376 G. A. Waring — Reef Formations of the 



a beach-reef for 850 yards farther (see fig. 1), and then swings 

 landward and is lost, though its course ma) 7 be traced for some 

 distance farther by scattered and disintegrated fragments 25 

 to 50 yards back from the beach. The relation of the reef to 

 the beach along this stretch is shown by figure 5. Ponta Cai- 

 cara is formed of fresh-looking, pale-yellow, very hard stone 

 which closely resembles the reef rock. The exposure at this 

 place has not the usual long and narrow form of the typical 



Fig. 4. 



Fig. 4. Lithitied beach near Ponta Caigara. 



reefs, however. The material extends from the base of a large 

 dune down to the surf, where it exposes a steep face to the 

 beach for a few yards. The western end of the lithified mass 

 terminates abruptly in a vertical face 6 or 8 feet high that 

 trends straight inland and disappears beneath the drifting sand 

 100 yards from the beach. The dip of the material here 

 exposed seems to be about 10 degrees to the northeast, while 

 the beach-reef farther east dips at low angles uniformly north- 

 ward, into the sea. 



The reef or lithified beach that extends almost uninterrupt- 

 edly from some distance east of Caigara light to the jDoint of 

 the same name, appears to be the westernmost area of any con- 

 siderable extent of the typical calcareous reef formation. 



By reference to the general map of Plate IX it will be seen 

 that no streams of importance drain the area between the 

 courses of Rio Ceara-Mirim and Rio Salgado (which enters 

 tide water at Macau). None of the small streams that enter 

 the ocean between these two rivers have calcareous sandstone 

 reefs at their mouths. The reefs that are present along this 



