. Elements of geology : a text-book for colleges and for the general reader. Geology. 332 PALAEOZOIC SYSTEM OF ROCKS. the coal-measures, therefore, are here found, though imperfectly devel- oped, and the coal not workable. The Carboniferous day is already dawning. Animals. In accordance with our prescribed plan, all we can do in describing Devonian animals is to touch prominent pointsâto notice what is going )out, what is coming in, some few characteristic forms, and to dwell only on what bears on evolution. Radiates.âAmong corals, the chain-corals (Halysitids) have disap- peared ; the other o
. Elements of geology : a text-book for colleges and for the general reader. Geology. 332 PALAEOZOIC SYSTEM OF ROCKS. the coal-measures, therefore, are here found, though imperfectly devel- oped, and the coal not workable. The Carboniferous day is already dawning. Animals. In accordance with our prescribed plan, all we can do in describing Devonian animals is to touch prominent pointsâto notice what is going )out, what is coming in, some few characteristic forms, and to dwell only on what bears on evolution. Radiates.âAmong corals, the chain-corals (Halysitids) have disap- peared ; the other orders continue under different species (Figs. 403- 406). Among Hydrozoa, the Graptolites are gone; among Crinoids, the Cystids are gone, but in their place the Blastoids (bud-like), those curious armless crinoids, with petalloid markings already spoken of as rare in the Silurian, become more abundant. The Crinids, or plumose- armed crinoids, continue undiminished. The Blastoids, however, are still more characteristic of the Carboniferous. We therefore defer their illustration to that period. Brachiopods.âBrachiopods are still very abundant, and still many of them of the characteristic Palaeozoic, square-shouldered type. Among. Fig. 409. FlG- 41°- Figs. Brachiopods: 407. Spirifer' fornacnia (afterâ Worthen): a. Ventral valve; b. Suture. 408. Spirifer perextensus (after Meek). 409. Orthis Livia. a, Don>al, b, Side view. 410. Strophomena rhomboidalis. spirifers, the long-winged species (Fig. 409) are very abundant and characteristic. We give a few figures of Devonian bivalves, both. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original LeConte, Joseph, 1823-1901. New York : D. Appleton and Co.
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