230 3. IGUANIDM 



hind the axilla, and usually a brown patch in front of the 

 shoulder. 



Length to anus 44 45 46 46 48 50 



Base of fifth to end of 



fourth toe 12 12 13 13 12^ 12 



Remarks. Brown-shouldered lizards are probably more 

 generally distributed in western North America than any 

 other species. They range from Texas to the Pacific Ocean 

 and from Idaho and Utah to Cape San Lucas. In such 

 a vast area one might well expect to find geographic varia- 

 tion, and such variation has been described. A number of 

 insular forms have been named, and the mainland specimens 

 have been divided, by Richardson, into three subspecies. The 

 group, however, is a fairly compact one. Some of the in- 

 sular species are well differentiated, but the characters as- 

 signed to the mainland subspecies are average differences in 

 scale-counts and proportions which, to some extent at least, 

 are so concealed by individual variation that identification 

 of specimens by means of a "key" is most difficult and un- 

 certain. The whole group is in need of thorough study and 

 revision. It may be that such study would result in the dis- 

 covery that geographical races are more local and numer- 

 ous, and individual variations Jess important, than they now 

 appear. Color differences in these lizards can be of little 

 aid, for the same individual lizard has been observed to dis- 

 play a whole series of patterns from longitudinal stripes and 



