A new species of pea crab Arcotheres Manning, 1993 (Pinnotheridae), is described from the windowpane shell, Placuna ephippium (Philipsson, 1788) (Placunidae) in Singapore. The species had previously been incorrectly identified as Arcotheres similis (Bürger, 1895) but with the redescription of the types by Ahyong & Ng (2007), this is now known to be a very different taxon. Arcotheres placunicola n. sp. is superficially similar to A. palaensis (Bürger, 1895) and A. guinotae Campos, 2001, but can easily be distinguished by the structures of the third maxilliped, as well as proportions of the chelae and ambulatory legs. The only other species known to live exclusively in placunid shells, A. placunae (Hornell & Southwell, 1909) from India, is markedly different in the form of the carapace and ambulatory leg structures.

A new species of pea crab Arcotheres Manning, 1993 (Pinnotheridae), is described from the window-pane shell, Placunaephippium (Philipsson, 1788) (Placunidae) in Singapore. The species had previously been incorrectly identified as Arcotheressimilis (Bürger, 1895) but with the redescription of the types by Ahyong & Ng (2007), this is now known to be a very different taxon. Arcotheres placunicola n. sp. is superficially similar to A. palaensis (Bürger, 1895) and A. guinotae Campos, 2001, but can easily be distinguished by the structures of the third maxilliped, as well as proportions of the chelae and ambulatory legs. The only other species known to live exclusively in placunid shells, A. placunae (Hornell & Southwell, 1909) from India, is markedly different in the form of the carapace and ambulatory leg structures.

Opinions and declarations Rendered by the International Commission on Zoological Nomenclature