(Fig. 27)
Type species. Bathyhalacarus quadricornis Sokolov & Jankovskaja, 1968.
Adults. In female and male GP and AP fused. Female GA with two to four pairs of slender pgs, genital sclerites with one to three pairs of sgs. Three pairs of gac arranged in line from about middle of GO posteriad (Fig. 27; Bartsch 1989 b: fig. 26). Ovipositor at rest generally extending beyond GO. Genital spines slender, their number and arrangement not known. Male GO slightly smaller than that of female. Three small pairs of gac in posterior part of GO (Bartsch 1989 b: fig. 24). GO surrounded by 25–50 pairs of slender pgs, genital sclerites with five pairs of sgs. Epimeral pores absent in both female and male.
Juveniles. One larval and two nymphal stages known. Deuto- and protonymphal GP separated from AP. Deutonymphal GP with two pairs of internal gac and pgs, and with (zero to) two pairs of sgs (Newell 1967: fig. 30; Bartsch 1982 a: figs 28, 41). Protonymphal GP with single pair of gac (Bartsch 2005 a: fig. 16); neither pgs nor sgs present. AE of larva with epimeral pores (Bartsch 2005 a: fig. 17).
Remarks. This genus is predominately found in the bathyal and abyssal zone of the Atlantic and Pacific Ocean. About a dozen species are described (Bartsch 2009 a).