4. Lias rock; a series of laminated limestones, with clay partings. Bone-bed, with numerous remains of fishes. _Obs._--The Lias is the grand depository of those tribes of marine reptiles, the _Ichthyosauri_ and _Plesiosauri_, whose remarkable forms, structure, and state of preservation, have excited the attention even of the most incurious. The collection of these remains in the British Museum, principally formed by Mr. Hawkins, is unrivalled.[19] [19] See "Petrifactions," p. 337-367. The Trias; or New Red Sandstone Formation,[20] (_Wond._ p. 533). This group of rocks consists of variegated marls, sandstones, and conglomerates, frequently of a red colour, with marine shells, crinoideans, fishes, and reptiles; marine and terrestrial plants. This series contains extensive deposits of rock-salt, and brine-springs. [20] Called by some geologists _Poikilitic_ (variegated) group. This formation comprises the _Trias_, or triple group, _viz._ the _Keuper_, _Muschelkalk_, and _Upper Bunter Sandstein_, of the German geologists. _Subdivisions_:-- 1. Variegated red, blue, and white marls, and shales, with gypsum and beds of rock-salt. (_Marnes irisées_ of the French.) 2. Variegated red and white sandstones. 3. Conglomerates formed of the detritus of the older rocks. 4. Bed mottled sandstone, and marls. (_Grès bigarré_ of the French.) _Obs._--To this formation belong the principal deposits in Leicestershire and other midland counties of England. Fossils are not generally abundant, but some localities yield highly interesting remains. The shelly limestone of Germany, called Muschelkalk, which contains the _Lily Encrinite_, &c. does not occur in England. Remains of Conifers allied to the Yew and Araucaria, are found near Coventry; and peculiar reptiles (_Labyrinthodons_) near Warwick. Palæozoic Epochs. The Permian Formation. (_Wond._ p. 533). The separation of the strata now termed _Permian_ from the _Triassic_, with which they were formerly classed, was first proposed by Sir Roderick Murchison, and is based on the fact that the fossils hitherto discovered are entirely distinct from any that occur in the Trias and subsequent formations; it is, therefore, inferred, that after the deposition of the so-called Permian strata, a complete change took place in the faunas and floras of the lands and seas, and the Trias is _at present_ regarded as the dawn of a new system of organic beings. The strata comprised in this group are variegated blue and red marls and sandstones, like those of the Triassic; magnesian or dolomitic limestones; and conglomerates more or less coloured with peroxide of iron. _Subdivisions_:-- 1. Red and white marls. 2. Yellow magnesian limestones, and dolomitic conglomerates of Yorkshire and Durham. 3. Marl-slate in thin layers, containing reptiles and fishes. The Keuper schiefer or copper-schist of Mansfeld. 4. Marls and variegated sandstones, sands, and clays.