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MILLSTONE GRIT,
600 feet thick.

CARBONIFEROUS, or
MOUNTAIN LIME-
STONE, 1800 feet
thick.

Sandstone, Shale, and Conglomerate, Shale and thin seams of coal-coal plants. [ Limestone and flagstone abounding in corals and marine shells; with layers and nodules of chert. Ores of copper, zinc, lead, barytes, and fluor spar. Limestone, with innumerable shells-spirifer, goniatite, orthoceratite, bellerophon, &c.

Varieties of black, bluish gray, and variegated marbles.

This system of rocks is developed in Ireland, France, Belgium, Spain, Russia, China, and America.

209. The organic remains of this period are of marine, fresh-water, and terrestrial origin. Ichthyolites-teeth, fins, Fig. 105.

Fossil Fish, Ohio.

spines, scales and coprolites of fishes, as well as the entire fish abound. The fishes belonged to the ganoid and placoid orders-sauroid-and in some instances, as in the Megalichthys, were of gigantic size.

Of the crustacea, the trilobites were still the principal representatives. Shell fish were very numerous and large; representatives of all the orders-multivalve and univalve, single-chambered and many chambered occur aggregated in masses, as they lived gregariously. Among the bivalves the Terebratula, Spirifer, and Inoceramus; and among uni

valves, the Goniatite, Orthoceratite, Bellerophon, Euomphalus and Ammonite, were frequently recurring genera.

Fig. 106.

A few spe

cimens of Co

leopterous insects-beetles, and of the scor

[graphic]

Pentacrinite.

pion have been

found in this

series. Of the

radiata, the

crinoid or encrinite family, of which the Pentacrinite is a member were most abundant; (§223) some of the limestones of

this group are composed almost exclu

sively of their remains, and are designated encrinal. The coral polyps formed extensive reefs. The marine fossils

of this period

are mostly confined to the lowest member of the systemthe carboniferous limestone, in which they are estimated to form at least three-fourths of the whole mass.

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210. In the organic remains of the upper members of the system—the coal-measures—the great abundance of vegetable fossils, indicating a most luxuriant growth of land plants, is the most striking feature. That coal is of vegetable origin, is abundantly proved by the organic structure which can be seen in it with the aid of a microscope. The Plumb differences observed in coals may be due to their origin from different plants. The coal occurs in strata of sandstones and shales, with intervening layers of ironstone and limestone, some of which appear to be of fresh-water, and some of marine origin. The beds of coal vary in thickness from the fraction of an inch to thirty feet; in one of the English coal-energy fields their aggregate thickness is one hundred and fifty feet. Both quar The number of beds also varies, sometimes exceding one hundred; the central beds are usually the thickest and purest... The coal-measures are often designated as basins because they present themselves in troughs or basin-shaped cavities.

211. The shales which underlie and overlie the beds of coal contain the best specimens of the coal plants, which occur between every succession of laminæ. The newly exposed roof of a coal mine presents a beautiful display of interlacing stems and leaves. "The most elaborate imitations of living foliage on the painted ceilings of Italian palaces bear no comparison with the beauteous profusion of extinct vegetable forms, with which the galleries of these instructive coal-mines are overhung. The roof is covered as with a canopy of gorgeous tapestry, enriched with festoons of most graceful foliage flung in wild irregular profusion over every portion of its surface. The effect is

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heightened by the contrast of the coal black color of these vegetables, with the light ground work of the rock to which they are attached. The spectator feels transported, as if by enchantment into the forests of another world; he beholds trees of form and character now unknown upon the surface of the earth, presented to his senses almost in the beauty and vigor of their primeval life; their scaly stems and bending branches, with their delicate foliage are all spread forth before him, little impaired by the lapse of indefinite ages, and bearing faithful records of extinct systems of vegetation, which began and terminated in times of which these relics are the infallible historians. Such are the grand natural herbaria, wherein these ancient remains of the vegetable kingdom are preserved in a state of integrity little short of their living perfection, under conditions of our planet which exist no more."*

212. Several hundred species of coal plants have been discovered which are allied in their generic characters to the ferns, canes, pines, cacti &c., but as species, became extinct $16.5p before or at the close of the carboniferous period. The Lp13y same species are mostly found in coal beds in Europe, Australia, the United States, and in Melville Island in 75° north latitude. The plants of the present period which most resemble the coal plants, live within the tropics, and are very much smaller than the corresponding members of the Flora of the carboniferous era. One of the most common fossils of the coal strata is the calamite, so called from its reed-like appearance. It was cylindrical, gradually tapering to a point, and frequently curved at the extremity; ribbed or furrowed longitudinally, and surrounded at intervals by horizontal rings or articulations. It was a branching plant with a hollow stem, woody tissue, and distinct bark. It has

* Dr. Buckland's Bridgewater Treatise, p. 458.

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been supposed analogous to the equisetum or horse-tail of the present day, but was much larger, attaining the size of fourteen inches diameter.

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