A diagnosis of the monostiliferous hoplonemertean genus Prosorhochmus is provided and the type-species, P. claparedii, is redescribed and illustrated from Plymouth and Anglesey material; the identification is related to Keferstein's (1862) original description. The taxonomic status of the remaining five species is re-evaluated. It is concluded that P. korotneffi and P. delagei are synonymous with P. claparedii, but that neither the generic nor specific position of P. viviparus, P. albidus or P. subterraneus can, at present, be determined. The importance of the genus Prosorhochmus to studies on the origins of terrestrial nemerteans is discussed.