Litophyton horseshoeensis sp. nov.

(Figs. 85d, 89b, 92-93)

Material examined. Holotype NTM C2256, Queensland, Horseshoe reef, Bommie Top, 11 November 1980, coll. P. Alderslade ; paratypes: NTM C 1366-68, 1370, 1379, Queensland, Swain reef, Sweet-lip reef, 15 November 1980, coll. P. Alderslade; NTM C 1392-95, Queensland, Bills reef, 8 November 1980, coll. P. Alderslade; NTM C1396, Queensland; Central reef, coll. P. Alderslade; NTM C2255; Queensland, Horseshoe reef, Bommie Top, 11 November 1980, coll. P. Alderslade; NTM C3992, Queensland, Great Barrier Reef, Davies reef, depth 5-10 m, 16 April 1981, coll. Z. Dinesen.

Description. The holotype is 7.5 cm high and 4.5 cm wide, the stalk is 1.5 cm long (Fig. 89b). The polyps are up to 0.6 mm wide and 0.5 high, grouped in spherical catkins.

Polyps. With irregular arrangement of sclerites in eight points (Fig. 85d). Abaxially and lateral point sclerites are spindles with simple tubercles and spines; abaxially up to 0.50 mm long, laterally they are up to 0.25 mm long (Fig. 92 a-b). Adaxially there are small, curved scales, up to 0.10 mm long, similar to those of the tentacles (Fig. 92c). The polyp stalk has straight rods, up to 0.10 mm long (Fig. 92d). Supporting bundle not projecting or slightly so, composed of spindles, up to 1.80 mm long, with simple tubercles and one spiny end (Fig. 92e).

Surface layer top stalk. Capstans, derivatives of capstans, spindles, and unilaterally spinose spindles, all with simple and complex tubercles (Fig. 92 f-g). Capstans 0.05-0.20 mm long; spindles up to about 0.60 mm long.

Surface layer base stalk. Capstans, thorny derivatives of capstans, spindles, and unilaterally spinose spindles, all with simple and complex tubercles (Figs. 92h, 93a). Capstans 0.05-0.15 mm long; spindles up to about 0.50 mm long.

Interior stalk. Spindles, up to 1 mm long, with pointed ends (Fig. 93c), and simple and complex tubercles (Fig. 93b). The smaller spindles often have side branches (Fig. 93b).

Etymology. Named after the holotype locality.

Distribution. Great Barrier Reef: Horseshoe reef, Sweet-lip reef, Bills reef, Central reef, Davies reef.

Remarks. NTM C1379 has somewhat longer internal stalk spindles, up to 1.20 mm long.

L. horseshoeensis resembles L. debilis (Kükenthal, 1895) (Ternate) (Figs. 69e, 77), but has many thorny derivatives of capstans in the surface of the base of the stalk.