362 3. IGUANIDM 



Remarks. One specimen has the frontoparietal separ- 

 ated from the supraoculars, and one has the anterior frontal 

 in contact with these plates. The cross-bars on the limbs may 

 be absent. 



This species and S. magister have been confused by 

 many herpetologists. Dr. Stejneger pointed out the chief 

 differences between these lizards. These differences are 

 in the length and shape of the scales forming the auricular 

 denticulation and in the coloration. Although these differ- 

 ences are not great, they are constant and the two species 

 may be distinguished readily. The ranges of the two over- 

 lap in the vicinity of Tucson. S. clarkii alone has been 

 found in Cochise and Santa Cruz counties, and only S. 

 magister in western Arizona, California, Nevada and Utah. 



Distribution. This lizard has been recorded from 

 Arizona, New Mexico, western Texas, and northern Mexico. 

 The localities given by Cope and Yarrow, with a few excep- 

 tions, cannot be considered reliable until the specimens have 

 been re-examined, for these authors did not distinguish be- 

 tween S. clarkii and S. magister. 



Reliable Arizona records indicate that this species prob- 

 ably is confined to four or five counties in the southeastern 

 part of the state. It has been collected in Graham (Fort 

 Grant), Greenlee (Clifton), Cochise (Paradise, Rucker 



