THE OLDEST AIR-BREATHERS.

[117]Natural Science, May, 1892.

"It is quite certain that Stigmariæ are not 'rhizomes which floated in water, or spread themselves out on the surface of mud.' Whether rhizomes or not, they grew in the soil, or in the upper layers of peaty deposits since changed into coal. The late Richard Brown and the writer have shown that they grew in the underclays or fossil soils, and that their rootlets radiated in these soils in all directions.[118]In one of my papers I have figured a Stigmarian root penetrating through an erectSigillaria, and Logan, in his Report of 1845, had alreadyfigured a similar example. The penetration of decaying stems by the rootlets ofStigmariais a fact well known to all who have studied slices of Carboniferous plants,[119]whileStigmariæare often found creeping inside the bark of erect and prostrate trunks. Besides this, as I have shown in 'Acadian Geology,' in the section of 5,000 feet of coal measures at the South Joggins (including eighty-one distinct coal groups, and a larger number of soils withStigmaria, or erect trees),SigillariaandStigmariaoccur together, and the latter nearly always either in argillaceous soils, or sands hardened into 'Gannister,' which are often filled with roots or rootlets, or on the surfaces of coal beds. On the other hand, the numerous bituminous limestones, and calcareous and other shales holding remains of fishes, crustaceans, and bivalve shells do not contain Stigmariain situ—the only exceptions being two beds of bituminous limestone, the upper parts of which have been converted into underclays. This section, and that of North Sydney—two of the most complete and instructive in the world—have afforded conclusive proof of this mode of growth ofSigillariaandStigmaria.

[118]Quart. Journ. Geol. Soc., vol. ii. p. 394 (1846);Ibid., vol. iv. p. 47 (1847);Ibid., vol. v. p. 355 (1849);Ibid., vol. v. pp. 23, 30.[119]Williamson has noticed this in his excellent Memoirs in thePhil. Trans.

[118]Quart. Journ. Geol. Soc., vol. ii. p. 394 (1846);Ibid., vol. iv. p. 47 (1847);Ibid., vol. v. p. 355 (1849);Ibid., vol. v. pp. 23, 30.

[119]Williamson has noticed this in his excellent Memoirs in thePhil. Trans.

"The objection to calling the Stigmariæ roots and their processes rootlets, appears to me a finical application of modern botanical usages to times for which they do not hold. We might equally object to the application of the term roots to those which spring from the earthed-up stems of Calamites, radiating as they do from nodes which, in the air, would produce branchlets. Grand' Eury's figures show abundant instances of this. We might also object to the exogenous stems described by Williamson, which belong to cryptogamous plants; and, unlike anything modern, are made up exclusively of scalariform tissue. If the articulation and regular arrangement of those gigantic root hairs, the rootlets, or 'leaves' ofStigmaria, are to be regarded as depriving them of the name which clearly describes their function, we may call them underground branches, though, by so doing, we set at nought both their function and their mode of growth."

Dr. Williamson, in a recent paper, expresses the same view in the following terms[120]:—"At that period (the Carboniferous age) no Angiosperms existed on the earth, and even the Gymnosperms were very far from reaching their modern development. Under these circumstances the Cryptogams chiefly became the giant forest trees of that remote age. To become such, they required an organization very different in some respects from that of their degraded living representatives. Hence we must not appeal to these degenerate types for illustrations and explanations of structures no longer existing. Still less must we turn to what we find in the Angiosperms, that wholly distinct race which has taken the place of the primæval Cryptogams in our woods. The primeval giants of the swampy forests had doubtless a morphology assigned to them, adapted to the physical conditions by which they were surrounded; but if even their dwarfed and otherwise modified descendants fail to throw light upon morphological details once so common, still less must we expect to obtain that light from the living and wholly different flowering plants."

[120]Natural Science, July, 1892.

