Three species of the polychaete genus Magelona are known from the neighbour-hood of Plymouth. One is the widely distributed M. papillicornis F. Müller, described first from the coast of Brazil (Müller, 1858) and subsequently frequently recorded for northern European coasts and the Mediterranean. Near Plymouth this species occurs in clean sand in the lower tidal region and offshore, as in Whitsand Bay. Of the other two species, one from clean sand near low water at Mill Bay, Salcombe, awaits description. The third has been known for many years but until now has not been recognized as an undescribed species. It was formerly abundant in the Rame Mud (a deposit of black sandy mud); thus Mare (1942, p. 542, as M. cincta Ehlers—a provisional identification by me) on 12 July 1939 found 120 per m, associated with large numbers of other polychaetes, lamellibranchs, etc. The locality was close to Ford's station No. 93 (Ford, 1923, chart facing p. 167, and p. 218 where the position is given as Rame Head, E. ½ N. Tregantle, N.½ E.). At this station on 20 February 1923 Ford had four specimens (recorded as M. papillicornis) from ⅕ m. On 11 August 1922 at station No. 53 close by (Rame Head, E., 1½ miles) he obtained thirteen specimens of the same species from 1/10 m, the substratum being black mud. Ford records papillicornis from other offshore mud or muddy-sand stations over a fairly wide area inside and outside Plymouth Sound, but in less abundance. It is certain that some of these records, especially those detailed above, are of the species taken by Mare and provisionally identified as cincta.