232 BULLETIN: MUSEUM OF COMPARATIVE ZOOLOGY. 



of the Vira^ao. They Tvere not seen, however, on the northern side of 

 the island. 



Mr. Agassiz has described similar forms on the Bermudas as serpuline 

 atolls. He observes, however, that they are also of Algae, corallines, and 

 of barnacles, and other invertebrates.^ 



The coral reef of Parahyha do Norte.^ — It nsed to be thought that 

 the reef of Pernambuco was a part of one almost unbroken system of 

 reefs extending along the whole coast of Brazil. There was for a long 

 while more or less difference of opinion as to whether these reefs were of 

 sandstone or of coral. As a matter of fact the Pernambuco reef is of 

 stone, and although stone reefs do occur at other places along the coast, 

 many of the reefs that were formerly supposed to be similar to that at 

 Pernambuco, and a continuation of it, have been found to be of coral. 

 Among these is the one at Parahyba do Norte, which was examined 

 by the writer while a member of the Commissao Geologica do Brazil. 

 The form of the Parahyba coral reef and the configuration of the coast 

 and of the land behind lead to the belief that this coral reef is built 

 upon and now conceals a reef of sandstone like those of Pernaml)uco 

 and Mamanguape, only somewhat lower than the latter ones. It is 

 worthy of note that the Parahyba reef lies across the mouth of an old 

 embayment or estuary that has silted up and built out the long flat 

 peninsula of Ponta da Matta. Corals could not have lived where the 

 reef now stands until after the peninsula was formed and after there 

 was a solid bottom to which the polyps could become attached. 



The lighthouse at the mouth of the Rio Parahyba do Norte stands 

 on the outer or seaward edge of the northernmost end of the Parahyba 

 reef; from this point the reef bears almost due south, keeping approxi- 

 mately parallel with the shore and on an average of HOO metres distant 

 from it. Lying between the reef and the river (Rn Parahyba do 

 Norte) is a narrow neck of land, on the northern point of which is a 

 little village known as Ponta da IMatta. 



The reef is approximately straight, with the irregular zigzag outer face 

 so common on coral reefs. It has a total length from the lighthouse to 

 the Barreta do P090 of nearly seven kilometres, and, with the exception 

 of two narrow passes, or barretas, barely wide enough for jangadas two 

 metres in width to pass, it is unbroken. 



The reef varies considerably in width, but everywhere it is higher en 



1 BulL Mus. Comp. Z06L, XXV. No. 2, p. 253-272, Plates XXII.-XXVI. 

 - The observations on the Paraliyba reef were made in 1875; a trip to Para- 

 hyha. in 1809 added notliing of importance to the earlier notes. 



