CHAPTER V.

THE DEVONIAN AGE.

Paradoxical as it may appear, this period of geological history has been held as of little account, and has even been by some geologists regarded as scarcely a distinct age, just because it was one of the most striking and important of the whole. The Devonian was an age of change and transition, in both physical and organic existence; and an age which introduced, in the Northern hemisphere at least, more varied conditions of land and water and climate then had previously existed. Hence, over large areas of our continents, its deposits are irregular and locally diverse; and the duration and importance of the period are to be measured rather by the changes and alterations of previous formations, and the ejection of masses of molten rock from beneath, then by a series of fossiliferous deposits. Nevertheless, in some regions in North America and Eastern Europe, the formations of this era are of vast extent and volume, those of North America being estimated at the enormous thickness of 15,000 feet, while they are spread over areas of almost continental breadth.

At the close of the Upper Silurian, the vast continental plateaus of the northern hemisphere were almost wholly submerged. No previous marine limestone spreads more widely then that of the Upper Silurian, and in no previous period have we much less evidence of the existence of dry land; yet before the end of the period we observe, in a few fragments of land plants scattered here and there in the marine limestones--evidence that islands rose amid the waste of waters. As it is said that the sailors of Columbus saw the first indications of the still unseen Western Continent in drift canes, and fragments of trees floating in mid ocean, so the voyager through the Silurian seas finds his approach to the verdant shores of the Devonian presaged by a few drift plants borne from shores yet below the horizon. The small remains of land in the Upper Silurian were apparently limited to certain clusters of islands in the north-eastern part of America and north-western part of Europe, with perhaps some in the intervening Atlantic On these limited surfaces grew the first land plants certainly known to us--herbs and trees allied to the modern club-mosses, and perhaps forests of trees allied to the pines, though of humbler type; and this wide Upper Silurian sea, with archipelagos of wooded islands, may have continued for a long time. But with the beginning of the Devonian, indications of an unstable condition of the earth's crust began to develop themselves. New lands were upheaved; great shallow, muddy, and sandy flats were deposited around them the domains of corals and sea-weeds were contracted and on banks, and in shallows and estuaries, there swarmed shoals of fishes of many species, and some of them of most remarkable organization. On the margins of these waters stretched vast swamps, covered with a rank vegetation.

But the period was one of powerful igneous activity. Volcanoes poured out their molten rocks over sea and land, and injected huge dykes of trap into the newly-formed beds. The land was shaken with earthquake throes, and was subject to many upheavals and subsidences. Violent waves desolated the coasts, throwing sand and gravel over the flats, and tearing up newly-deposited beds; and poisonous exhalations, or sudden changes of level, often proved fatal to immense shoals of fishes. This was the time of the Lower Devonian, and it is marked, both in the old world and the new, by extensive deposits of sandstones and conglomerates.

But the changes going on at the surface were only symptomatic of those occurring beneath. The immense accumulations of Silurian sediment had by this time so overweighted certain portions of the crust, that great quantities of aqueous sediment had been pressed downward into the heated bowels of the earth, and were undergoing, under an enormous weight of superincumbent material, a process of baking and semi-fusion. This process was of course extremely active along the margins of the old Silurian plateaus, and led to great elevation of land, while in the more central parts of the plateaus the oceanic conditions still continued; and in the Middle Devonian, in America at least, one of the most remarkable and interesting coral limestones in the world--the corniferous limestone--was deposited. In process of time, however, these clear waters became shallow, and were invaded by muddy sediments; and in the Upper Devonian the swampy flats and muddy shallows return in full force, and in some degree anticipate the still greater areas of this kind which existed in the succeeding Coal formation.

Such is a brief sketch of the Devonian, or, as it may be better called in America, from the vast development of its beds on the south side of Lake Erie, the _Erian_ formation. In America the marine beds of the Devonian were deposited on the same great continental plateau which supported the seas of the Upper and Lower Silurian, and the beds were thicker towards the east and thinned towards the west, as in the case of the older series. But in the Devonian there was much, land in the north-east of America; and on the eastern margin of this land, as in Gaspé and New Brunswick, the deposits throughout the whole period were sandstones and shales, without the great coral limestones of the central plateau. Something of the same kind occurred in Europe, where, however, the area of Devonian sea was smaller. There the fossiliferous limestones of the Middle Devonian in Devon, in the Eifel district, in France and in Russia, represent the great corniferous limestone of America; while the sandstones of South Wales, of Ireland, and of Scotland, resemble the local conditions of Gaspé and New Brunswick, and belonged to a similar area in the north-west of Europe, in which shallow water and land conditions prevailed during the whole of the Devonian, and which was perhaps connected with the corresponding region in Eastern America by a North Atlantic archipelago, now submerged. This whole subject is so important to the knowledge of the Devonian, and of geology in general, that I may be pardoned for introducing it here in a tabular form, taking the European series from Etheridge's excellent and exhaustive paper in the "Journal of the Geological Society."

