MEMOIRS. 



I. 



Exploratiom. of the Surface Fauna of the Gulf Stream, under the Auspices of the United 

 States Coast Surrey. — II.' The Tortugas and Florida Beefs. 



By ALEXANDER AGASSIZ. 



(Published by permission of Carlile P. Patterson and J. E. Hilgard, Superinteudents United States 



Coast and Geodetic Survey. 



Presented November 15, 1882. 



All naturalists who have visited the Florida Reefs have felt the ' difficulty of 

 applying Darwin's theory of reef formation to the peculiar conditions existing along 

 the Straits of Florida. Agassiz, Le Conte, and E. B. Hunt have each in succession 

 attempted to explain, from a different standpoint, the mode of formation of the 

 Florida Reefs. Agassiz stated, and his statement was afterward confirmed by Le 

 Conte, that the Florida Reefs had a distinctive character, and could not be explained 

 by subsidence, to which cause Darwin had ascribed the formation of barrier reefs 

 in general. The report of Agassiz on this subject, presented to Professor Bache in 

 1851, has been republished in full in the Memoirs of the Museum of Comparative 

 Zoology. In this report he has shown, not only that the southern extremity of 

 Florida is of comparatively recent growth, but that the causes by which it has for 

 the greater part been built up are still going on, and that we have a specimen or 

 sample as it were of the past action in the mode of growth of the present reef, keys, 

 and mud flats. He showed that the whole southern portion of Florida is built of 

 concentric barrier reefs, which have been gradually cemented into a continuous sheet 

 of land by the accumulation and consolidation of mud flats between them, — a process 



' For No. I. see Bulletin of the Museum of Comparative Zoology, Vol. IX. No. 7, p. 252. 1882. 



