Coal; its history and uses . ersists from the Carboniferous through thePermian to the Triassic period; it is represented by onegenus in the Oolite, and by two in the Chalk, and thelatest survivors retain all the features which define thegroup at its first appearance. The Artfhipterygian Ganoidsdescribed above exhibit a succession even more prolonged,and extending from the palaeozoic to the modern period. Another important section of the Coal Measure Ganoids includes the genera Palseoniscus ^ and Platysomus. Palseoniscus has been mnoh split up of late, and some writers now CHAP. IV. ANIMALS OF
Coal; its history and uses . ersists from the Carboniferous through thePermian to the Triassic period; it is represented by onegenus in the Oolite, and by two in the Chalk, and thelatest survivors retain all the features which define thegroup at its first appearance. The Artfhipterygian Ganoidsdescribed above exhibit a succession even more prolonged,and extending from the palaeozoic to the modern period. Another important section of the Coal Measure Ganoids includes the genera Palseoniscus ^ and Platysomus. Palseoniscus has been mnoh split up of late, and some writers now CHAP. IV. ANIMALS OF THE COAL MEASURES. 149 The first is of slender form ; the second flat, and very deepin the side. In both the scales are enamelled, rhombic,and strongly articulated, usually by spine and socket, tothose above, and by keel and gutter to those in the samerow. The tail is heterocercal (p. 143), and there are noscales upon the surface of the fins. The gape of themouth is very extensive. No jugular plates are present. •Tn- Fig, 29. Side view of Skull of Salmon. Srs. Jt. Brauchiostegal Bays(After Parker). but the gill-slit is bordered, as in most fishes where itoccurs, by a flexible valve of many overlapping brauchio-stegal rays, which closes against the clavicular arch, likea door upon its sill. The vertebral column is notochordal(p. 121), and there appear to be no ribs. Each fin bearsupon its fore edge a row of pointed overlapping scales(fulcra). The teeth are slender, conical, and usuallyminute, larger ones standing up at short and regular confine the name to a few species whicli occur only in Permian is done, however, ou the ground of minute diflferences, whose systematicvalue is very douhtful. 150 COAL. distances. Nearly every word of this description alsoapplies to Lepidosteus, a recent North American Ganoid,whicli differs mainly in the complete ossification of itsvertehrse, and the Palseoniscidse are hence pretty generallyregarded as forerunners of the Lepid
Size: 1734px × 1441px
Photo credit: © The Reading Room / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookcentury1800, bookdecade1870, bookpublisherlo, booksubjectcoal
