MAMMALS OP THE MEXICAN BOUNDAKY. 117 



rocky heights ; but the screw-bean, palo verde, acacia, ironwood, and 

 elder are abundant in the valleys. The smoother tracts are covered 

 by the choya, tasajo, and other cacti, mixed with sagebrush, grease- 

 wood, creosote bush, ocotillo, and Ephedra. Along the river are 

 patches of gourds, Baccharis, arrowwood, canes and tule. 



The writer, assisted by Mr. Holzner, collected energetically at this 

 station from January 9 to 25, 1894, and brought together a fine collec- 

 tion of mammals, birds, and fishes ; but plants and reptiles were scarce 

 at that season. A frog was taken from the stomach of a chaparral 

 cock ; mud turtles {Kinosternon sonoriense Le Conte) were numerous 

 in springs and in the Sonoyta River; one snake was obtained at 

 Santo Domingo; and a lizard {Uta stanshuriana Baird and Girard) 

 was found in some numbers. Reptiles were reported to have been 

 very numerous in the Sonoyta Valley in warm weather. Lieutenant 

 Gaillard speaks of the horned rattlesnakes, or " side winders," which 

 he killed between Gila Bend and Sonoyta as having seemed to -him 

 different from those on the deserts bordering on the Colorado River. 

 The latter were Grotalus cerastes Hallowell. 



Station No. 56. — Santo Domingo, Sonora, Mexico. Station 2 

 kilometers (l!5 miles) south of Monument No. 170, 670 kilometers 

 (417 miles) west of the Rio Grande, and 189 kilometers (117 miles) 

 east of the Colorado River. Altitude, 360 meters (1,181 feet). Fre- 

 quent visits were made to this locality in January and February, 

 1894, by myself and Mr. Holzner. 



Station No. 57. — Quitobaquita, at Monument No. 172, 678 kilo- 

 meters (421 miles) west of the Rio Grande and 181 kilometers (113 

 miles) east of the Colorado River. Altitude, 320 meters (1,050 feet). 

 The Quitobaquita Springs, at which our camp was made, are close 

 to the International Line, in Pima County, Arizona, at the foot of the 

 Sierra de Quitobaquita, whose altitude is 845 meters {2,772 feet). 

 The region is more barren than that around Sonoyta and Santo 

 Domingo. The La Abra Plain, on the east, is covered with coarse 

 chaparral; but the lower course of the Sonoyta River is through a 

 more open and sandy region, the soil being sandy loam and coarse 

 gravel, with the low places incrusted with alkali. The rock is gran- 

 ite, rhyolite, and basalt. 



Passing down the Sonoyta Valley from the town of Sonoyta, the 

 valley broadens at Santo Domingo into an extensive bottom, which 

 is largely under irrigation and cultivation. A small garden at 

 Quitobaquita is irrigated from springs emerging from a hillside on 

 the right (north) bank of the Sonoyta River and 1 mile from it, at 

 a point 8 kilometers (5 miles) below Santo Domingo. The Sonoyta 

 Valley is a little more than a mile in width at this part' between low 

 mountains of coarse granite rock. It is partly covered by patches of 

 creosote bushes, shrubbery, and cacti. The giant cereus is common 



