Family: Coscinodiscaceae Kützing
Genus: Coscinodiscus Ehrenberg
Scientific name: Coscinodiscus oculus-iridis Ehrenberg
Hustedt, 1930: p. 454, Figs. 252, 253; Allen and Cupp, 1935: p. 118, Fig. 15; Cupp, 1943: p. 63, Fig. 26, Pl. 3: 2; Hendey, 1964: p. 78, Pl. XXIV: 1; Hendey, 1970: p. 111; Simonsen, 1974: p. 17; Priddle and Fryxell, 1985: p. 138-139.
Cells disk-shaped. Central part of valves slightly concave. Diameter 120-150 µm. Areolae large. Rosette usually large, sometimes with a small central hyaline area. Areolae 3½-4½ in 10 µm near center, near marginal region 2½-3½ in 10 µm. Margin small, with radial striae corresponding to the outer areolae, about 7 in 10 µm. Chamber openings distinct. Outer closing membrane with delicate and scarcely visible poroids. Radial and secondary spiral rows well marked. Marginal spinulae not visible in valve view, the two asymmetrical processes small but usually distinct (Cupp, 1943).
Valve diameter 110-140 µm.
Widely distributed oceanic species.
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 (1.5*10^3 cells/l) was associated with the Strait of Hormuz area (St. 83). It has been previously reported from the inner RSA (Simonsen, 1974) and from Kuwaiti shore (Hendey, 1970) and coastal waters (Al-Kandari et al., 2009).