68 



bulletin: museum of comparative zoology. 



Sandy beds with boulders succeed to the shales for a few feet of 

 thickness. Shales come in again above this level, rarely with striated 

 pebbles. 



sw. 



HE. 



Fig. 17. — Section of Permian shales, boukler-beds. and sandstones at Rio 

 Nea:ro. 



The section, at the bridge (Fig. 17) above referred to, displays 

 sandstones at water-level somewhat cross-bedded and carrying 

 scattered pebbles and small blocks. I measured one granitic frag- 

 ment 16 inches long. 



On the south side of the Rio Negro along the road going eastward 

 towards Sao Bento yellow^ tillite beds with intercalated dark shales 

 contain many granitic boulders. A cobble eight inches in diameter 

 showed good striation. The boulders range from two to three feet 





Fig. is. — Section of fossiliferous Permian marine shales between boulder- 

 beds near Rio Negro. 



in diameter, all in the yellow sandy tillite, with \ery few small pebbles, 

 arguing for floating ice. A few kilometers along this road eastward 

 from the bridge where a small stream has cut a well-defined valley in 

 its descent to the Rio Negro, Dr. Oliveira found a marine fauna in 

 black shales intercalated betMeen two boulder-beds of the tillite series 

 (Fig. 18). I refer to this bed and its apparent significance elsewhere. 

 A few kilometers farther east by south along this road a new cut 

 near the small Rio da Vida nova displayed the shales and tillite beds 

 (Plates 23 anfl 24), at horizons closely corresponding to the beds above 



