BULLETIN: MUSEUM OF COMPARATIVE ZOOLOGY. 
IL 
Sketch of the Geology of the Coast in its Relations to the 
Stone and Coral Reefs. 
PAGE PAGE 
rec rofacdona . 21), B The relation of color to age. . . 18 
The Cretaceous . . 9 The Tertiary beds of the Ama- 
What is the age of the Bahía. beds? 9 РОВ. |. Т с ZU 
Conclusion regarding the Bahia The later Tertiary deposits EL 
Пещ y y. p t Recent deposits . . . 31 
The age of the other coast sedi- Conclusions regarding the geol- 
Meter nu, mov I OBY Ol tHE 00880 . 5... . . 82 
The discussion of the stone reefs of Brazil is both a geological and a 
geographical one. It is therefore necessary to get our geological orien- 
tation, — to have some idea of the general geological history of the 
region discussed, before treating of the reefs themselves. This is essen- 
tial, because the reefs are of late geological origin, and it is necessary 
to understand the geological history of the coast in order to see where 
the reefs came into that history. It is also the more necessary on ac- 
count of many statements in the present paper that do not agree with 
earlier publications regarding the geology of the region here treated. 
Pre-Cretaceous. — The principal feature of the coast geology with 
which we have to deal is a series of mechanical and organic sediments 
forming a plateau along nearly the whole of the coast from the northern 
part of the State of Rio Grande do Norte to the State of Espirito Santo, 
—a distance of nearly two thousand kilometres. Over most of this dis- 
tance these sediments rest upon crystalline rocks, — in some places 
granites, in other places gneisses, in others schists. These old crystalline 
rocks are cut here and there by eruptive dikes of later age. The age 
of the old underlying beds is not known, but the schist series looks very 
like the Algonkian of Van Hise, At one place — the Serra of Itabaiäna, 
in the State of Sergipe — thero are older sediments between the стув- 
talline rocks and the later sediments known to be of Cretaceous age. 
No fossils have been found in these lower beds, but from their position 
below the Cretaceous beds they have been provisionally assigned to the 
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