(Fig. 5 L)
Halecium tubatum Watson, 2008: 174 –175, fig. 10 A, B (in part).
Material examined. Holotype, BANZARE, Stn 105, 67° 46 'S 67 °03'E (Mawson Coast), 13 –02– 1931, 163 m; one microslide (Hydr. 710 / 12): F 147470.1, a hydrorhizal stolon giving rise to four stems.
Diagnosis. Stems with a single distal hydrotheca, relatively high and strongly widening distally. Rim strongly everted. Gonothecae unknown. Cnidome consisting of at least microbasic mastigophores?
Description. All the available material of this species consists of a hydrorhizal stolon giving rise to four stems provided with one or two basal rings (Fig. 5 L). Three stems provided with a single distal hydrotheca; fourth one without hydrotheca.
Hydrothecae relatively high and strongly widening distally (Fig. 5 L). Only one hydrotheca with diaphragm. Hydrothecal rim strongly everted (Fig. 5 L).
Only a single putative nematocyst could be observed.
Measurements (in µm). Hydrothecae: diameter at aperture c. 285, diameter at diaphragm c. 110, height c. 90. Cnidome: microbasic mastigophores? (6 x 2).
Remarks. The available material of this species could simply correspond to incipient stems of another haleciid. As indicated above, the hydrotheca in H. tubatum is quite wide, but this could be due to the microslide cover. This is a poorly characterized species, particularly taking into account the absence of gonothecae, the incipient, unbranched stems and the shape of the hydrotheca. In addition, there is practically no information about the cnidome. It should be considered as species inquirenda.
As indicated above, part of the material assigned by Watson (2008) to Halecium tubatum actually belong to H. interpolatum (cf. Fig. 5 H–J). It is worth mentioning that, in the material from F 147470.2, the origin of the stem is apparently through a quite long apophysis, in contrast to the basal rings of H. tubatum.
In relation to the remaining material assigned by Watson (2008) to H. tubatum, it should be necessary to reexamine it in order to clarify its systematic position.
Ecology and distribution. Halecium tubatum was found at depths from 163 to 502 m, off Mawson Coast and Knox Coast (Watson 2008).