. The ancient life-history of the earth; a comprehensive outline of the principles and leading facts of palaeontological science. Paleontology. Fig. ?]o.—Pentamerus K?nghtii. Wenlock and Ludlow. The right-hand figure shows the internal partitions of the shell. little of special interest; for though sufficiently numerous, they are rarely well preserved, and their true affinities are often un- certain. Amongst the most characteristic genera of this period may be mentioned Cardiola (fig. 71, A and C) and Pterinea ( Fig. 71.—Upper Silurian Bivalves. A, Cardiola interrupta,'W^QrAoc\i. and Ludl
. The ancient life-history of the earth; a comprehensive outline of the principles and leading facts of palaeontological science. Paleontology. Fig. ?]o.—Pentamerus K?nghtii. Wenlock and Ludlow. The right-hand figure shows the internal partitions of the shell. little of special interest; for though sufficiently numerous, they are rarely well preserved, and their true affinities are often un- certain. Amongst the most characteristic genera of this period may be mentioned Cardiola (fig. 71, A and C) and Pterinea ( Fig. 71.—Upper Silurian Bivalves. A, Cardiola interrupta,'W^QrAoc\i. and Ludlow; B, Pterinea sub/alcata, Wenlock; C, Cardiola fibrosa, Ludlow. (After Salter and M'Coy.) 71, B), though the latter survives to a much later date. The Univalves {Gasteropoda) are very numerous, and a few charac- teristic forms are here figured (fig. 72). Of these, no genus is perhaps more characteristic than Eiwmphalus (fig. 72, 3), with its flat discoidal shell, coiled up into an oblique spiral, and deeply hollowed out on one side; but examples of this group are both of older and of more modern date. Another very extensive genus, especially in America, is Platyceras (fig. 72, a and/), with its thin fragile shell—often hardly coiled up at all—its minute spire, and its widely-expanded, often sinuated mouth. The British Acroadm should probably be placed here, and the group has with reason been regarded as allied to the Violet-snails {laiithma) of the open Atlantic. The. 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 Nicholson, Henry Alleyne, 1844-1899. New York, A. L. Fowle
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Keywords: ., bookcentur, bookdecade1870, booksubjectpaleontology, bookyear1876
