Ammonite. An ammonite used in the paving in <a href="//commons.wikimedia.org/wiki/File:Chalice_Well_Gardens_-_geograph.org.uk_-_166907.jpg" title="File:Chalice Well Gardens - geograph.org.uk - 166907.jpg">166907</a> Glastonbury
<a rel="nofollow" class="external text" href="https://www.geograph.org.uk/profile/1601">Glyn Baker</a>
CC BY-SA 2.0
From <a rel="nofollow" class="external text" href="https://www.geograph.org.uk/photo/167895">geograph.org.uk</a>