[48]This hollow centre may be seen occasionally filled up by a sharp conical tooth like thephragmoconeof a belemnite.
[48]This hollow centre may be seen occasionally filled up by a sharp conical tooth like thephragmoconeof a belemnite.
The lower portion of the tooth exhibits a much more complicated texture. Externally it is marked by deep longitudinal furrows, that run down the enamelled sides and sink into the jaw. When cut across at this ribbed part, the tooth is found to present the most complex and graceful internal structure. The prominent ridges between the furrows are seen to be produced by crumpled folds of the substance of the tooth, which roll inwards towards the centre, coalescing with each other, and forming intricate groups of circling knots and folds. In some places they seem all but separated from each other into little circles, pierced with a central aperture, and recall the aspect of the upper layer in the scale of megalichthys. Each of these loops and folds presents a texture exactly similar to that of theupper part of the tooth. The same minute hair-like tubes, darkened and thickened in the long axis, radiate towards the centre; the same concentric bands run from centre to circumference; so that the lower part of the tooth seems, as it were, made up of a bundle of smaller teeth partially melted into each other. Between these loops and folds circular meshes frequently occur, and add to the complexity as well as the beauty of the whole structure. One of these sections, with all its twisting crumples, and folds, and knots, and coloured meshes, and encircled rings, bears no small resemblance to an antique polished table that has been cut out of the gnarled roots of a venerable oak. This complex structure arose from the mode of growth of the tooth; each prominent external ridge continually turning inwards down the furrow on either side, and mingling in freakish knots with the folds that had gone before.[49]
[49]For an acquaintance with the remarkable teeth of this ancient fish, more minute than it had been my good fortune to possess before, I am indebted to a most interesting series of microscopical preparations kindly lent me from his extensive collection by my friend Mr. Alexander Bryson of Edinburgh.
[49]For an acquaintance with the remarkable teeth of this ancient fish, more minute than it had been my good fortune to possess before, I am indebted to a most interesting series of microscopical preparations kindly lent me from his extensive collection by my friend Mr. Alexander Bryson of Edinburgh.
The internal bones of the holoptychius were of great size and strength, as befitted such a bulky ganoid. Some of them had a singular style of surface ornament, that somewhat resembled a frosted widow on a December morning. Their internal structure was loose and cancellated; the endo- being usually of a less compact texture than the exo-skeleton. Judging from the size of such bones, the carboniferous holoptychius must have been one of the bulkiest and most formidable denizens of the deep, reaching sometimes to a length of twenty feet or even more. Such an animal would have been, perhaps, quite a match for our hugest crocodile or alligator, for it must have swum about with a litheness and agility possessed by none of the saurian reptiles. Like that leviathan chosen by the Almighty, in an age long subsequent, as an illustration of His power and greatness, the holoptychius must have been king over all the inhabitants ofthe sea, and the magnificent language of Job, descriptive of the living animal, applies not less graphically to the extinct one: "Who can open the doors of his face? his teeth are terrible round about. His scales are his pride, shut up together as with a close seal. One is so near to another, that no air can come between them. He maketh the deep to boil like a pot: he maketh the sea like a pot of ointment. He maketh a path to shine after him; one would think the deep to be hoary."
Our survey has hitherto been directed to the denizens of carboniferous lake, river, and sea, and we have found them to be alike important in numbers and interesting in organization. It is otherwise, however, when we turn in search of the denizens of the carboniferous lands. The crowded trees and shrubs of the coal strata recalling as they do old forest-covered swamps, might seem to indicate the probability of a pretty numerous terrestrial fauna. Where are we to look for the fossilized relics of land animals, if not in the remains of a submerged land-surface? And yet, strange as it may seem, of the inhabitants of the land during the Coal-measure period we know almost nothing. "We have ransacked hundreds of soils replete with the fossil roots of trees,—have dug out hundreds of erect trunks and stumps, which stood in the position in which they grew,—have broken up myriads of cubic feet of fuel, still retaining its vegetable structure,—and, after all, we continue almost as much in the dark regarding the invertebrate air-breathers of this epoch, as if the coal had been thrown down in mid-ocean."[50]
[50]Sir Charles Lyell'sElements, fifth edition, p. 406.
[50]Sir Charles Lyell'sElements, fifth edition, p. 406.
