:i2 



G. A. Waring — Reef Formations of the 



ding planes dipping 3 degrees seaward, and lies partly as a 

 barrier, partly along the beach, suggesting that a little bay has 

 been washed out behind it as shown in fig. 3a. Its northern 

 end is buried in the beach. 



Near the village of Jacuma, a few miles northward, a small 

 reef of the rock extends from the beach into the surf. At a 

 low point beyond, a similar reef, which first appears in the 

 water, extends in a straight line in such a direction that it 



Fig. 2. 



Fig. 2. Bird's- eve view of reef at mouth of Rio Ceara-Mirim. 



passes for some distance along the beach and then disappears 

 in the water beyond the point (fig. 35). 



ISTo signs of a calcareous sandstone reef were found near the 

 mouth of Rio Maxaranguape, 4f miles farther north, though 

 this stream has a small perennial flow and contains much man- 

 grove in its lower portion. The South Atlantic equatorial 

 current flows westward from Africa and divides at Cabo Sao 

 Roque, part going northward and part southward along the 

 Brazilian coast. The southward-flowing current may have 

 been of influence in preventing the formation of a calcareous 

 sandstone reef at the mouth of the Maxaranguape, which is 

 only one mile south of the cape. The position of the Maxaran- 

 guape, near a projecting part of the coast, also appears not to be 

 favorable to the formation of a calcareous reef, for nearly all of 

 the prominent reefs described by Dr. Branner extend along 

 inward-curving beaches, northward from river mouths.* 



* This characteristic is well brought out by the several detailed maps of 

 reefs accompanying Dr. Branner's report (Ball. Mus. Comp. Zool., vii, 1904). 

 The northward discharge of river mouths, produced \>y drifting sand, is 

 mentioned by Olaf Pitt Jenkins, Geology of the Region about Natal, Rio 

 Grande do Norte, Brazil, Proc. Am. Phil. Soc. vol. lii, No. 211, p. 4, Sept.- 

 Oct., 1913. 



