Psolidium Ludwig, 1886

Davey, Nicola, 2013, The Psolidae of New Zealand and some additions to the Macquarie Ridge fauna (Echinodermata: Holothuroidea: Psolidae), Memoirs of Museum Victoria 70, pp. 51-67 : 60

Genus Psolidium Ludwig, 1886

Diagnosis. (After O’LoughlinandMaric,2008).Dendrochirotid holothuroids; small, up to 40 mm long; midbody arched dorsally in transverse section, flat ventrally; dorsal and lateral body covered with imbricating scales, usually macroscopically conspicuous, sometimes obscured by integument, scales irregular in size and arrangement; scales decreasing in size ventrolaterally, orally and anally; lacking large oral valves; extensible oral cone with anterior, anterior–dorsal or dorsal orientation; extensible anal cone with posterior, posterior– dorsal or dorsal orientation; tube feet dorsally and laterally in midbody, passing through scales.

Sole distinct, oval to elongate; discrete margin created by junction of small imbricating ventrolateral scales, with thin-walled, usually calcareous sole that lacks scales; peripheral band of tube feet, may be discontinuous across the interradii anteriorly and posteriorly; peripheral tube feet frequently of 2 sizes, those of outer series smaller; midventral radial series of tube feet present or absent.

Calcareous ring solid, plates subrectangular, radial and interradial plates with tapered anterior projections; radial plates with deep notch posteriorly, interradial plates with shallow concave indentation posteriorly; 10 dendritic tentacles, ventral 2 smaller.

Dorsal and lateral ossicles: multilayered or single-layered perforated plates (scales), always some with tube foot canals; integument covering scales may have cupped crosses, cups, ‘thorn’ ossicles (irregular branched rods pointed distally), buttons, perforated plates and rosettes; tube foot small endplates, and tube foot support ossicles that are irregular rods and plates, bent and curved, variably perforated.

Sole ossicles: interradii with small to large single-layered perforated plates (rarely with multilayering), smooth to variably knobbed and thickened, sometimes with cupped crosses, cups, thorn ossicles and rosettes; radii with additional tube foot ossicles, large endplates and tube foot support ossicles that are irregular rods and plates, bent and curved, variably perforated.