The Foot-prints of the Creator

by Hugh Miller

THE ASTEROLEPIS, ITS STRUCTURE, BULK, AND ASPECT.

With the reader, if he has accompanied me thus far, I shall now pass on to the consideration of the remains of the Asterolepis. Our preliminary acquaintance with the cerebral peculiarities of a few of its less gigantic contemporaries will be found of use in enabling us to determine regarding a class of somewhat resembling peculiarities which characterized this hugest Ganoid of the Old Red Sandstone.

Fig. 24.

Dermal tubercles of Asterolepis

(Mag. two diameters.)

The head of the Asterolepis, like the heads of all the other Cœlacanths, and of all the Dipterians, was covered with osseous plates,—its body with osseous scales; and, as I have already had occasion to mention, it is from the star-like tubercles by which the cerebral plates were fretted that M. Eichwald bestowed on the creature its generic name. Agassiz has even erected species on certain varieties in the pattern of the stars, as exhibited on detached fragments; but I am far from being satisfied that we are to seek in their peculiarities of style the characters by which the several species were distinguished. The stellar form of the tubercle seems to have been its normal or most perfect form as it was also, with certain modifications, that of the tubercle of the Coccosteus and Pterichthys; but its development as a complete star was comparatively rare: in most cases the tubercles existed without the rays,—frequently in the insulated pap-like shape, but not rarely confluent, or of an elongated or bent form; and when to these the characteristic rays were added, the stars produced were of a rather eccentric order,—stars somewhat resembling the shadows of stars seen in water. Individual specimens have already been found, on which, if we recognize the form of the tubercle as a specific character, several species might be erected. The accompanying wood-cut (fig. 24) represents, from a Thurso specimen, what seems to be the true normal pattern of these cerebral carvings. Seen in profile (b) the tubercles resemble little hillocks, perforated at their base by single lines of thickly-set caves; while seen from above, (a,) the narrow piers of bone by which the caves are divided take the form of rays. The reader will scarce fail to recognise in this print the coral Monticularia of Lamarck, or to detect, in at least the profile, the peculiarity which suggested the name.

Fig. 25.

SCALES OF ASTEROLEPIS.

(Nat. size.)

a. Inner surface of scale.

b. Exterior surface.

Fig. 26.

PORTION OF CARVED SURFACE OF SCALE.

(Mag. four diameters.)

The scales which covered the creature’s body (fig. 25) were, in proportion to its size, considerably smaller and thinner than those of the Holoptychius, which, however, they greatly resemble in their general style of sculpture. Each, on the lower part of its exposed field, was, we see, fretted by longitudinal anastomosing ridges, which, in the upper part, break into detached angular tubercles, placed with the apex downwards, and hollowed, leaf-like, in the centre; while that covered portion which was overlaid by the scales immediately above we find thickly pitted by microscopic hollows, that give to this part of the field, viewed under a tolerably high magnifying power, a honeycombed appearance. The central and lower parts of the interior surface of the scale (a) are in most of the specimens irregularly roughened; while a broad, smooth band, which runs along the top and sides, and seems to have furnished the line of attachment to the creature’s body, is comparatively smooth. The exterior carvings, though they demand the assistance of the lens to see them aright, are of singular elegance and beauty; as perhaps the accompanying wood-cut, (fig. 26,) which gives a magnified view of a portion of the scale immediately above (b) from the middle of the honeycombed field on the right side, to where the anastomosing ridges bend gracefully in their descent, may in some degree serve to show. I have seen a richly inlaid coat of mail, which was once worn by the puissant Charles the Fifth; but its elaborate carvings, though they belonged to the age of Benvenuto Cellini, were rude and unfinished, compared with those which fretted the armor of the Asterolepis.

Fig. 27.

CRANIAL BUCKLER OF ASTEROLEPIS.

(One fifth nat. size, linear.)

The creature’s cranial buckler, which was of great size and strength, might well be mistaken for the carapace of some Chelonian fish of no inconsiderable bulk. The cranial bucklers of the larger Dipterians were ample enough to have covered the corresponding part in the skulls of our middle-sized market-fish, such as the haddock and whiting; the buckler of a Coccosteus of the extreme size would have covered, if a little altered in shape, the upper surface of the skull of a cod, but the cranial buckler of Asterolepis, from which the accompanying wood-cut was taken, (fig. 27,) would have considerably more than covered the corresponding part in the skull of a large horse; and I have at least one specimen in my collection which would have fully covered the front skull of an elephant. In the smaller specimens, the buckler somewhat resembles a laborer’s shovel divested of its handle, and sorely rust-eaten along its lower or cutting edge. It consisted of plates, connected at the edges by flat squamous sutures, or, as a joiner might perhaps say, glued together in bevelled joints. And in consequence of this arrangement, the same plates which seem broad on the exterior surface appear comparatively narrow on the interior one, and vice versa; the occipital plate, (a,) which, running from the nape along the centre of the buckler, occupies so considerable a space on its outer surface, exhibits inside a superficies reduced at least one half. Like nine tenths of its contemporaries, the Asterolepis exhibits the little central plate between the eyes; but the eye orbits, unlike those of the Coccosteus, and of all the Dipterian genera, which were half-scooped out of the cranial buckler, half-encircled by detached plates, were placed completely within the field of the buckler,—a circumstance in which they resemble the eye orbits of the Pterichthys, and, among existing fish, those of the sea-wolf. The characteristic is also a distinctive one in Cuvier’s second family of the Acanthopterygii,—the “fishes with hard cheeks.” A deep line immediately over the eyes, which, however, indicated no suture, but seems to have been merely ornamental, forms a sort of rudely tatooed eyebrow; the marginal lines parallel to the lateral edges of the buckler were also mere tatooings; but all the others indicated joints which, though more or less anchylosed, had a real existence. So flat was the surface, that the edge of a ruler rests upon it, in my several specimens, both lengthwise and across; but it was traversed by two flat ridges, which, stretching from the corners of the latero-posterior, i. e. parietal, plates, (b, b,) converged at the little plate between the eyes, while along the centre of the depressed angle which they formed, a third ridge, equally flat with the others, ran towards the same point of convergence from the nape. The three ridges, when strongly relieved by a slant light, resemble not inadequately an impression, on a large scale, of the Queen’s broad arrow.

Fig. 28.

INNER SURFACE OF CRANIAL BUCKLER OF ASTEROLEPIS.

(One fifth nat. size, linear.)

The inner surface of the cranial buckler of Asterolepis, (fig. 28,)—that which rested on the cartilaginous box which formed the creature’s interior skull,—stands out in bolder relief from the stone than its outer surface, and forms a more picturesque object. Like the inner surfaces of the bucklers of Coccosteus and Pterichthys, but much more thickly than these, it was traversed by minute channelled markings, somewhat resembling those striæ which may be detected in the flatter bones of the ordinary fishes, and which seem in these to be mere interstices between the osseous fibres. And in the plates, as in the bones, they radiate from the centres of ossification, which are comparatively dense and massy, towards the thinner overlapping edges. These radiating lines are equally well marked in the cerebral bones of the human fœtus. The three converging ridges on the outer surface we find on the inner surface also,—the lateral ones a little bent in the middle, but so directly opposite those outside, that the thickening of the buckler which takes place along their line is at least as much a consequence of their inner as of their outer elevation over the general platform. A fourth bar ran transversely along the nape, and formed the cross beam on which the others rested; for the three longitudinal ridges may be properly regarded as three strong beams, which, extending from the transverse beam at the nape to the front, where they converged like the spokes of a wheel at the nave, gave to the cranial roof a degree of support of which, from its great flatness, it may have stood in need. In cranial bucklers in which the average thickness of the plates does not exceed three eighth parts of an inch, their thickness in the centre of the ridges exceeds three quarters. The head of the largest crocodile of the existing period is defended by an armature greatly less strong than that worn by the Asterolepis of the Lower Old Red Sandstone. Why this ancient Ganoid should have been so ponderously helmed we can but doubtfully guess; we only know, that when nature arms her soldiery, there are assailants to be resisted and a state of war to be maintained. The posterior central plate, the homologue apparently of the occipital bone, was curiously carved into an ornate massive leaf, like one of the larger leaves of a Corinthian capital, and terminated beneath, where the stem should have been, in a strong osseous knob, fashioned like a pike head. Two plates immediately over it, the homologues of the superior frontal bone, with the little nasal plate which, perched atop in the middle, lay between the creature’s eyes, resembled the head and breast in the female figure, at least not less closely than those of the “lady in the lobster;” the posterior frontal plates in which the outer and nether half of the eye orbits were hollowed formed a pair of sweeping wings, and thus in the centre of the buckler we are presented with the figure of an angel, robed and winged, and of which the large sculptured leaf forms the body, traced in a style in no degree more rude than we might expect to see exemplified on the lichen-encrusted shield of some ancient tombstone of that House of Avenel which bore as its arms the effigies of the Spectre Lady. Children have a peculiar knack in detecting such resemblances; and the discovery of the angel in the cranium of the Asterolepis I owe to one of mine.

