(Forbes and Goodsir, 1851)
Description
Umbrella globular, about as high as wide; jelly thick, especially in upper half of umbrella [Bougainvillia pyramidata ]; velum narrow. Four radial canals and ring canal narrow.
Gastric peduncle well developed, cone-shaped; manubrium short, with four perradial extensions on peduncle [B.pyramidata-meduse ]. Mouth with four oral tentacles inserted above mouth opening, dichotomously branched 4-5 times, terminating in nematocyst clusters.
Gonads situated adradially on base and perradial lobes of manubrium.
Four small, oval, marginal tentacular bulbs each with a group of 6-9 tentacles of one kind. Ocelli black, adaxial, round, situated on bulbs at the base of each tentacle [B.pyramidata-meduse ].
Young medusa with scattered nematocysts and four shallow interradial longitudinal furrows on exumbrella. Medusae reared from the hydroid: B.pyramidata-stages .
Size
Umbrella 6-8 mm high.
Colour
Manubrium yellowish-brown; marginal bulbs reddish brown or yellow.
Ecology
In British waters medusae were recorded from summer and autumn months.
Distribution in the North Sea
Southern and northern North Sea.
World distribution
E North Atlantic Ocean.
[After Russel, 1953a; Russell, 1953b; Kramp, 1959]