CHAPTER V.

Scenery of the carboniferous forests—Contrast in the appearance of coal districts at the present day—Abundance of animal life in the Carboniferous era—Advantages of palæontology over fossil-botany—Carboniferous fauna—Actiniæ—Cup-corals—Architecture of the present day might be improved by study of the architecture of the Carboniferous period—Mode of propagation of corals—A forenoon on the beach—Various stages in the decomposition of shells—Sea-mat—Bryozoa—Fenestella—Retepora—Stone-lilies—Popular superstitions—Structure of the stone-lilies—Aspect of the sea-bottom on which the stone-lilies flourished—Sea-urchins—Crustacea, their high antiquity—Cyprides—Architecture of the Crustacea and mollusca contrasted—King-crabs.

Theforms of vegetation that flourished during the Carboniferous era seem to have been in large measure marshy plants, luxuriating on low muddy delta-lands, like the cypress-swamps of the Mississippi, or the Sunderbunds of the Ganges. We can picture but faintly the general scenery of these old forests from the broken and carbonized remains that have come down to us. But though perhaps somewhat monotonous on the whole, it must have been eminently beautiful in detail. The sigillariæ raised their sculptured stems and lofty waving wreaths of fronds high over the more swampy grounds, while a thick underwood of ferns and star-leaved asterophyllites clustered amid the shade below. The lepidodendra shot forth their spiky branches from the margin of green islets, and dropped their catkins into the sluggish water that stole on among the dimpled shadows underneath. Tree-ferns spread out their broad pendant fronds, and wrapt the ground below in an almost twilight gloom, darker and deeper far than that

"Hospitable roofOf branching elms star-proof,"

"Hospitable roof

Of branching elms star-proof,"

which rose so often in the visions of Milton; or that "graceful arch" so exquisitely sung by Cowper, beneath which

"The chequered earth seems restless as a floodBrushed by the wind. So sportive is the lightShot; through the boughs, it dances as they dance,Shadow and sunshine intermingling quick,And darkening and enlightening, as the leavesPlay wanton, every moment, every spot."

"The chequered earth seems restless as a flood

Brushed by the wind. So sportive is the light

Shot; through the boughs, it dances as they dance,

Shadow and sunshine intermingling quick,

And darkening and enlightening, as the leaves

Play wanton, every moment, every spot."

Thickets of tall reeds rose out of the water, with stems massive as those of our forest-trees, encircled at regular distances by wreaths of pointed leaflets, and bearing on their summits club-like catkins. Far away, the distant hills lay shaggy with pine-woods, and nursed in their solitudes the springs and rivulets that worked a devious course through forest, and glen, and valley, until, united into one broad river, they crept through the rich foliage of the delta and finally passed away out to sea, bearing with them a varied burden of drift-wood, pine-trees from the hills, and stray leaves and cones from the lower grounds.

How different such a scene from that now presented by the very same areas of country! These old delta lands are now our coal-fields, and have exchanged the deep stillness of primeval nature for the din and turmoil of modern mining districts. In these ancient times, not only was man uncreated, but the earth as yet lacked all the higher types of vertebrated being. None of the animals that we see around us existed then; there were no sheep, nor oxen, horses, deer, nor dogs. Neither were the quadrupeds of other lands represented; the forests nourished no lions or tigers, no wolves or bears, no opossums or kangaroos. In truth, the land must have been a very silent one, for we know as yet of no animated existence that could break the stillness, save perchance some chirping grasshopper, or droning beetle, or quivering dragon-fly. No bee hummed along on errands of industry; it is doubtful, indeed, whether honey-yieldingflowers formed part of the carboniferous flora; no lark carolled blithely in the sky, nor rook croaked among the woods. All was still; and one might, perhaps, have stood on some of those tree-crested islets, and heard no sound but the rippling of the water along the reedy and sedgy banks, and the rustling of the gloomy branches overhead.

To one who muses on these bygone ages it is no unimpressive situation to stand in the midst of a large coal district and mark its smoking chimneys, clanking engines, and screaming locomotives, its squalid villages and still more squalid inhabitants, and its mingled air of commercial activity, physical wretchedness, and moral degradation. It is from such a point of view that we receive the most forcible illustration of those great changes whereof every country has been the scene, and which are so tersely expressed by one who has gazed on the revelations of geology with the eye of a true poet—

"There rolls the deep where grew the tree.O earth, what changes hast thou seen!There where the long street roars, bath beenThe stillness of the central sea."

"There rolls the deep where grew the tree.

O earth, what changes hast thou seen!

There where the long street roars, bath been

The stillness of the central sea."

