108 BULLETIN : MUSEUM OF COMPARATIVE ZOOLOGY. 



barrier) beaches or of old shore beaches. If they were originally barrier 

 bea,ches we should expect to find low, flat, newly made land lying be- 

 tween them and the high ground of terra firma. If they were originally 

 shore beaches we might expect to find them resting unconformably against 

 the older rocks of the headlands. This latter characteristic, however, is 

 not necessarily confined to in-shore beaches, but may belong to both bar- 

 riers and to spits formed well off" the main shore. 



The constant blowing of the winds on shore and the narrowness of the 

 continental shoulder have favored the near-shore formation of barrier 

 beaches along the Brazilian coast. 



At Cape Santo Agostinho the reef rock laps back against the granite 

 rocks of that headland. Both north and south of the cape the elevated 

 country falls away from the shore, leaving the region near the shore flat ; 

 but in no case is this flat belt more than two or three miles wide, save 

 where streams flow in through open valleys. North of the cape the 

 coast is low and flat all the way to Olinda, where a headland again reaches 

 the sea. The stone reefs off the mouth of Rio Goyanna are well out 

 from the land. The Mamanguape reef approaches a Tertiary (1) hill 

 only at its southern end ; the Natal reefs do the same. The Serinhaem 

 reefs stand well out from the hills, though one of them is now a beach 

 reef. At Bahia the stone reefs were formed against steep banks. At 

 Porto Seguro the reef is half a mile from the hill on which Villa Velha 

 stands, while south of these the high land swings abruptly inland, leaving 

 a low, flat region to the landward of the reef. At Parahyba do Norte 

 the land of the peninsula of Ponta do Matto, where the recent rock is 

 found, is all low. 



There are no lakes at present immediately behind the stone reefs, 

 though such lakes must have existed formerly. Lagoa de Almada, in 

 the State of Bahia, is a fresh-water lake, believed by Spix and Martins 

 to have been formerly an arm of the sea. Stone reef rocks are said to be 

 found in the vicinity of this lake, but no mention is made of the geo- 

 graphic relations of these rocks to the lake,^ There are no barrier 

 beaches along the northeast coast of Brazil now except those of coral. 



It is a noticeable characteristic of the shore forms behind the stone 

 reefs, that wherever there is a break in the reef, the new shore-line falls 

 awa)', forming an indentation like that just north of Gaibu (see p. 70). 



Structure of the stone reefs. — The structure here considered relates 

 only to gross structure, — the bedding and the relation of the beds to 



1 J. B. von Spix uiid C. F. P. von Martius, Reise in Brasilien, II., p. 684-685, 

 Munclien, 1828. 



