Redescription of Pinnixa haematosticta Sakai, 1934, its transfer to Indopinnixa Manning amp; Morton, 1987, and a reappraisal of Indopinnixa kumejima Naruse amp; Maenosono, 2012 (Decapoda: Brachyura: Pinnotheridae).

The poorly known pinnotherid crab, Pinnixa haematosticta Sakai, 1934, is redescribed on the basis of female holotype and additional specimens, including males and females, from Japan. The male characters of the species are documented for the first time. The species is transferred to Indopinnixa Manning Morton, 1987 because the male pleonal somites 35 are functionally fused, the telson is wide, and the maxilliped 3 with the dactylus is distinctly longer than the propodus. Indopinnixa kumejima Naruse Maenosono, 2012 is morphologically very similar to I. haematosticta n. comb., but a molecular phylogenetic analysis using partial fragments of the mitochondrial 16S rRNA gene supports the hypothesis that the two taxa as distinct. Morphologically, the two species are differentiated by the shape of the pereopod 4 merus (proportionally wider in I. haematosticta n. comb. than in I. kumejima). Our findings suggest that I. haematosticta n. comb. and I. kumejima are geographically distinct: I. haematosticta appears restricted to the Japanese mainland (Honshu to Kyushu) and Ohsumi Islands, while I. kumejima occurs in the Ryukyu and Ogasawara Islands.

A new species of Pinnixa (Crustacea: Decapoda: Brachyura: Pinnotheridae) associated with a tube worm, Chaetopterus cautus (Annelida: Polychaeta), from Tokyo Bay, Japan.

A new species of the pea crab genus Pinnixa White, 1846 (Pinnotheridae), P. banzu n. sp., is described and illustrated on the basis of four specimens from Banzu, an estuary of the Obitsu River, Kisarazu, Chiba Prefecture, Japan. All the specimens examined were associated with the polychaete tube worm Chaetopterus cautus Marenzeller, 1879 (Chaetopteridae). The new species is very similar to P. chaetopterana Stimpson, 1860 from the western Atlantic, P. occidentalis Rathbun, 1894 from northwest North America, and P. rathbuni Sakai, 1934 from East Asia. It is distinguished from the latter three species by characters of the carapace, ambulatory legs, male abdomen, and male first gonopod. It is suggested that previous records reporting on the association of P. rathbuni with Chaetopterus tube worms might be actually referred to the new species.