Sertularella simplex (Hutton, 1873)

Stems to 1 cm long, occasionally branched, arising from a tubular hydrorhiza. Stems smooth, proximal internode athecate, with a few indefinite annulations; nodes distinct, sloping alternately right and left. Internodes fairly long, 0.39-0.60 mm, becoming progressively shorter distally, until hydrotheca occupies about two thirds of internode. Width of internode below hydrotheca, 0.17-0.20 mm. Branches, when present, arising just below the hydrotheca, the first branch internode with 2-3 annulations. Tendrils present, growing from the distal ends of stems and from broken hydrothecae.

Hydrothecae with 3 internal submarginal teeth- 1 abcauline, 2 adcauline; thecal walls thin and smooth, length of free adcauline wall variable, 0.33-0.40 mm, fixed wall, 0.25-0.27 mm; abcauline wall, 0.52-0.54 mm; maximum width of hydrotheca, 0.22-0.27 mm. Margin showing occasional reduplications.