With the remarkable trees above referred to, there coëxisted a vast multitude of ferns, some arborescent, others herbaceous, tall, reed-like plants, the Calamites, allied to modern Mare's-tails, a very remarkable family of plants allied to modern Cycads and Pines; the Cordaites, which seem to have grown plentifully in certain parts of the coal areas—probably the drier parts, so that their remains sometimes constitute the greater part of small seams of coal. There were also true pine-like trees, though these would seem to have grown most abundantlyon the higher levels. Nor was strictly aquatic vegetation wanting. We find, both in the preceding Devonian and the Carboniferous, that the little aquatic plants now known as Rhizocarps, and structurally allied to the Ferns—such plants as the floating Salvinia, and the Pillworts of our swamps, were vastly abundant, and they may have filled and choked up with their exuberant growth many of the lakes and slow streams of the period, furnishing layers of cannel and "macrospore" coal, and earthly bitumen or Torbanite.

We have hitherto confined our attention to the great Carboniferous period, so called, as emphatically the age of coal; but this mineral, and allied forms of carbon, were produced both before and after. Even in that old Laurentian age, which includes the oldest rocks that we know, formed when the first land had just risen out of the waters, there are thick beds of graphite, or plumbago, chemically the same with anthracite coal, and which must have been produced by the agency of plants, whether terrestrial or aquatic. We may suppose that the plants of this remote age were of very humble type as much lower than those of the coal formation as these are lower than those of the present day; but if so, then, on the analogy of the Carboniferous, they would be high and complex representatives of those low types. But there is another and more startling possibility; that the Laurentian may have been a period when vegetable life culminated on the earth, and existed in its most complete and grandest forms in advance of the time when it was brought into subordination to the higher life of the animal. In the meantime, the Laurentian rocks are in a state of so extreme metamorphism that they have afforded no certain indication of the forms or structures of the vegetation of the period.

We find indications of plant life through all the Palæozoic groups succeeding the Laurentian; but it is not till we reach the Devonian, the system immediately preceding the Carboniferous,that we find an abundance of forms not essentially different from those of the Carboniferous, though similar in details. Only a few and very small beds of coal were accumulated in this age; but there was an immense abundance of bituminous shale enriched with the macrospores of Rhizocarps. The Ohio black shale, which is said to extend its outcrop across that state with a breadth of ten to twenty miles, and a thickness of 550 feet, is filled with macrospores of Protosalvinia, as is its continuation in Canada.

Above the great coal formation the Permian and Jurassic contain beds of coal, though of limited extent, and formed in the case of the two latter of very different plants from those of the Carboniferous. In the Cretaceous and Tertiary ages, after the abundant introduction of species of forest trees still living, coal making seems to have obtained a new impulse, so that in China and the western part of America there are coals of great extent and value, all made of plants of genera still existing. In the Cretaceous coal of Vancouver Island there are remains of such modern trees as the Poplars, Magnolias, Palmettos, Sequoias, and a great variety of other genera still living in America. Out of the remains of these, under favouring conditions, quite as good coal as that of the coal formation has been made, although the plants are so different. There is, indeed, reason to believe that those now rare trees, the Sequoias, represented at the present time only by the big trees of California, and their companion, the redwood, were then spread universally over the northern hemisphere, and formed dense forests on swampy flats which led to the accumulation of coal beds in which the trunks and leaves of the Sequoias formed main ingredients, so that Sequoia and its allies in this later age take the place of the Sigillariæ of the coal formation. Last of all, coal accumulation is still going on in the Everglades of Florida, the dismal swamp of Virginia, and the peat-bogs of the more northern regions. So the vegetable kingdomhas, throughout its long history, been continually depriving the atmosphere of its carbon dioxide, and accumulating this in beds of coal. In the earlier ages indeed, this would seem to us to have been its main use.

To the modern naturalist, vegetable life, with regard to its uses, is the great accumulator of pabulum for the sustenance of the higher forms of vital energy manifested in the animal. In the Palæozoic this consideration sinks in importance. In the Coal period we know few land animals, and these not vegetable feeders, with the exception of some insects, millipedes, and snails. But the Carboniferous forests did not live in vain, if their only use was to store up the light and heat of those old summers in the form of coal, and to remove the excess of carbonic acid from the atmosphere. In the Devonian period even these utilities fail, for coal does not seem to have been accumulated to any great extent, though the abundant petroleum of the Devonian is, no doubt, due to the agency of aquatic vegetation. In addition to scorpions, a few insects are the only known tenants of the Devonian land, and these are of kinds whose lame probably lived in water, and were not dependent on land plants. We may have much yet to learn of the animal life of the Devonian; but for the present, the great plan of vegetable nature goes beyond our measures of utility; and there remains only what is perhaps the most wonderful and suggestive correlation of all, namely, that our minds are able to trace in these perished organisms structures similar to those of modern plants, and thus to reproduce in imagination the forms and habits of growth of living things which so long preceded us on the earth.

