The name Loxothylacus variabilis was chosen for a Rhizocephalan parasite of Chlorodiella nigra (Forskål) and other crabs from the East Indian region to emphasize its pronounced variability in anatomical characters as well as in the peculiarities of the excrescences of the external cuticle (Boschma, 1940). In the materials collected by Dr. L. D. Brongersma, Dr. L. B. Holthuis, and Dr. M. Boeseman on the reef of Biak Island near New Guinea1) there are five specimens of Loxothylacus variabilis showing peculiarities which distinctly widen the range of variation of the species, leading to the ultimate result that parasites originally described as representatives of a separate species, Loxothylacus murex Boschma (1950), now prove to be conspecific with L. variabilis. Loxothylacus variabilis Boschma Loxothylacus variabilis Boschma, 1940, p. 280; 1947a, p. 277; 1947b, p. 1033; 1955, p. 47. Loxothylacus murex Boschma, 1950, p. 996; 1955, p. 33. Material examined: No. 1321, reef W. of Sorido, Biak Island, shallow water, February, 1955, 4 specimens on Cymo andreossyi (Audouin). One of the parasites (no. 1321B) solitary, 6 1/2 X 5 X 2 1/2 mm (fig. 1a, b), the remaining three on one host: no. 1321A1, 6 1/2 X 5 X 2 1/2 mm (fig. 1e, f), no. 1321A2, 5 X 4 X 2 mm (fig. 1g, h), and no. 1321A3, 4 X 3 X 1 1/2 mm (fig. 1i, j). No. 1323A, reef W. of Sorido, Biak Island, shallow water, February, 1955, 1 specimen on Actaea hirsutissima (Rüppell), 6 X 4 X 2 mm (fig. 1c, d). Moreover, the following specimens dealt with in previous papers were available: