IV. The Animal World in its Historical and Paleontological Development. It is so easy to observe that the earth's crust, from the deepest valleys to the highest mountain top contains innumerable animal remains, that even antiquity could not fail to notice it. But some two thousand years passed by before a correct knowledge was attained of the relations of these remains to the present world. Some thought they were sports of nature, products of creative power leading to no special object, but in a certain measure to be regarded as exercises preliminary to the actual creation of life; others considered the fossils as remains of living creatures, indeed, but of such as still existed, and which had been destroyed by overflows and subsequent withdrawals of the sea. The legend of the universal deluge, especially, derived great support from this second opinion. Only when, at the end of last century, the stratification of the earth's crust was revealed to science, after the outlines of a history of the solar system and of a special history of the earth or geology had been indicated by Kant and Laplace, only then arose the possibility and necessity of a real palæontology, or knowledge of prehistoric life. At the beginning of this century it was discovered that the fossils corresponding with the stra GEOLOGICAL FORMATIONS. 61 tification of the earth's crust follow each other in regular sequence, and that in this sequence they differ from the present creation, as they do from each other. We must make ourselves acquainted with the order of succession of these strata. They are the shelves in which the vegetable and animal remains lie stored. To arrange them was certainly possible only by taking the organisms which they contained as guides or clues. We, however, shall take this arrangement as our data, and, with the object we have in view, we shall naturally consider only those strata and rocks in which fossils— using this word in its widest interpretation—are or might be contained, those, namely, which are proved to be sedimentary, i.e. aqueous deposits. Our information is limited to a great part of Europe, numerous districts of America, and scattered points of the rest of the world. The following table gives the the arrangement of the sedimentary strata from above downwards : 6. Triassic formation or New Red Sandstone. Keuper or Variegated Marls. Variegated Sandstone. 7. Permian formation or Dyas. Zechstein (Magnesian Limestone or Dolomitic Conglomerate). 8. Carboniferous formation, Coal Measures. Millstone Grit. Mountain Limestone. 9. Devonian formation. 12. Laurentian formation. Although we are not writing on geology, a short explanation of these strata will be requisite, as their mutual relations also throw light on the nature and distribution of the contemporaneous organisms. All displacements of earth which we now see occurring by means of rain, rivers, sea and other natural forces which have taken place in historic times, in short, in the so-called Present, such as the great delta deposits, and the moraine formations of our glaciers, are ascribed to the Alluvium. It was formerly supposed that its limits might be distinguished from the Diluvium by the appearance of man, but as it is now, and always has been impossible to affirm anything positive respecting that epoch, and as, although a portion of the organisms of which the remains occur in the Diluvial strata is extinct, much more still exists, these two formations are inseparably intermingled. To the Diluvium belong the vast mud deposits of the great rivers, alternating with sand banks, the clay and loess formations caused by the removal of the soil TERTIARY FORMATION-CHALK. 63 by the drainage of the glaciers and the floods of running water, which at one time increased periodically to a degree truly colossal. The diluvial period, as it seems, includes, both in Europe and America, a repeated glacification of countries and vast portions of the world, of which the present state of Greenland may now give some idea. The period of the series of strata, comprised under the name of the tertiary formation, may be regarded as that during which, at least, the skeleton of the present continents finally attained its integral configuration. Within its limits fall the erection and upheaval of the great mountain chains, the Cordilleras, Alps, Himalayas, and others; the outlines of the continents were, meanwhile, in constant movement. This phenomenon, however, persists throughout all formations, and, as the geological characteristic of the tertiary formation, more stress should be laid on the separation of the earth's surface into climatic zones, approximating to the zones. of the present age. The names of the subdivisions are intended to indicate the relation of the animals then living to those of our world, as it was supposed that in the eocene the first animals the first animals identical with present species were to be found, more in the miocene, and, yet more, in the pliocene. To the chalk formation belong rocks of very various kinds, which can be reduced to one great geological period by means of their contents. If the quartzose sandstone of Saxon Switzerland represents this formation in the centre of Germany, it is from the white chalk of England and Northern France that it took its name. In America, the sandstone has been in a great measure ground down into sand, and in other places the strata are purely chalky or marly. But the vagueness of the limitations of strata in situation, and still more in time, may be estimated by the fact that we are fully justified in speaking of the chalk formation now going on, as is shown by the investigations of Carpenter and W. Thompson on the constitution of the deep seabottom of the Atlantic. To the early chalk period belongs a great fresh-water deposit, and likewise the Wealden, a formation of peat and bog occasioned by upheavals, which contains a number of remains of freshwater and terrestrial animals, besides a peculiar sort of coal. The oolitic strata appear more definite, mostly lying regularly over each other in distinct deposits, more rarely, as in the Alps, raised up by later dislocations. The rocks themselves, betray that the depositions took place in wide seas, for the most part calm or deep, and this is rendered a certainty by the scanty vegetal remains and the far more abundant animal remains which they contain. In the apparently very sharp limitation of the oolitic formation, both above and below, the older geology found a main prop for the assertion, that comparatively quiet periods of long duration alternated with catastrophes destroying and re-creating everything. To avoid any misapprehension we must, however, add that the oolitic period already possessed vast and highly integrated continents, as it will likewise be seen that during this era the higher terrestrial animals made. their appearance. The characters shown by the three great divisions. of the triassic formation are very various, especially as |