers, with which to pick up 

 the minute creatures on which it feeds. Of the milk teeth 

 of Shrews little is known : they are said to be absorbed 

 before birth, but accurate observations upon them are much 

 needed, their very existence being doubtful. 



The dentition of the Mole (Talpa) has been the subject of 

 much controversy, the determination of its canines, <fec., 

 presenting such difficulty that no less than five different 

 dental formula) have been assigned to it, 



In the front of the upper jaw come three small teeth, the 

 first being somewhat the largest, which are well within the 

 limits of the intermaxillary bone, and are doubtless incisors. 

 But the next tooth, which is very big, also appears to be 

 implanted in the intermaxillary bone, the suture passing 

 across its socket close to the back of its posterior root. 

 According to its implantation it therefore would be an 

 incisor ( ! ) but it is very unlike an incisor ; and it is two- 



( l ) I confess I cannot follow Mr. Spence Bate when, in his valuable 

 paper on the milk teeth of the mole, he says, " This tooth is implanted 

 within the limits of the premaxillary bones, the suture separating them 

 from the maxillary, passing through the posterior portion of its alveolus : 

 thus demonstrating that this deciduous tooth is the true homologue of that 

 of the canine in the mammalian type." Surely it would go to prove the 

 contrary, if accepted as evidence at all upon this point. 



