MATERIAL EXAMINED: TAE Stns 4, 98; NZOI Stns A448, A449, A450, A456, A470, A538; Eltanin Stns 162, 408, 410, 416, 496, 505, 557, 612, 1058, 1084, 1581, 1888, 2018, 2036; Hero Stns 2B, 3, 9, 11, 12B, 448; Swedish South Polar Expedition Stns 8, 23, 24, 32, 34; Richardson Stns, Arthur Harbour, Anvers Island, Antarctic Peninsula in five stations in 18-445 m; New Harbour, McMurdo Sound, 29 m, P.N. Slattery, 29 Oct 1974 and 8 Dec 1975; about 3 km west of Cape Spencer-Smith, White Island, McMurdo Sound, 100 m offshore, 67 m, University of Canterbury, Dec I976jan 1977.

DISTRIBUTION: Thyasira debilis has been recorded from 63°E, 89'E, 96°E, 97°E, from the Ross Sea, and from the Bellingshausen Sea around the antarctic continent, from the Antarctic Peninsula, South Shetlands, south Orkneys, South Sandwich Islands and South Georgia. It is particularly abundant in soft sediments along the Antarctic Peninsula in moderate depths. It is relatively common in the Ross Sea in 29-752 m, but occurs in water as shallow as 9 m elsewhere. A single live shell from Eltanin Stn 162 and a single valve from Eltanin Stn 557 cannot be separated from the antarctic forms so that its range may extend to the Magellanic region and off the Falklands.