Help with identifying this shell, please.

[wil9000]

Thank you for your help. I'm having a devil of a time id'ing this one. It's probably dead simple.
<a href="http://www.flickr.com/photos/wil9000/4818621367/" target="_blank"><!-- m --><a class="postlink" href="http://www.flickr.com/photos/wil9000/4818621367/">http://www.flickr.com/photos/wil9000/4818621367/</a><!-- m --></a>
<a href="http://www.flickr.com/photos/wil9000/4819244808/" target="_blank"><!-- m --><a class="postlink" href="http://www.flickr.com/photos/wil9000/4819244808/">http://www.flickr.com/photos/wil9000/4819244808/</a><!-- m --></a>

[paul monfils]

Looks like the upper valve of a Chama that has a serious case of Cliona celata, the boring sponge.  If SE United States, Chama macerophylla.

<a href="http://species-identification.org/species.php?species_group=sponges&id=184" target="_blank"><!-- m --><a class="postlink" href="http://species-identification.org/species.php?species_group=sponges&id=184">http://species-identification.org/speci ... ges&id=184</a><!-- m --></a>

.  <span class="petit">--Last edited by Paul Monfils on 2010-07-22 22:47:50 --</span>