Valves linear to lanceolate, usually sigmoid. Raphe usually sigmoid, central or excentric;striae finely punctate in oblique and transverse lines. Central nodule is usually small and rounded. Cells narrow in girdle view, with narrow connective zone, sometimes twisted or arcuate, or constricted in the middle. Chromatophores usually two bands, one on each valve.Each band is lobed or indented and sometimes differs in opposite valves. Numerous pyrenoids are present in most forms. Littoral or bottom species, are often occurring in the plankton (Cupp, 1943).
Hendey, 1970: p. 152, Pl. 6: 62.
Valve lanceolate, gently sigmoid, with acute apices. Median line more sigmoid than the valve, excentric. Transverse and oblique striae equidistant.
Cells length 98-120 µm; width 20-23 µm.
Mainly littoral species, but is frequently found in the plankton.
Sites of occurrence in RSA:
In Winter 2006 Cruise, this species occurred at most of the sites (refer sites map), encountered in 83.8 % of the samples, often in large numbers; maximum abundance (3.7*10^3 cells/l) was associated with the Iranian coast in the
central part of the inner RSA (St. 11a). Species has been previously reported from Kuwaiti shore (Hendey, 1970) and coastal waters (Al-Yamani et al., 2004; Al-Kandari et al., 2009).