Length to 13 mm (Orchomenella abyssorum 1). Eyes long, lunate, colourless in alcohol, glandular, ommatidia not evident; about 40 % as high as head. ART 1 of mandibular palp short, subquadrate; ART 2 long, linear; ART 3 lanceolate, slightly less than half length of proximal ART combined. Epimeral plate III smooth, with posteroventral corner at approximately 90° (posterior margin very weakly excavated distally, with weak, blunt tooth on corner). Dorsal process of urosomal segment I weakly overlapping next segment (Orchomenella abyssorum 4). Endopodite of UR III reaching top of, but not exceeding, main (first) ART of exopodite. See also characters given in key and in preface to key.