The brachyuran crab Pseudorhombila haswelli Miers, 1884, described on the basis of two juveniles from the Arafura Sea, is a poorly known species of uncertain systematic position. It was made the type and only species of Homoioplax Rathbun, 1914, and assigned to the Prionoplacinae (Goneplacidae). Subsequent revisions of the goneplacids showed Prionoplacinae to be a junior synonym of Eucratopsinae
Stimpson, 1871, as a member of the Panopeidae Ortmann, 1893, but no one has re-evaluated the position of Homoioplax. As a result, Homoioplax has remained in the Panopeidae as the only Indo-West Pacific representative of the family. This study assesses the systematic status of Homoioplax haswelli based on a re-examination of the type and other material of the species. Homoioplax haswelli is here attributed to Carcinoplax H. Milne Edwards, 1852 (Goneplacidae), justifying the recognition of the species described by Miers as C. haswelli. Moreover, Carcinoplax haswelli is shown to be a senior synonym of C. sinica Chen, 1984, described from the South China Sea. Therefore, C. haswelli is now known to range from southern Taiwan and the Philippines, through the South China Sea, northern Vietnam, the eastern waters of Singapore to the Madura Straits in eastern Java and Arafura Sea, northern Australia, at 25–187 m, but usually less than 100 m depth.
Pseudorhombila haswelli, Carcinoplax, new combination, senior synonym, C. sinica, New distribution, Goneplacidae.
