Rh. Rathbun— Geology of the Lower Amazonas. 467 
were Spirophytons, apparently belonging to the same species as 
those described from the Hamilton group of New York. 
e Devonian rocks in the Ereré region have suffered greatly 
by denudation, and are much dislocated and divided by trap 
dykes, making their study very difficult. Beds apparently of 
Devonian age have been found as far west as the Rio Uatuma, 
and, to the south of the Amazonas, on the Tapajos and Xingu. 
Of all the Paleozoic deposits of the Amazonian valley, the 
Carboniferous is exposed over the largest area, but, at the same 
time, presents the greatest difficulties to study. Being com- 
posed for the most part of soft rocks, it has been much denuded 
only widely-separated exposures remaining, of which it is 
difficult to determine the correlation of the several beds. It is, 
therefore, also impossible to estimate with certainty the thick- 
ness of the series, which probably exceeds 1,800 feet. The 
rocks are soft sandstones, shales and limestones, of which the 
remains. The fossiliferous beds, originally studied by Prof. 
Hartt and Mr. Derby on the Tapajos, were traced to the north 
of the Amazonas, on the Rios Maecurt, Curua, etc. The differ- 
quer, partially covering up the Devonian between Hreré and 
Maecurti locality, and has been found to the west, on the 
Rio Uatumé, and to the east, on the Rio Jauary near Prainha. 
There can be no doubt but that the Carboniferous really ex- 
-tends much farther west, and eastward, to near the Atlantic. 
From what has been said before, however, it will be under- 
stood that this formation is not exposed over the entire region 
above defined, although at one time it must have been con- 
tinuous there. It was observed on the principal rivers men- 
tioned, generally in the vicinity of the lower falls or rapids, 
and also at many intermediate localities, but is mostly covered 
up by more recent formations, or by dense forest growths, and 
over large tracts has been completely swept away. Notwith- 
standing the fact that the fossils of this group indicate an hori- 
zon, equivalent to the Coal Measures of North America, no 
- seams of coal have yet been found on the Amazonas. The 
beds lie as a rule nearly horizontal. 
