272 BULLETIN: MUSEUM OF COMPARATIVE ZOOLOGY. 
at high tide. This mass of rock is shaped like a pyramid, fifteen feet 
broad at the base, much honeycombed out by the waves." At another 
part near by I found an extensive area of Porites rock. nearly two feet 
above the level of low tide. 
Porites verrilli is at Maceio, as at every other place where we collected, 
the most abundant coral, and is by far the most important structural 
coral of the reef. It grows everywhere, even on the sand-covered inner 
edges of the reef, where no other coral can live except Favia conferta. 
Notwithstanding the abundance of this species, it grows only in small 
isolated heads, and in no place could I find large masses of Porites 
growing in such a way as to form any considerable addition to the reef. 
At one time it must have grown in huge heads all over the reef, for the 
older portions are nearly solid Porites rock, which can readily be seen 
wherever the reef has been excavated for lime. So while the greater 
part of the reef has been built up by this species in former times, for 
some reason it has been crowded out of the growing part of the reef, and 
is now scattered everywhere in small isolated masses with Havia con- 
ferta. This coral forms extremely solid and lasting rock, though it is 
not so dense and durable as that of the Millepores, nor so hard and 
tough as the rock of the Orbicella aperta. 
Porites branneri was found in only one place, growing in small heads, 
and appears to be rare here as elsewhere. 
Favia gravida is scattered all over the reef with Porites verrilli in small 
heads which form no thick layers of coral rock. Its distribution on this 
coral reef agrees exactly with what was already observed on the sand- 
stone reefs. 
Millepora aleicornis and Millepora braziliensis were found in great 
numbers, and the former was, next to Porites verrilli, the most important 
structural coral obtained, forming with the Porites the greater part of 
the old reef. Millepora aleicornis lives on the extreme outer edge of 
the reef in the heavy breakers where few other corals grow. In these 
exposed places it thrives, growing either in huge erect clusters on sub- 
merged bases of rock, or in overhanging masses many feet in extent on 
the extreme outer edge of the main reef. In these the corals grow either 
outward horizontally or downward from the under surface of these over- 
hanging ledges. In these single clusters all variations from the bluntly 
lobed to the slenderly pointed or fenestrated forms, until recently known 
ав distinct varieties, were found, showing clearly that these are all sim- 
ply different phases of this highly variable species. -Much of these 
1 This is an uptilted block that has been undermined by the waves. See pages 
160 and 161 of this report. — J. C. В. 
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