But the lifelessness of the carboniferous forests was amply compensated by the activity that reigned in river, lagoon, and sea. Coral groves gleamed white beneath the waves, fishes of many a shape disported in stream and lake, and the bulkier forms, armed in massive plates of bone, ascended the rivers or haunted the deeper recesses of the open sea. In some beds of rock the remains of these various animals lie crowded together like drifted tangle on the sea-shore, and the whole reminds us of a vast cemetery or charnel-house. The bones lie at all angles, many of them broken and disjointed as though the owner had died at a distance, and his remains, sadly mutilated on the way, had been borne to their last resting-place by the shifting currents; others lie all in place, covered with their armature of scales, as though the creature, conscious of approachingdissolution, had sought out a sheltered nook and there lain down and died. It is not uninteresting or uninstructive to tract; out in an old quarry stratum above stratum, each with its groups of once living things. I know of few employments more pleasant than to sit there, amid the calm stillness of a summer evening, when the shadows are beginning to steal along the valleys and creep up the hill-sides, and in that dim fading light to try in fancy to clothe these dry bones with life, to picture the time when they lived and moved in the glassy depths of lakes and seas, or amid the solitudes of jungles and forests, and so to spend a pleasant hour in reverie, till roused at last by the vesper song of the lark, or the low meanings of the night wind as it sighs mournfully through the woods.

The study of fossil animals embraces a much greater range of subject than that of fossil plants. Thefaunaof any particular geological formation, that is to say, its embedded animal remains, for the most part vastly exceeds in number itsflora, or vegetable remains, and is likewise usually better preserved. About the nature and affinities of several tribes of fossil plants there hangs an amount of uncertainty which renders them a dubious guide to the climatal and other conditions of the period and locality in which they lived. Generic distinctions among living plants often rest on the character of those parts which are the most perishable, such as flowers and seed-vessels. These delicate structures we, of course, can hardly look to find preserved in the rocks, and we have in place of them only detached leaflets, twigs, branches, and stems, often sorely mutilated in outward form, and presenting no trace of internal organization. But the tribes of the animal kingdom have, for the most part, harder frameworks. The minute infusoria, which by their accumulated remains help to choke up the delta of the Nile, and swarm by millions in every ocean of the globe, have their silicious or calcareous shells so minute that Ehrenberg has estimated a cubic inch of tripoli to contain forty-one thousand millions of them. The polypihave their internal calcareous skeletons, which abound in all the older limestones, and form the coral reefs of the present day. The mollusca, too, though, as their name imports, they have perishable bodies, are yet, in most cases, furnished with hard calcareous shells, that indicate by their various modifications of form and structure, the character of the animal that lived within them. They are found in all the formations from the earliest upwards, and as they vastly exceed in numbers all the other classes with which the geologist has to deal, they form the larger part of that basis of evidence from which he interprets the past history of organized existence. Hugh Miller loved to talk of them as the "shell alphabet," out of which the language of palæontological history should be compiled. The vertebrata, too, all have their hard skeletons, easily capable of preservation, whether it be in the form of the massive exo-skeleton of bone that characterized the older ganoidal fishes, or the compact endo-skeleton of the reptiles and mammals. A greater amount of attention is, therefore, due to the study of fossil animals, since they thus not only far exceed fossil plants in number, but possess a higher value as evidence of ancient physical conditions.

Thefaunaof the Carboniferous system is a very numerous one, exhibiting specimens of almost every class of animal life, from the tinyforaminiferup to the massive bone-covered sauroidal fish, and even to occasional traces of true reptilian remains. By far the larger number are peculiar to the sea, such as the molluscan tribes and corals; others are undoubtedly terrestrial organisms, such as the wings and wing-sheaths of several kinds of insects; while some appear to be peculiar to fresh or brackish water, such as shells allied to ourunioor river-mussel, and minute crustaceous animals known ascyprides, of which we have still representatives in our ponds and ditches. It is plain, then, that if we rightly ascertain the class or family to which one of these fossils belonged, we shall obtain a clueto the history of the physical geography, during Carboniferous times, of the district in which the fossil occurs. A bed of unios will tell us of old rivers and lakes that spread out their blue waters where now, perchance, there lie waving fields of corn. A bed of corals and stone-lilies will lay before us the bottom of an ancient ocean that rolled its restless waves where to-day, perhaps, the quarryman plies his task amid the gloom of dark pine-woods. In short, these organic remains are to the history of the earth what ancient monuments are to the history of man. They enable us to trace out the varied changes of our planet and its inhabitants down to the human era, just as the wooden canoe, the flint arrow-head, the stone coffin, the bronze sword, the iron cuirass, the ruined abbey, and the feudal castle, teach us the successive stages of progress in the history of our own country.