In another way Huxley has put the utilitarian aspect of the case so admirably, that I cannot refrain from quoting his clever apotheosis of nature in connection with the production of coal.

"Nature is never in a hurry, and seems to have had always before her eyes the adage, 'Keep a thing long enough, andyou will find a use for it.' She has kept her beds of coal for millions of years without being able to find a use for them; she has sent them beneath the sea, and the sea beasts could make nothing of them; she had raised them up into dry land, and laid the black veins bare, and still for ages and ages there was no living thing on the face of the earth that could see any sort of value in them; and it was only the other day, so to speak, that she turned a new creature out of her workshop, who, by degrees, acquired sufficient wits to make a fire, and then to discover that the black rock would burn.

"I suppose that nineteen hundred years ago, when Julius Cæsar was good enough to deal with Britain as we have dealt with New Zealand, the primæval Briton, blue with cold and woad, may have known that the strange black stone which he found here and there in his wanderings would burn, and so help to warm his body and cook his food. Saxon, Dane, and Norman swarmed into the land. The English people grew into a powerful nation; and Nature still waited for a return for the capital she had invested in ancient club mosses. The eighteenth century arrived, and with it James Watt. The brain of that man was the spore out of which was developed the steam engine, and all the prodigious trees and branches of modern industry which have grown out of this. But coal is as much an essential of this growth and development as carbonic acid is of a club moss. Wanting the coal, we could not have smelted the iron needed to make our engines; nor have worked our engines when we got them. But take away the engines, and the great towns of Yorkshire and Lancashire vanish like a dream. Manufactures give place to agriculture and pasture, and not ten men could live where now ten thousand are amply supported.

"Thus all this abundant wealth of money and of vivid life is Nature's investment in club mosses and the like so long ago. But what becomes of the coal which is burnt in yieldingthe interest? Heat comes out of it, light comes out of it, and if we could gather together all that goes up the chimney, and all that remains in the grate of a thoroughly burnt coal fire, we should find ourselves in possession of a quantity of carbonic acid, water, ammonia, and mineral matters exactly equal in weight to the coal. But these are the very matters with which Nature supplied the club mosses which made coal. She is paid back principal and interest at the same time; and she straightway invests the carbonic acid, the water, and the ammonia in new forms of life, feeding with them the plants that now live. Thrifty Nature, surely! no prodigal, but the most notable of housekeepers."[121]

[121]Contemporary Review, 1871.

All this is true and well told; but who is "Nature," this goddess who, since the far-distant Carboniferous age, has been planning for man? Is this not another name for that Almighty Maker who foresaw and arranged all things for His people "before the foundation of the world."

References:—On Structures in Coal,Journal Geological Society of London, xv., 1853. Contains results of microscopic study of Nova Scotia coals. Conditions of Accumulation of Coal,Ibid., xxii., 1866. Contains South Joggins section. Spore-cases in Coal,Am. Journal of Science, 3rd series, vol. I, 1871. Rhizocarps in the Devonian,Bulletin Chicago Academy, vol. I, 1886. "Acadian Geology and Supplement," 3rd edition, 1891, Cumberland Coal Field. "Geological History of Plants," chap, iv., London and New York, 2nd edition, 1892.

DEDICATED TO THE MEMORY OFMY FRIEND AND EARLY PATRON AND GUIDESIR CHARLES LYELL,To whom we are Indebted for so muchof the Scientific Basis of Modern Geology.

