Chapter 12

[132]"Supplement to Acadian Geology," pp. 43 and 50. These fishes are now known under the generic name Leptacanthus.

It is evident that the "Holing stone" indicates one of those periods in which the Albion coal area, or a large part of it, was under water, probably fresh or brackish, as there are no properly marine shells in this, or any of the other beds of this coal series. We may then imagine a large lake or lagune, loaded with trunks of trees and decaying vegetable matter, having in its shallow parts, and along its sides, dense brakes ofCalamites, and forests ofSigillaria,Lepidodendron, and other trees of the period, extending far on every side as damp pestilential swamps. In such a habitat, uninviting to us, but no doubt suited toBaphetes, that creature crawled through swamps and thickets, wallowed in flats of black mud, or swam and dived in search of its finny prey. It was, in so far as we know, the monarch of these swamps, though there is, as already stated, evidence of the existence of similar creatures of this type quite as large in other parts of the Nova Scotia coal field. We must now notice a smaller animal belonging to the same family of Labyrinthodonts.

The geology of Nova Scotia is largely indebted to the world-embracing labours of Sir Charles Lyell. Though much had previously been done by others, his personal explorations in 1842, and his paper on the gypsiferous formation, published in the following year, first gave form and shape to some of the more difficult features of the geology of the country, and brought it into relation with that of other parts of the world. In geological investigation, as in many other things, patient plodding may accumulate large stores of fact, but the magic wand of genius is required to bring out the true value and significance of these stores of knowledge. It is scarcely too much to say that the exploration of a few weeks, and subsequent study of the subject by Sir Charles, with the impulse and guidance given to the labours of others, did as much for Nova Scotia as might have been effected by years of laborious work under less competent heads.

Sir Charles naturally continued to take an interest in the geology of Nova Scotia, and to entertain a desire to explore more fully some of those magnificent coast sections which he had but hastily examined; and when, in 1851, he had occasion to revisit the United States, he made an appointment with the writer of these pages to spend a few days in renewed explorations of the cliffs of the South Joggins. The object specially in view was the thorough examination of the beds of the true coal measures, with reference to their contained fossils, and the conditions of accumulation of the coal; and the results were given to the world in a joint paper on "The remains of a reptile and a land shell discovered in the interior of an erect tree in the coal measures of Nova Scotia," and in the writer's paper on the "Coal Measures of the South Joggins";[133]while other important investigations grew out of the following up of these researches, and much matter inrelation to the vegetable fossils still remains to be worked up. It is with the more striking fact of the discovery of the remains of a reptile in the coal measures that we have now to do.

[133]Journal of the Geological Society of London, vols. ix. and x.; and "Acadian Geology."

The South Joggins Section is, among other things, remarkable for the number of beds which contain remains of erect trees imbeddedin situ: these trees are for the most part Sigillariæ, those great-ribbed pillar-like trees which seem to have been so characteristic of the forests of the coal formation flats and swamps, and so important contributors to the formation of coal. They vary in diameter from six inches to five feet. They have grown on underclays and wet soils, similar to those on which the coal was accumulated; and these having been submerged or buried by mud carried down by inundations, the trees, killed by the accumulations around their stems, have decayed, and their tops being broken off at the level of the mud or sand, the cylindrical cavities left open by the disappearance of the wood, and preserved in their form by the greater durability of the bark, have been filled with sand and clay. This, now hardened into stone, constitutes pillar-like casts of the trees, which may often be seen exposed in the cliffs, and which, as these waste away, fall upon the beach. The sandstones enveloping these pillared trunks of the ancient Sigillariæ of the coal, are laminated or bedded, and the laminæ, when exposed, split apart with the weather, so that the trees themselves become broken across; this being often aided by the arrangement of the matter within the trunks, in layers more or less corresponding to those without. Thus one of these fossil trees usually falls to the beach in a series of discs, somewhat resembling the grindstones which are extensively manufactured on the coast. The surfaces of these fragments often exhibit remains of plants which have been washed into the hollow trunks, and have been imbedded there; and in our explorations of the shore, we always carefully scrutinized such specimens, both with the view of observingwhether they retained the superficial markings of Sigillariæ, and with reference to the fossils contained in them. It was while examining a pile of these "fossil grindstones" that we were surprised by finding on one of them what seemed to be fragments of bone. On careful search other bones appeared, and they had the aspect, not of remains of fishes, of which many species are found fossil in these coal measures, but rather of limb bones of a quadruped. The fallen pieces of the tree were carefully broken up, and other bones disengaged, and at length a jaw with teeth made its appearance. We felt quite confident, from the first, that these bones were reptilian; and the whole, being carefully packed and labelled, were taken by Sir Charles to the United States, and submitted to Prof. J. Wyman of Cambridge; who recognised their reptilian character, and prepared descriptive notes of the principal bones, which appeared to have belonged to two species. He also observed among the fragments an object of different character, apparently a shell; which was recognised by Dr. Gould of Boston, and afterward by M. Deshayes, as probably a land-snail, and has since been namedPupa vetusta.

