(van Heurck) F.Reid & Round (1987: 224)
Synedra pelagica Hendey (1937: 335)
Synedra reinboldii van Heurck (1909: 23, pl. 3, fig. 35)
Hasle & Semina (1987: 189, figs 67–75), Hasle (1990: 133, pl. 17.1, figs 7–9), Moisan & Fryxell (1993: 293), Hasle & Syvertsen (1997: 267)
Cells needle-like, arcuate, tapering gradually towards the poles, solitary or in colonies; apical axis 800–3600 µm; transapical axis 3–10 µm; poles similar and without spines (cf. the spine -bearing Thalassiothrix antarctica ); striae on mantle, extending slightly onto the valve face, 8–10 in 10 µm; areolae with external cribra scattered over valve face. Labiate process at each pole. Chloroplasts numerous, discoid.
Endemic to the Southern Ocean, possibly circumpolar (Hasle, 1968; Reid & Round, 1987); Weddell Sea (Moisan & Fryxell, 1993); Indian Ocean sector of the Antarctic (Kopczyńska et al., 1986); Weddell-Scotia Confluence (Garrison et al., 1987).
Hasle (1990) noted that this species often occurs in association with Thalassiothrix antarctica : “They are approximately of the same length and width and are similar in cell shape, with Trichotoxon reinboldii being curved, but not sigmoidal. Trichotoxon reinboldii also forms colonies but, unlike Thalassiothrix antarctica , the cells are attached at either end resulting in pointed, ovoid colonies (Reid & Round 1987)”.