Psolidium dorsipes Ludwig 1886

Psolidium dorsipes Ludwig

Figures 1c; 4b

Psolidium dorsipes Ludwig, 1886: 9–10, pl. 2, fig. 9.— Ludwig, 1892: 349.— Ludwig, 1894: 135 (passim).— Perrier, 1904: 16.— Perrier, 1905: 48, pl. 2 figs 5–15, text figs G-H.— Ekman, 1925: 112–13, text fig. 26.— Deichmann, 1941: 142–44, pl. 29 figs 1–12.— Deichmann, 1947: 336–37.— Hickman, 1962: 60.— Pawson, 1969: 38, map 3.— Pawson and Valentine, 1981: 453.— Lambert, 1996: 28–30, table 1.

Material examined. South Atlantic Ocean, Argentina, Santa Cruz, E of Grande Bay, 92 m, USNM E2177 (2 specimens); E of Cabo Virgenes, 101 m, USNM 1114251 (5); near Strait of Magellan, 66 m, 1114252 (1); Tierra del Fuego, Staten I., E40823 (2); Cape Penas, 81 m, E40824 (2); R/V William Scoresby stn 834, Cape Virgenes, 0–38 m, BM(NH) 2008.3182 (1); Scotia Sea, E of Burdwood Bank, 419–483 m, E40825 (1).

South Pacific Ocean, Chile, Strait of Magellan, 36 m, E2178 (4); Cape Froward, 82 m, USNM 1081593 (1).

Diagnosis. Psolidium species up to 17 mm long; preserved form variably with low to high profile, short to elongate oval sole; dorsal and lateral scales conspicuous, smooth, up to 1.6 mm wide; dorsal and lateral tube feet conspicuous, numerous.

Sole: outer peripheral single series of smaller tube feet; inner peripheral single to double series of larger tube feet; mid-ventral (sole) radial single to zig-zag to double series of tube feet.

Dorsal ossicles: multi-layered plates (scales) thick, 0–2 canals and 0–2 marginal indentations for tube feet per scale; intergrade with large thick knobbed plates with developing secondary layers; perforated plates with thickenings (buttons), 100–150 μ m long, 3 to many perforations; thick smooth perforated plates, 150–200 μ m long; numerous shallow cups, oval, marginally with round knobs, biggest cups knobbed on cross and rim, 2 large central and 2 smaller end perforations, cups 40–60 μ m long.

Sole ossicles: shallow cups, oval, 2 large central and 2 smaller end perforations, some imperfectly formed, variably finely knobbed on margin to thickly knobbed on margin and cross, cups 40–70 μ m long; thickly knobbed, regular, 4-holed buttons, 80-100 μ m long, some irregular, up to 150 μ m long; shallow concave perforated plates variably knobbed on surface and margin, up to 16 perforations, up to 200 μ m long.

Distribution. Argentina (E of Grande Bay), Burdwood Bank, Falkland Is; Chile, Tierra del Fuego, Strait of Magellan; 10– 483 m.

Remarks. One Psolidium dorsipes specimen (USNM 1114251) has shallow cup-shaped indentations covering the sole that appear to indicate brood-protection under the body.