(a) Valve view, drawings of Malcolm Giffen, without scale. (b) Scan of illustrations from Desikachary et al (1987), showing robust striae and a distinct sternum. (c-f) Valve view, showing robust striae and a distinct sternum. These images were taken from Slide Br 426/52 of Malcolm Giffen depsoited in Hustedt Diatom Collection at Alfred Wegener Institute in Bremerhaven. (g-i) External view, based on clean material SZCZ16502 of natural samples from Juan de Nova in Mozambique Channel deposited in Palaeoceanology Unit, Faculty of Geosciences, University of Szczecin. (j) Internal view, the material is the same as Fig 6g–6i. (k) Incomplete girdle band (see arrow), the material is the same as Fig 6g–6i.