(de Haan, 1837)
The carapace not markedly convex, the grooves which separate the regions are almost obliterated. The gastric region has four very indistinct tubercles, two in the median line and one on either side close to the anterior one. The cardiac and intestinal regions are rounded, without any indication of tubercles. The hepatic region laterally produced into a laminar tooth, which is distinctly larger than the postocular tooth, the sinus between the two teeth being usually well concave. The branchial region with two dorsal tubercles, the anterior of which usually has one or two accessory tubercles (which are very often obliterated): the lateral branchial tooth is a little smaller than the hepatic tooth.
The pseudorostral spines are about one fifth the length of the carapace proper, their outer borders are almost parallel and their tips slightly incurved, and their bases thickly covered with curled hairs. The preocular spines prominent, projecting almost parallel to the pseudorostral spines, the posterior angle of the supraocular eave never marked by an angle. The postocular tooth is very small, while the hepatic spine is very large and compressed, its tip projecting horizontally outwards. The epibranchial spine is obtuse and slightly curved forwards, its base being broad. The basal segment of antenna has a small tooth at the antero-external angle. The pterygostomial region marked with a curved row of four tubercles.
Chelipeds of male are very stout; the ischium has a terminal tooth on the anterior border; the arm prismatic and its upper border with three low tubercles; the wrist short and irregular in shape, with its inner and outer borders obtusely cristate and its upper border with two very obtuse tubercles, which are sometimes almost confluent. The palm is very high and the upper border obtusely cristate near the base. The fingers are widely gaping at base, the movable finger has, typically, two large teeth, which are isolated from the teeth of the distal half. Ambulatory legs are not much compressed and are usually naked; the propodus has a bundle of hairs near the distal end of the posterior border. The dactylus is finely denticulated on upper and lower margins of the posterior border.
In the female, the carapace is usually extremely convex, so that the pseudorostral spines appear more deflexed than those of the male; the tubercles found on each region are also more distinct and more markedly haired. (Sakai, 1938: 255)
Type locality: Japan.
Range: Japan - (de Haan, 1837), Tokyo Bay and Kagoshima (Ortmann, 1893), Shimoda (Stimpson, 1907), Suruga Bay, Muroto-misaki, Bungo Strait, west of Mikuni and Tsugaru Strait (Yokoya, 1933), Shimoda (Sakai, 1935), Iwate Prefecture, Tokyo Bay, Sagami Bay, Izu Peninsula, Ise Bay, Kii Peninsula and Nagasaki (Sakai, 1938a), Sagami Bay (Sakai, 1965b), Akkeshi, Iwate Prefecture, Tokyo Bay, Sagami Bay, Shimoda, Mikawa Bay, Ise Bay, Wagu, Kii Nagashima, Kii Minabe, Muroto-misaki, Ashizuri-misaki, and Nagasaki (Sakai, 1976a), Amakusa (Yamaguchi et al., 1976), Kamaishi (Miyake, 1983), Nagasaki (Griffin & Tranter, 1986a), Soya Strait (Takeda & Miyauchi, 1992), Oshoro, Kikonai, Usujiri, Usu, Kushiro, Akkeshi, and Sea of Okhotsk (Komai et al., 1992); Korea - Zenra-nando, Keisho-nando, Keisho-hokudo, Kogen-do, Kankyo-nando, Kankyo-hokudo, Keiki-do and Kokai-do (Kamita, 1941), Sogcho, Songjeong Ri, Jugbyeon, Cheonbu, Guryongpo, Hae-undae, Mijo Ri, Sangchuja, Hoeng-gan, Seongsanpo, Udo Island, Yeosu, Bangjugpo, Impo, Daeheugsan Island, Eocheong Island, and Gyeogpo Ri (Kim, 1973); China - near Hong Kong (Stimpson, 1907), Liaodong Bay, Bo Hai Gulf, and Shandong Peninsula (Shen, 1932), Ningbo and Xiamen (Shen, 1940b); rocky, weedy coasts, not far from littoral line.