190 BULLETIN 15 4, UNITED STATES NATIONAL IMUSEUM 



In western Colorado Cary (il>Ll, p. '2ij) considered tlie arid '" Lower 

 Sonoran Zone " as its center of abundance, for here he found it 

 only in the hottest and lowest desert valleys. 



In referring to this subspecies in Nevada, Taylor (1912, p. 331:) 

 cites it as breeding in the " Lower Sonoran " elsewhere (referring to 

 Cary, 1911) and as "probably breeding in the Upper Sonoran" of 

 Nevada (Grinnell and Storer, 1924. p. 632, definitely assigned it to 

 the Upper Sonoran of the Yosemite region of California). Per- 

 haps it is simply restricted to the lower levels of the mountains. On 

 the sides of the dry Avashes and on the open, flat deserts in the vicinity 

 of the foothills, Taylor found the tessellated lizard in small num- 

 bers up to an altitude of 5,000 feet on the low ridges (Humboldt 

 County). Kuthven {1915h, p. 950), also working in Nevada, found 

 it only on the floor of Maggie Basin. He therefore considered it a 

 ground form confined to areas of fine soil. 



According to Kuthven (1907, p. 563) the habitat of this lizard at 

 Alamogordo, New Mex., is very well defined. Examples were rather 

 definitely restricted to the " Creosote bush association " on the allu- 

 vial slopes, where they were almost as characteristic of the area as 

 the creosote bush itself. On the greasewood plains at Tucson, Ariz., 

 he found the desert whiptail to be common and generally distributed. 

 It was also seen on the mesas, but more often in the " creosote bush 

 association " in the arroyos, and much less commonly in the " Sua- 

 liai'o-Ocotillo association " of the hills. Working in the same general 

 ]-ogion, Ortenburger and Ortenburger (1926, p. Ill) collected a 

 large number of these creatures and reported on the most of them 

 as " melanostethus " and on only a few of them as tesselJatus. In 

 regard to the latter, they stated that this was the least common form 

 of Cnemidophorous that they found. They took only three speci- 

 mens and " all of these were collected some distance up the canyons 

 in the foothills of the Santa Catalinas; that is, from 2 to 3 miles 

 from the desert floor." This seems to indicate (as elaborated above, 

 p. 174) that the presence or absence of a ventral suffusion of black 

 is correlated with the type of environment, the lighter form inhabit- 

 ing the more mountainous and less sandy districts, and the darker 

 form (often called " iiielcmostetJius ") the more sandy and less moun- 

 tainous parts. 



A remarkable uniformity in the type of habitat selected by these 

 lizards was observed by the writer in the summer of 1928 from 

 Western Texas to Eastern California. In general the areas with the 

 loosest soil supported the greatest numbers of individuals, and those 

 regions in which the soil was hard or packed relatively few of them. 

 Specimens taken in lieeves and El Paso counties, Texas, were all 

 found in somewhat sandy areas where they were afforded protection 



