A guide to the fossil invertebrate animals in the Department of geology and palaeontology in the British museum (Natural history) . of the earths crust from a great depth. In therocks of Tertiary age, such dried oozes are known as Tripolistone {KieselgvJir), and occur in many parts of the Eadiolaria from several of them were described byEhrenberg (1838-1873) under the name Polycistines. On Wall-casethe bottom shelf of Wall-case 9b, in the corner, is a largecore of the Miocene radiolarian marl of Barbados, from which 28 GUIDE TO THE FOSSIL INVEKTEBEATE ANIMALS. Gallery X. 400 species
A guide to the fossil invertebrate animals in the Department of geology and palaeontology in the British museum (Natural history) . of the earths crust from a great depth. In therocks of Tertiary age, such dried oozes are known as Tripolistone {KieselgvJir), and occur in many parts of the Eadiolaria from several of them were described byEhrenberg (1838-1873) under the name Polycistines. On Wall-casethe bottom shelf of Wall-case 9b, in the corner, is a largecore of the Miocene radiolarian marl of Barbados, from which 28 GUIDE TO THE FOSSIL INVEKTEBEATE ANIMALS. Gallery X. 400 species have been described; and a glass slide with^^^15^^^^ Eadiolaria from a similar rock in Cuba, with illustrativedrawings, is shown in Table-case 15. In these soft Cainozoicdeposits many Eadiolaria belong to species still living, andtheir skeletons are as perfect as those in modern ooze. Inthe Mesozoic and Palaeozoic rocks, however, the oozes havebeen changed, by pressure, or heat, or the percolation ofwater, into quartzites, cherts, and flinty shales, so different inappearance that it is not long since their radiolarian origin. Fig. 7.—Radiolarian rock from the Lower Culm at Carzantic Quarry, nearLaunceston, Cornwall. Photograph of a thin section as seen underthe microscope. Enlarged about 32 diameters. (From paper byHinde and Fox in the Quarterly Journal of the Geological Society, \ vol. li; by permission of the Council.) (See Table-case 15.) was discovered. This was done by examining thin sectionsof the rock under the microscope, when in some, less alteredthan most, the skeletons were recognised. Usually, however,the skeletons themselves have been dissolved, and there canonly be detected spots of transparent silica formerly depositedin the cavity of the skeleton. In this way Eadiolaria havebeen found in siliceous rocks as far back as to the Cambrianperiod. In illustration of this are exhibited specimens of theTable-case radiolarian chert and shale of Carboniferous age, found
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Keywords: ., bookauthorbr, bookcentury1900, bookdecade1900, booksubjectfossils
