Macrorhynchia philippina Kirchenpauer, 1872

Hydrorhiza reptant on substrate. Colonies variable in size from single stems a few centimetres long to large complex colonies of several stems to 200 mm high.

Stems erect, plumose, simple or branched, if branched, up to 4 mm wide at base, fascicled, polysiphonic tubes running parallel to near apex of branches. Two or three orders of branching may be present, branches straight, given off sparsely and irregularly from stem, branch internodes indistinct.

Hydrocladia frontal on branch, alternate, one on internode; hydrocladial internodes short, deep, nodes slightly oblique; two partial intranodal septa, one passing down from base of hydrotheca, the other from base of lateral nematotheca.

Hydrotheca saccate, adcauline wall flat or slightly convex in contact with internode, where free of internode attached to lateral nematotheca, a deep indentation in base at proximal end of adcauline wall, abcauline sinuate, rising abruptly behind margin, a deep V -shaped septum penetrating hydrotheca between mesial nematotheca and margin. Margin circular with a pair of opposite, low lobes.

Mesial nematotheca erect, tubular, parallel with hydrothecal abcauline wall, reaching to or beyond hydrothecal margin, tapering a little distally, terminal orifice circular, a little excavated on adcauline side, a secondary orifice above junction with hydrotheca and another, internal, connecting with hydrotheca. Lateral nematotheca long, tubular, inclined forward, overtopping hydrothecal margin, orifice circular or slightly excavated. A cauline nematotheca on branch at base of hydrocladium, short, body inflated, a circular orifice on a short neck.

Phylactocarp a modified hydrocladium given off from front of branch, phylactocarp about same length as gonotheca; proximal internode with a hydrotheca, next internode short, athecate, succeeding internode with two nematothecae and pedicel of gonotheca, following three to six internodes short with two long, digitate nematothecae with circular distal orifice.

Gonothecae large, lenticular, containing a degenerate medusa, one or two gonothecae, sometimes a male and a female, on same rachis, perisarc thin, female containing many small ova. At release, medusa ovoid, without mouth or canals but with a ring of strongly refringent granules around margin.

Colour: In life, stems and branches dark brown to black, hydrocladia pale grey, male gonophore purple to black, female cream to pale orange. The refringent granules on the released medusa sparkle blue and white when viewed under a microscope.