Earliest Discoveries—Footprints of Batrachians—Labyrinthodents of the Carboniferous—Microsauria of the Carboniferous—Other Types—Discoveries in Erect Trees—Invertebrate Air-breathers, Land Snails, Millipedes, Insects, Spiders And Scorpions—General Conclusions

Remains of Hylonomus Lyelli, Dawson, 1859.Coal Measures, South Joggins; Nova Scotia.Photograph of Type specimen somewhat enlarged,Geol. Magazine, 1891 (p. 279).(1) Cranial bones and mandibles; (1a) Sternal and shoulder bones; (2) Mandible;(3) Humerus, ribs and vertebræ; (4) Hind limb; (5) Pelvis; (6) Caudal vertebræ.Click on image to view larger sized.

THE OLDEST AIR-BREATHERS.

Animal life had its beginning in the waters, and to this day the waters are the chief habitat of animals, especially of the lower forms. If we divide the animal kingdom into great leading types, the lowest of these groups, the Protozoa, includes only aquatic forms; the next, that of the coral animals and their allies, is also aquatic. So are all the species of the Sea Urchins and Star Fishes. Of the remaining groups, the Mollusks, the Crustaceans, and the Worms are dominantly aquatic, only a small proportion being air-breathers. It is only in the two remaining groups, including the Insects and Spiders on the one hand, and the Vertebrate animals on the other, that we have terrestrial species in large proportion.

The same fact appears in geological time. The periods represented by the older Palæozoic rocks have been termed ages of invertebrates, and they might also be termed ages of aquatic animals. It is only gradually, and as it were with difficulty, that animals living in the less congenial element of air are introduced—at first a few scorpions and insects, later, land snails and amphibian reptiles, later still, the higher reptiles and the birds, and last of all the higher mammalia.

We need not wonder at this, for the conditions of life with reference to support, locomotion, and vicissitudes of temperature are more complex and difficult in air, and require more complicated and perfect machinery for their maintenance. Thus it was that probably half of the whole history of ourearth had passed away before the land became the abode of any large number and variety of animals; while it was only about the same time that the development of the vegetable kingdom became so complete as to afford food and shelter for air-breathers.

It is also worthy of note that it is only in comparatively recent times that we have been able to discover the oldest air-breathing animals, and geologists long believed that the time when animals had existed on the land was even shorter than it had actually been. This arose in part from the infrequency and rarity of preservation of the remains of the earliest creatures of this kind, and perhaps partly from the fact that collectors were not looking for them.

That there was dry land, even in the Cambro-Silurian period, we know, and can even trace its former shores. In Canada our old Laurentian coast extends for more than a thousand miles, from Labrador to Lake Superior, marking the southern border of the nucleus of the American continent in the Cambrian and Cambro-Silurian periods. Along a great part of this ancient coast we have the sand flats of the Potsdam Sandstone, affording very favourable conditions for the imbedding of land animals, did these exist; still, notwithstanding the zealous explorations of the Geological Survey, and of many amateurs, no trace of an air-breather has been found. I have myself followed the oldest Palæozoic beds up to their ancient limits in some localities, and collected the shells which the waves had dashed on the beach, and have seen under the Cambro-Silurian beds the old pre-Cambrian rocks pitted and indented with weather marks, showing that this shore was then gradually subsiding; yet the record of the rocks was totally silent as to the animals that may have trod the shore, or the trees that may have waved over it. All that can be said is that the sun shone, the rain fell, and the wind blew as it does now, and that the sea abounded in living creatures. The eyesof Trilobites, the weathered Laurentian rocks, the wind ripples in the Potsdam sandstone, the rich fossils of the limestones, testify to these things. The existence of such conditions would lead us to hope that land animals may yet be found in these older formations. On the other hand, the gradual failure of one form of life after another, as we descend in the geological series, and the rarity of fishes and land plants in the Silurian rocks and their absence from the Cambrian, might induce us to believe that we have here reached the beginning of animal life, and have left far behind us those forms that inhabit the land.

Even in the Carboniferous period, though land plants abound, air-breathers are not numerous, and most of them have only been recently recognised. We know, however, with certainty that the dark and luxuriant forests of the coal period were not destitute of animal life. Reptiles[122]crept under their shade, land snails and millipedes fed on the rank leaves and decaying vegetable matter, and insects flitted through the air of the sunnier spots. Great interest attaches to these creatures; perhaps the first-born species in some of their respective types, and certainly belonging to one of the oldest land faunas, and presenting prototypes of future forms equally interesting to the geologist and the zoologist.

