REPTILES. 319 



tation of being poison. Most of them lay eggs enclosed in a leathery 

 shell. Most of the 1,200 living species are confined to the warmer re- 

 gions of the earth. The sub-order appears in cretaceous, but the fossil 

 forms are few. A natural classification of the sub-order is still a desid- 

 eratum. That adopted here, based primarily upon the tongue, associates 

 together widely diverse forms. 



Section I. VERMILINGUIA. Old-world lizards with vermiform, 

 highly extensile tongue ; tongue papillose, its enlarged tip sheathed ; body 

 covered with small chagreen scales ; tail coiling vertically, and used as 

 organ of prehension. No anal or femoral pores. Orbits closed behind 

 by process of jugal; teeth acrodont; no teeth on palatines. Feet with the 



Fig, 313. Head of Chamelon with the tongue extended. 



toes in two groups. Only genus, Chamcsleon, with about 30 species. The 

 chameleons are noted for their color-changes, a feature which is shared to 

 a marked extent by the American genus Anolis (Jnfrd). There are two' 

 pigment layers in the skin, an upper bright yellow and a deeper dark brown 

 or black layer. The pigment cells in these layers are under control of the 

 sympathetic system, and according as one or the other becomes prominent 

 the color of the animal changes. 



Section II. CRASSILINGUIA. Lizards with thick, short, fleshy 

 tongue, usually rounded at the tip (never strongly emarginate), not protru- 

 sible, papillose or smooth ; tympanic membrane usually free. Ascala- 

 ■&Qtm. or geckoes have the feet with adhesive disks on the underside, and 

 usually granular or spinose scales. Teeth pleurodont ; no teeth on pal- 

 atines or pterygoids ; a circular fold in place of eyelids. Vertebrae amphi- 

 coelous. The geckoes receive their common name from their cry. They 

 occur in all the warmer regions of the world except the northeastern part 

 of the U. S. Possibly the group should be more strongly marked off from 

 other forms. Phyllodactylus occurs in California. Other genera are Platy- 

 dactylus, Ptychozoon, and Ascalabotes ; 200 species known. All are in- 

 sectivorous and have great powers of climbing. Iguanid^, lizards 

 of considerable size, without adhesive feet ; body compressed ; limbs, 

 long and slender ; often a comb of spines on the back ; pleurodont teeth ; 