The specimens were subsequently taken to London and reexamined by Prof. Owen, who confirmed Wyman's inferences, added other characters to the description, and named the larger and better preserved speciesDendrerpeton Acadianum, in allusion to its discovery in the interior of a tree, and to its native country of Acadia or Nova Scotia. It is necessary to state in explanation of the fragmentary character of the remains obtained, that in the decay of the animals imbedded in the erect trees at the Joggins, their skeletons have become disarticulated, and the portions scattered, either by falling into the interstices of the vegetable fragments in the bottom of the hollow trunks, or by the water with which these may have sometimes been partly filled. We thus usually obtain only separate bones; and though all of these are no doubt present in each case, it is often impossible in breaking up the hard matrix to recover more than a portion of them. The original description by Owen was therefore based on somewhat imperfect material, but additional specimens subsequently found have supplemented it in such a manner as to enable us somewhat completely to restore in imagination the form of the animal, which, though much smaller thanBaphetes, agrees with it in its sculptured bones, in its bony armature, especially beneath, and in its plicated teeth.

Humerus and Mandibles of Dendrerpeton Acadianum. Natural size, with one of the teeth enlarged. (From a Photograph.)The specimen illustrates the sculptured bones of Dendrerpeton and its plaited teeth, as well as large size and massive development of the arm bone.

Humerus and Mandibles of Dendrerpeton Acadianum. Natural size, with one of the teeth enlarged. (From a Photograph.)

The specimen illustrates the sculptured bones of Dendrerpeton and its plaited teeth, as well as large size and massive development of the arm bone.

In form,Dendrerpeton Acadianumwas probably lizard-like; with a broad flat head, short stout limbs and an elongated tail; and having its skin, and more particularly that of the belly, protected by small bony plates closely overlapping each other, and arrangeden chevron, in oblique rows meeting on the mesial line, where in front was a thoracic plate. It may have attained the length of two feet. The form of the head is not unlike that ofBaphetes, but longer in proportion; and much resembles that of the labyrinthodont reptiles of the Trias. The bones of the skull are sculptured as in Baphetes, but in a smaller pattern.

The fore limb of the adult animal, including the toes, must have been four or five inches in length, and is of massive proportions. The bones were hollow, and in the case of the phalanges the bony walls were thin, so that they are often crushed flat. The humerus, or arm bone, however, was a strong bone, with thick walls and a cancellated structure toward its extremities; still even these have sometimes yielded to the great pressure to which they have been subjected. The cavity of the interior of the limb bones is usually filled with calc-spar stained with organic matter, but showing no structure; and the inner side of the bony wall is smooth without any indication of cartilaginous matter lining it.

The vertebræ, in the external aspect of their bodies, remind one of those of fishes, expanding toward the extremities, andbeing deeply hollowed by conical cavities, which appear even to meet in the centre. There is, however, a large and flattened neural spine. The vertebræ are usually much crushed, and it is almost impossible to disengage them from the stone. The ribs are long and curved, showing a reptilian style of chest. The posterior limb seems to have been not larger than the anterior, perhaps smaller. The tibia, or principal bone of the fore leg is much flattened at the extremity, as in some Labyrinthodonts, and the foot must have been broad, and probably suited for swimming, or walking on soft mud, or both. That the hind limb was adapted for walking is shown, not merely by the form of the bones, but also by that of the pelvis.

The external scales are thin, oblique-rhomboidal or elongated-oval, marked with slight concentric lines, but otherwise smooth, and having a thickened ridge or margin, in which they resemble those of Archegosaurus, and also those ofPholidogaster pisciformis, described by Huxley from the Edinburgh coal field,—an animal which indeed appears in most respects to have a close affinity withDendrerpeton. The microscopic structure of the scales is quite similar to that of the other bones, and different from that of the scales of ganoid fishes, the shape of the cells being batrachian. For other particulars of its structure reference may be made to the papers named at the end of the chapter.

With respect to the affinities of the creature, I think it is obvious that it is most nearly related to the group of Lahyrinthodonts, and that it has the same singular mixture of batrachian and reptilian characters which distinguish these ancient animals, and which give them the appearance of prototypes of the reptilian class. A second and smaller species of Dendrerpeton was subsequently obtained at the Joggins, and others have been found, more especially by Fritsch, in the Carboniferous and Permian of Europe.

