270 BULLETIN: MUSEUM OF COMPARATIVE ZOOLOGY. 
inside of the reef. Its heads are very small, rarely more than two or 
three inches in diameter, and not more than an inch or so in thickness, 
This species varies considerably in the character of the walls between the 
cells. Typically they are thin and ungrooved, but in a few small speci- 
mens from the Mamanguape and Rio Grande do Norte reefs the walls 
were thick and decidedly concave. 
Porites brammeri is a rare coral and was found by the expedition only 
on the Rio Grande do Norte stone reef at Natal. One large head six 
inches in diameter, bluntly conical in shape and irregularly lobed, was 
collected. It is of a deep brown color in life. The cells resemble very 
much those of Porites verrill in form, but they are smaller, and the 
texture of the rock is much more porous. 
Millepora aleicornis was the only Millepore found on the sandstone 
reefs, and this one was observed in only one place, between two portions 
of the Pernambuco reef in about three feet of water at low tide. It 
formed here a clump a foot or so high, with a few smaller masses grow- 
ing about it. 
The Maceio coral reef. — The only true coral reef visited by the writer 
was the Maceio reef (see Fig. 94, p. 166), located about one hundred and 
fifty miles south of Pernambuco, off the town of Maceio, State of Alagóas. 
The reef is a splendid example of the great barrier reefs found along the 
Brazilian coast. The corals are very abundant, growing actively along 
the outer edge, and because of its easy accessibility from the shore, the 
reef is a good one for study. It is about three miles long, fully two 
thirds of a mile wide at its broadest part, and the whole of its upper sur- 
face is exposed at the lowest tides of each month. The reef is broadest at 
its northern end, where it joins a small point that forms the northern 
boundary of the Bay of Maceio. Here the reef is very firm and even, 
and it is possible to walk outward over two thirds of a mile of solid coral 
rock almost without any breaks. This part of the reef is apparently the 
oldest, and contains very few growing corals. From this point the reef 
runs nearly south at a distance of about half a mile from the shore, and 
becomes very irregular at the lower end, forming several small fragments 
of coral rock, one lying inside the other. This broken part of the reef 
abounds in growing corals along the narrow channels between the differ- 
ent sections of the reef, and the rock is much less solid, containing many 
pools and caverns that communicate with the outside, and all these 
channels are covered with corals of one kind or another. The coral rock 
formed at first is extremely irregular, existing in narrow ridges and 
ledges enclosing these hollow spaces in the reef; but as the growth con- 
