(Miers, 1879)
The contour of the carapace is somewhat different in both sexes, and the formation of the antero-lateral and postero-lateral borders of the carapace is variable. In the adult male the carapace is proportionally wider than in the female carapace, but in the smaller male the proportion of the carapace is similar to that of the female. In the male two lobular outgrowths directed posteriorly and weakly downwards from the posterior border of the carapace are distinctly separated from each other by a wide V-shaped incision, while in the female they are indistinctly separated by a shallow depression. In both sexes each of the antero-lateral borders of the carapace is usually nearly straight or slightly convex posteriorly with two or three very indistinct interruptions, but in some males a lobe is produced at the posterior end of the antero-lateral border, being separated from the epibranchial angle by a deep notch. In the female and smaller male the posterior end of the antero-lateral border and the epibranchial angle is united to form a straight border. The epibranchial angle is strongly produced and acute at the summit in the large male. The postero-lateral border behind the epibranchial angle is also strongly concave in the large male and rather shallowly in the smaller male and the female.
The formation of the chelipeds and ambulatory legs is similar in both sexes, though the male chelipeds are enormously developed. The upper surface of the merus is entirely flattened, and its anterior and posterior borders are crested. The outer border of the carpus and both borders of the palm are also thin. Both cutting edges of the fingers are thin, finely toothed and well interlocked throughout the lengths. In the ambulatory legs both borders of the merus and propodus, and the upper border of the carpus are sharply crested. In addition, at the middle of the upper surface of the carpus is a longitudinal high crest that extends along the whole length of the segment. The dactylus is as long as the propodus and densely tomentose.
The male abdomen consists of four pieces, the formula being 1 + 2 + R + T. The first two segments are linear, and the fused segment is very prominent. The fused segment is ornamented with a rounded prominence at each side of the proximal part, a longitudinal prominence at the middle and a small, median transverse tubercle near the distal end. The first male pleopod is curved outwards at the subterminal part and then distally inwards, the formation of the tip being complex. The abdominal formula of the female is 1 + 2 + 3 + R + T. (Takeda & Miyake, 1970a)
Type locality: Japan.
Range: Japan - (Miers, 1879b), coast of Kii Peninsula and Seto-Naikai (Sakai, 1965b), Kii Minabe and Seto-Naikai (Sakai, 1976a); East China Sea (Takeda & Miyake, 1970a); China - Jiaozhou Bay (Shen, 1937), Fujian (Dai & Yang, 1991).