DEVONIAN OF ERIAN.

DIVISIONS. CENTRAL AREAS.

Devon. Rhen. Prussia. New York.

{Pilton group:-- Clymenia, Cypridina, Chemung and Portage. { Brown calcareous etc. Shales, Sandstones Upper { shales, brown and limestones, and and shales. { yellow sandstone. sandstones. Plants and marine { Land plants and Plants and marine shells. { marine shells. shells.

{Ilfracombe group:-- Eifel limestone, Hamilton shales, { Grey and red Calceola shales, and Corniferous Middle { sandstones and etc. or cherty { flags, calcareous Corals, shells, limestone. { slates and etc. Many corals and { limestones, with shells, also { corals, etc. plants.

{Lynton group:-- Coblentz and Schoharie and { Bed and purple Wissenbach shales, Caudagalli grits. Lower { sandstones. Marine Rhenish greywacke, Oriskany { shells, etc. Spinier sandstones. { sandstone. Marine shells. { Marine shells.

DIVISIONS. MARGINAL AREAS.

Scotland. Ireland. Gaspé and New Brunswick.

{Yellow and red Yellow and red Red and grey { sandstones. sandstones, etc. sandstones, grits Upper {Fishes and plants. Plants, fishes, and shales, and { etc. conglomerates of { Gaspé and Mispeck. { Plants.

{Red shales and Grits and Grey and Red { sandstones, and sandstones of sandstones, and Middle { conglomerates. Dingle. grey and dark {Caithness flags. shales. Gaspé {Fishes and plants. and St. John. { Many plants and { fishes.

{Flagstones, shales Glengariff grits, Sandstone and { and conglomerates. etc. conglomerate. Lower {Fishes and plants. Gaspé and St. { John. { Plants and fishes.

A glance at this table suffices to show that when we read Hugh Miller's graphic descriptions of the Old Red Sandstone of Scotland, with its numerous and wonderful fishes, we have before us a formation altogether distinct from that of Devonshire or the Eifel. But the one represents the shallow, and the other the deeper seas of the same period. We learn this by careful tracing of the beds to their junction with, corresponding series, and by the occasional occurrence of the characteristic fishes of the Scottish strata in the English and German beds. In like manner a geologist who explores the Gaspé sandstones or the New Brunswick shales has under his consideration a group of beds very dissimilar from that which he would have to study on the shores of Lake Erie. But here again identity of relations to the Silurian below and the carboniferous above, shows the contemporaneousness of the beds, and this is confirmed by the occurrence in both series of some of the same plants and shells and fishes.

It will further be observed that it is in the middle that the greatest difference occurs. Sand and mud and pebble-banks were almost universal over our two great continental plateaus in the Older and Newer Devonian. But in the Middle there were in some places deeper waters with coral reefs, in others shallow flats and swamps rich in vegetation. Herein we see the greater variety and richness of the Devonian. Had we lived in that age, we should not have seen great continents like those that now exist, but we could have roamed over lovely islands with breezy hills and dense lowland jungles, and we could have sailed over blue coral seas, glowing below with all the fanciful forms and brilliant colours of polyp life, and filled with active and beautiful fishes. Especially did all these conditions culminate in the Middle Devonian, when what are now the continental areas of the northern hemisphere must have much resembled the present insular and oceanic regions of the South Pacific.

Out of the rich and varied life of the Devonian I may select for illustration its corals, its crustaceans, its fishes, its plants, and its insects.

