66 bulletin: museum of comparative zoology. 



tinctly striated pebble, a compound quartz-bearing rock, with one 

 well-rounded side and a surface of more recent fracture. The 

 rounded surface bore striae. The pebbles in this conglomerate are 



C'ofnr^acf blue pel hie 



Fig. 16. — Section of the conglomerate and overlying sandstones at Serrinha, 

 Parand, in the gorge of the IguassQ. 



rather closelj' scattered through a matrix of abundant sandstone of an 

 argillaceous character, suggesting the deposition of the mass by float- 

 ing ice. 



The whitish sandstone overlying this conglomerate is so like that 

 forming the base of the Devonian northward in the Serrinha ridge 

 that the question is raised whether this conglomerate belongs to the 

 Permo-Carboniferous series or to the Devonian. There is no appear- 

 ance of faulting in the neighboring district which I discerned. The 

 Devonian shales which separate the Devonian sandstone from the 

 basal Permian at Ponta Grossa on the north have at this distance on 

 the south disappeared, and it is possible that the Sandstone has also; 

 the Permian by overlap coming close down to if not in contact with 

 the Pre-Devonian east and north of Serrinha, the local resemblance 

 of the white sandstone to the typical Devonian being assignable to a 

 redeposition of those sandstones. The determination of the Devonian 

 age of the lower beds at Serrinha, should it be made, would introduce 

 another glacial epoch in south Brazil parallel to the case in South 

 Africa. In this report I have preferred to follow the tentative opinion 

 of Dr. Derby that the Serrinha section is Carboniferous (Permian). 

 This view involves at least two advances of the ice in Permian time. 



The Section at Lapa. — Lapa is a station on the railway south of Ser- 

 rinha. Along the line of railway southward from Serrinha after 

 surmounting and crossing the sandstones on the south bank of the 

 Iguassil the tillite beds are traversed by the train. Near and north of 

 Pi vary the campo surface is strewn with rounded stones. About 



