In the United States the Carboniferous is found underlying a number of areas. In Rhode Island there is a small one of highly metamor phosed rocks, in which the coal-beds have been nearly changed to anthracite. A large area ex tends from Pennsylvania southward to Alabama, and westward to Missouri and Arkansas and Texas. Along the Appalachians the prevailing rocks of this area are sandstones and shales, which contain many coal-scams and are much folded: but westward the folds die out, and limestones begin to predominate. Workable hells of coal are found in all the States of this area. In the Mississippi Valley the crinoidal limestones are important The Car boniferous section shows a variable thickness, having a maximum of nearly 8000 feet in Penn sylvania, and only 1200 to 1500 in Year Pottsville. Pa., there are twenty-five coal beds, whose aggregate thickness is 154 feet. In Alabama there are seventeen in one field. In the Western interior region, especially near the summits of the Rocky :Mountains, there are Carbonifermis strata consiiting, mostly of lime stones, with no coal. There are also scattered areas in the Great Basin region. and along the Pacific Coast and in the Arctic region. The eoal-beds are usually underlain by clay-beds, in which are sometimes found upright. roots and trunks of trees that grew in the Carbonif erous swamp.
In Europe, the coal measures of England are 3000 to 5000 feet thick, increasing even to 12,000 feet in South Wales. The Permino beds in Russia are of enormous extent, covering an area twice as large as France. Carboniferous rocks also occur in Germany, France, Belgium, and Austria. In China they extend over many thousand square miles as vast tablelands, and contain perhaps the richest coal deposits of the world. They are also extensively developed in India, and in Australia and Africa.
Both animal and vegetable remains are alum dant in the Carboniferous, and are in many well preserved. The abundance of the latter is easily understood when we remember that eoal has been formed by the accumulation of vege table matter, and we consequently find the plant fossils in the coal itself, as well as the inclos ing beds. There is a great uniformity of cluir acter in the plant life, the same genera and often the same species occurring in v:idely separated regions. About 2000 species are known which, with the exception of a few plants of doubtful relationship, may he referred to the following families: Eqnisetace.e. lyeopods, conifera, and ferns. Of the equisetaceze, the most abundant genus was Calamites (q.v.), which included sev eral species of large. tapering, reed-like plants that apparently flourished on the borders of the coal swamps. The lycopods were represented by the Sigillaria (q.v.) and the Lepidodendron (q.v.), closely related genera that are believed to have furnished a large part of the material for the formation of coal. The Sigillaria had gently tapering, fluted stems, which grew to a height of 50 feet or more, and had a diameter of 5 feet. The bases of the trunks, with their radiating roots, are often found in the clay that underlies the coal-seams, and for a long time they were supposed to be a distinct species. (See STIGMARIA.) The Lepidodendron bore a great resemblance in structure and appearance to the club-moss of the present day, but it attained gigantic proportions. Conifers were probably abundant in Carboniferous times: they differed widely. however, from existing conifers, and bore nut-like fruits, which have been frequently pre served. (See TRIGONOCARPUS.) The genus Clor daites, which appears to have been very abun dant, is classed by some botanists with the co nifers; by others, with the cycads. The fern family was represented by a large variety of specie., some of which were tree-ferns. The most common forms were Sphenopteris, Cyclop teris. Neuropteris, odontopteris. and Peeopteris. The animal remains of the Carboniferous system are both numerous and well preserved, but they are found in abundance in the Sub Carboniferous limestones. Corals and crinoids are numerous, both as regards individuals and species, and in places constitute great thicknesses of rock. :More than 050 specie; of crinoids have
been described from the Sub-Carboniferous of America alone. Among the brachiopods, Pro ductus, Spirifer, and Chonetes are most numer ous, while are represented by cephalo pods. gastropods, and lamellibranchs, some spe cies of which pass out of existence at the close of the period. Trilobites arc present. but not in such variety as in the earlier Paleozoic times, and they diminish rapidly toward the end. Crustaceans are abundant, especially Beyrichia and Estheria, and they show a rapid develop ment. Insects appear to have nourished in great numbers: the known varieties include spiders, dragon-flies, grasshoppers, and cock roaches. Among fishes, the ganoids and selaehi an- are represented. The ganoids, having their entire surface covered with scales, were limner some of them inhabited shallow water near the shore. and fed can crustaceans and shellfish, for which they had a formidable appa ratus of conical teeth of a very complicated structure. Others were inhabitants of deep water, and were more powerful and predaceous and more rapid in their movements. Their jaws were produced into a long snout, like the croco dile of the Ganges, and armed with a double series of enormous teeth, which were sometimes as much as 4 inches long by 2 inches broad, as in Alegalichthys (q.v.). dimensions rarely attained even by the largest known reptiles. Associated with these were a great number of sharks belong ing to the Cestraciontidce, a family of which we have only a single living representative. (See ('EsraActoNT.) They had a long. bony spine, to strengthen the dorsal tin, aml this enabled them to turn speedily in the water, as they re quired to do in seizing their prey. These spines are often found fossil. The only remains referred to a higher division of the animal king dom yet found belong to the saurian Stego eephaHa (q.v.). The Carboniferous also con tins the first traces of amphibians. Of these. only footprints were found in the Lower Carbon iferous, but in the coal measures the actual bones were met with. The Permian beds of both Europe and America have furnished the first reptilian remains; these belonged to the tribe Rhyncoce phalia, which is now nearly extinct.
The alternation of rocks of different character show that oscillation"; of the land surface must have been extensive and long continued. though not violent. Thus the great beds of coal indicate a period of inland shallow water in which swampy conditions existed. These must have c(littinned for a long period, for the coal-beds arc often very thick, and it has been calculated that an eighth of an inch of coal means at least one inch of plant accumulation. That these swamp areas became at times to some depth, due to the sinking of the land, is indicated by the pressure of limestone-lIeds over them, The (di mate that predominated during the Carbonifer ons was one of warmth and moisture, with the percentage of carbon dioxide in the atmosphere smnewhat greater than it is now, but not sarily excessive.
The great importance of the economic min erals in the Carboniferous has had much to do with our extensive knowledge t f it. It is esti mated that there are 400,000 square miles of the earth's surface underlain by productive coal fields. ('oAL.) In addition to the eoal de posits, many other useful minerals are found in the Carboniferous of the United States. The clay-beds associated with the coal-seams afford valuable supplies of tire-clays, pottery-clays. and brick-clays: iron ores are found in Pennsylvania. Kentucky. and Ohio. Building-stones are quar ried in the Carboniferous of many States. the sandstones of Berea. Ohio, being specially impor tant. The Lower Carboniferous strata furnish salt in Ohio. and West Virginia. and Elm. ore in :Missouri. Kansas. and Arkansas.
Consult: Dana. Manual of Geology (Ne• York, 1S113) ; Text-book of Gcoiogy (London, IS93) ; 1 ailed`'tales Geological Surrey Bulletin No..80 (Washington, 1891). See Co..i.; GEM. CLA y ; Iftos.