THE LIZARDS 93 



those species with the limbs so aborted the creature folds 

 them against the sides of the body and glides like a 

 snake, or where there is hut one fair of viicroscopic 

 limbs, these are of absolutely no use though going 

 through all the motions of walking during the animal's 

 gliding progress. In the degenerate family Amphis- 

 boenidoej not only the limbs ' and scales have disappeared, 

 but the pectoral and the pelvic arch have been reduced to 

 mere vestiges. 



The Tongue: The structure of the tongue varies 

 greatly among lizards. With many of them it is long, 

 black, deeply forked and snake-Hke; it is darted from 

 the mouth to examine objects in the lizard's path. On 

 others the tongue is flattened yet rather fleshy, and but 

 bluntly nicked at the tip ; in combination it is used as an 

 organ of investigation and to pull the food into the 

 animal's mouth. A number of lizards have a thick, 

 viscid tongue, employed in the same fashion as that of 

 the toad, namely: — to lap up small insect prey. The 

 true chameleons have an enormously long tongue — club- 

 shaped at the tip — that is darted at an insect which 

 sticks fast when squarely hit. 



The Teeth: With the arrangement of the teeth we 

 find an important character bearing on classification. 

 Two phases of development should be thoroughly un- 

 derstood. Some lizards have an acrodont, others a 

 pleurodont dentition. Acrodont lizards have the teeth 

 set along the edges of the j aws ; there are no well-defined 

 alveoli (sockets) or a longitudinal socket groove. Pleu- 

 rodont lizards have the teeth set in a deeply-cleft, longi- 

 tudinal, continuous socket. If it were not for these de- 

 cisive arrangements we would be unable to separate the 



1 Except with three genera having only a pair of practically useless front 

 limbs. 



