6 bulletin: museum of comparative zoology. 



lems that present themselves after a more thoughtful consideration of 

 the whole subject. 



Like so many of the problems that seem simple and easily disposed of 

 at the outset, this one has turned out to be much less simple than was 

 anticipated. And even now, after having worked at it for twenty-five 

 years, I am more than ever impressed with the complexity, difficulty, 

 and far-reaching nature of the problems surrounding these sandstone 

 reefs. Above all, it seems evident that any satisfactory theoi'y of these 

 reefs must include the study of the geographic development of the coast- 

 line, — a study not hitherto attempted. Certain theories that have been 

 advanced in explanation of or in connection with these reefs are not 

 discussed in the present paper because they are without the bases that 

 would entitle them to serious consideration. One of these is the theory 

 of their glacial origin.' It has already been shown that there is no satis- 

 factory evidence of glacial action in Brazil.^ Another is the theory of 

 the orographic relations of the reefs to the western Alps. This idea 

 was suggested to Liais by the once famous but now almost forgotten 

 Systemes de Montagnes of Elie de Beaumont.* 



The problems of the coral reefs have long been before the scientific 

 world. I have not been able to undertake any comprehensive study of 

 the coral reefs of Brazil, but I hope that this approaching of the subject 

 from the geological and geographical side may thro.v some light upon 

 these problems, so far at least as this particular coast is concerned. 

 In discussing the coral reefs I have endeavored to weigh the evidence at 

 my command and to reach logical conclusions unbiassed by any particular 

 theory. 



There are several related topics which it was intended to discuss in 

 connection with the ones here dealt with, such as the currents, winds, 

 tides, submarine topography, and submarine erosion, but the paper is 

 already too voluminous and those parts are omitted. 



A great desideratum in studying the history of the Brazilian coast is a 

 good topographic map. This does not exist. The hydi-ographic charts 

 are the only ones available, but these deal only with such features as 

 interest navigators, while the maps of the interior are often little more 

 than vague generalizations. It is cause for congratulation that several 

 of the Brazilian states imder the lead of Sao Paulo, whose survey is 



1 Nouvelle geographie universelle. Par 6. Reclus. Tome XIX. Amerique 

 du Sud, p. 222. Paris, 1894. 



2 Tlie supposed glaciation of Brazil. By J. C. Branner, Journ. Geol. I, p. 753-772. 



3 L'Espace Celeste. Par E. Liais, p. 544, 548. Comptes Rendus, 1860. L., 

 p. 762-763. 