[122]I shall use the term reptile here in its broad, popular sense, as including Batrachians as well as reptiles proper.

It has happened to the writer of these pages to have had some share in the finding of several of these ancient animals. The coal formation of Nova Scotia, so full in its development, so rich in fossil remains, and so well exposed in coast cliffs, has afforded admirable opportunities for such discoveries, which have been so far improved that at least twenty-five out of the not very large number of known Carboniferous land animals have been obtained from it.[123]The descriptions ofthese creatures, found at various times and at various places, are scattered through papers ranging in date from 1844 to 1891,[124]and are too fragmentary to give complete information respecting the structures of the animals, and their conditions of existence.

[123]It appears that about a hundred species of Carboniferous reptiles have been recognised on the continent of Europe, in Great Britain, and in the United States. They belong to a number of distinct types, all, however, being of batrachian affinities.

[124]Papers by Lyell, Owen, and the author, in theJournal of the Geological Society of London, i. ii. ix. x. xi. xvi. xvii. xviii.; "Acadian Geology," by the author; Papers inTrans. Royal Society of London,Am. Jl. of Science, andGeological Magazine.

Footprints.

It has often happened to geologists, as to other explorers of new regions, that footprints on the sand have guided them to the inhabitants of unknown lands, and such footprints, proverbially perishable, may be so preserved by being filled up with matter deposited in them as to endure for ever. This we may see to-day in the tracks of sandpipers and marks of rain-drops preserved in the layers of alluvial mud deposited by the tides of the Bay of Fundy, and which, if baked or hardened by pressure, might become imperishable, like the inscriptions of the old Chaldeans on their tablets of baked clay. The first trace ever observed of reptiles in the Carboniferous system consisted of a series of small but well-marked footprints found by Sir W. E. Logan, in 1841, in the lower coal measures of Horton Bluff, in Nova Scotia; and as the authors of most of our general works on geology have hitherto, in so far as I am aware, failed to do justice to this discovery, I shall notice it here in detail. In the year above mentioned, Sir William, then Mr. Logan, examined the coal fields of Pennsylvania and Nova Scotia, with the view of studying their structure, and extending the application of the discoveries as to beds with roots, or Stigmaria underclays, which he had made in the Welsh coal fields. On his return to England he read a paper on these subjects before the Geological Society of London, in which he noticed the subject of reptilian footprints at Horton Bluff. The specimen was exhibited at the meeting of the Society, and was, I believe, admitted, on the high authority of Prof. Owen, to be probably reptilian. Unfortunately Sir William's paper appeared only in abstract in the Transactions; and in this abstract, though the footprints are mentioned, no opinion is expressed as to their nature. Sir William's own opinion is thus stated in a letter to me, dated June, 1843, when he was on his way to Canada, to commence the survey which has since developed so astonishing a mass of geological facts.

Footprints ofHylopus Logani, Dawson, Lower Carboniferous, Nova Scotia.Natural size and reduced.These footprints were the first indications of Carboniferous land vertebrates ever observed; they were probably made by a Microsaurian and one of the earliest species of this type. They show a remarkable length of stride and development of limb.

Footprints ofHylopus Logani, Dawson, Lower Carboniferous, Nova Scotia.Natural size and reduced.

These footprints were the first indications of Carboniferous land vertebrates ever observed; they were probably made by a Microsaurian and one of the earliest species of this type. They show a remarkable length of stride and development of limb.

"Among the specimens which I carried from Horton Bluff, one is of very high interest. It exhibits the footprints of some reptilian animal. Owen has no doubt of the marks being genuine footprints. The rocks of Horton Bluff are below the gypsum of that neighbourhood; so that the specimen in question (if Lyell's views are correct[125]) comes from the very bottom of the coal series, or at any rate very low down in it, and demonstrates the existence of reptiles at an earlier epoch than has hitherto been determined; none having been previously found below the magnesian limestone, or, to give it Murchison's new name, the 'Permian era.'"

[125]Sir Charles Lyell had then just read a paper announcing his discovery that the gypsiferous system of Nova Scotia is Lower Carboniferous, in which he mentions the footprints referred to, as being reptilian.

