MY DEAR FRIEND:—You will probably be surprised to receive only a few lines from me after the time which has elapsed since my last letter. The truth is, that, since Obydos, I have passed from surprise to surprise, and that I have scarcely had time to take care of the collections we have made, without being able to study them properly. Thus, during the week we spent in the environs of Villa Bella, at Lago José Assú and Lago Maximo, we have collected one hundred and eighty species of fishes, two thirds of which, at least, are new, while those of my companions who remained at Santarem and upon the Tapajoz have brought back some fifty more, making already more than three hundred species, including those of Porto do Moz, of Gurupá, of Tajapurú, and of Monte Alégre. You see that before having ascended the Amazons for one third of its course, the number of fishes is more than triple that of all the species known thus far, and I begin to perceive that we shall not do more than skim over the surface of the centre of this great basin. What will it be when it becomes possible to study all its affluents at leisure and in the most favorable season! I have resolved to make more numerous stations in the upper part of the river and to stay as long as my strength and means will allow. Do not think, however, that I forget to whom I owe such a success. It is you who have put me on the path, by making known to me the resources of the forest, and, better still, by furnishing me with the means to profit by them. Thanks, a thousand times, thanks. I ought also to acknowledge the assistance afforded me by the agents of the Company, at all the points where we have touched. Our amiable commander has also exerted himself, and while I explored the lakes in the neighborhood of Villa Bella, he made a very fine collection in the Amazons, especially of the numerous small species always overlooked by fishermen. On the arrival of the Belem I received your kind letter and a part of the alcohol I had asked from Mr. Bond. I am writing to-day to ask him to send me a part to Teffé, and, somewhat later, more to Manaos. Thank you for the catalogue of Pará fishes; I shall give it back on our return, with the additions I shall make during the remainder of the voyage. Adieu, my dear friend. Ever yours, L. AGASSIZ. Footnote 64: In the course of the investigation, I have ascertained that this slaty rock, as well as the hard sandstone seen along the river-banks at Manaos, forms part of the great drift formation of the Amazons, and that there is neither old red sandstone, nor trias, here, as older observers supposed.—L. A. Footnote 65: TEFFÉ, 14 September, 1865.