424 BATS. 



retained. He suspects that the Shrews have but one dentition : the 

 minute size and rudimental state of the transitory teeth, and their 

 disappearance before birth having caused them to escape the obser- 

 vation of the accomphshed continuator of Cuvier's " Le9ons d' Anato- 

 mic Comparee."(l) 



CHAPTER VIII. 



TEETH OF CHEIROPTERA. 



165. The dental system presents more constancy in this than in 

 the preceding Order, and the different kinds of teeth are more easily 

 and unequivocally determinable. 



The canines are always present in both jaws, of the normal form 

 and with slightly variable proportions. The molar series never 

 exceeds g^, and is divisible into premolars and true molars, the latter 

 presenting two types of grinding surface ; in one of these the crowns 

 are bristled with sharp points, as in the foregoing order, and this type 

 characterizes the great bulk of the Cheiroptera, which may be called 

 true Bats or volant Insectivores ; the molars of the second type have 

 flat crowns and characterize the large frugivorous Bats which consti- 

 tute the aberrant genus Pteropus, and conduct towards the Quadru- 

 manous Order. 



The incisors are the most variable teeth in the Cheiroptera; 



(1) See the posthumous edition of the Legons, torn, iv, p. 242, where M. Duvernoy adds 

 to the text : " J'ai lieu de penser que tous les Insectivores n'ont pas cette succession de dents. 

 Je I'ai constatee, a la verite, dans les Tenrecs qui perdent leurs dents fort tard, au contraire 

 de certains Rongeurs les ayant trouvees encore, en partie, chez un individu dont la taille 

 etait a peu pres celle de I'adulte. M. Laurillard I'a vue dans les Chauve-souris et les Herissons. 

 Mais dans les Musaraignes je suis porte a croire qu'il n'y a qu'une seule dentition." M. de 

 Blainville goes further, and denies the existence of a deciduous series of teeth in the Mole, 

 Hedgehog and Tenrec, (Osteographie des Insectivores, p. 63) ; as, indeed, he likewise did with 

 regard to the Bats, (Compte Rendu de I'Academie des Sciences, Sept. 1837, p. 420.) M. 

 Rousseau, in his excellent " Memoire sur la Chauve-souris commune," read to the Academy 

 of Sciences, March 19th, 1838, described the deciduous dentition of that Cheiropter with all 

 the requisite detail, and its existence is admitted by M. de Blainville in the " Osteographie des 

 Che'iropteres," published in June 1840. Similar proofs will be found, if nature be rightly 

 consulted, that the other Insectivora, also, form no exception to the rule. 



