242 BULLETIN: MUSEUM OF COMPARATIVE ZOOLOGY. 
South of Barra Grande the line of coral reefs continues with breaks to 
the Porto de Pedras at the mouth of Rio Manguába. South of that 
place they are almost continuous to the mouth of Rio Camaragibe, —a 
distance of twenty-four kilometres. The seaward face of this reef aver- 
ages something more than a kilometre off the shore. 
At the Barreira do Boqueiräo an inner reef, having its northern end 
well off shore, swings round and comes squarely against the beach at its 
south end, the beach sands lying on top of the dead coral reef. 
At São Miguel dos Milagres (8. lat. 9° 18/ 30!) the coral reef is 
rather closer to the shore than usual. One kilometre south of there a 
coral reef is uncovered 
on shore for a short dis- 
tance; its south end 
swings outward away 
from the beach into deep 
water. 
Three kilometres 
south of São Miguel 
there is a coral reef un- 
covered on the beach at 
the mouth of a small 
stream. This piece of 
reef has been dead for a 
| long while. Its surface 
Fic. 97. Map showing positions of two coral reefs has been pitted and 
near São Miguel; the reef оп shore is dead and worn by waves and sand, 
is partly covered by sand. 
then buried beneath the 
encroaching beach sands, and now again it has been partly uncovered 
by the shifting currents. The freshly uncovered surface shows the com- 
position of the reef much better than it can be seen upon the ordinary 
dead or even upon living reefs. The rock is mostly coralline and most 
of the coral imbedded in this mass is Porites. The Porites form less 
than half of the rock, —perhaps a third of it. 
This piece of reef runs out more than one hundred metres from the 
shore at mean tide, and at low tide a width of nearly five hundred metres 
is exposed. 
One kilometre south of this exposure the sand flats exposed at low 
tide connect with and overlie the offshore dead coral reefs. The dead 
reef is exposed along the beach for more than two kilometres, and the 
water between it and the main reef outside (seaward) is very shallow 
and full of coral rock. 