The central limestones of the Devonian may be regarded as the head-quarters of the peculiar types of coral characteristic of the Palæozoic age. Here they were not only vastly numerous, but present some of their grandest and also their most peculiar forms. Edwards and Haime, in their "Monograph of British Fossil Corals" in 1854, enumerate one hundred and fifty well-ascertained species, and the number has since been largely increased; I have no doubt that my friend Dr. Bigsby, in his forth-coming "Thesaurus Devonicus," will more then double it. In the Devonian limestones of England, as for instance at Torquay, the specimens, though abundant and well preserved as to their internal structure, are too firmly imbedded in the rock to show their external forms. In the Devonian of the continent of Europe much finer specimens occur; but, perhaps, in no part of the world is there so clear an exhibition of them as in the Devonian limestones of the United States and Canada. Sir Charles Lyell thus expresses his admiration of the exposure of these corals, which he saw at the falls of the Ohio, near Louisville. He says, "Although the water was not at its lowest, I saw a grand display of what may be termed an ancient coral-reef, formed by zoophytes which flourished in a sea of earlier date then the Carboniferous period. The ledges of horizontal limestone, over which the water flows, belong to the Devonian group, and the softer parts of the stone have decomposed and wasted away, so that the harder calcareous corals stand out in relief. Many branches of these zoophytes project from their erect stems precisely as if they were living. Among other species I observed large masses, not less then five feet in diameter, of _Favosites Gothlandica_, with its beautiful honeycomb structure well displayed. There was also the cup-shaped _Cyathophyllum_, and the delicate network of _Fenestella_, and that elegant and well-known European species of fossil, the chain coral, _Catenipora escharoides_, with a profusion of others which it would be tedious to all but the geologist to enumerate. Although hundreds of fine specimens have been detached from these rocks to enrich the museums of Europe and America, another crop is constantly working its way out under the action of the stream, and of the sun and rain in the warm season when the channel is laid dry."[K] These limestones have been estimated to extend, as an almost continuous coral reef, over the enormous area of five hundred thousand square miles of the now dry and inland surface of the great American continental plateau. The limestones described by Sir Charles are known in the Western States as the "Cliff limestone." In the State of New York and in Western Canada the "Corniferous limestone," so called from the masses of hornstone, like the flint of the English chalk, contained in it, presents still more remarkable features. The corals which it contains have been replaced by the siliceous or flinty matter in such a manner that, when the surrounding limestone weathers away, they remain projecting in relief in all the beauty of their original forms. Not only so, but on the surface of the country they remain as hard siliceous stones, and may be found in ploughing the soil and in stone fences and roadside heaps, so that tons of them could often be collected over a very limited space. When only partly disengaged from the matrix, the process may be completed by immersing them in a dilute acid. The beauty of these specimens when thus prepared is very great not at all inferior to that of modern corals, which they often much resemble in general form, though differing in details of structure. One of the most common forms is that of the _Favosites_, or honeycomb coral, presenting regular hexagonal cells with transverse floors or tabulæ. Of these there are several species, usually flat or massive in form; but one species, _F. polymorpha_, branches out like the modern stag-horn corals. Another curious form, _Michelina_, looks exactly like a mass of the papery cells of the great American hornet in a petrified state, and the convex floors simulate the covers of the cells, so that it is quite common to find them called fossil wasps' nests. Some of the largest belong to the genus _Phillipsastrea_ or _Smithia_, which Hugh Miller has immortalized by comparing its crowded stars, with confluent rays, to the once-popular calico pattern known as "Lane's net"--a singular instance of the accidental concurrence of a natural and artificial design. Another very common type is that of the conical _Zaphrentis_, with a deep cut at top to lodge the body of the animal, whose radiating chambers are faithfully represented by it's delicate lamellæ. Perhaps the most delicate of the whole is the _Syringopora_, with its cylindrical worm-like pipes bound together by transverse processes, and which sometimes can be dissolved out in all its fragile perfection by the action of an acid on a mass of Corniferous limestone filled with these corals in a silicified state.

[K] "Travels in North America." second series.

These Devonian corals, like those of the Silurian, belong to the great extinct groups of Tabulate and Rugose corals; groups which present, on the one hand, points of resemblance to the ordinary coral animals of the modern seas, and, on the other, to those somewhat exceptional corals, the Millepores, which are produced by another kind of polyp, the Hydroids. Some of them obviously combine properties belonging to both, as, for example, the radiating partitions with the arrangement of the parts in multiples of four, the horizontal floors, and the external solid wall; and this fact countenances the conclusion that in these old corals we have a group of high and complex organization, combining properties now divided between two great groups of animals, neither of them probably, either in their stony skeletons or the soft parts of the animal, of as high organization as their Paleozoic predecessors. This sort of disintegration of composite types, or dissolution of old partnerships, seems to have been no unusual occurrence in the history of life.[L]

[L] Verril has suggested that the Tabulata may be divided into two groups, one referable to Actinoids, the other to Hydroids.

