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The Lepidodendra are generally held to have been gigantic clubmosses, which when fully developed attained to between fifty and sixty feet in height, and between five
Fig. 33. and six feet in breadth. Another, but much lower kind of plant met with in the strata in which those mentioned abound, is known as Asterophyllites—so named from the starlike leaves which, as in equisetum, surround the joints of
Asterophyllites equisetiformis. the stem.
The usual mode of classifying the rocks of this system, when regarded apart from local peculiarities, is to range them under four divisions, namely, the Upper Coal Measures, the Millstone Grit, Mountain Limestone, and Lower Coal Measures. These again are associated with shales, sandstones, ironstones, and, in some cases, with characteristic fresh-water deposits. The limestones have been formed in deep seas or in estuaries; the coal measures have been formed on land, and everywhere bear evidences of animal life and of vegetation, which could only have existed in connection with great swamps, and with a tropical climate. The vegetation must have been most luxuriant, consisting, however, mainly of lower forms, analogous to our ferns and reeds. A few resembling present cone-bearing trees have been discovered, the proportion being as one to a hundred. The leading characteristic of the fauna of the coal measures is, that we here meet with remains of air-breathing reptiles, though not for the first time, yet in circumstances which admit of no doubt as to the strata in which they are found.
In rocks hitherto held to belong to the true Old Red Sandstones, remains of an air-breathing reptile—Telerpeton Elginense, fig. 34—were discovered some years ago. Very recently traces of another-Hyperodapedon Gordoni—have been brought to light in the Elgin rocks, but doubts have come to be held as to the true age of the layers in which they were imbedded. Though it is most likely good reasons will be found for keeping the rocks in the place originally assigned to them in the geologic scale, yet these animal remains may be regarded from the same point of view as the straggling traces of plants in the same strata; and it may be affirmed that the writing on the rocks bears testimony to the appearance of air-breathing reptiles, at the same time with the plants which give distinct character to the coal measures. This fact
should be kept in mind in all attempts to harmonize the six days of creation with the fossiliferous strata. Here, too, insects are met with for the first time.
The stratified rocks which we have thus generally reviewed in their ascending order may be roughly estimated as at least fifty thousand feet Fig. 34.
thick, and giving, as has been done, the greatest possible prominence to the traces of past vegetation in them, it must be acknowledged that there is really no warrant as yet to associate the strata underlying the coal measures with a
period characterized by the presence of many plants. Corals, molluscs, and fishes constitute the paleontological features successively of those great epochs.
I have been thus careful in referring to the older deposits, because several of the best known and, perhaps, most influential theories of creation are linked up with them. But in order to an intellige appreciation of these theories, it is not necessary to dwell so long on the other series of rocks of which the crust of the earth is composed, until we come to the highest of all, which, as being nearest the human historical period, has come to have great importance attached to it. Taking our stand in imagination on the surface of the carboniferous group, and looking back as far as thought can find a resting point on matter—the point which lies on the threshold of that past eternity in which the Uncreated had ever been—the words of the psalmist seem full of significance (Ps. xcv.) :
“Let us come before his presence with thanksgiving,
And looking up from our imagined standing point to the present epoch and the introduction of man, the very changes which this earth has witnessed bear testimony to the presence and the watchful care of a faithful Creator :
“There rolls the deep where grew the tree;
O earth ! what changes hast thou seen.
There, where the long street roars, hath been
The next group, as we ascend, is the Permian, so called from its having its typical development in the Government of Perm, in Central Russia. It is known also as the New Red Sandstone, and consists of layers of magnesian and other limestones, marls and red sandstones, containing numerous
Fig. 35. fossils. Though an independent place in the geological system has rightly been assigned to it, this group may be regarded as connected with the underlying carboniferous, to the plants and animals of which its fossils bear much resem
Platisomus striatus-Carb. and Permian. blance, while in these respects it has nothing in common with the overlying beds of the trias. In its flora are found sea-weeds, reeds, ferns, club-mosses, palms, and cone-bearing trees. “After,” says Murchison, “balancing the whole of the botanical evidence, Göppert concludes with Brongniart and Morris, that this flora differs from all other fossil floras, and marks strikingly the close of the palæozoic times, of which it retains the family impress, whilst it is rigidly separated from all the vegetable products of secondary age.” Its fauna consists of corals, sea urchins (one species), molluscs, fishes (between fifty and sixty species), with unequally lobed tails (heterocercal)-in which the spine is seen prolonged into the upper lobe, as in living sharks and sturgeons — and of reptiles more highly developed than those of the carboniferous, from which indeed, as has been pointed out by Owen, they relatively differ, the reptiles of the coal measures having relations with the frogs, while several of those of the Permian are suggestive of the crocodilian types. Associated with them are others resembling those of
the coal measures. The remark made as to the fishes of the Old Red Sandstone is equally true of the reptiles of the Permian. They bear
witness to a structure as complex, elaborate, and complete as do any reptiles now living.
Yet higher forms of life are met with in the trias. The coming mammals and birds of epochs posterior to the triassic, are heralded by
those met with in this group of strata. One small insect-eating quadruped (Microlestes) is known to have lived at that remote period; and, if