The Ancient Life History of the Earth / A Comprehensive Outline of the Principles and Leading Facts of Palæontological Science

by Henry Alleyne Nicholson

The following diagrammatic section shows the general sequence of the Permian deposits in the north of England, where the series is extensively developed (fig. 133):—

GENERALISED SECTION OF THE PERMIAN ROCKS IN THE NORTH OF ENGLAND.

Fig. 133.

The record of the life of the Permian period is but a scanty one, owing doubtless to the special peculiarities of such of the deposits of this age with which we are as yet acquainted. Red rocks are, as a general rule, more or less completely unfossiliferous, and sediments of this nature are highly characteristic of the Permian. Similarly, magnesian limestones are rarely as highly charged with organic remains as is the case with normal calcareous deposits, especially when they have been subjected to concretionary action, as is observable to such a marked extent in the Permian limestones. Nevertheless, much interest is attached to the organic remains, as marking a kind of transition-period between the Palæozoic and Mesozoic epochs.

The plants of the Permian period, as a whole, have a distinctly Palæozoic aspect, and are far more nearly allied to those of the Coal-measures than they are to those of the earlier Secondary rocks; though the Permian species are mostly distinct from the Carboniferous, and there are some new genera. Thus, we find species of Lepidodendron, Calamites, Equisetites, Asterophyllites, Annularia, and other highly characteristic Carboniferous genera. On the other hand, the Sigillariods of the Coal seem to have finally disappeared at the close of the Carboniferous period. Ferns are abundant in the Permian rocks, and belong for the most part to the well-known Carboniferous genera Alethopteris, Neuropteris, Sphenopteris, and Pecopteris. There are also Tree-ferns referable to the ancient genus Psaronius. The Conifers of the Permian period are numerous, and belong in part to Carboniferous genera. A characteristic genus, however, is Walchia (fig. 134),

Fig. 134.—Walchia piniformis, from the Permian of Saxony, a, Branch; b, Twig, (After Gutbier.) distinguished by its lax short leaves. This genus, though not exclusively Permian, is mainly so, the best-known species being the W. Piniformis. Here, also, we meet with Conifers which produce true cones, and which differ, therefore, in an important degree from the Taxoid Conifers of the Coal-measures. Besides Walchia, a characteristic form of these is the Ullmania selaginoides, which occurs in the Magnesian Limestone of Durham, the Middle Permian of Westmorland, and the "Kupfer-schiefer" of Germany. The group of the Cycads, which we shall subsequently find to be so characteristic of the vegetation of the Secondary period, is, on the other hand, only doubtfully represented in the Permian deposits by the singular genus Nœggerathia.

The Protozoans of the Permian rocks are few in number, and for the most part imperfectly known. A few Foraminifera have been obtained from the Magnesian Limestone of England, and the same formation has yielded some ill-understood Sponges. It does not seem, however, altogether impossible that some of the singular "concretions" of this formation may ultimately prove to have an organic structure, though others would appear to be clearly of purely inorganic origin. From the Permian of Saxony, Professor Geinitz has described two species of Spongillopsis, which he believes to be most nearly allied to the existing fresh-water Sponges (Spongilla). This observation has an interest as bearing upon the mode of deposition and origin of the Permian sediments.

The Cœlenterates are represented in the Permian by but a few Corals. These belong partly to the Tabulate and partly to the Rugose division; but the latter great group, so abundantly represented in Silurian, Devonian, and Carboniferous seas, is now extraordinarily reduced in numbers, the British strata of this age yielding only species of the single genus Polycœlia. So far, therefore, as at present known, all the characteristic genera of the Rugose Corals of the Carboniferous had become extinct before the deposition of the limestones of the Middle Permian.

The Echinoderms are represented by a few Crinoids, and by a Sea-urchin belonging to the genus Eocidaris. The latter genus is nearly allied to the Archœocidaris of the Carboniferous, so that this Permian form belongs to a characteristically Palæozoic type.

A few Annelides (Spirorbis, Vermilia, &c.) have been described, but are of no special importance. Amongst the Crustaceans, however, we have to note the total absence of the great Palæozoic group of the Trilobites; whilst the little Ostracoda and Phyllopods still continue to be represented. We have also to note the first appearance here of the "Short-tailed" Decapods or Crabs (Brachyura), the highest of all the groups of Crustacea, in the person of Hemitrochiscus paradoxus, an extremely minute Crab from the Permian of Germany.