130 COMPARATIVE DENTAL ANATOMY 



bristle with cusps. The teeth of the Hedgehog 

 are fairly typical of the order. The Shrews have 

 the formula, — 



. 2-2 1-1 3-3 3-3 OA 



*' 2=2 C ' 0=0 P ' m - 3=3 m - 3=3 = 31 



The incisors are remarkable in the Shrews. The 

 centrals above are very large, are placed verti- 

 cally, and are a little recurved or hooked. A cusp 

 is developed behind the edge which makes a notch 

 across the face, into which the tips of the lower 

 incisors fit. The lower central is very large, lies 

 horizontally, and has the point bent upward, with 

 small tubercles raised to fit into the notch of the 

 upper central. These teeth make very effective 

 forceps for extracting insects from crevices in 

 rocks or the bark of trees. The lower central 

 extends backward and outward by a flange which 

 overlaps the alveolar border of the jaw; it is one- 

 third of the whole length of the jaw. The crush- 

 ing teeth are rather small, but have the character- 

 istic sharp cusps. The Moles have the formula, — 



. 3-3 1-1 4-4 3-3 AA 



>• 3=3 C - 1=1 P ' m ' 4=4 m ' 3=3 = U ' 



The first incisors above are small, but the third 

 is large like the canines, and has two roots. The 

 first two premolars are very small, then comes a 

 very large one, — all being armed with pointed 

 cusps. 



The order Cheiroptera contains only the fly- 



