BATS. 3 



or offering any distinct analogical relation to them. The 

 expansion of skin extended between the anterior and 

 posterior extremities of the Colugo, Galeopithecus, a genus 

 formerly referred to the present order, but which properly 

 belongs to the Quadrumana, of the Flying Squirrel, 

 Pteromys, amongst the Rodentia, and the Flying Opos- 

 sum, Petaurista, amongst the marsupial animals ; the 

 increased development of the fins in the Flying Fish, 

 Exocetus, and the cutaneous web supported by the elon- 

 gated ribs in the Flying Lizard, Draco, are all of them 

 examples of an expansion of the integument upon cer- 

 tain bones, for the purpose of enabling these animals to 

 take long and somewhat sustained leaps ; but to the 

 performance of this one action each of these structures 

 is strictly limited. There is no instance of a quadruped, 

 a fish, or a reptile, sustaining itself in the air by a succes- 

 sion of impulses given by any such organs as those now 

 alluded to. But in the Bats, the whole structure is 

 obviously modified to the fulfilment of this object. The 

 sternum, the ribs, and the bones composing the shoulder, 

 are all developed for the attachment of powerful muscles, 

 adapted to the rapid and continued movements of the 

 anterior extremity, which, although consisting essentially 

 of the same parts as that of man, has its different bones 

 so modified in form and extent, as to afford the most 

 admirable and complete support to an extensive expan- 

 sion of the skin, which thus forms a perfect and efficient 

 pair of wings. This modification principally consists in 

 the extraordinary development of the fingers, which are 

 greatly elongated for the purpose ; and upon which 

 the skin is stretched like the silk on the rods of an 

 umbrella. The skin which forms the flying membrane is 

 exceedingly thin, generally devoid of hair on both sides, 

 and is furnished with very slender transverse bands in 



B 2 