This ancient inhabitant of the coal swamps of Nova Scotiawas, in short, as we often find to be the case with the earliest forms of life, the possessor of powers and structures not usually, in the modern world, combined in a single species. It was certainly not a fish, yet its bony scales and the form of its vertebræ, and of its teeth, might, in the absence of other evidence, cause it to be mistaken for one. We call it a Batrachian, yet its dentition, the sculpturing of the bones of its skull, which were certainly no more external plates than the similar bones of a crocodile, its ribs, and the structure of its limbs, remind us of the higher reptiles; and we do not know that it ever possessed gills, or passed through a larval or fish-like condition. Still, in a great many important characters, its structures are undoubtedly batrachian. It stands, in short, in the same position with theLepidodendraandSigillariæunder whose shade it crept, which, though placed by palæobotanists in alliance with certain modern groups of plants, manifestly differed from these in many of their characters, and occupied a different position in nature. In the coal period the distinctions of physical and vital conditions were not well defined. Dry land and water, terrestrial and aquatic plants and animals, and lower and higher forms of animal and vegetable life, are consequently not easily separated from each other. This is no doubt a state of things characteristic of the earlier stages of the earth's history, yet not necessarily so; for there are some reasons, derived from fossil plants, for believing that in the preceding Devonian period there was less of this, and consequently that there may then have been a higher and more varied animal life than in the coal period.[134]

[134]See the author's paper on Devonian plants,Journal of the Geological Society, vol. xviii. p. 328.

The dentition ofDendrerpetonshows it to have been carnivorous in a high degree. It may have captured fishes and smaller reptiles, either on land or in water, and very probably fed on dead carcases as well. If, as seems likely, any of thefootprints referred to previously belong to this animal, it must have frequented the shores, either in search of garbage, or on its way to and from the waters. The occurrence of its remains in the stumps of Sigillaria, with land snails and millipedes, shows also that it crept in the shade of the woods in search of food; and in noticing coprolitic matter, in a subsequent page, I shall show that remains of excrementitious substances, probably of this species, contain fragments attributable to smaller reptiles, and other animals of the land.

All the bones ofDendrerpetonhitherto found, as well as those of the smaller reptilian species hereafter described, have been obtained from the interior of erect Sigillariæ, and all of these in one of the many beds, which, at the Joggins, contain such remains. The thick cellular inner bark of Sigillaria was very perishable; the slender woody axis was somewhat more durable; but near the surface of the stem, in large trunks, there was a layer of elongated cells, or bast tissue, of considerable durability, and the outer bark was exceedingly dense and indestructible.[135]Hence an erect tree, partly imbedded in sediment, and subjected to the influence of the weather, became a hollow shell of bark; in the bottom of which lay the decaying remains of the woody axis, and shreds of the fibrous bark. In ordinary circumstances such hollow stems would be almost immediately filled with silt and sand, deposited in the numerous inundations and subsidences of the coal swamps. Where, however, they remained open for a considerable time, they would constitute a series of pitfalls, into which animals walking on the surface might be precipitated; and being probably often partly covered by remains of prostrate trunks, or by vegetation growing around their mouths, they would be places of retreat and abode for land snails and such creatures. When the surface was again inundated or submerged, all such animals, with the remains of those which had fallen into the deeper pits, would be imbedded in the sediment which would then fill up the holes. These seem to have been the precise conditions of the bed which has afforded all these remains.

[135]See a paper by the author, on the Structures of Coal,Journal of the Geological Society, vol. xv.; also "Supplement to Acadian Geology."

A reptiliferous Treein situ, South Joggins, N. Scotia.This is a sketch of a tree which afforded remains of Dendrerpeton, Pupæ, etc.

A reptiliferous Treein situ, South Joggins, N. Scotia.

This is a sketch of a tree which afforded remains of Dendrerpeton, Pupæ, etc.

The history of a bed containing reptiliferous erect trees would thus be somewhat as follows:—

A forest or grove of the large-ribbed trees known asSigillariæ, was either submerged by subsidence, or, growing on low ground, was invaded with the muddy waters of an inundation, or successive inundations, so that the trunks were buried to the depth of several feet. The projecting tops having been removed by subaërial decay, the buried stumps became hollow, while their hard outer bark remained intact. They thus became hollow cylinders in a vertical position, and open at top. The surface having then become dry land, covered with vegetation, was haunted by small quadrupeds and other land animals, which from time to time fell into the open holes, in some cases nine feet deep, and could not extricate themselves. On their death, and the decomposition of their soft parts, their bones and other hard portions remained in the bottom of the tree intermixed with any vegetabledébrisor soil washed in by rain, and which formed thin layers separating successive animal deposits from each other. Finally, the area was again submerged or overflowed by water, bearing sand and mud. The hollow trees were filled to the top, and their animal contents thus sealed up. At length the material filling the trees was by pressure and the access of cementing matter hardened into stone, not infrequently harder than that of the containing beds, and the whole being tilted to an angle of 20°, and elevated into land exposed to the action of the tides and waves, these singular coffins present themselves as stony cylinders projecting from the cliff or reef, and can be extracted and their contents studied.

The singular combination of accidents above detailed was,of course, of very rare occurrence, and in point of fact we know only one set of beds at the South Joggins in which such remains so preserved occur; nor is there, so far as I am aware, any other known instance elsewhere. Even in the beds in question only a portion of the trees, about fifteen in thirty, have afforded animal remains. We have, however, thus been enabled to obtain specimens of a number of species which would probably otherwise have been unknown, being less likely than others to be preserved in properly aqueous deposits. Such discoveries, on the one hand impress us with the imperfection of the geological record; on the other, they show us the singular provisions which have been made in the course of geological time for preserving the relics of the ancient world, and which await the industry and skill of collectors to disclose their hidden treasures.