Fig. 29.

PLATE OF CRANIAL BUCKLER OF ASTEROLEPIS.

It is on this inner side of the cranial buckler, where there are no such pseudo-joinings indicated as on the external surface, that the homologies of the plates of which it is composed can be best traced. It might be well, however, ere setting one’s self to the work of comparison, to examine the skulls of a few of the osseous fishes of our coast, and to mark how very considerably they differ from one another in their lines of suture and their general form. The cerebral divisions of the conger-eel, for instance, are very unlike those of the haddock or whiting; and the sutures in the head of the gurnard are dissimilarly arranged from those in the head of the perch. And after tracing the general type in the more anomalous forms, and finding, with Cuvier, that in even these the “skull consists of the same bones, though much subdivided, as the skulls of the other vertebrata,” we will be the better qualified for grappling with the not greater anomalies which occur in the cranial buckler of the Asterolepis. The occipital plate, A, a, a, (fig. 29,) occupies its ordinary place opposite the centre of the nape; the two parietals, B, B, rest beside it in their usual ichthyic position of displacement; the superior frontal we find existing, as in the young of many animals, in two pieces, C, C; the nasal plate I, placed immediately in advance of it, is flanked, as in the cod, by the anterior frontals, D, D; the posterior frontals, F, F, which, when viewed as in the print, from beneath, seem of considerable size, and describe laterally and posteriorly about one half the eye orbits, have their area on the exterior surface greatly reduced by the overriding squamose sutures of the plates to which they join; and lastly, two of these overlying plates, E, E,—which, occurring in the line of the lateral bar or beam, are of great strength and thickness, and lie for two thirds of their length along the parietals, and for the remaining third along the superior frontals,—represent the mastoid bones. Such, so far as I have been yet able to read the cranial buckler of the Asterolepis, seem to be the homologies of its component plates.

Fig. 30.

PORTION OF UNDER JAW OF ASTEROLEPIS, (OUTER SIDE.)

(One half nat. size.)

Fig. 31.

PORTION OF UNDER JAW OF ASTEROLEPIS, (INNER SIDE.)

(One half nat. size.)

There were no parts of the animal more remarkable than its jaws. The under jaws,—for the nether maxillary consisted, in this fish, as in the placoid fishes, and in the quadrupeds generally, of two pieces joined in the middle,—were, like those of the Holoptychius, boxes of bone, which enclosed central masses of cartilage. The outer and under sides were thickly covered with the characteristic star-like tubercles; and along the upper margin or lip there ran a thickly-set row of small broadly-based teeth, planted as directly on the edge of the exterior plate as iron spikes on the upper edge of a gate (fig. 30.) Mr. Parkinson expresses some wonder, in his work on fossils, that, in a fine ichthyolite in the British Museum, not only the teeth should have been preserved, but also the lips; but we now know enough of the construction of the ancient Ganoids to cease wondering. The lips were formed of as solid bone as the teeth themselves, and had as fair a chance of being preserved entire; just as the metallic rim of a cogged wheel has as fair a chance of being preserved as the metallic cogs that project from it. Immediately behind the front row,—in which the teeth present the ordinary ichthyic appearance,—there ran a thinly-set row of huge reptile teeth, based on an interior platform of bone, which formed the top of the cartilage-enclosing box composing the jaw. These were at once bent outwards and twisted laterally, somewhat like nails that have been drawn out of wood by the claw of a carpenter’s hammer, and bent awry with the wrench, (fig. 31.) They were furrowed longitudinally from point to base by minute thickly-set striæ and were furnished laterally, in most of the specimens though not in all, with two sharp cutting edges. The reptile had as yet no existence in creation; but we see its future coming symbolized in the dentition of this ancient Ganoid: it, as it were, shows us the crocodile lying entrenched behind the fish. The interior structure of these reptile teeth is very remarkable. In the longitudinal section we find numerous cancelli, ranged lengthwise along the outer edges, but much crossed, net-like, within,—greatly more open towards the base than at the point,—and giving place in the centre to a hollow space, occasionally traversed by a few slim osseous partitions. In the transverse section these cancelli are found to radiate from the open centre towards the circumference, like the spokes of a wheel from the nave; and each spoke seems as if, like Aaron’s rod, it had become instinct with vegetative life, and had sprouted into branch and blossom. Seen in a microscope of limited field, that takes in, as in the accompanying print, (fig. 32,) not more than a fourth part of the section, the appearance presented is that of a well-trained wall tree. And hence the generic name Dendrodus, given by Professor Owen to teeth found detached in the deposits of Moray, when the creatures to which they had belonged were still unknown,—a name, however, which will, I suspect, be found synonymous rather with that of a family than of a genus; for so far as I have yet examined, I find that the dendrodic or tree-like tooth, was in at least the Old Red Sandstone, a characteristic of all the Cœlacanth family. I may mention, however, as a curious subject of inquiry, that the Cœlacanths of the Coal Measures seem to have had their reptile teeth formed of pure ivory,—a substance, which I have not yet detected among the reptile-fish of the Old Red. Towards the base of the reptile teeth of Asterolepis, the interstices between the branches greatly widen, as in the branches of a tree in winter divested of its foliage, (fig. 33, c;) the texture also opens towards the base in the fish-teeth, outside, in which, however, the pattern in the transverse section is greatly less complex and ornate than that which the reptile teeth exhibits. When cut across near the point, they appear each as a thick ring, (b,) traversed by lines that radiate towards the centre; when cut across about half way down, they somewhat resemble, seen under a high magnifying power those cast-iron wheels on which the engineer mounts his railway carriages, (a.) In the longitudinal section their line of junction with the jaw is marked by numerous openings, but by no line of division, and they appear as thickly dotted by what were once canaliculi, or life points, as any portion of the dermal bone on which they rest.

Fig. 32.

PORTION OF TRANSVERSE SECTION OF REPTILE TOOTH OF ASTEROLEPIS

a. Nat. size.

b. Mag. twelve diameters.

Fig. 33.

A. Section of Jaw of Asterolepis.

c. Reptile tooth as shown in section.

a, b, & c. Row of ichthyic teeth in dermal plate of jaw.

B. Magnified representatives of ichthyic teeth, a and b, in A.

It seems truly wonderful, when one considers it, to what minute and obscure ramifications that variety of pattern which nature so loves to maintain is found to descend. It descends in the fishes, both recent and extinct, to even the microscopic structure of their teeth; and we find, in consequence, not less variety of figure in the sliced fragments of the teeth of the ichthyolites of a single formation, than in the carved blocks of an extensive calico print-yard. Each species has its own distinct pattern, as if, in all the individuals of which it consisted, the same block had been employed to stamp it; and each genus its own general type of pattern, as if the same radical idea, variously altered and modified, had been wrought upon in all. In the Dendrodic (Cœlacanth?) family, for instance, it is the radical type, that from a central nave there should radiate, spoke-like, a number of arborescent branches; but in the several genera and species of the family, the branches belong, if I may so express myself, to different shrubs, and present dissimilar outlines. It has appeared to me, that at least a presumption against the transmutation of species might be based on those inherent peculiarities of structure which are thus found to pervade the entire texture of the framework of animals. If we find erections differing from one another merely in external form, we have no difficulty in conceiving how, by additions and alterations, they might be brought to exhibit a perfect uniformity of plan and aspect: transmutation,—development,—progression,—(if one may use such terms,)—seem possible in such circumstances. But if the buildings differ from each other, not only in external form, but also in every brick and beam, bolt and nail, no mere scheme of external alteration could ever induce a real resemblance. Every brick would have to be taken down, and every beam and bolt removed. The problem could not be wrought by the remodelling of an old house: the only mode of solving it would be by the erection of a new one.

