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ОглавлениеFig. 2.—Silurian merostomata. 1. Stylonurus. 2. Eurypterus. (After Woodward.)
Now, this fact is of great importance; for it helps us to understand the use of the four pairs of “jaw-feet” in our Sea-scorpions. What curious animals they must have been, using the same limbs for walking, holding their prey, and eating! Look at the broad plates at the base of the oar-like limbs, or appendages, with their tooth-like edges. These are the plates found by Hugh Miller’s quarrymen, and compared by them to the wings of seraphim. You will easily perceive that by a backward and forward movement, they would perform the office of teeth and jaws, while the long antennæ with their nippers—helped by the other and smaller appendages—held the unfortunate victim in a relentless grasp. And even these smaller limbs, you will see from the figure, had their first joints, near the mouth, provided with toothed edges like a saw.
With regard to the habits of Sea-scorpions, it would not be altogether safe to conclude that, because in so many ways they resembled king-crabs, they therefore had the same habit of burrowing into the soft muddy or sandy bed of the sea, as some authorities have supposed. Seeing that there is a difference of opinion on this subject, the author consulted Dr. Woodward on the question, and he said he thought it unlikely, seeing that, in some of them, such as the Pterygotus, the eyes are placed on the margin of the head-shield; for it would hardly care to rub its eyes with sand. Whether it chose at times to bury its long body in the sand by a process of wriggling backwards, as certain modern crustaceans do, we may consider to be an open question.
If only Sea-scorpions had not unfortunately died out, how interesting it would be to watch them alive, and to see exactly what use they would make of their long bodies, tail-flaps, and tail-spikes! Were they nocturnal in their habits, wandering about by night, and taking their rest by day? Such questions, we fear, can never be answered. But their large eyes would have been able to collect a great deal of light when the moon and stars feebly illumined the shallower waters of the seas of Old Red Sandstone times; and so there is nothing to contradict the idea.
Now, it is an interesting fact that young crabs, soon after they are hatched, have long bodies somewhat similar to those of our Sea-scorpions, with a head-shield under which are their jaw-feet, and then a number of free body-rings without any appendages. These end in a spiked tail. As the crab grows older, he ceases to be a free-swimming animal—for which kind of life his long body is well suited—tucks up his long tail, and takes to crawling instead. Thus his body is rendered more compact and handy for the life he is going to lead. Lobsters, on the other hand, can swim gently forwards, or dart rapidly backwards. Thus we see that the ten-footed crustaceans of the present day are divided into two groups—the long-tailed and free-swimming forms, such as lobsters, shrimps, and cray-fishes; and the short-tailed crawling forms, namely, the crabs. Now, in the same way, Pterygotus and its allies were long-tailed forms, while the king-crabs are short-tailed forms. So were the trilobites of old. Hence we learn that, ages and ages ago, before the days of crabs and lobsters, there were long-tailed and short-tailed forms of crustaceans, just as there are now, only they did not possess true walking legs. They belonged to quite a different order, called “thigh-mouthed” crustaceans, Merostomata, because their legs are all placed near the mouth; and, as we have already learned, were used for feeding as well as for purposes of locomotion.
Now, one of the many points of interest in Pterygotus and its allies is that they somewhat resemble the crab in its young or larval state. To a modern naturalist, this fact is important as showing that crustacean forms of life have advanced since the days of the sea-scorpions.
Their resemblance to land-scorpions is so close that, if it were not for the important fact that scorpions breathe air instead of water, and for this purpose are provided with air-tubes (or trachea) such as all insects have, they would certainly be removed bodily out of the crustacean class, and put into that in which scorpions and spiders are placed, viz. the Arachnida. But, in spite of this important difference, there are some naturalists in favour of such a change. It will thus be seen that our name Sea-scorpions is quite permissible.
Hugh Miller described some curious little round bodies found with the remains of the Pterygotus, which it was thought were the eggs of these creatures!
Finally, these extinct crustaceans flourished in those ages of the world’s history known as the Silurian and the Old Red Sandstone periods. As far as we know, they did not survive beyond the succeeding period, known as the Carboniferous.[6]
[6] The student should consult Dr. Henry Woodward’s valuable Monograph of the British Merostomata (Palæontographical Society), to which the writer is much indebted. With regard to the representation of Pterygotus anglicus in Plate I.., it has been pointed out by Dr. Woodward that the creature was unable to bend its body into such a position as is shown there. As in a modern lobster, or shrimp, there were certain overlapping plates in the rings, or segments, of the body, which prevented movement from side to side, and only allowed of a vertical movement.
