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bulletin: museum of compakative zoology. 



and the top of them, at a few places only, rises perhaps as much as a 

 metre above high tide. Sand dunes lie on top of these beds, and behind 

 the dunes the water soaks down, passes thi-ough the dunes, and following 

 along the top of the rocks issues as amber-colored springs on the beach. 



At one place a large spring has cut through the rock and comes out 

 two metres or more below its surface. Not a trace of a fossil could be 



Fig. 6. Theoretic section showing the relations of the Bahia Formosa beds 

 to the Cunhahu sandstone. 



found in a kilometre of exposure of this rock. The beds are horizontal, 

 but they do not appear in the Bahia Formosa section of the colored beds 

 which are cut clear down to the water's edge. The snuff-coloi-ed beds 

 must, therefore, rest unconformably against the valley originally cut by 

 the Cunhahu in these sediments. 



A few kilometres north of the Cunhahu and north of Kio Sibaiima, the 

 bluffs have lying against them at one place horizontally bedded sedi- 

 ments made of fragments derived 

 from these bluffs themselves. 



These beds contain no fossils, 

 and from the appearance of the 

 materials it is supposed that the 

 newer beds here were deposited 

 since the discoloration of the 

 bluffs. At this place the top 

 of the deposit is barely within 

 reach of the highest spring tides. 

 I am not at all sure that these 

 newer beds are related to the 

 snuff-colored ones. 



At the mouth of Rio Maman- 



guape, S. lat. 6° 46', on the point 



of land just east of the Barra de Mamanguape are exposed very dark 



sandstones, of about the same texture as the reef rocks and containing 



quartz, but in color from dark brown to perfectly black. Between the 



Fig. 7. Section through the bluff and 

 beach north of Rio Sibaiima. 



