skeleton OF bat ( Nycteris ). 
CHAPTEE IX. 
Bats,— Order Chiroptera. 
In some cases there is more or less difficulty, especially when we have to take 
extinct types into consideration, in finding well-marked characteristics by which 
the various orders of Mammals can be distinguished from each other. With hats, 
however, there is no such difficulty, since they are sharply distinguished from all 
other Mammals by possessing the power of true flight, for the purpose of which their 
fore-limbs are specially modified. We say true flight advisedly, for the reason 
that there is a kind of spurious flight possessed by certain other Mammals, such as 
flying squirrels and flying phalangers, which is quite different from the flight of 
hats, and does not entail any special modification of the structure of the fore-limbs. 
True flight, like that of birds and bats, is effected by means of alternate upward 
and downward strokes of the wings, and can be carried on as long as the muscular 
power of the flyer permits. Spurious flight, like that of the flying squirrels, is, on 
the other hand, nothing more than a prolongation of an upward or downward leap, 
by the aid of parachute-like expansions of the skin of the sides of the body, and 
