CHAPTER IV

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THE DEVONIAN SYSTEM, OR OLD RED SANDSTONE.

A geologist requires not, like the tourist, to be told of the various conflicting roads that run among the mountains, in what precise course he is to wend his way. He will follow his own pathways, roads of nature’s forming, guided by the strike and lie of the rocks rather than by the beaten tracks of every-day life. But come whither he will—through Glentilt, Glenericht, Glenbeg, and the Spittal, Glenisla, and Clova,—or along the Dee, the heights of Glentanner, and penetrating to the sources of the Esks—sure we are, when he reaches by any of those passes the frontiers of the Grampians, he will pause and gaze wistfully, thoughtfully, admiringly, ere he descends, upon the magnificent prospect that stretches before him, unrivaled by any on the terraqueous globe. The GRAN-PEN, _celticé_, the shelvy or precipitous summit, Romanized into Grampius, has its own inner charms, peaceful rock-girt valleys where princes dwell, and happy as Rasselas ever trod.—And escaped from these, what an outer world beneath, fertile, abundant, replete with everything that can charm the eye or interest the student. Looming in the far distance, the Lammermuirs, of silurian origin, can just be descried as a dark-blue line on the verge of the horizon; the Ochils and Lomonds, of carboniferous age, repose like islets on the pendant sky; while, in the foreground of the picture, there is the most charming variety of woodland, meadow, farmstead, town, and mansion, all as I now gaze upon them in their autumn coloring, invested with a Claud-like mellowness that speaks with a moral yet romantic sympathy to the heart. The round tower of Brechin, the moldering walls of Edzell, the frowning battlements of Glammis, the worn-out and now verdant ramparts of Dunsinane, have each their crowds of visitants, and are all within the compass of a single day’s journey.

The eye of the geologist is in search of another object as it wanders over that lovely scene: Kinnordie, the birth-place of Sir Charles Lyell, must ever be classic ground in the history of our science. It rests on the old red sandstone, and furnishes some of the most valuable illustrations in Sir Charles’s early sketches. What influences, may we here ask, gave being and shape to the ingenious and splendid generalizations of this accomplished geologist? Is it too much to assume that the philosopher, as well as the poet, is all his life-long captive to first impressions, that the scenes of his boyhood claim “a local habitation” for many of his future speculations, and that his most matured trains of thinking have been dependent upon casual circumstances? Born and educated in the shadow of the Grampians, who can doubt that the spirit within was early stirred to lofty views as he gazed upon their elevated forms, and wondered how their peaks rose so high in air, and were thus lifted above the valleys? May it not be presumed, though the philosopher himself may have no recollection of the matter, that his speculations regarding the alternate elevation and depression of land and sea had its germ in some such happy moment of mountain inspiration? Byron owned the influence in all its power, when, in the rocky defiles and dark pine forests of Lochnagar, he had early communings with spiritual beings, the wreathe-forms and kelpies of the streams; and in visions imparted amidst the wilds of the Dee, prepared his mind for the daring flights of the Alps. The geologist had here all the materials of after-thought, which in his various essays and works he has so skillfully expanded—from his explorations of Bakie-loch with its alluvions, peat, marl, shells, and horns, in which he had the type of some of his Alpine tertiaries—the old canoe and ripple-mark here too, the representatives of their far-sundered ages and onward to his bold speculations on the elevatory hypothesis, of which the Grampians, as well as Sidlaws, supplied him with ample illustrations.

The descent from the mountains upon the series of rocks that occupy the plains, is one not merely of space, but likewise of time. A geological epoch has vanished, and a new order of things has been called into existence. This implies a change in the animal as well as in the mineral kingdom. The change may not have been sudden, but it has been thorough and pervading, accompanied by circumstances that show a general shift in the sea-bottom, and causes that have been nearly uniform in their operation over the surface of the globe. The shift in the sea-bottom is detected in the elevation of the silurian group of rocks, which have been lifted from a horizontal into a highly-inclined position: in some instances they are nearly vertical; and in most cases where the igneous rocks occur, they are bent and twisted, greatly altered and disrupted, by the process of upheaval to which they have been subjected.

