(a) TABELLARIEÆ
Frustule in zone view rectangular, in valve view linear or linear-elliptical, sometimes constricted in the middle, symmetrical to both axes, not cuneate; with two or more septa or annuli.
Chromatophores numerous, granular.
Rhabdonema.—Frustules with numerous septate partitions having one or several foramina. Transverse costæ or rows of coarse puncta.
Tabellaria.—Frustules with two to six nearly straight septa. Transverse striæ subtly punctate.
Grammatophora.—Frustules with two sinuate perforate curved septa. Transverse striæ subtly punctate.
Striatella.—Frustules with alternate partitions, septate or partly so.
Attheya.—Frustules not septate but with numerous annuli.
Rhabdonema Kuetz. (1844)
(rhabdos, a rod, and nema, a thread)