It won't be Branchiura sowerbyi because of the postion of the parapodia/gills: B sowerbyi has gill-filaments on the tail only. If the appendages would be filamentous gills and not -more complex- parapods (like in Polychaetes) Oligochaet a species Branchiodrilus ssp would be possible in freshwater samples: that species has got gills from segment VI on which are accompanied with simple-pointed and fine needle chaetae.