BRANNER: THE STONE REEFS OF BRAZIL. OL 
The sandstone reef lies at a higher level on the beach than the coral 
reef, and has throughout most of its length a decided seaward dip. At 
the southern end of its contact with the beach, however, the dip is re- 
versed and the bedding looks very much as if it had been formed by 
sand washed over and behind a low beach or spit. The rock is in some 
places rather soft, in others it is quite hard and rings when struck with 
the hammer. It contains many shells of living forms of mollusks, es- 
pecially mariscos, and also calcareous Algae. 
Certain features about the southern end of these reefs 
in connection with the coast history. 
There is here a mangrove Swamp being encroached upon by the sea, — 
a somewhat unusual process. The Swamp, as will be seen from the 
sketch, was formerly protected by the reefs, but the sea has gradually 
broken down this barrier and, encroaching upon the shore about its 
southwest end, has attacked the mangroves. Та the embayment south 
of the existing swamp and reefs the shallow bay contains a great many 
dead stumps of mangrove trees still standing in place. 
The stone reefs of the Pratagy, Alagoas. — The Rio Pratagy is a small 
stream, not more than sixty metres wide, entering the ocean eleven or 
twelve kilometres north of Maceio. Where this stre 
sandstone reef lies square across its mouth. 
Both north and south of the Pratagy and within a short distance are 
other reefs or fragments of stone reefs that may be considered as parts 
of the one in front of the river's mouth, . 
The chief features of the topography of most of this part of the coast 
consist of a flat-topped plateau of Tertiary sediments rising abruptly 
from near sea-level to an elevation of from fifty to a hundred metres, 
The margin of this plateau is cut across here and there by streams com- 
ing down from the interior and forming, especially near the coast, rather 
steep-sided, flat-bottomed valleys. 
It is through one of these valleys that the Rio Prat, 
Sea. The narrow strip between the mouth of the river and the foot of 
the Tertiary escarpment is low, flat, and mostly sandy, but near the 
stream covered with Mangrove swamps. Just back of the beach and 
parallel with it is a somewhat higher bank of sand, apparently blown 
up from the shore. 
The first or most northern of the Pratagy reefs begins on or near the 
beach one kilometre northeast of the mouth of the river. It is here 
only fragmentary, — one large piece after another, but lying always in a 
line, a little way out from the high-water beach and Just covered at high 
are interesting 
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