Whoever has spent a few days on some rocky coast, must have noticed adhering to half-tide stones numerous solitaryactiniæ. Arrayed in all the colours of the rainbow—purple, green, and gold—these little creatures hang out their tentacles like so many flowers, and have hence received the popular name of sea-anemones. Their internal structure is no less beautiful. They resemble so many large plump gooseberries, and consist of a little sack suspended within a larger one. The outer sack is fringed along its upper edges with one or more rows of slim hollow tentacles, which diverge outwards like the petals of the daisy, and can be contracted at pleasure so as somewhat to resemble the daisy when folded up at sunset. The inner sack, which forms the stomach of the animal, has a short opening or gullet, at the upper part of which is the mouth lying in the centre of the cavity surrounded by the fringes of tentacles. The inner sack is connected with the outer by means of thin membranes, like so many partition-walls, which radiate inwards like spokes towards the axle of a wheel. The space between each of these membranes, or lamellæ, forms an independent chamber, but it has acommunication with those on either side by a window in each wall, and further opens upwards into the hollow tentacles, which, with minute orifices at their outer points, may be compared to chimneys. These chambers form the breathing apparatus of the little creature. Sea-water passes down through the tentacle into the hollow chamber below, whence, by the constant action of minute hairlike cilia that line the walls like tapestry, it is driven through the window into the next chamber, thence into the next, and so on, passing gradually through the tentacles back to the sea.

The actiniæ are of a soft perishable substance, but many of the otherAnthozoa, or flower-like animals, have hard calcareous skeletons. Of such a kind are the polypi that in the Pacific Ocean have raised those stupendous reefs and islands of coral. It does not appear that, during the Carboniferous period, there existed any reef-building zoophytes, but some of the most abundant forms of life belonged to a kindred tribe, and are known by the name ofCyathophyllidæ, or cup-corals.

As the name imports, the typical genus has a general cup-shaped form, but this is liable to many aberrations in the cognate genera. The younger specimens of one species (Cyathopsis fungites) have a curved outline somewhat like the bowl of a tobacco-pipe, whence the quarrymen know them as pipe-heads. The older individuals are generally more or less wrinkled and twisted, sometimes reaching a length of eight or nine inches, and have been named by the workmenrams'-horns.

Fig. 16.—Cyathopsis (clisiophyllum ?) fungites.

The annexed figure (Fig. 16) shows their general appearance and structure. The lower end was fixed to the rock like the flat sucker-like disc of the actinia. Around the outer margin there diverged one or more rows of slim tentacles, hollow, soft, and retractile, like those of the actinia. From the margin to the centre there radiated more than a hundred lamellæ, but these differed from the corresponding membranes of the modern animal, inasmuch as they were strengthened internally by askeleton of hard carbonate of lime; and to this difference we owe their preservation. They stand out in high relief upon weathered specimens, showing the long, narrow chambers that ran between them. Their walls were once doubtless hung with countless vibratile cilia, and perhaps pierced each with its window, through which the currents of water passed in their ceaseless progress to and from the sea. At the centre lay the mouth, communicating by a short gullet with the stomach, which occupied the central portion of the animal, and from the outer walls of which the lamellæ diverged like so many buttresses. In its youngest stages, the animal occupied the whole length of the cup, but, us it increased in size, it gradually retreated from the narrow end, which was then divided off by a thin calcareous membrane. At each successive stage of its growth, a new membrane was added, each further and further from the lower end, so that eventually the creature left below it a series of empty chambers all firmly built up. Thus, in a specimen six or eight inches long, there would in reality only be a small part tenanted—in fact merely the upper floor—all the lower storeys remaining silent and uninhabited. The house of this old-world architect differed widely in one respect from human dwellings. Man begins his basement story of the same dimensionsas those that are to succeed it, or, if any difference is made at all, the upper floors are built each less than the one below it, so that the whole structure tapers upward to a point, as in the Pyramids. But the cyathopsis reversed this latter process; it inverted the cone, commencing the smallest chamber at the bottom, and placing the widest at the top. Indeed, one is sometimes puzzled to conjecture how so bulky a building could be securely poised on so narrow a basis, and it is certainly difficult to see how the creature could move about with such a ponderous load to drag along. The snail carries his house on his back, yet it is a slim structure at the best; but the cup-coral must not merely have carried his house, but some dozen or two of old ones strung one after another to his tail. Perhaps, though free to move about and try change of residence in its youthful days, the creature gradually settled down in life, and took up its permanent abode in some favourite retreat, the more especially as in process of time it became what we should call a very respectable householder.

