Table 1.
Thyone scotiae Vaney, 1906 a: 400 -401, fig. 1.— Ekman 1925: 106 –108, fig. 24. Ypsilocucumis scotiae.— Panning, 1949: 455.— Pawson, 1969: map 3.
Caespitugo citriformis Gutt, 1990: 105, figs 1, 5–7, table 2.— Gutt, 1991: 324 (new synonym). Crucella cf. hystrix Gutt, 1990.— O’Loughlin et al., 1994: 552, table 2.
Remarks. Thyone scotiae Vaney, 1906 a has a circum-polar distribution (M. O’Loughlin, pers. obs.). The distinguishing characters of Thyone scotiae Vaney, 1906 a and Caespitugo citriformis Gutt, 1990 are: body with narrowed tail; hard to parchment-like body wall; 10 tentacles with ventral pair small; cucumariid not phyllophorid calcareous ring; tube feet evenly distributed around body; body wall ossicles small knobbed plates, large irregular thick knobbed perforated plates with central secondary mesh thickening; posterior body with multi-layered ossicles. Caespitugo citriformis Gutt, 1990 is judged here to be a junior synonym of Thyone scotiae Vaney, 1906 a. Thyone Oken is an inappropriate genus for Thyone scotiae Vaney, since the calcareous rings of Thyone species have elongate composite posterior projections characteristic of family Phyllophoridae. Panning (1949) inappropriately referred T. scotiae to his new genus Ypsilothuria, diagnosed as having 10 equal tentacles. Thyone scotiae Vaney is referred here to Crucella Gutt, 1990 that has: body with narrowed tail; hard to parchment-like body wall; 10 tentacles with ventral pair small; cucumariid not phyllophorid calcareous ring; tube feet evenly distributed around body; body wall ossicles crosses with four perforated arms, with or without central secondary mesh thickening and spine. Gutt (1990) referred his now junior synonym species C. citriformis to his genus Caespitugo, but it is judged here that the senior synonym T. scotiae is more appropriately referred to Crucella Gutt, 1990 because of the multi-layering in the centre of some perforated plates, and some plates cross-shaped or with irregular arms. Caespitugo Gutt, 1990 becomes a junior synonym of Crucella Gutt, 1990.