[I]The aborigines of South. America deemed it wonderful that the Europeans who first visited them should, without previous concert, agree in reading after the same manner the same scrap of manuscript, and in deriving the same piece of information from it. The writer experienced on this occasion a somewhat similar feeling. His specimens seemed written in a character cramp enough to suggest those doubts regarding original meaning which lead to various readings; but the geologist and the naturalist agreed in perusing them after exactly the same fashion—the one in London, the other in Neufchatel. Such instances give confidence in the findings of science. The decision of Mr. Murchison I subjoin in his own words—his numbers refer to various specimens ofPterichthys: "As to your fossils 1, 2, 3, we know nothing of them here, (London,) except that they remind me of the occipital fragments of some of the Caithness fishes. I do not conceive they can be referrible to any reptile; for, if not fishes, they more closely approach to crustaceans than to any other class. I conceive, however, that Agassiz will pronounce them to be fishes, which, together with the curious genusCephalaspisof the Old Red Sandstone, form the connecting links between crustaceans and fishes. Your specimens remind one in several respects of theCephalaspis."
[I]The aborigines of South. America deemed it wonderful that the Europeans who first visited them should, without previous concert, agree in reading after the same manner the same scrap of manuscript, and in deriving the same piece of information from it. The writer experienced on this occasion a somewhat similar feeling. His specimens seemed written in a character cramp enough to suggest those doubts regarding original meaning which lead to various readings; but the geologist and the naturalist agreed in perusing them after exactly the same fashion—the one in London, the other in Neufchatel. Such instances give confidence in the findings of science. The decision of Mr. Murchison I subjoin in his own words—his numbers refer to various specimens ofPterichthys: "As to your fossils 1, 2, 3, we know nothing of them here, (London,) except that they remind me of the occipital fragments of some of the Caithness fishes. I do not conceive they can be referrible to any reptile; for, if not fishes, they more closely approach to crustaceans than to any other class. I conceive, however, that Agassiz will pronounce them to be fishes, which, together with the curious genusCephalaspisof the Old Red Sandstone, form the connecting links between crustaceans and fishes. Your specimens remind one in several respects of theCephalaspis."
PLATE I.
PLATE I.
I have placed one of the specimens before me. Imagine the figure of a man rudely drawn in black on a gray ground, the head cut off at the shoulders, the arms spread at full, as in the attitude of swimming, the body rather long than otherwise, and narrowing from the chest downwards, one of the legs cut away at the hip-joint, and the other, as if to preserve the balance, placed directly under the centre of the figure, which it seems to support. Such, at a first glance, is the appearance of the fossil. The body was of very considerable depth, perhaps little less deep proportionally from back to breast than the body of the tortoise; the under part was flat; the upper rose towards the centre into a roof-like ridge; and both under and upper were covered with a strong armor of bony plates, which, resembling more the plates of the tortoise than those of the crustacean, received their accessions of growth at the edges or sutures. The plates on the under side are divided by two lines of suture, which run, the one longitudinally through the centre of the body, the other transversely, also through the centre; and they would cut one another at right angles, were there not a lozenge-shaped plate inserted at the point where they would otherwise meet. There are thus five plates on the lower or belly part of the animal. They are all thickly tubercled outside with wart-like prominences, (seePlate I., fig. 4;) the inner present appearances indicative of a bony structure. The plates on the upper side are more numerous and more difficult to describe, just as it would be difficult to describe the forms of the various stones which compose the ribbed and pointed roof of a Gothic cathedral, the arched ridge or hump of the back requiring, in a somewhat similar way, a peculiar form and arrangement of plates. The apex of the ridge is covered by a strong hexagonal plate, fitted upon it like a cap or helmet, and which nearly corresponds in place to the flat central plate of the under side. There runs around it a border of variously formed plates, that diminish in size and increase in number towards the head, and which are separated, like the pieces of a dissected map, by deep sutures. They all present the tubercled surface. The eyes are placed in front, on a prominence considerably lower than the roof-like ridge ofthe back; the mouth seems to have opened, as in many fishes, in the edge of the creature's snout, where a line running along the back would bisect a line running along the belly; but this part is less perfectly shown by my specimens than any other. The two arms, or paddles, are placed so far forward as to give the body a disproportionate and decapitated appearance. From the shoulder to the elbow, if I may employ the terms, there is a swelling, muscular appearance, as in the human arm; the part below is flattened, so as to resemble the blade of an oar, and terminates in a strong, sharp point. The tail—the one leg on which, as exhibited in one of my specimens, the creature seems to stand—is of considerable length, more than equal to a third of the entire figure, and of an angular form, the base representing the part attached to the body, and the apex its termination. It was covered with small tubercled, rhomboidal plates, like scales, (seePlate I., fig. 3;) and where the internal structure is shown, there are appearances of a vertebral column, with rib-like processes standing out at a sharp angle. The ichthyolite, in my larger specimens, does not much exceed seven inches in length; and I despatched one to Agassiz, rather more than two years ago, whose extreme length did not exceed an inch. Such is a brief, and, I am afraid, imperfect sketch of a creature whose very type seems no longer to exist. But for the purposes of the geologist, the descriptions of the graver far exceed those of the pen, and the accompanying prints will serve to supply all that may be found wanting in the text. Fig. 1, inPlate I., and fig. 2, inPlate II., are both restorations—the first of the upper, and the second of the under, part of the creature. It may, however, encourage the confidence of the naturalist, who for the first time looks upon forms so strange, to be informed thatPlate I., with its two figures, was submitted to Agassiz during his recent brief stay in Edinburgh, and that he as readily recognized in it the species of the two kinds which it exhibits, as he had previously recognized the species of the originals in the limestone.
