Unknown flatworm

Unknown flatworm

Observation - Unknown flatworm - UK and Ireland. Description: Approximately 5cm long, black with brown dorsal stripe. Searched for identifying features, looks mos

Approximately 5cm long, black with brown dorsal stripe. Searched for identifying features, looks most similar to the New Zealand Flatworm, but this is much larger than 3cm and doesn't quite fit the description. Does not appear to have identifiable head hence not moon flatworm either.