262 BULLETIN: MUSEUM OF COMPARATIVE ZOOLOGY. 
those of Cretaceous age. In the rocks known to be of Tertiary age there 
is but little evidence of the existence of coral reefs. The geographic de- 
velopment of the coast, however, and the distribution of the reefs at the 
present time lead to the inference that the reefs, as they are now known, 
began their existence after the elevation and erosion of the Косепе Ter- 
tiary beds along the Brazilian coast. This is suggested, if it is not 
proved, by the fact that the present reefs grow upon the marine shelf 
cut by the sea in the Tertiary and older rocks, or they occupy areas that 
were submerged after the erosion of the Eocene beds had been in process 
for a considerable period. There has been much encroachment upon the 
land by the sea, and this encroachment has been followed up sharply by 
corals taking possession of the submarine shelves wherever the conditions 
were favorable until we now have coral reefs growing close to the sea 
bluffs. The reefs at and about the Abrolhos group are built upon sub- 
merged Tertiary rocks. They therefore began in the latter part of the 
Tertiary and have continued down to the present time. This seems to 
be true of all the large reefs: those of the Abrolhos, Parcel das Paredes, 
and those at Cape Sáo Roque; and these reefs are not only the largest, 
but likewise the oldest and probably the thickest of the reefs of the 
Brazilian coast. Many of these reefs, however, long ago finished their 
upward growth and are now growing only laterally. 
For reasons already given the barrier and fringing reefs that grow 
near the steep shores appear to be newer than the large offshore reefs. 
No line of demarcation, however, can be drawn between the large off- 
shore тее and the near-shore barrier and fringing reefs. They all 
merge together both in physical characters, in thickness, and in age, 
The coral reefs, therefore, antedate the stone reefs. This is shown by 
the occurrence of reef-building corals in the rocks of the stone reefs, and 
also by the relative positions of the two kinds of reefs, along the coasts. 
The coral reefs are also locally newer than the stone reefs, as is shown by 
the former growing upon the latter. The corals will continue to grow 
seaward from the stone reefs, while the latter will change but little. No 
elevated coral reefs are now known on the coast of Brazil. If the eleva- 
tions of Pliocene times killed some of the reefs, they were again taken 
possession of and new reefs grew upon the old ones as soon as they were 
resubmerged. 
The Brazilian coral reefs are almost everywhere narrow. The wid- 
est are those of the Abrolhos, Parcel das Paredes, Itassepanema, Ita- 
columis and Cape St. Roque, which are at most only about thirty-three 
kilometres wide. Some of the coral reefs connect with the land and 
