244 



BRANCH CHORDATA 



wriggling body motion. " Two aortic branches, a left and a 

 right, survive in lizards." 1 



Lizards are very various in size, shape, color, and habitat. 

 Most of them are terrestrial, some burrow, some are semi- 

 aquatic, and still others are arboreal. They are generally cov- 

 ered with horny epidermal plates. Lizards shed their skin 

 entire. 



The shoulder girdle and sternum are present. The " flying 

 dragons " of the Indo-Malayan countries have " a pair of wing- 



Fig. 200. Heloder'ma, a poisonous lizard. (From Holder's " Zoology," 

 American Book Co., Publishers.) 



like membranes supported by five or six elongated posterior 

 ribs, which they use as a parachute or fold up like a fan." 



Food. Most lizards are insectivorous, eating small animals 

 also, but some are herbivorous, living upon buds, blossoms, and 

 tender leaves of plants. 



Special Senses. The eyes are usually provided with an 

 upper and a lower movable eyelid and with a transparent nicti- 

 tating membrane. The tympanic membrane is situated in a 

 slight depression behind the eye. The tongue is free and both 

 jaws are armed with teeth. The mouth is not distensible. 



1 Packard. 



