This region, as might be supposed, is not destitute of inhabitants. Several tribes of Indians dwell within it all the year round. Among them are the Purupurus and Muras tribes, who, spending most of their time in their canoes, in the dry season build small huts on its sandy shores; and when the waters overflow it, form rafts, which they secure between the trees, sleeping in rude huts suspended from the stems over the deep water, and lighting their fires on masses of mud placed on their floating homes. They subsist entirely on fish, turtle, and manatee. Several species of trogons are peculiar to this submerged region. The curious black umbrella-bird is entirely confined to it, as is also the little bristle-tailed manakin. Several monkeys visit it during the wet season, for the sake of its peculiar fruits; and here the scarlet-faced urikari has its home. For miles and miles together the native traverses this region in his canoe, passing through small streams, lakes, and swamps, scraping the tree trunks, and stooping to pass between the leaves of the prickly palms, now level with the water--though raised on stems forty feet high--while everywhere round him stretches out an illimitable waste of waters, but all covered with the lofty virgin forest. In this trackless maze, by slight indications of broken twigs or scraped bark, he finds his way with unerring certainty. "This curious region," says Wallace, "extends from a little above Santarem to the confines of Peru, a distance of about 1700 miles; and varies in width on each side of the river from one to ten or twenty miles." TRIP UP AN IGARAPE INTO THE INTERIOR. Let us leave the mighty stream, and wander amidst the picturesque windings of an igarape, into the depths of the forest, with Professor Agassiz. Passing into its narrow entrance, the lofty trees arching overhead shelter the voyager in his light canoe from the glaring heat of the noonday sun. The air is cool and refreshing. Not a ripple stirs the water, save that caused by the paddles of the Indian crew. Clumps of the light and exquisitely graceful assai-palm shoot up everywhere on either side from the denser forest. Here and there the drooping bamboo dips its feathery branches into the water, covered sometimes to their very tips with the purple of convolvuli; yellow bignonias carry their golden clusters to the very summits of some of the more lofty trees; while white-flowering myrtles and orange-coloured mallows border the stream. Life abounds in this quiet retreat. Birds and butterflies are numerous on the margin of the water. Crabs of every variety of colour and size sit on the trunks of decaying logs, watching for their prey,-- to make their escape, however, with nimble feet, when pursued.