Wild animals are particularly abundant in this section of the country. All day long we could hear the raucous scream of long-tailed, multicolored macaws (_Ara_) as they flew two by two overhead. Many hawks sat alertly on dead snags near the water, and black-and-white gulls flapped hurriedly up and down along the river. Occasionally we caught a glimpse of a small flock of muscovies, the largest of South American ducks, as the great, black birds flew heavily up-stream. There were also black guans, resembling small turkeys, which sat quietly in the tops of tall trees until we approached quite near to them; then, emitting a loud, mule-like bray, they set their wings and soared across the river or down into the underbrush. At night the forest was usually quiet, reminding one of “Pools of Silence.” Occasionally, however, the still air was suddenly rent by the most unearthly noise that mortal man ever heard, and the woods rang with the wild, insane cackle of forest-rails (_Aramides_). Beginning with a shrill _oohoo-hee-cra_, the demoniacal chorus continued several minutes without interruption, swelling constantly and finally ending with a few low, explosive _cow-cow-cows_. A number of birds always sang together, and the first time one hears the performance it is enough to make the flesh creep and the hair to stand on end; but even after becoming somewhat accustomed to the noise, it falls short of conducing to peaceful slumber, suggesting as it does the agonized shrieks of some tortured spirit of the jungle. Night-monkeys (_Douroucouli_) were apparently plentiful, but we never saw them in the daytime. After darkness had fallen they began to move about in the tree-tops; one night a troop selected the tree under which we camped for the scene of their frolic, and kept us awake the greater part of the night. They jumped about in the branches, and from the swishing noises which reached us it was easy to imagine them enjoying a good swing up and down upon some particularly springy limb. They dropped leaves and twigs down upon the tent-fly, probably through accident, but perhaps prompted by the desire to find out if anything would happen. At frequent intervals they drew together in a close group to chatter in low, grunting tones, and then, coming to the conclusion that the queer-looking objects below them must be capable of performing some interesting action, again began to tempt fate by showering down more twigs and leaves. In many places the receding water of the river had left isolated pools; these were teeming with fish of many species; some of them were of large size. A number which we caught had practically the entire tail and fins eaten off; their cannibalistic brethren had no doubt taken advantage of the circumstances in which they were all placed, and begun to devour them piecemeal, at their leisure.