de Haan, 1841
A rather small species, its extreme length not exceeding about 16 mm. The carapace is rhomboidal in outline, the antero-lateral and postero-lateral borders being almost straight and the posterior border somewhat produced and rounded. The postocular neck is slender and dorsally carinate, the edge of the front with a median denticle.
The thoracic sinus is densely tomentose, its anterior boundary, which is the free edge of the pterygostomial plate, is almost straight, forming an obtuse angle with the roof of the sinus. The true postero-lateral borders are ridged only in their anterior half; the epimeral ridges are well developed and milled, dorsally visible in their whole extent; their anterior extremity ends in a sharp angle just above the base of the first ambulatory legs.
The chelipeds are stout, the arm is distally broadened and its anterior and posterior borders milled with a row of pearly granules; its upper proximal surface with a patch of velvety tomentum, beneath which several granules are concealed. The upper surface of this segment is also beaded with granules in longitudinal arrangement and with a patch of tomentum near the proximal end. Wrist is very small, palm is flattish and its inner border is finely milled but the other border is usually smooth. The ambulatory legs are all sensibly compressed. The posterior border of merus, the anterior border of carpus and both borders of propodus are carinate; the dactylus is broadly lanceolate in shape.
In the fresh specimen, the dorsum of the carapace is bluish purple, with two or three reddish spots on either side of the gastric region and with a small spot near the hepatic region. (Sakai, 1937)
Type locality: Japan.
Range: India - Coromandel coast (Alcock, 1896); Sri Lanka; Andaman Islands (Alcock, 1896); Japan - (de Haan, 1841), Maizuru (Ortmann, 1892), northern Japan Sea (Yokoya, 1933), Gobo, Nanki Shirahama, Onomichi and Nagasaki (Sakai, 1937a), Aratsu, Okinohata, Yanagawa City (Miyake, 1961), Amakusa, Sea of Ariake and Niigata (Miyake et al., 1962), Kii Peninsula, Tosa Bay and Seto-Naikai (Sakai, 1976a), Amakusa (Yamaguchi et al., 1976), off Kochi (Miyake, 1983); Vladivostok; China - Hong Kong (Stimpson, 1858c, 1907, Alcock, 1896, Shen, 1931), Shaotsun, Fujian Province (Shen, 1940b); Gulf of Tongking (Zarenkov, 1990); Philippines - north of Panay (Chen H., 1989); Indonesia - Flores and Salayar (Ihle, 1918); 21-100 m.