<p>This is not <i>P. lacteus</i>. It is either <i>Naticarius canrena</i> or possibly <i>Natica tedbayeri</i>.<strike>Polinices lacteus (Guilding, 1834) - apical view of a milk moonsnail shell.</strike>
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Family Naticidae - the naticids, like the muricids, prey on bivalves by boring through their shells.
<a rel="nofollow" class="external text" href="https://www.flickr.com/people/47445767@N05">James St. John</a>
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Incorrect ID here: <a rel="nofollow" class="external text" href="https://www.flickr.com/photos/jsjgeology/16189176151/">Polinices lacteus (milk moon snail) (San Salvador Island, Bahamas) 3</a>