CHAPTER III.
THE GREAT FISH-LIZARDS.
“Berossus, the Chaldæan saith: A time was when the universe was darkness and water, wherein certain animals of frightful and compound forms were generated. There were serpents and other creatures with the mixed shapes of one another, of which pictures are kept in the temple of Belus at Babylon.”—The Archaic Genesis.
Visitors to Sydenham, who have wandered about the spacious gardens so skilfully laid out by the late Sir Joseph Paxton, will be familiar with the great models of extinct animals on the “geological island.” These were designed and executed by that clever artist, Mr. Waterhouse Hawkins, who made praiseworthy efforts to picture to our eyes some of the world’s lost creations, as restored by the genius of Sir Richard Owen and other famous naturalists. His drawings of extinct animals may yet be seen hanging on the walls of some of our provincial museums; and doubtless others still linger among the natural history collections of schools and colleges.
Lazily basking in the sun, when it condescends to shine, and resting his clumsy carcase on the ground that forms the shore near the said geological island at Sydenham, may be seen the old fish-lizard, or Ichthyosaurus, that forms the subject of the present chapter. He looks awkward on land, as if longing to get into his native element once more, and cleave its waters with his powerful tail-fin. His “flippers” seem too weak to enable him to crawl on land. Moreover, the most recent discoveries of Dr. Fraas lead us to conclude that the Ichthyosaur never ventured to leave the “briny ocean” to bask upon the land.
This great uncouth beast presents some curious anomalies in his constitution, being planned on different lines to anything now living, and presenting, as so many other extinct animals do, a mixture, or fusion, of types that greatly puzzled the learned men of the time when his remains were first brought to light, after their long entombment in the Lias rocks forming the cliffs on the coast of Dorset. Some have christened him a “sea-dragon,” and such indeed he may be considered. But the name Ichthyosaurus, given above, has received the sanction of high authority, and, moreover, serves to remind us of the fact that, although in many respects a lizard, he yet retains in his bony framework the traces of a remote fishy ancestry. So we will call him a fish-lizard.
We remember in our young days the amiable endeavours of Mr. “Peter Parley” to introduce us to the wonders of creation; and his account of the Ichthyosaurus particularly impressed itself on our youthful imagination. How surprised that inestimable instructor of youth would be could he now see the still more wonderful remains that have been brought to light from Europe, Asia, Africa, and America!
The curious quotation given at the head of the present chapter refers to a widespread belief, prevalent among the highly civilised nations of antiquity, that the world was once inhabited by dragons, or other monsters “of mixed shape” and characters. To the student of ancient history traces of this curious belief will be familiar. Sir Charles Lyell refers to such a belief when he says, in his Principles of Geology, “The Egyptians, it is true, had taught, and the Stoics had repeated, that the earth had once given birth to some monstrous animals that existed no longer.” It may be surprising to some, but it is undoubtedly the fact, that modern scientific truths were partly anticipated by the civilised nations of long ago. Take the ideas of the ancients as interpreted from the records of Egypt, Chaldæa, India, and China; and you will find that our discoveries in geology, astronomy, and ethnology go far to prove that the traditions of these ancient peoples, however derived, after making due allowance for Oriental allegory and poetic hyperbole, are not far from the truth. To the Babylonian tradition of the monstrous forms of life at first created we have already alluded; but in other fields of discovery we find the same foreshadowing of discoveries made in our own day. Take the vast cycles of Egyptian tradition, wherein the stars returned to their places after a circle of constant change, only to start again on their unwearied round; the atomic theory of Lucretius, now expanded and incorporated into modern chemistry; or the philosopher’s pregnant saying—Omne vivum ex ovo (“Every living thing comes from an egg”). These and other examples might be cited to show how true the old saying is, “There is nothing new under the sun.” In the writings of ancient authors may be found singular notices of bones and skeletons found in “the bowels of the earth,” which are referred to an imaginary era of long ago, when giants of huge dimensions walked this earth. One is inclined sometimes to wonder whether the old fables of griffins and horrid dragons may not be to some extent based upon the occasional discovery, in former times, of fossil bones, such as evidently belonged to animals the like of which are not to be seen nowadays. (See chaps. xiii. and xiv.)
