Cucumaria (Semperia) bouvetensis Ludwig & Heding, 1935: 188 –189, figs 46, 47. Ludwigia bouvetensis.— Panning, 1949: 431.
Ocnus bouvetensis. — Panning, 1971: 29 (by implication of synonymy of Ludwigia with Ocnus). Trachythyone baja Hernández, 1987: 161 –165, fig. 1, pl.
Trachythyone bouvetensis. — Gutt, 1991: 322, 324. — Massin, 1992 a: 190 –191.
Remarks. Cucumaria bouvetensis Ludwig & Heding, 1935 has the diagnostic characters of Trachythyone Studer, 1876: 8 and 2 small dendritic tentacles; Cucumaria -like calcareous ring; tube feet dorsally and laterally, and on 3 ventral radii; body wall ossicles large perforated plates and small spinous cups with 4 – armed cross. Panning (1949) initially referred the species to Ludwigia Reiffen, and then by implication to Ocnus Forbes when he (Panning 1971) judged Ludwigia to be a junior synonym of Ocnus. The species has been referred to Trachythyone by Gutt (1991) and Massin (1992 a). The species is formally referred here to Trachythyone.
When he erected his new species Trachythyone baja (Antararctic Peninsula and South Georgia), Hernández (1987) did not distinguish it from Trachythyone bouvetensis (Ludwig & Heding, 1935) (Bouvet I.). I have examined specimens (NMV) of Trachythyone bouvetensis from South Georgia, South Sandwich Is, South Shetland Is and Prydz Bay. The Hernández description and illustrations of Trachythyone baja are good descriptions of Trachythyone bouvetensis. The two species are judged here to be synonyms.
Species of Trachythyone on the coast of Antarctica are: Trachythyone bouvetensis (Ludwig & Heding, 1935); Trachythyone cynthiae sp. nov. (below); Trachythyone mackenzieae sp. nov. (below); Trachythyone maxima Massin, 1992 a and possibly Trachythyone parva (Ludwig, 1874) (listed in Gutt, 1991; not confirmed in this work).