76 STORY OP THE REPTILES 



argue slightly for a land origin for all three- jointed 

 limbs, whether legs or paddles. 



As a rule, there is not anj marked opposition of 

 the thumb or big toe in the reptiles. In the chame- 

 leon proper (not our little Florida lizard, so-called) 

 the toes are bunched wonderfully (for grasping) into 

 twos on one side of a twig and threes opposite 

 (Fig. 38). 



But most reptiles with limbs climb by claws, or 

 claws and toe-pads combined, as in the geckos (see 

 Fig. 60). One order of fossil reptiles had the little 

 finger greatly lengthened, by which it doubtless flew 

 by means of a skin-membrane attached. 



Claws 



The claw, as such, came in fully with the toed rep- 

 tiles, and is now often sharp and clinging. In the 

 tortoises claws are present to aid the creature in 

 scrambling along, and in burrowing. In fact these 

 creatures walk almost exlclusively by the claws, or push 

 by them rather. But the more aquatic turtles have 

 some missing usually. The pond-turtle omits one; 

 and those with flippers may have only two on each 

 limb. In the crocodilians, where the toes are four 

 behind and five in front, there are only three claws 

 to each foot. 



Another thing which came in with the reptiles 

 more fully was the act of walking on the toes only, 

 leaving the heel high up. This is a practice found in 

 many mammals, such as dogs, horses, etc. Most rep- 

 tiles are flat-footed walkers, however, while some 



