Cirolana mclaughlinae n. sp. is described from specimens collected in the Ross Sea, Antarctica. The species is characterised by the head having a prominent anterior marginal ridge, lacking a rostrum, and being dorsally depressed; the posterior submarginal surfaces of pereonites 5-7 and the pleonites are nodulose and pitted; the pleotelson has weakly concave lateral margins converging to a narrowly rounded apex, the dorsal surface is provided with a low, longitudinal median ridge. The genus has a world-wide distribution, but has hitherto not been recorded from polar waters, the previous most southerly record being at about 44°S.
Crustacea, Isopoda, Cymothoida, Cirolanidae, Cirolana, Antarctica, Ross Sea, new species.