Photomicrograph (PPL) of gastropods in a lime mudstone from the Gastropod Limestone Member of the Cretaceous Kootenai Formation, SW Montana.
<a href="//commons.wikimedia.org/wiki/User:Rygel,_M.C." title="User:Rygel, M.C.">Michael C. Rygel</a>
CC BY-SA 4.0
<span class="int-own-work" lang="en">Own work</span>