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THE ANCIENT
LIFE-HISTORY
OF THEĀ EARTH

Chapter 14:

THE PERMIAN PERIOD.


The Permian formation closes the long series of the Palæozoic deposits, and may in some respects be considered as a kind of appendix to the Carboniferous system, to which it cannot be compared in importance, either as regards the actual bulk of its sediments or the interest and variety of its life-record. Consisting, as it does, largely of red rocks—sandstones and marls—for the most part singularly destitute of organic remains, the Permian rocks have been regarded as a lacustrine or fluviatile deposit; but the presence of well-developed limestones with indubitable marine remains entirely negatives this view. It is, however, not improbable that we are presented in the Permian formation, as known to us at present, with a series of sediments laid down in inland seas of great extent, due to the subsidence over large areas of the vast land-surfaces of the Coal-measures. This view, at any rate, would explain some of the more puzzling physical characters of the formation, and would not be definitely negatived by any of its fossils.

A large portion of the Permian series, as already remarked, consists of sandstones and marls, deeply reddened by peroxide Page 193 of iron, and often accompanied by beds of gypsum or deposits of salt. In strata of this nature few or no fossils are found; but their shallow-water origin is sufficiently proved by the presence of the footprints of terrestrial animals, accompanied in some cases by well-defined "ripple-marks." Along with these are occasionally found massive breccias, holding larger or smaller blocks derived from the older formations; and these have been supposed to represent an old "boulder-clay," and thus to indicate the prevalence of an arctic climate. Beds of this nature must also have been deposited in shallow water. In all regions, however, where the Permian formation is well developed, one of its most characteristic members is a Magnesian limestone, often highly and fantastically concretionary, but containing numerous remains of genuine marine animals, and clearly indicating that it was deposited beneath a moderate depth of salt water.

It is not necessary to consider here whether this formation can be retained as a distinct division of the geological series. The name of Permian was given to it by Sir Roderick Murchison, from the province of Perm in Russia, where rocks of this age are extensively developed. Formerly these rocks were grouped with the succeeding formation of the Trias under the common name of "New Red Sandstone." This name was given them because they contain a good deal of red sandstone, and because they are superior to the Carboniferous rocks, while the Old Red Sandstone is inferior. Nowadays, however, the term "New Red Sandstone" is rarely employed, unless it be for red sandstones and associated rocks, which are seen to overlie the Coal-measures, but which contain no fossils by which their exact age may be made out. Under these circumstances, it is sometimes convenient to employ the term "New Red Sandstone." The New Red, however, of the older geologists, is now broken up into the two formations of the Permian and Triassic rocks—the former being usually considered as the top of the Palæozoic series, and the latter constituting the base of the Mesozoic.

In many instances, the Permian rocks are seen to repose unconformably upon the underlying Carboniferous, from which they can in addition be readily separated by their lithological characters. In other instances, however, the Coal-measures terminate upwards in red rocks, not distinguishable by their mineral characters from the Permian; and in other cases no physical discordance between the Carboniferous and Permian strata can be detected. As a general rule, also, the Permian rocks appear to pass upwards conformably into the Page 194 Trias. The division, therefore, between the Permian and Triassic rocks, and consequently between the Palæozoic and Mesozoic series, is not founded upon any conspicuous or universal physical break, but upon the difference in life which is observed in comparing the marine animals of the Carboniferous and Permian with those of the Trias. It is to be observed, however, that this difference can be solely due to the fact that the Magnesian Limestone of the Permian series presents us with only a small, and not a typical, portion of the marine deposits which must have been accumulated in some area at present unknown to us during the period which elapsed between the formation of the great marine limestones of the Lower Carboniferous and the open-sea and likewise calcareous sediments of the Middle Trias.

The Permian rocks exhibit their most typical features in Russia and Germany, though they are very well developed in parts of Britain, and they occur in North America. When well developed, they exhibit three main divisions: a lower set of sandstones, a middle group, generally calcareous, and an upper series of sandstones, constituting respectively the Lower, Middle, and Upper Permians.

In Russia, Germany, and Britain, the Permian rocks consist of the following members:—

1. The Lower Permians, consisting mainly of a great series of sandstones, of different colours, but usually red. The base of this series is often constituted by massive breccias with included fragments of the older rocks, upon which they may happen to repose; and similar breccias sometimes occur in the upper portion of the series as well. The thickness of this group varies a good deal, but may amount to 3000 or 4000 feet.

2. The Middle Permians, consisting, in their typical development, of laminated marls, or "marl-slate," surmounted by beds of magnesian limestone (the "Zechstein" of the German geologists). Sometimes the limestones are degenerate or wholly deficient, and the series may consist of sandy shales and gypsiferous clays. The magnesian limestone, however, of the Middle Permians is, as a rule, so well marked a feature that it was long spoken of as the Magnesian Limestone.

3. The Upper Permians, consisting of a series of sandstones and shales, or of red or mottled marls, often gypsiferous, and sometimes including beds of limestone.

