68 SAURIA. 



tlirougli which they pass. A comparison of the 

 progression of these, however, and even of the 

 Slow-worm, with that of the true Snakes, will 

 show that the latter only employ the free ter- 

 mination of their ribs as organs of locomo- 

 tion. In these the ribs serve absolutely and 

 perfectly the function of feet, and with the ex- 

 ception of their being covered with integument, 

 their action is exactly that of the multitudinous 

 feet in the Scolopendra or Julus, the whole 

 series of ribs coming into contact in succession. 

 At the same time, it is upon the lateral pres- 

 sure of successive portions of it, that the Serpents 

 mainly depend for the rapidity of their progres- 



sion." 



The Sauria are, we believe, exclusively land- 

 animals, none of them being' fitted for inhabiting 

 the water, though some are able to swim, in 

 emergency. Most of them are terrestrial, but not 

 a few are arboreal, more or less entirely, from the 

 Chameleon^ which, with liis opposible toes, chmbs 

 about the branches of trees, to the little Anoles, 

 which run about the trunks and leap from leaf 

 to leaf; and some, as the Geckos, inhabit the 

 crevices of old buildings, among the rafters of 

 which they crawl in all positions, frequently with 

 the back downward. These last are rather slow 

 in their motions, and the Chameleons are still more 

 deliberate ; but the characteristic of the Order is 

 extreme agihty, and some of the ground Lizards 

 dart to and fro, and skim the surface of the earth 

 with the rapidity of a bird. In one genus, Draco, 

 the skin of the sides is stretched upon a prolonga- 

 tion of the ribs, and acts as a parachute, or as the 



* British Reptiles, Introd. xx. 



