40 VERTEBRATA. MAMMALIA. 



with conical points, feed chiefly on insects ; while 

 those in which they are quite trenchant, are exclu- 

 sively flesh-eaters, their food being the flesh of other 

 vertebrata. The lower jaw has merely a vertical 

 motion, the joint being like a hinge. Cuvier divides 

 them into three sub-orders, the first being the 



SUB-ORDER I. CHEIROPTERA.* 



This is a strongly-marked and very distinguishable 

 group of animals, recognised by the single character 

 of a membranous extension of the skin, commencing 

 at the neck, enveloping the arm and hand, and pro- 

 ceeding thence to the hind limbs, and in most species 

 even to the end of the tail. For the purpose of 

 expanding this membrane, the four fingers of the 

 anterior limbs are enormously lengthened, resem- 

 bling the ribs of an umbrella, and with this appa- 

 ratus the animal is enabled to perform a sustained 

 and perfect flight, resembling more the flitting of a 

 butterfly, however, than the flight of a bird, but 

 possessing great celerity of motion. Extremely deli- 

 cate and supple, this membrane is capable of being 

 contracted into innumerable wrinkles, so that when 

 the animal folds its long fingers together upon the 

 arm, and brings the arm close to the side, we are 

 astonished to observe into how small a space the 

 long and broad wings are compressed. The thumb 

 of the fore feet, however, is free, and being furnished 

 with a sharp hooked claw, affords aid to the Bat in 

 its somewhat awkward attempts at progression on 



ir, a hand, and frt^ov, ptero?i, a wing. 



