Megastraea undosa (synonyms: <i>Lithopoma undosum</i>, <i>Astraea undosa</i>) in situ.
<a rel="nofollow" class="external text" href="https://www.flickr.com/photos/26216388@N02">Ed Bierman</a>
CC BY 2.0
originally posted to <b><a href="//commons.wikimedia.org/wiki/Flickr" class="mw-redirect" title="Flickr">Flickr</a></b> as <a rel="nofollow" class="external text" href="https://www.flickr.com/photos/26216388@N02/2464984658">Underwater snails</a>