SAURIA IGUANIDAE UTA SYMMETRICA. 597 



taken in the desert of the Gila by Mr. Arthur Schott. No specimens are 

 contained in my collections. 



'22. Uta ornata, Bd. & Gir. 



Uta ornata. BD. & GIR., Proc. Acacl. Nat. Sci. Phila., 1852, 120. BD., U. S. & Mex. 



Bound. Snrv., ii, pt. ii, 1859, Reptiles, 7. COPE. Clieck.List, 1875, 48. 

 Uta ornata var. linearis, BD., I. c. (Los Nogales). 



Obtained by the naturalists of the United States and Mexican Bound- 

 ary Survey at various points along the line, and therefore properly to be 

 included in the present connection. 



?Uta symmetrica, Bd. (=ornataf) 



Uta symmetrica, BD., Proc. Acad. Nat. Sci. Phila., 1858, p. . Id., U. S. & Mex. 



Bound. Surv., ii, pt. ii, 1859, Reptiles, 7. COPE, Proc. Aead. Nat. Sci. 



Phila., ISC'), 303. 



" Larger dorsal scales in four regular series, two on either side of the 

 median smaller ones ; head short, depressed, one and a half times as wide 

 as deep ; tail one and a half times the head and body ; general color light- 

 brown above, the belly white ; sides with broad transverse bands of black- 

 ish ; size of U. ornata. Gila River." (Saird.^) 



The above description may be supplemented with a statement of the 

 great variation in coloration during life of different specimens, as observed 

 by me. This variation, which I have no reason to presume to be confined 

 to the present species of the genus, is mainly dependent upon the character 

 of the rocks 'which the animals frequent. Out of great numbers of speci- 

 mens procured in one locality, namely, Bero Springs, near Fort Wingate, N. 

 Mex., and unquestionably the same species, almost the only color mark com- 

 mon to all was the pale yellow throat. Some were plain silvery-white be- 

 low, others were bright greenish-olive on the belly. Above, the color ranges 

 from a deep grayish-black, to a dull grayish-brown with dark lateral streak. 

 I satisfied myself that the same individual assumed these different colors 

 according to the kind of rocks it happened to be upon. The blackish speci- 

 mens were invariably found upon dark lava rocks, the lighter ones upon 

 yellowish sandstone. We have here an interesting case of protective assimi- 

 lation. The same thing has been noted by Dr. H. C. Yarrow, as this gentle- 

 man informs me, in other cases, and it is doiibtless of more general occur- 

 rence than has been fully recognized by naturalists. The common Fence 



