FLYING LIZARD. 



379 



struments for assisting it in its distant leaps through the air, 

 it is again the ribs which are resorted to for furnisliing the 

 basis of such an apparatus. On each side of the dorsal ver- 

 tebrae, as is seen in the skeleton of this animal (Fig. 222,) 

 the eight posterior ribs on each side, instead of having the 

 usual curvature inwards, and instead of being continued 

 round to encircle the body, are extended outwards and elon- 

 gated, and are covered with a thin cuticle, derived from the 

 common integuments. The ordinary muscles which move 

 the ribs still remain, but with greatly increased power, and 

 serve to flap these strangely formed wings at the pleasure of 

 the animal, during its short aerial excursions. 



222 



Among the mammalia, we meet with a few species which 

 have a broad membrane, formed of a duplicature of the skin, 

 extended like a cloak from the fore to the hind extremities, 

 and enabling the animal to flutter in the air, and to break its 

 fall during its descent from the branches of trees. Struc- 

 tures of this kind are possessed by the Sciurus volans^ or 



