THE ALLIES OF THE SQUIRREL 



427 



shrews are the smallest mammals known. They generally 

 live in burrows like the moles. They somewhat resemble 

 mice, from which they can be distinguished by the different 

 plan of the teeth. 



Bats. The Chirop'tera (Gr. cheir, "hand"; pteron, 

 "wing") are marked off from all other mammals by the 

 possession of wings, which are 

 formed of skin stretched over 

 the bones of the arm, includ- 

 ing also the legs and some- 

 times the tail. 



. So well adapted for aerial 

 locomotion have the bats (Fig. 

 224) become that progress on 

 the ground is almost impos- 

 sible. The sense of touch is 

 greatly developed not only on 

 the muzzle but on the wings as 

 well, so that the animals are 

 able to avoid obstacles in their 

 nocturnal flights. During the 

 day bats hang themselves up 

 by their legs in caves and in 

 hollow trees to sleep. Some 

 species feed on insects, others 

 on fruit, and some, the vam- 

 pire bats of Central and South America, feed on blood. The 

 latter have the teeth peculiarly adapted to cutting the skin 

 of animals. The esophagus is so narrow that no solid mat- 

 ter can pass down it. 



Primates. The Prima'tes (Lat. primus, " first") include 

 the monkeys, apes, and man. The teeth are generally 

 adapted to a diet of both plant and animal food ; the five 

 toes and fingers are separate and are usually provided with 



Fig. 224. Photograph of a bat 



