A new polychaete, Pileolaria aurita new species, of the family Spirorbidae from the Pacific coast of Honshu, Japan is described. This species clearly differs from all other species of Pileolaria Claparède, 1868 in the morphology of the brood chamber, which bears distally two cone-shaped projections resembling cat ears. Besides, it is the only species of Pileolaria with collar chaetae that lack cross-striation. Worms were found at depths of 20–22 m attached to empty oyster shells directly or to bryozoans covering those shells. The shells were collected from sandy bottoms below artificial reefs constructed for recreational scuba diving.