Geology notes in this an epoch or age of organic existence. The superjacent series of rocks are seen lying unconformably upon the silurians, that is, the older series had been consolidated and upheaved, and a period of intervening time had elapsed before the deposition of the newer. The fossils imbedded are likewise distinct and peculiar—one and the same over the superficial area of the globe—and thus we learn to mark the great and interesting cosmical changes which had already begun to be effected. We are now among the Old Red Sandstone, or Devonian system of rocks, so denominated from their great development in that district of the sister kingdom.

As contrasted with the former system, the rocks of this period indicate considerable disturbance in the waters of the ocean, currents and agitations widely prevailing, and perhaps also deeper seas. The crust of the earth was still rising, and the mountains becoming higher, and these effects would necessarily follow. A superior order of animals were introduced. The fishes, which begin to appear in the upper beds of the silurian group, are now increased both in numbers and in variety of structures. The invertebrata were the prevailing types of the former age. The old red sandstone is pre-eminently characterized by the vertebrata, when, completely adapted to the element to be inhabited, mailed and plated over with thick horny scales, huge bony heads, fins and tails of corresponding strength and size; the Sauroid family appear upon the stage, capable all of buffeting the waves and fulfilling their destiny amid the greatest commotions. The fish of this early period are generally well preserved, even better than those of the tertiary age, in consequence of their osseous scales being harder than the bones, and which, from their interlocked arrangement, have contributed to preserve the general form of the body when the inner skeleton has disappeared and every other part and organ have been destroyed.

The old red sandstone formation is very extensively distributed in the northern counties, forming a great belt round the coast from Caithness-shire to Aberdeenshire, and consisting of three well-marked divisions, the lower, middle, and upper series of beds. The strata flank the northern walls of the Grampians and their out-liers, traversing the great central or Caledonian valley for a hundred miles, and training round the western coast by Oban, the shores of Mull and Morven. They are of great thickness in many places; and in some of the beds, as at Cromarty, Lethen-bar, and Gamrie, contain nearly all the fossils peculiar to the formation.

The order of Ganoid fishes, which afterward fulfill so distinguished a part in the kingdom of nature, is wholly absent from the silurian group, while, in the Devonian, nearly thirty genera, and considerably above sixty species, have been described and named. The scales of these creatures would appear to have been richly ornamented, enameled, and shining, and hence the term Ganoid applied to the order. In the northern districts, beyond Ben Mac-Dhui, the following genera, with several species belonging to each, have been found, namely, coccosteus, cheiracanthus, cheirolepis, dipterus, diplopterus, diplocanthus, glyptolepis, osteolepis, pterichthys. The principal localities of these fossils are—the Dipple on the Spey, Tynet Burn in Banffshire, Seat-Craig near Elgin, Altyre on the Findhorn, Clune, and Lethen-bar in Nairnshire, Gamrie, Cromarty, and various places in Sutherland and Caithness. Shetland is chiefly composed of the old red sandstone, which yields abundantly the fossils peculiar to the deposit. The formation extends through the Orkney islands, inexhaustibly fertile in organic remains, and among which have been found plates and fragments of the Asterolepis, the largest of all the genera belonging to the period: the head and jaws, at least, appear to have been of enormous dimensions, and portions of the inner skeleton must have been bony, contrary to the general cartilaginous structure of the class. The Placoids of the subjacent rocks have many resemblances to the cestracions, centrinæ, and spinaxes of our present seas, their scales being set like plates at irregular distances over the body. The Ganoids, on the other hand, whose scales were continuous, and enveloped the entire animal, have no affinities to any living types.

Specimens of vegetable organisms are very common in some of the flagstones of Orkney, resembling, in some instances, the Lycopodiaceæ, or club-mosses, so abundant in the carboniferous strata: and branching fucoid plants, of which portions have been found from two to three feet in length, and of nearly the same diameter of stem throughout. But in tracing the COURSE of CREATION in this department of her works, the most important fact to relate is, the discovery of a coniferous lignite, imbedded in the old red sandstone of Cromarty. This interesting relic was obtained from these beds, several years ago, by Mr. Miller; and, though still of that remote age an instantia solitaria of its kind, like the foot-print of Robinson Crusoe, it is the sure token of a race that inhabited the island, and harbinger of a luxuriant flora then waving along the shores of the boundless waters. These northern localities, on the mainland, as well as in the islands, are also remarkable for their shell-beds in this deposit, while very few of such organisms have yet been detected in any of the Scottish rocks of the system to the south of the Grampians. The relics are confined to one species of shell, resembling in general appearance the form of the Cyclas, and are found in various quarries in the district.

