MAMMALS. 



377 



on the other hand, there are no such limitations to the 

 flight. The wing in the bats consists of a very thin mem- 

 brane supported upon a framework composed of the body 

 and the bones of the fore limbs. These latter are elon- 

 gated, four of the fingers excessively so (fig. 165); and 



FIG. 165. Skeleton of bat. 



between these fingers and extending back to the body and 

 the hind limbs is the web of the wing. The thumb, how- 

 ever, is not involved in the wing, but forms a claw of great 

 use in supporting the body, although when at rest they 

 usually hang, head downwards, by the five claws of the 

 hind feet. The jaws are provided with incisors, canines, 

 premolars, and molars. Bats are social animals, occur- 

 ring in large numbers in caves, deserted buildings, and 

 the like, where they spend the day, and it is remarkable 

 that these colonies are usually entirely male or female. In 

 a rough way the bats may be divided into fruit-eating and 

 insect-eating forms, their habits being correlated with 