In North America, the Permian rocks appear to be confined to the region west of the Mississippi, being especially well developed in Kansas. Their exact limits have not as yet been Page 195 made out, and their total thickness is not more than a few hundred feet. They consist of sandstones, conglomerates, limestones, marls, and beds of gypsum.

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.
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 Page 196 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
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 Page 197 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.

Page 198 Amongst the Mollusca, the remains of Polyzoa may fairly be said to be amongst the most abundant of all the fossils of the Permian formation, The principal forms of these are the fronds of the Lace-corals (Fenestella, Retepora, and Synocladia), which are very abundant in the Magnesian Limestone of the north of England, and belong to various highly characteristic species (such as Fenestella retiformis, Retepora Ehrenbergi, and Synocladia virgulacea). The Brachiopoda are also represented in moderate numbers in the Permian. Along with species of the persistent genera Discina, Crania, and Lingula, we still meet with representatives of the old groups Spirifera, Athyris, and Streptorhynchus; and the Carboniferous Productœ yet survive under well-marked and characteristic types, though in much-diminished numbers. The species of Brachiopods here figured (fig. 135) are characteristic of the Magnesian Limestone in Britain and of the Fig. 135
Fig. 135.—Brachiopods of the Permian formation. a, Producta horrida; b, Lingula Credneri; c, Terebratula elongata; d and e, Camarophoria globulina. (After King.)
corresponding strata on the Continent. Upon the whole, the most characteristic Permian Brachiopods belong to the genera Producta, Strophalosia, and Camarophoria.

The Bivalves (Lamellibranchiata) have a tolerably varied development in the Permian rocks; but nearly all the old types, except some of those which occur in the Carboniferous, have now disappeared. The principal Permian Bivalves belong to the groups of the Pearl Oysters (Aviculidœ) and the Trigoniadœ, represented by genera such as Bakewellia and Schizodus; the true Mussels (Mytilidœ), represented by species which have been referred to Mytilus itself; and the Arks (Arcadœ), represented by species of the genera Arca (fig. 136) and Byssoarca. The first and last of these three families have a very ancient origin; but the family of the Trigoniadœ, though Page 199 feebly represented at the present day, is one which attained its maximum development in the Mesozoic period.

The Univalves (Gasteropoda) are rare, and do not demand special notice. It may be observed, however, that the Fig. 136
Fig. 136.—Arca antiqua. Permian.
Palæozoic genera Euomphalus, Murchisonia, Loxonema, and Macrocheilus are still in existence, together with the persistent genus Pleurotomaria. Pteropods of the old genera Theca and Conularia have been discovered; but the first of these characteristically Palæozoic types finally dies out here, and the second only survives but a short time longer. Lastly, a few Cephalopods have been found, still wholly referable to the Tetrabranchiate group, and belonging to the old genera Orthoceras and Cyrtoceras and the long-lived Nautilus.

Amongst Vertebrates, we meet in the Permian period not only with the remains of Fishes and Amphibians, but also, for the first time, with true Reptiles. The Fishes are mainly Ganoids, though there are also remains of a few Cestraciont Fig. 137
Fig. 137.—Platysomus gibbosus, a "heterocercal" Ganoid, from the Middle Permian of Russia.
Sharks. Not only are the Ganoids still the predominant group of Fishes, but all the known forms possess the unsymmetrical ("heterocercal") tail which is so characteristic of the Palæozoic Ganoids. Most of the remains of the Permian Fishes have been obtained from the "Marl-slate" of Durham and the corresponding "Kupfer-schiefer" of Germany, on the horizon Page 200 of the Middle Permian; and the principal genera of the Ganoids are Palœoniscus and Platysomus (fig. 137).

The Amphibians of the Permian period belong principally to the order of the Labyrinthodonts, which commenced to be represented in the Carboniferous, and has a large development in the Trias. Under the name, however, of Palœosiren Beinerti, Professor Geinitz has described an Amphibian from the Lower Permian of Germany, which he believes to be most nearly allied to the existing "Mud-eel" (Siren lacertina) of North America, and therefore to be related to the Newts and Salamanders (Urodela).