Allied to the cyathopsis is another and still more beautiful coral, described so long ago as the latter part of the seventeenth century by the Welsh antiquary and naturalist, Lhwyd, under the name ofLithostrotion. Although many perfect specimens of it have been found, and it is usually as well preserved as any of its congeners, men of science have been sadly at a loss what to call it. Four or five synonyms may be found applied to it in different works on palæontology. There seems now, however, a tendency to return to the name that old Lhwyd gave it two centuries ago; the family to which it belongs, and of which it is the type, has accordingly been termed theLithostrotionidæ, and the species in questionLithostrotion striatum(Fig. 17). It differed from the cyathopsis in several respects, but chiefly in this, that it lived in little congregated groups or colonies, whereas the cyathopsis, like our own actinia, dwelt alone.

Fig. 17.—Lithostrotion striatum.

Each of these colonies was formed of a cluster of hexagonal, or rather polygonal pillars, fitting closely into each other, like the basaltic columns of Fingal's Cave, and springing from a common base at the sea bottom.[30]Each pillar constituted the abode of a single animal, and resembled generally the stalk of the cyathopsis. It had the same minute diverging partitions running from the outer walls towards the centre, and the same thin diaphragms, which, stretching horizontally across the interior of the column at short intervals, marked the successive stages of the animal's growth. Within these partitions, which vary from forty to eighty in number, there runs an inner circular tube with thin lamellæ and diaphragms. The exterior of the columns is ribbed longitudinally by a set of long fine striæ, which give somewhat the appearance of the fluting on a Corinthian pillar. The columns, moreover, are not straight, but have an irregular, wrinkled outline, so that, by a slant light, they look like some old pillar formed of many layers of stone, the joints of which have wasted away, producing an undulating profile in place of the original even one. But in these ancient coral columns there is no blunted outline, no worn hollow; the sculpturing stands out as sharp and fresh, and the wavy curves as clearly defined, as though the creature had died but yesterday. They resemble no order of human architecture, save faintly, perhaps, some of the wavy outlines of the Arabesque.

[30]Sir Roderick Murchison figures in hisSiluria, p. 282, a gigantic specimen, which measured two feet four inches in width.

Despite all the improvements and inventions of modern times, classic architecture has made no progress since the days of Pericles. All that we do now is but to reproduce what theGreeks created 2000 years ago, and he is reckoned the best architect who furnishes the best imitation. Our architects might find some useful hints, however, by studying the lowlier orders of nature. They would see there patterns of beauty far more delicate than the Grecian capital, and more light and airy than the Gothic shaft. And whether or not they could found a new order of architecture, they could not fail to discover many modifications and improvements upon some of the old. They could not readily light upon a more graceful form than that of the lithostrotion, would they but picture it as it grew at the bottom of the old carboniferous sea. A group of hexagonal pillars, firmly compacted together like those of the Giant's Causeway, or Fingal's Cave, rose from a white calcareous pediment, as columns from the marble steps of an Athenian temple. Each side of the pillar had a wavy undulating surface, delicately fluted by long slender striæ, the whole being so arranged that the convexities of one surface fitted into the sinuosities of the adhering one. Each pillar was crowned above by a capital, consisting of the soft vibratile tentacles of the animal, that hung over like so many acanthus leaves. Of the form of these tentacles, their design and grouping, we know nothing save what may be gathered from the analogy of living corals. There can be little doubt, however, that, like the flower-shaped buds of the existing reef-building polyps, they must have been eminently beautiful, and in strict keeping with the graceful column which they crowned.

Another kindred form was that known as thelithodendron. It, too, grew in colonies, and seems to have closely resembled the last, save that the pillars, in place of being six-sided, were round. I have seen a bed of these corals several yards in extent, and seven or eight inches deep, where the individuals were closely crowded together, so as to resemble a series of tobacco-pipe stems, or slim pencils set on end. The tubes, however, were not all quite straight; many being more or lesscurved, and sometimes crossing their neighbours obliquely. The internal arrangement was on the same plan as in the two previous corals. The same numerous partitions ran from the exterior wall towards the central tube, the same thick-set diaphragms crossed the entire breadth of the column, imparting the same minute honey-combed appearance to a cross section. The exterior of the column (inL. fasciculatum) was likewise traversed by the same longitudinal striæ.

