brannek: the stone eeefs of brazil. 



13.- 



eastern and western ends ; so has Lagoa Gururupira ; Lagoa de Araruama 

 has the peaks of Cabo Frio at one end and the hills of Ponta de Sagua- 

 rema at the other. These lakes thus stand on the sites of sunken coastal 

 valleys whose mouths have been closed by the shore waste, and whose 

 upper ends have been silted up by materials brought down by streams. 



Sand banks or bars are liable to be built across any sharp curve in a 

 coast-line ; behind these bars lakes and pools are formed, and later these 



Fig. 70. Bird's-eye view of the region about Trai(;ao and the mouth of Rio 

 Mamanguape, showing the relation of tiie stone reefs to the shores. 



silt up, forming marshes and eventually land. On the Brazilian coast 

 some of the lakes !\re fresh and some of them are brackish according as 

 the influx of fresh water is large or small. 



At Trai(j-ao, State of Parahyba do Xorte, the Lagoa de Sinimbu, a 

 fresh-water lake, is shut in by a narrow neck of sand that compels the 

 drainage to find an outlet to the sea through the Mamanguape Eiver 

 several kilometres away. The entire seaward rim of tliis lake is made 

 of recent sands. Soutli of Trait^'ao this barrier is about two hundred 