I may add that I believe all the trees, about thirty in number, which have become exposed in this bed since its discovery, have been ransacked for such remains; and that while the majority have afforded some reward for the labour, some have been far more rich than others in their contents. It is also to be observed that owing to the mode of accumulation of the mass filling the trees, the bones are usually found scattered in every position, and those of different species intermingled; and that being often much more friable than the matrix, much labour is required for their development; while after all has been done, the result is a congeries of fragments. A few specimens only have been found, showing skeletons complete, or nearly so, and I shall endeavour to figure one or two of these by way of illustration in the present chapter.

The beds on a level with the top of the reptiliferous erect trees are arenaceous sandstones, with numerous erectCalamites. I have searched the surfaces of these beds in vain for bones or footprints of the reptiles which must have traversed them, and which, but for hollow erect trees," would apparently have left no trace of their existence. On a surface of similar character, sixty feet higher, and separated by three coals, with their accompaniments, and a very thick compact sandstone, I observed a series of footprints, which may be those ofDendrerpetonorHylonomus.

A typical Carboniferous Microsaurian,Hylonomus LyelliRestoration showing dermal armour and ornaments. Skeleton restored from measurements of the bones of the type specimen figured at the beginning of the chapter.

Species of Microsauria. Hylonomus Lyelli.

In the original reptiliferous tree discovered by Sir C. Lyell and the writer, at the Joggins, in 1851, there were, beside the bones ofDendrerpeton Acadianum, some small elongated vertebræ, evidently of a different species. These were first detected by Prof. Wyman, in his examination of these specimens, and were figured, but not named, in the original notice of the specimens. In a subsequent visit to the Joggins I obtained from another erect stump many additional remains of these smaller reptiles, and, on careful comparison of the specimens, was induced to refer them to three species, all apparently generically allied. I proposed for them the generic nameHylonomus, "forest dweller." They were described in the Proceedings of the Geological Society for 1859, with illustrations of the teeth and other characteristic parts.[136]The smaller species first described I namedH. Wymani; the next in size, that to which this article refers, and which was represented by a larger number of specimens, I adopted as a type of the genus, and dedicated to Sir Charles Lyell. The third and largest, represented only by a few fragments of a single skeleton, was namedH. aciedentatus. This I had subsequently to remove to a new genus,Smilerpeton.

[136]Journal of Geological Society, vol. xvi.

Hylonomus Lyelliwas an animal of small size. Its skull is about an inch in length, and its whole body, including the tail, could not have been more than six or seven inches, long. The bones appear to have been thin and easily separable; and evenwhen they remain together, are so much crushed as to render the shape of the skull not easily discernible. They are smooth on the outer surface to the naked eye; and under a lens show only delicate, uneven striæ and minute dots. They are more dense and hard than those ofDendrerpeton, and the bone-cells are more elongated in form. The bones of the snout would seem to have been somewhat elongated and narrow. A specimen in my possession shows the parietal and occipital bones, or the greater part of them, united and retaining their form. We learn from them that the brain case was rounded, and that there was a parietal foramen. There would seem also to have been two occipital condyles, as in modern Batrachians. Several well-preserved specimens of the maxillary and mandibular bones have been obtained. They are smooth, or nearly so, like those of the skull, and are furnished with numerous sharp, conical teeth, anchylosed to the jaw, in a partial groove formed by the outer ridge of the bone. In the anterior part of the lower jaw there is a group of teeth larger than the others. The total number of teeth in each ramus of the lower jaw was about forty, and the number in each maxillary bone about thirty. The teeth are perfectly simple, hollow within, and with very fine radiating tubes of ivory. The vertebras have the bodies cylindrical or hour-glass shaped, covered with a thin, hard, bony plate, and having within a cavity of the form of two cones, attached by the apices. This cavity was completely surrounded by bone, as it is filled with stained calc-spar in the same manner as the cavities of the limb bones. It was probably occupied by cartilage. The vertebræ were apparently bi-concave, and are furnished with upper and lateral processes similar to those of small lacertian animals. The ribs are long, curved, and at the proximal end have a shoulder and neck. They are hollow, with thin hard bony walls. The anterior limb, judging from the fragment procured, seems to have been slender, with long toes, four or possibly five in number. Theposterior limb was longer and stronger, and attached to a pelvis so large and broad as to give the impression that the creature enlarged considerably in size toward the posterior extremity of the body, and that it may have been in the habit of sitting erect. The thigh bone is large and well-formed, with a distinct head and trochanter, and the lower extremity flattened and moulded into two articulating surfaces for the tibia and fibula, the fragments of which show that they were much shorter. The toes of the hind feet have been seen only in detached joints. They seem to have been thicker than those of the fore foot. Detached vertebræ, which seem to be caudal, have been found, and show that the tail was long and probably not flattened. The limb bones are usually somewhat crushed and flattened, especially at their articular extremities, and this seems to have led to the error of supposing that this flattened form was their normal condition; there can be no doubt, however, that it is merely an effect of pressure. The limb bones present in cross section a wall of dense bone with elongated bone-cells, surrounding a cavity now filled with brown calc-spar, and originally occupied with cartilage or marrow. I desire to specify the above points because I believe that most of the creatures referred by Fritsch, Credner, and other European naturalists to the Microsauria are of inferior grade to Hylonomus, though admitted to present points of approximation to the true reptiles. Woodward has recently described the remains of a Microsaurian from the English coal formation. Nothing is more remarkable in the skeleton of this creature than the contrast between the perfect and beautiful forms of its bones, and their imperfectly ossified condition, a circumstance which raises the question whether these specimens may not represent the young of some reptile of larger size.

