. Elements of geology, or, The ancient changes of the earth and its inhabitants as illustrated by geological monuments. Geology. Ch. XXin.] FOSSIL FISH OF FERMIAN MARL-SLATE. 461 type. Some of this same tribe of shells, such as Athyris Roissyi, allied to Terebratida, are specifically the same as fossils of the car- boniferous rocks. Avicida, Area, and Schizodus (see above, fig. 492), and other lamellibranchiate bibalves, are abundant, but spiral uni- valves are very rare. The compact limestone (No. 4) also contains organic remains, espe- cially bryozoa, and is intimately connected with the pre
. Elements of geology, or, The ancient changes of the earth and its inhabitants as illustrated by geological monuments. Geology. Ch. XXin.] FOSSIL FISH OF FERMIAN MARL-SLATE. 461 type. Some of this same tribe of shells, such as Athyris Roissyi, allied to Terebratida, are specifically the same as fossils of the car- boniferous rocks. Avicida, Area, and Schizodus (see above, fig. 492), and other lamellibranchiate bibalves, are abundant, but spiral uni- valves are very rare. The compact limestone (No. 4) also contains organic remains, espe- cially bryozoa, and is intimately connected with the preceding. Be- neath it lies the marl-slate (No. 5), which consists of hard, calcareous shales, marl-slate, and thin-bedded limestones. At East ThicMey, in Durham, where it is thirty feet thick, this slate has yielded many fine specimens of fossil fish of the genera Palceoniscus, Pygopterus, Ccela- canthus, and Platysomus, genera which are all found in the coal- measures of the Carboniferous epoch, and which therefore, says Mr. King, probably lived at no great distance from the shore. But the Permian species are peculiar, and, for the most part, identical with those found in the marl-slate or copper-slate of Thuringia. Fig. Ecstored outline of a fish of the genus Palceoniscus, Agass. Palceothrissum, Blainville. The PalcBoniscus above mentioned belongs to that division of fishes which M. Agassiz has called " Heterocercal," which have their tails unequally bilobate, like the recent shark and sturgeon, and the verte- bral column running along the upper caudal lobe. (See fig. 500.) Fig. 500. Fig. 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
