branxer: the stoxe reefs of brazil. 55 



mouth of the river here a hundred metres wide. West of this branch of 

 the river is exposed at low tide a portion of the inner reef. This inner 

 reef is here from ten to eighteen metres wide and three hundred metres 

 long; at low tide it connects with and forms part of the beach. The rock 

 is in places of a reddish color, and is not as hard as that of the outer reef. 

 Fifty metres west of the inner reef and exposed on the river bank at low 

 tide is a soft pebbly sandstone, iu texture very like the reef rock, but 

 containing no shells and varying iu color from a dark brown to perfectly 

 black. These black beds underlie Mamanguape Point and are barely 

 covered at high tide. The Mamanguape Point itself is of white sand to 

 a depth of eight or nine metres, heaped up here by the wind, but thin- 

 ning and disappearing east of the village of Barra do Mamanguape. Be- 

 neath this sand the black rocks pass westward round the point and up 

 the river to and beneath the village, above which it is still visible here 

 and there. These black sandstones are about on a level with the outer 

 reef. They appear to have been colored by organic matter. In places 

 they are strongly false bedded. (Compare geology of Ptio Formoso.) 



TJie consolidated beaches of Parahyha do Norte. — At the entrance to 

 the Rio Parahyha do Norte, State of Parahyha do Norte, the gi'eat reef 

 on which the lighthouse stands is of coral. This will be described in the 

 second part of the present paper. / 



Properly speaking, there is no sandstone reef in the vicinity of this 

 port. The coral reef is only about one kilometre from the shore, with 

 which it is parallel. From the Ponta da Matta southward for something 

 more than a mile the beach is low, flat, and sandy, and planted with coco 

 palms. Beyond this to the south begin to appear evidences of an old 

 consolidated sand beach, and these signs continue for nearly twelve hun- 

 dred metres. The beach, however, continues to be sandy, and the pen- 

 insula west of it is still low and flat. Loose blocks of the sandstone of 

 the consolidated beach are sparsely scattered over the beach in some 

 places, and in others the bed is exposed in place. The exposures are all 

 between high and low water marks, and so far as was seen, are confined 

 to the beach, where they are generally overlain by a metre or more of 

 sand and soil. 



The peninsula lying between Rio Parahyha and the ocean is narrow- 

 est one kilometre south of Fortaleza da Barra, and at or very near this 

 narrowest part the remains of a consolidated beach are uncovered. This 

 exposure is between the village of Cabedello and the beginning of the 

 mangrove swamp on the right side of the river, and is nearer the swam].. 

 The exposure is between high and low tides, the rock not very hard, and 