What a revolution in letters, knowledge, and civilization since the days of the Romans! This, their Ultima Thule! and a science in the very rocks of which they never even dreamed. Proud they were of their fabled origin from the twin boys suckled by the wolves. Here are the spoils of ages long anterior to their myths of remotest genealogy—families of creatures that had fulfilled their destiny—buried in the sand, and upheaved into lofty mountains, while the Seven Hills of their proud city slept beneath the waves.

We now proceed to trace the order of the formation southward of the Grampian chain.

1. The conglomerate, a deep red and well-marked deposit, skirts the base of the mountains, and in some places is of vast thickness, betwixt Stonehaven and Blairgowrie. This rock is composed of fragments of the primary series, gneiss, mica-slate, quartz, and porphyry; the granite constitutes the paste in which these are set and agglutinated together. Excellent sections are to be seen in those localities, where the principal rivers, the North and South Esks, the Wast Water, the Isla, and the Ericht, make their passage in debouching upon the plains. In all these defiles the cliffs are precipitous, and often very picturesque, their variegated and bright flesh-colored sides forming a pleasing contrast with the dark waters as they eddy into pools, or dash headlong over their broken ledges. A momentary inspection of this composite rock leaves not the shadow of a doubt upon the mind as to its derivative origin, while its vicinity to the great chain where its several ingredients are to be found as directly points to the quarry whence it was hewn: not, it may be, slowly accumulating, as generally asserted, during the lapse of indefinite periods of time, but rapidly brought together and consolidated, as so many of the sharp angular edges of the materials most unequivocally attest. The finer beds that occur in the vicinity would seem to have been the talus or outgoing of the coarser conglomerate, formed of the minute particles of the same ingredients which had accumulated in the more tranquil hollows of the sea-bottom. The slaty fissile sandstone of Coventry Quarry near Fettercairn (so remarkably tilted up and welded literally to the igneous dyke), stretching throughout the north-east and south-west parts of the counties of Kincardine and Forfar, and prevailing over the districts of Auchtergaven, Crieff, and Callander, may be mistaken in many places for the clay-slate itself slightly altered in texture and appearance.

These conclusions as to the derivative origin of the conglomerate are fully confirmed and borne out by the fact, that the deposit is everywhere found precisely where such materials would be collected, all around the shores of the Scottish Highlands, overlying or fringing the base of the crystalline rocks, filling up the creeks and bays of the primeval world. After thousands of years the massive blocks of syenite, chiseled and half-dressed, are still lying in the quarries of Upper Syria, while the cities for which they were preparing are heaps of ruins in the desert. Nature, left to her own operations, treasures up the waste occasioned by the elements and other forces, and by thus raising outworks and buttresses protects her crystal foundations against the inroads of consuming time.

2. Forming an outer zone or rampart, and overlapping the conglomerate, a gray fossiliferous sandstone constitutes the next member of the Devonian group. This deposit is widely extended, and consists of several beds. One of these is a fine-grained, compact building stone. Another, the well-known flag-stone, is of a more slaty texture, of a dark-blue color, and abounds in mica. These sandstones occupy a great part of the sea-ward barrier by Montrose, Arbroath, and the high grounds of Carmylie. They fold over the Sidlaws on both acclivities of the range, where they form a well defined example of what geologists term the _anticlinal_ and _synclinal_ axes, that is, the rock curves and reduplicates, like a soft flexible substance, according to the undulations of the surface. The several beds cross the Tay in the direction of Dundee, and emerge on the opposite banks at Wormit-bay, Parkhill, and Newburgh; ranging eastward along the northern slope of the Ochils by Norman’s Law and the high table-land of Balmerino.

3. A limestone rock, termed CORNSTONE, from its practical application to grinding purposes in England, occupies a place among the old red sandstone series. This deposit occurs in thin bands of a dull yellowish or blue-colored stone, containing numerous cherty nodules, and, where compact, is of a sub-crystalline texture. The cornstone generally contains more of silicious than of calcareous matter, and is consequently not much prized for building or agricultural purposes. In Scotland no organisms have been as yet detected in it, but in England it yields abundantly remains of the cephalaspis and various crustaceans. This rock is not co-extensive with the other members of the group, nor do we find it continuous in any part of the district which it occupies. It is generally found in small detached patches, as at Glen-Finlay, Meigle, Cargill, on the north of the Sidlaws; at Ballendean, Rait, Meurie, in the Carse of Gowrie; at Parkhill, Newburgh, Clunie, Kinnaird, on the south bank of the Tay; and at Newton and Craigfoodie, on the southern face of the Ochils. At the Newburgh station of the Edinburgh and Northern Railway the cornstone is inclosed among the eruptive rocks, partaking of their common induration, and, except in its distinct lamination, cannot be distinguished in color or texture from the traps.