Fig. 34.

MAXILLARY BONE?

(One fourth nat. size, linear.)

Of the upper maxillary bones of the Asterolepis, I only know that a considerable fragment of one of the pieces, recognized as such by Agassiz, has been found in the neighborhood of Thurso by Mr. Dick, unaccompanied, however, by any evidence respecting its place or function. It exhibits none of the characteristic tubercles of the dermal bones, and no appearance of teeth; but is simply a long bent bone, resembling somewhat less than the half of an ancient bow of steel or horn,—such a bow as that which Ulysses bended in the presence of the suitors. By some of the Russian geologists this bone was at first regarded as a portion of the arm or wing of some gigantic Pterichthys. In the accompanying print (fig. 34) I have borrowed the general outline from that of a specimen of Professor Asmus, of which a cast may be seen in the British Museum; while the shaded portion represents the fragment found by Mr. Dick. The intermaxillary bones, like the dermal plates of the lower jaw, were studded by star-like tubercles, and bristled thickly along their lower edges with the ichthyic teeth, flanked by teeth of the reptilian character. The opercules of the animal consisted, as in the sturgeon, of single plates (fig. 35) of great massiveness and size, thickly tubercled outside, without trace of joint or suture, and marked on their under surface by channelled lines, that radiate, as in the other plates, from the centre of ossification. That space along the nape which intervened between the opercules, was occupied, as in the Dipterus and Diplopterus, by three plates, which covered rather the anterior portion of the body than the posterior portion of the head, and which, in the restoration of Osteolepis, (fig. 13,) appear as the plates, 9, 9, 9. I can say scarce any thing regarding the lateral plates which lay between the intermaxillaries and the cranial buckler, and which exist in the Osteolepis, fig. 13, as the plates 2, 4, 5, 6, and 7; nor do I know how the snout terminated, save that in a very imperfect specimen it exhibits, as in the Diplopterus and Osteolepis, a rounded outline, and was set with teeth.

Fig. 35.

INNER SURFACE OF OPERCULUM OF ASTEROLEPIS.

(One fifth nat. size, linear.)

Fig. 36.

HYOID PLATE.

(One ninth nat. size, linear.)

That space comprised within the arch of the lower jaws, in which the hyoid bone and branchiostegous rays of the osseous fishes occur, was filled by a single plate of great size and strength, and of singular form, (fig. 36;) and to this plate, existing as a steep ridge running along the centre of the interior surface, and thickening into a massy knob at the anterior termination, that nail-shaped organism, which I have described as one of the most characteristic bones of the Asterolepis, belonged. In the Osteolepis, the space corresponding to that occupied by this hyoid plate was filled, as shown in fig. 14, by five plates of not inelegant form; and the divisions of the arch resembled those of a small Gothic window, in which the single central mullion parts into two branches atop. In the Holoptychius and Glyptolepis there were but two plates; for the central mullion, i. e. line of division, did not branch atop; and in the Asterolepis, where there was no line of division, the strong nail-like bone occupied the place of the central mullion. The hyoidal armature of the latter fish was strongest in the line in which the others were weakest. Each of the five hyoid plates of the Osteolepis, or of the two plates of the Glyptolepis or Holoptychius, had its own centre of ossification; and in the single plate of Asterolepis, the centre of ossification, as shown by the radiations of the fibre, was the nail-head. This head, placed in immediate contact with the strong boxes of bone which composed the under jaw, just where their central joining occurred, seems to have lent them a considerable degree of support, which at such a juncture may have been not unnecessary. In some of the nail-heads, belonging, it is probable, to a different species of Asterolepis from that in which the nail figured in [page 7], and the plate in the opposite page, occurred,—for its general form is different, (fig. 37,)—there appear well-marked ligamentary impressions closely resembling that little spongy pit in the head of the human thigh-bone to which what is termed the round ligament is attached. The entire hyoid-plate, viewed on its outer side, resembles in form the hyoid-bone,—or cartilage rather,—of the spotted dog-fish, (Scyllium stellare;) but its area was at least a hundred times more extensive than in the largest Scyllium, and, like all the dermal plates of the Asterolepis, it was thickly fretted by the characteristic tubercles. In the Ray, as in the Sharks, the piece of thin cartilage of which this plate seems the homologue, is a flat, semi-transparent disk; and there is no part of the animal in which the progress of those bony molecules which encrust the internal framework may be more distinctly traced, as if in the act of creeping over what they cover, in slim threads or shooting points,—and much resembling new ice creeping in a frosty evening over the surface of a pool.

Fig. 37.

NAIL-LIKE BONE OF HYOID PLATE.

(One half nat. size.)

That suite of shoulder-bones that in the osseous fishes forms the belt or frame on which the opercules rest, and furnishes the base of the pectorals, was represented in the Asterolepis, as in the sturgeon, by a ring of strong osseous plates, which, in one of the two species of which trace is to be found among the rocks of Thurso, were curiously fretted on their external surfaces, and in the other species comparatively smooth. The largest, or coracoidian plate of the ring, as it occurs in the more ornate species, (fig. 38,) might be readily enough mistaken, when seen with only its surface exposed for the ichthyodorulite of some large fish, allied, mayhap, to the Gyracanthus formosus of the Coal Measures; but when detached from the stone, the hollow form and peculiar striæ of the inferior surface serve to establish its true character as a dermal plate. The diagonal furrowings which traversed it, as the twisted flutings traverse a Gothic column moulded after the type of the Apprentice Pillar in Roslin chapel, seem to have underlaid the edge of the opercule; at least I find a similar arrangement in the shoulder-plates of a large species of Diplopterus, which are deeply grooved and furrowed where the opercule rested, as if with the design of keeping up a communication between the branchiæ and the external element, even when the gill-cover was pressed closely down upon them. And,—as in these shoulder-plates of the Diplopterus the furrows yield their place beyond the edge of the opercule to the punctulated enamel common to the outer surface of all the creature’s external plates and scales,—we find them yielding their place, in the shoulder-plates of the Asterolepis, to the starred tubercles.

Fig. 38.

SHOULDER (i. e. CORACOID?) PLATE OF ASTEROLEPIS.

(One third nat. size, linear.)

Fig. 39.

DERMAL BONES OF ASTEROLEPIS.

(One third nat. size, linear.)

Fig. 40.

INTERNAL BONES OF ASTEROLEPIS.

(One half nat. size, linear.)

