The eastern Pacific hermit crab species of the genus Calcinus Dana, 1851 are reviewed. Calcinus mclaughlinae n. sp. is described from Clipperton Island, and is considered a sibling species of C. californiensis Bouvier, 1898, known from the Gulf of California and the mainland coast of Mexico. Two other species, C. explorator Boone, 1930, mostly insular in distribution, and C. obscurus Stimpson, 1859, distributed from El Salvador to Peru, are also considered sibling. These four species are similar but can be clearly separated by coloration, and to some extent armature of the ocular acicles. They are morphologically close to the western Atlantic congener Calcinus tibicen (Herbst, 1791). The taxonomic status of Calcinus chilensis (H. Milne Edwards, 1836), reported from Chile, and questionably Peru, is considered uncertain.
Crustacea, Decapoda, Anomura, Diogenidae, Calcinus, eastern Pacific, Clipperton, zoogeography, sibling species, new species.