Northeast Coast of Brazil. 383 



and the resulting protected surfaces are studded with subangu- 

 lar quartz pebbles up to an inch in size. Fallen blocks form 

 a breakwater along the front of the cliff (fig. 11). These 

 blocks contain numerous seams which are filled with pebbles 

 and shells cemented together with lime carbonate, while a few 

 seams J to 4 inches wide are filled with small, silvery-white 

 mollusk shells closely matted together as if they had grown 

 thus. 



On the slopes behind the cliffs at Tres Irmaos the surface is 

 dotted with fragments of calcified brush roots and branches. 



Fig. 9. 



Fig. 9. Ponta Mel as seen from a coasting steamer. 



Some of the fragments attain the size of a man's arm, and 

 many can hardly be distinguished by sight alone from the asso- 

 ciated fragments of wood. This form of petrifaction appears 

 to have been effected while the bushes were covered by dune 

 sand, which has now drifted past and left them exposed again. 

 Some calcareous matter has also penetrated downward into the 

 sandstone of the cliff and is seen as lighter-colored masses. In 

 the dune areas near Ponta Peducto and Ponta Mel similar 

 calcified fragments were seen, less well-developed, and in a 

 wide expanse of dun-colored dunes and sand knolls about half- 

 way between Ponta Jacare and Macau, beyond the inland 

 reach of the tidal inlets, considerable areas are dotted by whit- 

 ened and sand-worn conch shells and by bone-white fragments 

 of lime carbonate that resemble roots and twigs. 



Reefs. 



In practically every place where cliffs have been formed 

 along the coast, a fringe-reef of the same material extends out 

 into the water. In a few places there is very little difference 



Am. Jour. Sci.— Fourth Series, Vol. XXXVII, No. 221.— May, 1914. 



