i8o 



VERTEBRATE ANIMALS OF THE UNITED STATES 



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

 and a nictitating membrane. Most lizards possess the vestiges of\ 

 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. 



nhJTL 



ILJclL SL 



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

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

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

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

 fro7n Cope), 



The tongue is well developed and usually protractile, and may be bifid 

 or not. The tail is mostly long and fragile and easily broken off; it 

 grows again, but the lost vertebas are not regenerated. jMost lizards 

 lay eggs; a few are ovo viviparous. 



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 

 vegetarians. Metachrosis is common, and in some species, as the 

 chameleon, very remarkable. About 2,700 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 g families. 



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

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