The illustrious Cuvier, in his day, considered the fish-lizard to be one of the most heteroclite and monstrous animals ever discovered. He said of this creature that it possessed the snout of a dolphin, the teeth of a crocodile, the head and breast-bone of a lizard, the paddles of a whale or dolphin, and the vertebræ of a fish! No wonder that naturalists and palæontologists, whose realm is the natural history of the past, were obliged to make a new division, or order, of reptiles to accommodate the fish-lizard. It is obvious that a creature with such very “mixed” relationships would be out of place in any of the four orders into which living reptiles, as represented by turtles, snakes, lizards, and crocodiles are divided. Here is what Professor Blackie says of the Ichthyosaurus—
"Behold, a strange monster our wonder engages!
If dolphin or lizard your wit may defy.
Some thirty feet long, on the shore of Lyme-Regis,
With a saw for a jaw, and a big staring eye.
A fish or a lizard? An ichthyosaurus,
With a big goggle eye, and a very small brain,
And paddles like mill-wheels in chattering chorus,
Smiting tremendous the dread-sounding main.”
A glance at our restoration, Plate II., will show that the fish-lizard was a powerful monster, well endowed with the means of propelling itself rapidly through the water as it sought its living prey, to seize it within those cruel jaws. The long and powerful tail was its chief organ of propulsion; but the paddles would also be useful for this purpose, as well as for guiding its course. The pointed head and generally tapering body suggests a capability of rapid movement through the water; and since we know for certain that it fed on fishes, this conclusion is confirmed, for fishes are not easily caught now, and most probably were not easily caught ages ago.
The personal history of the fish-lizard, merely as a fossil or “remain,” is interesting; so much so, that we may perhaps be allowed to relate the circumstances of his début before the scientific world, in the days of the ever-illustrious Cuvier, to whom we have already alluded. But England had its share of illustrious men, too, though lesser lights compared to the founder of comparative anatomy—such as Sir Richard Owen, on whom the mantle of his friend Cuvier has fallen; Conybeare, De la Beche, and Dean Buckland.
These scientific men, aided by the untiring labours of many enthusiastic collectors of organic remains, have been the means of solving the riddle of the fish-lizard, and of introducing him to the public. By this time there is, perhaps, no creature among the host of Antediluvian types better known than this reptile.
The remains of fish-lizards have attracted the attention of collectors and describers of fossils for nearly two centuries past. The vertebræ, or “cup-bones,” as they are often called, of which the spinal column was composed, were figured by Scheüchzer, in an old work entitled Querelæ Piscium; and, at that time, they were supposed to be the vertebræ of fishes. In the year 1814 Sir Everard Home described the fossil remains of this creature, in a paper read before the Royal Society, and published in their Philosophical Transactions. This fossil was first discovered in the Lias strata of the Dorsetshire coast. Other papers followed till the year 1820. We are chiefly indebted to De la Beche and Conybeare for pointing out and illustrating the nature of the fish-lizard; and that at a time when the materials for so doing were far more scanty than they are now. Mr. Charles König, Mr. Thomas Hawkins, Dean Buckland, Sir Philip Egerton, and Professor Owen have all helped to throw light on the structure and habits of these old tyrants of the seas of that age, which is known as the Jurassic period. They lived on, however, to the succeeding or Cretaceous period, during which our English chalk was forming; but the Liassic age was the one in which they flourished most abundantly, and developed the greatest variety.
In the year 1814 a few bones were found on the Dorsetshire coast between Charmouth and Lyme-Regis, and added to the collection of Bullock. They came from the Lias cliffs, undermined by the encroaching sea. Sir Everard’s attention being attracted to them, he published the notices already referred to. The analogy of some of the bones to those of a crocodile, induced Mr. König, of the British Museum, to believe the animal to have been a saurian, or lizard; but the vertebræ, and also the position of certain openings in the skull, indicated some remote affinity with fishes, but this must not be pressed too far. The choice of a name, therefore, involved much difficulty; and at length he decided to call it the Ichthyosaurus, or fish-lizard. Mr. Johnson, of Bristol, who had collected for many years in that neighbourhood, found out some valuable particulars about these remains. The conclusions of Dean Buckland, then Professor of Geology at Oxford, led Sir Everard to abandon many of his former conclusions. The labours of the learned men of the day were greatly assisted by the exertions of Miss Anning, an enthusiastic collector of fossils. This lady, devoting herself to science, explored the frowning and precipitous cliffs in the neighbourhood of Lyme-Regis, when the furious spring-tide combined with the tempest to overthrow them, and rescued from destruction by the sea, sometimes at the peril of her life, the few specimens which originated all the facts and speculations of those persons whose names will ever be remembered with gratitude by geologists.
