circum-oral canal

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circum-oral canal (ring canal) Part of the water-vascular system in echinoderms (Echinodermata). The madreporite allows water into a canal that feeds the circum-oral canal, located close to the upper surface of Aristotle's lantern. Five radial water vessels extend from the circum-oral canal up the centre of each ambulacrum and from these vessels the tube-feet, used in locomotion and respiration, occur at intervals.