96 
them contains a few crystals of carbonate of lime; other 
specimens have this space quite filled up, and the sur- 
rounding stone broken away; of such is the upper 
figure : some casts are beautified with octohedral crystals 
of pyrites. 
A Trochus nearly resembling this is found in some 
parts of Normandy, but comparison wil} prove that they 
are distinct species. 
