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(Johnston, 1833)

Description
Umbrella hemispherical to slightly higher, perhaps becoming slightly lower in specimens approaching maximum size [T.bairdi-habitus ]; jelly very thick. Velum fairly narrow, less than 1/4 of bell radius.
Stomach small, four-sided, attached to conical gastric peduncle by cross-shaped base forming four triangular pouches between its dorsal wall and end of peduncle; gastric peduncle highly contractile (Kramp, 1919) but normally extending slightly beyond umbrella margin; mouth hence entirely outside umbrella, having four large pointed lips with much-folded margins. Radial canals four, extending from bell edge to end of peduncle; they and ring canal narrow.
Gonads linear, folded, on either side of each radial canal leaving canal itself free; on subumbrella and gastric peduncle, extending from near stomach (i.e. from proximal end of peduncle) to ring canal [T.bairdi-habitus ].
Normally 16 marginal tentacles, even perhaps in largest specimens; with oval/oblong carrot-shaped bases. About 200-250 marginal swellings; no lateral cirri. Closed marginal vesicles about half as numerous as marginal swellings, each with 4-20 concretions.

Size
Diameter up to ca 65 mm.

Colour
Marginal tentacles pale pink or faint brownish at base; gonads milky-white.

Ecology
Medusae have been recorded from the plankton off the British east coast in every month except April and June (Russell, 1953a; also Hamond, 1957, for the only March record) but the species is commonest in winter and was considered by Russell to release gametes from November to January.

Depth range
Cool waters; recorded mostly in coastal plankton but its unusual longevity suggests that it might occur also in the open ocean.

Distribution in the North Sea
Recorded only from the North Sea and adjacent waters; also from the Baltic Sea.

World distribution
Norwegian Sea and the 'northern North Sea' (Russell, 1963d) recorded it additionally as far north as the, and its unusual longevity would I seem to make it potentially of more widespread occurrence in the NE Atlantic than just in the North Sea.
Other species of Tima have been recorded from different parts of the North Atlantic Ocean (Kramp, 1961; Petersen, 1962) but the validity of some is in doubt. One of the nominal species, from NE America, may prove conspecific, extending the range of T. bairdi considerably.

[After Cornelius, 1995a]

Tima bairdi