W.Greg. Manguin (1960: 304, pl. 14, figs 154, 155a–c)
Andreoli et al. (1995: 472, fig. 10, SEM of C. costata)
Cells solitary, elliptical; apical axis 13.5–27 µm; transapical axis 9–13 µm. Transapical costae slightly radiating, comparatively broad. Intercostal areas composed of double rows of alternating areolae (Fig. a). Raphe-valve slightly concave; R-valve costae 12 in 10 µm, with a submarginal non-areolate band creating a discontinuity of costae towards the margins. Raphe a simple fissure with approximately parallel sides with small nodules at valve centre. Pseudoraphe-valve with a narrow pseudoraphe; P-valve costae c. 5 in 10 µm.
Coastal waters near Davis Station, East Antarctica; Cape Margérie, Terre Adélie (Manguin, 1960).
Cells collected in the present study were 13.5–18 µm long (apical axis).
Cocconeis cells are solitary and heterovalvate. One valve (the P-valve) is typically convex and bears a pseudoraphe; the other (the R-valve) is concave (or at least less convex than the P-valve) and bears a central raphe-sternum. Valve structure is usually of broad, non-areolate, transapical costae alternating with striae (intercostal areas) that contain uniseriate or multiseriate poroids (areolae). The arrangement of striae and costae on the P-valve often differs from that on the R-valve.