Two new species of the hermit crab genus Lithopagurus Provenzano, 1968 are described and illustrated together with an illustrated and detailed diagnosis of the type species, L. yucatanicus Provenzano, 1968 that is included for comparative purposes. This genus, heretofore monotypic and known only from off the Atlantic coast of Mexico, is now reported from two widely separated Pacific areas, the Indonesian Kai Islands and the Fiji Islands. In having 13 pairs of gills and one pair of pleopods modified as gonopods, Lithopagurus is included in the Pylopaguropsis group within the family Paguridae, and would appear most closely allied to the monotypic Tomopaguroides Balss, 1912. Species of Lithopagurus are very characteristic, with large operculate or semioperculate right chelipeds, reduced and somewhat bulbous pleons; males with paired and modified second pleopods, but lacking all unpaired pleopods; females with only unpaired pleopods 2-4; and telsons without lateral indentations and with terminal margins lacking median clefts. Lithopagurus boucheti n. sp., from the Fiji Islands, is morphologically quite similar to its Atlantic counterpart, L. yucatanicus, whereas L. tribulomanus n. sp., from the Kai Islands, is very distinctive. All three now recognized species have been collected from relatively deep water, 146-540 m, but little is known about their habitats other than one specimen of L. yucatanicus reportedly was occupying a piece of lithistid sponge at the time of collection.
Crustacea, Decapoda, Anomura, Paguridae, Lithopagurus, western Pacific, new species.