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 sj^ecies of Area, the date-fish among the Molkisca, 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, Avho 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 
Knowledge." 
The Kei/s. 
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. AYe need only, therefore, describe in detail a certain number which 
may serve as illustrative of various steps toward comjjletion. 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 diy 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 bouldei's, 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 