4. A rock-marl underlies the cornstone in the form of a reddish, variegated sandstone, and contains about fifteen per cent. of lime. Deep sections of this calcareo-arenaceous deposit are displayed along the basin of the Tay, on both sides, from the confluence of the Isla to Stanley, at Pitcairn Green on the Almond, and occupy the ridge from Methven to Crieff. A remarkable vein of serpentine skirts the base of the Grampians in a south-east and north-west direction, of a beautiful dark olive-green, in some places of a blue and whitish color, and at Cortachie Bridge, where it crosses the Esk, containing crystals of diallage. This dyke widens in some parts to nearly ninety feet, of a hard compact texture, and, as the marble of the district on the lakes of Clunie, it is extensively used for ornamental purposes.

5. The geologist, as he pursues his journey by either of the lines of railway that intersect Forfarshire, has still many interesting localities and objects before him. Traversing “the fertile plains of Gowrie” by the Perth and Dundee Junction, he enters at Inchture upon a higher member of the old red sandstone, a fine-grained yellow-spotted bed. The deposit first appears to the eastward of Inchture, in the den of Balruddery, where its outcrop is seen immediately to overlie the gray fossiliferous beds.—The same variety emerges on the opposite bank of the Tay at Birkhill; at Abernethy, where it abuts at nearly right angles against the trap in a small ravine to the south of the village; whence it skirts the base of the Ochils, and occupies the center of Strathearn at Dumbarnie. The Clash-bennie sandstone, doubly interesting from having furnished the first and best specimen of holoptychius, the type of its age, may be regarded as an extension of the Balruddery and Inchture rock. The beds vary a little in their lithological characters, as well as in the deep flesh-color predominant in the latter; still the spherical markings are there, and, as their organic remains are identical, their position in the series may be considered as one and the same. The yellow or upper beds of the old red sandstone fall next to be considered; but these, from their geographical limits, are deferred to the subsequent chapter.

6. Approaching Perth by the Midland Junction, the geologist cannot fail to be arrested by the vast accumulations of sand and gravel, which everywhere present themselves, sometimes in the deep cuttings and railway sections; sometimes in the shape of rounded hillocks or long narrow ridges; and at other places as extended plateaux or sea-margins of different elevations. Along the whole western and southern slopes that overhang the city, these objects give a pleasing variety to the landscape, and form interesting subjects of speculation as to their origin, doubtless the gathered wreck of all the rocks we have been contemplating; for after a careful examination of their contents the conclusion cannot be avoided, that with much of the spoil of the primary rocks, we have here the detrital waste of the entire old red sandstone series. The Carpow cutting, in Strathearn near Newburgh, contains large rounded masses of all the varieties, with their peculiar ichthyolites; the gray, red, and yellow deposit that prevails in Fifeshire, and one solitary patch of which still exists _in situ_, near the Kirk of Dron, as if on purpose to mark its ancient and more extended boundaries. Nodules and bowlders of the cornstone are likewise abundant. In the vicinity of Perth, the waste of the yellow sandstone is to be found, unmixed in several spots, consisting of thick beds of fine argillaceous sand.

Similar masses of gravelly debris are spread over the middle-basin of the Earn, from Forteviot to Muthil. The Scottish Central cleaves its way for ten miles through scarcely any other material. The dreary monotony of these endless hillocks, around Auchterarder and Blackford, is relieved in part by the fine undulating grassy braes of the Ochils, and the richly-wooded rising grounds skirting the left bank of the river. The geologist’s eye wanders eastward, through the district occupied by the lower basin of the Tay, where the whole was one great estuary or strait, and these the shoals covered by the ancient waters. The eastern shores, from Wormit-bay to Leuchars, are accordingly characterized by vast accumulations of sand and gravel, originating in the same causes and deposited at the same period.

