378 G. A. Waring — JReef Formations of the 



Other Occurrences of Calcareous Sandstone. 



Although the materials of the headland near Caicara light 

 and of Ponta Caicara are similar in composition to those of the 

 well-developed reefs, they resemble hardened masses of sand 

 rather than elongated spits, and this character is exhibited by 

 other occurrences that were noted farther west. 



The first one of these occurrences is 6 miles west of Ponta 

 Caicara, at Ponta Jacare. Here the typical gray, lime- 

 cemented sand with layers of gravel and shells is exposed for 

 about 100 yards along the beach ; but instead of forming a 

 reef or a lithified beach, the rock extends from the base of a 



Fig. 6. 



Fig. 6. Region near Ponta Reducto, showing relation of lowlands to the 

 reef. 



great sand dune to the water 25 yards away, where it forms a 

 ledge 5 or 6 feet above half-tide level and dips 8 degrees to 

 the north, seaward. This is the westernmost exposure of the 

 reef rock that was seen along the beach in the journey between 

 Rio Grande do Norte and Macau. It could not be definitely 

 learned by inquiry whether or not rock is exposed along any 

 part of the coast between Ponta Jacare and Macau ; and this 

 portion of the coast, which is low and intersected by tidal 

 inlets, was not traversed. It is believed, however, that no 

 reefs are present along this stretch of dunes and tidal inlets. 



At a few places west of Macau the calcareous sandstone 

 was observed near ports that were visited on coasting steamers, 

 the first one west of Macau being Areia Branca. Along the 

 ocean east of the entrance to this port the beach is bordered 



