94 BULLETIN : MUSEUM OF COMPARATIVE ZOOLOGY. 



The reef rock contains shells of marine mollusks now living along this 

 coast, and Capanema ^ mentions seeing pieces of pottery imbedded in it. 



The rock has been extensively quarried for flagging and for building 

 purposes. 



When I revisited the reef at this place in August, 1899, I found west 

 of the lighthouse only one big slab of the reef rock. This slab is 

 5 X 2.1 X 0.5 metres. It lies loose upon the projecting points of the 

 crystalline rocks of the beach as if it had been tossed there by the waves. 



There must have been a beach reef at this place formerly, but it has 

 now all been removed by man and the surf save this one slab and a few 

 isolated patches of heavy conglomerates here and there among the ragged 

 points of the crystalline rocks beneath them. 



Among these conglomerates several fragments of bones were noted. 



The following description of the Rio Vermelho reef, which I did not 

 examine, is taken from Hartt : ^ " The reef at Rio Vermelho illustrates 

 very well the general character of these consolidated beaches. It is 

 composed of layers of calcareous sandstone and conglomerate, often 

 somewhat irregular, dipping seaward, the dip being only a few degrees, 

 or about that of an oi'dinary sand beach. The height of the reef is very 

 uniform. In the finished and isolated reefs, as that of Peruambuco and 

 the one under consideration, the recent rise of the land has brought this 

 level somewhat above that of the sea. The solidified portion is seen to 

 be but a sheet of varying thickness lying on the surface of the beach. 

 On the inner side it is quite thin, and from the action of water behind 

 it is undermined and broken off, until, at last, it forms a low perpen- 

 dicular wall, undermined below and sometimes projecting several feet. 

 Usually this side of the reef is flanked by a slope of sand or mud, and 

 sometimes by large oblong blocks of sandstone. (See cut on p. 109.) 

 The surface of the reef is, broadly speaking, horizontal, but it is marked 

 by longitudinal rjdges and much worn away, sometimes honeycombed 

 and exceedingly rough with large, shallow or deep irregular pools of 

 water, the homes of several species of corals, etc. The whole mass is 

 divided by joints into great blocks. On the seaward edge the reef is 

 often worn away by the waves and undermined, presenting always a per- 

 pendicular wall to the sea. The upper bed almost always projects a 

 little, and the great blocks broken from it lie in front, which aiford some 

 protection to the reef. One often finds a depth of twelve to fifteen feet 



1 Guilherme S. de Capanema. Trabalhos da Commissao Scientifica de Ex- 

 ploracao. Introduc9ao. I. CXXXVII. 



2 C. F. Hartt, Geology and pliysical gcograpliy of Brazil, p. 344-345. 



