MAMMALS OF THE MEXICAN BOUKDAEY. 123 



Reptiles. — In February, 1894, we observed but few species of liz- 

 ards here, among them Uta stanshuriana Baird and Girard, Bcelo- 

 porus clarlcii Baird and Girard, and a horned toad (specimen No. 

 41) that assumed two very different phases of coloration — gray on 

 the granite debris around the base of the mountains and red on the 

 Lechuguilla Desert east of the mountains, where the soil was red. 

 Corresponding colorations w6re observed in the jack rabbits of this 

 region. By pulling hard the men extracted from the crevice of a 

 rock the tail of a huge lizard called the chuck-walla {Sauromalus 

 ater Dumeril) , respecting which Mr. Joe H. "\ATieeler wrote in April, 

 1893, from this place as follows : 



Lizards very large, 12 to IG inches in length ; with black heads and legs and 

 dirty or brick-colored backs and bellies ; tail of a dusty gray ; seen on highest 

 peaks of the Tinajas Mountains. 



Mr. Wheeler also noted dichromatism in the horned toad and the 

 occurrence of the tiger rattlesnake {Grotaliis tigris Kennicott) in 

 these mountains. 



Lieutenant Gaillard thus describes and figures one of two snakes 

 taken between the ranges of the Gila Mountains in April, 1893: 

 " I saw one in alcohol. It is about 6 inches long, and smaller around 



A R A T? A 



than a lead pencil. It is colored thus (i, q j g .): A, A, 



jet black bands entirely around the snake; B, B, splotches of red, 

 with pink edges." This was probably an individual of Ghilomenis- 

 cus ductus Cope, in which the natural coloring had not yet faded in 

 alcohol. I remember this species as appearing quite rgd in life. 



Station No. 64. — Yuma Desert, Monument No. 200, 835 Idlometers 

 (519 miles) west of the Eio Grande and 24 kilometers (15 miles) east 

 of the Colorado Eiver. Altitude, 45 meters (148 feet). This is the 

 most barren desert on the Mexican Line, though there is more animal 

 life upon it than was supposed by the members of Major Emory's sur- 

 veying party. Only four species of plants — sagebrush, creosote bush, 

 ephedra, and a coarse grass — were discovered on the middle portion 

 of the Yuma Desert, although tender annuals doubtless spring up 

 after rains and soon disappear. The only birds seen were a pair of 

 ravens, which were feeding at deserted camps of the Monument-Build- 

 ing Party. Of mammals, a large species of kangaroo rat, a long- 

 eared fox, a jack rabbit, and a small ground squirrel were quite com- 

 mon. At Monument No. 200, two beetles {Elcodes grandicoUis and 

 E. acuticauda), a desert cricket (Stenopalmatus talpa), a solpugid 

 (Datames calif ornicus) , and a scorpion {Hadrurus hirsutus Wood) 

 were collected by myself. I camped there from March 15 to 16, 1894. 

 Lizards were abundant, and the following were collected : 



Dipsosaurus dorsalis (Baird and Girard) ; Crotaphytus wisUsenii 

 Baird and Girard ; Callisaurus draconoides ventralis (Hallowell) ; 

 Uma rufopimctata Cope. 



