descriptions with variation in detail only. The reef 

 structure of Barbados alone has never been satisfactorily 

 explained. It appears however, that at some time in the 

 past the island was submerged and a layer of limestone 

 was deposited. During subsequent periods this was 

 added to by the growth of a series of fringing reefs 

 which were formed at various times, while the relative 

 levels of land and water were changing, so that they 

 formed a series of terraces. Many of these old reefs are 

 now elevated above sea-level. 



Reef formations are present to a limited extent off 

 the coast of Mexico on the Campeche Bank, where they 

 form the Alacran reef; and near Vera Cruz. Apart 

 from these the Gulf of Mexico has no significant reef 

 formations. 



The British Honduras reefs are well developed. They 

 extend almost continuously for over 125 miles, which 

 is the longest continuous formation in the West Indies. 

 Both bank and barrier reefs are found here. 



An imperfect atoll occurs at Los Roques, 70 miles 

 north of the coast of Venezuela, and reefs are also 

 present to a limited extent off the shores of Jamaica. 



The Lesser Antilles all possess living reefs of the 

 marginal sea type which are now elevated above sea 

 level and have grown upon platforms formed by the 

 abrasion of wave action during the glacial period. For 

 further detailed descriptions of these and of the other 

 Atlantic Reefs reference should be made to the excellent 

 account of Vaughan (1919). A more recent and ex- 

 haustive discussion of the formation of reefs throughout 

 the world is to be found in the magnificent work of 

 Davis (1928) , in which the theory of the marginal seas 

 is thoroughly expounded. 



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