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ARACHNIDA (Spiders)-Spiders, Scorpions, Mites.
2. VERMES, or Worms Proper.
II. MOLLUSCA, subdivided into Mollusca and Molluscoida.
1. Mollusca, or Shell-fish Proper. CEPHALOPODA (Head-footed)—Cuttle-fish, Octopus, Calamary, Nautilus. PTEROPODA (Wing-footed)—Clio, Hyalæa. GASTEROPODA (Belly-footed)—Snails, Slugs, Whelks, Cowries. ACEPHALA (Headless)—Oysters, Mussels, Cockles, Shipworms. BRACHIOPODA (Arm-footed)— Terebratula, Lingula.
2. MOLLUSCOIDA, or Mollusc-like Animals. TUNICATA (Coated, but Shell-less) — 3 biphora:
\_Biphora, Simple and Compound
? Ascidians. Polyzoa (Compound animals))
Flustra, Eschara, Plumatella, &c. BRYOZOA (Moss-like-animals) S
III. RADIATA, or ZOOPHYTES-Ray-like Animals.
IV. PROTOZOA, or LOWEST-LIFE—Globular Animals.
Such are the leading facts connected with the nature, history, and arrangement of fossils. Much more might have been stated respecting the positions in which they occur and the geographical conditions which they thereby indicate, and a more detailed account might have been given of the chemical theories of petrifaction ; but enough has been mentioned to convey to the reader a fair idea of what fossils really are,* how they are formed, and how indispensable their study is to the right interpretation of the history of our planet. With this preliminary knowledge he will peruse with greater zest and intelligence the Sketches that follow; and be better able to trace through the ascending stages of time that plan of vital development, the elucidation of which has conferred on modern geology its highest interest and most enduring attraction.
Nor is it Geology alone that has benefited by the discoveries of the palæontologist. Botany and Zoology have also acquired new interest, and the whole study of Life assumed a broader and more philosophical bearing. Restricted to existing forms, the biologist was often perplexed by anomalies he could not solve, and for want of connections he could not trace; but now that Palæontology has revealed its myriad forms, and exhibited a Scheme of Life ever ramifying, yet ever interblending in its remotest ramifications, a clearer and steadier light has been thrown across the path of its investigations. Even to the ordinary observer of nature, how much more exalted the conceptions of life which the science of palæontology imparts ! How
* Fossils are sometimes arranged into the following classes :--First, the actual substance; secondly, the substance replaced by other substances; thirdly, the cast or mould of the substance and this may be either of the hard or of the soft substance ; and, fourthly, those fossils which are now generally called physiological impressions, such as footprints, being certain evidence of the animal having been there. Under whatever class they may be arranged, their preservation will depend partly on their own composition, partly on the nature of the stratum in which they are imbedded, and partly on the chemical changes to which that stratum may have been subsequently subjected. The investigation of these particulars, however, belongs more to the professed palæontologist than to the readers of general geology.
marvellous that, numerous and varied as are the plants and animals of the present day, they form but the merest fraction of those that have successively adorned the earth's surface, each succeeding age being characterised by its own special forms, ascending and still ascending in variety and complexity, yet all interwoven into one grand and harmonious Life-system !
THE OLD RED SANDSTONE.
INTEREST ATTACHED TO THE SYSTEM FROM THE LABOURS OF AGASSIZ,
HUGH MILLER, AND OTHERS—ITS POSITION IN WORLD-HISTORY NATURE OF ITS STRATA-HOW FORMED-LOWER, MIDDLE, AND UPPER FORMATIONS-TERRAQUEOUS ASPECTS OF THE PERIOD-ITS FLORA AND FAUNA--GIGANTIC CRUSTACEA – VARIED AND ABUNDANT FISH-REMAINS-GEOGRAPHICAL OR EXTERNAL CONDITIONS OF THE OLD RED ERA-ECONOMIC PRODUCTS DERIVED FROM THE SYSTEM-GENERAL REVIEW.
THERE is the ring of antiquity in the very title of our subject, and yet old as the Old Red Sandstone may be, it is younger by unnumbered ages than the Laurentian, the Cambrian, and the Silurian. These earlier sediments were converted into hard and crystalline strata, and upheaved into dry land, long before it was deposited, and in many instances they formed the hills and precipices from which its materials were derived. Its place in the earth's chronology will be seen at a glance from the accompanying tabulation ; but its interest as a formation arises less from its antiquity than from the fact of its being the first in which vertebrate remains decidedly occur, and from the circumstance that its history has been rendered classical by the labours of some of our leading geologists. Hugh Miller's • Old Red Sandstone,' Agassiz' Monograph of its fossil fishes, the investigations of De la Beche, Murchison, Pander, Huxley, the American States Surveyors, and others, have all contributed to this result; and during the last thirty years there are few systems whose names, at least, have been more familiar to the ordinary,reader. But since Agassiz elaborated his monograph, and Miller penned his sketches, more extensive information has been obtained, and it is the object of the present chapter to display that newer knowledge in an intelligible and attractive form.
Arranging the rock-formations of the crust in chronological order, it will be seen that the Old Red Sandstone holds a middle place among the palæozoic or primeval :
Quaternary or Recent, . . 1 CAINOZOIC.
It does not belong to the very oldest, whose rocks have been rendered crystalline by metamorphism, and whose fossils have been sorely obliterated, but it is still very ancient, and hence the interest that attaches to its old-world forms, the outlines of which and their habits of life the pen of the palæontologist can for the most part restore. The composition and origin of its strata are, generally speaking, of easy determination. Conglomerates that were once pebble and shingle beaches; sandstones and flagstones resulting from shore-formed sands; concretionary and coralline limestones chiefly of animal origin ; and shales and marlstones, the consolidated muds of the deeper waters. Here and there we have bituminous shales, partly of animal and partly of vegetable impregnation; and at still wider in