The Devonian or Old Red Formation. (_Wond._ pp. 204 and 751). Conglomerates, quartzose grits, sandstones, marls, and limestones; the prevailing colour is a dull red. Shells, corals, and ganoid fishes, of a very peculiar type. Reptiles, (Telerpeton; _Batrachians?_ _Chelonians?_); the most ancient reptilian remains hitherto discovered. _Ferns_, _Lepidodendrons_, and other trees of the carboniferous flora; fluviatile plants with batrachian ova(?). _Subdivisions_:-- 1. Sandstone, quartzose conglomerates, and shale, with but few fossils. 2. Flagstones, marls, and concretionary limestones; provincially termed _corn-stones_; laminated reddish and greenish micaceous sandstones (_prov. tilestones_). Peculiar genera of fish; orthocerata, and many species of marine shells. _Obs._--The term Devonian, by which the series of strata comprehended in this formation is now generally distinguished by geologists, was first proposed by Sir R. Murchison, as being more precise than the name formerly applied to this group. In Scotland, where the formation is of vast extent, it was first characterized by its peculiar ganoid fishes (Pterichthys, Coccosteus, Cephalaspis), and will probably always there retain the original name of Old Red.[22] In Devonshire it is marked by the presence of shells of a character intermediate between those of the Silurian and Carboniferous systems. The sandstones are in various states of induration, and when slaty, are employed for roofing. The red colour predominates in the marls, and is derived from peroxide of iron. The formation of these rocks has manifestly resulted from the waste of ancient slate rocks, the detritus of which is cemented together into coarse conglomerates. In South Devonshire (at Torquay, Babbicombe, &c.), beautiful coralline marbles occur in this formation. [22] See the charming volume of Mr. Hugh Miller, entitled "The Old Red Sandstone, or New Walks in an Old Field." The Silurian System. (_Wond._ p. 765). Marine limestones, sandstones, shales, and calcareous flagstones, characterized by peculiar types of corals, crinoideans, mollusks, and crustaceans, constitute this important and extensive system of rocks; the _Grauwacké_, or Transition series of the earlier geologists. _Subdivisions_:-- UPPER SILURIAN. 1. _Ludlow rocks_;--slightly micaceous grey-coloured sandstones. Blue and grey argillaceous limestones. Dark-coloured shales and flagstones, with concretions of earthy limestone, containing marine shells, Orthocerata, Spirifers, and Trilobites. _Fishes._ 2. _Wenlock_, or _Dudley limestone_;--sub-crystalline blue and grey limestone, abounding in Trilobites, Crinoidea, Polyparia, Spirifers, Orthocerata, &c. 3. _Wenlock shale_;--dark grey argillaceous shale, with nodules of sandstone. LOWER SILURIAN.