IDing Shells

[khyber]

Hello,

Could use some help identifying these shells:

From Uruguay, approx 39cm.  Want to say it's a Odontocymbiola Magellanica, but it's way too big according to textbooks.

<a href="http://img509.imageshack.us/img509/8038/uru2.jpg" target="_blank"><!-- m --><a class="postlink" href="http://img509.imageshack.us/img509/8038/uru2.jpg">http://img509.imageshack.us/img509/8038/uru2.jpg</a><!-- m --></a>

<a href="http://img407.imageshack.us/img407/7881/uru1.jpg" target="_blank"><!-- m --><a class="postlink" href="http://img407.imageshack.us/img407/7881/uru1.jpg">http://img407.imageshack.us/img407/7881/uru1.jpg</a><!-- m --></a>

<a href="http://img407.imageshack.us/img407/5724/uru3.jpg" target="_blank"><!-- m --><a class="postlink" href="http://img407.imageshack.us/img407/5724/uru3.jpg">http://img407.imageshack.us/img407/5724/uru3.jpg</a><!-- m --></a>


From Costa Rica, Pacific side:

<a href="http://img3.imageshack.us/img3/4387/costariccm.jpg" target="_blank"><!-- m --><a class="postlink" href="http://img3.imageshack.us/img3/4387/costariccm.jpg">http://img3.imageshack.us/img3/4387/costariccm.jpg</a><!-- m --></a>


Any help would be great,
Thanks