192 VERTEBRATE ANIMALS OF THE UNITED STATES 



together with the length of the head, body and tail in millimeters and 

 that of the tail alone. The color markings are also important, but it 

 must be remembered that many hzards are extremely variable in color, 

 as well as exhibiting metachrosis in a high degree. Young animals 

 also often differ totally from the adult in coloration. The character 

 of the scales or plates and the differences between those on the back and 

 the belly are sometimes important, as well as the number of transverse 

 and longitudinal rows. Those immediately in front of the anus are 

 often of characteristic form and number. The plates on the head are 

 usually characteristic and a description of them often enters into a 

 detailed description (Fig. 99), the supraocular scales over the eye, and 

 the upper and lower labials, which bound the lips, being especially 

 important. The character of the tongue is also usually to be noticed; 

 in some families it is thick and little protractile, in others it is similar 

 to the tongue of snakes and may be projected from the mouth as 

 an important tactile organ. In most lizards a row, sometimes double, 

 of conspicuous pores is present on the inner surface of the thigh; 

 they are the femoral pores (Fig, 103). The teeth are usually conical 

 and are never set in alveoU, but become ankylosed usually to the 

 bone of the jaw, either by their base to the edge of the jaw bone, 

 when they are spoken of as acrodont teeth, or by their side just inside 

 the edge of the bone, when they are called pleurodont teeth. 



Key to the Families of American Lacertilia 



ai Legs present. 



h\ Skin soft, with minute granular scales. 



Ci Eyes like those of snakes, without functional eyelids ... i. Gctikonida: . 



02 Eyehds present 2. Euhlepharidce. 



hi Skin usually scaly. 



Ci Tongue thick and not protractile 3- Iguanida. 



C2 Tongue protractile. 



di Conspicuous lateral fold present 4- AnguidcB. 



do No such lateral fold. 



ei Body large and thick; no femoral pores 6. EelodermatidcB. 



62 Body very small and slender; femoral pores 

 present or not. 

 f 1 Femoral pores present. 



gi No movable eyelids; pupils vertical. ... 7. Xantusiidce. 



g2 Eyelids movable; pupils round 8. TeiidcB. 



ii Femoral pores absent 9- Scincida. 



Ki Legs wanting; body vermiform. 



bi No scales present; eyes concealed 10. LeposternidcB. 



bo Scales present; eye a narrow slit 5- AnniellidiB. 