Both these corals seem to have beenfissiparous, that is to say, they propagated by splitting into two parts, each of which formed the base of a new column with a new animal. The evidence for this statement rests on the fact, that many of the tubes are seen to bifurcate in their course, so that two new tubes are produced equal in size and completeness to the old one from which they proceed. Another mode of generation which, in at least its earlier stages, would produce a somewhat similar appearance is calledgemmation, and consists in the protrusion of a bud or gemmule from the side of the animal, which shortly develops into a new and perfect individual. It is probable, however, that the ordinary mode of propagation among these old corals was the usual one by impregnated ova. These ova, like those of our sea-anemones, were probably generated within the partitions, between the central stomach and the outer wall, whence they passed down into the stomach, and were ejected by the mouth of the parent as little gemmules, furnished with the power of locomotion by means of vibratile cilia. Some of theMedusafamily possess this three-fold mode of propagation; but, in all, the last-mentioned is the most usual.

Has the reader ever stretched himself along the shore, while, perhaps, a July sun blazed overhead, and a fitful breeze came over the sea, just strong enough to chase ashore an endless series of rippling wavelets, and breathe over his temples a delicious and refreshing coolness? Thus placed, and gazing dreamily now, perchance, at the distant sails like white specksalong the boundary line of sea and sky; now at the gulls wheeling in broad circles through the air, and shooting swift as arrows down into the blue water, he must often have turned to look for a little at the sand which, heaped up in little mounds around him, formed a couch well-nigh as soft as the finest down. Many a varied fragment entered into the composition of that sand. Mingled among the minuter quartzy particles lay scores of shells, some with the colour not yet faded, and the valves still together—the delicate tellina, with its polished surface, and its flush of pink; the cardium with its strong white plaited sides, and the turritella with its circling spire; some were worn down and sorely effaced, others broken into fragments by the ceaseless grinding of the waves. It was pleasant labour in such a sultry noon to pick out the shells of one species in all stages of decay. TheTrochus lineatus, or Silver Willie, as young ramblers by the sea-shore love to call it, showed well the process of destruction. The perfect shell, cast ashore, perhaps, by the last storm, and still uninjured by the tides, displayed its russet epidermis, or outer skin, covered with fine brown zig-zag lines, running across the whorls from the creature's wide pearl-lined mouth to the apex. A second shell exhibited a surface that had begun to suffer; the point had been divested of its thin outer skin, and laid bare the silvery coating of pearl below. A third had undergone a still longer period of abrasion, for the whole of the epidermis was gone, and the surface gleamed with a pearly iridescence. In yet a fourth, this bright exterior had been in large measure worn away, and the blunted, rounded shell displayed the dull white calcareous substance of which it was mainly built up. But there were other objects of interest in the sand: bits of tangle, crusted over with a fine net-work of gauze, and fragments of thin leaf-like membrane, consisting of a similar slender network known popularly as thesea-mat, occasionally turned up among the pebbles and shells. No one who met with theseorganisms for the first time could fail to be struck with the extreme delicacy of finish, if one may so speak, that characterizes them. And yet he might be puzzled to know what to make of them. The leaf-like membrane, at a first glance, looks not unlike some of the flat-leaved algæ, and such the observer might readily take them to be. Such, too, they were long regarded by naturalists; but a more careful examination of them showed that the so-called plants really belonged to the animal kingdom, and that the supposed leaves were, in truth, the organic dwelling-places of minute zoophytes, of which many hundreds lay grouped together on every square inch. For many years these little creatures were called "celliferous corallines," and classed among the polypi, that great tribe which has its representatives in every ocean, from the coral reefs of the Pacific to the little bell-shapedhydraamid the tangle of our own seas. But the microscope—that lamp which lights us into the inner recesses of nature—revealed at last their true character. Fixed to one spot, living in communities, and exceedingly minute, in short, with many of the outward features of the true corallines, they were yet found to possess a structure so complex and highly organized, as to entitle them to rank among the higher tribes of the invertebrate animals, and they are now accordingly pretty generally subjoined to the mollusca, under the name ofBryozoa.

Each bryozoon consists externally of a single horny or calcareous cell, sometimes furnished with a valve-like lid that folds down when the animal withdraws itself. When danger is past, and the creature begins again to emerge, the upper parts, which were drawn in like the inverted finger of a glove, are pushed out until a series of tentacles, covered with minute hair-like bodies, called cilia, are expanded. The vibratile motion of these cilia causes a constant current in the direction of the mouth, which lies in the centre of the hollow whence the tentacles spring; animalcules are in this way brought in rapidsuccession within reach of the mouth, and form a never-failing source of nourishment. The interior is greatly more complex than that of thepolypi. The stomach is connected above with a cavity like the gizzard of a bird, furnished with pointed sides, which serve to triturate the food before it passes into the stomach. There is also a distinct intestine. The muscular action for the expansion and retraction of the animal is highly developed, and the generative system is a greatly more complex one than that of the polyps already referred to. In short, however closely they might be thought to resemble the corals in outward form, their internal structure undoubtedly links them with a much higher type of organization, and justifies the naturalist in subjoining them as a sub-order to the mollusca.

