282 BULLETIN: MUSEUM OF COMPARATIVE ZOOLOGY. 
of the Viração. They were 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 Parahyba do Norte? — It used 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. Asa 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 а member of the Commissäo 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 Pernambuco 
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 1100 metres distant 
from it. Lying between the reef and the river (Rio Parahyba do 
Norte) is a narrow neck of land, on the northern point of which is a 
little village known as Ponta da Matta. 
The reef is approximately straight, with the irregular zigzag outer face 
во common on coral reefs. It has a total length from the lighthouse to 
the Barreta do Pogo 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 on 
1 Bull. Mus. Comp. Zoól., XX V. No. 2, р. 258-272, Plates XXIL-XX VI. 
2 The observations on the Parahyba reef were made in 1875; a trip to Para- 
hyba in 1899 added nothing of importance to the earlier notes. 
