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 .

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).