EchinodermataE*chi`no*der"ma*ta\ ([-e]*k[imac]`n[-o]*d[~e]r"m[.a]*t[.a]), n. pl. [NL., fr. Gr. 'echi^nos hedgehog, sea urchin + de`rma, -atos, skin.] (Zo["o]l.) One of the grand divisions of the animal kingdom. By many writers it was formerly included in the Radiata. [Written also Echinoderma.] Note: The species usually have an exterior calcareous skeleton, or shell, made of many pieces, and often covered with spines, to which the name. They may be star-shaped, cylindrical, disk-shaped, or more or less spherical. The body consists of several similar parts (spheromeres) repeated symmetrically around a central axis, at one end of which the mouth is situated. They generally have suckers for locomotion. The group includes the following classes: Crinoidea, Asterioidea, Ophiuroidea, Echinoidea, and Holothurioidea. See these words in the Vocabulary, and also Ambulacrum.
|radially symmetrical marine invertebrates including e.g. starfish and sea urchins and sea cucumbers|