CHEIROPTERA. 



547 



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

 as well, are unguiculate, or furnished with claws ; 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 different 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 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 

 crevices amongst the rocks, where they suspend themselves by 

 means of the short thumbs, which are provided with curved 

 claws. In their flight, though they can fly in the genuine and 

 proper sense of the term, and can turn with great ease, they 



Fig. 209. Skeleton of Fox-bat (Pteropus)zSter Owen. 



are by no means as rapid and as active as are the true birds. 

 The tail is sometimes short, sometimes moderately long, and 

 is usually included in a continuation of the leathery patagium, 