This extract is of interest, not merely as an item of evidence in relation to the matter now in hand, but as a mark in the progress of geological investigation. For the reasons above stated, the important discovery thus made in 1841, and published in 1842, was overlooked; and the discovery of reptilian bones by Von Dechen, at Saarbruck, in 1844, and that of footprints by Dr. King in the same year, in Pennsylvania,have been uniformly referred to as the first observations of this kind. Insects and Arachnidans, it may be observed, had previously been discovered in the coal formation in Europe.

The original specimen of these footprints is still in the collection of the Geological Survey of Canada, and a cast which Logan kindly presented to me is exhibited in the Peter Redpath Museum of McGill University. It is a slab of dark-coloured sandstone, glazed with fine clay on the surface; and having a series of seven footprints in two rows, distant about three inches; the distance of the impressions in each row being three or four inches, and the individual impressions about one inch in length. They seem to have been made by the points of the toes, which must have been armed with strong and apparently blunt claws, and appear as if either the surface had been somewhat firm, or the body of the animal had been partly water-borne. In one place only is there a distinct mark of the whole foot, as if the animal had exerted an unusual pressure in turning or stopping suddenly. One pair of feet—the fore feet, I presume—appear to have had four toes touching the ground; the other pair show only three or four, and it is to be observed that the outer toe, as in the larger footprints discovered by Dr. King, projects in the manner of a thumb, as in the cheirotherian tracks of the Trias. At a later date another series of footprints, possibly of the same animal, was obtained at the same place by Prof. Elder, and is now in the Peter Redpath Museum. Each foot in this shows five toes, and it is remarkable that the animal was digitigrade and took a long step for its size, indicating a somewhat high grade of quadrupedal organization. No mark of the tail or belly appears. The impressions are such as may have been made by animals similar to some of those to be described in the sequel.

Shortly afterward, Dr. Harding, of Windsor, when examining a cargo of sandstone which had been landed at that place fromParrsboro', found on one of the slabs a very distinct series of footprints, each with four toes, and a trace of the fifth. Dr. Harding's specimen is now in the museum of King's College, Windsor. Its impressions are more distinct, but not very different otherwise from those above described, as found at Horton Bluff. The rocks at that place are probably of nearly the same age with those of Parrsboro'. I afterward examined the place from which this slab had been quarried, and satisfied myself that the beds are Carboniferous, and probably Lower Carboniferous. They were ripple-marked and sun-cracked, and I thought I could detect some footprints, though more obscure than those in Dr. Harding's slab. Similar footprints are also stated to have been found by Dr. Gesner, at Parrsboro'. All of these were from the lowest beds of the Carboniferous system.

I have since observed several instances of such impressions at the Joggins, at Horton, and near Windsor, showing that they are by no means rare, and that reptilian animals existed in no inconsiderable numbers throughout the coal field of Nova Scotia, and from the beginning to the end of the Carboniferous period. Most of these, when well preserved, shew five toes both on the anterior and posterior limb. On comparing these earlier Carboniferous footprints with one another, it will be observed that they are of similar general character, and may have been made by one kind of animal, which must have had the fore and hind feet nearly of equal size, and a digitigrade mode of walking. Footprints of similar form are found in the coal formation, as well as others of much larger size. The latter are of two kinds. One of these shows short hind feet of digitigrade character and a long stride, in this resembling the smaller footprints of the Lower Carboniferous, which are remarkable for the length of limb which they indicate by the distance between the footprints. The other kind shows long hind feet, as if the whole heel were brought down to theground in a plantigrade manner. These have also the outer toe separated from the others, and sometimes provided with a long claw. The fore foot is sometimes smaller than the hind foot, and differently formed.[126]In these respects they resemble the great Labyrinthodont Batrachians of the subsequent Trias. Their stride also is comparatively short, and the rows of impressions wide apart, as if the body of the animal had been broad, and its limbs short.

[126]Fine slabs of these footprints have been presented by Mr. Sandford Fleming to the Geological Survey of Canada.

