74 FLORIDA GEOLOGICAL SURVEY— SIXTH ANNUAL REPORT. 



calcium phosphate, while the lobster as a whole contained .76 per 

 cent.* The aquatic plants also utilize some of the phosphorus m 

 solution in the water and through them the phosphorus passes to 

 the skeleton of vegetable feeding aquatic animals, and through 

 them in turn to the carniverous animals. 



The phosphorus taken from solution by chemical action is evi- 

 dently considerable, since nodules of chemical origin, high in phos- 

 phates are found somewhat abundantly in the bed of the ocean. 

 Some of these nodules, reported by Clarke,t contain 19.96 to 

 23.54 p'er cent of phosphoric acid. 



The amount of phosphate that finds its way into the sediment- 

 ary formations through organic and chemical agencies is thus un- 

 doubtedly considerable resulting in the enrichment of certain depos- 

 its which, if not themselves workable, at least serve as an impor- 

 tant source of phosphate from which by further concentration work- 

 able phosphate deposits are formed. 



In this respect the deposition of calcium phosphate is analogous 

 to that of the related mineral calcium carbonate, although of the 

 carbonate much more extensive deposits accumulate than of the 

 phosphate. The carbonate, as is well known, is not only a much 

 more abundant constituent of the superficial formations of the 

 earth than is the phosphate, but, under the conditions that nor- 

 mally exist on and near the surface of the earth, is also a much 

 more soluble mineral. Moreover it would seem from some of 

 the experiments that have been recorded that when the two- min- 

 erals occur together the carbonate is taken up by preference, leav- 

 ing the phosphate, thus giving in effect a degree of selective solu- 

 bility favoring the carbonate. The carbonate, therefore, is carried 

 in solution by the surface and ground waters in much larger quan- 

 tities than is the phosphate, and is also apparently readily avail- 

 able as a skeleton-building material. Accordingly the aquatic life 

 of the earth has utilized the carbonate largely in building pro- 

 tective skeletons. This is true not only of the corals and of the mol- 

 lusks of marine and fresh waters, but also of many other organisms, 

 important among which by reason of their abundance are the uni- 

 cellular foraminifera. Indeed in such abundance have the organ- 

 isms with calcareous skeletons flourished, under the favorable con- 



*BulI. 330, U. S. Geol. Siirv., p. 448, 1908. 

 tBiill. 330, U. S. Geol. Sun'., p. 105, 1908. 



