Elements of geology, or, The ancient changes of the earth and its inhabitants as illustrated by geological monuments / by Sir Charles Lyell.

  • Lyell, Charles, Sir, 1797-1875.
Date:
1865
Catalogue details

Licence: Public Domain Mark

Credit: Elements of geology, or, The ancient changes of the earth and its inhabitants as illustrated by geological monuments / by Sir Charles Lyell. Source: Wellcome Collection.

Provider: This material has been provided by King’s College London. The original may be consulted at King’s College London.

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    lacustrine strata, which must once have filled a hollow, have been denuded, and shaped out into hills aud valleys, on the site of the ancient lakes. Fig 1GG. I5ed of indusial limestone, interstratilied with freshwater marl, near Clermont (Kleinschrod). We may often observe iu our ponds the Phryganea (or Caddis- fly), in its caterpillar state, covered with small freshwater shells, which they have the power of fixing to the outside of their tubular cases, in order, probably, to give them weight and strength. The individual figured iu the annexed cut, which belongs to a species very abundant in England, has covered its case with shells of a small Planorbis. In the same manner a large species of caddis-worm which swarmed in the Eocene lakes of Auverame was accustomed to attach to O its dwelling the shells of a small spiral Larva of recent p/iryganea.* univalve of the genus Paludinu. A hun- dred of these minute shells are sometimes seen arranged around one tube, part of the central cavity of which is often empty, the rest, being filled up with thin concentric layers of travertin, lhe cases have been thrown together confusedly, and often lie, as in fig. 168., at right angles one to the other. When we consider that ten or twelve tubes are packed within the compass of a cubic inch, and that some single strata of this limestone are six feet thick, and may be traced over a considerable area, we may form some idea of the count- less number of insects and mollusca which contributed their integu- * I believe that the British specimen here figured is P. rhombica, Linn.