62 3. IGUANID.^ 



dilated, except in the Central American Basiliscinse. Some 

 species of Sceloporus and Phrynosoma are ovoviviparous. 

 The iguanians of the area we are considering may be distin- 

 guished by the following: 



Synopsis of Genera 

 a. — A dorsal crest composed of one longitudinal series of 

 enlarged scales. 



b. — Tail with whorls of strong spinelike scales. 



Ctenosaura. — p. 64. 



b'. — Tail without enlarged strongly spinose scales. 



Dipsosaurus. — p. 71. 



a". — No dorsal crest. 

 bb. — Head without spines. 



c. — One or more well developed transverse gular 



folds; or a lateral fold between limbs. 

 d. — Superciliaries not imbricate. 



Ear with strong denticulation and neck with 

 numerous spinose tubercles on lateral folds; size 

 very large; tail scarcely longer than distance from 

 snout to vent. 



Sauromalus. — p. 84. 



d'. — Superciliaries imbricate. 



e. — Supralabials strongly imbricate; symphyseal 



plate smaller than largest infralabial. 

 f. — Interparietal plate much smaller than ear- 

 opening; toes fringed laterally with prominent 

 movable spines. 



Uma.— p. 131. 



i'. — Interparietal plate larger than ear-opening; or 

 toes without later fringe of long spine-like 

 scales. 

 g. — An ear-opening. 



Callisaurus. — p. 138. 



