Haploniscus unicornis Menzies, 1956

(Fig. 15)

Synonymy: Haploniscus unicornis Menzies, 1956: 8, fig. 3; Menzies, 1962: 96, fig. 6E–G.

Holotype: female stage V, 1.7 mm, slightly damaged. AMNH cat. no. 11759, coll: RV Vema, 12 November 1956, V-7-1, north rim, Puerto Rico Trench, Atlantic, 20°32.2’ N 60°28.1’ W, 4983–5001m depth.

Description (holotype female). Body (Fig. 15 A, B, E) oval, length about 2.8 width. Head length 0.6 width. Rostrum damaged. Lateral margins of pereonites damaged, pereonites 3–6 broadest, body tapering anteriorly and posteriorly. Posterior angles of pereonites 3–7 and anterior angles of pereonites 3–4 acute; posterior part of pereonite 7 as wide as basis of pleotelson, resulting in smooth outline of posterior body in dorsal view. Pleotelson length 0.35 body length, 1.2 width, lateral margins tapering posteriorly; pleotelson process length 0.1 pleotelson length, 1.2 width.

Antenna 2 (Fig. 15 C) peduncular article 3 length about 1.4 width, dorsal tooth shorter than article width; article 4 0.7 article 3 length, 1.1 width; distal articles missing.

Maxilliped with 3 retinacula (contrary to Menzies’ original description). Distribution. Known from the type locality in the Puerto Rico Trench and from South of the Azores (Chardy 1974; see discussion).