Navicula planamembranacea Hendey
Hendey, 1964: p. 188, Fig. 8.
Cells usually solitary; valves highly vaulted and flattened in transapical plane. Raphe separating the valve face into two unequal parts; central nodule slightly depressed, usually with four stronger and more widely spaced interstriae, reaching valve margin and producing the impression of a pseudo-stauros (Hendey, 1964). Small raphe fins near valve ends and one on each side of the central nodule. Numerous small and rounded chloroplasts. Pervalvar axis 15- 30 µm, apical axis 66-90 µm, transapical axis 8-10 µm, transapical striae 28-30 in 10 µm (Hasle and Syvertsen, 1997).
Cells length 47-72 µm; width 35-40 µm.
Species has been previously reported from north Atlantic Ocean.
Sites of occurrence in RSA:
In Winter 2006 Cruise, this species occurred at various sites (refer sites map), usually in small numbers; however, it was quite abundant at some localities; maximum abundance (1.4*10^3 cells/l) was associated with the Sea of Oman (St. 25a).