[Hydromedusae] Simple canal which runs around the umbrella margin linking the ends of the radial canals; occasionally the circular canal is not hollow but consists of a solid core of endodermal cells (e.g., Genus Proboscidactyla, Laingiomedusae). In the Narcomedusae, in which the umbrella margin is deeply cleft into broad flaps, a circular canal may be present or not; when present the marginal canal follows the edge of the margin of the exumbrellar flaps and is called "peripheral canal system", the vertical parts of which are the peronial canals.

[Cubo-/Scyphomedusae] The narrow canal or duct around the perimeter of the umbrella linking the ends of the radial canals. Not present in all genera.
See also Intermediate canal.

Alternative form for Circular canal : Ring canal.