Opisthosyllis Langerhans, 1879: 541 Syllinae (Polychaeta, Syllidae) from Australia. Part. 2. Genera Inermosyllis, Megasyllis n. gen., Opisthosyllis, and Trypanosyllis Martín, Guillermo San Hutchings, Pat Aguado, María Teresa Zootaxa 2008 2008-08-01 1840 1 53 84RB7 Langerhans 1879 [238,458,1026,1052] Polychaeta Syllidae Opisthosyllis Animalia Phyllodocida 21 22 Annelida genus      Opisthosyllis Langerhans, 1879: 541.   Diagnosis. Body of medium to large size (5> 10 mmin length) with numerous segments. Prostomium with 3 antennae, 2 pairs of eyes and sometimes 1 pair of eyespots, and 2 palps. Palps basally fused. Two pairs of tentacular (peristomial) cirri; some species with an occipital flap, differentiated from peristomium. Antennae, tentacular, anal, and dorsal cirri distinctly articulated. Pharynx with tooth located posterior to anterior rim, typically inserted behind middle of pharynx; anterior margin of pharynx surrounded by crown of soft papillae. Compound chaetae with falcigerous blades; capillary dorsal and ventral simple chaetae present. Ventral cirri digitiform to ovate. Reproduction by means of stolons.   Remarks.About 15 species have been described as  Opisthosyllis, mostly from tropical waters; and two more species were added by Aguado et al.(2008). Four species have been previously reported from Australia, and another one is reported here.