Laonice sacculata (Moore, 1923)

Prostomium blunt, anteriorly truncate or rounded (T-shaped), anterior margin with entire anterior margin. Caruncle present, continuing back to chaetiger 3 (tapering posterior portion, that fades out on the dorsum of somite 3). Occipital antenna present. Nuchal organ short, at most one segment long. 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 3. Dorsal branchiae absent from many median and posterior chaetigers, last present on chaetiger 65 (reducing rapidly in size from about chaetiger 55). 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 present (reaching from the dorsal border of the notopodium only about half way to the middle of the dorsum). 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 29–32 (starting approximately here). Chaetigers 2–4 similar, not strongly differentiated. Chaetiger 5 unmodified, similar to subsequent chaetigers. Posterior modified notochaetae absent. Neurochaetae of chaetiger 1 simple capillaries similar to those of subsequent chaetigers. Neuropodial hooded hooks present, first present on chaetiger 55. Neuropodial hooded hooks with accessory tooth or teeth above the main fang. Shaft of neuropodial hooded hooks of constant thickness, lacking a constriction. Neuropodial spines absent. Embedded bunches of notopodial needle chaetae absent.

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:
Moore, J.P. 1923. The polychaetous annelids dredged by the U.S.S. Albatross off the coast of southern California in 1904. IV. Spionidae to Sabellariidae. Proceedings of the Academy of Natural Sciences of Philadelphia. 75: 179-259.