We have thus two types of quadrupedal footprints, to the first of which I have given the name Hylopus, and have restricted the term Sauropus,[127]to the second. The first apparently belongs to the usually small reptiles of the groupMicrosauria, which had a well-marked lizard-like form, with well-developed limbs, and perhaps also to some of the smaller Labyrinthodonts, the second to the group ofLabyrinthodontia, which were often of large size and with stout and short limbs and plantigrade hind feet. There are also some small and uncertain tracks, which may have been made by newt-like animals with short feet, and a singular trail of large size, and with a row of impressions at each side (Diplichnites),[128]which, if made by a vertebrate animal, would seem to indicate that serpentiform shape which we know belonged to some Carboniferous Batrachians.

[127]Given by King.[128]Impressions and Footprints of Animals,Am. Jour. Sci., 1873.

[127]Given by King.

[128]Impressions and Footprints of Animals,Am. Jour. Sci., 1873.

The bones of these animals, however, hitherto found in Nova Scotia, may all have belonged to the two groups first named, the Labyrinthodontia and Microsauria, and I shall proceed to give some examples of each of these.

In leaving the footprints, I may merely mention that the animals which produced them may, in certain circumstances, have left distinct impressions only of three or four toes,when they actually possessed five, while in other circumstances all may have left marks; and that, when wading in deep mud, their footprints were altogether different from those made on hard sand or clay. In some instances the impressions may have been made by animals wading or swimming in water, while in others the rain marks and sun cracks afford evidence that the surface was a subaërial one. They are chiefly interesting as indicating the wide diffusion and abundance of the creatures producing them, and that they haunted tidal flats and muddy shores, perhaps emerging from the water that they might bask in the sun, or possibly searching for food among the rejectamenta of the sea, or of lagunes and estuaries.

The Labyrinthodonts of the Coal Period, Baphetes Planiceps and Dendrerpeton Acadianum.

In the summer of 1851 I had occasion to spend a day at the Albion Mines in the eastern part of Nova Scotia, and on arriving at the railway station in the afternoon, found myself somewhat too early for the train. By way of improving the time thus left on my hands, I betook myself to the examination of a large pile of rubbish, consisting of shale and ironstone from one of the pits, and in which I had previously found scales and teeth of fishes. In the blocks of hard carbonaceous shale and earthy coal, of which the pile chiefly consisted, scales, teeth and coprolites often appeared on the weathered ends and surfaces as whitish spots. In looking for these, I observed one of much greater size than usual on the edge of a block, and on splitting it open, found a large flattened skull, about six inches broad, the cranial bones of which remained entire on one side of the mass, while the palate and teeth, in several fragments, came away with the other half. Carefully trimming the larger specimen, and gathering all the smaller fragments, I packed them up as safely as possible, andreturned from my little excursion much richer than I had hoped.

The specimen, on further examination, proved somewhat puzzling. I supposed it to be, most probably, the head of a large ganoid fish; but it seemed different from anything of this kind with which I could compare it; and at a distance from comparative anatomists, and without sufficient means of determination, I dared not refer it to anything higher in the animal scale. Hoping for further light, I packed it up with some other specimens, and sent it to the Secretary of the Geological Society of London, with an explanatory note as to its geological position, and requesting that it might be submitted to some one versed in such fossils. For a year or two, however, it remained as quietly in the Society's collection as if in its original bed in the coal mine, until attention having been attracted to such remains by the discoveries made by Sir Charles Lyell and myself in 1852, at the South Joggins, and published in 1853,[129]the Secretary or President of the Society re-discovered the specimen, and handed it to Sir Richard Owen, by whom it was described in December, 1853,[130]under the name ofBaphetes planiceps, which may be interpreted the "flat-headed diving animal," in allusion to the flatness of the creature's skull, and the possibility that it may have been in the habit of diving.

[129]Journal of Geological Society of London, vol. ix.[130]Journal of Geological Society, vol. x.; and additional notes, vol. xi.

[129]Journal of Geological Society of London, vol. ix.

[130]Journal of Geological Society, vol. x.; and additional notes, vol. xi.

