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The shells out of the layers of brown limestone, included in the black calcareous shale-rock, which latter, as just stated, replaces the white siliceous sandstone, consist of: Pecten Dufreynoyi, d'Orbigny, "Voyage" Part Pal. Turritella Andii, d'Orbigny, "Voyage" Part Pal. Astarte Darwinii, E. Forbes. Gryphaea Darwinii, E. Forbes. An intermediate form between G. gigantea and G. incurva.
In the subsoil of the lias clay there are large numbers of a fossil shell, Gryphea incurva, known locally as "devils claws"; they certainly have a demoniac claw-like appearance, and worry the drainers by catching on the blade of the draining tool, and preventing its penetration into the clay.
Pauses also of vast duration may have occurred in the deposition of strata, allowing time for the modification of organic life throughout the globe, slowly brought about by variation accompanied by extinction of the original forms. Gryphaea incurva, Sowerby. Avicula inaequivalvis, Sowerby. Avicula cygnipes, Phil. Lower Lias, Gloucestershire and Yorkshire. a. Lower valve. b.
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