Found a pretty nice big shell beachcombing....need ID help.

[paul monfils]

This is Astraea undosa, also called Lithopoma undosa, the "waved (or wavy) turban shell".  The animal that lived in it was a "gastropod" or in layman's terms, basically a snail. When alive it has a deeply sculptured "door" or "operculum" that tightly closes the aperture of the shell when the snail withdraws inside.  I don't know how fast this species grows, so I don't know how many years it would take to attain this size, which is about as large as this species gets.  

The bottom image on this page:

<a href="http://www.gastropods.com/2/Shell_292.html" target="_blank"><!-- m --><a class="postlink" href="http://www.gastropods.com/2/Shell_292.html">http://www.gastropods.com/2/Shell_292.html</a><!-- m --></a>

shows a shell with the operculum in place. That shell also has the fibrous outer covering that the animal produces, called the "periostracum".  The top image shows a shell like yours, with the periostracum removed with bleach (though your pictures of your shell do show some remnants of periostracum).  <span class="petit">--Last edited by Paul Monfils on 2008-12-24 19:13:29 --</span>