The dermal covering of this animal is represented in part by oval bony scales, which are so constantly associated with its bones that I can have no doubt that they belonged to it, being,perhaps, the clothing of its lower or abdominal parts. But the most remarkable and unexpected feature of this little creature was the beautiful and ornate scaly covering of its back and sides. Modern Batrachians are characteristically naked, and though we know that some fossil species had coverings below of bony scales, these seemed rather to ally them with bony fishes. One of the specimens of Hylonomus had associated with it a quantity of crumpled shining skin, black and carbonaceous, and which may perhaps have been tanned and so preserved by the water filling the hollow tree impregnated with solution of tannin from the bark. This skin was covered with minute overlapping scales, which, under the microscope, showed the structure of horn rather than of bone. Besides these ordinary scales there were bony prominences, like those of the horned frog, on the back and shoulders, and a species of epaulettes made of long horny bristles curved downward, and apparently placed at the edges of the shoulders. Besides these there were in front and at the side rows of pendants or lappets, all no doubt ornamented with colouring, though now perfectly black. It may be asked what was the use of the ornate covering, and perhaps the question raises that perplexing problem, of the use of beauty in a world where there were no animals with higher æsthetic faculties than those of Batrachians. Scudder suggests a somewhat prosaic use in supposing them to be an armour against the venomous scorpions which were the contemporaries of these little reptiles, and some of them almost as large in size. But the word "venomous" raises another question, for we only infer that the scorpions were venomous from modern analogy and traces of an inflated joint at the end of the tail in some specimens. We have no absolute certainty that the subtle and complex organic poison of the scorpion, and his beautiful injection syringe for placing it under the skin, were perfected at this early time. Thus we have in the far back Carboniferous age a creature aselaborately ornamented and protected as any of the modern lizards, and this, let it be observed, constitutes another and important departure from that batrachian type to which these animals are supposed to conform. I may add here that subsequently portions of skin were found, which from their size probably belonged toDendrerpeton, and that these also were scaly and had lappets, though they did not appear to have the horny tubercles and fringes. It may be asked why such advanced characters should be found in Nova Scotia alone. The answer is that the circumstances of preservation in the erect trees were peculiar, and that only animals of purely terrestrial habits could find access to them, whereas the remains of reptiles found in the Carboniferous elsewhere are in aqueous beds in which aquatic forms were more likely to be preserved, and in which all the soft parts were certain to perish.

It is evident from the remains thus described, that we have inHylonomus Lyellian animal of lacertian form, with large and stout hind limbs, and somewhat smaller fore limbs, capable of walking and running on land; and though its vertebræ were imperfectly ossified externally, yet the outer walls were sufficiently strong, and their articulation sufficiently firm, to have enabled the creature to erect itself on its hind legs, or to leap. They were certainly proportionately larger and much more firmly knit than those ofDendrerpeton. Further, the ribs were long and much curved, and imply a respiration of a higher character than that of modern Batrachians, and consequently a more highly vitalized muscular system. If to these structural points we add the somewhat rounded skull, indicating a large brain, we have before us a creature which, however puzzling in its affinities when anatomically considered, is clearly not to be ranked as low in the scale of creation as modern tailed Batrachians, or even as the frogs and toads. We must add to these also, as important points of difference, the bony scales with which it was armed below, and the ornate apparatusof horny appendages, with which it was clad above. These last, as described in the last section, show that this little animal was not a squalid, slimy dweller in mud, likeMenobranchusand its allies, but rather a beautiful and sprightly tenant of the coal-formation thickets, vying in brilliancy, and perhaps in colouring, with the insects which it pursued and devoured. Remains of as many as eight or ten individuals have been obtained from three erect Sigillariæ, indicating that these creatures were quite abundant, as well as active and terrestrial in their mode of life.

