In the examination of the different beds of the three-barred formation, our author discovered a well-marked bone, like a petrified large roofing nail, in a grayish-colored layer of hard flag, about 100 yards over the granite, and about 160 feet over the upper stratum of the conglomerate. This singular bone, which Mr. Miller has represented in a figure, was probably the oldest vertebrate organism yet discovered in Orkney. It was 5⅞ inches long, 2¼ inches across the head, and ³⁄₁₀ths of an inch thick in the stem, and formed a characteristic feature of the Asterolepis, as yet the most gigantic of the ganoid fishes, and probably one of the first of the Old Red Sandstone. In his former researches, our author had found that all of the many hundred ichthyolites which he had disinterred from the Lower Old Red Sandstone were comparatively of a small size, while those in the Upper Old Red were of great bulk; and hence he had naturally inferred, that vertebrate life had increased towards the close of the system—that, in short, it began with an age of dwarfs, and ended with an age of giants; but he had thus greatly erred, like the supporters of the development system, in founding positive conclusions on merely negative evidence; for here, at the very base of the system, where no dwarfs were to be found, he had discovered one of the most colossal of its giants. After this most important discovery, Mr. Miller extended his inquiries easterly for several miles along the bare and unwooded Lake of Stennis, about fourteen miles in circumference, and divided into an upper arm lower sheet of water by two long promontories jutting out from each side and nearly meeting in the middle. The sea enters this lake through the openings of a long rustic bridge, and hence the lower division of the lake “is salt in its nether reaches, and brackish in its upper ones; while the higher division is merely brackish in its nether reaches, and fresh enough in its upper ones to be potable.” The fauna and flora of the lake are therefore of a mixed character, the marine and fresh water animals having each their own reaches, though each kind makes certain encroachments on the province of the other.