Figures 2 e, 3 a, c, e; table 1.
Trachythyone sp. MoV 2003 O’Loughlin et al., 1994: 552.
Material examined. Holotype. Eastern Antarctica, Prydz Bay, 67 ° 41 'S 77 ° 16 'E, 333–341 m, ANARE AA 91 stn 75, C.C. Lu & T.N. Stranks, 17 Feb 1991, NMV F 165718.
Paratypes. Type locality and date, NMV F 68087 (3); Prydz Bay, 307–319 m, ANARE 87 stn 23, NMV F 165717 (5); 188–208 m, ANARE 87 stn 31, NMV F 161551 (2).
Other material. Enderby Land, 193 m, BANZARE stn 41, SAM K 2423 (2); 220 m, BANZARE stn 42, SAM K 2422 (32); 690–911 m, 50 °E ANARE, NMV F 61505 (1); MacRobertson Land, 177 m, BANZARE stn 107, SAM K 2424 (6); 109–121 m, ANARE, NMV F 69119 (2); 118 m, NMV F 68667 (1); Fram Bank, 145– 150 m, NMV F 68093 (5); 304 m, NMV F 161483 (3); 105–114 m, NMV F 68666 (1); 204–216 m, NMV F 68665 (2); 795–830 m, NMV F 68664 (1); 98–301 m, NMV F 68091 (2); 444–453 m, NMV F 68098 (7); Prydz Bay, 307–319 m, NMV F 161511 (2); 505–578 m, NMV F 161491 (1); 405–439 m, NMV F 68069 (1).
Diagnosis. Body elongate, fusiform, tapered posteriorly, distinct tail; up to 60 mm long (preserved, excluding tentacles); body wall parchment-like, thin, calcareous, not rugose; 10 dendritic tentacles, ventral pair small; tube feet thin, elongate, not retractile, in radial series, predominantly single spaced series, sometimes zig-zag to double rows, radial rows symmetrical around body, series do not cross introvert; calcareous ring lacking posterior prolongations, radial plates with narrow sub-rectangular anterior projection, interradial plates with digitiform projection tapered anteriorly, all plates with rounded notch posteriorly; single polian vesicle; gonad tubules long, thin, unbranched.
Mid-dorsal body wall ossicles thick perforated plates, spinous cups; plates elongate, narrow, predominantly 2 perforations wide, plates up to 608 µ m long, lacking knobs over most of plate, some plates with knobs and terminal pointed spines at one end, not spinous spires; cups round to slightly oval, typically 64 µ m long (up to 72 µ m), deep, bluntly spinous, spines sub-digitiform, cups frequently closed by bridges across rim. Multi-layered scale ossicles anally, irregular pear shape, up to 680 µ m long. Tentacle ossicles rod-derived perforated plates, round to oval to elongate, curved to bent to cupped, thick blunt margin and surface spines, plates up to 880 µ m long.
Distribution. Eastern Antarctic coast, 50 °– 77 °E, 98– 911 m.
Etymology. Named for my esteemed and valued colleague the late Cynthia Gust Ahearn, formerly Echinoderm Museum Specialist in the United States National Museum of Natural History in the Smithsonian Institution in Washington DC, with particular appreciation of Cynthia’s role in sending the BANZARE collection of holothuroids to Museum Victoria for my attention.
Remarks. The distinguishing diagnostic characters of Trachythyone cynthiae sp. nov. amongst Antarctic and Sub-Antarctic Trachythyone species (T. bouvetensis, T. mackenzieae sp. nov. (below), T. maxima and possibly T. parva) are: predominantly single radial series of non-retractile tube feet; narrow body wall plates, frequently with knobs and marginal spines at one end; frequent closure of cups by bridges across rim.