34 MAMMALIA ORDER ILCHIROPTERA. 



well-developed collar-bones ; but the hind-quarters are feeble and weak. In 

 many bats the delicate sense of touch, by which they are enabled to avoid 

 coming into collision with objects when flying in the dark, appears to be 

 mainly situated in the wing-membranes and in the delicate skin of the fre- 

 quently large ears, the latter often having an inner earlet, or tragus. 

 In a large number of species there are, however, expansions of the skin in 

 the region of the nose ; these nose-leaves sometimes merely taking the form 

 of a triangular single or double plate standing up above the muzzle, whereas 

 in other cases they assume a marked appearance, covering a greater portion 

 of the face. These organs appear to be entirely sensory in function ; and it 

 is quite possible that bats may possess some special sense of which we have 

 no cognizance. 



Ordinary bats have teeth very similar to those of the order Insectivora (the 

 next in the series), and there is no doubt that these animals are derived 

 from some early members of the latter group which have gradually become 

 adapted for true flight ; the transition having probably been effected by the 

 development of a parachute-like expansion of the skin of the sides of the 

 body and limbs. In habits all bats are nocturnal, and the majority are 

 insectivorous, although a few have taken to blood-sucking. There is, how- 

 ever, one important group the fruit-bats which are entirely frugivorous, and 

 in these the teeth have quite lost the cusped structure distinctive of ordinary 

 bats, and have assumed an altogether peculiar conformation. All the fruit- 

 bats are of comparatively large dimensions ; and in this group are included 

 the largest representatives of the entire order. A certain number of bats 

 have acquired the habit of licking out the honey from the corollse of flowers, 

 and for this purpose their tongues have become modified into elongated 

 protrusile organs, frequently terminating in a bush-like expansion of delicate 

 filaments. 



Although one bat, at least, extends as far north as the Arctic circle, the 

 members of the order obtain their maximum development in tropical arid 

 subtropical countries ; and it is to such regions of the Old World that the 

 fruit-bats are confined, that group being entirely unknown in America. 



The number of bats known to science is between four and five hundred, 

 which are arranged in rather more than eighty genera, distributed under six 

 family-groups. As bats are Mammals with which the ordinary student has 

 but little to do, this large assemblage will be treated much more briefly than 

 most of the other orders ; such genera as are mentioned not having separate 

 paragraphs to themselves. 



Popularly known by the highly inappropriate title of flying-foxes, the 



fruit-bats form not only a family by themselves, but likewise a subordinal 



group differing from a second one, in which are contained all 



Fruit-Bats. the members of the order. From other bats this group of 



Family Ptero- Megachiroptera, as it is called, is chiefly distinguished by the 



podidce. characters of the molar teeth, which have low, rounded 



crowns, elongated in the antero-posterior direction, and 



divided by a distinct longitudinal ridge ; such teeth being far better adapted 



for fruit-eating than are the cusped molars of ordinary bats. From other 



bats, fruit-bats are also distinguished by the structure of the wing, in which 



there are three joints in the second or index finger, whereas in the other 



members of the order the number of such joints is reduced to two, or even 



one. Another peculiarity of the group is to be found in the complete circle 



formed by the base of the conch of the ear ; while the tail, if present, is 



