(de Haan, 1833)
The outline of carapace is almost regularly quadrangular, the lateral borders only slightly arched and are entire; the dorsal surface smooth but some oblique striae occur on either lateral posterior portion. The edge of front is straight and is superiorly bordered by the postfrontal ridge which is also entire. The male chela is very high and perfectly smooth, the movable finger is extremely curved and the immovable finger also curved inward at tip, so that an extensive gap is left between them. The life colour of carapace variable by individual and also by developmental stage, the chelipeds of adult specimen invariably crimson red but those of the juvenile form, whitish or yellowish. (T. Sakai, 1939: 680)
Type locality: Japan.
Range: Japan - (de Haan, 1833), Tokyo, Enoshima, Tanagawa, Maizuru, Kochi, and Amami-Oshima (Ortmann, 1894a), Shimoda and Amami-Oshima (Stimpson, 1907), Shimoda (Sakai, 1935), Kesen-gun, Tateyama Bay, Misaki, Shimoda, Gobo, Seto, Wakayama, Tatsugahama, Ehime Prefecture and Nagasaki (Sakai, 1939), Sagami Bay (Sakai, 1965b), Hakata Bay (Hashiguchi & Miyake, 1967), from Sendai Bay to Kyushu and Okinawa (Sakai, 1976a), Amakusa (Yamaguchi et al., 1976), Yamagata Prefecture (Suzuki S., 1979), Kagoshima (Miyake, 1983), Sagami Bay and Onagawa Bay (Niem, 1996); Korea - Zenra-nando, Zenra-hokudo, Chusei-nando and Keiki-do (Kamita, 1941), East Sea, Korea Strait, Cheju-do, and Yellow Sea (Kim, 1973), Mosulpo, Cheju-do (Kim & Chang, 1985); Taiwan - T'ai-pei (Sakai, 1939), Putsuchuang and T'ai-pei (Lin, 1949), Tan-shui (Niem, 1996); China - Hong Kong (Stimpson, 1907), south of Shandong Peninsula (Shen, 1932), Ningbo, Haimen, Fuzhou, Tsimei, Liuwutien, and Xiamen (Shen, 1940b), Guangdong, Fujian, Zhejiang, Jinagsu and Jiaozhou Bay (Dai & Yang, 1991), Qingdao (Niem, 1996); Vietnam - Phuc-Son, Annam (Niem, 1996); Singapore (Ortmann, 1894a); near seashore or muddy banks of freshwater stream.