Page:First impressions of England and its people.djvu/90

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FIRST IMPRESSIONS OF

to decide, to the Orthoceras bullatum; a small, imperfectly conical ⟨coral⟩, that more resembled the Stromatopora concentrica of the ⟨Wenlock⟩ rocks, than any of the other Silurian corals figured by Murchison; and a few minute sprigs of the Favosites polymorpha. The concretionary character of the limestone of the deposit has militated against the preservation of the larger organisms which it encloses. Of the smaller shells, many are in a beautiful state of keeping: like some of the comparatively modern shells of the Oolite, they still retain unaltered the silvery lustre of the nacre, and present outlines as sharp and well defined, with every delicate angle unworn, and every minute stria undefaced, as if inhabited but yesterday by the living molluscs; whereas most of the bulkier fossils, from the broken and detached nature of the rock,—a nodular limestone embedded in strata of shale,—exist as mere fragments. What perhaps first strikes the eye is the deep-sea character of the deposit, and its general resemblance to the Mountain Limestone. Nature, though she dropped between the times of the Silurian and Carboniferous oceans many of her genera, and, with but a few marked exceptions, all her species,[1] seems to have scarce at all altered the general types after which the productions of both oceans were moulded.

I could find in this quarry of the Aymestry Limestone no trace of aught higher than the Cephalopoda,—none of those plates, scales, spines, or teeth, indicative of the vertebrate animals, which so abound in the Lower Old Red Sandstones of Scotland. And yet the vertebrata seem to have existed at the

  1. ↑ "Upwards of eight hundred extinct species of animals have been described as belonging to the earliest or Protozoic and Silurian period and of these, only about one hundred are found also in the overlying Devonian series; while but fifteen are common to the whole Palæozoic period, and not one extends beyond it." (Ansted, 1844.)
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