In Echinodermata, an area of the body surface (covered in most classes by calcitic (see calcite) plates), that overlies one of the radial canals of the internal water vascular system, and bears the tube feet. In some echinoderms, e.g. Asteroidea, Blastoidea, and Crinoidea, the ambulacrum is marked by a deep linear depression, the ambulacral groove. Typically, echinoderms have five ambulacral areas, or a multiple of five. See echinoidea.

Ambulacrum