W R Brooks A Brief Treatise of Geology

ISBN 13: 9781236768094

A Brief Treatise of Geology

9781236768094: A Brief Treatise of Geology
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This historic book may have numerous typos and missing text. Purchasers can usually download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1884 edition. Excerpt: ...as the first specimen of this great class. 24g.--3. Annuloida. Echinoderms. A few fragments of encrimltes are found in the Calciferous, but a considerable number of species have been discovered in the Chazy. The order Crin0idea(encri11ites) is divided into three principal families: Cystoideae, Blastoideae and Crinoideae. The C'rin0ide0e-had five principal arms, more or less branched, and usually long stems. The Blast0ids=bud-like, had no arms, but instead five regions on the box or body of perforated plates, like the sea urchin. The C_2/st0ids'----"ibladder-like, had either no arms, or one or two, and a short usually tapering, stem. The Crinoids were more abundant FOSSILB or THE csusnun PERIOD. 118 in Silurian and Devonian times, and one or two species exist at present. The blastoids were exceedingly numerous in the Subcarboniferous period which was an age of encrinites. The cystoids all perished in the Silurian. The encrinites of the Canadian appear to be blastoids or eystoids. The bodies of all encrinites are composed of small polygonal plates, and the stems and arms of small, short, or flat circular joints and there was nothing but the living tissue to hold these joints and plates together. So that when dead and the tissues decayed, they naturally fell apart and were scattered, unless they were allowed to remain perfectly undisturbed until they were buried up. So, while encrinite joints are the commonest of fossils it is comparatively rare to find an entire head, and still more rare to find an entire encrinite with head and stem coinplete. The first and oldest Star fish, Stenaster, appears in Quebec rocks in Newfoundland. The star fish are echinoderms as well as the crinoids. 250.--4. Annulosa. This great subkingdom is still...

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