large herds of the Palæotherium, the ancient Pachyderm, reconstructed with such accuracy by Cuvier, are feeding along its banks; and a tall bird of the Heron or Pelican kind stands watching by the water's edge. In the Miocene the vegetation looks still more familiar, though the Elephants roaming about in regions of the Temperate Zone, and the huge Salamanders crawling out of the water, remind us that we are still far removed from present times. Lastly, we have the ice period, with the glaciers coming down to the borders of a river where large troops of Buffalo are drinking, while on the shore some Bears are feasting on the remains of a huge carcass.

It is, however, with the Carboniferous age that we have to do at present, and I will not anticipate the coming chapters of my story by dwelling now on the aspect of the later periods. To return, then, to the period of the coal, it would seem that extensive freshets frequently overflowed the marshes, and that even after many successive forests had sprung up and decayed upon their soil, they were still subject to submergence by heavy floods. These freshets, at certain intervals are not difficult to understand, when we remember, that, beside the occasional influx of violent rains, the earth was constantly undergoing changes of level, and that a subsidence or upheaval in the neighborhood would disturb the equilibrium of the waters, causing them to overflow and pour over the surface of the country, thus inundating the marshes anew.

That such was the case we can hardly doubt, after the facts revealed by recent investigations of the Carboniferous deposits. In some of the deeper coal-beds there is a regular alternation between layers of coal and layers of sand or clay; in certain localities, as many as ten, twelve, and even fifteen coal-beds have been found alternating with as many deposits of clay or mud or sand; and in some instances, where the trunks of the trees are hollow and have been left standing erect, they are filled to the brim, or to the height of the next

layer of deposits, with the materials that have been swept over them. Upon this set of deposits comes a new bed of coal with the remains of a new forest, and above this again a layer of materials left by a second freshet, and so on through a number of alternate strata. It is evident from these facts that there have been a succession of forests, one above another, but that in the intervals of their growth great floods have poured over the marshes, bringing with them all kinds of loose materials, such as sand, pebbles, clay, mud, lime, etc., which, as the freshets subsided, settled down over the coal, filling not only the spaces between such trees as remained standing, but even the hollow trunks of the trees themselves.

Let us give a glance now at the animals which inhabited the waters of this period. In the Radiates we shall not find great changes; the three classes are continued, though with new representatives, and the Polyp Corals are increasing, while the Acalephian Corals, the Rugosa and Tabulata, are diminishing. The Crinoids were still the most prominent representatives of the class of Echinoderms, though some resembling the Ophiurans and Echinoids (Sea-Urchins) began to make their appearance. The adjoining wood-cut represents a characteristic Crinoid of the Carboniferous age.

at from the side of the flat valve, showing the straight cut of the line of juncture between the valves and the rising curve of the opposite one, which looks like a hooked beak when seen in profile. Other species of Bivalves were also introduced, approaching more nearly our Clams and Oysters, or, as they are called in scientific nomenclature, the Lamellibranchiates. They differ from the Brachiopods chiefly in the higher character of their breathing - apparatus; for they have free gills, instead of the net-work of vessels on the lining skin which serves as the organ of respiration in the Brachiopods. We shall always find, that, in proportion as the functions are distinct, and, as it were, individualized by having special organs appropriated to them, animals rise in the scale of structure. The next class of Mollusks, the Gasteropods, or Univalves, with spiral shells, were numerous, but, from their brittle character, are seldom found in a good state of preservation.

The Chambered Shells, or the Cephalopods, represented chiefly in the earlier periods by the straight Orthoceratites described in a previous article, are now curled in a close coil, and the internal structure of their chambers has become more complicated. The subjoined wood

cut represents a characteristic Chambered Shell of the Carboniferous age. Goniatites is the scientific name of these later forms. If we had looked for them in the Devonian period, we should have found many with looser coils than these, and some only slightly curved in the shape of a horn. These, as well as the perfectly straight forms, still exist in the coal period, but the Goniatites with close whorls are the more numerous and more characteristic.

The Articulates have gained their missing class since the close of the Devonian period, for Insects have come in, and that division of the Animal Kingdom is therefore complete, and represented by three classes, as it is at present. Of the Worms little can be said; their traces are found as before, but they are very imperfectly preserved. There are still Trilobites, but they are very few in number, and other groups of Crustacea have

I here present one of our common HorseShoe Crabs above one of these old-world Crustaceans, and it will be seen, that, while the latter preserves some of the Trilobitic characters, such as the marked articulations on the posterior part of the body and their division into three lobes, yet in the prominence of its anterior shield, its more elongated form, and tapering extremity, it resembles its modern representative. In some of them, however, there is no such sharp point as is here figured, and the body terminates bluntly. There were a large number of these Entomostraca in the Carboniferous period, a group which is chiefly represented among living Crustacea by an exceedingly minute kind of Shrimp; but in those days they were of the size of our Crabs and Lobsters, or even larger, and the Horse-Shoe Crab still maintains their claim to a place among the larger and more conspicuous members of the class.

