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BRANNER: THE STONE REEFS OF BRAZIL. 273 
exposed portions of the reef seems to be solid Millepore rock, which is 
certainly being constantly added to by the rapid growth of this species at 
the present time. This Millepore rock is the most dense and durable of 
all, though it is extremely brittle, and, because of its mode of growth, is 
more easily broken than that of either Porites verrilli or Orbicella aperta. 
Millepora braziliensis grows all over the reef, but in small, isolated 
heads that add but little to the reef structure. 
Orbicella aperta grows in regular heads that are sometimes two feet 
or more in diameter, and with an even greater depth of clean, unbroken 
rock, which is very tough and tenacious. This species would be a 
very important structural coral if it were moro abundant, but it grows 
only in isolated masses which add comparatively little to the reef. It is 
found in the more sheltered places of the outer edge of the reef, and 
forms beautiful, conspicuous heads, because of the large cells and promi- 
nence of the polyps that look very much like small, encrusting anem- 
ones. The rock is porous but remarkably tough and durable. 
Mussa harttii is the most striking coral of the Maceio reef, It com- 
pletely lines the borders of the sheltered lagoons that are constantly 
filled with the fresh water of the outside. It is a densely branching 
species forming huge clumps of nearly a solid mass of short thick stems, 
These clumps rise to а height of ten or fifteen feet in the sheltered coves, 
but are usually only a foot or so high and as broad along the outer edge 
of the reef. These smaller clusters grow in the greatest profusion wher- 
ever the water is clear and the force of the waves is not too great. The 
thick stems are white surmounted by polyps of a brilliant lavender hue, 
that are extremely showy because of their large size and bright colors, 
The stems are very fragile, however, and this species adds to the reef by 
the accumulation of its broken fragments. After a time the clusters 
become too heavy for the weak stems, and the waves play havoc with 
the whole mass, scattering the branches all over the reef, Some of the 
best collecting of the whole reef is to be had in these Mussa heads, which 
harbor an immense variety of crustaceans, echinoderms, worms, etc. 
Symphyllia harttii grows in the same locations as its near relative 
Mussa harttii, and resembles it very strikingly in appearance. The color 
and size of the polyps are about the same as those of Mussa, but Sym- 
Phyllia grows in low solid heads, while Mussa forms branching clusters. 
утра is also very much less abundant than Mussa. 
1 Dr. T. W. Vaughan, to whom I am indebted for corrections in the nomencla- 
ture, tells me that Symphyllia harttii is, as Verrill at first suspected, only a growth 
form of Mussa harttü. J. C. B. 
VOL. XLIV. 18 
