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 jSIauianguape and Rio Grande do Norte reefs the walls 

 were thick and decidedly concave. 



Porites brannei'i 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 ii'regularly lobed, was 

 collected. It is of a deep brown color in life. The cells resemble very 

 much those of Porites verrilU in form, but they are smaller, and the 

 texture of the rock is much more porous. 



Millepora alcicornu was the only Millepore found on the sandstone 

 reefs, and this one was observed in only one place, between two portions 

 of the Peruambuco 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 

 Avas 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 Alagoas. 

 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 Avide 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 coi-al 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 ai'e 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- 



