(Herbst, 1804)
Carapace about three-quarters as long as broad, with the posterior margin in the form of two semicircular dorsally-concave lobes. The foliaceous lateral margins are scalloped, each into four blunt teeth: in front of the first of these (which is rounded off), on either side, is a thickened marginal nodule; and the last, on either side, are united by a coarse granular ridge running across the carapace parallel with the posterior margin, which it cuts off from the rest of the carapace. This ridge culminates, in the middle line, in a coarse granular tubercle.
The middle of the carapace forms a coarsely-granular eminence surmounted by 3 tubercles in a triangle. From it six blunt coarsely-granular ridges radiate, as follows: one forwards, in the middle line, to the front; one backwards, in the middle line, to the transverse ridge; one obliquely forwards, across the hepatic region on either side, to the nodule on the hepatic margin; and one obliquely backwards to the penultimate lateral tooth on either side. The spaces between the ridges are markedly concave, and are usually smooth.
The front hardly projects beyond the eyes, and has a coarse thickened granular edge: it is usually obscurely bilobed, and never quadridentate.
The surfaces of the external maxillipeds, of the pterygostomial regions, of the thoracic sterna, and of the proximal part of the male abdomen are distinctly granular.
The chelipeds in the adult male are 1 3/4 times, in the adult female about 1 1/4 times the length of the carapace: the arm has only its outer border carinate the carina being coarse and granular; the base of its upper surface, the inner border, and the base of the under surface and the under border are also granular to the naked eye: the outer edges of the wrist and hand are coarsely and inconspicuously carinate: the fingers are stout, are rather strongly bent inwards, and have the opposed edges almost edentulous: the dactylus is more than three-quarters the length of the outer border of the hand, in both sexes.
The true legs are not much longer than the arm, and are compressed: in all the merus and propodite are sharply carinate dorsally and ventrally, the carpus has two sharp dorsal crests, and the dactylus is closely pubescent.
The abdomen of the male consists of two linear basal pieces and a small triangular apical piece, and between the two a long triangular plate with a median sub-terminal tooth.
Length of carapace of the largest male, 15 mm., breadth 20 mm.: length of carapace of largest female 16 mm., breadth 22 mm.
Old spirit specimens are uniform flesh-colour: but fresh spirit specimens are a bright brick red, with the wings of the carapace, and a medium longitudinal band including the front, yellowish white. (Alcock, 1896)
Type locality: East Indies.
Range: Persian Gulf (Alcock, 1896, Stephensen, 1945); India - Orissa coast, Tinnevelly coast, Palk Straits, and Bombay (Alcock, 1896); Japan - Kii Peninsula and Osaka Bay (Sakai, 1955a, 1976), Osaka Bay (Sakai, 1965b), coast of Takamatsu (Sakai, 1976a), Suruga Bay and Amakusa (Yamaguchi et al., 1976); China - Xiamen (de Man, 1881), Hong Kong (Alcock, 1896, Stimpson, 1907); 20-35 m.