With respect to the affinities of this species, I think it is abundantly manifest that it presents no close relationship with any reptile hitherto discovered in the Carboniferous system, except perhaps some of the smaller forms in the Permian of Europe, with which Credner and Fritsch have compared it. It is scarcely necessary to say that the characters above described entirely remove this animal from the Labyrinthodonts. Equal difficulties attend the attempt to place it in any other group of recent or extinct Batrachians or proper reptiles. The structures of the skull, and of some points in the vertebræ, certainly resemble those of Batrachians; but, on the other hand, the well-developed ribs, evidently adapted to enlarge the chest in respiration, the pelvis, and the cutaneous covering, are unexampled in modern Batrachians, and assimilate the creature to the true lizards. I have already, in my original description of the animal in 1859, expressed my belief thatHylonomusmay have had lacertian affinities, but I do not desire to speak too positively in this matter;[137]and shall content myself with stating the following alternatives as to the probable relations of these animals, (1) They may have been true reptiles of low type, and with batrachian tendencies. (2) They may have been representatives of a new family of Batrachians, exhibiting in some points lacertian affinities. (3) They may havebeen the young of some larger reptile, too large and vigorous to be entrapped in the pitfalls presented by the hollow Sigillaria stumps, and in its adult state losing the batrachian peculiarities apparent in the young. Whichever of these views we may adopt, the fact remains, that in the structure of this curious little creature we have peculiarities both batrachian and lacertian, in so far as our experience of modern animals is concerned. It would, however, accord with observed facts in relation to other groups of extinct animals, that the primitive Batrachians of the coal period should embrace in their structures points in after times restricted to the true reptiles. On the other hand, it would equally accord with such facts that the first-born of Lacertians should lean towards a lower type, by which they may have been preceded. My present impression is, that they may constitute a separate family or order, to which I would give the name ofMicrosauria, and which may be regarded as allied, on the one hand, to certain of the humbler lizards, as the Gecko or Agama, and, on the other, to the tailed Batrachians.

[137]I am glad to say that Fritsch and Credner now lean to the same view.

It is likely thatHylonomus Lyelliwas less aquatic in its habits thanDendrerpeton, Its food consisted, apparently, of insects and similar creatures. The teeth would indicate this, and near its bones there are portions of coprolite, containing remains of insects and myriapods. It probably occasionally fell a prey toDendrerpeton, as bones, which may have belonged either to young individuals of this species or to its smaller congenerH. Wymani, are found in larger coprolites, which may be referred with probability toDendrerpeton Acadianum. This coprolitic matter, which is somewhat plentiful on some of the surfaces in the erect trees, also informs us that the imprisoned animals may in some cases have continued to live for some time, feeding on such animals as may have fallen into their place of confinement, which was destined also to be their tomb. Some other points of interest appear on theexamination of this excrementitious matter. It contains much carbonate of lime, indicating that snails or other mollusks furnished a considerable part of the food of the smaller reptiles. Some portions of it are filled with chitinous fragments, parts of millipedes or insects, but usually so broken up as scarcely to be distinguishable. One curious exception was a part of the head of an insect containing a portion of one of its eyes. The facets of this can be readily seen with the microscope, and are similar to those of modern cockroaches. About 250 of these little eyes are discernible, and they must have been much more numerous. Two points are of interest here: First, the perfection of the compound eye for vision in air. It had long before, in the case of the Trilobites, been used for seeing under water. Secondly, the great age of the still ubiquitous and aggressive family of the cockroaches. In point of fact the oldest known insect, the Protoblattina of the Silurian, is one of these creatures, and they are the most abundant insects in the Carboniferous, so that if they now dispute with us the possession of our food, they may at least put in the claim of prior occupancy of the world. In one mass a quantity of thickish crust or shell appears, which under the microscope presents a minutely tubular and laminated appearance. It may have belonged to some small crustacean or large scorpion on which aDendrerpetonmay have been feeding before it fell into the pit in which it was entombed.

Dolichosoma longissimum, a serpentiform Permian Batrachian after Fritsch. This and Hylonomus are opposite or extreme types in regard to general form.

In addition to the reptilian species above noticed, the erect trees of Coal Mine Point have afforded several others. There is a second and smaller species of Dendrerpeton (D. Oweni) and other forms belonging to the group of Microsauria of which Hylonomus is the type. A second species of that genus (H. Wymani) has already been mentioned. A similar creature, but of larger size and with teeth of a wedge or chisel shape, has been referred to a distinct genus,Smilerpeton. It seems to have been rare, and the only skeleton found is very imperfect. Its teeth are of a form that may have served even for vegetable food, as their sharp edges must have had considerable cutting power. Another curious form of tooth appears in the genusHylerpeton. It has the points worked into oblique grooves separated by sharp edges, which must have greatly aided in piercing tough integument. These creatures seem to have been of stout and robust build, with large limbs. Still another generic type (Fritschia) is represented by a species near to Hylonomus in several respects, and with long and beautifully formed limb bones, but with the belly protected with rod-like bodies instead of scales. In this respect Hylerpeton is somewhat intermediate, having long and narrow scales on the belly instead of the oval or roundish scales of Hylonomus. All these last-mentioned forms are Microsaurians, with simple teeth and well-developed ribs and limbs, and smooth cranial bones. Two other species are represented by portions of single skeletons too imperfect to allow them to be certainly determined.