The parts preserved in my specimen are the bones of the anterior and upper part of the skull in one fragment, and the teeth and palatal bones in others. These parts were carefully examined and described by Owen, and the details will be found in his papers referred to in the note. We may merely observe here that the form and arrangement of the bones showed batrachian affinities, that the surface of the cranium was sculptured in the manner of the group ofLabyrinthodonts, and that the teeth possessed the peculiar and complicated plication of the ivory and enamel seen in creatures of this type. The whole of these characters are regarded as allying the animal with the great crocodilian frogs of the Trias of Europe, first known asCheirotherians, owing to the remarkable hand-like impressions of their feet, and afterwards asLabyrinthodonts, from the beautifully complicated convolutions of the ivory of their teeth.

Unfortunately the original specimen exhibited only the head, and after much and frequent subsequent searching, the only other bones found are a scapula, or shoulder bone, and one of the surface scales which served for protection, and which indicate at least that the creature possessed walking limbs and was armed with bony scales sculptured in the same manner with the skull bones.

Of the general form and dimensions ofBaphetes, the facts at present known do not enable us to say much. Its formidable teeth and strong maxillary bones show that it must have devoured animals of considerable size, probably the fishes whose remains are found with it, or the smaller reptiles of the coal. It must, in short, have been crocodilian, rather than frog-like, in its mode of life; but whether, like the Labyrinthodonts, it had strong limbs and a short body, or like the crocodiles, an elongated form and a powerful natatory tail, the remains do not decide. One of the limbs or a vertebra of the tail would settle this question, but neither has as yet been found. That there were large animals of the labyrinthodontal form in the coal period is proved by the footprints discovered by Dr. King in Pennsylvania, which may have been produced by an animal of the type ofBaphetes, as well as by those ofSauropus unguiferfrom the Carboniferous of Nova Scotia, and which would very well suit an animal of this size and probable form. On the other hand, that there were large swimming reptiles seems establishedby the discovery of the vertebræ ofEosaurus Acadianus, at the Joggins, by Marsh.[131]The locomotion ofBaphetesmust have been vigorous and rapid, but it may have been effected both on land and in water, and either by feet or tail, or both. A jawbone found at the Joggins in Nova Scotia, and to which I have attached the nameBaphetes minor, may have belonged to a second species. Great Batrachians allied to Baphetes, but different specifically or generically, have since been found in the coal formations of Great Britain, the continent of Europe and the United States.

[131]Silliman's Journal, 1859.

With the nature of the habitat of this formidable creature we are better acquainted. The area of the Albion Mines coal field was somewhat exceptional in its character. It seems to have been a bay or indentation in the Silurian land, separated from the remainder of the coal field by a high shingle beach, now a bed of conglomerate. Owing to this circumstance, while in the other portions of the Nova Scotia coal field the beds of coal are thin, and alternate with sandstones and shales, at the Albion Mines a vast thickness of almost unmixed vegetable matter has been deposited, constituting the "main seam" of thirty-eight feet thick, and the "deep seam," twenty-four feet thick, as well as still thicker beds of highly carbonaceous shale. But, though the area of the Albion coal measures was thus separated, and preserved from marine incursions, it must have been often submerged, and probably had connection with the sea, through rivers or channels cutting the enclosing beach. Hence beds of earthy matter occur in it, containing remains of large fishes. One of the most important of these is that known as the "Holing stone," a band of black highly carbonaceous shale, coaly matter, and clay ironstone, occurring in the main seam, about five feet below its roof, and varying in thickness from two inches to nearly two feet. It was from this band that the rubbish heap in which I found theskull ofBaphetes planicepswas derived. It is a laminated bed, sometimes hard and containing much ironstone, in other places soft and shaly, but always black and carbonaceous, and often with layers of coarse coal, though with few fossil plants retaining their forms. It contains large round flat scales and flattened curved teeth, which I attribute to a fish of the genusRhizodus, resembling, if not identical with,R. lancifer, Newberry. With these are double-pointed shark-like teeth, and long cylindrical spines of a species ofDiplodus, which I have namedD. acinaces.[132]There are also shells of the minuteSpirorbis, so common in the coal measures of other parts of Nova Scotia, and abundance of fragments of coprolitic matter, or fossil excrement, sometimes containing bones and scales of fishes.

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