138 BULLETIlSr 15 4, UNITED STATES NATIONAL MUSEUM 



significant that the only specimen taken in a dry arroyo at Tucson 

 is a ' medium sized ' indiA^idual with botli striiDes and spots, Avhile 

 the largest specimens were only found in the willow-poplar associa- 

 tion along the streams." Working in the same general region, 

 Ortenburger and Ortenburger (1926, p. 110) found fevplexus. to be 

 " almost as common on the tops of the foothills as down in the can- 

 3'On. In very few^ cases was this species found as far down as the 

 wide sandy washes at the mouths of the canyons where it is replaced 

 by Tiielanostethus { = tessellatus). In general, the local ranges of 

 these tAvo forms do not overlap." While collecting in southern 

 Arizona, the writer found perpl earns in areas of sand and rocks in 

 which there Avas little vegetation. Eight miles north of Bernardino 

 it occurred in an open, barren space where its only protection was a 

 few scattered rocks and patches of short grass. Here it was asso- 

 ciated with Pht'iinosoma cornufuni and Ilolhi'oolda inaenlata approx- 

 imans. In the region of Old Fort Buchanan, two specimens were 

 taken as they were foraging near the top of a high, rocky bank that 

 had been cut for the roadbed below, and near Crittenden perplexus 

 was found in a mesquite thicket where the ground was covered by 

 sand and rocks. 



Thus, the Sonoran race runner may be regarded as an inhabitant 

 of the transitional rock-sand zone. An area of much fine sand, 

 although preferred by tessellatus, is apparently not selected by per- 

 plexus^ and the presence of too many rocks seems also to restrict its 

 distribution. In this manner pcrplexns has avoided the fine sand of 

 tlie lower districts and the rocks of the higher altitudes, becoming 

 confined chiefly to the foothill region. 



General hehavior. — The Sonoran lizard is an excee(Hngly timor- 

 ous animal, as described by Cones (1875, p. 603), and it darts out 

 of sight at the least alarm. '* It is one of the very swiftest of its 

 agile tribe and the eye can scarcely follow it while running at its 

 best on level ground." " It is a ground-dwelling form, and seems 

 not to be able to climb," according to Woodbury (li>28, p. 18), who 

 added that " When disturbed it will dart for shelter to a near-by 

 bush or plant. After a rain one was seen to run into a puddle of 

 muddy water to hide.^* When picked from the pool it lay limp 

 and motionless, but it was, however, ready to spring into action at 

 the first sign of relaxation of the hold on it. One of the rangers 

 reports seeing one of these lizards outrun a Crotaphytus which was 

 chasing it." 



The general activity of perplexiis reminds one of its close rel- 

 ative, sexlineahis^ which occurs to the east. As in that species, the 

 maximum activity seems to be reached in the morning, when many 

 individuals may usually be seen in favorable habitats. 



^^ For ii similar observation in rogard to giihnis see p. 119. 



