(Rathbun, 1907)

The carapace is rather narrow and strongly convex fore and aft; the dorsal surface is well divided into regions by shallow interregional furrows; each region is covered with small granules and provided with sparse longish plumose and simple hairs; the interregional furrows are filled with thick short tomentum; the epigastric (1M), protogastric (2M) and mesogastric (3M) regions are well demarcated; 2M is entire and 3M is shallowly trilobate; the anterior end of 3M is nearly at the level of the anterior margin of 2M; of the antero-lateral regions only an anterior region is distinctly isolated, which may represent the united 1, 2 and 3L; the areolae 4L and 5L are rather prominent, but not deeply separated; 6L is small and indistinctly separated from 5L by a shallow furrow; the posterior and postero-lateral regions are rather indistinct.
The front, supraorbital and antero-lateral aborders are bordered with a thin light-coloured rim which is marked by a closed deep fissure on the median line, two on the supraorbital border and three on the antero-lateral border. The front is produced and truncated near the median fissure and obliquely truncated laterally or only slightly sinuate. Of four lobes of the antero-lateral border the hindmost is smaller than the preceedings. The postero-lateral border is strongly convergent and its dorsal surface is concave in the middle for the reception of the last ambulatory leg.
The infraorbital border bears a small notch near the external orbital angle; it is fringed with setae at its middle portion, its lateral and inner portion being granulated; the inner angle of the basal antennal segment is just touched with the ventral prolongation of the front, while its outer angle is not raised to the level of the prominent inner infraorbital angle; the antennal flagellum is fine, and about one and a half as long as the major diametre of the orbit.
The chelipeds are short, heavy and unequal. The merus is very short and entirely concealed under the carapace. The outer surface of the carpus is covered with a short tomentum and very scant long hairs and with minute granules; those granules on the carpus become larger and spiniform distally; its inner angle is provided with a spiniform granule and a row of several small granules below the main one. The palm is swollen, and its outer surface is provided with conical and spiniform granules which are disposed nearly without linear arrangement; otherwise its outer surface is also filled with a thick short tomentum and provided with scant long hairs. The fingers are very short and stout, and the tips are rounded and obtuse; the immovable finger of the larger chela bears a large molar-like tooth and provided with two brush-like tufts of hairs on the outer surface, one on the inner surface; the immovable finger of the smaller chela is nearly like the larger one, but the large tooth is three-toothed at its tip; on account of the short immovable finger, the movable finger is very vertical; its proximal half is provided with granules of good size and several longish hairs like the palm; the cutting edge of the movable finger bears a large tooth near the proximal end, and the outer and inner surfaces are also provided with some small tufts of hairs.
The ambulatory legs are rather stout and bordered with hairs of various length. The upper surfaces of the carpus and propodus and last merus are covered with short tomenta. The upper borders except for that of the dactylus are rather acute, but not crested. The male abdomen is seven-jointed, and the first male pleopod is Pilumnus-like. (Taskeda & Miyake, 1969c: 101)

Type locality: Papeete, Tahiti.
Range: Mauritius (Bouvier, 1915b, Michel, 1964); Japan - Kamiyama-jima, Okinawa (Takeda & Miyake, 1969c); Caroline Islands - Kusaie (Rathbun, 1907); Line Islands - Palmyra (Edmondson, 1923); Tahiti (Rathbun, 1907).

Kingdom Animalia
Phylum Arthropoda
Class Crustacea
Order Decapoda
Suborder Pleocyemata
Infraorder Heterotremata
Superfamily Xanthoidea
Family Pilumnidae
Subfamily Pilumninae
Genus Actumnus
Species Actumnus digitalis

Status in World Register of Marine Species

Not included in WoRMS database

Scientific synonyms and common names

Platypodia digitalis Rathbun, 1907: 38, pl. 1, fig. 6, pl. 9, fig. 4. -- Edmondson, 1923: 13.
Actumnus carinatus Bouvier, 1914: 704 (nomen nudum). -- Bouvier, 1915b: 258, figs 26-27. -- Michel, 1964: 22.
Actumnus digitalis Takeda & Miyake, 1969c: 101, figs 3-4.

Tahiti-íbotegani [Japanese]
ibotegani, Tahiti- [Japanese]

Bouvier, E.L., 1914. Sur la faune carcinologique de l'île Maurice. Compte-rendu hebdomadaire des Séances de l'Académie des Sciences, Paris, 159: 698-704. [1914/XI]

Bouvier, E.L., 1915b. Décapodes marcheurs (Reptantia) et Stomatopodes recueillis à l'île Maurice par M. Paul Carié. Bulletin scientifique de la France et de la Belgique, sér. 7, 48(3): 178-318 (1-141), figs 1-42, pls 4-7. [1915/V]

Edmondson, C.H., 1923. Crustacea from Palmyra and Fanning Islands. Bulletin of the Bernice P. Bishop Museum, Honolulu, 5: 1-43, figs 1-3, pls 1-2.

Michel, C., 1964. Checklist of the Crustacea Brachyura (Crabs) recorded from Mauritius. Mauritius Institute Bulletin, 6(1): 1-48.

Rathbun, M.J., 1907. Reports on the Scientific Results of the Expedition to the Tropical Pacific, in charge of Alexander Agassiz, by the U.S. Fish Commission Steamer Albatross, from August, 1899 to March, 1900, Commander Jefferson F. Moser, U.S.N., commanding - IX. Reports on the scientific results of the expedition to the eastern tropical Pacific, in charge of Alexander Agassiz, by the U.S. Commission Steamer Albatross from October, 1904 to March, 1905, lieut.-commander L.M. Garrett, U.S.N., commanding - X. The Brachyura. Memoirs of the Museum of Comparative Zoology at Harvard College, 35(2): 23-74, pls 1-9.

Takeda, M. & S. Miyake, 1969c. Pilumnid crabs of the family Xanthidae from the West Pacific. II. Twenty-one species of four genera, with descriptions of four new species. OHMU, 2(7): 93-156, figs 1-18.

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