1 20 Bulletin of Laboratories of Denison University [Voi. xi. 
11. No dorsal crest. 
A. Head without spines, 
a. One or more transverse gular folds. 
b. Toes with a lateral fringe of movable spines, . Uma. 
bb. Toes without spines. 
c. Supralabial plates strongly imbricated; symphyseal 
plate smaller than the largest infralabial. 
d. An ear opening, . . . Callisamus. 
dd. No ear opening, . . . Holbiookia. 
cc. Supralabials not imbricated ; symphyseal not smaller 
than the largest infralabial. 
e. No large interparietal plate ; caudal scales small, 
not strongly keeled or pointed, 
f. Ear without strong denticulations and neck with- 
out spinose tubercles ; supercilaries imbricate ; 
tail long and tapering, . . Crotophytus. 
ff. Ear with strong denticulations and neck with 
numerous spinose tubercles on lateral folds; super- 
cilaries not imbricate ; tail scarcely longer than 
distance from snout to vent, . Sauromalus. 
ee. A very large interparietal plate ; caudal scales 
large, strongly keeled, and sharply pointed, Uta. 
aa. No complete transverse gular fold, . Sceloporus. 
AA. Head with large spines posteriorly, . Pluynosoma. 
Genus. Dipsosaurus. 
The single species of this genus, Dipsosaurus dorsalis, Bd. 
and Gd., has been found in the Colorado and Mojave Deserts 
and is abundant in the neighborhood of Yuma. It probably 
does not occur within our limits. It is entirely vegetarian in 
habit. 
Genus. Uma. 
4 
The two known species of Uma are not known to occur in 
our region, they being, like the last and the following, desert 
loving animals. 
Genus. Callisaurus. 
Callisaurus ventralis, the only species, within the United 