PLATE II.
PLATE II.
Agassiz, in the course of his late visit to Scotland, found six species of thePterichthys[J]—three of these, and the wings of a fourth, in the collection of the writer. The differences by which they are distinguished may be marked by even an unpractised eye, especially in the form of the bodies and wings. Some are of a fuller, some of a more elongated, form; in some the body resembles a heraldic shield, of nearly the ordinary shape and proportions; in others the shield stretches into a form not very unlike that of a Norway skiff, from the midships forward. In some of the varieties, too, the wings are long and comparatively slender; in others shorter, and of greater breadth: in some there is an inflection resembling the bend of an elbow; in others there is a continuous swelling from the termination to the shoulder, where a sudden narrowing takes place immediately over the articulation. I had inferred somewhat too hurriedly, though perhaps naturally enough, that these wings, or arms, with their strong sharp points and oar-like blades, had been at once paddles and spears—instruments of motion and weapons of defence; and hence the mistake of connecting the creature with the Chelonia. I am informed by Agassiz, however, that they were weapons of defence only, which, like the occipital spines of the river bull-head, were erected in moments of danger oralarm, and at other times lay close by the creature's side; and that the sole instrument of motion was the tail, which, when covered by its coat of scales, was proportionally of a somewhat larger size than the tail shown in the print, which, as in the specimens from whence it was taken, exhibits but the obscure and uncertain lineaments of the skeleton. The river bull-head, when attacked by an enemy, or immediately as it feels the hook in its jaws, erects its two spines at nearly right angles with the plates of the head, as if to render itself as difficult of being swallowed as possible. The attitude is one of danger and alarm; and it is a curious fact, to which I shall afterwards have occasion to advert, that in this attitude nine tenths of thePterichthysof the Lower Old Red Sandstone are to be found. We read in the stone a singularly preserved story of the strong instinctive love of life, and of the mingled fear and anger implanted for its preservation—"The champions in distorted postures threat." It presents us, too, with a wonderful record of violent death falling at once, not on a few individuals, but on whole tribes.
[J]Agassiz now reckons ten distinct species ofPterichthys—P. arenatus,P. cancriformis,P. cornutus,P. major,P. Milleri, P. latus,P. oblongus,P. productus,P. testudinarius, andP. hydrophilus; of these, nine species belong to the Lower, and one—thePterichthys hydrophilus—to the Upper Old Red Sandstone.
[J]Agassiz now reckons ten distinct species ofPterichthys—P. arenatus,P. cancriformis,P. cornutus,P. major,P. Milleri, P. latus,P. oblongus,P. productus,P. testudinarius, andP. hydrophilus; of these, nine species belong to the Lower, and one—thePterichthys hydrophilus—to the Upper Old Red Sandstone.
PLATE III.
PLATE III.
Next to thePterichthysof the Lower Old Red I shall place its contemporary theCoccosteusof Agassiz, a fish which, in some respects, must have somewhat resembled it. Both were covered with an armor of thickly tubercled bony plates, and both furnished with a vertebrated tail. The plates of the one, when found lying detached in the rock, can scarcely be distinguished from those of the other: there are the same marks, as in the plates of the tortoise, of accessions of growth at the edges—the same cancellated bony structure within, the same kind of tubercles without. The forms of the creatures themselves, however, were essentially different. I have compared the figure of thePterichthys, as shown in some of my better specimens, to that of a man with the head cut off at the shoulders, one of the legs also wanting, and the arms spread to the full. The figure of theCoccosteusI would compare to a boy's kite. (SeePlate III., fig. 1.) There is a rounded head, a triangular body, a long tail attached to the apex of the triangle, and arms thin and rounded where they attach to the body, and spreading out towards their termination like the ancient one-sided shovel which we see sculptured on old tombstones, or the rudder of an ancient galley.[K]The manner in which the plates are arranged on the head is peculiarly beautiful; but I am afraid I cannot adequately describe them. A ring of plates, like the ring-stones of an arch, runs along what may be called the hoop of the kite; the form of the keystone-plate is perfect; the shapes of the others are elegantly varied, as if for ornament; and what would be otherwise the opening of the arch, is filled up with one large plate, of an outline singularly elegant. A single plate, still larger than any of the others, covers the greater part of the creature's triangular body, to the shape of which it nearly conforms. It rises saddle-wise towards the centre: on the ridge there is a longitudinal groove ending in a perforation, a little over the apex, (Plate III., fig. 2;) two small lateral plates on either side fill up the base of the angle; and the long tail, with its numerous vertebral joints, terminates the figure.
[K]I have since ascertained that these seeming arms or paddles were simply plates of a peculiar form.
[K]I have since ascertained that these seeming arms or paddles were simply plates of a peculiar form.