The cells are grouped at short intervals along a horny or calcareous substance, that sometimes encrusts sea-weed, or spreads out as a flat leaf-like membrane, or rises into cup-shaped or dendritic forms. A series of cells constituting a separate and independent colony, is termed a polypidom. The cells are further connected together by an external jelly-like integument, in which they are sunk, and which serves to secrete the calcareous particles from the sea.

It is interesting to know that creatures so minute and yet so complexly organized, existed abundantly in the seas of the Carboniferous period. No less than fifty-four species are enumerated as having been obtained from the carboniferous strata of the British Islands, and scarcely a year passes without one or two new species being added to the list. The most frequent belong to the genusFenestella, or little window, a name indicative of the reticulated grouping of the branches like the wooden framework of a window. Each of these branches, or interstices, as they are called, was more or less straight, being connected with that on either side by a row of transverse bars, just as the central mullion of an abbey window is connected with the flanking ones by means of cross-bars of stone. Not unfrequently some of the branches subdivide into two, as we saw to be the case among the cup-corals.

Fig. 18.—a, Fenestella oculata (M'Coy), nat. size;b, magnified portion of the same.

Fig. 18illustrates the relative disposition of these branches. Ina, the natural size of the fossil is given;bis a portion of the same magnified, to show the form and arrangement of the ribs and cross-bars. Each rib is seen to have two sides separated by a rounded ridge. Along each side there runs a row of circular hollows or cells, every one of which once formed the abode of a distinct bryozoon. The back or inner surface of the branch, was ribbed and granulated irregularly, without any cells. The connecting bars or dissepiments have no cells, and served merely to bind the interstices together into one firm organically-united polypidom. Such fragments as that here figured are the most usual traces to be found of these animals among the carboniferous rocks. But perfect specimens are sometimes met with which show how delicate and graceful a structure the polypidom of some of the fenestellæ must have been. All these bars sprung from a common point as their basis, and rose up in the form of a cup. It was, in short, a cup of network, hung with waving tentacles and quivering cilia. I have seen some dissections of flowers in which all the softer tissue had been removed, so as to present only the harder veinings of the leaves with their thousand ramifications bleached to a delicate whiteness. Out of theseskeleton-leaves there were formed groups of lilies, crocuses, geraniums, and roses, like patterns of the finest gauze. Some of the larger-stemmed leaves that had been artistically moulded into a tulip form, seemed not inaptly to represent the general contour of the skeleton of the old carboniferous fenestella.

An allied form is called theRetepora. It differed from the previous organism in having the ribs not straight, but irregularly anastomosing, that is, running into and coalescing with each other, so as to form a close network with oval interspaces, like a piece of very minute wire-fence. Each of these wavy libs was completely covered over on one side with oval pores or cells, which, as in the fenestella, formed the abode of the living animals. The differences in organization between the animal of fenestella and that of retepora can, of course, only be matter of speculation. The general structure in both must, however, have been pretty much alike. The former genus is now no longer extant, but the latter, which was ushered into the world during the era of the Old Red Sandstone, still lives in the deeper recesses of the ocean, and manifests in its structure and habits the leading characteristics of bryozoan life.

What rambler among old lime-quarries is not familiar with the stone-lily, so abundant an organism in most of the Palæozoic and many of the Secondary limestones? In some beds of the carboniferous limestone its abundance is almost incredible. I have seen a weathered cliff in which its remains stood out in bold relief, crowded together, to use an expression of Dr. Buckland's, "as thickly as straws in a corn-rick." The joints of this animal, known now asentrochior wheel-stones, forced themselves on the notice of men during even the middle ages, and an explanation was soon found for their existence. From their occurring largely about the coast at Holy Island, they were set down as the workmanship of Saint Cuthbert.

"On a rock by Lindisfarne,St. Cuthbert sits and toils to frameThe sea-born beads which bear his name."

"On a rock by Lindisfarne,

St. Cuthbert sits and toils to frame

The sea-born beads which bear his name."

The aged saint was represented as employing his nights in this highly intellectual task, sitting on a lone rock out in the sea, and using an adjacent one as his anvil.

"Such tales had Whitby's fishers told,And said they might his shape behold,And hear his anvil sound,A deaden'd clang,—a huge dim formSeen but, and heard, when gathering stormAnd night were closing round."

