MAMMALIA 379 



are not discharged. When irritated, the hedgehog rolls itself into 

 a ball with its head tucked between its feet. Hedgehogs feed on 

 slugs and insects, but also eat small mammals and frogs, and are 

 protected on account of their value as snake killers. Some Euro- 

 peans are very fond of the flesh of the hedgehog. 



Fossil Relatives of the Insectivora. — The living families of 

 moles, shrews and hedgehogs arose in the Eocene period. Related 

 forms occurred in the Jurassic. R. C. Andrews has discovered in 

 Mongolia fossil skulls with teeth of the insectivorous ty^pe, indicating 

 the pattern from which insectivores, carnivores, and possibly pri- 

 mates may have evolved. 



Order IV. Chiroptera. — Clawed animals with fore-limbs modi- 

 fied for flight, the bones, especially those of the second to the fifth 

 digits, being greatly elongated so as to support a broad web of skin 

 extending back to the hind-limbs. The sternum has a keel for the 

 attachment of the pectoral muscles, which are important to the 

 movements of flight. The dentition is complete. The cerebral 

 hemispheres are smooth and do not overlap the cerebellum. Anal 

 glands, furnishing a strong, even offensive smelling secretion, are 

 common. Although bats are swift fliers they do not have air spaces 

 in their bones as do some of the birds. There are more than six 

 hundred species of bats, which at first were classed with birds. 



The Megachiroptera are large, diurnal forms, sometimes called 

 fruit bats, fox bats, or "" flying foxes." They destroy fruits and on 

 this account have been barred from admission into some states. 

 The larger fruit bats are eaten by the natives of the East Indies. 

 The hammerheaded bat is found in Africa. 



The Microchiroptera include the leaf -nosed bats, the vampire bats 

 and the smaller common forms. The leaf-nosed bat is found in 

 California and Mexico and has a wedge-shaped leaf of naked skin 

 just behind the nostrils. The javelin bat, ranging from South Amer- 

 ica to Mexico, is a vampire or blood-sucker, attacking horses, cattle 

 and men. It reaches a length of four inches. An extremely large 

 form from South America, erroneously called the " great vampire," 

 is not at all injurious, but feeds on fruits and nuts. It is twenty- 

 eight inches in length. 



The naked bats of Borneo have thick leathery skins and a scent 

 gland on their neck. Under each arm they have a mammary pouch 

 in which the young are carried and nursed until they are able to fly. 



The cominon bats ( Vespertilionidae) are found all over the world. 