Fig. 3.—Ichthyosaurus intermedius.
Probably our readers are already more or less familiar with the drawings of the fossilised remains of Ichthyosauri to be seen in almost every text-book of geology. (Fig. 3 is from Owen’s British Fossil Reptiles.) But we recommend all who take an interest in the world’s lost creations to pay a visit to the great Natural History Museum, at South Kensington. The fossil reptile gallery contains a magnificent series of Ichthyosauri, about thirty in number. Of these a large number were obtained through the exertions of the late Mr. T. Hawkins, a Somersetshire gentleman, who was a most ardent collector of fossil reptiles, and who devoted himself with great enthusiasm and unsparing energy to the acquisition of a truly splendid collection of these most interesting relics of the past. Nearly sixty years ago he arranged for the purchase of his treasures by the authorities of the British Museum, and thus his collection became the property of the nation.
His specimens were figured and described by him in two large folio volumes. The first was published in 1834, under the title, Memoirs of the Ichthyosauri and Plesiosauri; his second, with the same plates, in 1842, under the quaint title of The Book of the Great Sea-Dragons. The large lithographic drawings of his fine specimens were beautifully executed by Scharf and O’Neil. The plates are the only really valuable part of these two curious and ill-written books. His descriptions are not of much value, and his pages are encumbered with a vast amount of extraneous matter. The author is immensely proud of his collection, and his vanity is conspicuous throughout. Instead of confining himself to descriptions of what he found, and how he found them, he continually wanders into all sorts of subjects that are, to say the least, irrelevant. In one place he introduces ancient history and mythology; in another, Old Testament chronology; in another, the unbelieving spirit of the age; and here and there indulges in vague unphilosophical speculations. Altogether his two volumes are a curious mixture of bigotry, conceit, and unrestrained fancy, and they afforded to the present writer no small amusement. One rises from the perusal of such men’s writings with a strong sense of the contrast between the humble and patient spirit in which our great men of to-day, such as Professor Owen, study nature and record their observations, and the vague, conceited outpourings of some old-fashioned writers.
Mr. Hawkins tells us that his youthful attention was directed to the Lias quarries, near Edgarly, in Somersetshire, in consequence of some strange reports. It was said that the bones of giants and infants had, at distant intervals, been found in them. These quarries he visited, and, by offers of generous payment, induced the workmen to keep for him all the remains they might find. In this way he finally obtained the co-operation of all the quarrymen in the county.
Plate II.
FISH-LIZARDS. Ichthyosaurus communis. Ichthyosaurus tenuirostris. Length about 22 feet. Fishes, Dapedius, etc. A smaller species.
Mr. Hawkins thus expresses his delight on obtaining an Ichthyosaurus which was pointed out to him by Miss Anning, near the church at Lyme-Regis, in the year 1832: “Who can describe my transport at the sight of the colossus? My eyes the first which beheld it! Who shall ever see them lit up with the same unmitigated enthusiasm again? And I verily believe that the uncultivated bosoms of the working men were seized with the same contagious feeling; for they and the surrounding spectators waved their hats to an ‘Hurra!’ that made hill and mossy dell echoing ring.”
This specimen, however, got sadly broken in its fall from the cliff; but in time he put all the pieces together again. Speaking of his own collection, he says, “This stupendous treasure was gathered by me from every part of England; arranged, and its multifarious features elaborated from the hard limestone by my own hands. A tyro in collecting at the age of twelve years, I then boasted of all the antiquities that were come-at-able in my neighbourhood, but, finding that everybody beat my cabinet of coins, I addressed myself to worm-eaten books, and last to fossils.” Before he was twenty years of age he had obtained a very fine collection of organic remains.
