Bdellouridae usually without copulatory bursa and with the behavioural trait of attaching the tail end to the substratum. Ejaculatory duct lined with either an infranucleate or nucleate epithelium. Eyes usually with two retinal cells.
This subfamily contains the following genera: Nerpa Marcus, 1948, Pentacoelum Westblad, 1935, Syncoelidium Wheeler, 1894, and Bdelloura Leidy, 1851.