I have now a very large collection of genera and species of Silurian fossils, many of them known forms, and many new. M'Coy is going to examine, describe, and figure the new ones. I shall, I hope, soon be able to define the boundaries of the Upper and Lower Silurian rocks in this colony. Melbourne stands on “May Hill Sandstone;” and to the eastward I find a very gradually-ascending series, including probably Wenlock, Ludlow, Devonian, and true Carboniferous rocks, with Oolitic coal-bearing beds resting unconformably on the Palæozoic strata. To the westward there is a descending series, from Melbourne towards Ballarat, which I much suspect to be Cambrian. Lingulæ , like those of Tremadoe, are abundant in the rock associated with the Bendigo gold-quartz mines. In beds which I take to be equivalents of the Llandeilo flags, Trilobites are very abundant—many of them recognizable European species. I enclose a list of genera (p. 537). This list is now, however, much increased, and is being added to daily. Gold-bearing quartz-veins extend throughout the Silurian rocks; and their richness appears to me to be dependent more on their proximity to some granitic or other plutonie mass than on the age of the rocks in which they occur. As far as I am aware, these gold-quartz veins do not extend into the Oolitic (?) coal-bearing rocks, which are evidently of newer date than any of the granitic masses I have yet examined. At Steiglitz (fig. 1), we have granite ( a ) intruded among Silurian sandstone