<i>Hyponome</i>, with its single included species, <i>H. sarsi</i>, was described as a living cystidean, a group of extinct Paleozoic echinoderms. It proved to be only the detached visceral mass of a comatulid crinoid, later described as <i>Zygometra</i>, probably <i>Z. microdiscus</i>. Although <i>Hyponome</i> and <i>H. sarsi</i> were described first, neither name has been used in over a century. Both names are being proposed for rejection by the ICZN.