The Australian Cladocera are revised on the basis of numerous samples, collections in the Australian Museum and a critical consideration of the literature. Six families are represented in inland waters of Australia: Sididae, Chydoridae, Macrothricidae, Moinidae, Bosminidae, and Daphniidae. Altogether 125 species in 40 genera were found, 15 species being new: Pseudosida australiensis n.sp., Archepleuroxus baylyi n. gen., n.sp., Rak obtusus n. gen., n.sp., Rak labrosus n. gen., n.sp., Australochydorus aporus n. gen., n.sp., Rhynchochydorus australiensis n. gen., n.sp., Alona macracantha n.sp., Alona investis n.sp., Alona setuloides n.sp., Biapertura rusticoides n.sp., Monospilus diporus n.sp., Monospi/us elongatus n.sp., Echinisca williamsi n.sp., Echiniscaflagellata n.sp., and Simocephalus victoriensis n.sp. One new subspecies is recognized: Alona davidi vermiculata n.subsp. Some 49 species (including the new species) are recorded in Australia for the first time. In addition, the presence of a further 6 species of marine Cladocera in the families Podonidae and Sididae is noted. The cladoceran fauna of Australia, besides including many cosmopolitan and pantropical forms, also has some species widely distributed in the Holarctic, some Gondwanaland species, and a large number (46) of endemics. Keys to all families and genera of Cladocera are given as well as keys for Australian species. Ecology, community structure, faunal composition and zoogeography are considered. The revision provides a basis for the identification of Australian Cladocera and for further taxonomic studies.

We report the results of a polarized-2-beta-decay experiment carried out in the Fermilab Proton Center charged-hyperon beam. These results are based on 49 671 observed 2 -+ n e -V decays. The 2-beam had a nominal momentum of 250 GeV/c and was produced by 400-GeV/c protons impinging on a Cu target. At a production angle of 2.5 mrad, the polarization was (23.6f 4.31%. The decay asymmetries of the electron ( a , = -0.519+0.104), neutron ( a , = +0.509+0.102), and antineutrino (a,= -0.230f 0.061) were measured and used to establish sign and approximate magnitude of the axial-vector-to-vector form-factor ratio g , / f , . The form-factor ratios g , / f l / and f 2 / f were determined most sensitively from the neutron and electron center-of-mass spectra, respectively. We obtain 1 g , / f l -0.237g,/f1 =0.327i0.007i0.019 and f , ( O ) / f , ( 0 ) = -0.96 f0.07k0.13, where the stated errors are statistical and systematic, respectively. A general fit that includes the asymmetries and makes the conventional assumption g , =O gives the final value g , ( O ) / f , ( 0 ) = -0.328k0.019. The data are also compatible with positive values for g , / f , combined with corresponding reduced values for g , / f , / .

Material from the Early Cretaceous age collected 6 km west of the Hotont Somon (Mongolia) includes numerous impressions of Anomopoda. These show biramous segmented antennae and their setae, valves, head shields, mandibles, the distal part of the post-abdomen, claws and the gut containing food material. Prochydorus rotundus sp. nov., Arckoxus mirobifis sp. nov. and Archeoxus ventrosus sp. nov. are described and attributed to a new family Prochydoridae. The material demonstrates that the prochydorid-type of organization is geologically ancient.

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The aim of this study is to revise the aduncus-like species of the genus Pleuroxus Baird, 1843 (Chydoridae, Cladocera) from the southern hemisphere and test the accuracy of subgeneric differentiation within this genus according to Frey (1993a). Pleuroxus wittsteini Studer, 1878 from the Kerguelen archipelago is re-examined with special attention to thoracic limbs. Forgotten P. carolinae (Methuen, 1910) from the mountains of South Africa is redescribed in detail; it is a species having nine to ten setae in filter plate II, and six to seven setae in filter plate IV, which is a plesiomorphic, non-oligomerized state. Brief descriptions are also provided for P. scopuliferus (Ekman, 1900) and P. varidentatus Frey, 1993. A new species, P. hardingi sp. nov., is reported from high altitudes of the Bolivian Andes; this species was previously misidentified as P. aduncus by Harding (1955). A key for identification of aduncus-like species in the southern hemisphere (except Australia and New Zealand) is proposed. Frey's (1993a) system for differentiation of the subgenera of Pleuroxus is found to be vulnerable in view of the new data. New studies, most probably using genetic methods, are needed for the construction of a consistent phylogenetic tree for the genus.