(Linnaeus, 1764)
This species closely resembles the next common species, Leucosia rhomboidalis, from which it is distinguished by a comparatively larger size, by it shorter postorbital neck and its broader front. The thoracic sinus is very deep, the edge of the pterygostomial plate, which defines the anterior boundary of the sinus is convex and granular, while in rhomboidalis the edge is not strongly convex and not granular. The antero-lateral borders are almost straight but the postero-lateral borders are markedly more convex. The upper surface of the carapace with indistinct longitudinal stripes of darker hue but with no ocelli of purplish colouration as in the next species. (Sakai, 1937)
Type locality: Asia.
Range: India - mouth of Hooghly River (Alcock, 1896); Sri Lanka; Japan - Kobe (Miers, 1886), Amakusa, Sea of Ariake and Tsuyazaki (Miyake et al., 1962), Noto Peninsula, coast of Echizen, Yonago, and Tosa Bay (Sakai, 1976a), Amakusa (Yamaguchi et al., 1976), Kushimoto (Miyake, 1983), Yokosuka and Tosa Bay (Muraoka, 1998); Taiwan - Hsiak'unhsen (Lin, 1949); China - Guangxi, Guangdong (Dai & Yang, 1991); Hong Kong (Miers, 1886); Gulf of Thailand; Indonesia - Borneo; Arafura Sea (Miers, 1886); Torres Strait (Miers, 1884a); Australia - Cape Jaubert (Rathbun, 1924c); 30-80 m.