Grunow Heiden, in Heiden & Kolbe (1928: 605, tab. 2, fig. 53)
Peragallo (1921: 56)
Cells solitary or joined together at valve surface, lanceolate; apical axis 21–27 µm; transapical axis 5.6–6.5 µm; pervalvar axis c. 2.9 µm. Transapical striae 12–19 in 10 µm, straight but slightly radiating towards the cell apices. Raphe central; endings expanded into pores; terminal endings hooked in the same direction.
Coastal waters off Davis Station, East Antarctica; Antarctic coldwater species (Kozlova, 1964).
Material collected near Davis Station consistently showed finer valve striation (striae 17–19 in 10 µm) than previous descriptions (striae 12–15 in 10 µm; Heiden & Kolbe, 1928). The less common N. gelida var. antarctica Heiden (Heiden & Kolbe, 1928) has larger cells (apical axis 34–64 µm; transapical axis 13–15 µm) with slightly coarser valve striation (striae 8.5–11 in 10 µm).