1878.] 343 [Rathbun. 



studies. There is little necessity for going minutely over the details 

 of his first few trips to that country. Accounts of them have been 

 published, and are easily accessible. 



The primary object of the Thayer Expedition was the investi- 

 gation of the distribution of the fresh-water fishes of Brazil, but 

 much time was also devoted to the study of its geology. No new 

 fossiliferous deposits or localities were discovered, and of those 

 already known, only the Cretaceous at Bahia, and the Post-Pliocene 

 of Lagoa Santa, were explored. Prof. Agassiz limited himself 

 mostly, in his geological work, to the examination of the superficial 

 deposits at Bio de Janeiro and on the Amazonas, which were studied 

 in connection with the question of glaciers. Hartt was retained near 

 Rio for some time, in making examinations of the many cuttings 

 around that city. After this work was completed, his field of explo- 

 ration lay mostly between Bio and Bahia, where, with Mr. E. Cope- 

 land of Boston as a companion, he carefully studied the geological 

 and other features of the coast and of the principal river basins lead- 

 ing to it. Lanje collections of the fresh water fishes of the rivers and 

 of the marine animals of the coast and reefs were made. The region 

 from Bio to Bahia is entirely metamorphic, consisting mostly of 

 gneisses, covered in large part with loose or only partially consol- 

 idated materials, without fossils. In consequence of this absence of 

 fossils, no results in systematic geology were obtained, but, neverthe- 

 less, Hartt's studies of the geology of this monotonous tract were of 

 great interest. At the Colonia Leopoldina, in southern Bahia, he 

 had the opportunity of observing the customs, etc., of the now nearly 

 extiuct Botocudo Indians. 



In the neighborhood of Porto Seguro he explored the coral and 

 sandstone reefs, which latter are such a prominent feature on the Bra- 

 zilian coast. He was the first to carefully work out the structure and 

 mode of formation of these sandstone reefs, although Darwin's short 

 description of them is not far from correct. 



After Hartt had returned to the United States from the 

 Thayer Expedition, he felt that he had left unfinished some of 

 the more important of the investigations he had made in Brazil. 

 He was unable to report as fully as he wished on many subjects 

 of interest which he had in part studied. So in 186 7 he returned 

 to Bahia, to better perfect his old work and continue his obser- 

 vations. He worked out the geology on the line of the Bahia 

 railroad in detail, and collected some fossils from the Cretaceous 



