Cocconeis costata Gregory

6. Cocconeis costata Gregory (Figs 6–8)

Basionym: Gregory 1855, p. 39, pl. 4, fig. 10.

References: Hustedt 1933, p. 332, fig. 785; Romero & Rivera 1996, p. 321, figs 2–16; Witkowski et al. 2000, p. 104, pl. 38, figs 36–38.

Description: Valves elliptical to linear-elliptical, 8–19 μm long, 5–8 μm wide. SV: sternum narrow and linear. Central area not developed. Transapical striae parallel in the middle, radiate towards the apices, biseriate to triseriate, 9–10 in 10 μm, but pluriseriae on a stria unresolvable in LM. RV: raphe straight, the central ends of raphe expanded externally, but slightly deflected in opposite directions internally; sternum very narrow. Central area transversely expanded as hyaline fascia up to the margins. Transapical striae biseriate, parallel in the middle, radiate towards the apices, 14–15 in 10 μm.

Remarks: This is ubiquitous or cosmopolitan taxon, occurring on the coasts from the Mediterranean to the northern Arctic Ocean (Hustedt 1933), occurred frequently near Cape Town coast of South Africa (Giffen 1970) and in the Kerguelen Islands of the southern Indian Ocean (Riaux-Gobin 1994), along the Pacific Ocean coasts of Chile, including parts of the Subarctic and Arctic (Romero & Rivera 1996), and in western Baltic Sea (Witkowski et al. 2000). Along the Seogwipo coast of Jeju Island, it was rarely found as epiphytes on seaweeds of some samples; it is herein newly described for South Korea.