Ophiomusium australe H. L. Clark, 1928 .

Figures 6 a, b

Ophiomusium australe H. L. Clark, 1928; Baker, 1979; O’Hara, 1990. Ophiomusium aporum H. L. Clark, 1928; Baker, 1979.

Holotype SAM K256, Spencer or St Vincent Gulfs, South Australia, depth unknown.

Main Features: This species was originally described by Clark as a variety (now = subspecies) of O. simplex Lyman 1878 . However, in 1979 I examined the type and concluded that australe was a valid species, and synonymized O. aporum with it (Baker 1979). The disc plates are smooth and overlapping, and the radial shields are separated by 3 plates decreasing in size towards the arm. At the interradial margin of the disc are two overlapping tumid plates. The oral shields, post-oral plate and the two tumid marginal plates make up the ventral surface. There are two exposed tentacle pores, each with a scale. The genital slits are short—one lateral plate long. There are two triangular ventral arm plates and gradually diminishing dorsal plates on each arm. The lateral arm plates carry 2 small spines.