100 CLASS MAMMALIA. 



most precise and scientific notions concerning these ani- 

 mals, is unquestionably M. Geoffroy St. Hilaire. The cha- 

 racter of the incisive teeth, and its modifications, had ori- 

 ginated the modes of division to which we have alluded. 

 This acute observer soon perceived that one circumstance 

 connected with these teeth, the fact of their being most fre- 

 quently indented or crenulated, had proved a source of error 

 even to the most expert zoologists. Pallas, for instance, 

 reckoned eight incisors in the lower jaw of the vesp. pictus, 

 instead of six, the real number ; and Daubenton had not re- 

 marked as many in the upper jaw of the ferrum equinum. 



Another fact respecting these was calculated to mislead 

 observers. This is, that being smaller than their alveoli 

 or beds, they are easily detached from thence, and are 

 found wanting in some individuals. 



These teeth are also considerably dependant on the or- 

 gans in their vicinity. In other animals, there is usually 

 but one modification or condition for those organs, which 

 are situated near the incisive teeth. They are generally 

 contained within fixed limits, and do not interfere with the 

 development of the intermaxillary bone, which itself sup- 

 plies the incisors with a suitable basis and degree of soli- 

 dity. This arrangement being unaffected by any thing im- 

 mediate, the incisors grow in their proper beds, according 

 to the action exercised upon them by the constituent ele- 

 ments of the whole being. Accordingly, as they are in- 

 fluenced by causes, disseminated as it were through the en- 

 tire system of organization, they may be employed to indi- 

 cate these causes in a general way, and consequently will 

 form a most excellent generic character. 



But the contrary to all this takes place in the Cheiroptera. 

 Their organs of sense are complicated in consequence 

 of the tendency of the dermis to acquire such considerable 

 augmentation. 



The organ of smelling, among others, is very frequently 



