At Chilón we entered the heart of the giant-cactus forest--and it can be properly known by no other name. The country, far as the eye can see, is covered with the thorny plants; some of the giant club-cacti rear their fluted columns to a height of sixty to seventy-five feet, and are of majestic appearance. There are also immense clumps of prickly-pear and several other varieties, while low, trailing kinds hug the rocky earth; the latter are rather unpleasant as one frequently strikes against them in walking, and the sharp spines penetrate shoe-leather and are extracted from the foot with difficulty; mules frequently get them into their noses while nibbling on leaves or the few blades of coarse grass, and are driven almost frantic with the pain. Many of the club-cactus plants bore an abundance of round fruit about two inches in diameter and covered with long, velvety down; when the outer covering was brushed off a smooth, red berry was revealed; it is very sweet and the flavor reminds one of strawberries. Chilón is a settlement of twenty-five or thirty huts; its elevation above sea-level is five thousand six hundred feet, but the climate is very hot. We put up in one of the hovels where there was also a corral for the mules, and proceeded to work along the banks of the Rio Chilón, which is a small tributary of the Rio Mizque. The stream is rapid and shallow, and flows over a rock-strewn bed. Numbers of fish, including rays, were plainly visible through the clear water. The majority of the birds inhabiting the thorny jungle that grows on both sides of the watercourse, were still of the arid upland type; but there was a further encroachment of a foreign fauna, and the brown-shouldered orioles, coral-billed tinamou, and red-tailed parrakeets left no doubts in our minds of the origin of their distribution. They were the advance ranks of a stream of bird-life flowing up the valley of the Rio Grande and its tributaries, where conditions are at least somewhat similar to those obtaining in the chaco country to the east, which is their normal habitat. Apparently the red-tailed parrakeets were mating. Large groups sat on the branches of some stunted tree, preening one another’s plumage, and emitting queer ani-like wails. If one observed closely, however, it could be seen that the flocks were always broken up into pairs that were snuggled up as closely together as possible.