It will excite no surprise, therefore, should we remark that the various beds of old red sandstone now so disjoined, or appearing only as patches, once covered the greater part of the district traced above, extending from the Ochils across the Sidlaws to the Grampians. Nor can there be difficulty in finding an adequate cause for their up-break, especially in the upper members of the group. Consider not merely the constant waste arising from aqueous abrasion and meteroic influences, but also the tearing effects occasioned by the convulsive throes and elevatory movements of the Grampian, Sidlaw, and Ochil ranges, either singly, or, as it may have happened, in combination, when the overlying rocks must have been shattered and broken in every direction, and rendered capable of easy transportation. Although belonging to a posterior geological epoch, these hillocks of gravel and sand are thus the collected records of primeval times, attesting that mighty agencies have been at work in rending the globe, re-adjusting its materials, and preparing them for future combinations.

How speedily, in these first days of creation, does geology make us acquainted with the liability to change and mutation stamped upon all earthly things! The mountains are raised up, and their earliest struggles are to get down again. Nor is it the law of matter, if we may use the expression, to rise. The waters seek the hollows of the earth, because they are material. The rocks, more solid, are subject to the same principle of gravitation, and their course is downward, and their natural place the bottom of the waters. When the rocks were separated from and elevated above the waters, it was not by any virtue or power in themselves to assume these positions. The separation as well as the elevation were the results of direct arrangement; both certainly provided for in the original plan, and yet not the less brought about against their own material tendencies by a special agency. Geology thereby establishes the fact, that the mountains were raised up and the dry land COMMANDED to appear. And now, decomposing and wasting down, we see them seeking back to their old places, to be there re-constructed, and to subserve other purposes.

THE ORGANIC REMAINS, which fall next to be described, are confined to three of the beds, as enumerated above. The first of these, in the order of superposition, is the micaceous flagstone of Carmylie and Arbroath, likewise extending along the south bank of the Tay, and distinguished by the vegetable culmiferous impressions with which it abounds. These, in some places, are so numerous, as to cover the entire surface of the rock. The idea of an ancient marsh is immediately called up in the mind, as one sees stone after stone split up, and all the interstices mottled and streaked over with the stems and leaves of the plants which were fed by its waters. While we write, every pond, and every lake in the neighborhood has crept quietly under its carpeting of ice, a congelation of the living with the dead. How beautiful and distinctly delineated the culms and leaves of the chara locked in its crystal embrace; the flower of the juncus yet lingers on the stalk; and there, how gracefully float the long broad continuous stems of the scirpus lacustris! The pike and perch, both typified in the olden rocks, may be seen motionless as a stone, or softly buoyant as the down, in the clear depths below. Not so brightly, but now as fixedly set, and as minutely preserved, are the fragments of the flora of the Devonian age: if blackened and jetty in their hoary antiquity, these films of mica give light and relief to the darker background of the picture; and shapes, too, were there sporting in the waters,—the seraphim and buckler-headed cephalaspis,—which painter never conceived, nor poet feigned.

These fossils are not in a state of petrifaction, but generally consist in the form of an easily-separated film of carbonaceous matter, or more frequently as a simple coaly marking. Sometimes, but very rarely, the plant is found betwixt the slaty layers, as it were in a dried state, and still perfectly flexible; and the impressions not unfrequently resemble the narrow striated leaves of the alopecurus geniculatus, the floating foxtail-grass, with its knotted culms. There are other specimens, that look like the bark of trees, or the branches of the gnarled oak, ribbed and jointed crosswise. The round dotted patches, varying from the size of a garden pea to an inch in diameter, not unlike, in shape and appearance, the form of a compressed strawberry, are very plentiful. Dr. Fleming, in Cheek’s “Edinburgh Journal” for February, 1831, has figured this organism in connection with the stem, which thereby forms a graceful and well-defined flowering plant, while Sir Charles Lyell considers these berry-shaped forms to be the relics of the ova of some gasteropoda of the period. But at Wormit and Parkhill they are so uniformly, and in such numbers, associated with the culmiferous and leaf impressions, as most strongly to vindicate their claim to a vegetable origin. We have in our collection several specimens, with this organism separated certainly from the culm, but still in such closeness and proportionate size, as, with little aid from the imagination, to infer their former connection, and assign to them a place among the phanerogamous and seed-yielding plants. If so, we cannot too highly prize these relics, regarding them, as they undoubtedly are, among the oldest of organic substances—the first of the green herbs that sprung from the earth—the fragile flower, that withers often in a day, there to attest the mandate of primeval creation. How many seasons have returned; how many seed-times and harvests have covered the fields; what revolutions and changes over all these hills and plains, since that flinty rock formed the soil, and these vegetables sprung from its fertility! They are not admitted among the economic order of the gramineæ; nor whether of marine, semi-marine, or lacustrine origin, have geologists been able to determine.

