Key to the species of Pannychia (see also Table 1)

1. Dorsal papillae arranged in up to four rows in each radius. Rod ossicles present in dorsal and/or ventral body walls........ 2

- Dorsal papillae arranged in two rows in each radius. Rod ossicles absent in dorsal and ventral body walls............... 3

2. White or yellowish color of tentacles, tube feet and ventral body wall and high density of ossicles in dorsal body walls...................................................................................... P. henrici Ludwig, 1894

- Whole body skin dark violet, maximum diameter of large wheel ossicles in dorsal body walls not exceeding 200 µm, and dorsal and ventral body ossicles are distributed in low density.................................. P. virgulifera Ohshima, 1915

3. Small wheel ossicles in dorsal and ventral body walls with rim teeth........................... P. rinkaimaruae sp. nov.

- Small wheel ossicles in dorsal and ventral body walls without rim teeth........................................... 4

4. Mid-sized wheel ossicles, having rounded triangular rim teeth but calcareous membrane incompletely covering the nave, present in dorsal and ventral body walls. In addition, perforated wheel ossicles, disk-shaped with about 30 perforations, present in dorsal body walls.............................................................. P. nagasakimaruae sp. nov.

- Neither mid-sized wheel nor perforated wheels present in dorsal and ventral body walls.............................. 5

5. Maximum diameter of large wheel ossicles in dorsal body walls exceeds 300 µm................................................................................................ P. taylorae O’Loughlin in O’Loughlin et al., 2013

- Maximum diameter of large wheel ossicles in dorsal body walls does not exceed 240 µm........... P. moseleyi Théel, 1882