An illustrated catalogue of type specimens of the bathyal brittlestar genera Ophiomusium Lyman and Ophiosphalma H. L. Clark (Echinodermata: Ophiuroidea).

Type specimens of 61 species of the bathyal ophiuriod genera Ophiomusium Lyman and Ophiosphalma H.L. Clark are illustrated and their main features outlined, to form a partial catalogue for current and future workers. Thirty-nine species of Ophiomusium and 22 of Ophiosphalma are recognised, based largely on the number of exposed tentacle pores on the basal ventral arm plates. Most of the Ophiosphalma listed here are new combinations from their original genus, Ophiomusium. Ophiomusium sculptum Verrill is a junior subjective synonym of O. acuferum Lyman, and Ophiosphalma fimbriatum (Koehler) is a junior subjective synonym of O. glabrum (Lütken & Mortensen). The subspecies Ophiomusium fimbriatum atlanticum Hertz and Ophiomusium facunda muta Hertz are elevated to full species.  Because of their bathyal habitat (<4000 m), representatives of these genera are relatively rare in collections, and it will require fresh material of a range of sizes, for morphological comparison and for DNA analysis, to reliably confirm their taxonomic validity and clarify their relationships.