Ophiomusium Lyman 1869

Ophiomusium Lyman, 1869: 322 [type species Ophiomusium eburneum Lyman, 1869 by monotypy] Ophiomusa Hertz, 1927: 102 [type species Ophiomusium lymani Wyville-Thompson, 1873 by monotypy; synonymized by H. L. Clark, 1941].

Generic description: Disc diameter up to 30 mm, arms three times d.d. Dorsal disc plates usually large, often porcellaneous, with either smooth, finely granular, or low conical stumps. Plates closely soldered. Radial shields mostly adjoined in adults. Ventral disc plates usually smooth, and large. Oral shield dominant. Oral papillae fused or separated. Genital slits adjacent to 1st, 2nd, or 3rd ventral arm plates, often sinuous, and with lateral papillae. Arms moniliform, with large lateral plates meeting above and below, bearing 1–13 arm spines.

Spines usually short, ventral-most longest, sometimes bifurcate. Dorsal and ventral arm plates may only be present on basal arm segments; if present further on arm, they become progressively very small. Tentacle pores present on all ventral arm segments, but only readily observable as exposed pores on the first two arm segments. Usually a scale on each pore.