When, however, he complains of the Philistine dulness and stupidity of quarrymen, who often, in their ignorance, break up finds of almost priceless value, we can fully sympathize.
In general contour the body of the fish-lizard was long and tapering, like that of a whale (see Plate II.). It probably showed no distinct neck. The long tail was its chief organ of propulsion. We notice two pairs of fins, or paddles; one on the fore part of the body, the other on the hinder part, like the pectoral and abdominal fins of a fish. The skin was scaleless and smooth, or slightly wrinkled, like that of a whale. No traces of scales have ever been found; and if such had existed, they would certainly have been preserved, since those of fishes and crocodiles of the Jurassic period have been found in considerable number and variety. It is therefore safe to conclude that such were absent in this case. In the Lias strata, at least, the specimens are often preserved with most wonderful completeness (see p. 47).
The long and pointed jaws are a striking feature of these animals. The eyes were very large and powerful, and specially adapted, as we shall see presently, to the conditions of their life.
It might, perhaps, be asked whether the fish-lizards breathed, like fishes, by means of gills. That question can easily be answered; for if they had possessed gills for taking in water and breathing the air dissolved therein, they would reveal the fact by showing a bony framework for the support of gills, such as are to be found in all fishes. These structures, known as “branchial arches,” are absent; therefore the fish-lizards possessed lungs, and breathed air like reptiles of the present day. Their skulls show where the nostrils were situated; namely, near the eyes, and not at the end of the upper jaw-bone. There are also passages in the skull leading from the nostrils to the palate, along which currents of air passed on their way to the lungs. Being air-breathers, they would be compelled occasionally to seek the surface of the sea, in order to obtain a fresh supply of the life-giving element—oxygen; but, being cold-blooded and with a small brain, needing a much less supply of oxygen for its work, the fish-lizards had, like fishes, this advantage over whales, which are warm-blooded—that their stern-propeller, or tail-fin, could take the form best adapted for a swift, straight-forward course through the water.
In the whale tribe the tail-fin is horizontal; and this is so on account of their need, as large-brained, warm-blooded air-breathers, of speedy access to the atmospheric air. Were it otherwise, they would not have the means of rising with sufficient rapidity to the surface of the sea; for they have only one pair of fins. But the fish-lizards had two pairs of these appendages, and the hinder or pelvic pair no doubt were of great service in helping the creatures to come up to the surface when necessary.
Thus we see that the whale, with its one pair of paddles, has a tail specially planned with a view to rapid vertical movement through the water; while in the fish-lizards, who did not require to breathe so frequently, the tail-fin was planned with a view to swift and straight movement forward as they pursued their prey, and they were compensated by having bestowed upon them an extra pair of paddles. Thus we learn how one part of an animal is related to and dependent upon another, and how they all work together with the greatest harmony for certain definite purposes (see p. 6).
Fig. 4.—(A) Lateral and (B) profile views of a tooth of Ichthyosaurus platyodon (Conybeare), Lower Lias, Lyme Regis, Dorsetshire, (C) Tooth of Ichthyosaurus communis (Conybeare), Lower Lias, Lyme Regis, Dorset.
These great marine predaceous reptiles literally swarmed in the seas of the Lias period, and no doubt devoured immense shoals of the fishes of those times, whose numbers were thus to some extent kept down. There is clear proof of this in the fossilised droppings—known as “coprolites,”—which show on examination the broken and comminuted remains of the little bony plates of ganoid fishes that we know were contemporaries of these reptiles. Probably young ones were sometimes devoured too.
It was in the period of the Lias that fish-lizards attained to their greatest development, both in numbers and variety; and the strata of that period have preserved some interesting variations. It will be sufficient here to point out two, namely, Ichthyosaurus tenuirostris—an elegant little form, in which the jaws, instead of being massive and strong, were long and slender like a bird’s beak; and also Ichthyosaurus latifrons (Fig. 5), with jaws still more bird-like. Our artist has attempted to show the former variety in our illustration (Plate II.). A most perfect example of this pretty little Ichthyosaur, from the Lower Lias of Street in Somerset, has recently been presented to the National Collection at South Kensington by Mr. Alfred Gillett, of Street, and may be seen there. In this group of fish-lizards the eyes are relatively larger, and we should imagine that they were very quick in detecting and catching their prey; their paddles also have larger bones.