I would emphasize here that the vertebrate animals found in the erect trees are necessarily a selection from the most exclusively terrestrial forms, and from the smaller species of these. The numerous newt-like and serpentiform species found in the shales of the coal formation could not find access to these peculiar repositories, nor could the larger species of the Labyrinthodonts and their allies, even if they were in the habit of occasionally prowling in the forests in search of prey, and this would scarcely be likely, more especially as the waters must have afforded to them much more abundant supplies of food. Of the numerous species figured by Fritsch, Cope and Huxley, only a few approach very near to the forms entrapped in the old hollow Sigillariæ, though several have characters half batrachian and half reptilian.

Invertebrate Air-breathers.

The coal formation rocks have afforded Land Snails, Millipedes, Spiders, Scorpions and Insects, so that all the great types of invertebrate life which up to this day can live on land already had representatives in this ancient period. Some of them, indeed, we can trace further back, the land snails probably to the Devonian, the Millipedes to the same period, and the Scorpions and insects as far as the Silurian. No land vertebrate is yet known, older than the Lower Carboniferous, but there is nothing known to us in physical condition, to preclude the existence of such creatures at least in the Devonian.

It would take us too far afield to attempt to notice the invertebrate land life of the Palæozoic in general. This has been done in great detail by Dr. Scudder. I shall here limit myself to the animals found in our erect trees, and merely touch incidentally on such others as may be connected with them.

I have already mentioned the occurrence of a land-snail, a true pulmonate mollusk, in the first find by Lyell and myself at Coal Mine Point, and this was the first animal of this kind known in any rocks older than the Purbeck formation of England. It is one of the groups of so-called Chrysalis-shells, scarcely distinguishable at first sight from some modern West Indian species, and distinctly referable to the modern genus Pupa. It was namedPupa vetusta, and a second and smaller species subsequently found was namedP. Bigsbyi, and a third of different form, and resembling the modern snails, bears the nameZonites priscus. The only other Palæozoic land mollusks known at present are a few species found in the coal formation of Ohio, and a fragment supposed to indicate another species from the Devonian plant-beds of St. John's, New Brunswick. This last is the oldest known evidence of pulmonate snails. If we ask the precise relations of these creatures to modern snails, it may be answered that of the two leading subdivisions of the group of air-breathing snails (Pulmonifera), the Operculate, or those with a movable plate to close the mouth of the shell, and the Inoperculate, or those that are destitute of any such shelly lid or operculum to close the shell, the first has been traced no farther back than the Eocene. The second or inoperculate division, includes some genera that are aquatic and some that are terrestrial. Of the aquatic genera no representatives are known in formations older than the Wealden and Purbeck, and these only in Europe. The terrestrial group, or the family of theHelicidæ, which, singularly enough, is that which diverges farthest from the ordinary gill-bearing Gasteropods, is the one which has been traced farthest back, and includes the Palæozoic species. It is further remarkable that a very great gap exists in the geological history of this family. No species are known between the Carboniferous and the early Tertiary, though in the intervening formations there are many fresh-water and estuarine deposits in which such remains might be expected to occur. There is perhaps no reason to doubt the continuance of the Helicidæ through this long portion of geological time, though it is probable that during the interval the family did not increase much in the numbers of its species, more especially as it seems certain that it has its culmination in the modern period, where it is represented by very many and large species, which are dispersed over nearly all parts of our continents.

Carboniferous Land Snails.Pupa vetusta, Dawson, andConulus priscus, Carpenter, with egg ofPupa vetusta—the whole considerably magnified.

Carboniferous Land Snails.

Pupa vetusta, Dawson, andConulus priscus, Carpenter, with egg ofPupa vetusta—the whole considerably magnified.

I published in 1880, in theAmerican Journal of Science, a fragment of what seemed to be a land-snail, from the Middle Erian plant-beds of St. John, New Brunswick (Strophia grandava, figured here), but have mentioned it with some doubt in the text. Mr. G. F. Matthew has, however, recently communicated to the Royal Society of Canada a second species, found by Mr. W. I. Wilson in the same beds, and which he namesPupa primava. It is accompanied with a scorpion and a millipede. Thus the existence of Land Snails of the Pupa type in the Devonian may be considered as established.

The mode of occurrence of the Palæozoic Pulmonifera in the few localities where they have been found is characteristic. The earliest known species,Pupa vetusta, was found, as already stated, in the material filling the once hollow stem of a Sigillaria at the South Joggins in Nova Scotia, and many additional specimens have subsequently been obtained from similar repositories in the same locality, where they are associated with bones of Batrachians and remains of Millipedes. Other specimens, and also the speciesZonites priscus, havebeen found in a thin, shaly layer, containingdébrisof plants and crusts of Cyprids, and which was probably deposited at the outlet of a small stream flowing through the coal-formation forest. The two species found in Illinois occur, according to Bradley, in an underclay or fossil soil which may have been the bed of a pond or estuary, and subsequently became a forest subsoil. The Erian .species occurs in shales charged with remains of land plants, and which must consequently have received abundant drainage from neighbouring land. It is only in such deposits that remains of true land snails can be expected to occur; though, had fresh-water or brackish water Pulmonates abounded in the Carboniferous age, their remains should have occurred in those bituminous and calcareo-bituminous shales which contain such vast quantities ofdébrisof Cyprids, Lamellibranchs and fishes of the period, mixed with fossil plants.

