DEPOSITS OF NORTH WAXES. 3G7 



eruptive rocks were a source of the phosphoric acid, as his experience 

 had shown him that all these rocks contain apatite in greater or less 

 amount. Analyses which he had made of limestones, almost wholly 

 composed of shells and containing Crustacea, showed so small an 

 amount of phosphoric acid that he thought the amount of phosphorus 

 contained in these organisms had generally been overrated. He asked 

 the Fellows present where he could find reliable analyses of the shells 

 of Mollusca and Crustacea, as he had met with very few. 



Mr. Gwyn Jeffreys remarked that though the nacreous layer of 

 the freshwater Unio and Anodonta may have so much phosphate of 

 lime, marine shells, such as oysters, contain only about 1| per cent., 

 and the beds in question were stated to be not of freshwater but of 

 marine origin. The shells of Crustacea might perhaps contain 

 more. 



Q. J. G. S. No. 123. 2 c 



