CHAPTER VI 
The Passa Dois Series 
Above the Palermo shales, there comes a series of shales, sandy 
heds, and limestones which are well exposed along the upper waters of 
Rio Passa Dois, a stream which parallels the Estrada do Rio do Rasto for 
several kilometers, and hence these beds have heen designated from 
that river. 
The character of the series as a whole isof a soft and shaly na- 
ture, although somecherty beds often occur near the center as well 
as some sandy layers. The total thickness of the Passa Dois series as 
estimated from its crop along the Estrada do rio do Rasto of Santa Ca- 
tharina is 223 metres. 
These beds above the Tubardo seris were studied only inciden- 
tally and therefore hastilly, so that the measurements given are 
approximate. 
The series as sxhibited in Santa Catharina is made up of three 
members, namelly, the Rocinha Limestone at, top separated from the 
Traty black shale at base by the intervening Estrada do Rio do Rasta 
gray and variegated shales holding fossil wood, fossil crustacean 
remais, and cherty concretions. 
The Iraty Black Shale 
At the base af the Passa Dois series, there comes a thick, and 
widely persistent black shale, extending from §. Paulo, through 
Parana, and Santa Catharina, to and across Rio Grande do Sul. It 
appears to be generally petroliferous so that on freshly broken and 
unweathered surfaces it always gives oul the odor of petroleum. 
This formation has been designated from Iraty in the state of 
Paranda where it crops in a railway cutting about 3 kilometers south 
from the Iraty station, and contains vast numbers of the remains of 
a fossil reptile which Dr. Mc Gregor, of the American Museum of Na- 
tural History, New York, has named Mesosaurus brasiliensis, 
