Geology of Sydney. 
374 
Oligocene (Or. oligos, few ; kainos , new). A name used 
by many Continental geologists as synonymous with 
the Lower Miocene. 
Olivine. A mineral ; a magnesium and iron silicate. 
Palaeaster (Gr. palaios, ancient ; aster, a star). An 
extinct genus of Star-fishes. 
Palaeontology (Gr. palaios , ancient ; onta , living things, 
logos , discourse). The science of fossil remains or of 
extinct organized beings. 
Palaeozoic (Gr. palaios , ancient; zoe , life). Applied 
to the oldest of the great geological epochs. 
Pecopteris (Gr. peko , I comb ; pteris , a fern). An extinct 
genus of fern. 
Pecten (Lat. a comb). The genus of bivalve molluscs 
comprising the Scallops. 
Pentamerus (Gr. pente , five ; meros , a part or division). 
An extinct genus of Brachiopods, with septa dividing 
the shell into five chambers. 
Phacops (Gr, phakos , a lentil ; ops, the eye). A genus of 
Trilobites. 
Phanerogams (Gr. phaneros , visible ; gamos , marriage). 
Plants which have the organs of reproduction con- 
spicuous, and which bear true flowers. 
Phyllotheca. (Gr. phullon , a leaf ; theke , a box). Species 
of Horsetail. For description see Text — pages 167 and 
171. 
Placoid (Gr. plax, a plate ; eidos, form). Applied to the 
irregular bony plates, grains, or spines, which are found 
in the skin of various fishes (Elasmobranchii). 