"Such tales had Whitby's fishers told,

And said they might his shape behold,

And hear his anvil sound,

A deaden'd clang,—a huge dim form

Seen but, and heard, when gathering storm

And night were closing round."

But these wheel-stones were not the only geological curiosities to which this simple mode of explanation was applied. In the same storied neighbourhood there occur in considerable numbers the round whorled shells of the genusAmmonites. These were gravely set down as petrified snakes wanting the head, and their petrifaction and decapitation were alike reverently ascribed to the power of the sainted abbess of Whitby.

"They toldHow of a thousand snakes each oneWas changed into a coil of stoneWhen holy Hilda prayed."

"They told

How of a thousand snakes each one

Was changed into a coil of stone

When holy Hilda prayed."

The stone-lily belonged to that large class of animals ranked together asEchinodermata, a name taken from one of the leading subdivisions of the group—theEchinior sea-urchins. It seems to have been one of the earliest forms of life upon our planet, its disjointed stalks occurring largely in some of the oldest Silurian limestones. In the Secondary ages it began gradually to wane, until at the present day its numerous genera appear to be represented by but thecomatulaand thepentacrinite, two tiny forms that float their jointed arms in the profounder depths of the sea.

Fig. 19.—a, Cyathocrinites planus.b, Encrinal stem, with uniform joints.c, Single joint, or wheelstone.

As its name imports, the stone-lily or encrinite had a plant-like form. It consisted of a long stalkfixed by the lower end to the sea-bottom, and supporting above a lily-shaped cup, in which were placed the mouth and stomach (Fig. 19a). The stalk consisted of circular plates (some of them not so thick as a sixpence), having their flat sides covered with a set of minute ribs radiating from the centre, and so arranged that the prominent lines of one joint fitted into corresponding depressed lines of the adhering ones. The centre of each joint was pierced by a small aperture, like the axle of a wheel, which, when the stem was entire, formed part of the long tube or canal that traversed the centre of the stem, and served to convey aliment to the remotest part of the animal. Detached joints have thus a wheel-like appearance (Fig 19c), and hence their common name of wheel-stones. In many species they were not all of the same diameter, but alternately larger and smaller, as if the stem had been made up of a tall pile of sixpences and threepenny pieces in alternate succession. This variation gives a remarkably elegant contour to the stalk. The flower-shaped cup consisted of a cavity formed of geometric calcareous plates, and fringed along its upper margin with thick calcareous arms, five or ten in number, that subdivided into still more slender branches, which were fringed along their inner side with minutecirrior feelers. All these subdivisions, however fine, were made up of calcareous joints like the stalk, so that every stone-lily consisted of many thousand pieces, each perfect in its organization and delicate in its sculpturing. One species peculiar to the Liassic formation (Extracrinus Briareus) has been calculated to contain one hundred and fifty thousand joints!

The effect of this minute subdivision was to impart the most perfect flexibility to even the smallest pinnule. The flower could instantly collapse, and thus the animals on which the encrinite preyed were seized and hurried to the central mouth. The lower part of the cup, orpelvis, as it is called, contained the stomach and other viscera, and communicated with themost distant part of the body by the central alimentary canal.

But while this continued the general type on which the encrinites were constructed, it received many minor modifications. These were effected chiefly on the form and arrangement of the cup-shaped body and its appendages, and form now the basis of our classification into genera and species. Thus, in the genus known asPlatycrinus, the lower part of the cup consists of two rows of large hexagonal or polygonal plates fitting closely into each other, while the upper part rises into a dome-like elevation formed of smaller polygonal plates, which have often a mammillated exterior. The arms sprang from the widest part of the body where the large pieces of the lower cup were succeeded by the small pieces of the upper. In an Irish species (P. triacontadactylus), the arms subdivided into thirty branches, each fringed with minuter pinnules and folding round the central elevated spire, as the petals of a crocus close round its central pistil. In another encrinite (Poteriocrinites conicus), the cup was shaped like an inverted cone, the point being affixed to the summit of the stalk, and the broad part throwing out from its edges the lateral arms. TheWoodocrinus macrodactylushad such gigantic arms as well-nigh to conceal the position of the cup, which relatively was very small in size. They sprang from near the base of the cup, five in number, but soon subdivided each into two, the ten arms thus produced being closely fringed with the usual jointed calcareous pinnules.

