PLATE I. Page. Trachypora Wilkinsoni, Etli. fil. ... ... ... ... 26 Fig. 1. Portion of a branch, showing the distribution of the corallites, and a central abortive branch, x 1J. Fig. 2. Portion of another branch, in which the septal ridges are better defined, x 1 Fig. 3. Small part of a corallum on which the calices open in a contrary direction from opposite ends, x 1|. Fig. 4. Bifurcating corallum, naturally fractured, showing the corallites in section in the centre of the branches, with tabulae in sitn,; the calice mouths around the periphery separated by the highly-thickened w r alls, x 2. Fig. 5. Small part of Fig. 4 enlarged four times to show these characters more distinctly, x 4. Fig. 6. Another stem naturally fractured, x 2. Fig. 7. A stem partially split with the stellate calices admirably shown at the base, x 2J- Fig. 8. Portion of a corallum, from which the whole of the calcareous matter has been dissolved, leaving the fluted internal casts of the corallites as inverted cones, connected by cross-bars which are the inorganic infilling of the pores of com- munication, magnified. Figs. 1-6, from Mulbring. 7, ,, Shoalhaven. 8, „ Boorook.