(Haeckel, 1864)
Description
Umbrella nearly hemispherical with thick jelly especially in apical region. Velum narrow, ca 1/10 bell radius [Eutima gegenbauri ].
Stomach short, cross-shaped in section, situated at end of very long prismatic gastric peduncle, broad based but tapering, narrow along most of length, extending far beyond umbrella. Mouth four-lipped, with crenulate margin. Four straight radial canals and ring canal narrow, radial canals continuing along gastric peduncle.
Eight gonads, four on radial canals on subumbrella each extending from (or just on) base of gastric peduncle nearly to ring canal, and four overlying middle third each radial canal on peduncle [E.gegenbauri-habitus ].
Marginal tentacles 8-16, hollow, possibly sometimes up to 32 (Russell, 1953a: 371); thick and smooth, without basal swellings. 60-80 or more marginal swellings with adaxial papillae. Spiral lateral cirri present, one, rarely two, on each side of marginal tentacles and swellings. Eight closed marginal vesicles each with 6-12 or more concretions.
Young specimens: E.gegenbauri-juvenile.
Size
Diameter of fully grown medusa up to 20 mm, perhaps sometimes more; other details not recorded.
Colour
Stomach, gonads and marginal tentacles greenish or bluish green, sometimes with yellow tinge.
Ecology
In the British Isles, medusae are reported in plankton usually in late summer and autumn, but also in January as well as July-October at Plymouth, to November in the Clyde (Russell, 1953a).
Depth range
— Medusa in coastal plankton.
— Hydroid once recorded on stones and shells; otherwise unknown.
Distribution in the North Sea
Northern North Sea off Scotland, Oslo Fjord, Skagerrak, German Bight.
World distribution
NE Atlantic from Scotland to the Mediterranean Sea, the Adriatic Sea and the Canaries and Morocco; on the U.S. coast from North Carolina; recorded from China twice.
[After Cornelius, 1995a]