The size and arrangement of the joints of the stalk also differed in different genera. The Woodocrinus and many others had them alternately broad and narrow, like a string of buttons of unequal sizes; others had all the joints of the same relative diameter (Fig. 19b), so that the stalk tapered by a uniform line from base to point. I may add, that on some specimens of both these kinds of stems, we can notice small, solitaryareolæ, or scars, which may mark the points of attachment of cirri, or littletentacles, like those on the stem of the existing Pentacrinite. But though each of these varieties of stem is peculiar to a certain number of genera, there is often so little distinction among the detached fragments, that it becomes difficult, indeed impossible, to assign each to its appropriate individual. We may say, that certain encrinal stalks could not have belonged to a poteriocrinus, and others could never have fitted on to the cup of an actinocrinus; but we cannot often say positively to what species they actually would have fitted. There can, however, be no doubt about their being encrinites, and so we have in them a safe and evident test for the origin of the rock in which their remains occur. But to this I shall afterwards revert.

In the meantime, I would have the reader to fix the stone-lily in his memory as peculiarly and emphatically a marine animal, dwelling probably in the deeper and stiller recesses of the ocean, like the Pentacrinite of existing times. Let him try to remember it, not in the broken and sorely mutilated state in which we find it among the blocks of our lime-quarries, but as it must have lived at the bottom of the carboniferous seas. The oozy floor of these old waters lay thickly covered with many a graceful production of the deep, submarine gardens of

"Violet, asphodel, ivy, and vine-leaves, roses and lilies,Coral and sea-fan, and tangle, the blooms and the palms of the ocean."

"Violet, asphodel, ivy, and vine-leaves, roses and lilies,

Coral and sea-fan, and tangle, the blooms and the palms of the ocean."

Amid this rich assemblage of animated forms, the stone-lilies must have occupied a conspicuous place. Grouped in thick-set though diminutive forests, these little creatures raised their waving stems, and spread out their tremulous arms, like beds of tulips swaying in the evening air. Their flower like cups, so delicately fringed, must have presented a scene of ceaseless activity as they opened and closed, coiling up while the animal seized its prey, or on the approach of danger, and relaxing again when the food had been secured, or when the symptoms of a coming enemy had passed away. Only from this animatedaction would one have been apt to conjecture these organisms to be other than vegetable. They lived, too, not in detached patches, like the tulip-beds of the florist, but, to judge from the abundance of their remains, must have covered acre after acre, and square mile 'after square mile, with a dense growth of living, quivering flowers. As one individual died out, another took its place, the decaying steins and flowers meanwhile falling to pieces among the limy sediment that lay thickly athwart the sea-bottom, and contributing, by their decay and entombment, to build up those enormous masses of rock, known as the mountain-limestone, which stretch through Yorkshire and the central counties into Wales.

In addition to the stone-lilies, the carboniferous rocks contain the remains of several other kinds ofEchinodermata. Some of them find their nearest modern analogues among the sea-urchins so common on our shores; but I pass on to notice another very interesting class of fossils known by the name ofCrustacea, and still abundantly represented, the crab and lobster being familiar examples.

The Crustacea, so called from the hard crust or shell which envelops them, form, with all their orders and genera, a very numerous family. They are of interest to us as containing among their number some of the oldest forms of life. Away down in the lower Silurian rocks, among the most ancient fossiliferous strata, we find the crustacean with its armour of plates and its prominent sessile eyes set round with lenses, still visible on the stone. Thus, on the first page of the stony records of our planet's history are these primeval organisms engraved. In some localities, where oxide of iron is largely present, they are coated with a bright yellow efflorescence, and stand out from the dull grey stone like figures embossed in gold.[31]On all the subsequent leaves of this ancient chronicle, we can detect the remains of crustacean life, and many tribes still swarm in our seas and lakes. It is interesting, however, as marking the onward progress of creation, to notice that, though this great family has continued to live during all the successive geological ages, its members have ever been changing, the older types waning and dying out, while newer genera rose to supply for a time their place, and then passed away before the advance of other and yet later forms. The trilobites that meet us on the very verge of creation, swarmed by millions in the seas of the Silurian ages, diminished gradually during the era of the Old Red Sandstone, and seem to have died out altogether in the times of the Coal. In no ocean of the present day is a trace of any of their many genera to be seen. Thedecapods, of which our common crab is a typical form, began to be after the trilobites had died out. In all the subsequent eras they gradually increased in numbers, and at the present day they form the most abundant order of crustacean life. The history of these two divisions, to adopt Agassiz's mode of representation, may be illustrated by two long tapering bands like two attenuated pyramids. The one has its broad base resting upon the existing now, and thinning away into the past, till at last it comes to a point. At a little interval the apex of the other begins, and gradually swells outward as it recedes, till the wide base terminates at the first beginnings of life.

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