FLORIDA REEFS. 11 



Among the creatures mentioned above are many which bore deeply into 

 the stems of the corals, or into the mass of the coral rock. 



Such are different species of Area, the date-fish among the Molliisca, and 

 many worms, especially Serpula among articulates, the agency of which in 

 the formation of the keys will be described hereafter. All these animals 

 and plants contribute, more or less, to augment the mass of solid materials 

 which is accumulating upon the reef, and increase its size. Not only are 

 the hard parts of shells, echinoderms, worms, or their broken fragments, 

 heaped among the detritus of the corals, but occasionally even the bones of 

 fishes and turtles, which are very numerous along the reef, may be found in 

 the coral formations. 



The decaying soft parts of all these animals undoubtedly have their 

 influence upon the chemical process by which the limestone particles of 

 their solid frame are cemented together in the formation of compact 

 rocks. Upon this point we may expect further information from Pro- 

 fessor Horsford, who is now submitting to chemical analysis all the 

 variety of rocks and the solid stems of the different corals obtained in 

 Florida. Respecting the relations of the solid and soft parts of the living 

 coral, and their mode of growth, we would refer to a paper of ours now in 

 press, to appear in the next volume of the " Smithsonian Contributions to 

 Knowledo-e." 



'D" 



The Keys. 



The main range of keys has a very uniform character; the separate 

 keys differing from each other chiefly in their more or less advanced forma- 

 tion. We need only, therefore, describe in detail a certain number which 

 may serve as illustrative of various steps toward completion. Some consist 

 simply of accumulated coral boulders heaped upon an old coral reef rising 

 more or less above the sea-level. Upon this foundation fragments of the 

 more brittle kinds of coral, shells, coral sand, are heaped as they are 

 upon the dry rocks west of Sand Key or upon Rock Key, east of Sand Key, 

 a formation resembling, indeed, that of Sand Key itself, or the Sambos or 

 Looe Key. Such a comparison shows at once the connection between 

 these larger keys and the incipient keys upon the reef We have only to 

 imagine the accumulation of coral boulders, corals, shells, and coral sand 

 upon the small keys of the reef to be continued and increased till this cap 

 of loose materials should extend several miles along the rising crest of the 