The specimen first obtained in 1887 having been taken by Sir Charles Lyell to the United States, and submitted to the late Prof. Jeffries Wyman, the shell in question was recognised by him and the late Dr. Gould, of Boston, as a land shell. It was subsequently examined by M. Deshayes and Mr. Gwyn Jeffries, who concurred in this determination; and its microscopic structure was described by the late Prof. Quekett, of London, as similar to that of modern land shells. The single specimen obtained on this occasion was somewhat crushed, and did not show the aperture. Hence the hesitation as to its nature, and the delay in naming it, though it was figured and described in the paper above cited in 1852. Better specimens showing the aperture were afterward obtained by the writer, and it was named and described by him in his "Air-breathers of the Coal Period," in 1863. Owen, in his "Palæontology," subsequently proposed the generic nameDendropupa. This I have hesitated to accept, as expressing a generic distinction not warranted by the facts; but shouldthe shell be considered to require a generic or sub-generic distinction, Owen's name should be adopted for it. There seems, however, nothing to prevent it from being placed in one of the modern sub-genera of simple-lipped Pupæ. With regard to the form of its aperture, I may explain that some currency has been given to an incorrect representation of it, through defective specimens. In the case of delicate shells like this, imbedded in a hard matrix, it is of course difficult to work out the aperture perfectly; and in my published figure in the "Air-breathers," I had to restore somewhat the broken specimens in my possession. This restoration, specimens subsequently found have shown to be very exact.

As already stated, this shell seems closely allied to some modern Pupæ. Perhaps the modern species which approaches most nearly to it in form, markings and size, isMacrocheilus Gosseifrom the West Indies, specimens of which were sent to me some years ago by Mr. Bland, of New York, with the remark that they must be very near to my Carboniferous species. Such edentulous species asPupa(Leucochila)fallaxof Eastern America very closely resemble it; and it was regarded by the late Dr. Carpenter as probably a near ally of those species which are placed by some European conchologists in the genusPupilla.

Pupa vetustahas been found at three distinct levels in the coal formation of the South Joggins. The lowest is the shale above referred to. The next, 1,217 feet higher, is that of the original discovery. The third, 800 feet higher, is in an erect Sigillaria holding no other remains. Thus, this shell has lived in the locality at least during the accumulation of 2,000 feet of beds, including a number of coals and erect forests, as well as beds of bituminous shales and calcareo-bituminous shale, the growth of which must have been very slow.

In the lowest of these three horizons the shells are found, as already stated, in a thin bed of concretionary clay of darkgrey colour, though associated with reddish beds. It containsZonites priscusas well, though this is very rare, and there are a few valves ofCythereand shells ofNaiaditesas well as carbonaceous fragments, fronds of ferns,Trigonocarpa, etc. ThePupæare mostly adult, but many very young shells also occur, as well as fragments of broken shells. The bed is evidently a layer of mud deposited in a pond or creek, or at the mouth of a small stream. In modern swamps multitudes of fresh-water shells occur in such places, and it is remarkable that in this case the only Gasteropods are land shells, and these very plentiful, though only in one bed about an inch in thickness. This would seem to imply an absence of fresh-water Pulmonifera. In the erectSigillariæof the second horizon the shells occur either in a sandy matrix, more or less darkened with vegetable matter, or in a carbonaceous mass composed mainly of vegetabledébris. Except when crushed or flattened, the shells in these repositories are usually filled with brownish calcite. From this I infer that most of them were alive when imbedded, or at least that they contained the bodies of the animals; and it is not improbable that they sheltered themselves in the hollow trees, as is the habit of many similar animals in modern forests. Their residence in these trees, as well as the characters of their embryology, are illustrated by the occurrence of their mature ova. One of those, which I have considered worth figuring, has been broken in such a way as to show the embryo shell.

They may also have formed part of the food of the reptilian animals whose remains occur with them. In illustration of this I have elsewhere stated that I have found as many as eleven unbroken shells ofPhysa heterostrophain the stomach of a modernMenobranchus. I think it certain, however, that both the shells and the reptiles occurring in these trees must have been strictly terrestrial in their habits, as they could not have found admission to the erect trees unless the ground hadbeen sufficiently dry to allow several feet of the imbedded hollow trunks to be free from water. In the highest of the three horizons the shells occurred in an erect tree, but without any other fossils, and they had apparently been washed in along with a greyish mud.[138]

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