Thorunna horologia Rudman, 1984

Yonow, Nathalie, 2012, Opisthobranchs from the western Indian Ocean, with descriptions of two new species and ten new records (Mollusca, Gastropoda), ZooKeys 197, pp. 1-130 : 39-40

Thorunna horologia Rudman, 1984 cf. http://species-id.net/wiki/Thorunna_cf_horologiaFig. 14Plate 55

Thorunna horologia . - Debelius & Kuiter 2007: 199, right image only (South Africa).

Thorunna sp 3. - Gosliner et al. 2008: 253 (Indonesia).

Material.

Sri Lanka: 5 × 4 mm pres., Pigeon Island, Trincomalee, 16 m depth, April 1995, leg. SG Buttress & RC Anderson.

Description.

The single specimen appears to have been stocky with little mantle overlap in life. Margin permanently convoluted with three indentations: one behind rhinophores, largest in centre of body, one just beyond gills. Colour opaque white with violet pigment concentrated around edges and on head around and between rhinophores. Thin sub-marginal white line around the violet, followed by translucent margin with orange in patches and in permanent folds, most especially the central one in which there was orange pigment overlying the submarginal white line. Rhinophores very large with translucent stalk and white core covered in 13 orange-red lamellae; rhinophoral pockets with low violet rim. Eight gills simply pinnate, arranged in circle around anal papilla; white ‘core’ and orange lamellae; orange line along both inner and outer edges of each gill. Foot pale violet, darker concentration of violet in band around metapodium.

The preserved specimen is translucent cream, with a thin mantle skirt. The rhinophores are retracted but some of the gills are extended: they are simply pinnate. The foot is convoluted laterally but anteriorly it is relaxed. The bilaminate margin spans the entire width and the upper lamina is notched. The oral tentacles are plump rounded structures (Fig. 14).

Remarks.

This specimen differs from Thorunna horologia , also found in the western Indian Ocean: horologia is opaque white with red marginal and orange-yellow sub-marginal lines, a single deep indentation which is red, and a white foot with a violet band on the margin ( Rudman 1984, Gosliner et al. 2008).