ABCDEFGHIJKLMNOPQRSTUVWXYZ

Authority

(Grunow) Hust. (Hustedt, 1958: 129, fig. 81)

Class

Diatomophyceae

Order

Centrales

Family

Hemidiscaceae

Synonyms

Coscinodiscus (curvatulus var.?) divisus Grunow (1884: 31, pl. 4, fig. 16)
Actinocyclus cholnokyi (Grunow) VanLand. (VanLandingham, 1967: 83)

top

Basionym

Coscinodiscus divisus Grunow (1878: 125; 1884: 83, pl. D, fig. 16)

Additional References

Hustedt (1958: 129, figs 82, 83), Priddle & Fryxell (1985: 104, fig. A), Fryxell (1990: 112, tab. 14.1), Moisan & Fryxell (1993: 493)

Description

Cells solitary, cylindrical. Valves flat, with rounded edges, 41–70 µm diameter. Striae on valve mantle forming slightly fasciculate decussate rows, 20–24 in 10 µm. Areolae 7–9 in 10 µm. Labiate processes 8–15 µm apart, laterally expanded. Pseudonodulus marginal, areolate or eroded.

Distribution

Antarctic, cosmopolitan (Fryxell, 1990); South Atlantic (Hustedt, 1958).

Comments

There is confusion regarding the correct name of this species. Simonsen (1974) considered A. divisus to be conspecific with A. curvatulus, whereas VanLandingham (1967) regarded it as a synonym of A. cholnokyi, and Fryxell et al. (1986) included it in the synonymy of Azpeitia neocrenulata (VanLand.) G.A.Fryxell & Watkins.

Species of Actinocyclus have the following diagnostic features: radial, usually fasciculate areolation; a marginal ring of labiate processes, laterally expanded internally; a marginal pseudonodulus (sometimes difficult to distinguish); and radial, hyaline bands (see Villareal & Fryxell, 1983 and Watkins & Fryxell, 1986 for further details).

top