Does the reader possess a copy of Lyell's lately published elementary work, edition 1838? If so, let him first turn up the description of the Upper Silurian rocks, from Murchison, which occurs in page 459, and mark the form of the trilobiteAsaphus caudatus, a fossil of the Wenlock formation. (SeeSil. Sys.,Plate VII.) The upper part, or head, forms a crescent; the body rises out of the concave with a sweep somewhat resembling that of a Gothic arch; the outline of the whole approximates to that of an egg, the smaller end terminating in a sharp point. Let him remark, further, that this creature was acrustaceousanimal, of the crab or lobster class, and then turn up the brief description of the Old Red Sandstone in the same volume, page 454, and mark the form of theCephalaspis, or buckler-head—afishof a formation immediately over that in which the remains of the trilobite most abound. He will find that the fish and the crustacean are wonderfully alike. The fish is more elongated, but both possess the crescent-shaped head, and both the angular and apparently jointed body.[L]They illustrate admirably how two distinct orders may meet. They exhibit the points, if I may so speak, at which the plated fish is linked to the shelled crustacean. Now, theCoccosteusis a stage further on; it is more unequivocally a fish. It is aCephalaspiswith an articulated tail attached to the angular body, and the horns of the crescent-shaped head cut off.
[L]Really jointed in the case of the trilobite; only apparently so in that of theCephalaspis. The body of the trilobite, like that of the lobster, was barred by transverse, oblong, overlapping plates, and between every two plates there was a joint; the body of theCephalaspis, in like manner, was barred by transverse, oblong, overlapping scales, between which there existed no such joints. It is interesting to observe how nature, in thus bringing two such different classes as fishes and crustacea together, gives to the higher animal a sort of pictorial resemblance to the lower, in parts where the construction could not be identical without interfering with the grand distinctions of the classes.
[L]Really jointed in the case of the trilobite; only apparently so in that of theCephalaspis. The body of the trilobite, like that of the lobster, was barred by transverse, oblong, overlapping plates, and between every two plates there was a joint; the body of theCephalaspis, in like manner, was barred by transverse, oblong, overlapping scales, between which there existed no such joints. It is interesting to observe how nature, in thus bringing two such different classes as fishes and crustacea together, gives to the higher animal a sort of pictorial resemblance to the lower, in parts where the construction could not be identical without interfering with the grand distinctions of the classes.
Some of the specimens which exhibit this creature areexceedingly curious. In one, a coprolite still rests in the abdomen; and a common botanist's microscope shows it thickly speckled over with minute scales, the indigestible exuviæ of fish on which the animal had preyed. In the abdomen of another we find a few minute pebbles—just as pebbles are occasionally found in the stomach of the cod—which had been swallowed by the creature attached to its food. Is there nothing wonderful in the fact, that men should be learning at this time of day how the fishes of the Old Red Sandstone lived, and that there were some of them rapacious enough not to be over nice in their eating?
The under part of the creature is still very imperfectly known: it had its central lozenge-shaped plate, like that on the under side of thePterichthys, but of greater elegance, (seePlate III., fig. 3,) round which the other plates were ranged. "What an appropriate ornament, if set in gold!" said Dr. Buckland, on seeing a very beautiful specimen of this central lozenge in the interesting collection of Professor Traill of Edinburgh,—"What an appropriate ornament for a lady geologist!" There are two marked peculiarities in the jaws of theCoccosteus, as shown in most of the specimens, illustrative of the lower part of the creature, which I have yet seen. The teeth, instead of being fixed in sockets, like those of quadrupeds and reptiles, or merely placed on the bone, like those of fish of the common varieties, seem to have been cut out of the solid, like the teeth of a saw or the teeth in the mandibles of the beetle, or in the nippers of the lobster, (Plate III., fig. 4;) and there appears to have been something strangely anomalous in the position of the jaws—something too anomalous, perhaps, to be regarded as proven by the evidence of the specimens yet found, but which may be mentioned with the view of directing attention to it."Do not be deterred," said Agassiz, in the course of one of the interviews in which he obligingly indulged the writer of these chapters, who had mentioned to him that one of his opinions, just confirmed by the naturalist, had seemed so extraordinary that he had been almost afraid to communicate it,—"Do not be deterred, if you have examined minutely, by any dread of being deemed extravagant. The possibilities of existence run so deeply into the extravagant, that there is scarcely any conception too extraordinary for nature to realize." In all the more complete specimens which I have yet seen,the position of the jaws is vertical, not horizontal; and yet the creature, as shown by the tail, belonged unquestionably to the vertebrata. Now, though the mouths of the crustaceous animals, such as the crab and lobster, open vertically, and a similar arrangement obtains among the insect tribes, it has been remarked by naturalists, as an invariable condition of that higher order of animals distinguished by vertebral columns, that their mouths open horizontally. What I would remark as very extraordinary in theCoccosteus—not, however, in the way of directly asserting the fact, but merely by way of soliciting inquiry regarding it—is, that it seems to unite to a vertebral column a vertical mouth, thus forming a connecting link between two orders of existences, by conjoining what is at once their most characteristic and most dissimilar traits.[M]
[M]These statements regarding the character of the teeth and the position of the jaws of theCoccosteushave been challenged by very high authorities. I retain them, however, in this edition in their original form, as first made nearly six years ago. In at least two of my specimens of Coccosteus the teeth and jaw form unequivocally but one bone—a result, it is not improbable, of some after anchylosing process, but which still solicits inquiry as not yet definitely accounted for. The matter of fact in the case is certainly one which should be determined, not analogically, but on its own proper evidence, as furnished by good specimens. As for the remark regarding the probable position of the creature's jaws, it was ventured on at first, as the reader may perceive, with much hesitation, and must now be regarded as more doubtful than ever. Its repetition here, however, will, I trust, be regarded as simply indicative of a wish on the part of the writer, that the question be kept open just a little longer, and that further examination be made. There is certainly something very peculiar about the mouth of the Coccosteus not yet understood, and singularly formed plates, connected with it, which have not been introduced into any restoration, and the use of which in the economy of the animal seem wholly unknown. [1850.—I have at length found a very perfect specimen of the nether jaw ofCoccosteus, and am prepared to show that it was of a character altogether unique. It had its two groups of from six to eight teeth, (exactly where, in the human subject, the molars are placed,) that seem to have acted on corresponding groups in the intermaxllaries, and two other groups of from three to five teeth placed at right angles with these, direct in the symphysis, and that seem to have acted on each other. But though these unique teeth of the symphysis formed a vertical line of mouth, it joined on at right angles to a transverse line of the ordinary type, as the upright stroke of the letter T joins on to the horizontal line a-top.] Fourth Edition.