A few detached bones, that bear on their outer surfaces the dermal markings, must have belonged to that angular-shaped portion of the head which intervened between the cranial buckler and the intermaxillary bone; but the key for assigning to them their proper place is still to find; and I suspect that no amount of skill on the part of the comparative anatomist will ever qualify him to complete the work of restoration without it. I have submitted to the reader the cranial bucklers of five several genera of the ganoids of the Old Red Sandstone; but no amount of study bestowed on these would enable even the most skilful ichthyologist to restore a sixth; nor is the lateral area of the head, which was, I find, variously occupied in each genus, less difficult to restore than the buckler which surmounted it. Two of the more entire of these dermal bones I have figured (fig. 39, a and b) in the hope of assisting future inquirers, who, were they to pick up all the other plates, might yet be unable, lacking the figured ones, to complete the whole. The curiously-shaped plate a, represented in its various sides by the figures 1, 2, 3, is of an acutely angular form in the transverse section, (the external surface, 1, forming an angle which varies from thirty to forty-five degrees with the base, 3;) and as it lay, it is probable when in its original place, immediately under the edge of the cranial buckler, it may have served to commence the line of deflection from the flat top of the head to the steep descent of the sides, just as what are technically termed the spur-stones in a gable-head serve to commence the line of deflection from the vertical outline of the wall to the inclined line of the roof, or as the spring-stones of an arch serve to commence the curve. A few internal bones in my possession are curious, but exceedingly puzzling. The bone a, fig. 40, which resembles a rib, or branchiostegous ray, of one of the ordinary fishes, formed apparently part of that osseous style which in fishes such as the haddock and cod we find attached to the suite of shoulder-bones, and which, according to Cuvier, is the analogue of the coracoidian bone, and, according to Professor Owen, the analogue of the clavicle. Fig. b is a mere fragment, broken at both ends, but exhibiting, in a state of good keeping, lateral expansions, like those of an ancient halbert. Fig. c, 41, which is also a fragment, though a more considerable one, bears in its thicker and straighter edge a groove like that of an ichthyodorulite, which, however, the bone itself in no degree resembles. Fig. d is a flat bone, of a type common in the skeleton of fishes, but which, in mammals, we find exemplified in but the scapulars. It seems, like these, to have furnished the base to which some suite of movable bones was articulated,—in all likelihood that proportion of the carnal bonelets of the pectoral fins which are attached in the osseous fishes to its apparent homologue, the radius. Fig. e, a slim light bone, which narrows and thickens in the centre, and flattens and broadens at each end, was probably a scapula or shoulder-blade,—a bone which in most fishes splices on, as a sailor would say, by squamose jointings, to the coracoidian bone at the one end, and the super-scapular bone at the other. As indicated by its size, it must have belonged to a small individual: it is, however, twice as long, and about six times as bulky, as the scapula of a large cod.

Fig. 41.

INTERNAL BONES OF ASTEROLEPIS.

(One third nat. size, linear.)

Fig. 42.

ISCHIUM OF ASTEROLEPIS.

(One half nat. size, linear.)

Of the bone represented in fig. 42, I have determined, from a Cromarty specimen, the place and use: it formed the interior base to which one of the ventral fins was attached. In all fishes the bones of the hinder extremities are inadequately represented: in none do we find the pelvic arch complete; and to that nether portion of it which we do find represented, and which Professor Owen regards as the homologue of the os ischium or hip-bone, the homologues of the metatarsal and toe-bones are attached, to the exclusion of the bones of the thigh and leg. In the Abdominales,—fishes such as the salmon and carp,—that have the ventrals placed behind the abdomen, in the position analogous to that in which the hinder legs of the reptiles and mammals occur, the ischiatic bones generally exist as flat triangular plates, with their heads either turned inwards and downwards, as in the herring, or outwards and downwards, as in the pike; whereas in some of the cartilaginous fishes, such as the Rays and Sharks, they exist as an undivided cartilaginous band, stretched transversely from ventral to ventral. And such, with but an upward direction, appears to have been their position in the Asterolepis. They seem to have united at the narrow neck A, over the middle of the lower portion of the abdomen; and to the notches of the flat expansion B,—notches which exactly resemble those of the immensely developed carpal bones of the Ray,—five metatarsal bones were attached, from which the fin expanded. It is interesting to find the number in this ancient representative of the vertebrata restricted to five,—a number greatly exceeded in most of the existing fishes, but which is the true normal number of the vertebrate sub-kingdom as shown in all the higher examples such as man, the quadrumana, and in most of the carnaria. The form of this bone somewhat resembles that of the analogous bone in those fishes, such as the perch and gurnard, cod and haddock, which have their ventrals suspended to the scapular belt; but its position in the Cromarty specimen, and that of the ventrals in the various specimens of the Cœlacanth family in which their place is still shown, forbids the supposition that it was so suspended,—a circumstance in keeping with all the existing geological evidence on the subject, which agrees in indicating, that of the low type of fishes that have, monster-like, their feet attached to their necks, the Old Red Sandstone does not afford a trace. This inferior type, now by far the most prevalent in the ichthyic division of the animal kingdom, does not seem to have been introduced until near the close of the Secondary period, long after the fish had been degraded from its primal place in the fore front of creation. In one of my specimens a few fragments of the rays are preserved, (fig. 43, b.) They are about the eighth part of an inch in diameter: depressed in some cases in the center, as if, over the internal hollow formed by the decay of the cartilaginous centre, the bony crust of which they are composed had given way; and, like the rays of the thornback, they are thickened at the joints, and at the processes by which they were attached to the ischiatic base. It may be proper, I should here state, that of some of the internal bones figured above I have no better evidence that they belonged to the Asterolepis, than that they occur in the same beds with the dermal plates which bear the characteristic star-like markings,—that they are of very considerable size,—and that they formed no part of the known fishes of the formation.

Fig. 43.

a. Single joint of ray of Thornback.

b. Single joint of ray of Asterolepis.

Fig. 44.

COPROLITES OF ASTEROLEPIS.

(Nat. Size.[18])

On exactly the same grounds I infer that certain large coprolites of common occurrence in the Thurso flagstones, which contain the broken scales of Dipterians, and exhibit a curiously twisted form, (fig. 44,) also belonged to the Asterolepis; and from these, that the creature was carnivorous in its habits,—an inference which the character of its teeth fully corroborates; and farther, that, like the sharks and rays, and some of the extinct Enaliosaurs, it possessed the spiral disposition of intestine. Paley, in his chapter on the compensatory contrivances palpable in the structure of various animals, refers to a peculiar substitutory provision which occurs in a certain amphibious animal described in the Memoirs of the French Academy. “The reader will remember,” he says, “what we have already observed concerning the intestinal canal,—that its length, so many times exceeding that of the body, promotes the extraction of the chyle from the aliment, by giving room for the lacteal vessels to act upon it through a greater space. This long intestine, whenever it occurs, is in other animals disposed in the abdomen from side to side, in returning folds. But in the animal now under our notice, the matter is managed otherwise. The same intention is mechanically effectuated, but by a mechanism of a different kind. The animal of which I speak is an amphibious quadruped, which our authors call the Alopecias or sea-fox. The intestine is straight from one end to the other but in this straight, and consequently short intestine, is a winding, cork-screw, spiral passage, through which the food, not without several circumvolutions, and, in fact, by a long route, is conducted to its exit. Here the shortness of the gut is compensated by the obliquity of the perforation.” This structure of intestine, which all the true Placoids possess, and at least the Sturiones among existing Ganoids, seems to have been an exceedingly common one during both the Palæozoic and Secondary periods. It has left its impress on all the better preserved coprolites of the Coal Measures, so abundant in the shales of Newhaven and Burdie House, and on those of the Lias and Chalk. It seems to be equally a characteristic of well nigh all the bulkier coprolites of the Lower Old Red Sandstone.[19] In these, however, it manifests a peculiar trait, which I have failed to detect in any of the recent fishes; nor have I yet seen it indicated, in at least the same degree, by the Carboniferous or Secondary coprolitic remains. In the bowels which moulded the coprolites of Lyme-Regis, of the Chalk, and of the Newhaven and Granton beds, a single screw must have winded within the cylindrical tube, as a turnpike stair winds within its hollow shaft; and such also is the arrangement in the existing Sharks and Rays; whereas the bowels which moulded the coprolites of the Lower Old Red Sandstone must have been traversed by triple or quadruple screws laid closely together, as we find the stalk of an old-fashioned wine-glass traversed by its thickly-set spiral lines of thread-like china. And so, while on the surface of both the Secondary and Carboniferous coprolites there is space between the screw-like lines for numerous cross markings that correspond to the thickly set veiny branches which traverse the sides of the recent placoid bowel, the entire surface of the Lower Old Red coprolites is traversed by the spiral markings. Is there nothing strange in the fact, that after the lapse of mayhap millions of years,—nay, it is possible, millions of ages,—we should be thus able to detect at once general resemblance and special dissimilarity in even the most perishable parts of the most ancient of the Ganoids?

