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Authority

G.C.Wall. (Wallich, 1860: 42, pl. 2, figs 3, 4)

Class

Diatomophyceae

Order

Centrales

Family

Hemidiscaceae

Synonyms

Euodia cuneiformis (G.C.Wall.) Schütt (1896: 100, fig. 174D, E)
Euodia inornata Castrac. (Castracane, 1886: 149, pl. 12, fig. 1)
Euodia radiata Castrac. (Castracane, 1886: 150, pl. 12, fig. 4)

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Basionym

N/A

Additional References

Hendey (1937: 264; 1964: 94, pl. 22, fig. 9), Fryxell & Hasle (1973: 76, figs 18, 19), Hasle & Syvertsen (1997: 128, pl. 22, tab. 28)

Description

Cells solitary(?). Valves flat, semi-lanceolate to almost semicircular; dorsal margin strongly convex; ventral margin weakly convex, often with a median inflation on the ventral side; apical axis 40–174 µm; transapical axis 30–90 µm. Areolae in irregular radial fascicles, but in short parallel lines the towards the valve centre where 6–12 in 10 µm, and in irregular or tangential sectors towards the margin and poles where 10–18 in 10 µm. Poles with small inconspicuous processes; central hyaline area and rosette absent; ventral margin of valve with small spinules and a small partially occluded pseudonodulus midway along margin. Labiate processes 1–2 in 10 µm along ventral margin only, with 1 on either side of the pseudonodulus. Girdle simple, lacking intercalary bands. Chloroplasts numerous, small, spherical.

Distribution

Coastal waters near Davis Station, East Antarctica; South Atlantic, 47°19.75’S 11°05’E to 49°50’S 08°32.5’E (Hendey, 1937).

Comments

Hendey (1937) referred all specimens, including a series of intermediate forms which “made it impossible to recognise the value of nomenclatural species and varieties”, to H. cuneiformis. The genus now includes only two species, H. cuneiformis and the warm-water H. kanayanus Simonsen (Simonsen, 1972).

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