Five species of Dynomenidae are recorded from Guam, Mariana Islands. Two new species of Dynomene are described. Distinctive characters of D. kroppi n. sp. are: carapace width/length ratio= 1.1, six small, blunt anterolateral teeth, and five or six spines on inner margins of walking leg dactyli; and for D. guamensis n. sp. are: carapace width/length ratio = 1.3, five acute anterolateral teeth, two prominent frontal swellings, two tubercles behind postorbital corner, and seven or eight spines on inner margins of walking leg dactyli. Nine new records and one new dromiid species are reported from Guam: the distinctive characters of Cryptodromia pitiensis n.sp. are: carapace width/length ratio= 1.3, a prominent swelling above the anterolateral margin, carapace surface mostly smooth, but areolate and with scattered tubercles. Nine new dromiid records are also reported for Tonga and Samoa. Five new dromiid records are reported, based on material collected by the Albatross Expedition, 1907-1910, to the Philippine Islands. A total of 29 dynomenid and dromiid species are reported from the Mariana and Philippine Islands, of which only seven species are shared. New keys are provided to identify species of Dynomene, Sphaerodromia and Cryptodromia. Dynomenids and primitive dromiids share similar gonopod characters. Advanced dromiids have gonopods whose derived structure may be linked to the longer sternal sutures 7/8 in females. The third maxilliped crista dentata, as found in podotreme crabs, is absent from all Eubrachyura. Tooth-like maxilliped marginal tubercles in these crabs should be called the marginal dentata. Podotreme crabs show a variety of coxal and sternal abdominal locking mechanisms linked to the presence of uropods.
Crustacea, Decapoda, Brachyura, Cryptodromia, Cryptodromiopsis, Dromidiopsis, Dynomene, Hirsutodynomene, Lauridromia, Paradynomene, Sphaerodromia, Takedromia, Indo-Pacific, gonopods, new species.