PERMIAN, MAGNESIAN • LIMESTONE, or Dias group, is the lower division of the new red sandstone rocks, 'which were separated, chiefly on paleontological grounds, from the upper portion, and being, in 1841. without a collective were called Permian by Murchison, because he found them largely developed in that portion of Russia which composed the ancient kingdom .of Termia, or Biarmia. The name magne 'sian limestone is given to them 'because of the predominant deposit; and dins has been proposed by some German geologists, to correspond with trias, the name universally accepted for the upper section of the net' red sandstone series.
The Permian strata occupy in Russia an area twice the size of France, and contain an abundant and varied suite of fossils. They are also largely developed in Germany, and as they have been there carefully studied and described by numerous geologists, the rocks of that country may be considered as the types of the group. They have been thus grouped: 1. Bunterschiefer. 2. Zechstein, 3. Kupferschiefer or Merge]. 4. Rothe-todt liegende.
The bunterschiefer consists of red and mottled marl and sandstone, which have been separated from the triassic bunter sandstein, because of the occurrence in them of fossils which have a paleozoic facies. The zechstein is chiefly a compact limestone with beds of colored clays, and cellular magnesia(' limestone. The well-known stinkstein belongs to this series; it is a dark-colored and highly bituminous limestone, which gives out an offensive odor when struck or rubbed. The name zechstein (literally, rninestone) was given to these beds, because they must be mined or cut through to reach the kupfer schiefer below. This latter is a marl slate, richly impregnated with copper pyrites, for which it was extensively wrought. It contains numerous beautifully preserved fossil fish belonging to the genera palmaiscus. cmlacanthus, platysorus, etc. The strange name of rothe-todtliegende (red dead-layers) was given to a large deposit of red sandstone and conglomerate, by the miners, because the copper obtained from the beds above died out when they reached these red rocks.
The succession of rocks given by Murchison as occurring in Permia are easily co-related with those of Germany. They are (1). conglomerates and sandstones, contain ing the remains of plants; (2), red sandstones and shales, with copper ore and vegetable remains; and (3), sandstones, grits, and fossilifcrous limestones, with interstratified beds of marl and gypsum, the marls occasionally containing plants and also seams of impure coal.
In England the Permian rocks are somewhat extensively developed in Durham, where they have been described by Sedgwick and King. From this county they continue in a narrow strip bordering the carboniferous beds clown the center of England until they are lost near Nottingham. In Cheshire, Shropshire, Stafford, and Warwick, they underlie the salt-bearing triassic rocks. The Durham strata are grouped as follows: 1. Concretionary and amorphous limestone =Bunterschiefer.
2. Brecciated and pseudo-brecciated limestone 3. Fossiliferous ......... '''' • " ' =Zechstein.
4. Compact limestone 5. Marl slate..... ' ) —Kupterschiefer.
6. Inferior various-colored sandstone —Rothe-todtliegende.
The fractured bones and teeth of saurians found in the basement bed of the sixth group were considered the earliest evidence of the existence of reptiles until the discov ery of the arehegosaurus in thobarboniferous rocks.
The known organic remains of this period are neither remarkable nor abundant. Many paleozoic forms became extinct within this period; among them are the remark able sigillaria and the neuropteris of the coal-beds, the well-known brachiopod, producta, and several genera of heterocercal-tailed fish. Some new forms appear, the most impor tant of which are the. labyrinthodont reptiles, which, though• beginning in the upper carboniferous beds, increase in number in the Permian, and reach their maximum devel opment in the succeeding triassic group.