Derby.] J- '4 [Feb. 21, 



No satisfactory sub-division of the Carboniferous beds of the Amazonas 

 can as yet be made. The fossiliferous beds at the different localities appear 

 to belong to the same limited horizon, and to present always the same 

 fossils. It is true that Mr. Smith found at Cuiumu and Curucaea, near 

 Alenguer, fossils having a different aspect from those from the other locali- 

 ties, but they are so poorly preserved as to be unrecognizable. The fossils 

 of the calcareous beds are mostly Brachiopods and Corals, while Lamelli- 

 branchs are most abundant in the shales and sandstones ; but there are 

 many species in common, and the beds are so closely related stratigraphi- 

 cally, that I am inclined to consider the differences in their fossils as due to 

 differences in the nature of the sediments, rather than to a difference in 

 horizon. 



While the Paheozoic deposits were being laid down in the Amazonian 

 region, it is to be supposed that the other margins of the ancient Archean 

 and Silurian islands received their quota of deposits and, in fact, in the 

 outhern part of Brazil, in the regions now constituting the provinces of 

 Rio Grande do Sul, Santa Catharina, Parana and the southern part of Sao 

 Paulo, extensive Carboniferous and Devonian beds were laid down. It is 

 stated also that Carboniferous deposits are to be found in the provinces of 

 Maranhao and Matto-Grosso, on the Guapore and Upper Paraguay ; but, 

 although this seems extremely probable, the fact is not as yet well verified. 

 In the Andean region enormous deposits were formed, during the whole of 

 the Palaeozoic. The best known of these are the Carboniferous beds, 

 which appear in the central part of the Cordilheiras, at lake Titicaca, and 

 in the province of Arque in Bolivia ; and on the eastern slope of the Andes, 

 at Cochabamba and Santa Cruz de la Sierra, in Bolivia, and on the upper 

 Pachetea, in Peru. 



The beds referred to the Cretaceous, have only been recognized with 

 certainty in the mountains of Erere. We have seen that the Curua shales 

 of the Devonian series, form in general the base of these mountains. In one 

 place, near the base of Tajuri, these shales are followed by Carboniferous 

 limestones, but in general the Carboniferous beds are lacking throughout 

 the Erere region, and the Devonian shales are followed by heavy beds of 

 coarse, hard sandstone. In a section made in a hill between Tajuri and 

 Erere, there are three distinct beds of coarse massive sandstone, separated 

 by beds of micaceous sandy shales, the whole series having a thickness of 

 about 300 feet. Of these three beds of sandstone, the upper or middle, or 

 the two united, form the principal mass of the Serras of Erere and Paituna. 

 In the first of these serras were found, in 1871, fragments of fossilized wood, 

 which were referred by Dr. Dawson to the dycotyledonous group of plants, 

 and in the last voyage we found, in Paituna, a thin bed of argillaceous 

 sandstone, intercalated in the coarser beds of the serra, which was crowded 

 with fossil leaves, belonging to various genera of the same group of plants. 



The leaves and woody structure of tropical plants have been too little 

 studied to permit of the specific, and perhaps the generic, determina- 

 tion of these plants. They are, however, of the utmost importance in the 



