MAMMALS OP THE MEXICAN BOTJNDABY. 119 



Species of the following ge:iera also occur: Typha, Efhedra, 

 Phoradendron (red-berried, on nearly all the trees, but thriving 

 especially upon the mesquite), Atriplex, Amaranthus, Cactus, EcM- 

 nocereus, Echinocactus,Opuntia,Lycium (called "cuanvir ""by Mexi- 

 cans), Cucurbita (palmate-leaved), Xanthium (called " cadillo " by 

 Mexicans), Trixis (a woody species), and Artemisia. Other plants 

 not identified by specimens were called " chamizo," " rama amarilla," 

 " chicura " (a coarse composite), and " yerba de la flecha " (a small, 

 bushy tree, in canyons and arroyos, from Nariz Mountain to La Re- 

 preso ; has a double-seeded fruit, and in February red leaves ; said to 

 be very poisonous if taken as a decoction). 



Station No. 58. — Rancho de Agua Dulce, Sonoyta River, Sonora, 

 Mexico. This place is about 6.4 kilometers (4 miles) southwest 

 of Monument No. 173, 690 kilometers (429 miles) west of the Rio 

 Grande, and 169 kilometers (105 miles) east of the Colorado River. 

 Altitude, 280 meters (919 feet). The writer made several visits to 

 this place in January and February, 1894, collecting plants, birds, 

 and mammals. Lagunas of the Sonoyta River between Agua Dulce 

 and Cerro Blanco are the resort of many aquatic birds. The rock is 

 coarse granite, rhyolite, and basalt. Spherulitic nodules are abun- 

 dant in obsidian flows, which, alternating with sheets of rhyolite, 

 form a high bluff on the right bank of the Sonoyta at Agua Dulce. 



When the surveying party was working in this vicinity during the month of 

 June, 1893, the heat was intense, the maxtmum temperature in the shade re.ich- 

 ing 118° F. The standard thermometer used was not graduated sufficiently high 

 to give the temperature in the sun after 8 or 9 o'clock a. m., at which time it 

 ranged from 130° to 140° F., the temperature in the shade at the same time 

 ranging from 95° to 105° F., a ratio which would seem to indicate an average 

 maximum sunshine temperature- during June of about 150° F. The temperature 

 during June, 1893, must be considered, however, as in excess of the average, for 

 a themometer record kept at Sonoyta and covering a period of several years 

 showed this to have been the hottest June during the period covered by the 

 observations. (D. D. Gaillard in Report of International Boundary Commis- 

 sion, p. 23.) 



Station No. 59. — ^La Represo, at Monument No. 179, 715 kilonje- 

 ters (444 miles) west of the Rio Grande, and 144 kilometers (90 

 miles) east of the Colorado River. Altitude, 210 meters (689 feet). 

 This camp is in the eastern part of the Tule Desert. A small collec- 

 tion was made by the author and Mr. Holzner February 8 and 9, 1894. 



Vegetation. — In traveling from the Sonoyta River at Agua Dulce 

 to La Represo we crossed, about midway, a broad forest of the sinita 

 {Cereus schottii Engelmann), one of the largest and most singular of 

 the cacti, which we never saw elsewhere. It occupied a Trial pais 

 region, covered with scoriaceous basalt. This forest of giant cacti 

 stretched away as far as the eye cotild reach into Arizona and Sonora. 

 We ascertained that the range of the largest North American cactus. 