[M]These statements regarding the character of the teeth and the position of the jaws of theCoccosteushave been challenged by very high authorities. I retain them, however, in this edition in their original form, as first made nearly six years ago. In at least two of my specimens of Coccosteus the teeth and jaw form unequivocally but one bone—a result, it is not improbable, of some after anchylosing process, but which still solicits inquiry as not yet definitely accounted for. The matter of fact in the case is certainly one which should be determined, not analogically, but on its own proper evidence, as furnished by good specimens. As for the remark regarding the probable position of the creature's jaws, it was ventured on at first, as the reader may perceive, with much hesitation, and must now be regarded as more doubtful than ever. Its repetition here, however, will, I trust, be regarded as simply indicative of a wish on the part of the writer, that the question be kept open just a little longer, and that further examination be made. There is certainly something very peculiar about the mouth of the Coccosteus not yet understood, and singularly formed plates, connected with it, which have not been introduced into any restoration, and the use of which in the economy of the animal seem wholly unknown. [1850.—I have at length found a very perfect specimen of the nether jaw ofCoccosteus, and am prepared to show that it was of a character altogether unique. It had its two groups of from six to eight teeth, (exactly where, in the human subject, the molars are placed,) that seem to have acted on corresponding groups in the intermaxllaries, and two other groups of from three to five teeth placed at right angles with these, direct in the symphysis, and that seem to have acted on each other. But though these unique teeth of the symphysis formed a vertical line of mouth, it joined on at right angles to a transverse line of the ordinary type, as the upright stroke of the letter T joins on to the horizontal line a-top.] Fourth Edition.
I am acquainted with four species ofCoccosteus—C. decipiens,C. cuspidatas,C. oblongus, and a variety not yet named; and many more species may yet be discovered.[N]Of all the existences of the formation, this curious fish seems to have been one of the most abundant. In a few square yards of rock I have laid open portions of the remains of a dozen different individuals belonging to two of the four species, theC. decipiensandC. cuspidatus, in the course of a single evening. None of the other kinds have yet been found at Cromarty.These two differed from each other in the proportions which their general bulk bore to their length—slightly, too, in the arrangement of their occipital plates. TheCoccosteus latus, as the name implies, must have been by much a massier fish than the other; and we find the arch-like form of the plates which covered its head more complete: the plate representing the keystone rests on the saddle-shaped plate in the centre, and the plates representing the spring-stones of the arch exhibit a broader base. The accompanying print (Plate III.) represents theCoccosteus cuspidatus. The average length of the creature, including the tail, as shown in most of the Cromarty specimens, somewhat exceeded a foot. A few detached plates from Orkney, in the collection of Dr. Traill, must have belonged to an individual of fully twice that length.
[N]A fifth species has been namedC. maximus.
[N]A fifth species has been namedC. maximus.
The Elfin-fish of Gawin Douglas.—The Fish of the Old Red Sandstone scarcely less curious.—Place which they occupied indicated in the present Creation by a mere Gap.—Fish divided into two great Series, the Osseous and Cartilaginous.—Their distinctive Peculiarities.—Geological Illustration of Dr. Johnson's shrewd Objection to the Theory of Soame Jenyns.—Proofs of the intermediate Character of the Ichthyolites of the Old Red Sandstone.—Appearances which first led the Writer to deem it intermediate.—Confirmation by Agassiz.—TheOsteolepis.—Order to which this Ichthyolite belonged.—Description.—Dipterus.—Diplopterus.—Cheirolepis.—Glyptolepis.
