In some the throat has two cross-folds, with large six-sided scales within; and of these some have the ventral shields small, long, and smooth, while others have them much broader. The former are known as the Teguexins (_Teius_ and _Callopistes_), and the latter as the Ameivas (_Ameiva_, and three other genera). One species of Teguexin, _Teius teguexin_, may commonly be seen alive in the London Zoological Gardens. This is a large and powerful Lizard, exceeding five feet in length when full grown, and extremely active. It feeds on small living animals of any kind, and will even devour poultry, and especially their eggs, for which latter it manifests an especial liking, as observed in captivity. Sometimes it has been known to prey on other and kindred Lizards, as the Ameivas. The teeth of this species are strong, and the reptile can bite with great force. It is a bold and determined combatant when attacked, and if it succeeds in seizing its foe, retains its hold with pertinacity. Its flesh is eaten by some people, who consider it excellent. Together with a second species, _T. nigropunctatus_, it inhabits Brazil, and the two species of _Callopistes_ are also South American, one at least of them occurring in Chili. The species of this family, although strong and agile, never ascend trees, but range at will the hot sandy plains or the dense and damp underwood on the margins of lakes and rivers, into which they plunge when alarmed, and remain below the surface until the danger has passed away, their capacious lungs and imperfect circulation permitting them to endure a very long immersion without inconvenience. The Ameivas have a long whip-like tail, and peculiarly elongated toes on their hind feet. The species of _Ameiva_ and _Cnemidophorus_ are numerous, and the genera _Dicrodon_ and _Acrantus_ are founded each of them upon a single species. In general these are Lizards which correspond with the ordinary _Lacertidæ_ of the Old World. One species only, _Cnemidophorus sex-lineatus_, inhabits the Southern States of North America; there are at least four others in Mexico, and the rest belong to South America and the Antilles. "The _Ameiva dorsalis_," writes Mr. Gosse, "is one of the most common of the reptiles of Jamaica, and is as beautiful as abundant. Its colours are striking, but not showy, and its countenance has a very meek expression. All its motions are elegant and sprightly; when it is proceeding deliberately, its body is thrown into latent curves the most graceful imaginable; but when alarmed its swiftness is so excessive that it appears as if it literally _flew_ over the ground, and the observer can scarcely persuade himself that it is not a bird. It is very timid, and though its toes are not formed as in the Geckos and Anoles, for holding on against gravity, I have seen a large Ameiva run with facility on the side of a dry wall, along the perpendicular surfaces of the large stones."