_February 1st._—On Tuesday evening we reached Porto do Moz, on the river Xingú, where we had expected to be detained several days, as Mr. Agassiz wished especially to obtain the fishes from this river, and, if possible, from its upper and lower course, between which rapids intervene. He found, however, his harvest ready to his hand. Senhor Vinhas, with whom, when stopping here for a few hours on his voyage up the river, he had had some conversation respecting the scientific objects of his visit to the Amazons, has made during our absence one of the finest collections obtained in the whole course of our journey, containing, in separate lots, the fishes from above and below the cascade. By means of this double collection, which Mr. Agassiz has already examined carefully, he ascertains the fact that the faunæ on either side of the falls are entirely distinct from each other, as are those of the upper and lower courses of the Amazons, and also those of its tributaries, lakes, and igarapés. This is a most important addition to the evidence already obtained of the distinct localization of species throughout the waters of the Amazonian Valley. We regretted that, on account of the absence of Senor Vinhas from the town, we could not thank him in person for this valuable contribution. Finding that the efforts of this gentleman had really left nothing to be done in this locality, unless, indeed, we could have stayed long enough to make collections in all the water-basins connected with the Xingu, we left early in the morning and reached Gurupá yesterday. This little town stands on a low cliff some thirty feet above the river. On a projecting point of this cliff there is an old, abandoned fort; and in the open place adjoining it stands a church of considerable size, and seemingly in good repair. But the settlement is evidently not prosperous. Many of its houses are ruinous and deserted, and there is even less of activity in the aspect of the place than in most of the Amazonian villages. We heard much of its insalubrity, and found very severe cases of intermittent fever in one or two of the houses we entered. While Mr. Agassiz made a call upon the subdelegado, who was himself confined to his room with fever, I was invited to rest in the open veranda of a neighboring house, which looked pretty and attractive enough; for it opened into a sunny garden, where bananas and oranges and palm-trees were growing. But the old woman who received me complained bitterly of the dampness, to which, indeed, her hoarse cough and rheumatism bore testimony; and a man was lying in his hammock, slung under the porch, who was worn to mere skin and bone with fever. Here also we received some valuable specimens, collected, since our previous visit, by the subdelegado and one or two other residents.