156 BULLETIN 15 4, UNITED STATES NATIONAL MUSEUM 



and concentration of the dark pigment on the upper surfaces in- 

 stead of the lower ones. The resulting intensification of this pigment 

 is accompanied by a better definition of the light sections of the color 

 pattern. Here, in the upper levels, the under surfaces are usually 

 white, often wnth only a few black spots, which, however, are usually 

 well developed and prominent, although at times absent. In this 

 environment the lizard is conspicuous only when viewed on an 

 extensive, unicolored background. 



Some discussion in support of the general views just expressed 

 occurs in the literature. In the region of Death Valley there is a 

 great deal of variation in the amount of black markings and in their 

 intensity (Stejneger, 1893). "The dorsal pattern is quite distinct 

 in some, while in others it looks as if it had faded out. On the 

 otlier hand, the black suffusion of the throat and breast is equally 

 variable, but neither sex, age, season, nor locality seems to account for 

 this variation, except that is is usually absent in the youngest." 

 Ivater writers have agreed with Stejneger in general, but evidence 

 of local variation was advanced by Meek (1905, p. 13) wdio found 

 that "Individuals of this species living in sandy areas are mucli 

 lighter than those living in the mountains." Another conclusion of 

 the same sort is suggested by Gadow (1906, p. 370), who wrote, 

 while synonymizing stejneffcri with tesseUatu<s, that " It would be 

 interesting to ascertain to what extent the more distinctly striped 

 individuals coincide in their habitat with those districts which are 

 decidedly not deserts, as in Texas {f/rahamil) and California [mun- 

 dus and 8teinegGri)P As outlined above and maintained below, this 

 coincidence is here held to be very striking. 



Examples from sandy areas in the Turtle Mountains of south- 

 eastern California have the dorsal markings almost obliterated, as 

 noted by Camp (1916, p. 529), while those from the higher levels are 

 darker and with much more distinct dorsal markings. Both in 

 specific localities and in general regions this tendency seems to hold 

 and, as found by Atsatt (1913, p. 39), "On a general survey of 

 masses of material one feels that the effect of the environment upon 

 the individual has been great." Quoting further, we find that 

 " Associated with the dryness and intense light of the desert environ- 

 ment there seems to be a sharp contrast in the extremes of light and 

 dark in the color patterns of the reptiles. With the colors of the 

 yellow, buff and brown sands of the higher levels and of the Pacific 

 area the ground hues of Phrynosoma hlahivUJii hJainvilUi^ Cnemido- 

 phorus stejnegeri, Lampr^opeltis getidus hoylil and Grotalus t'uber 

 harmonize, while the patterns themselves have the darker shades of 

 that group of colors. In the yet higher altitudes * * * where 

 the light is subdued by the large amount of shade and the dark colors 

 of the foliage and where the air is more humid, the darkening of 



