Zygophylax antipathes (Lamarck, 1816)

Stems woody, very brittle, main stem fascicled (up to 2mm thick in large colonies), the fasciculations decreasing distally along the branches. Branches given off randomly around main stem, some of the younger branches monosiphonic.

Hydrothecae alternate, 0.32-0.34 mm deep (margin to diaphragm), arising from an apophysis at 45 degrees to stem, frequently a short segment (a broken and regenerated pedicel of an earlier hydrotheca) between hydrothecal pedicel and apophysis.

Adcauline thecal wall convex, 0.30-0.37 mm long, usually smooth, sometimes a little undulated; abcauline wall straight or slightly concave, 0.30-0.36 mm long. Margin usually with a distinctly everted rim 0.17 mm in diameter, occasionally with 1 reduplication. Diaphragm near base of hydrotheca transverse, occasionally oblique.

Nematothecae rare, observed from hydrothecal apophysis and polysiphonic tube of stem.

Colour deep reddish brown.