Hasthe reader ever heard of the "griesly fisch" and the "laithlie flood," described by that minstrel Bishop of Dunkeld "who gave rude Scotland Virgil's page?" Both fish and flood are the extravagances of a poet's dream. The flood came rolling through a wilderness of bogs and quagmires, under banks "dark as rocks the whilk the sey upcast." A skeleton forest stretched around, doddered and leafless; and through the "unblomit" and "barrant" trees
"The quhissling wind blew mony bitter blast;"
"The quhissling wind blew mony bitter blast;"
the whitened branches "clashed and clattered;" the "vile water rinnand o'erheid," and "routing as thonder," made "hideous trubil;" and to augment the uproar, the "griesly fisch," like the fish of eastern story, raised their heads amid the foam, and shrieked and yelled as they passed. "The grim monsters fordeafit the heiring with their sellouts;"—they were both fish and elves, and strangely noisy in the latter capacity; and the longer the poet listened, the more frightened he became.The description concludes, like a terrific dream, with his wanderings through the labyrinths of the dead forest, where all was dry and sapless above, and mud and marsh below, and with his exclamations of grief and terror at finding himself hopelessly lost in a scene of prodigies and evil spirits. And such was one of the wilder fancies in which a youthful Scottish poet of the days of Flodden indulged, ere taste had arisen to restrain and regulate invention.
Shall I venture to say, that the ichthyolites of the Old Red Sandstone have sometimes reminded me of the "fisch of the laithlie flood?" They were hardly less curious. We find them surrounded, like these, by a wilderness of dead vegetation, and of rocks upcast from the sea; and there are the foot-prints of storm and tempest around and under them. True, they must have been less noisy. Like the "griesly fisch," however, they exhibit a strange union of opposite natures. One of their families—that of theCephalaspis—seems almost to constitute a connecting link, says Agassiz, between fishes and crustaceans. They had, also, their families of sauroid, or reptile fishes—and their still more numerous families that unite the cartilaginous fishes to the osseous. And to these last the explorer of the Lower Old Red Sandstone finds himself mainly restricted. The links of the system are all connecting links, separated by untold ages from that which they connect; so that, in searching for their representatives amid the existences of the present time, we find but the gaps which they should have occupied. And it is essentially necessary from this circumstance, in acquainting one's self with their peculiarities, to examine, if I may so express myself, the sides of these gaps,—the existing links at both ends to which the broken links should have pieced,—in short, all those more striking peculiarities of the existingdisparted families which we find united in the intermediate families that no longer exist. Without some such preparation, the inquirer would inevitably share the fate of the poetical dreamer of Dunkeld, by losing his way in a labyrinth. In passing, therefore, with this object from the extinct to the recent, I venture to solicit, for a few paragraphs, the attention of the reader.
Fishes, the fourth great class in point of rank in the animal kingdom, and, in extent of territory, decidedly the first, are divided, as they exist in the present creation, into two distinct series—the osseous and the cartilaginous. The osseous embraces that vast assemblage which naturalists describe as "fishes properly so called," and whose skeletons, like those of mammalia, birds, and reptiles, are composed chiefly of a calcareous earth pervading an organic base. Hence the durability of their remains. In the cartilaginous series, on the contrary, the skeleton contains scarce any of this earth: it is a framework of indurated animal matter, elastic, semi-transparent, yielding easily to the knife, and, like all mere animal substances, inevitably subject to decay. I have seen the huge cartilaginous skeleton of a shark lost in a mass of putrefaction in less than a fortnight. I have found the minutest bones of the osseous ichthyolites of the Lias entire after the lapse of unnumbered centuries.
The two series do not seem to precede or follow one another in any such natural sequence as that in which the great classes of the animal kingdom are arranged. The mammifer takes precedence of the bird, the bird of the reptile, the reptile of the fish; there is progression in the scale—the arrangement of the classes is consecutive, not parallel. But in this great division there is no such progression; the osseous fish takes no precedence of the cartilaginous fish,or the cartilaginous, as a series, of the osseous. The arrangement is parallel, not consecutive; but the parallelism, if I may so express myself, seems to be that of a longer with a shorter line;—the cartilaginous fishes, though much less numerous in their orders and families than the other, stretch farther along the scale in opposite directions, at once rising higher and sinking lower than the osseous fishes. The cartilaginous order of the sturgeons,—a roe-depositing tribe, devoid alike of affection for their young, or of those attachments which give the wild beasts of the forest partners in their dens,—may be regarded as fully abreast of by much the greater part of the osseous fishes, in both their instincts and their organization. The family of the sharks, on the other hand, and some of the rays, rise higher, as if to connect the class of fish with the class immediately above it—that of reptiles. Many of them are viviparous, like the mammalia—attached, it is said, to their young, and fully equal even to birds in the strength of their connubial attachments. The male, in some instances, has been known to pine away and die when deprived of his female companion.[O]But then, on the other hand, the cartilaginous fishes, in some of their tribes, sink as low beneath the osseous as they rise above them in others. The suckers, for instance, a cartilaginous family, are the most imperfect of all vertebral animals; some of them want even the sense of sight; they seem mere worms, furnished with fins and gills, and were so classed by Linnæus; but though now ascertained to be in reality fishes, they must be regarded as the lowest link in the scale—as connecting the class with the classVermes, just as the superior cartilaginous fishes may be regarded as connecting it with the classReptilia.
