132 CLASS MAMMALIA. 



characters sufficiently marked, to be entitled to the rank of 

 generic distinctions. 



We shall not trouble our readers with any details con- 

 cerning the species of the megadermata, which, with their 

 characters, will be found in the table. 



The genus or sub-genus nycteris, was established by 

 M. Desmanets and M. Geoffroy St. Hilaire, and afterwards 

 admitted by Illiger. 



These bats have teeth similar in number and in form to 

 those of the vespertilio. 



A single, but a very essential difference distinguishes 

 these teeth from the teeth of the vespertilio : this is the 

 disposition of the incisors. 



They are smaller, especially the lower ones, which are 

 hardly to be distinguished by a single view ; above, they 

 are not (as in the Lemurs) separated in pairs, but, on the 

 contrary, they are arranged on a continuous line, commen- 

 surate with the intermaxillary bone. 



This bone, subservient in the bats, to the variations 

 which distinguish the organ of smelling, possesses a 

 movement peculiar to itself. It is raised or lowered (oscil- 

 lating as if on an axis) by the upper lip, which is of a thick- 

 ness and consistence adequate to the operation of directing 

 it. Diminished as it is at its points of articulation, it 

 cannot participate in the fixedness of the other bony 

 parts. 



It is, doubtless, in consequence of the domination of the 

 surrounding organs, that the intermaxillary bone is so re- 

 markably small. It does not project beyond the canines, 

 whence it happens that the upper jaw is shorter than 

 the lower, and appears almost truncated. Another result 

 of this is, that the incisors of the two jaws do not corres- 

 pond, and resting edgeways, their summits are never worn, 

 which remain v/ith two lobes above, and three indentations 

 below. 