I must advert, in passing, to a peculiarity exemplified in the state of keeping of the bones of this ancient Ganoid, in at least the deposits of Orkney and Caithness. The original animal matter has been converted into a dark-colored bitumen, which in some places, where the remains lie thick, pervades the crevices of the rocks, and has not unfrequently been mistaken for coal. In its more solid state it can hardly be distinguished, when used in sealing a letter,—a purpose which it serves indifferently well,—from black wax of the ordinary quality; when more fluid, it adheres scarce less strongly to the hands than the coal-tar of our gas-works and dock-yards. Underneath a specimen of Asterolepis, first pointed out to me in its bed among the Thurso rocks by Mr. Dick, and which, at my request, he afterwards raised and sent me to Edinburgh, packed up in a box, there lay a quantity of thick tar, which stuck as fast to my fingers, on lifting out the pieces of rock, as if I had laid hold of the planking of a newly tarred yawl. What had been once the nerves, muscles, and blood of this ancient Ganoid still lay under its bones, and reminded me of the appearance presented by the remains of a poor suicide, whose solitary grave, dug in a sandy bank in the north of Scotland, had been laid open by the encroachments of a river. The skeleton, with pieces of the dress still wrapped round it, lay at length along the section; and, for a full yard beneath, the white dry sand was consolidated into a dark-colored pitchy mass, by the altered animal matter which had escaped from it, percolating downwards, in the process of decay.

In consequence of the curious chemical change which has thus taken place in the animal juices of the Asterolepis, its remains often occur in a state of beautiful preservation: the pervading bitumen, greatly more conservative in its effects than the oils and gums of an old Egyptian undertaker, has maintained, in their original integrity, every scale, plate, and bone. They may have been much broken ere they were first committed to the keeping of the rock, or in disentangling them from its rigid embrace; but they have, we find, caught no harm when under its care. Ere the skeleton of the Bruce, disinterred after the lapse of five centuries, was recommitted to the tomb, such measures were taken to secure its preservation, that, were it to be again disinterred, even after as many more centuries had passed, it might be found retaining unbroken its gigantic proportions. There was molten pitch poured over the bones, in a state of sufficient fluidity to permeate all the pores, and fill up the central hollows, and which, soon hardening around them, formed a bituminous matrix, in which they may lie unchanged for a thousand years. Now, exactly such was the process to which nature resorted with these gigantic skeletons of the Old Red Sandstone. Like the bones of the Bruce, they are bones steeped in pitch; and so thoroughly is every pore and hollow still occupied, that, when cast into the fire, they flame like torches. Though black as jet, they still retain, too, in a considerable degree, the peculiar qualities of the original substance. The late Mr. George Sanderson of Edinburgh, one of the most ingenious lapidaries in the kingdom, and a thoroughly intelligent man, made several preparations for me, for microscopic examination, from the teeth and bones; and though they were by far the oldest vertebrate remains he had ever seen, they exhibited, he informed me, in the working, more of the characteristics of recent teeth and bone than any other fossils he had ever operated upon. Recent bone when in the course of being reduced on the wheel to the degree of thinness necessary to secure transparency, is apt, under the heat induced by the friction, to acquire a springy elasticity, and to start up from the glass slip to which it has been cemented; whereas bone in the fossil state usually lies as passive, in such circumstances, as the stone which envelopes it. Mr. Sanderson was, however, surprised to find that the bone of the Asterolepis still retained its elasticity, and was scarce less liable, when heated, to start from the glass,—a peculiarity through which he at first lost several preparations. I have seen a human bone that had for ages been partially embedded in a mass of adipocere, partially enveloped in the common mould of a churchyard, exhibit two very different styles of keeping. In the adipocere it was as fresh and green as if it had been divested of the integuments only a few weeks previous; whereas the portion which projected into the mould had become brittle and porous, and presented the ordinary appearance of an old churchyard bone. And what the adipocere had done for the human bone in this case, seems to have been done for the bones of the Asterolepis by the animal bitumen.

Fig. 45.

HYOID PLATE OF THURSO ASTEROLEPIS.[20]

(One fifth the nat. size, linear.)

The size of the Asterolepis must, in the larger specimens, have been very great. In all those ganoidal fishes of the Old Red Sandstone that had the head covered with osseous plates, we find that the cranial buckler bore a certain definite proportion,—various in the several genera and species,—to the length of the body. The drawing-master still teaches his pupils to regulate the proportions of the human figure by the seven head-lengths which it contains; and perhaps shows them how an otherwise meritorious draftsman,[21] much employed half an age ago in drawing for the wood-engraver, used to render his figures squat and ungraceful by making them a head too short. Now, those ancient Ganoids which possessed a cranial buckler may, we find, be also measured by head-lengths. Thus, in the Coccosteus decipiens, the length of the cranial buckler from nape to snout equalled one fifth the entire length of the creature from snout to tail. The entire length of the Glyptolepis was equal to about five one half times that of its cranial buckler. The Pterichthys was formed in nearly the same proportions. The Diplopterus was fully seven times the length of its buckler: and the Osteolepis from six and a half to seven. In all the cranial bucklers of the Asterolepis yet found, the snout is wanting. The very fine specimen figured in [page 99] (fig. 28) terminates abruptly at the little plate between the eyes, the specimen figured in [page 98] (fig. 27) terminates at the upper line of the eye. The terminal portion which formed the snout is wanting in both, and we thus lack the measure, or module, as the architect might say, by which the proportions of the rest of the creature were regulated. We can, however, very nearly approximate to it. A hyoid plate in my collection (fig. 45) is, I find, so exactly proportioned in size to the cranial buckler, (fig. 28,) that it might have belonged to the same individual; and by fitting it in its proper place, and then making the necessary allowance for the breadth of the nether jaw, which swept two thirds around it, and was surmounted by the snout, we ascertain that the buckler, when entire, must have been, as nearly as may be, a foot in length. If the Asterolepis was formed in the proportions of the Coccosteus, the buckler (fig. 28) must have belonged to an individual five feet in length; if in the proportions of the Pterichthys or Glyptolepis, to an individual five and a half feet in length; and if in those of the Diplopterus or Osteolepis, to an individual of from six and a half to seven feet in length. Now I find that the hyoid plate can be inscribed—such is its form—in a semicircle, of which the nail-shaped ridge in the middle (if we strike off a minute portion of the sharp point, usually wanting in detached specimens) forms very nearly the radius, and of which the diameter equals the breadth of the cranial buckler, along a line drawn across at a distance from the nape, equal to two thirds of the distance between the nape and the eyes. Thus, the largest diameter of a hyoid plate which belonged to a cranial buckler a foot in length is, I find, equal to seven one quarter inches, while the length of its nape somewhat exceeds three five eighth inches. The nail of the Stromness specimen measures five and a half inches. It must have run along a hyoid plate eleven inches in transverse breadth, and have been associated with a cranial buckler eighteen one eighth inches in length; and the Asterolepis to which it belonged must have measured from snout to tail, if formed, as it probably was, in the proportions of its brother Cœlacanth the Glyptolepis, eight feet three inches; and if in those of the Diplopterus, from nine feet nine to ten feet six inches. This oldest of Scottish fish—this earliest-born of the Ganoids yet known—was at least as bulky as a large porpoise.

It was small, however, compared with specimens of the Asterolepis found elsewhere. The hyoid plate figured in [page 110], (fig. 36,)—a Thurso specimen which I owe to the kindness of Mr. Dick,—measures nearly fourteen inches, and the cranial buckler of the same individual, fifteen one fourth inches, in breadth. The latter, when entire, must have measured twenty-three one half inches in length; and the fish to which it belonged, if formed in the proportions of the Glyptolepis, ten feet six inches; and if in those of the Diplopterus, from twelve feet five to thirteen feet eight inches in length. Did the shield still exist in its original state as a buckler of tough, enamel-crusted bone, it might be converted into a Highland target, nearly broad enough to cover the ample chest of a Rob Roy or Allan M’Aulay, and strong enough to dash aside the keenest broadsword. Another hyoid plate found by Mr. Dick measures sixteen one half inches in breadth; and a cast in the British Museum, from one of the Russian specimens of Professor Asmus, (fig. 46,) twenty-four inches. The individual to which this last plate belonged must, if built in the shorter proportions, have measured eighteen, and if in the longer, twenty-three feet in length. The two hyoid plates of the specimen of Holoptychius in the British Museum measure but four and a half inches along that transverse line in which the Russian Asterolepis measures two feet, and the largest Thurso specimen sixteen inches and a half. The maxillary bone of a cod-fish two and a half feet from snout to tail measures three inches in length. One of the Russian maxillary bones in the possession of Professor Asmus measures in length twenty-eight inches. And that space circumscribed by the sweep of the lower jaw which it took, in the Russian specimen, a hyoid plate twenty-four inches in breadth to fill, could be filled in the two-and-a-half-feet cod by a plate whose breadth equalled but an inch and a half. Thus, in the not unimportant circumstance of size, the most ancient Ganoids yet known, instead of taking their places, agreeably to the demands of the development hypothesis, among the sprats, sticklebacks, and minnows of their class, took their place among its huge basking sharks, gigantic sturgeons, and bulky sword-fishes. They were giants, not dwarfs.

