BATS. 429 



constant, but always much less than the second premolar, and with 

 a simple obtuse crown. The second premolar is the largest ; the 

 succeeding teeth diminish in size to the last true molar : the crown of 

 each of these teeth is impressed by a longitudinal excavation, the 

 outer border of which is produced into a long conical cusp, which 

 in the second lower premolar resembles the crown of the canine, 

 especially in certain African Roussettes, as Pt. Whitei, Bennett : this 

 pointed lobe gradually subsides in the following teeth ; it is a little 

 higher than the inner boundary of the triturating depressed surface 

 in the penultimate molars, is almost obsolete in the small posterior 

 molar above, and quite lost in the still smaller one below. In Pt. 

 Whitei and Pt. macrocephalus the last small molar would seem to be 

 wanting in both jaws, according to Messrs. Ogilby and Bennett. (1) 



166. Structure and Succession. — In the normal or Insectivorous 

 Bats the teeth so closely resemble those of the small terrestrial 

 Insectivores in composition and structure, as to render a particular 

 description of them almost superfluous in the present work. 



When the fangs of the long and slender incisors and canines 

 are completed, the pulp-cavity contracts as it approaches the apex 

 of the fang to a linear fissure, and is finally closed by the external 

 cement. The calcigerous tubes descend almost vertically from the 

 closed end to the lowest part of the dentine, in a direction diametri- 

 cally opposite to that of the tubes which rise from the upper end of 

 the pulp-cavity to the summit of the crown. Through a great extent 

 of the middle part of the tooth the tubuli, forming a slight bend as 

 they leave the pulp-cavity, pass transversely to the outer surface. 

 In the crowm the tubuli gradually bend upwards until they acquire 

 a vertical direction at the middle ; at the opposite termination of the 

 fang, the tubuli gradually bend downwards from the transverse to 

 the vertical direction. The primary curve of the tubuli at the base 

 of the crown presents its concavity towards the fang; that of the 

 tubuli near the end of the fang is concave towards the crown : in 

 both, the concavity is towards the centre of the tooth. The short 

 trunks of the dentinal tubes are i^^oth of an inch thick : in the fang 

 they seem to be grouped in fasciculi. The dentinal cells are well defined 

 near the periphery of the crown ; they present a diameter of j^th 



(1) Zool. Trans, vol. ii, p. 34. 



