During 1950-51 pendulum gravity observations were made at 59 stations throughout Australia using invar pendulums on loan from the Department of Geodesy at Cambridge University. A national gravity base station was established at Melbourne. Subsequent comparisons with gravity meter ties suggest that the pendulum value is about 2 mgal. low. The standard errors of the gravity differences from Melbourne to the other stations have been estimated from internal consistency of the pendulum observations and from comparison with gravity meter measurements; the mean standard error is about 0.6 mgal. A small systematic difference from gravity meter values is assumed to be caused by the effect of the earth's magnetic field on the pendulums; after correction for this, the results agree fairly well with the American calibration system. Free air, Bouguer and isostatic anomalies have been calculated for all stations. The isostatic anomalies are for both Airy-Heiskanen and Pratt-Hayford hypotheses, and for four different assumed crustal thicknesses in each case. The isostatic and Bouguer anomalies are predominantly negative. A degree of isostatic compensation is present, but some large anomalous areas are uncompensated. The pendulum survey forms a basic network to which past and future gravity surveys can be referred.

Mollusca from the Nanutarra Formation, a recently defined strata! unit cropping out along the north-eastern edge of the Carnarvon Basin of Western Australia, are described and the age of the' formation is discussed. The fossils occur largely as moulds of the original shells, so that their study has been based mainly on artificially prepared casts. Of about 48 forms recorded in the paper, only one (Pseudavicula anomala) has been definitely referred to a previously described species, four (Maccoyella aff. corbiensis. M. aff. barklyi, M. aff. moorei, and Modiolus aff. ensi/ormis) have been assigned qualified identifications with known species, and 18 are described as new; the remainder have been given only generic identifications, owing to the limitations of the material. The new species are as follows:-Nuculana hoelscheri, Glycymeris mckellari, Pacitrigonia? nanutarraensis, Pterotrigonia australiensis, "[socyprina" fairbridgei, "Corbicellopsis," nanutarraensis, Lucina macroporum, Mutiella? teicherti, Protocardia wapeti, Astarte (Nicaniella) mcwhaei, Eriphyla playjordi, Pleuromya ashburtonensis, Panopea glaessneri. CQrbula nanutarraensis, Muricotrochus? australiensis, Purpurina? yanreyensis, Procerithium (Rhabdocolpus) brunnschweileri, and" Acteonina" australiensis. Apart from the species of Pseudavicula, Maccoyella, and Modiolus, which have been identified, mostly with qualification, with Australian Lower Cretaceous species, the fossils bearing particularly on the age of the formation are those belonging to the genera Pterotrigonia (hitherto solely Cretaceous apart from one record from the Tithonian), Eriphyla (hitherto mainly Cretaceous, but known from the Upper Jurassic), Glycymeris (known from the Cretaceous but not from the Jurassic), and large Panopea (resembling several Cretaceous species and unlike any from the Jurassic). No species belongs to an exclusively Jurassic group. It is concluded that, notwithstanding palaeobotanical evidence of a Jurassic age, the Nanutarra Formation should be most probably referred to the Lower Cretaceous. It has yielded no ammonites or brachiopods.

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These documents have been scanned by the GA Library. Please refer to the document for contents.

These documents have been scanned by the GA Library. Please refer to the document for contents.

These documents have been scanned by the GA Library. Please refer to the document for contents.

These documents have been scanned by the GA Library. Please refer to the document for contents.