Internal spiral is paper thin.
Outer shell can be incredibly thick / strong.
There seems to be protein incorporated with calcium salts.
It feels incredible that the mantle of a sea gastropod is able to engineer so exactly the molecules to create unique structures
The outside tip of a shell is incredibly hard
and the inside paper thin.
This is important in making models of work, especially tall thin shells, to avoid bulky crochet inside.
X rays of Seashells
http://shellography.com The Art of the Ocean by Dr Thad Thomas, 4 galleries incl x rays.
YouTube, the seashell x ray man, 22 August 2010
Mathematics of Seashells by Xahlee, 2006-05.
The Algorithmic Beauty of Seashells, by HansMeinhardt,Przemyslaw,Prusinkiewics and DeborahRFowler. from Amazon.....