SEM study of species of Oswaldella Stechow, 1919 (Cnidaria, Hydrozoa, Kirchenpaueriidae), with an annotated checklist of the species of the genus Author Molinero, A. González Author Peña Cantero, A. L. text Zootaxa 2015 4052 4 401 441 journal article 10.11646/zootaxa.4052.4.1 93f6d085-8e63-4d1e-89c1-f950128b2a61 1175-5326 245887 47EF6E9D-9064-4899-B3DD-276FF7C969EB Oswaldella shetlandica Stepanjants, 1979 ( Figs 12 , 16 L, 18D, 20E) Material examined. Spanish Antarctic Expedition Bentart 2006: Stn Low 45 , Hespérides , February 2006 , 63.43171°S , 62.2116°W (Low Island , Antarctic Peninsula), 86 m (Department of Zoology, University of Valencia, BENTART 2006—LOW 45). Description. Polysiphonic, unbranched stems, up to 170 mm high, divided into internodes. Angle between cauline apophyses and stem ca. 45°. Cauline apophyses with four nematophores: two axillary ones, each emerging through simple hole in perisarc, and two other nematophores, each emerging through a strongly developed ‘mamelon’ ( Fig. 12 B). Hydrocladia much branched ( Fig. 12 A), with up to fourth-order hydrocladia. First hydrocladial internode bifurcated, with two similar prongs ( Fig. 12 A). End of distal internodes peak-shaped ( Fig. 12 A, E). Mesial inferior nematophore emerging from very strongly marked swelling at proximal third of internode ( Fig. 12 C–E); without nematotheca ( Fig. 12 C–E). Hydrotheca elongate, placed on middle of internode. Abcauline wall convex at distal part. Free part of adcauline wall much separated from internode ( Fig. 12 D). Mesial superior nematophore arising at axil between internode and free part of adcauline wall ( Fig. 12 D). Hydrothecal aperture kidney-shaped ( Fig. 12 D), adcaudally directed; free part of adcauline wall strongly directed inwards ( Fig. 12 D). Gonothecae pear-shaped, with distal, large, circular aperture; female gonotheca ( Fig. 12 F) much larger than male one. Remarks. Cauline apophyses with a single ‘mamelon’ have also been reported (cf. Peña Cantero & Vervoort 2004 ). The relatively large size of the aperture of the ‘mamelons’ is noteworthy ( Fig. 12 B).