Specimens collected by the Swedish Expedition to the White Nile in 1901 have been identified as Rhadinorhynchus niloticus Meyer, 1932. On the basis of this material, including the first recorded females, the species has been restudied. Points wherein the individuals are unlike the forms included in the family Rhadinorhynchidae are presented in detail. A new genus, Tenuisentis, is proposed with Rhadinorhynchus niloticus as type. This new genus becomes type of a new family, the Tenuisentidae, which is assigned to the order Eoacanthocephala.