If the Devonian witnessed the culmination of the Palæozoic corals, its later stages saw the final decadence of the great dynasty of the Trilobites. Of these creatures there are in the Devonian some large and ornate species, remarkable for their spines and tubercles; as if in this, the latter day of their dominion, they had fallen into habits of luxurious decoration unknown to their sterner predecessors, and at the same time had found it necessary to surround their now disputed privileges with new safeguards of defensive armour. Not improbably the decadence of the Trilobites may have been connected with the introduction of the numerous and formidable fishes of the period.

But while the venerable race of the Trilobites was preparing to fight its last and unsuccessful battle, another and scarcely less ancient tribe of crustaceans, the Eurypterids, already strong in the Silurian, was armed with new and formidable powers. The _Pterygotus anglicus_, which should have been named _scoticus_, since its head-quarters are in Scotland, was in point of size the greatest of known crustaceans, recent or fossil. According to Mr. Henry Woodward, who has published an admirable description and figures of the creature in the Palæontographical Society's Memoirs, it must have been six feet in length, and nearly two feet in breadth. Its antennæ were, unlike the harmless feelers of modern Crustacea, armed with powerful claws. Two great eyes stood in the front of the head, and two smaller ones on the top. It had four pairs of great serrated jaws, the largest as wide as a man's hand. At the sides were a pair of powerful paddles, capable of urging it swiftly through the water as it pursued its prey; and when attacked by any predaceous fish, it could strike the water with its broad tail, terminated by a great flat "telson," and retreat backward with the rapidity of an arrow. Woodward says it must have been the "shark of the Devonian seas;" rather, it was the great champion of the more ancient family of the lobsters, set to arrest, if possible, the encroachments of the coming sharks.

The Trilobites and Eurypterids constitute a hard case for the derivationists. Unlike those Melchisedeks, the fishes of the Silurian, which are without father or mother, the Devonian crustaceans may boast of their descent, but they have no descendants. No distinct link connects them with any modern crustaceans except the Limuli, or horse-shoe crabs; and here the connection is most puzzling, for while there seems some intelligible resemblance between the adult Eurypterids and the horse-shoe, or king-crabs, the latter, in their younger state, rather resemble Trilobites, as Dr. Packard has recently shown. Thus the two great tribes of Eurypterids and Trilobites have united in the small modern group of king-crabs, while on the other hand, there are points of resemblance, as already stated, between Trilobites and Isopods, and the king-crabs had already begun to exist, since one species is now known in the Upper Silurian. So puzzling are these various relationships, that one naturalist of the derivationist school has recently attempted to solve the difficulty by suggesting that the Trilobites are allied to the spiders! Thus nature sports with our theories, showing us in some cases, as in the corals and fishes, partnerships split up into individuals, and in others distinct lines of being converging and becoming lost in one slender thread. Barrande, the great palæontologist of Bohemia, has recently, in an elaborate memoir on the Trilobites, traced these and other points through all their structures and their whole succession in geological time thereby elaborating a most powerful inductive argument against the theory of evolution, and concluding that, so far from the history of these creatures favouring such a theory, it seems as if expressly contrived to exclude its possibility.

But, while the gigantic Eurypterids and ornate Trilobites of the Devonian were rapidly approaching their end, a few despised little crustaceans,--represented by the _Amphipeltis_ of New Brunswick and _Kampecaris_ of Scotland,--were obscurely laying the foundation of a new line of beings, that of the Stomapods, destined to culminate in the Squillas and their allies, which, however different in structure, are practically the Eurypterids of the modern ocean. So change the dynasties of men and animals.

"Thou takest away their breath, they die, They return to their dust; Thou sendest forth Thy Spirit, They are created; Thou renewest the form of the earth."

