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Geology of Sydney. 
Arenaceous (Lat. arena , sand). Sandy, or composed of 
grains of sand. 
Argillaceous (Lat. argilla , clay). Clayey. 
Articulata (Lat. articulus , a little joint). A division of 
the animal kingdom, comprising Insects and Crusta- 
ceans, characterised by the possession of jointed bodies 
or jointed limbs. The term Arthropoda (Gr. arthron , 
a joint ; pous , gen. podos , a foot,) is now more usually 
employed. 
Asteroid (Gr. aster , a star; and eicfos, form). Star-shaped, 
or possessing radiating lobes or rays like a star-fish. 
Asterophyllites (Gr. aster, a star ; phullon , a leaf). A 
genus of Palaeozoic plants, with leaves in whorls. 
Athyris (Gr. a , without ; thuris , a door). A genus of 
Brachiopods. 
Atrypa (Gr. a, without ; trupa , a hole). A genus of 
Brachiopods. 
Augite. (Gr. auge, brightness), a mineral ; a silicate of 
magnesia, lime and iron ; usually green or dark green 
in colour. 
Avicula (Lat., aviculus , a little bird). The genus of Bivalve 
Molluscs comprising the Pearl-oysters. 
Azoic (Gr. a , without ; zoe, life). Destitute of traces of 
living beings. 
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Barytes (Gr. barus , heavy). Barium Sulphate. 
Basalt. A rock of igneous origin, dark in colour and 
compact in structure, composed chiefly of a felspar, 
augite, olivine, and some magnetite. 
