LACERTILIA AND CROCODILIA. 44 1 



imbricated scales. Good examples are the Tapayaxin {Agama 

 orbicularis) of South America, and the hideous Moloch horridus 

 of Australia. Here also belongs the curious little Frill Lizard 

 {Chlamydosaurus) of Australia, which has the neck fiirnished 

 on each side with a membranous plaited frill, which can be 

 erected at will. More remarkable than the true Iguanas is the 

 little Flying Dragon {Draco volans) of the East Indies and 

 Indian Archipelago. In this singular little Lizard there is a 

 broad membranous expansion on each side, formed by a fold 

 of the integument, supported upon the anterior false ribs, which 

 run straight out from the spinal column. By means of these 

 lateral expansions of the skin, the Draco volans can take long 

 flying leaps from tree to tree, and can pursue the insects on 

 which it feeds ; but the lateral membranes simply act as para- 

 chutes, and there is no power of true flight, properly so called. 



The last family of the living Lizards which requires notice 

 is that of the Chamceleontida, containing the familiar little 

 Chatnceleo Africanus, which occurs abundantly in the north of 

 Africa and in Egypt, and is so well known for its power of 

 changing its colour under irritation or excitement. In this 

 genus the eye (fig. 172) is of large size, and is covered by a 

 single circular lid, formed by a coalescence of the two lids, 

 and perforated centrally by a small aperture, by which the 

 rays of light reach the pupil. The Chameleon is naturally a 

 sluggish animal, but it catches its food, consisting of insects, 

 by darting out its long, fleshy, and glutinous tongue — an opera- 

 tion which it effects with the most extraordinary rapidity. 



The tail in the Chameleons is round and prehensile, the body 

 compressed, and the skin like shagreen. The toes are adapted 

 for the arboreal life and scansorial habits of the animal, being 

 so arranged as to form two equal and opposable sets. The 

 lungs are excessively voluminous. The Chameleons are ex- 

 ceedingly sluggish and slow in their movements, and are con- 

 fined to the warmer parts of the Old World. 



Distribution of Lacertilia in Time. — The geological 

 range of the true Lacertilia is not by any means very great, 

 nor, with a single exception, are their remains of much import- 

 ance. The earliest traces of Lizards in the stratified series are 

 found in the fresh-water strata of the Purbeck beds at the 

 summit of the Jurassic series. Several small Lizards occur 

 here, and have been described under the names of Nathetes, 

 Macellodon, Saurillus, and Echinodon. The most remarkable 

 fossil Lizard, however, is the Mosasaurus of the Chalk. This 

 gigantic reptile occurs at the very summit of the Cretaceous 

 series, in what is known as the Maestricht Chalk. The skull 



