The Subterranean World

by G. Hartwig

CHAPTER II.
FOSSILS.

General Remarks—Eozoon Canadense—Trilobites—Brachiopods—Pterichthys Milleri—Oldest Reptiles—Wonderful Preservation of Colour in Petrified Shells—Primæval Corals and Sponges—Sea-lilies—Orthoceratites and Ammonites—Belemnites—Ichthyosaurus and Plesiosaurus—Pterodactyli—Iguanodon—Tertiary Quadrupeds—Dinotherium—Colossochelys Atlas—Megatherium—Mylodon—Glyptodon—Mammoth—Mastodon—Sivatherium Giganteum—Fossil Ripple-marks, Rain-drops, and Footprints—Harmony has reigned from the beginning.

The fossil remains of plants and animals, which have successively flourished, and passed away since the first dawn of organic life, occupy a prominent place among the wonders of the subterranean world. A medal that has survived the ruin of empires is no doubt a venerable relic, but it seems to have been struck but yesterday when compared with a shell or a leaf that has been buried millions of years ago in the drift of the primeval ocean, and now serves the geologist as a waymark through the past epochs of the earth’s history.

AMMONITES HENLEYI (MIDDLE LIAS).

If we examine the condition in which the fossils have been preserved in the strata successively deposited on the surface of our globe, we find that in general only parts of the original plant or animal have escaped destruction, and in these fragments also the primitive substance has often been replaced by other materials, so that only their form or their impression has triumphed over time. While soft and delicate textures have either been utterly swept away, or could only be preserved under the rarest circumstances (as, for instance, the insects and flowers inclosed in amber), a greater degree of hardness or solidity naturally gave a better chance of escaping destruction. Thus among plants the most frequent fossil-remains are furnished by stems, roots, branches, fruit-stones, leaves; and, among animals, by corals, shells, calcareous crusts, teeth, scales, and bones. But the few memorials that have thus survived the lapse of ages enable us to form some idea of the multitudes that have entirely perished; and the petrified shell of the Ammonite, or the jointed arms of the Encrinite, are proofs of the existence of the world of tiny beings which served them for their nourishment and have been utterly swept away. If we consider that the number of all the known species of fossil plants hardly amounts to 3,000, while the Flora of the present day, as far as it has been examined by systematical botanists, numbers at least 250,000 species; that the host of living insects is probably still more numerous, although not much more than 1,500 extinct species of this class are known to us; and that, finally, the remains of all the extinct crustaceous fishes, reptiles, and warm-blooded animals are far outnumbered by the species actually living—we may form some idea of the vast multitudes that have left no trace behind, and whose total loss will for ever confine within narrow limits our knowledge of the past phases of organic creation. This loss appears still greater when we consider the enormous extent of time during which the fossils known to us have successively existed, and that a part only of the comparatively small number of the orders, genera, and species to which they belong existed at one and the same epoch. But as, owing to the hard texture and mode of life which are so eminently favourable for the preservation of shells, we have been enabled to collect about 11,000 fossil species, a number not much inferior to that of the molluscs of the present day, we may justly conclude that the more perishable forms of life, of which, consequently, fewer vestiges have been preserved, were comparatively as numerous, and that ever since the first dawn of organic life our earth has borne an immense variety of plants and animals.

Though comparatively but few species have been preserved, yet sometimes the accumulation of fossil remains is truly astonishing. In the carboniferous strata we not seldom find more than one hundred beds of coal interstratified with sandstones, shales, and limestones, and extending for miles and miles in every direction. How luxuriant must have been the growth of the forests that could produce masses such as these, and what countless multitudes of herbivorous insects must have fed upon their foliage or afforded food to carnivorous hordes scarcely less numerous than themselves! The remains of corals, encrinites, and shells often form the greater part of whole mountain ranges, and, what is still more remarkable, mighty strata of limestone or flint are not seldom almost entirely composed of the aggregated remains of microscopical animals.

After these remarks on fossils in general, I will now briefly point out some of the most striking of the species so preserved to us as they successively appeared upon the stage of life.

In the Lower Laurentian Rocks, the most ancient strata known, only one fossil has hitherto been found. The Eozoon canadense, as it has been called, belonged to the Rhizopods, which occupy about the lowest grade in the scale of animal existence. Its massive skeletons, composed of innumerable cells, would seem to have extended themselves over submarine rocks, their base upwards of twelve inches in width and their thickness from four to six inches. Such is the antiquity of the Eozoon that the distance of time which separated it from the Trilobites of the Cambrian formation may be equal to the vast period which elapsed between these and the Tertiary ages. In other words, it is beyond our imagination to conceive.