Feb., 1911.] Literature on Geology of South America. 
2 75 
On the Pacific slope of the Andes from Patagonia northward 
the old formations show a similar three-fold division and are said 
to have essentially the same characteristics. It is probable, 
however, that these formations are of much later age. 
PALEOZOIC. 
The Lower Paleozoic Rocks. The lower Paleozoic formations 
of South America are not always recognizable and are perhaps 
wanting in some regions where later formations occur, but it is 
probable that a portion of the crystalline schists, quartzites and 
slates which have been referred to the pre-Cambrian are in reality 
early Paleozoic formations. In the Amazon region Derby says 
that the Silurian rests unconformably “on an extensive series of 
quartzites superior to” 6 the gneiss, but the age of this assemblage 
of rocks is not suggested. In this same region Ivatzer maps the 
Silurian as unconfonnable on a series of metamorphic rocks 7 , which 
appear to be of pre-Cambrian age. 
In Bolivia and northwestern Argentine occur outcrops of 
sandstones and quartzites in which a fauna of Upper Cambrian 
age ( Agnosias , Olenus, Conocoryphe and Ptychoparia ) has been 
collected. 8 The base of this series of rocks is not exposed and its 
thickness is unknown. In this same general region (Bolivia and 
Argentine) the Ordovician is represented by yellow argillaceous or 
quartzitic sandstones and black shales which are thought to rep- 
resent the same horizon as the Orthoceras limestone (base of 
Ordovician) of the Baltic. 9 Among the fossils collected from 
this horizon are Illacnus, Orthoceras and Eudoceras from the 
sandstone, and four genera of graptolites from the black pvritic 
shales exposed along Rio Corauhuata at Culi, Bolivia. 10 DeLap- 
parent says this same fauna also occurs near Lima, Peru; and 
again along the coast of Venezuela between Caracas and Puerto 
Cabello, the finding of Ordovician fossils, among which is Calyni- 
mene senaria, 11 indicates the presence of this system. 
Silurian rocks are reported to occur along the coast of Chili 
but they are highly metamorphosed 12 and have not been well 
described. In southwestern Brazil, southern Peru and north- 
western Argentine the Silurian rocks outcrop almost continuously 
6. Derby, O. A., Amer. Jour. Sci., 3d ser., Vol. XIX, 1880, p. 324. 
7. Katzer, Friederich, Grundzuge der Geologie des unteren Amazonas- 
gebietes. 1903. (Leipzig), p. 216. 
8. Kayser, E., Beitrage zur Kenntniss einiger palaeozoisher Faunen 
Sudamerikas (Reviewed by Freeh). Neues Jahrbuch fur Mineralogie, 
Geologie und Palaeontologie. Band II, 1S98, p. 472. 
.0. DeLapparent, A., T reate de Geologie, Tome III, p. 808. 
10. Evans, J. W., Quart. Jour. Geol. Soc. London, Vol. LXII, 1906, 
p. 431. 
11. Drevermann, Neues Jahrbuch, Band I, 1904, p. 91. 
12. Forbes, David, Quart. Jour. Geol. Soc. London, Vol. XVII, 1860, 
