As part of a study dealing with polychaetes (Annelida: Polychaeta) from soft bottoms of the western coasts of Acapulco Bay, southern Mexican Pacific, 574 specimens of the genus
Syllis Lamarck, 1818 were analyzed. Nine species are reported, of which
Syllis garciai (Campoy, 1982) and
Syllis glarearia (Westheide, 1974) are new records for the Mexican Pacific.
Syllis magnipectinis (Storch, 1967), described from the Red Sea, is newly reported in the eastern Pacific; notes on its morphological variations and its distribution range are herein included. Additionally, two new species of
Syllis are described:
Syllis antoniae n. sp., is closely related to
S. vivipara Krohn, 1869, but it has bidentate falcigers with a smaller subdistal tooth and some falcigers with coarse spines on the edge.
Syllis deleoni n. sp., is characterized by having bidentate falcigers with broad teeth and coarse spines and the body densely covered with papillae.