(de Haan, 1835)
Carapace regularly quadrangular, the groove separating the gastric and cardiac regions is deeply demarcated. The frontal margin shallowly concave in the middle portion, the postfrontal ridge four lobed but not sharply defined. The lateral borders are entire and parallel, only insensibly divergent near the posterior angle; the oblique striae on the postero-lateral surfaces are well impressed. The wrist is covered with squamiform tubercles, palm is almost smooth, the tubercles being usually worn out in full-grown specimens; its inner distal angle is produced into a spine and two or three oblique ridges occur on the superior surface, one or two of which are furnished with short setae, the superior border of the movable finger is furnished with a row of 18-19 transverse ridges, the row is lined with fine granules along the inner side in proximal half; merus of ambulatory legs is a good deal broader.
The early-known Sesarma rupicola Stimpson is, in my opinion, only the female of this species, the oblique pectinated ridges on the upper border of palm in female and also in juvenile specimens are very often represented only by granules, and the transverse tubercles on the upper border of the movable finger are, in such specimens, smaller than those of the adult male. (T. Sakai, 1939: 682)
Type locality: Japan.
Range: Mergui Archipelago (Alcock, 1900b); Japan - (de Haan, 1835), Amami-Oshima (Ortmann, 1894a, Stimpson, 1907), Shimoda (Sakai, 1935), Misaki, Shimoda, Ise Bay, Sakura-jima and Nagasaki (Sakai, 1939), Sagami Bay (Sakai, 1965b), Hakata Bay (Hashiguchi & Miyake, 1967), south of Boso Peninsula on Pacific side, Oga Peninsula on Japan Sea side, southwards to Okinawa (Sakai, 1976a), Amakusa (Yamaguchi et al., 1976), Nanki Shirahama (Miyake, 1983), Okukubi River, Okinawa (Shokita et al., 1998); Korea - Cheju-do and Inch'on (Sakai, 1939), Cheju-do, Zenra-nando, Zenra-hokudo, Chusei-nando, Keiki-do, Kokai-do and Heian-nando (Kamita, 1941), Korea Strait, Cheju-do, and Yellow Sea (Kim, 1973), Cheju-do (Kim & Chang, 1985); Taiwan - Putsuchuang (Lin, 1949); China - Shandong Peninsula (Shen, 1932), Hainan Island (Shen, 1936), Ningbo and Hainan Island (Shen, 1940b), Guangdong, Fujian, Zhejiang and Shandong Peninsula (Dai & Yang, 1991); Indonesia - Sulawesi; above high tidal mark.