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Thus, near Clifton, on the Avon, as well as at numerous places around the Bristol basin from the Mendip Hills to Tortworth, there is a celebrated "bone-bed," almost entirely made up of ichthyolites. It occurs at the base of the Lower Limestone shales immediately resting upon the passage beds of the Old Red Sandstone.
Until 1859 there was no example of a fossil fish older than the bone-bed of the Upper Ludlow, but in that year a specimen of Pteraspis was found at Church Hill, near Leintwardine, in Shropshire, by Mr.
These fish belong to the genera Acrodus, Hybodus, Gyrolepis, and Saurichthys. Hybodus plicatilis, Agassiz. Teeth. Saurichthys apicalis, Agassiz. Tooth; natural size and magnified. Gyrolepis tenuistriatus, Agassiz. Scale; natural size and magnified. Remains of saurians, Plesiosaurus among others, have also been found in the bone-bed, and plates of an Encrinus.
It has been called the Trias by German writers, or the Triple Group, because it is separable into three distinct formations, called the "Keuper," the "Muschelkalk," and the "Bunter-sandstein." In certain grey indurated marls below the bone-bed Mr.
The dorsal position of the siphuncle, however, clearly distinguishes the Goniatite from the Nautilus, and proves it to have belonged to the family of the Ammonites, from which, indeed, some authors do not believe it to be generically distinct. Psammodus porosus, Agassiz. Bone-bed, Mountain Limestone. Cochliodus contortus, Agassiz. Bone-bed, Mountain Limestone.
At the base of the Downton sandstones there occurs a bone-bed which deserves especial notice as affording the most ancient example of fossil fish occurring in any considerable quantity.
Scudder, introduces us to the sounds of the Devonian woods, bringing before our imagination the trill and hum of insect life that enlivened the solitudes of these strange old forests. Classification of the Silurian Rocks. Ludlow Formation and Fossils. Bone-bed of the Upper Ludlow. Lower Ludlow Shales with Pentamerus. Oldest known Remains of fossil Fish.
BRITISH. Bituminous schists of Gamrie, Caithness, etc., with numerous fish. BRITISH. Arbroath paving-stones, with Cephalaspis and Pterygotus. FOREIGN. Oriskany sandstone of Western Canada and New York. BRITISH. Upper Ludlow formation, Downton sandstone, with bone-bed. FOREIGN. Niagara limestone, with Calymene, Homalonotus, etc. BRITISH. Bala and Caradoc beds.
Wonderful accumulations of fish remains are found at the base of the system, in the bone-bed of the Bristol coal-field, as well as in a similar bed at Armagh. Many fishes were armed with powerful conical teeth, but the majority, like the existing Port Jackson shark, were possessed of massive palates, suited in some cases for crushing, and in others for cutting. Archegosaurus minor.
The jaws are greatly elongated so as to give a beak-like form in all but this region is specially long and narrow in the "beaked whales" known to zoologists by the name Ziphius, in which it consists of a solid piece of ivory-like bone, which we find in a fossil state in the bone-bed of the Suffolk Crag.
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