REPTILIA 249 



The members of this sub-order are distinguished from the other 

 sub-orders of hzards by the fact that the vertebrae are proccelous and 

 solid, and that the ventral portions of the clavicles are not dilated. 



It is proposed to describe the characters of a few well-known species 

 with particular reference to their special adaptive features: a curso- 

 rial type, an arboreal type, a volant type, an aquatic type, a fossorial 

 type and an ant-eating type. 



Lacerta viridis (Fig. 138, B) the common European "wall lizard" is 

 an excellent example of generalized lizard. It is a small type with 

 long slender proportions, is a beautiful green above and yellow below. 

 It runs very swiftly upon the ground and over rocks and hides in thick- 

 ets and under any available shelter. From some such generalized 

 type as this have radiated all of the more specialized types. 



Sceloporus spinosus (Fig. 138, E), one of the commonest American 

 lizards, is a good example of an arboreal type, though it also has a 

 strong hking for the ground if there are thickets available. It is a 

 rusty-colored lizard, harmonizing wonderfully with the bark of the 

 mesquite and other trees which it haunts. During the heat of the day 

 it lies basking on the trunk or exposed branches of trees, and retires 

 to holes in trees or among the roots at night. In the winter it hiber- 

 nates in shallow holes in the ground or under stones or other shelters. 

 During the cool of the day they are actively in search of food, which 

 consists mainly of tree-inhabiting insects. In the breeding season 

 the male takes on a steely blue sheen about the throat and head. The 

 courtship and mating activities are rather striking. The male stands 

 in front of the female with his brilliant throat inflated and thus dis- 

 played to the utmost; then raises himself up and down on the fore legs 

 with a quick rhythm. This the female seems to watch as though fas- 

 cinated and is soon won. The nest is dug in loose soil in the form of 

 a fairly deep tunnel in a sloping bank. Excavation of the nest is ac- 

 compUshed with the hind feet as in tortoises. The eggs, which are 

 much like tortoise eggs in appearance, number a dozen or more, and 

 when laid are in a stage equivalent to about a 72-hour chick. 



Draco volans (Fig. 138, C), the flying dragon, is the best example of 

 the volant type of lizard. The body is dorso-ventrally depressed and 

 the skin is stretched out into two fan-shaped, folding membranes, 

 which are supported on five or six of the greatly elongated ribs. On 

 the neck are three hooks which probably enable the animal to secure 

 a hold when alighting from a flight. The wings are mere parachutes 



