(Miers, 1879)
Small species; the carapace elongate quadrangular and the length just equal to the width, the dorsal surface moderately convex and covered with short piles. The front a good deal more produced than in Hemigrapsus penicillatus, the free margin entire and almost straight or very slightly convex. The antero-lateral borders are straight and parallel, the three antero-lateral teeth are narrower and sharper, all being subequal in size and directed more forwards than in the two species already described.
Chelipeds are symmetrical, not much stouter; the wrist with its inner angle feebly produced into a tooth; the palm has a feeble longitudinal ridge on the outer surface, extending along the inferior border, the fingers not much gaping.
The ambulatory legs are much slenderer and longer than in Hemigrapsus penicillatus; the second and third pairs are subequal and much longer than the first and last pairs which are also subequal; in each pair, the dactylus is longer than the propodus and its tip sharp and curved.
The stridulating organ of male is composed of 5 or 6 tubercles, which are almost confluent. (T. Sakai, 1939: 674)
Type locality: Otarunai, Tokyo Bay, and Korea Strait, Japan.
Range: Japan - Otarunai, Tokyo Bay, and Korea Strait (Miers, 1879b), Tokyo Bay and Nagasaki (Ortmann, 1894a), Mutsu Bay (Yokoya, 1928), Shimoda (Sakai, 1935), Kesen-gun, Shimoda and Nagasaki (Sakai, 1939), Sagami Bay (Sakai, 1965b), Oshoro Bay, Iwate Prefecture, Oga Peninsula, Sagami Bay, Izu Shimoda, Mikawa Bay, and Nagasaki (Sakai, 1976a), Amakusa (Yamaguchi et al., 1976), Tobishima, Yamagata Prefecture (Suzuki S., 1979), Oshoro, Hokkaido (Komai et al., 1992), Misaki, Mikawa Isshiki and Kii Minabe (Muraoka, 1998); Korea - Tong-yeong and Jangseungpo (Kamita, 1941); China - north of Shandong Peninsula (Shen, 1932), Shandong Peninsula and Liaodong Peninsula (Dai & Yang, 1991); littoral to 20 m.