THE CHEIROPTERA. 385 



racoid. The clavicle, wliicli is very strong, is perforated by a 

 great foramen, and at the middle of its posterior margin sends 

 oif a truncated reentering process. ■ Proximally, it furnishes 

 an articuhir surface for the humerus. In the carpus there is a 

 distinct centrale, and a large accessory C-shaped bone lies on 

 its radial side. The pubes are separate at the symphysis, and 

 an accessory styloid bone is connected with the naviculare of 

 the foot. 



The distribution of the Insectivora is singular in this 

 respect, that, although they are met with, under very various 

 climatal conditions, throughout the Old World and North 

 America, there are none in South America or Australia. 



In the fossil condition they are not certainly known to 

 occur in strata older than the tertiary. 



III. The Cheiroptera. — The Clielroptera may be regard- 

 ed as exceedingly-modified Insectivora^ having their nearest 

 ally in Galeopithecus, 



They possess one or tvv^o pair of pectoral teats ; and the 

 fore-limbs are very long, some of. the digits particularly being 

 immensely elongated. There is a pataghmi^ or expansion of 

 the integument, uniting the fore-limbs with the body, and ex- 

 tended, as a membranous web, between the elongated fingers. 

 Of these, the third, fourth and fifth, and very frequently the 

 second, are devoid of nails. The pollex always has a claw- 

 like nail. When the animal is resting upon the ground, the 

 thigh is twisted upward and backward, in such a manner that 

 its extensor face looks forward, and its flexor face backward. 

 In consequence of this the knee looks upward and backward, 

 and the toes are turned backward and slightly outward. Un- 

 der the same circumstances, all the digits of the manus are 

 flexed upon their metacarpal bones ; and the folded-up wing- 

 rests against the side of the body, while the pollex, with its 

 claw, is extended forward. In this position the animal shufiles 

 along, with considerable rapidity; hauling itself forward by 

 the claws on the pollices, and shoving itself along, by extend- 

 ins' the hind-limbs. 



The favorite attitude of a Bat, when at rest, however, is 

 that of suspension by the claws of one or both legs, with the 

 head downward and the pataghim folded over it like a cloak. 

 The most active movement of the Bat is efi'ected by flight, the 

 fore-limbs being extended, and \\\q patagium^ which they sup- 

 port, playing the part of the feathers of a bird's wing. 



The cervical vertebrae are remarkably large in proportion 

 IV 



