File:A guide to the fossil invertebrate animals in the Department of geology and palaeontology in the British museum (Natural history) (1907) (14756448336).jpg

Identifier: guidetofossilinv00brit (find matches)
Title: A guide to the fossil invertebrate animals in the Department of geology and palaeontology in the British museum (Natural history)
Year: 1907 (1900s)
Authors: British Museum (Natural History). Dept. of Geology Bather, Francis Arthur, 1863-
Subjects: Fossils
Publisher: London, Printed by order of the Trustees
Contributing Library: Smithsonian Libraries
Digitizing Sponsor: Biodiversity Heritage Library

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d in several distinctgenera. In some the earlier coils are close, but the lastformed part of the shell is less close, as in the SilurianOphidioceras (Fig. 92 a), or even straight, as though unwound,as in the Ordovician Lituites. In these two genera the shellaperture is contracted. In Trochoceras also the shell is notclosely coiled, its special feature, however, is that the coilsare not in one plane, but rise in a spire, something like asnail-shell. Beginning in the Cambrian, this genus lasts toDevonian times, but is most abundant in the Silurian rocksof Bohemia, England, and the United States. Trocholites, anOrdovician genus from North America, Europe, and India, M 162 GUIDE TO THE FOSSIL INVEETEBEATE ANIMALS. Gallery has three or four whorls closely coiled in one plane. TheaWe-case Ordovician and Silurian rocks of Bohemia furnish several2. specimens of a flat closely coiled shell, called Barrandeoceras, after the great palaeontologist of Bohemia; an example from Dudley is also shown.
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c Fig. 92.—Palaeozoic Nautiloidea. a, Ophidioceras simplex, Silurian,Bohemia, b, Hercoceras mirum, Devonian, Bohemia, c, Apheleceras7nutahile, and d, Vestinautilus multicarinatus, Carboniferous Lime-stone, Ireland. All slightly less than natural size. (From Foord.) The coiled cone of the preceding shells is generallycircular or elliptical in section, and has a smooth or slightlyornamented surface. There are others in which the cone isflattened or grooved, and the surface bears more markedornament. Thus Trigotioceras, found in tlie Carboniferous MOLLUSCA—CEPHALOPODA. 163 Limestone of Ireland, has its outer face so flattened that thecone is almost triangular in section. Hercoccras, from theDevonian rocks of Bohemia, has a row of projecting tuberclesarranged along its length; the shell is not very closelycoiled, and its aperture is partly closed (Fig. 92 h). TheCarboniferous Apheleceras (JJiscites) is flattened and soloosely coiled that there is usually an open space in thecentre; or

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