The reign of fishes began in the Upper Silurian, for in the rocks of this age, more especially in England, several species have been found. They occur, however, only in the newer beds of this formation, and are not of large size, nor very abundant. It is to be observed that, in so far as the fragments discovered can be interpreted, they indicate the existence already of two distinct types of fishes, the Ganoids, or gar-fishes, protected with bony plates and scales, and the Placoids, or shark-like fishes; and that in the existing world these fishes are regarded as occupying a high place in their class. Further, these two groups of fishes are those which throughout a large portion of geological time continue to prevail to the exclusion of other types, the ordinary bony fishes having been introduced only in comparatively recent periods. With the Devonian, however, there comes a vast increase to the finny armies; and so characteristic are these that the Devonian has been called the age of fishes _par excellence_, and we must try, with the help of our illustration, to paint these old inhabitants of the waters as distinctly as we can. Among the most ancient and curious of these fishes are those singular forms covered with broad plates, of which the _Pteraspis_ of the Upper Silurian is the herald, and which are represented in the Lower Devonian by several distinct genera. Of these, one of the most curious is the _Cephalaspis_, or buckler-head, distinguished by its broad flat head, rounded in front and prolonged at the sides into two great spines, which project far beyond the sides of the comparatively slender body. This fish, it may be mentioned, is the type of a family highly characteristic of the Lower Devonian, as well as of the Upper Silurian, and all of which are provided with large plate-like cephalic coverings, sometimes with a long snout in front, and, in so far as is known, a comparatively weak body and tail. They were all probably ground-living creatures, feeding on worms and shell-fishes, and "rooting" for these in the mud, or burrowing therein for their safety. In these respects they have a most curious analogy to the Trilobites, which in habits they must have greatly resembled, though belonging by their structure to an entirely different and much higher class. So close is this resemblance, that their head-shields used to be mistaken for those of Trilobites. The case is one of those curious analogies which often occur in nature, and which must always be distinguished from the true affinities which rest on structural resemblances. Another group of small fishes, likewise cuirassed in bony armour of plates, may be represented by the _Pterichthys_, with its two strong bony fins at the sides, which may have served for swimming, but probably also for defence, and for creeping on or shovelling up the mud at the bottom of the sea. But, besides the Ganoids which were armed in plated cuirasses, there were others, active and voracious, clad in shining enamelled scales, like the bony pikes of the American rivers and the _Polypterus_ of the Nile. Some of these, like the _Diplacanthus_, or "double-spine" were of small size, and chiefly remarkable for their sharp defensive bony spines. Others, like _Holoptychius_ (wrinkled-scale) and _Osteolepis_ (bone-scale), were strongly built, and sometimes of great size. One Russian species of _Asterolepis_ (star-scale) is supposed to have been twenty feet in length, and furnished with strong and trenchant teeth in two rows. These great fishes afford a good reason for the spines and armour-plates of the contemporary trilobites and smaller fishes. Just as man has been endeavouring to invent armour impenetrable to shot, for soldiers and for ships, and, on the other hand, shot and shells that can penetrate any armoury so nature has always presented the spectacle of the most perfect defensive apparatus matched with the most perfect weapons for destruction. In the class of fishes, no age of the world is more eminent in these respects then the Devonian.[M] In addition to these fishes, there were others, represented principally by their strong bony spines, which must have been allied to some of the families of modern sharks, most of them, however, probably to that comparatively harmless tribe which, furnished with flat teeth, prey upon shell-fishes. There are other fishes difficult to place in our systems of classification; and among these an eminent example is the huge _Dinichthys_ of Newberry, from the Hamilton group of Ohio. The head of this creature is more then three feet long and eighteen inches broad, with the bones extraordinarily strong and massive. In the upper jaw, in addition to strong teeth, there were in front two huge sabre-shaped tusks or incisors, each nearly a foot long; and corresponding to these in the massive lower jaw were two closely joined conical tusks, fitting between those of the upper jaw. No other fish presents so frightful an apparatus for destruction; and if, as is probable, this was attached to a powerful body, perhaps thirty feet in length, and capable of rapid motion through the water, we cannot imagine any creature so strong or so well armed as to cope with the mighty _Dinichthys_.

[M] Many of these were discovered and successfully displayed and described by Hugh Miller, and are graphically portrayed in his celebrated work on the "Old Red Sandstone," published in 1841.

