23 



Rio, from July, 1877, ^o January, 1878, can be best under- 

 stood from the final report of Prof. Hartt, made to the 

 Minister of Agriculture last December, an English trans- 

 lation of which is appended to this paper. 



The following brief account of the state of systematic 

 geology in Brazil, at the time of Prof. Hartt's death, will 

 assist us in understanding what he had accomplished in 

 that important branch of research, since the publication of 

 his book in 1870. The scanty material on this subject in 

 my possession, necessarily renders this summary very 

 incomplete. 



Laurent ian. — Composing the greater part of the plateau 

 and mountain range of Guayana, the plateau of central 

 Brazil, with the Serra do Mar and Serra do Mantiqueiro, 

 and the Chiquitos plateau of Bolivia. This series is 

 mainly composed of gneiss, gneiss-granite and syenite. 

 Every effort was made to find traces of Eozoon, or of 

 other fossils, in the limestones of this age, in the provinces 

 of Rio de Janeiro and Sao Paulo, but without success. 



Huronian and Loiver Silurian.— T\\q metamorphic de- 

 posits, lying on the southern edge of the plateau of 

 Guayana and on the northern edge of that of Brazil, and 

 consisting mostly of quartzites, metamorphic schists and 

 crystalline limestones, the former still showing stratifica- 

 tion, and wind and wave structure, have been referred to 

 the Huronian and Lower Silurian. To the north of the 

 Amazonas the}' have been examined on the Trombetas; 

 to the south of the Amazonas, on the Tapajos and, doubt- 

 fully, on the Tocantins. (Observations by Mr. Derby 

 and others.) The gold-bearing rocks of Minas Geraes 

 are probably of this age, as well as the metamorphic 

 series of some of the other provinces. 



Upper Siliir ian. ~\nc\ud.es the sandstones and shales 

 underlying the Devonian, to the north of the Amazonas, 

 and containing Arthrophyciis Harlani, Lingula cuneata, etc. 

 (Derby.) 



Devonian. — The heavy series of sandstones, sandy shales, 

 etc., with an abundance of fossils, at localities on the 

 Maecuru and Curua, (Derby), and at Erer^, are equivalent 



