Sertularella quadridens (Bale, 1884)

Hydrorhiza a bunch of tubular stolons; stolons creeping up stems to proximal hydrothecae but not forming fasciculations.

Stems monosiphonic, pinnately branched in one plane, to 110 mm high, lower stem perisarc thick, thinning distally, hydrocladia up to 10 mm long, given off alternately from proximal part of stem internode, nodes deep, transverse to oblique, inclined opposite directions; three hydrothecae on internode between each hydrocladium, one in axil below node, one opposite and one below hydrocladium, axillar hydrotheca narrow at base, adcauline wall becoming free at or just below junction with cauline node.

Hydrocladia arising from apophysis in top third of internode, proximal part with several constrictions in perisarc, internodes variable in length bearing two to five hydrothecae on each side, nodes deep, transverse to slightly oblique.

First hydrocladial hydrotheca on lower side of hydrocladium, hydrothecae thereafter subalternate, not in contact, tubiform to flask-shaped, widest about middle, adcauline wall gently convex or sometimes with a slight flexure where adcauline wall becomes free, wall two thirds to almost entirely adnate; free wall (when present) continuing curve of adnate part. Abcauline wall almost straight or a shallow sinuous curve, a short outward deflection of the wall just below margin; length: wall free than hydrocladiate hydrothecae. Floor of hydrotheca flat, thick, in mature hydrothecae a knot of perisarc at base of adcauline wall often extending into a spur. Margin circular, tilted upwards at an angle of 30°- 45° to hydrocladial axis with four equidistant low, pointed cusps, one adcauline, one abcauline and two lateral, rim thickened, operculum of four equal triangular, fairly thick flaps; margin not replicated.

Gonothecae large, borne below hydrothecae in midstem region; gonotheca slender, barrel-shaped, pedicel contiguous with body, perisarc thick, with eight deep, widely separated annular flanges passing around body, these fading out proximally; body between flanges finely vertically striated, distal end wide, tubular, orifice large, depressed into apex with four prominent equidistant, outwardly turned protuberances, operculum not visible, gonophore female.

Colour: Live colonies golden yellow.