104 BULLETIN: MUSEUM OF COMPARATIVE ZOOLOGY. 
The Devonian shales in central eastern Parana give rise to a longi- 
tudinal valley but the non-resistent character of these rocks is locally 
counteracted by intrusions of diabase. The western side of this 
longitudinal valley, where it is developed, is formed by sandstones and 
conglomerates of the basal Permian. Ponta Grossa stands on the 
western side of this valley. 
The sandstone and conglomeratic members of the Permian form an 
irregular grouping of uplands separated by river valleys. The level 
at which the hilltops stand, intermediate between that of the lowlands 
and the trap plateau and the Devonian cuesta probably indicates 
an intermediate stand of the land, the date of which is difficult 
to determine. The valleys of such rivers as the Tieté in Sao Paulo 
certainly have been excavated since the Tertiary deposits which 
underlie the city of that name. It seems highly probable therefore 
that the uplands in the Permian tracts antedate not only these Tertiary 
deposits but also the erosion of the depressions in which the beds were 
accumulated. The date of the evanescent peneplain with which the 
summits of the upland areas accord must be placed therefore in early 
Tertiary time. 
The westward flowing drainage of the planalto gives rise to the 
dissection of the Permian terrane by long westward aligned valleys 
such as those of the Paranapanema and the Rio Negro, but the 
tributaries of the latter river including such large streams as the 
Tibagy flow obliquely across the trend of the Permian belt on courses 
expressing the resolution of the double control of the westward dip of 
the formation on the one hand and of the slope towards the master 
stream developed by concentration of the drainage on the other. The 
Rio Negro displays a rectangular adjustment of its course to the 
strike and dip of the Permian strata. 
In the latitude of Curityba there is traceable westward from the 
vicinity of that city a divide between the waters which drain northward 
into the Paranapanema and southward into the Rio Iguasst. This 
watershed includes the Serrinha, passes south of the towns of Pal- 
meira and Iraty and thence joins on the west the trap escarpment 
known as the Serra da Esperanca. The great extent of the drainage 
basin of the Rio Paranapanema as compared with that of the com- 
bined Iguassii and Rio Negro in the Permian terrane is apparently a 
consequence of the antilinal axis, which, normal to the are of the 
outcrops in eastern Parandé and southern Sao Paulo, caused the 
Palaeozoic beds along this east-west line to stand relatively high and 
erode more rapidly. As a result of this distribution of the drainage 
a 
