Holothurioidea

:  a class of echinoderms comprising the sea cucumbers and having a more or less elongate form usually with well-marked bilateral symmetry and differentiated dorsal and ventral surfaces, a flexible but tough and muscular body with the skeleton reduced to scattered ossicles or spicules, a water-vascular system with radial ambulacral vessels and tube feet for creeping, respiratory trees, Cuvierian organs, and strong branched tentacles about the mouth — compare trepang