CHEIROPTERA. 



51 



but which have no opposable thumb to their fore-feet. Their food is animal, 

 and the more exclusively so, as their grinders are the more trenchant. Such 

 as have them who'ly or partly tuberculous, take more or less vegetable aliment, 

 and those in which they are bristled with points live principally on insects. 

 The articulation of their lower jaw, being transversely directed and hinge-like, 

 allows of no lateral motion; it can only open and shut. 



Although the convolutions of the brain are still tolerably well marked, it has 

 no third lobe, nor does it cover the cerebellum any more than in the following 

 families ; the orbit is not separated from the temporal fossa in the skeleton ; 

 the cranium is narrowed and the zygomatic arches widened and raised, in 

 order to give more strength and volume to the muscles of their jaws. Their 

 predominant sense is that of smell, and their pituitary membrane is generally 

 spread over numerous bony laminae. The fore-arm has still the power of re- 

 volving in nearly all of them, although with less facih'ty than in the Quadru- 

 mana, and they never have the thumb of the anterior extremities opposed to 

 the other toes. On account of the substantial nature of the ah'ment, and to 

 avoid the putrefaction it would undergo by remaining too long in an elongated 

 canal, their intestines are less voluminous, as represented below. 



There is a great variety in their forms and in the details of their organi- 

 sation, which produces analogous differences in their habits, to such an 

 extent as makes it impossible to arrange their genera on one line, and compels 

 us to form them into several families, which are variously connected by mul- 

 tiplied relations. 



FAMILY I. 



CHEIROPTERA. 



This family still retains some affinity with the Quad- 

 rumana. Their distinguishing character consists in 

 a fold of the skin, which, commencing at the sides 

 of the neck, extends between their four feet and toes, 

 supports them in the air, and even enables such of 

 them to fly as have their hands sufficiently developed 

 for that purpose. This disposition required strong 

 LVj MnPflf c ^ av ^ c ^ es an d large scapulae to give the necessary 



V V Mffliiiil solidity to the shoulder, but it was incompatible with 



the rotation of the fore-arm, which would have 

 diminished the force of the stroke requisite for flight. 

 They have all four great canini, but the number of their incisors varies. 

 They have long been divided into two genera, founded upon the extent of their 

 organs of flight. The first of these, however, requires several subdivisions. 



VESPERTILIO, Linnceus. 



The arms, fore-arms and fingers of the Bats are excessively lengthened, form- 

 ing, with the membrane that occupies their intervals, true wings, possessing 



K -2 