Fig. 46.

HYOID PLATE OF RUSSIAN ASTEROLEPIS.

(One twelfth the natural size, linear.)

But what of their organization? Were they fishes low or high in the scale? On this head we can, of course, determine merely by the analogies which their structure exhibits to that of fishes of the existing period; and these point in three several directions;—in two of the number, directly on genera of the high Ganoid order; and in the third, on the still higher Placoids and Enaliosaurs. No trace of vertebræ has yet been found; and so we infer—lodging, however, a precautionary protest, as the evidence is purely negative, and therefore it some degree inconclusive—that the vertebral column of the Asterolepis was, like that of the sturgeon, cartilaginous. Respecting its external covering, we positively know, as has been already shown, that, like the Lepidosteus of America and the Polypterus of the Nile, it was composed of strong plates and scales of solid bone; and, regarding its dentition, that, as in these last genera, and even more decidedly than in these, it was of the mixed ichthyic-reptilian character,—an outer row of thickly-set fish-teeth being backed by an inner row of thinly-set reptile-teeth. And its form of coprolite indicates the spiral disposition of intestine common to the Rays and Sharks of the existing period, and of the Ichthyosauri of the Secondary ages. Instead of being, as the development hypothesis would require, a fish low in its organization, it seems to have ranged on the level of the highest ichthyic-reptilian families ever called into existence. Had an intelligent being, ignorant of what was going on upon earth during the week of creation, visited Eden on the morning of the sixth day, he would have found in it many of the inferior animals, but no trace of man. Had he returned again in the evening, he would have seen, installed in the office of keepers of the garden, and ruling with no tyrant sway as the humble monarchs of its brute inhabitants, two mature human creatures, perfect in their organization, and arrived at the full stature of their race. The entire evidence regarding them, in the absence of all such information as that imparted to Adam by Milton’s angel, would amount simply to this, that in the morning man was not, and that in the evening he was. There, of course, could not exist, in the circumstances, a single appearance to sanction the belief that the two human creatures whom he saw walking together among the trees at sunset had been “developed from infusorial points,” not created mature. The evidence would, on the contrary, lie all the other way. And in no degree does the geologic testimony respecting the earliest Ganoids differ from what, in the supposed case, would be the testimony of Eden regarding the earliest men. Up to a certain point in the geologic scale we find that the Ganoids are not; and when they at length make their appearance upon the stage, they enter large in their stature and high in their organization.

FISHES OF THE SILURIAN ROCKS—UPPER AND LOWER.
THEIR RECENT HISTORY, ORDER, AND SIZE.

But the system of the Old Red Sandstone represents the second, not the first, great period of the world’s history. There was a preceding period at least equally extended, perhaps greatly more so, represented by the Upper and Lower Silurian formations. And what is the testimony of this morning period of organic existence, in which, so far as can yet be shown, vitality, in the planet which man inhabits, and of whose history or productions he knows anything, was first associated with matter? May not the development hypothesis find a standing in the system representative of this earliest age of creation, which it fails to find in the system of the Old Red Sandstone?

It has been confidently asserted, not merely that it may, but that it does. Ever since the publication, in 1839, of Sir Roderick Murchison’s great work on the Silurian System, it had been known that the remains of fishes occur in a bed of the “Ludlow Rock,”—one of the most modern deposits of the Upper Silurian division; and subsequent discoveries both in England and America, had shown that even the base of this division has its ichthyic organisms. But for year after year, the lower half of the system,—a division more than three thousand feet in thickness,—had failed, though there were hands and eyes busy among its deposits, to yield any vertebrate remains. During the earlier half of the first great period of organic existence, though the polyparia, radiata, articulata, and mollusca, existed, as their remains testified, by myriads, fish had, it was held, not yet entered upon the scene; and the assertors of the development theory founded largely on the presumed fact of their absence. “It is still customary,” says the author of the “Vestiges of Creation,” in his volume of “Explanations,” “to speak of the earliest fauna as one of an elevated kind. When rigidly examined, it is not found to be so. In the first place, it contains no fish. There were seas supporting crustacean and molluscan life, but utterly devoid of a class of tenants who seem able to live in every example of that element which supports meaner creatures. This single fact, that only invertebrated animals now lived, is surely in itself a strong proof that, in the course of nature, time was necessary for the creation of the superior creatures. And if so, it undoubtedly is a powerful evidence of such a theory of development as that which I have presented. If not, let me hear an equally plausible reason for the great and amazing fact, that seas were for numberless ages destitute of fish. I fix my opponents down to the consideration of this fact, so that no diversion respecting high molluscs shall avail them.” And how is this bold challenge to be met?

Most directly, and after a fashion that at once discomfits the challenger.

It might be rationally enough argued in the case, that the author of the “Vestiges” was building greatly more on a piece of purely negative evidence,—the presumed absence of fish from the Lower Silurian formations,—than purely negative evidence is, from its nature as such, suited to bear; that only a very few years had passed since it was known that vertebrate remains occurred in the Upper Silurian, and only a few more since they had been detected in the Old Red Sandstone; nay, that within the present century their frequent occurrence in even the Coal Measures was scarce suspected; and that, as his argument, had it been founded twelve years ago on the supposed absence of fishes from the Upper Silurian, or twenty years ago on the supposed absence of fishes from the Old Red Sandstone, would have been quite as plausible in reference to its negative data then as in reference to its negative data now, so it might now be quite as erroneous as it assuredly would have been then. Or it might be urged, that the fact of the absence of fish from the Lower Silurians, even were it really a fact, would be in no degree less reconcilable with the theory of creation by direct act, than with the hypothesis of gradual development. The fact that Adam did not exist during the first, second, third, fourth, and fifth days of the introductory week of Scripture narrative, furnishes no argument whatever against the fact of his creation on the sixth day. And the remark would of course equally apply to the non-existence of fishes during the Lower Silurian period, had they been really non-existent at the time, and to their sudden appearance in that of the Upper. But the objection admits of a greatly more conclusive answer. “I fix my opponents down,” says the author of the “Vestiges,” “to the consideration of this fact,” i. e. that of the absence of fishes from the earliest fossiliferous formations. And I, in turn, fix you down, I reply, to the consideration of the antagonist fact, not negative, but positive, and now, in the course of geological discovery, fully established, that fishes were not absent from the earliest fossiliferous formations. From none of the great geological formations were fishes absent,—not even from the formations of the Cambrian division. “The Lower Silurian,” says Sir Roderick Murchison, in a communication with which, in 1847, he honored the writer of these chapters, “is no longer to be viewed as an invertebrate period; for the Onchus (species not yet decided) has been found in the Llandeilo Flags and in the Lower Silurian rocks of Bala. In one respect I am gratified by the discovery; for the form is so very like that of the Onchus Murchisoni of the Upper Ludlow rock, that it is clear the Silurian system is one great natural-history series, as is proved, indeed, by all its other organic remains.” It may be mentioned further, in addition to this interesting statement, that the Bala spine was detected in its calcareous matrix by the geologists of the Government Survey, and described to Sir Roderick as that of an Onchus, by a very competent authority in such matters,—Professor Edward Forbes, and that the annunciation of the existence of spines of fishes in the Llandeilo Flags we owe to one of the most cautious and practised geologists of the present age,—Professor Sedgwick of Cambridge.

