Ambasia Boeck, 1871: 97.— Stebbing, 1906: 51.— Lincoln, 1979: 62.— Barnard & Karaman, 1991: 461.
Type species. Gammarus atlanticus Milne Edwards, 1830, by monotypy.
Diagnosis. Eyes present or absent. Mouthparts forming quadrate bundle. Labrum and epistome continuous, but differentially produced, prominent, coalesced, epistome dominant in projection and subsharp. Incisor ordinary, molar absent; palp attached strongly proximal. Inner plate of maxilla 1 weakly setose; outer plate with 6 spines; palp 2 -articulate, large. Inner and outer plates of maxilliped well developed, palp scarcely exceeding outer plate, dactylus vestigial. Antenna 2, peduncular article 1 comma shaped. Coxa 1 slightly shortened and partly covered by coxa 2. Gnathopod 1 short, simple, articles 5 and 6 subequal, elongate; dactylus small. Article 6 of gnathopod 2 greatly shorter than article 5, ordinary, propodus minutely chelate. Inner ramus of uropod 2 without notch. Uropod 3 ordinary, peduncle ordinary, inner ramus strongly shortened, outer ramus 2 -articulate. Telson elongate, deeply cleft. (Diagnosis revised according to Barnard & Karaman, 1991).
Distribution. Marine, Boreal East Atlantic and Arctic, often on starfishes, 20–1400 m (Barnard & Karaman 1991).