(Takeda & Miyake, 1969)
Small species. Carapace convex anteriorly, sculptured on anterior and antero-lateral regions; prominent convex region demarcated just inside first antero-lateral tooth; dorsal surface smooth, without granules, provided with several tufts of brush-like hairs. Antero-lateral border with two stout teeth and a vestigial third behind external orbital angle; first tooth bears a tip anteriorly, acute at tip, second tooth blunt at tip, less prominent than the first; vestigial third tooth capped with a minute spinule. Subhepatic region with a granulated prominence. Chelipeds subequal; merus with a stout subterminal tooth on upper border; carpus strongly nodular on outer surface; its inner angle armed with an acute tubercle tipped with spiniform granule; palm also nodular on upper border, with granules and scant plumose hairs on upper and outer upper surfaces; upper border of palm about half as long as its lower border; fingers sharply, irregularly toothed on cutting edges. Ambulatory legs proportionally slender, with sparse hairs; each merus of first three pairs with a stout spine on upper border, produced, acute at upper distal portion; carpus and propodus with two prominent, large humps on upper border, one proximally and the other distally. (Takeda, 1998)
Diagnosis: Carapace slightly convex anteriorly and sculptured on anterior and antero-lateral regions; dorsal surface smooth and provided only with scattered tufts of brush-like hairs. Antero-lateral border with two stout teeth and with a vestigial third. Subhepatic region with a low prominence. Outer surface of carpus and upper border of palm of cheliped nodular. Each merus of first three pairs of ambulatory legs with a spine on upper border, and carpus and propodus each with two humps on upper borders.
Description of holotype: The carapace is convex anteriorly, and sculptured on the anterior and antero-lateral regions; a prominent convex region is demarcated just inside the first antero-lateral tooth; the dorsal surface is smooth without granules and provided with several tufts of brush-like hairs; they are symmetrically disposed, viz. behind each frontal lobe, on the eyestalk, on the protogastric region, near the second antero-lateral tooth, at the base of the third antero-lateral tooth and at each end of the gastro-cardiac suture. The front is produced most in the middle, declivous and by a V-shaped median sinus cut into two oblique lobes, each of which is only slightly concave in the middle and bears no lateral lobule; its lateral corner is only slightly produced and separated from the less prominent supraorbital angle by a shallow depression. The supraorbital border bears two shallow depressions, its external angle being only slightly produced and subacute. The infraorbital border bears a deep notch near the external orbital angle; its middle portion is deeply excavated, so that the angle which is thus produced between the notch and the excavation is rather strongly produced and as prominent and acute as the inner infraorbital angle. The basal antennal segment is not reached the short ventral prolongation of the front. The antennal flagellum is fine and only slightly longer than the major diametre of the orbit.
The antero-lateral border is armed with two prominent teeth behind the external orbital angle; the first tooth bears a tip anteriorly and acute at the tip, while the second tooth is blunt at the tip and less prominent than the first; behind them the antero-lateral border ends in a vestigial third tooth which is capped with a minute spinule. The subhepatic region bears a granulated prominence. The postero-lateral border is nearly straight and rather weakly convergent.
The chelipeds are subequal. The merus is armed with a stout subterminal tooth on the upper border. The carpus is nodular on the outer surface, those nodules being nearly same size and about eight in number; its inner angle is armed with an acute tubercle tipped with spiniform granule. The palm is also nodular on the upper border, and on the upper and outer upper surfaces covered with granules and scant plumose hairs that are beaded somewhat into longitudinal series; those nodules are four in number, the distal one being the most prominent; the upper border of the palm is about half as long as its lower border. The fingers are sharply and irregularly toothed on the cutting edges; the pigments are restricted to the distal half in the movable finger.
The ambulatory legs are proportionally slender and covered with sparse hairs. Each merus of the first three pairs is armed with a stout spine on the upper border, and is produced and acute at the upper distal portion. Each carpus and propodus are provided with two prominent, large humps on the upper borders, one proximally and the other distally. (Takeda & Miyake, 1969c)
Type locality: To-jima Islet, Kii Peninsula, Japan.
Range: Japan - Kii Peninsula (Takeda & Miyake, 1969c), Maga-jima, Kagoshima Prefecture (Takeda, 1977b), Tanegashima (Takeda, 1976b); Palau (Takeda & Miyake, 1969c).