Sibogaster Döderlein, 1924

Sibogaster Döderlein, 1924 View in CoL .

Sibogaster Döderlein, 1924: 63 View in CoL ; A.M. Clark, 1993: 283 (checklist only); Mah, 2016: 129 View Cited Treatment .

Diagnosis. Abactinal plates smooth, bare (no accessories on plate surface-although embedded glassy bosses present in S. digitatus ), weakly convex, round to polygonal in outline. M arginal plates elongate, mostly smooth, bare ( S. digitatus has fewer than 6 granules on one or two interradial superomarginals). Inferomarginals adjacent to actinal surface covered with variably abundant granules. Actinal plates covered by granules. Adambulacral plates rectangular in shape. Furrow spines numerous, six to 15. Subambulacral spines. thickened relative to furrow spines. Remaining granulation identical to others on actinal surface.

Comments. Sibogaster currently includes 3 species, the tropical Pacific S. digitatus , the Atlantic and Pacific S. bathyheuretor and the widely occurring S. nieseni , which have been recorded from 640 to 4175 m, but primarily from bathyal and abyssal depths (1000 to 5000 m). Specimens reported herein are the first from Australian waters.