430 BATS. 



of an inch. The fibrous structure of the enamel is very conspicuous ; 

 at the side of the crown the fibres make a short curve on leaving the 

 dentine concave towards the grinding surface, and then make a 

 longer bend in the opposite direction. This structure may be clearly 

 seen in the canines of the Rhinolophus ferrum-equinum. 



The microscopic structure of the teeth of the frugivorous 

 Bats appears worthy of a fuller notice. I have examined it more 

 particularly in the canine and molar teeth of the Great Roussette 

 {Pteropus edulis).{l) The crown of the canine has an entire in- 

 vestment of enamel; the fang is covered by clear cement, thickest 

 at its extremity but without radiated cells. The tubuli of the 

 dentine are nj;^th of an inch in diameter at their origins, and are 

 there about the same distance apart ; they slightly diverge from 

 one another as they proceed from the summit of the pulp-cavity, 

 in the usual radiated direction ; the primary curves of the tubes which 

 proceed to the sides of the crown being gently concave towards the 

 summit in the greater part of their course, with both extremities 

 slightly bent in the opposite directions ; at the beginning of the fang 

 they pass outwards, and gradually acquire a curve convex towards 

 the crown ; lower down they are more irregularly bent, and near the 

 apex of the fang, again present the curve concave towards the crown. 

 The tubuli in the crown rarely dichotomize, and accordingly by their 

 divergence leave wider interspaces of the clear basal substance, which 

 receive the small lateral branches that are sent off from both sides 

 of the tube, subalternately, throughout its course. The tubes dimi- 

 nish in size, like arteries after division, and near the enamel are 

 resolved into fine ramuli, which anastomose or dilate into minute opake 

 cells. The secondary undulations are extremely faint in the crown ; 

 they become stronger as the tubes descend into the fang, crossing 

 each other and producing, with the side-branches, a rich arborescent, 

 and interlaced appearance, which becomes more complex as the tubes 

 approach their termination near the cement, into which they push many 

 terminal ramuli : in this clear substance they dilate into minute opake 

 cells ; but, as has been already observed, there are no normal radiated 

 Purkingian cells in the cement of the canine tooth. 



The tubuli of the dentine of the crown of the molar tooth differ 



(1) PI. 113, 113A. 