The Insects were few, and, as I have said above, of a kind which seeks a moist atmosphere, or whose larvæ live altogether in water. They are not usually well preserved, as will be seen from the broken character of the one here repre

sented, although the wood-cut is made from a better specimen than is often found. We have, however, remains enough to establish unquestionably the fact of their existence in the Carboniferous period, and to show us that the type of Articulates was already represented by all its classes.

Not so with the Vertebrates. Fishes abound, but their class still consists, as

before, of the Ganoids, those fishes of the earlier periods built on the Gar-Pike and Sturgeon pattern, and the Selachians, represented now by Sharks and Skates. In the Carboniferous period we begin to find perfectly preserved specimens of the Ganoids, and the adjoining wood-cut rep

resents such a one. of Selachians we have again one lingering representative in our own times to give us the clue to its ancestors, -as the Gar-Pike explains the old Ganoids, and the Chambered Nautilus helps us to understand the Chambered Shells of past times. The so-called Port-Jackson Shark has features which were very characteristic of the Carboniferous Sharks and are lost in the modern ones, so that it affords us a sort of link, as it were, and a measure of comparison, between those now living and the more ancient forms. It is an interesting fact that this only living representative of the Carboniferous Shark should be found in New Holland, because it is there, in that isolated continent, left apart, as it would seem, for a special purpose, that we find reproduced for us most fully the character of the Animal Kingdom in earlier creations.

The first Mammalia in the world were pouched animals, having that extraordinary attachment to the mother after birth which characterizes the Kangaroo. In New Holland almost all the Mammalia are pouched, and have also the imperfect organization of the brain, as compared with the other Mammalia, which accompanies that peculiar structural feature; and although the American Opossum makes an exception to the rule, it is nevertheless true that this type of the Animal Kingdom is now confined almost exclusively to New Holland. Whether

this living picture of old creations in modern garb was meant to be educational for man or not, it is at least well that we should take advantage of it in learning all it has to teach us of the relations between the organic world of past and present times.

There were a great variety of the Selachians in the Carboniferous period. The wood-cuts below represent a tooth and

a spine from one of the most characteristic groups, but I have not thought it worth while to enumerate or to figure others here, for there are no perfect specimens, and their structural differences consist chiefly in the various form and appearance of the teeth, scales, and spines, and would be uninteresting to most of my readers. I would refer the more scientific ones, who may care to know something of these details, to my investigations on Fossil Fishes, published many

years since under the title of "Recherches sur les Poissons Fossiles."

Although the Vertebrate division of the Animal Kingdom still waited for its higher classes, yet it had received one important addition since the Silurian and Devonian periods. The Carboniferous marshes were not without their reptilian inhabitants; but they were Reptiles of the lowest class, the so-called Amphibians, those which are hatched from the egg in an immature condition, undergoing metamorphosis after birth. They have no hard scales, and lay a large number of eggs. I am unable to present any figure of one of these ancient Reptiles, as they are found in so imperfect a state of preservation that no plates have been made from them. I would add in connection with this subject that I believe a large number of animals found in the Carboniferous deposits, and referred to the class of Reptiles, to be Fishes allied to Saurians.

Before leaving the Carboniferous period, let us see what territory the United States has conquered from the Ocean during that time. All its central portion, from Canada to Alabama, and from Western Iowa, Missouri, and Arkansas to Eastern Virginia, was raised above the water. But as yet the Alleghanies and the Rocky Mountains did not exist; a great gulf ran up to the mouth of the Ohio, for the Mississippi had not yet accumulated the soil for the fertile valley through which it was to take its southern course; the Coral-Builders had still their work to do in constructing the peninsula of Florida; and, indeed, all the borders of the continent of North America, as well as a large part of its Western territory, were still to be added. But although its central portion held its ground and was never submerged again, yet the continent was slowly subsiding during the middle geological periods, so that, instead of enlarging gradually by the increase of deposits, its limits remained much the same.

This accounts for the very scanty traces to be found in America of the secondary deposits; for the Permian, Triassic, and