Description of holotype: Carapace transversely elliptical, not markedly convex; dorsum well divided into regions which are convex and thickly covered with minute granules of various size; interregional furrows deep and linear; frontal region convex laterally; epigastric region (1M) more or less circular, and widely and shallowly separated from supraorbital and protogastric regions, and shallowly and narrowly from frontal region; protogastric region (2M) subdivided into inner smaller and outer larger subregions by a longitudinal deep furrow; mesogastric region (3M) prominent, its anterior end just reaching the level of posterior end of 1M; metagastric region (4M) linear, but strongly convex fore and aft, being medially followed by a minute areolet; antero-lateral regions (1-6L) distinct except for 1L which is only faintly demarcated and nearly confluent with 2L; 3L prominent and oblique in direction, 4L rounded and obtusely pointed at its dorsal tip, 5L very prominent and evenly convex as a whole, 6L triangular, about half of 5L and ornamented with a small round tip at median part of inner border just outside of 4M; a small areola behind 4 and 5L; cardiac region (1P) large and provided with an accessory areolet at median part of its posterior border; intestinal region (2P) not prominent and indistinctly subdivided into two.
Front with two convex lobes in dorsal view, which are nearly confluent with each other, but a median slit is still traceable; lateral end of each frontal lobe curved downward and thus deeply separated from supraorbital angle; inner half of supraorbital border raised, while outer half is thick, but not raised at all.
Antero-lateral border of carapace strongly arched, granulated and more or less crested; no distinct teeth or lobes, but three equidistant tuberculated granules may represent three lobes; anterior part directed toward subhepatic region, and anterior one-fourth of antero-lateral border forms a roof of subhepatic cavity; anterior end curved downward to form anterior boundary of subhepatic cavity; in dorsal view, therefore, anterior end of antero-lateral border not directly connected with external orbital angle. Postero-lateral surface of carapace deeply excavated to receive last ambulatory leg; postero-lateral border much shorter than antero-lateral border, markedly granulated, forming a strong angle at junction with antero-lateral border, curving horizontally inward and then running obliquely to junction with posterior border of carapace.
Subhepatic cavity long and more or less streamlined; its roof and anterior border rather strongly crested, but posterior narrow end and lower border not distinctly defined; bottom surface of cavity with scattered granules of good size.
Both chelipeds rather heavy, nearly equal in size, or the left hardly larger; outer surfaces of merus, carus and palm roughened by minute granules of various size, but inner surfaces nearly smooth and truncated to fit tightly to carapace; merus small and for its most part disguised under carapace; carpus large and equipped with a strong crest which forms an outer border of carpus, posterior end of crest curving and extending shortly onto upper surface; palm with about four longitudinal rows of granules on outer surface and some tubercles with aggregated granules on outer upper surfaces; fingers sharply toothed; each finger with four or five conical teeth on cutting edge and two or three longitudinal furrows throughout length.
Ambulatory legs not stout; anterior border of each merus thin and fringed with thick plumose hairs; posterior border truncated, and its upper border thus formed rather strongly crested; anterior border of each carpus armed with several sharp granules and stiff setae; upper border ornamented with a strong longitudinal crest which curved anteriorly, and thus anterior half of upper surface deeply excavated along its crest; in propodus a similar crest developed on proximal half of upper surface, and distal surface markedly roughened by granules. (Takeda, 1980d)
Type locality: Kerama-retto, Ryukyu Islands, Japan.
Range: Japan - Kerama-retto, Ryukyu Islands (Takeda, 1980d).