Hello, I found high abundances of these ribbon worms ( nemerta ) in my samples from a marina in Brittany (France) and I would like to put a species name on these considering their abundance.
I figured they might be a Tetrastemmidae due to the four eyes in rectangular pattern. Tetrastemma Cephalophorum has a very similar head to my candidates, however the color pattern is quite different since usually only have two longitudinal streaks.
Oerstedia dorsalis (Prosorhochmidae) might also be a possibility.
The individuals are 1 cm-1.3 cm max. length and 1 mm-2 mm wide (cylindrical). Since they were found in a marina they don't necessarily are indigenous to Europe.