Atherospio Mackie & Duff, 1986

Prostomium blunt, anteriorly truncate or rounded, anterior margin bifid, with anterior margin indented. Lateral horns absent. Caruncle present. Occipital antenna present. Nuchal organ short, at most one segment long. Eyes present; 4 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 7. Dorsal branchiae absent from many median and posterior chaetigers, last present on chaetiger 12. Dorsal branchiae continuous. Dorsal branchiae partially or wholly fused with notopodial lamellae (on some or all chaetigers), all simple. 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 absent. Ventral crests absent. Chaetiger 1 notopodium present. Chaetiger 1 notochaetae present. Neuropodial lobe of chaetiger 2 rounded, approximately symmetrical. Neuropodial lobes of posterior chaetigers a single lobe. Interparapodial pouches absent. Chaetigers 2–4 similar, not strongly differentiated. Chaetiger 5 unmodified, similar to subsequent chaetigers. Posterior modified notochaetae absent. Notopodial hooded hooks absent. Neurochaetae of chaetiger 1 simple capillaries similar to those of subsequent chaetigers. Neuropodial hooded hooks present, first present on chaetiger 18–20. Neuropodial hooded hooks with accessory tooth below the main fang, 1 accessory tooth (bidentate). Shaft of neuropodial hooded hooks of constant thickness, lacking a constriction. Neuropodial sabre chaetae absent. Neuropodial spines present, aristate (on chaetigers 4 & 5 only). Embedded bunches of notopodial needle chaetae absent. Pygidium surrounded by a ring of filiform anal cirri.

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:
Mackie, ASY and Duff, AA. 1986. Atherospio disticha gen. et sp. nov. (Polychaeta: Spionidae) from Loch Tuirnaig, west coast of Scotland. Ophelia 25, 139-146.