Of the ANIMAL REMAINS of fishes belonging to the gray sandstone, the Cephalaspis Lyellii was one of the earliest discovered, as it still constitutes one of the most remarkable of these fossil relics. The head of this creature, and hence the name buckler-headed, is large in proportion to the body, forming nearly one-third of its length. The outline is rounded in the form of a crescent, the lateral horns inclining slightly toward each other, while the anterior or central parts project considerably outward; this peculiarity of structure is occasioned by the intimate anchylosis of all the plates which compose the cranium. The body resembles in appearance an elongated spindle, swelling out on the ridge of the back, and narrowing to the extremity of the tail, which terminates in a long slender point. How like, peradventure, the very dagger with which the murderous Thane of Glammis threatened to render—

“The multitudinous seas incarnadine, Making the green one red!”

The sanguineous fluid, in those days, was not indeed very plentiful; but the sharp-horned orthoceræ, and the swift predaceous nautili were cotemporaries; and hence, either for protection or attack, we find that, while the head of the Cephalaspis was one entire plate of enameled bone in the upper division, the body was wrapped in a closely woven net-work of bony scales, of peculiar form, and differing from the scales of every other genus of ganoids. The scales along the center of the sides are so high, that their breadth exceeds their length eight or ten times, occupying more than half the height of the animal. Everywhere meshed in smaller but equally impervious nettings, there are of the larger scales, from twenty-six to thirty covering the sides, thereby completing a mail-clad figure of a singularly warlike aspect, and bidding defiance, like his great anti-type, to all his foes,—“let fall thy blade on vulnerable CRESTS”—but now, like Banquo’s ghost, “the bones are marrowless.”

These curious fossils were first detected in the quarries at Glammis, by Sir Charles Lyell, and from their striking resemblance to the cephalic shield of certain trilobites, were supposed, for a time, to belong to the class of crustaceans. The beds of Carmylie and Balruddery, yield these organisms in the greatest abundance. One solitary specimen, a fragment of two inches in length, of the smaller scaly net-mesh, has been obtained by me in the gray rock, on the south bank of the Tay. The heads are uniformly in the best state of preservation; indeed hundreds of these lie entire, where no part of the body has left the trace of an impression. M. Agassiz assigns, as the reason of this, the great difference that exists in the structure of these two parts, and especially in the disproportion of their dimensions and forms, which would offer a distinct resistance to the pressure to which the animals must have been exposed. “If, on the other hand,” he adds, “the heads usually present their superior surface to us, it is because their inferior surface, the cavity of the mouth, the branchial arch and sinuosities of the inferior bones of the cranium, are points of support comparatively more solid, and more adapted for sustaining the matter which has filtered into them, than a larger surface slightly convex, which would naturally be detached from the rock wherever a separation was found in it.”

