Origin of sea urchinso named because of its spines
sea urchinsea urchin
any of various orders of echinoid echinoderms having a somewhat globular body of fused skeletal plates studded with long, calcareous, movable spines
Any of various echinoderms of the class Echinoidea, having a soft body enclosed in a rounded, radially symmetrical, calcareous skeleton covered with long spines.
white sea urchin
(plural sea urchins)
- attributive form of sea urchin
- sea-urchin look
- Accepting the homology of these apical systems with the calycinal system, the theory would regard the aboral pole of a sea-urchin or starfish as corresponding in everything, except its relations to the sea-floor, with the aboral pole of a fixed echinoderm.
- - Supposed calycinal systems of free-moving Echinoderms. A, regular sea-urchin (Cidaris); B, sea-urchin with a suranal plate (Salenia); C, developing ophiurid (Amphiura); D, young starfish (Zoroaster).