Translations:AY Honors/Shells - Advanced/Answer Key/131/en
From Pathfinder Wiki
The marine gastropod Cypraea chinensis, the Chinese Cowry, showing partially extended mantle
The giant clam (Tridacna gigas) is the largest extant bivalve
Fossil shell covered in calcite crystals
In those molluscs which have a shell, the shell grows gradually over the lifetime of the mollusc by the addition of calcium carbonate to the leading edge or opening, and thus the shell gradually becomes longer and wider, in an increasing spiral shape, to better accommodate the growing animal inside. The animal also thickens the shell as it grows, so that the shell stays proportionately strong for its size.
