. Elements of geology, or, The ancient changes of the earth and its inhabitants as illustrated by geological monuments. Geology. Ch. XXYIL] LOWER LUDLOW SHALE. 555 bites, agreeing specifically with those of the subjacent Wenlock lime- stone, that it is scarcely distinguishable from it by its fossils alone. Nevertheless, many of the organic remains are common to the Aymes- try limestone and the Upper Ludlow, and several of these are not found in the Wenlock.'* According to Mr. Lightbody, the Aymestry limestones should be considered as subordinate to the Lower Ludlow shales next to be men- tione
. Elements of geology, or, The ancient changes of the earth and its inhabitants as illustrated by geological monuments. Geology. Ch. XXYIL] LOWER LUDLOW SHALE. 555 bites, agreeing specifically with those of the subjacent Wenlock lime- stone, that it is scarcely distinguishable from it by its fossils alone. Nevertheless, many of the organic remains are common to the Aymes- try limestone and the Upper Ludlow, and several of these are not found in the Wenlock.'* According to Mr. Lightbody, the Aymestry limestones should be considered as subordinate to the Lower Ludlow shales next to be men- tioned, as in some places these shales with their characteristic fossils occur both above and below b. Lower Ludlow Shale.—This mass is a dark gray argillaceous de- posit, containing, among other fossils, many large chambered shells of genera scarcely known in newer rocks, as the Phragmoceras of Brod- erip, and the Trochoceras of Barrande (see figs. 628, 629). The latter is partly straight and partly convoluted in a very flat spire. The Orthoceras Ludense (fig. 630), as well as the cephalopod last mentioned, is almost peculiar to this member of the series. Tig. 629. *m&'. 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 Lyell, Charles, Sir, 1797-1875. New York, D. Appleton and co.
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Keywords: ., bookcentury1800, bookdecade1860, booksubjectgeology, bookyear1868