Fig. 5.—Skull of Ichthyosaurus latifrons.
There is a remarkably fine specimen at Burlington House, in the rooms of the Geological Society, of an Ichthyosaurus' head, which the writer found, on measuring, to be about five feet six inches long. A cast of this head is exhibited at South Kensington. The largest of the specimens in the National Collection is twenty-two feet long and eight feet across the expanded paddles; but it is known that many attained much greater dimensions. Judging from detached heads and parts of skeletons, it is probable that some of them were between thirty and forty feet long. A specimen of Ichthyosaurus platyodon in the collection of the late Mr. Johnson, of Bristol, has an eye-cavity with a diameter of fourteen inches. This collection is now dispersed.
With regard to their habits, Sir Richard Owen concludes that they occasionally sought the shores, crawled on the strand, and basked in the sunshine. His reason for this conjecture (which, however, is not confirmed by Dr. Fraas’s recent discoveries) is to be found in the bony structure connected with the fore-paddles, which is not to be found in any porpoise, dolphin, grampus, or whale, and for want of which these creatures are so helpless when left high and dry on the shore.[7] The structure in question is a strong bony arch, inverted and spanning across beneath the chest from one shoulder to the other. A fish-lizard, when so visiting the shore for sleep, or in the breeding season, would lie or crawl, prostrate, with its under side resting or dragging on the ground—somewhat after the manner of a turtle.
[7] It is, perhaps, hardly necessary to remark that whales are not fishes, but mammals which have undergone great change in order to adapt themselves to a marine life. Their hind limbs have practically vanished, only a rudiment of them being left.
It is a curious fact that this bony arch resembles the same part in those singular and problematical mammals, the Echidna and the Platypus, or duck-mole.
The enormous magnitude and peculiar construction of the eye are highly interesting features. The expanded pupil must have allowed of the admittance of a large quantity of light, so that the creature possessed great powers of vision.
The organic remains associated with fish-lizards tell us that they inhabited waters of moderate depth, such as prevails near a coast-line or among coral islands. Moreover, an air-breathing creature would obviously be unable to live in "the depths of the sea;" for it would take a long time to get to the surface for a fresh supply of air.
Perhaps no part of the skeleton is more interesting than the curious circular series of bony plates surrounding the iris and pupil of the eye. The eyes of many fishes are defended by a bony covering consisting of two pieces; but a circle of bony overlapping plates is now only found in the eyes of turtles, tortoises, lizards, and birds, and some alligators. This elaborate apparatus must have been of some special use; the question is—What service or services did it perform? Here, again, we find answers suggested by Owen and Buckland. It would aid, they say, in protecting the eye-ball from the waves of the sea when the creature rose to the surface, as well as from the pressure of the water when it dived down to the bottom—for even at a slight depth pressure increases, as divers know. But it appears that the ring of bony plates fulfilled a yet more important office, thereby enabling the fish-lizards to play admirably their part in the world in which they lived, and to succeed in the struggle of life; for even in those remote days there must have been, as now, a keen competition among all animals, so that the victory was to those that were best equipped.
Would it not be an advantage for them to have the power of seeing their finny prey whether near or far? Certainly it would; and so we are told that, by bringing the plates a little nearer together, and causing them to press gently on the eye-ball, so as to make the eye more convex—that is, bulging out—a nearer object would be the better discerned. On the other hand, by relaxing this pressure, thus enlarging the aperture of the pupil and diminishing the convexity, a distant object would be focussed upon the retina. In this manner some birds alter the focus of their eyes while swooping down on their prey.
What a wonderful arrangement! We often hear of people having two pairs of spectacles—with lenses of different curvature—one for reading, and the other for seeing more distant objects than a book held in the hand. But here is a creature that possessed an apparatus far more simple and effective than that supplied by the optician! Dr. Buckland, speaking of these “sclerotic plates,” as they are called, says they show “that the enormous eye of which they formed the front was an optical instrument of varied and prodigious power, enabling the Ichthyosaurus to descry its prey in the obscurity of night and in the depths of the sea.” But the last expression must be taken in a limited sense (see Fig. 6).
Fig. 6.—Head of Ichthyosaurus platyodon.
