Stimpsoplax setirostris (Stimpson, 1858) n. comb.

(Fig. 12)

Rhynchoplax setirostris Stimpson, 1858: 109 –110. — Tesch 1918: 18. — Sakai 1938: 198–199, fig. 2. — Sakai 1965: 63–64, pl. 25 fig. 3. — Sakai 1976: 148–149, figs 76b, 77, pl. 46 fig. 3.

Rhynchoplax messor— Yokoya 1929: 761–762, fig. 1.

Halicarcinus yangi Shen, 1932: 279 –283, figs 169–171.

Halicarcinus setirostris— Lucas 1980: 163. — Dai & Yang 1991: 115–116, fig. 58. –– Ng & Chuang 1996: 48. — Ng et al. 1999: 89–90, fig. 5. — Ng & Jeng 1999: 531–532. — Ng et al. 2001: 15.

Material examined. Japan. Chiba Prefecture, Tateyama, Banda, 30–60 m, 22 May 1990, dredge, coll. M. Osawa, CBM-ZC 295 (1 male, 3.6 mm; 1 ovigerous female, 3.3 mm, selected from many specimens); Uraga Strait, off Takeoka, Futtsu, 20–40 m, 29 October 1997, commercial gill net, coll. T. Komai, CBM-ZC 4440 (1 male, 3.9 mm). Shizuoka Prefecture, Zenisu Bank, S of Omae-zaki, 34°00.58'N, 138°50.36'E, 104 m, 30 April 2004, RV Tanseimaru, KT04-6 cruise, stn ZS-1(2), dredge, coll. H. Kotsuka, CBM-ZC 9957 (1 female, 3.1 mm). China. East China Sea, on fine sand, 135 m, ZRC 1999.1223 (1 male). Qingdao, Jiao-Jhou Wan, on sand and broken shells, 25 m, ZRC 1999.1224 (1 ovigerous female).

Supplementary diagnosis. Carapace with subhepatic region bearing broadly triangular lobe partially visible from dorsal view and 1 prominent subconical tubercle inferior to subhepatic lobe (not visible from dorsal view). Distribution. East Asian endemic: Japan (Honshu to Kyushu), Taiwan, China, 25– 135 m.

Remarks. Apart from its defining generic characters, Stimpsoplax setirostris is recognisable by the possession of conspicuously long slender ambulatory legs with non-falcate dactyli (setting it apart from species of Rhynchoplax). The broadly triangular subhepatic lobe, which is visible in dorsal view, is also characteristic of the species. Yokoya’s (1928) figure of Rhynchoplax messor from ‘Takaiso Zaki’, Aomori Prefecture, Japan, is more probably of S. setirostris . Although it is ‘well known’ (Ng et al. 1999) the species has been only superficially illustrated. Sakai (1976) figured the habitus and gonopod 1 and Ng et al. (1999) variation in the rostrum. Specimens from Chiba Prefecture, Japan, are figured more completely here.