Cocconeis pinnata Greville

17. Cocconeis cf. pinnata W. Gregory ex Greville (Fig. 22)

Basionym: Greville 1859, p. 79, pl. 6, fig. 1.

References: Hustedt 1933, p. 330, fig. 783; Witkowski et al. 2000, p. 112, pl. 37, figs 14, pl. 39, fig. 10; Riaux-Gobin et al. 2014c, p. 85, figs 7–43.

Description: Valve elliptical to ovoid, 28–31 μm long, 20–21 μm wide. SV: sternum broadly lanceolate, central area not differentiated. Transapical striae robust, raised, biseriate, but uniseriate towards the inner, and radiate towards the apices, 3–4 in 10 μm. Marginal area of valve lacking areolae to make a hyaline band. No RV observed.

Remarks: Striae on valves are biseriate with large puncta, but uniseriate towards the margins of valve. These characteristics of striae are consistent with those of Hustedt (1933) and Witkowski et al. (2000), but the width of sternum of SV is different each other. However, according to the inspection of the type specimens, the striae are uniseraite on valve and biseriate towards the margins (Riaux-Gobin et al. 2014c). For this reason, this taxon collected in the local area is named C. cf. pinnata.

This species is distributed along the coasts of Europe, from the Mediterranean to the northern Arctic (Hustedt 1933); it has also been reported for the west Iberian coast of North Portugal (Resende et al. 2007), King George Island, Antarctica (Al-Handal & Wulff 2008), and elsewhere, in the Mediterranean (Majewska et al. 2013). In the Seogwipo coast, it occurred very rarely as epiphytes on seaweed from small rock pools (St. 2); it is herein newly described for South Korea.