IGUANID^E. LXXI. 169 



with overlapping scales; mouth not dilatable; tongue 

 free; jaws always with teeth. Limbs four, distinct, 

 rarely rudimentary and hidden by the skin ; a pectoral 

 arch developed. Feet usually with five digits, the 

 phalanges normally 2, 3, 4, 5, 3 or 4. Tail usually long 

 and in many cases very brittle, readily broken by a 

 slight blow; this is owing to a thin, unossified, trans- 

 verse septum, which traverses each vertebra. " The 

 vertebra naturally breaks with great readiness through 

 the plane of the septum, and when such lizards are 

 seized by the tail, that appendage is pretty certain to 

 part at one of these weak points" (Huxley). Vent a 

 cross slit; urinary bladder present. The great majority 

 of the numerous species belong to tropical and sub- 

 tropical regions. 



FAMILY LXXL IGUANID^E. 



(The Iguanas.) 



New World lizards of various habits; the tongue short 

 and thick and the eyes diurnal with round pupils; scales 

 imbricated, those on the belly small and rhombic. Feet 

 for walking; toes unequal. Tail with more or less dis- 

 tinct whorls of scales, which are commonly spinous. 

 Warmer parts of America. Genera about sixty; species 

 one hundred and fifty, or more. (Gray.) 

 * Body moderately depressed ; head broad, not spinous ; ventral 



plates not keeled SCELOPORUS, 1. 



** Body much depressed ; head armed with stout spines. 



PHRYNOSOMA, 2. 



/. SCELOPORUS, Wiegmann. TREE SWIFTS. 



= Tropidolepis, Cuvier. 



1. S. undulatus, (Harlan ) PINE TREE LIZARD. 

 SWIFT. Greenish, bluish, or bronzed, with black, wavy 

 cross bands above ; throat and sides of belly usually with 

 8 



