REPTILES 



191 



Order 2. 'La.certiMa. (Sauria). Lizards. Elongated reptiles whose 

 bodies are covered with scales, and with usually two pairs of penta- 

 dactyle limbs and a transverse anal opening. The head is of firmer 

 structure than in the snakes, the two halves of the lower jaw being 

 immovably bound together and the upper jaw being firmly joined with 

 the cranium ; the quadrate bone is, however, movable as in the snakes. 

 The tympanum is not at the surface, and the ear-opening is often pro- 

 tected by special scales. The eye has a upper and a lower lid and a 

 nictitating membrane. Most Hzards possess the vestiges of a pineal 

 eye, which often appears on the top of the head just back of the paired 

 eyes. Teeth are always present and are either acrodont or pleurodont, 



and are often present on the gums as well 

 as the jaws. The tongue is well developed 

 and usually protractile, and may be bifid 

 or not. The tail is mostly long and fragile 



r^IciL 6^L 



Fig. 99. — Head of a lizard {Plestiodon fasciatus): a, dorsal view; b, lateral view: F, 

 frontal; FP, frontoparietal; laL, infralabial; Ifn, interfrontonasal; IL, lower labial; In, 

 internasal; IP, interparietal; L, loreal; N, nasal; Oc, occipital; P, parietal; Pef, prefrontal; 

 PL, preloreal; R, rostral; Sc, superciliary; SL. upper labial; Soc, supraocular; T, temporal 

 from Cope). 



and easily broken off; it grows again, but the lost vertebrae are not 

 regenerated. Most lizards lay eggs; a few are ovoviviparous. 



Habits and Distribution. — Lizards feed mainly on insects and worms^ 

 and are mostly active, terrestrial animals. The larger species feed also 

 on birds, small mammals and eggs. A number of species are vege- 

 tarians. Metachrosis is common, and in some species, as the cham- 

 eleon, very remarkable. About 1,300 species are known, which inhabit 

 the warmer regions of the earth. About 100 species are known in this 

 country, ranging, in one or two cases, as far north as Canada: they are 

 grouped in 10 famihes. 



On the Identification of Lizards. — The size and general form, 

 whether elongate or not, or large or small, are first to be observed. 



