Sakai, 1935
The genus Lophoplax contained two species; the one, Lophoplax sculpta (Stimpson), was described from Oshima and the other, Lophoplax bicristata Tesch, from Makassar Strait and Key Islands. The present species is allied to L. bicristata, however, the following points appear to afford specific features.
1. The general feature of the body resembles that of L. bicristata, but the regions of the carapace are not clearly sculptured and are less markedly granulated.
The hairs covering the carapace are very short and sparse; no prominences or thick ridges upon the carapace. Antero-lateral prominences are five as in the other species.
The front vertically deflexed, bilobed, free edge of each lobe is thickened and callous, the breadth in this region seems to be narrower than in bicristata.
2. Of external maxillipeds, the antero-external angle of the merus is not produced, contrary to that of bicristata, while, the inner borders and the suture between merus and ischium are irregularly granulated as well as in the inner border of the exognath. The inner gap between merus and ischium is not so remarkable in the present species.
3. Chelipeds are symmetrical, merus is provided with two prominences on the upper ridge; one, at the distal end is very thick, the other, subdistal, is smaller and pointed. Carpus is bulky, with a large tooth at the inner angle which is stronger than that of bicristata; outer angle has no teeth. Two longitudinally disposed smooth, callous prominences are on the upper surface, while in Lophoplax bicristata only a large sub-square prominence is found in the middle of this surface. The colour in living animal is yellowish vermilion.
Palm is provided with granules and strong setae, the former are much more prominent than in the oher species and are arranged in longitudinal rows. Fingers strong, much longer than in bicristata, in which the palm is "twice as long as the fingers".
The fixed finger is strongly deflexed inward to the long axis of the palm and the movable finger is also when it is retracted; the tips are pointed and slightly cross each other when closed. The outer surface of the fingers are provided with longitudinal rows of closely-set granules, while in the inner surface, two rows of granules are found on the movable finger and two shallow grooves on the immovable finger.
4. Ambulatory legs are much more slender than in the other species, the penultimate pair measuring about 2.3 times as long as the length of the carapace, while in the other species the proportion is only 1.5.
All the segments are sub-cylindrical and are furnished with short brown hairs; a shallow longitudinal groove on the upper surface of each carpus, while in bicristata, the merus is provided with 6-8 tubercles on the anterior border.
5. Of the characteristics of the abdomen, the comparison is impossible for the new species is represented by a single female and the other species by two males. (Sakai, 1935)
Type locality: off Yoshihama, west of Sagami Bay, Japan, 30-40 m.
Range: Japan - off Yoshihama, Sagami Bay (Sakai, 1935, 1939, 1976), Mikawa Bay (Sakai, 1976a), Shiono-misaki (Takeda, 1979a); 30-100 m.