A collection (35-112 m) from the Marquesas Islands, French Polynesia, contains three new dromiid species. The distinctive characters of Dromidiopsis richeri n. sp. include three anterolateral teeth and a dense fringe of setae behind the frontal margin. For Cryptodromia marquesas n. sp., the distinctive characters are a strong subhepatic tooth visible dorsally and the presence of five swellings on the branchial area, which give the carapace surface a sculptured appearance and for Cryptodromia erioxylon n. sp., a covering of very fine, soft setae, a minutely denticulated orbital margin and a prominent tubercle behind the postorbital corner. There are three new records: Dromia dormia (Linnaeus, 1763), Cryptodromiopsis unidentata (Rüppell, 1830) and Cryptodromia hilgendorfi De Man, 1888. New keys are provided for the identification of the known species of Dromidiopsis and Cryptodromia. Dromia wilsoni (Fulton & Grant, 1902) and the first female specimen of Cryptodromiopsis plumosa (Lewinsohn, 1984) are reported from Hawaii. Sponges carried by the dromiids were identified to genus and most of these constitute new records for the Marquesas Islands. The fauna of French Polynesia now includes 11 dromiid and five dynomenids while the Hawaiian Islands have five and four species respectively. Four dromiids and three dynomenids are shared. Diversity is greatest in shallow (< 100 m) water. Sperm transfer in dromiids is poorly understood. The first gonopod is only tubular distally and cannot enter the female spermathecal aperture, while the second is longer and needle-like. The long, muscular extension of the vas deferens is the main conduit for sperm, thus taking over the role of the first gonopod in eubrachyurans.
Crustacea, Decapoda, Brachyura, Dromiidae, Dynomenidae, Porifera, French Polynesia, Hawaii, Marquesas Islands, key, reproductive structures, sperm transfer, new species.