606 REPTILIA. 



Some Families of Lacertilia. 



In the Geckos (Geckonidte) the vertebrae are biconcave or amphi- 

 ccelous, the tongue is short and fleshy, the eyelids are rudimentary, the 

 teeth are pleurodont, the toes bear numerous plaits, by means of which 

 they adhere to smooth surfaces, e.g. Platydactylus. 



The Agamas ( Agamidae) are acrodont lizards common in the Eastern 

 hemisphere. Examples. Agama; Draco, with the skin extended on 

 long prolongations of five or six posterior ribs ; Cklamydosaurus, an 

 Australian lizard, with a large scaled frill around the neck, sometimes 

 running on its hind-legs ; Moloch, another Australian form bristling 

 with sharp spikes. 



The Iguanas (Iguanidae) are pleurodont lizards, represented in the 

 warmer parts of the New World. Examples. Iguana, an arboreal 

 lizard, with a large distensible dewlap ; Amblyrkynckus or Oreocephalus 

 cristatus, a marine lizard confined to the Galapagos Islands ; Anolis, 

 the American chameleon, with powers of rapid colour-change ; 

 Phrynosonia, the American "horned toad," with numerous horny 

 scales, and a collar of sharp spines suggesting in miniature that of 

 some of the extinct Reptiles. 



The slow-worms (Anguidse) are limbless lizards, with serpentine 

 body, long tail, rudimentary girdles and sternum. The British species, 

 Anguis fragilis, is neither blind nor poisonous ; the tail breaks very 

 readily ; the young are hatched within the mother. 



The poisonous Mexican lizard (Helodenna snspectum] measures over 

 a foot in length, and is covered with bead-like scales. 



The water-lizards (Varanidre) are large semi-aquatic forms of carni- 

 vorous habit, most at home in Africa, but represented also in Asia and 

 Australia. The Monitor of the Nile, Varamis ntloticiis, may attain a 

 length of 5 or 6 ft., and is noteworthy because of its fondness for the 

 eggs and young of Crocodiles. 



The Amphisbrenide are degenerate subterranean lizards, without 

 limbs, with rudimentary girdles, with no sternum, with small covered 

 eyes, with hardly any scales. 



The Lacertide are Old World acrodont lizards, such as Pseudopits 

 (Europe and S. Asia) ; Lacerta viridis, the green lizard of Jersey and 

 S. Europe ; L. agilis, the British grey lizard ; L. mnralis, abundant 

 about ruins in S. Europe ; L. or Zootoca vivipara, the British scaly 

 lizard. 



The Chameleons (Chamreleontide) are very divergent lizards, 

 mostly African. There is one genus, Chaimeleo. The head and the 

 body are compressed ; the scales are minute ; the eyes are very large 

 and movable, with circular eyelids pierced by a hole ; the tympanum is 

 hidden ; the tongue is club-shaped and viscid ; the digits are divided 

 into two sets, and well adapted for prehension ; the tail is prehensile ; 

 the power of colour-change is remarkably developed. 



The Chamseleons exhibit numerous anatomical peculiarities. As in 

 the Amphisbenas, there is no epipterygoid nor interorbital septum. 

 The pterygoid does not directly articulate with the quadrate, which is 

 ankylosed to the adjacent bones of the skull. 



