Cells straight, but usually forming somewhat twisted chains. Apertures oval or squarishoblong as a result of the hammerlike ends of the cells. Cell wall very weakly siliceous,without visible sculpturing. Intercalary bands absent. Pervalvar axis of the cell usually short.Chromatophores are numerous and small. All species marine pelagic (Cupp, 1943).
Hustedt, 1930: p. 777, Fig. 453; Allen and Cupp, 1935: p. 143, Fig. 76; Cupp, 1943: p. 147,Fig. 105; Crosby and Wood, 1958: p. 511, Pl. 36: 30; Simonsen, 1974: p. 33; Ricard, 1987: p.189, Fig. 341.
Cells straight, flat, often united into long ribbonlike chains. In girdle view with small, linear middle part with more or less long, thin processes on the poles of the apical axis. Length of apical axis 70-95 µm, pervalvar axis 12-15 µm. Intercalary bands absent; pervalvar axis, therefore, always very short. Cells in valve view small linear-elliptical, valve surface between the processes, flat; the apertures, therefore, almost right-angled or very large oblongs, in pervalvar direction, usually wider than the cell. Structure of the membrane extremely difficult to see (Cupp, 1943).
Cells length 80-90 µm; width 14-16 µm.
Oceanic species with distribution from the tropical to temperate latitudes of all oceans.
Sites of occurrence in RSA:
In Winter 2006 Cruise, this species was commonly observed at many sites (refer sites map),often in large numbers; maximum abundance (6.7*10^3cells/l) was associated with the central part of the inner RSA (St. 36). It has been previously reported from the inner RSA (Simonsen, 1974) and from Kuwaiti waters (Al-Kandari et al., 2009).