(n) :
Any echinoderm of the order Clypeasteroida, having a flat, disk-shaped body with the mouth in a mid-ventral position, and living in sand, on or near the surface.
(n) :
Any echinoderm of the order Clypeasteroida, having a flat, disk-shaped body with the mouth in a mid-ventral position, and living in sand, on or near the surface.