1 40 Bulletin of Laboratories of Denison University [Voi. xi. 
pores; males with enlarged preanal plates; lateral teeth tricus- 
pid; pterygoid teeth; no sternal ribs ; no sternal fontanelle. 
These large and very active lizards occur in the southwest states 
and northern Mexico. They are predaceous and even cannibal 
in their habits. Two species are known to occur in New Mexico. 
Crotophytus Wislizenii, Baird and Girard- 
Crotophytus wislizenii, Bd. and Gd. Proc. Acad. Sci., 
Phila., 1852; Stanisbury’s Exp. Salt Lake, 1853; Baird, Mex. 
Bound. Surv. 1859; Botdenger, Cat. Liz. Brit. Mus. ; Van Den- 
burgh, Bui. Cal. Acad. Sci. V. 
Crotophytus gambelii, Baird and Girard, /. cit. 
Description : Body slender and strong ; head large, de- 
pressed and broad behind; head plates small, larger toward the 
snout; snout convex; three to five longitudinal rows of shields 
between the supraocular regions; nostrils nearer the end of 
head than the orbit; superciliaries small, imbricate; a long sub- 
ocular plate; rostral plate very low; supralabials of nearly equal 
size; lower labials somewhat larger than the upper, bordered 
below by several series of small plates larger than the gulars; 
symphyseal plate large; tympanic opening large oblique; one 
strong gular fold with sometimes two additional ones; back and 
sides covered with small granules merging into the larger scales 
of the belly; latter imbricate and sometimes keeled; irregular 
lateral dermal folds; tail cylindrico-conical, more than twice as 
long as the head and body; males with enlarged postanal plates. 
Color: Upper parts browish gray, the head darker, with 
creamy white lines surrounding the orbits and in the supra- 
ocular regions and the snout; back crossed with alternating light 
lines; between each pair of which a round spot of brown; the 
proximal part of tail like the back, the distal part ringed with 
dark; upper surface of limbs marbled or spotted. With age 
the spots on the back break up, the bands disappear or become 
more marked and the whole color fades. No two specimens 
are exactly alike. There is a change during the breeding sea- 
son, especially in the females, 
