Sertularia tongensis (Stechow, 1919)

Stolon tubular, rugose; stems to 5 mm high, unbranched, lower stem of same diameter as stolon, proximal internode athecate, stem thereafter thecate, internodes with 2 alternate hydrothecae, nodes distinct, oblique, sloping alternately left and right, usually a small tumescence above and below node.

Hydrothecae on both stolon and caulus, all of same shape. Stolonal hydrothecae widely spaced, on a short pedicel, cauline hydrothecae sessile, displaced slightly towards front of stem; hydrotheca tubular, narrowing slightly to margin, adcauline wall convex, about half free of internode, abcauline wall contiguous with border of internode, almost straight to weakly concave; floor of hydrotheca transverse to internodal axis; margin quadrangular (anterior view), rim with 4 cusps, lateral cusps sharp with deep semicircular embayment between, operculum of four fragile triangular valves.

Hydranth with 10–12 tentacles; no evidence of an abcauline caecum in contracted or extended hydranths.

Gonotheca irregularly obovoid, usually widening distally, body deeply crumpled, some gonothecae with 1 or 2 deep flanges, body narrowing into a rather wide, smooth pedicel, some arising from within stolonal hydrothecae, apex of gonotheca a short inverted funnel, orifice circular. Perisarc rather thin, fragile at hydrothecal margin, operculum and gonotheca.

Colour: colony pale yellowish-white.