MAMMALS OP THE MEXICAN BOUND AEY. 19 



in width, bordered with mesquite, palo verde, and acacia trees. The 

 mountains and hills throughout the region are covered with a thin 

 flow of lava, which reaches a little way out on the plain. The tops 

 of the hills are red lava, the foothills black or dark gray scoria. A 

 long range — the Sierra Pinta — extends from near the Boundary as 

 far as the eye can reach to the northwest. This presents a curious 

 appearance, from its eastern half being covered with black " mal 

 pais," or volcanic scoria, which abruptly ends in a sharply defined 

 but irregular line, corresponding to the tortuous course of a vertical 

 ridge. The western half of this range of mountains is of granite 

 and very light in color, the eastern half being almost black. At 

 Monument No. 181 the line crosses a scoria-bestrewn divide on which 

 Gereus giganteus grows; and then another broad sandy plain, cov- 

 ered with fine yellowish grass and the creosote bush, is crossed. This 

 is the most dismal part, of the dreaded Tule Desert. On the western 

 edge of this plain, which rises toward the Tule Mountains, giant 

 cacti, a species of Gylindropuntia called " tasajo " by the Mexicans, 

 and an agave are found on the rocky sides of the mountains — the first 

 agaves seen since we left Pozo de Luis, at which point Dasylirion also 

 disappeared. The road here entered a narrow defile among the Tule 

 Mountains, which are mostly granite, with large veins of white 

 quartz, dipping to the east. These mountains, which at a distance 

 appear to be a solid range, are found to be a collection of isolated 

 peaks and sharp ridges cut down between to the general base level, 

 so that it is possible to ride among them without crossing high 

 divides. After riding 8 kilometers (5 miles) through the separated 

 Mountain masses, Tule Wells was reached. The teams had advanced 

 to near the western edge of the Tule Desert, where it became neces- 

 sary _.? .lem to halt for the night. Having a good horse, I rode 

 ahead ^o .lie Tule Wells for the purpose of watering the horse, and 

 camped there until the next day, when the teams arrived, much 

 jaded by the long pull across the deep sand of the Tule Desert. We 

 remained at Tule WeUs until February 14, exploring the Tule Moun- 

 tains and surrounding country. I made visits, on February 10, 12, 

 and 14, to a nameless range of mountains northwest of Tule Wells, 

 which I have called the Granite Mountains. 



February H to 23, 1894- — Camp was moved from Tule Wells to 

 Tina j as Altas February 14, on which day I crossed the Granite 

 Mountains on horseback and rode across the Lechuguilla Desert, 

 the Lechuguilla Mountains, and across the eastern portion of the 

 Yuma Desert as far as Monument No. 198, returning the same night 

 to where the camp had been located at Tina j as Altas, at the east base 

 of the Gila Mountains, 8 kilometers (5 miles) north of the Boundary, 

 in Yuma County, Arizona. From February 14 to 23 we were camped 



