Help with Costa Rican shell ID

[parthicus]

Hello everyone,
New member here.  I have just taken some photos of shells found on my Costa Rican vacation this past December.  All were found by beachcombing along the Pacific coast in Puntarenas province, Costa Rica.  Here are the photos on Flickr (descrïption includes my best effort so far at ID):
<a href="http://www.flickr.com/photos/23911267@N06/4945787379/" target="_blank"><!-- m --><a class="postlink" href="http://www.flickr.com/photos/23911267@N06/4945787379/">http://www.flickr.com/photos/23911267@N06/4945787379/</a><!-- m --></a>
<a href="http://www.flickr.com/photos/23911267@N06/4945787957/" target="_blank"><!-- m --><a class="postlink" href="http://www.flickr.com/photos/23911267@N06/4945787957/">http://www.flickr.com/photos/23911267@N06/4945787957/</a><!-- m --></a>
<a href="http://www.flickr.com/photos/23911267@N06/4945788519/" target="_blank"><!-- m --><a class="postlink" href="http://www.flickr.com/photos/23911267@N06/4945788519/">http://www.flickr.com/photos/23911267@N06/4945788519/</a><!-- m --></a>
<a href="http://www.flickr.com/photos/23911267@N06/4946374068/" target="_blank"><!-- m --><a class="postlink" href="http://www.flickr.com/photos/23911267@N06/4946374068/">http://www.flickr.com/photos/23911267@N06/4946374068/</a><!-- m --></a>
<a href="http://www.flickr.com/photos/23911267@N06/4946374616/" target="_blank"><!-- m --><a class="postlink" href="http://www.flickr.com/photos/23911267@N06/4946374616/">http://www.flickr.com/photos/23911267@N06/4946374616/</a><!-- m --></a>
I would be grateful for any ID help or other comments.  This was my first visit to a tropical beach, and I was really impressed by how colorful and interesting the shells were- much more exciting than along the New Jersey and Maryland beaches I usually visit!  I especially liked the cowries- I might start collecting them.  Thanks again for any help.