The skin of lizards, like that of snakes, is nor mally covered with scales, the thin, horny coat ing of which is shed periodically; but the amphis bamas have nearly lost all scales, and the glass snake (Anguis) sheds its skin in one piece. In many eases, however, the scales are not typical, but appear as little tubercles (osteoderms), such as are seen in the geckos and Gila monster, so that the whole skin looks granular or 'pebbled'; or these dermal ossifications may be confined to the scales or shields of the head, as in the Lacer tile. The skin is entirely devoid of glands, al though certain minute excretory organs lie under the cutis of the thighs. Lizards vary greatly in color; the numerous desert-dwelling forms are, as a rule, of dull hue, and capable of little change, while forms dwelling in forests or grassy places are often highly colored, and have great power of metachrosis, as is familiar in chameleons. The ehromatophores, according to Gadow, are im bedded in the deeper layers of the cutis, and send out movable contractile processes, in which their pigmental protoplasm is conveyed toward or away from the surface. Black, red, yellow and white, with their combinations of gray and brown, are the usual colors. The white pigment is made up of guanin salts. Blue and green are structural colors which are not traceable to pigment. (For the method of service of these voluntary color changes in adaptation to surroundings, see META cunoSts.) In addition to protective coloration, some lizards are defended by horns and spines, which sometimes cover the entire body, as in the horned toads and the inoloch (qq.v.), and some times grow only upon certain parts, most fre quently the tail. Others have defensive or men acing appendages and corresponding habits, such as are manifested by the frilled lizards, the basi the iguana, and others that make them-. selves look terrifying, when in fact, like all the rest (except Heloderma), they are harmless.
Lizards are found in all the warmer regions of the earth: their northern limit is about the annual isotherm of 50° F. .(See Slap under
DISTRIBUTION OF NIAIAI.S.) They are most numerous in tropical and warm countries; none occur in polar lands. In temperate regions they pass the winter in a state of torpidity concealed under ground and di•bris, or in hollow trees. Many are restricted to deserts, and have acquired interesting adaptations for resisting the blowing sand and otherwise withstanding the hardships of a hot and barren habitat. Other families are arboreal, or dwell among rocks. One species (of the Galapagos Islands) is marine, and several African and Oriental lizards are more or less completely aquatic. Most of these swift and agile reptiles are insectivorous, but some are carnivo rous or even cannibalistic, and certain sluggish forms, as the iguanas, are herbivorous, and their flesh is palatable and nutritious for human use. The eating of noxious grubs and insects is a val uable service by lizards to man; and these little animals furnish food for a great variety of Other reptiles, birds, and beasts of prey.
CLAssmeArmx. The lizards are regarded by recent authorities as one of two sections (the other being the snakes) of an order of reptiles, usually called Squamata. Pr. Gadow in a late (1900) review of the matter regards the lizards as an order (Antosauri, or Lacertilia), divisible into three sections: (1) tfrekones(vertebne amphicielous) contains the family Geckonidm, comprising the geckos proper (Geekonime), the Eublapharime, and the Uroplatinx. See GECKO.
(2) Lacerter (vertebrae proccelous) contains the ordinary lizards—agamas, iguanas, African zonu rids, glass-snakes, heloderms, monitors. South American tejids, typical Old World lizards (Lacertithe), skinks, and several small families including the degraded aniphisbenas and snake like aniellids of California and the pygopodes of Austr 'ia.
(3) Chamo.lrontes—a single family with 50 or 60 species. See CHAMELEON.