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.
Holoptychius Noblissimus.