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BRANNER: THE STONE REEFS OF BRAZIL. 159 
simply an inference based upon the supposition that these organisms 
would affect the rock along the line where they grow. 
2. Elevated sea-urchin burrows. — The boring sea-urchins of this coast 
(Echinometra subangularis) can live in places where at low tide the 
waves break over them occasionally, or they can live in tide-pools, But 
so far as I can learn they do not live in places where they are completely 
uncovered at low tide. 
A few kilometres north of Cabo Santo Agostinho, at а point of land 
known ав. Pedras Pretas are many exposures of a massive black trachyte 
upon the sea beach and rising in the hills above. There are three or 
more places where these trachyte masses in place are bored by sea-urchins. 
These rocks, and one other and larger exposure, are in place, while a 
third one may possibly be a loose block. The parts bored with these 
holes are between high and low tide levels. As will be seen from the illus- 
tration the exposures of these bored faces are such that it does not seem 
possible that sea-urchins could live in them if uncovered even at low tide. 
Of the several exposures of such borings at this Cape not one is found 
beyond the reach of high tide. То put these holes all below low tide 
would require a depression of two metres. 
It should be added that no such holes were found in the granites 
exposed at Pedra do Porto and Pedra do Conde in the southern part of 
the State of Pernambuco a short way north of Rio Una, but on Cabo 
Santo Agostinho on the south side of the Cape and west of the sand 
reef there are a few holes in the granites between tide-levels that look 
as if they might have been made or partly made by sea-urchins. 
3. The death and decay of the coral reefs. —The decay and erosion of 
the upper surface of the stone reefs I have not seen mentioned as evidence 
of elevation. The illustration given herewith shows a characteristic fan- 
tastic form common upon the stone reefs of the coast. These forms have 
the bedding of the original sand layers distinctly preserved and there 
can be no question about their being the remnants of upper beds that 
have been removed by erosion. This erosion, however, may have been 
produced either by the ordinary processes of weathering and removal by 
the waves, or it may have been the work of the surf. The form here 
represented is still quite within the reach of the surf at high tide. These 
forms cannot therefore be accepted as evidence of elevation. I do not, 
however, feel so confident in regard to the meaning of the decay of the 
upper portion of the coral reefs of the coast. I know of no reason why 
the stone reefs may not have been consolidated at any elevation at which 
they are now found. But in the case of the coral reefs the rock can be 
