550 MANUAL OF ZOOLOGY. 



the Old World are represented in America by the Ameivce, 

 some of which attain a length of several feet. 



Very closely allied to the true Lizards are the Varanida or 

 Monitors which are indeed chiefly separated by the compara- 

 tively trivial fact that the abdomen and head are covered with 

 small non-imbricating scales, and not with large "scuta." The 

 tongue is protrusible and fleshy, like that of the Snakes. The 

 teeth are lodged in a common alveolar groove, which has no 

 internal border ; and there are no palatal teeth. The tail has 

 a double row of carinated scales, and is cylindrical in the 

 terrestrial forms, and compressed in those whose habits are 

 aquatic. The Monitors are exclusively found in the Old 

 World (Asia, Africa, and Australia), and are the largest of all 

 the recent Lacertilia ; the Varanus Niloticus of Egypt attaining 

 a length of six feet, and the Hydrosaurus salvator of the East 

 Indian Archipelago attaining to as much as eight feet. The 

 Heloderma horridum of Mexico is sometimes placed here. 



The Iguanidcz constitute another large family of Lizards, 

 belonging (if the Agamidcz be excluded) entirely to the New 

 World. The tongue is thick, fleshy, notched at its extremity 

 only, and not protrusible. Mostly there is a dorsal crest, and 

 a goitre or throat-pouch. The body is covered with imbri- 

 cated scales. They are often divided into " ground-iguanas," 

 in which the body is flat and depressed, and "tree-iguanas," 

 in which the body is compressed. The members of the genus 

 Iguana itself (fig. 301) are confined to South America and the 

 West Indies, and are distinguished by having the throat fur- 

 nished with a pendulous dewlap or fold of skin, the edge of 

 which is toothed. The back and tail, too, are furnished with 

 an erect crest of pointed scales. The common Iguana (/. 

 tuberculata) attains a length of from four to five feet, and 

 though not of a very inviting appearance, is highly esteemed 

 as food. The Basilisks (Basiliscus) have the top of the head 

 furnished with a membranous sac, which can be distended 

 with air at will. 



The family of the Agamida is closely allied to that of the 

 Iguanidce, proper, and represents it in the Old World. The body 

 is covered with imbricated, generally rhombic, scales ; the tongue 

 is thick and non-protrusible ; the eyes have eyelids ; and the 

 teeth are implanted on the edge of the bones of the jaws. 



The Lizards of this group are distributed over nearly the whole of the 

 Old World (principally Asia, Africa, and Australia), and are either 

 arboreal or terrestrial in habit. Good examples are the Stellio vulgaris 

 of the Levant, the Agama imiricata of Australia, and the hideous Moloch 

 horridus of the same country. Here also belongs the curious little Frill 