The difference between the fishes of the Devonian and those of the modern seas is well marked by the fact that, while the ordinary bony fishes now amount to probably 9,000 species, and the ganoid fishes to less then thirty, the finny tribes of the Devonian are predominantly ganoids, and none of the ordinary type are known. To what is this related, with reference to conditions of existence? Two explanations, different yet mutually connected, may be suggested. One is that armour was especially useful in the Devonian as a means of defence from the larger predaceous species, and the gigantic crustaceans of the period. that this was the case may be inferred from the conditions of existence of some modern ganoids. The common bony pike of Canada (_Lepidosteus_), frequenting shallow and stagnant waters, seems to be especially exposed to injury from its enemies. Consequently, while it is rare to find an ordinary fish showing any traces of wounds, a large proportion of the specimens of the bony pike which I have examined have scars on their scales, indicating injuries which they have experienced, and which possibly, to fishes not so well armed, might have proved fatal. Again, in the modern Amia, or mud-fish, in the bony pike and _Polypterus_, there is an extremely large air-bladder, amply supplied with blood-vessels, and even divided into cells or chambers, and communicating with the mouth by an "air-duct." This organ is unquestionably in function a lung, and enables the animal to dispense in some degree with the use of its gills, which of course depend for their supply of vital air on the small quantity of oxygen dissolved in the water. Hence, by the power of partially breathing air, these fishes can live in stagnant and badly aerated waters, where other fishes would perish. In the case of the _Amia_, the grunting noises which it utters, its habit of frequenting the muddy creeks of swamps, and its possession of gill-cleaners, correspond with this view. It is possible that the Devonian fishes possessed this semi-reptilian respiration; and if so, they would be better adapted then other fishes to live in water contaminated with organic matter in a state of decay, or in waters rich in carbonic acid or deficient in oxygen. Possibly the palæozoic waters, as well as the palæozoic atmosphere, were less rich in pure oxygen then those of the present world; and it is certain that, in many of the beds in which the smaller Devonian fishes abound, there was so much decaying vegetable matter as to make it probable that the water was unfit for the ordinary fishes. Thus, though at first sight the possession of external armour and means to respire air, in the case of these peculiar fishes, may seem to have no direct connection with each other, their obvious correlation in some modern ganoids may have had its parallel on a more extensive scale among their ancient relatives. Just as the modern gar-fish, by virtue of its lungs, can live in stagnant shallows and hunt frogs, but on that account needs strong armour to defend it against the foes that assail it in such places; so in the Devonian the capacity to inhabit unaërated water and defensive plates and scales may have been alike necessary, especially to the feebler tribes of fishes. We shall find that in the succeeding carboniferous period there is equally good evidence of this.

We have reserved little space for the Devonian plants and insects; but we may notice both in a walk through a Devonian forest, in which we may include the vegetation of the several subordinate periods into which this great era was divisible. The Devonian woods were probably, like those of the succeeding carboniferous period, dense and dark, composed of but few species of plants, and these somewhat monotonous in appearance, and spreading out into broad swampy jungles, encroaching on the shallow bays and estuaries. Landing on one of these flats, we may first cast our eyes over a wide expanse, covered with what at a distance we might regard as reeds or rushes. But on a near approach they appear very different; rising in slender, graceful stems, they fork again and again, and their thin branches are sparsely covered with minute needle-like leaves, while the young shoots curl over in graceful tresses, and the older are covered with little oval fruits, or spore-cases; for these plants are cryptogamous, or flowerless. This singular vegetation stretches for miles along the muddy flats, and rises to a height of two or three feet from a knotted mass of cylindrical roots or root-stocks, twining like snakes through and over the soil. This plant may, according as we are influenced by its fruit or structure, be regarded as allied to the modern club-mosses or the modern pill-worts. It is _Psilophyton_, in every country one of the most characteristic plants of the period, though, when imperfectly preserved, often relegated by careless and unskilled observers to the all-engulfing group of fucoids. A little further inland we see a grove of graceful trees, forking like _Psilophyton_, but of grander dimensions, and with the branches covered with linear leaves, and sometimes terminated by cones. These are _Lepidodendra_, gigantic club-mosses, which were developed to still greater dimensions in the coal period. Near these we may see a still more curious tree, more erect in its growth, with rounded and somewhat rigid leaves and cones of different form, and with huge cable-like roots, penetrating the mud, and pitted with the marks of long rootlets. This is _Cyclostigma_, a plant near to the _Lepidodendron_, but distinct, and peculiar to the Devonian. Some of its species attain to the dimensions of considerable trees; others are small and shrubby. Another small tree, somewhat like the others, but with very long shaggy leaves, and its bark curiously marked with regular diamond-shaped scars, is the _Leptophleum_. All these plants are probably allied to our modern club-mosses, which are, however, also represented by some low and creeping species cleaving to the ground. A little further, and we reach a dense clump of _Sigillariæ_, with tall sparsely forking stems, and ribbed with ridges holding rows of leaf-scars a group of plants which we shall have further occasion to notice in the coal formation; and here is an extensive jungle of _Calamites_, gigantic and overgrown mares'-tails, allies of the modern equisetums.

