186 HIGH SCHOOL ZOOLOGY. 



and as the bats are nocturnal creatures, the nerve-terminations 

 in it constitute one of the chief channels through which sensa- 

 tions reach the brain. In further accordance with their noc- 

 turnal habits, the bats have small eyes, and large ears ; they 

 hybernate in cold climates, where they are often to be found in 

 large numbers, hanging in some cave or building, by the claws 

 of the hind feet, wrapped up in the patagium. The bats are 

 characteristically insectivorous forms, very few are fruit-eating^ 

 but the dentition of the two groups indicates a sharp contrast 

 between them. As the patagium does not merely serve to break 

 the force of a fall or to permit of an oblique leap, but is a true 

 organ of flight, the pectoral muscles require to be specially 

 developed to permit of such use of the anterior extremity, and 

 consequently the sternum is provided with a crest, and the 

 clavicles are stronger than they are elsewhere among mammals. 

 It is not surprising that the bats should be the most widely 

 distiibuted of Mammalia. 



The fruit-bats are abundant in eastern tropical countries, and attain 

 the largest size of any members of the order. Pteropus, the fox-bat, so 

 called on account of the pointed snout, may be mentioned as a type of 

 this section, the fruit-eating habits of which are indicated by the blunt 

 tubercles of the molars. In the insectivorous bats, on the other hand, 

 the tubercles of the molars are sharp or coalesce into a W-shaped 

 cutting edge. The snout is short, and the external ears are of large 

 size. Two groups are recognized — those in which the external nose is 

 provided with a membranous expansion round the nostrils, and those in 

 which there is no such membranous expansion. To the former belong 

 the vampire-bats of S. America {Desmodiis), which attack and suck the 

 blood of horses and mules. With that exception, they are mostly insect- 

 eating forms, but the genus Vanipyrus of Guiana lives chiefly on 

 fruit. The ordinary bats ( Vespertillonidce), with the nose destitute of 

 the membrane, are represented by two genera in our region, as examples 

 of which may be mentioned the little brown bat ( Vespertilio subulatus) 

 and the red bat (Atalapha noveboracensis). 



40. As the Australian continent is peopled by a remarkably 



primitive mammalian fauna, so also the Island of Madagascar 



possesses chai'acteristic mammals which ai'e found nowhere else, 



