| 1887 Challengeria xiphodon - Haeckel p. 1648 [not figured] |
| 1900 Challengeria xiphodon - Jørgensen p. 91 [not figured] |
| 1901 Protocystis xiphodon - Borgert p. XV27-28; fig. 28 |
| 1905 Protocystis xiphodon - Jørgensen p. 141 [not figured] |
| 1911 Protocystis xiphodon - Borgert p. 433 pl. 31, figs. 4-5 |
| 1976 Protocystis xiphodon - Bjørklund pl. 12, fig. 4 |
| 1981 Protocystis xiphodon - Takahashi and Honjo p. 156; pl. 11, fig. 14 |
| 1991 Protocystis xiphodon - Takahashi pl. 52, figs. 1-3 |