It might well be supposed that no record had been preserved from which we could learn anything about the nature of the skin of our fish-lizard; but even this wish has been partly fulfilled, to the delight of all geologists. Certain specimens have been obtained, from the Lias of England and Germany, that show faithful impressions of the skin that covered the paddles. A specimen of this nature has lately been presented to the national treasure-house at South Kensington by Mr. Montague Brown. On the inner side of the paddle was a broad fin-like expansion, admirably adapted to obtain the full advantage of the stroke of the limb in swimming.[8]
[8] Mr. Smith Woodward informs the writer that specimens have lately been found near Würtemberg, with evidence of a triangular fin on the back. Plate II. has been redrawn for this edition, to make it more in harmony with Dr. Fraas’s discoveries. (See Appendix V.)
Speaking of the limbs, it should be mentioned that the bones of each finger, instead of being elongated and limited in number to three in each of the five fingers, are polygonal in shape and arranged in as many as seven or eight rows, while those of each finger are exceedingly numerous. Thus the whole structure forms a kind of bony pavement which must have been very supple. Such a limb would be one of the most efficient and powerful swimming organs known in the whole animal kingdom. In whales the fingers of the flippers are of the usual number, namely, five. Some species of fish-lizards had as many as over a hundred separate little bones in the fore-paddle.
Another question naturally suggests itself: Were they viviparous, or did they lay eggs like crocodiles? This question seems to have been answered in favour of the first supposition; and in the following interesting manner. It not infrequently happens that entire little skeletons of very small individuals are found under the ribs of large ones. They are invariably uninjured, and of the same species as the one that encloses them, and with the head pointing in one direction. Such specimens are most probably the fossilised remains of little fish-lizards, that were yet unborn when their mothers met with an untimely end (see p. 51). In some cases, however, they may be young ones that were swallowed. (See Appendix V.)
The jaws of these hungry formidable monsters were provided with a series of formidable teeth—sometimes over two hundred in number—inserted in a long groove, and not in distinct sockets, as in the case of crocodiles. In some cases, sixty or more have been found on each side of the upper and lower jaws, giving a total of over two hundred and forty teeth! The larger teeth may be two inches or more in length.
The jaws were admirably constructed on a plan that combined lightness, elasticity, and strength. Instead of consisting of one piece only, they show a union of plates of bone, as in recent crocodiles. These plates are strongest and most numerous just where the greatest strength was wanted, and thinner and fewer towards the extremities of the jaw. A crocodile, Sir Samuel Baker says, in his Wild Beasts and their Ways, can bite a man in two; and no doubt our fish-lizard would have been glad to perform the same feat! But in his pre-Adamite days the opportunity did not present itself.
The spinal column, or backbone, with its generally concave vertebræ, must have been highly flexible, as is that of a fish, especially the long tail which the creature worked rapidly from side to side as it lashed the waters.
The hollows of these concave vertebræ must have been originally filled up with fluid forming an elastic bag, or capsule. To get a clearer idea of this, take a small portion of the backbone of a boiled cod, or other “bony” fish, and you will see on pulling it to pieces, the white, jelly-like substance that fills up the hollows between the vertebræ. In this way Nature provides a soft cushion between the joints, that allows of a certain amount of movement, while, at the same time, the column holds together. The backbone of a fish may not inaptly be compared to a railway train. Each of the carriages represents a vertebra, and the buffers act as cushions when the train is bent in running round a curve. After all, we must learn from Nature; and many of the greatest mechanical and engineering triumphs of to-day are based upon the methods used by Nature in the building up and equipment of vegetable and animal forms of life.
It may, perhaps, be inquired whether there is any evidence for the existence of a tail-fin, such as is shown in our illustration. To this it may be replied that the presence of such an appendage is as good as proved by a certain flattening of the vertebræ at the end of the tail, detected by Owen. The direction of this flattening is from side to side, and therefore the tail-fin must have been vertical, like that of a fish. In one specimen Sir Richard Owen has detected as many as 156 vertebræ to the whole body.
Our description of the fish-lizard has, we trust, been sufficient—although not couched in the language used by men of science—to give a fair idea of its structure and habits.
In conclusion, a few words may be said about the ancestry and life-history of these ancient monsters. Palæontologists have good reason to believe that they were descended from some early form of land reptile. If so, they show that whales are not the first land animals that have gone back to the sea, from which so many forms of life have taken their rise.