[O]Some of the osseous fishes are also viviparous—the "viviparous blenny," for instance. The evidence from which the supposed affection of the higher fishes for their offspring has been inferred, is, I am afraid, of a somewhat equivocal character. The love of the sow for her litter hovers, at times, between that of the parent and that of the epicure; nor have we proof enough, in the present state of ichthyological knowledge, to conclude to which side the parental love of the fish inclines. The connubial affections of some of the higher families seem better established. Of a pair of gigantic rays (Cephaloptera giorna) taken in the Mediterranean, and described by Risso, the female was captured by some fishermen; and the male continued constantly about the boat, as if bewailing the fate of his companion, and was then found floating dead.—See Wilson's articleIchthyology,Encyc. Brit., seventh edition.
[O]Some of the osseous fishes are also viviparous—the "viviparous blenny," for instance. The evidence from which the supposed affection of the higher fishes for their offspring has been inferred, is, I am afraid, of a somewhat equivocal character. The love of the sow for her litter hovers, at times, between that of the parent and that of the epicure; nor have we proof enough, in the present state of ichthyological knowledge, to conclude to which side the parental love of the fish inclines. The connubial affections of some of the higher families seem better established. Of a pair of gigantic rays (Cephaloptera giorna) taken in the Mediterranean, and described by Risso, the female was captured by some fishermen; and the male continued constantly about the boat, as if bewailing the fate of his companion, and was then found floating dead.—See Wilson's articleIchthyology,Encyc. Brit., seventh edition.
Between the osseous and the cartilaginous fishes there exist some very striking dissimilarities. The skull of the osseous fish is divided into a greater number of distinct bones, and possesses more movable parts, than the skulls of mammiferous animals: the skull of the cartilaginous fish, on the contrary, consists of but a single piece, without joint or suture. There is another marked distinction. The bony fish, if it approaches in form to that general type which we recognize amid all the varieties of the class as proper to fishes, and to which, in all their families, nature is continually inclining, will be found to have a tail branching out, as in the perch and herring, from the bone in which the vertebral column terminates; whereas the cartilaginous fish, if it also approach the general type, will be found to have a tail formed, as in the sturgeon and dog-fish, on both sides of the hinder portion of the spine, but developed much more largely on the under than on the upper side. In some instances, it is wanting on the upper side altogether. It may be as impossible to assign reasons for such relations as for thosewhich exist between the digestive organs and the hoofs of the ruminant animals; but it is of importance that they should be noted.[P]It may be remarked, further, that the great bulk of fishes whose skeletons consist of cartilage have yet an ability of secreting the calcareous earth which composes bone, and that they are furnished with bony coverings, either partial or entire. Their bones lie outside. The thorn-back derives its name from the multitudinous hooks and spikes of bone that bristle over its body; the head, back, and operculum of the sturgeon are covered with bony plates; the thorns and prickles of the shark are composed of the same material. The framework within is a framework of mere animal matter; but it was no lack of the osseous ingredient that led to the arrangement—an arrangement which we can alone refer to the will of that all-potent Creator, who can transpose his materials at pleasure, without interfering with the perfection of his work. It is a curious enough circumstance, that some of the osseous fishes, as if entirely to reverse the condition of the cartilaginous ones, are partially covered with plates of cartilage. They are bone within, and cartilage without, just as others are bone without and cartilage within.
[P]Dr. Buckland, in hisBridgewater Treatise, assigns satisfactory reasons for this construction of tail in sharks and sturgeons. Of the fishes of these two orders, he states, "the former perform the office of scavengers, to clear the water of impurities, and have no teeth, but feed, by means of a soft, leather-like mouth, capable of protrusion and contraction, on putrid vegetables and animal substances at the bottom; and hence they have constantly to keep their bodies in an inclined position. The sharks employ their tail in another peculiar manner—to turn their body, in order to bring their mouth, which is placed downwards beneath the head, into contact with their prey. We find an important provision in every animal, to give a position of ease and activity to the head during the operation of feeding."—Bridgewater Treatise, p. 279, vol. i., first ed.
[P]Dr. Buckland, in hisBridgewater Treatise, assigns satisfactory reasons for this construction of tail in sharks and sturgeons. Of the fishes of these two orders, he states, "the former perform the office of scavengers, to clear the water of impurities, and have no teeth, but feed, by means of a soft, leather-like mouth, capable of protrusion and contraction, on putrid vegetables and animal substances at the bottom; and hence they have constantly to keep their bodies in an inclined position. The sharks employ their tail in another peculiar manner—to turn their body, in order to bring their mouth, which is placed downwards beneath the head, into contact with their prey. We find an important provision in every animal, to give a position of ease and activity to the head during the operation of feeding."—Bridgewater Treatise, p. 279, vol. i., first ed.
