This fossil coral abounds in that division of the Silurian formation termed the Wenlock or Dudley limestones, wherever these deposits occur. The most exquisite specimens are obtained from the Falls of the Ohio, at Louisville, in the United States of America. A coral reef of the Silurian epoch here exists in the bed of the mighty stream of fresh water, almost as perfect as when growing in its native sea! The river dashes over the entire mass in the season of high water; but in those periods when the stream is low, the ridge of coral is exposed, and its surface then presents the most extraordinary display of Silurian corals, of numerous species and genera, standing in relief on the more compact masses of the rock. The substance of the corals, being siliceous, resists the action of the cataract, while the softer calcareous matter which filled up the interstices of the tubes, lamellæ, &c. of the zoophytes, is washed away atom by atom; and natural dissections are formed, which art would in vain attempt to imitate. Dr. Yandell, of the Medical College, Louisville, and Dr. Clapp, of New Albany, have splendid collections from the Falls, which every geologist and intelligent traveller who visits Kentucky should not fail to examine: the masses of Astreæ, Madrepores, &c. are so fresh in their aspect, as not to be readily distinguished from the recent specimens of the same genera which are placed beside them.[26] [Footnote 26: See Sir Charles Lyell's Travels in the United States; and Drs. Yandell and Shumard's "Contributions to the Geology of Kentucky." Louisville, 1847.] Fig. 5, is a transverse section of a mass of chain-coral from Dudley. Fig. 6. The same, as seen by transmitted light. [Illustration: Plate XXXVI.] PLATE XXXVI. Various Fossil Corals from different Formations. Figs. 1, 2, 3. (_Cyathophyllum turbinatum_, of Goldfuss.) These three turbinated or top-shaped corals are referable to a genus of which many species are exceedingly abundant in the Wenlock or Dudley limestone of the Silurian System. They belong to the Anthozoa, or flower-like corals. The living animal, of which the _coral_ is but the durable earthy fabric or skeleton, bore a close analogy to the sea-anemone, or animal flower (_Actinia_), of our coasts. Each of these specimens belonged but to a single animal: the Cyathophylla are not, like the tubipores previously described, an aggregation of numerous individual polypes.[27] [Footnote 27: For a popular account of the nature of Corals and the animals which form them, see Wonders of Geology, vol. ii. Lect. vi. p. 589.] Fig. 4. A small coral (_Fungia_) from Dudley.