Stimpson, 1858
A common black Pinnotheres obtained from Ostrea spinosa growing on various coasts of Japan, which I identified with Stimpson's species with some question; the description given by the original author is too brief and without figure.
Carapace 1.25 times as broad as long, subtrapezoidal in outline, the shoulders of carapace rounded, postero-lateral borders weakly convex and the posterior border very broad and a little concave in the middle. The dactylus of the external maxillipeds is a little exceeding the tip of propodus. The chelipeds are not very stout. The ambulatory legs are very slender and the dactyli of the first two pairs are subequal and relatively shorter (more exactly, those of the second pair are a little longer than those of the first pair), those of the third and fourth pairs are longer. Asymmetry of length of legs and of dactyli are usually remarkable, i.e. the dactylus of the third leg of right side is very often longer than that of the left side, while the dactylus of the fourth leg of right side is shorter than that of the opposite side. The third leg of right side is also longer than that of the left side, while in fourth pair, the reverse is the case.
Pinnotheres purpureus Alcock from Andamans seems to stand very near to this species. (T. Sakai, 1939: 588)
Type locality: Ogasawara-shoto, Japan.
Range: Japan - Ogasawara-shoto (Stimpson, 1858b, 1907), Shimoda (Sakai, 1935), Tateyama Bay, Shimoda, Suruga Bay and Nanki Shirahama (Sakai, 1939), Sagami Bay (Sakai, 1965b), Manazuru and Ogasawara-shoto (Suzuki H., 1972), Miura Peninsula, Manazuru, Shimoda, Kii Shirahama, Kii Minabe, and Ogasawara-shoto (Sakai, 1976a), Gobo (Miyake, 1983), Manazuru and Tosa Bay (Muraoka, 1998); Taiwan; China - Hainan Island (Dai et al., 1980, Dai & Yang, 1991).