But how apply all this to the Geology of the Old Red Sandstone? Very directly. The ichthyolites of this ancient formation hold, as has been said, an intermediate place, unoccupied among present existences, between the two series, and in some respects resemble the osseous, and in some the cartilaginous tribes. The fact reminds one of Dr. Johnson's shrewd objection to the theory embraced by Soame Jenyns in hisFree Inquiry, and which was the theory also of Pope and Bolingbroke. The metaphysician held, with the poet and his friend, that there exists a vast and finely graduated chain of being from Infinity to nonentity—from God to nothing; and that to strike out a single link would be to mar the perfection of the whole.[Q]The moralist demonstrated, on the contrary, that this chain, in the very nature of things, must be incomplete at both ends—that between that whichdoes, and that which does not exist, there must be an infinite difference—that the chain, therefore, cannot lay hold onnothing. He showed, further, that between the greatest of finite existences and the adorable Infinite there must exist another illimitable void—that the boundless and the bounded are as widely separated in their natures and qualities as the existent and the non-existent—that the chain, in short, cannot lay hold on Deity. He asserted, however, that not only is it thus incomplete at both ends, but that we must regard it as well nigh as incomplete in many of its intermediate links as at its terminal ones; that it is already a broken chain, seeing that between its various classes of existence myriads of intermediate existences might be introduced, by graduating more minutely what must necessarily be capable of infinite gradation; and that, to base an infidel theory on the supposed completeness of what is demonstrably incomplete, and on the impossibility of a gap existing in what is already filled with gaps, is just to base one absurdity on another.[R]Now, we find the Geology of what may be termed the second age of vertebrated existence (for the Lower Old Red Sandstone was such) coming curiously in to confirm the reasonings of Johnson. It shows us the greater part of the fish of an entire creation thus insinuated between two of the links of our own.
[Q]"See, through this air, this ocean, and this earth,All matter quick, and bursting into birth;Above, how high progressive life may go!Around, how wide! how deep extend below!Vast chain of being! which from God began—Nature's ethereal, human angel, man,Beast, bird, fish, insect—what no eye can see,No glass can reach; from Infinite to thee—From thee to nothing. On superior powersWere we to press, inferior might on ours;Or in the full creation leave a void,Where, one step broken, the great scale's destroyed:From Nature's chain, whatever link you strike,Tenth, or ten thousandth, breaks the chain alike."Essay on Man.
[Q]
"See, through this air, this ocean, and this earth,All matter quick, and bursting into birth;Above, how high progressive life may go!Around, how wide! how deep extend below!Vast chain of being! which from God began—Nature's ethereal, human angel, man,Beast, bird, fish, insect—what no eye can see,No glass can reach; from Infinite to thee—From thee to nothing. On superior powersWere we to press, inferior might on ours;Or in the full creation leave a void,Where, one step broken, the great scale's destroyed:From Nature's chain, whatever link you strike,Tenth, or ten thousandth, breaks the chain alike."Essay on Man.
"See, through this air, this ocean, and this earth,All matter quick, and bursting into birth;Above, how high progressive life may go!Around, how wide! how deep extend below!Vast chain of being! which from God began—Nature's ethereal, human angel, man,Beast, bird, fish, insect—what no eye can see,No glass can reach; from Infinite to thee—From thee to nothing. On superior powersWere we to press, inferior might on ours;Or in the full creation leave a void,Where, one step broken, the great scale's destroyed:From Nature's chain, whatever link you strike,Tenth, or ten thousandth, breaks the chain alike."
Essay on Man.
[R]The following are the well-stated reasonings of Dr. Johnson, a writer who never did injustice to an argument for want of words to express it in:—"The scale of existence from Infinity to nothing cannot possibly have being. The highest being not infinite must be at an infinite distance from Infinity. Cheyne, who, with the desire inherent in mathematicians to reduce every thing to mathematical images, considers all existence as a cone, allows that the basis is at an infinite distance from the body, and in this distance between finite and infinite there will be room forever for an infinite series of indefinable existence."Between the lowest positive existence and nothing, whenever we suppose positive existence to cease, is another chasm infinitely deep, where there is room again for endless orders of subordinate nature, continued forever and ever, and yet infinitely superior to nonexistence."To these meditations humanity is unequal. But yet we may ask, not of our Maker, but of each other, since on the one side creation, whenever it stops, must stop infinitely below infinity, and on the other infinitely above nothing, what necessity there is that it should proceed so far either way—that being so high or so low should ever have existed. We may ask, but I believe no created wisdom can give an adequate answer."Nor is this all. In the scale, wherever it begins or ends, are infinite vacuities. At whatever distance we suppose the next order of beings to be above man, there is room for an intermediate order of beings between them; and if for one order, then for infinite orders, since every thing that admits of more or less, and consequently all the parts of that which admits them, may be infinitely divided; so that, as far as we can judge, there may be room in the vacuity between any two steps of the scale, or between any two points of the cone of being, for infinite exertion of infinite power."—Review of "A Free Inquiry."
[R]The following are the well-stated reasonings of Dr. Johnson, a writer who never did injustice to an argument for want of words to express it in:—
"The scale of existence from Infinity to nothing cannot possibly have being. The highest being not infinite must be at an infinite distance from Infinity. Cheyne, who, with the desire inherent in mathematicians to reduce every thing to mathematical images, considers all existence as a cone, allows that the basis is at an infinite distance from the body, and in this distance between finite and infinite there will be room forever for an infinite series of indefinable existence.
"Between the lowest positive existence and nothing, whenever we suppose positive existence to cease, is another chasm infinitely deep, where there is room again for endless orders of subordinate nature, continued forever and ever, and yet infinitely superior to nonexistence.
"To these meditations humanity is unequal. But yet we may ask, not of our Maker, but of each other, since on the one side creation, whenever it stops, must stop infinitely below infinity, and on the other infinitely above nothing, what necessity there is that it should proceed so far either way—that being so high or so low should ever have existed. We may ask, but I believe no created wisdom can give an adequate answer.
