CHEIROPTERA. 623 



CHAPTER LXXXI. 



CHEIROPTERA. 



ORDER XI. CHEIROPTERA.* This order is undoubtedly " the 

 most distinctly circumscribed and natural group " in the whole 

 class of the Mammalia. In many respects, however, it would 

 be advantageous to regard the Cheiroptera as a sub-order of 

 the next order (namely, the Insectivord) specially modified to 

 lead an aerial life ; just as the Pinnigrada are regarded as a 

 mere section of the Carnivora specially modified to suit an 

 aquatic life. 



The Cheiroptera are essentially characterised by the fact that 

 the anterior limbs are longer than the posterior, the digits of 

 the fore-limb, with the exception of the pollex, being enor- 

 .mously elongated (fig. 266). These elongated fingers are 

 united by an expanded membrane or "patagmm," which is 

 also extended between the fore and hind limbs and the sides 

 of the body, and in many cases passes also between the hind- 

 limbs and the tail. The patagium thus formed is naked, 

 or nearly so, on both sides, and it serves for flight. Of the 

 fingers of the hand, the pollex, and sometimes the next finger 

 as well, is unguiculate, or furnished with a claw ; but the 

 other digits are destitute of nails. In the hind limbs all the 

 toes are unguiculate, and the hallux is not in any respect dif- 

 ferent from the other digits. Well-developed clavicles are 

 always present, and the radius has no power of rotation upon 

 the ulna. The mammary glands are two in number, and are 

 placed upon the chest. There are teeth of three kinds, and 

 the canines are always well developed. The molars are tuber- 

 culate or grooved in the frugivorous forms, and cuspidate in 

 the insectivorous species. The ulna is sometimes quite rudi- 

 mentary. The bones are not pneumatic. The testes are ab- 

 dominal except during the breeding season. The stomach is 

 complex and the intestine long in the fruit-eating Bats ; but 

 the reverse of this obtains amongst the insectivorous forms. 

 The Cheiroptera are cosmopolitan in their distribution, and the 

 oldest known species is from the Eocene Rocks. 



The Bats are all crepuscular and nocturnal in their habits, 

 and are sometimes carnivorous, sometimes frugivorous. The 

 eyes are small, but the ears are very large, and their sense of 

 touch is most acute. During the day they retire to caves or 



* The Cheiroptera were placed by Linnaeus in his order Primates, which 

 contained also the Lemurs, the Apes, and Man. 



