| Mesostoma lingua (Abildgaard, 1789) | 1930 or earlier | | | |
| Bothromesostoma personatum (Schmidt, 1848) | 1930 or earlier | | | |
| Macrostomum tuba Graff, 1882 | 1930 or earlier | | | lakes, ponds, and rice fields, middle Japan. |
| Placocephalus fuscatum (Stimpson, 1858) | 1898 or earlier | | | Buitenzorg auf Java, Natuna-Inseln, überdies auch in Japan und Indien. |
| Strongylostoma radiatum (Müller, 1774) | 1953 or earlier | | | |
| Mesostoma productum (Schmidt, 1848) | 1930 or earlier | | | |
| Bothromesostoma personatum (Schmidt, 1848) | 1929 or earlier | | | |
| Rhynchoscolex simplex Leidy, 1852 | 1953 or earlier | | | Japan. |
| Microstomum lineare (Müller, 1773) | 1953 or earlier | | | Japan |
| Prorhynchus stagnalis Schultze, 1851 | 1953 or earlier | | | |
| Geocentrophora sphyrocephala de Man, 1876 | 1953 and earlier | | | Japan |
| Ozametra arbora (Ozaki, 1932) | 1932 or earlier | | | fom Stichopus japonicus (Stichopodidae) |
| Anoplodium mediale Ozaki, 1932 | 1932 or earlier | | | from Stichopus japonicas (Stichopodidae). |