LIZARD, a subclass of reptiles, whose anatomical features and classification have been described under LACERTILIA. A general account of their habits and ecology has been reserved for the present article. Lizards as a group are of comparatively recent origin, most of the fossils known not being older than the middle of the Tertiary, when representatives of many of the modern genera were in exist ence. The Pleistocene rocks of Queensland have furnished skeletons of several gigantic extinct representatives of the monitor family, one of which (Megalonia) was about 30 feet long. The lizards, as a 'group, are remarkable for the great variety in •size and'.shane, and in the character of the skin-armature and the dentition. These variations are usually mani festly adaptations to the local environment.
Lizards abound in all the warmer parts of the world, most numerously in the tropics. In North America only three or four species pass the northern boundary of the United States, penetrating southern Ontario in the east and British Columbia on the Pacific side of the continent, where, in the arid Southwest, most of the species known in this country are to be seen. Most kinds of lizard:, are re stricted in range, being adapted to a definite sort of environment, Ow families may have a very wide distribution. Thus that of the geckos (q.v.) is spread all over the tropical and subtropical zone of the Old World, and also in South America; and it includes both arboreal and terrestrial forms, diversified by modifications of the type to meet conditions as different as are the steaming Jun les of Malaya from sandy deserts of Persia and Africa. On the other hand the big monitors (Varanidcr), scattered from the Nile to the Philippines and Australia, are able to seek their prey on burning desert ground, in and under water. and the branches of forest-trees. This is a case of remarkable versatility, for there is little adap tive alteration of structure in the family. Again, similarity of habitat and local influ ence sometimes produce striking likenessi in appearance in totally disconnected species, as, for example, our spiny-coated horned toads and the Australian molochs (q.v.), which are not at all related structurally. A large number
of lizards belonging to widely different families have taken to a more or less complete under ground life; and in these the limbs show reduction from a slight degree in some to en tire absence in others, for instance the boa-like glass-snake (q.v.). Many species are good swimmers, and are of aquatic habit to a large extent, but only one truly marine species is known — the large, gregarious sea-lizard (Am blyrhynchios) of the Galapagos Islands, which feeds on seaweed, gathered at a considerable depth; yet it is reluctant to take to the water except for food. The American iguanas, how ever, although reside': s of tree-tops, stay as near to rivers as they can and plunge into them for safety whenever frightened.
Lizards are primarily terrestrial animals, and most sorts run with amazing swiftness, usually on all four feet, but the curious frilled lizard (q.v.) of Australia holds up its fore parts and runs on its hind legs when in haste. Except a few heavy forms, and those that dwell in burrows, lizards are extremely agile, climb ing walls and tree-trunks, and running and leaping about their branches, with speed and precision; and some Oriental species, as the flying dragon (q.v.), have . expansions of the skin about the forearms enabling them to make long, sailing leaps through the air.
The senses of sight and hearing are highly developed, as is requisite for their livelihood. Most species are carnivorous, the larger kinds feeding on small mammals, birds and their eggs, and the lesser reptiles, including other lizards. These are seized by a rush and leap, and are passed down the throat whole, Many of the smaller kinds live altogether on worms and insects, the latter caught in most cases' by a swift dart and recovery of the sticky tongue, a method peculiarly characteristic of the chameleons (q.v.). The tongue in this group assumes a wide variety of shapes, in some families having a slender, forked form' like that in snakes, and acting only as a feeler: One lizard only, the Gila monster (q.v.), is aided by the injection of poison into its victim when he bites it, and this is the most sluggish of all its race. The iguana family and certain other species eat vegetable food.