126 Bulletin of Laboratories of Denison University [Voi. xi. 
Color : back grey, yellow or brown, with indistinct mot- 
tlings of brown anteriorly ; a black bar or collar in front of each 
shoulder ; head nearly uniform ; faint brownish rings on the 
tail ; central patch of blue on throat of adult males ; lateral 
band of blue bordered with black ; a dark area in front of 
thighs ; under parts white or yellowish. 
Measurements: Total length, 194mm.; Length to anus, 
85 mm.; Lengh of tail, 109 mm.; Snout to ear, 20 mm.; Width 
of head, 18 mm.; Fore leg, 39 mm.; Hind leg, 54 mm.; Base 
of fifth to end of fourth toe, 23 mm. 
ScelopuS Clarhii, Baird and Girard, Proc. Acad. Nat. Sci. Phil. 1S52. 
Baud, U. S. and Mex. Boundary Surv. , 1859; Cope, 
Proc. Acad. Nat. Sci. Phil., 1866; Cope, Check List, 1875. 
Coues, Synopsis of the Reptiles of Arizona, 1875. (Fig.) 
Yafrow, Check List of N. Am. Reptilia, 1882. Stejniger, N. 
Am. Fauna, No. 7. Van Denhurg, Cal. Acad. Sci., V. 
The relation between this species and Sceloporus magister, 
which is confessedly very close, has been discussed in extenso, 
in N. Am. Fauna, No. 7, by Stejniger, who claims that the 
two species are constantly distinguished by a difference in the 
spines guarding the ear openings ; these modified spines being 
smaller and less acute in S. clarkii. There is said to be a differ- 
ence in habit also and although the habitats overlap in south- 
eastern Arizona, the stations affected by the two species are said 
to be different, S. magister affecting an arboreal life while S. 
clarkii is found upon the rocks. It is probably that this species 
will be found in the extreme south-western part of the territory. 
The species extends into Mexico an unknown distance. 
Farther south, it is said to be replaced by S. boulengeri, which 
is similar to S. clarkii but has fewer femoral pores, short and 
broad ear spines and a very broad interparietal. S. acanthinus 
is said to be modification of the same type still further to the 
south. 
