LIZARD (OF. lizard, lizard, Fr. laard, Sp., Port. lagarto, It. laccrta, lizard, from Lat. lacer tus, lactrta, lizard). A reptile of the order I..acer Ulla or Autosauria, characterized structurally by the fact that the halves of the lower jaws are connected by symphysis, that is, fused solidly together in front, while those of serpents are connected by an elastic band; and by the fact that the teeth are fixed. 'the vertebra are prooe lous (except in most of the geckos). and have 'intercentra,' espeeially in the tail. The eaudal of most forms have a transverse septum of cartilage, forming a line of weakness—the point where the tail breaks oil, as frequently hap pens. The ribs of the trunk articulate by their capitula only, the reduced tubercula being con nected with the by ligaments. In some groups the post-sternal ribs meet in the median abdominal line, forming bony loops; in the (ly ing dragons. ;he ribs support wing-like ex pansion. Most lizards are provided with fully developed limbs and five-toed feet; but the feet are modified in the chameleons (q.v.), and in some degraded forms, as the glass-snake and especially the amphislnena (q.v.), which burrow, the limbs have been lost not only externally but in some eases the pelvic and pectoral girdles have completely disappeared, accompanied by an elon gation of the body, so that these lizards are serpent-like in form and manners. The skull is modified principally in the composition of the temporal arches; the quad rate bone is movable except in the degraded families. The hyoid appa ratus, extended into the tongue. is always present and well developed. In the Old World lizards the teeth are planted along the top of the ridge of the jaw (aerodont), while in the New World species they arc fastened to the inner side of the ridge (pleurodont). In one American genus (Teius), the teeth of the yonng are pleurodont, but in the adult they become acrodont. The tongue is variously developed, but is always fur nished with many tactile or with gustatory cor puscles. When the tongue is very long and nar row, it is generally forked, and in such cases, for example in the monitors, it is used almost en tirely as a sensory organ. In most lizards it assists in catching the food, and in some families is an elaborate instrument. Salivary glands are wholly labial, and in a single genus (IIelo derma ) become poison-sacs. The digestive organs present little peculiarity, except in the cloaca, which is much modified in correlation with the strange copulatory apparatus, consisting of paired organs external to the cloaca, each a tube of erectile tissue, which can be everted like the finger of a glove. When at rest and withdrawn,
the organs form slight conical longitudinal swell ings on either side of the root of the tail. Only one organ is inserted at a time. Most lizards lay eggs, in some cases having a hard shell, but more often a parchment-like covering. The em bryos are usually much advanced before the extrusion of the egg, and some species, as the American horned toads, are practically vivipa rous. The embryos within the hard-shelled eggs hare an 'egg-tooth' or hard point upon the end of the snout, to assist them in breaking out. Certain mysterious organs beneath the ventral skin, largely composed of fat, and hence called 'fat-bodies' (consult Butler, Proceedings of the Zoulogical Society of London, 1SS9), seem to be related to the sexual functions. Lizards (except degraded subterraneous forms) have good ears and eyes, the latter with movable eyelids (except in geckos) and a nictitating membrane; but des ert-dwelling and other unusual forms have spe cial adaptations elsewhere spoken of, e.g. under CHAMELEON. Binocular vision, of course, does not occur here, any more than in other animals whose eyes look sidewise.
Externally, lizards assume a great variety of shapes, from the toad-like proportions of the moloch to the vermiform aspect of an amphis bama; but usually the head is shapely, the neck apparent, and the tail long and distinct. The tail, indeed, is of much importance in many eases as a whip-like weapon, or as a means of safety by the ease with which it breaks oil' when seized, thereby giving the animal a chance to escape. By some species it is voluntarily thrown off in such an emergency, enabling the lizard to run to a refuge while the surprised foe is occupied with the east-off and wriggling tail. Such lizards have the power of regenerating a tail, or rather a substitute for one, since the new tail contains in place of real vertebra only a non-segmented rod or tube of fibro-cartilage. In most of the higher lizards the muscles, skins, and scales are reproduced, but among a variety of lower forms the scaling is abnormal, and is sometimes a reversion to an ancestral form. Consult Bou longer, Proceedings of the Zolilogica[ Society of Lando7), 1888, page 351; and id., 1891, page 46t. See REGENERATION.