Lamprey mouths from ventral (not to scale):
<p>Top: <a href="https://en.wikipedia.org/wiki/Mordaciidae" class="extiw" title="en:Mordaciidae">Mordaciidae</a> (<a href="https://en.wikipedia.org/wiki/Chilean_Lamprey" class="extiw" title="en:Chilean Lamprey">Chilean Lamprey</a> left, <a href="https://en.wikipedia.org/wiki/Short-headed_Lamprey" class="extiw" title="en:Short-headed Lamprey">Short-headed Lamprey</a> right)<br>
Center: Geotriidae (<a href="https://en.wikipedia.org/wiki/Pouched_Lamprey" class="extiw" title="en:Pouched Lamprey">Pouched Lamprey</a>)<br></p>
Bottom: <a href="https://en.wikipedia.org/wiki/Petromyzontidae" class="extiw" title="en:Petromyzontidae">Petromyzontidae</a> (<a href="https://en.wikipedia.org/wiki/Sea_Lamprey" class="extiw" title="en:Sea Lamprey">Sea Lamprey</a> left, <a href="https://en.wikipedia.org/wiki/European_River_Lamprey" class="extiw" title="en:European River Lamprey">European River Lamprey</a> right)
W.Wing
1851
<i>Proceedings of the Zoological Society of London</i> (<a rel="nofollow" class="external text" href="https://archive.org/details/lietuvostsrmoksl50liet">vol. 1851</a>, <a rel="nofollow" class="external text" href="https://archive.org/stream/lietuvostsrmoksl50liet#page/n693/mode/1up">plate Pisces IV</a>)