(de Haan, 1833)
The dorsal surface of carapace is perfectly flat but the groove separating gastric and cardiac regions is well demarcated. The front is nearly a little less than half the extreme width of carapace, its median portion is broadly concave. The lateral borders are markedly convergent posteriorly, and are cut into three teeth, the first (= external orbital angle) and second equally long but the latter more acuminate; the third tooth is rather rudimentary. Chelipeds are equal; the wrist has a spiniform tooth at the inner angle, but it is perfectly worn out in full-grown specimens; the fingers leave an extensive hiatus between them, but in juvenile specimens, they leave no hiatus at all; the tips of both fingers are only feebly hollowed. The movable finger in juvenile specimen is uniformly toothed along the cutting edge but in adult state, it has a large process near the middle portion. The stridulating organ is composed of 9 or 13 tubercles in the male, and numerous fine tubercles in the female. The life colour is much variable by individual and also by developmental stages; in very young specimens, the carapace is very often perfectly snow-white. (T. Sakai, 1939: 676)
Type locality: Japan.
Range: Japan - (de Haan, 1833), Kobe (Miers, 1886), Tokyo Bay, Katsuyama, Sagami Bay, Nagasaki, and Amami-Oshima (Ortmann, 1894a), Okinawa, Amami-Oshima, Kikaishima, Ogasawara-shoto, Kagoshima Bay, Shimoda, and Hakodate Bay (Stimpson, 1907), Mutsu Bay (Yokoya, 1928), Shimoda (Sakai, 1935), Muroran, Mutsu Bay, Kesen-gun, Tateyama Bay, Tokyo Bay, Misaki, Izu Peninsula, Ise Bay, Seto, Gobo, Tosa Bay, Miyazaki, Sakura-jima and Nagasaki (Sakai, 1939), Hachijo-jima (Sakai, 1954), Aratsu, Okinohata, Yanagawa City (Miyake, 1961), Sagami Bay (Sakai, 1965b), Muroran, Hokkaido to coast of Kyushu and Okinawa (Sakai, 1976a), Amakusa (Yamaguchi et al., 1976), Yamagata Prefecture (Suzuki S., 1979), Kamaishi (Miyake, 1983), Oshoro, Kikonai, Hakodate, Usu, Abashiri, and Rishiri (Komai et al., 1992), Ginowan, Okinawa (Shokita et al., 2000); Korea - Kankyo-hokudo, Kankyo-nando, Kogen-do, Keisho-hokudo, keisho-nando, Zenra-nando, Zenra-hokudo, Chusei-nando and Kokai-do (Kamita, 1941), East Sea, Korea Strait, Cheju-do, and Yellow Sea (Kim, 1973), Cheju-do (Kim & Chang, 1985); China - Hong Kong (Stimpson, 1907), Shandong Peninsula (Shen, 1932), Hainan Island (Shen, 1936), Shaotsun, Tsimei, Liuwutien, and Hainan Island (Shen, 1940b), Guangdong, Fujian, Zhejiang, Jiangshu and Shandong Peninsula (Dai & Yang, 1991); Taiwan - (Dai & Yang, 1991), Tan-shui (Sakai, 1939), Ta-chia, Chi-lung, Tan-shui, Chihpun, and P'eng-hu (Lin, 1949); between high and low tidal marks.