The Pampas of South America are not less famous in Geology for the remains of Gigantic quadrupeds, than the Lias of England for its colossal marine reptiles. These vast undulating plains, which present to the eye for nine hundred miles a waving sea of grass, consist chiefly of stratified beds of gravel and reddish mud; and it is in these beds that the remains of many unshapely but powerful terrestrial animals have been found embedded. So abundant are they, that it is said a line drawn in any direction through the country would cut through some skeleton or bones. Indeed, Mr. Darwin is of opinion that the whole area of the Pampas is one wide sepulchre of these extinct animals. It will be enough for our purpose to describe one in particular, which, from its prodigious bulk, has received the appropriate name of Megatherium, or the Great Wild Beast.
The Megatherium, like the Ichthyosaurus and the Plesiosaurus, had many affinities with the existing creation. In its head and shoulders it resembled the sloth which still browses on the green foliage of the trees in the dense forests of South America; while in its legs and feet it combined the characteristics of the Ant-Eater and the Armadillo. But it was eminently distinguished from these and all the other modern representatives of the family to which it belonged by its colossal proportions. It was often twelve feet long and eight feet high; its fore-feet were a yard in length and twelve inches in breadth, terminating in gigantic claws; its haunches were five feet wide, and its thigh bone was three times as big as that of the largest elephant. “His entire frame,” as Dr. Buckland has admirably observed and carefully demonstrated, “was an apparatus of colossal mechanism, adapted exactly to the work it had to do; strong and ponderous, in proportion as this work was heavy, and calculated to be the vehicle of life and enjoyment to a gigantic race of quadrupeds, which, though they have ceased to be counted among the living inhabitants of our planet, have, in their fossil bones, left behind them imperishable monuments of the consummate skill with which they were constructed,—each limb, and fragment of a limb, forming co-ordinate parts of a well adjusted and perfect whole; and through all their deviations from the form and proportions of the limbs of other quadrupeds, affording fresh proofs of the infinitely varied and inexhaustible contrivances of Creative Wisdom.”
“This Leviathan of the Pampas, as it has been justly called, became first known in Europe toward the close of the last century. In the year 1789 a skeleton was dug up, almost entire, about three miles southwest of Buenos Ayres, and was presented by the Marquis of Loreto to the Royal Museum at Madrid, where it still remains. Since that time other specimens, besides numerous fragments, have been discovered, chiefly through the zeal and energy of Sir Woodbine Parish; by the aid of which the form, structure, and consequently the habits of this clumsy and ponderous animal have been fully ascertained. The complete skeleton which forms so prominent an object of attraction in the British Museum, and which is represented in the woodcut on the adjoining page, is only a model; but it has been constructed with great care from the original bones, some of which are to be found in the wall-cases of the same room, and others in the Hunterian Museum of the Royal College of Surgeons.”[78]
Fig. 21.—The Megatherium. From the British Museum. Length 12 feet; Height 8 feet.
Closely allied to the Megatherium, but somewhat less colossal in its dimensions, is the Mylodon. Its remains are found associated with those of the Megatherium and other great animals of the same family, in the superficial gravels of South America. A splendid specimen, which measures eleven feet from the fore part of the skull to the end of the tail, was dug up, in the year 1841, a few miles north of Buenos Ayres. It is well figured in the adjoining woodcut, which we reproduce, by kind permission of the Author, from Dr. Haughton’s admirable Manual of Geology.
Fig. 22.—Mylodon Robustus, from Buenos Ayres.
Passing from the petrified fish, and the reptiles, and the quadrupeds, that thus come forth, as it were, from their graves to bring us tidings of an extinct creation, we must next turn our attention for a moment to Fossil Shells. These relics of the ancient world, which are scattered with profuse abundance through all the strata of the Earth’s Crust, may seem, indeed, of little value to the careless observer; but to the practised eye of science they are full of instruction. They have been aptly called the Medals of Creation; for, stamped upon their surface they bear the impress of the age to which they belong; and they constitute the largest, we may say, perhaps, the most valuable part of those unwritten records from which the Geologist seeks to gather the ancient history of our Globe.
As regards the prodigious abundance of Fossil Shells preserved in the Crust of the Earth, it is unnecessary for us here to speak. We have already seen that the great mass of many limestone formations is composed almost exclusively of such remains, broken up into minute fragments, and more or less altered by chemical agency; and besides, there are quarries within the reach of all, where they may collect at pleasure these interesting relics of the olden time. But there are one or two facts of peculiar significance connected with Fossil Shells, which it may be useful briefly to set down. In the first place, we would remind our readers that there is a marked and well-known difference between the shells of those animals that can live only in the sea, of those that inhabit rivers, and of those, finally, that frequent the brackish waters of estuaries. Now it has been made clear beyond all reasonable doubt, by the explorations of Geologists, that sea-shells abound in great numbers far away from the present line of coast, in the heart of vast continents. And they are found, not merely on the surface, but buried deep in the Crust of the Earth, and overlaid, in many cases, by numerous strata of solid rock, thousands of feet in thickness. It is also to be observed that they occur at all heights above the level of the ocean; having been discovered at an elevation of eight thousand feet in the Pyrenees, ten thousand in the Alps, thirteen thousand in the Andes, and above eighteen thousand in the Himalaya.[79] Such are the phenomena which are constantly forcing themselves on the attention of the Geologist, and which involve a number of problems that he cannot help attempting to investigate and explain. He is instinctively impelled to ask himself, how can the shells of marine animals have come to exist so far away from the sea? how have they been buried in the Crust of the Earth? how have they been lifted up to the highest pinnacles of lofty mountains?