(de Man, 1887)
The carapace is about 1.35 times as broad as long, the dorsal surface naked and smooth, moderately convex in both directions and the regions ill-defined. There are two parallel transverse ridges on the lateral surface, one on hepatic region and the other on epibranchial, the latter arising from the last antero-lateral tooth.
There are also a pair of ridges on epibranchial region (very often obliterated) and also on frontal surface parallel to the frontal margin. These ridges are beaded with fine granules and usually furnished with several hairs. The front bilobate, the median frontal sinus broadly V-shaped, and the lateral angle of each lobe marked with a small lobule, which is well separated from the supraorbital angle. Antero-lateral borders are four-toothed, the first or the external orbital angle is broad and its anterior border almost transverse; the second is largest and also subtruncate on external border, the third is acuminate and a little smaller, the last one very small and also salient. The margins of these teeth and also the frontal lobes are bordered with fine flat granules
Chelipeds are extremely unequal, each segment is naked and glabrous, not at all tuberculated or granulated; ambulatory legs are very slender and sparingly haired. (T. Sakai, 1939: 542)
Type locality: Mergui Archipelago.
Range: Mergui Archipelago (de Man, 1887b, Alcock, 1898); Japan - Sagami Bay (Rathbun, 1932, Sakai, 1965b), Shimoda (Sakai, 1935), Shimoda and Nanki Shirahama (Sakai, 1939), Amami-Oshima (Takeda & Miyake, 1969c), Sagami Bay, Izu Peninsula, Ise Bay, Kii Peninsula, Toyama Bay, and coast of Fukui Prefecture (Sakai, 1976a), Nanki Shirahama (Miyake, 1983), Manazuru, Shimoda, Izu Peninsula, Kii Minabe, Nanki Shirahama and Shimabara (Muraoka, 1998); Korea - Cheju-do (Kamita, 1941), Seogwipo, Udo Island, Hanrim, Seongsanpo, Guryongpo, and Mijo Ri (Kim, 1970, 1973), Pophwan-ri and Piyangdo (Kim & Chang, 1985); Taiwan; China - Guangdong and Guangxi (Dai & Yang, 1991).