(Figs 6, 16 F, 17 F, 19 F)
Material examined. New Zealand Antarctic Expedition TAN0802: Stn 180, Tangaroa, 29 February 2008, 69.4318°S, 178.8195°W (off Cape Adare, Ross Sea,), 447–455 m (NIWA 37896).
Description. Monosiphonic, unbranched stems, up to 70 mm high, divided into internodes. Angle between cauline apophyses and stem ca. 45 °. Cauline apophyses with three nematophores, two axillary ones (Fig. 6 B), each emerging through simple hole in perisarc, and a third nematophore emerging through ‘mamelon’ (Fig. 6 A–B).
Hydrocladia unbranched (Fig. 6 A) or bifurcated. Mesial-inferior nematophore emerging from strongly marked swelling at proximal third of internode (Fig. 6 D); without nematotheca (Fig. 6 C–D). Hydrotheca placed on middle of internode (Fig. 6 A, C–D). Hydrotheca elongate. Adcauline wall mostly adnate, but with a distinct free portion (Fig. 6 D). Abcauline wall almost straight, but slightly convex basally and typically with slight concavity just under hydrothecal rim (Fig. 6 C–D). Hydrothecal aperture circular, perpendicular to long axis of internode, rim even (Fig. 6 C–D).
Gonothecae fusiform. Male gonotheca with circular, subterminal aperture. Female gonotheca with wide, circular, distal opening (Fig. 6 E).
Remarks. Until now only mature male gonothecae and immature female ones were known (cf. Peña Cantero et al. 1997); we have found mature female gonothecae (Fig. 6 E).