Diurodrilus westheideisp.n. is described in terms of the location of the sensoria, ventral ciliated cells, ciliophores, adhesive toes and a big anal cone. Specimens were collected in mid winter at Disko Island, West Greenland. The ultrastructure ofD. subterraneusRemane, collected in the summer at Disko Island and Ystad, Sweden, is discussed with new information on the systematic status of this aberrant genus as indicated by the cuticle, pharyngeal area, ciliophores and the spermatozoa. Diurodrilidae fam.n. is introduced for the genusDiurodrilus, here placed in Polychaeta.