252 



BULLETIN : MUSEUM OF COMPARATIVE ZOOLOGY. 



seen that these reefs ai'e a long way out from the shore. In order to 

 spend a second day on them it was necessary to anchor our boat and 

 remain there over night. When the tide was high, except that the sea 

 ■was not very rough, to all appearances we might have been anchored in 

 the middle of the ocean. 



The water was a little short of two metres deep on the higlier parts 

 of the reef at high tide ; judging by the posts planted on the reef, I take 

 it that the tides here rise about three metres. 



These reefs are traversed by irregular channels from one to ten 

 metres deeper than the top of the reef, and varying in width from three 

 or four metres to half a kilometre or more. The whale-fishers of the 

 Barra de Caravellas have planted here and there along these channels 

 tall poles to serve as guides in sailing across the reefs wlien the w-ater 

 is shallow on top of the rocks, and to mark anchoring places for their 

 boats at night. 



"When the tide is ebbing the first visible signs of the reef are muddy- 

 looking splotches in the water ; these get browner and yellower as the 

 water gets shallower, until the rocks begin to appear at the surface. 

 When the reef is quite uncovered it has a deep yellow color, — between 

 lemon and orange. The water itself looks yellow and muddy over the 

 reefs, but this is deceptive, for it is perfectly clear, — at least it was so 

 during my visit. 



The Lixa reef is the flattest and smoothest I have seen on the coast 

 of Brazil. Except on the edges, where it is always more or less ragged, 



it has the appearance of being 

 one solid compact mass of coral 

 rock built up to an even level. 

 The view over its surface at low 

 tide reminds one of a great prairie 

 covered with short dead grass, tlie 

 sky line unbroken save here and 

 there by a few black points, — 

 blocks of the reef rock broken 

 out by fishermen in search of squid or fish. 



The top of the reef is dead so far as the corals are concerned. Only 

 two forms were found alive in the shallow pools on the surface, — Porites 

 and Faria, — aud these are all small and apparently stunted. Otlier 

 polyps are also abundant, but the patches are small and the species few. 

 Living corals are found only along- the edges and over the bottom of 

 the channels that cut the reef, and in the isolated patches that rise 



Fig. 100. 



Profile of the edge of Lixa 

 coral reef. 



I 



