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In the fresh water chalk formation of Steinheim, near Heidenheim, in Würtemberg, scientists have found, on the same place, in an uninterrupted series of strata, the snail valvata or paludina multiformis in all imaginable transitions from the flat winding, showing the form of a chess-board, up to the sharp form of a tower.
NEWER FRESHWATER BEDS. A. Coarse river gravel, with shells of Anodon, Valvata, Cyclas, Succinea, Limnaea, Paludina, etc., seeds of Ceratophyllum demersum, Nuphar lutea, scales and bones of pike, perch, salmon, etc., elytra of Donacia, Copris, Harpalus, and other beetles. C. Yellow sands. Mr.
Cyprides from the Upper Purbeck. a. Cypris gibbosa, E. Forbes. b. Cypris tuberculata, E. Forbes. c. The highest of the three divisions is purely fresh-water, the strata, about fifty feet in thickness, containing shells of the genera Paludina, Physa, Limnaea, Planorbis, Valvata, Cyclas, and Unio, with Cyprides and fish.
The great dirt-bed or vegetable soil containing the roots and stools of Cycadeae, which I shall presently describe, underlies these marls, and rests upon the lowest fresh-water limestone, a rock about eight feet thick, containing Cyclas, Valvata, and Limnaea, of the same species as those of the uppermost part of the Lower Purbeck, or above the dirt-bed.
Finely laminated sands and clays, with thin layer of lignite, and shells of Cyclas and Valvata, and with Mytilus in some beds. 4. Glacial boulder till. 5. Contorted drift. 6. Gravel overlying contorted drift.
Now, as none of these last, or the unimuscular bivalves, are fresh-water, we may at once presume a deposit containing any of them to be marine. Planorbis euomphalus, Sowerby; fossil. Limnaea longiscala, Brongniart; fossil. Paludina lenta, Brand.; fossil. Succinea amphibia, Drap. Valvata piscinalis, Mull.; fossil. Physa hypnorum, Linne; recent. Auricula; recent. Melania inquinata, Def.
This conspicuous freshwater mussel is no longer an inhabitant of the British Isles, but still lives in the Seine, and is still more abundant in the Loire. With these, moreover, is found a peculiar variety of Valvata piscinalis. If we consult Dr.
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