Oswaldella vervoorti Pena Cantero & Garcia Carrascosa 1998

Oswaldella vervoorti Peña Cantero & García Carrascosa, 1998

(Figs 14, 16 O, 18G, 20G)

Material examined. United States Antarctic Research Program (USARP): Stn 721/1063, Hero, 19 December 1971, 62°19.0’S, 59°11.4’W (Nelson Island, South Shetland Islands), 44 m (USNM 1003380).

Description. Monosiphonic, unbranched stems, up to 95 mm high, divided into internodes. Angle between cauline apophyses and stem ca. 45°. Cauline apophyses with two axillary nematophores, each emerging through hole in apophysis perisarc, provided with slight abcauline projection of perisarc, and another one emerging through strongly developed ‘mamelon’, provided with relatively large aperture (Fig. 14 B).

Hydrocladia branched (Fig. 14 A), with up to fourth-order hydrocladia. First hydrocladial internode bifurcated, with two similar prongs (Fig. 14 A). Mesial inferior nematophore emerging from marked swelling at proximal third of internode (Fig. 14 C–D); with relatively large, claw-shaped nematotheca (Fig. 14 C–E). Hydrotheca elongate, placed on distal half of internode. Abcauline wall roughly straight; adcauline wall mostly adnate (Fig. 14 D). Hydrothecal aperture perpendicular to long axis of internode, sub-circular, adcauline side more or less straight; rim even (Fig. 14 C–D).

Immature gonothecae, inverted cone-shaped (Fig. 14 A, F).

Remarks. Although only up to second-order hydrocladia were observed in the material examined (Fig. 14 A), up to fourth-order hydrocladia have been described (cf. Peña Cantero & García Carrascosa 1998).