216 



LACERTILIA. 



rnovably articulated with the parotic process of the temporal region 

 and supports the lower jaw, the rami of which are firmly connected 

 at the symphysis. 



The dentition of the Lizards in form, structure and mode of 

 fixture of the teeth, presents far greater diversity than does that of 

 the Snakes ; it is however not so complete since the palate has never 

 an inner row of teeth, but only small lateral groups on the pterygoids. 

 The teeth are almost always attached directly to the bone, either on 

 the edge of the jaw (Acrodont), or on the inner side of the jaw 

 (Pleurodont). This distinction corresponds to the geographical dis- 

 tribution of the Iguanas^ those found in the eastern hemisphere being 

 Acrodonts, and those in the western Pleurodonts. The shape of 

 the tongue seems important, and the principal groups are distin- 

 guished and named according to this characteristic. 



Most Lizards have eyelids, an exposed tympanic membrane and a 

 tympanic cavity. Only the Amphisbcenas and Geckos are without 

 eyelids, and have the same arrangement for covering the eyes as have 

 the Snakes. In the Scincoidece the lower eyelid can be raised like a 

 transparent curtain without hindering the sight. In the Chamcelion- 

 idce the single eyelid is a muscular cutaneous ring of skin with 

 circular opening. 



The integument of Lizards resembles in its general features that 

 of Snakes, but presents much greater variety. Sometimes there are 

 flat or keeled scales, sometimes scutes and larger plates, for the distri- 

 bution of which on the head the terminology already described for 

 Snakes is used. In addition, more irregular hardenings of the 

 skin may occur warty protuberances which give the skin an appear- 

 ance similar to that of the Toads (Geckonidce). On the other hand 

 there are often cutaneous lobes on the throat, crests on the back and 

 on the top of the head, also folds of skin on the sides of the trunk, on 

 the neck, etc. Although the skin of Lizards is in general poor in 

 glands, yet in many forms cutaneous glands and corresponding rows 

 of pores along the inner side of the thigh (fig. 634, SP] and in front 

 of the anus are constantly present. 



As a rule, the females after copulation (which in temperate regions 

 takes place in summer) lay a small number of eggs ; some genera 

 are viviparous (Anguis, Seps). Most are harmless, and are useful 

 by destroying Insects and Worms ; larger species, as the Iguana, are 

 hunted for the sake of their flesh. By far the greater number, and 

 all the larger and more beautifully coloured species inhabit <*he 

 warmer and hot countries. 



