Feb., 1911.] Literature on Geology of South America. 
277 
under the name Arthrophycus harlani Con. 19 and hence may be 
the upper part of the Ordovician. Silurian strata are recognized 
by fossils to the north of the river only. Those called Silurian to 
the south are identified as such by their petrographic appearance 
and stratigraphic occurrence. 
Devonian. The Devonian of South America is known in 
Brazil, Peru, Bolivia, Argentine and the Falkland Islands. 
In Brazil strata referred to this system are found in the state 
of Para on both sides of the Lower Amazon; in the province of 
Mato Grasso in central Brazil and the province of Parana in 
southern Brazil. 20 In the Lower Amazon region it is best exposed 
on the north side of the valley where it forms a narrow belt along 
the border of the Silurian. O. A. Derby divided the Devonian of 
this region into three groups 21 as follows: The Maeeuru, consist- 
ing of about 30 feet of massive coarse white or yellowish sandstone 
which is sometimes hard and sometimes a mere bank of sand. It 
contains an abundance of well-preserved fossils. This group 
rests on the Silurian, perhaps conformably, and is followed by 
the Erere group consisting principally of thin-bedded fine-grained 
micaceous sandstone with a subordinate amount of black shale. 
These sandstones are generally white in color but weather red, 
while the shale weathers to a whitish color. Near the base some 
cherty sandstone occurs. The whole group is quite fossiliferous 
and those forms occurring in the shale are different from those in 
the sandstone. Derby says there are thirteen distinct beds and 
the total thickness is about 200 feet. Above this lies the Curua 
group, consisting, in the lower part, of about 300 feet of well- 
laminated almost slaty black shale, with concretionary beds con- 
taining the cone-in-cone structure and having a strong odor of 
petroleum. In the upper part the group consists of an equal 
amount (300 feet) of chocolate colored shale mottled with spots 
of a darker color and banded parallel to the bedding with various 
colored layers. This rock is mostly a clay mixed with much 
finely divided mica and sand. The lower part of these red- 
brown shales and the upper part of the black shales are abund- 
antly marked with Spirophyton. This group is followed by 
about 50 feet of coarse sandstone of undetermined age and then 
follows (upper) Carboniferous rocks with distinctive fossils. 
19. Katzer, Friederich, Grundzuge der Geologie des unteren Amazon- 
asgebietes, 1903, p. 210. 
20. Thomas, Ivor, Zeitschr. d. deutsch. Geol. Ges., Yol. 57. 1905, 
p. 234. 
21. Proc. Am. Phil. Soc. for 1879, pp. 169-171. 
