Permian System, so named by Murchison from the kingdom of Perm in Russia, where it occupies an area twice the size of France, rests upon the Carboniferous system, conformably in Bohemia, unconformably in England. In Germany, where it is well developed, it is called Dgas, from having two main divisions. It varies considerably in the mineral character and relative thickness of its different members, but is mainly a great series of red sandstones, sometimes containing brecciated conglomerates, and magnesian limestone. Its chief outcrop in England is a narrowband extending due north and south from the neighbourhood of Nottingham, east of the Derbyshire and Yorkshire and of the Newcastle coal-fields, along which line the Magnesian Limestone presents a scarped edge to the west. The subdivisions of the system in England and Germany are: -
England. Germany. St. Bees' Sandstone, with Bunter-Schiefer (variegated gypsum. shales). Magnesian Limestone. Zechstein (mine-stone). Marl Slate. Kupfer - Schiefer (copper slates). Penrith, or Lower Red, Sand- Rothtodtliegende (red dead - stone, with brockrams. i.e. non-metalliferous - layers). The Lower Red Sandstone is 3,000 feet thick near Penrith, Cumberland, but only 250 feet in the east of England. It contains beds of breccia known as hrochrams, containing large ice-scratched stones derived from the older rocks of the Welsh mountains. The Marl-slate is a thin bed of brown shale, chiefly seen in Durham, representing the bituminous copper-bearing bed of the Harz Mountains. The Magnesian Limestone, 600 feet thick, occurs chiefly in the eastern area, where .it has yielded the building-stone for York Minster and the Houses of Parliament. The St. Bees' Sandstone, 600 feet thick in Cumberland, is far less to the east, where it passes conformably up into the Trias. Fossils are few in the Permian, but are Palaeozoic in type, the plants belonging mainly to Carboniferous genera, as also do the brachiopods. The polyzoan Fenestella retiformis, the brachiopod Productns horridus, the fish Platysomus and Palcconiscus, and the lizard Proterosaurus, in the Marl-slate, are characteristic. Labyrinthodont footprints occur in the Penrith Sandstone, near Dumfries. Permian conditions have been compared to those of the Caspian Sea at present, many species being dwarfed as if by unsuitable surroundings, such as cold or intensely saline waters.