STRUCTURE OF BATS 



877 



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

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

 of which have very long metacarpals, while the thumb is 

 short. The phalanges are usually reduced to two. The 

 pectoral girdle is strong ; there is a long curved clavicle, a 

 large triangular scapula, a long coracoid process ; the pre- 

 sternum bears a slight keel on which are inserted some of 



WWM 





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Fig. 519. — Outline of a bat's wing. 



The patagium or fold of skin, beginning on the side of the neck, 

 passes along the pre-axial margin of the ann, skips the thumb, 

 IS continued between the other digits and metacarpals to the 

 hind-limb. Thence, forming the inter-femoral membrane it is 

 continued to the tail. The inter-femoral membrane probably 

 helps in aerial steering, and against it the bat, sinking for a few 

 feet is able to press a beetle that it is gripping in its jaws, so that 

 it can give it a second bite without losing it. Besides the main 

 trumpet or pinna of the ear, there is an extra-piece, the tragus, 

 well developed in most bats. 



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 cartil- 

 aginous prolongation or calcar, which supports the fold of 

 skin between limb and tail ; the five toes are clawed. 



