5. SAUROMALUS 95 



ported by Belding from Guaymas, Mexico, probably indi- 

 cates its occurrence in Sonora. 



Remarks. This species is very similar to S. ater. It 

 differs chiefly in the larger and more strongly keeled scales 

 on the limbs. 



12. Sauromalus interbrachialis Dickerson 

 ESPIRITU SANTO ISLAND CHUCKWALLA 



Sauromalus ater YARROW, Bull. U. S. Nat. Mus., No. 24, 1883, p. 51 

 (part) ; BELDING, West American Scientist, Vol. Ill, No. 24, p. 97. 



Sauromalus species STEJNEGER, Proc. U. S. Nat. Mus., Vol. 14, 1891, 

 p. 409; VAN DENBURGH & SLEVIN, Proc. Cal. Acad. Sci., Ser. 4, 

 Vol. 4, pp. 132, 148. 



Sauromalus interbrachialis DICKERSON, Bull. Amer. Mus. Nat. Hist., Vol. 

 XLI, 1919, p. 463 (type locality, La Paz, Lower California, 

 Mexico); NELSON, Mem. Nat. Acad. Sci., Vol. XVI, 1921, pp. 

 114, 115, 171. 



Description. Head and body large, much depressed, 

 the latter very broad. Head almost triangular, with nar- 

 row rounded snout, and covered with small plates largest 

 on frontal and temporal regions. Nostrils opening upward, 

 outward and slightly backward, in rounded plates a little 

 nearer to end of snout than to orbits. Superciliaries like 

 supraoculars, small and juxtaposed. Suboculars all short, 

 but slightly keeled. Rostral plate very small. Labial 

 plates small of about equal size. Symphyseal plate 

 long but very narrow. Several series of slightly 'enlarged 

 sublabials, passing gradually into the finely granular gulars. 

 Gular fold covered with very small scales. Ear-opening 

 large, almost vertical, with strong anterior ,denticulation of 

 spinose scales. A strong fold on each side of neck, bear- 

 ing numerous spinose tubercles. Scales on back and sides 

 small, largest medially and on strong lateral fold, smooth 



