References:
Round, F. E., Crawford, R. M. & Mann, D. G. (1990). The Diatoms: Biology and Morphology of the Genera. Cambridge University Press, Great Britain. pp. 256-257
Description:
Valves are tri-undulate with narrowed slightly capitate apices ending in finely porate pseudocelli; valve mantle sharply downturned, valve surface is irregularly porate, corrugated with irregularly sized and spaced areolae (corrugation is somewhat thicker between valve face and mantle and finer on valve mantle); no obvious annulus; off-centre rimoportula has S-shaped slit, opening into an inconspicuous indentation in central inflation; copulae several, plain and complete; conspicuous pseudosepta occur internally between constrictions, with lesser developed pseudosepta sometimes present (especially near apices); Podzorski (1985) describes valves as being linear-elliptic in outline, with short individuals having only one swelling present; valve mantle strongly developed, proportionately constant in length (25-35µm); punctae on valve surface are in radiate rows (about 10 in 10µm, irregularly arranged within the rows), but are either irregular or in more or less distinct rows on mantle (often parallel to pervalvar axis); apical poles always finely punctate (22-25 radial rows in 10µm); girdle band with fine areolate punctae (about 12-14 pervalvar rows in 10µm) arranged in irregular quincunx pattern; apical axis is 25-250µm, transapical axis is 25-50µm
