Ectopleura exxonia (Watson, 1978)

Hydrorhiza a matted reticulum penetrating 5-6 mm into the surface of horny sponge, perisarc of hydrorhiza thick.

Stems simple, perisarc thick proximally, becoming thinner distally, reaching a height of 2-3 mm above surface of sponge. Width of stem below hydranth, 0.15-0.25 mm.

Hydranth variable in shape, capable of great distension, from globular to spindle shaped. Length of body including oral tentacles (preserved) 0.7-1.0 mm; width 0.3-0.5 mm (hydranth partially distended).

Tentacles filiform, 12-14 aboral, 0.75-1.23 mm long and 0.06-0.1 mm wide at base, and 13-15 short oral tentacles 0.25-0.35 mm long; inner surface of aboral tentacles furnished with conspicuous pads of nematocysts (stenoteles, none discharged).

Gonophores cryptomedusoid, borne in tight clusters of 10-12 in various stages of development on a short blastostyle arising between the bases of aboral tentacles. Mature gonophores irregularly elongate, but individual shape variable due to pressure of surrounding gonophores. Length of mature gonophore 0.2 mm.

Colour: Body of hydranth and tentacles translucent white, gonophores pink (preserved material).