Amidst these trees, every open glade is filled with delicate ferns of marvellous grace and beauty; and here and there a tree-fern rears its head, crowned with its spreading and graceful leaves, and its trunk clad with a shaggy mass of aërial roots--an old botanical device, used in these ancient times, as well as now, to strengthen and protect the stems of trees not fitted for lateral expansion. Beyond this mass of vegetation, and rising on the slopes of the distant hills, we see great trees that look like pines. We cannot approach them more nearly; but here on the margin of a creek we see some drift-trunks, that have doubtless been carried down by a land flood. One of them is certainly a pine, in form and structure of its wood very like those now living in the southern hemisphere; it is a _Dadoxylon_. Another is different, its sides rough and gnarled, and marked with huge irregular ridges; its wood loose, porous, and stringy, more like the bark of modern pines, yet having rings of growth and a true bark of its own, and sending forth large branches and roots. It is the strange and mysterious _Prototaxites_, one of the wonders of the Devonian land, and whose leaves and fruits would be worth their weight in gold in our museums, could we only procure them. A solitary fragment further indicates that in the yet unpenetrated solitudes of the Devonian forests there may be other trees more like our ordinary familiar friends of the modern woods; but of these we know as yet but little. What inhabitants have these forests? All that we yet know are a few large insects, relatives of our modern May-flies, flitting with broad veined wings over the stagnant waters in which their worm-like larvæ dwell, and one species at least assuming one of the properties of the grasshopper tribe, and enlivening the otherwise silent groves with a cricket-like chirp, the oldest music of living things that geology as yet reveals to us; and this, not by the hearing of the sound itself, but by the poor remains of the instrument attached to a remnant of a wing from the Devonian shales of New Brunswick.

A remarkable illustration of the abundance of certain plants in the Devonian, and also of the slow and gradual accumulation of some of its beds, is furnished by layers of fossil spore-cases, or the minute sacs which contain the microscopic germs of club-mosses and similar plants. In the American forests, in spring, the yellow pollen-grains of spruces and pines sometimes drift away in such quantities in the breeze that they fall in dense showers, popularly called showers of sulphur; and this vegetable sulphur, falling in lakes and ponds, is drifted to the shore in great sheets and swathes. The same thing appears to have occurred in the Devonian, not with the pollen of flowering plants, but with the similar light spores and spore-cases of species of Lepidodendron and allied trees. In a bed of shale, at Kettle Point, Lake Huron, from 12 to 14 feet thick, not only are the surfaces of the beds dotted over with minute round spore-cases, but, on making a section for the microscope, the substance of each layer is seen to be filled with them; and still more minute bodies, probably the escaped spores, are seen to fill up their interstices. The quantity of these minute bodies is so great that the shale is combustible, and burns with much flame. A bed of this nature must have been formed in shallow and still water, on the margin of an extensive jungle or forest; and as the spore-cases are similar to those of the Lepidodendra of the coal-measures, the trees were probably of this kind. Year after year, as the spores became ripe, they were wafted away, and fell in vast quantities into the water, to be mixed with the fine mud there accumulating. When we come to the coal period, we shall see that such beds of spore-cases occur there also, and that they have even been supposed to be mainly instrumental in the accumulation of certain beds of coal. Their importance in this respect may have been exaggerated, but the fact of their occurrence in immense quantities in certain coals and shales is indisputable.

This is but a slender sketch of the Devonian forests: but we shall find many of the same forms of plants in the carboniferous period which succeeds. With one thought we may close. We are prone to ask for reasons and uses for things, but sometimes we cannot be satisfied. Of what use were the Devonian forests? They did not, like those of the coal formation, accumulate rich beds of coal for the use of man. Except possibly a few insects, we know no animals that subsisted on their produce, nor was there any rational being to admire their beauty. Their use, except as helping us in these last days to complete the order of the vegetable kingdom as it has existed in geological time, is a mystery. We can but fall back on that ascription of praise to Him "who liveth for ever and ever," on the part of the heavenly elders who cast down their crowns before the throne and say, "Thou art worthy, Lord, to receive the glory, and the honour, and the might; because Thou didst create all things, and by reason of _Thy will_ they are and were created."