So much for the fact of the existence of vertebrata in the Lower Silurian formations, and the argument founded on their presumed absence. Let me now refer—their presence being determined—to the tests of size and organization. Were these Silurian fishes of a bulk so inconsiderable as in any degree to sanction the belief that they had been developed shortly before from microscopic points? Or were they of a structure so low as to render it probable that their development was at the time incomplete? Were they, in other words, the embryos and fœtuses of their class? or did they, on the contrary, rank with the higher and larger fishes of the present time?

It is of importance that not only the direct bearing, but also the actual amount, of the evidence in this case, should be fairly stated. So far as it extends, the testimony is clear; but it does not extend far. All the vertebrate remains yet detected in the Silurian System, if we except the debris of the Upper Ludlow bone-bed, might be sent through the Post-Office in a box scarcely twice the size of a copy of the “Vestiges.” The naturalist of an exploring party, who, in crossing some unknown lake, had looked down over the side of his canoe, and seen a few fish gliding through the obscure depths of the water, would be but indifferently qualified, from what he had witnessed, to write a history of all its fish. Nor, were the some six or eight individuals of which he had caught a glimpse to be of small size, would it be legitimate for him to infer that only small-sized fish lived in the lake; though, were there to be some two or three large ones among them, he might safely affirm the contrary. Now, the evidence regarding the fishes of the Silurian formation very much resembles what that of the naturalist would be, in the supposed case, regarding the fishes of the unexplored lake; with, however, this difference, that as the deposits of the ancient system in which they occur have been examined for years in various parts of the world, and all its characteristic organisms, save the ichthyic ones, found in great abundance and fine keeping, we may conclude that the fish of the period were comparatively few. The palæontologist, so far as the question of number is involved, is in the circumstances, not of the naturalist who has only once crossed the unknown lake, but of the angler who, day after day, casts his line into some inland sea abounding in shell-fish and crustacea, and, after the lapse of months, can scarce detect a nibble, and, after the lapse of years, can reckon up all the fish which he has caught as considerably under a score. The existence of this great division of the animal kingdom, like that of the earlier reptiles during the Carboniferous period, did not form a prominent characteristic of those ages of the earth’s history in which they began to be.

The earliest discovered vertebral remains of the system—those of the Upper Ludlow rock—were found in digging the foundations of a house at Ludford, on the confines of Shropshire, and submitted, in 1838, by Sir Roderick Murchison to Agassiz, through the late Dr. Malcolmson of Madras. I used at the time to correspond on geological subjects with Dr. Malcolmson,—an accomplished geologist and a good man, too early lost to science and his friends,—and still remember the interest which attached on this occasion to his communication bearing the Paris post-mark, from which I learned for the first time that there existed ichthyic fragments greatly older than even the ichthyolites of the Lower Old Red Sandstone, and which made me acquainted with Agassiz’s earliest formed decision regarding them. Though existing in an exceedingly fragmentary condition,—for the materials of the thin dark-colored layer in which they had lain seemed as if they had been triturated in a mortar,—the ichthyologist succeeded in erecting them into six genera; though it may be very possible,—as some of these were formed for the reception of detached spines, and others for the reception of detached teeth,—that, as in the case of Dipterus and Asterolepis, the fragments of but a single genus may have been multiplied into two genera or more. And minute scale-like markings, which mingled with the general mass, and were at first regarded as the impressions of real scales, have been since recognized as of the same character with the scale-like markings of the Seraphim of Forfarshire, a huge crustacean. Even admitting, however, that a set of teeth and spines, with perhaps the shagreen points represented in [page 54], fig. 2, b, in addition, may have all belonged to but a single species of fish, there seem to be materials enough, among the remains found, for the erection of two species more. And we have evidence that at least two of the three kinds were fishes of the Placoid order, (Onchus Murchisoni and Onchus tenuistriatus,) and—as the supposed scales must be given up—no good evidence that the other kind was not. The ichthyic remains of the Silurian System next discovered were first introduced to the notice of geologists by Professor Phillips, at the meeting of the British Association in 1842.[22] They occurred, he stated, in a quarry near Hales End, at the base of the Upper Ludlow rock, immediately over the Aymestry Limestone, and were so exceedingly diminutive, that they appeared to the naked eye as mere discolored spots; but resolved under the microscope into scattered groupes of minute spines, like those of the Cheiracanthus, with what seemed to be still more minute scales, or, perhaps,—what in such circumstances could scarce be distinguished from scales,—shagreen points of the scale-like type. The next ichthyic organism detected in the Silurian rocks occurred in the Wenlock Limestone, a considerably lower and older deposit, and was first described in the “Edinburgh Review” for 1845 by a vigorous writer and masterly geologist, (generally understood to be Professor Sedgwick of Cambridge,) as “a characteristic portion of a fish undoubtedly belonging to the Cestraciont family of the Placoid order.” In the “American Journal of Science” for 1846, Professor Silliman figured, from a work of the States’ Surveyors, the defensive spine of a Placoid found in the Onondago Limestone of New York,—a rock which occurs near the base of the Upper Silurian System, as developed in the western world;[23] and in the same passage he made reference to a mutilated spine detected in a still lower American deposit,—the Oriskany Sandstone. In the Geological Journal for 1847, it was announced by Professor Sedgwick, that he had found “defences of fishes” in the Upper Llandeilo Flags, and by Sir Roderick Murchison, that the “defence of an Onchus” had been detected by the geologists of the Government survey, in the Limestone near Bala. Sir Roderick referred in the same number to the remains of a fish found by Professor Phillips in the Wenlock Shale. And such, up to the present time, is the actual amount of the evidence with which we have to deal, and the dates of its piecemeal production. Let us next consider the order of its occurrence in the geologic scale.

The better marked sub-divisions of the Silurian System, as described in the great work specially devoted to it, may be regarded as seven in number. An eight has since been added, by the transference of the Tilestones from the lower part of the Old Red Sandstone group, to the upper part of the Silurian group underneath; but in order the better to show how ichthyic discovery has in its slow course penetrated into the depths, I shall retain the divisions recognized as those of the system when that course began. The highest or most modern Silurian deposit, then, (No. 1 of the accompanying diagram,) is the Upper Ludlow Rock; and it is in the superior strata of this division that the bone-bed discovered in 1838 occurs; while the exceedingly minute vertebrate remains described by Professor Phillips in 1842 occur in its base. The division next in the descending order is the Aymestry Limestone, (No. 2;) the next (No. 3.) the Lower Ludlow rock; then (No. 4.) the Wenlock or Dudley Limestone occurs; and then, last and oldest deposit of the Upper Silurian formation, the Wenlock shale, (No. 5.) It is in the fourth, or Wenlock Limestone division, that the defensive spine described in the “Edinburgh Review” for 1845 as the oldest vertebrate organism known at the time, was found;[24] while the vertebrate organism found by Professor Phillips belongs to the fifth, or base deposit of the Upper Silurian. Further, the American spines of Onondago and Oriskany, described in 1846, occurred in rocks deemed contemporary with those of the Wenlock division. We next cross the line which separates the base of the Upper from the top of the Lower Silurian deposits, and find a great arenaceous formation, (No. 6,) known as the Caradoc Sandstones; while the Llandeilo Flags, (No. 7,) the formation upon which the sandstones rest, compose, according to the sections of Sir Roderick, published in 1839, the lowest deposit of the Lower Silurian rocks. And it is in the upper part of this lowest member of the system that the ichthyic defences, announced in 1847 by Professor Sedgwick, occur. Vertebrate remains have now been detected in the same relative position in the seventh and most ancient member of the system, that they were found to occupy in its first and most modern member ten years ago. But this is not all. Beneath the Lower Silurian division there occur vast fossiliferous deposits, to which the name “Cambrian System” was given, merely provisionally, by Sir Roderick, but which Professor Sedgwick still retains as representative of a distinct geologic period; and it is in these, greatly below the Lower Silurian base line, as drawn in 1839, that the Bala Limestones occur. The Plynlimmon rocks (a)—a series of conglomerate, grauwacke, and slate beds, several thousand yards in thickness—intervene between the Llandeilo Flags and the Limestones of Bala, (b.) And, of consequence, the defensive spine of the Onchus, announced in 1847 as detected in these limestones by the geologists of the Government Survey, must have formed part of a fish that perished many ages ere the oldest of the Lower Silurian formations began to be deposited.

