Elements of geology, or, The Elements of geology, or, The ancient changes of the earth and its inhabitants as illustrated by geological monuments elementsofgeolog00lyel Year: 1868 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 subordin
Elements of geology, or, The Elements of geology, or, The ancient changes of the earth and its inhabitants as illustrated by geological monuments elementsofgeolog00lyel Year: 1868 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&'
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