Our planet, its past and future; or, Lectures on geology . cribing the shape of the shell,and the other its supposed position intime. In Wisconsin, many ft)rms of trilo-biles have been discovered in it; someslabs being covered with the casts ofD,„,c,..is. ^,^gj^^_ pjg_ 2 represents one from the Piitsdani sandstone, Mazomania, Wis. The triloblte was an articulate animal covered witha thin crust, or shell; and varied in size, from that of asmall beetle to a large crab or lobster. The head, whichwas crescent-shaped, was furnished with two eyes,composed of a number of lenses lik
Our planet, its past and future; or, Lectures on geology . cribing the shape of the shell,and the other its supposed position intime. In Wisconsin, many ft)rms of trilo-biles have been discovered in it; someslabs being covered with the casts ofD,„,c,..is. ^,^gj^^_ pjg_ 2 represents one from the Piitsdani sandstone, Mazomania, Wis. The triloblte was an articulate animal covered witha thin crust, or shell; and varied in size, from that of asmall beetle to a large crab or lobster. The head, whichwas crescent-shaped, was furnished with two eyes,composed of a number of lenses like those of a dragon-fly, whicli, in many species, have been beautifully pre-served. The body was composed of many small plates,iulded over each other as they are in the tail of alobster, and divided lengthwise by two furrows into threelobes, from which the name of trilobite was given to appear to have swarmed in the early oceans as theshrimps, prawns, and crabs do now, or as the king-crabs•jn the New-Jersey coast, — animals that more nearly. LRCTURES ON K^ reseinble llic ti-ik)l)ite than any others Ajund on mirAthintic shore. Hundreds of species have heen diN-covcred; and hundreds more, doubtless, remain to hediscovered. Most of the fossil forms Ibund in the Potsdam saui]-stone aie small; but, in the geological rooms at ^I>ntre;d,tracks of what api)car to have been large crustaceans(if some kind may be seen. Some of these tracks arc inparallel lines, and not less than seven inches wide. It is not uncommon to find upon slabs of this sandstonewavy appearances, that plainly indicate ripple-marks madeon tiie shore of a shallow sea. Several species of fu-coids, or seaweeds, have been discovered in it in NewYoik and in Canada. These leafless marine plants arethe oldest types of vegetation known to have existed. The vegetable kingdom has been divided into sixclasses. The first includes the seaweeds, the lowest ofvegetables; the second, the mosses and liverwo
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