Diagnosis (amended from O’Loughlin et al. 2009). Body with narrowed tail, hard to parchment-like body wall; tentacles 10 with the ventral two reduced; tube feet evenly distributed around entire body; calcareous ring simple, without posterior prolongations; body-wall ossicles as crosses with four regular or irregular arms, small-knobbed perforated plates with or without a secondary mesh thickening and end spine; posterior body wall with multi-layered ossicles.
Type species. Thyone scotiae Vaney, 1906.