(Heiden) Hasle, Syvertsen & Medlin (1994: 255, figs 61–67, 79–92, 142d)
Nitzschia aciculariformis Manguin (1957: 132, pl. 7, fig. 45)
Cymatosira laevis Heiden, in Heiden & Kolbe (1928: 558, pl. 6, fig. 131)
Only solitary cells observed. Valves lanceolate, tapering to rounded or rostrate ends; apical axis 14–62 µm; transapical axis 3.5–5.6 µm. Transapical striae parallel, 12–14 in 10 µm. Areolae poroid. Each valve end with an apical field of 4–8 longitudinal slits through the valve wall. Labiate process solitary, close to one valve end.
Coastal waters off Plough I., near Davis Station, East Antarctica; type locality, Gaussberg, “Gauss ” Expedition, 1902 (Heiden & Kolbe, 1928).
Some species formerly included in Fragilaria and Synedra have been transferred to Synedropsis on the basis of their valve striation, the occurrence and structure of labiate processes and apical pore (slit) fields and the nature of the girdle (Hasle et al., 1994). Synedropsis hyperboreoides and S. laevis were collected in the present study, and several other species, e.g. S. fragilis, S. recta, S. lata var. lata and S. lata var. angustata, have been described from Antarctic locations (Hasle, 1994).