The authors describe and illustrate Wardium canarisi n. sp. (Cestoda: Hymenolepididae), an intestinal parasite of Arenaria melanocephala (Aves: Charadrii) from Alaska, characterised by a strobila 20-40 mm long, 10 aploparaksoid hooks 19-21 microm long, a short cylindrical cirrus (40 microm) covered with very minute spines (0.2 microm), and a short (8-18 microm) and extremely narrow (1 microm) copulatory vagina. These characters have no equivalent, even approximate, among the 27 species of Wardium parasitic in the Charadrii which are reviewed. The genus Debrosia Spassky, 1987 appears to be justified.