Feb., 1911,] Literature on Geology of South America. 277 



under the name Arthrophycus harlani Con.^^ and hence may be 

 the upper part of the Ordovieian. Sikirian 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, Peiti, 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.-'^ In the Lower Amazon region it is best exposed 

 on the north side of the valley where it fonns a narrow belt along 

 the border of the Silurian. O. A. Derby divided the Devonian of 

 this region into three groups-^ as follows: The Maecuru, consist- 

 ing of about 30 feet of massive coarse white or yellow4sh 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 confoniiably, 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 

 chcrty 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, Grundziige der Geologie des unteren Amazon- 

 asgebietes, 190.3, p. 216. 



20. Thomas, Ivor, Zeitschr. d. deutsch. Geol. Ges., Vol. 57, 1905, 

 p. 234. 



21. Proc. Am. Phil. Soc. for 1879, pp. 169-171. 