THE DEN OF BALRUDDERY presents us with a group of very remarkable fossils, comprising, in an area of the gray sandstone of a few square yards, innumerable impressions of the plant-markings already noticed, multitudes of the Cephalaspis, spines, and other ichthyolites, along with two entirely new genera of fishes of the order of Placoids. The sandstone here is of a very slaty character, splitting up into thin layers, betwixt every one of which some organism or other has impressed its form; and the different kinds are often so promiscuously huddled together, as to suggest the idea of some violent commotion in the element which collected and destroyed them. In the “Synoptical Table of British Fossil Fishes,” by M. Agassiz, we find inserted a _Parexus recurvus_, and a _Clematius reticulatus_, from this locality; they are represented simply as ichthyodorulites, no complete specimens of the creatures having been presented to him, nor indeed have any been as yet obtained. One of the specimens in the Balruddery collection, when returned by M. Agassiz, was labeled as a _Palæocarcinus alatus_: and in the 14th Livraison of his “Poisson Fossiles,” he thus writes:—“Enfin j’en dois aussi plusieurs espèces à M. Webster de Balruddery. Parmi ses échantillons j’en ai trouvé plusieurs d’un grand intérêt, parce qu’ils m’ont fait connaître que le genre Pterygotus que j’avais établi, il y a plusieurs années, sur des fragmens très-imparfaits, n’appartient point à la classe de poissons, mais bien en celle des crustaces. Une pareille erreur semble à peine possible, et cependant elle paraît excusable lorsque je ferai connaître les caractères de ce fossile; des botanistes célèbres n’avaient pas hésité à les ranger parmi les Algues. Les Seraphius fossiles des carrières de Forfarshire, que M. Lyell a soumit à la Section de Geologie de l’Association Britannique réunie à Edinbourg en 1834, sont des ces mêmes crustaces gigantesques du terrain Dévonien. Ils offrent des rapports éloignés avec les Entomestracés gigantesques du terrain houiller, décrits sous les noms d’Edotea et d’Eurypterus.” The Lobster, accordingly, of Balruddery is the first discovery of its fossil kind; portions of nearly every organ of the body have been found, so as to make the restoration of the crustacean complete: a creature of at least four feet in length, and as in the fishes of this epoch, the shelly covering is dotted all over with enameled scale-like markings. This magnificent collection remains still undescribed, hundreds of the specimens, from the minute to the gigantic, and of the greatest diversity of character, being only detached fragments of the structures to which they belonged; but enough have we there to testify as to the early prolific abundance of Nature, and that, throughout all ages, her types and forms of life are wonderfully allied.

The interesting locality of Balruddery is succeeded by another in the ascending order of the strata, but lower on the plain of the Carse of Gowrie,—Clashbennie, situated about six miles to the westward. This rock is well entitled to be denominated the Holoptychius Bed, as here the first complete specimen of that remarkable genus was obtained, and of which there are three species in the deposit, namely, H. Giganteus, Noblissimus, and Murchisoni. Three other genera, of the ganoid order of fishes, have left their relics in this bed, some of them in a beautiful state of preservation: these are Glyptosteus reticulatus, Phyllolepis concentricus, and Glyptolepis elegans, all named and described by M. Agassiz.

The Holoptychius ranks among the family of Cœlacanthes, and the term Holoptychius (holos, entire; and ptyche, a wrinkle) is applied to the fossil from the circumstance of the scales being covered with wrinkled dots or markings, the enameled surface of which is indented with deep undulating furrows. Another characteristic feature of this genus consists in the distant position of the ventrical fins, being considerably removed toward the tail, and in the arrangement of the branchial organs, which form two large plates between the branches of the inferior ray, as in the genus Megalichthys. The structure of the “nageoirs,” the rounded form of the ventrical fin, and the manner in which the rays of its anterior edge are insensibly prolonged, in connection with their relative thinness, are also marked distinctions. The head of the Holoptychius is remarkably small in comparison with the size of the body, which, in the Clashbennie specimen measures thirty inches in length by twelve in breadth. The scales are still disproportionately larger than either the head or body, some of them being nearly three inches in length by two and a half in breadth, with a corresponding thickness. The structure of the dermal covering is beautiful in the extreme; it is composed of these scale-plates, articulating, and laced together in such a way as to combine the greatest possible strength with the highest degree of flexibility; and, protected by a rich coating of enamel, it must have been capable of the greatest endurance, and of resisting any pressure. Two thickly set rows of teeth; one inner, and extremely minute, the other large and pointed, completed the equipments of a mouth adapted to seize and crush to powder any intruder upon its pasturage. The vertebral column extended to the extremity of the tail, which was forked or divided into two unequal lobes, a contrivance of nature that enabled the animal to turn quickly on its back before striking its prey. This form of the tail is called the HETEROCERCAL; it is characteristic of most of the fishes of the period, and prevailed during the palæozoic age; when it gave way, at the era of the chalk formation, to what is termed the HOMOCERCAL structure, and which still exists in the fishes of the current epoch.

The Phyllolepis is a very striking genus of the same family, and has also been noticed at considerable length by the Swiss naturalist. The scales, or other plates, which covered the body of this fish are of enormous dimensions, being nearly half a foot in diameter, and rounded to an obtuse angle. What distinguishes them from all other scales, and

## particularly from those of the Holoptychius, with which they have certain

external resemblances, is their extreme tenuity, consisting simply of a film of enamel spread over a thin osseous membrane, scarcely so thick as the blade of a knife, and varying from three to five inches in diameter. Their surface is smooth, or slightly marked with concentric wrinkles parallel to the edge of the scale. Two species of this genus have been found, one in the old red, and the other in the coal formation. In the Clashbennie sandstone only a few detached scales have been detected, but sufficiently well preserved to show the superposition, or imbrication, perhaps, in which they stood relatively to each other, the wrinkles serving as grooves by which their adhesion was more firmly effected. One decided characteristic of this organ in the _Phyllolepis concentricus_ is, that it is a little raised toward the middle, whence it again declines or sinks on all sides, after the manner of a roof.

