Protankyra

Östergren, 1898

33 species

Tentacles digitate, 12, rarely 13 or 14. Digits 2 on each side. Cartilaginous ring wanting. Polian vesicles 2-10 or rarely only one. Stone canals usually single, but rarely several. Stock of anchors more or less branched, or only finely toothed; arms usually serrate, vertex without knobs. Anchor plates without a handle, with numerous irregular perforations also with either smooth or dentate margins. (Deichmann, 1930)

Anchors and anchor plates of one or more kinds; anchors sometimes asymmetrical. Anchor plates usually rounded, with numerous perforations, of which central perforations not conspicuously larger than others. Perforations with smooth or spinous margins. Usually more than 3 Polian vesicles. (Pawson, 1970)