Coscinodiscus marginatus Ehrenberg (1843: 412) (Fig. 9)

References: Hendey 1964, p. 78, pl. 22, fig.2; Desikachary 1988, pl. 537, figs 1–4, pl. 538, figs 1–6.

Features: Diameter 41–70 μm.

Description: Valves circular, convex with large hexagonal areolae arranged in quincunx structure. Marginal areolae smaller in size, central area absent. Valve margin broad.

Remarks: Deposited from the plankton.

Ecology and Distribution: A widely distributed pelagic species. Previously reported from the Gulf (Al-Kandari et al. 2009). Frequent in Basra corals.