Cells solitary, elliptical; apical axis 87 µm; transapical axis 57 µm. Raphe-valve not seen. Pseudoraphe-valve convex near the margin, concave in central area around pseudoraphe. Pseudoraphe narrow, but expanded centrally and at both ends; P-valve transapical striae fine (not visible by LM), discontinuous, curved and radiating, uniseriate; areolae slit-like, 20 in 10 µm (Fig. c). Areas immediately around pseudoraphe and from c. midway from centre to margin are finely punctate (Fig. b, d).
Coastal waters of Inexpressible I., Ross Sea, Antarctica.
Insufficient material was available to determine the identity of this sample.
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.