MAMMALS OF Till'. MEXICAN BOUNDARY. 123 



Reptiles. — In February, L894, we observed fcrnl few species of liz- 

 ards here, among them Uta stansburiana Baird and Girard, Scelo- 

 porus clarkii Baird and Girard, and a horned load (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 were 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 11. Wheeler wrote in April. 

 L893, from this place as follows: 



Lizards very large, 12 to 16 inches in length; with black heads and legs and 

 dirty or hrick-colored hacks and hcllios : tail of a dusty gray; seen on highest 

 peaks di' the Tinajas Mountains. 



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

 occurrence of the tiger rattlesnake (Crotalus 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 



than a lead pencil. It is colored thus (,. q — -,,): A, A, 



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

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

 ci/x ductus Cope, in which the natural coloring had not vet failed in 

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



Station No. 64. — Yuma Desert, Monument Xo. 200. 835 kilometers 

 (519 miles) west of the Rio Grande and 21 kilometers ( 15 mile-) easl 

 of the Colorado River. Altitude, 15 meters (118 feet). This i- 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 1 

 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 grandicollis and 

 A', acuticauda), a deserl cricket (Stenopalmatus talpa), a solpugid 

 (Datames calif ornicus) , and a scorpion (Hadrurns hirsutus Wood) 

 were collected by myself. 1 camped there from March L5 to L6, 1894. 

 Lizards were abundant, and the following were collected: 



Dipsosaurus dorsalis (Baird and Girard); ( Jrota phytus wislisenii 

 Baird and Girard: Callisaurus draconoides ventralis (Hallowell) ; 

 / T ma rufopunctata Cope. 



