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Authority

(Roper) Grunow ex Pelletan (1889: 158, fig. 417)

Class

Diatomophyceae

Order

Centrales

Family

Hemidiscaceae

Synonyms

Actinocyclus coscinodiscoides A.Mann (1937: 19, pl. 1, fig. 5)
Roperia tesselata var. coscinodiscoides (A.Mann) Kolbe (1955: 176)

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Basionym

Eupodiscus tesselatus Roper (1858: 19, pl. 3, fig. 1a, b)

Additional References

Simonsen (1974: 22), Fryxell et al. (1986: 24, figs 25, 32.3, 32.4), Ricard (1987: 43, figs 40–46), Hasle & Syvertsen (1997: 130, pl. 22)

Description

Cells discoid. Valves circular to oval; apical axis 25–70 µm. Areolation irregular to eccentric, 6–7 in 10 µm at valve centre, smaller and c. 14 in 10 µm near the margin. Marginal labiate processes 1–2 in 10 µm. Pseudonodulus prominent, near the margin and close to one labiate process, operculate. Chloroplasts numerous, small.

Distribution

Coastal waters near Davis Station, East Antarctica; sub-Antarctic Pacific, to 57°S (Hasle, 1976a).

Comments

The cells found near Davis Station measured 25–40 µm in diameter. In all cases, the pseudonodulus is operculate, thus belonging to the “simplex” type of Ross & Sims (1972), i.e. “Type C” of Simonsen (1975: 83, text fig. 1).

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