Bothriocidaris
Bothriocidaris is an extinct genus of echinoid from the Ordovician. It grew to in size and fed on plankton.
[Image:Britannica Echinoderma 5.jpg|left|thumb|400px|Bothriocidaris globulus. from the Encyclopædia Britannica, 1911. The short spines which were attached to the tubercles are not drawn.]