198 BULLETIN: MUSEUM OF COMPARATIVE ZOOLOGY. 
The stratigraphic relations of the reefs to the Tertiary beds are 
matters of conjecture rather than. observation. There are, to begin 
with, but few places along the coast where both Pliocene beds and 
sandstone reefs occur side by side. One of these is at Rio Formoso, 
Estado de Pernambuco, where the stone reef is one and a half kilometres 
from the Pliocene exposures on Ше Praia da Gamella. 
At Serinhaem the Tertiary is exposed on the side of the river at the 
town, and the reef does not touch them. 
At Mamanguape the relations of the Tertiary sandstones and the 
reefs appear to be as shown in Figure 8, page 29, 
At Во Formoso and Serinhaem the Tertiary is considerably higher 
than the sandstone reef; at the Mamanguape locality, there seems to 
be but little or no difference of level. 
On the shore of the mainland opposite Catá on Пара са Island, 
Bahia, there is a long low sandstone bank that I take to be Pliocene. 
There are no stone reefs near this, however. 
At other places the relations of the stone reefs to rocks of known age 
are not shown, but there are no facts in my possession that are not in 
accord with the theory that the stone reefs are newer than any other 
consolidated sedimentary beds along the Brazilian coast. 
Physiographic relations. — The relation of the reefs to the adjacent 
shores is accepted as evidence of the recent date of some of the reefs, 
while the process of their formation strongly suggests, if it does not 
prove, that the low, flat lands behind the stone reefs are underlain by 
other stone reefs. Seashores are rarely at a standstill; they are either 
being cut away or built out. Their elevation, as compared with that of 
the land and their marginal position relative to the flat country behind 
them, show that the reefs and the flat lands are genetically related, and 
that they are of about the same age. These flat lands are partly recent 
deposits ; but they also extend back into the Pliocene. Their origin 
is discussed in Chapter V. One of the most striking features of the 
external stone reefs is their proximity to and parallelism with the shores 
behind them. If a stone reef had been in existence for a long time, 
speaking geologically, it would have been either obliterated by the 
encroaching sea, or it would have been buried under the encroaching 
Тапа, 
The fossils in the reefs. — The fossils found in the reef rock, so far as 
they are now known, are the remains of animals now living in the seas 
along side of the reefs. At Pernambuco, Rio Formoso, and Mamanguape 
the most common fossils are the shells of “mariscos” (a species of 
