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ing that in all cases it must have been equally slow, and then reasoning on this theory, as if it were true in fact and applicable to every portion of mud laid down in the bottom of our inland lakes, or left by our rivers on the way to the sea. Yet on this principle conclusions have recently been formed as to the length of the human historical period, from observations made in the valley of the Nile and elsewhere, which, as shall be shown, is wholly unwarranted.
Looking at the rock now under notice, we can see that, if the ocean at any one period contained in its waters in a state of wild unrest, all the material necessary for its formation, the time required for laying it down, when it became calm, would be comparatively much shorter than it could have been had the soil needed to be floated by rivers into the ocean. In the former case, the action of one year would show a greater result than that of ten thousand years in the latter. It is not indeed alleged that the epoch of the Old Red Sandstone was brief. The rounded pebbles and the vast thickness of the strata tell a very different tale. These remarks are made simply with the view of indicating, that in all cases we are not necessarily shut up to the "immense period theory."
The distinctive fossils found in the Old Red Sandstone are fishes. Pterichthys oblongus (fig. 18) was discovered by Mr. Hugh Miller in
the north of Scotland. "Imagine,” he Fig. 18.
says, “the figure of a man rudely drawn in black on a grey ground, the head cut off by the shoulders, the arms spread at full, as in the attitude of swimming, the body rather long than otherwise, and narrowing from the chest downwards, one of the legs cut away at the hipjoint, and the other, as if to preserve
the balance, placed directly under the Pterichthys oblongus.
centre of the figure, which it seems to support. Such, at first glance, is the appearance of the fossil.” Another form of the Old Red Sandstone fishes is the Coccosteus cuspidatus (fig. 19). It is named Coccosteus from kokkos, a berry, and os, a bone, from the berry-like excrescences on the plates which cover its head and body. It is found in the Caithness flags. The spear-shaped form of the tail led to its specific name. Cephalaspis Lyellii (fig. 20) has given its name to a family, the Cephalaspidæ or Buckler-headed fishes, whose structure indicates habits like those of the sturgeon.
At the top of this formation, and rising into the carboniferous series is the well known Holoptychius (all-wrinkled) nobilissimus-fig. 21.
Coccosteus cuspidatus. . The leaves of the " Book of Stone" come now to unfold the history of higher forms of life than they have previously done. It is true that the uppermost members of the Silu
Fig. 20. rian series contain the remains of fishes, but these form no distinctive characteristic of the Silurian. They come as hints of the mind of the Creator, thrown out as to what he was about to do in the next great step of manifestation— heralds of the creation which was about to be realized by him who had laid the
Cephalaspis Lyellit. foundations of the earth, in order to rest a series of creations on them. Remains of fish are very numerous. “They seem to have been introduced not by in
Fig. 21. dividuals and pairs, but by whole myriads.” As to organization, too, they will stand comparison with the highest types now living in our seas. “The first created fish, like the first forms of those of other orders, was as marvellously constructed as the last which made its appearance.” In
Holoptychius nobilissimus. variety they might almost be held to exceed present forms. Had old Du Bartas got a glimpse of the picturesque shapes of the Old Red
Sandstone fishes, his homely muse would have found even greater difficulty in accounting for them than he has in dealing with fish of the present seas :
"As a rare painter draws (for pleasure) here
A sweet Adonis, a foul Satyre there:
The usual way of indicating the next great series in the ascending order, is to group together several distinct formations under the one name Carboniferous, on the ground that the rocks so named bear evidence, in the middle members of the series, of immense quantities of carbonate of lime in the ocean, and in the highest and lowest members of carbonic acid gas in the atmosphere. On Plate I. specimens of carboniferous corals are shown in figs. 8 and 9. Favosites is so called from its honeycomb-like appearance. It occurs in the Silurian, Old Red Sandstone, and Carboniferous systems. Syringopora, or Pipe-pore coral, fig. 9, is, in many respects, like the Organ-pipe coral of the Pacific. Fig. 1 represents a family highly characteristic of this series of strata, the Productidæ, which are met with in great numbers in the limestones of the period, but which also occur in the Old Red Sandstone and Permian. The Ammonite family, figs. 2 and 3, range from the Devonian to the Chalk. They have no true representatives in recent seas. The Bellerophon, fig. 6, was a single-chambered shell, remotely allied to the modern Glass-shell (Carinaria). More than twenty species occur in the mountain limestone. Pleurotomaria, fig. 7, ranges from the Lower Silurian to the Chalk. Among recent shells the nearest resemblance to it is found in the well known Top-shell of our coasts (Trochus). The bivalve, fig. 5, is met with in great abundance in carboniferous strata. It obtains its name, Spirifer, or Coil-bearer, from a hard spiral process which occurs inside of the valves, and which was used by the living forms to sustain and move the hair-fringed arms of the mollusc. The following cuts represent other characteristic forms.
The Lithostrotion is met with in the mountain limestone. It was a zoophite which grew in clusters. Each animal inhabited a six-sided pillar-like stalk-a number of which formed a colony.
Productus Giganteus. This Productus is one of the best marked and best known of the family. The Pleurorhynchus is more rare.
Sphenopteris affinis. But the chief characteristic of the great carboniferous period is the abundant and luxuriant flora of the coal measures. Some of the forms Fig. 27. Fig. 28.
Neuropteris gigantea. are as distinctly marked by their beauty as others are by their bulk and strength; of the former the ferns supply striking illustrations.
Some of the trees of the coal period must have reached a great size. The roots of several are of frequent occurrence. Of these the well known stigmaria presents many features of interest.
Stigmaria was the root of the Sigillaria, a dicotyledonous plant abundant in the coal epoch.
Lepidodendron Sternbergii. Fig. 31 represents the root (stigmaria) and the stalk of the Sigillaria. Another form plentiful at the same time was the Lepidodendron.