Abstract
On some Fossil Fish Remains found in the Ufipir Beds of the Yoredale Series at Leyburn, in Yorkshire, by James W. Davis, F.G.S.—The red limestone forms the upper part of the main limestone of Phillips, being separated from it by only one foot of shale or plate. It is about 100 feet below the millstone grits, the intermediate beds being composed of grits and shales with one bed of limestone about 16 or 18 feet thick. A peculiar aggregation of fish remains has been discovered in the red beds by Mr. Wm. Horne of Leyburn, They comprise nearly forty species, the majority of which are peculiar to the beds; others like Cladodus and Petalodus are common to the Mountain Limestone, and do not appear to differ either in size or otherwise from those of the lower massive limestone. The representatives of the genera Psamodus, Cochliodus, and Polyrhizodus, which are found abundantly in the lower limestone, and are of great size and importance, are in this locality comparatively small and rare, and appear to indicate that the fishes they represent were gradually becoming extinct. Their representatives are not known to occur in the superimposed Millstone Grits either in this locality or any other. There are in addition species of Megalichthys and Pleurodus, which are characteristic of the coal measures. The presence of so varied a fauna naturally leads to the inference that the circumstances under which they existed were not those usually characteristic of the aggregation of limestones, but rather indicate a shallow or shore deposit with occasional influxes of fresh water. Megalichthys and Pleurodus are fishes which in the coal measures probably lived in fresh or brackish water; and though they may have been adapted to exist in marine conditions, the occurrence of beds of sand and shale intercalated with the thin limestones of the Yoredales evidently shows the proximity of land, and it is probable that they were carried to their present position by rivers, and there deposited with the marine forms with which they are associated. The supposition that the water was brackish may account for the small size of some of the genera already mentioned and their final extinction in the grits and shales which succeed the limestone. The great fishes whose remains are found in the lower lime stone, represented by Ctenacanthus, Orthacanthus, and others, are absent, the only species hitherto found being those of the curious Cladcuanthus and Physonemus.
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The British Associaton: Section C—Geology . Nature 28, 577–583 (1883). https://doi.org/10.1038/028577b0
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DOI: https://doi.org/10.1038/028577b0