. Elements of geology, or, The ancient changes of the earth and its inhabitants as illustrated by geological monuments. Geology. Oh. XYIL] UPPER GREENSAND. 331 niart to Clathraria Lyellii, Mantell, a species common to the ante- cedent Wealden period. The Pterodactyl of the Kentish chalk, above allnded to, was of gigantic dimensions, measuring 16 feet 6 inches from tip to tip of its outstretched winffs. Some of its elongated bones were at first mis- taken by able anatomists for those of birds ; of which class no osse- ous remains have as yet been derived from the white chalk, although Fossils o
. Elements of geology, or, The ancient changes of the earth and its inhabitants as illustrated by geological monuments. Geology. Oh. XYIL] UPPER GREENSAND. 331 niart to Clathraria Lyellii, Mantell, a species common to the ante- cedent Wealden period. The Pterodactyl of the Kentish chalk, above allnded to, was of gigantic dimensions, measuring 16 feet 6 inches from tip to tip of its outstretched winffs. Some of its elongated bones were at first mis- taken by able anatomists for those of birds ; of which class no osse- ous remains have as yet been derived from the white chalk, although Fossils of the Upper Greensand. Fig. 323. Fig. a. Terebrirostra lyra. } Upper Greensand. b. Same, seen in profile, f France. Ammonites RTiotomageiisu. Upper Greensand. they have been fouud (as will be seen in the annexed figures) in the Upper Greensand. Tipper Greensand (A. 4, Table, p. 314).—The lower chalk without flints passes gradually downwards, in the south of England, into an argillaceous limestone, " the chalk marl," already alluded to, in which ammonites and other cephalopoda, so rare in the higher parts of the series, appear. This marly deposit passes in its turn into beds called the Upper Greensand, containing green particles of sand of a chloritic mineral. In parts of Surrey, calcareous matter is largely intermixed, forming a stone called jirestone. In the cliffs of the southern coast of the Isle of "Wight, this upper greensand is 100 feet thick, and con- tains bands of siliceous limestone and calcareous sandstone with no- dules of chert. The Upper Greensand is regarded by Mr. Austen and Mr. D. Sharpe as a littoral deposit of the Chalk Ocean, and, therefore, contempora- neous with part of the chalk marl, and even, perhaps, with some part of the white chalk. For as the land went on sinking, and the cretace- ous sea widened its area, white mud and chloritic sand were always forming somewhere, but the line of sea-shore was perpetually varying its position
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Keywords: ., bookcentury1800, bookdecade1860, booksubjectgeology, bookyear1868