Finally, we meet in the Permian deposits with the first undoubted remains of true Reptiles. These are distinguished, as a class, from the Amphibians, by the fact that they are air-breathers throughout the whole of their life, and therefore are at no time provided with gills; whilst they are exempt from that metamorphosis which all the Amphibia undergo in early life, consequent upon their transition from an aquatic to a more or less purely aerial mode of respiration. Their skeleton is well ossified; they usually have horny or bony plates, singly or in combination, developed in the skin; and their limbs (when present) are never either in the form of fins or wings, though sometimes capable of acting in either of these capacities, and liable to great modifications of form and structure. Though there can be no doubt whatever as to the occurrence of genuine Reptiles in deposits of unquestionable Permian age, there is still uncertainty as to the precise number of types which may have existed at this period. This uncertainty arises partly from the difficulty of deciding in all cases. whether a given bone be truely Labyrinthodont or Reptilian, but more especially from the confusion which exists at present between the Permian and the overlying Triassic deposits. Thus there are various deposits in different regions which have yielded the remains of Reptiles, and which cannot in the meanwhile be definitely referred either to the Permian series or to the Trias by clear stratigraphical or palæontological evidence. All that can be done in such cases is to be guided by the characters of the Reptiles themselves, and to judge by their affinities to remains from known Triassic or Permian rocks to which of these formations the beds containing them should be referred; but it is obvious that this method of procedure is seriously liable to lead to error. In accordance, however, with this, the only available mode of determination in some cases, the remains of Thecodontosaurus and Palæosaurus discovered in the dolomitic conglomerates Page 201 near Bristol will be considered as Triassic, thus leaving Protorosaurus[20] as the principal and most important Fig. 138
Fig. 138.—Protorosaurus Speneri, Middle Permian, Thuringia, reduced in size. (After Von Meyer.) [Copied from Dana.
representative of the Permian Reptiles.[21] The type-species of the genus Protorusaurus is the P. Speneri(fig. 138) of the "Kupfer-schiefer" of Page 202 Thuringia, but other allied species have been detected in the Middle Permian of Germany and the north of England. This Reptile attained a length of from three to four feet; and it has been generally referred to the group of the Lizards (Lacertilia), to which it is most nearly allied in its general structure, at the same time that it differs from all existing members of this group in the fact that its numerous conical and pointed teeth were implanted in distinct sockets in the jaws—this being a Crocodilian character. In other respects, however, Protorosaurus approximates closely to the living Monitors (Varanidœ); and the fact that the bodies of the vertebræ are slightly cupped or hollowed out at the ends would lead to the belief that the animal was aquatic in its habits. At the same time, the structure of the hind-limbs and their bony supports proves clearly that it must have also possessed the power of progression upon the land. Various other Reptilian bones have been described from the Permian formation, of which some are probably really referable to Labyrinthodonts, whilst others are regarded by Professor Owen as referable to the order of the "Theriodonts," in which the teeth are implanted in sockets, and resemble those of carnivorous quadrupeds in consisting of three groups in each jaw (namely, incisors, canines, and molars). Lastly, in red sandstones of Permian age in Dumfriesshire have been discovered the tracks of what would appear to have been Chelonians (Tortoises and Turtles); but it would not be safe to accept this conclusion as certain upon the evidence of footprints alone. The Chelichnus Duncani, however, described by Sir William Jardine in his magnificent work on the 'Ichnology of Annandale,' bears a great resemblance to the track of a Turtle.

[Footnote 20: Though commonly spelt as above, it is probable that the name of this Lizard was really intended to have been Proterosaurus—from the Greek proteros, first; and saura, lizard: and this spelling is followed by many writers.]

[Footnote 21: In an extremely able paper upon the subject (Quart. Journ. Geol. Soc., vol. xxvi.), Mr Etheridge has shown that there are good physical grounds for regarding the dolomitie conglomerate of Bristol as of Triassic age, and as probably corresponding in time with the Muschelkalk of the Continent.]

No remains of Birds or Quadrupeds have hitherto been detected in deposits of Permian age.

LITERATURE.

The following works may be consulted by the student with regard to the Permian formation and its fossils:—

(1) "On the Geological Relations and Internal Structure of the Magnesian Limestone and the Lower Portions of the New Red Sandstone Series, &c."—'Trans. Geol. Soc.,' ser. 2, vol. iii. Sedgwick.
(2) 'The Geology of Russia in Europe.' Murchison, De Verneuil, and Von Keyserling.
(3) 'Siluria,' Murchison.
(4) 'Permische System in Sachsen.' Geinitz and Gutbier.
(5) 'Die Versteinerungen des Deutschen Zechsteingebirges,' Geinitz.
(6) 'Die Animalischen Ueberreste der Dyas.' Geinitz.
Page 203 (7) 'Monograph of the Permian Fossils of England' (Palæontographical Society). King.
(8) 'Monograph of the Permian Brachiopoda of Britain' (Palæontographical Society). Davidson.
(9) "On the Permian Rocks of the North-West of England and their Extension into Scotland"—'Quart. Journ. Geol. Soc.,' vol. xx. Murchison and Harkness.
(10) 'Catalogue of the Fossils of the Permian System of the Counties of Northumberland and Durham.' Howse.
(11) 'Petrefacta Germaniæ.' Goldfuss.
(12) 'Beiträge zur Petrefaktenkunde.' Munster.
(13) 'Ein Beitrag zur Palæontologie des Deutschen Zechsteingebirges.' Von Schauroth.
(14) 'Saurier aus dem Kupfer-schiefer der Zechstein-formation.' Von Meyer.
(15) 'Manual of Palæontology.' Owen.
(16) 'Recherches sur les Poissons Fossiles.' Agassiz.
(17) 'Ichnology of Annandale.' Sir William Jardine.
(18) 'Die Fossile Flora der Permischen Formation.' Gœppert.
(19) 'Genera et Species Plantarum Fossilium.' Unger.
(20) "On the Red Rocks of England of older Date than the Trias"—'Quart. Journ. Geol. Soc.,' vol. xxvii. Ramsay.


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