The country now rapidly grows wilder; tall forest replaces llanos or scattered growth, and the camps of rubber-collectors dot the river-banks. One afternoon, as we poled quietly along, we came upon a huge anaconda coiled up on a sand-bank; all about were iguanas three or four feet long, digging nesting burrows in the loose sand. The snake had just caught one of the big lizards and was crushing it into a limp mass, but the others paid not the slightest attention to the tragedy which was being enacted in their midst, and ran about or worked but a few feet away. When we approached to within twenty feet the anaconda dropped its victim and flung itself into the water; some of the iguanas followed it, and others scampered away over the sand. That night we reached the low, sandy island of Tanaja and, ascending one of the branches of the river, made camp on the rocky mainland. The water was sluggish and shallow, so that we could easily see the muddy bottom six or eight feet below. As the boat moved slowly along we became aware of masses of black, flitting shadows underneath, and soon made out vast shoals of fish of various sizes that literally covered the bottom. There were rays, electric eels, catfish, and _piranhas_ by the thousands, besides many others which we could not identify; the reason for their congregating in this shallow place is hard to guess. The boulders on the bank were dotted with what we at first took to be lichens; but examination showed them to be night-hawks (_Chordeiles rupestris_) of a light gray color, which clung to the rounded tops silent and immovable, as if carved out of stone. When we paddled across to the island a short while after, we found scores of others, but these were the females squatting on one or two fragile speckled eggs which had been laid in shallow hollows scooped out of the warm sand. They were very tame and permitted me to walk up to within a few feet of them; then they took wing and with noiseless, graceful flaps flew a short distance away and dropped back on the sand. Flocks of red-and-blue macaws flew screaming across the river in quest of some favorite tree in which to spend the night, far in the depths of the forest; after them trailed parrots of various sizes and colors, always flying two by two. Herons flapped lazily up-stream, and snake-birds perched on snags looked down at the masses of fish below, apparently regretting their limited capacity for eating. Exciting as this naturally must be to a field-naturalist, it was but a foretaste of what we were to find each day farther up the river. As the morning of January 24 sped by, the water of the Orinoco began to assume a dark color, and by four o’clock that afternoon we had reached the mouth of the Atabapo; an hour and a half later we had ascended the clear red water of that river for a distance of three miles, and tied the _piragua_ to the ledge below San Fernando.