Snail shells are made of calcium carbonate with a protective chitin coating, no?
Chitin is thicker on land and freshwater snails, calcium carbonate primarily thicker on saltwater snails.
Just being nit picky...and bored.
http://dictionary.reference.com/sear...acum&x=52&y=12
Chitin is like cellulose which I assume is similar to the stuff mushrooms are made of?
(Its the stuff dreams are made of...)