Mesenchytraeus kuril sp. n. is described from a small spring entering Lake Kuril'skoe, southern Kamcatka Peninsula. It is characterised by small body dimensions, the presence of septal glands at 3/4-5/6, by short spermathecae uniting before the connection with the oesophagus and equipped with simple, sperm-filled diverticula, and by simple sperm ducts and penial bulbs.
Three new species of oribatid mites belonging to the genus Epidamaeus are described from Mongolia. Epidamaeus granulatus sp. nov. differs from its closely related species in the presence of three setae on trochanter III, the strongly curved spinae adnatae directed anteromedially, and the very thick and strongly barbed notogastral setae. Epidamaeus culterisetosus sp. nov. can be distinguished from its congeners by the table-knife-like notogastral setae of the d, l, and h series ; the distally expanded sensilli ; the absence of prodorsal tubercles Da and Bp ; the relatively long and distally projected tubercle Sp ; the different direction of the spinae adnatae ; the long posterior notogastral setae ps_1, ps_2, and ps_3 ; the smooth epimeral and ano-genital setae ; and the different number of setae on tarsi I, III, and IV. Epidamaeus mongolicus sp. nov. is easily distinguishable from the other known species by the strongly developed tectum of the podocephalic fossa, the presence of three pairs of well developed prodorsal tubercles (Ba, Bb, and Da), and the absence of enantionhvses E2 and V.
A new calanoid copepod, Ridgewayia stygia, is described from a submarine cave in Palau in the Western Pacific. The new species is most similar to a Caribbean species, R. fosshageni, but can be distinguished from the latter by the location of the female genital operculum and the structure of the fifth legs of both sexes. The affinities of the new species appear to lie with the North Atlantic/Mediterranean R. marki species-group rather than the Indo-West Pacific R. typica species-group. This discovery suggests that, within the Tethys Sea, westward dispersal of marine copepods from the Caribbean Province extended as far as the western Central Pacific rather than only to the eastern Central Pacific.
Two new species of Munnogonium are described from Japan as the first record of this genus from the Western Pacific. Munnogonium armigerum sp. nov. is distinguished from the most similar species, M. adensis Miiller, 1991, by its anterior four pereonites armed with some acute teeth laterally, though the two species share the uniramous uropod and the distomesially projected article 3 of antenna 2. Munnogonium orientale, sp. nov. shows similar sexual dimorphism to that of M. maltinii (Schiecke and Fresi, 1972) : the article 3 of antenna 2 is twice as broad in males as in females. The present new species differs from all its congeners in having a short anterodorsal projection of the head, pleopod 1 with a pair of long, broad, lateral projections, and male coxal plates 1-4 with one spine each.
Critical examination of abundant material from various localities in Japan and the Russian Far East has revealed that three distinct species have been confounded under the name Pagurus brachiomastus (Thallwitz, 1891). The holotype of Pagurus brachiomastus is no longer extant ; thus, in the interest of nomenclatural stability, a neotype is designated. Pagurus brachiomastus is redescribed and two new species, P. proximus and P. simulans, are described and illustrated. Differences in morphology and coloration are discussed. The three species are, for the most part, geographically or bathymetrically separated, although their distributions may partly overlap.
Leucosiid crabs obtained by dredging at depths of 35-106 m off the Osumi Islands, southwest Japan, are referred to 12 species in seven genera. A new species, Cryptocnemus trigonus, is described, and three rare species unknown since their original descriptions, viz., Cryptocnemus macrognathus Ihle, 1915, Ebalia longispinosa Ihle, 1918, and Nursia elegans Ihle, 1918, are added to the carcinological fauna of Japan. Pseudophilyra dinops Takeda, 1977 is synonymized with P. tridentata Miers, 1879, and the records of P. tridentata from Japanese waters are corrected to P. intermedia Ihle, 1918.
Eight species of the genus Paraleuctra are recognized in Japan, six of them being described as new herein : P. ezoensis from Hokkaido and P. ambulans, P. similis, P. hokurikuensis, P. angulata, and P. concava from Honshu. An apterous and a short-winged species are included. A neotype is designated for Leuctra okamotoa Claassen, 1936 ; this species is now transferred from Rhopalopsole to the present genus and is regarded as a senior subjective synonym of P. gracilis Kawai, 1967. Paraleuctra cercia (Okamoto, 1922) is redescribed and regarded as a senior subjective synonym of both P. forficularis (Okamoto, 1922) and L. higashiyamae Kohno, 1965. Paraleuctra elongata Kawai, 1967 is transferred to Rhopalopsole, and P. nipponica (Okamoto, 1922) and Rhopalopsole gifuensis Kohno, 1965 are transferred to Perlomyia. A key is provided for Asian species of Paraleuctra.