(Rathbun, 1898)
The carapace is smooth, and strongly convex in a fore and aft direction; the depth is 0.7 times the length of the carapace. The frontal region is 0.25 times the breadth of the carapace, and 0.45 times the distance between the external orbital teeth. The antero-lateral margin of the carapace is smooth or obsolete. The exopod of the third maxilliped reaches the proximal third of the merus; the merus is slightly shorter than broad.
In the male the 7th abdominal segment is 0.8 times as long as broad and longer than the 6th. The 6th segment is half as long as broad. The penultimate segment of the first pleopod is slightly curved inwards, and 6.0 times the length of the ultimate; the ultimate segment is strongly curved outwards; the synovial membrane is 4.0 times as long as broad.
The chelipeds are unequal in males, but subequal in females. The carpus of the large cheliped bears indistinct striae and one large spine of the inner portion. The fingers have a large gape when closed. The palm is smooth; it is 0.7 times as long as broad, and about half the length of the dactylus. The dactylus is 0.9 times the length of the chela. The small cheliped is similar in shape to those of the females; the fingers are not gaping when closed. The ambulatory legs are stout. The 2nd ambulatory leg is 1.6 times the breadth of the carapace; the propodus is 2.8 times as long as broad. (Minei, 1973)
Type locality: Okinawa, Japan.
Range: Japan - Okinawa (Stimpson, 1907), Amami-Oshima (Sakai, 1976a), Okinawa-jima (Rathbun, 1898a, 1905, Bott, 1970, Minei, 1973), Kerama-retto (Stimpson, 1907), Amami-Oshima, Okinawa-jima, Tokashiki-jima, and Kume-jima (Minei, 1981).