1879. | Brazilian Corals and Coral Reefs. 547 
Almost everywhere along the inner edge, but more commonly at 
the ends of the reef and about the openings through it, we find 
many outlying masses which are often partly continuous with the 
low, inner surface, but more frequently quite detached. They 
attain all heights up to that of the lower surface, but never reach 
above it; the average depth of water around them is between 
three and four feet. The outliers on the outside of the reef are 
merely low, ragged, angular projections from the reef itself, and 
are never much exposed, even at low tide. 
Between the two divisions of the reef, the elevated outer por- 
tion and the flat inner one, there is the most marked contrast. 
While the latter has been completely smoothed and rounded off, 
so that scarcely any angles remain upon it, the former retains all 
the possible roughness that could be brought together on so nar- 
row an area. The entire raised mass of rock is full of holes of 
every imaginable size and shape, the margins of which are always 
acutely angulated. Every little surface that is not pointed in 
itself is surmounted by a large and strong barnacle with sharply- 
edged valves, and large clusters of digitate projections stand up 
at frequent intervals. This combination of surface is a very unin- 
viting one to look upon, but it is far less pléasant to climb over 
it or walk along its upper part. The outer slope is by far the 
most irregular, as the waves, aided by an army of sea-urchins, 
have broken into it and hollowed out thousands of ragged holes, 
which, lying concealed beneath the seaweeds, might lead to many 
accidents were the reef more frequented. 
The outer portion of the reef is of a dark and rather rich 
brown color when wet by the waves, but nevertheless has quite a 
dead appearance. Examining carefully this brown rock, it is seen 
to consist generally of an accumulation of very small worm tubes, 
closely packed together and forming a very hard mass. The sur- — 
face of the low inner level is of a much lighter color, a rather 
faded brown, and looks even more lifeless than the part we have 
been describing; no barnacles or other large animals grow 
upon it. 
What forms of life occur about the reef? On the outer side, 
reaching to a height of a foot or slightly more above ordinary 
low tide, is a luxuriant growth of seaweeds. Over the same zone, 
but not so apparent, spread encrusting nullipores, which, though 
resembling lichens in form, are so highly charged with lime as to 
