Sakai, 1963
The carapace of this new species is markedly broader than long, sub-hexagonal in outline. The dorsal surface is rather depressed, thickly covered with minute granules. There are a number of tubercles of various sizes on each region, i.e. one pair of good size on the anterior portion of the gastric region, and another pair of smaller size in front of them. The cardiac and intestinal regions are respectively convex, each marked with a conical tubercle in the middle portion, and four or five additional small ones on either side of the cardiac region. A tubercle of good size is present on the inner branchial surface; in front and in rear of this, a number of smaller ones may be present.
The front is composed of two obtuse processes, below which the anterior extremity of the epistome can be seen from the dorsal size. There are two upper orbital fissures, but both supra- and preorbital teeth are absent. The hepatic region is produced into a conical process, which projects obliquely downward; posterior to this, the lateral border is marked with four triangular teeth, of which the third and fourth are large, located at the broadest portion of the carapace.
On the dorsal surface of the carapace, there are characteristic eroded grooves, which are symmetrically disposed, i.e. a pair, which are long and oblique, located between the hepatic and branchial regions; another pair, which are longitudinal, located on either side of the cardiac and intestinal regions, and furthermore, three narrow ones between the antero-lateral teeth. The posterior border is marked with an obtuse process in the middle portion.
The chelipeds are rather robust; the merus has four and the carpus has three longitudinal rows of tubercles, the propodus also has two or three indistinct rows and its outer border bears two prominent processes. The dactylus is very slender (i.e. compressed) compared with the immovable finger, the prehensile edge of both is uniformly marked with minute teeth.
The ambulatory legs are very slender, each segment is subcylindrical, covered with microscopic granules, interspersed with several longish hairs. The merus has a few high tubercles along the posterior border.
Measurements: Female holotype, length of carapace 5.0 mm, width of same 6.0 mm. (T. Sakai, 1963)
Type locality: Amadaiba, off Hayama, Sagami Bay, Japan, 65 m.
Range: Japan - Sagami Bay (Sakai, 1963, 1965, 1976), Ogasawara-shoto (Takeda, 1977a).