CHEIROMYS. ORDER CHEIROPTERA. 181 



almost the whole length of the jaw ; whilst their points are sharp, 

 and resemble the end of a ploughshare. Between these and the 

 molars, there is a wide interval, as in the Rodents ; the molars, 

 however, are not formed in the manner of theirs, with transverse 

 ridges of enamel, but are simple in their structure. It is doubtful 

 whether the front teeth are to be regarded as incisors or canines; 

 it is not improbable that they really represent the latter, since in 

 several of the Lemuridaa we find the real incisors very small, 

 whilst the canines project forwards, and almost take their place. 

 The bony portion is completely surrounded by enamel ; which 

 is not the case in the Rodentia, in whose cutting- teeth the 

 enamel occupies the front edge only : and it is believed that the 

 teeth do not continue to grow from permanent pulps, as in that 

 order (ANIM. PHYSIOL. 177)- One of the points in which the 

 Aye- Aye strongly resembles the Rodentia, is the position of the 

 mammary glands ; which are situated near the groin, and not 

 on the chest, as in the Quadrumana generally. But in the 

 Tarsiers ( 162), two pairs of mammae are present, one on the 

 chest, the other in the groin ;* so that the Aye- Aye does not 

 depart so widely, in this respect, from the general type of the 

 Lemurs, as would be at first supposed. 



ORDER III. CHEIROPTERA. 



1 65. The animals of this Order, all of them commonly known 

 as Bats, are distinguished from all other Mammalia by the power 

 of flight; that is. they are able not only to sustain themselves in 

 the air, but also to move through it in any direction they may 

 desire (ANIM. PHYSIOL. 668, 669). This power they derive 

 from the peculiar conformation of the anterior member, the bones 

 of which are very much prolonged, especially those of the fingers; 

 and constitute a framework (like that of an umbrella), over 

 which is spread a thin membrane, continued from the skin of the 

 body, but not clothed with hair. The organs thus formed are 



* The same conformation sometimes presents itself in the Human female. 



