In February 1965 larvae of Sabellaria spinulosa Leuckart removed from the plankton off Plymouth were reared for settlement experiments (Wilson, 1970b). Among the early stages in the rearing dishes there appeared several Sabellarian-type larvae which after a few days growth became conspicuous by their larger size, longer and straighter bristles, and by their general appearance being different from the more numerous Sabellaria larvae. It soon became apparent that they closely resembled a larva found in February 1927 which was described and illustrated many years ago (Wilson, 1929, p. 242, text figs. 4, 5), at which time it was attributed in all probability to Pallasia murata Allen, now Lygdamis muratus (Allen). Apart from two species of Sabellaria whose larvae were known, this was and still is the only other Sabellarian recorded from the coasts of Devon and Cornwall and adjacent offshore waters of the English Channel. In most years since 1965 varying numbers of this species of larva have been obtained in January and February, and have several times been reared through metamorphosis to early tube-building stages, these latter confirming by their distinctive characters that the above early attribution was correct. Work on a description of the development was begun but it was not until 1974, when work on colony formation of Sabellaria alveolata (L.) was virtually completed, that close attention could be given to it, and experiments on settlement carried out. In the meantime Bhaud (1969) had described and illustrated the development from larvae in winter plankton off Banyuls-sur-Mer, wrongly attributing them to Phalacrostemma cidariophilum Maranzella, while criticizing my identification of my 1927 larva.