BRANNER: THE STONE REEFS OF BRAZIL. 73 
south of the Rio Tatuóca is a small isolated Tertiary hill, and the hydro- 
graphic chart shows another of similar form a little further south. 
The essential features of the geology of the region consist of a ridge of 
granite and granite porphyries, and other crystalline and metamorphic 
rocks of the Cape having an east-west trend, and with Tertiary sediments 
deposited against and over them. Denudation has stripped off most of 
the beds that lay upon the Cape crystalline rocks, and has carved out the 
embayment that now opens south of it. The shore of the bay from 
the Barra do Suäpe to the village of the same name is all of crystalline 
rocks ; a little west of the village a promontory of Tertiary (?) beds 
projects into the valley. This hill is of mottled yellow, red, and white 
clays and sands ; there are no granites exposed where the Rio Suápe 
washes its base. 
At the village of Suápe the beach on the flat is all sandy, and barely 
high enough to keep the salt water at high tides from flowing over into 
the fresh-water marsh lying just west of it. Tradition says that the bay 
at this northern end is rapidly cutting away its western shore. The coco 
palm stumps standing in the bay from one hundred and fifty to two hun- 
dred metres out from the present beach bear out this tradition. 
At low tide great sandy flats are uncovered in the b 
ern end and south of Cambóa Point the bay is but 
pool some twenty to fifty metres wide, into w 
On the sea side of this pool is the wall-like reef, and on the land side a 
bank of white sand five or six metres in height. The sand flats about 
the mouth of the Ipojüca and in this arm of the bay swarm with myriads 
of little fiddler crabs. These sands also contain a great number of deli- 
cate pink shells of bivalves. 
ay. At its south- 
a narrow and shallow 
hich the tide-water backs, 
The sand ridge on the land side is a wind accumulation ; behind it the 
country drops off again to a somewhat lower level. 
The Cabo Santo Agostinho reef properly speaking begins on the beach 
of the cape itself, just north of the Barra do Suäpe and a few hundred 
metres north of the old fort. The rocks of the cape just here aro coarse- 
grained granites, and the reef rock lies unconformably against, and 
attached to, these granites. There are several of these reef fragments 
separated from one another by breaks of various lengths and strewn along 
the beach over a distance of a kilometre to the north of the fort. The 
section is essentially the same for all these remnants. 
The fragment nearest the fort is fifty-three metres 
metres Jong. The next fra 
and about fifty metres wide, 
wide by forty-five 
gment to the north is ninety metres long 
All these reef remnants have 
a gentle sea- 
