In the collections of the Leiden Museum I found three groups of specimens, which had been classified as Charybdis erythrodactyla (Lam.). I also examined Charybdis acutifrons (de Man), of which hitherto only one specimen (the type specimen) has been mentioned in literature. It appeared that Dr J. G. de Man did not observe that this specimen has seven antero-lateral teeth, of which the second and fourth are very small. This species belongs to one of the three above-mentioned groups. The three groups show very distinct differences. Therefore I consider them to be three species, viz., Ch. erythrodactyla (Lam.), Ch. acutifrons (de Man), and Ch. obtusifrons nov. spec. In a subsequent publication I hope to discuss the place of these species in the genus Charybdis and the literature on Ch. erythrodactyla (Lam.). In the following descriptions I only mention the most important literature. Charybdis erythrodactyla (Lam.) (figs. 1—5) Material: One male and one female (Mus. Godeffroy), Marquesas, coll. Leiden Museum. These specimens are identical with those mentioned by Randall (Thalamita pulchra, Journ. Acad. Nat. Sci. Philad., vol. 8, 1839 (1840), p. 117, pl. 4), Milne-Edwards (Thalamita Teschoiraei, 1851, Ann. Sc. Nat., Zool. (3), vol. 16, p. 250, pl. 10, figs. 5, 6, 7), Rathbun (1906, Bull. U. S. Fish Comm. for 1903, pt. 3, p. 872, pl. 4) and Boone (Bull. Vanderbilt Marine Museum, vol. 5, 1934, p. 57, pls. 18 and 19), probably also with the specimens of Nuka-Hiva (coll. Paris Museum) determined by A. M.-Edwards and figured by Nobili (1906, Bull. Scient. Fr. Belg., vol. 40, p. 118, fig. 3). Description: The carapace is rather convex, bare, with some rather faint