In the production of this work several friends and collaborators have materially assisted, their aid considerably increasing its value. It is therefore with grateful thanks that the author acknowledges the help and encouragement given by Professor E. W. Skeats, D.Sc., who has not only been good enough to write the Introductory passages, but who has carefully gone over the MS. and made many helpful suggestions. Mr. W. S. Dun, F.G.S., Palaeontologist to the Geological Survey Branch of the Department of Mines, Sydney, has also rendered generous help in giving the benefit of his full acquaintance of the palaeontology of his own State. To the Trustees of the National Museum the author is under special obligations for permission to photograph many unique fossil specimens in the Museum collection, comprising Figs. 3, 16-18, 20-22, 28-31, 35, 39, 40, 45, 46, 51-54, 57, 62, 78, 79, 127, 133, 136, 147 and 148. The author's thanks are also due to Dr. E. C. Stirling, M.D., M.A., F.R.S., for permission to use Figs. 143, 144 and 145, whilst similar privileges have been accorded by Prof. A. G. Seward, F.R.S., Dr. F. A. Bather, F.R.S., and Mr. C. L. Barrett. Prof. T. W. Edgeworth David, F.R.S., has kindly cleared up some doubtful points of stratigraphy and further increased the author's indebtedness by the loan of a unique slide of Radiolaria figured on p. 69. Mr. Eastwood Moore, to whom special thanks are due, has greatly added to the pictorial side of this work by his skillful help in preparing many of the illustrations for the press, as well as in the drawing of the several maps. The grouped sets of fossils have been especially drawn for this work by the author. They are either copied from authentic specimens or from previously published drawings; references to the authorities being given in the accompanying legends. Dr. T. S. Hall has kindly read the section on Graptolites and Mammalia. For many helpful suggestions and the careful reading of proofs, thanks are especially owing to Mr. W. E. G. Simons, Mr. R. A. Keble, and to my wife. INTRODUCTION. Geological Department, The University, Melbourne.