The little land-shell already noticed as having been detected by Sir Charles Lyell in the carboniferous rocks of Nova Scotia, seems to be as yet the only air-breathing mollusc obtained from rocks of such high antiquity. Insect remains have been detected in the English coal-fields belonging to two or three species of beetles; while on the Continent, wing-sheaths and other fragments of cockroaches, scorpions, grasshoppers, locusts, crickets,&c., have been detected. But the most remarkable traces of air-breathers consist in various indications of the existence of reptiles during the Carboniferous era. Fragmentary skeletons, with detached bones and plates, have been found in Bavaria and America, together with long tracks of footprints, from which it appears that during the time our coal-seams were forming, there swam through the sluggish deltas, or crept amid the dank luxuriant foliage, strange lizard-like forms, large enough to leave behind them on the soft yielding mud or sand the impress of their double pair of toed feet. But of these animals we have much to learn. Some of them have bequeathed to us merely their dismembered broken bones; others have left but the imprints of their toes. Yet even these remains, trifling as they may seem, become of importance when we remember that they demonstrate fishes not to have been the highest types of being during the epoch of the Coal, and show that while the bulky holoptychius held the supremacy of the waters, lizard-like forms of a less formidable type seem, so far as we know, to have ruled it over the land.
In fine, then, no one can glance at a list of the carboniferous fauna without perceiving either that the animated world of that ancient epoch must have had a very different proportioning from what now obtains, or that we have only a meagre and fragmentary record of it. That the latter conclusion is the more philosophical will appear if we reflect upon the many chances that exist against the entombment and preservation of animal remains, especially of those peculiar to the land. How very small a proportion of the remains of animals living in our own country could be gathered from the surface-soil of any given locality, and how very inadequate would be the meagre list of species thus obtained, as representing the varied and extensive fauna of Great Britain! In contrasting, then, the rich abundance of marine organisms with the extreme paucity of terrestrial animals among the carboniferous rocks, it would be toohasty to infer a corresponding disproportion originally. It must be admitted that the rarity of air-breathers, after such long-continued and extensive explorations among terrestrial and lacustrine beds, presents a difficult problem, only (if at all) to be cleared away by patient and persevering investigation. With this preliminary caution, we may regard the carboniferous fauna as peculiarly rich in marine species. The sea-bottoms swarmed with stone-lilies, cup-corals, and net-like bryozoa, mingled with the various tribes of molluscan life—the brachiopods with their long ciliated arms; the bivalves and gastropods with their coloured shells that recall some of the most familiar objects of our shores; and the cephalopods with their groups of siphonated chambers, straight as in the orthoceras, or gracefully coiled as in the goniatite. The seas swarmed, too, with fishes belonging to the two great orders of ganoids and placoids, the latter represented now by our sharks and rays, though the exact type of the ancient genera is retained only by the cestracion or Port-Jackson shark; the ganoids, with their strong armour of bone, represented by but two genera, the lepidosteus of the American rivers, and the polypterus of the Nile,—two fishes that seem but as dwarfs when placed side by side with the gigantic holoptychius of the coal-measures. The rivers and estuaries of the same period seem to have been frequented by immense shoals of the smaller ganoidal fishes that fed on decaying matter brought down from the land, and perhaps, too, on the minute Crustacea that lay strewed by myriads along the bottom. Into these busy scenes the bulkier monsters from the sea made frequent migrations, perhaps in some cases ascending the rivers for leagues to spawn, and returning again to their places at the mouth of the estuary or in open sea. The rivers and lakes swarmed with small crustaceous animals, and nourished, too, shells like those of our pearl-mussels. The land—so luxuriantly clothed with vegetable forms—was hummed over by beetles, chirupped over by grasshoppers and crickets, and crawledover by four-footed reptiles, that united in their structure the lizard and the frog. But of the general grade and proportions of its denizens we still remain in ignorance. From all that yet appears, the scenery of these forests must have been dark, silent, and gloomy, buried in a solitude that was startled by no tiger's roar, no cattle's low, and neither cheered with the melody of birds nor gladdened by the presence of man.
We have lingered, perhaps, too long over the remains of these old carboniferous animals. But the delay may be not without its use if, by thus bringing before us some of the more marked points in the structure of creatures that for ages peopled our planet, it broaden our view of creation; and by lifting the curtain from off a dim, distant period of our world's long history, it show, amid all diversities of arrangement, and all varieties of form, still the same grand principles of design, and the same modes of working as those which we can see and compare among the living forms around us. It is something to be assured that the race of man has been preceded by many other races, lower indeed in the scale of being, but manifesting, throughout the long centuries of their existence, ideas of mechanism and contrivance still familiar to us, and serving in this way to link the human era with those that have gone before, as parts of one grand scheme carried on by one great Creator.