"Nor is this all. In the scale, wherever it begins or ends, are infinite vacuities. At whatever distance we suppose the next order of beings to be above man, there is room for an intermediate order of beings between them; and if for one order, then for infinite orders, since every thing that admits of more or less, and consequently all the parts of that which admits them, may be infinitely divided; so that, as far as we can judge, there may be room in the vacuity between any two steps of the scale, or between any two points of the cone of being, for infinite exertion of infinite power."—Review of "A Free Inquiry."
It is now several years since I was first led to suspect that the condition of the ichthyolites of the Old Red Sandstone was intermediate. I have alluded to the comparative indestructibility of the osseous skeleton, and the extreme liability to decay characteristic of the cartilaginous one. Of a skeleton in part osseous and in part cartilaginous, we must, of course, expect, when it occurs in a fossil state, to find the indestructible portions only. And when, in every instance, we find the fossil skeletons of a formation complete in some of their parts, and incomplete in others—the entire portionsinvariably agreeing, and the wanting portions invariably agreeing also—it seems but natural to conclude that an original difference must have obtained, and that the existing parts, which we can at once recognize as bone, must have been united to parts now wanting, which were composed of cartilage. The naturalist never doubts that the shark's teeth, which he finds detached on the shore, or buried in some ancient formation, were united originally to cartilaginous jaws. Now, in breaking open all the ichthyolites of the Lower Old Red Sandstone, with the exception of those of the two families already described, we find that some of the parts are invariably wanting, however excellent the state of preservation maintained by the rest. I have seen every scale preserved and in its place—one set of both the larger and smaller bones occupying their original position—jaws thickly set with teeth still undetached from the head—the massy bones of the skull still unseparated—the larger shoulder-bone, on which the operculum rests, lying in its proper bed—the operculum itself entire—and all the external rays which support the fins, though frequently fine as hairs, spreading out distinct as the fibres in the wing of the dragon-fly, or the woody nerves in an oak-leaf. In no case, however, have I succeeded in finding a single joint of the vertebral column, or the trace of a single internal ray. No part of the internal skeleton survives, nor does its disappearance seem to have had any connection with the greater mass of putrescent matter which must have surrounded it, seeing that the external rays of the fins show quite as entire when turned over upon the body, as sometimes occurs, as when spread out from it in profile. Besides, in the ichthyolites of the chalk, no parts of the skeleton are better preserved than the internal parts—the vertebral joints, and the internal rays. The reader musthave observed, in the cases of a museum of Natural History, preparations of fish of two several kinds—preparations of the skeleton, in which only the osseous parts are exhibited, and preparations of the external form, in which the whole body is shown in profile, with the fins spread to the full, and at least half the bones of the head covered by the skin but in which the vertebral column and internal rays are wanting. Now, in the fossils of the chalk, with those of the other later formations, down to the New Red Sandstone, we find that the skeleton style of preparation obtains; whereas, in at least three fourths of the ichthyolites of the Lower Old Red, we find only what we may term the external style. I had marked, besides, another circumstance in the ichthyolites, which seemed, like a nice point of circumstantial evidence, to give testimony in the same line. The tails of all the ichthyolites, whose vertebral columns and internal rays are wanting, are unequally lobed, like those of the dog-fish and sturgeon, (both cartilaginous fishes,) and the body runs on to nearly the termination of the surrounding rays. The one-sided condition of tail exists, says Cuvier, in no recent osseous fish known to naturalists, except in the bony pike—a sauroid fish of the warmer rivers of America. With deference, however, to so high an authority, it is questionable whether, the tail of the bony pike should not rather be described as a tail set on somewhat awry, than as a one-sided tail.
All these peculiarities I could but note as they turned up before me, and express, in pointing them out to a few friends, a sort of vague, because hopeless, desire, that good fortune might throw me in the way of the one man of all the world best qualified to explain the principle on which they occurred, and to decide whether fishes may be at once bony and cartilaginous. But that meeting was a contingency rather tobe wished than hoped for—a circumstance within the bounds of the possible, but beyond those of the probable. Could the working-man of the north of Scotland have so much as dreamed that he was yet to enjoy an opportunity of comparing his observations with those of the naturalist of Neufchatel, and of having his inferences tested and confirmed?
The opportunity did occur. The working-man did meet with Agassiz; and many a query had he to put to him; and never, surely, was inquirer more courteously entreated, or his doubts more satisfactorily resolved. The reply to almost my first question solved the enigma of nearly ten years' standing. And finely characteristic was that reply of the frankness and candor of a great mind, that can afford to make it no secret, that, in its onward advances on knowledge, it may know to-day what it did not know yesterday, and that it is content to "gain by degrees upon the darkness." "Had you asked me the question a fortnight ago," said Agassiz, "I could not have replied to it. Since then, however, I have examined an ichthyolite of the Old Red Sandstone in which the vertebral joints are fortunately impressed on the stone, though the joints themselves have disappeared, and which, exactly resembling the vertebra? of the shark, must have been cartilaginous." In a subsequent conversation, the writer was gratified by finding most of his other facts and inferences authenticated and confirmed by those of the naturalist. I shall attempt introducing to the reader the peculiarities, general and specific, of the ichthyolites to which these facts and observations mainly referred, by describing such of the families as are most abundant in the formation, and the points in which they either resemble or differ from the existing fish of our seas.