During the long Mesozoic period fish-lizards played the part that whales now play in the economy of the world; and they resembled the latter, not only in general shape, but in the situation of the nostrils (near the eye), and in their teeth and long jaws. But these curious resemblances must not be interpreted to mean that whales and fish-lizards are related to each other. They only show that similar modes of life tend to produce artificial resemblances—just as some whales, in their turn, show a superficial resemblance to fishes.
With regard to the particular form of reptile from which the fish-lizard may have been derived, no certain conclusion has at present been arrived at. This is chiefly from want of fuller knowledge of early forms, such as may have existed in the previous periods known as the Carboniferous and Trias (see Appendix I.). But there are certain features in the skulls, teeth, and vertebræ that suggest a relationship with the Labyrinthodonts, or primæval salamanders that flourished during the above periods, or at least from amphibians more or less closely allied to them. They cannot by any possibility be regarded as modified fishes; for fishes have gills instead of lungs.
The fish-lizards played their part, and played it admirably; but their days were numbered, and the place they occupied has since been taken by a higher type—the mammal. As reptiles, they were eminently a success; but, then, they were only reptiles, and therefore were at last left behind in the struggle for existence, until finally they died out, at the end of the Cretaceous period, when certain important geographical and other changes took place, helping to cause the extinction of many other strange forms of life, as we shall see later on (see p. 147).
They had a wide geographical range; for their remains have been discovered in Arctic regions, in Europe, India, Ceram, North America, the east coast of Africa, Australia, and New Zealand.
In American deposits they are represented by certain toothless forms, to which the name Sauranodon (“toothless lizard”) has been given. These have been discovered by Professor Marsh, in the Jurassic strata of the Rocky Mountains. They were eight or nine feet long, and in every other respect resembled Ichthyosaurs. As we have endeavoured to indicate in our illustration, the fish-lizards flourished in seas wherein animal, and doubtless vegetable life was very abundant. Any one who has collected fossils from the Lias of England will have found how full it is of beautiful organic remains, such as corals, mollusca, encrinites, sea-urchins, and other echinoids, fishes, etc.
The climate of this period in Europe was mild and genial, or even semi-tropical. Coral reefs and coral islands varied the landscape. There is just one more point of interest that ought not to be omitted; it refers to the manner in which these reptiles of the Lias age met their deaths, and were thus buried up in their rocky tombs. Sir Charles Lyell and other writers point out that the individuals found in those strata must have met with a sudden death and quick burial; for if their uncovered bodies had been left, even for a few hours, exposed to putrification and the attacks of fishes at the bottom of the sea, we should not now find their remains so completely preserved that often scarcely a single bone has been moved from its right place. What was the exact nature of this operation is at present a matter of doubt.
CHAPTER IV.
THE GREAT SEA-LIZARDS AND THEIR ALLIES.
“The wonders of geology exercise every faculty of the mind—reason, memory, imagination; and though we cannot put our fossils to the question, it is something to be so aroused as to be made to put the questions to one’s self.”—Hugh Miller.
The fish-lizards, described in our last chapter, were not the only predaceous monsters that haunted the seas of the great Mesozoic age, or era. We must now say a few words about certain contemporary creatures that shared with them the spoils of those old seas, so teeming with life. And first among these—as being more fully known—come the long-necked sea-lizards, or Plesiosaurs.
The Plesiosaurus was first discovered in the Lias rocks of Lyme-Regis, in the year 1821. It was christened by the above name, and introduced to the scientific world by the Rev. Mr. Conybeare (afterwards Dean of Llandaff) and Mr. (afterwards Sir Henry) de la Beche. They gave it this name in order to distinguish it from the Ichthyosaurus, and to record the fact that it was more nearly allied to the lizard than the latter.[9] Conybeare, with the assistance of De la Beche, first described it in a now-classic paper read before the Geological Society of London, and published in the Transactions of that Society in the year 1821. In a later paper (1824) he gave a restoration of the entire skeleton of Plesiosaurus dolichodeirus; and the accuracy of that restoration is still universally acknowledged. This fine specimen was in the possession of the Duke of Buckingham, who kindly placed it at the disposal of Dr. Buckland, for a time, that it might be properly described and investigated.
