Family Golfingiidae

1. Branched tentacles carried on four to eight stem-like outgrowths of oral disk........ Themiste........2 – Tentacles not carried on stem-like outgrowths..............................................................................3

2. Hooks present.................................................... Themiste (Themiste) pyroides (Chamberlin, 1919) – Hooks absent................................................................... Themiste (Themiste) hennahi Gray, 1828

3. Two nephridia........................................................................................................ Nephasoma........4 – One nephridium...............................................................................................................................5

4. Hooks present..................... Nephasoma (Nephasoma) pellucidum pellucidum (Keferstein, 1865) – Hooks absent...................................................... Nephasoma (Nephasoma) elachea (Fisher, 1952)

5. Anus usually located on anterior trunk; epidermal holdfast or attachment papillae often present; retractor muscles highly fused but usually with 2–4 origin points................ Phascolion........6 – Anus situated on distal half of introvert; epidermal attachment papillae absent; retractor muscles appear as single column, without separate origin points......................................... Onchnesoma....7

6. Tentacles reduced to lobes at the end of the introvert, which is about equal in length to the trunk................................................................................ Phascolion (Montuga) pacificum Murina, 1957 – 10–30 well-developed tentacles usually present........................................................................................................................................................ Phascolion (Phascolion) strombus (Montagu, 1804)

7. Cylindrical body, without papillae.................................. Onchnesoma magnibathum Cutler, 1969

– Spherical or pear-shaped body, with papillae......................................................................................................................................... Onchnesoma steenstrupii steenstrupii Koren & Danielssen, 1876