Syllidia Quatrefages, 1866 (Psamathini, Hesionidae, Polychaeta) is revised based on examination of all extant types, other museum specimens, and a large number of newly collected specimens.
Syllidia hongkongensis, new species, is described from Hong Kong and Hawaii, and
Syllidia armata Quatrefages, 1866 from western France is redescribed.
Syllidia hongkongensis is unique within the genus in having neuropodial lobes and neurochaetae from segment 3, rather than from segment 4. The generic names
Magalia Marion and Bobretzky in Marion 1874 and
Pseudosyllidia Czerniavsky, 1882 are treated as junior synonyms of
Syllidia, and the specific names
Magalia assimilis Pryde, 1914,
M. capensis McIntosh, 1924, and
Psamathe britannica Chamberlin, 1919 as junior synonyms of
S. armata; the latter two represent new synonymies. A lectotype is designated for
P. britannica.
Syllidia inermis (Ehlers, 1912) from the Antarctic is treated as
incertae sedis; it belongs within Psamathini but is not a member of
Syllidia.
Syllidia liniata Hartmann-Schröder, 1962 from Peru appears close to
S. armata, but is regarded as a
nomen dubium and requires recollection of specimens and redescription.
