VERTEBRATA. 
347 
which are adapted for flight, the fingers being immense¬ 
ly lengthened, and united by a membranous web. The 
toes, and one or two of the fingers, are armed with hooked 
Fiq. 339.—Bat (Vespertilio). 
nails. The clavicles are remarkably long, and the ster¬ 
num is of great strength ; but the whole skeleton is ex¬ 
tremely light, though not filled with air, as in Birds. The 
eyes are small, the ears large, and the sense of touch is 
very acute. The favorite attitude of a Bat when at rest 
is that of suspension by the claws, with head downward. 
They are all nocturnal. 
Fig. 340.—Skeleton of a Bat. 
