BIEDS OF ARGENTINA, PARAGUAY, URUGUAY, AND CHILE 9 



Negro. At night on November 21 I reached the station of Rio Negro 

 and obtained quarters in the village of General Roca, 2 kilometers 

 distant. The valley of the Rio Negro here was about G kilometers 

 wide, with a line of low rolling hills of sand and water-worn gravel 

 at the north, cut by winding valleys that became steep-sided bar- 

 rancas where first they opened on the flats below, and then disap- 

 peared. The region was arid and had vegetation of the usual desert 

 types. Thorny mesquites (Prosopis strombulifera) were common, 

 mingled with a yellow-flowered shrub {Caesalpina fraecox)^ and 

 creosote bush {Covillea divaricata and G. nitida). An opuntia 

 {Opuntia hickeni) and a turkey-head cactus {Echinopsis leucantha) 

 was fairly common. The valley floor, sloping gently to the Rio 

 Negro, 5 kilometers from Roca, was covered with a scrub of atriplex 

 {Atriplex lampa and A. crenatifolia) and creosote bush. Consider- 

 able areas were cleared, and, under irrigation, yielded abundant 

 crops. The actual flood plain of the stream was of sandy loam, 

 interspersed with much gravel. Here were thickets of willows, some 

 attaining the size of trees, and baccharis (Baccharis dracunifolia) , 

 with a varied flora of herbs. Cottonwoods and tamarisk {7'auiaHx 

 gallica) have been planted along irrigation ditches. The Rio Negro 

 is a broad, swiftly-running stream, rather heavy with grayish white 

 sediment. Its course was broken by low islands bordered by small 

 channels, and little lagoons of quiet water were common. On the 

 opposite shore a rock escarpment, with steep talus-strewn slopes at 

 the base, rose to an elevation of 100 to 125 meters. The soil in gen- 

 eral in this area was strongly alkaline. The crested tinamou, small 

 flycatchers, finches, and odd tracheophones were common, while water 

 birds abounded along the river. The region supported an avifauna 

 far different from that of country covered previously. (PI. 16.) 



On the evening of December 5 I continued west by rail and 

 on December 6 reached Zapala, in the Gobernacion de Neuquen, a 

 town of 30 or 40 houses, at that time the terminus of the railroad, 

 located on a broad flat on the watershed between the Limay and 

 Neuquen Rivers, in sight of the distant snow-capped Cordillera. 

 Here the land was thrown into broad ridges, with shallow depressions 

 between that led down into a broad valley draining to the eastward. 

 The region was arid, but supported various shrubs and a certain 

 amount of grass. Elevation was about 900 meters, and the region 

 lay in a higher life zone than Roca, except for certain hot north- 

 facing valleys. Violent winds were frequent. Small seed snipe 

 were here on their breeding grounds. Work was continued here 

 until December 11. (PL 17.) 



On December 12 I arrived in Bahia Blanca, Buenos Aires, and on 

 the following day visited the flats about the bay at Ingeniero White, 

 the port for the city. Here were broad stretches of alkaline barrens 



