Halopteris plagiocampa
Stem 7 mm high, monosiphonic, perisarc very thin, smooth, internodes long with distinct transverse nodes, a row of four equidistant nematothecae on front of internode; opposite pairs of hydrocladia given off distally on internode.
Hydrocladial apophysis short, with two transverse distal nodes; hydrocladia opposite, directed upwards at 35°- 60° to stem axis. Hydrocladial internodes variable in length, usually long and slender, proximal internode athecate with one small mesial nematotheca c lose to transverse proximal node, internodes thereafter with strongly oblique proximal node and transverse distal node. Hydrothecate internode shorter than proximal internode, hydrotheca seated on distal half.
Hydrotheca deep, almost tubular, set an angle of 40° to hydrocladial axis, floor shallowly convex, free adcauline wall short, decidedly concave, abcauline wall straight, margin circular, rim not everted.
Nematothecae all bithalamic, mesial proximal on athecate internode, small, basal chamber stout, cup shallow, broad, mesial inferior similar, basal chamber more robust, nematotheca not reaching base of hydrotheca; lateral nematotheca inserted without pedicel below adnate adcauline wall, not reaching hydrothecal margin, basal chamber long, cup shallow and broad, a little excavated on adcauline side; cauline nematothecae similar to mesials; no lateral nematothecae associated with cauline hydrotheca.
Indonesia, Japan and northern Australia.
Subtidal, epizoic on other hydroids.