108 BULLETIN: MUSEUM OF COMPARATIVE ZOOLOGY. 
barrier) beaches or of old shore beaches. If they were originally barrier 
beaches we should expect to find low, flat, newly made land lying be- 
tween them and the high ground of terra firma. If they were originally 
shore beaches we might expect to find them resting unconformably against 
the older rocks of the headlands. This latter characteristic, however, is 
not necessarily confined to in-shore beaches, but may belong to both bar- 
riers and to spits formed well off the main shore. ; 
The constant blowing of the winds on shore and the narrowness of the 
continental shoulder have favored the near-shore formation of barrier 
beaches along the Brazilian coast. 
At Cape Santo Agostinho the reef rock laps back against the granite 
rocks of that headland. Both north and south of the cape the elevated 
country falls away from the shore, leaving the region near the shore flat ; 
but in no case is this flat belt more than two or three miles wide, save 
where streams flow in through open valleys. North of the cape the 
coast is low and flat all the way to Olinda, where a headland again reaches 
the sea. The stone reefs off the mouth of Rio Goyanna are well out 
from the land. The Mamanguape reef approaches a Tertiary (?) hill 
only at its southern end; the Natal reefs do the same. The Serinhaem 
reefs stand well out from the hills, though one of them is now a beach 
reef. At Bahia the stone reefs were formed against steep banks, At 
Porto Seguro the reef is half a mile from the hill on which Villa Velha 
stands, while south of these the high land swings abruptly inland, leaving 
a low, flat region to the landward of the reef. At Parahyba do Norte 
the land of the peninsula of Ponta do Matto, where the recent rock is 
found, is all low. 
There are no lakes at present immediately behind the stone reefs, 
though such lakes must have existed formerly. Lagöa de Almada, in 
the State of Bahia, is a fresh-water lake, believed by Spix and Martius 
to have been formerly an arm of the sea. Stone reef rocks are said to be 
found in the vicinity of this lake, but no mention is made of the geo- 
graphic relations of these rocks to the lake." There are no barrier 
beaches along the northeast coast of Brazil now except those of coral. 
It is a noticeable characteristic of the shore forms behind the stone 
reefs, that wherever there is a break in the reef, the new shore-line falls 
away, forming an indentation like that just north of Gaibá (see p. 70). 
Structure of the stone reefs. — The structure here considered relates 
only to gross structure, — the bedding and the relation of the beds to 
1 J, B. von Spix und С. Е. Р, von Martius, Reise in Brasilien, П., p. 684-685. 
Miinchen, 1828, 
