CHIROPTERA. 719 



limbs are connected by a parachute, and the annuals can glide from tree 

 to tree, "sometimes traversing a space of seventy yards with a descent 

 of only about one in five." The upper and lower incisors are compressed, 

 multicuspidate, the lower deeply pectinated. Two species of this genus 

 live in the forests of the Malayan region. They are nocturnal, and feed 



= '-3 

 on leaves and fruit. The dentition is . There are numerous skeletal 



3123 

 peculiarities. 



Order 8. Chiroptera — Bats. 



Bats are specialised Mammals related to Insectivores. 

 They have the power of flight, the fore limbs being modified 

 as wings. The wing is mainly due to an extension of the 

 skin stretched between the very long fingers. The fold of 

 skin usually begins from the shoulder, extends along the 

 upper margin of the arm to the base of the thumb, thence 

 between the fingers, and along the sides of the body to the 

 hind legs or even to the tail. Contrasted with the wing of a 

 bird, that of a bat has a rudimentary ulna beside a long 

 curved radius, a wrist with six bones, five free digits with 

 long metacarpals on the four fingers. The shoulder girdle 

 is very strong, there is a long curved clavicle, a large tri- 

 angular scapula, a long coracoid process ; the presternum 

 bears a slight keel on which are inserted some of the muscles 

 used in flight. The thumb is always clawed ; the other 

 digits are unclawed, except in most frugivorous bats, where 

 the second digit bears a claw. 



The hind limb is relatively short and weak, the pelvic 

 girdle is also weak, and in most cases the pubic symphysis 

 is loose in the males, unformed in the females. The knee is 

 turned backwards like the elbow, the ankle has a cartilaginous 

 prolongation or calcar which supports the fold of skin 

 between limb and tail, the five toes are clawed. 



The vertebral column is short, there is little mobility 

 between the vertebrze, neural spines are absent behind the 

 third cervical except in Pteropidse, the caudal vertebrae are 

 very simple. The ribs are usually flat. The inaximum 



2133 



dentition is — ; the milk teeth are very different from the 



3133 

 permanent set. All the bones are slender, and have relatively 



large medullary canals. 



The cerebral hemispheres are smooth and leave the 



cerebellum uncovered. The spinal cord is at first very 