The sandstones flanking the hill of Kinnoul, and stretching along the left bank of the Tay, by Scone and Lethendy, appear to be a continuation of the Clashbennie beds, as also those occupying the ridges by Ruthven and Dupplin, where they assume much of the fissile character and micaceous aspect of the Carmylie flag-stone, but everywhere destitute of organic remains in the whole western district from Perth to Callander. The absence of fossils from particular beds has been accounted for in various ways. But even in the same series of rocks, and where there is no break in the continuity of the strata, it is a maxim of geology that the range of fossils is not always co-extensive with the mineral deposits. Then, as now, the explanation is, that the slightest physical changes affected the tastes and habits of the animal kingdom; the direction and strength of a current; the depth of water; the character and qualities of the sea-bottom; the force of tidal action; the season of the year, being, it is well known, singly sufficient to produce great differences as to the migrations and favorite haunts of almost every aquatic race. And hence it is laid down as a recognized principle in the science, that a particular bed of rock within certain limits is not to be excluded from its place in a system, and another substituted therein, by the mere presence or absence of a certain class of fossils. Individuals, too, will often outlive the family to which they belong, and be found in certain localities intermixed with the races of a higher group of rocks.—And these remarks are applicable to all the formations, less or more, from the lowest fossiliferous strata to the latest of the tertiaries. Applied to the old red sandstone, they serve to explain the fact that, while the precise relative position of the western beds in the district under review cannot in every instance be determined, large spaces or areas are entirely destitute of organic remains which in the eastern, and not distant, localities are detected in the greatest abundance and variety. The system of rocks is unquestionably the same, but neither cephalaspis, parexus, clematius, holoptychius, glyptosteus, phyllolepis, nor glyptolepis, ever would seem to have frequented these parts; whether for the reasons above assigned, or for any other local cause, or simply that they did not like the region—as the grouse and ptarmigan, even now, will not descend to the plains—is one of the recondite problems of animal life connected with the new as well as the older state of things. These beds may yet, however, be discovered to be fossiliferous, as the smallest space in local distance may reveal their hidden stores, to reward the diligent observer, and add to our knowledge of the aboriginal fauna of the district.

The lesson farther taught by the varied phenomena which have passed under review in this chapter would seem to be, that there is nothing fixed or permanent in such arrangements of nature.—These are the beginnings of creation, and both as respects organic and inorganic matter, change and re-construction have prevailed from the earliest periods to which our researches can penetrate.—The Divine Architect did not complete things as we now see them, in one initial act; nor, as we regard quiescence and stability, were the elements and forces of nature so balanced as not to interfere even in violent collision with one another. A world is called into existence. Storms and commotions rend its frame.—Sea and land contend for mastery. And everything within its bounds, like the flux of time, like day and night, summer and winter, life and death, is observed to have emerged into being and form, to have assumed new arrangements, then to have perished; or gradually, as its nature might be, to have consumed away.

No reason can be assigned for all this, as the law or order of events, except the appointment of Him who made and continues the constitution of nature as it is. No adequate cause of creation can ever be conceived but that of the Divine Goodness; and while we never can expect fully to comprehend the wisdom that planned, and the power that carried into effect, the purposes of that wisdom, still the very effort to attain knowledge concerning them, fulfills one great object for which man is made curious about the works of his Maker. In contemplating the wonders of those days, the variety, adaptation and perfection of everything in itself as then constructed, he will always refer to that Infinite Intelligence through whose goodness he is permitted to enjoy knowledge. In becoming wiser he will become better. His increasing knowledge will be made subservient to a more exalted faith in that everlasting “Word” who framed the worlds; and in proportion as the vail becomes thinner through which he sees the origin and course of things, he will admire all the more the brightness of Him who was the true light which lighteth every man that cometh into the world.

[Illustration: Holoptychius Noblissimus.]

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