Let us now, after this survey of both the amount of our materials, and the order and time of their occurrence, pass on to the question of size, as already stated. Did the ichthyic remains of the Silurian System, hitherto examined and described, belong to large or to small fishes? The question cannot be altogether so conclusively answered as in the case of those Ganoids of the Lower Old Red Sandstone whose dermal skeletons indicate their original dimensions and form. In fishes of the Placoid order, such as the Sharks and Rays, the dermal skeleton is greatly less continuous and persistent than in such Ganoids as the Dipterians and Cœlacanths; and when their remains occur in the fossil state, we can reason, in most instances, regarding the bulk of the individuals of which they formed part, merely from that of detached teeth or spines, whose proportion to the entire size of the animals that bore them cannot be strictly determined. We can, indeed, do little more than infer, that though a large Placoid may have been armed with but small spines or teeth, a small Placoid could not have borne very large ones. And to this Placoid order all the Silurian fish, from the Aymestry Limestone to the Cambrian deposits of Bala inclusive, unequivocally belong. Nor, as has been already said, is there sufficient evidence to show that any of the ichthyic remains of the Upper Ludlow rocks do not belong to it. It is peculiarly the order of the system. The Ludlow bone-bed contains not only defensive spines, but also teeth, fragments of jaws, and shagreen points; whereas, in all the inferior deposits which yield any trace of the vertebrata, the remains are those of defensive spines exclusively. Let us, then, take the defensive spine as the part on which to found our comparison.

One of the best marked Placoids of the Upper Ludlow bone-bed is that Onchus Murchisoni to which the distinguished geologist whose name it bears refers, in his communication, as so nearly resembling the oldest Placoid yet known,—that of the Bala Limestone. And the living fishes with which the Onchus Murchisoni must be compared, says Agassiz, though “the affinity,” he adds, “may be rather distant,” are those of the genera “Cestracion, Centrina, and Spinax.” I have placed before me a specimen of recent Spinax, of a species well known to all my readers on the sea-coast, the Spinax Acanthias, or common dog-fish, so little a favorite with our fishermen. It measures exactly two feet three inches in length; and of the defensive spines of its two dorsals,—these spear-like thorns on the creature’s back immediately in advance of the fins, which so frequently wound the fisher’s hand,—the anterior and smaller measures, from base to point, an inch and a half, and the posterior and larger, two inches. I have also placed before me a specimen of Cestracion Phillippi, (the Port Jackson Shark,) a fish now recognized as the truest existing analogue of the Silurian Placoids. It measures twenty-two three fourth inches in length, and is furnished, like Spinax, with two dorsal spines, of which the anterior and larger measures from base to point one one half inch, and the posterior and smaller, one one fifth inch. But the defensive spine of the Onchus Murchisoni, as exhibited in one of the Ludlow specimens, measures, though mutilated at both ends, three inches and five eighth parts in length. Even though existing but as a fragment, it is as such nearly twice the length of the largest spine of the dog-fish, unmutilated and entire, and considerably more than twice the length of the largest spine of the Port Jackson Shark. The spines detected by Professor Phillips, in an inferior stratum of the same upper deposit, were, as has been shown, of microscopic minuteness; and when they seemed to rest on the extreme horizon of ichthyic existence as the most ancient remains of their kind, the author of the “Vestiges” availed himself of the fact. He regarded the little creatures to which they had belonged is the fœtal embryos of their class, or—to employ the language of the Edinburgh Reviewer—as “the tokens of Nature’s first and half-abortive efforts to make fish out of the lower animals.” From the latter editions of his work, the paragraph to which the Reviewer refers has, I find, been expunged; for the horizon has greatly extended, and what seemed to be its line of extreme distance has travelled into the middle of the prospect. But that the passage should have at all existed is a not uninstructive circumstance, and shows how unsafe it is, in more than external nature, to regard the line at which, for the time, the landscape closes, and heaven and earth seem to meet, as in reality the world’s end. The Wenlock spine, though certainly not microscopic, is, I am informed by Sir Philip Egerton, of but small size; whereas the contemporary spine of the Onondago Limestone, though comparatively more a fragment than the spine of the Upper Ludlow Onchus,—for it measures only three inches in length,—is at least five times as bulky as the largest spine of Spinax Acanthias. Representing one of the massier fishes disporting amid the some four or five small ones, of which in my illustration, the naturalist catches a glimpse in fording the unknown lake, it at least serves to show that all the Silurian ichthyolites must not be described as small, seeing that not only might many of its undetected fish have been large, but that some of those which have been detected were actually so. Another American spine, of nearly the same formation,—for it occurs in a limestone, varying from twenty to seventy feet in thickness, which immediately overlies that of the Onondago deposit, though still more fragmentary than the first, for its length is only two three eighth inches,—maintains throughout a nearly equal thickness,—a circumstance in itself indicative of considerable size; and in positive bulk it almost rivals the Onondago one. Of the Lower Silurian and Bala fishes no descriptions or figures have yet appeared. And such, up to the present time, is the testimony derived from this department of Geology, so far as I have been able to determine it, regarding the size of the ancient Silurian vertebrata. “No organism,” says Professor Oken, “is, nor ever has one been, created, which is not microscopic.” The Professor’s pupils and abettors, the assertors of the development hypothesis, appeal to the geological evidence as altogether on their side in the case; and straightway a few witnesses enter court. But, lo! among the expected dwarfs, there appear individuals of more than the average bulk and stature.

Fig. 47.

a. Posterior Spine of Spinax Acanthias.

b. Fragment of Onondago Spine.

(Natural Size.)

Still, however, the question of organization remains. Did these ancient Placoid fishes stand high or low in the scale? According to the poet, “What can we reason but from what we know?” We are acquainted with the Placoid fishes of the present time; and from these only, taking analogy as our guide, can we form any judgment regarding the rank and standing of their predecessors, the Placoids of the geologic periods. But the consideration of this question, as it is specially one on which the later assertors of the development hypothesis concentrate themselves, I must, to secure the space necessary for its discussion, defer till my next chapter. Meanwhile, I am conscious I owe an apology to the reader for what he must deem tedious minuteness of description, and a too prolix amplitude of statement. It is only by representing things as they actually are, and in the true order of their occurrence, that the effect of the partially selected facts and exaggerated descriptions of the Lamarckian can be adequately met. True, the disadvantages of the more sober mode are unavoidably great. He who feels himself at liberty to arrange his collected shells, corals, and fish-bones, into artistically designed figures, and to select only the pretty ones, will be of course able to make of them a much finer show than he who is necessitated to represent them in the order and numerical proportions in which they occur on some pebbly beach washed by the sea. And such is the advantage, in a literary point of view, of the ingenious theorist, who, in making figures of his geological facts, takes no more of them than suits his purpose, over the man who has to communicate the facts as he finds them. But the homelier mode is the true one. “Could we obtain,” says a distinguished metaphysician, “a distinct and full history of all that has passed in the mind of a child, from the beginning of life and sensation till it grows up to the use of reason,—how its infant faculties began to work, and how they brought forth and ripened all the various notions, opinions, and sentiments which we find in ourselves when we come to be capable of reflection,—this would be a treasure of natural history which would probably give more light into the human faculties than all the systems of philosophers about them since the beginning of the world. But it is in vain,” he adds, “to wish for what nature has not put within the reach of our power.” In like manner, could we obtain, it may be remarked, a full and distinct account of a single class of the animal kingdom, from its first appearance till the present time, “this would be a treasure of natural history which would cast more light” on the origin of living existences, and the true economy of creation, than all the theories of all the philosophers “since the beginning of the world.” And in order to approximate to such a history as nearly as possible,—and it does seem possible to approximate near enough to substantiate the true readings of the volume, and to correct the false ones,—it is necessary that the real vestiges of creation should be carefully investigated, and their order of succession ascertained.