Laonice sarsi Söderström, 1920

Prostomium blunt, anteriorly truncate or rounded (T- or bell-shaped), anterior margin with entire anterior margin. Caruncle present, continuing back to chaetiger 2–14. Occipital antenna present (comparatively short, erect). Nuchal organ long, extending back more than one segment, extending posteriorly to chaetiger 2–14. Eyes present; 2 eyes. Palps simple, lacking basal sheath. Dorsal ridge connecting bases of branchiae on chaetiger 1 absent. Prominent dorsal collar on setiger 2 absent. Dorsal branchiae present, first present on chaetiger 2 (sometimes as late as 5). Dorsal branchiae absent from many median and posterior chaetigers, last present on chaetiger 6–33 (but completely absent on some small specimens). First branchiae without process at base on anterior face. Accessory branchiae arising from posterior part of notopodium absent. Ventral branchiae absent. Chaetiger 3 without filament at base of branchiae. Dorsal crests with no complete dorsal membranes but incomplete membranes reaching no more than two fifths body width. Ventral crests absent. Chaetiger 1 notopodium present. Neuropodial lobe of chaetiger 2 rounded, approximately symmetrical. Neuropodial lobes of posterior chaetigers a single lobe. Interparapodial pouches present. Interparapodial pouches on chaetigers 14–81. Chaetigers 2–4 similar, not strongly differentiated. Chaetiger 5 unmodified, similar to subsequent chaetigers. Posterior modified notochaetae absent. Notopodial hooded hooks present, first on chaetiger(s) 33 (1–5 per fascicle). Neurochaetae of chaetiger 1 simple capillaries similar to those of subsequent chaetigers. Neuropodial hooded hooks present, first present on chaetiger 16–39 (4–13 per fascicle). Neuropodial hooded hooks with accessory tooth or teeth above the main fang, 1 accessory tooth (bidentate) (in side view). Shaft of neuropodial hooded hooks of constant thickness, lacking a constriction. Neuropodial sabre chaetae present, in ventral-most positions, first on chaetiger(s) 10–26 (up to 4 per fascicle). Neuropodial spines absent. Embedded bunches of notopodial needle chaetae absent. Pygidium with 1 pair of short and thick ventral cirri, and up to 7 pairs of longer and thinner dorsal cirri, a cirriform central-most medial appendage positioned between ventral cirri may also be present.

Description generated from: Wilson, RS & McDiarmid, H 2013. Spionidae (Polychaeta)- A DELTA database of genera, and Australian species. Version 2; originally published as In RS Wilson, PA Hutchings & CJ Glasby (eds) Polychaetes: An Interactive Identification Guide. CSIRO Publishing, Melbourne.

Additional references:
Söderström, A. 1920. Studien über die Polychätenfamilie Spionidae. Uppsala University Dissertation