BATS. 81 



the radius (r), the ulna (u) being rudimentary. The thumb (px} is 

 short, free from the flying-membranes, and provided with a claw 

 (ph) ; while the other fingers are long, slender, and clawless, with 

 the exception of the index, corresponding to our fore finger, which 

 in some genera also possesses a claw. Clavicles (cl) are well 

 developed in all the species. 



The hind limbs, on the other hand, are thin and feeble, and dif- 

 ferent from those of all other mammals in that they are rotated 

 backwards, so that the knee, like the elbow, is directed backwards. 

 Those species which are provided with a flying-membrane between 

 the hind le<rs have it supported by a long cartilaginous process or 

 spur, which is attached to the heel. 



Bats are primarily divided into two groups, Frugivorous and 

 Insectivorous. The members of the first are distinguished by their 

 generally large size, large, smooth, and comparatively blunt teeth, 

 well-developed postorbital processes, and by the presence of three 

 phalanges to their index fingers. To this group belong the large 

 Fruit-Bats or Flying Foxes (Pteropus), represented by the skeleton 

 of Pteropus jubatus, and other genera, all of which live entirely 

 on fruit, and are restricted to the Old World. 



The Bats of the insectivorous division are of small size, and have 



Fig. 40. 



A B 



Skulls of (A) Noctule ( Vesper ugo noctuld) and (B) Blood-sucking Bat 

 (Desmodus rufus). 



teeth covered with minute sharp-pointed cusps, as in the Insecti- 

 vora ; they have no postorbital processes, and only one, or rarely 

 two, phalanges in their index fingers. 



