On a collection of shallow-water hydroids (Cnidaria: Hydrozoa) from Guadeloupe and Les Saintes, French Lesser Antilles Author Galea, Horia R. text Zootaxa 2008 1878 1 54 journal article 10.5281/zenodo.184149 086e0d63-8af0-4ad1-8884-03fa56b5ea98 1175-5326 184149 Halopteris alternata ( Nutting, 1900 ) (fig. 8A–D) Plumularia alternata Nutting, 1900 : 62 , pl. 4 figs 1–2. Halopteris alternata — Schuchert, 1997 : 42 , fig. 14.— Ansín Agís et al . 2001 : 152 , fig. 66. Halopteris diaphana — Migotto, 1996 : 45 , fig. 9D–E [not H. diaphana ( Heller, 1868 ) ]. Halopteris diaphana diaphana — Vervoort, 1968 : 58 , fig. 27 [not H. diaphana ( Heller, 1868 ) ].? Halopteris sp.—Hirohito, 1995: 248, fig. 83D. Material examined . Stn. 2 : 22.01.2008 —several sterile stems, on stems of Pennaria disticha Goldfuss, 1820 , concretions and algae; 26.01.2008 —several stems, up to 10 mm high, some with gonothecae of both sexes, on algae and rock; 01.04.2008 —numerous stems, 7–9 mm high, some fertile, on green algae. Stn. 3 : 26.01.2008 —numerous plumes, up to 10 mm high, gonothecae rare, on algae and sponge; 01.04.2008 —several sterile stems, up to 1.4 cm high; on various algae. Stn. 4 : 22.03.2008 —numerous stems, up to 1.5 cm high, some fertile, on brown algae. Stn. 6 : 28.03.2008 —two sterile stems, 6 mm high, on sponge. Stn. 7 : 25.03.2008 —a few sterile stems, up to 2 cm high, on various algae; 27.03.2008 —several sterile colonies, 6–9 mm high, on various algae, concretions, and stem of P. disticha . FIGURE 8 . A to D: Halopteris alternata (Nutting, 1900) —fragment of stem (A); male (B) and female (C) gonothecae; nematocysts (D). E: Halopteris diaphana (Heller, 1868) —fragment of stem. Scale bars: 10 µm (D); 200 µm (B, C); 300 µm (A); 400 µm (E). Type locality . Barracuda Rocks, West Indies, Caribbean. Remarks . This species is easily distinguishable by the presence of a laterally-displaced, axillar nematotheca behind the cauline hydrothecae. For recent descriptions and synonymy, see Schuchert (1997) and Ansín Agís et al . (2001) . Although not very accurate, the description provided by Hirohito (1995) of Halopteris sp. from Japan allows me to assign his material to H. alternata . Fortunately, one axillar nematotheca, laterally-displaced towards the stem apophysis is clearly figured behind each cauline hydrotheca (fig. 83D). Distribution . Preponderently recorded from the western Atlantic, with some records form the eastern Atlantic (for more details, see Ansín Agís et al . 2001 ). Possibly occuring in Japan (Hirohito 1995). The Caribbean records are summarized by Calder & Kirkendale (2005) .