| Convoluta convoluta (Abildgaard, 1806) | prior to 1905 | littoral | | |
| Polycystis naegelii Kölliker, 1845 | 1913 or earlier | | | living among plants in the litoral zone. |
| Microstomum rubromaculatum Graff, 1882 | 1913 or earlier | | | Atlantic Ocean (Concarneau). |
| Microstomum lucidum Fuhrmann, 1898 | 1898 or earlier | | | Atlantic Ocean. |
| Omalostomum claparedii (Van Beneden, 1870) | 1870 or earlier | | | |
| Proxenetes gracilis Graff, 1882 | 1913 or earlier | | | beach water. |
| Proxenetes flabellifer Jensen, 1878 | 1913 or earlier | | | beach water. |
| Proxenetes gracilis Graff, 1882 | 1898 or earlier | | | |
| Promesostoma ovoideum (Schmidt, 1852) | 1898 or earlier | | | |
| Promesostoma ovoideum ovoideum Graff, 1905 | 1913 or earlier | | | |
| Trigonostomum setigerum setigerum Schmidt, 1852 | 1913 or earlier | | | |
| Trigonostomum penicillatum (Schmidt, 1857) | 1913 or earlier | | | |
| Polycystis mamertina (Graff, 1874) | 1913 or earlier | | | |
| Phonorhynchus helgolandicus (Metschnikow, 1865) | 1913 or earlier | | | |
| Plagiostomum violaceum Fuhrmann, 1896 | 1896 or earlier | littoral | | |
| Plagiostomum dioicum (Mecznikow, 1865) | 1913 or earlier | | | |
| Plagiostomum fabrei Fuhrmann, 1896 | 1896 or earlier | | | |
| Plagiostomum vittatum (Frey & Leuckart, 1847) | 1913 or earlier | | | |
| Plagiostomum vittatum (Frey & Leuckart, 1847) | 1898 or earlier | | | |
| Pseudostomum klostermanni (Graff, 1874) | 1913 or earlier | | | |
| Monoophorum durum Fuhrmann, 1896 | 1898 or earlier | | | |
| Enterostomum flavibacillum Jensen, 1878 | 1913 or earlier | | | |
| Monocelis fusca Örsted, 1843 | 1913 or earlier | | | |
| Monocelis lineata (Müller, 1773) | 1913 or earlier | | | |
| Monocelis lata Francotte, 1882 | 1882 or earlier | | | |
| Monocelis longiceps (Duges, 1830) | 1913 or earlier | | | |
| Allostoma durum (Fuhrmann, 1896) | 1898 or earlier | | | |
| Beauchampiola oculifera (de Beauchamp, 1927) | prior to 1927 | | | found on the Atlantic coast near Concarneau. |
| Provortex balticus (Schultze, 1851) | 1898 or earlier | | | |
| Jensenia oculifera de Beauchamp, 1927 | 1926 or earlier | | | |
| Macrorhynchus coeruleus Fuhrmann, 1898 | 1896 or earlier | | | on red algae in laboratory of Forest, Bay of Concarneau. |
| Allostoma durum (Fuhrmann, 1896) | 1896 or earlier | | | in the marsh, Bay of Concarneau. |
| Microstomum lucidum Fuhrmann, 1898 | 1896 or earlier | | | Bay of Concarneau. |
| Plagiostomum violaceum Fuhrmann, 1896 | 1896 or earlier | | | amongst algae, Bay of Concarneau. |
| Proporus venenosus (Schmidt, 1852) | 1905 or earlier | | | Nordatlantischer Ozean (Concarneau). |